Clinical trial of three 10% carbamide peroxide bleaching products.
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BACKGROUND: A profusion of commercial bleaching systems exists on the market today, but there are few clinical comparisons of these systems. METHODS: In this study, three different commercial 10% carbamide peroxide bleaching systems were used by 24 patients in an overnight protocol for two weeks. Each patient used two of the bleaching products simultaneously in a side-by-side comparison. RESULTS: The mean onset of tooth whitening was 2.4 +/- 1.7 days. Tooth sensitivity was the most frequent side effect, as 64% of the patients reported tooth sensitivity occurring after 4.8 +/- 4.1 days and lasting for 5.0 +/- 3.8 days. Although intrapatient differences were recorded for the three commercial 10% carbamide peroxide bleaching systems by the patients, there were no statistical differences in the time of onset of subjective tooth whitening and the onset, frequency and duration of tooth sensitivity among the three commercial bleaching systems when compared pairwise or independently (p < 0.05). CONCLUSION: Selection of which bleaching product to use should be based on the concentration of the active ingredient, the viscosity of the product and other marketing features. Further research is needed to investigate the causes of tooth sensitivity and methods to reduce its severity and frequency. (+info)
Role of ornithine in the N-acetylglutamate turnover in the liver of rats.
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We determined whether the synthesis and degradation of N-acetylglutamate would regulate urea synthesis when the ornithine status was manipulated. Experiments were done on two groups of rats, each being treated with ornithine or saline (control). The plasma concentration of urea and the liver concentration of N-acetylglutamate in rats given ornithine were each significantly higher than in the control rats. Compared with the control rats, the liver N-acetylglutamate degradation was significantly lower in those rats treated with ornithine. Treatment of the rats with ornithine did not affect N-acetylglutamate synthesis in the liver. An inverse correlation between the liver N-acetylglutamate degradation and liver concentration of N-acetylglutamate was found. These results suggest that the lower degradation of N-acetylglutamate in the ornithine treatment group would be likely to increase the hepatic concentration of this compound and stimulate urea synthesis. (+info)
Oxidative refolding of recombinant prochymosin.
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The disulphide-coupled refolding of recombinant prochymosin from Escherichia coli inclusion bodies was investigated. Prochymosin solubilized from inclusion bodies is endowed with free thiol groups and disulphide bonds. This partially reduced form undergoes renaturation more efficiently than the fully reduced form, suggesting that some native structural elements existing in inclusion bodies and remaining after denaturation function as nuclei to initiate correct refolding. This assumption is supported by the finding that in the solubilized prochymosin molecule the cysteine residues located in the N-terminal domain of the protein are not incorrectly paired with the other cysteines in the C-terminal domain. Addition of GSH/GSSG into the refolding system facilitates disulphide rearrangement and thus enhances renaturation, especially for the fully reduced prochymosin. Based on the results described in this and previous papers [Tang, Zhang and Yang (1994) Biochem. J. 301, 17-20], a model to depict the refolding process of prochymosin is proposed. Briefly, the refolding process of prochymosin consists of two stages: the formation and rearrangement of disulphide bonds occurs at the first stage in a pH11 buffer, whereas the formation and adjustment of tertiary structure leading to the native conformation takes place at the second stage at pH8. The pH11 conditions help polypeptides to refold in such a way as to favour the formation of native disulphide bonds. Disulphide rearrangement, the rate-limiting step during refolding, can be achieved by thiol/disulphide exchange initiated by free thiol groups present in the prochymosin polypeptide, GSH/GSSG or protein disulphide isomerase. (+info)
Assessing dialysis adequacy and dietary intake in the individual hemodialysis patient.
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BACKGROUND: Urea kinetic modeling (UKM) and food records are widely used to assess the dialysis adequacy. Clinicians use these methods in individual patients to decide whether the dialysis prescription should be adjusted. We determined the variation in UKM parameters and dietary intake within individual patients in order to determine the required number of UKM measurements, and the number of food recording days to assess dialysis adequacy and dietary intake reliably. METHODS: Session-to-session variation in urea reduction ratio (URR), Kt/V, urea distribution volume (UDVDDQ), and protein catabolic rate (PCR) was determined during three mid-week dialysis sessions in 50 stable hemodialysis patients on three-times per week hemodialysis with a Kt/V of 0.98 +/- 0.13 (mean +/- SD). The dialysis prescription was kept constant. The day-to-day variation in dietary protein intake (DPI) and dietary energy intake (DEI) was determined from seven-day food records. The 90th percentile value of the coefficient of variation (CV) was used to determine the number of measurements. RESULTS: The variation in URR [CV, 2.4% (0.3 to 9.5) median (range)] and in Kt/V [CV, 4.0% (0.6 to 11.6)] was small in the majority of the patients. The variation in UDVDDQ [CV, 4.9% (0.3 to 25.7)] and PCR [CV, 9.3% (0.8 to 28.5)] was considerably larger. The variation in DPI [CV, 17.3% (8.4 to 64.0)] was larger than that in DEI [CV, 12.9% (5.0 to 33.0)]. To assess the URR within +/- 10% of its true value, the average of two measurements was required. Reliable assessment of Kt/V required three measurements. URR and Kt/V could be assessed reliably from a single measurement in 86 and 66% of the patients, but we were not able to distinguish these patients beforehand. Reliable estimation of UDVDDQ required six measurements. The required number of measurements for PCR, DPI, and DEI was determined using a precision of +/- 20%. To assess PCR reliably, three measurements were needed. Estimation of DPI and DEI required seven and five food recording days, respectively. CONCLUSIONS: The session-to-session variation in URR and Kt/V is small in stable hemodialysis patients. Nevertheless, the averaged value of two to three measurements is required to assess the dose of dialysis reliably. Assessment of dietary intake requires at least three PCR measurements or food records for at least one week. Basing clinical decisions on a single dialysis adequacy assessment is an unjustified practice that should be abandoned. (+info)
Trends in clinical indicators of care for adult peritoneal dialysis patients in the United States from 1995 to 1997. ESRD Core Indicators Workgroup.
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BACKGROUND: This article describes the changes in four core indicator variables: dialysis adequacy, hematocrit, serum albumin, and blood pressure in peritoneal dialysis CAPD and cycler patients over a three-year period. METHODS: A national random sample of adult peritoneal dialysis patients in the United States was drawn each study period. Clinical data abstraction forms were completed by facility staff for patients selected for the sample, returned to the respective network, then forwarded to the Health Care Financing Administration for analysis. RESULTS: The mean weekly Kt/V urea for CAPD patients increased from 1.91 in 1995 to 2.12 in 1997 (P < 0.001) and for cycler patients, from 2.12 in 1996 to 2.24 in 1997 (P < 0.05). The mean weekly creatinine clearance for CAPD patients increased from 61.48 liter/week/1.73 m2 in 1995 to 65.84 liter/week/1.73 m2 in 1997 (P < 0.05). For cycler patients, it increased from 63.37 liter/week/1.73 m2 in 1996 to 67.45 liter/week/1.73 m2 in 1997 (P < 0.05). Despite this increase in adequacy values, less than 40% of peritoneal dialysis patients in 1997 had weekly Kt/V urea or creatinine clearance values that met subsequently published National Kidney Foundation's Dialysis Outcomes Quality Initiative (DOQI) guidelines. These data suggest that the dialysis prescription may not be adequately modified to compensate for increased body weight and for decreased residual renal function as years on dialysis increase. The average hematocrit value increased modestly in both CAPD and cycler patients from 1995 to 1997, and the number of patients with a hematocrit of less than 25% decreased from 6% in 1995 to 1.4% in 1997 (P < 0.001). Both serum albumin values and systolic and diastolic blood pressure values were essentially unchanged during the three-year period of observation. CONCLUSIONS: Despite improvements in dialysis adequacy and hematocrit values, there remains much room for improvement in these core indicator values. (+info)
Cycler adequacy and prescription data in a national cohort sample: the 1997 core indicators report. Health Care Financing Administration Peritoneal Dialysis Core Indicators Study Group.
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BACKGROUND: The Health Care Financing Administration Peritoneal Dialysis Core Indicator Project obtains data yearly in four areas of patient care: dialysis adequacy, anemia, blood pressure, and nutrition. METHODS: Adequacy and dialysis prescription data were obtained using a standardized data abstraction form from a random sample of adult U.S. peritoneal dialysis patients who were alive on December 31, 1996. RESULTS: For the cohort receiving cycler dialysis, 22% were unable to meet the National Kidney Foundation Dialysis Outcome Quality Initiatives (NKF-DOQI) dialysis adequacy guidelines because they did not have at least one adequacy measure during the six-month period of observation. Thirty-six percent of patients met NKF-DOQI guidelines for weekly Kt/V urea, 33% met guidelines for weekly creatinine clearance (CCr), and 24% met guidelines for both urea and creatinine clearances. The mean weekly adequacy values were 2.24 +/- 0.56 for Kt/V urea and 67.5 +/- 24.4 liter/1.73 m2 for CCr, and the median values were 2.20 and 62.25 liter/1.73 m2, respectively. The mean prescribed 24-hour volume was 12,040 +/- 3255 ml, and the median prescribed volume was 11,783 ml. Only 60% of patients were prescribed at least one daytime dwell. By logistic regression analysis, risk factors for an inadequate dose of dialysis included being in the highest quartile of body surface area (odds ratio = 3.3 for CCr and 3.4 for Kt/V urea) and a duration of dialysis greater than two years (odds ratio = 4.2 for CCr and 2.1 for Kt/V urea). CONCLUSION: There is much room for improvement in providing an adequate dose of dialysis to cycler patients. Practitioners should be more aggressive in increasing dwell volumes, adding daytime dwells, and adjusting nighttime dwell times in order to compensate for the loss of residual renal function over time. These changes can only be accomplished if practitioners measure periodically the dose of dialysis as outlined in the NKF-DOQI guidelines. (+info)
High peritoneal residual volume decreases the efficiency of peritoneal dialysis.
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BACKGROUND: Wide variation in peritoneal residual volume (PRV) is a common clinical observation. High PRV has been used in both continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis to minimize the time of a dry peritoneal cavity and to achieve better dialysis. However, the impact of PRV on peritoneal transport is not well established. In this study, we investigated the effect of PRV on peritoneal transport characteristics. METHODS: Peritoneal effluents were collected in 32 male Sprague-Dawley rats after a five-hour dwell with 1.36% glucose solution. Forty-eight hours later, a four hour dwell using 25 ml of 3.86% glucose solution and frequent dialysate and blood sampling was done in each rat with 125I-albumin as a volume marker. Before the infusion of the 3.86% glucose solution, 0 (control), 3, 6, or 12 ml (8 rats in each group) of autologous effluent (serving as PRV) was infused to the peritoneal cavity. RESULTS: After subtracting the PRV, the net ultrafiltration was significantly lower in the PRV groups as compared with the control group: 13.4 +/- 0.5, 12.0 +/- 1.0, 11.7 +/- 1.7, and 8.9 +/- 0.4 ml for 0, 3, 6, and 12 ml PRV groups, respectively (P < 0.001). The lower net ultrafiltration associated with higher PRV was due to (a) a significantly lower transcapillary ultrafiltration rate (Qu) caused by a lower osmotic gradient, and (b) a significantly higher peritoneal fluid absorption rate (KE) caused by an increased intraperitoneal hydrostatic pressure. No significant differences were found in the diffusive mass transport coefficient for small solutes (glucose, urea, sodium, and potassium) and total protein, although the dialysate over plasma concentration ratios values were higher in the high-PRV groups. The sodium removal was significantly lower in the PRV groups as compared with the control group (P < 0.01). CONCLUSION: Our results suggest that a high PRV may decrease net ultrafiltration through decreasing the Qu, which is caused by a decreased dialysate osmolality, and increasing the KE caused by an increased intraperitoneal hydrostatic pressure. The high volume of PRV also decreased the solute diffusion gradient and decreased peritoneal small solute clearances, particularly for sodium. Therefore, a high PRV may compromise the efficiency of dialysis with a glucose solution. (+info)
Comparison of metabolism of free fatty acid by isolated perfused livers from male and female rats.
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Livers from normal, fed male and female rats were perfused with different amounts of [1-14C]oleate under steady state conditions, and the rates of uptake and utilization of free fatty acid (FFA) were measured. The uptake of FFA by livers from either male or female rats was proportional to the concentration of FFA in the medium. The rate of uptake of FFA, per g of liver, by livers from female rats exceeded that of the males for the same amount of FFA infused. The incorporation by the liver of exogenous oleic acid into triglyceride, phospholipid, and oxidation products was proportional to the uptake of FFA. Livers from female rats incorporated more oleate into triglyceride (TG) and less into phospholipid (PL) and oxidation products than did livers from male animals. Livers from female rats secreted more TG than did livers from male animals when infused with equal quantities of oleate. The incorporation of endogenous fatty acid into TG of the perfusate was inhibite) by exogenous oleate. At low concentrations of perfusate FFA, however, endogenous fatty acids contributed substantially to the increased output of TG by livers from female animals. Production of 14CO2 and radioactive ketone bodies increased with increasing uptake of FFA. The partition of oleate between oxidative pathways (CO2 production and ketogenesis) was modified by the availability of the fatty acid substrate with livers from either sex. The percent incorporation of radioactivity into CO2 reached a maximum, whereas incorporation into ketone bodies continued to increase. The output of ketone bodies was dependent on the uptake of FFA, and output by livers from female animals was less than by livers from male rats. The increase in rate of ketogenesis was dependent on the influx of exogenous FFA, while ketogenesis from endogenous sources remained relatively stable. The output of glucose by the liver increased with the uptake of FFA, but no difference due to sex was observed. The output of urea by livers from male rats was unaffected by oleate, while the output of urea by livers from females decreased as the uptake of FFA increased. A major conclusion to be derived from this work is that oleate is not metabolized identically by livers from the two sexes, but rather, per gram of liver, livers from female rats take up and esterify more fatty acid to TG and oxidize less than do livers from male animals; livers from female animals synthesize and secrete more triglyceride than do livers from male animals when provided with equal quantities of free fatty acid. (+info)