Disturbance mediates the effects of nutrients on developing assemblages of epibiota

Local dynamics such as resource enhancement (e.g. nutrient supply) and stochastic events of destruction (disturbances that provide new space) are hypothesized to counteractively affect species diversity and composition. We tested the independent and interactive effects of nutrients and disturbance on the development of assemblages of epibiota attached to vertical surfaces in an oligotrophic system. Nutrient concentrations were manipulated at three levels (ambient, medium and high) while disturbance was manipulated by removing biomass at seven frequencies (0×, 2×, 3×, 4×, 5×, 7×, 12×). Nutrient and disturbance regimes had opposing effects on diversity such that species richness increased with resource enhancement (nutrients) and declined with disturbance. These results support the model that increased heterogeneity of distribution of limiting resources allows the coexistence of species with low and high resource requirements.     

High-resolution structure of HLA-A*0201 in complex with a tumour-specific antigenic peptide encoded by the MAGE-A4 gene

The heterotrimeric complex of the human major histocompatibity complex (MHC) molecule HLA-A*0201, beta2-microglobulin and the decameric peptide GVYDGREHTV derived from the melanoma antigen (MAGE-A4 protein has been determined by X-ray crystallography at 1.4 A resolution. MAGE-A4 belongs to a family of genes that are specifically expressed in a variety of tumours. MAGE-A4-derived peptides are presented by MHC molecules at the cell surface to cytotoxic T-lymphocytes. As the HLA-A*0201:MAGE-A4 complex occurs only on tumour cells, it is considered to be an appropriate target for immunotherapy. The structure presented here reveals potential epitopes specific to the complex and indicates which peptide residues could be recognised by T-cell receptors. In addition, as the structure could be refined anisotropically, it was possible to describe the movements of the bound peptide in more detail.     

Influence of single-level lumbar degenerative disc disease on the behavior of the adjacent segments—A finite element model study

The current study investigated mechanical predictors for the development of adjacent disc degeneration. A 3-D finite element model of a lumbar spine was modified to simulate two grades of degeneration at the L4–L5 disc. Degeneration was modeled by changes in geometry and material properties. All models were subjected to follower preloads of 800 N and moment loads in the three principal directions of motion using a hybrid protocol. Degeneration caused changes in the loading and motion patterns of the segments above and below the degenerated disc. At the level (L3–L4) above the degenerated disc, the motion increased due to moderate degeneration by 21% under lateral bending, 26% under axial rotation and 28% under flexion/extension. At the level (L5-S1) below the degenerated disc, motion increased only during lateral bending by 20% due to moderate degeneration. Both the L3–L4 and L5-S1 segment showed a monotonic increase in both the maximum von Mises stress and shear stress in the annulus as degeneration progressed for all loading directions, expect extension at L3–L4. The most significant increase in stress was observed at the L5-S1 level during axial rotation with nearly a ten-fold increase in the maximum shear stress and 103% increase in the maximum von Mises stress. The L5-S1 segment also showed a progressive increase in facet contact force for all loading directions with degeneration. Nucleus pressure did not increase significantly for any loading direction at either the caudal or cephalic adjacent segment. Results suggest that single-level degeneration can increase the risk for injury at the adjacent levels.     

Neurochemical coding of myenteric neurons in the guinea-pig antrum

Electrophysiological studies of myenteric neurons in the guinea-pig antrum suggest that different neuroactive compounds are involved in synaptic transmission. It is not known what neurotransmitters and neuropeptides are present and to what extent they colocalize. Immunohistochemical stainings were performed on whole-mount preparations of the guinea-pig antrum. Immunoreactivity for neuron-specific enolase was used as a general marker and was set at 100%. There was no overlap between cholinergic and nitrergic neurons, resulting in two separate subpopulations. The presence of choline acetyltransferase immunoreactivity was used to identify the cholinergic subset, which accounted for 56% of the cells. Immunoreactivity for nitric oxide synthase, on the other hand, was displayed in 40.7% of the neurons. Substance-P immunoreactivity was present in 37.4% of the cells and vasoactive intestinal peptide and neuropeptide Y in 21.7% and 28.6%, respectively. Small subsets of neurons had immunoreactivity for serotonin (3.9%), calretinin (6.8%) and calbindin (0.5%). Colocalization studies revealed several subgroups of neurons, containing one or more of the screened markers. Though some similarity is found in the chemical coding of the antrum compared to that of the small intestine and the corpus, remarkable differences can be seen in the occurrence of some subpopulations. Cholinergic neurons are not as predominant as in other parts of the gut, serotonin presence is doubled and some vasointestinal-peptide-positive neurons express substance P. These differences might reflect the highly specialized function of the antrum; however, the exact role of these classes remains to be established.     

The addition of CO2 to traditional taste solutions alters taste quality

Previous studies of the effect of carbonation on taste perception have suggested that it may be negligible, manifesting primarily in increases in the perceived intensity of weak salt and sour stimuli. Assuming CO2 solutions in the mouth stimulate only trigeminal nerve endings, this result is not altogether surprising; however, there are neurophysiological data indicating that CO2 stimulates gustatory as well as trigeminal fibers. In that case, carbonation might alter the quality profile of a stimulus without producing substantial changes in overall taste intensity--much as occurs when qualitatively different taste stimuli are mixed. To address this possibility, subjects were asked to rate the total taste intensity of moderate concentrations of stimuli representing each of the basic tastes and their binary combinations, with an without added carbonation. They then subdivided total taste intensity into the proportions of sweetness, saltiness, sourness, bitterness and 'other taste qualities' they perceived. The addition of carbonation produced only small increases in ratings of total taste intensity. However, rather dramatic alterations in the quality profiles of stimuli were observed, particularly for sweet and salty tastes. The nature of the interaction is consistent with a direct effect of carbonation/CO2 on the gustatory system, although the possibility that at least some of the observed effects reflect trigeminal-gustatory interactions cannot be ruled out.      

Functional and biochemical characterization of mouse P40/IL-9 receptors

The existence of saturable and specific binding sites for mouse P40/IL-9 was demonstrated on a variety of factor-dependent T cell lines derived from Th clones by long term culture in the presence of P40-containing T cell supernatants. Scatchard transformation of the data obtained with one such line was consistent with the existence of a single class of receptors with a Kd of approximately 100 pM and a density of 3000/cell. P40 binding to these cells was followed by rapid internalization of the ligand. P40-receptors (P40-R)3 were also found on certain Th clones maintained in conventional cultures, especially after stimulation with Ag and APC. Only T cell clones that proliferated in response to P40 showed significant levels of binding, suggesting that the regulation of P40-R expression is an important element in the control of P40-responsiveness. In accord with this idea, fresh T cells, cytolytic T cell clones and a wide variety of other cells including B cells and fibroblasts, which do not proliferate in response to P40, showed no significant binding. However, P40-R were not restricted to a few unusual Th clones. They were also detected on several T cell tumors, on macrophages and on mast cell lines. The latter point is of particular interest in view of the mast cell growth factor activity recently ascribed to P40. Cross-linking studies with T-cell lines and mast cells indicated that the P40-R consists of a 64-kDa glycoprotein, the molecular mass of which is reduced to 54 kDa on treatment with N-glycosidase F.     

Screening Global Positioning System Location Data for Errors Using Animal Movement Characteristics

Abstract: Animal locations estimated by Global Positioning System (GPS) inherently contain errors. Screening procedures used to remove large positional errors often trade data accuracy for data loss. We developed a simple screening method that identifies locations arising from unrealistic movement patterns. When applied to a large data set of moose (Alces alces) locations, our method identified virtually all known errors with minimal loss of data. Thus, our method for screening GPS data improves the quality of data sets and increases the value of such data for research and management.     

Host‐plant genotype mediates supply and demand of animal food in an omnivorous insect

1. Omnivorous predators can protect plants from herbivores, but may also consume plant material themselves. Omnivores and their purely herbivorous prey have previously been thought to respond similarly to host‐plant quality. However, different responses of omnivores and herbivores to their shared host plants may influence the fitness, trophic identity, and population dynamics of the omnivores. 2. The aim of the present study was to show that an omnivorous heteropteran (Anthocoris nemorum L.) and two strictly herbivorous prey species respond differently to different genotypes of their shared host plant, Salix. Some plant genotypes were sub‐optimal for the omnivore, although suitable for the herbivores, and vice versa. 3. The contrasting patterns of plant suitability for the omnivore and the herbivores highlight an interaction between plant genotype and omnivores' access to animal food. Plant genotypes that were sub‐optimal for the omnivore when herbivores were experimentally excluded became the best host plants when herbivores were present, as in the latter situation additional prey became available. By contrast, the quality of plant genotypes that were intrinsically suitable for omnivores, did not improve when herbivores were present as these plant genotypes were intrinsically sub‐optimal for herbivores, thus providing omnivores with almost no additional animal food. 4. The differential responses of omnivores and their prey to the same host‐plant genotypes should allow omnivores to colonise sub‐optimal host plants in their capacity as predators, and to colonise more suitable host plants in their capacity as herbivores. It may thus be difficult for Salix to escape herbivory entirely, as it will rarely be unsuitable for both omnivores and pure herbivores at the same time.