Nonfunctional Tricarboxylic Acid Cycle and the Mechanism of Glutamate Biosynthesis in Acetobacter suboxydans

Acetobacter suboxydans does not contain an active tricarboxylic acid cycle, yet two pathways have been suggested for glutamate synthesis from acetate catalyzed by cell extracts: a partial tricarboxylic acid cycle following an initial condensation of oxalacetate and acetyl coenzyme A. and the citramalate-mesaconate pathway following an initial condensation of pyruvate and acetyl coenzyme A. To determine which pathway functions in growing cells, acetate-1-(14)C was added to a culture growing in minimal medium. After growth had ceased, cells were recovered and fractionated. Radioactive glutamate was isolated from the cellular protein fraction, and the position of the radioactive label was determined. Decarboxylation of the C5 carbon removed 100% of the radioactivity found in the purified glutamate fraction. These experiments establish that growing cells synthesize glutamate via a partial tricarboxylic acid cycle. Aspartate isolated from these hydrolysates was not radioactive, thus providing further evidence for the lack of a complete tricarboxylic acid cycle. When cell extracts were analyzed, activity of all tricarboxylic acid cycle enzymes, except succinate dehydrogenase, was demonstrated.     

Electron microscopic studies on the foraminiferAllogromia laticollaris arnold mitosis in agamonts

Summary During mitosis in multinucleated agamonts ofAllogromia laticollaris the nucleolar substance cannot be demonstrated in the nuclei, but only in the cytoplasm as large opaque bodies, some of which are surrounded by two membranes. Only a few smaller bodies are still present within vacuoles of young agamonts formed subsequent to the dividing state. Since the nuclear envelope persists during karyokinesis, the division spindle is localized intranuclearly. The component continuous microtubules, which prefer the nuclear periphery, are mostly visible as bundles, whereas the microtubules running to the chromosomes appear single and less numerous. Centrosomes can be noticed not only at elongated but also at ovoid or irregularly shaped nuclei. These centrosomes represent round or elliptic bodies surrounded by a membrane and consist of granular and fibrillar material. They occur within the perinuclear space and are restricted to the state of karyokinesis.     

Temperature dependence of the aminoacylation of tRNA by Bacillus stearothermophilus aminoacyl-tRNA synthetases

Valine specific transfer RNA (tRNA^Val) was isolated from Bacillus stearothermophilus and Escherichia coli by chromatography on benzoylated DEAE–cellulose (BD–cellulose). Likewise isoleucine specific transfer RNA (tRNA^Ile) was isolated from B. stearothermophilus and from Mycoplasma sp. Kid. The thermal denaturation profiles (melting curves) of the two tRNA^Val species in the presence of Mg^{+ +} were nearly identical. However, the T_m for the Kid tRNA^Ile was about 10°C lower than that for the B. stearothermophilus tRNA^Ile. A nuclease and tRNA-free aminoacyl-tRNA synthetase (AA-tRNA synthetase) preparation from B. stearothermophilus was able to function efficiently at temperatures up to 80°C in the aminoacylation of all four tRNA species. Determination of the amino acid-acceptor activity of each tRNA species as a function of temperature of the aminoacylation reaction showed in each case a strong correlation between the loss of acceptor activity and the thermal denaturation profile of the tRNA. Evidence is presented that the loss in acceptor activity is most likely due to a change in structure of the tRNA as opposed to denaturation of the enzyme. These results further support the idea that correct secondary and/or tertiary structure must be maintained for tRNA to be active as a substrate for the AA-tRNA synthetase.     

Aufnahme von Trypanblau und Ferritin in die Blasenzellen des Bindegewebes von Helix pomatia und Cepaea nemoralis (Stylommatophora,Pulmonata)

Zusammenfassung Untersuchungen des Bindegewebes der stylommatophoren Pulmonaten Helix pomatia and Cepaea nemoralis zeigen, daß die Blasenzellen des Bindegewebes befähigt sind, Substanzen aus der Hämolymphe aufzunehmen. Licht- und elektronenmikroskopische Untersuchungen ausgewählter Bindegewebsbereiche, die in bestimmten Zeitintervallen nach der Injektion von Trypanblau oder Ferritin in die Körperhöhle präpariert wurden (Stufenuntersuchungen), ergaben, daß — mit Ausnahme einiger Blutzellen — ausschließlich die Blasenzellen die injizierten Substanzen aufgenommen hatten. Weder andere Bindegewebszellen noch die Zellen von Organen (u.a. Gonaden, Schlundringganglien), die von Bindegewebe umgeben werden, enthielten diese Substanzen oder hatten sie akkumuliert. Die elektronenmikroskopischen Aufnahmen zeigen, daß die Aufnahme von Ferritin in die Blasenzellen wahrscheinlich durch Pinocytose erfolgt.

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Uptake of trypan blue and ferritin into the globular cells of the connective tissue of Helix pomatia and Cepaea nemoralis (Stylommatophora, Pulmonata)

Summary Investigations of the connective tissue of the stylommatophoran pulmonates Helix pomatia and Cepaea nemoralis have demonstrated, that so-called globular cells have the capability for the uptake of substances out of the hemolymph. Light- and electron-microscopic investigations of pieces of connective tissues fixed at different intervals after the injection of Trypane Blue or Ferritin into the cavity of the body give striking evidence for the uptake of these substances exclusively into the globular cells (with the exception of some blood cells). Neither other connective tissue cells nor cells of the organs (e.g. gonads, central nervous ganglions) surrounded by connective tissue incorporate or accumulate the injected substances. The uptake of Ferritin into the cytoplasm of the globular cells, normally filled with a high amount of glycogen, takes place by pinocytosis.

     

Fluoreszenzmikroskopische Untersuchungen mit Pseudoisocyaninchlorid am Schlundring einiger stylommatophorer Pulmonaten

Zusammenfassung Durch Anwendung von Pseudoisocyaninchlorid lassen sich im zentralen Nervensystem von stylommatophoren Pulmonaten in allen Schlundringganglien Neurosekretzellen fluoreszenzmikroskopisch nachweisen. In den Cerebralganglien bilden sie mit ihren ausleitenden Axonen das bereits bei einigen Gastropoden bekannte geschlossene neurosekretorische System. In den übrigen Ganglien liegen die neurosekretorischen Zellen einzeln oder in Gruppen zusammen und bilden kein System. Es konnte nachgewiesen werden, daß in Visceral-Parietaganglien der untersuchten Arten die meisten sekretorischen Neurone vorkommen. Die Zahl der neurosekretorischen Zellen in den einzelnen Ganglien ist zumindest für die hier untersuchten Arten wahrscheinlich artspezifisch, ihre topographische Lage in den Ganglien aber bei allen Arten identifizierbar ähnlich. Bei allen untersuchten Pulmonaten fanden sich nur im Procerebrum keine neurosekretorischen Zellen. Die vielfältigen, über die Darstellung der Neurosekretzellen hinaus feststellbaren fluoreszenzmikroskopischen Erscheinungen in den Nerven- und Gliazellen, in der Fasermasse der Ganglien, den Kommissuren und Nerven und im Bindegewebe um die Ganglien, wurden mit Hilfe anderer lichtmikroskopischer Färbungen vergleichend untersucht; die Ergebnisse werden diskutiert.

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Fluorescence-microscopic investigations with pseudoisocyanin on the central nervous system of some stylommatophoran pulmonates

Summary Using fluorescence microscopy with pseudoisocyaninchloride one can demonstrate the well known cells and axons of the neurosecretory system in the cerebral ganglia of some gastropod pulmonates. In the other ganglia of the central nervous system-except procerebrum-single secretory neurones or groups of neurosecretory cells occur. These secretory neurones do not build up a neurosecretory system. The majority of these cells is concentrated in the visceral-parietal ganglia. The specific elements are topographically identifiable relative to each other in the ganglia of each species of pulmonates investigated. Other fluorescence-microscopic investigations of the neurones, glial cells and the neuropil of the ganglia, commissures and nerves and in the connective tissue surrounding the ganglia are described in comparison with other light microscopical findings obtained by staining methods; the results are discussed.

     

Studie zur intrachromosomalen Bruchverteilung bei menschlichen Leukocyten

Zusammenfassung Die intrachromosomale Verteilung von spontanen und durch unterschiedliche mutagene Agentien induzierte Chromosomenaberrationen in vitro wird statistisch analysiert. Neben einer gesicherten, nicht zufällig ungleichmäßigen, intrachromosomalen Verteilung von Chromatid-und Isochromatidbrüchen unter Einwirkung des jeweiligen mutagenen Agens wird eine nicht zufällig unterschiedliche Verteilung von spontanen und unterschiedlich induzierten Bruchfrequenzen in den vor allem von Defizit und Überschuß betroffenen gleichnamigen Segmenten festgestellt. Es muß offenbleiben, ob die unterschiedlichen Bruchverteilungsmuster auf verschiedene Bruchentstehungsmechanismen zurückzuführen sind.

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Summary The intrachromosomal distribution of spontaneous and by different mutagenous agents induced chromosomal aberrations in vitro is statistically analysed. The intrachromosomal distribution of chromatid-and isochromatidbreaks under the influence of the respective mutagenous agents as well as the distribution of spontaneous and diversly induced break frequencies mainly in those correspondent segments, which are affected by deficiency and excess, is significantly different.

     

Polytene chromosomes and nucleic acid metabolism during macronuclear development in Euplotes

Polytene chromosomes in two species of Euplotes, E. woodruffi and E. eurystomus, have been described during the macronuclear development following conjugation. In these two species, the giant chromosomes appear briefly in the macronuclear anlagen and disappear completely later. DNA synthesis begins concomitantly with the appearance of the giant chromosomes and reaches a peak at the maximum stage of polyteny. Shortly thereafter DNA begins to break down and the breakdown products leave the macronuclear anlagen, reducing the DNA content in the anlagen to the amount present at the earlier stages of the polytene development of the chromosomes. A later phase of DNA synthesis occurs in the anlagen with the appearance of replication bands comparable to the bands which double the DNA in the somatic macronucleus. These replication bands initiate several rounds of DNA synthesis which finally lead to the development of the vegetative macronucleus. RNA synthesis occurs uniformly on the giant chromosomes and no special RNA producing puffs or other regions are noticed on them.Research supported by American Cancer Society grant E 434 to David M. Prescott and by the Deutsche Forschungsgemeinschaft to Dieter Ammermann.     

Book reviews

Ohne Zusammenfassung

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Book reviews

     

Synthese und Abbau der Nucleinsäuren während der Entwicklung des Makronukleus von Stylonychia mytilus (Protozoa,Ciliata)

Zusammenfassung Es wurde die Nukleinsäuresynthese während der Entwicklung der Makronukleusanlage vom diploiden Kern zum polyploiden Makronukleus untersucht. Die Nucleinsäuren wurden mit ³H-Thymidin und ³H-Uridin markiert. Dabei ergab sich:1.Während einer ersten Polyploidisierungsphase baut die Anlage ³H-Thymidin in ihre DNS ein. Am Ende dieser Phase ist die nunmehr polyploide Anlage stark markiert. Einige Stunden später jedoch, während der DNS-armen Phase, ist der größte Teil der Markierung verschwunden (Autoradiographien). Daraus wird gefolgert, daß die meiste DNS aus der Anlage verschwindet. Scintillationsspektrometrische Messungen zeigten, daß die DNS-Menge der Exkonjuganten um mehr als 90% reduziert wird. Diese Ergebnisse stimmen mit spektrophotometrischen Befunden (Ammermann, 1965) überein. 2. Auf das DNS-arme Stadium folgt eine zweite Polyploidisierungsphase, in welcher der endgültige polyploide Makronukleus heranwächst. Dabei wird neu aufgenommenes Thymidin eingebaut. 3. Weder in der Anlage mit Riesenchromosomen (am Ende der ersten Polyploidisierungsphase) noch in der DNS-armen Anlage noch in den Fragmenten des alten Makronukleus konnte eine RNS-Synthese nachgewiesen werden. Sie setzt erst mit dem Beginn der zweiten Polyploidisierungsphase ein (Autoradiographien).

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Synthesis and decomposition of nucleic acids during macronuclear development in Stylonychia mytilus

The synthesis of nucleic acids during the development of the macronuclear anlage from a diploid nucleus to the polyploid macronucleus has been studied. The nucleic acids were labeled with ³H-thymidine and ³H-uridine. The following results have been obtained: 1. In the first polyploidization stage the anlage incorporates ³H-thymidine into its DNA. At the end of this stage the anlage is polyploid and strongly labeled. Some hours later, during the DNA-poor stage, most of the labeling has disappeared (autoradiographs). This indicates that most of the anlagen-DNA is decomposed. Scintillation counter measurements showed that only about 9 per cent of the DNA stays within the exconjugants. These data agree with earlier spectrophotometric results (Ammermann, 1965). 2. The DNA-poor stage is followed by a second polyploidization stage in which the definitive polyploid macronucleus develops. Completely new thymidine is incorporated during this stage. 3. RNA synthesis does not occur neither in the giant chromosome anlage (end of the first polyploidization stage), nor in the DNA-poor stage, nor in the fragments of the old macronucleus. RNA synthesis starts at the beginning of the second polyploidization stage (autoradiographs).

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.