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Biomedical subjects

M Tamai

Publications and source records attributed to M Tamai.

At least 73 records · Page 4Linked to original sources
PubMed1999

Changes of GABA metabolic enzymes in acute retinal ischemia.

It is reported that GABA accumulates in Müller cells in ischemic and diabetic rat retina. To investigate the mechanism of GABA accumulation in Müller cells, we localized GABA and glutamate in ischemic rat retina and measured the activity of GAD and GABA-T, enzymes involved in GABA metabolism. Using general anesthesia, we incised the bulbar conjunctiva of the rat around the limbus and clamped the left optic nerve. A sham operation was performed on the right eyes. Ocular ischemia was sustained for 30, 60 and 90 minutes. Rat eyes were enucleated immediately after ischemia and prepared for immunohistochemistry and enzyme activity measurement. Glutamate-like immunoreactivity (Glu-IR) in the sham-operated rat retina was observed in all retinal layers, showing intense staining in the nerve fiber layer (NFL), ganglion cell layer (GCL), and inner plexiform layer (IPL). Glu-IR increased in the outer plexiform layer (OPL) and outer nuclear layer (ONL) in an ischemic time-dependent manner. GABA-like immunoreactivity (GABA-IR) in sham-operated rat retina was observed in NFL, GCL, IPL and inner nuclear layer (INL). When the ischemic time was extended, GABA-IR intensely stained Müller cells. GAD activity was not changed in ischemic rat retina as compared to normal rat retina, but GABA-T activity was significantly decreased in ischemic rat retina. These results suggested that glutamate was induced by ischemia and was converted to GABA by GAD activity. Increased GABA was not metabolized because GABA-T activity was decreased. GABA accumulation in Müller cells progressed during the change in activity of these metabolic enzymes.

4-Aminobutyrate Transaminase↗
PubMed1999

Elevated adrenomedullin in the vitreous of patients with proliferative vitreoretinopathy.

PURPOSE: To explore the possible involvement of adrenomedullin in the pathophysiology of proliferative vitreoretinopathy. METHODS: The radioimmunoassay technique was used to determine immunoreactive adrenomedullin concentrations in the vitreous fluid from 41 eyes of 41 patients undergoing vitrectomy for a variety of retinal conditions, including proliferative vitreoretinopathy, proliferative diabetic retinopathy, age-related macular degeneration, and macular hole. RESULTS: Immunoreactive adrenomedullin levels in the vitreous of patients with proliferative vitreoretinopathy were significantly higher than those of patients with proliferative diabetic retinopathy (P < .005), age-related macular degeneration (P < .001), and macular hole (P < .0001). CONCLUSION: Adrenomedullin may be involved in the pathophysiology of proliferative vitreoretinopathy.

Adrenomedullin↗
PubMed1999

Monitoring of the thromboxane A2/prostacyclin ratio in the urine of patients with retinal vascular occlusion through the low-dose-aspirin therapy using the gas chromatography/selected ion monitoring method.

We determined the levels of the stable urinary metabolites of thromboxane A2 and prostacyclin, 11-dehydro-thromboxane B2 (11-dehydro-TXB2) and 2,3-dinor-6-keto-prostaglandin F1alpha (2,3-dinor-6-keto-PGF1alpha) in patients with retinal vascular occlusion (RVO) to elucidate the change of the thromboxane A2/prostacyclin (TX/PGI) ratio with this disease and the effect of low-dose-aspirin therapy. 11-Dehydro-TXB2 and 2,3-dinor-6-keto-PGF1alpha were converted to 1-methyl ester-propylamide-9,12,15-tris-dimethylisopropylsilyl ether derivative and 1-methyl ester-6-methoxime-9,12,15-tris-dimethylisopropylsilyl ether derivative, respectively, and applied to a gas chromatography/selected ion monitoring. The average level of 11-dehydro-TXB2 in 30 patients with RVO was 1038 +/- 958 pg/mg creatinine. It was significantly higher than that of 27 healthy volunteers, which was 616 +/- 294 pg/mg creatinine (p < 0.05 with unpaired t-test). However, 2,3-dinor-6-keto-PGF1alpha levels were not significantly different between these two groups. The average ratio of TX/PGI in the RVO patients was 32 +/- 26 and it was significantly higher than that of healthy volunteers, 17 +/- 10 (p < 0.01). Patients with central retinal artery occlusion or branch retinal artery occlusion showed greatly high 11-dehydro-TXB2 levels and TX/PGI ratios, although the number of patients was limited in the current study. After the administration of low-dose aspirin (40 mg/day) for about 1 month, the TX/PGI ratio decreased to around the normal level. Following the levels for up to 10 months, they also remained at the normal level. These observations suggested that the 11-dehydro-TXB2 levels and the TX/PGI ratio reflect the pathological conditions of RVO and are useful markers of the treatment.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

Serum hepatocyte growth factor levels in Henoch-Schönlein purpura.

BACKGROUND: Henoch-Schönlein purpura (HSP) is the most common form of vasculitis in children. The potential role of hepatocyte growth factor (HGF) in acute immune-mediated vasculitis has not been elucidated. METHODS: Serum HGF levels were determined in patients with HSP. RESULTS: In patients with acute-phase HSP, mean (+/- SD) serum HGF levels were 0.32 +/- 0.14 ng/mL and were significantly higher than those in the control group (0.11 +/- 0.10 ng/mL). This elevation of serum HGF levels recovered to control levels in parallel with improvement of the clinical symptoms. CONCLUSIONS: It is suggested that elevation of serum HGF levels in patients with acute-phase HSP may reflect endothelial cell damage or dysfunction in HSP.

Acute Disease↗
PubMed1999

Choline acetyltransferase activity in collateral sprouting of peripheral nerve after surgical intervention: experimental study in rats.

The purpose of this study was to establish an assay of choline acetyltransferase (ChAT) activity to investigate the regeneration of injured peripheral nerve, repaired by end-to-end or end-to-side neurorrhaphy. Murine sciatic and peroneal nerves were exposed, and the peroneal nerve was transected at a site 5 mm from its ramification. For end-to-side neurorrhaphy, an epineurotomy producing a 5-x5-mm window was carried out on the tibial nerve, just above the level of gastrocnemius muscle ramification. The peroneal nerve stump was then sutured end-to-side to the tibial nerve window. For end-to-end neurorrhaphy, the peroneal stump was directly sutured end-to-end. ChAT activity was measured at a site distal to the peroneal stump at 1 to 3 months postoperatively, and the results were compared among four groups: 1) end-to-end neurorrhaphy group; 2) end-to-side neurorrhaphy group; 3) unrepaired group; and 4) positive controls. ChAT activity in the end-to-side neurorrhaphy yielded approximately two-thirds the value of the end-to-end neurorrhaphy, and more than half the value of positive controls at 3 months postoperatively. Histologic sections of the end-to-side and end-to-end sutured peroneal nerve demonstrated large numbers of myelinated axons and Schwann cells at the third postoperative month. All the results demonstrated that end-to-side neurorrhaphy is comparable to well-performed end-to-end neurorrhaphy, thus providing another option for surgical treatment of avulsion nerve injury and massive nerve defect.

Anastomosis, Surgical↗
PubMed1999

Quantifying leukocyte dynamics and plugging in retinal microcirculation of streptozotosin-induced diabetic rats.

PURPOSE: To determine leukocyte kinetics in the retinal microcirculation of streptozotosin-induced diabetic rats. METHODS: Rats were made diabetic with intraperitoneal injection of streptozotosin. For one month after injection, the alteration of the velocity and plugging of leukocytes were investigated using acridine orange, which stains leukocytes, and scanning laser ophthalmoscopy. Blood plasma protein levels, such as fibrinogen and alpha1- and alpha2- globulin, were also measured. RESULTS: Throughout the observational period, mean leukocyte velocity was similar between diabetic (1.53+/-0.45 mm/sec) and age-matched control (1.58+/-0.23 mm/sec) rats, but the coefficient of variation of the velocity in the diabetic rats was twice as large as that in the control rats. Plugging was increased in a sigmoidal fashion and saturated for 5 weeks or later. No differences were seen in plasma protein levels between groups. CONCLUSIONS: Within one month of the hyperglycemic condition, the velocities of leukocytes in capillaries were more varied and the leukocytes were plugged time-dependently. This action occurred not because the blood fibrinogen and globulin levels were altered, but because of the leukocyte-endothelium interaction. In streptozotosin-induced diabetic rats, retinopathy usually cannot be found during the fundus examination and fluorescein angiography. In the level of the microcirculation, however, some of the disorders have already occurred.

Acridine Orange↗
PubMed1999

Quantitative analysis of leukocyte dynamics in retinal microcirculation of rats with short-term ischemia-reperfusion injury.

PURPOSE: To characterize the time course of complete recovery of leukocyte velocities in the retinal microcirculation of rats from short-term (5-minute) retinal ischemia. METHODS: After 5 minutes of retinal ischemia produced by clamping the optic nerve, resulting in the occlusion of both central retinal artery and the central retinal vein, we used acridine orange (AO) and a scanning laser ophthalmoscope (SLO) to observe the velocities of leukocytes in precapillary arteriole ( v(a)), capillary (v(c)) and postcapillary venule (v(v)). Measurements were taken at reperfusion time points of 5, 10, 15, 20, 30, 40, 50, 60 and 80 minutes for the ischemic eyes and at 12, 22, 42 and 62 minutes for the control eyes, respectively. RESULTS: Each control velocity was arteriole 25.1 +/- 4.3 mm/ s; venule 16.9 +/- 3.2 mm/s; and capillary 1.54 +/- 0.31 mm/s, respectively. The leukocyte velocities after 5 minutes of ischemia in arteriole and venule recovered completely within 80 minutes of reperfusion; however, the recovery patterns were different. The recovery pattern showed a biphasic increase in arterioles and a monophasic increase in venules. The velocity in capillaries half recovered rapidly, within 5 minutes of reperfusion, but the subsequent recovery was slower and was not complete even at 80 minutes of reperfusion. CONCLUSIONS: In this study, leukocyte velocities in arterioles, venules and capillaries exhibited different recovery patterns following retinal ischemia and subsequent reperfusion. Capillaries, at least within 80 minutes of reperfusion, may have difficulty recovering completely from even short-term (5-minute) ischemia.

Acridine Orange↗
PubMed1999

Molecular cloning of cDNA encoding a novel microphthalmia-associated transcription factor isoform with a distinct amino-terminus.

Microphthalmia-associated transcription factor (MITF) is a basic helix-loop-helix-leucine zipper protein, and plays an important role in the development of various cell types, such as neural-crest-derived melanocytes and optic-cup-derived retinal pigment epithelium. Three isoforms of MITF with distinct amino-termini have been described. These include melanocyte lineage-specific MITF-M, heart-type MITF-H, and the recently identified MITF-A. Here we identify a fourth isoform, MITF-C, with a unique amino-terminus of 34 amino acid residues, which shares about 43% sequence identity with putative transactivation segments of two previously identified leukemogenic factors, ENL and AF-9. Reverse transcription-polymerase chain reaction analysis revealed that MITF-C mRNA is expressed in many cell types, including retinal pigment epithelium, but is undetectable in melanocyte-lineage cells. In contrast, MITF-A and MITF-H mRNAs are coexpressed in all cell types examined. Transient cotransfection assays suggested that MITF-C, like other MITF isoforms, functions as a transcriptional activator of certain target genes, but its transactivation specificity for the target promoters is different from those of other MITF isoforms. Therefore, isoform multiplicity provides MITF with differential expression patterns as well as functional diversity.

Amino Acid Sequence↗
PubMed1999

In vivo cisplatin resistance depending upon canalicular multispecific organic anion transporter (cMOAT).

The in vitro sensitivities to cisplatin of AH66 and AH66F cells, a variant obtained from AH66 cells, were very similar, when assayed in a medium containing 5% fetal bovine serum (FBS), whereas in the in vivo experiments AH66F cells were sensitive and AH66 cells were highly resistant to cisplatin. In this study, we examined the mechanism of the in vivo cisplatin resistance of AH66 cells. The in vitro cisplatin sensitivity of AH66 cells was lowered by changing FBS to 5% ascites fluid (ASF) in the assay medium and the sensitivity in FBS by treatment with buthioninesulfoximine (BSO). The sensitivity of AH66F cells was not changed by these treatments. Moreover, after culture in 5% ASF for 48 h, the accumulation of cisplatin in AH66 cells was decreased and the efflux of cisplatin from the cells was accelerated. The accumulation of cisplatin in AH66 cells in ASF was increased by pretreatment with BSO, sodium azide or probenecid. Then, we examined the expression of the glutathione (GSH) conjugate efflux pump family. Among them, only the expression of canalicular multispecific organic anion transporter (cMOAT) in AH66 cells was decreased by culture in FBS and enhanced by ASF. These results suggest that some substances contained in ASF enhanced the expression of cMOAT in the plasma membrane of AH66 cells and this transporter actively extruded cisplatin-GSH conjugate from the cells. Consequently, AH66 cells afford a cisplatin-resistant tumor in the host.

Animals↗
PubMed1999

Bamboo-joint-like appearance of the stomach: a histopathological study.

A bamboo joint-like (BJL) appearance is an endoscopic finding characterized by swollen longitudinal folds transversed by erosive fissures or linear furrows, and it seems to be associated with Crohn's disease (CD). We performed gastroduodenoscopy in 1781 patients, and found BJL lesions in 15 (65.2%) of 23 CD patients and 20 (1.1%) of 1758 non-CD patients. Histological examination of the biopsy specimens showed sharp, fissure-like erosion or mucosal cleft in 7 (50%) out of 14 CD patients and one (20%) out of 5 non-CD patients. All cases with fissure-like erosion or, mucosal cleft revealed lymphoid aggregates, eosinophilic infiltration and edema in the superficial portion of the surrounding lamina propria. Epithelioid granuloma was seen at the base of the fissure-like erosion in two cases with CD. Our results indicated that fissure-like erosion or mucosal cleft in gastric biopsy specimens reflects the BJL appearance, and that such findings may provide a diagnostic clue to CD.

Adult↗
PubMed1999

Lens epithelial changes and mutated gene expression in patients with myotonic dystrophy.

AIMS: Examination of the expression of the mutated allele of myotonic dystrophy protein kinase gene and lens epithelial cell changes in patients with myotonic dystrophy. METHODS: Six eyes from three patients with myotonic dystrophy underwent cataract surgery. The lens epithelium was photographed to examine the morphological changes. mRNAs were extracted to determine myotonic dystrophy protein kinase gene expression in the lens epithelium and peripheral blood. Age matched lens epithelial cells from senile cataracts were used as controls. RESULTS: All eyes showed iridescent or posterior subcapsular lens opacity. The expression of the myotonic dystrophy protein kinase gene with trinucleotide repeat expansion was evaluated by reverse transcriptase polymerase chain reaction, Southern blotting, and sequence analysis. Lens epithelial cell densities were extremely reduced in the patients compared with the control group. CONCLUSION: To the authors' knowledge, this is the first report to describe the relation between lens epithelial cell changes and mutated gene expression in patients with myotonic dystrophy. The gene may be mitotically unstable in the lens epithelial cells; it may influence cell density and lens epithelial function, and it may lead to the development of typical subcapsular lens opacity.

Adult↗
PubMed1999

Serum hepatocyte growth factor levels in patients with renal diseases.

The serum levels of hepatocyte growth factor (HGF) were determined in patients with various renal diseases. In patients with acute-phase acute renal failure (ARF) and chronic tubulointerstitial nephritis (chronic TIN), the serum HGF levels were 0.55 +/- 0.24 and 0.44 +/- 0.37 ng/ml (mean +/- SD), respectively, and were significantly higher than that in the control group (0.12 +/- 0.12 ng/ml). The serum HGF level tended to be high also in patients with active-phase steroid-sensitive nephrotic syndrome (SSNS). The serum levels of HGF were not elevated in patients with IgA nephropathy (IgAN), Henoch-Schönlein purpura nephritis (HSPN), membranoproliferative glomerulonephritis (MPGN), poststreptococcal acute glomerulonephritis (PSAGN), unilateral renal atrophy, unilateral nephrectomy, or proximal tubular dysfunction. These observations suggest that glomerular disorders cause no apparent elevation of the serum HGF level, and that elevation of the serum HGF level may be associated with tubulointerstitial damage in renal diseases.

Adolescent↗
PubMed1999

Administration of nerve growth factor, brain-derived neurotrophic factor and insulin-like growth factor-II protects phosphate-activated glutaminase in the ischemic and reperfused rat retinas.

Phosphate-activated glutaminase (PAG) activity decreases markedly in the early period of ischemia. The decrease of the enzyme activity is reversible if the ischemic period is relatively short, but it becomes irreversible after 90 minutes of ischemia. The deterioration is a functional damage of the retinas caused by ischemia. We studied effects of growth factors and neurotrophic factors on protection of PAG in the ischemic and reperfused rat retinas. Before ischemia, 1 microl of growth factors or neurotrophic factors (0.1 microg/microl for insulin-like growth factor-I [IGF-I], insulin-like growth factor-II [IGF-II], brain-derived neurotrophic factor [BDNF], nerve growth factor [NGF]; 1 microg/microl for basic fibroblast growth factor [bFGF]) were injected into the vitreous cavity of the left eyes of anesthetized Sprague Dawley rats. As a control, phosphate buffered saline was injected to the right eyes. To induce ischemia, we clamped left eyes for 90 minutes after bulbar conjunctival incision all around limbus. The rat retinas were homogenized with distilled water 1 day after reperfusion and used for PAG assay. Retinal ammonia concentration was also determined as a ischemic marker. About 80% decrease of retinal PAG activity and 50% increase of retinal ammonia concentration were observed after 90 minutes of ischemia and 1 day of reperfusion as compared with unoperated normal eyes. IGF-II, BDNF and NGF had protective effects on the retinal PAG activity, whereas IGF-I, bFGF, stable bFGF were less effective. In addition, IGF-II and BDNF suppressed elevation of retinal ammonia concentration. BDNF, NGF and IGF-II have marked effect on the protection of PAG activity in the ischemic and reperfused rat retinas, whereas bFGF, which is very effective for the protection of ischemic cell death, shows moderate effect.

Animals↗
PubMed1999

Susceptibility of weakly ouabain-sensitive Na, K-ATPase isoform in ischemic and reperfused rat retinas.

It is possible that Na, K-ATPase may play some roles in ischemic damage of nervous tissue. To determine whether Na, K-ATPase is affected in ischemic and reperfused retina, we measured enzyme activities. Retinal ischemia was induced by clamping the optic nerve of female adult Sprague-Dawley (SD) rats for 90 minutes. At 0.5, 2 and 24 hours after reperfusion, rat eyes were enucleated, and the retinas were removed. In addition to unseparated, total ouabain-sensitive Na, K-ATPase activity, we measured weakly ouabain-sensitive (alpha) and highly ouabain-sensitive (alpha[+]) isoform activities separately by ATP hydrolysis. Total ouabain-sensitive Na, K-ATPase activity, alpha and alpha(+) isoform activities showed no significant difference from sham-operated contralateral eyes at 0.5 and 2 hours of reperfusion. After 24 hours of reperfusion, total ouabain-sensitive Na, K-ATPase activity decreased to 63% of the control. The activities of alpha and alpha(+) isoforms were 47% and 72%, respectively. The ratios of the alpha and alpha(+) isoform activities (alpha/alpha[+]) significantly decreased at 2 and 24 hours of reperfusion. Activity in a isoform decreased markedly in reperfused rat retinas. This response may be beneficial for reducting the oxidative stress in reperfused retinas.

Animals↗
PubMed1999

Cytokine gene expression after subretinal transplantation.

Transplantation study of neural retina, retinal pigment epithelial (RPE), or iris pigment epithelial (IPE) cells have been performed not only in animal model but in human age-related macular degeneration, and some of the findings reported with cystoid macular edema may have been due to graft rejection. In this investigation, we examined cytokine gene expression by reverse transcriptase-polymerase chain reaction at the transplanted subretinal space. Transplantation was performed in normal Royal College of Surgeon's rats using cultured human RPE and rat IPE. They were followed without immunosupression. Gene expression for melanogenesis of transplanted human RPE was observed only in the early days after transplantation. Rat interleukin (IL)-1alpha, -1beta1, -2, -6, interferon gamma, and tumor necrosis factor alpha (TNF alpha) genes were also expressed after the early days of transplantation. Cytokine expression was observed not only after cell transplantation but also after vehicle-only injection, which was considered a reaction to the surgical trauma. However, statistically significant amount of expressions of IL-1alpha, -1beta, and -6 were observed after the early days of transplantation of human RPE or IL-1alpha, -1beta, and TNF alpha of rat IPE, if we compare them to vehicle-only injection. These cytokines may play an important role for the local reaction after transplantation.

Animals↗