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Biomedical subjects

M Cárdenas

Publications and source records attributed to M Cárdenas.

At least 37 records · Page 2Linked to original sources
PubMed1997

Transient alteration of the reproductive function in nephrotic rats.

The reproductive function of male and female rats with induced nephrotic syndrome was examined by assessing hormonal levels, the estrous cycle pattern and fertility. Measurements were carried out on day 10 (nephrotic stage) and on day 30 (remission stage) after treatment (a single s.c. dose of puromycin aminonucleoside 15 mg/100 g body wt.). Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone (P4) from both sexes as well as 17beta-estradiol (E2) in females and total testosterone (tT) in males were assayed at both phases of the illness by specific radioimmunoassays; free and urine testosterone (fT, uT) was also determined in male rats on day 10. The estrous cycle was followed alongside the study through vaginal smears, while fertility was estimated by the rate of pregnancies (females) or pregnancy induction (males), and by the litter size. The results showed that most serum hormone levels, except FSH in females, were significantly reduced at the nephrotic stage of the illness, returning to their normal values after 30 days. Besides, on day 10, fT was found reduced in nephrotic males, while uT concentrations remained unmodified. The ovulatory cycle of nephrotic rats was disrupted on day 3 and not restored until day 23; nevertheless, the reproductive function, measured as a fertility index, was fully reinstalled at the remission stage. Interestingly, the capacity of fertilization of the nephrotic males was not entirely abolished during the acute phase, since 37% of the animals were fertile. Moreover, on day 30 the reproductive function in nephrotic males was totally recovered. The data from this study show the existence of reversible endocrine disorders in rats bearing nephrotic syndrome; such changes are manifested during the acute phase of the illness as a temporary cessation of the reproductive processes.

Animals↗
PubMed1997

The use of the plasma concentration-effect relationship as a tool for the study of the mechanism of action of naloxone effects on mood and endocrine function.

The relationship between naloxone-plasma concentrations and their effects on mood and endocrine function was studied. Ten healthy volunteers received 1.0 mg/kg i.v. naloxone or placebo following a randomized double-blind design. Effects on mood, determined by a visual analogue scale and luteinizing hormone (LH) and naloxone-plasma concentrations were measured at selected times. Naloxone induced significant effects on confusion, bewilderment and indifference, and an increment in LH levels. The timecourse of the responses on confusion and bewilderment was similar to that of naloxone-plasma concentration, suggesting that these effects are directly related to the action of naloxone on its receptors. Responses for indifference and LH, however, exhibited a delayed onset. This delay could be due to an indirect action, i.e. to the participation of additional physiological mechanisms in a cascade-like manner. The results show that analysis of the concentration-effect relationship can be a useful tool for understanding naloxone effects on mood and endocrine function.

Adult↗
PubMed1996

Studies on the relative in-vitro biological potency of the naturally-occurring isoforms of intrapituitary follicle stimulating hormone.

In the present study, we analysed and compared the relative in-vitro biological activity of the various intrapituitary human follicle stimulating hormone (FSH) isoforms employing two different bioassay systems. FSH was fractionated by chromatofocusing (pH range 7.10 to < 3.80) and the several isoforms isolated were quantified at multiple dose levels by three highly specific immunoassay systems: radioimmunoassay (RIA), enzyme-immunoassay (EIA) and immunoradiometric assay (IRMA), as well as by two in-vitro bioassays, one that measures the amount of oestrogen produced by rat granulosa cells in culture and the other that determines the amount of cAMP produced by a human fetal cell line (293) expressing the recombinant human FSH receptor. The relative in-vitro biological activity of each FSH isoform, expressed as the bioassay/ immunoassay (B/I) activity ratio (B/RIA, B/EIA and B/IRMA ratios) varied with its elution pH value. Regardless of the immunoassay or bioassay method employed, less acidic FSH isoforms exhibited higher B/I ratios than their more acidic counterparts [B/RIA, B/EIA and B/IRMA ratios for isoforms with elution pH values > 4.5 = 1.05 +/- 0.13, 0.99 +/- 0.10 and 1.15 +/- 0.08 (rat oestrogen bioassay), and 2.75 +/- 0.34, 2.20 +/- 0.25 and 2.96 +/- 0.35 (human cAMP production bioassay) respectively. Ratios for isoforms with pH values < 4.5 = 0.71 +/- 0.06, 0.47 +/- 0.05 and 0.63 +/- 0.06 (rat oestrogen assay), and 1.80 +/- 0.26, 1.10 +/- 0.09 and 1.44 +/- 0.13 (cAMP assay) respectively (P < 0.05 for isoforms with pH < 4.5 compared with those isoforms with pH > 4.5)]. Furthermore, statistically significant direct relationships between the B/RIA, B/EIA and B/IRMA ratios and elution pH value of each isoform was identified by regression analysis [rat assay: r = 0.844, 0.800 and 0.780 (P < 0.01); human assay: r = 0.730, 0.845 and 0.821 (P < 0.01), for their corresponding B/RIA, B/EIA and B/IRMA ratios respectively]. The finding of significant differences in relative in-vitro biological potency among the various intrapituitary FSH isoforms strongly suggests that the shifts towards the production and secretion of more basic or acidic FSH molecules occurring in certain specific physiological conditions (e.g. puberty and menstrual cycle), may represent an important mechanism through which the anterior pituitary regulates gonadal function.

Adult↗
PubMed1995

Effects of alpha adrenergic stimulation on time independent potassium current of isolated ventricular myocytes.

The role of alpha adrenergic receptor stimulation on ventricular electrical activity is controversial. The aim of the present paper was to study a wide range of concentrations of alpha adrenergic agonists on the electrical properties of guinea pig's heart isolated ventricular myocytes. The experiments were performed according to the single electrode voltage clamp technique. Phenylephrine and epinephrine (in the presence of propranolol) were used at concentrations from 1 x 10(-9) to 10(-5) M. It was observed that both agonists induce an increase in the time independent inward rectifying potassium current (IK1), that could explain the shortening of the action potential. All the observed effects were dose-dependent and disappeared during washout. These results could explain, at least partially, some of the electrical changes observed during ischemia.

Action Potentials↗
PubMed1995

Pituitary-ovarian dysfunction in rats with induced nephrotic syndrome.

The reproductive hormonal profile was evaluated in female rats with experimental nephrotic syndrome induced with a single subcutaneous dose of puromycin aminonucleoside (PAN). Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone (P4), testosterone and 17 beta-estradiol (E2) were determined sequentially in control and experimental groups on days 1, 3, 7 and 10 after PAN administration. Prolactin levels were also assessed on day 10. In both groups, vaginal smears were taken daily throughout the study to evaluate cyclic histological changes. At the end of the experiment the histological appearance of the ovaries was evaluated by light microscopy. Nephrotic rats had a rapid loss of the estrous cycle starting on day 4, which set them at diestrus. At the same time the hormonal evaluation indicated a gradual decrease in E2, LH and P4 concentrations, starting from days 3, 7 and 10, respectively. No significant changes were noted in FSH or testosterone values. Besides, on day 10, prolactin concentrations remained unmodified. Even though most hormonal levels were found low on day 10, all values except E2 (undetectable) corresponded to the interval reported for the diestrus phase. Likewise, histological examination of ovarian tissue from nephrotic rats showed a considerable increase in the number of atretic follicles. These findings indicate that female rats with nephrotic syndrome develop an important endocrine dysfunction that probably involves steroidogenic tissues (ovary and/or adrenal gland), and suggest the existence of a hypothalamic-hypophyseal impairment.

Animals↗
PubMed1993

[Cerebral abscess caused by Toxoplasma gondii and AIDS. Report of a case with anatomo-pathological study].

We report a 47 year old woman that presented to the hospital with an intracranial hypertension syndrome, a right hemiparesis and a several months history of progressive malaise and behavioral disturbances. During the hospital stay, positive HIV antibodies were detected and CAT scan showed a profound left parietal rounded hypodense lesion. The patient died 21 days after admission and the postmortem pathological study showed a deep abscess in the left basal ganglia, with recognizable Toxoplasma gondii trophozoites.

Acquired Immunodeficiency Syndrome↗
PubMed1993

[Preliminary study of HTLV-I seroprevalence in Chilean Indian populations].

Aiming to seek the origin and define the prevalence of HTLV-1 infections, 464 blood samples from aboriginal populations proceeding from isolated regions of the north and south of Chile were studied. Antibodies against HTLV were measured with agglutination tests and confirmed with immuno-fluorescence and Western Blotting. Seven out of 107 (6.5%) blood samples from Atacama indians, 2 out of 202 (1%) from Mapuche indians and 3 out of 155 (1.9%) from Huilliche aborigines were positive. These results highlight an important presence of the virus in indigenous populations, specially in the extremes of the country. These findings could suggest an indigenous (mongoloid) origin of HTLV-1 in Chile, specially in Chiloe, where apparently there has been no contact with african or japanese populations, that could be the origin of the contamination.

Adolescent↗
PubMed1992

Multiple sclerosis in Chile.

So far as we know this series of 68 cases is one of the first clinical accounts of multiple sclerosis in South America. Average age of onset was 30.7 years and female:male ratio was 2:1. The most frequent initial symptom was motor impairment and less frequent was visual loss. Most affected site of involvement in established cases was the optic nerve. There were no familial cases. The severity of the disease in Chile proved to be the same as elsewhere. No characteristic clinical pattern peculiar to the region emerged.

Chile↗
PubMed1989

Multiple sclerosis following optic neuritis in Chile.

Twenty three unselected cases of optic neuritis were re-examined between 2 and 18 years after the onset of the disease, with a mean of 9.7 years. Only 8/23 (35%) had unilateral non-recurrent disease. One patient only (4.3%) went on to develop multiple sclerosis. These findings support the impression that demyelinating disease varies considerably in Latin America compared with northern industrialised countries.

Adolescent↗
PubMed1975

Electrocardiographic criteria for the diagnosis of left anterior fascicular block. Left axis deviation and delayed intraventricular conduction.

The two current criteria for diagnosis of left anterior fascicular block (LAFB) were evaluated; they are marked left axis deviation (LAD) and a delay in the time of inscription of the intrinsicoid deflection (ID) in lead aVL asynchronous to V6. From 400 electrocardiograms with a LAD of --30 degrees or greater, 62 percent showed asynchronous activation of the left ventricle. There was only a general relationship between the degree of LAD and delayed ID in aVL. The incidence of delayed ID in aVL was as follows: 2 percent with mean frontal QRS axis at 0 degrees; 9 percent at --15 degrees; 41 percent at --30 degrees; 69 percent at --45 degrees; 82 percent at --60 degrees; and 100 percent at --75 degrees or greater. The lack of correlation between both criteria in many instances questions their validity. The LAD alone should not be considered synonymous with LAFB. Recognition of delayed inscription of the ID in aVL is a useful supplemental criterion for diagnosis.

Bundle-Branch Block↗
PubMedDate not supplied

Differences in heart rate variability between cardioinhibitory and vasodepressor responses to head-up tilt table testing.

BACKGROUND: Patients with syncope show different responses to head-up tilt (HUT) test, which may be due to different pathophysiological mechanisms. METHODS: HUT (70 degrees) was performed in 24 patients who experienced recurrent syncope. Nine patients had a cardioinhibitory (CI) response, 7 patients had a vasodepressor (VD) response, and 8 patients had a mixed (MX) response. Heart rate variability was analyzed at 60-sec periods during HUT. RESULTS: Total spectrum (TS) was greater at rest and 1 min after syncope in the CI and MX groups as compared to the VD group. Low frequency spectrum (LF) was significantly greater during rest and the first minute after syncope in the CI groups as compared with the VD group. After the rest period, the CI and MX groups showed more elevated high frequency spectrum (HF) values than the VD group (p < 0.01). One minute after syncope, the HF increased in the CI and MX groups but not in the VD group (p < 0.01). The VD group showed higher LF/HF ratio from the beginning of rest (3.9 +/- 4.1) as compared to the CI and MX groups (p < 0.01). This difference was most significant 2 min before syncope occurred. The CI and MX groups showed greater pNN50 and rMSSD as compared to the VD group. CONCLUSIONS: Our results suggest that vagal tone is higher in subjects showing cardioinhibitory and mixed responses to HUT. In contrast, patients with a vasodepressor response showed predominantly sympathetic activity. These findings suggest that there are different pathophysiological mechanisms underlying syncope.

Adolescent↗
PubMedDate not supplied

Repeatability of heart rate variability during simple cardiovascular reflex tests on healthy subjects.

BACKGROUND: Our purpose was to determine the repeatability, after 2 weeks, of frequency domain measures of heart rate variability (HRV) during simple cardiovascular reflex tests. METHODS: Twenty healthy volunteers aged 29.3 +/- 2.5 years were assessed twice (at weeks 0 and 2). Continuous electrocardiogram and minute-to-minute blood pressure were recorded during spontaneous and metronome-paced breathing (0.2 Hz). Under paced breathing, two tests were performed: 1) active change of posture: 5 min supine position, 5 min seated upright, and 5 min standing up, and 2) cold pressor test: the right hand was immersed in cold water (5 degrees C) for 2 min. RESULTS: Paced breathing elicited a significant increase of the high-frequency (HF) component of HRV. This effect was repeatable on 95% of the subjects. Active change of posture induced a significant increase of the heart rate with an increase of the low-frequency/high-frequency ratio of HRV. Although repeatability was better for the response to being seated upright than for the response to being standing up, it was always higher than 90%. The cold pressor test induced a significant increase of the heart rate and blood pressure, but with variable changes on the HRV measurements (either a decrease or an increase). Repeatability of responses was evident for 95-100% of the subjects. Although repeatability of HRV measurements in the same subject during the tests was higher than 95%, coefficients of repeatability reflected large differences among the subjects. CONCLUSIONS: The results suggest that it is not advisable to use isolated HRV changes to interpret the response to simple cardiovascular reflex tests in groups of healthy subjects.

Cardiovascular Physiological Phenomena↗
PubMedDate not supplied

Orthostatic hypotension, 2001.

Upright posture requires rapid and effective circulatory and neurologic compensations to maintain blood pressure and consciousness. Although it has been recognized over the past 100 years or more that the act of standing may cause hypotension in patients with autonomic dysfunction, only recently several of the pathophysiologic mechanisms resulting in orthostatic intolerance have been discovered. In patients with orthostatic hypotension, failure of reflex vasoconstriction causes pooling of blood in the legs during standing. Not everyone with a postural blood pressure drop requires treatment, nor does everyone with posturally induced symptoms have orthostatic hypotension. This review will discuss current knowledge of a broad, heterogeneous group of disturbances in the autonomic nervous system, each of which is manifested by hypotension, orthostatic intolerance, and often syncope.

Humans↗
PubMedDate not supplied

[Atrioventricular conduction disorders following total correction of tetralogy of Fallot. Analysis of the electrogram of the bundle of His].

A study was made of the electric activity of the atrioventricular (AV) conduction system in basal conditions and with atrial stimulation in order to discover the type, severity and prognosis of the AV disturbance in cases of total correction of tetralogy of Fallot. The authors studied thirteen patients from the Paediatric Department of the National Institute of Cardiology who had undergone such surgery, 7 males, 6 females from 3 to 22 years old. All presented advanced RBBB and sinus rhythm; in the immediate postoperative period, one presented complete transitory A-V block which required a stand by pacemaker; in 2 cases there was a first degree AV block; in two other, LAH and LPH. In 5 cases atrial stimulation was made with single charges and progressive frequency. Measurements were taken at the customary intervals. In basal conditions, prolongation of the AH interval was only found in 2 patients, both with first degree AV block in the peripheral EKG; both patients were taking digitalis. The HV interval was longer than normal in 3 cases, with one of these showing also a lengthened AH interval. The atrial stimulation showed prolonged ventricular activation in 2 cases, one of them with normal basal HV interval. The authors conclude that this procedure permits: 1) The discovery of alterations in the AV conduction system which could not be found in a peripheral EKG. 2) Localization of the site of the lesion. 3) The finding of disturbances of the ventricular conduction by atrial stimulation. 4) Identification of those patients who, after a complete correction of tetralogy of Fallot, show a potential high risk of developing complete complete AV block or of sudden death. 5) The establishment of a real prognosis in these patients.

Adolescent↗