The extent and patterns of usage of Agent Orange and other herbicides in Vietnam

Herbicides including Agent Orange were sprayed by United States forces for military purposes during the Vietnam War (1961-1971) at a rate more than an order of magnitude greater than for similar domestic weed control. In 1974, the US National Academy of Sciences published estimates of the extent and distribution of herbicides sprayed. Here we present revised estimates, developed using more-complete data. The spray inventory is expanded by more than seven million litres, in particular with heavily dioxin-contaminated herbicides. Estimates for the amount of dioxin sprayed are almost doubled. Hamlet census data reveal that millions of Vietnamese were likely to have been sprayed upon directly. Our identification of specific military herbicide targets has led to a more coherent understanding of spraying. Common errors in earlier interpretations of the spray data are also discussed.     

Cold exposure: Effects on hepatic tryptophan oxygenase and tyrosine aminotransferase,plasma tryptophan and tyrosine,and brain monoamines

Résumé L'exposition des souris à une basse temp'erature a abouti à la production rapide de tryptophane oxygénase et de tyrosine aminotransférase. Malgré l'augmentation de l'activité enzymatique, les niveaux plasmatiques de tryptophane et de tyrosine furent augmentés d'une manière significative pendant le temps de l'exposition. Les niveaux de norepinéphrine et de sérotonine du cerveau n'en ont cependant pas été affectés.

---

---

Acknowledgment. The authors would like to thank Army SP'sM. Devine, T. Nielson, andG. Johnson for expert technical assistance.

---

In counducting the research described in this report, the investigators adhered to the Guide for Laboratory Animal Facilities and Care, as promulgated by the Committee on the Guide for Laboratory Animal Facilities and Care of the Institute of Laboratory Animal Resources, National Academy of Sciences — National Research Council.     

Strategies for dissecting epigenetic mechanisms in the mouse

Epigenetics generally refers to heritable changes in gene expression that are independent of nucleotide sequence. With complete genome sequences in hand, understanding the epigenetic control of genomes is the next step towards comprehending how the same DNA sequence gives rise to different cells, lineages and organs. Epigenetics also contributes to individual variation in normal biology and in disease states. The mouse provides a unique opportunity to understand how epigenetic differences contribute to both development and disease in a tractable mammalian system. Here we discuss current approaches and protocols used to study epigenetics in the mouse, including loss-of-function studies, mutagenesis screens, somatic cell nuclear transfer, genomics and proteomics.     

Effects of sleep deprivation on the periodicity of tyrosine metabolism in mice

Résumé La privation de sommeil pendant 96 h a crée des ruptures dans la périodicité d'enzyme-tyrosine-aminotransférase du foie, à cause de l'induction. Des concentrations hépatiques de tyrosine ont augmenté alors que sa présence dans le plasma fut sans effet. La privation de sommeil affecte non seulement les rhythmes quotidiens naturels, mais, si elle est prolongée, elle intensifie la réponse de «stress» généralisé peut-être au point d'affecter notablement l'effet de l'acide amidé.

---

---

Acknowledgments. We wish to express our appreciation to SP-5R. Cotter and SP-5 Th.Speitel for their technical assistance.     

The composition of Taft E s o constants: An application of biased alternatives to least squares

Summary A systematic analysis of the composition of E _s ^o like rate constants clearly revealed that Taft E _s ^o -values depend upon the size of the substituents. Further evidence in favor of this view is adduced even in a case where OLS led to the conclusion that E _s ^o should be completely independent of the size of the substituents, since biased estimators (PCRA, LRRA) showed that this statement is not correct. Furthermore, it seems that the magnitude of the steric effect represented by E _s ^o is a function of the thickness of the substituent along 2 directions perpendicular on its main axis and is not influenced by its length.Acknowledgment. We would like to thank Prof. J.T. Webster, Department of Statistics, Southern Methodist University, Dallas, for sending us s computer program of latent root regression analysis. We also thank the referees whose insightful comments were most helpful in improving the presentation.