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Biomedical subjects

A Ortega

Publications and source records attributed to A Ortega.

At least 127 records · Page 7Linked to original sources
PubMed1997

Effect of the organic Ca2+ channel blocker D-600 on sarcoplasmic reticulum Ca2+ uptake in skeletal muscle.

Experiments were undertaken to study the possibility that the calcium channel blocker D-600 (gallopamil), which penetrates into muscle cells (20), facilitates excitation-contraction coupling in skeletal muscle (7) by a direct effect on the sarcoplasmic reticulum (SR). The effects of D-600 were studied on single phasic muscle fibers, either intact or split open. D-600 potentiated twitches in intact fibers at concentrations lower than those reported in whole muscles. In split fibers, the force produced by caffeine-induced Ca2+ release from the SR was reversibly inhibited by 5 microM D-600, when added to the Ca2+ loading solution. This inhibitory effect was inversely related to temperature, and it was dose dependent. When D-600 was added after Ca2+ loading and before caffeine exposure, or during the caffeine exposure itself, it did not inhibit Ca2+ release, but rather increased the development of force. We conclude that, apart from the blocking effect that D-600 may have on the voltage sensor, the drug penetrates into the myoplasm and affects excitation-contraction coupling by inhibiting the SR Ca2+ pump. This may be the consequence of a conformational change in the transmembrane Ca2+ binding domain of the ATPase.

Animals↗
PubMed1997

A longitudinal study of transmission of tuberculosis in a large prison population.

The purpose of this study was to determine the extent of transmission of tuberculosis in a large prison population over an 18-mo period. Restriction-fragment-length polymorphism (RFLP) analysis of isolates of Mycobacterium tuberculosis was performed, using the insertion sequence IS6110 and the plasmid pTBN12. Patients infected with strains having the same fingerprint were grouped in clusters. Medical records were reviewed and movement of inmates among prisons was examined for selected patients. Tuberculosis was diagnosed in 216 inmates (case rate = 2,283 per 100,000 per year). Isolates from 210 (97%) patients were fingerprinted, 155 (74%) were grouped in 25 clusters, and 55 (26%) showed a unique fingerprint. Recent infection was inferred in 62% of these patients. Eighty-four percent (161 of 192) of patients tested were human immunodeficiency virus (HIV)-positive, of whom 121 were in clusters and 40 were not (p = 0.74). Patients in clusters were less adherent with tuberculosis treatment than those not in clusters (p < 0.05), and prison transmission of resistant strains was observed. It is crucial that infection control guidelines be fully implemented in the prison setting to prevent tuberculosis transmission.

Adult↗
PubMed1997

Pulmonary paragonimiasis and tuberculosis in Sorsogon, Philippines.

The clinical epidemiology of pulmonary paragonimiasis and tuberculosis was investigated in a known endemic municipality of Sorsogon, Philippines. Records of diagnosed tuberculosis patients on treatment and follow up at the local Rural Health Unit over a two year period from 1993 to 1994 were reviewed to provide an overview of pulmonary tuberculosis in the area, specifically to describe the population at risk, the basis for diagnosis and the proportion of case notification who were sputum negative. Patients from the same group of individuals as well as undiagnosed tuberculosis patients with productive cough, fever with chest and/or back pain, or hemoptysis were examined to look into clinical manifestations, duration of symptoms, history of crab-eating and sputum examination results for acid-fast bacilli and Paragonimus. There was difficulty in determining the number of non-responders as the records did not have any provision for the recording of such. Annual tuberculosis case notification rates for the two years (374 and 401 per 100,000 population) were higher than the national figure in 1991 (325 per 100,000 population) indicating that tuberculosis is still a major health problem in the area and tuberculosis control efforts may have to be more aggressive to better contain the disease. Twenty-six out of 160 individuals surveyed were sputum smear positive for Paragonimus. Paragonimiasis rates were not significantly different in the two groups (15.6% vs 16.9%, respectively) indicating that there is a need for routine sputum examination for Paragonimus which is not available at present. Only six patients surveyed were sputum smear positive for acid-fast bacilli. A high index of suspicion is necessary to diagnose paragonimiasis and to be able to differentiate it from tuberculosis. The diagnosis may be suggested by a patient's place of origin being a known endemic area, a long period of chronic cough and the habit of eating raw or insufficiently cooked crabs or crayfish. Laboratories in endemic areas should have the capacity to differentiate between the two infections by being able to provide the routine laboratory procedures necessary for definitive diagnosis and treatment.

Adolescent↗
PubMed1996

Cholesterol increases the thermal stability of the Ca2+/Mg(2+)-ATPase of cardiac microsomes.

The effect of membrane cholesterol on the thermal inactivation of Ca2+/Mg(2+)-ATPase activity of bovine cardiac microsome was measured and compared to the thermal denaturation profiles of the microsomes as measured by differential scanning calorimetry (DSC). Inactivation, defined as loss of activity, and denaturation, defined as conformational unfolding, were irreversible under the conditions used. Both thermal inactivation of Ca2+/Mg(2+)-ATPase activity and thermal denaturation were shifted to higher temperatures in microsomes enriched with cholesterol (37 +/- 5 micrograms cholesterol/mg protein, cholesterol/phospholipid molar ratio 0.31) compared to control microsomes (15 +/- 3 micrograms cholesterol/mg protein, molar ratio 0.12). Thermal inactivation was measured by two methods: first, measuring activity at room temperature as a function of heating to elevated temperatures at 1 K/min, where inactivation temperatures (T1, temperature of half activity) were 58.9 +/- 0.3 degrees C for control membranes and 59.9 +/- 0.1 degrees C for cholesterol-enriched membranes, respectively. Second, measuring ATPase activity as a function of time at constant temperature, where T1 values of 57.6 +/- 0.5 degrees C and 59.2 +/- 0.5 degrees C were determined for control and cholesterol-enriched membranes, respectively. DSC profiles of microsomal membranes consisting of a number of overlapping peaks were obtained. A well resolved component (transition C) was observed with a transition temperature (T 1/2) of 58.2 degrees C. This T 1/2, which is a measure of conformational stability, correlates with the T1 for Ca2+/Mg(2+)-ATPase activity and is 1.9 +/- 0.6 K higher in cholesterol-enriched membranes. Thus, the increased resistance to inactivation appears to be due to increased conformational stability of the protein induced by cholesterol, demonstrating that a change in lipid composition can influence the stability of an integral membrane protein in a natural membrane. The increased stability is of sufficient magnitude to account for the previously observed correlation between cholesterol content and resistance to heat shock in several cell lines.

Animals↗
PubMed1996

Membrane healing and restoration of contractility after mechanical injury in isolated skeletal muscle fibers of the frog.

In single isolated skeletal muscle fibers of the frog, we studied (i) the recovery from large sarcolemmal mechanical injuries of the response to electric stimulation and (ii) the integrity of the sarcolemma under the light microscope. In Ringer's solution, the damaged cells stopped contracting and deteriorated completely within 1 hr. In the presence of phosphatidylcholine (0.025 g/ml in Ringer's solution), the injured cells initially responded with local twitches. Within 0.5 hr, contractility and membrane integrity started to recover and both were back to control levels within 3 hr. When these cells were placed back in normal Ringer's solution, they remained viable and active for several hours. Our results suggest that phosphatidylcholine can protect muscle fibers from the effects of sarcolemmal injury.

Animals↗
PubMed1996

Entamoeba histolytica: involvement of pp125FAK in collagen-induced signal transduction.

The interaction of Entamoeba histolytica trophozoites with collagen involves cell adherence, formation, and release of electron dense granules (EDGs) containing collagenase activity leading to the degradation of the bound protein. The binding is thought to be mediated by an "integrin-like" collagen receptor. Since the signal transduction mechanisms triggered by the collagen-trophozoite interaction are unknown, but clearly involve cytoskeletal organization, we decided to explore the role of protein tyrosine phosphorylation in this process. Collagen induces a time-dependent increase in the phosphorylation of several polypeptides migrating around 67 and 110 kDa. One polypeptide of the high-molecular-weight component was identified as a 125-kDa protein with very similar epitopes to the focal treatment was a 42-kDa polypeptide related to the mitogen activated protein kinase (MAPK) family. Our results suggest that tyrosine phosphorylation is involved in collagen signaling in amoebas and that pp125FAK and p42MAPK homologs may play an active role in turning on the genetic program that enables the parasite to invade its host.

Animals↗
PubMed1996

Effect of melatonin on beta-tubulin and MAP2 expression in NIE-115 cells.

Physiological concentrations of the pineal hormone melatonin induce an increase of microtubules in neuroblastoma NIE-115 cells. This effect is due to an increase in the polymerization state of tubulin. Concomitantly, higher levels of soluble beta-tubulin are present in the treated cells. Unexpectedly, no significant changes in the levels of beta-tubulin or its mRNA occur in the presence of melatonin reflecting perhaps a strict control of its steady state in a physiological context. In contrast, higher amounts of microtubule-associated-protein 2 are found when the cells are exposed to melatonin. These findings support the idea that tubulin polymerization process is one of the targets of melatonin action. Furthermore, our results might explain the increase in the length and number of neurites present in these cells when they are treated with this hormone.

Biopolymers↗
PubMed1996

Changes in rat brain muscarinic receptors after inhibitory avoidance learning.

It is widely accepted that cerebral acetylcholine is necessary for learning and memory, but little is known about the type of muscarinic receptors involved in these functions. To investigate this problem, [3H]-N-methyl-scopolamine which binds to different types of muscarinic receptors, [3H]-Pirenzepine an M1 receptor antagonist, and [3H]-Oxotremorine-M which binds mainly to M2 receptors, were used as ligands to look for possible changes in muscarinic receptor density in neostriatum (NEO), hippocampus (HIP), amygdala (AMY), and temporo-parietal neocortex (CTX), after testing for retention of inhibitory avoidance, trained with high or low footshock intensities. After low reinforcement there was an M1 postsynaptic receptor up-regulation in NEO, HIP, and CTX, and an M2 presynaptic receptor down-regulation in HIP, which suggests a concerted pre- and postsynaptic cholinergic activation in this area. An up-regulation of both M1 and M2 receptors was detected in CTX of low and high footshocked animals, which indicates the presence of a cortical postsynaptic M2 receptor.

Amygdala↗
PubMed1996

Penetrating cardiac injuries.

Penetrating cardiac injuries pose a tremendous challenge to any trauma surgeon. Time, sound judgment, aggressive intervention, and surgical technique are the most important factors contributing to positive outcomes. This article extensively reviews the history, surgical management, and techniques needed to deal with these critical injuries. This year commemorates the one hundredth anniversary of the first successful repair of a cardiac injury.

Animals↗
PubMed1996

Apoptosis: a mechanism of cell killing and lymphoid organ impairment during acute African swine fever virus infection.

Induction of programmed cell death has been described during infection with many different viruses. We have investigated the influence of African swine fever virus (ASFV) on apoptosis of different cell populations during in vitro and in vivo infection. We observed apoptosis in ASFV-infected monocyte/macrophage and peripheral blood mononuclear cell cultures. Apoptosis was demonstrated in these cells by DNA fragmentation, DNA staining and DNA-associated histone fraction detection assays. Flow cytometry analysis of infected cultures also showed morphological and functional alterations, including changes in the cell cycle and percentage of cell fractions stained with propidium iodide. After in vivo infection with three different virulent strains of ASFV, apoptosis of infected cells from the mononuclear phagocytic system and closely related elements from different tissues was observed. Additionally, infected pigs showed an intense degree of apoptosis of lymphocytes, which are not infected by the virus. In lymph nodes and other lymphoid organs, broad bands of apoptotic cells presented typical nuclear changes under light microscopy. The occurrence of DNA fragmentation was confirmed in these tissues using terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling. These findings, together with the pathological observations in infected pigs of a depletion in cell populations in lymphoid organs, suggest that virus interference with programmed cell death plays a central role in pathogenesis of this disease, being responsible for lymphoid organ impairment in acute ASFV infection.

Acute Disease↗
PubMed1996

Tropism of human adenovirus type 5-based vectors in swine and their ability to protect against transmissible gastroenteritis coronavirus.

The infection of epithelia] swine testicle and intestinal porcine epithelial (IPEC-1) cell lines by adenovirus type 5 (Ad5) has been studied in vitro by using an Ad5-luciferase recombinant containing the firefly luciferase gene as a reporter. Porcine cell lines supported Ad5 replication, showing virus titers, kinetics of virus production, and luciferase expression levels similar to those obtained in human 293 cells, which constitutively express the 5'-end 11% of the Ad5 genome. The tropism of Ad5-based vectors in swine and its ability to induce an efficient immune response against heterologous antigens expressed by foreign genes inserted in these vectors has been determined. Ad5 vectors replicate and express heterologous antigens in porcine lungs and mediastinal and mesenteric lymph nodes. Significant levels of heterologous antigen expression were also demonstrated in the small intestine (jejunum and ileum), but Ad5 replication in this organ was very poor, suggesting that Ad vectors undergo an abortive replication in the porcine small intestine. The tissues infected by Ad5 were dependent on the inoculation route. The oronasal route appeared to be best for inoculation of bronchus-associated lymphoid tissue infection, while the intraperitoneal route was best for gut-associated lymphoid tissue infection. Epithelial cells of bronchioles, macrophages, type II pneumocytes, and follicular dendritic cells were identified as targets for Ad5, while epithelial cells of the intestine were not infected by Ad5. Viruses with a deletion from 79.5 to 84.8 map units in the E3 region, with or without heterologous inserted genes, replicated to lower levels in porcine tissues than did wild-type Ad5. It was also shown that an Ad5 recombinant expressing the four antigenic sites (A, B, C, and D) of transmissible gastroenteritis coronavirus (TGEV) spike protein induced in swine immune responses which neutralized TGEV infectivity. In addition, porcine serum from Ad-TGEV-immune animals provide passive protection when mixed with fully virulent TGEV and orally administered to highly susceptible newborn piglets. These results taken together indicate that swine may be a good animal model for human Ad5 lung infection to aid in the evaluation of candidate adenovirus vaccines and that Ad5 may be suitable as a recombinant viral vaccine or for other applications in swine.

Adenoviruses, Human↗
PubMed1996

Influence of the intake of fortified breakfast cereals on dietary habits and nutritional status of Spanish schoolchildren.

A study was performed on the breakfast habits of 200 schoolchildren between 9 and 13 years of age. The subjects were classified into two groups: group C, children who consumed fortified breakfast cereals (65 boys and 35 girls), and group NC, children who did not (64 boys and 36 girls). The different dietary habits and the nutritional status of the two groups were analyzed. Haematological, biochemical, anthropometric, and dietary data were collected, the latter involving a 5-day food record. The children of the C group were found not only to have a more complete and nutritive breakfast, but also showed better dietary patterns for the rest of the day. Their lipid intake (% kJ) was lower and the carbohydrate intake (g/d and % kJ) higher than in the NC children. The intakes of thiamine, pyridoxine, folates, and beta-carotenes were also higher in group C. Better dietary habits were reflected in higher blood levels of some important compounds. Group C children had higher retinol, serum folate, and riboflavin levels than NC children. The percentage of children with hypercholesterolaemia (serum cholesterol > 4.5 mmol/l) was higher amongst those of the NC group: 37% as compared with 18% of the C children.

Adolescent↗
PubMed1996

[Tuberculous hepatosplenic abscess, human immunodeficiency virus infection and multiresistant tuberculosis].

BACKGROUND: Tuberculosis (TB) with liver and/or spleen abscess (HSA) formation in HIV-positive patients is uncommon. PATIENTS AND METHODS: One hundred and thirty-seven HIV positive patients with TB were studied from January 93 to June 95. Patients with tuberculous HSA were enrolled in the study. Diagnosis was obtained by recovery of Mycobacterium tuberculosis in clinical specimens and the presence of hypoechogenic lesions in liver and/or spleen. RESULTS: M. tuberculosis isolates were resistant to some of the usual drugs in 51 patients. Twenty of these patients had HSA (39%) and in 18 patients the antibiotic sensitivity testing showed resistance to isoniazid, rifampin, ethambutol, and streptomycin. The remaining 86 patients had episodes of TB with drug-susceptible microorganism and only three patients had HSA (3%) (p < 0.001). The 23 patients with tuberculous HSA had a mean CD4+ lymphocyte count of 33 x 10(6) cells/L (2-111) and 7 had a previous episode of TB. The abdominal echography showed hepatosplenomegaly in all cases. Abscesses were located at the liver in 12 patients (52%), spleen in 18 (78%) and both organs in 7 (30%). In 16 cases a corticosteroid therapy was indicated. In the 3 patients with susceptible TB and HSA the clinical course was good. The 20 patients with resistant TB died. CONCLUSION: Abdominal TB in HIV-positive patients and HSA formation appears to be more common in severely immunosuppressed patients, with resistant TB and its mortality rate is high. The response to therapy with antituberculous drugs is slow and sometimes the administration of corticosteroids is necessary for the resolution of symptoms.

Abdominal Abscess↗