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Biomedical subjects

R A Clark

Publications and source records attributed to R A Clark.

At least 271 records · Page 15Linked to original sources
PubMed1988

Transforming growth factor-beta stimulates the expression of fibronectin by human keratinocytes.

Transforming growth factor beta (TGF-beta) is a 25-kD protein which has regulatory activity over a variety of cell types. It is distinct from epidermal growth factor (EGF) and EGF analogs, and exerts its action via a distinct receptor. Its effect on proliferation or differentiation can be positive or negative depending on the cell type and the presence of other growth factors. It also modulates the expression of cellular products. TGF-beta causes fibroblasts to increase their production of the extracellular matrix components, fibronectin and collagen. Human keratinocytes (HK) are known to have TGF-beta receptors. We wished to study the effect of TGF-beta on the production of extracellular matrix proteins by human keratinocytes in culture. Human keratinocytes were grown in serum-free defined medium (MCDB-153) to about 70% confluence. Following a 16-h incubation in medium lacking EGF and TGF-beta, cells were incubated for 12 h in medium containing varying concentrations of EGF and TGF-beta. Cells were then labeled with 35S-methionine for 10 h in the same conditions. Labeled proteins from the medium were analyzed by SDS-PAGE and autoradiography. TGF-beta at 10 ng/ml induced a sixfold increase in the secretion of fibronectin, as well as an unidentified 50-kD protein. Thrombospondin production was also increased, but not over a generalized twofold increase in the production of all other proteins. EGF, at 10 ng/ml, caused a smaller additive effect. TGF-beta may be an important stimulator of extracellular matrix production by human keratinocytes.

Cells, Cultured↗
PubMed1988

Beta-adrenoceptor responses to high doses of inhaled salbutamol in patients with bronchial asthma.

1. Fourteen asthmatics (mean +/- s.e. mean baseline FEV1 62 +/- 6% of predicted) were given cumulative doubling doses of salbutamol by metered-dose inhaler as follows: 100 micrograms, 200 micrograms, 500 micrograms, 1000 micrograms, 2000 micrograms, 4000 micrograms. 2. Airways, tremor, haemodynamic and cyclic AMP responses were measured at each dose increment (made every 20 min). 3. There was a linear log dose-response relationship for each airways parameter (FEV1, VC, sGaw, FEF 50%). The plateau in the dose-response curve was not reached within our dose range. These changes were also mirrored in cyclic AMP responses. 4. There was a wide range in maximum airways response expressed in terms of absolute increase over baseline (95% confidence intervals: delta FEV1 667-1483 ml; delta VC 689-1695 ml; delta sGaw 0.92-4.50 s-1 kPa-1; delta FEF 50% 0.94-2.15 l s-1). Patients with a lower baseline showed a greater response in terms of percent increase in FEV1 (r = -0.83, P less than 0.001). There was however, no correlation between baseline airway calibre and the dose required for maximum bronchodilatation. 5. There were objective increases (mean +/- s.e. mean) in both heart rate (maximum delta HR of 14 +/- 5 beats min-1 at 4000 micrograms) and tremor power (maximum delta Tr of 115 +/- 44% at 2000 micrograms). These were not dose limiting side-effects as subjective symptoms were infrequent at higher doses. 6. Higher than conventional doses of salbutamol given by metered-dose inhaler may produce a distinct improvement in airways response without significant side-effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1988

Neurologic complications of pelvic intraarterial chemoembolization performed with collagen material and cisplatin.

In three patients neurologic complications developed after chemoembolization procedures were performed with cisplatin and a new collagen material. Three patients with dominant unilateral stage III cervical carcinoma were entered into an investigative protocol attempting to control regional disease and pain with chemoembolization. All three patients had previously undergone surgery, radiation therapy, and intraarterial chemoembolization or chemoinfusion. Each case was complicated by neurologic deficits. A collagen material was administered that acts at a precapillary level and reduces the likelihood of collateral flow. The size of the material enables it to embolize the small feeding vessels of the spinal cord and peripheral nerves. The patients in this study also had predisposing factors to neurologic sequelae including the previous therapy and the contributing neurotoxicity of cisplatin. The neurologic complications in these patients are not easily explained by knowledge of the neurovascular anatomy. Even with meticulous technique, intraarterial chemoembolization of the pelvis with cisplatin and collagen can be complicated by serious neurologic deficits.

Adult↗
PubMed1988

Dose-ranging evaluation of the serotonin antagonist GR-C507/75 (GR38032F) when used as an antiemetic in patients receiving anticancer chemotherapy.

GR-C507/75 (GR38032F) antagonizes the 5-HT3 (serotonin) receptor and prevents cisplatin-induced emesis in animals. In this dose-ranging trial, 44 patients with cancer receiving chemotherapy known to produce nausea and vomiting (including cisplatin, cyclophosphamide, and doxorubicin) received three intravenous (IV) infusions of GR-C507/75 every two hours beginning 30 minutes before chemotherapy. Ten dosage levels were explored, ranging from 0.04 mg/kg to 0.35 mg/kg in each of the three infusions. Toxicities were mild and included sedation, dizziness, headache, transient elevations of SGOT or alanine aminotransferase (ALT), and dry mouth. No akathisia or acute dystonic reactions were observed. Antiemetic effects were seen in patients receiving cisplatin at 120 mg/m2. GR-C507/75 can be safely administered on this schedule at IV dosages up to 0.35 mg/kg in patients receiving chemotherapy. Further studies of this agent at higher dosages and by different schedules are appropriate.

Adult↗
PubMed1988

Control of chemotherapy-induced diarrhea with the synthetic enkephalin BW942C: a randomized trial with placebo in patients receiving cisplatin.

Diarrhea commonly occurs following the administration of cisplatin. BW942C, a pentapeptide, is a synthetic enkephalin shown to control castor oil-induced and traveler's diarrhea. To assess the safety and efficacy of BW942C in controlling diarrhea caused by cisplatin, 30 adults with lung cancer who had already experienced diarrhea (three or more loose bowel movements) during the 24-hour period following a prior cisplatin administration were randomized to receive either BW942C or placebo during the next cisplatin course. All patients received a concomitant antiemetic regimen including metoclopramide, dexamethasone, and lorazepam during all courses. Patients administered BW942C experienced less diarrhea (27% v 67%, P = .02). Twenty-seven percent of patients given the pentapeptide had loose bowel movements as opposed to 93% who received placebo (P = .0002). There were no significant differences in the incidence and degree of vomiting and other treatment-related side effects observed between the placebo and treatment groups. We conclude that oral BW942C is more effective than placebo in controlling diarrhea following cisplatin chemotherapy.

Adult↗
PubMed1988

Potential roles of fibronectin in cutaneous wound repair.

Fibronectin has many potential roles in wound repair, including chemotactic factor activity for monocytes, fibroblasts, and endothelial cells; opsonin activity and opsonin promoter activity for microorganism and tissue debris; substratum for cell migration and localization; and a scaffold for building extracellular matrix. Although fibronectin has been reported to have intrinsic growth-promoting ability, coisolation of authentic growth factors with fibronectin raises doubts about this observation. Whether the addition of exogenous fibronectin to wounds can augment healing is a question for future studies.

Acute-Phase Reaction↗
PubMed1988

Delayed pressure urticaria histologically resembles cutaneous late-phase reactions.

In a recent study, all patients with delayed pressure urticaria (DPU) developed late cutaneous reaction (LCR) after intradermal injection of compound 48/80 and after skin testing with certain food antigens. In the present study, we analyzed the histologic changes in the pressure lesions and compared them with those found in normal skin injected with diluent and in LCR to 48/80. The study included five patients with DPU associated with chronic urticaria (CU) and four patients with CU but without DPU. Six to eight hours after pressure challenge and intradermal skin testing with 48/80 and diluent, skin biopsy specimens were obtained from the pressure lesions, the LCRs, and normal skin (diluent injection). Specimens were assessed by Giemsa staining of 1-micron sections and immunofluorescence of frozen sections. Total cells were counted in each specimen. Interstitial deposits of fibrin were observed by immunofluorescence in LCR and pressure lesions. The total numbers of infiltrating cells in the dermis among LCR sites and pressure lesions were not significantly different, while both LCR sites and pressure lesions contained significantly more infiltrating cells than did normal skin injected with saline diluent. The differential counts in LCR and DPU were mostly mononuclear cells. Infiltrates in the DPU and LCR were mostly perivascular. No histopathologic changes were seen at skin sites challenged with pressure in the control patients with CU without clinical manifestations of DPU. We conclude that lesions seen in DPU are morphologically similar to classic LCR.

Adult↗
PubMed1987

Antiemetic control and prevention of side effects of anti-cancer therapy with lorazepam or diphenhydramine when used in combination with metoclopramide plus dexamethasone. A double-blind, randomized trial.

Combinations of metoclopramide and dexamethasone given intravenously control vomiting caused by high doses of cisplatin. Lorazepam and diphenhydramine are useful adjuncts to antiemetics. In a double-blind trial, 120 patients receiving high-dose cisplatin (120 mg/m2) for the first time were randomly assigned to receive either lorazepam (1.5 mg/m2) or diphenhydramine (50 mg) intravenously, 45 minutes prior to cisplatin. In addition, all patients received intravenous dexamethasone (20 mg) 40 minutes prior to chemotherapy along with metoclopramide (3 mg/kg) 30 minutes before and 90 minutes after cisplatin. Patients were directly observed in the hospital after cisplatin administration and completed a subjective assessment questionnaire. Overall, 60% of patients experienced no vomiting, and 83% had two or fewer emetic episodes during the study. There were no significant differences in objective antiemetic control between the two regimens. Only 3% of patients receiving lorazepam experienced treatment-related restlessness as opposed to 19% given diphenhydramine (P = 0.007). Less recall of chemotherapy administration (P less than 0.001), more sedation (P = 0.003), and transient enuresis while sedated (P = 0.0002) were characteristic of patients receiving lorazepam. Patient-generated ratings revealed less anxiety (P = 0.0001) for those individuals given the lorazepam-containing combination. Both regimens were well accepted, with 89% of patients receiving the lorazepam combination and 83% of those given the diphenhydramine regimen wishing to receive the same drugs in the future. Some degree of delayed vomiting occurred in 85% of patients during the 4-day period following this study. During the time that patients are at the greatest risk for emesis, the 24 hours immediately following cisplatin, three drug antiemetic combinations of either lorazepam or diphenhydramine with metoclopramide plus dexamethasone stopped cisplatin-induced emesis for the majority of patients and lessen other treatment-related side effects. Less restlessness and anxiety were observed among individuals receiving the lorazepam-containing combination.

Adult↗
PubMed1987

The neutrophil glycoprotein Mo1 is an integral membrane protein of plasma membranes and specific granules.

The glycoprotein Mo1 has previously been demonstrated to be on the cell surface and in the specific granule fraction of neutrophils and to be translocated to the cell surface during degranulation. It is not known, however, whether Mo1 is an integral membrane protein or a soluble, intragranular constituent loosely associated with the specific granule membrane. Purified neutrophils were disrupted by nitrogen cavitation and separated on Percoll density gradients into four fractions enriched for azurophilic granules, specific granules, plasma membrane, and cytosol, respectively. The glycoproteins in these fractions were labeled with 3H-borohydride reduction, extracted with Triton X-114, and immunoprecipitated with 60.3, an anti-Mo1 monoclonal antibody Mo1 was detected only in the specific granule and plasma membrane fractions and partitioned exclusively into the detergent-rich fraction consistent with Mo1 being an integral membrane protein. In addition, treatment of specific granule membranes with a high salt, high urea buffer to remove absorbed or peripheral proteins failed to dissociate Mo1. These data support the hypothesis that Mo1 is an integral membrane protein of plasma and specific granule membranes in human neutrophils.

Antibodies, Monoclonal↗
PubMed1987

Immunosuppression by activated human neutrophils. Dependence on the myeloperoxidase system.

An in vitro model system was used to define the mechanism of interaction between human neutrophils and lymphocytes. Blood mononuclear leukocytes were exposed to purified neutrophils in the presence of a neutrophil-activating agent (phorbol ester, lectin, or opsonized particle). The treated mononuclear cells displayed a marked decrease in both natural killer activity and mitogen-dependent DNA synthesis, but no change in viability. This functional suppression was dependent on neutrophil number, stimulus concentration, and duration of exposure. Lymphocytes were protected by addition of catalase, but not superoxide dismutase. Neutrophils defective in oxidative metabolism (chronic granulomatous disease) failed to suppress lymphocyte function unless an H2O2-generating system, glucose oxidase plus glucose, was added. The patients' neutrophils provided a factor, possibly myeloperoxidase, which interacted with the glucose oxidase system. The immunosuppressive effect of normal neutrophils was diminished when chloride was omitted from the cultures and was enhanced when chloride was replaced by iodide. Myeloperoxidase-deficient neutrophils were partially defective in suppressing lymphocytes and this was corrected by addition of purified myeloperoxidase. Paradoxically, azide caused enhancement of suppression that depended on the neutrophil oxidative burst, but not on myeloperoxidase and was mediated at least in part by an effect of azide on the target mononuclear leukocytes. These data indicate that suppression of lymphocyte function by activated neutrophils is mediated by the secretion of myeloperoxidase and H2O2 that react with halides to form immunosuppressive products. Moreover, the mononuclear leukocytes contain an azide-sensitive factor, probably catalase, which provides partial protection against injury by neutrophil products. These dynamic interactions may be important local determinants of the immune response.

Cell Survival↗
PubMed1987

NADPH oxidase of human neutrophils. Subcellular localization and characterization of an arachidonate-activatable superoxide-generating system.

The superoxide-forming NADPH oxidase of human neutrophils was studied in subcellular fractions of unstimulated cells. Purified neutrophils were disrupted by nitrogen cavitation and separated on Percoll density gradients into four fractions: alpha, azurophil granules; beta, mostly specific granules; gamma, plasma membrane, and cytosol. NADPH-dependent O2-. formation by these fractions was quantitated as the rate of superoxide dismutase-inhibitable reduction of ferricytochrome c. In the presence of cytosol, NADPH, and either arachidonic acid (optimum 90 microM) or sodium dodecyl sulfate (optimum 160 microM), 70-75% of the oxidase was in the beta fraction and about 25% was in the gamma fraction. A similar distribution was found for cytochrome b559 and FAD, two putative components of the oxidase. The reaction rates observed with arachidonic acid activation were sufficient to account for 25-75% of the O2-. generated by intact neutrophils. The properties of the beta and gamma enzymes were similar and closely resembled those of the oxidase in intact neutrophils or disrupted prestimulated cells. These included resistance to azide and cyanide, a pH optimum of 7.4, and a preference for NADPH (Km approximately 40-45 microM) rather than NADH (Km approximately 2.5 mM) as the electron donor. The combination of beta and gamma fractions displayed additive activity. The activatable oxidase required Mg2+ but not Ca2+. ATP was required for maximum reaction rates. When beta and gamma membranes were preincubated with cytosol and arachidonic acid in the presence of millimolar Mg2+ and then ultracentrifuged membrane-bound O2-. -forming activity was recovered in the pellet and the enzyme required only NADPH (i.e. no cytosol, arachidonic acid, or Mg2+) for expression of activity. These data suggest that cytosol contains a Mg2+-dependent oxidase-activating factor. Molecular sieve chromatography of cytosol indicated a single peak of activity (i.e. ability to activate O2-. generation by beta and/or gamma fraction) eluting with molecules of about 10,000 daltons.

Arachidonic Acid↗
PubMed1987

Lymphokines and platelets promote human monocyte adherence to fibrinogen and fibronectin in vitro.

Monocytes must accumulate in areas of tissue injury and inflammation to effect phagocytosis, antigen presentation, and monokine production. Fibrinogen/fibronectin matrices have been demonstrated in healing wounds and in delayed-type hypersensitivity skin reactions. We have developed an in vitro system for investigation of the ability of fibrinogen and fibronectin matrices to serve as substrata for human peripheral blood monocyte adherence. Monocyte adherence was greatest on matrices of both fibrinogen and fibronectin, less to fibrinogen alone, and least to fibronectin alone. Lymphokines increased adherence of monocytes to all three surfaces but not to albumin-coated surfaces. Addition of platelets also caused a dose-dependent increase in monocyte adherence to all three surfaces. This increased adherence was not a simple function of arachidonic acid metabolites, stable platelet products, nor monocyte binding sites on the platelet membrane. The effect of platelets was not additive to the effect of lymphokines. We conclude that fibrinogen and fibronectin provide a framework for monocyte adherence and that factors present in areas of inflammation and wound healing, such as lymphokines and platelets, can augment this adherence. Such adherence facilitates the transformation of monocytes into macrophages in vitro and may also foster such transformation in vivo.

Blood Platelets↗