Biomedical subjects

A Kamiya

Publications and source records attributed to A Kamiya.

At least 91 records · Page 5Linked to original sources

PubMed1998

Amrinone, a selective phosphodiesterase III inhibitor, improves microcirculation and flap survival: a comparative study with prostaglandin E1.

BACKGROUND: Amrinone, a selective phosphodiesterase (PDE) III inhibitor, is a newly developed agent that possesses a combination of positive inotropic and vasodilating properties as a result of preventing the degradation of cAMP and it has recently been licensed for treatment of heart failure alone. Amrinone is expected to be useful for the treatment not only of heart failure but also of peripheral circulatory disorders, including vascular disease, and for ischemic flaps, because it improves microcirculatory hemodynamics. To investigate potential therapeutic applications of amrinone, we evaluated its ability to improve microcirculatory hemodynamics and flap survival. MATERIALS AND METHODS: The rat skinfold chamber technique was employed to quantify microcirculation directly in vivo. The improved survival area of random flaps in rats treated with amrinone was examined to assess therapeutic efficacy of this drug. Its effects were compared with those of prostaglandin E1 (PGE1), which has been widely approved as an agent for improving hemodynamics. RESULTS: Microcirculatory blood flow and flap survival area were significantly increased in both amrinone- and PGE1-treated animals, compared to the saline-treated controls. The ameliorating effects of amrinone were comparable to those of PGE1. CONCLUSIONS: The results of this study suggest amrinone to be a potentially useful drug not only for treating heart failure but also for improving microcirculation in patients with vascular diseases and for postoperative care after reconstructive surgery.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1998

In vivo measurement of morphometric and hemodynamic changes in the microcirculation during angiogenesis under chronic alpha1-adrenergic blocker treatment.

The effect of chronic administration of the alpha 1 blocker prazosin on microvascular angiogenesis was studied in rabbit ear chamber to investigate the role of concomitant increase in flow-oriented wall shear stress in vascular remodeling during angiogenesis. Rabbits were treated with prazosin hydrochloride (50 mg/liter in water) orally after ear chambers were installed. The microcirculation in the chamber was observed and recorded from 4 to 23 postoperative day (POD) by an intravital videomicroscope. The total vascular area (TA) were quantified as a morphometric parameter. Changes in wall shear stress in venules (20-40 micron ID) were calculated from flow velocity, vessel diameter, and in vivo blood viscosity. TA was significantly increased in the prazosin-treated animals. The levels of shear stress, which was increased 1.43 times by prazosin on 9 POD, gradually decreased toward the control level on 13 POD and they almost coincided on 21 POD. These findings experimentally provided supporting evidence that shear stress is probably involved in the adaptive response as one of mechanical factors regulating vascular remodeling during angiogenesis.

Adrenergic alpha-Antagonists↗

PubMed1998

Biological effects of static magnetic fields on the microcirculatory blood flow in vivo: a preliminary report.

There have been few studies of the effect of static magnetic fields on microcirculatory haemodynamics in vivo. The rat skinfold transparent chamber technique was used, which provides an excellent means of observing and quantifying direct in vivo microvascular haemodynamic responses to static magnetic fields up to 8 T. An intravital videomicroscope was used to measure the changes in blood flow before and after exposure to a magnetic field for 20 min in a horizontal type superconducting magnet with a bore 100 mm in diameter and 700 mm long. After exposure, microcirculatory blood flow showed an initial increase for about 5 min followed by a gradual decrease and a return to the control value. It is hypothesised that these changes represent rebound hyperaemia following reduced blood flow during exposure.

Animals↗

PubMed1998

Decreased brain intracellular pH measured by 31P-MRS in bipolar disorder: a confirmation in drug-free patients and correlation with white matter hyperintensity.

The authors have previously reported decreased intracellular pH (pHi) in the frontal lobes in euthymic bipolar patients treated with lithium using 31P-MRS. White matter hyperintensity (WMHI) is frequently seen in bipolar disorder. To examine a possible effect of lithium on pHi and the relationship between pHi and WMHI, seven drug-free euthymic bipolar patients were examined, and T2-weighted MRI were examined in 14 previously reported bipolar patients. Drug-free patients showed significantly lower pHi than controls. WMHI was associated with low pHi and increased phosphodiester peak. These results suggest that decrease of pHi is not an effect of lithium but is instead related to the pathophysiology of illness. Decrease of pHi and increase of the PDE peak may be the biochemical basis of WMHI in bipolar disorder.

Adult↗

PubMed1998

Angiomyolipoma of the liver: case report and collective review of cases diagnosed from fine needle aspiration biopsy specimens.

We experienced a rare case of primary angiomyolipoma (AML) of the liver, preoperatively diagnosed by fine needle aspiration biopsy (FNAB). Radiographic imaging revealed characteristic features of an angiomyolipoma. The diagnosis was confirmed by the presence of epithelioid smooth muscle cells, mature fat cells and blood vessels in the biopsy tissue. Our review of the literature showed this to be the eleventh case to be diagnosed in this way. Despite this preoperative diagnosis, the lesion was resected because of its pleomorphic histological features. Histologically, the epithelioid smooth muscle component included cells with a bizarre appearance and occasional hyperchromatic nuclei, and furthermore, occasional mitotic figures were observed. In own MEDLINE search of the literature we found 11 cases of AML of the liver for which the diagnoses were established by FNAB, and the same features were present in 5 cases for which surgical excision was contemplated.

Angiomyolipoma↗

PubMed1998

Malignant fibrous histiocytoma originating from the chest wall: report of a case and collective review of cases.

Malignant fibrous histiocytomas occur principally as a mass of the extremities, abdominal cavity, or retroperitoneum in adults. However, they only rarely occur in the chest wall. A rare case of primary malignant fibrous histiocytoma originating from the chest wall is herein presented. The 36 previously reported cases are also reviewed. Of the 32 patients who underwent a resection as the initial treatment, 10 (31.3%) had a local recurrence. Of the 37 patients with this disease, 9 (25.0%) had subsequent metastases. The majority of the deaths (36.1%) from this disease occurred within the first 12 months. The patients who undergo surgical and adjuvant therapy must therefore be monitored carefully by frequent examinations.

Aged↗

PubMed1998

Microbial contamination of 'sterile water' used in Japanese hospitals.

We examined the following samples of water from 10 hospitals for microbial contamination: water obtained using an ultra filtration system (UF water), a reverse osmosis system (RO water), a water distillation system (distilled water) and tap water. UF water and RO water are used for handwashing before surgery, and distilled water for the preparation of drugs. All 10 samples of tap water examined were contaminated with < 10 colony forming units (cfu)/mL. Thirteen (68%) of 19 samples of UF water, nine (53%) of 17 samples of RO water and 15 (79%) of 19 samples of distilled water were contaminated with 10(1)-10(4) cfu/mL. The majority of micro-organisms were non-fermentative bacteria such as Sphingomonas paucimobilis and CDC gr. IV C-2. Japanese hospitals commonly use UF water and RO water for preoperative handwashing under the assumption that it is sterile. Our results suggest, however, that these types of water are inferior microbiologically to tap water. Distilled water from the dispensary was also contaminated with micro-organisms. The available chlorine content of tap water was 0.17-0.42 ppm and that of UF water (from tap water) 0-0.06 ppm. There was no available chlorine in RO water or distilled water (each from tap water). The reduction or disappearance of available chlorine appears to be associated with microbial contamination of UF water, RO water and distilled water.

Chlorine↗

PubMed1998

Preparation of hydroxyapatite-granule-implanted superplastic titanium-alloy.

In order to obtain a biomaterial that has both biological affinity and high mechanical strength, hydroxyapatite (HAp) granules were implanted into the surface of superplastic titanium-alloy. HAp granules (32-38 microm diameter) were spread over a superplastic titanium-alloy substrate and pressed to implant the granules into the substrate. This was achieved at 17 MPa, 750 degrees C for 10 min. Only the tops of the granules, which were surrounded by the alloy, remained exposed and they were firmly stuck in the substrate. The granules were enclosed in titanium-alloy and a reaction layer was formed at their interface. The HAp-implanted titanium-alloy composites are expected to be useful as biomaterials, such as artificial bones and dental roots.

Journal Article↗

PubMed1998

Responses of muscle sympathetic nerve activity to lower body positive pressure.

To evaluate the response of vasomotor sympathetic nerve activity to lower body positive pressure (LBPP), muscle sympathetic nerve activity (MSNA) was microneurographically recorded from the tibial nerve in 10 healthy young men, along with hemodynamic variables and echocardiogram, during exposure to incremental LBPP at 10, 20, and 30 mmHg in the supine position. MSNA was suppressed to a similar extent (27%) at 10- and 20-mmHg LBPP. However, at 30-mmHg LBPP, MSNA tended to increase but was still nearly at the control value. Mean arterial pressure was elevated (11%), total peripheral resistance markedly increased (36%), and stroke volume and cardiac output tended to decrease at 30-mmHg LBPP. Heart rate remained unchanged throughout the procedures. Left atrial dimension significantly increased during 10- and 30-mmHg LBPP, indicating an increased cardiac filling. These results suggest that the inhibitory effect of the cardiopulmonary baroreflex on MSNA at 10- and 20-mmHg LBPP could be counteracted by the sympathoexcitatory effect of the intramuscular pressure-sensitive mechanoreflex at 30-mmHg LBPP. However, the increment of total peripheral resistance at 30-mmHg LBPP may not depend exclusively on this small enhancement of MSNA.

Adult↗

PubMed1998

Head-up suspension in humans: effects on sympathetic vasomotor activity and cardiovascular responses.

We hypothesized that muscle sympathetic nerve activity (MSNA) and cardiovascular responses to the conventional head-up tilt (HUT) are different from those to head-up suspension (HUS) because of antigravity muscle activity. The MSNA from the tibial nerve, heart rate, blood pressure, stroke volume, cardiac output, and calf blood flow were measured in 13 healthy young subjects. Left atrial diameter was measured by two-dimensional echocardiography in another nine subjects. The resting MSNA and cardiovascular responses at a low level (20 degrees) of orthostasis were similar during both modes. At higher levels (40 and 60 degrees), the responses of MSNA, heart rate, stroke volume, and cardiac output were significantly stronger and there was a smaller reduction in calf blood flow during HUT than during HUS (P < 0.05). Left atrial diameter was decreased significantly from the resting values during HUT and HUS without any significant difference between the modes of orthostasis. The results provide evidence that the engagement of antigravity muscles during HUT may have additive effects on sympathetic vasoconstrictor and cardiovascular responses to orthostatic stress.

Adult↗

PubMed1998

A quicker preparation method for autologous fibrin glue.

To establish a quicker preparation procedure for cryoprecipitate (Cryo) from a patient's autologous plasma, to be used as fibrin glue, we examined the effects of various conditions on the concentrations and yields of coagulation factors in Cryo. Human plasma from healthy volunteers was divided and treated under various freezing, shaking and defrosting conditions. The concentrations of fibrinogen, plasminogen, fibronectin, and factor XIII in Cryo were then measured. Results were as follows: (1) concentrations and yields of plasma components in Cryo obtained from plasma stored at -20 degrees C were significantly higher than those in Cryo from plasma stored at -80 degrees C; (2) shaking at 70 cycles/min during the freezing process had a favorable effect on the concentrations and yields of coagulation factors in the Cryo; (3) a shaking thaw process in a cold water bath was a rapid method for obtaining adequate yields of coagulation factors; (4) shaking in the defrosting process did not affect the yields of coagulation factors. These results indicated that Cryo containing high concentrations of coagulation factors could be prepared easily and rapidly from a patient's autologous plasma (within 4-5 h).

Blood Coagulation Factors↗

PubMed1998

Urinary metabolites of valproic acid in epileptic patients.

The urinary excretion of valproic acid (VPA) and its metabolites (3-keto VPA, 3-OH VPA, and VPA-glucuronide) in 6 epileptic patients was studied using gas chromatography-mass spectrometry. The amount of VPA and 3-OH VPA excreted in the urine was low (0.1-0.5% of the dose of VPA and 0.6-1.5% of the dose of 3-OH administered). The amount of 3-keto VPA and glucuronide (VPA-Glu) excreted was marked (5.8-26.2% and 13.1-88.7% of the dose of VPA administered, respectively). The urinary excretion of VPA and its metabolites by patients who have taken a normal amount of a VPA preparation was almost the same as that of healthy volunteers. Two epileptic patients who took a large amount of the VPA preparation showed a high excretion of VPA-Glu without an increase in their plasma VPA-Glu.

Adolescent↗

PubMed1998

Macrostatin, a novel macromolecular inhibitor of topoisomerases produced by Streptomyces avermitilis no. C-127.

A novel inhibitor of topoisomerases designated as Macrostatin has been isolated from the culture filtrate of Streptomyces avermitilis strain No. C-127 and purified by successive chromatography on Dowex, activated charcoal, gel filtration and cellulose. It is an acidic macromolecule having 45 kD molecular weight as determined by gel filtration. Macrostatin inhibited topoisomerase I and II in a noncompetitive manner with Ki = 3.7 and 1.3 nM respectively. Macrostatin differed from well-known inhibitors of topoisomerase such as camptothecin, etoposide and doxorubicin which induce topoisomerase-mediated DNA cleavage by stabilizing the cleavable complex or intercalation into DNA strands. Macrostatin had neither ability to stabilize the cleavable complex nor ability to intercalate into DNA strands. It was suggested that Macrostatin inhibits topoisomerase by a direct action on the enzyme.

Binding, Competitive↗

PubMed1998

Sympathetic nerve responses in humans to short and long term simulation of microgravity.

The present paper aimed to review findings obtained by our researches to elucidate sympathetic nerve mechanisms of cardiovascular deconditioning in humans exposed to short and long term simulation of microgravity. Sympathetic nerve activity in humans has been so far investigated using indirect methods by analyzing the activities of effector organs, such as heart rate, blood flow, blood pressure, sweating etc. or by measuring the plasma nor-adrenaline level. Now we have a technique called microneurography which has enabled us to measure directly the sympathetic nerve activity form human peripheral nerves. The microneurography technique was used for the first time before, during and after the Space Shuttle "Neurolab" mission launched in April 1998 to elucidate how sympathetic nerve activity in astronauts is modified by exposure to microgravity in space. In this paper, we would like to present our recent findings concerning sympathetic nerve responses to short and long term microgravity simulated by different methods.

Bed Rest↗

PubMed1998

Changes in muscle sympathetic nerve activity and effect of breathing maneuvers during microgravity induced by parabolic flight in humans.

UNLABELLED: This study aimed to clarify how muscle sympathetic nerve activity (MSNA) in humans, which plays an important role in blood pressure control against gravity, is altered under microgravity (microG) conditions, and how the MSNA change is modified by breathing maneuvers. Ten subjects seated themselves in a jet aircraft with their knees extended. MSNA was recorded microneurographically from the left tibial nerve with simultaneous monitoring of ECG, blood pressure, respiration, and intrathoracic blood volume estimated by the impedance method during parabolic flight in a jet aircraft. In half of the parabolas, their respiration was controlled at 0.25 Hz by a metronome. RESULTS: MSNA was enhanced under hypergravity just before microG entry, and immediately suppressed by microG induced by parabolic flight. The suppression was more marked with controlled than with uncontrolled respiration (51.6 +/- 7.2 vs 82.8 +/- 2.5%, mean +/- SE, 1G=100%). MSNA changes during microG correlated significantly to changes in blood pressure and intrathoracic blood volume. The blood pressure fall 10 to 15 sec after microG entry was less prominent with controlled than with uncontrolled respiration. We conclude that changes in arterial blood pressure and intrathoracic blood volume modulate MSNA during microG induced by parabolic flight, depending largely on breathing maneuvers.

Adult↗

PubMed1998

Muscle sympathetic nerve activity and plasma norepinephrine during 6 degrees head-down bed rest.

Alterations in autonomic function are evident during spaceflight. These conditions are also simulated by ground-based experimental models of a microgravity environment such as 6 degrees head-down bed rest (BR). They include a reduction in baroreflex function, a decrease in vagal tone and a loss of circulatory blood volume during weightlessness. However, it is not clear whether vasomotor sympathetic outflow, which controls peripheral vascular tone neurally, and plasma norepinephrine concentration will change or not during weightlessness. The purpose of the present study is to examine changes in vasomotor sympathetic nerve activity during six days of 6 degrees head-down BR. Vasomotor sympathetic nervous activity was evaluated by the direct recording of muscle sympathetic nerve activity (MSNA) by a use of microneurographic technique. MSNA on the sixth day during BR was the same as that in a horizontally supine position before BR (before BR; 15.4 +/- 1.6 bursts/min, during BR; 16.7 +/- 3.5 bursts/min), though plasma norepinephrine concentrations during BR were reduced by 25% compared with those before BR (before BR; 263 +/- 33 pg/ml, during BR; 193 +/- 79 pg/ml, p < 0.05). This dissociation cannot be determined precisely, but it suggests the possibility of peripheral changes in terminal sympathetic nerve endings, etc.

Adult↗

PubMed1998

Effects of lower body positive pressure on muscle sympathetic nerve activity.

To elucidate the role of vasomotor sympathetic nerve activity response to lower-body positive pressure (LBPP), muscle sympathetic nerve activity (MSNA) along with blood pressure, electrocardiogram, transthoracic impedance and echocardiogram were recorded in ten healthy young men at 10, 20 and 30 mmHg LBPP in the supine position. We found that MSNA was suppressed (27%) at both 10 and 20 mmHg LBPP but tended to increase at 30 mmHg LBPP. Mean arterial pressure (11%) and total peripheral resistance (36%) increased despite a tendency toward decreased stroke volume and cardiac output at 30 mmHg LBPP. Heart rate remained unchanged. The left atrial dimension significantly increased during 10-30 mmHg LBPP, indicating an increase in cardiac filling. These results suggest that LBPP at levels less than 20 mmHg suppressed MSNA by the translocation of blood from the lower body to the thorax, thus stimulating the cardiopulmonary baroreceptors which in turn inhibited vasomotor sympathetic nerve activity. However, LBPP at 30 mmHg tended to enhance MSNA through the activation of intramuscular (pressure-sensitive) receptors which could counteract the inhibitory effect of cardiopulmonary baroreflexes on MSNA.

Adult↗

PubMed1997

Raf/MAPK and rapamycin-sensitive pathways mediate the anti-apoptotic function of p21Ras in IL-3-dependent hematopoietic cells.

The Ras signal transduction pathway is activated by a number of hematopoietic cytokines and is implicated in the prevention of apoptotic death in hematopoietic cells. Recent studies have provided evidence that the downstream of Ras is highly divergent and several independent pathways appear to mediate distinct biological functions of Ras. In the present study, we investigated the downstream pathway(s) of Ras responsible for the maintenance of hematopoietic cell survival by using various mutants of signaling molecules. Activation of the Raf/MAPK pathway in interleukin (IL) 3-dependent cells by expression of an oncogenic Raf or a Ras mutant (G12V/T35S) prevented apoptosis following IL-3 deprivation. In contrast, another Ras mutant (G12V/V45E), which is apparently incapable of activating MAPK, efficiently blocked apoptosis as well. It is therefore likely that the activation of the Raf/MAPK pathway is not an absolute requirement for the prevention of apoptosis, and there appears to be a Raf/MAPK-independent pathway that contributes to hematopoietic cell survival. Since Ras(G12V/V45E) was able to cause the phosphorylation of p70/S6 kinase, we inhibited the S6 kinase pathway by rapamycin and by wortmannin, and found that the anti-apoptotic function of Ras(G12V/V45E), but not of Ras(G12V), was critically influenced by both inhibitors. These results indicate that the Raf/MAPK and a rapamycin/wortmannin-sensitive pathways mediate Ras function to prevent apoptotic death in hematopoietic cells.

Androstadienes↗