Search PubMed⌕ Search

Biomedical subjects

K Nakazawa

Publications and source records attributed to K Nakazawa.

At least 19 recordsLinked to original sources
PubMed2003

Effects of subthalamic nucleus stimulation on the micturation reflex in cats.

High frequency stimulation (HFS) of the subthalamic nucleus (STN) has been performed to reverse motor dysfunction in severe parkinsonian patients. Recent studies suggested that neural circuitry in the basal ganglia might regulate micturition function as well. In 15 adult male cats under ketamine anesthesia, in which spontaneous isovolumetric micturition reflex had been generated, we performed electrical stimulation and extracellular single unit recording in the STN. Electrical stimulation applied in the STN elicited inhibition of the micturition reflex. None of the responses was facilitatory. Effective amplitude of the electrical stimulation for evoking inhibitory responses was less than 50 microA, which gradually increased and exceeded 250 microA as the location of the stimulation exceeded an area of the STN. Effective frequency of the electrical stimulation with given stimulus intensity was 50 Hz and higher. Total 10 neurons were recorded in the STN that were related to urinary storage/micturition cycles. All neurons were tonically active throughout storage/micturition cycles with storage phase predominance, with almost constant firing activities during the storage phase. In conclusion, our results showed that HFS-STN inhibited the micturition reflex and there were micturition-related neuronal firings in the STN in cats, suggesting the STN may be involved in neural control of micturition. The results also provide an implication that clinical HFS-STN may alter urinary function in parkinsonian patients.

Animals↗
PubMed2003

Energy expenditure during walking with weight-bearing control (WBC) orthosis in thoracic level of paraplegic patients.

STUDY DESIGN: Comparative study of the effectiveness of walking exercise with a newly developed gait orthosis, the weight-bearing control (WBC) orthosis, for thoracic level of paraplegic patients. OBJECTIVES: To test its feasibility as a rehabilitation alternative for paraplegic patients, the energy consumption and cost during walking with WBC were calculated and compared with the values of conventional orthoses given in previous reports. SETTING: National Rehabilitation Center for the Disabled, Japan. METHODS: Four paraplegic patients with traumatic spinal cord injuries ranging from T8 to T12 participated. Experiments were conducted after 3 months of the orthotic gait training with WBC. The cardiorespiratory parameters were continuously measured at rest and during walking with a telemetric device. The steady-state value of the oxygen uptake (V(O2)), heart rate (HR), the energy consumption (J/kg/s) and energy cost (J/kg/m) were calculated. RESULTS: The average walking speed was 19.0 +/- 2.58 m/min. The steady-state value of the V(O2) and HR were 16.08 +/- 1.93 ml/kg and 147.3 +/- 10.94 b/min, respectively. The energy cost during orthotic walking tended to be better than the values of conventional orthoses, whereas the energy consumption was almost similar. CONCLUSION: WBC enables thoracic level of paraplegic patients to walk at relatively higher speed than conventional orthoses under similar energy expenditure. The special devices equipped with WBC are therefore considered to lead to improvement of the energy cost of walking. The physical intensity presumed by cardiorespiratory responses during walking with WBC is suited to promote their aerobic capacity. Therefore, it is concluded that the WBC orthosis could be an effective alternative in rehabilitation for thoracic level of paraplegic patients.

Adult↗
PubMed2003

Successful en-bloc resection of large superficial tumors in the stomach and colon using sodium hyaluronate and small-caliber-tip transparent hood.

En-bloc resection is desirable for accurate histopathological assessment of tissue specimens obtained using endoscopic mucosal resection (EMR). A new EMR method using sodium hyaluronate and a small-caliber-tip transparent hood has been developed. This is a peeling-off method using a needle-knife for mucosal and submucosal incisions. Long-lasting submucosal thickening resulting from an injection of sodium hyaluronate, and good visualization of the submucosal tissue with the aid of a small-caliber-tip transparent hood, make the cutting procedures easy and safe. A large superficial gastric cancer and a large villous tumor of the sigmoid colon were endoscopically resected using this method. En-bloc endoscopic resection was successful in both patients. The gastric lesion was an well-differentiated intramucosal adenocarcinoma, completely resected in a specimen measuring 97 x 50 mm. The colonic lesion was an intramucosal well-differentiated adenocarcinoma in adenoma, completely resected in a specimen measuring 70 x 55 mm in diameter. No significant complications were noted in either patient. The new method of EMR using sodium hyaluronate and the small-caliber-tip transparent hood is a promising method for endoscopic en-bloc resection of large superficial neoplastic lesions, both in the stomach and the colon.

Adenocarcinoma↗
PubMed2003

The clinical features of takotsubo cardiomyopathy.

BACKGROUND: Cardiologists have recently recognized a reversible form of heart failure of unknown origin characterized by a takotsubo-shaped hypokinesis of the left ventricle on left ventriculography. AIM: To clarify the clinical features of this cardiomyopathy. DESIGN: Observational study. METHODS: Seven patients with reversible ventricular dysfunction were followed for 4.5 years. Clinical course, routine examinations, and cardiac catheterizations in each patient were documented. RESULTS: The cardiomyopathy developed in six elderly female and one male patients (mean age 75.3 years), all of whom had been exposed to stress. Cardiac enzymes did not significantly increase, but serum norepinephrine increased remarkably (1.19 ng/ml). Coronary angiography revealed normal coronary arteries. However, left ventriculography showed akinesis in the apical segments, together with hyperkinesis in the basal segments (a takotsubo shape). The abnormal kinesis normalized within 17.4 hospital days without any treatment in five patients, and with haemodynamic support for 3 days in the other two. Endocardial biopsies did not suggest any specific pathology. The cardiac events did not recur over a 1-4 year follow-up. DISCUSSION: Coronary vasospasm, myocarditis and other substantial diseases previously described were ruled out as the cause of takotsubo cardiomyopathy in our subjects. Prognosis was good without any form of treatment, provided that the patients survived the severe heart failure state. Catecholaminergic or adrenoceptor-hyperactive cardiomyopathy may be the cause of this cardiomyopathy.

Aged↗
PubMed2003

Efficacy of a polyurethane foam/spheroid artificial liver by using human hepatoblastoma cell line (Hep G2).

We invesigated the availability of human hepatoblastoma cell line (Hep G2), compared with human primary hepatocytes (HH) and porcine primary hepatocytes (PH), as a cell source for the hybrid artificial liver support system (HALSS) by using polyurethane foam (PUF). All three kinds of hepatocytes spontaneously formed spherical multicellular aggregates (spheroids) of 100-200 microm diameter in the pores of PUF within 3 days of culture. In a PUF stationary culture, Hep G2 spheroids recovered the ammonia removal activity that was lost in monolayer culture, although the removal for each unit cell number was about one tenth that of HH spheroids and about one eighth of PH spheroids. The synthesis activities of albumin and fibrinogen of each unit cell number of Hep G2 were also upregulated by PUF spheroid culture, and were about twice as high as in monolayer culture. The albumin secretion activity of Hep G2 spheroids was almost the same as that of PH spheroids. HH scarcely secreted these proteins in this experiment, probably because they were cultured in a serum-free medium. In the PUF module in a circulation culture, HH had high ammonia removal and low synthesis activities similar to stationary culture. Hep G2 proliferated to a high cell density, such as about 4.8 x 10(7) cells/cm3-module at 10 days of culture. Although Hep G2 spheroids had low ammonia removal activity in each cell, the removal rate in the PUF module was almost the same as for PH at 7 days of culture because of the high cell density culture by cell proliferation. The albumin secretion rate by Hep G2 in the PUF module also increased with cell proliferation and was about 10 times higher than the initial for the rate for PH at 7 days of culture. These results suggest that Hep G2 is a potential cell source PUF-HALSS.

Albumins↗
PubMed2003

Progressive changes in arterial oxygenation during one-lung anaesthesia are related to the response to compression of the non-dependent lung.

BACKGROUND: Arterial oxygenation can change during one-lung ventilation for reasons that are not fully understood. METHODS: We studied patients during anaesthesia and one-lung ventilation, with an inspiratory oxygen fraction of 0.8. Arterial blood gas values were recorded every 10 s with a continuous intra-arterial sensor. The non-dependent lung was compressed several times during the surgical procedure, using a retractor. The change in Pa(O(2)) during and after compression of the non-dependent lung was measured. RESULTS: Pa(O(2)) increased significantly when the non-dependent lung was compressed, and decreased when the compression was released. The first compression of the non-dependent lung transiently increased Pa(O(2)), but the effect of the second compression on oxygenation was more marked and persistent. Pa(O(2)) increased by more than 13 kPa at 10 min after the second compression in four patients (responder group). Arterial oxygenation improved markedly in patients in this group during the surgical procedure. CONCLUSION: Oxygenation can improve during one-lung ventilation in some patients. This improvement is partly related to a marked increase in Pa(O(2)) during compression of the non-dependent lung.

Aged↗
PubMed2002

Development of a hybrid artificial liver using polyurethane foam/hepatocyte spheroid culture in a preclinical pig experiment.

We describe a preclinical study of our original hybrid artificial liver support system (HALSS) for a clinical trial. We designed a HALSS comprising a multi-capillary polyurethane foam packed-bed module (MC-PUF module) containing a total 200 g (2 x 10(10) cells) porcine hepatocytes, and an extracorporeal circulation device. Almost all porcine hepatocytes in the MC-PUF module formed many spherical multicellular aggregates (spheroids). This extracorporeal circulation device was improved to promote solute exchange between a living body and a MC-PUF module by including a plasma bypass line in the circulation loop. The efficacy of the HALSS was evaluated using a 25-kg pig with warm ischemic liver failure by portocaval shunt and ligation of hepatic artery (HALSS group, n=3). As a control experiment, the same system without hepatocytes in the module was used with the same kind of liver failure pig (Control group, n=3). The blood ammonia in the control group was 143 N-microg/dl at the start of circulation, and rapidly increased to 351 N-microg/dl at 2 hours and to 704 N-microg/dl at 6 hours. But the blood ammonia in the HALSS group was completely suppressed, and remained less than the hepatic coma level (over 200 N-microg/dl) during the circulation time. The blood glucose in the control group gradually decreased, and became less than 40 mg/dl within 6 hours of circulation. But the blood glucose in the HALSS group was maintained well, and remained the normal glucose level (50 - 105 mg/dl) for more than 20 hours of circulation. Improvement in blood creatinine and lactate, and the stabilization of vital signs and urinary excretion, were observed in the HALSS group. The survival time of the pigs in the HALSS group was 19.3 hours compared with 8.9 hours in the control group. In conclusion, our HALSS was effective to stabilize the general conditions of the body in addition to supporting various liver functions. These results suggest that our HALSS has a strong possibility to be used in treating liver failure patients. We have applied for approval of the clinical trial of our HALSS to our institutional ethics committee.

Animals↗
PubMed2002

Recovery of rats with fulminant hepatic failure by using a hybrid artificial liver support system with polyurethane foam/rat hepatocyte spheroids.

We studied the recovery of rats with fulminant hepatic failure (FHF) by treating them with our original hybrid artificial liver support system (HALSS). FHF was induced by a two-thirds partial hepatectomy and 10 minutes of hepatic ischemia. Rats with FHF were treated with a polyurethane foam/spheroid HALSS including 2.0 x 10(8) hepatocytes for 1 hour (HALSS group, n = 5), and with the same system without hepatocytes in the artificial liver module as a control experiment (sham-HALSS group, n = 3). The level of blood constituents, ammonia, glucose and creatinine, showed no major difference between the two groups at the end of treatment. All rats in the sham-HALSS group died within 5 hours after treatment. However, the level of blood constituents of rats with FHF in the HALSS group improved with time, and all rats in the HALSS group recovered. Liver tissue of rats treated with HALSS showed cell mitosis and improvement from injury. These results indicated that our HALSS has a strong possibility to induce recovery from hepatic failure.

Ammonia↗
PubMed2001

Fatal hemophagocytic syndrome after living-related liver transplantation: a report of two cases.

BACKGROUND: Hemophagocytic syndrome (HPS) is a serious hematological disorder caused by activated T lymphocytes in immunologically compromised patients. There is no report of HPS in liver transplant recipients. METHODS: Among 135 patients who underwent living-related liver transplantation between June 1990 and October 2000, HPS developed in two pediatric patients (1.5%) on the 15th and 134th postoperative day, respectively. The courses of these patients were evaluated. RESULTS: The cause of HPS was unknown in patient 1 and suspected to be Epstein-Barr virus infection in patient 2. The course of patient 2 was also complicated by posttransplant lymphoproliferative disorder. Both patients had high fever, pancytopenia, coagulopathy, and marked elevation of serum-soluble interleukin 2 receptor, serum ferritin, and urine beta2-microglobulin levels. The diagnosis was established based on clinical findings, laboratory data, and bone marrow biopsy. Both patients died in an acute course despite intensive care. CONCLUSIONS: HPS should be recognized as a severe hematological complication in liver transplant patients. Prompt institution of adequate treatment is necessary to prevent fatality.

Critical Care↗
PubMed2001

Antisense oligodeoxynucleotide targeted to Midkine, a heparin-binding growth factor, suppresses tumorigenicity of mouse rectal carcinoma cells.

Midkine (MK), a heparin-binding growth factor, is overexpressed in a wide range of human carcinomas and is believed to contribute to tumorigenesis and tumor progression. To develop an antitumor reagent, we designed a phosphorothioate antisense oligodeoxynucleotide molecule based on the secondary structure of MK mRNA. The antisense MK at the dosage of 5 microM suppressed MK production by CMT-93 mouse rectal carcinoma cells after cationic liposome-mediated transfection, to 13% of that in control cultures. The growth of CMT-93 cells and their colony formation in soft agar were inhibited by the addition of the antisense MK, whereas the control reagent, the sense MK, showed no effects. On s.c. injection into nude mice, CMT-93 cells transfected with the antisense MK formed tumors much smaller than those by control cells. Finally, untreated CMT-93 cells were inoculated to nude mice, and 7 days later the antisense MK (50 microM) with atelocollagen was directly injected into the preformed tumor region to evaluate the curative effect; the injection was repeated at the interval of 2 weeks. During the period of 10-41 days after initiation of therapy, the rate of increase of tumor volume treated with the antisense MK was found to be about 4.2-fold lower than that seen after treatment with the sense MK. On this occasion, proliferation of tumor cells as estimated by 5-bromodeoxyuridine incorporation was strongly inhibited, whereas angiogenesis was less affected. These findings strongly suggested the usefulness of MK antisense oligodeoxynucleotide as a new reagent for cancer therapy.

Amino Acid Sequence↗
PubMed2001

Modulation by estrogens and xenoestrogens of recombinant human neuronal nicotinic receptors.

The effects of estrogens and xenoestrogens on human neuronal nicotinic acetylcholine receptor/channels were examined by expressing recombinant channels in Xenopus oocytes. When functional channels were expressed with alpha3 and beta4 subunits, estrogens (17beta-estradiol, 17alpha-estradiol, 17alpha-ethynylestradiol and diethylstilbestrol) and xenoestrogens (bisphenol A, p-nonylphenol and p-octylphenol) inhibited an ionic current activated by acetylcholine at concentrations up to 100 microM. When the subunit combination was changed to alpha4beta2, diethystilbestrol and the xenoestrogens inhibited the acetylcholine-activated current, but 17beta-estradiol or 17alpha-estradiol did not. For 17alpha-ethynylestradiol, the current through the alpha4beta2 receptor/channel was inhibited at 1 microM, but it was markedly enhanced at 10 and 100 microM. Tamoxifen (10 microM), an antiestrogen, itself inhibited the acetylcholine-activated current but did not antagonize the current modulations induced by the estrogens and the xenoestrogens. These and additional results suggest that human neuronal nicotinic acetylcholine receptors are the targets of non-genomic actions of estrogens and xenoestrogens.

Acetylcholine↗
PubMed2001

Observation of a (6)(LambdaLambda)He double hypernucleus.

A double-hyperfragment event has been found in a hybrid-emulsion experiment. It is identified uniquely as the sequential decay of ( 6)(LambdaLambda)He emitted from a Xi(-) hyperon nuclear capture at rest. The mass of ( 6)(LambdaLambda)He and the Lambda-Lambda interaction energy DeltaB(LambdaLambda) have been measured for the first time devoid of the ambiguities due to the possibilities of excited states. The value of DeltaB(LambdaLambda) is 1.01+/-0.20(+0.18)(-0.11) MeV. This demonstrates that the Lambda-Lambda interaction is weakly attractive.

Journal Article↗
PubMed2001

Lower excitability of the corticospinal tract to transcranial magnetic stimulation during lengthening contractions in human elbow flexors.

The purpose of this study was to characterize the neuromuscular control during shortening (SHO) and lengthening (LEN) contractions by investigating the input-output (I/O) property in the corticospinal tract. To this end, the relation between various stimulus intensities applied via transcranial magnetic stimulation and the size of motor evoked potentials was investigated in six healthy subjects during elbow flexion and extension. The measured I/O property demonstrates a sigmoidal shape, and is characterized by a plateau value, maximum slope and threshold. The results demonstrated that both the plateau value and maximum slope were significantly lower during LEN contraction than during SHO contraction (P<0.05), whereas the threshold was found not to be significantly different. These results suggest that both the maximum excitation level and the gain of the corticospinal tract are reduced during LEN contractions.

Action Potentials↗
PubMed2001

Purification and characterization of N-acetylglucosaminyl sulfotransferase from chick corneas.

N-Acetylglucosaminyl(GlcNAc) sulfotransferase, which transfers sulfate from adenosine 3'-phosphate 5'-phosphosulfate to GlcNAc at the nonreducing end of oligosaccharides, was purified 887-fold with a 8.4% yield from 2-day-old chick corneas by chromatography on CM-Sepharose, WGA-agarose, GlcNAc-agarose, and 3',5'-ADP-agarose columns. The purified enzyme has an optimum pH of 6.0 (Mes buffer) and specifically transfers a sulfate to GlcNAc at the nonreducing end but not to internal GlcNAc. The enzyme was stimulated by protamine and Mn(2+). SDS-polyacrylamide gel electrophoresis of the purified enzyme still showed two main bands (66 and 55 kDa) with some minor bands. It appears that this enzyme competes with beta-galactosyltransferase in binding to the nonreducing GlcNAc residue on KS synthesis; this suggests that the sulfation of the GlcNAc residue is coupled with the elongation of the KS chain.

Animals↗
PubMed2001

Partial pressure of oxygen and partial pressure of carbon dioxide of perfluorocarbon liquid during partial liquid ventilation: their regional difference and their dependence on tidal volume and positive end-expiratory pressure level.

OBJECTIVE: To investigate the regional partial pressure of oxygen (PO2) and partial pressure of carbon dioxide (PCO2) of the perfluorocarbon liquid (PpfcO2, PpfcCO2) during partial liquid ventilation (PLV). DESIGN: Prospective, controlled study. SETTING: A research laboratory at a university medical center. SUBJECTS: Thirteen Japanese white rabbits. INTERVENTIONS: After the tracheostomy, PLV was started with perflubron (15 ml/kg) following saline lung lavage. Fractional inspired oxygen (FIO2) was 1.0, respiratory rate was 30 bpm and tidal volume (VT) was 30 ml. Two epidural catheters (18 gauge) were inserted from the rubber diaphragm interposed in the respiratory circuit to sample perflubron. One catheter was inserted into the left lower lobe bronchus and placed at 5-6 cm distal from the carina (DISTAL). The other one was inserted at the tip of the endotracheal tube (PROXIMAL). Then the effect of the larger VT (50 ml) or positive end-expiratory pressure (PEEP; 10 cmH2O) to the gas tension in perflubron was examined. MEASUREMENTS AND MAIN RESULTS: (1) In the lower VT (30 ml) with 0 cmH20 PEEP, DISTAL PpfcO2 was significantly lower than PROXIMAL PpfcO2 (265 72 vs 386 +/- 47 mmHg, p < 0.0001), and DISTAL PpfcCO2 was significantly higher than PROXIMAL PpfcCO2 (51.1 +/- 14.4 vs 42.4 +/- 11.8 mmHg (p = 0.0007)), (2) the higher VT setting increased PpfcO2 (p = 0.0001) and decreased PpfcCO2 (p < 0.0001), although the gas tension gradient was significant, (3) 10 cmH2O PEEP increased PpfcO2 (p = 0.0004) and decreased PpfcCO2 (p = 0.0089) in the DISTAL sample. CONCLUSION: There was a difference in gas tension in perflubron between the central airway and the peripheral dependent lung region, and gas tension in perflubron was affected by the VT and the PEEP level.

Analysis of Variance↗