PubMed Health⌕ Search

Biomedical subjects

N Sugimoto

Publications and source records attributed to N Sugimoto.

At least 19 recordsLinked to original sources
PubMed1995

Thermodynamic parameters to predict stability of RNA/DNA hybrid duplexes.

The thermodynamic parameters (delta H degree, delta S degree, and delta G degree 37) for 16 nearest-neighbor sets and one initiation factor are presented here in order to predict stability of RNA/DNA hybrid duplexes. To determine the nearest-neighbor parameters, thermodynamics for 68 different hybrid sequences (136 single-stranded oligonucleotides) with 5-13 nucleotide length including several duplexes with identical nearest-neighbors were measured by UV melting procedure. These sequences were selected to have many different combinations of nearest-neighbor pairs, and so that the number of the 16 nearest-neighbor sequences in the oligomers were as equal as possible. The structures of the hybrids were also investigated by measuring circular dichroism spectra. Comparing delta G degree 37 values of the hybrids with DNA/DNA and RNA/RNA parameters reported previously (Breslauer, K.J., Frank, R., Blöcker, H., & Marky, L.A. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 3746-3750; Freier, S.M., Kierzek, R., Jaeger, J.A., Sugimoto, N., Caruthers, M.H., Neilson, T., & Turner, D.H. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 9373-9377), RNA/RNA double helix is the most stable of the three kinds of helixes with the same nearest-neighbor sequences. Which is more stable between DNA/DNA and RNA/DNA hybrid duplexes depends on its sequence. Calculated thermodynamic values of hybrid formation with the present parameters reproduce the experimental values within reasonable errors.

Base Sequence↗
PubMed1995

Female reproductive properties and prenatal development of a senescence-accelerated mouse strain.

Female reproductive properties, early embryonic development, and serum estradiol and progesterone levels of the senescence-accelerated mouse (SAM)-prone (SAM-P) strain were compared with those of a SAM-resistant (SAM-R) strain. The reproductive life span of SAM-P (from 11.4 to 25.0 weeks old) was shorter than that of SAM-R (11.1 to 41.6 weeks old), and the total number of SAM-P pups was 41.7% less than from SAM-R. The reproductive senescence of SAM-P is more accelerated than that of SAM-R. At 15 weeks old, the maximum litter size of SAM-P was noted and was 33.7% smaller than that of SAM-R. Although no differences in the numbers of ovulated and fertilized ova were observed between two strains, the number of implants in SAM-P was 21.6% less than in SAM-R. Cell cleavage was delayed in embryos of SAM-P (8% morula, at day 2 of pregnancy) compared to SAM-R (48%). At day 3 of pregnancy, 9% and 33% of the embryos were blastocysts in SAM-P and SAM-R, respectively. At day 1 of pregnancy, serum estradiol level in SAM-P was 18.2% higher than in SAM-R, whereas the serum progesterone level in SAM-P was 46.2% lower than in SAM-R. The unbalance of estradiol and progesterone levels in SAM-P was considered to be the cause of the delay in early embryonic development, and then the decrease of implantation and a smaller litter size.

Aging↗
PubMed1995

Influence of alpha-deoxyadenosine on the stability and structure of DNA. Thermodynamic and molecular mechanics studies.

The alpha anomer of deoxyadenosine (alpha) and an abasic site (tetrahydrofuran, F), which are DNA lesions produced by free radicals, were site-specifically incorporated in 9-mer duplexes d(TGAGXGTAC).d-(GTACNCTCA), where X = alpha or F and N = A, G, C, or T. Their influence on thermodynamic stability and structure of DNA was assessed by UV-melting measurements and molecular mechanics calculations. UV-melting studies revealed that a duplex containing an alpha T pair was as stable as the parental duplex containing an AT pair at the same site. Furthermore, the stability of duplexes containing alpha varied depending on the base opposite this lesion, with the Tm decreasing in the following order: alpha T > alpha C approximately alpha A > alpha G. On the contrary, an abasic site introduced in the same site showed a significantly greater destabilizing effect than alpha, but variation of Tm with the bases opposite F was less evident. To delineate the molecular mechanism of thermodynamic effects of an alpha lesion, molecular mechanics calculations were performed for the same duplexes as used for UV-melting measurements. The results suggest that the structural perturbation introduced into DNA by an alpha N pair is alpha G > alpha A > alpha C > alpha T, showing a parallel correlation with the destabilizing effects of alpha N pairs. On the basis of these results, it is discussed how the perturbations introduced by these DNA lesions may influence the selection of nucleotides opposite the lesions by DNA polymerases and the interaction with DNA repair enzymes such as Escherichia coli endonuclease IV and exonuclease III.

Base Sequence↗
PubMed1995

Shifts of thermoeffector thresholds in heat-acclimated rats.

1. Heat-acclimated (HA) rats, kept under a 12:12 h light-dark regime, were subjected to an ambient temperature (Ta) of 33 degrees C for 5 h in the last half of the dark phase for 3 weeks. Control rats were kept under a 12:12 h light-dark regime at a constant Ta of 24 degrees C. 2. After the acclimation period, the rats were then placed in a metabolic chamber at a Ta of 26.5 degrees C, and body core temperature was gradually increased and decreased using an intravenous thermode. Thermoeffector thresholds were determined by the hypothalamic temperature (T(hy)) at the onset of warm-induced tail skin vasodilatation and cold-induced thermogenesis measured by oxygen consumption. 3. Each rat was subjected to the experiment twice, once in the first half and once in the last half of the dark phase, on different days in random order. 4. In HA rats, T(hy) at the onset of both skin vasodilatation and thermogenesis were significantly lower in the last half of the dark phase compared with the first half. In control rats, however, there were no such differences between the two halves. 5. The results suggest that in rats acclimated to daily heat exposure, thermoeffector thresholds shift to lower temperatures only during the period of day when the rats had previously been exposed to heat.

Adaptation, Physiological↗
PubMed1995

On the mechanism of preferential incorporation of dAMP at abasic sites in translesional DNA synthesis. Role of proofreading activity of DNA polymerase and thermodynamic characterization of model template-primers containing an abasic site.

DNA polymerase preferentially incorporate dAMP opposite abasic sites (A-rule). The mechanism of the A-rule can be studied by analyzing three dissected stages of the reaction including (i) initial nucleotide insertion, (ii) proofreading excision of the inserted nucleotide and (iii) extension of the nascent primer terminus. To assess the role of the stage (ii) in the A-rule, kinetic parameters of the proofreading excision of primer terminus nucleotides opposite abasic sites were determined using E.coli DNA polymerase I Klenow fragment. The relative efficiency of the excision (Vmax/Km) revealed that removal of A was the least favored of the four nucleotides, but the differences in the efficiencies between excision of A and the other nucleotides was less than 2-fold. In addition, in an attempt to reconcile kinetic data associated with the stage (i) or (ii), the differences in free energy changes (delta delta G degrees) for the formation of model template-primer termini containing XN pairs (X = abasic site, N = A, G, C or T) were determined by temperature dependent UV-melting measurements. The order of delta delta G degrees was XG > XA = XC > or = XT, with delta delta G degrees being 0.5 kcal/mol for the most stable XG and the least stable XT. Based on these data, the role of the stage (ii) and energetic aspects of the A-rule are discussed.

Base Sequence↗
PubMed1995

The enterotoxin of Clostridium perfringens type A binds to the presynaptic nerve endings in neuromuscular junctions of mouse phrenic nerve-diaphragm.

The enterotoxin of Clostridium perfringens type A, a channel-pore forming protein toxin, inhibited neuromuscular transmission in isolated mouse phrenic nerve-diaphragm preparation at low concentrations of calcium. We investigated immunohistochemically the localization of the binding sites of the enterotoxin in the preparation under the conditions in which the enterotoxin reduced maximally the amplitudes of the twitch tension elicited by electrical stimulations to the phrenic nerve. Under the conditions, double immunohistochemical staining of the preparation with (1) rabbit anti-enterotoxin IgG-rhodamine-labeled goat anti-rabbit IgG and (2) mouse anti-synaptophysin (one of the synaptic vesicle-specific membrane proteins)-fluorescein isothiocyanate (FITC)-labeled goat anti-mouse IgG showed that the enterotoxin binds specifically to most of the sites which were stained with anti-synaptophysin exactly in the same configurations having the shapes of the nerve endings in the endplates. The thin section electron micrographs of the enterotoxin-intoxicated preparation showed no alterations in the ultrastructure of the neuromuscular junction and the nerve endings filled with numerous synaptic vesicles. The present results, together with our previous electrophysiological findings, indicate that the enterotoxin binds specifically to the presynaptic nerve endings and inhibits neurotransmitter release at the neuromuscular junction.

Animals↗
PubMed1995

Effect of digital nerve blockade on heat-induced vasoconstriction in the human finger.

The present study was performed to investigate the mechanism of heat-induced vasoconstriction (HIVC) in human fingers. The left fingers of five male subjects were immersed in water controlled at an initial temperature of 35.0 degrees C. The blood flows (BF) of the left index and fourth fingers were measured continuously with laser-Doppler flowmeter probes, and the temperatures of the middle finger and water bath were also monitored continuously using thermistor probes. Arterial blood pressure and heart rate were measured every minute before and during local finger warming. A local anesthetic (0.5% bupivacaine hydrochloride) or saline at a volume of 5.0-8.0 ml was aseptically injected into the base of the fourth or index finger, respectively. After finger BFs had been stabilized for > or = 10 min, the fingers were warmed by raising the water bath temperature from 35.0 to 41.5 degrees C in 14 min. The BF of the index finger fell significantly for 6 min after local warming was commenced (at water bath temperatures between 35.5 and 37.5 degrees C) without associated changes in mean arterial blood pressure, indicating the occurrence of HIVC. Then BF increased toward prewarming levels. The local anesthetic injection, however, completely abolished HIVC in the fourth finger. These results suggest that, in humans, innervation to finger vessels is indispensable for producing HIVC and hence that a local mechanism, such as myogenic vascular response to high temperature, may not be involved in the induction of HIVC.

Blood Pressure↗
PubMed1995

Thermoregulatory responses of rats acclimated to heat given daily at a fixed time.

Body core temperature of rats acclimated to heat given daily at a fixed time falls during the previous heat exposure time. In the present study, thermoregulatory responses of heat-acclimated rats were examined during the specific period. Heat-acclimated rats were subjected to an ambient temperature of 32 degrees C for approximately 5 h in the first half or last half of the dark phase for 14 days while control rats were kept at 24 degrees C. Then the rats were placed in a direct calorimeter and were warmed for 30 min with an intraperitoneal electric heater. Measurements were made twice in the first and last halves of the dark phase. Body warming significantly increased body core temperature in all rats. In the heat-acclimated rats, heat production (M) was significantly depressed during the previous heat exposure time but not during the other period. Body warming had little effect on M in the control rats during either period. The results suggest that rats acclimated to heat given at a fixed time daily respond to an acute heat load with a pronounced reduction of M. However, such a response was observed only during the period when the rats had been previously exposed to heat.

Acclimatization↗
PubMed1995

Bordetella bronchiseptica dermonecrotizing toxin stimulates assembly of actin stress fibers and focal adhesions by modifying the small GTP-binding protein rho.

We studied the biochemical mechanism of morphological changes in cells treated with Bordetella dermonecrotizing toxin (DNT). DNT caused the morphological changes of serum-starved MC3T3-E1 cells from flat shapes to reflactile ones. These changes were accompanied by the assembly of actin stress fibers and focal adhesions, which is known to be regulated by the small GTP-binding protein rho. Clostridium botulinum C3 exoenzyme, which ADP-ribosylates and inactivates rho protein, 'rounded' the cells within 2 hours after addition to the extracellular fluid and their rounded shapes were maintained for at least 10 hours. However, when the cells were co-treated with C3 exoenzyme and DNT, they were rounded at 2 hours but recovered an apparently intact morphology after 3-8 hours of incubation. rho proteins in lysates from DNT-treated cells and untreated cells were radiolabeled by [32P]ADP-ribosylation with C3 exoenzyme and analyzed by SDS-polyacrylamide gel electrophoresis. Whereas the lysate from untreated cells showed a single band of [32P]ADP-ribosylated rho protein, the lysate from DNT-treated cells showed an additional two bands as well as the band identical to that of the lysate from untreated cells. Recombinant rhoA protein treated with DNT in vitro also showed a mobility shift in SDS-polyacrylamide gel electrophoresis. These results indicate that DNT causes the assembly of actin stress fibers and focal adhesions by directly modifying rho protein.

ADP Ribose Transferases↗
PubMed1995

Mobility inhibition and nematocidal activity of asarone and related phenylpropanoids on second-stage larvae of Toxocara canis.

The in vitro effect of asarone, the nematocidal principle of the rhizome of Acorus calamus, on second-stage larvae of Toxocara canis is composed of two independent actions: one is a fast acting inhibition of the larval mobility and the other is a slow acting larvicidal action. Mobility of the larvae was rapidly inhibited when they were incubated with asarone. Dye exclusion assay revealed that larvae were alive at this stage, and their mobility was restored after the first inhibition, suggesting that this effect was temporary and reversible. However, when the mobility decreased again during prolonged incubation, the cellular viability of larvae disappeared, showing that they were killed by the compound. The above two-stage effect of asarone was almost identical in two geometrical isomers ((E)- and (Z)-asarone). Di- and tri-methoxypropenyl or propylbenzenes carrying two methoxy groups at a vicinal position on a benzene ring showed, more or less, a two-stage effect of this type. These two actions were suggested to be separable by an appropriate modification of the structure.

Allylbenzene Derivatives↗
PubMed1995

[A case of productive aspergilloma on the inner wall of a cavity, in which perbronchial fiberoptic bronchoscopy within the cavity was useful for the diagnosis and therapeutic evaluation].

A 45-year-old man complaining of bloody sputum was admitted. He had been treated for pulmonary tuberculosis since October 1988. He had bloody sputum in October 1989. His chest X-ray findings showed a cavitary lesion with a thickened and irregular wall in the right upper lobe. Fiberoptic bronchoscopy revealed white nodules on the cavity wall and the biopsy specimen from the nodule yielded a fungus granuloma. Aspergillus fumigatus was cultured from the sputum obtained after the bronchoscopy. Based on these findings, endobronchial aspergillosis and productive aspergilloma on the inner wall of a cavity was diagnosed. He was treated with oral anti-fungal drugs for 4 years. On chest X-ray films taken in June 1993, the cavity had enlarged, and the thickening and irregularity of the cavity wall had disappeared. Transbronchial fiberoptic bronchoscopy within the cavity showed whitish nodules and the cytology specimen obtained from the nodules by brushing yielded fungi, he was treated with oral itraconazol. Six months later, re-examination of the cavity revealed that the wall had become thinner and that the nodules on the inner wall had disappeared. This case illustrates the importance of bronchoscopy, in the diagnosis and evaluation of treatment of productive aspergilloma on the inner wall of a cavity.

Administration, Oral↗
PubMed1994

RNA/DNA hybrid duplexes with identical nearest-neighbor base-pairs have identical stability.

Energetic behaviors of eight pairs of RNA/DNA hybrid duplexes with identical nearest neighbors have been investigated by UV melting analysis. In the pairs with identical nearest-neighbor pairs, the melting curve traces at the same strand concentration were very similar. The average difference in stabilization energy of these pairs was 4%, which was about expected within experimental error. These results indicate that the nearest-neighbor model is valid for predicting the stability of RNA/DNA hybrid duplexes as well as RNA/RNA and DNA/DNA duplexes.

Base Composition↗
PubMed1994

Bordetella bronchiseptica dermonecrotizing toxin stimulates protein synthesis in an osteoblastic clone, MC3T3-E1 cells.

The effects of Bordetella bronchiseptica dermonecrotizing toxin on protein synthesis in an osteoblastic clone, MC3T3-E1 cells, were investigated. The rate of protein synthesis in the serum-starved cells was increased by the toxin after a latent period of about 4 h, and reached 2.5 times that of the control 24 h after addition of toxin. The toxin raised the level of protein synthesis even in actively proliferating cells. The stimulatory effect of the toxin on protein synthesis occurred earlier than other toxic events so far reported, such as the stimulation of DNA synthesis and the inhibition of osteoblastic differentiation, and was apparently dependent on the toxin concentrations over the range 0.05 ng ml-1 to 6.0 ng ml-1. Therefore, the stimulatory effect of the toxin on protein synthesis could be useful in determining the mode of action of the toxin.

Animals↗
PubMed1994

Changes in hypothalamic temperature of rats after daily exposure to heat at a fixed time.

Rats were subjected to an ambient temperature (Ta) of 33 degrees C for ca. 5 h during the last half of the dark phase for 5, 14 or 28 consecutive days (heat-exposed rats, HE), while control rats were kept at a constant Ta of 24 degrees C. After the heat exposure schedule, the levels of hypothalamic temperature (T(hy)) as an index of body core temperature in the HE were significantly lower than those of the controls for 2-4 h in the last half of the dark phase. The low levels of T(hy) persisted during the specific period for 1, 3 and 6 days after the end of the 5-, 14- and 28-day heat exposure schedules, respectively. These results confirm that, in rats subjected to daily heat exposure for ca. 5 h at a fixed time per day, their T(hy) falls during the period when the rats were previously exposed to heat, and suggest that the duration of the specific T(hy) change observed after completing the heat exposure schedule depends on the length of the heat exposure schedule.

Animals↗
PubMed1994

A new method for automatic identification of coronary arteries in standard biplane angiograms.

A new computerized method for analyzing biplane coronary arteriograms was proposed. The method extracted the vessels in an image, detected branching points, and identified vessel segments according to their anatomical names. The method was applied to a pair of orthogonal projection images acquired in the right anterior oblique and left anterior oblique views. It recognized the corresponding vessel segments in the images and labeled them correctly by their anatomical names. For diameter measurement, a combined first and second derivative filter process was applied to the images along the skeleton lines of the extracted vessel segments. We also designed a method of representation in which vessel diameters measured in the two projection images could be displayed in a single image.

Cineangiography↗
PubMed1994

Limitation of detection and evaluation of coronary arterial stenosis by densitometry.

In coronary cineangiography, both X-ray absorption and light scatter in the image intensifier tend to degrade image quality, and so affect the accuracy of densitometric measurement of vessel diameter. To investigate this problem, we compared the accuracy and precision of the densitometric method and the edge detection method in the automated detection of stenosis in both vessel phantom and clinical studies. In the phantom study, the X-ray penetration was varied by altering the thickness of the model, and the change in the measured diameter obtained by each of the two methods was evaluated simultaneously. A difference of 5 mm in the thickness of the model was found to alter significantly (P < 0.01) measurement of the diameter obtained using the densitometric method, but not that obtained by the edge detection method. In the clinical part of the study, the accuracy of each method in the automated detection of coronary stenosis was evaluated. With respect to the detection of stenosis, the level of disagreement between the assessment of the 3 observers and what was detected by densitometry (22.8%) was 2.9 times higher than the disagreement between the observers' assessment and what was detected using the edge detection method (7.9%). When the background density of the coronary cineangiogram along the axis of the vessel was uneven, many vessel segments which had been evaluated as normal when edge-detection was used were evaluated as stenosed when densitometry was used. This study, then, demonstrates that the Lambert-Beer law does not apply in cases where the thickness of the subject varies in different locations along the axis of the same vessel. We therefore conclude that densitometry is not a reliable means of assessing coronary stenosis in such cases, due to veiling-glare and scatter, and recommend that it not be routinely used in the automated detection of coronary arterial stenosis.

Absorptiometry, Photon↗