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.      

The relationship between women's subjective and physiological sexual arousal

Previous literature presents discordant results on the relationship between physiological and subjective sexual arousal in women. In this study, the use of hierarchical linear modeling (HLM) revealed a significant concordance between continuous measures of physiological and subjective sexual arousal as assessed during exposure to erotic stimuli in a laboratory setting. We propose that past studies that have found little or no association between the two measures may have been in part limited by the methodology and statistical analyses employed.     

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.      

Determination of the transvalvular gradient using continuous wave Doppler in patients with mitral stenosis. Correlation with the hemodynamic method

In order to assess the reliability of Doppler echocardiography in the determination of mean mitral gradient 38 consecutive patients (pts) affected by rheumatic mitral valve stenosis (MS) were analyzed by continuous wave Doppler echocardiography (CWD). Cardiac catheterization (CATH) was performed within 24 hours from echocardiographic examination. The mean diastolic mitral gradient (MG) at CATH was calculated by planimetry from simultaneously recorded left ventricular and pulmonary artery wedge pressure. The maximal velocity profile through the mitral valve was used to calculate pressure gradient by CWD. A mean mitral gradient was calculated for each patient by the planimetered velocity profile throughout diastole. MG determined by CATH ranged from 6 to 31 mmHg (mean 15.2 +/- 6.0); MG determined by CWD ranged from 4 to 18 mmHg (mean 10 +/- 3.7). The correlation between CWD and CATH by linear regression analysis was: y = 0.53 X + 1.8; r = 0.85; p less than 0.001. Mean % error of CWD in the assessment of MG was 34.7%. In conclusion this study indicates that CWD seems systematically underestimate MG with respect to CATH. The identification of CWD flow tracings "optimal" for analysis could not represent the maximal velocity of transmitral jet, which is a complex three dimensional entity. In addition non-simultaneous determinations of gradient and day-to-day variations in cardiac output may account for discrepancies between CWD and CATH measurements.     

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.