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Biomedical subjects

E Valle

Publications and source records attributed to E Valle.

At least 37 records · Page 2Linked to original sources
PubMed1993

Purification and characterization of aminopeptidase yspI from Schizosaccharomyces pombe.

Aminopeptidase yspI was purified to apparent homogeneity from the fission yeast Schizosaccharomyces pombe. The molecular mass of the native enzyme was estimated to be 184 kDa by gel filtration chromatography. A value of 92 kDa was calculated after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme is thus a dimer with two identical subunits. Optimum pH for cleavage of synthetic aminoacyl-4-nitroanilides is 7.0. Mercury ions, EDTA and chloroquine were found to be potent inhibitors of aminopeptidase yspI activity. Substrate specificity studies indicate that the purified enzyme cleaves L-lysine-4-nitroanilide with high efficiency.

Amino Acid Sequence↗
PubMed1993

The evolution of long interspersed repeated DNA (L1, LINE 1) as revealed by the analysis of an ancient rodent L1 DNA family.

All modern mammals contain a distinctive, highly repeated (> or = 50,000 members) family of long interspersed repeated DNA called the L1 (LINE 1) family. While the modern L1 families were derived from a common ancestor that predated the mammalian radiation approximately 80 million years ago, most of the members of these families were generated within the last 5 million years. However, recently we demonstrated that modern murine (Old World rats and mice) genomes share an older long interspersed repeated DNA family that we called Lx. Here we report our analysis of the DNA sequence of Lx family members and the relationship of this family to the modern L1 families in mouse and rat. The extent of DNA sequence divergence between Lx members indicates that the Lx amplification occurred about 12 million years ago, around the time of the murine radiation. Parsimony analysis revealed that Lx elements were ancestral to both the modern rat and mouse L1 families. However, we found that few if any of the evolutionary intermediates between the Lx and the modern L1 families were extensively amplified. Because the modern L1 families have evolved under selective pressure, the evolutionary intermediates must have been capable of replication. Therefore, replication-competent L1 elements can reside in genomes without undergoing extensive amplification. We discuss the bearing of our findings on the evolution of L1 DNA elements and the mammalian genome.

Animals↗
PubMed1992

Changes in central and peripheral nervous system function during hypoglycemia in man: an electro-physiological quantification.

We measured somatosensory evoked potentials (SEP) in normal subjects during acute (group A) and moderately prolonged (group B) hypoglycemia. We considered the following parameters: peripheral conduction velocity (wrist-Erb CV), conduction time (CT) between brachial plexus and the cervical cord (Erb-N13) and central CT from the cervical cord/lower brainstem lemniscal pathway to the cortex (N13-N20). In group A, the electrophysiological parameters did not change significantly throughout the study. In group B, mean N13-N20 CT increased from a basal values of 5.82 +/- 0.11 to 6.22 +/- 0.11 msec at 105 min (p less than 0.02) and 6.33 +/- 0.11 msec at 120 min (p less than 0.05). This study indicates that neither acute nor moderately prolonged hypoglycemia influence the peripheral nerve function in normal subjects and provides evidence that hypoglycemia as low as 2.4 mmol/L, lasting more than 60 min, can significantly increase the conduction time of central somatosensory pathways.

Adult↗
PubMed1992

[Brain death and prolonged fetal survival].

The Authors presents in detail a case of a 25-year-old primigravida that had fatal intracranial bleeding at the beginning of the 15th week of gestation, whose vital function are sustained for 49 days. Despite the insuccess to bring the pregnancy to a gestational period favorable to induce the delivery, they analyse the problems connected to the maternal maintenance and to the fetal growth.

Adult↗
PubMed1992

Angiographically occult brainstem vascular malformation: a longitudinal comparison of magnetic resonance imaging (MRI) and multimodal evoked potential (EP) recordings.

Over a period of several years, a patient with angiographically occult vascular malformation (AOVM) involving the brainstem was longitudinally studied by means of serial Magnetic Resonance Imaging (MRI) and multimodal Evoked Potential (EP) recordings (visual-VEP, brainstem auditory-BAEP, somatosensory--SEP--by stimulating median and peroneal nerves). MRI did contribute to an accurate definition of AOVM features. In particular, it was able to follow over time the AOVM size, and to discriminate between recent and old bleedings. Multimodal EP recordings displayed different pathological BAEP and peroneal SEP values, which documented a transient segmental brainstem involvement (related to the presence of hemorrhage), along with persistent and probably irreversible signs of diffuse brainstem dysfunction. Thus, MRI and EP assessment is useful in monitoring the clinical course of brainstem occult vascular malformations.

Brain Neoplasms↗
PubMed1991

Abnormalities of cognitive functions in IDDM revealed by P300 event-related potential analysis. Comparison with short-latency evoked potentials and psychometric tests.

The possible influence of diabetes on the higher mnestic and cognitive functions has been investigated. The P300 wave latency, an endogenous electrophysiological event, was explored and compared with the multimodal short-latency evoked potential (EP) recordings (visual [VEP], brainstem auditory [BAEP], and median and tibial nerve somatosensory EPs [mSEP and tSEP, respectively]) and psychometric test measures in 16 insulin-dependent diabetic (IDDM) patients, in 16 age- and (IDDM) sex-matched nondiabetic subjects, and in a large normal reference population. The age of subjects, the duration of IDDM, and the metabolic control of patients were taken into account. P300 values were significantly increased in IDDM versus matched control subjects (P less than 0.001), and 3 patients showed values above the reference value range. Abnormal VEP recordings were present in 1 of 16 patients, BAEP in 3 of 16, mSEP in 7 of 16, and tSEP in 6 of 16. Digit-span backward test results were significantly (P less than 0.02) modified in the diabetic cohort. There was no tendency for anomalies of P300, short-latency EPs, and psychometric test values to be contemporarily present, except in 1 patient. Electrophysiological or psychometric abnormalities were not clearly correlated with the duration of IDDM or the degree of short-term metabolic control. These findings give evidence that 1) higher cognitive functions may be affected in diabetes as documented by P300 analysis and short-term memory tests, 2) endogenous electrophysiological analysis highlights neuropsychological changes not detectable by psychometric tests, 3) an alteration of evoked potentials was present in half of the IDDM subjects studied, and 4) anomalies of the CNS are patchily distributed in diabetes.

Acoustic Stimulation↗
PubMed1990

Amplification of an ancestral mammalian L1 family of long interspersed repeated DNA occurred just before the murine radiation.

Each mammalian genus examined so far contains 50,000-100,000 members of an L1 (LINE 1) family of long interspersed repeated DNA elements. Current knowledge on the evolution of L1 families presents a paradox because, although L1 families have been in mammalian genomes since before the mammalian radiation approximately 80 million years ago, most members of the L1 families are only a few million years old. Accordingly it has been suggested either that the extensive amplification that characterizes present-day L1 families did not occur in the past or that old members were removed as new ones were generated. However, we show here that an ancestral rodent L1 family was extensively amplified approximately 10 million years ago and that the relics (approximately 60,000 copies) of this amplification have persisted in modern murine genomes (Old World rats and mice). This amplification occurred just before the divergence of modern murine genera from their common ancestor and identifies the murine node in the lineage of modern muroid rodents. Our results suggest that repeated amplification of L1 elements is a feature of the evolution of mammalian genomes and that ancestral amplification events could provide a useful tool for determining mammalian lineages.

Animals↗
PubMed1989

Separation of different types of afterpotentials following penicillin-induced paroxysmal depolarization shifts of neurons in the motor cortex of the rat.

Afterpotentials of penicillin-induced paroxysmal depolarization shifts (PDS) of neurones in the motor cortex of the rat in vivo were investigated with intracellular recordings. Following the PDS, 4 different types of afterpotentials were observed: fast afterhyperpolarizations with an average duration of 600 ms, fast afterdepolarizations with an average duration of 700 ms, slow afterhyperpolarizations with an average duration of 1.9 s and slow afterdepolarizations with an average duration of 1.8 s. The fast and slow afterpotentials could occur in various combinations with the exception of a fast afterhyperpolarization followed by a slow afterdepolarization. Neurones displaying afterdepolarizations had higher resting membrane potentials than those displaying afterhyperolarizations, i.e. the polarity of the afterpotential depended on membrane potential. Experiments with intracellular Cl- injection indicated that the fast but not the slow afterpotentials are associated with an increase in membrane Cl- conductance. The slow afterhyperpolarizations are suggested to result from a calcium-dependent or a synaptically generated potassium current.

Animals↗
PubMed1989

The mechanism of intracellular acidification induced by glucose in Saccharomyces cerevisiae.

Addition of glucose or fructose to cells of Saccharomyces cerevisiae adapted to grow in the absence of glucose induced an acidification of the intracellular medium. This acidification appeared to be due to the phosphorylation of the sugar since: (i) glucose analogues which are not efficiently phosphorylated did not induce internal acidification; (ii) glucose addition did not cause internal acidification in a mutant deficient in all the three sugar-phosphorylating enzymes; (iii) fructose did not affect the intracellular pH in a double mutant having only glucokinase activity; (iv) glucose was as effective as fructose in inducing the internal pH drop in a mutant deficient in phosphoglucose isomerase activity; and (v) in strains deficient in two of the three sugar-phosphorylating activities, there was a good correlation between the specific glucose- or fructose-phosphorylating activity of cell extracts and the sugar-induced internal acidification. In addition, in whole cells any of the three yeast sugar kinases were capable of mediating the internal acidification described. Glucose-induced internal acidification was observed even when yeast cells were suspended in growth medium and in cells suspended in buffer containing K+, which supports the possible signalling function of the glucose-induced internal acidification. Evaluation of internal pH by following fluorescence changes of fluorescein-loaded cells indicated that the change in intracellular pH occurred immediately after addition of sugar. The apparent Km for glucose in this process was 2 mM. Changes in both the internal and external pH were determined and it was found that the internal acidification induced by glucose was followed by a partial alkalinization coincident with the initiation of H+ efflux. This reversal of acidification could be due to the activity of the H+-ATPase, since it was inhibited by diethylstilboestrol. Coincidence between internal alkalinization and the H+ efflux was also observed after addition of ethanol.

Carbohydrates↗
PubMed1989

Multimodal evoked potentials in neuro-Behçet: a longitudinal study of two cases.

Two neuro-Behçet patients have been studied, over a period of several months, by means of peroneal and median somatosensory- (SEP), brainstem auditory- (BAEP), and visual- (VEP) evoked potentials. In both patients, peroneal SEP showed evidence of a pathological reduction in the central conduction velocity without a related deep sensation impairment, while VEP changes were consistent with the visual disorders. Conversely, BAEP and median SEP findings did not show disease-related abnormalities. The observed anomalies were detectable irrespective of the clinical phase of the disease. Thus, evoked potential assessment is useful in providing objective evidence for evaluating and monitoring CNS damage in neuro-Behçet's syndrome.

Adult↗
PubMed1989

A longitudinal study of multimodal evoked potentials in diabetes mellitus.

Abnormal findings in visual (VEP), brainstem auditory (BAEP) and somatosensory (SEP) evoked potentials at early stages of Type 1 and Type 2 diabetes have recently been reported by our group. Our aim here was to perform a longitudinal study in diabetic patients at an early stage of the disease using a combined evoked potential analysis in order to evaluate the variation of neurological abnormalities over time. Nine Type 1 and 12 Type 2 diabetic patients were examined and a second recording was carried out after a mean interval of 15.7 months +/- 6.2 SD. VEP, BAEP and SEP were measured in all patients. At the first recording electrophysiological abnormalities, present in both Type 1 and Type 2 diabetes were more evident when a multimodal evaluation was used (44.4% and 66.7% respectively). The follow-up study showed that overall neurological abnormalities persisted in all those patients who had previously presented pathological values. Whereas the number of patients with pathological values remained unmodified, a tendency to progression, namely the number of nervous levels with electrophysiological abnormalities, was observed. Thus, our study confirms the appearance of anatomofunctional disorders in the central nervous system in short-term diabetes, shows the persistence of neurological impairment in such patients and reveals a progressive segmental involvement at different nervous levels.

Acoustic Stimulation↗
PubMed1988

Transcriptional regulation of genes for plant-type ribulose-1,5-bisphosphate carboxylase/oxygenase in the photosynthetic bacterium, Chromatium vinosum.

The content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the photosynthetic purple sulfur bacterium, Chromatium vinosum, grown either heterotrophically or autotrophically, was highly correlated with the level of 2.0-kb mRNA encoding genes for both large (rbcL) and small (rbcS) subunits. This result indicates the transcriptional regulation of Rubisco biosynthesis in Chromatium cells. In the analysis of transcripts for rbcL and rbcS in Escherichia coli transformed by a plasmid bearing both genes downstream of E. coli tac promoter (pCKS1), the mRNAs were found to be the same sizes as those from Chromatium. However, we were unable to detect mRNA for Rubisco in E. coli harboring a plasmid containing the genes for Rubisco and its own promoter without any E. coli promoters (pCUB1). In the in vitro transcription experiment of pCKS1 and pCUB1 by E. coli RNA polymerase, it was observed that the enzyme could not recognize the Rubisco promoter. Therefore, we have purified RNA polymerase from Chromatium cells and developed a homologous in vitro transcription system. We have detected factor(s) for transcriptional regulation from either heterotrophically or autotrophically grown cells of Chromatium using the homologous in vitro transcription system.

Chromatium↗
PubMed1988

Early detection of neurological involvement in IDDM and NIDDM. Multimodal evoked potentials versus metabolic control.

Clarification of the extent and mechanisms of damage to the central nervous system in diabetes is a frontier of current neurological research. Our aim was to obtain ample electrophysiological documentation of possible neurological abnormalities in both insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetic patients with a short duration of disease and without overt complications, taking into account metabolic control. Group 1 comprised 11 IDDM patients, and group 2 included 14 NIDDM patients treated with diet alone; the duration of disease was less than 4 yr, and no concomitant clinical complications were present. Age- and sex-matched normal subjects formed groups 3 and 4. Pattern visual evoked potentials (VEP), brain stem auditory evoked potentials (BAEP), and somatosensory evoked potentials (SEP; after the stimulation of both median and tibial nerves) were recorded in all subjects, and metabolic control was evaluated in terms of glycemia and glycosylated hemoglobin. In group 1, significant abnormalities were found in the latency values of VEP, median SEP, and tibial SEP compared with control subjects. Similar latency abnormalities were shown in group 2 for VEP, median SEP, and tibial SEP values and for wave I latency of BAEP. Glycosylated hemoglobin values were correlated with BAEP and SEP abnormalities in many patients in both groups. Furthermore, in group 2, glycemic values correlated with SEP abnormalities. We therefore conclude that neurophysiological abnormalities are present at different levels in IDDM and NIDDM patients only a few years after clinical diagnosis and before the appearance of overt complications, and these abnormalities seem to be correlated with metabolic control status.

Adult↗
PubMed1987

Prognostic value of early somatosensory evoked potentials during carotid surgery: relationship with electroencephalogram, stump pressure and clinical outcome.

The authors have reported on the prognostic value of continuous monitoring of somatosensory evoked potentials (SEP) in a survey of 25 patients who underwent carotid surgery. SEP recordings were correlated with the EEG, stump pressure (SP) values and clinical outcome. A non-cephalic reference was used for SEP recordings to allow the analysis of both subcortical and cortical components. During surgery the conduction time between SEP peaks relating to the subcortical components remained stable or showed minimum variations in all patients. During carotid clamping, SEP variations were observed in 9 out of 25 cases (36%). The application of an intraluminal shunt was accompanied by the return to normal values in 7 out of 9 patients. In the remaining two cases SEP abnormalities continued post-operatively and were accompanied by new neurological deficits. EEG changes during carotid clamping were associated with SEP modifications in 6 out of 7 cases, although they were not always correlated. Results confirm that SEP recordings provide useful data concerning the function of the CNS in anaesthetized patients and that, being sensitive to CBF changes, SEP monitoring acts as an indicator of cerebral ischaemia.

Adult↗
PubMed1987

External K+ affects the internal acidification caused by the addition of glucose to yeast cells.

In glucose-grown cells of Saccharomyces cerevisiae, collected during the stationary phase of growth, the addition of K+ to the external medium reversed glucose-induced internal acidification in 2 min. However, in ethanol-grown cells external K+ did not reverse the effect of glucose even after 20 min. The presence or absence of external K+ did not alter the modification of trehalase and fructose-1,6-bisphosphatase induced by glucose. It is concluded that transient acidification may be sufficient to cause the associated transient increase in cAMP.

Benzoates↗
PubMed1987

Event-related potentials as a tool in the evaluation of cognitive functions in young subjects through the execution of a simple task.

Event-related potentials (ERPs) were recorded in 20 student volunteers. Three recordings were performed using aural stimuli of 4,000 (rare tones) and 250 Hz. In the target recording subjects were asked to count the rare tones. Endogenous and exogenous components of ERP recordings were analyzed. During the target recording N2 and P3 components were observed at 200 ms and approximately 300 ms, respectively, in addition to N1 (100 ms) and P2 (180 ms). The N2 and P3 waves are indicative of analysis at a higher cognitive level and have been termed the 'response set'. The P3 wave appeared to be stable in all subjects and may represent a useful electrophysiological method to explore mnemonic and cognitive functions in man.

Adolescent↗
PubMed1986

Trehalase activation in yeasts is mediated by an internal acidification.

It has been reported that the addition of glucose, uncouplers and nystatin to yeast cells grown in a sugarfree medium causes trehalase activation; it has been postulated that this activation might be mediated by the depolarization of the plasma membrane. In this article the values of membrane potential and pH gradient across the plasma membrane of Saccharomyces cerevisiae have been determined under the same conditions as those in which trehalase is activated. Membrane potential was evaluated from the distribution of triphenylmethylphosphonium, the pH gradient from the distribution of benzoic acid across the plasma membrane. When the effect of several agents on the two components of the electrochemical proton gradient across the plasma membrane of ethanol-grown yeast cells were studied, under trehalase activation conditions, the following observations were made. (a) The addition of glucose activated trehalase and caused internal acidification of the cells, but had practically no effect on the membrane potential. (b) The addition of 200 mM KCl depolarized the cell membrane but did not affect the internal pH, nor trehalase activity. (c) Although carbonyl cyanide m-chlorophenylhydrazone depolarized the cells at external pH 6.0 and 7.0, it only activated trehalase at an external pH 6.0, leading to the acidification of the internal medium at this pH. (d) Nystatin caused an increase in the triphenylmethylphosphonium accumulation at external pH 6.0 and 7.0, but only activated trehalase at external pH 6.0, causing acidification of the cell interior at this pH. (e) Activation of trehalase was also observed when the internal acidification was caused by addition of a weak acid such as acetate. It is concluded that trehalase activation is mediated by an intracellular acidification and is independent of the membrane potential.

Culture Media↗