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Biomedical subjects

S Homma

Publications and source records attributed to S Homma.

At least 199 records · Page 11Linked to original sources
PubMed1993

The effect of bupivacaine hydrochloride on skeletal muscle fiber type transformation by low frequency electrical stimulation.

Bupivacaine hydrochloride (bupivacaine HCl) is known to induce the degeneration and regeneration of skeletal muscles. We examined the priming effect of chronic and continuous nerve stimulation (5 Hz) on regenerating pectoralis major muscle after a single injection of bupivacaine HCl (3 mg/kg). Pectoralis muscle stimulated for 24 days after bupivacaine HCl injection contained 55.4 +/- 8.2% type 1 muscle fibers (n = 4). Control pectoralis major muscle stimulated for 34 days without bupivacaine HCl injection, in contrast, contained 37.7 +/- 5.5% type 1 fibers (n = 5). Therefore, the stimulated pectoralis major muscle with bupivacaine HCl injection contained a significantly larger number of type 1 fibers than that without bupivacaine HCl injection. Undifferentiated myosatellite cells produced by bupivacaine HCl may be primed to differentiate into type 1 cells by chronic low frequency electrical stimulation.

Animals↗
PubMed1993

Transcranial Doppler with contrast injection for the detection of patent foramen ovale in stroke patients.

Right-to-left shunt through a patent foramen ovale was searched for in 80 patients with acute ischemic stroke by simultaneously performing transthoracic two-dimensional echocardiography and transcranial Doppler during agitated saline injection. A patent foramen ovale was detected by echocardiography in 14 patients (17.5%). Transcranial Doppler correctly identified all 14 patients, and 7 more patients in whom echocardiographic findings were indeterminate. Prevalence of patent foramen ovale by transcranial Doppler was therefore 26.3% (21 of 80 patients). Concordance between the two tests was 91.3% (73 of 80 patients). The delivery of contrast material to cerebral vessels is therefore demonstrable by transcranial Doppler in all patients diagnosed by contrast echocardiography, suggesting that paradoxical embolization through a patent foramen ovale may be more frequent than previously thought. Transcranial Doppler with contrast injection is a valid alternative in case of poor echocardiographic image quality.

Cerebral Arteries↗
PubMed1993

In vivo and in vitro activation of macrophages with a cyanine photosensitizing dye, platonin.

A cyanine photosensitizing dye, platonin, is a potent macrophage-activating agent. Four days after the administration to mice of small amounts of platonin (20-40 ng/mouse), peritoneal macrophages exhibited greatly enhanced Fc-receptor-mediated phagocytic and superoxide-generating capacities. Much higher doses (more than 3000 ng/mouse) did not have this effect. Photodynamic experiments for macrophage activation were performed by exposing mouse peritoneal cells (mixture of macrophages and B and T lymphocytes) to white fluorenscent light (3 J m-2s-1) in media containing various low concentrations of platonin. A short exposure to white fluorescent light (5 s, 15 J m-2) of peritoneal cells in a medium containing 3 ng platonin/ml produced a maximal level of phagocytic capacity of macrophages. Although platonin absorbs light poorly at wavelengths longer than 630 nm, the region of the spectrum in which the tissues are transparent allows reasonable penetration of light. Thus, we designed experiments in which peritoneal cells were exposed to a red fluorescent light (0.5 J m-2s-1). In a medium containing 10 ng platonin/ml with 15 J m-2 red light, a markedly enhanced ingestion activity of macrophages was observed. Photodynamic treatment of peritoneal macrophages alone did not activate macrophages. Thus, participation of nonadherent cells is required for photodynamic activation of macrophages, implying that a macrophage-activating factor is generated within the nonadherent cells and transmitted to macrophages.

Animals↗
PubMed1993

The lung in polyarteritis nodosa: a pathologic study of 10 cases.

Polyarteritis nodosa (PAN) is characterized by necrotizing arteritis of medium-sized and small arteries in various organs. Pulmonary artery involvement in PAN has been considered rare. Previously, it also has been thought that patients with PAN do not have interstitial pneumonitis and fibrosis. A detailed pathologic analysis of pulmonary diseases associated with PAN was made in 10 autopsy cases of PAN. Arteritis affecting bronchial arteries was present in seven patients (70%). The data obtained suggest that arteritis in the lung in patients with PAN is more common than has been recognized previously. Diffuse alveolar damage (DAD) involving all lobes bilaterally was present in five patients; it was acute in two patients and organizing in three. In the patients with organizing DAD the degree of fibrosis in the interstitium differed among the lobes, and the fibrosis was more severe in the lower lobe than in the other lobes. Two patients presented with interstitial fibrosis with honeycomb lung of the posterior and lateral basal segments of the lower lobes of both lungs; in one of these patients interstitial fibrosis was present in an area of organizing DAD. Five patients died of respiratory failure resulting from DAD. In conclusion, it is important to consider DAD and interstitial fibrosis as complications of PAN.

Adolescent↗
PubMed1993

Baroreceptor control of vasopressin-producing cells in streptozotocin diabetic rats.

Electrical activities of the vasopressin (AVP)-producing cell in the supraoptic nucleus of the streptozotocin diabetic (STZ-DM) rat were recorded extracellularly and compared with those in the control rat. Higher hematocrit (45.3 +/- 0.5%, mean +/- SE) and lower mean blood pressure (MBP) (89.5 +/- 2.1 mmHg) suggested that STZ-DM rats were hypovolemic and hypotensive. The mean discharge rates of AVP cells were 15.2 +/- 3.1 Hz (STZ-DM) (p < 0.05 vs. control) and 8.8 +/- 0.8 Hz (control), respectively. Pressor and depressor responses were caused by phenylephrine (1.5 and 2.9 micrograms/kg, i.v.) and nitroprusside (1.5 micrograms/kg, i.v.), respectively, during the recording the AVP cells. Pressor and depressor responses linearly (STZ-DM; gamma = -0.7071, control; gamma = -0.9262) decreased and increased the discharge activity of the cells in both experimental groups, respectively. The MBP-neuronal activity relationship in STZ-DM did not differ statistically from that in the control. These results suggest that cardiovascular regulation of AVP release is well retained in STZ-DM rats.

Action Potentials↗
PubMed1993

Vitamin D-binding protein (group-specific component) is the sole serum protein required for macrophage activation after treatment of peritoneal cells with lysophosphatidylcholine.

In vitro treatment of mouse peritoneal cells with 1 micrograms lysophosphatidylcholine (lyso-Pc)/mL in serum free-0.1% egg albumin-supplemented RPMI 1640 medium for 30 min, followed by 3 h cultivation in a medium supplemented with human serum, resulted in a greatly enhanced Fc-receptor-mediated phagocytic activity of macrophages. Vitamin D-binding protein (group-specific component [Gc]) of alpha 2-globulin fraction was shown to be the sole serum glycoprotein required for the generation of a potent macrophage-activating factor. When a mixture of lysophosphatidylcholine (lyso-Pc)-treated nonadherent and adherent cells were cultured in a medium supplemented with a small amount of purified Gc protein (1 ng/mL), a greatly enhanced activation of macrophages was demonstrated. The generation of macrophage-activating factor from purified Gc protein was far more efficient than that from whole serum, indicating that a serum component is inhibitory to the activation process of macrophages. While three other major serum glycoproteins (alpha 2-macroglobulin, alpha 2-HS-glycoprotein and haptoglobin) were neither stimulatory nor inhibitory to lyso-Pc-primed macrophage activation, serum albumin (competitively with Gc protein) appeared to be inhibitory to the process of macrophage activation.

Animals↗
PubMed1993

Force and histochemical changes in rabbit pectoral muscle induced by chronic electrical stimulation for use in cardiac assistance.

Before the application of skeletal muscle in a cardiac-assist device, a preconditioning procedure is required in order to overcome the easy fatigability of this muscle. We evaluated the effect of preconditioning muscles while keeping their collateral blood supply. In 15 male rabbits, a skeletal muscle ventricle (SMV) was constructed from silicone and pectoralis major muscle with minimal dissection. In six rabbits, the muscle was electrically preconditioned. The pressure generated by the SMV was measured under various conditions. Histochemical fiber grouping was performed using myosin ATPase staining. The pressure rose with preconditioning despite an increase in slow-twitch fibers. The cross-sectional area of both slow-twitch and fast-twitch fibers increased significantly. The rise in pressure is attributable to muscle hypertrophy. The use of muscles with minimal dissection may avoid or shorten the vascular delay because of a well maintained blood supply and nearly isometric preconditioning.

Animals↗
PubMed1993

Effects of furosemide on renal oxygen consumption after ischemia in normal and streptozotocin diabetic rats.

Normal and streptozotocin diabetic rats were subjected to ischemic injury by unilateral renal artery occlusion for 60 min. The cortical and the medullary oxygen consumption (QO2) in the postischemic and the control, contralateral nonischemic, kidneys were measured 1 h, 1 day, and 1, 2 and 4 weeks for normal rats and 1 day, and 1 and 4 weeks for diabetic rats after ischemia. The effects of furosemide on QO2 of the cortex and the medulla of normal and diabetic rats were studied. The diabetic kidney was more vulnerable to ischemic injury than the normal kidney. Furosemide-sensitive active transport function in the medulla of the diabetic kidney was higher than that of the normal kidney. Furosemide did not decrease the cortical QO2 significantly in the control and the postischemic kidneys of normal and diabetic rats. In contrast, the medullary QO2 of the control kidney in both rats was significantly reduced by furosemide at every period after ischemia. In the medullary QO2 of the postischemic kidney, there were no significant decreases at any period after ischemia in the diabetic rats and only after a 1-hour period for normal rats. However, 4 weeks after ischemia, there was no statistically significant difference in the medullary QO2 inhibition by furosemide between the control and the postischemic kidneys in both normal and diabetic rats. We conclude that the furosemide-sensitive active transport function in the medulla recovers by the 4th week after ischemia in normal and diabetic rats.

Animals↗
PubMed1993

Comparison of diagnostic techniques for the detection of a patent foramen ovale in stroke patients.

BACKGROUND AND PURPOSE: The prevalence of a patent foramen ovale has been shown to be increased in patients with ischemic stroke. Transesophageal echocardiography, transthoracic echocardiography, and transcranial Doppler examination with contrast injection can all be used to search for a patent foramen ovale. We compared the accuracy of these techniques for identifying a patent foramen ovale in 49 patients with acute ischemic stroke or transient ischemic attack. METHODS: Transcranial Doppler examination of the right middle cerebral artery was performed during simultaneous transthoracic echocardiography with aerated saline injection, and again during transesophageal echocardiography; the latter was adopted as the "gold standard" for assessing the sensitivity of the other two tests. RESULTS: Contrast transesophageal echocardiography detected a patent foramen ovale in 19 of 49 patients (39%), during normal respiration in 15 of them and during Valsalva maneuver in 4. Transcranial Doppler correctly identified 13 patients with a patent foramen ovale and all 30 patients without it. Therefore, the sensitivity of transcranial Doppler was 68% (13/19), and its specificity 100% (30/30). The 6 patients misclassified by transcranial Doppler (false negatives) had a very small right-to-left shunt detected by transesophageal echocardiography. Contrast transthoracic echocardiography was found to be the least sensitive test, detecting a patent foramen ovale in only 9 of 19 patients (47%). The specificity of transthoracic echocardiography was 100% (30/30 patients). The low sensitivity of transthoracic echocardiography was principally due to the suboptimal image quality obtained in false-negative patients. Both transcranial Doppler and transthoracic echocardiography were more sensitive in patients with cryptogenic stroke than in patients with stroke of determined origin. This may indicate the presence of larger, more easily detectable shunts in patients with cryptogenic stroke. CONCLUSIONS: Transesophageal echocardiography is more sensitive than transcranial Doppler examination in detecting a patent foramen ovale, but only in cases of minimal right-to-left shunts, the clinical relevance of which remains to be established. The sensitivity of transthoracic echocardiography is heavily hampered by the frequency of inadequate heart visualization.

Aged↗
PubMed1993

Vascular distribution of paradoxical emboli by transcranial Doppler.

BACKGROUND AND PURPOSE: Paradoxical embolism through a patent foramen ovale is a contributory mechanism to stroke and may be diagnosed by contrast echocardiography. The intracranial distribution of these emboli has not been previously reported. METHODS: We used transcranial Doppler combined with agitated saline contrast injection to determine whether there was a preferential distribution of the contrast into the anterior or posterior intracranial circulation of patients with an acute stroke or transient ischemic attack. RESULTS: Forty-nine patients were studied--27 men and 22 women, with a mean age of 62.7 +/- 13.3 years (range, 29 to 85 years). Microcavitations were detected in the proximal right middle cerebral artery in 12 of 49 patients (24%). A patent foramen ovale was confirmed in all cases by simultaneous transesophageal echocardiography. Of the 12 patients, microcavitations were also detected in the proximal basilar artery in nine (75%). CONCLUSIONS: While paradoxical embolism appears to occur more frequently in the anterior circulation, the high rate of detection of microcavitations in the basilar artery suggests that paradoxical embolism to the posterior intracranial circulation may be more frequent than generally believed.

Adult↗
PubMed1993

Postischemic recovery process of renal oxygen consumption in normal and streptozotocin diabetic rats.

We tried to study in depth the recovery process in the cortical and the medullary oxygen (O2) consumption of normal and streptozotocin diabetic rat kidneys after ischemia. It was found that the cortical and the medullary O2 consumption decreased after ischemia, reaching their lowest levels at 1 day after every ischemic duration in normal and diabetic kidneys. In the period prior to ischemia to 1 day after ischemia, no significant difference was seen in the decrease in O2 consumption between the cortex and the medulla in normal kidney, whereas the medullary O2 consumption significantly decreased compared with the cortical O2 consumption in diabetic kidney. From 1 day to 4 weeks after ischemia, the increase in the cortical O2 consumption was significantly higher than that in the medulla of normal kidney. In contrast, the increase in the medullary O2 consumption was significantly higher than that in the cortex of diabetic kidney. Consequently, up to 4 weeks after ischemia, the decrease in the cortical O2 consumption was significantly lower than in the medulla of normal kidney, while there was no significant difference regarding the decrease in O2 consumption between the cortex and the medulla in diabetic kidney. These results suggest that there is a clear difference in the postischemic recovery process of O2 consumption between the cortex and the medulla, and also between normal and diabetic rat kidneys.

Animals↗
PubMed1993

Both beta-1 and beta-2 adrenoceptors are coupled to the cyclic AMP system in connecting tubules of rabbit nephron.

The connecting tubule (CNT), a segment interposed between distal convoluted tubules and collecting ducts, is a well defined segment in the rabbit nephron and have been shown to contain adenylate cyclase activity which is responsive to the beta agonist isoproterenol (ISO) and the nonselective beta blocker propranolol. We examined whether ISO also increased cAMP levels in the intact microdissected CNT in the presence of 1-methyl-3-isobutyl-xanthine and, in particular, which subtype of beta adrenoceptors was stimulated. ISO increased cAMP contents in a dose-dependent way (ED50 approximately equal to 10(-7) M) and the maximal stimulation was achieved at 1 microM ISO. Norepinephrine also elevated cAMP content in the CNT to the same extent as ISO. The increase in cAMP stimulated by ISO and norepinephrine was inhibited by 1 microM propranolol but not by 1 microM phenoxybenzamine. ISO-induced cAMP increased was blocked by the beta-1 antagonist metoprolol and also by the beta-2 antagonist ICI-118551 independently in a dose-dependent manner, and maximal inhibition was observed at 1 microM of both antagonists. These results indicate that both beta-1 and beta-2adrenoceptors appear to be located in the rabbit CNT and both can be positively coupled to adenylate cyclase to generate cAMP accumulation.

Adrenergic alpha-Antagonists↗
PubMed1993

Effects of theophylline, verapamil, and mannitol on oxygen consumption of ischemic rat kidneys.

This study was designed to determine, through the measurement of oxygen consumption (QO2), whether pretreatment and posttreatment with theophylline, verapamil, and mannitol provide protection from damage in the cortex and medulla of rat kidneys subjected to 60 and 120 minutes of ischemia. QO2 levels in both tissues were examined 1 day after each ischemia. After 60 minutes of ischemia, pretreatment with theophylline and verapamil primarily provided protection from ischemic change in cortical QO2. Pretreatment with mannitol provided protection from both cortical and medullary changes in QO2, but posttreatment with mannitol only protected cortical QO2. After 120 minutes of ischemia, only pretreatment with verapamil was effective in protecting cortical QO2 from ischemic injury. These observations demonstrate that theophylline, verapamil, and mannitol are effective in protecting renal QO2 in the ischemic kidney. During this study, it became clear that there were differences in the effectiveness of theophylline and verapamil on QO2 in the ischemic kidney between pretreatment and posttreatment, and also between the cortex and the medulla.

Animals↗