哺乳动物消化道内食物滞留时间的影响因素

食物通过消化道的速率是消化道功能的一个重要量度.影响通过率的因素很多,往往是许多因素相互作用以控制通过率,同时通过率又影响消化道的许多功能.通过率是指单位消化道内容物经混合、消化、发酵和吸收等过程后滞留在消化道中的时间量度,所以通常用平均滞留时间(mean retention time,MRT)来描述食物在整个消化道或每个器官中的通过率(passage rate).所谓平均滞留时间是指消化道内容物在消化道的可吸收部位开始消化到残渣排出所需要的时间[1].Blaxter等[2]提出用如下公式计算平均滞留时间:     

黄羊消化道内不同大小食物颗粒的分布

研究了黄羊消化道内7个部位（瘤胃、网胃、瓣胃、皱胃、小肠、盲肠和直肠）食物粒径的分布规律。粒径大于0．1mm的大颗粒食物,在瘤、网胃中所占的比例较大,分别为57．8％和39．41％,在瓣胃以及瓣胃以下的消化道内容物中所占的比例急剧下降,小于10％;而粒径小于1．0mm的食物颗粒在瓣胃以及瓣胃以下的消化道中所占的比例却显著地增大,瓣胃中所占的比例为88％－95．2％。由于食物营养质量的季节性变化,黄羊消化道内食物粒径分布也呈现出明显的季节性变化。     

生态生物化学（九）：哺乳动物对食物的选择

哺乳动物是动物界发展程度最高的类群,胎生、哺乳是其主要特征。哺乳纲(Mammalian)现有3500余种,广泛分布于全球。从食性上可将哺乳动物分为植食性、肉食性和杂食性几类。大多数哺乳动物是杂食性的,能取食多种植物或动物。这一讲主要介绍植食性哺乳动物以及人对食物的选择。动物从食物中获取营养成份,以满足自身生长发育的需要。动物主要的营养成份是蛋白     

黑水虻幼虫的发育速率及食物转化率研究

本文研究了黑水虻Hermetia illucens幼虫取食花生麸的发育速率及其食物转化率。仔细考察了黑水虻卵孵化后,其幼虫平均体重的增长情况,结果显示,黑水虻在实验条件下（T=30℃,RH=60%）,幼虫发育的参考周期为20 d,其中最初5 d体重增长9433倍,从第6 d至第10 d体重增长7倍,最后10 d体重增长095倍,从初孵幼虫到老熟幼虫体重增长148667倍,发育期内的体重增长趋势类似于逻辑斯谛曲线,而第5 天（W=143 g/百头虫）与第10 天（W=1145g/百头虫）则为逻辑斯谛曲线的两个拐点。食物转化率测定结果表明,黑水虻幼虫取食花生麸的转化率为2888%。     

光周期和高脂食物对高山姬鼠消化道形态的影响

为探讨光周期和高脂食物对栖息于横断山地区高山姬鼠Apodemus chevrieri消化道形态的影响,将成年雌性高山姬鼠分别驯化于长光照低脂、高脂食物和短光照低脂、高脂食物条件下,7周后测定动物的体重、总消化道、胃、小肠、大肠、盲肠的长度及其含内容物重、去内容物重、干重。结果表明:短光低脂组总消化道长显著大于其他组,短光组的小肠长度显著大于长光组。总消化道含内容物重、去内容物重,胃去内容物重、干重以及大肠和盲肠的各项指标均是低脂食物组显著大于高脂食物组。而小肠干重则是高脂食物组显著大于低脂食物组。以上结果表明,高山姬鼠在光周期和食物质量不同的条件下,可能通过调节消化道形态来维持正常的能量代谢和生理机能。高山姬鼠的消化道在不同光周期和食物质量条件下表现出的变化模式,可能与其光照和食物资源季节性波动的野外生存环境有关,从一方面反映了该物种在不同环境下的生存机制和适应对策。     

狍冬季消化道形态特征及食物颗粒分布

1999年1月在黑龙江省通河县小东林场猎杀14只狍,应用解剖学方法和湿筛法分别对狍冬季消化道形态特征及消化道内食物颗粒分布进行了研究。结果表明,狍复胃中瘤胃比例最大,占71.3±2.6%,其次为皱胃(11.5士2.2%),瓣胃(9.7士2.3%),网胃(7.6士0.9%0);瘤胃粘膜中,瘤胃前庭区(ACF)是最重要的消化和吸收部位之一,具有最大的乳突密度、乳突长度和粘膜赓面扩张系数,显著高于其它区域(P< 0.05 ),后背盲囊区(DBF)次之;网瓣口在狍食物颗粒流通中起到了重要的调节作用,消化道食物颗粒分布中,大颗粒食物(>1.00mm)在瘤网胃中的比例为35.06±10.76%,显著高于其在瓣胃、皱胃及其它消化道内的比例(P<0.05),而小于1.00 mm的食物颗粒在瓣胃以下消化道中有明显的增加(P<0.05), 1.00mm为冬季通过狍网瓣口的临界食物颗粒大小。狍为适应冬季食物营养质量下降,通过增加瘤网胃容量、缩小网瓣口来改变消化道形态而增加食物颗粒在瘤网胃内的滞留时间,使富含纤维素的食物充分发酵和分解以获得更多的能量,从而产生营养适应性的季节变化。     

哺乳动物的消化策略（英文）

理解动物的营养生态位是充分理解其整个生态学的基础,对于害兽控制和物种保护也很重要,食肉动物的小肠很发达,这可能与对食物的高消化能力有关;杂食性动物有更复杂的胃肠器官,其后端有可进行发酵的盲肠,消化物的平均滞留时间（mean retention times,MRTs)更长;最长的平均滞留时间见于食草动物,其消化道内高密度的微生物种群对不同滞留区内的消化物进行发酵,但是,并不是所有的食草动物都能够最大程度地消化植物纤维,只有反刍动物、骆驼和个体较大的后肠发酵动物（hindgut fermenter)能够具有这种能力,对比而言,许多其它的食草动物,如前肠发酵的有袋类和小型的后肠发酵动物如兔子、田鼠和负鼠等,它们具备可以使植物纤维消化效率最大的消化系统,可以在食物中的纤维素含量非常高的情况下仍能处理大量的食物。这些不同的消化策略使哺乳动物具有广幅的营养生态位。     

7种荒漠啮齿动物食物组成与消化道长度的比较

对荒漠地带几种啮齿动物在自然环境中夏季主要食物组成以及消化道长度的适应性变化进行了比较。三趾跳鼠(Dipus sagitta)、五趾跳鼠(Allactage sibirica)、子午沙鼠(Meriones meridianus)和红耳鼠兔(Ochotona erythrotis)胃内的主要食物成分为当年生植物嫩茎、叶和部分灌木韧皮部分，灰仓鼠(Cricetulus migratorius)及黑线仓鼠(C．barabensis)食物组成中种子、花和浆果以及昆虫出现较高的频率，小家鼠(Mus musculus)的食物构成以种子类为主，与食物组成相适应，总消化道和各器官长度存在明显的种间差异，而且各器官间盲肠和大肠长度的种间差异明显大于小肠的种间差异，胃和盲肠及其内容物的重量也存在显著的种间差异，但小肠和大肠及其内容物重量的种间差异则不显著。其结果验证了下述假设：栖息于同一生境的植食性小哺乳类具有不同食物资源利用模式，而同域共存物种消化道形态结构的差异是对食物资源利用种间权衡的功能反应[动物学报49(2)：171—178，2003]。     

原尾蜥虎的选择体温、热耐受性和食物同化的热依赖性

(Tsel)、热耐受性和体温对食物同化的影响。Tsel无显著的日时间变化,两性个体的Tsel、临界低温(CTMin)和临界高温(CTMax)无显著的差异。Tsel、CTMin和CTMax的平均值分别为30.9℃、3.2℃和43.3℃。体温对动物食物通过时间有显著的影响。在25℃-33℃范围内,食物通过时间随体温升高而缩短;体温超过33℃后,食物通过时间随体温升高而延长。温度对原尾蜥虎的摄食量、表观消化系数(ADC)和同化效率(AE)有显著的影响。在25℃-37℃范围内,动物在低体温下(25℃和27℃)的摄食量、ADC和AE小于更高体温下动物的对应数值。种间比较结果显示,原尾蜥虎是生活于南方的蜥蜴中具有较强耐受极端体温的种类。     

食物中碘的测定方法

目前,用于碘测定的方法繁多,包括分光光度法、滴定法、电感耦合等离子质谱法（ICP-MS）、中子活化法（NAA）、原子吸收光谱法、色谱法、电化学法、电感耦合等离子发射光谱法（ICP-OES）、X射线荧光光谱法、快速检测试剂盒等。其中,砷铈催化分光光度法较为成熟、准确,ICP-MS法技术先进,准确性高,而滴定法简便快捷。其他方法因仪器昂贵,技术要求高或氧化消解过程复杂、准确性低等未能得到广泛应用。     

Digesta Passage,Digestibility and Behavior in Captive Gorillas Under Two Dietary Regimens

Gorilla adaptation has been debated in recent years given the wide variation among diets of gorillas in different habitats. Gorillas are the largest of living primates, have large colons and should be capable of processing tough foods. Preliminary captive studies have suggested that they may well have long average gut retention times relative to smaller hominoids, which should facilitate digestive efficiency in their wild counterparts. Indeed, wild gorillas consume large amounts of fibrous foods as staples or fall-back foods across their range, in response to habitat-related or seasonal changes in fruit availability. Fluctuations in diet might be matched by changes in digesta passage and digestibility, with possible selective retention of harder to digest items. We further studied digestive processes via chemical cobalt and chromium markers to track liquid and solids, as they passed through the guts of gorillas at the San Francisco Zoo (SFZ). In addition, we examined the effects of variation in captive diets on intake, digesta passage, digestion and behavior. The SFZ gorillas exhibited high digestibility coefficients, and gut passage was long relative to those of smaller-bodied hominoids. The results permit us to understand more fully the relationships of digestive processes to adaptation and dietary flexibility in the wild and to inform the development of dietary recommendations to improve the well-being of captive gorillas.     

The Effect of Coprophagy on the Digesta Passage through the Gut of the Daurian Pika Ochotona dauurica (Ochotonidae,Lagomorpha)

Biology Bulletin - Fibrous food passage through the digestive tract of Daurian pika (Ochtona dauurica) was studied by means of multiple dose marking of food by neutral plastic markers. Contrary to...     

Fluid and particle retention in captive okapi (Okapia johnstoni)

Retention time of food in the digestive tract is among the key variables that describe the digestive strategy of a herbivore. Mean retention time (MRT) was measured on 4 captive specimens of the okapi, a strictly browsing ruminant. Retention time was quantified on different diets, using Co-EDTA (fluid phase) and Cr-mordanted fibres (1–2 mm) (particle phase) as pulse-fed markers. Average food intake was 55–65 g DM/(kg BW^0.75*d). Fecal excretion of the markers was quantified over 10 days. Different models to calculate retention time and passage rate in the gastrointestinal tract (GIT) and the reticulorumen (RR) were applied. Average MRT_particleGIT was quantified to be 47 ± 8 h and MRT_fluidGIT 36 ± 5 h. Concerning estimation of retention times in the reticulorumen, MRT_particleRR was quantified to be 27 ± 7 h, while MRT_fluidRR was 17 ± 4 h. The quotients MRT_particle/MRT_fluid were quantified to be 1.3 ± 0.1 for the GIT and 1.6 ± 0.2 for the RR. Compared to data established with comparable markers, the okapi has low coefficients of MRT_particle/MRT_fluid. A less well developed retention mechanism for fibres compared to species like cattle or sheep can be explained by a comparatively high fermentation rate and low digestibility of the natural food of the okapi—browse—in comparison to grass.     

哺乳动物卵母细胞凋亡的研究进展

细胞凋亡是发育过程中的基本生命现象,除各种体细胞凋亡外,生殖细胞的发生过程中也发生细胞凋亡。就雌性生殖系而言,细胞凋亡是其发育过程中的一个重要组成部分。在哺乳动物中,超过99．9％的雌性生殖细胞都会在卵子发生的不同阶段发生凋亡。有三种学说解释这一现象：1)被忽视死亡;2)因缺陷死亡;3)自我牺牲死亡。本文主要综述了哺乳动物卵母细胞凋亡的现象、卵母细胞凋亡学说、线粒体遗传与卵母细胞凋亡的关系以及凋亡的分子机理,同时还探讨了卵母细胞凋亡的生物学意义。     

Digesta passage rates in the Florida manatee (Trichechus manatus latirostris)

The Florida manatee, Trichechus manatus latirostris (Sirenia: Trichechidae), is an herbivorous marine mammal found within coastal areas throughout the state of Florida, which feeds on both fresh and salt water sea grasses. Manatees, like other Sirenians, are a tropical species with little tolerance for water temperatures below 20°C, rely on a relatively poor nutritional food source, and have a low metabolic rate. Although manatees are hindgut fermenting herbivores, they are very efficient at extracting nutrients from the plants on which they feed. Slow passage rates of digesta have been suggested to be a factor in this increased efficiency. Two studies monitored the digesta passage times and mixing of particulate digesta within the manatee digestive tract using MicroGrits colored corncob grit as a fecal marker. Fecal samples were collected subsequently from four manatees in Study 1 and 3 manatees in Study 2, grit pieces removed, counted, and measured. The digesta passage times ranged from 6 and 10 days in Study 1, and 4.3 and 8.3 days in Study 2, supporting data presented in previous studies. When two different colored markers were administered on sequential days, minimal to no mixing was seen in recovered feces, suggesting that the digesta from a given day traveled through the tract as a bolus. Less than 1% of the marker fed was recovered and we hypothesize that perpendicular folds of the large intestine may be the major contributing factor, with pieces being retained and eventually digested. Zoo Biol 26:503–515, 2007. © 2007 Wiley‐Liss, Inc.     

The Decline of Isochores in Mammals: An Assessment of the GC ContentVariation Along the Mammalian Phylogeny

Whether isochores, the large-scale variation of the GC content in mammalian genomes, are being maintained has recently been questioned. It has been suggested that GC-rich isochores originated in the ancestral amniote genome but that whatever force gave rise to them is no longer effective and that isochores are now disappearing from mammalian genomes. Here we investigated the evolution of the GC content of 41 coding genes in 6 to 66 species of mammals by estimating the ancestral GC content using a method which allows for different rates of substitution between sites. We found a highly significant decrease in the GC content during early mammalian evolution, as well as a weaker but still significant decrease in the GC content of GC-rich genes later in at least three groups of mammals: primates, rodents, and carnivores. These results are of interest because they confirm the recently suggested disappearance of GC-rich isochores in some mammalian genomes, and more importantly, they suggest that this disappearance started very early in mammalian evolution.This article contains online supplementary material.     

Gut region-specific accumulation of reactive oxygen species leads to regionally distinct activation of antioxidant and apoptotic marker molecules in rats with STZ-induced diabetes

The aim of this study was to seek possible links between the regionality along the digestive tract and the accumulation of reactive oxygen species, the effectiveness of the antioxidant defense system and the sensitivity to the types of demise in different gut regions of rats with streptozotocin-induced diabetes. Significant changes were observed in the oxidative status and in the activity of the antioxidant defense system in the diabetic colon; the peroxynitrite production was doubled, the level of hemoxygenase-2 protein was increased 11-fold and the expression of anti-apoptotic bcl-2 was also increased. The segment-specific vulnerability of the gastrointestinal tract induced by hyperglycemia was also confirmed by electron microscopy, demonstrating the presence of severe necrosis in the colon of the diabetic rats. No remarkable histopathological alterations were seen in the duodenum of the diabetic animals and there were likewise no significant changes in the production of peroxynitrite in their duodenum, whereas the level of the free radical scavenger metallothionein-2 was increased ∼300-fold.ConclusionThe spatially restricted vulnerability observed along the digestive tract could originate from a high level of oxidative stress via peroxynitrite production.     

Politics,Pride, and Precedent: The United States and Canada in the Northwest Passage

The issue of the status of the Northwest Passage has ebbed and flowed in U.S.-Canada relations for decades, but the effect of global warming in the Arctic has moved this issue from the largely academic and legalistic realms to the forefront of bilateral (and international) relations. Intimately linked to Canadian nationalism, U.S. adherence to the doctrine of freedom of the seas, and to politics in both nations, the opposing positions held by the two states can no longer afford to be implacably held. Rather, it is time to put pride and politics aside and return to the “special relationship” between Canada and the United States in order to effect meaningful and mutually beneficial continental security.     

长江流域兽类物种多样性的分布格局

共记录了长江流域内兽类280种,隶属于11目36科135属,特有种和受威胁物种分别有14种和154种。根据兽类分布特点,依据山系和水系将长江流域分为19个区域,除了江源区外,物种丰富度、G-F多样性指数和特有种比例,从上游到下游区域总体趋势是随海拔降低逐渐降低,形成以四川盆地和沅江为分界线的3个数量级;利用Jaccard物种相似性系数对长江流域内19个区域进行聚类分析,发现整个流域分成4部分:江源区;横断山区、川西高原、云南高原、四川盆地和秦巴山区;贵州高原、江南丘陵、鄱阳湖平原和长江三角洲;淮阳山地、两湖平原和长江下游平原,基本反映了流域内自然地理环境及我国大陆地势三级台阶变化的特点。     

消化道癌原代培养体外药敏试验的研究

目的 研究肠癌、胃癌、肝癌细胞在8种不同抗癌药物作用下的细胞抑制率,以筛选出敏感的化疗药物.方法 采用四甲基偶氮唑蓝着色法（MTT）,对97例消化道癌（43例肠癌、33例胃癌、21例肝癌）新鲜瘤组织进行原代细胞培养,同时进行顺铂（DDP）、丝裂霉素（MMC）、卡铂（CBP）、5-氟尿嘧啶（5-FU）、表阿霉素（EADM）、长春新碱（VCR）、羟基喜树碱（OPT）和环磷酰胺（CTX）8种常用化疗药物敏感检测,并对其结果作比较.结果 在肠癌中高度敏感率大于50%药物依次为MMC、5-FU、DDP、CBP.总敏感率大于50%的药物依次为DDP、MMC、5-FU、CBP.在胃癌中高度敏感率大于50%的药物依次为DDP、CBP.总敏感率大于50%的药物依次为DDP、CBP、MMC、5-FU、CTX、VCR.其中胃癌对CTX、VCR的敏感率明显高于肠癌细胞（P＜0.05）.肝癌细胞中高度敏感率＞50%的药物为零,而总敏感率＞50%的药物依次排序为MMC、EADM、CBP.结论 消化道肿瘤细胞对化疗药物的选择虽有一定共性,但同种肿瘤的不同个体对同种化疗药物的敏感性差异却存有显著性.体外检测消化道肿瘤对化疗药物的敏感性可为临床化疗提供指导.