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Biomedical subjects

L Perez

Publications and source records attributed to L Perez.

At least 37 records · Page 2Linked to original sources
PubMed2000

Hedgehog induces opposite changes in turnover and subcellular localization of patched and smoothened.

Secreted signaling proteins of the Hedgehog family organize spatial pattern during animal development. Two integral membrane proteins have been identified with distinct roles in Hedgehog signaling. Patched functions in Hedgehog binding, and Smoothened functions in transducing the signal. Current models view Patched and Smoothened as a preformed receptor complex that is activated by Hedgehog binding. Here we present evidence that Patched destabilizes Smoothened in the absence of Hedgehog. Hedgehog binding causes removal of Patched from the cell surface. In contrast, Hedgehog causes phosphorylation, stabilization, and accumulation of Smoothened at the cell surface. Comparable effects can be produced by removing Patched from cells by RNA-mediated interference. These findings raise the possibility that Patched acts indirectly to regulate Smoothened activity.

Animals↗
PubMed2000

Glycosyltransferase activity of Fringe modulates Notch-Delta interactions.

Ligands that are capable of activating Notch family receptors are broadly expressed in animal development, but their activity is tightly regulated to allow formation of tissue boundaries. Members of the fringe gene family have been implicated in limiting Notch activation during boundary formation, but the mechanism of Fringe function has not been determined. Here we present evidence that Fringe acts in the Golgi as a glycosyltransferase enzyme that modifies the epidermal growth factor (EGF) modules of Notch and alters the ability of Notch to bind its ligand Delta. Fringe catalyses the addition of N-acetylglucosamine to fucose, which is consistent with a role in the elongation of O-linked fucose O-glycosylation that is associated with EGF repeats. We suggest that cell-type-specific modification of glycosylation may provide a general mechanism to regulate ligand-receptor interactions in vivo.

Alkaline Phosphatase↗
PubMed2000

Essential role of p38alpha MAP kinase in placental but not embryonic cardiovascular development.

p38alpha MAP kinase is activated in response to many cellular stresses and also regulates the differentiation and/or survival of various cell types in vitro, including skeletal muscle cells and cardiomyocytes. Here we show that targeted inactivation of the mouse p38alpha gene results in embryonic lethality at midgestation correlating with a massive reduction of the myocardium and malformation of blood vessels in the head region. However, this defect appears to be secondary to insufficient oxygen and nutrient transfer across the placenta. When the placental defect was rescued, p38alpha(-/-) embryos developed to term and were normal in appearance. Our results indicate that p38alpha is required for placental organogenesis but is not essential for other aspects of mammalian embryonic development.

Animals↗
PubMed2000

[Histologic study of experimental spleen transplant in rats].

BACKGROUND: The objective of this paper was to demonstrate that the grafts of cervical splenic transplantation on rats using our experimental model present a normal histological appearance. METHODS: Isogenic consanguineous Lewis rats 12 weeks old and weighing 250 gr. were used. Histological findings of a group of 25 cervical splenic grafts transplanted by means of splinting vascular venous microanastomoses and a group of 25 splenic grafts autotransplanted in the omentum were compared with a control group. The specimens were assigned according to a score of 0 to 4, following Moore's histological criteria. RESULTS: All grafts in transplanted and autotransplanted groups had a score of 3 or 4. Then, all splenic grafts from the transplanted group had histological findings very similar to a normal spleen. In the autotransplantation group, the percentage of grafts with a score 3 (60%) was superior to the transplantation group (46%). However, the transplantation group presented a percentage of score 4 (54%), superior to the autotransplantation group (40%). CONCLUSIONS: In our study all grafts from the cervical spleen transplantation group had histological findings very similar to a normal spleen. The percentage of spleens with histological normality in the transplantation group was superior to the autotransplantation group. However, there was no statistical significance.

Animals↗
PubMed1999

Insulin activates protein kinases C-zeta and C-lambda by an autophosphorylation-dependent mechanism and stimulates their translocation to GLUT4 vesicles and other membrane fractions in rat adipocytes.

In rat adipocytes, insulin provoked rapid increases in (a) endogenous immunoprecipitable combined protein kinase C (PKC)-zeta/lambda activity in plasma membranes and microsomes and (b) immunoreactive PKC-zeta and PKC-lambda in GLUT4 vesicles. Activity and autophosphorylation of immunoprecipitable epitope-tagged PKC-zeta and PKC-lambda were also increased by insulin in situ and phosphatidylinositol 3,4,5-(PO(4))(3) (PIP(3)) in vitro. Because phosphoinositide-dependent kinase-1 (PDK-1) is required for phosphorylation of activation loops of PKC-zeta and protein kinase B, we compared their activation. Both RO 31-8220 and myristoylated PKC-zeta pseudosubstrate blocked insulin-induced activation and autophosphorylation of PKC-zeta/lambda but did not inhibit PDK-1-dependent (a) protein kinase B phosphorylation/activation or (b) threonine 410 phosphorylation in the activation loop of PKC-zeta. Also, insulin in situ and PIP(3) in vitro activated and stimulated autophosphorylation of a PKC-zeta mutant, in which threonine 410 is replaced by glutamate (but not by an inactivating alanine) and cannot be activated by PDK-1. Surprisingly, insulin activated a truncated PKC-zeta that lacks the regulatory (presumably PIP(3)-binding) domain; this may reflect PIP(3) effects on PDK-1 or transphosphorylation by endogenous full-length PKC-zeta. Our findings suggest that insulin activates both PKC-zeta and PKC-lambda in plasma membranes, microsomes, and GLUT4 vesicles by a mechanism requiring increases in PIP(3), PDK-1-dependent phosphorylation of activation loop sites in PKC-zeta and lambda, and subsequent autophosphorylation and/or transphosphorylation.

Adipocytes↗
PubMed1998

Mapping of linear antibody epitopes of the glycoprotein of VHSV, a salmonid rhabdovirus.

Antibody linear epitopes of the glycoprotein G (gpG) of the viral haemorrhagic septicaemia virus (VHSV), a rhabdovirus of salmonids, were mapped by pepscan using overlapping 15-mer peptides covering the entire gpG sequence and ELISA with polyclonal and monoclonal murine and polyclonal trout antibodies. Among the regions recognized in the pepscan by the polyclonal antibodies (PAbs) were the previously identified phosphatidylserine binding heptad-repeats (Estepa & Coll 1996; Virology 216:60-70) and leucocyte stimulating peptides (Lorenzo et al. 1995; Virology 212:348-355). Among 17 monoclonal antibodies (MAbs), only 2 non-neutralizing MAbs, 110 (aa 139-153) and IP1H3 (aa 399-413), could be mapped to specific peptides in the pepscan of the gpG. Mapping of these MAbs was confirmed by immunoblotting with recombinant proteins and/or other synthetic peptides covering those sequences. None of the neutralizing MAbs tested reacted with any of the gpG peptides. Previously mapped MAb resistant mutants in the gpG did not coincide with any of the linear epitopes defined by the pepscan strategy, suggesting the complementarity of the 2 methods for the identification of antibody recognition sites.

Animals↗
PubMed1998

PDGF-receptor tyrosine kinase blocker AG1295 selectively attenuates smooth muscle cell growth in vitro and reduces neointimal formation after balloon angioplasty in swine.

BACKGROUND: Signaling through protein tyrosine kinases (PTKs) is a major contributor to the transmission of mitogenic stimuli to the interior of the cell and nucleus. The present study was designed to determine the effect of the tyrphostin AG1295, a selective blocker of PDGF-receptor PTK, on the growth of porcine and human smooth muscle cells (SMCs) in culture, on the outgrowth kinetics of SMCs from porcine and human arterial explants, and on neointimal formation after balloon injury in pigs. METHODS AND RESULTS: SMCs for culture were obtained from porcine abdominal aortas, human internal mammary arteries, and endarterectomy tissue from a single human carotid artery. Addition of AG1295 to SMCs before PDGF stimulation completely inhibited PDGF-beta-receptor tyrosine phosphorylation without affecting the level of PDGF-beta-receptor. AG1295 resulted in a selective, reversible inhibition of SMC proliferation in culture (76%) with only mild (13.5%) inhibition of endothelial cell proliferation. The number of SMCs accumulating around explants of porcine carotid arteries and human endarterectomy specimens 12, 15, 19, 22, and 24 days after plating was reduced by 82% to 92% in AG1295-treated compared with nontreated specimens, and initiation of SMC outgrowth was markedly delayed. The numbers of cells accumulated 10 days after initiation of outgrowth were significantly lower in treated versus control explants. Local intravascular delivery of AG1295-impregnated polylactic acid-based nanoparticles (130+/-25 nm) to the site of balloon injury to porcine femoral arteries resulted in significant reductions in intima/media area ratio and luminal cross-sectional area narrowing by neointima compared with contralateral control arteries to which empty nanoparticles were applied (0.15+/-0.07 versus 0.09+/-0.03, P=.046 and 20+/-4% versus 10+/-4%, P=.0009, n=6 for both). CONCLUSIONS: The tyrphostin AG1295, a selective blocker of PDGF-receptor kinase, exerts a marked inhibitory effect on the activation, migration, and proliferation of porcine and human SMCs in vitro and an approximately 50% inhibitory effect on neointimal formation after balloon injury in porcine femoral arteries when delivered via biodegradable nanoparticles. Further studies appear to be warranted to evaluate the applicability of this novel approach to the interventional setting.

Angioplasty, Balloon↗
PubMed1998

Purification of the glycoprotein G from viral haemorrhagic septicaemia virus, a fish rhabdovirus, by lectin affinity chromatography.

A new method for the isolation of glycoprotein G from viral haemorrhagic septicaemia virus (VHSV), a fish rhabdovirus, was developed by using affinity chromatography with immobilized Concanavalin A (ConA). The glycoprotein G was isolated from detergent solubilized concentrated virions and from large-volume virion-free supernatants from VHSV infected cells (soluble form). The purity achieved was higher than 85%. The estimated recovery of the initial glycoprotein G present in the virions was between 20 and 50%. These glycoprotein G preparations showed the presence of about 30% of trimers by ultracentrifugation, reacted with antibodies to the phosphatidylserine binding domain (p2) in a pH-dependent manner by ELISA and bound phosphatidylserine in a pH-dependent manner by solid-phase binding assays. These data suggest that ConA purified glycoprotein G conserved most of its native properties and conformation.

Animals↗
PubMed1998

The first clinical and epidemiological programme on renal disease in Bolivia: a model for prevention and early diagnosis of renal diseases in the developing countries.

BACKGROUND: The prevalence and incidence of renal diseases in developing countries are not known. This lack of knowledge is an obstacle to the adoption of preventive measures which may be of great value in a social and economic environment where treatment options for end-stage renal failure are simply not available to the vast majority of the population. Urinalysis, a simple and inexpensive test, remains a cornerstone in the evaluation of the kidney and may also be easily employed in mass screening for renal abnormalities in a developing country. METHODS: An educational campaign on renal diseases was conducted in three selected areas of Bolivia. Urine samples were collected and sent to one of 21 participating clinical centers. Fresh urine specimens were screened using a dipstick for chemical analysis and by microscopic urinalysis after centrifugation. In those patients in whom urinary abnormalities were found, further investigations were carried out in order to define the diagnosis; these patients were enrolled in a 3-year follow-up program. RESULTS: Apparently healthy subjects (n = 14,082) were referred to the First Clinical and Epidemiological Program of Renal Diseases from rural and metropolitan areas in Bolivia. Urinary abnormalities were detected in 4261 subjects at first screening. The most common form of urinary abnormality was hematuria, which was found in 2010 (47% of positively screened subjects). Other renal abnormalities were leukocyturia (41%) and proteinuria (11%). Confirmatory tests and further clinical studies were then carried out in 1019 people. On a second screening 35% of the subjects had no urinary abnormalities; in the remaining people the following diagnosis were made: asymptomatic urinary-tract infection (48.4%), isolated benign hematuria (43.9%), chronic renal failure (1.6%), renal tuberculosis (1.6%). Other diagnosis were: renal stones 1.3%, diabetic nephropathy 1% and polycystic kidney diseases 1.9%. CONCLUSIONS: This study helped define for the first time the frequency of asymptomatic renal diseases in Bolivia. It shows that it is possible to screen a large population of patients at relatively low cost, providing the framework for further action that may help in the prevention and timely diagnosis of renal diseases.

Adolescent↗
PubMed1998

Trauma patients 75 years and older: long-term follow-up results justify aggressive management.

BACKGROUND: Long-term survival rate and functional status after trauma for one of the fastest growing segments of the population, patients 75 years and older, is poorly documented. METHODS: Trauma patients 75 years and older who were discharged from our Level I trauma center between June 1988 and July 1992 (n = 279) were contacted by mail or phone. Public death records were used to identify patients who had died. A stepwise logistic regression analysis was performed to determine predictors of poor outcome (death within 6 months). Main outcome measures included mortality and self-assessed functional status. RESULTS: A minimum 4-year follow-up was obtained for 81% of the 279 study patients. The mean follow-up period was 5.4 +/- 1.1 years. Mean age at time of injury was 81 +/- 5 years (range, 75-101 years); mean Injury Severity Score was 9.4 +/- 7.7. At follow-up, 132 patients (47%) had died, 93 patients (33%) were contacted, and 54 patients (19%) could not be located. Twelve percent of patients survived less than 6 months after discharge. Poor survival was predicted by preexisting diseases (dementia, p = 0.001; hypertension, p = 0.02; and chronic obstructive pulmonary disease, p = 0.05) and not by age or severity of injury. The mean age of patients still living was 85 +/- 3.9 years (range, 79-99 years), and 77 of 93 patients were living in an independent setting (33 alone, 44 with spouse or family); of these, 57% reported no difficulties in performing 12 of 14 activities of daily living. CONCLUSION: Despite higher than expected mortality after discharge, aggressive management of trauma patients 75 years and older is justified by the favorable long-term outcome.

Activities of Daily Living↗
PubMed1998

Forage of different physical forms in the diets of lactating Granadina goats: nutrient digestibility and milk production and composition.

To determine whether the energy balance of goats or characteristics of the diet consumed were the principal factors that determined milk production, feeding and digestion trials were carried out using two groups of 5 Granadina goats. The concentrate fraction of both diets was the same, but the forage fraction of the diets differed. In diet 1, the forage was in the form of long alfalfa hay, and, in diet 2, forage was in the form of pelleted alfalfa. Intake and the forage to concentrate ratio of the two diets were not significantly different, although diet 2 was more digestible. The amount of fat and protein in the milk depended on energy intake and not on dietary treatment. The milk protein of goats fed diet 2 was higher in casein. No sensible differences were noted in the fatty acid composition of the milk. Nitrogen and metabolizable energy utilization for milk production was greater for goats fed diet 2. According to the results obtained, it would seem advantageous to use pelleted alfalfa rather than alfalfa hay in the diets of goats.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Marginal microleakage around enamel and cementum surfaces of two compomers.

The purpose of this study was to evaluate the marginal microleakage of two compomers, placed in enamel and cementum. The buccal and lingual surfaces of twenty human premolar teeth were used. Materials used were Dyract and Compoglass. Teeth were randomly divided into 4 groups of 5 teeth each. Materials were handled according to the instructions of the manufacturer. Class V cavities were prepared with enamel and cementum margins. The groups with etched surfaces was done using 37% phosphoric acid. Two percent fuchsin was used for microleakage study. Results were evaluated using an analysis of ANOVA. These showed that microleakage in enamel was significantly less than in cementum. No significant differences in microleakage were seen between the two materials or between etched and unetched surfaces.

Acid Etching, Dental↗
PubMed1997

Conditioned immunomodulation: investigations of the role of endogenous activity at mu, kappa, and delta opioid receptor subtypes.

The present investigations were designed to determine the role of activity at mu, kappa, and delta opioid receptor subtypes in conditioned immunomodulation by evaluating the effects of selective opioid receptor antagonists on conditioned stimulus-induced alterations in immune status. Lewis rats were exposed to an aversive conditioned stimulus that was developed through pairings with electric footshock. This aversive conditioned stimulus induces a reduction in splenic natural killer cell activity, splenocyte proliferation in response to mitogens, and diminished levels of interferon-gamma (IFN-gamma) production by splenocytes. Intracerebroventricular (i.c.v.) administration of the opioid antagonist naltrexone or the mu 1-selective antagonist naloxonazine blocked conditioned alterations of immune status, indicating that activity at mu-opioid receptors is involved in conditioned immunomodulation. Further support for the involvement of mu-opioid receptors within the central nervous system is provided by data showing that peripheral administration of naloxonazine, at doses shown to be effective when administered i.c.v., had no effect on conditioned alterations of immune status. Ventricular administration of the kappa receptor antagonist nor-binaltorphimine (nor-BNI) did not antagonize the immunomodulatory effects of the conditioned stimulus. Administration of the delta receptor antagonist naltrindole also did not antagonize the conditioned alterations of immune status. Collectively, the results of this study indicate that the alterations of immune status produced by an aversive conditioned stimulus require activity at mu-opioid receptors, possibly mu 1, within the central nervous system.

Animals↗
PubMed1996

The structural proteins of infectious pancreatic virus are not glycosylated.

The major capsid protein, VP2, of infectious pancreatic necrosis virus, a nonenveloped icosahedral virus, contains six N-glycosylation consensus sequences (Asn-X-[Thr/Ser]). Since VP2 contains the major virus-neutralizing epitopes, the possible role for glycosylation in capsid formation and antigenicity was examined. The carbohydrate content of the virion proteins was determined by chemical detection, pulse-chase experiments,[3H]mannose labeling, and alteration of protein migration on sodium dodecyl sulfate-polyacrylamide gels after tunicamycin treatment. No glycosylation of any virion protein was observed when the carbohydrate nature of the glycoprotein of infectious hematopoietic necrosis virus was detected.

Animals↗
PubMed1995

Terminal differentiation of spontaneous rheumatoid factor-secreting B cells from rheumatoid arthritis patients depends on endogenous interleukin-10.

OBJECTIVE: The presence of serum rheumatoid factor (RF) and spontaneous RF-secreting B cells is a common feature in most patients with rheumatoid arthritis (RA). This study analyzed the cytokine(s) that controls the final maturation of B cells capable of spontaneous IgM-RF secretion in vitro. METHODS: RA patients' peripheral blood mononuclear cells (PBMC), as well as adherent and nonadherent cell fractions, were cultured, and spontaneous IgM-RF and interleukin-10 (IL-10) secretion were determined by enzyme-linked immunosorbent assay. RESULTS: The RF+ RA PBMC, but not PBMC from RF- RA patients or healthy controls, actively produced IgM-RF in a linear manner for 14 days. This activity depended on the presence of fetal calf serum and did not require cellular DNA synthesis. Spontaneous IgM-RF secretion depended on IL-10, as deduced from the following findings: 1) IL-10, but not a variety of cytokines including IL-6, restored missing IgM-RF secretion by PBMC in serum-free supplemented cultures; 2) the addition of anti-IL-10, but not anti-IL-6, blocking antibodies inhibited PBMC IgM-RF secretion, and this effect could be reversed by exogenous IL-10; and 3) RA PBMC actively produced IL-10 in vitro. The cells responsible for endogenous IL-10 production were found in the adherent cell fraction. Finally, IL-10 induced IgM-RF, but not total IgM, secretion by RA PBMC. CONCLUSION: In patients with RA, circulating B cells capable of spontaneous IgM-RF secretion require IL-10 production by adherent cells to reach terminal maturation.

Arthritis, Rheumatoid↗
PubMed1995

The population of Cuba: the growth and characteristics of its labor force.

"This paper analyzes Cuba's current demographic picture, and emphasizes the characteristics of its labor force that will influence dynamic change. Overall, the contribution of the labor force to the development of a market economy is likely to be positive, given its low dependency ratio, the high level of education, and the value placed on entrepreneurship."

Americas↗
PubMed1995

Corticotropin-releasing hormone is involved in conditioned stimulus-induced reduction of natural killer cell activity but not in conditioned alterations in cytokine production or proliferation responses.

Research from our laboratory has demonstrated that the presentation of an aversive conditioned stimulus produces pronounced suppression of several in vitro measures of immune status. The present study was designed to evaluate the role of central corticotropin-releasing hormone (CRH) in the mechanisms mediating these conditioned effects. The aversive conditioned stimulus was a distinct environment that had previously been associated with electric footshock. Lewis rats received intraventricular administration of either buffered saline or a dose of the CRH-selective receptor antagonist alpha-helical CRH(9-41) (0, 0.5, 5, or 50 micrograms) prior to exposure to the aversive conditioned stimulus or home cage control treatment. The aversive conditioned stimulus produced decreases in splenic natural killer cell activity, splenocyte responsiveness to the mitogens concanavalin A (ConA), phytohemagglutinin (PHA), lipopolysaccharide (LPS), and the combination of ionomycin and phorbol myristate acetate (PMA), blood leukocyte responsiveness to ConA and PHA, and the production of interleukin-2 and interferon-gamma by activated splenocytes. The conditioned stimulus also produced an increase in plasma levels of corticosterone. Pretreatment with alpha-helical CRH(9-14) completely blocked the conditioned stimulus-induced suppression of natural killer cell activity. The CRH antagonist had no attenuative effect on the conditioned suppression of splenocyte or blood leukocyte proliferation in response to mitogens, or the production of interleukin-2 or interferon-gamma by activated splenocytes. There was also no effect of alpha-helical CRH(9-14) on the conditioned stimulus-induced increase in plasma corticosterone. These findings suggest that conditioned stimulus-induced suppression of natural killer cell activity is mediated by a mechanism that involves activity at central CRH receptors, and that this conditioned modulation is independent of HPA activation. Furthermore, these results indicate that the mechanisms involved in conditioned stimulus-induced suppression of proliferative or cytokine production responses are distinct from those involved in the modulation of natural killer cell activity.

Animals↗