Shigeko Fushimi

Expression of insulin-like growth factors in remyelination following ethidium bromide-induced demyelination in the mouse spinal cord

Insulin‐like growth factors, IGF‐I and IGF‐II, play important roles in development and myelination in the CNS, but little is known about the response of IGF after demyelination. The present study investigated the expression of IGF and their cognitive receptors in the process of remyelination following ethidium bromide (EBr)‐induced demyelination in the adult mouse spinal cord. The present results, in a quantitative real‐time PCR, showed significant increases in the levels of the mRNA for both IGF‐I and IGF‐II during both the demyelination and remyelination stages. The levels of IGF‐I receptor (IGF‐IR) mRNA increased from 10 days to 4 weeks after the EBr injection. The levels of IGF‐II receptor (IGF‐IIR) mRNA decreased for 6 days and then increased 10 days after the EBr injection. In situ hybridization studies showed the cells expressing IGF‐I mRNA to be mainly macrophage‐like cells, while those expressing IGF‐II mRNA were predominantly Schwann cell‐like cells invading the demyelinating lesion. The immunoreactivity for the IGF‐IR and IGF‐IIR increased in various kinds of cells within and around the demyelinating lesions from 6 days to 4 weeks after the EBr injection. These results suggest that locally produced IGF could partly be involved in some mechanisms underlying remyelination processes following the EBr‐induced demyelination in the mouse spinal cord.

17β-Estradiol inhibits chondrogenesis in the skull development of zebrafish embryos

17beta-Estradiol (E2) plays important roles in the development and differentiation of the gonad and central nervous systems, but little is known regarding the effects of exogenous E2 on chondrogenesis in skeletal development. In the present study, we found that treatment with E2 1-5 days post-fertilization (dpf) at concentrations above 1.5x10(-5)M increased the mortality rate in zebrafish embryos. Morphological analysis showed that treatment with E2 1-5dpf caused abnormal cartilage formation in a dose-dependent manner at concentrations above 5x10(-6)M. E2 1-5dpf at 1.5x10(-5)M caused defects of the ethmoid plate, parallel cleft of the trabecular cartilage, and hypoplasia of Meckels cartilage and the ceratohyal cartilage. The sensitivity of embryos to E2 depended on the developmental stage. In early chondrogenesis (1-2dpf), the embryos were highly sensitive to E2, leading to hypoplasia of the cartilage. In situ hybridization studies showed that expression levels of patched1 (ptc1) and patched2 (ptc2) receptor mRNAs were markedly decreased by exposure to 2x10(-5)M E2 1-2dpf. However, the expression levels of sonic hedgehog (shh) and tiggywinkle hedgehog (twhh) mRNAs were constant in the E2-treated embryos. In addition, the estrogen receptor antagonist ICI 182,780 did not completely abolish the effects of E2, suggesting that E2 may not inhibit chondrogenesis through its nuclear estrogen receptor. These results suggest that exposure to exogenous E2 possibly inhibits chondrogenesis via inhibition of the hedgehog (Hh) signal transduction system.

The reaction of glial progenitor cells in remyelination following ethidium bromide-induced demyelination in the mouse spinal cord

The present study investigated how glial progenitor cells participated in the process of remyelination following ethidium bromide (EBr)‐induced demyelination in the adult mouse spinal cord.

Immunohistochemical distribution of cation-dependent mannose 6-phosphate receptors in the mouse central nervous system: comparison with that of cation-independent mannose 6-phophate receptors

Most mammalian cells express two types of mannose 6-phosphate (M6P) receptors (MPRs), which are involved in the sorting of lysosomal enzymes within the cells. They are referred to as cation-dependent (CD-) MPR and cation-independent (CI-) MPR/insulin-like growth factor II receptor (IGF-IIR), based on their divalent cation requirements and the ability to bind IGF-II. The complementary actions of these two related but distinct MPRs in the sorting function suggest that they have different immunohistochemical distributions. To address this issue, we investigated the cellular distribution of CD-MPR immunoreactivity in the adult mouse central nervous system (CNS), and compared it with that of CI-MPR/IGF-IIR immunoreactivity, which we had previously investigated. These two immunoreactivities were localized in neurons of the CNS, with more intense labeling in the medial septal nucleus, the nucleus of the Brocas diagonal band, layers IV-VI of the cerebral neocortex, layers II-III of the entorhinal cortex, the habenular nucleus, the median eminence, several nuclei and structures of the brainstem, the Purkinje cell layer of the cerebellum, and in the ventral horn of the spinal cord. Although intense immunoreactivities of both MPRs were observed in the same groups of neurons in the same regions, the spatial differences in immunoreactive intensity for CI-MPR/IGF-IIR were greater, particularly in the telencephalon such as the basal forebrain and cerebral cortex, than those for CD-MPR. These findings suggest that CD-MPR is ubiquitously necessary for the general function of neurons, whereas CI-MPR/IGF-IIR is selectively necessary for certain region- and neurotransmitter-specific functions of neurons.

Does methamphetamine affect bone metabolism

There is a close relationship between the central nervous system activity and bone metabolism. Therefore, methamphetamine (METH), which stimulates the central nervous system, is expected to affect bone turnover. The aim of this study was to investigate the role of METH in bone metabolism. Mice were divided into 3 groups, the control group receiving saline injections, and the 5 and 10mg/kg METH groups (n=6 in each group). All groups received an injection of saline or METH every other day for 8 weeks. Bone mineral density (BMD) was assessed by X-ray computed tomography. We examined biochemical markers and histomorphometric changes in the second cancellous bone of the left femoral distal end. The animals that were administered 5mg/kg METH showed an increased locomotor activity, whereas those receiving 10mg/kg displayed an abnormal and stereotyped behavior. Serum calcium and phosphorus concentrations were normal compared to the controls, whereas the serum protein concentration was lower in the METH groups. BMD was unchanged in all groups. Bone formation markers such as alkaline phosphatase and osteocalcin significantly increased in the 5mg/kg METH group, but not in the 10mg/kg METH group. In contrast, bone resorption markers such as C-terminal telopeptides of type I collagen and tartrate-resistant acid phosphatase 5b did not change in any of the METH groups. Histomorphometric analyses were consistent with the biochemical markers data. A significant increase in osteoblasts, especially in type III osteoblasts, was observed in the 5mg/kg METH group, whereas other parameters of bone resorption and mineralization remained unchanged. These results indicate that bone remodeling in this group was unbalanced. In contrast, in the 10mg/kg METH group, some parameters of bone formation were significantly or slightly decreased, suggesting a low turnover metabolism. Taken together, our results suggest that METH had distinct dose-dependent effects on bone turnover and that METH might induce adverse effects, leading to osteoporosis.

Association between estrogen receptor α polymorphisms and equol production, and its relation to bone mass

To investigate the relationship between estrogen receptor polymorphisms and equol production and its effect on bone turnover, 139 workers (mean age 38.3+/-11.1 years) in Japan were recruited. Bone mineral density (BMD), bone turnover markers, and serum equol were measured at a health examination. DNA samples were prepared to detect the estrogen receptor alpha (ERalpha) polymorphism and were digested by PvuII. The number of equol producers was 57. No statistically significant differences were observed in bone mineral density and bone turnover markers between each ERalpha polymorphism and equol production. Since the adjusted odds ratio indicated that interaction itself decreased the risk of osteosono-assessment index (OSI) reduction using logistic regression analysis, further analysis was performed divided by each ERalpha polymorphism. Although the crude odds ratio showed no relationship between equol producers and non-producers, the adjusted odds ratio showed that equol producers with ERalpha pp had a significantly decreased risk of OSI reduction. Although this study was cross-sectional, both equol production and ERalpha polymorphism are closely associated with each other in relation to BMD.

Alterations in bone turnover by isoflavone aglycone supplementation in relation to estrogen receptor α polymorphism

Soybean isoflavones have structural similarity to estrogen and have attracted much attention due to their prevention of postmenopausal symptoms. It is critical for women to maintain a high bone mineral density (BMD) prior to menopause to prevent osteoporosis. In the present study, the effect of isoflavone aglycone (IA) supplementation on bone turnover was examined in relation to the estrogen receptor α (ERα) polymorphism. Natural isoflavones are glycosides that must be hydrolyzed to aglycones by intestinal microflora to have an effect. To avoid interference by flora, IA (30 mg/day) (but not isoflavones) or a placebo were administered as a supplement for 3 months to a Japanese population consisting of 81 premenopausal women. Due to variations in the intestinal flora, some but not all subjects were able to further metabolize IA into equol. Differences between equol producers and non-producers were also considered. To estimate BMD, the osteo-sono-assessment index (OSI) was determined by measuring bone density at the calcaneus and levels of bone biochemical markers (bone-specific alkaline phosphatase, α-carboxylated osteocalcin, undercarboxylated osteocalcin and deoxypridinoline) before and after supplementation. DNA samples from the subjects were examined for the presence of the XbaI restriction fragment length polymorphism (RFLP) in intron 1. According to univariate analysis, IA had a favorable effect on the OSI of subjects with the X allele, with X designated RFLP undigested by XbaI, although the difference was not statistically significant. Alterations in the levels of bone biochemical markers were also not significant. Thus, a further logistic regression analysis was performed. This indicated that subjects with the XX homozygote administered the IA supplement were less likely to have reduced OSI values. Although equol has been proposed to have the highest phytoestrogen activity, its effect was not apparent. Thus, low-dose IA supplementation is useful for maintaining BMD in premenopausal XX subjects, independent of equol.

5HTT polymorphisms are associated with job stress in the Japanese workers

Recently, the number of workers who suffer from job stress was increasing in Japan because of a prolonged recession, increasing number of elderly workers, and structural reorganization of companies. On the other hand, polymorphism associated with depression or alcoholism was detected. Relationship between job stress and these polymorphisms were investigated. Brief job stress questionnaire was assessed for 243 employees who worked at a manufacturing company and a local hospital in Japan (mean age 40.8 years). Alcohol consumption and smoking habit were assessed as lifestyle factors. DNA samples were prepared to detect polymorphisms of 5HTT, aldehyde dehydrogenase 2 (ALDH2), D2 dopamine receptor (DRD2), and cytochrome p450 2A6 (CYP2A6) genes. The level of depressed mood by job stress was significantly higher among carriers of two short alleles of the 5HTT regulatory region compared with carriers of one or two long alleles (Mann-Whitney U, p<0.05). In a logistic regression analysis, the s/s allele of the 5HTT had a tendency to be a risk of depressed mood. When subjects had high supervisors support, depressed mood was significantly lower irrespective of 5HTT polymorphism. Job stress may elicit biological responses that contribute to depressed mood in relation to 5HTT polymorphism.

Spinal cord lesions of multiple sclerosis

The neuropathological findings of the spinal cord lesions of six human multiple sclerosis cases are described. The spinal cord was extensively necrotic and occasionally cystic in five remitting and relapsing cases. The lesions became more severe as the disease course prolonged and relapses increased. The spinal cords of two cases in particular, with a duration of illness of more than 5 years, were severely atrophic. In these cases, peripheral type remyelination was prominent, although central type remyelination was minimal. In contrast, in mouse spinal cords, in which experimental demyelination and remyelination were induced by ethidium bromide, the degree of central type remyelination and peripheral type remyelination was almost the same. Longitudinal sections of the transitional zone between the areas of central type remyelination and peripheral type remyelination contrained Ranvier nodes, in which central type myelin and peripheral type myelin were situated side by side around a central type axon. These transitional zones were similar to those of the normal transitional zone between the central nervous system and peripheral nervous system of the nerve roots. One chronic progressive case, despite the very long duration of illness, showed classical sharply demarcated demyelinated lesions with marked fibrillary gliosis. The spinal cord of this case was not atrophic and axons were well preserved.