Effects of arterial pH and carbon dioxide on pancreatic exocrine H+/HCO3- secretion and secretin-dependent translocation of cytoplasmic vesicles in pancreatic duct cells

Role for malic enzyme, pyruvate carboxylation, and mitochondrial malate import in glucose-stimulated insulin secretion

Pyruvate cycling has been implicated in glucose-stimulated insulin secretion (GSIS) from pancreatic beta-cells. The operation of some pyruvate cycling pathways is proposed to necessitate malate export from the mitochondria and NADP(+)-dependent decarboxylation of malate to pyruvate by cytosolic malic enzyme (ME1). Evidence in favor of and against a role of ME1 in GSIS has been presented by others using small interfering RNA-mediated suppression of ME1. ME1 was also proposed to account for methyl succinate-stimulated insulin secretion (MSSIS), which has been hypothesized to occur via succinate entry into the mitochondria in exchange for malate and subsequent malate conversion to pyruvate. In contrast to rat, mouse beta-cells lack ME1 activity, which was suggested to explain their lack of MSSIS. However, this hypothesis was not tested. In this report, we demonstrate that although adenoviral-mediated overexpression of ME1 greatly augments GSIS in rat insulinoma INS-1 832/13 cells, it does not restore MSSIS, nor does it significantly affect GSIS in mouse islets. The increase in GSIS following ME1 overexpression in INS-1 832/13 cells did not alter the ATP-to-ADP ratio but was accompanied by increases in malate and citrate levels. Increased malate and citrate levels were also observed after INS-1 832/13 cells were treated with the malate-permeable analog dimethyl malate. These data suggest that although ME1 overexpression augments anaplerosis and GSIS in INS-1 832/13 cells, it is not likely involved in MSSIS and GSIS in pancreatic islets.

A novel capsaicin derivative VOA induced relaxation in rat mesenteric and aortic arteries: involvement of CGRP, NO, cGMP, and endothelium-dependent activities

The vasorelaxant effects of N-[4-O-[2-methoxy, phenoxyethylaminobutyl]-3-methoxy benzyl]-nonamide (VOA), a novel capsaicin derivative, and associated releasing activities of nitric oxide (NO) and calcitonin gene-related peptide (CGRP) were investigated in this study. Systemic administration of VOA decreased blood pressure and heart rate in a dose-dependent manner in both normotensive as well as spontaneously hypertensive rats. Nw-nitro-L-arginine methyl ester (L-NAME), glibenclamide, and capsazepine inhibited VOA-induced hypotension. In phenylephrine-precontracted rat aortic rings and mesenteric arteries with intact endothelium, VOA caused a concentration-dependent relaxation. This relaxation was reduced after endothelium was removed or pretreated with L-NAME, methylene blue, 1 H-[1,2,4]oxidazolol [4,3-a] quinoxalin-1-one, tetraethylammonium, glibenclamide, CGRP (8-37), or capsazepine, respectively. In endothelially denuded vessel rings, tetraethylammonium, glibenclamide, CGRP (8-37), and capsazepine also reduced VOA-induced relaxation. In high potassium (80 mmol/L)-precontracted rat aortic rings with intact endothelium, VOA failed to induce relaxation. VOA induced a concentration-dependent increase of CGRP-like enzyme immunoreactivity, which was also significantly inhibited by capsazepine. In human umbilical vein endothelial cells, VOA increased NO release and guanosine-3', 5'-cyclic monophosphate level, which were significantly inhibited by L-NAME. The Western blot analysis on human umbilical vein endothelial cells indicated that VOA increased the expression of endothelium nitric oxide synthase. In conclusion, VOA might exert its relaxation effects in rat vascular smooth muscle through the CGRP/KATP channel and the NO/ cGMP pathway.

Effects of varying impulse number on cotransmitter contributions to sympathetic vasoconstriction in rat tail artery

We examined the contributions of the cotransmitters norepinephrine (NE), ATP, and neuropeptide Y (NPY) to sympathetically evoked vasoconstriction in the rat tail artery in isolated vascular rings by using 1-100 stimulation impulses at 20 Hz. Phentolamine (2 microM), the alpha-adrenoceptor antagonist, markedly reduced responses to all stimuli, although responses to lower impulse numbers were reduced less than responses to longer trains. The purinergic receptor antagonist suramin (100 microM) reduced all responses, but to a much greater extent with few impulse trains. Responses were further reduced or abolished by addition of the second antagonist. Any remaining responses were abolished by the NPY-Y(1) receptor antagonist BIBP-3226 (75 nM). NPY had a direct agonist action and potentiated sympathetically mediated responses. NPY (75 nM) potentiated responses and BIBP-3226 decreased responses to 2- and 20-impulse trains. Both affected responses from 2 impulses to >20 impulses, but there was no preferential effect on purinergic contributions to responses because neurally released NPY potentiated both "pure" NE and ATP responses equally. We conclude that all three cotransmitters contribute significantly to vascular responses and their contribution varies markedly with impulse numbers. There is considerable synergy between cotransmitters, especially with lower impulse numbers where NPY contributions are greater than expected.

Substance P modulates nicotinic responses of intracardiac neurons to acetylcholine in the guinea pig

Application of substance P (SP) to intracardiac neurons of the guinea pig causes slow depolarization and increases neuronal excitability. The present study was done to determine the influence of SP on fast excitatory responses of intracardiac neurons to ACh. Intracellular recording methods were used to measure responses of intracardiac neurons in whole mount preparations of atrial ganglionated nerve plexus from guinea pig hearts. Local pressure ejection of 100 microM SP (1 s) from a glass micropipette caused slow depolarization of all neurons (n = 38) and triggered action potential generation in 47% of the cells tested. Bath application of SP (0.5-100 microM) caused a dose-dependent depolarization of intracardiac neurons but rarely evoked action potentials, even at the highest concentration. However, such treatment with SP enhanced nicotinic responses evoked by local pressure ejections of ACh (10 mM, 10- to 100-ms duration) in 77% of intracardiac neurons studied (n = 52). A significant increase in amplitude of ACh-evoked fast depolarization occurred during treatment with 0.5 microM SP (13.0 +/- 1.8 mV for control vs. 17.7 +/- 1.9 mV with SP present, n = 7, P = 0.019). At higher concentrations of SP, enhancement of the response to ACh resulted mainly in action potential generation. However, responses to ACh were attenuated by SP in 15% of the intracardiac neurons studied. This attenuation occurred primarily during exposure to 10 and 100 microM SP and was manifest as a reduction in amplitude of nicotinic fast depolarization or inhibition of ACh-evoked action potentials. These findings support the conclusion that SP could function as a neuromodulator and neurotransmitter in intracardiac ganglia of the guinea pig.

Endogenous tachykinins cause bradycardia by stimulating cholinergic neurons in the isolated guinea pig heart

The purpose of this study was to determine if endogenous tachykinins can cause bradycardia in the isolated perfused guinea pig heart through stimulation of cholinergic neurons. Capsaicin was used to stimulate release of tachykinins and calcitonin gene-related peptide (CGRP) from cardiac afferents. A bolus injection of 100 nmol capsaicin increased heart rate by 26 +/- 7% from a baseline of 257 +/- 14 beats/min (n = 6, P < 0.01). This positive chronotropic response was converted to a minor bradycardic effect in hearts with 1 microM CGRP-(8-37) present to block CGRP receptors. The negative chronotropic response to capsaicin was markedly potentiated in another group of hearts with the further addition of 0.5 microM neostigmine to inhibit cholinesterases. In this group, capsaicin decreased heart rate by 30 +/- 10% from a baseline of 214 +/- 6 beats/min (n = 8, P < 0.05). This large bradycardic response to capsaicin was inhibited by 1) infusion of neurokinin A to desensitize tachykinin receptors or 2) treatment with 1 microM atropine to block muscarinic receptors. The latter observations implicate tachykinins and acetylcholine, respectively, as mediators of the bradycardia. These findings support the hypothesis that endogenous tachykinins could mediate axon reflexes to stimulate cholinergic neurons of the intrinsic cardiac ganglia.

Importance of gastrin-releasing peptide on acid-induced secretin release and pancreaticobiliary and duodenal bicarbonate secretion

BACKGROUND

Exogenous gastrin-releasing peptide (GRP) stimulates the release of secretin from the small intestine and pancreaticobiliary bicarbonate secretion in pigs. As acid is the principal stimulant of secretin release, the purpose of this study was to examine the importance of GRP in acid-induced secretin release and to determine whether GRP contributes to the regulatory function of acid-induced pancreaticobiliary bicarbonate secretion in anaesthetized pigs.

METHODS AND RESULTS

Intravenous infusion of GRP (500 pmol/kg.h) increased significantly portal vein plasma concentrations of secretin from 1.3 to 5.4 pmol/l and GRP from 0.5 to 340 pmol/l, pancreatic bicarbonate secretion from 0.01 to 5.9 mmol/h, and hepatic bicarbonate secretion from 0.3 to 3.3 mmol/h, whereas duodenal mucosal bicarbonate secretion remained unchanged. Intravenous infusion of the GRP antagonist BIM-26226 completely abolished the GRP-induced secretin release and pancreatic and hepatic bicarbonate secretion. Furthermore, repeated infusions of GRP did not cause desensitization, and BIM-26226 therefore proved to be an effective GRP antagonist. Duodenal perfusion with acid (pH 1.5, 3.8 mmol/h) significantly increased portal vein plasma concentrations of secretin from 0.4 to 2.8 pmol/l, pancreatic bicarbonate secretion from 0.005 mmol/h to 0.19 mmol/h, hepatic bicarbonate secretion from 0.63 to 2.17 mmol/h, and duodenal mucosal bicarbonate secretion from 0.1 to 1.20 mmol/h. Of importance, infusion of BIM-26226 did not significantly alter the effect of intraduodenal acidification on plasma secretin release and pancreaticobiliary and duodenal bicarbonate secretion.

CONCLUSIONS

Thus, we conclude that GRP likely plays an insignificant role in a possible peptidergic regulation of acid-induced intestinal secretin release and that GRP has no regulatory function in acid-induced pancreaticobiliary bicarbonate secretion. Furthermore, GRP has no effect on duodenal bicarbonate secretion.

Apical recruitment of CFTR in T-84 cells is dependent on cAMP and microtubules but not Ca2+ or microfilaments

Previous studies from this laboratory have demonstrated that chloride transport induced by forskolin, but not ionomycin, in T84 cells is highly dependent on an intact microtubular network. Using an antibody raised against a region of the R domain of CFTR, we now show by indirect immunofluorescence that forskolin causes relocation of CFTR to the apical domain of T84 cells. T84 cells grown on transparent filters were incubated with agonists and/or cytoskeletal inhibitors prior to fixation, permeabilization, and staining with the antibody. A 30 second stimulation with forskolin (10 microM) caused a twofold increase in relative fluorescence intensity at the apical surface. In contrast, a 30 second exposure to ionomycin (2 microM), had no effect on the distribution of CFTR-related fluorescence. Incubation of the cells with nocodazole (33 microM), a microtubule disrupting agent, prevented the forskolin-induced rise in CFTR fluorescence at the apical surface. However, incubation of the cells with cytochalasin D, an actin inhibitor, was without effect on forskolin-related re-distribution of CFTR-associated fluorescence. In double label experiments using antibodies against both beta-tubulin and actin, CFTR-related fluorescence was found to co-localize with the microtubule network, but not with actin filaments. These observations are consistent with the microtubule-dependent acute recruitment of CFTR to the apical plasma membrane of T84 cells in response to elevations in intracellular cAMP.

Secretin causes H+/HCO3- secretion from pig pancreatic ductules by vacuolar-type H(+)-adenosine triphosphatase

BACKGROUND/AIMS

Secretin stimulates pancreatic ductules to secrete HCO3- into pancreatic juice and H+ into interstitial fluid. The aim of the present study was first to examine whether ductular H+ secretion is inhibited by micromolar concentrations of bafilomycin A1, which blocks vacuolar H(+)-adenosine triphosphatase by specific action, and secondly to test for evidence of ductular Na+/HCO3- cotransport.

METHODS

Ductular H+ secretion was estimated from the rate of intracellular pH recovery after acid-loading (24 mmol/L NH4Cl) microdissected pancreatic ductules from pig, mounted in a flow-through perfusion chamber on the stage of a fluorescent microscope. Intracellular pH was measured using the fluorescent pH indicator 2'7'-bis (carboxyethyl)-5,6-carboxyfluorescein and dual-wave-length excitation of fluorescence. The ducts were superfused perfused with either HCO3(-)-free HEPES-containing buffers or HCO3(-)-containing buffers.

RESULTS

Secretin (10(-8) mol/L) induced a net H+ secretion of 1.87 +/- 0.23 mumol.mL cell vol-1.min-1 that was blocked by 10(-6) mol/L bafilomycin A1 and was unaffected by Na+ substitution with choline using HEPES superfusion buffers. Secretin-stimulated ductules superfused with bicarbonate-containing, Cl(-)-free buffers showed Na(+)-dependent and 4,4'-diisothiocyanostilbene-2, 2'-disulfonic acid-inhibitable alkalinization of intracellular pH.

CONCLUSIONS

Secretin causes H+/HCO3- secretion from pancreatic ductules by a mechanism involving vacuolar-type H(+)-adenosine phosphatase. Pancreatic ductules also show Na+/HCO3- cotransport, which may account for a small fraction of secreted bicarbonate.

Immunohistochemical study of catecholamine enzymes and neuropeptide Y (NPY) in the rostral ventrolateral medulla and bulbospinal projection

The purpose of this study was to determine whether neuropeptide Y (NPY) terminals in the intermediolateral spinal cord originate from the rostral ventrolateral medulla (RVLM). Immunohistochemical staining of tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), phenylethanolamine-N-methyltransferase (PNMT), and NPY in the rat brainstem and spinal cord were performed in this study in order to examine consequences of lesions of the RVLM and of intracisternal injections of 6-hydroxydopamine (6-OHDA) on catecholamine and NPY immunoreactivity in the intermediolateral column (IML) of rats. In addition, ricin, a retrograde neurotoxin, was applied in the superior cervical ganglion (SCG) to determine its effect on catecholamine and NPY immunoreactivity in the IML. Computer-aided image analysis was used to quantify the immunohistochemical changes in the RVLM and spinal cord. The results demonstrated that many catecholamine- and NPY-containing neurons and/or fibers existed in the RVLM and their terminals were found in the IML. After administration of 6-OHDA intracisternally, the catecholamine and NPY immunoreactivities were decreased both in the brainstem and IML of the spinal cord. Following unilateral microinjection of 6-OHDA into the RVLM, the number of NPY- and catecholamine-containing neurons decreased and there was a reduction in neuron terminals on the ipsilateral side. After injection of ricin into the SCG, the catecholamine and NPY neurons of the medulla were not affected, whereas their terminals in the IML decreased ipsilaterally. These results indicate that most of the catecholamine- and NPY-immunoreactive terminals found in the IML originated in the RVLM. These terminals appear to project towards the superior cervical ganglia.

Structural changes of the exocrine pancreas in a patient with cholecystolithiasis

The exocrine pancreas has been studied histologically, morphometrically, and ultrastructurally in a patient with cholecystolithiasis in comparison with three control patients free from gastrointestinal or pancreatic diseases. In the gallstone-bearing patient, acinar cells undergo a significant increase in the average cell area and average zymogenic area (i.e., the portion of acinar cell cytoplasm occupied by zymogen granules). In addition, these cells showed cytological signs of enhanced synthesis of secretory proteins and increased formation and release of zymogen granules. The findings concerning centroacinar/ductular cells are consistent with a significant increase in their number and average cell area that is associated with ultrastructural signs of enhanced functional activity.

Na(+)-H+ exchange is not important for pancreatic HCO3- secretion in the pig

Pancreatic inter- and intralobular duct cells extrude H(+)-ions to interstitial fluid when they secrete HCO3- to pancreatic juice. This study assesses the potential importance of Na(+)-H(+)-ion exchange for H(+)-ion extrusion and secretion of HCO3-, using the Na(+)-H+ exchange blockers amiloride and hexamethylene-amiloride. Intracellular pH (pHi) in inter- and intralobular pancreatic duct epithelium was measured using BCECF fluorescence. H(+)-ion efflux was measured using a NH4Cl prepulse, acid-loading technique. In HCO3(-)-free media, pHi recovery following acid loading was blocked by amiloride (10(-4) M) and hexamethylene-amiloride (10(-6) M), demonstrating amiloride- and hexamethylene-amiloride-sensitive Na(+)-H+ exchange. However, 5 x 10(-6) M hexamethylene-amiloride did not reduce secretin-dependent pancreatic HCO3- secretion in vivo. Maximal H(+)-efflux through Na(+)-H+ exchange was 1.5 +/- 0.2 mumol min-1 ml cell volume-1, i.e. less than 1% of estimated net H(+)-ion efflux during HCO3- secretion.

CONCLUSION

amiloride- and hexamethylene amiloride sensitive Na(+)-H+ exchange is not important for secretin-dependent pancreatic HCO3- secretion in the pig. Other mechanisms for H+ extrusion dominate.

Differential effects of galanin and neuropeptide Y on extracellular norepinephrine levels in the paraventricular hypothalamic nucleus of the rat: a microdialysis study

Evidence suggests that the peptides galanin (GAL) and neuropeptide Y (NPY) interact with the amine norepinephrine (NE) in the hypothalamic paraventricular nucleus (PVN) to stimulate feeding behavior. To directly investigate the nature of these interactions, extracellular levels of PVN NE were monitored in freely-moving rats using the microdialysis/HPLC technique. Following PVN administration of GAL (0.3 nmol), NPY (78 pmol) or Ringer's solution, local NE levels were measured at 20-min intervals for 2 hrs postinjection, under two feeding conditions, namely, in the presence or absence of food. The results demonstrate different effects of these peptides on endogenous NE levels. Following GAL administration, PVN NE levels were enhanced by 80 to 90%, up to 40 min postinjection, independent of food availability. In contrast, following NPY injection, NE levels were significantly reduced 20 min postinjection with food absent, and when food was available, NE levels tended to be enhanced. These results, consistent with pharmacological and biochemical studies, reveal different patterns of peptide-amine interactions in the PVN.

Secretin dissipates red acridine orange fluorescence from pancreatic duct epithelium

This study was undertaken to elucidate whether duct cells in the pancreas contain acidic cytoplasmic compartments regulated by secretin. Microdissected pancreatic ducts from pigs were examined by acridine orange (AO) and 2',7'-biscarboxyethyl-5(6)-carboxyfluorescein/tetraacetoxymethy l ester (BCECF/AM) epifluorescence microscopy. Estimated cytoplasmic pH using BCECF fluorescence was 7.43 +/- 0.04 and was not changed by altering CO2 tension in the incubation medium. The epithelium of acridine orange incubated peripheral interlobular pancreatic ducts exhibited green and red fluorescence; the colour depending on the experimental conditions. Red epithelial fluorescence was seen in resting pancreatic ducts and was greatly accentuated by raising CO2 in the incubation medium from 5.5 to 10 kPa. The red fluorescence was abolished by secretin, or following incubation with chloroquine or NH4Cl or the protonophores carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) or carbonyl cyanide m-chlorophenylhydrazone (CCCP), leaving uniform green fluorescence. These findings suggest that pancreatic duct cells contain CO2-dependent acidic compartments which vanish during secretin stimulation and which may be cytoplasmic tubulovesicles.

Colchicine blocks the effects of secretin on bile duct cell tubulovesicles and plasma membrane geometry and impairs ductular HCO3- secretion in the pig

Secretin causes the bile duct cells to secrete HCO3-. To examine whether the transformation of duct cell ultrastructure that follows secretin stimulation depends on microtubules and is important for ductular HCO3- secretion, we examined the effect of colchicine on ductular HCO3- secretion and on the morphology of cells lining bile ductules of anaesthetized pigs. Colchicine blocked secretin-dependent cytoplasmic clearance of tubulovesicles and prevented expansion of the basolateral plasma membrane in duct cells and reduced the ductular HCO3- secretory response from 132 +/- 25 mumol min-1 to 97 +/- 14 mumol min-1. In contrast, lumicolchicine did not affect secretin-dependent tubulovesicle clearance or plasma membrane geometry or ductular HCO3- secretion. Accordingly, secretin-dependent cytoplasmic clearance of tubulovesicles in bile duct cells appears to depend on microtubules and to be important for ductular HCO3- secretion.

Effects of stimulation of the superior cervical Ganglia and local application of noradrenaline on electrical activity of the Syrian hamster pineal gland

Abstract The effects of electrical stimulation of either or both superior cervical ganglia and the effects of local application of L-noradrenaline on the spontaneous electrical activity of hamster pineal cells were evaluated. Extracellular recordings from pineals of anaesthetized hamsters revealed that the spontaneous electrical activity was mainly regular with interspike intervals attributed between 12 to 20 ms during the daytime and mainly irregular with interspike intervals of 1 to 250 ms during the night. Following stimulation of the superior cervical ganglia, either unilaterally or bilaterally, or local application of noradrenaline, the responses of these pineal cells fell into three major categories: A) non-responsive, B) excited, and C) inhibited. There was no relationship between the magnitude or form of response and the source of stimulus i.e. the right superior cervical ganglia or the left superior cervical ganglia. Almost all inhibited responses from electrical stimulation of the superior cervical ganglia could be correlated with inhibited responses from the local application of noradrenaline whereas excited responses could not. In general, these results suggest that the spontaneous electrical activity of some pineal cells is influenced by inputs from the superior cervical ganglia and that the inhibitory input is likely to be mediated through the release of noradrenaline. The excitatory input from the superior cervical ganglia is probably mediated by another neurotransmitter. The heterogeneity of responses suggests that different receptors or different cell types may be involved.

Colchicine inhibits the effects of secretin on pancreatic duct cell tubulovesicles and HCO3- secretion in the pig

Secretin stimulation clears the cytoplasm of intralobular pancreatic duct cells in pigs of tubulovesicles and causes these cells to secrete HCO3- into the pancreatic juice. To determine whether the clearance of cytoplasmic tubulovesicles involves the microtubule system and is important for initiation of HCO3- secretion, the effect of the microtubule poison colchicine on duct cell morphology and pancreatic HCO3- secretion was measured in anaesthetized pigs. Before colchicine, secretin reduced the density of tubulovesicles in the cytoplasm of pancreatic duct cells from 92 +/- 8 U to 8 +/- 2 U and initiated pancreatic secretion of 176 +/- 21 mumols min-1 HCO3-. After colchicine, secretin failed to lower duct cell tubulovesicle density and caused the secretion of only 77 +/- 14 mumols min-1 HCO3-. By contrast, lumicolchicine, an isomer of colchicine that does not affect microtubules, did not inhibit pancreatic HCO3- secretion. Colchicine did not reduce carbonic anhydrase or Na,K-ATPase activities in in-vitro assays. The clearance of tubulovesicles from the cytoplasm of pancreatic duct cells therefore seems to be microtubule-dependent and important for the pancreatic HCO3- secretion.

Neuropeptide Y: presence in sympathetic and parasympathetic innervation of the nasal mucosa

The occurrence of neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) in the sympathetic and parasympathetic innervation of the nasal mucosa was studied in various species including man. A dense network of NPY-immunoreactive (IR) fibres was present around arteries and arterioles in the nasal mucosa of all species studied. NPY was also located in nerves around seromucous glands in pig and guinea-pig, but not in rat, cat and man. The NPY-IR glandular innervation corresponded to about 20% of the NPY content of the nasal mucosa as revealed by remaining NPY content determined by radioimmunoassay after sympathectomy. These periglandular NPY-positive fibres had a distribution similar to the VIP-IR and PHI-IR nerves but not to the noradrenergic markers tyrosine hydroxylase (TH) or dopamine-beta-hydroxylase (DBH). The NPY nerves around glands and some perivascular fibres were not influenced by sympathectomy and probably originated in the sphenopalatine ganglion where NPY-IR and VIP-IR ganglion cells were present. The venous sinusoids were innervated by NPY-positive fibres in all species except the cat. Dense NPY and DBH-positive innervation was seen around thick-walled vessels in the pig nasal mucosa; the latter may represent arterio-venous shunts. Double-labelling experiments using TH and DBH, and surgical sympathectomy revealed that the majority of NPY-IR fibres around blood vessels were probably noradrenergic. The NPY-positive perivascular nerves that remained after sympathectomy in the pig nasal mucosa also contained VIP/PHI-IR. The major nasal blood vessels, i.e. sphenopalatine artery and vein, were also densely innervated by NPY-IR fibres of sympathetic origin. Perivascular VIP-IR fibres were present around small arteries, arterioles, venous sinusoids and arterio-venous shunt vessels of the nasal mucosa whereas major nasal vessels received only single VIP-positive nerves. The trigeminal ganglion of the species studied contained only single TH-IR or VIP-IR but no NPY-positive ganglion cells. It is concluded that NPY in the nasal mucosa is mainly present in perivascular nerves of sympathetic origin. In some species, such as pig, glandular and perivascular parasympathetic nerves, probably of VIP/PHI nature, also contain NPY.

The exocrine pancreas in patients with hyperinsulinemic hypoglycemia. A morphometrical and ultrastructural study

The exocrine pancreas has been studied morphometrically and ultrastructurally in 12 patients with insulin-producing tumors in comparison with control patients free from gastrointestinal or pancreatic diseases and with normal glucose homeostasis. Light microscopical examination and morphometrical data revealed that in the insulinoma-bearing patients acinar cells undergo a marked and significant decrease in zymogen granule content, together with a slight reduction in the mean cell area. Such changes were accompanied by ultrastructural features indicating increased production and exocytosis of zymogen granules. The findings concerning centroacinar/ductular cells are consistent with an increase in their number and mean cell area, and an enhancement of their functional activity. In synthesis, both the enzyme- and bicarbonate-secreting cells appear to be greatly stimulated in conditions of chronic hyperinsulinemic hypoglycemia owing to the presence of insulinomas.