Impact of human influences on the vegetation of the Western Himalaya

Summary Effects of human influences on the vegetation of the Western Himalaya have been reviewed. Impacts of forest management practices, over-grazing, surface mining, defence and development operations, and road building activities, are severe in the region. This has created an alarming situation for soil and water conservation. Increased soil loss and runoff pose a threat to various reservoirs built for various uses and have increased hazards of erosion and floods in the Indus and Ganga basin regions.Nomenclature follows Hooker (1872–1897) and Gupta (1968).     

Secretion of proteoglycans by chondrocytes. Influence of colchicine, cytochalasin B, and beta-D-xyloside.

Chondrocytes obtained from epiphyseal cartilage of fetal guinea pigs or ear cartilage of young rabbits were cultured in monolayer. The influence of colchicine, cytochalasin B, and p-nitrophenyl-β-d-xylopyranoside on secretion of proteoglycans was investigated. Radioactive sulfate was used as a precursor. As observed previously in other systems, β-d-xylosides initiated the synthesis of free chondroitin sulfate chains, competing with the endogenous proteoglycan core protein acceptor. The molecular weights of the chondroitin sulfate chains synthesized both on the xyloside and on the core-protein acceptor in maximally stimulated cells were similar and significantly lower than in proteoglycans synthesized in the absence of xyloside. The size of the chondroitin sulfate chains synthesized on the xyloside was inversely related to the concentration of this compound. This finding suggests that the chain length is dependent on the ratio between available acceptor and chain-lengthening enzymes or precursors. Cytochalasin B, a microfilament-modifying agent, inhibited proteoglycan synthesis, without any effect on secretion. Cells treated with cytochalasin B could be stimulated with β-d-xyloside to synthesize free chondroitin sulfate chains to the same relative degree as cells with intact microfilaments. Colchicine, an antimicrotubular agent, partially inhibited synthesis and secretion of proteoglycan. However, cells treated with colchicine could be stimulated with β-d-xyloside to synthesize and secrete free chondroitin sulfate chains to about the same relative degree as cells with intact microtubules. The data suggest that microtubules may have a facilitatory rather than an obligatory role in the secretion of proteoglycans and that at least part of the effect of colchicine is located at or after the site of glycosaminoglycan synthesis.     

Preparation and spectroscopic characterization of molecular species of brain phosphatidylserines

This study describes the first preparation and spectroscopic characterization of naturally occurring phospholipids separated according to degree of unsaturation. Phosphatidylserines (PS) have been prepared from bovine brain and shown to be pure by extensive thin layer chromatographic analysis as well as by infrared spectroscopy and fatty acid analysis. The PS has been separated according to degree of unsaturation and prepared using AgNO3-impregnated silica gel H thin-layer chromatography. Fatty acid analysis of the two principal PS subfractions indicates that they are enriched in the molecular species 1-octadecanoyl-2-docosahexaenoyl-sn-glycero-3-phosphorylserine and 1-octadecanoyl-2-octadecenoyl-sn-glycero-3-phosphorylserine. The identity of the two PS subfractions was further verified by rechromatographing on several thin layer systems and by infrared spectroscopy. With the use of a 100 MHz Fourier transform nuclear magnetic resonance (NMR) spectrometer, the spectra of bovine whole brain, white matter, gray matter, monoenoic, and hexaenoic PS were obtained. Distinct proton resonances were assigned to double bond protons, protons adjacent to a double bond, and protons between two double bonds, using fatty acid methyl ester standards. The various PS preparations gave different intensities of the various proton resonances which correlated with differences in fatty acid composition. The method provides a convenient, non-destructive spectroscopic method for distinguishing monoenoic and polyunsaturated species of intact phospholipids. Electron spin resonance studies of nitroxide-labelled cholestane in sonicated PS vesicles showed greater probe motion as the unsaturation of the acyl chains was increased. The hexaenoic PS vesicles were more fluid than monoenoic PS vesicles at all temperatures in the range 10-55 degrees C. These results suggest that neuronal membranes are more fluid than myelin membranes as neuronal membranes contain more hexaenoic phospholipids.     

Investigation of the pH dependence of proton uptake by porcine heart mitochondrial malate dehydrogenase upon binding of NADH

The pH dependence of proton uptake upon binding of NADH to porcine heart mitochondrial malate dehydrogenase (l-malate: NAD⁺ oxidoreductase, EC 1.1.1.37) has been investigated. The enzyme has been shown to exhibit a pH-dependent uptake of protons upon binding NADH at pH values from 6.0 to 8.5. Enzyme in which one histidine residue has been modified per subunit by the reagent iodoacetamide (E. M. Gregory, M. S. Rohrbach, and J. H. Harrison, 1971, Biochim. Biophys. Acta253, 489–497) was used to establish that this specific histidine residue was responsible for the uptake of a proton upon binding of NADH to the native enzyme. It has also been established that while there is no enhancement of the nucleotide fluorescence upon addition of NADH to the iodoacetamide-modified enzyme, NADH is nevertheless binding to the modified enzyme with the same stoichiometry as with native enzyme. The data are discussed in relation to the involvement of the essential histidine residue in the catalytic mechanism of “histidine dehydrogenases” recently proposed by Lodola et al. (A. Lodola, D. M. Parker, R. Jeck, and J. J. Holbrook, 1978, Biochem. J.173, 597–605) and the catalytic mechanism of “malate dehydrogenases” recently proposed by L. H. Bernstein and J. Everse (1978, J. Biol. Chem.253, 8702–8707).     

Similarity between 5'- and 3'-terminal nucleotide sequences and double-stranded RNA-derived sequences of eukaryotic mRNA

It has been reported recently that parts of the nucleotide sequences present in the 5′- and 3′-terminal regions of cytoplasmic mRNA are derived from double-stranded hairpin structures of heterogeneous nuclear RNA—a putative mRNA precursor (Naora, 1979). In order to explore the nature of double-stranded hairpin structures, using the sequencing data of human and rabbit globin mRNA and hen ovalbumin mRNA, we examined the following possibility: that certain regions of both the 5′- and 3′-terminal nucleotide sequences of mature mRNA were present in double-stranded hairpin structures covalently linked to both sides of the message sequence in the precursor mRNA molecule and that these double-stranded hairpin structures are similar to each other. The results support the above possibility by showing substantial similarity of nucleotide sequences between the 5′- and 3′-terminal regions of these mRNAs in terms of the formation of similar double-stranded hairpin structures.     

Inhibition of rat mixed lymphocyte cultures by suppressor macrophages.

Normal rat spleens contain suppressor cells which can inhibit proliferative and cytotoxic responses of lymphocytes to alloantigens in vitro. The suppressor cells are adherent, phagocytic, resistant to treatment with ATS and C, radioresistant, resistant to treatment with mitomycin C, apparently absent from the thymus, and found in very high concentrations in peritoneal exudates. These characteristics indicate that the suppressor cell is a macrophages and not a T cell. When suppressor cells were removed from spleen cell suspensions, strong in vitro proliferative and cytotoxic responses to alloantigens could consistently be observed.     

Aphid transmission and a polypeptide are specified by a defined region of the cauliflower mosaic virus genome

Infection of young turnip leaves with an aphid-transmissible isolate, Cabb B-JI, of cauliflower mosaic virus (CaMV) causes synthesis of an Mr 18 000 polypeptide (p18) which co-purifies with virus inclusion bodies. This polypeptide is not detectable in leaves infected with either of two aphid non-transmissible isolates. Campbell and CM4-184. Construction in vitro, of hybrid genomes between Cabb B-JI and Campbell isolates demonstrates that aphid transmissibility and presence of p18 is dependent on the small genome fragment from the BstEII site to the XhoI site. A deletion made in this fragment within open reading frame (ORF) II causes loss of aphid transmissibility and also terminates production of p18. We conclude that aphid transmissibility and the presence of p18 are related to the expression of ORF II of the CaMV genome.     

Serratia marcescens chitinase: One-step purification and use for the determination of chitin

The extracellular chitinase produced by Serratia marcescens was obtained in highly purified form by adsorption-digestion on chitin. After gel electrophoresis in a nondenaturing system, the purified preparation exhibited two major protein bands that coincided with enzymatic activity. A study of the enzyme properties showed its suitability for the analysis of chitin. Thus, the chitinase exhibited excellent stability, a wide pH optimum, and linear kinetics over a much greater range than similar enzymes from other sources. The major product of chitin hydrolysis was chitobiose, which was slowly converted into free N-acetylglucosamine by traces of β-N-acetylglucosaminidase present in the purified preparation. The preparation was free from other polysaccharide hydrolases. Experiments with radiolabeled yeast cell walls showed that the chitinase was able to degrade wall chitin completely and specifically.     

Binding properties of 23S,25-dihydroxyvitamin D3: an in vivo metabolite of vitamin D3

23$\text{S}$,25-Dihydroxyvitamin D₃ was isolated from the plasma of vitamin D₃-toxic pigs. An ultraviolet absorbance spectrum confirmed its purity. The configuration of the 23-hydroxyl group was determined to be S by comparison of the natural product with synthetic 23$\text{R}$,25- and 23$\text{S}$,25-dihydroxyvitamin D₃ by high-pressure liquid chromatography. The affinity of both 23$\text{S}$,25- and 23$\text{R}$,25-dihydroxyvitamin D₃ for the plasma vitamin D binding protein was similar to vitamin D₃. Thus, with respect to the plasma vitamin D binding protein, 23$\text{S}$,25-dihydroxyvitamin D₃ is the least potent, naturally-occurring, dihydroxylated vitamin D₃ metabolite known.     

Monoclonal antibodies directed against the sugar sequence of lacto-N-fucopentaose III are obtained from mice immunized with human tumors

Four hybridomas obtained from mice immunized with human adenocarcinomas of colon or stomach produce antibodies that bind specifically in solid-phase radioimmunoassay to the ceramide pentasaccharide that contains the lacto-N-fucopentaose III sequence of sugars. Binding of the antibodies to the glycolipid is inhibited by lacto-N-fucopentaose III,

but not by structurally related oligosaccharides. The antibodies bind to glycolipids of erythrocytes, granulocytes, and certain normal and malignant tissues.