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Biomedical subjects

R D Powell

Publications and source records attributed to R D Powell.

At least 37 records · Page 2Linked to original sources
PubMed1980

Biophysical evaluation of the tumorigenic response to implanted polymers.

An evaluation of the biophysical changes of methylcholanthrene induced tumor (M4) in laboratory animals receiving four different alloplastic implants was conducted. The implants are silicone, polyether urethane, poly(methyl methacrylate), and bioglass. The tumor was allowed to grow to a large size in 28 days and then removed by shelling it from the surrounding tissue. Three different analytic volumetric measurements were carried; size in cm3, volume in milliliters and weight in grams. Statistical analysis on the three different analytic measurements did not disclose any significant differences in tumor growth potential between the control and the experimental groups. We conclude that in this study we were unable to demonstrate any tumor "facilitation" effect by any of the implantable polymers used. Therefore, there is no contraindication in using the polymers to reconstruct defects produced by cancer ablative procedures.

Animals↗
PubMed1980

Growth characteristics and pathogenesis of experimental Pneumocystis carinii pneumonia.

Pneumocystis carinii pneumonia was produced in two groups of rats by the administration of corticosteroids, a low-protein (8%) diet, and tetracycline in the drinking water. A third group not on corticosteroids or a low-protein diet served as controls. Members of the first group were sacrificed weekly for 8 weeks, and lungs were examined. A highly significant correlation was found between the histopathological assessment of the intensity of P. carinii infection and the number of cysts counted in enzyme-digested lungs. P. carinii progressively filled alveoli, and cyst counts increased from less than or equal to 10(4) to 10(9) cysts/g of lung at peak intensity of infection at 7 to 8 weeks. The second group of rats was placed on a regular diet and tapering doses of corticosteroids after week 4, and they were sacrificed at varying intervals for up to 21 weeks. P. carinii was not cleared from the lungs until after week 13 (more than 6 weeks after discontinuation of all steroids). Histologically, there was an increased prominence of alveolar macrophages and the progressive development of interstitial mononuclear cell infiltrate and fibrosis. Thus, P. carinii grows grows slowly in vivo and interacts with specific host cells. The resulting changes may be important in the pathogenesis of the infection and in the clearance of the organism from the lung after immunocompetence has been restored.

Animals↗
PubMed1980

Phagocytic tumor cell activity in oat cell carcinoma of the lung.

Biopsy specimens from 14 patients with oat cell carcinoma of the lung metastatic to bone marrow and from one patient with a localized tumor were examined for evidence of phagocytic activity by tumor cells. Phagocytic activity was observed in tumor cells in 90 per cent of the bone marrow biopsy specimens, 90 per cent of the cytology specimens, and 70 per cent of the biopsy specimens of other tissues. The cell most often phagocytosed was the leukocyte. Seventeen other tumors metastatic to bone marrow were studied and only one evidenced phagocytic activity.

Bone Marrow Diseases↗
PubMed1979

Treatment of Pneumocystis carinii pneumonia with trimethoprim-sulfamethoxazole and pentamidine: efficacy and toxicity.

A 39-year-old man with Pneumocystis carinii pneumonia responded poorly to oral trimethoprim-sulfamethoxazole (TMP-SMX) therapy, despite excellent serum concentrations of the drug. He developed severe thrombocytopenia when pentamidine was added to the regimen. This case illustrates problems of drug efficacy and toxicity in the treatment of P carinii pneumonia and suggests caution in the use of TMP-SMX and pentamidine in combination.

Adult↗
PubMed1979

Experimental Pneumocystis carinii pneumonia in different strains of cortisonized mice.

Pneumocystis carinii pneumonia was produced in eight different strains of mice by the administration of corticosteroids, low (8%)-protein diet, and tetracycline in the drinking water. Heavier degrees of P. carinii infection were most consistently found in C3H/HeN mice; intermediate levels occurred in BALB/c AnN, C57BL/6N, B10.A(2R), AKR/J, and Swiss Webster mice; lighter degrees were found in DBA/2N and DBA/IJ mice. Histopathologically, P. carinii organisms were morphologically indistinguishable from human and rat P. carinii, and elicited a predominantly mononuclear response that was similar among the various mouse strains. The optimal cortisone acetate regimen was 1 mg injected subcutaneously twice weekly. Higher doses shortened the life span of the mice, presumably by inducing overwhelming bacterial infection. This problem occurred not only in different strains of mice, but also in the same strain of mice obtained from different breeders. Thus, cortisonized mice should be useful in the study of experimental P. carinii infection. Success of this model depends on the corticosteroid dose, as well as the strain, source, general health, and preexisting microbial flora of the mice chosen for study.

Animals↗
PubMed1979

Malaria vaccine development.

Prospects for the development of effective malaria vaccines have greatly improved over the last 15 years. For further progress to be achieved rapidly, the need for clinical research centres, where exposure and re-exposure to infection can be carefully controlled, is paramount. At such centres, it is possible to evaluate the safety and efficacy of vaccine preparations, using different strams and species of parasite, and to undertake studies in both nonimmune and partially immune volunteers. However, as efficacy under these conditions may not be a good indicator of efficacy under other conditions, the results of such studies should be complemented by field trials in endemic areas. It seems probable that vaccines may show degrees of partial effectiveness in relation to different strains, species, intensities of parasite inocula, and hosts.

Animals↗
PubMed1978

Chemoprophylaxis and malaria in American servicemen returning from Vietnam.

Information relating to chemoprophylaxis and malaria in 49 men who served with the United States Armed Forces in Vietnam and who developed overt malaria after departure from Vietnam indicated that: 1) compliance with intended chemoprophylactic regimens was far optimal; 2) a history of recent prophylactic ingestion of chloroquine was not a reliable indicator of infection with chloroquine-resistant Plasmodium falciparum: 3) reported ingestion of half or more of an intended terminal chemoprophylactic regimen was associated with a prolongation of the time that elapsed before initial post-departure episodes of vivax malaria; and 4) such partial compliance with intended terminal chemoprophylaxis may have been associated with a decreased incidence of second post-departure episodes of vivax malaria.

Adult↗
PubMed1977

Difficult diagnosis of malaria.

Symptoms suggested malaria in a patient who had recently returned to the United States from Africa, but blood smears were persistently negative for malaria parasites. The diagnosis was established in an unusual way when a laboratory technician detected malaria parasites in a lupus erythematosus cell preparation.

Adult↗
PubMed1976

Ovarian morphology in women with anosmia and hypogonadotropic hypogonadism.

Ovarian biopsies from five women with the syndrome of hypogonadotropic hypogonadism and anosmia who had not previously received exogenous gonadotropins were evaluated with special emphasis on follicular morphology. Follicular development past the primordial stage was rarely observed, suggesting that early stages of follicular maturation require amounts of gonadotropins in excess of those secreted in these women.

Female↗
PubMed1976

Hepatic adenoma associated with oral contraceptive use: an unusual clinical presentation.

A young woman who had taken contraceptive steroids for many years had the acute onset of abdominal pain because of central necrosis and hemorrhage into a hepatic adenoma. She had multiple lesions confined to one lobe of the liver. Persistent pyrexia and leukocytosis were also prominent clinical findings. She has had no evidence of recurrence of this problem during the seven years following right hepatic lobectomy. A review of the anabolic and contraceptive steroid-associated hepatic neoplasms is presented with comments directed toward the recognition of the critical clinical sequelae that can befall the patient with hepatic adenoma. Although all the patients in the steroid-treated group have tumors with benign and striking histologic similarity, microscopic evidence of malignant invasion of surrounding tissue is occassionally noted.

Adenoma↗
PubMed1975

Malaria in Iowa.

Explore the source record for details and available documents.

Adolescent↗
PubMed1972

Flowering and Growth Response of Peanut Plants (Arachis hypogaea L. var. Starr) at Two Levels of Relative Humidity.

Peanut plants (Arachis hypogaea L. var. Starr) grown under two different relative humidities were used in all experiments. All plants were germinated and grown to flowering in the greenhouse. At this time, one group was moved to a growth room under 95% relative humidity. After 50 days the humidity of the growth room was lowered to 50%. The second group was moved into a growth room at 50% relative humidity and after 50 days the humidity was raised to 95%.Flowering rates of plants under high humidity were greater than rates of those plants under low humidity. Flowering was stimulated by transfer from low to high humidity, and these plants set the largest percentage of pegs, maintained a high rate of ethylene production by 2-centimeter peg sections, a high growth rate of intact pegs, and they had a higher mean content of gibberellins than plants transferred from a high to a low humidity. The plants in the high to low transfer had the least number of flowers, formed the lowest percentage of pegs, had about 50% less ethylene production by 2-centimeter peg sections, and the peg growth rate declined about 50%.Maximum ethylene production occurred during initial stages of peg growth (1- to 5-millimeter sections), and gibberellin content was generally higher in these peg sections. Thus, high humidity enhanced flowering, peg formation, and peg growth rate. A causal relationship between these effects of high humidity and the growth regulator status of the developing fruit is indicated.

Journal Article↗