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Biomedical subjects

M Vázquez

Publications and source records attributed to M Vázquez.

At least 19 recordsLinked to original sources
PubMed1995

Cortical potentials during gap and non-gap paradigms using manual responses in humans.

An experiment was conducted on naive human subjects to measure the time benefits on finger reaction times produced by the offset of a central fixation point 200 ms before the appearance of a target stimulus in the periphery. Subjects produced a shift advancement of manual reaction times. Simultaneously, the event-related potentials were recorded. The gap paradigm induced offset visual evoked potentials and a frontal negativity, it also induced a higher P300 than the non-gap condition. The results suggest that the gap promotes the speeding of the response by a cortical priming.

Adult↗
PubMed1995

Nevus sebaceus: clinical outcome and considerations for prophylactic excision.

BACKGROUND AND OBJECTIVE: Nevus sebaceus is a hamartoma of the skin with the potential to develop benign and malignant neoplasms. Prophylactic surgical excision has been advocated, usually before puberty, to prevent their occurrence; however, it is the clinical impression of the authors that the development of cutaneous neoplasms is infrequent and, if they develop, they are usually benign and nonaggressive. Our objective was to investigate the clinical outcome and histopathologic findings of every single nevus sebaceus that had been excised in our institution in a five-year period. METHODS: Two hundred and twenty-five consecutive cases, coded as nevus sebaceus corresponding to 175 patients were submitted to our institution between September 1987 and May 1992, and were identified among a total of 64,827 specimens. All cases were reviewed histopathologically and clinical information was obtained from the records. Specimens from 10 patients were excluded. RESULTS: A total of nine benign neoplasms (5.4%) were identified in the 165 patients. Three patients were in their second decade of life, two in their third, two in the fifth and two in the sixth. There were five trichoblastomas, three specimens of syringocystadenoma papilliferum, and one aprocrine cystadenoma. No malignant neoplasms were found. Six of the tumors were removed either for prophylactic or cosmetic reasons and in only three cases were the neoplasms suspected clinically and excised. CONCLUSIONS: If this same tendency prevails in other prospective studies, we strongly believe that prophylactic excision of all nevus sebaceus is not warranted. Excision should be recommended only when benign or malignant neoplasms are clinically suspected or for cosmetic considerations.

Adolescent↗
PubMed1995

Selective modification of rat hepatic microsomal fatty acid chain elongation and desaturation by fibrates: relationship with peroxisome proliferation.

1. The time-course of the effect of clofibrate (CFB), bezafibrate (BFB) and gemfibrozil (GFB) on lipid plasma levels and palmitoyl-, palmitoleoyl- and gamma-linolenoyl-CoA elongase, delta-9, delta-6 and delta-5 desaturase activities, and microsomal electron transport chains, as well as the correlation with the peroxisomal proliferation phenomenon have been studied in male Sprague-Dawley rats. 2. As reported in our previous work, the three drugs behave as peroxisomal proliferators (the order of potency was BFB > CFB > or = GFB) and induced a clear reduction in both plasma cholesterol and triglyceride levels. 3. Palmitoyl-CoA elongation activity was increased by the three drugs (BFB = GFB > CFB), whereas palmitoleoyl-CoA elongation activity was only enhanced by GFB. Elongation activity was not modified by fibrates when gamma-linolenoyl-CoA was used as substrate. These results are in accordance with the existence of three different elongation systems for saturated, mono- and polyunsaturated fatty acids. 4. delta-9, delta-6 and delta-5 desaturase activities were increased by the three fibrates, with an order of potency BFB > CFB = GFB for delta-9 and delta-5, and GFB > BFB = CFB for delta-6. 5. Of the enzyme activities integrated in the microsomal electron transport chains, NADH cytochrome b5 reductase was not affected by fibrate treatment, NADPH cytochrome c reductase activity was enhanced (BFB = GFB > CFB), whereas NADH cytochrome c reductase activity was reduced by CFB and BFB. 6. The increase in Delta-9 and Delta-5 desaturase activities was highly dependent on the peroxisomal proliferation phenomena, whereas the increase in Delta-6 desaturase activity and the decrease in NADH cytochromec reductase was mainly independent. The modifications of palmitoyl-CoA elongase and NADPH cytochrome c reductase activities, as well as plasma lipid levels, were partially correlated with peroxisomal beta-oxidation, but the r2 values obtained point to the existence of additional independent mechanisms.7. As man is assumed to be a species refractory to peroxisomal proliferation, only those fibrate effectsnot absolutely related to this phenomenon are expected to appear after fibrate therapy.

Acetyltransferases↗
PubMed1995

Anion exchanger immunoreactivity in human salivary glands in health and Sjögren's syndrome.

Salivary gland ducts play a relevant role in saliva secretion through transport processes. Na(+)-independent chloride-bicarbonate anion exchangers (AE) may be involved in these processes by generating ion fluxes into the salivary secretion. In Sjögren's syndrome, a disorder with gland dysfunction, there might be an impaired expression of AE proteins. Here we study AE immunoreactivities in human salivary glands, both in health and in Sjögren's syndrome. Immunohistochemistry was carried out on salivary glands from normal subjects and patients with Sjögren's syndrome, using two monoclonal antibodies against AE1 and AE2. Normal salivary glands showed AE2 immunoreactivity, which was restricted to the epithelium of the ducts, with no staining at the acini. A strong positivity was seen in the basolateral portion of the striated ducts, while interlobular duct cells showed a discrete positivity at their apical pole. In salivary glands from most of the patients with Sjögren's syndrome, AE2 immunoreactivity was absent in the ducts as well as in the acini. In both normal and diseased salivary glands, AE1 immunoreactivity was only located at the erythrocyte membrane. The recently reported AE0 was discarded because no AE0 message was found in salivary glands by reverse transcription polymerase chain reaction. In conclusion, AE2 immunoreactivity is observed in the ducts of normal salivary glands, particularly in the striated ducts. AE2 immunoreactivity is virtually absent in salivary glands from patients with Sjögren's syndrome, which may reflect either a loss of AE2 after inflammatory atrophy, or a primary defect occurring in the disease.

Adult↗
PubMed1994

Nucleotide sequence of the Rhizobium etli nodS gene.

The complete nucleotide sequence of the nodS gene from the bean-nodulating Rhizobium etli, presumably encoding a methyltransferase, was determined. A phylogenetic analysis of five different NodS proteins from three genera of Gram- soil bacteria, Azorhizobium, Bradyrhizobium and Rhizobium, was performed.

Amino Acid Sequence↗
PubMed1994

Identification of a 20-kDa protein with calcium uptake transport activity. Reconstitution in a membrane model.

This paper presents results of experiments designed to further purify the membrane system involved in mitochondrial calcium transport. A partially purified extract, which transported calcium with a specific activity of 1194 nmol 45Ca2+/mg protein/5 min, was used to obtain mouse hyperimmune serum. This serum inhibited calcium uptake both in mitoplasts and in vesicles reconstituted with mitochondrial proteins containing cytochrome oxidase. Western blot analysis of the semipurified fraction showed that the serum recognized specifically two antigens of 75 and 20 kDa. Both antibodies were purified by elution from the nitrocellulose sheets and their inhibition capacity was analyzed. The antibody that recognized the 20-kDa protein produced a higher degree of inhibition than the other one.

Animals↗
PubMed1994

Relationship between plasma lipids and palmitoyl-CoA hydrolase and synthetase activities with peroxisomal proliferation in rats treated with fibrates.

1. The time-course of the effect of clofibrate (CFB), bezafibrate (BFB) and gemfibrozil (GFB) on lipid plasma levels and palmitoyl-CoA hydrolase and synthetase activities, as well as the correlations with the peroxisomal proliferation phenomenon have been studied in male Sprague-Dawley rats. 2. The administration of the three drugs caused a significant reduction in body weight gain, accompanied with a paradoxical increase in food intake in groups treated with BFB and GFB. 3. Drug treatment produced gross hepatomegaly and increase in peroxisomal beta-oxidation, and these parameters were strongly correlated. The order of potency was BFB > CFB > or = GFB. 4. Both plasma cholesterol (BFB approximately CFB > GFB) and triglyceride (BFB approximately GFB > CFB) levels were reduced in treated animals. There was an inverse correlation between these parameters and peroxisomal beta-oxidation, although the peroxisomal proliferation seemed to explain only a small part of the hypolipidemic effect observed. 5. Cytosolic and microsomal (but not mitochondrial) palmitoyl-CoA hydrolase activities were increased by the three drugs (BFB > CFB > GFB), probably by inducing the hydrolase I isoform, which is insensitive to inhibition by fibrates in vitro. The increased hydrolase activities were directly and strongly correlated with peroxisomal beta-oxidation. 6. Palmitoyl-CoA synthetase activity was also increased by the treatment with fibrates (BFB > CFB > GFB), probably as a consequence of the enhancement of hydrolase activities. 7. Some of the effects of fibrate treatment can be explained, at least in part, in terms of peroxisomal induction and caution should be exercised in the extrapolation of these results to species, such as man,that are insensitive to peroxisomal proliferation.

Animals↗
PubMed1993

Fibrates modify rat hepatic fatty acid chain elongation and desaturation in vitro.

Three fibric acid derivatives, clofibric acid (CFB), bezafibrate (BFB), and gemfibrozil (GFB), mainly used in the treatment of hypertriglyceridaemic or mixed hyperlipidaemic states, have been tested for their ability to modify fatty acid chain elongation and desaturation in vitro. Both endogenous and exogenous (saturated, monounsaturated and polyunsaturated) fatty acid elongations were inhibited by fibrates at concentrations well within the physiological range (IC50 values for GFB were between 0.1 and 0.3 mM). The potency order was GFB > BFB > CFB. Inhibition was not due to an impairment of the activation step from free fatty acids to acyl-CoAs, as palmitoyl-CoA synthetase was only slightly inhibited (IC50 value for GFB = 2.8 mM). Fibrates (GFB) appeared to behave as mixed non-competitive inhibitors with respect to malonyl-CoA when the rate limiting step of elongation, the condensing enzyme, is assayed. Further, delta 6 and delta 5 desaturates were inhibited by the three drugs (GFB > BFB > CFB), although not to the same extent as the elongation system. In contrast, delta 9 desaturase activity was not affected by fibrates.

Acetyltransferases↗
PubMed1993

Gemfibrozil modifies acyl composition of liver microsomal phospholipids from guinea-pigs without promoting peroxisomal proliferation.

Treatment with gemfibrozil modifies acyl composition of hepatic microsomal phosphatidylcholine and phosphatidylethanolamine in guinea-pigs. Palmitic (16:0) and palmitoleic (16:1) fatty acids are increased, and stearic (18:0) and oleic (18:1) are decreased; further, while linoleic acid [18:2 (n-6)] is increased by gemfibrozil treatment, the other constituents of the n-6 fatty acids family, including arachidonic acid [20:4 (n-6)], are decreased. As gemfibrozil is a potent inhibitor of fatty acid elongation in vitro (Sánchez et al., FEBS Lett 300: 89-92, 1992), the inhibition of this enzyme system by gemfibrozil treatment could be responsible for the observed results in vivo. These changes in fatty acid composition are accompanied by a decrease in serum lipids and, more important, are independent of peroxisomal proliferation.

Animals↗
PubMed1993

Cytosolic lipogenic enzymes: effect of fibric acid derivatives in vitro.

The effect of fibric acid derivatives, clofibric acid (CFB), bezafibrate (BFB), and gemfibrozil (GFB) on hepatic cytosolic enzymatic activities involved in saturated fatty acid synthesis has been estudied in vitro. From all the activities tested (fatty acid synthetase, acetyl-CoA carboxylase, ATP-citrate lyase, malic enzyme, malic dehydrogenase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase), only acetyl-CoA carboxylase and glucose-6-phosphate dehydrogenase were significantly inhibited by fibrates, with the following order of potency: GFB > BFB > > CFB. The characteristics of the inhibition phenomena (IC50, kinetic analysis, time and protein dependence, etc) and their transcendence to the effects of fibric acid derivatives in vivo are discussed.

Animals↗
PubMed1993

The NodL and NodJ proteins from Rhizobium and Bradyrhizobium strains are similar to capsular polysaccharide secretion proteins from gram-negative bacteria.

The NodL and NodJ nodulation proteins have been described in different Rhizobium and Bradyrhizobium species. The nodLJ genes belong to the nod regulon. Other genes from this regulon are involved in the biosynthesis and modification of lipo-oligosaccharide molecule(s) which are morphogenic signals when acting on legume roots. It has been proposed that the NodL and NodJ proteins belong to a bacterial inner membrane transport system of small molecules. Nucleotide sequencing of Mudll PR13 insertions in the nodulation region of the symbiotic plasmid from a Rhizobium leguminosarum bv. phaseoli strain CE3 has revealed the presence of nodL and nodJ-related sequences downstream of nodC. Computer nucleotide sequence analysis of the entire NodL and NodJ sequences from R. leguminosarum bv. viciae and Bradyrhizobium japonicum strains show that both proteins are similar to the KpsT and KpsM proteins from Escherichia coli K1 and K5 strains, to the BexB and BexA proteins from Haemophilis influenzae and to the CtrD and CtrC proteins from Neisseria meningitidis, respectively. Except for the NodL and NodJ proteins, all of them have been involved in the mechanism of secretion of polysaccharides in each of their harbouring species. On the basis of the similarity found, we propose that the NodL and the NodJ proteins could be involved in the export of a lipo-oligosaccharide.

ATP-Binding Cassette Transporters↗
PubMed1993

Malignant melanoma in children.

BACKGROUND: While significant risk factors for malignant melanoma may initially develop or are first seen in childhood, the actual occurrence of this neoplasm in prepubertal children is uncommon. METHODS: A retrospective study of malignant melanoma in Puerto Ricans up to 16 years of age occurring from 1973 to 1990 was carried out by identifying those cases in the Puerto Rico Cancer Registry. RESULTS: A total of seven cases were found consisting of three boys and four girls with ages ranging from 22 months to 16 years and comprising 0.94% of the total melanomas. In three of the seven cases, there was a history of a previously existent small congenital melanocytic nevus on the area. Three cases were Clark's level I, two level II, and in two cases with proved metastatic disease, Clark's level of invasion were not reported. Those cases with Clark's level I and II had a 100% 5-year survival. CONCLUSIONS: Although rare, malignant melanoma in children can be as aggressive as in adults. Among the known factors predisposing to malignant melanoma, three out of seven cases developed within a small congenital nevus, two of which occurred during the first decade of life. Due to the rarity of this event in our population, it appears unreasonable to excise all small congenital nevi during the first decade of life. Even for those who advocate excision of all small congenital nevi, the evidence at present suggests that such small nevi very rarely undergo malignant change before puberty and therefore a policy of observation in childhood and offering excision around the time of puberty is perfectly logical.

Adolescent↗
PubMed1992

Inhibition of rat liver microsomal fatty acid chain elongation by gemfibrozil in vitro.

Gemfibrozil, a hypolipidemic drug mainly used in the treatment of hypertriglyceridemic states, strongly inhibits the rat hepatic microsomal fatty acid chain elongation system in vitro. The inhibition is independent on the reducing cofactor used in the assay. Furthermore, gemfibrozil seems to act by inhibiting the rate-limiting step of the elongation process, the condensing reaction, without discriminating among the proposed three different condensing enzymes, devoted to condensation of saturated, mono-unsaturated and polyunsaturated acyl-CoA substrates.

Animals↗
PubMed1992

[Current status of lung transplantation].

Lung transplant has started to develop clinically during the last decade being a valid alternative for a great number of pulmonary diseases. A review of the three types of transplant is presented: single lung, double lung, and heart-lung transplant. We specially point out the indications of those surgical procedures. Furthermore, we expose the attitude towards most of the post-surgery problems: post-surgical follow up, immunosuppression therapy, diagnosis and treatment of graft rejection, main opportunistic infections as well as obliterans bronchiolitis, which is the long term most important complication.

Bronchiolitis Obliterans↗
PubMed1991

Novel organization of the common nodulation genes in Rhizobium leguminosarum bv. phaseoli strains.

Nodulation by Rhizobium, Bradyrhizobium, and Azorhizobium species in the roots of legumes and nonlegumes requires the proper expression of plant genes and of both common and specific bacterial nodulation genes. The common nodABC genes form an operon or are physically mapped together in all species studied thus far. Rhizobium leguminosarum bv. phaseoli strains are classified in two groups. The type I group has reiterated nifHDK genes and a narrow host range of nodulation. The type II group has a single copy of the nifHDK genes and a wide host range of nodulation. We have found by genetic and nucleotide sequence analysis that in type I strain CE-3, the functional common nodA gene is separated from the nodBC genes by 20 kb and thus is transcriptionally separated from the latter genes. This novel organization could be the result of a complex rearrangement, as we found zones of identity between the two separated nodA and nodBC regions. Moreover, this novel organization of the common nodABC genes seems to be a general characteristic of R. leguminosarum bv. phaseoli type I strains. Despite the separation, the coordination of the expression of these genes seems not to be altered.

Acyltransferases↗
PubMed1990

Bullous pemphigoid and malignancy.

Bullous pemphigoid has been reported in multiple publications to be associated with malignant neoplasms of different internal organ systems. This relationship was studied among forty patients seen at the Dermatology Clinics of the Puerto Rico Medical Center. The study demonstrated that Puerto Rican patients with bullous pemphigoid do not show an increased incidence of internal malignancy when compared with the general population matched for age, sex and study period. We conclude that extensive diagnostic studies for malignant neoplasms should not be the standard of care in patients with bullous pemphigoid. Additional studies should be guided by the clinical history and physical findings.

Adult↗
PubMed1989

Campylobacter jejuni chromosomal sequences that hybridize to Vibrio cholerae and Escherichia coli LT enterotoxin genes.

Campylobacter jejuni is one of the main etiologic agents of gastrointestinal illness in developing and developed areas throughout the world. Isolation of enterotoxin-producing C. jejuni has been associated with clinical symptoms of a watery-secretory type of diarrhea. Although physiological and immunological relatedness has been demonstrated between the C. jejuni enterotoxin (CJT), the Vibrio cholerae enterotoxin (CT), and the heat-labile cholera-like Escherichia coli enterotoxin (LT), nucleotide sequence similarity between C. jejuni DNA and either the toxA, toxB, eltA or eltB genes remained to be shown. We found that binding to ganglioside GM1 prevented recognition of CJT by monoclonal antibodies directed to either CT or LT. This indicates antigenic similarity between the three enterotoxins in the ganglioside GM1-binding site. Therefore we searched for corresponding similarities at the DNA level and found, by oligodeoxynucleotide hybridization, C. jejuni chromosomal nucleotide sequences similar to the coding region for a postulated ganglioside GM1-binding site on toxB and eltB.

Amino Acid Sequence↗