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.     

(-) deprenyl induces activities of both superoxide dismutase and catalase but not of glutathione peroxidase in the striatum of young male rats

Daily s.c. injection of (-)deprenyl (2.0 mg/kg/day) for three weeks in young male rats caused a threefold increase in superoxide dismutase (SOD) activity in the striatum of the brain compared with the value in saline-injected control rats. Furthermore, the activity of catalase (but not of glutathione peroxidase) was also increased significantly by deprenyl treatment. The results confirmed the previous findings of Knoll on SOD activity and furthermore provided evidence that the activity of catalase is also significantly induced by the drug, which was not found in the previous study.     

Immunohistochemical localization of plasma retinolbinding protein and prealbumin in human pancreatic islets

Summary This study was undertaken, employing the immunoenzyme method, to confirm the presence of retinol-binding protein in human pancreatic islets, and to compare its distribution with that of prealbumin, insulin, glucagon, somatostatin and pancreatic polypeptide. It was found that most islet cells contained retinol-binding protein, although centrally located cells showed stronger reactivity than those in the peripheral region. The distribution of each of the five polypeptides differed from that of retinolbinding protein, indicating that these peptides did not cross-react with anti-retinol-binding protein antibody. Islet cells which contained prealbumin, on the other hand, were mostly classified as A cells. Further studies are necessary to confirm whether the islet cells produce retinol-binding protein or only store it.     

High and testosterone-dependent glucose 6-phosphatase activity in epithelium of mouse seminal vesicle

For study of the mechanism of seminal fructogenesis, glucose 6-phosphatase activity was examined cytochemically (a method modified from that of Wachstein and Meisel) and biochemically (the method of Leskes et al.) in seminal vesicles from normal, castrated, and castrated and testosterone-treated mice. The reaction product for the activity was localized in the endoplasmic reticulum and nuclear envelope of all cell types composing the seminal vesicle. In normal seminal vesicle, the reaction product was apparently more abundant in columnar and basal cells than in other cell types. Ten, 20, and 30 days after castration, the abundant amount of reaction product in columnar and basal cells decreased to the level in other cell types. In animals treated with testosterone after castration, however, the reaction product in columnar and basal cells remained abundant. If fructose 6-phosphate was added to the reaction medium in place of glucose 6-phosphate, the amount and pattern of deposition of the reaction product did not change. Changes in biochemical activity in castrated or castrated and testosterone-treated animals paralleled the cytochemical results. The results show that the high activity in columnar and basal cells is under the control of testosterone, and the role of this enzyme is probably to release fructose into the seminal fluid.     

Isolation and Sequencing of a Genomic Clone for Mouse Brain Specific Small RNA

We isolated a mouse genomic clone that hybridized with small RNA present in the cytoplasm of the brain. The RNA was about 150 nucleotides long. This RNA seemed to be specific to the brain, since it was not found in the liver or kidney. The clone DNA contained a sequence homologous to 82-nucleotide "identifier" core sequence of cDNA clones of rat. The sequence contained a split promoter for RNA polymerase III and was flanked by a 12-nucleotide direct repeat (ATAAATAATTTA).     

Ultrastructural studies on the effect of Triton WR-1339 on macrophage-mycobacteria interaction

Mycobacterium bovis (BCG organisms) suspended in saline or a 5% solution of a non-ionic detergent, Triton WR-1339, was injected intraperitoneally into mice. Electron-microscopic observation was carried out on peritoneal exudate cells harvested therefrom. Electron-lucent vacuoles limited by the membrane structure were found in macrophages of the mice injected with BCG suspended in the detergent, but not in polymorphonuclear leukocytes or lymphocytes. Mycobacterial cells were present within such vacuoles. Without the detergent, the ingested mycobacterial cells were in close contact with the phagosomal membrane. Within the electron-lucent vacuoles, however, such close contact was not present. These observations, together with other collateral findings, led us to a view that Triton WR-1339 may inhibit the interaction between mycobacteria and the phagosomal membrane by intervening between them thus making the progress of infection delayed.     

Differentiation of Photorespiratory Activity between Mesophyll and Bundle Sheath Cells of C4 Plants II. Peroxisomes of Panicum miliaceum L.

Peroxisomes were isolated by sucrose density gradient centrifugationfrom mesophyll and bundle sheath protoplasts of a C₄ plant,Panicum miliaceum L. The equilibrium density in the gradientwas 1.25 for bundle sheath peroxisomes and 1.23 for mesophyllperoxisomes, the former density being similar to that of peroxisomesof wheat mesophyll protoplasts. Photorespiratory and other microbody enzymes were assayed forthe peroxisomes of P. miliaceum to detect possible differentiationat an enzyme level. The specific activities of photorespiratoryenzymes, except for hydroxypyruvate reductase, in bundle sheathperoxisomes were 40–60% of those in wheat peroxisomes,when compared on a protein basis, and only 20–30% in mesophyllperoxisomes. However, peroxisomes from both cell types containedsignificant levels of all the enzymes involved in the photorespiratoryglycolate pathway, when compared with castor bean glyoxysomes.The activity of hydroxypyruvate reductase in the peroxisomesof P. miliaceum was comparable to or higher than that in wheatperoxisomes. Two ß-oxidation enzymes and urate oxidasewere detected in the peroxisomes in a similar level to thatin wheat peroxisomes. These results suggest that the peroxisomes of mesophyll andbundle sheath cells of P. miliaceum are essentially similarto those of C₃ plants, and that they cannot be differentiatedexcept for a difference in equilibrium density in a sucrosegradient. (Received December 24, 1984; Accepted April 9, 1985)     

Cytochemical glucose-6-phosphatase activity in the cells of mouse pancreas and submandibular gland

Ultrastructural localization of glucose-6-phosphatase activity was studied in the cells of the pancreas and submandibular gland of the mouse using a incubation medium modified from that of Wachstein & Meisel (1956). In pancreatic acinar cells, the reaction product for the enzyme activity was not found even after 90 min of incubation with three changes of the medium. However, the reaction product was localized in the endoplasmic reticulum and nuclear envelope of all other cell types composing the pancreas and submandibular gland. The reaction product appeared in moderate to abundant amounts in acinar cells and striated duct cells of the submandibular gland, and in the B cells, A and D cells of the pancreatic islet, but it was scarce in other cell types.     

Differentiation of Photorespiratory Activity between Mesophyll and Bundle Sheath Cells of C4 Plants I. Glycine Oxidation by Mitochondria

Mitochondria were isolated from mesophyll protoplasts and bundlesheath protoplasts or strands which were obtained by enzymaticdigestion of six C₄ species: Zea mays, Sorghum bicolor, Panicummiliaceum, Panicum capillare, Panicum maximum and Chloris gayana,representative of three C₄ types. Photorespiratory glycine oxidationand related enzyme activities of mesophyll and bundle sheathmitochondria were compared. Mesophyll mitochondria showed good P/O ratios with malate andsuccinate as substrate but lacked the ability to oxidize glycine.On the other hand, mitochondria isolated from bundle sheathprotoplasts of P. miliaceum and bundle sheath strands of Z.mays possessed glycine oxidation activity similar to that ofmitochondria from C₃ plant leaves. The two enzymes involvedin glycine metabolism in mitochondria, serine hydroxymethyltransferaseand glycine decarboxylase, were also assayed in the mitochondriaof the two cell types. The activities of the two enzymes inbundle sheath mitochondria were in the range found in C₃ mitochondria.In contrast, the activities in mesophyll mitochondria were eithernot detectable or far lower than those in bundle sheath mitochondriaand ascribed to contaminating bundle sheath mitochondria. The present results indicate the deficiency of a complete glycineoxidation system in mesophyll mitochondria and also a differentiationbetween mesophyll and bundle sheath cells of C₄ plants withrespect to the photorespiratory activities of the mitochondria. (Received June 8, 1983; Accepted August 29, 1983)