Improved Thermophysical and Mechanical Properties in LiNaSO4 Composites for Thermal Energy Storage

Solid-solid phase-change materials have great potential for developing compact and low-cost thermal storage systems. The solid-state nature of these materials enables the design of systems analogous to those based on natural rocks but with an extraordinarily higher energy density. In this scenario, the evaluation and improvement of the mechanical and thermophysical properties of these solid-solid PCMs are key to exploiting their full potential. In this study, LiNaSO4-based composites, comprising porous MgO and expanded graphite (EG) as the dispersed phases and LiNaSO4 as the matrix, have been prepared with the aim of enhancing the thermophysical and mechanical properties of LiNaSO4. The characteristic structure of MgO and the high degree of crystallinity of the EG600 confer on the LiNaSO4 sample mechanical stability, which leads to an increase in the Young's modulus (almost three times higher) compared to the pure LiNaSO4 sample. These materials are proposed as a suitable candidate for thermal energy storage applications at high temperatures (400-550 °C). The addition of 5 wt.% of MgO or 5% of EG had a minor influence on the solid-solid phase change temperature and enthalpy; however, other thermal properties such as thermal conductivity or specific heat capacity were increased, extending the scope of PCMs use.

Systematic Collaborative Reanalysis of Genomic Data Improves Diagnostic Yield in Neurologic Rare Diseases

Many patients experiencing a rare disease remain undiagnosed even after genomic testing. Reanalysis of existing genomic data has shown to increase diagnostic yield, although there are few systematic and comprehensive reanalysis efforts that enable collaborative interpretation and future reinterpretation. The Undiagnosed Rare Disease Program of Catalonia project collated previously inconclusive good quality genomic data (panels, exomes, and genomes) and standardized phenotypic profiles from 323 families (543 individuals) with a neurologic rare disease. The data were reanalyzed systematically to identify relatedness, runs of homozygosity, consanguinity, single-nucleotide variants, insertions and deletions, and copy number variants. Data were shared and collaboratively interpreted within the consortium through a customized Genome-Phenome Analysis Platform, which also enables future data reinterpretation. Reanalysis of existing genomic data provided a diagnosis for 20.7% of the patients, including 1.8% diagnosed after the generation of additional genomic data to identify a second pathogenic heterozygous variant. Diagnostic rate was significantly higher for family-based exome/genome reanalysis compared with singleton panels. Most new diagnoses were attributable to recent gene-disease associations (50.8%), additional or improved bioinformatic analysis (19.7%), and standardized phenotyping data integrated within the Undiagnosed Rare Disease Program of Catalonia Genome-Phenome Analysis Platform functionalities (18%).

The RD-Connect Genome-Phenome Analysis Platform: Accelerating diagnosis, research, and gene discovery for rare diseases

Rare disease patients are more likely to receive a rapid molecular diagnosis nowadays thanks to the wide adoption of next generation sequencing. However, many cases remain undiagnosed even after exome or genome analysis, because the methods used missed the molecular cause in a known gene, or a novel causative gene could not be identified and/or confirmed. To address these challenges, the RD-Connect Genome-Phenome Analysis Platform (GPAP) facilitates the collation, discovery, sharing and analysis of standardised genome-phenome data within a collaborative environment. Authorised clinicians and researchers submit pseudonymised phenotypic profiles encoded using the Human Phenotype Ontology, and raw genomic data which is processed through a standardised pipeline. After an optional embargo period, the data is shared with other platform users, with the objective that similar cases in the system and queries from peers may help diagnose the case. Additionally, the platform enables bidirectional discovery of similar cases in other databases from the Matchmaker Exchange network. To facilitate genome-phenome analysis and interpretation by clinical researchers, the RD-Connect GPAP provides a powerful user-friendly interface and leverages tens of information sources. As a result, the resource has already helped diagnose hundreds of rare disease patients and discover new disease causing genes. This article is protected by copyright. All rights reserved.

Short communication: effect of storage and preservation on total bacterial counts determined by automated flow cytometry in bulk tank goat milk

This study was designed to evaluate the effects of different storage conditions on total bacterial count (TBC) determinations made in goat bulk tank milk using an automated flow cytometry method. The storage conditions tested were storage temperature (refrigeration at 4 and 10 degrees C or freezing at -20 degrees C), the use of a preservative (no preservative, NP; azidiol, AZ; or bronopol, BR), and the age of the milk samples for each analytical condition (storage times at 4 degrees C: from 0 h to 5 d for NP; and from 0 h to 22 d for AZ and BR; storage times at 10 degrees C: from 24 h to 2 d for NP and from 24 h to 22 for AZ and BR; storage times at -20 degrees C: from 24 h to 22 d for NP, AZ, and BR). Significant effects on individual bacterial count (IBC) variation were shown by the bulk tank milk sample, preservative, storage temperature, interaction preservative x storage temperature, and milk age within the interaction preservative x storage temperature. In preserved samples, the highest IBC were obtained for AZ and the lowest counts were obtained in samples preserved with BR. Because of the variation in IBC recorded in BR-preserved samples, we recommend that BR should not be used for TBC determinations using the automated flow cytometry method. The NP samples stored at 4 and 10 degrees C showed significantly higher IBC at 24 h postcollection, also invalidating these analytical conditions for TBC analyses. The practical implications of our findings are that goat milk samples preserved with AZ and stored at 10 or 4 degrees C are appropriate for TBC by the BactoScan flow cytometry method for up to 24 h and 11 d postcollection, respectively.

Detection limits of four antimicrobial residue screening tests for beta-lactams in goat's milk

This study was conducted to compare the detection limits (DL) of several antibiotic residue screening tests with the maximum residue limits (MRL) authorized by the EU according to the guidance for the standardized evaluation of microbial inhibitor tests of the International Dairy Federation. Composite antibiotic-free milk samples from 30 primiparous Murciano-Granadina goats in good health condition were used to prepare test samples spiked with different concentrations of each antimicrobial. In total, 5,760 analytical determinations of 10 beta-lactam antibiotics (penicillin-G, ampicillin, amoxicillin, cloxacillin, oxacillin, dicloxacillin, cefadroxyl, cefalexin, cefoperazone, and cefuroxime) were performed using 4 antibiotic residue screening tests: the brilliant black reduction test BRT AiM (AiM-Analytik in Milch Produktions-und Vertriebs GmbH, München, Germany), Delvotest MCS (DSM Food Specialties, Delft, the Netherlands), Eclipse 100 (ZEU-Inmunotec SL, Zaragoza, Spain), and the Copan Milk Test (CMT; Copan Italia SpA, Brescia, Italy). For each method, we estimated the detection limits of the antimicrobial agents using a logistic regression model. Using the CMT and Delvotest on samples spiked with the 8 antibiotics for which MRL were available, DL were at or below the MRL. The BRT test provided DL at or below the MRL for all of the agents except cefalexin, whereas the Eclipse 100 method failed to detect 4 antibiotics (ampicillin, amoxicillin, cloxacillin, and cefoperazone) at MRL or below. Logistic regression-determined levels of agreement were highest for the CMT method (98.6 to 100%) and lowest for Eclipse 100 (66.3 to 100%). In general, agreement levels indicated good correlation between observed results and those predicted by logistic regression. The lowest b values (closely related to test sensitivity) were recorded for the cephalosporins (0.074 to 0.430) and highest for penicillin G, ampicillin, and amoxicillin (11.270 to 11.504). Delvotest and CMT best fulfilled IDF criteria for the ideal test for detecting antibiotic residues in milk.

Evaluation of the MilkoScan FT 6000 Milk Analyzer for Determining the Freezing Point of Goat's Milk Under Different Analytical Conditions

The aim of this research was to evaluate the Milko-Scan FT 6000 (Foss Electric, Hillerød, Denmark) for determining the freezing point (FP) of goat's milk under different analytical conditions. The FP was determined in duplicate in 1,800 milk aliquots obtained from 45 bulk tank milk samples from 10 Murciano-Granadina goat herds, using the MilkoScan method and a reference thermistor cryoscopy method (Advanced Instrument Inc., Norwood, MA). Five different preservation strategies--no preservative, preservation with azidiol (0.006 or 0.018 g of sodium azide/100 mL), and preservation with bronopol (0.020 or 0.040 g/100 mL)--were then used to preserve the milk. For each preservation strategy, 8 different amounts of water were added (0, 1, 2, 3, 4, 5, 6, or 7% total volume). The results obtained with each method under these 40 analytical conditions were examined by comparison of means, comparison of the standard deviations of repeatability (s(r) and its relative value s(r)%), and a regression analysis. Under most analytical conditions, the FP was recorded as lower by the MilkoScan method, with a mean difference of 1.5 m degrees C compared with the reference method. Both methods showed similar repeatabilities (the overall s(r)% was 0.22% for the MilkoScan method and 0.20% for the reference method). In comparisons of the 2 methods, the highest regression coefficients were obtained with aliquots containing >3% added water. The best regression coefficients (0.85 to 1.02) were obtained for milk samples preserved with bronopol at 0.020 g/100 mL. These results allow the MilkoScan method to be used with goat's milk for screening purposes. The factors of added water, preservative, analytical method, lactose concentration, and the effect of the bulk tank milk sample within each lactose group contributed significantly to the observed variation in FP. For practical purposes, either of the bronopol concentrations could be used when determining the FP of goat's milk with the methods tested. However, the increase in the concentration of sodium azide in the azidiol formula contributed to an important reduction in the FP recorded. Thus, the type and concentration of preservative should be taken into account when interpreting FP values.

Influence of Storage and Preservation on Fossomatic Cell Count and Composition of Goat Milk

This study was designed to evaluate the effects of different test conditions on the somatic cell count (SCC) and composition of goat milk. To this end, 3600 tests were performed on 1800 aliquots taken from 40 goat milk samples using a combined instrument set-up based on flow cytometry for SCC and Fourier transform infrared analysis for fat, total protein, lactose, total solids, and freezing point determinations. The conditions tested were storage temperature (refrigeration and freezing), use of a preservative [no preservative (NP), azidiol (AZ), and bronopol (BR)], and age of the milk samples at each storage temperature (24 h to 42 d at refrigeration temperature and 21 to 105 d at freezing temperature). Significant effects on logSCC variation were shown by the storage temperature, the preservation treatment, the interaction of storage temperature x preservation treatment, and milk age within the interaction of storage temperature x preservative. Highest counts were recorded in the BR-preserved milk samples (logSCC = 5.877), and lowest counts were recorded in milk samples preserved using AZ (logSCC = 5.803). The use of frozen/thawed samples led to a significantly decreased logSCC for the treatments AZ and NP; the logSCC was not modified when BR-preserved frozen/thawed samples were analyzed. During storage, variations in the SCC observed for BR-preserved samples stored at refrigeration temperature for up to 25 d and at freezing temperature for all times tested were always < 10%. The preservation treatment was the main factor affecting the milk composition variables examined. Highest values of most variables were obtained in the BR-preserved samples, and the lowest values were obtained in the AZ-preserved samples. The freezing point was lower in the preserved samples than in the NP samples. The levels of milk constituents recorded in the BR-preserved samples were independent of both the storage temperature and age of milk sample. Our findings indicate that the freezing point of goat milk must be interpreted according to the preservative used.

Effect of Clinical Contagious Agalactia on the Bulk Tank Milk Somatic Cell Count in Murciano-Granadina Goat Herds

From 19 herds of Murciano-Granadina goats, weekly bulk tank somatic cell count (BTSCC) were performed from October to April, and suspicious milk (n = 182), synovial fluid, and ocular swabs (n = 15) from diseased goats were processed for mycoplasma isolation and identification. Also BTSCC from 65 herds were determined (n = 2693). A mixed model procedure was used to establish the effect of the herd and the lactation month on the BTSCC. Monthly rolling values were calculated for each herd using data collected over the preceding 3 complete months, and 4 different BTSCC thresholds were considered: 1,750,000, 1,500,000, 1,000,000, and 750,000 cells/mL. The mean log BTSCC for the 7-mo study period was 5.89 +/- 0.28 for herds without mycoplasma detection from clinical cases, 5.91 +/- 0.31 for mycoplasma-infected herds without clinical contagious agalactia (CA), and 6.47 +/- 0.32 for the herd with clinical CA. The posthoc tests revealed that only the herd that suffered a clinical CA outbreak showed counts that were significantly higher. No significant differences were found for BTSCC between herds not showing clinical episodes of CA, regardless of whether the mycoplasma had been isolated or not. The 1,750,000-cells/mL threshold would only be surpassed by a few herds with serious mastitis problems (clinical outbreak of CA for example). Seventy percent of the goat herds studied were in compliance with the proposed European Union legal limit of 1,500,000 cells/mL for goat milk.

Effect of freezing goat milk samples on recovery of intramammary bacterial pathogens

With the aim of evaluating the effect of freezing goat milk samples on recovery of intramammary pathogens, 1200 milk samples from udder halves with subclinical intramammary infection were studied. Samples (20 ml) were frozen at -20 and at -80 degrees C. Thawing was carried out at room temperature at 7, 14, 21, 28, 58, 118, 178, 236 and 730 days after collection and bacteriological analyses were carried out to determine the number of colony forming units/ml (CFU/ml). Mixed model statistical analysis showed that bacterial group, temperature of storage, interaction of bacterial group and temperature of storage and the interaction of bacterial group, time and temperature of storage were statistically significant effects. For coagulase negative staphylococci (CNS), least squares means of log CFU/ml recovered at -20 and -80 degrees C were not different. Nevertheless, for Gram negative bacilli (GNB) a significant decrease was detected in samples frozen at -20 vs. -80 degrees C. At both temperatures and at different times of storage, significant increases were detected between log CFU/ml of CNS and values on day zero. At -20 degrees C, a significant decrease in GNB recovery was detected between freezing days zero and 730. This difference was not detected when goat milk samples infected by GNB were frozen at -80 degrees C. The results show that frozen milk samples can be useful in goat subclinical mastitis control programs.

Daily delivery of dietary nitrogen to the periphery is stable in rats adapted to increased protein intake

Dietary nitrogen was traced in rats adapted to a 50% protein diet and given a meal containing 1.50 g (15)N-labeled protein (HP-50 group). This group was compared with rats usually consuming a 14% protein diet and fed a meal containing either 0.42 g (AP-14 group) or 1.50 g (AP-50 group) of (15)N-labeled protein. In the HP group, the muscle nonprotein nitrogen pool was doubled when compared with the AP group. The main adaptation was the enhancement of dietary nitrogen transferred to urea (2.2 +/- 0.5 vs. 1.3 +/- 0.1 mmol N/100 g body wt in the HP-50 and AP-50 groups, respectively). All amino acids reaching the periphery except arginine and the branched-chain amino acids were depressed. Consequently, dietary nitrogen incorporation into muscle protein was paradoxically reduced in the HP-50 group, whereas more dietary nitrogen was accumulated in the free nitrogen pool. These results underline the important role played by splanchnic catabolism in adaptation to a high-protein diet, in contrast to muscle tissue. Digestive kinetics and splanchnic anabolism participate to a lesser extent in the regulation processes.

Postprandial modulation of dietary and whole-body nitrogen utilization by carbohydrates in humans

BACKGROUND

Sucrose exerts a sparing effect on whole-body protein metabolism, mainly during the absorptive phase.

OBJECTIVE

We aimed to characterize the acute postprandial effect of addition of sucrose on deamination of dietary and endogenous nitrogen, with particular consideration being given to the effects of bioavailability.

DESIGN

Twenty-one subjects equipped with ileal tubes ingested (15)N-labeled soy protein combined with [(13)C]glycine, with (n = 10) or without (n = 11) sucrose. Dietary and endogenous ileal flow of nitrogen were determined from the ileal effluents. The kinetics of dietary amino acid transfer to the blood were characterized by (13)CO(2) enrichment in breath and (15)N enrichment in plasma amino acids. Deamination of dietary and endogenous amino acid was determined from body urea, urinary nitrogen, and (15)N enrichment.

RESULTS

(13)CO(2) recovery in breath and (15)N plasma amino acid enrichments were highly correlated (R:(2) >/= 0.95, P: < 0.001, for both meals) and markedly delayed by sucrose (half-(13)CO(2) recovery: 274 min compared with 167 min), whereas exogenous and endogenous ileal nitrogen kinetics and balances remained unchanged. Addition of sucrose halved the early (0-2 h) deamination peak of dietary nitrogen and reduced endogenous nitrogen oxidation over the first 4 h. Both were reduced by 18-24% over the 8-h period after the meal.

CONCLUSIONS

Without changing the nitrogen absorptive balance, sucrose markedly affected the bioavailability profile, which is governed by gastric emptying. Endogenous and dietary nitrogen were not spared in the same way and over the same periods, showing that the metabolism of endogenous and dietary nitrogen may be affected differently by nutritional modulation, even if the effects are of a similar magnitude over the entire postprandial period.

Nutritional value of [15N]-soy protein isolate assessed from ileal digestibility and postprandial protein utilization in humans

The purpose of this work was to assess the true oro-ileal digestibility, and to concurrently quantify the deamination of absorbed dietary nitrogen to examine the postprandial nutritional value of a soy protein isolate (SPI) in humans. To assess bioavailability and bioutilization of SPI, 10 healthy volunteers ingested 30 g of SPI, intrinsically and uniformly [15N]-labeled, added with 100 g of sucrose and water up to a final volume of 500 mL. True ileal digestibility was assessed by the [15N]-dilution method for 8 h by means of a naso-intestinal intubation technique. To describe and quantify exogenous nitrogen deamination for the same time period, urine and plasma samples were collected. True oro-ileal digestibility of SPI nitrogen was 91%. The amount of absorbed SPI amino acids used for nonoxidative disposal, i.e., postprandial biological value, was 86% 8 h after meal ingestion. Hence, net postprandial protein utilization of SPI was 78%. Compared to previous data that were assessed under the same condition in humans, the nutritional value of SPI is 92% of that in milk protein concentrate.

Net postprandial utilization of [15N]-labeled milk protein nitrogen is influenced by diet composition in humans

The aim of this study was to follow the fate of dietary nitrogen to assess the postprandial utilization of purified milk protein and to determine the acute influence of energy nutrients. For this purpose, a [15N]-labeling dietary protein approach was used. Twenty-five subjects swallowed an ileal tube and ingested [15 N]-milk protein alone or supplemented with either milk fat or sucrose. The absorption and postprandial deamination of dietary protein was monitored for 8 h. Sucrose delayed the absorption of protein longer than fat, but the ileal digestibility did not differ among groups (94.5-94.8%). Sucrose, but not fat, significantly reduced the postprandial transfer of [15N]-milk nitrogen to urea. Consequently, the net postprandial protein utilization (NPPU) of milk protein calculated 8 h after meal ingestion was 80% when ingested either alone or supplemented with fat and was significantly greater with sucrose (NPPU = 85%). This study shows that energy nutrients do not affect the nitrogen absorption but modify the metabolic utilization of dietary protein in the phase of nitrogen gain. Our method provides information concerning the deamination kinetics of dietary amino acids and further allows the detection of differences of dietary protein utilization in acute conditions. The diet composition should be carefully considered, and protein quality must be determined under optimal conditions of utilization.

Assessment of net postprandial protein utilization of 15N-labelled milk nitrogen in human subjects

The nutritional quality of milk proteins, evaluated both in terms of digestibility and postprandial oxidation and retention in human subjects, was investigated in this study. Five healthy adult volunteers were given 480 ml 15N-labelled milk (i.e. 190 mmol N). 15N was subsequently determined at the ileal level, using a naso-intestinal intubation technique, as well as at the faecal level. Plasma and urine were sampled for 8 h after meal ingestion. Dietary exogenous N recovered at the terminal ileum after 8 h reached 8.6 (SE 0.8) mmol while the amount collected in the faeces was 6.5 (SE 0.7) mmol after 5 d. The true ileal and faecal digestibilities were 95.5 (SE 0.4)% and 96.6 (SE 0.4)% respectively. The appearance of [15N]amino acids in the plasma was rapid and prolonged. The measurement of 15N in the body urea pool and in the N excreted in the urine allowed us to calculate the deamination occurring after [15N]milk protein absorption. The net postprandial protein utilization (i.e. NPPU = (Nabsorbed-Ndeaminated)/Ningested), calculated as an index of protein quality 8 h after milk ingestion, was 81.0 (SE 1.9)%. Our data confirm that milk protein has a high oro-ileal digestibility in man and demonstrate that milk protein has a high NPPU, an index corresponding to a period in which the dietary protein retention is maximal.

[15N]-labeled pea flour protein nitrogen exhibits good ileal digestibility and postprandial retention in humans

The aim of the present study was to evaluate postprandial absorption of pea protein as well as exogenous nitrogen retention in humans. For this purpose, after fasting overnight, seven healthy adults (4 males and 3 females) ingested [15N]-labeled pea protein (195 mmol N). Ileal effluents were collected for 8 h at 30-min intervals using a nasointestinal intubation technique. Urine and plasma samples were collected for 24 h. The [15N]-enrichment was determined in the intestinal samples, in the plasma amino acids and urea as well as in the urinary urea and ammonia fractions. The true gastroileal absorption of pea protein was 89.4 +/- 1.1%. This absorption was correlated with a significant increase (P < 0.05) in [15N]-enrichment in the plasma amino acids and in the nitrogen incorporated into the body urea pool for 1 h following pea ingestion. The enrichment remained significantly higher than the basal values in these pools 24 h after pea ingestion. The recovery of total urinary exogenous nitrogen after 22 h was 31.1 +/- 9.3 mmol N. Moreover, the kinetics of [15N]-labeled pea amino acids deamination reached a plateau of 39 mmol. Under these conditions, pea nitrogen retention represented 78% of the absorbed dietary nitrogen in healthy humans. The present results demonstrate the good true nitrogen digestibility and retention of pea protein in humans.

Whole-body protein turnover in humans fed a soy protein-rich vegetable diet

OBJECTIVES

This study was designed to compare the whole-body protein turnover in humans after the ingestion of a soy protein-rich vegetable diet with that of a control group fed a western animal protein-rich diet.

SUBJECTS

Twelve male volunteers were divided into two groups of six subjects who were given for two weeks either a 85% vegetable protein diet (diet VP) or a control western animal protein-rich diet (diet AP).

INTERVENTIONS

Whole-body protein turnover was estimated at the end of the two-week controlled diet period using the [15N]-glycine end-product method. Nitrogen flux rates were determined in the fed state (1.3 g protein/kg) over a 9 h period after the dose of [15N]-glycine was given.

RESULTS

After the 9 h of the test, the urinary ammonia excretion was significantly higher in the group receiving the diet AP than that in the group receiving the diet VP (P < 0.05). In contrast, there was no significant difference for both total nitrogen and urea nitrogen excretions. Both the protein synthesis and the protein breakdown were similar in both groups. In the same way, the net protein deposition measured in the fed state during 9 h was similar for both diets at 0.07 g/kg/h.

CONCLUSIONS

Young adults fed 1.3 g/kg/d of either meat or vegetable protein-rich diet for two weeks did not show a different protein turnover.

Fasting and postprandial polyamine concentrations in the human digestive lumen

Polyamines are essential to cellular proliferation and differentiation. The gastrointestinal tract could represent a major source of polyamines in the body; however, there is little information regarding the presence of polyamines in the human intestinal chyme, and the source of these intraluminal polyamines remains unclear. The aims of our study were to determine the concentrations and flow rates of polyamines in the human intestinal lumen and to estimate the contribution from food to these concentrations. Polyamine concentrations and flow rates were determined after 12 h of fasting in jejunal (n = 25) and ileal (n = 9) effluents collected by the slow-marker perfusion technique. Kinetic studies were performed after water ingestion (no polyamines) in the jejunum (n = 6) and ileum (n = 5) and in the jejunum after a yogurt test meal (polyamine content: 2.8 mumol putrescine, 2.1 mumol cadaverine, 2.1 mumol spermidine, and 1.9 mumol spermine; n = 9). There were significant polyamine concentrations in the lumen of the human gut during the fasting state, suggesting endogenous secretion. Higher polyamine concentrations were observed in the jejunum than in the ileum (P < 0.05), suggesting proximal absorption. Kinetic studies showed a 25% transitory increase in the jejunal putrescine flow rate after ingestion of the yogurt test meal, suggesting that dietary polyamines are fully absorbed.

The gastro-ileal digestion of 15N-labelled pea nitrogen in adult humans

The aim of the present study was to determine the gastro-ileal behaviour of pea protein in humans. For this purpose, twelve healthy volunteers were intubated with an intestinal tube located either in the jejunum (n 5) or in the ileum (n 7). After fasting overnight, they ingested 195 mmol N of [15N]pea. Intestinal samples were collected for 6 h in the jejunum and for 8 h in the ileum. Before meal ingestion the basal liquid flow rate (ml/min) was 2.01 (SD 0.31) in the jejunum and 2.02 (SD 0.33) in the ileum. After meal ingestion the liquid phase of the meal peaked in the 40-60 min period in the jejunum and in the 150-180 min period in the ileum. The jejuno-ileal transit time of the liquid phase of the meal was 102 min. The basal flow rate of endogenous N (mmol N/min) was 0.22 (SD 0.15) in the jejunum and 0.16 (SD 0.10) in the ileum. The endogenous N flow rate peaked significantly (P < 0.05) in the jejunum in the 40-60 min period whereas no stimulation of endogenous N could be detected in the ileum after meal ingestion. A significantly increased (P < 0.05) concentration of exogenous N was detected in the jejunum during the 20-320 min period and during the 90-480 min period in the ileum. The overall true gastro-ileal absorption of pea N was 89.4 (SD 1.1)% with 69 (SD 14)% absorbed between the stomach and the proximal jejunum and 20.4% between the proximal jejunum and the terminal ileum. The percentage of ethanol-insoluble fraction (PN) in the exogenous N at the terminal ileum increased significantly (P < 0.05) to 75% after 360 min. These results suggest that heat-treated pea protein has a digestibility close to that of animal protein.

A 15N-leucine-dilution method to measure endogenous contribution to luminal nitrogen in the human upper jejunum

OBJECTIVE

This study was done to investigate whether an intraveinous infusion of 15N-leucine was accurate to differentiate between endogenous and exogenous nitrogen in the human jejunum after meal ingestion.

SUBJECTS

Four healthy human volunteers equipped with an upper jejunal tube.

INTERVENTIONS

The jejunal effluents were collected both under fasting conditions and after ingestion of 300g of yoghurt. The nitrogen, amino acid composition and 15N-leucine enrichment were determined in the digesta.

RESULTS

During fasting, the jejunal flow rates (mmol/h) of both total nitrogen and amino acids were stable (6.9 +/- 2.7 and 1.88 +/- 0.79, respectively). After yoghurt ingestion, the flow rate of total nitrogen increased to 28.6 +/- 5.8mmol/h at 2h. The 15N-leucine enrichment in plasma reached a plateau at 4.3 mole % excess after one hour and did not vary significantly after meal ingestion. The 15N-leucine enrichment of the endogenous secretion (Ee) in the jejunum was fitted by the equation: Ee = 2.18[1 - 2.05 x exp( - 0.42 x t)]. After yoghurt ingestion, the enrichment in jejunal secretions decreased during the first 80 min. The endogenous nitrogen, calculated from the 15N-enrichment, significantly increased from 20 to 40min after meal ingestion compared to the basal value (P < 0.05). The estimation of the exogenous nitrogen and amino acid yield 300min after yoghurt ingestion indicated that 62 +/- 30% of the exogenous nitrogen and 75 +/- 12% of the amino acids were absorbed in the upper jejunum.

CONCLUSIONS

The 15N-leucine-dilution method appears to be a convenient method to differentiate between the exogenous and endogenous contributions to nitrogen fluxes in the intestinal digesta of humans. It can be used in association with dietary protein labelling or in substitution when no labelled dietary proteins are available to compare the digestion as well as the absorption of meals at different levels of the intestine.

Gastrojejunal kinetics and the digestion of [15N]beta-lactoglobulin and casein in humans: the influence of the nature and quantity of the protein

The evolution and luminal effects of different quantities of casein and beta-lactoglobulin were investigated in the upper jejunum of 35 volunteers who ingested 400 mL water with either beta-lactoglobulin or casein in either low or high doses (72.6 mmol N, Lbetalg; 71.7 mmol N, LCas; 368.2 mmol N, Hbetalg; 386.8 mmol N, HCas). The flow rate of the liquid effluents as well as the nitrogen movements were measured and the exogenous ([15N]) and endogenous nitrogen fractions analyzed in the upper jejunum after milk protein ingestion. The basal jejunal liquid flow rate (mL/min) was 3.88+/-1.84 and peaked in the 0-20 min period for water (9.92+/-3.72) and Lbetalg (7.27+/-3.08) and during the 20-40 min period for LCas (5.69+/-2.49), HCas (6.32+/-1.85), and Hbetalg (6.11+/-2.31). One hour after water, LCas, Lbetalg, Hbetalg, and HCas ingestion, 100%, 95%, 85%, 71%, but only 38% of the liquid phase of the meal were passed through the jejunum, respectively. The flow rate of the endogenous nitrogen was 12.93+/-5.22 mmol N/h before meal ingestion; remained unchanged after water, LCas or Hbetalg ingestion; but increased significantly (P<0.05) after Lbetalg and HCas ingestion. The net disappearance of exogenous nitrogen in the upper jejunum 240 min after HCas, Lbetalg, LCas and Hbetalg ingestion was 82.6+/-9.5%, 61.6+/-9.6%, 58.4+/-14.7%, and 44.7%+/-24.4%, respectively. The exogenous fraction of protein nitrogen recovered in the upper intestinal lumen represented 43.3% of the ingested Hbetalg nitrogen, but only 4.9% of the ingested HCas nitrogen. In conclusion, casein and beta-lactoglobulin present differences in both the intestinal kinetics of amino acid delivery and in the nature of the products in the intestinal lumen. These differences have to be taken into account from both nutritional and physiologic points of view for the utilization of these proteins in humans.

Exogenous and endogenous nitrogen flow rates and level of protein hydrolysis in the human jejunum after [15N]milk and [15N]yoghurt ingestion

Milk and yoghurt proteins were 15N-labelled in order to measure the flow rate of exogenous N during digestion in the human intestine. After fasting overnight, sixteen healthy volunteers, each with a naso-jejunal tube, ingested either [15N]milk (n 7) or [15N]yoghurt (n 9). Jejunal samples were collected every 20 min for 4 h. A significant stimulation of endogenous N secretion was observed during the 20-60 min period after yoghurt ingestion and the 20-40 min period after milk ingestion. The endogenous N flows over a 4 h period did not differ between the groups (44.3(SEM 6.5) mmol for milk and 63.5(SEM 5.9) mmol for yoghurt). The flow rates of exogenous N indicated a delayed gastric emptying of the yoghurt N compared with N from milk. The jejunal non-protein N (NPN) flow rate increased significantly after milk and yoghurt ingestion due to an increase in the exogenous NPN flow rate. The NPN fraction of exogenous N ranged between 40 and 80%. The net gastro-jejunal absorption of exogenous N did not differ significantly between milk (56.7(SEM 8.5)%) and yoghurt (50.9(SEM 7)%). The high level of exogenous N hydrolysis is in accordance with the good digestibility of milk products. Fermentation modifies only the gastric emptying rate of N and does not affect the level of diet hydrolysis, the endogenous N stimulation or the digestibility rate.

Metabolism of enterostatin in rat intestine, brain membranes, and serum: differential involvement of proline-specific peptidases

The degradation of enterostatin (VPDPR), a potent inhibitor of food intake, by intestinal brush-border membranes, brain membranes, and rat serum has been investigated in the presence of specific inhibitors. Hydrolysis by intestinal membranes was found to be 10 and 100 times faster than in serum and brain membranes, respectively. Enterostatin hydrolysis by intestinal and brain membranes involves the removal of C-terminal arginine by carboxypeptidase P, leading to the production of des-Arg-enterostatin, and the splitting of the Pro2-Asp3 bond by dipeptidyl aminopeptidase IV (DPP IV). A small amount of the potent anorectic peptide Pro2-Asp3-Pro4 was released during hydrolysis of des-Arg-enterostatin by brain membranes and rat serum. In rat serum, enterostatin degradation was mainly due to DPP IV.

[Premedication with clonidine in the neurosurgical patient: sedation, anesthetic requirements and hemodynamic perfusion]

OBJECTIVES

To analyze the effect of premedication with clonidine on postoperative sedation, anesthetic requirements and hemodynamic repercussions in patients undergoing craniotomy due to supratentorial intracranial pathology.

PATIENTS AND METHODS

Twenty ASA I/II patients in a double-blind prospective study were assigned randomly to receive lorazepam (0.03 mg/kg/po, n = 10) or clonidine (0.005 mg/kg/po, n = 10) the night before and 90 minutes before surgery. Arterial pressure and heart rate were monitored continuously during and immediately after surgery (first 24 hours). Anesthetic induction was achieved with thiopental (maximum 6 mg/kg) and maintained with O2/N2O and an infusion of alfentanyl (1 microgram/kg/min). Hemodynamic response to surgical stimulus was treated with additional boluses of alfentanyl up to a maximum dose of 0.1 mg/kg and with an increase in infusion dosage to 2 micrograms/kg/min. When these were ineffective, isoflurane was given. All patients were extubated in the operating room.

RESULTS

No differences in level of sedation were found between the two groups. The infusion dose and total amount of alfentanyl given were smaller for patients treated with clonidine (0.8 +/- 0.04 vs 0.6 +/- 0.01 microgram/kg/min and 22.4 +/- 5.3 vs 17.5 +/- 4.9 mg, respectively) (p < 0.05). No differences were found in isoflurane requirements (5/5 vs 2/8). Mean arterial pressure and heart rate were lower with clonidine from 3 minutes after intubation until the patient's arrival in the recovery room (p < 0.05), with marked bradycardia (49 +/- 5 vs 73 +/- 7 bpm) (p < 0.05) upon intubation.

CONCLUSIONS

Premedication of neurosurgical patients with clonidine offers no advantages over lorazepam with respect to sedation. Nevertheless, clonidine may offer advantages with respect to the amount of alfentanyl required and attenuation of perioperative adrenergic response.

Cardiomyopathy and phaeochromocytoma

A case is presented of phaeochromocytoma with catecholamine-induced cardiomyopathy. The difficulties in the management when left ventricular failure occurred are reported and the importance of monitoring pulmonary artery pressure during the anaesthetic procedure is stressed.

Acute pulmonary oedema due to lithium intoxication

We present a case of acute lithium ion intoxication in which the main clinical feature was respiratory failure secondary to pulmonary oedema possibly due to myocardial depression, associated with profound stupor. The initial lithium ion concentrations were 3.15 mmol/l in plasma and 27.6 mmol/l in urine. Under symptomatic treatment with oxygen, digitalis and diuretics, both the pulmonary and the neurological disorders reverted gradually, in parallel with the decreasing plasma lithium ion concentrations.