Sexual advertisement and immune function in an arachnid species (Lycosidae)

A simple version of the immunocompetence handicap hypothesizesthat through condition-dependence, the size of the sexual traitmay be positively related to immune function at the populationlevel. In the present study, we investigated the relationshipbetween sexual advertisement and immune function in a naturalpopulation of male wolf spiders, Hygrolycosa rubrofasciata (Araneae:Lycosidae). Males of H. rubrofasciata have a costly and condition-dependentacoustic signal, courtship drumming. In the mating season, malesdrum against dry leaves while wandering around the habitat searchingfor receptive females. Males increase their mating success byincreasing their drumming rate and mobility. We used drummingrate and mobility measured without female proximity as estimatesof sexual advertisement. As estimates of male immune function,we used encapsulation rate and lytic activity. Encapsulationrate is a common challenging technique, which measures immuneresponse against multicellular parasites. Lytic activity isa monitoring technique, which measures immune response againstpathogens. Our results show that males with higher drummingrate had higher encapsulation rate. This suggests that femalesmight use drumming rate as a signal for choosing males withgood immunocompetence. Moreover, our results show that maleswith higher mobility had higher lytic activity. As females aremore likely to encounter those males that have higher mobility,this might also select males with better immune function. Ourresults suggest that the immunocompetence handicap might workalso among spiders, although we could not assess the causalityof the relationship between sexual selection and immune functionin this correlational study.     

Antagonism of kainic acid lesions in the mouse hippocampus by U-54494A and U-50488H.

A morphometric study of kainic acid- (KA) induced lesions was designed for the study of the interaction of the diamines U-5449A and U-50488H with excitatory amino acids, and the dose-response relationship thereof. IC50S determined for binding at the kappa receptor and other opioid receptors demonstrated the lack of kappa activity of U-54494A, a structurally related analog of U-50488H. Both opiate kappa receptor related anticonvulsant diamines were tested for their ability to protect the mouse hippocampus from the cytopathological changes induced by KA in neurons and glia. The damage observed with i.c.v. KA in mouse was restricted to neurons of the CA3 pyramidal region and glia of the hippocampus. It involved massive cell loss and shrunken neurons with dark cytoplasm and nuclei. Groups treated with combinations of KA and U-54494A or U-50488H showed scarce damage, but patches of necrotic changes were still observed. Control animals treated with saline (i.c.v.) and U-54494A (s.c.) or U-50488H (s.c.) did not suffer any noticeable alterations of the polymorphic layers of the hippocampal formation. Image analysis of the CA3 area of the hippocampus was used to quantitate the vacuolization induced by KA lesions in the control and treated groups. By this method, both U-54494A and U-50488H were shown to protect this area in a dose-related fashion as evidenced by reduced vacuolization. The anticonvulsant properties of these compounds may result in the antagonism of the excitotoxic lesions. More specifically, the ability of these diamines to block depolarization-induced influxes of Ca++ may protect the CA3 cells from the cytotoxic effects of persistent depolarization.     

Effect of sodium ion on the affinity of naloxone for the kappa opioid receptor

Several investigators have observed that sodium ion enhances the binding of naloxone to opioid receptors. This effect has generally been attributed to allosteric modulation of the state of the mu receptor. However, a recent claim has been made that the enhancement does not involve a change in the mu receptor, but instead occurs because naloxone becomes a more kappa-specific drug when sodium ion is present in high concentration. Since the claim was not based on experimental evidence from binding studies involving known high-affinity kappa ligands, we have investigated the competition of naloxone for the kappa site using [3H]U-69593 as the marker for receptor binding. Assays were carried out in the presence and absence of 100 mM NaCl. The results of the study indicate that sodium ion does not increase the affinity of naloxone or U-69593 for the kappa receptor.     

Transformation of Bacillus amyloliquefaciens protoplasts with plasmid DNA

Abstract A method for efficient polyethylene glycol (PEG)-mediated transformation of Bacillus amyloliquefaciens protoplasts with plasmid DNA is described. The best conditions found for protoplast regeneration included using 0.45 M sucrose both during the cultivation of the cells and (as an osmotic stabilizer) during their treatment with lysozyme, whereas 0.25 M sodium-succinate was added to the regeneration plates. Under these conditions about 5–10% of input cells regenerated. The highest transformation frequency with plasmid DNA was obtained with a PEG 6000 concentration of 22.5% (w/v). Transforming B. amyloliquefaciens strains with the plasmid pUB110 isolated from B. amyloliquefaciens resulted in 2–4 · 10⁵ transformants/μg DNA, 100–1 000-times as high as with DNA from Bacillus subtilis , suggesting a restriction barrier between the two species. Transformation of B. amyloliquefaciens with plasmids pC194 or pE194 cop -6 gave poor yields and no restriction barrier could be demonstrated for these plasmids. However, by curing pC194 from one of the transformants, a mutant strain compatible to both the plasmids could be isolated, yielding 2–3·10⁴ transformants/μg DNA. Both laboratory and industrial B. amyloliquefaciens strains could be transformed with the procedure.     

Inverse electrocardiographic transformations: dependence on the number of epicardial regions and body surface data points

The inverse problem of electrocardiography, the computation of epicardial potentials from body surface potentials, is influenced by the desired resolution on the epicardium, the number of recording points on the body surface, and the method of limiting the inversion process. To examine the role of these variables in the computation of the inverse transform, Tikhonov's zero-order regularization and singular value decomposition (SVD) have been used to invert the forward transfer matrix. The inverses have been compared in a data-independent manner using the resolution and the noise amplification as endpoints. Sets of 32, 50, 192, and 384 leads were chosen as sets of body surface data, and 26, 50, 74, and 98 regions were chosen to represent the epicardium.The resolution and noise were both improved by using a greater number of electrodes on the body surface. When 60% of the singular values are retained, the results show a trade-off between noise and resolution, with typical maximal epicardial noise levels of less than 0.5% of maximum epicardial potentials for 26 epicardial regions, 2.5% for 50 epicardial regions, 7.5% for 74 epicardial regions, and 50% for 98 epicardial regions. As the number of epicardial regions is increased, the regularization technique effectively fixes the noise amplification but markedly decreases the resolution, whereas SVD results in an increase in noise and a moderate decrease in resolution. Overall the regularization technique performs slightly better than SVD in the noise-resolution relationship.There is a region at the posterior of the heart that was poorly resolved regardless of the number of regions chosen. The variance of the resolution was such as to suggest the use of variable-size epicardial regions based on the resolution.     

Apoptosis Induced via AMPA-Selective Glutamate Receptors in Cultured Murine Cortical Neurons

Abstract: We have investigated the mechanisms of cell death induced by long-term exposure to the glutamate receptor agonist ( S )-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate [( S )-AMPA]. Using primary cultures of pure neurons (95%) grown in serum-free conditions, we found that 24-h exposure to ( S )-AMPA (0.01–1,000 µ M ) induced concentration-dependent neuronal cell death (EC₅₀ = 3 ± 0.5 µ M ) with cellular changes including neurite blebbing, chromatin condensation, and DNA fragmentation, indicative of apoptosis. ( S )-AMPA induced a delayed cell death with DNA fragmentation occurring in ∼50% of cells at concentrations between 100 and 300 µ M detected using terminal transferase-mediated dUTP nick end-labeling (TUNEL) and agarose gel electrophoresis. Apoptotic chromatin condensation was detected using 4,6-diamidino-2-phenylindole, a fluorescent DNA binding dye. Cell death induced by ( S )-AMPA was attenuated by the AMPA receptor-selective antagonist LY293558 (10 µ M ) and the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 50 µ M ), yielding EC₅₀ values of 73 ± 5 and 265 ± 8 µ M , respectively, and was unaffected by the NMDA receptor antagonist MK-801 (10 µ M ). The number of apoptotic nuclei induced by 300 µ M ( S )-AMPA (57%) was also reduced substantially by the antagonists LY293558 and CNQX, with only 20% and 18% of neurons, respectively, staining TUNEL-positive at 24 h. In addition, cycloheximide (0.5 µg/ml) also inhibited ( S )-AMPA-induced DNA fragmentation and cell death. Our results show that long-term exposure to AMPA can induce substantial neuronal death involving apoptosis in cultured cortical neurons, suggesting a wide involvement of AMPA-sensitive glutamate receptors in excitotoxic injury and neurodegenerative pathologies.     

Role of agonist and antagonist muscle strength in performance of rapid movements

Six subjects performed rapid self-terminated elbow movements under different mechanical conditions prior to, and 5 weeks after an elbow extensor strengthening programme. Despite the large difference in the strengths of elbow flexors and extensors, the pretest did not demonstrate significant differences between the movement time of flexion and extension movements performed under the same mechanical conditions. The results obtained in the posttest demonstrated a decrease in movement time (i.e. an increase in movement speed) in both elbow flexion and extension movements under some mechanical conditions. In addition, flexion movements demonstrated a relative increase in the acceleration time (acceleration time as a proportion of the movement time). It was concluded that the strength of both the agonist and antagonist muscles was important for the performance of rapid movements. Stronger agonists could increase the acceleration of the limb being moved, while stronger antagonists could facilitate the arrest of the limb movement in a shorter time, providing a longer time for acceleration.