Quantitative analysis of the in situ Fourier transform infrared absorption and emission spectrum of gas-phase SiO (Deltav = 1 and 2) produced in Si-N-O fiber growth.

The in situ Fourier transform infrared (FT-IR) spectrum of gasphase SiO produced in silicon oxynitride fiber growth has been quantitatively analyzed. Both absorption and emission FT-IR spectra at a spectral resolution of 0.5 cm(-1) were produced from the reaction zone at 1450 degrees C. The fundamental and hot bands were observed with vibrational levels up to v = 7. For the purposes of quantitative analysis the individual vibration-rotation integrated line strengths for the three main isotopes,( 28)SiO,( 29)SiO, and( 30)SiO, were calculated based on ab initio quantum chemical calculations of the electric dipole moment function and the transition moment. Vibrational anharmonicity and Hermann-Wallis correction factors were also incorporated. From the line strengths at specific temperatures and the known Dunham coefficients, the absorbance spectrum was simulated with best fits giving the averaged SiO concentration in the 400 mm reaction zone of 1.0 x 10(17) molecules/cm(3). Such quantitative measurements demonstrate the power of in situ infrared (IR) spectroscopy combined with quantum chemical calculations. The rapid determination of synthetic calibration datasets for chemometric analysis can thus lead to correlation of gas-phase species concentrations with fiber growth properties and subsequently to real-time process control.

Assessment of vitamin B-12, folate, and vitamin B-6 status and relation to sulfur amino acid metabolism in neonates.

BACKGROUND: Total serum homocysteine (tHcy) has been used as an indicator of intracellular vitamin B-12, vitamin B-6, and folate status in adults, but data for neonates and infants are lacking. Vitamin B-12 deficiency may have fatal effects on neurologic development in infants; therefore, early diagnosis is crucial. OBJECTIVE: Our aim was to provide a reference range for tHcy in neonates and to explore the relation of tHcy to 1) serum vitamin concentrations, 2) the product of the transsulfuration pathway (cysteine), and 3) nutritional factors. DESIGN: tHcy, cysteine, folate, vitamin B-12, and vitamin B-6 were measured in 123 healthy, breast-fed neonates. The influence of nutrition (formula or human milk) on these variables was investigated in 60 infants. RESULTS: The mean (+/-SD) tHcy concentration was 7.8 +/- 3.1 micromol/L. tHcy showed a linear association with log vitamin B-12 (r = -0.64, P: < 0. 001), red blood cell folate (r = -0.33, P: < 0.001), and cysteine (r = 0.36, P: < 0.001). The strongest linear association was found between tHcy and the ratio of log cysteine to log vitamin B-12 (r = 0.71, P: < 0.0001). We found more neonates with probable tissue deficiencies of vitamin B-12 and folate on the basis of tHcy measurements than was expected from the analysis of serum vitamin concentrations alone (15.4% compared with 9.7%). Breast-fed infants had significantly lower vitamin B-12 concentrations and significantly higher serum tHcy and cysteine concentrations and ratios of log cysteine to log vitamin B-12 than did formula-fed infants (P: < 0.001). CONCLUSIONS: tHcy can be used as a functional indicator of vitamin B-12 and folate status in neonates. The ratio of cysteine to vitamin B-12 can be used as an additional index of impaired intracellular Hcy metabolism. tHcy and cysteine concentrations in infants are affected by nutritional factors.

A temperature-dependent switch from chaperone to protease in a widely conserved heat shock protein.

Misfolding or unfolding of polypeptides can occur as a consequence of environmental stress and spontaneous mutation. The abundance of general chaperones and proteases suggests that cells distinguish between proteins that can be refolded and "hopeless" cases fated to enter the proteolytic pathway. The mechanisms controlling this key metabolic decision are not well understood. We show here that the widely conserved heat shock protein DegP (HtrA) has both general molecular chaperone and proteolytic activities. The chaperone function dominates at low temperatures, while the proteolytic activity is present at elevated temperatures. These results show that a single cellular factor can switch between two key pathways, controlling protein stability and turnover. Implications of this finding for intracellular protein metabolism are discussed.

How should renal hemodynamic data be indexed in obesity?

Clearance data are customarily indexed to body surface area of 1.73 m2. This study examined whether this standard procedure gives correct values for renal perfusion in obese subjects. In 215 subjects who varied in age, gender, height, weight, obesity, and mean arterial blood pressure, RPF was determined by measuring the clearance of (131I)para-aminohippuric acid. Multiple regression analysis of the whole study group revealed that age (beta = -0.44, P < 0.001), height (beta = +0.25, P < 0.01), and arterial blood pressure (beta = -0.19, P < 0.01) were independent predictors of RPF, but that weight or body mass index was not. When related to body surface area, RPF appeared to decline with increasing obesity as follows: normal weight, 609 +/- 153 mL/min per 1.73 m2; overweight, 572 +/- 149 mL/min per 1.73 m2; severely overweight, 530 +/- 145 mL/min per 1.73 m2 (P < 0.012). In contrast, RPF related to height reflected a pattern concordant with the multiple regression analysis: normal weight, 3.76 +/- 0.9 mL/min per meter; overweight, 3.86 +/- 1.0 mL/min per meter; and severely overweight, 3.86 +/- 1.0 mL/min per meter (not significant). A separate repetition of the whole analysis for both normotensive (N = 55) and hypertensive subjects (N = 160) revealed a result similar to that found for the whole group. Thus, our results show that obesity was not a determinant of RPF, and when related to body surface area, inappropriately low values of RPF were calculated for obese patients. It was concluded that RPF values correlate with height and not with surface area in obese subjects.

Salt intake as a determinant of cardiac hypertrophy.

Sodium homeostasis profoundly influences the cardiovascular system in normotensive and hypertensive subjects and is related to cardiovascular morbidity and mortality independently of other cardiovascular risk factors, including hypertension. Left ventricular hypertrophy has a variety of negative effects on myocardial structure and function and is a risk factor per se. Dietary salt intake either estimated by daily sodium excretion or calculated by the food consumed throughout 24 h has been repeatedly found to be a strong and, in particular, blood pressure-independent predictor of left ventricular posterior wall thickness and left ventricular mass. Dietary salt intake participates in the hypertrophic process via mechanisms not yet clearly defined. Experimental data and results of the TOMHS study further suggest that salt restriction reduces the degree of left ventricular hypertrophy.

Salt intake, blood pressure, and cardiovascular structure.

Epidemiologic data revealed that a low sodium intake might have a favorable influence on blood pressure throughout an individual's lifetime. Sodium restriction was reported to lead to a modest fall in blood pressure in some studies, although a few groups of hypertensive patients experienced a rise in blood pressure. Left ventricular hypertrophy has been demonstrated to be related to cardiovascular morbidity and mortality independent of other risk factors. Dietary salt intake participates in the hypertrophic process independent of other determinants. Thus, 24-hour urinary sodium excretion has been reported to correlate with left ventricular mass independent of levels of arterial pressure. Three different mechanisms may link dietary salt intake to myocardial hypertrophy: the renin-angiotensin-aldosterone system, the sympathetic nervous system, and fluid volume homeostasis. Whether salt restriction reduces cardiovascular structural damage independent of arterial pressure has not been determined.

Perfusion scintigraphy and color-coded duplex sonography in a minimally perfused renal allograft.

Both, 99mTc DTPA perfusion scintigraphy and color-coded duplex sonography are reliable methods to quantitatively and qualitatively assess kidney transplant perfusion. In this case, minimal perfusion could be detected in a kidney allograft with marked vascular rejection by the scintigraphic analogous scan, whereas color-coded duplex sonography failed.

Toxic megacolon complicating Crohn's colitis.

Toxic megacolon complicating ulcerative colitis has been a well-recognized entity since its original description in 1950. The presence of toxic megacolon frequently has precluded a diagnosis of Crohn's colitis. Recent literature, however, has demonstrated that the incidence of toxic megacolon associated with Crohn's colitis (4.4-6.3%) may be higher than that in ulcerative colitis (1-2.5%). Differentiation between these two catastrophic forms of colitis is important in respect to prognosis and long-term results. Medical management of toxic megacolon may be initially successful in either type of colitis. Surgical intervention is indicated if the patient's condition does not improve within 48-72 hours. A subtotal colectomy with an ileostomy and mucous fistula is probably the treatment of choice for most of these extremely ill patients. The influence of the type of colitis on the results of subsequent management of the rectal stump remains unresolved.

Colorectal infarction following resection of abdominal aortic aneurysms.

Infarctions of the colon and rectum (incidences approximately 1 and 0.5 per cent, respectively) are caused by compromised collateral circulation to the colon and rectum, usually as a result of arteriosclerotic disease of the superior and inferior mesenteric arterial systems, as well as the hypogastric arteries. Patients who have colorectal ischemia after operations for abdominal aortic aneurysms have diarrhea (sometimes bloody), abdominal pain, and distention. The diagnosis may be established by sigmoidoscopic examination. Treatment includes surgical removal of the compromised bowel and creation of a temporary or permanent end colostomy. Prevention of this complication is aided by preservation of primary and collateral circulation, avoidance of hypotension, and preoperative bowel preparation.

Experimental evaluation and clinical application of intraoperative counterpulsation without balloon pumping.

Cardiac assistance in the form of counterpulsation (CP), created by intraaortic balloon pumping (IABP), has recently been utilized to wean patients from cardiopulmonary bypass (CPB) after conventional modalities have failed. The use of IABP, however, is often delayed because it is not part of the standard CPB setup and requires an additional cutdown, an arterial graft, and the retrograde insertion of a foreign body into the arterial tree. To eliminate the disadvantages of IABP, an alternate technique for CP has been developed. A pneumatially actuated external blood reservoir connected via a "Y" connector to the standard arterial line of the CPB circuit can provide pulsatile flow, and when synchronized with the EKG, CP with or without CPB. Experimental evaluation with dogs comparing this technique with IABP has shown that the former can create comparable CP pressure curves to the latter. The technique was applied to 11 patients undergoing either aorto-coronary bypass surgery and/or valvular surgery. Two of the 11 patients could come off CPB only with the assistance of CP. Coronary bypass graft flow, when measured, increased by 25% due to CP in two out of seven patients. The arterial CP technique has proven to be easily adapted to clinical settings and provides immediate and effective CP when required.