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Biomedical subjects

R B Clark

Publications and source records attributed to R B Clark.

At least 163 records · Page 9Linked to original sources
PubMed1985

Phosphatidate and monooleylphosphatidate inhibition of fibroblast adenylate cyclase is mediated by the inhibitory coupling protein, Ni.

It has previously been shown that monooleylphosphatidate (MOPA) and phosphatidate inhibit cAMP accumulation in VA13 and WI-38 fibroblasts. In this study we investigated whether this inhibition might be due to a decrease in adenylate cyclase activity. Our results showed that both MOPA and phosphatidate inhibit prostaglandin E1-stimulated adenylate cyclase in WI-38 membranes in a concentration-dependent manner with half-maximal inhibitions at 0.1 and 0.5 microM, respectively, and maximal inhibitions of 35-55%. A 5 microM concentration of structurally similar lipids caused no significant inhibition. The inhibitory effects of MOPA and phosphatidate on adenylate cyclase were GTP dependent, greater at low concentrations of Mg2+, eliminated following treatment of cells with islet-activating protein, nonadditive with carbachol, and noncompetitive with prostaglandin E1. Collectively these data suggested that MOPA and phosphatidate inhibitions of cAMP accumulation were due at least in part to an Ni-mediated inhibition of adenylate cyclase. Furthermore, the inhibitions showed the same characteristics normally associated with hormonal inhibition of this enzyme.

Adenosine Diphosphate Ribose↗
PubMed1985

Cervical chlamydial infections: diagnostic accuracy of the Papanicolaou smear.

To assess the reliability and accuracy of the Papanicolaou smear for the detection of cervical Chlamydia trachomatis infections, we obtained chlamydial cultures and cervical smears from 252 patients attending a gynecologic service during an eight-month time period. In 12 of these patients (4.8%), the cervical culture was positive for chlamydiae but the cytologic smear was negative for chlamydial inclusions. Five smears (2.2%) were cytologically positive for chlamydiae but were negative by culture. In none of the patients were both culture and smear positive for chlamydiae. In our experience the smear was a completely unreliable test for the diagnosis of cervical C trachomatis infections. The cytologic smear should not replace culture for the detection of chlamydial infections.

Chlamydia Infections↗
PubMed1984

Generation of phenotypic helper/inducer and suppressor/cytotoxic T-cell lines from cerebrospinal fluid in multiple sclerosis.

The investigation of cell-mediated events in man has been largely limited to the study of the cells in the peripheral circulation. The study of T cells from localized anatomic compartments has been difficult due to the small numbers of cells usually obtainable from these sites. Investigation of such compartmentalized responses theoretically may yield information relating to both normal immunoregulation and autoimmune diseases--information that may not be obtainable through the investigation of the circulating cellular immune system. Utilizing cerebrospinal fluid (CSF) lymphocytes from patients with multiple sclerosis as a model of compartmentalized immunologically relevant cells, the technology for the generation of long-term T-cell lines from compartments both in continuous culture and after cryopreservation and that consist of both helper/inducer and suppressor/cytotoxic phenotypes have been generated. The 10(4) to 10(5) CSF cells obtained initially from individual patients have often been expanded into greater than 10(8) total cells within 4 months. The ability to generate large, stable, cryopreservable helper and suppressor/cytotoxic T-cell lines from limited access compartments will allow for new investigative approaches into both normal immunoregulation and autoimmune diseases in man.

Antigens, Surface↗
PubMed1984

Generation of long-term T-cell lines from synovial fluid.

Investigations of human autoimmune diseases have largely involved study of circulating T cells. The development of T-cell cloning technology has made possible the study of the small numbers of T cells found at sites of pathological involvement in autoimmune diseases. In this initial communication, the feasibility of in vitro propagation of synovial fluid T cells from patients with arthritis is demonstrated. The generation of long-term, phenotypic helper/inducer, as well as phenotypic suppressor/cytotoxic, interleukin 2-dependent synovial fluid T-cell lines from patients with arthritis is reported. The ability to generate such synovial fluid T-cell lines should now allow for new investigative approaches to human autoimmune arthritic diseases.

Arthritis, Rheumatoid↗
PubMed1984

Phenotypic factors correlated with the absence of virulence among gentamicin-resistant Pseudomonas aeruginosa strains.

Previous reports have suggested that clinical strains of gentamicin-resistant Pseudomonas aeruginosa (GRPA) generally produce only superficial infections (wounds, urinary tract infections) in contrast to their more invasive gentamicin-susceptible counterparts (GSPA). In view of this finding, a comparative study of a number of phenotypic properties of 20 GRPA and GSPA strains (10 isolates) was assessed to determine how closely related these two populations are and how their phenotypic properties might reflect virulence. GRPA isolates were found to be more adherent to buccal cells than their susceptible counterparts (P = 0.0001). Motility, however, was generally restricted in the GRPA population when compared with GSPA isolates (P = 0.02), although on the basis of zone diameters, some strains overlapped into the other group. Enzymatically, GSPA isolates produced significantly more lipase activity against C-14 lipids than GRPA strains (P = 0.04). No differences were recorded between the two populations in dye sensitivity or in their ability to grow on minimal media at 37 and 42 degrees C. Only 35% of the GRPA isolates agglutinated in 1 of the 17 monospecific antisera reactive for P. aeruginosa. The results of this study suggest that in vivo-generated GRPA strains possess phenotypic properties intermediate between those described for in vitro-derived GRPA isolates and their progenitor GSPA strains. The increased adherence of clinical GRPA isolates to buccal cells may explain their predilection to produce wound and urinary tract infections, whereas their lack of systemic dissemination may be partially due to decreased motility and to reduced lipase production.

Adhesiveness↗
PubMed1984

Biotyping and exoenzyme profiling as an aid in the differentiation of human from bovine group G streptococci.

Group G streptococci were isolated from throat and extrapharyngeal cultures from 75 patients during an 18-month period. Of 29 throat isolates, 18 were recovered from patients with pharyngitis, 8 were of unknown significance, and 3 were of questionable etiology. Clinical significance could be ascribed to 13 of 46 extrapharyngeal isolates recovered from wound, urinary tract, blood, and conjunctival cultures. Extrapharyngeal isolates recovered from stool, sputum, and vaginal cultures were considered nonsignificant. A total of 96 group G streptococcal strains (including 21 human and 14 bovine strains from outside sources) were tested for exoenzyme production and subjected to a large battery of biochemical tests. Bovine and human isolates could be distinguished on the basis of trehalose fermentation, litmus milk reduction, and production of beta-D-glucuronidase, hyaluronidase, and fibrinolysin. Eight distinct biotypes could be discerned on the basis of fermentation of trehalose, raffinose, and lactose and esculin hydrolysis. All isolates that fermented raffinose were associated with infection. These results support the concept of two distinctly different epidemiological reservoirs of group G streptococci in humans and bovines.

Animals↗
PubMed1984

Value of blood agar for primary plating and clinical implication of simultaneous isolation of Aeromonas hydrophila and Aeromonas caviae from a patient with gastroenteritis.

The simultaneous recovery of Aeromonas hydrophila and Aeromonas caviae from the stool of a 49-year-old woman with watery diarrhea was facilitated through the use of a blood agar medium which detected the hemolytic capability of A. hydrophila. In vitro phenotypic tests support the conclusion that only the A. hydrophila isolate was clinically significant.

Aeromonas↗
PubMed1984

Long-term T-cell lines from the tears of patients with vernal conjunctivitis.

Previous studies of the tears and conjunctival tissue of vernal conjunctivitis (VC) have suggested that cellular immune mechanisms may be important in the inflammatory process of this ocular disease. However, little information is available in support of a cell-mediated immune mechanism because of the difficulty of tissue access and the small numbers of mononuclear cells in the tear secretions. Tear secretions of VC patients contain few lymphocytes (estimated 10(3) per 300 microliters of tears). Tear lymphocytes from 5 of 7 VC patients were propagated in culture in the presence of interleukin 2. In 2 months of culture the tear lymphocytes were expanded to 5 x 10(6)-10(7) cells. Phenotyping studies with monoclonal antibodies showed that all cell lines exhibited T-cell markers. In 2 of 3 tear specimens which were initially cultured in the presence of the putative specific antigen, i.e. rye grass or ragweed antigen E, the OKT4 helper/inducer phenotype predominated while the cell lines without antigen exhibited mostly the OKT8 phenotypes. These studies demonstrated the feasibility of generating long-term IL-2 dependent T-cell lines from the tear secretions of patients with VC which will enable the study of localized cellular immune processes in external ocular disease.

Antibodies, Monoclonal↗
PubMed1984

Regional anesthesia.

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Anesthesia, Conduction↗
PubMed1983

Photoaffinity labeling of the beta-adrenergic receptor from cultured lymphoma cells with [125I]iodoazidobenzylpindolol: loss of the label with desensitization.

The beta-adrenergic antagonist [125I]iodoazidobenzylpindolol ( [125I]IABP) specifically photolabeled two polypeptides in membrane preparations from wild-type (WT) and coupling protein-deficient cyc- cultured lymphoma cells. The molecular weights of the two polypeptides determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis were 65,000 and 55,000. They were labeled in a ratio of approximately 1:1. Pretreatment of intact WT or cyc- cells with 1.0 microM epinephrine for 15 min (desensitization) resulted in a greater loss of the 55,000 Mr polypeptide (40-60%) relative to the 65,000 Mr peptide (10-30% loss). An 18- to 24-hr pretreatment of WT cells with terbutaline (down-regulation) led to a greater than 90% reduction of the photolabeling of both polypeptides, whereas a similar pretreatment of cyc- cells resulted in no further loss of labeled receptor than that observed after only a 15-min pretreatment with epinephrine. There was no indication of a change in the electrophoretic mobility of the [125I]IABP-labeled receptors after either short- or long-term agonist pretreatment. These data provide direct evidence for heterogeneity of the beta-adrenergic receptor in lymphoma cells. The differential loss of the [125I]IABP labeling in the two polypeptides suggests a functional heterogeneity as well.

Adenylyl Cyclases↗
PubMed1983

Morphological aberrations of nutritionally deficient streptococci: association with pyridoxal (vitamin B6) concentration and potential role in antibiotic resistance.

A strain of a nutritionally deficient streptococcus was shown to undergo morphological aberrations according to pyridoxal concentrations in the growth medium. Filamentous rod-shaped cells, observed by electron microscopy, predominated in the presence of decreasing concentrations. Multiple invaginations in the outer cell wall suggested inhibition of binary fission. Penicillin antimicrobial studies performed in the presence of similar pyridoxal concentrations indicated a relationship between filamentous forms and penicillin susceptibility.

Cell Membrane↗
PubMed1983

Effect of dithiothreitol on the beta-adrenergic receptor of S49 wild type and cyc- lymphoma cells: decreased affinity of the ligand-receptor interaction.

Dithiothreitol (DTT) treatment of WT or cyc- lymphoma membranes resulted in the simultaneous loss of epinephrine-stimulated adenylate cyclase activity and beta-adrenergic antagonist binding. The treatment produced no significant decrease in NaF-stimulated activity and only a partial loss of the PGE1 stimulation. Epinephrine partially protected against the loss of epinephrine-stimulated cyclase activity. The decrease in beta-adrenergic stimulation of adenylate cyclase was characterized by over a 100-fold increase in Kact for epinephrine stimulation of adenylate cyclase (10 mM DTT for 30 min) with no effect on the Vmax. We have previously shown that two polypeptides (Mr = 55,000 and 65,000 daltons) are specifically labeled by [125I]iodoazidobenzylpindolol (IABP) in WT and cyc-. The IABP photolabeling of the 55,000 dalton beta-receptor polypeptide was preferentially reduced by 1.0 mM DTT, whereas 10 mM DTT eliminated the photolabeling of both polypeptides. The effects of DTT were not due to either scavenging of the nitrene or reduction of the azide. A reduction in epinephrine stimulation of adenylate cyclase was also observed after treatment of intact WT, and the effects were readily reversed in the cells by washout of the DTT. The DTT effects on membranes were not reversed by washout. Our results demonstrate that the oxidized state of the lymphoma beta-receptor is necessary for maximum sensitivity to agonist stimulation of adenylate cyclase and that low concentrations of reducing agent selectively decrease specific photo-labeling of the 55,000 dalton beta-receptor polypeptide.

Adenylyl Cyclases↗
PubMed1982

Ultrastructural analysis of the effects of erythromycin on the morphology and developmental cycle of Chlamydia trachomatis HAR-13.

The effect of erythromycin (10 micrograms/ml) on the morphology and developmental cycle of Chlamydia trachomatis HAR-13 was examined by electron microscopy. When the antibiotic was added later than 24 h post infection, the HAR-13 morphology or developmental cycle was not altered. Addition at 18 or 24 h post infection inhibited glycogen production, blocked the transformation of the reticulate body to elementary body, and produced ghost bodies and reticulate bodies twice the diameter of untreated reticulate bodies. When erythromycin was added within 12 h post infection, the conversion of the elementary body to reticulate body was inhibited. Erythromycin (10 micrograms/ml) was bactericidal to strain HAR-13 throughout the developmental cycle.

Chlamydia trachomatis↗
PubMed1982

Block of locust muscle glutamate receptors by delta-philanthotoxin occurs after receptor activations.

One component (delta-philanthotoxin (delta-PTX) of the venom from the wasp Philanthus triangulum blocks transmission postsynaptically at excitatory synapses on locust muscle. delta-PTX depresses both the iontophoretic glutamate potential and the excitatory junctional current (e.j.c.) in a glutamate receptor activation-dependent manner. The rate of recovery from the effects of the toxin is reduced following either prolonged application of L-glutamate or repetitive iontophoretic application of this amino acid or high frequency neural stimulation of the muscle in the presence of delta-PTX. The decay phase of the e.j.c. is shortened by delta-PTX. The effects of delta-PTX on the e.j.c. are not voltage dependent. The open-close kinetics of glutamate channels in extrajunctional muscle membrane are modified by delta-PTX as shown by patch clamp analysis. The mean life time of the glutamate channel is reduced, whilst the mean interval between single opening events is increased with the events often occurring in bursts. These data are consistent with glutamate channel blocking by this toxin. It is proposed that the toxin blocks open channels gated by both junctional and extrajunctional glutamate receptors on locust muscle. It is further proposed that delta-PTX enters a compartment of the muscle through the glutamate open channels and that it can also block the open channels from this site.

Animals↗