Total Gly Research Articles

Influence of increasing glycine concentrations in reduced crude protein diets fed to broilers from 0 to 48 days

Two experiments investigated broiler growth performance and processing characteristics when fed increasing Gly concentrations in reduced CP diets fed from 0 to 48 d. In experiment 1, birds were allocated to 1 of 4 dietary treatments: a control (CTL) diet containing feed-grade L-Met, L-Lys, and L-Thr, a reduced CP (RCP) diet with additions of feed-grade L-Val and L-Ile, or the RCP diet with moderate (M Gly) or high Gly (H Gly) inclusion levels to achieve a total Gly + Ser of 100 or 112%, respectively, of the CTL diet. Birds in experiment 2 were assigned to 1 of 6 dietary treatments: a CTL diet, a RCP diet, or a low CP (LCP) diet without or with added Gly to achieve 88, 100, 112, or 124% total Gly + Ser concentrations of the RCP diet. For experiment 1, 0 to 14 d broiler performance was similar (P > 0.05) among dietary treatments. From 0 to 48 d, broilers fed the H Gly diet had the lowest (P = 0.006) body weight gain (BWG) and highest (P = 0.003) feed conversion ratio (FCR). Feeding either the RCP or M Gly diet resulted in similar (P > 0.05) growth and processing characteristics to the CTL. For experiment 2, increasing Gly levels in the LCP diet linearly reduced (P ≤ 0.027) 0 to 14 d FI and FCR. From 0 to 48 d, broilers had similar (P > 0.05) performance when fed the CTL or RCP diet, but had a higher (P < 0.001) FCR when fed the LCP88 diet. Increasing Gly levels linearly reduced (P = 0.033) FCR. Total breast meat yield was negatively affected (P ≤ 0.020) when feeding the LCP88 diet and did not respond to Gly levels. In conclusion, effects of increasing total Gly + Ser levels on 0 to 48 d broiler performance are likely dependent on the content of dietary CP and other potentially interacting nutrients.

Evaluation of branched-chain amino acids in male Cobb MV × 500 broiler chickens by using Box-Behnken response surface design

Data pertaining to the branched-chain amino acids (BCAA) are of particular importance due to the positioning of valine (Val) and isoleucine (Ile) as limiting amino acids (AA) in conventional diets. Similarly, current research evaluating their potential interaction is sparse. Therefore, two experiments were conducted using Box-Behnken design (BBD) to determine performance and carcass responses to BCAA and glycine (Gly) supplementation in male broilers from 15–34 days (Experiment 1) and 15–35 days (Experiment 2). In Experiment 1, 13 experimental diets were formulated to contain various levels of digestible BCAA supplementation based on BBD. Inclusion levels for the BCAA were based on ratios to digestible lysine (Lys) and included: 65, 75, and 85 for digestible Val; 58, 66, and 74 for digestible Ile; and 110, 130, and 150 for digestible leucine (Leu). Diets for Experiment 2 were formulated in a similar manner and design, but total glycine + serine (Gly + Ser) inclusions were substituted for Leu. Inclusion levels were the same for Val and Ile as in Experiment 1 and ratios to digestible Lys of 131, 151, and 171 for total Gly + Ser. Fifteen-hundred and sixty male broilers were distributed across 78 pens and randomly assigned to 13 experimental diets in each Experiment. Body weight (BW) gain, feed intake, and feed conversion ratio (FCR) were determined for the experimental grower period in both Experiments. On day 35 (Experiment 1) or 36 (Experiment 2), six birds per pen were processed for the evaluation of carcass traits. Data were analyzed for linear, quadratic, and interactive effects. In Experiment 1, increased Leu inclusion linearly increased (P < 0.10) FCR at 35 days and interactions between Ile and Val were observed for BW gain (P < 0.10) and FCR (P < 0.05). Interactions between Ile and Val and Leu and Val significantly affected breast meat weight (P < 0.10) and yield (P < 0.05). These interactions were primarily driven by the inclusion of Val, which depressed breast meat yield, although no linear or quadratic effects of Val were detected. In Experiment 2, interactions between Gly + Ser and Ile were found on total breast yield (P < 0.10). Interactions were also observed between Ile and Val, and Gly + Ser and Val for leg quarter yield (P < 0.10). Unlike in Experiment 1, interactions between Ile and Val were not observed for BW gain, FCR, or total breast yield. Results from these experiments highlight the importance of evaluating relevant interactions between potentially co-limiting AA when conducting trials determining AA requirements.

The effect of reduced dietary glycine and serine and supplemental threonine on growth performance, protein deposition in carcass and viscera, and skin collagen abundance of nursery pigs fed low crude protein diets.

Thirty five barrows (initial body weight [BW]: 15.1 ± 1.0 kg) were used to determine the effect of partially replacing Gly + Ser with Thr in reduced crude protein (CP) diets on growth performance, protein deposition in carcass and viscera, and skin collagen abundance during the late nursery phase to 25 kg BW. Pigs were individually fed one of five iso-nitrogenous diets (n = 7) for 21 d. The basal diet met estimated essential amino acids (AA) requirements by using all essential AA plus Gly and Ser in free form (CON; 12.1% CP; as-fed, analyzed contents). The remaining four diets were formulated by reducing total Gly and Ser concentrations to 60% or 20% of the CON diet. The N removed with Gly and Ser was replaced with either crystalline Thr or Glu. Total analyzed Thr made up either 1.59% (T1; 12.5% CP) or 2.34% (T2; 12.2% CP) of the Thr-supplemented diets, and total analyzed Glu made up either 3.47% (G1; 12.7% CP) or 4.64% (G2; 12.9% CP) of the Glu-supplemented diets. Pigs were slaughtered on day 21 to determine body composition and skin collagen abundance via bright field microscopy. Overall, average daily gain (ADG) and G:F and final carcass weights were greater for pigs fed diets supplemented with Glu (G1 + G2) vs. those fed diets supplemented with Thr (T1 + T2; P < 0.05, P = 0.060, and P = 0.050 for ADG, G:F, and final carcass weight, respectively); intermediate values were observed for CON. Nitrogen retention in carcass plus viscera and the AA profile of deposited protein in the carcass were not influenced by dietary treatment. Pigs fed the T2 and G2 diets had greater retention of Thr (vs. CON and G2) and Glu (vs. CON and T2) in the viscera protein, respectively (P < 0.05). The apparent utilization efficiency of standardized ileal digestible Thr for protein deposition in carcass plus viscera was less for pigs fed T2 (15.1%) vs. those fed CON (56.7%) or G2 (58.6% ± 2.9%) diets (P < 0.001). Only pigs fed T1 had skin collagen abundance not different from CON; pigs fed G1, G2, and T2 had reduced skin collagen abundance compared with CON and T1 (P < 0.01). Using Glu as an N source when Gly and Ser were reduced to 60% and 20% of CON in reduced CP diets maintained ADG for pigs between 15 and 25 kg BW, whereas supplying Thr as a N source reduced ADG and carcass weight. When dietary Gly and Ser were supplied at 60% of CON, only Thr supplementation rescued skin collagen abundance. Therefore, supplemental Thr at excess levels is not sufficient to replace N from Gly and Ser in reduced CP diets fed to late nursery pigs, despite supporting skin collagen abundance as a secondary indicator of Gly status.

Response of broilers to gradual dietary protein reduction with or without an adequate glycine plus serine level

This study was aimed to probe broiler responses to the maintenance of adequate level of glycine plus serine in low crude protein (CP) diets by glycine (Gly) addition from 8 to 42 days of age. A total of 1152 7-d-old birds were divided into 8 groups and fed with one of the following diets: (I) normal CP diet; (II, III vIV V) diets with 1.5%, 3%, 4.5% and 6% points less CP than normal diet, respectively; (VI, VII, VIII) diets with 3%, 4.5% and 6% points reduced CP than the normal CP diet, respectively, and added with Gly to achieve 2.32% total Gly + Ser. Each treatment was replicated with 12 cages. Results showed that dietary CP reduction by 3% or higher compromised (p < .05) growth performance and carcase traits of broilers. Gly fortification in the diet with a 4.5% CP reduction produced similar accumulative growth performance relative to normal-CP group. When Gly fortification in the diet with a 6% CP reduction, the accumulative growth performance were improved (p < .05) but were still inferior (p < .05) to those in normal-CP group. Gly fortification supported a similar (p > .05) abdominal fat percentage of birds fed the diet containing 4.5% points less CP as compared with birds fed the normal-CP diet. Comparatively, Gly fortification in the diet with a 6% CP reduction resulted in breast muscle yield, serum UN content on d 21 and albumin content on d 42 comparable to (p > .05) those in normal-CP group. Collectively, the absence of Gly addition allowed dietary CP reduction by no more than 3% to obtain normal performance and carcase traits of broilers. Gly fortification in the diet with a 3% CP reduction induced no improvements in growth performance and carcase traits of broilers. However, maintain a level of 2.32% total Gly + Ser via Gly fortification enabled a reduction of dietary CP by 4.5% without deteriorating the accumulative growth performance and carcase traits of broilers. Highlights Gly addition that provides 2.32% total Gly + Ser allows dietary CP reduction of 4.5% without compromising the accumulative growth performance and carcase traits of broilers. Maintaining 2.32% total Gly + Ser via Gly fortification could not completely overcome the depression of growth performance in broilers fed the diet with a 6% CP reduction.

Effects of feeding reduced crude protein diets on growth performance, nitrogen excretion, and plasma uric acid concentration of broiler chicks during the starter period

An experiment (2 trials) was conducted to determine the effects of feeding reduced crude protein (CP) diets to Ross × Ross 708 male broilers while maintaining adequate essential amino acid (AA) concentrations on growth performance, nitrogen excretion, and plasma uric acid (UA) concentration during the starter period. In trial 1, 11 dietary treatments were fed from 1 to 18 d of age containing 1.20% digestible Lys. Diet 1 (23.2% CP) was formulated with DL-Met, L-Lys, and L-Thr to contain 1.70 total Gly + Ser to digestible Lys ratio whereas diets 2 (23.4% CP) to 11 were formulated with additional Gly to contain 1.90 total Gly + Ser to digestible Lys ratio. Free AA were added sequentially in the order of limitation (L-Val, L-Ile, L-Arg, L-Trp, L-His, L-Phe, and L-Leu) from diets 3 to 10 to decrease CP content from 22.6 to 18.8%, respectively. In diet 11, L-Gln was added to increase the CP content to 23.4%. Feed conversion of broilers fed diet 2 was lower (P < 0.05) than those consuming diets 6 to 11 from 1 to 17 d of age. Nitrogen excretion (mg/b/d) decreased (P < 0.001) by 14.1% when broilers were fed diet 4 compared with birds fed diet 2 from 15 to 16 d of age. Broilers fed diet 4 had lower (P = 0.011) plasma UA concentration than birds fed diet 2 at 18 d of age. In trial 2, 8 dietary treatments containing 1.25% digestible Lys and 1.70 total Gly + Ser to digestible Lys ratio were fed from 1 to 21 d of age. Diet 1 (24.0% CP) was supplemented with DL-Met, L-Lys, and L-Thr. Free AA (L-Val, Gly, L-Ile, L-Arg, L-Trp, L-His, and L-Phe) were sequentially supplemented in the order of limitation to decrease CP content in diets 2 to 8 from 23.8 to 20.3%. Broilers fed diet 1 had higher (P < 0.05) body weight gain and lower (P < 0.05) feed conversion when compared with diet 7 or 8. Plasma UA concentration of broiler provided diets 4 to 8 was lower (P < 0.05) compared with diet 1 at 21 d of age. Placing a minimum on dietary CP percentage may not be necessary when proper AA ratios are implemented in diet formulation.

Effects of glycine and glutamine supplementation to reduced crude protein diets on growth performance and carcass characteristics of male broilers during a 41-day production period

Glycine has been reported to be conditionally essential for broilers fed reduced crude protein diets during the starter period. Research evaluating dietary Gly responses subsequent to the starter period is sparse. This experiment was conducted to ascertain the effects of feeding reduced crude protein diets supplemented with Gly and/or L-Gln (nitrogen source) on growth performance and carcass characteristics of broilers during a 41-day production period. Eight dietary treatments were utilized with the negative control diets formulated to contain approximately 2.4 and 0.29% points lower crude protein and total Gly + Ser concentrations, respectively, than the positive control diets. The 6 other diets were formulated to contain intermediate concentrations of total Gly + Ser and/or crude protein (nitrogen) by adding Gly and/or L-Gln, respectively, to the negative control diets. Glycine appeared to have more pronounced effects than nitrogen contribution on feed conversion ratio and body weight gain of broilers during starter and grower periods, whereas Gln improved feed conversion of broilers in the finisher period. Total breast meat weight and yield of broilers provided diets with the additions of Gly and L-Gln were higher than those receiving diets with only Gly or L-Gln supplementation. The positive outcomes on growth performance and carcass characteristics suggested that providing adequate total Gly + Ser and nitrogen concentrations in diet formulation may be necessary for broilers when dietary CP content was reduced approximately by 2.4% points during a 6-week production period.

Avaliação de níveis de glicina+serina em dietas de frangos de corte com reduzido teor de proteína bruta

O experimento foi conduzido em delineamento inteiramente ao acaso para avaliar os efeitos de diferentes níveis de glicina+serina (gli+ser) total em dietas de baixa proteína bruta (PB) sobre o desempenho e características de carcaça de frangos de corte de um a 21 dias de idade. Foram utilizadas 750 aves, distribuídas em cinco tratamentos, cinco repetições e 30 aves por unidade experimental. As dietas utilizadas continham 190g/kg de PB e níveis de gli+ser de 16,7; 19,2; 21,7 e 24,2g/kg; a dieta controle continha 230g/kg de PB. Avaliaram-se os efeitos dos níveis de glicina+serina sobre o desempenho e composição de carcaça. Os dados foram submetidos à análise de variância e os resultados obtidos com as dietas de baixos níveis proteicos com diferentes níveis de gli+ser foram comparados à dieta controle pelo teste de Dunnett. Os níveis de gli+ser apresentaram efeito linear sobre a conversão alimentar, ganho de peso e peso aos 21 dias, sendo o nível de 24,2g/kg de gli+ser com resultado semelhante à dieta controle. A redução proteica aumentou o conteúdo de extrato etéreo na carcaça.

Particulate-facilitated leaching of glyphosate and phosphorus from a marine clay soil via tile drains

Losses of commonly used chemical pesticides from agricultural land may cause serious problems in recipient waters in a similar way to phosphorus (P). Due to analytical challenges concerning determination of glyphosate (Gly), transport behaviour of this widely used herbicide is still not well known. The objective of the present study was to quantify and evaluate leaching of Gly in parallel with P. Leaching losses of autumn-applied Gly (1.06 kg ha−1) via drainage water were examined by flow-proportional sampling of discharge from 20 drained plots in a field experiment in eastern Sweden. Samples were analysed for Gly in particulate-bound (PGly) and dissolved (DGly) form. The first 10 mm water discharge contained no detectable Gly, but the following 70 mm had total Gly (TotGly) concentrations of up to 6 µg L−1, with 62% occurring as PGly. On average, 0.7 g TotGly ha−1 was leached from conventionally ploughed plots, compared with 1.7 g TotGly ha−1 from shallow-tilled plots (cultivator to 12 cm working depth). Higher Gly losses occurred in snowmelt periods in spring, but then with the majority (60%) as DGly. All autumn concentrations of PGly in drainage water were significantly correlated (p<0.001) to the concentrations of particulate-bound phosphorus (PP) lost from the different plots (Pearson correlation coefficient 0.84), while PP concentrations were in turn significantly correlated to water turbidity (Pearson correlation coefficient 0.81). Leaching losses of TotGly were significantly lower (by 1.3 g ha−1; p<0.01) from plots that had been structure-limed three years previously and ploughed thereafter than from shallow-tilled plots. Turbidity and PP concentration also tended to be lowest in discharge from structure-limed plots and highest from shallow-tilled plots. This difference in TotGly leaching between soil management regimes could not be explained by differences in measured pH in drainage water or amount of discharge. However, previously structure-limed plots had significantly better aggregate stability, measured as readily dispersed clay (RDC), than unlimited plots. The effects of building up good soil structure, with strong soil aggregates and an appropriate pore system in the topsoil, on mitigating Gly and P losses in particulate and dissolved form should be further investigated.

Effects of glycine supplementation at varying levels of methionine and cystine on the growth performance of broilers fed reduced crude protein diets

Two experiments were conducted to investigate Gly addition to reduced crude protein corn–soybean meal (C-SBM) diets with varying levels of TSAA achieved by varying Met and Cys. The experiments were conducted with female Ross 708 broilers in brooder batteries from 0 to 18 d posthatching. Treatments had 6 replicates with 6 broilers/pen. Diets in all experiments were fed without or with Gly supplementation to contain 2.32% total Gly + Ser. All diets were C-SBM based and formulated to contained 1.27% standardized ileal digestible Lys supplemented with 0.20% Lys (0.394% Lys·SO4) and to meet or exceed the requirement of all nutrients except Met and Cys where appropriate. Experiment 1 consisted of 8 dietary treatments. Three ratios of Met to Cys (60:40, 50:50, and 40:60) were used on a mole for mole basis to achieve 0.063 mol of TSAA/kg of feed and a positive control with Met:Cys of 50:50 at 0.76 TSAA:Lys. Glycine supplementation did not affect ADG or ADFI; however, G:F was increased (P = 0.003) with Gly supplementation. An increase in Cys and a decrease in Met resulted in a decrease (P = 0.028) in ADG but had no effect on ADFI or G:F. In experiment 2, Met was kept constant at a marginal level of 0.45% and Cys was increased in 0.05% increments from 0.35 to 0.50%. Glycine supplementation had no main effect on ADG, ADFI, or G:F; however, Gly increased G:F at the lower levels of Cys but not at the higher levels (Gly × Cys, P = 0.031). A linear decrease (P = 0.071) was found in ADFI with increasing Cys supplementation. These data indicate that Gly increased G:F in female broilers fed suboptimal levels of Met and Cys but not at Cys levels at or above the requirement. This implies that the synthesis of Cys accounts for a portion of the increased G:F observed from Gly supplementation in female broilers fed reduced CP C-SBM diets.

The glycine plus serine requirement of broiler chicks fed low-crude protein, corn-soybean meal diets

SUMMARY Low-protein, amino acid-supplemented, all-vegetable diets for broilers may not result in optimal FCR unless they are supplemented with Gly. Three experiments were conducted to determine the Gly + Ser requirement in a low-CP, corn- and soybean meal-based diet with 0.25% l-Lys·HCl, a level which previously had been shown to result in optimal growth performance of broilers as long as it is supplemented with Gly to maintain a minimum of 2.32% total Gly + Ser. Glycine addition to the diet did not affect ADG or ADFI but decreased FCR. When the FCR data from all 3 experiments were combined, the total Gly + Ser minimum requirement was estimated to be 2.10% (P < 0.014) in 0- to 18-d-old broilers. The response to Gly was not a result of added N from Glu.

The interactive effects of glycine, total sulfur amino acids, and lysine supplementation to corn-soybean meal diets on growth performance and serum uric acid and urea concentrations in broilers

Four experiments were conducted to determine the interactive effects of Gly, TSAA, and Lys in corn-soybean meal diets on growth performance of broilers. All experiments were conducted with female Ross x Ross 308 or 708 broilers in brooder batteries from 0 to 18 d posthatching. Treatments had 5 to 8 replications with 5 or 6 broilers per replicate pen. Diets in all experiments were fed without or with Gly (2.32% total Gly + Ser). All diets contained 0.25% l-Lys.HCl except in experiment 1, where no crystalline Lys was added. In experiment 1, the total dietary Lys level was 1.26% with TSAA:Lys of 0.72 and 0.76. Increasing TSAA:Lys increased (P < 0.07) G:F. The main effect of Gly was not significant for ADG, ADFI, or G:F; however, G:F was increased by Gly in broilers fed 0.72 but not in those fed 0.76 TSAA:Lys (Gly x TSAA:Lys, P < 0.03). In experiment 2, the total dietary Lys level was 1.26% with TSAA:Lys of 0.51, 0.68, 0.72, and 0.76. Glycine addition did not affect ADG, ADFI, or G:F; however, increasing TSAA:Lys linearly increased (P < 0.01) ADG, ADFI, and G:F and the response was quadratic for ADG and G:F. Experiment 3 was similar to experiment 2 except the total dietary Lys level was 1.35%. Glycine addition increased (P < 0.03) G:F and decreased (P < 0.04) serum uric acid (SUA) and serum urea N concentrations. Also, increasing TSAA:Lys linearly and quadratically (P < 0.02) increased ADG, ADFI, and G:F. In experiment 4, broilers were fed 2 levels of total dietary Lys (1.26 and 1.35%), 3 levels of TSAA:Lys (0.72, 0.76, and 0.80), and without or with Gly supplementation up to a total of 2.32% Gly + Ser. Glycine addition increased ADG (P < 0.02) and G:F (P < 0.01). The increase in G:F with Gly was not the same for all TSAA:Lys (Gly x TSAA:Lys, P < 0.07). Increasing Lys increased (P < 0.01 to 0.10) ADG, ADFI, and G:F. Glycine addition increased ADG and ADFI more in broilers fed 1.35% Lys than in those fed 1.26% Lys (Lys x Gly, P < 0.09). Glycine addition increased SUA in broilers fed 1.26% Lys but decreased SUA in broilers fed 1.35% Lys (P < 0.01). Glycine addition decreased SUA in broilers fed the TSAA:Lys of 0.80 but not at the other TSAA:Lys (P < 0.08). These data indicate that Gly increased G:F and decreased SUA in diets with 1.35% Lys and excess TSAA.

Dietary glycine and threonine interactive effects in broilers

Little information is available regarding the interaction of dietary Thr and Gly on the potential metabolic sparing effects, live production, or breast meat yield of broilers. To test these potential interactions, 432 one-day-old Ross 308 male broilers were fed a common diet up to 21 d of age, and then fed 1 of 6 experimental diets. A factorial arrangement of treatments consisted of 3 dietary levels of standardized digestible Thr (0.57, 0.61, and 0.65%) in combination with 2 levels of total Gly + Ser (1.55 and 1.65%). Experimental diets were fed from 21 to 42 d of age, with live performance, carcass traits, and free blood plasma levels of Gly, Ser, and Thr serving as evaluation criteria. Interactions (P ≤ 0.05) were observed for BW gain, feed consumption, carcass and breast meat weight, and carcass yield, all showing improvements with increasing dietary Thr in combination with low dietary Gly + Ser treatments. Circulating plasma Gly, Ser, and Thr were affected by their respective dietary status.

In vivo detection of brain glycine with echo‐time‐averaged 1H magnetic resonance spectroscopy at 4.0 T

A single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) method is described that enables the in vivo measurement of endogenous brain glycine (Gly) levels in human subjects. At 4.0 T, TE-averaging (1)H-MRS dramatically attenuates the overlapping myo-inositol (mI) resonances at 3.52 ppm, permitting a more reliable measure of the Gly singlet peak. This methodology initially is described and tested in phantoms. The phantom data infers that the 3.55-ppm peak predominantly is Gly with a smaller contribution from mI. The composite resonance thus is differentiated from pure Gly and mI and is labeled Gly*. The mI contribution was calculated as <2% of the total Gly* signal for a 1:1 mI/Gly mixture. The technique subsequently was used to acquire TE-averaged (1)H-MRS data from the occipital cortex of healthy control subjects. The resultant spectra closely resembled experimental phantom data. LC-model analysis provided a means for quantifying TE-averaged (1)H-MRS spectra and a mean test-retest variability measure of 15% was established for brain Gly* levels in studies of six healthy subjects.

SERINE AND GLYCINE TRANSPORT IN FETAL OVINE HEPATOCYTES

43 Serine (ser) and glycine (gly) are poorly transported across the placenta from the mother to the fetus. Although we have shown that the fetal liver is an important primary site of fetal ser synthesis for the unique fetal metabolism of ser and gly, the regulation of this unique fetal ser and gly metabolism is uncertain. The goal of this study was to characterize ser and gly transport in primary cultures of fetal ovine hepatocytes. Transport was determined after primary culture of hepatocytes from term (≈135 days) fetal lambs using sodium free or sodium containing KRP and the appropriate U-14C labeled amino acid after overnight culture. (Table) At 300µM concentrations, sodium dependent transport was inhibited by NEM (ser 36±9% and gly 37±2%) with similar inhibition by MeAIB. There was competitive inhibition of total gly transport by ser but not of ser transport by gly. Sodium free gly transport was higher in low glucose (1.1 mM) media (881±76) compared to high glucose (10 mM) media (510±60 p=0.004). Gly transport was inhibited by sarcosine. These data suggest that ser is primarily transported via system L and ASC in term fetal ovine hepatocytes while gly is transported primarily by system L with less of a contribution from ASC and gly. There is a contribution from system A to both ser and gly transport in term fetal ovine hepatocytes. The predominance of ser transport over gly at physiologic concentrations suggests that inward cellular amino acid transport of ser and gly is not likely to be a regulatory mechanism that would favor ser biosynthesis in fetal ovine hepatocytes except in conditions that would favor sodium free transport.TABLE

901–88 Rapid Genetic Screen for Common β-Myosin Heavy Chain Mutations Causing Familial Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM), an autosomal dominant disease and the most common cause of sudden death in the young, is diagnosed by echocardiographic detection of cardiac hypertrophy. Unfortunately, the hypertrophy is usually not detectable until adolescence, which may be too late since sudden death often occurs as the first symptom. The availability of a clinical genetic assay to detect mutations would provide a definitive diagnosis, independent of clinical features and can be made at or before birth. Computer analysis showed most of the known mutations in the βMHC gene involve a restriction enzyme recognition site which can be exploited as a rapid genetic screening test. Accordingly, we employed polymerase chain reaction (PCR) to amplify the involved region of the gene followed by enzyme restriction digestion for 15 known mutations in 122 families with HCM. Fourteen families were positive and 108 negative. Ten families carried one of the three mutations known to have a high incidence of sudden death with 26 offspring having the mutation and at risk for sudden death while 49 did not have the mutation and are not at risk of developing HCM. Four families had one of the three known benign mutations with 23 offspring having the mutation and 21 without. The mutations were confirmed by sequencing and shown to be co-inherited with the disease. This test provides for a definitive genetic diagnosis and identifies those with the mutation and at risk for HCM and those without who will not develop HCM. Genetic counseling can be given prior to development of symptoms and those with mutations having a high incidence of sudden death are candidates for electrophysiology testing and possible implantation of cardiac defibrillators or amiodarone therapy. The test requires only a blood sample, is simple to perform and results are available in 48 hours. Over 25 of the βMHC mutations have now been shown to be amenable to rapid genetic diagnosis using PCR and restriction enzyme digestion. Mutation Prognosis No. of Families Arg 719 Trp malignent 4 (3.3% of total) Arg 403 Gln malignent 3 (2.5% of total) Arg 453 Cys malignent 3 (2.5% of total) Leu 908 Val benign 2 (1.6% of total) Val 606 Met benign 1 (0.8% of total) Gly 741 Arg benign 1 (0.8% of total)