Near infra-red interactance for nutritional assessment of dialysis patients.
BACKGROUND: Malnutrition is a common problem in dialysis patients and may affect up to one-third of patients. Near-infrared interactance (NIR) is a novel approach to estimate body composition and per cent total body fat. METHODS: We used near-infrared interactance (Futrex 5000) to estimate the body composition including body fat percentage, as well as subjective global assessment (SGA), anthropometric measurements including mid-arm circumference (MAC), triceps and biceps skinfold thickness, calculated mid-arm muscle circumference (MAMC), body mass index (BMI), and laboratory values. NIR score, SGA assessment and anthropometric parameters were measured shortly after the end of a dialysis session. NIR measurement was made by placing a Futrex sensor on the nonaccess upper arm for several seconds. Serum albumin, transferrin (reflected by total iron binding capacity), and total cholesterol concentrations were performed as well. RESULTS: Thirty-four patients (20 men and 14 women) were selected from a pool of 120 haemodialysis patients. Their ages ranged from 26 to 86 years (58+/-14 years). Time on dialysis ranged from 8 months to 19 years (4.5+/-4.6 years). NIR scores were significantly different in three SGA groups: (A) well-nourished, 32.5+/-6.9%; (B) mildly to moderately malnourished, 29.2+/-5.3%; and (C) severely malnourished, 23.2+/-10.2% (P<0.001). Pearson correlation coefficients (r) between the NIR score and nutritionally relevant parameters were significant (P<0.001) for body mass index (r=+0.81), mid-arm circumference (r=+0.74), triceps skin fold (r=+0.54), biceps skin fold (r=+0.55), and mid-arm muscle circumference (r=+0.54). An inverse correlation was also found between NIR and years dialysed (r=-0.49, P=0.004), denoting a lesser body fat percentage according to NIR for patients dialysed longer. NIR was correlated with serum transferrin (r=+0.41, P=0.016) and cholesterol (r=+0.39, P=0.022) and marginally with serum albumin (r=+0.29, P=0.097). CONCLUSIONS: We conclude that NIR, which can be performed within seconds, may serve as an objective indicator of nutritional status in haemodialysis patients. More comparative and longitudinal studies are needed to confirm the validity of NIR measurements in nutritional evaluation of dialysis patients. (+info)
Dose-dependent effects of DNA-damaging agents on p53-mediated cell cycle arrest.
We examined the dose-dependent effects of DNA-damaging agents on G1 arrest in isogenic human cell lines differing in their p53 status. As expected, 5 or 20 Gy of ionizing radiation induced a p53-dependent G1 arrest. In contrast, UV light or actinomycin D induced a modest G1 arrest that was p53-dependent only at lower doses. At higher doses, cells were arrested in G1 in a p53-independent manner coinciding with inhibition of RNA synthesis and abolished cyclin E expression. Interestingly, expression of cyclin E was enhanced after exposure to moderate doses of UV light and actinomycin D, and this enhancement was suppressed by wild-type p53. We propose that agents inducing transcription-blocking DNA lesions will at higher doses inhibit the progression of cells into S phase by a p53-independent mechanism involving the attenuation of E2F-mediated transcription of genes, such as cyclin E. (+info)
The ability of p53 to activate downstream genes p21(WAF1/cip1) and MDM2, and cell cycle arrest following DNA damage is delayed and attenuated in scid cells deficient in the DNA-dependent protein kinase.
scid mouse embryonic fibroblasts are deficient in DNA-dependent protein kinase activity due to a mutation in the C-terminal domain of the catalytic subunit (DNA-PKcs). When exposed to ionizing radiation, the increase in levels of p53 was the same as in normal mouse embryonic fibroblasts. However, the rise in p21(WAF1/cip1) and mdm2 was found to be delayed and attenuated, which correlated in time with delayed onset of G1/S arrest by flow cytometric analysis. The p53-dependent G1 checkpoint was not eliminated: inactivation of p53 by the E6 protein in scid cells resulted in the complete loss of detectable G1/S arrest after DNA damage. Immunofluorescence analysis of normal cells revealed p53 to be localized predominantly within the cytoplasm prior to irradiation and then translocate to the nucleus after irradiation. In contrast, scid cells show abnormal accumulation of p53 in the nucleus independent of irradiation, which was confirmed by immunoblot analysis of nuclear lysates. Taken together, these data suggest that loss of DNA-PK activity appears to attenuate the kinetics of p53 to activate downstream genes, implying that DNA-PK plays a role in post-translational modification of p53, without affecting the increase in levels of p53 in response to DNA damage. (+info)
Tonic accommodation, age, and refractive error in children.
PURPOSE: An association between tonic accommodation, the resting accommodative position of the eye in the absence of a visually compelling stimulus, and refractive error has been reported in adults and children. In general, myopes have the lowest (or least myopic) levels of tonic accommodation. The purpose in assessing tonic accommodation was to evaluate it as a predictor of onset of myopia. METHODS: Tonic accommodation was measured in children enrolled in the Orinda Longitudinal Study of Myopia using an infrared autorefractor (model R-1; Canon, Lake Success, NY) while children viewed an empty lit field or a dark field with a fixation spot projected in Maxwellian view. Children aged 6 to 15 years were measured from 1991 through 1994 (n = 714, 766, 771, and 790 during the 4 years, successively). Autorefraction provided refractive error and tonic accommodation data, and videophakometry measured crystalline lens curvatures. RESULTS: Comparison of the two methods for measuring tonic accommodation shows a significant effect of age across all years of testing, with the lit empty-field test condition yielding higher levels of tonic accommodation compared with the dark-field test condition in children aged 6 through 11 years. For data collected in 1994, mean (+/-SD) tonic accommodation values for the lit empty-field condition were significantly lower in myopes, intermediate in emmetropes, and highest in hyperopes (1.02 +/- 1.18 D, 1.92 +/- 1.59 D, and 2.25 +/- 1.78 D, respectively; Kruskal-Wallis test, P < 0.001; between-group testing shows each group is different from the other two). Age, refractive error, and Gullstrand lens power were significant terms in a multiple regression model of tonic accommodation (R2 = 0.18 for 1994 data). Lower levels of tonic accommodation for children entering the study in the first or third grades were not associated with an increased risk of the onset of myopia, whether measured in the lit empty-field test condition (relative risk = 0.90; 95% confidence interval = 0.75, 1.08), or the dark-field test condition (relative risk = 0.83; 95% confidence interval = 0.60, 1.14). CONCLUSIONS: This is the first study to document an association between age and tonic accommodation. The known association between tonic accommodation and refractive error was confirmed and it was shown that an ocular component, Gullstrand lens power, also contributed to the tonic accommodation level. There does not seem to be an increased risk of onset of juvenile myopia associated with tonic accommodation. (+info)
Path integration absent in scent-tracking fimbria-fornix rats: evidence for hippocampal involvement in "sense of direction" and "sense of distance" using self-movement cues.
Allothetic and idiothetic navigation strategies use very different cue constellations and computational processes. Allothetic navigation requires the use of the relationships between relatively stable external (visual, olfactory, auditory) cues, whereas idiothetic navigation requires the integration of cues generated by self-movement and/or efferent copy of movement commands. The flexibility with which animals can switch between these strategies and the neural structures that support these strategies are not well understood. By capitalizing on the proclivity of foraging rats to carry large food pellets back to a refuge for eating, the present study examined the contribution of the hippocampus to the use of allothetic versus idiothetic navigation strategies. Control rats and fimbria-fornix-ablated rats were trained to follow linear, polygonal, and octagonal scent trails that led to a piece of food. The ability of the rats to return to the refuge with the food via the shortest route using allothetic cues (visual cues and/or the odor trail available) or using ideothetic cues (the odor trail removed and the rats blindfolded or tested in infrared light) was examined. Control rats "closed the polygon" by returning directly home in all cue conditions. Fimbria-fornix rats successfully used allothetic cues (closed the polygon using visual cues or tracked back on the string) but were insensitive to the direction and distance of the refuge and were lost when restricted to idiothetic cues. The results support the hypothesis that the hippocampal formation is necessary for navigation requiring the integration of idiothetic cues. (+info)
Measurement of the eye's near infrared wave-front aberration using the objective crossed-cylinder aberroscope technique.
We used the crossed-cylinder aberroscope technique to obtain the near infrared (784 nm) wave-front aberration of the human eye. We compared the results with those obtained under the same conditions using red light (633 nm). Other than the greater retinal scattering of the near infrared light, third- and fourth-order wave-front aberrations are similar in both wavelengths. Values of the calculated near infrared point spread function show a typical half-height width of around 2 arcmin, which is in good agreement with previous work. (+info)
Photo-oxidative killing of human colonic cancer cells using indocyanine green and infrared light.
Despite of the approval of Photofrin in various countries, chemically defined sensitizers for photodynamic therapy (PDT) are still needed for the absorption of light in the infrared spectrum, which provides a maximal penetration of light into tissue. Therefore, both the efficacy and the mechanism of action of the clinically approved dye indocyanine green (ICG) and laser irradiation were investigated in vitro. For the investigation of phototoxic effects, HT-29 cells were incubated 24 h prior to irradiation by using different concentrations of ICG (10-500 microM). In each experiment, cells were irradiated using a continuous wave (cw)-diode laser (lambda(ex) = 805 nm, 30 J cm(-2), 40 mW cm(-2)). After laser irradiation, cell viability of dark control and of cells incubated with 500 microM ICG was 1.27+/-0.11 or 0.28+/-0.05 respectively. Using 100 microM ICG and D2O, cell viability was further decreased from 0.46+/-0.03 (H2O) to 0.11+/-0.01 (D2O). Using D2O and 100 microM ICG, the concentration of malondialdehyde, a marker of lipid peroxidation, increased from 0.89+/-0.10 nmol 10(-6) cells to 11.14+/-0.11 nmol 10(-6) cells. Using 100 microM ICG and laser irradiation sodium azide or histidine (50 mM), quenchers of singlet oxygen reduced the cell killing significantly. In contrast, when using mannitol, a quencher of superoxide anion and hydroxyl radical, cell killing was not inhibited. According to the present results, photoactivated ICG seems to kill colonic cancer cells due to the generation of singlet oxygen and the subsequent formation of lipid peroxides. Therefore, ICG might present a promising photosensitizer for PDT; first clinical results confirm these findings. (+info)
High resolution in vivo intra-arterial imaging with optical coherence tomography.
BACKGROUND: Optical coherence tomography (OCT) is a new method of catheter based micron scale imaging. OCT is analogous to ultrasound, measuring the intensity of backreflected infrared light rather than sound waves. OBJECTIVE: To demonstrate the ability of OCT to perform high resolution imaging of arterial tissue in vivo. METHODS: OCT imaging of the abdominal aorta of New Zealand white rabbits was performed using a 2.9 F OCT imaging catheter. Using an ultrashort pulse laser as a light source for imaging, an axial resolution of 10 micrometer was achieved. RESULTS: Imaging was performed at 4 frames/second and data were saved in either super VHS or digital format. Saline injections were required during imaging because of the signal attenuation caused by blood. Microstructure was sharply defined within the arterial wall and correlated with histology. Some motion artefacts were noted at 4 frames/second. CONCLUSIONS: In vivo imaging of the rabbit aorta was demonstrated at a source resolution of 10 micrometer, but required the displacement of blood with saline. The high resolution of OCT allows imaging to be performed near the resolution of histopathology, offering the potential to have an impact both on the identification of high risk plaques and the guidance of interventional procedures. (+info)