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Biomedical subjects

I Hernandez

Publications and source records attributed to I Hernandez.

53 records · Page 3Linked to original sources
PubMed1992

Salt intake and angiotensin II alter microvessel density in the cremaster muscle of normal rats.

This study investigated the effect of salt intake and angiotensin II (ANG II) levels on microvessel density (MVD). Rats with indwelling arterial and venous catheters were placed on either a high-salt (HS; 4%) or a low-salt diet (LS; 0.4%) for 2 or 4 wk, and blood pressure, heart rate, and plasma renin activity were measured. Plasma ANG II was fixed at normal levels in half of the rats on HS by continuous intravenous infusion of ANG II (5 ng.kg-1.min-1). Samples of cremaster muscle were examined histologically to determine MVD. No difference in MVD was observed between HS and LS groups after 2 wk. After 4 wk on HS, MVD was reduced (22.4%, P less than 0.05) compared with the LS group. In rats fed HS, ANG II infusion induced a significant dose-dependent increase in MVD from 85.11 +/- 3.34 to 98.94 +/- 4.62 (ANG II, 5 ng.kg-1.min-1) and to 107.60 +/- 7.00 (ANG II, 10 ng.kg-1.min-1) (P less than 0.05), with no change in blood pressure. Maintenance of ANG II levels for 4 wk blocked the rarefaction due to salt. These results suggest that the decrease in MVD due to salt could be the result of a dietary-induced fall in plasma ANG II levels.

Angiotensin II↗
PubMed1991

Cardiocirculatory responses to AII and AVP in conscious rats.

Cardiac and peripheral circulatory responses to changes in afterload with angiotensin II (AII) and vasopressin (AVP) were investigated in ganglion-blocked (hexamethonium) conscious rats. Cardiac output (CO) was measured by thermodilution. Both hormones were infused at a dose adjusted to increase mean arterial pressure 70% above baseline. AVP (11.4 +/- 2.2 ng/kg/min, n = 6) decreased CO from 43.4 +/- 2.3 to 34.1 +/- 2.9 ml/min/100 g (p less than 0.001), whereas AII (33.4 +/- 7.4 ng/kg/min, n = 7) increased CO from 38.7 +/- 2.6 to 44.9 +/- 3.4 ml/min/100 g (p less than 0.01). Heart rate did not change with the increase in afterload with either vasoconstrictor. To study whether the different effects of AII and AVP on CO may be explained by their different actions on the venous system, changes in venous tone were evaluated by measuring mean circulatory filling pressure (MCFP) and determining the pressure gradient for venous return (PGVR). AVP changed neither MCFP nor PGVR, whereas AII increased both these parameters, 20.7 +/- 2.8% (p less than 0.01) and 20.3 +/- 6.4% (p less than 0.01), respectively, above control. We also examined the effects of AII and AVP on ventricular dynamics: left ventricular systolic pressure and left ventricular dP/dtmax increased as aortic pressure was increased in a similar manner with both vasoconstrictors. However, AVP induced a greater increase in left ventricular end diastolic pressure than AII. Our results indicate that AII induces an increase in preload by its effect on venous tone, which is adequate to increase cardiac output. The decrease in cardiac output induced by increasing afterload with AVP can be explained by two mechanisms: an inadequate venous return and a failure of the left ventricle to overcome the increased afterload.

Angiotensin II↗
PubMed1991

Role of intrarenal angiotensin II in mediating renal response to volume expansion.

Natriuresis induced by extracellular volume expansion (ECVE) is accompanied by a decrease in renin release and by an increase of renal interstitial hydrostatic pressure (RIHP). This study was undertaken to examine, in anesthetized dogs, the relative role of intrarenal angiotensin II (ANG II) changes in mediating natriuresis, diuresis, and increases in RIHP induced by two different levels of volume expansion (1.5 and 5% body wt in 45 min) with isotonic saline. Intrarenal ANG II levels were maintained in the right kidney throughout the experiment by simultaneously infusing captopril (0.8 micrograms.kg-1.min-1) and ANG II (1 ng.kg-1.min-1) into the right renal artery. In response to 5% ECVE, increases in RIHP, natriuresis, and diuresis were inhibited in the right kidney by 55, 40, and 47% respectively, when compared with the left kidney. Significant increases occurred in plasma atrial natriuretic peptide (ANP) levels during 5% ECVE. Maintenance of constant intrarenal ANG II levels during 1.5% ECVE completely abolished the increment of RIHP and diuresis and inhibited the natriuretic response by 80% in the right kidney when compared with the left kidney. Plasma ANP levels did not change during the 1.5% ECVE. No differences between kidneys were found when the intrarenal effects of ANG II were blocked with saralasin before saline loading. These results suggest that increases in RIHP, natriuresis, and diuresis during ECVE are partially mediated by decreases in intrarenal ANG II levels. Furthermore, these results indicate that the role of intrarenal ANG II levels in mediating the renal response to ECVE is more important when plasma ANP levels do not change than when they are increased.

Angiotensin II↗
PubMed1991

How can we combat excess mortality in Harlem: a one day survey of substance abuse in adult general care.

Our hypothesis was that a one-day survey of all patients hospitalized on Adult General Care would demonstrate a need for expanded addiction services in a municipal teaching hospital in East Harlem. We interviewed 276 patients in Adult General Care on February 16, 1990 to assess whether they abused drugs or alcohol or were hospitalized for reasons related to substance use. Of the 276 patients interviewed, 18 percent used alcohol alone, 14 percent used drugs alone, 17 percent used both drugs and alcohol and 2 percent were hospitalized for reasons related to substance use. One hundred forty or 51 percent of all patients were admitted because of substance use and its sequelae or as a result of violence associated with the buying or selling of drugs. The percentage was highest on one medical floor where 89 percent of the patients were substance users and on medical floors in general where the average was 60 percent. Forty patients or 14 percent were known to be HIV seropositive. Given the high mortality in Harlem, the results of our one-day survey indicate a need for expanded addiction services.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Effect of a chronic infusion of atrial natriuretic peptide on vascular reactivity in normotensive and renal hypertensive rats.

In a previous study, we found that a long-term infusion of atrial natriuretic peptide (ANP) produced a sustained reduction of mean arterial pressure and peripheral vascular resistance in two-kidney, one-clip (2K-1C) hypertensive rats, whereas in control rats it had only a transient effect on cardiac output. However, plasma levels of ANP were actually 3-fold higher in normotensive than in hypertensive rats. Previous studies suggested that plasma ANP levels might modulate the vascular reactivity to the peptide. The present study examined whether the lack of chronic hemodynamic effects of ANP in control rats was due to changes in vascular reactivity to the peptide. In control rats, vascular reactivity to ANP was reduced 50% by a chronic infusion of ANP. However, in 2K-1C hypertensive rats, a long-term infusion of ANP had no effect on the vascular reactivity to ANP. The results of the present study indicate that the lack of persistent hemodynamic effects of a chronic infusion of ANP in control rats may be due to a decrease in the vascular reactivity to the peptide. The sustained hypotensive and vasodilatory effects of a long-term infusion of ANP in 2K-1C hypertensive rats are associated with no changes in the vascular reactivity to ANP.

Animals↗
PubMed1989

Pupil responsiveness in diabetes mellitus.

The authors compared pupil responsiveness to light, convergence, and the effects of topical cocaine 4%, epinephrine 1%, phenylephrine 1%, homatropine 10%, and pilocarpine 1% in a group of 62 diabetics with a sex- and age-matched group of normal subjects. The duration of disease, metabolic control, and type of diabetes mellitus, the presence and severity of diabetic retinopathy, and evidence of systemic vegetative neuropathy were considered. It was found that sympathetic denervation was related significantly to the duration of disease and to the development of systemic autonomic neuropathy. There were also signs of iris myopathy in the pupil alterations of long-standing diabetics, explaining the poor pupil responsiveness to mydriatics occasionally found in these patients. Pupillary autonomic diabetic neuropathy should be considered an early and major sign of the development of systemic vegetative diabetic disease.

Adolescent↗
PubMed1988

Vascular and adrenal reninlike activity in chronically diabetic rats.

The aim of this work was to investigate, in an experimental model of diabetes mellitus, the levels of renin activity in vascular and adrenal tissues and their relationship to several circulating renin-angiotensin system components. Rats with chronic (12 weeks) streptozocin-induced diabetes showed a significant decrease in plasma renin activity (PRA), plasma renin concentration, and plasma aldosterone. However, plasma trypsin activatable inactive renin concentration was increased (11.65 +/- 1.40 vs 6.73 +/- 0.57 ng angiotensin I/ml/hr; p less than 0.001), as were aortic reninlike activity (p less than 0.001) and adrenal renin, both in the zona glomerulosa (p less than 0.01) and the fascicular-reticular-medullary portion (p less than 0.001) with respect to an age-matched control group. After bilateral nephrectomy, plasma renin-angiotensin system components (PRA and plasma active and inactive renin concentrations) as well as aortic and fascicular-reticular-medullary renin activity significantly decreased in both control and diabetic rats. However, glomerular renin activity increased in control nephrectomized rats to the levels observed in diabetic animals but did not change in diabetic nephrectomized rats. The parallel changes of aortic and fascicular-reticular-medullary renin activity and plasma inactive renin concentration in diabetes and nephrectomy suggest an interdependent relationship, whereas the increase of glomerular renin activity in diabetic and nephrectomized animals, both with low levels of PRA, suggests the existence of a local autonomic renin-angiotensin system regulated by plasma feedback. Tissue renin-angiotensin system alterations in diabetes could mean that a pathogenic factor is involved in long-term diabetic complications or that only a compensatory physiological process is at work.

Adrenal Glands↗
PubMed1988

Adrenal and vascular renin-like activity in chronic 'two-kidney, one-clip' hypertensive rats.

In order to study the vascular and adrenal renin angiotensin system in the chronic phase (4 months after clipping) of 'two-kidney, one-clip' hypertension in rats, systolic blood pressure, plasma renin activity, and tissue renin-like activity in both aorta and adrenal have been measured. Renin activity in adrenal gland was studied in both the zona glomerulosa (GLO) and the remainder of the gland. Results showed an increase in vascular renin activity in chronic hypertensive rats. Moreover it was found that GLO of hypertensive rats presented a significant increase in renin-like activity compared with controls (349.43 +/- 43.86 versus 167 +/- 34.25 ng AI/g/20 h, p less than 0.01) and the fasciculata-reticular-medullar (FRM) portion also showed greater renin activity (345.16 +/- 64.36 versus 57.90 +/- 4.83 ng AI/g/20 h, p less than 0.01). The higher levels of vascular and FRM renin-like activity in chronic renal hypertension are probably a consequence of plasma renin increase. This hypothesis is supported by the fact that bilateral nephrectomy in normal rats induces a significant decrease in plasma renin activity and both aortic and FRM renin-like activity. On the other hand the GLO renin-like activity could depend on both plasma renin and local synthesis since bilateral nephrectomy induces an increase in the renin-like activity in this tissue. These data support the idea that aortic and FRM renin are, at least in part, due to plasma renin uptake and GLO renin is an autonomic system.

Adrenal Glands↗
PubMed1987

Role of prostaglandin and angiotensin II in ANP-induced natriuresis.

The aim of the present study was to examine if the natriuresis induced by a dose of ANP that does not alter glomerular filtration rate (GFR) or mean arterial pressure (MAP) is accompanied by changes in renin release urinary excretion of prostaglandins and intrarenal blood flow distribution. It was found that the intrarenal infusion of ANP (8-33) at a dose of 0.05 micrograms/kg min in seven anaesthetized dogs did not produce any change in GFR or MAP, but its natriuretic effect was similar to that induced by a larger dose (0.3 micrograms/kg min, n = 5) that produces significant changes in both MAP and GFR. The natriuresis induced by the lower dose of ANP was associated with a redistribution of RBF to the deep cortical nephrons and with an increase (p less than 0.05) in urinary excretion of prostaglandins E2 and 6 keto-F1 alpha. Renin secretion rate decreased by a 54% (p less than 0.05). The role of angiotensin II (AII) suppression on the natriuresis induced by ANP was examine in another experimental group (n = 6). It was found that the infusion of ANP during fixed intrarenal levels of AII produced a natriuretic effect that was significantly lower (38%) than that produced by the infusion of ANP alone. The results of this study show that the natriuresis induced by ANP is not necessarily produced by an increase in GFR and is associated with a redistribution of RBF to the deep cortex an increase in urinary excretion of prostaglandins and a decrease of renin release. These results also suggest that the natriuretic effect of ANP is partly mediated by the intrarenal suppression of AII.

Angiotensin II↗
PubMed1981

Eighth nerve alcoholic neuropathy: a case report with light and electron microscopic findings.

A 55-year-old man with symptoms of hearing loss, balance disturbance, and facial weakness was treated by translabyrinthine eighth cranial nerve trans-section. The patient also had a history and physical signs of chronic alcoholism and peripheral polyneuropathy. Results of laboratory tests revealed concomitant nutritional deficiency. Histopathological examination of the eighth nerve showed extensive degeneration of both myelinated and unmyelinated nerve fibers in both cochlear and vestibular divisions. Light and electron microscopic features of the degenerative process were compatible with previously described pathology of experimentally induced Wallerian-like degeneration. Alcoholic neuropathy as the cause of hearing loss and balance disturbance--and probably facial paresis--is suggested.

Alcoholism↗
PubMed1981

Vestibular nerve compression in eighth-nerve tumors.

The superior vestibular nerve was studied histologically in 25 patients who underwent removal of inferior vestibular nerve schwannoma. In most cases, the nerve fibers were structurally normal but the endoneurial space showed various degrees of capillary stasis and/or extravasation of red blood cells. Increased fibrosis of the endoneurial space was seen in about two-thirds of the cases; it was mild in all except two cases. The endoneurial space appeared edematic in about one-third of the cases. Wallerian degeneration of individual fibers was occasionally observed in most cases and was severe in the two cases with moderate or severe endoneurial fibrosis. In about one-third of the cases there were large numbers of myelinated nerve fibers with thinned myelin sheaths. The observed structural changes are compatible with those seen in human and experimentally induced chronic compressive or entrapment neuropathies. Thus, early symptoms of eighth-nerve tumors might develop due to direct compression of the eighth-nerve trunk within the internal auditory canal.

Cranial Nerve Neoplasms↗
PubMed1977

Spontaneous closure of ureterocolic fistula secondary to diverticulitis.

An 88-year-old woman with spontaneous closure of a ureterocolic fistula secondary to sigmoid diverticulitis is described. Initially, the patient was subjected to proximal transverse colostomy to divert the fecal stream. She was rehospitalized for a sigmoid colectomy, and left ureteral catheterization as well as a retrograde pyelogram showed spontaneous closure of the ureterocolic fistula. A review of the literature reveals that specific involvement of the ureter secondary to inflammatory bowel disease is rare. Most of the cases reported previously have alluded to active and radical measures. We do not recommend a radical resection in the acute stage, especially when the tissue planes may be obliterated owing to inflammation and difficulty in structure identification may lead to inadvertent injury.

Aged↗
PubMedDate not supplied

The differences between the structural repertoires of VH germ-line gene segments of mice and humans: implication for the molecular mechanism of the immune response.

Although human and murine antibodies are similar when considering their diversification strategies, they differ in the proportion by which kappa and lambda type chains are present in their receptive V, repertoires. It has been shown that this difference implies a divergence in the structural repertoire of the kappa and lambda genes of these species. Nonetheless, the differences in VH have not been systematically studied. In this paper a systematic characterization of the VH structural repertoire of mice is made, so that a comparison with the VH structural repertoire of humans, described in detail elsewhere, could be properly accomplished. Our study shows the structural repertoire of mice to be dominated by canonical structure class 1-2 (approximately 60%), while in humans the dominant one is class 1-3 (approximately 40%). Analysis of the evolutionary relationships between human and mice suggest that this divergence may have a functional meaning. The implications of such findings are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Angiogenesis in the latissimus dorsi muscle using different regimens of electrical stimulation and pharmaceutical support.

It is our contention that the prevention of ischemia-reperfusion injuries immediately after latissimus dorsi muscle (LDM) mobilization and enhancement of angiogenesis will be effective in improving cardiomyoplasty results. The investigations were performed on adult sheep. Three hours after LDM mobilization, various stages of leukocyte-endothelium interaction were revealed: leukocytes binding to the endothelium, leukocyte destruction of endothelium, and leukocytes leaving capillaries through gaps in the endothelium. Fifty-six days after mobilization various stages of necrosis were discernible. The area occupied by capillaries was 3.45 +/- 0.26% vs. 3.99 +/- 0.24% in control muscle; most of the endothelial cells exhibited morphologic degeneration. Electrical stimulation with 60 CPM actually decreased the capillary density to 2.15 +/- 0.7%, and most of the endothelial cells were damaged, with disrupted plasma membranes. Muscle subjected to 15 CPM increased the percent of capillaries to 5.01 +/- 0.56%, and endothelial cells appeared normal in ultrastructure. Pharmaceutical support prevented muscle damage and accelerated revascularization. After 56 days of autologous biological glue (ABG) application, the area occupied by capillaries was 5.57 +/- 0.24%. This increased to 8.47 +/- 0.72% when aprotinin (proteinase inhibitor) was added to ABG, and to 9.40 +/- 1.24% with pyrrolostatin (free radical scavenger). Both ABG application with aprotinin and electrical stimulation at 15 CPM prevent the LDM from postmobilization damage, and increase angiogenic potential.

Animals↗
PubMedDate not supplied

Comparative clinical efficacy of two different single-dose ciprofloxacin treatments for uncomplicated gonorrhea.

The clinical efficacies of two different single-dose, oral treatments with ciprofloxacin were evaluated in a double-blind randomized study of 50 men with gonococcal urethritis. Two groups of patients were studied. The 25 patients in group A (age, 18-32 years; mean = 26.2) received a single dose of 250 mg of ciprofloxacin; the 25 in group B (age, 16-42 years; mean = 26.3) received a single dose of 100 mg of ciprofloxacin. The minimal inhibitory concentrations of ciprofloxacin for all the isolates were less than or equal to 0.0015 microgram/ml. Neisseria gonorrhoeae was eradicated from all 50 patients; 80% of them were clinically cured, and 20% developed postgonococcal urethritis. There was no significant difference between the two treatments evaluated. We conclude that a single oral dose of 100 mg of ciprofloxacin could be an alternative treatment for uncomplicated gonorrhea in men. Neither treatment prevented the development of postgonococcal urethritis.

Adolescent↗