Biomedical subjects

K Takezawa

Publications and source records attributed to K Takezawa.

At least 19 recordsLinked to original sources

PubMed2001

Determination of catecholamines and their 3-O-methyl metabolites in mouse plasma.

The determination of catecholamines and their 3-O-methyl metabolites in a single mouse plasma is necessary to understand the role of the sympathetic nervous activity, while the inactivation of catecholamines by catechol-O-methyltransferase indicates the activity of blood pressure regulation in animals. Here we report the basal catecholamines and their 3-O-methyl metabolite concentrations obtained from 15 microL of mouse plasma utilizing semi-microcolumn high-performance liquid chromatography (HPLC)-peroxyoxalate chemiluminescence detection system. The concentrations were 6.63 +/- 1.37 pmol/mL plasma, 0.49 +/- 0.10 pmol/mL plasma, 5.25 +/- 2.30 pmol/mL plasma, 3.23 +/- 0.84 pmol/mL plasma, 0.44 +/- 0.11 pmol/mL plasma, and 3.39 +/- 1.67 pmol/mL plasma for norepinephrine, epinephrine, dopamine, normetanephrine, metanephrine and 3-methoxytyramine, respectively (n = 5-7). Further, when blood pressure was reduced by minoxidil, plasma catecholamines were found to be significantly increased by the baroreflex-mediated response in mouse.

Animals↗

PubMed2001

A method for the measurement of catechol-O-methyltransferase activity using norepinephrine, an endogenous substrate.

We propose a highly sensitive method for the measurement of catechol-O-methyltransferase (COMT) activity with norepinephrine (NE), an endogenous native substrate. The product, normetanephrine, was determined by high-performance liquid chromatography (HPLC)-peroxyoxalate chemiluminescence reaction detection or, if required, less sensitive fluorescence detection. For the measurement of membrane-bound (MB)-COMT activity in the rat erythrocyte, the HPLC-peroxyoxalate chemiluminescence reaction detection was employed. Soluble (S)- and MB-COMT activities in the rat erythrocyte were 22.9 +/- 2.5 and 4.62 +/- 1.23 pmol min-1 (mg protein)-1, respectively (n = 5). The Km values obtained for S- and MB-COMT were 366 +/- 31 mumol l-1 and 12.0 +/- 1.1 mumol l-1, respectively (n = 5), suggesting that the use of NE as a substrate would give more precise information on the role of both isoenzymes. However, with dihydroxybenzoic acid as an artificial substrate, the Km values for S- and MB-COMT were similar, with values of 69.2 +/- 11.4 mumol l-1 and 72.2 +/- 9.2 mumol l-1, respectively. The proposed method is thought to be useful for the measurement of both S-COMT and MB-COMT activities, and would give us critical information on the role of metabolism of catecholamines in rat tissues.

Animals↗

PubMed2000

An automatic analyzer for catecholamines and their 3-O-methyl metabolites using a micro coulometric flow cell as a postcolumn reactor for fluorogenic reaction.

A coulometric flow cell for a miniaturized LC system was developed. The cell was examined, as 3-O-methyl catecholamines were converted to their relative omicron-quinones for subsequent fluorometric and chemiluminescence detection. Its performance was evaluated in comparison with commercially available amperometric and coulometric detectors in terms of specification of the low dead volume and high conversion efficiency. The fully automated small-bore LC analyzer for simultaneous determination of catecholamines and their 3-O-methyl metabolites included precolumn pretreatment, column switching, column separation, postcolumn oxidative conversion, fluorometric derivatization, and chemiluminescence detection. The detection limits were 0.3-2.0 fmol for catecholamines and their 3-O-methyl metabolites. Because of the high sensitivity, the required volume of rat plasma sample was only 15 microL.

Animals↗

PubMed2000

Automatic semi-microcolumn liquid chromatographic determination of catecholamines in rat plasma utilizing peroxyoxalate chemiluminescence reaction.

A fully automated and highly sensitive method with a semi-microcolumn liquid chromatography system for the determination of rat plasma catecholamines (CAs) was developed. Automated on-line extraction of CAs in diluted plasma using a precolumn packed with strong acidic cation exchange resin was coupled with separation of CAs on a semi-microcolumn (250 x 1.5 mm id). fluorogenic derivatization with ethylenediamine and finally postcolumn peroxyoxalate chemiluminescence detection utilizing bis[2-(3,6,9-trioxadecanyloxycarbonyl)-4-nitrophenyl]oxalate (TDPO) and hydrogen peroxide. The detection limits were 0.91, 0.36 and 1.1 fmol for norepinephrine (noradrenaline), epinephrine (adrenaline) and dopamine, respectively, at a signal-to-noise ratio of 3. A good linearity of the calibration curve for each CA was observed in the range of 5.0 to 500 fmol for each CA using N-methyldopamine (N-MeDA) as an internal standard. The RSD for the proposed method (n = 5) were 3.7-9.5% for the intra-day assay and 6.6-10.0% for the inter-day assay. The volume of rat plasma required for the determination of CAs was 10 microliters.

Animals↗

PubMed2000

Differences in the effects of 20 K- and 22 K-hGH on water retention in rats.

Antidiuretic actions induced by two growth hormone (GH) isoforms (20 K- and 22 K-hGH; 0.2 and 2.0 mg/kg) were evaluated in rats, as fluid retention may cause oedema, one of the adverse effects of GH. Both GH isoforms (2.0 mg/kg) suppressed urine excretion in hypophysectomized rats (P< 0.01), but only the 22 K-hGH isoform (2.0 mg/kg) suppressed urine excretion in intact rats (P< 0.01). In addition, prolactin (PRL) suppressed urine excretion in intact rats (P< 0.05). In conclusion, 20 K-hGH has less potency in causing urine retention than 22 K-hGH and since 20 K-hGH is missing 15 amino acids found in 22 K-hGH, these amino acids may be important for the antidiuretic action of GH. Since prolactin suppressed urine excretion, a part of the antidiuretic action of GH may be related to PRL-R activation.

Animals↗

PubMed2000

Combining regression trees and radial basis function networks.

We describe a method for non-parametric regression which combines regression trees with radial basis function networks. The method is similar to that of Kubat, who was first to suggest such a combination, but has some significant improvements. We demonstrate the features of the new method, compare its performance with other methods on DELVE data sets and apply it to a real world problem involving the classification of soybean plants from digital images.

Models, Statistical↗

PubMed2000

New approach for measurement of sympathetic nervous abnormality in conscious, spontaneously hypertensive rats.

We previously reported a highly sensitive chemiluminescence high-performance liquid chromatographic method to determine catecholamines in plasma. In this study, we employed this method to measure the cardiac function and plasma norepinephrine (NE) concentration in conscious rats. Benidipine, 1,4-dihydropyridine calcium antagonist (4 mg/kg), and beta-blocker (propranolol, 30 mg/kg) were administered orally to conscious spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) rats, and blood pressure, heart rate and plasma NE levels were measured. Plasma NE concentration was used as an index of sympathetic nervous system activity in conscious rats. The basal plasma NE levels were significantly higher in SHRs than in WKY rats (P<0.05), indicating the activity of the basal sympathetic nervous system in SHRs was elevated. The sensitivity of the baroreflex-mediated sympathetic nervous response was reduced in SHRs as compared to that in WKY rats. The concomitant administration of benidipine and a beta-blocker decreased heart rate without affecting the baroreflex-mediated sympathetic nervous response, indicating that propranolol might suppress mainly the cardiac beta-adrenoceptor. The present study suggested the high activity of the basal sympathetic nervous system and the reduced response of the baroreflex-mediated sympathetic nervous system in SHRs compared to WKY rats in the conscious condition.

Animals↗

PubMed1999

Potent antitumor activity of MS-247, a novel DNA minor groove binder, evaluated by an in vitro and in vivo human cancer cell line panel.

We synthesized a novel anticancer agent MS-247 (2-[[N-[1-methyl-2-[5-[N-[4-[N,N-bis(2-chloroethyl) amino] phenyl]] carbamoyl]-1H-benzimidazol-2-yl] pyrrol-4-yl] carbamoyl] ethyldimethylsulfonium di-p-toluenesulfonate) that has a netropsin-like moiety and an alkylating residue in the structure. We evaluated antitumor activity of MS-247 using a human cancer cell line panel coupled with a drug sensitivity database and subsequently using human cancer xenografts. The average MS-247 concentration required for 50% growth inhibition against a panel of 39 cell lines was 0.71 microM. The COMPARE analysis revealed that the differential growth inhibition pattern of MS-247 significantly correlated with those of camptothecin analogues and anthracyclins, indicating that MS-247 and the two drug groups might have similar modes of action. MS-247 exhibited remarkable antitumor activity against various xenografts. A single i.v. injection of MS-247 significantly inhibited the growth of all 17 xenografts tested, which included lung, colon, stomach, breast, and ovarian cancers. In many cases, MS-247 was more efficacious than cisplatin, Adriamycin, 5-fluorouracil, cyclophosphamide, VP-16, and vincristine and was almost comparable with paclitaxel and CPT-11; these are the most clinically promising drugs at present. MS-247 was noticeably more effective than paclitaxel (in HCT-15) and CPT-11 (in A549, HBC-4, and SK-OV-3). The toxicity of MS-247, indicated by body weight loss, was reversible within 10 days after administration. The MS-247 mode of action showed DNA binding activity at the site where Hoechst 33342 bound, inhibited topoisomerases I and II (as expected by the COMPARE analysis) blocked the cell cycle at the G2-M phase, and induced apoptosis. These results indicate that MS-247 is a promising new anticancer drug candidate to be developed further toward clinical trials.

Animals↗

PubMed1999

Simultaneous automatic determination of catecholamines and their 3-O-methyl metabolites in rat plasma by high-performance liquid chromatography using peroxyoxalate chemiluminescence reaction.

A highly specific and sensitive automated high-performance liquid chromatographic method for the simultaneous determination of catecholamines (CAs; norepinephrine, epinephrine, and dopamine) and their 3-O-methyl metabolites (normetanephrine, metanephrine, and 3-methoxytyramine) is described. Automated precolumn ion-exchange extraction of diluted plasma is coupled with HPLC separation of CAs and their 3-O-methyl metabolites on an ODS column, postcolumn coulometric oxidation, fluorescence derivatization with ethylenediamine, and finally peroxyoxalate chemiluminescence reaction detection. The detection limits were about 3 fmol for norepinephrine, epinephrine, and dopamine, 5 fmol for normetanephrine, and 10 fmol for metanephrine and 3-methoxytyramine (signal-to-noise ratio of 3). Fifty microliters of rat plasma was used and 4-methoxytyramine was employed as an internal standard. The relative standard deviations for the method (n = 5) were 2.5-7.6% for the intraday assay and 6.3-9.1% for the interday assay. The method was applicable to the determination of normetanephrine and metanephrine in 50 microl of rat plasma.

Animals↗

PubMed1998

Pulmonary cryptococcosis and pituitary Cushing's disease.

Pulmonary cryptococcosis was diagnosed by examining smears obtained by fine-needle aspiration (FNA) in a patient with pituitary Cushing's disease. FNA allowed for rapid diagnosis and prompt treatment of a potentially serious infection. The patient fully recovered from her pulmonary disease. Although opportunistic infections may occur in patients with endogenous Cushing's syndrome, it is rare to see such infections in the subset of patients with pituitary Cushing's disease. Hypercortisolism associated with Cushing's syndrome appears to induce a transitory immune deficiency state and opens a window of opportunity for certain infectious agents such as Cryptococcus neoformans to exploit. To our knowledge, this is the third such case reported in this clinical setting, and the first diagnosed by FNA.

Cryptococcosis↗

PubMed1998

Molecular characterization of Warthin tumor.

OBJECTIVE: Warthin tumor of the salivary gland is composed of oncocytic epithelium with a prominent follicular lymphoid infiltrate. The purpose of this study was to characterize the clonality of this lymphoid component by means of polymerase chain reaction technology. STUDY DESIGN: DNA was isolated from paraffin-embedded tissue from 20 cases of typical Warthin tumor of the salivary gland and amplified by polymerase chain reaction to assess B- and T-cell clonality. RESULTS: No dominant clonal populations were identified in any tumor. However, minor clonal expansions of both B and T cells were detected in up to 50% of tumors (immunoglobulin H, 50%; T-cell antigen receptor beta, 10%; T-cell antigen receptor gamma, 5%). No tumors showed evidence of bcl-2 proto-oncogene translocation, whereas 95% contained detectable Epstein-Barr virus DNA. CONCLUSION: The B- and T-cell components of Warthin tumor are polyclonal with oligoclonal expansion of both T and B cells in some lesions.

Adenolymphoma↗

PubMed1996

Roles of the suprachiasmatic nucleus and vasoactive intestinal peptide in the response of plasma arginine vasopressin to osmotic challenge.

To clarify the role of neurons containing a vasoactive intestinal peptide (VIP)-like substance (VIP neurons) in the hypothalamic suprachiasmatic nucleus (SCN) in regulation of the plasma arginine vasopressin (AVP) concentration, we examined the effects of bilateral lesions of the SCN and intracranial injection of VIP on the increase in the plasma AVP concentration caused by ip injection of hypertonic (3.6%) saline in rats. The increase in the plasma AVP concentration after ip injection of hypertonic saline was significantly suppressed in rats with bilateral lesions of the SCN. Furthermore, the increase in the plasma AVP concentration elicited by ip injection of hypertonic saline was enhanced by intracerebro-ventricular injection of VIP and suppressed by a VIP antagonist, [Lys1,Pro2,5,Arg3.4,Tyr6]VIP. However, the same dose of VIP injected into the heart had no effect on the increase in the plasma AVP concentration caused by ip injection of hypertonic saline. These results suggest that the SCN and intracranial VIP play important roles in the regulation of the plasma AVP concentration and support the possibility that VIP neurons in the SCN enhance the response of plasma AVP to osmotic challenge.

Animals↗

PubMed1995

Suppressive effect of vasopressin on the hyperglycemic response to intracranial injection of 2-deoxy-D-glucose.

Vasopressin (VP) is a peptide consisting of 9 amino acids which acts as a neurotransmitter or neuromodulator in the central nervous system. Neurons containing VP project to some nuclei in the hypothalamus that have a role in energy metabolism. To clarify the possible role of VP on glucose metabolism in the brain, we examined the effect of intracranial injection of VP on the hyperglycemia induced by 2-deoxy-D-glucose (2DG) and obtained the following results. The hyperglycemic and hyperglucagonemic responses induced by 2DG were significantly suppressed and enhanced by co-injections of VP and a VP-antagonist with 2DG, respectively. However, co-injections of either VP or a VP-antagonist with 2DG had no effect on the change in plasma insulin concentration. These findings suggest that central VP plays a suppressive role in the hyperglycemic and hyperglucagonemic responses to 2DG.

Animals↗

PubMed1995

Delirium in critical care unit patients admitted through an emergency room.

Two hundred thirty-eight patients admitted consecutively to a critical care unit through an emergency room were assessed prospectively for the presence of delirium. Thirty-eight patients (16%) developed delirium. Delirium occurred with equal frequency in all disease categories. The presence of abnormal head imaging which required medical intervention did not predict the development of delirium. The median delay between admission and the development of delirious was 4 days, however, one-fourth of the patients were delirious on the day of admission. The patients with abnormal head imaging who required medical intervention had a higher frequency of onset of delirium on the first day compared with patients without. The delirium lasted a median of 5 days and resolved within a week in over 70% of patients. These results confirm that delirium is frequently present in patients who require acute critical care after emergency room evaluation. In this population, serious medical disease is a better predictor of the development of delirium than the presence of abnormal brain imaging which required medical intervention. Although delirious patients have longer lengths of stay, the presence of delirium does not predict higher mortality, as has been reported in other populations. This could be because delirious patients admitted to the critical care unit through the emergency room have fewer premorbid medical problems predisposing them to poor outcome.

Adult↗

PubMed1995

Towards the development of a fluorescent in situ hybridization based genotoxicologic assay for aneuploidy detection in sperm.

Fluorescent in situ hybridization (FISH) is a molecular cytogenetic technique which allows an analysis of chromosome copy number in interphase cells. The cytological examination of spermatozoa is routinely performed as part of semen analysis. While this analysis is only a component of the evaluation of an infertile male, the aetiology of many cases of infertility remains unknown. FISH on semen smears can yield information on chromosome-specific aneuploidy due to constitutional and acquired chromosomal abnormalities as found with cancer or exposure to genotoxic substances. The ability to analyse germ cells directly is a useful adjunct to GTG-banding analysis of meiotic chromosomes, an invasive and extremely labour-intensive procedure. The work of 2 years in developing and optimizing a FISH-based assay in routinely processed semen smears is described.

Aneuploidy↗

PubMed1990

Antigenic and catalytic disparity in the distribution of cytochrome P-450-dependent 25-hydroxyvitamin D3-1 alpha- and 24-hydroxylases.

Chick 25-hydroxyvitamin D3-1 alpha-hydroxylase, a cytochrome P-450 monooxygenase with a molecular weight of 57 kDa, can be isolated as described by Mandel et al. (1990 b). Under normal physiological circumstances, it occurs exclusively in kidney mitochondria. An isozyme of the 1 alpha-hydroxylase, known as the 24-hydroxylase, which uses the same substrate to yield an isomeric product, is also a cytochrome P-450 monooxygenase, has a molecular weight of 55 kDa, and like-wise occurs in kidney mitochondria. The amino-terminal sequences of the first 10 residues of the two isozymes are 100% homologous. Monoclonal antibodies of the IgM class raised against the 1 alpha-hydroxylase, which quantitatively discriminate against other P-450 cytochromes of mitochondrial or microsomal origin, recognize and interact with the 24-hydroxylase as an antigen. In the present study we show that the intestine, which is the only non-renal tissue with demonstrable 24-hydroxylase activity, gives a positive peroxidase-antiperoxidase immunohistochemical reaction using the monoclonal antibodies against the 1 alpha-hydroxylase. The reactions revealed that the antigen in the kidney is restricted to the cortical proximal tubular cells while in the intestine, the antigen is localized in the enterocytes of the villi. In kidney medullary or intestinal crypt cells, or in liver, heart and lung tissues where 1 alpha-hydroxylase or 24-hydroxylase activity could not be detected using cell or tissue homogenates, the immunohistochemical reactions were also negative.(ABSTRACT TRUNCATED AT 250 WORDS)

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗

PubMed1989

Natriuretic effect of atriopeptin III in rats with papillary necrosis.

This study compared the effects of atriopeptin III (AP III) on sodium excretion and renal interstitial hydrostatic pressure (RIHP) in control rats and in rats pretreated with 2-bromoethylamine (BEA) to produce papillary necrosis. In control rats, infusion of AP III (100 ng.kg-1.min-1) increased sodium excretion from 2.2 +/- 0.7 to 6.4 +/- 0.9 microeq.min-1.g kidney wt-1 and RIHP from 6.8 +/- 0.7 to 8.7 +/- 0.9 mmHg, whereas glomerular filtration rate and renal blood flow were unaltered. Similar results were obtained in rats pretreated with BEA 48 h before the experiment. In rats studied 6 wk after BEA treatment, the papilla was absent and there was atrophy of juxtamedullary nephrons. AP III did not alter sodium excretion or RIHP in this group of rats. These results indicate that 1) an intact renal papilla and/or juxtamedullary nephron population may be required for the natriuretic effect of AP III; 2) the papillary injury 48 h after BEA is not sufficient to abolish the natriuretic response to AP III; and 3) elevations in RIHP may play a role in the natriuretic response to AP III.

Acetazolamide↗

PubMed1987

Atriopeptin III alters renal medullary hemodynamics and the pressure-diuresis response in rats.

The effects of atriopeptin III on the renal response to changes in renal perfusion pressure (RPP) were examined in uninephrectomized and adrenalectomized rats. Neural influences on the kidney were eliminated by renal denervation. Plasma levels of antidiuretic hormone (ADH), angiotensin II, aldosterone, corticosterone, and norepinephrine were controlled by intravenous infusion. Infusion of atriopeptin III at a dose of 30 or 100 ng X kg-1 X min-1 increased plasma levels of atrial natriuretic peptide from 101 +/- 8 pg/ml to 424 +/- 16 and 2,553 +/- 308 pg/ml, respectively. In control rats, increasing RPP in two steps from 100 to 125 to 150 mmHg produced sixfold increases in sodium and water excretion. The slopes of the relationships between fractional sodium and water excretion and RPP were enhanced by approximately 10, 20, and 40% in the rats infused with the 30, 100, and 500 ng X kg-1 X min-1 dose of atriopeptin III. Renal blood flow and glomerular filtration rate were not significantly different in vehicle- and atriopeptin III-infused rats at any RPP studied. Papillary blood flow measured with a laser-Doppler flowmeter increased 15% within the first 5 min of infusion of atriopeptin III at a dose of 100 ng X kg-1 X min-1. Cortical blood flow was not significantly altered. The rise in papillary blood flow during atriopeptin III infusion, however, may be a consequence and not the cause of the natriuresis and diuresis, since urine flow increased before significant changes in papillary blood flow were detected. These studies suggest that atrial natriuretic factor could influence the long-term control of arterial pressure by altering renal medullary hemodynamics and promoting the elimination of sodium and water. The plasma levels of atrial natriuretic peptide needed to alter the pressure-natriuresis relationship, however, may exceed levels that can be attained in vivo with endogenous release.

Animals↗