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Biomedical subjects

C Bryant

Publications and source records attributed to C Bryant.

At least 73 records · Page 4Linked to original sources
PubMed1986

Practical aspects of implementing increased dietary fiber intake.

Two hundred twenty dietitians participated in a workshop conference on Health Implications of Dietary Fiber. They were given lectures to increase their knowledge base, and then in group sessions answered questions and wrote concensus opinions. The results are the content of this paper. The topics covered and responses are reported in four categories, diabetes and obesity, hyperlipidemia, hypertension and coronary heart disease, gut function and gastrointestinal disease, and cancer. Specific recommendation for implementing high fiber diets are made in each category. However, the dietitians expressed caution on accepting all of the conclusions expressed in the literature on the value of fiber and believed much education and instruction is needed in order to increase dietary fiber intake.

Colonic Neoplasms↗
PubMed1985

Refolding a disulfide dimer of cytochrome c.

A covalent dimer of Saccharomyces cerevisiae iso-1 cytochrome c is stabilized by an interchain disulfide bond involving the cysteine residue penultimate to the C-terminus. The individual chains in the dimer appear to retain the tertiary structural features characteristic for monomeric cytochrome c albeit with some perturbation. The dimer is reversibly denatured by heat, urea, or guanidine hydrochloride in a single cooperative transition whose midpoint is less than that of the monomeric protein. The kinetic profile observed for the refolding of the denatured dimer is characteristic for monomeric cytochromes except for a markedly enhanced slow-phase amplitude.

Circular Dichroism↗
PubMed1985

Deletion of the terminal sequences from cytochromes c.

A 12-residue helical segment was deleted from the amino terminus of human heart cytochrome c by cleavage with cyanogen bromide. The resultant hemepeptide (13-104)H is rather insoluble in aqueous solution at neutral pH. Analysis of the crystallographic model with the terminal segment removed as well as qualitative spectral analysis of a transiently soluble sample of (13-104)H suggests that the hemepeptide retains little of the conformation of the native protein. By contrast, hemepeptide (1-80)H obtained by deletion of the carboxyl terminus is quite soluble at neutral pH. Spectral and hydrodynamic measurements suggest that the heme is encapsulated in an apolar cluster stabilized in part by axial ligation of the heme iron.

Amino Acid Sequence↗
PubMed1984

Spectral studies of horse heart porphyrin cytochrome c.

Removal of the heme iron from cytochrome c to generate porphyrin cytochrome c relieves the quenching of porphyrin fluorescence and enhances the fluorescence of the single tryptophan residue and the 4 tyrosine residues. The intensity of the porphyrin fluorescence is not perturbed by denaturation of the protein at neutral pH using either urea or guanidine hydrochloride. However, the amplitude of tryptophan fluorescence is increased by these denaturants from 5 to about 85% of a model tryptophan residue using solutions of 2 microM tryptophan. In contrast to cytochrome c, the tryptophan fluorescence amplitude of denatured porphyrin cytochrome c is independent of pH over the range pH 3.0 to 7.4. Acidification of solutions of either native or denatured porphyrin cytochrome c markedly alters both the visible absorbance and fluorescence of the protein consistent with protonation of two pyrrole nitrogens on the porphyrin. Preliminary analysis of the spectral changes occurring in the acid transition suggests the presence of an intermediate form having only one of these two pyrrole nitrogens protonated.

Animals↗
PubMed1984

Energy metabolism of adult Haemonchus contortus in vitro: a comparison of benzimidazole-susceptible and -resistant strains.

In vitro biochemical characteristics of three strains of Haemonchus contortus, benzimidazole-susceptible, mebendazole-resistant and thiabendazole-resistant isolates, were investigated. Steady-state pool sizes of glucose and metabolic intermediates, including adenine nucleotides and end-products revealed no differences between adult worms resistant or susceptible to benzimidazoles in 30-60 min incubations. Possible regulatory steps in the glycolytic pathway are identified as those involving the enzymes hexokinase, phosphofructokinase and pyruvate kinase. The major component of carbohydrate reserves was trehalose, some glycogen was present and the glucose pool was small. On incubation for 18 h in vitro, carbohydrates were metabolised in all three strains. However, in the benzimidazole-susceptible worms there was a preferential use of the glycogen reserves to maintain energy metabolism. All three strains had similar levels of total lipid, total protein and free amino acid and these did not change on incubation. The major products found in the medium on incubation, in vitro, for 18 h were propionate, acetate and propanol, with smaller amounts of ethanol, lactate and malate. All three strains produced a similar sum total of end-products; however, in the mebendazole-resistant strain there appeared to be a diversion of carbon flow to the ethanol-producing pathway. Carbon dioxide production in 60 min incubations was measured using radioactively labelled glucose. A greater output of labelled CO2 was noted under aerobic than anaerobic conditions. This was particularly true of the mebendazole-resistant strain and, in this strain, was sensitive to cyanide. The extent to which metabolic differences noted in the three strains may be related to benzimidazole resistance is not readily apparent.

Amino Acids↗
PubMed1983

Observations on the fumarate reductase system in Haemonchus contortus and their relevance to anthelmintic resistance and to strain variations of energy metabolism.

Fumarate reductase activity in a thiabendazole-resistant strain of Haemonchus contortus was found to be significantly lower than that from a susceptible strain. However, the fumarate reductase activity in a mebendazole-resistant strain did not differ from that in the susceptible strain, even though it was cross-resistant to thiabendazole. Published reports of fumarate reductase activity in strains of H. contortus susceptible or resistant to benzimidazoles were reassessed. A second, unrelated Australian thiabendazole-resistant strain also proved to have significantly diminished fumarate reductase activity, whereas two American strains, one resistant to thiabendazole and one to cambendazole, possess fumarate reductase activities indistinguishable from corresponding susceptible strains. It therefore appears that the phenomenon of benzimidazole resistance cannot be generally correlated with diminished fumarate reductase activity, although in the specific case of the Australian thiabendazole-resistant strains it may be a contributory factor.

Animals↗
PubMed1983

Mebendazole concentrations in sheep plasma.

Formulated mebendazole was administered to sheep by intraruminal injection at dose rates of 12.5, 25, 50 or 100 mg/kg bodyweight. The concentrations of mebendazole and two major metabolites were measured by high-performance liquid chromatography in plasma taken at intervals up to 48 hours after treatment. At 12.5 mg/kg the peak plasma concentration was 0.22 +/- 0.03 microM mebendazole, rising to 0.76 +/- 0.04 microM at 100 mg/kg. Peak plasma concentrations occurred between nine and 24 hours for all dose rates and declined rapidly. Two major metabolites were detected; their concentrations exceeded that of mebendazole at all dose rates.

Animals↗
PubMed1982

Alcohol-induced alterations in calcium metabolism in the pregnant rat.

The effect of alcohol ingestion during pregnancy on maternal calcium metabolism was investigated by allowing pregnant rats to ingest Purina Rat Chow ad libitum along with 20% ethanol in their drinking water from day 6 to 19 of pregnancy. Ethanol constituted 50% of the caloric intake and resulted in blood levels of 98 mg/dl on day 19 of gestation. Control rats were pair-fed with rat Chow and dextrimaltose was isocalorically substituted for ethanol in the drinking water. Alcohol consumption was attended by decreased serum levels of calcium (7.3 +/- 0.5 versus 9.5 +/- 0.3 mg/dl, p less than 0.01), and phosphorus (5.7 +/- 0.5 versus 7.5 +/- 0.3 mg/dl, p less than 0.01), as well as by lowered tubular reabsorption of phosphate (88.6 +/- 4.6 versus 95.0 +/- 0.7%, p less than 0.05). The fasting urinary calcium/creatinine ratio (Ca/Cr), an index of bone resorption, was increased in the alcohol-consuming rats (0.41 +/- 0.08 versus 0.24 +/- 0.04, p less than 0.05). In contrast, alcohol administered to nonpregnant female rats for the same time period and resulting in blood levels of 129 mg/dl had no effect on serum calcium, phosphorus, tubular reabsorption of phosphate, or fasting urinary Ca/Cr. The data suggest that alcohol ingestion during pregnancy, a time of increased calcium requirement, produces biochemical changes consistent with secondary hyperparathyroidism.

Animals↗
PubMed1981

Effect of age on serum immunoreactive parathyroid hormone and its biological effects.

Immunoreactive parathyroid hormone (iPTH) levels, nephrogenous cAMP (ncAMP), and tubular maximum phosphate reabsorption (TmP) were measured in 10 young and 12 healthy volunteers. The fasting urinary calcium to creatinine ratio (Ca:Cr) was also quantitated as an index of bone resorption. Aging was attended by increased iPTH levels (6.9 +/- 0.8 vs. 3.4 +/- 0.4 mu leq/ml; P less than 0.01) as well as increased ncAMP levels (2.48 +/- 0.28 vs. 1.12 +/- 0.21 nmol/100 ml glomerular filtrate; P less than 0.005) and decreased TmP (2.9 +/- 0.2 vs. 4.1 +/- 0.2 mg/100 ml glomerular filtrate; P less than 0.005), indicating that the increased iPTH levels reflected the biological effects of the hormone. A significant positive correlation of iPTH and ncAMP and a significant negative correlation of iPTH and TmP were observed. The Ca:Cr was increased in the older volunteers (0.10 +/- 0.02 vs. 0.05 +/- 0.01; P less than 0.05). The elderly subjects had significantly decreased daily calcium ingestion, serum phosphate and albumin, and creatinine clearance. Our findings suggest that the increased biological effects of PTH in the elderly subjects may contribute to the increases in Ca:Cr and bone loss that occur with age.

Adult↗