Effects of diabetes on the expressed and total activities of 3-hydroxy-3-methylglutaryl-CoA reductase in rat liver in vivo. Reversal by insulin treatment.

The expressed and total activities of HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase (EC 1.1.1.34) were measured in microsomal fractions prepared from cold-clamped liver samples [Easom & Zammit (1984) Biochem. J. 220, 733-738] from control or insulin-treated diabetic animals. Streptozotocin-induced diabetes resulted in a marked decrease in total activity of HMG-CoA reductase and in the fraction of the enzyme in the active form, but appreciable effects were only observed in the liver of animals in which the blood glucose was above 20 mM. Intravenous infusion of insulin into diabetic rats resulted in a rapid (less than 20 min) and total dephosphorylation of the enzyme in vivo without any change in total activity. Longer-term (4 h) treatment with insulin (injected intraperitoneally) produced a rapid increase in expressed/total HMG-CoA reductase activity ratio to about 90%, followed, after a lag of 2-3 h, by a 5-6-fold increase in total activity. These observations are discussed with respect to the possible role of insulin in generating and maintaining the respective diurnal rhythms in total and in expressed/total HMG-CoA reductase activity ratio observed for normal animals in vivo [Easom & Zammit (1984) Biochem. J. 220, 739-745].     

Detoxification of ochratoxin A,a food contaminant: Prevention of growth of Aspergillus ochraceus and its production of ochratoxin A

The toxicity of ochratoxin A (OTA), a mycotoxin produced by fungi ofAspergillus orPenicillium genera is now well documented. Its nephrotoxicity, immunosuppression, teratogenicity, and carcinogenicity have been widely studied. Physical and biochemical methods have been studied to prevent these toxinogenicAspergillus andPenicillium from producing OTA, and/or to destroy the mycotoxin when already produced in a liquid or a solid medium. Repeated freezing at ? 20?C and thawing at + 26?C aleatory reduce OTA production in a liquid medium. Exposure to UV B for different periods of time is efficient in preventing OTA production in a liquid medium. Gamma-irradiation from 2 to 5 kGy gives good results in preventing the production of OTA or destroying it when already produced. Carboxypeptidase is very efficient at 5 units/50 ml in a liquid medium for cleaving the OTA already produced.     

Diurnal changes in the fraction of 3-hydroxy-3-methylglutaryl-CoA reductase in the active form in rat liver microsomal fractions.

'Initial' and 'total' activities of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) were measured in cold-clamped samples of liver from rats at 2h intervals throughout the 24h light/dark cycle. Initial activities were obtained in microsomes (microsomal fractions) isolated and assayed in the presence of 100mM-KF, whereas 'total' activities were measured in microsomes prepared from the same homogenates but washed free of KF and incubated with exogenous partially purified rat liver protein phosphatase. The initial/total-activity ratio for HMG-CoA reductase underwent a diurnal cycle, which had a nadir 4h into the light phase (when initial activity was 28% of total activity) and a peak 12h later, i.e. 4h into the dark phase (when initial activity was 80% of total activity). These low and high points of the cycle were separated by gradual steady changes in the ratio. The characteristics of this diurnal cycle were different from those of the cycle observed for total activity, which had a plateau of high activity between 2 and 10h into the dark cycle preceded and succeeded by a very rapid increase and decrease, respectively, in the total activity of HMG-CoA reductase. The combination of the two cycles resulted in the dampening of the resultant cycle for the initial or effective activity of HMG-CoA reductase, such that the changes in initial activity around the beginning and and end of the dark phase were more gradual than would otherwise have been the case if the initial/total-activity ratio for HMG-CoA reductase were constant throughout the diurnal cycle. The physiological implications of the observed diurnal variation in the fraction of hepatic HMG-CoA reductase in the active form are discussed.     

Evidence for a role of microfilaments in insulin release from purified beta-cells

To determine if the failure of purified beta-cells to secrete insulin in response to a glucose stimulus results from the absence of a cytoskeletal response, the effects of cytochalasins D and B on glucose-induced insulin release were investigated. Glucose alone failed to stimulate insulin release whereas glucose in the presence of glucagon, theophylline, cytochalasin D or B markedly potentiated insulin release. Cytochalasin D potentiated insulin secretion in a dose-dependent manner, and the combination of theophylline and cytochalasin D resulted in an insulin secretory response no greater than that produced by either agent alone. Both glucagon and theophylline are believed to mediate their effects via cAMP, however, cytochalasin D did not affect beta-cell cAMP levels. These results suggest that the inability of purified beta-cells to release insulin may result from the absence of the necessary modulation of the state of the microfilaments.     

The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

Ca2+-dependent dephosphorylation of kinesin heavy chain on beta-granules in pancreatic beta-cells. Implications for regulated beta-granule transport and insulin exocytosis

The specific biochemical steps required for glucose-regulated insulin exocytosis from beta-cells are not well defined. Elevation of glucose leads to increases in cytosolic [Ca2+]i and biphasic release of insulin from both a readily releasable and a storage pool of beta-granules. The effect of elevated [Ca2+]i on phosphorylation of isolated beta-granule membrane proteins was evaluated, and the phosphorylation of four proteins was found to be altered by [Ca2+]i. One (a 18/20-kDa doublet) was a Ca2+-dependent increase in phosphorylation, and, surprisingly, three others (138, 42, and 36 kDa) were Ca2+-dependent dephosphorylations. The 138-kDa beta-granule phosphoprotein was found to be kinesin heavy chain (KHC). At low levels of [Ca2+]i KHC was phosphorylated by casein kinase 2, but KHC was rapidly dephosphorylated by protein phosphatase 2B beta (PP2Bbeta) as [Ca2+]i increased. Inhibitors of PP2B specifically reduced the second, microtubule-dependent, phase of insulin secretion, suggesting that dephosphorylation of KHC was required for transport of beta-granules from the storage pool to replenish the readily releasable pool of beta-granules. This is distinct from synaptic vesicle exocytosis, because neurotransmitter release from synaptosomes did not require a Ca2+-dependent KHC dephosphorylation. These results suggest a novel mechanism for regulating KHC function and beta-granule transport in beta-cells that is mediated by casein kinase 2 and PP2B. They also implicate a novel regulatory role for PP2B/calcineurin in the control of insulin secretion downstream of a rise in [Ca2+]i.     

Nuclear gene trees and the phylogenetic relationships of the mangabeys (Primates: Papionini)

Phylogenetic relationships of mangabeys within the Old World monkey tribe Papionini are inferred from analyses of nuclear DNA sequences from five unlinked loci. The following conclusions are strongly supported, based on congruence among trees derived for the five separate gene regions: (1) mangabeys are polyphyletic within the Papionini; (2) Cercocebus is the sister taxon to the genus Mandrillus; and (3) Lophocebus belongs to a clade with Papio and Theropithecus, with Papio as its most likely sister taxon. Morphologically based phylogenies positing mangabey monophyly were evaluated by mapping the sequences for each locus on these trees. The data seem to fit these trees poorly in both maximum-parsimony and likelihood analyses. Incongruence among nuclear gene trees occurred in the interrelationships among Lophocebus, Papio, and Theropithecus. Several factors that may account for this incongruence are discussed, including sampling error, random lineage sorting, and introgression.      

Identification of genes involved in the mutualistic colonization of the nematode <Emphasis Type="Italic">Heterorhabditis bacteriophora</Emphasis> by the bacterium <Emphasis Type="Italic">Photorhabdus luminescens</Emphasis>

Background  

Photorhabdus are Gram negative entomopathogenic bacteria that also have a mutualistic association with nematodes from the family Heterorhabditis. An essential part of this symbiosis is the ability of the bacterium to colonize the gut of the freeliving form of the nematode called the infective juvenile (IJ). Although the colonization process (also called transmission) has been described phenomonologically very little is known about the underlying molecular mechanisms. Therefore, in this study, we were interested in identifying genes in Photorhabdus that are important for IJ colonization.     

Synthesis and structure-activity relationships of novel benzoxaboroles as a new class of antimalarial agents

A series of boron-containing benzoxaborole compounds was designed and synthesized for a structure-activity relationship investigation surrounding 7-(HOOCCH₂CH₂)-1,3-dihydro-1-hydroxy-2,1-benzoxaborole (1) with the goal of discovering a new antimalarial treatment. Compound 1 demonstrates the best potency (IC₅₀ = 26 nM) against Plasmodium falciparum and has good drug-like properties, with low molecular weight (206.00), low ClogP (0.86) and high water solubility (750 μg/mL at pH 7).     

Two human ULBP/RAET1 molecules with transmembrane regions are ligands for NKG2D

We characterized two novel members of the RAET1/ULBP gene cluster, RAET1E and RAET1G. The encoded proteins were similar to the ULBP in their class I-like alpha1 and alpha2 domains, but differed in that, instead of being GPI-anchored, their sequences were type 1 membrane-spanning molecules. Both proteins were capable of being expressed at the cell surface. Both proteins bound the activating receptor NKG2D, and RAET1G bound the human CMV protein UL16. The expression of diverse NKG2D-binding molecules in different tissues and with different properties is consistent with multiple modes of infection- or stress-induced activation.