Trophosome in vestimentifera Ridgeia piscesae Jones, 1985 (Annelida, Siboglinidae) develops from cells of the coelomic lining

The structure of early juvenile specimens of vestimentifera Ridgeia piscesae (Annelida, Siboglinidae) was studied. As adults, vestimentiphers are deprived of the intestine and have a trophosome, in which cells chemoautotrophic bacteria are living. In early juvenile individuals of 280-300 microns in size, it was found that trophosome develops from cells of the coelomic lining on the surface of the intestine and on the side walls of the body. This structure of the rudiment of the trofosome suggests that the bacteria are first captured by the cell wall of the body and then transferred to the cell on the surface of the intestine.

Possible Role of WT1 in a Human Fetus with Evolving Bronchial Atresia, Pulmonary Malformation and Renal Agenesis

The association of peripheral bronchial atresia and congenital pulmonary airway malformation (CPAM) has recently been recognised, but the pathology of the lesions evolving together has not been described. We present autopsy findings in a 20 week fetus showing areas of peripheral bronchial destruction and airway malformation consistent with developing CPAM in the right lung supporting a causal relationship between these lesions. This fetus also had congenital heart defect, bilateral renal agenesis and syndactyly. We identified another fetus from our autopsy files, with bilateral renal agenesis, similar right sided pulmonary malformation and cardiac defects. Similar bilateral renal agenesis and defects of the heart and lungs are found in wt1−-/– mice and we have investigated the expression of WT1 in these fetuses. We hypothesise that the cardiac, liver, renal and possibly lung lesions in these two cases may arise due to mesenchymal defects consequent to WT1 misexpression and discuss evidence for this from the scientific literature. We used immunoperoxidase stains to analyse WT1 expression in autopsy hepatic tissue in both fetuses. We also investigated the expression of α-smooth muscle actin (α-SMA), a marker of activated hepatic stellate cells/myofibroblasts, and desmin in hepatic mesenchyme and compare these findings with control fetuses, without congenital malformations. We found reduced WT1 expression in hepatic mesothelium in both fetuses with malformations. There was also increased expression of α-SMA in liver perisinusoidal cells, as seen in the wt1−-/– mouse model. We therefore propose that abnormality of WT1 signalling may be an underlying factor, as WT1 is expressed in coelomic lining cells from which mesenchyme is derived in many organs.

Histological examination of the chaetognathan morphological structure in the region of a supposed trunk-tail septum

A histological examination was conducted based on sections done in series in transverse and longitudinal directions of Aidanosagitta macilenta (Sagittidae, Chaetognatha) in a region which includes the anterior parts of the testes and the posterior part of the ovaries. We found that, in mature individuals (the 4th stage of maturation), the anterior parts of the testes are located in front of the posterior part of the ovaries. The anterior parts of the testes have a ventral position adjoining the ventral muscular bands. The ovaries are located more dorsally than the testes at the level of lateral fi elds. A transverse trunk-tail septum between testes and ovaries was not revealed. These data support an idea that a structure which was earlier treated as a tail-trunk septum is actually the anterior edges of the testes. Both longitudinal coelomic cavities continue into the tail region without any transverse septa. The paired tail cavities as can be seen from their composition and functions represent the testes consisting of a peripheral compact portion with undifferentiated germ cells and a space where the maturation of cells occurs. The tail is distinguished anatomically as a post-anal portion of the body but it is not a true segment as it is not separated from a trunk part of the body by the trunk-tail septum. The body of Chaetognatha consists of two true parts (segments). A mesenterial septum divides the body longitudinally-symmetrically from a trunk-head septum down only to the caudal end of the gut. In the tail region there is a medial septum formed by the medial walls of testes. Gonads in both females and males do not have any duct connecting them with a gut cavity. The ovaries and the testes are covered by a coelomic lining and a duct between the ovaries and the testes is absent.