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Biomedical subjects

A Hernandez

Publications and source records attributed to A Hernandez.

At least 181 records · Page 10Linked to original sources
PubMed1985

Restriction-modification systems in Streptomyces antibioticus.

Several restriction systems were detected in different strains of Streptomyces antibioticus by using actinophages as biological indicators. Adsorption of phages to the bacteria, together with the study of the efficiency of plating gave an initial indication of restriction in three strains. The alternation of efficiency of plating values obtained from restricting and nonrestricting hosts, gave evidence for the presence of a restriction-modification system in another strain. No common modification systems were detected among the different strains tested. Two specific endonucleases with a possible role in restriction were detected in strains ATCC 11891 and ETH 7451, respectively.

Adsorption↗
PubMed1985

Bone scintigraphic changes in osteonecrosis of the femoral head.

Bone scanning with 99mTc will detect osteonecrosis of the femoral head before changes appear in conventional radiographs. There is no liner correlation between the intensity of the scintigraphic picture and the clinical stage of the disease. The 99mTc labels newly formed hydroxyapatite crystals and may be helpful in detecting disease in a contralateral asymptomatic hip or confirming the diagnosis in the suspected hip.

Adult↗
PubMed1984

Long-term effects of early undernutrition on reactivity of the rat parietal association cortex.

Cortical reactivity of the parietal association area was studied in undernourished rats after short and long rehabilitation periods. Undernutrition was induced during lactation by increasing litter size from 8 to 18 pups per nurse. At either 40 or 100 days of age, cortical chronaxie, and both fatigability and latencies of direct cortical evoked responses were determined. At the two ages, results showed that early postnatal malnutrition induced higher chronaxies, greater fatigability and longer latencies of the responses compared with normal animals, indicating the existence of long-term functional alterations of that cortical area.

Animals↗
PubMed1984

Adult intussusception with autoamputation and preservation of bowel continuity.

We present a case of adult intussusception with autoamputation and preservation of bowel continuity. Our patient, a 65-year-old man, passed a 65-cm segment of large bowel per anus with spontaneous recovery and with a two-month follow-up free of symptoms secondary to the intussusception. Mesenteric ischemia secondary to angiography with distal embolization two weeks prior to the event may have been a precipitating factor in this unusual form of intussusception.

History, 19th Century↗
PubMed1984

Effect of weight training on blood pressure and hemodynamics in hypertensive adolescents.

Six adolescents with persistent essential hypertension were examined to determine the effect of weight training on their blood pressure and hemodynamics. Five had first completed an endurance training program; one subject trained only by weight lifting. All subjects were reevaluated after 5 +/- 2 months of weight training, and 12 +/- 2 months after cessation of training. Endurance training resulted in an increase in VO2max and decreases in systolic and diastolic blood pressure. After weight training, VO2max had decreased to the level found prior to endurance training, and body weight was significantly increased. Systolic blood pressure after weight training was 17 +/- 4 mm Hg lower than when measured initially (P less than 0.01). Weight training maintained the reduction in diastolic pressure elicited by endurance exercise in those who initially had diastolic hypertension. Cessation of all forms of training resulted in no change in body weight, body fat, or VO2max from the values measured after weight training. Systolic pressure increased significantly with the cessation of training to a value not different from that measured initially. Diastolic pressure also increased after cessation of training, but was still below the initial value. The only significant hemodynamic change found was a reduction in systemic vascular resistance in response to weight training. Weight training in hypertensive adolescents appears to maintain the reductions in blood pressure achieved by endurance training, and may even elicit further reductions in blood pressure.

Adipose Tissue↗
PubMed1984

Cortical and thalamic effects of local application of pentazocine to the rat somatosensory cortex.

Cortical and thalamic somatosensory evoked activity was studied following local application of 3% pentazocine to the primary somatosensory SI area (PSA) or to the parietal association area (PAA) of the rat cerebral cortex. At cortical level pentazocine affected the responsiveness of the two cortical areas in a way at least in part opposite. In PSA it essentially depresses the negative wave of the responses, whereas in PAA it increases both the positive and the negative components of the evoked potentials. The changes observed were restricted to the cortical region on which the drug was applied. At thalamic level, administration of pentazocine to the PSA or the PAA did not modify the bioelectrical activity recorded from the center median-parafascicular complex. It is concluded that pentazocine has a direct influence on cortical neurons involved in somatosensory processes. The failure of pentazocine-induced cortical changes to modulate neuronal activity at thalamic level is discussed.

Administration, Topical↗
PubMed1984

Effect of exercise training on plasma catecholamines and haemodynamics of adolescent hypertensives during rest, submaximal exercise and orthostatic stress.

Twelve adolescents with essential hypertension were studied to determine the effect of exercise training on plasma catecholamine concentrations, blood pressure and cardiovascular haemodynamics at rest and during submaximal exercise and orthostatic stress. Maximal oxygen consumption (VO2max) increased 13% with training while body weight and body fat did not change. Resting systolic and diastolic blood pressures decreased significantly with training, while plasma norepinephrine and epinephrine levels were unchanged. The increase in systolic blood pressure in response to standing was significantly lower after training, while the plasma catecholamine response was not significantly different. At the same absolute work rate after training, the subjects' systolic and diastolic blood pressures, heart rates, and plasma norepinephrine and epinephrine levels were significantly lower than before training. At the same relative work rate after training, the blood pressure response was the same as before training despite significantly higher plasma norepinephrine levels. Thus, the training-induced changes in resting blood pressures and blood pressure responses to orthostatic and submaximal exercise stress cannot be attributed to decreases in plasma catecholamine levels.

Adaptation, Physiological↗
PubMed1984

Effect of early iron deficiency on reactivity of the rat parietal association cortex.

The effect of early iron deficiency on the reactivity of the rat parietal association cortex was studied by determining excitability thresholds, fatigability and extension of the responsive field to direct cortical stimulation. Iron deficiency during the period of rapid brain growth caused a significant increase of cortical chronaxie values as well as increased fatigability of direct cortical responses, indicating a detrimental effect on the axodendritic synapses. Since the parietal association area plays an important role in brain association processes, a dysfunction of this cortical area could be a causal link between early iron deficiency and behavioral or learning deficits.

Anemia↗
PubMed1984

Management of childhood hypertension.

The pathogenesis of primary hypertension remains unknown despite extensive investigation. Recent publications provide evidence that primary hypertension may have its inception in childhood or possibly in infancy. Longitudinal studies are needed to determine whether the infant and child with primary hypertension becomes a hypertensive adult. What is also needed is a genetic marker other than elevated blood pressure that may specifically identify the primary hypertensive person. We recommend nonpharmacologic therapeutic intervention in the pediatric patient with primary hypertension. More intensive investigation of pediatric patients with primary hypertension should be encouraged and supported. The complex puzzle of primary hypertension is more likely to be solved if discovered at the inception of the disease in infancy or childhood rather than in the later irreversible stage in adulthood.

Adolescent↗
PubMed1984

The use of biodegradable norethisterone implants as a 6-month contraceptive system.

The effects of a 6-month contraceptive system of biodegradable norethisterone (NET) implants on the menstrual cycle, estradiol and progesterone levels, the presence of side effects, its contraceptive effectiveness, and the NET levels achieved were studied in a group of nine women. There was practically no disruption of the menstrual cycle and no important side effects. Ovulation was inhibited in four subjects, and another four subjects remained ovulatory. In all the subjects a cyclic secretion of estradiol was maintained. No pregnancies occurred. The circulatory levels of NET were very stable throughout the 6-month period of implant use.

Adult↗
PubMed1983

Temporal summation in rat prefrontal pyramidal cells. Differential effects of pre- and postsynaptic neurochemical manipulations.

The influence of both reserpine-induced depletion of catecholamines and chlorpromazine-induced blockade of dopamine receptors on integrative properties of rats prefrontal pyramidal cells was studied by evocating threshold direct cortical responses with different trains of electrical pulses. Catecholamine depletion results in increased pulse train stimulating currents for eliciting threshold cortical responses, whereas chlorpromazine blockade of dopamine receptors results in higher time constants characterizing postsynaptic temporal summation. It is suggested that the leaky-integrator neuron model may be a discriminating paradigm for detecting electrophysiologically the pre- or postsynaptic level of occurrence of some synaptic disorders.

Animals↗
PubMed1983

Effect of exercise training on the blood pressure and hemodynamic features of hypertensive adolescents.

Twenty-five adolescents (aged 16 +/- 1 years) whose blood pressure (BP) was persistently above the 95th percentile for their age and sex were studied before and after 6 +/- 1 months of exercise training and again 9 +/- 1 months after the cessation of training. Maximal oxygen consumption (VO2) increased significantly with training. There was no change in body weight or sum of skinfolds. Both systolic and diastolic BP decreased significantly with training; however, complete BP normalization was not achieved. When the subjects were retested 9 +/- 1 months after cessation of training, systolic BP and VO2 max had returned to pretraining levels; however, diastolic BP was still below pretraining levels in the subjects who had diastolic hypertension initially. Except in subjects who initially had an elevated cardiac output, no consistent hemodynamic changes were found with training or cessation of training to account for the reductions in BP. The subjects whose resting cardiac outputs were high initially had significantly lower cardiac outputs after training as a result of decreases in both heart rate and stroke volume; however, vascular resistance remained unchanged. Sedentary control subjects with similar BP had no significant change in any of the variables measured over a similar period. These data indicate that moderate endurance exercise training can lower BP in otherwise healthy hypertensive adolescents as an initial therapeutic intervention.

Adolescent↗
PubMed1983

Dysrhythmias following the Senning operation for dextro-transposition of the great arteries.

Twenty-nine patients have undergone the Senning operation for repair of dextro-transposition of the great arteries (TGA) since 1979 at St. Louis Children's Hospital. The early mortality has been comparable to that reported for the Mustard operation (10%). Electrocardiograms (ECGs) following the Senning operation reveal abnormalities similar to those noted after the Mustard operation; 63% of survivors were in normal sinus rhythm 1 week postoperatively, and 86% demonstrated normal sinus rhythm at a mean of 15 months after operation. Twenty-four hour ambulatory monitoring revealed normal sinus rhythm in 35% and occasional premature atrial or ventricular contractions in another 30%. No cases of sudden unexpected death have been noted, and no pacemakers have been inserted. Possible mechanisms for rhythm disturbances following venous transposition operations are discussed.

Arrhythmias, Cardiac↗