Selective antagonism by Mg2+ of amino acid-induced depolarization of spinal neurones.

In the isolated frog or rat spinal cord, low concentrations of Mg2+ (0.5-1.00 mM) markedly depress, in a substantially Ca2+-independent manner, ventral root depolarizations produced by dorsal root stimulation and by certain amino acids (e.g. N-methyl-D-aspartate and L-homocysteate) but do not depress depolarizations produced by other excitatory amino acids (e.g. kainate and quisqualate). L-Aspartate-induced depolarizations are more sensitive to Mg2+ then are L-glutamate-induced depolarizations.     

Aberrant lipid metabolism disrupts calcium homeostasis causing liver endoplasmic reticulum stress in obesity

The endoplasmic reticulum (ER) is the main site of protein and lipid synthesis, membrane biogenesis, xenobiotic detoxification and cellular calcium storage, and perturbation of ER homeostasis leads to stress and the activation of the unfolded protein response. Chronic activation of ER stress has been shown to have an important role in the development of insulin resistance and diabetes in obesity. However, the mechanisms that lead to chronic ER stress in a metabolic context in general, and in obesity in particular, are not understood. Here we comparatively examined the proteomic and lipidomic landscape of hepatic ER purified from lean and obese mice to explore the mechanisms of chronic ER stress in obesity. We found suppression of protein but stimulation of lipid synthesis in the obese ER without significant alterations in chaperone content. Alterations in ER fatty acid and lipid composition result in the inhibition of sarco/endoplasmic reticulum calcium ATPase (SERCA) activity and ER stress. Correcting the obesity-induced alteration of ER phospholipid composition or hepatic Serca overexpression in vivo both reduced chronic ER stress and improved glucose homeostasis. Hence, we established that abnormal lipid and calcium metabolism are important contributors to hepatic ER stress in obesity.     

Evidence against Ha-ras-1 involvement in sporadic and familial melanoma

It was recently reported that different rare alleles at the Ha-ras-1 locus occurred at a significantly higher combined frequency in cancer patients than in an unaffected population. In particular, melanoma patients were reported to have a significantly higher frequency of such alleles. We have examined the frequency of rare Ha-ras-1 alleles in a large number of cases of sporadic melanoma. Our results indicate that the distribution of rare alleles in this population does not differ from that found in normal populations. Also, to test the hypothesis that a hereditary predisposition to melanoma could be inherited via an allele at the Ha-ras-1 locus, we examined the transmission of the segment of the short arm of chromosome 11 (11p) carrying the Ha-ras-1 locus in a number of families previously shown to exhibit a hereditary predisposition to melanoma and its precursor lesion, the dysplastic nevus syndrome (DNS). Our genetic linkage results thus obtained strongly exclude the association of a predisposition to melanoma or the precursor lesion with the inheritance of the Ha-ras-1 locus or the segment of chromosome 11 on which it is located. These results imply that hereditary predisposition to melanoma is associated with genes other than the Ha-ras-1 locus, contradicting the original suggestion of Krontiris et al., made on the basis of either an inadequate sample size or other misleading experimental factors.     

Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin

Vertebrates achieve internal homeostasis during infection or injury by balancing the activities of proinflammatory and anti-inflammatory pathways. Endotoxin (lipopolysaccharide), produced by all gram-negative bacteria, activates macrophages to release cytokines that are potentially lethal. The central nervous system regulates systemic inflammatory responses to endotoxin through humoral mechanisms. Activation of afferent vagus nerve fibres by endotoxin or cytokines stimulates hypothalamic-pituitary-adrenal anti-inflammatory responses. However, comparatively little is known about the role of efferent vagus nerve signalling in modulating inflammation. Here, we describe a previously unrecognized, parasympathetic anti-inflammatory pathway by which the brain modulates systemic inflammatory responses to endotoxin. Acetylcholine, the principle vagal neurotransmitter, significantly attenuated the release of cytokines (tumour necrosis factor (TNF), interleukin (IL)-1beta, IL-6 and IL-18), but not the anti-inflammatory cytokine IL-10, in lipopolysaccharide-stimulated human macrophage cultures. Direct electrical stimulation of the peripheral vagus nerve in vivo during lethal endotoxaemia in rats inhibited TNF synthesis in liver, attenuated peak serum TNF amounts, and prevented the development of shock.     

Luminal alkalinization by guinea-pig cecum in vitro, an electro-neutral process.

Guinea-pig cecum was found to alkalinize its mucosal media in vitro at a chemical equivalents rate greater than the short circuit current (ISC). Alkalinization was inhibited by conditions which did not affect ISC and by low mucosal Na suggesting an electro--neutral process, dependent on Na.     

Association of mastopoiesis with haemopoietic tissues in the neonatal rat

Summary Mast cells in the newborn rat occur in haemopoietic foci of liver and spleen, but disappear from those foci as extramedullary haemopoiesis ceases during the initial postnatal month. At the same time, mast cells increasingly populate bone marrow and connective tissues of heart, lung, stomach and portal tract of liver.J. L. D. acknowledges Scholarships from the National Health and Medical Research Council of Australia while working on this project for the degree of B. Sc. (Med.), the University of New South Wales, and subsequently from the National Heart Foundation of Australia.