Search PubMed⌕ Search

Biomedical subjects

A Cruz

Publications and source records attributed to A Cruz.

At least 55 records · Page 3Linked to original sources
PubMed2000

[Analysis of participation in surveys in 5 countries: the importance for public health research].

This study compares participation rates and reasons for nonresponse in surveys conducted in five countries of Latin America and the Caribbean. The objective of the surveys was to measure the prevalence of risk behaviors affecting the transmission of human immunodeficiency virus. The surveys were based on probability samples of the population of both sexes between 15 and 49 years old, except in Mexico, where only men were included. Proportions of three components of participation were estimated: residences interviewed, interviewed residences with eligible persons, and eligible persons who completed the interview. In addition, an overall index that combined the three components was calculated. The overall response rate ranged from 35.6% in Mexico to 81.4% in Chile. The component with the greatest variability was the participation of eligible persons, which ranged from 50% in Mexico to 95% in Cuba. These values were lower than what had been expected, especially among men, and will serve to guide future surveys, since rejection rates higher than the ones expected in the protocol should be considered. The results make it possible to infer the validity of the prevalence estimates for the various observed risk behaviors. The results also establish a benchmark to calculate the sample size in future surveys and to improve research methodology.

Adolescent↗
PubMed1999

Dietary intake of selenium and its concentration in breast milk.

Selenium concentration was measured in the breast milk of 30 mothers at different stages of lactation and various body mass indices (BMI). For a maternal mean selenium intake meeting 100% of the Recommended Daily Allowance, mean milk selenium concentration was 14.06 ng/mL (range: 10.0-24.7 ng/mL). No significant correlation was found between the concentration of milk selenium with the stage of lactation, BMI, or dietary selenium intake.

Adult↗
PubMed1999

Chlorinated hydrocarbons in coastal lagoons of the pacific coast of Nicaragua.

A screening for persistent chlorinated hydrocarbons was carried out in December 1995 in the main coastal lagoons on the Pacific side of Nicaragua, where most of the country's agriculture and pesticide use has been taking place for decades. Results for a wide range of organochlorine pesticides in lagoon sediments show levels that generally were very low in Estero Real, Estero Padre Ramos, and estuary of San Juan del Sur. For example, total DDTs in these lagoons averaged 4.5 +/- 3.4 ng g-1 dry weight, which may be considered a baseline level for the region. Other compounds such as HCHs, BHC, endosulfan, heptachlor, endrin, toxaphene, and aroclors were present in concentrations even lower, generally below 1 ng g-1 dry weight. However, sediments of the Esteros Naranjo-Paso Caballos system at Chinandega district contained pesticide residues in much higher levels, attaining maximum values of 1,420 ng g-1 and 270 ng g-1 dry weight, respectively, for toxaphene and total DDTs. Other compounds such as aroclors, chlordane, endosulfan, and dieldrin were also present in the sediments of this lagoon system, but in lower concentrations. The very high concentrations of toxaphene and DDTs in this lagoon are a result of the intensive use of these pesticides in cotton growing in the district of Chinandega. Due to the long environmental half-lives of these compounds (t(1/2) > 10 years in temperate soils), their concentrations in lagoon sediments will likely remain high for years to come. Based on these results, the development of the new shrimp farming activities in the Pacific coastal lagoons should be restricted to selected areas.

Animals↗
PubMed1999

A technique to preserve the shape of the calcaneus after massive osteomyelitis.

Osteomyelitis of the os calcis challenges the reconstructive surgeon. We present the case of a patient in which massive medullary osteomyelitis of the calcaneus was treated with a technique that preserves the bone shape. The medullary cavity of the bone was first emptied, preserving the cortical shell. Then a free muscle flap was used to fill up the dead space. Three months later autologous bone grafts were packed into the cavity. Full weight-bearing was commenced 4 months after this procedure. In the latest follow-up, 2 1/2 years, the patient has had no recurrence or difficulty with walking.

Adult↗
PubMed1999

Increased expression of VE-cadherin correlates temporally with differentiation of a restrictive endothelial barrier during normal angiogenesis in vivo.

The purpose of this study was to evaluate temporal expression of VE- and N-cadherins within the angiogenic chick chorioallantoic membrane (CAM). Whether their relative patterns of expression changed in conjunction with abrupt differentiation of the restrictive CAM endothelial barrier between days 4.5 and 5.0 of the 21 days gestation was evaluated. Immunoblots against VE-cadherin depicted an increase of VE-cadherin expression between days 4.5 and 5.0, but no change in expression was detected between days 5.0 and 6.0. N-cadherin expression, on the other hand, remained uniform from day 4.5 to day 6.0. Immunogold-labeled anti-VE-cadherin was found exclusively on the CAM endothelium, and principally along the lateral inter-endothelial junctions. Hence, VE-cadherin expression by the angiogenic endothelium was similar to that of adult endothelium. That VE-cadherin expression by the CAM endothelium was increased between days 4.5 and 5.0 serves to suggest a temporal correlation with the ontogeny of restrictive barrier function in angiogenic endothelium in vivo.

Allantois↗
PubMed1999

Epilepsy and neurocysticercosis in an Andean community.

BACKGROUND: Taenia solium neurocysticercosis (NCC) has been documented as one of the major causes of epilepsy in developing countries. However, methodological limitations have hindered the evaluation of the epidemiological relationship between cysticercosis and epilepsy at the community level. METHODS: We used the WHO protocol for epidemiological evaluation of neurological disorders to conduct a door-to-door survey among 2723 residents of San Pablo del Lago, an Ecuadorean rural community in which T. solium taeniasis/cysticercosis was known to be endemic. The WHO protocol was complemented by neuroimaging and immunological tests to confirm the diagnosis of this infection. RESULTS: In all 31 people suffering from active epilepsy were detected (prevalence 11.4 per 1000, 95% CI:7.7-15.4); 26 agreed to undergo a computer tomography (CT) examination, and 28 agreed to have blood drawn for serodiagnosis. Fourteen of the 26 (53.8%) had CT changes compatible with NCC and six of the 28 (21.4%) tested positive in the enzyme-linked immunoelectro-transfer blot (EITB) assay. In a seizure-free random sample of this population, 17 of 118 (144 per 1000) subjects examined by CT and 10 out of 96 (104 per 1000) examined by EITB had evidence of this infection. The differences between the epilepsy group and the random sample of the population were statistically significant (OR = 6.93, 95% CI: 2.7-17.5, P < 0.001) for CT diagnosis, but not for EITB results (OR = 2.75, 95% CI: 0.8-7.1, P > 0.12, NS). CONCLUSIONS: These findings confirm that T. solium NCC is a significant cause of epilepsy at the community level in Andean villages of Ecuador. It is important to initiate effective public health interventions to eliminate this infection, which may be responsible for at least half of the cases of reported epilepsy in Ecuador.

Adolescent↗
PubMed1999

Arterial oxygenation during one-lung ventilation: combined versus general anesthesia.

UNLABELLED: The optimal anesthetic management of patients undergoing thoracotomy for pulmonary resection has not been definitely determined. We evaluated whether general i.v. anesthesia (propofol-fentanyl) provides superior PaO2 during one-lung ventilation (OLV) compared with thoracic epidural anesthesia (TEA) with supplemental local and general anesthetics. We studied 60 patients who had prolonged periods of OLV for elective thoracic surgery for lung cancer and who were prospectively randomized into two groups. In 30 patients (GA group), fentanyl/propofol/rocuronium anesthesia was used. Another 30 patients (TEA group) were anesthetized with propofol/rocuronium/epidural thoracic bupivacaine 0.5%. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during the entire study. Arterial and venous blood gases were recorded before surgery in a lateral position with two-lung ventilation, 15 and 30 min after OLV (OLV + 15 and OLV + 30, respectively) in all patients. We measured PaO2, venous central oxygen tension, arterial and central venous oxygen saturation, venous admixture percentage (Qs/Qt%), and arterial and central venous oxygen content. The mean values for PaO2 during OLV in the GA group after 15 min (175 mm Hg) and 30 min (182 mm Hg) were significantly (P < 0.05) higher compared with the TEA group (120 and 118 mm Hg, respectively). Furthermore, Qs/Qt% was significantly (P < 0.05) increased in the TEA group during OLV. There were no other significant differences. We conclude that using the TEA regimen is associated with a lower PaO2 and a larger intrapulmonary shunt during OLV than with total i.v. anesthesia alone. IMPLICATIONS: Sixty patients undergoing elective lung surgery during a prolonged period of intraoperative one-lung ventilation were studied and randomized to receive general i.v. anesthesia or general i.v. anesthesia combined with thoracic epidural anesthesia. The arterial oxygenation in the first group was better than that in the second group during one-lung ventilation.

Aged↗
PubMed1999

[Analysis of productivity, quality and cost of first grade laboratories: blood biometry].

OBJECTIVE: Assessment of productivity, quality and production costs and determination of the efficiency of top grade clinical laboratories in Mexico. METHODS: Ten laboratories were selected from among the total number (52) existing in Mexico City, and the Donabedian model of structure, process and results were applied. Blood count was selected as a tracer. RESULTS: The principal problems found were: inadequate distribution of trained human resources, poor glass material, inadequate analytic process and low productivity. These factors are reflected in the unit costs, which exceed reference laboratory costs by 200%. Only 50% of the laboratories analyzed generate reliable results. Only 20% of the laboratories studied operate efficiently. CONCLUSIONS: To solve the problems identified requires integral strategies at different levels. A specific recomendation for the improvement of quality and productivity is an assessment of the cost/benefit of creating a central laboratory and using the remaining sites exclusively for the collection of samples.

Biometry↗
PubMed1999

The role of medical problems and behavioral risks in explaining patterns of prenatal care use among high-risk women.

OBJECTIVE: To examine the associations between maternal medical conditions and behavioral risks and the patterns of prenatal care use among high-risk women. DATA SOURCE/STUDY DESIGN: Data on over 25,000 high-risk deliveries to African American and white women using multinomial logistic regression to predict the odds of adequate-plus care relative to three other categories of care. DATA COLLECTION/EXTRACTION METHODS: Data were extracted from records maintained by the University of Florida/Shands Hospital maternity clinic on all deliveries between 1987 and 1994; records for white and for African American women were subset to examine racial differences in medical conditions, health behaviors, and patterns of prenatal care use. PRINCIPAL FINDINGS: Net of sociodemographic and fertility-related characteristics, African American and white women with late antepartum conditions and hypertension problems had significantly higher odds of receiving adequate-plus care, as well as no care or inadequate care, relative to adequate care. White women with gynecological disease and medical/surgical problems were significantly less likely to receive no care or inadequate care, as were African American women with gynecological disease. CONCLUSIONS: Maternal medical conditions explain much but not all of the adequate-plus prenatal care use. More than 13 percent of African American women and 20 percent of white women with no reported medical problems or behavioral risks used adequate-plus care. Additional research is needed to understand this excess use and its possibilities in mediating birth outcomes.

Adolescent↗
PubMed1998

Rotational dynamics of spin-labelled surfactant-associated proteins SP-B and SP-C in dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol bilayers.

Pulmonary surfactant proteins SP-B and SP-C have been isolated from porcine lungs and selectively labelled with 2,2,6, 6-tetramethylpiperidine-N-oxyl (TEMPO)-isothiocyanate at their N-terminal amine ends, to analyse the mobility of both proteins on the nanosecond time scale using electron spin resonance (ESR) spectroscopy. Reconstitution of the labelled forms of these proteins in bilayers of dipalmitoylphosphatidylcholine (DPPC) or dipalmitoylphosphatidylglycerol (DPPG) results in much broader and anisotropic ESR spectra, indicating a large restriction in rotational mobility of the protein-attached probe when inserted in membranes. Distinctive differences were found between the ESR spectra of the two polypeptides, that were consistent with intrinsic differences in mode of interaction of SP-B and SP-C with phospholipid bilayers. The mobility of the protein spin probes was sensitive to temperature on the time scale of conventional spin-label ESR. Both proteins, TEMPO-SP-B and TEMPO-SP-C, showed considerable increases in mobility at temperatures above the pretransition of pure DPPC. Finally, the mobility of the spin probes attached to both SP-B and SP-C was more restricted in DPPG than in DPPC bilayers, demonstrating that electrostatic interactions of the positively charged residues at the protein surface influence the rotational dynamics of the proteins in anionic lipid bilayers. Although some residual segmental mobility of the thiourea-linked probes cannot be discounted, the results clearly reflect preferential differences in overall protein dynamics in gel and fluid phases of the two phospholipids that could be important for the biophysical properties of surfactant bilayers and monolayers.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1998

Depth profiles of pulmonary surfactant protein B in phosphatidylcholine bilayers, studied by fluorescence and electron spin resonance spectroscopy.

Pulmonary surfactant-associated protein B (SP-B) has been isolated from porcine lungs and reconstituted in bilayers of dipalmitoylphosphatidylcholine (DPPC) or egg yolk phosphatidylcholine (PC) to characterize the extent of insertion of the protein into phospholipid bilayers. The parameters for the interaction of SP-B with DPPC or PC using different reconstitution protocols have been estimated from the changes induced in the fluorescence emission spectrum of the single protein tryptophan. All the different reconstituted SP-B-phospholipid preparations studied had similar Kd values for the binding of the protein to the lipids, on the order of a few micromolar. The depth of penetration of SP-B into phospholipid bilayers has been estimated by the parallax method, which compares the relative efficiencies of quenching of the protein fluorescence by a shallow or a deeper spin-labeled phospholipid probe. SP-B tryptophan was found to be located 10-13 A from the center of bilayers, which is consistent with a superficial location of SP-B in phosphatidylcholine membranes. Parallax experiments, as well as resonance energy transfer from SP-B tryptophan to an acceptor probe located in the center of the bilayer, indicate that there are significant differences in the extent of insertion of the protein, depending on the method of reconstitution. SP-B reconstituted from lipid/protein mixtures in organic solvents is inserted more deeply in PC or DPPC bilayers than the protein reconstituted by addition to preformed phospholipid vesicles. These differences in the extent of insertion lead to qualitative and quantitative differences in the effect of the protein on the mobility of the phospholipid acyl chains, as studied by spin-label electron spin resonance (ESR) spectroscopy, and could represent different functional stages in the surfactant cycle.

Animals↗
PubMed1998

An overview of the marine food poisoning in Mexico.

In the course of the last decade, huge events related to harmful algal blooms (HAB) have severely affected the environment in Mexico, even causing several human casualties. The tally of the toxins known up to date in Mexican waters includes: neurotoxin shellfish poisoning (NSP), paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), tetrodotoxin (TTX) or puffer fish poisoning, ciguatera fish poisoning (CFP) and diarrhetic shellfish poisoning (DSP). Actual epidemiological figures profoundly modified the trends manifested on previous decades. Notwithstanding that the red tides are a long time known phenomena in Mexican coasts, no regular observation of the marine environment has been set up. Although there are monitoring activities for PSP toxins on the shellfish culturing facilities that are exploited for export to the U.S.A., these are only effectively applied on specific spots of the Mexican coasts, implying that the biggest part of the country coastal zones are not formerly surveyed. The misleads caused by the medical conception that food poisoning events are mainly due to microbial contamination, is among the factors why the marine food poisoning events are a neglected disease. In spite of the fact that no official statistics consider HAB related events as a subject of research or further monitoring by the health authorities, sporadic scientific documents related to poisoning events were produced in Mexico. An interesting picture is presented for most of the marine toxins mentioned. Trend and prognosis estimates made with such scarce information, provide a minimum measurement of the reality and urge the need for a permanent monitoring program on the Mexican coasts, a place with one of the greatest marine toxin diversity worldwide.

Animals↗
PubMed1998

"Warmth-insensitive fields": evidence of sparse and irregular innervation of human skin by the warmth sense.

Although more acute in some areas of the body than in others, temperature sensitivity is assumed to be present throughout the skin. Only when very small stimuli have been used (e.g., approximately 1 mm2) has sensitivity to warming or cooling appeared discontinuous. Here we report the discovery of patches of skin several square centimeters in area within which heating cannot be detected until skin temperature exceeds the thresholds of C heat-sensitive nociceptors (>41 degrees C). These warmth-insensitive fields (> or = 5 cm2), which appear to lack low-threshold warm fibers, were also found to have reduced responsiveness to non-painful heating and significantly higher heat pain thresholds compared to surrounding areas of skin. The existence of such sites corroborates reports that warm fibers are rare in human cutaneous nerves and confirms the classical theory that cutaneous innervation by the warmth sense is punctate and sparse. The insensitive areas also provide unique opportunities for assessing the contribution of the low-threshold warmth system to perception of heat and heat pain, and their existence in healthy young adults contraindicates use of warmth sensitivity in neurological assessments of C-fiber function.

Adult↗
PubMed1998

Involvement of tyrosine phosphorylation of p185(c-erbB2/neu) in tumorigenicity induced by X-rays and the neu oncogene in human breast epithelial cells.

Ionizing radiation is the exogenous agent best proven to induce breast cancer. c-erbB2/neu amplification and overexpression are known to occur in breast cancer and are correlated with aggressive tumor growth and poor prognosis. We have developed simian virus 40-immortalized cell lines from normal human breast epithelial cells (HBECs) with luminal and stem-cell characteristics. In this study, we examined whether x-rays and a mutated neu oncogene are capable of inducing tumorigenicity in these cells. The results indicated that x-rays were effective in converting immortal non-tumorigenic HBECs to weakly tumorigenic cells that then could be transformed to highly tumorigenic cells by the neu oncogene. The in vitro growth of these tumorigenic cells was significantly faster than that of the parental non-tumorigenic cells in growth factor- and hormone-supplemented or -depleted media. The neu oncogene, however, had no tumorigenic effect on immortal non-tumorigenic cells. The expression of p185(c-erb82/neu) was elevated in neu-transduced immortal or weakly tumorigenic cell lines. However, only in the latter was p185(c-erbB2/neu) found to be phosphorylated at tyrosine residues. Thus, x-rays appear to induce a genetic alteration that confers weak tumorigenicity on immortal HBECs and interacts with p185(c-erbB2/neu) directly or indirectly to give rise to fast-growing tumors.

Animals↗
PubMed1997

Different modes of interaction of pulmonary surfactant protein SP-B in phosphatidylcholine bilayers.

Pulmonary surfactant-associated protein B (SP-B) has been incorporated into vesicles of dipalmitoyl phosphatidylcholine (DPPC) or egg yolk phosphatidylcholine (PC) by two different procedures to characterize the dependence of lipid-protein interactions on the method of reconstitution. In method A the protein was dissolved in a small volume of either methanol or 60% (v/v) acetonitrile and injected into an aqueous phase containing phospholipid vesicles. In method B the vesicles were prepared by injection of a mixture of phospholipid and SP-B dissolved in methanol or aqueous acetonitrile. Both methods of reconstitution led to the extensive interaction of SP-B with PC bilayers as demonstrated by co-migration during centrifugation, marked protection against proteolysis, change in the fluorescence emission intensity of SP-B, and protection of SP-B tryptophan fluorescence from quenching by acrylamide. SP-B promoted the rapid adsorption of DPPC on an air/liquid interface irrespective of the method of protein reconstitution. However, the interfacial adsorption activity of SP-B reconstituted by method B remained stable for hours, but that of SP-B prepared by method A decreased with time. Electron microscopy showed that the injection of SP-B into an aqueous phase containing PC or DPPC vesicles (method A) induced a rapid aggregation of vesicles. By contrast, a much longer time was required for detecting vesicle aggregation when the protein was reconstituted by co-injection of SP-B and phospholipids (method B). The presence of 5% (w/w) SP-B in DPPC bilayers prepared by method B broadened the differential scanning calorimetry thermogram and decreased the enthalpy of the transition. In contrast, the injection of SP-B into preformed DPPC vesicles (method A) did not influence the gel-to-liquid phase transition of DPPC bilayers. Taken together, these results indicate that the mode and extent of interaction of SP-B with surfactant phospholipids depends on the conditions of preparation of lipid/protein samples, and that care should be taken in the interpretation of findings from reconstituted systems on the role of these surfactant proteins in the alveolar space.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Combinations of fluorescently labeled pulmonary surfactant proteins SP-B and SP-C in phospholipid films.

Hydrophobic pulmonary surfactant (PS) proteins B (SP-B) and C (SP-C) modulate the surface properties of PS lipids. Epifluorescence microscopy was performed on solvent-spread monolayers of fluorescently labeled porcine SP-B (R-SP-B, labeled with Texas Red) and SP-C (F-SP-C, labeled with fluorescein) in dipalmitoylphosphatidylcholine (DPPC) (at protein concentrations of 10 and 20 wt%, and 10 wt% of both) under conditions of cyclic compression and expansion. Matrix-assisted laser desorption/ionization (MALDI) spectroscopy of R-SP-B and F-SP-C indicated that the proteins were intact and labeled with the appropriate fluorescent probe. The monolayers were compressed and expanded for four cycles at an initial rate of 0.64 A2 x mol(-1) x s(-1) (333 mm2 x s x [-1]) up to a surface pressure pi approximately 65 mN/m, and pi-area per residue (pi-A) isotherms at 22 +/- 1 degrees C were obtained. The monolayers were microscopically observed for the fluorescence emission of the individual proteins present in the film lipid matrix, and their visual features were video recorded for image analysis. The pi-A isotherms of the DPPC/protein monolayers showed characteristic "squeeze out" effects at pi approximately 43 mN/m for R-SP-B and 55 mN/m for F-SP-C, as had previously been observed for monolayers of the native proteins in DPPC. Both proteins associated with the expanded (fluid) phase of DPPC monolayers remained in or associated with the monolayers at high pi (approximately 65 mN/m) and redispersed in the monolayer upon its reexpansion. At comparable pi and area/molecule of the lipid, the proteins reduced the amounts of condensed (gel-like) phase of DPPC monolayers, with F-SP-C having a greater effect on a weight basis than did R-SP-B. In any one of the lipid/protein monolayers the amounts of the DPPC in condensed phase were the same at equivalent pi during compression and expansion and from cycle to cycle. This indicated that only minor loss of components from these systems occurred between compression-expansion cycles. This study indicates that hydrophobic PS proteins associate with the fluid phase of DPPC in films, some proteins remain at high surface pressures in the films, and such lipid-protein films can still attain high pi during compression.

1,2-Dipalmitoylphosphatidylcholine↗