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Biomedical subjects

K Nakazawa

Publications and source records attributed to K Nakazawa.

At least 127 records · Page 7Linked to original sources
PubMed1999

Lupus nephritis in juvenile myelomonocytic leukemia.

A 13-year-old girl developed lupus nephritis and Hashimoto thyroiditis in the chronic phase of juvenile myelomonocytic leukemia (JMML). At age 7 months, she was diagnosed as having JMML based on the hepatosplenomegaly, leukocytosis, thrombocytopenia, increased levels of fetal hemoglobin, and spontaneous in vitro growth of granulocyte-macrophage progenitors. At the onset of JMML, she had hypergammaglobulinemia, antinuclear antibodies, rheumatoid factors and anti-smooth muscle antibody. She had been placed on oral 6-mercaptopurine for about 12 years, with clinical improvement. At age 13 years, she was found to have hematuria and proteinuria. She also developed arthritis and Raynaud's phenomenon as well. She had antinuclear antibodies, rheumatoid factors, LE phenomenon, beta-1C (C3) nephritic factor (C3NeF), antithyroid antibodies, and hypocomplementemia. The renal biopsy specimens revealed a diffuse increase in the mesangial cells and matrix by light microscopy, and intense staining of IgG, Clq and C3 by immunofluorescence microscopy. The hormonal study ultimately showed decreased thyroid functions. So she was diagnosed as lupus nephritis and Hashimoto thyroiditis. The patient is the first example to show close relationship between stem cell abnormalities in JMML and development of overt autoimmune disorders.

Adolescent↗
PubMed1999

[Fusion of medicine and technology in endoscopic surgery].

Although endoscopic surgery has become widespread and is currently used in a wide range of general, thoracic, urologic, gynecologic, and orthopedic procedures, many major difficulties remain because sensorial information is restricted to a two-dimensional image, and effector instruments have limited maneuverability due to the rigid shaft axis fixed to the abdominal wall by the entry trocar. To overcome these problems, advanced engineering technology has been introduced in laparoscopic surgery which includes three-dimensional video imaging, robotic laparoscopic cameraholders, telemanipulated flexible effector instruments, and tactile feedback. A voice-controlled robotic laparoscopic holder (AESOP200, Computer Motion Inc. USA) provides stable support for the laparoscope during laparoscopic surgery performed by a single surgeon. A new computer-assisted telemanipulation robot (Intuitive Surgical Inc. USA) permits the performance of completely endoscopic coronary artery bypass and Nissen fundoplication. Furthermore, price reductions and technological advances in telecommunications have made telementoring in endoscopic surgery available for routine clinical use, and intercontinental surgical video teleconferences fruitful opportunities for discussing technical details. The fusion of medicine and technology in endoscopic surgery would overcome difficulties in the conventional endoscopic approach.

Humans↗
PubMed1999

[A multicenter study for evaluating a new intubating laryngeal mask airway].

A multicenter study was performed to evaluate the success of endotracheal intubation using an intubating laryngeal mask (ILM, Fastrach) in patients in ASA status I or II, aged 20 years or more, who underwent general anesthesia. A total of 191 patients were studied, and 24 of them were estimated difficult to intubate by the ordinary method with laryngoscope. Endotracheal intubation was successfully performed through ILM in 162 of the 191 (success rate of 84.8%). The mean time required for intubation in these successful cases was 19.1 seconds. The success rate did not depend on the clinical experience of anesthesiologists, and the individual success rate was improved as they became more experienced. Of the 24 patients who had been estimated difficult to intubate with laryngoscope, 23 were successfully intubated with success rate of 95.8%. In summary, endotracheal intubation through ILM was easy regardless of the anesthesiologist's experience, and seemed to be valuable for patients who were difficult to intubate.

Adult↗
PubMed1999

[A case of AIDS-associated primary CNS lymphoma difficult to differentiate from toxoplasmic encephalitis by clinical symptoms, neuroimages, and therapeutic responses].

We reported a 24-year-old Thai woman who developed primary CNS lymphoma (PCNSL) associated with acquired immunodeficency syndrome. It was difficult to distinguish PCNSL from toxoplamic encephalitis in this case by clinical symptoms, findings of CT and MRI, and therapeutic responses for toxoplasmosis. It is important to make a definite diagnosis of PCNSL by brain biopsy to treat appropriately, because this disorder could be fatal if it is not treated by corticosteroid, radiation, or other proper methods.

Adult↗
PubMed1999

[Investigation of radiation safety management of nuclear medicine facilities in Japan; contamination of radioactivity in the draining-water system. A Working Group of Japanese Society of Nuclear Medicine for the Guidelines of Nuclear Medicine Therapy].

Radiation safety management condition in Japanese nuclear medicine facilities were investigated by the questionnaire method. The first questionnaire was asked in all Japanese 1,401 Nuclear Medicine facilities. Answers from 624 institutes (44.5%) were received and analyzed. The radiation-safety management in nuclear medicine institutes was considered to be very well performed everyday. Opinion for the present legal control of nuclear medicine institutes was that the regulation in Japan was too strict for the clinical use of radionuclides. The current regulation is based on the assumption that 1% of all radioactivity used in nuclear medicine institutes contaminates into the draining-water system. The second questionnaire detailing the contamination of radioactivity in the draining-water system was sent to 128 institutes, and 64 answers were received. Of them, 42 institutes were considered to be enough to evaluate the contamination of radioactivity in the draining-water system. There was no difference between 624 institutes answered to the first questionnaire and 42 institutes, where the radioactivity in the draining-water system was measured, in the distribution of the institute size, draining-water system equipment and the radioactivity measuring method, and these 42 institutes seemed to be representative of Japanese nuclear medicine institutes. Contamination rate of radioactivity into the draining system was calculated by the value of radioactivity in the collecting tank divided by the amount of radionuclides used daily in each institute. The institutes were divided into two categories on the basis of nuclear medicine practice pattern; type A: in-vivo use only and type B: both in-vivo and in-vitro use. The contamination rate in 27 type A institutes did not exceed 0.01%, whereas in 15 type B institutes the contamination rate distributed widely from undetectable to above 1%. These results indicated that the present regulation for the draining-water system, which assumed that 1% of all radioactivity used in nuclear medicine institutes contaminated into draining-water system, should be reconsidered in nuclear medicine facilities where radionuclides are used only in in-vivo studies.

Health Facilities↗
PubMed1999

Effects of long-term bed rest on H-reflex and motor evoked potential in lower leg muscles during standing.

Maximal H-reflex amplitude (Hmax) compared with maximal M-response (Mmax) has been generally used to assess the efficacy of the monosynaptic transmission from Ia afferents to alpha motoneurons in spinal cord. In previous studies, it has been demonstrated that H-reflex in soleus muscle (SOL) is inhibited during free standing due to an increase in presynaptic inhibition of the Ia afferent terminals to SOL motoneurones (Katz et al. 1988, Koceja et al. 1993). Transcranial magnetic stimulation (TMS) of human motor cortex excites the corticospinal system monosynapticaly connecting to spinal alpha motoneurones. However, it is not clear whether or not the motor evoked potentials (MEPs) in SOL and tibialis anterior (TA) muscles induced by TMS are modulated during standing (Ackermann et al. 1991, Lavoie et al. 1995). Considering that postural control functions change with exposure to weightlessness, we supposed that the excitability of SOL and TA spinal motoneurons from Ia afferents and/or corticospinal tracts during free standing would change after long-term bed rest (BR). The aim of this study was to investigate the effect of BR on H-reflex and MEP in SOL and TA during free standing.

Adult↗
PubMed1999

Gravity-dependent modulation of Ia afferent in human.

Recent work has shown that the H-reflex excitability of the human soleus motoneurones is modulated in reduced gravity and accompanied by a corresponding change in electromyographic (EMG) activity during space flight mission or different gravitational load. Spinal reflexes are often viewed as stereotyped motor patterns with limited scope for modification. However, recent evidence suggests that even short-latency, largely monosynaptic reflexes show a high degree of modulation during simple human motor activities such as walking and standing, and that the pattern of modulation can be specifically altered for the different functional requirements of each activity. Capady and Stein have demonstrated that H-reflex amplitude of the soleus increases progressively during the stance phase and reaches its peak amplitude late in the stance phase during walking. However, during running, the H-reflex is found to be significantly smaller than during walking, suggestion a modified spinal reflex gain for the different functional requirements of the motor behaviors. It is well documented that gravitational loads on the human body, spinal cords are much higher during standing in the water than standing in land. Little is known about the occurrence and influence of neural modulation in spinal cord during different gravitational load, which was not induced by posture but by voluntary background activity. The purpose of the present study was consequently to investigate how to effect is controlled H-reflex modulated during reduced gravity standing in a water in normal subjects.

Adult↗
PubMed1998

Glycosyltransferase and sulfotransferase activities in chick corneal stromal cells before and after in vitro culture.

The expression type of proteoglycan in corneal stromal cells is known to change markedly when the cells are cultured in vitro. To determine which enzyme is primarily responsible for this change in chick corneal stromal cells, the activities of various glycosyltransferases and sulfotransferases were determined before and after in vitro culture of the cells. The activities of N-acetylglucosaminyltransferase, galactosyltransferase, and sulfotransferase, which are involved in keratan sulfate synthesis, were assayed using pyridylaminated N-acetyllactosamine-containing oligosaccharides as acceptor substrate; the activities of N-acetylgalactosaminyltransferase, glucuronyltransferase, and sulfotransferase, which are involved in chondroitin sulfate synthesis, were assayed using pyridylaminated chondrooligosaccharides as acceptor substrate. Of these enzymes, the sulfotransferase activity toward degalactosylated, pyridylaminated lacto-N-neotetraose and N-acetyllactosamine dimer (probably GlcNAc-6-sulfotransferase) decreased markedly after in vitro culture, whereas the galactosyltransferase activity increased. The chondroitin sulfate-sulfotransferase activities toward pyridylaminated chondrooligosaccharides hardly changed after in vitro culture. The marked decrease in the activity of the keratan sulfate-sulfotransferase corresponds to the marked decrease in keratan sulfate biosynthesis when the cells are cultured in vitro. These findings suggest that keratan sulfate-sulfotransferase (GlcNAc-6-sulfotransferase) is a key enzyme in keratan sulfate biosynthesis and that its decrease is primarily responsible for the marked decrease in keratan sulfate synthesis after in vitro culture.

Animals↗
PubMed1998

An asparagine residue regulating conductance through P2X2 receptor/channels.

Single channel currents were recorded from Xenopus oocytes expressing wild-type and mutated P2X2 receptors. When 100 mM Na+ was used as the permeant cation, unitary currents of about 80 pS were recorded from the oocyte expressing the wild-type channels. The single channel conductance was roughly halved when Asn333 was replaced by Ile (N333I). A similar decrease in single channel currents was also observed when 100 mM Li+ or Cs+ was used as the permeant cation. With two other mutants, in which Asp315 was replaced by Val (D315V) or Tyr330 was replaced by lie (T333I), single channel conductance was almost the same as that of the wild-type channels. The results suggest that Asn333, which is believed to be involved in the channel pore, plays an essential role in ion transport through P2X2 receptor/channels.

Animals↗
PubMed1998

An aspartic acid residue near the second transmembrane segment of ATP receptor/channel regulates agonist sensitivity.

Charged or polarized amino acid residues near or within the second transmembrane (M2) segment of neuronal ATP receptor/channels (P2X2 receptors) were neutralized by site-directed mutagenesis, and the properties of the mutants were electrophysiologically characterized using Xenopus oocytes. When Asp315 was substituted with Val (D315V), the sensitivity to ATP was reduced by about 60-fold. The sensitivity to ATP was not affected by the neutralization of Lys324, which is involved in a Walker type A ATP-binding sequence, Lys366, Tyr330, or Asn333. With D315V channels, the sensitivities to other agonists (ADP, ATP gamma S, and 2-methylthio ATP) were also reduced. The sensitivities to antagonists (suramin and Cibacron Blue F3GA) were, however, not affected by this neutralization. The results suggest that Asp315, which is assumed to be present in the extracellular region near the M2 segment of P2X2 receptor/channels, serves to maintain agonist sensitivity.

Adenine Nucleotides↗
PubMed1998

Pigmented human skin equivalent--as a model of the mechanisms of control of cell-cell and cell-matrix interactions.

The melanin pigment system in human skin is extraordinarly well developed and assures the photoprotection of the skin against harmful solar radiation. Specific cell-cell interactions between one melanocytes and keratinocytes play a fundamental role in the regulation of melanogenesis and melanin pigementation, the two key elements of this system, giving rise to the concept of a structural, functional collaborative 'epidermal melanin unit,' Early experiments strongly suggested that melanocyte growth and differentiation are regulated by paracrine factors from keratinocytes and other skin cells. In addition, co-culture studies with keratinocytes has shown that the extracellular matrix acts as a local environmental signal for dendrite formation and melanogenesis. Attempts to reconstruct pigmented human skin in vitro have made great progress over the last decade. The behavior of cells in these pigmented human skin equivalents closely resembles that in vivo, and the cells can still respond to appropriate extrinsic regulatory stimuli such as ultraviolet radiation. Keratinocytes and fibroblasts have been shown to be active partners in the regulation of melanocyte distribution, viability and other differentiation functions, presumably by direct contact and the effects of various soluble paracrine factors. By reproducing cell-cell and cell-matrix interactions, these culture systems provide a promising experimental model for investigating regulation of the skin pigmentary system and the role of photoprotection against harmful solar radiation.

Cell Communication↗
PubMed1998

Continuous intra-arterial blood gas monitoring during oesophagectomy.

PURPOSE: To evaluate the clinical usefulness of the continuous intra-arterial blood gas (CIABG) monitoring system, Paratrend 7, during differential lung ventilation (DLV) in 12 patients undergoing oesophagectomy. METHODS: Anaesthesia was induced with propofol and was maintained with isoflurane, oxygen and air, supplemented by an epidural infusion of mepivacaine. Arterial samples for estimation of blood gases (ABG) were taken just before and 5, 10, 20, 30, 60, and 90 min after the pleura was opened. The pH, PO2, and PCO2 values displayed by the CIABG monitor, which were recorded prior to the arterial blood sampling, were compared with the results of ABG analysis. RESULTS: Eighty-four blood samples were obtained and the ranges for the measured variables were PCO2 24.8-57.4 mmHg, PO2 47-449 mmHg, and pH 7.30-7.49. The correlation between CIABG and ABG measurements was strong and significant (r values: PCO2 0.80, PO2 0.93, pH 0.94). The overall bias +/- precision between the two methods was PCO2 0.9 +/- 3.1 mmHg, PO2 -1 +/- 40 mmHg, %PO2 0.8 +/- 21.6%, pH 0.00 +/- 0.02. For PO2 values < 150 mmHg, the biases +/- precision were PO2 -5 +/- 17 mmHg, %PO2 -2.1 +/- 20.7%. CONCLUSION: The agreement between CIABG and ABG measurements was better for PCO2 and pH than for PO2. Although the CIABG system is clinically useful for monitoring trends in blood gas changes, the accuracy of the PO2 value may be unacceptable during DLV because the error is theoretically < 34 mmHg with 95% reliability in the clinically important range of PO2, < 150 mmHg.

Anesthesia, Inhalation↗
PubMed1998

Phase-dependent electromyographic activity of the lower-limb muscles of a patient with clinically complete spinal cord injury during orthotic gait.

We examined the lower-limb electromyographic (EMG) activity from a patient with clinically complete spinal cord injury during orthotic gait. A newly developed gait orthosis was used to obtain bipedal locomotion. The surface EMG data during the gait together with the biomechanical variables were collected by way of a radio EMG system. A cyclic EMG activation pattern corresponding to the gait cycles were observed in each of the paralyzed lower-limb muscles during the orthotic gait. Although the EMG activation did not seem to contribute toward generating the gait, it showed some similarities to that of the infant stepping or immature gait. These results might be regarded as one of the indirect pieces of evidence that suggest the existence of a spinally originating motor mechanism underlying human locomotion.

Adult↗
PubMed1998

Differences in stretch reflex responses of elbow flexor muscles during shortening, lengthening and isometric contractions.

Stretch reflexes were evoked in elbow flexor muscles undergoing three different muscle contractions, i.e. isotonic shortening (SHO) and lengthening (LEN), and isometric (ISO) contractions. The intermuscle relationships for the magnitude of the stretch reflex component in the eletromyographic (EMG) activities of two main elbow flexor muscles, i.e. the biceps brachii (BB) and the brachioradialis (BRD), were compared among the three types of contractions. The subjects were requested to move their forearms sinusoidally (0.1 Hz) against a constant pre-load between elbow joint angles of 10 degrees (0 degrees = full extension) and 80 degrees during SHO and LEN, and to keep an angle of 45 degrees during the ISO. The perturbations were applied at the elbow angle of 45 degrees in pseudo-random order. The EMG signals were rectified and averaged over a period of 100 ms before and 400 ms after the onset of the perturbation 40-50 times. From the ensemble averaged EMG waveform, the background activity (BGA), short (20-50 ms) and long latency (M2, 50-80, M3, 80-100 ms) reflex and voluntary activity (100-150 ms) components were measured. The results showed that both BGA and reflex EMG activity of the two elbow flexor muscles were markedly decreased during the lengthening contraction compared to the SHO and ISO contractions. Furthermore, the changes of reflex EMG components in the BRD muscle were more pronounced than those in the BB muscle, i.e. the ratios of M2 and M3 magnitudes between BRD and BB (BRD:BB) were significantly reduced during the LEN contractions. These results would suggest that the gain of long latency stretch reflex EMG activities in synergistic muscles might be modulated independently according to the model of muscle contraction.

Adult↗
PubMed1998

Recovery of retching after lesions involving the nucleus of the solitary tract.

The nucleus of the solitary tract (NTS) in the caudal brainstem receives various inputs that trigger vomiting. Chemical (kainic acid) NTS lesions in decerebrate, paralyzed cats temporarily suppressed fictive vomiting induced by different emetics. Subsequently, retching but not expulsion, resumed in 2-3.5 h. Since the NTS does not appear essential for retching, antiemetic drugs targeted at the NTS may not completely suppress vomiting.

Animals↗
PubMed1998

A study on home health care support information system for health evaluation.

The need for home health care has been increasing in Japan and the application of various techniques such as medical informatics are desired to support home health care services. Therefore, we developed an information system for health evaluation of the elderly including patients at home by applying multifunctional telephone set and an IC memory card, by which complaints, symptoms, and conditions by them can be collected, recorded, and transmitted to medical facilities. We also conducted an experiment for trial use of the system with the cooperation of elderly female volunteers. It was recognized that the elderly volunteers could operate the system with the help of public health nurses and their health information could be collected by the system. Although the developed system has some problems, it was suggested that the system would be useful for the support of health evaluation of elderly at home.

Aged↗