Glucagon receptors in endothelial and Kupffer cells of mouse liver

To determine whether hepatic sinusoidal cells contain glucagon receptors and, if so, to study the significance of the receptors in the cells, binding of [125I]-glucagon to nonparenchymal cells (mainly endothelial cells and Kupffer cells) isolated from mouse liver was examined by quantitative autoradiography and biochemical methods. Furthermore, the pathway of intracellular transport of colloidal gold-labeled glucagon (AuG) was examined in vivo. Autoradiographic and biochemical results demonstrated many glucagon receptors in both endothelial cells and Kupffer cells, and more receptors being present in endothelial cells than in Kupffer cells. In vivo, endothelial cells internalized AuG particles into coated vesicles via coated pits and transported the particles to endosomes, lysosomes, and abluminal plasma membrane. Therefore, receptor-mediated transcytosis of AuG occurs in endothelial cells. The number of particles present on the abluminal plasma membrane was constant if the amount of injected AuG increased. Therefore, the magnitude of receptor-mediated transcytosis of AuG appears to be regulated by endothelial cells. Kupffer cells internalized the ligand into cytoplasmic tubular structures via plasma membrane invaginations and transported the ligand exclusively to endosomes and lysosomes, suggesting that the ligand is degraded by Kupffer cells.     

Immunocytochemical localization of cathepsins B, H, and their endogenous inhibitor, cystatin beta, in islet endocrine cells of rat pancreas

To determine the characteristics of lysosomes in rat islet endocrine cells, we examined the precise localization of cathepsins B, H, and L and their specific inhibitors, cystatins alpha and beta, using immunocytochemical techniques. By use of serial semi-thin sections, we detected immunoreactivity for cathepsin B in insulin-, glucagon-, somatostatin-, and pancreatic polypeptide-positive (PP) cells. Strong immunoreactivity for cathepsin H was seen in A-cells and weak immunoreactivity in PP cells, but none in others. Immunodeposits for cystatin beta were demonstrated in B-cells. Brief dipping of thin sections in 1% sodium methoxide before the following immunocytochemical reaction enhanced specific deposits of immunogold particles on the target organelles. Use of a double-immunostaining technique showed co-localization of insulin with cystatin beta in many secretory granules. This suggests that cystatin beta may regulate converting enzymes participating in the maturation process of insulin. By use of an immunogold technique, heterogeneous localization of cathepsins B and H in lysosomes was also found among islet cells at the light microscopic level. This may be due to the difference in peptides degraded in lysosomes among the cells.     

Mutagenicity of 30 chemicals in Salmonella typhimurium strains possessing different nitroreductase or O-acetyltransferase activities

Salmonella typhimurium YG1021, YG1024, YG1026 and YG1029 are new derivatives of the Ames tester strains TA98 and TA100, with elevated 'classical' nitroreductase or acetyl-CoA:N-hydroxyarylamine O-acetyltransferase level. Thirty mutagens with different structures were tested using these strains and the sensitivities were compared with those of the conventional strains and of the enzyme-deficient strains. Elevated O-acetyltransferase activity of the indicator strains specifically increased their ability to detect the mutagenicity of aromatic nitro, amino and hydroxylamino compounds, whereas the strains with high nitroreductase activity were very sensitive to some nitroaromatics. The combined use of the isogenic tester strains with different metabolic capacities was quite useful to assess the intracellular metabolic activation and detoxification mechanisms of chemical mutagens.     

External characteristics and associated developmental changes in two species of Sulawesi macaques,Macaca tonkeana andM. hecki,with special reference to hybrids and the borderland between the species

The degree of intergradation between two species of Sulawesi macaques,Macaca tonkeana andM. hecki, was studied by examining the diagnostic external characteristics of more than 100 monkeys kept as pets by natives. Two possible hybrid monkeys were found and both originated from the borderland between the two species, located in the most proximal region of the northern peninsula of Sulawesi. The previously postulated wide area of integradation between the two species at the possible contact zone was, however, not recognized, and typical examples oftonkeana orhecki were found to be present on the two sides of a narrow “hybrid” zone which was defined by direct observations. Furthermore, despite considerable individual variations, we were able to allocate most monkeys to one or other of the species. Each of ten external characteristics of the members of both species more or less encompassed the individual variations, but may undergo changes with the development of the monkeys. The mechanisms of reproduction of hybrid monkeys and the maintenance of differences between the species are discussed.     

A novel MHC class I-related molecule expressed on mouse thymic stroma cells and mature lymphocytes

A monoclonal antibody (mAb) TP-3 has been established by immunizing rats with the BALB/c mouse thymic epithelial cell line TEL-2. The TP-3 antigen is expressed on stroma cells of thymus, spleen, and lymph node in syngeneic BALB/c mice (H-2 ^d ). This antigen is also expressed at a low level on the cell surface of immature thymocytes, and at a high level on mature T and B cells. In allogeneic mice such as C57BL/6 (H-2 ^b ) or C3H (H-2 ^k ), no cells expressed the TP-3 antigen. Using H-2 congenic mice, reactivity with mAb TP-3 was found to map to a region of H-2D ^d L ^d or between D ^d and Qa, suggesting that TP-3 is a major histocompatibility complex (MHC) class I antigen. However, immunoprecipitation analysis indicated that this antigen is not identical to the classical mouse class I molecules in terms of molecular size, antigenicity, and tissue distribution.     

Biosensor system for continuous flow determination of enzyme activities. II. Simultaneous determination of plural enzyme activities.

A biosensor system for continuous flow determination of plural enzyme activities was prepared from the combination of two pyruvate sensors, a prereactor and a flow cell. This system was applied to the simultaneous determination of lactic dehydrogenase (LDH) and glutamic-pyruvic transaminase (GPT) activities in the same sample. These enzyme activities can be determined by measuring pyruvate produced by the enzyme reactions as follows. The amount of pyruvic acid can also be determined from the amount of oxygen consumed upon oxidation of pyruvic acid by pyruvate oxidase. (Formula: see text). Therefore, both of the detectors for the determination of lactic dehydrogenase and glutamic-pyruvic transaminase activities were prepared from the combination of a pyruvate oxidase membrane and an oxygen electrode. Pyruvate oxidase was covalently immobilized on a membrane prepared from cellulose triacetate. A linear relation was obtained between the output current and LDH or GPT activities in the range of 50 to 3,600 IU l-1 or 6 to 1,000 IU l-1, respectively. Each assay of these enzyme activities was completed within 15 min. The results obtained had a precision of ca. 4%. The sensor was stable for more than 25 days at 5 degrees C.