A close halo of large transparent grains around extreme red giant stars

An intermediate-mass star ends its life by ejecting the bulk of its envelope in a slow, dense wind. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust, which is then accelerated by radiation pressure, entraining the gas and driving the wind. Explaining the amount of mass loss, however, has been a problem because of the difficulty of observing tenuous gas and dust only tens of milliarcseconds from the star. For this reason, there is no consensus on the way sufficient momentum is transferred from the light from the star to the outflow. Here we report spatially resolved, multiwavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the Hertzsprung-Russell diagram. When imaged in scattered light, dust shells were found at remarkably small radii (less than about two stellar radii) and with unexpectedly large grains (about 300 nanometres in radius). This proximity to the photosphere argues for dust species that are transparent to the light from the star and, therefore, resistant to sublimation by the intense radiation field. Although transparency usually implies insufficient radiative pressure to drive a wind, the radiation field can accelerate these large grains through photon scattering rather than absorption--a plausible mass loss mechanism for lower-amplitude pulsating stars.     

A Cenozoic record of the equatorial Pacific carbonate compensation depth

Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5?kilometres during the early Cenozoic (approximately 55?million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.     

Isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla

Biologically active peptide hormones and neurotransmitters have been shown to be enzymatically liberated from larger, inactive precursor molecules by tissue-specific post-translational processing, particularly at the typical cleavage signals of paired basic residues. Subsequent N-terminal or C-terminal modifications may be of importance in regulating the biological activities of these peptides. C-terminal alpha-amidation is considered to be essential for the biological function of several non-opioid peptides. Here we present the isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla. Amidorphin and the recently isolated octapeptide metorphamide (adrenorphin) are the only endogenous opioid peptides in mammals known to possess a C-terminal amide group. The amino acid sequence of amidorphin corresponds to the sequence 104-129 of bovine proenkephalin A. Very high concentrations of amidorphin were detected in bovine adrenal medulla and in a further endocrinological system, the hypothalamic-neurohypophyseal axis. Amidorphin may therefore be considered to be a major gene product of the opioid peptide precursor proenkephalin A in these endocrine tissues.     

Resistance of mice suppressed for IgM production to Babesia microti infection.

The immunological mechanisms responsible for overcoming infections with Babesia, an intra-erythrocytic protozoan, are not fully understood. Although high titres of specific anti-babesial antibodies have been observed in several species of animals, and protection has been obtained by transfer of large volumes of recovery serum, the role of antibody in the immune response to an infection is uncertain. The present study investigates the nature of B-cell participation during Babesia microti infections by observing the course of the disease in mice in which IgM production has been suppressed from birth and which contain no B cells. The results show that, in contrast to control mice, which develop and subsequently clear circulating parasitaemias, suppressed mice show an unexpected resistance to infection as reflected by a virtual absence of parasites in the peripheral circulation.     

32P, 33P and 35S: selecting a label for nucleic acid analysis.

The advent of 33P nucleotide triphosphates has widened the options available for labelling nucleic acids. Choosing the most appropriate label requires a careful consideration of experimental needs and circumstances.     

Effects of monovalent cations on the responses of motoneurones to different groups of amino acid excitants in frog and rat spinal cord

Summary Classification of excitatory amino acids into different groups, of possible value for transmitter identification, can be made on the basis of the differential effects of altered external [Na⁺] and [K⁺] on motoneurone depolarization in frog and immature rat spinal cord.Acknowledgments. We thank Mr D. J. Oakes for skilled technical assistance. This work was supported from the Medical Research Council.     

Unborn children (protection) bill

Enoch Powell's Unborn Children (Protection) Bill passed a second reading in the British House of Commons on 22 February 1985. The authors contend that most informed scientists are dismayed because, if enacted into law, the bill would criminalize the in vitro fertilization of any human oocytes except for purposes of "embryo insertion," and many promising avenues of research would be blocked. While the pro-life lobby maintains that the development of possible methods to cure genetic diseases does not require research on human embryos, Evans and McLaren cite scientific data to argue that such research is necessary to insure that embryos chosen for implantation are chromosomally normal, to study the etiology of chromosomal disorders and eventually develop therapies for them, to improve IVF procedures, and to develop new contraceptive techniques.