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R D Powers

Publications and source records attributed to R D Powers.

At least 73 records · Page 4Linked to original sources
PubMed1983

Modification of encephalomyocarditis virus-induced diabetes in mice by antiviral agents.

The current study used a murine model of diabetes induced by the D variant of encephalomyocarditis virus (DEMC) to determine the protective effect of exogenous antiviral agents. Antivirals, which were found to inhibit the development of DEMC virus cytopathic effect in L-929 cell monolayers, were administered intraperitoneally beginning 12 h prior to DEMC virus challenge. Arildone (500 mg/kg per day) or murine interferon (3.2 X 10(6) IU/kg per day) significantly reduced the incidence of hyperglycemia at 4 days after virus challenge. The incidences of hyperglycemia were 96% in untreated, 62% in arildone, and 0% in interferon treated mice. In other experiments we found that interferon (1.6 X 10(6) IU/kg per 12 h X 3) significantly protected mice against diabetes when administered at the time of virus infection or beginning 12 h afterwards. This effect was associated with reductions in average viral titers in the heart and pancreas of infected animals relative to untreated, infected mice. The results of these studies suggest that picornavirus induced diabetes may be prevented or ameliorated by the use of antiviral agents.

Animals↗
PubMed1983

Effects of dexamethasone and surgical hypotension on the stomach of dogs: clinical, endoscopic, and pathologic evaluations.

Effects of dexamethasone and surgical hypotension on the gastric mucosa of 15 dogs was evaluated by clinical, endoscopic, and pathologic studies. Dexamethasone produced acute reddening of the gastric mucosa with frank hemorrhage, digested blood, and possible gastric erosions, whereas dogs treated by surgical hypotension did not have marked changes in the gastric mucosa. Gastrointestinal disease observed in dogs with spontaneous spinal cord injury that were given dexamethasone and decompressive spinal surgery was not produced. The role of corticosteroids and surgical hypotension in the pathogenesis of gastric lesions and the potential for spinal cord injury to produce gastrointestinal disease is discussed.

Animals↗
PubMed1983

Effects of dexamethasone and surgical hypotension on hepatic morphologic features and enzymes of dogs.

Effects of corticosteroids and surgical stress on hepatic morphologic features and enzymes were studied in 18 mature dogs of mixed breeding: group 1, control (n = 3); group 2, dexamethasone (n = 5); group 3, dexamethasone and surgery (n = 5); and group 4, surgery (n = 5). Dexamethasone (2.2 mg/kg of body weight twice a day subcutaneously) was administered for 8 days in groups 2 and 3 dogs. All dogs were anesthetized with thiopental for 10 minutes on days 0, 2, and 4. On day 2, dogs in groups 3 and 4 were intubated and maintained on methoxyflurane and oxygen, and a liver biopsy, hemilaminectomy (T13-L1), and 15 minutes of hypotension (75/45 mm of Hg) induced by methoxyflurane were done. Serum alkaline phosphatase (ALP) activity, ALP isoenzymes, and alanine aminotransferase (ALT) activity were determined on days 0, 2, 3, 5, and 8. All dogs were euthanatized and necropsied on day 8. Serum hepatic enzyme activity and hepatic morphologic characteristics were normal for group 1 control dogs. The mean ALP and ALT were significantly (P less than 0.05) increased in dogs in groups 2, 3, and 4. In group 2, the mean ALP (days 5 to 8) and ALT (day 8) were significantly (P less than 0.05) increased. In group 3, the mean ALP and ALT activities were significantly increased on days 2 to 8. In group 4, the mean ALP was significantly increased on days 2 to 8 and the mean ALT was significantly increased on days 3 and 5. All other values were normal. A single isoenzyme band (Rf = 0.399 +/- 0.023, mean +/- SD) was identified in all dogs. Hepatic morphologic changes attributed to dexamethasone were mild-to-moderate vacuolation in a diffuse distribution on day 2 (group 3) and aggregates of moderate-to-severe vacuolation in mainly a periportal distribution on day 8 (groups 2 and 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗
PubMed1982

Changes in mouse oocyte membrane potential and permeability during meiotic maturation.

Mouse oocytes spontaneously undergo meiotic maturation when removed from the ovary and cultured in vitro. This paper describes the changes in cell surface membrane potential from the germinal vesicle (GV) stage (- 46 mV, inside negative), through germinal vesicle breakdown (GVBD) (- 31 mV), to the polar body (PB) stage (- 17 mV). Radioisotope tracer flux experiments established the total exchangeable internal K at the GV stage in 190 mM, the K efflux rate coefficient as 6.7 X 10(-5) sec-1) and the K permeability as 46.7 X 10(-8) cm sec-1. In comparison with previous results with PB stage oocytes, this suggests that the membrane potential depolarization is caused largely by a decrease in K permeability. When GVBD is blocked with 0.11 mM dibutyryl cyclic AMP, the membrane potential does not depolarize. This suggests a linkage between depolarization and GVBD. However, incubation in 80 mM K medium, which depolarizes the oocyte, does not trigger GVBD. It is concluded that membrane depolarization by itself is not sufficient to cause GVBD.

Animals↗
PubMed1982

Noniatrogenic rectal tears in three horses.

Rectal tears were detected in three horses treated for colic. Based on historical, clinical, and postmortem findings, the tears could not be attributed to the attending veterinarian and were therefore not iatrogenic (physician induced). One tear was attributable to an infarction that presumably resulted from thromboembolism; 1 tear occurred without any evidence of external cause and resulted in such severe peritonitis that the cause and resulted in such severe peritonitis that the cause could not be determined, and 1 tear occurred during rectal palpation by the owner, before he called the veterinarian. Postmortem examination of the last horse revealed lesions suggestive of thromboembolism. It was concluded that thromboembolism may have caused or predisposed to two of the rectal tears and could not be ruled out in the third.

Animals↗
PubMed1982

Two sites for calcium action in compaction of the mouse embryo.

Compact mouse morulae were decompacted in calcium-free medium and allowed to recompact in standard embryo culture medium. When the recompaction medium contained trifluoperazine (TFP)(0.05 mM), an inhibitor of the calcium-dependent protein calmodulin, the embryos failed to recompact. This effect could not be overcome by either db-cAMP (1.0 mM) or theophylline (0.75 mg/ml). When the recompaction medium contained less than standard calcium (0.085 or 0.17 mM) the embryos recompacted at a slower rate than in control medium (1.7 mM). The calcium ionophore A23187, at concentrations up to 1.5 X 10(-3) mM, had no significant stimulatory effect upon the recompaction rte of embryos in the reduced calcium medium. In addition, the calcium antagonist Verapamil (0.3 mM), which blocks calcium uptake by cells, significantly inhibited recompaction in standard culture medium. Large doses of diazepam inhibited recompaction only slightly in standard culture medium. Large doses of diazepam inhibited recompaction only slightly in standard culture medium. We conclude that calcium uptake into the cytoplasm is required for recompaction, but that cell surface calcium is also required and is rate-limiting under these experimental conditions.

Animals↗
PubMed1982

Activity of 2-(3,4-dichlorophenoxy)-5-nitrobenzonitrile (MDL-860) against picornaviruses in vitro.

The newly synthesized compound 2-(3,4-dichlorophenoxy)-5-nitrobenzonitrile (MDL-860) has been found to inhibit picornavirus replication. In multiple growth cycle experiments, 1 microgram of MDL-860 per ml caused a reduction in virus yield of at least 1.0 log10 50% tissue culture infectious doses per 0.2 ml for 8 of 10 enteroviruses and 72 of 90 rhinovirus serotypes. This antiviral activity was dependent on both compound concentration and virus inoculum size. At concentrations that had no toxic effects on cell cultures, MDL-860 did not inhibit cytopathic effect or hemadsorption activity due to coronavirus 229-E, vesicular stomatitis virus, herpes simplex virus type 1, adenovirus, influenza virus A, or parainfluenza virus 1. Compound concentrations up to 25 micrograms/ml did not cause cytopathic effect in short-term cultures of rhesus monkey, WI-38, or HeLa cells; 10 micrograms/ml did not inhibit the replication of HeLa cells. The mechanism of action of MDL-860 has not been defined, although it was not directly virucidal and appeared to inhibit picornaviruses specifically at an early step in the virus-host cell interaction.

Antiviral Agents↗
PubMed1982

Combined effects of calcium and dibutyryl cyclic AMP on germinal vesicle breakdown in the mouse oocyte.

Mouse oocytes were cultured in the presence of dibutyryl cyclic AMP (dbcAMP) and various agents that affect cytoplasmic calcium concentrations. Treatment that inhibited calcium uptake potentiated the inhibitory effect of dbcAMP and treatments which stimulated cellular calcium uptake overcame the effect of dbcAMP. Elevated extracellular calcium (greater than 10 mM) significantly decreased the inhibitory effect of concentrations of dbcAMP up to 150 microM when compared to control levels of calcium (1.7 mM). In addition, the calcium ionophore A23187 (greater than 1 microM) significantly overcame the effect of dbcAMP in media that contained 1.7 or 20 mM calcium. In the presence of 41 microM-dbcAMP the calcium antagonist verapamil increased (in a dose-dependent fashion) the percentage of oocytes blocked at the germinal vesicle stage, from 21% with 10 microM-verapamil to 99% with 200 microM. A similar dose-dependent, reversible potentiation of the effect of dbcAMP was found with tetracaine, which also lowers cytoplasmic calcium concentrations. These results suggest that a minimum level of cytoplasm calcium is required for the initiation of germinal vesicle breakdown and that the action of dbcAMP is mediated by its effect upon this calcium.

Animals↗
PubMed1981

The effect of calcium on the first meiotic division of the mammalian oocyte.

In the mammalian ovary, fully grown oocytes are arrested at the diplotene stage of the first meiotic division. While oocytes in vivo resume meiosis only in response to a preovulatory surge of gonadotropic hormones, oocytes isolated from the ovaries and cultured in vitro will spontaneously resume meiosis. Both in vivo and in vitro, meiotic maturation proceeds through the extrusion of the first polar body, where it is again arrested until fertilization. We have used the spontaneous, in vitro maturation of the mouse oocyte to examine the role of calcium in germinal vesicle breakdown (GVBD) and polar body extrusion. In calcium-free medium or in the presence of concentrations of lanthanum greater than 0.5 mM, the oocytes degenerate rapidly. However, there does not appear to be any effect upon maturation that can be distinguished from a general toxicity of these media. In contrast, two treatments that are known to inhibit transmembrane calcium movements, verapamil and tetracaine each, individually, inhibit polar body formation. They have no effect on GVBD. In addition, oocytes cultured in media containing a higher calcium concentration than control media (greater than 10 mM versus 1.71 mM) show a significantly higher percentage of polar body formation. We conclude that, in these culture conditions, extracellular calcium is not required for GVBD but is required for the completion of the first meiotic division of a mammalian oocyte.

Animals↗
PubMed1980

Filaroides hirthi in a dog: fatal hyperinfection suggestive of autoinfection.

Progressive dyspnea in a dog began 1 month after it had been hit by a car. Radiographs revealed diffuse interstitial and alveolar pneumonia. Large numbers of embryonated eggs were observed in bronchial washings; and many small nematodes, later identified as Filaroides hirthi, were found in the fine needle aspirates of pulmonary tissue. Numerous nematode larvae were demonstrated on fecal flotation. The severe hyperinfection strongly suggested autoinfection, probably associated with depressed immunologic competence due to chronic stress.

Animals↗
PubMed1977

Dorsal laminectomy techniques in the dog.

The effects of various lengths of complete dorsal laminectomy were compared with the effects of Funkquist method B laminectomy on the spinal cord of dogs. Complete dorsal laminectomies were done on L1 (group 1), L1 and L2 (group 2), and L1, L2, and L3 (group 3). Dogs of group 4 had Funkquist method B laminectomies on L1 and L2. Complete dorsal laminectomy on 1 vertebra and Funkquist method B laminectomy on 2 vertebrae did not result in any clinically untoward signs. In conjuction with these results, there was no dorsoventral flattening of the spinal cords and minimal microscopic damage within the spinal cords. If 2 or 3 vertebrae had a complete laminectomy, tonic spasticity of the pelvic limbs developed after surgery. Dorsoventral flattening of the spinal cord and moderate to severe microscopic damage were seen in the spinal cords of these dogs.

Animals↗