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Biomedical subjects

L A Lopez

Publications and source records attributed to L A Lopez.

18 recordsLinked to original sources
PubMed2005

Dehydroleucodine inhibits vascular smooth muscle cell proliferation in G2 phase.

Vascular smooth muscle cell (VSMC) proliferation plays an important role in the development of atherosclerosis and in the vascular changes seen in hypertension. Dehydroleucodine (DhL) is a sesquiterpene lactone that inhibits cell proliferation in plant cells. In this paper, we study the effect of DhL in the proliferation of VSMCs stimulated with 10% fetal bovine serum (FBS). Very low concentrations of DhL (2-6 microM) inhibited VSMC proliferation and induced cell accumulation in G2. DhL did not affect the dynamics of 3H-thymidine incorporation, and did not modify either the activity of DNA polymerase or the incorporation of deoxyribonucleotides in an in vitro assay. Moreover, DhL did not induce apoptosis in VSMCs. These results indicate that DhL, in very low concentration, induces a transient arrest of VSMCs in G2. Our data show that VSMCs are especially sensitive to DhL effect, suggesting that DhL could be potentially useful to prevent the vascular pathological changes seen in hypertension and other vascular diseases.

Animals↗
PubMed1996

Postnatal intussusception in a premature infant, causing jejunal atresia.

The authors report on a 5-week-old boy who presented with bilious gastric aspirates. He became intolerant to feedings after 1 week of adequate feeding and passage of stools. Based on clinical and radiological findings, the diagnosis of intestinal obstruction was made. During laparotomy, atresia of the proximal jejunum was found. The lumen of the distal segment contained an intussusceptum. The blind ends were resected, and end-to-end anastomosis was performed.

Anastomosis, Surgical↗
PubMed1996

Prevalence of abnormal levels of serum tumour markers in elderly people.

The study was conducted to evaluate the prevalence of abnormal levels of several serum tumour markers in an institutionalized elderly population. Serum tumour markers assay of carcinoembryonic antigen (CEA), the carbohydrate antigens CA 19-9, CA 72-4 and CA 15-3 (Enzymun-test, Boehringer Mannheim GmbH Diagnostic), alpha-fetoprotein (AFP) and prostate specific antigen (PSA) (Abbot Diagnostic Division) were performed in 228 unselected, institutionalized elderly subjects, whose mean age (SD) was 82.4 (5. 79) range (66-99 years). Patients with acute or neoplastic diseases were excluded from the study. The serum markers were also measured in 52 healthy young adults (controls). Using the established threshold values, 92 subjects (40%) were found to have at least one elevated marker. PSA was elevated in 33%, CA 19-9 in 16%, CEA in 11. 5%, CA 15-3 in 11%, CA 72-4 in 8% and AFP in 3%. We found a significant difference in the serum levels between the two groups for CEA, CA 19-9. CA 15-3, and PSA (p < 0.0001). Healthy aged people appear to have an elevated prevalence of elevated levels of serum tumour markers. The results suggest that apart from PSA, elevated antigen levels in elderly subjects are related to the ageing process itself rather than to occult pathology.

Aged↗
PubMed1996

Effects of prenatal care on neonates born to drug-using women.

This study examined whether prenatal care ameliorates the adverse effects of illicit drug use during pregnancy. We reviewed medical records of 336 women who delivered at the university hospital for results of urine drug screens, maternal history, infant outcome, and presence of prenatal care. Ninety-one women tested positive for illicit drugs, of whom 60 obtained prenatal care. We associated use of marijuana with increased risk of fetal distress; cocaine use with decreased birth weight, smaller head circumference, anemia, and meconium-stained amniotic fluid; and multiple drug use with decreased weight and meconium-stained fluid. Drug-using women who obtained prenatal care delivered infants of greater weight and with larger head circumferences than did those who obtained no care (p < .05). These results confirm the adverse effects of illicit drug use during pregnancy.

Adolescent↗
PubMed1995

Substance use during pregnancy and peripartum complications in a triethnic population.

To study the effects of illicit drug use during pregnancy on maternal health, we reviewed the records of women who delivered at the University of Texas Medical Branch between June 1, 1989, and February 28, 1990, for peripartum history and results from drug urinalysis screens. After controlling for age at delivery, gravidity, race/ethnicity, and use of alcohol or tobacco, elevated relative risk estimates were observed among women who had positive urinalysis for syphilis, gonorrhea, pregnancy-induced hypertension, chorioamnionitis, asthma, and postpartum hemorrhage. These findings confirm that pregnant women who use illicit drugs are at increased risk for serious health complications.

Adult↗
PubMed1993

Steric inhibition of cytoplasmic dynein and kinesin motility by MAP2.

Using several in vitro motility assays, we found that motility driven by the microtubule (MT) motors, kinesin and cytoplasmic dynein, could be inhibited by MAP2 but not by tau protein or the MT-binding proteolytic fragment of MAP2. In MT gliding assays, even the presence of one MAP2 molecule per sixty-nine tubulin dimers caused an inhibition of about 75% of MT motility at low concentrations of both motors. The percent inhibition of motility decreased with increasing concentration of either motor, suggesting that the inhibition was the result of competition for access to the MT surface. The decrease in the number of moving MTs with MAP2 was correlated with an increase in the frequency of release of moving MTs from the motor-coated glass. In assays of in vitro vesicular organelle motility and formation of ER networks, the presence of MAP2 inhibited small vesicle movements and to a lesser extent ER network formation. To determine if competition for specific sites on the MT or coating of the MT surface inhibited motility, we used tau protein and the chymotryptic MT-binding fragments of MAP2 to coat MTs. No inhibition was observed and there was even an increase in the number of attached and moving MTs in the gliding assay with tau-coated MTs. Because MAP2, tau and the chymotryptic MT-binding fragments of MAP2 bind to the same domain on tubulin, masking of the MT surface sites does not appear responsible for the inhibition of motility by MAP2. Rather, we suggest that the sidearm of MAP2 interfered with the interaction of motors with MTs and caused a dramatic increase in the rate of MT release. In vivo, MAP2 could play a major role in the generation of cellular polarity even at substoichiometric levels by inhibiting transport on microtubules in specific domains of the cytoplasm.

Animals↗
PubMed1990

Tetanus toxin-induced protein kinase C activation and elevated serotonin levels in the perinatal rat brain.

A single intracerebral injection of tetanus toxin (TeTox) is able to produce a time-dependent translocation of Ca2(+)-phosphatidylserine-dependent protein kinase C (PKC) in close-to-term rat brain. TeTox-triggered translocation of PKC is dose- and time-dependent, can be prevented by tetanus antitoxin, and does not occur upon administration of toxin fragments B and C. TeTox-triggered PKC translocation is accompanied by a time-dependent increase in brain serotonin (5-HT). Increase of brain 5-HT is independent of monoamine oxidase inhibition by pargyline. Phorbol ester and TeTox cause a significant increase in serotonin while H-7, a kinase inhibitor, does not affect serotonin levels but abolishes the effect of TeTox. Gangliosides prevent TeTox-triggered 5-HT increase. The data are consistent with the possibility that TeTox acts effectively on the serotonergic innervation, presumably in conjunction with PKC to cause accumulation of serotonin.

Animals↗
PubMed1987

Differential antigen-presenting cell requirements of hapten-specific T cell lines restricted to class II determinants.

We used a panel of class II-restricted T cell lines (TCL), generated against trinitrophenyl (TNP)-modified autologous peripheral blood mononuclear cells (PBMC), to examine the antigen-presenting functions of various PBMC-derived class II-positive cell types, including adherent cells, B + null cells, and activated T cells. However, activated T cells and transformed or activated B cells differed in their ability to present TNP to the TCL; TNP-modified activated lymphocytes stimulated only a subset of the class II-restricted TCL that responded to class II-positive resting cells. Moreover, certain antigen-specific TCL distinguished between antigen presented on activated T cells and transformed B cells. The differences in stimulatory capacity for particular TCL did not appear to reflect differences in the expression of class II molecules or in the ability of these cells to deliver hormonal signals or process antigen. Instead, the data suggest that differences in the ability of the cells to recognize antigen on the surface of different class II-positive cells may be a function of a secondary cell surface interaction.

Antigen-Presenting Cells↗
PubMed1986

The in vivo effect of low body temperatures on the degree of polymerization of tubulin in brain and testes: a comparison among some species of vertebrates.

The tubulin of both brain and testes of the amphibian Bufo spinulosus, Leptodactylus ocellatus and Odontophrynus occidentalis and of the fish Salvelinus fontinalis were partially depolymerized when the animals were maintained on ice for 90 min. Recovery of the animals at room temperature restored the normal degree of polymerization in both organs. The cerebral tubulin of the saurian Phymatura palluma and of the mammalian Myotis chiloensis instead, were not depolymerized in these conditions. The results suggest that the depolymerization in vivo of tubulin by lowering body temperature at 0-2 degrees C, is common to many, but not all species of vertebrates. The existence of a cold stabilizing factor in the brain of some species is suggested. A comparison is made between these results and those of other authors who observed microtubule disaggregation by cold with the electron microscope.

Amphibians↗
PubMed1985

Oligosaccharide-dependent and independent Qa-1 determinants.

A contribution of N-linked oligosaccharides to determinants recognized by alloreactive cytotoxic T lymphocytes has not been demonstrated. Employing cloned CTL and tunicamycin, an inhibitor of protein glycosylation, we found that carbohydrate addition was required for the formation of two of six Qa-1 determinants. The other determinants were detectable on nonglycosylated Qa-1 molecules, similar to observations in most reports that allodeterminants on class I molecules are not dependent on glycosylation for serologic detection. Examination of TM-treated, Con A-activated lymphoblasts revealed a direct correlation between the determinants defined by the reactivity of CTL clones with target cells from four Qa-1 genotypes and their dependence on carbohydrate side chains for expression. Most anti-Qa-1b CTL clones recognized either a glycosylation-dependent determinant found only on Qa-1b cells or glycosylation-independent determinants on both Qa-1b and Qa-1c cells. Similarly, clones that killed only Qa-1a cells recognized a glycosylation-independent determinant. However, clones reactive with both Qa-1a and Qa-1d cells recognized a glycosylation-dependent determinant on Qa-1a molecules and a glycosylation-independent determinant on Qa-1d molecules. This result indicates that such clones recognize cross-reactive conformational determinants, not carbohydrate itself. Thus, N-linked oligosaccharides serve to stabilize the conformation of some Qa-1 determinants, but others remain intact on nonglycosylated molecules. The absence of similar data for H-2K/D/L molecules suggest that a reexamination of other class I antigens with cloned CTL is in order to determine whether Qa-1 molecules are unique.

Animals↗
PubMed1982

In vivo and in vitro effect of cold on the degree of polymerization of tubulin in toad brain and testis.

The tubulin of both brain and testis of the toad Bufo arenarum was partially depolymerized when the animals were maintained on ice for 90 minutes or 17 hours. Recovery of the animals at room temperature restored the normal degree of polymerization in both organs. Normalization of the polymerization degree also occurred in organs separated from cooled animals and incubated in vitro for 90 minutes at 20 degrees C. When the organs were cooled in vitro, only testicular tubulin underwent depolymerization, and in a degree similar to that occurring by incubation at 20 degrees C. The results suggest that the mechanisms regulating tubulin depolymerization in vivo are different from those taking place in vitro.

Animals↗
PubMed1979

Absorbability of plant sterols and their distribution in rabbit tissues.

Rabbits were fed a low cholesterol diet containing 2% plant sterols for 10 weeks to determine the absorbability of these sterols and their deposition in the tissues. We found campesterol and beta-sitosterol in the blood and tissues. The plasma campesterol levels were 4.34--13.3 mg/100 ml, whereas, beta-sitosterol levels were 0.41--1 mg/100 ml. Stigmasterol was not detected. The total plasma plant sterol concentration was about 10% of the total plasma sterol. The mean terminal plasma cholesterol concentration averaged 60% higher (55 vs. 88 mg/100 ml, P less than 0.001) than the mean initial value. Campesterol was the preponderant sterol in all tissues studied, including the aorta. Sitosterol was found in small amounts in the tissues of the abdominal organs. Stigmasterol was not detected in any tissue studied. Esterified campesterol and sitosterol were detected in trace amounts in most tissues. Campesterol and sitosterol, particularly the former, accumulated in the tissues including the aorta.

Animals↗
PubMedDate not supplied

Epidermolysis bullosa associated with congenital localized absence of skin, fetal abdominal mass, and pyloric atresia.

A 2320-g male infant was delivered at 35 weeks gestation to a mother who had polyhydramnios. He had a combination of congenital localized absence of skin, unilateral hydronephrosis, and hydroureter due to ureterovesical obstruction, and nonbilious vomiting due to pyloric atresia. Blistering of the skin developed after birth. Epidermolysis bullosa simplex was confirmed by electron microscopy of a skin biopsy specimen. We describe this patient, who had three unusual manifestations of epidermolysis bullosa.

Abnormalities, Multiple↗