bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of lumenal contents on colonic cell replacement.
Authors: Stragand J , Hagemann R F
Published: December 2017

Recent studies have shown that the rate of colonic cell renewal can be altered through fasting and refeeding, which produces a marked depression and transient stimulation, respectively. In the present study, the role of physical versus nutritional stimulation in the colonic fasting-refeeding response and the renewal of the functional colonic compartment were evaluated via a nondestructive colonic ligation procedure. The results reported herein suggest that physical stimulation by lumenal factors is in part required to initiate the colonic hyperplasia seen after refeeding. Blood-borne nutritional factors, in the absence of physical stimulation, cannot alone stimulate colonic cell production. Additional evidence is presented which suggests that this physical stimulation may be manifested through the lumenal distension produced by the newly ingested food materials. The results are discussed from the viewpoint of influencing the functional colonic compartment and physiological capacity.
Ascorbic acid flux across mucosal border of guinea pig and human ileum.
Authors: Mellors A J , Nahrwold D L , Rose R C
Published: December 2017

The unidirectional influx of L-[14C]ascorbic acid (vitamin C) across the mucosal border of guinea pig and human ileum was determined. Influx follows saturation kinetics, indicating that a carrier mechanism is operative. The maximal influx in guinea pig ileum bathed in Ringer is 140 nmol/cm2-h and the ascorbic acid concentration greater than 6 mM , or when the tissue is bathed in Na-free media, influx is approximately linearly related to the ascorbic acid concentration, and absorption by simple diffusion may predominate. With mucosal ascorbic acid concentration of 0.28 mM, influx is reduced by at least 70% when Na-free media is used; however, influx is not dependent on the intracellular Na concentration. The brush border mechanism appears to be stereospecific and not closely coupled to cellular metabolism. A model of transport is favored that features a carrier-mediated transport mechanism for simultaneous entry of ascorbic acid and Na across the brush border. This model is similar in nature to, but functionally distinct from, the sodium-gradient mechanism postulated to effect sugar and amino acid transport in mammalian ileal mucosa.
Enhanced riboflavin incorporation into flavins in newborn riboflavin-deficient rats.
Authors: Muttart C , Chaudhuri R , Pinto J , Rivlin R S
Published: December 2017

The incorporation of a subcutaneous injection of [14C]riboflavin (2.5 muCi/100 g body wt) into flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and flavins bound covalently to proteins was determined at 1, 6, and 18 h in liver, cerebrum, and cerebellum from progeny of normal and maternally riboflavin-deficient Holtzman rats. Radioactivity remaining as riboflavin was also determined under these circumstances. Experiments were initiated within 24 h of birth. In both groups of newborn rats, the incorporation of radioactive riboflavin into covalently bound flavins in liver and brain proceeded more slowly than into the other flavin fractions. In addition, radioactivity incorporated into covalently bound flavins comprised a relatively smaller proportion of the total amount incorporated in brain than in liver. In progeny of riboflavin-deficient dams, an increased rate of incorporation of riboflavin into all three flavin derivatives, particularly FAD, was observed in liver and brain, compared to results in normal progeny. These data provide evidence that maternal riboflavin deficiency enhances the incorporation of riboflavin into tissue flavins in liver, cerebrum, and cerebellum from newborn rats.
Feeding in response to insulin but not to 2-deoxy-D-glucose in the hamster.
Authors: Ritter R C , Balch O K
Published: December 2017

Adult hamsters did not increase their food intake in response to subcutaneous injection of 2-deoxy-D-glucose (2DG) at doses of 50, 200, 350, 500, 750, 1,000, or 1,500 mg/kg. The failure to feed in response to 2DG was apparent regardless of time of testing and length of test. Hamsters did display marked hyperglycemia after 2DG treatment. Therefore, hamsters do detect and form neural responses to 2DG. In contrast to 2DG, injection of regular insulin, 2, 4, or 8 U/animal, caused hamsters to significantly increase their food intake over a 5-h test period. Furthermore, injection of 4 U of protamine zinc insulin twice daily also caused pronounced increases in food intake and weight gain by hamsters. Because hamsters do not seem to posses a feeding response to 2DG-induced glucoprivation, it seems unlikely that insulin elicits feeding via the glucoprivic control in this species. The results suggest that 1) hamsters lack the glucoprivic control of feeding behavior as exercised by 2DG, 2) 2DG and insulin treatments are not equivalent ingestive challenges, and 3) insulin-induced feeding may result in part from activation of a nonglucoprivic control of food intake.
Dietary iodine and accumulation of radioiodine in thyroids of chickens.
Authors: Newcomer W S
Published: December 2017

Groups of hatchling white leghorn cockerels were fed a basic, semisynthetic low-iodine diet to which various amounts of iodide were added: 0 up to 100 microgram I/g feed. Growth rates were unaffected by the range of dietary iodine content. A transitory goiter occurred only in the group fed the basic low-I diet. Half-life of 131I in the thyroid increased directly and fractional turnover rate inversely with increase of dietary iodine. Trichloroacetic acid-soluble iodine in serum did not accurately reflect variation of dietary iodine. However, effective clearance and binding rate constants did decrease proportionally to dietary iodine increase beyond the first 3-5 days. Concentration of iodine in thyroid was directly proportional to dietary iodine after 10 days. There was no consistent correlation between thyroxine or triiodothyronine and dietary iodine except in general terms of high and low dietary iodine groups. The avian thyroid exhibits great lability in adjusting functionally to a wide range of dietary iodine contents.
Intestinal O2 consumption and 86Rb extraction during arterial hypoxia.
Authors: Shepherd A P
Published: December 2017

Earlier reports indicated that arterial hypoxia not only dilated intestinal resistance vessels but also increased capillary filtration coefficients. The latter finding was interpreted as reflecting an increased number of perfused capillaries. Because both increased blood flow and increased capillary density would tend to maintain tissue oxygenation in spite of arterial hypoxia, the main purpose of this paper was to determine how effectively intestinal O2 utilization is maintained during arterial hypoxia. Therefore, I perfused isolated loops of canine small bowel at constant arterial pressure. Under this condition, reducing arterial PO2 to a mean value of 46 +/- 2.4 mmHg caused blood flow to increase to 146% of control, and O2 consumption was kept within 26% of control. In gut loops perfused at constant blood flow, arterial hypoxia depressed O2 uptake still further, but measurements of 86Rb extraction confirmed that the density of the perfused capillary bed increased. Thus, the responses of both resistance and exchange vessels tend to maintain O2 delivery to intestinal tissue during arterial hypoxia.
Interdigestive motor activity of Heidenhain pouches in relation to main stomach in conscious dogs.
Authors: Itoh Z , Takayanagi R , Takeuchi S , Isshiki S
Published: December 2017

A great number of studies using Heidenhain pouches have been reported, but most of them have been concerned with secretory activity. Studies on the motor activity of the pouch are few, and our knowledge about it is rather limited. In the present study, therefore, long-term changes in contractile activity of the Heidenhain pouches were recorded simultaneously with those of the main stomach in conscious dogs by means of chronically implanted force transducers. It was found that during the interdigestive state Heidenhain pouches contracted precisely in association with the main stomach. During this time a series of strong contractions arose simultaneously in the Heidenhain pouch and the main stomach, lasted for 24.2 +/- 1.90 min, and then ceased abruptly. Such strong contractions were followed by a long period of motor quiescence lasting for 86.9 +/- 6.06 min. These characteristic recurring episodes in the Heidenhain pouch and the main stomach lasted during the interdigestive state but were inhibited by the ingestion of food or intravenous administration of pentagastrin. These findings indicate that the interdigestive motor activity of the stomach is strongly controlled by a humoral factor(s) rather than the parasympathetic nervous system; however, we also propose a possible role for the sympathetic nervous system for coordinated occurrence of the interdigestive contractions between the Heidenhain pouch and the main stomach.
Effect of thoracic vagotomy and vagal stimulation on esophageal function.
Authors: Kravitz J J , Snape W J , Cohen S
Published: December 2017

The purpose of this study was to determine the effect of thoracic vagotomy and thoracic vagal stimulation upon esophageal peristalsis and lower esophageal sphincter (LES) function in the opossum. The thoracic portion of the vagus nerve was sectioned in the upper or lower thorax. Bilateral, but not unilateral, thoracic vagotomy above the level of the heart abolished peristalsis and LES relaxation in response to swallowing or cervical vagal electrical stimulation. Thoracic vagotomy at the level of the ventricle or below did not alter either peristalsis or LES relaxation during swallowing or cervical vagal stimulation. Secondary peristalsis and its associated LES relaxation was unaltered by thoracic vagotomy at any level. Electrical stimulation of the distal end of the upper thoracic vagus elicited both peristalsis and LES relaxation. Electrical stimulation of the distal end of the lower thoracic vagus elicited both peristalsis and LES relaxation. Electrical stimulation of the distal end of the lower thoracic vagus, as well as stimulation of the vagal branches to the terminal esophagus, gave only LES relaxation. These studies suggest that: a) the major extrinsic vagal innervation mediating primary peristalsis terminates in the upper portion of the esophagus, whereas the vagal innervation mediating LES relaxation responses are present throughout the length of the esophagus; and b) secondary peristalsis and its associated LES relaxation occurs independent of extrinsic vagal innervation.
Spike bursts in rabbit oviduct. I. Effect of ovulation.
Authors: Talo A , Hodgson B J
Published: December 2017

Electrical activity of rabbit oviducts was recorded in vitro at 18, 24, and 68 h after injection of human chorionic gonadotropin. An array of eight suction electrodes 1-2 mm apart was moved sequentially to cover nearly the whole oviduct. The frequency of spike bursts, pacemaker frequency, percentage of nonpropagating bursts, and probability of propagating in the uterine direction varied steeply within a few millimeters along the oviduct. On the average, spreading was only slightly prouterine. Compared to 18 and 24-h, 68-h oviducts showed higher frequency of activity and longer distances of propagation, particularly in the isthmus. The activity extended to 65.8 and 69.6% of the distance from the fimbriae at 18 and 24 h, respectively, and at 68 h to 70.8% and 84.6% in those oviducts that contained and did not contain ova, respectively. Ova were recovered on the uterine side of the border of activity or in regions in which the percentage of nonpropagating bursts was high or, at 18 and 24 h, in segments containing local regions of inactivity. Apparently, frequency of activity, the degree to which propagation of activity deviates from randomness, and the length of the inactive area regulate the location of ova in the isthmus.
Spike bursts in rabbit oviduct. II. Effects of estrogen and progesterone.
Authors: Hodgson B J , Talo A
Published: December 2017

Electrical activity of rabbit oviducts was recorded in vitro at 48 h after injection of human chorionic gonadotropin (HCG), 18 or 24 h after HCG with progesterone pretreatment, and 48 or 68 h after HCG with estrogen treatment 24 or 0 h after HCG, respectively. Frequency of spike bursts, pacemaker frequency, percentage of nonpropagating bursts, and probability of propagating in the uterine direction were obtained. Estrogen treatment decreased frequency of activity; at 48 h distance of propagation was increased and activity extended to 72.4% of the length of the oviduct compared to 65.7% in oviducts removed 48 h after HCG without estrogen. Only the ampullary-isthmic junction was active at 68 h after estrogen and HCG injection. Progesterone increased frequency and imposed a uterine bias, and activity extended to 73.6% of the length of the oviduct. These data support the hypothesis that properties of activity in the active area and the location of the active-inactive border regulate the location of ova in the isthmus of the rabbit oviduct.
Histaminergic pharmacology of primate lower esophageal sphincter.
Authors: Brown F C , Dubois A , Castell D O
Published: December 2017

We have studied the lower esophageal sphincter (LES) response to exogenous histamine and to H1- and H2-blocking agents in the awake baboon. Increasing intravenous bolus doses of histamine produce an increase in LES pressure with a maximum response at a dose of 12 microgram/kg. H1-receptor blockade with chlorpheniramine over a wide dose range did not alter basal LES pressure but did abolish the response of the LES to exogenous histamine. H2-receptor blockade with cimetidine at doses markedly inhibiting gastric acid secretion (2 mg/kg.h) did not alter basal LES pressure or the response of the LES to exogenous histamine. In addition, cimetidine did not alter the response of the LES to pentagastrin and bethanechol. Although histamine and histamine receptors are important in gastric secretion, they appear to have no identifiable role in the maintenance of basal LES smooth muscle tone in the baboon. These results demonstrate the presence of a stimulatory H1 receptor on baboon LES smooth muscle, but provide no evidence for the presence of an H2-inhibitory receptor. As opposed to the parietal cell, the LES response to pentagastrin and bethanechol does not require a H2 receptor.
Responses of feline esophagus to cervical vagal stimulation.
Authors: Dodds W J , Stef J J , Stewart E T , Hogan W J , Arndorfer R C , Cohen E B
Published: December 2017

We used an in vivo feline model to study striated and smooth-muscle esophageal responses to cervical vagal stimulation (VS). Circular esophageal contractions were measured by intraluminal pressure sensors and longitudinal contractions by a force transducer. Responses to VS were recorded before and after giving succinylcholine, atropine, or both. Circular contractions characteristic of striated and smooth muscle were recorded from the mid- and distal esophagus, respectively. With increases in VS frequency, the striated muscle showed rapid, repetitive twitches progressing to tetany. These fast contractions had a square-wave configuration at VS greater than or equal to 10 Hz and were abolished by succinylcholine. In contrast, the slow-twitch circular responses of smooth muscle showed no repetitive twitches and had a bell-shaped configuration. Two types of circular smooth-muscle contractions were observed: 1) A wave "on contractions" occurred 0.5-1.0 s after VS onset, regardless of stimulus length, and 2) infrequent B wave "off contractions" occurred only after stimulus cessation. The longitudinal esophageal contractions had a compound wave form with both striated and smooth-muscle components. Atropine abolished the slow component of the longitudinal contraction, the circular A wave, and peristalsis in the distal esophagus. We conclude that cholinergic motor neurons are an important pathway for eliciting peristalsis in feline esophageal smooth muscle.
GnRH membrane binding: identification, specificity, and quantification in nonpituitary tissues.
Authors: Heber D , Marshall J C , Odell W D
Published: December 2017

Utilizing biologically active 125I-labeled gonadotropin-releasing hormone (125I-GnRH), specific binding with two affinites [KA (high) = 3.2 x 10(8) M-1, KA (low) = 10(5) M-1] were identified in membrane preparations derived from the 10,800 x g pellet of rat pituitary. GnRH-specific low affinity sites (KA - 10(5) M-1) were identified in liver, spleen, renal cortex, lung, testis, ovary, and cardiac muscle. Hypothalamic tissue demonstrated both high- and low-affinity binding. When 125I-GnRH was bound and dissociated, the labeled GnRH retained fully ability to rebind to fresh membrane preparations. That is, binding was not associated with loss of biological activity of GnRH. However, when unbound 125I-GnRH was exposed to the membrane fraction of liver, almost all receptor binding activity disappeared. The presence of low-affinity binding sites in peripheral tissues raises several possibilities: 1) they act as a simple reservoir mediating metabolic clearance of GnRH; 2) they represent enzyme binding sites involved in degradation of GnRH; 3) they mediate peripheral actions of GnRH; or 4) they are simply a cellular membrane constituent unrelated to target actions of GnRH.
Effects of thyroxine on protein turnover in rat skeletal muscle.
Authors: Flaim K E , Li J B , Jefferson L S
Published: December 2017

The effects of thyroxine (T4) on protein turnover in skeletal muscle were studied using normal, thyroidectomized (thyrex), and hypophysectomized (hypox) rats. Thyrex rats had a depressed growth rate that was accompanied by 50% reductions in the level of RNA and the rate of protein synthesis in gastrocnemius muscle, as determined in the perfused hemicorpus. Protein synthetic efficiency (protein synthesis per unit RNA) was decreased by 18%. Daily treatment of thyrex rats with T4 at different dose levels for up to 16 days led to improved growth rates, elevated RNA concentrations, and increased protein synthesis rates. The primary effect of T4 was to increase the protein synthetic capacity of muscle. Protein degradation, determined in the perfused hemicorpus, and activity of a lysosomal protease, determined in unperfused muscle, were reduced in the thyrex condition. Treatment of thyrex rats with T4 increased protein degradative rates, but not protease activity. Hypox rats, which also exhibited depressed skeletal muscle protein synthesis, responded to T4 and combined T4 and growth hormone with marked improvements in protein synthesis.
Simultaneous analysis of families of sigmoidal curves: application to bioassay, radioligand assay, and physiological dose-response curves.
Authors: DeLean A , Munson P J , Rodbard D
Published: December 2017

Physiological and pharmacological studies of hormones, drugs, and neurotransmitters often generate families of sigmoidal dose-response curves. Optimally efficient data analysis should involve simultaneous description of all curves, rather than fitting each one individually. We have developed a general computerized method to describe the dose-response curves in terms of basal and maximal responses, ED50, and curve shape or steepness. This facile method permits rigorous statistical analysis, provides a basis for pooling of information from separate experiments, and allows one to test which characteristics are shared by various curves.
Transplantation of pancreatic beta-cells prevents development of hypothalamic obesity in rats.
Authors: Inoue S , Bray G A , Mullen Y S
Published: December 2017

The present experiments have tested the hypothesis that ventromedial hypothalamic (VMH) lesions enhance insulin secretion by neural mechanisms. Rats were made diabetic by injecting streptozotocin to destroy their own pancreatic beta-cells. Subsequently, transplants of fetal pancreatic tissue were placed under the renal capsule. VMH lesions were placed in rats whose diabetes was cured with transplants as well as sham-transplanted animals. The animals were followed for 4 wk. The lesioned rats with pancreatic transplants gained no more weight than the sham-operated controls. There was no significant rise in insulin in the transplanted rats after VMH lesioning, but the VMH lesioned rats with intact pancreatic tissue showed the expected rise in insulin. Food intake rose 71% in the VMH lesioned rats with intact beta-cells, but only 23% in the VMH lesioned rats with transplants. Hypertrophy of the pancreatic islets was also observed in the VMH lesioned rats with an intact pancreas, but was not found in the VMH lesioned rats with a transplanted pancreas. Thus, transplantation of pancreatic tissue beneath the renal capsule of diabetic rats prevented the characteristic hyperphagia, hyperinsulinemia, and obesity in VMH lesioned rats whose pancreas was free from intact innervation. The results support the hypothesis that neural mediation of the rise in insulin is the primary factor in the development of hypothalamic obesity.
Effect of toxigenic Escherichia coli on myoelectric activity of small intestine.
Authors: Burns T W , Mathias J R , Carlson G M , Martin J L , Shields R P
Published: December 2017

When exposed to cholera toxin (CT), distal ileal loops of the rabbit small intestine showed an alteration in myoelectric activity. This alteration was defined as the migrating action potential complex (MAPC). The purpose of this study was to determine, using myoelectric recording techniques, the effects of live toxigenic Escherichia coli (TEC) on motility. Live TEC, live nontoxigenic E. coli (NTEC), and culture filtrates of these organisms were studied. Live TEC and its filtrate induced MAPC activity similar to that of CT. Live TEC induced a mean of 3.8 MAPCs/h, significantly greater than induced by live NTEC. TEC filtrate induced a mean of 14.2 MAPCs/h, significantly greater than NTEC filtrate. Heating the TEC filtrate to 100 degrees C before use resulted in a significant decrease of MAPC activity. This experiment demonstrated that live TEC and its culture filtrate altered ileal myoelectric activity. The effect may have been mediated by a heat-labile enterotoxin. This study suggests that alterations in small intestinal motility may be important in the pathogenesis of TEC diarrhea.
Electrical and mechanical effects of molecular variants of CCK on antral smooth muscle.
Authors: Morgan K G , Schmalz P F , Go V L , Szurszewski J H
Published: December 2017

Intracellular microelectrode and standard organ bath techniques were used to study in vitro the effects of three molecular forms of the peptide cholecystokinin on the electrical and mechanical activities of canine antral circular muscle. Three forms were studied: the carboxyl-terminal octapeptide of cholecystokinin (CCK-OP), the molecule containing 33 amino acid residues (CCK33), and the peptide termed "cholecystokinin variant" that contains 39 amino acids (CCK39). All three forms increased the force and frequency of spontaneous contractions. They also increased the frequency and the amplitude and duration of the plateau of the gastric action potential. Atropine did not block any of these effects, suggesting that the action of these peptides was largely due to a direct action on the smooth muscle. Complete dose-response curves were determined for the effect of these peptides on the force and frequency of contraction for muscle strips and for the effect on amplitude of the plateau and frequency of the action potential for single cells. CCK39 and CCK-OP had similar potencies and both forms were more potent than CCK33.
Plasma kinetics and urinary excretion of exogenous human and salmon calcitonin in man.
Authors: Huwyler R , Born W , Ohnhaus E E , Fischer J A
Published: December 2017

The metabolism and the urinary excretion of synthetic human and salmon calcitonin-(1--32) [hCT-(1--32), sCT-(1--32)] administered by constant infusions for 240 min were investigated in eight normal subjects. On gel filtration of plasma obtained during the infusions mainly intact hCT-(1--32) and sCT-(1--32) were recognized with homologous radioimmunoassay systems. During constant infusions to equilibrium of 0.04 mg hCT-(1--32) and sCT-(1--32), the metabolic clearance rates (MCR) amounted to 8.4 +/- 1.1 and 3.1 +/- 0.1 ml/kg per min, respectively (P less than 0.01). When hCT-(1--32) was infused at rates of 1 and 4 mg/240 min, the MCR were lower than with 0.04 mg hCT-(1--32), but still higher than with 0.04 mg sCT-(1--32). The half-lives of disappearance of hCT-(1--32) were faster compared to sCT-(1--32), but the difference was not statistically significant. The urinary clearance of hCT-(1--32) determined during the 1 and 4 mg/240 min infusions of hCT-(1--32), as well as of sCT-(1--32) determined during the 0.04-mg infusions of sCT-(1--32) was about 0.1% of the MCR. The half-lives of disappearance of hCT- and sCT-(1--32) incubated in vitro in plasma and urine ranged from 17 to more than 72 h, and the degradation did not affect our calculations of the metabolic breakdown of exogenous CT in vivo.
Osmotic flow of water in isolated frog gastric mucosa.
Authors: Durbin R P
Published: December 2017

A gravimetric procedure was used to measure net volume flow across bullfrog gastric mucosa mounted between chambers. A portion of the net volume flow towards the lumen was coupled to acid production. With an isotonic solution instilled on the luminal surface, the secreted acidity (ratio of increase in acid output to increase in volume flow) was hypertonic, in agreement with previous reports in mammalian stomach. Dilution of the secretory solution to 10% of normal nearly abolished the net volume flow coupled to acid production so that the mean secreted acidity rose to 1.87 M. Other experiments in which gastric juice was collected from this preparation showed that secretion into an initially empty lumen was only slightly hypertonic, as in mammalian stomach. The results indicate that instillation of secretory solution dilutes the endogenous osmotic gradient due to secreted HC1. This gradient is probably just outside the apical surface of the oxyntic cells of stomach.
Prostaglandins and tetrodotoxin-insensitive relaxation of opossum lower esophageal sphincter.
Authors: Daniel E E , Crankshaw J , Sarna S
Published: December 2017

Field stimulation with pulses of 0.5 or 5 ms relaxed isolated strips of lower esophageal sphincter (LES) of the opossum; only responses to 0.5-ms pulses were inhibited by tetrodotoxin. Black widow spider venom prevented relaxation to both stimuli; thus both stimuli may release nonadrenergic inhibitory mediator. Isoproterenol, but not PGEs or ATP, was a consistent relaxant of LES. PGF2alpha (approximately 1 microgram/ml) and stable endoperoxides (approximately 10 ng/ml) stimulated LES muscle. Doses of indomethacin (IDM) or 5,8,11,14-eicosatetraynoic acid (ETA), which inhibited contractions to arachidonic acid increased then abolished LES tone, inhibited relaxations to 5-ms pulses and less effectively to 0.5-ms pulses. Inhibition of relaxation preceded loss of tone. Tone could be restored by carbachol, PGEs, or PGF2alpha and relaxation after IDM but not ETA was also restored. Prostaglandins may participate in functioning of nonadrenergic inhibitory nerves and in maintaining sphincter tone. Cells that did not appear to be smooth muscle were in gap junction contact with smooth muscles and closely apposed to nerves with small agranular vesicles. A role for these structures, which are postulated to be interstitial cells, in tetrodotoxin-insensitive prostaglandin-related release of nonadrenergic inhibitory mediator was proposed.
Effect of solute-coupled volume absorption on oxygen consumption in cat ileum.
Authors: Valleau J D , Granger D N , Taylor A E
Published: December 2017

The effects of solute-coupled volume absorption on blood flow, oxygen consumption, and vascular resistance were analyzed in autoperfused segments of cat ileum. Intestinal absorption was stimulated by placing either Tyrode solution, Tyrode + glucose, or Tyrode + taurocholate into the ileal lumen. Net volume absorption rates (Jv,m) were determined using a volume recovery method. Oxygen consumption (VO2) increased during the absorption of all solutions. The absorption of Tyrode solution plus glucose caused the greatest increase in VO2, whereas Tyrode plus taurocholate resulted in the smallest increase. For Tyrode solution and Tyrode plus glucose absorption, the increased VO2 was due predominantly to an increased blood flow, whereas the increased VO2 with taurocholate resulted from an increased oxygen extraction. A linear relationship between the change in VO2 during transport and Jv,m was aquired for Tyrode solution, and Tyrode + glucose. The results indicate that the oxygen requirements of the absorbing intestine are dependent on both the rate of transport and the solutes being transported.
Altered copper absorption in tumor-bearing and estrogen-treated rats.
Authors: Cohen D I , Illowsky B , Linder M C
Published: December 2017

Intestinal copper absorption was studied in normal, tumor-bearing and estrogen-treated rats, using 64Cu(NO3)2. Rats bearing Dunning mammary tumors (DMBA 5A) of more than 2 g absorbed 70-100% more of an intragastric copper dose than controls, and a much larger percentage was found in the plasma, with less in liver and kidney. The distribution of copper measured chemically mimicked these findings, and the enhanced capacity for absorption was also demonstrated in vitro with everted duodenal segments. Further examination of the intestinal mucosa revealed that binding of radioactive copper to a 10,000-dalton component of the cytosol was inversely proportional to the amount absorbed into the body, tumor-bearing rats retaining much less in, and transferring much more from, the intestine than controls. Daily injection of 17 beta-estradiol over 2 wk had the reverse effect. It is concluded that the absorption of copper is an endogenously regulated process that may be altered by cancer and estrogen treatment and mediated by the extent of its binding to a component (possibly metallothionein) within the mucosal cell.
Glucose intolerance following chronic metabolic acidosis in man.
Authors: DeFronzo R A , Beckles A D
Published: December 2017

The effect of chronic metabolic acidosis (0.1 g/(kg . day) X 3 days) on carbohydrate metabolism was examined with the glucose-clamp technique in 16 healthy volunteers. Hyperglycemic clamp. Plasma glucose concentration is acutely raised and maintained 125 mg/dl above the basal level. Because the glucose concentration is held constant, the glucose infusion rate is an index of glucose metabolism (M). Following NH4Cl, M decreased from 8.95 +/- 1.12 to 7.35 +/- 0.76 (P less than 0.05) despite an increased plasma insulin concentration (I) 23 +/- 9%, P less than 0.05). Consequently the M/I ratio, an index of tissue sensitivity to insulin, decreased by 32 +/- 5% (P less than 0.005). Euglycemic clamp. Plasma insulin concentration is acutely raised and maintained 101 +/- 3 microU/ml above basal and plasma glucose is held constant at the fasting level by a variable glucose infusion (M). Following NH4Cl both M and M/I decreased by 15 +/- 4% (P = 0.005) and 15 +/- 5% (P = 0.01), respectively. Metabolic acidosis had no effect on basal [3-3H]glucose production or the percent of decline (91 +/- 4%) following hyperinsulinemia. Both hyperglycemic and euglycemic clamp studies indicate that impaired glucose metabolism following metabolic acidosis results from impaired tissue sensitivity to insulin.
Antihypertensive effect of progesterone in rats with mineralocorticoid-induced hypertension.
Authors: Wambach G , Higgins J R
Published: December 2017

Uninephrectomized, saline-fed male Sprague-Dawley rats were given DOCA 5 mg per week alone or together with progesterone 20 mg per week for 6 weeks (phase I). Subsequently, the doses of DOCA and progesterone were doubled and the rats were studied for an additional 6 wk (phase II). Progesterone prevented DOCA-induced hypertension during phase I. Phase II blood pressures were higher in DOCA-progesterone-treated animals than in controls, but remained lower than in animals treated with DOCA alone. At the end of phase II the animals were killed, and blood samples and skeletal muscle samples were taken for analysis of electrolyte content. DOCA-treated animals were found to have an increased rate of potassium excretion, an increase in muscle sodium concentration, and a decrease in muscle potassium concentration compared to the controls. Progesterone treatment significantly blunted the DOCA-induced changes in muscle electrolyte concentrations and increased the rate of sodium excretion. No hypotensive effect was observed when progesterone in doses similar to those of phase I was administered to spontaneously hypertensive rats. Thus, in experimental mineralocorticoid hypertension, the hypotensive effect of progesterone appears to correlate closely with its mineralocorticoid antagonistic properties.
Effects on rat parotid amylase and Ca of alpha- and beta-adrenergic sympathetic stimulation.
Authors: Jirakulsomchok D , Schneyer C A
Published: December 2017

The roles of alpha- and beta-adrenergic receptors in the regulation of the secretion of amylase and calcium from rat parotid gland were studied by using direct electrical stimulation of the sympathetic innervation to the gland in the presence of selective adrenergic blocking agents. When phenoxybenzamine was administered intraperitoneally 25 min prior to nerve stimulation, the highest [Ca] (12-14 meq/liter) and amylase activity (1,000 mg/microliter) in the evoked saliva were observed. On the other hand, stimulation of the nerve in the presence of propranolol evoked a saliva that contained the lowest [Ca] (5-6 meq/liter) and amylase activity (170 mg/microliter). Furthermore, salivary flow (4.27 +/- 0.42 microliter/min X g) induced by sympathetic nerve stimulation in the presence of phenoxybenzamine was higher than that induced by sympathetic nerve stimulation in the presence of propranolol (2.55 +/- 0.39 microliter/min X g). Therefore, it was concluded that beta-adrenergic receptors play the major role in the regulation of salivary flow and the secretion of amylase and calcium, whereas alpha-adrenergic receptors play a minor role in the regulation of these parameters.
Insulin secretion by isolated perfused rat and mouse pancreas.
Authors: Lenzen S
Published: December 2017

A method for isolation and perfusion of a pancreas preparation consisting of pancreas, stomach, proximal duodenum, and spleen is described. Basic characteristics of regulation of insulin secretion from the perfused pancreas isolated from rats, albino mice, obese mice (ob/ob), and black mice were identical. Viability and stability of the pancreas preparation during perfusion were maintained as documented by measurements of oxygen consumption of the pancreas preparation, perfusion pressure, and pH of the perfusion medium. The insulin-secretory capacity of the pancreas of different animal species was compared. Insulin secretion by the perfused rat and obese (ob/ob) mouse pancreas was much more potent than that by the pancreas of lean albino and lean black mice. D-Glucose-induced insulin secretion from the pancreas was decreased after fasting of the animals and was dependent on glucose concentration and presence of calcium in the perfusion medium. D-Glyceraldehyde, tolbutamide, D-mannose, dihydroxyacetone, L-leucine, and L-arginine also induced insulin secretion from the pancreas. D-Fructose, D-galactose, L-glucose, 3-O-methyl-D-glucose, N-acetylglucosamine, D-xylose, D,L-glyceric acid, pyruvate, L-lactate, and theophylline did not provoke insulin secretion.
Effect of phosphorus depletion on intestinal calcium and phosphorus absorption.
Authors: Lee D B , Brautbar N , Walling M W , Silis V , Coburn J W , Kleeman C R
Published: December 2017

Intestinal calcium (Ca) hyperabsorption is a well-documented feature of experimental phosphorus depletion (PD). To further evaluate the effect of PD on Ca absorption we studied metabolic balance and in vitro everted duodenal sac uptake of Ca and phosphorus (P) in weanling male rats. Animals were assigned to three dietary groups: normal, 0.3% P ad libitum (NP); low, 0.03% P ad libitum (LP); and normal, 0.3% P but pair-fed with assigned LP mates (NP-PF). Results indicate that although PD led to an early but unsustained increase in 45Ca uptake by the everted duodenal sac in vitro, net intestinal Ca retention is consistently decreased in rats on the LP diet compared with rats eating either the NP or NP-PF diet. The reduction in net intestinal Ca absorption is reflected by an increase in fecal Ca, both in absolute quantities and in proportion to dietary Ca intake. The initial negative P balance after the initiation of the LP diet was promptly, albeit precariously, corrected. This was associated with a sustained increase in duodenal 32P uptake in vitro and virtual cessation of growth. Because the biosynthesis of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and its accumulation in intestinal mucosa have been reported to increase with PD, our study represents an example in which the physiological interrelationship between the activity of 1,25(OH)2D3 and intestinal Ca absorption may be dissociated.
Role of pancreatic polypeptide in canine gastric acid secretion.
Authors: Parks D L , Gingerich R L , Jaffe B M , Akande B
Published: December 2017

The interrelationships of canine pancreatic polypeptide (cPP) and gastric acid secretion were studied in dogs following infusion of histamine or pentagastrin. Pentagastrin stimulated gastric acid release 30-fold and simultaneously increased plasma cPP secretion by an average of 120 pg/ml. Although histamine stimulated gastric acid secretion to a comparable degree, it had no effect on plasma cPP levels. Three mechanisms of inhibition of acid secretion (cimetidine, duodenal acidification, and somatostatin) had different effects on pancreatic polypeptide (PP) levels. With a background infusion of pentagastrin, cimetidine did not affect cPP levels. In contrast, somatostatin dramatically inhibited both gastric fistula output and cPP release. Finally, a 10-min duodenal irrigation with 0.1 N HCl resulted in a brief spike in cPP levels (from 266 +/- 12 to 347 +/- 31 pg/ml) at the time of greatest inhibition of histamine-stimulated acid secretion. Infusions of histamine + porcine pancreatic polypeptide (pPP) at concentrations of 1.0 and 2.25 microgram/kg per h and of pentagastrin + pPP at 2.25 microgram/kg per h closely simulated postprandial cPP levels (mean 1306 +/- 18 pg/ml at 30 min) but produced no change in gastric fistula output. These studies demonstrated that PP levels and rates of gastric acid secretion are unrelated and that at physiologic concentrations PP plays no significant role in the regulation of gastric acid secretion.
Plasma secretin concentrations in fasting and postprandial states in dog.
Authors: Kim M S , Lee K Y , Chey W Y
Published: December 2017

In four dogs with a modified Herrara pancreatic fistula and gastric cannula and three dogs with two duodenal cannulas, ingestion of a meat meal resulted in a significant and sustained increase in the mean plasma immunoreactive secretin concentrations, from mean fasting levels of less than 10 pg/ml to 25--55 pg/ml. This increase in the plasma secretin concentration coincided with a marked increase in pancreatic bicarbonate output and frequent decreases in the mean proximal duodenal pH to less than 4.5 from the range of 6.5 in the fasting state. Intravenous administration of cimetidine, 150 mg, produced a marked suppression of postprandial increases in both pancreatic bicarbonate output and plasma secretin concentration. Moreover, the postprandial duodenal pH rarely reached below 5.0 after cimetidine administration. These studies indicate that plasma secretin concentration does increase significantly after a meal. The postprandial increase in plasma secretin concentration appears to depend on the gastric acid delivered in the proximal duodenum. A possible physiological role of secretin in the pancreatic secretion after a meal is indicated by these findings.
Scanning esophageal impedance probe for measurement of luminal cross section.
Authors: Mary D A , North P J , Hunt J N
Published: December 2017

A scanning esophageal probe for measuring luminal cross section is described. Current is injected into electrode assemblies so that a variable voltage output directly proportional to interelectrode impedance and inversely proportional to cross-sectional area of the medium around the electrodes may be measured. The device is capable of measuring the cross section of glass cylinders. It was used in one esophagus to measure the cross-sectional area of different sizes of swallowed bolus. The probe offers a safe and repeatable method of studying dynamic changes in luminal dimensions of the esophagus.
Effects of colchicine and vinblastine on in vitro gastric secretion.
Authors: Kasbekar D K , Gordon G S
Published: December 2017

The effects of colchicine and vinblastine on in vitro bullfrog gastric mucosal preparations were studied with respect to H+ and pepsinogen secretion. In the concentration range of 1--50 mM, an initial but transient colchicine-mediated stimulation of H+ secretion is followed by a dose-dependent inhibition. The transient stimulation of H+ secretion can be confirmed in resting preparations in the absence of added secretagogues. In the same concentration range, colchicine inhibits pepsinogen secretion to a greater degree than H+ secretion. Vinblastine (10(-5)--5 X 10(-4) M) was more effective than colchicine in inhibiting both H+ and pepsinogen secretion. The kinetics of inhibition of secretion by both colchicine and vinblastine were slow. Cytochalasin B had no effect on either secretion.
Neonatal gastric motility in dogs: maturation and response to pentagastrin.
Authors: Malloy M H , Morriss F H , Denson S E , Weisbrodt N W , Lichtenberger L M , Adcock E W
Published: December 2017

Postnatal changes in the pH of gastric secretions, gastric motility, serum gastrin concentration, and response of the stomach to pentagastrin administration were studied in 15 beagle puppies from birth to 5 wk of age. Motility was monitored manometrically via twin-lumen catheters 3--6 h postprandially. Mean gastric pH was stable at 5.85 until the 7th postnatal day when pH decreased to 3.45; pH then increased to a mean value of 4.95 through the 18th day. Antral contractions increased from 0.2 contractions per min on the day of birth to a maximum 2.3 contractions per min on the 11th day and then gradually declined. Pentagastrin (8.0 microgram/kg sc) had no effect on gastric pH or motility until the 2nd postnatal wk. Pentagastrin inhibited the rate and peak pressure of antral contractions from the 2nd through the 5th wk. Mean serum gastrin concentrations in six puppies were greater than values for adult dogs, attaining a preweaning maximum on the 9th day.
Age-dependent inhibition of suckling by cholecystokinin.
Authors: Blass E M , Beardsley W , Hall W G
Published: December 2017

The effects of exogenous cholecystokinin (10--40 U/kg body wt) on neonatal rat suckling were studied in 5-, 10-, 15-, and 20-day-old rats that were equipped with tongue cannulas. Milk (0.1 ml over 10 s) was delivered through the tongue cannula once every minute, providing a rat was still suckling. Cholecystokinin, a well-established inhibitor of adult rat feeding, did not reduce milk intake volume of 5- and 10-day-old rats. It did, however, depress milk intake of 15- and especially of 20-day-old rats. Despite its effect on milk intake, cholecystokinin never lengthened the latency to attach to the nipple and, paradoxically, reduced it on certain occasions. The implications of these findings for the events controlling various aspects of suckling behavior throughout the course of the nursing-suckling period in rats and for the mechanism of action of cholecystokinin are discussed.
Actions of peptides isolated from amphibian skin on amylase release from dispersed pancreatic acini.
Authors: Uhlemann E R , Rottman A J , Gardner J D
Published: December 2017

In dispersed acini prepared from guinea pig pancreas, peptides isolated from amphibian skin (caerulein, bombesin, litorin, and physalaemin) as well as eledoisin, a peptide isolated from the posterior salivary gland of a Mediterranean octopod, caused a significant increase in amylase release. Each amphibian peptide potentiated the stimulation of amylase release caused by vasoactive intestinal peptide or secretin in that the increase in amylase release caused by an amphibian peptide plus vasoactive intestinal peptide or secretin was significantly greater than the sum of the increase caused by each secretagogue acting alone. Potentiation of amylase secretion did not occur with an amphibian peptide plus cholecystokinin or carbachol.
Use of microspheres to measure small intestinal villus blood flow in the dog.
Authors: Bond J H , Levitt M D
Published: December 2017

The accuracy of using 7- to 10-micron microspheres to measure blood flow to dog small intestinal villi was studied. These spheres appear to pass unimpeded through the afferent arterioles of the villus and lodge at the villus tip because 1) virtually all villus spheres were located at the tip, 2) flow determined by visually counting spheres did not differ significantly from flow determined from radioactivity of the sheared-off villus layer, 3) the size distribution of spheres in the villus and subvillus layers was virtually identical to that administered, indicating no premature impaction of the larger spheres, and 4) spheres lodging in the submucosa during vasoconstriction did not subsequently migrate to the villi during vasodilatation. Studies with 25-micron spheres indicated that 28% of the 7- to 10-micron spheres shunted through vessels greater than 10 micron. Double isotope studies showed that lodges spheres do not migrate and that the injection of 2--4 X 10(6) spheres does not alter villus flow. Thus, 7- to 10-micron microspheres pass to and lodge in villus vessels in proportion to capillary flow and should provide an accurate estimate of villus nutrient blood flow.
Regulation of hepatic free fatty acid metabolism by glucagon and insulin.
Authors: Witters L A , Trasko C S
Published: December 2017

The roles of glucagon and insulin in the direct short-term regulation of hepatic free fatty acid (FFA) metabolism were studied in hepatocytes isolated from fed, fasted, and streptozotocin-induced diabetic rats. In fed animals, the principal metabolic product of palmitate metabolism was triglyceride, whereas ketones were the major product in fasted and diabetic animals. Glucagon at physiological concentrations increased ketogenesis and decreased triglyceride synthesis from palmitate in hepatocytes from fed rats at FFA concentrations 1.0 mM or less. Insulin had no effect on FFA metabolism when present as the sole hormone, but could antagonize the actions of submaximal concentrations of glucagon. The metabolism of palmitate in fasted or diabetic hepatocytes was unaffected by either hormone. Ketogenesis from octanoate was also unaffected by hormone addition in all cell types. These data are consistent with a locus of hormonal regulation at a step prior to beta-oxidation of fatty acid. Glucagon and insulin may modulate FFA metabolism by both intrahepatic and extrahepatic mechanisms.