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Biomedical subjects

H Yajima

Publications and source records attributed to H Yajima.

At least 55 records · Page 3Linked to original sources
PubMed1999

FGF7 and FGF10 directly induce the apical ectodermal ridge in chick embryos.

During vertebrate limb development, the apical ectodermal ridge (AER) plays a vital role in both limb initiation and distal outgrowth of the limb bud. In the early chick embryo the prelimb bud mesoderm induces the AER in the overlying ectoderm. However, the direct inducer of the AER remains unknown. Here we report that FGF7 and FGF10, members of the fibroblast growth factor family, are the best candidates for the direct inducer of the AER. FGF7 induces an ectopic AER in the flank ectoderm of the chick embryo in a different manner from FGF1, -2, and -4 and activates the expression of Fgf8, an AER marker gene, in a cultured flank ectoderm without the mesoderm. Remarkably, FGF7 and FGF10 applied in the back induced an ectopic AER in the dorsal median ectoderm. Our results suggest that FGF7 and FGF10 directly induce the AER in the ectoderm both of the flank and of the dorsal midline and that these two regions have the competence for AER induction. Formation of the AER of the dorsal median ectoderm in the chick embryo is likely to appear as a vestige of the dorsal fin of the ancestors.

Animals↗
PubMed1999

1,25-Dihydroxyvitamin D3 suppresses the expression of the VCAM-1 receptor, VLA-4 in human leukemic HL-60 cells.

Very late antigen-4 (VLA-4) is the complex with alpha4 and beta1 integrins, which is the receptors to fibronectin and VCAM-1. We evaluate the effect of 1,25(OH)2D3 on the expression of VLA-4 in human leukemic HL-60, U937 cells and human melanoma A375 cells. Flow cytometric analysis demonstrate that the expression of alpha4 integrin is negatively regulated in the cell lines we studied. The expression of beta1 integrin is also decreased in HL-60 and U937 cells. The mRNA expression of alpha4 integrin is significantly decreased by the treatment with 1,25(OH)2D3, whereas 1,25(OH)2D3 does not alter the expression of beta1 mRNA. The adhesion assay demonstrate that the number of adherent cells treated with 1, 25(OH)2D3 is significantly lower than that untreated on VCAM-1-coated wells. Because VCAM-1 is highly expressed in the endothelial cells, it is possible that 1,25(OH)2D3 prevents the attachment of the cells from the endothelial cells in vivo.

Antigens, CD↗
PubMed1999

Role of N-cadherin in the sorting-out of mesenchymal cells and in the positional identity along the proximodistal axis of the chick limb bud.

Mesenchymal cells from different stages of chick limb buds sort out in monolayer culture, suggesting the presence of different cell affinities dependent on their positions along the proximodistal axis. However, it is still not clear which molecules are responsible for the sorting-out. Here, we propose that N-cadherin, a cell-adhesion molecule, is involved in the sorting-out and is likely to be a component of the mechanism of proximodistal patterning in the developing limb. N-cadherin proteins accumulate in the distal region of the chick limb bud as limb development proceeds. In monolayer culture of distal mesenchymal cells, the stage-dependent levels of N-cadherin proteins are maintained during cell sorting. The results of this study have also demonstrated that an anti-N-cadherin monoclonal antibody, NCD-2, clearly inhibits the cell sorting. Moreover, removal of the apical ectodermal ridge or retinoic-acid treatment of distal cells, which results in a change in the pattern of sorting-out, inhibits the accumulation of N-cadherin proteins, suggesting that the distribution of these proteins is related to the positional identity that gives rise to the different shape and number of cartilage elements along the proximodistal axis.

Animals↗
PubMed1999

Requirement of PEST domain tyrosine phosphatase PEP in B cell antigen receptor-induced growth arrest and apoptosis.

Signaling events leading to B cell growth or apoptosis are beginning to be unravelled, but detailed information is still lacking. To identify signaling molecules involved in B cell antigen receptor (BCR)-initiated pathways, we used the immature B cell line, WEHI-231, to investigate protein tyrosine phosphatases (PTP) whose expression was modulated by BCR ligation. Among the PTP cloned by reverse transcription-PCR, mRNA expression of the proline-, glutamic acid-, serine- and threonine-rich (PEST) domain phosphatase (PEP) was selectively elevated 3.1-fold within 3 h after anti-IgM antibody stimulation. In contrast, expression of another PEST domain phosphatase, PTP-PEST, was unaffected. Western blot analysis revealed that 71% of PEP was located in the cytosolic fraction, while 29% was in the membrane fraction. To examine the direct contribution made by PEP to BCR-initiated signal transduction, we transfected an antisense PEP cDNA into WEHI-231 cells. Two stable clones were established in which PEP expression was reduced by 34% and 47%, respectively. Strikingly, BCR-mediated inhibition of DNA synthesis was significantly rescued in the clones, and G1 phase cell cycle arrest and apoptosis were almost completely ablated. Considered collectively, these results indicate that PEP is a positive, crucial regulator in determining B cell fate triggered by BCR engagement.

Amino Acid Sequence↗
PubMed1999

Characterization of a Neurospora crassa photolyase-deficient mutant generated by repeat induced point mutation of the phr gene.

We produced a photolyase-deficient mutant by repeat induced point mutation using the Neurospora crassa photolyase gene cloned previously. This mutation identified a new gene, phr, which was mapped on the right arm of linkage group I by both RFLP mapping and conventional mapping. To investigate the relationship between photoreactivation and dark repair processes, especially excision repair, double mutants of phr with representative repair-defective mutants of different types were constructed and tested for UV sensitivity and photoreactivation. The results show that the phr mutation has no influence on dark repair. Tests with CPD and TC(6-4) photoproduct-specific antibodies demonstrated that the phr mutant is defective in CPD photolyase and confirmed that there is no TC(6-4) photolyase activity in N. crassa. Furthermore, N. crassa photolyase is not a blue light receptor in the signal transduction that induces carotenoid biosynthesis.

Blotting, Southern↗
PubMed1999

Functional assay of NF-kappaB translocation into nuclei by laser scanning cytometry: inhibitory effect by dexamethasone or theophylline.

Nuclear factor-kappa B (NF-kappaB)/Rel transcription factors play an important role in the inducible regulation of a variety of cytokine genes in epithelial cells. We assessed accumulation of fluorescence-stained NF-kappaB into propidium iodide-stained nuclei using laser scanning cytometry. "Activity-specific" antibodies to the Rel A (p65) and NF-kappaB1 (p50) subunits of NF-kappaB were detected in the nuclei of A549 cells (an immortalized human type II alveolar epithelial cell line). Exposure to TNF-alpha caused p65 and p50 to translocate into nuclei in a dose- and time-dependent manner. Preincubation with dexamethasone for 24 h or 30 min, or with theophylline for 30 min before TNF-alpha stimulation attenuated the nuclear translocation of Rel A and p50. These findings suggest that theophylline, as well as dexamethasone, may inhibit translocation of NF-kappaB.

Antineoplastic Agents, Hormonal↗
PubMed1999

Osteocutaneous radial forearm flap for hand reconstruction.

We treated 5 patients (4 men and 1 woman) with bone and soft tissue defects or total thumb loss using an osteocutaneous radial forearm flap. Their ages at the time of surgery ranged from 27 to 65 years (mean, 53 years). Preoperative conditions were traumatic loss of the thumb in 3 cases and severe injuries with soft tissue and bone defects in 2. The length of the donated radius ranged from 2 to 7 cm (mean, 4.7 cm). In 4 patients the radial forearm flap was transposed, including the lateral antebrachial cutaneous nerve as a sensory flap. Simultaneous iliac bone grafting to the donor site was also performed in 4 of the cases. The follow-up period ranged from 44 to 87 months (mean, 64 months). All flaps survived over their full extent. Radiographic bone union was attained after 2 to 3 months (mean, 2.5 months). Two-point discrimination over the 4 sensory flaps ranged from 8 to 15 mm (mean, 10.8 mm). No radius fractures occurred. No patients showed signs of vascular insufficiency from sacrifice of the radial artery. The radial forearm flap provides thin skin of good texture together with bone for a 1-stage reconstruction. For patients with skin and bone defects of the hand, a radial forearm osteocutaneous flap is recommended. This flap is also recommended for patients with traumatic thumb loss, if the dorsalis pedis artery is absent, or if the patient declines using tissue from the foot.

Adult↗
PubMed1999

Choline acetyltransferase activity in collateral sprouting of peripheral nerve after surgical intervention: experimental study in rats.

The purpose of this study was to establish an assay of choline acetyltransferase (ChAT) activity to investigate the regeneration of injured peripheral nerve, repaired by end-to-end or end-to-side neurorrhaphy. Murine sciatic and peroneal nerves were exposed, and the peroneal nerve was transected at a site 5 mm from its ramification. For end-to-side neurorrhaphy, an epineurotomy producing a 5-x5-mm window was carried out on the tibial nerve, just above the level of gastrocnemius muscle ramification. The peroneal nerve stump was then sutured end-to-side to the tibial nerve window. For end-to-end neurorrhaphy, the peroneal stump was directly sutured end-to-end. ChAT activity was measured at a site distal to the peroneal stump at 1 to 3 months postoperatively, and the results were compared among four groups: 1) end-to-end neurorrhaphy group; 2) end-to-side neurorrhaphy group; 3) unrepaired group; and 4) positive controls. ChAT activity in the end-to-side neurorrhaphy yielded approximately two-thirds the value of the end-to-end neurorrhaphy, and more than half the value of positive controls at 3 months postoperatively. Histologic sections of the end-to-side and end-to-end sutured peroneal nerve demonstrated large numbers of myelinated axons and Schwann cells at the third postoperative month. All the results demonstrated that end-to-side neurorrhaphy is comparable to well-performed end-to-end neurorrhaphy, thus providing another option for surgical treatment of avulsion nerve injury and massive nerve defect.

Anastomosis, Surgical↗
PubMed1999

Free vascularized fibula grafts in surgery of the upper limb.

Twenty patients with intractable diseases in the upper extremity were treated using free vascularized fibula grafts. There were 13 men and seven women. Three patients had traumatic bone defects, five had post-traumatic nonunions, two had congenital pseudoarthroses, seven had defects after tumor resection, and three had other lesions. The reconstructed sites were the humerus in two patients, the radius and/or ulna in 17, and the metacarpal and phalangeal bones in one. The length of the bone defect ranged from 3 to 18 cm (mean: 8.4 cm). Follow-up periods ranged from 6 to 204 months. No patient required additional bone grafts. The mean period required to obtain radiographic bone union was 4.4 months. There were no cases with fractures of the grafted bone, but malunion occurred in four cases. The vascularized fibula graft is indicated in patients with large bone defects or intractable nonunions in the humerus, radius, and/or ulna.

Adolescent↗
PubMed1999

cAMP enhances insulin secretion by an action on the ATP-sensitive K+ channel-independent pathway of glucose signaling in rat pancreatic islets.

Cyclic AMP potentiates glucose-stimulated insulin release by actions predominantly at a site, or sites, distal to the elevation of the cytosolic free Ca2+ concentration ([Ca2+]i). Glucose also acts at a site, or sites, distal to the elevation of [Ca2+]i via the ATP-sensitive K+ channel (K+ATP channel)-independent signaling pathway. Accordingly, using rat pancreatic islets, we studied the location of the action of cAMP and its interaction with the glucose pathway. Forskolin, an activator of adenylyl cyclase, raised intracellular cAMP levels and enhanced KCl-induced (Ca2+ -stimulated) insulin release in the presence, but not in the absence, of glucose. Thus, cAMP has no direct effect on Ca2+ -stimulated insulin release. The interaction between cAMP and glucose occurs at a step distal to the elevation of [Ca2+]i because forskolin enhancement of KCl-induced insulin release, in the presence of glucose, was demonstrated in the islets treated with diazoxide, a K+ATP channel opener. The enhancement of insulin release was not associated with any increase in [Ca2+]i. Furthermore, the interaction between cAMP and glucose was unequivocally observed even under stringent Ca2+ -free conditions, indicating the Ca2+ -independent action of cAMP. This action of cAMP is physiologically relevant, because not only forskolin but also glucagon-like peptide 1, glucose-dependent insulinotropic polypeptide, and pituitary adenylyl cyclase activating polypeptide exerted similar actions. In conclusion, the cAMP/protein kinase A pathway has no direct effect on Ca2+ -stimulated insulin exocytosis. Rather, it strongly potentiates insulin release by increasing the effectiveness of the K+ATP channel-independent action of glucose.

Adenosine Triphosphate↗
PubMed1999

Augmentation of Ca2+-stimulated insulin release by glucose and long-chain fatty acids in rat pancreatic islets: free fatty acids mimic ATP-sensitive K+ channel-independent insulinotropic action of glucose.

Glucose augments Ca2+-stimulated insulin release from the pancreatic beta-cell in an ATP-sensitive K+ channel (K(ATP) channel)-independent manner. In studying the mechanisms underlying this action, we used rat pancreatic islets and examined the effects of exogenous free fatty acids (FFAs), which are precursors of long-chain acyl-CoA (LC-CoA), on KCl-induced Ca2+-stimulated insulin release. Myristate, palmitate, and stearate augmented insulin release induced by 50 mmol/l KCl in the presence of 2.8 mmol/l glucose. Added acutely, their potency was weak compared with that of glucose-induced augmentation. The FFA-induced augmentation became much greater, however, when islets were preincubated with FFAs under stringent Ca2+-free conditions (with 1 mmol/l EGTA) before the KCl stimulation. Under these conditions, 16.7 mmol/l glucose augmented 13-fold insulin release induced by 50 mmol/l KCl, whereas palmitate or myristate (both at a free concentration of 10 micromol/l) produced 5.8- and 5.2-fold augmentations. Effects of FFAs and glucose were concentration-dependent. The temporal profiles of augmentation induced by 11.1 mmol/l glucose and 10 micromol/l palmitate were similar. Glucose and palmitate caused almost identical augmentation patterns for the initial 10 min of stimulation; subsequently, glucose augmentation was better sustained than palmitate augmentation. This suggests the existence of a longer-term glucose-specific signaling moiety that cannot be mimicked by FFAs. Our results provide direct evidence that FFAs can mimic the K(ATP) channel-independent action of glucose. Taking these results together with previous results, we conclude that glucose augments Ca2+-stimulated insulin release, at least in part, by increasing malonyl-CoA and cytosolic LC-CoA. However, one or more other glucose-specific signaling molecules are required for the full expression of augmentation.

Adenosine Triphosphate↗
PubMed1999

Organization of connectin/titin filaments in sarcomeres of differentiating chicken skeletal muscle cells.

Very long, elastic connectin/titin molecules position the myosin filaments at the center of a sarcomere by linking them to the Z line. The behavior of the connectin filaments during sarcomere formation in differentiating chicken skeletal muscle cells was observed under a fluorescent microscope using the antibodies to the N terminal (located in the Z line), C terminal (M line), and C zone (myosin filament) regions ofconnectin and was compared to the incorporation of alpha-actinin and myosin into forming sarcomeres. In early stages of differentiating muscle cells, the N terminal region of connectin was incorporated into a stress fiber-like structure (SFLS) together with alpha-actinin to form dots, whereas the C terminal region was diffusely distributed in the cytoplasm. When both the C and N terminal regions formed striations in young myofibrils, the epitope to the C zone of A-band region, that is the center between the A-I junction and the M-line, initially was diffuse in appearance and later formed definite striations. It appears that it took some time for the N and C terminal regions of connectin to form a regular organization in a sarcomere. Thus the two ends of the connectin filaments were first fixed followed by the specific binding of the middle portion onto the myosin filament during sarcomere formation.

Animals↗
PubMed1999

[Pranlukast allows reduction of inhaled steroid dose without deterioration in lung function in adult asthmatics].

We undertook a community based case-control study to measure the effect of pranlukast on the reduction of inhaled steroid in adult asthmatics. Forty-one adults completed a run-in period of 4 weeks on 800 microgram of beclomethasone dipropionate (BDP) documenting twice daily peak expiratory flow (PEF) and symptom score and therapeutic score on a standard diary. Forced expiratory volume in one second (FEV1.0), V50, V25 was measured once during the run-in period. Patients were then randomized to receive either pranlukast with 400 microgram of BDP or 400 microgram alone for 8 weeks. There was no difference in the symptom score and therapeutic between the two groups at any time point. However, morning and evening % PEF run-in expressed as a % of the PEF average during the run-in period was significantly lower at 8 weeks in the groups without pranlukast. There were subjects in the group without pranlukast (35.3%) compared to those with (20.8%) who had a 10% or more reduction in % PEF from the run-in period. The patients with an FEV1.0 < 80% predicted who were randomized to the control group were more likely (5 of 7) to have a fall in % PEF run-in and those randomized to received pranlukast were less likely to have a fall in % PEF run-in though this was not significant (2 of 6). In this study, pranlukast has demonstrated steroid sparing effect. Severe asthmatics (FEV1.0 < 80%) who deteriorate after reduction of inhaled steroid may benefit most from pranlukast. Larger studies are now required to explore this important effect.

Administration, Inhalation↗
PubMed1999

Secondary reconstruction of the extensor tendons and overlying soft tissue deficiency.

Reverse-flow pedicled radial forearm tendocutaneous flap transfers were performed to reconstruct simultaneous skin and tendon defects in the dorsum of the hand in six patients. All flaps survived and four of six patients obtained good functional results. To obtain satisfactory functional outcome, early surgical repair is critical after trauma. The only disadvantage of this operation is unacceptable donor site morbidity.

Adult↗
PubMed1998

Small-angle neutron scattering and dynamic light scattering studies of N- and C-terminal fragments of ovotransferrin.

In order to rationalize the physicochemical heterogeneities between the N- and C-lobes of ovotransferrin (OTf), we have analyzed the structural characteristics of the isolated fragments corresponding to the N- and C-terminal halves of OTf (OTf/2N and OTf/2C) with and without iron by means of small-angle neutron scattering (SANS) using the contrast variation method with solvents of various D2O/H2O mixtures, and dynamic light scattering (DLS) measurements. The analyses of the internal structural characteristics from SANS data revealed that the radius of gyration (Rg) for both fragments decreased to the same extent with iron binding, and the structural distortion of OTf/2C was smaller than that of OTf/2N, decreasing with iron uptake. The DLS studies showed that the change in the diffusion coefficient induced by iron binding to OTf/2C was greater than that to OTf/2N. It was inferred that the OTf/2C molecule tends to become more compact on the whole by iron binding as compared to the OTf/2N molecule.

Animals↗
PubMed1998

Multiple digit formation in Xenopus limb bud recombinants.

We prepared recombinant limb buds of Xenopus tadpoles by grafting a mesenchyme mass of the hindlimb bud. The Xenopus recombinant limb buds with dissociated and reaggregated mesenchyme developed more than 30 digits with cartilage segmentation, while those with undissociated mesenchyme developed a limb with normal cartilage pattern. Before the formation of multiple digits, a patchy expression pattern of fgf-8, an AER marker, was observed in the distal region of recombinant limb buds. shh, a ZPA (zone of polarizing activity) marker, was expressed broadly in the distal region of recombinants. Recombinant limb buds with the reaggregated mesenchyme of anterior halves formed anterior digits with claws, and those with the mesenchyme of posterior halves formed posterior digits without claws. The temporal and spatial changes in the potency of multiple digit formation are discussed with reference to the regenerative capacity of Xenopus limb buds.

Animals↗
PubMed1998

Temporary internal fixation of the scaphotrapezio-trapezoidal joint for the treatment of Kienböck's disease: a preliminary study.

Temporary scaphotrapezio-trapezoidal (STT) fixation with Kirschner wires (K-wires) has been used in the treatment of 16 cases of Kienböck's disease since 1988. Twelve of these cases with a follow-up of at least 1 year were reviewed. Eight patients were women and 4 were men and the average age at the time of surgery was 44 years (range, 20-67 years). Five cases were treated with temporary STT fixation and vascular bundle implantation (group V), and 7 cases were treated with temporary STT fixation and tendon roll implantation (group T). K-wires were removed between 16 and 26 weeks after surgery (average, 18.6 weeks) in group V, and between 8 and 13 weeks (average, 9.7 weeks) in group T. The follow-up periods ranged from 12 to 92 months (average, 38 months). Postoperative wrist pain disappeared in 7 cases and decreased in 5. The postoperative arc of wrist flexion and extension increased from 97 degrees to 108 degrees in group V and from 85 degrees to 103 degrees in group T. Grip strength improved from 22.2 to 30.6 kg in group V and from 11.4 kg to 17.7 kg in group T. X-ray evaluation revealed that the mean carpal height ratio was 0.488 before surgery, 0.489 during STT fixation, and 0.480 at the final follow-up. The carpal height decreased in 3 cases (2 in group V and 1 in group T). The postoperative radioscaphoid angle improved in all cases during K-wire insertion and regressed after removal of the K-wire, eventually showing a decrease in 4 cases, an increase in 3 cases, and no change in 5 cases.

Adult↗