RESUMEN
KEY MESSAGE: The widely divergent species 4xTrifolium ambiguum and 2xT.occidentale are inter-fertile long after speciation (including polyploidisation) has occurred. Tri-species hybrids (T. repens × T. ambiguum × T. occidentale) have the potential to achieve introgression of stress resistant traits from both wild species into white clover. Trifolium ambiguum and T. occidentale are geographically, adaptionally and phenotypically contrasting species in the white clover section (Trifoliastrum) of the genus. T. ambiguum occurs as a high-altitude polyploid series (2x, 4x, 6x) in W Asia and NE Europe. T. occidentale is a diploid coastal species, occurring at sea level in W Europe. This study investigated hybridisation between 4xT. ambiguum and 2xT. occidentale and considered the significance of the hybrids for introgression breeding of white clover. Partially fertile F1 hybrids between 4xT. ambiguum and 2x and 4xT. occidentale were generated by embryo rescue. Hybrid plant morphology and fertility varied widely and hybrids generally expressed traits from both species. Advanced generation (F2-F5) 4x hybrids were highly fertile and constitute a new synthetic allotetraploid species. FISH analyses of 4x hybrids showed multivalent chromosome configurations with homoeologous associations between T. ambiguum and T. occidentale chromosomes. Crosses of the hybrids with T. repens produced fertile tri-species progeny. These very divergent species remain inter-fertile long after speciation (including polyploidisation) has occurred. Tri-species hybrids have the potential to achieve introgression of stress resistance traits from both wild species into white clover.
Asunto(s)
Genoma de Planta , Hibridación Genética , Fitomejoramiento/métodos , Poliploidía , Trifolium/genética , Genotipo , Geografía , Fenotipo , Trifolium/crecimiento & desarrolloRESUMEN
Background and aims Traits related to root depth distribution were examined in Trifolium repens × T. uniflorum backcross 1 (BC1) hybrids to determine whether root characteristics of white clover could be improved by interspecific hybridization. Methods Two white clover cultivars, two T. uniflorum accessions and two BC1 populations were grown in 1 -m deep tubes of sand culture. Maximum rooting depth and root mass distribution were measured at four harvests over time, and root distribution data were fitted with a regression model to provide measures of root system shape. Morphological traits were measured at two depths at harvest 3. Key Results Root system shape of the hybrids was more similar to T. uniflorum than to white clover. The hybrids and T. uniflorum had a higher rate of decrease in root mass with depth than white clover, which would result in higher proportions of root mass in the upper profile. Percentage total root mass at 100-200 mm depth was higher for T. uniflorum than white clover, and for Crusader BC1 than 'Crusader'. Roots of the hybrids and T. uniflorum also penetrated deeper than those of white clover. T. uniflorum had thicker roots at 50-100 mm deep than the other entries, and more of its fine root mass at 400-500 mm. The hybrids and white clover had more of their fine root mass higher in the profile. Consequently, T. uniflorum had a higher root length density at 400-500 mm than most entries, and a smaller decrease in root length density with depth. Conclusions These results demonstrate that rooting characteristics of white clover can be altered by hybridization with T. uniflorum, potentially improving water and nutrient acquisition and drought resistance. Root traits of T. uniflorum are likely to be adaptations to soil moisture and fertility in its natural environment.
RESUMEN
Effects of aging and oxidative stress were studied in cerebral microvessels and microvessel-depleted brain from 6-, 18-, and 24-month-old C57Bl/6J mice exposed to normoxia, 24 or 48 h hyperoxia, or 24 h hyperoxia followed by 24 h normoxia. Microvessels lacked smooth muscle and consisted predominantly of endothelium. Following exposure and isolation of microvessel and parenchymal proteins, Western blot analysis was performed for detection of cytosolic thioredoxin 1 (TRx 1) and mitochondrial thioredoxin 2 (TRx 2), protein carbonyl, and mitochondrial superoxide dismutase (MnSOD). Both microvessel and parenchymal TRx 1 levels were increased by hyperoxia; however, the microvascular response was limited and delayed in comparison to that of the parenchymal fraction. Whereas TRx 2 levels in microvessels were increased in older mice, irrespective of exposure condition, hyperoxia per se had little or no apparent effect. Parenchymal cells showed no age-related increase in TRx 2 level under normoxic conditions, but showed increased levels following hyperoxia. Microvessel MnSOD was lower than that in parenchymal cells, but increased with age under normoxia, and also was correlated with the duration of hyperoxia. Although hyperoxia augmented MnSOD levels in young (6 months) and middle-aged (18 months) animals, the response was less pronounced in microvessels from senescent, 24-month-old mice. Unlike microvessels, which showed a sustained age-related increase in MnSOD level under each exposure condition, parenchymal cells from normoxic mice showed no increase, and hyperoxia-induced elevations declined with prolonged 48 h exposure. These results indicate that the microvessel endothelium is (1) subjected to a more intense oxidative environment than neurons and glia and (2) is limited by aging in its ability to respond to oxidative insult.
Asunto(s)
Envejecimiento , Hiperoxia/metabolismo , Microcirculación/metabolismo , Estrés Oxidativo , Telencéfalo/irrigación sanguínea , Animales , Análisis de los Gases de la Sangre , Western Blotting , Química Encefálica , Separación Celular , Citosol/metabolismo , Electroforesis en Gel de Poliacrilamida , Endotelio Vascular/química , Endotelio Vascular/citología , Endotelio Vascular/metabolismo , Proteínas de la Membrana/análisis , Proteínas de la Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Microcirculación/química , Microcirculación/citología , Mitocondrias/enzimología , Músculo Liso Vascular/citología , Músculo Liso Vascular/metabolismo , Superóxido Dismutasa/metabolismo , Telencéfalo/química , Telencéfalo/citología , Tiorredoxinas/análisis , Tiorredoxinas/metabolismo , Factores de TiempoRESUMEN
The breakdown of 5-fluoro-2'-deoxyuridine (FdUrd) to 5-fluorouracil (FUra) is catalyzed by the pyrimidine nucleoside phosphorylases, uridine phosphorylase and thymidine phosphorylase. The effects of nucleoside phosphorylase inhibitors on FdUrd and FUra elimination by the isolated perfused rat liver were investigated. The inhibitor was injected into the perfusion reservoir 5 min before FdUrd or FUra, and serial perfusion fluid samples were collected for fluoropyrimidine analysis. The disappearance of each fluoropyrimidine followed Michaelis-Menten kinetics, as shown previously. 6-Benzyl-2-thiouracil, a thymidine phosphorylase-selective inhibitor, and 1-(2'-deoxy-beta-D-glucopyranosyl)thymine, a uridine phosphorylase-selective inhibitor, each decreased the rate of FdUrd disappearance (apparent Ki, 1.4-1.6 and 3.8 mM, respectively) but had no direct effect on FUra disappearance. However, 6-benzyl-2-thiouracil decreased the peak concentration of FUra derived from administered FdUrd and increased the t 1/2 of disappearance of derived FUra due to its delayed formation. 2,6-Dihydroxypyridine, a uridine phosphorylase-selective inhibitor, decreased the rate of FdUrd disappearance (apparent Ki, 12.4-16.2 microM) and directly inhibited FUra elimination (apparent Ki, 4.3-5.3 microM). 2,4-Dihydroxypyridine, which does not inhibit pyrimidine nucleoside phosphorylases, directly inhibited FUra elimination (apparent Ki, 77 microM) and also decreased the rate of FdUrd disappearance, possibly due to product (FUra) inhibition. It was concluded that the hepatic elimination of FdUrd is slowed by pyrimidine nucleoside phosphorylase inhibitors and that some of these drugs block FUra, as well as FdUrd, elimination.
Asunto(s)
Floxuridina/farmacocinética , Fluorouracilo/farmacocinética , Hígado/metabolismo , Pentosiltransferasa/antagonistas & inhibidores , Animales , Cinética , Masculino , Perfusión , Piridinas/farmacología , Pirimidina Fosforilasas , Ratas , Ratas EndogámicasRESUMEN
The effect of penicillin on the renal tubular secretion of methotrexate (MTX) in rhesus and cynomolgus monkeys was studied in vivo and in vitro. In stop-flow experiments in ketamine-anesthetized monkeys, the ratios of urine/plasma MTX concentration to urine/plasma inulin concentration of proximal tubular samples were about 2-fold greater than the base-line free-flow values of 3.3 to 4.8, indicating net proximal tubular secretion. MTX secretion was inhibited by penicillin, which lowered the base-line U/PMTX/U/Pinulin ratios to 0.8 to 1.3; the effect persisted over a 30-min period after discontinuation of penicillin administration. Penicillin also slowed the disappearance of MTX from plasma over a 2-hr period after i.v. bolus administration of MTX. In experiments with renal cortical slices, MTX uptake at 25 degrees was linear over the initial 30 min. The uptake Km and Vmax were 0.09 mM and 0.11 mumol/g of tissue/30 min, respectively. Penicillin competitively inhibited MTX uptake; the Ki was 0.83 mM. MTX efflux from preloaded slices (incubated with 0.5 mM MTX for 45 min) was a first-order process with an initial t1/2 of 7.1 min, which decreased to 2.0 min in the presence of 1.36 mM penicillin. It was concluded that MTX and penicillin share a common secretory system in the kidney and that penicillin blocks MTX secretion by inhibiting cellular uptake and stimulating efflux.
Asunto(s)
Corteza Renal/metabolismo , Túbulos Renales/metabolismo , Metotrexato/metabolismo , Penicilinas/farmacología , Animales , Técnicas In Vitro , Corteza Renal/efectos de los fármacos , Túbulos Renales/efectos de los fármacos , Cinética , Macaca fascicularis , Macaca mulatta , Penicilinas/metabolismoRESUMEN
The influence of dose and hepatic blood flow on the elimination of 5-fluoro-2'-deoxyuridine (FdUrd) by the isolated perfused rat liver were investigated. FdUrd (1-20 mg; 4-81 mumol) was injected into the perfusion reservoir and serial samples were collected for chromatographic determination of plasma FdUrd and 5-fluorouracil concentrations. The decrease in FdUrd concentration from values above 100 microM was linear with time (apparent zero order); at concentrations below 30-40 microM the decline became exponential (apparent first order). Semilogarithmic plots of FdUrd concentration/dose versus time obtained with different doses were not superposable, indicating Michaelis-Menten elimination. At a perfusion rate of 20 ml/min, the apparent Vmax and Km for FdUrd disappearance were 14-19 nmol/ml/min and 161-194 microM, respectively. FdUrd clearance during first-order elimination was 8-11 ml/min. After FdUrd administration, 5-fluorouracil concentration reached 10-15% of the initial FdUrd concentration, then decreased with a half-life of 4-7 min. Fifty-four % of the dose of [2-14C]FdUrd was converted to 14CO2. At a dose of 20 mg, first-order clearance of FdUrd increased from 7 to 12 ml/min as hepatic flow increased from 10 to 30 ml/min. Less than 1% of the dose of [6-3H]FdUrd was incorporated into macromolecules. It was concluded that hepatic elimination of FdUrd is dependent on both dose and blood flow.
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Floxuridina/metabolismo , Hígado/metabolismo , Animales , Velocidad del Flujo Sanguíneo , Floxuridina/farmacocinética , Circulación Hepática , Tasa de Depuración Metabólica , Perfusión , RatasRESUMEN
The influences of dose and hepatic blood flow on the elimination of 5-fluorouracil (FUra) by the isolated perfused rat liver were investigated. FUra was injected into the perfusion reservoir and then serial blood samples were collected over 2-3 h. FUra concentration was determined chromatographically. In some experiments, the conversion of [2-14C]FUra to 14CO2 was also determined. With livers perfused at 20 ml/min, the initial decrease in plasma FUra concentration was linear with time (apparent zero-order kinetics); at concentrations below about 25 microM, the decrease became exponential (apparent first-order kinetics). Semilogarithmic plots of FUra concentration/dose versus time obtained with different doses were not superposable, consistent with saturable (Michaelis-Menten) elimination. Vmax and Km were 6-11 nmol/ml/min and 33-45 microM, respectively. Hepatic clearance during first-order elimination was close to 20 ml/min. About 84% of the dose was converted to CO2, indicating that catabolic metabolism was the principal route of elimination. As hepatic blood flow increased from 10 to 30 ml/min, Vmax was unchanged but Km decreased progressively from 84 to 32 microM, and clearance increased from 12 to 29 ml/min. It was concluded that hepatic FUra elimination is highly dependent upon both dose and blood flow.
Asunto(s)
Fluorouracilo/farmacocinética , Hígado/metabolismo , Animales , Relación Dosis-Respuesta a Droga , Cinética , Hígado/irrigación sanguínea , Perfusión , Ratas , Flujo Sanguíneo Regional , Factores de TiempoRESUMEN
The I-R element at the R locus destabilizes kernel pigmentation giving the variegated pattern known as stippled ( R-st). In trans linkage phase with R-st the element was shown to act as a modifier of stippled, intensifying seed spotting in parallel with effects of the dominant linked modifier M-st. Presence of I-R in the genome was, therefore, shown to be detectable as a modifier of R-st. When this test was used, new modifiers resembling M-st were often detected following mutations of R-st to the stable allele R-sc. Such mutations evidently occurred by transposition of I-R away from the R locus to a site where it was identifiable as a modifier. M-st may be such a transposed I-R. Analysis of mutations to R-sc during the second (sperm-forming) mitosis in pollen grains showed that some of the transposed I-R elements were linked with R, whereas others assorted independently. Their strengths varied from barely discernible to a level equal to M-st. Overreplication frequently accompanied transposition at the sperm-forming mitosis, leading to transposed I-R elements in both the mutant and nonmutant sperm.
RESUMEN
The absorption, distribution, and elimination of caffeine, 2 mg/kg by mouth, were evaluated in six smokers and six nonsmokers before and on the fourth day of administration of cimetidine, 300 mg by mouth every 6 hr. Caffeine absorption, assessed by the maximal serum caffeine concentration (C max) and the time to reach Cmax (t max), was very rapid relative to elimination. The total body clearance (TBC) of caffeine was higher (2.49 +/- 0.35 and 1.59 +/- 0.19 ml/kg/min, P less than 0.05) and the elimination half-life (t1/2) shorter (190 +/- 15 and 276 +/- 30 min, P less than 0.05) in smokers than nonsmokers, but Cmax, tmax, and the apparent volume of distribution (Vd, app) did not differ (P greater than 0.05). Cimetidine decreased the TBC of caffeine by 31% (to 1.73 +/- 0.28 ml/kg/min, P less than 0.05) and by 42% (to 0.92 +/- 0.11 ml/kg/min, P less than 0.01) in smokers and nonsmokers. The increases in t1/2 were 45% (to 276 +/- 25 min, P less than 0.05) and 96% (to 542 +/- 123 min, P less than 0.05). Cmax, tmax, and Vd, app were unaffected by cimetidine. Caffeine induced similar slight increases in blood pressure and pulse rate in smokers and nonsmokers both before and during cimetidine dosing.
Asunto(s)
Cafeína/metabolismo , Cimetidina/farmacología , Guanidinas/farmacología , Fumar , Adulto , Cafeína/sangre , Semivida , Humanos , Absorción Intestinal/efectos de los fármacos , Cinética , Masculino , Persona de Mediana Edad , Factores de Tiempo , Distribución TisularRESUMEN
The cysteine (Cys) precursor 2(R,S)-n-propylthiazolidine-4(R)-carboxylic acid (PTCA) was shown previously to maintain near normal levels of hepatic GSH and GSSG at 24 hr and to protect against hepatic necrosis and mortality at 48 hr after toxic doses of acetaminophen (APAP) in mice. Studies were performed in C57BL/6 mice to determine: (a) the time course of APAP-induced hepatic sulfhydryl depletion, and (b) the effectiveness of PTCA in preventing APAP-induced decreases in sulfhydryl concentrations at the time of maximal depletion. APAP (400-800 mg/kg in 50% propylene glycol; 2.65-5.29 mmol/kg) and PTCA (1-5 mmol/kg 30 min after APAP) were administered i.p. Hepatic GSH, GSSG, and Cys concentrations were determined by HPLC. Hepatocellular damage was assessed by elevations in serum glutamate-pyruvate transaminase (SGPT) activity and histopathologic examination. APAP and PTCA produced dose-dependent effects. At 4 hr after the highest dose of APAP, hepatic GSH and Cys concentrations were reduced to 5 and 14%, respectively, of values in vehicle-treated controls, and the GSSG concentration was below the sensitivity of the analytical method. At 24 hr, recovery of hepatic sulfhydryls was incomplete, and there was hepatic necrosis with an approximately 100-fold increase in SGPT activity. At the highest dose of PTCA, the concentrations of GSH, Cys, and GSSG at 4 hr after APAP (800 mg/kg) were 66, 116, and 111%, respectively, of vehicle controls. PTCA in doses of 1.75 to 5 mmol/kg attenuated the APAP-induced increases in SGPT activity. It was concluded that the protective effect of PTCA is most likely related to prevention of hepatic sulfhydryl depletion.
Asunto(s)
Acetaminofén/antagonistas & inhibidores , Hepatopatías/prevención & control , Tiazoles/farmacología , Acetaminofén/toxicidad , Aldehídos/farmacología , Analgésicos no Narcóticos/antagonistas & inhibidores , Analgésicos no Narcóticos/toxicidad , Animales , Enfermedad Hepática Inducida por Sustancias y Drogas , Cisteína/metabolismo , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Glutatión/metabolismo , Disulfuro de Glutatión/metabolismo , Hígado/efectos de los fármacos , Hepatopatías/metabolismo , Hepatopatías/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Profármacos/uso terapéutico , Sustancias Protectoras/farmacologíaRESUMEN
The cysteine (Cys) precursor 2(RS)-n-propylthiazolidine-4(R)-carboxylic acid (PTCA) has been shown to protect against acetaminophen (APAP)-induced hepatic GSH, GSSG, and Cys depletion and hepatic necrosis. The aim of this study was to determine the effects of PTCA on the concentrations of sulfhydryl compounds in extrahepatic tissues, including renal cortex, whole blood, and brain, in C57BL/6 mice treated with hepatotoxic doses of APAP. PTCA (1-5 mmol/kg, i.p.) was administered 30 min after the administration of APAP at a dose (800 mg/kg; 5.29 mmol/kg, i.p.) that depleted hepatic GSH and Cys at 4 hr by 95 and 86%, respectively. Tissue concentrations of GSH and Cys were determined by HPLC. At 4 hr following APAP administration, renal cortical GSH and Cys concentrations were decreased to 64 and 39%, respectively, of vehicle-treated control values, and blood concentrations were decreased to 87 and 30%, respectively, of vehicle controls. Brain GSH and Cys were not depleted by APAP. PTCA at 5 mmol/kg (i) attenuated the APAP-induced depletion of GSH and Cys at 4 hr in renal cortex (78 and 65%, respectively, of vehicle controls), (ii) prevented APAP-induced Cys depletion in blood (670% of vehicle controls) with no effect on GSH concentration (94% of vehicle controls), and (iii) increased GSH and Cys concentrations in brain (119 and 411%, respectively, of vehicle controls). The results demonstrate a high degree of tissue selectivity in the APAP-induced depletion of GSH and Cys, and in the effectiveness of PTCA in maintaining and even elevating sulfhydryl levels in extrahepatic tissues of APAP-treated mice.
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Acetaminofén/farmacología , Corteza Renal/efectos de los fármacos , Profármacos/farmacología , Compuestos de Sulfhidrilo/metabolismo , Tiazoles/farmacología , Analgésicos no Narcóticos/farmacología , Animales , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Cisteína/metabolismo , Interacciones Farmacológicas , Glutatión/deficiencia , Glutatión/metabolismo , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Técnicas In Vitro , Corteza Renal/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Compuestos de Sulfhidrilo/sangre , Distribución TisularRESUMEN
An easily constructed arterial catheter was designed for use in experiments requiring serial blood sampling from conscious, free-moving animals (Fischer 344 rat). It can be implanted chronically, at least several days before use, into the femoral artery, without interference of movement or damage by the animal. The catheter assembly is worn subdermally until the distal portion is exteriorized for blood sampling. The proximal tip of the catheter is occluded with a removable plug before implantation, thereby eliminating the necessity of daily flushing prior to use. The catheter has been used extensively in studies of the blood-brain barrier involving the bolus injection of [14C]sucrose into the jugular vein of conscious, unrestrained rats. Tracer concentration in plasma and whole blood was subsequently determined from arterial blood samples collected serially over a 20-min period following injection of the tracer.
Asunto(s)
Barrera Hematoencefálica , Catéteres de Permanencia , Sacarosa/sangre , Animales , Permeabilidad Capilar , Arteria Femoral , Venas Yugulares , Ratas , Ratas Endogámicas F344RESUMEN
Intravenously injected [14C]sucrose was used as a small molecular weight (342 daltons), hydrophilic tracer for determination of 2450 MHz CW microwave and ambient heat effects on rat blood-brain barrier permeability in the cerebral cortex, hypothalamus, cerebellum and medulla. The tracer was injected 4 min following exposure of conscious, unrestrained rats to microwaves at 0 or 65 mW/cm2 for 30 or 90 min (SAR approximately equal to 13.0 W/kg) or to ambient heat (42 +/- 2 degrees C) for 90 min. Comparison of mean permeability-surface area products (PA) and uptake ratios between sham and microwave-exposed animals revealed a statistically significant (P less than 0.05) decrease of both PA and uptake ratios for the hypothalamus, cerebellum and medulla of rats exposed to microwaves for 30 min. This decrease was not apparent for rats exposed to microwaves for 90 min. A pertinent observation, with regard to this latter group of animals, was the increased circulating levels of the tracer when colonic temperature was raised to approximately 41.4 degrees C or higher.
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Barrera Hematoencefálica/efectos de la radiación , Calor , Microondas , Animales , Presión Sanguínea/efectos de la radiación , Hematócrito , Hipertermia Inducida , Masculino , Pulso Arterial/efectos de la radiación , Ratas , Ratas Endogámicas F344 , Sacarosa/metabolismoRESUMEN
Significantly elevated levels of sodium fluorescein (MW 376) were found only in the brains of conscious rats made considerably hyperthermic (colonic temperatures greater than 41.0 degrees C) by exposure to ambient heat (42 +/- 2 degrees C) for 90 min or 2450 MHz CW microwave energy at 65 mW/cm2 (SAR approximately equal to 13.0 W/kg) for 30 or 90 min. For microwave-exposed rats, fluorescein levels within the cortex and hypothalamus appeared to increase with increasing duration of exposure. This trend was not apparent in the cerebellum or medulla. Exposure to ambient heat resulted in increased fluorescein with the cortex, hypothalamus and medulla, but not the cerebellum, and, in general, ambient heat was not as effective as microwave energy in raising tracer concentrations within the brain. By far the greatest elevation of fluorescein dye in the brain occurred in those animals whose blood-brain barrier had been opened osmotically by intracarotid injection of 10 M urea. It is suggested that increased levels of sodium fluorescein found in the brain tissue of ambient heat and microwave-exposed rats most likely represent technically derived artifact and not a breakdown of the blood-brain barrier.
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Barrera Hematoencefálica/efectos de la radiación , Calor , Microondas , Animales , Fluoresceína , Fluoresceínas , Hipertermia Inducida , Soluciones Hipertónicas , Masculino , Ratas , Ratas Endogámicas F344 , Urea/farmacologíaRESUMEN
Alteration of blood-brain barrier (BBB) permeability by 2450 MHz CW microwaves was assessed semi-quantitatively after intravenous injection of horseradish peroxidase (HRP) and exposure of conscious, unrestrained rats to incident power densities of 0, 20 or 65 mW/cm2 for 30, 90 or 180 min. Additional rats were exposed to ambient heat (42 +/- 2 degrees C) for 30 or 90 min. None of the brain regions studied, with the exception of the normally leaky pineal gland, showed extracellular HRP leakage attributable to microwave or thermally-induced breakdown of the blood-brain barrier. The mean ratio of HRP-labeled microvessel endothelium/total number of microvessels counted was determined for each brain region. Mean values for the cortex, hypothalamus, cerebellum and medulla of microwave-exposed and heated rats were consistently below those of corresponding sham levels. This decrease appeared to correlate inversely with power density and duration of exposure. Statistically significant deviation (P less than 0.05) from sham mean values occurred in the cortex, hypothalamus, cerebellum and medulla of animals made hyperthermic with ambient heat or exposure to microwaves at 65 mW/cm2 (specific absorption rate approximately equal to 13.0 W/kg) for 30 or 90 min. Additionally, electron microscopic evaluation of ultrathin sections taken from each of the 4 brain regions revealed no significant extravasation of HRP indicative of microwave or ambient heat-induced disruption of the blood-brain barrier.
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Barrera Hematoencefálica/efectos de la radiación , Calor , Microondas , Animales , Encéfalo/irrigación sanguínea , Peroxidasa de Rábano Silvestre , Hipertermia Inducida , Masculino , Microcirculación/ultraestructura , Microscopía Electrónica , Ratas , Ratas Endogámicas F344RESUMEN
Measurement of temperature within the cerebral cortex, hypothalamus, cerebellum and medulla of rats sham-, heat- or microwave-exposed revealed the presence of a thermal gradient within the brain. In all groups, cerebral cortex and the cerebellum were cooler than the deeper hypothalamus and medulla. Exposure to 2450 MHz CW microwaves or ambient heat (42 +/- 2 degrees C) resulted in measurable elevation of regional brain temperature, but without alteration of temperature gradients normally observed within the brain. Exposure to 20 mW/cm2 (SAR approximately equal to 4 W/kg) for 30, 90 or 180 min induced a small, but significantly (U = 0, P less than 0.05) increased temperature of the colon, and in each region of the brain studied. Exposure to an incident power density of 65 mW/cm2 (SAR approximately equal to 13.0 W/kg) for 30 or 90 min or to ambient heat (42 +/- 2 degrees C) for 90 min resulted in a substantially greater thermal response as indicated by higher colonic and brain temperatures. Comparison of regional brain temperature with individual colonic temperatures is expressed as delta T = t degrees Cbrain--t degrees Ccolon. In general delta T values for ambient heat or microwave-exposed rats did not differ significantly from those of sham-exposed animals. Exposure to microwaves or ambient heat did not alter the general relationships between regional brain and colonic temperatures, i.e., cortical and cerebellar temperatures were always below and hypothalamic and medullary temperatures always above corresponding colonic temperatures. The plotted temperature data (brain vs colonic temperature) indicate a linear relationship between brain and colonic temperatures. Levels of sodium fluorescein (NAFl), horseradish peroxidase (HRP) and [14C]sucrose (described in preceding papers) within the brain show a high correlation (P less than 0.05) with brain temperature. Suppression of blood-brain barrier permeability to hydrophilic tracers was most pronounced at brain temperatures exceeding approximately 40 degrees C and is demonstrated to be temperature dependent.
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Barrera Hematoencefálica/efectos de la radiación , Calor , Microondas , Animales , Temperatura Corporal , Encéfalo/fisiología , Fluoresceína , Fluoresceínas , Peroxidasa de Rábano Silvestre , Hipertermia Inducida , Masculino , Pinocitosis , Ratas , Ratas Endogámicas F344 , SacarosaRESUMEN
The authors consider the empirical validity of the Graduate Record Examination (GRE) as a predictor of various kinds of performance in a graduate psychology program, including 1st- and 2nd-year grades; professors' ratings of students' dissertations; and professors' ratings of students' analytical, creative, practical, research, and teaching abilities. On the basis of the triarchic theory of intelligence, the GRE was predicted to be of some use in predicting graduate grades but of limited or no use in predicting other aspects of performance. In fact, the test was found to be useful in predicting 1st-year grades but not other kinds of performance, with one exception--performance on the GRE Analytical test was predictive, but only for men. The authors conclude that there is a need to develop better theory-based tests.
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Logro , Evaluación Educacional/normas , Psicología/educación , Estudios Transversales , Estudios de Evaluación como Asunto , Femenino , Humanos , Masculino , Psicología/normas , Análisis de Regresión , Estudios Retrospectivos , Criterios de Admisión EscolarRESUMEN
A case of germ cell neoplasm in an undescended retroperitoneal testicle is reported. CT revealed a large mass most consistent with a chronic hematoma. MRI demonstrated findings typical for neoplasm, and this was confirmed on biopsy.
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Criptorquidismo/complicaciones , Imagen por Resonancia Magnética , Neoplasias de Células Germinales y Embrionarias/diagnóstico , Neoplasias Retroperitoneales/diagnóstico , Neoplasias Testiculares/diagnóstico , Tomografía Computarizada por Rayos X , Humanos , Masculino , Persona de Mediana Edad , Neoplasias de Células Germinales y Embrionarias/diagnóstico por imagen , Neoplasias Retroperitoneales/diagnóstico por imagen , Neoplasias Testiculares/complicaciones , Neoplasias Testiculares/diagnóstico por imagenRESUMEN
Primary lymphoepithelioma-like carcinoma (LELC) of the lung is a neoplasm seen most commonly in the nasopharynx of individuals from south China and Taiwan, and is strongly associated with the Epstein-Barr virus. The case of a 62-year-old Chinese man with a rare primary lung T2N1M0 LELC of the left lower lobe is presented. The lesion was further notable because of the presence of necrotizing granulomatous inflammation. The patient was treated with surgical resection. After it was determined that the neoplasm was of primary lung origin, adjunctive chemotherapy was initiated. The role of adjunctive chemotherapy in this setting is discussed.