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Biomedical subjects

M Kedinger

Publications and source records attributed to M Kedinger.

At least 109 records · Page 6Linked to original sources
PubMed1979

Developmental pattern of rat intestinal brush-border enzymic proteins along the villus--crypt axis.

At various postnatal stages, intestinal epithelial cells were isolated sequentially from villus tip to crypt base by successive EDTA treatments. According to the localization of marker enzymic activities, isolated cells were pooled into three cell compartments: villus (V), lower villus and upper crypt (VC) and crypt (C). Purified brush-border-membrane proteins were separated by 7.5%-polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. Enzymic activities could be assigned to some protein bands: maltase/glucoamylase (protein band 3), sucrase-isomaltase (protein bands 3 and 6), lactase (protein band 5) and alkaline phosphatase (region of protein bands 8 and 9). The findings suggest the following. (1) Sucrase-isomaltase activities appeared in compartment C at 17 days with a simultaneous increase of the pre-existing protein band 3 and appearance of a well-defined protein band in position 6; the enzymic complex remained still present in the crypt cells until adulthood. From the day 21 onwards, sucrase-isomaltase was detected in compartments VC and V. (2) Lactase was only present in the three cell compartments until day 21; at this developmental stage its activity completely disappeared from compartment C, in spite of the persistence of a weak protein band. (3) Alkaline phosphatase activity could be detected as a single peak corresponding to protein band 9 in all three cell compartments until day 21; thereafter it was replaced by two peaks of activity showing a less precise correlation with the well-defined protein bands 8 and 9. In the crypt cells of the adult rat, however, the preweaning situation, which was regularly observed, is an unexpected phenomenon. (4) Maltase and glucoamylase did not display any marked qualitative or quantitative modifications either along the villus-crypt axis or during the period of postnatal development studied. Evidence is given from the present data that each brush-border enzyme investigated has a specific developmental pattern.

Age Factors↗
PubMed1979

Turnover studies of human intestinal brush border membrane glycoproteins in organ culture.

Turnover in organ culture of human small intestinal membrane glycoproteins was measured by the pulse-chase technique, using 14C-glucosamine, 14C-fucose or 14C-leucine as tracers. Apparently, low degradation rates were found for the major high-molecular-weight proteins which co-migrated on SDS-polyacrylamide gels with maltase-glucoamylase, lactase-phlorizin-hydrolase and sucrase-isomaltase enzymic activities. In contrast, an unidentified glycoprotein appearing on gels next to alkaline phosphatase exhibited a higher degradation rate with an apparent half-life of about 30 h, this being similar to the half-life of total glycoprotein as measured in mucosal homogenates. The results obtained with the pulse-chase technique were confirmed by double isotope experiments using 14C-leucine and 3H-leucine as tracers. These findings indicate that in organ culture there is a low basic turnover of human intestinal membrane glycoproteins which co-migrate on gels with known glycosidase enzymic activities.

Cell Membrane↗
PubMed1979

Chick embryo pancreatic transplants reverse experimental diabetes of rats.

The effectiveness of xenogeneic embryonic tissue in the treatment of experimental diabetes has been investigated in rats. The splenic lobes (80) of 15- to 18-d-old chick embryos, composed almost exclusively of endocrine tissue, were implanted directly into the hepatic parenchyma of the rat recipient. The biochemical and metabolic changes in the recipients suggest that embryonic transplants of 15-d-old chick pancreases were able to significantly improve, for a prolonged period of time (18 mo), the diabetic state of nonimmunosuppressed rats. None of the recipients of 18-d-old embryos splenic lobes exhibited a long-term improvement of the diabetic state after transplantation. The complete destruction of the pancreatic B cells of the recipients was assessed by: (a) immunocytochemical investigations of the recipient's pancreas, (b) measurement of insulin in the liver and pancreas of the recipients and (c) in situ vascular perfusion of their pancreas submitted to high glucose challenge. The results suggest that pancreatic tissue of the 15-d-old embryos is immunologically immature lacking one or several lymphocyte subsets implicated in the afferent lood of "non-self" recognition.

Animals↗
PubMed1978

Re-evaluation of the techique of organ culture for studying gluten toxicity in coeliac disease.

In vitro cytotoxicity of four different gluten fractions was tested in organ culture for up to 48 hours using flat intestinal biopsies from children with coeliac disease. The fractions were (1) a peptic-tryptic digest of gliadin containing a moderate amount of alpha-gliadin, (2) a peptic-tryptic digest of gluten (Frazer fraction III) froma strain of wheat with a high content of alpha-gliadin, (3) alpha-gliadin, and (4) alpha-GT-18,000, a tryptic fragment of alpha-gliadin. The latter three fractions were toxic to coeliac patients in vivo. In vitro, however, none of these fractions proved to be cytotoxic. When added to the culture medium they were not capable of inhibiting the regeneration of the surface epithelium as visualised by histology and electron microscopy. The only difference between cultures with and without gluten fractions was that the former produced slightly more mucus when maintained in vitro as observed in the dissecting microscope. Furthermore, for Frazer fraction III the absence of apparent toxicity was confirmed by the behaviour of brush border enzyme activities during culture. Our results are not in accordance with those reported in the literature. We believe that the criteria used at the present time for the assessment of gluten toxicity in vitro should be extended to include the process of enterocyte desquamation.

Celiac Disease↗
PubMed1978

Sucrase and lactase synthesis in suckling rat intestine in response to substrate administration.

The intestinal brush border disaccharidases separated by gel electrophoresis were studied after oral administration of a high sucrose or lactose diet to 11-day-old suckling rats during 3 days. Some modifications of the brush border protein and eyzyme patterns could be attributed to the effect of the basic diet: increase of glucoamylase, appearance of a weak sucrase activity and of a second molecular form of maltase. However, the specific action of a given disaccharide on the synthesis of the corresponding hydrolytic enzyme could be clearly demonstrated. Indeed, the electrophoretic pattern after sucrose or lactose feeding showed a marked increase of the protein bands corresponding to sucrase-isomaltase or lactase activities.

Administration, Oral↗
PubMed1978

Separation and characterization of intestinal brush border enzymes in adult rats and in suckling rats under normal conditions and after hydrocortisone injections.

Adult and suckling (13 days old) rat intestinal brush borders have been purified by the procedure of Schmitz et al. (25). Enzymatic proteins have been separated by polyacrylamide gel electrophoresis. In the adult rat, enzyme proteins have been separated by polyacrylamide gel electrophoresis. In the adult rat, enzyme activities in order from the origin were: maltase/glucoamylase/sucrase-isomaltase (protein band 3), lactase (protein band 5), maltase/sucrase-isomaltase (protein band 6) and alkaline phosphatase (protein bands 8 and 9). In the suckling rat, protein band 5 associated with lactase activity was found to be markedly higher compared to the adult rat. Gels were completely devoid of sucrase-isomaltase activity while protein band 3 was strikingly reduced and protein band 6 absent. After hydrocortisone administration to suckling rats, a new band associated with sucrase-isomaltase activity appeared in position 6, whereas protein band 3 markedly increased with the simultaneous appearance of sucrase-isomaltase activity.

Aging↗
PubMed1977

Establishment of serum based essentiall free of proteolytic activity for the culture of mouse pancreatic islets.

The present study demonstrates that a) serum based culture medium degrades 125I inhibits its proteolytic activity leading to the recovery of more insulin secreted by islets cultured in the presence of high glucose concentration alone or with glucagon; c) aprotinin also favoured the accumulation of secreted insulin by protecting the hormone from a residual degradative capacity of the hear treated serum.

Animals↗
PubMed1977

Biosynthesis of brush border glycoproteins by human small intestinal mucosa in organ culture.

The incorporation of [14C]glucosamine into brush border glycoproteins by human small intestinal mucosa in organ culture has been investigated. The experiments were based on the observations that (1) isolated brush border membrane fragments from cultured explants showed an unchanged pattern of protein bands and brush border enzyme activities on sodium dodecyl sulfate/polyacrylamide gels after electrophoresis and (2) the rate of overall [14C]glucosamine incorporation measured in the tissue homogenate remained constant up to 48 h. After 24 h of culture, the radioactivity peaks on gels due to incorporation of [14C]glucosamine were found exclusively in the high molecular weight region and corresponded to protein bands identified as maltase-glucoamylase, lactase, sucrase-isomaltase, enterokinase and alkaline phosphatase. Enzymatic activity could not be assigned to the three remaining labelled bands. Most of these glycoproteins were already labelled after 5 h. Newly glycosylated brush border enzymes remained predominantly associated with the brush border membrane of intact cells with little release into the medium up to 24 h.

Cell Membrane↗
PubMed1977

Intestinal enzymes activities in isolated villus and crypt cells during postnatal development of the rat.

A modification of Weiser's (1973) cell isolation method was used in order to study the developmental pattern of various intestinal enzyme activities in villus and crypt cells of normal rats from 5 days after birth until 8 weeks. Alkaline phosphatase and enterokinase activities were always located in the upper villus zone during postnatal development. Enterokinase activity was higher in the upper villus cells during the third week of life than after this period. Aminopeptidase activity was located in the crypt cells during the first week, its maximum activity remained in this area until the third week. At this time, sucrase activity appeared in the crypt cells, then aminopeptidase and sucrase activities rose to the villus zone during the fourth week. Amylase activity was detected along the entire crypt-villus axis 5 days after birth, reaching maximum activity in crypt cells at the end of the first week and in the upper villus cells after the fourth week. In contrast with the other enzymes studied almost all amylase activity was soluble in the youngest animals whereas at weaning most of the activity appeared in a particulate form in the villus cells. But in the crypt cells the ratio between particulate and soluble form remained unchanged until the adult stage. Various hypotheses are advanced to explain the patterns of evolution of the different enzymes.

Alkaline Phosphatase↗
PubMed1977

Intrahepatic transplantation of pancreatic islets in the rat.

Islets of Langerhans from isogeneic donor rats were transplanted directly into the hepatic parenchyma of recipients which had been made severely diabetic by streptozotocin (glycaemia ranging between 400 and 1090 mg%). Complete control lasting up to 13 months was achieved in 65% of recipients by using 600-800 islets. Following intravenous glucose administration, each rat responded similarly to normal rats with a rapid but reduced release of insulin. Cytoimmunofluorescence and electron microscopic studies demonstrated the presence of both functional insulin and glucagon cells, within the transplanted islets. It is suggested that for various reasons direct intrahepatic transplantation might become the preferred method for islets.

Animals↗
PubMed1975

Isogenic and allogenic transplatation of isolated langerhans islets into the liver.

This preliminary experimental report confirms the previous interest of isolated endocrine islet transplantation. Moreover a new "privileged position" for the islets grafts is proposed and is as uneventful as a liver biopsy. The functional value of this grafting procedure has been assessed on biological and functional criteria. The transplanted islets are easily retrievable and histological and especially immunocytochemical studies demonstrate the morphological behaviour of such islets. Finally the preliminary survival of allogeneic grafts into the liver supports the concept of the role of the liver during enhancement of facilitation and will be the subject of further investigations.

Animals↗
PubMed1975

Organ culture of adult guinea-pig intestine. III. Mitotic-activity and cellular migration.

The mitotic activity and the cellular migration have been studied in explants of adult guinea pig intestine cultured for 24 hours. The mitotic index after a significant increase in the first hours of culture, decreases steadily thereafter. The DNA synthesis persists in the crypts for 24 hours at least and cell migration can be observed. These results demonstrate that organ culture of adult intestine may be used as a model for the study of intestinal function.

Animals↗