Cutting edge: precursor frequency affects the helper dependence of cytotoxic T cells.

Generation of CTL immunity often depends on the availability of CD4 T cell help. In this report, we show that CTL responses induced by cross-priming can be converted from CD4-dependent to CD4-independent by increasing the frequency of CTL precursors. In the absence of CD4 T cells, high numbers of CTL precursors were able to expand in number and become effector CTL. The ability of high frequencies of CD8 T cells to override help was not due to their ability to signal CD40 via expression of CD154. These findings suggest that when precursor frequencies are high, priming of CD8 T cell responses may not require CD4 T cell help.     

SURROGATE MOTHERING:EXPLOITATION OR EMPOWERMENT?

The morality of surrogate mothering is analyzed from a "consequentialist" framework which attempts to separate those consequences that invariably accompany a given act from those that accompany it only in particular circumstances. Critics of surrogacy argue that it transfers the burden and risk of pregnancy onto another woman, separates sex and reproduction, and separates reproduction and childrearing; none of these acts is necessarily wrong, either morally or for women's or society's basic interests. While surrogate mothering can be rendered immoral if women are coerced into the practice or become victims of subordinating or penalizing contracts, it has the potential to empower women and increase their status in society by providing a job that is less risky and more enjoyable than other jobs women are forced to take and by achieving greater social recognition for reproductive labor.     

ARE PREGNANT WOMEN FETAL CONTAINERS?

Purdy explores the argument that women's rights to control their bodies should be subordinated to the welfare of their fetuses. She gives examples ofinstances where women's decisions about pregnancy and childbirth have been overridden by physicians and judges. She examines the nature of the mother fetus relationship, the social context of the current conflict between maternal and fetal rights, and the extent of a woman's legally enforceable duty to her fetus. Purdy acknowledges that women may owe a reasonable duty to their fetuses to try to prevent disease or handicap. However, given the uncertainties of modern medicine, the value-laden nature of many physicians' decisions, and the lack of adequate adequate prenatal care, women should not be held responsible for situations that are due largely to society's shortcomings. Purdy concludes that it is unjust to use the law to coerce women into accepting medical advice.     

Estrogen hydroxylase activity in the human placenta at term

Placental estrogen hydroxylase (EH) enzyme activity was measured at term using the catechol-O-methyl transferase coupled method in normal and high risk conditions. The identity and ratio of products formed during incubation of microsomes as analysed by high performance liquid chromatography in chronic hypertension, toxemia and diabetes mellitus was not different from controls. The mean enzymatic activity was also not different among the conditions studied as expressed mean +/- SE pmol/min/mg, protein: chronic hypertension (7.8 +/- 1), toxemia (8 +/- 1.6), diabetes mellitus (6.1 +/- 0.9) and controls (8.3 +/- 1.5). The cofactor dependence of EH was studied showing that NADPH is a better substrate for the enzyme than NADH.     

Construction of interleukin-1 alpha mutants using unequal contamination of synthetic oligonucleotides.

Proteins without readily available three-dimensional structural data present a difficult problem in the exploration of structure/function relationships. Saturation mutagenesis using contaminated oligonucleotides can identify potentially interesting regions of such a protein. This technique, in which synthesized oligonucleotides contain low-level base substitutions, allows random mutations to be placed throughout a gene sequence. Using double-stranded cassettes, a region of the human interleukin-1 alpha gene has been altered using such mutagenic oligonucleotides. However, instead of contaminating both strands of the gene sequence at the same level, each strand of the insert was contaminated at a different level. Several recombinants were sequenced and the effects of the mutations on the activity of the proteins were examined. Contaminating the two oligonucleotides at different levels produced a significantly different distribution of nucleotide changes from that seen if both strands were contaminated at the same level. The observed distribution followed the average of the distributions for each of the two contamination levels. This resulted in roughly equal frequencies of 1 to 5 nucleotide changes per clone with very few clones containing the wild-type nucleotide sequence. This helped overcome the redundancy in the genetic code, resulting in a high frequency of amino acid changes, and allowed changes at every amino acid to be sampled in a small number of mutants. This procedure can allow a gene sequence to be screened rapidly by removing most wild-type sequences from analysis while making sure that there are many amino acid changes in the resultant mutants.     

Acute lethality after x-irradiation of Tribolium confusum adults

Recently emerged adults of Tribolium confusum, maintained at 30° in flour-yeast medium, were exposed to X-ray doses between 8 and 75 kR at dose rates of 225 or 1000 R/min. In all cases, there was no significant mortality for about 10 days, and all deaths attributable to the irradiation occurred during the next 10 to 15 days; after the lower doses, many insects survived this critical period and then lived on for many months. The relative dose-independence of the survival-time of decedents suggested that there is a specific mode of death, i.e., an as-yet-unrecognized acute lethal syndrome. Irradiated beetles incubated at 22° exhibited about twice as great a delay in the onset of mortality, and a mortality period with about twice the duration, as those at 30°, suggesting the necessity of a sequence of metabolic events in the development of lethality. Beetles on a cornstarch diet were at least as radioresistant as beetles on flour yeast; beetles at 22° were distinctly more sensitive than those kept at 30°. Older beetles, exposed 4 or 10 months after emergence, showed progressive increases in acute radiosensitivity. Implications of these findings for radiobiological investigations on adult insects are discussed.

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Lethalite aigüe apres irradiation aux rayons X des adultes de Tribolium Confusum

Résumé La plupart des insectes utilisés dans les expériences de radiobiologie ont une longévité relativement brève à l'état adulte. De ce fait, il est difficile ou impossible de distinguer la mortalité aigüe liée à des mécanismes spécifiques d'une diminution nonspécifique de la résistance à un stress.La longévité des adultes de Tribolium rend possible de séparer ces deux catégories de réponses, elle peut aussi permettre la mise en évidence des différents modes de léthalité aigüe.Des adultes récemment formés de Tribolium confusum, maintenus à 30° dans le milieu farine-levure, ont été exposés à des doses de rayons X de 8 à 75 kR aux taux de 225 ou 1000 R/min. Dans tous les cas, il n'y a pas eu de mortalité significative pendant 10 jours, et toutes les morts attribuables à l'irradiation ont eu lieu au cours des 10 à 15 jours suivants; après les doses les plus faibles, beaucoup d'insectes ont survécu à cette période critique et ont alors vécu de nombreux mois. L'indépendance relative par rapport à la dose de la durée de la survie des descendants suggère l'existence d'un mode spécifique de mortalité, ou d'un syndrome léthal aigu.Les insectes irradiés en élevage à 22° ont présenté un délai de début de mortalité environ le double et une durée de la période de mortalité environ double de ceux enregistrés à 30°. Ceci représente un Q₁₀ d'environ 2,3, qui suggère la nécessité d'une succession de phénomènes métaboliques dans le développement de la léthalité.Des insectes sur un régime à base d'amidon de maïs étaient au moins aussi radiorésistants que ceux sur farine et levure; les insectes à 22° furent sans conteste plus sensibles que ceux élevés à 30°. Des coléoptères plus âgés, exposés 4 ou 10 mois après leur formation, ont montré des augmentations progressives dans la radiosensibilité aigüe.Ces résultats ont deux conséquences importantes pour d'autres recherches radiobiologiques sur les insectes adultes. La mise en évidence de l'existence d'un syndrome léthal spécifique et de ses délais de manifestation devrait accélérer l'analyse des facteurs intervenant dans la mort des insectes irradiés; d'autre part dans toute expérimentation radiobiologique sur des insectes adultes, les imagos doivent être d'un âge uniforme et connu.

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This work was supported by U. S. Public Health Service, NIH Grant GM-10208. During 1964–1965, the senior author held a Special Fellowship (1-F3-GM23423), U. S. Public Health Service, at the Department of Zoology, University of Cambridge; he is indebted to Professor C. F. A. Pantin, F. R. S., and other members of the Department, and especially to Dr. George Salt, F. R. S., both for extending use of their facilities and for many illuminating discussions.     

Rapid Extraction of DNA and rRNA from Sediments by a Novel Hydroxyapatite Spin-Column Method

We describe a novel hydroxyapatite spin-column method of nucleic acid extraction from natural sediments by which DNA and rRNA can be extracted separately. This very rapid method produces pure nucleic acid that can be utilized in some of the most common molecular biological procedures used in the analysis of natural microbial communities.