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Biomedical subjects

J Ruiz

Publications and source records attributed to J Ruiz.

At least 127 records · Page 7Linked to original sources
PubMed2000

Disuse bone loss in hindquarter suspended rats: partial weightbearing, exercise and ibandronate treatment as countermeasures.

The purpose of this study was to evaluate potential countermeasures for bone loss during long-term space missions in the hindquarter suspended rat, including partial weight bearing (surrogate for artificial gravity) episodic full weight bearing (2 hour/day full weight bearing) and treatment with the third generation bisphosphonate ibandronate (Roche). Graded mechanical loading was studied by housing the animals on a novel servo controlled force plate system which permitted the titration of mechanical force at varying frequency and amplitude and different levels of weight bearing. The force plate, which forms the cage floor, is a glass platform supported by an 18" diameter speaker cone filled with expanding polyurethane foam. An infrared optical sensor attached to the speaker cone yields a voltage linearly related to vertical displacement of the glass platform. The dynamic force on the paw was computed as a product of the apparent mass of the animal on the platform at rest and the acceleration of the platform determined from the second derivative of the optical sensor output. The mass of the animal on the platform was varied by adjusting tension on the tether suspending the animal. Mechanical impact loading was titrated with the force plate resonating at different frequencies, including 3 Hz and 16 Hz.

Animals↗
PubMed1999

Optimal conditions for alumina coating formation on the MA956 superalloy for prosthetic bearing applications.

An experimental study of the oxidation treatment at high temperature of the ODS MA956 superalloy was conducted in an attempt to achieve a protective alumina scale for biomedical applications. A quadratic response-surface model was developed in order to study the effects of treatment time and temperature (in the range of 1000 degrees C to 1250 degrees C) on scale thickness. The obtained model adequately represents the experimental response and shows that the thickness gradients of the layer increase with the temperature for each exposure time and decrease steadily to zero as the treatment time increases. The microstructural characterization reveals that the alumina scale formed at or above 1000 degrees C consists of an alpha-alumina phase. Treatments at temperatures above 1150 degrees C give rise to an alumina scale with some defect probability. An increase in the temperature up to 1200 degrees C gives rise to the appearance of some blistering of the superficial scale. An oxidation treatment of 100 h at 1100 degrees C was found to be the best for guaranteeing the formation of a defect-free, compact, adherent, and continuous alpha-alumina scale thick enough to support satisfactory wear and biological conditions.

Alloys↗
PubMed1999

Pleomorphic rhabdomyosarcoma of the uterus in a postmenopausal woman with elevated serum CA125.

BACKGROUND: Pure rhabdomyosarcoma of the uterus is an exceedingly rare tumor. While there are no commonly associated tumor markers, a previously reported case confirmed CA125 production by a pure uterine rhabdomyosarcoma. CASE: We describe a postmenopausal woman who presented with vaginal bleeding and was diagnosed with pleomorphic rhabdomyosarcoma of the uterus. Of particular interest was an elevated serum CA125 level at presentation. Immunohistochemical staining with CA125 antibody, however, showed no activity within the tumor. Despite aggressive therapy, the patient experienced distant nodal metastases and succumbed to the disease within 25 months of diagnosis. CONCLUSION: Our patient illustrates the typical presentation and aggressive behavior of this rare neoplasm. While serum CA125 may be a useful tumor marker in selected patients, elevated levels do not directly reflect tumor burden when associated with negative immunohistochemical staining.

CA-125 Antigen↗
PubMed1999

Six-year prospective study of risk and prognostic factors in patients with nosocomial sepsis caused by Acinetobacter baumannii.

In this prospective study, the risk factors associated with nosocomial sepsis Caused by Acinetobacter baumannii or Pseudomonas aeruginosa were compared. Prior use of broad-spectrum antibiotics, urinary tract catheter, prior surgery, and mechanical ventilation were significantly associated with nosocomial sepsis caused by Acinetobacter baumannii. The mean prognostic factors significantly associated with mortality were known focus of infection, multiresistant Acinetobacter baumannii, and inappropriate antibiotic treatment. Adequate knowledge of these findings is important to ensure appropriate management of patients and rational use of antibiotics.

Acinetobacter↗
PubMed1999

Evolution of resistance among clinical isolates of Acinetobacter over a 6-year period.

The aim of this report was to study the evolution of susceptibilities of 1532 clinical isolates of Acinetobacter recovered over a period of 6 years. The minimal inhibitory concentrations (MICs) of 15 antimicrobial agents were determined for all the isolates. The respective percentages of resistant strains in the years 1991 and 1996 were as follows: ciprofloxacin, 54.4% and 90.4%; tobramycin, 33% and 71.8%; amikacin, 21% and 83.7%; ampicillin plus sulbactam, 65.7% and 84.1%; ceftazidime, 57.4% and 86.8%; ticarcillin, 70% and 89.4%; trimethoprim plus sulfamethoxazole, 41.1% and 88.9%; and imipenem, 1.3% and 80%. The MIC90s of ciprofloxacin, sparfloxacin, biapenem, meropenem, imipenem, cefepime, cefpirome, and rifampicin against 250 imipenem-resistant Acinetobacter strains were >32, >32, 128, >256, 256, >256, 256, and 16 mg/l, respectively. With serious infections, it was necessary to resort to the use of colistin, the only antibiotic active in vitro.

Acinetobacter↗
PubMed1999

[Benign metastasizing pulmonary leiomyomatosis. A report of 3 cases].

The benign metastasizing leiomyoma is an uncommon variety of leiomyoma, tumor derived from smooth muscular tissue. The benign metastasizing leiomyoma affects a middle age women, with antecedents of uterine leiomyoma, the pulmonary lesions appeared as a multiple nodules, without systemic affectation. We present three cases of benign metastasizing leiomyoma that de diagnosis was made for biopsy by thoracotomy; and in one case the markers from estrogens' receivers were positive.

Biopsy↗
PubMed1999

Risk factors for lower airway bacterial colonization in chronic bronchitis.

The aim of this study was to determine the prevalence and risk factors for lower airway bacterial colonization (LABC) in stable chronic bronchitis (CB). Forty-one outpatients with CB were enrolled in the study (age 63.8+/-9.1 yrs (mean+/-SD); forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) 62.8+/-11.2; current/former smokers 24/17). All patients had normal chest radiographs and an indication for performing fibreoptic bronchoscopy (pulmonary nodule, remote haemoptysis). The protected specimen brush (PSB) was used for bacterial sampling, and concentrations > or = 1,000 colony-forming units (cfu) x mL(-1) were considered positive for LABC. The repeatability of the procedure in CB was assessed in a random subsample of 18 subjects. A 72.2% quantitative agreement was found in the repeatability assessment of the PSB technique. Positive PSB cultures, obtained in 9 out of 41 (22%) patients, mainly yielded Haemophilus influenzae. The logistic regression model, used to determine which variables were related to colonization, showed that LABC was associated with current smoking (odds ratio (OR) 9.83, confidence interval (CI) 1.16-83.20) and low FVC (OR 0.73, CI 0.65-0.81). Age and FEV1 were not related to LABC. It was concluded that the prevalence of LABC in stable CB is high (22%), and current smoking is an important risk factor.

Bacteria↗
PubMed1999

Intratumoral injection of bone-marrow derived dendritic cells engineered to produce interleukin-12 induces complete regression of established murine transplantable colon adenocarcinomas.

Stimulation of the antitumor immune response by dendritic cells (DC) is critically dependent on their tightly regulated ability to produce interleukin-12 (IL-12). To enhance this effect artificially, bone marrow (BM)-derived DC were genetically engineered to produce high levels of functional IL-12 by ex vivo infection with a recombinant defective adenovirus (AdCMVIL-12). DC-expressing IL-12 injected into the malignant tissue eradicated 50-100% well established malignant nodules derived from the injection of two murine colon adenocarcinoma cell lines. Successful therapy was dependent on IL-12 transfection and was mediated only by syngeneic, but not allogeneic BM-derived DC, indicating that compatible antigen-presenting molecules were required. The antitumor effect was inhibited by in vivo depletion of CD8+ T cells and completely abrogated by simultaneous depletion with anti-CD4 and anti-CD8 mAbs. Mice which had undergone tumor regression remained immune to a rechallenge with tumor cells, showing the achievement of long-lasting systemic immunity that also was able to reject simultaneously induced concomitant untreated tumors. Tumor regression was associated with a detectable CTL response directed against tumor-specific antigens probably captured by DC artificially released inside tumor nodules. Our results open the possibility of similarly treating the corresponding human malignancies.

Adenocarcinoma↗
PubMed1999

Gene therapy of viral hepatitis and hepatocellular carcinoma.

Gene therapy represents an attractive approach to treat a great variety of diseases, both inherited and acquired, and it is moving slowly from a proof-of-principle phase to a wide application in most medical fields. Liver cancer and viral hepatitis are natural targets for this new therapeutic alternative due to the lack of success of conventional antitumoral and antiviral treatments and the ominous prognosis related with liver tumours. Gene therapy for viral hepatitis is aimed to boost the patient immune response against viral antigens or to make cells resistant to infection by blocking the viral life cycle. Gene transfer techniques applied to the treatment of hepatocellular carcinoma include drug sensitization by suicide genes, genetic immunotherapy, normal tissue protection by transfer of the multidrug resistance gene, replacement of tumour suppressor genes, inhibition of oncogenes and modifications of the biology of the tumour (antiangiogenesis). However, major advances in our understanding of the regulation of gene expression, design of the expression cassettes and development of more efficient gene transfer vectors are mandatory before gene therapy can become a widely used therapeutic modality.

Carcinoma, Hepatocellular↗
PubMed1999

Decreased production of AmpC-type beta-lactamases associated with the development of resistance to quinolones in Citrobacter freundii strains.

The effect of fluoroquinolones in Citrobacter freundii strains that results in a decreased expression of cephalosporin-hydrolysing beta-lactamases was studied. Resistance to broad-spectrum cephalosporins and penicillins in two C. freundii clinical isolates was associated with moderate production of chromosomal AmpC-type-beta-lactamase in addition to changes in the outer membrane proteins profile with respect to wild-type C. freundii strains. Ten quinolone-resistant mutants were derived from the two clinical isolates using increasing fluoroquinolone concentrations. The level of susceptibility to cephalosporins and meropenem of these 10 mutants was increased and was associated with a 3.6-32% diminution in the hydrolyzing activity of their periplasmic extracts containing beta-lactamases on cephaloridine as compared with those from their parent strains. Susceptibility to cephalosporins and meropenem, as well as the expression of chromosomal AmpC-type-beta-lactamase in C. freundii strains, was influenced by the exposure to quinolones.

Anti-Infective Agents↗
PubMed1999

Mechanisms of resistance to ampicillin, chloramphenicol and quinolones in multiresistant Salmonella typhimurium strains isolated from fish.

Mechanisms of antibiotic resistance and epidemiological relationships were investigated for five multiresistant strains of Salmonella typhimurium isolated from fish in India. Four strains showed resistance to nalidixic acid, chloramphenicol, tetracycline, co-trimoxazole, gentamicin and beta-lactam antibiotics. The remaining strain was susceptible to all beta-lactam antibiotics tested and to co-trimoxazole but resistant to the other antibiotics tested. Epidemiological analysis performed by REP-PCR showed that the five isolates belonged to the same clone. Resistance to nalidixic acid was related to a single mutation in the gyrA gene. Chloramphenicol resistance was related to the production of chloramphenicol acetyl-transferase. An OXA-1 beta-lactamase, located in an integron, was responsible for resistance to ampicillin. These results indicate the health hazard posed by the fact that S. typhimurium may acquire or develop several mechanisms of resistance to a variety of antibiotics, including quinolones, and can thus cause disease in humans which may be difficult to treat.

Ampicillin↗
PubMed1999

Mechanisms involved in the development of resistance to fluoroquinolones in Escherichia coli isolates.

Eighteen quinolone-resistant isolates of Escherichia coli were selected by exposing ten clinical isolates to increasing concentrations of norfloxacin and lomefloxacin. The mutant isolates showed a multiple-antibiotic-resistance phenotype. All of them contained single mutations in gyrA consisting of the substitution of Ser-83-->Leu (n = 14), Val (n = 1) or Ala (n = 1) and the substitution of Asp-87-->Asn (n = 2). Only one concomitant mutation in parC (Ser-80-->Arg) was detected. Four parent isolates exhibited a single mutation in gyrA which required < or = 12 mg/L of norfloxacin to be inhibited. Fluoroquinolone resistance, in the 18 quinolone-resistant mutants, was a result of mutations affecting DNA gyrase plus decreased fluoroquinolone uptake. This latter mechanism of resistance was a combined effect of an absence of OmpF and an increase in active efflux in eight isolates, or an increased active efflux alone in the remaining ten selected mutants.

Anti-Infective Agents↗