Expression pattern of vasa in gonads of sea cucumber Apostichopus japonicus during gametogenesis and reproductive cycle

The vasa gene is a reliable germline marker to study the origin and development of germ cells and gonads, although the gene product (mRNA or protein) varies between different species. However, there has been little study on vasa genes in holothuroids to date. Here we determined the expression characteristics of the Apostichopus japonicus vasa gene (Aj-vasa) during gametogenesis in the ovary and testis using in situ hybridization and immunohistochemistry. During oogenesis, the expression pattern of Aj-vasa coincided at the mRNA and protein levels. Intensive signals in oogonia decreased gradually with the development of oocytes. Interestingly, the pattern was different during spermatogenesis. The Aj-vasa mRNA level was the highest in spermatogonia, reduced in spermatocytes, low in spermatids and absent in spermatozoa, but the Aj-VASA protein was restricted to spermatogonia and early spermatocytes. These expression characteristics of Aj-vasa persisted in both male and female gonads throughout the reproductive cycle. Our findings show that Aj-vasa mRNA is a good marker for studying the origin and migration of germline cells; moreover, Aj-VASA is a useful tool to identify spermatogonia in A. japonicus. Our findings indicate that Aj-vasa is vital in the development and differentiation of germ cells.     

The reproductive biology of closely related coral species: gametogenesis in<Emphasis Type="Italic"> Madracis</Emphasis> from the southern Caribbean

Reproductive patterns were studied in closely related coral species of the genus Madracis on Curaçao, Netherlands Antilles. Gonadal development of six sympatric species was examined over a 13-month period. Reproductive differences among Madracis species are small. All species are hermaphroditic brooders and show similar patterns in gamete development. Timing of gamete maturation is positively correlated with seawater temperature in all species. Oocyte development typically begins in June and precedes the development of spermaries. Mature gametes, male and female, are present from August to November when seawater temperatures reach their yearly maximum. Developmental pathways for male and female gametes are identical among species. Interspecific differences exist in the number and size of oocytes. Our data indicates that differences in gametogenic development between closely related, but ecologically different subspecies are small or absent and do not necessarily match with species separations based on morphological criteria.Communicated by Topic Editor D. Barnes     

Antimicrobial proteins in chicken reproductive system

Antimicrobial activity was detected in the ovary and oviduct tissues of healthy mature White Leghorn hens, Gallus gallus. Two antimicrobial proteins were purified to homogeneity using acid extraction followed by multiple steps of chromatography and the pure proteins were further characterized biochemically. Peptide mixtures obtained after enzymatic digestion of the chicken antimicrobial proteins were analyzed using peptide mass fingerprinting and partial sequencing by tandem nanoelectrospray mass spectrometry and the proteins were identified as histones H1 and H2B. Chicken histone antimicrobial proteins were active against both Gram-positive and Gram-negative bacteria. The abundance of these proteins in the reproductive tissues and their broad-spectrum antimicrobial nature may indicate their defensive role against pathogens during the follicle development in the ovary and egg formation in the oviduct. The discovery of antimicrobial histones in chicken reproductive system provides further evidence that histones may play a role in innate immunity against microorganisms in a wide range of animal species.     

A freeze-fracture study of the digestive tract of the parasitic nematode Trichinella

Freeze-fracture preparations of the esophagus and intestine of larvae and adults of the nematode Trichinella spiralis illustrate the distribution of intramembranous particles in membranes of a number of cell types, and several specializations were found. Esophageal glands are prominently linked by gap junctions, but gap junctions were not found between intestinal cells. Muscle cells of the esophagus have rectilinear arrays of particles, thought to be points of adherence of the muscles to the esophageal epithelium. Clusters of particles are associated with these arrays and particle-free areas (probably Z bodies) also occur. Intestinal cells have small particles in their microvilli, large particles in the cells' apical membranes, and intermediate size particles, similar to membranes of other cells, in the lateral and basal membranes. Apical smooth septate junctions and tricellular junctions occur between intestinal cells.     

The effects of prostomium and proventriculus removal on sex determination and gametogenesis inTyposyllis pulchra (Polychaeta: Syllidae)

Summary The prostomium alone or the prostomium and proventriculus of reproductiveTyposyllis pulchra were periodically removed at known stages of oogenesis and the gametes were examined by transmission electron microscopy. If the proventriculus and prostomium were simultaneously removed prior to day 3 of the stolonization sequence, before gonial differentiation, the time reruired for stolon formation and concomitant gametogenesis was shortened; the animals, all of which had previously reproduced as females, produced only ultrastructurally normal sperm. Spermatogenesis in these induced males began earlier in the stolonization period than in normal males. However, the cytological events of spermatogenesis were not accelerated. When the same operation was performed after differentiated oocytes were present, gamete cytodifferentiation and development time did not appear to be affected and the animals remained female. Removal of the prostomium alone, formerly thought to have no effect, caused high mortality and if removed prior to day 3 appeared to prevent both stolonization and gametogenesis. Ultrastructural investigation of these animals shows that gonads are maintained, but that gonial cells fail to differentiate or produce gametes. The subsequent removal of the proventriculus and regenerating prostomium from these animals allows them to mature as induced males. This suggests a prostomial role in regulating the endocrine activity of the proventriculus during the reproductive cycle.     

Alternative morphs and plasticity of vulval development in a rhabditid nematode species

The nematode species Rhabditis sp. SB347 (Family Rhabditidae) in standard culture conditions displays two developmental morphs with distinct modes of sexual reproduction: (1) females and males that develop through four feeding juvenile (larval) stages; (2) self-fertile protandric hermaphrodites that develop through an obligatory non-feeding third juvenile stage, the dauer larva. In females and males, somatic gonad development begins in the first larval stage, whereas in hermaphrodites it is delayed to the second larval stage. Vulval development also differs between females and hermaphrodites: (1) the P8.p cell divides in females but stays undivided in hermaphrodites; (2) the number, timing, and source of inductive signals from the gonad to the vulval precursor cells differ between the two morphs. These results show that discrete vulva developmental routes can be adopted by animals of the same genotype.Edited by D. Tautz     

The molecular size of nematode acetylcholinesterases and their separation from nematode allergens

The molecular size of nematode acetylcholinesterases, and their separation from nematode allergens. International Journal for Parasitology 3: 735–741. Acetylcholinesterases and allergens were derived from two parasitic nematodes, Nippostrongylus brasiliensis which parasitises rats and Trichostrongylus colubriformis which infects sheep and guinea pigs.

Chromatographic studies indicated that the mol. wt of nematode acetylcholinesterases lies between 65,000 and 75,000. The acetylcholinesterases of both species were separated from nematode allergens whose mol. wt is in the range of 10,000–50,000.

γG binding antigens of T. colubriformis were located in fractions with a mol. wt range of 30,000–150,000. γE binding activity was confined to allergenic material with a mol. wt of less than 70,000.