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.     

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.      

Lymphocyte response of leprosy patients to human-derived and purified armadillo-derived Mycobacterium leprae, BCG and PPD.

The lymphocyte transformation test was applied to compare in vitro lymphocyte responses of tuberculoid (high resistant) and lepromatous (low resistant) leprosy patients to purified Mycobacterium leprae derived from experimentally infected armadillos and crude M. leprae derived from man, as well as to bacille Calmette-Guérin (BCG) and purified protein derivative (PPD). It was found that the purification procedure using enzymic digestion did not affect the immunogenicity of armadillo-derived M. leprae as compared with the crude human-derived preparation, although 2.5-5-fold higher doses of the purified organisms were required to elicitate equivalent lymphocyte responses. The result indicated the suitability of purified armadillo-derived M. leprae as the standard antigen for lymphocytes transformation tests in leprosy. The cross-reactivity studies show a close relationship between PPD and BCG, but not between M. leprae and PPD or BCG.     

The CTLA-4 gene region of chromosome 2q33 is linked to, and associated with, type 1 diabetes. Belgian Diabetes Registry

Susceptibility to autoimmune insulin-dependent (type 1) diabetes mellitus is determined by a combination of environmental and genetic factors, which include variation in MHC genes on chromosome 6p21 (IDDM1) and the insulin gene on chromosome 11p15 (IDDM2). However, linkage to IDDM1 and IDDM2 cannot explain the clustering of type 1 diabetes in families, and a role for other genes is inferred. In the present report we describe linkage and association of type 1 diabetes to the CTLA-4 gene (cytotoxic T lymphocyte associated-4) on chromosome 2q33 (designated IDDM12). CTLA-4 is a strong candidate gene for T cell- mediated autoimmune disease because it encodes a T cell receptor that mediates T cell apoptosis and is a vital negative regulator of T cell activation. In addition, we provide supporting evidence that CTLA-4 is associated with susceptibility to Graves' disease, another organ- specific autoimmune disease.      

A method for genotyping murine arylamine N-acetyltransferase type 2 (NAT2): a gene expressed in preimplantation embryonic stem cells encoding an enzyme acetylating the folate catabolite p-aminobenzoylglutamate.

Mice have three arylamine N-acetyltransferase (NAT) isoenzymes (NAT1, NAT2, and NAT3) of which NAT2 is known to be polymorphic. Humans have two polymorphic isoenzymes, NAT1 and NAT2. The isoenzymes mouse NAT1 and human NAT2 are expressed predominantly in the liver and intestine and are involved in drug and xenobiotic metabolism. Mouse NAT2 and human NAT1 have a widespread tissue distribution and the folate catabolite p-aminobenzoylglutamate (pAB-Glu) has been proposed as a candidate endogenous substrate. All mice have detectable NAT2 activity, although inbred mouse strains have either a fast or slow acetylator phenotype conferred by the presence of either NAT2*8 (fast) or NAT2*9 (slow) alleles at the NAT2 locus. In this report, we describe a simple method for distinguishing these murine alleles by polymerase chain reaction followed by restriction fragment length polymorphism analysis. We compared the tissue distribution of the acetylation activity found in both fast (C57BL/6J) and slow (A/J) acetylating strains of mice using pAB-Glu and p-aminobenzoic acid as probe substrates. It has previously been demonstrated that murine NAT2 is expressed in the neural tube prior to closure (Stanley L, Copp A, Rolls S, Smelt V, Perry VH and Sim E, Teratology 58: 174-182, 1998). We demonstrate here that murine NAT2 is expressed in preimplantation embryonic stem cells. Murine NAT2 is likely to be expressed prior to neurulation and this may be important in view of the protective role of folate in neural tube development.     

The vasa vasorum and angioplasty

Interruption of flow in the vasa vasorum may lead to medial necrosis and aneurysm formation. The purpose of this study was to determine whether angioplasty produces significant alterations in the morphology or blood flow of the vasa vasorum of the dilated artery. The morphology of the canine vasa vasorum was studied before and after angioplasty; in a separate experiment vessel wall blood flow (VWBF) in canine carotid arteries was measured after angioplasty to determine whether physiologic regulation of the blood flow was disrupted by arterial dilation. No morphologic changes could be demonstrated in the vasa vasorum of the dilated artery; however, VWBF was increased by 1194 +/- 215% (mean +/- standard error, p less than 0.01) between 90 and 120 minutes after angioplasty. VWBF in the adjacent nondilated arterial segment was also increased (720 +/- 177% between 10-30 minutes, p less than 0.01) but returned toward normal after 60 minutes. Adenosine caused a "paradoxical" decrease in VWBF (p less than 0.05) of the dilated arterial segment while causing increased VWBF (p less than 0.05) in the thoracic aorta. Angioplasty appears to produce persistent hyperemia in the dilated arterial wall. A paradoxical response to adenosine suggests that vasa vasorum in the dilated arterial segment are maximally vasodilated. This may be due to mechanical disruption of vasomotor tone or to release of vasoactive substances.