The Dynamics of Sustained Reentry in a Loop Model with Discrete Gap Junction Resistance

Dynamics of reentry are studied in a one dimensional loop of model cardiac cells with discrete intercellular gap junction resistance ($R$). Each cell is represented by a continuous cable with ionic current given by a modified Beeler-Reuter formulation. For $R$ below a limiting value, propagation is found to change from period-1 to quasi-periodic ($QP$) at a critical loop length ($L_{crit}$) that decreases with $R$. Quasi-periodic reentry exists from $L_{crit}$ to a minimum length ($L_{min}$) that is also shortening with $R$. The decrease of $L_{crit}(R)$ is not a simple scaling, but the bifurcation can still be predicted from the slope of the restitution curve giving the duration of the action potential as a function of the diastolic interval. However, the shape of the restitution curve changes with $R$.Comment: 6 pages, 7 figure

Genetic Background Can Result in a Marked or Minimal Effect of Gene Knockout (GPR55 and CB2 Receptor) in Experimental Autoimmune Encephalomyelitis Models of Multiple Sclerosis

PMCID: PMC379391

Bartonella quintana in Cynomolgus Monkey (Macaca fascicularis)

We identified a Bartonella quintana strain by polymerase chain reaction amplification, cloning, and sequencing of DNA extracted from lysed erythrocytes and cultured colonies grown from peripheral blood collected from a captive-bred cynomolgus monkey (Macaca fascicularis). This report describes naturally acquired B. quintana infection in a nonhuman primate

Composição e estrutura da ictiofauna demersal na Baía dos Pinheiros, Paraná

Between May of 2003 and April of 2004 the temporal changes were monitored in the structure of the demersal ichthyofauna of the Bay of Pinheiros (Paraná), through three bottom trawls accomplished monthly in each one of the four areas between the access bar and the most internal areas. In the 144 accomplished trawls 58 species belonging to 25 families were collected, totaling 18154 fishes. The families that presented larger wealth of species were Sciaenidae (15 species), Ariidae (5), Tetraodontidae (4), Engraulidae (4), Carangidae (4), Paralichthyidae (3) and Haemulidae (3). The species Stellifer rastrifer, Cathorops spixii, Chirocentrodon bleekerianus, Cynoscion leiarchus, Stellifer brasiliensis, Achirus lineatus and Micropogonias furnieri dominated in number of individuals, representing 91,4% of the total capture. Significantly, there was larger capture of number of fishes in April. Between the indexes of diversity of Shannon-Wiener and eveness of Pielou differences were not observed. Through the grouping analyses and ordination of the dominant species two groups were formed in the level of 70% of similarity. The first was composed by the dominant species S. rastrifer, C. spixii and C. leiarchus, and the second was formed by C. jamaicensis and P. harroweri, presents almost exclusively in the summer and autumn.Between May of 2003 and April of 2004 the temporal changes were monitored in the structure of the demersal ichthyofauna of the Bay of Pinheiros (Paraná), through three bottom trawls accomplished monthly in each one of the four areas between the access bar and the most internal areas. In the 144 accomplished trawls 58 species belonging to 25 families were collected, totaling 18154 fishes. The families that presented larger wealth of species were Sciaenidae (15 species), Ariidae (5), Tetraodontidae (4), Engraulidae (4), Carangidae (4), Paralichthyidae (3) and Haemulidae (3). The species Stellifer rastrifer, Cathorops spixii, Chirocentrodon bleekerianus, Cynoscion leiarchus, Stellifer brasiliensis, Achirus lineatus and Micropogonias furnieri dominated in number of individuals, representing 91,4% of the total capture. Significantly, there was larger capture of number of fishes in April. Between the indexes of diversity of Shannon-Wiener and eveness of Pielou differences were not observed. Through the grouping analyses and ordination of the dominant species two groups were formed in the level of 70% of similarity. The first was composed by the dominant species S. rastrifer, C. spixii and C. leiarchus, and the second was formed by C. jamaicensis and P. harroweri, presents almost exclusively in the summer and autumn

Prevalence of Bartonella henselae and Bartonella clarridgeiae in cats in the south of Brazil: a molecular study

Bartonella spp are the causative agent of cat scratch disease in humans. Cats are the natural reservoir of these bacteria and may infect humans through scratches, bites or fleas. Blood samples from 47 cats aged up to 12 months were collected for this study. All animals were lodged in municipal animal shelters in the Vale do Sinos region, Rio Grande do Sul, Brazil. Bartonella spp were detected by genus-specific polymerase chain reaction (PCR) and when the PCR was positive, the species were determined by DNA sequencing. A Giemsa-stained blood smear was also examined for the presence of intraerythrocytic elements suggestive of Bartonella spp infection. Phylogenetic analysis was also performed for all positive samples. Using molecular detection methods, Bartonella spp were detected in 17.02% (8/47) of the samples. In seven out of eight samples confirmed to be positive for Bartonella spp, blood smear examination revealed the presence of intraerythrocytic elements suggestive of Bartonella spp. Phylogenetic analysis characterized positive samples as Bartonella henselae (5) or Bartonella clarridgeiae (3). To the best of our knowledge, this is the first molecular study demonstrating the presence of Bartonella spp in cats from the Southern Region of Brazil

Clinical implications of a possible role of vitamin D in multiple sclerosis

Hypovitaminosis D is currently one of the most studied environmental risk factors for multiple sclerosis (MS) and is potentially the most promising in terms of new clinical implications. These practical consequences, which could be applied to MS patients without further delay, constitute the main purpose of this review. Vitamin D is involved in a number of important general actions, which were not even suspected until quite recently. In particular, this vitamin could play an immunomodulatory role in the central nervous system. Many and varied arguments support a significant role for vitamin D in MS. In animal studies, vitamin D prevents and improves experimental autoimmune encephalomyelitis. Epidemiologically, latitude, past exposure to sun and the serum level of vitamin D influence the risk of MS, with, furthermore, significant links existing between these different factors. Clinically, most MS patients have low serum levels of vitamin D and are in a state of insufficiency or even deficiency compared to the international norm, which has been established on a metabolic basis. Large therapeutic trials using vitamin D are still lacking but the first results of phase I/II studies are promising. In the meantime, while awaiting the results of future therapeutic trials, it can no longer be ignored that many MS patients have a lack of vitamin D, which could be detected by a serum titration and corrected using an appropriate vitamin D supplementation in order to restore their serum level to within the normal range. From a purely medical point of view, vitamin D supplementation appears in this light to be unavoidable in order to improve the general state of these patients. Furthermore, it cannot currently be ruled out that this supplementation could also be neurologically beneficial