Two classes of endothelin receptors mediating contraction in esophageal muscularis mucosae

Endothelin (ET) causes contraction of the esophageal muscularis mucosae. To characterize the ET receptor subtypes involved in contraction, we measured contraction of isolated muscularis mucosae strips caused by ET-related peptides and binding of (125)I-ET-1 to cell membranes prepared from the guinea pig esophageal muscularis mucosae. Autoradiography demonstrated (125)I-ET-1 binding to the muscularis mucosae and muscularis propria. ET-1 caused tetrodotoxin and atropine-insensitive contraction of esophageal muscularis mucosae strips. The relative potencies for ET isopeptides to cause contraction were ET-1=ET-2>ET-3. FR-139317, an ET(A) receptor antagonist, or BQ-788, an ET(B) receptor antagonist, alone did not alter responses to ET-1. However, the combination of both antagonists almost abolished the ET-1-induced contraction, indicating synergistic inhibition. Desensitization to sarafotoxin S6c, an ET(B) receptor agonist, failed to abolish the response to ET-1, which was completely inhibited by FR-139317. These indicate the involvement of both ET(A) and ET(B) receptors in the contraction. Binding of (125)I-ET-1 to cell membranes of the muscularis mucosae was saturable and specific. Analysis of dose-inhibition curves demonstrated the presence of ET(A) and ET(B) receptors.This study demonstrates that the esophageal muscularis mucosae possesses both ET(A) and ET(B) receptors mediating muscle contraction. There is cooperation between these two subtypes of ET receptors in the esophagus mediating muscle contraction.     

Unique properties of muscularis mucosae smooth muscle in guinea pig urinary bladder

The muscularis mucosae, a type of smooth muscle located between the urothelium and the urinary bladder detrusor, has been described, although its properties and role in bladder function have not been characterized. Here, using mucosal tissue strips isolated from guinea pig urinary bladders, we identified spontaneous phasic contractions (SPCs) that appear to originate in the muscularis mucosae. This smooth muscle layer exhibited Ca(2+) waves and flashes, but localized Ca(2+) events (Ca(2+) sparks, purinergic receptor-mediated transients) were not detected. Ca(2+) flashes, often in bursts, occurred with a frequency (～5.7/min) similar to that of SPCs (～4/min), suggesting that SPCs are triggered by bursts of Ca(2+) flashes. The force generated by a single mucosal SPC represented the maximal force of the strip, whereas a single detrusor SPC was ～3% of maximal force of the detrusor strip. Electrical field stimulation (0.5-50 Hz) evoked force transients in isolated detrusor and mucosal strips. Inhibition of cholinergic receptors significantly decreased force in detrusor and mucosal strips (at higher frequencies). Concurrent inhibition of purinergic and cholinergic receptors nearly abolished evoked responses in detrusor and mucosae. Mucosal SPCs were unaffected by blocking small-conductance Ca(2+)-activated K(+) (SK) channels with apamin and were unchanged by blocking large-conductance Ca(2+)-activated K(+) (BK) channels with iberiotoxin (IbTX), indicating that SK and BK channels play a much smaller role in regulating muscularis mucosae SPCs than they do in regulating detrusor SPCs. Consistent with this, BK channel current density in myocytes from muscularis mucosae was ～20% of that in detrusor myocytes. These findings indicate that the muscularis mucosae in guinea pig represents a second smooth muscle compartment that is physiologically and pharmacologically distinct from the detrusor and may contribute to the overall contractile properties of the urinary bladder.     

Distribution of interstitial cells of Cajal in tunica muscularis of the canine rectoanal region

Electrical and mechanical activity of the circular muscle layer in the rectoanal region of the gastrointestinal tract undergoes considerable changes in the site of dominant pacemaking activity, frequency, and waveform shape. The present study was performed to determine whether changes in the structural organization of the circular layer or in the density, distribution, and ultrastructure of interstitial cells of Cajal (ICC) could account for this heterogeneity in electrical and mechanical activities. Light microscopy revealed that the structural organization of the circular muscle layer underwent dramatic morphological changes, from a tightly packed layer with poorly defined septa in the proximal rectum to one of discrete muscle bundles separated by large septae in the internal anal sphincter. Kit immunohistochemistry revealed a dense network of ICC along the submucosal and myenteric borders in the rectum, whereas in the internal anal sphincter, ICC were located along the periphery of muscle bundles within the circular layer. Changes in electrical activity within the circular muscle layer can be partially explained by changes in the structure of the muscle layer and changes in the distribution of ICC in the rectoanal region of the gastrointestinal tract.     

The blood microcirculatory bed of the tunica muscularis of the human esophagus in postnatal ontogeny]

The analysis of morphological and morphometrical data of the muscular membrane and its blood microcirculatory bed has demonstrated that their development during the postnatal ontogenesis advances unevenly. An intensified growth and development of the muscular membrane morphological structures, including its blood microcirculatory bed occurs from 3 up to 30 years of life. Their maximal growth is noted from 12 up to 30 years of age. The stages of intensified development of the muscular membrane and its blood microcirculatory bed change into stages of retarded growth, where processes of involutive character preponderate. This is especially noticeable from 60 and more years of age. The stages noticed in the muscular membrane development and its blood microcirculatory bed are characterized both by general and topographical morphofunctional peculiarities specific for every stage of organogenesis.     

Effects of cold storage on the function of isolated pancreatic islets

Isolated pancreatic islets from Lewis rats were stored at 4 °C for periods up to 96 hr. A normal pattern of insulin secretion in response to high glucose concentrations was demonstrated in islets stored for up to 48 hr but not in islets stored for longer than this time. The 4 °C environment may be adequate for temporary storage of isolated pancreatic islets but is not suitable for their long-term preservation.     

The fine structure of striated muscle fibres of tunica muscularis of the intestine in some teleosts

Summary The muscular layer of the fish oesophagus is made up exclusively of striated muscles, which form a circular and a longitudinal layer. The intestinal muscular layer of the tench, which is an exception among the vertebrates in this respect, consists of two layers of striated muscles and a layer of smooth ones. The organization of striated muscle fibres is described from the muscular layer of the alimentary canal in four species: the tench, crucian carp, gudgeon and stone-loach. The fibres of the oesophagus differ from each other in diameter, length of sarcomeres, glycogen content and, in the case of one species, organization of SR. On the basis of the organization of sarcomeres all the fibres examined must be counted among the slow-contracting ones (broad Z line). The sarcoplasmic reticulum is organized according to the Z type except for the fibres of the oesophageal muscles in which the SR represents the A-I type. Two types, en grappe and en plaque, of nerve endings have been observed. The presence of relatively large dense core vesicles seems to indicate their adrenergic origin.This work has been supported by the Polish Academy Sciences.     

热激处理对冷藏枇杷果实冷害的生理作用

枇杷(Eriobotrya japonica Lindl.)果实采后经48～52℃、10 min的热激处理,然后2～5℃贮藏,通过对贮藏期间果实冷害级别、呼吸速率、过氧化物酶、过氧化氢酶、苯丙氨酸解氨酶活性和质膜相对透性变化的分析,研究贮前热激处理对冷藏枇杷果实冷害的生理作用.结果表明,2～5℃低温可诱导枇杷果实呼吸速率和苯丙氨酸解氨酶活性异常升高,果实冷害程度与苯丙氨酸解氨酶活性之间呈正相关,相关系数r=0.926.热激处理能降低冷藏条件下(2～5℃)枇杷果实呼吸速率的异常升高,减轻由于低温胁迫造成的果肉细胞膜损伤,提高枇杷果实的过氧化物酶和过氧化氢酶活性,降低苯丙氨酸解氨酶的活性.贮前热激处理有推迟和减轻枇杷果实冷害症状发生、降低果肉低温劣变的作用.贮前热激处理结合低温冷藏是延长枇杷果实贮藏寿命的有效措施之一.     

Effects of cold exposure on calcitonin secretion in the young rat

The effects of cold exposure on calcitonin (CT) secretion were evaluated in young rats. Acute cold exposure (5 h to 5 degrees C) induced a rise in plasma CT concentrations and a decrease in thyroidal CT stores without change in total and ionized plasma calcium levels. The cold activation of sympathico-adrenomedullary axis and the inhibition of CT response to cold after beta-antagonist treatment might suggest that endogenous catecholamines can enhance CT secretion in young rats. Cold adaptation (3 weeks to 5 degrees C) induced a fall in plasma calcium concentration and a rise in thyroidal CT stores without change in plasma CT levels. The high plasma glucocorticoid levels which are known to occur during chronic cold exposure could be involved in the rise of thyroidal CT content in cold adapted rats.     

Physiological and growth responses of Cedrus libani seedlings to cold storage

The effects of cold storage duration on the physiological characteristics and growth of two-year-old Taurus cedar (Cedrus libani A. Rich) seedlings were studied. Taurus cedar seedlings were lifted in December, January and February and stored at +4 °C (cold storage) for 0, 2, 3 and 4 months. Xylem water potential (Ψ), shoot (SMC) and root moisture (RMC) contents, root growth potential (RGP), root electrolyte leakage (REL) and total carbohydrate contents were determined before and after the cold storage. The survival and growth were also evaluated at the end of the first growing season. Ψ, SMC and RMC, RGP and total carbohydrate contents were dramatically affected by the storage duration. The decrease in total carbohydrate contents during the storage showed a parallelism with RGP and survival. It was also found that storage duration had important effects on survival and growth. While survival was above 85 % even after storage of 4 months in seedlings that were lifted in December and January, this rate was reduced to 30 % after storage of 4 months in seedlings that were lifted in February. Total carbohydrate content and RGP can be used as an indicator of survival after cold storage.     

Effect of chronic exposure to cold on isoprenaline-induced cAMP accumulation and relaxation in the rat aorta

Rats chronically exposed to cold (5 degrees C for 5 weeks) develop hypertension. Isoprenaline-induced vascular smooth muscle relaxation is increased in these animals. Our main objective was to compare isoprenaline-induced relaxation of aortae isolated from control and cold-acclimated rats and attempt to relate the differences to changes in receptor parameters (affinity and reserve) and signaling mechanisms. Isoprenaline (10(-9)-10(-5) M)-induced relaxation was enhanced significantly (p < 0.05) in aorta segments from cold-acclimated rats. There was a significant (p < 0.05) increase in the potency of isoprenaline but with no change in affinity. Isoprenaline produced 50% of the maximum response while occupying about 50% and about 15% of the receptors in isolated rat aorta segments from control and cold-treated rats, respectively. Forskolin and db-cAMP also concentration-dependently relaxed aorta segments from control and cold-acclimated rats. There was no difference in potency or maximum response to forskolin (which directly activates adenylyl cyclase) and db-cAMP. cAMP concentrations in the presence of isoprenaline were significantly (p < 0.05) higher in aorta segments from rats chronically exposed to cold when compared with aorta segments from control rats. These findings suggested that altered mechanisms upstream of activation of adenylyl cyclase are involved in the increased beta-adrenoceptor-induced relaxation.     

Preserved vascular reactivity of rat renal arteries after cold storage

In cultured renal tubular cells hypothermia results in cell damage caused by iron-dependent formation of reactive oxygen species. It is unknown whether cold preservation affects function of renal vessels. Rat renal arcuate arteries were stored in a physiological salt solution at 4 degrees C for 24h and compared to control arteries (not stored). To some of the stored arteries the iron chelator 2,2'-dipyridyl was added. Endothelium-independent vasoconstriction was assessed by cumulative concentration-response curves for potassium and phenylephrine in a small vessel myograph. Endothelium-independent vasodilation was assessed with sodium nitroprusside and endothelium-dependent vasodilation with histamine. Cold storage for 24h did not affect vascular reactivity of renal small arteries and no influence of the iron chelator was seen. Since 24h of cold storage considerable damages renal tubular cells both in vitro and after kidney transplantation, these results suggest that renal arteries are less sensitive to cold-induced damage than tubular cells.     

Effects of physical conditioning in man on thermal responses to cold air

Thermal responses of ten relatively unfit young men (six lean, four obese) were determined during duplicate exposures of two hours each in air of 10°C. Mean heat production ( ), rectal (T_re), esophageal (T_es), skin (T_s), and subcutaneous (T_sc) temperatures were continuously measured during each exposure. All subjects were then physically conditioned for nine weeks, which increased their work capacity and maximal oxygen intake. On duplicate retesting, , T_re and T_es remained essentially similar to preconditioning values. Mean skin temperature (T_s) of both groups was lower following conditioning, due primarily to lower skin temperatures of the chest, thigh, forearm and upper arm. Toe temperature was unchanged. The T_sc to T_s gradients for the forearm and upper arm were greater in both groups after conditioning. Increased vasoconstriction and a different peripheral circulation pattern in the cold may result from physical conditioning.

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Zusammenfassung Die Wärmereaktionen von 10 relativ untrainierten jungen Männern (6 schlank, 4 fett) wurden im Doppelversuch während 2 Stunden Exponierung bei 10°C untersucht. Die Messungen der mittleren Wärmebildung ( ), rektalen (T_re), Oesophagus (T_es), Haut (T_s) und subkutanen (T_sc) temperaturen erfolgten fortlaufend während jeder Exponierung. Danach wurden alle Personen 9 Wochen körperlich trainiert. Dies führte zu einem signifikanten Anstieg der Arbeitsleistung und maximalen O₂-Aufnahme. Bei doppelter Wiederholung der Untersuchung ergaben sich für , T_re und T_es gleiche Werte wie vorher. Nach dem Training was T_s bei beiden Gruppen tiefer, als Folge tieferer Temperaturen über der Brust, den Oberschenkeln und den Armen. Die Zehentemperatur war unverändert. Die T_sc — T_s Grandienten waren am Vorder- und Oberarm in beiden Gruppen nach dem Training grösser. Eine erhöhte Vasokonstriktion und veränderte periphere Zirkulation in der Kälte ist wahrscheinlich Folge des Trainings.

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Resume La réaction à la chaleur de 10 jeunes gens relativement peu entraînés (6 maigres et 4 gras) a été examinée par l'exposition de 2 × 2 heures à 10°C. On a mesuré en permanence durant chaque exposition la production moyenne de chaleur ( ) et les températures rectale (T_re), de l'oesophage (T_es), de la peau (T_s) et subcutanée (T_sc). Ensuite, toutes ces personnes subirent un entraînement durant 9 semaines. Ceci eut pour conséquence une augmentation significative des aptitudes au travail musculaire et de l'absorption maximum de O₂. De nouvelles mesures répétées deux fois ont donné les mêmes valeurs que précédemment pour , T_re et T_es. Après l'entraînement, les deux groupes présentaient des valeurs inférieures pour T_s en raison de températures plus basses sur la poitrine, la cuisse et les bras. La température des orteils n'avait pas changé. Le gradient T_sc — T_s avait augmenté chez les deux groupes au bras et à l'avant-bras. Une constriction vasculaire plus élevée et une modification de la circulation périphérique sont probablement les conséquences d'un certain entraînement.

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This investigation was supported by Contract No AF 41 (609)-2696 from the Aerospace Medical Division (AFSC) Department of the Air Force.