Respiratory and cardiovascular responses to hypoxia in the Australian lungfish

Simultaneous measurements of pulmonary blood flow (qPA), coeliacomesenteric blood flow (qCoA), dorsal aortic blood pressure (PDA), heart rate (fH) and branchial ventilation frequency (fv) were made in the Australian lungfish, /Neoceratodus forsteri, /during air breathing and aquatic hypoxia. The cho­linergic and adrenergic influences on the cardiovascular system were investigated during normoxia using pharmacological agents, and the presence of catecholamines and serotonin in different tissues was investi­gated using histochemistry. Air breathing rarely occurred during normoxia but when it did, it was always associated with increased pulmonary blood flow. The pulmonary vasculature is influenced by both a cho­linergic and adrenergic tonus whereas the coeliacomesenteric vasculature is influenced by a β-adrenergic vasodilator mechanism. No adrenergic nerve fibers could be demonstrated in /Neoceratodus /but catecholamine-containing endothelial cells were found in the atrium of the heart. In addition, serotonin-­immunoreactive cells were demonstrated in the pulmonary epithelium. The most prominent response to aquatic hypoxia was an increase in gill breathing frequency followed by an increased number of air breaths together with increased pulmonary blood flow. It is clear from the present investigation that /Neoceratodus /is able to match cardiovascular performance to meet the changes in respiration during hypoxia.

Asset Price Instability and Policy Responses: The Legacy of Liberalisation

The debate about the dynamics and potential policy responses to asset inflation has intensified in recent years. Some analysts, notably Borio and Lowe, have called for 'subtle' changes to existing monetary targeting frameworks to try to deal with the problems of asset inflation and have attempted to developed indicators of financial vulnerability to aid this process. In contrast, this paper argues that the uncertainties involved in understanding financial market developments and their potential impact on the real economy are likely to remain too high to embolden policy makers. The political and institutional risks associated with policy errors are also significant. The fundamental premise that a liberalised financial system is based on 'efficient' market allocation cannot be overlooked. The corollary is that any serious attempt to stabilize financial market outcomes must involve at least a partial reversal of deregulation.

Antibody responses and protective immunity to recombinant vaccinia virus-expressed bluetongue virus antigens

The role of individual viral proteins in the immune response to bluetongue virus (BTV) is not clearly understood. To investigate the contributions of the outer capsid proteins, VP2 and VP5, and possible interactions between them, these proteins were expressed from recombinant vaccinia viruses either as individual proteins or together in double recombinants, or with the core protein VP7 in a triple recombinant. Comparison of the immunogenicity of the vaccinia expressed proteins with BTV expressed proteins was carried out by inoculation of rabbits and sheep. Each of the recombinants was capable of stimulating an anti-BTV antibody response, although there was a wide range in the level of response between animals and species. Vaccinia-expressed VP2 was poorly immunogenic, particularly in rabbits. VP5, on the whole, stimulated higher ELISA titers in rabbits and sheep and in some animals in both species was able to stimulate virus neutralizing antibodies. When the protective efficacy of VP2 and VP5 was tested in sheep, vaccinia-expressed VP2, VP5 and VP2 + VP5 were protective, with the most consistent protection being in groups immunized with both proteins. (C) 1997 Elsevier Science B.V.

Analysis of tissue responses to fin tagging in Australian carcharhinids

Tissue responses to the application of Rototags and Jumbo Rototags in the first dorsal fin of Carcharhinus melanopterus, C. obscurus and C. plumbeus were examined. The acute response included tissue tearing and haemorrhage and was present by 5 days post-tagging. The intermediate response had begun by 20 days post-tagging and continued beyond 207 days. This response involved decreased red blood cell activity as the inflammatory response commenced. The chronic response had begun by 301 days and was complete by 553 days with a layer of fibrous connective tissue walling off the tag. External damage to the fin was caused by continued abrasion by the tag. Repair scales were observed at 242 days using scanning electron microscopy and were confirmed histologically in 61- and 553-day samples. Repair scales were not seen in areas of continuous abrasion. No infection was observed in tissues surrounding the wound. Disruption of the fin surface was observed due to abrasion by the tag, but did not appear to cause a severe tissue reaction. The tissue responses observed were consistent with a normal, but relatively slow, healing in the vicinity of the tag wound. Use of Rototags or Jumbo Rototags appears to be an efficient way of marking elasmobranchs with minimal damage to the shark. (C) 1998 The Fisheries Society of the British Isles.

Adjustment to a low-control situation: Reexamining the role of coping responses

The aim of the study was to test a revised conceptualization of the role of coping in adjustment to a low-control stressor-women's adjustment to a failed in vitro fertilization (NF) attempt. Data were collected prior to the IVF treatment (Time I) and twice after the failed NF attempt (1 to 2 weeks after finding out the results, n = 171, and fi weeks later, n = 139). Initial adjustment was assessed at Time I, whereas measures of coping and both self-report and partner ratings of adjustment were obtained at Times ? and 3. As predicted, escapist strategies and problem-management strategies (mainly at Time ?) were associated with poor adjustment, whereas problem-appraisal coping was associated with better adjustment., There was also support for the proposed positive relationship between adjustment and emotional approach coping (on self-report adjustment).

Vaccine-induced Th1-type responses are dominant over Th2-type responses in the short term whereas pre-existing Th2 responses are dominant in the longer term

The effect of adjuvant on induction of human papillomavirus type 16 E7 protein-specific cytotoxic T lymphocytes (CTL) and immunoglobulin G (IgG)(2a) antibody was studied in C57BL/6 J mice immunized with various adjuvants and E7 protein. Quil-A adjuvant, but not complete Freund's adjuvant (CFA) or Algammulin, induced a T-helper 1 (Th1)-type response to E7, which was characterized by CTL activity against a tumour cell line transfected with E7 protein and by E7-specific IgG(2a). All tested adjuvants elicited comparable levels of E7-specific IgG(1). The longest duration and greatest magnitude of CTL response was seen following two immunizations with the highest dose of E7 and Quil-A. Simultaneous immunization with a Th1 and a T helper 2 (Th2)-promoting adjuvant gave a Th1-type response. However, E7 and Quil-A were unable to induce a Th1-type response (as measured by the inability to generate anti-E7 IgG(2a) antibody) in animals with a pre-existing Th2-type response to E7. These results suggest that saponin adjuvants may be suitable for immunotherapy in humans where a Th1-type response is sought, provided that there is no pre existing Th2-type response to the antigen.

Effects of stimulus modality and task condition on blink startle modification and on electrodermal responses

Participants in Experiments 1 and 2 performed a discrimination and counting task to assess the effect of lead stimulus modality on attentional modification of the acoustic startle reflex. Modality of the discrimination stimuli was changed across subjects. Electrodermal responses were larger during task-relevant stimuli than during task-irrelevant stimuli in all conditions. Larger blink magnitude facilitation was found during auditory and visual task-relevant stimuli, but not for tactile stimuli. Experiment 3 used acoustic, visual, and tactile conditioned stimuli (CSs) in differential conditioning with an aversive unconditioned stimulus (US). Startle magnitude facilitation and electrodermal responses were larger during a CS that preceded the US than during a CS that was presented alone regardless of lead stimulus modality. Although not unequivocal, the present data pose problems for attentional accounts of blink modification that emphasize the importance of lead stimulus modality.

Likelihood-based estimation of the regression model with scrambled responses

A significant problem in the collection of responses to potentially sensitive questions, such as relating to illegal, immoral or embarrassing activities, is non-sampling error due to refusal to respond or false responses. Eichhorn & Hayre (1983) suggested the use of scrambled responses to reduce this form of bias. This paper considers a linear regression model in which the dependent variable is unobserved but for which the sum or product with a scrambling random variable of known distribution, is known. The performance of two likelihood-based estimators is investigated, namely of a Bayesian estimator achieved through a Markov chain Monte Carlo (MCMC) sampling scheme, and a classical maximum-likelihood estimator. These two estimators and an estimator suggested by Singh, Joarder & King (1996) are compared. Monte Carlo results show that the Bayesian estimator outperforms the classical estimators in almost all cases, and the relative performance of the Bayesian estimator improves as the responses become more scrambled.

Histologic and immunohistochemical responses after aortic valve allografts in the rat

Background. Human aortic valve allografts elicit a cellular and humoral immune response. It is not clear whether this is important in promoting valve damage. We investigated the changes in morphology, cell populations, and major histocompatibility complex antigen distribution in the rat aortic valve allograft. Methods. Fresh heart valves from Lewis rats were transplanted into the abdominal aorta of DA rats. Valves from allografted, isografted, and presensitized recipient rats were examined serially with standard morphologic and immunohistochemical techniques. Results. In comparison with isografts, the allografts were infiltrated and thickened by increased numbers of CD4(+) and CD8(+) lymphocytes, macrophages, and fibroblasts. Thickening of the valve wall and leaflet and the density of the cellular infiltrate was particularly evident after presensitization. Endothelial cells were frequently absent in presensitized allografts whereas isografts had intact endothelium. Cellular major histocompatibility complex class I and II antigens in the allograft were substantially increased. A long-term allograft showed dense fibrosis and disruption of the media with scattered persisting donor cells. Conclusions. The changes in these aortic valve allograft experiments are consistent with an allograft immune response and confirm that the response can damage aortic valve allograft tissue. (C) 1998 by The Society of Thoracic Surgeons.

Cytomegalovirus evasion of natural killer cell responses

Natural killer (NK) cells are an important component of the innate cellular immune system. They are particularly important during the early immune responses following virus infection, prior to the induction of cytotoxic T cells (CTL). Unlike CTL, which recognize specific peptides displayed on the surface of cells by class I MHC, NK cells respond to aberrant expression of cell surface molecules, in particular class I MHC, in a non-specific manner. Thus, cells expressing low levels of surface class I MHC are susceptible to recognition by NK cells, with concomitant triggering of cytolytic and cytokine-mediated responses. Many viruses, including the cytomegaloviruses, downregulate cell surface MHC class I: this is likely to provide protection against CTL-mediated clearance of infected cells, but may also render infected cells sensitive to NK-cell attack. This review focuses upon cytomegalovirus-encoded proteins that are believed to promote evasion of NK-cell-mediated immunity. The class I MHC homologues, encoded by all cytomegaloviruses characterised to date, have been implicated as molecular 'decoys', which may mimic the ability of cellular MHC class I to inhibit NK-cell functions. Results from studies in vitro are not uniform, but in general they support the proposal that the class I homologues engage inhibitory receptors from NK cells and other cell types that normally interact with cellular class I. Consistent with this, in vivo studies of murine cytomegalovirus indicate that the class I homologue is required for efficient evasion of NK-cell-mediated clearance. Recently a second murine cytomegalovirus protein, a C-C chemokine homologue, has been implicated as promoting evasion of NK and T-cell-mediated clearance in vivo.

Human and murine cytomegalovirus evasion of cytotoxic T lymphocyte and natural killer cell-mediated immune responses

Herpesviruses, such as human and murine cytomegalovirus, possess an impressive array of genes believed to assist in virus survival against the host immune response. In this review, we cover the rapidly growing area of cytomegalovirus evasion of cellular immunity, specifically cytotoxic T lymphocytes and natural killer cells. The proposed mechanisms of action of viral proteins involved in blocking peptide presentation to CD8(+) T cells, namely, interference with peptide generation, inhibition of peptide assembly with class I MHC and retention/destabilization of class I MHC complexes, are described. In addition, recent evidence implicating the viral class I MHC-like proteins as inhibitors of natural killer cell-mediated clearance is reviewed, (C) 1998 Academic Press.

Bird responses at inherent and induced edges in the Murray Mallee, South Australia. 1. Differences in abundance and diversity

We quantified differences in the abundance and diversity of bird species at inherent (naturally occurring) and induced (human-created) edges in the Murray Mallee, South Australia, to explore the effects of anthropogenic landscape modification. Bird species were classified into edge response categories based on numerical differences in abundance between the edge and interior of habitat patches. 'Open-country' species (e.g. Australian Magpie and Little Raven) increased in abundance near induced edges, but were rarely recorded > 200 m into patch interiors or at inherent edges. The Australian Ringneck, Red Wattlebird, Spiny-cheeked Honeyeater, Singing Honeyeater and White-eared Honeyeater increased in abundance near each inherent edge and were classified as 'edge-users'. However, their responses at induced edges varied between sites. The Yellow-plumed Honeyeater, Spotted Pardalote, White-browed Babbler, Chestnut Quail-thrush and Southern Scrub-robin decreased in abundance near one or more induced edges and were classified as 'edge-avoiders' at these sites. The Yellow-plumed Honeyeater, Spotted Pardalote, Chestnut Quail-thrush and Southern Scrub-robin are considered mallee habitat specialists in eastern Australia. These species may be particularly affected by anthropogenic modification of mallee vegetation.