Search PubMed⌕ Search

Biomedical subjects

M Yamaguchi

Publications and source records attributed to M Yamaguchi.

At least 1,513 records · Page 84Linked to original sources
PubMed1986

Intraindividual changes in theophylline clearance during constant aminophylline infusion in children with acute asthma.

Intraindividual changes in theophylline clearance were examined in 13 children with acute exacerbation of asthma receiving a 72-hour constant intravenous infusion of aminophylline. The mean (+/- SD) first, second, and third clearances measured at 24, 48, and 72 hours after the infusion increased from 58.1 +/- 13.8 to 69.7 +/- 28.0 to 84.1 +/- 36.3 ml/hr/kg, respectively (P less than 0.02 from the first and P less than 0.05 from the second). Our results suggest that substantial intraindividual changes in theophylline clearance can occur over a rather short time during intravenously administered aminophylline therapy for acute asthma in children. We recommend that plasma theophylline concentrations be monitored frequently and that aminophylline infusion rate be adjusted on the basis of the measured theophylline concentration data during an acute episode of asthma in the pediatric patient.

Acute Disease↗
PubMed1986

Calcitonin action on ATP citrate lyase activity in the hepatic cytosol of fed rats and its calcium-calmodulin dependency.

The effect of calcitonin (CT) on ATP citrate lyase activity in the hepatic cytosol was investigated after a single subcutaneous administration of the hormone to fed rats. Administration of CT (synthetic [Asu107] eel CT; 80 MRC mU/100 g body weight) produced significant increases in ATP citrate lyase activity and calcium content in the hepatic cytosol of intact and thyroparathyroidectomized rats. Those alterations were also observed with the dose of CT at physiological level. The increased cytosolic ATP citrate lyase activity resulting from CT administration was prevented by treatment with 10 microM EGTA. This enzyme activity was restored by addition of calcium ion (2.5-10 microM). The rise in enzyme activity of CT-treated rats was markedly reduced by the presence of W-7 (10 and 100 microM), a calmodulin inhibitor, in the enzyme assay system, while that of control rats was not significantly altered by the drug. These results suggest that CT increases ATP citrate lyase activity in the hepatic cytosol of fed rats, and that this hormonal regulation may depend on calmodulin, and be mediated through raised calcium in the cytosol.

ATP Citrate (pro-S)-Lyase↗
PubMed1986

Calcitonin increases fatty acid synthetase activity dependently of calcium-calmodulin in the hepatic cytosol of fed rats.

The effect of calcitonin (CT) on fatty acid synthetase activity in the hepatic cytosol was investigated after a single subcutaneous administration of the hormone to fed rats. Administration of CT (synthetic [Asu1,7] eel CT; 80 MRC mU/100 g body weight) produced significant increases in fatty acid synthetase activity and calcium concentration in the hepatic cytosol of intact and thyroparathyroidectomized rats. The hormonal effect on the enzyme activity was not observed in rats fasted for 24 h. The increase in fatty acid synthetase activity by CT administration was completely inhibited by treatment with 10 microM EGTA. This enzyme activity was restored by addition of calcium ion (2.5-10 microM). The increased enzyme activity of CT-treated rats was markedly reduced by addition of W-7 (15 microM), a calmodulin inhibitor, in the enzyme assay system. Moreover, the cytosolic enzyme activity of normal rat liver was markedly raised by in vitro addition of both calcium ion (5 microM) and calmodulin (2.5 micrograms). These results suggest that CT increases fatty acid synthetase activity in the hepatic cytosol of fed rats, and that this hormonal regulation may depend on calmodulin, and be mediated through raised calcium in the cytosol.

Animals↗
PubMed1986

DNA binding site for a factor(s) required to initiate simian virus 40 DNA replication.

Efficient initiation of DNA replication in the absence of nonspecific DNA repair synthesis was obtained by using a modification of the system developed by J.J. Li and T.J. Kelly [(1984) Proc. Natl. Acad. Sci. USA 81, 6973-6977]. Circular double-stranded DNA plasmids replicated in extracts of CV-1 cells only when the plasmids contained the cis-acting origin sequence for simian virus 40 DNA replication (ori) and the extract contained simian virus 40 large tumor antigen. Competition between plasmids containing ori and plasmids carrying deletions in and about ori served to identify a sequence that binds the rate-limiting factor(s) required to initiate DNA replication. The minimum binding site (nucleotides 72-5243) encompassed one-half of the simian virus 40 ori sequence that is required for initiation of replication (ori-core) plus the contiguous sequence on the late gene side of ori-core containing G + C-rich repeats that facilitates initiation (ori-auxiliary). This initiation factor binding site was specific for the simian virus 40 ori region, even though it excluded the high-affinity large tumor antigen DNA binding sites.

Animals↗
PubMed1986

Distribution and Metabolism of sym-Homospermidine and Canavalmine in the Sword Bean Canavalia gladiata cv Shironata.

The unusual polyamines, sym-homospermidine (homoSPD) and canavalmine (CAN), were found in the seed of Canavalia species such as C. gladiata, C. ensiformis, and C. brasilensis, but not in those of other leguminous crops. To examine the distribution and metabolism of homoSPD and CAN in sword bean, C. gladiata cv Shironata, polyamine analysis was carried out throughout the life cycle of this plant. During seed germination, putrescine (PUT), spermidine (SPD), and spermine (SPM) were accumulated in the radicle and hypocotyl. HomoSPD and CAN were, however, maintained at very low levels over a 6-day period of germination. In nodulated sword bean plants, a large quantity of homoSPD was found in the root nodule. CAN was detected exclusively in the senescent nodule at very low concentrations. These polyamines were not detected in any other organs including root, stem, leaf, vine, flower, and pod, while PUT, SPD, and SPM were always found in those organs. As plants reached the reproductive stage, homoSPD and CAN appeared in the immature seed and their concentrations increased as seed formation progressed. By contrast, the level of SPM continuously decreased during seed development. In developing seeds, considerable accumulation of canavanine, an analog of arginine, which is a precursor in polyamine biosynthesis, was also observed.

Journal Article↗
PubMed1986

Fractionation and Estimation of Particle-Attached and Unattached Bradyrhizobium japonicum Strains in Soils.

Rhizobial cells attached or unattached to soil particles were estimated. Nonsterile soils into which antibiotic-resistant mutants of Bradyrhizobium japonicum had been introduced were fractionated by a centrifugation technique into two fractions: A, which contained mainly rhizobial cells attached to soil particles, and F, which contained mainly rhizobial cells unattached to them. Rhizobial counts decreased in both fractions during incubation of the soil at 30 degrees C, with a concomitant decrease in the proportion of the count of fraction F to that of fraction A. Sonication of fraction A of the soil incubated for more than 3 weeks caused an increase in the rhizobial count. The ratio of the count of fraction A estimated by the plant infection method to that estimated by the dilution plate method increased after 5 days of soil incubation. More than 90% of the indigenous rhizobia in an agricultural field existed in fraction A. These results suggest that the majority of rhizobial cells are attached to soil particles.

Journal Article↗
PubMed1986

Initiation of simian virus 40 DNA replication in vitro: aphidicolin causes accumulation of early-replicating intermediates and allows determination of the initial direction of DNA synthesis.

Aphidicolin, a specific inhibitor of DNA polymerase alpha, provided a novel method for distinguishing between initiation of DNA synthesis at the simian virus 40 (SV40) origin of replication (ori) and continuation of replication beyond ori. In the presence of sufficient aphidicolin to inhibit total DNA synthesis by 50%, initiation of DNA replication in SV40 chromosomes or ori-containing plasmids continued in vitro, whereas DNA synthesis in the bulk of SV40 replicative intermediate DNA (RI) that had initiated replication in vivo was rapidly inhibited. This resulted in accumulation of early RI in which most nascent DNA was localized within a 600- to 700-base-pair region centered at ori. Accumulation of early RI was observed only under conditions that permitted initiation of SV40 ori-dependent, T-antigen-dependent DNA replication and only when aphidicolin was added to the in vitro system. Increasing aphidicolin concentrations revealed that DNA synthesis in the ori region was not completely resistant to aphidicolin but simply less sensitive than DNA synthesis at forks that were farther away. Since DNA synthesized in the presence of aphidicolin was concentrated in the 300 base pairs on the early gene side of ori, we conclude that the initial direction of DNA synthesis was the same as that of early mRNA synthesis, consistent with the model proposed by Hay and DePamphilis (Cell 28:767-779, 1982). The data were also consistent with initiation of the first DNA chains in ori by CV-1 cell DNA primase-DNA polymerase alpha. Synthesis of pppA/G(pN)6-8(pdN)21-23 chains on a single-stranded DNA template by a purified preparation of this enzyme was completely resistant to aphidicolin, and further incorporation of deoxynucleotide monophosphates was inhibited. Therefore, in the presence of aphidicolin, this enzyme could initiate RNA-primed DNA synthesis at ori first in the early gene direction and then in the late gene direction, but could not continue DNA synthesis for an extended distance.

Animals↗
PubMed1986

Brain temperature in the rat midbrain reticular formation is regulated by bombesin and TRH.

We investigated the effects of intraventricular (ivt) injection of bombesin on the TRH-induced increase in temperature in the midbrain reticular formation (mrf) of the rat brain under pentobarbital anesthesia. Ivt injection of TRH in a dose of 3 nmol significantly antagonized the decrease in brain temperature induced by pentobarbital, and this antagonistic action of TRH was dose-related. Ivt injection of 3-300 pmol bombesin produced a dose-related decrease in brain temperature in response to 3 nmol TRH injection. The present data provide evidence that bombesin and TRH produce opposite actions on thermoregulation of the mrf in the rat.

Animals↗
PubMed1986

A quantitative analysis of reservoir function of the human pulmonary "venous" system for the left ventricle.

By definition, the pulmonary "venous" system consists of the pulmonary veins and the left atrium. The stiffness of the pulmonary "venous" (P'V') system and the left ventricle (LV) at the end of the slow filling period (at the point of pre-a) were estimated sequentially in a total of 26 patients, divided into a control group and mitral stenosis (MS), angina pectoris (AP), hypertrophic cardiomyopathy (HCM) groups. The stiffness (delta P/delta V) of the P'V' system was estimated from the pulmonary artery wedge (PAW) pressure tracings and the stroke volume. The stiffness (dP/dV) of LV was obtained from the pressure-volume (P-V) relationship of LV with a model of P = beaV. The present study is aimed primarily at obtaining factual information. The stiffness of the P'V' system was 0.063 +/- 0.022 mmHg/ml (mean +/- SD) in the control group and 0.052 +/- 0.006 mmHg/ml in the HCM group (p greater than 0.1). The stiffness of LV in diastole was 0.091 +/- 0.016 mmHg/ml in the control group and 0.199 +/- 0.056 mmHg/ml in the HCM group (p less than 0.01). The ratio of the stiffness of LV in diastole to that of the P'V' system was 1.6 +/- 0.6 in the control group and 3.8 +/- 0.7 in the HCM group. The volume elastic constant (a) of the P'V' system was 0.008 +/- 0.005 ml-1 in the control group and the values of (a) occupied a range of 0.007 to 0.008 ml-1 in the remaining 3 groups of patients. The values of (a) of LV were 0.011 +/- 0.004 ml-1 in the control group and 0.022 +/- 0.007 ml-1 in the HCM group (p less than 0.01). The present study suggests that the P'V' system is usually 2 to 3 times more complaint than LV in diastole. On the other hand, the P'V' system remained compliant in spite of the decreased compliance of LV in diastole in the HCM group, maintaining the reservoir function with which pulmonary edema is prevented.

Adolescent↗
PubMed1986

Pulmonary vein blood flow velocity waveform--with special reference to pulmonary "systolic runoff" in patients with atrial septal defect.

In order to evaluate the magnitude of pulmonary "systolic runoff", we studied the pulmonary vein blood flow velocity waveform by positioning a catheter-tip velocity-pressure transducer into the extraparenchymal pulmonary vein just distal to the left atrium. We recorded blood flow velocity and pressure simultaneously, and subsequently identified the zero blood flow velocity with blood flow velocity level of the pulmonary artery in diastole. Patients with atrial septal defect were used as subjects because of the technical ease although the altered hemodynamics were present. Two kinds of flow velocity waveforms were consistently demonstrated. One was a waveform of two peaks with the first peak in late systole and the second peak in early diastole (n = 9). The other was a waveform of one peak with a summit near the end of systole (n = 5). On the assumption that the blood flow velocity waveform obtained with this method is roughly equivalent to the flow volume waveform, we initiated the second study. The area encompassed between the actual flow velocity waveform and the line of zero flow velocity was divided into two compartments, i.e., ventricular systole (S) and diastole (D). The ratios of the area in systole to the sum of the areas in systole and diastole, i.e., (S)/[S) + (D], which are analogous to the pulmonary "systolic runoff", were 0.45 +/- 0.07 (mean +/- SD, n = 13). This suggests that about 40% of the right ventricular stroke volume flows into the pulmonary veins, the left atrium and a portion of the right atrium through the atrial septal defect during ventricular systole.

Adolescent↗
PubMed1986

The corrected collagen content in paraquat lungs.

Biochemical analysis of collagen in a fibrosing lung often betrays its collagen-rich appearance in histopathology. This is due to the liability of lung tissue to extreme change in weight or volume in the presence of edema, hemorrhage, or other lesions, producing a great error in the biochemical data obtained from it. On morphometry of arterial density in lung section, we established a method for calculating the degree to which a given lung is transformed from a standard state of expansion, according to which we may correct for the content of collagen per lung volume. This method was applied to 14 autopsy paraquat lungs with various grades of fibrosis. Increase in collagen was shown to begin at about the 20th day of intoxication and advance thereafter, a finding in good accordance with lung morphology. The longer the survival, the less uniform the intrapulmonary distribution of collagen; even a severely fibrosing lung retained non-fibrotic areas.

Adult↗
PubMed1986

Enhancement of vitamin D3 effect on bone metabolism in weanling rats orally administered zinc sulphate.

The interaction of vitamin D3 and zinc on bone metabolism was investigated in the femur of weanling rats. Oral administration of vitamin D3 (1.0 micrograms/100 g body weight) did not cause any increase in the zinc accumulation in the femoral tissue following treatment with zinc sulphate (1.0 mg Zn/100 g). Administration of vitamin D3 or zinc produced significant increases the alkaline phosphatase activity and DNA content of the femoral diaphysis but not of the epiphysis. The increase in alkaline phosphatase activity was enhanced additionally by simultaneous administration of vitamin D3 and zinc. Moreover, the increase in DNA content was enhanced markedly (about 4 times) by these treatments. At a dose of 0.5 micrograms of vitamin D3 per 100 g, DNA content was at the control level. This level was increased about 2 times by simultaneous administration of zinc (1.0 mg/100 g). The increase in alkaline phosphatase activity following simultaneous administration of vitamin D3 and zinc was significantly inhibited by treatment with cycloheximide, actinomycin D, or mitomycin C. Also, the increase in DNA content was completely inhibited by mitomycin C treatment. The present data suggest that the combination of vitamin D3 and zinc has a multiple effect on the stimulation of bone growth and mineralization in weanling rats, and that this effect is based on a stimulation of the DNA synthesis in bone cells.

Administration, Oral↗
PubMed1986

Antagonism by thyrotropin-releasing hormone of brain temperature in response to pentobarbital in the rat: possible involvement of cholinergic mechanism.

The effects of thyrotropin-releasing hormone (TRH) on brain temperature in response to pentobarbital were examined in male rats. After intraperitoneal injection of pentobarbital sodium (55 mg/kg body wt), the rats were fixed stereotaxically and received intraventricular (ivt) injection of varying doses (0.03-30 nmol) of TRH and 17 nmol atropine. Following the injection of 3 nmol TRH, 100 nmol of carbocholine was administered in the same manner. A thermocouple microprobe was unilaterally placed in the midbrain reticular formation so that brain temperature was continuously monitored at room temperature. Brain temperature after pentobarbital injection progressively decreased. While ivt injection of saline did not affect this change in temperature, ivt administration of TRH produced a dose-dependent antagonism of the brain hypothermia induced by pentobarbital. Atropine injection also reversed the pentobarbital-induced decrease in brain temperature. Carbocholine injection led to a significant decrease in brain temperature in response to TRH administration. The present study indicates that brain TRH may play a pivotal role in brain thermoregulation and its mechanism may involve at least in part the central cholinergic pathway in the rat.

Animals↗
PubMed1986

Assignment of the gene for human DNA polymerase beta (POLB) to chromosome 8.

A cloned cDNA segment of 442 bp which contains the region coding the N-terminal sequence of rat DNA polymerase beta polypeptide was used as a probe in Southern hybridization analysis to identify the gene for this enzyme. This probe hybridized with DNA from mouse and human in addition to rat DNA, and the BamHI fragment containing DNA polymerase beta gene sequence was unique in size in each species: 15.8 kb for rat DNA, 8.7 kb for mouse DNA and 10.1 kb for human DNA. DNA extracted from a panel of 12 independent human-mouse somatic cell hybrids was analyzed by Southern blot hybridization with the cloned cDNA probe. The results indicate that the gene for the human DNA polymerase beta sequence (POLB) is located on chromosome 8.

Animals↗