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Biomedical subjects

J Rojas

Publications and source records attributed to J Rojas.

At least 73 records · Page 4Linked to original sources
PubMed1989

Electrophysiological evidence for receptors for vasoactive intestinal peptide and angiotensin II on astrocytes of cultured rat central nervous system.

Electrophysiological studies have been made of the actions of vasoactive intestinal peptide (VIP) and angiotensin II (Ang II) on astrocytes in explant cultures of rat brain stem and spinal cord. Addition of VIP to the bathing solution at concentrations of 10(-8) to 10(-6) M caused hyperpolarizations. Ang II at the same concentrations depolarized the majority of astrocytes tested. At 10(-9) M, both peptides had no action or only small effects. In approximately one third of the cells, the depolarizations by Ang II were accompanied by rhythmic oscillations. The Ang II antagonist saralasin reversibly blocked the depolarizations by Ang II. These findings, together with autoradiographic binding studies from our laboratory strongly suggest the existence of VIP and Ang II receptors on astrocytes.

Angiotensin II↗
PubMed1989

[Hodgkin's disease associated with infection by human immunodeficiency virus].

We present four patients with Hodgkin's disease and human immunodeficiency virus infection (HIV). Three patients were addicts to parenteral drugs. The disease was very advanced at the time of diagnosis, stage IVB in all cases. Histologic types were mixed cellularity in two cases, nodular sclerosis in one case and it was not typifiable in the remaining case. The disturbances of cell-mediated immunity that the patients presented were those of the acquired immunodeficiency syndrome (AIDS) as well as the infectious complications. Response to treatment was poor with a high incidence of bone marrow toxicity; three patients died during the first 3 months after the diagnosis (X = 7.3 months). We emphasize the necessity of considering different prognostic and therapeutic approaches for the HD in these patients in contrast with those of seronegative patients. We pose some questions suggested by the review of the literature and the data of this series.

Adult↗
PubMed1989

Lung vascular permeability changes in lambs with hyaline membrane disease.

To investigate the mechanism of pulmonary edema in hyaline membrane disease (HMD), lymph from the efferent duct of the mediastinal lymph node was collected in premature lambs before and after delivery by cesarean section. Mean lymph flow in 7 lambs with histologically verified HMD increased progressively over 4 h after delivery to 3 times the fetal value, while lymph flow in 7 lambs without HMD increased to 3.5 times at 1 h and decreased thereafter. At 4 h after birth, lung lymph flow was significantly higher in lambs with HMD than in lambs without HMD (0.70 +/- 0.15 (SEM) vs 0.43 +/- 0.07 ml.h-1.kg-1). Lymph/plasma concentration ratio for small endogenous protein fractions (effective molecular radius, 3.6 and 3.8 nm) was significantly higher in lambs with HMD than in lambs without HMD at 2-4 h. Postmortem extravascular lung water was significantly higher in lambs with HMD (6.1 +/- 0.5 vs 4.3 +/- 0.3 ml/g dry lung weight). It is concluded that lung water is high in lambs with HMD, which appears to be a result both of delayed absorption of fetal lung liquid and increased permeability of the pulmonary exchange vessels.

Animals↗
PubMed1989

[Conconi test on the bicycle ergometer].

Several recent papers on the Conconi procedure tested on an ergometric bicycle have shown that the deflection of the heart rate is rarely seen if the procedure follows the usual protocol where the work duration remains the same at each work level. According to the di Prampero formula, work can be expressed as the energy cost of running (C), multiplied with covered distance. Therefore it is important, as in the current 400 m-track Conconi test, to keep work and not time constant at each work level. Consequently we examined heart rate and lactate profile in four groups of athletes, in following an experimental design respecting this condition. In all ergometric test runs, we observed the sought after heart rate deflection with the following lactate values: Physical education students (female) heart rate 169 with 4.6 mmol/l lactate Physical education students (male) heart rate 169 with 5.03 mmol/l lactate Amateur cyclists heart rate 178 with 2.44 mmol/l lactate Professional cyclists heart rate 171 with 1.98 mmol/l lactate.

Adult↗
PubMed1987

Lung water and vascular permeability-surface area in premature newborn lambs with hyaline membrane disease.

Extravascular lung water and vascular permeability-surface area products were measured with a multiple indicator dilution method in 6 premature lambs with hyaline membrane disease 1-5 hours following delivery by cesarean section. The indicators used were 51Cr-labelled erythrocytes, 125I-albumin, 3H-water, and 14C-urea. Results were compared with previously obtained data in newborn lambs without hyaline membrane disease also delivered by cesarean section. Extravascular lung water was significantly higher in lambs with hyaline membrane disease [23.2 +/- 1.0 (SEM) vs. 10.7 +/- 1.4 ml/kg body wt]. Vascular permeability-surface area products for 14C-urea were significantly lower in lambs with hyaline membrane disease (0.30 +/- 0.10 vs 0.78 +/- 0.11 ml/s per kg). It is concluded that extravascular lung water is high in lambs with hyaline membrane disease. Permeability-surface area products for 14C-urea is low in lambs with hyaline membrane disease, which probably indicates a decrease in detectable surface area for exchange due to derecruitment or hypoperfusion of pulmonary exchange vessels in edematous and hypoxic areas of the lungs.

Animals↗
PubMed1986

Effect of epidermal growth factor on lung liquid secretion in fetal sheep.

Fetal lung liquid secretion depends on active transport of chloride ions. Chloride secretion in the stomach is inhibited by epidermal growth factor (EGF). For this reason, the effect of EGF on lung liquid secretion was measured using the impermeant-tracer technique in chronically-prepared fetal sheep. Infusion of EGF over 4 h resulted in decreased lung liquid secretion (from 4.2 +/- 0.6 to 1.7 +/- 0.8 ml/h, P = 0.02) and significant dose related tachycardia. During the infusion, plasma epinephrine levels increased from 27 +/- 5 to 67 +/- 13 pg/ml (P = 0.05) and norepinephrine levels increased from 257 +/- 31 to 544 +/- 69 pg/ml (P = 0.01). Since it is known that beta-adrenergic agonists inhibit lung liquid secretion, subsequent studies were performed with beta-adrenergic blockade using propranolol. Infusion of EGF and propranolol resulted in a significant decrease in lung liquid secretion (from 8.9 +/- 2.1 to 3.0 +/- 1.1 ml/h, P = 0.03). Infusion of propranolol alone had no demonstrable effect on lung liquid secretion. It is concluded that acute EGF infusion increases heart rate and stimulates catecholamine secretion in fetal sheep. EGF also inhibits lung liquid secretion, an effect which appears to be independent of a possible indirect catecholamine effect.

Animals↗
PubMed1984

Effects of methylprednisolone on the response to group B streptococcal toxin in sheep.

The effects of pretreatment with methylprednisolone on the reaction to a toxin isolated from group B beta-hemolytic streptococci, type III, were studied in seven sheep instrumented for chronic measurements of pulmonary lymph flow and pulmonary artery and left atrial pressure. Each sheep was infused with toxin alone on one day and with methylprednisolone plus toxin on a different day in random order. The toxin alone caused a two-phase reaction. After the infusion of toxin, alone, in the initial phase, pulmonary artery pressure increased from 16 +/- 1 to 45 +/- 5 mm Hg and the rectal temperature rose from 39.5 +/- 0.14 to 40.8 +/- 0.18 degree C. During the second phase, the peripheral blood granulocyte count decreased to 10% of baseline values and the lung lymph protein clearance increased from 5.1 +/- 1.1 to 11.2 +/- 1.8 ml/h, suggesting increased pulmonary vascular permeability. Methylprednisolone pretreatment did not alter the initial phase of pulmonary hypertension or the febrile response but completely abolished the granulocytopenia and the increased pulmonary vascular permeability. These effects are unlikely to be related to inhibition of prostaglandin synthesis. Prevention of the lung vascular injury by methylprednisolone may be related to inhibition of granulocyte accumulation in the lung.

Animals↗
PubMed1984

Indication for interstitial brachytherapy in carcinoma of the uterine cervix.

More than 40 patients with gynecological, genitourinary, and gastrointestinal malignancies, both primary and recurrent but confined to the pelvis, were treated with interstitial irradiation over a four-year period. Interstitial irradiation was the choice of treatment for early carcinoma of the prostate, carcinoma of the anal canal less than T2, recurrent carcinoma of the uterine cervix, and carcinoma of the cervical stump. The authors' experience in treating recurrent carcinoma of the uterine cervix with interstitial irradiation is the basis for the indications for selecting the technique of interstitial irradiation presented.

Brachytherapy↗
PubMed1983

Early onset group B streptococcal disease. Seven year experience and clinical scoring system.

Early onset group B streptococcal disease was reviewed for the seven year period between 1975 to 1981 at Vanderbilt University Medical Center. One hundred and twenty cases were identified. The disease varied from asymptomatic bacteremia to fatal cardiopulmonary collapse. Factors associated with a poor outcome were prematurity, low Apgar score at 5 min, the presence of shock, leukopenia, rupture of membranes for more than 12 hours, and a delay in treatment after the onset of symptoms. A scoring system for probability of death based on these 6 factors was then developed. Over the seven year period mortality decreased from 50% to 10%. The only factor identified with the decrease in mortality was a significant decrease in the number of hours between the onset of symptoms and the beginning of treatment. Early recognition and prompt treatment seem to be the major causes of the decreasing mortality over the seven years of this report.

Apgar Score↗
PubMed1983

Effects of cyclooxygenase inhibition on the response to group B streptococcal toxin in sheep.

The effects of cyclooxygenase inhibition on the reaction to a toxin isolated from group B beta-hemolytic streptococci, type III, were studied in seven sheep instrumented for chronic measurement of pulmonary lymph flow, pulmonary artery and left atrial pressures. Each sheep was infused with toxin alone on one day and with indomethacin plus toxin on a different day in random order. The toxin alone caused a two-phased reaction. After the infusion of toxin, alone, in the initial phase, pulmonary artery pressure increased from 16.5 +/- 1.2 mmHg to 47.1 +/- 4.8 mmHg and the rectal temperature rose from 39.7 +/- 0.13 degree C to 40.9 +/- 0.16 degree C. During the second phase, the granulocyte count decreased to less than 10% of baseline values and the lymph protein clearance increased from 4.8 +/- 1.2 ml/h to 10.02 +/- 1.4 ml/h, suggesting increased pulmonary vascular permeability. Indomethacin pretreatment prevented the initial phase of pulmonary hypertension, the increases in thromboxane and prostacyclin metabolites in lung lymph, and the febrile response to toxin infusion but did not modify the granulocytopenia or the increased pulmonary vascular permeability. It appears that the hemodynamic changes are independent from the pulmonary vascular changes, and that prostaglandin endoperoxides or their metabolites are necessary for the fever and the acute pulmonary hypertension.

Animals↗
PubMed1983

Pulmonary hemodynamic and ultrastructural changes associated with Group B streptococcal toxemia in adult sheep and newborn lambs.

A toxin isolated from Group B beta-hemolytic streptococci, Type III was infused into adult sheep and newborn lambs. A two-phased reaction was observed. There was an initial phase of pulmonary hypertension and high flow of protein-poor lymph. This was followed by a second phase when pressures returned to baseline but lymph flow remained twice the baseline values and protein concentration in lymph increased. During the second phase there was a significant increase in lymph protein clearance, suggestive of increased microvascular permeability to protein. The absolute granulocyte count decreased to 10% of baseline values by 60 min after the infusion, and was followed by a variable return to baseline. The sheep with the largest changes in protein clearance were those who had the slowest return to baseline values. Pathologic examination of lung tissue revealed there was capillary dilation, interstitial edema, and large numbers of granulocytes in the lungs. The basement membranes of both capillaries and arterioles showed disruption and widening, along with fragmentation of the internal elastic membrane. This study provides morphologic and physiologic evidence of increased pulmonary vascular permeability after injection of streptococcal toxin associated with granulocyte trapping in the lung. We postulate that granulocytes may be involved as mediators of the pulmonary vascular injury.

Animals↗
PubMed1982

A quantitative model for hyaline membrane disease.

A model based on the course of 31 infants with uncomplicated hyaline membrane disease is described. Based on data collected over the first 12 hr of life, it predicts the course of an infant for the next 60 hr, and estimates the outcome in terms of length of oxygen requirement and assisted ventilation. For the construction of the model, right-to-left intra- and extra-pulmonary shunting, expressed as venous admixture, was considered as the principal mechanism of hypoxemia in hyaline membrane disease and mean applied proximal airway pressure was used to quantify management. The model provides an objective estimate of severity early in the course of disease, uses variables routinely available in an intensive care unit, and its use would strengthen the interpretation of clinical studies in which the comparability of experimental and control groups is critical.

Humans↗