18S rRNA gene sequences and phylogenetic relationships of European hard-tick species (Acari: Ixodidae)

The complete 18S rRNA gene sequences of the following six European hard-tick species were obtained by direct PCR cycle sequencing and silver-staining methods: Rhipicephalus pusillus, Boophilus annulatus, Dermacentor marginatus, Hyalomma lusitanicum, Haemaphysalis punctata, and Ixodes ricinus. Differences observed in the sequence alignment of these six species together with the 18S rRNA gene sequences of 13 other hard-tick species demonstrate that this gene is a good marker for supraspecific differentiation as well as genus grouping among hard ticks. Phylogenetic analyses strongly support that Hyalomma species share a common ancestor with Rhipicephalinae and, consequently, Hyalomminae should no longer be considered an independent subfamily. However, no definitive conclusion could be reached to support or oppose the separation of the subfamilies Haemaphysalinae and Amblyomminae. Accepted: 15 July 1997     

Shoulder instability: impact of glenohumeral arthrotomography on treatment

We used arthrotomography to study the glenoid labrum in 114 patients. Sixty-nine of the patients had anatomic instability of the shoulder (including recurrent dislocation and subluxation of the shoulder), and 45 patients had functional instability of the shoulder (denoted by chronic pain, clicking of the joint, and the sensation that an unstable condition exists without the objective signs of it). Labral tears were revealed arthrotomographically in 86% of the patients with anatomic instability, while only 40% of the patients with functional instability had labral abnormalities, and these were primarily of minor severity. Fifty-six patients (44 of whom had anatomic instability; 12, functional instability) required surgery. The surgical findings were correlated with the arthrotomographic findings, and no false-positive results were revealed. However, arthrotomography demonstrated only part of the pathologic condition of two patients. These results confirm that there is a strong correlation between labral pathologic conditions and anatomic instability of the shoulder. Arthrotomographic studies have a great impact on the selection of therapy in cases of both anatomic and functional instability of the shoulder.     

Linkage of the MHC to familial multiple sclerosis suggests genetic heterogeneity. The Multiple Sclerosis Genetics Group

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system. While its etiology is not well understood, genetic factors are clearly involved. Until recently, most genetic studies in MS have been association studies using the case-control design testing specific candidate genes and studying only sporadic cases. The only consistently replicated finding has been an association with the HLA-DR2 allele within the major histocompatibility complex (MHC) on chromosome 6. Using the genetic linkage design, however, evidence for and against linkage of the MHC to MS has been found, fostering suggestions that sporadic and familial MS have different etiologies. Most recently, two of four genomic screens demonstrated linkage to the MHC, although specific allelic associations were not tested. Here, a dataset of 98 multiplex families was studied to test for an association to the HLA-DR2 allele in familial MS and to determine if genetic linkage to the MHC was due solely to such an association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta) in the MHC demonstrated strong genetic linkage (parametric lod scores of 4.60, 2.20 and 1.24, respectively) and a specific association with the HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results by HLA-DR2 status showed that the linkage results were limited to families segregating HLA-DR2 alleles. These results demonstrate that genetic linkage to the MHC can be explained by the HLA-DR2 allelic association. They also indicate that sporadic and familial MS share a common genetic susceptibility. In addition, preliminary calculations suggest that the MHC explains between 17 and 62% of the genetic etiology of MS. This heterogeneity is also supported by the minority of families showing no linkage or association with loci within the MHC.      

The inferior alveolar artery in its bony course

Based on the dissection of 30 hemi-mandibles, the authors report a study of the inferior alveolar artery in its intraosseous course. On morphologic considerations they propose a classification of the collaterals into two groups: the principal collaterals destined for the teeth and the bony alveolar tissue and the secondary collaterals destined for the sheath and the nerve as well as the bony tissue around the canal. Loss of the teeth and absorption of the alveolar bone modify the caliber of the inferior alveolar arterial axis, the distribution of its collaterals and possibly its mode of termination. These facts suggest a consideration of the vascularization of the mandible in terms of four sectors. They arrive at practical conclusions that may be drawn from this study in stomatology.     

Transitory subependymal cysts in the developing rat rhombencephalon

Summary A bilaterally symmetrical cystic cavity is situated in the subependymal neuropil of the rostral rhombencephalon of the rat during the perinatal period of ontogeny. These cysts are formed by the confluence of enlarged extracellular spaces in this region between E18 and E20. The cysts are present for about 2 weeks but disappear on about P15 without trace. They have a maximal volume of about 0.004 to 0.006 mm³ on P2, with a rostrocaudal extension of about 200 m. Their shape is characterized by a medial convexity and a lateral concavity, and they have their maximal circumference at about the middle of the rostrocaudal axis. The caudal portion is juxtaposed to the subependyma, while the rostral part lies in the neuropil of the presumptive griseum centrale pontis. In the lumen and the wall of the cysts are found numerous macrophages, hlioblasts and some degenerating axons and dendrites.The significance of these cysts in the context of morphogenesis and the origin of the numerous macrophages within them are both unresolved.