Fine-structural and immunohistochemical study of anterior pituitary cells of Snell dwarf mice

Summary Snell dwarf mice display remarkable retardation of growth after birth and are known to lack prolactin (PRL), thyroid stimulating hormone (TSH) and growth hormone (GH). The aim of this study was to determine the reason for these hormonal deficiencies. We examined the fine structure of the gland and its immunohistochemical staining pattern with respect to antisera raised against PRL, TSH, GH, adrenocorticotrophic hormone (ACTH) and luteinizing hormone (LH). The gland of control mice reacted immunohistochemically against all antisera used, whereas only ACTH-producing cells (ACTH cells) and LH-producing cells (LH cells) were distinguished in the dwarf mice. ACTH cells in dwarf mice varied in cell shape, although they were similar in size to those of controls. The distribution of secretory granules in the cytoplasm varied from cell to cell. LH cells in the dwarf mice showed immature features, having poorly developed rough endoplasmic reticulum and Golgi apparatus. The cells were about half the size of controls, and secretory granules were smaller. In dwarf mice, non-granulated cells were encountered in addition to granulated ACTH and LH cells. Some of them formed small clusters, characteristic cell junctions being found between the cells; they thus appeared to be follicular cells. The above results suggest that hormone deficiency in Snell dwarf mice is a result of a defect in the hormoneproducing cells in the gland.     

Scanning electron-microscopic studies on the three-dimensional structure of sarcoplasmic reticulum in the mammalian red,white and intermediate muscle fibers

Summary The three-dimensional structure of the sarcoplasmic reticulum (SR) in the red, white and intermediate striated muscle fibers of the extensor digitorum longus muscle of the rat was examined under a field-emission type scanning electron microscope after removal of cytoplasmic matrices by the osmium-DMSO-osmium procedure.In all three types of fibers, the terminal cisternae and transverse tubules form triads at the level of the A-I junction. Numerous slender sarcotubules, originating from the A-band side terminal cisternae, extend obliquely or longitudinally and form oval or irregular shaped networks of various sizes in front of the A-band, then become continuous with the tiny mesh (fenestrated collar) in front of the H-band. The A-and H-band SR appears as a single sheet of anastomotic tubules. Numerous sarcotubules, originating from the I-band side terminal cisternae, extend in threedimensional directions and form a multilayered network over the I-band and Z-line regions. At the I-band level, paired transversely oriented mitochondria partly embrace the myofibril. The I-band SR network is poorly developed in the narrow space between the paired mitochondria, but is well developed in places devoid of these mitochondria.The three-dimensional structure of the SR is basically the same in all three muscle fiber-types. However, the SR is sparse on the surface of mitochondria, so the mitochondria-rich red fiber has a much smaller total volume of SR than the mitochondria-poor white fiber. Moreover, the volume of SR of the intermediate fiber is intermediate between the two.     

Molecular characterization of mutant actin genes which induce heat-shock proteins in Drosophila flight muscles

Heat-shock proteins (hsps) are constitutively induced by the mutant actins in the Drosophila indirect flight muscles (IFM). We compared primary structures of the mutant actin genes (KM75 and HH5) which induce hsps and of the non-inducing alleles (KM129 and KM88). The KM75 actin has lost 20 amino acids at the C-terminus. The HH5 actin has only one amino acid substitution, from Gly-336 to Ser. In KM129, the C-terminal part of actin is replaced by novel amino acids. KM88 is a null allele, with an amber mutation early in the coding region of the mutated actin gene. Although all of the KM75, HH5 and KM129 actins have defects near the C-terminus, only hsp-inducing mutant actins cause enlargement of the IFM nuclei as well as a disruption of myofibrils even in the presence of two copies of the normal genes. We further consider the underlying mechanisms linking these features of the hsp-inducing alleles.     

Metabolism of exogenous galactosylceramide in the twitcher mouse brain

The in vivo metabolism of galactosylceramide (gal-cer) in normal mice and in twitcher mice, a model of human GLD, was examined following intracerebral administration of gal-cer containing [1-¹⁴C]stearic acid. In normal mice, gal-cer was hydrolyzed to ceramide within 6 hours and ceramide was hydrolyzed to sphingosine and fatty acid. Most of the released fatty acid was immediately incorporated into other lipids. About 75% of injected gal-cer was hydrolyzed 80 hours after the injection, while in the twitcher mouse, only 17% of gal-cer was hydrolyzed. These results show that degradation of gal-cer is impaired in the twitcher mouse brain, but contradict to the fact that there was no evidence of any accumulation of gal-cer in the brain. This discrepancy may be due to the different sorting routes of biosynthesized and exogenously-administered gal-cer in the mouse brain. Most of the biosynthesized gal-cer is incorporated into myelin, while the injected gal-cer is incorporated into lysosomes.     

Connexin43 Is Another Gap Junction Protein in the Peripheral Nervous System

Abstract: That many cells express more than one connexin (Cx) led us to examine whether Cxs other than Cx32 are expressed in the PNS. In addition to Cx32 mRNA, Cx43 and Cx26 mRNAs were detected in rat sciatic nerve by northern blot analysis. Cx43 mRNA, but not Cx26 mRNA, was expressed in both the primary Schwann cell culture and immortalized Schwann cell line (T93). The steady-state levels of the Cx43 mRNA in the primary Schwann cell culture increased 2.0-fold with 100 µ M forskolin, whereas that of P₀ increased 7.0-fold. Immunoreactivity to Cx43 was detected on western blots of cultured Schwann cells, T93 cells, and sciatic nerves but not on blots of PNS myelin. Immunohistochemical study using human peripheral nerves revealed that anti-Cx43 antibody stained cytoplasm around nucleus of Schwann cells but not myelin, confirming western blot results. Although P₀ expression was markedly decreased by crush injury of the sciatic nerves, Cx43 expression showed no apparent change. Developmental profiles showed that Cx43 expression in the sciatic nerve increased rapidly after birth, peaked at about postnatal day 6, and then decreased gradually to a low level. In adult rats, the Cx43 mRNA value was much lower than that of Cx32. These findings suggest that Cx43 is localized in Schwann cell bodies and that, compared with P₀, its expression is less influenced by axonal contact and cyclic AMP levels. The high expression on postnatal day 6 indicates that Cx43 may be related to PNS myelination. Cx43 is another gap junction, but its function appears to differ from that of Cx32, as judged by the differences in their localization and developmental profiles.     

Inhibition of the proliferation of cultured immortalized schwann cells by forskolin with a decreased basal level of diacylglycerol

The repetitive passages of a Schwann cell culture results in the appearance of immortalized cells. In order to investigate the direct effects of cyclic AMP (cAMP) on Schwann cell proliferation, we used the immortalized Schwann cells because the responses of a short-term Schwann cell culture to agents increasing the intracellular cAMP are more complicated and it does not seem that all of them are due to the direct effects of cAMP. By adding up to 200 M of forskolin, an adenylate cyclase activator, to the culture medium, Schwann cell proliferation was inhibited and the intracellular 1,2-diacylglycerol (DG) level was decreased in a dose-dependent manner to 44 and 53% of the control values, respectively. The protein phosphorylation activity in the cytosol from the cell treated with 100 M forskolin, assayed with myelin basic protein as the acceptor, decreased to 78% and this inhibition was then reversed by the addition of 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeable DG, to the assay mixture. The cell proliferation inhibited by forskolin was also restored by the addition of OAG. These data suggest that cAMP inhibits both the activity of protein kinase C (PKC) and consequently cell proliferation through suppression of intracellular DG level, an activator of PKC. Since the inositol 1,4,5-triphosphate level and the hydrolysis of phosphatidylcholine to DG and phosphorylcholine were not affected, forskolin therefore appears to suppress the de novo synthesis of DG.     

Comparison of production efficiency among field crops related to nitrogen nutrition and application

It has been generally considered that the low productivity of Leguminosae is caused by accumulation in the reproductive organs of a large amount of protein and lipid, since the biochemical costs of synthesizing these compounds is higher than that for carbohydrate. However, we report here on results which show that: the growth efficiencies (dry matter accumulated/ (dry matter accumulated + respiration)) of reproductive organs of Gramineae and Leguminosae were similar; the growth efficiency of rice in the vegetative stage was greater than that of soybean and field bean, regardless of nitrogen application rate; and when ¹⁴CO₂, ¹⁴C-sucrose or ¹⁴C-asparagine were introduced to the leaf at the maturation stage, respiratory loss of the introduced ¹⁴C was greater in soybean and field bean, especially in the light, than in rice. Thus, it is assumed that the low productivity in Leguminosae is caused by a larger respiratory loss under both dark and light condition in the shoot, and not in the reproductive organs.     

Effect of piperonyl butoxide and diphenylamine on lipid peroxidation in ozonated chloroplasts

Lipid peroxide (LPO) formation was remarkable when isolatedtobacco chloroplasts were bubbled with high concentrations ofozone, though the fatty acid composition and the fractionationpattern of glycolipids and phospholipids in the chloroplastlipids changed little after ozone fumigation of the leaves.Piperonyl butoxide (PB), a potent protectant against ozone injury,strongly inhibited LPO formation in ozonated chloroplasts. PBalso prevented ozone-induced decreases in the amounts of linolenicand linoleic acids in the chloroplast lipids. These resultssuggest that PB inhibition of LPO formation may be involvedin the protective mechanism against ozone phytotoxicity. However,the mode of PB action differed on some points from that of diphenylamine,which is an antioxidant and also effective against ozone injury.The mode of PB action is discussed. ¹ Present address: The Central Research Institute, Japan Tobacco& Salt Public Corporation, Umegaoka, Midori-ku, Yokohama227, Japan. (Received July 5, 1976; )     

Effects of heat treated cells of intestinal lactic acid bacteria in rats fed a deoxycholic acid diet

Effects of the administration of heat treated cells of intestinal lactic acid bacteria were examined in rats fed a deoxycholic acid (DCA) diet. Male Wistar rats were given a 0.25% DCA diet with or without the heat treated cells of Enterococcus faecalis AD 1001 (EFH-1) or Lactobacillus reuteri AD 0002 (LRH-2) for 4 weeks. Abnormal increases in serum GOT, GPT, UN and lipoproteins were observed in the rats fed the DCA diet. Furthermore, severe lesions in the kidney as well as in the liver were found in these rats. On the contrary, the increases in serum GOT, UN, VLDL and LDL were significantly suppressed, and markedly fewer lesions in the liver and the kidney were observed in the rats fed the DCA diet plus EFH-1 or LRH-2.