Testes and ovaries are structurally and functionally different organs, but they originate from the same gonadal primordium. Here, we propose how a tissue composed of germ cells and sox9b-expressing cells underlain by a basement membrane develops a functionally common unit that reserves sexually indifferent or unfixed germline stem cells in both the ovaries and testes of adult medaka. During tes...

The chicken embryo has long been a useful model organism for studying development, including sex determination and gonadal differentiation. However, manipulating gene expression specifically in the embryonic avian gonad has been difficult. The viral vector RCASBP can be readily used for embryo-wide transgene expression; however global mis-expression using this method can cause deleterious off-t...

Intercellular cell-survival signals play a major role in animal development [1]. In the nematode Caenorhabditis elegans, however, the stereotyped cell deaths that occur reproducibly during development are regulated in a cell-autonomous fashion (or, in a few cases, by a death-inducing signal) [2]. We show here the existence of a cell-survival signal acting on the vulval precursor cells in two ne...

in this study, the morphological and histological studies of male and female gonads in mudskipper, periophthalmus waltoni koumans, 1941 from helleh estuary (bushehr province, southwestern iran) were performed to determine its gonadal development stages and histo-morphological characteristics. sampling was done from april 2010 to march 2011 and a total of 81 individuals were collected by hand ne...

In M33 cockerels, the rapid phase of testicular growth and the onset of sperm production were advanced either by increasing daylengths or an interrupted-night photoschedule; they were delayed by constant short days (8L). The results observed under constant long days (16L) were intermediate. In this strain, the cockerels maintained their mean testicular weight during the adult period while their...

In order to determine the r61e played by the central nervous system in regulating blood meal size, the ventral nerve cord was cut at various sites along its length in the female mosquito, Aedes aegypti. When the cord was cut anterior to the second abdominal ganglion, massive hyperphagia resulted, many females ruptured, and blood intake was more than four times that of the untreated controls. As...

Studies on the zebrafish model have contributed to our understanding of several important developmental processes, especially those that can be easily studied in the embryo. However, our knowledge on late events such as gonad differentiation in the zebrafish is still limited. Here we provide an analysis on the gene sets expressed in the adult zebrafish testis and ovary in an attempt to identify...

In 14 cases of the Turner syndrome and pure gonadal dysgenesis streak gonads were studied histologically. In cases where the 46,XX line was unimpaired the blood vessels of the gonad showed severe degeneration in at least 30 to 50%. These streak gonads usually contained some of the characteristic ovarian elements as well as the vascular lesions. In gonosomal monosomy, on the other hand, a simila...

In sex determination, globally acting genes control a spectrum of tissue-specific regulators to coordinate the overall development of an animal into one sex or the other. In mammals, primary sex determination initially occurs in the gonad, with the sex of other tissues specified as a secondary event. In insects and nematodes, globally acting regulatory pathways have been elucidated, but the mor...