Circular smooth muscle preparations isolated from the rat proximal colon periodically generated two different amplitudes and frequencies of phasic contractions: large phasic contractions (LPC) with a frequency of about 1.5 times/min and small phasic contractions (SPC) with a frequency of about 9 times/min. Preparations with no attached longitudinal smooth muscle layer (and also myenteric layer) generated SPC alone, while those with no attached submucosal layer generated only LPC, indicating that the pacemakers of the LPC and SPC are distributed in the myenteric and submucosal layers, respectively. In intact preparations, transmural nerve stimulation (TNS) applied for 1-2 min with different frequencies (0.2-2 Hz) inhibited the phasic contractions. The amplitude of LPC was reduced at >0.25 Hz and abolished at >0.3 Hz, while the amplitude but not the frequency of SPC was reduced at >0.5 Hz (in a frequency-dependent way). The TNS-induced inhibitory responses were augmented by atropine and attenuated by N^ω-nitro-L-arginine (L-NA). In the presence of L-NA and atropine, TNS elicited biphasic (inhibitory and following excitatory) responses. The former were not antagonized by apamin, guanethidine or suramin, while the latter were antagonized by capsaicin, suggesting an innervation by non-adrenergic non-cholinergic non-nitrergic (NANCNN) inhibitory and peptidergic excitatory nerves, respectively. In preparations with the longitudinal muscle layer removed, TNS inhibited only the amplitude of SPC, which was augmented by atropine and antagonized by L-NA. In intact preparations, muscarinic stimulation with acetylcholine increased the frequency of LPC, while nitrergic stimulation with sodium nitroprusside reduced the amplitude and frequency of LPC, and also the amplitude but not the frequency of SPC. These results indicate that the rat proximal colon has two types of pacemaker cells. Myenteric pacemaker cells which receive predominantly nitrergic, but also cholinergic, peptidergic and NANCNN innervation, and submucosal pacemaker cells that are not markedly influenced by intramural nerves.

View full abstract

The present experiments were carried out to investigate the usefulness of measuring peripheral tissue metabolism for the clinical assessment of shock. Male Wistar/ST rats (8 weeks-old) were used. All rats were placed in a supine position while anesthetized. A tube for measuring arterial pressure and collecting blood samples was cannulated into the femoral artery. For microdialysis, the introducer was inserted into the subcutaneous tissue in the abdominal wall. Blood was exsanguinated to maintain the mean arterial pressure at 40 ± 5 mmHg. Mean arterial pressure, arterial blood gas and serum lactate levels were measured. Microdialysis was performed to quantify the levels of lactate and pyruvate in the subcutaneous tissue. Six rats died due to hemorrhagic shock by 350 min (Group D) while six rats had survived for the 350 min period after exsanguination (Group A). These data was obtained at intervals of 50 min after exsanguination up to a period of 250 min and compared between Groups A and D. In Group A, serum lactate levels did not increase throughout the entire period of observation. Serum lactate levels in Group D transiently increased, but did not show a dramatic increase during the blood pressure maintenance period. In particular, serum lactate levels increased again after a period of more than 150 min following exsanguination. Lactate levels in the subcutaneous tissue gradually increased and were significantly higher in Group D than that in Group A after 150 min. The L/P ratio in Group A remained fairly constant during the period of observation. In contrast, the L/P ratio in Group D increased gradually, and was significantly higher than that in Group A after 100 min. It was concluded that the continuous increase in the L/P ratio in the subcutaneous tissue in Group D was indicative of tissue circulatory failure and of an abnormality in tissue oxygen metabolism prior to the detection of the collapse of compensatory mechanisms appearing in the vital signs. These findings suggest that measuring the L/P ratio is useful for the clinical assessment and monitoring of shock.

View full abstract

The family of signal transducer and activator of transcription (STAT) factors play a critical role in the signaling of many cytokines. In addition to the involvement of STAT6 in allergic bronchial asthma, both STAT1 and STAT3 have also been implicated. However, there is little information whether or not the T helper 2 cytokines, which cause several key features of allergic asthma, really induce the activation of STAT1 and/or STAT3 in bronchial smooth muscle (BSM) cells. In the present study, the effects of interleukin-13 (IL-13) and IL-4 on activation of these STAT molecules were examined in cultured human bronchial smooth muscle cells (hBSMCs). After a starvation period, the hBSMCs were treated with 100 ng/ml of IL-13 or IL-4. Total protein samples were prepared at intervals of 1, 3, 6, 12 and 24 hours after the cytokine treatment, and Western blot analyses for total and tyrosine-phosphorylated STATs molecules were conducted. As a result, ut was found that both IL-13 and IL-4 caused a significant increase in the levels of phosphorylated STAT1. Examination of the time-course revealed a peak of STAT1 phosphorylation at 1 hr after cytokine application. In contrast, neither IL-13 nor IL-4 induced phosphorylation of STAT3. Neither of these cytokines changed the protein expression of the STATs themselves. These findings suggest that STAT1, but not STAT3, might also be one of the crucial signal transducers in the development of BSM hyper-responsiveness, which is one of the causes of AHR in asthmatics.

View full abstract

The incidence of vascular disorders is markedly lower in cycling, pre-menopausal women and post-menopausal women receiving estrogen-progestogen therapy than in men or untreated postmenopausal women. Clinical studies demonstrate that estrogen-progestogen therapy in pre-menopausal women is associated with increased arterial vascular risk. However, the mechanism of estrogen-progestogen therapy in arterial vascular complications remain unclear. Therefore, the present study aimed at investigating whether chronic administration of combined oral contraceptive (OC) containing progestogen with androgenic property alters endothelium-dependent relaxation responses of the aorta to histamine and acetylcholine. The experiments have been studied on aortic rings obtained from vehicle-treated and OC-treated female Sprague-Dawley rats. Isometric reactivity of aortic rings was recorded with a strain gauge transducer. The maximum contractile response of the aortic rings to noradrenaline in the OC-treated group was not significantly different from that in the vehicle-treated group. Both acetylcholine and histamine caused relaxation of the noradrenaline pre-contracted aortic rings. The relaxation response to acetylcholine in rings from vehicle-treated and OC-treated rats did not differ significantly, while relaxation response to histamine was significantly attenuated in aortic rings from OC-treated rats. In conclusion, the results from the present study suggest that the increased arterial vascular risk associated with OC administration might involve altered endothelium-dependent relaxation via histaminergic-mediated mechanism, but not via muscarinergic-mediated mechanism.

View full abstract

Local differences in the electrogastrographic (EGG) indices were studied. The indices include the spectral frequency, the instability factor (IF) of the spectral frequency, and the power content in addition to the usual power amplitude of 5 frequency groups as follows: the 1-cpm group (0-2.4), the 3-cpm group (2.5-4.9), the 6-cpm group (5.0-7.4), the 8-cpm group (7.5-9.9), and the 10-cpm group (10.0-12.9). In general, the infraumbilical frequency and the IF of both of the 3- and 6-cpm groups were higher than those of the epigastric frequencies. In contrast, both the epigastric power amplitude and the power content of the 3- and 6-cpm groups were higher than those of the infraumbilical ones. Mapping of the absolute power amplitude and superimposing the maximal power foci further visualized and clarified the local differences in the epigastric and infraumbilical myoelectrical activity, especially of gastric and colonic activity.

View full abstract

Our aim was to investigate the effects of ageing on the vascular contractility of carotid and basilar arteries from guinea-pigs, in a model of total stenosis. Moreover, we attempted to identify whether total stenosis of the left common carotid (stenosed) in adult guinea-pigs, would affect the contractions of contralateral carotid (intact) and basilar arteries to different vasoconstrictors. With this purpose, the left carotid was occluded with a silk thread at a position close to its origin. Vascular reactivity experiments using standard muscle bath were performed 7, 15, 30, and 90 days after carotid occlusion. Reactivity of carotid and basilar arteries to endothelin-1, phenylephrine and KCl was reduced with ageing in naive guinea-pigs. The endothelin-1 and KCl-induced contractions were unaltered in arteries from SHAM-operated animals. Moreover, phenylephrine-induced contractions were reduced in both carotids from 7 days SHAM-operated guinea-pigs, when compared to naive group. Stenosis induced progressive reduction in the contraction induced by endothelin-1, phenylephrine and KCl in the stenosed carotid, when compared to their respective age-matched naive and SHAM groups. Interestingly, an increased contractile-response to vasoconstrictor agents in all the contralateral carotids was observed. Stenosis (30 and 90 days) also induced an increase in the contractions induced by endothelin-1 in the basilar artery. Conversely, phenylephrine and KCl-induced contractions were reduced in basilar arteries 7, 15, 30 and 90 days after stenosis. These results showed that stenosis in adult guinea-pigs induce alterations of vascular reactivity in arteries distant from the site of injury. Thus, in spite of the common use of contralateral carotid as control, it must be aware of the potential alteration induced by stenosis in the vascular motility of such vessels. Additionally, it was verified a relationship between the period of stenosis and the alterations in the vascular reactivity to these vasoconstrictors.

View full abstract