Ovulation and the mechanism of follicle rupture

Summary The rabbit Graafian follicles are encircled by a capillary network between the theca interna and the avascular membrana granulosa. After injection of an ovulatory dose of human chorionic gonadotrophin (HCG) the theca interna cells showed an increase in the amount of smooth endoplasmic reticulum, lipid droplets and mitochondria with tubular cristae. In addition, considerably more junctions, similar to the abutment nexuses of granulosa cells were found; annular nexuses also appeared. At 4 hours after injection of HCG a prominent oedema was evident in the theca interna layer, particularly in the apical region.Small fenestrations in the endothelium of the blood capillaries increased in amount after HCG injection, and close to the time of ovulation, large gaps or perforations, 1–3 in diameter, were found in the thin, distended part of the endothelial cells. The surrounding basement membrane became fragmented and partly lost, so that a seemingly free passage from the capillary lumen to the interstitium was eventually established. Leakage of fluid, causing interstitial oedema, presumably proceeds until the pressure in the pericapillary interstitium has risen to the pressure in the capillaries. Some hours before and up to ovulation the pericapillary interstitium has also broad communications with the cavity of the follicles. Therefore, both pressure and fluid can be passed from the capillaries-via the interstitium-to the follicle antrum. However, influx of fluid with subsequent follicle expansion and ovulation-at constant pressure-does not occur until the tensile strength of the follicle wall has decreased.This investigation was supported by grants from the Swedish Medical Besearch Council (Projects No. B72-12X-78-07A, B73-12X-78-08B and B74-12X-78-09C). The technical assistance of Miss Ingalis Fransson, Miss Kerstin Nilsson, and Mrs. Ulla-Britt Westman is greatly appreciated.     

Correlation between microtubular number and transport activity of hypothalamo-neurohypophyseal secretory neurons

Summary The lower pituitary stalk has been studied in rats given hypertonic saline for four days and in rats with congenital diabetes insipidus (GDI), that is, in two groups of animals in which there is evidence of an increase in the transport of polypeptides down the axons of the tractus hypophyseus.A quantitative ultrastructural analysis of this tract, the first yet made, has demonstrated that in normal animals it is composed of unusually small axons, over half of which are less than 300 nm in diameter.In this tract there is a significant increase in axonal diameter and microtubular content in animals given hypertonic saline for four days. In adult rats with CDI, these changes are even more marked, a feature which is correlated with the fact that in these animals the transport of polypeptides has probably been abnormal since birth.An alteration in the microtubular content of neurons has not previously been observed either in physiologically stressed animals or in diseased animals; such alterations suggest the participation of microtubules in polypeptide transport. The narrow diameter of axons in the tractus hypophyseus of the normal animal raises the possibility of the extravesicular transport of such polypeptides.Abbreviations used ADH antidiuretic hormone - AF aldehyde fuchsin - CDI congenital diabetes insipidus - HNS hypothalamo-neurohypophysiel system - NSM neurosecretory material - NSV neurosecretory vesicle - PVN paraventricular nucleus - SON supraoptic nucleus This paper is dedicated to Professor W. Bargmann.We are grateful to Miss Pauline Chapman for technical assistance.This project is supported by the Medical Research Council.     

An unstable locus in soybeans

Summary Investigation of a variegated condition in the soybean variety Lincoln indicates instability at the Y locus. Leaf sectors of chlorophyll-less yellow tissue occur in distinct heritable patterns; some leaves have small flecks of yellow tissue (late occurring mutations) and others possess large areas or whole leaflets (early occurring mutations).There is evidence that this allele, Y ₁₈ ^m , mutates to the wild type, Y, which is green and stable and to the recessive, y, which is yellow and lethal in the seedling condition. (With an increase in the amount of yellow tissue there is an increase in the frequency of lethals.) However, changes from one type to the other are observed, and patterns of variegation representing different states of the instability are described. These depend upon the time and frequency of mutation events.Evidence is presented to support the hypothesis that this instability is controlled by a factor that resides at the locus. Such a factor governs the timing of the mutation events and is related to similar elements in maize, which are part of specific mutable systems. Control of variegation of the Y ₁₈ ^m locus is compared with the models proposed for the cases of instability in maize.

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Zusammenfassung Die Untersuchung eines variegaten Zustandes bei der Sojabohnensorte Lincoln führte zum Nachweis einer Instabilität des Y-Locus. Blattsektoren mit chlorophyllfreiem gelbem Gewebe traten in bestimmten erblichen Mustern auf. Einige Blätter wiesen kleine Flecken gelben Gewebes auf (spät eingetretene Mutationen), während andere große Flächen oder vollständig gelbe Blättchen besaßen (früh eingetretene Mutationen).Es gibt Beweise dafür, daß das entsprechende Allel Y ₁₈ ^m sowohl zum stabilen Wildtypallel Y, mit grünem Phänotyp, als auch zum rezessiv gelben y, das im Sämlingsstadium letal wirkt, mutiert. (Eine Zunahme der Menge gelben Gewebes ist mit einer Zunahme der Letalfrequenz verbunden.) Umwandlungen eines Typs zu einem anderen werden beobachtet und Variegationsmuster beschrieben, die unterschiedliche Stadien der Instabilität verkörpern. Diese hängen von dem Zeitpunkt und der Frequenz der Mutationsereignisse ab.Es werden Beweise vorgelegt, die die Hypothese stützen, daß diese Instabilität durch einen Faktor kontrolliert wird, der sich am Locus befindet. Ein Faktor dieser Art kontrolliert das zeitliche Auftreten der Mutationsereignisse. Er ist mit ähnlichen Elementen des Maises verwandt, die Teile eines spezifisch mutablen Systems sind. Die Kontrolle der Variegation durch den Y ₁₈ ^m -Locus wird mit den Modellen verglichen, die für die Fälle der Instabilität beim Mais vorgeschlagen wurden.

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Joint contribution from the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa (Projects 1335 und 1179) as Journal Paper No. 5635.

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Former Agronomist, Crops Research Division, ARS, USDA, and Professor Iowa State University; now Research Director, Peterson Seed Company.     

Effect of Temperature on the Potential and Current Thresholds of Axon Membrane

The effect of temperature on the potential and current thresholds of the squid giant axon membrane was measured with gross external electrodes. A central segment of the axon, 0.8 mm long and in sea water, was isolated by flowing low conductance, isoosmotic sucrose solution on each side; both ends were depolarized in isoosmotic KCl. Measured biphasic square wave currents at five cycles per second were applied between one end of the nerve and the membrane of the central segment. The membrane potential was recorded between the central sea water and the other depolarized end. The recorded potentials are developed only across the membrane impedance. Threshold current values ranged from 3.2 µa at 267deg;C to 1 µa at 7.5°C. Threshold potential values ranged from 50 mv at 26°C to 6 mv at 7.5°C. The mean Q₁₀ of threshold current was 2.3 (SD = 0.2), while the Q₁₀ for threshold potentials was 2.0 (SD = 0.1).     

Vegetative Entwicklung und Blütenbildung in axenischen Kulturen der InsektivoreDrosera pygmaea DC.

Zusammenfassung Drosera pygmaea läßt sich in organismenfreier Reinkultur auf Agar oder Fließpapier mit organischen wie anorganischen Lösungen kultivieren.Die größten Pflänzchen hatten beim vorläufigen Abschluß der Arbeit einen Durchmesser ihrer Blattrosette von höchstens 2 cm, etwa ein halbes Hundert Blätter mit wenig mehr als 1/2 cm Blattstiellänge und Blattspreiten, die kaum je 2 mm Durchmesser erreichten.Je nach den Bedingungen war die Spreite scheibenförmig oder unentfaltet rundlich; auch die Ausbildung der Randtentakeln war sehr unterschiedlich.In vielen Kulturen traten Blüten (bis zu 8 an einer Pflanze) auf, und zwar auf organischem wie vor allem auch auf anorganischem Substrat.Die Kronblätter traten als weiße, sich bald rosa färbende Kuppel aus dem grünen Kelch hervor; sie entfalteten sich aber nicht, sondern die Blüte entwickelte sich, ohne sich geöffnet zu haben, weiter zur samentragenden Frucht.Im Gegensatz zuUtricularia exoleta, die nur bei Gegenwart von aus Tieren stammender Substanz Blüten bildet, kann beiDrosera pygmaea der gesamte Entwicklungsablauf von der Keimung bis zur Samenbildung auf rein mineralischer Unterlage stattfinden.Mit 10 TextabbildungenMit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Factors Controlling the Production of Lysogenic Cultures of B. megatherium

(1) The proportion of infected B. megatherium cells which develop lysogenic colonies depends on the number and kind of infecting virus particles and on the culture medium in which the cells are growing. (2) Cells infected with 100 or more T virus particles (from megatherium 899) in yeast extract peptone disintegrate, produce very few virus particles, and less than one lysogenic colony per 10⁷ infected cells. Cells infected with one or a few particles produce 500 to 1000 virus particles each and about 30 lysogenic colonies per 10⁷ infected colonies. (3) T phage obtained from lysogenic magatherium KM cultures produces many more lysogenic cells than does the original megatherium 899 virus. (4) Cells infected with megatherium 899 T virus in peptone medium and then transferred to asparagine medium give rise to 10⁶ lysogenic colonies per 10⁷ infected cells and this transformation will occur even after the infected cells have been in peptone for 60 to 90 minutes and are beginning to produce virus particles. (5) Continued growth of KM strain with either C or T virus from megatherium 899 for several hundred generations in the steady state apparatus results in a lysogenic strain which produces several different types of virus.     

Ein Beitrag zur Biosynthese und Physiologie von Kaffein und Trigonellin beiCoffea arabica

Summary Whole young plants were allowed to fix photosynthetically C¹⁴O₂ for 12 hours. The absolute amount and the specific activity of trigonelline, caffeine and glucose in developing and adult leaves were subsequently determined during up to five weeks. There is a rapid incorporation of photosynthetically fixed carbon into trigonelline in both developing and adult leaves. The specific activity of caffeine however increases to any extent only in young developing leaves. It can be concluded that both trigonelline and caffeine are synthesized in leaves ofCoffea arabica. Other problems of the metabolism and translocation of the two substances are discussed.

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Mit 5 Textabbildungen