April Harkins - Academia.edu (original) (raw)
Papers by April Harkins
Med Sci Sport Exercise, 2008
ECS transactions
Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The meth... more Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The method is recyclable because majority (>88%) of [BMIm(+)Cl(-)], an ionic liquid (IL), used as the sole solvent, was recovered for reuse. Experimentally, it was confirmed that unique properties of each component remain intact in the composites, namely bactericide (from KER and CS) and anti-inflammatory property (from KER). Specifically, the composites were examined for their anti-inflammatory influence on macrophages. The cells were imaged and immunophenotyped to determine the quantity using the macrophage marker CD11b. The 75:25 [KER+CS] composite was found to have the least amount of CD11b macrophages compared to other composites. Bactericidal assays indicated that all composites, except the 25:75 [KER+CS], substantially reduce the growth of organisms such as vancomycin resistant Enterococcus (VRE) and Eschericia coli. The results clearly indicate that the composites possess all properti...
Arbeitsphysiologie
The purpose of this study was to compare exercise-induced analgesia in young women after a fatigu... more The purpose of this study was to compare exercise-induced analgesia in young women after a fatiguing isometric contraction during different phases of the menstrual cycle. Twenty female subjects performed a submaximal (25% maximal voluntary contraction) isometric contraction until task failure during both the mid-follicular and mid-luteal phases of their menstrual cycle. Pain perception (i.e., pain threshold and pain ratings) was measured before and after the isometric fatiguing contraction. Other measures included mean arterial pressure, heart rate, and anxiety levels. Time to task failure of the fatiguing contraction was similar for the two phases of the menstrual cycle. Following the performance of the isometric contraction: (1) pain thresholds increased and pain ratings decreased; (2) anxiety levels increased; and (3) mean arterial pressure and heart rate increased. These changes were not dependent on the phase of the menstrual cycle. Thus, the menstrual cycle phase does not infl...
Physiology & Behavior
Hoeger Bement, M.K., A. Weyer, M. Keller, A. Harkins, and S.K. Hunter. Anxiety and stress can pre... more Hoeger Bement, M.K., A. Weyer, M. Keller, A. Harkins, and S.K. Hunter. Anxiety and stress can predict pain perception following a cognitive stressor. PHYSIOL BEHAV 000-000. The purpose of this study was to investigate the influence of a cognitive stressor on pain perception and determine individual characteristics that may predict the pain response. Twenty-five subjects participated in three sessions: one familiarization and two experimental. The experimental sessions involved measurement of pain perception before and after 1) mental math tasks (stressor session) and 2) quiet rest (control session). Pain threshold and ratings were assessed with a mechanical noxious stimulus. Changes in stress and anxiety were examined with self-reported and physiological measures including questionnaires, visual analogue scales, and salivary cortisol levels. During the control session, stress and anxiety decreased and pain reports remain unchanged. During the stressor session, stress and anxiety inc...
ECS Transactions, 2014
Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The meth... more Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The method is recyclable because majority (>88%) of [BMIm + Cl -], an ionic liquid (IL), used as the sole solvent, was recovered for reuse. Experimentally, it was confirmed that unique properties of each component remain intact in the composites, namely bactericide (from KER and CS) and anti-inflammatory property (from KER). Specifically, the composites were examined for their anti-inflammatory influence on macrophages. The cells were imaged and immunophenotyped to determine the quantity using the macrophage marker CD11b. The 75:25 [KER+CS] composite was found to have the least amount of CD11b macrophages compared to other composites. Bactericidal assays indicated that all composites, except the 25:75 [KER+CS], substantially reduce the growth of organisms such as vancomycin resistant Enterococcus (VRE) and Eschericia coli. The results clearly indicate that the composites possess all properties needed for effective use as a wound dressing.
Clinical Orthopaedics and Related Research®, 2015
Background Muscle fatigability can increase when a stressful, cognitively demanding task is impos... more Background Muscle fatigability can increase when a stressful, cognitively demanding task is imposed during a low-force fatiguing contraction with the arm muscles, especially in women. Whether this occurs among older adults ([ 60 years) is currently unknown. Questions/purposes We aimed to determine if higher cognitive demands, stratified by sex, increased fatigability in older adults ([ 60 years). Secondarily, we assessed if varying cognitive demand resulted in decreased steadiness and was explained by anxiety or cortisol levels.
ISRN Obstetrics and Gynecology, 2011
Chlamydia, with its Chlamydia trachomatis etiology, is the most common bacterial sexually transmi... more Chlamydia, with its Chlamydia trachomatis etiology, is the most common bacterial sexually transmitted infection in the United States and is often transmitted via asymptomatic individuals. This review summarizes traditional and molecular-based diagnostic modalities specific to C. trachomatis. Several commercially available, FDA-approved molecular methods to diagnose urogenital C. trachomatis infection include nucleic acid hybridization, signal amplification, polymerase chain reaction, strand displacement amplification, and transcription-mediated amplification. Molecular-based methods are rapid and reliable genital specimen screening measures, especially when applied to areas of high disease prevalence. However, clinical and analytical sensitivity for some commercial systems decreases dramatically when testing urine samples. In vitro experiments and clinical data suggest that transcription-mediated amplification has greater analytical sensitivity than the other molecular-based methods currently available. This difference may be further exhibited in testing of extragenital specimens from at-risk patient demographics. The development of future molecular testing could address conundrums associated with confirmatory testing, medicolegal testing, and test of cure.
Physiology & Behavior, 2010
a b s t r a c t . Anxiety and stress can predict pain perception following a cognitive stressor. ... more a b s t r a c t . Anxiety and stress can predict pain perception following a cognitive stressor. PHYSIOL BEHAV 000-000. The purpose of this study was to investigate the influence of a cognitive stressor on pain perception and determine individual characteristics that may predict the pain response. Twenty-five subjects participated in three sessions: one familiarization and two experimental. The experimental sessions involved measurement of pain perception before and after 1) mental math tasks (stressor session) and 2) quiet rest (control session). Pain threshold and ratings were assessed with a mechanical noxious stimulus. Changes in stress and anxiety were examined with selfreported and physiological measures including questionnaires, visual analogue scales, and salivary cortisol levels. During the control session, stress and anxiety decreased and pain reports remain unchanged. During the stressor session, stress and anxiety increased and pain reports were variable among subjects. Based on the pain response to mental math, subjects were divided into three groups (increase, decrease or no change in pain). The increase-pain group (n = 8) had lower baseline stress and anxiety, lower baseline pain reports, and large anxiety response following the mental math. In contrast, the decrease-pain group (n = 9) had higher baseline stress and anxiety levels, higher baseline pain reports, and a large increase in cortisol levels. Thus, the differential response in the changes in pain perception was related to anxiety and stress levels prior to and during the cognitive stressor, indicating that psychosocial characteristics can help determine the stress-induced pain response.
Medicine & Science in Sports & Exercise, 2009
Medicine & Science in Sports & Exercise, 2011
This study determined the contribution of supraspinal fatigue to the sex difference in neuromuscu... more This study determined the contribution of supraspinal fatigue to the sex difference in neuromuscular fatigue for a low-intensity fatiguing contraction. Because women have greater motor responses to arousal than men, we also examined whether cortical and motor nerve stimulation, techniques used to quantify central fatigue, would alter the sex difference in muscle fatigue. In study 1, cortical stimulation was elicited during maximal voluntary contractions (MVC) before and after a submaximal isometric contraction at 20% MVC with the elbow flexor muscles in 29 young adults (20 ± 2.6 yr, 14 men). In study 2, 10 men and 10 women (19.1 ± 2.9 yr) performed a fatiguing contraction in the presence and absence of cortical and motor nerve stimulation. Study 1: Men had a briefer time to task failure than women (P = 0.009). Voluntary activation was reduced after the fatiguing contraction (P < 0.001) similarly for men and women. Motor-evoked potential area and the EMG silent period increased similarly with fatigue for both sexes. Peak relaxation rates, however, were greater for men than women and were associated with time to task failure (P < 0.05). Force fluctuations, RPE, HR, and mean arterial pressure increased at a greater rate for men than for women during the fatiguing contraction (P < 0.05). Study 2: Time to task failure, force fluctuations, and all other physiological variables assessed were similar for the control session and stimulation session (P > 0.05) for both men and women. Supraspinal fatigue was similar for men and women after the low-force fatiguing contraction, and the sex difference in muscle fatigue was associated with peripheral mechanisms. Furthermore, supraspinal fatigue can be quantified in both men and women without influencing motor performance.
Medicine & Science in Sports & Exercise, 2009
Medicine & Science in Sports & Exercise, 2008
The Journal of Pain, 2008
ABSTRACT Low-intensity, long-duration isometric contractions produce significant exercise-induced... more ABSTRACT Low-intensity, long-duration isometric contractions produce significant exercise-induced analgesia. There are also sex differences in pain perception before and after isometric contractions. To understand the mechanisms involved in the sex difference of exercise-induced analgesia, we investigated the influence of cortisol levels during different phases of the menstrual cycle before and after low-intensity and long-duration isometric contractions. Twenty female subjects (20.9 +/- 1.0 years) participated in three experimental sessions that were separated by ~one week. In session 1, subjects were familiarized to the pain device, instructed on how to use the ovulation kit, and performed 3 maximal voluntary contractions (MVC). Sessions 2 and 3 were randomly assigned according to the subject's phase of the menstrual cycle. One session took place during the mid-follicular phase (5-8 days past menses) and the other session during the mid-luteal phase (7-9 days past ovulation). During these last two sessions, pressure-induced pain ratings and thresholds were assessed before and after a sustained isometric contraction at 25% MVC force held until task failure. Salivary cortisol levels were measured at four different time points: 1) baseline, 2) 20 min following the first pain test, 3) immediately after the isometric contraction, and 4) 20 min following the static contraction. Pain perception and salivary cortisol levels did not differ during the different phases of the menstrual cycle (p> 0.05). Pain thresholds increased and pain ratings decreased following the performance of the static contractions (p= 0.0001 and 0.001, respectively). Salivary cortisol levels did not change following the pain test or the isometric fatiguing contraction (p> 0.05). There was no association between the absolute or relative changes in cortisol levels with pain ratings or pain threshold (p> 0.05). In conclusion, changes in cortisol levels are not associated with exercise-induced analgesia or phases of the menstrual cycle. Supported by a grant from APS (MHB).
Journal of Clinical Microbiology, 2014
Two important preanalytical protocols performed on liquid-based cytological specimens, namely, au... more Two important preanalytical protocols performed on liquid-based cytological specimens, namely, automated cytology processing and glacial acetic acid (GAA) treatment, may occur prior to the arrival of specimens in a molecular diagnostics laboratory. Ninety-two ThinPrep vials previously positive for high-risk human papillomavirus (HPV) via the Cervista HPV HR test were preselected and alternated with 92 previously negative ThinPrep vials. The specimen set was processed in a consecutive fashion by an automated cytology processor without fastidious decontamination precautions. Carryover potential was subsequently assessed by performance of the Aptima HPV assay on aliquots from reprocessed ThinPrep vials. All previously negative Thin-Prep vials yielded a negative result following routine automated cytology processing, despite close proximity to known-positive ThinPrep vials. In separate experiments, aliquots from 236 ThinPrep vials were forwarded for tandem analysis with and without GAA treatment. Data from GAA-and mock-treated specimens generated by Aptima HPV were compared to correlate data generated by Cervista. A 99.2% concordance of Aptima HPV results from GAA-treated and mock-treated specimens was noted. This result differed from the concordance result derived from Cervista (91.5%; P < 0.0002). Of the initially positive Cervista results, 21.9% reverted to negative following GAA treatment; the correlate value was 2.7% for Aptima HPV (P ؍ 0.01). While deleterious effects of GAA treatment on genomic DNA were noted with Cervista (P ؍ 0.0015), GAA treatment had no significant effects on Aptima HPV specimen signal/cutoff ratios or amplification of internal control RNA (P > 0.07). The validity of an Aptima HPV result is independent of GAA treatment and routine automated cytology processing.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2014
Journal of Biomedical Materials Research Part A, 2013
We have successfully developed a simple and totally recyclable method to synthesize novel, biocom... more We have successfully developed a simple and totally recyclable method to synthesize novel, biocompatible, and biodegradable composite materials from cellulose (CEL) and chitosan (CS). In this method, [BMIm þ Cl À ], an ionic liquid (IL), was used as a green solvent to dissolve and synthesize the [CELþCS] composites. Since, the IL can be removed from the composites by washing them with water, and recovered by distilling the washed solution, the method is totally recyclable. Spectroscopic and imaging techniques including XRD, FTIR, NIR, and SEM were used to monitor the dissolution, to characterize and to confirm that CEL and CS were successfully regenerated. More importantly, we have successfully demonstrated that [CELþCS] composite is particularly suited for many applications including antimicrobial property. This is because the composites have combined advantages of their components, namely superior chemical and mechanical stability (from CEL) and bactericide (from CS). Results of tensile strength measurements clearly indicate that adding CEL into CS substantially increase its tensile strength. Up to 5Â increase in tensile strength can be achieved by adding 80% of CEL into CS. Results of in vitro antibacterial assays confirm that CS retains its antibacterial property in the composite. More importantly, the composites reported here can inhibit growth of wider range of bacteria than other CS-based materials prepared by conventional methods; that is over 24 h period, the composites substantially inhibited growth of bacteria such as MRSA, VRE, S. aureus, E. coli. These are bacteria that are often found to have the highest morbidity and mortality associated with wound infections.
Journal of Applied Physiology, 2009
This study compared the time to task failure for a submaximal fatiguing contraction in the presen... more This study compared the time to task failure for a submaximal fatiguing contraction in the presence and absence of a cognitive stressor in men and women. In study 1, 10 men and 10 women (22 +/- 3 yr of age) performed an isometric fatiguing contraction at 20% maximal voluntary contraction force until task failure with the elbow flexor muscles during two separate sessions. Subjects performed a mental-math task during one of the fatiguing contractions that aimed to increase anxiety and stress (stressor session). Salivary cortisol and reported levels of arousal (visual analog scale for anxiety, and State-Trait Anxiety Inventory scores) were elevated during the stressor session compared with a control session for both sexes (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Time to task failure, however, was briefer during the stressor session compared with control (P = 0.005) but more so for the women (27.3 +/- 20.1%) than the men (8.6 +/- 23.1%) (P = 0.03). The briefer time to task failure was associated with target force (r(2) = 0.21) and accompanied by a higher mean arterial pressure, heart rate, and rate-pressure product during the fatiguing contraction in the stressor session compared with control in women. In study 2 (11 men and 8 women, 20 +/- 3 yr of age), time to task failure was similar for a fatiguing contraction with simple mental-math that did not increase stress (mental-attentiveness session) and control for both men and women. The greater change in fatigability of women than men with performance of a cognitive stressor involved initial strength and increases in indexes of sympathetic neural activity and cardiac work compared with control conditions.
FEMS Yeast Research, 2010
Phospholipase D1 (PLD1) is an important enzyme involved in lipid-mediated signal transduction and... more Phospholipase D1 (PLD1) is an important enzyme involved in lipid-mediated signal transduction and membrane dynamics in eukaryotes. PLD1 preferentially hydrolyzes phosphatidylcholine to phosphatidic acid. This potent second messenger is involved in cytoskeletal reorganization, secretion, and membrane trafficking in eukaryotic cells. In Saccharomyces cerevisiae, PLD1 is involved in polarized growth and morphogenesis during pheromone response and sporulation. The presence of a PLD activity in Schizosaccharomyces pombe is demonstrated. PLD activity was able to hydrolyze a fluorescently labeled analog of phosphatidylcholine and was capable of performing the transphosphatidylation reaction characteristic of PLDs. Schizosaccharomyces pombe PLD activity was unaffected by phosphatidylinositol 4,5 bisphosphate (PIP(2)), but was slightly stimulated by oleate. PLD activity was shown to increase when the S. pombe cells underwent mating and sporulation. Here, we also report the molecular cloning of the first phospholipase D isoform from an S. pombe genomic DNA library (EMBL accession no. FN547388). Comparisons of three divergent yeasts, S. pombe, S. cerevisiae, and Candida albicans, with respect to the PLD enzymes revealed differences in regulation by oleate and PIP(2). Even with high homology in the protein sequences between the PLD1 enzymes of S. cerevisiae, C. albicans, and S. pombe, there was variation with the effects of the regulators.
FEMS Yeast Research, 2008
Phospholipase D1 (PLD1), which is the product of the SPO14 gene, has been shown to play a role in... more Phospholipase D1 (PLD1), which is the product of the SPO14 gene, has been shown to play a role in the process of polarized cell growth (PCG) during the pheromone response in Saccharomyces cerevisiae. PLD1 hydrolyzes phosphatidylcholine to produce phosphatidic acid (PA) and a free choline headgroup. This study investigated the interactions of PLD1 and PA with two proteins known to be involved in the cellular signaling leading to PCG in yeast, the small GTPase Cdc42p and the PAK family kinase Ste20p. Constitutively activated Cdc42p stimulates PLD1 activity. Protein-lipid binding blots confirmed the specific binding of Ste20p to the PLD1 product, PA. Finally, kinase activity assays provided evidence for the stimulation of Ste20p by PA. These findings highlight the important interactions among PLD1, Cdc42p and Ste20p during PCG in S. cerevisiae.
European Journal of Applied Physiology, 2009
The purpose of this study was to compare exercise-induced analgesia in young women after a fatigu... more The purpose of this study was to compare exercise-induced analgesia in young women after a fatiguing isometric contraction during different phases of the menstrual cycle. Twenty female subjects performed a submaximal (25% maximal voluntary contraction) isometric contraction until task failure during both the mid-follicular and mid-luteal phases of their menstrual cycle. Pain perception (i.e., pain threshold and pain ratings) was measured before and after the isometric fatiguing contraction. Other measures included mean arterial pressure, heart rate, and anxiety levels. Time to task failure of the fatiguing contraction was similar for the two phases of the menstrual cycle. Following the performance of the isometric contraction: (1) pain thresholds increased and pain ratings decreased; (2) anxiety levels increased; and (3) mean arterial pressure and heart rate increased. These changes were not dependent on the phase of the menstrual cycle. Thus, the menstrual cycle phase does not influence the magnitude of exercise-induced analgesia.
Med Sci Sport Exercise, 2008
ECS transactions
Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The meth... more Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The method is recyclable because majority (>88%) of [BMIm(+)Cl(-)], an ionic liquid (IL), used as the sole solvent, was recovered for reuse. Experimentally, it was confirmed that unique properties of each component remain intact in the composites, namely bactericide (from KER and CS) and anti-inflammatory property (from KER). Specifically, the composites were examined for their anti-inflammatory influence on macrophages. The cells were imaged and immunophenotyped to determine the quantity using the macrophage marker CD11b. The 75:25 [KER+CS] composite was found to have the least amount of CD11b macrophages compared to other composites. Bactericidal assays indicated that all composites, except the 25:75 [KER+CS], substantially reduce the growth of organisms such as vancomycin resistant Enterococcus (VRE) and Eschericia coli. The results clearly indicate that the composites possess all properti...
Arbeitsphysiologie
The purpose of this study was to compare exercise-induced analgesia in young women after a fatigu... more The purpose of this study was to compare exercise-induced analgesia in young women after a fatiguing isometric contraction during different phases of the menstrual cycle. Twenty female subjects performed a submaximal (25% maximal voluntary contraction) isometric contraction until task failure during both the mid-follicular and mid-luteal phases of their menstrual cycle. Pain perception (i.e., pain threshold and pain ratings) was measured before and after the isometric fatiguing contraction. Other measures included mean arterial pressure, heart rate, and anxiety levels. Time to task failure of the fatiguing contraction was similar for the two phases of the menstrual cycle. Following the performance of the isometric contraction: (1) pain thresholds increased and pain ratings decreased; (2) anxiety levels increased; and (3) mean arterial pressure and heart rate increased. These changes were not dependent on the phase of the menstrual cycle. Thus, the menstrual cycle phase does not infl...
Physiology & Behavior
Hoeger Bement, M.K., A. Weyer, M. Keller, A. Harkins, and S.K. Hunter. Anxiety and stress can pre... more Hoeger Bement, M.K., A. Weyer, M. Keller, A. Harkins, and S.K. Hunter. Anxiety and stress can predict pain perception following a cognitive stressor. PHYSIOL BEHAV 000-000. The purpose of this study was to investigate the influence of a cognitive stressor on pain perception and determine individual characteristics that may predict the pain response. Twenty-five subjects participated in three sessions: one familiarization and two experimental. The experimental sessions involved measurement of pain perception before and after 1) mental math tasks (stressor session) and 2) quiet rest (control session). Pain threshold and ratings were assessed with a mechanical noxious stimulus. Changes in stress and anxiety were examined with self-reported and physiological measures including questionnaires, visual analogue scales, and salivary cortisol levels. During the control session, stress and anxiety decreased and pain reports remain unchanged. During the stressor session, stress and anxiety inc...
ECS Transactions, 2014
Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The meth... more Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The method is recyclable because majority (>88%) of [BMIm + Cl -], an ionic liquid (IL), used as the sole solvent, was recovered for reuse. Experimentally, it was confirmed that unique properties of each component remain intact in the composites, namely bactericide (from KER and CS) and anti-inflammatory property (from KER). Specifically, the composites were examined for their anti-inflammatory influence on macrophages. The cells were imaged and immunophenotyped to determine the quantity using the macrophage marker CD11b. The 75:25 [KER+CS] composite was found to have the least amount of CD11b macrophages compared to other composites. Bactericidal assays indicated that all composites, except the 25:75 [KER+CS], substantially reduce the growth of organisms such as vancomycin resistant Enterococcus (VRE) and Eschericia coli. The results clearly indicate that the composites possess all properties needed for effective use as a wound dressing.
Clinical Orthopaedics and Related Research®, 2015
Background Muscle fatigability can increase when a stressful, cognitively demanding task is impos... more Background Muscle fatigability can increase when a stressful, cognitively demanding task is imposed during a low-force fatiguing contraction with the arm muscles, especially in women. Whether this occurs among older adults ([ 60 years) is currently unknown. Questions/purposes We aimed to determine if higher cognitive demands, stratified by sex, increased fatigability in older adults ([ 60 years). Secondarily, we assessed if varying cognitive demand resulted in decreased steadiness and was explained by anxiety or cortisol levels.
ISRN Obstetrics and Gynecology, 2011
Chlamydia, with its Chlamydia trachomatis etiology, is the most common bacterial sexually transmi... more Chlamydia, with its Chlamydia trachomatis etiology, is the most common bacterial sexually transmitted infection in the United States and is often transmitted via asymptomatic individuals. This review summarizes traditional and molecular-based diagnostic modalities specific to C. trachomatis. Several commercially available, FDA-approved molecular methods to diagnose urogenital C. trachomatis infection include nucleic acid hybridization, signal amplification, polymerase chain reaction, strand displacement amplification, and transcription-mediated amplification. Molecular-based methods are rapid and reliable genital specimen screening measures, especially when applied to areas of high disease prevalence. However, clinical and analytical sensitivity for some commercial systems decreases dramatically when testing urine samples. In vitro experiments and clinical data suggest that transcription-mediated amplification has greater analytical sensitivity than the other molecular-based methods currently available. This difference may be further exhibited in testing of extragenital specimens from at-risk patient demographics. The development of future molecular testing could address conundrums associated with confirmatory testing, medicolegal testing, and test of cure.
Physiology & Behavior, 2010
a b s t r a c t . Anxiety and stress can predict pain perception following a cognitive stressor. ... more a b s t r a c t . Anxiety and stress can predict pain perception following a cognitive stressor. PHYSIOL BEHAV 000-000. The purpose of this study was to investigate the influence of a cognitive stressor on pain perception and determine individual characteristics that may predict the pain response. Twenty-five subjects participated in three sessions: one familiarization and two experimental. The experimental sessions involved measurement of pain perception before and after 1) mental math tasks (stressor session) and 2) quiet rest (control session). Pain threshold and ratings were assessed with a mechanical noxious stimulus. Changes in stress and anxiety were examined with selfreported and physiological measures including questionnaires, visual analogue scales, and salivary cortisol levels. During the control session, stress and anxiety decreased and pain reports remain unchanged. During the stressor session, stress and anxiety increased and pain reports were variable among subjects. Based on the pain response to mental math, subjects were divided into three groups (increase, decrease or no change in pain). The increase-pain group (n = 8) had lower baseline stress and anxiety, lower baseline pain reports, and large anxiety response following the mental math. In contrast, the decrease-pain group (n = 9) had higher baseline stress and anxiety levels, higher baseline pain reports, and a large increase in cortisol levels. Thus, the differential response in the changes in pain perception was related to anxiety and stress levels prior to and during the cognitive stressor, indicating that psychosocial characteristics can help determine the stress-induced pain response.
Medicine & Science in Sports & Exercise, 2009
Medicine & Science in Sports & Exercise, 2011
This study determined the contribution of supraspinal fatigue to the sex difference in neuromuscu... more This study determined the contribution of supraspinal fatigue to the sex difference in neuromuscular fatigue for a low-intensity fatiguing contraction. Because women have greater motor responses to arousal than men, we also examined whether cortical and motor nerve stimulation, techniques used to quantify central fatigue, would alter the sex difference in muscle fatigue. In study 1, cortical stimulation was elicited during maximal voluntary contractions (MVC) before and after a submaximal isometric contraction at 20% MVC with the elbow flexor muscles in 29 young adults (20 ± 2.6 yr, 14 men). In study 2, 10 men and 10 women (19.1 ± 2.9 yr) performed a fatiguing contraction in the presence and absence of cortical and motor nerve stimulation. Study 1: Men had a briefer time to task failure than women (P = 0.009). Voluntary activation was reduced after the fatiguing contraction (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) similarly for men and women. Motor-evoked potential area and the EMG silent period increased similarly with fatigue for both sexes. Peak relaxation rates, however, were greater for men than women and were associated with time to task failure (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Force fluctuations, RPE, HR, and mean arterial pressure increased at a greater rate for men than for women during the fatiguing contraction (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Study 2: Time to task failure, force fluctuations, and all other physiological variables assessed were similar for the control session and stimulation session (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05) for both men and women. Supraspinal fatigue was similar for men and women after the low-force fatiguing contraction, and the sex difference in muscle fatigue was associated with peripheral mechanisms. Furthermore, supraspinal fatigue can be quantified in both men and women without influencing motor performance.
Medicine & Science in Sports & Exercise, 2009
Medicine & Science in Sports & Exercise, 2008
The Journal of Pain, 2008
ABSTRACT Low-intensity, long-duration isometric contractions produce significant exercise-induced... more ABSTRACT Low-intensity, long-duration isometric contractions produce significant exercise-induced analgesia. There are also sex differences in pain perception before and after isometric contractions. To understand the mechanisms involved in the sex difference of exercise-induced analgesia, we investigated the influence of cortisol levels during different phases of the menstrual cycle before and after low-intensity and long-duration isometric contractions. Twenty female subjects (20.9 +/- 1.0 years) participated in three experimental sessions that were separated by ~one week. In session 1, subjects were familiarized to the pain device, instructed on how to use the ovulation kit, and performed 3 maximal voluntary contractions (MVC). Sessions 2 and 3 were randomly assigned according to the subject's phase of the menstrual cycle. One session took place during the mid-follicular phase (5-8 days past menses) and the other session during the mid-luteal phase (7-9 days past ovulation). During these last two sessions, pressure-induced pain ratings and thresholds were assessed before and after a sustained isometric contraction at 25% MVC force held until task failure. Salivary cortisol levels were measured at four different time points: 1) baseline, 2) 20 min following the first pain test, 3) immediately after the isometric contraction, and 4) 20 min following the static contraction. Pain perception and salivary cortisol levels did not differ during the different phases of the menstrual cycle (p> 0.05). Pain thresholds increased and pain ratings decreased following the performance of the static contractions (p= 0.0001 and 0.001, respectively). Salivary cortisol levels did not change following the pain test or the isometric fatiguing contraction (p> 0.05). There was no association between the absolute or relative changes in cortisol levels with pain ratings or pain threshold (p> 0.05). In conclusion, changes in cortisol levels are not associated with exercise-induced analgesia or phases of the menstrual cycle. Supported by a grant from APS (MHB).
Journal of Clinical Microbiology, 2014
Two important preanalytical protocols performed on liquid-based cytological specimens, namely, au... more Two important preanalytical protocols performed on liquid-based cytological specimens, namely, automated cytology processing and glacial acetic acid (GAA) treatment, may occur prior to the arrival of specimens in a molecular diagnostics laboratory. Ninety-two ThinPrep vials previously positive for high-risk human papillomavirus (HPV) via the Cervista HPV HR test were preselected and alternated with 92 previously negative ThinPrep vials. The specimen set was processed in a consecutive fashion by an automated cytology processor without fastidious decontamination precautions. Carryover potential was subsequently assessed by performance of the Aptima HPV assay on aliquots from reprocessed ThinPrep vials. All previously negative Thin-Prep vials yielded a negative result following routine automated cytology processing, despite close proximity to known-positive ThinPrep vials. In separate experiments, aliquots from 236 ThinPrep vials were forwarded for tandem analysis with and without GAA treatment. Data from GAA-and mock-treated specimens generated by Aptima HPV were compared to correlate data generated by Cervista. A 99.2% concordance of Aptima HPV results from GAA-treated and mock-treated specimens was noted. This result differed from the concordance result derived from Cervista (91.5%; P < 0.0002). Of the initially positive Cervista results, 21.9% reverted to negative following GAA treatment; the correlate value was 2.7% for Aptima HPV (P ؍ 0.01). While deleterious effects of GAA treatment on genomic DNA were noted with Cervista (P ؍ 0.0015), GAA treatment had no significant effects on Aptima HPV specimen signal/cutoff ratios or amplification of internal control RNA (P > 0.07). The validity of an Aptima HPV result is independent of GAA treatment and routine automated cytology processing.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2014
Journal of Biomedical Materials Research Part A, 2013
We have successfully developed a simple and totally recyclable method to synthesize novel, biocom... more We have successfully developed a simple and totally recyclable method to synthesize novel, biocompatible, and biodegradable composite materials from cellulose (CEL) and chitosan (CS). In this method, [BMIm þ Cl À ], an ionic liquid (IL), was used as a green solvent to dissolve and synthesize the [CELþCS] composites. Since, the IL can be removed from the composites by washing them with water, and recovered by distilling the washed solution, the method is totally recyclable. Spectroscopic and imaging techniques including XRD, FTIR, NIR, and SEM were used to monitor the dissolution, to characterize and to confirm that CEL and CS were successfully regenerated. More importantly, we have successfully demonstrated that [CELþCS] composite is particularly suited for many applications including antimicrobial property. This is because the composites have combined advantages of their components, namely superior chemical and mechanical stability (from CEL) and bactericide (from CS). Results of tensile strength measurements clearly indicate that adding CEL into CS substantially increase its tensile strength. Up to 5Â increase in tensile strength can be achieved by adding 80% of CEL into CS. Results of in vitro antibacterial assays confirm that CS retains its antibacterial property in the composite. More importantly, the composites reported here can inhibit growth of wider range of bacteria than other CS-based materials prepared by conventional methods; that is over 24 h period, the composites substantially inhibited growth of bacteria such as MRSA, VRE, S. aureus, E. coli. These are bacteria that are often found to have the highest morbidity and mortality associated with wound infections.
Journal of Applied Physiology, 2009
This study compared the time to task failure for a submaximal fatiguing contraction in the presen... more This study compared the time to task failure for a submaximal fatiguing contraction in the presence and absence of a cognitive stressor in men and women. In study 1, 10 men and 10 women (22 +/- 3 yr of age) performed an isometric fatiguing contraction at 20% maximal voluntary contraction force until task failure with the elbow flexor muscles during two separate sessions. Subjects performed a mental-math task during one of the fatiguing contractions that aimed to increase anxiety and stress (stressor session). Salivary cortisol and reported levels of arousal (visual analog scale for anxiety, and State-Trait Anxiety Inventory scores) were elevated during the stressor session compared with a control session for both sexes (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Time to task failure, however, was briefer during the stressor session compared with control (P = 0.005) but more so for the women (27.3 +/- 20.1%) than the men (8.6 +/- 23.1%) (P = 0.03). The briefer time to task failure was associated with target force (r(2) = 0.21) and accompanied by a higher mean arterial pressure, heart rate, and rate-pressure product during the fatiguing contraction in the stressor session compared with control in women. In study 2 (11 men and 8 women, 20 +/- 3 yr of age), time to task failure was similar for a fatiguing contraction with simple mental-math that did not increase stress (mental-attentiveness session) and control for both men and women. The greater change in fatigability of women than men with performance of a cognitive stressor involved initial strength and increases in indexes of sympathetic neural activity and cardiac work compared with control conditions.
FEMS Yeast Research, 2010
Phospholipase D1 (PLD1) is an important enzyme involved in lipid-mediated signal transduction and... more Phospholipase D1 (PLD1) is an important enzyme involved in lipid-mediated signal transduction and membrane dynamics in eukaryotes. PLD1 preferentially hydrolyzes phosphatidylcholine to phosphatidic acid. This potent second messenger is involved in cytoskeletal reorganization, secretion, and membrane trafficking in eukaryotic cells. In Saccharomyces cerevisiae, PLD1 is involved in polarized growth and morphogenesis during pheromone response and sporulation. The presence of a PLD activity in Schizosaccharomyces pombe is demonstrated. PLD activity was able to hydrolyze a fluorescently labeled analog of phosphatidylcholine and was capable of performing the transphosphatidylation reaction characteristic of PLDs. Schizosaccharomyces pombe PLD activity was unaffected by phosphatidylinositol 4,5 bisphosphate (PIP(2)), but was slightly stimulated by oleate. PLD activity was shown to increase when the S. pombe cells underwent mating and sporulation. Here, we also report the molecular cloning of the first phospholipase D isoform from an S. pombe genomic DNA library (EMBL accession no. FN547388). Comparisons of three divergent yeasts, S. pombe, S. cerevisiae, and Candida albicans, with respect to the PLD enzymes revealed differences in regulation by oleate and PIP(2). Even with high homology in the protein sequences between the PLD1 enzymes of S. cerevisiae, C. albicans, and S. pombe, there was variation with the effects of the regulators.
FEMS Yeast Research, 2008
Phospholipase D1 (PLD1), which is the product of the SPO14 gene, has been shown to play a role in... more Phospholipase D1 (PLD1), which is the product of the SPO14 gene, has been shown to play a role in the process of polarized cell growth (PCG) during the pheromone response in Saccharomyces cerevisiae. PLD1 hydrolyzes phosphatidylcholine to produce phosphatidic acid (PA) and a free choline headgroup. This study investigated the interactions of PLD1 and PA with two proteins known to be involved in the cellular signaling leading to PCG in yeast, the small GTPase Cdc42p and the PAK family kinase Ste20p. Constitutively activated Cdc42p stimulates PLD1 activity. Protein-lipid binding blots confirmed the specific binding of Ste20p to the PLD1 product, PA. Finally, kinase activity assays provided evidence for the stimulation of Ste20p by PA. These findings highlight the important interactions among PLD1, Cdc42p and Ste20p during PCG in S. cerevisiae.
European Journal of Applied Physiology, 2009
The purpose of this study was to compare exercise-induced analgesia in young women after a fatigu... more The purpose of this study was to compare exercise-induced analgesia in young women after a fatiguing isometric contraction during different phases of the menstrual cycle. Twenty female subjects performed a submaximal (25% maximal voluntary contraction) isometric contraction until task failure during both the mid-follicular and mid-luteal phases of their menstrual cycle. Pain perception (i.e., pain threshold and pain ratings) was measured before and after the isometric fatiguing contraction. Other measures included mean arterial pressure, heart rate, and anxiety levels. Time to task failure of the fatiguing contraction was similar for the two phases of the menstrual cycle. Following the performance of the isometric contraction: (1) pain thresholds increased and pain ratings decreased; (2) anxiety levels increased; and (3) mean arterial pressure and heart rate increased. These changes were not dependent on the phase of the menstrual cycle. Thus, the menstrual cycle phase does not influence the magnitude of exercise-induced analgesia.