Biomedical subjects
G Oliver
Publications and source records attributed to G Oliver.
Cycling, a manometric phenomenon due to repetitive episodes of gastroesophageal reflux and clearance.
We studied intraesophageal pressure changes in patients with symptoms of gastroesophageal reflux and an abnormal 24-hr pH monitoring record (N = 52). Our method was simultaneous esophageal manometry and pH monitoring. We observed a three-component esophageal manometric sequence (EMS). When this sequence recurred over and over, we termed this phenomenon "cycling." We found cycling in 35% of the patients (18/52). Those with cycling had lower basal LES pressures, more acid exposure, and an increased incidence of endoscopic esophagitis. That cycling resulted from repeated reflux events and their esophageal clearance was documented by scintigraphy during simultaneous manometry and pH monitoring (N = 7 patients). Cycling was found on the routine esophageal manometry record of 25% of symptomatic patients (N = 112) with an abnormal 24-hr pH score. In conclusion, cycling represents an esophageal manometric phenomenon due to repetitive reflux events. Its recognition during esophageal manometry may denote a severe reflux diathesis.
Presence of an L(+)-lactate dehydrogenase in cells of Lactobacillus delbrueckii ssp. bulgaricus.
Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842 was cultured in a chemostat and growth conditions were varied as required. Synthesis of L(+)-lactate was observed in all cases as well as activity of L(+)-lactate dehydrogenase in cell-free extracts. This enzyme was responsible for the formation of the L(+) isomer of lactate, since a lactate racemase was not present.
Vertebrate homeodomain proteins: families of region-specific transcription factors.
Vertebrate homeodomain proteins are transcription factors whose genes can be isolated via a conserved DNA-binding domain called the homeobox. We review recent studies suggesting that one function of these genes is the early subdivision of the embryo along the antero-posterior axis into 'fields' of cells with different developmental potential.
Complementary homeo protein gradients in developing limb buds.
A new human homeo box-containing gene designated Hox-5.2 was cloned and mapped to human chromosome 2. This homeo box is related in sequence to Abdominal-B, a Drosophila homeotic gene that specifies identity of posterior segments. An antibody probe was made using a human Hox-5.2 fusion protein and was found to stain posterior regions of mouse, chicken, and Xenopus embryos. Unexpectedly, when the distribution of Hox-5.2 antigen was compared with that of X1Hbox 1 antigen, a non-overlapping and mutually exclusive pattern was detected (e.g., in developing limb buds, intestine, and somites). Regions expressing Hox-5.2 do not express X1Hbox 1 protein, and vice versa. Hox-5.2 antigen is detected strongly in developing fore- and hindlimb buds, where it forms a gradient of nuclear protein throughout most of the mesenchyme. This gradient is maximal in distal and posterior regions. Hox-5.2 expression is activated in Xenopus limb regeneration blastemas, as expected for any gene involved in pattern formation. As described previously, a gradient of X1Hbox 1 protein can be detected in the forelimb. The latter gradient has the opposite polarity to that of Hox-5.2. i.e., maximal in anterior and proximal mesoderm. These two opposing gradients (and possibly others) could be involved in determining positional values in developing limb buds.
Superoxide dismutase activity in some strains of lactobacilli: induction by manganese.
Dialyzed cell-free extract of lactobacilli was found to contain superoxide dismutase activity by using a test system in which superoxide ion is generated by xanthine oxidase. The specific activities of Lactobacillus acidophilus ATCC 4356, Lactobacillus murinus ATCC 35020, Lactobacillus acidophilus CRL 358, Lactobacillus plantarum ATCC 8014, Lactobacillus casei CRL 431, Lactobacillus plantarum CRL 353, Lactobacillus fermentum ATCC 9338, Lactobacillus buchneri NCDO 110, and Lactobacillus fermentum CRL 251 were between 0.06 and 0.43 U/mg protein. The presence of superoxide dismutase activity was demonstrated when the strains were grown in media containing Mn2+ ions. Superoxide dismutase of lactobacilli may be an Mn enzyme since it was not inhibited by either cyanide or azide ions. However, the cell-free extract of Lactobacillus murinus ATCC 35020 contains superoxide dismutase activity sensitive to both ions.
Amino acid sequence analysis of the glutamate synthase enzyme from Escherichia coli K-12.
The amino acid sequence for the two subunits of the glutamate synthase of Escherichia coli K-12 was compared to the protein sequences compiled in the National Biomedical Research Foundation databank. Similarities were detected between the small glutamate synthase subunit and three members of the flavin-containing pyridine nucleotide-disulphide oxidoreductase superfamily, and also with three members of a lactate dehydrogenase family. Two segments in this glutamate synthase subunit showed similarity to regions previously proposed as part of dinucleotide-binding sites in some members of these two families. Similarity can be extended if the predicted secondary structure is considered. Based on these data, residues 148-260 and 289-409 in the small GOGAT subunit are proposed as dinucleotide-binding regions. Comparison of the amino acid sequence of the large glutamate synthase subunit with the glutamine phosphoribosylamine:pyrophosphate phosphoribosyltransferases of B. subtilis and E. coli revealed a significant similarity between the amino termini of these three enzymes. In these last two amidotransferases, the glutamine-binding site has been located in their amino-terminal region. The comparison with a second group of glutamine amidotransferases did not show any significant global similarity with the large glutamate synthase subunit. However, this polypeptide contains a small segment that shares similarity with a 13-amino acid segment proposed as part of the glutamine-binding site in this second group of amidotransferases.
Influence of Lactobacillus in the gastrointestinal tract.
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A gradient of homeodomain protein in developing forelimbs of Xenopus and mouse embryos.
The expression of the homeodomain protein XIHbox 1 in developing Xenopus limbs was analyzed using specific antibodies. In the forelimb bud mesoderm XIHbox 1 shows a clear antero-posterior gradient that is strongest in the anterior and proximal region of the forelimb. Hindlimb bud mesoderm is devoid of XIHbox 1, indicating an early molecular difference between arm and leg. The innermost ectodermal cell layer is positive throughout the forelimb and hindlimb bud ectoderm, but no other areas of the skin. Similar results are obtained in developing mouse limbs, suggesting that XIHbox 1 participates in forelimb development in a variety of tetrapods. In early tadpoles analyzed at stages preceding limb bud formation, the lateral plate mesoderm is positive in the region corresponding to the earliest "field" of forelimb information, but not in the hindlimb field. These results suggest a molecular link between morphogenetic fields, gradients, and homeobox genes in vertebrate development.
Fatty acid dependent hydrogen peroxide production in Lactobacillus.
Lactobacillus leichmanii growing in complex medium supplemented with decanoic acid accumulated high concentrations of hydrogen peroxide in the culture. The H2O2-generating system was specifically induced by one of the saturated fatty acids from 4:0 to 16:0 or oleic acid. The induction of this system was associated with the presence of a fatty acyl-CoA-dependent H2O2-generating activity in the cell-free extracts. This activity is shown for the first time in a procaryote organism.
Differential antero-posterior expression of two proteins encoded by a homeobox gene in Xenopus and mouse embryos.
The X.laevis XlHbox 1 gene uses two functional promoters to produce a short and a long protein, both containing the same homeodomain. In this report we use specific antibodies to localize both proteins in frog embryos. The antibodies also recognize the homologous proteins in mouse embryos. In both mammalian and amphibian embryos, expression of the long protein starts more posteriorly than that of the short protein. This difference in spatial expression applies to the nervous system, the segmented mesoderm and the internal organs. This suggests that each promoter from this gene has precisely restricted regions of expression along the anterior-posterior axis of the embryo. Because the long and short proteins share a common DNA-binding specificity but differ by an 82 amino acid domain, their differential distribution may have distinct developmental consequences.
Aspartate aminotransferase of Lactobacillus murinus.
Aspartate aminotransferase from Lactobacillus murinus is thermostable, its activity being not changed for two months at temperatures between 4 and -70 degrees C. Maximum activity was observed at 40 degrees C and pH 7.3 in phosphate buffer (30 mmol/L). delta G* Value of 26.3 kJ/mol was calculated from the Arrhenius plot. The Km values for L-aspartate and 2-oxoglutarate at pH 7.3 were 25 and 100 mmol/L, respectively. Sodium maleate and glutamate acted as inhibitors of the enzyme activity. The Ki values for sodium maleate with L-aspartate of 2-oxoglutarate as variable substrates were 1.1 and 0.5 mmol/L, respectively. The Ki values for glutamate with L-aspartate or 2-oxoglutarate were 8.0 and 4.0 mmol/L, respectively. An inhibitory effect was observed with 1 mM Hg2+ ions (1 mmol/L). The activity of the enzyme was diminished by only 12% in the absence of pyridoxal 5'-phosphate.
Malolactic enzyme in Lactobacillus murinus.
The malolactic enzyme of Lactobacillus murinus is inducible. The induction is produced by L-malic acid only in the presence of glucose and amino acids and occurs at the transcription level. The enzyme, purified to homogeneity, has a Mr of 220,000 and consists of 2 apparently identical subunits (Mr = 110,000) that were observed after treatment with sodium dodecyl sulphate. NAD+ protected the enzyme against inactivation and its addition, after dissociation, restored the malolactic activity. Maximum enzyme activity was observed at 37 degrees C and pH 5.5. At pH values substantially different from the optimum, a positive cooperativity between substrate molecules was observed. The activation energy of the reaction was 8,000 and 16,200 cal mol-1 for temperatures above and below 30 degrees C, respectively. Malolactic enzyme catalyzes the NAD+ and manganese-dependent reaction; L-malate----L-lactate + CO2. The stoichiometry of the reaction was confirmed. The malolactic transformation occurs by a compulsory-order mechanism. NAD+ bound first to the protein, independently of malate concentration. Mn2+ acts as an allosteric activator. Malate bound to the complex enzyme-NAD-Mn2+. Oxamate, fructose 1,6-diphosphate and malonate acted as non-competitive inhibitors, whereas citrate and L-tartrate produced a competitive inhibition. This enzyme can be distinguished from the malic enzyme of pigeon liver (E.C.1.1.1.40) and from the true malic enzymes (E.C.1.1.1.38 and E.C.1.1.1.39).
Arginine dihydrolase pathway in Lactobacillus buchneri: a review.
The arginine dihydrolase system was studied in homo- and hetero-fermentative lactic acid bacteria. This system is widely distributed in Betabacteria lactobacilli subgroup (group II in Bergey's Manual). It is generally absent in the Thermobacterium lactobacilli subgroup (group IA in Bergey's Manual) and also in the Streptobacterium subgroup (group IB in Bergey's Manual). It is present in some species of the genus Streptococcus (groups II, III and IV in Bergey's Manual). In Lactobacillus buchneri NCDO110 the 3 enzymes of the arginine dihydrolase pathway, arginine deiminase, ornithine transcarbamylase and carbamate kinase, were purified and characterized. Arginine deiminase was partially purified (68-fold); ornithine transcarbamylase was also partially purified (14-fold), while carbamate kinase was purified to homogeneity. The apparent molecular weight of the enzymes was 199,000, 162,000 and 97,000 for arginine deiminase, ornithine transcarbamylase and carbamate kinase respectively. For arginine deiminase, maximum enzymatic activity was observed at 50 degrees C and pH 6; for ornithine transcarbamylase it was observed at 35 degrees C and pH 8.5, and for carbamate kinase at 30 degrees C and pH 5.4. The activation energy of the reactions was determined. For arginine deiminase, delta G* values were: 8,700 cal mol-1 below 50 degrees C and 380 cal mol-1 above 50 degrees C; for ornithine transcarbamylase, the values were: 9,100 cal mol-1 below 35 degrees C and 4,300 cal mol-1 above 35 degrees C; for carbamate kinase, the activation energy was: 4,078 cal mol-1 for the reaction with Mn2+ and 3,059 cal mol-1 for the reaction with Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)
Cheese industry development and research in Argentina.
Research and development projects concerning cheese industry in Argentina are described in this study. Regional strains of lactic acid bacteria were isolated from different ecological pockets and their taxonomic profiles were determined. Proteolytic and acid activity as well as diacetyl production were analyzed. Results obtained depended on the species and strains under consideration. The cell permeabilization using 20 to 40% ethanol improved the acid production by lactic acid bacteria. Freeze-drying was used for culture preservation. The optimal conditions for obtaining the highest survival rate were determined. Best results were obtained by using 0.75 M adonitol as a cryoprotectant. The rehydration conditions to be used depended on the bacterial species. Freeze-dried cultures showed good viability and activity up to 1 year of storage at 4 degrees C.
Sequence conservations in vertebrate homeo-box mRNAs.
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Systemic augmentation of the immune response in mice by feeding fermented milks with Lactobacillus casei and Lactobacillus acidophilus.
This study investigates the effect of feeding fermented milks with Lactobacillus casei, Lactobacillus acidophilus and a mixture of both micro-organisms on the specific and non-specific host defence mechanisms in Swiss mice. Animals fed with fermented milk for 8 days (100 micrograms/day) showed an increase in both phagocytic and lymphocytic activity. This activation of the immune system began on the 3rd day, reached a maximum on the 5th, and decreased slightly on the 8th day of feeding. In the 8-day treated mice, boosted with a single dose (100 micrograms) on the 11th day, the immune response increased further. The feeding with fermented milk produced neither hepatomegaly nor splenomegaly. These results suggest that L. casei and L. acidophilus, associated with intestinal mucosae, can influence the level of activation of the immune system. The possible clinical application of fermented milks as immunopotentiators is also discussed.
Effect of cultivation conditions on proteinase production by Lactobacillus murinus.
Proteinase production by Lactobacillus murinus was influenced by temperature, glucose concentration, initial pH and nitrogen sources. Maximum proteinase production occurred at 45 degrees C, pH 6.6 and with 0.5% (W/V) glucose. Tryptone, peptone and gelatin inhibited it.