Survivor curves for Leptospira autumnalis Akiyami A based on most-probable-number values.
The validity of survivor curves for Leptospira autumnalis Akiyami A based on most-probable-number values is supported by the following observations: (i) linear regression lines fell within most of the 95% confidence intervals; (ii) linear correlation coefficients (r) were consistently high (i.e., near -1); and (iii) statistical tests for goodness of fit usually accepted the linear model. These tests are consistent with an exponential death rate for the test organism in defined solutions. The influence of temperature and pH on survival was demonstrated by showing a statistically significant difference in survivor curve slopes.
Interaction of leptospires with human polymorphonuclear neutrophils
The role of the polymorphonuclear neutrophils (PMN) in defense against leptospires has not been adequately studied, in part, because of difficulty in quantitating pathogenic leptospires. By using pour plates to quantitate nonpathogenic leptospires and the most-probable-number procedure to quantitate the pathogenic leptospires, we examined the interactions of nonpathogenic Leptospira biflexa and pathogenic Leptospira interrogans serovar icterohemorrhagiae with human neutrophils. Phase-contrast, scanning electron, and transmission electron microscopic observations were made. Leptospires were incubated with PMN at 37 degrees C and tumbled together. There was no ingestion or killing of nonpathogenic leptospires (with no serum) or of pathogenic organisms (with 10% normal serum). However, when leptospires were incubated with PMN (without serum) in a pellet and then resuspended, 91 +/- 6% of nonpathogenic leptospires were removed from the supernatant, and 93 +/- 4% of these organisms were killed. The pathogenic leptospires became cell associated in a pellet, but were not killed by PMN even in the presence of 10% normal serum. Observations of morphological interactions indicated that PMN phagocytized the nonpathogenic leptospires in the absence of serum and that the pathogenic leptospires attached to but were not ingested by neutrophils in the presence of 10% normal serum. PMN do not seem to be an efficient defense factor for pathogenic leptospires in nonimmune hosts. The virulence of leptospires appears to be related to their ability to resist killing by serum and to resist ingestion and killing by neutrophils.
Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes
Background After domestication, the evolution of phenotypically-varied sheep breeds has generated rich biodiversity. This wide phenotypic variation arises as a result of hidden genomic changes that range from a single nucleotide to several thousands of nucleotides. Thus, it is of interest and significance to reveal and understand the genomic changes underlying the phenotypic variation of sheep breeds in order to drive selection towards economically important traits. Review Various traits contribute to the emergence of variation in sheep phenotypic characteristics, including coat color, horns, tail, wool, ears, udder, vertebrae, among others. The genes that determine most of these phenotypic traits have been investigated, which has generated knowledge regarding the genetic determinism of several agriculturally-relevant traits in sheep. In this review, we discuss the genomic knowledge that has emerged in the past few decades regarding the phenotypic traits in sheep, and our ultimate aim is to encourage its practical application in sheep breeding. In addition, in order to expand the current understanding of the sheep genome, we shed light on research gaps that require further investigation. Conclusions Although significant research efforts have been conducted in the past few decades, several aspects of the sheep genome remain unexplored. For the full utilization of the current knowledge of the sheep genome, a wide practical application is still required in order to boost sheep productive performance and contribute to the generation of improved sheep breeds. The accumulated knowledge on the sheep genome will help advance and strengthen sheep breeding programs to face future challenges in the sector, such as climate change, global human population growth, and the increasing demand for products of animal origin.