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Biomedical subjects

J M O'Brien

Publications and source records attributed to J M O'Brien.

At least 109 records · Page 6Linked to original sources
PubMed1989

Mutagenicity of merocyanine 540-mediated photosensitization.

Merocyanine 540 (MC 540) is a photosensitizing dye with antineoplastic and antiviral properties. Because photoexcited MC 540 generates singlet molecular oxygen and possibly other reactive oxygen species there is concern that MC 540-mediated photosensitization may be mutagenic. In this paper, we report on the induction of ouabain- and 6-thioguanine-resistant mutants in Chinese hamster ovary (CHO) cells by MC 540 and light. Incubation with merocyanine 540 in the dark was not mutagenic. Simultaneous exposure to dye and high-intensity (70-75 W/m2) white or green light caused a small but significant increase in the frequency of both ouabain- and 6-thioguanine-resistant mutants. Similar increases in mutation frequencies were observed when the cells were exposed to white or green light in the absence of dye. When the fluence rate of the white light source was reduced by 50% (i.e., to 35 W/m2) but the duration of exposure doubled to keep the fluence constant, dye-mediated photosensitization and exposure to light alone generated few if any mutants. These results indicated that MC 540-mediated photosensitization is not mutagenic (as defined by the employed assays) as long as a nonmutagenic light source is used to excite the photosensitizer. They caution against the use of very powerful light sources in clinical applications of MC 540-mediated photosensitization.

Animals↗
PubMed1988

[3H]dexamethasone binding to plasma membrane-enriched fractions from liver of nonadrenalectomized rats.

Using liver from nonadrenalectomized adult male rats, binding sites for [3H]dexamethasone in particulate fractions are demonstrated. The binding is thermolabile, saturable, and specific for glucocorticoid. The apparent dissociation constant (Kdapp) for [3H]dexamethasone (0.48 +/- 0.084 microM) is 60-fold greater than that for cytosolic receptor (7.9 +/- 1.5 nM). The Kdapp for [3H]cortisol in particulate fractions is 2.5-fold lower than for [3H]dexamethasone (Kdapp = 0.18 microM). The binding capacities for particulate and cytosolic glucocorticoid-binding sites also differ significantly, with particulate sites at least 9.1-fold more concentrated than cytosolic sites in liver tissue. Particulate sites are determined in Percoll density gradients to have a density of 1.039 g/cc. Saturable [3H]dexamethasone radioactivity coelutes from these gradients with the plasma membrane marker enzyme 5'-nucleotidase. Adrenalectomy causes the complete loss of particulate binding sites by 6 days postadrenalectomy; however, these sites can be regenerated to two thirds of the nonadrenalectomy level by 20-30 days postadrenalectomy.

Adrenal Glands↗
PubMed1988

Obstetric ultrasound training for family physicians. Results from a multi-site study.

A practical program to train family physicians in obstetric ultrasound was tested with 13 family physicians. Each physician completed 6.5 days of course work and ultrasound laboratory apprenticeship prior to beginning a clinical preceptorship of approximately 14 months' duration. During the clinical preceptorship the physicians performed ultrasound studies in their own offices. All studies were reviewed by a local consultant radiologist utilizing examination data sheets and videotapes. At the conclusion of the training program, the physicians took a combined practical and written proficiency examination administered by an independent sonographer. Eight physicians completed the training, performing during the preceptorship an average of 78 examinations. The rated performance of the physicians improved markedly over the course of the preceptorship. During the last segment of the preceptorship the radiologist preceptors rated 94 percent of the ultrasound studies as acceptable, compared with 79 percent rated acceptable at the beginning of the preceptorship. Seven of the eight physicians completing the protocol took the proficiency examination: all passed. This study can provide a blueprint for an individual family physician to design his own training, or it can guide an academic department of family medicine in developing and evaluating ultrasound training programs for residents and practicing physicians.

Education, Medical, Continuing↗
PubMed1988

Xanthogranulomatous pyelonephritis. A reappraisal and immunohistochemical study.

The clinicopathologic features of 17 patients with xanthogranulomatous pyelonephritis are described, together with results on a number of histochemical and immunohistochemical techniques that were used to demonstrate the variety of cells involved. Based on our clinicopathologic data and review of the literature, we believe that xanthogranulomatous pyelonephritis should be regarded as a destructive, and, at times, tumefactive inflammatory process that may complicate chronic pyelonephritis. The initiation of this process remains an enigma. However, there appears to be three main features that are associated with xanthogranulomatous pyelonephritis: pelvicalyceal obstruction, ulceration of the pelvicalyceal urothelium, and bacterial infection.

Adult↗
PubMed1986

Ectopic beta-human chorionic gonadotropin production by bladder urothelial neoplasia.

Endocrine manifestations are rarely observed in bladder urothelial neoplasia. To our knowledge, only 11 cases of choriocarcinoma have been reported in this site, and recently the production of beta-human chorionic gonadotropin has been demonstrated in these tumors by applying the immunoperoxidase technique. Of 104 transitional cell neoplasms of the bladder, we demonstrated by the indirect immunoperoxidase technique beta-human chorionic gonadotropin production in 12 neoplasms, 11 of which were grade 3 and 4 transitional cell carcinomas.

Aged↗
PubMed1985

Transitional cell carcinoma of the upper renal tract in rubber workers.

We report two patients where transitional cell carcinoma of the upper urinary tract developed after occupational exposure to known carcinogens, in the rubber industry. Although carcinoma of the bladder is well recognized in this context, to our knowledge, this association has not been reported previously.

Carcinoma, Transitional Cell↗
PubMed1985

Identification of a trans-dominant mutation affecting proline dehydrogenase in Escherichia coli.

L-Proline dehydrogenase catalyzes the oxidation of L-proline to delta 1-pyrroline-5-carboxylate, a reaction that is an important step in the utilization of proline as a carbon or nitrogen source by bacteria. A mutant of Escherichia coli K-12 lacking L-leucyl-tRNA:protein transferase had been found previously to contain about five times as much proline dehydrogenase activity as its parent strain. This difference has now been shown to be due to the presence in the parent strain of a previously unrecognized mutation. This mutation, which has been designated put-4977, specifically affects proline dehydrogenase rather than proline uptake. Although proline dehydrogenase remains inducible by L-proline in strains carrying the mutation, there is a premature cessation of differential synthesis during induction that results in a lower specific activity. The mutation shows about 50% P1-mediated cotransduction with pyrC and is therefore located at about 22 min on the E. coli chromosome. Merodiploids containing a normal F' factor still exhibit decreased enzyme activity, indicating that the put-4977 mutation is trans-dominant. The mutation cannot be detected in present stocks of the transferase-deficient mutant, suggesting that this mutant is a revertant for put-4977.

Acyltransferases↗
PubMed1985

Idiopathic hydronephrosis. Light microscopic features and pathogenesis.

A histological study of surgical specimens of idiopathic hydronephrosis demonstrated an abnormal muscle arrangement at the ureteropelvic junction in 18 of 26 cases. We believe this abnormality to be the cause in these cases. At this junction, the muscle bundles, instead of displaying the normal interwoven (braided) pattern, are arranged into an outer circular and an inner longitudinal layer. This abnormal muscle arrangement can be attributed to local failure of the physiological uncoiling during growth and development.

Adolescent↗
PubMed1984

Spoken and signed naming of foods after receptive exclusion training in severe retardation.

Two low-functioning mentally retarded subjects learned to name food items after receptive exclusion training, conducted as follows: The subjects first learned to select a small number of foods in a two-choice matching-to-sample task. For one subject, the samples were dictated names; for the other, the samples were manual signs. They also learned to name these "known" foods, either orally or by signing. On exclusion trials, a known food was displayed with a new food whose corresponding name or sign had not yet been learned, and a novel sample (spoken or signed), corresponding to the new food, was presented. The subjects typically selected the new food immediately, apparently by "excluding" the food related to the known sample. If a known sample was presented, however, the subjects continued to select the known food correctly. Periodically during exclusion training with a number of new foods, the subjects were tested for production of food names or signs. With few exceptions, the subjects produced the food names without direct training, often after only a few receptive exclusion trials. The results suggest strategies for teaching simple receptive and expressive relations to severely mentally retarded individuals.

Adolescent↗
PubMed1984

Association of hydrogen metabolism with unitrophic or mixotrophic growth of Methanosarcina barkeri on carbon monoxide.

Methanosarcina barkeri was adapted to grow on carbon monoxide by sequential transfer of the culture in medium that contained CO (100% of culture headspace). These experiments document the ability of the organism to grow slowly (65-h doubling time) and to produce methane and CO2 either on CO as the sole carbon and energy source or by the simultaneous consumption of methanol and CO. During growth on CO as carbon and energy source, net hydrogen formation occurred when the CO partial pressure in the culture headspace was greater than 20% CO, but hydrogen was consumed when the CO concentration was below this value.

Carbon Monoxide↗