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Biomedical subjects

M Torres

Publications and source records attributed to M Torres.

At least 73 records · Page 4Linked to original sources
PubMed1999

Function of the cytoskeleton in human neutrophils and methods for evaluation.

The cytoskeleton plays a critical role in the determination of cell shape and serves as a scaffold for critical cellular enzymes and adhesion molecules. It provides structural integrity for the cell and regulates the function of many biochemical events that are critical to cellular function. The microfilamentous cytoskeleton participates in force generation necessary for shape change and motion. In neutrophils and other motile cells, polymerization of actin likely drives extension of the lamellae and participates in force generation through interaction with myosin, by polymerization alone and by osmotic mechanisms. Here, we will focus on the microfilamentous cytoskeleton in the neutrophil and briefly review its function as well as some direct and indirect methods that have been used to asses its role in neutrophil function. The discussion will address general approaches and leaves the details of the methods to the references.

Animals↗
PubMed1999

Conserved regulation of proximodistal limb axis development by Meis1/Hth.

Vertebrate limbs grow out from the flanks of embryos, with their main axis extending proximodistally from the trunk. Distinct limb domains, each with specific traits, are generated in a proximal-to-distal sequence during development. Diffusible factors expressed from signalling centres promote the outgrowth of limbs and specify their dorsoventral and anteroposterior axes. However, the molecular mechanism by which limb cells acquire their proximodistal (P-D) identity is unknown. Here we describe the role of the homeobox genes Meis1/2 and Pbx1 in the development of mouse, chicken and Drosophila limbs. We find that Meis1/2 expression is restricted to a proximal domain, coincident with the previously reported domain in which Pbx1 is localized to the nucleus, and resembling the distribution of the Drosophila homologues homothorax (hth) and extradenticle (exd); that Meis1 regulates Pbx1 activity by promoting nuclear import of the Pbx1 protein; and that ectopic expression of Meis1 in chicken and hth in Drosophila disrupts distal limb development and induces distal-to-proximal transformations. We suggest that restriction of Meis1/Hth to proximal regions of the vertebrate and insect limb is essential to specify cell fates and differentiation patterns along the P-D axis of the limb.

3T3 Cells↗
PubMed1999

Phosphorylation of tyrosine hydroxylase by cGMP-dependent protein kinase in intact bovine chromaffin cells.

The phosphorylation of the enzyme tyrosine hydroxylase by the cGMP pathway was investigated in chromaffin cells from the bovine adrenal medulla. The nitric oxide donor, sodium nitroprusside, and the natriuretic peptide, C-type natriuretic peptide, which are able to increase cGMP levels and cGMP-dependent protein kinase activity, produced significant increases in the phosphorylation level of tyrosine hydroxylase in a time- and concentration-dependent manner. The pretreatment of the cells with the soluble guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one blocked the effect of sodium nitroprusside. This result indicates that cGMP production by this enzyme mediated this effect. Experiments performed with a cGMP-dependent protein kinase inhibitor, the Rp-isomer of 8-(4-chlorophenylthio)-cyclic guanosine monophosphorothioate, which blocked the effects of both sodium nitroprusside and C-type natriuretic peptide, demonstrated that the phosphorylation increases evoked by both compounds were mediated by the activation of cGMP-dependent protein kinase. In cells incubated with the adenylyl cyclase activator, forskolin, an increase in the phosphorylation level of the tyrosine hydroxylase was also found. When cells were treated simultaneously with forskolin and sodium nitroprusside or C-type natriuretic peptide, an additive effect on tyrosine hydroxylase phosphorylation was not observed. This suggests that cAMP- and cGMP-dependent protein kinases may phosphorylate the same amino acid residues in the enzyme. Western blot analysis of soluble extracts from chromaffin cells detected specific immunoreactivity for two different commercial antibodies raised against cGMP-dependent protein kinase (both Ialpha and Ibeta isoforms). Electrophoretic mobility correlates with that of purified PKG Ialpha. Because the phosphorylation of the tyrosine hydroxylase correlates with increases in its enzymatic activity and thus with augmentation in the cell capacity to synthesize catecholamines, our results indicate that a cGMP-based second messenger pathway participates in catecholamine biosynthesis regulation in chromaffin cells, a mechanism which may be widespread in other catecholamine-synthesizing cells.

Amino Acid Sequence↗
PubMed1999

Activation of several MAP kinases upon stimulation of rat alveolar macrophages: role of the NADPH oxidase.

Zymosan-activated serum (ZAS), a source of C5a, stimulates the rat alveolar macrophages (AM) to release superoxide anion. Here we show that treatment of rat AM with ZAS induced a time-dependent increase in the tyrosine phosphorylation of several proteins (116, 105-110, 82-78, 66-72, 62, 45, 42, and 38 kDa). This increase was sensitive to genistein, a tyrosine kinase inhibitor. ZAS stimulated the tyrosine phosphorylation and activation of three members of a family of serine/threonine kinases known as the mitogen-activated protein kinases (MAPK), i.e., ERK1 and ERK2, as assessed by immunoblotting, immunoprecipitation, and phosphotransferase activity, and p38 MAPK, as determined by immunoblotting with phospho-specific antibodies. In addition, ZAS induced the tyrosine phosphorylation of the SHC proteins and their association with GRB2, suggesting a role for this complex in the activation of the ERK pathway. Addition of extracellular catalase during ZAS stimulation significantly reduced the tyrosine phosphorylation response and the activation of ERK1 and ERK2 and their activator MEK1/2 while it did not affect that of p38 MAPK and MKK3/MKK6. Superoxide dismutase marginally increased the response to ZAS, supporting a role for hydrogen peroxide. In contrast to the results with AM, stimulation of human neutrophils with ZAS in the presence of catalase minimally altered the activation of ERK1 and ERK2. These data show that, in ZAS-stimulated rat AM, activation of the respiratory burst and production of hydrogen peroxide via superoxide dismutation are largely responsible for the activation of the ERK pathway through an upstream target.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Periodic formation of nascent lamellae is driven by changes in the stable F-actin pool of polymorphonuclear neutrophils after stimulation with chemotactic peptide and cross-linking of CD18 or CD61.

Cell motility and changes in cell shape are largely powered by actin polymerization and depolymerization. Eight to ten second periodic changes in human polymorphonuclear neutrophil (PMN) shape were detected by video-image analysis of PMN crawling on a surface and by right angle light scattering (RALS) in suspended PMN. However, sustained RALS oscillations in suspended PMN requires pre-treatment with an inhibitor of phosphatidylinositol 3-kinase or an activator of protein kinase C. Here, we show that cross-linking of the beta(2) (CD18) or beta(3) (CD61), but not beta(1) (CD 29) integrins in the presence of a low dose of formyl-Methionyl-Leucyl-Phenylalanine (fMLP) enables similar 8-s periodic RALS oscillations in suspended PMN in response to stimulation with two consecutive doses of chemoattractants. This effect did not appear to be due to increased surface expression of CD18 or CD61. RALS oscillations occurred in phase with 8-s oscillations in the stable F-actin pool and peaks in F-actin correlated with predominance of cells exhibiting a nascent lamella. Thus, simulation of surface attachment by CD18 and CD61 cross-linking after exposure to fMLP in suspended cells supports shape oscillations that are the result of actin-driven cyclic extension/retraction of nascent lamellae at the same frequency as the shape changes previously observed in crawling PMN.

Actins↗
PubMed1999

Effect of intradialytic parenteral nutrition on delivered Kt/V.

The purpose of the study is to determine the effect of intradialytic parenteral nutrition (IDPN) and its components on delivered Kt/V (Kt/Vd). Nineteen patients undergoing routine outpatient hemodialysis and receiving IDPN were enrolled onto this prospective, crossover study. To reduce the confounding of time, assigned treatment in the first week was random, with patient crossover in the fourth week. Patients served as their own controls. In the successive 6 weeks, patients received IDPN solutions differing in whether amino acids (AAs), dextrose, or lipids were included or excluded. The primary end point was Kt/Vd, measured with a single-pool, variable-volume urea kinetic model. Other factors with the potential to impact on Kt/Vd were controlled and/or monitored. The administration of IDPN with all three components resulted in a significantly reduced mean Kt/Vd. When patients received AA-containing solutions, mean Kt/Vd was significantly less than when IDPN was withheld. Administration of solutions without AA resulted in a mean Kt/Vd not significantly different from mean Kt/Vd when IDPN was withheld. The mean prescribed Kt/V did not differ from mean Kt/Vd when IDPN was withheld. Simulation analyses of increased urea generation (Gu) showed an increase in patient urea volume and decreased Kt/V similar to the study findings. AA-containing IDPN solutions resulted in a significant reduction in Kt/Vd, possibly mediated by increased Gu. Administration of IDPN solutions may have important clinical and economic consequences that warrant further investigation.

Aged↗
PubMed1999

ED hemodialysis for treatment of renal failure emergencies.

Patients with chronic renal failure (CRF) are at risk for unique medical emergencies, many of which require hemodialysis for their definitive treatment. This study describes the use of emergency department (ED) hemodialysis in the management of CRF patients. A retrospective chart review was conducted of patients who underwent ED hemodialysis at a regional dialysis center between April 1994 and September 1996. Data were collected on presenting complaint, ED diagnosis, indication for hemodialysis, ED pharmacologic treatment, ED airway management, cardiovascular stability, and disposition. Fifty episodes of ED hemodialysis were identified in 37 different patients. Presenting complaints included: shortness of breath, 38 (69%); weakness, 8 (15%); chest pain, 3 (5%); and other, 6 (11%). ED diagnoses included: congestive heart failure, 36 (65%); hyperkalemia, 13 (24%); and other, 6 (11%). Indications for hemodialysis included: cardiovascular instability, 33 (38%); respiratory distress, 22 (26%); cardiac monitoring, 16 (19%), timing, 13 (15%); and other, 2 (2%). Predialysis stabilization included: nitroglycerin, 29 (26%); sublingual captopril, 17 (15%); calcium chloride, 13 (11%); sodium bicarbonate, 12 (11%); insulin/dextrose, 11 (10%); none, 12 (11%); and other, 18 (16%). Airway support included: noninvasive pressure support ventilation (NPSV), 9 (18%); and endotracheal intubation, 6 (12%). NPSV was provided with a bilevel positive airway pressure system. Three of the endotracheal intubation patients were weaned to NPSV during dialysis, and all NPSV patients were weaned from respiratory support during their hemodialysis in the ED. Some patients had more than one problem. Sixteen patients (32%) were admitted, while 34 (68%) were discharged, including 3 NPSV patients and 22 initially unstable patients. ED hemodialysis in conjunction with additional medical care is a useful emergency medicine technique that can prevent hospital admission in patients with acute renal emergencies.

Acute Disease↗
PubMed1999

Fate of fumonisin B(1) in corn kernel steeping water containing SO(2).

Six 100 ppm fumonisin B(1) (FB(1)) solutions were prepared by dissolving pure standard in six different solvents containing SO(2). Two of the solvents contained 0.2 or 0.4% SO(2) in distilled water. The other four solvents were obtained by steeping corn kernels at 60 degrees C in a 0.2% SO(2) aqueous solution for 6, 12, 24, or 48 h. After the addition of FB(1), all solutions were maintained at 60 degrees C for 7 days. Fumonisin B(1) content in each solution was determined in triplicate by HPLC. Steeping corn kernels in 0.2% solution at 60 degrees C for 6 h seems to be the most effective treatment to decrease the amount of FB(1).

Carboxylic Acids↗
PubMed1999

Procedure for radiolabeling gizzerosine and basis for a radioimmunoassay.

A method for the labeling of gizzerosine (GZ), a biogenic amine found in fish meal, is described. The labeling procedure with (125)I using a water-soluble Bolton-Hunter reagent and a mild water-insoluble oxidant (Iodogen) reagent is rapid and reproducible. The (125)I-GZ hapten was demonstrated to be immunologically active in a radioimmunoassay developed with polyclonal antibodies to GZ absorbed with a histamine-Sepharose column. The curves were linear in the range of 0.0001 and 0.1 microgram/mL. Samples of fish meal previously extracted of histamine with methanol and submitted to acid hydrolysis were contaminated with known amounts of GZ and submitted to the assay. The fish meal samples contaminated with GZ show a dose-response effect similar to the standard curve, and apparently the other component present in the sample did not interfere with the binding of the antibodies to (125)I-GZ. These data indicate the suitability of the radioimmunoassay to determine specifically GZ in fish meal.

Animals↗
PubMed1999

Comparative effects of several nitric oxide donors on intracellular cyclic GMP levels in bovine chromaffin cells: correlation with nitric oxide production.

1. Sodium nitroprusside, S-nitroso-N-acetyl-D,L-penicillamine, Spermine NONOate and DEA NONOate raised cyclic GMP levels in bovine chromaffin cells in a time and concentration dependent manner with different potencies, the most potent being DEA/NO with an EC50 value of 0.38 +/- 0.02 microM. 2. Measurements of NO released from these donors revealed that DEA/NO decomposed with a half-life (t1/2) of 3.9 +/- 0.2 min. The t1/2 for SPER/NO was 37 +/- 3 min. SNAP decomposed more slowly (t1/2 = 37 +/- 4 h) and after 60 min the amount of NO produced corresponded to less than 2% of the total SNAP present. The rate of NO production from SNAP was increased by the presence of glutathione. 3. For DEA/NO and SPER/NO there was a clear correlation between nitric oxide production and cyclic GMP increases. Their threshold concentrations were 0.05 microM and maximal effective concentration between 2.5 and 5 microM. 4. For SNAP, threshold activation was seen at 1 microM, whereas full activation required a higher concentration (500-750 microM). The dose-response for SNAP increases in cyclic GMP was shifted nearly two orders of magnitude lower in the presence of glutathione. At higher concentrations an inhibition of cyclic GMP accumulation was found. This effect was not observed with either the nitric oxide-deficient SNAP analogue or other NO donors. 5. Although NO-donors are likely to be valuable for studying NO functions, their effective concentrations and the amount of NO released by them are very different and should be assessed in each system to ensure that physiological concentrations of NO are used.

Animals↗
PubMed1999

Long-acting lacidipine versus short-acting nifedipine in the treatment of asymptomatic acute blood pressure increase.

We compared antihypertensive efficacy and safety of a single administration of equipotent doses of lacidipine versus nifedipine in the hypertensive urgencies. Twenty-nine asymptomatic essential hypertensive patients (nine men, 20 women) with a mean age of 55.03+/-11.19 years and baseline diastolic blood pressure (DBP) of > or =120 mm Hg after resting 30 min, not taking antihypertensive drugs for the last 24 h, were randomized in a single-blind fashion to receive lacidipine, 4 mg (LCD, 15 patients) or short-acting nifedipine, 20 mg (NFD, 14 patients) in a single dose. Blood pressure (BP) and heart rate (HR) were taken every 30 min during the first 8 h and every 2 h until 24 h of follow-up. Baseline BP values were similar in the two groups (LCD, 222.5+/-32.8/124.6+/-8.4 mm Hg vs. NFD, 215.9+/-20.6/128+/-7.7 mm Hg; p = NS). Both drugs promoted a significant reduction of systolic blood pressure (SBP; 169.6+/-27.8 vs. 170.6+/-25.3 mm Hg) and diastolic blood pressure (DBP; 104.1+/-16 vs. 102.9+/-12.4 mm Hg) after 8 h. However, either SBP (165+/-27.3 vs. 190.6+/-18.2 mm Hg; p = 0.008) and DBP (99.9+/-12.3 vs. 117.2+/-11.4 mm Hg; p = 0.001) were significantly higher in the NFD group after 24-h dosing. Eleven patients in the LCD group had a decrease in BP >25% of the baseline value both 8 and 24 h after the dose. Although 10 patients showed the same response in the NFD group 8 h after the dose, only four patients maintained these values at 24 h. One patient treated with NFD had a transient cerebrovascular ischemic attack. No adverse effects were observed in the LCD group. We conclude that the long-acting calcium antagonist lacidipine was more effective than the short-acting nifedipine in both controlling BP and maintaining this BP reduction over 8 h in essential hypertensive patients with acute asymptomatic BP increase.

Adolescent↗
PubMed1999

Personality and clinical predictors of recurrence of depression.

OBJECTIVE: To help clinicians more accurately predict outcomes of treatment for depression, variables associated with recurrence of depression in the year after treatment were examined in a group of patients who completed treatment for an index episode of depression. METHODS: Forty-two depressed patients who participated in a double-blind pharmacological treatment study were followed for one year after treatment was discontinued. Length of treatment for the index episode was determined by clinicians and ranged from eight to 76 consecutive weeks. Eighteen patients who had a recurrent episode (43 percent) and 24 patients who did not (57 percent) were compared on sociodemographic and clinical variables, including scores on the Eysenck Personality Questionnaire (EPQ). RESULTS: A combination of three variables predicted recurrence of depression in 90 percent of cases. They were an elevated EPQ score on the neuroticism subscale, a short duration of treatment of the index episode, and a slow onset of response to treatment of the index episode. CONCLUSIONS: The findings suggest that personality traits, treatment duration, and variations in response to treatment might have an impact on long-term treatment outcome. Clinicians should consider these factors when making treatment decisions for depressed patients.

Adult↗
PubMed1999

Prevalence and risk of cysticercosis and taeniasis in an urban population of soldiers and their relatives.

To determine markers of Taenia solium transmission and risk factors in an urban community, we studied 1,000 soldiers from a military camp in Mexico City and their relatives. Serum samples were used to detect antigens and antibodies and fecal specimens were examined for Taenia coproantigens and helminth eggs. Prevalences of 12.2% and 5.8% for cysticercosis were found among soldiers and their relatives, respectively. Taeniasis was found in 0.5% and none of the groups, respectively. Relatives of soldiers positive for cysticercosis and taeniasis markers ate more pork from street stores than restaurants or markets compared with relatives of soldiers without these indicators of infection. Also, 12.0% of the relatives of positive soldiers had a history of expelling tapeworm proglottids in the feces in contrast to 3.7% of the family members of the control group. Prevalence values and risk factors in this urban population are similar to those of previous studies performed in rural populations.

Adult↗