Synthesis and deposition of chitin in larvae of the Australian sheep blowfly,Lucilia cuprina

Chitin synthesis in third-instar Lucilia cuprina larvae cultured at 23 °C was investigated using in vivo and in vitro systems, the latter with whole and with homogenized integuments. Synthesis was at a maximum between 24 and 48h after ecdysis from the second instar. Chitin was deposited in layers, and labeled GlcNAc was rapidly cleared from the hemolymph. In in vitro homogenate systems, the rapid conversion of UDP-([¹⁴C]GlcN)Ac to ([¹⁴C]GlcN)Ac and its 1-phosphate derivative contributed to the low incorporation of this precursor into chitin. The extent of the conversion was reduced by the addition of KCN or phenylthiourea. In in vivo and in vitro tissue systems the level of incorporation of ([¹⁴C]ClcN)Ac was higher than that of UDP-([¹⁴C]GlcN)Ac. However, in in vitro homogenate systems there was no difference unless UTP was added when the level of incorporation of only ([¹⁴C]GlcN)Ac was increased (by a factor of 9). Incorporation of UDP-([¹⁴C]GlcN)Ac, but not that of ([¹⁴C]GlcN)Ac, was decreased when larvae were deprived of food. Soluble oligosaccharides were detected in in vitro homogenate systems. They were formed during chitin synthesis and may represent newly initiated chitin chains. A reappraisal of current ideas on chitin synthesis in insects is needed.     

在高浓度1,4-丁二醇中酶促合成去B链C端六肽胰岛素

用含80％1,4-丁二醇的混合溶剂,以胰蛋白酶酶促,由去八肽胰岛素(DOI)合成了去六肽胰岛素(DHI),总产率为35％。1,4-丁二醇的溶解性能好,在浓度高达80—90％时不明显抑制酶活力,DOI的氨基无需保护,溶液中无高聚物或沉淀形成。     

Leucine biosynthesis in Alcaligenes eutrophus H16: Influence of amino acid additions on the formation of active α-isopropylmalate synthase and α-acetohydroxy acid synthase

The -isopropylmalate synthase of the chemolithoautotrophic Alcaligenes eutrophus H16 is apparently a soluble enzyme but is strongly adsorbed to cell particles in ruptured cell suspensions. This was not observed with -acetohydroxy acid synthase or threonine deaminase. The formation of these regulatory enzymes of the branched chain amino acid biosynthesis pathway generally decreased with decreased growth rates. The addition of 5 mM valine plus isoleucine with and without 5 mM threonine caused a 6.6- and a 4-fold increase, respectively, in the formation of active -isopropylmalate synthase, but caused a strong decrease in the -actohydroxy acid synthase. The level of active -isopropylmalate synthase is apparently regulated by the level of leucine; whereas, the level of the -acetohydroxy acid synthase and threonine deaminase is influenced by the presence of several amino acids. A catabolic threonine deaminase was not encountered.Abbreviations IRS -Isopropylamalate - AHA -acetohydroxy acid - TDA throninedeaminase This paper is dedicated to Professor H. G. Schlegel, University Göttingen, on the occasion of his 60th birthday. I am grateful to a great teacher and scientist, who in his unique way stimulated enthusiasm and fascination in microbiology in his students throughout the years     

Cytokinin-induced switch in development in excised cotyledons of radiata pine cultured in vitro

Cotyledons of Pinus radiata D. Don were cultured under shoot-forming (plus cytokinin) and elongating (minus cytokinin) conditions. Using. autoradiographic and precursor incorporation techniques, the sites and rate of macromolecular synthesis were examined during the first five days in culture. Active incorporation of ³H-thymidine, ³ H-uridine and ³H-leucine occurred. In shoot-forming cotyledons the incorporation became preferentially located in the epidermal and sub-epidermal cell layers in contact with the medium. In elongating cotyledons, in contrast, incorporation was randomly distributed, and the amount of incorporation declined with time. Biochemically, differences in DNA, RNA and total protein synthetic patterns were observed. In elongating cotyledons the rates of RNA and protein synthesis were higher during the first 48 h than in shoot-forming tissues, after which the synthetic rates were similar. Two peaks of newly formed DNA were observed in both tissues. These findings indicate that the cytokinin-induced changes in developmental pathways began within 24 h in culture.     

Insulin Binding in Four Regions of the Developing Rat Brain

Specific insulin binding has been demonstrated in partially purified membranes prepared from four regions of the developing rat brain. Insulin binding to brain membranes demonstrated kinetics and hormonal specificity that were quite similar to those reported for traditional insulin target tissues (e.g., liver and adipose tissue), and binding was significantly correlated with receptor concentration. Binding in the olfactory bulbs, cerebrum, cerebellum, and hypothalamus all reached highest values at 15 days of postnatal life, with the olfactory bulbs generally showing the greatest binding at all ages studied. A temporal relationship was found between insulin binding to brain membranes in the postnatal rat and plasma membrane protein synthesis, especially in the cerebellum and olfactory bulbs.     

Nematicides and Nonconventional Soil Amendments in the Management of Root-Knot Nematode on Cotton

Granular and liquid commercial humates, with micronutrients, and a microbial fermentation product were compared in several combinations with nematicides for their effects on cotton lint yield and root-knot nematode suppression. Fumigant nematicides effectively reduced cotton root galling caused by root-knot nematodes, and cotton lint yields increased. Organophosphates and carbamates were not effective. Occasionally, cotton lint yields were increased or maintained with combination treatments o f humates, micronutrients, and a microbial fermentation product, but galling o f cotton roots by root-knot nematodes was usually not reduced by these treatments.     

Characterization and Biosynthesis of Cyclic-AMP-Binding Proteins in the Rat Central Nervous System

Cyclic-AMP-binding proteins in membrane and soluble fractions from rat forebrain were compared; membrane fractions included smooth and rough microsomes and a plasma membrane fraction enriched in synaptic membranes. Protein fractions were treated with 8-azido-[32P]cyclic AMP and ultraviolet irradiation to covalently tag cyclic-AMP-binding proteins. Labeled proteins were then analyzed by two-dimensional gel electrophoresis (2DGE) and fluorography. The soluble CNS proteins contained two major cyclic-AMP-binding species at 48K (48K 5.5 and 48K 5.45), differing slightly in their isoelectric points. Another protein was seen at 54K (54K 5.3) adjacent to the beta-tubulin subunits in the 2D electrophoretogram. The analysis of the smooth microsome and plasma membrane fractions differed from the soluble fraction in that there were two cyclic-AMP-binding proteins adjacent to the beta-tubulin region (54K 5.3 and 52K 5.3) differing slightly in apparent molecular weight. The membrane fractions also contained a cyclic-AMP-binding protein at 54K 5.8. The 52K 5.3 and 54K 5.8 species were unique to the membrane fractions. The rough microsomes did not contain detectable amounts of cyclic-AMP-binding proteins. Free polysomes were isolated from brain tissue, and translation products were analyzed by cyclic AMP affinity chromatography and immunopurification with antibodies to the brain specific type II regulatory subunit. The translation products that were found to bind cyclic AMP Sepharose are as follows: 48K 5.5, 48K 5.45, 52K 5.3, and 54K 5.8. These species comigrated with proteins that were photoaffinity-labeled in cytosol and membrane fractions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phospholipid Biosynthesis in Myelin: Presence of CTP: Phosphoethanolamine Cytidylyltransferase in Purified Myelin of Rat Brain

Highly purified myelin from rat brain was previously shown to contain the ethanolaminephosphotransferase which completes the synthesis of phosphatidyl ethanolamine. We have now obtained evidence for the presence in myelin of CTP:phosphoethanolamine cytidylyltransferase, the enzyme catalyzing formation of CDP-ethanolamine. Myelin was isolated by two different procedures, one based on the Norton-Poduslo method and the other involving repetitive gradients with osmotic shocking deferred to the end. The fact that activity remained constant through all but the earliest steps suggested that the enzyme is intrinsic to myelin. Comparison of subcellular fractions revealed that approximately half the total activity was in the supernatant, the remainder being distributed among the particulate fractions. Relative specific activity of myelin was 27-31% that of microsomes, thus eliminating the possibility of appreciable contamination by the latter. The possibility of adsorption of the soluble enzyme by myelin was rendered unlikely by retention of activity after washing the myelin with buffered sodium chloride or sodium taurocholate. Furthermore, relative specific activity of the cytidylyltransferase was 10-fold higher than that of lactate dehydrogenase (a cytosolic marker) in myelin. The apparent Km for CTP was approximately the same for myelin and microsomes, but that for phosphoethanolamine was significantly higher for myelin.     

Releaser and primer pheromones in Collembola

In Collembola, pheromones appear to be present in the faecal pellets. Pheromone release after cessation of faeces production points to the digestive tract as a possible site of biosynthesis.During the pre-moulting periods Collembola do not react to pheromones, possibly due to their low activity at that time, whereas the production of the pheromones continues.Starvation periods of up to 14 days diminish pheromone release but do not cause complete cessation. Production per animal seems to decrease at increasing densities.The effect of pheromones on the reproductive efficiency of Collembola is discussed in the context of their physiological and behavioural ecology.     

Patterns of protein synthesis during the germination of pea axes,and the effects of an interrupting desiccation period

As germination of axes of Pisum sativum L. seeds progressed, profound quantitative and qualitative changes occurred in the patterns of protein synthesis. This was shown by fluorography of gels following two-dimensional polyacrylamide gel electrophoresis separation of [³⁵S]methioninelabelled proteins. The effects of desiccation during germination on these in-vivo protein-synthesis patterns were followed. Desiccation differentially affected the synthesis of proteins. Usually, however, upon rehydration following desiccation the types of proteins being synthesized were recognizable as those synthesized earlier during imbibition of control, once-imbibed axes: seeds imbibed for 8 h, and then dried, did not recommence synthesis of proteins typical of 8-h-imbibed control seeds, but rather of 4-h-imbibed control seeds. Seeds imbibed for 12 h, and then dried and rehydrated, synthesized proteins typical of 4-h-and 8-h-control seeds. Thus drying of germinating pea axes caused the proteinsynthesizing mechanism to revert to producing proteins typical of earlier stages of imbibition. Drying during germination never caused the seed to revert to the metabolic status of the initial mature dry state, however.Abbreviation DR dried and rehydrated