Effect of tryptophan on transport properties of newborn rabbit jejunum.

The effect of tryptophan on sodium and chloride fluxes was determined simultaneously on paired flat-sheet preparations of newborn rabbit jejunum under short-circuit conditions. In the absence of amino acids, the newborn rabbit jejunum actively absorbed sodium, and possibly bicarbonate, whereas chloride appeared to be distributed passively across the jejunum. Tryptophan (2 mM) caused an increment in short-circuit current (Isc) that was due to an increase in net active sodium flux and had no significant effect on tissue conductance. At a 10 mM concentration, tryptophan initially increased Isc, although not to as large a degree as phenylalanine or alanine, and then caused a progressive decline that reached a plateau around 60 min. The reduction in Isc was attributed primarily to abolition of sodium absorption and stimulation of chloride secretion. Tryptophan reduced the unidirectional fluxes of sodium, increased those of chloride, and decreased total tissue conductance. These results suggest that 10 mM tryptophan initially causes a predicted increase in sodium absorption, followed by an inhibition of sodium absorption and stimulation of chloride secretion. The mechanism of action of tryptophan resulting in changes in ion fluxes is unknown.

Pulse upstroke in Africans.

Electro-acoustic time intervals are measured on sphygmorecordings from the QRS to the Korotkoff sound. Simultaneously recorded brachial cuff pressures plotted against the interval for each beat constitute a sphygmochronogram. For a series of 56 individuals free of cardio-respiratory disease who presented at University College Hospital, Ibadan, the parameters of the sphygmochronogram showed expected intercorrelation but there was an unexpectedly short ti (electro-acoustic time interval at the inflection) of 0.16 + 0.02s, compared with 0.21 + 0.02s for series in the U.S.A. and Portugal. Values for dP/dt init. (rate of pressure rise in early ejection) were not reported for these series but our results are similar to those from Sweden.

Synaptic activation of erratic burst-type myenteric neurons in cat small intestine.

To study further the ongoing spike discharge of burst-type myenteric neurons, extracellular recordings were made with either Teflon-insulated Pt wire electrodes (tip diam, 20 micrometers) or 3 M NaCl-filled glass micropipettes (tip diam, 1-2 micrometers). Presynaptic fibers to the erratic bursters were activated by electrical shocks delivered through Teflon-insulated Pt wire electrodes. Single electrical shocks applied to either the surface of the ganglion or an interganglionic connective elicited bursts of spikes that had parameters (interspike intervals and spikes per burst) that closely resembled the spontaneously occurring bursts in the same neuron. The latencies of the responses to electrical stimulation ranged from 5 to 30 ms. The responses were reversibly abolished when the concentration of Mg2+ in the bathing solution was elevated to 12 mM. The responses to electrical stimulation were unaffected by atropine, hexamethonium, d-tubocurarine, epinephrine, norepinephrine, methysergide, morphine, naloxone, and substance P. The ongoing burst-type discharge of cat myenteric neurons appeared to reflect a synaptic event that could be mimicked by electrical stimulation of presynaptic fibers. The identity of the neurotransmitter that elicits the burst-type discharge is unknown. The transmitter is probably not acetylcholine, serotonin, norepinephrine, an opiatelike peptide, nor substance P.

Tryptophan transport by isolated newborn rabbit jejunum.

Segments of newborn or adult rabbit jejunum were mounted as flat sheets in flux chambers. Mucosal-to-serosal (Jm leads to s) and serosal-to-mucosal (Js leads to m) fluxes of tryptophan (Try), phenylalanine (Phe), and alanine (Ala) were measured in the absence of electrochemical gradients. In the presence of Na, J Try s leads to m increased linearly with concentration, whereas the relationship of J Try m leads to s and concentration contained both linear and saturating components. The relationship of net Try flux and concentration was in accord with Michaelis-Menten kinetics. Ouabain (10(-3) M) abolished net Na fluxes in both newborn and adult rabbit jejunum and abolished net Try flux in the adult, but did not reduce net Try flux to zero in the newborn. In the presence of Na-free solutions small net fluxes of Try, Phe, and Ala occurred in the newborn. Addition of 10(-4) M 2,4-dinitrophenol abolished net Try flux in ouabain-treated newborn rabbit jejunum that was bathed by either Na-free or Na-containing solutions. In the presence of Na, Phe and Ala reduced J Try m leads to s, and Try reduced the fluxes of Phe and Ala. Phe inhibited J Try m leads to s in Na-free solutions, and Try reduced J Phe m leads to s. These results suggest that the newborn rabbit jejunum resembles the adult in that Try is absorbed primarily by a Na-dependent system. These results show that the newborn differs from the adult in that Try is absorbed by a system that is independent of Na but requires metabolic energy.

Jejunal transport properties of piebald mouse model for Hirschsprung's disease.

Unidirectional fluxes of alanine, methionine, and Na were measured in jejunal segments from 3- to 4-wk-old normal (N) mice or mice with congenital (P) or induced (I) megacolon in the absence of electrochemical gradients. Short-circuit currents were 286.8 +/- 16.3 and 302.1 +/- 32.6 mu A/cm2 for P and I mice, respectively, and were approximately 1.5-2 times greater than in N mice. Tissue conductances averaged 42.3 +/- 0.6 and 39.3 +/- 3.4 mS/cm2 for P and I mice, respectively, and were twice those found in N mice. Net Na absorption was 2-3 times greater in P than N mice and was increased by addition of alanine. Alanine and methionine were actively absorbed and the net fluxes of alanine were 2-3 times greater in p and I mice than in normals. Unidirectional alanine influx was enhanced in P and I mice. Jmax of 9.7 +/- 2.6 and 14.2 +/- 1.0 micro M x cm-2 x h-1 were obtained for N and P mice, respectively. These results show that the transport properties of jejunal mucosa of mice with megacolon differ from those of N mice. Mice with megacolon absorb alanine and Na at a greater rate than N mice and the enhanced amino acid absorptive rate can be explained by an increased alanine influx, probably due to an increased number of active transport carriers.

Esophageal duplication cyst. Case report.

A patient with an esophageal cyst is reported. Esophageal duplication cysts account for a very small percentage of benign esophageal tumors and are infrequently symptomatic. Patients with esophageal cysts seek treatment when a complication such as bleeding or infection causes these cysts to enlarge. The diagnosis may be made with barium swallow and esophagoscopy although the exact histopathology is not defined until surgery. Surgical excision is recommended at the time of cyst discovery whether symptoms are present or not.

Achlorhydria and benign gastric ulcer.

A 76 year-old man with a benign gastric ulcer and pernicious anemia is reported. The etiology of the ulcer is unexplained.

Does 5-hydroxytryptamine influence "purinergic" inhibitory neurons in the intestine?

Intrinsic inhibitory neurons to guinea pig taenia coli and small bowel circular muscle were activated by transmural electrical stimulation, and the postinhibitory contractile response of the muscle was utilized to evaluate whether or not the neuronal action of 5-hydroxytryptamine (5HT) was associated with the inhibitory neurons. The postinhibitory contractile responses of the small intestinal circular muscle were unaffected by 5HT. The 5HT antagonist methysergide also did not affect the poststimulus contractile response of the circular muscle. The amplitude and area under the contractile curve of the poststimulus contractile response of the taenia coli were reduced and the amplitude of the relaxation response to electrical stimulation was increased in one-half of the preparations after application of 5HT. Methysergide did not alter the poststimulus contractile response of the taenia coli. 5HT is implicated as a neurotransmitter substance for slow synaptic excitation within the enteric nervous system of the guinea pig small intestine; however, the 5HT synapses do not appear to be present on the "purinergic" inhibitory neurons nor on neurons that synaptically influence the inhibitory neurons.

Parallel pathways for ion transport across rat gastric mucosa: effect of ethanol.

Transmural fluxes of 22Na or 36Cl across the isolated rat gastric mucosa were measured simultaneously with [3H]mannitol in an attempt to separate transmural ionic movement into cellular and noncellular components. The relationships between mannitol flux and the fluxes of Na and Cl are characteristic of simple diffusion, suggesting that mannitol traverses the isolated epithelium largely via noncellular pathways. The total tissue conductance can be described as the sum of two components, one of which is highly correlated with the transmural mannitol flux and presumably represents the conductance of a noncellular leak path. The cellular components of the mucosa-to-serosa Na flux and of both Cl fluxes are highly correlated with the short-circuit current. Exposure of the mucosal surface of the epithelium to 4% ethanol reduces the short-circuit current and increases the electrical conductance. Ethanol inhibits the active transport of Na and Cl and increases the apparent permeability of noncellular pathways for transmural ionic diffusion.

Laboratory aids in the diagnosis of pancreatitis.

The diagnosis of both acute and chronic pancreatitis continues to be a challenge despite the development of new techniques and the refinement of old methods. The problem is best approached by the application of a combination of tests which can provide a reasonable degree of sensitivity and specificity applicable to the different forms of pancreatitis. In acute pancreatitis an elevation of serum amylase and amylase/creatinine clearance ratio is diagnostically useful. In chronic pancreatitis, several tests are needed to enhance the diagnostic yield, and such tests can include the secretin-pancreozymin test, ERCP, fecal fat measurement, Lundh test meal, and the administration of the synthetic peptide BZ-Ty-PABA.

Effects of some gastrointestinal hormones on two muscle layers of duodenum.

The duodenums of opossums and cats were cut into strips 2 mm wide and 2-2.5 cm long. Strips cut in the oral-caudal axis were called longitudinal strips; those cut at 90 degrees to that axis were called circular strips. Cholecystokinin (CCK) and cerulein stimulated phasic contractions of circular muscle of opossum duodenum, but had no effect on the longitudinal muscle. The effect of CCK was not blocked by tetrodotoxin (10(-7)M), indicating a direct muscle stimulation. CCK had no effect of both muscle layers of the cat duodenum. Vasoactive intestinal peptide raised tension in longitudinal muscle, but reduced tension in circular muscle of opossum duodenum. Glucagon slightly reduced tension in both longitudinal and circular muscle of opossum duodenum. It also inhibited contractions of circular muscle caused by acetylcholine. Pentagastrin and secretin had no effect on either muscle layer in either species. These findings suggest that the circular and longitudinal muscle layers of the duodenum respond differently to at least some gastrointestinal hormones. Also, there is species variation in response to gastrointestinal hormones.

A comparison of intrinsic nerve supplies of two muscular layers of duodenum.

The duodenums of opossums and cats were cut into strips 2 mm wide and 2-2.5 cm long. Strips cut in the direction of the oral-caudal axis were called longitudinal strips, and those cut at 90 degrees to that axis were called circular strips. Each muscle strip was stimulated with trains of electrical rectangular pulses (10 Hz, 50-70 V, 0.5 ms). In the longitudinal strips, electrical field stimulation caused contraction, and this contraction was abolished by atropine, 10(-7) M. In the circular strips, electrical field stimulation caused relaxation. This relaxation was abolished by tetrodotoxin, 10(-7) M, but it was not affected by antagonists to adrenergic and cholinergic transmission, nor by some gastrointestinal hormones. Reserpinization of the opossums or alteration of the frequencies of electrical field stimulation from 0.1-50 Hz did not affect or alter the relaxation of the circular strips or the contraction of the longitudinal strips. These findings suggest that the longitudinal muscle is dominated by an excitatory cholinergic innervation, and the circular muscle is dominated by a nonadrenergic, noncholinergic inhibitory innervation.