Haptic information stabilizes and destabilizes coordination dynamics

Goal-directed, coordinated movements in humans emerge from a variety of constraints that range from 'high-level' cognitive strategies based oil perception of the task to 'low-level' neuromuscular-skeletal factors such as differential contributions to coordination from flexor and extensor muscles. There has been a tendency in the literature to dichotomize these sources of constraint, favouring one or the other rather than recognizing and understanding their mutual interplay. In this experiment, subjects were required to coordinate rhythmic flexion and extension movements with an auditory metronome, the rate of which was systematically increased. When subjects started in extension on the beat of the metronome, there was a small tendency to switch to flexion at higher rates, but not vice versa. When subjects: were asked to contact a physical stop, the location of which was either coincident with or counterphase to the auditor) stimulus, two effects occurred. When haptic contact was coincident with sound, coordination was stabilized for both flexion and extension. When haptic contact was counterphase to the metronome, coordination was actually destabilized, with transitions occurring from both extension to flexion on the beat and from flexion to extension on the beat. These results reveal the complementary nature of strategic and neuromuscular factors in sensorimotor coordination. They also suggest the presence of a multimodal neural integration process-which is parametrizable by rate and context - in which intentional movement, touch and sound are bound into a single, coherent unit.

Further studies on an intermediate host murine model showing that a primary Echinococcus granulosus infection is protective against subsequent oncospheral challenge

We describe the use of a murine model to evaluate resistance against subsequent challenge following a primary infection with oncospheres of Echinococcus granulosus. Mice (Kunming strain) were infected with hatched oncospheres of Echinococcus granulosus; 21 days later a second challenge was given by a different route of infection. A primary infection by intraperitoneal (i.p.) injection stimulated 100 and 90.5% protection in terms of reduced cyst numbers against a secondary infection given subcutaneously (s.c.) or intravenously (i.v.) respectively. A primary infection given s.c. followed by i.p. or i.v. challenge resulted in 84.0 and 100% protection, respectively. Intravenous infection followed by i.p. or s.c. challenge resulted in 98.5 and 69.4% protection, respectively. With the i.v. route of infection, almost all resultant cysts were present in the lungs. The data show that a primary infection with oncospheres can induce total or a high degree of protection against a subsequent challenge and confirms that natural (concomitant) immunity can be stimulated in the intermediate host as the result of a primary infection. This may explain the decline in hydatid infection in sheep older than 2 years in hyper-endemic areas such as those found in Xingjiang, China. These older sheep may have been earlier infected and have subsequently self-cured, with the primary infection stimulating an immune response that protects the intermediate host animals from further infection. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

Outcomes of cephalosporin treatment for serious infection due to apparently susceptible organisms producing extended-spectrum b-Lactamases: Implications for the clinical microbiology laboratory

Although extended-spectrum beta-lactamases (ESBLs) hydrolyze cephalosporin antibiotics, some ESBL-producing organisms are not resistant to all cephalosporins when tested in vitro. Some authors have suggested that screening klebsiellae or Escherichia coli for ESBL production is not clinically necessary, and when most recently surveyed the majority of American clinical microbiology laboratories did not make efforts to detect ESBLs, We performed a prospective, multinational study of Klebsiella pneumoniae bacteremia and identified 10 patients who were treated for ESBL-producing K. pneumoniae bacteremia with cephalosporins and whose infecting organisms were not resistant in vitro to the utilized cephalosporin. In addition, we reviewed 26 similar cases of severe infections which had previously been reported. Of these 36 patients, 4 had to be excluded from analysis. Of the remaining 32 patients, 100% (4 of 4) patients experienced clinical failure when MICs of the cephalosporin used for treatment were in the intermediate range and 54% (15 of 28) experienced failure when MICs of the cephalosporin used for treatment were in the susceptible range, Thus, it is clinically important to detect ESBL production by klebsiellae or E, coli even when cephalosporin MICs are in the susceptible range (less than or equal to 8 mug/ml) and to report ESBL-producing organisms as resistant to aztreonam and all cephalosporins (with the exception of cephamycins).

The effects of stress management on symptoms of upper respiratory tract infection, secretory immunoglobulin A, and mood in young adults

Objective: To investigate the efficacy of a stress management programme on symptoms of colds and influenza in 27 university students before and after the examination period. Method: The incidence of symptoms, levels of negative affect, and secretion rate of secretory immunoglobulin A (sIgA) were recorded for 5 weeks before treatment, for the 4 weeks of treatment, and for 8 weeks after treatment in treated subjects and in 25 others who did not participate in stress management. Results: Symptoms decreased in treated subjects but not in controls during and after the examination period. Although sIgA secretion rate increased significantly after individual sessions of relaxation, resting secretion rate of sIgA did not increase over the course of the study. Negative affect decreased after examinations in both groups, but was not affected by treatment. Conclusion: Stress management reduced days of illness independently of negative affect and sIgA secretion rate. Although the component of treatment responsible for this effect has yet to be identified, psychological interventions may have a role in reducing symptoms of upper respiratory tract infection. (C) 2001 Elsevier Science Inc. All rights reserved.

Tidal effects on groundwater dynamics in unconfined aquifers

The variation of seawater level resulting from tidal fluctuations is usually neglected in regional groundwater flow studies. Although the tidal oscillation is damped near the shoreline, there is a quasi-steady-slate rise in the mean water-table position, which may have an influence on regional groundwater flow. In this paper the effects of tidal fluctuations on groundwater hydraulics are investigated using a variably saturated numerical model that includes the effects of a realistic mild beach slope, seepage face and the unsaturated zone. In particular the impact of these factors on the velocity field in the aquifer is assessed. Simulations show that the tidal fluctuation has substantial consequences for the local velocity field in the vicinity of the exit face, which affects the nearshore migration of contaminant in coastal aquifers. An overheight in the water table as a result of the tidal fluctuation is observed anti this has a significant effect on groundwater discharge to the sea when the landward boundary condition is a constant water level. The effect of beach slope is very significant and simplifying the problem by considering a vertical beach face causes serious errors in predicting the water-table position and the groundwater flux. For media with a high effective capillary fringe, the moisture retained above the water table is important in determining the effects of the tidal fluctuations. Copyright (C) 2001 John Wiley & Sons, Ltd.

Dynamics of a mesoscopic charge quantum bit under continuous quantum measurement

We present the conditional quantum dynamics of an electron tunneling between two quantum dots subject to a measurement using a low transparency point contact or tunnel junction. The double dot system forms a single qubit and the measurement corresponds to a continuous in time readout of the occupancy of the quantum dot. We illustrate the difference between conditional and unconditional dynamics of the qubit. The conditional dynamics is discussed in two regimes depending on the rate of tunneling through the point contact: quantum jumps, in which individual electron tunneling current events can be distinguished, and a diffusive dynamics in which individual events are ignored, and the time-averaged current is considered as a continuous diffusive variable. We include the effect of inefficient measurement and the influence of the relative phase between the two tunneling amplitudes of the double dot/point contact system.

Rapid transplacental infection with bovine pestivirus following intranasal inoculation of ewes in early pregnancy

Despite the importance of congenital viral infections in both veterinary and human medicine, only limited experimental work has been carried out to elucidate the mechanisms involved in transplacental virus infections. To further an understanding of fetal infection with pestiviruses, the distribution of bovine pestivirus in the uterine and fetal tissues of ewes in early pregnancy, following a natural route of infection, was investigated. On the 18th day of pregnancy, nine ewes were inoculated by the intranasal route with 1 X 10(5) 50% tissue culture infective doses of an Australian isolate of noncytopathic bovine pestivirus (bovine viral diarrhea virus genotype 1). All ewes were ovariohysterectomized at approximately 100 hours postinfection. Samples from the reproductive tract and conceptus were examined histologically and tested for bovine pestivirus by nested reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry and for interferon-tau mRNA expression by nonnested RT-PCR. Although no histopathologic changes were observed in the maternal or fetal tissues, virus was detected in the reproductive tract of all nine ewes and in all of the conceptuses examined. Al; the time of surgery, only two of the nine ewes were demonstrably viremic. This study demonstrates that bovine pestivirus can spread from a natural site of infection to the ovine fetus within 4 days in the absence of maternal immunity and despite the presence of interferon expression in the reproductive tract.

Reproductive dynamics of endeavour prawns, Metapenaeus endeavouri and M-ensis, in Albatross Bay, Gulf of Carpentaria, Australia

The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort, and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths < 50 m and was concentrated particularly in inshore waters ( 50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (

Pediculus humanus capitis infestations in the community: A pilot study into transmission, treatment and factors affecting control

Head lice (Pediculus humanus capitis) infestations affect schoolchildren worldwide, creating social, economic and health consequences for families. Problems with self-detection, chronic infestations and classroom transmission are compounded by increasing resistance of the lice to pediculicides. Public health strategies are based on limited research and little is known about transmission dynamics. Mismanagement and transmission in the general community are blamed for control failure. The purpose of this study was to explore community head-lice experience in Brisbane, Australia, and to identify critical factors underlying control failure. A home-based pilot survey used physical examination to verify transmission and treatment patterns which were self-reported by a group of trace-contact families in addition to other unconnected participants. The survey was enlarged to further compare therapy outcomes and suspected risk factors. The findings reinforce those of previous studies - that children attending school and early childhood centres, and subsequently their families, are most at risk of contracting pediculosis capitis, and some may carry lice for years. First-line (pediculicidal) treatment and even additional physical methods of hand-picking and fine-toothed combing usually fail to eradicate lice quickly and completely (overall cure-rate 39 per cent, n = 84 cases). Failures were linked to hair characteristics. Public education alone may not control pediculosis. Accurate diagnosis requires considerable experience; a strong case exists for returning to institutional surveillance.

Experimental infection of Australian brushtail possums, Trichosurus vulpecula (Phalangeridae : Marsupialia), with Ross River and Barmah Forest viruses by use of a natural mosquito vector system

Brushtail possums, Trichosurus vulpecula Kerr, were experimentally infected with Ross River (RR) or Barmah Forest (BF) virus by Aedes vigilax (Skuse) mosquitoes. Eight of 10 animals exposed to RR virus developed neutralizing antibody, and 3 possums developed high viremia for < 48 hr after infection, sufficient to infect recipient mosquitoes. Two of 10 animals exposed to BF virus developed neutralizing antibody. Both infected possums maintained detectable neutralizing antibody to BF for at least 45 days after infection (log neutralization index > 2.0 at 45 days). Eight possums did not develop neutralizing antibody to BF despite exposure to infected mosquitoes. These results suggest that T. vulpecula may potentially act as a reservoir species for RR in urban areas. However, T. vulpecula infected with BF do not develop viremia sufficient to infect mosquitoes and are unlikely to be important hosts for BF.

Apoptotic deletion of Th cells specific for the 19-kDa carboxyl-terminal fragment of merozoite surface protein 1 during malaria infection

Immunity induced by the 19-kDa fragment of merozoite surface protein 1 is dependent on CD4(+) Th cells. However, we found that adoptively transferred CFSE-labeled Th cells specific for an epitope on Plasmodium yoelii 19-kDa fragment of merozoite surface protein 1 (peptide (p)24), but not OVA-specific T cells, were deleted as a result of P. yoelii infection. As a result of infection, spleen cells recovered from infected p24-specific T cell-transfused mice demonstrated reduced response to specific Ag. A higher percentage of CFSE-labeled p24-specific T cells stained positive with annexin and anti-active caspase-3 in infected compared with uninfected mice, suggesting that apoptosis contributed to deletion of p24-specific T cells during infection. Apoptosis correlated with increased percentages of p24-specific T cells that stained positive for Fas from infected mice, suggesting that P. yoelii-induced apoptosis is, at least in part, mediated by Fas. However, bystander cells of other specificities also showed increased Fas expression during infection, suggesting that Fas expression alone is not sufficient for apoptosis. These data have implications for the development of immunity in the face of endemic parasite exposure.

Parasite infection rather than tactile stimulation is the proximate cause of cleaning behaviour in reef fish

Cleaning behavior is a popular example of non-kin cooperation. However, quantitative support for this is generally sparse and the alternative, that cleaners are parasitic: has also been proposed. Although the behaviour involves some of the most complex and highly developed interspecific communication signals known, the proximate causal factors for why clients Seek cleaners are controversial. However, this information is essential to understanding the evolution of cleaning. I tested whether clients seek cleaners in response to parasite infection or whether clients seek cleaners for tactile stimulation regardless of parasite load. Parasite loads oil client fish were manipulated and clients exposed to cleaner fish and control fish hehind glass. I found that parasitized client fish spent more time than unparasitized fish next to a cleaner fish. In addition; parasitized clients spent more rime next to cleaners than next to control fish whereas unparasitized fish were not attracted to cleaners. This study shows, I believe for the first time, which is somewhat surprising, that parasite infection alone causes clients to seek cleaning by cleaners and provides insight into how this behaviour evolved.

Bitter-sweet symphony: defining the role of dendritic cell gp120 receptors in HIV infection

Background: Dendritic cells (DC) are believed to be one of the first cell types infected during HIV transmission. Recently a single C-type lectin receptor (CLR), DC-SIGN, has been reported to be the predominant receptor on monocyte derived DC (MDDC) rather than CD4. The role of other CLRs in HIV binding and HIV binding by CLRs on other types of DC in vivo is largely unknown. Objectives and study design: Review HIV binding to DC populations, both in vitro and in vivo, in light of the immense interest of a recently re-identified CLR called DC-SIGN. Results and conclusions: From recent work, it is clear that immature MDDC have a complex pattern of HIV gp120 binding. In contrast to other cell types gp120 has the potential to bind to several receptors on DC including CD4 and several types of C type lectin receptor, not just exclusively DC-SIGN. Given the diverse types of DC in vivo future work will need to focus on defining the receptors for HIV binding to these different cell types. Mucosal transmission of HIV in vivo targets immature sessile DCs, including Langerhans cells which lack DC-SIGN. The role of CLRs and DC-SIGN in such transmission remains to be defined. (C) 2001 Elsevier Science B.V. All rights reserved.