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981.
An aneurysm that develops within a normal segment of the ascending aorta in a child with asymptomatic and previously undiagnosed congenital heart disease at the atrial level is most unusual and highly lethal. This report describes a child who had successful corrective surgery for this anomaly. 相似文献
982.
Flowering in Xanthium strumarium: INITIATION AND DEVELOPMENT OF FEMALE INFLORESCENCE AND SEX EXPRESSION 下载免费PDF全文
Vegetative plants of Xanthium strumarium L. grown in long days were induced to flower by exposure to one or several 16-hour dark periods. The distribution of male and female inflorescences on the flowering shoot was described, and a scoring system was designed to assess the development of the female inflorescences. The time of movement of the floral stimulus out of the induced leaf and the timing of action of high temperature were shown to be similar for both the apical male and lateral female inflorescences. 相似文献
983.
984.
985.
A technique of modelling the left ventricle for the purpose of volume determination has been devised. Two-dimensional echocardiographic data from the apical four chamber and two chamber views are used to pattern the ventricle as a stack of elliptical discs. The method has been validated for an array of regular geometric shapes commonly associated with ventricular architecture. The relative advantages of this model are discussed. 相似文献
986.
Two-dimensional echocardiographic imaging of the mitral valve orifice was attempted in 26 patients with isolated mitral stenosis. The intention was to examine further the clinical usefulness and limitations of this technique for estimating the severity of mitral stenosis. Technically adequate recordings of the mitral orifice were obtained in 20 patients (77%). Mitral valve area calculated from echocardiography compared favorably to the valve area derived from cardiac catheterization with the use of the Gorlin formula (r = 0.95). The average difference between the two methods was 0.109 cm(2). Two-dimensional echocardiography does provide clinically useful data for predicting the degree of mitral stenosis in the majority of patients provided that critical technical limitations are recognized. 相似文献
987.
David E. Leonard 《Entomologia Experimentalis et Applicata》1968,11(3):291-304
The crowding of larvae of Porthetria dispar in laboratory cultures incuced physiological and morphological differences. Larvae which were crowded developed faster than isolated larvae, but the development of instars varied in a characteristic manner. In crowded larvae (1) instar I was longer, (2) instars II–IV were shorter, (3) in males the penultimate and last instar were shorter, (4) in females the penultimate and last instar were longer, (5) in both sexes the pupal period was shorter. The pupal weights from crowded larvae were less, indicating a loss of fecundity. Crowding larvae increased the percentage of larvae which had increased survival. Phalaris tuberosa tended to cause high mortality in Rhopaea. Trifolium than the coloration of adults reared in isolated cultures.
Zusammenfassung In Laboratoriumszuchten gedrängt aufgezogene Schwammspinner-Raupen entwickelten sich schneller als einzeln gehaltene. Die in dichten Freilandpopulationen beobachtete raschere Entwicklung ist daher wahrscheinlich eine dichteabhängige Wirkung. Die gesteigerte Entwicklungsrate der gedrängt aufwachsenden Larven war nicht das Ergebnis einer allgemeinen Wachstumsbeschleunigung aller Stadien. Das Stadium 1 gedrängter Raupen dauert länger, während die Stadien II–IV kürzer waren. Bei den Männchen waren das vorletzte und letzte Stadium kürzer, bei Weibchen länger. Die Puppenzeit war bei dicht aufwachsenden Larven in den beiden Geschlechtern kürzer, auch wenn die Puppen dann isoliert gehalten wurden. —Zusammenpferchung erhöhte den Prozentsatz der Raupen, die ein zusätzliches Larvenstadium durchliefen. Raupen, die zusätzliche Häutungen durchmachten, haben ein längeres erstes Stadium und wiesen höhere Puppengewichte auf. Auf Grund des verlängerten ersten Stadiums und eines veränderten Spinnverhaltens wurde kürzlich vermutet, daß diese Raupen sich leichter zerstreuen. Das Auftreten eines höheren Prozentsatzes von Larven mit überzähligen Stadien könnte ein Mechanismus zur Sicherung des Abwanderns aus Gebieten sein. wo die Nahrungsvorräte erschöpft sind. Höhere Fruchtbarkeit könnte dazu beitragen, die geringere Überlebenschance abwandernder Raupen auszugleichen.Die Falter von gedrängt aufgezogenen Raupen waren heller gefärbt. Dies steht im Gegensatz zu anderen Arten, von denen bei hoher Dichte eine Verdunkelung der Färbung angegeben wird.相似文献
988.
Induction and development of increased ion absorption in corn root tissue 总被引:25,自引:22,他引:3 下载免费PDF全文
Washing excised or intact primary roots of corn (Zea mays L., WF9 × M14) in aerated distilled water or dilute salt solutions for 2 hours induced doubling of the rate of accumulation of various nutrient ions and solutes. This response to washing depended upon aerobic metabolism, but involved no increase in aerobic respiration. Excision of root tissue was not required as the effect could be obtained with intact root systems. Increased phosphate absorption followed after a lag period of 30 to 40 minutes and continued for 6 hours before leveling off at about 3.5 times the initial rate. Chloramphenicol was not inhibitory to the development of increased absorption, while inhibitors of RNA and protein synthesis were. Auxins and kinetin were also inhibitory, but so was the antiauxin, 2,4,6-trichlorophenoxyacetic acid. 相似文献
989.
Increased Membrane-bound Adenosine Triphosphatase Activity Accompanying Development of Enhanced Solute Uptake in Washed Corn Root Tissue 总被引:14,自引:12,他引:2 下载免费PDF全文
Washing of excised corn (Zea mays L., variety WF9×M14) root tissue is accompanied by an increase in (Mg2+ + K+)-stimulated adenosine triphosphatase. This is the adenosine triphosphatase described by Fisher, Hansen, and Hodges as positively correlated with ion accumulation rates. The increase in activity is confined to the microsomal fraction. A close parallel exists between increases in adenosine triphosphatase and phosphate absorption, and they respond similarly to inhibitors of RNA and protein synthesis. However, the amplitude of change is much smaller in adenosine triphosphatase. Possible reasons for this discrepancy are discussed. 相似文献
990.