Daniel Guzman | University of Cambridge (original) (raw)

Papers by Daniel Guzman

Research paper thumbnail of Content Validity of the Geriatric Depression Scale in Inpatient Health Care Settings

The content validity of the Geriatric Depression Scale (GDS) for use in inpatient health care set... more The content validity of the Geriatric Depression Scale (GDS) for use in inpatient health care settings was evaluated. Clinical experience has shown that one or more questions may not be appropriate in such settings. These questions ask about behaviors or feelings with which the examinee may not be able to identify with because they have been in an inpatient setting during the past week. Twenty-five Subject Matter Experts (SMEs) evaluated the GDS-30 as to whether each item appropriately assesses the construct of depression for inpatients in a medical care setting. SMEs were identified by an online search of the Florida Division of Medical Quality Assurance database; inclusion criteria are presented. Nineteen SMEs held a Ph.D. and six held a Psy.D. Years of post-licensure practice experience ranged from 10 to 48 years with a mean of 23.12 years (SD = 10.07). Using the Content Validity Ratio, four questions emerged as inappropriate (statistically significant at, or below, an alpha leve...

Research paper thumbnail of Screening method for assessing verbal learning efficiency using the Cognistat

Applied Neuropsychology: Adult, 2017

The Cognistat is a widely used neurobehavioral screening instrument that addresses functioning ac... more The Cognistat is a widely used neurobehavioral screening instrument that addresses functioning across multiple domains. Unlike many popular neuropsychological tests, the Cognistat does not currently assess learning efficiency for verbal material. The purpose of this study was to develop a screening method for assessing verbal learning efficiency with the Cognistat, investigate the effects of two demographic variables (age and gender) on performance, and to establish cutoff scores for impairment. Participants were 253 volunteers between the ages of 18 and 96 years. Participants were classified into two age groups: 18-64 years and 65 þ years. The data revealed a significant age and gender performance difference. Implications for the present findings and for future research are presented.

Research paper thumbnail of Heroin attenuates the negative consequences of cocaine in a runway model of self-administration

Pharmacology Biochemistry and Behavior, 2004

It has been presumed that the combination of cocaine (COC)+heroin (HER) is more reinforcing than ... more It has been presumed that the combination of cocaine (COC)+heroin (HER) is more reinforcing than either of the two drugs alone, thus leading to their coadministration ("speedballing"). An alternative hypothesis is that HER serves to attenuate the undesired negative effects of COC. To test this notion, male Sprague-Dawley rats (n=31) were trained to run a straight alley for a daily intravenous (IV) injection of COC (1.0 mg/kg/injection) for 14 trials. Studies in our laboratory have shown that such animals begin to exhibit approach-avoidance behaviors ("retreats") stemming from concurrent positive and negative associations with the goal box (which, in turn, are the result of COC's immediate rewarding and subsequent dysphoric actions). Thus, retreats can be used as a reliable index of COC's anxiogenic side effects. Following 14 COC-reinforced trials, animals were split into three groups matched on mean retreat frequency. One group (n=11) received IV COC (1.0 mg/kg/injection) for seven additional trials; the remaining two groups (n=10 each) received an IV injection of COC mixed in a single solution with either a low dose (0.025 mg/kg/injection) or a high dose (0.1 mg/kg/injection) of HER. It was hypothesized that adding HER would attenuate the negative consequences of COC administration and thereby produce a reliable decrease in the occurrence of retreats. The resulting data were consistent with this hypothesis, suggesting that "speedballing" in human addicts may be motivated by a desire to reduce the negative impact of COC use.

Research paper thumbnail of The effects of medial prefrontal cortex infusions of cocaine in a runway model of drug self-administration: Evidence of reinforcing but not anxiogenic actions

European Journal of Pharmacology, 2009

In previous work we have shown that rats running a straight alley for intravenous (i.v.) or intra... more In previous work we have shown that rats running a straight alley for intravenous (i.v.) or intracerebroventricular (i.c.v.) injections of cocaine develop an ambivalence about entering the goal box that results from cocaine's mixed reinforcing and anxiogenic properties. What remains unclear is whether or not cocaine's opposing properties stem from actions on a common neuronal system or from dual actions on separate systems-one related to reward and another to anxiogenic responses. One way to address this question is to deliver cocaine into discrete brain areas as a means of assessing whether or not the positive and negative effects of the drug can be spatially dissociated. Given the putative role of mesocorticolimbic dopamine pathways in the mediation of cocaine-reinforced behavior, the current study examined the cocaine-seeking behavior of rats permitted to run an alley once each day for bilateral medial prefrontal cortex microinjections of cocaine (0.0, 12.5, 25 or 50μg/0.5 μl per side) delivered upon goal-box entry. The results demonstrated that undrugged animals are highly motivated to seek medial prefrontal cortex cocaine without any evidence of negative or anxiogenic effects at any dose. These results are therefore consistent with suggestions of a medial prefrontal cortex involvement in the reinforcing actions of cocaine, and indicate that the dual and opposing actions of the drug can be dissociated and hence may be mediated by the drug's actions on separate neuronal systems.

Research paper thumbnail of Runway self-administration of intracerebroventricular cocaine: evidence of mixed positive and negative drug actions

Behavioural Pharmacology, 2007

In previous work from our laboratory, animals running for intravenous cocaine developed a unique ... more In previous work from our laboratory, animals running for intravenous cocaine developed a unique approachavoidance 'retreat behavior' that was hypothesized to result from cocaine's well documented reinforcing (positive) and anxiogenic (negative) properties. To assess the role of central mechanisms in producing cocaine's positive and negative effects, we assessed whether or not animals running a straight alley for intracerebroventricular applications of cocaine would produce a similar behavioral profile to that previously observed with intravenous applications. Retreat frequency and location were measured in male Sprague-Dawley rats trained to run an alley for one of four doses of intracerebroventricularadministered cocaine (0, 25, 50 or 100 lg cocaine/ infusion). Testing involved a single trial per day over 14 consecutive days with a single infusion of cocaine delivered upon goal box entry. The 100 and 50 lg intracerebroventricular cocaine groups exhibited significantly higher retreat frequencies than the 25 and 0 lg groups and the nature and magnitude of the behavior was comparable to that previously observed with intravenous cocaine. These results suggest that the intracerebroventricular self-administration of cocaine results in mixed positive and negative consequences and therefore likely stem from the drug's actions within the central nervous system. Behavioural Pharmacology

Research paper thumbnail of Poly(3-hydroxybutyrate) production by Halomonas boliviensis in fed-batch culture

Applied Microbiology and Biotechnology, 2007

High poly(3-hydroxybutyrate) (PHB) content and volumetric productivity were achieved by fed-batch... more High poly(3-hydroxybutyrate) (PHB) content and volumetric productivity were achieved by fed-batch culture of Halomonas boliviensis using a defined medium. Initial shake flask cultivations in a minimal medium revealed that the growth of H. boliviensis was supported only when the medium was supplemented with aspartic acid, glycine, or glutamine. Addition of 0.1% (w/v) glutamine in the medium resulted in the highest cell dry weight (CDW; 3.9 g l −1). Glutamine was replaced by the less expensive monosodium glutamate (MSG) in the medium without any notable change in the final cell density. Effect of initial concentrations of NH 4 Cl and K 2 HPO 4 on cell growth and PHB accumulation by H. boliviensis was then analyzed using a fed-batch fermentation system. The best conditions for PHB production by H. boliviensis were attained using 0.4% (w/v) NH 4 Cl and 0.22% (w/v) K 2 HPO 4 and adding MSG intermittently to the fermentor. Poly(3-hydroxybutyrate) content and CDW reached 90 wt.% and 23 g l −1 , respectively, after 18 h of cultivation. In order to increase CDW and PHB content, MSG, NH 4 Cl, and K 2 HPO 4 were initially fed to the fermentor to maintain their concentrations at 2%, 0.4%, and 0.22% (w/v), respectively, and subsequently their feed was suppressed. This resulted in a CDW of 44 g l −1 , PHB content of 81 wt.%, and PHB volumetric productivity of 1.1 g l −1 h −1 .

Research paper thumbnail of Content Validity of the Geriatric Depression Scale in Inpatient Health Care Settings

The content validity of the Geriatric Depression Scale (GDS) for use in inpatient health care set... more The content validity of the Geriatric Depression Scale (GDS) for use in inpatient health care settings was evaluated. Clinical experience has shown that one or more questions may not be appropriate in such settings. These questions ask about behaviors or feelings with which the examinee may not be able to identify with because they have been in an inpatient setting during the past week. Twenty-five Subject Matter Experts (SMEs) evaluated the GDS-30 as to whether each item appropriately assesses the construct of depression for inpatients in a medical care setting. SMEs were identified by an online search of the Florida Division of Medical Quality Assurance database; inclusion criteria are presented. Nineteen SMEs held a Ph.D. and six held a Psy.D. Years of post-licensure practice experience ranged from 10 to 48 years with a mean of 23.12 years (SD = 10.07). Using the Content Validity Ratio, four questions emerged as inappropriate (statistically significant at, or below, an alpha leve...

Research paper thumbnail of Screening method for assessing verbal learning efficiency using the Cognistat

Applied Neuropsychology: Adult, 2017

The Cognistat is a widely used neurobehavioral screening instrument that addresses functioning ac... more The Cognistat is a widely used neurobehavioral screening instrument that addresses functioning across multiple domains. Unlike many popular neuropsychological tests, the Cognistat does not currently assess learning efficiency for verbal material. The purpose of this study was to develop a screening method for assessing verbal learning efficiency with the Cognistat, investigate the effects of two demographic variables (age and gender) on performance, and to establish cutoff scores for impairment. Participants were 253 volunteers between the ages of 18 and 96 years. Participants were classified into two age groups: 18-64 years and 65 þ years. The data revealed a significant age and gender performance difference. Implications for the present findings and for future research are presented.

Research paper thumbnail of Heroin attenuates the negative consequences of cocaine in a runway model of self-administration

Pharmacology Biochemistry and Behavior, 2004

It has been presumed that the combination of cocaine (COC)+heroin (HER) is more reinforcing than ... more It has been presumed that the combination of cocaine (COC)+heroin (HER) is more reinforcing than either of the two drugs alone, thus leading to their coadministration ("speedballing"). An alternative hypothesis is that HER serves to attenuate the undesired negative effects of COC. To test this notion, male Sprague-Dawley rats (n=31) were trained to run a straight alley for a daily intravenous (IV) injection of COC (1.0 mg/kg/injection) for 14 trials. Studies in our laboratory have shown that such animals begin to exhibit approach-avoidance behaviors ("retreats") stemming from concurrent positive and negative associations with the goal box (which, in turn, are the result of COC's immediate rewarding and subsequent dysphoric actions). Thus, retreats can be used as a reliable index of COC's anxiogenic side effects. Following 14 COC-reinforced trials, animals were split into three groups matched on mean retreat frequency. One group (n=11) received IV COC (1.0 mg/kg/injection) for seven additional trials; the remaining two groups (n=10 each) received an IV injection of COC mixed in a single solution with either a low dose (0.025 mg/kg/injection) or a high dose (0.1 mg/kg/injection) of HER. It was hypothesized that adding HER would attenuate the negative consequences of COC administration and thereby produce a reliable decrease in the occurrence of retreats. The resulting data were consistent with this hypothesis, suggesting that "speedballing" in human addicts may be motivated by a desire to reduce the negative impact of COC use.

Research paper thumbnail of The effects of medial prefrontal cortex infusions of cocaine in a runway model of drug self-administration: Evidence of reinforcing but not anxiogenic actions

European Journal of Pharmacology, 2009

In previous work we have shown that rats running a straight alley for intravenous (i.v.) or intra... more In previous work we have shown that rats running a straight alley for intravenous (i.v.) or intracerebroventricular (i.c.v.) injections of cocaine develop an ambivalence about entering the goal box that results from cocaine's mixed reinforcing and anxiogenic properties. What remains unclear is whether or not cocaine's opposing properties stem from actions on a common neuronal system or from dual actions on separate systems-one related to reward and another to anxiogenic responses. One way to address this question is to deliver cocaine into discrete brain areas as a means of assessing whether or not the positive and negative effects of the drug can be spatially dissociated. Given the putative role of mesocorticolimbic dopamine pathways in the mediation of cocaine-reinforced behavior, the current study examined the cocaine-seeking behavior of rats permitted to run an alley once each day for bilateral medial prefrontal cortex microinjections of cocaine (0.0, 12.5, 25 or 50μg/0.5 μl per side) delivered upon goal-box entry. The results demonstrated that undrugged animals are highly motivated to seek medial prefrontal cortex cocaine without any evidence of negative or anxiogenic effects at any dose. These results are therefore consistent with suggestions of a medial prefrontal cortex involvement in the reinforcing actions of cocaine, and indicate that the dual and opposing actions of the drug can be dissociated and hence may be mediated by the drug's actions on separate neuronal systems.

Research paper thumbnail of Runway self-administration of intracerebroventricular cocaine: evidence of mixed positive and negative drug actions

Behavioural Pharmacology, 2007

In previous work from our laboratory, animals running for intravenous cocaine developed a unique ... more In previous work from our laboratory, animals running for intravenous cocaine developed a unique approachavoidance 'retreat behavior' that was hypothesized to result from cocaine's well documented reinforcing (positive) and anxiogenic (negative) properties. To assess the role of central mechanisms in producing cocaine's positive and negative effects, we assessed whether or not animals running a straight alley for intracerebroventricular applications of cocaine would produce a similar behavioral profile to that previously observed with intravenous applications. Retreat frequency and location were measured in male Sprague-Dawley rats trained to run an alley for one of four doses of intracerebroventricularadministered cocaine (0, 25, 50 or 100 lg cocaine/ infusion). Testing involved a single trial per day over 14 consecutive days with a single infusion of cocaine delivered upon goal box entry. The 100 and 50 lg intracerebroventricular cocaine groups exhibited significantly higher retreat frequencies than the 25 and 0 lg groups and the nature and magnitude of the behavior was comparable to that previously observed with intravenous cocaine. These results suggest that the intracerebroventricular self-administration of cocaine results in mixed positive and negative consequences and therefore likely stem from the drug's actions within the central nervous system. Behavioural Pharmacology

Research paper thumbnail of Poly(3-hydroxybutyrate) production by Halomonas boliviensis in fed-batch culture

Applied Microbiology and Biotechnology, 2007

High poly(3-hydroxybutyrate) (PHB) content and volumetric productivity were achieved by fed-batch... more High poly(3-hydroxybutyrate) (PHB) content and volumetric productivity were achieved by fed-batch culture of Halomonas boliviensis using a defined medium. Initial shake flask cultivations in a minimal medium revealed that the growth of H. boliviensis was supported only when the medium was supplemented with aspartic acid, glycine, or glutamine. Addition of 0.1% (w/v) glutamine in the medium resulted in the highest cell dry weight (CDW; 3.9 g l −1). Glutamine was replaced by the less expensive monosodium glutamate (MSG) in the medium without any notable change in the final cell density. Effect of initial concentrations of NH 4 Cl and K 2 HPO 4 on cell growth and PHB accumulation by H. boliviensis was then analyzed using a fed-batch fermentation system. The best conditions for PHB production by H. boliviensis were attained using 0.4% (w/v) NH 4 Cl and 0.22% (w/v) K 2 HPO 4 and adding MSG intermittently to the fermentor. Poly(3-hydroxybutyrate) content and CDW reached 90 wt.% and 23 g l −1 , respectively, after 18 h of cultivation. In order to increase CDW and PHB content, MSG, NH 4 Cl, and K 2 HPO 4 were initially fed to the fermentor to maintain their concentrations at 2%, 0.4%, and 0.22% (w/v), respectively, and subsequently their feed was suppressed. This resulted in a CDW of 44 g l −1 , PHB content of 81 wt.%, and PHB volumetric productivity of 1.1 g l −1 h −1 .