Disruption of gallbladder smooth muscle function is an early feature in the development of cholesterol gallstone disease

Background Decreased gallbladder smooth muscle (GBSM) contractility is a hallmark of cholesterol gallstone disease, but the interrelationship between lithogenicity, biliary stasis, and inflammation are poorly understood. We studied a mouse model of gallstone disease to evaluate the development of GBSM dysfunction relative to changes in bile composition and the onset of sterile cholecystitis. Methods BALB/cJ mice were fed a lithogenic diet for up to 8 weeks, and tension generated by gallbladder muscle strips was measured. Smooth muscle Ca²⁺ transients were imaged in intact gallbladder. Key Results Lipid composition of bile was altered lithogenically as early as 1 week, with increased hydrophobicity and cholesterol saturation indexes; however, inflammation was not detectable until the fourth week. Agonist‐induced contractility was reduced from weeks 2 through 8. GBSM normally exhibits rhythmic synchronized Ca²⁺ flashes, and their frequency is increased by carbachol (3 μm ). After 1 week, lithogenic diet‐fed mice exhibited disrupted Ca²⁺ flash activity, manifesting as clustered flashes, asynchronous flashes, or prolonged quiescent periods. These changes could lead to a depletion of intracellular Ca²⁺ stores, which are required for agonist‐induced contraction, and diminished basal tone of the organ. Responsiveness of Ca²⁺ transients to carbachol was reduced in mice on the lithogenic diet, particularly after 4–8 weeks, concomitant with appearance of mucosal inflammatory changes. Conclusions & Inferences These observations demonstrate that GBSM dysfunction is an early event in the progression of cholesterol gallstone disease and that it precedes mucosal inflammation.     

Regional differences in gastrointestinal motility disturbances during acute necrotising pancreatitis

Patients with acute pancreatitis often suffer from intestinal motility disturbances but the mechanism of this dysfunction is largely unknown. We studied the effect of acute necrotising pancreatitis (ANP) on in vivo gastrointestinal motility and in vitro intestinal contractility in mice. ANP was induced non-invasively by feeding young female mice a choline-deficient ethionine-supplemented (CDE) diet during 72 h. Gastric emptying and intestinal transit were measured in vivo 15 min after intragastric gavage of a semiliquid Evans blue bolus. Gastric and intestinal neuromuscular function was determined in vitro on isolated muscle strips. ANP significantly decreased gastric emptying from 61.2 +/- 9.8 to 34.9 +/- 7.1% and intestinal transit from 63.4 +/- 5.6 to 32.5 +/- 5.4%. ANP did not affect receptor-dependent and receptor-independent gastric muscle contractions except the contractions to substance P, which were slightly inhibited. In intestinal muscle strips, ANP significantly decreased contractions to EFS, carbachol, PGF(2alpha), substance P and KCl. Our results show that ANP delays gastric emptying in vivo, associated with a specific reduction in substance P contractility in vitro. ANP also impairs intestinal transit in vivo, associated with a non-specific reduction of intestinal contractility in vitro. We conclude that ANP impairs gastrointestinal motility in mice with underlying regional differences in the pathogenic mechanisms.     

Differences in longitudinal smooth muscle response along the length of the rabbit small intestine

To determine whether there is a gradient in the ability of longitudinal smooth muscle along the length of the small intestine to develop tension we prepared longitudinal muscle strips from proximal (P), medial (M) and distal (D) segments of small intestine removed from 900–1200 g New Zealand white rabbits (n = 9). Isometric tension was recorded in standard tissue baths perfused with oxygenated Krebs solution and 10^?6m tetrodotoxin. Basal and active (the response to 10^?5m carbachol) length-tension curves were generated, and the length at which tissues developed maximal active tension (the optimum length or L_o) was determined for P, M and D tissues. Then the dose-response to carbachol (over the range 10^?2-10^?4m ) was determined for each of the P, M and D tissues at L_o. Non-linear regression was used to determine the dose at which the contractile response was half maximal (the ED so), and the maximum tension generated (T_m) by the tissue at each location. The basal tension generated in response to graded stretch increased exponentially between 100 and 140% of initial length and was not significantly different for P, M and D tissues. The active tension generated in response to 10^?5m carbachol peaked at 125% of initial length; the L_o for P, M and D tissues was identical. With tissues equilibrated at L_o, dose-response curves for carbachol and graded concentrations of KCl showed a significant increment in maximal tension generated, but no significant difference in ED₅₀ in the more distal compared to proximal segments. Thus, the passive elastic properties and L_o were identical for the three regions of small intestine examined. However, there was a significant increase in active tension generated in distal compared to more proximal regions of the small intestine, which was not associated with a change in the ED₅₀ value for carbachol. As the response occurs in the presence of tetrodotoxin and can be reproduced with KCl depolarization, it probably reflects post-receptor changes in smooth muscle function.     

Age-related changes in rat colon mechanics

To determine whether myogenic factors are responsible for slowed colonic transit in senescent rats, maximum shortening velocity (V₀), compliance of the series elastic component (SEC), measurements of passive force in calcium-depleted tissue and peak isometric force (F₀) were examined in proximal and distal colonic circular smooth muscle from 6- and 30-monthold Fischer rats (n = 5). After mucosa was removed, measurements were made on strips stimulated with 80 m>m KCl in a 2.5 m>m Ca²⁺ Kreb's solution. Muscle strips were quick released at peak isometric force (F₀) to afterloads of 60% of F₀. The changes in muscle length from zero to 40 msec and 1 to 2 sec after release during isotonic contraction were used to calculate the SEC and V₀ as a fraction of total muscle length. Passive force (F_p) was measured in 2.5 m>m Ca²⁺ Kreb's solution and in a zero Ca²⁺, 0.1 m>m EGTA solution to determine the contribution of contractile and passive elements to passive force. The results of these studies indicate there is no difference in the V₀ (L₀/sec) of adult (8.4 ± 1.5) and aged (7.5 ± 2.0) animals (P ± 0.05). Peak force (F₀) in the distal colon of the aged rats was greater than adult rats (1.23 ± 0.1 vs 0.85 ± 0.01 kg/cm², P = 0.05). The stiffness of the parallel elastic component and the length-tension relationship were similar in adult and aged animals. Negligible decreases in F_p were observed in zero calcium medium. However, basal contractile tone was elevated in aged animals (P = 0.05). These studies indicate basic differences in aged colonic circular muscle that may contribute to altered bowel transit and function during ageing.     

Does ICC pacing require functional gap junctions between ICC and smooth muscle in mouse intestine?

We tested the hypothesis that interstitial cells of Cajal (ICC) pace longitudinal and circular muscle of mouse intestine through gap junctions. Carbenoxolone (10(-6), 10(-5), 10(-4) mol L(-1)), an inhibitor of gap junction conductance, was applied to segments of longitudinal or circular muscle with contractions driven by ICC after inhibition of nerve function by tetrodotoxin (10(-6) mol L(-1)) and L-NOARG (10(-4) mol L(-1)). Carbenoxolone concentration- and time-dependently inhibited the amplitude of contraction (0.2-1.5 g in controls) of segments of longitudinal muscle, but had no effect on the frequency of contractions (from 36-54 min). It also inhibited the amplitude of contractions of circular muscle segments and reduced the frequency slightly at 10(-4) mol L(-)1. Carbenoxolone inhibited tonic contractions of longitudinal but not circular segments to 60 mmol L(-1) KCl, suggesting that it directly inhibited contractions of longitudinal muscle. The responses to pacing by electrical field stimulation (40 V cm(-1), 50-100 ms, 1 Hz) after block of nerve function were reduced insignificantly in amplitude, and not in frequency in both longitudinal and circular segments. We conclude that it is likely that only gap junctions within circular muscle are involved in pacing of muscle by ICC. Carbenoxolone also has effects on muscle contractility in longitudinal muscle.     

Muscle contractility dysfunction precedes loss of motor unit connectivity in SOD1(G93A) mice

Introduction: Electrophysiological measurements are used in longitudinal clinical studies to provide insight into the progression of amyotrophic lateral sclerosis (ALS) and the relationship between muscle weakness and motor unit (MU) degeneration. Here, we used a similar longitudinal approach in the Cu/Zn superoxide dismutase (SOD1[G93A]) mouse model of ALS. Methods: In vivo muscle contractility and MU connectivity assays were assessed longitudinally in SOD1(G93A) and wild type mice from postnatal days 35 to 119. Results: In SOD1(G93A) males, muscle contractility was reduced by day 35 and preceded MU loss. Muscle contractility and motor unit reduction were delayed in SOD1(G93A) females compared with males, but, just as with males, muscle contractility reduction preceded MU loss. Discussion: The longitudinal contractility and connectivity paradigm employed here provides additional insight into the SOD1(G93A) mouse model and suggests that loss of muscle contractility is an early finding that may precede loss of MUs and motor neuron death. Muscle Nerve 59 :254–262, 2019     

Myogenic regional responsiveness to cholinergic and vipergic stimulation in human colon

Background Differences in the actions of enteric neurotransmitters on colonic circular and longitudinal muscle layers have not been clearly determined, nor the possible existence of intrinsic myogenic phenotypes that might contribute to regional differences in human colon motor activity. The aim of this study was to analyze the direct pharmaco‐mechanical coupling of carbachol (CCh) and vasoactive intestinal polypeptide (VIP) on human colonic smooth muscle strips and cells. Methods Circular and longitudinal muscle strips and cells were obtained from 15 human specimens of ascending and sigmoid colon. Both isometric tension on muscle strips and contraction and relaxation on cells were measured in response to increasing CCh and VIP concentrations. Key Results Circular muscle strips of ascending colon were more sensitive to the effect of CCh than that of sigmoid colon, EC₅₀ values being, respectively, 4.15 μmol L^?1 and 8.47 μmol L^?1 (P < 0.05), although there were no differences in maximal responses. No regional differences were observed in longitudinal muscle strips or in smooth muscle cells. Maximal responses to CCh were higher on circular than longitudinal muscle strips and cells throughout the colon. A greater sensitivity to VIP was observed in ascending colon compared with sigmoid colon, both in circular (EC_50: 0.041 and 0.15 μmol L^?1, respectively, P < 0.01) and longitudinal (EC_50: 0.043 and 0.09 μmol L^?1, respectively, P < 0.05) strips, and similar differences were observed in longitudinal smooth muscle cells (EC_50: 44.85 and 75.24 nmol L^?1, respectively, P < 0.05). Conclusions & Inferences Regional myogenic differences in pharmaco‐mechanical coupling between the enteric neurotransmitters and smooth muscle contribute to the complex regional motor patterns of human colon.     

In vitro contractility of stimulated and non-stimulated human gallbladder muscle

Abstract In an attempt to define, more clearly, the nature of gallbladder contraction we obtained muscle strips from human gallbladder wall, removed at cholecystectomy. Samples were taken from various areas of the gallbladder to seek evidence of a dominant axis of contraction. The strips were stimulated with increasing concentrations of cholecystokinin-8 (CCK-8) and carbachol, and, to determine maximal contractile force, 0.25 M potassium chloride. No differences were seen between samples taken from the longitudinal, circular and oblique axes. In a second series of experiments, samples were taken from the body and neck regions of the gallbladder. In these, it was seen that the samples from the body contracted more forcefully than those of the neck tissue and that they were more sensitive to carbachol stimulation. The difference in response to CCK-8 measured in the strips from the body and cystic duct/neck of the gallbladder cannot be explained by a difference in sensitivity to CCK-8, but is mainly due to the difference in the amount of muscle tissue present. Strips from the body are more sensitive to muscarinic stimulation that those from the neck. Overall, there is a functional difference in sensitivity between the body and neck which would serve to facilitate bile flow into the common bile duct during gallbladder contraction.     

Neurones in the chicken ureter are innervated by substance P- and calcitonin gene-related peptide-containing nerve fibres: Immunohistochemical and electrophysiological evidence

Numerous ganglia or single neurones immunoreactive to protein gene-product 9.5 (PGP) were demonstrated in the chicken ureter. Ganglia were observed in the main nerve trunks accompanying the ureter (400–2,000 cells), in the adventitia (1–45 cells; density; 79 ± 12 ganglia/cm²; mean ± S.E.M.), in the circular muscle (1–9 cells; 76 ± 10 ganglia/cm²) and in the longitudinal muscle (1–8 cells; 232 ± 41 ganglia/cm²). Most of the PGP-positive neurones in the nerve trunk ganglia (∼66%) and in the smooth muscle layers (85%) were encircled by a dense plexus of varicose nerve fibres containing both substance P (SP) and calcitonin gene-related peptide (CGRP). SP-positive somata were rarely observed. Immunogold electron microscopy revealed that SP- and CGRP-immunoreactivity were colocalised in the same dense core vesicles. A strong reduction of SP-positive nerve fibres was observed in organ cultures of the ureter, indicating their extrinsic origin. The fibres might originate from the dorsal root ganglia, where SP and CGRP were colocalised in 20–30% of the neurones. The sensitivity of ureteric neurones to SP and CGRP was investigated in recordings obtained from mechanosensitive nerve fibres with cell bodies located in or adjacent to the ureter (U-G units). The majority (71%) of the U-G units was excited by local application of SP in a dose-dependent manner. The SP-sensitive U-G neurones had higher mechanical thresholds (29 ± 5 mmHg) as opposed to the SP-insensitive ones (10 ± 3 mmHg). Repeated applications of high doses of SP to the U-G units resulted in desensitisation and reduced the response to mechanical stimuli. None of the U-G units responded to local application of CGRP, but all U-G units were excited by acetylcholine. The data support the hypothesis that SP-containing primary afferents are involved in the modulation of the activity of ureteric neurons in the chicken. J. Comp. Neurol. 380:105–118, 1997. © 1997 Wiley-Liss. Inc.     

Changes in neostriatal DA metabolism after carbachol or atropine microinjections into the substantia nigra

Short infusions (10 min) of carbachol or atropine (5 · 10^?4M) were performed unilaterally in the substantia nigra of the rat. Immediately after, neostriatal dopamine (DA) metabolism was investigated within 15 min.Carbachol infusion produced an increase of the neostriatal DA content. In animals pretreated with Ro 4-4602, a synthesis inhibitor of DA, carbachol application did not change the initial accumulation of newly formed [³H]DOPA from intravenously injected [³H]tyrosine. In such treated animals the normal rate of DA disappearance was reduced.Intranigral atropine infusion produced no change in the neostriatal DA concentration. The initial accumulation of newly formed [³H]DOPA from [³H]tyrosine, in Ro 4-4602 pretreated animals was increased. In such treated animals the normal rate of DA disappearance was activated.In conclusion, intranigral application of carbachol or atropine produced immediate and opposite effects on neostriatal DA metabolism. Carbachol inhibited DA utilization. Atropine activated both DA synthesis and utilization.     

Autoradiographic localisation of muscarinic receptors in guinea-pig intestine: Distribution of high and low affinity agonist binding sites

Muscarinic receptors mediate a variety of intestinal functions including smooth muscle contraction, ganglionic transmission and water and electrolyte secretion. In this study, we have used [³H]quinuclidinyl benzilate ([³H]QNB) in an in vitro autoradiographic method to map the distribution of muscarinic receptors in guinea-pig ileum, colon and caecum. In addition, the relative distribution of low and high affinity agonist binding sites was assessed by the addition of the muscarinic agonist, carbachol, to selectively inhibit the binding of [³H]QNB to the high affinity sites. Although quantitative differences existed, the overall distribution of muscarinic receptors was similar in the 3 regions of intestine examined. Autoradiograph grains were found distributed over the myenteric and sub-mucous plexuses, the longitudinal and circular muscle layers and in the case of the colon, the muscularis mucosa. The inclusion of carbachol demonstrated that a greater proportion of high affinity sites were associated with the musculature than with the enteric plexuses. These findings are discussed in relation to the role of muscarinic mechanisms in intestinal motility and secretion.     

Effect of 2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced ileitis on the motor function of non-inflamed rat gastric fundus.

During intestinal inflammation, motility disturbances are not restricted to inflamed regions, but may also occur in remote non-inflamed sites of the gastrointestinal tract. Our aim was to investigate the motor function of the gastric fundus after the induction of terminal ileitis in the rat. Ileal inflammation was induced by intraluminal installation of 2,4,6-trinitrobenzenesulphonic acid (TNBS) into the ileum. Inflammation was assessed both histologically and biochemically. Contractions and relaxations of longitudinal muscle strips from the gastric fundus were studied 36 h and 1 week later. During the acute phase of ileal inflammation (36 h), the non-inflamed stomach was distended. The contractility of longitudinal muscle strips of the gastric fundus was decreased due to a post-receptor defect. In addition, nonadrenergic noncholinergic (NANC) relaxations were inhibited due to neuronal dysfunction. Aortic contractility remained normal and the mere presence of food in the stomach did not account for the disturbed neuromuscular function in the gastric fundus. Ablation of extrinsic primary afferent neurones by capsaicin further impaired gastric fundus contractility. Transection and re-anastomosis of the jejunum reversed the effect of TNBS-induced ileitis on the neuromuscular function of the gastric fundus. One week after TNBS, cholinergic neurotransmission was increased in the gastric fundus. During acute ileitis, smooth muscle cell contractility and inhibitory NANC neurotransmission are inhibited in the non-inflamed gastric fundus. This phenomenon may be mediated by intrinsic connections within the enteric nervous system.     

Gallbladder motility in vitro in men with gallstones following Billroth II gastric resection

Abstract Gastric surgery induces an increased incidence of gallstones. To investigate the changes in gallbladder kinetics after gastric resection, 20 male patients were studied: ten patients undergoing cholecystectomy for gallstones developed after Billroth II gastric resection and ten patients undergoing cholecystectomy for cholelithiasis without previous abdominal surgery. Longitudinal strips from the gallbladder wall were suspended in an organ bath and the isometric tension recorded. Dose-response curves to cholecystokinin-octapeptide and carbachol were obtained. Half the maximal response to cholecystokinin-octapeptide was 0.50 ± 0.11 times 10^?7 M in the first group and 1.36 ± 0.37 times 10^?7 m in the second group (P < 0.05). The ED₅₀ to carbachol was 24.33 ± 2.69 times 10^?7 M in the gastrectomy group and 40.39 ± 5.01 times 10^?7 M in the control group (P < 0.01). There was no significant difference in the maximal contractile response either to cholecystokinin-octapeptide or carbachol in the two groups. Our study shows an increased gallbladder sensitivity to cholecystokinin-octapeptide and carbachol in patients with gallstones developed after Billroth II gastric resection.     

Involvement of chloride channels in the receptormediated activation of longitudinal colonic muscle

In gastrointestinal smooth muscle, intracellular Cl- is maintained at levels higher than its electrochemical equilibrium. Therefore, Cl- efflux through receptor-mediated opening of Cl- channels should result in membrane depolarization and may be sufficient to activate voltage-sensitive calcium channels (VSCCs). To determine the contribution of Cl- channels to receptor-mediated contraction of the longitudinal muscle layer of the rabbit distal colon, we studied the mechanical response of muscle strips to substance P, carbachol and potassium depolarization following the depletion of Cl- i, and in the presence of the Cl- channel blocker 5-nitro-2-(3-phenylpropyl-amino)-benzoate (NPPB). A 60-min incubation of tissues in a HEPES-buffered solution in which NaCl had been replaced by Na isethionate (or Na gluconate) in equimolar amounts resulted in disappearance of phasic contractions, and in a partially reversible reduction of the tonic response to substance P and carbachol, but not to KCl depolarization. When the agonist was applied to tissues in control solution, or to Cl-(-)depleted tissues in a solution in which Na+ was acutely replaced in equimolar amounts by N-methyl-D-glucosamine, the mechanical response to substance P and carbachol was almost abolished. Acute Na+ replacement alone without prior Cl- depletion did not abolish phasic contractions, but reduced the tonic response to substance P and carbachol. Similar to the effect of Cl- depletion, incubation of tissues in NPPB (6.6 x 10(-5) M) reduced the tonic response to substance P and carbachol, and abolished phasic contractions. These findings are consistent with a contribution of a Cl- channel to the receptor-mediated activation of colonic smooth muscle. In addition, the data suggest that transient Cl- channel mediated depolarizations may play a role in the generation of phasic contractions.     

The role of rectal chloride secretion in childhood constipation

Background Disturbance in fluid secretion, driven by chloride secretion, might play a role in constipation. However, disturbed chloride secretion in those patients has yet to be evaluated. Therefore, the aim of this study was to compare chloride secretion in rectal biopsies of children with functional constipation (FC) to those without constipation. Methods To measure changes in short circuit current (I_sc in μA cm^?2) reflecting chloride secretion, intestinal biopsies from children with constipation, to either exclude or diagnose Hirschsprung’s disease, and from children without constipation (controls) undergoing colonoscopy for screening of familial adenomatous polyposis, juvenile polyps or inflammatory bowel disease (IBD), were compared and studied in Ussing chambers. Following electrogenic sodium absorption blockade by amiloride, chloride secretory responses to calcium‐linked (histamine, carbachol) and cAMP‐linked (IBMX/forskolin) secretagogues were assessed. Key Results Ninety‐six patients (46 FC) participated; nine FC patients (n = 1 congenital syndrome and n = 8 technical problems) and 13 controls (n = 6 IBD; n = 7 technical problems) were excluded. No significant difference was found in mean (±SE) basal chloride currents between children with FC and controls (9.6 ± 1.1 vs 9.2 ± 0.8; P = 0.75, respectively). Responses to calcium‐linked chloride secretagogues (histamine and carbachol) were significantly higher in controls (33.0 ± 3.0 vs 24.5 ± 2.3; P = 0.03 and 33.6 ± 3.4 vs 26.4 ± 2.7; P = 0.05 following histamine and carbachol, respectively). Conclusions & Inferences Calcium‐linked chloride secretion is disturbed in children with FC. Whether this defect occurs at the level of histamine receptors, components of receptor‐linked signal transduction pathways or basolateral Ca²⁺‐sensitive K⁺ channels enhancing the electrical driving force for apical chloride secretion, remains to be explored.     

High resolution manometry patterns distinguish acid sensitivity in non-cardiac chest pain

Background High resolution manometry (HRM) has demonstrated two distinct smooth muscle contraction segments in the esophageal body; changes in these segments typify certain esophageal disorders. We investigated segmental characteristics in subgroups of non‐cardiac chest pain (NCCP). Methods 32 NCCP subjects were segregated into a GERD group (ambulatory pH testing off antisecretory therapy showing elevated total acid exposure time, AET ≥ 4.0% and positive symptom association probability, SAP) and an acid sensitive group (normal AET and positive SAP). HRM Clouse plots were analyzed; smooth muscle segment lengths, pressure amplitude peaks were measured for segment 2 and segment 3 (proximal and distal smooth muscle segments). Pressure volumes were determined in mmHg cm^?1 s^?1 for each peristaltic segment, and ratios of segment 3 : segment 2 calculated. Values were compared to a cohort of 14 normal controls. Key Results A distinctive shift in peak contraction amplitude to segment 3 was evident in the acid sensitive group (segment 2, 100.03 ± 11.06 mmHg, segment 3, 145.23 ± 10.29 mmHg, P = 0.006). Pressure volumes were similarly shifted to segment 3 (segment 2: 855.3 ± 135.1 mmHg cm^?1 s^?1, segment 3: 2115.2 ± 218.6 mmHg cm^?1 s^?1, P < 0.005). In contrast, peak amplitude and pressure volume were near equal in the two segments in GERD and control groups. A threshold segment 3 : segment 2 pressure volume ratio of 1.9 had the best performance characteristic for segregating acid sensitivity subjects from all GERD and control subjects. Conclusions & Inferences Shift in contractile vigor to the third peristaltic segment may be seen in acid sensitive subjects. HRM characteristics of smooth muscle contraction segments are of value in making this determination.     

常温肝内胆管缺血时间的安全时限：极限值在哪？

背景：胆道缺血再灌注损伤是肝移植、肝切除和肝动脉栓塞化疗后胆管损伤的主要原因之一。但是,常温下肝脏究竟能够耐受多长时间的肝内胆管缺血目前尚无定论。 目的：利用兔胆道缺血再灌注损伤模型,分析兔肝内胆管缺血的安全时限。 方法：将家兔以抽签法随机分为假手术组、肝动脉和胆总管联合阻断1.5,2,2.5,3 h 组。假手术组只游离胆总管、肝总动脉及门静脉,肝动脉和胆总管联合阻断1.5,2,2.5,3 h 组用无损伤动脉夹平左、右肝管开口上缘夹闭肝动脉和胆总管及疏松结缔组织,阻断1.5,2,2.5,3 h后去除动脉夹即恢复肝动脉或胆道血流。术后1周统计动物存活情况,并进行肝功能检测。 结果与结论：假手术组及肝动脉和胆总管联合阻断1.5 h组动物术后1周无死亡,阻断2 h存活率为87.5%,随着阻断胆道血流时间的延长,动物生存率逐渐下降,提示动物耐受胆道血流阻断的最大安全时限为2 h。胆道缺血 2 h 以内肝脏病理组织学变化相对较轻,以细胞水肿和炎细胞浸润为主,坏死灶呈点状或小片状,以可逆性损伤为主;而缺血 2 h 以上胆管上皮坏死脱落明显,肝坏死呈多灶性、大片状,损伤不可逆。组织学变化同样证实2 h可能是常温下兔耐受肝内胆管血流阻断的最大安全时限。     

Effects of ATP and adenosine on contraction amplitude of rat soleus muscle at different temperatures

Introduction: The aim of this study was to evaluate the effects of adenosine 5′‐triphosphate (ATP) and adenosine on the contractility of mammalian skeletal muscle under hypothermic conditions. Methods: Contractions of isolated rat soleus muscle were induced by either electrical stimulation (ES) or carbachol at physiological temperatures (37°C) and hypothermic conditions (30–14°C) and recorded in the presence of ATP, adenosine, suramin, and 8‐(p‐sulfophenyl)‐theophylline (8‐SPT). Results: At 37°C, incubation of the muscles with ATP inhibited ES‐induced contractions; the inhibitory effect of ATP disappeared at 14°C. Adenosine inhibited ES‐induced contractions at all temperature levels; 8‐SPT fully prevented the action of adenosine. ATP and adenosine did not significantly affect carbachol‐induced contractions at 37°C, while at lower temperatures ATP potentiated them. Suramin fully prevented effects of ATP. Conclusions: ATP is involved in both pre‐ and postsynaptic regulation of rat soleus muscle contractility, and these processes are significantly more pronounced at low temperatures. Muscle Nerve 55 : 417–423, 2017     

Effects of pH on membrane resistance in normal and dystrophic mouse skeletal muscle fibers

Membrane cable properties of skeletal muscle fibers of dystrophic mice (Rej-129) and their littermate controls were examined using a conventional two-microelectrode recording technique. Fibers from dystrophic mice had a decreased membrane resistivity (R_m) compared with those from normal mice (517 ± 27 vs 642 ± 34 Ω ? cm²), while the internal resistivities (R_i) did not differ significantly. The increase in membrane specific conductance was due to an increased Cl^? conductance (g_Cl) (2304 vs 1346 μS/cm² for normal fibers), although the K⁺ conductance (g_K) was actually decreased (234 vs 369 μS/cm² for normal fibers). With changes in pH, membrane conductances of normal and dystrophic skeletal muscle fibers varied differently, mainly due to differences in effects on the Cl^? conductance. This contrast may be due to altered regulation of internal pH in dystrophic muscle.     

Oesophagitis-induced changes in capsaicin-sensitive tachykininergic pathways in the ferret lower oesophageal sphincter

Prolonged oesophageal acidification may impair lower oesophageal sphincter (LOS) function in reflux disease. The aim of this study was to investigate aspects of altered LOS innervation in a model of oeso-phagitis. Oesophagitis was induced by acid (HCl, 0.15 M ) and pepsin (0.1% w/v) infusions in anaesthetized ferrets. LOS muscle strip responses to the following stimuli were measured in vitro from control and acid/pepsin-treated ferrets: electrical field stimulation (EFS; 1–50 Hz), potassium chloride KCl; 20 m M ), substance P, [β-Ala⁸]-neurokinin A 4-10, [Sar⁹, Met (O₂)¹¹]-substance P (all 10⁻¹⁰to 10⁻⁶ M ) and capsaicin (10⁻⁸to 10⁻⁶ M ). LOS relaxation occurred in response to all stimuli except [β-Ala⁸]-neurokinin A 4-10, which evoked contraction. In muscle strips from acid/pepsin-treated animals there were no differences in amplitude or sensitivity of relaxation following EFS, KCl or substance P vs controls. However, the inhibitory response to capsaicin was increased four-fold (10⁻⁸ M ; P < 0.05) and an increased sensitivity of the inhibitory response to [Sar⁹, Met(O₂)¹¹]-substance P occurred (pD₂ = 8.64 ± 0.12acid/pepsin-treated vs 7.94 ± 0.24 control, P < 0.05). We conclude that in acute oesophagitis, increased sensitivity of capsaicin-activated inhibitory pathways occurs in which activation of NK-1 receptors plays an integral role in the ferret LOS.