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Biomedical subjects

S Paul

Publications and source records attributed to S Paul.

At least 109 records · Page 6Linked to original sources
PubMed1999

Mycobacterium tuberculosis catalase and peroxidase activities and resistance to oxidative killing in human monocytes in vitro.

Mycobacterium tuberculosis has a relatively high resistance to killing by hydrogen peroxide and organic peroxides. Resistance may be mediated by mycobacterial catalase-peroxidase (KatG) and possibly by alkyl hydroperoxide reductase (AhpC). To determine the interrelationship between sensitivity to H2O2, catalase and peroxidase activities, and bacillary growth rates measured both intracellularly in human monocytes and in culture medium, we examined one laboratory strain, two clinical isolates, and three recombinant strains of M. tuberculosis with differing levels of KatG and AhpC. Five of the mycobacterial strains had intracellular doubling times of 27 to 32 h, while one KatG-deficient clinical isolate (ATCC 35825) doubled in approximately 76 h. Killing of mycobacteria by exogenously added H2O2 was more pronounced for intracellular bacilli than for those bacilli derived from disrupted monocytes. Strains with no detectable KatG expression or catalase activity were relatively sensitive to killing (43 to 67% killing) by exogenous H2O2. However, once even minimal catalase activity was present, mycobacterial catalase activity over a 10-fold range (0.56 to 6.2 U/mg) was associated with survival of 85% of the bacilli. Peroxidase activity levels correlated significantly with resistance of the mycobacterial strains to H2O2-mediated killing. An endogenous oxidative burst induction by 4beta-phorbol 12beta-myristate 13alpha-acetate treatment of infected monocytes reduced the viability of the KatG null strain (H37Rv Inhr) but not the KatG-overexpressing strain [H37Rv(pMH59)]. These results suggest that mycobacterial resistance to oxidative metabolites (including H2O2 and other peroxides) may be an important mechanism of bacillary survival within the host phagocyte.

Bacterial Proteins↗
PubMed1999

Survival of Mycobacterium avium and Mycobacterium tuberculosis in acidified vacuoles of murine macrophages.

Despite the antimicrobial mechanisms of vertebrate phagocytes, mycobacteria can survive within the phagosomes of these cells. These organisms use various strategies to evade destruction, including inhibition of acidification of the phagosome and inhibition of phagosome-lysosome fusion. In contrast to mycobacteria, Coxiella burnetii, the etiologic agent of Q fever, inhabits a spacious acidified intracellular vacuole which is prone to fusion with other vacuoles of the host cell, including phagosomes containing mycobacteria. The Coxiella-infected cell thus provides a unique model for investigating the survival of mycobacteria in an acidified phagosome-like compartment. In the present study, murine bone marrow-derived macrophages were infected with either Mycobacterium avium or Mycobacterium tuberculosis and then coinfected with C. burnetii. We observed that the majority of phagocytosed mycobacteria colocalized to the C. burnetii-containing vacuole, which maintained its acidic properties. In coinfected macrophages, the growth of M. avium was not impaired following fusion with the acidified vacuole. In contrast, the growth rate of M. tuberculosis was reduced in acidified vacuoles. These results suggest that although both species of mycobacteria inhibit phagosome-lysosome fusion, they may be differentially susceptible to the toxic effects of the acidic environment in the mature phagolysosome.

Animals↗
PubMed1999

The changing patterns of the Part 2 MRCOG examination.

Several changes to the Part 2 Membership of the Royal College of Obstetricians and Gynaecologists (MRCOG) examination have taken place over the last 2 years. The pass rate fell drastically from 38% in 1998 to 15% in March-May 1999 following a change in the marking system. This article gives a few suggestions about approaches to the examination.

Educational Measurement↗
PubMed1999

A factor that prevents EDTA-induced cell-growth inhibition: purification of transthyretin from chick embryo brain.

We previously reported the inhibition of cell-growth in Neuro-2A cells, mouse neuroblastoma, by Zn2+ chelation with EDTA. This paper describes the purification of a factor that prevents EDTA-induced cell-growth inhibition from chick embryo brain. The purified factor has a molecular mass of 16 kDa on SDS-polyacrylamide gel electrophoresis under reducing conditions. This factor prevents the cell-growth inhibition in a dose-dependent manner and also binds thyroxine. Analysis of the N-terminal amino acid sequence revealed that 40 residues coincide with the sequence of chicken liver transthyretin.

Amino Acid Sequence↗
PubMed1999

CNS drug discovery in the 21st century. From genomics to combinatorial chemistry and back.

The discovery of new drugs for psychiatric and neurological disorders has been greatly facilitated by advances in molecular biology, genetics and chemistry. Several examples are given of how these revolutionary advances have been applied to the discovery of new drugs that selectively modify serotonergic neurotransmission, including compounds which may prove to be more effective antidepressants.

Antidepressive Agents↗
PubMed1999

Thyroid hormone-induced maturation of astrocytes is associated with the expression of new variants of vimentin and their phosphorylation.

The role of thyroid hormone (TH)-induced vimentin expression in promoting the maturation of astrocytes has been investigated. Comparative immunocytochemical staining with vimentin antibody demonstrated distinctly different patterns of expression of vimentin during the progressive maturation of astrocytes of normal and TH-deficient astrocyte cultures. [35S]Methionine labeling of cells showed a significant decline in the level of vimentin in the hypothyroid cultures at all ages from day 5 to 20. Western blot analysis suggested that the maturation of normal astrocytes was associated with the appearance of several acidic and basic variants of vimentin, whose expression was significantly delayed or reduced in the TH-deficient astrocytes. In normal astrocyte cultures, two acidic variants of vimentin, one of similar molecular weight and the other of lower molecular weight, were found to be phosphorylated during the final transformation of the epithelioid form into the mature stellate form. None of these phosphorylated forms was evident in the TH-deficient astrocytes. This was further confirmed by negative immunocytochemical staining of 5- to 18-day-old cultures of TH-deficient astrocytes with antibody TM71, specific to phosphorylated vimentin, compared with age-matched normal astrocytes, which displayed consistent positive staining. The overall results indicate that TH-induced expression of phosphorylated forms of vimentin may be essential for the intracellular organization of the cytoskeleton in a way conducive to the morphological maturation of astrocytes.

Animals↗
PubMed1999

Calcium-dependent cleavage of striatal enriched tyrosine phosphatase (STEP).

Striatal enriched phosphatase (STEP) is a family of protein tyrosine phosphatases enriched within the CNS. A member of this family, STEP61, is a membrane-associated protein located in postsynaptic densities of striatal neurons. In this study, we demonstrate that STEP61, is cleaved into smaller isoforms. To clarify the mechanism of cleavage, STEP61 was transiently expressed in NT2/D1 neuronal precursor cells. Exposure of transfected cells to the calcium ionophore, A23187, or to thapsigargin resulted in the rapid cleavage of STEP61. Pretreatment with the calpain inhibitor, calpeptin, or EGTA prevented proteolysis. One of the cleavage products has a relative molecular mass of 33 kDa (STEP33). A protein with the identical mobility is detected following calpain treatment of STEP61 fusion protein or postsynaptic densities purified from rat striatum. Exposure of primary neuronal cultures to glutamate also led to a significant increase in the concentration of a low molecular weight form of STEP. Taken together, these results suggest that in response to a rapid influx of calcium, STEP61, is proteolytically cleaved by calpain, leading to the release of a smaller isoform. This model may explain the rapid appearance of STEP33 in response to transient hypoxia-ischemia in the brain as cells attempt to counter the increase in tyrosine phosphorylation levels following neuronal insults.

Animals↗
PubMed1999

New approaches for the elderly show significant results.

Capital Health is Canada's largest integrated academic health region, serving a base population of more that 800,000 people in the city of Edmonton and surrounding communities. Capital Health provides a complete range of health services, including transplantation, children's cardiac surgery, innovative community health programs, rehabilitation services, continuing care, palliative care, public health, health promotion and disease prevention. Capital Health's large, integrated health system manages resources well, responds quickly and creatively to challenges and opportunities and blends institutional healthcare with community care and population health. Capital Health is a key partner with the University of Alberta Health Sciences Faculties and provides a rich environment for health research and education.

Aged↗
PubMed1998

A genome-wide search for chromosomal loci linked to mental health wellness in relatives at high risk for bipolar affective disorder among the Old Order Amish.

Bipolar affective disorder (BPAD; manic-depressive illness) is characterized by episodes of mania and/or hypomania interspersed with periods of depression. Compelling evidence supports a significant genetic component in the susceptibility to develop BPAD. To date, however, linkage studies have attempted only to identify chromosomal loci that cause or increase the risk of developing BPAD. To determine whether there could be protective alleles that prevent or reduce the risk of developing BPAD, similar to what is observed in other genetic disorders, we used mental health wellness (absence of any psychiatric disorder) as the phenotype in our genome-wide linkage scan of several large multigeneration Old Order Amish pedigrees exhibiting an extremely high incidence of BPAD. We have found strong evidence for a locus on chromosome 4p at D4S2949 (maximum GENEHUNTER-PLUS nonparametric linkage score = 4.05, P = 5. 22 x 10(-4); SIBPAL Pempirical value <3 x 10(-5)) and suggestive evidence for a locus on chromosome 4q at D4S397 (maximum GENEHUNTER-PLUS nonparametric linkage score = 3.29, P = 2.57 x 10(-3); SIBPAL Pempirical value <1 x 10(-3)) that are linked to mental health wellness. These findings are consistent with the hypothesis that certain alleles could prevent or modify the clinical manifestations of BPAD and perhaps other related affective disorders.

Adult↗
PubMed1998

Autoantibody catalysis: no longer hostage to Occam's razor.

Autoantibody catalysis is now a well-established phenomenon, but the initial finding of autoantibody-catalyzed VIP cleavage was suspected to be an artefact by certain practitioners of designer antibody catalysis, mainly because of conceptual complexities not foreseen in our training about the immune system and about the mechanisms of biological catalysis. Confirmation that antibodies can acquire proteolytic activity by entirely natural means has emerged, ironically, in part from the field of designer catalytic antibodies. Recent studies have provided insight into the molecular strategies whereby antibodies can combine antigen binding with chemical catalysis, and the contributions of innate and adaptive immune mechanisms in the proteolytic activity. The history of this field illustrates the dangers of assuming that novel observations must fit into the simple confines of established theories. Scientific theories are changeable entities, dependent on empirical data and interpretations of the data, and their growth is better served by keeping an open mind.

Amino Acid Sequence↗
PubMed1998

Inhibition of activating transcription factor 1- and cAMP-responsive element-binding protein-activated transcription by an intracellular single chain Fv fragment.

Activating transcription factor 1 (ATF1) and cAMP-responsive element (CRE)-binding protein (CREB) activate transcription through CREs located in the promoters of cellular and viral genes. We previously described a monoclonal antibody (mAb41.4) that prevents ATF1 binding to DNA and reduces CRE-driven promoter activity in vitro (Orten, D. J., Strawhecker, J. M., Sanderson, S. D., Huang, D., Prytowsky, M. B. , and Hinrichs, S. H. (1994) J. Biol. Chem. 269, 32254-32263). A single chain Fv (scFv) fragment from the mAb41.4-expressing hybridoma was generated to provide a means to investigate transcription factor function via intracellular expression of the scFv fragment. The affinity of scFv4 (subgroup: VL kappa-III, VH miscellaneous) for ATF1 was similar to that of the parental mAb and the Fab fragment, but it demonstrated greater inhibitory activity and reacted with CREB. scFv4 disrupted the binding of both ATF1 and CREB in electrophoretic mobility shift assays and reduced expression of CRE-driven expression in vitro. Transient expression of scFv had no effect on the non-CRE-containing adenovirus major late promoter. The proliferating cell nuclear antigen promoter, containing two CREs, was significantly more sensitive to inhibition by scFv than the cytomegalovirus immediate-early promoter, containing five CREs. Cotransfection of either ATF1 or CREB in the presence of scFv restored basal levels of expression. The intracellular expression of scFv provides a unique means to investigate the roles of the transcription factors ATF1 and CREB.

Activating Transcription Factor 1↗
PubMed1998

Raloxifene effects on vasomotor and other climacteric symptoms in postmenopausal women.

Introduction and Objectives: Raloxifene, a novel selective estrogen receptor modulator (SERM), is under investigation for the prevention of osteoporosis in postmenopausal women. Like traditional estrogen replacement therapy, raloxifene has beneficial effects on bone and on serum lipids whereas, in contrast to estrogen's adverse effects in the breast and uterus, raloxifene is an estrogen antagonist in the breast and is nonstimulatory in the uterus. This study examines the effects of raloxifene 60 mg/day compared with placebo on: 1) the incidence of vasomotor symptoms: hot flashes (flushing) and sweating (including night sweats), 2) the severity and time course of hot flashes, and 3) the relation of hot flashes to baseline subject characteristics and study discontinuations. Additionally, the study explores the effects of raloxifene 60 mg/day compared with placebo on other climacteric symptoms that affect the quality of life of postmenopausal women, such as depression, insomnia, mood lability and genitourinary complaints.Methods: Integrated data from five randomized, placebo-controlled studies involving 1,165 healthy, postmenopausal women, with up to 30 months of study drug exposure, were analyzed. The incidence and severity of hot flashes and other climacteric symptoms were compared in patients treated with placebo or raloxifene (60 mg/day) via open-ended, non-directed subject self-assessment questionnaires. Data were analyzed for subgroup-by-therapy interactions using many baseline subject characteristics such as age, body mass index, smoking, alcohol, and years post-menopause, as well as preexisting conditions such as hot flashes, sweating, insomnia, depression, and history of hysterectomy. The overall incidence of other climacteric symptoms were reported as adverse events.Results: The increase in overall incidence of hot flashes in raloxifene-treated (24.6%) and placebo-treated (18.3%) subjects was modest, but statistically significant. However, this difference was significant only during the first 6 months of therapy, raloxifene (20.1%) compared with placebo (14.4%). After 6 months of treatment, there was no statistically significant difference in the incidence of hot flashes between the two treatment groups. The majority of hot flashes in raloxifene-treated subjects were subject-assessed as "mild-to-moderate" in severity (89%). The incidence of hot flashes reported as "severe" did not differ significantly in raloxifene- or placebo-treated subjects. Subgroup analyses revealed the overall incidence of hot flashes to be highest for both raloxifene and placebo-treated subjects, in younger (age < 55 years) women (P =.004), in women who had previously experienced hot flashes (P =.031), and in women having had hysterectomies (P <.001). Within each of these subgroups, there was no statistical difference in the incidence of hot flashes between the raloxifene and placebo groups. Between the two treatment groups, there was no difference in the overall incidence of subject discontinuations from study due to hot flashes. The occurrence of the other common vasomotor symptom, sweating (which includes night sweats), was not statistically different for the raloxifene- or placebo-treated subjects.Genitourinary complaints are often symptoms related to vaginal dryness, such as dyspareunia and decreased libido, as well as other symptoms of vaginitis and leukorrhea. No statistically significant differences occurred for raloxifene- or placebo-treated subjects in reports of these genitourinary symptoms. Similarly, for the other common climacteric symptoms; depression, insomnia, and mood lability, no significant differences in incidence between the raloxifene and placebo treatment groups were observed.Conclusions: Raloxifene (60 mg/day) treatment modestly increased the incidence of hot flashes compared with placebo, however, this difference was only statistically significant during the first 6 months of treatment. There were no differences in the severity of hot flashes between treatment groups, and this symptom did not adversely affect subjects' study participation. In both the raloxifene and placebo treatment groups, young postmenopausal women (age < 55), those with baseline hot flashes, and those with histories of hysterectomy were most likely to experience hot flashes. Raloxifene therapy did not affect the occurrence of other climacteric symptoms commonly affecting the quality of life of women after menopause.

Journal Article↗
PubMed1998

Effects of raloxifene on serum lipids and coagulation factors in healthy postmenopausal women.

CONTEXT: Raloxifene is a selective estrogen receptor modulator that has estrogen-agonistic effects on bone and estrogen-antagonistic effects on breast and uterus. OBJECTIVE: To identify the effects of raloxifene on markers of cardiovascular risk in postmenopausal women, and to compare them with those induced by hormone replacement therapy (HRT). DESIGN: Double-blind, randomized, parallel trial. SETTING: Eight sites in the United States. PARTICIPANTS: 390 healthy postmenopausal women recruited by advertisement. INTERVENTION: Participants were randomized to receive 1 of 4 treatments: raloxifene, 60 mg/d; raloxifene, 120 mg/d; HRT (conjugated equine estrogen, 0.625 mg/d, and medroxyprogesterone acetate, 2.5 mg/d); or placebo. MAIN OUTCOME MEASURES: Change and percent change from baseline of lipid levels and coagulation parameters after 3 months and 6 months of treatment. RESULTS: At the last visit completed, compared with placebo, both dosages of raloxifene significantly lowered low-density lipoprotein cholesterol (LDL-C) by 12% (P < .001), similar to the 14% reduction with HRT (P < .001). Both dosages of raloxifene significantly lowered lipoprotein(a) by 7% to 8% (P < .001), less than the 19% decrease with HRT (P<.001). Raloxifene increased high-density lipoprotein-2 cholesterol (HDL2-C) by 15% to 17% (P < .05), less than the 33% increase with HRT (P < .001). Raloxifene did not significantly change high-density lipoprotein cholesterol (HDL-C), triglycerides, or plasminogen activator inhibitor-1 (PAI-1); whereas HRT increased HDL-C by 11% and triglycerides by 20%, and decreased PAI-1 by 29% (for all, P < .001). Raloxifene significantly lowered fibrinogen by 12% to 14% (P < .001), unlike HRT, which had no effect. Neither treatment changed fibrinopeptide A or prothrombin fragment 1 and 2. CONCLUSIONS: Raloxifene favorably alters biochemical markers of cardiovascular risk by decreasing LDL-C, fibrinogen, and lipoprotein(a), and by increasing HDL2-C without raising triglycerides. In contrast to HRT, raloxifene had no effect on HDL-C and PAI-1, and a lesser effect on HDL2-C and lipoprotein(a). Further clinical trials are necessary to determine whether these favorable biochemical effects are associated with protection against cardiovascular disease.

Aged↗
PubMed1998

Heparin-binding EGF-like growth factor in the human prostate: synthesis predominantly by interstitial and vascular smooth muscle cells and action as a carcinoma cell mitogen.

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is an activating ligand for the EGF receptor (HER1/ErbB1) and the high-affinity receptor for diphtheria toxin (DT) in its transmembrane form (proHB-EGF). HB-EGF was immunolocalized within human benign and malignant prostatic tissues, using monospecific antibodies directed against the mature protein and against the cytoplasmic domain of proHB-EGF. Prostate carcinoma cells, normal glandular epithelial cells, undifferentiated fibroblasts, and inflammatory cells were not decorated by the anti-HB-EGF antibodies; however, interstitial and vascular smooth muscle cells were highly reactive, indicating that the smooth muscle compartments are the major sites of synthesis and localization of HB-EGF within the prostate. In marked contrast to prostatic epithelium, proHB-EGF was immunolocalized to seminal vesicle epithelium, indicating differential regulation of HB-EGF synthesis within various epithelia of the reproductive tract. HB-EGF was not overexpressed in this series of cancer tissues, in comparison to the benign tissues. In experiments with LNCaP human prostate carcinoma cells, HB-EGF was similar in potency to epidermal growth factor (EGF) in stimulating cell growth. Exogenous HB-EGF and EGF each activated HER1 and HER3 receptor tyrosine kinases and induced tyrosine phosphorylation of cellular proteins to a similar extent. LNCaP cells expressed detectable but low levels of HB-EGF mRNA; however, proHB-EGF was detected at the cell surface indirectly by demonstration of specific sensitivity to DT. HB-EGF is the first HER1 ligand to be identified predominantly as a smooth muscle cell product in the human prostate. Further, the observation that HB-EGF is similar to EGF in mitogenic potency for human prostate carcinoma cells suggests that it may be one of the hypothesized stromal mediators of prostate cancer growth.

Carcinoma↗
PubMed1998

Pressure measurements during injection of corticosteroids.

Corticosteroid injection into the orbit, eyelid and larynx is a common treatment for inflammation and neoplasm. Complications include embolisation into the ocular circulation resulting in permanent loss of vision. The overall aim of the reported research is to develop an injection cannula and monitoring system which can prevent inadvertent embolisation into the ocular circulation during injection of corticosteroids. To that end, a special cannula was designed that allows simultaneous estimation of pressure at the tip of the cannula and flow rate during injection. The cannula was tested with backpressures corresponding to physiological ranges of 0 to 125 mmHg and injection flow rates of 3 to 11 cm3 min-1. The estimated pressure at the tip of the cannula during injection of corticosteroids was compared with direct pressure measurements. The results show that the mean estimated pressure is linearly related to the mean measured pressure with a slope of 0.99 and correlation coefficient of 0.99. Statistical analyses show that with standard error of estimate (SEE) of 2.14 mmHg, the estimated pressure is well within the 95% prediction interval limits of the measured values. The estimation of pressure from the cannula and monitoring system was accurate and warrants further testing in animal models.

Administration, Topical↗
PubMed1998

Mechanism and functional role of antibody catalysis.

The light (L) chain of a model antibody (Ab) was deduced to contain a serine protease-like catalytic site capable of cleaving peptide bonds. The catalytic site is encoded by a germline VL gene. The catalytic activity can potentially be improved by somatic sequence diversification and pairing of the L chain with the appropriate heavy chain. Autoimmune disease is associated with increased synthesis of antigen (Ag)-specific Abs, but the reasons for this phenomenon are not known. Only recently has attention turned to the functional role of the catalytic function. Preliminary studies confirm that the catalytic cleavage of peptide bonds is a more potent means to achieve Ag neutralization, compared to reversible Ag binding. Administration of a monoclonal Ab to VIP in experimental animals induces an inflammatory response in the airways, suggesting that catalytic autoantibodies to this peptide found in airway disease and lupus are capable of causing airway dysfunction. The phenomenon of autoantibody catalysis can potentially be applied to isolate efficient catalysts directed against tumor or microbial Ags by exposing the autoimmune repertoire to such Ags or their analogs capable of recruiting the germline VL gene encoding the catalytic site.

Animals↗
PubMed1998

Inhibition of chemotaxis in A7r5 rat smooth muscle cells by a novel panel of inhibitors.

1. Arginine-specific ADP-ribosyltransferase (ART) activity has been implicated in white cell chemotaxis. In this study, we examined the capacity of a panel of structurally unrelated inhibitors and pseudosubstrates of ART to inhibit chemotaxis of A7r5 rat vascular smooth muscle cells in response to PDGF-BB. 2. The IC50 values for nicotinamide (12 mM) and novobiocin (165 microM) were similar to those observed for inhibition of chemotaxis by human polymorphonuclear neutrophil leucocytes (PMN), whereas vitamins K3 (IC50=22 microM) and K1 (IC50=95 microM) were less potent than previously described in PMNs. The pseudo-substrates for the enzyme (DEA-BAG, agmatine and arginine-methylester) also inhibited A7r5 chemotaxis, and in addition inhibited cell adhesion at similar concentrations. Vitamin K3 was unique among the inhibitors of ART, in that it also inhibited cell adhesion. 3. A rat ART1 transcript was amplified by rtPCR from rat skeletal muscle, and was noted to share 94% homology with the mouse ART1 cDNA sequence. No such transcript could be detected in A7r5 cells by Northern blot analysis or rtPCR. 4. Evidence for ART activity on the surface of A7r5 cells was investigated using 32P-NAD+ as substrate, and labelled membrane proteins were observed with MWt values of 116, 100, 90 and 70 kDa. Exposure of the labelled proteins to phosphodiesterase yielded 32P-AMP, and hydrolysis with NaOH yielded 32P-NAD+. These results indicated that the labelled proteins were adducts with NAD+, and not the products of ART activity. The absence of ART catalytic activity in A7r5 cells was confirmed in protocols designed to show ADP-ribosylation of agmatine. 5. We conclude that the chemotactic activity of A7r5 cells is independent of ART activity, and the mechanism whereby the novel panel of inhibitors reduced cell migration remains undefined.

Animals↗