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Biomedical subjects

L Cervantes

Publications and source records attributed to L Cervantes.

15 recordsLinked to original sources
PubMed2003

Differential expression and subcellular distribution of dystrophin Dp71 isoforms during differentiation process.

Dp71 is the major product of the Duchenne muscular dystrophy gene in the brain. In order to study the function of Dp71 in the nervous system we examined the expression of Dp71 isoforms in PC12 rat pheochromocytoma cell line, a well-established system to study neuronal differentiation. We show by reverse transcriptase-polymerase chain reaction and Western blot assays that PC12 cells express two Dp71 isoforms. One isoform lacks exon 71 and the other isoform lacks exons 71 and 78 (Dp71d and Dp71f isoforms respectively). Nerve growth factor-induced neuronal differentiation of PC12 cells results in differential regulation of the expression and subcellular localization of Dp71 isoforms: a) the amount of Dp71f protein increases nine-fold in total extracts while Dp71d increases up to seven-fold in nuclear extracts; b) Dp71f relocates from the cytoplasm to neuritic processes, being prominent at varicosities and the growth cone; c) Dp71d relocates almost entirely to the nucleus and is detected to a lower extent in the cytoplasm and neuritic processes. Dp71f co-localizes with beta-dystroglycan and synaptophysin while Dp71d co-localizes with beta-dystroglycan in the nucleus. Dp71d accumulates at cell-cell contacts where Dp71f is absent. These results suggest that Dp71d and Dp71f associate with different subcellular complexes and therefore may have distinct functions in PC12 cells.

Animals↗
PubMed2001

Overweight in elderly Mexican women of a marginal community.

Obesity is a main risk factor in the development of diseases, which are causes of death in elderly population. Socio-economic characteristics had an impact in the prevalence of obesity. The purpose of this study was to estimate the prevalence of obesity in elderly Mexican women living in a marginal community and compare their results with those of women of urban and rural areas in Mexico. The study has a cross sectional design. Standardised nutritionist carried out the measurements. The international techniques recommended were used to measure weight and height. To estimate the proportion of overweight and obesity, the body mass index (BMI) was used following the WHO categories. A total of 249 elderly women were examined. The mean age was 71.6 (sd 7.8). No difference in age was found in the three communities visited (p>0.05). The mean BMI in the urban women was 26.7 (sd 4.6), in the rural 24.5 (sd 3.9), and in the marginal group 28.6 (sd 5.5) (p<0.0001). The proportion of overweight and obese women was in the urban group 60.7%, in the rural 36.2%, and in the marginal women 76.5% (p<0.001). The results of this study indicated the presence of a high prevalence of overweight and obesity in elderly women of urban and particularly in the marginal areas. Marginality seams to be a risk marker of obesity in elderly women in Mexico. Intervention programs aimed to decrease the prevalence of obesity and improve nutritional condition in this group are urgent.

Aged↗
PubMed2000

In Rhizobium etli symbiotic plasmid transfer, nodulation competitivity and cellular growth require interaction among different replicons.

Bacteria belonging to the genus Rhizobium are able to develop two different lifestyles, in symbiotic association with plant roots or through saprophytic growth. The genome of Rhizobium strains is constituted by a chromosome and several large plasmids, one of them containing most of the genes involved in symbiosis (symbiotic plasmid or pSym). Our model strain Rhizobium etli CFN42 contains six plasmids. We have constructed multiple plasmid-cured derivatives of this strain and used them to analyze the contribution of these plasmids to free-living cellular viability, competitivity for nodulation, plasmid transfer, and utilization of diverse carbon sources. Our results show that the transfer of the pSym is strictly dependent on the presence of another plasmid; consequently under conditions where pSym transfer is required, nodulation relies on the presence of a plasmid devoid of nodulation genes. We also found a drastic decrease in competitivity for nodulation in multiple plasmid-cured derivatives when compared with single plasmid-cured strains. Cellular growth and viability were greatly diminished in some multiple plasmid-cured strains. The utilization of a number of carbon sources depends on the presence of specific plasmids. The results presented in this work indicate that functional interactions among sequences scattered in the different plasmids are required for successful completion of both lifestyles.

Carbon↗
PubMed1990

Characterization of two DNA populations of Giardia lamblia.

Total DNA was isolated from the parasitic protozoan Giardia lamblia and separated into two distinct populations of different densities by centrifugation through CsCl gradients containing Hoechst dye 33258. The two populations obtained were characterized by restriction enzyme analysis and nucleic acid hybridization. The less-dense population contains non-repetitive DNA and may encode mainly structural genes, such as those for alpha- and beta-tubulin. Digestion of the DNA with several restriction endonucleases showed that the denser band was composed of a 5.5 kb unit which contains the G. lamblia ribosomal RNA cistron in tandem repeated organization.

Animals↗
PubMed1988

Cloning, sequencing, and expression in Ficoll-generated minicells of an Escherichia coli heat-stable enterotoxin gene.

The gene encoding a heat-stable enterotoxin of Escherichia coli was cloned as a 960-bp fragment from a plasmid isolated from a Mexican strain of human origin. Deoxyribonucleotide sequencing unveiled a 216-bp open reading frame similar to that of a previously sequenced ST-toxin gene. The gene is preceded by a proposed binding site for the cAMP-mediated positive regulator (CAP) that is part of a 23-bp inverted repeat. The proposed CAP site is followed by a 6A, 1T, and 6A deoxyribonucleotides. Minicells containing the toxin gene, which were isolated from Ficoll gradients, shown to preserve the localization of intracellular and periplasmic enzymes, allowed the detection of a biosynthetically radiolabeled polypeptide with an apparent Mr 8400. The data suggest that the enterotoxin genes estA2, estA3, and estA4 are very similar, even in clinical strains isolated from distinct geographical locations; that the transcription of heat-stable enterotoxin genes is controlled by the cAMP-mediated positive regulatory system, and that the heat-stable enterotoxins are initially synthesized as 72 amino acid precursors to yield the extracellular active 18-19 amino acid polypeptides.

Amino Acid Sequence↗
PubMed1987

Electron microscopy and biochemical properties of polyamine-compacted DNA.

We have obtained polyamine-compacted DNA and analyzed it by electron microscopy employing the method described by Dubochet, suitable for the study of complexes in which the main interactions are of ionic character. In addition, we have developed a simple biochemical method, based on the action of pancreatic DNase I, to demonstrate the condensation of DNA with spermidine. DNA-spermidine complexes are resistant to the action of DNase I, and there is a strong correlation between the presence of condensed DNA forms, both as toroids and as cylinders, and the insensitivity to DNase I activity. We have also shown that pBR322 DNA-spermidine complexes are transcriptionally active in the presence of Escherichia coli RNA polymerase. This supports the data concerning the biological activity of spermidine-condensed DNA.

DNA↗
PubMed1980

Advances in gastric emptying studies by means of computerized scintigraphy.

Gastric emptying studies were begun in 1833. However, as information on this phenomenon became more available it became more difficult to unify studies in order to make them more applicable for the study and treatment of functional disturbances and organic diseases. In this work an innocuous, objective and precise method is described, that consists of the study of gastric emptying in two stages in healthy individuals. In the first, basic substances of food were administered and in the second, usual 1,050 calorie meals all marked with Technetium-99 m macroaggregates, were given. Two scintillation cameras were used coupled to computerized data processing systems from where quantitative information and black and white Polaroid pictures were obtained. In the first stage, six healthy volunteers were studied who received basic food substances in different sessions. In the second stage, 10 healthy volunteers were studied who received a type of meal common in our environment. In all cases gastric emptying curves were obtained plotting radioactivity counts v.s. time. Weibull's distribution was the statistical method applied. According to the ingested substances, results showed different emptying curves of a complex exponential type. Although gastric emptying is immediate, it is parallel to the presence of plateaus in the initial part of the study; an apparently delayed phenomenon that had been overlooked and is explained in the discussion part of this paper. Results obtained have offered the possibility of an abundant volume of studies that should clarify existing doubts in the future with a wide field for clinical application.

Adolescent↗
PubMedDate not supplied

Construction and characterization of new cloning vehicles. V. Mobilization and coding properties of pBR322 and several deletion derivatives including pBR327 and pBR328.

A DNA sequence essential for the R64drd11 + ColK-mediated conjugal transfer of pBR322 has been located in a 540 bp HaeIII fragment (HaeIII-2) between the vegetative origin of replication and the tetracycline resistance (Tcr) gene of this vector. The pBR322 derivatives pBR327 and pBR328 lack this DNA sequence and are not mobilized by conjugation. Two derivatives of pBR328 were constructed by re-inserting the HaeIII-2 fragment in both orientations into the chloramphenicol-resistance gene of the same vector. One orientation of the HaeIII-2 fragment permitted mobilization by conjugation while the opposite orientation prevented mobilization. Further examination of pBR322 and derivatives revealed that the region between the origin of replication and Tcr gene also plays a role in regulating plasmid copy number.

Bacterial Proteins↗