Quantification of gut injury with diamine oxidase activity: development of a fission neutron RBE and measurements with combined injury in mouse models

Plasma and small intestine diamine oxidase (DAO) activities were measured on Days 2, 4, and 6 following irradiation of mice with a range of doses of fission neutrons and 60Co. With increasing doses of radiation, plasma DAO activity increased on Day 2 and intestinal DAO activity decreased on Day 4; moreover, the approximate relative biological effectiveness values for these changes in activity were 5.81 for plasma DAO activity on Day 2 and 3.88 for intestinal DAO activity on Day 4. On Day 6 relatively high levels of radiation caused DAO activity in the small intestine to remain depressed whereas low levels resulted in recovery with activities at or near controls. In animals with combined injury (radiation plus 30% surface burn or wound), changes in DAO activity in the intestine were similar to those with radiation alone; plasma DAO activity, in contrast to radiation alone, did not show an increase at the 2-day mark. These dose-dependent relationships should provide a basis for using DAO as a potential indicator of biological damage from radiation exposure within the lethal range.     

胰高血糖素样肽-2对小鼠小肠缺血/再灌注损伤的保护作用

目的:观察胰高血糖素样肽-2(GLP-2)对缺血/再灌注损伤小鼠小肠的保护效应.方法:采用肠缺血/再灌注(I/R)模型,将32只小鼠随机分为4组(n=8)假手术(Sham)组、I/R组、I/R GLP-2保护组和I/R 谷氨酰胺(GLN)阳性对照组.光镜观察小肠黏膜形态学改变.检测小肠绒毛高度和隐窝深度;小肠组织二胺氧化酶(DAO)活性;肠系膜淋巴结(MLN)细菌易位率.结果:与假手术组相比,I/R组部分小肠绒毛坏死脱落,绒毛高度下降,隐窝变浅(P＜0 01);小肠组织DAO活性降低(P＜0.01);MLN细菌易位率增加(P＜0.05).与I/R组比,GLP-2组肠绒毛损害明显减轻,DAO活性回升(P＜0.01),细菌易位率回降(P＜0.05).结论:GLP-2对缺血/再灌注损伤小鼠小肠的形态结构及肠屏障功能具有保护作用.     

Biochemical, physiological and pathophysiological aspects of intestinal diamine oxidase

Studies were performed on the distribution and properties of intestinal diamine oxidase (DAO) previously called histaminase. DAO activity is high in the gastrointestinal tract of all investigated species. The highest values are in the aboral part of the small intestine: where DAO is localized in the mucosa, predominantly in the top villus region. A high reaction velocity of human intestinal DAO is observed with putrescine, methylhistamine and histamine. H2 receptor antagonists and an agonist (impromidine) inhibit intestinal DAO. The physiological and pathophysiological significance of intestinal DAO in the regulation of histamine and putrescine levels is described, as is the possibility that DAO may act as a growth retardant.     

急性冷胁迫对中华鳖幼鳖肠道黏膜组织的影响

为了探究急性冷胁迫对中华鳖(Pelodiscus sinensis)幼鳖肠道不同区段黏膜组织学特征的影响, 实验检测了急性冷胁迫前后血清二胺氧化酶(Diamine oxidase, DAO)的活性, 同时观察了急性冷胁迫前后中华鳖肠道黏膜的相关组织形态的差异。DAO活性显示: (1)在第一次急性冷胁迫实验中, 中华鳖血清DAO活性随急性冷胁迫时间的增加而呈现降低趋势, 并在冷胁迫到达48h降到了最低水平; (2)在急性冷胁迫及复温实验中, 中华鳖血清DAO的活性, 在冷胁迫3d后显著降低, 但随着温度的恢复, DAO活性又恢复到正常水平。组织病理结果显示: (1)急性冷胁迫对中华鳖肠道(回肠后段和大肠)黏膜上皮的形态没有明显影响; (2)急性冷胁迫对回肠后段的杯状细胞数目、肠绒毛长度和绒毛长度/隐窝深度的比值没有显著影响, 但会使回肠后段黏膜厚度显著降低; (3)急性冷胁迫会使大肠的杯状细胞数目降低。这表明急性冷胁迫会改变中华鳖肠道黏膜的结构, 但在不同的肠段, 这种改变是不同的。回肠后段和大肠在同样的冷胁迫方式下黏膜机械屏障的不同变化情况, 提示中华鳖肠道各段对急性冷胁迫具有特殊的应对方式。     

参麦注射液对严重烫伤大鼠肠道屏障功能的保护作用

目的:探索参麦注射液对30% Ⅲ°烫伤早期肠道屏障功能的保护作用,为参麦注射液防治肠源性感染提供实验依据。方法:Wistar大鼠60只,随机分为正常对照组、模型对照组,地塞米松5 mg/kg组、参麦注射液5、10、15 mg/kg组,每组10只,使用烫伤仪建立30% Ⅲ°烫伤动物模型,立即腹腔注射相应的药物,每天1次。烫伤72 h后,检测肝脏、脾脏、肠系膜淋巴结细菌移位量、血浆内毒素、二胺氧化酶(DAO)、肿瘤坏死因子-α(TNF-α)及白细胞介素-6(IL-6)水平和肠粘膜分泌型免疫球蛋白A(sIgA)的水平。结果:与正常对照组比较,模型组肝脏、脾脏、肠系膜淋巴结细菌移位量,血浆内毒素、DAO、TNF-α及 IL-6和肠黏膜sIgA水平明显升高(P＜0.01);与模型组比较,地塞米松组和参麦注射液5、10、15 mg/kg组肝脏、脾脏、肠系膜淋巴结细菌移位量,血浆内毒素、DAO、TNF-α及 IL-6和肠黏膜sIgA水平明显降低(P＜0.05或P＜0.01)。结论:参麦注射液可减轻严重烫伤引起的肠粘膜损伤,效果与地塞米松相当,高剂量组效果更好。     

Protective effects of N-acetylcysteine on intestinal functions of piglets challenged with lipopolysaccharide

The neonatal small intestine is susceptible to damage by endotoxin, but effective methods for prevention and treatment are lacking. N-acetylcysteine (NAC) is a widely used precursor of L: -cysteine for animal cells and plays an important role in protecting cells against oxidative stress. This study was conducted with the lipopolysaccharide (LPS)-challenged piglet model to determine the effects of NAC on intestinal function. Eighteen piglets were randomly allocated into control, LPS and LPS?+?NAC groups. The control and LPS groups were fed a corn- and soybean meal-based diet, and the LPS?+?NAC group was fed the basal diet +500?mg/kg NAC. On days 10, 13 and 20 of the trial, the LPS and LPS?+?NAC groups received intraperitoneal administration of LPS (100?μg/kg BW), whereas the control piglets received saline. On day 20 of the trial, D-: xylose (0.1?g/kg BW) was orally administrated to all piglets 2?h after LPS or saline injection, and blood samples were collected 1?h thereafter. One hour blood xylose test was used to measure intestinal absorption capacity and mucosal integrity, and diamine oxidase (DAO) was used as a marker of intestinal injury. On day 21 of the trial, pigs were killed to obtain the intestinal mucosa. Compared to the control, LPS challenge reduced (P?相似文献   

分光光度法测定血和小肠组织二胺氧化酶活性

本研究应用分光光度法,测定了健康人血,大鼠小肠组织和血二胺氧化酶（ＤＡＯ）活世。本法简便、经济、速度快、重复性好,测定ＤＡＯ活性,能反应小肠结构和功能情况,对实验和临床均有实用价值。     

梗阻性黄疸大鼠胆汁内、外引流术后血浆二胺氧化酶活性变化与肠粘膜屏障变化的相关性研究

目的:探讨梗阻性黄疸大鼠行胆汁内、外引流术后血浆二胺氧化酶的活性变化与肠粘膜屏障的关系。方法:取健康成年雄性SD大鼠60只,随机分为四组:梗阻性黄疸组(OJ)、胆汁外引流组(ED)、胆汁内引流组(ID)及假手术对照组(SH),各组均15只;SH组、OJ组在术后第7天处死大鼠并采集标本,ID组、ED组于引流术后7天处死大鼠并采集标本,检测各组大鼠血浆DAO的活性,光镜下观察末端回肠组织粘膜形态学变化。结果:OJ组大鼠肠粘膜损伤明显,粘膜变薄、绒毛稀疏、上皮完整性受到破坏并伴有炎性细胞浸润,ID、ED组大鼠肠粘膜有不同程度的恢复,ID组更接近SH组;OJ组血浆DAO水平显著升高,明显高于SH、ID、ED组(8.183±0.211 vs 3.570±0.280、3.978±0.269、5.051±0.328 U/L,P0.01),ID组较ED组下降更明显,二者差异有统计学意义(P0.01),ID组血浆DAO水平略高于SH组,二者差异无统计学意义(P0.05);各组血浆DAO变化与肠粘膜组织病理学变化一致。结论:胆汁内、外引流术可降低梗阻性黄疸大鼠血浆DAO水平,内引流术效果优于外引流术;血浆DAO的变化可反映梗黄大鼠肠粘膜屏障损伤及修复情况。     

myo-inositol action on gerbil intestine: alterations in alkaline phosphatase activity upon phosphatidylinositol depletion and repletion in vivo

The influence of phosphatidylinositol (PI) on intestinal alkaline phosphatase activity was studied in myo-inositol deficient gerbils. A reduction of membrane PI in intestinal mucosa to 30-40% of the control was produced by feeding female gerbils a myo-inositol-deficient diet containing coconut oil for 2 weeks. As expected, the animals developed typical intestinal lipodystrophy with abnormal fat accumulation. In the PI-depleted animal, intestinal alkaline phosphatase activity was reduced to 20-30% of the control group. The levels of both membranous and soluble enzymes in intestinal mucosa were affected, but there were no changes in liver, kidney and plasma levels. When the lipodystrophic gerbils were given dietary myo-inositol, the complete repletion of intestinal membrane PI to the control level occurred 36 h later, whereas membrane-bound alkaline phosphatase activity in intestine was not restored to the control level until 72 h later. Administration of cycloheximide or actinomycin D did not block this enzyme induction. Lymphatic output of triacylglycerol into the bloodstream was stimulated 10-fold at 18 h of myo-inositol repletion, but there was no parallel increase in the activity of alkaline phosphatase in plasma during this early phase of intestinal recovery. Thus, these data suggest a possible regulatory role of PI in the processing and/or turnover of alkaline phosphatase in vivo, but a negative role of alkaline phosphatase in lipid transport across gerbil intestine.     

New aspects in the study of the mechanism of intestinal absorption of thiamine in rats

Intestinal absorption of thiamine was studied in rats using such metabolic inhibitors as ouabain, sodium azide and theophylline. These substances changed certain biochemical parameters of the mucosa in the small intestine affecting the level of thiamine transport across the intestinal epithelium. It was found that the intestinal transport of thiamine at lower concentration was an active process depending on the activity of Na, K, Mg-ATPase in the intestinal microvilli, and on the activity of mitochondrial processes. The used metabolic inhibitors increased the intestinal diffusion of thiamine at its higher concentration suggesting that these inhibitors changed membrane permeability by affecting enterocyte homeostasis. At both studied concentrations thiamine was rapidly absorbed from the digestive tract reaching the state of saturation which suggested a carrier character of this transport.     

Origin and deposition of basement membrane heparan sulfate proteoglycan in the developing intestine

The deposition of intestinal heparan sulfate proteoglycan (HSPG) at the epithelial-mesenchymal interface and its cellular source have been studied by immunocytochemistry at various developmental stages and in rat/chick interspecies hybrid intestines. Polyclonal heparan sulfate antibodies were produced by immunizing rabbits with HSPG purified from the Engelbreth-Holm-Swarm mouse tumor; these antibodies stained rat intestinal basement membranes. A monoclonal antibody (mAb 4C1) produced against lens capsule of 11-d-old chick embryo reacted with embryonic or adult chick basement membranes, but did not stain that of rat tissues. Immunoprecipitation experiments indicated that mAb 4C1 recognized the chicken basement membrane HSPG. Immunofluorescent staining with these antibodies allowed us to demonstrate that distribution of HSPG at the epithelial-mesenchymal interface varied with the stages of intestinal development, suggesting that remodeling of this proteoglycan is essential for regulating cell behavior during morphogenesis. The immunofluorescence pattern obtained with the two species-specific HSPG antibodies in rat/chick epithelial/mesenchymal hybrid intestines developed as grafts (into the coelomic cavity of chick embryos or under the kidney capsule of adult mice) led to the conclusion that HSPG molecules located in the basement membrane of the developing intestine were produced exclusively by the epithelial cells. These data emphasize the notion already gained from previous studies, in which type IV collagen has been shown to be produced by mesenchymal cells (Simon- Assmann, P., F. Bouziges, C. Arnold, K. Haffen, and M. Kedinger. 1988. Development (Camb.). 102:339-347), that epithelial-mesenchymal interactions play an important role in the formation of a complete basement membrane.     

双歧杆菌四联活菌片 对重症脑卒中患者肠道功能的影响

目的探讨双歧杆菌四联活菌片对重症脑卒中患者肠道菌群及肠黏膜屏障功能的影响。方法选择重庆市人民医院2017年1月至2017年11月收治的100例重症脑卒中患者,随机将入选患者分为治疗组和对照组各50例。治疗组在常规肠内营养(EN)治疗基础上联用双歧杆菌四联活菌片治疗,对照组给予常规EN治疗。比较两组患者治疗前后营养状况、肠道菌群数量和肠黏膜屏障功能。比较两组患者治疗后消化道并发症发生率。结果治疗前,两组患者营养状况、肠道菌群数量和肠黏膜屏障功能差异无统计学意义(P0.05)。治疗后,两组患者营养状况指标白蛋白(ALB)、血红蛋白(Hb)和三头肌肌围(MAMC)水平,肠道有益菌(双歧杆菌、乳杆菌和拟杆菌)数量均有所上升,肠黏膜屏障功能指标二胺氧化酶(DAO)、D-乳酸水平及肠道有害菌数量(小梭菌和肠球菌)均降低。与对照组相比,治疗组患者ALB、Hb和MAMC水平,肠道双歧杆菌、乳杆菌和拟杆菌数量均显著升高,DAO、D-乳酸水平和小梭菌、肠球菌数量均显著降低,差异有统计学意义(P0.05)。治疗组患者消化道并发症发生率均低于对照组(P0.05)。结论双歧杆菌四联活菌片能够显著改善脑卒中患者的营养状况,有效调节菌群失衡,改善肠黏膜屏障功能,降低并发症发生。     

双歧杆菌四联活菌片联合美沙拉嗪对溃疡性结肠炎患者肠黏膜氧化应激损伤的修复作用

目的探讨双歧杆菌四联活菌片联合美沙拉嗪对溃疡性结肠炎(UC)患者肠黏膜氧化应激损伤的修复作用。方法选取2016年10月至2018年12月我院内科门诊就诊的活动期轻、中度UC患者92例,随机分为观察组和对照组各46例。两组患者均给予美沙拉嗪肠溶片1.0 g/次,4次/d,口服。观察组在此基础上加用双歧杆菌四联活菌片1.5 g/次,3次/d,口服。两组均连用8周。观察两组患者治疗前后血清氧化应激指标[氧化低密度脂蛋白(ox-LDL)和过氧化脂质(LPO)]、肠黏膜屏障受损情况指标[血清降钙素原(PCT)和二胺氧化酶(DAO)]及肠镜下肠黏膜评分变化,并比较临床效果。结果治疗8周后,两组患者血清ox-LDL、LPO、PCT和DAO水平及肠黏膜评分均较治疗前显著下降(均P<0.05),且治疗后观察组患者上述指标水平下降幅度大于对照组(均P<0.05)。观察组患者临床总有效率(95.65%)高于对照组(82.61%),差异有统计学意义(χ^2=4.04,P<0.05)。结论双歧杆菌四联活菌片联合美沙拉嗪对轻中度活动性UC患者的疗效显著,能降低患者血清ox-LDL、LPO、PCT和DAO水平,对肠黏膜氧化应激损伤具有良好的修复作用。     

Low serum diamine oxidase (DAO) activity levels in patients with migraine

Histamine intolerance is a disorder in the homeostasis of histamine due to a reduced intestinal degradation of this amine, mainly caused by a deficiency in the enzyme diamine oxidase (DAO). Among the several multi-faced symptoms associated with histamine intolerance, headache is one of the most recognized and disabling consequences. The aim of this study was to determine the prevalence of DAO deficiency in patients with a confirmed migraine diagnosis according to the current International Headache Society (IHS) and in non-migraine subjects. DAO activity was assessed in a total of 198 volunteers recruited at the Headache Unit of the Hospital General de Catalunya, 137 in the migraine group and 61 as a control group. DAO enzyme activity in blood samples was determined by ELISA test. Values below 80 HDU/ml (Histamine Degrading Unit/ml) were considered as DAO deficient. Mean value of DAO activity from migraine population (64.5 ± 33.5 HDU/ml) was significantly lower (p < 0.0001) than that obtained from healthy volunteers (91.9 ± 44.3 HDU/ml). DAO deficiency was more prevalent in migraine patients than in the control group. A high incidence rate of DAO deficiency (87%) was observed in the group of patients with migraine. On the other hand, 44% of non-migranous subjects had levels of DAO activity lower than 80 HDU/ml. Despite the multifactorial aetiology of migraine, these results seem to indicate that this enzymatic deficit could be related to the onset of migraine.     

Development and fate of the postovulatory follicle complex,postovulatory follicle,and observations on folliculogenesis and oocyte atresia in ovulated common snook,Centropomus undecimalis (Bloch, 1792)

The common snook, Centropomus undecimalis , was induced to ovulate using a time‐release, GnRH analogue. Ovulation occurred the afternoon or evening the day after hormone administration. The time of ovulation was established within half an hour. At ovulation, three fish per time‐group were divided into 0, 6, 12, 18 hr and one thru five days post‐ovulation to study changes in the postovulatory follicle complex (POC). Histology of the ovaries revealed changes in the POC, postovulatory follicle (POF) and oocyte atresia through five days post‐ovulation. Within 24 hr, nuclei of the POF cells lost their initial spherical or oval configuration, and by four days the basement membrane within the POC had fragmented. There was a temporal separation between ovulation and post‐ovulation folliculogenesis; that is, in that the formation of new follicles commenced within the germinal epithelium between 12–48 hrs after ovulation. Morphology of the POC was best revealed with the reticulin stain; it is composed of the POF and postovulatory theca (POT). These are separated by a basement membrane, reflecting the origin of a follicle from a germinal epithelium while the theca is derived from stroma. The POF is composed of the former follicle cells that surrounded and contacted the oocyte during its development; the follicle is composed of the oocyte and its surrounding follicle cells. The POC is composed of a prominent basement membrane separating the POT from the POF. The reticulin stain clearly defines compartmentation in the ovary and supports redefinition of the POF as the follicle cells that formerly surrounded the oocyte prior to ovulation. J. Morphol. 278:547–562, 2017. © 2017 Wiley Periodicals, Inc.     

Increased plasma post-heparin diamine oxidase activity and plant sterol levels in streptozotocin diabetic rat.

Plasma post-heparin diamine oxidase (DAO) activity and plasma levels of plant sterols were examined in streptozotocin diabetic rats fed with chow containing plant sterols, to investigate the enzyme activity in relation to the morphological changes of small intestine as well as sterol absorption in the diabetic rats. Diabetic rats showed increased small intestinal mass and surface area compared with control rats. Plasma post-heparin DAO activity and plant sterol level were also increased more than 2.5-fold in the diabetic rats. Insulin treatment improved these abnormalities. Plasma DAO activity correlated to both the small intestinal hyperplastic change and plasma plant sterol levels. These results indicate that plasma post-heparin DAO activity may be used as a marker of intestinal hypertrophy as well as ability to absorb dietary sterols.     

Development and ultrastructure of Besnoitia oryctofelisi tachyzoites,tissue cysts,bradyzoites, schizonts and merozoites

Development and structure of different life cycle stages of Besnoitia oryctofelisi which has a rabbit-cat life cycle was studied by light and transmission electron microscopy. For light microscopy, Besnoitia oryctofelisi-infected tissues were stained with haematoxylin-eosin, periodic acid Schiff (PAS) reagent, and immunohistochemically with rabbit anti-B. oryctofelisi polyclonal antibodies and anti-BAG-1 antibodies. In vitro and in vivo-derived tachyzoites were 5-6 microm long and they were found to divide by endodyogeny. In tachyzoites, the nucleus was often central, and micronemes were few and located anterior to the nucleus. Earliest tissue cysts were seen in gerbils starting 12 days p.i. Early tissue cysts had an outer PAS-positive cyst wall, a middle PAS-negative host cell layer, and an inner PAS-negative parasitophorous vacuolar membrane. Organisms in early tissue cysts were PAS-negative, did not stain with anti-BAG-1 antibodies, and amylopectin granules and enigmatic bodies were absent. Tissue cysts beginning 17 days p.i. contained organisms that became PAS-positive and reacted with anti-BAG-1 antibodies, indicating they were bradyzoites. Immunoreactivity with polyclonal anti-B. oryctofelisi antibodies suggested that Besnoitia species bradyzoites are encapsulated by the host cell. Bradyzoites (10 microm) were about twice the length of tachyzoites and contained enigmatic bodies characteristic of Besnoitia bradyzoites. Unlike tachyzoites and tissue cysts, schizonts were located intravascularly in the lamina propria of the small intestine of cats. Merozoites were 5-6 microm long, had few rhoptries and amylopectin granules, had numerous micronemes and had a terminal nucleus.     

八珍制剂对~(60)Co辐射小鼠微生态失调的促恢复作用

目的　观察中药八珍制剂对60 Co辐射小鼠微生态失调的调整作用。方法　60 Co辐射昆明种小鼠制成微生态失调模型 ,用中药八珍制剂对其进行调整 ,检测肠道膜菌群与腔菌群中双歧杆菌、乳酸杆菌、肠杆菌、肠球菌及肝脏细菌易位数量 ,血浆内毒素水平 ,小肠黏膜中二胺氧化酶的活性和丙二醛的含量等指标 ,观测中药对辐射性微生态失调的调整作用。结果 :中药八珍制剂具有调整小鼠肠道菌群失调 ,降低肠道菌易位和血浆内毒素水平 ,减少丙二醛含量 ,升高肠黏膜中二胺氧化酶的活性。中药治疗组各项指标与自然恢复组相比 ,差异均有显著性(P <0 .0 0 1或P <0 .0 1或P <0 .0 5 )。结论　八珍制剂对60 Co辐射小鼠微生态失调有促恢复作用     

Reducing colonization of Salmonella Enteritidis in chicken by targeting outer membrane proteins

AIMS: To evaluate the ability of Salmonella enterica ser. Enteritidis outer membrane proteins (OMPs) of 75.6 and 82.3 kDa to inhibit or reduce in vivo colonization of S. Enteritidis on intestinal mucosa in chickens. METHODS AND RESULTS: Nine-week-old specific-pathogen-free chickens were subcutaneously immunized with 75.6 or 82.3 kDa protein, and challenged with a virulent strain of S. Enteritidis. Chickens were killed, and portions of small intestine and caecum were removed at necropsy. The population of S. Enteritidis attached to chicken intestinal mucosa was determined. The population of S. Enteritidis recovered from the small intestine and caecum of chickens immunized with 75.6 or 82.3 kDa protein was significantly (P < 0.05) lower than that recovered from the control birds. CONCLUSIONS: Salmonella Enteritidis OMPs 75.6 kDa and 82.3 kDa were effective in reducing colonization of S. Enteritidis on intestinal mucosa in chickens. SIGNIFICANCE AND IMPACT OF THE STUDY: Salmonella Enteritidis OMPs 75.6 or 82.3 kDa could be used as potential vaccines to reduce S. Enteritidis colonization in chickens.     

Radiation effects on diamine oxidase activities in intestine and plasma of the rat

Diamine oxidase (DAO; EC 1.4.3.6) activity was measured in plasma and in ileal tissue homogenates prepared from male Sprague-Dawley rats euthanized at 1-15 days after acute whole-body irradiation with 14.5-MeV electrons. Animals irradiated with 1 Gy showed no diminution in plasma and ileal DAO activities through Day 13 relative to nonirradiated controls. Animals irradiated with 5, 10, and 12 Gy displayed marked declines in ileal DAO activity, with levels reaching a nadir on Day 3. This was paralleled by a decrease in plasma DAO activity in all three dose groups. Recovery of ileal and plasma DAO levels was later seen as early as Day 4 in animals irradiated with 5- and 10-Gy doses, but animals receiving 12 Gy did not survive beyond Day 3. The relationship between radiation dose and levels of plasma and ileal DAO on Day 3, the time of maximum decrease at all doses, was also investigated. Ileal DAO activity decreased almost linearly between 2 and 8 Gy. Plasma DAO activity closely paralleled the dose dependency of the ileal levels. These data suggest that plasma DAO activity might be useful as a biologic marker of intestinal epithelial injury and recovery after acute radiation exposure.