Biomedical subjects

L C Lopez

Publications and source records attributed to L C Lopez.

24 records · Page 2Linked to original sources

PubMed1984

Isolation and characterization of a sperm-specific gene family in the nematode Caenorhabditis elegans.

The major sperm protein (MSP) of the nematode Caenorhabditis elegans is a low-molecular-weight (15,000) basic protein implicated in the pseudopodial movement of mature spermatozoa. Its synthesis occurs in a specific region of the gonad and is regulated at the level of transcription (M. Klass and D. Hirsh, Dev. Biol. 84:299-312, 1981; S. Ward and M. Klass, Dev. Biol. 92:203-208, 1982; Klass et al., Dev. Biol. 93:152-164, 1982). A developmentally regulated gene family has been identified that codes for this MSP. Whole genomic blots, as well as analysis of genomic clone banks, indicate that there are between 15 and 25 copies of the MSP gene in the nematode genome. Southern blot analysis also indicates that there is no rearrangement or amplification within the MSP gene family during development. No evidence was found of methylation at various restriction sites surrounding the MSP gene family, and similarly, no correlation between methylation and expression was observed. Three distinct members of this MSP gene family have been cloned, and their nucleotide sequences have been determined. Differential screening of a cDNA clone bank made from polyadenylated mRNA from adult males yielded 45 male-specific clones, 32 of which were clones of MSP genes. One of these cDNA clones was found to contain the entire nucleotide sequence for the MSP, including part of the 5' leader and all of the 3' trailing sequence. Genomic clones bearing copies of the MSP genes have been isolated. At least one of the members of this gene family is a pseudogene. Another member of the MSP gene family that has been cloned from genomic DNA contains the entire uninterrupted structural sequence for the MSP in addition to a 5' flanking sequence containing a promoter-like region with the classic TATA box, a sequence resembling the CAAT box, and a putative ribosome-binding sequence. The 3' trailing sequences of the genomic and the cDNA clones contain an AATAAA polyadenylation site.

Amino Acid Sequence↗

PubMed1984

Localization of the human glucagon gene (GCG) to chromosome segment 2q36----37.

Hybridization of a 3H-labeled bovine glucagon cDNA plasmid to human metaphase chromosomes revealed significant labeling of the distal portion of the long arm of chromosome 2. A large portion (37%) of the cells analyzed exhibited labeling of the 2. A significant percentage (40%) of the labeled sites on the 2 were in segment 2q36----37. Therefore, the human glucagon gene (GCG), was assigned to this segment. Localization of the glucagon gene, whose chromosomal assignment was previously not known, demonstrates the general applicability of in situ hybridization as a powerful gene mapping technique.

Chromosome Mapping↗

PubMed1983

Mammalian pancreatic preproglucagon contains three glucagon-related peptides.

We have isolated cDNA clones encoding bovine pancreatic preproglucagon. Twenty-five putative preproglucagon clones were selected by screening 3,100 clones of a fetal bovine pancreas cDNA library with a synthetic oligodeoxynucleotide probe. The probe was a mixture of synthetic 17-base DNA oligomers constructed to correspond to the six carboxyl-terminal amino acids (residues 24-29) of mature glucagon. Restriction mapping of six of these clones suggested that they represented a single mRNA species. Primary sequence analysis of one clone containing a 1,200-base-pair DNA insert revealed that it contained an essentially full-length copy of glucagon mRNA. Analysis of the cDNA suggested a protein coding sequence of 540 nucleotides and 5'- and 3'-untranslated regions of 90 and 471 nucleotides, respectively. This cDNA sequence encoded a 20-amino acid signal sequence followed by one for glicentin, a 69-amino acid polypeptide containing an internal glucagon moiety that has been found in porcine intestines. Glicentin is followed by two additional glucagon-like peptides, each flanked by paired basic amino acids (Lys, Arg) characteristic of prohormone processing. These polypeptide sequences show striking homology with those for glucagon and other members of the glucagon family of peptides.

Amino Acid Sequence↗

PubMedDate not supplied

Cell surface galactosyltransferase as a recognition molecule during development.

Recent results from our laboratory suggest that a variety of cellular interactions during development are mediated, in part, by the binding of a cell surface enzyme, galactosyltransferase (GalTase), to its specific lactosaminoglycan (LAG) substrate on adjacent cell surfaces and in the extracellular matrix. Our present interest in surface GalTase developed from earlier biochemical studies of a series of morphogenetic mutations in the mouse which map to the T/t-complex. These studies identified a specific defect in the regulation of surface GalTase activity on morphogenetically abnormal cells, while eight other enzymes showed normal activity. This led us to consider the unique function of surface GalTase in those cell interactions that are influenced by mutations of the T/t-complex. By using a multidisciplinary approach, which included genetic, biochemical and immunological probes, we have found that GalTase functions as a surface receptor during fertilization, early embryonic cell adhesions, and embryonic cell migration on basal lamina matrices. Recently, we have examined the expression of surface GalTase during spermatogenesis, as well as the fate of sperm GalTase following the acrosome reaction. This paper summarizes the results of these studies, as well as others, which suggest that GalTase functions as a surface receptor during those cell interactions regulated by the T/t-complex alleles.

Animals↗

PubMedDate not supplied

La desesperacion: migrant and seasonal farm workers living with HIV/AIDS.

Migrant seasonal farm workers (MSFWs) in south Texas are predominantly Mexican American and represent one of the most impoverished and medically underserved populations in the United States. La Frontera is a collaborative partnership between the University of Texas Health Science Center at San Antonio, migrant organizations, and HIV service delivery organizations to study and address special needs of MSFWs in Hidalgo and Maverick counties of south Texas. The purpose of this qualitative study is to explore the health-seeking experiences of HIV-positive MSFWs living in the La Frontera service area. Denzin's interpretive interactionism methodology guided the study. Thirteen participants were interviewed and audiotaped as they described their experiences. Findings from content analysis of the interviews revealed a description of the life of an HIV-positive MSFW as la desesperacion (a separate way of life). After their diagnosis of HIV/AIDS, the major themes in their lives were living in secrecy (a silent cry), finding and receiving health care, and accepting the disease (may it be the will of God).

Adaptation, Psychological↗

PubMedDate not supplied

Utilizing a 24-hour dietary recall and culturally specific diabetes education in Mexican Americans with diabetes.

Two objectives were established for this study: 1) to assess the impact of a culturally specific, intensive diabetes education program on dietary patterns, and 2) to assess nutrient consumption relative to the Recommended Dietary Allowances. The study population consisted of elderly Mexican Americans with diabetes living in Harlingen and Brownsville, Texas. The experimental group (n = 78) participated in an intense, 2-hour nutrition education session, while the control group (n = 74) did not. The education session was conducted for groups of eight subjects via videotapes and interactive discussion. All groups experienced significant weight loss except the women in the experimental group. After the education program, however, the experimental women had increased the percentage of calories consumed daily from carbohydrate. Mean calcium consumption was substantially less than the RDA in all groups, and inadequate amounts of ascorbic acid and vitamin A often were consumed. Intensive, frequent, long-term follow-up appears essential for more sustained results.

Cultural Characteristics↗