Autoregulation of a segmentation gene in Drosophila: combinatorial interaction of the even-skipped homeo box protein with a distal enhancer element

Autoregulation has been implicated in the expression of many patterning genes in Drosophila, but the molecular details of this process are largely unknown. In the case of the segmentation gene even-skipped (eve), autoregulation is important for the specification of sharp stripes of gene expression at the onset of gastrulation. Here, we use a combination of DNA binding and P-transformation assays to characterize the cis- and trans-acting factors responsible for autoregulation. We show that eve autoregulation is mediated, at least in part, by a 100-bp minimal autoregulatory sequence (MAS) located approximately 5 kb upstream from the eve transcription start site. Multimerization of a 200-bp DNA fragment that encompasses the MAS drives optimal autoregulatory activity, comparable to that obtained with the native distal enhancer element located between -5.9 and -5.2 kb. The MAS contains two eve protein-binding sites, as well as binding sites for two nuclear factors present in early embryos. Directed mutagenesis of these binding sites suggests that both the eve protein and nuclear factors are essential for autoregulation. These results provide evidence that the eve protein acts combinatorially with other transcription factors to enhance its own expression.

Dispersion studies of a single-mode triangular-index fiber with a trench by the vector mode analysis

A Runge-Kutta procedure was used for investigating the dispersion characteristics of single-mode triangular-index fibers with a trench in the cladding. Numerical results on the total dispersion, its sensitivities to the core radius, wavelength, index difference variations, and its influence on the fiber's bandwidth-length product are presented. Some interesting features, due to the presence of a trench, are pointed out. One salient feature is the appearance of dispersion flattening over a certain wavelength range near 1.55 microm for b/a = 2 and c/a > 2.7 (a = core radius, b = inner trench radius, c = outer trench radius) where the total dispersion is low, yielding a bandwidth-length product as high as 10(4) GHz . km. The presence of a trench has not been investigated previously.

[Study on change in zinc concentration for diabetic cataractous lenses in rats by means of XIXA]

The SD rats were injected with streptozotocin to induce diabetic cataract. Element Zn as well as K, Ca, Mn, Fe, Cu, Pb, Se, etc. in the eye lenses was determined by means of X-ray induced X-fluorescence analysis (XIXA). Compared to values for normal healthy rats, the concentration of Zn and Fe in the cataractous lenses increased, the concentration of K decreased, and that of the others did not change prominently. The change in Zn concentration was probably to meet the needs of the metabolic adjustment in the eye lenses, which would not be the reason for directly inducing diabetic cataract.

Conservation between coding and regulatory elements of Rhizobium meliloti and Rhizobium leguminosarum dct genes

Complementation of Rhizobium leguminosarum dct mutants with a cosmid bank yielded Rhizobium meliloti homologs of the dctA, dctB, and dctD genes. The genes dctB and dctD are thought to form a two-component system which responds to the presence of C4-dicarboxylates to regulate expression of a transport protein encoded by dctA. DNA sequence analysis showed that dct coding and intergenic regions, including putative binding sites for the dctD protein and sigma 54-RNA polymerase, were highly conserved between these two Rhizobium species. Mutation of R. meliloti dctD showed that it was not essential for symbiotic nitrogen fixation but was needed for growth on succinate and the expression of a dctA-lacZ fusion gene in free-living cells. Hybridization of R. meliloti genomic DNA with probes representing the central portion of dctD potentially identified more than 20 similar regulatory genes, all of which are likely to depend upon the alternative sigma factor encoded by rpoN and stimulate transcription in a manner very similar to ntrC activation of glnA in enteric bacteria.

Phonosurgical studies: fat-graft reconstruction of injured canine vocal cords

Damage to the vocal cords can result in scarring and impaired vibration and can manifest clinically as hoarseness and loss of vocal power. If the vibratory characteristics could be restored in these scarred vocal cords, the vocal intensity and efficiency of phonation also should improve. In an effort to enhance the vibration of damaged vocal cords, we implanted a submucosal fat autograft within the injured vocal cord cover layer of dogs 6 weeks after unilateral mucosal excision had been performed. Three months postoperatively these animals were compared to normal dogs and those with mucosal excision but no fat-grafting. Acoustic and biomechanical measures of phonation were collected from an excised larynx preparation. We found that the fat-augmented vocal cords had lower threshold pressures for phonation, greater vocal intensity, and more efficient acoustic output than injured vocal cords without the fat-grafting. These results provide a foundation for further research on reconstructive surgery of damaged vocal cords.