A neural cocktail-party processor

Sensory segmentation is an outstanding unsolved problem of theoretical, practical and technical importance. The basic idea of a solution is described in the form of a model. The response of neurons within the sensory field is temporally unstable. Segmentation is expressed by synchronization within segments and desynchronization between segments. Correlations are generated by an autonomous pattern formation process. Neuronal coupling is the result both of peripheral evidence (similarity of local quality) and of central evidence (common membership in a stored pattern). The model is consistent with known anatomy and physiology. However, a new physiological function, synaptic modulation, has to be postulated. The present paper restricts explicit treatment to the peripheral evidence represented by amplitude modulations globally present in all components of a sound spectrum. Generalization to arbitrary sensory qualities will be the subject of a later paper. The model is an application and illustration of the Correlation Theory of brain function.This work has been supported by Grant I/37-821 of the Stiftung Volkswagenwerk.     

Ein Beitrag zur Bekämpfung der Fritfliege in der Roggenzüchtung

Ohne ZusammenfassungMit 2 Abbildungen     

Excess information at bacteriophage T7 genomic promoters detected by a random cloning technique.

In our previous analysis of the information at binding sites on nucleic acids, we found that most of the sites examined contain the amount of information expected from their frequency in the genome. The sequences at bacteriophage T7 promoters are an exception, because they are far more conserved (35 bits of information content) than should be necessary to distinguish them from the background of the Escherichia coli genome (17 bits). To determine the information actually used by the T7 RNA polymerase, promoters were chemically synthesized with many variations and those that function well in an in vivo assay were sequenced. Our analysis shows that the polymerase uses 18 bits of information, so the sequences at phage genomic promoters have significantly more information than the polymerase needs. The excess may represent the binding site of another protein.     

Characterization of the secondary structure of calmodulin in complex with a calmodulin-binding domain peptide.

The interaction between calcium-saturated chicken calmodulin and a peptide corresponding to the calmodulin-binding domain of the chicken smooth muscle myosin light chain kinase has been studied by multinuclear and multidimensional nuclear magnetic resonance methods. Extensive 1H and 15N resonance assignments of calmodulin in the complex have been obtained from the analysis of two- and three-dimensional nuclear magnetic resonance spectra. The assignment of calmodulin in the complex was facilitated by the use of selective labeling of the protein with alpha-15N-labeled valine, alanine, lysine, leucine, and glycine. These provided reference points during the main-chain-directed analysis of three-dimensional spectra of complexes prepared with uniformly 15N-labeled calmodulin. The pattern of nuclear Overhauser effects (NOE) seen among main-chain amide NH, C alpha H, and C beta H hydrogens indicates that the secondary structure of the globular domains of calmodulin in the complex closely corresponds to that observed in the calcium-saturated state of the protein in the absence of bound peptide. However, the backbone conformation of residues 76-84 adopts an extended chain conformation upon binding of the peptide in contrast to its helical conformation in the absence of peptide. A sufficient number of NOEs between the globular domains of calmodulin and the bound peptide have been found to indicate that the N- and C-terminal regions of the peptide interact with the C- and N-terminal domains of calmodulin, respectively. The significance of these results are discussed in terms of recently proposed models for the structure of calmodulin-peptide complexes.     

The protein encoded by a growth arrest-specific gene (gas6) is a new member of the vitamin K-dependent proteins related to protein S, a negative coregulator in the blood coagulation cascade.

A set of growth arrest-specific genes (gas) whose expression is negatively regulated after serum induction has previously been described (C. Schneider, R. M. King, and L. Philipson, Cell 54:787-793, 1988). The detailed analysis of one of them, gas6, is reported here, gas6 mRNA (2.6 kb) is abundantly expressed in serum-starved (48 h in 0.5% fetal calf serum) NIH 3T3 cells but decreases dramatically after fetal calf serum or basic fibroblast growth factor stimulation. The human homolog of gas6 was also cloned and sequenced, revealing a high degree of homology and a similar pattern of expression in IMR90 human fibroblasts. Computer analysis of the protein encoded by murine and human gas6 cDNAs showed significant homology (43 and 44% amino acid identity, respectively) to human protein S, a negative coregulator in the blood coagulation pathway. By using an anti-human Gas6 monospecific affinity-purified antibody, we show that the biosynthetic level of human Gas6 fully reflects mRNA expression in IMR90 human fibroblasts. This finding thus defines a new member of vitamin K-dependent proteins that is expressed in many human and mouse tissues and may be involved in the regulation of a protease cascade relevant in growth regulation.     

The human complement component C8B gene: structure and phylogenetic relationship

The eighth component of human complement (C8) is a serum protein that consists of three chains (, and ), encoded by three separate genes, viz., C8A, C8B, and C8G. In serum, the -subunit is non-covalently bound to the disulfide-linked - subunit. Using a full-length C8 cDNA probe, we isolated several clones from human genomic DNA libraries. Four clones covering the complete cDNA sequence were characterized by TaqI restriction mapping and were shotgun subcloned into M13. C8-cDNA-positive clones were partially sequenced to characterize the 12 exons of the gene with sizes from 69 to 347 bp. All intron-exon junctions followed the GT-AG rule. By using polymerase chain reaction (PCR) primers located in the adjacent intron sequences, all 12 exons of the C8B gene could be amplified from genomic DNA. All fragments showed the expected sizes. The sizes of eight introns could be determined by using primer pairs that amplified two exons and the enclosed intron, and by restriction mapping. These analyses and the insert sizes of the genomic clones indicate that the C8B gene has a total size of approximately 40 kb. The polymorphic TaqI site of the C8B gene localized in intron 11 could be demonstrated by direct restriction fragment analysis of a PCR fragment containing exons 11 and 12, and the enclosed intron 11. Homology comparison of the C8B gene with C8A and C9 on the basis of the exon structure confirmed the ancestral relationship known from the protein level.