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Biomedical subjects

M Kawata

Publications and source records attributed to M Kawata.

At least 19 recordsLinked to original sources
PubMed1997

Short inverted repeats function as hotspots of intermolecular recombination giving rise to oligomers of deleted plastid DNAs (ptDNAs).

We have determined the nucleotide sequences around the junction points of oligomeric-deleted ptDNAs possessing a head-to-head or tail-to-tail configuration from long-term cultured cell lines and albino plants. It was shown that DNA rearrangement occurred by direct fusion of deleted ptDNAs in an inverted orientation, which was linked by an asymmetrical sequence of 254-698 bp derived from either of the ptDNAs joined. It is notable that inverted repeats of 7-14 bp flank the asymmetrical sequences at each of the junction points. These features of the DNA sequence around the junction points are commonly observed in oligomeric ptDNA with a large-scale deletion regardless of the cell lines employed. It is suggested that the short inverted repeats are involved in the intermolecular recombination of ptDNA.

Base Sequence↗
PubMed1997

Astrocytic lineage analysis by detection of GFAP promoter activity in vitro.

To survey the emergence and onset of differentiation of the astrocytic lineage in the developing mouse cerebral wall, the promoter activity of a 2.5 kb 5'-flanking region of glial fibrillary acidic protein (GFAP) was measured in individual developing brain cells using a retrovirus-mediated gene transfer system. We identified precursors for astrocytes in primary culture of embryonic mouse cerebral wall cells by detection of GFAP promoter activity, which was detected approximately 3 days prior to the appearance of GFAP immunoreactivity. Since retroviruses only integrate into the chromosomes of actively proliferating cells, cells detected by this method should have been mitotically active at the time of retroviral infection on day 15 postfertilization (E15). Furthermore, we observed that cells activating GFAP promoter were located near the ventricular surface of cultured cerebral wall slices as a cluster of spherical cells. These results demonstrate that precursor cells for astrocytes exist within the germinative zone of developing cerebral wall, and that these cells are mitotically active on day E15, which is a late stage of neuronal production period in the mouse cerebral wall. The morphology, location and mitotic activity of these cells suggest that they are unlikely to be cells that have been transformed from radial glial cells.

Animals↗
PubMed1996

Neuro-glial neurotrophic interaction in the S-100 beta retarded mutant mouse (Polydactyly Nagoya). III. Transplantation study.

The hippocampus and caudo-dorsal cortex of the homozygote of polydactyly mutant mouse (Polydactyly Nagoya, Pdn/Pdn) were markedly reduced in S-100 beta positive astrocytes and serotonergic fibers as compared to the heterozygote (Pdn/+) and wild type (+/+) [39]. The Pdn/Pdn mice die within 2 days after birth, so it is impossible to examine postnatal changes. To demonstrate the developmental change of Pdn/Pdn hippocampal tissue, we transplanted hippocampal pieces of neonatal Pdn/Pdn and +/+ mice into the right and left hippocampus of the same adult +/+ mice, respectively, and immunocytochemically examined them. Two weeks after transplantation, +/+ hippocampal tissue contained a large number of glial fibrillary acidic protein (GFAP) and S-100 beta positive astrocytes and a number of serotonergic fibers. While Pdn/Pdn hippocampal tissue contained numerous GFAP positive astrocytes, S-100 beta positive astrocytes and serotonergic fibers were not observed. Two months after transplantation, GFAP and S-100 beta were expressed in the Pdn/Pdn hippocampal tissue similar to the +/+ tissue. Serotonergic fibers were distributed in the +/+ tissue, while no serotonergic fibers were observed in the Pdn/Pdn transplant tissue. In contrast, no difference was observed in the tyrosine hydroxylase positive fibers between Pdn/Pdn and +/+ grafts. The expression of 5-HT1A receptor-like immunoreactivity was higher in the +/+ tissue than that of Pdn/Pdn tissue. The present results suggest that the expression of S-100 beta in the astrocytes of early stage of transplantation is a critical for fiber ingrowth of serotonergic neurons and expressions of 5-HT1A receptor.

Animals↗
PubMed1996

The alteration of glucocorticoid receptor-immunoreactivity in the rat forebrain following short-term and long-term adrenalectomy.

To examine the effect of short-term and long-term adrenalectomy (ADX) on the glucocorticoid receptor (GR) expression, we performed an immunohistochemical study on the rat forebrain. One day after ADX, the GR-immunoreactivity significantly decreased or disappeared in most forebrain structures, while relatively strong GR-immunoreactivity was still found within the hypothalamus especially in the arcuate nucleus (ARC) and the parvocellular paraventricular nucleus (PVN). Two weeks following ADX, GR-immunoreactive cells disappeared in many structures of the forebrain including most parts of hypothalamus while moderate GR-immunoreactivity was still observable in the ARC and PVN. More than 3 months after ADX, the rats still survived when they received replacement of corticosterone during the first 2 weeks following the operation. Moderate GR-immunoreactivity in the ARC and PVN of the hypothalamus was exhibited whereas no immunoreactive cells remained in the cerebral cortex, thalamus and other forebrain structures when these animals showed obvious cell death in the granule cells of the dentate gyrus, identified with the silver impregnation method for degenerating cells. Massive cell loss in this hippocampal region is an indicator of a complete ADX, in addition to the blood corticosterone level. These results demonstrate topographic differences of GR expression in the rat forebrain after ADX with only continuous immunoreactivity in the ARC and PVN of the hypothalamus, suggesting that some neurons in the ARC and PVN could keep active GR probably in order to maintain their survival after removing the adrenal gland.

Adrenalectomy↗
PubMed1996

Alteration of serotonergic innervation in the suprachiasmatic nucleus of the rat following removal of input fibers from retina and lateral geniculate nucleus.

To examine the influence of afferent input to the suprachiasmatic nucleus (SCN) on the development of serotonergic fibers in the SCN, afferent fibers from the retina and lateral geniculate nucleus (LGN) were eliminated in neonatal rats. Eight weeks after lesion, the distribution pattern of serotonergic fibers in the SCN was examined immunohistochemically. Neither bilateral enucleation nor LGN ablation altered the serotonergic fiber distribution in the SCN as compared to the normal adult rat. However, following combined lesions of bilateral enucleation and bilateral LGN ablation, the density of serotonergic fibers decreased throughout the SCN. The present results indicate that both retino-hypothalamic and geniculo-hypothalamic fibers may play an important role in the development of serotonergic innervation in the SCN in vivo.

Animals↗
PubMed1996

The perinatal ontogeny of estrogen receptor-immunoreactivity in the developing male and female rat hypothalamus.

Developmental expression of the estrogen receptor (ER) in rat hypothalamus was examined using immunohistochemistry. In the medial preoptic nucleus and ventromedial nucleus ER-immunoreactivity was detected as early as E17, whereas ER protein expression in the periventricular preoptic nucleus and arcuate nucleus was delayed until E19. These results show that following a region specific onset of the ER protein expression sex differences in ER levels are already detectable during the perinatal period.

Animals↗
PubMed1996

Effects of the addition of hyaluronate segments with different chain lengths on the viscoelasticity of hyaluronic acid solutions.

The effects of the addition of sodium hyaluronate segments (sHA) with different chain lengths on the viscoelasticity of high molecular weight sodium hyaluronate (HA) aqueous solutions were studied. The additive effects of sHA depended on the chain length of sHA. Shorter sHA decreased storage (G') and loss (G") moduli, whereas longer sHA increased both moduli. In physiological saline, the effects of the addition of sHA depended on the chain length of sHA, as in aqueous solutions, except that shorter segments did not decrease both moduli. The effects of the addition of monosaccharides, i.e., N-acetyl glucosamine (GlcNAc) and sodium glucuronate (GlcANa), were also studied. Although GlcNAc increased G' and G", GlcANa decreased both moduli. A shift factor "A," which depended on chain-length effects, a sugar effect, and a salt effect, was developed to explain these additive effects quantitatively.

Carbohydrate Sequence↗
PubMed1996

Organization of regenerating serotonergic fibers in the hippocampal formation.

To evaluate the capacity of fiber outgrowth of serotonergic and dopaminergic neurons from the dorsal raphe tissue, the following three experiments were performed; (1) fetal mesencephalic raphe tissue was transplanted into the ventricle near the denervated hippocampal formation of adult rats, (2) fetal mesencephalic raphe and neonatal hippocampal tissues were transplanted into the anterior eye chamber of adult rats, and (3) fetal mesencephalic raphe tissue was explanted together with the neonatal hippocampal tissue. The extent of the fiber outgrowth was examined immunohistochemically using serotonin and tyrosine hydroxylase (TH) antisera. Three months after transplantation into the host brain, serotonin-immunoreactive (ir) fibers from raphe graft were densely distributed throughout the graft and in the host hippocampal formation, and TH-ir fibers were restricted to an area near the somata of TH-ir neurons. In particular, hyperinnervation of serotonin-ir fibers was observed in the molecular layer of the dentate gyrus. Two months after intraocular transplantation, mesencephalic raphe tissue contained a large number of serotonin- and TH-ir neurons and fibers. The distribution pattern of outgrowing serotonin-ir fibers in the hippocampal tissue was similar to that observed following intraventricular transplantation. Two weeks after explantation, the raphe tissue contained numerous serotonin-ir neurons and their fibers. These fibers extended into the hippocampal tissue in the same manner as the intraventricular and intraocular transplants. These results indicate that the intrinsic factors of hippocampal tissue influence the organization of serotonergic fibers in the hippocampal formation.

5,6-Dihydroxytryptamine↗
PubMed1996

Exposure of postnatal rats to glucocorticoids suppresses the development of choline acetyltransferase-immunoreactive neurons: role of adrenal steroids in the development of forebrain cholinergic neurons.

Rat forebrain cholinergic neurons undergo dynamic developmental changes, showing a continuous increase in choline acetyl-transferase (ChAT) activity, during the early postnatal period. In adult rats, increases in circulating glucocorticoids result in decreases in activity of forebrain neuronal ChAT, thus raising the possibility that postnatal development of forebrain cholinergic neurons results from low levels of these hormones. In the rat, the first 2 weeks postnatally are characterized by very low levels of adrenal steroids. To understand the role of endogenous glucocorticoids in the development of forebrain cholinergic neurons, we studied the changes in ChAT immunoreactivity in forebrain cholinergic neurons of postnatal rats which had received daily subcutaneous injection of the synthetic glucocorticoid dexamethasone for 8 days. Immunohistochemical analysis of the rat pup forebrain revealed nearly complete obliteration of ChAT-immunoreactive neurons in the caudate-putamen, especially in the dorsolateral region of the rostral part. At the same stage, treatment with dexamethasone induced significant decreases in both number and length of dendritic branches of ChAT-immunoreactive neurons in the substantia innominata and the diagonal band. Despite the marked alterations in the caudate-putamen and diagonal band, the ChAT-immunoreactive neurons in other forebrain structures such as globus pallidus and medial septal nucleus showed little change. In the caudate-putamen, Nissl staining and specific labeling for nuclear DNA fragmentation exhibited no increase in number of dying cells following dexamethasone treatment, therefore indicating that the loss of ChAT immunoreactivity is not due to glucocorticoid-induced cholinergic cell death. These observations demonstrated that the development of cholinergic neurons in rat pups was inhibited by prolonged glucocorticoid exposure, suggesting that low levels of adrenal steroids may promote the postnatal development of these neurons.

Adrenal Cortex Hormones↗
PubMed1996

Gastrointestinal physiology-regulated dogs for bioavailability evaluation of an oral controlled-release dosage form composed of pulsatile release granules.

Gastrointestinal (GI) physiology-regulated beagle dogs (regulated dogs) were regulated by a combined treatment using intramuscular pentagastrin and intravenous atropine sulfate. In the regulated dogs, the gastric pH was shifted to around 2, and the GI transit time was prolonged to approximate that in humans. Pranoprofen, an acidic anti-inflammatory agent, was granulated around sucrose seeds, and then coated with low substituted hydroxypropyl cellulose used as a swelling agent to afford plain granules (A-granule). Then, A-granule was coated stepwise with ethyl cellulose used as an outer shell material to afford two kinds of pulsatile release granules (B- and C-granules). In the dissolution study using pH 1.2 and 6.8 media, A-, B- and C-granules exhibited lag times of 0, 1 and 2h, respectively. Even in intact beagle dogs, the absorption profiles for A- and B-granules corresponded with those expected from the dissolution profiles. In contrast, the bioavailability of C-granule was only 35% in the intact dogs, but was 55% in the regulated dogs. Thus, the absorption of pranoprofen from pulsatile release granules after a longer lag time should be influenced by the location in the GI tract. Next, a controlled-release (CR) dosage form of pranoprofen was tentatively prepared by combining A-, B- and C-granules at the ratio of 3:4:3 (w/w in contents of pranoprofen). The bioavailability of the CR dosage form was significantly diminished in the intact dogs, being about 70% as much as that in the regulated dogs. Therefore, the regulated dogs would be superior to the intact dogs in avoiding the underestimation of the bioavailability of a CR dosage form with a pulsatile release property.

Animals↗
PubMed1996

A case of Crush syndrome with giant negative T waves and reversible left ventricular dysfunction.

A 54-year-old male experienced the Hanshin earthquake at 5:46 am on Jan. 17, 1995. He was rescued after being buried under his house for 20 h. After being treated at two hospitals, he was admitted to our hospital with acute renal failure caused by crush syndrome. The maximal serum creatinine kinase level was 35,000 IU/L (CK-MM: 100%), and the maximal myoglobin level was 12,600 ng/ml. An electrocardiogram showed inverted T waves in V5,6 which later became giant negative T waves, and a QS pattern in a VL and V1-6. Two-dimensional echocardiography showed a hypokinetic left ventricle. He was treated with hemodialysis 13 times. Cardiac contraction gradually improved to the normal level. Coronary angiography revealed normal coronary arteries and acetylcholine did not induce coronary spasm. Biopsy specimens from the right ventricular septum showed slight degeneration. 201Tl imaging showed hypoperfusion except in the anterior wall and 123I-MIBG imaging showed a perfusion defect except in the anterior wall. After about 1 month, only 201Tl imaging showed improvement. We believe that myocardial ischemia, cardiac sympathetic nerve damage and/or cardiac contusion caused giant negative T waves and left ventricular dysfunction. This is a rare case which showed significant myocardial damage with crush syndrome.

3-Iodobenzylguanidine↗
PubMed1996

Phenotypic alterations of neuropeptide Y, vasoactive intestinal peptide and choline acetyltransferase in rat cultured chromaffin cells as effected by nerve growth factor and glucocorticoid.

We assessed changes in neuropeptide Y (NPY), vasoactive intestinal peptide (VIP) and choline acetyltransferase (ChAT) immunoreactivities when neonatal rat chromaffin cells were cultured in a medium containing nerve growth factor (NGF), or the synthetic glucocorticoid dexamethasone (DEX), examining whether their expression was correlated with the morphological changes induced by NGF and DEX. All of the chromaffin cells in culture were tyrosine hydroxylase (TH)-immunopositive regardless of whether they extended processes. TH-immunoreactive materials of NGF-treated chromaffin cells were distributed in all the cytoplasmic processes, even at the tips of growth cones. The percentage of NPY-positive chromaffin cells did not change markedly when treated with NGF or DEX throughout the 14 days in culture. The proportion of VIP-positive chromaffin cells increased gradually in the NGF-treated group and that of ChAT-positive cells in the group was similar to VIP. The morphological alterations induced by NGF were not correlated with the changes in proportions of NPY-, VIP- or ChAT-positive chromaffin cells. The percentages of VIP- or ChAT-immunopositive chromaffin cells in the NGF-treated group showed much greater increases than those in the DEX-treated group. These findings suggest that NGF might modulate the phenotypic changes of neuropeptides and amines in rat chromaffin cells.

Animals↗
PubMed1996

The effects of nerve growth factor on newborn rat dorsal root ganglion neurons in vitro: a scanning electron microscopic observation.

The effects of nerve growth factor (NGF) on the three-dimensional structure of newborn rat dorsal root ganglion (DRG) neurons, in vitro, were examined by scanning electron microscopy. Throughout the culture in both NGF treated and control groups, two types of structures of the surface were recognized, smooth surfaced and rough surfaced neurons. Growth cones and varicosities of the processes were observed after 12 hours of culture in NGF-treated groups, in contrast they were observed after 24 hours in control groups. The size and number of growth cone and varicosity was greater in NGF-treated groups than in control groups. NGF elongated the processes of DRG neurons after 24 hours of culture. NGF also significantly increased the number of surviving neurons after 48-72 hours of culture. Rough surfaced neurons were more sensitive than smooth surfaced neurons to NGF in enhancing survival. These results suggest that NGF may induce maturation of DRG neurons through elongation of its processes and the formation of growth cones and varicosities. Furthermore, the perikaryal projections of DRG neurons may be related to neuron survival after NGF treatment.

Animals↗
PubMed1995

Age-related decrease of serotonergic fibres and S-100 beta immunoreactivity in the rat dentate gyrus.

The age-related changes of serotonergic fibres and S-100 beta-positive astrocytes in the rat dentate gyrus were examined using immunohistochemistry. A significant reduction in the number of the serotonergic fibres and S-100 beta-positive astrocytes was observed throughout the dentate gyrus of the aged rat. A positive correlation was noted between the decrease of serotonergic fibres and S-100 beta-positive astrocytes in the aged rat dentate gyrus. These findings support the hypothesis that the age-related degeneration of serotonergic fibres in the dentate gyrus is caused by the decrease in serotonergic neurotrophic factor S-100 beta in the astrocytes.

Aging↗
PubMed1995

Water deprivation induces regional expression of c-fos protein in the brain of inbred polydipsic mice.

We studied the effects of water deprivation on the expression of c-fos protein (Fos) in the brain of inbred polydipsic mice, STR/N strain, that show extreme polydipsia without a lack of vasopressin in the body. Non-polydipsic mice, ICR strain, were used as controls. All male animals were deprived of water for 24 and 48 h. Fos-like immunoreactivity (Fos-LI) in the brain was studied by immunohistochemical techniques. In both groups of mice water deprivation induced a remarkable increase in Fos-LI in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei, the median preoptic nucleus (MnPO), the organum vasculosum laminae terminalis (OVLT) and the subfornical organ (SFO). A far more increase, however, was seen in the MnPO, the SFO and the area postrema (AP) of the polydipsic mice compared to those of the non-polydipsic control mice. In the nucleus of the tractus solitarius (NTS) and in the anteroventral part of the PVN (avPVN), water deprivation caused a clear increase in Fos-LI in the polydipsic mice, while in the non-polydipsic mice the same treatment induced no Fos-LI in the NTS and no change in the avPVN. These results indicate that neurons in the circumventricular organs and the NTS are strongly activated by water deprivation in the polydipsic mice, suggesting that these brain structures play an important role in the polydipsia.

Animals↗
PubMed1995

Role of neuropeptide Y projection on the development of serotonergic innervation in the suprachiasmatic nucleus of the rat, shown by triple intraocular grafts.

In our previous paper, the intraocular double grafts of fetal mesencephalic raphe and suprachiasmatic nucleus (SCN) demonstrated that the serotonergic fibers from raphe tissue did not show a dense innervation of SCN [28]. To examine the influence of NPY innervation from lateral geniculate nucleus (LGN) on the development of serotonergic fibers in the SCN, fetal mesencephalic raphe, SCN and LGN tissues were transplanted together into the eye chamber of adult rat. 6 weeks after transplantation, triple grafts were immunohistochemically examined. The SCN cell cluster was recognized by vasoactive intestinal polypeptide (VIP)- and arginine vasopressin (AVP)-immunoreactive neurons and The SCN cell cluster also contained a large number of serotonin-immunoreactive fibers from raphe tissue and a moderate number of neuropeptide Y (NPY)-immunoreactive fibers from LGN tissue. The present results provide information on possible NPY-serotonin interactions in the developing SCN.

Animals↗
PubMed1995

Oxytocin-producing and vasopressin-producing eosinophils in the mouse spleen: immunohistochemical, immuno-electron-microscopic and in situ hybridization studies.

Oxytocin-like and vasopressin-like immunoreactive cells, and the cells expressing mRNAs for these peptides in the spleen of the C57BL/6 mouse were studied by immunohistochemistry, immuno-electron microscopy and in situ hybridization. Immunoreactive cells were distributed mainly in the splenic cord and marginal zone, whereas there were few in the lymphocyte-packed periarteriolar-lymphoid sheath, lymphoid follicle and germinal center. More numerous vasopressin-positive cells were seen in the splenic cord. The colocalization of oxytocin-like and vasopressin-like immunoreactivity in the same cells was identified by the investigation of mirror sections. By the pre-embedding immuno-electron-microscopic method using antisera against oxytocin and vasopressin, immunopositive reaction products were localized in the matrix around the specific granules, small clear vesicles and mitochondrial membrane of the eosinophils. No immunoreactivity to these peptides was found within the specific granules of the eosinophils. In situ hybridization with synthetic oligonucleotide probes labeled with 32P revealed the presence of mRNAs for oxytocin and vasopressin in the cells of the spleen, the distribution of the mRNAs for these peptides being the same as that of immunopositive cells. These observations suggest that eosinophils synthesize both oxytocin and vasopressin and store them in the matrix. Possible differences in the mechanism of synthesis and storage of these peptides between peripheral eosinophils and hypothalamic neurons are discussed.

Animals↗