Möglicher Einfluß chemischer Gleichgewichte auf Viskosität und Relaxationszeit im Erdinnern

Summary A thermodynamic consideration shows that SiO₂ may be reduced to Si by hydrogen at the temperatures present in the earth's interior. The reaction can be expected to involve a rapid change of viscosity with depth inside the earth, required for the explanation of the seismic discontinuity at 2,900 km.     

Targeted mutation of Cyln2 in the Williams syndrome critical region links CLIP-115 haploinsufficiency to neurodevelopmental abnormalities in mice

Williams syndrome is a neurodevelopmental disorder caused by the hemizygous deletion of 1.6 Mb on human chromosome 7q11.23. This region comprises the gene CYLN2, encoding CLIP-115, a microtubule-binding protein of 115 kD. Using a gene-targeting approach, we provide evidence that mice with haploinsufficiency for Cyln2 have features reminiscent of Williams syndrome, including mild growth deficiency, brain abnormalities, hippocampal dysfunction and particular deficits in motor coordination. Absence of CLIP-115 also leads to increased levels of CLIP-170 (a closely related cytoplasmic linker protein) and dynactin at the tips of growing microtubules. This protein redistribution may affect dynein motor regulation and, together with the loss of CLIP-115-specific functions, underlie neurological alterations in Williams syndrome.     

A new approach to isotonic agglomerative hierarchical clustering

Hierarchical clustering methods must be isotonic for the construction of ultrametric. We present a general strategy to widen the class of isotonic methods implemented by agglomerative algorithms. At each step of the agglomeration we allow one of several admissible pairs to be chosen. Then under mild assumptions an appropriate definition of admissibility guarantees isotony. Moreover we consider the use of the new methods to compute locally optimal ultrametrics. Two examples demonstrate the ability to define new agglomerative methods superior to their traditional competitors.     

Suppression and enhancement of humoral immune response toToxoplasma gondii by passive antibody

Summary Anti-toxoplasma antibodies administered passively to mice may lead to suppression or enhancement (reported for the first time with Protozoan parasites) of subsequent antibody response when these animals are later infected withToxoplasma gondii. The outcome is dependent on infecting strain of Toxoplasma and the antigen-antibody ratio.     

<Emphasis Type="Italic">Cis</Emphasis>–<Emphasis Type="Italic">trans</Emphasis> interactions of cell surface receptors: biological roles and structural basis

Cell surface receptors bind ligands expressed on other cells (in trans) in order to communicate with neighboring cells. However, an increasing number of cell surface receptors are found to also interact with ligands expressed on the same cell (in cis). These observations raise questions regarding the biological role of such cis interactions. Specifically, it is important to know whether cis and trans binding have distinct functional effects and, if so, how a single cell discriminates between interactions in cis versus trans. Further, what are the structural features that allow certain cell surface receptors to engage ligand both on the same as well as on an apposed cell membrane? Here, we summarize known examples of receptors that display cis–trans binding and discuss the emerging diversity of biological roles played by these unconventional two-way interactions, along with their structural basis.     

Investigation of gas concentration cell based on LiSiPO electrolyte and Li_2CO_3,Au electrode

Solid lithium ion conducting electrochemical cells using LiSiPO as solid electrolyte and Li2CO3 mixed with Au as electrodes were prepared and employed as chemical sensors for the detection of CO2 gas.The EMF of the cell depends on the concentration of CO2 in air according to the partial pressure dependence of Nernst's law in the investigated range from 100 to 2000 ppm over the temperature range from 473 K to 673 K.     

Rapid developmental switch in the mechanisms driving early cortical columnar networks

The immature cerebral cortex self-organizes into local neuronal clusters long before it is activated by patterned sensory inputs. In the cortical anlage of newborn mammals, neurons coassemble through electrical or chemical synapses either spontaneously or by activation of transmitter-gated receptors. The neuronal network and the cellular mechanisms underlying this cortical self-organization process during early development are not completely understood. Here we show in an intact in vitro preparation of the immature mouse cerebral cortex that neurons are functionally coupled in local clusters by means of propagating network oscillations in the beta frequency range. In the newborn mouse, this activity requires an intact subplate and is strongly synchronized within a cortical column by gap junctions. With the developmental disappearance of the subplate at the end of the first postnatal week, activation of NMDA (N-methyl-D-aspartate) receptors in the immature cortical network is essential to generate this columnar activity pattern. Our findings show that during a brief developmental period the cortical network switches from a subplate-driven, gap-junction-coupled syncytium to a synaptic network acting through NMDA receptors to generate synchronized oscillatory activity, which may function as an early functional template for the development of the cortical columnar architecture.