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Biomedical subjects

A Kobayashi

Publications and source records attributed to A Kobayashi.

At least 109 records · Page 6Linked to original sources
PubMed2000

Characterization of a novel member of the FGFR family, HrFGFR, in Halocynthia roretzi.

The cDNA for a novel member of the FGFR family, named HrFGFR, was isolated from a Halocynthia roretzi cDNA library prepared at the mid-tailbud stage. This cDNA was 3507b long, and the deduced amino acid sequence contained a motif characteristic of the vertebrate FGFRs. The existence of a single copy of the FGFR homologue gene in H. roretzi was suggested by restriction site analysis of multiple clones. HrFGFR mRNA was expressed strongly in the posterior region in the epidermis from the middle neurula stage. By contrast, Xenopus FGFR homologues are expressed in the anterior region and are known to induce anterior neural formation. A transition of the region expressing FGFR might have induced the more complicated brain or head formation characteristic of vertebrates.

Amino Acid Sequence↗
PubMed2000

Thermogenesis mediated by a capsaicin-sensitive area in the ventrolateral medulla.

Systemic administration of capsaicin elicits heat production, which can be observed in decerebrated preparations but is blocked by spinal transection. To identify the critical locus involved in the capsaicin-induced thermogenesis in the brainstem, we studied the effect of capsaicin on rats with bilateral electrolytic lesions in the premotor areas of sympathoadrenal preganglionic neurons. Lesions in the rostral ventrolateral medulla (RVLM), but not in other regions, largely attenuated the capsaicin-induced heat production. Unilateral microinjection of 30-100 nl capsaicin (0.5%, w/v) into the RVLM elicited a heat production response, whereas capsaicin injection in neighboring areas or vehicle injection into the RVLM did not affect heat production. These results suggest that the thermogenic effect of capsaicin is mediated, at least in part, by some capsaicin-sensitive structure in the RVLM.

Animals↗
PubMed2000

Cloning of a coproporphyrinogen oxidase promoter regulatory element binding protein.

Coproporphyrinogen oxidase [CPO] gene promoter regulatory element (CPRE) plays an important role in CPO gene regulation. To isolate a CPRE binding protein, we performed Southwestern screening of K562 cDNA expression library using CPRE as a probe and isolated a cDNA clone which encoded a novel protein, Klp1 (K562 cell-derived leucine-zipper-like protein 1). Klp1 mRNA was highly expressed in K562 cells, HeLa cells, and brain as a single transcript (1.4 kb). Gel mobility shift assays revealed that Klp1 specifically binds to CPRE. Computational analysis revealed that Klp1 has a leucine-zipper-like structure, a Leu-X-X-Leu-Leu motif, and a putative nuclear localization signal in the basic amino acid rich region. Transfection of the Klp1 expression vector into THP-1 cells resulted in transcriptional activation of a reporter construct containing CPRE. These results indicate that Klp1 is a DNA sequence-specific transcription factor that regulates gene expression of genes that contain CPRE in their regulatory region.

Adult↗
PubMed2000

Lim1 activity is required for intermediate mesoderm differentiation in the mouse embryo.

During gastrulation and early organogenesis, Lim1 is expressed in the visceral endoderm, the anterior mesendoderm, and the lateral mesoderm that comprises the lateral plate and intermediate mesoderm. A previous study has reported that kidneys and gonads are missing in the Lim1 null mutants (W. Shawlot and R. R. Behringer, 1995, Nature 374, 425-430). Results of the present study show that in the early organogenesis stage mutant embryo, the intermediate mesoderm that contains the urogenital precursor tissues is disorganized and displays diminished expression of PAX2 and the Hoxb6-lacZ transgene. When posterior epiblast cells of the Lim1 null mutant embryo were transplanted to the primitive streak of wild-type host embryos, they were able to colonize the lateral plate and intermediate mesoderm of the host, suggesting that Lim1 activity is not essential for the allocation of epiblast cells to these mesodermal lineages. However, most of the mutant cells that colonized the lateral and intermediate mesoderm of the host embryo did not express the Hoxb6-lacZ transgene, except for some cells that were derived from the distal part of the posterior epiblast. Lim1 activity may therefore be required for the full expression of this transgene that normally marks the differentiation of the lateral plate and intermediate mesoderm.

Animals↗
PubMed2000

Induction of aquaporin-4 water channel mRNA after focal cerebral ischemia in rat.

Aquaporin-4 (AQP4) is a member of a water-selective channel aquaporin-family and mainly expressed in the several structures of the brain and in the collecting duct of the kidney. Here we show its functional involvement in the water homeostasis of the ischemic brain. The expression of AQP4-mRNA is increased in the peri-infarcted cortex during the observation period ( approximately 7 days) after MCA-occlusion, maximally on day 3. The change corresponds to the generation and resolution of brain edema monitored by MRI. The signals for the mRNA are predominantly observed in glial cells in the molecular and outer granular layer of the peri-infarcted cortex. These results indicate that AQP4 plays a role in post-ischemic edema formation.

Animals↗
PubMed2000

Oxidative stress abolishes leptomycin B-sensitive nuclear export of transcription repressor Bach2 that counteracts activation of Maf recognition element.

The mammalian transcription activator Nrf2 plays critical roles in executing oxidative stress response by binding to the regulatory DNA sequence Maf recognition element. Bach2 is an Nrf2-related transcription repressor and a tissue-specific partner of the Maf oncoprotein family. We show here how Bach2 is regulated by an oxidative stress-sensitive conditional nuclear export. In cultured cells, Bach2 was localized in cytoplasm through its C-terminal evolutionarily conserved cytoplasmic localization signal (CLS). The CLS directed leptomycin B-sensitive nuclear export of reporter proteins, suggesting its dependence on the nuclear exporter Crm1/exportin 1. However, the CLS sequence does not bear a resemblance to the leucine-rich class of nuclear export signal, and mutagenesis analysis indicated that a stretch of nonhydrophobic amino acids is essential for its activity. Oxidative stressors aborted the CLS activity and induced nuclear accumulation of Bach2. Whereas oxidative stress is known to activate MARE-dependent transcription, overexpression of Bach2 in cultured cells silenced the inducibility of MARE. The results suggest that Bach2 mediates nucleocytoplasmic communication to couple oxidative stress and transcription repression in mammalian cells.

Amino Acid Sequence↗
PubMed2000

DNA aptamers that bind to chitin.

We have succeeded in the acquisition of DNA aptamers that recognize chitin using in vitro selection. The obtained DNA aptamers have the stem-loop or bulge loop structures with guanine rich loop clusters and the clockwise B-form stems.

Base Sequence↗
PubMed2000

FDG PET in the clinical evaluation of sarcoidosis with bone lesions.

We report a case of sarcoidosis with osseous involvement. Whole-body fluorine-18-fluorodeoxyglucose (FDG) PET scanning demonstrated multiple sites of FDG uptake in the hilar lymph nodes, right ulna, bilateral feet, and subcutaneous tissue of the extremities. FDG PET scanning provides useful information for the detection of sarcoidosis with systemic distribution, even when osseous lesions are included.

Adult↗
PubMed2000

The relation of fat-free mass to maximum exercise performance in patients with chronic obstructive pulmonary disease.

To assess the factors determining maximum exercise performance in patients with chronic obstructive pulmonary disease (COPD), we examined nutritional status with special reference to body composition and pulmonary function in 50 stable COPD patients. Nutritional status was evaluated by body weight and body composition, including fat mass (FM) and fat-free mass (FFM) assessed by bioelectrical impedance analysis (BIA). Exercise performance was evaluated by maximum oxygen uptake (Vo(2max)) on a cycle ergometer. A total of 50 patients (FEV(1) = 0.98 L) was divided randomly into either a study group (group A, n = 25) or validation group (group B, n = 25). Stepwise regression analysis was performed in group A to determine the best predictors of Vo(2max) from measurements of pulmonary function and nutritional status. Stepwise regression analysis revealed that Vo(2max) was predicted best by the following equation in group A: Vo(2max) (mL/min) = 10.223 x FFM (kg) + 4.188 x MVV (L/min) + 9.952 x DL(co) (mL/min/mmHg) - 127.9 (r = 0.84, p < 0. 001). This equation was then cross-validated in group B: Measured Vo(2max) (mL/min) = 1.554 x Predicted Vo(2max) (mL/min) - 324.0 (r = 0.87, p < 0.001). We conclude that FFM is an important factor in determining maximum exercise performance, along with pulmonary function parameters, in patients with COPD.

Aged↗
PubMed2000

Lack of integrative control of heat production and heat loss after capsaicin administration.

Body temperature is usually regulated by opposing controls of heat production and heat loss. However, systemic administration of capsaicin activates heat loss and heat production simultaneously. Because capsaicin receptors are located mainly on primary sensory neurons and body temperature is regulated by the central nervous system, we investigated the brain mechanisms involved in these capsaicin-induced thermal responses. For this purpose, we examined the effects of spinalization and decerebration on these responses in artificially ventilated, urethane-anesthetized rats. Cervical spinal transection largely attenuated both responses, showing the critical involvement of the brain. Colonic temperature (Tc) did not change after the capsaicin administration to the spinalized rats. Decerebration between the hypothalamus and midbrain prevented the capsaicin-induced heat loss and enhanced the capsaicin-induced heat production. Consequently, Tc increased without a hypothermic period. The results show that capsaicin activates brainstem-controlled heat production and forebrain-controlled heat loss separately.

Animals↗
PubMed2000

Clinical evaluation of sonoelasticity measurement in liver using ultrasonic imaging of internal forced low-frequency vibration.

The aim of this study is to evaluate liver elasticity noninvasively. We have already proposed an ultrasonic imaging system that can reconstruct vibration maps inside tissue under forced mechanical vibration. With this system, shear elastic properties of soft tissue can be evaluated as vibration velocities. Theoretically, these velocities increase with the increase of tissue elasticity. Sonoelasticity imaging was performed on 236 patients with chronic hepatitis and liver cirrhosis, and 50 healthy volunteers. The average of the velocities was 598.8 +/- 151.7 cm/s in healthy volunteers, 984.4 +/- 362.5 cm/s in chronic hepatitis and 1189.0 +/- 411.7 cm/s in liver cirrhosis. The average velocity of Child C group was statistically faster than those of Child A and B groups. Fibrotic rate from biopsy specimens statistically had the strongest positive correlation with velocities. With our system, the degree of liver fibrosis and function can be estimated objectively and noninvasively.

Adult↗
PubMed2000

Formate protects photosynthetic machinery from photoinhibition.

In plants, environmental adversity often leads to the formation of reactive oxygen species (ROS) because of excess light energy. We found that incubation of rice leaves under high light intensity together with CO2-depleted air seriously damaged photosynthesis; however, the application of potassium formate (2 mM) before the photoinhibitory treatment protected the photosynthesis of the plant from photoinhibition. Further analysis revealed that formate protects PSII, RuBisCO, and FBPase from photoinhibition. Formate is thought to be involved in endogenous radical scavenging and/or in the supply of CO2, derived from the formate, thereby reducing oxidative damage to the photosystems under photoinhibitory conditions.

Journal Article↗
PubMed2000

Formate dehydrogenase in rice plant: growth stimulation effect of formate in rice plant.

NAD-dependent formate dehydrogenase (FDH, EC 1.2.1.2.) plays a key role in the final step of the catabolism of methanol in methylotrophs. In certain plant species, this enzyme is a mitochondrial and NAD-dependent enzyme. In this study, the complete cDNA sequence of the rice (Oryza sativa cv Hinohikari) FDH gene, which contains an open reading frame (ORF) of 1128 bp, was determined. The sequence corresponds to a protein of 376 amino acids and shows strong homology to the NAD-dependent FDHs from other plants. Our experimental results showed that the expression of the rice cDNA in Escherichia coli induced FDH activity, indicating that the cDNA encodes a functional peptide of FDH. The application of formate to the roots of rice seedlings leads to growth increment both in terms of the length of the aerial part and the fresh weight. The FDH activity and the accumulation of FDH transcripts were strongly enhanced in the root portions of the formate-fed plants. This enhancement indicates that the transcriptional regulation which responds to formate functions in the rice plant, and that formate can act as an effective inducer for FDH activity.

Journal Article↗
PubMed2000

Antioxidative activity in the pericarp and seed of Japanese pepper (Xanthoxylum piperitum DC).

The antioxidative activity of the dried pericarp and seed of Japanese pepper was studied. The ethyl acetate extract from the pericarp and the methanol extract from the seed showed strong antioxidative activity against linoleic acid by the ferric thiocyanate and thiobarbituric acid (TBA) methods. Japanese pepper contained 3.9 and 2.9 mg/100 g of dry weight (dw) of tocopherols in the pericarp and seed, respectively, alpha-Toc in the former constituting 82% of total tocopherol and gamma-Toc in the latter constituting 96%. Arbutin and magnoflorine were isolated as antioxidants and their chemical structures determined by instrumental analyses. The contents of arbutin evaluated as the trifluoroacetate derivative by GC-MS were 35 and 3.0 mg/100 g of dw in the pericarp and seed, respectively. Magnoflorine was present only in the seed, and not in the pericarp. Both arbutin and magnoflorine exhibited antioxidative activity against linoleic acid and radical-scavenging activity against the DPPH radical.

Antioxidants↗
PubMed2000

Analysis of glycosidically bound aroma precursors in tea leaves. 1. Qualitative and quantitative analyses of glycosides with aglycons as aroma compounds.

Twenty-six synthetic glycosides constituting aglycons of the main tea aroma compounds ((Z)-3-hexenol, benzyl alcohol, 2-phenylethanol, methyl salicylate, geraniol, linalool, and four isomers of linalool oxides) were synthesized in our laboratory as authentic compounds. Those compounds were used to carry out a direct qualitative and quantitative determination of the glycosides as aroma precursors in different tea cultivars by capillary gas chromatographic-mass spectrometric (GC-MS) analyses after trifluoroacetyl conversion of the tea glycosidic fractions. Eleven beta-D-glucopyranosides, 10 beta-primeverosides (6-O-beta-D-xylopyranosyl-beta-D-glucopyranoside) with aglycons as the above alcohols, and geranyl beta-vicianoside (6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside) were identified (tentatively identified in the case of methyl salicylate beta-primeveroside) in fresh tea leaves and quantified on the basis of calibration curves that had been established by using the synthetic compounds. Primeverosides were more abundant than glucosides in each cultivar we investigated for making green tea, oolong tea, and black tea. Separation of the diastereoisomers of linalool and four isomers of linalool oxides by GC analyses is also discussed.

Calibration↗
PubMed2000

Isolation of novel glucosides related to gingerdiol from ginger and their antioxidative activities.

Two novel glucosides of 6-gingerdiol were isolated from fresh ginger (Zingiber officinale Roscoe). Their structures were determined as 1-(4-O-beta-D-glucopyranosyl-3-methoxyphenyl)-3,5-dihydroxydecane (1) and 5-O-beta-D-glucopyranosyl-3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)deca ne (2) by HRFAB-MS and NMR analyses, and the absolute configurations of both aglycons were identified as (3S,5S) by a comparison with synthetic compounds. After incubating these glucosides with acetone powder prepared from fresh ginger, they were confirmed to have been hydrolyzed to 6-gingerdiol by HPLC. This result suggests that these glucosides are the precursors or intermediates of 6-gingerdiol. To recognize their function, their antioxidative activities were investigated and compared to that of their aglycon, 6-gingerdiol, by a linoleic acid model system and by their DPPH radical-scavenging ability. Although 1 did not indicate any activity, 2 had as strong activity as the aglycon in both measurements.

Acetone↗
PubMed2000

Effect of particles and interface conditions on fibrous tissue interposition between bone and implant. A particle challenge model in rabbit.

Interposed fibrous tissue at bone-implant interfaces was quantitatively measured in the presence or absence of polyethylene (PE) or alumina particles. Three different conditions of the interface were designed by implanting a pre-polymerized polymethylmethacrylate (PMMA) plug (plug group), a doughy PMMA (injection group) and a hydroxyapatite (HA) plug (HA group) in the hole drilled at the intercondylar notch of rabbit knees. PE (170+/-18 microm) or alumina particles (88+/-26 microm) were repeatedly administered into the knee joints at one month intervals (six times). All animals were sacrificed seven months after the implantation. The bone-implant interface was histomorphometrically examined using undecalcified ground sections. In the plug group, the PE particles significantly increased the extent of the interposed fibrous tissue (p < 0.05), while the alumina particles showed no effect. In contrast, both particles showed no significant effects in the injection and the HA groups. These results indicate that both particle characteristics and conditions of the bone-implant interface affected particle-induced fibrous tissue interposition. The loose PMMA plug with PE particles induced the greatest amount of fibrous tissue interposition.

Journal Article↗