PubMed Health⌕ Search

Biomedical subjects

G S Shephard

Publications and source records attributed to G S Shephard.

68 records · Page 4Linked to original sources
PubMed1985

Lack of a relationship between plasma pyridoxal phosphate levels and ischaemic heart disease.

The 'vitamin B6-homocysteine theory' has been proposed as an alternative to the widely accepted lipid hypothesis in the aetiology of ischaemic heart disease (IHD). In a cross-sectional study of 71 white men with evidence of IHD and 110 male controls (all aged 45-54 years) we have been unable to demonstrate any differences in plasma pyridoxal phosphate (PLP) levels between the groups. It is therefore unlikely that deficiency of vitamin B6 has a primary causal role in development of IHD. However, 31% of the overall study population had low plasma PLP levels, and the possibility that underlying vitamin B6 deficiency may facilitate the actions of the primary risk factors for IHD therefore cannot be excluded.

Coronary Disease↗
PubMed1985

Low plasma pyridoxal-5'-phosphate levels in children with the nephrotic syndrome.

Of 35 children with the nephrotic syndrome in relapse, 88% were found to have low circulating plasma pyridoxal-5'-phosphate (PLP) levels. Remission of the syndrome was associated with spontaneous normalization of plasma PLP levels in 23 such children. A significant (P less than 0,001) positive correlation (r = 0,81) was found between plasma albumin and PLP levels and a significant (P less than 0,001) negative correlation (r = -0,66) between plasma PLP and serum cholesterol levels. The low plasma PLP levels may be due to enhanced urinary excretion of albumin-bound PLP in view of the severe proteinuria which characterizes the nephrotic syndrome.

Adolescent↗
PubMed1984

Gas chromatographic analysis of amino acids in physiological fluids: a critique.

The available methodology for sample purification prior to gas chromatographic analysis of amino acids in physiological fluids and tissue extracts is analysed. It would appear that over the past ten years the method of choice is that of an ion-exchange purification step, and little, if any, progress has been achieved in sample purification procedures. The inherent disadvantages of such a methodology are not only perpetuated but also cast some considerable doubt on the accuracy of the quantitative analysis of amino acids.

Amino Acids↗
PubMed1984

Plasma vitamin E values in the newborn.

Plasma vitamin E values of newborn infants in a Coloured population of Cape Town have been determined. The mean plasma alpha-tocopherol value was 3,2 +/- 0,8 mg/l. A significant correlation between the plasma alpha-tocopherol level and plasma total lipid content (r = 0,45; P less than 0,001) and plasma cholesterol level (r = 0,65; P less than 0,001) has been found. However, maternal and neonatal plasma vitamin E levels were unrelated.

Adolescent↗
PubMed1984

Biochemical vitamin B6 deficiency in adults with chronic glomerulonephritides with and without the nephrotic syndrome.

Thirty four patients suffering from chronic glomerulonephritides with and without the nephrotic syndrome and with an average age of 35 years were studied. Twenty eight of the patients underwent renal biopsy, as part of their management, and the histological classification was as follows: 7 membranous glomerulonephritis, 3 proliferative glomerulonephritis, 11 mesangiocapillary glomerulonephritis, 2 minimal change disease, 2 mesangial proliferative and 3 diffuse proliferative glomerulonephritis. Fourteen of the patients were on therapeutic diets mainly high protein - low salt and low cholesterol. Eighty three per cent of these patients were found to be biochemically deficient in vitamin B6 as judged by plasma pyridoxal-5-phosphate levels. No correlations were found between vitamin B6 and serum albumin, histological type of renal disease, duration of illness or serum cholesterol. By contrast, none of the patients with histologically similar disease that were daily receiving 25mg pyridoxine orally at the time of study were deficient. The importance of vitamin B6 deficiency in the nephrotic syndrome is discussed and it would appear that supplementary vitamin B6 should form part of the overall management of these patients.

Adolescent↗
PubMedDate not supplied

The effect of a single gavage dose of fumonisin B(1) on the sphinganine and sphingosine levels in vervet monkeys.

This is the first report of sphinganine (Sa) and sphingosine (So) levels determined in serum and urine of vervet monkeys (Cercopithecus aethiops) dosed with pure fumonisin B(1) (FB(1)). Initially, experimental vervet monkeys were given a single gavage dose of either 1 or 10 mg FB(1) /kg body weight. Blood and urine were sampled daily and on day seven the monkeys were terminated and the kidneys and livers harvested. In a subsequent experiment, other vervet monkeys were similarly dosed and blood and urine samples were collected over a 50-day period. In the high-dose monkeys the serum Sa/So ratio, as well as levels of serum cholesterol and liver function enzymes, increased during the first week after dosing and remained elevated for several weeks thereafter. The urinary Sa/So ratio and the serum renal function indicators showed a more rapid response and a correspondingly more rapid return to pre-dosing levels. In the low-dose monkeys serum Sa and the Sa/So ratio were the only parameters to increase above the control levels. The Sa/So ratio in liver and kidney tissue showed an elevation over controls in a dose-dependent manner. The serum Sa/So ratio was exclusively elevated above the control levels in the low- and high-dose monkeys and seems more relevant as a marker for fumonisin exposure than any of the other indicators.

Administration, Oral↗
PubMedDate not supplied

Elimination and excretion of a single dose of the mycotoxin fumonisin B2 in a non-human primate.

The mycotoxin fumonisin B2 (FB2), which can be present at significant levels in maize infected with the fungus Fusarium moniliforme, was dosed both iv and by gavage to vervet monkeys. It was rapidly eliminated from the plasma of vervet monkeys dosed i.v. with 2 mg FB2/kg body mass. The concentration of FB2 in plasma after the iv dose was characterized by an initial distributional phase and a subsequent elimination phase with a mean half-life of 18 min. When two monkeys were dosed by gavage with a single bolus (7.5 mg/kg body mass), only one showed detectable trace levels of FB2 in plasma (25-40 ng/ml over the 3-5 hr period after dosing). This indicates that, like FB1, FB2 has a limited bioavailability. Urinary excretion of FB2 was extremely low, even after i.v. dosing. In total, a mean of 4.1% of the i.v. dose and 0.2% of the gavage dose was recovered in urine over a 7-day period. The predominant route of excretion was via the faeces, mainly as the unmetabolized toxin or as a partially hydrolysed analogue, with the latter accounting for between 6% and 47% of the dose. Limited amounts (maximum of 1.1%) of the fully hydrolysed aminopolyol backbone of FB2 were recovered in faeces.

Animals↗
PubMedDate not supplied

Production of mycotoxins by selected Fusarium graminearum and F. crookwellense isolates.

Corn cultures (five isolates each of Fusarium graminearum Group 1 from wheat crowns, Group 2 from scabby wheat grains and from ear rot of corn and five isolates of F. crookwellense) were screened for their ability to produce deoxynivalenol (DON), nivalenol (NIV), fusarenon-x (FUS-X) and zearalenone (ZEA). Nine of the ten F. graminearum isolates from wheat produced DON (5-165 micrograms g-1) but none produced either NIV or FUS-X. Conversely, 3/5 and 2/5 of the F. graminearum isolates from corn produced NIV (5-40 micrograms g-1) and FUS-X (5-7 micrograms g-1), respectively, while none produced DON. All but one of the F. graminearum isolates produced ZEA (2-1160 micrograms g-1). None of the F. crookwellense isolates produced DON, but 5/5 and 4/5 produced NIV (6-170 micrograms g-1) and FUS-X (3-90 micrograms g-1), respectively, and all produced ZEA (605-1030 micrograms g-1). The results confirmed previous findings on the presence of two distinct F. graminearum chemotypes.

Food Microbiology↗
PubMedDate not supplied

Fumonisin-contaminated maize: physical treatment for the partial decontamination of bulk shipments.

Ten maize samples, randomly selected from a bulk shipment imported into South Africa, were characterized by a wide distribution in particulate size. Following fractionation by sieving through a 3 mm screen, the 'kernels' (fractions > or = 3 mm) corresponding to between 80.0 and 95.3% of the samples by mass, were contaminated with total fumonisin levels of between 530 and 1890 ng/g. Conversely, those fractions termed 'fines' (< 3 mm) had significantly higher total fumonisin concentrations of between 12,340 and 27,460 ng/g, and accounted for between 4.7 and 20.0% of the samples by mass. The data indicated that removal of the 'fines' resulted in overall reductions in total fumonisin levels of between 26.2 and 69.4%. It is suggested that initial removal of 'fines' from bulk shipments of maize, prior to further processing, could be considered as a preliminary fumonisin-decontamination procedure.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Fumonsin B1, B2, and B3 content of commercial unprocessed maize imported into South Africa from Argentina and the USA during 1992.

The widespread occurrence of F. moniliforme and the toxic effects of its secondary metabolites, the fumonisins B1(FB1), B2(FB2) and B3(FB3), make it imperative that fumonisin contamination of maize, a major constituent of animal feed as well as the staple diet of many populations, be closely monitored to reduce the risk of fumonisin exposure. Equine leukoencephalomalacia and porcine pulmonary oedema have been associated with the intake of feed heavily contaminated with fumonisins. In addition, high levels of fumonisins in the maize-based staple diets of certain populations have been linked to a high incidence of oesophageal cancer in the Transkei region of South Africa and in Linxian and Cixian Counties, China. Bulk shipments of maize imported into South Africa from the USA and Argentina during 1992 were sampled at the port of entry to determine fumonisin levels. Of the 79 samples from two US shipments, all were positive for fumonisins, with FB1 constituting approximately 71% of the total fumonisins with an overall mean of 2.35 micrograms/gFB1. The maximum FB1 level observed was 3.9 micrograms/g. These levels contrast with those obtained from two Argentinian bulk shipments, which also were all positive for fumonisins, but had a mean FB1 level of 0.31 microgram/g and a maximum observed level of 0.7 microgram/g FB1 measured over 47 composite samples.

Animals↗
PubMedDate not supplied

Plasma vitamin levels in patients on prolonged total parenteral nutrition.

Vitamins are essential in total parenteral nutrition (TPN), their importance being highlighted by repeated past documentation of various vitamin deficiencies particularly in patients on long-term parenteral nutrition therapy. This study evaluated the efficacy of water- (Soluvit) and fat-soluble (Vitalipid) vitamin supplementation in patients receiving total parenteral nutrition using the three in one 3-liter bag system. All patients received water-soluble vitamin supplements daily. Fat-soluble vitamin supplements were administered on a daily or twice weekly basis. Twenty-two patients were studied. In seven of the 22 patients vitamin status was assessed on more than one occasion during TPN support, thus bringing the total number of observations to 30. The mean duration of TPN support was 35 days. Eight of the observations were made during less than 10 days, three between 11-19 days, 15 between 20-60 days, and four during more than 60 days of TPN support. Biochemical deficiency as judged by subnormal enzyme activity or vitamin levels were present in 10% of the patients for thiamin, 3% for riboflavin, and 6% for nicotinic acid. By contrast 83% of the patients had low plasma vitamin C and B6 levels. Low plasma vitamin A and E levels were also present in 43 and 40% of the patients, respectively. According to the plasma concentrations of the vitamins studied it would appear that the commercial vitamin preparations used in this study are inadequate in maintaining optimal vitamin status.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Worldwide survey of fumonisin contamination of corn and corn-based products.

As part of a comprehensive risk assessment study for fumonisins, reliable data on exposure of populations to these dietary toxins must be obtained. To assess the extent of worldwide exposure, the published literature on the contamination of food and feed supplies has been reviewed and supplemented with unpublished material from various international sources. Fumonisin contamination of corn and corn-based products occurs in many countries. Animal mycotoxicoses such as equine leukoencephalomalacia and porcine pulmonary edema are caused by heavily contaminated animal feeds. For example, as much as 330 micrograms/g fumonisin B1 (FB1) has been found in swine feed. Although commercially available refined corn products for human consumption are generally contaminated at levels below 1 microgram/g FB1, individual products in certain countries can reach far higher levels. Health risks associated with consumption of these products depend on the extent to which they are consumed in a varied diet. Home-grown corn in certain rural areas, where it also constitutes the staple diet, can be contaminated at > 100 micrograms/g. Consumption of corn contaminated at these high levels has been associated with a high incidence of esophageal cancer in these areas.

Animal Feed↗
PubMedDate not supplied

Liquid chromatographic determination of fumonisins B1, B2, and B3 in corn: AOAC-IUPAC Collaborative Study.

A liquid chromatographic (LC) method for simultaneous determination of fumonisins B1 (FB1), B2 (FB2), and B3 (FB3) in corn was subjected to a collaborative study involving 12 participants from 10 countries, in which the accuracy and reproducibility characteristics of the method were established. Mean analyte recoveries from corn ranged from 81.1 to 84.2% for FB1 (at a spiking range of 500 to 8000 ng/g), from 75.9 to 81.9% for FB2 (at a spiking range of 200 to 3200 ng/g), and from 75.8 to 86.8% for FB3 (at a spiking range of 100 to 1600 ng/g). The valid data were statistically evaluated after exclusion of outliers. Relative standard deviations for within-laboratory repeatability ranged from 5.8 to 13.2% for FB1, from 7.2 to 17.5% for FB2, and from 8.0 to 17.2% for FB3. Relative standard deviations for between-laboratory reproducibility varied from 13.9 to 22.2% for FB1, from 15.8 to 26.7% for FB2, and from 19.5 to 24.9% for FB3. HORRAT ratios, calculated for the individual toxin analogues, ranged from 0.75 to 1.73. The LC method for determination of fumonisins B1, B2, and B3 in corn (at concentrations of 800-12800 ng total fumonisins/g) has been adopted by AOAC INTERNATIONAL.

Chromatography, Liquid↗