Emergence of third-stage larvae of Umingmakstrongylus pallikuukensis from three gastropod intermediate host species

We investigated the emergence of third-stage larvae (L3) of Umingmakstrongylus pallikuukensis from the slugs Deroceras laeve, Deroceras reticulatum, and the snail Catinella sp. in the laboratory and from D. laeve on the tundra. Third-stage larvae emerged from 8 of 8 D. laeve and 8 of 8 D. reticulatum housed at 20 C in darkness and from 9 of 10 D. laeve and 5 of 5 Catinella sp. housed at 21 C with 10-12 hr of light/day. Larvae emerged from D. laeve and D. reticulatum over a wide range of infection intensities (2-179 and 20-65, respectively), and the patterns of emergence were independent of intensity. The majority of the L3 emerged from most of the Deroceras spp. by 58 or 60 days postinfection (PI). Lower rates of emergence were observed from Catinella sp. Larvae emerged from D. laeve on the tundra by 10 wk PI and were recovered from the vegetation in some experimental enclosures the following year. Third-stage larvae survived in tap and distilled water at 0-4 C for 13 mo. Emergence of L3 of U. pallikuukensis from the intermediate host may increase the temporal and spatial availability of L3 and enhance their survival and transmission.     

Contrasting Results of Culture-Dependent and Molecular Analyses of Mycobacterium avium subsp. paratuberculosis from Wood Bison

Reduced to near extinction in the late 1800s, a number of wood bison populations (Bison bison athabascae) have been re-established through reintroduction initiatives. Although an invaluable tool for conservation, translocation of animals can spread infectious agents to new areas or expose animals to pathogens in their new environment. Mycobacterium avium subsp. paratuberculosis, a bacterium that causes chronic enteritis in ruminants, is among the pathogens of potential concern for wood bison management and conservation. In order to inform translocation decisions, our objectives were to determine the M. avium subsp. paratuberculosis infection status of wood bison herds in Canada and to culture and genetically characterize the infective strain(s). We tested fecal samples from bison (n = 267) in nine herds using direct PCR for three M. avium subsp. paratuberculosis-specific genetic targets with different copy numbers within the M. avium subsp. paratuberculosis genome. Restriction enzyme analysis (REA) and sequencing of IS1311 were performed on seven samples from five different herds. We also evaluated a panel of different culture conditions for their ability to support M. avium subsp. paratuberculosis growth from feces and tissues of direct-PCR-positive animals. Eighty-one fecal samples (30%) tested positive using direct IS900 PCR, with positive samples from all nine herds; of these, 75% and 21% were also positive using ISMAP02 and F57, respectively. None of the culture conditions supported the growth of M. avium subsp. paratuberculosis from PCR-positive samples. IS1311 REA and sequencing indicate that at least two different M. avium subsp. paratuberculosis strain types exist in Canadian wood bison. The presence of different M. avium subsp. paratuberculosis strains among wood bison herds should be considered in the planning of translocations.     

Protostrongylid parasites and pneumonia in captive and wild thinhorn sheep (Ovis dalli)

We describe health significance of protostrongylid parasites (Parelaphostrongylus odocoilei and Protostrongylus stilesi) and other respiratory pathogens in more than 50 naturally infected Dall's sheep (Ovis dalli dalli) from the Mackenzie Mountains, Northwest Territories (1998-2002) as well as in three Stone's sheep (O. d. stonei) experimentally infected with P. odocoilei (2000-2002). Histological lesions in the brain and distribution of P. odocoilei in the muscles of experimentally and naturally infected sheep were consistent with a previously hypothesized "central nervous system to muscle" pattern of migration for P. odocoilei. Dimensions of granulomas associated with eggs of P. odocoilei and density of protostrongylid eggs and larvae in the cranial lung correlated with intensity of larvae in feces, and all varied with season of collection. Prevalence of P. stilesi based on the presence of larvae in feces underestimated true prevalence (based on examination of lungs) in wild Dall's sheep collected in summer and fall. Similarly, counts of both types of protostrongylid larvae in feces were unreliable indicators of parasitic infection in wild Dall's sheep with concomitant bacterial pneumonia associated with Arcanobacterium pyogenes, Pasteurella sp., and Mannheimia sp. Diffuse, interstitial pneumonia due to P. odocoilei led to fatal pulmonary hemorrhage and edema after exertion in one experimentally infected Stone's sheep and one naturally infected Dall's sheep. Bacterial and verminous pneumonia associated with pathogens endemic in wild Dall's sheep in the Mackenzie Mountains caused sporadic mortalities. There was no evidence of respiratory viruses or bacterial strains associated with domestic ruminants, from which this population of wild sheep has been historically isolated.     

A Reaction-Diffusion Model of Cholinergic Retinal Waves

Prior to receiving visual stimuli, spontaneous, correlated activity in the retina, called retinal waves, drives activity-dependent developmental programs. Early-stage waves mediated by acetylcholine (ACh) manifest as slow, spreading bursts of action potentials. They are believed to be initiated by the spontaneous firing of Starburst Amacrine Cells (SACs), whose dense, recurrent connectivity then propagates this activity laterally. Their inter-wave interval and shifting wave boundaries are the result of the slow after-hyperpolarization of the SACs creating an evolving mosaic of recruitable and refractory cells, which can and cannot participate in waves, respectively. Recent evidence suggests that cholinergic waves may be modulated by the extracellular concentration of ACh. Here, we construct a simplified, biophysically consistent, reaction-diffusion model of cholinergic retinal waves capable of recapitulating wave dynamics observed in mice retina recordings. The dense, recurrent connectivity of SACs is modeled through local, excitatory coupling occurring via the volume release and diffusion of ACh. In addition to simulation, we are thus able to use non-linear wave theory to connect wave features to underlying physiological parameters, making the model useful in determining appropriate pharmacological manipulations to experimentally produce waves of a prescribed spatiotemporal character. The model is used to determine how ACh mediated connectivity may modulate wave activity, and how parameters such as the spontaneous activation rate and sAHP refractory period contribute to critical wave size variability.     

Cascading Effects of Climate Change: Do Hurricane‐damaged Forests Increase Risk of Exposure to Parasites?

Increased parasitism in animals in disturbed habitats is often understood to be the result of increased disease susceptibility due to low food availability resulting in nutritionally stressed and immunocompromised individuals. Such habitat change, however, might also lead to increased exposure to disease. In this article, we test measures of susceptibility and exposure to explain the prevalence and intensity of directly and indirectly transmitted helminths in black howler monkeys (Alouatta pigra) following a hurricane in Belize. None of these parasites were predicted by direct measures of susceptibility (as measured by fruit consumption and fecal cortisol levels). Rather, directly transmitted parasites (Trichuris sp. and strongylid type eggs.) were predicted by host density and group size, both measures of exposure. Similarly, only the consumption of Cecropia peltata, a fast growing pioneer that has a mutualistic relationship with ants predicted levels of the indirectly transmitted trematode Controrchis spp., also suggesting exposure. Cecropia peltata also increased in density post‐hurricane, was high in digestible protein, sugar, and salt and eaten by monkeys more frequently than predicted based on distribution. These data suggest that in this hurricane‐damaged forest the ingestion of this abundant and nutritious pioneer species increased exposure of the monkeys to Controrchis through ingestion of ant intermediate hosts. These results may point to a pattern true of pioneer species in general, leaving animals in disturbed forests with higher levels of parasitism as a result of changes to forest structure. As severe weather events are expected to increase, this suggests a cascading effect of climate change on ecosystem interactions and disease ecology.     

Clinical patterns in asthma based on proximal and distal airway nitric oxide categories

Background

The exhaled nitric oxide (eNO) signal is a marker of inflammation, and can be partitioned into proximal [J''aw_NO (nl/s), maximum airway flux] and distal contributions [CA_NO (ppb), distal airway/alveolar NO concentration]. We hypothesized that J''aw_NO and CA_NO are selectively elevated in asthmatics, permitting identification of four inflammatory categories with distinct clinical features.

Methods

In 200 consecutive children with asthma, and 21 non-asthmatic, non-atopic controls, we measured baseline spirometry, bronchodilator response, asthma control and morbidity, atopic status, use of inhaled corticosteroids, and eNO at multiple flows (50, 100, and 200 ml/s) in a cross-sectional study design. A trumpet-shaped axial diffusion model of NO exchange was used to characterize J''aw_NO and CA_NO.

Results

J''aw_NO was not correlated with CA_NO, and thus asthmatic subjects were grouped into four eNO categories based on upper limit thresholds of non-asthmatics for J''aw_NO (≥ 1.5 nl/s) and CA_NO (≥ 2.3 ppb): Type I (normal J''aw_NO and CA_NO), Type II (elevated J''aw_NO and normal CA_NO), Type III (elevated J''aw_NO and CA_NO) and Type IV (normal J''aw_NO and elevated CA_NO). The rate of inhaled corticosteroid use (lowest in Type III) and atopy (highest in Type II) varied significantly amongst the categories influencing J''aw_NO, but was not related to CA_NO, asthma control or morbidity. All categories demonstrated normal to near-normal baseline spirometry; however, only eNO categories with increased CA_NO (III and IV) had significantly worse asthma control and morbidity when compared to categories I and II.

Conclusions

J''aw_NO and CA_NO reveal inflammatory categories in children with asthma that have distinct clinical features including sensitivity to inhaled corticosteroids and atopy. Only categories with increase CA_NO were related to poor asthma control and morbidity independent of baseline spirometry, bronchodilator response, atopic status, or use of inhaled corticosteroids.     

石耳科(子囊菌亚门)的间断分布和替代现象

本文报道了石耳科的两个亚洲的,也是美洲以外的新记录种,即角石耳与深色石耳。进一步证实了单果石耳在南大西洋的,即南美洲和南部非洲的间断分布。对于上述种类以及本科其它一些种类的间断分布和替代现象进行了分析讨论。     

Avoiding biohazards in medical, veterinary and research laboratories

Personnel in medical, veterinary or research laboratories may be exposed to a wide variety of pathogens that range from deadly to debilitating. For some of these pathogens, no treatment is available, and in other cases the treatment does not fully control the disease. It is important that personnel in laboratories that process human or microbiological specimens follow universal precautions when handling tissues, cells, or microbiological specimens owing to the increasing numbers of individuals infected with hepatitis C and HIV in the US and the possibility that an individual may be asymptomatic when a specimen is obtained. Similar precautions must be followed in laboratories that use animal tissues owing to the possibility of exposure to agents that are pathogenic in humans. Personnel with conditions associated with immunosuppression should evaluate carefully whether or not specific laboratory environments put them at increased risk of disease. We offer here some general approaches to identifying biohazards and to minimizing the potential risk of exposure. The issues discussed can be used to develop a general safety program as required by regulatory or accrediting agencies, including the Occupational Safety and Health Administration.     

Identifying critical regions for spike propagation in axon segments

Morphological reconstructions of axon segments reveal the abundance of geometrical ultrastructures that can dramatically affect the propagation of Action Potentials (AP). Moreover, deformations and swellings in axons resulting from brain traumas are associated to many neural dysfunctions and disorders. Our aim is to develop a computational framework to distinguish between geometrical enlargements that lead to minor changes in propagation from those that result in critical phenomenon such as reflection or blockage of the original traveling spike. We use a few geometrical parameters to model a prototypical shaft enlargement and explore the parameter space characterizing all possible propagation regimes and dynamics in an unmylienated AP model. Contrary to earlier notions that large diameter increases mostly lead to blocking, we demonstrate transmission is stable provided the geometrical changes occur in a slow manner. Our method also identifies a narrow range of parameters leading to a reflection regime. The distinction between these three regimes can be evaluated by a simple function of the geometrical parameters inferred through numerical simulations. We suggest that evaluating this function along axon segments can detect regions most susceptible to (i) transmission failure due to perturbations, (ii) structural plasticity, (iii) critical swellings caused by brain traumas and/or (iv) neurological disorders associated with the break down of spike train propagation.