Biomedical subjects
Publications and source records attributed to R Garcia.
The study of a population treated according to orthodontico-surgical process with only a LE FORT I osteotomy allowed us to determinate the moderate influence on each element of curtain profile (nose, lips and chin). The comparison between relative moving of maxillary and the one of each cutaneous structures enable us to define the sagittal and vertical displacement's ratios of curtain profile.
The authors describe a new case of full trisomy 22 in a malformed newborn female, who died shortly after birth. Pathologic findings include cardiac, vascular, renal, gastrointestinal, genital and cerebral malformations. The study of C-heteromorphisms shows a paternal origin of the aneuploidy (non-disjunction at meiosis II).
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The secretory pathways of atrial natriuretic factor have been investigated in atrial and ventricular cardiocytes of control and cardiomyopathic Syrian hamsters in severe congestive heart failure with four antibodies: a monoclonal antibody (2H2) against rat synthetic atrial natriuretic factor (101-126), which is directed against region 101-103 of rat atrial natriuretic factor (99-126), and polyclonal, affinity-purified antibodies produced in rabbits against synthetic C-terminal atrial natriuretic factor (101-126), synthetic N-terminal atrial natriuretic factor (11-37) or the putative cleavage site of atrial natriuretic factor (98-99): atrial natriuretic factor (94-103). Application of the immunogold technique on thin frozen sections (immunocryoultramicrotomy) revealed an identical picture with the four antibodies. In atria of both control and cardiomyopathic hamsters where atrial natriuretic factor secretion is regulated, the atrial natriuretic factor propeptide travels, uncleaved, from the Golgi complex to immature and mature secretory granules. In ventricles of control hamsters, where secretion is constitutive, the atrial natriuretic factor propeptide travels from the Golgi complex to secretory vesicles. In the ventricles of hamsters with severe congestive heart failure, the Golgi complex is larger, secretory vesicles more abundant and a few secretory granules are present in approximately 20% of cardiocytes. Here again, the peptide travels uncleaved in all these pathways. These results reveal the pathways of secretion of atrial natriuretic factor in atrial and ventricular cardiocytes and indicate that the propeptide is not cleaved intracellularly.
A selective and sensitive high-performance liquid chromatographic method is described for determination of hydralazine and its metabolites in human plasma. The method involves pre-column derivatization with 2-hydroxy-1-naphthaldehyde at pH 1.2. The reaction product and Methyl Red used as internal standard are extracted into dichloromethane and chromatographed in the reversed-phase mode on an ODS-2 column using acetonitrile-aqueous triethylamine phosphate buffer (80:20, v/v) at pH 3 as eluent. The plasma calibration curve of hydralazine is linear in the concentration range 10-500 ng ml-1. The detection limit is 1 ng ml-1 and the relative standard deviation is less than 2.4. In vivo pharmacokinetics of hydralazine in two volunteers after oral administration of 50 mg of the drug is studied using the proposed LC method.
STUDY OBJECTIVE: The aim was to study glomerular and vascular atrial natriuretic factor (ANF) receptors and their relationship with the post-receptor effects of the peptide in experimental heart failure. DESIGN: Binding sites ANF were studied in renal glomerular and mesenteric artery membranes. The natriuretic and relaxing effects of ANF were evaluated in the intact animal and in noradrenaline precontracted aortic strips respectively. Plasma and tissue ANF levels were also assessed. EXPERIMENTAL MATERIAL: The study was performed on cardiomyopathic (UM-X7.1) hamsters (n = 15) with a moderate degree of heart failure. Age matched Golden Syriam hamsters (n = 15) were used as controls. MEASUREMENTS AND MAIN RESULTS: Cardiomyopathic hamsters presented lower blood pressure, body weight, and plasma Na+, and higher heart weight than normal hamsters. Plasma ANF (1-98) and (99-126) levels and ventricular ANF content were higher in cardiomyopathic hamster than in controls. ANF and frusemide decreased blood pressure, and increased diuresis and natriuresis in normal hamsters. The blood pressure reduction by ANF in cardiomyopathic hamsters was approximately of the same magnitude as in normal hamsters but their renal response was blunted. The blood pressure lowering effect of frusemide was similar in both cardiomyopathic and normal hamsters, but the diuretic and natriuretic responses were greatly reduced in the former. Glomerular ANF receptor density was higher and receptor affinity was lower in cardiomyopathic hamsters than in controls. Noradrenaline precontracted vascular strips from cardiomyopathic hamster were more sensitive to the relaxant effect of ANF than those from controls. No differences in either density or affinity of vascular receptor were observed. CONCLUSIONS: The results suggest that the renal hyporesponsiveness of cardiomyopathic hamsters to ANF is not due to a down regulation of glomerular ANF receptors. The fact that the natriuretic response to frusemide is also blunted suggest the involvement of other factors.
STUDY OBJECTIVE - The aim of the study was to develop a new procedure to produce abdominal aortocaval shunts in the rat without vascular microsurgery. PROCEDURE - The inferior vena cava and abdominal aorta were exposed by laparotomy. The aorta was punctured caudal to the left renal artery with an 18 gauge disposable needle which was advanced into the vessel, perforating the adjacent wall between aorta and vena cava and penetrating the latter. A bulldog vascular clamp was placed across the aorta cephalic to the puncture, the needle was withdrawn, and the aortic puncture point was sealed with a drop of cyanoacrylate glue. The clamp was removed 30 s later. Patency of the shunt was verified visually by swelling of the vena cava and admixture of arterial and venous blood. No local haemorrhages were seen. The laporatomy was then closed. The procedure takes less than 10 min. RESULTS - Of 11 rats which received this procedure, only one died within 24 h. All the other animals were killed 4 weeks after operation. Nine of these 10 animals had developed cardiac hypertrophy of about the same magnitude. There were no changes in sham operated controls. CONCLUSIONS - This is a reproducible, simple and rapid method of developing high output heart failure and cardiac hypertrophy in the rat which could be useful in many laboratories.
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Endothelin is a novel endothelium-derived vasoconstrictor peptide. We investigated its effect on atrial natriuretic factor (ANF) release and on several cardiovascular and renal parameter, since ANF release is induced via hemodynamic changes in response to angiotensin II, another vasoconstrictor peptide. Male Sprague-Dawley rats were infused intravenously for 60 min with either saline or endothelin at 10, 50 or 100 ng/kg per min and then allowed to recover for 20 min. A third group was splenectomized 24 h before infusion with 100 ng/kg per min endothelin. Mean arterial, left ventricular end-diastolic and central venous pressures (dP/dtmax), heart rate, plasma ANF-(1-98) concentration, urinary volume, urinary sodium excretion and hematocrit were evaluated. Mean arterial pressure was elevated by both medium and high endothelin doses, and with the high dose this elevation was sustained beyond the infusion period. No increases in either left ventricular end-diastolic or central venous pressures were observed at any dose level. In fact, in rats infused with 100 ng endothelin there was a progressive decline in central venous pressure and a raised hematocrit, even in the splenectomized group, suggesting a loss of plasma volume. All three dose levels elevated the dP/dtmax at different infusion times. The heart rate was not modified by any endothelin dose. Despite the decreased central venous pressure and unaltered left ventricular end-diastolic pressure, the 100 ng/kg per min endothelin infusion induced a threefold increase in plasma ANF levels; these were correlated with changes in the dP/dtmax (r = 0.49, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Since glomerular and vascular atrial natriuretic factor (ANF) receptor density may vary inversely with circulating ANF concentration, and the latter may respond to changes in blood pressure, we investigated whether ANF receptors are modified by a pressor agent, angiotensin II. Rats were infused intraperitoneally for 6 days with either a non-pressor (200 ng/kg per min) or pressor dose (800 ng/kg per min) of angiotensin II. Blood pressure was higher and plasma renin activity lower in the pressor than in the non-pressor or sham-infused groups. Plasma ANF was elevated only in animals infused with a pressor dose of angiotensin II. Glomerular ANF receptor density was higher in the non-pressor (Bmax = 1308 +/- 360 fmol/mg protein) and lower in the pressor (Bmax = 459 +/- 13 fmol/mg protein) than in the sham-infused group (Bmax = 755 +/- 303 fmol/mg protein). In vitro, angiotensin II-precontracted isolated glomeruli from animals infused with a pressor dose of angiotensin II were less sensitive to the relaxant effect of low ANF concentrations (10(-12) and 10(-11) mol/l) than those receiving a non-pressor dose of angiotensin II or sham-infused. Vascular ANF receptor density was similar in the control and non-pressor groups (Bmax = 64 +/- 12 and 62 +/- 20 fmol/mg protein, respectively) and decreased in the pressor group (Bmax = 30 +/- 4 fmol/mg protein). Norepinephrine-precontracted aorta strips from rats receiving a non-pressor dose of angiotensin II were more sensitive to the relaxant effect of ANF.(ABSTRACT TRUNCATED AT 250 WORDS)
Several analogs of the atrial natriuretic factor (ANF) were synthesized by the solid-phase method using the acetamidomethyl (Acm) group for sulfhydryl protection. The compounds were tested in a receptor binding assay using bovine adrenal zona glomerulosa cell membranes and in the rat diuresis/natriuresis assay. Substitution of tyrosine in position 116 of ANF(101-126) and of the analog [3-Mpr105]ANF(105-126)(3-Mpr = 3-mercaptopropionic acid) did not alter the biological activity profiles and, therefore, these two analogs in radioiodinated form will be useful for enzymatic degradation and clearance studies. Replacement of 3-mercaptopropionic acid with 2-mercaptopropionic acid in [3-Mpr105]ANF(105-126) resulted in an analog with very low potency in both assay systems, presumably as a consequence of the steric bulk and/or local conformational restriction produced by the methyl group attached to the alpha-carbon in position 105. The analog [3-Mpr105,Nva109]ANF(105-126)(Nva = norvaline) showed very low affinity in the receptor binding assay but displayed considerable diuretic/natriuretic activity. The obtained biological activity profiles suggest that in comparison with other ANF peptides the des-amino ANF(105-126) analogs may have a somewhat longer half-life in vivo, or alternatively, may indicate a more complex situation of ANF receptor or binding site heterogeneity.
We investigated whether rats with high-output heart failure [aortocaval (AC) shunts] release atrial natriuretic factor (ANF) and excrete sodium after moderate volume expansion (VE) as do sham-operated controls. Mean arterial blood pressure was lower (92.5 +/- 4.4 vs. 114.0 +/- 1.3 mmHg) and relative heart weight was higher (545.6 +/- 35.1 vs. 253.8 +/- 9.8 mg/100 g body wt) in animals with AC shunts than in their controls. Central venous pressure (CVP) was elevated (3.61 +/- 0.36 vs. 0.37 +/- 0.94 mmHg) and heart rate decreased (332.5 +/- 8 vs. 370.0 +/- 9.9 beats/min) in AC rats. This group also presented lower basal urinary sodium excretion (UNaV), urinary volume, and hematocrit than their sham-operated controls. Basal plasma COOH- and NH2-terminal ANF levels were greatly elevated in AC shunt animals (165.43 +/- 55.73 and 1,692.98 +/- 305.63 fmol/ml, respectively) when compared with the controls (14.27 +/- 1.49 and 331.67 +/- 29.84 fmol/ml, respectively). VE was performed in conscious rats 3 times at 15-min intervals with human plasma protein fraction. The effect of VE on CVP, left-ventricular end-diastolic pressure, the increases in plasma COOH- and NH2-terminal ANF, and the diuretic and natriuretic responses were similar in both experimental groups. U(NA)V was positively correlated with plasma COOH- (r = 0.50, P less than 0.01) and NH2- (r = 0.60, P less than 0.001) terminal ANF only in the controls. One main peak of immunoreactive ANF corresponding to the elution time of a small peptide such as ANF-(99-126) was detected in the plasma of AC animals after VE. We conclude that ANF release and natriuresis are conserved after moderate VE in a rat model of moderate high-output experimental heart failure.
The receptor for atrial natriuretic peptide (ANP) in the rat renal papilla was characterized pharmacologically. After solubilization and irreversible binding with disuccinimidylsuberate, it was shown on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) to be made of a single peptide of 125 kDa. The regulation of the renal papillary ANP receptor was studied in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. DOCA-salt rats had suppressed plasma renin activity and increased plasma ANP concentrations (408 +/- 35 vs. 133 +/- 12 pg/ml in uninephrectomized controls, P less than 0.01). The renal papilla was hypertrophied in DOCA-salt hypertensive rats (93 +/- 1 vs. 52 +/- 1 mg, P less than 0.01). The density of ANP sites in the papilla was significantly higher in DOCA-salt rats (141 +/- 31 fmol/papilla) than in controls (34 +/- 8 fmol/papilla, P less than 0.01). Affinity of sites in DOCA-salt rats and controls was similar. The production of guanosine 3',5'-cyclic monophosphate (cGMP) in renal papilla in response to ANP was significantly higher in DOCA-salt rats. In contrast to the renal papillary ANP receptor, acid-washed vascular and glomerular ANP sites were significantly decreased in density in DOCA-salt hypertensive rats. In blood vessels and glomeruli, both the high- and low-molecular mass receptor (as detected on SDS-PAGE under reducing conditions) was proportionately decreased in density in DOCA-salt hypertensive rats. The present results suggest that an increased number of ANP receptors and exaggerated cGMP response to ANP in the renal papilla may underlie the increased natriuretic responsiveness of the kidney to ANP in DOCA-salt hypertensive rats.
In vitro autoradiographic studies showed that high-affinity atrial natriuretic factor (ANF) binding sites are present on rat choroid plexus (Kd = 83.8 pM, Bmax = 22.9 fmol/mg protein). Guanylate cyclase-coupled receptors (ANF-R1) represent 30% and non-guanylate cyclase-coupled ANF receptors (ANF-R2) represent 70% of the total ANF receptors present in this tissue. To provide detailed cellular localization of the binding sites, the technique of electron-microscopic autoradiography was applied using 125I-ANF (Ser 99-Tyr 126) as an in vivo ligand. In order to identify possible binding sites at the basolateral and the apical aspects of the choroid plexus, the ligand was injected into the carotid artery or into the lateral cerebral ventricles, respectively. Light-microscopic autoradiography demonstrated that ANF binds specifically to choroid plexus regardless of its route of administration. Electron-microscopic autoradiography showed that silver grains were localized primarily on epithelial cells of the choroid plexus (96-99%) and marginally on endothelial and pial cells. In choroidal epithelial cells, ultrastructural analysis of silver grain distribution revealed that, at 2 min after intracarotid or intracerebroventricular 125I-ANF injection, lysosomes were the most distinctly labeled organelle (highest relative specific radioactivity). HPLC Chromatographic analysis disclosed that 96-99% of choroid plexus-bound ANF was already degraded 2 min after injection and that at least 63-66% of the degradation took place at the plasma membrane. These results indicate that ANF binding sites are present on both aspects of choroidal epithelium, and suggest that ANF is very quickly degraded in choroid plexus by membrane-associated as well as lysosome-associated processes.
We investigated the localization of atrial natriuretic factor (ANF) mRNA and of immunoreactive ANF in the vena cava and sinus node of rat and, for comparative purposes, in atria and ventricles. In situ hybridization with an ANF cRNA probe revealed that the supradiaphragmatic portion of the inferior vena cava contains almost as much mRNA as the atria, whereas the levels were less in the superior vena cava and higher than in ventricles in the sinus node. Immunoreactive ANF (high Mr form) was found to be 22 times less abundant in the supradiaphragmatic vena cava and 148 times less abundant in the superior vena cava than in atrial cardiocytes. The wall of the supradiaphragmatic portion of the vena cava and the valve (eustachian valve) that separates the atrial cavity from that of the vein are made up of atrial-like cardiocytes containing secretory granules. The subendothelial area of the superior vena cava also contains atrial-like cardiocytes with secretory granules, whereas the outer portion of the vein is made up of "transitional cells" without or with only a few secretory granules. Secretory granules in the vena cava and nodal cells, as well as transitional cells, contain immunoreactive ANF. With immunocryoultramicrotomy, virtually all cells, whether atrial-like, transitional, or nodal, and even those without secretory granules, were found to contain immunoreactive ANF in their Golgi complex and in secretory vesicles in the vena cava and in the sinus node.
The active uptake of ascorbic acid by isolated rat adrenocortical cells increases with ascorbic acid concentration, depends on time and calcium, and is inhibited by ACTH concentrations required for maximal steroidogenesis. Lipopolysaccharide of Escherichia coli 0111:B4 modifies the ascorbic acid uptake in a calcium-dependent manner. At low calcium concentrations, lipopolysaccharide exerts a stimulatory effect on ascorbic acid transport and at high concentrations lipopolysaccharide produces a dose-dependent inhibitory effect. This inhibition of the ascorbic acid transport by the endotoxin can alter the ascorbic acid accumulation in the adrenal gland during endotoxin shock.
Because adrenal participation in the defense mechanisms against endotoxic shock is essential for survival, adrenal gland function during reversible endotoxicosis was studied. The injection of E. coli LPS into rats produces an increase in plasma corticosteroids (maximum at 2-4 hr post-endotoxin injection) and ACTH levels (maximum at 2 hr post-endotoxin injection), which return to control values at the recovery phase. Nevertheless, ACTH-induced steroidogenesis in cells isolated from adrenal glands of endotoxemic rats is clearly impaired, even at 2 hr post-endotoxin injection when corticosteroid levels are maximal. During reversible endotoxic shock there is also a depletion of adrenal ascorbic acid (maximum at 2-4 hr post-endotoxin injection) and a decrease in adrenal cytochrome P-450 levels. These data suggest that impairment of the adrenal gland function could involve mechanisms at the receptor level (desensitization by the high plasma ACTH levels or a direct effect of LPS) and/or at post-receptor steps (decrease in adrenal cytochrome P-450 levels related to the diminution in adrenal ascorbic acid content).
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