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Biomedical subjects

T Quesada

Publications and source records attributed to T Quesada.

At least 73 records · Page 4Linked to original sources
PubMed1983

[Participation of the renin-angiotensin system in experimental renovascular hypertension].

Hypertension was induced in Wistar rat by means of a clip in the left renal artery. After two weeks (acute stage) and sixteen weeks (chronic stage) the animals had a significant increase in arterial pressure (AP) and plasma renin activity (PRA). At both stages, nephrectomy or revascularization of the ischemic kidney returned AP and PRA to the normal level, both in the short term (1 day) and long term (60 days).

Animals↗
PubMed1983

[Hemodynamic changes in the acute phase of experimental hypertension].

The arterial pressure, heart rate, cardiac output, stroke volume, total peripheral resistance and plasma angiotensin II were measured in Wistar rats and 24 hours after arterial renal constriction by a clip (0.20 mm d.i.). The results were compared with those obtained in a sham operated group. The experimental group showed an increase in arterial pressure and total peripheral resistance without changes in heart rate, cardiac output and stroke volume. In hypertensive animals there was a greater level of plasma angiotensin II than in control group. These studies have demonstrated that 24 hours after renal arterial stenosis the increase in arterial pressure can be mediated by an increased activity of the renin-angiotensin system.

Angiotensin II↗
PubMed1982

Inhibition of the renin-angiotensin system by pinealectomy in female rats.

The influence of the pineal gland on the renin-angiotensin system has been studied in female rats. Pinealectomy produces a decreased plasma renin activity (PRA) concomitant with an increased corticosterone level, and with no changes in plasma aldosterone. Administration of indol melatonin reverses the effects of pinealectomy. On the other hand ovariectomy induces an increased PRA while decreasing corticosterone and aldosterone levels. However when pinealectomy and ovariectomy are both performed, neither PRA nor corticosterone changes. These results suggest that the pineal gland may exert an influence on the renin-angiotensin system via adrenal and/or ovarian pathways.

Aldosterone↗
PubMed1980

The effect of orthostatism, passive tilting and recumbent exercise on renin release.

Three postural tests, orthostatism, passive tilting and recumbent exercise, were applied to fourteen normal volunteers. Orthostatism and tilting produce a significant increase in plasma renin activity (PRA) and plasma renin concentration (PRC), without changes in plasma renin substrate concentration (PSC). Recumbent exercise induces an inhibition of PRA and PRC and does not changes PSC. The present study seems to suggest that sympathetic activity and intravascular blood volume could play an important role in the responses of the renin-angiotensin system to postural changes.

Adult↗
PubMed1979

Effect of sodium and osmolarity on renin secretion.

The effect of changes in sodium and osmolarity on renin secretion has been studied in the isolated perfused rat kidney. Perfusion with low sodium buffer (110 mM/l) produced a significant increase in renin secretion compared with control experiments (Na+:135 mM/l). Since the presence of tubules seems necessary for such an effect to take place, it suggests that the high renin secretion stimulated by a low sodium buffer centers in the Macula densa. Perfusion with high sodium buffer (170 mM/l; osmolarity 350 mOs/l) induces a stimulation on renin release. However, a greater rise in renin is achieved in control experiments if choline chloride increases the osmolarity from 300 to 350 mOs/l. All this suggests that high sodium buffer, independently of its osmotic effect, has an inhibitory role on renin release.

Animals↗
PubMed1978

[Effects of postural changes and volume depletion on renin-angiotensin system (author's transl)].

The effects of orthostatism and furosemide tests on different parameters of renin-angiotensin system have been studied in 14 normal human subjects. Both tests produced a significant increase in plasma renin activity and plasma renin concentration. Plasma substrate concentration was slightly, but significantly, increased on the furosemide test. Plasma aldosterone rose in both tests, while aldosterone urinary excretion decreased after orthostatism and increased after furosemide.

Adult↗
PubMed1977

An immunological study of nine proteins in CSF and serum of a group of epileptic patients.

The concentrations of nine proteins, alpha-1-acid glycoprotein, antitrypsin, prealbumin, transferrin, albumin, IgG, ceruloplasmin, IgA and alpha-2-macroglobulin, have been determined in the serum and CSF of two groups of patients, one control and one experimental, by an immunological method. The experimental group were patients suffering from grand mal epilepsy. The control group showed no detectable neurological disorder. In the group of grand mal epileptics, only prealbumin showed a significant elevation in CSF when compared with the control group. In contrast, the rest of the proteins are decreased with respect to the controls except for alpha 1-acid glycoprotein and transferrin. The results from this study also suggest that something more than an ultrafiltration process dependent upon molecular weight, is important in determining the concentration of some serum proteins in the CSF.

Adult↗
PubMed1977

The effects of EDTA and EGTA on renin secretion.

1 The effects of the disodium salt of ethylenediamine tetra-acetate (EDTA) and 1, 2, bis, 2 aminoethoxyethane-NNN'N'-tetra-acetic acid (EGTA) on renin secretion and vascular resistance were studied in the isolated perfused kidney of the rat. 2 Both substances produced a significant increase of renin release 3 In the absence of calcium and magnesium, EDTA still increased rein release and there was now a considerable increase of perfusion pressure. 4 The rise of pressure but not the rise of renin was inhibited by the removal of potassium from the perfusate when EDTA was administered in the absence of calcium. 5 Propranolol and phenoxybenzamine had no effect on the vasoconstrictor action of EDTA. 6 EGTA was less effective as a renin releaser than EDTA until magnesium was removed from the perfusate. Furter, it had only a small effect on perfusion pressure in contrast to EDTA.

Animals↗
PubMed1977

Stimulation of renin release by prostaglandin E2.

The effect of different doses of prostaglandin E2 on renin secretion in isolated perfused rat kidney has been studied. The infusion of 5 ng/ml of prostaglandin E2 produced a significant rise on renin secretion compared with control group. A dosage increase of prostaglandin E2 (10 and 50 ng/ml) produced an increase in the released renin. From this a correlation between doses and responses can be obtained. The perfusion pressure was slightly--but significantly--modified with the highest dose of prostaglandin (50 ng/ml). The possible pathways of action are dicussed.

Animals↗
PubMed1976

Simultaneous measurement of renin and renin substrate concentration in human plasma by a simple kinetic method.

A simple kinetic method is described for measurement of plasma renin concentration (PRC) and plasma renin substrate concentration (PRS) in human plasma. It is based on the radioimmunological determination of angiotensin I generated when a plasma sample is incubated at 37 degrees C for 2, 4, 6 and 8 h. The use of exogenous renin and renin substrate preparations are not required. The specific velocity constant of reaction (K) was used to deduce the PRC. PRS determination was based on the stoichiometric conversion of renin substrate to angiotensin I. PRC and PRS have been determined in plasma from healthy subjects, plasma from health subjects 3 h after oral furosemide administration and in plasma from women, 12-20 weeks normally pregnant.

Angiotensin II↗
PubMed1976

[Kinetics of renin reaction in rat plasma (author's transl)].

Important kinetic aspects of renin reaction were studied in order to evaluate the parameters that regulate the formation rate of angiotensin I. This rate decreased throughout the incubation period of normal rat plasma and it showed a linear increase when plasma was incubated with renin-substrate. When renin was added to normal rat plasma a plateau in the angiotensin I formation rate occurred after 4-6 hours. When plasma samples containing increasing amounts of renin-substrate were incubated, the velocity of their reaction increased in proportion to the renin-substrate concentration. Under these incubation conditions, the reaction between endogenous renin and renin-substrate in normal rat plasma, proved to be a first kinetic order with respect to the substrate.

Angiotensin II↗
PubMed1976

[Ceruloplasmine in schizophrenic and in epileptic patients (author's transl)].

Ceruloplasmine was measured in serum of normal, schizophrenic and epileptic patients through the use of oxidase and immunological methods. The measurements were correlated to find: the reliability of oxidase method as an index of ceruloplasmine concentration and the immunological identity of this protein in the three groups of individuals. The results showed that the oxidase method served as a good index of ceruloplasmine concentration in the sera and that an immunological identity among the three groups exised. A significant correlation between the serum oxidase activity and the ceruloplasmine immunological determination was, further, observed.

Ceruloplasmin↗
PubMed1976

[Immunological and oxidase measurement of ceruloplasmin in pregnant women and newborn (author's transl)].

Ceruloplasmin measurements were made by oxidase and immunochemical methods in serum from three groups of people, normal, pregnant women and their newborns. Whatever the method ceruloplasmin showed a decrease in the newborns and an increase in pregnant women as compared with the normal controls. The three groups showed a significant correlation between both measurement. The correlation ratio between the two methods of measurement in the newborns is significantly different from the pregnant and the normal groups. It appears that ceruloplasmin in the newborns' serum has a lower oxidase activity per molecule than that from adult's serum.

Ceruloplasmin↗
PubMed1975

Blockade of renin release by lanthanum.

1. The effects of lanthanum on renin release and renal vasoconstriction were studied in the isolated perfused rat kidney. 2. Lanthanum reduced noradrenaline-induced renal vasoconstriction. 3. Lanthanum prevented isoprenaline-induced and glucagon-induced stimulation of renin secretion.

Animals↗
PubMed1975

The effects of cyclic adenosine 3',5'-monophosphate and guanosine 3',5'-monophosphate and theophylline on renin secretion in the isolated perfused kidney of the rat.

1. The influence of cyclic adenosine 3',5'-monophosphate (cyclic AMP), cylic guanosine 3',5'-monophosphate (cyclic GMP) and theophylline on renin secretion was examined in the isolated kidney of the rat perfused with Krebs dextran solution. 2. Neither cyclic AMP (10(-6) to 10(-4) M) nor dibytyryl cyclic AMP (10(-5) M) produced an increase in renin secretion. 3. Cyclic GMP and 8 Br-cyclic GMP caused a small rise in renin secretion in some experiments but this effect was independent of the dose and its physiological significance is uncertain. 4. Theophylline (10(-6) to 10(14) M) caused a significant elevation in renin secretion which was not blocked by (+)-propranolol. Theophylline with cyclic AMP or cyclic GMP did not produce an amplified effect. 5. Despite previous suggestions that cyclic AMP stimulated renin secretion, this could not be confirmed in the present preparation. Since there is no evidence that cyclic AMP or cyclic GMP (or their derivatives, dibutyryl cyclic AMP and 8 Br-cyclic GMP) enter the cells, it will be necessary to study their activity in isolated juxtaglomerular cells to define a possible role.

Animals↗