Endocytosis following dopamine D2 receptor activation is critical for neuronal activity and dendritic spine formation via Rabex-5/PDGFRß signaling in striatopallidal medium spiny neurons.

Aberrant dopamine D2 receptor (D2R) activity is associated with neuropsychiatric disorders, making those receptors targets for antipsychotic drugs. Here, we report that novel signaling through the intracellularly localized D2R long isoform (D2LR) elicits extracellular signal-regulated kinase (ERK) activation and dendritic spine formation through Rabex-5/platelet-derived growth factor receptor-ß (PDGFRß)-mediated endocytosis in mouse striatum. We found that D2LR directly binds to and activates Rabex-5, promoting early-endosome formation. Endosomes containing D2LR and PDGFRß are then transported to the Golgi apparatus, where those complexes trigger Gαi3-mediated ERK signaling. Loss of intracellular D2LR-mediated ERK activation decreased neuronal activity and dendritic spine density in striatopallidal medium spiny neurons (MSNs). In addition, dendritic spine density in striatopallidal MSNs significantly increased following treatment of striatal slices from wild-type mice with quinpirole, a D2R agonist, but those changes were lacking in D2LR knockout mice. Moreover, intracellular D2LR signaling mediated effects of a typical antipsychotic drug, haloperidol, in inducing catalepsy behavior. Taken together, intracellular D2LR signaling through Rabex-5/PDGFRß is critical for ERK activation, dendritic spine formation and neuronal activity in striatopallidal MSNs of mice.

Functional analysis of platelet-derived growth factor receptor-ß in neural stem/progenitor cells.

Activation of neural stem/progenitor cells (NSPCs) is a potential therapeutic strategy of neurological disorders. In this study, NSPCs of subventricular zone were isolated and cultured from platelet-derived growth factor-ß-receptor-knockout (PDGFR-ß(-/-)) mice of postnatal day 1 (P1) and P28, and the roles of PDGFR-ß were examined in these cells. In PDGFR-ß-preserving control NSPCs, stem cell activities, such as numbers and diameters of secondary neurospheres, cell proliferation and survival rates, were significantly higher in P1 NSPCs than those in P28 NSPCs. In PDGFR-ß(-/-) NSPCs, most of these parameters were decreased as compared with age-matched controls. Among them, the decrease of secondary neurosphere formation was most striking in P1 and P28 PDGFR-ß(-/-) NSPCs and in P28 control NSPCs as compared with P1 control NSPCs. PCR-array and following quantitative real-time PCR (qRT-PCR) analyses demonstrated that expressions of fibroblast growth factor-2 (FGF2) and exons IV-IX of brain-derived neurotrophic factor (BDNF) were decreased, and noggin was increased in P1 PDGFR-ß(-/-) as compared with P1 controls. Addition of BDNF rescued the number and diameter of secondary neurospheres in P1 PDGFR-ß(-/-) NSPCs to similar levels as controls. The expressions of PDGFs and PDGFRs in control NSPCs were increased along with the differentiation-induction, where phosphorylated PDGFR-ß was co-localized with neuronal and astrocyte differentiation markers. In controls, the neuronal differentiation was decreased, and the glial differentiation was increased from P1 to P28 NSPCs. Compared with P1 controls, neuronal differentiation was reduced in P1 PDGFR-ß(-/-) NSPCs, whereas glial differentiation was comparable between the two genotypes. These results suggest that PDGFR-ß signaling is important for the self-renewal and multipotency of NSPCs, particularly in neonatal NSPCs. BDNF, FGF2, and noggin may be involved in the effects of PDGFR-ß signaling in these cells. Accordingly, the activation of PDGFR-ß in NSPCs may be a novel therapeutic strategy of neurological diseases.

SH2-containing inositol 5'-phosphatase 2 selectively impairs hypothalamic insulin signalling and regulation of food intake in mice.

SH2-containing inositol 5'-phosphatase 2 (SHIP2) is a lipid phosphatase that negatively regulates the metabolic signalling of insulin in peripheral tissues; however, the expression of SHIP2 in the hypothalamus and its functional roles are largely unknown. In the present study, immunohistochemical analysis demonstrated that SHIP2 protein exists in neuronal cells expressing neuropeptide Y and pro-opiomelanocortin in the arcuate nucleus of the hypothalamus in C57BL/6J mice. Interestingly, the expression levels of SHIP2 in the hypothalamus were elevated in aged C57BL/6J mice and diabetic db/db mice. To clarify the significance of the increased expression of SHIP2 in the hypothalamus, we examined the central effects of insulin and leptin in transgenic mice overexpressing SHIP2 (SHIP2-Tg). Accumulation of phosphatidylinositol (3,4,5)-trisphosphate and phosphorylation of Akt in the hypothalamus, induced by i.c.v. injection of insulin, were attenuated in SHIP2-Tg compared to wild-type mice, whereas leptin-induced phosphorylation of signal transducer and activator of transcription 3 in the hypothalamus was comparable between them. The suppression of food intake after i.c.v. administration of insulin (but not leptin) was attenuated consistently in SHIP2-Tg. In addition, SHIP2-Tg showed increased food consumption after starvation and become heavier with visceral fat accumulation than wild-type mice, despite normal levels of oxygen consumption and spontaneous movement. These results suggest that SHIP2 contributes to the regulation of food intake mainly via the attenuation of insulin signalling in the hypothalamus of mice.

Deletion of platelet-derived growth factor receptor-ß improves diabetic nephropathy in Ca²âº/calmodulin-dependent protein kinase IIα (Thr286Asp) transgenic mice.

AIMS/HYPOTHESIS: The activation of platelet-derived growth factor receptor-ß (PDGFR-ß) signalling is increased in the glomeruli and tubules of diabetic animals. In this study, we examined the role of PDGFR-ß signalling during the development of diabetic nephropathy. METHODS: We recently generated pancreatic beta cell-specific Ca(2+)/calmodulin-dependent protein kinase IIα (Thr286Asp) transgenic mice (CaMKIIα mice), which show very high plasma glucose levels up to 55.5 mmol/l and exhibit the features of diabetic nephropathy. These mice were crossed with conditional knockout mice in which Pdgfr-ß (also known as Pdgfrb) was deleted postnatally. The effect of the deletion of the Pdgfr-ß gene on diabetic nephropathy in CaMKIIα mice was evaluated at 10 and 16 weeks of age. RESULTS: The plasma glucose concentrations and HbA(1c) levels were elevated in the CaMKIIα mice from 4 weeks of age. Variables indicative of diabetic nephropathy, such as an increased urinary albumin/creatinine ratio, kidney weight/body weight ratio and mesangial area/glomerular area ratio, were observed at 16 weeks of age. The postnatal deletion of the Pdgfr-ß gene significantly decreased the urinary albumin/creatinine ratio and mesangial area/glomerular area ratio without affecting the plasma glucose concentration. Furthermore, the increased oxidative stress in the kidneys of the CaMKIIα mice as shown by the increased urinary 8-hydroxydeoxyguanosine (8-OHdG) excretion and the increased expression of NAD(P)H oxidase 4 (NOX4), glutathione peroxidase 1 (GPX1) and manganese superoxide dismutase (MnSOD) was decreased by Pdgfr-ß gene deletion. CONCLUSIONS/INTERPRETATION: The activation of PDGFR-ß signalling contributes to the progress of diabetic nephropathy, with an increase in oxidative stress and mesangial expansion in CaMKIIα mice.

Suppression of antibody-mediated arthritis in mice by Fab fragments of the mediating antibodies.

BACKGROUND AND PURPOSE: Fab fragments (Fabs) of antibodies maintain the ability to bind specific antigens, but lack the binding site for complement as well as the site for binding to receptors on effector cells, such as macrophages that play an important role in inflammation. In the present study, we investigated whether Fabs specific for ovalbumin (OVA) were specifically able to suppress anti-OVA antibody-mediated arthritis (AOA-MA) in mice. EXPERIMENTAL APPROACH: AOA-MA was induced by i.v. injection of purified anti-OVA antibodies into naïve mice followed by intra-articular (left ankle) challenge with the antigen. Anti-OVA Fabs prepared by digestion of anti-OVA antibodies with papain were injected i.v. immediately after administration of the intact antibodies. Normal Fabs were used as a control. Arthritis was assessed by thickness of the joints (caliper) and by histology of paw sections, stained with haematoxylin and eosin. KEY RESULTS: AOA-MA was markedly suppressed by anti-OVA Fabs, but not by control Fabs. Histologically, mice treated with control Fabs showed marked oedema of synovial tissues with a large number of inflammatory cells including neutrophils, whereas animals given anti-OVA Fabs had mild oedema of the synovium and sparse infiltration of such cells. The antigen-specific suppression of joint inflammation by anti-OVA Fabs was associated with reduced consumption of complement. In vitro studies showed that anti-OVA Fabs significantly blocked the binding of intact anti-OVA antibodies to OVA. CONCLUSIONS AND IMPLICATIONS: Antibody-mediated arthritis appears to be specifically down-regulated by Fabs that competitively inhibit the binding of antibodies to antigens.

Retinal nerve fiber layer thickness in patients with retinitis pigmentosa.

PURPOSE: To study retinal nerve fiber layer (RNFL) thickness in patients with retinitis pigmentosa (RP). DESIGN: Cross-sectional observational study. METHODS: One hundred and thirty-seven eyes of 137 patients with RP were examined. The effect of age, gender, laterality, inheritance trait, spherical equivalent refractive error, visual acuity, and the extent of visual field defect on RNFL thickness measured with optical coherence tomography were analyzed by a multiple linear regression model. RESULTS: The average RNFL thickness was 104.1+/-21.7 microm. The multiple R(2) for the model was 0.349. Among the variables studied, ageing and being male were significant risk factors for thinner RNFL thickness. RNFL thickness was not correlated with inheritance trait, laterality, refractive error, visual acuity, or the extent of visual field defect. CONCLUSION: RNFL thickness in RP patients was not correlated with visual function but ageing as in the normal subjects. Currently proposed therapies, including photoreceptor rescue/transplantation and visual prosthesis, are based on the premise that the inner retinal structures are relatively retained despite the profound loss of photoreceptors. The present result supports this notion.

Optical coherence tomographic pattern and focal electroretinogram in patients with retinitis pigmentosa.

PURPOSE: The foveal function of patients with retinitis pigmentosa (RP) has been estimated by visual acuity (VA) or visual field (VF) tests. In the present study, the potential of optical coherence tomography (OCT) and focal electroretinogram (fERG) for monitoring macular function in RP patients was investigated. DESIGN: Cross-sectional observational study. METHODS: A total of 56 eyes of 56 patients with RP underwent ophthalmic examination including VA, VF, fERG, and OCT. Patients were morphologically divided into three groups by the appearance of photoreceptor inner/outer segment junction (IS/OS) that were depicted with OCT; type 1: no IS/OS visible, type 2: IS/OS was visible but the length was < or =2 mm, and type 3: IS/OS >2 mm was confirmed. Functional results for VA and fERG were compared and analysed based on the three groups. RESULTS: The average VA of type 1 patients was significantly lower than that of types 2 or 3 patients (P<0.001). There were no significant VA differences detected between types 2 and 3 patients. While most of the type 1 patients (21/22) showed non-recordable fERG, 3 out of 18 type 2 patients and none of type 3 patients showed non-recordable fERG. Significant differences of the fERG amplitudes were observed among the three groups (a-wave, b-wave, and OP, P<0.001 in all three components). However, the implicit time showed no difference between type 2 and 3. CONCLUSIONS: Analysing the IS/OS with OCT and the amplitudes of fERG may be helpful for monitoring RP patients in addition to VA and VF.

Photoreceptor integrity and visual acuity in cystoid macular oedema associated with retinitis pigmentosa.

AIMS: To assess the correlation between macular morphology and visual acuity in retinitis pigmentosa (RP) patients with cystoid macular oedema (CME). DESIGN: Retrospective cross-sectional study. PATIENTS AND METHODS: Forty-one eyes of 25 RP patients with CME. Patients underwent cross-sectional scans with optical coherence tomography (Stratus OCT). Age, total retinal thickness, photoreceptor thickness, and the transverse and vertical lengths of the cystoid space were measured. Correlation between visual acuity and each of the measurements were examined. Additionally, the status of the inner segment/outer segment junction (IS/OS) was classified as being absent, discontinuous, or distinct. Measurements were then compared among the three groups. RESULTS: Total retinal thickness or photoreceptor thickness was not correlated with visual acuity. There was a correlation between the transverse length of the cystoid space and visual acuity, although the correlation coefficient was weak (r=0.30). The logMAR visual acuity in the IS/OS absent group (0.67+/-0.43) was worse than that seen in the IS/OS discontinuous (0.22+/-0.19) or IS/OS distinct groups (0.07+/-0.16) (P<0.001). CONCLUSIONS: When monitoring CME associated with RP, the status of IS/OS is the essential parameter that needs to be examined.

Circulating hematopoietic stem cells in patients with choroidal neovascularization secondary to pathologic myopia.

BACKGROUND: Emerging evidences suggest that circulating hematopoietic stem cells (HSCs) affect the pathogenesis of choroidal neovascularization (CNV), however, the roles of HSCs in CNV remain unclear in human population. The current study was designed to investigate the role of HSCs in the pathogenesis of CNV secondary to pathologic myopia (PM). METHODS: We clinically documented 78 patients with CNV in PM, and 35 of 78 patients and 28 age-matched controls were experimentally analysed. Functional analyses of HSCs were performed using an ex vivo culture system. RESULTS: We disclosed colony-forming units of endothelial cell (CFU-EC) were markedly lower in patients with bilateral CNV compared to those with unilateral CNV (13.8+/-3.7 vs 45.9+/-7.8, P<0.001). Systemic characteristics between both groups showed no significant difference. To identify local ocular factors that may affect the occurrence of CNV, clinical parameters were compared with the following groups in all enrolled subjects: eyes with CNV vs without CNV in unilateral affected patients, and primary affected eyes vs secondary affected eyes in patients with bilateral CNV. However, no statistically significant factors were identified in any of the groups. CONCLUSIONS: Circulating HSCs may play a role in the bilateral involvement of CNV in PM patients as one of the systemic factors. Further prospective and longitudinal studies are required.

Photodynamic therapy combined with low-dose intravitreal triamcinolone acetonide for age-related macular degeneration refractory to photodynamic therapy alone.

AIM: To examine the effects of photodynamic therapy (PDT) with verteporfin combined with low-dose intravitreal triamcinolone acetonide (IVTA) for exudative age-related macular degeneration (AMD) that is resistant to PDT alone. DESIGN: Retrospective case series. METHODS: A retrospective review was performed, using the medical records of 22 eyes of 21 patients who consecutively received combined PDT and 2 mg of IVTA for exudative AMD with a suspected chorioretinal anastomosis or for AMD that was resistant to prior PDT alone. Only those patients who could be followed up for more than 12 months after this combined therapy were enrolled in the study. Best corrected visual acuity and intraocular pressure measurements were taken during each examination. Colour photography, fluorescein/indocyanine green angiography and optical coherence tomography were carried out at baseline and every 3 months thereafter. Need for retreatment was based on dye leakage and the presence of serous retinal detachement (SRD) seen by optical coherence tomography. RESULTS: Visual acuity improved or was maintained in the majority of patients, with the mean change between baseline and the last visit being an improvement of 0.94 lines (p = 0.45). Seventeen (77%) of the 22 eyes showed improved or maintained visual acuity after 12 months of follow-up. Eight (36%) of the 22 eyes continued to show an SRD at the 12-month follow-up; this corresponded to unchanged or even decreased leakage of dye. The mean number of retreatments was 1.36, but the incidence of side effects accompanying treatment was not as high as that reported previously for combined therapy that utilised higher-dose IVTA. CONCLUSIONS: PDT combined with low-dose IVTA for exudative AMD seems to be as effective and safe as combined therapy with the higher-dose IVTA that was reported previously.

A case of novel de novo paired box gene 6 (PAX6) mutation with early-onset diabetes mellitus and aniridia.

BACKGROUND: Paired box gene 6 (PAX6) is a transcription factor involved in eye development. Mutations of PAX6 cause congenital eye anomalies, such as aniridia. PAX6 is also involved in the development of the endocrine pancreas, and reported to be a genetic factor common to aniridia and glucose intolerance, although the latter is usually mild. Here, we describe a case of PAX6 mutation with early-onset diabetes mellitus. CASE REPORT: A 27-year-old woman was referred to our clinic. She was diagnosed having diabetes at the age of 15 with negative glutamic acid decarboxylase (GAD) antibody. Insulin treatment was started at age 24. Because she had aniridia, PAX6 gene mutation was investigated and a heterozygous 2-bp deletion (c.402del2) was identified. Her parents did not have aniridia and PAX6 mutations. Heterozygous PAX6 mutation may cause glucose intolerance. However, cases of early-onset diabetes mellitus have not been reported. Her parents did not have diabetes, but their insulinogenic indices were low (0.25 and 0.3, respectively). We thought her early-onset diabetes was partly as a result of PAX6 mutation and partly because of an unknown insulin secretory defect inherited from her parents. We could not find any mutations in HNF-1alpha, -1beta, -4alpha, IPF-1, ISL-1, BEAT2/NeuroD1, PAX4, and amylin genes. CONCLUSIONS: We report a case of PAX6 gene mutation with early-onset diabetes mellitus and aniridia. Low insulin secretory capacity in her parents suggested that her insulin secretory defect is as a result of not only PAX6 mutation but other genetic factors inherited from her parents.

Genetic analysis of cataract in Ihara epileptic rat.

We analyzed the mode of inheritance of cataract in the Ihara epileptic rat (IER) by crossing experiments, and mapped cataract-related genes by linkage analysis. Cataract did not develop in the F1 animals, but it developed in both male and female animals of backcross and F2. The occurrence rate of cataract was 48.5% in the backcross progeny and 19.4% in the F2 progeny. Thus, the character was considered to be inherited by the autosomal recessive mode. We found two groups that differed according to the time of onset among the backcross and F2 progeny: an early-onset group (EOG), in which cataracts developed by about 4 months after birth, and a late-onset group (LOG), in which cataracts developed 8 months or more after birth. Linkage analysis indicated the presence of one cataract gene each on Chromosome (Chr) 8 and Chr 15, and the cataract was demonstrated to be governed by more than one gene. The gene on Chr 8 was named Catil, and that on Chr 15. Cati2. Catil was involved in the occurrence of cataract, and the conditions required for cataract to develop were Cati1i/Cati1i or Cati1i/Cati1w. However, in the cataract rats with Cati1i/ Cati1w, the allele of Cati2 was always Cati2i/Cati2i. Cati2 was involved in the timing of onset of the cataract, and the precondition for early onset was Cati2i/Cati2i.

Simultaneous induction of galectin-3 phosphorylated on tyrosine residue, p21(WAF1/Cip1/Sdi1), and the proliferating cell nuclear antigen at a distinctive period of repair of hepatocytes injured by CCl4.

The period of repair of hepatocytes injured by CCl4 and signaling proteins intrinsic to this period were examined. A 30 kDa polypeptide detected by immunoblot analysis using anti-phosphotyrosine antibody in livers from rats 48 to 72 h after administration of a single dose of CCl4 was identified as galectin-3 induced in cytoplasm of periportal hepatocytes and phosphorylated on tyrosine residue(s). Simultaneously, these hepatocytes induced p21(WAF1/Cip1/Sdi1) in the nucleus and the proliferating cell nuclear antigen in both the nucleus and the cytoplasm, suggesting that hepatocytes during this distinctive period are quiescent and repair cellular damage. Trabecular architecture of hepatocytes with the proliferating cell nuclear antigen only in the nucleus was found at 96 h. These findings indicate that galectin-3 is a novel member of signaling proteins downstream of tyrosine kinase, and suggest that it plays roles in supporting repair or survival of the injured hepatocytes rather than their proliferation that is likely to be initiated later than 72 h.

DNA/RNA-dependent ATPase activity is associated with ATBF1, a multiple homeodomain-zinc finger protein.

The AT motif-binding factor 1 (ATBF1)-A is a large transcription factor containing four homeodomains and 23 zinc finger motifs. It has a number of motifs involved in transcriptional regulation, and in addition, several motifs found in enzymes, such as ATPases and helicases. In this study, we examined whether ATPase activity is associated with the ATBF1-A molecule. A 263-amino acid segment of the ATBF1-A molecule, termed AHZ, which contains the ATPase A-motif, homeodomain IV and zinc finger 21, was expressed in Escherichia coli in the form of glutathione S-transferase fusion protein and analyzed for ATPase activity. We found that AHZ was able to hydrolyze ATP with K(m) 10.6 microM and K(cat) 0.055 min(-1) at 5 mM Mg(2+) and pH 7.75. AHZ retained bacterial DNA and removal of the DNA resulted in 70% decrease in ATPase activity. The addition of double- or single-stranded DNAs restored 70-75% ATPase activity and that of RNA restored 50-55% activity. Site-directed mutagenesis of the A-motif resulted in 34% reduction of ATPase activity with no significant loss of bound DNA. In contrast, mutation of homeodomain IV and zinc finger 21 resulted in 90 and 80% reduction of ATPase, respectively, with the loss of the ability to bind to DNA and RNA. These results show that ATBF1 has at least one enzyme activity in addition to regulation of DNA transcription. The ATPase activity associated with ATBF1-A is DNA/RNA-dependent and unique in that it requires both homeodomain and zinc finger motifs.

The mouse ZFH-4 protein contains four homeodomains and twenty-two zinc fingers.

We isolated the mouse zfh-4 cDNA which is 12 kb long and capable of encoding a 3,550-amino acid protein containing four homeodomains and 22 zinc fingers including two pseudo zinc finger motifs. The mouse ZFH-4 is 51% homologous to the mouse ATBF1 and 23% to the Drosophila ZFH-2. The homeodomain and zinc finger regions are highly conserved between ZFH-4 and ATBF1 except that one zinc finger is missing in ZFH-4. Analysis of partial genomic sequences showed that the mouse zfh-4 and ATBF1 genes are similar in exon-intron organization. RT-PCR analysis of zfh-4 transcripts in adult mouse tissues showed that zfh-4 expression was low but reproducibly detectable in brain, heart, lung and muscle. In these mouse tissues, ATBF1 transcripts were poorly amplified by PCR under the conditions where zfh-4 transcripts were amplified, suggesting that the expression of zfh-4 mRNA is higher than that of ATBF1 mRNA. Other comparative analysis suggests functional similarities and dissimilarities between ZFH-4 and ATBF1.

Immunohistochemical characterization of glomerular PDGF B-chain and PDGF beta-receptor expression in diabetic rats.

Platelet-derived growth factor (PDGF) was found to contribute to the pathophysiological process in the development and progression of glomerulosclerosis characterized by mesangial cell proliferation and accumulation of extracellular matrix. To examine the role of PDGF in the development of diabetic nephropathy, we conducted immunohistochemical analysis for PDGF B-chain (PDGF-B) and PDGF beta-receptor (PDGFR-beta) in the glomeruli of streptozotocin-induced diabetic rats. At 2, 4, and 12 weeks after the onset of diabetes, the expression of PDGF-B in glomeruli of diabetic rats was increased significantly as compared to control or diabetic rats treated with insulin. Similar changes were observed on PDGFR-beta immunostaining. The immunostaining of mirror sections revealed the existence of PDGF-B or PDGFR-beta not only in mesangial cells but also in visceral epithelial cells. Glomerular volume was significantly increased in diabetes. This early glomerular abnormality was prevented by an inhibition of PDGF system with trapidil as well as by the treatment of insulin. Our results suggest that the activation of the PDGF system in glomerular cells might play an important role in the development of early glomerular lesion in diabetes.

Histidine 20, the crucial proximal axial heme ligand of bacterial heme oxygenase Hmu O from Corynebacterium diphtheriae.

The hemin complex of Hmu O, a 24-kDa soluble heme degradation enzyme in Corynebacterium diphtheriae, is coordinated axially to a neutral imidazole of a proximal histidine residue in Hmu O. To identify which of the eight histidines in Hmu O is the proximal heme ligand, we have constructed and expressed the plasmids for eight His --> Ala Hmu O mutants. Reconstituted with hemin, the active site structures and enzymatic activity of these mutants have been examined by EPR, resonance Raman, and optical absorption spectroscopy. EPR of the NO-bound ferrous heme-Hmu O mutant complexes reveals His(20) as the proximal heme ligand in Hmu O, and this is confirmed by resonance Raman results from the ligand-free ferrous heme-H20A. All eight His --> Ala mutants bind hemin stoichiometrically, proving that none of the histidines is essential for hemin-Hmu O formation. However, His(20) is crucial to Hmu O catalysis. Its absence by point mutation has inhibited the conversion of hemin to biliverdin. The ferric heme-H20A complex is pentacoordinate. Resonance Raman of the CO-bound ferrous heme-H20A corroborates this and reveals an Fe-C-O bending mode, delta(Fe-C-O), the first reported for a pentacoordinate CO-bound hemeprotein. The appearance of delta(Fe-C-O) in C. diphtheriae Hmu O H20A but not mammalian HO-1 mutant H25A indicates that the heme environment between the two heme oxygenases is different.

Role of PDGF B-chain and PDGF receptors in rat tubular regeneration after acute injury.

Various polypeptide growth factors are generally considered to be involved in the regulation of the nephrogenic process both after acute renal injury and during renal development. Because platelet-derived growth factor B-chain (PDGF-B) has been reported to be expressed in immature tubulus of the developing kidney, PDGF-B could play a role in the process of tubulogenesis. We examined the expression of PDGF-B and PDGF receptors alpha and beta and their localization in kidneys after ischemia/reperfusion injury. The mRNA expressions of PDGF-B, PDGFR-alpha, and PDGFR-beta were enhanced after injury. In the immunohistochemical analysis and/or in situ hybridization, PDGF-B and PDGFR-alpha, beta were expressed after reperfusion in the S3 segment of the proximal tubuli, where they were not expressed normally. The expressions of proliferating cell nuclear antigen and vimentin were concomitantly observed with PDGF-B and PDGFRs in the tubular cells of injured S3 segment at 48 hours after injury. Next, the inhibition of the PDGF-B/PDGFRs axis with either Trapidil or Ki6896, which was found to inhibit the phosphorylation of PDGFR-beta selectively, resulted in a rise of serum creatinine, higher mortality rate, abnormal regenerating process, and suppressed proliferation of tubular epithelial cells. These findings suggest that the PDGF-B/PDGFRs axis is involved in the proliferation of injured tubular cells and plays an important role in the regeneration of tubular cells from acute ischemic injury.

A mutation in the microtubule-associated protein tau in pallido-nigro-luysian degeneration.

We detected a missense mutation in exon 10 of tau that causes a substitution at codon 279 (N279K) in a Japanese patient with a familial background of parkinsonism and dementia originally described as pallido-nigro-luysian degeneration. This mutation is the same as one seen in a Caucasian family with pallido-ponto-nigral degeneration. The similarities between these two families suggest a common genetic mechanism that may account for the peculiar distribution of neuroglial degeneration with tauopathy.

Mossy fiber sprouting in the dentate gyrus in a newly developed epileptic mutant, Ihara epileptic rat.

We examined the correlation between seizure activity and development of mossy fiber sprouting in the hippocampal formation using Timm staining in a newly developed Ihara epileptic rat (IER). The sprouting of mossy fibers were clearly shown in the inner molecular portion of the dentate gyrus and in the stratum oriens of CA3 pyramidal cell layer with repeated seizures. A positive correlation between the frequency of generalized tonic and clonic convulsions and the Timm staining score in molecular layer of dentate gyrus was revealed. Sprouting of mossy fiber in IER seems to be linked with seizure activities resulting from epileptic bursts, not to the genetic mutation.