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Biomedical subjects

P Clark

Publications and source records attributed to P Clark.

At least 145 records · Page 8Linked to original sources
PubMed1994

Isolation of endothelial cells from human term placental villi using immunomagnetic beads.

Chorionic villi excised from freshly delivered human term placentae and small endothelial cell aggregates were released from them by the sequential use of collagenase and trypsin. The endothelial cells were further isolated by rosetting with magnetic polystyrene beads which were coated with QB END/40, the endothelial-specific monoclonal antibody (mAb) to thrombomodulin. Cell rosettes were plated on gelatin coated Petri dishes. The cells initially grew as discrete colonies but reached confluence within 7 days. The monolayers were sub-cultured five times, and grew to confluence each time. All the cells were immunoreactive to the endothelial markers von Willebrand factor, QB-End/40 and Ulex europaeus-1 lectin. They did not show immunoreactivity to trophoblast markers (mAbs ED341 and ED235). The isolated cells could also incorporate acetylated low-density lipoprotein. Most of the cells possessed an elongated morphology, though some were slightly spread and polygonal in shape. The cell monolayers did not resemble the typical cobblestone appearance of endothelial cells isolated from large vessels. Ultrastructurally, most of the cells resembled placental microvascular cells in shape and frequency of caveolae; undifferentiated cell-cell contacts and extracellular matrix material was observed. Human placental microvascular endothelial cells may offer an in vitro model which complements the use of the perfused term placental lobule in studies of microvascular permeability.

Endothelium, Vascular↗
PubMed1994

Esperamicin P, the tetrasulfide analog of esperamicin A1.

A minor congener of esperamicin A1 [1], designated esperamicin P (BMY-41339, 2), was isolated from a fermentation broth of Actinomadura verrucosospora and determined to differ from esperamicin A1 by having a methyl tetrasulfide moiety instead of a methyl trisulfide. It was active against xenografted tumors in mice and exhibited antimicrobial activity. Interconversions of 2 and 1 have been observed for DMSO solutions of both congeners at room temperature.

Actinomycetaceae↗
PubMed1994

Elevated plasma endothelin concentrations in heart failure; an effect of angiotensin II?

Endothelin is a powerful vasoconstrictor that may be partly responsible for the increases in venous and arterial tone characteristic of heart failure. The release of endothelin from endothelial cells in culture is stimulated by angiotensin II. We investigated the relationship between plasma concentrations of immuno reactive endothelin-1 and angiotensin II in 25 patients with heart failure and eight with ischaemic heart disease but normal left ventricular function. Plasma concentrations of endothelin and angiotensin II were correlated (Spearman rank correlation coefficient of 0.72; P < 0.0001) in patients with heart disease. Plasma concentrations of angiotensin II and endothelin were higher in those patients with heart failure. Angiotensin II was infused over a 3 h period in eight healthy volunteers. Infusion of angiotensin II increased plasma concentrations of angiotensin II to levels greater than those usually found in patients with severe heart failure but induced only a modest rise in plasma concentrations of immunoreactive endothelin-1 (0.77 +/- 0.16 to 1.03 +/- 0.03 pmol.l-1, P < 0.02). Increased plasma concentrations of angiotensin II and endothelin-1 both appear to reflect the presence and severity of heart failure. Although a significant correlation exists between plasma concentrations of angiotensin II and endothelin in patients with heart failure, the relationship may not be causal.

Adult↗
PubMed1994

The frequency of glove contamination during cesarean delivery.

OBJECTIVE: To determine the frequency of glove contamination associated with fetal extraction during cesarean delivery. METHODS: The study was performed in 25 women having scheduled or unscheduled cesarean delivery. Surgeons double-gloved for all procedures. Immediately before and after delivery of the fetus, the dorsal aspect of the fingers and hand of the surgeon's outer glove was swabbed with cotton-tip applicators and cultured for aerobic and anaerobic organisms. Only the glove from the hand that was used to deliver the infant was cultured. RESULTS: Nine of 25 cultures (36%, 95% confidence interval [CI] 17-55) performed immediately before fetal extraction were positive for staphylococci. No other organisms were isolated. Cultures performed following fetal extraction showed non-staphylococcal bacteria in 11 of 14 (79%, 95% CI 58-100) laboring women and one of 11 (9%, 95% CI 0-26) nonlaboring women, a statistically significant difference (P < .01). In the laboring patients, non-staphylococcal bacteria were isolated with similar frequency from the dorsal aspect of the hand (seven of 14, 50%, 95% CI 24-76) and the fingers (ten of 14, 71%, 95% CI 47-95). These cultures yielded mostly bacterial species from the Enterobacteriaceae family. CONCLUSION: In laboring patients with ruptured membranes, delivery of the fetal head frequently results in contamination of the surgeon's glove with pathogenic bacteria. This finding may partially explain the increased frequency of post-cesarean endometritis associated with manual extraction of the placenta.

Bacteria↗
PubMed1994

Modulation of scatter factor/hepatocyte growth factor activity by cell-substratum adhesion.

Scatter factor/hepatocyte growth factor (SF/HGF) is a multifunctional growth and motility factor whose activities vary with cell type. Here, the composition of the substratum was found to profoundly alter the scattering activities of SF/HGF, but not its mitogenetic effects, in MDCK cells. Whereas enhancement of DNA synthesis and induction of cell flattening by SF/HGF were independent of substratum composition (i.e. occurred on both fibronectin and vitronectin surfaces), colony dispersion as a result of cell separation fails to occur or is markedly reduced on surfaces where vitronectin is the major adhesive ligand. Prolonged exposure of non-scattering cultures to SF/HGF resulted in cells at colony margins producing long protrusions, which indicate that the motility of these cells is stimulated but 'frustrated' by the lack of breakdown of cell-cell adhesion. Scattering therefore appears to comprise two major components: increased motility and breakdown of cell-cell adhesion. The pathway leading to the breakdown of cell-cell contacts is modulated by downstream signals from extracellular matrix receptors. When cultured on immobilised fibronectin, vitronectin or a surface containing both, colony dissociation correlates with the presence of fibronectin, suggesting that positive signals from fibronectin receptors are required for SF/HGF-induced cell separation. Comparison of the findings in this study with those of a recent report on the modulation of SF/HGF-induced tubulogenesis by ECM (Santos, O. F. P. and Nigam, S. K. (1993) Dev. Biol. 160, 293-302), where vitronectin in type-1 collagen gels alters the pattern of SF/HGF-induced MDCK tubule formation from highly branched to long and unbranched, suggests that cell motility enhancement leads to tubule formation whereas the breakdown of cell-cell adhesion is required for tubule branching.

Animals↗
PubMed1994

Peripartum infection associated with vaginal group B streptococcal colonization.

OBJECTIVE: To determine the frequency of peripartum infection in parturients colonized with group B streptococci. METHODS: We screened 915 obstetric patients for group B streptococcal colonization using selective broth media; 823 had vaginal cultures performed within 2 weeks preceding delivery and received complete follow-up. Vaginal group B streptococcal colonization and other risk factors for peripartum maternal infection were assessed using univariate and multivariate logistic modeling. RESULTS: Two hundred sixteen women (26%, 95% confidence interval [CI] 23-29) were colonized with group B streptococci. Chorioamnionitis or endometritis occurred in 45 of 216 colonized women (21%, 95% CI 15.6-26.4) and 72 of 607 women who were not colonized (12%, 95% CI 9-15; P < .01). When confounding variables were controlled in a multivariate analysis, the association between group B streptococcal colonization and chorioamnionitis, but not endometritis, was confirmed (odds ratio 3.6, 95% CI 2.1-6.2). The risk of chorioamnionitis increased in a stepwise fashion with light (odds ratio 1.9, 95% CI 1.0-3.7), moderate (odds ratio 2.6, 95% CI 1.3-5.2), and heavy (odds ratio 3.2, 95% CI 1.5-6.6) colonization. CONCLUSION: Intrapartum vaginal colonization with group B streptococci is an important independent risk factor for chorioamnionitis.

Chorioamnionitis↗
PubMed1993

Hydroxychloroquine compared with placebo in rheumatoid arthritis. A randomized controlled trial.

OBJECTIVE: To assess the efficacy of hydroxychloroquine, 400 mg daily, for rheumatoid arthritis. DESIGN: Six-month, double-blind, randomized trial. SETTING: Ambulatory referral clinic in a Mexico City, Mexico, teaching hospital. PATIENTS: A total of 126 patients with early rheumatoid arthritis were randomly assigned to receive hydroxychloroquine, 400 mg/d, or placebo; 121 patients completed the study. RESULTS: Hydroxychloroquine showed a clinically and statistically significant improvement over placebo in joint score (20% greater mean improvement; 10% more patients improved by > 50%); pain (40% greater mean improvement; 19% more patients improved by > 50%); grip strength (22% greater mean improvement; 21% more patients improved by > 50%); patient global assessment (16% more patients stated they had improved); and physician global assessment (12% more patients were judged to have improved). Side effects were mild, and no patients in the hydroxychloroquine group required discontinuation of therapy. Patient compliance with the study medication was high. CONCLUSION: Hydroxychloroquine is moderately effective in early rheumatoid arthritis.

Adult↗
PubMed1993

Crystal structure of human immunodeficiency virus type 1 reverse transcriptase complexed with double-stranded DNA at 3.0 A resolution shows bent DNA.

The crystal structure of a ternary complex of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) heterodimer (p66/p51), a 19-base/18-base double-stranded DNA template-primer, and a monoclonal antibody Fab fragment has been determined at 3.0 A resolution. The four individual subdomains of RT that make up the polymerase domains of p66 and p51 are named fingers, palm, thumb, and connection [Kohlstaedt, L. A., Wang, J., Friedman, J. M., Rice, P. A. & Steitz, T. A. (1992) Science 256, 1783-1790]. The overall folding of the subdomains is similar in p66 and p51 but the spatial arrangements of the subdomains are dramatically different. The template-primer has A-form and B-form regions separated by a significant bend (40-45 degrees). The most numerous nucleic acid interactions with protein occur primarily along the sugar-phosphate backbone of the DNA and involve amino acid residues of the palm, thumb, and fingers of p66. Highly conserved regions are located in the p66 palm near the polymerase active site. These structural elements, together with two alpha-helices of the thumb of p66, act as a clamp to position the template-primer relative to the polymerase active site. The 3'-hydroxyl of the primer terminus is close to the catalytically essential Asp-110, Asp-185, and Asp-186 residues at the active site and is in a position for nucleophilic attack on the alpha-phosphate of an incoming nucleoside triphosphate. The structure of the HIV-1 RT/DNA/Fab complex should aid our understanding of general mechanisms of nucleic acid polymerization. AIDS therapies may be enhanced by a fuller understanding of drug inhibition and resistance emerging from these studies.

Base Sequence↗
PubMed1993

Effect of luminal growth factor preservation on intestinal growth.

Intestinal atrophy contributes to the clinical difficulties of patients who cannot eat normally. Atrophy is prevented by luminal food proteins but not by the equivalent aminoacids. This observation is not explained by current theories of intestinal physiology. Epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) are secreted into the gut lumen. We speculated that these are digested by pancreatic enzymes in fasting juice, but preserved when food proteins block the active sites of these enzymes. Studies based on molecular size and bioactivity confirmed that fasting human jejunal juice destroys EGF and TGF alpha. EGF, but not TGF alpha, was preserved when the milk protein casein or an enzyme inhibitor were present; elemental diets were ineffective. Diversion of pancreatic juice to the mid point of the small intestine in rats significantly increased luminal EGF-like bioactivity and all variables of growth in the proximal enzyme-free segment. Our findings support a novel mechanism of control of intestinal growth, which has important clinical implications. The addition of enzyme-inhibiting proteins such as casein to elemental diets may preserve intestinal integrity and function.

Animals↗
PubMed1993

Rare alpha 1 antitrypsin allele PI W and a history of infant liver disease.

We present a consanguinous couple whose three of four children are homozygous for a rare slow alpha 1 antitrypsin allele PI*W. All three children had abnormal liver function in infancy and two died in infancy of liver disease. The eldest child and both parents were heterozygous for the PI*W allele and were unaffected. Therefore, although serum levels are not markedly reduced, homozygotes appear to be at increased risk of developing liver disease.

Alleles↗
PubMed1993

Duplication (20p) in association with thyroid carcinoma.

We report on a girl with short stature, mental retardation, mutism, "coarse" facial appearance, and papillary-follicular thyroid carcinoma. She had dup(20p) derived from a paternal balanced translocation [(12p;20p)]. We speculate that the carcinoma in our patient may be related to the deletion of material from 12p resulting in absence of genetic material normally required for the suppression of thyroid tumorigenesis.

Adenocarcinoma↗
PubMed1993

Metabolic changes in axotomized fetal and early postnatal hamster facial motoneurons: an autoradiographic study.

The developing facial neurons of a series of hamsters ranging in age from the 14-day fetus to the 9 day postnatal were axotomized. Postoperative times were graded for each age so that the retrograde response could be observed before any significant amount of cell degeneration or death occurred. The incorporation of tritiated uridine was followed by the autoradiographic procedure. Although grain counts, relative to control values, were significantly reduced only in the axotomized fetus and at 24 hours postoperatively in 4-day postnatal animals, there was also a repression of isotopic incorporation in all the other axotomized animals. These results support data obtained from previous work with the hamsters which indicate that it is not until after the nerve cell nucleolus reaches full cytomorphic maturity (between 15 and 20 days postnatal age in hamster facial neurons) that the axotomized neurons respond with significantly increased incorporation levels of isotope over that of control neurons.

Animals↗
PubMed1993

Rapid intrapartum detection of group B streptococcal colonization with an enzyme immunoassay.

OBJECTIVE: The purpose of this study was to determine the accuracy of a rapid immunoenzyme assay for detecting intrapartum colonization with group B streptococci. STUDY DESIGN: Three rayon-tipped swabs were used to collect specimens from the posterior vaginal wall of 424 preterm and term patients in labor. Three tests were performed on specimens obtained from the first 182 patients: semiquantitative culture on blood agar, culture in selective Todd-Hewitt broth, and ICON Strep B (Hybritech, San Diego) immunoconcentration assay. For the remaining 242 patients, the ICON test was performed only when the Todd-Hewitt broth culture was positive. RESULTS: The prevalence of positive cultures was 23%. For the first 182 patients, the immunoassay had a sensitivity of 11%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 78%. The overall sensitivity for all 424 patients was 9%. In eight women with heavy colonization, defined as an inoculum of > 10(5) cfu/ml the sensitivity of the assay was 100%. In the study population there were three cases of group B streptococcal sepsis in infants whose mothers were only lightly colonized. None of these cases of colonization were detected by the assay. CONCLUSION: The ICON immunoconcentration assay is very sensitive in identifying heavy group B streptococcal colonization of > 10(5) cfu/ml but quite insensitive in detecting lower levels of colonization. Thus it is not a suitable test for general screening.

Culture Media↗
PubMed1993

Characteristics of normal larynges under flexible fiberscopic and stroboscopic examination: an Australian perspective.

The purpose of this study was to investigate the structure and function of larynges of 35 subjects with normal voices. Volunteers aged between 20 and 50 years with no history of voice disorders or laryngeal surgery, no current allergies, no formal voice training, and no hyperactive gag reflex were required to perform various vocal manoeuvres that were carried out under continuous and stroboscopic light. An assessment form was devised to record the condition and function of the larynx. The videotapes of the procedure were rated by experienced judges. The Australian Fiberscopic Profile was devised to record the relevant parameters under continuous light. Videostroboscopic ratings were carried out using the Bless protocol rating. High interjudge agreement was found across the two rating profiles.

Adolescent↗
PubMed1993

Dilution kinetics of H(2)18O for the measurement of total body water in preterm babies in the first week after birth.

The aim of this study was to determine the kinetics of H(2)18O equilibration and elimination in preterm babies for the estimation of total body water. Thirteen, clinically stable, preterm babies of less than 32 weeks' gestation were studied in the first week after birth. Blood and urine samples were obtained for baseline measurement of 18O:16O ratio and 1 ml/kg of 10% H(2)18O (0.1 g/kg isotope) administered orally. Eleven blood samples were obtained over the next six hours and between one and four over the next 18 hours. During the same 24 hour period between three and eight urine samples were also obtained. The dilution space at zero time (volume of distribution or total body water) was estimated using double exponential curve fitting using all available points, from single samples and from linear regression on the log data using two or three samples. Equilibration time was variable and showed a significant correlation with percentage change in body weight from birth. For blood samples, the median time to equilibrium was 81 minutes (range 2 to 191). A plateau phase was not detected, with H(2)18O enrichment declining after the point of maximum enrichment. The median volume of distribution at time 0, based on double exponential curve fit analysis, was 859 ml/kg (range 755 to 995). The volume of distribution, estimated from linear regression on the log data using two serum samples obtained at three and six hours, approximated most closely to that based on exponential curve fit analysis with a median difference of -4 ml/kg (range -41 to 73). It was concluded that in most situations blood sampling at three and six hours may be acceptable. However, as equilibration time is variable and influenced by the state of expansion or depletion of body water compartments, when studying overhydration states, multiple sampling is advised in order to be certain that the elimination phase has been reached.

Blood Specimen Collection↗
PubMed1993

Immunoelectron characterisation of the inter-endothelial junctions of human term placenta.

The molecular constituents of the paracellular clefts in human placental microvessels were investigated using antibodies against PECAM-1, pan-cadherin, A-CAM (N-cadherin), cadherin-5 and two types of integrins (those recognised by antibodies to the beta 1 chain and alpha v beta 3). Ultrastructural localisation of these molecules in ultrathin frozen sections of human term placentae was attempted using colloidal gold immunocytochemistry, after establishing their presence by indirect immunofluorescence. At the light microscopical level, the endothelial paracellular clefts were found to be immunoreactive to the antibodies against PECAM-1, cadherin-5 and pan-cadherin, but not the integrins. The latter showed diffuse distribution in the endothelium and in the abluminal interstitial space. PECAM-1 and pan-cadherin were also seen in the cytoplasm and luminal surface of the endothelium. Immunoelectron studies revealed that the cadherins and PECAM-1 were present in the wide regions of the paracellular clefts, but not in tight junctional regions. Using immunocytochemistry, these wide junctional areas were found to be associated with the cytoskeletal linking molecules vinculin and alpha-actinin. These regions may therefore contain adherens-type junctions. Cadherin-5, localised by two different monoclonal antibodies, 7B4 and TEA, was the only antigen which was cleft-specific, the others also being seen in the cytoplasm of the microvascular endothelium. Cadherin-5 and pan-cadherin were co-localised in the same wide junction, but were usually seen to occupy different microdomains of, and different wide zones of, the same cleft. The cell adhesion molecules localised in the paracellular wide junctions of the human placental microvessels may play a role in maintaining the intercellular spacing between endothelial cells, and may be part of a paracellular "fibre matrix" with permeability-restricting properties.

Actinin↗