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Biomedical subjects

A Navarro

Publications and source records attributed to A Navarro.

At least 19 recordsLinked to original sources
PubMed1992

Primary structure of an agonist binding subunit of the nicotinic acetylcholine receptor from bovine adrenal chromaffin cells.

Activation by acetylcholine of a nicotinic acetylcholine receptor on the membrane of bovine chromaffin cells leads to membrane depolarization and to the subsequent triggering of catecholamine secretion. It is evident that acetylcholine receptors play a central role in the initial phase of the secretion process and, therefore, an extensive characterization of their molecular components and properties is of fundamental interest. With this intention, we have screened bovine adrenal medullary cDNA libraries with a probe coding for a fragment of the rat muscle acetylcholine receptor alpha subunit. Several cDNA clones were isolated. The longest cDNA had an open reading frame encoding a 495-amino acid protein with a molecular weight of 56,911. The deduced primary structure contains features that indicate that the encoded protein is an alpha or acetylcholine binding subunit, and, in fact, it manifests significant sequence similarity to previously cloned alpha subunits. Sequence identity is particularly high with the alpha 3 subunit, which is expressed in the rat pheochromocytoma PC12 cell line and in several brain areas, and, consequently, it is considered a component of a neuronal acetylcholine receptor. Accordingly, the present results suggest that the agonist binding subunit of the nicotinic acetylcholine receptor from bovine chromaffin cells is an alpha 3-type subunit, corroborating previous immunological and pharmacological evidence for the presence of a neuronal nicotinic receptor in chromaffin cells.

Acetylcholine↗
PubMed1992

Quantified ultrastructural study of spermatozoa in unexplained failure of in vitro fertilization.

Failure of in vitro fertilization or very low cleavage rates may occur even though oocyte and semen parameters seem satisfactory. Quantified ultrastructural study of spermatozoa was performed in such cases of failure (n = 6) or low cleavage rate (< 20%; n = 4). Through 1 to 11 retrievals, the number of inseminated oocytes ranged from 14 to 145. The results were compared to those of six fertile men. Quantification was achieved by cataloguing cell defects of the spermatozoon heads and mid-/principal pieces of the flagella. Using the data from each specimen, the percentages of total cellular abnormalities in the head/mid-/principal pieces were established. At the level of the head overall percentages for six groups of defects were determined. The overall percentage of combined head abnormalities, defined as the presence of at least three of these six defects on the same spermatozoon head, was established. Statistical differences among control and patient groups were analyzed by nonparametric Mann-Whitney U test. The percentages of anomalies of the midpiece and of the principal piece were not significantly different between patients and controls. Motility assessed by spermogram was considered "functionally uncompromised." In eight patients the percentage of cell alterations of the head (93-100 vs 77.3 +/- 6.4%) and the percentage of combined anomalies of the head (78.1-100 vs 60.8 +/- 8.5%) were significantly different between patients and controls. In two cases, the percentages established for all head parameters considered were not globally different from those observed in controls. Thus in 8 cases of 10, electron microscopy with quantified analysis supplied valuable evidence about the poor quality of these sperm samples judged as normal under light microscopy and may provide an explanation for their impaired fertilizability.(ABSTRACT TRUNCATED AT 250 WORDS)

Fertilization in Vitro↗
PubMed1992

Growth in malnutrition related to gastrointestinal diseases: coeliac disease.

Coeliac disease in children is frequently associated with a slow growth rate. This observation may be linked to the malabsorption that occurs in these patients; however, the underlying mechanism remains unknown. To better understand this phenomenon, we have studied the growth patterns of 153 patients with coeliac disease for 2-9 years. Gastro-intestinal biopsies were performed before and after gluten exclusion. In a second group of 79 children, somatostatin levels and binding properties in the plasma and jejunal mucosa were measured. In a third group of 40 patients we measured insulin-like growth factor I (IGF-I) and IGF-binding protein 3 (IGF-BP3) levels. We found that in children diagnosed before 2 years of age weight was the most affected growth parameter. In children diagnosed after this age, height was more affected. Suppression of gluten intake induced an acceleration of growth velocity. Although plasma levels of somatostatin were not significantly altered, somatostatin concentrations in the jejunal mucosa of patients in the active phase of the disease were significantly elevated (p < 0.05). Children with coeliac disease exhibited significantly lower levels of IGF-BP3 when compared to patients with normal stature and growth velocities. In contrast, these patients showed an increase in IGF-BP3 levels after gluten exclusion from the diet.

Body Height↗
PubMed1991

Association of Escherichia coli HEp-2 adherence patterns with type and duration of diarrhoea.

373 (59%) out of 636 faecal specimens obtained during the first 2 years of life of 72 Mexican children yielded adherent Escherichia coli (HEp-2 cells). Strains with localised adherence were significantly associated with acute non-bloody diarrhoea, whereas strains with aggregative adherence were significantly associated with persistent diarrhoea. Half the strains with localised adherence were not enteropathogenic E coli serotypes nor did they hybridise with an enteropathogenic E coli adherence factor DNA probe. All strains with localised adherence gave a positive fluorescent actin staining (FAS) assay, irrespective of serotype. One-third of children colonised by aggregative strains had bloody diarrhoea. Isolation of strains with diffuse adherence was not related to type or duration of diarrhoea but was generally associated with isolation of another pathogenic organism.

Acute Disease↗
PubMed1991

Episodic cluster headache and narcolepsy: a case report.

A patient who first presented with episodic cluster headache later developed narcolepsy. In spite of REM sleep alterations associated with narcolepsy, the frequency and distribution of pain attacks did not change when narcolepsy occurred and were similar to those seen in cases of episodic cluster without narcolepsy. The lack of influence of narcolepsy on the pattern of cluster pains questions the role of REM sleep states in triggering pain in episodic cluster.

Adolescent↗
PubMed1991

Interrelationship of capsule thickness and breast hardness confirmed by a new measurement method.

All implants initiate a foreign-body response that leads to their encapsulation by scar tissue. In order to better understand this encapsulation process and the differences between soft (comfortable) and firm (contracted) breasts, we studied 22 patients who had come in for reaugmentation during a 2-year period. The capsules removed were prepared and measured using a new method. The capsules were (1) removed and stored in physiologic solution until the time of measurement (30 minutes to 2 hours) and (2) measured using a Mitutoyo dial-thickness gauge (MDTG) that employs a uniform pressure of 85 gm. The measurements revealed that soft breasts (Baker 1) have the thinnest scar-tissue capsules, which ranged in thickness from 0.002 to 0.010 inches. Firm breasts yielded the thickest capsules. Baker 3 measured between 0.010 and 0.078 inches thick, and Baker 4 measured between 0.018 and 0.162 inches thick. We also compared the precision of measurement between the MDTG and a standard (screw-type) micrometer by taking a series of readings on a soft, pliable substance (textured silicone rubber).

Breast↗
PubMed1991

Two beta-glycanase genes are clustered in Bacillus polymyxa: molecular cloning, expression, and sequence analysis of genes encoding a xylanase and an endo-beta-(1,3)-(1,4)-glucanase.

Two genes, xynD and gluB, encoding a xylanase and an endo-beta-(1,3)-(1,4)-glucanase (lichenase) from Bacillus polymyxa have been cloned and expressed in Escherichia coli and Bacillus subtilis. A sequenced DNA fragment of 4,466 bp contains both genes, which are separated by 155 bp. The xynD and gluB genes encode proteins of 67.8 kDa (XYND) and 27 kDa (GLUB). Two peptides with molecular masses of 62 and 53 kDa appear in cell extracts of E. coli and culture supernatants of B. subtilis clones containing the xynD gene. Both peptides show xylanase activity in zymogram analysis. The XYND enzyme also shows alpha-L-arabinofuranosidase activity. The XYND peptide and the xylanase XYNZ from Clostridium thermocellum (O. Grépinet, M. C. Chebrou, and P. Béguin, J. Bacteriol. 170:4582-4588, 1988) show 64% homology in a stretch of about 280 amino acids.

Amino Acid Sequence↗
PubMed1991

[Patterns in the household acceptance of oral rehydration therapy in a cohort of rural mothers].

The household acceptance of oral rehydration solution salts was studied in a cohort of 75 rural mothers over a two year period. The study was carried out in a rural Mexican village between August 1985 and February 1988. There were 636 episodes of diarrhea, with an average of four episodes per child per year. There were no deaths due to diarrhea or its complications and only 2% of these episodes required the use of parenteral solutions. Acceptance of oral rehydration remained around 50% during subsequent bouts of diarrhea. Variables such as a medium high socioeconomic level of the family, and the reading of journals and newspapers by the mother and the presence of water supply in the home were significantly associated with the acceptance of oral rehydration treatment. On the other hand, families classified as traditional rejected the procedure with significantly higher frequency. The data presented indicates the need for redesigning oral rehydration, treatment programs to increase their impact at the community level.

Adult↗
PubMed1991

[A comparative study between the use of the Spicer-Edwards method and the coagglutination reaction for identifying Salmonella antigens].

A comparative study between tube agglutination using Spicer-Edwards antisera and a coagglutination method using Staphylococcus aureus Cowan 1 (NCTC 8530) protein A to detect Salmonella flagellar antigens was carried out. A total of 39 Salmonella strains belonging to eight serogroups of the Kauffmann-White scheme were typed by both methods. Each serogroup include monophasic and biphasic strains. Statistical analysis of the results showed that the coagglutination method was more sensitive and specific that the classic tube agglutination method normally used in different laboratories. The use of less antiserum in the coagglutination method to detect Salmonella antigens without loss of specificity or sensitivity represents an important saving for clinical laboratories and for epidemiologic research that require the identification of these antigens.

Agglutination Tests↗
PubMed1991

[Etiology of bloody diarrhea in children from a rural community].

The etiology of bloody diarrhea was investigated in a cohort of 75 children followed longitudinally from birth during the first two years of life in a rural Village of Central Mexico. Of a total of 636 episodes of diarrhea, 71 (11%) showed presence of blood. A single associated pathogen was isolated in 59 (83%) of 71 children; 35% showed the presence of enteroaggregative E. coli (EAEC), 11% of E. coli producing Shiga-like toxins (SLT) I and/or II; 13% of Shigella, 7% of Campylobacterjejuni or enterotoxigenic E. coli (ETEC) and 4% enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), Salmonella, Giardia lamblia or Hymenolepis nana. Mixed cultures were found in 16% of cases during the first year and in 18% during the second. These were mainly combinations of C. jejuni, with ETEC or EAEC. In 78% of children with bloody diarrhea the episode was single event during the first two years of life, lasting on average seven days. Epidemiologically, the incidence of bloody diarrhea rose steadily during the first two years of life, with a significant decrease after the tenth month. Prevalence was affected by seasonality in all pathogens, except for EAEC that had an endemic frequency. In the case of Shigella and SLT-producing E. coli clustering of cases and isolation of serologically identical strains indicated that infections were the result of common source outbreaks.

Diarrhea, Infantile↗
PubMed1991

[The comparative treatment with lovastatin and bezafibrate of primary hypercholesterolemia. A randomized and double-blind trial].

The efficacy and tolerability of lovostatin (L) and bezafibrate (B) were compared in a total of 39 patients, 24 males and 15 females, 59 +/- 9 years old. Showing a total serum cholesterol superior to 250 mg/dl and total serum triglycerides inferior to 350 mg/dl, after 1 month on a low cholesterol diet and another on placebo, were eligible for participation. After randomization 19 treated with L started with 20 or 40 mg at night according to baseline cholesterol under or above 300 respectively and 20 with B received 200 mg tid. If after 6 weeks of therapy cholesterol remained above 200, the doses of L or matching placebo in those with B was double while dose of B or matching placebo remained constant. Cholesterol, triglycerides, LDL-cholesterol and HDL-cholesterol were determined using an enzymatic analytical method. Apolipoproteins were obtained by radial immunodiffusion. Routine hematological analysis and blood chemistry safety tests were performed at baseline and every 6 weeks during active treatment. The average most important results, after 12 weeks of treatment, comparing L vs B were: 1) cholesterol was reduced 26 vs 10% (p less than 0.001); 2) LDL-cholesterol decreased 35 vs 15% (p less than 0.001); 3) HDL-cholesterol increased 5 vs 19% (p = NS); 4) triglycerides diminished 15 vs 18% (p = NS). Three patients in L and 1 in B showed adverse events and two of them, one each group, were drop-out. In summary: a) L was more effective lowering total cholesterol and LDL-cholesterol; b) B was more potent decreasing triglycerides and increasing HDL-cholesterol; c) both drugs showed good tolerability.

Apolipoproteins A↗
PubMed1990

Risk of diarrhea during the first year of life associated with initial and subsequent colonization by specific enteropathogens.

The incidence of colonization by enteropathogenic, enterotoxigenic, enteroinvasive, and enterohemorrhagic Escherichia coli (detected by DNA hybridization with specific radiolabeled probes), Salmonella sp., Shigella sp., Campylobacter jejuni, and rotavirus was related to the presence of diarrhea in a cohort of 75 rural infants followed longitudinally during the first year of life. The study was carried out between August 1985 and February 1987 in the village of Lugar Sobre la Tierra Blanca, in the state of Morelos, 180 km southwest of Mexico City. Intestinal colonization by specific enteropathogens was followed with fecal cultures taken every fortnight and every time a child had diarrhea. Pathogens isolated from cultures taken in the 48 hours prior to the initiation of the diarrheal episode were considered to be associated with the disease. Diarrhea was detected in 82% of the children with initial isolation of enterohemorrhagic E. coli and in 64% of the children with enteropathogenic E. coli or Shigella sp. The risk of diarrhea associated with the initial isolation of other pathogens was lower, at 41% for rotavirus and approximately 25% for enterotoxigenic E. coli, Salmonella sp., and C. jejuni. Initial colonization by the enteropathogens studied, whether or not they were associated with diarrhea, prevented disease, but not colonization by the same organism, when the children were reinfected during the first year of life. Enteropathogenic E. coli adherence factor, human or porcine heat-stable enterotoxins, fimbrial colonization factor antigens, and Shiga-like toxins I and II were important pathogenic characteristics related to the presence of diarrhea and to protection against subsequent infection by the same organisms.

Campylobacter Infections↗
PubMed1990

Misreporting of maternal mortality in Puerto Rico.

Maternal mortality (MM) continues to be a problem that plagues many developed and underdeveloped countries around the world. It has been estimated that the minimum amount of underreporting in the U.S. to be 20%, resulting in MM rates that may be substantially higher than reported. The national goal for the MM for the year 1990 has been set at 5/100,000, and at the present trend it is expected that this may be achieved among the white population, but not among minorities. P.R. reported a maternal mortality rate of 5/100,000 in 1975. It was suspected that such a low rate was due to underreporting, a study was undertaken to investigate that possibility. The results indicated that there was severe underreporting of maternal deaths during 1978 = 79. Recently, there has been a growing concern that the level of underreporting in PR continues to be high. Since there has been no evidence that the surveillance has improved, the Dept. of Health requested from the Dept. of Ob-Gyn of the University of Puerto Rico Medical School and the Dept. of Maternal and Child Health to conduct a study to find out if the previous findings held true for recent years. The study was based on the review of selected medical records corresponding to deaths of women of childbearing age whose causes of death, as coded in the death certificate, were considered as having a high probability of masking a misreported maternal death. It was decided to investigate those deaths occurring in 1982, to see if the results of the previous study had caused any impact on the surveillance of maternal deaths in Puerto Rico.

Death Certificates↗
PubMed1989

Differential thionin block staining of nerve cells and fibers for paraffin-embedded material in mammalian central nervous system.

A differential staining method of myelinated fibers and nerve cell bodies applicable to whole blocks of mammalian central nervous tissue is described. Experimental material fixed by perfusion or necropsy material fixed in block can be used. Blocks of 2 mm in thickness were obtained with a vibratome, immersed in 50% ethanol for 7 h and stained for 1 week in the following solution: 0.3% thionine, 5% formaldehyde and 5% acetic acid. After the staining period the blocks were washed in distilled water, dehydrated through graded alcohols, cleared in butyl acetate and infiltrated in paraffin. Sections of 10 microns in thickness were obtained, attached to slides, dewaxed in xylene and coverslipped with mounting media in the usual manner.

Animals↗