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991.
Chronic continuous infusion of norepinephrine (NE) or epinephrine (Epi) subcutaneously in rats resulted in a rapid elevation of systolic blood pressure (SBP) by 40 mm Hg. Pressure remained high for the duration of the infusion but rapidly returned to control levels after its termination. Pronounced hypertrophy of the thoracic aorta, abdominal aorta and heart was evident within 2 days of the initiation of NE infusion and a plateau was attained by 5 days of infusion. The activity of tissue ornithine decarboxylase (ODC), the rate limiting enzyme in polyamine biosynthesis, was elevated preceeding the onset of tissue hypertrophy, and returned to control levels coincidentally with the cessation of accelerated tissue growth. It is concluded that high blood pressure in this animal model of hypertension is dependent upon the continued presence of exogenous catecholamine, and that pronounced cardiovascular hypertrophy perse is not sufficient to maintain the hypertension. The elevation and decline of vascular ODC activity is consistent with reports that in other tissues an elevation of ODC activity is an obligatory early event in hypertrophy.  相似文献   
992.
3-Epivitamin D3, the 3 alpha epimer of vitamin D3, was synthesized, and its biological activity in the rat was evaluated. It was found to be approximately 4 times less active on a weight basis than vitamin D3 with respect to intestinal calcium transport, bone calcium mobilization, and calcification score as determined by the line-test assay. Tritiated 3-epivitamin D3 was prepared, and its metabolism in the rat was compared with that of vitamin D3 to investigate the reasons for this diminished activity. 3-Epivitamin D3 was converted to two polar metabolites, for which the chromatographic properties and the origin of biosynthesis (in the liver and kidney, respectively) correspond to 25-hydroxy-3-epivitamin D3 and 1 alpha,25-dihydroxy-3-epivitamin D3. The fact that the concentration of 1 alpha,25-dihydroxy-3-epivitamin D3 in the intestine is half that of 1 alpha,25-dihydroxyvitamin D3 may be one explanation for the reduced biological activity of this epimer.  相似文献   
993.
In the mercuri- and halo-cyclizations of PGF2α methyl ester and its 11,15-bis(α-ethoxyethyl)-ether (or other protected forms) the exo-PGI1 derivative predominates independent of reagent and degree of protective of the PGF2α sample used. Diastereomerically pure samples of exo- and endo-PGI1 and prostacyclin (PGI2) were prepared. PGI0 epimers were prepared: catalytic hydrogenation of PGI2 Me ester provides exclusively the endo isomer. PGI2 methyl ester was found to be stable to extensive chromatography on silica, and to storage for at least a year in anhydrous ethanol at −20°C. At pH 7.4 in 2:1 H2O:EtOH, the ester has a half-life in excess of 5 hr at 25°C. A reproducible small scale (0.4–3 mg) synthesis of prostacyclin uses a modification of Whittaker's iodocyclization followed by DBN treatment. This procedure, developed with 15-3H-PGF2α, proved widely applicable to PGF2α analogs and diastereomers. The following prostacyclins (in the Me ester and Na salt forms) bearing the 5-en-6-yl ether unit were prepared in this way: ent-PGI2, rac-PGI2, 15-epi-PGI2, ent-15-epi-PGI2, 11-epi-PGI2, 8,9,12-epi-PGI2, -PGI2, 13,14-dihydro-PGI2, and 13,14-dihydro-15-epi-PGI2. NMR comparisons for the methyl esters reveal that of the resonances (H-5,9,11,15) that appear at δ4.0±0.6 ppm, the most deshielded is H-9 so long as the 5,6-olefin is . The 8 ,9 -6,9-oxido- -5,6-ene unit is most readily characterized by its strong positive dichroic absorption at 210–230 nm. CD spectroscopy not only serves to confirm the presence of this unit in analogs, but also can be used for quantitative analysis of PGI2 solutions and for monitoring the rate of hydrolytic cleavage of these enol ethers.  相似文献   
994.
Observations of age-sex class associations of three young female and five young male bonnet macaques born in the spring, 1975, were taken semiannually over three years beginning in the fall, 1975. Analysis reveals several patterns: (1) both males and females show continuous decline in association with age mates; (2) solitary time of females peaks at 1.5 years after which they begin to associate with adult females; (3) solitary time of males peaks at 2.5 years after which they associate predominantly with sub-adult males; (4) both males and females showed higher association with juveniles of the same sex than of opposite sex; and (5) both males and females showed annual cycles of association with some age-sex classes. These results are best understood with reference to the natural breeding cycle of the animals and the different life histories of male and female macaques in the wild.  相似文献   
995.
Zusammenfassung Es gibt Männer, die mit dem Nagelschen Anomaloskop untersucht als protanop befunden und daraufhin für rotgrünblind erklärt werden, die aber im täglichen Leben nicht nur rote Kleidungsstücke unmittelbar als rot erkennen, sondern auch Verkehrslichter ohne weiteres als rot bzw. grün wahrnehmen. Die Träger dieser bisher verkannten Varietät des Farbensinns unterscheiden sich von voll farbentüchtigen Männern durch eine wesentlich höhere Schwelle ihres Rotgrünsinns; sie ist X-gekoppelt erblich.Die Dreifarbentheorie ist unhaltbar, weil sie mit dem Vorkommen echter Rotgrünblindheit, bei der als Grundfarben nur Gelb und Blau wahrgenommen werden, unvereinbar ist. Normal Farbentüchtige sollte man daher nicht wie bisher normale Trichromate nenne; denn sie können vier Grundfarben (Rot, Gelb, Grün, Blau) wahrnehmen; sie sind also Tetrachromate. Ein solcher Terminus erübrigt sich aber. Nachdem die Dreifarbentheorie und mit ihr die Trichromaten erledigt sind, genügt die Bezeichnung normal Farbentüchtige.
Experience with a formerly mistaken variety of color vision. Theoretical and practical consequences
Summary Some men are thought to be protanopes if studied with Nagel's anomaloscope, yet they are not only able to recognise in everyday life red clothing immediately as red, but also see traffic lights as red and green, respectively. Men affected with this formerly mistaken variety of colour vision differ from those with normal colour vision by their higher threshold of red-green perception. The variety is X-linked.The three-colour theory cannot be reconciled with the existence of genuine redgreenblindness, in which the only basic colours seen are yellow and blue. Persons with normal colour vision should not be called normal trichromates, as they perceive four basic colours red, yellow, green and blue. They are tetrachromatic. This term is unnecessary, however. As the three-colour theory and the expression trichromate are obsolete, it is sufficient to refer to normal colour vision.
  相似文献   
996.
Spindle dynamics and arrangement of microtubules   总被引:2,自引:1,他引:1  
Changes in microtubule (MT) arrangement were studied in endosperm of Haemanthus katherinae. Individual cells were selected in the light microscope and sectioned perpendicular or parallel to the long axis of the spindle. The following data and conclusions were drawn: During anaphase kinetochore fibers (bundles of kinetochore MTs) always intermingle with non-kinetochore (continuous) fibers (bundles of non-kinetochore MTs). The latter often branch and some free ends are present. Often one non-kinetochore fiber is connected with more than one kinetochore fiber, explaining why chromosomes may lose their ability for independent movement. During anaphase kinetochore fibers move to the poles, the number of kinetochore MTs decreases by one-half and the MTs tend to become more splayed out. At the same time the number of MTs between trailing chromosome arms increases, probably representing segments of kinetochore MTs which break during anaphase. The number of non-kinetochore MTs in the equatorial region at anaphase is twice the number of non-kinetochore MTs in metaphase. The above data agree perfectly with those in polarized light and indicate that a simple sliding system does not exist in the spindle of Haemanthus.  相似文献   
997.
The results of studies of Micrasterias rotata (Grev.) Ralfs, M. thomasiana Archer (biradiate and uniradiate forms) and Closterium sp. using one- and two-dimensional vibrating probes show that transcellular ionic currents are detectable only around cells undergoing expansion of the primary cell wall (half-cell); current enters local regions of expansion and exits over both the rigid surface of the secondary wall and regions of the primary wall where hardening of the wall prevents further expansion. Current densities remain at steady levels until expansion stops with maturation of the primary wall, whereupon currents are no longer detectable. The temporal and spatial correlation between the currents and regions of wall expansion is particularly evident because morphogenesis of the half-cell is a determinate process. Measurements of inward currents ranged from 0.1 to 5.4 A · cm–2, and outward currents ranged from-0.05 to -1.5 A · cm–2 measured at 18 from the cell surface. The results of ion substitution and channel-blocker studies indicate that the currents may be carried at least in part by Ca2+, Cl, H+ and K+ ions. The possible role of a Ca2+ influx during tip growth in desmids is discussed.This work was conducted at the National Vibrating Probe Facility, Marine Biological Laboratory, Woods Hole, Mass., USA. Dr. Lionel F. Jaffe, Director of the Facility, and Dr. Jeremy D. PickettHeaps, University of Colorado, Boulder, USA, provided valuable guidance and support, and gave unstinting encouragement during these studies. Dr. Franklin M. Harold provided support for the writing of this paper during C.L.T.'s postdoctoral year at the National Jewish Center for Immunology and Respiratory Research, Denver. Mr. Alan Shipley and Mr. Steve Dixon provided talented technical assistance. C.L.T. is grateful for support received from a National Institutes of Health Pre-doctoral Training Grant in the Department of Molecular, Cellular and Developmental Biology, University of Colorado. The work was supported by N.I.H. grants 5 P41 RR01395 and 3 P41 RR01395-02S1 (to L.F.J.), National Science Foundation grants No. BSR 82 14199 and PCM 83 09331 (to J.P.-H.), and No. DCB 86 18694 (to F.M.H.).  相似文献   
998.
999.
Social behavior of the giant Chacoan peccary, also known as the taguá, is relatively unknown due to the harsh environment and endangered status of the population. In order to characterize feeding and social behaviors, a group of 7 adults, 2 juveniles, and 3 infants was observed in their feeding area for 99.25 hours over 18 days during October and November 1989. All animals were housed in a 2 ha natural-habitat enclosure in the Chaco of Paraguay. It was determined that these peccaries fed in intervals throughout daylight hours and that juveniles spent more time per approach in the feeding area than adult males. It was also observed that infants were accepted and well tolerated by the entire group, including adult males. These observations have relevance to taguá behavior in the wild and provide new insights into social patterns of this recently discovered species.  相似文献   
1000.
Proteinases and peptidases from the intestinal tract of fifth-instar larvae of Heliothis (= Helicoverpa) zea (Boddie) (Lepidoptera:Noctuidae) were characterized based on their substrate specificity, tissue of origin, and pH optimum. Activity corresponding to trypsin, chymotrypsin, carboxypeptidases A and B, and leucine aminopeptidase was detected in regurgitated fluids, midgut contents, and midgut wall. High levels of proteinase activity were detected in whole midgut homogenates, with much lower levels being observed in foregut and salivary gland homogenates. In addition, enzyme levels were determined from midgut lumen contents, midgut wall homogenates, and regurgitated fluids. Proteinase activities were highest in the regurgitated fluids and midgut lumen contents, with the exception of leucine aminopeptidase activity, which was found primarily in the midgut wall. Larvae fed their natural diet of soybean leaves had digestive proteinase levels that were similar to those of larvae fed artificial diet. No major differences in midgut proteinase activity were detected between larvae reared under axenic or xenic conditions, indicating that the larvae are capable of digesting proteins in the absence of gut microorganisms. The effect of pH on the activity of each proteinase was studied. The pH optima for the major proteinases were determined to be pH 8.0-8.5 for trypsin, when tosyl-L-arginine methyl ester was used as the substrate; and pH 7.5-8.0 for chymotrypsin, when benzoyl-L-tyrosine ethyl ester was used as the substrate.  相似文献   
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