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Biomedical subjects

R Parker

Publications and source records attributed to R Parker.

At least 163 records · Page 9Linked to original sources
PubMed1990

Treatment of androgenic disorders with dexamethasone: dose-response relationship for suppression of dehydroepiandrosterone sulfate.

Glucocorticoids are effective in suppressing androgens in many women whose levels of these steroids are elevated. Their use has been controversial because of inconsistent reports about efficacy and concern about safety. We investigated the dose-response relationship for suppression of dehydroepiandrosterone sulfate (DHEAS) with the use of dexamethasone. Thirty women with an initial DHEAS value of greater than or equal to 300 micrograms/dl were studied. All had cystic or inflammatory acne, hirsutism, or androgenic alopecia. Dexamethasone was given as a single bedtime dosage of 0.125, 0.250, or 0.375 mg. Mean dosage required for suppression was 0.256 mg daily. Suppression of the DHEAS level to less than or equal to 200 micrograms/dl was achieved with 0.125 mg in 25% of women, 0.250 mg in an additional 50%, and 0.375 mg in a further 20%. Most patients were taking spironolactone when the study was performed. Effective suppression is attained with dexamethasone doses significantly lower than previously thought. Use of these doses was not associated with a significant incidence of adverse effects.

Acne Vulgaris↗
PubMed1990

Translation and a 42-nucleotide segment within the coding region of the mRNA encoded by the MAT alpha 1 gene are involved in promoting rapid mRNA decay in yeast.

In yeast, the mRNA encoded by the MAT alpha 1 gene is unstable (t1/2 = 5 min) and the mRNAs encoded by the ACT1 gene (t1/2 = 30 min) and the PGK1 gene (t1/2 = 45 min) are stable. To understand the RNA structural features that dictate mRNA decay rates in yeast, we have constructed PGK1/MAT alpha 1 and ACT1/MAT alpha 1 gene fusions and analyzed the decay rates of the resultant chimeric transcripts. Fusion of a MAT alpha 1 segment containing 73% of the coding region and the 3' untranslated region to either of the stable genes is sufficient to cause rapid decay of the chimeric mRNAs (t1/2 = 6-7.5 min). Sequences required for this rapid decay are not found in the MAT alpha 1 3' untranslated region but are located within a 42-nucleotide segment of the coding region that has a high content (8 out of 14) of rare codons. Introduction of a translational stop codon upstream of this region stabilizes the hybrid mRNAs, indicating that the rapid decay promoted by these sequences is dependent on ribosomal translocation.

Base Sequence↗
PubMed1990

Breast cancer and dietary and plasma concentrations of carotenoids and vitamin A.

A case-control study of breast cancer was conducted in Buffalo. Participants completed a food frequency questionnaire and donated a fasting blood sample before definitive workup for breast masses. Dietary and plasma concentrations of carotenoids and retinol for 83 women found to have breast cancer were compared with those of 113 women found to be free of breast cancer (control subjects). There were no case-control differences in dietary estimates of vitamin A intake or in plasma alpha-carotene and lycopene. However, subjects with breast cancer had lower concentrations of plasma beta-carotene than did control subjects (P = 0.02). There was no overall association between plasma retinol and breast cancer but a positive relationship was observed between retinol and breast cancer in the subgroup with low beta-carotene values. These results suggest that low plasma beta-carotene is associated with increased risk of breast cancer. Other studies will need to determine whether low carotene concentrations are a subtle effect of the disease or might be causally related to breast cancer.

Adult↗
PubMed1990

Erythrocyte fatty acids, plasma lipids, and cardiovascular disease in rural China.

Cardiovascular disease (CVD) mortality (coronary heart disease, hypertensive heart disease, and stroke), plasma lipids, and red blood cell fatty acid composition were examined in an ecologic study in 65 rural counties in the People's Republic of China. Means of plasma total cholesterol, triglyceride, low-density-lipoprotein (LDL) cholesterol, and high-density-lipoprotein (HDL) cholesterol concentrations were substantially lower and the ratio of HDL cholesterol to total cholesterol was higher in this Chinese population than in Western populations. Mortality rates for CVD in China were well below Western values. Within China neither plasma total cholesterol nor LDL cholesterol was associated with CVD. A strong inverse correlation between red blood cell oleate concentrations and CVD was observed. However, red blood cell oleate concentrations were not associated with plasma cholesterol but were strongly negatively associated with arachidonate concentrations, suggesting potential diminution of CVD by oleate through reduced platelet aggregability. The results indicate that geographical differences in CVD mortality within China are caused primarily by factors other than dietary or plasma cholesterol.

Adult↗
PubMed1990

Day case surgery.

Explore the source record for details and available documents.

Ambulatory Surgical Procedures↗
PubMed1990

Fine-needle aspiration for diagnosis of intranodal squamous-cell carcinoma metastatic from the skin.

Fine-needle aspiration is a useful way to determine the presence of squamous-cell carcinoma in enlarged lymph nodes of patients at high risk for metastases. Advantages include a high degree of accuracy, outpatient as well as inpatient availability, and negligible potential for seeding of malignant cells. Cutaneous oncologists should consider using this technique in patients with lymphadenopathy and a previous history of cutaneous squamous cell carcinoma.

Aged↗
PubMed1990

Identification and comparison of stable and unstable mRNAs in Saccharomyces cerevisiae.

We developed a procedure to measure mRNA decay rates in the yeast Saccharomyces cerevisiae and applied it to the determination of half-lives for 20 mRNAs encoded by well-characterized genes. The procedure utilizes Northern (RNA) or dot blotting to quantitate the levels of individual mRNAs after thermal inactivation of RNA polymerase II in an rpb1-1 temperature-sensitive mutant. We compared the results of this procedure with results obtained by two other procedures (approach to steady-state labeling and inhibition of transcription with Thiolutin) and also evaluated whether heat shock alter mRNA decay rates. We found that there are no significant differences in the mRNA decay rates measured in heat-shocked and non-heat-shocked cells and that, for most mRNAs, different procedures yield comparable relative decay rates. Of the 20 mRNAs studied, 11, including those encoded by HIS3, STE2, STE3, and MAT alpha 1, were unstable (t1/2 less than 7 min) and 4, including those encoded by ACT1 and PGK1, were stable (t1/2 greater than 25 min). We have begun to assess the basis and significance of such differences in the decay rates of these two classes of mRNA. Our results indicate that (i) stable and unstable mRNAs do not differ significantly in their poly(A) metabolism; (ii) deadenylation does not destabilize stable mRNAs; (iii) there is no correlation between mRNA decay rate and mRNA size; (iv) the degradation of both stable and unstable mRNAs depends on concomitant translational elongation; and (v) the percentage of rare codons present in most unstable mRNAs is significantly higher than in stable mRNAs.

Blotting, Northern↗
PubMed1990

The perceived effects of drug messages on use patterns in adolescents.

Following a survey of over 5,000 students in north central Idaho and southeast Washington, an interviewing strategy was implemented with 223 adolescents randomly selected by their principals. The strategy was designed to learn: 1) which sources have utility and credibility with youth in providing drug information; 2) whether different message content and delivery style have differential effects upon that group; and 3) whether widely held perceptions voiced by parents and teachers about their ineffectiveness as information sources were accurate. Double-blind interviews, arranged to protect respondent anonymity, were conducted by trained interviewers from a research methods class. No interview was held when either an interviewer or respondent knew the other. Among the important findings of the study were that: 1) parents and teachers are trusted, credible sources of drug information; 2) doctors, nurses, law officers, and clergy are also credible but not visible to youth; 3) the evil media and celebrity fears of parents and teachers are largely ungrounded in adolescent perception; and 4) factual information from credible sources emphasizing the range of types of negative consequences associated with drug use can exert powerful effects upon adolescents' reported personal use of drugs.

Adolescent↗
PubMed1989

Viable and nonviable aortic homografts in the subcoronary position: a comparative study.

One hundred fifty-five freeze-dried, 63 frozen, and 337 Hanks'-antibiotic solution preserved or nutrient-antibiotic solution preserved homografts used for isolated aortic valve replacement have been followed for 1 to 20 years (mean, 5.3 years), a total of 2,931 patient-years of follow-up information. Overall survival, valve-related death, primary tissue failure, failure due to surgical technical error, infective endocarditis, and overall event-free survival have been assessed and compared. Overall survival 20 years after operation was 51.6% +/- 8.1% with a low incidence of sudden death. The method and length of preservation did not have any effect on the long-term performance or the mode of failure of the homografts. The rate of primary tissue failure was apparently higher with valves preserved in a solution containing calf serum, but the difference was not significant. It is concluded that long-term patient survival and quality of life after aortic valve replacement with a homograft are excellent. The current study, however, could not verify the existence of a significant difference between the three assessed methods of homograft preservation. Furthermore, it could not prove the importance of cellular viability or the existence of clinically significant immunological factors other than the calf serum content of the nutrient medium.

Adult↗
PubMed1989

Genetic methods for identification and characterization of RNA-RNA and RNA-protein interactions.

Two general strategies using pseudorevertants have been useful in identifying RNA-RNA and RNA-protein interactions, direct synthesis of compensatory changes to test models or in vivo selection of suppressors. The most successful application of these approaches has been in the elucidation of RNA-RNA interactions, in a large part because the rules for RNA base pairing are, at least partially, understood. Beyond the initial identification of interactions, suppressors also provide important starting points for further analysis. In the case of an unknown gene product (i.e., the RNA16 gene product), the suppressor provides a route to cloning and analysis of the gene. In addition, the construction of a specific suppressor in a RNA molecule can provide a starting point for the dissection of the biogenesis and function of that RNA. This aspect is most important when the RNA in question normally provides an essential cellular role or is encoded by a multigene family. For example, the construction of a message-specific 16 S RNA in Escherichia coli should, in principle, allow for a genetic dissection of rRNA biogenesis and function.

Base Composition↗
PubMed1989

Effect of water as a diluent on the glass transition behaviour of malto-oligosaccharides, amylose and amylopectin.

The glass transition behaviour of amorphous malto-oligomers from dimer to hexamer was investigated as a function of diluent (water) concentration using differential scanning calorimetry. The glass transition temperatures of the pure compounds ranged from 364 K for maltose to 448 K for maltohexaose. At low diluent concentrations the addition of water strongly depressed Tg. From the measurement of Tg and the heat capacity increment, delta Cp, of the transition for the pure compounds it was possible to predict the Tg of the malto-oligomer/water mixtures using a thermodynamic approach developed by Couchman. From the measurements on the malto-oligomers it was possible to obtain, by extrapolation, the high DP limits of delta Cp and Tg, which are appropriate to amylose and amylopectin. The predicted variation of Tg with diluent concentration for these materials was compared with the experimentally observed behaviour.

Amylopectin↗
PubMed1989

Time trends in incidence rates of first hip fracture in the Uppsala Health Care Region, Sweden, 1965-1983.

Time trends from 1965 through 1983 for age-specific and age-standardized rates of first hospital admission for a proximal femur fracture were studied in the Uppsala Health Care Region, Sweden, using a centralized register for inpatient care. During the 19-year study period, 29,277 hospital admissions for a first hip fracture were recorded in this population of about 1.5 million persons. The total number of first hip fracture admissions per year increased for both sexes. Age-standardized admission rates for both cervical and trochanteric fractures increased in men (average change per year of 1.8% and 2.6%, respectively) in contrast to the decreased admission rate for cervical fractures (-1.6% per year) and a stable rate for trochanteric fractures (0.4% per year) in women. The cumulative rate of cervical or trochanteric fracture at ages 30-79 years increased 46% in men (from 42/1,000 population in 1965 to 61.5/1,000 population in 1983) in contrast to a 24% decrease in women (from 134/1,000 population in 1965 to 101.5/1,000 population in 1983). The female:male ratio of age-standardized incidence rates decreased for both types of fracture during the study period. This finding of stable or decreasing rates of hip fracture in women contrasts with the findings of most previous studies.

Adult↗
PubMed1989

Fast neutron teletherapy in advanced epidermoid head and neck cancer. A review.

An extensive review of clinical studies employing fast neutron teletherapy for advanced epidermoid carcinomas of the head and neck is presented. Head and neck tumors have represented an excellent study site because of their accessibility to physical examination for measurement of tumor response, and because early neutron beams have had poor depth dose characteristics, making the treatment of more deeply seated tumors technically difficult. A summary of the major trials comparing neutron and mixed-beam (combination neutron and photon) therapy with conventional therapy indicates no conclusive evidence of improvement in local control or survival rates for the experimental arms. Exceptions to this are the Hammersmith experience and the slightly higher lymph node control rates seen in two studies. An evaluation of toxicity indicates that with the new generation of cyclotrons, complication rates may approach parity with those of photon linear accelerators.

Carcinoma, Squamous Cell↗
PubMed1989

Fast neutron radiation for inoperable and recurrent salivary gland cancers.

The current standard treatment of salivary gland cancers consists of surgical resection, with or without postoperative low linear energy transfer (LET) radiation, resulting in high locoregional control rates. However, tumor control prognosis is poor when conventional radiation is used alone for advanced, inoperable cases. An extensive review of the world's literature on fast neutron irradiation for inoperable, unresectable, or recurrent malignant salivary gland neoplasms is presented and compared with the experience using conventional low LET radiotherapy. The pooled data indicate a locoregional control rate of 67% for fast neutrons versus 25% for photons and/or electrons in the treatment of such advanced disease. The radiobiological rationale supporting this observed increase in tumor control is discussed. The overall significant late complication rate is 19%, but several suboptimal treatment factors were present that contributed substantially to the reported toxicity. With the modern machines and treatment techniques now available, the evidence overwhelmingly supports the role of fast neutron radiation as the treatment of choice for inoperable and recurrent salivary gland cancers.

Energy Transfer↗
PubMed1989

Correlation of breath sounds with diagnoses of lung dysfunction: experimental observations.

An investigation has been undertaken to determine whether there is any correlation between the spectral analyses of breath sounds at the mouth and the diagnosis of lung dysfunction in a small number of patients. The results of the investigation have shown that it is possible to differentiate between the spectral characteristics of the breath sounds of people who are: (a) normal; (b) asthmatic adult, both before and after the administration of a bronchodilator drug; (c) asthmatic adult, treated with an inhaled steroid, both before and after the administration of a bronchodilator drug; (d) asthmatic child, both before and after the administration of a bronchodilator drug. The possible applications of the technique are discussed.

Adult↗
PubMed1989

Youth, identity, and homosexuality: the changing shape of sexual life in contemporary Brazil.

This essay examines the relationship between homosexuality and adolescence in contemporary Brazil, focusing on a distinction between two rather different systems of sexual meanings that have structured the experience of same-sex relations: a traditional model of the sexual universe that continues to dominate sexual life in rural areas, and a more modern set of notions that has become increasingly important in the cities. It examines the ways in which these rather different systems have affected the experience of same-sex desires and practices during youth or adolescence, and suggests some of the ways in which the emergence of a gay subculture in urban Brazil has transformed the range of sexual possibilities and choices currently available to young men and women.

Adaptation, Psychological↗