Experimental allergic encephalomyelitis-prophylactic and therapeutic treatment with the cyclooxygenase inhibitor piroxicam (Feldene)

Prophylactic administration of Piroxicam (Feldene), a reversible inhibitor of prostaglandin biosynthesis, significantly reduced the occurrence of paralytic signs and the amount of antibodies against myelin basic protein in the model of mild acute experimental allergic encephalomyelitis in the Lewis rat. Mononuclear infiltration of the central nervous system remained unaffected. A therapeutic intervention with piroxicam, however, increased paresis and CNS pathology. Immunohistochemical studies revealed an increased proportion of ED1-positive macrophages and monocytes in the infiltrates of the spinal cord in animals treated with piroxicam. Possible reasons for the different effects of the prophylactic and therapeutic treatment are discussed in the study.

Quantification of thioguanine-resistant lymphocytes from mice irradiated in vivo

Adult mice were Co-60 gamma irradiated, and 7 months later splenocytes were isolated, cultured in microwells, and the frequency of hprt-deficient mutants was determined by measuring the cloning efficiency in media with 6-thioguanine. The mutant frequency at 2, 4, and 6 Gy was 1.6 x 10(-5), 4.4 x 10(-5), and 12.7 x 10(-5), respectively. The frequency of spontaneous mutants was 2.5 x 10(-6). The effect of metabolic cooperation on the cloning efficiency of thioguanine-resistant T-cells in selective medium was evaluated in co-cultures with wild-type T-cells. We found that the growth of hprt-deficient T-cells is supported in the presence of thioguanine-inactivated wild-type splenocytes up to a cell density of 5 x 10(5) cells per well. When cell density was higher, cell growth was inhibited. Possibilities and limitations of cloned lymphocytes for the analysis of somatic mutations that occur in vivo are discussed.

Characterization of the IL-2-receptor on rheumatoid arthritis synovial fluid T cells

We studied the hypoproliferative response of synovial fluid (SF) T cells in rheumatoid arthritis (RA) using a mitogenic monoclonal antibody (MoAb) specific for the T-cell antigen receptor-associated CD3 complex. RASF T cells are defective in their proliferative response and in the induction of the Tac (p55) component of the IL-2-receptor (IL-2-R) when stimulated with anti-CD3 monoclonal antibody (MoAb). However, fresh RASF T cells bear demonstrable IL-2-R in cross-linking experiments which are not seen in unstimulated peripheral blood (PB). These receptors are functional since RASF T cells proliferate in response to recombinant IL-2 (rIL-2) better than fresh PB T cells from either normal or RA patients. Scatchard analysis indicates increased (4-fold) numbers of high affinity IL-2-R on (phytohaemagglutinin) PHA-activated RASF T cells as compared with comparably activated RAPB T cells. Phorbol myristate acetate (PMA) induces Tac antigen expression in RASF but does not lead to proliferation. The hyporesponsiveness of RASF T cells does not appear to result from lack of IL-2-R, lack of IL-2-R inducibility, or proliferative potential.

Protection against experimental allergic encephalomyelitis with complete Freund's adjuvant is unaffected by prostaglandin synthesis inhibition

Pretreatment with complete Freund's adjuvant blended with aluminium hydroxide (ALU-CFA) prevents the clinical as well as histological manifestation of experimental allergic encephalomyelitis (EAE) in Lewis rats. Suppression of prostaglandin biosynthesis with the cyclooxygenase inhibitor piroxicam (10 mg/kg body weight) from day 2 before to day 17 after EAE induction could not restore responsiveness in pretreated animals. In contrast piroxicam increased ALU-CFA-induced suppression of autoantibodies against myelin basic protein. In controls not pretreated with ALU-CFA, clinical signs of EAE were attenuated by piroxicam, whereas mononuclear infiltration of the brain remained unchanged. Therefore it is unlikely that prostaglandins exert an important function in the regulation of immune responses in this model of autoimmunity.

An experiment in surgical education--the first international exchange of residents. The letters of Halsted, Küttner, Heuer, and Landois

Dr William Halsted firmly believed that the young physician achieved greater surgical maturity by observing the practice of surgery in countries in addition to his own. To promote this belief, Halsted initiated the concept of exchanging residents between training programs in different lands. This article presents a review of that historic first international exchange of residents. This glimpse into the past is accomplished by presenting previously unpublished letters of Halsted; Hermann Küttner, director of a surgical clinic in Germany; George Heuer, a resident from The Johns Hopkins Hospital, Baltimore; and Felix Landois, a resident from Küttner's clinic.

Determination of G-values for single and double strand break induction in plasmid DNA using agarose gel electrophoresis and a curve-fitting procedure

Covalently closed circular double-stranded DNA (CC) of native plasmids was used to determine the yield of single strand breaks (ssb) and double strand breaks (dsb) as a consequence of X-irradiation. One ssb transforms DNA of the CC form to the nicked circular form (NC), whereas one dsb produced either directly or from random coincidence of single strand breaks transforms DNA of the CC as well as of the NC form to linear DNA molecules (LI form). Plasmids with more than one dsb are cleaved to linear fragments. DNA (30-800 micrograms/ml) was irradiated in air-saturated sodium phosphate buffer. The different forms of DNA were separated by gel electrophoresis and their amounts measured fluorometrically using ethidium bromide. Large linear DNA fragments with the same electrophoretic mobility as the LI form were considered by using a curve-fitting procedure. From the quantitative changes of each conformation D37 values of ssb and dsb were calculated as a function of the DNA concentration. Finally G-values were calculated by competition plots. The following yields were determined: Gssb 3.4 X 10E-8 molJ-1, and Gdsb 3.3 X 10E-10 molJ-1. Gdsb refers only to those dsb produced directly. Yields are related to strand breaks without further treatment by heat or alkali.