Scanning electron microscope observation of the dog mesenteric lymph node

Summary The perfused large mesenteric lymph node of the dog was observed under the scanning electron microscope.The lymph sinus contains reticulum cells which mostly are two-dimensionally formed stellate plates oriented in a uniform direction. Large round macrophages are loosely fixed by the reticulum cell processes. No intermediate type between both cells has been observed. Macrophages having a few long tentacle-like projections are densely covered by clubbed cytoplasmic processes. Smaller round cells, probably plasma cells and lymphocytes also remained in the sinus.The pulp of the node is built up by reticulum cells, much smaller than those in the sinus, and by densely packed round cells including a few macrophages.The trabeculae and the reticulum of the nodal parenchyme form a continuous structure.Cordial thanks are expressed to Dr. Toshihiro Ishii, Professor of Anatomy of the Tohoku University Medical School, for his valuable advice. Thanks are also due to the kind cooperation of Mr. Akira Kubotsu of the Central Research Laboratories, Kuraray Co. Ltd.     

A new synthesis of purine arabinosides by a combination of chemical and enzymatic reaction

The synthesis of hypoxanthine, 2-chlorohypoxanthine, and 2-methylhypoxanthine arabinoside by an enzymatic transarabinosylation and their chemical conversion to biologically interesting purine arabinosides are described. Some of the synthesized compounds were tested for the inhibition of DNA synthesis in cultured tumor cells.     

Stereoselective Synthesis of threo-4,4,4-Trichlorothreonine

threo-4,4,4-Trichlorothreonine was synthesized completely stereoselectively through trans-4-alkoxycarbonyl-5-trichloromethyl-2-oxazoline, which was prepared almost quantitatively by the reaction of 2-isocyano acetate with chloral in the presence of an organic base. Several derivatives of these compounds were also synthesized.

Furthermore, the stereochemistry of the resulting trichlorocompounds was chemically elucidated. The trichlorothreonine was easily converted into threo-threonine by hydrogenation over Pd/C in the presence of NaHCO₈.     

Mechanical properties ofChlorella cell walls as determined by the suspension method

The so-called suspension method was employed to measure the mechanical properties ofChlorella cell walls. This method worked well for the present sample. The ratio of compressibility of the cell wall to that of water was 0.62 at room temperature at frequencies of 1.5 and 2.0 MH_z. Temperature dependence of compressibility was similar to that of many polymer samples. A difference of compressibility was observed at two different stages of the cell cycle ofChlorella, but any difference of volume viscosity was not as obvious. The more extensive the enlargement growth of the cell, the larger was the compressibility. The existence of a relaxation mechanism in the order of microseconds was postulated from measurements of the frequency dependence of the attenuation of sound waves.     

Muscarinic acetylcholine receptor (mAChR) inhibitor from snake venom: interaction with subtypes of human mAChR.

Snake venoms can contain a variety of well-studied neurotoxins, especially nicotinic acetylcholine receptor inhibitor, normally called postsynaptic neurotoxin. Karlsson first reported muscarinic acetylcholine receptor (mAChR) inhibitor from snake venom. In a previous study in our laboratory, we found a mAChR inhibitor from Naja naja sputatrix venom that bound to rat brain synaptosomes. Brain synaptosomes contain all subtypes of mAChRs, and thus the exact selectivity of the inhibitor could not be determined. mAChR inhibitor from N. naja sputatrix venom was purified and the binding to all human mAChR subtypes (M1, M2, M3, M4, and M5) was investigated and is reported in this communication. The inhibitor bound to all subtypes of the human mAChR, but showed considerably high selectivity for the M5 subtype. It was also found that the reduction of disulfide bonds in the inhibitor eliminated the binding to the mAChR. This suggests that a specific tertiary conformation maintained by disulfide bonds is essential for binding to the mAChR. An oligo peptide, QIHDNCYNE, comparable to a part of the inhibitor molecule, was synthesized and studied for its binding to the mAChR. The synthetic peptide did not show any binding activity, suggesting this portion of the inhibitor molecule is not involved in mAChR binding. The selective binding of the M5 mAChR subtype to antagonists has not yet been reported. Therefore, the purified inhibitor reported in this communication may be a useful tool to clarify the mechanism of muscarinic cholinergic transmission.     

Quantitative detection of DNA damage in the neuronal cells of the cerebellum and cerebrum by the analysis of Feulgen hydrolysis curves

Touch smears of the cerebellum and cerebrum of ageing rats were fixed with methanol, hydrolyzed with 2 N HCl at various temperatures and for various periods, and stained with pararosaniline-Schiff reagent. The hydrolysis curves were determined by fluorescence cytophotometry and were computer fitted to the Bateman function to determine the kinetic parameters, the initial yield of apurinic acid or single-stranded DNA (y0), and the rate constants for depurination or denaturation (k1) and depolymerization (k2). The values for k1 (1/k1 is correlated with the degree of chromatin condensation) and k2 (which reflects the degree of DNA instability) steadily increased with age. The values for y0, which may indicate the degree of DNA denaturation or damage present before acid hydrolysis, also increased with age in both the cerebellum and cerebrum; however, this value was lower in the cerebellum until 15 weeks, with the situation being reversed after 35 weeks, the cross-over time being at about 25 weeks. The values of lnk1 and lnk2 were plotted as the function of the reciprocal of the absolute temperature (T) (Arrhenius plot) for both the cerebellum and cerebrum of 15- and 74-week-old rats, and the activation energies (E) for depurination and depolymerization were calculated from the slopes. In particular, the values of E for k2 decreased much more quickly with age and were smaller in cerebellum. In conclusion, the degree of DNA damage and DNA instability steadily increases in both the cerebellum and cerebrum of ageing rats, and this process is much faster in the cerebellum.     

Mapping of the alpha-1,6-fucosyltransferase gene, FUT8, to human chromosome 14q24.3.

Alpha-1,6-Fucosyltransferase (alpha1,6FucT) is involved in the biosynthesis of asparagine-linked glycoprotein oligosaccharides. In this study, we isolated a genomic clone for the human alpha1,6FucT gene (FUT8) and mapped it by fluorescence in situ hybridization to chromosome 14q24.3. This study suggests a distinct localization of FUT8 from genes for other human fucosyltransferases reported to date.     

Immunosuppressive effects of the heat shock protein 90-binding antibiotic geldanamycin.

Ansamycin antibiotic, geldanamycin has a unique pharmacological effect to bind to heat shock protein 90 (hsp90) and deplete hsp90 substrates. We investigated the immunopharmacological effects of geldanamycin. Geldanamycin depleted cellular Raf-1 of rat splenic cells without affecting the steady state levels of hsp90 and downstream mitogen activated protein (MAP) kinases, ERK1 and ERK2. In parallel, it inhibited mitogen-induced nuclear factor-kappa B (NF-kappa B) activation in these cells. Geldanamycin also had a potent suppressive effect on recall antigen-induced T cell proliferation, with an IC50 value of 1 nM. In vivo, geldanamycin suppressed the progression of adjuvant-induced arthritis dose-dependently. These results suggest that geldanamycin exerts an immunosuppressive effect partly through destabilizing Raf-1, and raise a new strategy for the prevention of inflammatory diseases.     

Ecology and seasonal distribution of Vibrio parahaemolyticus in aquatic environments of a temperate region

Abstract An environmental survey was done to study the ecology and distribution of Vibrio parahaemolyticus in 5 selected stations in Okayama Prefecture, which included fresh, brackish, and marine aquatic environments. Water and plankton samples were collected monthly for quantitative and qualitative analyses during the period October, 1987 to October, 1989 for V. parahaemolyticus . The pathogen was not detected from fresh water environments. A seasonality of the organism was observed in brackish and marine environments where average salinity ranged between 0.39 and 1.28%.Plankton samples yielded higher densities of V. parahaemolyticus compared with water samples. By applying several enrichment techniques, the pathogen was detected quite frequently during the winter months in the environments with temperatures ranging between 10 and 14°C. The identification following conventional tests, by the API 20E system and by serological methods reveal that the API 20E system is satisfactory to identify V. parahaemolyticus and further confirms that the serological method could be a simpler and more rapid procedure for V. parahaemolyticus identification.