Limiting amino acids for a corn and soybean meal diet in weaned calves less than three months of age

Holstein bull calves (n = 51) weaned at 6 wk of age were used in four N balance trials for 4 wk (Trials 1 to 3) or for 2 wk (Trial 4) from 8 wk of age to identify limiting amino acids for a corn and soybean meal diet. The calves were trained to maintain reflex closure of the reticular groove throughout the trials. In Trial 1, administration of .111 g of DL-methionine plus .333 g of L-lysine monohydrochloride/kg BW through the reticular groove increased N retention compared with the control that received isonitrogenous L-glutamine, but administration of .333 g L-lysine monohydrochloride/kg BW alone did not increase N retention in Trial 2. In Trial 3, administration of .111 g of DL-methionine/kg BW improved N balance compared with the control, although the improvement was not detected when DL-methionine was restricted to .022 g/kg BW. In Trial 4, administration of the mixture of .111 g of DL-methionine, .333 g of L-lysine monohydrochloride, and .055 g of L-tryptophan/kg BW increased N retention in calves compared with calves that received an isonitrogenous mixture of .111 g of DL-methionine and .274 g of L-glutamine/kg BW, or .111 g of DL-methionine, .055 g of L-tryptophan, and .234 g of L-glutamine/kg BW. The present results suggest that methionine was the first-limiting and that lysine was probably the second-limiting amino acid for the corn and soybean meal diet in weaned calves less than 11 wk of age, although tryptophan may be either co-limiting with lysine or third-limiting.     

硫对含草酸钠铝酸钠溶液蒸发排盐的影响

通过添加不同量的硫酸钠和硫化钠,研究硫对含一定浓度草酸钠(Ns)的铝酸钠溶液蒸发排盐的影响。结果表明,当Ns=6g/L时,硫酸钠对铝酸钠溶液中Na_2CO_3、硫盐、Na_2C_2O_4和NaAlO_2的结晶析出均有影响,随着添加量的增加,盐析出率均增大,排盐率也增大,当Ns=6g/L时,排盐率达到92.02%,排盐渣中存在Na_2CO_3、Na_2C_2 O4、NaAlO_2·1.25H_2O、Na_2SO_4以及Na_6CO_3(SO_4)_2、Na_4(SO_4)1.39(CO_3)0.61等结晶复盐;添加硫化钠也可以增加盐析出率与排盐率,但是效果不明显,在当Ns=6g/L时,排盐率仅为71.71%,结晶物相有Na_2CO_3、Na_2C_2O_4、NaAlO_2·1.25H_2O以及Na_2S,Na_2S2O_3,Na_2SO_3等,并不存在结晶复盐;随着硫化钠添加量的增加,抽滤时间增长,增加了排盐的难度,硫化钠滞留在溶液中,继续对生产产生危害,需要引入氧化剂将硫化钠充分氧化为硫酸钠,才能达到良好的强化排盐效果。     

H_2O_2和Na_2SO_4晶种对高硫种分母液强化排盐的影响

研究添加Na_2SO_4晶种及H_2O_2对高硫种分母液蒸发排盐的影响及机理。结果表明,H_2O_2或Na_2SO_4的添加能促进母液排盐,且随其添加量增加,碳酸钠、硫盐的析出率及总排盐率均增加。当添加4.5g/L的Na_2SO_4晶种时,排盐率增加至73%;添加6mL H_2O_2时,母液排盐率为67.96%,相比未添加时增加了8.73个百分点;复合添加6mL H_2O_2和4.5g/L Na_2SO_4晶种时,排盐率达到78.26%,且溶液黏度降低明显,NaAlO_2的析出率降低。与原液排盐渣相比,添加Na_2SO_4晶种或H_2O_2排盐渣有Na_6CO_3(SO_4)_2复盐的析出,且排盐渣成分变化较大。     

Influence of predeprivation diet nutrient density and sodium chloride content on nutrient losses and repletion in lambs

Six crossbred lambs (32+/-2 kg) in a 6 x 6 Latin square design were used to determine the effects of predeprivation diet nutrient density and NaCl content on nutrient losses during periods of feed and water deprivation and nutrient repletion. Treatments consisted of two predeprivation dietary nutrient densities (low [LOW] and moderate [MOD]) and three NaCI intakes (0, 2, or 4 g/d) in a 2 x 3 factorial arrangement. During the 4-d predeprivation phase, lambs fed the M0D diet had greater (P < .05) K retention and lower (P < .01) Na retention than lambs fed the LOW diet. Retention of Na increased linearly (P< .01), whereas retention of K decreased linearly (P < .O01) with increasing NaCl intakes. During the 3-d deprivation phase, lambs fed the MOD diet had lower (P < .01) Na losses than lambs fed the LOW diet. Losses of Na increased linearly (P < .01), whereas losses of K decreased linearly (P < .05) with increasing NaCl intakes. During the predeprivation and deprivation phases, cumulative losses of K were greater (P < .05) and cumulative losses of Na were lower (P < .05) in lambs fed the LOW diet than in lambs fed the MOD diet. Cumulative losses of K increased linearly (P < .05) as predeprivation NaCl intake increased. Predeprivation NaCl intakes did not affect (P > .10) total retention of water, Na, or K for the overall 14-d sampling period. Predeprivation salt intakes affected Na and K losses during a simulated marketing-transport period. However, after 7 d on the realimentation diet, predeprivation diet nutrient density and NaCl intake did not affect the balance of these nutrients.     

Nitrogen utilization in pigs fed diets with soybean and rapeseed products leading to different ileal endogenous nitrogen losses

Nitrogen (N) balance was determined in 36 pigs (BW 24 to 30 kg) fed diets inducing different ileal endogenous N losses (ENL). We tested the hypothesis that enhanced ENL may be indicative of a higher recycling of endogenous proteins that will induce a greater urinary N loss and a lower efficiency of the dietary N utilization for retention. The cornstarch-based diets contained either soy concentrate (SC), soybean meal (SBM), a mixture of toasted and untoasted soybean meal (mSBM), dehulled-toasted rapeseed cake (RC1), non-dehulled-toasted rapeseed cake (RC2), or dehulled-untoasted rapeseed cake (RC3). The diets were balanced for their content of apparent ileal digestible (ID) CP (108 g/kg feed) and apparent ID of Lys, Thr, Met+Cys, Trp, and Ile. Feeding level was 2.7 times ME for maintenance per kilogram BWx75 and restricted to 88% of the requirements for ID Lys as the first-limiting amino acid. During a 5-d period, urine and feces were collected daily in metabolism cages. Compared with the SC diet (low ENL), the diets with SBM (medium ENL) and mSBM (high ENL) resulted in a greater (P < .05) urinary N excretion. Nitrogen retention tended to be less (P = .08) in pigs fed diets that caused greater ENL. The utilization of ID N for retention in pigs fed the mSBM diet was lower (P < .05) than for those fed the SC diet. There were no differences in urinary N excretion, N retention, and the utilization of ID N for retention in pigs fed the rapeseed diets of different fiber contents (hulls as the NDF source). We concluded that, at similar intakes of the first-limiting ID amino acid, N retention in pigs fed soybeans tended to be reduced by greater ENL as induced by antinutritional factors (e.g., trypsin inhibitors). Rapeseed hulls, as the predominant fiber source, do not affect N retention and the utilization of ID N for retention.     

Protein requirements of growing steers limit-fed corn-based diets

In Exp. 1, six steers (254 kg) were used in a 6 x 4 incomplete Latin square to determine the effects of solvent-extracted soybean meal alone or in combination with rumen-protected methionine and lysine on N balance in steers limit-fed a high-corn diet to gain 1.1 kg/d. The basal diet contained (DM basis) 80% rolled corn, 15% alfalfa, and .9% urea (13.9% CP), and 2 or 4% soybean meal replaced corn to give CP concentrations of 14.8 and 15.6%, respectively. Each diet was fed with and without 5 g/d of Smartamine-ML (.75 and 2.0 g of rumen-protected methionine and lysine, respectively). Nitrogen retention increased linearly (P = .09) with level of soybean meal. Rumen-protected methionine and lysine had no effect on N balance. In Exp. 2, seven steers (233 kg) were used in a 7 x 4 incomplete Latin square experiment to investigate optimal levels and sources of CP for steers limit-fed to gain 1 kg/d. Treatments included a negative-control diet (urea; 11.7% CP) and six diets containing either 13.5, 15.4, or 17.2% CP with either solvent-extracted or expeller-processed soybean meal. Diets provided 75, 87.5, 100, or 112.5% of estimated CP requirement for a gain of 1 kg/d. The basal diet contained 83% rolled corn, 15% alfalfa, and .2% urea. Nitrogen retention increased linearly (P = .006) with soybean meal addition, and no differences were observed between CP sources. The CP system underpredicted the protein requirements of limit-fed steers under our conditions.     

Effects of a dietary mixture of meat and bone meal, feather meal, blood meal, and fish meal on nitrogen utilization in finishing Holstein steers

Our objective was to determine to what extent rate and efficiency of protein gain in finishing cattle can be enhanced by feeding an amino acid-balanced mixture of undegraded intake proteins. The Cornell Net Carbohydrate and Protein System (CNCPS) model was used to formulate a corn-based diet that would meet the rumen requirements for 410-kg large-framed steers with an estrogen implant and fed an ionophore. The CNCPS model was also used to formulate a highly undegradable intake protein (UIP) mixture from meat and bone meal, blood meal, fish meal, and hydrolyzed feather meal to provide the amino acids needed to supplement those derived from microbial protein to better meet amino acid requirements for growth. Four Holstein steers weighing 407 kg were offered a 90:10 concentrate-forage diet at hourly intervals at 95% of ad libitum intake. The steers were injected with 500 microg of estradiol-17beta at 12-h intervals to mimic the effects of an estrogenic implant. Treatments planned consisted of inclusion of the UIP mixture at 0, 2.5, 5, and 7.5% of the diet DM. Dry matter intake was fixed at 6.4 kg/d, and DM digestibility was not significantly affected by varying the amount of UIP addition. Apparent digestibility of N increased (P = .011) from 63.8 to 65.8, 70.7, and 71.5%, the amount of N absorbed increased (P = .001) from 73 to 84, 100, and 106 g/d, and N balance increased (P = .003) from 20 to 30, 33, and 39 g/d when UIP was fed at 0, 2.6, 5.2, and 7.8% of diet DM, respectively. The efficiency of N use increased 39.7%, and biological value increased 31.6% when the UIP mixture was added to the diet. Circulating concentrations of plasma urea N (PUN) were increased (P = .017) from 4.5 for the control diet to 5.7, 6.2, and 6.1 mg/dL when the UIP mixture was added at 2.6, 5.2, and 7.8%, respectively. Corresponding IGF-I concentrations were also increased from 491 to 558 and 624 ng/mL with 2.6 and 5.2% levels of UIP addition. Plasma glucose, NEFA, and insulin concentrations were not affected by feeding the UIP mix. The rate and efficiency of N use for growth improved with addition of an amino acid-balanced UIP mixture to the diet.     

Interrelationships between dietary protein level, energy intake, and nitrogen retention in pregnant gilts

Two experiments were conducted to study the effects of dietary protein levels and DE intake on N retention in pregnant gilts. Thirty-two gilts were used in Exp. 1 to investigate the response to eight levels of dietary CP ranging from 50 to 235 g/kg (3.3 to 14.5 lysine/kg). Gilts were given 1,400 g of feed daily throughout pregnancy; diets contained similar balances of amino acids and similar amounts of DE (3.60 to 3.63 Mcal/kg). Thirty gilts in Exp. 2 were allocated during pregnancy to six levels of feeding ranging from 1.1 to 3.1 kg/d. The common diet given to gilts contained 3.49 Mcal of DE/kg, 155 g of CP/kg, and 10.7 g of lysine/kg and was considered adequate in protein. Nitrogen balance trials were conducted during early, mid-, and late pregnancy and collection periods of 5 d duration commenced on d 30, 58, and 86 in Exp. 1 and d 30, 58, and 93 in Exp. 2. The average live weights of pigs on all treatments within each collection period were similar and were 112.5, 123.3, and 136.6 kg and 120.7, 136.3, and 158.3 kg in Exp. 1 and 2, respectively. At each stage of pregnancy increments of dietary protein increased N retention up to an inflection point, after which N retention remained at a constant level. The maximum rates of N retention, 10.0, 12.1, and 16.5 g/d during early, mid-, and late pregnancy, occurred at 142, 133, and 162 g of CP/kg, respectively; the corresponding dietary lysine:DE values were 2.4, 2.3, and 2.7 g of lysine/Mcal of DE.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dietary protein restriction alters glucose but not protein metabolism in non-insulin-dependent diabetes mellitus

We determined whether a customary diet high or low in protein (1) influences postabsorptive amino acid catabolism, nitrogen (N) balance, and hepatic glucose output (HGO) in normal subjects or patients with non-insulin-dependent diabetes mellitus (NIDDM) or (2) alters blood glucose levels in NIDDM. Eight normal young adults and five obese middle-aged persons with NIDDM consumed low-protein (0.8 g/kg lean body mass [LBM]) or high-protein (3.0 g/kg LBM) diets at maintenance energy for consecutive 7-day periods. Fasting and average blood glucose and N balance were measured daily. The level of dietary protein had no effect on the basal plasma leucine rate of appearance (Ra) or urinary 3-methylhistidine excretion in either subject group. Basal leucine oxidation (and by inference, whole-body amino acid catabolism) was reduced on the low-protein diet but basal HGO was not, and although exogenous glucose effectively suppressed HGO, it did not reduce leucine oxidation with either diet. After adaptation to the low-protein diet, N balance in both the normal and NIDDM subjects was close to zero. The low-protein diet reduced the fasting and daily blood glucose of the diabetic subjects by approximately 2 mmol/L (P < .05). We conclude that physiologic variation in dietary protein does not affect basal whole-body protein turnover or HGO in either normal young adults or obese middle-aged NIDDM subjects. However, protein restriction to the level of the average daily requirement significantly reduces postabsorptive and average daily blood glucose concentrations in persons with NIDDM.     

Early detection and control of risk factors in diabetic nephropathy

An influx of neutrophils into the airways is a common feature observed during pulmonary inflammation induced by air pollutants, including sulfur dioxide and sulfates. In the present study focusing on the in vitro interactions of sodium sulfite (Na2SO3) with human neutrophils, we confirm results indicating that this sulfite induces superoxide production (O2-) by itself. We demonstrated that this response can occur more rapidly than previously reported (within 5 min), and that Na2SO3 can act as a priming agent, in a concentration-dependent fashion, to the bacterial tripeptide N-formyl-methionine-leucine-phenylalanine (fMLP) by increasing O2-production. In addition, our results show that Na2SO3 induces gene expression in human neutrophils in a concentration-dependent manner as assessed by incorporation of 5-[3H] uridine into total RNA. However, it does not induce cell shape changes. We also demonstrated that Na2SO3 does not modulate neutrophil apoptosis nor reverse the well-known delaying effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on apoptosis. We conclude that Na2SO3 acts rapidly on neutrophil physiology, within a few minutes with respect to superoxide production, and a few hours (4 h) with respect to gene expression without altering a biological process such as the rate of apoptosis evaluated after a long period of incubation (20 h). We further conclude that Na2SO3-induced production of O2does not drive neutrophils to undergo apoptosis, a mechanism known to occur in other conditions. Therefore, the potential toxicity of Na2SO3 during pulmonary inflammation or lung-associated diseases may be related to its ability to induce superoxide production without altering neutrophil apoptosis rate.     

Cell vs. noncell airway temporal response in rats exposed to sulfur dioxide

A modification of the sulfur dioxide (SO2)-exposed rat model proposed by Reid for the study of chronic bronchitis was employed to evaluate mucus retention and cytologic changes. Rats were exposed to from 600 to 700 ppm of SO2 for 3 hours per day, and groups were examined after 0, 9, 18, and 30 hours of cumulative exposure. Tracheal mucus retention and statistically significant increases (two- to four-fold) in the amount of solid material (cellular and mucus) recovered by bronchia lavage developed as a function of exposure time. The increase in bronchial solids was primarily due to inflammatory cells. The goblet cell population in secondary bronchi declined initially, with a significant increase after 30 hours of exposure (P less than .001). The cytologic data provide additional support to Reid's suggestion that the SO2-exposed rat may be considered as a chronic bronchitis model.     

用工业Al2O3管制备的银/硫酸银参比电极的性能及应用

以工业氧化铝管作隔膜材料制备了高温用Ａｇ／Ａｇ２ＳＯ４（摩尔分数Ｎ＝０．１）－Ｎａ２ＳＯ４参比电极。在硫酸钠熔盐（９００℃）中对其性能进行检测校定,表明在高温熔盐条件下,作为电化学测试用的参比电极具有结构简单,稳定性、重现性好的特点,可以完成各种电化学参数的测量。实验标定了这种以工业氧化铝管作隔膜材料的电极作为熔盐中碱度测量用钠探头的特性,给出了该体系下计算碱度值的定量公式。     

Lysine deficiency in postweaned calves fed corn and corn gluten meal diets

Holstein bull calves (n = 36) weaned at 6 wk of age were used in six trials to examine the response of N balance to postruminal administration of lysine with or without methionine in postweaned calves receiving diets based on corn and corn gluten meal. Calves were younger than 3 mo of age in Trials 1 and 2 but older than 3 mo in Trials 4 to 6. L-Lysine monohydrochloride was supplemented with or without DL-methionine twice daily through the reticular groove, except in Trial 4, in which N supplements were infused through duodenal cannulas. L-Glutamine was used as a nonspecific N source in every trial, and casein was a positive control in Trials 4 and 5. When daily CP intake from the diet was 3.9 g/kg BW, lysine was limiting for calves less than 11 wk of age (Trials 1 and 2) but not limiting for calves greater than 12 wk of age (Trial 3). No amino acid seemed to be limiting for calves greater than 20 wk of age (Trial 4) when daily CP intake was 4.1 g/kg BW, but lysine was limiting when CP intake was restricted to 3.0 g/kg BW when calves were more than 17 wk of age (Trial 5). However, lysine was not limiting above 18 wk of age (Trial 6) when CP intake was increased to 3.8 g/kg BW by adding urea to the diet. Results suggest that lysine may be limiting for corn and corn gluten meal diets only when ruminal microbial protein synthesis is restricted.     

D-methionine provides excellent protection from cisplatin ototoxicity in the rat

Cisplatin (CDDP) is a widely used chemotherapeutic agent. Unfortunately, CDDP is highly ototoxic. We tested D-methionine (D-Met), a sulfur containing compound, as an otoprotectant in male Wistar rats. Complete data sets were obtained for five groups of five animals each, including a treated control group (16 mg/kg CDDP), an untreated control group (administered an equivalent volume of saline) and three groups that received either 75, 150, or 300 mg/kg D-Met 30 min prior to the 16 mg/kg CDDP dosing. Auditory brainstem response (ABR) thresholds were obtained in response to clicks, and 1 kHz, 4 kHz, 8 kHz, and 14 kHz toneburst stimuli, before and 3 days after drug administration. Scanning electron microscopy (SEM) was used to examine the outer hair cells of the apical, middle and basal turns of the cochlea. Animal weight was measured on the first and final day. D-Met provided excellent otoprotection even at the lowest level with complete otoprotection obtained for the 300 mg/kg dosing as measured by both ABR and SEM. D-Met also markedly reduced weight loss and mortality. All animals receiving D-Met (15/15) survived to the end of the study period as opposed to only 5/10 of the treated controls.     

高浓度H_2SO_4体系中Cl~-和SO_4~(2-)对N235萃取钒的影响

采用加盐萃取法从高酸浸出液中直接分离富集钒,考察了酸度、N235浓度、氯化钠浓度、硫酸钠浓度对N235萃取分离高浓度硫酸溶液中钒的影响,并确定了萃合物的结构。结果表明,Cl~-和SO_4~(2-)对硫酸体系钒的萃取均有一定提高,但Cl~-的作用效果更显著。在不加盐的条件下,采用20%N235为萃取剂,磺化煤油为稀释剂,硫酸浓度1mol/L,萃取时间10min,相比A/O=1∶1,经单级萃取,硫酸体系中钒萃取率仅为30%左右;加入一定量的NaCl、Na_2SO_4后,钒萃取率分别达到80%、47%。Cl-作用于硫酸体系时,与钒以离子缔和形式形成萃合物(R_3N)_x·(VO_2~+·Cl~-)_y;SO_4~(2-)的加入可促进VO_2SO_4~-的形成,使萃取率提高。     

Effect of NIDDM on the kinetics of whole-body protein metabolism

We postulated that dietary protein utilization and body protein metabolism are altered in hyperglycemic individuals with non-insulin-dependent diabetes mellitus (NIDDM). This was tested by estimating the kinetics of protein metabolism in obese NIDDM patients in the hyperglycemic state of isoenergetic feeding and in the normoglycemic state induced by the prolonged use of a very-low-energy diet (VLED) and comparing them with results in obese nondiabetic subjects studied previously. Seven obese subjects with NIDDM (one male, six females, body mass index = 35.8 +/- 2.0 kg/m2) were given a 1.7 MJ (410 kcal) all protein (93 g/day) diet derived from hydrolyzed collagen and supplemented with tryptophan and methionine, which provides 16% of its amino acids as essential, a multivitamin and mineral supplement, and 16 mmol KCl for 42 days. During the seven-day isoenergetic diet and at weeks 4 and 6 of the VLED, amino nitrogen (N) flux rate was calculated from the urine [15N]urea enrichment by using the 60-h oral [15N]glycine method to obtain the integrated feeding-fasting metabolism. Rates of synthesis (S) and breakdown (B) were calculated from N flux. At day 7 of the isoenergetic diet, whole-body N flux, S, B, and resting metabolic rate (RMR) were 12-24% greater (P < 0.05) in the NIDDM subjects than observed in nondiabetic obese subjects. Mean plasma glucose decreased (P < 0.05) from the isoenergetic period (14.9 +/- 2.4 mM) to 7.2 +/- 1.2 mM at week 4 and 6.5 +/- 1.1 mM at week 6 of the VLED. RMR declined progressively by 25% at week 5 of the VLED. Corresponding significant (P < 0.05) decreases from isoenergetic feeding to weeks 4 and 6 of the VLED occurred in whole-body N flux (from 51 +/- 2 to 42 +/- 1 g N/day), in S (from 38 +/- 3 to 24 +/- 1 g N/day), and in B (from 39 +/- 3 to 26 +/- 1 g N/day) resulting in net losses (S-B). S-B was significantly more negative (P < 0.05) in NIDDM than in the nondiabetic obese subjects at week 4 (-1.5 +/- 0.5 vs. 0.9 +/- 0.3 g N/day) but not at week 6 (-1.3 +/- 0.4 vs. -0.9 +/- 4 g N/day). During the VLED, N balance became less negative with time but never reached equilibrium in NIDDM. Thus, abnormal protein metabolism is present in NIDDM in the isoenergetic fed state with moderate hyperglycemia and persists during a VLED that restores glycemia to near normal.     

Effect of amino acid supplementation on whole-body protein turnover in Holstein steers

We used the [15N]glycine single-dose urea end-product technique to measure whole-body protein turnover in six Holstein steers (250 +/- 18 kg). Steers were implanted with Revalor-S and continuously infused abomasally with water (4 L/d) or amino acids (AA; in 4 L/d water) in a crossover experiment (two 14-d periods). The AA infusion contained the following (g/d): lysine (5.3), methionine (3.3), threonine (3.2), tryptophan (1.0), histidine (2.1), and arginine (5.5). Steers were fed a diet containing 85% rolled corn, 10% prairie hay, and 1.1% urea (DM basis) at 2.16% of body weight. Nitrogen retention tended (P = .15) to increase with AA infusion, from 27.9 to 32.9 g N/d. Amino acid infusion numerically increased whole-body protein turnover from 168.6 to 183.2 g N/d, protein synthesis from 152.6 to 169.3 g N/ d, and protein degradation from 124.7 to 136.4 g N/d. Enhanced protein accretion may have resulted from a larger increase in protein synthesis than in degradation. The tendency for increased N retention is interpreted to suggest that the implanted, lightweight Holstein steers fed a corn-urea diet in our study were able to respond to AA supplementation, suggesting that at least one of the infused AA was limiting in the basal diet. Protein turnover data suggest that cattle, like other animals, may increase protein synthesis and protein degradation in response to supplementation with limiting AA. The [15N]glycine single-dose urea end-product technique for measuring whole-body protein turnover in cattle may be useful.     

The sparing action of inorganic sulphate on sulphur amino acids in practical broiler diets: preliminary trials with young chicks

1. In three trials marked responses to Na2SO4 were obtained, both in terms of growth rate and of food/gain ratio. In a fourth trial the chicks responded to graded additions of synthetic methionine but not to inorganic sulphate. 2. The response of the chicks to Na2SO4 depended on the amount of sulphur amino acids in the diets, being absent or difficult to demonstrate in severely deficient diets or in those adequately supplemented, respectively. 3. Sodium sulphate cannot replace more than about 0-05% supplementary methionine. 4. Usually the efficacy of Na2SO4 in improving performance appeared to range from 40% to 60% that of synthetic methionine.     

The effect of ionic strength and specific anions on substrate binding and hydrolytic activities of Na,K-ATPase

The physiological ligands for Na,K-ATPase (the Na,K-pump) are ions, and electrostatic forces, that could be revealed by their ionic strength dependence, are therefore expected to be important for their reaction with the enzyme. We found that the affinities for ADP3-, eosine2-, p-nitrophenylphosphate, and V(max) for Na,K-ATPase and K+-activated p-nitrophenylphosphatase activity, were all decreased by increasing salt concentration and by specific anions. Equilibrium binding of ADP was measured at 0-0.5 M of NaCl, Na2SO4, and NaNO3 and in 0.1 M Na-acetate, NaSCN, and NaClO4. The apparent affinity for ADP decreased up to 30 times. At equal ionic strength, I, the ranking of the salt effect was NaCl approximately Na2SO4 approximately Na-acetate < NaNO3 < NaSCN < NaCl04. We treated the influence of NaCl and Na2SO4 on K(diss) for E x ADP as a "pure" ionic strength effect. It is quantitatively simulated by a model where the binding site and ADP are point charges, and where their activity coefficients are related to I by the limiting law of Debye and Hückel. The estimated net charge at the binding site of the enzyme was about +1. Eosin binding followed the same model. The NO3- effect was compatible with competitive binding of NO3- and ADP in addition to the general I-effect. K(diss) for E x NO3 was approximately 32 mM. Analysis of V(max)/K(m) for Na,K-ATPase and K+-p-nitrophenylphosphatase activity shows that electrostatic forces are important for the binding of p-nitrophenylphosphate but not for the catalytic effect of ATP on the low affinity site. The net charge at the p-nitrophenylphosphate-binding site was also about +1. The results reported here indicate that the reversible interactions between ions and Na,K-ATPase can be grouped according to either simple Debye-Hückel behavior or to specific anion or cation interactions with the enzyme.     

Alteration of laminin production in small-cell lung carcinoma: possible correlation with the absence of the basement membrane

The amount of protein recommended to minimise N loss in critically ill patients receiving total parenteral nutrition (TPN) varies in the literature. Therefore, we studied the effect of increased protein intake on the N balance, administering TPN with either 1.2 g protein/kg/day (low N diet) or 1.8 g protein/kg/day (high N diet). Fifteen mechanically ventilated critically ill patients were studied in a surgical intensive care unit. After at least two days of standard TPN, patients were randomly assigned to either the low or the high N diet. Ten patients were studied on the low N diet and 11 on the high N diet; 6 patients were studied on both diets. Nonprotein energy was supplied according to estimated energy requirements. For five consecutive days, the N balance was measured daily. Total urinary nitrogen (TUN) was analysed using the Kjeldahl method. There was no difference in N balance between the groups. On the low N diet, N balance was -0.113 +/- 0.088 and on the high N diet -0.113 +/- 0.109 g N/kg/day. In patients studied twice, N balance was -0.087 +/- 0.054 and -0.050 +/- 0.060 g N/kd/day respectively. Results of a previous pilot study showed that in 20 similar patients the N balance became 80% less negative (from -5.7 +/- 5.1 to -1.1 +/- 8.2 g N/day) when protein intake was increased from 0.9 to 1.5 g/kg/day. Since these results are consistent with other studies, we conclude that the optimal range of protein supply in this type of critically ill patients is approximately 1.1-1.5 g protein/kg/day.