Postnatal development of somatostatin levels and its binding sites in rabbit gastric mucosa

Using a specific radioimmunoassay technique, we have determined somatostatin-like immunoreactivity (SLI) in acid extracts of gastric (fundic and antral) mucosa as well as the specific binding of ¹²⁵I-Tyr¹¹-somatostatin to cytosol of the stomach of 0 to 150 days postnatal rabbits. The levels of somatostatin in both fundus and antrum decreased from birth up to day 5 followed by a sharp increase from 5 to 10 days, then decreased progressively until day 35. After this age, the somatostatin concentration remained relatively stable. The number of specific somatostatin binding sites of both high- and low-affinity increased gradually (without changes in the affinity values) with the development of rabbits, reaching the adult level by 35 days. However, there was an apparent lack of high-affinity sites immediately after birth (day 0). The somatostatin binding sites had characteristics identical with those found in adult animals with regard to their respective specific ligands.     

Cytochemical and biochemical studies on the differentiation of microperoxisomes in the small intestine of the fetal mouse

The localization of catalase activity during the morphogenesis of duodenum and ileum has been studied in Swiss ICR mouse embryos from the 16th day of fetal life until birth. Catalase activity was also measured by a spectrophotometric method. Few diaminobenzidine-positive microperoxisomes are present at 15 days of gestation in undifferentiated cells of the stratified epithelium lining the lumen of duodenum and ileum. The number of microperoxisomes increases considerably in the duodenal enterocytes at 17 days; the highest concentration of microperoxisomes is attained at 18 days, after which time their number becomes stable until 4 weeks after birth. Biochemically, catalase activity is barely detected at 15 days in the first half of the small intestine, but afterwards it increases steadily up to 1 day after birth. In the ileum, the increase in microperoxisome number is far less important than in the duodenal enterocytes and reaches a maximum at 19 days of gestation, that is, immediately at birth. The level of catalase activity in the second half of the small intestine is also much lower than that measured in the first half. These results are discussed in relation to the biogenesis of microperoxisimes in the small intestine before birth.     

Somatostatin binding sites in cytosolic fraction of rabbit intestinal mucosa: distribution throughout the intestinal tract

Specific binding sites for somatostatin have been identified in cytosolic fraction of both small and large intestinal mucosa. The stoichiometric data suggested the presence of two classes of binding sites in each part of the intestine. The binding capacity varied depending on the segment considered (rectum greater than duodenum = jejunum greater than ileum, caecum and colon). However, the affinities of the binding sites were similar throughout the whole intestinal mucosa, with the exception of rectum which showed higher Kd values. The binding sites were shown to be highly specific for somatostatin since neuropeptides such as vasoactive intestinal peptide, neurotensin, substance P and Leu-enkephalin did not show any effect upon somatostatin binding.     

Regional differences in the appearance of adult-type glycosphingolipids in the small intestine of inbred rats at weaning time

The small intestine of 15- to 33-day-old rats was cut into four segments: duodenum, proximal jejunum, distal jejunum, and ileum. Neutral glycosphingolipids and gangliosides were purified from each segment and analyzed by thin-layer chromatography in order to study the developmental appearance of adult-type glycolipids at each level of the small intestine. Type 1 A-6 glycolipid was first detected in the ileum at 15 days and subsequently in the jejunum and duodenum at 19 days of age. N-Glycolylneuraminic acid was expressed first in the ileum at 17 days, then in the proximal jejunum at 21 days, but only after 29 days in the duodenum. In each region, 6-8 days were required between first detection and full expression of N-glycolylneuraminic acid. The presence of 2-hydroxylated fatty acids in glucosylceramide was found first in the ileum at 19 days, 2-3 days before appearing in the duodenum and proximal jejunum. A period of 2-3 days was necessary to reach full adult-type level of 2-hydroxylated fatty acids in glucosylceramide. These results show that adult-type glycolipids appear earlier in the distal than in the proximal region of the rat small intestine, and that different glycolipids appear at different times and at different rates. The finding that the biochemical differentiation of the whole small intestine expands over a period of 3 days to 2 weeks, depending on the region and the glycolipid, before being fully completed indicates that, in addition to the time lag observed between the distal and the proximal region, the new cells arising from the crypt of Lieberkhün after 15 days of age are not at once fully differentiated.     

Growth and morphological changes in the small and the large intestine in piglets during the first three days after birth.

Growth and morphological changes in the small and the large intestine of piglets were examined during the first three days after birth. There was a 72% increase in small intestinal weight, virtually all of which occurred during the first day and was due primarily to a 115% increase in the weight of the mucosa. Associated with the tissue weight gain there was a 24% increase in small intestinal length, a 15% increase in small intestinal diameter, a 33-90% increase in villus height and a 14-51% increase in villus diameter, during the first day. The cellular population in the small intestinal mucosa, as indicated by its DNA content, increased progressively with age, and at three days had increased by 84-154%. The percentage increase in mucosal DNA content was highest in the duodenum, intermediate in the jejunum and lowest in the ileum. Histological features and tissue protein contents revealed a transient epithelial cellular swelling related to intracellular accumulation of protein on the first day. Protein accumulation was evident in the jejunum and ileum but not in the duodenum. The positions of the nuclei in the epithelial cells suggested that on the first day protein absorption was at a more advanced stage in the jejunum and the proximal ileum than in the distal ileum. Large intestinal weight increased by 33% during the first day and had doubled by the third day, and this weight gain was due to both mucosal and non-mucosal tissue growth. Villus-like structures were observed in the caecum and the proximal colon in piglets at birth and one day after birth but not in piglets three days after birth. It is speculated that such villus-like structures may have a functional significance during the transition to complete dependence on oral nutrition in newborns.     

Distribution,ontogeny and ultrastructure of somatostatin immunoreactive cells in the pancreas and gut

Summary Somatostatin cells are numerous in the pancreas and digestive tract of mammals as well as birds. In the pancreas of chicken, cat and dog they occur in both the exocrine parenchyma and in the islets. In the rat and rabbit, somatostatin cells have a peripheral location in the islets, whereas in the cat, dog and man the cells are usually more randomly distributed. In the stomach of rabbits and pigs, somatostatin cells are more numerous in the oxyntic gland area than in the pyloric gland area, whereas the reverse is true for the cat, dog and man. In the cat, pig and man, somatostatin cells are fairly numerous in the duodenum, whereas in the rat, rabbit and dog they are few in this location. In the remainder of the intestines somatostatin cells are few but regularly observed. Somatostatin cells are numerous in the human fetal pancreas and gut. In the fetal rat, somatostatin cells first appear in the pancreas and duodenum (at about the 16–17th day of gestation) and subsequently in the remainder of the intestine. Somatostatin cells do not appear in the gastric mucosa until after birth. Three weeks after birth, somatostatin cells show the adult frequency of occurrence and pattern of distribution. In the chicken, somatostatin cells are numerous in the proventriculus, absent from the gizzard, abundant in the gizzard-duodenal junction (antrum), infrequent in the duodenum and virtually absent from the remainder of the intestines. No immunoreactive cells can be observed in the thyroid of any species nor in the ultimobranchial gland of the chicken. In the chick embryo, somatostatin cells are first detected in the pancreas and proventriculus (at about the 12th day of incubation). They appear in the remainder of the gut much later, in the duodenum at the 16th day, in the antrum at about the 19th day and still later in the lower small intestine. The ultrastructure of the somatostatin cells was studied in the chicken, rat, cat and man; the cells were identified by the consecutive semithin/ultrathin section technique. The somatostatin cells display the properties of the D cell. There was no difference in granule ultrastructure between somatostatin cells in the gut and the pancreas. The granules, which are the storage site of the peptide, are round, supplied with a tightly fitting membrane and have a moderately electron-dense, fine-granulated core. The mean diameter of the somatostatin granules is smallest in rat (155–170 nm) and largest in the chicken (270–290 nm).     

Regional variation in ontogeny of class II antigens in enterocytes of mouse small intestine.

The ontogeny of major histocompatibility class II antigens in small intestine enterocytes of postnatal C3H/He mice was investigated. Cryosections of duodenal, jejunal, and ileal segments from 7-, 14-, 16-, 20-, 21-, 23-, 25-, 27-, 28-day-old and 7-week-old mice were stained for the class II antigens with MRC OX6 monoclonal antibodies by peroxidase-antiperoxidase labelling. In adults, the duodenum exhibited least expression of class II antigens that increased progressively towards the ileum. The expression in the villous epithelium was first seen in the duodenum and jejunum 21 days after birth but the ileal enterocytes did not exhibit any class II antigens. The earliest appearance (21 days postnatal) of class II antigens in the enterocytes coincides with the age of weaning which suggests that immunologic stimulation by ingested antigens after weaning may influence expression of these antigens. At day 28 after birth, the duodenum and jejunum expressed levels comparable to those in the adults. The first expression of the antigens seen in the ileum was at day 28 postpartum. Crypt epithelium of the three regions of the small intestine showed expression similar to that of corresponding regional villous enterocytes. We conclude that there is an age-dependent regional variation in the expression of class II antigens in enterocytes, and the expression increases with age. The variation in expression of the class II antigens in enterocytes of postnatal mice is attributed to the developmental status of the tissue. The nature of postnatal expression of the antigens is important since an early appearance of these antigens may have implications in autoimmunity.     

Phosphatidylcholine synthesis in the developing small intestine.

1. Phosphatidylcholine synthesis in the foetal, newborn and adult small intestine of rats was studied by determination of cytidine diphosphocholine-1,2-diacylglycerocholine phosphotransferase (cholinephosphotransferase) and acyl-CoA-1-acyl-sn-glycerol-3-phosphocholine acyltransferase (lysophosphatidylcholine acyltransferase) activities and the incorporation of [1-14C]oleic acid into phosphatidylcholine. 2. Cholinephosphotransferase activity was low in foetal jejunum and ileum, increased 3-4 fold in the ileum by 6 days of age and by 12 days in the jejunum. Jejunal activity remained constant throughout weaning; ileal activity gradually decreased to values 25% of that of the jejunum. 3. Lysophosphatidylcholine acyltransferase activity was high in foetal jejunum and ileum, decreased 70% immediately after birth in the jejunum and increased to adult values by 12 days of age. Ileal activity decreased by 20% after birth, but decreased more rapidly at weaning to 30% of the activity in jejunum. 4. Initial rates and steady-state incorporation of [1-14C]oleic acid into phosphatidylcholine by jejunal rings of 10 day-old rats exceeded that observed in jejunal rings from adult rats by 2-4-fold. 5. In the postnatal jejunum, neither cholinephosphotransferase and lysophosphatidylcholine acyltransferase activities nor oleic acid incorporation were stimulated by cortisone administration in vivo.     

Allosteric activation of brain hexokinase by magnesium ions and by magnesium-ion–adenosine triphosphate complex

1. The highest blood concentrations of ketone bodies were found at 5 days of age, after which time the concentration fell to reach the adult value by 30 days of age. 2. Both mitochondrial and cytoplasmic hydroxymethylglutaryl-CoA synthase activities were detected, with highest activities being found in the mitochondria at all stages of development. Activity of the mitochondrial enzyme increases rapidly immediately after birth, showing a maximum at 15 days of age, thereafter falling to adult values. The cytoplasmic enzyme, on the other hand, increased steadily in activity after birth to reach a maximum at 40 days of age, after which time activity fell to adult values. 3. Both mitochondrial and cytoplasmic aceto-acetyl-CoA thiolase activities were detected, with the mitochondrial enzyme having considerably higher activities at all stages of development. The developmental patterns for both enzymes were very similar to those for the corresponding hydroxymethylglutaryl-CoA synthases. 4. The activity of heart acetoacetyl-CoA transferase remains constant from late foetal life until the end of the suckling period, after which time there is a gradual threefold increase in activity to reach the adult values. The activity of brain 3-oxo acid CoA-transferase increases steadily after birth, reaching a maximum at 30 days of age, thereafter decreasing to adult values, which are similar to foetal activities. Although at all stages of development the specific activity of the heart enzyme is higher than that of brain, the total enzymic capacity of the brain is higher than that of the heart during the suckling period.     

La TEP des tumeurs neuroendocrines de l’intestin grêle

This article focuses on the indication and the choice of tracer for PET/CT in case of neuroendocrine tumours (NET) of the small intestine, which are the most common digestive NETs. PET/CT can be used to search for the primary NET in case of detection of a metastasis, for staging and determination of resectability, for restaging, for optimising and determining the efficacy of therapeutic modalities in extended or recurrent forms. Currently, three types of PET tracers are routinely used: FDG can be useful in the case of aggressive NET especially the duodenum and proximal jejunum, FDOPA is the best tracer in the case of NET of distal jejunum or of ileum, the labeled somatostatin analogues ⁶⁸Ga in the case of well-differentiated NET from the duodenum or proximal jejunum, or irrespective of the location of primary NET if treatment with somatostatin analogue is intended, to confirm the overexpression of somatostatin receptors by lesions.     

The effect of dietary supplementation of nitric oxide donor and inhibitor on nNOS expression in and motility of the small intestine of broilers

Abstract

We investigated the effect of dietary supplementation of sodium nitroprusside (SNP), a nitric oxide (NO) donor, and N-nitro-L-arginine methyl ester (L-NAME), a NO inhibitor, on neuronal nitric oxide synthase (nNOS) expression in and motility of small intestinum in broilers. A total of 560, one-day-old Ross 308 hybrid mixed sex broiler chicks were divided randomly into one control and seven treatment groups for a 42 day feeding trial including starter phase (0–21 days) and grower phase (22–42 days). The control group was fed a basal diet and the experimental groups were the fed basal diet supplemented with 25, 50, 100 and 200 mg/kg SNP and 25, 50 or 100 mg/kg L-NAME. Ten chickens from each group were sacrificed to collect samples on days 21 and 42. The expression patterns of nNOS immunoreactivity in nerve fibers were determined by immunohistochemistry. In the contractility studies, longitudinal isolated strips of duodenum, jejunum and ileum were treated with 10^?5 M L-arginine and 10^?4 M SNP. Immunohistochemistry revealed that nNOS expression was not detectable in the duodenum or ileum of either the control or experimental groups. On the other hand, nNOS immunoreactivity in the jejunum control group showed a strong reaction on day 21, but the reaction was weak on day 42. nNOS expression clearly was suppressed on day 21 by the diet supplemented with L-NAME, while the diet supplemented with SNP stimulated nNOS expression on day 21. Contractility experiments revealed that spontaneous contractility of isolated strips of duodenum, jejunum and ileum showed no significant difference among groups. Spontaneous contractions of all strips were inhibited by L-arginine and SNP in all groups. The percentage inhibition rate of spontaneous contractions of jejunum application on days 21 and 42 after L-arginine decreased in the group supplemented with 100 mg/kg L-NAME. The percentage inhibition rate on day 21 after SNP application decreased in both groups that received 50 and 100 mg/kg L-NAME. We demonstrated the expression pattern of nNOS in nerve fibers in jejunum of broiler chickens. Contractility studies revealed that the NOS-NO pathway may play a role in smooth muscle contraction of small intestine of chickens. Feeding strategies that supplement NO donor and NO inhibitor can be of physiological importance to small intestine motility owing to alteration of nNOS expression in the jejunum.     

Molecular cloning, distribution and ontogenetic expression of the oligopeptide transporter PepT1 mRNA in Tibetan suckling piglets

The gene encoding the oligopeptide transporter PepT1 (HGMW-approved gene symbol SLC15A1) from Tibetan porcine intestine was cloned. The open reading frame of this cDNA encodes 708 deduced amino acid residues that show high sequence similarity with its ovine and bovine counterparts. The putative protein has 12 putative transmembrane domains, including many structural features that are highly conserved among the vertebrate orthologs. PepT1 mRNA expression can be detected in duodenum, jejunum and ileum from Tibetan pigs at 28 days by RT-PCR. Real-time PCR analysis indicated that the jejunum had the highest expression of PepT1 when compared with the duodenum and ileum. PepT1 mRNA expression in the duodenum and proximal jejunum increases continuously from day 1 to day 14: expression was highest at day14 (P < 0.01) and then decreased gradually from day 21 to day 35. Our findings show that PepT1 mRNA expression in the distal jejunum increased gradually with age in suckling Tibetan piglet, and this may have important implications for amino acid and protein nutrition in young animals.     

Ontogeny of d-Mannose Transport and Metabolism in Rat Small Intestine

Oral mannose therapy is used to treat congenital disorders of glycosylation caused by a deficiency in phosphomannose isomerase. The segmental distribution and ontogenic regulation of d-mannose transport, phosphomannose isomerase, and phosphomannose mutase is investigated in the small intestine of fetuses, newborn, suckling, 1-month-old, and adult rats. The small intestine transports d-mannose by both Na⁺-dependent and Na⁺-independent transport mechanisms. The activities of both systems normalized to intestinal weight peak at birth and thereafter they decreased. In all the ages tested, the activity of the Na⁺-independent mechanism was higher than that of the Na⁺/mannose transport system. At birth, the Na⁺-independent d-mannose transport in the ileum was significantly higher than that in jejunum. Phosphomannose isomerase activity and mRNA levels increased at 1 month, and the values in the ileum were lower than in jejunum. Phosphomannose mutase activity in jejunum increased during the early stages of life, and it decreased at 1 month old, as does the amount of mannose incorporated into glycoproteins, whereas in the ileum, they were not affected by age. The phosphomannose isomerase/phosphomannose mutase activity ratio decreased at birth and during the suckling period, and increased at 1 month old. In conclusion, intestinal d-mannose transport activity and metabolism were affected by ontogeny and intestinal segment.     

Histological characteristics of the intestinal mucosa of the rat during the first year of life

In spite of the widespread use of rats in gastrointestinal research, there is a lack of information on the qualitative and quantitative histological characteristics. Therefore, a study was performed in 69 male Wistar rats with ages ranging from one day to one year old. The features studied included: height and number of villi in the duodenum, jejunum and ileum, and depth and number of crypts in the duodenum, jejunum, ileum, colon and rectum. Morphometric observations were expressed in a mathematical logarithmic curve that showed a normal, pattern of intestinal growth for each intestinal level. The number of villi in the small intestine decreased from 1 to 35 days of age, whereas the other intestinal parameters all increased during the same period. After 35 days the rates of increase or decrease were lower. The quantification of these intestinal changes provides a new complementary pattern as a reference for research as indicators of normality or malfunction in the rat intestine.     

Prenatal and postnatal development of the small intestine in the insectivore Suncus murinus

The development of the small intestine in the insectivore Suncus murinus was noted during the period from 21 days' gestation to 20 days after birth. At 21 days of gestation, the proximal small intestine exhibited the beginning of villus formation, whereas the distal small intestine preserved the stratified epithelium. Stratified epithelium in the distal small intestine changed into a single layer by 24 days' gestation. At 26 days' gestation, each epithelial cell was immature; but by 28 days mature-looking epithelial cells were found. The shape of the villi changed from cuboid to columnar during the same period. The connective-tissue cores of the villi began to develop at 7 days after birth in the proximal small intestine and at 15 days after birth in the distal small intestine. Crypts appeared at 15 days after birth. Endocytosis of epithelial cells took place at 28 days of gestation. In the proximal small intestine, supranuclear vesicle clusters were observed first at birth; they began to decrease both in number and size at 10 days' gestation and then disappeared completely by 20 days after birth. In the distal small intestine, large supranuclear vacuoles were observed first at 28 days of gestation. Although these vacuoles invariably were found up to 15 days after birth, they also disappeared completely by 20 days. Epithelial cells showed a structure similar to those of the adult after weaning.     

Somatostatin and the interdigestive migrating motor complex in man

The relationship between somatostatin and the interdigestive migrating motility complex (MMC) was determined in human volunteers. Motor activity was monitored manometrically by means of seven perfused catheters: four in the stomach, one in the duodenum, two in the jejunum. Blood samples were drawn every 10 min and radioimmunoassayed for motilin, pancreatic polypeptide and somatostatin. In four volunteers two activity fronts (AF) were recorded and somatostatin levels correlated to the manometric data. The start of an AF in the upper duodenum was accompanied by somatostatin peaks. Peak values, taken as the mean of the levels in the sample obtained after the start of an AF, the preceding sample and the next one, averaged 32 +/- 4 pM compared to 12 +/- 2 pM in the remaining period. In four volunteers somatostatin was infused in doses of 1.2, 2.4 and 4.8 pM/kg per min over three consecutive periods of 90 min, causing dose-dependent increments in plasma somatostatin levels of 7, 32 and 76 pM. In all volunteers and for all doses all gastric activity was completely inhibited. In the intestine phase 2 was abolished but phase 3 stimulated: during somatostatin infusion phase 3 occurred with an interval of 39 +/- 6 min. Motilin and PP levels were decreased. As the two lowest infusion doses caused increases in somatostatin levels that might be considered as physiological, somatostatin seems to have a physiological role in the regulation of the migrating motor complex. We propose that it facilitates the progressing of the activity front into the small intestine.     

Post-Mortem Autodigestion of the Intestinal Mucosa of the Turkey

A gradient of post-mortem activity exists in the small intestine of the turkey. It is manifested by immediate disturbance of intestinal epithelium of the duodenum, a somewhat similar but lessened effect in the jejunum, and a long delayed action in the ileum. The recognition of such a gradient stresses the rapidity with which one must proceed in handling such tissues for technical studies. In preparing intestinal tissues for histological examination, the duodenum and jejunum must be removed immediately after killing the specimen, opened, washed carefully with warm saline to eliminate excess debris, ferments and mucous, and fixed forthwith.     

Interaction of epidermal growth factor with specific binding sites of enterocytes isolated from rat small intestine during development

Isolated enterocytes from rat small intestine were characterized for their specific binding of epidermal growth factor (EGF). Intestinal epithelial cells were isolated at 4 degrees C to minimize the loss of receptor sites during the isolation procedure. 125I-labelled EGF binding to enterocytes from adult rats was found to be specific, saturable, temperature dependent and trypsin sensitive. Binding performed in the presence of a lysosomotropic agent (NH4Cl) increased the time required to reach maximal binding at 25 degrees C. NH4Cl had no significant effect on the time-course of EGF binding at 4 degrees C and 37 degrees C. A Scatchard plot showed a curvilinear relationship indicating that EGF binds to enterocytes with more than one binding site. Developmentally, enterocytes from fetuses and pups showed characteristic temperature dependence and trypsin sensitivity, but with different levels of binding to EGF. Specific EGF binding was demonstrably higher in enterocytes from small intestine of term fetuses. EGF binding to isolated enterocytes declined rapidly after birth, and the level stayed fairly constant thereafter. Pretreatment of enterocytes from fetal intestine with mature rat milk led to a dose-dependent decrease in EGF binding. These results suggest the presence of endogenous milk factors that modify EGF binding and account for, at least partly, the observed rapid decrease of EGF binding after birth.