Biomedical subjects

K Hongo

Publications and source records attributed to K Hongo.

At least 91 records · Page 5Linked to original sources

PubMed1993

Mechanism of the effects of acetylcholine on the contractile properties and Ca2+ transients in ferret ventricular muscles.

1. We investigated the mechanism of signal transduction during the effect of muscarinic receptor stimulation on Ca2+ transients, tension, Ca2+ sensitivity and the cross-bridge cycling rate (CCR). 2. Membrane-permeable derivatives of cyclic GMP (8-bromo-cyclic GMP and dibutyryl cyclic GMP) did not cause any significant changes in the peaks of Ca2+ transients and tension and the time courses of either signal modulated by isoprenaline (Iso) (0.1 microM). 3. Nitroprusside (0.1-1 mM) likewise did not change the peaks or the time courses of Ca2+ transients and tension in the Iso-treated preparations. 4. In papillary muscles excised from ferrets treated with pertussis toxin (islet-activating protein, IAP), which is known to abolish the function of GTP-binding proteins (Gi, Go and Gt), similar changes in Ca2+ transients and tension produced by treatment with Iso (0.1 microM) were noted as in non-IAP-treated preparations. However, no effects of acetylcholine (ACh; 1 microM) on either signal were observed. 5. The relation between [Ca2+]i and tension measured during the steady state of tetanic contraction was shifted to the right by Iso (0.1 microM), and cyclic GMP derivatives (1 mM) did not change the altered relation. In the IAP-treated preparations, ACh (1 microM) did not influence the relation altered by Iso (0.1 microM). 6. Cyclic GMP derivatives (1 mM) did not alter the Iso (0.1 microM)-increased CCR measured by perturbation analysis. ACh (1 microM) did not restore the Iso-increased CCR in the IAP-treated preparations. 7. These results suggest that signal transduction in muscarinic receptor stimulation is primarily mediated by inhibition of adenylate cyclase via IAP-sensitive GTP-binding proteins, and that cyclic GMP does not play an important role in the effect of muscarinic receptor stimulation on Ca2+ transients, tension, Ca2+ sensitivity or CCR.

Acetylcholine↗

PubMed1993

Alterations in intracellular calcium and tension of activated ferret papillary muscle in response to step length changes.

1. To study the effects of mechanical constraints on the calcium (Ca2+) affinity of cardiac troponin C, we analysed the tension and aequorin light (AL, intracellular Ca2+) transients in response to a step length change in aequorin-injected ferret right ventricular papillary muscles. The muscle preparations were continuously activated with ouabain (10(-4) M) (ouabain contracture) or with high frequency stimuli in the presence of ryanodine (5 microM) (tetanic contraction). 2. The tension transient in response to either the release or stretch was oscillatory: tension decreased rapidly during the release and then increased, after which it lapsed into a new steady level in a series of damped oscillations. The opposite was true for the stretch. The oscillatory responses were conspicuous and less damped in ouabain-activated preparations (oscillation frequency of 2.2-2.3 Hz at 22 degrees and 4.5-4.6 Hz at 30 degrees C) and much more damped in ryanodine-treated preparations. 3. The transient AL response was also oscillatory, the time course of which corresponded to that of the transient tension response. Regardless of the difference in the time course of the transients in two different preparations and at two different temperatures, the increase in AL corresponded to the decrease in tension, likewise the decrease in AL to the increase in tension. 4. The mean level of AL after release was lower than the control level present just prior to the release in ouabain-activated preparations, but the AL after release finally returned to the nearly control level in ryanodine-treated preparations. 5. When the ryanodine-treated muscle was further treated with 2,3-butanedione monoxime (BDM) (20 mM), the tetanic tension decreased remarkably without affecting the AL signal. The tension transient of this preparation was quite similar to that of the resting muscle, which changed in a nearly stepwise fashion; AL was hardly affected by step length changes, as in the resting muscle, in spite of the higher AL level. 6. These results suggest that the Ca2+ affinity of cardiac troponin C is increased with an increase in tension (i.e. the cross-bridge attachment) and decreased with a decrease in tension i.e. the cross-bridge detachment), and that the mean [Ca2+]i is lowered by release, at least in a Ca(2+)-overloaded condition, mainly through the sarcoplasmic reticulum.

Aequorin↗

PubMed1993

Functional image of dynamic computed tomography in diagnostic and prognostic evaluation of ischemic stroke within the first 6 hours.

BACKGROUND AND PURPOSE: It is important to make a diagnosis before a low-density area appears on computed tomography for appropriate management of acute ischemic stroke. We report the diagnostic and prognostic usefulness of functional image of dynamic computed tomography for acute ischemic stroke. METHODS: Forty-seven patients with ischemic strokes within 6 hours of ictus underwent dynamic computed tomography in which functional images were obtained. These findings were compared with angiographic findings, follow-up computed tomography, and clinical outcome. RESULTS: The functional images were categorized into three groups: (1) cortical type: abnormalities on time to peak image and/or corrected mean transit time image involving mainly cortical structures (29 cases); (2) noncortical type: abnormalities on either or both images limited to noncortical structures (7 cases); and (3) normal type: no abnormalities on both images (11 cases). Cortical type as a diagnostic test for arterial trunk occlusion had a good sensitivity (100%), specificity (95%), and accuracy (98%). Infarction volume on follow-up computed tomography correlated with extension of prolonged time-to-peak area (r = .80, P < .01) and that of prolonged corrected mean transit time area (r = .81, P < .01). Cortical type was associated with significantly unfavorable outcome (P < .01). CONCLUSIONS: Functional image of dynamic computed tomography findings predicted arterial trunk occlusion, infarction volume, and clinical outcome. Therefore, this technique would be useful not only for indicating definitive angiography and subsequent therapy but for evaluating the effectiveness of surgical or medical recanalization.

Acute Disease↗

PubMed1993

Intraoperative protection of cranial nerves and arteries by split silicone tube.

The authors describe the usefulness of split silicone tubing to protect the cranial nerves and arteries during microneurosurgery. The inner diameter of the tube varied from 1.0 to 3.3 mm with a thickness of 0.125 mm. Application of the tube protects the nerves and arteries from mechanical trauma, electrical injury, and dryness.

Adult↗

PubMed1993

Subarachnoid hemorrhage presenting an "abnormal movement"--case report.

A 61-year-old male presented with subarachnoid hemorrhage manifesting an abnormal movement as the initial symptom. The movement was rhythmic with phases: tongue protrusion with eyes wide open, and tongue retraction with eyes closed, lasting for about 10 minutes. Neuroradiological methods identified a small aneurysm as the origin of the hemorrhage. The movement never after recurred clipping the aneurysm and clot drainage. Transient increase in the intracranial pressure was thought to be the cause.

Facial Muscles↗

PubMed1993

Vertebral artery section for treating arterial compression of the medulla oblongata. Case report.

A case of a 30-year-old man who showed progressive pyramidal tract signs caused by compression of the left vertebral artery is presented. Initial decompression of the vertebral artery by placing a piece of sponge between the artery and medulla had no long-term effect. The left vertebral artery distal to the origin of the posterior inferior cerebellar artery was then sectioned, decompressing the medulla oblongata. The patient's symptoms improved postoperatively. This is the first reported case of brain-stem compression by an elongated vertebral artery treated by sectioning of the artery.

Adult↗

PubMed1992

Cerebrovascular effects of substance P after experimental subarachnoid haemorrhage.

The vasoactive effects of substance P (SP), as well as the content of cyclic guanine monophosphate (cGMP), were determined in the rabbit basilar artery after subarachnoid haemorrhage (SAH). Out of 47 rabbits, 24 were subjected to a SAH, induced by injecting 5 ml of autologous arterial blood into the cisterna magna; 23 were used as controls. In 20 animals (10 SAH and 10 controls), isometric tension recording of isolated rings of the basilar artery--dissected 2 days after SAH--was employed to assess the dose-dependent vasodilatation to SP (10(-10) to 10(-6) M) after precontraction with serotonin (10(-8) to 10(-5) M). In 15 animals (8 SAH and 7 controls), the basal cGMP content was measured in the basilar artery 2 days after SAH. In the other 12 animals (6 SAH and 6 controls), the increase in cGMP content was measured in the basilar artery after a 10-minute incubation with SP (10(-6) M). SP caused significantly less dilatation in animals subjected to SAH than in controls, especially for concentrations between 10(-9) and 10(-6) M (p < 0.001). The cGMP content in the arteries 2 days after SAH was significantly lower than in control arteries (31.5 +/- 7.3 against 57.3 +/- 4.3 pmoles/g tissue). In the preparations incubated with SP, the increase of cGMP was 440 +/- 115% in the control arteries, and only 97 +/- 30% in the arteries after SAH. It is concluded that the vasodilator activity of SP is significantly impaired after SAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

[Seizure-inducing factors in the patients with childhood epilepsy].

We evaluated the seizure-inducing factors in 264 patients with childhood epilepsy. One hundred and thirty-six patients (51.5%) exhibited some kind of inducing factors. Non-specific inducing factors were commonly recognized, such as "febrile state" (29.2%), "fatigue after exercise" (15.2%), "sleep disturbance" (9.1%), "psychic stress" (8.3%) and "emotional change" (6.8%). Specific inducing factors, which related to reflex epilepsy, was recognized in only 7 patients. "Febrile state" was dominant in young children, but the other nonspecific inducing factors were dominant in adolescent. Incidences and kinds of inducing factors also related to the epileptic syndromes an seizure prognosis. The patients with symptomatic partial epilepsies (64.3%) and grand mal on awakening (85.7%) had significantly more inducing factors, and the patients with refractory seizures had a higher incidence and more variable kinds of inducing factors than the patients with well-controlled seizures. These results suggest that seizure-inducing factors are recognized in children as well as in adults, and the clarification of inducing factors is important to the management of epilepsy, particularly of intractable epilepsy.

Adolescent↗

PubMed1991

Fatal meningitis due to Staphylococcus cohnii. Case report.

We report a case of fatal meningitis due to Staphylococcus (S.) Cohnii in a 63-year-old male. S. Cohnii is often isolated from farm animals and known to be less pathogenic in humans. To our knowledge, S. Cohnii has not yet been reported to cause infection of the central nervous system in humans.

Humans↗

PubMed1991

A study of the effectiveness of the iron-chelating agent deferoxamine as vasospasm prophylaxis in a rabbit model of subarachnoid hemorrhage.

The pathogenesis of cerebral vasospasm occurring after subarachnoid hemorrhage (SAH) is unknown. Several lines of experimentation have suggested a free radical mechanism in the etiology of vasospasm. Iron is an important catalyst in the generation of free radicals and lipid peroxides in response to tissue injury. We hypothesize that the elaboration of iron from the subarachnoid clot might result in enhanced generation of free radicals and lipid peroxidation. If so, then treatment with deferoxamine, an iron-chelating compound, might reduce the formation of free radicals and thereby ameliorate vasospasm. This hypothesis was examined in a rabbit model of experimental cerebral vasospasm. New Zealand White rabbits were divided into the following experimental groups: control (normal) animals (n = 7), control animals treated with deferoxamine (n = 3), animals subjected to SAH and killed on Day 2 (n = 7), animals subjected to SAH on Day 2 and treated with deferoxamine (n = 9), animals subjected to SAH killed on Day 3 (n = 7), and animals subjected to SAH on Day 3 and treated with deferoxamine (n = 7). Deferoxamine treatment (50 mg/kg/8 hours) was begun 16 hours before the induction of SAH and continued until the animals were killed by perfusion fixation. The basilar artery caliber was assessed using morphometric techniques. The diameter of the basilar arteries in the control animals was 0.64 +/- 0.02 mm. Deferoxamine treatment alone did not alter the artery diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Mechanism of enlargement of major cerebral collateral arteries in rabbits.

Major cerebral collateral arteries enlarge following bilateral ligation of the common and internal carotid arteries. The purpose of this investigation was to determine the relative contribution of cellular hypertrophy versus cellular hyperplasia to this vessel change in a morphometric analysis as well as the functional properties of remodeled vessels in an in vitro study. We assessed cell number and vessel dimensions by morphometric analysis of 16 perfusion-fixed rabbit basilar arteries. Results demonstrated significant increases in luminal diameter from 761 to 946 microns (p less than 0.01), medial cross-sectional area from 5.1 x 10(4) to 7.6 x 10(4) micron2 (p less than 0.005), smooth muscle cell volume from 9.19 x 10(5) to 1.44 x 10(6) micron3 (p less than 0.0005), and overall arterial length from 17.41 to 20.36 mm (p less than 0.005) in basilar arteries from the eight ligated rabbits compared with the eight sham-operated controls. Smooth muscle cell volume fraction and cell numerical density were unchanged whereas the number of cells per unit length of artery was increased significantly from 21.5 to 31.0 cells/micron (p less than 0.05). These data indicate that smooth muscle cell hyperplasia rather than hypertrophy contributes to increases in vessel mass. Functional properties of the basilar arteries from 10 ligated and 10 normal control rabbits were analyzed in vitro. Results showed increased contraction to potassium chloride (approximately 74%) (p less than 0.01) and increased sensitivity of smooth muscle to acetylcholine (p less than 0.05) while maximal relaxation was the same as control in the ligated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1991

[Regional cerebral blood flow in moyamoya disease using 123-I IMP-SPECT--follow up study before and after therapy].

The recent development of a new radiopharmaceutical 123 I-isopropyl-p-iodoamphetamine (IMP), which is taken up by the brain from the blood flow, has offered a possibility of constructing scintigraphy maps of regional cerebral blood flow (rCBF) using single photon emission CT. We evaluated the clinical utility of this method in moyamoya disease. Five patients with moyamoya disease, who were examined by IMP-SPECT before and after bypass operations, were selected. On the IMP images before operations, all patients showed focal or global decrease of rCBF. There was a good correlation between the area and degree of rCBF abnormalities and severity of clinical symptoms and stage on angiography. The area of rCBF decrease coincided with the dominant area of rebuild-up phenomena on EEG. On the IMP images just after operations, the rCBF changed for the worse transiently in three patients, and the crossed cerebellar diaschisis appeared in two patients. On the IMP images 3 months after operations, the rCBF increased in company with the improvement of clinical symptoms. The increased rCBF on the point of operation was recognized in two patients with good prognosis. These results suggest that IMP-SPECT is a noninvasive and useful method of assessing the effects of therapy as well as the characteristic hemodynamic abnormalities in moyamoya disease.

Amphetamines↗

PubMed1990

Pharmacological reversibility of experimental cerebral vasospasm.

Using a morphometric technique, the pharmacological reversibility of luminal narrowing after experimental subarachnoid hemorrhage (SAH) was investigated. For vasodilation, a "cocktail" consisting of 10(-4) M papaverine, 2 x 10(-4) M sodium nitroprusside, and 10(-5) M adenosine was administered intra-arterially. Forty-two rabbits were divided into six groups: control (normal animals); control plus cocktail (normal animals perfused with the cocktail before fixation); SAH (animals sacrificed 48 hours subsequent to intracisternal injection of 1.5 ml/kg of arterial blood); SAH plus cocktail (SAH plus perfusion with the cocktail); BaCl2 (animals sacrificed 10 minutes after intracisternal injection of 2 ml of 3 x 10(-3) M BaCl2); and BaCl2 plus cocktail (BaCl2 animals perfused with the cocktail). The diameter of the basilar arteries in the control and the control plus cocktail groups was not significantly different. BaCl2 reduced the diameter 44% and SAH reduced the diameter 27%. There were no significant differences between the diameter of the BaCl2 plus cocktail group and SAH plus cocktail group when compared with the control or the control plus cocktail group. Morphological examination by light and transmission electron microscopy showed luminal narrowing and corrugation of the elastic lamina with few degenerative or proliferative changes of the vessel wall in animals with SAH. These results suggest that cerebral vasospasm is caused initially by smooth muscle contraction rather than by proliferative vasculopathy and that it is not an irreversible process.

Adenosine↗

PubMed1990

Modulation of Ca2+ transients and contractile properties by beta-adrenoceptor stimulation in ferret ventricular muscles.

1. The mechanism of modulation of Ca2+ transients and contraction by beta-adrenoceptor stimulation was studied in ferret ventricular muscles using aequorin to measure intracellular Ca2+. 2. Peaks of tension and light transients were increased by isoprenaline (10(-9) - 5 x 10(-7) M) which also abbreviated their time courses. 3. Time-to-peak tension was significantly shortened by 5 x 10(-9) M-isoprenaline and time-to-peak light was abbreviated by 10(-9) M-isoprenaline. 4. The time for the light to decay was shortened at 10(-9) M-isoprenaline. However, a higher concentration of isoprenaline (10(-8) M) was required for significant shortening of the half-relaxation time (TR50). 5. When isoprenaline was removed and beta-blocker (bupranolol, 1 microM) was applied, the time course of the light transients recovered but the time course of relaxation did not recover. 6. The relationship between [Ca2+]i and tension in tetanic contraction produced in the presence of ryanodine (5 microM) was shifted to the right by isoprenaline (10(-8) M). This was recovered by the replacement of isoprenaline with bupranolol (1 microM). 7. Isoprenaline (10(-7) M) added to the solution containing 20 mM [Ca2+]O and Bay K 8644 (1 microM), which produced maximal tension, caused a large light signal and enhancement of the initial phasic tension in tetanic contraction. However, the replacement of isoprenaline with bupranolol after immersing the preparation in 20 mM [Ca2+]O solution with Bay K 8644 and isoprenaline, did not significantly change the tension level, although the light signal decreased. Similar results were obtained in the ventricular muscle of young rats. 8. These results suggest that the dose dependence of modulation of the contractile element and sarcoplasmic reticulum (SR) by beta-adrenoceptor stimulation differs, and that additional factors, other than the faster Ca2+ uptake by SR and the decrease in Ca2+ sensitivity of the contractile element, might be involved in the shortening of the half-relaxation time by beta-adrenoceptor stimulation. In addition, beta-adrenoceptor stimulation does not produce a marked change in the maximal tension level.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1990

Pharmacological activities of synthetic human cholecystokinin-33 of which tyrosine was sulfated by arylsulfotransferase.

The pharmacological activities of synthetic human CCK-33, in which a tyrosine molecule was sulfated by arylsulfotransferase, were investigated in the rat and the guinea-pig. The activities were compared with those of non-sulfated CCK-33 (CCK-33NS), CCK-8 and CCK-4. CCK-33 was about 100 fold more potent than non-sulfated CCK-33(CCK-33NS) but was about 20 fold less potent than CCK-8 in the contraction of the isolated gallbladder of the guinea-pig. In rat pancreatic secretion, intravenous CCK-33 and CCK-8 showed almost the same activity. The potency of each was about 1000 fold more than the individual potency of CCK-33NS, non-sulfated CCK-8 (CCK-8NS) and CCK4. There were no significant differences in gastric acid stimulatory activities among CCK-33, CCK-8, CCK-4, but the activities of CCK-33NS and CCK-8NS were less than those of CCK-33 and CCK-8, respectively. CCK-33 and CCK-8 produced a reduction in the intake of powder chow in doses of 10(-8) and 3 x 10(-8) mol/kg i.p., but CCK-33NS, CCK-8NS and CCK-4 did not. In conclusion, the activities of synthetic human CCK-33 are almost the same as those of CCK-8 on exocrine pancreatic secretion, gastric acid secretion and food intake, but less than CCK-8 on isolated gallbladder contraction.

Animals↗

PubMed1990

Pharmacological activity of angiotensin-II modified by tyrosine sulfation.

An angiotensin-II analogue with a sulfated tyrosine residue was prepared by arylsulfotransferase treatment of synthetic human angiotensin-II. Its biological activities were studied in isolated smooth muscles, and its effect on blood pressure was determined. The sulfated angiotensin-II (AII-S) was about 15-30 fold less potent than angiotensin-II (AII) for ileum contraction and gallbladder contraction. The hypertensive potency of AII-S was about 30-fold less than that of AII.

Angiotensin II↗

PubMed1990

Vasoactive intestinal polypeptide (VIP) stimulates fibrinolytic system in the rat.

We have studied the fibrinolytic effect of VIP in rats. Intravenous injection of VIP enhanced blood fibrinolytic activity in a dose-related manner. The euglobulin fraction obtained from intact rat plasma incubated with VIP did not produce an increase in fibrinolytic activity, while dextran sulfate (DS) and urokinase (UK) showed the activity. VIP solution placed on a plasminogen-rich fibrin plate did not show fibrinolysis. VIP had neither a plasminogen activator nor plasmin activity. VIP may release plasminogen activators into the blood.

Animals↗

PubMed1990

Effects of length change on intracellular Ca2+ transients in ferret ventricular muscle treated with 2,3-butanedione monoxime (BDM).

Quick release of the right ventricular papillary muscle of ferrets, injected with aequorin, from Lmax (initial length) to 92% Lmax during twitch response produced an extra-light signal of aequorin. 2,3-Butanedione monoxime (BDM) at 10 mM decreased the peak tension to less than 10% of that in control and the light signal to 70%. In the BDM-treated muscle, the extra-light in response to the quick release did not occur. A quick stretch from Lmax to 103% Lmax, in the presence and absence of BDM, did not cause any changes in the light signal. The results indicate that the extra-light signal in the quick release is tension dependent. The tension reduction by the quick release decreases the affinity of troponin-C (Tn-C) for Ca2+ without affecting Ca2+ handling system in intact cardiac muscle.

Aequorin↗