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Biomedical subjects

M Morell

Publications and source records attributed to M Morell.

At least 91 records · Page 5Linked to original sources
PubMed1984

Enzymes of sucrose breakdown in soybean nodules: alkaline invertase.

The specific activities of acid and alkaline invertases (beta-d-fructofuranoside fructohydrolase, EC 3.2.1.26), sucrose synthase (UDPglucose: d-fructose 2-alpha-d-glucosyltransferase, EC 2.4.1.13), hexokinase (ATP: d-hexose 6-phosphotransferase, EC 2.7.1.1), and fructokinase (ATP: d-fructose 6-phosphotransferase, EC 2.7.1.4) were determined in soybean (Glycine max L. Merr cv Williams) nodules at different stages of development and, for comparison, in roots of nonnodulated soybeans. Alkaline invertase and sucrose synthase were both involved in sucrose metabolism in the nodules, but there was only a small amount of acid invertase present. The nodules contained more phosphorylating activity with fructose than glucose. Essentially all of the alkaline invertase, sucrose synthase, and fructokinase were in the soluble fraction of nodule extracts whereas hexokinase was in the bacteroid, plant particulate, and soluble fractions.Soybean nodule alkaline invertase was partially purified and shown to be a beta-d-fructofuranosidase which was specific for sucrose. The pH optimum was 7.6 and the K(m) for sucrose was 10 millimolar. Fructose was a competitive inhibitor. Tris was a noncompetitive inhibitor and the enzyme was very sensitive to inhibition by heavy metals.

Journal Article↗
PubMed1984

Renin-angiotensin system in hypothyroid rats: effects of potassium iodide and triiodo-L-thyronine.

Kinetic studies of the renin-angiotensin system (RAS) were carried out by measuring plasma renin activity (PRA), plasma renin concentration (PRC) and plasma renin substrate (PRS). Changes in this system were studied during hypothyroidism, after administration of propylthiouracil (PTU), and in thyroidectomized rats. A significant decrease in PRA and PRC was observed in those animals previously treated with PTU. However, a significant increase in PRC, and a decrease in PRS, were found in T animals, but no changes in PRA were observed. In these animals, after daily administration of potassium iodide for 1 week (T + KI), no changes in RAS were observed in comparison with T rats. Nevertheless, administration of daily doses of triiodo-L-thyronine (T + T3) induced a significant increase in PRA, leaving PRC unaltered. In this case the changes in PRA were related to the increase in PRS after T3 treatment. These results suggest that two different mechanisms were involved in renin release, one activated in T rats and the other in pharmacological hypothyroidism.

Animals↗
PubMed1984

Effects of two different experimental situations of hypothyroidism on serum aldosterone concentration and plasma renin in rats.

When hypothyroidism is induced surgically in early steps of development in the rat, an increase in serum aldosterone concentration (AC), in absence of changes in plasma renin activity (PRA), is observed. In contrast, in propylthiouracil (PTU) induced hypothyroidism, in adult animals, both AC and PRA decrease. Potassium iodide (KI) or triiodo-L-thyronine (T3) administration to thyroidectomized rats restores AC to normal levels, increasing PRA during the latter treatment. A close relationship between AC and plasma renin concentration (PRC) is observed in these experimental situations. The decrease in urinary aldosterone concentration (ACu), and the relation found between AC/ACu ratio and T3 concentration, suggest that metabolic clearance of aldosterone might be related to peripheric T3 levels in thyroidectomized animals, treated with KI or T3. These observations support the hypothesis, previously reported, which suggests different mechanisms involved in the control of aldosterone and renin release during the two different types of hypothyroidism.

Aldosterone↗
PubMed1983

[Effect of experimental changes in thyroid function on oxidative metabolism and glutamate dehydrogenase activity in the limbic system of the rat].

The oxidative metabolism and GDH activity has been studied in the following regions of the brain: frontal cortex, as tissue control, adenohypophysis, hypothalamus and limbic system in adult male rats subjected to alterations of the thyroid function due to excess (by hyperthyroidism with L-thyroxine and thyrotoxicosis with Tri-iodothyronine) or defect (chronic hypothyroidism by thyroidectomy, 131-I treatment and low iodine diet). A different influence of the H.T. was observed in these animals according to the areas studied and the experimental situation induced. All this seems to indicate an oxidative metabolic pattern peculiar to each area of the brain following H.T. administration. On the other hand, the decrease of the QO2 in chronic hypothyroidism in the majority of the areas studied is remarkable. In GDH results activity increased or decreased depending on the absence or presence of thyroid hormones.

Animals↗
PubMed1983

[Effects of bilateral nephroadrenectomy on the composition of perilymphatic fluid in the rat].

The examination of osmolality and ionic composition of plasma and perilymphatic liquid of nephroadrenectomized rats was performed by systematic methods. Significant increases in osmolality, Na and K concentrations were found in perilymph of nephroadrenectomized animals. The functional importance of these findings is evaluated, and the influence of blood labyrinth barrier and osmotic mechanisms on these results is discussed. Simultaneously, the possibility that similar mechanisms might be involved in the pathogenesis of Meniere's disease is pointed out. A possible route on pathogenical and clinical studies in labyrinth pathology is enhanced.

Adrenalectomy↗
PubMed1982

[A new spectrofluorimetric method for renal renin activity: a comparative study with other methods].

A new spectrofluorimetric method for protein estimation has been developed and applied to study the renin-angiotensin system. The fluorometric reagent, 1-4-diamino-2-3-dichloro-anthraquinone, is introduced in this field and used for the first time. Renal semipurified rat renin is incubated with a synthetic substrate (N-acetyl-tetra-decapeptide) at 0 degrees C and 37 degrees C, at optimal pH, during 3 hours. The incubated mixture is studied by bioassay (BA), radioimmunoassay (RIA) and spectrofluorimetric analysis (SFA), and values obtained with these methods are compared. Blank samples for spectrofluorimetric analysis were prepared by substituting the incubated mixture with the unincubated components of the reaction. Its fluorescence values were subtracted from those of the incubated mixture. Precision and sensitivity for RIA and SFA were similar in both cases, but different in the case of BA. Renal renin activity (RRA) values for RIA (7.15 x 10-(3) nM/ml angio. I/3 h) and SFA (7.08 x 10-(3) nM/ml angio. I/h) were statistically equal (t = 1.05; p less than 0.05), while RRA values for BA (6.23 x 10-(2) nM/ml angio. I/3 h), were higher and significantly different from the statistical point of view. The graphical representation of RRA values for RIA versus SFA values gives an objective expression where RRA(RIA) = 0.78 RRA(SFA) + 0.02.

Animals↗
PubMed1982

[Comparison of adsorption capacity for FSH between kaolin and montmorillonite. Biological and immunological activity relation (author's transl)].

The adsorption capacity of urinary FSH has been studied comparatively with kaolin and montmorillonite, a new type of bentonite, never used before in gonadotrophin adsorption. To measure adsorption capacity, two different assay methods were used: bioassay (for biological activity of the kaolin and montmorillonite extracts) and radioimmunoassay (RIA) for the immunological activity of FSH in both extracts. From the present results a biological activity increase was observed in montmorillonite extracts, while no significant differences between immunological activity of FSH were found in either extract. These findings suggest that montmorillonite could replace kaolin in gonadotrophins extraction and purification methods.

Adsorption↗
PubMed1982

[Propranolol effect on renin-angiotensin system kinetics during experimental hyperthyroidism (author's transl)].

The basal levels of angiotensin I (A. I), plasma renin activity (PRA), plasma renin substrate (PRS) and plasma renin concentration (PRC) were estimated in hyperthyroid rats before and after propranolol treatment. Serum levels of triiodothyronine (T3), thyroxine (T4), angiotensin I both basal and generated by incubation of plasma samples were measured by radioimmunoassay, while, PRC and PRS were evaluated by triiodothyronine or thyroxine treatment induced a decrease in PRS and an increase in PRC whereas triiodothyronine alone produced an increase in the basal levels of angiotensin I and PRA. The propranolol in euthyroid animals not only decreased the basal levels of angiotensin I and PRA, but also prevented the PRC increase in hyperthyroid rats, while restoring at the same time the basal levels of angiotensin I and PRA.

Angiotensin I↗
PubMed1982

Effects of hyper- and hypothyroidism on the basal levels of angiotensin I and kinetic parameters of renin-angiotensin system in male rats.

The basal levels of angiotensin I and kinetic parameters of renin-angiotensin system were studied under control, hyper- and hypothyroidism conditions. The serum levels of triiodothyronine (T3) and thyroxine (T4) and plasma angiotensin II have been measured radioimmunoassay. Hyperthyroidism was induced by 5.5 micrograms/200 g of T3 or 100 micrograms/200 g of T4 administration for 12 days, and hypothyroidism by propylthiouracil (PTU) administration of 1 mg/200 g for 12 days. Basal levels of angiotensin I and plasma renin activity (PRA) increased after T3 injection, were not altered by T4 and decreased after PTU administration. T3 and T4 induced an increase in plasma renin concentration (PRC), while PTU induced a decrease in PRC. Plasma renin substrate (PRS) decreased in hyperthyroid rats and was unchanged by experimentally induced hypothyroidism. A good correlation between T3 serum levels and PRA was found, but there was no such correlation between T4 serum levels and PRA.

Angiotensin I↗
PubMed1980

Stimulatory action of angiotensin II on water and electrolyte transport by the proximal colon of the rat.

In segments of isolated proximal colon from bilaterally adrenalectomized and nephrectomized rats 10(-12) g angiotensin/ml added to the serosal medium stimulated fluid transfer and sodium transport whose increase was accompanied by a decrease in transepithelial potential difference and short circuit current. Transepithelial electrical resistance remained unchanged. Replacement of chloride by sulphate in the bathing medium blocked the response to angiotensin. This suggested that angiotensin stimulated a coupled NaCl transport. Administration of aldosterone also blocked the response to angiotensin, suggesting that a low concentration of endogenous aldosterone is partly responsible for the action of angiotensin. This would explain the necessity for some form of pretreatment such as bilateral adrenalectomy and nephrectomy. Hydraulic conductivity of proximal colon sacs was computed from the variation in the water flow from serosa to mucosa in response to an osmotic shock. A significant (P < 0.01) increase in the hydraulic conductivity of the proximal colon of bilaterally adrenalectomized and nephrectomized rats was found when 10(-12) g angiotensin/ml was present in the serosal bathing medium. The observed decrease in the transepithelial potential difference has been related to an action of angiotensin on the paracellular shunt pathway.

Adrenalectomy↗