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Biomedical subjects

J R Goldberg

Publications and source records attributed to J R Goldberg.

9 recordsLinked to original sources
PubMed1997

Electrochemical response of CoCrMo to high-speed fracture of its metal oxide using an electrochemical scratch test method.

A new test method was used to rapidly produce a controlled, repeatable scratch on the surface of CoCrMo (ASTM F75) samples, resulting in fracture of the surface oxide. Current transients resulting from ionic dissolution and repassivation of the exposed reactive alloy were measured with the samples potentiostatically held in phosphate-buffered saline. The effects of potential, contact load, pH, aeration, and proteins on the magnitude of the current transients and time constants for repassivation were determined. Using the scratch test apparatus, topographic images of scratched surfaces were constructed and used to measure scratch depth. Aeration had no significant effect on peak currents and time constants owing to the availability of oxygen from the hydrolysis of water. Peak current behavior reflected the transition regions observed in polarization curves. A decrease in peak currents in the presence of albumin may have been due to barrier effects of the adsorbed protein preventing water from reaching the sample surface, or lubrication resulting in less material removed from the surface during scratching. Peak currents and scratch depth increased with load. A model used to predict repassivation behavior was in agreement with experimental results.

Electrochemistry↗
PubMed1988

Altered triiodothyronine metabolism in Zucker fatty rats.

Genetically obese Zucker fatty rats require two autosomal recessive genes (fa/fa) to express the obese phenotype. The obese Zucker rat (fa/fa) has decreased total and free serum T3 concentrations, but normal serum T4 concentrations, compared to those in their lean littermates. To elucidate the mechanism of these differences, we measured the MCR and production rate (PR) of T4 and T3 in the three genotypes of 4-month-old male Zucker rats (Fa/Fa, Fa/fa, and fa/fa). In addition, 5'-deiodinase activity in liver, kidney, and brown adipose tissue homogenates was determined. T4 MCRs were equivalent in all three genotypes, but a decreased T3 MCR was seen in Fa/fa and fa/fa rats. An additive effect of the fa gene was noted with respect to the decrease in T3 MCR (Fa/Fa, 42.0 +/- 1.5; Fa/fa, 38.7 +/- 2.4; fa/fa, 34.7 +/- 3.4 ml/h; P less than 0.05). Whole body T4 PRs were equal in all three genotypes, but the T3 PR was decreased in the fa/fa rat by 25% compared to that in the homozygous lean rats (15.7 +/- 2.1 vs. 21.2 +/- 2.4 ng/h; P less than 0.005). Liver and kidney 5'-deiodinase activities were decreased in the fa/fa rat by 34% (P less than 0.005) and 20% (P less than 0.01), respectively. Brown adipose tissue and pituitary 5'-deiodinase activity were similar in all three genotypes. These results show a reduction in T3, but not T4, MCR in obese Zucker rats. Whole body T3 production and type I 5'-deiodinase activity were decreased in the obese (fa/fa) rats. These results suggest that decreased T4 to T3 conversion is responsible for the decreased T3 production rate in the fatty rat and may contribute to its obesity.

Animals↗
PubMedDate not supplied

Mifepristone (RU 486): current knowledge and future prospects.

Mifepristone (RU 486) has received recent attention for its effects as an abortifacient. Mifepristone has not yet been approved for use in the United States. The Food and Drug Administration issued an "approvable letter" in September 1996, but mifepristone will not be available in the United States until a new manufacturer is found. Experience with mifepristone is extensive in Europe, and there have been retrospective studies and large, controlled clinical trials of its efficacy. It is most efficacious when administered to women who are less than 8 weeks pregnant, in a single 600-mg oral dose followed 48 hours later by administration of intravaginal misoprostol. This regimen has a success rate of 98%, as do most surgical abortive procedures. The most frequent adverse effect is painful contractions, which occur in up to 93% of women, with oral analgesia required in as many as half the cases. Large-scale surveys of women who elected medical abortion reported high patient satisfaction. Mifepristone is likely to have additional clinical uses. Researchers are exploring mifepristone's potential uses in cervical ripening and labor induction; contraception; delivery after intrauterine demise; treatment of breast cancer, unresectable meningioma, and prostate cancer; amelioration of endometriosis; and management of Cushing syndrome.

Abortifacient Agents, Steroidal↗
PubMedDate not supplied

Reversal of central benzodiazepine effects by intravenous flumazenil.

The purpose of this study was to determine the efficacy of flumazenil in safely expediting patient recovery from benzodiazepine sedation. This double-blind, randomized, placebo-controlled study involved 30 patients who received conscious sedation induced by intravenous midazolam given for a dental surgical procedure. Patients who received flumazenil were rated significantly more alert than were placebo-treated patients at 5 and 15 min following test drug administration. They also had significantly superior scores on the digital symbol substitution test and on tests in a comprehensive modified neurological examination 5 min after receiving flumazenil. Group differences were not as impressive on recall and recognition tests. However, flumazenil patients scored somewhat more favorably than the placebo group patients in identifying simple objects they had been shown during the observation period following surgery. Flumazenil appears to be a promising drug for reversing midazolam conscious sedation.

Adult↗