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Biomedical subjects

G E Mitchell

Publications and source records attributed to G E Mitchell.

At least 73 records · Page 4Linked to original sources
PubMed1979

Mammary transfer of vitamin E in cows treated with vitamin A or linoleic acid.

The effect of an intravenous injection of vitamin A alcohol and subcutaneous injections of linoleic acid on the mammary transfer of an intravenous injection of vitamin E acetate was studied with 15 Holstein cows. The cows received either an intravenous injection of 3 g vitamin E acetate (controls), intravenous injections of 3 g vitamin E acetate and 1 million IU vitamin A alcohol, or an intravenous injection of 3 g vitamin E acetate and subcutaneous injections totaling 40 g of linoleic acid. Milk samples were at 12-h intervals, two prior to and six following treatment. The main influence of vitamin A alcohol and linoleic acid on mammary transfer of vitamin E was to delay secretion of vitamin E in milk. However, total secretion of vitamin E was not reduced by injection of either vitamin A alcohol or linoleic acid. Vitamin E injection produced substantial increases in vitamin E in milk, but less than 1% of the dose could be accounted for in the milk.

Animals↗
PubMed1979

Bioassay of vitamin A in liquid supplements.

Vitamin A bioassay techniques based on liver storage in the chick were adapted for the assay of vitamin A in molasses based liquid supplements for cattle. Methods of administering the assayed supplement to the chicks were: 1) direct dosing of the supplement via four crop infusions at hourly intervals and 2) ether extraction, suspension in cottonseed oil with solvent removal in vacuo followed by direct crop dosing. The last method allowed a larger dosage with fewer analytical problems. Five sequential extractions were required for 97% recovery of the vitamin A from the molasses supplement. With the higher dosage range, the variance of response was a function of dose level. Transformation to a log dose - log response curve allowed a linear plot with homogeneity of variance. Detection of a 10% loss of vitamin A potency (P less than .10) was estimated to require 27 chicks per treatment by the slope ratio bioassay procedure.

Animal Feed↗
PubMed1976

Peripheral effects of fenfluramine.

1 The peripheral cardiovascular effects of the centrally acting anorexigenic agent, fenfluramine hydrochloride, have been investigated in the rat. 2 After intravenous administration of fenfluramine, an immediate hypotensive response, followed by a reflex rise in blood pressure was recorded. This was followed by a prolonged fall in blood pressure which frequently failed to return to pre-drug levels. 3 The antagonists, propranolol and atropine, failed to inhibit this hypotensive effect of fenfluramine. 4 The effects of 5 mg/kg fenfluramine for 1h on the blood pressure responses to the sympathomimetic amines, tyramine, methoxamine and metaraminol were studied. 5 The responses to the indirectly acting tyramine were reduced by 50% following fenfluramine, while those to the directly acting methoxamine remained unaffected by the drug. Responses to metaraminol, an amine with both direct and indirect actions, were also unaffected to a significant degree by fenfluramine. 6 Studies on rat isolated vas deferens again showed that responses to tyramine are greatly reduced following fenfluramine. 7 In addition fenfluramine itself produced spontaneous contractions of the vas deferens. These contractions were blocked by the alpha-adrenoceptor blocking agents phentolamine and thymoxamine. 8 It is suggested that fenfluramine exerts an effect at the adrenergic nerve terminal, either by displacing noradrenaline stores or by inhibition of the amine uptake process.

Amines↗
PubMed1976

Mammary transfer of vitamin A alcohol and ester in lactating dairy cows.

The effect of intravenous injection of vitamin A alcohol and vitamin A ester on the vitamin A concentration of bovine milk was studied. Holstein cows received either an intravenous injection of 1 million international units (IU) of vitamin A alcohol, 1 million international units of vitamin A palmitate, or served as controls. Blood serum and milk were sampled at intervals prior to and following injection. Mean concentrations of vitamin A in milk at time 0 were 59.0, 52.0, and 58.4 mug/100 ml for the control, alcohol, and palmitate treatments. Mean contrations of vitamin A in milk, expressed as mug/100 ml or mug/g fat of cows receiving vitamin A alcohol at +195, +451, and +678 min postinjection, were greater than concentrations for either control cows or cows receiving palmitate. Partition of milk Vitamin A at +195 min postinjection for cows injected with vitamin A alcohol showed 4.1% of the recovered vitamin A in the alcohol and 95.9% in the ester form. Injection of vitamin A palmitate had little effect on milk vitamin A concentration. Vitamin A in serum (mug/100 ml) at 195 min after vitamin A alcohol injection was higher (100.4) than for either control (84.0) or cows injected with vitamin A palmitate (89.0).

Animals↗
PubMed1975

Methionine replacement value of N-acetylmethionine and homocysteinethiolactone hydrochloride for growing rats.

The ability of young growing rats to absorb DL-homocysteinethiolactone hydrochloride (HCTL-HCl) and N-acetyl-DL-methionine (NAM) and to use them for growth when fed a methionine-deficient diet was studied. In situ intestinal absorption studies demonstrated that both compounds are readily absorbed. Intestinal half-times were 24 minutes for NDTL-HCl and 44 minutes for NAM. Adding molar equivalents of 0.2 or 0.4% methionine to a 0.2% methionine basal diet fed ad libitum resulted in 28-day gains that were 83.2 and 91.1%, respectively, for NCTL-HCl and 94.6 and 99.8% for NAM of the average gain resulting when DL-methionine was added at equivalent levels. Feed efficiencies were also significantly (P smaller than 0.05) improved over rats fed the basal diet. Increasing the HCTL-HCl addition to 0.6% reduced feed intake and gain but not feed efficiency.

Acetates↗
PubMed1975

Vitamin A alcohol and vitamin A palmitate transfer from ewes to lambs.

The effects of pre-partum intravenous injections of vitamin A alcohol and vitamin palmitate on vitamin A levels in the plasma and livers of newborn lambs and in colostrum were studied with twenty mature Romney ewes. Injecting ewes with 250000 IU of vitamin A alcohol significantly (P less than .05) increased vitamin A levels in the blood (77%) and livers (75%) of newborn lambs. Differences between effect of vitamin A alcohol and vitamin A palmitate on either blood or liver levels in lambs were not significant. Transfer of injected vitamin A to lamb liver was inefficient (0.37% for palmitate, 0.12% for alcohol). There was 52% more vitamin A in colostrum from alcohol-injected than from palmitate-injected ewes. Although consistent with a postulation of preferential mammary transfer of vitamin A alcohol, this difference was not statistically significant (P greater than .05).

Alcohols↗