Propriorezeptive Kontrolle der Erregungsmuster eines Schaben-Motoneurons

Bei der Schabe Periplaneta americana L. wurde untersucht, welche Korrelationen zwischen propriorezeptiven Afferenzen und der Efferenz von Bein-Motoneuronen bestehen. Die Afferenzen wurden durch mechanische Reizung einzelner oder mehrerer Sensillen eines Borstenfeldes am Coxa-Trochanter-Gelenk ausgelöst. Die Efferenzen wurden an einem einzelnen, identifizierbaren Motoneuron des Mesothorax-Beinnerv 5 beobachtet. Die Aktivität dieses Motoneurons am unbeeinflußten Präparat wird Grundaktivität genannt. Ihre Frequenz liegt zwischen ≥ 0 und ≤ 15 Spikes/sec (Tab. 1). Nach Abtrennen der Coxa (distal vom Ableitort) oder der Abdominalkonnektive sinkt die Grundaktivität des Motoneurons ab, steigt dann im Verlauf von einigen Minuten wieder an; ihre Frequenz erreicht aber nicht so hohe Werte wie vorher (Abb. 2). Wenn die Unterschlund-Prothoraxkonnektive durchtrennt werden, nimmt die Spike-Aktivität im Beinnerv zu und bleibt über Stunden erhöht. Bei Reizung von Borsten am Coxa-Trochanter-Gelenk treten im Beinnerv 5 sensorische Spikes auf. Bei einmaligem Abbiegen einer einzelnen Borste schnellt ihre Frequenz maximal auf 600—700 Spikes/sec und klingt dann sehr rasch ab. Bei vibratorischer Reizung einzelner Borsten ist die Spikefrequenz im Bereich zwischen 100 und 500 (gelegentlich 700) Hz annähernd gleich der Reizfrequenz (Abb. 3, 4). In dem Beinnerv-Motoneuron steigt kurz (etwa 35—90 msec) nach Beginn eines Vibrationsreizes auf eine einzelne Borste die Spike-Aktivität sprungartig auf eine höhere, konstantbleibende Frequenz (je nach Präparat 24—59 Spikes/sec) an (Abb. 6). Nach Reizende fällt sie sogleich (≤ 500 msec) auf den Wert der Grundaktivität oder tiefer ab. Dasselbe gilt bei gleichzeitiger Reizung mehrerer Borsten (Tab. 2). Die ganglionäre Überleitungszeit der Borstenfaser-Erregungen auf das Beinnerv-Motoneuron beträgt im Minimum 2—3 msec. Die Grundaktivität der Bein-Motoneurone beruht auf Erregungszuflüssen von sensorischen Fasern im Beinnerv, von Interneuronen des Bauchmarks (damit wohl indirekt von Cercal-Sensillen) und wahrscheinlich von anderen, unbekannten Neuronen, die in der Peripherie oder im Zentrum liegen. Die Afferenzen von den Borstenfeldern am Coxa-Trochanter-Gelenk enthalten Angaben über die Bewegungen und wahrscheinlich auch über die jeweilige Stellung dieses Gelenks. Die Erregungen von den Coxa-Trochanter-Borstenfeldern werden im zugehörigen Thoraxganglion mit einer Verzögerungszeit von 1—2 msec monosynaptisch auf das Bein-Motoneuron übertragen.     

Characterization of a mutant of Schizosaccharomyces pombe lacking cytochrome b-566

1. A chromosomal respiration-deficient mutant of the petite-negative yeast Schizosaccharomyces pombe was isolated. Its mitochondria show respiration rates of about 7% of the wild-type respiration with NADH and succinate as substrate, and 45% with ascorbate in the presence of tetramethyl-p-phenylenediamine. Oxidation of NADH and succinate is insensitive to antimycin and cyanide and that of ascorbate is much less sensitive to cyanide than the wild type.

2. The amounts of cytochromes c₁ and aa₃ are similar in the mutant and wild type. Cytochrome b-566 could not be detected in low-temperature spectra after reduction with various substrates or dithionite. A b-558 is, however, present.

3. The b-cytochromes in the mutant are not reduced by NADH or succinate during the steady state even after addition of ubiquinone-1. QH₂-3: cytochrome c reductase activity is very low and succinate oxidation is highly stimulated by phenazine methosulphate.

4. Antimycin does not bind to either oxidized or reduced mitochondrial particles of the mutant.

5. In contrast to the b-cytochromes of the wild type, b-558 in the mutant reacts with CO.

6. Cytochromes aa₃, c and c₁ are partly reduced in aerated submitochondrial particles isolated from the mutant and the EPR signal of Cu (II), measured at 35°K, is detectable only after the addition of ferricyanide. In the mutant, a signal with a trough at g = 2.01 is found, in addition to the signal at g = 1.98 found in the wild type.

7. The ATPase activity of particles isolated from the mutant is much lower than in the wild type but is still inhibited by oligomycin.     

On the contents of the cortical granules from Xenopus laevis eggs

The extruded contents of the cortical granules in eggs of Xenopus laevis were solubilized by exposure to divalent metal ion chelators. Chelator extraction of cortical granule (CG) material from intact fertilized or artificially activated eggs was quantitated by fluorescence spectroscopy. The isolated fertilization envelope, formed upon interaction between CG material and the preexisting vitelline envelope, was also subject to extraction. An ultrastructural analysis revealed that chelator exposure resulted in the disruption of the structural integrity of the CG-derived F-component of the fertilization envelope. CG material was isolated from Xenopus ova by three procedures: (1) extrusion from artificially activated, dejellied eggs; (2) extraction of intact, fertilized eggs; and (3) extraction of isolated fertilization envelopes. Only 4–5% of the CG protein recovered by extrusion or by extraction of the intact fertilized egg could be associated with the isolated fertilization envelopes. One predominant polypeptide fraction with an identical relative mobility was demonstrated in all CG preparations upon polyacrylamide gel electrophoresis in SDS. Polymeric forms of CG protein were detected in chelator extracted preparations. The presence of an intact jelly coat during CG breakdown was a prerequisite to the transformation of the vitelline envelope to a fertilization envelope with altered physicochemical characteristics. Further, the CG-derived F-component of the fertilization envelope did not appear to play a critical role in determining the physicochemical properties of the fertilization envelope.     

Evidence for a K+-stimulated Na+ efflux at the plasmalemma of barley root cells

Summary The influence of K⁺ on the Na⁺ fluxes of barley root cells was investigated. A increased K⁺ concentration (K⁺ influx) results in a transient increase of the plasmalemma efflux of Na⁺ followed by a decrease, and in a decrease of the cytoplasmic content and the tonoplast influx of Na⁺. These results are consistent with a Na-K-pump at the plasmalemma.     

The morphology of the Limulus visual system

Summary The lateral rudimentary eye of Limulus polyphemus, the horseshoe crab, is located beneath the posterior border of the compound eye. It consists of a bipartite mass of guanophores and about 100 associated photoreceptor cells. These neurons, up to 150 in diameter, have standard attributes of arthropod retinula cells and send large, uninterrupted axons to the brain. Their cytoplasm contains conspicuous clumps of residual bodies and variable, but usually extensive, masses of glycogen and glycoprotein. Hence, these neurons are not neurosecretory in the strict sense, notwithstanding axonal transport of glycogen masses toward the brain. Efferent axons to the rudimentary eye terminate in synaptoid fashion on the axon hillock of sensory cells. Since the rudimentary eye does not transmit impulses to the brain, but is photosensitive, its function may reside in a metabolic responsiveness to long-term changes in illumination.This study constitutes publication No. 430 from the Oregon Regional Primate Research Center, supported by Grants FR00163 and EY00392 from the National Institutes of Health and by a Bop Hope Grant-in-Aid from Fight-for-Sight, Inc.The author wishes to thank Mrs. Audrey Griffin for patient and excellent technical assistance.     

Zur genetik der 6-Phosphogluconatdehydrogenase (EC:1.1.1.44) bei Säugern

Zusammenfassung Das Enzym 6-PGD zeigt bei den verschiedensten Species einen genetisch gesteuerten Polymorphismus, der sich bei elektrophoretischer Darstellung in einer Variabilität des Isoenzymmusters äußert. Die Befunde bei den bislang untersuchten Säugern unter Einschluß des Menschen lassen sich formalgenetisch nach dem Modell: 1 Genlocus mit multipler Allelie interpretieren. Zur Prüfung der Frage, ob das Säugergenom einheitlich nur ein Gen für dieses Enzym enthält oder ob bei einzelnen Species eine Duplikation dieses Gens existiert, wurdene eine Anzahl Säuger verschiedener Ordnungen untersucht. In einer ersten Mitteilung wird hier über 6 verschiedene Species der Microtinae berichtet. Die Befunde sprechen durchweg für die Existenz von jeweils nur 1 Genlocus der 6-PGD. Bei Microtus oeconomus wurden 2 Allele an diesem locus nachgewiesen, bei Microtus ochrogaster 3 verschiedene Allele. Durch Familienuntersuchungen bei diesen beiden Species werden alle möglichen Kombinationen dieser Allele nachgewiesen.

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The genetics of 6-PGD (EC: 1.1.1.44) in various mammals I. Studies on 6 species of Microtinae, Rodentia. Isoenzyme polymorphism and family studies in Microtus oeconomus and Microtus ochrogaster

Summary The enzyme 6-PGD exhibits a genetically determined polymorphism which results in a variability of the isoenzyme pattern. In mammals so far examined the findings are to be interpreted according to the model of multiple alleles at one single gene locus. In order to test whether the mammalian genome is uniformly endowed with one single locus for this enzyme or whether a duplication of this locus is present in certain species, we examined various mammals of different orders. Our results in this first communication on 6 different Microtinae species are all in agreement with the assumption of a single 6-PGD locus. In Microtus oeconomus 2 alleles could be demonstrated and in Microtus ochrogaster 3 different alleles. Family studies performed with both species revealed the occurrence of all the expected combinations of these alleles.

     

The effects of flexion and rotation on the length patterns of the ligaments of the knee

Measurements have been made of the lengths of the ligaments in human knee joint specimens. The ligaments considered were the lateral collateral, medial collateral, anterior cruciate and posterior cruciate. The ligament length patterns were determined for twelve specimens at flexions of 0, 30, 60, 90 and 120°, in neutral, internal rotation and external rotation at each angle. The collateral ligaments steadily diminished by about 20 per cent in length from 0 to 120° flexion, rotation having little effect. The anterior cruciate gradually increased 10 per cent from 0 to 120° flexion and the posterior cruciate, was 10 per cent longer at 0° flexion than at all other angles for which length was constant. The action of the cruciates was therefore somewhat reciprocal. Rotation had a significant effect on cruciate lengths, affecting the anterior more than the posterior cruciate. Computations were made of the change in length of the anterior and posterior fibres of each cruciate ligament, in relation to the central fibres. Reciprocal functions between fibres were demonstrated.     

NESTING OF THE PURPLE-THROATED CARIB HUMMINGBIRD

We present data on certain parts of the nesting biology of the Purple-throated Carib Humming- bird Eulampis jugularis on the island of Dominica, British West Indies. We watched two nests with eggs and young and a single nest under construction. Incubation was in short periods averaging about six minutes. Females at both nests with eggs continued adding material to the nest until the end of incubation. We suggest that this common practice among hummingbirds may insure that a limited amount of energy at the time of initial nest-building and egg-production is optimally apportioned between the two activities. Brooding ceased in one nest when the young were about 13 days old. Feeding rates stayed relatively constant at one to two per hour throughout the nearly complete nestling period in one nest. Average time per feeding declined, apparently as the female-young interaction became more efficient with maturation of the young. Nesting females foraged on both insects and nectar. We could not be sure what they were feeding the young. Defence of the nest varied with the position of the female and the type of intruder. The aggressive behaviour associated with defence varied according to the size and type of intruder. We concluded that for the one nest of Eulampis for which we had the most complete data, had there been three young, the female would have been unable to provide sufficient food to nourish them. However, the universal clutch size of two and nearly universal promiscuity in humming- birds is strong evidence that factors other than the ability of adults to feed more than two young are important in determining clutch size.     

Die Nachwirkung von Produkten resistenter interspezifischer Reben-Arthybriden in unbehandelten Nachzuchtgenerationen (dargestellt in Versuchen mit Hühnern)

Zusammenfassung (Zum besseren Verständnis der zitierten genealogischen Zusammenhänge wird auf Tab. 1 S. 353 (Material und Methodik) verwiesen.)Durch eine 6–8 Wochen anhaltende Verfütterung der Produkte — Weine wie (alkoholfreie) Säfte — von relativ resistenten Reben-Arthybriden, die aus Kreuzungen sensitiver Vitis vinifera-Varietäten mit ± resistenten amerikanischen Wildreben (F₁, F₂R) hervorgegangen waren, ließ sich bei Hühnern eine Prägung auslösen, die bei ihren unbehandelten F₁-Nachkommen in über 40% der Fälle zu Mißbildungen hauptsächlich der Ständer und des Gefieders führte. Diese Effekte hatten sich mehrfach reproduzieren lassen.Normal gehaltene F₁-Geschwister behandelter Eltern, miteinander verpaart, ergaben in der F₂ wiederum, einen gewissen Prozentsatz (8–11%) der gleichen Aberrationen an Ständern und Gefieder wie bei der F₁. Dabei spielte es keine Rolle, ob Normale, Anomale oder Krüppel miteinander gekreuzt worden waren.Wurden F₂-Geschwister miteinander verpaart, so reduzierte sich der Effekt in der F₃ auf 0,9–2,2% an Mißbildungen. Dem zahlenmäßigen Rückgang der Häufigkeit von Aberranten entsprach ebenso ein allgemein verminderter Grad der betreffenden Schädigung.Normale aus der F₃ brachten mit normalen Individuen ihrer Elterngeneration verpaart (F₃ × F₂) keine mißbildeten Nachkommen hervor, während bei der reziproken Kreuzung (F₂- × F₃-) aus den Eiern dieser anomalen F₂- noch 4,7% der Tiere mit mißbildeten Ständern und 21,9% mit defekten Federn schlüpften.In der F₅, hervorgegangen aus miteinander verpaarten Normalen der F₄R, traten weitere 4,6% an Beinmißbildungen und 6,9% an Feder-Anomalien auf.Dagegen fanden sich keine Anomalien mehr, wenn Standard- mit einem aberranten F₄- verpaart worden waren. In den Kontrollen traten keine Mißbildungen auf.Die einmal in der p₁ durch die Versuchstränken gesetzte Prägung erwies sich in 5 Generationen zwar sowohl nach der Zahl der in der Folge entstandenen Anomalien als auch hinsichtlich des Schweregrades ihrer Ausprägung als regressiv, ohne daß in diesem Zeitraum jedoch ein völliges Abklingen des Einflusses bei allen Tieren zu verzeichnen gewesen wäre.Es wird vermutet, daß die Effekte vorwiegend aufgrund latent vorhandener Veränderungen im weiblichen Keimplasma ausgelöst werden, die — möglicherweise durch Umweltfaktoren begünstigt — die Entwicklung der Embryonen individuell beeinflussen.Die Wirkungen im Erscheinungsbild gleichen etwa den durch Vitamin B₂-Mangel hervorgerufenen Anomalien, so daß möglicherweise auch in unserem Fall etwa eine stoffliche Blockierung im Vitaminhaushalt der Embryonen als Ursache der beobachteten Mißbildungen nicht auszuschließen ist. Die weitgehende Normalisierung der Feder-Defekte anläßlich der ersten echten Mauser, zeitlich mit der beendeten Resorption des (mütterlich geprägten) Dotters im Küken und mit der Autonomisierung des Vitaminhaushaltes im Jungtier einhergehend, deutet in diese Richtung. Eine Rehabilitierung der Beinmißbildungen ließ sich in keinem Fall feststellen.Die zweimalige Behandlung derselben Hühner und Hähne in zwei aufeinanderfolgenden Jahren scheint sich im Effekt nicht additativ auszuwirken. Vielmehr gestattet offenbar die zwischenzeitlich normale Haltung, durch den relativ hohen physiologischen Umsatz besonders bei den weiblichen Tieren (Eiproduktion, Mauser) begünstigt, eine weitgehende Normalisierung des Keimplasmas.

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After-effects in untreated progenies from chickens treated with the products from resistant interspecific grape-vine hybrids

Summary Feeding hens and cocks for 6–8 weeks with the products — wines and juices — from ± resistant interspecific grapevine varieties (F₁, F₂R), i.e. from crosses between sensitive types of Vitis vinifera and ± resistant American wild types, led to physiological changes of the treated animals. These changes became evident by more than 40% of malformations, especially of legs and plumage, among the individuals of their untreated F₁ progeny. These effects proved to be reproducable.Among the F₂-individuals from crosses between untreated F₁ brothers and sisters 8–11 % of the chickens again carried anomalies of the same kind as found in F₁. No relation could be observed between the number of F₂ malformations and the types of F₁-parents: both of them had been either normal, slightly anomalous or crippled.In the following generation (F₃) from F₂ brothers and sisters, again selected for equal types (normals, slightly anomalous or crippled ones) and crossed among themselves or to standard-, the number of malformations became reduced to 0,9–2,2%. From this generation on severely crippled types were almost lacking and only slightly anomalous ones showed up, characterized by crippled toes and/or plumage defects.The following crosses between F₃ and F₂ did not give rise to anomalies among the progeny of the next generation, as was the case when normal (F₂ 1966) were crossed to standard-, while from the reciprocal combination (F₂ × F₃) again 4,7% of the F₄R chickens hatched with moderately or slightly deformed feet besides 21,9% of individuals with defective feathers.Among the chickens of the following generation (F₅) from crosses between normal F₄R brothers and sisters there resulted another 4,6% and 6,9% of individuals with crippled toes (slight type) and defective wing feathers, respectively. On the other hand only normal chickens hatched from the eggs of standard- crossed to an anomalous from F₄R. The controls were free from anomalies.Thus the effects of experimental beverages fed once to the P₁, had caused in the following generations (F₁– F₅) certain numbers of individuals with malformations, developing in declining numbers and with gradually reduced severity. The 5 generations observed did not suffice for a complete rehabilitation.It is suggested that the effects were caused by latent though increasingly reduced changes within the female germ plasm, coming about by some unknown substance(s) immanent to the relatively resistant grape-vine cultivars used. Individually acting upon the embryological development, environmental influences are supposed to add to the effects.Since the types of malformations of legs and plumage can easily be compared to those observed in cases of vitamin B₂-deficiency in the diet of chicks, the substance(s) applied with the beverages possibly reduce(s) the embryonic exploitation rate of vitamins, too. Another hint in that direction could be the more or less complete normalization of the plumage defects at the time of the first moulting, i.e. when the maternal egg yolk probably has become fully absorbed by the growing chicken and the exploitation of vitamins has turned autonomous. Rehabilitation of crippled legs never has been found.Treating the same animals in two successive years, with some months of water-feeding in between, does not seem to give an additive effect as to the number of anomalies developing in both F₁-generations. During the interval of normal feeding the relatively high turnover, especially in hens, by the building up of eggs and by moulting, apparently causes a general normalization within the germ plasm before the second treatment.Nothing is known about the type of substance (s) fed with the products from resistant grape-vines, nor do we know anything about the pattern of their action and reaction, leading to changes within the germ plasm and finally reducing the utilization of vitamins in chick embryos from individuals once treated in some former generation.