Migration and division of cleavage nuclei in the gall midge,Wachtliella persicariae

Summary In the eggs ofWachtliella persicariae the cleavage nuclei move relative to the surrounding ooplasm. This active migration is caused by an organelle whose ultrastructure was studied throughout the mitotic cycle. It consists of a greatly enlarged polar cytaster derived from the mitotic apparatus, linked to the nucleus by 100 Å filaments. The microtubules of the cytaster were found only during periods of active nuclear migration, i.e., from the onset of anaphase to the early prophase of the next mitotic cycle. They are always solitary and follow the course of the astral rays, which are known to temporarily adhere to peripheral structures of the egg cell and to exert tractive forces. In contrast to the cytaster microtubules, the microtubules in the spindle are bundled and persist from early metaphase through late telophase.During ontogenesis the first migration cytaster is built up between 3 and 12 min after oviposition near the anterior egg pole, in the vicinity of the sperm nucleus. In non-inseminated eggs time lapse films show a migration cytaster to develop autonomously in a region free from nuclei, but it does not follow the normal path of the male pronucleus. In several cases the female pronucleus, which remains without a cytaster of its own, was observed to move to the cytaster generated in the absence of the male pronucleus. Whether or not it is adhering to a nucleus, the cytaster divides into two at the correct time, i.e, corresponding to the first cleavage division in fertilized eggs. In some non-inseminated eggs this type of pseudocleavage has been observed to occur repeatedly, giving rise to an increasing number of anucleate cytasters.     

Effects of moderate short-term potassium depletion in normal humans the role of prostaglandins

The role of prostaglandins (PG) in the effects of potassium (K⁺)depletion was studied in six normal women. A mean K⁺-deficit of 220 mEq was induced with and without concomitant treatment with indomethacin (150 mg/day). Mean serum K⁺ concentration decreased from 4.2 ± (S.E.) 0.1 to 3.2 ± 0.1 mEq/L without indomethacin and from 4.1 ± 0.1 to 3.2 ± 0.1 mEq/L with indomethacin. “Supine” and “upright” plasma renin activity (PRA) and plasma norepinephrine concentration (NE) were unaltered by K⁺ -depletion alone but decreased with indomethacin. Plasma aldosterone (PA) was suppressed during K⁺-depletion (control: 7.2 ± 2.6 ng/dl supine, 19.3 ± 8.1 ng/dl upright; K⁺-depletion: 2.6 ± 0.3 ng/dl supine, 5.5 ± 1.3 ng/dl upright) and was paralleled by a decrease in urinary aldosterone. K⁺-depletion decreased urinary PGE₂ from 667 ± 133 to 343 ± 60 ng/day (P < 0.025) without a change in PGF₂. The dose of exogenous angiotensin II (A II) which increased diastolic blood pressure by 20 mm Hg (pressor dose) was 7.1 ± 1.4 ng/kg/min during control and increased to 11.0 ± 0.7 ng/kg/min during K⁺-depletion (P < 0.05). Indomethacin increased the sensitivity to A II both during control (pressor dose: 4.9 ± 0.6 ng/kg/min) and K⁺- depletion (pressor dose: 6.0 ± 1.0 ng/kg/min). These results indicate that in healthy subjects, moderate short-term K⁺-depletion does not affect PRA or NE but decreases production of aldosterone and PGE₂ by the kidney. The changes in vascular sensitivity to exogenous A II during K⁺-depletion and indomethacin and the decreases in plasma NE and PRA during indomethacin may be explained by changes in vascular vasodilator PG.     

Gel gradient electrophoresis, isoelectric focusing and two-dimensional techniques in horizontal, ultrathin polyacrylamide layers

An ultrathin layer, horizontal polyacrylamide gel system for electrophoresis, isoelectric focusing and two-dimensional techniques is described. Gel slabs 240 micron thin for unidimensional, or 360 micron thin for two-dimensional runs are cast on cellophane foils as support. The sample is loaded in pockets pre-cast in the gel (2--3 microliter size) or in trenches for two-dimensional experiments. The second dimension is routinely performed in concave exponential gel gradients, spanning an acrylamide concentration from 4% to 22.5%. The sensitivity with the common Coomassie Blue stain is very high, well below 0.1 microgram protein/band. Zymogram detections can be developed within a few minutes, thus retaining the band sharpness of the focused zones or of the bands separated in pore gradient electrophoresis. Sample handling, staining and destaining and gel drying and storage are greatly simplified and performed in a fraction of the time needed for conventional, thick gels in the 1-2 mm thickness range.     

Phylogenie und verbreitungsgeschichte der eomeropidae (insecta: mecoptera) ein beispiel fur die anwendung der phylogenetischen systematik in der palaontologie

The colonisation history of the Eomeropidae (syn.: Notiothaumidae) is discussed based on the phylogenetic relationships among the five known genera of this family and their geographic distribution. Between the Recent South-AmericanNotiothauma andEomerope from the Tertiary of North America and eastern Asia exists a sister-group relationship. Together with the more plesiomorphous generaBlattomerope andPronotiothauma from the Triassic of Kirghizia they form a monophyletic group of higher rank, but it is not clear whetherBlattomerope, Pronotiothauma orBlattomerope + Pronotiothauma are the sister-group ofEomerope + Notiothauma. The most primitive genus of the Eomeropidae isThaumatomerope, also from the Triassic of Kirghizia. According to these relationships the Eomeropidae are supposed to have evolved in the northern hemisphere. From hereNotiothauma as one of the most highly evolved genera or its direct ancestor migrated to the south, probably in Mesozoic times. It seems less probable that the Eomeropidae were a cosmopolitan group and that incidentally the plesiomorphous sister-groups of bothNotiothauma andEomerope + Notiothauma as well as the most plesiomorphous genus of this family, are known from the northern hemisphere only. Penny’s assumption thatNotiothauma must have had its origin among Mecoptera with few costal cross-veins is rejected. The Eomeropidae and the Meropeidae arose directly from ancestors with numerous costal cross-veins. In spite of this the two families evidently do not form a monophyletic group (e.g. “Protomecoptera”) as the similarities between them are due to symplesiomorphies, as previous authors have pointed out. A synapomorphous character shared by Eomeropidae and Meropeidae is not known. The method of deducing the colonisation history of a taxon from the geographic distribution of its closest allies is briefly discussed.     

Phase-plane analyses of the Michaelis-Menten reaction equations

The irreversible Michaelis-Menten scheme may be reduced to a pair of autonomous first-order differential equations. The phase-plane behaviour of these is investigated.     

The structural organization of the intracerebral giant fiber system of cephalopods

Summary The course of the two intracerebral first-order giant axons of cephalopods at their chiasma, and the fine structure of the contact area between the crossing axons are examined by light and electron microscopy in species of three taxonomic groups (Loligo vulgaris, Sepia officinalis, Illex coindeti). In addition to the well known chiasma of the adult Loligo in which the two axons are fused (Young, 1939), three other chiasma types are described. In each of them there are synapse-like contact areas that suggest a passage of impulses from one axon to the other. (1) The larval Loligo shows a chiasma with crossed axons and contralaterally descending branches; at the apposed membranes in the chiasma there are clusters of electron-transparent vesicles. (2) In the adult Sepia each crossing axon has an ipsi- and a contralaterally descending branch; the apposed membranes of the decussating axons show symmetrical synapse-like areas characterized by a monolayer of electron-transparent vesicles on each side and a regular cleft of 100 Å width. (3) In the adult Illex each axon has only an ipsilaterally descending branch and there are at the point of decussation two crossed collaterals; large masses of electron-transparent vesicles are found on each side of the apposed membranes of the collaterals and the membranes show an increased electron density. It is argued that the four chiasma types serve the same function, i.e., the establishment of functional bilaterality of the giant fiber system. By structural analogy with other, both structurally and functionally known synapses it is suggested that in the decussation of Sepia impulses pass in both ways from one axon to the other. Data of the embryological development of the giant fiber system are summarized.Work supported by the Deutsche Forschungsgemeinschaft (Ma. 259) and by NATO Research Grant No. 273. The collaboration of Dipl. Zool. Elisabeth Braendle from the Zoological Institute of the University Zürich in the examination of the Illex chiasma is gratefully acknowledged.     

Studies of multipolar mitoses in euploid tissue cultures

Cultures of kidney epithelium and fibroblasts of 39 specimens of Microtus agrestis were investigated. In all 77 cultures multipolar mitoses were found. They were studied in living state and after pulse labelling with ³H-thymidine. The ploidy of the multipolar mitoses and of their daughter nuclei was determined by measuring the relative Feulgen-DNA content and by counting the predominantly constitutive heterochromatic sex chromosomes. Constitutive heterochromatin was demonstrated by late replication, retarded separation of the chromatids in anaphase, heteropycnosis and by the Giemsa technique of Arrighi and Hsu (1971). The latter stained also the spindle apparatus of mitoses.—In living cells, transformation of multipolar mitoses into bipolar mitoses was observed. The chromosomes of multipolar mitoses are separated into complete genomes; the daughter nuclei can be haploid, diploid, triploid or tetraploid. The chromosomes of haploid and triploid metaphases were studied with the Giemsa banding technique. The banding pattern shows an exact monosomy and trisomy, respectively, for each chromosome. Haploid nuclei are likely to be viable only in multinucleate cells, whereas triploid cells behave like diploid cells during the S period and the mitosis.Dedicated to Prof. Dr. K. Goerttler on the occasion of his 75th birthday.Supported by the Bundesministerium für Bildung und Wissenschaft of the Federal Republic of Germany.     

Incorporation of Labeled Precursors into the RNA and Proteins of Lactic Dehydrogenase Virus

Lactic dehydrogenase virus was grown in primary mouse embryo cells and labeled with (3)H-uridine and (3)H-amino acids. Concentrated and purified virus was banded by isopycnic centrifugation in sucrose gradients, and infectivity and radioactivity were found to correspond at a density of 1.17 g/cm(3). The extracted viral RNA was resolved by electrophoresis in polyacrylamide-agarose mixed gels, and the mol wt was estimated to be 6.0 x 10(6).     

Hemmung glykogenbildender Enzyme durch 2,4-Dichlorphenoxyazetat (2,4-D)

Zusammenfassung An Schnitten vom Skelettmuskel der Ratte wird histochemisch die Hemmung glykogenbildender Enzyme durch 2,4-D in vitro nachgewiesen. Phosphorylase (Glucose-1-phosphatAmylose-Transglucosidase) und Transglucosidase (Amylo-1,6-Glucosidase, Branching Enzyme) werden durch Konzentrationen von 1 mM//l 2,4-D in der Inkubationslösung eben sichtbar gehemmt; bei 15 mM/l ist die Hemmung komplett und irreversibel. Weniger konstant ist die Wirkung von 2,4-D auf die UDPG-Glykogen-Synthetase. Die Hemmungskonzentrationen liegen hier etwa zwischen 8 und 30 mM/l 2,4-D. Es wird gezeigt, daß histochemisch die Hemmung der Phosphorylase und Transglucosidase weder kompetitiv zu G-1-p erfolgt, noch durch A-5-MP, Insulin-, Pyridoxal-5-Phosphatoder Cystein-Zusatz aufgehoben werden kann. Der mutmaßliche Mechanismus der Wirkung von 2,4-D auf die glykogenbildenden Enzyme und auf den Stoffwechsel mit dem Übergang zum Pentose-Phosphat-Zyclus bei der Pflanze und dem Anstieg der Glykolyse-Metabolite beim Warmblüter werden erörtert.

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Summary Inhibition of glycogen-forming enzymes by 2,4-D in vitro is histochemically established in sections of rat skeletal muscle. Phosphorylase (Glucose-1-phosphate amylosetransglucosidase) and transglucosidase (branching enzyme) are evenly inhibited at concentrations of 1 mM/l 2,4-D in the respective incubation media. Inhibition is complete and irreversible with 15 mM/l. Less constant results are obtained with UDPG-glycogen-synthetase. Respective concentrations vary between 8 and some 30 or more mM/l 2,4-D. Inhibition of phosphorylase and transglucosidase is histochemically shown neither being competitive to glucose-1-phosphate nor being antagonized by A-5-MP, insulin, pyridoxal-5-phosphate or cystein. The presumptive mode of action of 2,4-D on these enzymes and on metabolism, viz. on the metabolic shift to the pentose-phosphate-cycle in plants and on the increase of glycolytic metabolites in animals, are discussed.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.