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Biomedical subjects

A Palma

Publications and source records attributed to A Palma.

At least 55 records · Page 3Linked to original sources
PubMed1994

Effects of diverse omega-conopeptides on the in vivo release of glutamic and gamma-aminobutyric acids.

omega-Conopeptides are antagonists of subtypes of neuronal calcium channels. Two omega-conopeptides, SVIB and MVIIC, have recently been identified which have a novel specificity for these ionophores. We have tested the actions these peptides, as well as the more selective MVIIA, on the release of glutamic acid and gamma-aminobutyric acid (GABA) in the hippocampus in vivo. For the assay of peptide effects on release, we used microdialysis to deliver multiple pulses of elevated potassium to the brain extracellular fluid. Peptide effects were quantitated from the decrement of the release with peptide perfused through the probes, in comparison to that in control experiments. Synthetic MVIIC caused a 40-50% decrement in the release of both glutamate and GABA at a probe concentration of about 200 nM. Synthetic SVI-B caused a 50% block at about 20-40 microM, while about 200 microM of MVIIA was required for 50% block. Chromatographic experiments showed that differences in potency between MVIIC and MVIIA were not explained by differential degradation. Blockade of release was also observed in the thalamus. MVIIC provides a tool for investigating the role of calcium mediated release of glutamate and GABA in physiological and pathological processes in the mammalian brain in vivo.

Amino Acid Sequence↗
PubMed1994

[The concept of stress and the role of hypothalamic and extra-hypothalamic corticotropin-releasing factor (CRF) in the integration of the neuroendocrine and immune responses. Clinical and experimental aspects].

Several evidences suggest the existence of a bidirectional link between the immune and neuroendocrine systems. This relationship explains how a "non cognitive" stimulus (as antigen) can activate the neuroendocrine axis through the inflammatory substances (cytokines) in the same manner as a stress response. A disregulation of this response can determine the basis for a pathological situation. The key-peptide of the stress response is hypothalamic CRF, though also extra-hypothalamic sources, such as the cells of the immune system, are present and could play an important role in the peripheral regulation of stress response.

Adrenocorticotropic Hormone↗
PubMed1993

Prediction of single and multivessel coronary disease in patients after myocardial infarction according to quantitative ultrasound wall-motion analysis.

Regional changes in left ventricular size and function characterize left ventricular remodeling and start very early after myocardial infarction. We studied the diagnostic value of left ventricular dyssynergic patterns in predicting the presence of single versus multivessel disease (MVD). Fifty-three consecutive patients with acute myocardial infarction were studied by ECG, two-dimensional echocardiography, and angiography during the same hospitalization. Thirty-eight normal subjects served as the control group. According to the angiographic findings, the patients were categorized as having: single-vessel disease (SVD, n = 17), two-vessel disease (n = 17), and three-vessel disease (n = 19). Two-dimensional echocardiography was performed and optimal frames from five cardiac cycles were digitized and quantitatively analyzed off-line with a microcomputer. Echocardiographic wall-motion analysis demonstrated a depressed regional segmental thickening in the infarcted area that was characteristic for each echocardiographic view. In the segments remote from the infarcted area, however, the three patient groups displayed differences in function that ranged from hyperkinetic in patients with SVD to hypokinetic in patients with MVD. Patients with SVD constantly displayed a wider range of segmental thickening when compared with patients with MVD and the control group (p < 0.05). In conclusion, patients with SVD after myocardial infarction display compensatory hyperkinesis of remote segments, which is attenuated in patients with MVD. The present study introduces new parameters of segmental myocardial function that might be helpful in predicting SVD and MVD in patients after myocardial infarction.

Adult↗
PubMed1993

Diagnostic value of left ventricular dyssynergy patterns in ischemic and non-ischemic cardiomyopathy.

BACKGROUND: The distinction between ischemic and non-ischemic cardiomyopathy has important clinical implications. The objective of the present study was to investigate whether left ventricular dyssynergy patterns, detected by quantitative analysis of ultrasound images, differed in these two pathological processes. METHODS: Fifty-six consecutive patients with congestive heart failure (New York Heart Association functional class II-IV) secondary to depressed left ventricular systolic function (ejection fraction < or = 35% during diagnostic cardiac catheterization) were studied. Twenty patients were eliminated from further analysis because they met one or more exclusion criteria. The remaining 36 were divided into two groups based on the presence (ischemic cardiomyopathy) or absence (non-ischemic cardiomyopathy) of a > or = 50% narrowing of the luminal diameter in one or more coronary arteries. In all patients, a standard two-dimensional echocardiographic study was obtained. Apical four- and two-chamber views with optimal endocardial and epicardial resolution were selected for analysis, and the left ventricular contour was divided into six segments of interest. Optimal endocardial and epicardial resolution were defined according to an original internal quality score system. For each of the six segments of interest, regional ejection fraction and regional segmental thickening were estimated. Data analysis was then performed on the average values of regional ejection fraction and regional segmental thickening obtained across the entire left ventricular contour. In each patient, regional ejection fraction range and regional segmental thickening range were calculated by subtracting the minimum from the maximum value of regional ejection fraction and regional segmental thickening obtained across a left ventricular contour. RESULTS: Regional ejection fraction and regional segmental thickening did not differ significantly between the two groups. However, regional ejection fraction range and regional segmental thickening range were significantly greater in patients with ischemic cardiomyopathy than in patients with non-ischemic cardiomyopathy [28.32 +/- 11.17 versus 14.74 +/- 7.73% (P < 0.001) and 47.80 +/- 16.00 versus 24.64 +/- 9.39% (P < 0.001), respectively]. Overlap of findings was observed in 20% of the values for regional ejection fraction range but in only 14% of those for regional segmental thickening range. CONCLUSIONS: Patients with ischemic cardiomyopathy demonstrate a non-uniform dyssynergy that can be differentiated from a more uniform hypokinesis observed in those with non-ischemic cardiomyopathy. Computerized ultrasonic image analysis can distinguish characteristic dyssynergic patterns in patients with cardiomyopathy. Measurements of segmental wall thickening provide a more accurate assessment of regional function.

Adult↗
PubMed1991

Effects of pH on acetylcholine receptor function.

We have examined the effects of changing extracellular pH on the function of nicotinic acetylcholine receptors from Torpedo californica using ion flux and electrophysiological methods. Agonist-induced cation efflux from vesicles containing purified, reconstituted receptors showed a monotonic dependence on external hydrogen ion concentration with maximal fluxes at alkaline pH and no agonist-induced efflux at pH's less than approximately 5. A similar pH dependence was measured for the peak agonist-activated membrane currents measured in microelectrode voltage-clamped Xenopus oocytes induced to express Torpedo receptor through mRNA injection. Half-maximal inhibition occurred at a similar pH in both systems, in the range of pH 6.5-7.0. Single-channel currents from Torpedo ACh receptors measured in patch-clamp recordings were also reduced in amplitude at acid pH with an apparent pKa for block of less than 5. Measurements of channel kinetics had a more complicated dependence on pH. The mean channel open time determined from patch-clamp measurements was maximal at neutral pH and decreased at both acid and alkaline pH's. Thus, both channel permeability properties and channel gating properties are affected by the extracellular pH.

Animals↗
PubMed1991

[Proposal for the teaching and application of informatics at medical schools].

Informatics is the discipline that process efficiently all the necessary data to obtain information. The data acquisition, processing and interpretation is realized through traditional as well as automated means. Medical Informatics is the union of all methods of informatics in medicine including the preparation of medical data required for the application of these methods. Due to the need to keep up with the increasing amount of data that modern medicine is receiving and efficiently process it to obtain meaningful information, we propose the creation of a department of Medical Informatics in our Medical School to: 1) Teach the basic principles of medical informatics to undergraduate and graduate students, including lectures in: Information technics, medical terminology, medical linguistics, international classification of diseases, Hospital informations Systems, practical application of computing in medicine as Oncocyn, Mycin, etc., as well as external data bases. 2) Help the health sciences personnel to obtain and transfer medical information through the National and International Electronic Networks of Medical Information.

Education, Medical↗
PubMed1990

Functional role of the cysteine 451 thiol group in the M4 helix of the gamma subunit of Torpedo californica acetylcholine receptor.

Previous chemical modification studies of the acetylcholine receptor [Yee, A.S., Corey, D.E., & McNamee, M.G. (1986) Biochemistry 25, 2110-2119] were extended by using fluorescent N-pyrenylmaleimide to alkylate purified Torpedo californica nicotinic acetylcholine receptor (AChR). Peptide sequencing of the tryptic fragments of the labeled AChR gamma subunit identified cysteines 416, 420, and 451 as the modified residues. The functional role of Cys-451 in the M4 transmembrane domain of the AChR gamma subunit was further investigated by studying the functional consequences of the site-specific mutation of this cysteine to either serine or tryptophan by using AChR mRNAs injected into Xenopus laevis oocytes. Both mutants displayed about 50% reduction in the normalized channel activity of the receptor measured as the ACh-induced conductance per femtomole of surface alpha-bungarotoxin binding sites. However, the mutations did not change other AChR functional properties such as agonist binding ability, the slow phase of desensitization, and blockade by competitive and noncompetitive antagonists. The significant reduction in AChR ion channel activity associated with the above point mutations, especially the simple change of the -SH group on Cys-451 to the -OH group, suggests that this thiol group in the M4 helix of gamma subunit may play an important role in AChR ion channel function. Previous site-directed mutations of the Cys-416 and -420 residues showed a decreased response when both of these residues were changed to phenylalanine, but not when they were changed to serine [Pradier, L., Yee, A.S., & McNamee, M.G. (1989) Biochemistry 28, 6562-6571].(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Regulation of nicotinic acetylcholine receptor function by adenine nucleotides.

1. Nicotinic acetylcholine receptors (nAChR)4 from BC3H1 cells (which express a skeletal muscle-type receptor) and from Torpedo californica electric organ were expressed in Xenopus laevis oocytes and studied with a voltage-clamp technique. 2. We found that bath application of ATP in the micromolar to millimolar range increased the ACh-elicited current in both muscle and electrocyte receptors. The effect of ATP increased with successive applications. This "use-dependent" increase in potentiation was Ca2+ dependent, while the potentiation itself was not. 3. Four other nucleotides were tested on muscle nAChR: ADP, AMP, adenosine, and GTP. Of these, only ADP was a potentiator, but its effect was not use dependent. Neither ATP nor ADP affected the resting potential of the oocyte membrane. 4. ADP potentiated the response to suberyldicholine and nicotine, as well as ACh. 5. Finally, ADP reversed the phencyclidine-induced block of ACh currents in oocytes expressing muscle nAChR.

Acetylcholine↗
PubMed1990

[Tachyarrhythmia caused by paroxysmal atrial fibrillation following heat stress].

The Authors describe a case of paroxysmal atrial fibrillation, in young patients with apparently healthy hearts due to heat stress and expound the pathogenetic mechanisms. They point out the importance of a complete cardiologic examination: sometimes paroxysmal atrial fibrillation is an initial symptom of silent cardiovascular disease.

Adult↗