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31.
The granular layer is the input layer of the cerebellar cortex. It receives information through mossy fibers, which contact local granular layer interneurons (GLIs) and granular layer output neurons (granule cells). GLIs provide one of the first signal processing stages in the cerebellar cortex by exciting or inhibiting granule cells. Despite the importance of this early processing stage for later cerebellar computations, the responses of GLIs and the functional connections of mossy fibers with GLIs in awake animals are poorly understood. Here, we recorded GLIs and mossy fibers in the macaque ventral-paraflocculus (VPFL) during oculomotor tasks, providing the first full inventory of GLI responses in the VPFL of awake primates. We found that while mossy fiber responses are characterized by a linear monotonic relationship between firing rate and eye position, GLIs show complex response profiles characterized by “eye position fields” and single or double directional tunings. For the majority of GLIs, prominent features of their responses can be explained by assuming that a single GLI receives inputs from mossy fibers with similar or opposite directional preferences, and that these mossy fiber inputs influence GLI discharge through net excitatory or inhibitory pathways. Importantly, GLIs receiving mossy fiber inputs through these putative excitatory and inhibitory pathways show different firing properties, suggesting that they indeed correspond to two distinct classes of interneurons. We propose a new interpretation of the information flow through the cerebellar cortex granular layer, in which mossy fiber input patterns drive the responses of GLIs not only through excitatory but also through net inhibitory pathways, and that excited and inhibited GLIs can be identified based on their responses and their intrinsic properties.  相似文献   
32.
Predator species identification is an important step in understanding predator‐prey interactions, but predator identifications using kill site observations are often unreliable. We used molecular tools to analyse predator saliva, scat and hair from caribou calf kills in Newfoundland, Canada to identify the predator species, individual and sex. We sampled DNA from 32 carcasses using cotton swabs to collect predator saliva. We used fragment length analysis and sequencing of mitochondrial DNA to distinguish between coyote, black bear, Canada lynx and red fox and used nuclear DNA microsatellite analysis to identify individuals. We compared predator species detected using molecular tools to those assigned via field observations at each kill. We identified a predator species at 94% of carcasses using molecular methods, while observational methods assigned a predator species to 62.5% of kills. Molecular methods attributed 66.7% of kills to coyote and 33.3% to black bear, while observations assigned 40%, 45%, 10% and 5% to coyote, bear, lynx and fox, respectively. Individual identification was successful at 70% of kills where a predator species was identified. Only one individual was identified at each kill, but some individuals were found at multiple kills. Predator sex was predominantly male. We demonstrate the first large‐scale evaluation of predator species, individual and sex identification using molecular techniques to extract DNA from swabs of wild prey carcasses. Our results indicate that kill site swabs (i) can be highly successful in identifying the predator species and individual responsible; and (ii) serve to inform and complement traditional methods.  相似文献   
33.
Trypanosoma cruzi strains from distinct geographic areas show differences in drug resistance and association between parasites genetic and treatment response has been observed. Considering that benznidazole (BZ) can reduce the parasite burden and tissues damage, even in not cured animals and individuals, the goal is to assess the drug response to BZ of T. cruzi II strains isolated from children of the Jequitinhonha Valley, state of Minas Gerais, Brazil, before treatment. Mice infected and treated with BZ in both phases of infection were compared with the untreated and evaluated by fresh blood examination, haemoculture, polymerase chain reaction, conventional (ELISA) and non-conventional (FC-ALTA) serologies. In mice treated in the acute phase, a significant decrease in parasitaemia was observed for all strains. Positive parasitological and/or serological tests in animals treated during the acute and chronic (95.1-100%) phases showed that most of the strains were BZ resistant. However, beneficial effect was demonstrated because significant reduction (p < 0.05%) and/or suppression of parasitaemia was observed in mice infected with all strains (acute phase), associated to reduction/elimination of inflammation and fibrosis for two/eight strains. BZ offered some benefit, even in not cured animals, what suggest that BZ use may be recommended at least for recent chronic infection of the studied region.  相似文献   
34.
The productivity gradient between adjacent habitats can fluctuate over time due to seasonal cycles and lead to both habitats being alternately subsidized. Although this process is well known for prey subsidies in stream-riparian forest ecotones, few studies are available for other systems or subsidy types. Moreover, the effects of transport intensity on this expected alternate subsidy exchange are still poorly understood. We assessed whether subsidy input and allochthonous carbon assimilation by resident benthic invertebrates alternated between adjacent mangroves and salt marshes during peaks of detritus productivity (summer and winter, respectively) in a subtropical estuary, by using detritus trapping techniques and stable isotope ratios. Sampling was performed simultaneously in the sheltered (inner sector) and exposed (outer sector) regions of the estuary to assess the influence of different physical conditions on the intensity of subsidy flow. Transport of mangrove litter into the salt marsh occurred mainly in the summer in both sectors; however, most of the litter remained trapped in the marsh boundary. The mixing model also showed that there was little influence of allochthonous carbon in the diet of salt marsh benthic invertebrates. Marsh litter supply to mangroves did not vary significantly between seasons but was significantly higher in the outer than in the inner sector. Likewise, the mixing model showed great contribution of salt marsh carbon to the diet of benthic invertebrates from the outer-sector mangroves, whereas autochthonous carbon predominated in those from the inner mangroves. Our findings reinforce the model that trophic connectivity relies on the relative proportion of allochthonous (subsidy) and autochthonous resources rather than only on asymmetric productivity between habitats. Differences in the proportion of resources result from interaction among productivity, permeability, and transport vectors that lead to many states of trophic connectivity.  相似文献   
35.

Background and Aims

Strongly coherent sandsheaths that envelop perennial roots of many monocotyledonous species of arid environments have been described for over a century. This study, for the first time, details the roles played by the structural development of the subtending roots in the formation and persistence of the sheaths.

Methods

The structural development of root tissues associated with persistent sandsheaths was studied in Lyginia barbata, native to the Western Australian sand plains. Cryo-scanning electron microscopy CSEM, optical microscopy and specific staining methods were applied to fresh, field material. The role of root hairs was clarified by monitoring sheath development in roots separated from the sand profile by fine mesh.

Key Results and Conclusions

The formation of the sheaths depends entirely on the numerous living root hairs which extend into the sand and track closely around individual grains enmeshing, by approx. 12 cm from the root tip, a volume of sand more than 14 times that of the subtending root. The longevity of the perennial sheaths depends on the subsequent development of the root hairs and of the epidermis and cortex. Before dying, the root hairs develop cellulosic walls approx. 3 µm thick, incrusted with ferulic acid and lignin, which persist for the life of the sheath. The dead hairs remain in place fused to a persistent platform of sclerified epidermis and outer cortex. The mature cortex comprises this platform, a wide, sclerified inner rim and a lysigenous central region – all dead tissue. We propose that the sandsheath/root hair/epidermis/cortex complex is a structural unit facilitating water and nutrient uptake while the tissues are alive, recycling scarce phosphorus during senescence, and forming, when dead, a persistent essential structure for maintenance of a functional stele in the perennial Lyginia roots.  相似文献   
36.
The serine-170 (S170) calcium-dependent protein kinase phosphorylation site of maize (Zea mays L.) sucrose synthase (SUS) (EC 2.4.1.13) has been implicated in the post-translational regulation of SUS protein stability. To clarify the proteolytic process and the role of phosphorylation, SUS degradation and proteasome activities were studied in the maize leaf elongation zone. Size-exclusion chromatography resolved two peaks of proteasome-like proteolytic activity. The large molecular mass ( approximately 1350 kDa) peak required Mg(2+) and ATP for maximal activity and was inhibited by the proteasome inhibitors MG132 and NLVS. Anion-exchange chromatography resolved a similar proteolytic activity that was activated by ATP, characteristics that are consistent with those of a 26S-proteasome. Appropriately, immunoblotting revealed the presence of a 26S-proteasome subunit and highly ubiquitinated proteins within the active fractions eluted from both columns. The smaller molecular mass ( approximately 600 kDa) peak represented only 40% of the total proteasome-like activity and is likely a maize 20S-proteasome as it was activated in vitro by low levels of sodium dodecyl sulfate (SDS). S170 phosphorylated SUS (pS170-SUS) was detected as both high molecular mass (HMM) forms and proteolytic fragments that co-eluted with 26S-proteasome activities on both size-exclusion and anion-exchange columns. Conditions that maintained maximal 26S-proteasome activity reduced the amounts of pS170-SUS recovered. In vitro, the 26S-proteasome degraded SUS and proteasome-specific inhibitors reduced SUS proteolysis. HMM-SUS conjugates were produced in vitro and immunoprecipitations suggested that some SUS might be ubiquitinated in vivo. The results suggest that S170 phosphorylation promotes the formation of HMM, ubiquitin-SUS conjugates that can be targeted for 26S-proteasome-dependent degradation.  相似文献   
37.
Atherothrombotic cardiovascular disease associated with hyperhomocysteinemia has been proposed to result, at least in part, from increased vascular oxidative stress. Here we characterize one mechanism by which homocyteine may induce a vascular cell type-specific oxidative stress. Our results show that L-homocysteine at micromolar levels stereospecifically increases lipid peroxidation in cultured endothelial cells, but not in vascular smooth muscle cells or when medium is incubated in the absence of cells. Consistent with these observations, homocysteine also increases the formation of intracellular reactive oxygen species. The pro-oxidant effect of homocysteine can be fully replicated by an equivalent concentration of homocystine (i.e., an oxidized form of homocysteine), but not with cysteine or glutathione. Homocyst(e)ine-dependent lipid peroxidation is independent of H(2)O(2) and alterations in glutathione peroxidase activity, but dependent on superoxide. Mechanistically, the pro-oxidant effect of homocysteine appears to involve endothelial nitric oxide synthase (eNOS), as it is blocked by the eNOS inhibitor L-N(G)-nitroarginine methyl ester. Thus, homocyst(e)ine actively promotes oxidative stress in endothelial cells via an eNOS-dependent mechanism.  相似文献   
38.
39.
Genome integrity is jeopardized each time DNA replication forks stall or collapse. Here we report the identification of a complex composed of MMS22L (C6ORF167) and TONSL (NFKBIL2) that participates in the recovery from replication stress. MMS22L and TONSL are homologous to yeast Mms22 and plant Tonsoku/Brushy1, respectively. MMS22L-TONSL accumulates at regions of ssDNA associated with distressed replication forks or at processed DNA breaks, and its depletion results in high levels of endogenous DNA double-strand breaks caused by an inability to complete DNA synthesis after replication fork collapse. Moreover, cells depleted of MMS22L are highly sensitive to camptothecin,?a topoisomerase I poison that impairs DNA replication progression. Finally, MMS22L and TONSL are necessary for the efficient formation of RAD51 foci after DNA damage, and their depletion impairs homologous recombination. These results indicate that MMS22L and TONSL are genome caretakers that stimulate the recombination-dependent repair of stalled or collapsed replication forks.  相似文献   
40.
We explored associations between SNPs in cytokine/cytokine receptor genes and cellular immunity in subjects following primary smallpox vaccination. We also analyzed the genotype–phenotype associations discovered in the Caucasian subjects among a cohort of African-Americans. In Caucasians we found 277 associations (p < 0.05) between gene SNPs and inter-individual variations in IFN-α, IL-12p40, IL-1β, IL-2, and TNF-α secretion levels. A collection of SNPs in the IL1RN, IL2RB, IL4R, IL6, IL10RB, IL12A, and IL12RB2 genes had consistent associations among both Caucasians and African-Americans. A regulatory SNP (rs452204) in the IL1RN gene was significantly associated with higher levels of IL-2 secretion in an allele dose-dependent manner in both race groups (p = 0.05 for Caucasians and p = 0.002 for African-Americans). IL12RB2 polymorphism rs3790567 was associated with a dose-related decrease in IL-1β secretion (p = 0.009 for Caucasians and p = 0.01 for African-Americans). Our results demonstrate that variations in smallpox vaccine-induced cytokine responses are modulated by genetic polymorphisms in cytokine and cytokine receptor genes.  相似文献   
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