Structural modification on silica glass surface induced by thermal poling for second harmonic generation.

O-K edge XANES spectroscopy evidences structural modification induced by thermal poling treatment in surfaces of bulk Herasil silica glass presenting second harmonic generation. Considering model silicon dioxide clusters, calculations based on full multiple scattering approach have been performed in order to explain accurately the differences observed on XANES spectra at different stage of the poling treatment. These structural modifications on extreme surface affect both network and defects by breaking Si-O-Si bridging bonds. Despite of the formation of bridging bond occurring during the thermal depoling -which erases the SHG inside the glass-, the initial structure of the unpoled sample is not reproduced.

Use of weighed diet records in the evaluation of diets with different protein contents in patients with type 2 diabetes.

Compliance with diets containing different amounts of protein was studied in 15 nonobese type 2 diabetes patients (13 males aged 38-69 y). A method based on interviews and training in the technique of weighed diet records was used. Protein intake recorded by the patients was evaluated on the basis of 24-h nitrogen output (criterion standard measurement). Three diets were prescribed in random order, each lasting 4 wk: usual diet (UD), chicken diet (CD) (both with 1.2-1.5 g protein/kg body wt), and low-protein diet (LPD; with 0.5-0.8 g protein/kg body wt). Diets were isoenergetic and similar in fat content. Nutritional status was not altered during the study according to anthropometric indexes (body mass index, triceps skinfold thickness, midupper arm muscle area, and waist-to-hip ratio) and laboratory data (serum albumin, hematocrit, and lymphocyte values). The correlation of protein intake recorded on the weighed diet records with that estimated by nitrogen output was 0.64 for the UD (P = 0.01), 0.79 for the CD (P < 0.001), and 0.66 for the LPD (P = 0.008). No difference was found in mean protein intake (g/kg body wt) calculated from the weighed diet records and nitrogen output for the UD (1.37 compared with 1.36 g/kg body wt) and CD (1.38 compared with 1.32 g/kg body wt). With the LPD, patients did not consume more protein than prescribed, but underreported their actual protein intake by 13% (0.68 compared with 0.78 g/kg body wt, P < 0.05) . In conclusion, the method of weighed diet records was sufficiently accurate for assessing protein intake in this sample of type 2 diabetes patients.

Pre- and postnatal protein undernutrition increases hepatic carnitine palmitoyltransferase I activity and decreases enzyme sensitivity to inhibitors in the suckling rat.

Rats were pair-fed isocaloric diets containing either 25% (control diet) or 6% protein (low-protein diet) during the 5 weeks prior to conception and through the gestation and lactation periods; then, carnitine palmitoyltransferase I (CPT-I) activity was determined in liver and skeletal muscle mitochondria isolated from the corresponding pups. Maternal protein undernutrition increased the activity of hepatic CPT-I all along the suckling period, whereas the activity of the skeletal muscle enzyme was unaffected. Moreover, the sensitivity of hepatic CPT-I to inhibition by both malonyl-CoA and 4-hydroxyphenylglyoxylate was decreased in the low-protein group. These alterations in the properties of hepatic CPT-I may be involved in the appearance of hyperketonemia in the rat pup upon maternal administration of low-protein diets.