An overview of factors influencing sex determination and gonadal development in birds

The morphological development of the embryonic gonads is very similar in birds and mammals, and recent evidence suggests that the genes involved in this process are conserved between these classes of vertebrates. The genetic mechanism by which sex is determined in birds remains to be elucidated, although recent studies have reinforced the contention that steroids may play an important role in the structural development of the testes and ovaries in birds. So far, few genes have been assigned to the avian sex chromosomes, but it is known that the Z and W chromosomes do not share significant homology with the mammalian X and Y chromosomes. The commercial importance of poultry breeding has motivated considerable investment in developing physical and genetic maps of the chicken genome. These efforts, in combination with modern molecular approaches to analyzing gene expression, should help to elucidate the sex-determining mechanism in birds in the near future.     

Sex chromosomes and sex-determining genes: insights from marsupials and monotremes

Comparative studies of the genes involved in sex determination in the three extant classes of mammals, and other vertebrates, has allowed us to identify genes that are highly conserved in vertebrate sex determination and those that have recently evolved roles in one lineage. Analysis of the conservation and function of candidate genes in different vertebrate groups has been crucial to our understanding of their function and positioning in a conserved vertebrate sex-determining pathway. Here we review comparisons between genes in the sex-determining pathway in different vertebrates, and ask how these comparisons affect our views on the role of each gene in vertebrate sex determination.     

Uninterrupted protein synthesis is essential for survival in the early stages of carbontetrachloride-induced hepatocellular necrosis in the mouse

Summary The fatal syndrome produced by cycloheximide given 6 h after a hepatonecrogenic dose of CCl₄ is due neither to direct toxic synergism between CCl₄ and cycloheximide nor to transient sinusoidal thrombosis. It is suggested that survival in the presence of unknown factors released from dying liver cells requires uninterrupted protein synthesis. The life-saving effect of sterilization of the intestine by antibiotics indicates that the gut flora or its products play a vital role in pathogenesis.Acknowledgments. I wish to thank Mr C. R. West for carrying out the statistical analysis, Mrs Brenda Brooks for histological processing, and Berk Pharmaceuticals Ltd for information on Ancrod defibrination in mice.     

Effects of kallidinogenase on urinary kallikrein excretion and plasma prostanoid concentrations in patients with essential hypertension

Summary The effects of kallidinogenase on urinary kallikrein excretion, plasma immunoreactive prostanoids and platelet aggregation were investigated in patients with essential hypertension. Urinary kallikrein excretion and plasma 6-keto PGF₁ concentration were significantly decreased in these patients. Significant decreases in blood pressure, as well as significant increases of urinary kallikrein excretion and plasma 6-keto PGF₁ concentration after kallidinogenase administration were also observed.