Local haemostasis in brain tumours.

The thromboplastic activity and the fibrinolytic activity were examined in 7 human meningiomas and 6 gliomas obtained at neurosurgery. Two different haemostatic patterns emerged, meningiomas having lower thromboplastic and higher fibrinolytic activity than that of gliomas. This difference might help to explain the better haemostatic capacity of gliomas during and after operation than that of meningiomas.     

A voltage-gated ion channel model inferred from the crystal structure of alamethicin at 1.5-A resolution

The crystal structure of alamethicin in nonaqueous solvent has been determined, and refined at 1.5-A resolution. The molecular conformation of the three crystallographically independent molecules is largely alpha-helical with a bend in the helix axis at an internal proline residue. The helix structure is highly amphipathic as most of the solvent-accessible polar atoms lie on a narrow strip of surface parallel to the helix axis. Molecular models for the voltage-gated ion channel, with n-fold symmetry and based on the molecular conformations observed in the crystal, are characterized by strong surface complementarity, a hydrophilic interior and a hydrophobic exterior. The channel structures are stabilized by a hydrated annulus of hydrogen-bonded glutamine residues which produce the greatest restriction in the channel diameter.     

Gastric mucus effusion elicited by oral copper compounds: Potential anti-ulcer activity

Summary In rats, both Cu(I) and Cu(II) show an irritancy profile not shared with Cu^o or Zn(II) or Ni(II). The gastric response to Cu(II), i.e. copius fluid and mucus secretion, can protect the stomach from the acute ulcerative effects of aspirin or physical stress administered subsequently.to whom all enquiries should be addressed, Supported by grants from the National Health and Medical Research Council (Austr.) and University of Tasmania Research Commitee.Acknowledgments: ProfessorsW. R. Walker (Newcastle, Austr.) andL. Field (Nashville, Tenn.) for gifts of Cu(I) and Zn complexes;Dr. J. R. J. Sorenson (Cincinnatti, Ohio) for illuminating discussion; Drs.D. D. Perrin (Canberra) andR. P. Agarwal (Washington D. C.) for providing stability constants and much helpful advice.     

Different postsynaptic events in two types of retinal bipolar cell

The first synapse in the vertebrate visual system is made between the photoreceptors and the biopolar cells. Bioplar cells fall into two distinct classes according to whether the cell hyperpolarizes or depolarizes to small centred spots of light. Most evidence indicates that the light-induced hyperpolarization of the photoreceptprs suppresses transmitter release from the synaptic terminals, and it is probable that the differences between the two bipolar cell classes results from the different actions of the photoreceptor transmitter. In analysing the membrane potential fluctuations in both types of bipolar cell we find that the voltage noise spectra differ. It is to be expected that postsynaptic noise would be composed of the sum of noise generated in and transmitted from the cones and the noise arising from the statistical nature of synaptic transmission. We report here evidence for two such components in the voltage noise spectra recorded from each type of bipolar cell. The differences in the frequency distribution of the presumed transmitter-related components indicates that the transmitter generates events of longer duration in the depolarizing biopolar cells.