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Biomedical subjects

M Vargas

Publications and source records attributed to M Vargas.

At least 91 records · Page 5Linked to original sources
PubMed1994

Anti-arrhythmic profile of a garlic dialysate assayed in dogs and isolated atrial preparations.

The effects of garlic (Allium sativum L., Liliaceae) dialysate were studied on arrhythmias induced in anaesthetized dogs and on isolated left rat atria. Garlic dialysate suppressed premature ventricular contractions (PVC) and ventricular tachycardia (VT) in ouabain-intoxicated dogs as well as the ectopic rhythms induced by isoprenaline (10(-6) M) and aconitine (10(-8) M) on electrically driven left rat atria. The effective refractory period (ERP) and the sinus node recovery time (SNRT) of isolated rat atria were prolonged in a dose-dependent manner by the administration of this extract. Garlic dialysate decreased the positive inotropic and chronotropic effects of isoprenaline in a concentration-dependent manner. These last effects were increased by propranolol. The results suggest that garlic dialysate has a significant antiarrhythmic effect in both ventricular and supraventricular arrhythmias.

Aconitine↗
PubMed1994

Optic tract atrophy with cerebral arteriovenous malformations: direct and transsynaptic degeneration.

Three patients with postgeniculate cerebral arteriovenous malformations (AVM) had band atrophy of the contralateral optic nerve. One patient had homonymous hemioptic hypoplasia. These cases might have been construed as demonstrating transsynaptic degeneration across the lateral geniculate nucleus to the anterior visual pathway. However, neuroimaging studies revealed abnormal deep venous drainage remote from the AVM nidus that directly involved the lateral geniculate nucleus and posterior optic tract.

Adult↗
PubMed1994

Chronic mountain sickness and chronic lower respiratory tract disorders.

To determine whether chronic lower respiratory tract disorders contributed to the development of chronic mountain sickness (CMS), we compared hemoglobin (Hb), oxygen saturation (SaO2), peak expiratory flow rate (PEFR), and CMS scores (CMSsco) in 97 normal men at high altitude with those of men at high altitude with acute (ARD; n = 12), chronic upper (CURD; n = 33), and chronic lower (CLRD; n = 34) respiratory diseases. The clinical diagnosis of the different types of respiratory disorders was based on the results of a questionnaire and physical examination performed during an epidemiologic study. The CLRD group had higher CMSsco and Hb concentrations, and lower SaO2 and PEFR values when compared with the other groups. The frequency of low PEFR and SaO2 and high Hb and CMSsco was substantially higher in men with CLRD when compared with normal subjects. The results support the hypothesis that there is an association between signs and symptoms of CMS, as measured by the CMSsco, and CLRD. The chronic hypoxemia, product of chronic lung diseases, would cause excessive erythrocytosis and increase the signs and symptoms of CMS. Studies of Hb, PEFR, pulse oximetry, and CMSsco are recommended for early detection of high-altitude natives at risk of developing CMS.

Adult↗
PubMed1993

Turbidity of hyperimmune equine antivenom: the role of phenol and serum lipoproteins.

Twenty batches of polyvalent antivenom produced at the Instituto Clodomiro Picado were analyzed for turbidity, both before and after freezing-thawing and lyophilization. Eight batches became turbid upon freezing-thawing, and this change correlated with high levels of cholesterol, triglycerides and lipoproteins, especially beta-lipoprotein. Since normal horse serum does not become turbid after freezing-thawing, despite the fact that it has high lipoprotein levels, the possibility was raised that phenol, used as a preservative during serum fractionation, might affect lipoproteins, inducing the appearance of turbidity after freezing-thawing. This hypothesis was tested by fractionating a sample of hyperimmune serum either without phenol or using two different phenol concentrations (0.1 g/dl and 0.25 g/dl). Results showed that, although the three samples had the same cholesterol and triglyceride levels before fractionation, only the one having 0.25 g/dl phenol became turbid upon freezing-thawing, containing a diffuse lipoprotein band on electrophoresis. This finding suggests that turbidity in equine antivenoms depends on the interaction of at least three factors: (a) freezing, (b) high initial cholesterol and lipoprotein concentration in the serum, and (c) addition of phenol during fractionation of serum.

Animals↗
PubMed1992

Experimental cardiovascular depressant effects of garlic (Allium sativum) dialysate.

The objectives of this work were to investigate the effects of a garlic dialysate on diastolic blood pressure (DBP), heart rate (HR) and electrocardiogram (ECG) of anaesthetized dogs and its effects on frequency and tension of isolated rat atria. Garlic dialysate led to a drop in DBP (from 112.5 +/- 3.67 to 70 +/- 3.16 mmHg) and a decrease in HR (from 198 +/- 9.81 to 164 +/- 16.59 beats/min) in a dose-dependent manner. The ECG showed a regular sinus bradycardic rhythm. The addition of garlic dialysate to isolated left rat atria evoked a decrease in tension development. Frequency, measured by spontaneous beating of the right atria, was also reduced. Both effects were dose-dependent. In addition to these effects, the positive inotropism and chronotropism induced by addition of isoproterenol 10(-9) M, were partially antagonized by preincubation of the rat atria with the garlic dialysate. The above findings can be explained by a depressant effect on automaticity and tension development in the heart, suggesting a beta-adrenoceptor blocking action produced by the garlic dialysate.

Anesthesia↗
PubMed1992

Improved Methods for Cultivation of the Extremely Thermophilic Bacterium Thermotoga neapolitana.

Growth medium components and cultivation conditions for the extremely thermophilic bacterium Thermotoga neapolitana were optimized. A defined marine salts medium was formulated. Trace amounts of iron stimulated growth of T. neapolitana, while zinc inhibited growth at concentrations exceeding 11.1 muM. Other trace metals had no effect on its growth. Of the vitamins tested, only biotin was required for optimal growth. A defined mineral medium containing 5 g of carbohydrates per liter as the carbon source and 0.5 g of cysteine per liter as the sulfur source and reductant supported growth. Growth was stimulated by inclusion of vitamin-free Casamino Acids. Elemental sulfur, cystine, and dimethyl disulfide in the growth medium enhanced growth. Elemental sulfur and cystine relieved growth inhibition by hydrogen. T. neapolitana formed colonies in 2 days on plates of complex medium solidified with gellan gum and in 4 days on defined medium. The efficiency of plating was determined when growing cultures were sampled both aerobically and anaerobically and plated under aerobic and anaerobic conditions. Mean plating efficiencies were improved by sampling the growing cultures under strictly anaerobic conditions. Little or no improvement was obtained by inoculating plates inside an anaerobic chamber. Plating efficiencies of approximately 80% were obtained. Polycarbonate jars with aluminum lids withstood repeated incubation at 77 degrees C without significant deterioration of the anaerobic seal and provided the most consistent results.

Journal Article↗
PubMed1992

First record of Angiostrongylus cantonensis (Chen, 1935) (Nematoda: Metastrongylidae) in the Dominican Republic.

Rats, Rattus norvegicus, trapped in some sections (barrios) of the city of Santo Domingo, the capital of the Dominican Republic showed that 5 of them from two barrios harbored the nematode Angiostrongylus cantonensis in the pulmonary artery. Macerated and digested terrestrial snails, Subulina octona, collected from the backyards of houses where the rats were trapped contained L2 and L3 larvae of the nematode. The morphology of the adult worms and the larvae was consistent with that described for A. cantonensis in the literature. This is the first report of this Oriental and Western Pacific nematode in the Dominican Republic and the fourth in the Americas. Gastrointestinal hemorrhage, a rare symptom due to another species, the American A. costaricensis, which occurs in mesenteric arterioles of rodents and humans, is in the recent literature; the patient was a 41-year old Dominican. Thus the Dominican Republic is the first country in the Western Hemisphere to have the two species of Angiostrongylus.

Angiostrongylus cantonensis↗
PubMed1992

Effects of G-6-PD deficiency, experimentally induced or genetically transmitted, on the sorbitol pathway activity. In vitro and in vivo studies.

Aldose reductase catalyzes the NADPH-linked reduction of hexoses to their respective sugar-alcohols, which are involved in the pathogenesis of "sugar-cataracts". In the lenses, the reaction catalyzed by G-6-PD is the source of NADPH supply blocking sugar-alcohol formation and consequently prevents or delays the onset of "sugar-cataracts". We have investigated the effect of G-6-PD deficiency, either experimentally induced or genetically transmitted, on the sorbitol accumulation in whole cells incubated in high glucose media and on the "sugar-cataracts" formation in a galactosemic rat model. We also screened 31 Negro male adults with diabetes mellitus for red cell G-6-PD deficiency. G-6-PD deficiency produced a significant inhibition on sorbitol accumulation in rat lenses and human red cells incubated in 50 mM glucose. In the galactosemic rat model G-6-PD deficiency experimentally induced with acetaminophen delayed the development of cataracts. Finally, two diabetic individuals were G-6-PD deficient and did not show cataracts whereas cataracts were identified in six other diabetic patients.

Acetaminophen↗
PubMed1991

Metabolic effects of cyanate on mice at sea level and in chronic hypobaric hypoxia.

In order to evaluate the toxic effects of Sodium Cyanate (NaOCN), it was orally administered to growing mice at sea level (SL-CN) and to mice chronically exposed to intermittent hypobaric hypoxia (IHH-CN). The effects on body weight, in-vivo O2 consumption (VO2) and the respiratory function of liver mitochondria were evaluated. At sea level, the animals on cyanate lost weight in contrast with the controls that gained weight. When exposed to IHH, the controls lost weight and the animals on cyanate regained weight. After 2 months observation the weights of the IHH-CN and IHH-C were similar. The VO2 after one month of treatment was similar in the SL-C and in the SL-CN but it was lower in the IHH-CN when compared with IHH-C. The substrate-stimulated respiration of isolated liver mitochondria (ST4) was not affected by NaOCN, but the ADP-stimulated respiration (ST3) was reduced. The ratio ST3/ST4 (RCR) was also lower. These changes were present in both SL and in IHH and were much larger after three months of treatment. The toxic effects of chronic administration of NaOCN are discussed.

Administration, Oral↗
PubMed1991

Inhibition of acid secretion from parietal cells by non-human-infecting Helicobacter species: a factor in colonization of gastric mucosa?

Helicobacter pylori has been shown to produce a protein that inhibits acid secretion from parietal cells. We have examined other non-human-infecting Helicobacter species for this property by measuring the uptake of [14C]aminopyrine into rabbit parietal cells as an indirect assessment of acid secretion. Helicobacter felis and an isolate from a rhesus monkey were shown to inhibit acid secretion. Isolates of Helicobacter mustelae gave variable responses. Whole bacteria and cell-free sonicates impaired the uptake of [14C]aminopyrine. We also tested other bacteria, including Escherichia coli, Proteus vulgaris, Klebsiella oxytoca, and Campylobacter jejuni. As whole organisms, these control bacteria had little effect on acid secretion, but sonicates caused pronounced inhibition that was partially heat labile. Pronase treatment of H. pylori destroyed its inhibitory effect. These results suggest that most Helicobacter species, but not all isolates, are able to inhibit acid secretion from rabbit parietal cells. This property may be a factor in the establishment of long-term infection by these species.

Aminopyrine↗
PubMed1990

Schistosomiasis mansoni in the Dominican Republic; prevalence and intensity in various urban and rural communities, 1982-1987.

Surveys to detect foci of schistosomiasis mansoni endemicity in the Dominican Republic were carried out from 1982 to 1987 and showed that the disease is far more widely distributed in the country than previously thought. New foci (San Rafael del Yuma, Batey Palo Bonito, Maicillo, Nisibon and additional barrios in the city of Higuey) were found in the eastern provinces, and other completely new foci (Bayaguana, Sabana Rey (Cotui) and Jarabacoa) in the center of the country and in the National District (Guerra) were also detected. Prevalence rates in the various barrios (sections) of the city of Higuey varied between 7.4% and 24.6%, whereas they were 10.2% in Maicillo, 7.8% in El Valle and 9.9% in El Seibo. The intensity of infection was very low as judged by eggs per gram of feces. Serodiagnosis using the circumoval precipitin test raised the infection rate from that indicated by stool examination, as in Maicillo, or both results were equal, as in Las Palmillas.

Adolescent↗
PubMed1990

Biological control of Biomphalaria glabrata by Thiara granifera under laboratory conditions.

The effect of the snail Thiara granifera on the snail Biomphalaria glabrata, intermediate host of Schistosoma mansoni in the Dominican Republic, was evaluated. Plastic aquaria, 3 and 1.5 gallons in capacity, were used. The aquaria were either unpartitioned or partitioned by a fine screen into two equal compartments, and the two snail species were introduced in different proportions. The results over a 1-year period showed that T. granifera effectively reduced the fecundity of B. glabrata, especially when the initial densitites of the two species were equal or where T. granifera was more abundant. There was still competition, although starting at a later date, when the density of T. granifera was half that of B. glabrata. The competitive interaction does not seem to be due to competition for food but to a chemical factor(s), possibly water-soluble pheromones.

Analysis of Variance↗
PubMed1990

[Exudative enteropathy in heart insufficiency--apropos of 3 clinical cases].

Severe hypoproteinaemia due to increased intestinal protein losses, known as exudative enteropathy, was seen in three patients (two with rheumatic valvular heart disease and one with congenital heart disease). The authors review the relationship between serum proteins and cardiac disease, describing the diagnostic methods and the prognosis. From a clinical point of view, protein-losing enteropathy should be suspected in patients with right heart failure and severe hypoalbuminaemia. Recognition of this syndrome is important because the treatment of the cardiac lesion may reduce or remove this rare complication.

Adolescent↗
PubMed1989

Effect of a Campylobacter pylori protein on acid secretion by parietal cells.

The uptake of [14C]-aminopyrine by rabbit gastric epithelial cells was used as an indirect assay for acid secretion from parietal cells. Campylobacter pylori strains, isolated from the stomachs of 3 patients with chronic gastritis, duodenal ulcer, and near-normal mucosa, respectively, inhibited acid secretion as effectively as 10(-4) mol/l cimetidine. The inhibition occurred with whole organisms and with sonicates. Preliminary characterisation suggested that the inhibition was due to a nondialysable protein. The inhibitor was not toxic to gastric epithelial cells. This bacterial product may explain the hypochlorhydria seen in man acutely infected with C pylori.

Aminopyrine↗
PubMed1988

Protection against Salmonella typhi infection in mice after immunization with outer membrane proteins isolated from Salmonella typhi 9,12,d, Vi.

The current studies were undertaken to assess the ability of the outer membrane proteins (OMPs) of Salmonella typhi to induce protection against challenge with the bacteria in mucin. OMPs were isolated as described by Schnaitman (J. Bacteriol. 108:553-556, 1971) and were found to be contaminated with approximately 4% lipopolysaccharide (LPS). Immunization with as little as 30 micrograms of OMPs conferred 100% protection to mice challenged with up to 1,000 50% lethal doses (LD50) of two strains of S. typhi (9,12,d, Vi and Ty2). In addition, 30% protection against challenge with up to 500 LD50 of Salmonella typhimurium was achieved. Immunization with LPS at doses equivalent to those found in the OMPs was considerably inferior to the OMPs in the induction of an immune status. Moreover, LPS was effective only when the challenge was performed with S. typhi 9,12,d, Vi (40% protection to 100 LD50). An antiserum raised in rabbits reacted mainly against the bands of the molecular weights corresponding to the so-called porins contained in the OMP preparation as shown by Western blotting (immunoblotting). This rabbit antiserum protected 100% of mice against challenge with 100 LD50 of either strain of S. typhi and 80% of mice against challenge with the same LD50 of S. typhimurium. These results indicate the usefulness of OMPs in the induction of active immunity against S. typhi in mice.

Animals↗
PubMed1987

Regional distribution of the membrane-bound pyroglutamate amino peptidase-degrading thyrotropin-releasing hormone in rat brain.

The brain regional distribution of membrane-bound pyroglutamate aminopeptidase-degrading thyrotropin-releasing hormone (TRH) in rat was studied using a specific radiometric assay. The distribution was not homogeneous: a 10-fold difference was observed between regions. The highest activity was detected in olfactory bulb while the lowest was in the cervical part of spinal cord. There was no correlation with the regional distribution of enzyme activity vs TRH levels, previously reported TRH receptors or in vitro TRH release. The differential distribution of this enzyme is consistent with the hypothesis that it is responsible for extracellular degradation of neuroactive peptides.

Aminopeptidases↗
PubMed1987

Simple spectrophotometric determination of urinary albumin by dye-binding with use of bromphenol blue.

This procedure for routine quantification of albumin in urine is based on the dye-binding properties of albumin with bromphenol blue. The absorbance of 100 microL of urine mixed with 3 mL of color reagent is measured against blank reagent at 610 nm after 30 s. Results vary linearly with albumin concentration up to 6 g/L. The reaction is pH independent in the physiological range. It is not subject to substantial interference by uric acid, creatinine, calcium, sodium chloride, or bilirubin. The presence of globulins produces a small positive error. Within-run precision (CV) was 4.8, 1.5, and 0.9%, and day-to-day precision was 11.2, 2.0, and 1.9%, for samples containing albumin at about 0.1, 1.0, and 6.0 g/L, respectively. Results by a radial-immunodiffusion method (x) correlated well with those by the proposed method (y): r = 0.986; y = 0.98x + 0.096; n = 64. The method can also be used to detect globulins, such as Bence Jones protein, by measuring the ratio of the absorbance at 30 min to that at 30 s.

Adolescent↗