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Biomedical subjects

A Flores

Publications and source records attributed to A Flores.

At least 37 records · Page 2Linked to original sources
PubMed2001

Nitric oxide in the afferent synaptic transmission of the axolotl vestibular system.

This study was performed using intracellular and multiunit extracellular recording techniques in order to characterize the role of nitric oxide in the afferent synaptic transmission of the vestibular system of the axolotl (Ambystoma tigrinum). Bath application of nitric oxide synthase inhibitors N(G)-nitro-L-arginine (0.01microM to 10microM) and N-nitro-L-arginine methyl ester hydrochloride (0.1microM to 1000microM) elicited a dose-dependent decrease in the basal discharge of the semicircular canal afferent fibers. N(G)-Nitro-L-arginine also diminished the response to mechanical stimuli. Moreover, N(G)-nitro-L-arginine (1microM) produced a hyperpolarization associated with a decrease in the spike discharge and diminished the frequency of the excitatory postsynaptic potentials on afferent fibers recorded intracellularly. Nitric oxide donors were also tested: (i) S-nitroso-N-acetyl-DL-penicillamine (0.1microM to 100microM) increased the basal discharge and the response to mechanical stimuli. At the maximum effective concentration (100microM) this drug affected neither the amplitude nor the frequency of the excitatory postsynaptic potentials. However, it slightly depolarized the afferent neurons and decreased their input resistance. (ii) 3-Morpholino-sydnonimine hydrochloride did not significantly affect the basal discharge or the mechanically evoked peak response of afferent neurons at any of the concentrations used (1microM to 1000microM). However, after 10min of perfusion in the bath, 1microM and 10microM 3-morpholino-sydnonimine hydrochloride significantly modified the baseline of the mechanically evoked response, producing an increase in the mean spike discharge of the afferent fibers. These results indicate that nitric oxide may have a facilitatory role on the basal discharge and on the response to mechanical stimuli of the vestibular afferent fibers. Thus, nitric oxide probably participates in the sensory coding and adaptative changes of vestibular input in normal and pathological conditions.

Action Potentials↗
PubMed2001

Isoenzyme variability of five principal triatomine vector species of Chagas disease in Mexico.

Triatoma barberi, T. dimidiata, T. longipennis, T. pallidipennis and T. picturata, all key Chagas disease vectors in Mexico, were analysed by multilocus enzyme electrophoresis (MLEE) at 17 putative loci. The majority of insect specimens studied were collected from domestic and peridomestic structures from multiple geographic locations while others were collected from sylvatic areas. T. barberi was the least polymorphic species (P(0.95)=0.18), with polymorphism rates of the other species ranging from 0.29 to 0.50. T. barberi, a member of the protracta complex, clustered apart from the other studied species by Nei's genetic distance with >1.36, and at least eight loci were found to be diagnostic for this species. T. dimidiata was more related to T. longipennis, T. pallidipennis and T. picturata (phyllosoma complex) than to T. barberi, with a genetic distance averaging 0.36 with the phyllosoma complex species. In contrast, the genetic distances between the three phyllosoma complex species were not significantly different from zero, and there were no species-specific loci differentiating among them. The results strongly support the grouping of these three species in one complex, separate from the two other species studied.

Animals↗
PubMed2001

Influence of highly active anti-retroviral therapy on response to treatment and survival in patients with acquired immunodeficiency syndrome-related non-Hodgkin's lymphoma treated with cyclophosphamide, hydroxydoxorubicin, vincristine and prednisone.

Combined highly active anti-retroviral therapy (HAART) with protease and reverse transcriptase inhibitors has modified the natural history of opportunistic infections and neoplasms in human immunodeficiency virus (HIV)-infected patients. We analysed the influence of HAART on the response to treatment and survival in a series of 58 patients with acquired immune deficiency syndrome (AIDS)-related non-Hodgkin's lymphoma (NHL) treated with CHOP (cyclophosphamide, hydroxydoxorubicin, vincristine and prednisone). Two groups of patients were included: (i) forty-one patients diagnosed with NHL between 1988 and 1996 who were not treated with HAART; (ii) seventeen patients diagnosed since 1996, who were receiving or commenced HAART when NHL was diagnosed. The response rate to CHOP was higher in group 2 (13 out of 17 cases; 75%) than in group 1 (14 out of 41 cases; 34%) (P = 0.003). The 2-year probability of event-free survival (EFS) [95% confidence interval (CI)] for group 1 was 0.5 (0.24-0.74), whereas for group 2 it was 0.85 (0.61-0.90) (P = 0.024). The lymphoma-free survival (LFS) was also significantly different for both groups (2-year LFS probability 0.53 vs. 1.0, P = 0.04). The median (95% CI) overall survival (OS) for group 1 was 7 months (range, 3-10.8 months), whereas it was not reached in group 2 (P = 0.0015). In the multivariate analysis for remission attainment, the only variables with a higher probability to achieve complete remission (CR) were HAART (P = 0.01) and International Prognostic Index score 1 (P = 0.02). The only statistically significant variable in the multivariate analysis for EFS was HAART (P = 0.049) and the variables with prognostic value for OS in the multivariate analysis were B symptoms (P = 0.01) and HAART (P = 0.003). Patients with AIDS-related NHL treated with CHOP and HAART had a higher CR rate than those treated only with CHOP. In this study, HAART was an independent prognostic factor for CR, OS and EFS in patients with AIDS-related NHL.

Adult↗
PubMed2001

Does cisapride influence cardiac rhythm? Results of a United States multicenter, double-blind, placebo-controlled pediatric study.

BACKGROUND: Major concerns about serious cardiac side effects underlie the recent decision by the FDA and Janssen Pharmaceutica (Titusville, NJ) to make cisapride available only through a limited access program. Concerns have grown despite the fact that most instances of prolonged QTc and other ventricular arrhythmias occurred while the drug was used concomitantly with contraindicated drugs. This study sought to analyze electrocardiograms (ECGs) from a multicenter pediatric study and to identify abnormalities in QTc interval associated with cisapride use. METHODS: Children between 6 months and 4 years of age were enrolled if they manifested symptoms of gastroesophageal reflux not responding to medical therapy for at least 6 weeks. In 49 subjects, ECGs obtained before and after randomization to receive 0.2 mg/kg dose three times daily or placebo were reviewed independently and blindly by two pediatric cardiologists. Placebo and active drug groups were compared for QTc and for change in QTc from baseline values after 3 to 8 weeks of treatment. RESULTS: Mean QTc among patients taking the drug was 408+/-18 ms. None was higher than 450 ms. Change between baseline and subsequent QTc at 3 to 8 weeks of treatment was 2+/-20 ms. CONCLUSIONS: In our study group of children without underlying cardiac disease or electrolyte imbalance, cisapride was found to have no significant effect on cardiac electrical function compared with placebo. These results are consistent with the drug's record of exceedingly infrequent cardiac events. Because the availability of this prokinetic is threatened, its safety and the safety and efficacy of alternative treatment options (including surgery) should be studied further.

Arrhythmias, Cardiac↗
PubMed2001

Colonic diversion for intractable constipation in children: colonic manometry helps guide clinical decisions.

BACKGROUND: Colonic manometry helps discriminate functional and behavioral causes for childhood constipation from colonic neuromuscular disease. METHODS: Of 375 colonic manometries performed for clinical indications, 12 could not be interpreted because of chronic colonic dilation. Based on colonic manometries that showed either no contractions or an absence of the gastrocolonic response or an absence of high-amplitude propagating contractions, the authors recommended diverting colostomies or ileostomies in 12 chronically constipated children (mean age, 4 years; range, 2-14 years, 5 boys). Before study, medical treatment was ineffective in all children. These children had persistently dilated colons with pathologic diagnoses of intestinal neuronal dysplasia (n = 4), hypoganglionosis (n = 2), hollow visceral myopathy (n = 1), and normal (n = 5). RESULTS: Six to 30 months after diversion, the authors restudied all the children. Eleven of 12 diverted colons were no longer dilated. In two patients, abnormal motility involving the entire colon was unchanged from the initial study, small bowel motility was abnormal, and we recommended no further surgery. In two cases, the colon remained abnormal but small bowel motility was normal, and we recommended subtotal colectomy and ileoproctostomy. In four cases, the left colon remained abnormal, but the right colon was normal, and we recommended reanastomosis after left hemicolectomy. In four cases, motility in the diverted colons was normal, including a gastrocolonic response and high-amplitude propagating contractions, and the authors recommended reanastomosis. Defecation problems resolved in 10 of 12 when followed up 5 to 30 months after treatment. CONCLUSION: These data suggest that in some cases of intractable childhood constipation associated with colonic distention, temporary diversion improved colonic motility. Colonic manometry may be used to predict which patients will benefit from resection or reanastomosis.

Adolescent↗
PubMed2001

A clinic-based molecular epidemiologic study of tuberculosis in Monterrey, Mexico.

SETTING: A tuberculosis clinic associated with a university hospital in Monterrey, Mexico, an urban community with high tuberculosis incidence. OBJECTIVE: To determine the diversity of DNA fingerprint patterns and the extent of drug resistance of Mycobacterium tuberculosis isolates from patients who attended the clinic. DESIGN: Isolates of M. tuberculosis obtained from 186 patients during the period from 31 January 1996 to 31 March 1998 were tested for susceptibility to isoniazid, rifampicin, ethambutol and streptomycin. Demographic data and the social history of each patient were obtained prospectively by interview. The IS6110 DNA fingerprints were obtained for 166 of the 186 isolates. Secondary typing was carried out on isolates with fewer than six copies of IS6110. RESULTS: Thirty-two per cent of the tested isolates (60/ 186) were drug-resistant, and 18% (33/186) were multidrug-resistant. Approximately 55% of the resistant isolates (33/60) were attributed to acquired resistance. A total of 106 different IS6110 fingerprint patterns were observed among the 166 fingerprinted isolates. Based on both IS6110 and pTBN12 fingerprinting, 65 (39%) of the 166 isolates were part of 22 DNA fingerprint clusters. Various drug susceptibility patterns were seen in most clusters. CONCLUSION: Fingerprint clustering indicates extensive recent transmission of tuberculosis in patients attending the clinic. The prevalence of drug-resistant tuberculosis is high.

Adult↗
PubMed2000

Comparative study of strongyle infections of cattle and buffaloes in Mindanao, the Philippines.

Faecal samples were collected from 500 cattle and 385 buffaloes belonging to backyard farmers from 24 villages in the province of Bukidnon, Mindanao, the Philippines. Strongyle nematode infections were studied on these samples by faecal egg counts and infective larvae differentiation. The effects of animal species and age on the prevalence and intensity of infections were studied. The overall prevalence of strongyle infection was 53% for cattle and 28% for buffaloes. The prevalence decreased with increasing age in both animal species. Faecal egg counts were significantly lower in buffaloes than in cattle. Adult animals had lower egg counts than calves. This age effect was most pronounced in buffaloes. Six genera of strongyle nematodes were identified from the faecal cultures in both animal species, Mecistocirrus, Haemonchus, Trichostrongylus, Cooperia, Bunostomum and Oesophagostomum. The distribution of larvae did not vary much with age.

Animals↗
PubMed2000

Rat liver nucleotide pyrophosphatase/phosphodiesterase is an efficient adenylyl transferase.

Rat liver nucleotide pyrophosphatase/phosphodiesterase I (NPP/PDE) catalysed efficiently the transfer of adenylate from ATP to alcohols (methanol, ethanol, propanol, ethylene glycol, glycerol, 2, 2-dichloroethanol and glycerol 2-phosphate), which acted as adenylate acceptors competing with water with different efficiencies. NPP/PDE kinetics in alcohol/water mixtures were accounted for by rate equations for competitive substrates, modified to include alcohol negative co-operativity and, depending on the nature of the alcohol, enzyme denaturation by high alcohol concentrations or activation by low alcohol concentrations. The correlation of alcohol efficiencies with alcohol acidities, the comparison of rat liver with snake venom NPP/PDE, and the different effects of ionic additives on the efficiencies of glycerol 2-phosphate and glycerol provided evidence for interaction of the alcohols with a base catalyst, a non-polar and a cationic subsite in the active centre of rat liver NPP/PDE. The enzyme thus appears to be well suited to act as transferase, and we propose that NPP/PDE could be an adenylylating agent in the membrane.

Adenosine Monophosphate↗
PubMed2000

Comparison of different biomaterials for glaucoma drainage devices: part 2.

BACKGROUND: Inflammation associated with biomaterials may contribute to the failure of glaucoma drainage devices. OBJECTIVE: To compare the inflammatory reaction associated with the insertion of Krupin silicone, Molteno polypropylene, and Acrosof end plates in the subconjunctival space of rabbits. METHODS: Similar-sized glaucoma end plates made of 3 different biomaterials were sutured to the sclera in the superotemporal quadrant of the rabbit eye. Thirty eyes of 15 albino New Zealand rabbits were randomly assigned to the 3 groups. Conjunctival vascular hyperemia was graded in a masked fashion among the 3 groups. At the end of 3 weeks, the enucleated eyes were examined histologically and by scanning electron microscopy. RESULTS: Molteno polypropylene was associated with more inflammation both in clinical observations and based on histological grading. Silicone and Acrosof were associated with less intense inflammation. One polypropylene end plate was extruded on day 21. CONCLUSIONS: Polypropylene appears to be more inflammatory than silicone. Flexible biomaterials appear to be less inflammatory than rigid ones. CLINICAL RELEVANCE: Bleb failure following glaucoma drainage device implantation could be related to the biomaterial-associated inflammation. Choosing a biomaterial with the least inflammatory potential might enhance the success rate of the glaucoma drainage device. Arch Ophthalmol. 2000;118:1081-1084

Animals↗
PubMed2000

Pressure wire kinking, entanglement, and entrapment during intravascular ultrasound studies: a potentially dangerous complication.

The simultaneous use of intravascular ultrasound catheters and sensor-tipped guidewires is gaining acceptance during coronary interventions as a means to gain further insights on the significance of coronary stenoses. Herein we describe four patients in whom the distal tip of the pressure wire became entrapped during an intravascular ultrasound examination. In the four patients, a localized kinking of the pressure wire initially prevented the removal of the imaging catheter and eventually the wire-catheter assembly had to be retrieved as a unit into the guiding catheter. In one patient, unraveling of the distal part of the pressure wire was noticed. In two patients, a complete loop with further kinking of the pressure wire was induced during the maneuvers performed to withdraw the imaging system. Three patients experienced transient angina. Although in our patients this technical problem was not associated with any clinical sequelae, interventional cardiologists should be aware of the potential complications associated with the combined use of these two intracoronary diagnostic tools.

Cardiac Catheterization↗
PubMed2000

Guidewire-induced coronary pseudostenosis as a source of error during physiological guidance of stent deployment.

Coronary pseudostenoses are a known result of the interaction between tortuous vessels and guidewires and are generally handled by the interventionalist as inocuous side effects of intracoronary instrumentation. The present report demonstrates that pseudostenosis may have hemodynamic relevance and may constitute an important source of error when physiological guidance of percutaneous procedures is performed using sensor-tipped guidewires.

Aged↗
PubMed2000

Regulation of septation: a novel role for SerC/PdxF in Salmonella?

The sfiW locus of Salmonella enterica, previously identified by mutations that suppress the cell division defect of His-constitutive (His(c)) strains, corresponds to serC, the bifunctional gene for phosphoserine-oxoglutarate aminotransferase (SerC) and 2-ketoerythroic acid 4-phosphate transaminase (PdxF). SerC- mutants form small, nearly spherical cells in a wild-type (His+) background, suggesting that the SerC/PdxF product acts as a septation antagonist. Suppression of His(c) filamentation by serC mutations may be explained by loss of the anti-septation activity of SerC/PdxF. The isolation of serC alleles that have lost their biosynthetic activities but are still able to inhibit septum formation suggests that the anti-septation activity of the SerC/PdxF product is unrelated to its known roles in serine and pyridoxine biosynthesis.

Aldehyde Oxidoreductases↗
PubMed2000

[Proximal vein by-pass in the treatment of venous stenosis in expanded polytetrafluoroethylene prosthesis for hemodialysis].

OBJECTIVE: To show the long-term results of 97 politetraflouroethylene dialysis grafts submitted to a graft by-pass to treat graft-vein stenosis. MATERIALS AND METHODS: Venous stenoses were studied and diagnosed by means of fistulography in cases with fistula dysfunction or during surgery for graft thrombectomy. Both early and late complication rates were studied, as well as primary and secondary patency rates. RESULTS: Number of cases, 97. Mean age, 58 years (7-79). Diabetic nephropathy: 19.5%. Types of grafts in which stenoses developed: straight forearms 13; loop forearm 9; 6 mm upper arm 36; 6-8 mm upper arm 34; brachio-jugular 4; femoro-femoral 1. Overall follow-up time: 2,427 graft-months. Mean follow-up time: 21 +/- 5 months. Late complication rate: 0.30 episodes per graft-year of follow-up. Re-stenosis rate: 0.12 graft-year of follow-up. Primary cumulative patency rate: 70%, 62%, 51%, 45% at one, two, three and four years, respectively. Secondary cumulative patency rate: 87%, 79%, 74% and 71% at one, two, three and four years, respectively (p < 0.0016). No differences were observed between secondary patency observed after by-pass to treat dysfunction or thrombosis (p = 0.09259). DISCUSSION: In our experience, by-pass to proximal vein is associated with good results both at short and long term, probably because the intimal hyperplasia area is excluded and because by-pass is performed on an already dilated vein. The procedure can be performed under local anesthesia and in an outpatient basis between dialysis, with little discomfort for the patient.

Adolescent↗
PubMed2000

The relationship between idiopathic thrombocytopenic purpura and pernicious anaemia.

Some reports on the simultaneous presence of chronic idiopathic thrombocytopenic purpura (ITP) and pernicious anaemia (PA) may be found in the literature. However, little is known about the coexistence of these autoimmune disorders. For this reason, we studied the prevalence of PA in a series of patients with a diagnosis of chronic ITP by means of the analysis of the concentration of the most sensitive marker of type A atrophic (autoimmune) gastritis, serum pepsinogen I. Serum pepsinogen I was low in 20.3% of the 133 patients studied. Gastrin was elevated in 15. 2% of patients, but the coexistence of both abnormalities was rather low (7.6% of patients). However, the progressive decrease in serum cobalamin as biochemical abnormalities related with atrophic gastritis appeared was noticeable. The time to progression to frank PA from type A atrophic gastritis may span some years.

Adult↗
PubMed2000

The metabolic use of energy from dietary fat in broilers is affected by fatty acid saturation.

1. Two experiments were performed to evaluate the effect of dietary fat on performance and fat and protein accretion in broiler chickens according to the degree of saturation. 2. The first experiment was designed to test 2 sources of dietary fat and 3 levels of dietary energy using a factorial (2x3) experimental design. The foods were formulated to maintain a constant ratio of energy to protein (and other nutrients). There were no significant differences in weight gain, intake, final body weight or food to gain ratio between broilers fed on diets differing solely in the degree of fat saturation. Broilers fed on diets containing animal fat showed higher whole-body fat retention (P=0.02) and lower protein accretion (P=0.03) than those fed on diets containing vegetable oils. 3. In the second experiment, only 1 concentration of fat (tallow, lard or sunflower oil) was incorporated into the experimental diets, providing different energy to protein ratios. The carcase protein content was not affected by dietary fat source, while total fat accretion (P=0.01) and energy retention (P=0.14) were highest in broilers fed on a diet containing tallow. 4. The findings suggest that the degree of saturation of dietary fats affects their metabolic use and fat accumulation in broiler chickens.

Animal Feed↗
PubMed2000

Effect of the inclusion time of dietary saturated and unsaturated fats before slaughter on the accumulation and composition of abdominal fat in female broiler chickens.

The aim of this experiment was to assess the effects of four different feeding programs designed to include tallow, a saturated fat at 0, 8, 12, and 28 d prior to slaughter on female broiler performance and the deposition, fatty acid profile, and melting point of abdominal fat. The following treatment groups were established according to dietary inclusion--from 21 to 49 d of age--of: sunflower oil (SUN), sunflower oil followed by tallow during the last 8 d (SUN + 8TALL), sunflower oil followed by tallow during the last 12 d (SUN + 12TALL), and tallow (TALL). The diets were designed to be isoenergetic and isonitrogenous. Abdominal fat deposition increased linearly with increasing number of days in which birds were fed the tallow-enriched diet. However, linear and quadratic response patterns were found between days before slaughter in which the birds were fed the tallow-enriched diet and abdominal fat melting points. This result suggested an exponential response in which 85% of the maximum level was already attained when the dietary fat type changed from an unsaturated to a saturated condition during the last 8 d of the feeding period. The use of an unsaturated fat source during the first stages of growth, and the substitution of a saturated fat for a few days before slaughter, may offer the advantage of lower abdominal fat deposition and an acceptable fat fluidity compared with the use of a saturated fat source during the whole growing and finishing period.

Abdomen↗