The feminisation of medical practice.
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Humans↗
Biomedical subjects
G Silver
Publications and source records attributed to G Silver.
Dexamethasone-mediated regulation of 3-methylcholanthrene-induced cytochrome P-450d mRNA accumulation in primary rat hepatocyte cultures.
We have previously demonstrated that cytochrome P-450c and P-450d mRNAs can be induced by 3-methylcholanthrene (MCA) in primary cultures of rat hepatocytes grown in serum-free hormonally defined medium (HDM) plus minimal salts (Silver, G., and Krauter, K. S. (1988) J. Biol. Chem. 263; 11802-11807). Such cultures were used to investigate the role of the individual hormonal components present in the medium in the hydrocarbon-mediated induction process. Replacing HDM with minimal salts plus 10% fetal bovine serum (FBS) resulted in a 4-fold reduction in the accumulation of P-450d mRNA in response to MCA. In contrast, no effect was seen on induced levels of P-450c mRNA. Mixing experiments, in which primary cultures of hepatocytes were grown in medium containing HDM plus 10% FBS, indicated that there was no negative acting component present in FBS, but rather there was a positive acting component present in the mixture of hormones in HDM which permitted P-450d induction by MCA. Testing the effects of singly deleting each of the 10 components in HDM on MCA-induced P-450d expression demonstrated that dexamethasone was the only factor which affected the induction of P-450d. Deletion of this component from HDM resulted in a 4-fold decrease in the maximum MCA induced expression of P-450d mRNA. Moreover, supplementation of minimal salts plus 10% FBS with dexamethasone restored full P-450d inducibility by MCA. Deletion of the other components from HDM had no effects on P-450d mRNA accumulation. Although substratum clearly contributed to the quality of primary hepatocyte cultures, we were unable to demonstrate any role of the substratum on MCA induction of P-450d. In vitro nuclear run-on experiments revealed that dexamethasone had little effect on the rate of transcription of the P-450d genes. Therefore, the effect of dexamethasone on induction must be at the posttranscriptional level.
Animals↗
Aryl hydrocarbon induction of rat cytochrome P-450d results from increased precursor RNA processing.
We have previously demonstrated that cytochrome P-450d mRNA accumulation is induced at a posttranscriptional level by 3-methylcholanthrene (MCA) in primary cultures of rat hepatocytes grown in serum-free hormonally defined medium. Using dactinomycin chase experiments in this culture system, we found that MCA had no effect on the P-450d mRNA half-life. In addition, induction of P-450d occurred both in the presence and in the absence of protein synthesis inhibitors. An analysis of nuclear precursors showed that the accumulation of the primary transcript of the P-450d gene was induced to the same extent as that of the mature mRNA after MCA treatment and that the pattern of accumulation of precursors differed between treated and control liver cells. Since P-450d induction is thought to be a receptor-mediated event, these data are consistent with a model in which a direct interaction occurs between the receptor-ligand complex and the primary transcript.
Animals↗
Periventricular echodensities detected by cranial ultrasonography: usefulness in predicting neurodevelopmental outcome in low-birth-weight, preterm infants.
Forty-eight low-birth-weight, preterm graduates of the University of Washington's neonatal intensive care unit who had received periodic, serial scanning by means of cranial ultrasonography during the first 4 to 6 weeks of life were longitudinally observed in an interdisciplinary neurodevelopmental follow-up program to a mean corrected age of 18 months. Mean birth weight for the sample was 1286 g; mean gestational age was 29 weeks. Periventricular echodensities were graded from 0 to 3, with 0 indicating no densities and 3 indicating cystic formation. Intracranial hemorrhage was graded in the conventional manner from 0 to IV. Neurodevelopmental outcome was assessed by means of a neurologic examination and the Bayley Scales of Infant Development. To synthesize the results, neurodevelopmental outcome for each subject was classified as normal, demonstrating minor abnormalities, or demonstrating major abnormalities. Multiple statistical analyses with various subgroupings of subjects consistently indicated severe intracranial hemorrhage (grades III and/or IV) to be a better predictor of overall neurodevelopmental outcome than grade of periventricular echodensity, including small cysts. These results suggest a wide range of outcomes after detection of periventricular echodensities and caution against communicating overly pessimistic prognoses in many cases.
Cerebral Hemorrhage↗
Expression of cytochromes P-450c and P-450d mRNAs in cultured rat hepatocytes. 3-Methylcholanthrene induction is regulated primarily at the post-transcriptional level.
Primary cultures of adult rat hepatocytes grown in serum-free hormonally defined medium were shown, for the first time, to be capable of supporting the 3-methylcholanthrene-inducible expression of cytochrome P-450d. Such cultures were used to investigate the mechanism of the induction of cytochrome P-450c and P-450d mRNAs. After 1 day of growth in culture, P-450c and P-450d mRNAs were induced 33- and 28-fold, respectively, by 3-methylcholanthrene treatment. A similar magnitude of induction was achieved after 2-5 days growth in culture. However, the relative abundance of the two mRNAs before and after treatment decreased linearly over the 5-day time course. Kinetic analysis revealed that induction of both genes was rapid and could be observed less than 2 h following treatment. Accumulation of both mRNAs was linear for 8 h, reaching a plateau by 12 h. Expression then remained constant for at least 12 additional hours. In vitro nuclear run-on experiments revealed a 3.9- and 2.0-fold transcriptional induction of the P-450c and P-450d genes, respectively. This is in contrast to the large induction of accumulation of these mRNAs observed at steady state. Thus, the 3-methylcholanthrene induction of P-450c and P-450d mRNAs in the hepatocyte cultures appeared to be mediated primarily at the post-transcriptional level. Experiments on rat liver showed that, in vivo, P-450d is also regulated primarily at the post-transcriptional level. However, P-450c was found to be regulated primarily transcriptionally.
Animals↗
Window of opportunity.
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Delivery of Health Care↗
The Ah domain of the mouse. Induction of proteins by the carcinogen 3-methylcholanthrene.
The effect of the carcinogen 3-methylcholanthrene (MCA) on protein accumulation in mouse tissues was examined. Administration of the hydrocarbon (250 mg/kg, intraperitoneally) to high-responder C57BL/6 (B6) mice resulted in the induction of five proteins in liver tissue. Quantitative analysis revealed that maximal induction of all five proteins occurred 2 days after MCA administration, with liver protein concentrations returning close to control values by 7 days after the treatment. No consistent effects on the concentrations of other liver proteins were seen. Cell-fractionation studies demonstrate that these proteins appear to be non-microsomal in origin. The induction of the five proteins was tissue-specific, since MCA had no effect on protein accumulation in the B6-mouse kidney, spleen or heart. In addition, their induction appeared to be correlated with the Ah locus, since MCA administration had no effect on the concentrations of the five proteins in the liver of the low-responder DBA/2 (D2) mouse strain. Comparing the extent and time course of this induction with that of previously characterized MCA-induced enzymes, we suggest that these five proteins may represent a new, previously unidentified, set of MCA-induced proteins.
Animals↗
Ketanserin modulates rabbit foot cooling in the presence or absence of exogenous serotonin.
Since hypothermic conditions augment sensitivity to vasoactive amines like serotonin (5-HT) and 5-HT is associated with the etiology of Raynaud's phenomenon, this amine perhaps plays a role in cold-induced vasoconstriction. To determine if 5-HT participated in normal peripheral cooling and if ketanserin (KET), a 5-HT blocker, modulated such cooling, four groups of New Zealand white rabbits (N = 33) were studied. The femoral artery was cannulated to allow perfusion of a hindlimb. Thermistors were implanted in the footpad and rectum. The hindfoot was exposed to a 15 degrees C bath for 30 min, while footpad and rectal temperatures were recorded. During cold exposure, 5-HT (5 x 10(-2) M, group 1), KET (0.1 mg/kg) + 5-HT (group 2), KET (group 3), or saline (group 4) was perfused through the hindlimb. Groups 2 and 3 were also pretreated with KET (0.1 mg/kg perfused over 30 min). The rabbit footpad cooled rapidly when exposed to exogenous 5-HT (group 1). KET treatment in the presence of exogenous 5-HT (group 2) was associated with a significantly (P less than 0.05) reduced cooling rate. KET treatment in the absence of exogenous 5-HT (group 3) was also associated with a significantly (P less than 0.05) elevated limb temperature when compared to controls (group 4). This suggested that endogenous 5-HT participated in limb cooling. Therefore, as noted for Raynaud's disease, 5-HT may also influence peripheral cooling of tissues free of such pathologies.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Therapeutic regimens in acute experimental hemorrhagic pancreatitis. Effects of hydration, oxygenation, peritoneal lavage, and a potent protease inhibitor.
In this study we evaluated the effects of hydration, oxygenation, peritoneal lavage, and the protease inhibitor gabexate mesilate in acute hemorrhagic pancreatitis induced by feeding mice a choline-deficient, ethionine-supplemented diet. Different groups of mice were kept at various concentrations of O2 (21%, 35%, and 45% O2), or were treated by either s.c. injections or i.p. injections of electrolyte solution at various doses (0, 4, 6, or 8 ml/day). Further groups were treated either with i.p. lavage, lavage with 1.5 mg/ml of gabexate, or i.p. injections of 100 mg/kg of gabexate without lavage. The potential benefits of the various regimens were assessed by measuring survival, various biochemical and histologic features, and alterations in hematocrit, pH, and blood gases. Increasing O2 concentrations reversed hypoxemia and acidosis, but had no effect on biochemical or morphologic alterations and did not improve survival. However, hydration by s.c. fluid markedly improved survival and normalized the hematocrit without having major effects on biochemical or morphologic alterations. Intraperitoneal fluid did not improve survival. Gabexate injections without lavage had a slight effect on survival and serum amylase concentration and very little effect on histology. Lavage without gabexate had a greater effect on survival, serum amylase, and histology. Addition of gabexate to the lavage fluid increased the beneficial effect of lavage. Increases in amylase and activated trypsin in ascites were markedly reduced by lavage and even more so by lavage with addition of gabexate. We conclude that sufficient hydration appears to be an important factor in supportive care for severe acute pancreatitis, whereas oxygenation without sufficient hydration has no major benefit. Peritoneal lavage with gabexate showed the greatest benefit of the various regimens for acute severe pancreatitis and is worthy of clinical trials.
Acute Disease↗
Therapeutic gain factors for fractionated radiation treatment of spontaneous murine tumors using fast neutrons, photons plus O2(1) or 3 ATA, or photons plus misonidazole.
Therapeutic gain factors (TGFs) have been determined for three spontaneous tumors of the C3H mouse treated by photons + normobaric oxygen (O2(1) ATA), photons + hyperbaric oxygen (O2 3 ATA), photons + misonidazole, or fast neutrons. The tumors were early generation isotransplants of spontaneous tumors: MCaIV, a mammary carcinoma; FSaII, a fibrosarcoma; and SCCVII, a squamous cell carcinoma. The tumors, transplanted to the right leg, were 6 mm at start of treatment. Normal tissue responses studied were acute reaction of normal skin (all treatment modalities) and LD50 following irradiation of the upper abdomen (in test of photons + O2 at 1 or 3 ATA). Thus both the tumor and normal tissues would be classified as "acute responding." All subject tissues were at congruent to 34.5-35 degrees C at irradiation. Treatments were based on d(25)Be or p(43)Be fast neutron beams, 60Co and 137Cs photon beams. Treatments were given in 5 or 15 equal doses in 5 days. For photon treatments, TGFs (air/O2 3 ATA) were substantially and significantly larger than 1 for all three tumor systems treated at small or large doses per fraction when related to skin or abdominal tissue responses. The TGFs (air/O2 1 ATA) were greater than 1 at small doses per fraction for MCaIV and FSaII for skin as the normal tissue; the TGFs for all three tumors and at all doses per fraction would be greater than 1 when related to upper abdominal tissues. TGFs (O2 1 ATA/O2 3 ATA) for photon irradiation greater than 1 were found only for SCCVII and that obtained for both large and small doses per fraction. Misonidazole achieved impressive TGFs (air/air + miso or air/O2 1 ATA + miso); the drug was tested only at 10-12 Gy/fraction and relative to skin. RBEs(FN) for the three tumors were lower at 1.5-2 Gy(FN)/fraction than at 5-6 Gy(FN)/fraction, i.e. the opposite to that reported for normal tissue (RBE increases with decreasing dose per fraction). A TGF (relative to skin reaction) greater than 1 for fast neutron therapy was found only for SCCVII when treated at large doses/fraction; this was true for air or O2 1 ATA conditions.
Animals↗
New scourge: old challenge.
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Acquired Immunodeficiency Syndrome↗
Discordant priorities.
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Legislation, Medical↗
Regulation of myofibrillar accumulation in chick muscle cultures: evidence for the involvement of calcium and lysosomes in non-uniform turnover of contractile proteins.
The effect of calcium on myofibrillar turnover in primary chick leg skeletal muscle cultures was examined. Addition of the calcium ionophore A23187 at subcontraction threshold levels (0.38 microM) increased significantly rates of efflux of preloaded 45Ca+2 but had no effect on total protein accumulation. However, A23187 as well as ionomycin caused decreased accumulation of the myofibrillar proteins, myosin heavy chain (MHC), myosin light chain 1f (LC1f), 2f (LC2f), alpha-actin (Ac), and tropomyosin (TM). A23187 increased the degradation rate of LC1f, LC2f, and TM after 24 h. In contrast, the calcium ionophore caused decreased degradation of Ac and troponin-C and had no effect on the degradation of MHC, troponin-T, troponin-I, or alpha, beta-desmin (Dm). In addition, A23187 did not alter degradation of total myotube protein. The ionophore had little or no effect on the synthesis of total myotube proteins, but caused a marked decrease in the synthesis of MHC, LC1f, LC2f, Ac, TM, and Dm after 48 h. The mechanisms involved in calcium-stimulated degradation of the myofibrillar proteins were also investigated. Increased proteolysis appeared to involve a lysosomal pathway, since the effect of the Ca++ ionophore could be blocked by the protease inhibitor leupeptin and the lysosomotropic agents methylamine and chloroquine. The effects of A23187 occur in the presence of serum, a condition in which no lysosomal component of overall protein degradation is detected. The differential effect of A23187 on the degradative rates of the myofibrillar proteins suggests a dynamic structure for the contractile apparatus.
Animals↗
Pentobarbital anesthesia and the response of tumor and normal tissue in the C3Hf/sed mouse to radiation.
Studies of the effect of pentobarbital anesthesia on the radiation response have been performed using early generation isotransplants of three spontaneous tumors of the C3H mouse: a mammary carcinoma (MCaIV), a fibrosarcoma (FSaII), and a squamous cell carcinoma (SCCVII). The enhancement ratio of pentobarbital [ER(PB)] for TCD50 as the end point was greater than or equal to 1 for all conditions tested. The ER(PB) for O2 3 ATA conditions and two equal doses was 1.46, 1.72, and 2.21 for MCaIV, FSaII, and SCCVII, respectively. The ER(PB) using MCaIV was the same for O2 and carbogen at 1 or 3 ATA. Also, tumor size of MCaIV did not significantly affect the ER(PB) for O2 3 ATA conditions. Further, with the two-dose protocol the anesthesia and the hyperbaric oxygen needed to be used at the second dose; condition at the first dose was not critical. For fractionated irradiation of MCaIV (10 and 15 equal doses) the ER(PB) was smaller than for two-dose treatment; also the effect was less for intratumor temperature of 35 degrees C than 26-27 degrees C. There was no effect of the anesthesia on the acute response of normal skin of the leg. Lung damage by hyperbaric oxygen was not an important factor in these results. Additionally, ERs were computed for O2 at 3 ATA. This ER(O2 3 ATA) was larger for anesthesized than conscious mice. The ER(O2 3 ATA) for MCaIV was high (greater than 1.5) even for radiation given in 10 or 15 equal doses.
Anesthesia↗