Cytogenetic study of F1 hybrids betweenCrepis dinarica andCrepis froelichiana (Asteraceae)

Crepis dinarica andC. froelichiana are two closely related species of theC. praemorsa complex. Even though they exhibit the same chromosome number (2n = 8) and similar idiogram shape, they differ widely in quantity and distribution of heterochromatin bands. The hybrids between these two species comprise three morphological types. Parental genomes were distinguished in hybrids by Giemsa differential staining (C-banding). Although meiosis presents only a few abnormalities (about 2.4%), the percentage of aborted pollen grains is very high (90%).     

Collagen type conservation during metamorphic repatterning of the dermal fibers in salamanders

The orientation of the fibers in the dermis of the tiger salamander, Ambystoma tigrinum, undergoes a dramatic repatterning at metamorphosis. The pre-metamorphic, larval dermis is a tight layer composed of crossed fibers that wind helically around the trunk. This condition is retained by neotenic adults which do not undergo metamorphosis. In contrast, the neotenic adults which do not undergo metamorphosis. In contrast, the metamorphosed adult dermis consists of a superficial, loose network of fibers invested with large multicellular glands--the stratum spongiosum--and a deeper tight layer of fibers--the stratum densum. However, unlike the crossed fibers of the pre-metamorphic dermis, there is no preferred orientation to the fibers in either layer of the post-metamorphic dermis. In order to evaluate whether these two distinctly different fiber patterns are constructed from biochemically similar fibers, the collagen types present in the pre- and post-metamorphic dermis were determined using SDS-polyacrylamide gel electrophoresis. Type I collagen is the predominant collagen of the dermis and the same major collagen types are present for all individuals, whether pre- or post-metamorphic. Thus, the major types of collagen that compose the dermal fibers do not change during metamorphic repatterning of the dermis.     

XX/XO-Mosaik bei einem männlichen Individuum mit Kleinwuchs und Hypospadie

Zusammenfassung Bei einem normal intelligenten, kleinwüchsigen, 219/12 jährigen Mann mit Hypospadie, fraglicher rudimentärer Vagina und hypergonadotropem Hypogonadismus findet man bei der Biopsie des nur 7 ml großen linken Hodens eine gleichförmige tubuläre Atrophie mit Fehlen des Keimepithels und eine diffuse, kleinherdige Leydigzellwucherung. Sex-Chromatin in den Leydigzellen, im Mundabstrich und Drumsticks negativ. Karyotyp in den Lymphocyten und im Knochenmark normal weiblich (46,XX), in den Fibroblasten jedoch 45,XO.Somit weist dieser Patient Testesgewebe auf, das Y-Chromosom ist aber unauffindbar. Zur Klärung dieser Diskrepanz scheint das Vorhandensein einer dritten, zahlenmäßig stark in den Hintergrund tretenden, ein Y enthaltenden Zellpopulation die naheliegendste Hypothese zu sein.Eine Zwillingsschwester kam im Neugeborenenalter ad exitum; die Blutgruppenuntersuchungen beim Patienten und seiner Familie machen aber einen Blutchimärismus sehr unwahrscheinlich.Das klinische Bild unseres Patienten ist vollkommen verschieden von demjenigen, das beim XX/XO-Mosaik üblicherweise beobachtet wird und läßt sich auch vom klassischen Klinefelter-Syndrom deutlich abgrenzen. Es zeigt Ähnlichkeiten mit einigen Fällen von XO/XY-Mosaik.

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Summary In a normally intelligent man of 219/12 years the following main physical findings were present: short stature, hypospadias, possibly a rudimentary vagina, hypergonadotropic hypogonadism, small testis (7 ml) with tubular dystrophy consisting in absence of germinal epithelium and localized proliferation of Leydig's cells. Sex chromatin in buccal mucosa cells was negative; no drumsticks were found in neutrophils. The karyotype in lymphocyte cultures and bone-marrow preparations was 46,XX; in several independent fibroblast cultures 45,XO.The most likely explanation for the presence of testicular tissue seems to be the existence of an undiscovered cell population containing a Y-chromosome.A twin sister of the patient died in early infancy; blood group investigations gave no indications for the presence of blood chimerism.The clinical picture of this patient is entirely different from that of the usual XX/XO mosaics, it also clearly differs from Klinefelter's syndrome but shows some similarities to cases of XO/XY mosaicism.

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Direktor: Prof. Chr. Hedinger     

Quantum Requirement for Photosynthesis in Chlorophyll-Deficient Plants with Unusual Lamellar Structures

Neither an over-all deficiency of chlorophyll, nor an increased enzymatic capacity for maximal rates, nor an unusual lamellar structure was found to change the number of quanta required for the evolution of one molecule of oxygen in healthy aurea mutants of tobacco. The average minimal quantum number remains 10 (efficiency 0.1) as in many algae and typical higher plants. Most of the time the optimal efficiency depends on the availability of some far-red radiation, particularly in the blue region of the spectrum where blue light alone is rather inefficient. These results fit an explanation offered earlier in connection with the hydrogen or acetate photometabolism of algae in far-red light.     

Coated-vesicle formation in vitro: conflicting results using different assays

Cell-free systems provide essential tools for elucidating the molecular mechanisms underlying complex cellular processes such as vesicular transport. The biochemical utility of these model systems is strengthened by assays that allow rapid, quantitative detection of the events being studied. Two model systems have recently been developed to reconstitute coated-vesicle budding, and two different biochemical assays are used to detect this event. Striking differences in the biochemical requirements for 'coated-vesicle budding' are detected by these two assays, suggesting that two distinct events are being measured. These findings have wide implications for the use of cell-free assay systems in cell biology.     

Testosterone-regulated expression of enzymes involved in steroid and aromatic hydrocarbon catabolism in Comamonas testosteroni.

The effect of testosterone as the sole carbon source on protein expression was analyzed in Comamonas testosteroni. Testosterone simultaneously induced the expression of steroid- and aromatic hydrocarbon-catabolizing enzymes and repressed one amino acid-degrading enzyme. It is suggested that steroids play a regulative role in catabolic enzyme synthesis during adaptive growth of C. testosteroni.     

Photooxidation reactions of diphenylcarbazide and their DCMU-sensitivity in thylakoids of the blue-green alga Oscillatoria chalybea

Thylakoids of Oscillatoria chalybea are able to split water. The Hill reaction of these thylakoids is sensitive to DCMU. Diphenylcarbazide can substitute for water as the electron donor to photosystem II with these fully functioning thylakoids. However, the diphenylcarbazide photooxidation is completely insensitive to 3-(3,4-dichlorophenyl)-N-N-dimethyl urea (DCMU) at high diphenylcarbazide concentrations. In with Tris-treated Oscillatoria thylakoids the water splitting capacity is lost and diphenylcarbazide restores electron transport through photosystem II as occurs with higher plant chloroplasts. However, also these photoreactions are insensitive to DCMU. If diphenylcarbazide acts in Oscillatoria as an electron donor to photosystem II the result suggests that diphenylcarbazide feeds in its electrons behind the DCMU inhibition site. This in turn indicates that in Oscillatoria the site of inhibition of DCMU is on the donor side of photosystem II.Abbreviations Used DCMU 3-(3,4-dichlorophenyl)-N-N-dimethyl urea - DPC diphenylcarbazide - DCPiP 2,6-dichlorophenol indophenol - TMB tetramethyl benzidine - A-2-sulf anthraquinone-2-sulfonate