饲喂半胱胺对绵羊小肠主要消化酶活性的影响

选取健康、体重相近的小尾寒羊公羔48只，随机分为4组，每组分别饲喂添加0、7．5、15和22．5mg／kgBW的半胱胺日粮，研究绵羊日粮中添加不同剂量的半胱胺对小肠内容物淀粉酶、胰蛋白酶和糜蛋白酶活性的影响。结果表明：绵羊小肠不同部位（十二指肠、空肠和回肠）淀粉酶、胰蛋白酶和糜蛋白酶活性不同，空肠淀粉酶、胰蛋白酶和糜蛋白酶活性显著高于十二指肠和回肠。绵羊日粮中添加不同剂量的半胱胺可影响小肠食糜中淀粉酶、胰蛋白酶和糜蛋白酶活性，随着日粮半胱胺添加量的增加，绵羊小肠内容物淀粉酶、胰蛋白酶和糜蛋白酶活性随之增高，但半胱胺的添加量达到一定程度时（22．5mg／kgBW），小肠内容物淀粉酶、胰蛋白酶和糜蛋白酶活性反而降低。因而在绵羊日粮中添加半胱胺时，一定要选择适宜的添加量。     

Differences in the digestive tract characteristics of broiler chickens fed on complete pelleted diet or on whole wheat added to pelleted protein concentrate

1. The effects of whole grains of wheat on the digestive tract of broiler chickens was studied. A complete pelleted feed was compared with free choice feeding of whole wheat and a pelleted protein concentrate, given from 7 to 29 d of age. 2. Pepsin activity in proventriculus tissue was lower in whole wheat-fed birds than in complete diet-fed birds. The weight (g/kg body weight) of the gizzard was higher in whole wheat-fed birds and its contents had a lower pH. 3. In the intestine, there were no differences in deoxyribonucleic acid (DNA) concentration, protein/DNA, ribonucleic acid (RNA)/DNA, RNA/protein ratios or alkaline phosphatase activity expressed per tissue weight. The weight (g/kg body weight) of the duodenum was lower in whole wheat-fed birds and its contents had a higher pH. Also the activities of alkaline phosphatase and leucine aminopeptidase in the duodenum, and maltase in the ileum, expressed per unit of bird weight, were lower in whole wheat-fed birds. 4. These results suggest that whole grain feeding increases the chemical (pepsin in proventriculus) and physical (gizzard muscle) functionality of the upper part of the digestive tract but decreases the digestive capacity of the intestine. Higher gizzard functionality may play a positive role in the control of bacterial populations. The lower digestive enzyme activities in the intestine may be detrimental in situations of mucosal deterioration caused by intestinal disease.     

Phase 1 and phase 2 metabolic activities along the small intestine in adult male sheep

Maté, L., Virkel, G., Lifschitz, A., Sallovitz, J., Ballent, M., Lanusse, C. Phase 1 and phase 2 metabolic activities along the small intestine in adult male sheep. J. vet. Pharmacol. Therap. 33 , 537–545. Metabolic activities of several xenobiotic metabolizing enzymes were evaluated in both hepatic and enteric subcellular fractions obtained from Corriedale × Merino crossbreed rams by using a biochemical approach. Microsomes obtained from the different segments of sheep small intestinal mucosa displayed cytochrome P450 (CYP)‐dependent N‐demethylations but not O‐deethylase activities apparently occurred. CYP‐mediated N‐demethylations neither decreased nor increased along the small intestinal mucosa. Percentages of activity for erythromycin N‐demethylase in the small intestine were between 29% (duodenum) and 45% (ileum) from that measured in the liver, whereas those determined for triacetyl‐oleandomycin N‐demethylation ranged between 10% (duodenum) and 15% (jejunum) of the same hepatic activity. Conversely, metabolic rates for aminopyrine and chlorfeniramine N‐demethylations in the gut mucosa ranged between 3% and 7% compared to their respective hepatic enzyme activities. Sheep enteric mucosa also displayed metabolic reactions typically mediated by flavin‐containing monooxygenases (FMOs), carbonyl reductases (CBRs), carboxylesterases (CES), glutathione S‐transferases (GSTs) and uridine diphosphoglucuronyltransferases (UGTs). The FMO‐mediated sulfoxidation of methimazole was 2.6‐fold higher (P < 0.01) in the ileal compared to the duodenal mucosa. Percentages of activity for the microsomal CBR‐dependent biotransformation of menadione were between 12% (ileum) and 19% (duodenum–jejunum) of the total activity measured in the liver; metabolic rates measured in duodenum and jejunum were ～1.7‐fold higher (P < 0.05) than that observed in the ileum. The microsomal CES activity (using p‐nitrophenyl acetate as substrate) was around twofold higher in duodenum (P < 0.05) and jejunum (P < 0.01) in comparison to the ileum. Cytosolic GST‐dependent activities (toward 1‐chloro, 2,4‐dinitrobenzene) were similar in the mucosa of duodenum, jejunum and ileum. Microsomal UGT activities (toward 1‐naphthol) in duodenum and jejunum were three‐ and fourfold higher, respectively, compared to that measured in the ileum. The small intestinal mucosa may play a critical defensive role due to its involvement in the detoxification of toxic compounds prior to absorption. In addition, gut metabolic reactions may contribute to the presystemic metabolism of orally administered drugs. These results are a further contribution to the understanding of the relevance of the extra‐hepatic metabolism of xenobiotics in ruminant species.     

谷氨酰胺替代饲用抗生素对黄羽肉鸡免疫器官指数及小肠黏膜免疫的影响

本试验旨在研究基础日粮中添加谷氨酰胺替代饲用抗生素对黄羽肉鸡免疫器官指数及小肠黏膜免疫的影响。将180只1日龄体重相近、健康的黄羽肉鸡随机分为5个处理组,每个处理组3个重复,每个重复12只。阴性对照组饲喂基础日粮,阳性对照组在基础日粮中添加0.3 g/kg那西肽和0.25 g/kg硫酸黏杆菌素,试验Ⅰ、Ⅱ、Ⅲ组分别在基础日粮中添加1、2、3 g/kg谷氨酰胺。结果显示,试验Ⅰ、Ⅱ、Ⅲ组黄羽肉鸡免疫器官重量及免疫器官指数与阳性、阴性对照组相比差异均不显著(P＞0.05),且各试验组之间差异也不显著(P＞0.05)。45 d 时,试验Ⅰ、Ⅱ组黄羽肉鸡十二指肠、空肠肠黏膜蛋白质中溶菌酶的含量低于阳性对照组,但差异不显著(P＞0.05);与阳性对照组相比,试验Ⅰ、Ⅱ、Ⅲ组和阴性对照组的十二指肠内容物中细菌数量均显著提高(P＜0.05)。77 d时,试验Ⅰ、Ⅱ、Ⅲ组十二指肠、空肠、回肠肠黏膜蛋白质中溶菌酶的含量均与阳性对照组差异不显著(P＞0.05);十二指肠黏膜蛋白质中分泌型免疫球蛋白A的含量均低于阳性、阴性对照组;回肠内容物中乙酸、丙酸及总酸的浓度均低于阳性对照组,高于阴性对照组。因此,在基础日粮中添加谷氨酰胺替代饲用抗生素可能会提高黄羽肉鸡的细胞免疫水平,改善小肠黏膜免疫功能。     

Species differences in hepatic biotransformation of the anthelmintic drug flubendazole

Flubendazole (FLBZ) is a broad‐spectrum benzimidazole anthelmintic used in pigs, poultry, and humans. It has been proposed as a candidate for development for use in elimination programmes for lymphatic filariasis and onchocerciasis in humans. Moreover, FLBZ has shown promise in cancer chemotherapy, particularly for neuroblastoma. This work investigated the hepatic carbonyl‐reducing pathway of FLBZ in different species, including humans. Microsomal and cytosolic fractions were obtained from sheep, cattle, pig, hen, rat, and human liver. Both subcellular fractions of each species converted FLBZ into a reduced metabolite (red‐FLBZ). The rate of microsomal red‐FLBZ production was highest in sheep (1.92 ± 0.13 nmol/min.mg) and lowest in pigs (0.04 ± 0.02 nmol/min.mg); cytosolic red‐FLBZ production ranged from 0.02 ± 0.01 (pig) to 1.86 ± 0.61 nmol/min.mg (sheep). Only subcellular fractions from sheep liver oxidized red‐FLBZ to FLBZ in a NADP⁺‐dependent oxidative reaction. Liver microsomes from both pigs and humans transformed FLBZ to red‐FLBZ and a hydrolyzed metabolite. Very significant differences in the pattern of FLBZ metabolism were observed among the tested species and humans. These results reinforce the need for caution in extrapolating data on metabolism, efficacy, and safety of drugs derived from studies performed in different species.     

Comparative metabolism of R(-)-fenoprofen in rats and sheep

The chiral inversion of 2-arylpropionic acids occurs in many species. It is a unique reaction specific to this group of drugs. In this study R-(-)-fenoprofen (R-(-)-FPF) was used as a model compound to investigate metabolic chiral inversion in sheep in vivo and in vitro and to compare the data with the results obtained in rats. Metabolic inversion in sheep was 80%. The apparent mean values of Km and V _max of thioester formation were: 392 μm and 2.08 nmol/min/mg in sheep and 500 μm and 22 nmol/min/mg in rats. For hydroxylation, the apparent mean values were V_max: 0.02 nmol/min/mg in rats and 0.01 nmol/min/mg in sheep. There was no correlation between in vitro thioesterification and in vivo chiral inversion in sheep as compared to rats. In sheep most of the thioester formed underwent inversion (80%) while in rats, where in vitro thioesterification was greater, in vivo inversion was less (42%). In consequence, in rats other metabolic pathways for R(-)-FPF-CoA, such as incorporation into triacylglycerols and conjugation with amino acids, may be quantitatively more important     

犊牛胰腺和小肠消化酶变化规律的研究

试验选用黑白花公犊牛21头,研究我国常规饲养管理条件下0～6月龄犊牛胰腺与小肠中主要消化酶的发育规律和变化模式。结果表明:小肠中胰蛋白酶、淀粉酶和脂肪酶活性随月龄的增长而增强,且在空肠段中酶活性均较高,6月龄分别达到11.73、914.03U/g蛋白质和423.23U/g蛋白质,乳糖酶则随月龄的增长活性降低;胰淀粉酶活性随月龄显著增长(P<0.05),0月龄胰脏内淀粉酶活性为177.19U/g蛋白质,2月龄酶活达5605.67U/g蛋白质,比0月龄增长32倍;脂肪酶活性0～1月龄间差异不显著(P>0.05),2月龄酶活显著增高(P<0.05)。由此可见各种消化酶的变化规律是不同的,它们在十二指肠、空肠和回肠的分布具有明显的区域性,空肠是营养物质消化的主要部位。     

Histological studies on cow intestinal mucosa and electron microscopic studies of the ruminal epithelium of cows fed a deficient diet for a prolonged time]

Histological and histochemical studies were carried out on the gastro-intestinal mucosa of three experimental cows (roughages/maize silage) and three control animals. The animals were slaughtered on termination of the long-term trial. Mucosa samples were taken, for further study, from the rumen, the duodenum, the jejunum, the large intestine and the appendix. Histochemical analysis did not reveal any essential differences in the activities of non-specific esterase, alkaline and acid phosphatase and lactic acid dehydrogenase in the mucosa of the rumen, the large and the small intestine and the appendix of both the experimental animals and the controls. The experimental animals were found to exhibit a higher rate of glutamate-dehydrogenase activity in the ruminal mucosa and in the mucosa of the large and small intestine. A higher succinate dehydrogenase activity was observed in the ruminal mucosa of the experimental animals, relative to that of the controls, while the activity in the intestinal mucosa was decreased. Only slight changes were noted in the activity of the enzymatic systems tested. Electron microscopic studies did not reveal any differences in the ultrastructure of the epithelial cells of the ruminal mucosa in both the experimental animal and the controls.     

Biochemical aspects of the toxic effects of Supermethrin and the histochemical activity of alkaline phosphatase, acid phosphatase and non-specific esterase in subchronic poisoning in sheep]

Fifteen Slovak Merino sheep were included in the experiment. The animals weighing 21-28 kg were divided into three groups per five animals. In a six-week feeding experiment the animals of group I were given 50 mg supermethrin per kg live weight per day while those of group II received 200, and from week four of the experiment 300 mg supermethrin per kg live weight per day. During the experiment changes of aspartate aminotransferase (EC 2.6.1.1), alanine aminotransferase (EC 2.6.1.2), acetylcholine esterase (EC 3.1.1.7), urea und creatinine levels in blood serum were observed. Six weeks after supermethrin treatment the sheep were slaughtered and histochemical evaluation of alkaline phosphatase (EC 3.1.3.2), acid phosphatase (EC 3.1.3.1) and non-specific esterase (EC 3.1.1.1) was carried out in liver, kidney, duodenum, jejunum and ileum. In the course of the experiment changes of the enzymatic activities of aspartate aminotransferase observed in both experimental groups of sheep were similar to those seen in the control group of animals (Tab. I). As compared to the starting values, no significant changes in the activity of alanine aminotransferase were observed in group II of the experiment and in the controls. However, a significantly decreased alanine aminotransferase activity could be seen in the blood serum of sheep of group I (Tab. II). In both experimental groups of animals no significant changes in the acetylcholine esterase could be seen (Tab. III). As compared to the starting values, no significant changes were observed in creatinine levels of the control and the 1st experimental group of sheep (Tab. IV). In the sheep of the 2nd group a temporary significant decrease (p < 0.05) in creatinine levels was seen. The dynamics of urea levels was similar to starting values in all animals throughout the experiment Tab. V). In the control group of animals (Fig. 1) the high density of reaction product of alkaline phosphatase was determined in the microvilli of enterocytes of the small intestine. In the small intestine of the animals of both experimental groups, the activity of this enzyme was shown to be located in the same zone (Fig. 2). In all experimental animals in the parenchyma of the liver and kidney no significant changes could be observed. In both experimental and control animals the high activity of acid phosphatase was demonstrated to be located especially in the cytoplasma of enterocytes. The activity of non-specific esterase was located in the cytoplasma of enterocytes of the small intestine, in the intestinal crypts its activity was slight up to high.(ABSTRACT TRUNCATED AT 400 WORDS)     

Influence of abomasal carbohydrates on small intestinal sodium-dependent glucose cotransporter activity and abundance in steers

Most animals adapt readily to increased supplies of carbohydrate in the intestinal lumen by increasing enzymes for degradation and increasing glucose transporter activity. However, the extent of upregulation of Na+-dependent glucose cotransporter 1 (SGLT1) activity and content in response to increased delivery of carbohydrate to the small intestinal lumen of ruminants is unclear. Therefore, an experiment was conducted to determine the effect of glucose and starch hydrolysate on the activity and abundance of SGLT1 in the small intestine of steers. In a randomized complete block design, 40 crossbred beef steers (243+/-2 kg BW) were fed 0.163 Mcal of ME/(kg BW0.75(d; W), 0.215 Mcal of ME/(kg BW0.75 x d; 2M), or 0.163 Mcal ME/(kg BW0.75 x d) and infused for 35 d into the rumen (R) or abomasum (A) with 12.6 g/(kg BW0.75 x d) of starch hydrolysate (S) or into the abomasum with 14.4 g/(kg BW0.75 x d) of glucose (G). Steers were slaughtered, and brush-border membrane vesicles were prepared from the small intestinal samples obtained from five equidistant sites along the intestine. Maltase activity in vesicles and homogenates differed with intestinal sampling site (quadratic, P < 0.001). Steers on the AG treatment yielded a greater intestinal maltase activity (38 nmol glucose x mg protein(-1) x min(-1)) compared with the AS, RS, W, or 2M treatments (34, 26, 23, and 23 nmol glucose x mg protein(-1) x min(-1) respectively [SEM = 3; P = 0.02]). Sodium-dependent glucose uptake averaged 18.4+/-3.94 pmol glucose/(mg protein x s) and was not affected by treatment, but uptake decreased distally along the intestine (P < 0.001). There was no effect of treatment on SGLT1 protein abundance, but SGLT1 protein abundance increased linearly from the duodenum to the ileum (P = 0.05). The inverse relationship between glucose uptake and SGLT1 abundance suggests that the regulation of brush border Na+-dependent glucose transport capacity is complex, involving factors other than the presence of luminal carbohydrate.     

Dehydrogenase activity in small intestine mucosa in experimental coccidiosis in suckling pigs]

The activities of 3-beta-hydroxybutyrate dehydrogenase (EC. 1.1.1.30.; HBD) and isocitrate dehydrogenase (EC. 1.1.1.41; ICD) were evaluated microdensitometrically in the mucosa of duodenum, jejunum and ileum of 19 conventional piglets infected on the first day after parturition (DAP) with oocysts of Eimeria debliecki coccidium (infection dose of 200,000 oocysts). The two investigated enzymes are deposited in mitochondria which are dispersed in the supra-, para- and infranuclear region of absorption cells (Fig. 1). The synthesis of the two dehydrogenases was investigated in the small intestine mucosa in the period of 1st to 10th day after infection (DAI). The HBD and ICD activities were also followed in the small intestine of four control conventional piglets at the age of 2-5 days (Tab. I). The two dehydrogenases could be characterized by a topographic gradient; it means that their activity was increasing in the small intestine mucosa through duodenum in an aboral direction. The ICD activity is higher in the intestinal mucosa of healthy piglets (Figs. 2 and 3), where its topic concentration was more marked while the HBD activity is dispersed in enterocytes (Fig. 4). In infected piglets the density of the two enzymes was demonstrated to decrease already in the starting period of experimental infection, and it reaches the lowest values for the first time on DAI 5-6 (Fig. 5, Tab. II), then on DAIs 9 (HBD; Fig. 6, graph 11)) or 8 (ICD, Fig. 7 and 10). In the period of experimental infection no statistically significant predisposition to the hypoactivity of target dehydrogenases nor its marked shift were observed. Somewhat rapid resumption of synthesis was demonstrated as soon as on DAI 8 in ICD (Fig. 8); its activity on DAI 10 in the intestinal mucosa corresponded to the 93% activity of this dehydrogenase recorded in the small intestine of control piglets. The density of HBD to the same day (DAI 10) reached in the intestinal mucosa of infected piglets the values making only 44.7% of those demonstrated in the intestinal mucosa of the control group of animals.     

Developmental changes in morphometry of the small intestine and jejunal sucrase activity during the first nine weeks of postnatal growth in pigs

The objective of this study was to investigate the development of small intestinal size and digestive capacity of the jejunum in growing pigs. The weight, length, surface area, and mucosa weight of the small intestine were measured when pigs were 1, 3, 5, and 9 wk of age. Sucrase and alkaline phosphatase (ALP) activities of the jejunal brush-border membrane, prepared by differential centrifugation and Mg2+ precipitation, were determined at the respective postnatal stages. Body weights increased 7-fold from 2.7 kg at 1 wk to 23.32 kg at 9 wk postnatal. Body weight gains were greater (P < 0.05) from wk 3 to 5 than from wk 1 to 3. Weights of the small intestine and of the intestinal mucosa increased faster (P < 0.05) from 3 to 5 wk than from 1 to 3 wk; the slowest increase occurred from 5 to 9 wk. Weights of the duodenum, jejunum, and ileum, and mucosa from the respective sections increased (P < 0.05) as pigs grew from 3 to 9 wk. Mucosa weight relative to the weight of the section was greater (P < 0.05) for the duodenum and jejunum than for the ileum at 9 wk of age. Between the ages of 3 and 9 wk, the increase in mucosa weight was highest for the jejunum followed by the duodenum and the ileum. The increase was greatest for the duodenum followed by the jejunum and the ileum when mucosal weight was expressed per unit of appropriate intestinal section weight. There was a 55-fold increase in jejunal sucrase activity from 1 to 9 wk; the greatest rate of increase occurred between 5 and 9 wk. Total jejunal ALP activities in pigs at 9 wk was greater (P < 0.05) than at 5 wk, which in turn was greater than at 1 wk of age. In summary, increases in BW during the first 9 wk of postnatal growth in pigs are accompanied by significant developmental changes in digestive capacity including intestinal weights, length, and area as well as jejunal brush-border sucrase and ALP activities.     

Stimulatory effect of cold acclimation on skeletal muscle branched-chain α-keto acid dehydrogenase in rats

The effects of cold-acclimation (3 weeks at 4°C) on the actual activities of branched-chain α-keto acid dehydrogenase (BCKDH) and pyruvate dehydrogenase (PDH) complexes in the skeletal muscle and liver of normal 6-week-old rats were studied. The activities of BCKDH and PDH complexes were assayed using [1–¹⁴C] α-ketoisocaproate and [1-¹⁴C]pyruvate, respectively. Cold-acclimation markedly stimulated the activity of BCKDH, and slightly but significantly increased the activities of PDH and citrate synthase (CS) in the skeletal muscle, but did not alter PDH, BCKDH or CS activities in the liver. The increase in muscle BCKDH activity (control rats, 1.45 ± 0.54 mU/g wet wt; cold-acclimated rats, 2.54 ± 0.50 mU/g wet wt; 75% increase: P  = 0.001) was much greater than the increases in PDH activity (84 ± 16 mU/g wet wt and 111 ± 25 mU/g wet wt; 32% increase: P  = 0.020) or CS activities (27 ± 3 μmol/min per g wet wt and 31 ± 2 μmol/min per g wet wt; 14% increase: P  = 0.046). These results suggest that, unlike PDH, BCKDH is not directly associated with the mitochondrial oxidative activity of the skeletal muscle of cold-acclimated rats. This study provides the first evidence that BCKDH in skeletal muscle responds selectively to cold-acclimation.     

Relationships of weight gain and behavior to digestive organ weight and enzyme activities in piglets

Organ weights and digestive enzyme contents of the pancreas, stomach and duodenum were measured in 75 nursing piglets at 21 d of age. Piglets were given creep feed from 10 d of age. Creep feed intake was less than 1.5 g.d-1.piglet-1 up to d 18; on d 19 and 20 it averaged 15 g.d-1.piglet-1. On d 10, piglets went to the feeder more frequently than on the following days. Feeding bouts were longer on d 16, 17 and 18 just prior to the increase in creep feed consumption. Means and SE for the parameters studied at 21 d of age were 7.01 +/- .18 mg for pancreas weight; 61,499 +/- 4,091 units of amylase (UA) and 1,510 +/- 110 UA/mg DNA; 2,962 +/- 189 units of chymotrypsin (UC) and 68.94 +/- 3.92 UC/mg DNA; 8.76 +/- .35 g for fundic mucosa weight; 558,875 +/- 49,287 units of pepsin (UP) and 12,338 +/- 1,175 UP/mg DNA; 1.75 +/- .06 g for duodenum weight; 1.39 +/- .07 units of maltase (UM) and .14 +/- .006 UM/mg DNA. Day-0 weight was not correlated with 21-d gain. Feeding behaviors were correlated positively with 21-d gains. Feeding behaviors and behaviors were correlated positively to pancreas total and specific enzyme contents as well as to stomach and duodenum weights, RNA/DNA ratios of the pancreas and the stomach and protein/DNA of the pancreas but were correlated negatively with specific and total pepsin and maltase activities. Variation was large in enzyme activities (cv = 35 to 82%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Intestinal morphology, brush border and digesta enzyme activities of broilers fed on a diet containing Cu2+-loaded montmorillonite

1. A total of 320 1-d-old Arbor Acres broiler chicks were used to investigate the effect of Cu(2+)-loaded montmorillonite (CM) on the growth performance, intestinal morphology and activities of brush border enzyme in the intestinal mucosa and digestive enzyme in the intestinal digesta of broilers. 2. The chicks were assigned randomly into 4 groups with 80 chicks per treatment. The 4 dietary treatments were: basal diet only (control group), basal diet + 2 g montmorillonite/kg, basal diet + 1 g CM/kg, and basal diet + 2 g CM/kg. The chicks were raised in cages and feed and water were provided ad libitum for a period of 42 d. 3. The addition of CM to the diet of broilers significantly increased body weight and feed efficiency. Similarly, birds receiving montmorillonite had higher feed efficiency than the control after 42 d of feeding. 4. Data on villus height and crypt depth for duodenum, jejunum and ileum indicated that treating the diet of broilers with either CM or montmorillonite improved the mucosal morphology of the small intestine. 5. The presence of CM in the diet of broilers significantly increased the activities of maltase, aminopeptidase N and alkaline phosphatase in small intestinal mucosa. However, the activities of protease, trypsin, chymotrypsin, amylase and lipase in small intestinal digesta of broilers fed on the CM-supplemented diet were slightly higher than control values.     

盐度对瘤背石磺(Onchidium struma)消化酶活性的影响

为探讨盐度对瘤背石磺(Onchidium struma)不同消化器官蛋白酶、淀粉酶和纤维素酶活性的影响,试验选用1 200只个体均一的瘤背石磺[初均重(16.82±2.14)g]随机分成5组,分别置于不同盐度梯度(5、15、25、35和45)下饲养,期间用海泥与螺旋藻粉(m∶m=5∶1)拌饲投喂。每组设置3个重复,每个重复80只,饲养30 d后测定消化道不同器官蛋白酶、淀粉酶和纤维素酶活性。试验结果显示:1)各消化酶在幽门胃、贲门胃、肝胰腺和肠中均有分布,但各消化器官之间酶活性差异显著(P<0.05)。不同消化器官中蛋白酶活性由大到小依次为幽门胃[(91.46±0.57)U/g]、肝胰腺[(72.63±0.59)U/g]、肠[(44.78±0.66)U/g]和贲门胃[(40.12±0.45)U/g];淀粉酶活性由大到小依次为肝胰腺[(87.11±1.31)U/mg]、幽门胃[(45.72±1.06)U/mg]、肠[(26.52±1.05)U/mg]和贲门胃[(23.68±0.82)U/mg];纤维素酶活性以肝胰腺[(2.02±0.01)U/mg]最高,其次是肠[(1.01±0.01)U/mg],最低的是幽门胃[(0.53±0.01)U/mg]。2)盐度对各种消化酶活性的影响差异显著(P<0.05)。除肝胰腺中的蛋白酶以外,幽门胃、贲门胃、肝胰腺和肠中各消化酶活性随盐度升高均呈先上升后下降的趋势,且淀粉酶和纤维素酶分别在盐度15和25时活性最高,盐度45时活性最低。试验结果表明,低盐度(盐度5～25)对各消化器官消化酶活性均具有激活作用;其中,盐度15～25时消化酶活性最高,有利于瘤背石磺对饵料的消化吸收;而当盐度高于25时,则会抑制消化酶活性。     

Synthesis of citrulline from ornithine by the small intestinal mucosa of cattle

Three segments of cattle small intestine (duodenum, upper jejuno‐ileum and lower jejuno‐ileum) were examined in an in vitro system for activity of ornithine carbamoyltransferase (OCT; EC 2.1.3.3) which is involved in the synthesis of citrulline (Cit) from ornithine (Orn). The mucosa of the three segments of small intestine was collected from Japanese black cattle, homogenized and then centrifuged. The supernatant fraction was used as the crude OCT enzyme solution. The OCT activity was assayed by the production of Cit from Orn determined directly by HPLC. The optimal pH and temperature for OCT activities in the duodenum, upper jejuno‐ileum and lower jejuno‐ileum of cattle small intestine were 7.47 and 39°C. Little difference was observed between the three segments. The OCT activity in cattle kidney was also examined for comparison, and almost no activity was found. The OCT activities in crude enzyme solutions of the three segments of small intestine were stable for up to one month of storage at ?20°C in Tris HCl buffer solution. Finally, the role of the small intestine in supplying Cit as a precursor for arginine synthesis in cattle kidney was discussed.     

抗菌肽对发酵床饲养仔猪生长性能、消化酶及垫料理化性质的影响

试验旨在研究发酵床饲养模式下饲粮中添加抗菌肽对仔猪生长性能、胰腺和小肠内容物消化酶及小肠黏膜二糖酶和垫料蛋白酶、脲酶、铵态氮的影响。选用108头35日龄、体重13kg左右的健康苏钟猪随机分为3组,每组3重复,每重复12头,分别饲喂基础饲粮（对照组）、基础饲粮＋40mg/kg杆菌肽锌＋20mg/kg硫酸黏杆菌素（抗生素组）和基础饲粮＋300mg/kg抗菌肽（抗菌肽组）的试验日粮,试验期49d10结果表明：（1）各组间仔猪生长性能差异不显著（P〉0.05）。（2）与对照组相比,饲粮中添加抗菌肽能够显著提高仔猪胰腺、十二指肠和空肠内容物淀粉酶及空肠内容物胰蛋白酶活性（P〈0.05）;并显著提高仔猪十二指肠黏膜麦芽糖酶和空肠黏膜蔗糖酶、乳糖酶及回肠黏膜蔗糖酶活性（P〈0.05）;抗菌肽组十二指肠黏膜麦芽糖酶活性比抗生素组提高（P〈0.05）。（3）各组间发酵床垫料蛋白酶和脲酶活性及铵态氮含量差异不显著（P〉0.05）。综上所述,本试验条件下,饲粮添加300mg/kg的抗菌肽能够在一定程度上提高仔猪生长性能;提高胰腺、小肠内容物及小肠黏膜消化酶活性;同时不影响垫料蛋白酶、脲酶活性和垫料铵态氮含量。     

High performance liquid chromatography determination of cytochrome P450 1A and 2C activities in bovine liver microsomes

This study reports fluorescence high performance liquid chromatography (HPLC) and UV-Vis HPLC methods for the determination of 7-ethoxyresorufin O-deethylase (EROD) and tolbutamide methylhydroxylase (TMH) activities, respectively, using bovine liver microsomes. The detection limits were 0.022 and 5.5 pmol on the column, respectively; intra-day and inter-day precisions (expressed as relative standard deviation) were <10%. Both methods showed enough sensitivity to allow for an accurate determination of enzyme kinetic parameters according to Michaelis-Menten plots and the results were: K(m)=0.23+/-0.051 microM, V(max)=0.488+/-0.035 nmol/min/mg protein for EROD activity, and K(m)=1010+/-155.7 microM, V(max)=0.089+/-0.006 nmol/min/mg protein for TMH activity. An Eadie-Hofstee plot analysis showed that in bovine liver microsomes, EROD and TMH activities followed a monophasic kinetic pattern. alpha-Naphthoflavone, a cytochrome P450 1A1/2 (CYP1A1/2) inhibitor, and sulfaphenazole, a cytochrome P450 2C9 (CYP2C9) inhibitor, decreased EROD and TMH activities, respectively. The sensitivity of the methods allowed the use of microsomes with low enzyme activity, such as those from veal calf liver. Thus, EROD and TMH activities may be adopted as markers for the evaluation of CYP1A and CYP2C9-like activities in liver microsomes from veal and beef cattle.