Studies of small intestine during development. I. Distribution and activity of beta-galactosidase.
TL;DR: The hypothesis that s-galactosidase in the fetal intestine is induced by circulating lactose is not supported by the evidence presented.
About: This article is published in Biochimica et Biophysica Acta.The article was published on 1962-08-13. It has received 238 citations till now. The article focuses on the topics: Small intestine & Ileum.
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TL;DR: A unit for disaccharidase activity is defined that is in accord with recommendations made by the Joint Sub-Commission on Clinical Enzyme Units of the International Unions of Biochemistry and of Pure and Applied Chemistry.
1,951Â citations
TL;DR: In this paper, the conditions of genetic selection that may have led some groups of men to have persistently high levels of intestinal lactase throughout life, and others not, are considered.
Abstract: The principal conclusion reached in Part I of this article (1) was that the group differences found in primary adult lactose intolerance among the world's peoples are largely genetic in origin. In this part, after a review of recent research that adds to Part I in important ways, we turn to a consideration of the conditions of genetic selection that may have led some groups of men to have persistently high levels of intestinal lactase throughout life, and others not. Low incidence of intolerance, it is held, would develop over time in a group that has an abundant milk supply, that has alternate foodstuffs inadequate in amount and quality, and that consumes milk in lactose-rich forms. Since such selection cannot have occurred among groups that did not use milk, areas of nonmilking in the modern world are first delimited. The origins and diffusion of dairying are then sketched to determine the length of time that milk was consumed in various regions. With the background thus gained, the present-day occurrence of various Old World groups with high and low incidences of intolerance is explained. All groups studied so far within the traditional areas of nonmilking are found to have high incidences of intolerance. Overseas groups, such as American Negroes, whose ancestors came from nonmilking regions also have high incidences of intolerance. Within the areas of milking in Africa and Europe, moreover, the known group differences in tolerance are found to be in accord with the hypothesis. Then, that the hypothesis may further be confirmed, specific additional research efforts are suggested.
263Â citations
01 Feb 1986
TL;DR: This review uses the rat as a model system for a discussion of the functional development of the gastrointestinal tract and finds that the neonate has hydrolytic activities which are specific for, and largely restricted to, the components of maternal milk.
Abstract: My aim in this review is to use the rat as a model system for a discussion of the functional development of the gastrointestinal tract. I should make it clear at the outset that since the rat is an altricial species, many of the enzymic changes that occur postnatally in the rat occur prenatally in other mammals, including humans (Grand et al. 1976; Lebenthal et al. 1983). Nevertheless, I believe that these studies in the rat. have posed some questions of broader importance and have pointed to some potential answers. Thus, the review is structured 90 as to emphasize the general lessons which have potential application in many species and in many organ systems. Because of space limitations, the review does not attempt to be comprehensive. To set the stage, it is important to realize that the process of spontaneous weaning in the rat is a precisely timed phenomenon which normally begins at 17 d of age and is complete by day 26 (Henning et al. 1979). Weaning constitutes a significant change in dietary composition which, in turn, necessitates changes in digestive function. The entire gastrointestinal tract of the rat is functionally immature at birth and during the first two postnatal weeks. There are extensive changes in digestive capacity during the third postnatal week, and the adult modes of digestion are fully operative by the end of the fourth week. These developmental changes in gastrointestinal function have been reviewed elsewhere in detail (Henning, 1981 ; Klein & McKenzie, 1983) and only those in the small intestine will be summarized here. In the small intestine of the rat, we find that the neonate has hydrolytic activities which are specific for, and largely restricted to, the components of maternal milk. This is demonstrated very nicely by a consideration of carbohydrate digestion. Milk is relatively low in total carbohydrates, and the carbohydrates present are those not geoerally found in adult diets. The major carbohydrate in the milk of most placental mammals is lactose (Jenness et al. 1964), and high activities of its disaccharidase, lactase (EC 3.2.1.23), are found in the intestinal mucosa of the sucking animals (Deren, 1968; Kretchmer, 1971). In the rat, lactase is detectable on day 18 of gestation, has maximal activity during the first week after birth, and then begins to decline, reaching adult values by the end of the fourth week (Doell & Kretchmer, 1962). Many other species, including the human, have lower lactase activity in the adult than in the newborn (Deren, 1968) and accordingly show an inability to utilize ingested lactose in the postweaning period (Kretchmer, 1971). Intestinal hydrolases that are involved in digestion of carbohydrate components of solid food are absent or low at birth, then appear or increase in activity, or both. Maltase (EC 3.2.1.20) has low activity during the first two postnatal weeks then
217Â citations
Cites background from "Studies of small intestine during d..."
...In the rat, lactase is detectable on day 18 of gestation, has maximal activity during the first week after birth, and then begins to decline, reaching adult values by the end of the fourth week (Doell & Kretchmer, 1962)....
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210Â citations
TL;DR: Injection of rats aged 3 to 9 days with hydrocortisone causes precocious development of invertase activity in the small intestine, suggesting that it does not act solely by hastening the normal maturation process.
Abstract: Injection of rats aged 3 to 9 days with hydrocortisone causes precocious development of invertase activity in the small intestine. The enzyme becomes fully active about 72 hours after injection of hydrocortisone. Invertase activity is also detectable when hydrocortisone is added to organ culture of intestine derived from 5-to 6-day old rats. Hydrocortisone does not appear to affect the activity of lactase, suggesting that it does not act solely by hastening the normal maturation process.
197Â citations
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TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
289,852Â citations
363Â citations
TL;DR: The epithelial brush border membrane has been isolated as a morphologically distinct entity from homogenates of intestinal mucosa and found to contain virtually all of the invertase and maltase activities of the unfractionated homogenate.
349Â citations
211Â citations
TL;DR: The incorporation of labelled leucine into the proteins of microsomal subtractions and in those of postmicrosomal fractions was studied comparatively in the pancreas of fasted and fed guinea pigs as well as in the liver and pancrea of fasting animals.
Abstract: Pancreatic tissue, (guinea pig) homogenized in 0.88 M sucrose, was fractionated by differential centrifugation into a nuclear, zymogen, mitochondrial, microsomal, and final supernatant fraction. The components of the particulate fractions were identified with well known intracellular structures by electron microscopy. The fractions were analyzed for protein-N and RNA, and were assayed for RNase and trypsin-activatable proteolytic (TAPase) activity. The zymogen fraction accounted for 30 to 40 per cent of the total TAPase and RNase activities, and its specific enzymatic activities were 4 to 10 times higher than those of any other cell fraction. The zymogen fraction was cytologically heterogeneous; zymogen granules and mitochondria represented its main components. More homogeneous zymogen fractions, obtained by successive washing or by separation in a discontinuous density-gradient, had specific activities 2 to 4 times greater than the crude zymogen fractions. Chymotrypsinogen was isolated by column chromatography from pancreas homogenates and derived cell fractions. The largest amount was recovered in the zymogen fraction. The final supernatant had properties similar to those of the trypsin inhibitor described by Kunitz and Northrop.
150Â citations