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Biomedical subjects

R H Smith

Publications and source records attributed to R H Smith.

At least 127 records · Page 7Linked to original sources
PubMed1983

Effects of level of dietary intake and physical form of protein supplement on the digestibilities of different dietary carbohydrates between mouth and abomasum of young steers.

Steers fitted with simple rumen and abomasal cannulas were given isoenergetic diets of rolled barley and chopped straw, pelleted together with some tapioca alone (B) or with some tapioca replaced by coarse soyabean meal (M) or finely ground soyabean flour (F). The diets were given at two levels to support 0.5 (L) and 1.0 (H) kg/d live weight gain. Chromic oxide and PEG were given as digesta flow markers. Mouth to abomasum digestibilities of different dietary sugars at the low level of intake (LB) were 0.65, 0.68, 0.59, 0.56 and 0.94 for arabinose, galactose, xylose, cellulose-glucose and starch-glucose respectively. Corresponding values at the higher level of intake (HB) were 0.55, 0.66, 0.55, 0.44 and 0.93 respectively. Supplementation with either soya bean meal or flour had no significant effects on the mouth to abomasum of dietary carbohydrate digestibilities at either level of feeding.

Abomasum↗
PubMed1983

Ribulose Bisphosphate Carboxylase Activity in Anther-Derived Plants of Saintpaulia ionantha Wendl. Shag.

Plants obtained from anther culture of the African violet, Saintpaulia ionantha Wendl. ;Shag' and vegetatively cloned copies of the parent anther donor plant were examined for their ploidy and ribulose-1,5-biphosphate carboxylase (RuBPcase) activity. The cloned parent plants were all diploid and did not vary much in their nuclear DNA, chlorophyll, and RuBPcase activity. Some of the anther-derived plants were similar to the parent plants while others were not. Different levels of ploidy were observed among the androgenetic plants. RuBPcase activities higher than that of the parent plants were found in some anther-derived plants. However, there was no direct correlation between ploidy and RuBPcase activity. Expression of nuclear genes from a single parent in the anther-derived plants and it's diploidization or plastid changes during early stages of microsporogenesis or androgenesis are suggested as possible reasons for the variations observed among them. This could be a useful technique to obtain physiological variants which could be agronomically desirable.

Journal Article↗
PubMed1983

Carbohydrate oxidation and storage in obese non-insulin-dependent diabetic patients. Effects of improving glycemic control.

We have determined total body carbohydrate and lipid oxidation rates in response to a standard breakfast in nine obese patients with non-insulin-dependent diabetes mellitus (NIDDM) and in seven age- and weight-matched controls. The patients with NIDDM were studied twice, once while in poor glycemic control (fasting blood glucose concentration 267 +/- 24 mg/dl, urinary glucose excretion 28.9 +/- 6.3 g/24 h) and again after modest glycemic improvement following 2 mo of fiber treatment (fasting blood glucose 227 +/- 19 mg/dl, urinary glucose excretion 10.7 +/- 1.9 g/24 h). Basal carbohydrate (CHO) oxidation rates were normal in patients with NIDDM before and after fiber treatment. However, in patients before fiber treatment the rise in CHO oxidation rates, the reciprocal fall in lipid oxidation rates, and the rise in serum insulin and C-peptide concentrations after the breakfast were all severely blunted. In addition, storage of ingested CHO was significantly reduced (from 55% to 32%, P less than 0.05). After fiber treatment, postbreakfast CHO oxidation rates had improved and were no longer significantly lower than control values. In contrast, CHO storage remained suppressed. We conclude that (1) basal CHO oxidation remained normal but that postbreakfast CHO oxidation was impaired in our obese patients with NIDDM. This impairment, however, appeared to be a relatively late event, occurring only during severely uncontrolled NIDDM. (2) Inability to dispose of CHO by storage appeared to be an earlier defect with a greater impact on glucose tolerance than the impairment of CHO oxidation.

Adult↗
PubMed1982

Glycosyl ureides in ruminant nutrition. 1. Preparation and estimation of lactosyl urea and other glycosyl ureides.

1. Glucosyl urea, lactosyl urea and galactosyl urea were prepared from pure sugars and urea and their purity confirmed by determination of their melting points, specific rotations and by mass spectrometry. 2. Using whey as a lactose source, a range of conditions were examined for the preparation of lactosyl urea on a laboratory scale. Yields of 60% were achieved when lactose and urea (molar ratio, urea: lactose 0:6) were reacted for 15 h in sulphuric acid at pH 2.0 and a temperature of 70 degrees. 3. Methods of detection and estimation of all three ureides in whey preparations and ruminant digesta samples were developed. Two quantitative methods, one involving acid-hydrolysis, the other ion-exchange chromatography, were used. The latter method enabled determination of individual quantities of ureides in mixtures.

Animal Nutritional Physiological Phenomena↗
PubMed1982

Glycosyl ureides in ruminant nutrition. 2. In vitro studies on the metabolism of glycosyl ureides and their free component molecules in rumen contents.

1. The fate of glucosyl urea (GU), lactosyl urea (LU) and corresponding mixtures of the free sugars and urea and their degradation products were examined during in vitro incubation of the compounds with rumen contents taken from donor sheep and steers at various stages of adaptation to these compounds. 2. The sugar-urea bond was virtually unattacked in rumen contents from unadapted sheep and steers but generally a slow release of the galactose moiety occurred. After feeding LU or GU to animals for a period of approximately 10 d, the rates of disappearance of both bound urea and sugar had increased, but were still markedly slower than those of the corresponding free sugars and urea. In vitro rates of degradation of both free lactose and urea also increased in response to the feeding of lactose and urea to rumen content donor animals. 3. Ammonia accumulation in rument contents when GU or LU were the substrates was notably lower than when equivalent amounts of glucose and urea or lactose and urea were the substrates. 4. Bacterial growth was estimated using an vitro method based on incorporation of 32P into bacterial nucleic acids. Markedly different patterns of bacterial growth were observed depending on whether LU or lactose and urea were the substrates.

Adaptation, Physiological↗
PubMed1982

Glycosyl ureides in ruminant nutrition. 3. In vivo studies on the metabolism of glycosyl ureides and corresponding mixtures of their free component molecules.

1. Steers and sheep were given basal diets of barley and straw (1:1, w/w), usually containing urea, which for certain experimental periods were supplemented with pure glucosyl urea (GU), pure lactosyl urea (LU) or a product prepared from whey concentrate (EW) which contained 65-80% of the lactose in the form of LU. 2. On the morning of an experiment ureide (or EW) was omitted from the feed and a dose of either ureide (or EW) or equivalent amounts of free lactose and urea (L + U) was added to the rumen within 30 min of feeding, together in some experiments with polyethylene glycol (PEG) as a fluid-phase marker. Samples of rumen contents, and in some experiments abomasal contents, were taken at intervals for up to 8 h. 3. For both steers and sheep given GU and LU for the first time (unadapted animals) there was little or no accumulation of ammonia in the rumen or cleavage of the sugar-urea bond. Galactose was, however, slowly liberated from LU. 4. For steers and sheep which had been given GU, LU or EW for approximately 7-10 d or more (adapted animals) some accumulation of ammonia occurred after adding GU or LU to the rumen, but for LU it occurred less rapidly and to a lower peak concentration than when L + U was added. In adapted animals cleavage of the sugar-urea bond in LU was virtually complete in 2-4 h. Degradation of the components of L + U was virtually complete within 1 h. 5. Recovery at the abomasum of ureide (present either as GU or LU) estimated from ureide: PEG values, appeared to be complete in experiments with unadapted sheep given a dose of EW. In adapted sheep only very small amounts of ureide in an EW dose (on average 6%) entered the abomasum undegraded. Amounts lost in this way appeared to be positively correlated with the rate of fluid turnover in the rumen.

Abomasum↗
PubMed1982

Effect of duodenal cannulation on abomasal emptying and secretion in the preruminant calf.

1. The effect of re-entrant cannulation of the duodenum on digesta flow from, and secretion into, the abomasum of the preruminant calf was studied. 2. Calves fitted with abomasal cannulas and, at the same time or later, with re-entrant duodenal cannulas were given, by abomasal infusion, test feeds containing glucose and minerals. Net volumes of secretory fluids entering the abomasum and amounts of digesta flowing to the duodenum were estimated from changes in concentrations of water soluble markers (phenol red and polyethylene glycol) in digesta samples collected from an abomasal cannula. 3. Amounts of abomasal contents, net volumes of secretory fluids and digesta flow to the duodenum for calves fitted with only an abomasal cannula did not differ significantly from those obtained for animals with abomasal and re-entrant duodenal cannulas. 4. Collecting digesta from a re-entrant cannula and returning it promptly to the animal did not affect net volumes of secretory fluids. Under these conditions with cannulas open to the atmosphere, rather than being connected together, the amounts of digesta entering the duodenum increased slightly but differences were not significant. 5. Weight gains of calves fitted with abomasal and duodenal cannulas were similar to those of intact animals. 6. It is concluded that in calves receiving liquid feeds duodenal re-entrant cannulation is a suitable preparation for investigating digestive processes of the abomasum.

Abomasum↗
PubMed1981

The effect of intermittent changes in tension on protein and collagen synthesis in isolated rabbit muscles.

Isolated intact rabbit muscles were incubated in a medium containing radioactive proline. The rates of synthesis of collagen and total muscle protein after incubation with a constant tension or intermittent mechanical stretching were compared with the rates in vivo. Muscles incubated under a constant tension synthesized protein at 22% of the rate observed in vivo; intermittent mechanical stretching resulted in an increase of 73% in the rate of protein synthesis, to 38% of that found in vivo. Collagen synthesis was affected in the same way as total protein synthesis by both types of incubation, therefore the relative rates of collagen and total protein synthesis were unchanged. ATP concentration in the isolate muscles and the uptake of glucose from the medium were increased by intermittent mechanical stretching. Incubating the muscles with a gas phase containing 5% O2 decreased the rate of protein synthesis, abolished the effect of intermittent mechanical stretching, lowered the concentration of ATP and increased the lactate concentration. The rate of protein synthesis in muscles maintained with a constant or intermittently applied tension was not affected by a previous period of incubation with the other type of stimulus.

Adenosine Triphosphate↗
PubMed1981

Disulphide exchange reactions in the control of enzymic activity. Evidence for the participation of dimethyl disulphide in exchanges.

The causative agent in kale poisoning of cattle is the disulphide, dimethyl disulphide. Typical signs of kale poisoning are circulating dimethyl disulphide in the blood, Heinz body (deposits of methaemoglobin) formation in the erythrocytes and loss of body weight. Experiments in vitro have demonstrated that dimethyl disulphide can participate in disulphide exchange reactions which have a controlling role on proteolytic enzymes. We chose the enzyme trypsin, the active centre of which is maintained by a significant disulphide bond and the enzyme papain which is a thiol protease, to illustrate the mechanisms involved in these disulphide exchange reactions.

Animals↗
PubMed1981

Intranasal immunization of mice against Pasteurella multocida.

A potassium thiocyanate (KSCN) extract of Pasteurella multocida serotype III:A was shown to protect mice from an intranasal challenge with up to 300 50% lethal doses of P. multocida. In addition to preventing death, bacteria were rapidly cleared from the lungs of immunized mice so that by 72 to 96 h postchallenge no bacteria were present in the lungs of immunized mice, whereas up to 10(9) bacteria were present in lungs of nonimmunized mice. Immunization by the intranasal route was slightly better than that by the intramuscular route. Protection was considered specific, since immunization with P. multocida protected only against P. multocida and not against Salmonella agona. Furthermore, a similar KSCN extract from P. haemolytica did not protect against P. multocida challenge. A comparison of the KSCN extract with a Formalin-killed bacterin suggested that the KSCN extract may be superior to the bacterin.

Administration, Intranasal↗