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Biomedical subjects

A Reyes

Publications and source records attributed to A Reyes.

At least 19 recordsLinked to original sources
PubMed1995

Effects of verapamil on the release of different neurotransmitters.

The effect of verapamil on resting and depolarization-induced monoamine release was investigated in rat hippocampal synaptosomes prelabeled with [3H]-5-hydroxytryptamine (HT) or [3H]-norepinephrine (NE) and rat striatal synaptosomes prelabeled with [3H]-dopamine (DA). Verapamil (50 microM) completely abolishes high K(+)-induced [3H]-NE release, but paradoxically facilitates high K(+)-induced [3H]-5-HT and [3H]-DA release. All these high K(+)-evoked responses were Ca2+ dependent. Verapamil does not modify [3H]-NE baseline release, but increases dose dependently [3H]-5-HT and [3H]-DA baseline release. Verapamil (10 microM, for 5 min) increases endogenous DA release (70%) and endogenous 5-HT release (40%) independently on the presence of external Ca2+. The total amount of these monoamines (released plus retained by the preparation) and their metabolites (DOPAC and 5-HIAA) was similar in control and verapamil-treated synaptosomes. Verapamil displaces [3H]-spiroperidol specific binding (Ki of 2.4 x 10(-6) M) and [3H]-SCH-23390 specific binding (Ki of 9 x 10(-6) M) from striatal synaptosomal membranes, and [3H]-5-HT specific binding (Ki of 3 x 10(-5) M) from hippocampal synaptosomal membranes. It is concluded that in addition to the Ca2+ antagonistic properties of verapamil on the Ca(2+)-dependent, depolarization-induced release of some neurotransmitters [gamma aminobutyric acid (GABA and NE)], another mechanism probably mediated by presynaptic receptors underlies the effects of verapamil on DA and 5-HT release from discrete brain regions.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

EEG activation patterns during the performance of tasks involving different components of mental calculation.

In this study we demonstrate the existence of different patterns of EEG activation during the performance of 4 different tasks involving different components of mental calculation in normal subjects. The EEG was recorded in all monopolar leads of the 10/20 system using linked ear lobes as reference. Absolute and relative power were calculated in the delta (1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz) and beta (12.5-19 Hz) bands. The tasks were presented randomly and the EEG segments preceding presentation of the stimulus were considered as the rest corresponding to the task requested by the stimulus. Tasks were of 4 different types, involving number comprehension, recognition of mathematical symbols, the calculation process and the spatial component. ANOVAs between the rest periods showed no differences in any band. Neither did ANOVAs between tasks. However, other variables (task minus rest), which were calculated as the differences in power between task and rest respectively, showed significant differences between tasks in the delta and beta bands in the frontal lobes. In addition, new variables were calculated as the difference between tasks, since many factors were common across several tasks. These variables correspond to the EEG change due to a specific component of mental calculation. Significant differences were obtained in delta and theta bands in right posterior areas and in the beta band in frontal areas. We concluded that the EEG differences observed during different components of mental calculation suggest the participation of different networks.

Adult↗
PubMed1995

Comparison of Z and multivariate statistical brain electromagnetic maps for the localization of brain lesions.

Conventional Z maps provide probability statements about the deviation of observed values from the norm. Galán et al. (1994) introduced Simultaneous Significance Probability Scales to detect abnormalities over the whole map, making use of the information provided by the topographic structure of dependencies. They also described multivariate brain electromagnetic (MBE) maps for compact presentation of complex spatio-temporal information. In this paper, using the distance-based localization receiver operating characteristic curves (DL-ROC curves), we compare the localization provided by computed tomography with that provided by Z and MBE maps in 61 patients with brain lesions. Maps were calculated for absolute power and relative power in delta, theta, alpha and beta bands for voltage and current source densities (CSD). In each patient, all maps were compared and the map with the highest value of the area of the DL-ROC curve was considered to be the "best map." Z maps of CSD were the "best maps" in 24 patients. In the voltage montage, we observed that multivariate maps add some information not contained in the Z maps. However, for CSD, Z maps were more accurate than multivariate maps. A very consistent finding was the observation that lesions were better detected by maps analyzing the delta band, while edema was better represented by maps in the theta range.

Brain Damage, Chronic↗
PubMed1995

Pelvic lymphadenectomy can be omitted in selected patients with carcinoma of the prostate: development of a system of patient selection.

OBJECTIVES: The prevalence of pelvic lymph node metastases in men with clinically localized prostate cancer has decreased dramatically over the past decade, possibly due to efforts at early detection. With a significantly lower incidence of pelvic node involvement, it may be possible to identify a segment of patients for whom pelvic lymph node dissection (PLND) may be omitted. This study was conducted to develop a method to select patients for whom PLND could be omitted. METHODS: We analyzed serum prostate-specific antigen (PSA), clinical stage, biopsy Gleason score, and final pathologic stage in 481 men with clinically localized prostate cancer. These variables were compared to the risk of positive pelvic lymph nodes. RESULTS: Logistic regression analysis determined that combining all three variables provided the best determination of final pathologic stage. A series of probability curves have been created to estimate the risk of positive lymph nodes in a given patient. Based on the distribution of patients in this study and using these probability functions, PLND could be avoided in up to 50% of patients with localized prostate cancer diagnosed by contemporary methods. CONCLUSIONS: In properly selected patients, pelvic lymphadenectomy can be omitted in the staging and treatment of localized prostate cancer.

Humans↗
PubMed1995

Angiotensin II receptor antagonist ameliorates renal tubulointerstitial fibrosis caused by unilateral ureteral obstruction.

Unilateral ureteral obstruction (UUO) results in tubulointerstitial fibrosis of the obstructed kidney (OBK). In this study we report that a specific angiotensin II (Ang II) receptor antagonists, SC-51316, ameliorates the expansion of the renal cortical interstitium in the OBK of the rat at five days of UUO. This is similar to the effect of an angiotensin converting enzyme (ACE) inhibitor, enalapril. SC-51316 (20 mg/liter in the drinking water) or enalapril (200 mg/liter in the drinking water) was administered beginning 24 hours before UUO and continued through five days after UUO. The relative volume of the tubulointerstitium (Vv) was measured by a point-counting method, and monocyte/macrophage infiltration, alpha smooth muscle actin (alpha SMA), proliferating cell nuclear antigen (PCNA), and collagen type IV (collagen IV) protein deposition were examined histologically using specific antibodies. We also examined the mRNA levels of transforming growth factor beta 1 (TGF-beta 1) and collagen IV by reverse transcription polymerase chain reaction. In untreated rats with UUO, Vv was remarkably expanded; collagen IV and alpha SMA protein deposition in the interstitium and PCNA labeling of nuclei were increased. These changes were significantly ameliorated by administration of an ACE inhibitor or an Ang II receptor antagonist. A monocyte/macrophage infiltration was evident in the OBK of untreated or Ang II receptor antagonist treated rats but was greatly reduced in the OBK of rats given enalapril. Increased expression of TGF-beta 1 mRNA and collagen IV mRNA was blunted (40 to 75%) by the administration of Ang II receptor antagonist or enalapril. The Ang II receptor antagonist or the ACE inhibitor did not affect the contralateral kidney of rats with UUO or the control kidney of normal rats. This study indicates that the renin-angiotensin system has a major role in the pathogenesis of the tubulointerstitial fibrosis of obstructive nephropathy. The tubulointerstitial fibrosis of obstructive nephropathy is most likely mediated by an increased level of Ang II in renal tissue.

Actins↗
PubMed1995

False-positive interpretations of carcinoma in exfoliative respiratory cytology. Report of two cases and a review of underlying disorders.

The false-positive interpretation of malignancy is a potential pitfall of exfoliative respiratory tract cytopathology. However, the underlying causes of this problem are still relatively under-recognized. The authors herein present two additional examples in which bronchial brushing and washing specimens were misinterpreted as showing carcinoma of the lung. The first case concerned a patient with a granulomatous mass that simulated a malignancy on chest radiographs and was the apparent cause of atypical bronchial squamous metaplasia (ABSM). Exfoliated cells from the latter process were thought to explain the false-positive cytologic result in that instance. In the second case, a large-cell angiocentric T-cell lymphoma replaced the lower lobe of the left lung. It was likewise associated with ABSM as the cause of a mistaken diagnosis of carcinoma in exfoliative respiratory cytology specimens, representing the first instance of such an association of which the authors are aware. Repeated evaluation of all bronchial cytology samples by several experienced pathologists yielded no reliable observations that might have been used to avoid an erroneous interpretation in either case. A review is provided of the spectrum of underlying conditions that may be associated with false-positive respiratory cytology results.

Adult↗
PubMed1993

Use of a yeast expression system for the isolation and analysis of drug-resistant mutants of a mammalian phosphodiesterase.

Saccharomyces cerevisiae strain PP5 has a phosphodiesterase (PDE) deficiency that results in heat-shock sensitivity due to the intracellular accumulation of cAMP. This strain also carries the cam mutation, which confers permeability to cAMP and, as shown here, to other compounds. Expression of rat type IV PDE in these cells caused them to revert to heat-shock resistance. Treatment of the transformed PP5 cells with rolipram, an antidepressant in humans and a potent inhibitor of type IV PDEs, reinstated sensitivity to heat shock. The biochemical properties of deletion mutants of this PDE were determined, and an active enzyme of minimum length was created. Reversion to heat-shock resistance was then used to select for PDE mutants refractory to the inhibitory effects of rolipram. Four mutants (A1, A2, A3, and A5) were isolated. Each carries a single point mutation; two have mutations in the same codon. Each mutant showed distinct properties, based on analysis of their substrate kinetics and IC50 values for a variety of inhibitors. Mutant A5 had a reduced activity for substrate, mutants A1 and A3 showed no change in substrate kinetics, and mutant A2 displayed an increase in activity. For most mutants, the drug resistance was confined to the class of drug used in the selection. This study shows that it is possible to recreate in yeast cells the susceptibility of mammalian enzymes to pharmacological agents. Our study also demonstrates that such systems can be used to select rare mutants useful in the analysis of drug-protein interactions.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Correlation between computed tomography and voltage and current source density spectral EEG parameters in patients with brain lesions.

In a group of patients with space-occupying brain lesions, CT measurements were correlated with absolute power (AP) and relative power (RP) of the delta, theta, alpha and beta EEG bands, calculated from the raw EEG potentials (EEGp) and from the Laplacian estimates also called "current source densities" (CSD). Rank correlations were calculated between the number of abnormal values in each band and the following CT measures: volume of the lesion and of the edema, density of the edema, percentage of ventricular collapse and midline shift. Abnormal spectral values are those which are significantly higher than the norm for the same age, in the delta and theta bands, and significantly lower in the alpha and beta bands. Spectral parameters obtained from the CSD showed higher correlations with CT measures than those calculated from the EEGp. In the Laplacian, all CT measures had a significant correlation with delta AP. Theta AP was significantly correlated with the volume and density of the edema, as well as with midline shift. Significant correlations were also observed with delta and alpha RP. However, changes in RP were considered to be a consequence of the increase in delta AP. Canonical correlation analyses between AP and RP calculated from EEGp or CSD and the first 3 CT measures showed that the volume of the lesion was only correlated with delta AP and RP. The volume and density of the edema showed a significant correlation with delta, theta and alpha AP calculated from EEGp and only with theta and alpha AP in the Laplacian. Since the EEGp tends to produce a more extensive and diffuse picture of abnormality, whereas the Laplacian acts as a spatial filter emphasizing local sources over distant sources, we concluded that edema is related not to delta activity, but to the theta and alpha power.

Adolescent↗
PubMed1992

Maturation of the coherence of EEG activity in normal and learning-disabled children.

The age effect on coherence has been studied in control (98) and learning-disabled (LD, 54) school-aged children (from 6.0 to 16.8 years old). The EEG recordings were made at rest in 15 leads, and 105 pairwise combinations for coherence were calculated (each lead was compared with all the rest) for delta, theta, alpha, beta and total frequency bands. A significant increase of coherence with age was found in both groups, with a different pattern of maturation. In the control group, a significant increase with age was found in the coherences between posterior regions and vertex (Cz). A significant decrease with age in the coherence between frontal areas was observed, especially in the theta band. The LD group showed a different pattern: no significant relation with age was found in the coherence between any lead and vertex. A high effect of age on coherence between temporal regions was observed with a predominance of the left side in comparison with the contralateral and the ipsilateral. No decrease in frontal coherence was found: in the same region where the control group showed negative values with age, the LD groups had no age effect. The results obtained are discussed as differences in brain organization, in myelogenesis and synaptogenesis and an explanation of the etiology of LD is proposed.

Adolescent↗
PubMed1992

Effect of intravenously administered aminophylline on ventilation/perfusion inequality during recovery from exacerbations of chronic obstructive pulmonary disease.

To investigate the effect of intravenously administered aminophylline and 100% O2 breathing on ventilation-perfusion (VA/Q) inequality, nine patients recovering from an acute exacerbation of chronic obstructive pulmonary disease (COPD) were studied. The design was double-blind, crossover, placebo-controlled for aminophylline, and a single-blind, controlled protocol for O2, patients being studied on two successive days. Forced spirometry, systemic hemodynamics, arterial pH, and blood gases were measured together with the VA/Q distribution using the multiple inert gas elimination technique, and then a loading dose of aminophylline (6 mg/kg body weight) or placebo was given over 20 min followed by a maintenance infusion at 0.9 mg/kg/h that was kept constant for the rest of the study. After 20 min of infusion the patient breathed either air or 100% O2 for another 30 min, and the measurements were repeated. Thereafter the inspired gas was shifted to the other FlO2 for 30 min, and a final set of measurements was made. The following day the procedure was repeated using the alternate drug. Aminophylline alone increased FVC and FEV1, but it produced no change in the group in ventilation, hemodynamics, blood gases, or the VA/Q distribution, although individual patients who had low VA/Q areas at baseline showed increases in these areas and worsening of log SD Q. Oxygen alone reduced cardiac output (QT) and caused modest further dispersion of the VA/Q distribution when compared with air breathing during placebo infusion (log SD Q 1.03 +/- 0.27 increased to 1.26 +/- 0.35, p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Visual evoked potentials, attention and mnemonic abilities in children.

We analyzed the correlation between attention and mnemonic processes and different visual evoked potential (VEP) parameters. A group of 34 children between 9 and 13 years old was studied. VEPs were recorded in C3, C4, P3, P4, O1, O2, T5 and T6 with linked ear lobes as reference. Two different types of stimuli were used: flash and checkerboard pattern. The power of VEPs was calculated as the sum of the square amplitude values for different time epochs. Correlation coefficients between left and right homologous VEPs were also computed. A visual selective attention task divided into 5 items of increasing difficulty and the Sternberg paradigm were applied. The performance was automatically evaluated by the computer, giving the number of correct responses (NCR) and other measures of performance. Correlation coefficients between VEP parameters and the scores obtained in the performance of tasks were calculated. It was observed that power in P3, P4, T5, and T6 and the correlation coefficients between central, parietal and temporal VEPs were positively correlated with NCR of both tasks. However, power in O1 and O2 was negatively correlated with NCR.

Adolescent↗
PubMed1992

Capacitation and acrosome reaction of human spermatozoa. An assisted reproduction approach.

In this paper we briefly review the recent advances in the understanding of human sperm capacitation, fundamentally focused to give help to the practitioners involved in assisted reproduction. Sperm capacitation has been the subject of study for many years in several animal species, but during the past ten years the advances in assisted reproduction procedures have made important contributions in the progress of this topic in relation to human spermatozoa. In this manuscript we analyze the metabolic, membranal and physiological changes observed in these cells during in vitro capacitation and their relationships with the female genital tract secretions, as well as with the homologous oocytes.

Acrosome↗
PubMed1992

The interaction of monovalent cations with fructose 1,6-bisphosphatase modified by N-ethylmaleimide and its relation with AMP inhibition.

The relationship between derivatization of reactive cysteine residues with N-ethylmaleimide and a partial desensitization of fructose 1,6-bisphosphatase to AMP inhibition was studied. AMP desensitization of the enzyme was found to be dependent on the activity assay conditions used. When the assay was performed in the presence of high levels of monovalent cations (150 mM), the AMP affinity of the enzyme decreased with the chemical modification. The apparent loss of sensitivity toward AMP was accompanied by an uptake of 1 mole of N-ethylmaleimide/mole of enzyme subunit. However, the modified enzyme did not show alteration in AMP inhibition in the absence of K+. Evidence was obtained that K+ induces a conformational change on the enzyme derivative, which hinders AMP interaction with the protein. The results point to the importance of selecting suitable conditions for the study of the regulatory properties in allosteric enzymes.

Adenosine Monophosphate↗
PubMed1991

Assessment of luteal function after surgical tubal sterilization.

To evaluate ovarian luteal function after tubal occlusion, a group of women who underwent Pomeroy sterilization were studied. A prospective group I (n = 16) were followed for one year and scheduled for blood sampling every other day during their luteal phase before surgical procedure and at 3 and 12 months thereafter. Group II (n = 15) included women who were studied during their luteal phase at 1 or 5 years post-surgery. Mid-luteal progesterone and estradiol serum levels were calculated by estimating the average of at least 3 values of serum samples obtained in days 20-25 of a menstrual cycle. The data suggest that no major changes occur in ovarian function after surgical tubal occlusion, as assessed by the mid-luteal hormone serum levels, and underscore the safety of this procedure.

Adult↗
PubMed1991

Effects of transport and racing on ionic changes in thoroughbred race horses.

1. Packed cell volume (PCV), blood glucose, total plasma proteins (TPP) and plasma electrolytes, osmolality, cortisol and aldosterone alterations produced by transport and racing, were investigated in race horses. 2. Plasma cortisol, sodium and blood glucose, found after transport, were higher, while aldosterone was lower than control levels. 3. After racing, PCV, blood glucose, TPP and plasma cortisol, sodium and osmolality were higher than control, while chloride diminished and aldosterone returned to control values. 4. These results demonstrate that transport and racing are different kinds of stressors, suggesting that the sympathetic system and hypophysis-suprarenal cortex axis have a dissimilar contribution to the physiological response.

Aldosterone↗
PubMed1991

Acid-base derangements during sorbent regenerative hemodialysis in mechanically ventilated patients.

OBJECTIVE: To assess acid-base derangements during sorbent regenerative hemodialysis in mechanically ventilated patients. DESIGN: Consecutive case series; prospective study. SETTING: An ICU in a university hospital. PATIENTS: Seven patients undergoing hemodialysis for acute renal failure who required mechanical ventilation for acute respiratory failure. INTERVENTIONS: Pulmonary and systemic hemodynamics, pH, and gas tensions in dialysate, arterial and mixed venous blood, and blood entering and leaving the dialyzer, were measured before, during, and after hemodialysis. MEASUREMENTS AND MAIN RESULTS: During the first 2 hrs of hemodialysis, dialysate pH decreased from 6.91 +/- 0.14 to 6.06 +/- 0.37 and PCO2 increased to 437 +/- 111 torr (58.2 +/- 14.8 kPa). Simultaneously, the patients lost bicarbonate into the bath. As a result, pHa decreased from 7.38 +/- 0.02 to 7.31 +/- 0.02. At the end of dialysis, pHa returned to normal. CONCLUSION: Sorbent hemodialysis in mechanically ventilated patients is accompanied by acidosis that may contribute to hemodynamic instability.

Acidosis↗