Consequences of concurrent Ascaridia galli and Escherichia coli infections in chickens

   

Three experiments were carried out to examine the consequences of concurrent infections with Ascaridia galli and Escherichia coli in chickens raised for table egg production. Characteristic pathological lesions including airsacculitis, peritonitis and/or polyserositis were seen in all groups infected with E. coli. Furthermore, a trend for increased mortality rates was observed in groups infected with both organisms which, however, could not be confirmed statistically. The mean worm burden was significantly lower in combined infection groups compared to groups infected only with A. galli. It was also shown that combined infections of E. coli and A. galli had an added significant negative impact on weight gain.     

The evolutionary radiation of Arvicolinae rodents (voles and lemmings): relative contribution of nuclear and mitochondrial DNA phylogenies

Background  

Mitochondrial and nuclear genes have generally been employed for different purposes in molecular systematics, the former to resolve relationships within recently evolved groups and the latter to investigate phylogenies at a deeper level. In the case of rapid and recent evolutionary radiations, mitochondrial genes like cytochrome b (CYB) are often inefficient for resolving phylogenetic relationships. One of the best examples is illustrated by Arvicolinae rodents (Rodentia; Muridae), the most impressive mammalian radiation of the Northern Hemisphere which produced voles, lemmings and muskrats. Here, we compare the relative contribution of a nuclear marker – the exon 10 of the growth hormone receptor (GHR) gene – to the one of the mitochondrial CYB for inferring phylogenetic relationships among the major lineages of arvicoline rodents.     

Integrin-regulated secretion of interleukin 4: A novel pathway of mechanotransduction in human articular chondrocytes

Chondrocyte function is regulated partly by mechanical stimulation. Optimal mechanical stimulation maintains articular cartilage integrity, whereas abnormal mechanical stimulation results in development and progression of osteoarthritis (OA). The responses of signal transduction pathways in human articular chondrocytes (HAC) to mechanical stimuli remain unclear. Previous work has shown the involvement of integrins and integrin-associated signaling pathways in activation of plasma membrane apamin-sensitive Ca2+-activated K+ channels that results in membrane hyperpolarization of HAC after 0. 33 Hz cyclical mechanical stimulation. To further investigate mechanotransduction pathways in HAC and show that the hyperpolarization response to mechanical stimulation is a result of an integrin-dependent release of a transferable secreted factor, we used this response. Neutralizing antibodies to interleukin 4 (IL-4) and IL-4 receptor alpha inhibit mechanically induced membrane hyperpolarization and anti-IL-4 antibodies neutralize the hyperpolarizing activity of medium from mechanically stimulated cells. Antibodies to interleukin 1beta (IL-1beta) and cytokine receptors, interleukin 1 receptor type I and the common gamma chain/CD132 (gamma) have no effect on me- chanically induced membrane hyperpolarization. Chondrocytes from IL-4 knockout mice fail to show a membrane hyperpolarization response to cyclical mechanical stimulation. Mechanically induced release of the chondroprotective cytokine IL-4 from HAC with subsequent autocrine/paracrine activity is likely to be an important regulatory pathway in the maintenance of articular cartilage structure and function. Finally, dysfunction of this pathway may be implicated in OA.     

alpha-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid subtype glutamate receptor (AMPAR) endocytosis is essential for N-methyl-D-aspartate-induced neuronal apoptosis

Excessive activation of the N-methyl-d-aspartate subtype glutamate receptor (NMDAR) is thought to be involved in mediating programmed cell death (apoptosis) in numerous central nervous diseases. However, the underlying mechanisms remain unknown. We report here that stimulation of NMDARs activates intracellular signaling cascades leading to apoptosis and facilitates clathrin-dependent endocytosis of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid subtype glutamate receptors (AMPARs). Both broad spectrum inhibitors of clathrin-dependent endocytotic processes and a specific inhibitor of AMPAR endocytosis selectively inhibit NMDA-induced apoptosis without affecting apoptosis produced by staurosporine. These results demonstrate that clathrin-dependent endocytosis of AMPARs is an essential step in NMDAR-mediated neuronal apoptosis. Our study not only identifies a previously unsuspected step in NMDA-induced apoptosis but also demonstrates that AMPAR endocytosis, in addition to attenuating synaptic strength as previously demonstrated in models of synaptic plasticity, may play a critical role in mediating other important intracellular pathways.     

Differential suppression of hyperglycemic,feeding, and neuroendocrine responses in anorexia

We have used the anorexia shown by rats given hypertonic saline to drink to investigate central mechanisms that can inhibit feeding. Rats dehydrated in this manner for 3 or 5 days showed a severe attenuation of the compensatory feeding observed after an overnight fast compared with control euhydrated rats or rats whose food was restricted to match the intake of anorexic rats. Food intake after injections of 2-deoxy-d-glucose (2-DG) was also significantly decreased in dehydrated animals compared with that after a 2-DG injection given before dehydration. However, all the dehydrated animals demonstrated a robust eating response after water was returned whether they had received injection of 2-DG or vehicle. Despite a profound reduction in 2-DG-induced feeding, other glucoregulatory responses to 2-DG remained intact in dehydrated animals. After 2-DG injection, corticosterone secretion and blood glucose were significantly elevated from preinjection values whether or not animals were dehydrated. Thus the mechanisms responsible for anorexia in dehydrated animals specifically target stimulatory feeding pathways but leave intact other counterregulatory glucometabolic motor events.     

Variation among natural isolates of Neurospora on small spatial scales

Although species of Neurospora are among the most studied model organisms in genetics and biochemistry, basic questions remain with respect to their ecology and population biology. In this study, we sought to clarify relationships among individuals over a small spatial scale, toward assessing both local variation and mode of colonization. Isolates of Neurospora were collected after fires in the Florida Everglades (May 1999), where abundant colonies appeared on diverse plants, including grasses and woody shrubs. Colonies were sampled in a linear fashion from two adjacent scorched sugarcane stems at one site and from a burned woody shrub at a distant second site. Species and mating types were assigned based on crossing behavior. Variation at two loci, het-c and frq, was determined by direct sequencing of PCR products. The results demonstrated substantial within- and among-species variation on a small scale, with up to three species and six different haplotypes occurring on a single stem. In total, four species and more than 10 genetically distinct individuals (haplotypes) were present across the three stems, often with multiple individuals occupying the same position. A permutation analysis revealed that individuals were not distributed randomly and that adjacent nodes on cane stems were more likely than chance to be colonized by the same haplotype. This suggests that visible eruptions of conidia on burned plants reflect substantial vegetative mycelial spread through subsurface tissues after primary colonization. Results also revealed that adjacent isolates from a single plant can possess different functional alleles at het-c, an observation meaningful in the context of the proposed role of het-c in self recognition.     

Theoretical ab initio study of the effects of methylation on structure and stability of G:C Watson-Crick base pair

Methylation of DNA occurs most readily at N(3), N(7), and O(6) of purine bases and N(3) and O(2) of pyrimidines. Methylated bases are continuously formed through endogenous and exogenous mechanisms. The results of a theoretical ab initio study on the methylation of G:C base pair components are reported. The geometries of the local minima were optimized without symmetry restrictions by the gradient procedure at DFT level of theory and were verified by energy second derivative calculations. The standard 6-31G(d) basis set was used. The single-point calculations have been performed at the MP2/6-31G(d,p), MP2/6-31++G(d,p), and MP2/6-311++G(2d,2p) levels of theory. The geometrical parameters, relative stability and counterpoise corrected interaction energies are reported. Also, using a variation-perturbation energy decomposition scheme we have found the vital contributions to the total interaction energy.     

Phytochrome control of flowering is temperature sensitive and correlates with expression of the floral integrator FT

In Arabidopsis flowering is accelerated by reduced red:far-red (R:FR) ratio which signals the presence of neighbouring vegetation. Hastened flowering is one component of the shade-avoidance syndrome of responses, which alter many aspects of development in response to the threat of potential competition. Of the red/far-red-absorbing photoreceptors it is phyB that plays the most prominent role in shade-avoidance, although other related phytochromes act redundantly with phyB. It is well established that the phyB mutant has a constitutively early flowering phenotype. However, we have shown that the early flowering phenotype of phyB is temperature-dependent. We have established that this temperature-sensitive flowering response defines a pathway that appears to be independent of the autonomous-FLC pathway. Furthermore, we have demonstrated that the phytochromes control the expression of the floral promoter FT. We have also shown that other phyB-controlled responses, including petiole elongation, are not sensitive to the same temperature change. This suggests that discrete pathways control flowering and petiole elongation, components of the shade-avoidance response. This work provides an insight into the phytochrome and temperature interactions that maintain flowering control.     

Wettable and unsinkable: the hydrodynamics of saccate pollen grains in relation to the pollination mechanism in the two New Zealand species of Prumnopitys Phil. (Podocarpaceae)

The pollination mechanism of most genera of the Podocarpaceae involves inverted ovules, a pollination drop and bisaccate pollen grains. Saccate grains have sometimes been referred to as 'non-wettable' due to their buoyant properties, while non-saccate pollen grains have been described as 'wettable'. The hydrodynamic properties of saccate pollen grains of seven podocarp species in five genera, Dacrydium Sol. ex G. Forst., Dacrycarpus (Endl.) de Laub., Manoao Molloy, Podocarpus L'Hér. ex Pers. and Prumnopitys Phil. have been tested in water, together with saccate and non-saccate pollen of four other conifer genera, Cedrus Trew (Pinaceae), Cephalotaxus Siebold & Zucc. ex Endl. (Cephalotaxaceae), Cupressus L. (Cupressaceae) and Phyllocladus Rich. ex Mirb. (Phyllocladaceae), and spores of three fern species and one lycopod species. All four spore types studied were non-wettable, whereas the bisaccate and trisaccate pollen types, like all other conifer pollen types, were wettable, enabling the grains to cross the surface tension barrier of water. Once past this barrier, grain behaviour was governed by presence or absence of sacci. Non-saccate and vestigially saccate grains sank, whereas saccate grains behaved like air bubbles, floating up to the highest point. In addition, the grains were observed to float in water with sacci uppermost, consistent with the suggestion that distally placed sacci serve to orientate the germinal furrow of the pollen grain towards the nucellus of an inverted ovule. Observations of pollen grains in the pollen chambers of naturally pollinated Prumnopitvs ovules confirmed this. The combination of buoyancy and wettability in saccate pollen has implications for the efficiency of the typical podocarp pollination mechanism.