Refine
Has Fulltext
- yes (24)
Is part of the Bibliography
- yes (24)
Year of publication
- 1972 (24) (remove)
Document Type
- Journal article (22)
- Book (1)
- Review (1)
Language
- English (15)
- German (8)
- Multiple languages (1)
Keywords
- Amphibian oocytes (2)
- Biochemie (2)
- Biologie (2)
- Electron microscopy (2)
- Organische Chemie (2)
- Physiologische Chemie (2)
- Actinomycin D (1)
- Chemical nature (1)
- Cross-bridges (1)
- Festkörperphysik (1)
No abstract available
Zum hurritischen Lexikon I
(1972)
No abstract available
The 130 chemical shifts were determined of the carbons in 12 cycloheptanes, 21 cycloheptanols, and 8 cycloheptanones. In some cyc1oheptanols and cyc1oheptanones, the assignments have been obtained unambiguously by the synthesis of deuterated derivatives and the use of paramagnetic-shift reagents. Substituent effects for the different types of groups have been calculated. The most informative data about the cyc10heptane conformations were provided by the relatively well understood I' effects. The results are generally in,good agreement with predictions based on the twist-chair form, which has been predicted by Hendrickson to be the most stable conformation. Pairs of cis-trans isomers are found to have rather characteristic differences in their 130 spectra. This fact was used to assign the resonances found for cis-trans mixtures of methyl-substituted cyc1oheptanols to specific isomers.
No abstract available
In einem Lemexperiment beurteilten 10 Vpn als Empfiinger die Blicksignale einer Person, die als Sender fungierte. Die Diskriminierungsleistung der Empfanger verbesserte sich als Folge von feedback-Informationen. Die verbesserte Leistung war unabhangig von der Sehscharfe und korrelierte nicht mit Extraversion und Neurotizismus. Fur Zielpunkte des Blicks, die weiter vom Gesicht entfemt waren, war die Leistung am Anfang schlechter und die Leistungsverbesserung ausgepragter. Die Ergebnisse werden im Hinblick auf eine gro6ere Genauigkeit bei der Beobachtung der Variablen 'Blick-Verhalten' diskutiert, was fUr Untersuchungen liber non-verbales Verhalten wichtig ist. FUr Beobachter werden Trainings-Programme vorgeschlagen, bei denen RUckmeldungen liber die tatsachliche Blickrichtung des Senders vermittelt werden konnen. Resume Au cours d'une experience sur l'apprentissage, 10 sujets se comportant comme des recepteurs ont juge les signaux du regard d'un envoyeur. En fournissant de la retroaction quant a la vraie direction du regard on a obtenu un apprentissage dans le sens d'une amelioration de la performance discriminatoire: l'amelioration etait independante de l'acuite visuelle des recepteurs et n'6tait pas correlative a l'extraversion ou au caractere nevrose des sujets. Au debut la performance etait plus mediocre et le progres dans l'apprentissage meilleur dans le cas des points de fixation qui etaient les plus eloignes du visage. On discute des resultats en vue d'ameliorer la precision des observateurs sur la variable 'comportement du regard' important dans les etudes sur la communication nonverbale. On propose un entralnement prealable des observateurs, entrainement qui permet une retroaction explicite quant a la vraie direction du regard.
No abstract available
Thin section electron microscopy of Actinomycin D treated Tetrahymena cells and amphibian oocytes (Xenopus laevis, Triturus aZpestris) reveal no reduction in the central granules in the nuclear pore complexes. Possible reasons for the diversity between these results and earlier observations using negatively stained isolated nuclear envelopes from the same objects are discussed. The results clearly show that the presence of central granules within the nuclear pores does neither depend on nuclear RNA synthesis nor does indicate nucleocytoplasmic RNA transport. This conclusion leads to a reconsideration of the nature of the central granule. The functioning of the central granule of the nuclear pore complexes is further discussed in connection with recent studies on the ultrastructure of various types of cisternal pores.
In order to investigate the chemical composition of the nuclear pore complexes isolated nuclei from mature Xenopus laevis oocytes were manually fractioned into nucleo· plasmic aggregates and the nuclear envelopes. The whole isolation procedure takes no more than 60- 90 sec, and the pore complexes of the isolated envelopes are well preserved as demonstrated by electron microscopy. Minor nucleoplasmic and cytoplasmic contaminations associated with the isolated nuclear envelopes were determined with electron microscopic morphometry and were found to be quantitatively negligible as far as their mass and nucleic acid content is concerned. The RNA content of the fractions was determined by direct phosphorus analysis after differential alkaline hydrolysis. Approximately 9% of the total nuclear RNA of the mature Xenopus egg was found to be attached to the nuclear envelope. The nonmembranous elements of one pore complex contain 0.41 X 10- 16 g RNA. This value agrees well with the content estimated from morphometric data. The RNA package density in the pore complexes (270 X 10- 15 g/fJ-3) is compared with the nucleolar, nucleoplasmic and cytoplasmic RNA concentration and is discussed in context with the importance of the pore complexes for the nucleo-cytoplasmic transport of RNA-containing macromolecules. Additionally, the results of the chemical analyses as well as of the 3H-actinomycin D autoradiography and of the nucleoprotein staining method of Bernhard (1969) speak against the occurence of considerable amounts of DNA in the nuclear pore complex structures.
Electron opaque cross-bridge structures span the inter- and intracisternal spaces and provide membrane-to-membrane connections between adjacent cisternae of dictyosomes of pollen tubes of Clivia and Lilium. Additionally, the classic intercisternal rods, characteristic of intercisternal regions near the maturing face of dictyosomes, are connected with the adjacent membranes through similar cross-bridge elements. We suggest that these structural links are responsible for maintaining the flattened appearance of the central parts of Golgi apparatus cisternae as well as for the coherence of cisternae within the stack. Observations on other plant (e.g. microsporocytes of Canna) and animal cells (e.g. rodent liver and hepatoma cells, newt spermatocytes) show that such an array of membrane cross-links is a universal feature of Golgi apparatus architecture. The cross-bridges appear as part of the complex "zone of exclusion" which surrounds dictyosomes, entire Golgi apparatus and Golgi apparatus equivalents in a variety of cell types.
Structural details of the dictyosomal pores in several plant cell types are described from tangential and cross sections of Golgi cisternae. Frequency distributions of the sizes of such Golgi pores are given and compared with the corresponding values of nuclear pores in the same cells. Golgi pore inner diameters are less homogeneously distributed and can be as small as 100 A or less. They are not simply cisterna I holes, but are often associated with centrally located electron dense granules or rods and with inner pore filaments. This organization, which is very common in dictyosomal pores in plant and animal cells, has some similarities with the structural architecture of nuclear envelope and annulate lamellar pore complexes. The particulate material associated with the dictyosomal pores shows spatial and structural relationship to cytoplasmic ribosomes. Possible modes of Golgi pore formation and some consequences of these observations for interpretation of nuclear pore structures are discussed.
New resonant-mode infrared absorption lines have been observed in NaCl with high concentrations of fluorine impurities. The quadratic concentration dependence of the strength of these lines indicates that they are due to pairs of fluorine impurities. At the resonant frequencies, the motion of some host ions appears to be as important as the motion of the impurities themselves.
The occurrence of stacked annulate tamellae is documented for a plant cell system, namely for pollen mother cells and developing pollen grains of Canna generalis. Their structural subarchiteeture and relationship to endoplasmie reticulum (ER) and nuclear envelope cisternae is described in detail. The results demonstrate structural homology between plant and animal annulate lamellae and are compatible with, though do not prove, the view that annulate lamcllar cisternae may originate as a degenerative form of endoplasmic retieulum.