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Biomedical subjects

R E Morris

Publications and source records attributed to R E Morris.

287 records · Page 16Linked to original sources
PubMedDate not supplied

Inhibition of the activity of pseudomonas toxin by methylamine.

Methylamine at a concentration of 20 mM protected mouse LM cell fibroblasts from the action of pseudomonas toxin. Nearly total protection was observed when cells were pretreated with amine before the addition to toxin and amine, when amine and toxin were added simultaneously, or when amine was added up to 30 min after toxin binding. Later addition of methylamine afforded partial protection of the monolayers. Using electron microscopy, we observed that toxin initially bound diffusely to the cell surface but rapidly moved to coated pits and was internalized after cells were warmed to 37 C. Methylamine blocked the clustering of toxin into coated-pit areas of the membrane but did not alter the overall level of toxin internalization. It is suggested that pseudomonas toxin enters mammalian cells by receptor-mediated endocytosis and that methylamine alters the entry process. In those instances in which partial protection was seen when methylamine was added after toxin internalization, the primary amine may be functioning by inactivation of lysosomal processing of the toxin.

ADP Ribose Transferases↗
PubMedDate not supplied

Prevalence of isolated urethral asymptomatic Chlamydia trachomatis infection in the absence of cervical infection in incarcerated adolescent girls.

BACKGROUND AND OBJECTIVES: Adolescent girls may have isolated asymptomatic urethral Chlamydia trachomatis infection. GOAL OF THIS STUDY: To determine if a single direct fluorescent antibody (DFA) slide can detect as many urethral and cervical infections as the use of separate slides and to determine if isolated urethral infection occurs. STUDY DESIGN: During pelvic examinations upon admission, DFA slides were prepared from the cervix, from the urethra, and with cells from both sites. RESULTS: Of 125 girls, 17 had C. trachomatis infection: 4 in the urethra only (24%), 5 in the cervical sample only (31%), 5 in both sites (31%), 3 had positive results only on the combined slide, and 1 had a positive result on the cervical slide and an inadequate urethral slide. CONCLUSION: Isolated urethral C. trachomatis infection occurs frequently, and sampling both sites as opposed to sampling the cervix alone increases the number of cases found by 24% (P < 0.002). Using a single slide to detect infection in both sites detects as many infections as using two separate slides.

Adolescent↗
PubMedDate not supplied

Sustained food vacuole formation by axenic Paramecium tetraurelia and the inhibition of membrane recycling by Alcian Blue.

It is believed that the uptake mechanism of some nutrients by Paramecium tetraurelia primarily involves transport through the cell surface, whereas the uptake of other compounds appears to be restricted to bulk transport during food vacuole (phagosome) formation. In this study, we established that, in axenically grown cells, food vacuole formation occurred at continuous rates over long periods. This information allows quantitation of the volume of media taken up by bulk transport. India ink and latex beads were shown to be inert food vacuole markers and carmine was found to have an initial stimulatory effect on phagosome formation rates. Cultures grown for 3.5 h or longer with the glycocalyx stain Alcian Blue, contained only three phagosomes/cell, whereas cells cultured with the other markers contained 15 phagosomes/cell. Electron microscopy of fecal material that accumulated at the bottom of Alcian Blue-grown cells demonstrated the presence of membranes, suggesting that the vacuolar membrane was eliminated during defecation. Neither cell lysis nor the formation of autophagous vacuoles was detected in Alcian Blue-grown cells, indicating that the stain was not cytotoxic at the concentrations used. Thus it appeared that the binding of Alcian Blue to the digestive vacuole membrane resulted in a loss of the vacuole membranes from the cell which reduced the amount of membranes retrieved and recycled and hence eventually reduced the rate of phagosome formation. Alcian Blue-treated cultures exhibited decreased rate of growth and final density, which is consistent with a decrease in bulk transport of nutrients resulting from reduced membranes of digestive cycle organelles available in the cell.

Alcian Blue↗
PubMedDate not supplied

Zymolyase treatment exposes p55 antigen of Pneumocystis carinii.

Rats exposed to Pneumocystis carinii mount antibody responses to a broad band migrating on western blot with an apparent molecular weight of 45-55 kDa. One antigen within this band, designated p55, is uniformly recognized by P. carinii exposed rats. Although the gene encoding the p55 antigen had been previously cloned, the location of this antigen within the organism was unknown. Prior attempts to localize the protein were unsuccessful. A monospecific polyclonal antiserum raised against a carboxyl-terminal 15-oligomer peptide yielded specific reactivity with a single 55 kDa band on a western blot of P. carinii. Using this antiserum, little to no reactivity could be detected with P. carinii organisms by immunofluorescence assay (IFA). However, zymolyase treatment of P. carinii dramatically increased the intensity and proportion of organisms reactive by IFA. Zymolyase, an enzyme with beta-1,3 glucanase activity, has previously been shown to remove the electron dense outer layer of the P. carinii cell wall, exposing an electron lucent layer. Immunoelectron microscopy performed on zymolyase treated organisms showed the majority of labeling occurs within the cell wall.

Animals↗
PubMedDate not supplied

New small molecule immunosuppressants for transplantation: review of essential concepts.

More immunosuppressive drugs than ever have recently graduated from the laboratory to extensive clinical trials of their safety and efficacy in patients undergoing transplantation. Although none of these drugs is perfect, they control different forms of rejection in stringent animal models more effectively than other immunosuppressants; yet these novel molecules suppress the immune system far more specifically than steroids and regimens that cause lymphopenia. Cyclosporin G and IMM 125 (analogues of cyclosporine) and FK506 are the only drugs that selectively inhibit T-cell proliferation by blocking cytokine synthesis. The primary action of rapamycin and leflunomide appears to be an inhibition of the actions of cytokines and growth factors on T, B, and some nonimmune cells. T and B cells are more sensitive than nonimmune cells to the depletion of purines and pyrimidines caused by mizoribine, mycophenolic acid, and brequinar sodium. Nucleotide depletion causes interruption of DNA synthesis and glycosylation of adhesion molecules in immune cells. Further differentiation of T and B cells after proliferation into fully functional immune cells is inhibited by unknown mechanisms by brequinar and deoxyspergualin. On the basis of preclinical studies, these drugs may effectively suppress clinical rejection that is (1) acute (all drugs), (2) chronic (rapamycin, leflunomide, and mycophenolic acid), or (3) antibody-mediated (brequinar, deoxyspergualin, mycophenolic acid, and rapamycin). Some drugs (FK506, deoxyspergualin, mycophenolic acid, rapamycin, and leflunomide) may reverse acute rejection refractory to conventional immunosuppression. These new drugs not only block different biochemical steps that normally lead to fully functional T and B cells after stimulation by alloantigen, but their toxicity profiles also differ. Results from preclinical studies predict that use of selected combinations of these drugs in patients will be more effective, less nephrotoxic, less myelotoxic, and less broadly immunosuppressive than current regimens based on cyclosporine, T-cell depletion, steroids, and azathioprine ... at least, that's the idea! Or as former Vice President Dan Quayle said, "It's a question of whether we're going to go forward into the future, or past to the back."

Animals↗
PubMedDate not supplied

Mechanism of the antiproliferative action of leflunomide. A77 1726, the active metabolite of leflunomide, does not block T-cell receptor-mediated signal transduction but its antiproliferative effects are antagonized by pyrimidine nucleosides.

BACKGROUND: Leflunomide, a novel immunosuppressive drug, prolongs experimental graft survival effectively and has been well tolerated in patients with rheumatoid arthritis. A77 1726, the active metabolite of leflunomide, inhibits lymphocyte proliferation in vitro. This study was conducted in Jurkat T cells to investigate the effects of A77 1726 on signal transduction pathways initiated by ligands of the T-cell receptor CD3 complex and to evaluate the effects of A77 1726 on nucleotide biosynthesis. METHODS: Tritiated thymidine incorporation and cell counts quantitated cell proliferation. Spectrofluorescence of Indo/AM dye measured intracellular Ca2+ mobilization. A luciferase assay quantitated interleukin-2 gene promoter activity in stimulated cells transfected with an interleukin-2 promoter-luciferase gene construct. Pyrimidine and purine nucleosides were used to assess antagonism of the antiproliferative activity of A77 1726. RESULTS: (1) A77 1726 dose-dependently inhibited the proliferation of Jurkat T cells (inhibitory concentration of 50% = 6 mumol/L); (2) A77 1726 did not decrease mobilization of intracellular Ca2+ stimulated by phytohemagglutinin or anti-CD3 monoclonal antibody; (3) A77 1726 did not inhibit interleukin-2 gene promoter activity in cells stimulated with ionomycin plus phorbol myristate acetate; (4) inhibition of cell proliferation by A77 1726 was antagonized by addition of uridine, cytidine, or 2(+)-deoxycytidine; (5) addition of uridine 24 hours after treatment with A77 1726 antagonized inhibition of proliferation; (6) A77 1726 was not antagonized by 2'-deoxyuridine, thymidine, adenosine, or guanosine. CONCLUSIONS: (1) A77 1726 inhibited Jurkat T-cell proliferation without inhibiting T-cell receptor-mediated signal transduction events, including tyrosine kinase-dependent intracellular Ca2+ mobilization and activation of the interleukin-2 gene promoter; (2) the antiproliferative effects of A77 1726 on Jurkat T cells are primarily due to interruption of de novo pyrimidine nucleotide biosynthesis. These data provide evidence for a novel in vitro mechanism of the antiproliferative action of this immunosuppressant.

Aniline Compounds↗
PubMedDate not supplied

Leflunomide prolongs pulmonary allograft and xenograft survival.

BACKGROUND: Leflunomide, an isoxazole derivative, has been shown to effectively prolong rodent allograft and cardiac xenograft survival. In vitro studies suggest that leflunomide inhibits the production of donor-specific antibodies and is capable of blocking both T- and B-cell proliferation. In light of the significant role that humoral immunity is believed to play in chronic pulmonary allograft rejection as well as hyperacute and accelerated acute xenograft rejection, we examined the efficacy of leflunomide in prolonging pulmonary allografts and xenografts and its effect on donor-specific antibody production. METHODS: Lungs from Brown Norway rats or Golden Syrian hamsters were orthotopically transplanted into Lewis rat recipients. Allograft recipients were treated daily for 14 days with vehicle, leflunomide (15 mg/kg/day orally), or cyclosporine (7.5 mg/kg/day orally) starting on the day of grafting (day 0). In xenograft recipients, leflunomide (20 mg/kg/day orally) or cyclosporine (7.5 mg/kg/day orally) treatment initiated on day 0 was continued until complete graft rejection; the leflunomide dosage was reduced to 10 mg/kg/day after day 14 because of weight loss and leukopenia. Graft viability was assessed with chest radiography in conjunction with open lung biopsies. Toxicity was monitored with body weight measurements, complete blood counts, and serum chemistries. Flow cytometric analysis of serum samples taken from graft recipients on day 7 was used to measure donor-specific immunoglobulin M and immunoglobulin G antibody titers. RESULTS: Allograft and xenograft control animals receiving vehicle yielded graft survival times of 6.0 +/- 0.0 and 5.4 +/- 0.6 days, respectively. Although xenograft recipients treated with cyclosporine (7.5 mg/kg/day orally) showed no significant graft prolongation, pulmonary allograft survival in recipients receiving cyclosporine alone was significantly prolonged to 28.2 +/- 0.7 days. Leflunomide-treated allograft (15 mg/kg/day orally) and xenograft (20 mg/kg/day orally) recipients displayed significant graft prolongation to 28.2 +/- 0.7 days and 15.8 +/- 3.3 days, respectively. Cyclosporine (7.5 mg/kg/day orally) enhanced the effect of leflunomide (20 mg/kg/day orally) in xenograft recipients with a mean graft survival time of 36.0 +/- 3.0 days achieved when both drugs were administered concomitantly. Cyclosporine significantly suppressed donor-specific immunoglobulin G antibody titers in both pulmonary allograft and xenograft recipients while not affecting immunoglobulin M levels. Leflunomide markedly suppressed both immunoglobulin G and immunoglobulin M donor-specific antibody titers in allograft and xenograft recipients. Except for mild leukopenia and anemia, both cyclosporine- and leflunomide-treated allograft recipients showed no evidence of toxic side effects after 14 days of therapy. However, leflunomide-treated xenograft recipients displayed significant weight loss, anemia, and leukopenia after 14 days of treatment with one death in each treatment group.

Administration, Oral↗