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Biomedical subjects

M Morell

Publications and source records attributed to M Morell.

At least 73 records · Page 4Linked to original sources
PubMed1987

Influence of thyroid hormone deficiency on the citrate synthase activity in rat brain regions during early postnatal development.

The developmental pattern of citrate synthase activity has been studied in the liver and several brain areas of hypothyroid rats during the 4 first weeks of life. While citrate synthase activity in the liver showed a rise during the 2 first weeks of life, different patterns of enzyme activity were found in the brain regions of euthyroid animals. Citrate synthase activity increased in the cerebellum, decreased in the cerebral cortex and did not change significantly in the brain stem during the period studied. In the liver and brain areas, too, a decrease in citrate synthase activity was observed during hypothyroidism. From the 2nd week of birth, the citrate synthase activity in the brain but not in the liver was found to have recovered. The newly elevated citrate synthase activity coincided with a slight increase in thyroid hormone serum levels.

Animals↗
PubMed1987

Effect of thyroid hormones on angiotensinogen production in the rat in vivo and in vitro.

The influence of thyroid hormones on angiotensinogen production was studied in vitro and in vivo. In the in-vitro system, angiotensinogen production rate (APR) of monolayer cultures of rat hepatocytes in response to tri-iodothyronine (T3) and thyroxine (T4) was assayed. In the in-vivo system, plasma angiotensinogen concentration (PAC) and liver angiotensinogen content (LAC) were measured in hyper- and hypothyroid rats. In both thyroid dysfunctions, a significant decrease of PAC was found compared with that in control animals; however, LAC showed a significant increase in hyperthyroidism and a marked decrease in hypothyroidism. As PAC is dependent upon both angiotensinogen production by the liver and angiotensinogen degradation by renin, the decrease in PAC observed in hyperthyroidism could be due to an increase in plasma renin concentration, which would overcome the increased synthesis of liver angiotensinogen observed in these animals. In fact, addition of various concentrations of T4 or T3 to monolayer cultures of adult rat hepatocytes significantly enhanced APR. This increase was greater and started earlier with T3 (1196.1 +/- 143.7 (S.D.) pg/mg protein per 6-h incubation; significant differences at the third hour of incubation) than with T4 (858.3 +/- 88.2 pg/mg protein per 6-h incubation; significant differences at the sixth hour of incubation). In addition, a close dose-response relationship was found in the cultures supplemented with T3. The different time-course in the response elicited by T3 and T4 on APR could be a consequence of the necessary transformation of T4 into T3 to acquire biological activity.

Angiotensinogen↗
PubMed1987

[L-thyroxine and triiodo-L-thyronine in the cerebrospinal fluid and hypothalamo-hypophyseal axis of hyper- or hypothyroid rats].

L-thyroxine and triiodo-L-thyronine concentrations in cerebrospinal fluid (CSF), hypothalamus and pituitary gland are measured in male albino-Wistar rats under several experimental thyroid disfunction : including hyperthyroidism induced by L-T3 and L-T4 treatments and surgical hypothyroidism. Radioimmunoassay is carried out by Nejad's method modified in this work. The pattern of thyroid hormone concentrations in CSF is similar to that in serum, but the values obtained are lower. Thyroid hormone concentrations in adenohypophysis as opposed to hypothalamus or cerebral cortex, show an inverse change to functional thyroid status.

Animals↗
PubMed1987

[Homologous radioimmunoanalysis of serum L-thyroxine and triiodo-L-thyronine in rats with hypo- and hyperthyroidism].

Total L-thyroxine and triiodo-L-thyronine serum concentrations have been measured in 70-day-old male rats under normal conditions (controls) and in rats subjected to several experimental alterations of the thyroid function: hyperthyroidism, hypothyroidism and substitutive treatments. Since some problems appear when standard curves are performed with hormone serum, as consequence of differences in the affinity and inhibitory effects between heterologous proteins at the antigen-antibody reaction, RIA in this work has been carried out with standard curves performed with rat serum maintaining similar protein concentrations in standard and problems. This modification avoids errors by the use of extraction methods and shows a high degree of similarity between standard and problems.

Animals↗
PubMed1986

Postnatal development of renin-angiotensin system in rats.

The changes occurring in several components of the rat renin-angiotensin system (RAS) were studied for the brief postnatal period, between the fourth and tenth week of life. The parameters were: plasma renin activity (PRA), plasma renin concentration (PRC), plasma renin substrate (PRS) and the plasma angiotensin II concentration (AII). A gradual decrease in PRA with age was noticed. Between the fourth and the eighth weeks of life, this was attributed to a corresponding decline in both PRC and PRS. However, between the eighth and tenth weeks, no changes in PRA could be detected, but PRC and PRS increased, perhaps as a consequence of the changes in renal function and the AII increase observed. In this second period, simultaneously with the RAS changes described, there was reduced sodium chloride excretion as the glomerular filtration rate (GFR) stabilized. The data presented suggest that this postnatal period is critical, in rats, for the maturation of the RAS component control mechanisms; they appear to be closely related to the development of the renal function.

Angiotensin II↗
PubMed1986

Noradrenaline as a possible mediator of angiotensin II induced fluid transport in rat ileum in vitro.

In isolated segments of ileum excised from bilaterally adrenalectomized and nephrectomized rats, 10(-12) M angiotensin or 10(-3) M noradrenaline added to serosal medium stimulated both fluid transfer and NaCl transport. The alpha adrenergic antagonist phentolamine blocked the stimulation of fluid transfer induced by angiotensin. These results are consistent with the hypothesis that noradrenaline may mediate the increase of intestinal fluid absorption induced by angiotensin in the rat. In segments of isolated ileum from normal rats 10(-12) M angiotensin only stimulated fluid transfer under one of the two following conditions when 10(-3) M imipramine, a noradrenaline uptake blocker, was present in the serosal medium; or when the rats had been previously treated with L-Dopa, a precursor of noradrenaline biosynthesis. These results suggested that the necessity for bilateral adrenalectomy and nephrectomy might be associated to the necessity of increasing the tissue levels of noradrenaline. Direct measurement of noradrenaline tissue content confirmed this.

Adrenalectomy↗
PubMed1986

[Changes in dehydrogenase glutamate in the rat brain caused by thyroid hormone deficiency].

The dependent GDH-NADPH activity in adenohypophysis and other cerebral areas, has been studied in hypothyroid rats, in which hypothyroidism has been induced surgically. After thyroidectomy a decrease of GDH activity in limbic system (amygdala, septum and hippocampus), and an increase of this enzyme in cortex and hypothalamus have been found, with no changes in adenohypophysis. The alterations of GDH activity, induced by thyroidectomy, have been corrected, although not uniformly in the different brain areas after L-T3 treatment.

Animals↗
PubMed1986

[Measurement of total triiodo-L-thyronine in rat serum by homologous radioimmunoanalysis].

A radioimmunoanalysis comparative study of total tri-iodo-L-thyronine patterns in human and rat sera revealed a quantitative difference between the amounts of labelled antigen which associated with the specific antibody in each case. At the same time, in another experiment, three different protein concentrations were dissolved in rat serum standards producing the results that, at lower protein concentrations a larger quantity of antigen/antibody complex was formed. These changes must be kept in mind for the L-T3 measurement in rat serum.

Animals↗
PubMed1985

Sucrose synthase of soybean nodules.

SUCROSE SYNTHASE (UDPGLUCOSE: d-fructose 2-alpha-d-glucosyl transferase, EC 2.4.1.13) has been purified from the plant cytosolic fraction of soybean (Glycine max L. Merr cv Williams) nodules. The native enzyme had a molecular weight of 400,000. The subunit molecular weight was 90,000 and a tetrameric structure is proposed for soybean nodule sucrose synthase. Optimum activity in the sucrose cleavage and synthesis directions was at pH 6 and pH 9.5 respectively, and the enzyme displayed typical Michaelis-Menten kinetics. Soybean nodule sucrose synthase had a high affinity for UDP (K(m), 5 micromolar) and a relatively low affinity for ADP (apparent K(m), 0.13 millimolar) and CDP (apparent K(m), 1.1 millimolar). The K(m) for sucrose was 31 millimolar. In the synthesis direction, UDPglucose (K(m), 0.012 millimolar) was a more effective glucosyl donor than ADPglucose (K(m), 1.6 millimolar) and the K(m) for fructose was 3.7 millimolar. Divalent cations stimulated activity in both the cleavage and synthesis directions and the enzyme was very sensitive to inhibition by heavy metals.

Journal Article↗
PubMed1985

Hexose kinases from the plant cytosolic fraction of soybean nodules.

The enzymes responsible for the phosphorylation of hexoses in the plant cytosolic fraction of soybean (Glycine max L. Merr cv Williams) nodules have been studied and a hexokinase (ATP:d-hexose 6-phosphotransferase EC 2.7.1.1) and fructokinase (ATP:d-fructose 6-phosphotransferase EC 2.7.1.4) shown to be involved. The plant cytosolic hexokinase had optimum activity from pH 8.2 to 8.9 and the enzyme displayed typical Michaelis-Menten kinetics. Hexokinase had a higher affinity for glucose (K(m) 0.075 millimolar) than fructose (K(m) 2.5 millimolar) and is likely to phosphorylate mainly glucose in vivo. The plant cytosolic fructokinase had a pH optimum of 8.2 and required K(+) ions for maximum activity. The enzyme was specific for fructose (apparent K(m) 0.077 millimolar) but concentrations of fructose greater than 0.4 millimolar were inhibitory. The native molecular weight of fructokinase was 84,000 +/- 5,000. The roles of these enzymes in the metabolism of glucose and fructose in the host cytoplasm of soybean nodules are discussed.

Journal Article↗
PubMed1985

Effect of thyroid hormones on the glycolytic enzyme activity in brain areas of the rat.

The glycolytic metabolism through the key enzymes, hexokinase, phosphofructokinase, pyruvate kinase and lactate dehydrogenase, have been studied in the brain areas: anterior cortex, amygdala, hypothalamus, septum and hippocampus in adult rats with pharmacologically induced hyperthyroidism. The oxidative metabolism of glucose is accelerated in most brain areas by treatment with high doses of T3, as is shown by the increase in HK activity, approaching normality on reducing the dose. This decrease can also by observed in the PFK activity through the effect of assayed doses of thyroxine. The anterior cortex is the only brain area that does not show significant variations of PK activity through the effects of treatment with thyroid hormones. On the other hand, a general inhibition of the glycolytic anaerobic pathway by treatment with T3 was observed.

Amygdala↗
PubMed1985

[The endocochlear potential in experimental renal insufficiency].

Endocochlear Potential (EP) was measured in male Wistar rats under control conditions and renal failure produced by means of bilateral nephrectomy. Results show a statistically significant (p less than 0.01) decrease in EP measured in animals with renal failure. This finding is in accordance with the decrease in Na-K ATPase activity found in the cochlea and other structures in human and experimental kidney insufficiency.

Animals↗
PubMed1985

[Effect of thyroid hormones on the activity of pyruvate kinase and lactate dehydrogenase in mature rat brain].

The enzymatic activities of two "key" enzymes of the glycolytic pathway, pyruvate kinase and lactic dehydrogenase, were studied in seven areas of the brain in male adult rats in states of pharmacologically induced hyper and hypothyroidism. The brain areas were: anterior cortex, adenohypophysis, hypothalamus, amygdaline nucleus, septum, hippocampus and cerebellum. In T3 treated animals, pyruvate kinase activity showed significant increase in all the areas studied while lactic dehydrogenase activity decreased. In propyl-thiouracil treated animals these enzyme activities showed no significant variations from those in animals of the control group.

Animals↗
PubMed1984

Aldosterone and plasma renin activity in hyperthyroid rats: effects of propranolol and propylthiouracil.

Variations in renin- angiotensin-aldosterone system (RAAS) in experimentally induced hyperthyroidism were studied. The changes observed in the RAAS in these conditions, evaluated through the plasma renin activity (PRA), are parallel to serum aldosterone concentration (AC). An increase in PRA and AC is produced following the administration of triiodothyronine, possibly through elevated adrenergic activity: beta-blocker, propranolol, returned the PRA and AC to normal. The active hormone is seen to be triiodothyronine, confirmed by using the antithyroid preparation, propylthiouracil, to inhibit the conversion of thyroxine. Propylthiouracil administration to hyperthyroid animals lowers the PRA and AC.

Aldosterone↗
PubMed1984

The influence of plasma renin substrate on the relationship between plasma renin activity and plasma renin concentration. An experimental study in hyper- and hypothyroid rats.

The effects of endogenous Plasma Renin Substrate (PRS) on the relationship between Plasma Renin Activity (PRA) and the Plasma Renin Concentration (PRC) have been studied in hyperthyroid rats, by I-triiodothyronine (T3) administration and in hypothyroid rats, by propylthiouracil (PTU) treatment, to clarify if PRA changes are an adequate index for evaluating the renin-angiotensin changes during the alterations in the thyroid function. Although in experimental situations studied the induced variation on PRC explains a 62 per cent of the changes in PRA, finding a good lineal correlation between both parameters (r = 0.79, P less than 0.001). Not only does PRS play an important role on the kinetic of the enzymatic reaction but also explains jointly with PRC up to a 85 per cent of PRA alterations. PRS changes become more important during thyrotoxicosis where they limit in a higher degree the velocity of reaction due to inverse relationship between PRC and PRS (r = 0.74, P less than 0.001).

Angiotensinogen↗