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Bandicoots and bilbies (Order Peramelemorphia) occupy a broad range of habitats across Australia and New Guinea, from open, arid deserts to dense forests. This once diverse group has been particularly vulnerable to habitat loss and introduced eutherian predators, and numerous species extinctions and range retractions have occurred. Understanding reasons for this loss requires greater understanding of their biology. Morphology of the pinnae and tympanic bullae varies markedly among species. As hearing is important for both predator avoidance and prey location, the variability in ear morphology could reflect specialization and adaptation to specific environments, and therefore be of conservation relevance. We measured 798 museum specimens representing 29 species of Peramelemorphia. Controlling for phylogenetic relatedness and head length, pinna surface area was weakly negatively correlated with average precipitation (rainfall being our surrogate measure of vegetation productivity/complexity), and there were no environmental correlates with effective diameter (pinna width). Controlling for phylogenetic relatedness and skull length, tympanic bulla volume was negatively correlated with precipitation. Species that inhabited drier habitats, which would be open and allow sound to carry further with less obstruction, had relatively larger pinnae and tympanic bullae. In contrast, species from higher rainfall habitats, where sounds would be attenuated and diffused by dense vegetation, had the smallest pinnae and bullae, suggesting that low-frequency hearing is not as important in these habitats. Associations with temperature did not reach statistical significance. These findings highlight linkages between hearing traits and habitat that can inform conservation and management strategies for threatened species. [ABSTRACT FROM AUTHOR]

Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and function. Here, we characterize the shape variation among 84 marsupial cranial endocasts of 57 species including fossils, using three‐dimensional geometric morphometrics and virtual dissections. Statistical shape analysis revealed four main patterns: over half of endocast shape variation ranges from elongate and straight to globular and inclined; little allometric variation with respect to centroid size, and none for relative volume; no association between locomotion and endocast shape; limited association between endocast shape and previously published histological cortex volumes. Fossil species tend to have smaller cerebral hemispheres. We find divergent endocast shapes in closely related species and within species, and diverse morphologies superimposed over the main variation. An evolutionarily and individually malleable brain with a fundamental tendency to arrange into a spectrum of elongate‐to‐globular shapes—possibly mostly independent of brain function—may explain the accommodation of brains within the enormous diversity of mammalian skull form. [ABSTRACT FROM AUTHOR]

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Since 1993, trends in perinatal human immunodeficiency virus (HIV) transmission have been monitored by use of chart review of patients identified at a central diagnostic laboratory. In the population studied, either pre- or postnatal antiretroviral therapy to the infant increased from 21% in 1993 to 95% in 1997. Concurrently, the number of HIV-infected infants declined from 25 in 1993 to 4 in 1997. The complete Pediatric AIDS Clinical Trials Group Protocol 076 regimen was the most effective in reducing transmission (3.1%). Twenty-two of 35 infants who became infected in 1995-1997 had mothers who did not receive antiretroviral therapy, although counseling practices improved with time. In 1995, 87% of the mothers of HIV-seropositive infants were counseled, whereas in 1997, 96% were counseled (P<.005). None of 59 infants tested had high-level phenotypic zidovudine resistance, although 5 (8.8%) of 57 infants had virus isolates with at least one mutation in the reverse transcriptase gene associated with reduced phenotypic susceptibility to zidovudine. Copyright © 1999 The University of Chicago [ABSTRACT FROM AUTHOR]

The effects of combining diltiazem, a calcium channel blocking agent, with beta adrenergic blockade were evaluated in 11 patients with obstructive coronary artery disease. All patients had stable angina pectoris and were receiving oral beta blocking therapy. Symptomatic, metabolic, coronary and systemic haemodynamic responses were monitored at rest and during atrial pacing. Following the administration of diltiazem, resting arterial blood pressure, systemic vascular resistance and heart rate fell significantly with no adverse effects on left ventricular function. During pacing diltiazem produced significant decreases in rate-pressure product and myocardial oxygen consumption. As a consequence there was a significant increase in mean pacing time to angina from 151±42 to 406±72s (P0.001). Concomitantly, myocardial lactate extraction was improved significantly from mean lactate production of −2±12% to mean lactate extraction of 12±7% (P>0.05). This study indicates that intravenous diltiazem can be administered to patients receiving chronic oral beta blockade without adverse haemodynami>c effects and that combination therapy has significant beneficial effects in coronary artery disease. [ABSTRACT FROM PUBLISHER]

The mechanisms underlying the abnormal responses to orthostatic stress in congestive heart failure are ill defined and little is known about the effects of specific therapy. In the present study intravascular pressures and plasma noradrenaline levels were measured in nine patients with heart failure subjected to 45° and 90° upright tilt. Studies were repeated during 4 weeks of vasodilator therapy with felodipine and again after felodipine withdrawal. Before the introduction of vasodilator therapy, tilt did not activate orthostatic reflexes despite significant reductions in left ventricular filling pressure and cardiac output. Thus, plasma noradrenaline, heart rate and systemic vascular resistance were unaffected and blood pressure fell. Felodipine resulted in a rapid and sustained improvement in left ventricular function but restoration of orthostatic reflexes was delayed and could be detected only after 48 h therapy. At this time, and during the subsequent 4 weeks, tilt-induced reductions in ventricular filling and cardiac output produced a normal rise in plasma noradrenaline and heart rate. A postural drop in blood pressure, however, was not averted because the direct action of felodipine on vascular smooth muscle prevented adrenergically-mediated increments in systemic vascular resistance. Felodipine withdrawal led to a prompt deterioration in left ventricular function. Orthostatic reflexes, however, were still intact 48 h later when tilt elicited a completely normal pattern of responses.These observations confirm that the abnormal responses to orthostatic stress in congestive heart failure are due principally to impairment of autonomic control mechanisms and are not related to the absence of venous pooling. Importantly the autonomic dysfunction is reversible with felodipine therapy. There is pronounced temporal dissociation between the changes in reflex responsiveness and the changes in left ventricular function. [ABSTRACT FROM PUBLISHER]

In an examination of the interaction between metazoan and bacterial pathogens, a laboratory model was developed with Nematospiroides dubius (a parasite of the upper intestine of the mouse) and enteropathogenic Escherichia coli O127. Weanling mice infected with N. dubius were orally inoculated with E. coli, and the distribution of both agents was studied in three 120-mm segments of intestine. In parasitized animals numbers of E. coli were 102–103 times greater in the lumen and wall of all portions of the intestine; the increase was most marked in the upper two segments. Although no bacteria were found in the liver of mice that were not parasitized, 103 E. coli/ g of tissue were cultured from parasitized animals. The altered distribution of E. coli was reflected by a greatly increased specific immune response. The mean number of plaque-forming cells to E. coli in the spleens of mice infected with N. dubius was 53,501, as compared with 1,497 in controls that were not parasitized (P < 0.001). These findings suggest that certain gastrointestinal parasites alter the growth and distribution of enteropathogenic E. coli, promoting colonization of the upper intestine where these organisms exert their pathogenicity. [ABSTRACT FROM PUBLISHER]

The establishment and course of a benign enteric infection with Escherichia coli O127 was studied in adult mice specifically immunized by the parenteral and oral routes, and in infant animals born and suckling of mothers immunized with E. coli O127 antigens. Although parenteral injection of living, formalinized, or heat-killed E. coli resulted in the production of intestinal as well as circulating antibody, it had no effect on the establishment, course, or duration of colonization in adult mice. Neither active oral immunization with 0 antigen nor passive oral immunization with specific immune sera had any effect; oral infection with E. coli O127 did not reduce susceptibility to reinfection two to three months later. Enteric colonization of infant animals born and suckling of immune mothers was not inhibited, as judged by the 50% infectious dose or rates of natural colonization with E. coli O127 from their mother's stools. Although bacteremia with E. coli O127 was less frequent in infants of immunized mothers, these infants acquired E. coli in liver and spleen as did nonimmune infants. Findings suggest that colonization of the intestine with certain strains of E. coli is not significantly affected by local or circulating antibody. [ABSTRACT FROM PUBLISHER]

X-linked immune deficient (Xid) mice fail to produce anti-phosphocholine (PC) antibodies even after immunization with Streptococcus pneumoniae. Consequently, Xid mice are extremely susceptible to infection with S. pneumoniae, PC-specific B cells appear to undergo clonal deletion in Xid mice; however, a new thymus-dependent form of PC, 6-(O-phosphocholine)hydroxyhexanoate (EPC), can rescue PC-specific B cells from the bone marrow presumably by providing T cell help before clonal deletion. Analysis of PC-specific IgG hybridomas from Xid mice revealed utilization of several V-D junctional variants of the VH1 gene segment rearranged to different D and JH gene segments. The majority of Xid anti-PC antibodies exhibit an Asp-->Gly95H replacement at the V-D junction. These Gly95H VH1 variants associate with kappa 1C L chains to produce anti-PC antibodies that: (1) have low relative affinity for PC, (ii) are heteroclitic for nitrophenylphosphocholine and (iii) fall to bind to or provide protection against S. pneumoniae. Single prototypic V-D variants of the T15 idiotype (Asp95H), M603 idiotype (Asn95H) and M167 idiotype (Asp95H-Ala96H) were also induced in Xid mice. The M603-like and M167-like antibodies bound to and protected against S. pneumoniae even though they exhibited Kas for PC which were lower than T15 idiotype+ antibodies. These data demonstrate that small changes in the V-D junctional sequence of the T15 (VH1) heavy chain alter L chain usage and the structure of the PC binding site so that the PC expressed on S. pneumoniae is no longer recognized. [ABSTRACT FROM AUTHOR]