In silico biophysics and hemorheology of blood hyperviscosity syndrome

Hyperviscosity syndrome (HVS) is characterized by an increase of the blood viscosity by up to seven times the normal blood viscosity, resulting in disturbances to the circulation in the vasculature system. HVS is commonly associated with an increase of large plasma proteins and abnormalities in the properties of red blood cells, such as cell interactions, cell stiffness, and increased hematocrit. Here, we perform a systematic study of the effect of each biophysical factor on the viscosity of blood by employing the dissipative particle dynamic method. Our in silico platform enables manipulation of each parameter in isolation, providing a unique scheme to quantify and accurately investigate the role of each factor in increasing the blood viscosity. To study the effect of these four factors independently, each factor was elevated more than its values for a healthy blood while the other factors remained constant, and viscosity measurement was performed for different hematocrits and flow rates. Although all four factors were found to increase the overall blood viscosity, these increases were highly dependent on the hematocrit and the flow rates imposed. The effect of cell aggregation and cell concentration on blood viscosity were predominantly observed at low shear rates, in contrast to the more magnified role of cell rigidity and plasma viscosity at high shear rates. Additionally, cell-related factors increase the whole blood viscosity at high hematocrits compared with the relative role of plasma-related factors at lower hematocrits. Our results, mapped onto the flow rates and hematocrits along the circulatory system, provide a correlation to underpinning mechanisms for HVS findings in different blood vessels.     

GDNF modulates HO-1 expression in substantia nigra postnatal cell cultures

Heme oxygenase-1 (HO-1) has been strongly highlighted because of its induction in many cell types by toxic stimuli, including oxidative stress. The intense HO-1 immunostaining in the substantia nigra of Parkinson disease (PD) patients suggests its involvement in the pathogenesis of this neurodegenerative disease. In this work we investigated HO-1 expression in rat substantia nigra postnatal cell cultures under conditions mimicking dopamine toxicity and its modulation by glial cell line-derived neurotrophic factor (GDNF), a potent neuroprotective factor for dopaminergic neurons. In neuron–glia cultures, we found that H₂O₂, a product of dopamine metabolism, or l-3,4-dihydroxyphenylalanine (l-DOPA), the dopamine precursor used in the therapy of PD, induced a fast up-regulation of HO-1 mRNA and protein levels, followed by a secondary down-regulation. H₂O₂ and l-DOPA also increased HO-1 expression in astrocyte cultures, but with a delayed time course in H₂O₂-treated cultures. HO-1 expression was decreased in neuron–glia cultures under conditions under which GDNF up-regulation was observed. Because exogenously applied GDNF prevented HO-1 up-regulation in cultures treated with H₂O₂ or l-DOPA, and antibody neutralization of GDNF prevented the secondary HO-1 down-regulation observed in neuron–glia cultures, we propose that GDNF negatively modulates HO-1 expression induced by oxidative stress. To our knowledge, this is the first report showing the modulation of HO-1 expression by GDNF.     

Tenoxicam Exerts a Neuroprotective Action after Cerebral Ischemia in Rats

In this study we investigated the effects of Tenoxicam, a type 2 cyclooxygenase (COX-2) inhibitor, on brain damage induced by ischemia-reperfusion. Male Wistar rats (18-month old average) were anesthetized and submitted to ischemia occlusion of both common carotid arteries (BCAO) for 45 min. After 24 h of reperfusion, rats were decapitated and hippocampi removed for further assays. Animals were divided into sham-operated, ischemia, ischemia + Tenoxicam 2.5 mg/kg, and ischemia + Tenoxicam 10 mg/kg groups. Tenoxicam was administered intraperitoneally immediately after BCAO. Histological analyses show that ischemia produced significant striatal as well as hippocampal lesions which were reversed by the Tenoxicam treatment. Tenoxicam also significantly reduced, to control levels, the increased myeloperoxidase activity in hippocampus homogenates observed after ischemia. However, nitrite concentrations showed only a tendency to decrease in the ischemia + Tenoxicam groups, as compared to that of ischemia alone. On the other hand, hippocampal glutamate and aspartate levels were not altered by Tenoxicam. In conclusion, we showed that ischemia is certainly related to inflammation and to increased free radical production, and selective COX-2 inhibitors might be neuroprotective agents of potential benefit in the treatment of cerebral brain ischemia.     

Stage-dependent effects of cell-to-cell connections on in vitro induced neurogenesis

NE-4C, a p53-deficient, immortalized neuroectodermal progenitor cell line, was used to investigate the role and importance of cellular interactions in neural commitment and differentiation. NE-4C cells give rise to neurons and astrocytes in the presence of all-trans retinoic acid, if they can establish intercellular contacts. Aggregation per se, however, was insufficient to induce large-scale neuron formation. In the absence of RA, the majority of the aggregated cells died. For neuron formation, therefore, concerted actions of RA and cellular interaction were needed. Electron microscopic and electrophysiological studies revealed that gap junctions were formed between the cells. Persistent blockage of communication via gap junctions with gap junction blockers, however, had no effects on neuron formation. If cell-to-cell connections were disrupted on the fourth day after induction, the rate of neuron production increased significantly. The contact interactions formed between already committed progenitor cells seemed to hinder the formation of novel neurons. The process resembled the phenomenon called "lateral inhibition" first observed in the course of neurogenesis in Drosophila. Our results indicate that NE-4C cells provide a useful model system to investigate the role of contact communication during some early steps of neurogenesis.     

Niche-specific association of Aeromonas Ribotypes from human and environmental origin

A total of 88 Aeromonas isolates from distinct locations and sources (39 from extraintestinal infections, 31 from diarrhoeic, ten from non-diarrhoeic faeces, all human, and eight from fresh water) were subjected to phenospecies identification, serotyping, ribotyping and detection of some virulence markers. The strains belonged to four different phenospecies marked by 19 O serogroups and 38 ribotypes. No strong correlation between these parameters was found, and no group, as defined by the typing methods, could be characterized with a particular set of virulence markers. There was a clear association of ribotypes with the source of the strains. Cluster analysis allowed the identification of a complex of ribotypes belonging to distinct but related sources, including clinical and environmental isolates. These results suggest that ribotyping may be an epidemiological tool suitable for the study of Aeromonas infections.     

Phylogeny shape and the phylogenetic comparative method

We explored the impact of phylogeny shape on the results of interspecific statistical analyses incorporating phylogenetic information. In most phylogenetic comparative methods (PCMs), the phylogeny can be represented as a relationship matrix, and the hierarchical nature of interspecific phylogenies translates into a distinctive blocklike matrix that can be described by its eigenvectors (topology) and eigenvalues (branch lengths). Thus, differences in the eigenvectors and eigenvalues of different relationship matrices can be used to gauge the impact of possible phylogeny errors by comparing the actual phylogeny used in a PCM analysis with a second phylogenetic hypothesis that may be more accurate. For example, we can use the sum of inverse eigenvalues as a rough index to compare the impact of phylogenies with different branch lengths. Topological differences are better described by the eigenvectors. In general, phylogeny errors that involve deep splits in the phylogeny (e.g., moving a taxon across the base of the phylogeny) are likely to have much greater impact than will those involving small perturbations in the fine structure near the tips. Small perturbations, however, may have more of an impact if the phylogeny structure is highly dependent (with many recent splits near the tips of the tree). Unfortunately, the impact of any phylogeny difference on the results of a PCM depends on the details of the data being considered. Recommendations regarding the choice, design, and statistical power of interspecific analyses are also made.     

Comparison between the toluidine blue stain and the Feulgen reaction for evaluation of rabbit sperm chromatin condensation and their relationship with sperm morphology

Sperm chromatin alteration is an important feature that can affect fertility of the male rabbit. This study compared toluidine blue staining with Feulgen reaction (as methods for evaluating chromatin alteration) and investigated the relationship between sperm morphology and chromatin alteration. Seven hundred rabbit ejaculates of animals with unknown fertility were used. Primary and secondary morphological sperm abnormalities were evaluated in semen smears with phase-contrast microscopy. Chromatin alterations were evaluated in semen smears stained with toluidine blue (pH 4.0 and 5.0) and with the Feulgen reaction. While the three methods were equally efficacious for identification of chromatin alterations, toluidine blue staining was more appropriate to characterize the intensity of chromatin alterations. The correlation between primary sperm defects and chromatin alteration was high and positive, suggesting that sperm chromatin structure affected sperm head morphology. The correlation between secondary sperm defects and chromatin alteration was also positive, but lower. The final chromatin compaction occurs in the epididymus, where secondary sperm defects originate. Therefore, the causes of secondary sperm defects could also intervene with final chromatin compaction. In summary, the toluidine blue stain was an effective means of evaluating the sperm chromatin alteration in rabbit spermatozoa.     

The Effect of Zn(II) Ions and Reactive Oxygen on the Uptake of Zinc and Production of Carotenoids by Selected Red Yeasts

Three strains of red yeast Rhodosporidium kratochvilovae, Rhodotorula glutinis and Sporidiobolus salmonicolor were studied for their responses to the presence metal stress, oxidative stress and a combination of these stress factors. For all yeast strains, the production of β‐carotene increased in stress conditions. The combination of H₂O₂ and Zn²⁺ significantly activated the pathways for the production of torularhodin in the strain R. glutinis (from 250 to 470 μg g^?1 DCW) as well as β‐carotene (from 360 to 1100 μg g^?1 DCW) and torulene (from 100 to 360 μg g^?1 DCW) in Sp. salmonicolor. Strains of R. glutinis and Rh. kratochvilovae bound the majority of Zn(II) ions to the fibrillar part of the cell walls, whereas the strain Sp. salmonicolor bound them to both extracellular polymers and the fibrillar part of the cell walls. A decrease in the ability of yeasts to tolerate higher concentrations of Zn(II) in the presence of free radicals (hydrogen peroxide) was also found.     

Information‐gathering as a response to manipulated signals in the eastern fence lizard,Sceloporus undulatus

Colorful visual signals are used across taxa to convey information during agonistic male‐male encounters, which are important for sexual selection. Although much is known about the information content of color signals, less is known about how receivers interpret this information. Here, using territorial Sceloporus undulatus lizards in a natural setting, we examined receiver response to intruders with different color patch sizes to determine (a) if patch size conveys information assessed during male‐male interactions and (b) if/how receivers modulate their behavioral responses to different types of behavioral signals. We found that larger lizards had longer and wider patches, indicating that the size of the patches may be one of the many characteristics of these patches that is used by males to convey information. Free‐ranging subject males also produced more headbob displays in response to intruders with small patches and took marginally longer to react to intruders with large patches. However, we found no differences in the aggressiveness of the response (i.e., fullshows). This indicates that patch size conveys information that is employed during territorial disputes, but that the response is primarily in terms of timing, allowing lizards to gather more information about intruders, instead of aggressive behavior (i.e., fullshows).     

Reproductive strategy of Psectrogaster rhomboides Eigenmann & Eigenmann, 1889, a freshwater fish from Northeastern Brazil

Several environmental parameters related to the spawning season of the freshwater fish, Psectrogaster rhomboides were identified. The hypothesis predicts synchrony of the spawning season with the rainy period, presenting a seasonal reproductive strategy. This study investigated the total body length and body mass, sex ratio, body size at first sexual maturity, gonadosomatic index, condition factor, fecundity and reproductive period of P. rhomboides in the natural environment. Twelve monthly samplings (mean n = 20) were carried out from March 2009 to February 2010. Fish were captured using 4 cm diameter cast nets and environmental parameters such as rainfall, temperature, dissolved oxygen concentration, pH and electrical conductivity of the water were registered. The sampled population of P. rhomboides (n = 444) showed a sex ratio of 1 : 1. Females attained first sexual maturity at 15 cm total length and males at 15.3 cm total length. Spawning occurred from March to May, with high gonadosomatic index values during the rainy season. This species is a total spawner, with a mean fecundity of 6188 (±367) mature oocytes. P. rhomboides presents a seasonal reproductive strategy, providing a population increase and exploitation of the environmental resources during the rainy period. Rainfall (196.5 ± 4.9 mm) and the concentration of dissolved oxygen (7.82 ± 0.7018 mg L^?1) were influential factors during the spawning season. Gonadosomatic index and the condition factor were negatively correlated during the gonadal development cycle of this species. The monthly gonadosomatic index values show that spawning begins when the rainy season is at its maximum and ends synchronously (females r = 0.9171; males r = 0.889) with the end of the rainy season.