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Biomedical subjects

R Medina

Publications and source records attributed to R Medina.

At least 73 records · Page 4Linked to original sources
PubMed1990

[Acute kidney insufficiency of obstetric origin. Experience at the Santo Tomas Hospital (1966-1981)].

The authors review 24 cases of acute renal failure of obstetric etiology occurred in Hospital Santo Tomás, which represents a frequency of 1.375/10,000, with a bimodal distribution and the main causes were toxemia of pregnancy and sepsis. All cases were of the oliguric type and a kidney biopsy was performed in 17 cases, revealing an acute tubular necrosis in 16 and a diffuse cortical necrosis in the other case. Two patients (8.3%) died and one did not received nephrology treatment as the other 23 patients. The fetal mortality was 37.5% and the Apgar was good in 2, fair in one and bad in 2. A 50% of the complications were infections and nine patients tolerated different surgical procedures after the installation of the acute renal failure. The follow-up of 12 patients shows no evidence of renal failure.

Acute Kidney Injury↗
PubMed1989

Interleukin-1, endotoxin or tumor necrosis factor/cachectin enhance the level of plasminogen activator inhibitor messenger RNA in bovine aortic endothelial cells.

It is known that either endotoxin (LPS) or interleukin-1 (IL-1) increase the activity of plasminogen activator inhibitor (PAI) in the culture media of human and bovine endothelial cells. We have confirmed these results in bovine aortic endothelial cells (BAEC). To determine if this effect was mediated by increases in the level of PAI messenger RNA (mRNA) we examined the effects of these cytokines on PAI mRNA levels in BAEC, using RNA blot analyses. Treatment of BAEC with either IL-1, LPS, or human recombinant tumor necrosis factor/cachectin (TNF) dramatically increased the level of PAI mRNA. Since elevated levels of PAI will decrease fibrinolytic potential, this mechanism is in concert with the known increase in in vivo procoagulant potential induced by these agents and could contribute to thromboembolic phenomena.

Animals↗
PubMed1989

Cyclic adenosine monophosphate as a second messenger in horizontal cell uncoupling in the teleost retina.

The reduction in the receptive field of horizontal cells of the teleost Eugerres plumieri observed upon dopamine (DA) superfusion is thought to be due to cell uncoupling. The possible mechanisms by which activation of DA receptors modify the electric coupling between horizontal cells were studied in the present work. It was found that the effect of DA in different preparations is mediated by a modification of intracellular concentration of cAMP and H+. The effects of intracellular injection of cAMP and H+ were studied in retinal horizontal cells of the teleost E. plumieri. A triple microelectrode was used to inject the ion iontophoretically, to pass current pulses, and to record voltages from the same cell, while a fourth microelectrode was used to record voltages from a neighboring cell in the same retinal layer. Responses evoked by light spots and annuli were evaluated simultaneously. Coupling ratios between neighboring horizontal cells ranged from 0.22 to 0.45. The intercellular resistance (Rc), 0.5-3.5 x 10(6) ohms, and that of the remaining cell membrane resistance (Rm), 2.5-18 x 10(6) ohms, were calculated by means of a passive electrical model that has a hexagonal array. The microinjection of H+ with injection current from +5 to +30 nA for 40 to 100 sec led to temporary and reversible light response reduction. The coupling ratio between two impaled cells was reduced by about 30%, and intercellular resistance (Rc) increment was 320% while cell membrane resistance (Rm) did not change consistently. There was also a temporary and reversible Rm reduction (70-85%) and an Rc increment of 170-330% when cyclic adenosine monophosphate was iontophoretically injected with current from -30 to -40 nA for 50 to 170 sec. The coupling ratio between two impaled cells was reduced by about 40%, and light responses recorded from the injected cell showed a reduction in amplitude with the same time course as that of the resistive changes. The injection of Lucifer yellow into a horizontal cell under normal conditions always results in pronounced fluorescence for more distant cells; however, under constant injection of H+ or cAMP only the injected cell is fluorescent, which provides direct evidence of the reduction in the effectiveness of coupling between horizontal cells. The observed effects of intracellular H+ or cAMP injection correspond to the resistive changes in Rc and coupling ratio that occur in the horizontal cell network upon superfusion with a dopamine (DA) solution.

Animals↗
PubMed1989

Cardiac and noncardiac atrial natriuretic factor (ANF) biosynthesis and storage and plasma ANF in the rat model of chronic ventricular dysfunction.

To evaluate the role of atrial natriuretic factor (ANF) in chronic heart failure (HF), the biosynthesis and storage of ANF in cardiac and noncardiac tissues and the level of plasma ANF were measured in rats exhibiting minimal [2-fold rise in left ventricular end diastolic pressure; myocardial infarct (MI) scar length, 25% left ventricle (LV)] and moderate-severe (3-fold rise in left ventricular end diastolic pressure; decreased contractility (dp/dtmax); MI scar length, 47% LV) chronic HF 30 and 60 days after coronary arterial ligation. In rats with moderate-severe HF (30 days post-MI), the cardiac ANF mRNA concentration (determined by dot blot analysis) increased in three heart chambers [LV, 6-fold; left atria (LA), 3-fold; right ventricle (RV), 2-fold], cardiac immunoreactive ANF (IRANF; determined by RIA) concentration increased on the left side (LV, 7-fold; LA, 33%), but was unchanged (RV) or reduced on the right side (right atria, 33%), and plasma IRANF increased 3-fold above sham control values. Excluding the LV (used for MI scar length), the pattern and magnitude of change in ANF mRNA concentration in moderate-severe HF at 60 days were similar to those at 30 days; the cardiac IRANF concentration at this time was the same (LA) or less than (RV, 66%) sham values, and plasma IRANF increased 6-fold above respective sham values. Generally, the changes in the concentrations of cardiac ANF message and peptide and levels of circulating ANF peptide were smaller in rats with minimal HF. The minute quantities of ANF mRNA and IRANF detected in noncardiac tissues (lung, liver, pituitary, aortic arch, brain, kidney, and salivary gland) were unaltered by HF. These findings show that chronic HF, as defined by hemodynamic and histological measurements, specifically and continuously stimulates atrial as well as ventricular ANF biosynthesis; levels of plasma and cardiac ANF are increased early in HF, but with time are subject to modulation. The cardiac ANF system is the prime locus for the effects of HF, as noncardiac ANF biosynthesis and storage are undisturbed by chronic HF.

Animals↗
PubMed1989

[Prostitutes of the east sector of Santiago: characteristics and pathology of sexual transmission].

We studied the frequency of venereal disease in 329 prostitutes working at massage parlours in Santiago. The mean age was 24 years and half of them had high school or university studies. In spite of frequent sexual contacts averaging 2.8 per day, the prevalence of significant venereal disease was not high in this group. Notably, AIDS infection was not detected. Vaginitis due to Trichomonas or Candida infection was the commonest problem and this was half as frequent among gum preservative users. Marital condition, age, obstetrical history and other variables were not related to genital infection.

Adult↗
PubMed1986

Cardiovascular effects and safety of dental anesthesia and dental interventions in patients with recent uncomplicated myocardial infarction.

To determine the cardiovascular effects and safety of dental anesthesia and dental interventions in patients within three weeks of uncomplicated acute myocardial infarction, 40 patients were studied. Twenty patients, group 1, underwent injectable local dental anesthesia with 2% lidocaine and 1:100 000 epinephrine. Group 2, 20 patients, underwent vigorous dental prophylaxis (13 patients) or dental extraction (seven patients) after local anesthesia. Heart rate, blood pressure, electrocardiograms, and symptoms were monitored before, during, and after the dental intervention. There were no significant hemodynamic changes or complications related to dental anesthesia or the dental procedures. One patient experienced an asymptomatic, uncomplicated, self-limited, eight-beat run of ventricular tachycardia two hours after dental extraction. Limited dental anesthesia and dental interventions were well tolerated by these patients with recent myocardial infarction.

Aged↗
PubMed1985

Effect of polyethylene glycol on the kinetic behaviour of pyruvate kinase and other potentially regulatory liver enzymes.

Assay in the presence of 10% polyethylene glycol has been systematically used with potentially regulatory liver enzymes as an indirect way to induce aggregation of enzymes corresponding to that which could occur at their physiological concentrations. Pyruvate kinase L was markedly affected by polyethylene glycol, as was muscle phosphorylase a, while pyruvate kinase M as well as glucokinase, fructose-1,6-bisphosphatase and other liver enzymes examined were not affected.

Adenosine Triphosphate↗
PubMed1985

The value of echocardiographic regional wall motion abnormalities in detecting coronary artery disease in patients with or without a dilated left ventricle.

To evaluate the usefulness of echocardiographic regional wall motion abnormalities (RWMA) in detecting coronary artery disease (CAD) in patients with left ventricular (LV) dysfunction and a normal-sized or dilated left ventricle, 103 patients were studied by two-dimensional echocardiography (2DE) and cardiac catheterization. In 60 patients (group I) who had LV dysfunction and a dilated left ventricle by echo (patients with dilated cardiomyopathy), RWMA were detected in 44 patients and 38 (86%) of them had significant CAD, usually two- or three-vessel obstruction; of the 16 patients with dilated cardiomyopathy (DCM) and diffuse LV hypokinesis, eight (50%) had evidence of CAD. Thus the presence of RWMA by 2DE had an 83% sensitivity, a 57% specificity, and a 77% predictive accuracy in detecting CAD in patients with DCM and thus in distinguishing ischemic from idiopathic DCM. In 43 patients with LV dysfunction but normal LV size (group II), the sensitivity, specificity, and predictive accuracy of RWMA in detecting significant CAD was 95%, 100%, and 95%, respectively. We conclude that the detection of RWMA by 2DE is highly suggestive of significant CAD in patients with LV dysfunction and normal-sized or dilated left ventricle; the finding, however, of diffuse LV hypokinesis does not exclude CAD in these patients, especially when the left ventricle is dilated.

Adult↗
PubMed1985

Norwalk virus gastroenteritis. An outbreak associated with a cafeteria at a college.

An explosive outbreak of gastrointestinal illness occurred among students and employees at a small college in Florida in November 1980. Common symptoms were diarrhea, nausea, weakness, abdominal cramps, chills, vomiting, and low-grade fever. Cases of illness were identified in 40% of 628 students and 15% of 162 employees who responded to a survey. Among students, there was a sevenfold excess risk associated with eating one or more meals at the campus cafeteria November 3-5 (p much less than 0.001). Tossed salad from one meal was strongly associated with illness (p less than 0.0001). Fecal contamination of the salad was documented, although the source of contamination was not identified. Person-to-person spread could not be demonstrated. Seroconversion to Norwalk antigen occurred in significantly more cases (5/6) than noncases (1/6) (p = 0.04).

Disease Outbreaks↗
PubMed1985

Update on cardiac pacemakers: description, complications, indications, and followup.

Great advances in pacemaker technology have produced devices capable of a vast array of physiologic adaptations formerly unimaginable, opening new possibilities in the pacemaker treatment of almost all rhythm disturbances. Nearly all units in use today are of the inhibited type, except for some antitachycardia applications. The AV-sequential mode (DVI) allows for preservation of AV synchrony, and the universal pacemaker (DDD) allows for a more physiologic response to a range of atrial rates. Programmability of numerous parameters has added a new dimension of adaptability to a variety of changing physiologic needs and pacemaker performance patterns, eliminating the need for surgical revision in many cases. The standard power source of today's pacemaker is the lithium chemistry cell, and the 5-year pacemaker is a reality, with 10 to 15 years of longevity distinctly possible in the near future. Almost all pacemakers use the transvenous route for access to the heart; new positive-fixation electrodes reduce displacement to a minimum; and new polyurethane or silicone-rubber leads have greatly simplified the techniques for implantation. Bipolar pacing systems are preferred, to avoid the oversensing of skeletal muscle interference--a problem that is especially important in triggered systems such as those used for antitachycardia applications. Threshold measurements are performed in millivolts at the time of implantation of most constant-voltage units, and current threshold measurements are useful for troubleshooting when failure to capture exists. Sensitivity parameters should be adjusted to sense the intracardiac signal; its amplitude should be determined in all cases, and measurement of the slew rate is useful when the amplitude is marginal. Recording of AV and VA conduction characteristics should be part of the routine implanting procedure, especially when simple blood pressure measurement during ventricular pacing indicates that this modality will be poorly tolerated and, therefore, implantation of a dual-chamber unit is contemplated. Different modalities of pacemaker malfunction have been reviewed, including the "cross-talk" phenomenon encountered with dual-chamber pacing. With the introduction of newer techniques, a host of pacemaker-mediated tachycardias have appeared, notably the "endless-loop" tachycardia of DDD pacemakers. This and other electrophysiologic phenomena of normal pacemaker function are bound to multiply as technology becomes more complex, but they should not be a problem if the programmable parameters are adapted to the electrophysiology of each particular patient.(ABSTRACT TRUNCATED AT 400 WORDS)

Arrhythmias, Cardiac↗
PubMed1984

Long-lasting behavioral effects of bromocriptine in cats.

The objective was to determine the behavioral effects and duration of action of bromocriptine (BC) doses from 6 to 60 mg/kg i.p. Cats were housed in large outdoors cages designed for prolonged observation using an ethological approach. Baseline behavior was measured after a 3 month period of habituation. The frequency of 12 behaviors was then scored continuously over 12 h following BC administration. Cats were also observed for one h at 24, 30, 36 and 48 h post-drug. The behavioral effects of BC were remarkably similar to those of LSD and psilocybin but lasted much longer. Treated cats showed hallucinatory-like and escape behavior. Abnormal involuntary movements such as limb flicks, abortive grooming, and head and body shakes were also evoked with a dose-dependent frequency. Lower doses (6-20) produced generalized arousal, but larger doses (30-60) resulted in a decrease in arousal. After 30 mg/kg, hallucinatory-like behavior and general activity (rubbing, treading, kneading) were high at 48 h post-drug, but there were no longer abnormal movements. Behavioral suppression followed the 60 mg/kg dose and peak effects were at 96 h post-injection. This model may prove useful to further study the neural basis of the psychoactive effects of BC.

Animals↗