Search PubMed⌕ Search

Biomedical subjects

A Yoshida

Publications and source records attributed to A Yoshida.

At least 163 records · Page 9Linked to original sources
PubMed2000

Changes in blood-retinal barrier permeability in form deprivation myopia in tree shrews.

To study the correlation between blood-retinal barrier (BRB) permeability and development of form deprivation (FD) myopia, FD was induced in tree shrews. The refractive error and the axial dimensions of the optical elements were measured. Ocular fluorescence was measured before and after fluorescein-Na injection. The inward permeability (P(in)) of the BRB was measured before and 15, 30, and 45 days after FD was induced. FD eyes became significantly myopic 15 days after FD was induced (P<0.01), and myopia progressed 45 days after FD was induced compared with untreated controls. Neither anterior chamber length nor lens thickness changed significantly. The vitreous chamber in FD eyes, however, was significantly elongated from 15 days after FD was induced (P<0.01) compared with controls. The P(in) ratio (P(in) [FD eye]/P(in) [untreated control]), increased significantly 45 days after FD was induced (P<0.05). In FD myopia in tree shrews, the BRB permeability increases abnormally. Impaired BRB function might be a secondary effect of myopia development rather than the cause of myopia.

Animals↗
PubMed2000

Transforming growth factor-alpha, epidermal growth factor receptor, and PCNA immunoexpression in uterine leiomyosarcomas and leiomyomas in B6C3F1 mice.

The role of growth factors in the development of murine uterine mesenchymal tumors is unknown. In this study, immunohistochemical expression of transforming growth factor alpha (TGF-alpha) and its receptor epidermal growth factor (EGF-R) was assessed in spontaneous uterine leiomyomas and leiomyosarcomas in B6C3F1 mice. Cell proliferation, which has been induced by some growth factors, was evaluated by immunohistochemical detection of an endogenous marker of cell proliferation, proliferating cell nuclear antigen (PCNA). PCNA labeling indices were determined and compared to the intensity and distribution of TGF-alpha staining in sequential sections of control myometrium or tumor tissue. Results showed uterine leiomyosarcomas had positive cytoplasmic staining for TGF-alpha; however, all uterine leiomyomas evaluated were negative. Positive EGF-R staining was also observed in the uterine leiomyosarcomas, but not in the leiomyomas. EGF-R immunoexpression was detected primarily within the cytoplasm of the leiomyosarcoma cells, with occasional nuclear immunoreactivity. Immunohistochemical staining for PCNA was more intense and there were increased numbers of positively staining nuclei in the leiomyosarcomas compared to samples of control myometrium or leiomyomas. The mean labeling index for the uterine leiomyosarcomas (7.40%) was significantly (p < 0.01) higher than that of leiomyomas (0.29%) and control uterine myometrium (0.13%). We conclude, that TGF-alpha and its receptor, EGF-R, are expressed more intensely in uterine leiomyosarcomas, compared to leiomyomas in B6C3F1 mice. Immunoexpression of TGF-alpha may be an important biomarker of malignancy in uterine smooth muscle tumors in mice. Futhermore, TGF-alpha may play a critical role in increased proliferation of uterine smooth muscle tumor cells as suggested by increased immunolocalization of PCNA in rodent leiomyosarcomas expressing TGF-alpha, although other factors regulating cell replication can not be ruled out.

Animals↗
PubMed2000

Apolipoprotein A-I gene expression is upregulated by polychlorinated biphenyls in rat liver.

Xenobiotics such as polychlorinated biphenyls (PCB) increase serum cholesterol level (especially high density lipoprotein cholesterol) and apolipoprotein A-I (apo A-I) level in rats. The effect of PCB on serum apo A-I and hepatic apo A-I gene expression and the relationship between apo A-I and drug-metabolizing enzymes in rats were investigated. Serum levels of cholesterol and apo A-I were increased by dietary addition of PCB in a dose-dependent manner (0-500 mg/kg diet). Hepatic apo A-I mRNA level was also elevated by PCB in a similar fashion. Serum level of cholesterol gradually increased during feeding period of PCB (200 mg/kg diet, 105 days) and reached a two-fold higher level in PCB group than in controls. The levels of serum apo A-I and hepatic apo A-I mRNA linearly elevated during feeding period of PCB and were increased 3- or 4-fold, respectively, compared to controls. Although acute administration (16 hr) of PCB, 3-methylcholanthrene, and phenobarbital induced cytochrome P-450 gene expression in the liver, hepatic apo A-I gene expression was not increased by these xenobiotics. These results indicated that the serum levels of cholesterol and apo A-I had positive correlation with hepatic level of apo A-I mRNA in rats fed PCB, and that hepatic apo A-I gene expression was dependent upon intake of PCB but was not directly related to the induction of drug-metabolizing enzymes. This study demonstrated that xenobiotic-induced hyper-alpha-cholesterolemia would be caused by the increased apo A-I gene expression and cholesterol synthesis in the liver, coordinately.

Journal Article↗
PubMed2000

Precise measurements of the gamma-ray emission probabilities of 186Re and 188Re.

Gamma-ray emission probabilities of 186Re and 188Re are important in nuclear medicine, and have been precisely measured by 4pibeta-gamma coincidence using a live-timed two-dimensional data-acquisition system. The gamma-ray emission probabilities of the 137.2 keV for 186Re and 155.1 keV for 188Re were 0.09487+/-0.00029 and 0.15425+/-0.00072, respectively.

Gamma Rays↗
PubMed2000

The role of the cleavage site 2'-hydroxyl in the Tetrahymena group I ribozyme reaction.

BACKGROUND: The 2'-hydroxyl of U preceding the cleavage site, U(-1), in the Tetrahymena ribozyme reaction contributes 10(3)-fold to catalysis relative to a 2'-hydrogen atom. Previously proposed models for the catalytic role of this 2'-OH involve coordination of a catalytic metal ion and hydrogen-bond donation to the 3'-bridging oxygen. An additional model, hydrogen-bond donation by the 2'-OH to a nonbridging reactive phosphoryl oxygen, is also consistent with previous results. We have tested these models using atomic-level substrate modifications and kinetic and thermodynamic analyses. RESULTS: Replacing the 2'-OH with -NH(3)(+) increases the reaction rate approximately 60-fold, despite the absence of lone-pair electrons on the 2'-NH(3)(+) group to coordinate a metal ion. Binding and reaction of a modified oligonucleotide substrate with 2'-NH(2) at U(-1) are unaffected by soft-metal ions. These results suggest that the 2'-OH of U(-1) does not interact with a metal ion. The contribution of the 2'-moiety of U(-1) is unperturbed by thio substitution at either of the nonbridging oxygens of the reactive phosphoryl group, providing no indication of a hydrogen bond between the 2'-OH and the nonbridging phosphoryl oxygens. In contrast, the 10(3)-fold catalytic advantage of 2'-OH relative to 2'-H is eliminated when the 3'-bridging oxygen is replaced by sulfur. As sulfur is a weaker hydrogen-bond acceptor than oxygen, this effect suggests a hydrogen-bonding interaction between the 2'-OH and the 3'-bridging oxygen. CONCLUSIONS: These results provide the first experimental support for the model in which the 2'-OH of U(-1) donates a hydrogen bond to the neighboring 3'-bridging oxygen, thereby stabilizing the developing negative charge on the 3'-oxygen in the transition state.

Animals↗
PubMed2000

Regulation of cell cycle and apoptosis by human immunodeficiency virus type 1 Vpr.

Biological effects of HIV-1 Vpr on CD4(+) cells were studied by an infection system. High-titered HIV-1 stocks pseudotyped with vesicular stomatitis virus G protein were prepared and used to inoculate into CD4(+ )T cells at high multiplicity of infection. Both cell- and virion-associated Vpr were demonstrated to arrest the cell cycle at the G2/M phase, and to induce cell apoptosis. Of note, morphologically apoptotic cells were shown to be arrested at the G2/M stage. No appreciable effect of Vpr on the anti-Fas antibody-mediated apoptosis was observed in this system.

Apoptosis↗
PubMed2000

Cell-dependent gag mutants of HIV-1 are crucially defective at the stage of uncoating/reverse transcription in non-permissive cells.

We have previously shown that some of the human immunodeficiency virus type 1 (HIV-1) gag matrix (MA), capsid (CA), and nucleocapsid (NC) mutants display host-cell-dependent replication potential, and that they are defective at the early phase of the virus replication cycle in non-permissive cells. To determine the defective replication stage of the cell-dependent mutants precisely, the processes of virus entry into cells and virus DNA synthesis were monitored by the highly sensitive enzyme-linked immunosorbent assay and polymerase chain reaction amplification analysis. The results obtained indicated that all the cell-dependent MA, CA and NC mutants are defective at the stage of uncoating/reverse transcription, and that a cellular factor(s) is involved in this process.

Capsid↗
PubMed2000

Cloning and molecular characterization of calpain, a calcium-activated neutral proteinase, from different strains of Schistosoma japonicum.

cDNA coding for calpain of Schistosoma japonicum were cloned and sequenced, and serological basis of host responses to calpain were analyzed. cDNA of calpain from S. japonicum of two different isolates, Yamanashi strain (Sj-J) and Hunan strain (Sj-C), were 2, 468 bp and 2, 465 bp in length, including the same number (2, 274) of open reading frame. Nucleotide sequence and amino acid sequence between the two calpains are 99.1% and 98.8% identity, respectively. Sj-J and Sj-C calpains were considered to be translated as a preproenzyme, and a 746-amino acid mature enzyme contains eight motifs without a signal peptide at the N-terminal based on the deduced amino acid sequences. mRNA for calpain were detectable in different developmental stages, however, sera obtained from mice immunized with recombinant calpain showed enhanced binding to cercarial antigen. Human sera from S. japonicum-infected individuals recognized the large subunit of schistosomal calpain, and light-infected sera showed stronger reactivities to the recombinant calpain than moderate/high infection cases. When we tested synthetic peptides, there were four common human B cell epitopes in schistosomal calpain, all of which are shared with S. mansoni. Together with these results, calpain of S. japonicum seems to be not only a vaccine candidate, but also a target antigen for immunodiagnosis of human schistosomiasis.

Amino Acid Sequence↗
PubMed2000

Differentiation of wing epidermal scale cells in a butterfly under the lateral inhibition model--appearance of large cells in a polygonal pattern.

Cellular pattern formations of some epithelia are believed to be governed by the direct lateral inhibition rule of cell differentiation. That is, initially equivalent cells are all competent to differentiate, but once a cell has differentiated, the cell inhibits its immediate neighbors from following this pathway. Such a differentiation repeats until all non-inhibited cells have differentiated. The cellular polygonal patterns can be characterized by the numbers of undifferentiated cells and differentiated ones. When the differentiated cells become large in size, the polygonal pattern is deformed since more cells are needed to enclose the large cell. An actual example of such a cellular pattern was examined. The pupal wing epidermis of a butterfly Pieris rapae shows a transition of the equivalent-size cell pattern to the pattern involving large cells. The process of the transition was analyzed by using the method of weighted Voronoi tessellation that is useful for treatment of irregularly sized polygons. The analysis supported that the pattern transition of the early stage of the pupal wing epidermis is governed by the lateral inhibition rule. The differentiation takes place in order of largeness, but not smallness, of the apical polygonal area in the differentiating region of the pupal wing.

Animals↗
PubMed2000

(-)1-(Benzofuran-2-yl)-2-propylaminopentane shows survival effect on cortical neurons under serum-free condition through sigma receptors.

1. The rapid cell death of cortical neurons in serum-free culture was rescued by the condition medium from the high-density culture, but not by brain-derived neurotrophic factor or basic fibroblast growth factor. 2. Similar rescue was observed by the addition of (-)BPAP, an impulse enhancer, and (+)-pentazocine, a sigma receptor agonist. These actions were blocked by BD1063, a sigma receptor antagonist. 3. (-)BPAP showed a weak displacement activity in the [3H]pentazocine binding to synaptic membranes from rat cerebral cortex. 4. These findings suggest that (-)BPAP and (+)-pentazocine have unique survival activity on cortical neurons through sigma receptors.

Animals↗
PubMed2000

Synthesizing oligomers from monomeric nucleotides in simulated hydrothermal environments.

Dimers and trimers of adenosine monophosphate (AMP) were synthesized from AMP in environments simulating hot vents on the sea floor of the primitive Earth. The simulated environments were made in the flow reactor, in which an aqueous solution of reactants was circulated from the hot to the cold region repeatedly. The oligomerization proceeded most significantly when the hot reaction solution at about 110 degrees C was abruptly ejected into the cold environment maintained at about 0 degree C.

Adenine Nucleotides↗
PubMed2000

Protective mechanisms against the intestinal nematode Strongyloides venezuelensis in Schistosoma japonicum-infected mice.

Mice infected with Schistosoma japonicum were resistant to the intestinal nematode, Strongyloides venezuelensis. The numbers of adult S. venezuelensis recovered from mice were significantly decreased when infections were given from 6 weeks after S. japonicum infection. Larval recovery from the lungs showed that significant numbers of subcutaneously inoculated S. venezuelensis larvae were eliminated by 3 days in S. japonicum-infected mice (P < 0.0001), while histology revealed that this was associated with massive eosinophilic infiltration in the lungs. In addition, adult S. venezuelensis worms implanted in the duodenum of S. japonicum-infected mice could not establish in the intestine. This failure was associated with mucosal mastocytosis. Activation of eosinophils and intestinal mast cells was correlated with elevated expression of mRNA for interleukin (IL)-3, IL-4, and IL-5 in S. japonicum-infected mice. Sera from S. japonicum-infected mice recognized S. venezuelensis larva antigens as strongly as those from S. venezuelensis-infected mice, although transfer of sera from S. japonicum-infected mice to normal recipient mice did not protect them from S. venezuelensis challenge infection. It was concluded that the mechanisms for larval killing and adult worm expulsion of S. venezuelensis in S. japonicum-infected mice were identical to those seen in infections with S. venezuelensis only.

Animals↗
PubMed2000

Hepatic resection: effective treatment for primary and secondary tumors.

BACKGROUND: Hepatic resection is an accepted therapeutic modality for isolated colorectal metastases (CRM) and primary hepatobiliary cancers (PC). Controversy continues regarding the safety, efficacy, and appropriateness of resection for noncolorectal metastases (NCM). METHODS: A retrospective review of 167 resections in 160 patients was performed to evaluate the impact of demographics and perioperative data on survival and recurrence. Statistical analyses were performed by Student t test, analysis of variance, and Kaplan-Meier survival estimates. RESULTS: Resections were performed for CRM, 110 of 167 (66%), NCM, 31 of 167 (19%), and PC, 26 of 167 (15%). The interval from primary to metastases was significantly longer in the NCM group than the CRM group (34.7+/-45.1 vs. 18.7+/-23.7 months; P<.01). Mean number of lesions was not different between groups; however, NCM were larger than CRM (5.9+/-4.5 vs 4.5+/-2.9 cm; P<.05). Operative complications were significantly greater for PC (54%) versus CRM and NCM (21% and 19%, respectively; P<.01), although length of stay was similar between groups. Perioperative mortality was 2%. Actuarial survival at 1 year, 3 years, and 5 years was CRM 91%, 54%, and 40%, PC 75%, 60%, and 38%, and NCM 68%, 36%, and not available, respectively (CRM vs. NCM; P<.01 at 3 years). CONCLUSIONS: Hepatic resection for primary and secondary malignancy can be performed with minimal morbidity and mortality. Resection of NCM is associated with a lower overall survival compared with CRM and PC. The disease-free interval from resection of the primary to metastasectomy is prolonged and hepatic recurrence infrequent after resection in the NCM group. These results suggest that tumor biology is a critical determinant of outcome after hepatic resection of primary and secondary hepatic tumors.

Aged↗
PubMed2000

Schistosoma mansoni infection cancels the susceptibility to Plasmodium chabaudi through induction of type 1 immune responses in A/J mice.

Susceptibility to Plasmodium chabaudi depends on the relative dominance of T(h)1/T(h)2 responses in host mice. A T(h)2-dominant response during the early phase of infection in susceptible A/J mice causes a fatal disease course due to severe malaria. Schistosoma mansoni is a potent inducer of a T(h)2-dominant response not only to the parasite antigens, but also to other antigens concurrently existing in the host animals. In spite of S. mansoni infection, these A/J mice escape death from malaria and showed accompanied enhanced production of IFN-gamma to malaria antigens. Treatment with anti-IFN-gamma mAb in S. mansoni-infected A/J mice abolished the resistance to malaria, indicating that IFN-gamma was responsible for the resistance to P. chabaudi in S. mansoni-infected A/J mice. Results in this study show that under certain circumstances, S. mansoni infection can promote type 1 immune responses in A/J mice that normally develop T(h)2 responses.

Animals↗
PubMed2000

Comparison of metabolic risk factors in patients with recurrent urolithiasis stratified according to age and gender.

OBJECTIVE: Little is known regarding the metabolic features associated with aging and gender in urolithiais patients. We compared the metabolic characteristics among 3 generations (young, middle-aged and old) with recurrent calcium-containing urinary stones. METHODS: One hundred and eighty-one patients with recurrent calcium-containing stones, including 71 patients aged </=45 years (group 1), 71 patients aged 46-60 years (group 2) and 39 patients aged >/=61 years (group 3), were investigated by metabolic evaluation. The frequencies of metabolic abnormalities, the value of each urinary constituent and the supersaturation index (AP(CaOx) index) were compared among subgroups of the 3 generations, containing both males and females. RESULTS: The number of metabolic abnormalities was the greatest in group 1, followed by group 2 and group 3. Hyperoxaluria was the most common abnormality in each group. Group 1 females showed a lower frequency of hypocitraturia than group 3 females. This was the only characteristic that showed a significant difference between the groups. Urinary calcium excretion was significantly greater in group 1 than in group 3. Urinary citrate excretion and the AP(CaOx) index were significantly higher in group 1 than in group 3 in females. Male patients had a significantly higher number of metabolic abnormalities than female patients, especially in group 1. CONCLUSION: Multiple metabolic abnormalities, particularly a high calcium excretion appear to be crucial factors in the development and recurrence of urolithiasis in young patients. Low urinary citrate excretion could play an important role in the occurrence of urolithiasis in elderly females.

Age Factors↗
PubMed2000

Flow-mediated vasodilation and plasma fibronectin levels in preeclampsia.

To clarify the vascular endothelial function in pregnant women with hypertensive disorders, we assessed the flow-mediated vasodilation in the radial artery and compared it with plasma fibronectin levels. We determined flow-mediated vasodilation by measuring the change in radial artery diameter during hyperemia in 58 normal pregnant women, 22 preeclamptic pregnant women, and 15 pregnant women with chronic hypertension. In 41 of the 95 pregnant women, we measured the plasma fibronectin levels. Flow-mediated vasodilation in preeclamptic women was significantly less than that in normal pregnant women (P:<0.001). In chronic hypertensive women, flow-mediated vasodilation was significantly less than that in normal pregnant women (P:<0.001) but more than that in preeclamptic women (P:<0.001). Flow-mediated vasodilation showed significant negative correlation with plasma fibronectin levels (P:<0.001, r=0.73). Our results indicate that the endothelial function can be noninvasively assessed in pregnant women with hypertensive disorders by measuring the flow-mediated vasodilation of the radial artery with high-resolution ultrasound.

Adult↗