Der cytologische Nachweis von doppelter Restitution beiFragaria

Double restitution has been observed cytologically for the first time in microsporogenesis of a F₁ hybridFragaria virginiana ×F. chiloensis . Restitution is probably due to irregularities affecting the spindle mechanism. Single or double restitution may depend upon the duration of the effect or upon the stage of meiosis affected. The occurrence of triades is indicative of a possible intracellular diversity. Although the reason which may cause restitution remains to be ascertained, maternal inheritance indicates an extrachromosomal cause.

     

Light and temperature dependence of the emission of cyclic and acyclic monoterpenes from holm oak (Quercus ilex L.) leaves

In a laboratory study, we investigated the monoterpene emissions from Quercus ilex, an evergreen sclerophyllous Mediterranean oak species whose emissions are light dependent. We examined the light and temperature responses of individual monoterpenes emitted from leaves under various conditions, the effect of heat stress on emissions, and the emission-onset during leaf development. Emission rate increased 10-fold during leaf growth, with slight changes in the composition. At 30 °C and saturating light, the monoterpene emission rate from mature leaves averaged 4·1 nmol m^–2 s^–1, of which α-pinene, sabinene and β-pinene accounted for 85%. The light dependence of emission was similar for all monoterpenes: it resembled the light saturation curve of CO₂ assimilation, although monoterpene emission continued in the dark. Temperature dependence differed among emitted compounds: most of them exhibited an exponential increase up to 35 °C, a maximum at 42 °C, and a slight decline at higher temperatures. However, the two acyclic isomers cis-β-ocimene and trans-β-ocimene were hardly detected below 35 °C, but their emission rates increased above this temperature as the emission rates of other compounds fell, so that total emission of monoterpenes exponentially increased from 5 to 45 °C. The ratio between ocimene isomers and other compounds increased with both absolute temperature and time of heat exposure. The light dependence of emission was insensitive to the temperature at which it was measured, and vice versa the temperature dependence was insensitive to the light regime. The results demonstrated that none of the models currently applied to simulate isoprene or monoterpene emissions correctly predicts the short-term effects of light and temperature on Q. ilex emissions. The percentage of fixed carbon lost immediately as monoterpenes ranged between 0·1 and 6·0% depending on temperature, but rose up to 20% when leaves were continuously exposed to temperatures between 40 and 45 °C.     

Morphological studies of the matrix in human hypothalamus

The variations of matrix and ependyma in the hypothalamus was histologicaly investigated in 120 human brains of both sexes from the 13 week old fetuses up to the end of the first year of postnatal life. The plane of cuts were in the region of the anterior hypothalamic nucleus, of the ventromedial nucleus, and the arcuate nucleus. We have found that the exhaustion of the matrix begins in the 14 week old embryo in the anterior and medial hypothalamus. A subependymale zone is present in these areas in the 17 week old embryo and exists up to 23 week. The one-cell-layer ependyma appears in the anterior are of the ventromedial nucleus at first in the 24 week week old embryo. After this the ependyma appears from the 25 to the 28 week old embryo in the regions of the anterior hypothalamic nucleus and the other areas of the ventromedial nucleus. In the immediate surrounding of the arcuate nucleus we observed the first alterations in the 15 week old embryo. The exhaustion of matrix is a continuous process up to the 23rd week. The boundary of the third ventricle remained to be a multilayer and in all stages of development cells were found, which reach into the lumen. Only after birth the multilayer boundary was reduced. At the end of the first year of postnatal life the one-layer ependyma was developed at a few sites. We could not find any significant variations of matrix exhaustion in the different sexes.     

Die Entstehung und Geschichte der großfrüchtigen GartenerdbeerenFragaria × ananassa Duch

Ohne ZusammenfassungMit 5 AbbildungenFrau Professor Dr.E. Schiemann zu ihrem 80. Geburtstag in Verehrung und Dankbarkeit gewidmet.     

Analysis of gamma c-family cytokine target genes. Identification of dual-specificity phosphatase 5 (DUSP5) as a regulator of mitogen-activated protein kinase activity in interleukin-2 signaling

Interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 form a family of cytokines based on their sharing the common cytokine receptor gamma chain, gamma(c), which is mutated in X-linked severe combined immunodeficiency (SCID). As a step toward further elucidating the mechanism of action of these cytokines in T-cell biology, we compared the gene expression profiles of IL-2, IL-4, IL-7, and IL-15 in T cells using cDNA microarrays. IL-2, IL-7, and IL-15 each induced a highly similar set of genes, whereas IL-4 induced distinct genes correlating with differential STAT protein activation by this cytokine. One gene induced by IL-2, IL-7, and IL-15 but not IL-4 was dual-specificity phosphatase 5 (DUSP5). In IL-2-dependent CTLL-2 cells, we show that IL-2-induced ERK-1/2 activity was inhibited by wild type DUSP5 but markedly increased by an inactive form of DUSP5, suggesting a negative feedback role for DUSP5 in IL-2 signaling. Our findings provide insights into the shared versus distinctive actions by different members of the gamma(c) family of cytokines. Moreover, we have identified a DUSP5-dependent negative regulatory pathway for MAPK activity in T cells.     

Characterizing the role of the microtubule binding protein Bim1 in Cryptococcus neoformans

During sexual development the human fungal pathogen Cryptococcus neoformans undergoes a developmental transition from yeast-form growth to filamentous growth. This transition requires cellular restructuring to form a filamentous dikaryon. Dikaryotic growth also requires tightly controlled nuclear migration to ensure faithful replication and dissemination of genetic material to spore progeny. Although the gross morphological changes that take place during dikaryotic growth are largely known, the molecular underpinnings that control this process are uncharacterized. Here we identify and characterize a C. neoformans homolog of the Saccharomyces cerevisiae BIM1 gene, and establish the importance of BIM1 for proper filamentous growth of C. neoformans. Deletion of BIM1 leads to truncated sexual development filaments, a severe defect in diploid formation, and a block in monokaryotic fruiting. Our findings lead to a model consistent with a critical role for BIM1 in both filament integrity and nuclear congression that is mediated through the microtubule cytoskeleton.