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Biomedical subjects

G M Ward

Publications and source records attributed to G M Ward.

At least 55 records · Page 3Linked to original sources
PubMed1986

Net energy value of ammoniated wheat straw.

Eight steers (327 kg average) were fed diets containing either nontreated or anhydrous NH3-treated wheat straw in a two-period crossover design. Intake and digestibilities of dry matter, gross energy, neutral detergent fiber, acid detergent fiber and crude protein were measured by total collection. Energy losses in urine and methane were determined. Heat production was determined by indirect respiration calorimetry on steers fed both diets and after they were fasted. Ammoniation of the straw raised its N content from .49 to 1.59% (P less than .001). Dry matter (DM) intake was increased (P less than .01) by the process from 1.0 to 1.3% of body weight. Digestibility coefficients of dry matter and energy, as well as those for fiber, were increased (P less than .001) by four percentage units or more. Crude protein digestibility, however, was depressed (P less than .001) from 67.8% to 53.5% by ammoniation. Urinary energy as a percentage of gross energy intake (GEI) was reduced (P less than .05) by NH3 treatment from 4.10 to 3.74%. Methane energy was not different (P greater than .10). Metabolizable energy was improved (P less than .001) by ammoniation, increasing from 45.2 to 50.0% of GEI. Daily heat production was higher (P less than .01) for steers consuming the ammoniated straw diet, increasing from 113.7 to 125.3 kcal/wt.75), and was due to higher metabolizable energy intake (MEI) since partial efficiency of MEI used for maintenance did not differ (P greater than .10) between diets. The higher net energy value of the ammoniated wheat straw diet (1.45 vs 1.26 kcal/g DM) was due mainly to decreased fecal loss and a slight decline in urinary loss.

Ammonia↗
PubMed1984

Absence of covalent binding by insulin to erythrocyte and reticulocyte insulin receptors.

We investigated whether insulin forms covalent bonds with its receptors on erythrocytes and reticulocytes, as it does in adipocytes (1). Of the [125I]-insulin specifically bound at 37 degrees C to human and rat erythrocytes and rat reticulocytes, only 1.5-2.3% was non-dissociable on extensive washing. When ghosts prepared from the washed cells were solubilized in Triton X-100, only 0.6-1.5% of the specifically bound radioactivity appeared in the void volume of a Sephadex G-50 column. Moreover in contrast to adipocytes, this high molecular weight radioactivity was not immunoprecipitable by antibodies to the insulin receptor and was dissociated during chromatography in sodium dodecyl sulphate. Thus we have been unable to demonstrate the formation of covalent bonds between insulin and its receptors on erythrocytes and reticulocytes. This finding is consistent with the hypothesis that covalent binding of insulin is a necessary receptor modification for insulin's metabolic effects.

Animals↗
PubMed1984

Abnormal dietary regulation of erythrocyte insulin receptor affinity in non-insulin-dependent diabetes mellitus.

Decreased insulin binding to receptors is associated with the insulin resistance of obese and non-obese non-insulin-dependent diabetics. 'Down Regulation' by elevated insulin levels has been suggested as the cause, but factors influencing receptor affinity have not been examined. To investigate the control of receptors in diabetes, 10 non-insulin-dependent diabetics and 10 normal subjects were studied after 6 d on low and 6 d on high calorie diets of fixed composition (700 and 2800 Kcal/70 kg of ideal body weight). The binding of insulin by erythrocytes of non-diabetics, as predicted, increased on the low and decreased on the high calorie diets, due to altered affinity. In contrast, the binding in the diabetics did not change significantly, and the responses to the low and high calorie diets were less than in the normal subjects (P less than 0.05 and P less than 0.001 respectively). Indeed, the insulin binding in all 5 non-obese diabetics changed in the opposite direction (P less than 0.01) to the non-diabetics, whereas the obese diabetics showed a mixed response. The changes in receptor binding in the diabetics was completely unrelated to the diurnal plasma insulin levels during 24 h studies. We conclude that the dietary regulation of erythrocyte insulin receptor affinity in non-insulin-dependent diabetes is abnormal, and insulin receptor affinity is regulated by factors other than insulin. The relation of this abnormality to the insulin resistance needs further investigation.

Aged↗
PubMed1984

Body composition. Methods of estimation and effect upon performance.

The assumption that is implicit in nearly all methods for determining body composition is that the fat-free body has a constant composition and that fat content can vary from some minimal amount to over 70 per cent. Fat estimations, however, are almost always indirect and are based upon estimating some fat-free component of the body. Some fifteen different methods are described in terms of the principle involved, the cost, and the applicability for routine use. A review is presented of a large number of regression equations that have been developed to predict body density from many types of anthropometric equations. The accuracy or comparative accuracy of body composition methods cannot be evaluated with human subjects. Methods can be validated only by using the method on an animal model, then performing chemical analyses on the same animal. Data of this type are limited.

Anthropometry↗
PubMed1983

Microbial decomposition of wood in streams: distribution of microflora and factors affecting [C]lignocellulose mineralization.

The distribution and lignocellulolytic activity of the microbial community was determined on a large log of Douglas fir (Pseudotsuga menziesii) in a Pacific Northwest stream. Scanning electron microscopy, plate counts, and degradation of [C]lignocelluloses prepared from Douglas fir and incubated with samples of wood taken from the surface and within the log revealed that most of the microbial colonization and lignocellulose-degrading activity occurred on the surface. Labeled lignocellulose and surface wood samples were incubated in vitro with nutrient supplements to determine potential limiting factors of [C]lignocellulose degradation. Incubations carried out in a nitrogenless mineral salts and trace elements solution were no more favorable to degradation than those carried out in distilled water alone. Incubations supplemented with either (NH(4))(2)SO(4) or organic nitrogen sources showed large increases in the rates of mineralization over incubations with mineral salts and trace elements alone, with the greatest effect being observed from an addition of (NH(4))(2)SO(4). Subsequent incubations with (NH(4))(2)SO(4), KNO(3), and NH(4)NO(3) revealed that KNO(3) was the most favorable for lignin degradation, whereas all three supplements were equally favorable for cellulose degradation. Supplementation with glucose repressed both lignin and cellulose mineralization. The results reported in this study indicate that nitrogen limitation of wood decomposition may exist in streams of the Pacific Northwest. The radiotracer technique was shown to be a sensitive and useful tool for assessing relative patterns of lignocellulose decay and microbial activity in wood, along with the importance of thoroughly characterizing the experimental system before its general acceptance.

Journal Article↗
PubMed1983

Pulsatile insulin has greater hypoglycemic effect than continuous delivery.

The relative hypoglycemic effects of pulsatile versus steadily infused insulin have been examined in six normal subjects in whom pancreatic insulin output was suppressed by somatostatin-14. Soluble insulin was infused continuously overnight on one occasion and on another occasion the same quantity was given in pulses of 2-min duration with a gap of 11 min. The mean plasma glucose concentrations were lower when pulsed insulin was given [mean for the last hour: 4.66 +/- 0.08 mmol/L (+/- SEM) versus 5.53 +/- 0.06 mmol/L (+/- SEM) for steady infusion], diverging significantly (P less than 0.05 paired t test) 7 h after the start of the study. The specific binding of 125I(A14)mono-iodo-insulin to monocytes was greater after pulsed insulin (2.9% with pulsed versus 2.4% with steadily infused insulin at tracer-only point; P less than 0.02 paired t test). Thus, intravenous insulin has greater hypoglycemic effect when pulsed, possibly mediated by greater insulin receptor binding.

Adult↗
PubMed1982

Insulin receptor binding increased by high carbohydrate low fat diet in non-insulin-dependent diabetics.

In comparison to a traditional low carbohydrate diet (LC), the effect of an isocaloric high carbohydrate, high fibre diet (HC) upon the insulin binding to mononuclear blood cells of seven non-insulin-dependent diabetics was examined. Each subject, in random order, took both diets for 6 weeks each. There was no significant difference in weight during either dietary period, but a significant (P less than 0.05) increase in the monocyte insulin binding activity on the HD diet (tracer specific binding: 4.2% HC; 3.5% LC). This was accompanied by a significantly (P less than 0.02) lower fasting plasma glucose concentration (LC = 7.1 mmol/l; HC = 6.1) without a significant change in the fasting plasma insulin level. In contrast to the usual low carbohydrate diet, a high carbohydrate diet tends to correct the lowered insulin receptor status observed in maturity-onset diabetics.

Body Weight↗
PubMed1982

Pulsatile, synchronous basal insulin and glucagon secretion in man.

The basal plasma insulin, glucagon, and glucose concentrations of 28 normal subjects were measured at 1-min intervals for periods of 45-120 min. Regular plasma insulin and/or glucagon cycles were detected in 11 subjects by autocorrelation (mean periods 13.1 and 13.7 min, respectively). Individual plasma insulin cycles were defined in all subjects (mean period 10.7 min, amplitude 1.1 mU/L), and were associated, after averaging, with plasma glucagon (amplitude 5.5 pg/ml) and plasma glucose (0.02 mmol/L) cycles. There was a significant correlation between the amplitudes of simultaneous plasma insulin and glucagon cycles (r = 0.23, P = less than 0.05, N = 124). Cross-correlation demonstrated a delay of 2 min between the changes in plasma insulin and glucagon. No comparable oscillations in plasma pancreatic polypeptide were detected. The synchronous pulsatile secretion of glucagon and insulin may be a mechanism by which insulin's hepatic effects are limited, thereby maintaining hepatic glucose production but allowing sufficient peripheral insulin concentrations to inhibit excessive catabolism. The simultaneous pulses of insulin and glucagon may be stimulated by a pacemaker, with the A-B intercellular connections producing insulin and glucagon synchrony.

Adult↗
PubMed1981

Comparison of two twice-daily insulin regimens: ultralente/soluble and soluble/isophane.

The relative efficacy of two twice-daily insulin regimens using highly purified insulins, once daily Ultratard with twice daily Actrapid (ultralente/soluble) and twice daily Actrapid with twice daily Retard (soluble/isophane), has been studied in 12 diabetics in a cross-over study. Control was optimised as an out-patient, and assessed by in-patient 24 hour profiles. Similar day-time glucose control was achieved, but the mean overnight plasma glucose concentrations were more steady on ultralente/soluble (0100, 0300, 0500, 0700, 0800 h values 5.6, 5.3, 5.8, 7.8, 10.4 mmol/l) than on soluble/isophane (4.3, 3.4, 5.2, 7.5, 12.2 mmol/l). The minimum overnight plasma glucose concentrations were lower (p less than 0.05) on soluble/isophane (mean 2.8 mmol/l) than on ultralente/soluble (mean 4.8 mmol/l), associated with higher (p less than 0.05) nocturnal free plasma insulin levels after the evening soluble/isophane injection. The plasma glucose rise between 0700 and 0800 h was greater (p less than 0.05) on soluble/isophane than on ultralente/soluble. The morning insulin injection should probably be taken immediately on rising, to prevent the pre-breakfast plasma glucose rise. The ultralente/soluble combination gave similar day-time plasma glucose control to soluble/isophane with less nocturnal hypoglycaemia.

Adult↗
PubMed1981

Heavy metal retention in tissues of cattle fed high cadmium sewage sludge.

A diet containing 11.5% (dry matter basis) of a moderately high Cd sewage sludge was fed to six Hereford steers for 106 days to simulate a high sludge intake from sludge-amended soils. At a mean live weight of 460 kg, the steers were slaughtered and liver, kidney, bone, muscle, lung, brain and spleen tissues were collected for heavy metal determinations; tissues were also collected at this time from six control steers fed the same diet with no sludge. The sludge-fed cattle consumed an average of 8.95 kg of diet dry matter/day and gained 1.13 kg/day. This feed intake was slightly higher, but the gain lower than that of control cattle. All gains were equal to those expected from intake of non-sludge diet components. This indicated that the sludge had approximately zero energy value and was acting as a dietary diluent. The sludge metal content (ppm, dry basis) was: Cd, 98; Hg, 18; Pb, 466; Cu, 1,733, and Zn, 1,733. Addition of sludge increased metal contents of the feedlot diet to 30 to 100 times that of the control. Retention of heavy metals in the total animal from sludge ingestion averaged .09%, .06% and .3% for Cd, Hg and Pb; no retention was noted from Cu and Zn. These low fractional retentions increased tissue Cd, Hg and Pb concentrations of liver and kidney tissues by five to 20-fold. Estimates of levels that would enter the human diet from average beef tissue consumption if all feedlot steers were fed sludge are presented for Cd, Hg and Pb. The data indicate that cattle are a moderately effective screen against the entry of these potentially toxic metals into the human diet.

Animal Feed↗
PubMed1978

Ionic milieu of bovine and ovine rumen as affected by diet.

Postprandial changes in osmolality, mineral, and volatile fatty acid concentrations in rumen fluid were examined in three cattle fed six widely differing diets. Mineral concentrations varied with diet and postprandial time. However, net changes in postprandial mineral concentrations did not contribute significantly to changes in osmotic pressure. There was an effect of diet and time after feeding on concentrations of volatile fatty acids. Postprandial changes in osmotic pressure were primarily due to changes in concentrations of volatile fatty acids. Magnesium oxide and sodium bicarbonate were fed to sheep to increase the osmotic pressure in rumen fluid. The salt supplement decreased acetate, propionate, heat, and methane production. However, rumen water flux was unaffected by the salt supplementation. Diets which produce hypertonic rumen fluid due to high mineral and/or concentrations of volatile fatty acids may reduce fermentation in rumen.

Animal Feed↗