Fatty acid composition of the lipids of Puffinus tenuirostris (Temminck) in relation to its diet

The fatty acid composition of lipids isolated from the depot fat, stomach contents, and proventricular oil of adult and chick Puffinus tenuirostris (Temminck) has been analysed. The diet of both adults and chicks is almost exclusively derived from the euphausiid Nyctiphanes australis Sars, and an attempt was made to determine whether dietary lipid affects the composition of depot fat, and whether individual fatty acids in the stomachs and proventricular oil can be used as markers for the origin of the diet. An apparent selectivity in the deposition of fatty acids in the fat depots can be explained by the conversion of fatty alcohols, derived from the euphausiid wax ester, into fatty acids of equivalent chain length and unsaturation. Hexadecadienoic acid appeared to be the only possible marker fatty acid from the euphausiid, but wide variations in its level limits its usefulness as a reliable index of the diet of Puffinus tenuirostris.     

EFFECT OF CYANIDE AND ELECTRICAL STIMULATION ON PHOSPHOINOSITIDE METABOLISM IN LOBSTER NERVES

The contents of phosphoinositides, ATP, glucose and lactate in leg and claw nerves of the lobster were determined. Nerves were also analysed after cyanide poisoning, after electrical stimulation, and 1 h after removing the leg from the lobster. Cyanide poisoning decreased the levels of ATP and glucose and increased the content of lactate but did not alter the levels of phosphoinositides. Nerves left in situ for 1 h after disconnection from the central nervous system exhibited a decrease in the content of tri-phosphoinositides (TPI) of 50 per cent, without changes in ATP, glucose or lactate. The TPI change was reversed after incubation for 1 h in oxygenated seawater. Nerves labelled in vivo with ³²P were removed and stimulated at 50 Hz for 5 min. The turnover of TPI phosphorus increased on stimulation in both normal and cyanide-poisoned nerves. In contrast, turnover of ATP increased after stimulation in normal nerves but not in cyanide-treated nerves. We sought to determine whether polyphosphoinositides play a greater role in resting metabolism of the nerve or in the conducting mechanisms. Our results make more likely the involvement of TPI in permeability changes of neural membranes during excitation.     

THE BINDING OF BOTULINUM TOXIN TO MEMBRANE LIPIDS: SPHINGOLIPIDS, STEROIDS AND FATTY ACIDS

A number of lipids known to be constituents of nerve-ending membranes were tested for their ability to inactivate botulinum toxin. Inactivation of the toxin by a lipid was taken as presumptive evidence that the lipid might be the in vivo receptor for the toxin. Several sphingolipids (sphingosine, galactosylceramide, glucosylceramide, lactosylceramide, cytolipin K and cytolipin R), steroids (cholesterol and deoxycholic acid) and fatty acids (palmitic acid, stearic acid, prostaglandin E₁) did not affect the potency of botulinum toxin, and thus were discounted as potential toxin receptors. However, the gangliosides did inactivate botulinum toxin rapidly (in less than 5 min), within a temperature range of 2°-40°C, and at ionic strengths of 0.05-0.40. Inactivation diminished as pH fell below 6. The activity of gangliosides in suppressing the potency of botulinum toxin was a function of the number of sialic acid residues in the lipid. Thus, the data suggest that a molecule containing sialic acid may be the receptor for the toxin.     

Specificity of compaction in meiotic chromosomes of the female Chinese hamster

This study describes the sequential alternation of compaction and decompaction in the chromosomes of the Chinese hamster oocyte from diakinesis to metaphase II. A series of micrographs show that the compact metaphase I chromosomes become greatly extended as they enter and pass through anaphase I. Once polarized, the presumptive oocyte chromosomes become exceedingly compact and form a tightly packed mass, each chromosome assuming contours to accomodate dovetailing with its neighbors, while the chromosomes consigned to the polar body remain extended and show signs of the incipient deterioration. Prior to ovulation, the chromosomes of the mass separate and begin to decompact, in part at least, by the previously postulated mechanism of uncoiling. Following ovulation, the chromosomes are greatly extended and, as the metaphase II complement, remain in that state until the advent of fertilization. — Evidence that the compaction patterns are ordered and chromosome specific is presented by observation of the two smallest chromosomes of the complement. At telophase I those chromosomes are markedly different in size and arm ratio; at metaphase II the differences are less pronounced and at mitotic metaphase the two smallest chromosome pairs are so similar in morphology as to be indistinguishable. It is proposed, therefore, that those two chromosomes differ in their fundamental morphology as revealed at the exceedingly compact state of telophase I oocyte chromosomes. Their subsequently established resemblance at mitotic metaphase may be due to allocycly on the part of one or both, resulting in two chromosomes of apparantly similar length and arm ratio.Supported by grants from the Institute of Child Health and Development of the National Institutes of Health, 5 RO1 HDO4846 and the Damon Runyan Foundation, DRG-907.Supported in part by CA-08748 from the Cancer Institute of the National Institutes of Health.