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Biomedical subjects

D Gage

Publications and source records attributed to D Gage.

17 recordsLinked to original sources
PubMed1992

Peptidoglycan composition in heterogeneous Tn551 mutants of a methicillin-resistant Staphylococcus aureus strain.

It was shown that Tn551 inactivation of two chromosomal (so-called auxiliary) loci other than the mec gene result in a dramatic reduction of methicillin resistance and decreased cell wall turnover and autolytic capacity in a methicillin-resistant Staphylococcus aureus strain (de Jonge, B. L. M., de Lencastre, H., and Tomasz, A. (1990) J. Bacteriol. 173, 1105-1110). To understand the mechanistic basis of these phenomena we have examined the status of the autolytic enzymes and the muropeptide composition of peptidoglycan using reversed-phase high-performance liquid chromatography and mass spectral analyses. While no differences could be detected in the number of autolytic hydrolases, the mutants showed major changes in peptidoglycan composition. Nine prominent muropeptides of the parental strain each carrying a pentaglycyl substituent were missing from the cell wall of one group of mutants. The second mutant lacked four parental muropeptides which were composed of the unsubstituted disaccharide pentapeptide and its alanyl-tetraglycine derivative. The auxiliary genes are genetic determinants involved with the biosynthesis of peptidoglycan precursors, the presence of which in the cell wall may be needed for optimal cell wall turnover.

Amino Acid Sequence↗
PubMed1992

Peptidoglycan composition of a highly methicillin-resistant Staphylococcus aureus strain. The role of penicillin binding protein 2A.

All clinical isolates of methicillin-resistant Staphylococcus aureus contain an extra penicillin binding protein (PBP) 2A in addition to four PBPs present in all staphylococcal strains. This extra PBP is thought to be a transpeptidase essential for the continued cell wall synthesis and growth in the presence of beta-lactam antibiotics. As an approach of testing this hypothesis we compared the muropeptide composition of cell walls of a highly methicillin-resistant S. aureus strain containing PBP2A and its isogenic Tn551 derivative with reduced methicillin resistance, which contained no PBP2A because of the insertional inactivation of the PBP2A gene. Purified cell walls were hydrolyzed into muropeptides which were subsequently resolved by reversed-phase high-performance liquid chromatography and identified by chemical and mass spectrometric analysis. The peptidoglycan composition of the two strains were identical. Both peptidoglycans were highly cross-linked mainly through pentaglycine cross-bridges, although other, chemically distinct peptide cross-bridges were also present including mono-, tri-, and tetraglycine; alanine; and alanyl-tetraglycine. Our experiments provided no experimental data for a unique transpeptidase activity associated with PBP2A.

Amino Acid Sequence↗
PubMed1992

Gastric capacity, gastric emptying, and test-meal intake in normal and bulimic women.

The role of the stomach in regulating appetite in bulimia nervosa was examined. Subjects were nine normal and nine bulimic women of similar age, height, and weight. Gastric capacity was estimated by filling a balloon in the stomach. The mean stomach capacity of bulimic subjects was significantly larger than that of normal subjects, as revealed by the larger balloon volume tolerated (P less than 0.01) and by the larger volume needed to produce a 5 cm H2O increase in intragastric pressure (P = 0.07). The intake of a liquid meal was also significantly larger for the bulimic subjects. Gastric-emptying rate of a liquid meal was significantly delayed in the bulimic subjects during the initial 5-15 min. In all subjects, test-meal intake correlated significantly with gastric capacity (r = 0.53). In the bulimic subjects, self-reported binge intake (J) also correlated significantly with gastric capacity (r = 0.75). Binge eating in bulimic subjects may enlarge gastric capacity, which could then promote even larger binges through positive feedback.

Adult↗
PubMed1991

Coordinate regulation of beta-lactamase induction and peptidoglycan composition by the amp operon.

The amp operon, which is located on the Escherichia coli chromosome, modulates the induction of plasmid-borne beta-lactamase genes by extracellular beta-lactam antibiotics. This suggests that the gene products AmpD and AmpE may function in the transduction of external signals. beta-Lactam antibiotics are analogs of cell wall components that can be released during cell wall morphogenesis of enterobacteria. The amp operon was studied to determine its importance in signal transduction during cell wall morphogenesis. The peptidoglycan compositions of amp mutants were determined by high-performance liquid chromatography and fast atom bombardment mass spectrometry. When a chromosomal or plasmid-borne copy of ampD was present, the amount of pentapeptide-containing muropeptides in the cell wall increased upon addition of the cell wall constituent diaminopimelic acid to the growth medium. These results suggest that beta-lactamase induction and modulation of the composition of the cell wall share elements of a regulatory circuit that involves AmpD. Escherichia coli requires AmpD to respond to extracellular signaling amino acids, such as diaminopimelic acid, and this signal transduction system may regulate peptidoglycan composition in response to cell wall turnover products.

Amino Acid Sequence↗
PubMed1991

Clinical trial of silicone-rubber gastric balloon to treat obesity.

A study was conducted to test the efficacy and safety of a 300 ml silicone-rubber gastric balloon for weight reduction. Eighty-six obese subjects were distributed into four groups: (1) gastric balloon only, (2) gastric balloon and prescribed 1000 kcal/day (239 kJ) diet, (3) 1000 kcal/day diet only, and (4) no treatment. The intervention period was 3 months. The balloon only group lost 3.2 kg +/- 0.9 (s.e.), the balloon and diet group lost 5.1 +/- 1.0 kg, the diet group lost 6.9 +/- 1.4 kg and the control group gained 0.6 +/- 0.5 kg. The three intervention groups each lost significantly more weight than the control group. The diet only group lost significantly more weight than the balloon only group. Body densitometry showed that the treatment groups lost a significant amount of body fat. Gastroscopy revealed three ulcers and two superficial erosions at balloon removal. The gastric balloons were well tolerated despite gastric spasms and nausea which abated after the initial 24-48 hours. Gastric capacity was determined in a subset of 19 subjects from the two balloon groups before the intervention by distending the stomach with a balloon and calculating the volume required to produce an increase in intragastric pressure of 5 cm H2O. Subjects with a smaller gastric capacity lost more weight with the balloon than subjects with a large capacity (r = 0.45, P less than 0.05). These results suggest that for improved efficacy, balloon volume may need to be larger than 300 ml or adjusted to the individual's gastric capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Composition↗
PubMed1990

Gastric balloon to treat obesity: a double-blind study in nondieting subjects.

To determine its efficacy and safety in treating obesity, a silicone-rubber balloon was passed into the stomach of 10 nondieting, obese subjects. In a counterbalanced sequence, the balloon was inflated with 400 mL for 1 mo and deflated for 1 mo. Lower intakes of solid and liquid test meals (NS), significantly slower gastric emptying, and concomitant changes in glucose, insulin, glucagon, and cholecystokinin concentrations consistent with slower emptying resulted during balloon inflation. After balloon inflation, one small gastric ulcer developed, which subsequently healed. Significant weight loss occurred during the second and third week of the inflation period (F[1,9] = 5.0, p less than 0.05). However, the weight loss was small and the significant effect did not continue through the fourth week.

Adult↗
PubMed1989

Aberrant fatty acyl alpha-hydroxylation in human neuroblastoma tumor gangliosides.

Abnormalities of ganglioside structure characterize the neoplastic state, and aberrant glycosylation has been implicated as underlying many new tumor ganglioside structures. However, variations in ceramide structure can also result in novel tumor gangliosides. To address systematically this aspect of ganglioside metabolism, we have initiated a study of the structures of the ceramide species of an oligosaccharide-homogeneous human tumor-derived ganglioside, GM2. The ganglioside was isolated from neuroblastoma tissue and purified by normal-phase high pressure liquid chromatography. Marked ceramide heterogeneity was observed; 18 individual ceramide species of neuroblastoma GM2 were separated by reversed-phase high pressure liquid chromatography and collected. Their structures were determined by a combination of negative- and positive-ion fast atom bombardment mass spectrometry and collisionally activated dissociation tandem mass spectrometry of the underivatized gangliosides. The striking finding was the detection of alpha-hydroxylation of a significant fraction of each of the major fatty acid species (16:0, 18:0, 20:0, 22:0, and 24:1); alpha-hydroxylated species quantitatively represented almost one-fifth of the total tumor GM2 species. Fatty acyl hydroxylation was also detected in the ceramide of several other human tumor gangliosides. In contrast, as previously known, fatty acyl hydroxylation was not detected in the normal human brain gangliosides GM3, GM2, and GM1. We propose that aberrant fatty acid alpha-hydroxylation is a novel and sometimes quantitatively significant characteristic of human tumor ganglioside metabolism.

Ceramides↗
PubMed1989

Unusual composition of peptidoglycan in Bordetella pertussis.

The composition of the peptidoglycan of Bordetella pertussis and the nature of its turnover products was determined by a new combination of analytical techniques: high performance liquid chromatography of an enzymatic peptidoglycan hydrolysate and fast atom bombardment mass spectrometry and fast atom bombardment collision-activated dissociation tandem mass spectrometry. Sixteen major components of the peptidoglycan were purified, and assignment of complete or partial chemical structures was achieved for nine and seven species, respectively. At this level of resolution, a previously unrecognized heterogeneity of monomeric (five new species; nine total) and dimeric species (five new species; five total) was detected. No species containing diaminopimelyl-diaminopimelic acid cross-links or lysyl-arginine substitutions were found. Previous estimates of total cross-linkage and average chain length were revised downward to 32% and 21 disaccharide residues, respectively. Detection of a chemically novel species, a disaccharide octapeptide monomer, in both the peptidoglycan hydrolysate and culture supernatant fluid, suggests that an N-acetyl-muramyl-L-alanine amidase acts on the intact peptidoglycan of Bordetella and participates in cell wall turnover. Five peptidoglycan turnover products were identified in the supernatant fluid of late logarithmic phase cultures, including the 1,6-anhydro monomeric species known as tracheal cytotoxin. Peptidoglycan turnover was detected at a low rate of approximately 10%/generation, a value sufficient to account for the generation of all tracheal cytotoxin found in culture supernatant fluids.

Bordetella pertussis↗
PubMed1989

In vitro developmental toxicity of five direct-acting alkylating agents in rodent embryos: structure-activity patterns.

Five direct-acting alkylating agents were examined qualitatively and quantitatively for their ability to produce developmental toxicity in rodent postimplantation embryos. These agents were structurally related and were capable of donating either a methyl (methylnitrosourea, MNU; methylnitronitrosoguanidine, MNNG; methyl methanesulfonate, MMS) or ethyl (ethylnitrosourea, ENU; ethyl methanesulfonate, EMS) group to nucleophiles. These agents' reactivities were known to differ. In day 10 rat embryos in vitro a single, 2-hour exposure was shown to be sufficient to elicit dose-dependent increases in embryo lethality and malformations. Qualitatively, the patterns of embryo malformations reported in treated embryos paralleled those observed in in vivo studies, especially in regard to adverse effects on central nervous system and craniofacial systems. Quantitatively, the order of potency of these agents in vitro was: MNNG greater than MNU greater than ENU greater than MMS greater than EMS. In vivo studies reported a different order of potency. In vitro, methylating agents were consistently more potent than ethylating agents. Other chemical properties such as nucleophilic reactivity or half-life under physiological conditions could not explain observed potency relationships. Future investigation of other chemical properties of these agents such as specific alkylation and carbamylation reactivities may expand these initial structure-activity observations.

Alkylating Agents↗
PubMed1989

Fast atom bombardment mass spectrometry (FAB-MS): analysis of complex carbohydrate chains of tissue kallikreins.

Molecular ions and fragment ions of underivatized and permethylated oligosaccharides derived from human urinary kallikrein and some model glycoproteins gave information about the sugar composition and arrangement of sugars. These ions were conveniently created by FAB-MS in a JEOL JMS-HX110 high field high resolution mass spectrometer. Glycoprotein samples were digested with N-glycanase and the asparagine(Asn)-linked oligosaccharides were separated from polypeptides by Sephadex G-50 chromatography. The mixture of oligosaccharides was converted to the reduced p-aminobenzoic ethyl ester (ABEE) derivative and the components separated by HPLC on an ion-exchange (AX-10) column. Individual components were analyzed by negative FAB-MS using glycerol as a matrix. Permethylated oligosaccharides were also analyzed by positive FAB-MS.

Carbohydrate Conformation↗
PubMed1988

A comparison of the effects of buspirone and diazepam on plasma corticosterone levels in rat.

The effect of the anxiolytic agents, buspirone and diazepam, on the hypothalamic-pituitary-adrenal axis (HPAA), indicated by changes in the concentration of corticosterone (CS) in plasma, were studied 1/2, 1, 2, 4, 6, 8 and 24 hr after administration of the drug (i.p.). Samples of plasma were collected in the mid-morning (0930-1130 hr) when activity in the hypothalamic-pituitary-adrenal axis in the rat and control levels of corticosterone were low and were repeated in the afternoon (1400-1600 hr) when activity in the hypothalamic-pituitary-arenal axis and levels of corticosterone were higher. At small doses (1 mg/kg) buspirone had a greater facilitating effect on the hypothalamic-pituitary-adrenal axis than did diazepam. In addition, buspirone had a greater maximum facilitatory effect (477%) on levels of corticosterone than diazepam (345%). However, buspirone (ED50 = 8.6 mumol/kg) and diazepam (ED50 = 8.7 mumol/kg) were equipotent. Administration of 1 mg/kg of buspirone in the morning increased the combined 1/2 and 1 hr circulating levels of corticosterone 75% above control levels. Diazepam, at 1 mg/kg, did not produce any significant changes in levels of corticosterone. Large doses (10 mg/kg) of buspirone increased morning levels of corticosterone by 328% and diazepam increased levels of corticosterone by 265%. During the afternoon small doses of buspirone or diazepam did not significantly alter levels of corticosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Gastric distention by balloon and test-meal intake in obese and lean subjects.

A study was conducted to determine the effects of various levels of gastric distension on spontaneous meal intake. A balloon was inserted into the stomach of four lean and four obese subjects before consumption of a lunch meal. On different days the balloon was filled with 0, 200, 400, 600, and 800 mL water in a random sequence. As balloon volume increased, food intake decreased, with a balloon volume of greater than or equal to 400 mL significantly reducing intake (p less than 0.01). There was no significant difference between lean and obese subjects. Because gastric emptying rate was not significantly slowed by a volume of 800 mL, between emptying was probably not a factor in inducing satiety. Discomfort was probably also not a factor because it was experienced by only two lean subjects at 800 mL. Most likely gastric distension itself triggered satiety signals.

Adult↗
PubMed1987

Gastric balloon reduces food intake and body weight in obese rats.

A less invasive method than gastric reduction surgery for treating obesity was tested by inserting balloons into the stomachs of obese rats. Male Sprague-Dawley rats were placed on a high fat diet. After 4 months, the rats weighed an average of 750 g or 23% more than rats on a chow diet. Balloons were then passed orally into the stomach, inflated with 10 ml of water, and detached from the inflating tube. Eight rats had inflated balloons; six rats had no balloons. The balloons, which could be palpated, remained inflated for 12 to 49 days with a mean of 25 days. During the period of inflation, rats with balloons consumed significantly less food (p less than 0.001) relative to rats without balloons. Gastric emptying rate was significantly slowed (p less than 0.0025) in rats with inflated balloons compared to rats with balloons that had deflated and rats with no balloons. Histology of the stomachs that held inflated balloons did not reveal pathology.

Animals↗
PubMed1986

Intragastric balloon reduces food intake and body weight in rats.

To test a less invasive method than gastric surgery for treating obesity, balloons were nonsurgically inserted in the stomachs of adult rats (mean wt = 537 g) for 8 wk. One group received balloons that were inflated with 7 ml of water, a second group had balloons inserted that were deflated, and a third group had no balloons inserted. Rats with inflated balloons ingested 27% less food (P less than 0.0005) during the 8 wk and weighted 16% less (P less than 0.05) at the end of this period than rats with deflated balloons or no balloons. Their food intake was significantly depressed through the 7th wk. The stomachs of the rats with inflated balloons were significantly heavier than the others with a thicker muscularis externa. Body composition was not significantly different among groups. A chronic intragastric balloon significantly reduced food intake and body weight.

Animals↗
PubMed1972

Dextrothyroxine.

Explore the source record for details and available documents.

Alanine Transaminase↗
PubMedDate not supplied

The redox state and the phosphorylation state of the mannitol-specific carrier of the E. coli phosphoenolpyruvate-dependent phosphotransferase system.

This review summarizes the recent developments in identifying the activity-linked cysteine as one of the phosphorylation sites on the mannitol-specific EII of the E. coli phosphoenolpyruvate-dependent mannitol transport system. Two phosphorylation sites have been identified, one being the HPr/P-HPr exchange site, the other being the mannitol/mannitol-P exchange site. The activity-linked cysteine and the second phosphorylation site are located in the same 14 residue peptide. Phosphorylation of the second site and phosphoryl group transfer to mannitol do not occur as long as the activity-linked cysteine is oxidized or alkylated. A kinetic scheme has been developed which accounts for the relationships between the redox state, the phosphorylation state and the activity of the carrier. Kinetics of the individual reactions determine whether the enzyme cycles through an oxidized/reduced state during a cycle of phosphorylation/dephosphorylation.

Carrier Proteins↗