Role of nitric oxide in the contraction of circular muscle in the rat portal vein

The role of nitric oxide in the electrical and mechanical activities of the rat portal vein was examined in circular muscle preparations with intact endothelium that were isolated from the longitudinal muscle layer. In contrast to the longitudinal muscle preparation, the circular muscle preparation did not show spontaneous phasic contraction. Inhibition of nitric oxide synthesis by Nomega-nitro-L-arginine (L-NNA) induced a tonic contraction. The contraction was inhibited by L-arginine, sodium nitroprusside or nifedipine. L-NNA did not induce contraction in endothelium-damaged preparations. The membrane potential of smooth muscle cells recorded in endothelium-intact preparations showed sporadic action potentials. L-NNA increased the frequency of action potentials without changing the resting membrane potential. The action potentials were inhibited by nifedipine. In the presence of L-NNA, sodium nitroprusside decreased the frequency of the action potentials without changing the resting membrane potential. These results indicated that contraction of rat portal vein circular muscles is inhibited tonically by nitric oxide, at least partly through inhibition of electrical activity.     

Some properties of the smooth muscle of rabbit portal vein

1. The morphology of the smooth muscle of the rabbit portal vein and its innervation were studied with fluorescence and electron microscopy. Two layers of smooth muscle were observed in the tunica media: an inner layer of circularly arranged muscle cells and an outer layer consisting of bundles of smooth muscle cells arranged in a near longitudinal direction. The membranes of neighbouring smooth muscle cells were occasionally fused to form ;tight junctions'.2. Bundles of non-myelinated nerve fibres were observed in the adventitia, and between bundles and layers of smooth muscle cells in the media. Studies on longitudinal sections with fluorescence microscopy revealed a network of varicose noradrenergic axons.3. Electrical and mechanical activity was recorded from longitudinal strips of smooth muscle from the media of the vein with a sucrose-gap apparatus.4. The preparation was spontaneously active under minimal resting tension (less than 150 mg) and at temperatures above 28 degrees C. Slow depolarizations led to a burst of spikes (multi-spike complexes), which corresponded to rhythmic contractions. In 10% of preparations, the interval between multi-spike complexes showed a slower depolarization, suggesting the record was from a pace-maker region.5. The frequency of spontaneous activity (3-27 beats/min) was very sensitive to changes in temperature and tension.6. Noradrenaline in low doses (0.01 mug) caused an increase in frequency of the multi-spike complexes. Higher doses (0.1-0.3 mug) initiated continuous high-frequency spiking, while very high doses (0.6-2.0 mug) caused maintained depolarization.7. Responses to repetitive electrical stimulation of the vein were qualitatively similar to those in response to exogenous noradrenaline. The relation between the mechanical response and the various parameters of stimulation was consistent with the stimulation of sympathetic nerve fibres in the wall of the vein.8. The actions of isoprenaline, phentolamine and propranolol indicated the presence of alpha ;excitatory' and beta ;inhibitory' adrenotrophic receptors on the smooth muscle.     

Electrical and mechanical properties of spontaneous contraction in hypertensive rat portal vein

Contractile and electrical activities of longitudinal smooth muscle of portal vein from normotensive Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) were compared. Amplitude and duration of spontaneous contraction of SHRSP portal vein were greater than those of WKY portal vein. No significant differences were observed in the resting membrane potentials between these preparations. Spontaneous spike activity appeared as a form of bursts. Duration of the burst and the number of spikes in each burst was greater in the portal vein of SHRSP than that of WKY. The amplitude of phasic and tonic components of K-contracture was also greater in SHRSP portal vein. Adrenergic and cholinergic nerves were not involved in the differences in contractions of the portal vein of these animal strains. Cross-sectional area of the longitudinal muscle layer was greater in SHRSP portal vein. These results suggest that the differences in spontaneous electrical activity are the cause of the differences in force and duration of the spontaneous contraction of portal vein from WKY and SHRSP, although the difference in excitation-contraction coupling of smooth muscle may be involved in much less extent.     

Effects of Dai-kenchu-to on spontaneous activity in the mouse small intestine.

The effects of Dai-kenchu-to (DKT), a Chinese medicine, on spontaneous activity of mouse small intestine were investigated. Experiments were carried out with tension recording and intracellular recording. DKT contracted mouse longitudinal smooth muscles in a dose dependent manner (0.1-10 mg/ml). Low concentration of DKT (0.1 mg/ml) did not contract the longitudinal muscles of mouse small intestine. DKT (0.1 mg/ml) inhibited contraction elicited by transmural nerve stimulation (TNS). DKT (1 mg/ml) evoked relaxation before contraction. The initial relaxation was abolished by Nomega-nitro-L-arginine (L-NNA). DKT (10 mg/ml)-induced contraction had two components: a transient rapid contraction and a following slow contraction. Atropine inhibited DKT (1 mg/ml)-induced contraction to about 50% of control. In the presence of atropine, tetrodotoxin (TTX) inhibited the contraction elicited by DKT (1 mg/ml) to about 80%. DKT depolarized the membrane and decreased the amplitude of pacemaker potentials recorded from in situ myenteric interstitial cells of Cajal (ICC-MY) with no alteration to the frequency, duration and maximum rates of rise in the presence of nifedipine and TTX. The same results were obtained in slow waves recorded from circular smooth muscle cells. These results indicate that DKT evoked both contraction and relaxation by releasing acetylcholine, nitric oxide and other excitatory neurotransmitters in mouse small intestine. DKT had no effects on pacemaker mechanisms and electrical coupling between ICC-MY and smooth muscle cells in mouse small intestine. The results also suggest that DKT may contract smooth muscles by depolarizing the membrane directly.     

人与猪肝门静脉显微结构成分的比较

目的：比较人与猪肝门静脉壁结构成分的异同,为猪一人异种肝移植提供理论依据。方法：取正常成人与不同月龄猪肝门静脉,常规石蜡包埋、切片,分染弹性纤维、胶原纤维和平滑肌,光镜观察,计算机图像分析系统测量各结构成分的相对含量。结果：随月龄的增长猪肝门静脉胶原纤维的含量逐渐升高,弹性纤维的含量相对稳定,平滑肌的含量在3月龄时最高,C厄值逐渐升高。与人相比,猪肝门静脉壁中胶原纤维和弹性纤维的含量较低,而平滑肌的含量则较高,5、6月龄时的C/E值与人相近。结论：人与猪肝门静脉壁各结构成分的含量存在差异,但从C僵值看,5、6月龄猪肝门静脉的力学特性与人相匹配,较适合用于移植。     

The vascular anatomy of the liver of the monitor lizard (genus varanus)

The gross and microscopic anatomy of the vasculature of the monitor lizard liver was studied. The portal vein has a peculiar arrangement of smooth muscle. The tunical media of the entering portal vein has bundles of smooth muscle cells separated by large numbers of collagenous fibers. The amount of smooth muscle decreases as the vessel decreases in diameter and soon one finds intermittent broad, thin bands of smooth muscle. As the caliber of the vessels continues to decrease, the smooth muscle bands become narrower and thicker so that they appear as doughnut-shaped sphincters. The sphincters are usually found at the beginning of each branch of the portal vein as well as along the course of veins between areas of branching. Some sphincters are found in direct contact with the outer capsule of the liver. Sphincters occur in the terminal branches of the portal vein just proximal to the sinusoids. Small numbers of scattered smooth muscle cells were seen arranged longitudinally, obliquely, or circularly in the smaller hepatic veins. Even the large hepatic veins had only small amounts of smooth muscle. At no place along the course of hepatic veins could smooth muscle sphincters equivalent to those seen around portal veins be found. The monitor lizard should be an excellent subject for physiological and pharmacological studies of regulation of intrahepatic portal vein blood flow.     

Uterus and endometrium: The three-dimensional organization of the smooth musculature in the ampulla of the human Fallopian tube: a new morpho-functional model

The three-dimensional organization of the smooth musculaturearound the human ampulla is revealed by means of scanning electronmicroscopy after NaOH maceration and ultrasonic microdissectionof the interstitial connective tissue. The muscular wall ofthe ampulla appears as a continuous network of randomly anastomosedsmooth muscle cell bundles that showed a multidirectional arrangement.The smooth muscle cell bundles modify their orientation alongtheir course, intertwine repeatedly with each other and dichotomize,generating new bundles with a different orientation from thatat the origin. These results demonstrate that the myosalpinxof the human ampulla is not organized into clear cut longitudinally,circularly or spirally arranged layers, as suggested in previouslight microscopy studies. In contrast, the presence of a networkof multidirectional smooth muscle cell bundles revealed in thisstudy suggests that there is no morphological evidence for unidirectionalperistalsis, and that the musculature is probably structurallydesigned to stir rather than push the tubal contents. Thesemorphological findings better explain the random pattern ofpropagation of the contraction waves and the electrical impulsesthrough the smooth musculature of the human ampulla, as postulatedin early experimental physiological studies. Further, they suggesta specific function for the ampullar musculature which may notbe only strictly related to tubal content transport.     

Three-dimensional morphology of c-Kit-positive cellular network and nitrergic innervation in the human gut.

CONTEXT:-c-Kit-positive interstitial cells of Cajal (ICC) appear to play a key role in the normal motility function and development of intestine. Nitric oxide is considered to be the most important messenger of inhibitory nonadrenergic, noncholinergic nerves in the enteric nervous system. OBJECTIVES: The aims of this study were to examine the distribution of nitrergic innervation and ICCs in normal human bowel and to demonstrate interconnections between ICCs and nitrergic nerves and smooth muscle fibers using histochemical and immunohistochemical double-staining methods with a whole-mount preparation technique and confocal laser scanning microscopy. METHODS: Full-thickness small and large bowel specimens were obtained at autopsy from 18 children who died of nongastrointestinal diseases. A whole-mount preparation was performed for all specimens, and double staining was carried out with nicotinamide adenine dinucleotide phosphate (reduced form, NADPH)-diaphorase and c-Kit immunohistochemistry. Double immunofluorohistochemistry with neuronal nitric oxide synthase and c-Kit using confocal laser scanning microscopy was also performed in all specimens. RESULTS: The whole-mount preparation facilitated 3-dimensional visualization of the meshlike network of NADPH-diaphorase-positive nerve fibers in the myenteric plexus surrounded by a reticular network of c-Kit-positive ICCs. The dense c-Kit-positive cellular network located between longitudinal and circular muscle layers and at the innermost part of circular muscle layer intermingled with the myenteric plexus. Short, fine processes of ICCs made connections with the muscle fibers and c-Kit-positive cells. CONCLUSIONS: The development of double-NADPH-diaphorase histochemistry and c-Kit immunohistochemistry staining technique in a whole-mount preparation provides an easy and useful method for investigating the association between c-Kit-positive cellular network and nitrergic neuronal network in the human bowel wall. The characteristic profiles of the c-Kit-positive cellular network and nitrergic neuronal network and their relationship with the smooth muscle fibers provide a morphologic basis for investigating intestinal motility disorders.     

Lactate dehydrogenase activity and isoform distribution in normal and hypertrophic smooth muscle tissue from the rat

The lactate dehydrogenase (LDH) activity and isoform distribution of LDH were investigated in tissue samples from the rat portal vein, aorta and urinary bladder. In addition, samples were obtained from hypertrophic urinary bladder. The total LDH activity per unit smooth muscle volume was higher in the urinary bladder compared to that in portal vein and aorta. Five LDH isoforms, reflecting different combinations of the two polypeptide chains denoted H and M, could be separated by agarose gel electrophoresis. The aorta contained more of the H form compared to the portal vein and urinary bladder. This difference suggests that the aorta, which is a slow smooth muscle, is more adapted for aerobic metabolism than the faster muscles of portal vein and urinary bladder. In the hypertrophic urinary bladder a shift in LDH isoform pattern towards less of the H form was found, which correlates with a better maintenance of contraction in anoxia in this type of hypertrophic smooth muscle.     

Structural Organization of Hepatic Portal Vein in Rat with Special Reference to Musculature,Intimal Folds,and Endothelial Cell Alignment

Structural organization of hepatic portal vein (HPV) was examined in adult rats by means of light and electron microscopy. Three characteristic features were found in the wall structure of rat HPV. (1) Tunica media consisted of two kinds of smooth muscle. The inner circular smooth muscle (CSM) was composed with one or two layer of smooth muscle cells, and was found in the entire length of the HPV and its tributaries. The outer longitudinal smooth muscle (LSM) was limited to a specific region of HPV; in particular it was well‐developed at distal half of HPV. CSM counteracts luminal hydrostatic pressure to prevent circumferential hyperextension of venous wall, whereas LSM is likely to counteract a tractive force produced by gravity and movement of small intestine. (2) Intima of HPV showed a unique feature, intimal folds, which protruded into the lumen and were aligned almost circumferentially. Intimal folds were found only at the same region where the LSM was well‐developed. Thus, LSM is presumably involved in the formation of intimal folds. (3) The endothelial cells between intimal folds were circumferentially aligned along the folds, although those in the other regions of HPV were arrayed along the longitudinal axis of HPV or the direction of blood flow as reported in other kinds of blood vessel. This finding implied that the circumferential blood flow locally occurs on the surface of intima between the intimal folds. Anat Rec, 2010. © 2010 Wiley‐Liss, Inc.     

Long-term engraftment of bone marrow-derived cells in the intimal hyperplasia lesion of autologous vein grafts

Intimal hyperplasia of autologous vein grafts is a critical problem affecting the long-term patency of many types of vascular reconstruction. Within intimal hyperplasia lesions, smooth muscle cells are a major component, playing an essential role in the pathological process. Given that bone marrow-derived cells may differentiate into smooth muscle cells in the neointima of injured arteries, we hypothesized that the bone marrow may serve as a source for some of the smooth muscle cells within intimal hyperplasia lesions of vein grafts. To test this hypothesis, we used an established mouse model for intimal hyperplasia in wild-type mice that had been transplanted with bone marrow from a green fluorescent protein (GFP+/+) transgenic mouse. High-resolution confocal microscopy analysis performed 2 and 8 weeks after grafting demonstrated expression of GFP in 5.4 +/- 0.8% and 11.9 +/- 2.3%, respectively, of smooth muscle cells within intimal hyperplasia lesions. By 16 weeks, GFP expression in smooth muscle cells was not detected by immunohistochemistry; however, real-time PCR revealed that 20.2 +/- 1.7% of the smooth muscle cells captured from the neointima lesion by laser capture microdissection at 16 weeks contained GFP DNA. Our results suggest that bone marrow-derived cells differentiated into smooth muscle cells within the intimal lesion and may provide a novel clinical approach for decreasing intimal hyperplasia in vein grafts.     

Description of the structural control systems of ovum transport in the quail oviduct

Some electronmicroscropic and light microscopic aspects of the quail oviduct have been studied in relation to ovum transport. Previously it has been shown that in this smooth muscle there exist spontaneous coordinated electrical and mechanical activity which suggests a good electrical and mechanical coupling of the muscle cells. The structural basis for this coupling is not known. The majority of muscle cell contacts observed were simple appositions and intermediate junctions. Less numerous were attachments of the interdigitation type. No nexuses or tight junctions were seen. Mechanical stretching or contraction of cells induced with 10^-4 M carbachol did not affect the contacts. The fine structure of the muscle cells did not differ from that described for other smooth muscles. Electronmicroscopically the muscle cell bundles could not be distinguished into separate layers, in the light microscope the cell bundles were spirally arranged. Stretching of the oviductal strips to the length to which the ovum stretches the muscular wall during ovum transport caused re-orientation of the muscle cell bundles. One-directional stretching turned the axes of the muscle cells and the collagen bundles parallel, while stretching in two direction made the tissue look like a network. The re-orientation of muscle cell bundles may be of importance in producing forces in the muscular tunic during ovum transport. The nerve supply to the muscle cells was negligible. These and previous results show that structurally the muscular wall of the quail oviduct is a dynamic unity in which the ovum via stretch induces the electrical and mechanical activity throughout the tissue. Innervation may play a minor role in controlling the contractions.     

L-arginine-induced current in portal venous smooth muscle cells.

In our previous report, we showed that L-arginine induced depolarization of smooth muscle cells of the rat portal vein with an increased contraction. To clarify the ionic mechanism of the membrane depolarization, the effect of L-arginine on the holding current was studied in freshly isolated smooth muscle cells of the rat portal vein. The whole-cell patch-clamp technique was used, with the membrane potential held at -60 mV. In the presence of Na+ in the perfusate, L-arginine 10 mM induced an inward current in about 50% of the cells. In Na+-deficient perfusate, L-arginine 10 mM increased the amplitude of the inward current in a Na+ concentration-dependent manner. BCH, an inhibitor of the Na+-dependent amino acid transporter, ceased the L-arginine-induced current. These results indicate that L-arginine induces an inward current via Na+-dependent mechanisms in rat portal venous smooth muscle cells.     

Effects of L-arginine on spontaneous contraction of the rat portal vein

The effects of L-arginine on spontaneous contraction of endothelium-denuded longitudinal preparations of the rat portal vein were studied. L-arginine increased the frequency of spontaneous contraction concentration-dependently between 10 microM and 1 mM. Changes in contraction amplitude and duration were not remarkable. D-arginine had a negligible effect on spontaneous contraction. N(omega)-nitro-L-arginine (1 mM) did not affect spontaneous contraction or the response to L-arginine. Addition of N(G)-monomethyl-L-arginine (1 mM), l-lysine (1 mM) or N-ethymaleimide (0.1 mM) increased the frequency of spontaneous contractions and inhibited the effect of L-arginine. Glibenclamide (10 microM) did not affect spontaneous contraction or the response to L-arginine. Spontaneous increase in concentration of intracellular Ca2+, estimated as the ratio of Fura-PE3 fluorescence occurred synchronously with spontaneous contraction. Spontaneous increase in concentration of intracellular Ca2+ occurred more frequently in the presence of L-arginine (1 mM). L-arginine (1 mM) also increased the number of action potential bursts/min in the longitudinal smooth muscle layer. L-arginine (1 mM) also depolarized cell membranes. This study indicates that L-arginine increases the frequency of spontaneous contraction of longitudinal muscle in the rat portal vein by membrane depolarization through mechanisms that do not involve nitric oxide or the inhibition of ATP-sensitive K+ channels.     

Morphological changes in femoral vein wall structure in presence of persistent vertical reflux

The article contains an analysis of different mechanisms of persistent chronic venous insufficiency formation and its impact on the condition of lower extremity magistral vein wall. The authors studied autopsy samples of femoral vein segments from 86 patients aged 56 to 64 years, who had died of non-cardiovascular diseases. The investigation revealed significant changes in the vein wall structure, associated with persistent overload caused by valvular insufficiency and continuous persistent vertical reflux. At the same time, valve cusp structure remodels. Histological studies show that the overload of the system of deep femoral vein segment primarily increases the bulk of longitudinal smooth muscle cells, which fulfill the main contractile function in contrast to circular smooth muscle cells, performing the tonic function. Further overload of all vein wall structures results in structural alterations, smooth muscle cell hypertrophy, forming of longitudinal smooth muscle cell fascicle, and finally, their dystrophic changes. These processes bring about clinical presentations of chronic venous insufficiency.     

The effect of length on the sensitivity to phenylephrine and calcium in intact and skinned vascular smooth muscle

The length dependency of the sensitivity to activators of the smooth muscle of different blood vessels is not yet fully understood. Muscle preparations of the aorta, the femoral artery and the portal vein of the rabbit were investigated for the length dependency of the sensitivity to phenylephrine and calcium in both intact and triton X- 100 skinned preparations. For intact smooth muscles we found that at increased preparation length, the sensitivity of contraction was increased. The femoral artery showed the largest effect and the portal vein the smallest. In the skinned preparations of the three preparations the calcium sensitivity was not dependent on the preparation length. We conclude that the changes of the sensitivity in intact preparations are not caused by changes of the calcium sensitivity of the contractile proteins.     

Accessory liver lobe attached to the wall of the gallbladder: a cadaveric case report

Accessory liver lobe is found incidentally during laparoscopy, laparotomy or autopsy performed for unrelated reasons. The occurrence of accessory liver lobe attached to the gallbladder is reported rarely in the literature. During regular dissection classes, we came across an accessory liver lobe in the wall of the gallbladder in an adult male cadaver. On its left, it was connected to the quadrate lobe by a short fold of peritoneum. On the right, it was attached to the wall of the gallbladder. The fragment was triangular in shape, and was 20 mm in length, 11 mm in width and 6 mm thick. The histology of the fragment revealed the unusual architecture of hepatic tissue with the absence of the classical hexagonal lobule pattern. Cords of hepatocytes surrounding the central vein, with an absence of portal canals, were observed. There were branches of hepatic artery, portal vein and hepatic duct in its peritoneal fold. Smooth muscle fibers were also observed along its attachment on the wall of the gallbladder. Awareness of the incidence of accessory liver lobe in the wall of the gallbladder is of clinical importance during the diagnosis and treatment of gallstones.     

门静脉高压症猪肺血管的结构重建及临床意义

目的:探讨门静脉高压症猪肺血管形态结构重建的特点。方法:采用健康2月龄湖北白猪14头,随机分为正常对照组和实验组,用四氯化碳建立门静脉高压症模型。取肺动脉和肺静脉,横断切片。用Pilloridine和Cy3-IgG分别染胶原纤维和平滑肌,弹性纤维自发荧光。在激光共聚焦显微镜下观察,用计算机图像分析系统测量各结构成分的相对含量。结果:与正常对照组相比,门静脉高压猪肺血管壁中胶原纤维、平滑肌的相对含量及胶原纤维与弹性纤维的比值(C/E)均增大,弹性纤维则减少。结论:门静脉高压时,猪肺血管的形态结构可发生重建,表现为胶原纤维增加,弹性纤维减少,导致C/E值的改变。肝肺联合移植时,移植材料间的结构成分的差异也应引起关注。