Frank Díaz | UNIVERSIDAD PRIVADA ANTENOR ORREGO (original) (raw)
Papers by Frank Díaz
Fatigue & Fracture of Engineering Materials & Structures, 2004
A B S T R A C T Thermoelastic stress analysis has been developed in recent years as a direct meth... more A B S T R A C T Thermoelastic stress analysis has been developed in recent years as a direct method of investigating the crack tip stresses in a structure under cyclic loading. This is a consequence of the fact that stress intensity factors obtained from thermoelastic experiments are determined from the cyclic stress field ahead of a fatigue crack, rather than inferred from measurement of the crack length and load range. In the present paper the results of fatigue crack growth tests performed on welded ferritic steel plates are reported. From the results it can be observed that the technique is sensitive to the effects of crack closure and the presence of tensile and compressive residual stresses due to welding.
Journal of Virology, 2004
JC virus (JCV), a human neurotropic polyomavirus, demonstrates a selective glial cell tropism tha... more JC virus (JCV), a human neurotropic polyomavirus, demonstrates a selective glial cell tropism that causes cell death through lytic infection. Whether these cells die via apoptosis or necrosis following infection with JCV remains unclear. To investigate the mechanism of virus-induced cell death, we used a human central nervous system progenitor-derived astrocyte cell culture model developed in our laboratory. Using in situ DNA hybridization, immunocytochemistry, electron microscopy, and an RNase protection assay, we observed that astrocytes support a progressive JCV infection, which eventually leads to nonapoptotic cell death. Infected astrocyte cell cultures showed no difference from noninfected cells in mRNA expression of the caspase family genes or in any ultrastructural features associated with apoptosis. Infected cells demonstrated striking necrotic features such as cytoplasmic vacuolization, watery cytoplasm, and dissolution of organelles. Furthermore, staining for caspase-3 and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling were not detected in infected astrocyte cultures. Our findings suggest that JCV-induced cell death of these progenitor cell-derived astrocytes does not utilize an apoptosis pathway but exhibits a pattern of cell destruction consistent with necrotic cell death.
Journal of Neurovirology, 2003
Since the initial description of progressive multifocal leukoencephalopathy (PML) in 1958, clinic... more Since the initial description of progressive multifocal leukoencephalopathy (PML) in 1958, clinical and basic science investigators have demonstrated a growing interest in the area of neurovirology, with a recent focus on polyomaviruses. In this review, the authors present an overview of the biological properties of the human polyomavirus, JC virus (JCV), and its association with PML as the etiologic agent. Additionally, the authors provide a discussion of the current understanding of JCV molecular pathogenesis and therapeutic strategies. Journal of NeuroVirology (2003) 9, 236-246.
Transplant International, 2007
Glia, 2006
Chemokines (chemoattractant cytokines) and their receptors are present in the brain and may play ... more Chemokines (chemoattractant cytokines) and their receptors are present in the brain and may play roles in both neurodevelopment and neuropathology. Increased brain levels of monocyte chemoattractant protein-1 (MCP-1), also known as CCL2, are found in patients with human immunodeficiency virus type 1 (HIV-1)-associated dementia and other acute and chronic neurologic diseases. Although the function of CCL2 in the brain is unclear, it is believed that upregulation of this chemokine during neuropathologic or neuroinflammatory conditions leads to recruitment of activated monocytes into the brain, where they differentiate into macrophages producing neurotoxic and inflammatory molecules. We recently showed that human fetal brainderived progenitor cells are susceptible to HIV-1 and JC virus infection, and that differentiation toward an astrocyte phenotype increased virus production from these cells. In the current study, we found that in the absence of infection, progenitors produced moderate levels of CCL2 (5.6 ng per million cells). Astrocyte differentiation over 3 weeks increased CCL2 protein levels 30-fold in a biphasic manner, whereas neuronal differentiation decreased production 20fold. Electromobility shift assays (EMSAs) demonstrated increased nuclear NF-jB levels within 2 h of initiating astrocyte differentiation, and inhibitors of NF-jB activation partially blocked the CCL2 increase in differentiating astrocytes. Transfection of progenitors with mutated CCL2 promoter/CAT reporter constructs showed that the distal promoter region, containing NF-jB and NF-I binding sites, is important for differentiation-induced CCL2 upregulation. Together these results suggest that the transcription factor NF-jB, and possibly NF-I, contribute to the upregulation of CCL2 chemokine production during the differentiation of human progenitor cells toward an astrocyte phenotype.
Laryngoscope, 2000
Objectives Objectives of the study are 1) to test the effectiveness of somnoplasty (radiofrequenc... more Objectives Objectives of the study are 1) to test the effectiveness of somnoplasty (radiofrequency volumetric tissue reduction of the soft palate) for the control of loud, socially disruptive, snoring; 2) to test the long-term efficacy of this treatment by spouse report; and 3) to compare the effectiveness of somnoplasty with another treatment.Study Design Twenty patients with complaints of loud snoring and a respiratory disturbance index no greater than 15 respiratory events per hour with sleep-related episodes of oxygen desaturation no lower than 80% were offered an experimental treatment. Ten were treated with somnoplasty, and a comparison group of 10 matched patients used an oral appliance. All were restudied in the laboratory wearing a device programmed to count minutes of sleep during which snoring was loud, soft, or absent.Methods For the 10 somnoplasty patients, a spouse rating of snoring determined whether the patient received one or more treatments. Five patients had a single treatment to three sites, and five others had two such treatments. Ten patients wore an oral appliance of the tongue-retaining type (Snore X, Fremont, CA).Results Seven of the 10 somnoplasty patients met the improvement criteria set for reduced loud snoring (a spouse rating of 3 or less on a 10-point scale, and 10% or less of sleep time in loud snoring in the laboratory). The comparison group also had a significant improvement in the percentage of sleep time in loud snoring while wearing the Snore X appliance.Conclusion Since there was no significant difference between the two groups in percentage of sleep time spent in loud snoring while treated, the choice of method to control snoring must be based on factors other than efficacy.
Biomaterials, 2003
Silk from the silkworm, Bombyx mori, has been used as biomedical suture material for centuries. T... more Silk from the silkworm, Bombyx mori, has been used as biomedical suture material for centuries. The unique mechanical properties of these fibers provided important clinical repair options for many applications. During the past 20 years, some biocompatibility problems have been reported for silkworm silk; however, contamination from residual sericin (glue-like proteins) was the likely cause. More recent studies with well-defined silkworm silk fibers and films suggest that the core silk fibroin fibers exhibit comparable biocompatibility in vitro and in vivo with other commonly used biomaterials such as polylactic acid and collagen. Furthermore, the unique mechanical properties of the silk fibers, the diversity of side chain chemistries for 'decoration' with growth and adhesion factors, and the ability to genetically tailor the protein provide additional rationale for the exploration of this family of fibrous proteins for biomaterial applications. For example, in designing scaffolds for tissue engineering these properties are particularly relevant and recent results with bone and ligament formation in vitro support the potential role for this biomaterial in future applications. To date, studies with silks to address biomaterial and matrix scaffold needs have focused on silkworm silk. With the diversity of silk-like fibrous proteins from spiders and insects, a range of native or bioengineered variants can be expected for application to a diverse set of clinical needs. r
... Correspondencia: Dr. FL Moreno-Martínez. Hemodinámica y Cardiología Intervencionista. Cardioc... more ... Correspondencia: Dr. FL Moreno-Martínez. Hemodinámica y Cardiología Intervencionista. Cardiocentro Ernesto Che Guevara. Cuba 610, CP 50200. Santa Clara. Villa Clara. Cuba. Correo electrónico: flmorenom@yahoo.com ...
Journal of Crystal Growth, 1986
Connective Tissue Research, 2005
An improved understanding of cellular responses during normal anterior cruciate ligament (ACL) fu... more An improved understanding of cellular responses during normal anterior cruciate ligament (ACL) function or repair is essential for clinical assessments, understanding ligament biology, and the implementation of tissue engineering strategies. The present study utilized quantitative real-time RT-PCR combined with univariate and multivariate statistical analyses to establish a quantitative database of marker transcript expression that can provide a "blueprint" of ACL wound healing. Selected markers (collagen types I and III, biglycan, decorin, MMP-1, MMP-2, MMP-9, and TIMP-1) were assessed from 33 torn ACLs harvested during reconstructive surgery. Trends were observed between postinjury period and marker expressions. Significant correlations between marker expression existed and were most prominent between collagen types I and III. Canonical correlation analysis established a relationship between patient demographics and a combination of all marker expressions. The currently observed trends and correlations may assist in identifying appropriate tissue samples and provide a baseline information of marker expression level that can support in vitro optimization of environmental cues for ligament tissue engineering application.
Fatigue & Fracture of Engineering Materials & Structures, 2004
A B S T R A C T Thermoelastic stress analysis has been developed in recent years as a direct meth... more A B S T R A C T Thermoelastic stress analysis has been developed in recent years as a direct method of investigating the crack tip stresses in a structure under cyclic loading. This is a consequence of the fact that stress intensity factors obtained from thermoelastic experiments are determined from the cyclic stress field ahead of a fatigue crack, rather than inferred from measurement of the crack length and load range. In the present paper the results of fatigue crack growth tests performed on welded ferritic steel plates are reported. From the results it can be observed that the technique is sensitive to the effects of crack closure and the presence of tensile and compressive residual stresses due to welding.
Journal of Virology, 2004
JC virus (JCV), a human neurotropic polyomavirus, demonstrates a selective glial cell tropism tha... more JC virus (JCV), a human neurotropic polyomavirus, demonstrates a selective glial cell tropism that causes cell death through lytic infection. Whether these cells die via apoptosis or necrosis following infection with JCV remains unclear. To investigate the mechanism of virus-induced cell death, we used a human central nervous system progenitor-derived astrocyte cell culture model developed in our laboratory. Using in situ DNA hybridization, immunocytochemistry, electron microscopy, and an RNase protection assay, we observed that astrocytes support a progressive JCV infection, which eventually leads to nonapoptotic cell death. Infected astrocyte cell cultures showed no difference from noninfected cells in mRNA expression of the caspase family genes or in any ultrastructural features associated with apoptosis. Infected cells demonstrated striking necrotic features such as cytoplasmic vacuolization, watery cytoplasm, and dissolution of organelles. Furthermore, staining for caspase-3 and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling were not detected in infected astrocyte cultures. Our findings suggest that JCV-induced cell death of these progenitor cell-derived astrocytes does not utilize an apoptosis pathway but exhibits a pattern of cell destruction consistent with necrotic cell death.
Journal of Neurovirology, 2003
Since the initial description of progressive multifocal leukoencephalopathy (PML) in 1958, clinic... more Since the initial description of progressive multifocal leukoencephalopathy (PML) in 1958, clinical and basic science investigators have demonstrated a growing interest in the area of neurovirology, with a recent focus on polyomaviruses. In this review, the authors present an overview of the biological properties of the human polyomavirus, JC virus (JCV), and its association with PML as the etiologic agent. Additionally, the authors provide a discussion of the current understanding of JCV molecular pathogenesis and therapeutic strategies. Journal of NeuroVirology (2003) 9, 236-246.
Transplant International, 2007
Glia, 2006
Chemokines (chemoattractant cytokines) and their receptors are present in the brain and may play ... more Chemokines (chemoattractant cytokines) and their receptors are present in the brain and may play roles in both neurodevelopment and neuropathology. Increased brain levels of monocyte chemoattractant protein-1 (MCP-1), also known as CCL2, are found in patients with human immunodeficiency virus type 1 (HIV-1)-associated dementia and other acute and chronic neurologic diseases. Although the function of CCL2 in the brain is unclear, it is believed that upregulation of this chemokine during neuropathologic or neuroinflammatory conditions leads to recruitment of activated monocytes into the brain, where they differentiate into macrophages producing neurotoxic and inflammatory molecules. We recently showed that human fetal brainderived progenitor cells are susceptible to HIV-1 and JC virus infection, and that differentiation toward an astrocyte phenotype increased virus production from these cells. In the current study, we found that in the absence of infection, progenitors produced moderate levels of CCL2 (5.6 ng per million cells). Astrocyte differentiation over 3 weeks increased CCL2 protein levels 30-fold in a biphasic manner, whereas neuronal differentiation decreased production 20fold. Electromobility shift assays (EMSAs) demonstrated increased nuclear NF-jB levels within 2 h of initiating astrocyte differentiation, and inhibitors of NF-jB activation partially blocked the CCL2 increase in differentiating astrocytes. Transfection of progenitors with mutated CCL2 promoter/CAT reporter constructs showed that the distal promoter region, containing NF-jB and NF-I binding sites, is important for differentiation-induced CCL2 upregulation. Together these results suggest that the transcription factor NF-jB, and possibly NF-I, contribute to the upregulation of CCL2 chemokine production during the differentiation of human progenitor cells toward an astrocyte phenotype.
Laryngoscope, 2000
Objectives Objectives of the study are 1) to test the effectiveness of somnoplasty (radiofrequenc... more Objectives Objectives of the study are 1) to test the effectiveness of somnoplasty (radiofrequency volumetric tissue reduction of the soft palate) for the control of loud, socially disruptive, snoring; 2) to test the long-term efficacy of this treatment by spouse report; and 3) to compare the effectiveness of somnoplasty with another treatment.Study Design Twenty patients with complaints of loud snoring and a respiratory disturbance index no greater than 15 respiratory events per hour with sleep-related episodes of oxygen desaturation no lower than 80% were offered an experimental treatment. Ten were treated with somnoplasty, and a comparison group of 10 matched patients used an oral appliance. All were restudied in the laboratory wearing a device programmed to count minutes of sleep during which snoring was loud, soft, or absent.Methods For the 10 somnoplasty patients, a spouse rating of snoring determined whether the patient received one or more treatments. Five patients had a single treatment to three sites, and five others had two such treatments. Ten patients wore an oral appliance of the tongue-retaining type (Snore X, Fremont, CA).Results Seven of the 10 somnoplasty patients met the improvement criteria set for reduced loud snoring (a spouse rating of 3 or less on a 10-point scale, and 10% or less of sleep time in loud snoring in the laboratory). The comparison group also had a significant improvement in the percentage of sleep time in loud snoring while wearing the Snore X appliance.Conclusion Since there was no significant difference between the two groups in percentage of sleep time spent in loud snoring while treated, the choice of method to control snoring must be based on factors other than efficacy.
Biomaterials, 2003
Silk from the silkworm, Bombyx mori, has been used as biomedical suture material for centuries. T... more Silk from the silkworm, Bombyx mori, has been used as biomedical suture material for centuries. The unique mechanical properties of these fibers provided important clinical repair options for many applications. During the past 20 years, some biocompatibility problems have been reported for silkworm silk; however, contamination from residual sericin (glue-like proteins) was the likely cause. More recent studies with well-defined silkworm silk fibers and films suggest that the core silk fibroin fibers exhibit comparable biocompatibility in vitro and in vivo with other commonly used biomaterials such as polylactic acid and collagen. Furthermore, the unique mechanical properties of the silk fibers, the diversity of side chain chemistries for 'decoration' with growth and adhesion factors, and the ability to genetically tailor the protein provide additional rationale for the exploration of this family of fibrous proteins for biomaterial applications. For example, in designing scaffolds for tissue engineering these properties are particularly relevant and recent results with bone and ligament formation in vitro support the potential role for this biomaterial in future applications. To date, studies with silks to address biomaterial and matrix scaffold needs have focused on silkworm silk. With the diversity of silk-like fibrous proteins from spiders and insects, a range of native or bioengineered variants can be expected for application to a diverse set of clinical needs. r
... Correspondencia: Dr. FL Moreno-Martínez. Hemodinámica y Cardiología Intervencionista. Cardioc... more ... Correspondencia: Dr. FL Moreno-Martínez. Hemodinámica y Cardiología Intervencionista. Cardiocentro Ernesto Che Guevara. Cuba 610, CP 50200. Santa Clara. Villa Clara. Cuba. Correo electrónico: flmorenom@yahoo.com ...
Journal of Crystal Growth, 1986
Connective Tissue Research, 2005
An improved understanding of cellular responses during normal anterior cruciate ligament (ACL) fu... more An improved understanding of cellular responses during normal anterior cruciate ligament (ACL) function or repair is essential for clinical assessments, understanding ligament biology, and the implementation of tissue engineering strategies. The present study utilized quantitative real-time RT-PCR combined with univariate and multivariate statistical analyses to establish a quantitative database of marker transcript expression that can provide a "blueprint" of ACL wound healing. Selected markers (collagen types I and III, biglycan, decorin, MMP-1, MMP-2, MMP-9, and TIMP-1) were assessed from 33 torn ACLs harvested during reconstructive surgery. Trends were observed between postinjury period and marker expressions. Significant correlations between marker expression existed and were most prominent between collagen types I and III. Canonical correlation analysis established a relationship between patient demographics and a combination of all marker expressions. The currently observed trends and correlations may assist in identifying appropriate tissue samples and provide a baseline information of marker expression level that can support in vitro optimization of environmental cues for ligament tissue engineering application.