Functional morphology of the neuropeptidergic light-yellow-cell system in pulmonate snails

The light yellow neuropeptidergic cell system of the basommatophoran snail Lymnaea stagnalis is homologous to the R3-R14 system of the opisthobranch Aplysia californica, and produces three different neuropeptides. Systems homologous to the light yellow cells of Lymnaea stagnalis have been investigated morphologically in two Basommatophora (Lymnaea ovata, Bulinus truncatus) and three Stylommatophora (Helix aspersa, Cepaea nemoralis, Deroceras reticulatum). To this end, an antibody to synthetic light-yellow-cell peptide-II and oligonucleotides to mRNAs encoding parts of peptide-I and peptide-III, were used. The in situ hybridization probes gave negative results. On the other hand, neuronal cell clusters were observed in the central nervous system of all specias studied by immunocytochemistry. These clusters were located in the ganglia of the visceral complex. The neurons project axons into all nerves of these ganglia, especially into the pallial nerves, into the connective tissue of the central nervous system, and into the neuropile of various ganglia. The morphology of the systems is similar to that of the light-yellow-cell system of Lymnaea stagnalis. In all species, the wall of the aorta was innervated by immunoreactive axons. Peripheral innervation by the light-yellow-cell system was investigated in Helix aspersa and Deroceras reticulatum. Serial and alternate sections of whole snails were studied. Reconstructions were made of the heart-kidney-lung complex of these animals. In both species, the muscular vessels of the pulmonary system at the right side of the body were strongly innervated by immunoreactive axons. Furthermore, immunopositive innervation was observed to muscles in the secondary ureter-pneumostome area. The light-yellow-cell system of pulmonates is thus probably involved in the regulation of blood pressure and urine release.     

Immunoelectrophoresis to detect differences between strains of Candida albicans

Summary Aqueous extracts of two parental strains ofCandida albicans and two mutants obtained from these strains were studied through immunoelectrophoresis and differential staining for protein and polysaccharide fractions after electrophoresis. Differences in antibody-antigen reactions, and protein and polysaccharide fractions could be detected between these strains. These differences reflected changes in synthesizing ability and genetic information inherent in these yeast cells.     

Interpolation method for accurate affinity ranking of arrayed ligand–analyte interactions

The values of the affinity constants (k_d, k_a, and K_D) that are determined by label-free interaction analysis methods are affected by the ligand density. This article outlines a surface plasmon resonance (SPR) imaging method that yields high-throughput globally fitted affinity ranking values using a 96-plex array. A kinetic titration experiment without a regeneration step has been applied for various coupled antibodies binding to a single antigen. Globally fitted rate (k_d and k_a) and dissociation equilibrium (K_D) constants for various ligand densities and analyte concentrations are exponentially interpolated to the K_D at R_max = 100 RU response level (K_D^R100).     

Digestive enzymes of human and nonhuman primates

All living organisms need to consume nutrients to grow, survive, and reproduce, making the successful acquisition of food resources a powerful selective pressure. However, acquiring food is only part of the challenge. While all animals spend much of their daily activity budget hunting, searching for, or otherwise procuring food, a large part of what is involved in overall nutrition occurs once the meal has been swallowed. Most nutritional components are too complex for immediate use and must be broken down into simpler compounds, which can then be absorbed by the body. This process, digestion, is catalyzed by enzymes that are either endogenous or produced by the host's microbial population .¹ Research shows that the nutritional value of food is partially constrained by the digestive abilities of the microbial community present in the host's gut and that these microbes rapidly adapt to changes in diet and other environmental pressures .² An accumulating body of evidence suggests that endogenously produced digestive enzymes also have been, and still are, common targets of natural selection, further cementing their crucial role in an organism's digestive system .^3–5     

Autism and Overcoming Job Barriers: Comparing Job-Related Barriers and Possible Solutions in and outside of Autism-Specific Employment

The aim of this study was to discover how individuals with autism succeed in entering the job market. We therefore sought to identify expected and occurred barriers, keeping them from taking up and staying in employment as well as to identify the solutions used to overcome these barriers. Sixty-six employed individuals with autism–17 of them with autism-specific employment–participated in an online survey. Results showed a variety of possible barriers. Individuals in autism-specific employment named formality problems–problems with organizational and practical process-related aspects of the job entry–most frequently while individuals in non-autism-specific employment mentioned social problems–obstacles concerning communication and human interaction–most. In terms of solutions, both groups used their own resources as much as external help, but differed in their specific strategies. In addition, correlations of an autism-specific employment with general and occupational self-efficacy as well as life and job satisfaction were examined. Possible implications of the results are discussed with regard to problem solving behavior and the use of strengths.     

Chemical Camouflage– A Frog's Strategy to Co-Exist with Aggressive Ants

Whereas interspecific associations receive considerable attention in evolutionary, behavioural and ecological literature, the proximate bases for these associations are usually unknown. This in particular applies to associations between vertebrates with invertebrates. The West-African savanna frog Phrynomantis microps lives in the underground nest of ponerine ants (Paltothyreus tarsatus). The ants usually react highly aggressively when disturbed by fiercely stinging, but the frog is not attacked and lives unharmed among the ants. Herein we examined the proximate mechanisms for this unusual association. Experiments with termites and mealworms covered with the skin secretion of the frog revealed that specific chemical compounds seem to prevent the ants from stinging. By HPLC-fractionation of an aqueous solution of the frogs'' skin secretion, two peptides of 1,029 and 1,143 Da were isolated and found to inhibit the aggressive behaviour of the ants. By de novo sequencing using tandem mass spectrometry, the amino acid sequence of both peptides consisting of a chain of 9 and 11 residues, respectively, was elucidated. Both peptides were synthesized and tested, and exhibited the same inhibitory properties as the original frog secretions. These novel peptides most likely act as an appeasement allomone and may serve as models for taming insect aggression.     

On the use of the logistic equation in models of food chains

In food chain models the lowest trophic level is often assumed to grow logistically. Anomalous behaviour of the solution of the logistic equation and problems with the introduction of mortality have recently been reported. As predation on the lowest trophic level is a kind of mortality, one expects problems with these food chain models. In this paper we compare two formulations for the lowest trophic level: the logistic growth formulation and the mass balance formulation with resources modelled explicitly. We examine the effects of both models on the dynamic behaviour of a tri-trophic microbial food chain in a chemostat. For this purpose bifurcation diagrams, which give the existence and stability of the equilibria of the nonlinear dynamic system, are used. It turns out that the dynamic behaviours differ in a rather large region of the control parameter space spanned by the dilution rate and the concentration of the resources in the reservoir. We urge that mass balance equations should be used in modelling food chains in chemostats as well as in ecosystems.