Identification and possible biological relevance of spermatozoal transglutaminase

Summary Normal human spermatozoa were demonstrated by dot immunoblot analysis and immunohistochemistry to possess transglutaminase (TGase). The immunological identification of spermatozoal TGase is consistent with reports by others of its biochemical identification and suggested role in sperm motility,and provides, in view of the immunoregulatory properties of seminal plasma TGase, presumptive identification of a means whereby spermatozoa, under normal physiological conditions, may possibly be protected from immunological attack within the female reproductive tract.     

Gigantecin: A novel antimitotic and cytotoxic acetogenin,with nonadjacent tetrahydrofuran rings,fromGoniothalamus giganteus (Annonaceae)

Summary Gigantecin (I), a novel tetrahydroxy-di-tetrahydrofuran fatty acid -lactone (acetogenin), was isolated from an ethanolic extract of the stem bark ofGoniothalamus giganteus Hook. f., Thomas (Annonaceae), by means of activity-directed fractionation (brine shrimp lethality test). This new compound is extremely cytotoxic to human tumor cells, inhibits crown gall tumors on potato discs, and is active in an assay designed to detect antimitotic agents (9 ASK).     

Saccadic oscillations facilitate ocular perfusion from the avian pecten

THE evolution of the eye is constrained by two conflicting requirements--good vascular perfusion of the retina, and an optical path through the retina that is unobstructed by blood vessels. Birds are interesting in that they have higher metabolic rates and thicker retinas than mammals, but have no retinal blood vessels. Nutrients and oxygen must thus reach the neurons of the inner retina either from the choroid through 300 micron of metabolically very active retina, or from the pecten, a pleated vascular structure protruding from the head of the optic nerve into the vitreous chamber, and more than a centimetre away from some retinal neurons. Despite the diffusional distance involved, several lines of evidence indicate that the pecten is the primary source of nutrients for the inner retina: the presence of an oxygen gradient from pecten to retina, the large surface area produced by macroscopic folds and by microscopic infoldings of the luminal and external surfaces of the capillary endothelium, extrusion of circulating fluorescein, high content of carbonic anhydrase and alkaline phosphatase, and retinal impairments after pecten ablation. Another peculiarity of birds, their saccadic oscillations, occur with a large cyclotor-sional component during every saccadic eye movement. In different species, saccades, which occur at intervals of 0.5-40 s, have up to 13 oscillations with frequencies of 15-30 Hz and ampliá-tudes of about 10 degrees. Therefore, as much as 12% of some birds' total viewing time may be subject to the image instability caused by the oscillations. Using fluorescein angiography, we show here that during every saccade, the pecten acts as an agitator which propels perfusate towards the central retina much more effectively than is observed during intersaccadic intervals.     

Amino-acid synthesis in carbonaceous meteorites by aqueous alteration of polycyclic aromatic hydrocarbons

It has been suggested that amino acids and other organic compounds found in carbonaceous meteorites formed by aqueous alteration in the meteorite parent bodies. Observations of carbonaceous material in interstellar grains and interplanetary dust particles indicate that condensed organic compounds may have been present in meteorite parent bodies at the time of aqueous alteration. One group of compounds thought to be representative of this carbonaceous material is the polycyclic aromatic hydrocarbons (PAHs). Recently it was proposed that PAHs condense on SiC grains in the molecular envelopes of carbon-rich red-giant stars, which would allow for their subsequent incorporation into meteorite parent bodies during accretion. This incorporation mechanism is supported by the identification of SiC grains in carbonaceous chondrites. The possibility therefore exists that PAHs, and/or other condensed organic compounds, represent the starting material for aqueous alteration which leads to the formation of amino acids and other water-soluble organic compounds. Here we present calculations of the distribution of aqueous organic compounds in metastable equilibrium with representative PAHs as functions of the fugacities of O2, CO2 and NH3. The results reported here for pyrene and fluoranthene, two PAHs with different structures but the same stoichiometry, differ greatly but indicate that the formation of amino and carboxylic acids is energetically favourable at probable parent-body alteration conditions. The actual reaction mechanisms involved could be revealed by consideration of isotope data for PAHs, amino acids, other organic compounds and carbonates in carbonaceous chondrites.     

MD Method in Solving Multiple Criteria Decision Problems Arising from Investment Systems

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A novel mechanism for jumping in the indian ant<Emphasis Type="Italic">Harpegnathos saltator</Emphasis> (Jerdon) (Formicidae,Ponerinae)

The Indian antHarpegnathos saltator may be unique among insects in using its jumping capacity not only as an escape mechanism but also as a normal means of locomotion, and for catching its prey in flight. High-speed cinematography used to analyse the various phases of the jump suggests thatHarpegnathos employs a novel jumping mechanism to mediate these behaviours: namely the synchronous activation of its middle and hindlegs. Electrophysiological recordings from muscles or nerves in pairs of middle and hindlegs show remarkably synchronous activity during fictive jumping, supporting the synchronous activation hypothesis.Harpegnathos is not the only ant to jump, and a cladistic analysis suggests that jumping behaviour evolved independently three times during ant evolutionary history.