Induced magnetic fields as evidence for subsurface oceans in Europa and Callisto

The Galileo spacecraft has been orbiting Jupiter since 7 December 1995, and encounters one of the four galilean satellites-Io, Europa, Ganymede and Callisto-on each orbit. Initial results from the spacecraft's magnetometer have indicated that neither Europa nor Callisto have an appreciable internal magnetic field, in contrast to Ganymede and possibly Io. Here we report perturbations of the external magnetic fields (associated with Jupiter's inner magnetosphere) in the vicinity of both Europa and Callisto. We interpret these perturbations as arising from induced magnetic fields, generated by the moons in response to the periodically varying plasma environment. Electromagnetic induction requires eddy currents to flow within the moons, and our calculations show that the most probable explanation is that there are layers of significant electrical conductivity just beneath the surfaces of both moons. We argue that these conducting layers may best be explained by the presence of salty liquid-water oceans, for which there is already indirect geological evidence in the case of Europa.     

Amino acid sequence of a four-iron-four-sulphur ferredoxin isolated from Bacillus stearothermophilus

A novel method of RNA fractionation based on a gradual release of the RNA molecules from ribonucleoprotein complexes has been used for the analysis of ribosomal and non-ribosomal complexes of rat liver cytoplasm. Adsorption of native ribonucleoproteins on a Celite column (occuring through only the protein moiety) followed by a consequent dissociation of RNP complexes brought about by various agents results in RNA fractionation in accordance with the tightness of the RNA-protein bonds. The cytoplasmic ribosomal and rapidly labelled non-ribosomal RNA species are separated into several fractions identified as 18S and 28S rRNA's, mRNA and messenger-like RNA. A relatively small fraction (about 10% of the total) of rRNA tenaciously bound to protein has been also revealed.     

False aneurysm of the ascending aorta after surgery for Marfan's syndrome. Report of a case and review of the literature

A case is described in which false aneurysm of the ascending aorta developed following corrective surgery for Marfan's syndrome. During the initial procedure, a dissecting aortic aneurysm and incompetent aortic valve were managed by replacing the valve with a Starr-Edwards prosthesis and the ascending aorta with a woven Dacron aortic prosthesis. Two years later the operation was repeated with the use of antibiotic cover, because the patient developed a paraprosthetic leak following subacute bacterial endocarditis with Staphylococcus aureus. The woman remained well for 6 months, after which she developed a false aneurysm of the ascending aorta and aortic incompetence which necessitated repeating the operation for a third time. The patient remains well one year later. Relevant literature available on false aneurysm of the ascending aorta is also reviewed.     

Hepatic sinusoidal responses to intraportal injections of phenylephrine and isoprenaline in the rat

1. Specific alpha- and beta-adrenoreceptor agonists, phenylephrine and isoprenaline, were injected intraportally into the intact rat liver under direct microscopic observation by an in vivo transillumination technique. 2. The diameter of a hepatic sinusoid and the intra-sinusoidal erythrocyte velocity were quantitatively measured, and the sinusoidal volume flow was calculated from these two parameters. 3. Results show that phenylephrine causes a sinusoidal constriction and an increased sinusoidal blood flow, whereas isoprenaline causes the opposite effects on the sinusoids. 4. All the sinusoidal responses to phenylephrine and isoprenaline were dose-dependent and were possibly related to the direct effect of these drugs on the sinusoids.     

Toward a pluralistic animal science: postliberal feminist perspectives

Women have not had the authority to define the conditions of animal agriculture or to develop strategies for addressing its problems because the field of animal science has been and remains dominated by men. Therefore, criteria for assessing the professional performance of animal scientists reflect the views of men and the experiences of masculinity. Recent attempts to improve the retention rates of women in the animal science profession have focused on socializing female protégés to the norms and expectations of the discipline. This approach is based on traditional liberal beliefs that all humans are essentially alike and that embodiment and(or) social location are irrelevant in understanding the world. Such socialization assumes that problems of gender inequity can be solved by providing opportunities for women to succeed in the existing system, with its existing norms. This approach ignores the possibility that the structure of women's lives and the normative commitments arising from women's experiences may be quite different from those of men. Professional reward structures that favor the life experiences and perspectives of men and ignore those of women coerce women into adopting values that may be incompatible with their identities. This not only devalues their perspectives and contributions, it forces them to commit self-betrayal. This is both harmful and antithetical to the idea of an empirically relevant science that blends multiple perspectives and understands diverse values. Substantive diversity in the animal science community requires standards that reflect and accommodate the pluralism in which we live.     

Temporal aspects of the effects of cooling on responses of single auditory nerve fibers

During an investigation of the effects of cochlear cooling on frequency tuning and input/output relations of single auditory nerve fibers in gerbil (Ohlemiller and Siegel (1994) Hear. Res. 80, 174-190), cooling-related changes in post-stimulus time histogram (PSTH) shape and phase-locking to tonebursts were characterized in a small sample of neurons. Local cochlear cooling by 5-10 degrees C below normal core temperature did not alter overall PSTH shape, although some evidence was found for a reduction in the time constants of rapid and short term rate adaptation. The relative contributions of rapid and short term response components appeared unaltered. Effects of cooling on phase-locking were assessed by calculating the synchronization index for responses to intense ( > 70 dB SPL) tonebursts at 0.5, 1.0, and 2.0 kHz. Synchronization filter functions exhibited modest reductions in both magnitude and the upper frequency limit of phase-locking. The effects of cooling on the temporal character of responses appear distinct from those of a simple reduction in stimulus intensity. Results are interpreted in terms of cooling-related changes in responses of cochlear hair cells and afferent neurons, and suggest that temperature artifacts are unlikely to underlie reported species differences in PSTH shape and phase-locking.