Effect of mild hypothermia on the vascular actions of phenylephrine in rat aortic rings

Intraoperative mild hypothermia is common. We have investigated the effects of mild hypothermia (34 vs 38 degrees C) on phenylephrine--(10(-8) to 10(-5) mol litre-1) induced contractions of rat aortic rings mounted for isometric tension recordings. A marked decrease in Emax (maximal tension) (P < 0.05) and significant increase in EC50 (phenylephrine concentration producing 50% of maximal tension) were observed at the lower temperature in endothelium intact rings, but there was no effect of temperature when the endothelium had been removed. The decreased contraction with hypothermia in the endothelium intact vessels was restored to 84% by administration of the nitric oxide synthase inhibitor L-NNA and a small additional amount of tone was restored in the presence of the cyclooxygenase inhibitor, indomethacin. We conclude that mild hypothermia markedly decreased phenylephrine-induced rat aortic contraction in vitro by endothelium dependent mechanisms, largely related to increased nitric oxide production or action.

Exogenous CCK and gastrin stimulate pancreatic exocrine secretion via CCK-A but also via CCK-B/gastrin receptors in the calf

A predominance of the pancreatic cholecystokinin (CCK) receptor of the B/gastrin subtype (CCK-B/G) was reported in calves older than 1 month. Specific CCK-A and CCK-B/G receptor antagonists (SR 27897 and PD 135158, respectively) were used to identify the CCK receptor subtype involved in exogenous CCK- and gastrin-induced exocrine pancreatic responses. Conscious calves (2 months old) with catheterized pancreas, jugular vein and duodenum were used; the pancreatic juice was continuously reinfused. CCK (30 pmol kg-1 min-1, 40 min) evoked an increase in pancreatic juice flow and enzyme secretion, while the same dose of gastrin increased enzyme secretion alone. CCK-induced pancreatic secretion was abolished by SR 27897 (15 nmol kg-1 min-1, 55 min) and reduced by PD 135158 (0.15 nmol kg-1 min-1, 55 min). Gastrin-induced enzyme secretion was reduced by PD 135158 (50% to 90%) and to a lesser extent by SR 27897 (50% to 60%). These results demonstrate that CCK and gastrin in the physiological range stimulate pancreatic exocrine secretion in calves and that these effects are partly mediated by CCK-B/G receptors. Although CCK-A receptors are not predominantly expressed, they seem to play a major role in the response of pancreatic exocrine secretion to CCK.

Characterization of a variable number tandem repeat region in the thiopurine S-methyltransferase gene promoter

Characterization of the genetic polymorphism of thiopurine S-methyltransferase enzyme (TPMT; EC 2.1.1.67) is required because of its clinical importance for patients exposed to thiopurine drugs. A number of point mutations have already been characterized in exons and introns of the TPMT gene. Here we report the identification of a polymorphic locus within the promoter region of the gene. This polymorphism was detected by polymerase chain reaction - single strand conformation polymorphism analysis of DNA samples from 54 unrelated European individuals. A total of five alleles with length variations were distinguished through the 5'-flanking region involved in the TPMT gene expression. Sequence analysis revealed that these variations were due to a variable number of tandem repeats (VNTR), ranging from four to eight repeats. Each repeat consists of 17 or 18 bp units and contains putative binding sites for transcription factors. The most frequent alleles harbour four or five tandem repeats, a heterozygosity rate of 0.44 was calculated, and a stable Mendelian inheritance of alleles was demonstrated. Analysis of the effect of each VNTR allele on promoter activity of a reporter gene was further performed in various cell lines by transient transfection assay. A modulatory effect of VNTR alleles was observed in vitro, but the repeat polymorphism did not display a significative role in TPMT gene regulation in vivo. Further studies need to be carried out to support the hypothesis that VNTR may contribute to the large interindividual variations of TPMT activity.

Gut regulatory peptide levels in bovine fetuses and their dams between the 3rd and 9th months of gestation

Several gut regulatory peptides were measured by radioimmunoassay between 3 and 9 months of gestation in the plasma of 91 bovine fetuses and their dams, in fetal gastric content and in amniotic fluid. During gestation, plasma peptide concentrations did not change in cows. Likewise, fetal plasma concentrations of cholecystokinin, somatostatin, secretin and vasoactive intestinal polypeptide showed no variation while those of gastrin, pancreatic polypeptide and gastric inhibitory polypeptide increased during the last 6 months. Peptide levels in the fetus were higher than or equal to maternal concentrations. At 8-9 months of gestation, gastrin, CCK, secretin and somatostatin concentrations in amniotic fluid were lower than those measured in fetal gastric content and in maternal and fetal plasma. Therefore, a substantial endogenous endocrine production of regulatory peptides by the fetus probably exists as early as the third month of gestation, accompanied by a release into the lumen of the gut.

Epidermal growth factor receptor and labeling index are independent prognostic factors in glial tumor outcome

The aim of this study was to perform a multivariate analysis including clinical and biological prognostic factors on glial tumor outcome. Seventy-nine patients were analyzed (48 men and 31 women; mean age = 56 years, range = 16-77 years): 7 had a benign glial tumor (grades 1 and 2), 21 had an anaplastic glial tumor (grade 3), and 51 had a glioblastoma (grade 4). Median follow-up was 17.9 months for patients who survived (50 patients died). Biopsies were obtained at time of diagnosis (complete tumor resection in 62 patients and stereotaxic biopsies in 17 patients). Epidermal growth factor receptor (EGFR) was measured by a binding assay, and labeling index (LI) was measured by tritiated thymidine incorporation. EGFR varied from 4 to 73,110 fmol/mg protein (mean = 3912 fmol/mg protein; median = 374 fmol/mg protein; n = 79). LI varied between 0.1 and 16.5% (mean = 6.2%; median = 5.2%; n = 40). Log10 EGFR was significantly and positively correlated with patient age. LI was significantly different according to tumor histology. Univariate Cox analysis (end point was cancer death) showed that age (P = 0.027), log10 EGFR (P = 0.025), and LI (P = 0.0019) were significant continuous variables, the survival being shortened when the covariable increased; tumor resection (P = 0.015, relative risk = 0.45) and histology (P = 0.0009) were significant categorical factors. A multivariate Cox analysis (forward selection) including age, histology, tumor resection, log10 EGFR, and LI revealed that log10 EGFR, LI, and tumor resection were the only independent significant predictors of survival. This multivariate approach reveals that the clinical prognostic factors of glial tumors, namely age and tumor histology, disappear, to the benefit of intrinsic characteristics of the tumor, i.e., EGFR expression and LI, suggesting that coupled EGFR and LI determination could be a useful tool for better evaluation of glial tumor outcome.

GluR5 kainate receptor activation in interneurons increases tonic inhibition of pyramidal cells

We studied the modulation of GABAergic inhibition by glutamate and kainate acting on GluR5-containing kainate receptors in the CA1 hippocampal region. Glutamate, kainate or ATPA, a selective agonist of GluR5-containing receptors, generates an inward current in inhibitory interneurons and cause repetitive action potential firing. This results in a massive increase of tonic GABAergic inhibition in the somata and apical dendrites of pyramidal neurons. These effects are prevented by the GluR5 antagonist LY 293558. Electrical stimulation of excitatory afferents generates kainate receptor-mediated excitatory postsynaptic currents (EPSCs) and action potentials in identified interneurons that project to the dendrites and somata of pyramidal neurons. Therefore glutamate acting on kainate receptors containing the GluR5 subunit may provide a protective mechanism against hyperexcitability.

Clinical features of X-linked nephrolithiasis in childhood

X-linked recessive nephrolithiasis (XRN) is a rare hereditary form of progressive renal failure characterized by (1) proximal tubular dysfunction and low molecular weight proteinuria; (2) hypercalciuria with nephrocalcinosis and nephrolithiasis. Because the clinical features are non-specific and variable, affected families in different parts of the world were initially thought to have several distinct syndromes. However, positional cloning of the relevant gene (CLCN5) demonstrated that these families have, in common, mutations affecting a chloride channel expressed throughout the renal tubule. To expand the description of early clinical and pathological manifestations of XRN, we describe three patients diagnosed in the 1st decade of life. Renal tubular dysfunction may be evident even in the neonatal period, hypophosphatemic rickets may develop in the first years of life, and nephrocalcinosis (but not nephrolithiasis) with glomerulosclerosis are consistent features in childhood. One of our patients is indistinguishable from the others on clinical grounds, yet no mutations of the coding regions of the CLCN5 gene were found, raising the possibility of genetic heterogeneity in the XRN syndrome.

Reversal of excitatory postsynaptic potential/spike potentiation in the CA1 area of the rat hippocampus

In the CA1 area of the hippocampus, low frequency and tetanic conditioning stimuli are known to trigger long-term depression and potentiation of synaptic responses respectively and to produce irreversible excitatory postsynaptic potential/spike potentiation, i.e. an increase of the probability of discharge of the neurons. Using simultaneous extracellular recordings in stratum radiatum and stratum pyramidale in the CA1 area of the rat hippocampus, brief application of the K+ channel blocker tetraethylammonium resulted both in long-term potentiation of synaptic responses and in excitatory postsynaptic potential/spike potentiation that could be reversed by subsequent low frequency or tetanic stimuli. Excitatory postsynaptic potential/spike potentiation and its subsequent reversal by an electrical conditioning stimulus were found to have an N-methyl-D-aspartate receptor-independent component. We conclude that the reversal of excitatory postsynaptic potential/spike potentiation can occur and that it does not require the induction of long-term modification of synaptic responses.

Interneurones are not so dormant in temporal lobe epilepsy: a critical reappraisal of the dormant basket cell hypothesis

One axiom at the basis of epilepsy research is that there exists an imbalance between excitation and inhibition. This abnormality can be achieved by an increase of excitation on principal cells, a decreased inhibition (i.e. disinhibition) or both. This review focuses on dysfunction of inhibition, and in particular on the 'dormant basket cell hypothesis'. This hypothesis states that, (1) interneurones are functionally disconnected from excitatory afferents, resulting in hyperexcitability of principal neurones and loss of paired pulse inhibition, (2) when properly activated, interneurones can still perform their task, i.e. suppress epileptiform activity and restore paired pulse inhibition. The aim of this review is to discuss the evidence in support of the 'dormant basket cell hypothesis'. We will first discuss the rationale underlying the hypothesis and the criteria needed to validate the hypothesis. We will then show that, (1) the key experimental data offered in support of the hypothesis (Bekenstein and Lothman, 1993. Dormancy of inhibitory interneurones in a model of temporal lobe epilepsy. Science 259, 97-100; Sloviter, 1991. Permanently altered hippocampal structure, excitability, and inhibition after experimental status epilepticus in the rat: the 'dormant basket cell' hypothesis and its relevance to temporal lobe epilepsy. Hippocampus 1, 41-66) are difficult to interpret, and (2) recent recordings from interneurones in epileptic tissue argue against the hypothesis. The 'dormant basket cell hypothesis' is then discussed in the broader context of disinhibition.

[Glutamatergic excitatory receptors and temporal lobe epilepsy]

Despite a considerable wealth of data, the mechanisms responsible for the generation of epileptic bursts in temporal lobe epilepsy (TLE) remain a mystery. Recently, research and therapy have focused on impairment of GABAergic inhibition in epilepsy. Several lines of evidence support this approach: 1-GABA is the main inhibitory neurotransmitter in the neuronal structures involved in TLE. 2-Enhancers of GABAergic inhibition (such as benzodiazepines or barbiturates) are commonly used as antiepileptic drugs. 3-Interictal discharges can be obtained following the pharmacological blockade of GABAA receptors. Since the axiom at the basis of epilepsy research states that the balance between inhibition and excitation is tipped toward excitation, we have addressed the following question: where are the loci most likely to be involved in such imbalance? We have limited our investigation to the excitatory side of the story. The main glutamatergic excitatory receptors (AMPA and NMDA) involved in TLE and their properties will be first addressed. We will focus on the excitatory synapses most likely involved in epileptogenesis. We have then specifically studied the effects of redox reagents on NMDA receptor-dependent epileptiform activity in a chronic animal model of TLE, the kainic acid lesioned rat hippocampus. We report that oxidizing drugs abolish evoked epileptiform discharges via a decrease by 50 p. 100 of NMDA receptor-mediated responses without affecting synaptic plasticity and thus memory and learning. The dormant cell hypothesis (i.e. the disconnection of inhibitory interneurons from their excitatory afferents) was also tested. We report that interneurons are not dormant in TLE and fire bursts of action potentials during spontaneous or evoked paroxismal activity.

Sternocostoclavicular hyperostosis in children: a report of eight cases

OBJECTIVE

The aim of this paper is to clarify the clinical and radiologic features of sternocostoclavicular hyperostosis by reviewing eight previously unpublished cases in children, identifying its similarities to chronic recurrent multifocal osteomyelitis and the differences between the pediatric and adult population affected with sternocostoclavicular hyperostosis. Appropriate imaging workup will obviate unnecessary diagnostic and therapeutic procedures.

MATERIALS AND METHODS

We investigated the clinical and imaging features of sternocostoclavicular hyperostosis in eight children (seven girls and one boy) and compared those features with the characteristic features of chronic recurrent multifocal osteomyelitis and sclerosing Garré's osteomyelitis to determine if sternocostoclavicular hyperostosis can justifiably be classified as a separate entity. All patients underwent one or more bone biopsies to determine the cause of the bone lesion(s).

RESULTS

Seven of the eight patients had involvement of the clavicle. Five of the eight patients had associated distant involvement in the pelvis, femur, tibia, fibula, talus, or sacroiliac joints. Except for predominant localization in the anterior chest wall, the symptoms, the clinical and imaging features, and the results of biopsy and histopathologic examination resemble those of chronic recurrent nonspecific sclerosing osteomyelitis. No skin lesion and no causative organism was found in any of the cases.

CONCLUSION

Sternocostoclavicular hyperostosis is a descriptive term used to designate a form of chronic sclerosing osteomyelitis. Its only distinctive feature is localization on one or more sites of the anterior chest wall.

The effects of perilymphatic tonicity on endolymph composition and synaptic activity at the frog semicircular canal

The effects of changes in perilymphatic tonicity on the semicircular canal were investigated by combining the measurements of transepithelial potential and endolymphatic ionic composition in the isolated frog posterior canal with the electrophysiological assessment of synaptic activity and sensory spike firing at the posterior canal in the isolated intact labyrinth. In the isolated posterior canal, the endolymph was replaced by an endolymph-like solution of known composition, in the presence of basolateral perilymph-like solutions of normal (230 mosmol/kg), reduced (105 mosmol/kg, low NaCl) or increased osmolality (550 mosmol/kg, Na-Gluconate added). Altered perilymphatic tonicity did not produce significant changes in endolymphatic ionic concentrations during up to 5 min. In the presence of hypotonic perilymph, decreased osmolality, K and Cl concentrations were observed at 10 min. In the presence of hypertonic perilymph, the endolymphatic osmolality began to increase at 5 min and by 10 min Na concentration had also significantly increased. On decreasing the tonicity of the external solution an immediate decline was observed in transepithelial potential, whereas hypertonicity produced the opposite effect. In the intact frog labyrinth, mEPSPs and spike potentials were recorded from single fibers of the posterior nerve in normal Ringer's (240 mosmol/kg) as well as in solutions with modified tonicity. Hypotonic solutions consistently decreased and hypertonic solutions consistently increased mEPSP and spike frequencies, independent of the species whose concentration was altered. These effects ensued within 1-2 min after the start of perfusion with the test solutions. In particular, when the tonicity was changed by varying Na concentration the mean mEPSP rate was directly related to osmolality. Size histograms of synaptic potentials were well described by single log-normal distribution functions under all experimental conditions. Hypotonic solutions (105 mosmol/kg) markedly shifted the histograms to the left. Hypertonic solutions (380-550 mosmol/kg, NaCl or Na-Gluconate added) shifted the histograms to the right. Hypertonic solutions obtained by adding sucrose to normal Ringer's solution (final osmolality 550 mosmol/kg) increased mEPSP and spike rates, but did not display appreciable effects on mEPSP size. All effects on spike discharge and on mEPSP rate and size were rapidly reversible. In Ca-free, 10 mM EGTA, Ringer's solution, the sensory discharge was completely abolished and did not recover on making the solution hypertonic. These results indicate that perilymphatic solutions with altered tonicity produce small and slowly ensuing changes in the transepithelial parameters which may indirectly affect the sensory discharge rate, whereas relevant, early and reversible effects occur at the cytoneural junction. In particular, the modulation of mEPSP amplitude appears to be postsynaptic; the presynaptic effect on mEPSP rate of occurrence is presumably linked to local calcium levels, in agreement with previous results indicating that calcium inflow is required to sustain basal transmitter release in this preparation.

Pancreatic beta-cell regeneration after 48-h glucose infusion in mildly diabetic rats is not correlated with functional improvement

We investigated the effect of glucose infusion on beta-cell regeneration in rats made mildly diabetic by a single injection of low dosage (35 mg/kg) streptozotocin (STZ). Nondiabetic (ND) and STZ rats were submitted to a 48-h glucose infusion (hyperglycemia approximately 22 mmol/l in both groups: ND and STZ hyperglycemic-hyperinsulinemic [ND HG-HI and STZ HG-HI rats]). Before infusion, beta-cell mass was 65% lower in STZ rats than in ND rats (2.0 +/- 0.02 vs. 5.5 +/- 0.6 mg), 1.6-fold increased in ND HG-HI rats (8.7 +/- 1.7 mg), and 2.7-fold increased in STZ HG-HI rats (5.4 +/- 0.9 mg). In ND HG-HI rats, beta-cell enlargement was related to an increase in beta-cell responsiveness to nutrient secretagogues both in vivo and in vitro, whereas in STZ HG-HI rats, no significant improvement in insulin secretion could be noticed. To determine the respective role of hyperglycemia and hyperinsulinemia on beta-cell area changes, ND and STZ rats were submitted to a 48-h hyperinsulinemic-euglycemic clamp. No modification of beta-cell mass was detected in either group. In conclusion, 48-h superimposed hyperglycemia was enough to restore beta-cell mass previously reduced by STZ injection. This effect seemed to be due to hyperglycemia rather than hyperinsulinemia alone. The data stress the dissociation between beta-cell regeneration and improvement in islet function in diabetic rats. Our model seems suitable for studying factors that can improve the plasticity and function of the pancreas in NIDDM.

Pharmacological characterization of ATP receptors in ampulla from frog semicircular canal

Phosphoinositidase C activities sensitive to purine and pyrimidine nucleotides have been identified earlier in ampulla from Rana ridibunda semicircular canal. The aim of this study was to characterize the pharmacological properties of other P2 receptors borne by this structure. A microassay was developed to measure the binding of [35S]adenosine 5'-O-(2-thiodiphosphate) ([35S]ADPbetaS) to a few ampullas microdissected from frog semicircular canals. When determined at 4 degrees C in the absence of divalent cations, [35S]ADPbetaS binding was saturable with incubation time and reversible after elimination of free radioligand. The dissociation kinetics were biphasic and comprised a major component that was rapidly reversible and a minor component that dissociated slowly. [35S]ADPbetaS binding was competitively inhibited by unlabeled ADPbetaS with an apparent dissociation constant of 0.48 +/- 0.09 microM and a Hill coefficient of 0.70 +/- 0.06, and Scatchard analysis revealed a minor class of high-affinity binding sites (RT1 = 52 +/- 11 fmol [35S]ADPbetaS bound/ampulla and Kd1 = 0.15 +/- 0.04 microM) and a major class of low-affinity binding sites (RT2 = 436 +/- 79 fmol [35S]ADPbetaS bound/ampulla and Kd2 = 2.0 +/- 0.8 microM). The pattern of stereospecificity for recognition of unlabeled structural ATP analogs was ADPbetaS >/= alpha, beta-methyleneadenosine 5'-triphosphate = ADP = adenosine 5'-O-(3-thiotriphosphate) > ATP = diadenosine tetraphosphate = AMP > 2'- and 3'-O-(4-benzoylbenzoyl)-adenosine 5'-triphosphate >/= 2-methylthioadenosine 5'-triphosphate > 2-desoxythymidine 5'-triphosphate = guanosine 5'-triphosphate = inosine-5'-triphosphate = xanthosine 5'-triphosphate = cytosine 5'-triphosphate = uridine 5'-triphosphate = uridine-5'-diphosphate, whereas cAMP and adenosine were devoid of activity. For antagonists, suramin revealed competitive inhibitor potencies, whereas reactive blue 2 and DIDS acted as pure noncompetitive inhibitors. Results suggest that the population of labeled receptors is heterogeneous and contains a low number of P2Y-like receptors and a large number of P2X-like receptors whose molecular subtypes and functions in endolymph homeostasis remain to be defined.

Peptones stimulate both the secretion of the incretin hormone glucagon-like peptide 1 and the transcription of the proglucagon gene

Truncated glucagon-like peptide (GLP)-1 is a potent incretin. Its synthesis and secretion are modulated by food, but the influence of individual nutrients remains to be established. The hypothesis that protein hydrolysates (peptones) can directly regulate both GLP-1 secretion and proglucagon (PG) gene transcription was tested in this study, ex vivo in the isolated vascularly perfused rat intestine and in vitro in the murine enteroendocrine cell line STC-1. Peptones were albumin egg hydrolysate (AEH) and meat hydrolysate (MH). We demonstrate in these two models that peptones dose-dependently stimulate GLP-1 release, whereas isocaloric quantities of bovine serum albumin or of an amino acid mixture had no stimulatory effect. A strong and rapid increase of PG RNA level was observed in STC-1 cells treated with peptones (14-fold and 7-fold increase after 4 h of incubation with 3% wt/vol MH and AEH, respectively). Peptones also increased the PG RNA level in the colonic PG-expressing cell line GLUTag. In contrast, peptones did not modify the PG RNA level in two pancreatic glucagon-producing cell lines, namely, the RINm5F and INR1G9 cells. The peptone effect in STC-1 cells was completely abolished by blocking transcription before MH treatment. The stability of proglugacon transcripts was not modified by MH treatment, but nascent transcripts were more abundant in STC-1 cells preincubated with MH. Finally, MH treatment strongly stimulated (15-fold stimulation) the transcriptional activity of two PG gene promoter fragments (-1100 and -350 base pair) linked to the CAT reporter gene transiently transfected in STC-1 cells. Overall, peptones evoke an as yet undescribed release of GLP-1 when brought into contact with native intestinal L-cells or with STC-1 enteroendocrine cells. The increased transcription of the glucagon gene in the latter system suggests an important role of protein hydrolysates in the control of not only the secretion but also the synthesis of the incretin hormone.

Resistance to endotoxin shock in spontaneously hypertensive rats

Septic shock involves systemic vasodilation mediated by proinflammatory cytokines. In essential hypertension, vascular and immune dysfunctions are closely associated. The response of hypertensive animals compared with normotensive controls to endotoxin (lipopolysaccharide; LPS) challenge is not known. Age-matched (12 weeks) normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were exposed to intravenous injection of 10 mg/kg LPS. Survival rate at 24 hours was markedly higher in SHR than in WKY (12 of 15 and 3 of 15, respectively; P<0.01). Survival of LPS-injected SHR was not related to their hypertension because hydralazine-treated SHR with normalized pressure had similar survival rates, and WKY made hypertensive by clipping of one renal artery showed fatality similar to that of normotensive WKY. Continuous arterial pressure and sequential plasma levels of interleukin-6 (IL-6) and tumor necrosis factor (TNF) were measured in LPS-treated SHR and WKY. Both the duration of the delayed hypotensive phase and the systemic release of IL-6 were much lower in SHR than WKY, whereas both acute hypotension and plasma TNF peak were equivalent. We further explored in vitro the inflammatory response and showed that LPS-activated whole blood from SHR produced less TNF and IL-6 than WKY LPS-activated whole blood. Our results indicate that SHR have a greater ability to resist endotoxic shock than WKY. This is not related to their hypertension but is associated with an attenuated inflammatory response to LPS.

Effects of simulated gastroesophageal reflux on the untraumatized rabbit larynx

OBJECTIVE

Gastroesophageal reflux (GER) has been shown, clinically and experimentally, to cause inflammation of traumatized laryngeal mucosa. This study was performed to determine if GER causes inflammation of untraumatized laryngeal mucosa.

METHOD

Sixteen adult New Zealand white rabbits underwent tube pharyngostomy under general anaesthesia without endotracheal intubation. After 7 days recovery, 1 mL/kg of normal saline or HCl (pH 1.5) with pepsin (0.3 mg/mL) was infused into the piriform sinus while the rabbit was under mild sedation: once, twice, or three times per day, for 14 consecutive days.

RESULTS

Rabbits that received HCl and pepsin exhibited various degrees of apnea and coughing. Eventually, most developed biphasic stridor on exertion. Histologically, the degree of laryngeal inflammation was greatest when GER was simulated three times per day. Glottic inflammation was greatest in one rabbit, which responded to GER simulation with paroxysmal coughing.

CONCLUSION

The mechanism of injury in GER laryngitis is postulated to be a combination of chemical trauma (due to HCl and pepsin) and mechanical trauma (due to an individually variable laryngeal chemoreflex). Further study of GER laryngitis in this new animal model is warranted.

Comparison of the kinetics of pancreatic secretion and gut regulatory peptides in the plasma of preruminant calves fed milk or soybean protein

Exocrine secretion from the pancreas and concentrations of cholecystokinin, gastrin, secretin, and somatostatin in plasma were measured in relation to feeding in 70- to 120-d-old preruminant calves fed either a milk diet or a soybean diet. Pancreatic fluid was continuously collected, measured, and reintroduced in catheterized calves. Blood samples were withdrawn for measurements of gut regulatory peptide concentrations in plasma. A slight increase in outflow of pancreatic fluid was observed 30 min before the milk diet was introduced but not before the soybean diet was fed. In contrast, concentrations and outflows of protein and trypsin immediately after feeding were higher when calves were fed the soybean diet. Overall, during the first 5 h postfeeding, the outflow of pancreatic fluid was 40% higher when the milk diet was fed than when the soybean diet was fed. No difference in outflow of protein was observed, but that of trypsin was 82% higher when the soybean diet was fed. This enhanced enzyme secretion could have been related to the increased plasma concentrations of gastrin and cholecystokinin after the soybean diet was fed. Secretin release was less in calves fed the milk diet that in calves fed the soybean diet during the first 2 h postfeeding, suggesting that this gut peptide along with gastrin and cholecystokinin, contributed to the stimulation of enzyme secretion. Plasma gut regulatory peptides could be influenced by the soybean diet, which does not coagulate in the stomach, inducing faster gastric emptying of protein and fat, and by the chemical form of protein from the soybean diet and the lower susceptibility of these proteins to protease compared with casein. However, the resulting enhancement of pancreatic trypsin secretion and activity seemed to be insufficient to increase the digestibility of soybean protein up to a level similar to that of milk.

Pro-epileptic changes in synaptic function can be accompanied by pro-epileptic changes in neuronal excitability

Repetitive sensory input, stroboscopic lights or repeated sounds can induce epileptic seizures in susceptible individuals. In order to understand the process we have to consider multiple factors. The output of a set of neurones is determined by the amount of excitatory synaptic input, the degree of positive feedback and their inherent electrical excitability, which can be modified by synaptic inhibition. Recent research has shown that it is possible to separate these phenomena, and that they do not always behave in unison.

Expression of SNARE proteins in enteroendocrine cell lines and functional role of tetanus toxin-sensitive proteins in cholecystokinin release

In neurons, synaptic vesicle exocytosis involves the formation of a core complex particle including syntaxin-1, synaptosomal-associated protein of 25 kDa (SNAP-25) and vesicle-associated membrane protein (VAMP)-2/synaptobrevin. The expression of these proteins was investigated in a panel of cell lines, including lines of endocrine and intestinal origin, by Western blotting and/or immunocytochemistry. The three core complex proteins were detected in the enteroendocrine, cholecystokinin (CCK)-secreting, cell lines STC-1 and GLUTag, and in the endocrine non-intestinal cell lines CA-77 and HIT-T15. In contrast, SNAP-25 and syntaxin-1 were undetected in the intestinal non-endocrine cell lines IEC-6, HT-29 and Caco-2, whereas a slight expression of VAMP-2 was documented in IEC-6 and HT-29 cells. Co-immunoprecipitation experiments indicated that syntaxin-1, SNAP-25 and VAMP-2 were present in a complex similar to that identified in brain. In the STC-1 cell line, treatment of streptolysin-O-permeabilized cells with tetanus toxin (Tetx) selectively cleaved VAMP-2 and VAMP-3/cellubrevin, and simultaneously abolished Ca2+-induced CCK secretion (IC50 approximately 12 nM). These results show that endocrine cell lines of intestinal origin express syntaxin-1, SNAP-25 and VAMP-2, and suggest a key role for a Tetx-sensitive protein (for example VAMP-2 and/or VAMP-3) in the CCK secretion by STC-1 cells.