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Biomedical subjects

J Cuevas

Publications and source records attributed to J Cuevas.

18 recordsLinked to original sources
PubMed1992

Hypoxia inhibits calcium influx in rabbit basilar and carotid arteries.

We examined the hypothesis that hypoxia inhibits Ca2+ influx in isolated rabbit common carotid, internal carotid, and basilar arteries. In arteries mounted for measurement of isometric tension and exposed to 122 mM K+ in Ca(2+)-free Krebs, cumulative addition of Ca2+ produced Ca(2+)-force relations that were right-shifted by hypoxia (PO2 approximately 15 Torr) with no decrease in maximum force attained. In arteries precontracted with 122 mM K+, exposure to hypoxia produced relaxations whose rates and magnitudes were enhanced by reductions in bath Ca2+ from 8.0 to 0.8 mM. Using an ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid method for 3-min 45Ca influx measurements, modified for use in rabbit basilar and carotid arteries, we found that resting levels of Ca2+ influx (mumol.min-1.kg dry wt-1) were significantly higher in basilar (67 +/- 1, n = 10) than in internal carotid (27 +/- 1, n = 12) or common carotid (33 +/- 1, n = 12) arteries. K+ stimulation increased Ca2+ influx more than two-fold compared with control in all three artery types, and hypoxia inhibited this increase by 74% in basilar, 49% in internal carotid, and 33% in common carotid arteries. Exposure to 10 microM serotonin and 100 microM uridine 5'-triphosphate (UTP) also increased Ca2+ influx, but these increases were less than observed during K+ contractions and averaged 10 (basilar), 31 (internal carotid), and 82% (common carotid) above control. Hypoxia completely inhibited serotonin- and/or UTP-induced increases in Ca2+ influx in basilar and internal carotid segments and inhibited 47% of this increase in the common carotid segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of H+ on ATP-regulated K+ channels in feline ventricular myocytes.

Using patch-clamp techniques, we examined the effects of pH on properties of ATP-regulated K+ channels in single myocytes isolated from cat left ventricles. ATP-K+ channels of inside-out patches were bilaterally exposed to 140 mM K+ solutions (22 degrees C). In the absence of ATP and Mg2+, the channels had a linear current-voltage relationship during hyperpolarizing pulses (20-100 mV negative to the reversal potential) at both intracellular pH (pHi) 7.4 and 6.5, but the slope conductance was 66 +/- 2 pS at pHi 7.4 and 46 +/- 2 pS at pHi 6.5. Lowering pHi from 7.4 to 6.5 increased the mean open time (from 15.9 +/- 4.6 to 35.9 +/- 7.9 ms, P less than 0.01) but decreased the open-state probability measured at 50 mV positive to the reversal potential (from 0.35 +/- 0.04 to 0.16 +/- 0.04, P less than 0.01). However, in the presence of both 0.2 mM ATP and 1 mM MgCl2, lowering pHi from 7.4 to 6.5 increased the mean open time (from 5.0 +/- 2.6 to 17.9 +/- 5.9 ms, P less than 0.01) and the open-state probability (from 0.025 +/- 0.010 to 0.098 +/- 0.024, P less than 0.01). These data indicate that increases in intracellular H+ concentration modulate cardiac ATP-K+ channel properties. Ischemia-associated decreases in pHi may enhance the opening of cardiac ATP-regulated K+ channels and resultant action potential shortening.

Adenosine Triphosphate↗
PubMed1990

Electrophysiological properties and responses to simulated ischemia in cat ventricular myocytes of endocardial and epicardial origin.

In multicellular preparations, there are differences in action potential configuration between endocardium and epicardium, and electrophysiological alterations induced by ischemia are more drastic in epicardium than in endocardium. The present study was designed to examine electrophysiological properties of single cardiac myocytes enzymatically isolated from the endocardial and epicardial surfaces of the cat left ventricle and to determine whether the differential responses to ischemia of intact tissue occur in single cells. Action potentials recorded from the isolated single cells of epicardial surface had lower action potential amplitude and a prominent notch between phase 1 and phase 2, compared with those of the cells isolated from the endocardial surface; these findings are similar to those in intact endocardial and epicardial preparations. Resting membrane potentials recorded from both endocardial and epicardial single cells were sensitive to the change in extracellular K+ concentration and had properties of a K+ electrode. Action potential duration was frequency dependent in both cell types and was shorter in epicardial cells than in endocardial cells at a stimulation rate of 3 Hz. When the cells were superfused with Tyrode's solution that was altered to mimic an ischemic environment in vivo (PO2, 30-40 mm Hg; pH 6.8; [K+], 10 mM; and glucose free), resting membrane potential, action potential amplitude, and action potential duration were reduced, and the refractory period was shortened in both endocardial and epicardial single cells, but there were no differences in the degree of changes in action potentials and refractory periods induced between the two cell types. Action potential changes induced by L-alpha-lysophosphatidylcholine (5-40 mg/l) were also similar in endocardial and epicardial single cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

Direct effects of graded hypoxia on intact and denuded rabbit cranial arteries.

In isolated rabbit common carotid, internal carotid, and basilar arteries denuded of endothelium, mounted for measurement of contractile activity, and contracted with 10 microM serotonin (common and internal carotid) or 100 microM uridine 5'-triphosphate (UTP; basilar), 20 min of severe (PO2 = 15 Torr) and moderate (PO2 = 35 Torr) hypoxia relaxed initial tensions to 17, 6, and 16% and 18, 7, and 61% of control, respectively. The corresponding values in arteries contracted with 120 mM potassium-Krebs solution were 42, 60, and 73% and 57, 72, and 88%. These data indicate that the main determinants of the responses to hypoxia were intrinsic to the vessel walls of these arteries and that complete depolarization attenuated but did not eliminate the effects of these mechanisms. Superimposed on these intrinsic mechanisms were the effects of the endothelium, which were evaluated by several methods, including integration of the area between the 20-min response time courses of corresponding intact and denuded segments. Positive and negative integrated area values indicated endothelial vasoconstrictor [endothelium-derived contracting factor (EDCF)] and vasodilator [endothelium-derived relaxing factor (EDRF)] influences, respectively. In common carotid, internal carotid, and basilar segments contracted with serotonin and/or UTP, these areas averaged 770, 354, and 44 min% during severe and 491, 189, and -411 min% during moderate hypoxia. Corresponding values during potassium contraction were 217, -271, and -356 min% and 52, -177, and -54 min%. Together, these findings suggest that 1) intrinsic vascular mechanisms contribute significantly to hypoxic cerebral vasodilation in the rabbit, 2) EDCF is more prominent but also may be more sensitive to depolarization than EDRF, 3) hypoxia promotes the simultaneous release of both EDCF and EDRF, and 4) the ratio of EDCF to EDRF released during hypoxia decreases as one moves from the rabbit common carotid to the internal carotid to the basilar arteries.

Animals↗
PubMed1989

[Is it possible to relate reflux esophagitis to epidermoid carcinoma of the esophagus?].

The authors present a retrospective study of 120 cases of epidermoid carcinoma of the esophagus, in which they proposed to investigate the etiopathogenic relation between gastroesophageal reflux and noplastic development. A statistically significant relation was found between esophagitis and cancer of the distal esophageal third, indicating the need for vigilance of patients with reflux and for randomized prospective studies to clarify the problem definitively.

Adult↗
PubMed1989

[Superficial gastric carcinoma. Clinical analysis].

While in Japan the incidence of superficial gastric cancer (CGS) is very high (35%), with a mean 5-year survival rate of 95%, in our environment it is infrequent. Although the global incidence of gastric cancer is declining, recently, since endoscopy became routine, an increase has been seen in the diagnosis of superficial gastric cancer. In the period between 1976-1982 two cases were diagnosed in our service, but between 1982-1986 the total number of cases found was 23, representing 0.37% of all the endoscopies performed (approx. 6,800) and 8.6% of those diagnostic of gastric cancer (266 cases). Of the lesions, 60.8% were located in the antral region and the most common accompanying symptomatology was ulcerative syndrome (47.3%). The predominant tumoral type was ulcerative (73.9%) (classification of the Japanese Endoscopy Society). The benefits of radiological study were nil, while endoscopic biopsy was diagnostic in 100% after an average of 1.8 (1-4) endoscopies per patient with 6-12 biopsy samples obtained in each endoscopy. Of these 23 patients, 8 underwent total gastrectomy, 14 partial gastrectomy and one refused surgical treatment. The survival was 91.3%, with a follow-up of 6 to 60 months, and two deaths were due to nontumoral causes.

Adult↗
PubMed1979

[Pheochromocytoma and sudden death (author's transl)].

Five cases of pheochromocytoma are described in which sudden death was the form of the initial clinical presentation in almost all of them. After a brief review on the history and the incidence of the tumor within the general population, diverse cases are analyzed from a clinical point of view and in relation to the data appeared in the literature. In the analysis of the symptoms emphasis is placed on the important psychomotor manifestations which are present in the majority of those patients and which causes serious difficulties in the initial diagnosis. All of the patients showed signs of shock at the time of being observed or during the course of this observation, and in the majority of them the presence of acute pulmonary edema was confirmed; facts which we attribute to an initial hypertensive episode associated to a left heart failure. The onset of the crisis in two patients was related to known triggering factors: anesthesia and sulpiride. In other two patients associated conditions were diagnosed: medullary carcinoma of the thyroid gland in one of them, and cystic necrosis of the middle layer of the aorta in the other.

Adult↗
PubMed1978

Response of intramuscular Walker 256 rat tumor to sustained-release cyclophosphamide and ARA-C capsules.

Randomly bred Sprague-Dawley rats with the intramuscular form of Walker 256 tumor growing in the right thigh region were treated with sustained-release cyclophosphamide capsules as well as with cytosine arabinoside capsules. A disk-shaped caps-le was implanted subcutaneously adjacent to the tumor mass. Tumor regression, weight gain, and prolongation of lifespan were observed in animals treated with cyclophosphamide capsules of 10 mg or 20 mg total drug content each. However, the walker 256 intramuscular tumor did not respond to ARA-C capsules implanted, and the animals died at the same rate as the controls, with large ulcerated tumor masses and some metastasis. The in vitro diffusion data of ARA-C capsules is shown. Gross and histological changes associated with cyclophosphamide administered in this manner are reported.

Animals↗
PubMed1977

Effects of subcutaneously implanted sustained-release cyclophosphamide capsules on Walker 256 solid rat tumor.

Complete regression of Walker 256 solid rat tumor was brought about by the subcutaneous implantation of a single sustained-release cyclophosphamide capsule adjacent to the tumor mass. Untreated control animals died within 3 weeks after receiving the tumor with large necrotic masses. Rats with sustained-release capsules experienced complete tumor regression within 28 days. Upon examination, the tissues around the previous tumor mass has regenerated, and no viable tumor cells could be found in the area where the previous tumor mass was. Around the implanted sustained-release cyclophosphamide capsule a fibrous sheath has developed over the 3 weeks it was in situ. This study suggests an alternate means of cytoxic drug administration in the treatment of solid tumors in experimental animals.

Animals↗
PubMedDate not supplied

Synaptophysinlike immunoreactivity in the Merkel cells of pig-snout skin.

Synaptophysin is a membrane glycoprotein (Mr 38,000) found in small vesicles with clear content. It is present in neurons and in a variety of neuroendocrine cells and neoplasms, including the neuroendocrine carcinoma of the skin (Merkel cell tumor). We report the presence of synaptophysinlike immunoreactivity in normal Merkel cells of the pig-snout epidermis and vibrissae. The immunostaining was primarily localized in the Merkel cell side opposite to the nerve terminal. This fact suggests that in Merkel cells, as well as in other neuroendocrine cells, synaptophysin could occur in small clear vesicles (accumulated in Merkel cells in the side opposite to the neurite) and not in the secretory granules themselves (which are concentrated in the cellular side apposed to the neurite).

Animals↗
PubMedDate not supplied

[IgG- and IgA-antibodies to the Epstein-Barr virus in the sera of patients with nasopharyngeal carcinoma in Cuba].

Sera from 24 patients with nasopharyngeal carcinoma (NPC) and from 60 normal subjects were examined for the presence of IgG and IgA antibody to various antigens associated with Epstein-Barr virus (EBV). The results indicate that NPC in Cuba, like in other countries, was accompanied by high titers of EBV-specific IgG antibody the levels of which differed markedly from those in normal subjects. Serological activity of the patients differed depending on the stage of the illness and its duration. Geometric mean antibody titers to the capsid antigen (VCA), D and R components of early antigen (EA) of EBV complex were higher in patients with extensive tumour process (III--IV stages) and in patients with the duration of the disease since the onset less than 3 years. Sera of the most patients contained EBV-specific IgA antibody which were practically completely absent in sera of the control subjects. Alongside with characteristic manifestations of responsiveness to EBV observed by other workers, patients with NPC in Cuba had specific features: higher antibody titers to VCA than in Caucasian subjects in the countries where this disease occurred sporadically, like in Cuba; high levels of antibody to EA, frequently exceeding those in patients with NPC from endemic zones (for instance in Chinese patients); prevalence of EBV-specific antibody to the R component of EA complex.

Adolescent↗
PubMedDate not supplied

Seasonal and diurnal variation of pollen from Gramineae in the atmosphere of Córdoba Spain.

We have carried out a study on the annual and diurnal variation of pollen from the Gramineae family in the atmosphere of Córdoba (Southern Spain) during three consecutive years. This family, according to its high sensitizing capacity and to data from allergologists, is responsible for most of the pollenoses diagnosed in the city. Pollen grains from Gramineae were found to occur in the atmosphere virtually throughout the year, starting in February. Yet, they reach their highest levels in spring, particularly in May and the first fortnight of June. Such levels decrease gradually during the summer and become virtually imperceptible from October. The concentration of pollen grains from Gramineae were found to be positively correlated with the average temperature, and negatively correlated with the average humidity. The diurnal variation pattern of the concentration of pollen grains from this family was rather homogeneous throughout the three years studied, with a marked increase early in the morning, a moderate decrease in the afternoon and stable values throughout the night.

Air↗
PubMedDate not supplied

[Chondrosarcoma of the sinuses: an infrequent tumor].

The case of 69 year old male patient who developed sinusal mesenchymal chondrosarcoma is presented. At the time of diagnosis the tumor had spread into the intracranial cavity, which explains why no surgical treatment was carried out. A combined palliative treatment of chemotherapy and radiotherapy was used which did not improve the course of the tumor. The rare location of this form of tumor is discussed. Also commented on are the therapeutic--both surgical and other modalities (chemotherapy and radiotherapy)--difficulties encountered with this condition, given the little experience accumulated with it and its habitual resistance to the therapeutical regimens employed.

Aged↗
PubMedDate not supplied

[Furosemide in the early diagnosis of acute renal insufficiency in the newborn infant].

The study included 13 infants under one year complaining of acute gastroenteritis and dehydration who were still in oliguria or anuria 6 hours after rehydration was initiated. They were given a single dose of furosemide at the rate of 1 mg/kg and indices of U/P of urea and osmolarity, ratio urea/plasmatic creatinine, urinary volume, natriuresis and evolution of urea plasmatic figures and of creatinine were determined. Four patients showed no response to the diuretic; all of them died and through clinical and histopathologic evaluation they were classified as having acute renal insufficiency (IRA). The nine patients showing response to the drug with an increase of 5 to 30 times the control figure for urine and natriuresis showed an index U/P of urea of 5.52 +/- 3.82, U/P of osmolarity of 1.32 +/- 09, ratio urea/plasmatic creatinine of 58.7 +/- 19.8 and the figures for urea and creatinine in blood turned normal within 2 to 4 days. This was classed as prerenal azotemia (APR). It is thus concluded that furosemide appears to be a good parameter to make an early differentiation of cases with IRA, but that this measure, the same as the rest of the indices cannot show an absolute value since there are important variations in each individual.

Acute Kidney Injury↗