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Biomedical subjects

O L Ramos

Publications and source records attributed to O L Ramos.

At least 73 records · Page 4Linked to original sources
PubMed1985

Sodium acetate, an arterial vasodilator: haemodynamic characterisation in normal dogs.

Sodium acetate (SA) has been implicated in hypotensive episodes of haemodialysis because of its vasodilatory effects. The haemodynamic correlates of the changes in blood pressure, cardiac output (CO) and total peripheral resistance (TPR) are well known but the site of action of SA (i.e. arteriolar, venular or both) is not yet clarified. We thus studied the changes in CO, TPR and mean arterial pressure (MAP) induced by four graded doses of SA (0.034 to 0.300 mEq/kg/min) in seven normal dogs. To evaluate the site of vasodilation we also measured the changes in cardiopulmonary volume (CPV), mean pulmonary artery pressure (MPAP) and mean transit time (MTT). From control to the highest infusion rate, CO increased from 1.63 +/- 0.20 to 3.59 +/- 0.38L/min (p less than 0.001), TPR decreased from 78.2 +/- 11.3 to 36.4 +/- 4.8A.U. (p less than 0.001). MAP rose significantly from 107.2 +/- 4.0 to 116.5 +/- 8.5 mmHg (p less than 0.05) and stroke volume was maintained (17.2 +/- 2.3 to 19.6 +/- 2.1 ml, NS) in spite of the marked tachycardia observed (heart rate from 106.1 +/- 7.6 to 194.8 +/- 9.1bpm, p less than 0.001). This was associated with increases in MPAP (from 13.3 +/- 0.7 to 19.6 +/- 2.1mmHg, p less than 0.01) and CPV (from 195.0 +/- 21.3 to 224.4 +/- 24.3ml, p less than 0.01) and marked decrease in MTT (from 7.74 +/- 0.73 to 3.78 +/- 0.22 sec, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1984

Acute hemodynamic and humoral effects of metoclopramide on blood pressure control improvement in subjects with diabetic orthostatic hypotension.

Metoclopramide (MCP), a dopaminergic antagonist, is effective in postural hypotension, but the mechanisms of action have not been well defined. We studied responses of mean arterial pressure (MAP), heart rate, cardiac output (CO), and total peripheral resistance (TPR) after 5 min of increasing degrees of head tilt (15 degrees to 90 degrees) before and after MCP (20 mg IV) in seven subjects with diabetic postural hypotension. Plasma renin activity (PRA) and plasma aldosterone levels (PA) were determined at each degree of tilt; responses to the cold pressor test were also assessed before and after MCP. Before MCP, the maximal degree of tilt tolerated was 75 degrees, while after MCP four subjects were able to support 90 degrees tilt. At 45 degrees tilt, the decreases in MAP were smaller after than before MCP (-7.6 +/- 3.3 and -28.1 +/- 8.5 mm Hg; means +/- SE). This was associated with responses of TPR to tilt after (from 18.6 +/- 2.6 to 24.0 +/- 3.9 arbitrary units [AU]) but not before (from 22.9 +/- 4.0 to 25.6 +/- 4.5 AU) MCP. Reductions in CO were of the same order before and after MCP. PRA responded to tilt better after than before MCP. Supine PA levels increased with MCP (delta PA = 5.4 +/- 0.7 ng/dl), but its response to tilt was unaltered. There were significant rises in MAP and HR during the cold pressor test after but not before MCP. Our data suggest that vasoconstriction is the main mechanism of MCP improvement in blood pressure response to an orthostatic stimulus in diabetic postural hypotension, possibly because of its antidopaminergic property.

Adult↗
PubMed1982

Pulmonary ventilation during hemodialysis.

During hemodialysis a decrease in pulmonary ventilation has been reported. The elimination of CO2 across the dialyzer has been suggested as the cause of the pulmonary hypoventilation. Our purpose was to analyze the factors that could have influenced the pulmonary ventilation of 7 patients with chronic renal failure during hemodialysis, performed against an acetate dialysate with constant addition of CO2, bubbling into the dialysis bath. In spite of the large volume of CO2 mainly as bicarbonate, eliminated across the dialyzer there was no significant decrease of ventilation. The values of pH in the venous line were extremely low and the values of PvCO2 were artificially maintained around 35.0 mm Hg. Thus, the total CO2 delivered to the lungs, but mainly the levels of pH and PCO2 in the venous line play an important role in the control of pulmonary ventilation of these patients.

Bicarbonates↗
PubMed1982

Dynamic evaluation of prolactin secretion in essential hypertension: evidence against hypothalamic-pituitary dopaminergic dysfunction.

Hyperprolactinemia has previously been noted in patients with essential hypertension and it has been suggested that the increased PRL levels in this condition may reflect reduced central dopaminergic activity. In the present study, PRL secretion was evaluated in 17 patients with essential hypertension and in 9 normal controls as an indirect index of hypothalamic-pituitary dopaminergic activity. PRL levels were measured basally, at night, and after TRH (200 micrograms, iv), metoclopramide (10 mg, orally), and L-dopa (500 mg, orally). Basal PRL levels were similar in both groups [essential hypertension, 301.2 +/- 176.2 microunits/ml; controls, 334.2 +/- 98.8 microunits/ml (mean +/- SD)]. No differences in PRL levels were found after TRH, L-dopa, and metoclopramide or during sleep between the 2 groups. When the patients were classified according to their PRA, no differences were noticed in either basal levels or the patterns of PRL response. It is concluded that PRL secretion is normal in patients with essential hypertension, which could be indirect evidence against reduced hypothalamic-pituitary dopaminergic activity in this disease. However, minor abnormalities not detected by PRL measurements could be involved in the pathogenesis of essential hypertension.

Adult↗
PubMed1982

Tetracaine, procaine and verapamil inhibition of fluid absorption in isolated perfused rabbit proximal convoluted tubules.

1. We determined the effect of local anesthetic and antiarrhythmic drugs which putatively increase cytosolic Ca2+ activity on fluid absorption (JV) by the isolated perfused proximal convoluted tubule of the rabbit. 2. Rabbit proximal convoluted tubules were perfused in vitro with an ultrafiltrate of modified Krebs-Henseleit solution containing 6.5 g/dl bovine albumin. 3. JV was measured before and after the addition of 2 mM tetracaine, 1 mM procaine or 5 microM verapamil, and after removal of the drugs from the bathing solution (recovery period). 4. All the drugs studied significantly inhibited JV in a reversible manner. 5. The data are consistent with the view that these drugs decreased the rate of fluid absorption in the proximal convoluted tubule by increasing cytosolic Ca2+ activity.

Absorption↗
PubMed1981

Etiopathogenesis of excess methylprednisolone arterial hypertension in the rat.

The blood pressure response to different doses of methylprednisolone was examined in the rat. It is concluded that doses varying from 2.5 mg/kg/week to 20 mg/kg/week of this agent caused clear-cut elevations in arterial pressure. The methylprednisolone-induced arterial hypertension was accompanied by elevation in Plasma Renin Activity and administration of captopril or saralasin caused significant drops in systemic arterial pressure. Concomitant long term administration of captopril and methylprednisolone caused a delay in appearance and smaller elevations in arterial pressure. It is concluded the methylprednisolone in the rat causes arterial hypertension which is at least partially dependent upon renin angiotensin system activation. However elevated blood pressure levels were noticeable even during chronic captopril administration leading to the conclusion that other mechanism (s) may participate in the pathogenesis of this experimental model of hypertension in rats.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1981

Inhibition of central angiotensin I conversion by oral captopril.

1. The central action of captopril (D-3-mercapto-methylpropanoyl-L-proline, SQ 14225) in the rat was evaluated by measuring the effect of the orally administered drug on responses to angiotensin I given intracerebroventricularly. 2. The pressor and dipsogenic effects of angiotensin I (20 ng) injected into the third ventricle were reduced by about 50% for 4 h following the oral administration of captopril, 20mg/kg. Both responses returned to pretreatment control values 8 h after captopril administration. 3. Orally administered captopril affects the action of angiotensin I on the central nervous system thus providing an alternative explanation for the hypotensive effect of captopril. This effect if probably due to the direct passage of captopril through the blood brain barrier.

Administration, Oral↗
PubMed1980

Chronic administration of cannabidiol to healthy volunteers and epileptic patients.

In phase 1 of the study, 3 mg/kg daily of cannabidiol (CBD) was given for 30 days to 8 health human volunteers. Another 8 volunteers received the same number of identical capsules containing glucose as placebo in a double-blind setting. Neurological and physical examinations, blood and urine analysis, ECG and EEG were performed at weekly intervals. In phase 2 of the study, 15 patients suffering from secondary generalized epilepsy with temporal focus were randomly divided into two groups. Each patient received, in a double-blind procedure, 200-300 mg daily of CBD or placebo. The drugs were administered for along as 4 1/2 months. Clinical and laboratory examinations, EEG and ECG were performed at 15- or 30-day intervals. Throughout the experiment the patients continued to take the antiepileptic drugs prescribed before the experiment, although these drugs no longer controlled the signs of the disease. All patients and volunteers tolerated CBD very well and no signs of toxicity or serious side effects were detected on examination. 4 of the 8 CBD subjects remained almost free of convulsive crises throughout the experiment and 3 other patients demonstrated partial improvement in their clinical condition. CBD was ineffective in 1 patient. The clinical condition of 7 placebo patients remained unchanged whereas the condition of 1 patient clearly improved. The potential use of CBD as an antiepileptic drug and its possible potentiating effect on other antiepileptic drugs are discussed.

Adult↗