Longitudinal measurements of MRI-T2 in boys with Duchenne muscular dystrophy: effects of age and disease progression.

Duchenne muscular dystrophy (DMD) is characterized by an increased muscle damage and progressive replacement of muscle by noncontractile tissue. Both of these pathological changes can lengthen the MRI transverse proton relaxation time (T2). The current study measured longitudinal changes in T2 and its distribution in the lower leg of 16 boys with DMD (5-13years, 15 ambulatory) and 15 healthy controls (5-13years). These muscles were chosen to allow extended longitudinal monitoring, due to their slow progression compared with proximal muscles in DMD. In the soleus muscle of boys with DMD, T2 and the percentage of pixels with an elevated T2 (⩾2SD above control mean T2) increased significantly over 1year and 2years, while the width of the T2 histogram increased over 2years. Changes in soleus T2 variables were significantly greater in 9-13years old compared with 5-8years old boys with DMD. Significant correlations between the change in all soleus T2 variables over 2years and the change in functional measures over 2years were found. MRI measurement of muscle T2 in boys with DMD is sensitive to disease progression and shows promise as a clinical outcome measure.

Alloplasmic male-sterile Brassica juncea with Enarthrocarpus lyratus cytoplasm and the introgression of gene(s) for fertility restoration from cytoplasm donor species.

A new cytoplasmic male sterility (CMS) source in Brassica juncea (2n = 36; AABB) was developed by substituting its nucleus into the cytoplasm of Enarthrocarpus lyratus (2n = 20; E(l)E(l)). Male sterility was complete, stable and manifested in either petaloid- or rudimentary-anthers which were devoid of fertile pollen grains. Male sterile plants resembled the euplasmic B. juncea except for slight leaf yellowing and delayed maturity. Leaf yellowing was due mainly to higher level of carotenoids rather than a reduction in chlorophyll pigments. Female fertility in male-sterile plants varied; it was normal in lines having rudimentary anthers but poor in those with petaloid anthers. Each of the 62 evaluated germplasm lines of B. juncea was a functional maintainer of male sterility. The gene(s) for male-fertility restoration ( Rf) were introgressed from the cytoplasm donor species through homoeologous pairing between A and E(l) chromosomes in monosomic addition plants (2n = 18II+1E(l)). The percent pollen fertility of restored F(1) ( lyr CMS x putative restorer) plants ranged from 60 to 80%. This, however, was sufficient to ensure complete seed set upon by bag selfing. The CMS ( lyr) B. juncea compared favourably with the existing CMS systems for various productivity related characteristics. However, the reduced transmission frequency of the Rf gene(s) through pollen grains, which was evident from the sporadic occurrence of male-sterile plants in restored F(1) hybrids, remains a limitation.

Dermo--epidermal adhesion and its effect on epidermal structure in the mouse.

Evidence is presented that dermo--epidermal adhesion is low in mouse ear. Consequently the pressure caused by mitotic activity in the basal epidermal layer is readily relieved by cell extrusion distally and the number of basal cells per unit skin area remains low. The rule then is that the number of distal cells per unit skin area must be equally low, and the epidermis is therefore thin. Conversely, dermo--epidermal adhesion is high in mouse sole-of-foot epidermis, and the mitotic pressure leads through cell crowding to a columnar basal epithelium. Furthermore, in the footpad centre, where adhesion is evidently highest, the baseline folds. With basal cell crowding and baseline folding there are more basal cells, and therefore more distal cells, per unit skin area. The epidermis is thick. Epidermal cells are regarded as equipotential. The different epidermal characteristics of the different body regions are determined by the combined actions of the local mitotic rate and the local strength of the dermal grip.