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Biomedical subjects

R D Powers

Publications and source records attributed to R D Powers.

At least 55 records · Page 3Linked to original sources
PubMed1990

Differential effects of testosterone and dibutyryl cyclic AMP on the meiotic maturation of mouse oocytes in vitro.

Fully grown, meiotically immature mouse oocytes were isolated and cultured under varying conditions with the aim of determining a) whether the inhibitory effects of testosterone on oocyte meiotic maturation require the synthesis of new oocyte proteins and b) if the meiosis-inhibiting effects of testosterone and dibutyryl cyclic AMP (dbcAMP) are distinct and can be differentiated. We found that the inclusion of puromycin in culture medium containing testosterone has no effect on the meiosis-inhibiting potency of testosterone or upon the reversibility of testosterone effects. We conclude that testosterone inhibits oocyte meiosis by a mechanism that is independent of protein synthesis. We also found that oocytes exposed to testosterone recover more rapidly, as evidenced by the timing of germinal vesicle breakdown (GVBD) following placement in a control medium, than do oocytes exposed to dbcAMP. Through further investigation of this phenomenon we have determined the sequence of testosterone and dbcAMP effects relative to the time course of GVBD. A testosterone-sensitive event occurs 20 min prior to GVBD, while the dbcAMP-sensitive event precedes GVBD by 41 min. The nature of this difference may involve the differential interaction of testosterone and dbcAMP with a set of puromycin-sensitive proteins that are required for GVBD. When oocytes were initially cultured in medium containing both puromycin and either testosterone or dbcAMP and then moved to medium containing puromycin alone the incidence of GVBD was reduced relative to oocytes never exposed to puromycin. This observation suggests that mouse oocytes contain proteins that are required for GVBD and that experience a high turnover rate. The degree of reduction in GVBD was a function of the length of puromycin exposure and was significantly greater in dbcAMP- than in testosterone-exposed oocytes. If oocytes were initially cultured in medium containing puromycin and dbcAMP, the rate of GVBD upon removal of dbcAMP was initially slow but increased with time. This observation is consistent with the hypothesis that dbcAMP inhibits oocytes at a point prior to the functioning of the puromycin-sensitive proteins. However, if oocytes were cultured in medium containing puromycin and testosterone the rate of GVBD following testosterone removal was not significantly reduced relative to oocytes that were not exposed to puromycin. This observation suggests that testosterone acts to inhibit meiosis at a site beyond the function of the puromycin-sensitive proteins or that testosterone causes a reduction in the turnover rate of these proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Ultrastructural observations of human and mouse oocytes treated with cryopreservatives.

The effects of the cryopreservative agents dimethylsulfoxide (DMSO) and propanediol (PROH) on mature human and mature mouse oocytes have been examined with transmission electron microscopy. Treatment of CD-1 mouse oocytes and human preovulatory oocytes in a stepwise manner with either DMSO or PROH up to 1.5 M appears to trigger the exocytosis of 70-80% of the cortical granules in all oocytes. Successive stages in premature dehiscence, including a loss in granule electron density, fusion of the granule-limiting membrane with the oolemma, and extrusion of the cortical granule core into the perivitelline space, have been observed in all human oocytes studied. In addition, all human DMSO- and PROH-treated oocytes exhibited crypt-like invaginations and clusters of endocytic vesicles that subtend the oolemma. The presence of these crypts and pinocytotic vesicles in treated oocytes may suggest a mechanism for the retrieval of cortical granule membrane that is inserted into the original plasmalemma during exocytosis. The paucity of cortical granules in treated mouse and human oocytes as it potentially relates to an impaired ability to elicit the cortical reaction at fertilization is discussed.

Animals↗
PubMed1988

Multiple authorship, basic research, and other trends in the emergency medicine literature (1975 to 1986).

As emergency medicine comes of age, it is interesting to examine the scientific nature of the specialty as reflected in the literature. Representative volumes of three emergency medicine journals were reviewed for number and type of article, institutional origin, article length, and number of authors. For Annals of Emergency Medicine, (AEM) volumes for 1975, 1980, and 1985 were studied. For The American Journal of Emergency Medicine (AJEM) and The Journal of Emergency Medicine (JEM), articles from the first 12 months of publication (1983 to 1984) and the complete 1986 issue were examined. Analysis of the scientific sections of the journals discloses some interesting trends. While the average article length has remained about the same (four to six pages), the average number of authors per article has steadily risen. The percentage of articles listing an academic origin has remained steady in AEM and JEM, but has risen in AJEM. Multicenter collaborations and basic science articles are appearing with significantly increased frequency. A noteworthy trend is the rise in multiple authorship of articles. There have been significant p less than 10(-4] increases in the number of multiple-authored (more than three authors) articles in AEM and JEM. As reflected by the literature, scientific progress in EM is maintaining a rapid pace. However, there are increasing numbers of papers with multiple authors. Listing of multiple authors on papers has prompted criticism of the literature in other medical specialties. If this trend continues, there may be a risk of compromising the integrity of the published research.

Authorship↗
PubMed1988

Emergency department patient literacy and the readability of patient-directed materials.

There are 20 million American adults who cannot read. The demographics of the illiterate population suggest that they represent a significant proportion of patients cared for in a teaching hospital emergency department. This study was designed to assess whether readability of written material given to patients in a university hospital ED matched the literacy level of these patients. Data were gathered from 111 consecutive adult ED patients. Results of the survey showed that although the median education level of ED patients was 10th grade, more than 40% could not be expected to read at the 8th grade level, and at least 20% could be considered functionally illiterate. Readability of ED patient-directed materials was measured using the Fry index. Hospital and commercially generated patients education materials ranged from 8th to 13th grade level; a patient-directed brochure from Virginia ACEP is written at a college reading level. Comprehension of the "leaving against medical advice" (AMA) form or a consent for surgery would require at least an 11th grade education. This study shows that there is an alarming discrepancy between ED patient literacy levels in our sample and the reading skills required to comprehend important written medical and legal information. More than 50% of ED patients in a teaching hospital may read below the level required to understand standard discharge instructions. In addition, understanding the "operative consent" and leaving AMA forms requires a level of education beyond that of the majority of ED patients. If patient-directed written material is to serve its purpose, then ED patient populations should be surveyed and the reading level of written material adjusted accordingly.

Adult↗
PubMed1988

Pregnancy after gamete intrafallopian transfer in a woman with primary infertility and in utero exposure to diethylstilbestrol. A case report.

In utero exposure to diethylstilbestrol (DES) has an adverse effect on reproductive performance and may be associated with infertility. Gamete intrafallopian transfer (GIFT) is a new reproductive technique that has been advocated as an alternative to in vitro fertilization in women with at least one normally functioning fallopian tube. The process involves the translaparoscopic placement of oocytes and sperm into the fallopian tube. The technique has been successful in treating infertility due to endometriosis, male factors and immunologic factors as well as unexplained infertility. We accomplished the first successful GIFT procedure in a woman with significant uterine effects from prenatal DES exposure. This technique may prove to be an effective treatment for infertile women with DES exposure who have no adequate explanation for their infertility.

Adult↗
PubMed1987

Incarceration of a section of small intestine by remnants of the ductus deferens in steers.

A 13-month-old Charolais steer was examined because of anorexia and weight loss of 1 week's duration. Initially, the steer passed tarry feces for 2 days, but no feces were passed for 4 days before examination. Palpation per rectum disclosed moderate distention of the small intestine and dark tenacious mucus in the rectum. Standing celiotomy was performed through the right paralumbar fossa, and a 60-cm segment of small intestine was found to be entrapped by a fibrous band between the caudal abdominal wall and the pelvic inlet. The band was transected and the intestine was freed. The intestine was judged to be viable and the abdomen was closed. Histologically, the fibrous band consisted of ductus deferens and adnexa; the intestine had become incarcerated through a rent in the mesoductus. Small intestine entrapment through a rent in the right mesoductus was diagnosed in 20 additional steers over a 10-year period. In all cases, the steers had been castrated when weighing more than 100 kg, by manual traction on the testicle and spermatic cord through a scrotal incision. Alternate means of castration that prevent disruption of the abdominal mesoductus may prevent development of this condition.

Animals↗
PubMed1987

Emergency department lumbar puncture: clinical application and utility of laboratory testing.

Lumbar puncture is an emergency department procedure for evaluating patients with suspected central nervous system infection or hemorrhage. To determine whether extensive testing of cerebrospinal fluid (CSF) obtained from emergency department patients was useful, charts of 104 adult patients who underwent lumbar puncture in a university hospital emergency department were reviewed. Examination of the CSF disclosed pleocytosis in 25 (24%) of the patients; the presence of red blood cells was considered to be clinically significant in two patients. An abnormal level of CSF protein was present in 62% of patients, and abnormal levels of glucose in 32%. Fungal element testing was negative each of the 72 times it was performed; Gram stain disclosed a bacterial pathogen in one patient. Cultures for fungus and tuberculosis were uniformly negative, as were all immunologic tests. Bacterial cultures grew a pathogen in one patient. No patient with a normal neurologic examination and normal initial CSF analysis was diagnosed subsequently as having acute central nervous system disease. The preponderance of negative or normal results of testing of CSF suggests that extensive testing may not be necessary for all patients. Limitation of sophisticated testing to only those samples with abnormal cell counts or chemistries or from patients at high risk should result in substantial cost saving without compromising patient care.

Adolescent↗
PubMed1987

Biologic characterization of canine melanoma cell lines.

Eight canine melanoma cell lines were established from tissues from 6 dogs with spontaneous primary or metastatic melanomas. Cell lines were characterized for morphologic features and growth patterns on plastic, pigmentation, ultrastructure, cloning efficiency in soft agar, and tumorigenicity in nude mice. Biologic properties of cell lines were distinct and preserved during 40 to 120 passages in vitro. All cell lines were clonogenic and tumorigenic.

Animals↗
PubMed1985

Periorchitis after tetramisole treatment in bulls implanted with Setaria labiatopapillos.

Thirteen mixed-breed beef bulls, 1 to 4 years old, were used to determine the effect of live and dead filarial nematodes, Setaria labiatopapillosa, placed in the vaginal cavity of the testes. When dead worms were used, granulomatous lesions developed on the tunica vaginalis parietalis in 7 of 8 testes. The lesions were similar to those seen in some clinical cases of periorchitis. Similar lesions developed in 5 of 6 testes after live worms were implanted in the vaginal cavity of the testes and tetramisole (8 mg/kg) was injected subcutaneously 6 days after implantation. When live worms were implanted and tetramisole was not given, lesions developed in 3 of 6 testes. It was concluded that the granulomatous reaction was a local response to dead or killed S labiatopapillosa.

Animals↗
PubMed1985

Serum chemistry abnormalities in adult patients with seizures.

To determine whether checking serum chemistries is a useful procedure, records were reviewed to identify patients presenting to a university hospital emergency department (ED) with seizures. In a six-month period, 112 adult patients made 126 visits for evaluation and treatment of recent seizures. Analyzing each visit individually, 111 patients (88.1%) had serum electrolytes determined; 96 (76.2%) had a serum calcium level measured; and 92 (73%) had a serum magnesium level measured. The overall incidence of seizures due primarily to derangements in serum chemistry was 2.4%, including two hypoglycemic seizures and one seizure related to hemodialysis. Severe aberrations in serum chemistries occurred most frequently in alcoholics; nonalcoholics had relatively few abnormal test results unless they had preexisting renal failure or diabetes mellitus. In ED patients, the incidence of seizures due primarily to derangements in serum chemistry is very low. Grouping of patients by medical history can help direct test ordering by identifying those at risk for abnormalities in serum chemistry.

Adolescent↗
PubMed1984

The MCAT revisited.

Explore the source record for details and available documents.

Educational Measurement↗
PubMed1984

Immune response of adults to sequential influenza vaccination.

Annual immunization against influenza is recommended for numerous individuals, but the antibody response to sequential vaccination has not been well characterized. Levels of hemagglutination-inhibition antibody were measured in adults given either two or three doses of trivalent influenza vaccine at six-month intervals. A significant rise in the number of individuals with antibody titers of greater than or equal to 40 was seen for all three antigens only after initial vaccination. Repeated vaccination was necessary to maintain adequate antibody levels only to the A/Brazil (H1N1) antigen; it did not significantly affect the proportions of individuals with protective levels of antibody to either the A/Bangkok (H3N2) or the B/Singapore 222/79 antigens. These findings do not support the current recommendation for annual immunization when the vaccine formulation has not changed.

Adolescent↗
PubMed1984

Painless aortic dissection: an unusual cause of syncope.

Presented is a case of syncope as the initial sign of a painless aortic dissection. The patient was stabilized by percutaneous drainage of a hemopericardium, and then underwent angiography and successful operative repair. Although uncommon, painless aortic dissection should be included in the differential diagnosis of a syncopal episode.

Aortic Dissection↗
PubMed1984

Endotracheal administration of emergency medications.

When vascular access is delayed or unreliable in emergency situations, an endotracheal tube provides a rapid and reliable route for administration of medication. Epinephrine, lidocaine, and atropine have shown clinical efficacy when given by the endotracheal route. There is evidence that other medications including naloxone and diazepam may also be suitable for endotracheal use, but clear-cut recommendations await further studies of pharmacokinetics and toxicity.

Adult↗