Biomedical subjects

T Maeda

Publications and source records attributed to T Maeda.

At least 109 records · Page 6Linked to original sources

PubMed2001

Development of a real-time hand dose monitor for personnel in interventional radiology.

Medical procedures denoted as interventional radiology require operation near an X ray beam, which brings high dose exposures to the operators' hands. For the effectual control of their extremity doses, a prototype of a real-time wrist dosemeter has been developed, hand dose monitor (HDM), based on a single silicon detector. Experiments were performed to test its response to diagnostic X rays. The HDM was highly sensitive and showed a linear response down to doses of a few tens of microsieverts. Though dose rate, energy and angular dependence of the response were observed in some extreme conditions, the HDM was proved to be of practical use if it was appropriately calibrated. Since an HDM enables personnel to check their hand doses on a real-time basis, it would enable medical staff to control the exposure themselves.

Calibration↗

PubMed2001

Dynamic changes of connexin-43, gap junctional protein, in outer layers of cumulus cells are regulated by PKC and PI 3-kinase during meiotic resumption in porcine oocytes.

Mammalian oocytes are surrounded by numerous layers of cumulus cells, and the loss of gap junctional communication in the outer layers of cumulus cells induces meiotic resumption in oocytes. In this study, we investigated the dynamic changes in the gap junctional protein connexin-43 in cumulus cells during the meiotic resumption of porcine oocytes. The amount of connexin-43 in all layers of cumulus cells recovered from cumulus-oocyte complexes was increased after 4-h cultivation. However, at 12-h cultivation, the positive signal for connexin-43 immunoreactivity was markedly reduced in the outer layers of cumulus cells. When these reductions of connexin-43 were blocked by protein kinase C (PKC) or phosphatidylinositol (PI) 3-kinase inhibitor, networks of filamentous bivalents (i.e., advanced chromosomal status) were undetectable in the germinal vesicle of the oocyte. After 28-h cultivation, when the majority of oocytes were reaching the metaphase I (MI) stage, the connexin-43 in the inner layers of cumulus cells was phosphorylated, regardless of mitogen-activated protein (MAP) kinase activation. These results suggest that the initiation of meiotic resumption, namely, the formation of networks of filamentous bivalents in germinal vesicle, is associated with the reduction of gap junctional protein connexin-43 in the outer layers of cumulus cells via the PKC and/or PI 3-kinase pathway. Moreover, the connexin-43 in the inner layers of cumulus cells is phosphorylated during meiotic progression beyond the MI stage, regardless of MAP kinase activation in cumulus cells surrounding the oocyte.

Animals↗

PubMed2001

Effects of ethanol on L-arginine transport in rat Ito cells in relation to nitric oxide production.

BACKGROUND: Nitric oxide (NO) is a potent mediator of hepatic sinusoidal hemodynamics that is synthesized in the hepatic stellate cells (Ito cells, fat-storing cells) and affects these cells. NO production may depend on the induction of inducible nitric oxide synthase and on transport of extracellular L-arginine. The precise mechanism that controls NO production in stellate cells was characterized recently. METHODS: Kinetic analysis of L-arginine transport and reverse transcription-polymerase chain reaction for cationic amino acid transporter (CAT) were carried out by using stellate cells prepared from the male Wistar rat. The effect of ethanol on L-arginine transport and NO production of stellate cells was assessed in the presence of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma. RESULTS: The L-arginine transport system functioning in the hepatic stellate cells was system y+, possibly mediated by CAT-1 and CAT-2B (Km approximately 50 microM). IFN-gamma in combination with TNF-alpha induced NO production with an enhancement in CAT-2B mRNA expression and L-arginine transport, whereas L-arginine transport and NO production were suppressed by coincubated ethanol. CONCLUSIONS: In hepatic stellate cells, ethanol has suppressive effects on NO production and extracellular L-arginine transport in the presence of TNF-alpha and IFN-gamma. The estimated Km of L-arginine transporter in hepatic stellate cells is very similar to the physiological L-arginine concentration in portal vein. Our findings may support the merit of further studies on the modulation of NO production via access to portal blood L-arginine concentration to control disturbed hepatic sinusoidal blood flow in patients with alcoholic liver disease.

Amino Acid Transport Systems, Basic↗

PubMed2001

Clinical and endoscopic features of adult T-cell leukemia/lymphoma with duodenal involvement.

We describe three cases of adult T-cell leukemia/lymphoma (ATLL) with duodenal involvement and provide a review of the literature. The first case, a 74-year-old woman with acute subtype of ATLL, had multiple polypoid lesions from the bulbus extending into the descending portion of the duodenum. The second case, a 70-year-old man with lymphoma subtype of ATLL, had a polypoid tumor in the descending portion of the duodenum and multiple protruded lesions in the small and large intestines. The third case, a 67-year-old man with lymphoma subtype of ATLL, had a flat-elevated lesion in the descending portion of the duodenum, as well as a gastric ulcerated lesion. Biopsies from these lesions showed mucosal invasion of ATLL cells in each case. All patients received combination chemotherapy, which was successful in the first and third cases, accompanied by the disappearance of gastroduodenal lesions.

Adult↗

PubMed2001

Adenosine A(2A) receptors mediate cardiovascular responses to hypoxia in fetal sheep.

Nonselective adenosine (ADO) receptor antagonists block hypoxia-induced bradycardia and hypertension in fetal sheep. This study was designed to determine the ADO receptor subtype that is involved in these cardiovascular responses. In chronically catheterized fetal sheep (>0.8 term), fetal hypoxemia was induced by having the ewe breathe a hypoxic gas mixture (9% O(2)-3% CO(2)-88% N(2)) for 1 h. Intra-arterial infusion of ZM-241385, an antagonist highly selective for ADO A(2A) receptors, to eight fetuses during normoxia significantly increased mean arterial pressure (MAP) from 42.5 +/- 2.0 to 46.1 +/- 2.0 mmHg without altering heart rate (HR). Infusion of a selective antagonist of ADO A(1) receptors [1, 3-dipropyl-8-cyclopentylxanthine (DPCPX)] elevated MAP and HR only after the infusion was terminated, although administration of the vehicle for ZM-241385 or DPCPX had no effect on MAP or HR. Isocapnic hypoxia with infusion of DPCPX or the vehicle for DPCPX or ZM-241385 produced a transient fall in HR, a rise in MAP, and a decrease in plasma volume. In contrast, ADO A(2A) receptor blockade abolished the hypoxia-induced bradycardia and hypertension and blunted the decline in plasma volume. We conclude that fetal ADO A(2A) receptors: 1) modulate AP during normoxia, and 2) mediate cardiovascular responses during acute O(2) deficiency.

Adenosine↗

PubMed2001

Adenosine A(1) and A(2A) receptors modulate sleep state and breathing in fetal sheep.

This study was designed to determine the adenosine (Ado) receptor subtype that mediates the depressant effects of Ado on fetal breathing and rapid eye movements (REM). In chronically catheterized fetal sheep (>0.8 term), intra-arterial infusion of N(6)-cyclopentyladenosine (CPA), an Ado A(1)-receptor agonist, increased the incidence of high-voltage electrocortical (ECoG) activity while virtually abolishing low-voltage activity, REM, and breathing. These effects were blocked by 9-cyclopentyl-1,3-dipropylxanthine (DPCPX), an Ado A(1)-receptor antagonist. Infusion of DPCPX alone increased breath amplitude but had no significant effect on inspiratory duration, breath interval, incidence of REM, or incidence of low-voltage activity. Ado A(2A)-receptor blockade with ZM-241385 increased the incidence of low-voltage ECoG activity, REM, and breathing but had no effect on breath amplitude or respiratory cycle. Both DPCPX and ZM-241385 eliminated the inhibitory effects of Ado on REM and breathing. We conclude that 1) Ado A(1) receptors tonically inhibit fetal respiratory drive, 2) Ado A(2A) receptors tonically inhibit REM-like behavioral state, and 3) both Ado A(1) and A(2A) receptors mediate the depressant effects of Ado on REM and breathing.

Adenosine↗

PubMed2001

Ileal neobladder for urinary bladder replacement following total pelvic exenteration for rectal carcinoma.

OBJECTIVE: The aim of this study was to determine the feasibility of using the ileal neobladder as a substitute for the urinary bladder following total pelvic exenteration for rectal carcinoma. PATIENTS AND METHODS: Between 1992 and 1998, we performed total pelvic exenteration with ileal neobladder in 5 men with rectal carcinoma. Four patients had primary tumors, and one had recurrent disease after low anterior resection for rectal carcinoma. Histological types were adenocarcinoma in 4 and squamous cell carcinoma in 1. Invaded organs were: the urinary bladder in 1, the urinary bladder and prostate in 2, the prostate and seminal vesicle in 1, and the prostate in 1. RESULTS: There was no operative death. In 1 patient, an ileal conduit was needed because of partial necrosis of the neobladder. Minor leakage on the dorsal wall of the neobladder occurred in 2 patients, which was successfully stopped with simple closure and a gluteus maximus fasciocutaneous flap, respectively. All except one patient with the ileal conduit could void via the urethra. Complete daytime urinary continence was achieved, but nocturnal continence was maintained with voiding once or twice per night. As the urodynamic state, the mean maximum flow rate was 20.9 ml/s (range 9.0-34.1), the mean average flow rate was 7.7 ml/s (range 3.0-11.0), and the mean voided volume was 285.5 ml (range 160-432). The mean length of follow-up was 47.8 months. One patient died of local recurrence 38 months postoperatively, and 1 died of pneumonia 10 months postoperatively. Both patients could void via the urethra until death. The other three patients are currently alive without any evidence of recurrence. CONCLUSIONS: Although total pelvic exenteration is a laborious surgical procedure, an ileal neobladder could be a good alternative to the urinary bladder enabling the patients to void via the urethra with urinary continence.

Adenocarcinoma↗

PubMed2001

Observed versus expected rates of unbalanced fetal karyotype at second trimester amniocentesis when one parent carries a balanced translocation.

Our purpose is to evaluate a model proposed by Stene et al. for estimating the risk of unbalanced progeny at the time of second trimester amniocentesis for 114 pregnancies of 71 couples, who are carriers of a reciprocal translocation. The overall estimated risk was 18%, 1.26 times higher than the observed risk (14%). There were no unbalanced fetuses in the 19 pregnancies of the no-risk group. In the low-risk group, the observed risk was highly correlated with the estimated risk. However, the estimated risks in the medium- and high-risk groups were much higher than the observed risks (2- and 1.5-fold). In the group ascertained through spontaneous abortions, the average estimated risk was 1.9 times higher than the observed risk. Although the model is useful in estimating individual empirical risks, it may be necessary to consider the type of ascertainments and add some modifications to calculate the risks in the second trimester.

Adult↗

PubMed2001

Regulation of calcitonin receptor by glucocorticoid in human osteoclast-like cells prepared in vitro using receptor activator of nuclear factor-kappaB ligand and macrophage colony-stimulating factor.

Using mouse osteoclast-like cells (OCs), we have shown that treatment with glucocorticoids (GCs) resulted in an increase in calcitonin (CT) binding by enhancing CT receptor (CTR) gene transcription. Additionally, treatment with GCs demonstrated increased sensitivity to CT. There is, however, scant information on the effects of GC or CTR regulation by GCs in human osteoclasts. In this study we examined CTR regulation by GCs and the effects of GCs and CT together in human OCs. OCs were prepared by treatment of peripheral blood mononuclear cells in vitro with soluble receptor activator of nuclear factor-kappaB ligand and macrophage colony-stimulating factor. Treatment of mature OCs with dexamethasone (Dex) resulted in a dose- and time-dependent increase in [(125)I]salmon CT (sCT) binding capacity. Treatment with Dex enhanced CTR messenger RNA (mRNA) expression, suggesting that CTR up-regulation is at least partly due to an increase in de novo CTR synthesis. Triamcinolone and prednisolone reproduced the Dex effect on [(125)I]sCT-specific binding and CTR mRNA expression, but 17beta-estradiol, progesterone, dehydroepiandrosterone, and aldosterone did not. A Scatchard plot analysis showed that Dex enhanced CTR number with a minimal change in the affinity to sCT. Autoradiographic studies using [(125)I]sCT showed that Dex enhanced the CTR density on individual multinuclear OCs. Up-regulation of [(125)I]sCT-specific binding and CTR mRNA expression was seen even in the presence of sCT, but the enhancement diminished subsequently at later times (36-48 h after sCT removal), which was consistent with our previous observation in mouse OCs. This suggests that GCs and CTs act on CTR expression differently, consistent with our previous work using mouse OCs, in which we found that GCs increased transcription of CTR gene expression, whereas CT reduced CTR mRNA stability. The results obtained in this study show that GC increased CTR expression and sensitivity to CT in cells of the human osteoclast lineage and provide the basis for understanding the beneficial effects of combination treatment with GCs and CTs in malignancy-associated hypercalcemia.

Acid Phosphatase↗

PubMed2001

Inositol-1,4,5-trisphosphate-binding proteins controlling the phototransduction cascade of invertebrate visual cells.

The main phototransduction cascade in invertebrate visual cells involves the turnover of phosphatidylinositol, an important biochemical mechanism common to many signal-transduction systems. Light-activated rhodopsin stimulates guanine nucleotide exchange on the Gq class of G-protein, which activates phospholipase C to hydrolyze phosphatidylinositol 4,5-bisphosphate to inositol-1,4,5-trisphosphate and diacylglycerol. Subsequently, inositol-1,4,5-trisphosphate-binding proteins continue the signal cascade. Here, we report on the first inositol-1,4,5-trisphosphate-binding proteins demonstrated in an invertebrate visual system with our investigation of the photosensitive rhabdoms of squid. We screened the ability of proteins to interact with inositol-1,4,5-trisphosphate by affinity column chromatography with an inositol-1,4,5-trisphosphate analogue. We detected an inositol-1,4,5-trisphosphate-binding affinity in phospholipase C, receptor kinase and five other proteins in the cytosolic fraction and, surprisingly, rhodopsin in the membrane fraction. A binding assay with (3)H-labelled inositol-1,4,5-trisphosphate demonstrated the inositol-1,4,5-trisphosphate affinity of each of the purified proteins. Since rhodopsin, receptor kinase and phospholipase C are involved upstream of phosphatidylinositol turnover in the signal cascade, our result suggests that phosphatidylinositol turnover is important in feedback pathways in the signalling system.

Animals↗

PubMed2001

Sustained hyperglycemia and insulin resistance induced by dietary restriction.

This investigation considered whether defects in insulin secretion and insulin action may result in the development of sustained hyperglycemia induced by refeeding standard chow pellets. Hyperglycemia, sustained for 36 h was induced, in mice that ate standard chow pellets ad libitum after 48 h fasting, but not 24 h fasting. In 48 h-fasted mice, serum insulin levels were remarkably low and the ability of insulin secretion to respond to glucose was decreased, although insulin-stimulated glucose disposal was not impaired. However, hyperinsulinemia was observed after refeeding for 12 h. The 12 h-refed mice had impaired glucose tolerance and were remarkably insulin resistant. These results suggest that hyperglycemia induced by the fasting-refeeding was caused by hyperphagia and the failure of insulin secretion, and maintained the resulting induced insulin resistance.

Animals↗

PubMed2001

Cytochrome c oxidase purified from a mercury-resistant strain of Acidithiobacillus ferrooxidans volatilizes mercury.

We suggested in our previous study that the plasma membrane cytochrome c oxidase of the mercury-resistant iron-oxidizing bacterial strain Acidithiobacillus ferrooxidans, SUG 202, is involved in Fe2+-dependent mercury volatilization. To study the involvement of A. ferrooxidans cytochrome c oxidase in mercury reduction, the cytochrome c oxidase was extracted from mercury-resistant and mercury-sensitive strains and purified. The Fe2+-dependent mercury volatilization activities of the oxidases from these strains were compared. The cytochrome c oxidase from strain SUG 2-2 volatilized 39% of the total Hg2+ (7 nmol) that had been added to a 10-ml reaction mixture (pH 3.8) in the presence of 10 micromol of Fe2+ after a 7-d incubation period at 30 degrees C. In contrast, the enzyme purified from the mercury-sensitive strain AP19-3 volatilized 3.5% of the total mercury under the same conditions. The boiled SUG 2-2 oxidase did not exhibit activity to volatilize mercury. Fe2+ reduced the oxidase from SUG 2-2 and Hg2+ oxidized the reduced enzyme. The purified SUG 2-2 oxidase is composed of three protein subunits with apparent molecular weights of 56,000 Da (alpha), 24,000 Da (beta), and 19,000 Da (gamma). The amount of mercury bound to the purified SUG 2-2 oxidase was 6.2 microg/mg protein and those bound to alpha-, beta- and gamma-subunits of the cytochrome c oxidase were 3.5, 2.6 and 0.7 microg/mg protein, respectively.

Journal Article↗

PubMed2001

Volatilization of mercury under acidic conditions from mercury-polluted soil by a mercury-resistant Acidithiobacillus ferrooxidans SUG 2-2.

Volatilization of mercury under acidic conditions from soil polluted with mercuric chloride (1.5 mg Hg/kg soil) was studied with resting cells of a mercury-resistant strain, Acidithiobacillus ferrooxidans SUG 2-2. When resting cells of SUG 2-2 (0.01 mg of protein) were incubated for 10 d at 30 degrees C in 20 ml of 1.6 mM sulfuric acid (pH 2.5) with ferrous sulfate (3%) and mercury-polluted soil (1 g), which contained 7.5 nmol of Hg, approximately 4.1 nmol of mercury was volatilized, indicating that 54% of the total mercury in the soil was volatilized. The amount of mercury volatilized from the soil was dependent on the concentration of Fe2+ added to the medium. When elemental sulfur, sodium tetrathionate, and pyrite were used as an electron donor for the mercury reduction, 16, 2.4 and 0.84%, respectively, of the total mercury added to the solution were volatilized. The optimum pH and temperature for mercury volatilization were 2.5 and 30 degrees C. Approximately 92% of the total mercury in a salt solution (pH 2.5) with resting cells of SUG 2-2 (0.01 mg of protein), ferrous sulfate (3%) and mercury-polluted soil (1 g) was volatilized by further addition of both resting cells and Fe2+ and by incubating for 30 d at 30 degrees C.

Hydrogen-Ion Concentration↗

PubMed2001

Mechanism of growth inhibition by tungsten in Acidithiobacillus ferrooxidans.

Cell growth of three hundred iron-oxidizing bacteria isolated from natural environments was inhibited strongly by 0.05 mM, and completely by 0.2 mM of sodium tungstate (Na2WO4), respectively. Since no great difference in the level of tungsten inhibition was observed among the 300 strains tested, the mechanism of inhibition by Na2WO4 was studied with Acidithiobacillus ferrooxidans strain AP19-3. When resting cells of AP19-3 were incubated in 0.1 M beta-alanine-SO4(2-) buffer (pH 3.0) with 0.1 mM Na2WO4 for 1 h, the amount of tungsten bound to the cells was 12 microg/mg protein. The optimum pH for tungsten binding to the resting cells was 2 to approximately 3. Approximately 2 times more tungsten bound to the cells at pH 3.0 than at pH 6.0. The tungsten binding was specifically inhibited by sodium molybdenum. However, copper, nickel, cadmium, zinc, manganese, cobalt, and vanadate did not disturb tungsten binding to the resting cells. The iron-oxidizing activity of AP19-3 was inhibited 24, 62, and 77% by 1, 5, and 10 mM of Na2WO4, respectively. Among the components of iron oxidation enzyme system, iron:cytochrome c oxidoreductase activity was not inhibited by 10 mM of Na2WO4. In contrast, the activity of cytochrome c oxidase purified highly from the strain was inhibited 50 and 72%, respectively, by 0.05 and 0.1 mM of Na2WO4. The amounts of tungsten bound to plasma membrane, cytosol fraction, and a purified cytochrome c oxidase were 8, 0.5, and 191 microg/mg protein, respectively. From the results, the growth inhibition by Na2WO4 observed in A. ferrooxidans is explained as follows: tungsten binds to cytochrome c oxidase in plasma membranes and inhibits cytochrome c oxidase activity, and as a results, the generation of energy needed for cell growth from the oxidation of Fe2+ is stopped.

Culture Media↗

PubMed2001

Antimicrobial susceptibilities of Campylobacter strains isolated from broilers in the southern part of Japan from 1995 to 1999.

Cecal contents (16 samples/each flock) of broilers derived from 212 flocks were investigated for colonization of Campylobacter from 1995 to 1999 in the southern part of Japan, and the isolates were tested for antimicrobial susceptibilities. C. jejuni-positive flocks numbered 42 (19.8%) and C. coli-positive ones 26 (12.3%); Campylobacter spp. were recovered from 68 flocks (32.1%) in total. MICs of ampicillin, erythromycin (EM), tetracycline, nalidixic acid (NA), norfloxacin (NFLX), and ofloxacin (OFLX) to these 68 Campylobacter isolates were determined. Quinolone-resistant Campylobacter isolates numbered 22 (32.4%). All the isolates except one were cross-resistant to NA, OFLX, and NFLX. A high frequency of quinolone-resistance was found in both C. jejuni and C. coli, whereas a high level of EM-resistance was found in only C. coli strains. All C. jejuni isolates were sensitive to EM.

Ampicillin↗

PubMed2001

Rat tripeptidyl peptidase I: molecular cloning, functional expression, tissue localization and enzymatic characterization.

We purified tripeptidyl peptidase I (TPP I) to homogeneity from a rat kidney lysosomal fraction and determined its physicochemical properties, including its molecular weight, substrate specificity and partial amino acid sequence. The molecular weight of the enzyme was calculated to be 280,000 and 290,000 by non-denaturing PAGE and gel filtration, respectively, and to be 43 000 and 46 000 on SDS-PAGE in the absence and presence of beta-ME, respectively. These findings suggest that the enzyme is composed of six identical subunits. The Km, Vmax, kcat and kcat/Km values of TPP I at optimal pH (pH 4.0) were 680 microM, 3.7 micromol x mg(-1) x min(-1), 33.1 s(-1) and 4.87 x 10(4) s(-1) x M(-1) for Ala-Ala-Phe-MCA, respectively. TPP I was significantly inhibited by PCMBS and HgCl2, and moderately by DFP. These findings also suggest that TPP I is an exotype serine peptidase that is regulated by SH reagent. TPP I released the tripeptide Arg-Val-Tyr from angiotensin III more rapidly than from Ala-Ala-Phe-MCA, and also released Gly-Asn-Leu from neuromedin B with the same velocity as from Ala-Ala-Phe-MCA. Angiotensin III and neuromedin B have recently been found to be good natural substrates for lysosomal TPP I. Furthermore, we determined the rat liver cDNA structure and deduced the amino acid sequence. The cDNA, designated as lambdaRTI-1, is composed of 2485 bp and encodes 563 amino acids in the coding region. By Northern blot analysis, the order for TPP I mRNA expression was kidney > or = liver > heart > brain > lung > spleen >> skeletal muscle and testis. In parallel experiments, the TPP I antigen was detected in various rat tissues by immunohistochemical staining.

Amino Acid Sequence↗

PubMed2001

The effect of propafenone on premature ventricular contractions (PVC): an analysis based on heart rate dependency of PVCs.

The effect of 450 mg/day propafenone for two weeks on premature ventricular contractions (PVCs) was studied in combination with an assessment of heart rate (HR) dependency of PVCs using Holter ECG monitoring in patients with more than 720 PVCs per day. The PVC-HR correlation was classified into positive (P), bidirectional (B), and flat and negative (FN) correlation groups. The positive group included only patients in whom PVC frequency increased with a heart rate increase, while the bidirectional group included patients with PVCs whose frequency increased at low heart rates and decreased at high heart rates. The FN group contained both flat (PVC frequency was almost fixed regardless of heart rate changes) and negative (PVC frequency decreased as heart rate increased) correlations. The effectiveness of propafenone was 70% in the positive group and 50% in the nonpositive group which included both bidirectional (67%) and FN (0%) groups, using a > 70% PVC reduction as a criterion of efficacy. From this, we concluded that propafenone is effective in patients showing either positive or bidirectional PVC-HR correlation. The coupling interval (CI) of PVCs was also prolonged by propafenone as a whole. The present study suggests that there are differences in the mechanism of PVC development in patients with flat or negative correlation and those with a positive or bidirectional correlation. Thus, this type of analysis contributes to an understanding of the action of antiarrhythmic agents, and may allow the prediction of their efficacy on PVCs.

Aged↗

PubMed2001

Possible role of heat shock protein (Hsp) 25 in the enamel organ during amelogenesis in the rat molar.

The postnatal expression of heat shock protein (Hsp) 25 during the amelogenesis of rat molars was investigated by immunocytochemistry and confocal microscopy. The localization pattern of Hsp 25-immunoreactivity in the inner enamel epithelium and ameloblast cell layer of the rat molars was almost identical to that in the rat incisors which we have previously reported: an intense Hsp25-immunoreactivity, which first appeared in the preameloblasts, was recognized in secretory ameloblasts and ruffle-ended ameloblasts with stage-specific immunointensity. Confocal microscopy with Hsp 25-antibody and rhodamine-labeled phalloidin clearly demonstrated the co-localization of Hsp 25 and actin filaments in the ameloblast layer, supporting our hypothesis that this molecule might serve to reinforce the ameloblast layer during enamel formation as well as the formation and maintenance of the ruffled border in ruffle-ended ameloblasts. Interestingly, the enamel free area cells, which essentially lack the ability for enamel formation, showed the Hsp 25-immunoreactivity during 4-11 days when they developed a ruffled border, but decreased in that immunoreactivity after postnatal 15 days following apoptosis. Since Hsp 25 has been shown to be a specific inhibitor of apoptosis, the enamel-free area cells contribute to determine the outline of dentin at the cusped area. These data support our previous hypothesis on the diverse functions of Hsp 25 in amelogenesis.

Actin Cytoskeleton↗