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Biomedical subjects

N Takeda

Publications and source records attributed to N Takeda.

At least 235 records · Page 13Linked to original sources
PubMed1997

Non-enzymatic hydrolyses of aryl esters of thymidine 3'-monophosphate as probes for the rate-determining step in DNA hydrolysis.

In order to shed light on the rate-limiting step in DNA hydrolysis, non-enzymatic hydrolyses of aryl esters of thymidine 3'-monophosphate have been kinetically examined. In alkaline solutions, these dinucleotide analogues were hydrolyzed far faster than was thymidylyl(3'-5')thymidine (TpT), indicating that the departure of the leaving group from the phosphorus atom is rate-limiting. The CeIV- and CeIV/PrIII combination-mediated hydrolyses of these analogues were also faster than the corresponding hydrolysis of the dinucleotide.

Cerium↗
PubMed1996

Mice with disrupted GM2/GD2 synthase gene lack complex gangliosides but exhibit only subtle defects in their nervous system.

Gangliosides, sialic acid-containing glycosphingolipids, are abundant in the vertebrate (mammalian) nervous system. Their composition is spatially and developmentally regulated, and gangliosides have been widely believed to lay essential roles in establishment of the nervous system, especially in neuritogenesis and synaptogenesis. However, this has never been tested directly. Here we report the generation of mice with a disrupted beta 1,4-N-acetylgalactosaminyltransferase (GM2/GD2 synthase; EC 2.4.1.92) gene. The mice lacked all complex gangliosides. Nevertheless, they did not show any major histological defects in their nervous systems or in gross behavior. Just a slight reduction in the neural conduction velocity from the tibial nerve to the somatosensory cortex, but not to the lumbar spine, was detected. These findings suggest that complex gangliosides are required in neuronal functions but not in the morphogenesis and organogenesis of the brain. The higher levels of GM3 and GD3 expressed in the brains of these mutant mice may be able to compensate for the lack of complex gangliosides.

Animals↗
PubMed1996

Myocardial adaptive changes and damage in ischemic heart disease.

Changes in two of the elements of myocardial subcellular organelles relating to cardiac energetics, ventricular myosin isozymes and mitochondrial DNA mutations, were examined using left ventricular tissue samples obtained at autopsy from patients with ischemic heart disease. Myosin isozymes were examined in tissues from nine patients with ischemic heart disease and 12 control patients with cancer but no heart disease. Extracted myosin was separated by pyrophosphate gel electrophoresis. The relative concentration of each component was determined by densitometry. Mitochondrial DNA mutations were evaluated in tissues from ten patients with myocardial infarction and 11 control patients with cancer but no heart disease. DNA was extracted and mitochondrial DNA mutations were detected by the polymerase chain reaction. Two bands were revealed by pyrophosphate gel electrophoresis. These contained VM-A, which exhibited faster electrophoretic mobility and was present in lower concentrations, and VM-B, which had a lower mobility and a higher concentration, respectively. SDS polyacrylamide gel electrophoresis showed that these two components contained the heavy chain and light chains 1 and 2 of myosin. VM-A concentrations tended to be higher in patients with ischemic heart disease than in controls. A 7.4-kb deletion was detected between the D-loop and the ATPase 6 genes of mitochondrial DNA from the myocardium of 6 out of 10 patients with myocardial infarction. The relative amounts of the two myosin isozymes could be altered by ischemic heart disease, although the functional significance of these components is unclear. The changes in the two myosin isozymes might be an adaptive change to disordered energy metabolism, but this change was small. The myocardial mitochondrial DNA deletions in patients with myocardial infarction were thought to result from ischemic damage.

DNA, Mitochondrial↗
PubMed1996

Troponin I phosphorylation in heart homogenate from diabetic rat.

Although cardiac myofibrillar ATPase activity has been shown to be depressed during the development of diabetic heart dysfunction, the mechanisms of this alteration are not fully understood. Since phosphorylation of troponin I (TnI) is known to decrease the myofibrillar ATPase activity, the present study was undertaken to examine the TnI phosphorylation capacity in the diabetic heart homogenate. For this purpose rats were made diabetic by injecting streptozotocin (65 mg/kg; i.v.) and the hearts were removed 8 wk later. Some 6 wk diabetic animals were injected with insulin (3 U/day) for 2 wk. TnI content in the heart homogenate was measured by immunoblot assay, the mRNA abundance for TnI gene was determined by Northern blot analysis and the in vitro phosphorylation level of TnI was estimated by the ratio of phosphorylated TnI and total (phosphorylated and unphosphorylated) TnI. No significant changes in TnI content and gene expression of TnI were observed in right and left ventricles from the diabetic rats. However, the phosphorylation of TnI was higher (approximately 40%) in the diabetic hearts; this change was reversible upon insulin treatment. These results regarding TnI phosphorylation measured under in vitro conditions suggest that increased phosphorylation of TnI may contribute toward the depression in cardiac myofibrillar ATPase activity in chronic diabetes.

Animals↗
PubMed1996

The sequential changes in DNA synthesis, glucose utilization, protein synthesis, and peripheral benzodiazepine receptor density in C6 brain tumors after chemotherapy to predict the response of tumors to chemotherapy.

BACKGROUND: Monitoring therapy in patients with brain tumors is very difficult and unreliable. It has been shown that there is no good correlation between tumor sensitivity measured in vitro and in situ tumor response to therapies. METHODS: Sequential changes in tumor size, number of DNA synthesizing cells (labelling index [LI]), glucose utilization (LCGU), protein synthesis (LCPS), and peripheral benzodiazepine receptor (PBR) density were examined after chemotherapy for seven days. This was done using antibromodeoxyuridine immunohistochemical stain and multiple tracer quantitative autoradiography in a C6 rat brain with an implanted glioma. On Day 10 after inoculation, the rats were divided into 5 experimental groups: (1) a nontreatment group (control Group 1); (2) a group received 5% dextrose intraarterial (IA) administration (control Group 2); (3) a group received 1,3-bis-(2-chloroethyl) nitrosourea (BCNU) intravenous (i.v.) administration (Group 3) (5% dextrose was solvent); (4) a group received BCNU IA administration (Group 4) (5% dextrose was solvent); and (5) a group received sarcosinamide chloroethyl nitrosourea (SarCNU) IA administration (Group 5) (solvent as for the BCNU group). RESULTS: Three treatments showed a significant decrease (P < 0.003) in tumor growth. The most effective treatment was BCNU IA and SarCNU IA was moderately effective. BCNU i.v. showed no effect on tumor growth when compared with the two control groups. The change in the peak LI correlated well with the peak LCGU. These parameters decreased markedly and significantly in both Group 4 and Group 5 from Day 1 after treatment. The rates of the decrease in these biologic factors also correlated well with a decrease in the tumor growth. The LCPS did not correlate with a decrease in the LI or LCGU. The dissociation constant (Kd) and densities of the receptors PBR (B max) did not change significantly in any of the treatment groups during the observation period. CONCLUSIONS: From the results presented, we concluded that changes in the LI and LCGU represent the most reliable parameters with which to predict the response or sensitivity of this glial tumor to the treatments applied. These data suggest that if changes in peak LCGU were measured in tumors using positron emission tomography, they might be instrumental in providing in vivo information about the sensitivity of a tumor to a given treatment without the need for repeated tumor biopsy.

Animals↗
PubMed1996

GABAergic inhibitory response of locus coeruleus neurons to caloric vestibular stimulation in rats.

We examined the effects of caloric vestibular stimulation on the neuronal activity of the locus coeruleus (LC) in urethane-anesthetized rats. The middle ear cavity was irrigated with hot (44 degrees C) or cold (30 degrees C) water through a polyethylene tube. Most neurons (hot water: 76%, 55/72; cold water: 90%, 19/21) exhibited suppression of neuronal discharge in response to caloric stimulation. The suppression of LC neuronal discharge following caloric stimulation occurred with a long latency (approximately 80 s), and lasted a long period of time (approximately 3 min). Neither caloric stimulation of the auricle, nor irrigation of the middle ear with water at 37 degrees C, nor caloric stimulation of the middle ear after labyrinthectomy inhibited LC neuronal discharge. The caloric stimulation-induced LC neuronal inhibition was significantly attenuated by the intravenous injection of picrotoxin and by the iontophoretic application of bicuculline methiodide. These findings indicate that the predominant effect of caloric vestibular stimulation on LC neuronal discharge is inhibitory, and that the caloric stimulation-induced LC neuronal inhibition is mediated by GABAA receptors located on the membrane of LC neurons. It is suggested that the suppressed activity of noradrenergic LC neurons is involved in the vestibulo-autonomic reflex.

Action Potentials↗
PubMed1996

Effects of caloric vestibular stimulation on prepositus hypoglossi neurons in rats.

In our previous study, we found that the majority of locus coeruleus (LC) neurons were inhibited by caloric stimulation and that the inhibition was mediated by gamma aminobutyric acid (GABAA) receptors. It has been reported that the nucleus prepositus hypoglossi (PrH) sends GABAergic inputs to the LC. In the present study, an attempt was made to determine whether PrH neurons contribute to the LC neuronal inhibition caused by caloric stimulation. We characterized the neuronal response in the PrH to caloric stimulation in rats. About three-fourths of PrH neurons showed various responses to both ipsi- and contralateral caloric stimulation, suggesting that PrH neurons receive bilateral vestibular inputs. However, these neurons were not activated by antidromic stimulation of the LC. The remaining one-fourth of the PrH neurons that were antidromically activated did not respond to caloric stimulation. Lesions in the PrH did not attenuate the LC neuronal inhibition caused by caloric stimulation. These findings suggest that the inhibition of LC neurons caused by caloric stimulation is not mediated by the PrH.

Animals↗
PubMed1996

Sex and age patterns of quantitative ultrasound densitometry of the calcaneus in normal Japanese subjects.

: The speed of sound (SOS), broadband ultrasound attenuation (BUA), and the stiffness index (stiffness), which was derived from SOS and BUA, were measured on the calcaneus using the Achilles ultrasound densitometer (Lunar) in normal Japanese woman (n = 473) and men (n = 218). Sex differences and age-related changes in these variables were investigated. In addition, the bone mineral density (BMD) of the lumbar vertebrae measured by dual X-ray absorptiometry (QDR-2000, Hologic) was compared with SOS, BUA, and stiffness. There were some decreases of ultrasound variables in both young adult men and women. BMD values were similar in young adults of both sexes. BMD was relatively stable in women from 20 to 49 years, then decreased at about 1.5%/year. Ultrasound variables were higher in males than females at all ages, and they decreased from age 20 onward in both sexes with an annual loss of about 0.6%. Age-related changes in SOS, BUA, and stiffness were different from those in BMD in normal Japanese subjects. The correlations between BMD and SOS and BUA and stiffness were higher in women (r = 0.51-0.64) than in men (r = 0. 43-0.49).

Absorptiometry, Photon↗
PubMed1996

Cardiac membrane Ca(2+)-transport in alloxan-induced diabetes in rats.

In order to determine if cardiac membrane Ca(2+)-transport activities are altered in chronic diabetes induced by alloxan, rats were given an intravenous injection of 65 mg/kg and the hearts were used 8 weeks later. Some 4 weeks, diabetic animals were injected with insulin (3 U/day) for 4 weeks. Both sarcolemmal (SL) and sarcoplasmic reticulum (SR) membranes were isolated from the ventricular tissue and their Ca(2+)-transporting activities were determined. SL Na(+)-dependent Ca2+ uptake, ATP-dependent Ca2+ uptake and Ca(2+)-stimulated ATPase activities were depressed in the diabetic heart. Likewise, SR ATP-dependent Ca2+ uptake activity in the diabetic heart was markedly decreased in comparison to the control preparations. These defects in diabetic SL and SR Ca(2+)-transport activities were prevented by treatment of diabetic animals with insulin. The results from the alloxan-rat model of diabetes support the view that membrane abnormalities with respect to Ca2+ handling may lead to the occurrence of intracellular Ca2+ overload and the development of diabetic cardiomyopathy.

Animals↗
PubMed1996

Mitochondrial DNA mutations in diabetic heart.

Mutations of mitochondrial DNA have been found in cardiomyopathic and diabetic patients as well as mitochondrial myopathic patients. Mitochondrial DNA mutations are maternally transmitted. It has also been reported that these mutations can be acquired under the influence of free radicals. This article is a mini-review about mutations of mitochondrial DNA related to the diabetic heart.

Cardiomyopathies↗
PubMed1996

Sequence of alterations in subcellular organelles during the development of heart dysfunction in diabetes.

Although changes in different subcellular organelles such as myofibrils, sarcoplasmic reticulum (SR), mitochondria and sarcolemma (SL), as well as in heart function have been reported to occur in chronic diabetes, their inter-relationships and functional significance are poorly understood. In order to gain information on this aspect, diabetes in rats was induced by an intravenous injection of streptozotocin and animals were assessed hemodynamically at 15-27 days. Ventricular tissue from several diabetic animals was pooled, subcellular organelles were isolated and their biochemical activities determined. Significant depressions in cardiac contractile and relaxation were observed to be associated with decreases in myofibrillar Ca(2+)-stimulated ATPase and SR Ca(2+)-pump activities at 21 days from the induction of diabetes. Likewise, the SL Na+-Ca2+ exchange and Ca(2+)-channel density were decreased at 21 days but the affinity of SL Ca(2+)-channels was increased in the diabetic heart. The SL Ca(2+)-pump and Na+-K+ ATPase activities were depressed at 18 and 24 days, respectively. Both alpha- and beta- adrenoceptor densities in SL were decreased at 27 days whereas no changes in mitochondrial function were observed at these early stages of diabetes. The SL low affinity Ca(2+)-binding was decreased while the low affinity Ca(2+)-ATPase activity was increased at 18 days following the induction of diabetes. These results indicate that SL defects precede those in SR, myofibrils or mitochondria and suggest that abnormalities in Ca(2+)-handling as well as interaction of Ca2+ with myofilaments in cardiomyocytes may lead to the development of heart dysfunction in chronic diabetes.

Adenosine Triphosphatases↗
PubMed1996

Application of a suture anchor technique for flap fixation to bone.

The authors have developed a technique for fixation of a flap to underlying bone. Their technique involves an anchor system which has been used for tenodesis and ligament repair in orthopedic bone and joint surgery. The anchor technique provides reliable fixation with simplicity of application. A wider use of this technique in reconstructive flap surgery is expected.

Bone and Bones↗
PubMed1996

The incidence of viremia and the heterogeneity of hepatitis C virus genotypes among blood donors, hemophiliacs and patients with chronic liver disease.

Hepatitis C Virus (HCV) is the major cause of parentally transmitted non-A, non-B hepatitis. We studied the incidence of HCV Viremia in blood donors, hemophiliacs and patients with chronic liver disease who are positive for antibodies to HCV, and then correlated the HCV genotypes among the three groups. 23 blood donors, 10 hemophiliacs and 97 patients with chronic liver disease were found to be positive for anti-HCV during this study period from June 1993 to December 1993. Only 3 (13%) blood donors, 6 (60%) hemophiliacs and 71 (73%) patients with chronic liver disease were found to be viremic when tested for HCV RNA by reverse transcriptase-polymerase chain reaction (RT-PCR). The low incidence of viremia among blood donors may be due to any one of the following three reasons. 1, the level of viremia was below the level of detection. 2, the viremia was intermittent with persistent infection. 3, the majority of cases represented resolved infection. The HCV genotypes were heterogeneous among the three groups. All the blood donors with viremia and 35 (50%) of patients with chronic liver disease, belonged to type II (1b). However only one (17%) of the hemophiliacs belonged to type II (1b). Studies have shown that the genotype I(1a) is the predominant type in the USA and Europe, whereas type II(1b) is more frequent in the Far East. It is also suggested that type II (1b) is associated with non-responsiveness to interferon therapy. Our hemophiliacs were treated with imported coagulation factors, thus they were probably exposed to the genotypes in the west. There was significant difference in the incidence of HCV type II (1b) among local blood donors and hemophiliacs (P = 0.005). However the difference between the hemophiliacs and the patients with chronic liver disease was not statistically significant. The number of patients in this study was too small to draw any firm conclusions. However the findings highlight the importance of studying the genotypes of patients with Hepatitis C infection due to their relevance in the management of these cases with interferon therapy.

Adolescent↗
PubMed1996

Molecular cloning of the rat NADH:ubiquinone oxidoreductase subunit and its up-regulation in the facial muscle after denervation: detected by means of differential display.

The differential display method was applied to identify gene expression which is especially up-regulated in the rat denervated skeletal muscle. Total RNA from normal and denervated facial muscles was isolated, amplified by PCR using certain primers, and separated by electrophoresis on polyacrylamide gel. PCR products which were apparently higher in the operated than in the control side were cut out from the gel and subsequently sequenced. One of the cDNA fragments obtained in the present study showed about 80% identity in nucleotide sequence and about 84% identity in amino acid sequence to one of the NADH: ubiquinone oxidoreductase (complex I) subunits from the bovine heart mitochondria (813). Complex I, the first and largest enzyme of the mitochondrial respiratory chain, transfers electrons from NADH to ubiquinone-10 (UQ-10). B13 is a 13 kDa subunit; deficiency of which causes incomplete or incorrect assembly of a functional complex I, resulting in one of the types of human mitochondrial myopathy. Northern blot analysis and in situ hybridization histochemistry confirmed that rat B13 mRNA expression was up-regulated after denervation and was distributed throughout whole muscle cell body. These findings suggest that up-regulation of the rat B13 mRNA expression after denervation plays an important role in the effective electron transfer from NADH to UQ-10 in skeletal muscle cells, resulting in restriction of lipid peroxidation and biological tissue damage.

Amino Acid Sequence↗