Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia

In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models' procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.

Refining the clinicopathological pattern of cerebral proliferative glomeruloid vasculopathy (Fowler syndrome): report of 16 fetal cases

Cerebral proliferative glomeruloid vasculopathy (PGV) is a severe disorder of brain angiogenesis, resulting in abnormally thickened and aberrant perforating vessels, forming glomeruloids with inclusion-bearing endothelial cells. This peculiar vascular malformation was delineated by Fowler in 1972 as a stereotyped lethal fetal phenotype associating hydranencephaly-hydrocephaly with limb deformities, called Fowler syndrome (FS) or "proliferative vasculopathy and hydranencephaly-hydrocephaly" or "encephaloclastic proliferative vasculopathy" (OMIM#225790). In PGV, the disruptive impact of vascular malformation on the developing central nervous system (CNS) is now well admitted. However, molecular mechanisms of abnormal angiogenesis involving the CNS vasculature exclusively remain unknown, as no genes have been localized nor identified to date. We observed the pathognomonic FS vascular malformation in 16 fetuses, born to eight families, four consanguineous and four non-consanguineous. A diffuse form of PGV affecting the entire CNS and resulting in classical FS in 14 cases, can be contrasted to two cases with focal forms, confined to restricted territories of the CNS. Interestingly in PGV, immunohistological response to a marker of pericytes (SMA, Smooth in PGV Muscle Actin), was drastically reduced as compared to a match control. Our studies has expanded the description of FS to additional phenotypes, that could be called Fowler-like syndromes and suggest that the pathogenesis of PGV may be related to abnormal pericyte-dependent remodelling of the CNS vasculature, during CNS angiogenesis. Gene identification will determine the molecular basis of PGV and will help to know whether the Fowler-like phenotypes are due to the same underlying molecular mechanisms.

Currarino syndrome shown by prenatal onset ventriculomegaly and spinal dysraphism

The most frequent cause of ventriculomegaly is spina bifida when associated with Arnold-Chiari type II malformation. We report on a prenatal diagnosis of severe ventriculomegaly in association with spinal dysraphism that was indicative of a Currarino syndrome (CS) due to a c.584delA, p.H195fsX28 truncated mutation within the HLXB9 gene. Physiopathology of the ventriculomegaly is discussed in reference to the fetopathological examination and CS embryopathology. In the present case, prognosis was poor and pregnancy termination was authorized. However, such a decision may be controversial in fetuses with less severe malformations on sonographic examination, since mutations in the HLXB9 gene can predict neither the severity nor the long-term prognosis of the disease. Due to a lack of genotype-phenotype correlation and the broad variability of phenotype in heterozygotes, clinical and genetic investigations among relatives are mandatory in all HLXB9 gene mutation cases, to detect asymptomatic CS cases and to prevent the occurrence of severe complications.

[Incidence and seroprevalence of canine ehrlichiosis in the Medjez El Bab region (northwestern Tunisia during 1994, 1995 and 1996]

A sero-epidemiological survey, realized in the Medjez El Bab region (North-West of Tunisia), has concerned 180 dogs which status has been determined during the study. The animals were identified, then underwent an annual blood sampling during three successive years, in order to search for antibodies against E. canis and E. chaffeensis by indirect immunofluorescence. The results show that, in all sero-positive dogs, the levels of antibodies against E. canis were higher than those against E. chaffeensis. The sero-prevalence of E. canis was 42.8%, 50% and 48.9%, in 1994, 1995 and 1996, respectively, and was higher than that against E. chaffeensis during the three year studies. The incidence of E. canis infection was 12.6% during the three years whereas E. chaffeensis infection did not exceed 4.7%.