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Biomedical subjects

K Hanada

Publications and source records attributed to K Hanada.

At least 91 records · Page 5Linked to original sources
PubMed1999

Escherichia coli mutM suppresses illegitimate recombination induced by oxidative stress.

DNA damage by oxidative stress is one of the causes of mutagenesis. However, whether or not DNA damage induces illegitimate recombination has not been determined. To study the effect of oxidative stress on illegitimate recombination, we examined the frequency of lambdabio transducing phage in the presence of hydrogen peroxide and found that this reagent enhances illegitimate recombination. To clarify the types of illegitimate recombination, we examined the effect of mutations in mutM and related genes on the process. The frequency of lambdabio transducing phage was 5- to 12-fold higher in the mutM mutant than in the wild type, while the frequency in the mutY and mutT mutants was comparable to that of the wild type. Because 7,8-dihydro-8-oxoguanine (8-oxoG) and formamido pyrimidine (Fapy) lesions can be removed from DNA by MutM protein, these lesions are thought to induce illegitimate recombination. Analysis of recombination junctions showed that the recombination at Hotspot I accounts for 22 or 4% of total lambdabio transducing phages in the wild type or in the mutM mutant, respectively. The preferential increase of recombination at nonhotspot sites with hydrogen peroxide in the mutM mutant was discussed on the basis of a new model, in which 8-oxoG and/or Fapy residues may introduce double-strand breaks into DNA.

Bacteriophage lambda↗
PubMed1999

Gene mutations of K-ras in gallbladder mucosae and gallbladder carcinoma with an anomalous junction of the pancreaticobiliary duct.

OBJECTIVE: In this study, we examined the mutational spectrum of K-ras in cases of gallbladder and gallbladder carcinoma with an anomalous junction of the pancreaticobiliary duct (AJPBD). METHODS: We examined 35 gallbladders with AJPBD (20 with hyperplasia, 15 with carcinoma) and 38 gallbladders without AJPBD (four normal gallbladders, four with hyperplasia, six with adenoma, 24 with carcinoma). Polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and direct sequencing were performed to detect mutations in codon 12 or 13 of K-ras. RESULTS: In the cases with AJPBD, the prevalences of K-ras mutation were 15% (3/20) in hyperplasia, 60% (6/10) in stage I carcinoma, and 100% (5/5) in stage II-IV carcinoma. In the cases without AJPBD, the prevalences of K-ras mutation were 0% (0/4) in normal gallbladder, 0% (0/4) in hyperplasia, 17% (1/6) in adenoma, 7% (1/16) in stage I carcinoma, and 38% (3/8) in stage II-IV carcinoma. Prevalences of K-ras mutation in hyperplasia and carcinoma with AJPBD were greater than those without AJPBD (p < 0.05). The point mutation of GGT to GAT in codon 12 was frequently observed in the cases with AJPBD. CONCLUSION: These results suggest that the specific K-ras mutation in codon 12 (GGT to GAT) may contribute to the early stage of carcinogenesis in the gallbladder with AJPBD.

Adenoma↗
PubMed1999

Correlation of skin phototype with facial wrinkle formation.

Facial wrinkle formation is a representative sign of photoaging. Skin can be divided into different skin phototypes (SPTs) depending on its sensitivity to solar radiation. We have determined the relationship between SPTs and deep and fine wrinkle scores on the faces of 230 Japanese subjects. This group was chosen because it is relatively easy to quantify acute and chronic sun damage in Japanese individuals. SPT in the Japanese subjects was classified into one of four groups, SPT-I to -IV according to Fitzpatrick's classification method. The subjects were further classified into indoor or outdoor workers. After photographing the outer canthus, deep and fine wrinkles were discriminated visually and scored from 1-11 and from 1-9, respectively. UV light was used as a photographic light source for clear depiction of the fine wrinkles. Higher scores were recorded for deep wrinkles in individuals with SPT-I, who are more sensitive to sunlight than those with SPT-III or IV, who are more tolerant to sunlight. However, the same tendency did not seem to be apparent for fine wrinkle scores. A high incidence of SPT-IV was seen in outdoor workers. Early detection of SPT-I in individuals who are sensitive to sunlight, may help to predict and prevent photoaging of deep wrinkles. Sensitivity to sunlight may play a part in determining an individual's choice of working environment.

Adult↗
PubMed1999

Re-innervation in the canine periodontal ligament of replanted teeth using an antibody to protein gene product 9.5: an immunohistochemical study.

The re-innervation process in the periodontal ligament of replanted canine teeth was examined by immunohistochemistry for protein gene product 9.5 (PGP 9.5), a general marker for neurons, and by electron microscopy. Within 1 week of replantation, the periodontal fibers had regenerated, filling the narrow spaces between the alveolar bone and the root surface around the cervical and apical regions. Near the root apex, however, no PGP 9.5-immunopositive nerve fibers were found in the regenerated periodontal ligament except for those in the alveolar half of the ligament. At 2 weeks after replantation, many nerve fibers positive for PGP 9.5 had ascended the periodontal ligament from the thick nerve bundles located near the root apex. Fine nerve endings showing complicated ramification were also present in the apical region. By 3 or 4 weeks after replantation, the vascular network was regenerated and principal periodontal fibers were re-established throughout the entire length of the periodontal ligament. The extensively ramified PGP 9.5-immunopositive structures had increased in thickness and density and showed characteristic tree-like profiles by 3 weeks. Electron microscopy confirmed that most of these structures were Ruffini-like endings, and demonstrated that such nerve terminals were almost regenerated by 4 weeks post-replantation. These results indicated that, in the periodontal ligament of replanted canine teeth, the regeneration of the nerve fibers including mechanosensory receptors first showed signs of regeneration by 2 weeks following tooth replantation and proceeded rapidly thereafter. Regeneration of the periodontal ligament including fiber architecture as well as vascular and neural elements was almost complete by 4 weeks after replantation.

Animals↗
PubMed1999

Condylar bony change and craniofacial morphology in orthodontic patients with temporomandibular disorders (TMD) symptoms: a pilot study using helical computed tomography and magnetic resonance imaging.

OBJECTIVE: To investigate how condylar bony changes relate to craniofacial morphology using helical CT and MRI. DESIGN: Craniofacial morphology of orthodontic patients with condylar bony changes was compared with Japanese standard. SETTING AND SAMPLE POPULATION: The Department of Orthodontics, Niigata University School of Dentistry, Twenty-nine subjects were selected from orthodontic patients (six males and 23 females, a mean age of 18.8 +/- 6.3 years) who were diagnosed by helical CT as having condylar bony changes. EXPERIMENTAL VARIABLE: Subjects were divided into two groups: a unilateral condylar bony change group (unilateral group) (four males and nine females) and a bilateral condylar bony change group (bilateral group) (two males and 14 females). OUTCOME MEASURE: Condylar bony changes were evaluated on reconstructed coronal and sagittal CT scans. Disk positions were evaluated by MRI scans. Five linear and four angular measurements in lateral and posteroanterior cephalograms were compared with those of an age- and sex-matched 'standard population' from the Japanese standard. RESULTS: In the bilateral group, osteophyte formation and erosion were the common bony changes and were present in adult as well as juvenile subjects. In the unilateral group, flattening was the most common features and erosion was only present in subjects below 19 years. Disk displacement without reduction was seen in 90.6% of the bilateral group, and in 76.9% of the unilateral group. Retrognathic mandibles were shown in the bilateral group. All subjects exhibited a lateral shift of the menton toward the condylar bony changed side in the unilateral group. CONCLUSION: Condylar bony changes might be progressive and unstable in adults of the bilateral group as well as in juveniles of the both groups. It appears that condylar bony changes may be related to a lateral shift of the mandible and a retrognathic mandible in orthodontic patients with TMD symptoms.

Adolescent↗
PubMed1999

Illegitimate recombination induced by overproduction of DnaB helicase in Escherichia coli.

Illegitimate recombination that usually takes place at a low frequency is greatly enhanced by treatment with DNA-damaging agents. It is thought that DNA double-strand breaks induced by this DNA damage are important for initiation of illegitimate recombination. Here we show that illegitimate recombination is enhanced by overexpression of the DnaB protein in Escherichia coli. The recombination enhanced by DnaB overexpression occurred between short regions of homology. We propose a model for the initiation of illegitimate recombination in which DnaB overexpression may excessively unwind DNA at replication forks and induce double-strand breaks, resulting in illegitimate recombination. The defect in RecQ has a synergistic effect on the increased illegitimate recombination in cells containing the overproduced DnaB protein, implying that DnaB works in the same pathway as RecQ does but that they work at different steps.

Bacterial Proteins↗
PubMed1999

Postnatal expression of calretinin-immunoreactivity in periodontal Ruffini endings in the rat incisor: a comparison with protein gene product 9.5 (PGP 9.5)-immunoreactivity.

The postnatal expression of immunoreactivity for calretinin, one of the calcium binding proteins, and for protein gene product 9.5 (PGP 9.5), a general neuronal marker, was investigated in mechanoreceptive Ruffini endings in the periodontal ligament of the rat incisor. Age-related changes in the expression of these two proteins in periodontal nerves were further quantified with a computerized image analysis. At 1 day after birth, a few PGP 9.5-immunoreactive nerve fibers and a still smaller number of calretinin-positive fibers were found in the periodontal ligament: they were thin and beaded in appearance and no specialized nerve terminals were recognized. Tree-like terminals, reminiscent of immature Ruffini endings, were recognizable in 4-day-old rats by PGP 9.5-immunohistochemistry, while calretinin-immunostaining failed to reveal these specialized endings. At postnatal 7-11 days when PGP 9.5-immunostaining could demonstrate typical Ruffini endings, calretinin-immunopositive nerve fibers merely tapered off without forming the Ruffini type endings. A small number of Ruffini endings showing calretinin-immunoreactivity began to occur in the periodontal ligament at 24-26 days after birth when the occlusion of the first molars had been established. At the functional occlusion stage (60-80 days after birth), the Ruffini endings showing calretinin-immunoreactivity drastically increased in number and density, but less so than those positive for PGP 9.5-immunoreaction. The delayed expression of calretinin suggests that the function of the periodontal Ruffini endings is established after the completion of terminal formation because Ca2+, which binds to calcium binding proteins including calretinin with high affinity, plays an important role in mechano-electric transduction.

Age Factors↗
PubMed1999

MR diagnosis of adenomyomatosis of the gallbladder and differentiation from gallbladder carcinoma: importance of showing Rokitansky-Aschoff sinuses.

OBJECTIVE: We evaluated the MR imaging features of adenomyomatosis of the gallbladder with particular emphasis on Rokitansky-Aschoff sinuses. MATERIALS AND METHODS: MR images of 17 patients with histologically proven adenomyomatosis were retrospectively reviewed. The presence of Rokitansky-Aschoff sinuses was evaluated and analyzed; four T2-weighted (fast spin-echo with a surface coil, with or without breath-holding, fast spin-echo with a phased-array coil with breath-holding, and half-Fourier rapid acquisition with relaxation enhancement with breath-holding) and two contrast-enhanced dynamic pulse sequences were studied. These six pulse sequences were separately rated on a 5-point scale by two radiologists for comparison. Interobserver differences were evaluated. Other MR findings were also analyzed. RESULTS: Among the six pulse sequences studied, three T2-weighted with breath-holding sequences were found to be superior to the other three sequences in showing Rokitansky-Aschoff sinuses. In particular, the half-Fourier rapid acquisition with relaxation enhancement was scored the highest by the two observers and received the highest kappa coefficient in our statistical analysis of the scoring. Diffuse-type adenomyomatosis typically showed early mucosal and subsequent serosal enhancement. Localized adenomyomatosis exhibited homogeneous enhancement, showing smooth continuity with the surrounding gallbladder epithelium. CONCLUSION: MR imaging may be able to provide important information in the diagnosis of adenomyomatosis.

Adenomyoma↗
PubMed1999

A novel fungal metabolite NG-061 enhances and mimics neurotrophic effect of nerve growth factor (NGF) on neurite outgrowth in PC12 cells.

During the course of our screening program for low molecular natural products with their ability to potentiate and/or mimic neurotrophic effect of NGF, a novel fungal metabolite, phenylacetic acid hydrazide derivative NG-061 was isolated from the fermentation broth of Penicillium minioluteum F-4627. NG-061 enhanced and mimicked neurotrophic effect of NGF on neurite outgrowth in a rat pheochromocytoma cell line PC12.

Animals↗
PubMed1998

Mammalian cell mutants resistant to a sphingomyelin-directed cytolysin. Genetic and biochemical evidence for complex formation of the LCB1 protein with the LCB2 protein for serine palmitoyltransferase.

Lysenin, a hemolytic protein derived from the earthworm Eisenia foetida, has a high affinity for sphingomyelin. Chinese hamster ovary (CHO) cells exhibited a high cytolytic sensitivity to lysenin, but treatment with sphingomyelinase rendered the cells resistant to lysenin. Temperature-sensitive CHO mutant cells defective in sphingolipid synthesis were resistant to lysenin, and this lysenin resistance was suppressed by metabolic complementation of sphingolipids. Selection of lysenin-resistant variants from mutagenized CHO cells yielded two types of sphingomyelin-deficient mutants, both of which showed less lysenin binding capability than wild-type cells. One mutant strain was severely defective in sphingomyelin synthesis but not glycosphingolipid synthesis, and another strain (designated LY-B) was incapable of de novo synthesis of any sphingolipid species and had no activity of serine palmitoyltransferase (SPT; EC 2.3.1.50) catalyzing the first step of sphingolipid biosynthesis. LY-B cells lacked the LCB1 protein, a component of SPT, and transfection of LY-B cells with the hamster LCB1 cDNA restored both SPT activity and sphingolipid synthesis to the cells. Expression of an affinity peptide-tagged LCB1 protein in LY-B cells caused the endogenous LCB2 protein to adsorb to a tag affinity matrix. In addition, an anti-hamster LCB2 protein antibody co-immunoprecipitated both SPT activity and the wild-type LCB1 protein with the LCB2 protein. Thus, cell surface sphingomyelin is essential for lysenin-induced cytolysis, and lysenin is a useful tool for isolation of sphingomyelin-deficient mutants. Moreover, these results demonstrate that the SPT enzyme comprises both the LCB1 and LCB2 proteins.

Acyltransferases↗
PubMed1998

Induction of keratinocyte proliferation and lymphocytic infiltration by in vivo introduction of the IL-6 gene into keratinocytes and possibility of keratinocyte gene therapy for inflammatory skin diseases using IL-6 mutant genes.

To understand biological function of IL-6 in the skin in vivo, we constructed a vector that strongly expressed human IL-6 in keratinocytes and introduced it into rat keratinocytes in vivo by the naked DNA method. The overexpression of IL-6 induced macroscopic erythema and histologically evident keratinocyte proliferation and lymphocytic infiltration in the treated area of rat skin. Since previous studies using IL-6 transgenic mice have not shown skin inflammation of these mice, our result provides the first evidence that IL-6 is related to the pathogenesis of inflammatory skin diseases. ELISA suggested that a certain degree of transgenic IL-6 expression in keratinocytes was required for inducing skin inflammation. Cytokine profile in rat keratinocytes after the gene introduction was examined by reverse transcriptase-PCR assay and revealed that gene expression of rat IL-1alpha and TNF-alpha showed no marked change until 24 h, whereas that of rat IL-6 and TGF-alpha increased with time. We then introduced and expressed the IL-6 mutant genes, which were designed to behave as IL-6Ralpha antagonists, and found that their ability to induce erythema was lower than that of the wild-type gene. Furthermore, preintroduction of some mutant genes delayed the erythema induced by postintroduction of the wild-type IL-6 gene, suggesting that the mutant forms of IL-6 prevent wild-type IL-6 from binding to IL-6Ralpha. This result indicates that keratinocyte gene therapy may be possible for inflammatory skin diseases using IL-6 mutant genes.

Animals↗
PubMed1998

Calretinin-like immunoreactivity in the regenerating periodontal ruffini endings of the rat incisor following injury to the inferior alveolar nerve.

Regeneration of calretinin (CR)-like immunoreactive (IR) nerve fibers was investigated in the periodontal ligament of the rat lower incisor following resection of the inferior alveolar nerve (IAN). In addition, the degeneration and regeneration processes of periodontal nerve fibers were examined by immunohistochemistry for protein gene product 9.5 (PGP 9.5), a general neuronal marker. In normal animals, the periodontal nerve fibers showing PGP 9.5-like immunoreactivity (LI) formed either periodontal Ruffini endings with expanded arborization and thin free nerve endings in the alveolar half of the ligament. Thick CR-IR nerve fibers also appeared in a dendritic fashion in the same region, but thin CR-IR nerve fibers were rarely observed. Five days following resection of the IAN, a major population of PGP 9.5-IR and all CR-IR nerve fibers disappeared except for some thin PGP 9.5-IR nerves in the periodontal ligament. Regenerated PGP 9.5-IR nerve fibers appeared around 7 days following resection, in contrast to a very small number of regenerated CR-IR nerve fibers. Around 14-21 days following resection, the number and terminal morphology of regenerated PGP 9.5-IR nerve fibers were comparable to those observed in normal animals, but the number of regenerated CR-IR nerve fibers was still smaller than that of normal animals. The number of regenerated CR-IR nerve fibers increased to return to normal by 56 days following injury. The delay of expression of CR-LI in the regenerated periodontal Ruffini endings suggests that functional recovery of periodontal Ruffini endings occurred after the completion of the regeneration of periodontal nerve fibers.

Animals↗