The hypnotic constituent ofStipa vaseyi,sleepy grass

Zusammenfassung Der ausStipa vaseyi isolierte wirksame Bestandteil (depressive Wirkung auf das Zentralnervensystem von Tieren) wurde chemisch und pharmakologisch als Diacetonalkohol identifiziert.

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This investigation was supported by U.S. Public Health Service research grant NB-04313-1, National Science Foundation undergraduate summer research award, and National Institutes of Health research career award 5-K3-NB-8641-02.     

Developmental genetics

Summary Of particular concern to the human geneticist are the effects of genetic abnormalities on development. To gain an understanding of these effects it is necessary to engage in a reciprocal process of using knowledge of normal developmental events to elucidate the mechanisms operative in abnormal situations and then of using what is learned about these abnormal situations to expand our understanding of the normal. True developmental genes have not been described in man, although it is likely that they exist, but many developmental abnormalities are ascribable to mutations in genes coding for enzymes and structural proteins. Some of these even produce multiple malformation syndromes with dysmorphic features. These situations provide a precedent for asserting that not only monogenic developmental abnormalities, but also abnormalities resulting from chromosome imbalance must ultimately be explicable in molecular terms. However, the major problem confronted by the investigator interested in the pathogenesis of any of the chromosome anomaly syndromes is to understand how the presence of an extra set of normal genes or the loss of one of two sets of genes has an adverse effect on development. Several molecular mechanisms for which limited precedents exist may be considered on theoretical grounds. Because of the difficulties in studying developmental disorders in man, a variety of experimental systems have been employed. Particularly useful has been the mouse, which provides models for both monogenic and aneuploidy produced abnormalities of development. An example of the former is the mutation oligosyndactylism which in the heterozygous state causes oligosyndactyly and in the homozygous state causes early embryonic mitotic arrest. All whole arm trisomies and monosomies of the mouse can be produced experimentally, and of special interest is mouse trisomy 16 which has been developed as an animal model of human trisomy 21 (Down syndrome). In the long run, the most direct approach to elucidating the genetic problems of human development will involve not only the study of man himself but also of the appropriate experimental models in other species.Acknowledgments. This review was written while the author was a Henry J. Kaiser Senior Fellow at the Center for Advanced Study in the Behavioral Sciences, Palo Alto, California. This work was supported by grants from the National Institutes of Health (GM-24309, HD-03132, HD-15583, HD-17001) and the American Cancer Society (CD-119) and by a contract from the National Institute of Child Health and Human Development (NOI-HD-2858).     

Oscillatory cluster patterns in a homogeneous chemical system with global feedback

Oscillatory clusters are sets of domains in which nearly all elements in a given domain oscillate with the same amplitude and phase. They play an important role in understanding coupled neuron systems. In the simplest case, a system consists of two clusters that oscillate in antiphase and can each occupy multiple fixed spatial domains. Examples of cluster behaviour in extended chemical systems are rare, but have been shown to resemble standing waves, except that they lack a characteristic wavelength. Here we report the observation of so-called 'localized clusters'--periodic antiphase oscillations in one part of the medium, while the remainder appears uniform--in the Belousov-Zhabotinsky reaction-diffusion system with photochemical global feedback. We also observe standing clusters with fixed spatial domains that oscillate periodically in time and occupy the entire medium, and irregular clusters with no periodicity in either space or time, with standing clusters transforming into irregular clusters and then into localized clusters as the strength of the global negative feedback is gradually increased. By incorporating the effects of global feedback into a model of the reaction, we are able to simulate successfully the experimental data.     

On the association between lysogeny and carcinogenicity in nitroquinolines and related compounds

Zusammenfassung In einer Serie von 16 Nitroquinolinen und verwandten Substanzen wurde eine gute Übereinstimmung zwischen Phageninduktion inEscherichia coli C-600 und Karzinogenese nachgewiesen.

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Supported by grants No. C-6516 and FR-05526 from the National Cancer Institute and Contract NO. PH 86-66-169 from the Division of Air Pollution, U.S.P.H.S. We thank Dr.Y. Kawazoe of the National Cancer Center Research Institute, Tokyo, for his generous gift of the compounds tested.