Role of neurogenic genes in establishment of follicle cell fate and oocyte polarity during oogenesis in Drosophila

Oogenesis in Drosophila involves specification of both germ cells and the surrounding somatic follicle cells, as well as the determination of oocyte polarity. We found that two neurogenic genes, Notch and Delta, are required in oogenesis. These genes encode membrane proteins with epidermal growth factor repeats and are essential in the decision of an embryonic ectodermal cell to take on the fate of neuroblast or epidermoblast. In oogenesis, mutation in either gene leads to an excess of posterior follicle cells, a cell fate change reminiscent of the hyperplasia of neuroblasts seen in neurogenic mutant embryos. Furthermore, the Notch mutation in somatic cells causes mislocalization of bicoid in the oocyte. These results suggest that the neurogenic genes Notch and Delta are involved in both follicle cell development and the establishment of anterior-posterior polarity in the oocyte.     

MuB protein allosterically activates strand transfer by the transposase of phage Mu.

The MuA and MuB proteins collaborate to mediate efficient transposition of the phage Mu genome into many DNA target sites. MuA (the transposase) carries out all the DNA cleavage and joining steps. MuB stimulates strand transfer by activating the MuA-donor DNA complex through direct protein-protein contact. The C-terminal domain of MuA is required for this MuA-MuB interaction. Activation of strand transfer occurs irrespective of whether MuB is bound to target DNA. When high levels of MuA generate a pool of free MuB (not bound to DNA) or when chemical modification of MuB impairs its ability to bind DNA, MuB still stimulates strand transfer. However, under these conditions, intramolecular target sites are used exclusively because of their close proximity to the MuA-MuB-donor DNA complex.     

Changes in soil microflora associated with control of Sclerotium Rolfsii by Furfuraldehyde

The efficacy of 2‐furfuraldehyde for control of Sclerotium rolfsii was studied in laboratory and greenhouse experiments. Mycelial growth of the fungus was reduced proportionally with concentrations of 0.1–0.5 ml furfuraldehyde l^‐1 agar medium, and viability of sclerotia diminished on exposure to 2‐furfuraldehyde vapours. Detectable populations of bacteria and fungi, including Trichoderma spp., were reduced significantly (9=0.05) when furfuraldehyde was added to the agar used for soil dilution plates of untreated soil. Repeated treatments of natural soil with the fumigant significantly increased populations of Trichoderma spp. and bacteria, but diminished numbers of actinomycetes. Increasing dosages applied to soil artificially infested with S. rolfsii caused a reduction of disease on lentil, Lens culinaris. Results indicate that the compound, when applied to field soil, changes the composition of soil microflora and has potential for integrated control of S. rolfsii.     

A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

Membrane transport proteins: implications of sequence comparisons.

Analyses of the sequences and structures of many transport proteins that differ in substrate specificity, direction of transport and mechanism of transport suggest that they form a family of related proteins. Their sequence similarities imply a common mechanism of action. This hypothesis provides an objective basis for examining their mechanisms of action and relationships to other transporters.     

Phorbol ester receptors in cerebral cortex of cats with GM1 gangliosidosis

The pathogenesis of neuronal dysfunction in the gangliosidoses is poorly understood. Studies of the feline gangliosidoses and in vitro experiments implicate ganglioside inhibition of protein kinase C (PKC) in the pathogenesis of these neurological diseases. Therefore, in the present study, the binding of [³H]phorbol-12, 13 dibutyrate was measured to determine the levels of PKC in cerebral cortex of cats with GM₁ gangliosidosis (mutant) and age matched normal siblings. This binding of ([³H]PDB) to cerebral cortex homogenates in both normal and mutant cats was highly specific. The specificity of receptors was ascertained also from displacement studies using nonradioactive phorbol ester analogues to displace [³H]PDB bound to its receptors. In both mutant and normal cat brain, phorbol 12, 13-dibutyrate (PDB), 4--phorbol 12,13-didecanoate (-PDA) and 4--phorbol 12,13-dibenzoate (-PDBz) were highly potent (approximately to same degree) and effective in displacing [³H]PDB. On the other hand, 4- phorbol 12,13-diacetate (-PDA) was a weak displacer and 4--phorbol did not displace the bound [³H]PDB in either normal or mutant brain. Scatchard analysis of the binding data indicated a homogenous single class of binding sites in normal and mutant brain (Normal: K_d=1.42×10^–7 M, B_max=8.40 pmoles/mg protein. Mutant: K_d=1.60×10^–7 M, B_max=10.00 pmoles/mg protein). Sphingosine inhibited the binding to approximately the same extent in normal and mutant cortex. These studies demonstrate the presence of highly specific, homogenous, single type phorbol ester receptors in cerebral cortex of cats with GM₁ gangliosidosis which are qualitatively and quantitatively similar to normal cat brain.     

DNA polymorphisms of the apolipoprotein AII and AI-CIII-AIV genes: a study in men selected for differences in high-density-lipoprotein cholesterol concentration.

We have investigated the frequencies of RFLPs of the apolipoprotein (apo) AII gene and of the apo AI-CIII-AIV gene cluster in 109 men, selected from a random sample of 1,910 men aged 45-59 years, to cover a wide range of plasma high-density-lipoprotein (HDL)-cholesterol concentration. There was no significant difference in apo AI or apo AII RFLP allele frequency between groups of individuals with high and low HDL-cholesterol concentration. However, the apo AI PstI RFLP showed an association with genetic variation determining the plasma concentration of apo AI in this sample. Genetic variation in the apo AI-CIII-AIV gene region, as defined by haplotypes, accounted for 16% of the phenotypic variance in the apo AI concentration and for 8% of the phenotypic variance in HDL-cholesterol concentration. There was no significant association between alleles of the apo AII MspI RFLP and genetic variation determining apo AII or HDL concentration. The data demonstrate that genetic variation in the apo AI-CIII-AIV gene cluster is involved in determining the serum concentration of apo AI in this sample of clinically well individuals.     

Dietary modulation of α-amylase activity in eight geographical strains of Sitophilus oryzae and Sitophilus zeamais

Rank transformation of specific activity values of -amylase across four strains of Sitophilus oryzae (L.) and four strains of S. zeamais Motschulsky indicates that levels of these predominant enzymes are highest in adults feeding on hulled barley or long-grain brown rice. Intermediate activity levels are found in weevils feeding on yellow corn (maize) and lowest levels are found in wheat-fed weevils. Although extracts prepared from barley contain inhibitory activity against two purified isoamylases from S. oryzae, levels of the naturally-occurring -amylase inhibitors against these two enzymes are about 2.2-fold and 6.1-fold, respectively, more concentrated in wheat. Ingestion of these amylase inhibitors and formation of an inactive enzyme:inhibitor complex with previously secreted amylase may account for the lower activity of amylase in weevils of both species feeding on wheat. Amylase levels across all strains feeding on a given diet are about 2-fold higher in S. oryzae than in S. zeamais. Significant differences in activity levels were also found between strains in both species. Since -amylase is a predominant digestive hydrolase in these species, the degree to which cereal diets affect amylase levels may indicate their suitability as potential hosts.

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Résumé La transformation de rang des valeur d'activité spécifique de l'-amylase de 4 souches de S. oryzae et de 4 souches de S. zeamais montre que les niveaux les plus élevés de ces enzymes prédominantes s'observent chez les adultes nourris d'orge mondé ou de riz brun á grains longs. Des niveaux intermédiaires d'activité ont été obtenus chez les insectes élevés sur maïs jaune, et les niveaux les plus faibles chez ceux élevés sur blé. Bien que les extraits préparés à partir d'orge présentent une activité inhibitrice de deux isoamylases purifiées de S. oryzae, les niveaux des inhibiteurs naturels -amylase de ces deux enzymes sont environ respectivement 2,2 et 6,1 fois plus concentrés dans le blé. L'ingestion de ces inhibiteurs d'amylase et la formation d'un complexe enzyme inactive/inhibiteur avec l'amylase secrétée antérieurement, peut rendre compte de la plus faible activité de l'amylase chez les charançons consommant du blé. Le niveau d'amylase de S. oryzae est 2 fois plus élevé que celui de S. zeamais pour toutes les souches élevées sur un régime donné. Des niveaux d'activité significativement différents ont été trouvés suivant les souches pour chacune des deux espèces. Puisque l'amylase est la principale hydrolase digestive de ces espèces, l'intensité de la modification des teneurs en amylase par la consommation de céréales peut indiquer leur adéquation comme hôtes potentiels.

     

Intramitochondrial factors controlling hepatic fatty acid oxidation at weaning in the rat

Fatty acid oxidation was studied in isolated liver mitochondria of rats during the suckling-weaning transition. The oxidation rate of oleyl-CoA and palmitoylcarnitine was reduced 2.5-fold in rats weaned on a high-carbohydrate diet compared to suckling rats, when acetyl-CoA produced by beta-oxidation was directed towards ketone-body synthesis. Weaning on a high-fat diet minimized this change. Channeling of acetyl-CoA towards citrate synthesis doubled the oxidation rate of both substrates in HC-weaned rats. Thus, in addition to changes in carnitine palmitoyltransferase I activity, the beta-hydroxymethylglutaryl-CoA synthase pathway is also involved in the decreased fatty acid oxidation at weaning. This was confirmed by measurement of beta-hydroxymethylglutaryl-CoA synthase pathway activity.     

A microfibril-generating factor from the cellulase of Trichoderma reesei

A combination of ionic strength reduction and diafiltration of Trichoderma reesei cellulate complex through a hollow fiber apparatus of 5000 molecular weight (MW) cutoff and subsequent passage of filtrate over a Spherogel-TSK 3000-SW column provided extracts that had the ability to generate microfibrils in filter paper and to disrupt filter paper and corn leaf tissue. Milligram quantities of material obtained from these extracts released small amounts of soluble carbohydrate from filter paper, required ferric iron for increased activity, and contained amino acids. Short fiber formation and disruption of filter paper during interaction with these extracts was enhanced by prior acid treatment and eliminated by prior base treatment. The amount of soluble carbohydrate hydrolyzed in 24 h from filter paper by whole cellulase complex was not changed by first disrupting the substrate with the extracts.