Complement-mediated binding of immunoglobulins to some endocrine cells of the pancreas and gut.

Unspecific binding of immunoglobulins to gastrin, somatostain and glucagon cells of the gastrointestinal mucosa or pancreas has been found to occur through a nonantigen-antibody mechanism mediated by the C14 fraction of complement. The phenomenon represents an important drawback in hormone immunohistochemistry, which can be overcome by using complement deprived, highly dilute anti-hormone sera.     

Cell counting and three-dimensional reconstruction to identify a cellular wave in human spermatogenesis

OBJECTIVE: To collect quantitative and stereologic data on the main cell types represented in the seminiferous tubule in order to produce a three-dimensional representation of the morphologic events of normal cell production and maturation. STUDY DESIGN: Three-dimensional reconstruction and differential cell counting were performed on serial sections of normal testicular tissue from normal young men through image analysis and computer-based rendering. RESULTS: Peculiar periodicity in the total number of tubular cells considered along the sequence of serial sections was recognized. Also, consensual periodicity pertaining to each cell type was recognized. Adjacent high cellularity and low cellularity segments included a fairly constant mixture of cell types considered. CONCLUSION: A newly defined cellular wave, composed of regular alternations of high and low cellularity segments, was identified in the normal human seminiferous tubule.     

Codon usage bias and the evolution of influenza A viruses. Codon Usage Biases of Influenza Virus

Background  

The influenza A virus is an important infectious cause of morbidity and mortality in humans and was responsible for 3 pandemics in the 20^th century. As the replication of the influenza virus is based on its host's machinery, codon usage of its viral genes might be subject to host selection pressures, especially after interspecies transmission. A better understanding of viral evolution and host adaptive responses might help control this disease.     

Determination, diversification and multipotency of mammalian myogenic cells

In amniotes, myogenic commitment appears to be dependent upon signaling from neural tube and dorsal ectoderm, that can be replaced by members of the Wnt family and by Sonic hedgehog. Once committed, myoblasts undergo different fates, in that they can differentiate immediately to form the myotome, or later to give rise to primary and secondary muscle fibers. With fiber maturation, satellite cells are first detected; these cells contribute to fiber growth and regeneration during post-natal life. We will describe recent data, mainly from our laboratory, that suggest a different origin for some of the cells that are incorporated into the muscle fibers during late development. We propose the possibility that these myogenic cells are derived from the vasculature, are multi-potent and become committed to myogenesis by local signaling, when ingressing a differentiating muscle tissue. The implications for fetal and perinatal development of the whole mesoderm will also be discussed.