Biomedical subjects
Publications and source records attributed to A Soler.
A case of oesophageal neurofibroma is reported; its low incidence among the benign tumours of the oesophagus is pointed out. The clinical, radiologic and histologic features of this very rare tumour are described.
The effects of changes in arterial pressure and in circulating volume on Plasma Renin Activity (PRA) in the intact rat were compared by two experimental procedures. Gradual volume depletion was induced by intraperitoneal injection of a hyperoncotic polyethyleneglycol solution (PEG) in absence of acute changes in Systolic Arterial Pressure (SAP). SAP was measured in the conscious state by the tail cuff technique. Plasma Protein Concentration (PPC) and Hematocrit (Hct) increases after PEG injection were compared as the index for measuring the Plasma Volume Reduction (PVR). PRA showed a significant (p less than 0.001) linear relationship with PPC, suggesting a direct dependence of renin secretion on volume depletion. Acute changes in the circulating volume were induced by controlled hemorrhages of 5.0, 10.0, 15.0 and 20.0 ml of blood/kg body weight. The increase in PRA showed a significant relationship with the changes in circulating volume, but it did not show any dependence on the changes in Mean Arterial Pressure (MAP). Our results suggest that, in the intact and conscious rat, renin secretion responds to the information from the cardiopulmonary volume receptors rather than to that from the high pressure receptors.
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The effects of changes in calcium on renin secretion have been studied in the isolated perfused rat kidney. Perfusion with free calcium buffer significantly decreases renin secretion as compared with control experiments (Ca++: 2.5 mM/l). Other calcium concentrations (1.25 mM/l) and 5 mM/l) do not affect basal renin secretion. When the renin release is previously increased by low sodium concentration (Na+: 110 mM/l) however, perfusion with high calcium buffer (Ca++: 5 mM/l) significantly inhibits this stimulation.
Plasma renin activity (PRA), plasma renin substrate (PRS), plasma renin concentration (PRC), and plasma aldosterone concentration (PAC) were measured in normal full-term newborn infants and infants up to 22 days after birth (36 in all). As compared to the control, PRA and PAC levels were significantly higher (p less than 0.001) in cord blood, and in 2 to 6 and 12 to 22 day old infants. The high values of PRA in 2 to 6 day old infants were due to the high PRS values. In cord blood and in 12 to 22 day old infants, however, the high levels of PRA reflect elevation of PRC. No correlation was found between PRA, PAC and serum potassium in cord blood and in 2 to 6 day old infants, but there was a significant correlation between the parameters (r = 0.72 and p less than 0.02) in 12 to 22 day old infants, indicating that at this age, as in healthy adults, the renin-angiotensin system and serum potassium seem to be the major stimuli for aldosterone secretion.
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.
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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.
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Acetylcholinesterase (E.C.3.1.1.7) was partially purified from rat brains stored in toluene. Extraction was performed using buffers containing non-ionic tensoactive detergents. Some properties of the enzyme were affected by the use of different activity measurement methods, such as the short-time radiometric or the long-time colorimetric method. There were two zones of maximum activity in the range pH 7.5-8.0 and 8.0-8.6, respectively. There seems to be a histidine residue in the enzyme that participates in the catalytic process. Thermal denuration presented first order kinetics and different thermodynamic parameters were obtained on using different incubation periods. On using the short-time activity measurement method there was activation at high substrate concentration, but with the long time method there was a marked inhibition produced by excess of substrate. However, if the enzyme was extracted from fresh rat brain, toluene untreated, these differences dissapeared. Gel filtration and disc electrophoresis showed the presence of multiple and interconvertible forms of the enzyme.
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