Early weanling and precocious development of small intestine in rats: genetic, dietary or hormonal control

Small intestinal development was followed in rats from 17 to 28 days of age in order to evaluate the interactions of diets, genetic preprogramming, and hormones in influencing developmental changes. Control pups, weaned naturally at 21-24 days, showed a gradual increase in body weight, intestinal length, and segmental mucosal weight, total DNA, and protein content. In contrast, pups weaned at 17 days showed an immediate increase in intestinal length, decrease in lactase, and precocious increase in sucrase and maltase. The changes in segmental mucosal weight, DNA and protein contents, however, paralleled that of controls. Pups nursed up to 25 days had a smaller body weight, shorter intestine, lighter mucosa, and lesser mucosal protein content. They showed no significant delay in the increase in sucrase and maltase together with a persistent higher level of lactase. Enterokinase and leucine aminopeptidase showed little change irrespective of the dietary modifications. Significant increases in segmental mucosal mass, DNA, and protein contents during the studied period were seen in all animals. At 19 days, early weaned pups had serum levels of corticosteroids about 3 times that of control or prolonged nursed pups. The results support the concept of an inherent biologic program as a basic control of intestinal ontogeny whereas dietary changes seem to have a modifying role and act directly, or in concert with, hormonal changes.

Effect of glucose and insulin on small intestinal brush border enzymes in fasted rats

Fasting reduced small intestinal length. It also decreased mucosal weight, DNA and protein content, and concentrations of enterokinase, maltase, and sucrase in both duodenal and jejunal segments. In contrast, the concentrations of lactase and leucine aminopeptidase were not affected. Concomitantly, serum insulin levels dropped to one-fifth of the control levels while serum glucose concentrations showed a lesser degree of reduction. Glucose supplementation alone raised the serum insulin level, prevented the decrease in DNA content, and showed a protective effect on mucosal protein, mucosal weight, mucosal thickness, and villus height. Glucose also protected the sucrase and maltase concentrations; more significantly for maltase in the jejunal segment. Insulin alone, although it increased the serum insulin level to that found with glucose supplementation alone, had no protective effect on the loss in protein, DNA, and most enzymes except for maltase concentration in the jejunal segment. Addition of insulin to glucose did not modify the glucose effect on the contents of DNA, protein, and concentrations of sucrase and maltase. These results suggest that the glucose effect on the mucosa is not mediated by insulin. In addition, the retention of both maltase and sucrase activities through only glucose supplementation suggests the loss of maltase and sucrase in fasting is due to nutrient rather than specific substrate restriction.

Role of corticoids independent of food intake in premature increase of pancreatic enzyme activities following early weaning in rats

The effects of early weaning and food deprivation on the development of pancreatic exocrine enzymes were compared in a rat model. Suckling rats, 15 days old, were weaned onto powdered laboratory diet. Within 24 hours, early weaned rats increased their pancreatic enzyme activities with amylase increased to twice that of the continuous suckling nonweaned littermates. During this period, early weaned rats lost weight and pancreatic growth ceased. Suckling rats of the same age (15 days old), when fasted or injected with hydrocortisone had similar increases in pancreatic enzyme activities within 24 hours. Serum corticosterone levels were increased in early weaned and fasted rats to three to four times that found in continuously suckling littermates. An additional 48 hours of treatment (up to day 18) maintained the high pancreatic enzymes in fasted and early weaned rats. These results show that the increase in pancreatic enzyme activities following early weaning was independent of food intake. The close relationship between serum corticosterone levels and pancreatic enzyme activities together with the ability of hydrocortisone to induce pancreatic enzyme concentrations in pups of the same age suggests the involvement of corticosteroid as a mediator of pancreatic development in early weaning. These experiments demonstrated the importance of endocrine factors in the pancreatic "adaptive" response to early weaning in the rat, and further emphasized the importance of evaluating endocrine changes following any nutritional alterations during the development period.

Corn syrup sugars: in vitro and in vivo digestibility and clinical tolerance in acute diarrhea of infancy

We evaluated the in vitro and in vivo digestibility and clinical tolerance of three corn syrup sugars (DE10, 15, 24) and one infant formula containing corn syrup sugar as the sole carbohydrate source (DE24). In vitro studies were conducted using human duodenal fluid and jejunal mucosa with normal enzyme activities. In vivo studies included intragastric perfusion studies and tolerance tests using the corn syrup sugars and a clinical formula trial in 32 infants with acute diarrhea. Results of the in vitro studies showed that each of the corn syrup sugars was well hydrolyzed by duodenal fluid and by mixtures of duodenal fluids and mucosal homogenates. Similarly, in vivo studies revealed significant hydrolysis in the proximal intestine, as measured during the perfusion studies, and adequate absorption, as indicated by a rise in serum glucose concentration during tolerance tests. Only patients who had a marginal serum glucose rise after a glucose meal had a blunted rise after a corn syrup feeding. More than 85% of the infants beginning the clinical trial tolerated the formula well and gained weight at or above the expected rate for age during the study interval. These data indicate that, except with severe mucosal injury and secondary monosaccharide intolerance, glucose polymers of the dextrose equivalents tested are suitable carbohydrate sources for infants recovering from acute diarrhea.

Diadenosine 5',5"'-P1,P4-tetraphosphate and related adenylylated nucleotides in Salmonella typhimurium

Salmonella typhimurium LT2 rapidly accumulates high levels of a family of five adenylylated nucleotides following exposure to a bacteriostatic quinone, 6-amino-7-chloro-5,8-dioxoquinoline. These compounds have been analyzed using our recently described two-dimensional thin layer chromatographic method. The five dinucleotides, which cannot be detected in exponentially growing cells, have been identified as diadenosine 5',5"'-P1,P4-tetraphosphate (AppppA), ApppGpp (guanosine 3'-diphosphate-5'-adenosine-5'-(P1,P3-triphosphate)), AppppG (adenosine 5'-guanosine-5'-(P1,P4-tetraphosphate)), ApppG (adenosine 5'-guanosine-5'-(P1,P3-triphosphate)), and ApppA (diadenosine 5',5"'-P1,P3-triphosphate). AppppA has been previously detected in vitro as an enzymatic product of aminoacyl-tRNA synthetases and in vivo at submicromolar levels in eucaryotic cells. The induced intracellular concentration of AppppA and the other adenylylated nucleotides in S. typhimurium is approximately 100-fold higher than that found in eucaryotic cells. We propose that these dinucleotides are alarmones, regulatory molecules signaling a particular metabolic stress.

IgE and IgD antibodies to cow milk and soy protein in duodenal fluid: effects of pancreozymin and secretin

Duodenal fluid IgE was reported to be increased in food allergy and in inflammatory conditions of the bowel. We studied the presence and specificity of IgE and IgD antibodies against alpha-casein, beta-lactoglobulin A, alpha-lactalbumin, bovine serum albumin and soy bean agglutinin using an enzyme-linked immunoassay (ELISA). Thirteen children with various intestinal diseases and thirteen normal adult volunteers were examined. In resting duodenal fluids, 8/13 of the children had IgE and 5/13 had IgD, while only 1/13 of the adults showed detectable IgE and IgD. After pancreozymin, 4/6 of the children and 4/8 of the adults showed detectable IgE and IgD in their duodenal fluids. After secretin, the duodenal fluids from 1/8 of the children and 2/8 of the adults had detectable IgE, while 6/13 children and 1/10 of the adults had IgD. The results indicate an increase in duodenal contents of IgE and IgD antibodies specific to cow's milk and soy protein after pancreozymin. Since this mediator is normally released during digestion, it is suggested that IgE and IgD antibodies specific for food proteins, may be involved in the physiological processing of foods in the intestine. In infants and children with gastrointestinal disease, the incidence of IgE and IgD antibodies specific for milk and soy proteins is higher in basal and pancreozymin-stimulated duodenal fluid when compared with control adults.

Mammary amylase: a possible alternate pathway of carbohydrate digestion in infancy

Mammary amylase is a possible alternate pathway of digestion of glucose polymers and starches, that is most important in early infancy when pancreatic amylase is low or absent in duodenal fluid and responds poorly to stimuli. Human breast milk contains 1000-5000 units of amylase/liter. In order to evaluate the likelihood that a significant proportion of mammary amylase activity would withstand passage through the stomach, purified and unpurified mammary amylase were exposed to acid and pepsin in vitro to simulate the gastric environment found in young infants. Both purified and unpurified enzymes were stable at pH 7.5 with little or no activity lost after 4 h, and approximately 80% retained at 6 h. When incubated at pH 3.5, one-third of unpurified enzyme activity was retained for 6 h; in contrast, the purified enzyme was acid labile losing 80% by 2 h. Addition of bovine serum albumin or breast milk proteins to purified enzyme protected the activity. When unpurified enzyme was exposed to a stepwise decline in pH from 6.5 to 3.5 over 4 h, 50% of the original activity was retained. Unless the concentration was greater than or equal to 3750 units/ml, the addition of varying concentrations of pepsin to defatted breast milk incubated at pH 3.5 did not affect any greater decay of enzyme activity despite evidence of peptic digestion of proteins in the reaction mixture. This study supports the possibility that ingested mammary amylase could retain a significant proportion of its original activity after exposure to acid and pepsin in the stomach of young infants.

Impact of development of the gastrointestinal tract on infant feeding

We have described the developmental pattern of the gastrointestinal tract under optimal conditions (i.e., low risk pregnancy and normal labor and delivery at term). The tissues do not develop simultaneously, and morphologic and functional development are not concurrent. An important consideration is the effect of suboptimal or even adverse conditions on the developmental sequence and attainment of maturity. Malnutrition during both the prenatal and postnatal periods may restrict the morphologic and biochemical development of the gastrointestinal tract. Dietary modifications have been shown to alter the developmental pattern of intestinal and pancreatic enzymes in animal models. Drugs and hormonal therapy given during pregnancy and early infancy have been known to cause developmental defects, but the specific effects on the gastrointestinal tract have not been evaluated. For further understanding of digestibility of nutrients and absorption in the perinatal period, these departures from the normal development of the gastrointestinal tract and the mechanisms by which these potential effects occur remain to be described. In view of these undetermined factors, in the case of intolerance or unavailability of milk from the natural mother, feedings should be individualized, with attention to direct measurement of enzyme concentrations, balance studies, or both, especially in the case of extreme prematurity or unusual requirements.

Pancreozymin and secretin enhance duodenal fluid antibody levels to cow's milk proteins

Duodenal fluid was collected from normal volunteers before and after stimulation with pancreozymin-cholecystokinin and secretin. Protein content, proteolytic enzyme activities, and antibody activities against cow's milk proteins, alpha-casein, and beta-lactoglobulin B, were measured in the duodenal fluid. After pancreozymin-cholecystokinin stimulation, immunoglobulin A and immunoglobulin M antibody activities rose to peak levels in 5-10 min. The increase in protein content and proteolytic enzyme activities after pancreozymin-cholecystokinin stimulation paralleled the increase in antibody activity against the two cow's milk proteins. Secretin, in spite of its known dilutional effect on duodenal fluid enzyme concentration, also produced a rise in immunoglobulin M and immunoglobulin A antibody activities. Only a slight increase in immunoglobulin G antibody activity was noted after both pancreozymin-cholecystokinin and secretin. It is suggested that, pancreozymin-cholecystokinin and secretin, in addition to their well-established effects on the release of digestive enzymes, also stimulate release of specific antibodies against food proteins. Release of antibody coincident with food intake may act in preventing the inadvertent absorption of antigenic food proteins.

Effect of early weaning and prolonged nursing on development of the rat pancreas

Pancreatic development was studied in rats 17-28 days of age. Control pups, weaned naturally at 21-24 days showed a gradual increase in body weight, pancreatic weight, total DNA and protein content with age. Pups weaned at 17 days showed a transient increase in pancreatic weight and protein content only at day 22; at no time did they show a difference in either DNA content or body weight. Pups nursed up to 25 days of age had a smaller body weight, but had DNA and protein content similar to control rats. Control pups showed gradual increases in lipase and trypsinogen with a sharp increase in amylase between days 22 and 25. Pups weaned at 17 days showed a precocious increase in trypsinogen and a sharp increase in amylase between days 19-22, but an immediate decrease in lipase which eventually returned to the control level at day 28. Pups nursed beyond the weaning stage showed an increase in lipase and trypsinogen but no sharp increase in amylase. A significant increase in all pancreatic enzymes, pancreatic mass, pancreatic DNA and protein content was seen in all groups of rats irrespective of their diet. The results suggest an inherent biological program as a basic control of pancreatic ontogeny with diet playing a modifying role.

The treatment of unstable trochanteric fracture by Ender's nailing: early results of a prospective trial

The early results of a prospective trial on the treatment of unstable trochanteric fractures of the femur by Ender's nailing are encouraging. The operation is easy to perform, reliable and carries little added risk of operative complications. Most of the patients could walk independently with a stick by the 6th post-operative week. The incidence of complications such as wound infection, hip joint penetration by the nails, superolateral cut out and backing out of the nails distally were low. External rotation deformity of the limb as well as knee pain continued to be problematic especially in the early post-operative period. However, this did not seem to affect rehabilitation and the pain became less of a problem with the passage of time. Early full weight-bearing did not significantly increase varus deformity or implant failure even in Kyle's Type III unstable fractures.

Effect of fasting and refeeding on pancreatic enzymes and secretagogue responsiveness in rats

Fasting reduced amylase and increased lipase concentrations but did not affect trypsinogen concentrations in the adult rat pancreas. Fasting also decreased the pancreatic contents of trypsinogen and amylase. A decrease in the responsiveness of dispersed pancreatic acini to carbachol was evident after 3 days of fasting but only at high concentrations of secretagogues. Acini regained their responsiveness, and enzyme concentrations returned to normal after refeeding. Serum insulin levels of fasted rats decreased to one-fourth of control levels but rose to normal 24 h after refeeding. Insulin or glucose given alone prevented the increase in lipase after fasting. Both insulin and glucose were needed to maintain the acinar response to secretagogues in fasted rats. Although cholecystokinin restored the protein and trypsinogen content in fasted rats, it did not correct the relative changes in the exocrine enzymes. There are therefore reversible changes in the exocrine pancreas after fasting. Insulin, glucose, and cholecystokinin seem to regulate these changes.

Collagen production by rat hepatocytes and sinusoidal cells in primary monolayer culture

The cellular sources of collagen in normal rat liver have been examined. Hepatocytes and nonparenchymal (sinusoidal) cells were isolated and established in primary monolayer culture. These cells were incubated with radiolabeled proline in the presence of l-ascorbate and beta-aminopropionitrile. Nondialyzable material was prepared from the cell layer and the medium from each type of culture. The level of collagen accumulation was determined by measuring labeled hydroxyproline and sensitivity to purified bacterial collagenase. In hepatocytes, collagen represented 0.2% of both secreted and cell-associated labeled protein. In sinusoidal cells, collagen was 3.2% of secreted and 1.1% of cell-associated proteins. The total secreted labeled collagen, expressed per microgram of DNA, was similar in hepatocytes and sinusoidal cells. However cell-associated collagen in hepatocyte culture was approximately 10-fold that present in sinusoidal cells. These findings indicate that, while collagen formation is a relatively important function of sinusoidal cells, in normal liver the contribution of hepatocytes to total hepatic collagen accumulation may be substantial.

Effect of pancreozymin and secretin on intraluminal enterokinase, trypsin, and chymotrypsin activities of cystic fibrosis and control children

Duodenal fluids from control and cystic fibrosis (CF) patients were assayed for enterokinase (EK), trypsin and chymotrypsin activities. CF patients as a group were found to have higher basal EK activity in spite of low trypsin and chymotrypsin activities. In control patients, pancreozymin (CCK) injection led to increases in specific activities of trypsin and chymotrypsin and a decrease in EK but did not change the total EK activities. Secretin administration led to decreases in specific activities of trypsin and chymotrypsin compared to post-CCK levels. The total EK activities were greatly increased following secretin administration. Thus, secretin may have direct influence on the release of EK into the duodenum. CCK and secretin have no effect on the specific activities of trypsin, chymotrypsin and EK in CF patients. EK release in CF patients is either constitutive and therefore not affected by CCK and secretin or it has been fully induced by the low trypsin content and becomes unresponsive to further hormonal stimulation.

The development of pancreatic function in premature infants after milk-based and soy-based formulas

Thirty-one premature infants who required nasojejunal feeding were evaluated for pancreatic exocrine function before and after feeding of milk-based or soy-based formulas for 30 days. The two groups were well matched for age and birth weight (about 1.5 kg). At birth, all infants had high basal secretion of trypsin and chymotrypsin, but low lipase and no amylase activity. Additionally, there was no response to pancreozymin (CCK). After 30 days of feeding with either soy or milk-based formulas, both groups showed a similar increase in body weight (to 1.8 kg) and basal secretion of trypsin, chymotrypsin, and lipase and failure to secrete amylase. The group that was fed milk-based formula failed to respond to CCK and secretin administration. Thus, soy- and milk-based formulas result in similar weight gain and similar basal pancreatic enzyme secretion while feeding with soy-based formula selectively increases the trypsin and lipase response to CCK.

Effect of intrauterine growth retardation on the activities of fetal intestinal enzymes in rats

The activities of maltase, lactase, alkaline phosphatase and enterokinase were followed in the small intestine of rats during prenatal development. These enzymes were detectable only after the 17th day of gestation. Furthermore, each enzyme exhibited a different pattern of prenatal presence. Maltase activity appeared first (day 18), followed by lactase and alkaline phosphatase (day 19) and then enterokinase (day 20). Except for enterokinase, all of the enzymes attained a level of activity close to the newborn levels at the final day of gestation. Induced intrauterine growth retardation during the 3rd trimester led to a decrease in intestinal weight proportional to the reduction of body weight. These decrease in size of the small intestine was caused by a reduction in cell number rather than cell size. Induced intrauterine growth retardation also resulted in a selective reduction in the specific activities of lactase and alkaline phosphatase, but not of enterokinase and maltase. These results suggest that reduction in maternofetal blood flow in the 3rd trimester of gestation will cause a selective decrease in some brush border enzymes (lactase and alkaline phosphatase) but does not effect others (maltase and enterokinase).

Development of functional responses in human exocrine pancreas

The ability of newborns to digest proteins, fats, and carbohydrates depends, to a large extent, on their level of exocrine pancreatic function. Building on the limited published data, we studied pancreatic enzyme activities in the duodenal fluid and the response of the exocrine pancreas to secretogogues in 15 premature and full-term infants at birth and at 30 days of age. We compared these findings to those obtained from identical studies of 17 children age 2 years and above. In addition, we measured the pancreatic exopeptidase, carboxypeptidase B, in relation to other pancreatic enzymes. The duodenal fluid of newborns and infants contained no amylase and negligible lipase. Carboxypeptidase B levels were also low compared to those in the older children. In contrast, chymotrypsin activity in infants was about 50% to 60% of level found in the older children. Trypsin activity, the highest of all the enzymes measured, was about the same in both newborns and older children, with a transient increase at 30 days. Administration of pancreozymin had no effect on pancreatic enzymes in the duodenal fluid of newborns and a slight effect on 1-month-old infants. But by age 2 years, a full response of the pancreas to pancreozymin was evident. In infants and newborns, responses to secretin were poor. Thus, the secretory response of the human pancreas to secretogogues, absent or minimal at birth, is acquired during the postnatal period.

Glucoamylase and disaccharidase activities in normal subjects and in patients with mucosal injury of the small intestine

The development of glucoamylase activity was compared to that of disaccharidase in the small intestinal mucosa of infants and children. By the age of one month, infants have glucoamylase and disaccharidase levels comparable to those of young adults, indicating that young infants may be able to digest and absorb starches. In infants and children with varying degrees of mucosal injury of the small intestine, the activities of glucoamylase decreased progressively with increasing severity of the villus atrophy. However, the reduction of lactase, palatinase, and sucrase activities was more severe than the loss of activities of glucoamylase and maltase. Thus, children and infants may tolerate polymers of glucose better than disaccharides when they have mucosal injury associated with prolonged diarrhea.

Bombesin-induced desensitization of enzyme secretion in dispersed acini from guinea pig pancreas

Incubating dispersed acini from guinea pig pancreas with bombesin and then washing the cells to remove bombesin reduced the subsequent stimulation of amylase secretion caused by bombesin, litorin, or ranatensin by as much as 80%, but did not alter the stimulation of amylase secretion caused by cholecystokinin, carbamylcholine, A23187 or vasoactive intestinal peptide. This bombesin-induced desensitization was reversible, and the onset of the process, as well as its reversal, were time and temperature dependent. Neither desensitization or resensitization were inhibited by abolishing protein synthesis. The concentrations of bombesin required to cause desensitization were in the same range as those required to stimulate amylase secretion. Incubating pancreatic acini with vasoactive intestinal peptide did not reduce the subsequent stimulation of amylase secretion caused by vasoactive intestinal peptide, bombesin, or cholecystokinin. These results indicate that bombesin-induced desensitization of pancreatic acini reflects changes that occur at or close to the bombesin receptor.

Fat necrosis

Fat necrosis has been found to be associated with many forms of pancreatitis, carcinoma of the pancreas and pancreatic trauma. The causative agents seem to be pancreatic lipase and colipase, which presumably escape from the pancreas during the development of the disease. The precise mechanism by which these factors attack the adipose tissue, leading to the formation of foci of fat necrosis, is not known. The pathologic finding of fat necrosis is not restricted to the peritoneal-retroperitoneal region, where a direct contact with these factors is the most likely cause. In other patients, fat necrosis involves peripheral tissues, notably in subcutaneous adipose tissue throughout the body, in joints of the hand and foot and in bone marrow. This is associated with additional complications dependent upon the sites involved and is manifested as skin lesions, polyarthritis and osteolytic defects in patients who sometime suffer from a primary pancreatic disease.