PubMed Health⌕ Search

Biomedical subjects

L Alvarez

Publications and source records attributed to L Alvarez.

At least 19 recordsLinked to original sources
PubMed1992

How is rat liver S-adenosylmethionine synthetase regulated?

The in vivo regulation of S-adenosylmethionine synthetase, a key enzyme in methionine metabolism, is so far unknown. The enzyme activity has been shown to be modulated by glutathione and the oxidation state of its sulfhydryl groups. Analysis of the protein sequence has revealed the presence of putative phosphorylation sites. A mixed regulatory mechanism combining phosphorylation and the oxido/reduction of sulfhydryl groups is proposed. The role of glutathione in this mechanism is also discussed.

Animals↗
PubMed1992

Expression of alpha-tropomyosin during cardiac development in the chick embryo.

A new monoclonal antibody (mAb) that recognizes alpha-tropomyosin in cardiac muscle cells was used in a qualitative (polyacrylamide gel electrophoresis and indirect immunofluorescence) and quantitative (fluorescence-activated cell sorting) study of the expression of this protein during heart development. alpha-Tropomyosin expression was weak in early stages of chick embryo development (Hamburger and Hamilton stage 18), and increased steadily until Hamburger Hamilton stage 40. In early stages, the protein was found mainly in cytoplasm, whereas by the final stages, it was more abundant in the cytoskeletal compartment. The mAb cross-reacted with alpha-tropomyosin in smooth and striated muscle cells from chickens, mice, and humans, but did not cross-react with nonmuscle tropomyosin.

Animals↗
PubMed1992

S-adenosylmethionine treatment prevents carbon tetrachloride-induced S-adenosylmethionine synthetase inactivation and attenuates liver injury.

Administration of carbon tetrachloride to rats resulted in induction of hepatic fibrosis and a 60% reduction of hepatic S-adenosylmethionine synthetase activity without producing any significant modification of hepatic levels of S-adenosylmethionine synthetase messenger RNA. The reduction of S-adenosylmethionine synthetase activity was corrected by treatment with S-adenosylmethionine (3 mg/kg/day, intramuscularly). Administration of carbon tetrachloride also produced a 45% depletion of liver glutathione (reduced form) that was corrected by S-adenosylmethionine treatment. After the rats received carbon tetrachloride, a 2.3-fold increase in liver collagen was observed; prolyl hydroxylase activity was 2.5 times greater than that seen in controls. These increases were attenuated in animals treated with carbon tetrachloride and S-adenosylmethionine. The attenuation by S-adenosylmethionine treatment of the fibrogenic effect of carbon tetrachloride was associated with a decrease in the number of rats in which cirrhosis developed.

Animals↗
PubMed1992

Serotonin increases the cAMP concentration and the phosphoenolpyruvate carboxykinase mRNA in rat kidney, small intestine, and liver.

Within 60 min of the administration of serotonin to fasted-refed rats, there was a 5-, 16-, and 20-fold stimulation of the mRNA coding for the cytosolic form of P-enolpyruvate carboxykinase in the kidney, small intestine and liver, respectively. This stimulation was 5-, 1.3-, and 2-fold higher than noted in the same tissue after 24 h of starvation. Dose- and time-response curves to serotonin in the three tissues were similar. The level of PEPCK mRNA in the liver was significantly elevated within 30 min of serotonin administration, whereas 60 min was required in the small intestine and the kidney. The direct effect of serotonin on PEPCK mRNA was also assessed in hepatocytes maintained in primary culture. Serotonin (10(-8) M to 10(-4) M) caused a dose-dependent increase in the level of PEPCK mRNA and a transient increase in cAMP concentration. Within the first min of serotonin (10(-6) M) addition to cells, cAMP concentration increased 4-fold and returned after 10 min to basal level. Therefore, these results provide functional evidence of serotonin action in the rat peripheric tissues and suggest that cAMP is involved in its intracellular signalling.

Animals↗
PubMed1992

Detection and hormonal regulation of the mRNA for cytosolic phosphoenolpyruvate carboxykinase in rat lung.

We have studied the presence of the messenger RNA (mRNA) for the cytosolic enzyme, phosphoenolpyruvate carboxykinase (PEPCK), in rat lung by Northern blot hybridization to a complementary DNA (cDNA) probe. Lung from normal rats contained substantial amounts of this mRNA, although its relative concentration was approximately six times lower than in liver. Fasting produced an eightfold increase in the content of the enzyme mRNA in lung, which could be reverted to normal values by glucose refeeding. Induced diabetes also resulted in a sevenfold increase of the levels of PEPCK mRNA in lung. Dexamethasone, thyroid hormone, dibutyryl cyclic adenosine monophosphate (cAMP), histamine, and serotonin also induced important accumulations of the enzyme mRNA without affecting the concentration of beta-tubulin mRNA measured as reference. Thus, the PEPCK gene appears to be regulated in a similar manner in lung and liver. The results suggest that PEPCK may be involved in lung metabolism in starvation, diabetes, and other specific hormonal situations.

Animals↗
PubMed1992

Evaluation of teratogenic potential of N-formylpiperidine in rats.

The teratogenic potential of a versatile solvent, N-formylpiperidine (NFP), was evaluated in the rat. Three groups of 25 mated female Sprague-Dawley rats were given 110, 220, or 440 mg/kg/day NFP in distilled water by gavage on Days 6 through 20 of gestation. A control group of 25 animals received distilled water on a comparable regimen. Maternal animals were observed daily for signs of toxicity; body weights and food consumption were measured at regular intervals throughout the study. All animals were euthanized on Gestation Day 21 and the fetuses examined for cleft palate and external abnormalities. One-half of the fetuses in each litter were examined for visceral anomalies while the remaining fetuses were examined for skeletal malformations after appropriate staining. One female in the high dosage group died on Gestation Day 12. Clinical signs of toxicity, observed in 6 females in the high dosage group, included tremors, convulsive movements, and an apparent weakness of the legs. Maternal toxicity, in terms of significantly decreased body weight and food consumption, was observed in the mid and high dosage groups. Food consumption was also significantly depressed for the first 4 days of dosing in the low dosage group. There was a significant increase in number of resorptions in the high dosage group when compared to controls. No effects were observed on other reproductive parameters. Mean fetal body weight was significantly lower in the high dosage group when compared to controls. While the incidence of fetal malformations on a litter basis was higher in the high dosage group, this change was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The effectiveness of skin cancer screening and continuing medical education programs toward increasing the survival of patients with malignant melanoma.

The 5-year survival rate for malignant melanoma has increased 40% over the last 50 years. During this same time period, the treatment for the disease has not changed significantly, and consists of wide excision of the primary tumour and perhaps regional node dissection. The purpose of this study was to investigate the possible impact of screening/education programs on melanoma survival. In 1987, a multimodality University-based Melanoma Treatment Center was established and programs were instituted for skin cancer screening and Continuing Medical Education (CME) of health care providers. During the last 5 years, 594 patients with newly diagnosed melanoma have been registered at the clinic. The number of patients with localized (stage 1 or 2, negative regional nodes) disease was 516 (85%). For all stages of disease, the 3-year actuarial survival for this screened population was 85%. From the National Cancer Database of 9879 patients registered with melanoma for 1988, 75% had localized disease and the 3-year survival was 76%. There were significant differences noted between the screened Florida population and the nationwide database using an odds ratio statistic. This involved a higher frequency of patients diagnosed with localized disease (odds ratio = 1.89 (1.49-2.40)) and a better survival (odds ratio = 1.79 (1.41-2.27)) in the screened population served by CME-educated community physicians.

Actuarial Analysis↗
PubMed1992

Electrophysiological effects of atracurium and vecuronium on normal and denervated hearts.

Atracurium and vecuronium offer some advantages with respect to other nondepolarizing muscle relaxants. However, their administration has been associated with episodes of bradycardia and asystole, the mechanism of which has not yet been clarified. In an effort to analyze the effects of these drugs on automaticity, refractoriness, and conduction, 30 dogs underwent heterotopic heart transplantation to establish a model in which a normal heart (recipient) and a denervated heart (donor) could coexist. The electrophysiological studies included the determination of cycle length (CL), sinoatrial conduction time (SACT), antegrade and retrograde atrio-ventricular (A-V) node and ventricular block points (ABP and RBP), as well as effective antegrade and retrograde A-V node (ARPAVN and RRPAVN) and ventricular refractory periods (VRPs) in both hearts. These parameters were measured in a basal state and after injection of pancuronium (0.5 mg/kg) in 10 animals, atracurium (0.5 mg/kg) in another 10 dogs, and vecuronium (0.12 mg/kg) in the remaining animals. The results showed that pancuronium produced a tachycardia, significantly facilitated A-V conduction in the donor and the recipient hearts, and lowered the A-V node refractoriness in the donor organ, while atracurium and vecuronium induced no changes from the baseline values, either in normal or denervated hearts. Based on the results of this study, the episodes of sustained bradycardia reported in association with atracurium and vecuronium are attributed to the absence of antagonism of vagal stimuli provoked by pancuronium, and/or by surgical or anesthetic manipulations.

Animals↗
PubMed1992

Glutaric aciduria type I: unusual biochemical presentation.

We describe a patient with glutaryl-coenzyme A dehydrogenase deficiency, demonstrated by a residual enzyme activity of only 1% in cultured fibroblasts. Although the clinical presentation was typical of glutaric aciduria type I, the urine concentrations of glutaric, glutaconic, and 3-hydroxyglutaric acids remained normal, even during episodes of clinical decompensation. An increased free glutarate level was demonstrated only in cerebrospinal fluid.

Carnitine↗
PubMed1992

Changes in tropomyosin during primary culture of embryonic myocardiocytes.

We chose the Hamburger and Hamilton's stage 29 (HH 29) to investigate the expression of tropomyosin in chick myocardiocytes during 14 days on culture. Throughout 14 days of cell culture, changes in cell morphology were accompanied by a redistribution of tropomyosin in different cell compartments. We used FACScan, SDS-PAGE and densitometric analysis to quantify total cell tropomyosin and concentrations of this protein in different cell fractions. Tropomyosin was found mostly in the cytoskeletal fraction than in the cytoplasmic. When we compared the densitometric values from SDS-PAGE of cells in different stages of development we found that in HH 19, tropomyosin was more abundant in the cytoplasmic than in the cytoskeletal fraction. By HH 29, the two fractions had become inverted, and in HH 39, tropomyosin was clearly more abundant in the cytoskeletal than in the cytoplasmic fraction. In the IFI analysis, tropomyosin was found to label the Stress fiber-like structures (SFL) in different patterns depending on the area of the cell which expressed this protein.

Animals↗
PubMed1992

Effect of fentanyl on cardiac automaticity and conduction: direct or mediated action?

The effects of fentanyl at a dose of 100 micrograms.kg-1 on cardiac automaticity, refractoriness and conduction have been studied in a model of heterotopic heart transplantation which combines a denervated heart (donor) and a non-denervated heart (recipient) in each of 20 dogs employed. Once the surgical procedure had been completed, cycle length, sinoatrial conduction time, antegrade and retrograde A-V node block points, cycle length at which 1:1 conduction ceases to exist and the antegrade effective refractory period of the A-V node and ventricles were measured. These parameters were determined in hearts both in the basal situation and 10 min after fentanyl injection. In the recipient organs, fentanyl produced statistically significant prolongation of cycle length, sinoatrial conduction time, antegrade block point and antegrade effective refractory periods of the A-V node and ventricles, with respect to the basal situation (P less than 0.01 for all these parameters); in 20% of cases, a complete A-V block was produced. In the donor hearts (denervated), prolongations of cycle length (P less than 0.01) and the antegrade block point (P less than 0.05), as compared with the basal situation, were recorded, but no other modifications were detected. To test whether these effects were due to the action of fentanyl, 10 animals were subsequently injected with naloxone, an agent which reverted the reported changes, although in the recipient organs, there persisted a slight prolongation of the cycle length with respect to basal measurements (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Quantification and distribution of troponin-T in cultures of chick embryo myocardiocytes.

We analyzed the distribution and labeling patterns of troponin-T, a protein involved in the regulation of striated muscle contraction, in myocardiocytes obtained from chick embryos in Hamburger and Hamilton's stage 25 and 39, and cultured for 8 days. Troponin-T expression was examined with indirect immunofluorescence, densitometry, fluorescence-activated cell sorting, electrophoresis and immunoblotting. The patterns of expression of troponin-T were compared with those of actin to determine possible correlations in different stages of chick embryo development and culture. Our findings show that in both stages of embryonic development, the cellular accumulation of troponin-T changed after 8 days of culture. Our results revealed a quantitative modification with time: after 4 days of culture there was a significant increase in this protein, followed by a slight additional increase after 8 days of culture. Flow cytometry findings confirmed these trends over time, showing a significant increase in positive cells after 4 days, followed by a smaller rise after 8 days of culture. In comparison with actin, this pattern was similar only in cells from Hamburger and Hamilton's stage 25 embryos.

Actins↗
PubMed1992

Detection of creatine kinase isoenzymes as tumoral markers of rhabdomyosarcoma.

We analyzed the expression profile of isoenzymatic fractions of creatine phosphokinase (EC 2.7.3.2) isotypes MM, MB and BB in three cell lines derived from embryonic rhabdomyosarcomas and a normal counterpart cell line. Electrophoretic data showed that the BB fraction was consistently expressed de novo, in contrast with its counterpart in normal tissue. The BB fraction may serve as new tumoral marker for the diagnosis of rhabdomyosarcoma. In addition, the appearance of macrocreatine kinase type-1 in this type of neoplasm may serve to reinforce the diagnosis when rhabdomyosarcoma is suspected.

Biomarkers, Tumor↗
PubMed1992

Are contraction and relaxation coupled in patients with and without congestive heart failure?

BACKGROUND: Although changes in contractility are often accompanied by changes in relaxation, a mathematical model of ventricular coupling has not been described. A model we examined suggests a hyperbolic relation between measurements of contraction and relaxation. We thus tested the hypothesis that relatively load-independent measurements of contractility (end-systolic elastance [Ees]) and relaxation (the slope of the tau-to-end-systolic pressure relation [R]) were coupled. METHODS AND RESULTS: To establish the validity of the model, an assessment of Ees and R was made in 30 subjects who underwent sequential digital ventriculography and micromanometer pressure measurements during atrial pacing (93 +/- 10 min-1) before and after graded doses of nitroprusside. To establish if a cyclic AMP (cAMP)-mediated intervention alters coupling, seven of the 30 subjects were studied before and after 3 months of beta-blockade. To determine if a non-cAMP-mediated intervention alters coupling, 12 other patients were studied before and after deslanoside. Nonlinear regression analysis for the initial 30 patients suggested a hyperbolic relation: (Ees) (R) = 1.05 (r = 0.79, p less than 0.001) with an inflection point near Ees = 1.02 mm Hg/ml. Thus, with normal or near-normal contractility, relaxation is normal and not load dependent (R is close to 0). With systolic dysfunction, relaxation becomes very afterload dependent and so must be normalized for load. After long-term beta-blockade in patients with severe left ventricular dysfunction, small improvements in contractility (elastance) occurred with larger changes in relaxation, but the curve describing the relation was not displaced. Acute administration of deslanoside resulted in a large increase in elastance and a smaller change in relaxation but did not alter coupling. However, the magnitude of the change in R was dependent on the predrug R value. CONCLUSIONS: These data suggest contraction and relaxation may be physiologically coupled with relaxation relatively preserved in early heart failure and more rapid deterioration in relaxation as elastance falls under 1.02 mm Hg/ml. Both beta-blockers (which may act through cAMP) and digitalis (which is cAMP independent) improve contraction and relaxation, but both mechanisms appear to maintain coupling. The hyperbolic relation between contraction and relaxation may have important implications regarding therapeutic response and selection of patients for clinical trials in heart failure.

Adrenergic beta-Antagonists↗
PubMed1992

Effectiveness of atenolol in the treatment of hypertension during pregnancy.

This study assessed the effectiveness of atenolol in the treatment of moderate and severe hypertension during pregnancy. Seventy patients (mean age, 30.3 +/- 6.0 years), 35.7% primiparous, were included. Three groups were formed according to Davey and MacGillivray's classification: 1) chronic hypertension without proteinuria (12 patients), 2) gestational hypertension without proteinuria (52 patients), and 3) preeclampsia (six patients). Treatment with atenolol was started when blood pressure was 150/100 mm Hg or higher after 48 hours' rest. The treatment lasted at least 1 week; follow-up was every 2 weeks up to week 36, and from then on, weekly up to delivery. If blood pressure exceeded 160/110 mm Hg and the fetus was not yet mature, a second drug was added. A significant decrease in blood pressure was observed in the three groups (group 1: 155.8 +/- 15.0/100.8 +/- 7.6 versus 135.0 +/- 12.9/85.0 +/- 6.7 mm Hg; group 2: 154.2 +/- 13.6/104.9 +/- 9.3 versus 129.6 +/- 10.2/83.7 +/- 9.1 mm Hg; group 3: 158.3 +/- 27.1/104.1 +/- 8.0 versus 129.1 +/- 6.6/87.5 +/- 6.1 mm Hg). The doses of atenolol were 62.5 +/- 23.0 mg/day in group 1, 70.0 +/- 30.0 mg/day in group 2, and 100.0 +/- 41.0 mg/day in group 3. There was no fetal mortality. No significant difference occurred in newborn body weights. Four babies from group 2 mothers had an Apgar score of less than 7 at 1 minute, but only one remained abnormal after 5 minutes. In the same group, three cases of respiratory distress were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Ictal head deviation: lateralizing significance of the pattern of head movement.

To resolve the controversy surrounding the lateralizing value of ictal head deviation, we analyzed head-turning movements in relation to the actions of the two divisions of the sternocleidomastoid muscle. In 12 (75%) of 16 patients with surgically confirmed lateralized seizure foci, the face rotated upward and contraversive to the hemisphere of seizure origin, consistent with activation of the ipsilateral sternomastoid muscle. One patient showed a sustained, downward ipsiversive head tilt consistent with the action of the ipsilateral cleidomastoid muscle, and three patients had a combined ipsiversive head tilt and contraversive face rotation. No patient exhibited ipsiversive upward face rotation or contraversive head tilting, as would be expected if the contralateral sternocleidomastoid were activated. Our findings indicate that hemispheric seizure foci activate one or both divisions of the ipsilateral sternocleidomastoid muscle. Accurate lateralization of the seizure focus is possible only when ictal head deviation is assessed in the context of the different actions of the sternomastoid and cleidomastoid muscle divisions.

Adolescent↗
PubMed1992

Late sudden cardiac death in the follow-up of patients having a heart valve prosthesis.

Eight hundred thirty-one patients with Björk-Shiley prostheses (341 aortic, 345 mitral, and 145 double) had a mean follow-up time of 68.2 months per patient. Of these, 24 (16% of all deaths) died suddenly: six of 42 with aortic valve replacement (14.3%), 12 of 56 with mitral valve replacement (21.4%), and six of 36 with double valve replacement (16.6%). This correlated with evidence of premature ventricular complexes detected in multiple routine 12-lead follow-up electrocardiograms (p less than 0.001 for simple aortic or mitral valve replacements and p less than 0.01 for combined aortic and mitral valve replacements). Premature ventricular complexes were significantly more frequent among those who died suddenly than among survivors and those who died of other causes (p less than 0.001 in both cases); there were no significant differences between the latter two groups. The actuarial risk of sudden death was significantly greater among those patients who had premature ventricular complexes than among those who did not have this disorder (p = 0.0002). We conclude that the presence of premature ventricular complexes, as an independent variable, was correlated with the risk of sudden death.

Adult↗