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Biomedical subjects

D David

Publications and source records attributed to D David.

At least 37 records · Page 2Linked to original sources
PubMed2000

Molecular epidemiology of rabies virus isolates from Israel and other middle- and Near-Eastern countries.

A total of 226 isolates of rabies virus from different areas of Israel, including three human isolates and one sample from South Lebanon were identified between 1993 and 1998 by direct immunofluorescence using monoclonal antibodies to the viral nucleoprotein (N). An epidemiological survey based on nucleotide sequence analysis of 328 bp from the C terminus of the N coding region and the noncoding region between the nucleoprotein and the phosphoprotein (NS gene) was performed. Phylogenetic analysis of the isolates from Israel showed that they were related geographically, but not according to host species. Five variants, related groups distributed among four geographical regions, were identified. In each region, rabies virus was isolated from more than one animal species. A comparison of the sequence analysis of rabies virus samples from the rest of world revealed a 2-nucleotide change that distinguished the Middle East variants from the rest.

Adult↗
PubMed2000

Defining patterns of benzodiazepine use in older adults.

Benzodiazepines are disproportionately prescribed to older adults. Elderly adults with comorbid medical and psychiatric conditions, elderly adults taking multiple medications, and elderly women are the most likely adults to continuously use benzodiazepines. These are also the groups of elderly who are likely to experience adverse effects, including falls, accidents, and motor vehicle crashes. Despite recommendations for short-term treatment and the potential risks of long-term use, some patients continue to receive benefit for extended time periods, occasionally years. Future research needs to be directed at improved identification of which patients will benefit from intermittent versus continuous treatment while minimizing risk for adverse side effects. In order to advance the study of the risks and benefits of benzodiazepine use, we have proposed a set of definitions for classification of use. These definitions can be used to develop clinical guidelines based on empirically derived clinical research models.

Aged↗
PubMed2000

Molecular genetic analysis of factor XI deficiency: identification of five novel gene alterations and the origin of type II mutation in Portuguese families.

Coagulation factor XI (FXI) deficiency is an inherited autosomal recessive mild bleeding disorder. In this study, we report the molecular genetic analysis of FXI deficiency in six unrelated families of Portuguese origin. The Jewish type II mutation was found in two families, of seemingly Portuguese origin. Haplotype analysis in these families demonstrated that this mutation is of Jewish origin. In the remaining families, five novel FXI mutations have been identified. Two of these mutations (FXI IVS K -10T-->A and FXI 1026G-->T, cd 324) affect the FXI pre-mRNA splicing. A further two (FXI 307 ins AAGCAAT, cd 85 and FXI 1072 del A, cd 340) introduce frameshifts leading to premature termination codons. The FXI splicing mutation, 1026G-->T cd 324, was found in compound heterozygosity with missense mutation FXI K518N. Analysis of the FXI mRNA from the latter genotype demonstrated new donor splice site usage. All reported mutations most likely result in functional null-alleles. In addition, three novel polymorphisms have been identified: at nt -138 in intron A, at codon D125 in exon 5 and at codon T249 in exon 8.

Alleles↗
PubMed1999

Characterization of a multi-lipopeptides mixture used as an HIV-1 vaccine candidate.

A multi-component vaccine has been defined, which contains six different synthetic 24- to 32-amino acid lipopeptides derived from the sequence of HIV-1 proteins. The physicochemical properties of the lipopeptide components were compatible with multi-dimensional analysis, using RP-HPLC, Edman sequencing, electrospray mass spectrometry, and 2D-NMR. Detailed analysis of the impurity profiles led to the detection and evaluation of the relative proportions of most by-products: several contaminants resulted from the formation of acetylated fragments, transpeptidation reactions with succinimide or piperidide formation, or methionine and/or tryptophan mono-oxidations. The first batch to be produced underwent extensive pharmacotoxicological testings to confirm its safety; this vaccine candidate has now been used in phase I clinical trials. Despite the complexity of such multi-lipopeptide vaccines, our findings suggest the possibility of preparing a clear and precise assignment of by-products to toxicologically qualified impurities in the eventuality of a future production of several successive batches.

AIDS Vaccines↗
PubMed1999

Biliary obstruction in hematopoietic cell transplant recipients: an uncommon diagnosis with specific causes.

Jaundice is a common problem in marrow transplant recipients. The incidence of bile duct obstruction in this setting is unknown. The purpose of this study was to determine the incidence of biliary obstruction, the causes, and outcomes following marrow transplant. Consecutive cases were reviewed at two major transplant centers in the United States from 1969 to 1996 at the Fred Hutchinson Cancer Research Center and 1989 to 1996 at the City of Hope National Medical Center. Nine cases of biliary obstruction were identified as a cause of jaundice in 7412 marrow transplant recipients, an incidence of 0.12%. The presentation was bimodal, with seven cases occurring prior to day 100 and two occurring 2 to 4 years after transplantation. The age distribution was 15 to 50 years and all patients had received allogeneic transplants. The causes of obstruction included gallbladder sludge (n=1), a duodenal hematoma (n=1), choledocholithiasis with biliary pancreatitis (n=1), bile duct infection (n=2), recurrent malignancy (n=1), choledocholithiasis associated with a benign stricture (n=1), Epstein-Barr virus-related lymphoproliferative disorder (n=1), and a benign stricture of unknown etiology (n=1). Biliary obstruction is a rare cause of jaundice in the post-transplant period. The presentation was similar to that of other post-transplant hepatobiliary problems, but with disparate causes.

Adolescent↗
PubMed1999

Emotional reactivity and debilitating beliefs during hospitalization predict future adjustment to first myocardial infarction in men.

Research efforts are being made to identify personality and cognitive variables predictive of poor adjustment following myocardial infarction. Sixty-two male patients were examined after a first and uncomplicated myocardial infarction to determine whether dispositional emotional reactivity and debilitating beliefs measured during hospitalization can predict work engagement, social activities involvement, and ambulation/independence six months later. A structural model with direct paths between emotional reactivity, debilitating beliefs, and the above outcomes, as well as partial mediation of emotional distress and illness preoccupation, was tested using the CALIS procedure. The model explained 33%, 48% and 82% of the variance in the three outcomes, respectively. Work engagement was indirectly related through emotional distress to earlier emotional reactivity and debilitating beliefs. Social activities involvement was both directly and indirectly related through emotional distress to debilitating beliefs; and also indirectly related through emotional distress to emotional reactivity. Ambulation/independence was directly and negatively related to debilitating beliefs. Prolonged emotional distress was predicted by emotional reactivity and debilitating beliefs. Illness preoccupation turned out to be an independent outcome that was positively related to emotional reactivity. Thus, measuring dispositional emotional reactivity and debilitating beliefs at the hospitalization stage may be helpful in detecting patients at risk of poor future adjustment.

Adult↗
PubMed1999

Genetic risk factors in acute coronary disease.

OBJECTIVE: We investigate whether each of the following: HPA-1, Factor V Leiden, prothrombin gene variant and the methylene tetrahydrofolate reductase gene (MTHFR) mutation, are risk factors for acute coronary disease in Portuguese patients. MATERIAL AND METHODS: 100 blood donors and 52 patients with an established diagnosis of myocardial infarction or unstable angina were evaluated for genetic risk factors, by determining HPA-1 genotype, Factor V Leiden, Prothrombin 20210 variant and MTHFR mutation. RESULTS: We found a prevalence of 2.0% for Factor V Leiden, 5.0% for the Prothrombin 20210 variant and 66% for the MTHFR mutation in blood donors. These values are similar to those found in the patients (1.9, 3.8 and 58%, respectively). We found that 28/100 controls had the PI(A2) polymorphism, a frequency statistically different from that in the patients (23/52). This difference was even more pronounced in patients less than 60 years old (27/96 vs. 13/24). CONCLUSION: Factor V Leiden, Prothrombin 20210 variant and MTHFR mutation do not seem to represent risk factors for acute coronary disease. However, the PI(A2) polymorphism could have a role in the pathogenesis of this disease. The presence of multiple genetic factors, more than single ones, could influence the development and outcome of myocardial infarction and unstable angina. Larger studies are needed in order to have a better insight into the pathophysiological mechanisms of this disease, along with its prevention and the development of new treatments.

Activated Protein C Resistance↗
PubMed1999

Psychotic symptoms in combat-related posttraumatic stress disorder.

BACKGROUND: Posttraumatic stress disorder (PTSD) is known often to be comorbid with other anxiety, mood, and substance use disorders. Psychotic symptoms have also been noted in PTSD and have been reported to be more common in Hispanic veterans. However, the occurrence of psychotic symptoms, including the degree to which they are accounted for by comorbid disorders, have received limited systematic investigation. Our study objectives were to assess psychotic symptoms according to DSM-III-R criteria in patients with a primary diagnosis of combat-related PTSD and determine the associations of those symptoms with psychiatric comorbidity and ethnicity. METHOD: Fifty-three male combat veterans consecutively admitted to a PTSD rehabilitation unit were assessed for psychotic symptoms and Axis I disorders. Ninety-one percent were Vietnam veterans; 72% were white, 17% were Hispanic, and 11% were black. Associations between psychotic symptoms and comorbid depression, substance use disorders, and minority status were compared by chi-square analyses; associations between psychotic symptoms and both PTSD and dissociative symptom severity were compared by t test analysis. RESULTS: Forty percent of patients reported a psychotic symptom or symptoms in the preceding 6 months. These symptoms featured auditory hallucinations in all but 1 case. The psychotic symptoms typically reflected combat-themes and guilt, were nonbizarre, and were not usually associated with formal thought disorder or flat or inappropriate affect. Psychotic symptoms were significantly associated with current major depression (p < .02), but not with alcohol or drug abuse or with self-rated PTSD and dissociation severity. Psychotic symptoms and current major depression were more common in minority (black and Hispanic) than white veterans (p < .002). CONCLUSION: Psychotic symptoms can be a feature of combat-related PTSD and appear to be associated with major depression. The association with minority status may be a function of comorbidity.

Adult↗
PubMed1998

Involvement of long chain fatty acid elongation in the trafficking of secretory vesicles in yeast.

Members of the synaptobrevin/VAMP family of v-SNAREs are thought to be essential for vesicle docking and exocytosis in both lower and higher eukaryotes. Here, we describe yeast mutants that appear to bypass the known v-SNARE requirement in secretion. Recessive mutations in either VBM1 or VBM2, which encode related ER-localized membrane proteins, allow yeast to grow normally and secrete in the absence of Snc v-SNAREs. These mutants show selective alterations in protein transport, resulting in the differential trafficking and secretion of certain protein cargo. Yet, processing of the vacuolar marker, carboxypeptidase Y, and the secreted protein, invertase, appear normal in these mutants indicating that general protein trafficking early in the pathway is unaffected. Interestingly, VBM1 and VBM2 are allelic to ELO3 and ELO2, two genes that have been shown recently to mediate the elongation of very long chain fatty acids and subsequent ceramide and inositol sphingolipid synthesis. Thus, the v-SNARE requirement in constitutive exocytosis is abrogated by mutations in early components of the secretory pathway that act at the level of lipid synthesis to affect the ability of secretory vesicles to sort and deliver protein cargo.

Alleles↗
PubMed1998

Regulatory dysfunction of the interleukin-2 receptor during HIV infection and the impact of triple combination therapy.

The interleukin-2 (IL-2)/IL-2 receptor (IL-2R) system is the main regulatory determinant of T cell reactivity. Although it is well known that IL-2 secretion is impaired during HIV infection, up to now IL-2R expression has not been extensively studied in HIV-infected patients despite the use of IL-2 in clinical therapy trials. We show here that IL-2R expression in HIV patients with high viral load (group 1 in the study) is greatly enhanced on B lymphocytes, CD8 T lymphocytes, and monocytes, but not on CD4 T lymphocytes, compared with noninfected individuals. Paradoxically, this modified IL-2R expression does not lead to increased IL-2 responsiveness, except for B lymphocytes. In patients receiving triple combination therapy (TCT, two reverse transcriptase inhibitors and one protease inhibitor) that has triggered a drastic reduction in plasma viral load and an increase in CD4 counts (group 2 patients), IL-2R expression is significantly lower than in group 1 patients. Moreover, cells involved in cellular immunity and CD4 T lymphocytes have the capacity to respond to IL-2 after TCT. These results allow us to anticipate a beneficial role of IL-2 immunotherapy in combination with TCT.

B-Lymphocytes↗
PubMed1998

Further analysis of interleukin-2 receptor subunit expression on the different human peripheral blood mononuclear cell subsets.

We have investigated the expression of the three components of the interleukin-2 receptor (IL-2Ralpha, IL-2Rbeta, and IL-2Rgamma) on the surface of the various peripheral blood mononuclear cell (PBMC) subsets by flow cytometry analysis. The PBMC were immediately isolated (ficoll) from blood collected on heparin as anticoagulant. The three IL-2R components are absent or only marginally detectable on CD4 T lymphocytes. No expression of the IL-2R chains is found for the B lymphocytes. In most donors, the three chains are not detectable on CD8 T lymphocytes, but for a few of them, IL-2Rbeta or IL-2Rgamma are clearly expressed. CD56 high (IL-2Ralpha+) and CD56 low (IL-2Ralpha-) natural killer (NK) cells express IL-2Rbeta, but not IL-2Rgamma. IL-2Rgamma is expressed by monocytes of all donors although with variable intensity. When blood is collected on other anticoagulants or when cells are isolated 1 day after collection, IL-2Ralpha, IL-2Rbeta, and IL-2Rgamma are largely expressed on the surface of most PBMC. This observation provides a possible explanation for divergent data previously reported on IL-2R expression. Finally, we show that IL-2Rgamma, which is not detectable on the cell surface of lymphocytes, is nevertheless expressed and stored as an intracellular component. This result is in agreement with the constitutive expression of the IL-2Rgamma gene and suggests a specific regulatory mechanism for IL-2Rgamma membrane translocation.

Anticoagulants↗
PubMed1998

Increased expression of neutrophil and monocyte adhesion molecules LFA-1 and Mac-1 and their ligand ICAM-1 and VLA-4 throughout the acute phase of myocardial infarction: possible implications for leukocyte aggregation and microvascular plugging.

OBJECTIVES: This study sought to evaluate expression of adhesion molecules on neutrophils and monocytes throughout the acute phase of myocardial infarction. BACKGROUND: Neutrophil and monocyte counts increase within days from onset of acute myocardial infarction. Because leukocytes are recruited to the involved myocardial region, we postulated that these activated cells would display an increased expression of adhesion molecules necessary for effective endothelial transmigration. METHODS: We measured the expression of neutrophil and monocyte lymphocyte function associated antigen-1 (LFA-1), Mac-1, very late after activation antigen-4 (VLA-4) and intercellular adhesion molecule-1 (ICAM-1) by flow cytometry throughout the acute phase of acute myocardial infarction in 25 patients and 10 age-matched control subjects. RESULTS: Expression of Mac-1 on neutrophils increased significantly, whereas no expression of VLA-4 and ICAM-1 was detected. The expression of LFA-1, Mac-1, VLA-4 and ICAM-1 on the monocyte cell membrane in patients with an acute myocardial infarction was increased compared with that in control subjects by 22% (on day 7), 67%, 13% and 44% (all on day 4), respectively (all p < 0.001). Elevated density of monocyte-specific CD14 in the AMI versus the control group was also shown (30%, p < 0.001). CONCLUSIONS: Increased expression of neutrophil and monocyte adhesion molecules may contribute to their adhesion to endothelium in the ischemic territory. This adhesion could feasibly precipitate vasoconstriction or add a local thrombotic effect due to tissue factor expression secondary to Mac-1 engagement. In addition, the manifestation of increased density of LFA-1 and Mac-1 by activated leukocytes with monocytes also expressing ICAM-1 suggests that leukocytes may form microaggregates that could cause microvascular plugging. This mechanism may facilitate the occurrence of the "no-reflow" phenomenon or slow coronary filling after acute myocardial infarction.

Aged↗