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Biomedical subjects

T Ohyama

Publications and source records attributed to T Ohyama.

At least 73 records · Page 4Linked to original sources
PubMed2000

The inhibitory effects of vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide on osteoclast formation are associated with upregulation of osteoprotegerin and downregulation of RANKL and RANK.

The presence of a network of peptidergic nerve fibers in the skeleton, expressing several neuropeptides including vasoactive intestinal peptide (VIP), has been demonstrated. This observation, together with our findings in vitro showing that VIP can regulate the activities of osteoblasts and osteoclasts as well as the recruitment of osteoclasts, has suggested the existence of a neuro-osteogenic interplay in bone metabolism. In the present study, the effects of VIP and pituitary adenylate cyclase-activating polypeptide (PACAP), two members of the VIP/secretin/glucagon superfamily, on osteoclast formation and mRNA expression of three key regulatory proteins involved in osteoclast formation have been investigated. VIP, PACAP-27, and PACAP-38, at concentrations of 10(-6) M, all significantly inhibited formation of tartrate-resistant acid phosphatase-positive multinuclear cells (TRAP + MNC) in mouse bone marrow cultures stimulated by 1, 25(OH)(2)-vitamin D3 (D3; 10(-8) M). By using semiquantitative RT-PCR, it was found that D3 upregulated the mRNA expressions of receptor activator of NF-kappaB ligand (RANKL) and receptor activator of NF-kappaB (RANK), whereas the expression of osteoprotegerin (OPG) was downregulated in mouse bone marrow cultures stimulated by D3 for 7 days. Both VIP and PACAP-38 decreased the stimulatory effects of D3 on RANKL and RANK expression, whereas the inhibitory effect of D3 on OPG expression was reversed by VIP and PACAP-38. These observations indicate that the inhibitory effects of VIP and PACAP on osteoclast recruitment are due to regulation of the expression of key proteins involved in later stages of osteoclast differentiation.

Animals↗
PubMed2000

Spontaneous porphyria of the Long-evans cinnamon rat: an animal model of Wilson's disease.

To confirm and extend our previous microspectrophotometric observations of 30-week-old male Long-Evans Cinnamon (LEC) rats, an animal model of human Wilson's disease, we analyzed the porphyrin patterns of the organs, urine, and plasma of LEC rats. Abnormal accumulation of porphyrins, especially highly carboxylated porphyrins (uro- and heptaporphyrin), in the kidneys and liver was seen in male and female LEC rats aged 30 weeks and also in 10-week-old rats, before the onset of spontaneous hepatic dysfunction. Accumulation of copper and iron in the kidneys was not observed in the 10-week-old rats. Massive accumulation of porphyrins was observed only in the kidneys of the 30-week-old male LEC rat, indicating that this symptom is related to sex and age. Renal accumulation of porphyrins was reflected in the rate of urinary porphyrin excretion. Hepatic accumulation of porphyrins appeared to be independent of sex and age. These results indicate that neither renal nor hepatic porphyrin accumulation is the result of renal deposition of metals or of spontaneous hepatic dysfunction and that porphyrinuria in the LEC rat is closely related to the renal accumulation of porphyrins. In contrast to these organs, a reduction in the porphyrin levels was observed in the brain of the LEC rat. This was independent of sex and age. The present work stresses the existence of an abnormal heme metabolism in the LEC rat, and thus, the necessity to study the heme metabolism in human Wilson's disease is strongly suggested.

Aging↗
PubMed2000

A cellular variant of supratentorial hemangioblastoma.

Supratentorial hemangioblastomas are rarely seen, especially in children and adolescents. We report the case of a 17-year-old male with supratentorial hemangioblastoma. Neuroimaging demonstrated a cystic lesion within the right parietal lobe. Systemic examination revealed no abnormality. The lesion was not attached to the dura and was not associated with von Hippel-Lindau disease. It was very difficult to confirm the final diagnosis of this case, in spite of extensive examination by light microscopy, immunohistochemical studies, and electron microscopy.

Adolescent↗
PubMed2000

Humoral human xenoreactivity against isolated pig pancreatic islets.

It is widely believed that the hyperacute rejection of vascularized xenografts in the pig-to-human combination is triggered by the binding of human preformed natural antibodies (PNAbs) to the Galalpha.(1,3)Gal epitope in pig endothelium and the subsequent activation of complement. However, it remains poorly defined whether xenogeneic pig pancreatic islets are damaged by antibody and complement-mediated mechanisms. We examined the expression of Galalpha(1,3)Gal on isolated adult pig islets and the presence of PNAbs in normal human sera directed against islets, using immunofluorescence staining and confocal laser scanning microscopy. The pig islets were not stained with Galalpha(1,3)Gal-specific lectin GSIB4, however, the exocrine cells reacted strongly with GSIB4, indicating that the Galalpha(1,3)Gal epitope was highly expressed on exocrine cells, but not on islets. Human sera showed weak reactivity of IgM and IgG class PNAbs to the islets, but strong reactivity to the exocrine cells. Furthermore, we investigated the cytotoxic effect of human serum on pig islets using an in vitro model of pig-to-human islet transplantation. The incubation of pig islets with normal human sera for 45 min resulted in less than 10% specific lysis despite the binding of PNAbs, whereas exposure of porcine aortic endothelial cells to the same human sera caused 56% complement-mediated lysis, determined using a MTT cytotoxic assay. These results support the view that pig islets might not undergo early antibody and complement-mediated rejection in humans.

Animals↗
PubMed2000

Metal-ion stoichiometry of the HIV-1 RT ribonuclease H domain: evidence for two mutually exclusive sites leads to new mechanistic insights on metal-mediated hydrolysis in nucleic acid biochemistry.

Crystallographic studies of the Mn(2+)-doped RNase H domain of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) have revealed two bound Mn2+ separated by approximately 4A and surrounded by a cluster of four conserved carboxylates. Escherichia coli RNase H is structurally similar to the RNase H domain of HIV-1 RT, but requires one divalent metal cation for its activity, implying either that the HIV-1 RT RNase H domain contrasts in its ability to bind two divalent metal ions, or that the crystallographic data reflect specific use of Mn2+ and/ or the doping technique employed. Metal binding stoichiometry has been determined for Mn2+ and the biologically more relevant Mg2+ cation by solution calorimetric studies of native and recombinant p66/p51 HIV-1 RT. Three Mn2+ ions bind to HIV-1 RT apo-enzyme: one at the DNA polymerase and two at the RNase H catalytic center, the latter being consistent with crystallographic results. However, only one Mg2+ ion is bound in the RNase H catalytic center. Several mechanistic implications arise from these results, including the possibility of mutually exclusive Mg2+ binding sites that might be occupied according to the specific reaction being catalyzed by the multifunctional RNase H domain. The occurrence of distinct binding stoichiometries for Mg2+ and Mn2+ to multifunctional enzymes has previously been reported.

Calorimetry↗
PubMed2000

Mechanisms of cerebellar learning suggested by eyelid conditioning.

Classical eyelid conditioning has been used to great advantage in demonstrating that the cerebellum helps to improve movements through experience, and in identifying the underlying mechanisms. Results from recent studies support the hypotheses that learning occurs in both the cerebellar nucleus and cortex, and that these sites make different contributions. Specifically, results indicate that the cerebellar cortex is responsible for temporally specific learning. A combination of experimental and computational studies has been important for arriving at these conclusions, which seem to be applicable to the broad range of movements to which the cerebellum contributes.

Animals↗
PubMed2000

Activin increases bone mass and mechanical strength of lumbar vertebrae in aged ovariectomized rats.

Activin is a member of the transforming growth factor-beta superfamily and is thought to be involved in the regulation of bone formation due to its presence in bone tissue and its osteogenic activity both in vitro and in vivo. We recently found that systemic administration of activin increased both tibial bone mass and mechanical strength in young growing rats. The present study investigated the effects of activin in aged ovariectomized (ovx) rats. Twelve-month-old Fischer rats were ovariectomized and maintained for 10 months. Recombinant human activin A (activin) or human parathyroid hormone 1-34 (PTH) was administered intramuscularly three times a week for 12 weeks. Activin (1 and 5 microg/kg) markedly increased lumbar vertebral bone mineral content and bone mineral density. Activin also increased the mechanical strength of the vertebral body, which was highly correlated to the bone mineral density of the vertebral body. The maximal response in bone mass and strength was observed at 1 microg/kg of activin, which was approximately equal to that induced by PTH at 40 microg/kg. Peripheral quantitative computed tomography revealed that activin enlarged the cross-sectional size of the vertebrae without changing the foramen area, indicating its effects on cortical shells. Histomorphometric analysis of cancellous bone of vertebral body in similar experiment showed that activin (3 microg/kg) increased bone volume and the mineralizing surface, although its effects were less than PTH. The present results indicate that low doses of activin are effective against vertebral bone loss in aged ovx rats.

Activins↗
PubMed2000

Isolation of replicational cue elements from a library of bent DNAs of Aspergillus oryzae.

Two fragments that could function as replicational cue elements were isolated from a genomic DNA digest of Aspergillus oryzae on the basis of abnormal behavior in polyacrylamide gel electrophoresis. The vector used in this study contained a scaffold-associated region of the Drosophila melanogaster ftz gene to provide nuclear retention. Neither fragment contained a yeast ARS consensus sequence or an eukaryotic topoisomerase II binding sequence. One of the fragments showed sequence homology with the mitochondrial replication origin of Candida utilis and a portion of mitochondrial DNA of Aspergillus nidulans. This plasmid carrying the cue fragment could also replicate in HeLa and NIH3T3 cells.

Animals↗
PubMed2000

Characterization of nicking of the nontoxic-nonhemagglutinin components of Clostridium botulinum types C and D progenitor toxin.

Clostridium botulinum C and D strains produce two types of progenitor toxins, M and L. Previously we reported that a 130-kDa nontoxic-nonhemagglutinin (NTNHA) component of the M toxin produced by type D strain CB16 was nicked at a unique site, leading to a 15-kDa N-terminal fragment and a 115-kDa C-terminal fragment. In this study, we identified the amino acid sequences around the nicking sites in the NTNHAs of the M toxins produced by C. botulinum type C and D strains by analysis of their C-terminal and N-terminal sequences and mass spectrometry. The C-terminus of the 15-kDa fragments was identified as Lys127 from these strains, indicating that a bacterial trypsin-like protease is responsible for the nicking. The 115-kDa fragment had mixtures of three different N-terminal amino acid sequences beginning with Leu135, Val139, and Ser141, indicating that 7-13 amino acid residues were deleted from the nicking site. The sequence beginning with Leu135 would also suggest cleavage by a trypsin-like protease, while the other two N-terminal amino acid sequences beginning with Val139 and Ser141 would imply proteolysis by an unknown protease. The nicked NTNHA forms a binary complex of two fragments that could not be separated without sodium dodecyl sulfate.

Amino Acid Sequence↗
PubMed2000

Conditioned and unconditioned behavioral-cognitive effects of a dopamine antagonist in rats.

Many drugs need to be taken multiple times to achieve a therapeutic effect. Researchers have identified several mechanisms to account for the slow onset of drug action, including drug accumulation and structural changes induced by drugs. This article provides an example of a new mechanism to account for this change in drug action. Stimuli that accompany drug administration may come to evoke conditioned responses (CRs), and these CRs may be the basis for changes in drug efficacy. Specifically, this research shows that a dopamine antagonist, pimozide, changes response rates through the direct action of the drug but changes time perception through the CRs elicited by drug administration.

Animals↗
PubMed2000

Influence of protrusive tooth contact on tapping point distribution.

This study investigated the influence of protrusive tooth contacts (tooth contacts during mandibular protrusion) on the tapping point distribution. Nine healthy subjects volunteered for this study and the protrusive tooth contact pattern, as well as the retrusive tooth contact pattern, was altered on four maxillary occlusal splints. The first splint was adjusted to make the sagittal incisal path of protrusion and retrusion equivalent to that of the natural dentition. The second and third splints had partial and complete elimination of the protrusive tooth contact, respectively. The fourth splint had complete elimination of both protrusive and retrusive tooth contacts. The subjects were asked to use each splint continuously for 1 week. The tapping point distribution was measured on the 7th day after insertion of each splint. The four experimental occlusal conditions were found to have a significant effect on the tapping point distribution. The complete elimination of the protrusive tooth contact caused an anterior tapping point location and an increase in the tapping point area. The former tendency was found to be independent of the presence of the retrusive tooth contact. In conclusion, it was suggested that the protrusive tooth contact plays a significant role in maintaining the consistency and stability of the tapping point.

Adult↗
PubMed2000

Involvement of keratinocyte activation phase in cutaneous graft healing: comparison of full-thickness and split-thickness skin grafts.

BACKGROUND: Little is known about keratinocytic activation in the graft take and healing process. OBJECTIVE: To investigate the clinical and molecular differences between pure epidermal sheet graft (PESG), split-thickness skin graft (STSG), and full-thickness skin graft (FTSG). METHODS: Three different thickness skin grafts (PESG, STSG, and FTSG) were performed onto three kinds of porcine wounds: shallow, deep, and full. Graft take, contraction, and Ki-67 and beta1 integrin expression in epidermis were studied. RESULTS: All grafts took well. As expected, full wounds covered by PESG and STSG contracted more than those covered by FTSG, whereas shallow wounds covered by FTSG contracted more than those covered by STSG. No difference in contracture was observed among deep wounds covered by PESG, STSG, and FTSG. Up-regulation of Ki-67 and beta1 integrin expression was greater in PESG and STSG, compared with little expression in FTSG. CONCLUSION: The keratinocytic activation phase may occur both in the STSG and PESG healing process, as well as serum imbibition, inosculatory, and revascularization phases.

Animals↗
PubMed2000

Fraction of the dark current carried by Ca(2+) through cGMP-gated ion channels of intact rod and cone photoreceptors.

The selectivity for Ca(2+) over Na(+), PCa/PNa, is higher in cGMP-gated (CNG) ion channels of retinal cone photoreceptors than in those of rods. To ascertain the physiological significance of this fact, we determined the fraction of the cyclic nucleotide-gated current specifically carried by Ca(2+) in intact rods and cones. We activated CNG channels by suddenly (<5 ms) increasing free 8Br-cGMP in the cytoplasm of rods or cones loaded with a caged ester of the cyclic nucleotide. Simultaneous with the uncaging flash, we measured the cyclic nucleotide-dependent changes in membrane current and fluorescence of the Ca(2+)-binding dye, Fura-2, also loaded into the cells. The ratio of changes in fura-2 fluorescence and the integral of the membrane current, under a restricted set of experimental conditions, is a direct measure of the fractional Ca(2+) flux. Under normal physiological salt concentrations, the fractional Ca(2+) flux is higher in CNG channels of cones than in those of rods, but it differs little among cones (or rods) of different species. Under normal physiological conditions and for membrane currents </=200 pA, the Ca(2+) fractional flux in single cones of striped bass was 33 +/- 2%, and 34 +/- 6% in catfish cones. Under comparable conditions, the Ca(2+) fractional flux in rod outer segments of tiger salamander was 21 +/- 1%, and 14 +/- 1% in catfish rods. Fractional Ca(2+) flux increases as extracellular Ca(2+) rises, with a dependence well described by the Michaelis-Menten equation. KCa, the concentration at which Ca(2+) fractional flux is 50% was 1.98 mM in bass cones and 4.96 mM in tiger salamander rods. Because Ca(2+) fractional flux is higher in cones than in rods, light flashes that generate equal photocurrents will cause a larger change in cytoplasmic Ca(2+) in cones than in rods.

Animals↗
PubMed2000

[Genetic characterization of Norwalk-like viruses (NLVs) detected in Japan from 1989 to 1998 and establishment of consensus primers].

By means of reverse transcription-polymerase chain reaction using various pairs of primers, 902 strains of Norwalk-like viruses (NLVs) were detected during 10 years from 1989 to 1998 in the nationwide area of Japan including Hokkaido and Okinawa. Nucleotide sequencing was done on 177 strains, and we found that 153 strains (86%) of them belonged to geno-group II (GII). GII could be classified into five subgroups (G2A, G2B, G2C, G2D and G2E) based on the amino acid sequences showing a similarity of more than 91%. Among them G2C and G2D (named JP1) as well as G2E (named JP2), which were occasionally identified in Japan (detection rate of 17%) but rarely detected in the other countries, revealed to form new subgroups. From the above analysis, three pairs of new primers were established as consensus primers for NLVs. All the three sets of primers, P1/P2,P1/P3 and Y1/Y2, amplified both GI and GII equally and efficiently.

Consensus Sequence↗
PubMed2000

Modulation of H reflex of pretibial muscles and reciprocal Ia inhibition of soleus muscle during voluntary teeth clenching in humans.

A previous study has demonstrated that the soleus H reflex is facilitated in association with voluntary teeth clenching in proportion with biting force in humans. The present study tried to elucidate the functional significance of this facilitation of the soleus H reflex, by examining 1) whether the facilitation of the H reflex is reciprocal or nonreciprocal between the ankle extensors and flexors and 2) whether the reciprocal Ia inhibition of crural muscles is facilitated or depressed in association with voluntary teeth clenching. The H reflex of the pretibial muscles was evoked by stimulation of the common peroneal nerve in seven healthy subjects with no oral dysfunction. The pretibial H reflex was facilitated in association with voluntary teeth clenching in a force-dependent manner. The facilitation started preceding the onset of electromyographic activity of the masseter muscle. Stimulation of the common peroneal nerve at low intensities subthreshold for evoking the M wave of the pretibial muscles inhibited the soleus H reflex after a short latency corresponding with a disynaptic inhibition, indicating that the reciprocal Ia inhibition was depressed in association with voluntary teeth clenching. Thus, the present study has shown that voluntary teeth clenching evokes a nonreciprocal facilitation of ankle extensor and flexor muscles and attenuated reciprocal Ia inhibition from the pretibial muscles to the soleus muscle. It is concluded that voluntary teeth clenching contributes to improve stability of stance rather than smoothness of movements.

Adult↗