All Amino Acids Research Articles

Effects of partially replacing fishmeal with corn gluten meal on growth, feed utilization, digestive enzyme activity, and apparent nutrient digestibility for juvenile white shrimp, Litopenaeus vannamei.

This experiment was conducted to assess the possibility of replacing fishmeal (FM, Fishmeal content of the control group: 30%) with corn gluten meal (CGM) at the following levels: 0, 10, 20, 30, 40, and 60%. The experimental diets, formulated to be isonitrogenous and isocaloric, were studied for their effects on growth, feed utilization, digestive enzyme activity and apparent nutrient digestibility in juvenile white shrimps, Litopenaeus vannamei (initial mean weight = 0.71 ± 0.01 g). Seven hundred twenty healthy and uniformed-size shrimp were distributed to six groups of three replicates, each with 40 shrimp in each tank (0.5 m3). Each experimental diet was fed to shrimp four times daily to apparent satiation at 7:00, 11:30, 17:00, and 21:30, respectively, for 8 weeks. At the end of the experiment, the total weight of fish in each tank was weighed and randomly selected for testing, including fish nutrient composition and digestive enzyme activity. Results showed that no significant differences were observed in the weight gain rate (WGR), feed coefficient rate (FCR) and specific growth rate (SGR) of shrimp after 30% FM was replaced with CGM (P > 0.05), but these indicators significantly decreased at higher replacement rates. As CGM content increased, the content of crude protein and phosphorus in the shrimp decreased significantly (P < 0.05), whereas the crude fat content first increased significantly and then decreased (P < 0.05). Compared to the control group, the protease activity was significantly lower in the 40% group and the lipase activity was significantly lower in the 60% group (P < 0.05). Amylase activity was significantly increased with increasing CGM levels (P < 0.05). The digestibility of protein and lipid was significantly reduced by CGM replacement of more than 30% FM (P < 0.05). As CGM content increased, the digestion of energy and dry matter was first significantly increased and then significantly decreased (P < 0.05). In the 30, 40, and 60% groups, the digestibility of all amino acids (AA), except methionine (Met), arginine (Arg) and serine (Ser), was significantly lower than in the control group (P < 0.05). In summary, FM could be partially replaced by CGM in the feed of L. vannamei. Based on the broken-line regression analysis of WGR, the optimal dietary CGM replacement was 27.47%.

212 Conditioning and Expansion Increases Nutritional Value of Soybean Expellers

Abstract Two experiments were conducted to test the hypothesis that different combinations of conditioning and expansion of soybean expellers increases nutritional value. Non-heat-treated soybean expellers (L-1) and soybean expellers conditioned for 60 s at 90ºC followed by expansion at 110ºC (L-2) were used. Two additional sources of soybean expellers (L-3 and L-4) were processed as L-2 with the exception that the initial conditioning was followed by long-term conditioning for 12 or 48 min at 100ºC before expansion. Analyzed trypsin inhibitor activity in L-1, L-2, L-3, and L-4 was 34.0, 23.1, 4.2, and 2.4 mg/g, respectively. In experiment 1, 10 cannulated barrows (54.22 ± 4.54 kg) were allotted to a replicated 5 × 4 Youden square with 5 diets and 4 periods and 8 replicates per diet. Each source of soybean expellers was included in one diet, and a N-free diet was also used. Data were analyzed by ANOVA using the Mixed Procedure of SAS. The standardized ileal digestibility (SID) of all amino acids (AA) in L-1 was less (P &amp;lt; 0.01) compared with L-2, L-3, and L-4 (Table 1), and SID of all AA in L-2 was less (P &amp;lt; 0.01) than in L-3 or L-4. In experiment 2, 40 barrows (17.52 ± 1.63 kg) were housed in metabolism crates and fed a corn diet or 4 diets based on corn and each source of soybean expellers. Feces and urine were collected using the marker-to-marker approach with 5-d adaptation and 4-d collection periods. Data were analyzed as in Exp. 1. The metabolizable energy (ME) in L-1 was less (P &amp;lt; 0.01) than in L-2, L-3, and L-4 (Table 1). In conclusion, the SID of AA in soybean expellers was maximized if 12 or 48 min of conditioning at 100ºC was used before expansion, but long-term conditioning did not increase ME.

Nutritive values of double-low rapeseed expellers and rapeseed meal with or without supplementation of multi-enzyme in pigs

Two experiments were conducted to evaluate the effects of adding multi-enzyme on the available energy concentration and standardized ileal digestibility (SID) of amino acids of double-low rapeseed expellers (RSE) and rapeseed meal (RSM) fed to growing pigs. In Experiment 1, a total of 36 growing barrows were fed six diets in a replicated 3 × 2 factorial design. Diets included a corn–soybean meal basal diet, RSE diet, and RSM diet with or without multi-enzyme (1000 U g−1 of cellulase, 10 000 U g−1 of xylanase, 2000 U g−1 of glucanase, and 10 000 U g−1 of protease). In Experiment 2, a total of 30 crossbred pigs were randomly allotted to five diets consisting of a nitrogen-free diet and four cornstarch-based diets containing RSE or RSM with or without multi-enzyme. Multi-enzyme supplementation significantly improved (P &lt; 0.05) the metabolizable energy (ME) value and apparent total tract digestibility (ATTD) of ether extract, neutral detergent fiber, and acid detergent fiber, and it tended to increase (P &lt; 0.10) the ATTD of gross energy and digestible energy in ingredients. With the exception of phenylalanine, multi-enzyme supplementation increased (P &lt; 0.05) the SID of crude protein (CP) and all amino acids (AA) in ingredients. Multi-enzyme supplementation enhanced fiber degradation and increased the ME value and SID of CP as well as most AA in double-low rapeseed co-products fed to pigs.

Effects of a combination of xylanase, amylase and protease, and probiotics on major nutrients including amino acids and non-starch polysaccharides utilization in broilers fed different level of fibers

This study evaluated the effects of a combination of xylanase, amylase, and protease (XAP), with probiotics (3 Bacillus spp.) supplementation on apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients in Cobb 500 broilers from 0 to 21 d. A completely randomized 2 × 4 factorial design (2 levels of fiber; 4 types of supplements) with 8 replicate cages (6 birds/cage) was used. Each low and high-fiber diet contained 500 FTU/kg Buttiauxella sp. phytase and was supplemented with: (a) none (control), (b) XAP (2,000 U xylanase + 200 U amylase + 4,000 U protease/kg diet), (c) probiotics (75,000 CFU/g of Bacillus spp.), or (d) XAP + probiotics. High fiber decreased (P < 0.05) nitrogen-corrected apparent metabolizable energy (AMEn), AID of all amino acids (AA), AID and ATTD of dry matter (DM), crude protein (CP), starch, and gross energy (GE). High fiber increased (P < 0.01) the flow of total non-starch polysaccharides (NSP) in both ileum and total tract. The XAP + probiotics increased (P < 0.01) AMEn as well as AID and ATTD of DM, CP, GE, starch, while alone, XAP yielded similar improvement except for DM compared with control. The supplemental XAP alone improved (P < 0.01) the digestibility of most of the AAs compared with control. Moreover, XAP + probiotics increased (P < 0.05) AID of all AA except arginine and serine compared with control. A fiber × supplements interaction (P < 0.05) was found for AID of histidine and threonine, and their digestibility in high-fiber diet was improved to a level comparable to low-fiber diet by XAP + probiotics. The flow of NSP in XAP group was 5 to 6% lower than in control while NSP flow in XAP + probiotic group was further 4% lower than that of XAP group (P < 0.01). The results infer that the combination of XAP and probiotics can effectively optimize the nutrient digestibility in broilers fed both low and high-fiber diets.

Low-protein diets supplemented with casein hydrolysate favor the microbiota and enhance the mucosal humoral immunity in the colon of pigs

BackgroundHigh-protein diets can increase the colonic health risks. A moderate reduction of dietary crude-protein (CP) level can improve the colonic bacterial community and mucosal immunity of pigs. However, greatly reducing the dietary CP level, even supplemented with all amino acids (AAs), detrimentally affects the colonic health, which may be due to the lack of protein-derived peptides. Therefore, this study evaluated the effects of supplementation of casein hydrolysate (peptide source) in low-protein (LP) diets, in comparison with AAs supplementation, on the colonic microbiota, microbial metabolites and mucosal immunity in pigs, aiming to determine whether a supplementation of casein hydrolysate can improve colonic health under very LP level. Twenty-one pigs (initial BW 19.90 ± 1.00 kg, 63 ± 1 days of age) were assigned to three groups and fed with control diet (16% CP), LP diets (13% CP) supplemented with free AAs (LPA) or casein hydrolysate (LPC) for 4 weeks.ResultsCompared with control diet, LPA and LPC diet decreased the relative abundance of Streptococcus and Escherichia coli, and LPC diet further decreased the relative abundance of Proteobacteria. LPC diet also increased the relative abundance of Lactobacillus reuteri. Both LP diets decreased concentrations of ammonia and cadaverine, and LPC diet also reduced concentrations of putrescine, phenol and indole. Moreover, LPC diet increased total short-chain fatty acid concentration. In comparison with control diet, both LP diets decreased protein expressions of Toll-like receptor-4, nuclear factor-κB, interleukin-1β and tumor necrosis factor-α, and LPC diet further decreased protein expressions of nucleotide-binding oligomerization domain protein-1 and interferon-γ. LPC diet also increased protein expressions of G-protein coupled receptor-43, interleukin-4, transforming growth factor-β, immunoglobulin A and mucin-4, which are indicators for mucosal defense activity.ConclusionsThe results showed that supplementing casein hydrolysate showed beneficial effects on the colonic microbiota and mucosal immunity and barrier function in comparison with supplementing free AAs in LP diets. These findings may provide new framework for future nutritional interventions for colon health in pigs.

Enzymatic Hydrolysis of a Collagen Hydrolysate Enhances Postprandial Absorption Rate-A Randomized Controlled Trial.

Collagen is characterized by its high content of glycine, proline and hydroxyproline, and is found to exert beneficial effects on joint pain related to activity and osteoarthritis. However, to exert any beneficial effects it is essential that collagen is optimally absorbed. This study aimed to investigate the postprandial absorption of collagen and elucidate the impact of an exogenous enzymatic hydrolysis on absorption rate and bioavailability. A randomized, blinded, cross-over study was conducted where ten healthy male subjects received either 35 g enzymatically hydrolyzed collagen protein (EHC), 35 g non-enzymatically hydrolyzed collagen protein (NC) or placebo (250 mL water) on three nonconsecutive days. Blood samples were drawn before, and up to 240 min following, ingestion and the blood metabolome was characterized by nuclear magnetic resonance (NMR)-based metabolomics. A significant increase in the plasma concentration of nearly all amino acids (AAs) was observed over a 240 min period for both EHC and NC. In addition, the absorption rate and bioavailability of glycine, proline and hydroxyproline were significantly higher for EHC (p < 0.05). In conclusion, ingestion of collagen hydrolysates increases postprandial plasma concentrations of AAs over a period of 240 min, and an enzymatic hydrolysis increases the absorption rate and bioavailability of the collagen-rich AAs glycine, proline and hydroxyproline.

Abstract 101: Tissue-specific Deletion of Collectrin in the Proximal Tubular Epithelium Increases Arterial Pressure and Augments Salt-sensitivity

Background: Collectrin ( Tmem27 ) is a key regulator of blood pressure (BP) and modulator of the bioavailability of nitric oxide (NO) and superoxide. It is highly expressed in the kidney in the proximal tubule (PT), collecting duct, and throughout the vascular endothelium. We reported that collectrin plays a critical role as a chaperone for the reabsorption of all amino acids (AAs) in the PT, and for the uptake of the cationic AA L-arginine (L-Arg) in endothelial cells. Global collectrin knockout ( Tmem27 Y/- ) mice display baseline hypertension (HTN), augmented salt-sensitive hypertension (SSH), and decreased renal blood flow. Objective and Methods: To determine the PT-specific effect of collectrin on BP homeostasis and salt sensitivity, we used the Cre -loxP approach and PEPCK-Cre to generate a mouse line lacking collectrin specifically in the PT-- PEPCK-Cre + Tmem27 Y/Flox mice. PEPCK-Cre - Tmem27 Y/Flox mice were used as control. Radiotelemetry was used to measure BP for 2 weeks at baseline and 2 weeks on high salt diet (HSD). Renal blood flow at baseline and on HSD was measured using contrast enhanced ultrasound in the same mice. Results: Successful deletion of collectrin in the PT was confirmed by assessing mRNA levels using real-time RT-PCR, immunohistochemistry staining of renal tissues using anti-collectrin antibody, and quantitation of protein from kidney cortex by Western analysis. Compared to control PEPCK-Cre - Tmem27 Y/Flox mice (n=6), PEPCK-Cre + Tmem27 Y/Flox mice (n=6) displayed significantly higher systolic BP (SBP) at baseline (120.0 ± 2.5 vs 131.6 ± 2.9 mm Hg; p = 0.014) and after HSD (135.3 ± 2.6 vs 151.5 ± 5.2 mm Hg; p = 0.019). Renal blood flow was not different between groups, at baseline nor after HSD. Conclusion: Collectrin in the PT plays an important role in blood pressure homeostasis and response to sodium intake, independent of renal blood flow. Increasing proximal tubular collectrin activity may be a novel therapeutic strategy for the treatment of hypertension and salt-sensitivity.

Apparent digestibility of wheat and coproducts in extruded diets for the Nile tilapia, Oreochromis niloticus

SUMMARY In the present study, we investigated the digestibility of wheat and its coproducts in extruded diets for juvenile Nile tilapia. Specifically, we evaluated the apparent digestibility coefficients (ADCs) of dry matter (ADCDM), gross energy (ADCGE), crude protein (ADCCP), essential amino acids (EAAs), and non-essential amino acids (NEAAs) in winter wheat, spring wheat, wheat middling, wheat bran, and wheat germ in a diet fed Nile tilapia. A reference diet and test diets were used, with 5.0g/kg chromic oxide (Cr2O3) as the external indicator. The ADCDM, ADCCP, and ADCGE were higher (P&lt; 0.05) in winter wheat, spring wheat, and wheat germ than for wheat middling and wheat bran. The ADCs of all amino acids (AAs) were &gt;80%, except for threonine in wheat middling and wheat bran, exceeding 90% for winter wheat and wheat germ. The values of all investigated ingredients were high for ADCCP, and the ADCs of EAAs and NEAAs. A strong negative correlation was detected for crude fiber and ash with the ADCs of dry matter, gross energy, and crude protein. In general, wheat ingredients have good digestibility of protein and amino acids, but high fiber content reduces CDAMS and CDAEB in extruded diets for Nile tilapia.

Bioavailability of D-methionine relative to L-methionine for nursery pigs using the slope-ratio assay.

This experiment was conducted to determine the bioavailability of D-methionine (Met) relative to L-Met for nursery pigs using the slope-ratio assay. A total of 50 crossbred barrows with an initial BW of 13.5 kg (SD = 1.0) were used in an N balance study. A Met-deficient basal diet (BD) was formulated to contain an adequate amount of all amino acids (AA) for 10–20 kg pigs except for Met. The two reference diets were prepared by supplementing the BD with 0.4 or 0.8 g L-Met/kg at the expense of corn starch, and an equivalent concentration of D-Met was added to the BD for the two test diets. The pigs were adapted to the experimental diets for 5 d and then total but separated collection of feces and urine was conducted for 4 d according to the marker-to-marker procedure. Nitrogen intakes were similar across the treatments. Fecal N output was not affected by Met supplementation regardless of source and consequently apparent N digestibility did not change. Conversely, there was a negative linear response (P < 0.01) to Met supplementation with both Met isomers in urinary N output, which resulted in increased retained N (g/4 d) and N retention (% of intake). No quadratic response was observed in any of the N balance criteria. The estimated bioavailability of D-Met relative to L-Met from urinary N output (g/4 d) and N retention (% of intake) as dependent variables using supplemental Met intake (g/4 d) as an independent variable were 87.6% and 89.6%, respectively; however, approximately 95% of the fiducial limits for the relative bioavailability estimates included 100%. In conclusion, with an absence of statistical significance, the present study indicated that the mean relative bioequivalence of D- to L-Met was 87.6% based on urinary N output or 89.6% based on N retention.

Quantitative estimates of the optimal balance between digestible lysine and the true protein contents of broiler feeds

Typical poultry feed formulation models have been developed for meeting the minimum specifications of the essential amino acids (EAAs), ignoring the importance of providing precise levels of the non-essential amino acids (NEAAs) that are required for maximum performance. Including true protein (TP) values in these models in relation to EAAs can most accurately account for the requirements of all amino acids (AAs) in the ration (essential, non-essential and excess EAAs).Data from recent research reports on the digestible lysine (dLys) requirements for maximum weight gain and minimum feed conversion ratio (FCR) were compiled from the literature. dLys requirements and the TP contents of the feeds were recalculated based on common ingredient composition values. Broken-line linear (BLL) and broken-line quadratic (BLQ) models were fitted to the data and compared.The dLys requirements of broilers (g/kg diet) for body weight gain (BWG) and FCR were found to increase linearly as a function of the true and crude protein contents of the diet. These relationships were not affected by either age or sex. As chickens aged, the dLys requirements decreased. However, the dLys requirement to TP ratio did not change with age for BWG or FCR.For maximum BWG and minimum FCR, the dLys requirements were estimated from the prediction models to be 4.92% ± 0.51 and 5.58% ± 0.70 of the TP level of the diet, using the BLL models, respectively.The good linear relationship between the dLys requirement and TP level allows the prediction of the variables from each other for use in feed formulation to represent the requirements of both EAAs and NEAAs.The dietary dLys requirements were estimated to be lower using the BLL vs. the BLQ models.TP was a better predictor of dLys requirements than crude protein (higher R2 values).

Levels of nitrogenous substances and amino acids in bodies of Ross 308 hybrid cocks and hens over the course of rearing

Over the course of Ross 308 hybrid broiler chick cock and hen rearing, whole chicken bodies including feathers were monitored for changes in the levels of nitrogenous substances, essential amino acids (EAA) and non-essential amino acids (NEAA). At five-day intervals (Days 1, 5, 9, 15, 20, 26, 30, 35 and 40 of rearing), randomly selected chickens were slaughtered after 24 h of fasting. Over the course of rearing, N-substance levels ranged from 629.1 to 429.0 g/kg dry matter in hen bodies and from 616.0 to 477.3 g/kg dry matter in cock bodies. N-substance levels were statistically significantly different in the two sexes on rearing Days 35 and 40 (P ≤ 0.01). The levels of all amino acids (AA) in dry body matter of chickens up to 15 days of age dropped significantly over time, while in the period from Day 20 to Day 40, some AA levels increased or reached the baseline. With most AA, the levels were lower in hens than in cocks over the course of the trial. At the end of the trial (Days 35 and 40), statistically significant differences between the sexes were found for most EAA (P ≤ 0.01; P ≤ 0.05). NEAA, except for Ser and Ala, were also significantly higher in cocks on Days 35 and 40 (P ≤ 0.01; P ≤ 0.05). Among the monitored EAA, the dry matter of the bodies of hens exhibited the highest levels of Leu, 8.70% on average, followed by Val 6.54%, Lys 5.26%, Ile 5.25%, Thr 4.84%, Phe 4.30%, Tyr 2.51% and Met 2.21%. Leu was also the most abundant in the cock bodies, 8.42% on average, followed by Val 6.30%, Lys 5.36%, Ile 5.06%, Thr 4.57%, Phe 4.45%, Tyr 2.88% and Met 2.17%. Knowledge of the levels of nitrogenous substances, EAA and NEAA in the whole bodies of broiler chickens including feathers will help to determine optimal rearing conditions.

Valine, isoleucine, arginine and glycine supplementation of low-protein diets for broiler chickens during the starter and grower phases

1. Two experiments were performed to study the supplementation of valine, isoleucine, arginine and glycine (Val, Ile, Arg, Gly) in low-protein diets for broiler chickens in the starter (1–21 d; Exp. 1) and grower (22–42 d; Exp. 2) phases.2. A low-crude protein (CP) diet was formulated to meet the requirements of all amino acids (AA) supplied by the control diet except for Val, Ile, Arg and Gly. The other experimental diets were obtained by the isolated or combined supplementation of the studied AA in the low-CP diet.3. Growth, serum parameters and litter characteristics were taken in both of the experiments. Carcass measurements were taken in Experiment 2.4. In the starter and grower phases, low-CP diets without supplementation resulted in birds with a poorer weight gain and feed conversion than those of the birds that received the control diet.5. In the starter phase, individual supplementation with Val and Gly, but not Ile and Arg, restored the weight gain of the birds, while diets with the addition of Val + Gly, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly restored their feed conversion.6. In the grower phase, weight gain was re-established at the same rate as the control diet for the diets supplemented with Val + Ile, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly. However, the feed conversion was restored only in birds that received the diet supplemented with all studied AA.7. The supplementation of Val and Gly in low-CP diets was sufficient to avoid adverse effects in the performance and serum parameters of broilers in the starter phase. However, birds in the grower phase required the combined supplementation of Val, Ile, Arg and Gly, to prevent compromised performance.

Carbamoylation correlates of cyanate neuropathy and cyanide poisoning: relevance to the biomarkers of cassava cyanogenesis and motor system toxicity

We sought to elucidate the protein carbamoylation patterns associated with cyanate neuropathy relative to cyanide poisoning. We hypothesized that under a diet deficient in sulfur amino acids (SAA), the carbamoylation pattern associated with cyanide poisoning is similar to that of cyanate neuropathy. Male rats (6–8 weeks old) were fed a diet with all amino acids (AAA) or 75%-deficiency in SAA and treated with 2.5 mg/kg/body weight (bw) NaCN, or 50 mg/kg/bw NaOCN, or 1 μl/g/bw saline, for up to 6 weeks. Albumin and spinal cord proteins were analyzed using liquid chromatography mass spectrometry (LC-MS/MS). Only NaOCN induced motor deficits with significant levels of carbamoylation. At Day 14, we found a diet-treatment interaction effect on albumin carbamoylation (p = 0.07). At Day 28, no effect was attributed to diet (p = 0.71). Mean number of NaCN-carbamoylated sites on albumin was 47.4% higher relative to vehicle (95% CI:16.7-86.4%). Only NaOCN carbamoylated spinal cord proteins, prominently, under SAA-restricted diet. Proteins targets included myelin basic and proteolipid proteins, neurofilament light and glial fibrillary acidic proteins, and 2', 3' cyclic-nucleotide 3'-phosphodiesterase. Under SAA deficiency, chronic but not acute cyanide toxicity may share biomarkers and pathogenetic similarities with cyanate neuropathy. Prevention of carbamoylation may protect against the neuropathic effects of cyanate.

Environmental perturbation effects on baseline δ15N values and zooplankton trophic flexibility in the southern California Current Ecosystem

Nitrogen isotopic compositions of zooplankton in the California Current Ecosystem (CCE) are known to vary over inter‐annual scales of climate variability, but the extent to which those changes are driven by variations in baseline phytoplankton δ15N values vs. zooplankton trophic position (TP) is poorly resolved. We use field samples collected during a large natural environmental perturbation, the 1998–1999 alternation between El Niño and La Niña states, to test the ability of large dominant CCE zooplankton Euphausia pacifica and Calanus pacificus to alter their TPs in response to environmental variability. To distinguish trophic changes from variations of δ15N values at the base of the food web, the zooplankton were assayed by Compound Specific Isotope Analysis of Amino Acids (CSIA‐AA). Linear mixed‐effect models were developed to utilize data from all amino acids (AAs), providing greater statistical power than the typical CSIA‐AA approach of using only phenylalanine and glutamic acid. We confirm a significant 15N enrichment of ∼ 2‰ at the base of the food web for all AAs and all zooplankton groups during the 1998 El Niño. This baseline enrichment in 15N has been speculated to occur during El Niño events but never conclusively shown. We also demonstrate a significantly elevated TP, implying increased carnivory during 1998, for E. pacifica while C. pacificus did not alter their TP between years. Lastly, TPs calculated from the standard CSIA‐AA equation with laboratory‐derived constants gave unrealistically low estimates, suggesting an assessment of these variables in situ is needed for an accurate application in natural systems.

PACE Force Field for Protein Simulations. 1. Full Parameterization of Version 1 and Verification

A further parametrization of a united-atom protein model coupled with coarse-grained water has been carried out to cover all amino acids (AAs). The local conformational features of each AA have been fitted on the basis of restricted coil-library statistics of high-resolution X-ray crystal structures of proteins. Potential functions were developed on the basis of combined backbone and side chain rotamer conformational preferences, or rotamer Ramachandran plots (ϕ, Ψ, χ1). Side chain-side chain and side chain-backbone interaction potentials were parametrized to fit the potential mean forces of corresponding all-atom simulations. The force field has been applied in molecular dynamics simulations of several proteins of 56-108 AA residues whose X-ray crystal and/or NMR structures are available. Starting from the crystal structures, each protein was simulated for about 100 ns. The Cα RMSDs of the calculated structures are 2.4-4.2 Å with respect to the crystal and/or NMR structures, which are still larger than but close to those of all-atom simulations (1.1-3.6 Å). Starting from the PDB structure of malate synthase G of 723 AA residues, the wall-clock time of a 30 ns simulation is about three days on a 2.65 GHz dual-core CPU. The RMSD to the experimental structure is about 4.3 Å. These results implicate the applicability of the force field in the study of protein structures.

Evaluation of soyabean meal as a protein source in canine foods

Eight adult female dogs (18.2±0.4 kg) were used in an experiment to determine the feeding value of soyabean meal (SBM) in a complete food fed to dogs. All foods contained graded concentrations of SBM (151–461 g/kg dry matter (DM)) resulting in foods that were 100, 150, 200 and 250 g/kg crude protein (CP). Daily dry matter intake averaged 296±10 g per day. An increase in SBM resulted in a decrease in fecal moisture from 389 to 265 g/kg (linear; P<0.001) and fecal DM output increased from 49.8 to 131.4 g per day (linear; P<0.001). Ileal DM flow increased from 56.6 to 200.7 g per day (linear; P<0.001). Small intestinal DM digestibility decreased from 0.81 to 0.34 (linear; P<0.001) and total tract DM digestibility decreased from 0.83 to 0.57 (linear; P<0.001) as SBM increased. Large intestinal DM digestibility increased from 0.12 to 0.34 with increasing SBM (linear; P<0.001). Crude protein fecal excretion increased from 10.0 to 27.5 g per day (linear; P<0.001) and ileal flow of CP increased from 10.6 to 38.1 g per day (linear; P<0.001) as SBM increased. Small intestinal CP digestibility decreased from 0.65 to 0.51 (linear; P<0.002) with increasing SBM. Large intestinal CP digestibility increased from 0.05 to 0.27 (linear; P<0.021) with increasing SBM. Total tract CP digestibility was unaffected by treatment ( P<0.267) as SBM increased. Disappearance of all amino acids (AA) (g per day), with the exception of cysteine and tryptophan, increased (linear; P<0.001) with increasing SBM. Glutamate had the highest disappearance ranging from 4.98 to 10.89 g per day. Tryptophan and cysteine had the lowest disappearance ranging from 0.35 to 0.43 g per day and 0.29 to 0.36 g per day, respectively. Arginine had the highest overall digestibility ranging from 0.85 to 0.88 whereas, threonine and cysteine had the lowest digestibility ranging from 0.39 to 0.57 and 0.30 to 0.60, respectively. These data indicate that SBM can adversely affect the digestibility of canine foods in concentrations greater than 150 g/kg of the food.

PROTEIN AMINO ACID COMPOSITION IN SECTIONS OF NEEDLE BIOPSIES: CHANGES IN CHRONIC HEPATITIS C

113 Objective: To measure in standard sections of needle biopsies all amino acids (AA) physiologically occuring in proteins, especially AA that indicate amount/function of specific proteins, e.g. hydroxyproline (Hyp) in collagens. Methods: Total tissue volume is calculated from the known thickness and the surface of a section, the latter determined by digital planimetry in a graphics facility (Nikon Microphot-SA microscope; Kontron ProgRes 3012 imaging system; Apple 8600/200 computer; Adobe Photoshop 4.0/NIH Image software). AA are measured in an automated HPLC facility using a Waters 474 scanning fluorescence detector. Each standard section of a needle biopsy, obtained for diagnostic purposes from patients with serologically confirmed hepatitis C and staged by a liver pathologist, was scanned, its total tissue volume calculated in µm3, hydrolyzed, and pre-column derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) [Cohen et al., Anal. Biochem. 211:279-87; 1993]. Separations were generated on a C18 column. This strategy, applicable to any histological specimen, generates results per unit volume, independent of tissue content of water or DNA. Results: 16 AA in each section were quantified in amole/µm3 (a, atto = 10-18). AA variability in repeat runs of the same section averaged 1%, in sequential sections of the same tissue 6%. With increasing disease activity, volume content of all AA decreased, but Hyp gradually increased 9-fold. Representative results for each major AA class are shown in the table.TABLEConclusions: In hepatitis C, volume content of only Hyp correlates with distinct patterns of fibrosis. The technique's minimal tissue demand will enhance localization studies that use microdissection or RT-PCR methods.