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Biomedical subjects

C Ortiz

Publications and source records attributed to C Ortiz.

At least 19 recordsLinked to original sources
PubMed2006

Nanoscale anisotropic plastic deformation in single crystal aragonite.

The nanoscale anisotropic elastic-plastic behavior of single-crystal aragonite is studied using nanoindentation and tapping mode atomic force microscopy imaging. Force-depth curves coaxial to the axis exhibited load plateaus indicative of dislocation nucleation events. Plasticity on distinct slip systems was evident in residual topographic impressions where four pileup lobes were present after indentation with a conospherical probe and distinct, protruding slip bands were present after indentation with a Berkovich pyramidal probe. A finite element crystal plasticity model revealed the governing roles of the {110}<001>slip system family, as well as the (100)[010], (100)[001], (010)[100], (010)[001], (001)[100] and (001)[010] systems.

Anisotropy↗
PubMed2004

Factors associated with condom use among young Denver inner city women.

BACKGROUND: Despite the availability of condoms and theoretically based interventions to promote their use, sexually active women aged 15 to 25 years continue to put themselves at risk for sexually transmitted diseases and unintended pregnancy. METHODS: One hundred ninety-eight inner city women were interviewed about knowledge and attitudes about condoms. Using the Transtheoretical Model, regression techniques were used to identify factors associated with condom use at last sex and the proportion of acts protected by a condom in the last 90 days. RESULTS: Constructs including intention to use (OR = 1.69, CI 1.07-2.65) and positive outcome expectancies (OR = 1.59, CI 1.03-2.46) were associated with condom use at last act of sexual intercourse. Similarly, intention to use condoms (RR = 1.58, CI 1.37-1.82), positive outcome expectancies (RR = 2.71, CI 2.41-2.99), perceived peer's use of condoms (RR = 2.25, CI 1.95-2.60), and number of places condoms were discussed (RR 1.05, CI 1.02-1.07) were associated with the proportion of protected acts. CONCLUSIONS: Constructs specified in the Transtheoretical Model are useful in describing condom use and have implications for targeting human immunodeficiency virus (HIV)/sexually transmitted diseases (STD)/unintended pregnancy interventions.

Adolescent↗
PubMed2003

Results in split liver transplantation.

INTRODUCTION: The shortage in cadaveric grafts has prompted the development of alternative surgical techniques to expand the donor pool. OBJECTIVE: To evaluate the feasibility of split liver transplantation using an observational, retrospective, and longitudinal study. MATERIALS AND METHODS: Between April 1986 and October 2002 we performed 875 liver transplants. From April 1991 to date, we performed 18 split liver transplantations in patients of mean age 42.27+/-25.65 years; five children and 13 adults; and 83.3% women. Urgent transplants accounted for 38.9%. Mean patient weight was 52.29+/-20.87 kg. Ex situ splitting was performed in 33%. The mean cold ischemia time was 460+/-265.69 minutes with a mean warm time of 64.33+/-11.78 minutes. Mean consumption of packed blood was 5.59+/-4.87 units; of frozen fresh plasma, 11.56+/-7.42 units; and of platelets 4.89+/-4.99 units. RESULTS: After a mean follow-up of 10.83+/-12.51 months, 55.56% of the recipients are alive. Actuarial patient and graft survival rates at 1 year are 55.6% and 44.12%, respectively. Actuarial patient and graft survival rates at 1 year, excluding operative mortality were 77% and 68%, respectively. Actuarial patient and graft survival rates at 1 year, comparing urgent and elective transplantations are: 14.29 and 14%, respectively, for urgent cases and 90.91 and 90% for elective ones. Operative mortality was 16.6% while mortality during follow-up was 26.6%. The late complications included arterial thrombosis (n=2): of whom the first needed liver retransplantation 4 months after split liver transplantation; chronic rejection (n=2), recurrence of hepatitis (n=1). CONCLUSIONS: Split liver transplantation is a useful way to expand the graft pool and shows better results in elective liver transplantation.

Adult↗
PubMed2003

Effect of strength and proprioception training on eversion to inversion strength ratios in subjects with unilateral functional ankle instability.

OBJECTIVES: To examine the effect of six weeks of strength and proprioception training on eversion to inversion isokinetic strength ratios (E/I ratios) in subjects with unilateral functional ankle instability. METHODS: Thirty eight subjects were randomly assigned to one of four treatment groups: strength training (S); proprioception training (P); strength + proprioception training (B); control (C). Isokinetic strength was tested before and after training using a Kin Com 125 automatic positioning isokinetic dynamometer. Subtalar joint eversion and inversion motions were tested both concentrically and eccentrically through a range of motion involving 40 degrees. All peak torque and average torque values were normalised for body mass. E/I ratios were calculated from average torque and peak torque measures by taking the concentric eversion value and combining it with the eccentric inversion value. Data were analysed using a mixed model analysis of variance with repeated measures on the test factor. Average torque and peak torque E/I ratios at 30 and 120 degrees/s were analysed separately. RESULTS: There were no significant differences in average torque and peak torque E/I ratios of the functionally unstable ankle for any of the groups after training compared with before. CONCLUSIONS: Six weeks of strength and proprioception training (either alone or combined) had no effect on isokinetic measures of strength in subjects with self reported unilateral functional instability. Further studies examining this agonist (concentric) to antagonist (eccentric) muscle group strength ratio are needed.

Adult↗
PubMed2001

Analysis of multicomponent formulations containing phenylpropanolamine hydrochloride, caffeine and diazepam by using LC.

A reverse phase high performance liquid chromatography assay was carried out for the simultaneous determination of three active principles present in tablets of different origin and wide commercial use in the Province of Córdoba (Argentina). Prescriptions, commercially available as appetite suppressants, very often include the active principles Phenylpropanolamine Hydrochloride (I), Caffeine (II) and Diazepam (III). Simultaneous determination of these three drugs: anorexic, central nervous stimulant and tranquilizer, respectively, in pharmaceutical dosage forms has not been reported. In this study these active principles are quantified. The only sample preparation necessary for the analysis was their dilution with acetonitrile. The resulting solution was filtered and analyzed on a column packed with Supelcosil LC-18 (5 microm) with acetonitrile:water (30:70 v/v) as initial mobile phase (0.4 ml min(-1)) and the detection was performed at 254 nm. Then a linear gradient up to 100% acetonitrile in 18 min (3.0 ml min(-1)) was applied. The procedure was simple and suitable for quality control. The calibration function was established in the ranges of 0.072-0.168 mg ml(-1) for I, 0.036-0.084 mg ml(-1) for II and 0.06-0.196 mg ml(-1) for III. The detection limits of these compounds were 12.8, 4.1 and 11.0 microg ml(-1), respectively with linear response. No chromatographic interference from the tablet excipients was found. The method described in this paper was validated following the analytical performance parameters required by the USP XXIV, and was successfully applied to the commercial tablets.

Caffeine↗
PubMed2001

Evaluation of mechanical and corrosion biocompatibility of TiTa alloys.

As-received and heat-treated Ti40Ta and Ti50Ta alloys were evaluated to determine their corrosion as well as mechanical performances and compared to Ti6A14V, a common material utilized for orthopedic (surgical) implants. Anodic potentiodynamic tests performed in Plasmalyte showed that all samples, except for the Ti50Ta specimen aged at 400 degrees C for 3 h gave a curve similar to that of Ti6A14V. Optical and TEM microscopy was performed to determine as-received and heat-treated microstructures. As-received materials showed an alpha precipitate in an alpha+beta and martensite matrix. Samples that were aged at 400 degrees C increased in the density and the length of the alpha precipitate. Vickers hardness measurements were performed to get an approximation of the tensile strengths. Aged Ti40Ta and Ti50Ta specimens produced the highest tensile values when compared to the Ti6A14V material, representing a 31% and 56% increase for the 3 h samples and an 18% and 58% increase for the 10 h samples. Of all the materials studied the Ti50Ta specimen aged for 10 h exhibited the best biocompatibility showing excellent corrosion resistance combined with the highest tensile strength (1089 MPa and 58% harder/stronger than Ti6A14V).

Journal Article↗
PubMed2001

Heat-shock responses in two leguminous plants: a comparative study.

Relative growth rates, basal and acclimated thermotolerance, membrane damage, fluorescence emission, and relative levels of free and conjugated ubiquitin and HSP70 were compared after 2 h of treatment at different temperatures between Prosopis chilensis and Glycine max (soybean), cv. McCall, to evaluate if the thermotolerance of these two plants was related to levels of accumulation of heat shock proteins. Seedlings of P. chilensis germinated at 25 degrees C and at 35 degrees C and grown at temperatures above germination temperature showed higher relative growth than soybean seedlings treated under the same conditions. The lethal temperature of both species was 50 degrees C after germination at 25 degrees C. However, they were able to grow at 50 degrees C after germination at 35 degrees C. Membrane damage determinations in leaves showed that P. chilensis has an LT(50) 6 degrees C higher than that of soybean. There were no differences in the quantum yield of photosynthesis (F(v)/F(m)), between both plants when the temperatures were raised. P. chilensis showed higher relative levels of free ubiquitin, conjugated ubiquitin and HSP70 than soybean seedlings when the temperatures were raised. Time-course studies of accumulation of these proteins performed at 40 degrees C showed that the relative accumulation rates of ubiquitin, conjugated ubiquitin and HSP70 were higher in P. chilensis than in soybean. In both plants, free ubiquitin decreased during the first 5 min and increased after 30 min of heat shock, conjugated ubiquitin increased after 30 min and HSP70 began to increase dramatically after 20 min of heat shock. From these data it is concluded that P. chilensis is more tolerant to acute heat stress than soybean.

Adaptation, Physiological↗
PubMed2001

[Colonic aganglionosis with ileal involvement. Ileocolic plasty].

During 1994 through 1999, we have treated five patients (3 boys, 2 girls) with total colonic aganglionosis (TCA) and ileal involvement. In three of them we performed a diverting ileostomy in the neonatal period and at the age of four and five months respectively in the remaining two patients, due to intestinal obstruction. In these two last patients a diagnosis of Hirschsprung's disease was made by anorectal manometry and rectal biopsies in the neonatal period. During laparotomy, a cutaneous ileostomy was created in all patients at the distal end of normal ileum, which was 30 to 110 cm (mean = 71 +/- 37 cm) from the ileocecal valve. After operation, a short bowel syndrome developed in three patients causing fluid and nutritional problems that required prolonged total parenteral nutrition (TPN). The definitive operative repair is performed at 4.5 to 14 months (mean = 8 +/- 3.7 months) by a 12 to 20 cm side-to-side ileocolostomy created between the ileum and aganglionic ascending color (Boley procedure) and ileorectal primary anastomosis (Rehbein procedure) using a circular stapler. Rectal dilatation, irrigation of the colon with saline, loperamide hydrochloride and resincholestyramine were begun in all patients postoperatively. Oral antibiotic prophylaxis, was given to the three patients who suffered from SBS. Oral feedings with semielemental diet were tolerated once stools were semiformed and TPN was discontinued at 8 to 34 days (mean = 21 +/- 1.7 days). postoperatively. After the definitive operation, enterocolitis developed in two patients, requiring one of them a short hospitalization during the episode. A possible explanation for the low incidence of enterocolitis in this series is the systematic postoperative use of irrigations of the colon with saline in all patients. These five patients have been followed-up for growth, development, bowel habit and continence. Follow-up has ranged from 15 to 62 months (mean = 32.2 +/- 19.2 months). Presently, all patients in this series have full enteral feeding and one to three bowel movements per day, with formed or semiformed stools. No patients is incontinent of stool. The patient's body weights (74 to 93%) and heights (89 to 92%) for their age were below average (four patients) or within normal range (one patient). Hemoglobin levels are within normal range in all patients. One patient has iron deficiency and another one has serum ferritin concentration below normal. Three patients have folic acid deficiency. Vitamin B12 absorption is normal in all patients. Although we can not conclude this is a better procedure than others, with is use we have obtained satisfactory results, with an excellent survival, scanty morbidity, a rapid return of bowel function and continence, and an acceptable physical development. During long-term follow-up, patients mus be evaluated for iron and folic acid deficiency.

Child↗
PubMed2000

Congestive heart failure in the United States: is there more than meets the I(CD code)? The Corpus Christi Heart Project.

BACKGROUND: Congestive heart failure (CHF) is increasing as a public health problem in the United States. The ability to quantify this problem has been limited by a lack of data regarding the validity of CHF identification. OBJECTIVE: To assess the validity of the use of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD) codes to identify hospitalizations with clinical evidence of an episode of acute CHF in data of The Corpus Christi Heart Project, a population-based surveillance program for hospitalized coronary heart disease. METHODS: The validation standard was a composite variable including the presence of physician diagnosed acute CHF or radiographic evidence of pulmonary edema. Data were abstracted from the medical records of 5083 patients identified as hospitalized for possible acute myocardial infarction, aortocoronary bypass surgery, percutaneous transluminal coronary angioplasty, and related revascularization procedures in the Corpus Christi Heart Project. Discharge diagnoses, a secondary source of data, were used to apply 3 computer algorithms to assess the assignment of ICD codes. RESULTS: The prevalence of clinically documented CHF was 27.1% (1376/5083). The ICD code 428 (CHF), assigned as the primary or a secondary discharge diagnosis, was associated with 62.8% sensitivity, 95.4% specificity, 83.5% positive predictive value, 87.4% negative predictive value, and a 24.8% underenumeration of CHF-related hospitalizations. An algorithm based on a series of ICD codes was associated with 67.1% sensitivity, 92.6% specificity, 77.1% positive predictive value, 88.3% negative predictive value, and a 13.0% underenumeration of CHF-related hospitalizations. CONCLUSIONS: Reliance on ICD codes results in the exclusion of one third of the patients with clinical evidence of acute CHF. This underenumeration is compounded by the typical reliance on the first listed diagnosis. Congestive heart failure may be a greater public health problem than currently recognized. The allocation of resources for relevant surveillance, research, medical care, and preventive efforts should be reevaluated.

Adult↗
PubMed2000

Mealiness assessment in apples and peaches using MRI techniques.

Mealiness (woolliness in peaches) is a negative attribute of sensory texture that combines the sensation of a desegregated tissue with the sensation of lack of juiciness. In this study, 24 apples cv. Top Red and 8 peaches cv. Maycrest, submitted to 3 and 2 different storage conditions respectively have been tested by mechanical and MRI techniques to assess mealiness. With this study, the results obtained on apples in a previous work have been validated using mathematical features from the histograms of the T2 maps: more skewed and the presence of a tail in mealy apples, similar to internal breakdown. In peaches, MRI techniques can also be used to identify woolly fruits. Not all the changes found in the histograms of woolly peaches are similar from those observed in mealy apples pointing to a different underlying physiological change in both disorders.

Food Technology↗
PubMed2000

[Influence of helminthic infections and nutritional status on immune response in Venezuelan children].

We investigated the influence of nutritional status, as determined from anthropometric measurement, and of helminthic infections on the immune response of children of low socioeconomic status in two rural communities in Venezuela: El Cardón in the state of Nueva Esparta and San Daniel in the state of Miranda. A total of 125 boys and girls between 2 and 15 years old participated in the study. Their socioeconomic stratum was determined by a modified Graffar method. A physical examination was performed, as was also an anthropometric evaluation that took into account three indicators--weight-for-height, weight-for-age, and height-for-age--according to parameters established by the World Health Organization. Other examinations included feces, secretory IgA in saliva, total serum IgE, and anti-Ascaris-specific immunoglobulins. The children in both of the communities were in strata IV and V of the of Graffar scale, with a significantly greater number of stratum V inhabitants in San Daniel (P < 0.001). The results suggest that exposure level and individual susceptibility to the parasites are determining factors in parasitic infection and immune system behavior. The intensity of the parasitic burden plays an important role in stimulating polyclonal IgE, which diminishes the effectiveness of the specific response to those infections. On the other hand, nutritional deficiencies could change the immune mechanisms of the mucous membranes, negatively influence the synthesis of secretory IgA, and stimulate the production of polyclonal IgE. Poor sanitary and socioeconomic conditions promote more exposure to gastrointestinal parasites and a deficient nutritional status, which modulates the immune response and affects serum IgE and secretory IgA production mechanisms.

Adolescent↗
PubMed1999

Extracellular HIV type 1 Tat protein induces CD69 expression through NF-kappaB activation: possible correlation with cell surface Tat-binding proteins.

The HIV-1 Tat protein, essential for HIV-1 gene expression and viral replication, is known to be secreted by infected cells and has pleiotropic effects on various cell functions. It seems that extracellular Tat may exert its functions on cellular targets by at least two different mechanisms, namely, by adsorptive endocytosis, and by a possible interaction with cell surface receptor(s). Here we report that extracellular Tat activates AIM/CD69 gene transcription through an NF-kappaB-dependent pathway in the erythroleukemia cell line K562. Tat induces NF-kappaB binding to DNA as a result of IkappaBalpha phosphorylation and degradation, which depend on the intracellular redox state. We found that the second Tat-coding exon is required for CD69 gene trans-activation, but not for HIV LTR gene transcription. Fluorescein-labeled Tat proteins were used to study cell surface binding sites and cellular uptake of the proteins. Full-length Tat protein has specific binding sites on the surface of K562 cells, whereas truncated Tat1-48, which is efficiently internalized by the cells, does not bind to the cell surface. Our results suggest that extracellular Tat may activate a cell surface-mediated pathway that induces intracellular signal transduction in K562 cells, leading to the activation of NF-kappaB and the transcription of NF-kappaB-dependent genes, such as CD69.

Antigens, CD↗
PubMed1999

Hydrophilic acrylic biomaterials derived from vitamin E with antioxidant properties.

Hydrogels based on polymeric derivatives of vitamin E for biomedical purposes have been prepared by copolymerization reaction of the alpha-tocopheryl methacrylate (V) with 2-hydroxyethyl methacrylate (H) in a range of composition between 5-20 wt % of V. The swelling behavior of the hydrogels in water, alkaline, and acidic media showed a slight decrease in the equilibrium water content with the content of V in the copolymer although in all cases it was superior to an EWC > 20%. The diffusion mechanism followed a Fickian behavior in all media. The values of the diffusion coefficients were in the range 2.5-1.6 10(-7) cm2/s. The states of water in the hydrogels were determined by DSC. A decrease in the content of freezing water was obtained with the V content for all media, and for all compositions lower values of freezing water were obtained in acidic or basic pHs than in distilled water. The copolymeric xerogels, analyzed by contact angle measurements, deviated from those expected taking into consideration those of the homopolymers and the average fraction of the monomers in the copolymer. The polar contribution dropped with the introduction of a small content (4 wt %) of the vitamin E-containing monomer, and it reached a value similar to that of poly-V for a composition of 49 wt % of V in the copolymer. This behavior is accounted for by the segregation of the macromolecular chains of both kinds of monomers, due mainly to differences in their polarity, molecular weights, and the reactivity of both monomers. Finally, thermogravimetric analysis showed a higher thermal (antioxidant) stability of the poly-V with respect to poly-H, giving rise to a residue of 18 wt %. The V-containing copolymers also showed an improved stability (antioxidant behavior), indicating the possibility of the V unit's interfering with the oxidative process, based on free-radical species, and, therefore, with the aging process at the cellular level.

Algorithms↗
PubMed1999

Mealiness assessment in apples using MRI techniques.

Small samples of Top Red apples stored 6 months under controlled atmosphere (expected to be non-mealy) and 2 degrees C (expected to be mealy) have been used for MRI imaging. Multi-slice-multi-echo magnetic resonance images (64*64 pixels) have been recorded with a 8 ms echo time. Three out of four apples corresponding to the sample maintained under controlled atmosphere did not developed mealiness while three out of four fruits corresponding to the sample stored at 2 degrees C became mealy after 6 months of storage. The minimum T2 values obtained for the mealy apples show to be significantly lower (F = 13.21) when compared with non-mealy apples pointing that a more desegregated structure and a lower juiciness content leads to lower T2 signal. Also, there is a significant linear correlation (r = -0.76) between the number of pixels with a T2 value below 35 ms within a fruit image and the deformation parameter registered during the Magness-Taylor firmness test. Finally, all T2 maps of mealy apples show a regional variation of contrast which is not shown for non-mealy apples. Significant differences (F = 19.43) between mealy and non-mealy apples are found in the histograms of the T2 maps as mealy apples show a skew histogram combined with a "tail" in their high T2 extreme which is not shown in the histograms of non-mealy apples. These histogram features are also shown for an apple showing internal breakdown indicating that in mealy apples there is a differential water movement that may precede internal breakdown.

Food Technology↗