Isolation and physiological study of an amylolytic strain of Lactobacillus plantarum

Summary An amylolytic lactic acid bacterium identified as Lactobacillus plantarum was isolated from cassava roots (Manihot esculenta var. Ngansa) during reting. The amylolytic enzyme synthesized was an extracellular -amylase with an optimum pH of 5.0 and an optimum temperature of 55° C. Cultured on starch, the strain displayed a growth rate of 0.43 h^–1, a biomass yield of 0.19 g·g^–1 and a lactate yield of 0.81 g·g^–1. The growth kinetics were similar on starch and glucose. Sufficient enzyme was synthesized and starch hydrolysis was not a limiting factor for growth. Biosynthesis of the enzyme was observed when the glucose concentration was less than 6.7 g·l^–1 and reached up to 4 IU·ml^–1 at the end of the fermentation. Offprint requests to: M. Raimbault     

Fluoride inhibits agonist-induced formation of inositol phosphates in rat cortex

Sodium fluoride inhibited carbachol, 5-hydroxytryptamine and noradrenaline stimulated formation of inositol phosphates in rat cerebral cortex. For example, carbachol (1 mM) induced a 337% increase of inositol phosphates above basal in 30 min which was reduced to 69% in the presence of NaF (10 mM). The IC50 for NaF was approximately 1.5 mM and inhibition was mediated by a decrease in maxima of the carbachol dose response curve rather than a shift to the right. This inhibitory action was not mimicked by NaBr or NaI, or by agents which increase cAMP. Inhibition did not appear to result from a toxic action of NaF since it had no effect on the formation of inositol phosphates by high K+; moreover, in higher concentrations NaF stimulated phospholipase C activity. Since fluoride ions are known to activate G-proteins in the concentrations used in this study, these results may indicate the existence of a novel G-protein linked to receptor inhibition of phospholipase C.     

H2a-specific proteolysis as a unique probe in the analysis of the histone octamer

We have utilized the H2a-specific protease as a unique probe to investigate the nature of the interactions between the protein subunits which form the core histone octamer. Upon incubation in high ionic strength media this protease, normally found tightly associated with isolated calf thymus chromatin, releases the 15 COOH-terminal amino acids of histone H2a by specifically cleaving the H2a polypeptide between Val114 and Leu115, yielding cleaved H2a (cH2a) and a free pentadecapeptide (Eickbush, T. H., Watson, D. K., and Moudrianakis, E. N. (1976) Cell 9, 785-792). We find that removal of this pentadecapeptide results in a marked dissociation of the octamer into its H2a:H2b dimer and H3:H4 tetramer subunits. Reconstitution experiments indicate that cH2a is capable of forming a dimer with H2b, but this cH2a:H2b dimer has a substantially lower affinity for the H3:H4 tetramer than native H2a:H2b dimer. Kinetic studies of H2a cleavage in high ionic strength solutions demonstrate that H2a molecules in the octamer are relatively resistant to proteolytic attack compared to H2a molecules in the dimer. The extent of this resistance, in response to various experimental parameters, is directly correlated to the strength of interaction between the H2a:H2b dimer and H3:H4 tetramer subunits. These reconstitution and kinetic experiments suggest that the histone domains proximal to the H2a cleavage site have an important function in maintaining the association of the histone octamer subunits.     

Positional Distribution of Acyl and Alk-1-enyl Groups in Grey and White Matter Ethanolamine and Choline Phosphoglycerides of a Marsupial, the Koala (Phascolarctos cinereus)

The major phosphoglycerides in grey and white matter from the brain of the koala have been separated and examined. The major polyunsaturated fatty acids present in both the diacyl- and alk-1-enyl acylglycerophosphorylethanolamines from grey matter were 22:6 omega 3, 20:4 omega 6, and 22:4 omega 6. In both grey and white matter, 22:6 omega 3 and 20:4 omega 6 were concentrated in the 2-position of diacylglycerophosphorylethanolamines and 22:4 omega 6 in the 2-position of alk-1-enylacylglycerophosphorylethanolamines; polyunsaturated fatty acid levels were higher in diacylglycerophosphorylethanolamines. Ethanolamine phosphoglyceride fractions from grey matter were enriched in polyunsaturated fatty acids compared with those from white matter. The acyl groups 18:0, 18:1, and 16:0 and their alk-1-enyl analogues were prominent in grey and white matter ethanolamine phosphoglycerides; 18:1 was dominant in white matter alk-1-enylacylglycerophosphorylethanolamines. The plasmalogen composition of ethanolamine phosphoglycerides was 55% in grey matter and 76% in white matter. Choline phosphoglycerides contained negligible plasmalogen and low polyunsaturated fatty acid levels. Diacylglycerophosphorylcholine was characterized by high levels of 16:0 and 18:1. Similar acyl group distributions were estimated in the 1-position in both grey and white matter, 16:0 being present at greater than 50%. The presence of the molecular species 18:0/22:6 omega 3 was indicated in grey matter diacylglycerophosphorylethanolamine, 18:1/18:1 in white matter alk-1-enylcylglycerophosphorylethanolamine, and 16:0/18:1 in white matter diacylglycerophosphorylcholine.     

Immunosuppressive activity of uterine luminal protein from steroid-treated ovariectomized heifers

Uterine luminal protein (ULP) collected from ovariectomized steroid-treated crossbred heifers was tested for immunosuppressive activity in vitro. Heifers were allotted to treatment groups and for 16 d received daily injections of the following steroids or vehicle: Control (C, corn oil only, n=10); estradiol-17beta (E(2), 1.1 mug/kg body wt, n=10); progesterone (P(4), 2.2 mg/kg body wt, n=10); and E(2)+P(4) (1.1 mug + 2.2 mg/kg body wt, n=9). On Day 17, uterine flushings were collected, concentrated and quantitated for total ULP. ULP was tested for suppression of lymphocyte blastogenesis. For each experiment, 5 x 10(5) bovine lymphocytes were incubated with 0.4 mug of phytohemagglutinin (PHA) and ULP (25 to 400 mug ULP/ml) using standard culture conditions. At 48 h, 0.5 muCi of (3H) thymidine was added to cultures with cells harvested at 60 +/- 1 h by automation. Incorporated thymidine was measured by scintillation chromatography. Mean total ULP values for C-, E(2)-, P(4)- and E(2)+P(4)-treated groups were 4.7, 8.4, 13.6, and 25.5 mg, respectively (E(2)+P(4)>C and E(2), P<0.05). ULP from all treatment groups suppressed (P<0.0001) lymphocyte blastogenesis (thymidine incorporation) to PHA; however, suppression was greater (P<0.0001) for ULP from E(2)- and P(4)-than C-treated heifers at 100 and 200 mug ULP/ml. In conclusion, E(2) and P(4) injections enhanced immunosuppressive activity of ULP secretions.     

Purification and characterization of maize ribulose-1,5-bisphosphate carboxylase

The ribulose-1,5-bisphosphate carboxylase/oxygenase purified from maize (a C₄ monocot) to homogeneity has a MW of532 000 and sedimentation coeffici     

Ultrastructural identification of corticotropes of the fetal rat

Corticotropes of rat fetuses aged 16, 18 and 21 days were localized by the indirect antibody-enzyme method on semithin sections of the pituitary. The development of the ultrastructure of these cells was observed on consecutive ultrathin sections. In comparison with previous data our present results show that identification of a fetal cell type cannot be based entirely on morphological criteria. The structural peculiarities of corticotropes obtained from studies in vivo are compared with those observed in cells maintained in vitro.