Prostaglandin D2 diminishes transmucosal potential difference in rat colonic mucosa in vitro in contrast to the increasing effect of prostaglandin E1

The effect of Prostaglandin D2 (PGD2) on ion transport was investigated in the rat colon in vitro. Ion transport across the intestinal mucosa was estimated by transmucosal potential difference (PD) and short circuit current (Isc) in the Ussing chamber. PGD2 added to the serosal reservoir induced a sustained reduction in PD and Isc at the concentration of higher than 10(-7)M, producing the maximal decrease at 10(-5)M. PGD2 at 10(-5)M completely blocked the increase in PD elicited by prostaglandin E1 (PGE1), theophylline, dibutyryl cAMP or serotonin. Adenylate cyclase activity was determined in the colonic mucosal homogenates after addition of PGD2 and PGE1. Treatment with PGD2 or PGE1 caused a significant increase in the enzyme activity. Combined treatment with both prostaglandins induced no more increase than that elicited by PGE1 alone. These results suggest that PGD2 has an anti-secretory effect on the rat colon and it may regulate the ion transport process through other mechanism than the modification of cyclic AMP concentration in mucosal cells.     

Natural cytotoxic cell-specific cytotoxic factor produced by IL-3-dependent basophilic/mast cells. Relationship to TNF

The murine IL-3-dependent mast cell line, PT18-A17, and the rat basophilic leukemia cell line, RBL-2H3, were found to mediate natural cytotoxic (NC) activity via the release of a soluble factor which specifically lysed NC-sensitive WEHI-164 but not NK-sensitive YAC-1 tumor cells. The release of this NC cell-specific cytotoxic factor was enhanced by triggering of both types of cells via IgE receptor bridging. This factor had activity on TNF-sensitive but not TNF-resistant cell lines and could be neutralized by two independently produced polyclonal anti-mouse TNF antisera. It was not neutralized by antibodies against mouse IFN-alpha/beta or IFN-gamma. Moreover, it was not neutralized by a monoclonal or a polyclonal anti-human TNF, demonstrating that the rodent TNF differed antigenically from human TNF. These results indicate that the cytotoxic factor released from a murine IL-3-dependent mast cell line and from a rat basophilic leukemia cell line is immunologically and functionally related to murine TNF.     

Chromosomal location of genes conditioning low amylose content of endosperm starches in rice,Oryza sativa L.

Summary Eight dull mutants that lower the amylose content of rice endosperm as well as waxy mutant and a cultivar with common grains were crossed in a diallele manner. The amylose content of F₁ and F₂ seeds was determined on the basis of single grain analysis. It was concluded that the low amylose content of dull mutants is under monogenic recessive control. Alleles for low amylose content are located at five loci designated as du-1, du-2, du-3, du-4 and du-5. These loci are independent of wx locus located on chromosome 6. The five du loci have an additive effect in lowering the amylose content. Two loci, du-1 and du-4, were found to be located on chromosomes 7 and 4, respectively.     

A radioenzymatic assay for quinolinic acid

A new and rapid method for the determination of the excitotoxic tryptophan metabolite quinolinic acid is based on its enzymatic conversion to nicotinic acid mononucleotide and, in a second step utilizing [3H]ATP, further to [3H] deamido-NAD. Specificity of the assay is assured by using a highly purified preparation of the specific quinolinic acid-catabolizing enzyme, quinolinic acid phosphoribosyltransferase, in the initial step. The limit of sensitivity was found to be 2.5 pmol of quinolinic acid, sufficient to conveniently determine quinolinic acid levels in small volumes of human urine and blood plasma.     

Accurate assay of dopa decarboxylase by preventing nonenzymatic decarboxylation of dopa

The nonenzymatic decarboxylation of dopa was completely blocked by both 2-mercaptoethanol and EDTA together over the wide range of pH. This finding made it possible to measure the activity of dopa decarboxylase precisely even at an alkaline pH value. The pH optimum of dopa decarboxylase was found to be pH 7.0 and the Km value for dopa was determined to be 4 X 10(-5) M.     

Changes in food intake and growth rate in mice under hypergravity.

Mice exposed to hypergravity, especially soon after start of exposure, diminished the body weight and the food intake. The amount of food intake was kept less than that of the ground control during hypergravity breeding for 2 weeks. Furthermore, the weight of testis relative to the body weight increased compared to that of 1 G control although the relative weights of liver and kidney were not changed. The purpose of this study was whether the low growth rate of the body weight and the increase of the relative testis weight were induced by the decrease of the food intake under hypergravity. We divided 3 weeks old male mice to 3 groups; the 1 G (ground control), the food restricted (FR) under 1 G, and the 3 G group. The 3 G group bred for 2 weeks under the centrifuge at 3 G. The FR group was given the same amount of food as the group ate. The changes in the body weight and the relative weights of testis, spleen and seminal vesicle of the FR group were similar to those of the 3 G group. The hunger test revealed that only the FR group was hunger. Our results suggested that the decrease of the food intake both in response to hypergravity and the food restriction induced the decrease of the body weight but the increase of the relative testis weight.     

Purification and characterization of rat dopamine beta-monooxygenase and monoclonal antibodies to the enzyme

Dopamine beta-monooxygenase was extensively purified from rat adrenal. The specific activity of the final preparation was approx. 1500 nmol/min per mg protein, which was much higher than the highest yet reported. As judged by gel filtration on Ultrogel AcA22, SDS-polyacrylamide gel electrophoresis, and cross-linking studies, the enzyme appeared to be composed of four identical subunits, each possessing a molecular weight of 88 000. The isoelectric point of the enzyme was estimated to be pH 6.6 in the presence of 8 M urea. Spleen cells from BALB/c mice immunized with rat dopamine beta-monooxygenase were fused to P3-X63-Ag8-653 mouse myeloma cells. From 55 hybrid cells, 10 stable clones secreting anti-dopamine beta-monooxygenase antibody were obtained. Antibody from one clone was coupled to CNBr-activated Sepharose 4B and the monoclonal antibody-Sepharose was shown to be very useful to isolate rat dopamine beta-monooxygenase from crude preparations.