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Biomedical subjects

J Lopez

Publications and source records attributed to J Lopez.

At least 127 records · Page 7Linked to original sources
PubMed1987

Atypical germ cells in prepubertal cryptorchid testes.

Four cases of prepubertal cryptorchid testes with atypical germ cells were studied. These cells were characteristically large, showing a wide, pale cytoplasm and a large nucleus with both fine and coarse granular chromatin. Ferritin was shown to be absent. It is possible that these cells are dysplastic in nature and that they could form the basis of a premalignant intratubular lesion. Thus periodic follow-up of these patients is recommended.

Child↗
PubMed1986

Changes in the protein fractions of human milk during lactation.

The changes in the absolute and relative contents of alpha- and kappa-caseins, lactoferrin, alpha-lactalbumin, serum albumin and lysozyme in human milk have been studied through the period of lactation. Protein fractions of 209 samples were analyzed by a discontinuous polyacrylamide gel electrophoresis method. beta- and kappa-caseins decreased from colostrum to mature milk although their relative percentages remained constant. They accounted for 12-15 and 9-13% of the total protein in human milk, respectively. Lactoferrin decreased in absolute and relative amounts with advancing lactation. This protein represented 32-19% of the human milk proteins. alpha-Lactalbumin slightly decreased from colostrum to transitional milk but there was an increase in mature milk by 16-30 days. The percentages of this protein in colostrum and mature milk were approximately 23 and 30%, respectively. Serum albumin also decreased with advancing lactation, but the differences between transitional and mature milk were not statistically significant. Lysozyme increased from colostrum to mature milk both in relative and absolute amounts. Colostrum contained about 262 micrograms/ml, and mature milk 1,246 micrograms/ml, representing 1.5 and 12.1% of total milk proteins.

Animals↗
PubMed1986

Neonatal diethylstilbestrol treatment: response of prolactin to dopamine or estradiol in adult mice.

The effects of neonatal diethylstilbestrol (DES) treatment on pituitary PRL response to dopamine (DA) inhibition or estrogen stimulation were studied in C3H/MTV+ mice at 10 weeks, 5 months and 8 months of age using synthesis and release of [3H]PRL by the pituitary as endpoints. In the DA study, anterior pituitaries from ovariectomized or intact, neonatally hormone-treated mice were incubated for 6 h in the presence or absence of DA. In the estrogen study, serum and anterior pituitaries were obtained from ovariectomized neonatally hormone-treated mice injected with oil or 17 beta-estradiol for 7 days before death. Neonatal treatment of mice with 2.5 micrograms/day DES altered basal [3H]PRL synthesis and release as well as circulating PRL concentrations. The results of analysis of variance indicated a significant interaction between the effects of neonatal hormone treatment and DA treatment on [3H]PRL release. Neonatal DES treatment did not alter the response of pituitary PRL to estrogen treatment at the ages examined.

Animals↗
PubMed1985

Unusual apparently constitutive interferons and antagonists in human placental blood.

We have detected seemingly uninduced interferons (IFNs) in 29/37 human placental samples obtained during caesarian sections at different periods of pregnancy, mostly around the 37th week. The amounts were usually low and did not enable us to correlate our findings with any physiological or pathological conditions. Occasionally the presence of IFN was masked by a lectin-like antagonist. Therefore, in a number of cases, substantially higher amounts of IFN were found after purification by affinity chromatography using concanavalin A, Cibacron blue, or antiserum to IFN-alpha, each coupled to Sepharose. Analysis by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed the presence of IFN-alpha and IFN-beta with molecular masses between 15 and 80 kilodaltons. Some of the high molecular weight components were neutralized either only by monospecific antiserum to IFN-alpha or, to the same extent, by antiserum to IFN-alpha or to IFN-beta, reminiscent of those previously reported after viral induction in the human amniotic membrane. We postulate that both IFNs and antagonist play a physiological role during fetal development.

Amnion↗
PubMed1985

fipB and fipC: two bacterial loci required for morphogenesis of the filamentous bacteriophage f1.

We describe the identification of two mutations in bacterial genes, designated as fipB and fipC, which resulted in temperature-sensitive morphogenesis of bacteriophage f1. These mutations mapped at separate loci but had to be present simultaneously to block f1 production at 41.5 degrees C. One mutation defined the locus fipB at 85.3 min on the Escherichia coli linkage map; the other defined the locus fipC, which mapped very close to rpsL at 73 min. Since these mutations did not appear to affect phage DNA replication, gene expression, or protein localization, they probably interfered with the its life cycle at the level of assembly. fipB mutants were partially deficient in adsorption of bacteriophage lambda, and fipB and fipC mutants leaked beta-lactamase into the medium, suggesting that the mutations affect outer-membrane structure or function.

Coliphages↗
PubMed1985

[Experimental pathogenicity of so-called atypical mycobacteria in mice, hamsters and meriones. Anatomo-pathological study].

Three animal species were used for the experimental pathogenicity of fourteen out of a total of thirty strains of atypical mycobacteria which were isolated from lymph nodes of healthy pigs in the surrounding area of Montevideo. White mice, hamsters and meriones were inoculated by intraperitoneal, intravenous or intracardiac routes. These animals were observed for either one year or until death, if death occurred during that year. Macroscopic and microscopic lesions were studied. Smears and cultures were also performed. This method led to a better knowledge of the pathogenicity of the following atypical mycobacteria species: Mycobacterium kansasii, MAIS complex and M. chelonae. It showed that some saprophyte strains belonging to terrae and vaccae complex were able to develop a pathogenicity. The hamster appeared to be the most sensitive animal.

Animals↗
PubMed1984

Effects of neonatal treatment with diethylstilbestrol and 17 alpha-hydroxyprogesterone caproate on in vitro pituitary prolactin secretion.

The effects of neonatal hormone treatment with diethylstilbestrol (DES) and 17 alpha-hydroxyprogesterone caproate (HPC) on days 1-5 of life on serum prolactin (PRL) levels and 3H-PRL synthesis and release were studied in C3H/MTV+ mice at 2, 4, 6, 8 and 10 weeks of age. Neonatal treatment of mice with 2.5 micrograms/day DES was the only treatment that affected the developmental pattern of serum PRL levels. Serum PRL levels were significantly decreased at 6 wks of age with this dose of DES. Neonatal treatment with 2.5 micrograms/day DES and 150 micrograms/day HPC affected the developmental pattern of H-PRL synthesis by the pituitary. At 10 wks of age 3H-PRL synthesis was significantly decreased by these doses of DES and HPC. The percent of 3H-PRL released did not differ between neonatally hormone treated and control animals, suggesting that neonatal treatment affected mechanisms that regulate PRL synthesis but not those that regulate release.

17-alpha-Hydroxyprogesterone↗
PubMed1984

RNA electropherotypes of human rotaviruses from North and South America.

Between April 1979 and December 1982, viral agents were found in 231 of 695 children admitted to the Texas Children's Hospital with gastroenteritis. Electron microscopic analysis showed that rotaviruses were the most common viral agents, and a seasonal pattern of rotavirus disease was observed. The migration patterns of the RNA segments of these rotaviruses on electrophoresis in polyacrylamide gels were compared with those of rotaviruses collected from other areas of the United States of America and from Argentina, Colombia and Mexico. A number of different RNA electropherotypes were found, including some patterns not previously reported.

Child↗
PubMed1983

Secretion kinetics of prolactin and growth hormone by mouse anterior pituitaries in long term organ cultures.

Long-term organ cultures of mouse anterior pituitaries provides a system for generating an enriched starting material for the purification of prolactin and growth hormone. Culturing 1 anterior pituitary per ml in serum-free medium for 12 days resulted in a total yield of 40.9 micrograms and 6.6 micrograms of prolactin and growth hormone, respectively. This yield represented a 1886% and 18% net increase over the control prolactin and growth hormone content in the unincubated pituitaries. Secondly, culturing of 1-5 anterior pituitaries per ml did not result in a negative feedback autoregulation in the culture system.

Animals↗
PubMed1983

Morphogenesis of filamentous bacteriophage f1: orientation of extrusion and production of polyphage.

Crosslinking reagents were used to interrupt the process of filamentous phage morphogenesis and investigate the orientation in which nascent virions are extruded through the host cell membrane. Infected bacteria with emerging phage particles were crosslinked with glutaraldehyde. Immunoferritin-labeling studies on these emerging phage using anti-A protein IgG suggested that extrusion begins with the C protein end. To confirm this, phage extruding from infected bacteria were frozen using the reversible crosslinker dimethyl 3,3'-dithiobis-propionimidate and fragments of emerging phage were isolated by shearing. Protein analysis of these fragments showed them to be enriched in C protein relative to A protein, as predicted if phage extrusion begins with the C protein end. The production of multiple-length phage particles (polyphage) by nonpermissive bacterial hosts infected with amber mutant phage strains was also studied. Polyphage were produced upon infection with amber mutants in genes III, VI, VII, and IX which code for proteins found at the ends of the mature phage particle. No polyphage were produced by mutants in the other genes tested. Gene III amber mutants produce noninfective polyphage, but those produced by genes VII and IX are infective. Gene VI amber mutants appear to produce unstable, noninfective polyphage particles.

Coliphages↗
PubMed1982

Isolation, purification, and characterization of mouse placental lactogen.

Mouse placental lactogen was purified 1840-fold from BALB/c placentae from days 14-18 of gestation with an overall yield of 29%. The purification procedure included alkaline homogenization and extraction, ammonium sulfate precipitation, hydrophobic interaction chromatography on Phenyl-Sepharose, ion-exchange chromatography on CM- and DEAE-cellulose, and gel exclusion chromatography on Sephadex G-100. On 10% alkaline polyacrylamide gels, mouse placental lactogen had an Rf of 0.19. Electrophoresis in gels containing NaDodSO4 showed a single band with a mobility corresponding to a Mr of 23,000 +/- 1000. The isoelectric point, determined by isoelectric focusing in 8 M urea/5% 2-mercaptoethanol, was 7.1. When tested in the pigeon crop sac assay, 10 micrograms of mouse placental lactogen produced stimulation comparable with that evoked by 10 micrograms of ovine prolactin. In the rabbit mammary gland radioreceptor assay, mouse placental lactogen was 150% more potent than ovine prolactin in displacing 125I-labeled ovine prolactin from rabbit mammary gland membranes. Iodinated purified mouse placental lactogen could be displaced from rabbit mammary gland membranes by mouse placental lactogen, mouse prolactin, and ovine prolactin. Ovine prolactin was 45% as avid as mouse placental lactogen is displacing 125I-labeled mouse placental lactogen from rabbit mammary gland membranes. Mouse placental lactogen did not crossreact with antisera to mouse prolactin or mouse growth hormone in a radioimmunoassay.

Animals↗
PubMed1982

Minor coat protein composition and location of the A protein in bacteriophage f1 spheroids and I-forms.

The filamentous bacteriophage f1 can be transformed into a spherical particle (spheroid) or an intermediate shortened filament with a flared end (I-forms) by exposure to a chloroform-water interface at 22 or 4 degrees C, respectively. The protein composition of bacteriophage f1 spheroids and I-forms was examined by separating the proteins from the purified. [35S]cysteine-labeled particles by sodium dodecyl sulfate-urea-polyacrylamide gel electrophoresis. Quantitation of the radioactivity on the gels showed that I-forms and spheroids contain the same complement of minor coat proteins as do untreated f1 phage. This composition is unchanged after removal of the DNA, either by digestion with micrococcal nuclease or by centrifugation of the particles through CsCl density gradients, indicating that none of the minor coat proteins is held in the particles solely through an interaction with the DNA. We also examined the location of the A protein in I-forms by decoration with ferritin-conjugated antibodies and examination under the electron microscope and found that the A protein is located specifically at the flared end of the I-form particle, through which the DNA is extruded and at which contraction into spheroids begins. The implications of these results with regard to the orientation of the DNA within the capsid and the process of infection are discussed.

Capsid↗
PubMed1982

Neural tube defects in Havana City--incidence and prenatal diagnosis.

An evaluation was made of all cases of neural tube defects born in seven gynaecological hospitals and obstetric centres of Havana, between 1970 and 1980. Neural tube defects were recordable from 492 infants out of 319,228 births. The families concerned were briefed in human genetics and informed about the possibility of prenatal diagnosis of anencephaly and bifid spine (spina bifida aperta). Some of them had a record of this defect. Amniocentesis was applied to 30 women with an empirical risk of 1:20, and alphafoetoprotein was analysed in their amniotic fluid. Anencephaly was diagnosed in one case and confirmed by termination of pregnancy. The occurrence of neural tube defects usually is of spontaneous nature, and incidence is relatively high. Therefore efforts are now being made to introduce a scheme of prenatal screening based on alphafoetoprotein assessment in the serum of pregnant women.

Amniocentesis↗