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Biomedical subjects

A J Matty

Publications and source records attributed to A J Matty.

At least 19 recordsLinked to original sources
PubMed1991

The effects of thyroid hormones and starvation on hepatic mitochondrial nucleic acids of rainbow trout (Oncorhynchus mykiss).

Twenty four hours after an intraperitoneal injection of thyroxine (T4; 4.4, 44 ng/g body wt) or triiodothyronine (T3; 3.3, 33 ng/g body wt), DNA and RNA were significantly reduced in isolated liver mitochondria of rainbow trout. Total liver DNA was increased with the higher doses in both T4- and T3-injected specimens while total RNA was significantly reduced with the same doses. Total circulating plasma T4 was reduced with the injections of T3 or starvation, and plasma T3 was increased severalfold with the T3 injections. Plasma T4 also increased fivefold after a higher dose of T4 injection while starvation significantly reduced the concentration, when measured by radioimmunoassay.

Animals↗
PubMed1983

Preliminary study on the effect of temperature on the transport of thyroxine (T4) into the body tissues and sub-cellular fractions of liver and muscle of carp, Cyprinus carpio.

In order to determine if the inability of thyroxine to induce cellular effects at low temperature is mediated through a temperature-sensitive system for the translocation of T4 into the nucleus, the effect of temperature on the uptake of T4 by body tissues and sub-cellular fractions of carp liver and muscle was studied in vivo. A single injection of 125I-T4 (1 micro C/10 g body weight) was given intraperitoneally to juvenile carp maintained at 15 and 25 C. Uptake from the peritoneal cavity was rapid. All the tissues exhibited maximum radioactivity at 2 hour after the injection. Fish kept at 25 C showed another peak at 8 hour and those at 15 C at 48 hour after the single injection. Transfer of T4 from the cytoplasm to nuclei was not blocked at lower temperatures. For example, in liver at 8 hour, nuclei from fish tissues kept at lower or higher temperatures had equal amounts of radioactivity. Muscle nuclei had 15% more radioactivity than liver nuclei when expressed as radioactivity/g tissue. Since there are comparable amounts of activity in the nuclei at both temperatures, some other mechanism/s than a simple block in transport from cytoplasm to nuclei is operating. There are some indications that nutritional status of fish may be playing some role in this respect.

Animals↗
PubMed1982

Inhibition of thyroidal iodine release by oestrogens in euthyroid subjects.

The effects of oestrogens on the release of thyroxine iodide (T4 I) and non-T4 I by the thyroid gland of 6 normal subjects and 3 thyrotrophin (TSH)-treated patients with hypopituitarism were assessed before, during and after treatment with 25 mg of Dienoestrol (Glaxo Lab.), orally, daily, during 8 days. Each subject received an iv injection of 150 microCi of 125I followed 6 days later by an iv injection of 75 microCi of [131I]T4. Blood samples and collections of urine were obtained every 12 h. From plasma and urinary (U) radioactivity, the ratio U[125I]/U[131I], U[125I]/PB[125I] and U[131I]/PB[131I] were obtained and served to calculate thyroidal iodine release and non-T4 I secretion by the thyroid gland. T4 I secretion was equivalent to T4 I disposal rate obtained by the semilogarithmic regression line of PB[131I]. In normal subjects, oestrogens decreased T4 I secretion from 491 +/- 57 (SD) nmol/day to 451 +/- 60 nmol (P less than 0.025), while in the same subjects serum TSH increased with oestrogens from 3.3 +/- 1.1 to 6.6 +/- 2.1 mU/l (P less than 0.01). The non-T4 I secretion had a mean of 585 +/- 307 nmol/day during control, 324 +/- 199 nmol during oestrogens (P less than 0.01) and 480 +/- 286 nmol oestrogens (P less than 0.05 vs oestrogens). In the TSH-treated patients oestrogens induced non-significant reductions in T4 I and non-T4 I secretion, although total iodine secretion decreased significantly (P less than 0.05). The data is consonant with a partial inhibition by oestrogens of thyroid gland release.

Adult↗
PubMed1981

Effects of quantity and quality of dietary protein on certain enzyme activities in rainbow trout.

The effects of variation in quality and quantity of dietary protein on certain tissue enzymes in rainbow trout (Salmo gairdneri) were examined. Trout were given for 9 weeks diets containing proteins of different quality (fish-meal, casein and corn gluten) and with protein energy levels ranging from 26 to 74% of total metabolizable energy. In the first experiment, activities of a number of enzymes were monitored by only hepatic serine pyruvate transaminase (SPT) activity changed in response to the dietary treatments--increasing as protein energy level was raised. In the second experiment, opposing glycolytic an gluconeogenic enzyme activities [pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK); phosphofructokinase (PFK) and fructose diphosphatase (FDP)] were measured. Gluconeogenic enzyme activities correlated positively and significantly with dietary protein energy level; glycolytic enzymes correlated negatively and significantly with this parameter for all three proteins. There was no consistent relationship between presumed equilibrium point of opposing enzyme activities and maximum weight gain for the three proteins. It is suggested that hepatic activities of SPT, PFK, PK, FDP and PEPCK will provide useful indices of protein status in trout.

Animals↗
PubMed1977

In vivo studies on thyroxine and triiodothyronine metabolism in the rat.

The reciprocal effects of loading amounts of thyroxine (T4) or triiodothyronine (T3) on the in vivo deiodination of their 125I-labelled isotopes by the rat were studied. It was found that the deiodination of a tracer amount of [125I]T3 as measured by the 24-h urinary 125iodide was significantly decreased after administration of a loading dose of non-radioactive T4. A similar decrease in deiodination of [125I]T3 was observed following the injection of a T3 load. In experiments in which the deiodination of [125I]T4 was assessed, the effects on this of loading doses of non-radioactive T4 or T3 differed; while stable T4 induced a significant decrease in deiodination of [125I]T4, stable T3 was without effect. The data is in agreement with the view that T4 and T3 share tissue deiodinating sites and that in such a system T4 appears to have a stronger avidity for those sites.

Animals↗
PubMed1976

Aspects of intestinal folate transport in the rat.

1. In vitro preparations of rat jejunum were used to study the metabolic dependence, the structural specificity, and the pH sensitivity of the folic acid absorption process. 2. The presence of 2:4 dinitrophenol, and the absence of oxygen, in the muscosal bathing medium both led to a decrease in the tissue accumulation and serosal transfer of folic acid by everted sacs. 3. 10-formylfolic acid, present in the mucosal medium at a molar ratio of 10:1 with labelled folic acid, appears to compete for tissue accumulation sites but has no significant effect on serosal transfer. 4. The efflux of folic acid from pre-loaded jejunal sacs is stimulated by the presence in the mucosal medium of the folic acid and related compounds. Pteroyl-L-glutamic acid, 10-formylfolic acid and methotrexate elicit a significant increase in the efflux rate; pteroyl-D-glutamic acid was significantly less effective and pteroic acid had no effect. 5. The uptake of folic acid by isolated jejunal cells prepared by enzymic disaggregation of the mucosa, was found to be influenced by the pH of the bathing medium, uptake being enhanced at a pH of between 5 and 6. 6. It is concluded that the effect of metabolic inhibitors and acid pH conditions on the uptake of folic acid in vitro is consistent with a passive absorption mechanism, influenced in intact preparations and in vivo by the jejunal pH microclimate. However the occurrence of competitive inhibition and stimulated efflux may indicate the existence of a structurally specific accumulation process at some site, or sites, within the mucosa.

Animals↗