Location of O-acetyl groups in the acidic d-xylan of mimosa scabrella (bracatinga). A study of O-acetyl group migration

Extraction with dimethyl sulfoxide of wood-meal of the stem of bracatinga (Mimosa scabrella), a south Brazilian hardwood, that was defatted and delignified by treatment with aqueous chlorine at 0–5° followed by extraction with cold ethanol, gave a soluble O-acetylated 4-O-methyl-d-glucurono-d-xylan having (1→4)-linked β-d-xylopyranosyl residues that were unsubstituted (65%) and 2-O-(14%), 3-O- (16%), and 2,3-di-O-acetylated (5%), as determined by methylation analysis. Another preparation obtained by use of refluxing ethanol in the delignification process showed neither removal nor migration of acetyl groups. By comparison with synthetic, partly O-acetylated d-xylans of known composition, ¹³C-n.m.r. spectroscopy indicated that O-acetyl group migration does not occur during treatment with cold aqueous chlorine, refluxing ethanol, or water at 70°. Methyl 2-O-acetyl-4-O-methyl-β-d-xylopyranoside (6) was also unaffected by aqueous chlorine. O-Acetyl group migration took place more readily in aqueous and dimethyl sulfoxide solutions of 6 than of O-acetyl-d-xylans. The lowest temperatures at which migration was observed in monosaccharides was at 50 and 70° for solutions in D₂O and (CD₃)₂SO, respectively.     

Discrimination of distinct proteinases at the four structural levels of rat liver mitochondria.

Rat liver mitochondrial fractions corresponding to four morphological structures (matrix, inner membrane, intermembrane space and outer membrane) contain proteinases that cleave casein components at different rates. Proteinases of the intermembrane space preferentially cleave kappa-casein, whereas the proteinases of the outer membrane, inner membrane and matrix fractions degrade alpha S1-casein more rapidly. Electrophoretic separation of the degradation products of alpha S1-casein and kappa-casein in polyacrylamide gels shows that different polypeptides are produced when the substrate is degraded by the matrix, by both membranes and by the intermembrane-space fraction. Some of the degradation products resulting from incubation of the caseins with the mitochondrial fractions are probably the result of digestion by contaminating lysosomal proteinase(s). The matrix has a high peptidase activity, since glucagon, a small peptide, is very rapidly degraded by this fraction. These observations strongly suggest that distinct proteinases, with different specificities, are associated respectively with the intermembrane space and with both membrane fractions.     

Lipopolysaccharide core mutants of Salmonella typhimurium containing D-glycero-D-manno-heptose

Mutants resistant to several hydrophobic membrane antagonists were isolated from a "deep rough" (rfaC) mutant of Salmonella typhimurium. The resistance was due to an alteration in the core region lipopolysaccharide composition as evidenced by altered bacteriophage and complement sensitivity and by compositional analysis. The principal change in carbohydrate composition was the predominance of the unusual heptose isomer D-glycero-D-manno-heptose. The unusually wide pleiotropic phenotype of this organism is suggested to be due to a fundamental change in the properties of the bacterial outer membrane.     

Acid hydrolases in the perinuclear secretion granules of the rat preputial gland. A light and electron microscope study

Synopsis Four acid hydrolases in the secretory cells and the sebum of the preputial sebaceous gland of the rat were incestigated cytochemically. A strong -glucuronidase activity was found to occur in the matrix of the perinuclear secretion granules, whereas the granule crystalloids were unreactive. The distribution of acid phosphatase at the light microscope level was similar, though the intensity of the reaction was lower and the number of positive granules smaller. By electron microscopy, the final reaction product of acid phosphatase occurred in patches at the periphery of the granule matrix, as well as in the vesicles adjoining the Golgi stacks, from which the perinuclear granules seemed to arise. In the sebum, the two hydrolases occurred in the background material between the unstained crystalloid masses. There was noN-acetyl--glucosaminidase or aryl sulphatase activity in the gland. The perinuclear granules appear to be secretory lysosomes which, after discharge from the disaggregating cell, release their acid hydrolases into the sebum.     

An electron microscope autoradiographic study of DOC conversion to corticosterone in the rat adrenal cortex

Summary Seven thymuses from children between 1 and 12 years were examined by electron microscopy. Biopsies had been taken during surgical correction of congenital heart defects.In all cases we found interdigitating reticulum cells (IRC) in the medulla and inner cortex. These cells resembled the IRC which have been described previously in the thymus-dependent regions of the spleen and lymph node. They were characterized by an irregularly shaped nucleus, narrow cisterns of rough endoplasmic reticulum, and widespread interdigitation and invagination of the cell membrane. The surfaces of the IRC were in close contact with those of small lymphocytes, sometimes polysomal lymphatic cells, epithelial cells, and occasionally with those of lymphatic cells containing ergastoplasm.The IRC is apparently a specific cell of thymus-dependent regions. It may be that the IRC in the thymus, lymph node, and spleen contribute to the microenvironment needed for the differentiation of T-cells.Supported by the Deutsche Forschungsgemeinschaft, SFB 111/CII and III.—We wish to thank Miss M. Neubert and Mrs. R. Köpke for their technical assistance and Mrs. M. Soehring for her help with the translation.     

Inverse Diauxy in the Yeast Hansenula anomala: Mutants Derepressed for Malic Acid Utilization in the Presence of Glucose

Utilization of l-malic acid by yeast strain Hansenula anomala IGC 4380 is subject to glucose repression. Derepressed mutants were obtained with UV light by use of the nonmetabolizable glucose analog 2-deoxyglucose as a selective agent. Three mutant strains degraded l-malic acid in the presence of up to 30% (wt/vol) glucose and are of potential interest for the biological deacidification of grape must. The mutant strains, as compared with the parent strain, displayed inverse diauxy in glucose-malate medium, glucose being metabolized only after malate consumption had been completed.