"Impoverished" and "enriched" living conditions influence the proliferation and survival of neurons in crayfish brain

New neurons are added to two bilateral clusters of neurons in crayfish brain throughout their lives. These interneurons are associated with the olfactory and accessory lobes, areas of the brain that receive primary olfactory information and higher order inputs from the visual and tactile receptor systems. The rate of cell proliferation in these four clusters, revealed by BrdU labeling, is sensitive to the living conditions of the animals: individuals isolated in small spaces (impoverished condition) exhibit a lower rate of cell proliferation in comparison to their siblings living together in larger areas (enriched condition), although both groups were fed to satiation. Reduction in the rate of proliferation can be measured 1 to 2 weeks after the animals are subjected to the impoverished condition. Counts of the labeled neurons that survive after 4 weeks of subjection to the two conditions show that fewer new neurons survive in the brains of animals that have lived for 2 weeks in the impoverished condition in comparison to their siblings living in the enriched conditions. Factors such as surface area, depth of water, and social interaction can all play a role in determining both the rate of new neuron production and the incorporation of the new neurons into the brain of freshwater crayfish. The results indicate a high degree of neuronal plasticity in the crayfish brain that is highly sensitive to the conditions under which the animals are kept.     

Efficacy of hyaluronic acid binding assay in selecting motile spermatozoa with normal morphology at high magnification

Background  

The present study aimed to evaluate the efficacy of the hyaluronic acid (HA) binding assay in the selection of motile spermatozoa with normal morphology at high magnification (8400x).     

Adult neurogenesis in the crayfish brain: Proliferation,migration, and possible origin of precursor cells

The birth of new neurons and their incorporation into functional circuits in the adult brain is a characteristic of many vertebrate and invertebrate organisms, including decapod crustaceans. Precursor cells maintaining life‐long proliferation in the brains of crayfish (Procambarus clarkii, Cherax destructor) and clawed lobsters (Homarus americanus) reside within a specialized niche on the ventral surface of the brain; their daughters migrate to two proliferation zones along a stream formed by processes of the niche precursors. Here they divide again, finally producing interneurons in the olfactory pathway. The present studies in P. clarkii explore (1) differential proliferative activity among the niche precursor cells with growth and aging, (2) morphological characteristics of cells in the niche and migratory streams, and (3) aspects of the cell cycle in this lineage. Morphologically symmetrical divisions of neuronal precursor cells were observed in the niche near where the migratory streams emerge, as well as in the streams and proliferation zones. The nuclei of migrating cells elongate and undergo shape changes consistent with nucleokinetic movement. LIS1, a highly conserved dynein‐binding protein, is expressed in cells in the migratory stream and neurogenic niche, implicating this protein in the translocation of crustacean brain neuronal precursor cells. Symmetrical divisions of the niche precursors and migration of both daughters raised the question of how the niche precursor pool is replenished. We present here preliminary evidence for an association between vascular cells and the niche precursors, which may relate to the life‐long growth and maintenance of the crustacean neurogenic niche. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009     

Immunization of sheep against infection with larvae of the blowfly Lucilia cuprina

Sheep were repeatedly exposed to a second stage excretory-secretory antigen preparation of Lucilia cuprina by intradermal injection (S group) or intranasal aerosol (I group) in an attempt to induce immunity to the larvae. Hypersensitivity responses to the injections were monitored and correlated with larval numbers at subsequent challenge. Intradermal injections showed that the immediate or IgE-mediated and the intermediate or Arthus response were the major skin hypersensitivity reactions to the larval antigens. At challenge there was no significant reduction in larval numbers between the S and the control group, however the Arthus reaction did show some correlation with larval recoveries in the S group. There was a significant reduction in larval numbers (P < 0.005 Mann-Whitney U Test) between the I and the control group. In addition, the animals which showed respiratory hypersensitivity to the aerosol during the immunization period had the lowest larval recoveries. The results of a second challenge in the I group did not show continued protection. It is suggested that the protective response was suppressed by exposure to antigens at the first challenge infection. Exudate samples recovered during the infection were analysed for protein amount and the results were correlated with larval survival. They suggested that two separate mechanisms of resistance are operating in this experiment. The first occurs early in the infection, is probably associated with immediate hypersensitivity, and may control the initiation of protein leakage. The second occurs later in the infection and may result in the leakage of proteins able to control larval survival.     

Routes to improving the reliability of low level DNA analysis using real-time PCR

Background  

Accurate quantification of DNA using quantitative real-time PCR at low levels is increasingly important for clinical, environmental and forensic applications. At low concentration levels (here referring to under 100 target copies) DNA quantification is sensitive to losses during preparation, and suffers from appreciable valid non-detection rates for sampling reasons. This paper reports studies on a real-time quantitative PCR assay targeting a region of the human SRY gene over a concentration range of 0.5 to 1000 target copies. The effects of different sample preparation and calibration methods on quantitative accuracy were investigated.     

Tetrapod phylogeny inferred from 18S and 28S ribosomal RNA sequences and a review of the evidence for amniote relationships [published erratum appears in Mol Biol Evol 1991 May;8(3):398]

The 18S ribosomal RNAs of 21 tetrapods were sequenced and aligned with five published tetrapod sequences. When the coelacanth was used as an outgroup, Lissamphibia (living amphibians) and Amniota (amniotes) were found to be statistically significant monophyletic groups. Although little resolution was obtained among the lissamphibian taxa, the amniote sequences support a sister-group relationship between birds and mammals. Portions of the 28S ribosomal RNA (rRNA) molecule in 11 tetrapods also were sequenced, although the phylogenetic results were inconclusive. In contrast to previous studies, deletion or down- weighting of base-paired sites were found to have little effect on phylogenetic relationships. Molecular evidence for amniote relationships is reviewed, showing that three genes (beta-hemoglobin, myoglobin, and 18S rRNA) unambiguously support a bird-mammal relationship, compared with one gene (histone H2B) that favors a bird- crocodilian clade. Separate analyses of four other genes (alpha- crystallin A, alpha-hemoglobin, insulin, and 28S rRNA) and a combined analysis of all sequence data are inconclusive, in that different groups are defined in different analyses and none are strongly supported. It is suggested that until sequences become available from a broader array of taxa, the molecular evidence is best evaluated at the level of individual genes, with emphasis placed on those studies with the greatest number of taxa and sites. When this is done, a bird-mammal relationship is most strongly supported. When regarded in combination with the morphological evidence for this association, it must be considered at least as plausible as a bird-crocodilian relationship.      

Molecular vaccines against parasites

Prophylactic vaccines can be expected to be one of the major practical outputs of parasitology research. Various groups within Australia have pursued the vaccine objective for several years, with particular emphasis on blood-stage falciparum malaria in man, intestinal helminths of sheep and cattle, cutaneous myiasis (blowfly strike) in sheep, cysticercosis in sheep and cattle, bovine babesiosis, and cattle ticks. Other vaccine programmes are concerned with giardiasis, filariasis, toxoplasmosis, fascioliasis, coccidiosis in poultry, cutaneous leishmaniasis and schistosomiasis japonica. For many years, the only available vaccine against a parasite in Australia has been the attenuated Babesia bovis vaccine produced by the Tick Fever Research Centre of the Queensland Department of Primary Industries. Strategies for achieving molecular vaccines are generally similar within the various research groups. They involve analysis of the immunology and immunochemistry of a model or in-vitro system; development of functional monoclonal antibodies; analysis of antibody specificities in clinically and/or functionally defined polyclonal sera; screening of cDNA or genomic expression libraries; peptide synthesis; identification of an appropriate vaccination schedule involving adjuvants or new recombinant DNA-based antigen delivery systems. Outlined below are five of the major vaccine programmes.     

The structural organization of glomerular neuropile in the olfactory and accessory lobes of an Australian freshwater crayfish,Cherax destructor

Summary The olfactory and accessory lobes of the crayfish, Cherax destructor contain glomeruli. Light microscope and electron microscope studies show that these glomeruli are the only regions of synaptic activity in the lobes and that at least four separate sets of axons meet within the glomeruli. The olfactory glomeruli are column shaped, complex structures with no large single pre- or postsynaptic elements. The accessory lobe glomeruli follow a more conventional pattern and each has one large axon ending in a terminal arborization where it makes synaptic contact with large numbers of smaller fibres. The large fibre is presynaptic.