Blur adaptation: clinical and refractive considerations

The human visual system is amenable to a number of adaptive processes; one such process, or collection of processes, is the adaptation to blur. Blur adaptation can be observed as an improvement in vision under degraded conditions, and these changes occur relatively rapidly following exposure to blur. The potential important future directions of this research area and the clinical implications of blur adaptation are discussed.     

Sequential gradient pneumatic compression enhances venous ulcer healing: a randomized trial

The treatment of venous ulcers has remained largely unchanged for centuries. The application of properly applied graduated compression bandages, the use of graduated compression stockings, and surgery have been shown to achieve healing. However, some ulcers persist despite appropriate management. A randomized study was undertaken to compare two regimens of treatment for such patients. Both regimens included ulcer debridement, cleaning, nonadherent dressing, and graduated compression stockings. In one regimen, sequential gradient intermittent pneumatic compression was applied for 4 hours each day. Only one of 24 patients in the control group had complete healing of all ulcers compared with 10 of 21 patients healed in the intermittent pneumatic compression group. The median rate of ulcer healing in the control group was 2.1% area per week compared to 19.8% area per week in the intermittent pneumatic compression group. The results indicate that sequential gradient intermittent pneumatic compression is beneficial in the treatment of venous ulcers.     

Serum ionic fluoride levels in haemodialysis and continuous ambulatory peritoneal dialysis patients

High serum fluoride (F-) in patients with chronic renal failure (CRF) and end-stage renal disease (ESRD) is associated with risk of renal osteodystrophy and other bone changes. This study was done to determine F- in normal healthy controls and patients with ESRD on haemodialysis (HD) or peritoneal dialysis (PD). Seventeen healthy controls (12 males, 5 females) and 39 ESRD patients on dialysis (17 males, 22 females) were recruited in the study in a community with 47.4 +/- 3.28 microM/l (range 44-51 microM/l) of F- content in drinking water. Control subjects showed a mean serum F- concentration of 1.08 +/- 0.350 microM/l. Males in control group showed slightly higher F- levels (1.15 +/- 0.334, range 0.55-1.9 microM/l) than females (0.92 +/- 0.370, range 0.6-1.5 microM/l). Mean serum F- concentration did not correlate significantly with age and sex among control subjects, whereas such correlation was observed in patients with ESRD on dialysis. Mean serum F- concentration was significantly higher in patients on dialysis (2.67 +/- 1.09, range 0.8-5.2 microM/l) than normal controls. When grouped according to sex, the mean serum F- concentration in males (3.05 +/- 1.04, range 1.8-5.2 microM/l) was significantly higher than females (2.38 +/- 1.08, range 0.8-5.2 microM/l). When patients were grouped according to age, it was observed that F- concentration was significantly higher in patients with age groups 21-70 (2.86 +/- 1.05) than those with age group 13-20 years (1.42 +/- 0.531). Thus F- concentration correlated with age and sex, being higher in males and above 20 years. Despite appreciable clearance of F- (39-90%) across the peritoneum, patients on CAPD showed higher serum F- concentration than those on HD (3.1 +/- 1.97 vs 2.5 +/- 1.137 microM/l). Of the total 39 patients on dialysis 39% had their serum F- concentration above 3.0 microM/l, posing the risk of renal osteodystrophy.      

Deletion of Brca2 exon 27 causes hypersensitivity to DNA crosslinks,chromosomal instability,and reduced life span in mice

The Brca2 tumor-suppressor gene contributes to genomic stability, at least in part by a role in homologous recombinational repair. BRCA2 protein is presumed to function in homologous recombination through interactions with RAD51. Both exons 11 and 27 of Brca2 code for domains that interact with RAD51; exon 11 encodes eight BRC motifs, whereas exon 27 encodes a single, distinct interaction domain. Deletion of all RAD51-interacting domains causes embryonic lethality in mice. A less severe phenotype is seen with BRAC2 truncations that preserve some, but not all, of the BRC motifs. These mice can survive beyond weaning, but are runted and infertile, and die very young from cancer. Cells from such mice show hypersensitivity to some genotoxic agents and chromosomal instability. Here, we have analyzed mice and cells with a deletion of only the RAD51-interacting region encoded by exon 27. Mice homozygous for this mutation (called brca2(lex1)) have a shorter life span than that of control littermates, possibly because of early onsets of cancer and sepsis. No other phenotype was observed in these animals; therefore, the brca2(lex1) mutation is less severe than truncations that delete some BRC motifs. However, at the cellular level, the brca2(lex1) mutation causes reduced viability, hypersensitivity to the DNA interstrand crosslinking agent mitomycin C, and gross chromosomal instability, much like more severe truncations. Thus, the extreme carboxy-terminal region encoded by exon 27 is important for BRCA2 function, probably because it is required for a fully functional interaction between BRCA2 and RAD51.     

Wavelets of excitability in sensory neurons

We have investigated variations in the excitability of mammalian cutaneous mechanoreceptor neurons. We focused on the phase dynamics of an action potential relative to a periodic stimulus, showing that the excitability of these sensory neurons has interesting nonstationary oscillations. Using a wavelet analysis, these oscillations were characterized through the depiction of their period as a function of time. It was determined that the induced oscillations are weakly dependent on the stimulus frequency, and that lower temperatures significantly reduce the frequency of the phase response. Our results reveal novel excitability properties in sensory neurons, and, more generally, could prove significant in the deduction of mechanistic attributes underlying the nonstationary excitability in neuronal systems. Since peripheral neurons feed information to the CNS, variable responses observed in higher regions may be generated in part at the site of sensory detection.     

Isolation and characterization of a 60-kilodalton salivary glycoprotein with agglutinating activity against strains of Streptococcus mutans.

A bacterial agglutinin specific for strains of Streptococcus mutans was isolated from human saliva. Physiochemical analyses showed the agglutinin to be a glycoprotein with a molecular weight of 60,000. The agglutinin aggregated four of the eight strains of Streptococcus mutans tested but did not aggregate the strains of Streptococcus salivarius, Streptococcus sanguis, and Streptococcus mitis tested. Chemical modification of carbohydrate moieties of the agglutinin with sodium metaperiodate had no effect on aggregation, whereas modification of the polypeptide portion with trypsin abolished aggregating activity. A set of five murine hybridoma antibodies was employed to further analyze the agglutinin. Two carbohydrate-specific antibodies, directed against D-mannose and N-acetylgalactosamine moieties, respectively, failed to block agglutinin- or whole saliva-mediated aggregation of S. mutans cells. In contrast, two antibodies directed against pronase-sensitive antigenic sites blocked both agglutinin- and saliva-mediated aggregation of S. mutans cells. Western blot analysis with the agglutinin-specific hybridoma antibodies demonstrated the agglutinin in whole saliva and in artificial tooth pellicles formed on hydroxyapatite beads incubated with saliva. These results suggest that a 60-kilodalton glycoprotein of human saliva is a bacterial agglutinin with specificity for certain strains of S. mutans. They further suggest that aggregation is mediated by polypeptide rather than carbohydrate determinants of the glycoprotein.