Total Body Nitrogen Research Articles

Successful Kidney Transplantation Is Associated With Weight Gain From Truncal Obesity and Insulin Resistance

The objective of this study is to compare changes in body composition, lifestyle factors, and metabolic responses occurring in living kidney transplant recipient patients after transplantation. The study was a single-site, prospective, observational study. To identify metabolic responses during the initial years after transplantation, we obtained state-of-the-art, high-resolution measurements of body composition from a 4-compartment model using dual-energy X-ray absorptiometry, air displacement plethysmography, and total body potassium and nitrogen counters. We also assessed dietary recalls and actigraphy before transplantation and 3- and 12-month after transplantation. The study was conducted at a quaternary care hospital outpatient transplant center and a United States Department of Agriculture Agricultural Research Service center. Thirty-one adults receiving a living donor kidney allograft were studied. The main outcome measures were change in body composition at 3months and 1year after transplantation, and this was correlated with the occurrence of insulin resistance. In patients receiving a successful kidney transplant from living donors treated with standard immunosuppression, significant increases in body weight were detected at 3 and 12months after transplantation (2.2kg, P=.03 and 6.6kg, P<.0001, respectively). Weight gain was principally due to adipose tissue accumulation in the truncal region. There was no increase in muscle mass or fluid accumulation. Weight gain was not associated with changes in resting energy expenditure or physical activity. Notably, increases in visceral and subcutaneous adipose tissue were positively correlated with insulin resistance. Successful transplantation was associated with increased insulin resistance and weight gain without increases in muscle or fluid. This metabolic pattern suggests potential interventions that could prevent or mitigate the consequences of adipose tissue accumulation in transplant recipients.

Energy requirements of early‐weaned Dorper cross‐bred female lambs

The net and metabolizable energy (NE and ME) requirements of Dorper cross-bred female lambs with BWs of 20-35kg were assessed in a comparative slaughter trial. Thirty-five Dorper×thin-tailed Han cross-bred female lambs weaned at ~50days of age (20.3±2.15kg BW) were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of seven randomly selected lambs fed adlibitum was slaughtered when the lambs reached an average BW of 28.5kg. The remaining 21 lambs were allotted randomly to three levels of dry matter intake: adlibitum or restricted to 70% or 40% of the adlibitum intake. All the lambs were slaughtered when the sheep fed adlibitum reached a BW of 35kg. Total body energy, nitrogen, fat, ash and moisture content were determined. In a digestibility trial, an additional 15 Dorper×thin-tailed Han cross-bred female lambs (28.7±1.75kg BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at the three feed intake levels. The maintenance requirements for NE and ME were 245.5 and 380.3kJ/kg metabolic shrunk body weight (SBW0.75 ) respectively. The partial efficiency of energy use for maintenance was 0.645. The NE requirements for growth ranged from 1.18 to 5.18MJ/d for the lambs gaining 100-350g/d from 20 to 35kg BW. Partial efficiency of ME for growth was 0.44. In conclusion, the current study suggests that the NE requirement for maintenance and growth of Dorper early-weaned cross-bred female lambs is lower than the current AFRC and NRC recommendations.

Nutritional status and the foraging behaviour of Bactrocera tryoni with particular reference to protein bait spray

AbstractPoisoned protein baits comprise a recognized method for controlling tephritid fruit flies in the form of a ‘lure‐and‐kill’ technique. However, little is known about how a fly's internal protein and carbohydrate levels (i.e. nutritional status) might influence the efficacy of this control. In the present study, the relationships between the internal levels of protein (as measured by total body nitrogen) and carbohydrate (as measured by total body carbon) of the fruit fly Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) are investigated, as well as its foraging behaviours in response to protein, fruit and cue‐lure (a male‐specific attractant) baits. Small cage behavioural experiments are conducted using flies from cultures of different nutritional status and wild flies sampled from the field during the fruiting cycle of a guava crop. For female flies, increasing total body nitrogen is correlated with decreased protein foraging and increased oviposition activity; increasing total body carbon levels generate the same behavioural changes except that the oviposition response is not significant. For males, there are no significant correlations between changes in total body nitrogen and total body carbon and protein or cue‐lure foraging. For wild flies from the guava orchard, almost all of them are sexually mature when entering the crop and, over the entire season, total body nitrogen and total body carbon levels are such that protein hunger is unlikely for most flies. The results infer strongly that the requirements of wild, sexually mature flies for protein are minimal and that flies can readily gain sufficient nutrients from wild sources for their physiological needs. The results offer a mechanistic explanation for the poor response of male and mature female fruit flies to protein bait spray.

Energy requirements for maintenance and growth of Dorper crossbred ram lambs

This study aimed to determine the energy requirements of Dorper crossbred sheep that have been used for meat production in China. Thirty-five 1/2 Dorper×1/2 thin-tailed Han crossbred noncastrated ram lambs [34.1±0.6kg body weight (BW)] were used in a comparative slaughter trial. Seven ram lambs were randomly selected as the baseline group and slaughtered at 35kg BW. The remaining 28 lambs were randomly divided into four groups of seven lambs each. Three of the four groups were fed a mixed diet either for ad libitum intake, 60% or 45% of the ad libitum intake. The three groups were slaughtered when the ram lambs that were fed ad libitum reached 50kg BW. The ram lambs from the fourth group were also fed ad libitum as an intermediate group and slaughtered at 43kg BW. Total body energy, nitrogen, fat, ash, and moisture content were measured. In a digestibility trial, another 15 ram lambs (41.3±0.8kg BW) were housed in metabolism cages to estimate the metabolizable energy (ME) value of the diet at the three levels of feed intake. The daily net energy (NE) requirement for maintenance was 263kJ/kg0.75 of BW or 278kJ/kg0.75 of shrunk BW (SBW), with a partial efficiency of ME utilization for maintenance of 0.69. The NE requirement for growth ranged from 1.12 to 5.31MJ/d for daily gains of 100–400g BW, or from 1.29 to 6.18MJ/d for daily gains of 100–400g SBW. The partial efficiency of ME utilization for growth was 0.46. The energy requirements of Dorper×thin-tailed Han crossbred ram lambs were lower than those recommended by the British or American nutritional systems.

Assessment of the associated particle prompt gamma neutron activation technique for total body nitrogen measurement in vivo

Total body nitrogen (TBN) can be used to estimate total body protein, an important body composition component at the molecular level. A system using the associated particle technique in conjunction with prompt gamma neutron activation analysis has been developed for the measurement of TBN in vivo. The system uses a compact D, T neutron generator (~107 n/s) coupled to an internal alpha-particle detector, and a counting system with six bismuth germinate detectors. 14 Subjects were scanned from shoulders to hips (20 min scan time, <0.4 mSv dose) generating complex spectra dominated by signals from C, O, H, and N, with significant peak overlap. Fractional contributions from these elements to regions of interests (ROI) spanning a 4–8 MeV range were determined by algorithms comparing ratios of interrelated ROIs. In addition, multi-component least squares fitting was done to further resolve individual peak activities (MATLAB R2011b). Total body potassium (TBK) was also measured using a whole body gamma counter. Predicted TBN values, based on fat-free mass estimated from TBK, were compared to measured TBN results. Measured versus predicted results for all subjects were not statistically different. Separating subjects by gender also showed no difference between measured and predicted values. The associated particle system showed good agreement with predicted TBN values, but measurement precision was not better than that commonly seen in traditional prompt gamma thermal neutron activation analysis systems.

Light aerobic physical exercise in combination with leucine and/or glutamine-rich diet can improve the body composition and muscle protein metabolism in young tumor-bearing rats

Nutritional supplementation with some amino acids may influence host's responses and also certain mechanism involved in tumor progression. It is known that exercise influences body weight and muscle composition. Previous findings from our group have shown that leucine has beneficial effects on protein composition in cachectic rat model as the Walker 256 tumor. The main purpose of this study was to analyze the effects of light exercise and leucine and/or glutamine-rich diet in body composition and skeletal muscle protein synthesis and degradation in young tumor-bearing rats. Walker tumor-bearing rats were subjected to light aerobic exercise (swimming 30 min/day) and fed a leucine-rich (3%) and/or glutamine-rich (4%) diet for 10 days and compared to healthy young rats. The carcasses were analyzed as total water and fat body content and lean body mass. The gastrocnemious muscles were isolated and used for determination of total protein synthesis and degradation. The chemical body composition changed with tumor growth, increasing body water and reducing body fat content and total body nitrogen. After tumor growth, the muscle protein metabolism was impaired, showing that the muscle protein synthesis was also reduced and the protein degradation process was increased in the gastrocnemius muscle of exercised rats. Although short-term exercise (10 days) alone did not produce beneficial effects that would reduce tumor damage, host protein metabolism was improved when exercise was combined with a leucine-rich diet. Only total carcass nitrogen and protein were recovered by a glutamine-rich diet. Exercise, in combination with an amino acid-rich diet, in particular, leucine, had effects beyond reducing tumoral weight such as improving protein turnover and carcass nitrogen content in the tumor-bearing host.

Total body nitrogen and total body carbon as indicators of body protein and body lipids in the melon fly Bactrocera cucurbitae: Effects of methoprene, a juvenile hormone analogue, and of diet supplementation with hydrolyzed yeast

The application of methoprene, and providing access to diet including hydrolyzed yeast, are treatments known to enhance mating success in the male melon fly Bactrocera cucurbitae Coquillett (Diptera: Tephritidae), supporting their use in mass rearing protocols for sterile males in the context of sterile insect technique (SIT) programmes. The objective of the present laboratory study was to investigate the effect of methoprene application and diet supplementation with hydrolyzed yeast (protein) on the turnover of body lipids and protein to confirm the feasibility of their application in melon fly SIT mass-rearing programmes. While females had access to a diet that included hydrolyzed yeast (protein), males were exposed to one of the following treatments: (1) topical application of methoprene and access to diet including protein (M+P+); (2) only diet including protein (M−P+); (3) only methoprene (M+P−) and (4) untreated, only sugar-fed, control males (M−P−). Total body carbon (TBC) and total body nitrogen (TBN) of flies were measured at regular intervals from emergence to 35 days of age for each of the different treatments. Nitrogen assimilation and turnover in the flies were measured using stable isotope (15N) dilution techniques. Hydrolyzed yeast incorporation into the diet significantly increased male body weight, TBC and TBN as compared to sugar-fed males. Females had significantly higher body weight, TBC and TBN as compared to all males. TBC and TBN showed age-dependent changes, increasing until the age of sexual maturity and decreasing afterwards in both sexes. Methoprene treatment did not significantly affect TBC or TBN. The progressive increase with age of TBC suggests that lipogenesis occurs in adult male B. cucurbitae, as is the case in other tephritids. Stable isotope dilution was shown to be an effective method for determining N uptake in B. cucurbitae. This technique was used to show that sugar-fed males rely solely on larval N reserves and that the N uptake rate in males with access to diet including hydrolyzed yeast was higher shortly after emergence and then stabilized. The implications of the results for SIT applications are discussed.

Preoperative body composition is influenced by the stage of operable pancreatic adenocarcinoma but does not predict survival after Whipple's procedure

ObjectivesCachexia is common in pancreatic cancer and may have an influence on longterm survival but few studies have investigated this in patients with operable tumours. Therefore, this study was carried out to document body composition status in patients with pancreatic adenocarcinoma (PCa) presenting for a Whipple's procedure (WP) and to relate the findings to histopathology and longterm survival. MethodsBody composition was measured 1 day before a WP for ductal PCa in 36 patients (15 men, 21 women) aged 41–81 years. Results for total body nitrogen (TBN), nitrogen index (NI), total body water (TBW), fat mass (FM) and total body potassium (TBK) were compared with results in 73 age- and sex-matched controls. Patients' survival and details from histopathology synoptic reports were documented. ResultsPatients undergoing WPs had low TBK values (P < 0.001) and females had lower body fat (P= 0.007) compared with controls. Five of 36 presented with significant protein deficiency, but this was not associated with a prolonged length of stay or reduced survival. The 12 patients who had involved surgical margins had larger tumours and reduced weight (P= 0.015), FM (P= 0.001), TBN (P= 0.045), TBK (P= 0.014) and survival (P= 0.036). However, multivariate Cox's regression analysis only included FM along with vascular invasion and margin status as independent predictors of survival. ConclusionsPCa patients undergoing a WP have reduced body fat and TBK compared with community controls while those with stage III tumours had greater deficits of fat, TBK and protein stores. However, preoperative body composition was a poor predictor of postoperative survival after pathological data were considered.

Monte Carlo efficiency calibration of a neutron generator-based total-body irradiator

Many body composition measurement systems are calibrated against a single-sized reference phantom. Prompt-gamma neutron activation (PGNA) provides the only direct measure of total body nitrogen (TBN), an index of the body’s lean tissue mass. In PGNA systems, body size influences neutron flux attenuation, induced gamma signal distribution, and counting efficiency. Thus, calibration based on a single-sized phantom could result in inaccurate TBN values. We used Monte Carlo simulations (MCNP-5; Los Alamos National Laboratory) in order to map a system’s response to the range of body weights (65–160 kg) and body fat distributions (25–60%) in obese humans. Calibration curves were constructed to derive body-size correction factors relative to a standard reference phantom, providing customized adjustments to account for differences in body habitus of obese adults. The use of MCNP-generated calibration curves should allow for a better estimate of the true changes in lean tissue mass that many occur during intervention programs focused only on weight loss.

Nutritional status of patients undergoing pelvic exenteration for primary or recurrent rectal cancer

Methods: 24 participants with Childs Pugh class B cirrhosis [17males:7females, mean age (range) 52.5(38-64)years] completed 2 months of study protocol. 12 participants were randomised into BCAA group, took 3 sachets (4g BCAA/ sachet) of BCAA supplement daily between meals and attended monthly clinic visits. 12 participants were randomised into Placebo group, took 3 sachets of a isonitrogenous supplement daily between meals and attended monthly clinic visits. At each clinic visit clinical assessments were made, serum samples were collected, then total body nitrogen (TBN) and total body potassium (TBK) were measured. The results of baseline and monthly measurements were compared using independent samples t-tests. Results: The Placebo group showed a greater increase (p 0.05) in TBN at month 2, TBK at months 2 and 3 than the BCAA group. The BCAA group showed a significant decrease (p 0.05) in serum GGT and ALP at month 3 compared to the baseline and the Placebo group. IGF-1 levels showed no significant change. Conclusion:

Changes in Body Composition with Weight Loss: Obese Subjects Randomized to Surgical and Medical Programs

To assess changes in body composition with weight loss in obese subjects randomized to a laparoscopic adjustable gastric band surgical program or a medical program using a very-low-energy diet and orlistat. Using body composition measurements by DXA, neutron activation for total body nitrogen, and whole body gamma counting for total body potassium, we studied changes in fat mass, fat distribution, fat-free mass, total bone mineral content, total body protein, and body cell mass at 6 (n = 61 paired) and 24 months (n = 53 paired) after randomization. At 24 months, the surgical group had lost significantly more weight (surgical, 20.3 +/- 6.5 kg; medical, 5.9 +/- 8.0 kg). There was favorable fat-free mass to fat mass loss ratios for both groups (surgical, 1:5.5; medical, 1:5.9). Changes in total body nitrogen or potassium were favorable in each group. A small reduction in mean bone mineral content occurred throughout the study but was not associated with extent of weight loss or treatment group. At 6 months, weight loss for both groups was similar (surgical, 14.1 +/- 4.5 kg; medical, 13.3 +/- 7.3 kg). The medical program subjects lost less fat-free mass and skeletal muscle and had increased total body protein. The proportion of body fat to limb fat remained remarkably constant throughout the study. Weight loss programs used in this study induced fat loss without significant deleterious effects on the components of fat-free mass.

Total body protein in healthy adolescent girls: validation of estimates derived from simpler measures with neutron activation analysis

Background: Little recent and accurate information about body protein content in healthy adolescent girls is available.Objective: The objective was to assess the total body nitrogen (TBN) and total body protein (TBPr) contents of fat-free mass (P:FFM) in a group of healthy adolescent girls and to validate previously published TBN prediction equations.Design: TBN was measured with in vivo neutron activation analysis (TBNNAA). Bone mineral density and FFM were measured with dual-energy X-ray absorptiometry (FFMDXA), total body water and FFM were measured with bioimpedance analysis, and FFM was assessed by measuring skinfold thicknesses in 51 girls with a mean (±SD) age of 14.7 ± 0.7 y. The validity of the TBN prediction equations was assessed with Bland-Altman analysis.Results: TBNNAA in our adolescent group was higher (1.49 kg) than values reported in earlier studies of women (1.25 and 1.31 kg), and P:FFM was slightly higher (23%) than that documented in adults (19–21%). Previously published TBN equations showed either systematic bias or wide limits of agreement.Conclusion: A predictive equation derived from the present study population based on FFMDXA improves the prediction of TBN for groups of young girls but may not be helpful for individuals in clinical settings.

Pharmacology Review: Sodium Phenylacetate and Sodium Benzoate in the Treatment of Neonatal Hyperammonemia

Ammonia is present in all body fluids and exists primarily as ammonium ion at physiologic pH. Hyperammonemia is defined as a blood ammonia concentration greater than about 100 mcmol/L in neonates or 50 mcmol/L in children and adults (precise cut-offs vary, depending on individual laboratory normative ranges). The concentration of ammonia is 10 times higher in tissue than in blood. A 5- to 10-fold increase in blood ammonia concentration usually is toxic to the nervous system. Hyperammonemia in the neonatal period, especially when due to inborn errors of metabolism, can progress rapidly and cause severe neurologic damage or early death. Hyperammonemia can be caused by inborn errors of metabolism as well as by a variety of acquired conditions (Tables 1 and 2). Urgent treatment is required because of the potential for irreversible neurologic sequelae that can, in many cases, be prevented by prompt diagnosis and institution of therapy. | Urea cycle defects | || | Amino acid transporter deficiencies | | Organic acidemias | | Fatty acid oxidation defects | | Pyruvate carboxylase deficiency | | Mitochondrial disorders | | Hyperinsulinism/hyperammonemia syndrome (glutamate dehydrogenase mutations) | | Delta1-pyrroline-5-carboxylate synthase deficiency | Table 1. Inborn Errors of Metabolism Associated With Hyperammonemia | Sampling artifact | || | Cardiovascular | | Perinatal asphyxia | | Liver failure | | Bacterial colonization (urease-positive organisms) | | Iatrogenic | Table 2. Causes of Acquired Hyperammonemia The combination of sodium phenylacetate (NAPA) and sodium benzoate (NABZ) in a 10%/10% solution is an intravenously administered United States Food and Drug Administration (FDA)-approved drug used as adjunctive therapy for …

Metabolically active portion of fat-free mass: a cellular body composition level modeling analysis.

The proportion of fat-free mass (FFM) as body cell mass (BCM) is highly related to whole body resting energy expenditure. However, the magnitude of BCM/FFM may have been underestimated in previous studies. This is because Moore's equation [BCM (kg) = 0.00833 x total body potassium (in mmol)], which was used to predict BCM, underestimates BCM by approximately 11%. The aims of the present study were to develop a theoretical BCM/FFM model at the cellular level and to explore the influences of sex, age, and adiposity on the BCM/FFM. Subjects were 112 adults who had the following measurements: total body water by (2)H(2)O or (3)H(2)O dilution; extracellular water by NaBr dilution; total body nitrogen by in vivo neutron activation analysis; and bone mineral by dual-energy X-ray absorptiometry. FFM was calculated using a multicomponent model and BCM as the difference between FFM and the sum of extracellular fluid and solids. The developed theoretical model revealed that the proportion of BCM to FFM is mainly determined by water distribution (i.e., E/I, the ratio of extracellular to intracellular water). A significant correlation (r = 0.90, P < 0.001) was present between measured and model-predicted BCM/FFM for all subjects pooled. Measured BCM/FFM [mean (SD)] was 0.584 +/- 0.041 and 0.529 +/- 0.041 for adult men and women (P < 0.001), respectively. A multiple linear regression model showed that there are independent significant associations of sex, age, and fat mass with BCM/FFM.

Body composition during GH replacement in adults – methodological variations with respect to gender

Men with growth hormone deficiency (GHD) may be more sensitive to GH treatment than women in terms of changes in body composition. We have studied whether age, body-mass index (BMI) and the different types of methodology used to assess body composition may explain these differences. Forty-four men and forty-four women with GHD, closely matched for age and BMI, were studied before and after 6 months of GH replacement. The dose of GH was individually adjusted. Body composition was assessed by measurements of potassium-40, total body nitrogen (TBN), tritiated water dilution, dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA). Four- and five-compartment models for body composition were also calculated. The total daily dose of GH was similar in men and women at 6 months. Serum insulin-like growth factor-I (IGF-I) was higher in men than women at baseline and after 6 months of treatment (P = 0.01, paired t-test). The increment was, however, similar. In women, GH treatment reduced body weight and increased TBN. In both men and women, total body water and body cell mass increased, while total body fat (BF) mass decreased. At baseline, mean total BF varied considerably depending on the methodology used, with the highest value obtained from DXA. The changes in BF were, however, less dependent on the methodology, but DXA and BIA demonstrated the largest inconsistency between men and women. These results suggest that gender differences in body composition in response to GH treatment are small, if adjustments are made for baseline factors such as age, BMI and dose of GH. Different methods of body composition measurements produce different results, but changes in response to GH administration are less inconsistent.

ESPEN Guidelines on Enteral Nutrition: Non-surgical oncology

Enteral nutrition (EN) by means of oral nutritional supplements (ONS) and tube feeding (TF) offers the possibility of increasing or ensuring nutrient intake in cases where normal food intake is inadequate. These guidelines are intended to give evidence-based recommendations for the use of ONS and TF in cancer patients. They were developed by an interdisciplinary expert group in accordance with officially accepted standards, are based on all relevant publications since 1985 and were discussed and accepted in a consensus conference. Undernutrition and cachexia occur frequently in cancer patients and are indicators of poor prognosis. EN should be started if undernutrition already exists or if food intake is markedly reduced for more than 7-10 days. Standard formulae are recommended for EN. Nutritional needs generally are comparable to non-cancer subjects. In cachectic patients metabolic modulators such as progestins, steroids and possibly eicosapentaenoic acid may help to improve nutritional status. EN is indicated preoperatively for 5-7 days in cancer patients undergoing major abdominal surgery. During radiotherapy of head/neck and gastrointestinal regions dietary counselling and ONS prevent weight loss and interruption of radiotherapy. Routine EN is not indicated during (high-dose) chemotherapy.

Metabolically‐active portion of fat‐free mass: a cellular body composition level modeling analysis

The proportion of fat-free mass (FFM) as body cell mass (BCM) is highly related to resting energy expenditure. However, the BCM/FFM ratio may have been underestimated in previous studies as the Moore equation (BCM = 0.00833 x TBK), which is typically used to predict BCM, underestimates BCM by ~11%. The aims of the present study were to develop a theoretical BCM/FFM model at the cellular level, and to explore the influences of sex, age, and adiposity on BCM/FFM. Subjects were 112 adults who had the following measurements: total-body water by 2H2O or 3H2O dilution; extracellular water by NaBr dilution; total-body nitrogen by in vivo neutron activation analysis; and bone mineral by DXA. FFM was calculated using a multicomponent model and BCM was calculated as the difference between FFM and the sum of extracellular fluid and solids. The developed theoretical model revealed that the proportion of BCM/FFM is mainly determined by water distribution (E/I, the ratio of extracellular to intracellular water). A significant correlation (r = 0.90, P < 0.001) was present between measured and model-predicted BCM/FFM for all subjects pooled. Measured BCM/FFM (mean +/− SD) was 0.584 +/− 0.041 and 0.529 +/− 0.041 for adult men and women (P < 0.001), respectively. A multiple linear regression model showed that there are independent significant associations of sex, age, and %fat with BCM/FFM. Variation in the BCM/FFM is mainly dependent on water distribution with a larger E/I associated with a smaller BCM/FFM. Supported by NIDDK PO1-42618.

Does growth hormone allow more efficient nitrogen sparing in postoperative patients requiring parenteral nutrition? A double-blind, placebo-controlled randomised trial

Growth hormone (GH) has a strong anabolic effect and is thought to be useful in improving the efficacy of parenteral nutrition (PN) to preserve muscle mass (MM) in the postoperative setting. Unfortunately, the negative clinical outcome of GH treatment in intensive care patients limits its use in this setting, but demands answers to the mechanism behind the action of this therapy. In a double-blind randomised controlled study consecutive patients after major abdominal surgery were divided into four groups of either 1/2-PN (0.13 g N/kg/day and 52% of calories as lipid) or full-strength PN (Full-PN) (0.3 g N/kg/day and 65% of calories as lipid) receiving daily injections of either GH (8-16 IU) or placebo for a period of 14 days postoperative. Outcome measures included MM derived from measures of total body potassium (40K counting) and total body nitrogen (TBN) (in vivo neutron capture technique); Fat mass from skin folds; serum insulin like growth factor-I (IGF-I) and its binding proteins (IGFBP). From 43 major upper GI surgical patients randomised 35 completed the study (one patient died from sepsis in the half-strength PN (1/2-PN)+GH group). 1/2-PN (n=11) lost TBN (P=0.001), MM (P=0.005) but not fat. Full-PN (n=9) maintained TBN, MM (P=0.056) and fat. 1/2-PN+GH (n=8) maintained TBN and fat but lost MM (P=0.038). Full-PN+GH (n=7) maintained TBN and MM but lost fat (P=0.018). Two-way ANOVA indicated that PN input (P=0.031) and not GH had a significant effect on MM. GH caused a significant rise in IGF-I levels (290+/-67 and 454+/-71 microg/l for 1/2-PN+GH and Full-PN+GH, respectively) and restored serum IGFBP3 and the acid labile subunit to normal, by the postoperative day 9. After major gastrointestinal surgery, GH causes a marked hepatic IGF-I response and nitrogen retention but its effect on body composition was more significant with a high PN input. Further, Full-PN alone was sufficient to prevent nitrogen loss and preserved MM and addition of GH does not provide further metabolic advantage.

Design considerations for a neutron generator-based total-body irradiator

The prompt- and delayed-gamma neutron activation techniques have been used for the non-invasive measurement of human body composition. In recent years, neutron irradiators have used only transuranic isotopic sources (238PuBe, 241AmBe, 252Cf). However, in today’s security-minded environment, the use of alternate neutron sources may provide some advantages. We have examined several designs for an irradiator that would use a high-output, miniature D-T neutron generator (MF Physics). The use of this type of neutron source will lessen the storage, security, and transport issues associated with continuous-output isotopic neutron sources. To determine the scientific impact of this decision, we have performed Monte Carlo simulations (MCNP-4B2; Los Alamos National Laboratory) to aid in the design of the irradiator system, evaluating shielding materials, collimation, and source-to-subject distance, for the measurement of total body nitrogen (TBN). Based on internal flux distributions within the simulated body region of a subject, several design options were identified. The final design will be selected based on the optimization of precision, dose, and exposure time.

Protein malnutrition and hypoalbuminemia as predictors of vascular events and mortality in ESRD

Background: It is proposed that chronic inflammation is common to the pathogenesis of malnutrition and vascular disease, both frequently observed in patients with end-stage renal disease. However, previous studies were unable to differentiate between true protein malnutrition and hypoalbuminemia. Methods: This study was undertaken to determine the associations between malnutrition, measured by total-body nitrogen (TBN), and albumin, a marker of both nutritional status and chronic inflammation, with mortality and morbidity. One hundred nine patients starting dialysis therapy underwent nutritional assessment (TBN level and anthropometric measurements), vascular risk assessment (hypertension, hypercholesterolemia, diabetes mellitus, and smoking status), and serum albumin measurement. Subsequent patient mortality and new vascular events were recorded. Results: Survival was associated independently with both TBN (hazard ratio [HR], 1.6; 95% confidence interval [CI], 1.1 to 2.5; P = 0.02 for every 10% decrease in nitrogen index) and serum albumin levels (HR, 1.1; 95% CI, 1.0 to 1.2; P = 0.004 for every 0.1-g/dL (1-g/L) decrease in serum albumin level) adjusted for other variables. Only low serum albumin level predicted subsequent vascular morbidity (HR, 2.2; 95% CI, 1.0 to 4.9; P = 0.049), as did increasing age (HR, 2.0; 95% CI, 1.4 to 3.0; P = 0.0004 for every 10-year increase in age) adjusted for other important risk factors. Conclusion: This study dissociates the effect of protein malnutrition and hypoalbuminemia on morbidity and mortality in patients starting dialysis therapy. Protein malnutrition and hypoalbuminemia are independently predictive of mortality, whereas hypoalbuminemia is predictive of vascular morbidity. The study supports the hypothesis that hypoalbuminemia is pathogenically associated with vascular disease, but dissociates this effect from protein malnutrition.