Biomedical subjects

M Nakashima

Publications and source records attributed to M Nakashima.

At least 253 records · Page 14Linked to original sources

PubMed1995

Direct measurement of superoxide-dependent chemiluminescence from rat skin following UV-dependent fluoroquinolone-induced dermatitis.

Fluoroquinolones are widely used for the treatment of bacterial infection. However, some members of the group cause UV-dependent dermatitis. Therefore, animal models are required to screen and predict if a derivative is likely to cause photodermatitis. Under anaesthesia, the hair on the dorsal side of rats was shaved, then a fluoroquinolone derivative, Y-26611 or ofloxacin was administered subcutaneously (SC) followed by irradiation of a 3 cm diameter circular area of the skin with UV-B(ultraviolet-B) for 45 min. Peak photodermatitis was observed 24 h after irradiation in Y-2611-treated skin. Leucocyte infiltration into the skin, mostly polymorphonuclear leucocytes, was verified by histological techniques. O2.- radical generated by activated leucocytes was detected directly from the skin by SC application of a sensitive O2.- -dependent luminescence reagent, MCLA. O2.- -dependent photon emission (chemiluminescence) from the skin was amplified by phorbol myristate acetate and was markedly suppressed by superoxide dismutase. This is the first report of direct detection of chemiluminescence from the skin of a living animal.

4-Quinolones↗

PubMed1995

Plant homologues of components of MAPK (mitogen-activated protein kinase) signal pathways in yeast and animal cells.

As they respond to numerous extracellular and intracellular stimuli, plants develop various morphological features and the capacity for a large variety of physiological processes during their growth. If we are to understand the molecular basis of such developments, we must elucidate the way in which signals generated by such stimuli can be transduced into plant cells and transmitted by cellular components to induce the appropriate terminal events. In yeast and animal systems, signal pathways that are known collectively as MAPK (mitogen-activated protein kinase) cascades have been shown to play a central role in the transmission of various signals. The components of these pathways include the MAPK family, the activator kinases of the MAPK family (the MAPKK family) and the activator kinases of the MAPKK family (the MAPKKK family). The members of each respective family are structurally conserved and signals are transmitted by similar phosphotransfer reactions at corresponding steps that are mediated by a specific member of each family in turn. Both cDNAs and genes that encode putative homologues of these components have recently been isolated from plant sources. Some of them have been shown to be related not only structurally but also functionally to members of the MAPK cascades of other organisms. These findings suggest that plants have signal pathways that are analogues to the MAPK cascades in yeast and animal cells but it remains to be proven that plant homologues do in fact constitute kinase cascades.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

Effects of volatile anesthetics on acetylcholine-induced relaxation in the rabbit mesenteric resistance artery.

BACKGROUND: Vascular endothelium plays an important role in the regulation of vascular tone. Volatile anesthetics have been shown to attenuate endothelium-mediated relaxation in conductance arteries, such as aorta. However, significant differences in volatile anesthetic pharmacology between these large vessels and the small vessels that regulate systemic vascular resistance and blood flow have been documented, yet little is known about volatile anesthetic action on endothelial function in resistance arteries. Furthermore, endothelium-dependent relaxation mediated by factors other than endothelium-derived relaxing factor (EDRF) has recently been recognized, and there is no information available regarding volatile anesthetic action on non-EDRF-mediated endothelium-dependent relaxation. METHODS: Employing isometric tension recording and microelectrode methods, the authors first characterized the endothelium-dependent relaxing and hyperpolarizing actions of acetylcholine (ACh) in rabbit small mesenteric arteries, and tested the sensitivities of these actions to EDRF pathway inhibitors and K+ channel blockers. They then examined the effects of the volatile anesthetics isoflurane, enflurane, and sevoflurane on ACh-induced endothelium-dependent relaxation that was sensitive to EDRF inhibitors and that which was resistant to the EDRF inhibitors but sensitive to blockers of ACh-induced hyperpolarization. The effects of the volatile anesthetics on endothelium-independent sodium nitroprusside (SNP)-induced relaxation were also studied. RESULTS: Acetylcholine concentration-dependently caused both endothelium-dependent relaxation and hyperpolarization of vascular smooth muscle. The relaxation elicited by low concentrations of ACh (< or = 0.1 microM) was almost completely abolished by the EDRF inhibitors NG-nitro-L-arginine (LNNA), oxyhemoglobin (HbO2), and methylene blue (MB). The relaxation elicited by higher concentrations of ACh (> or = 0.3 microM) was only attenuated by the EDRF inhibitors. The remaining relaxation, as well as the ACh-induced hyperpolarization that was also resistant to EDRF inhibitors, were both specifically blocked by tetraethylammonium (TEA > or = 10 mM). Sodium nitroprusside, a NO donor, produced dose-dependent relaxation, but not hyperpolarization, in the endothelium-denuded (E[-]) strips, and the relaxation was inhibited by MB and HbO2, but not TEA (> or = 10 mM). One MAC isoflurane, enflurane, and sevoflurane inhibited both ACh relaxation that was sensitive to the EDRF inhibitors and the ACh relaxation resistant to the EDRF inhibitors and sensitive to TEA, but not SNP relaxation (in the E[-] strips). An additional finding was that the anesthetics all significantly inhibited norepinephrine (NE) contractions in the presence and absence of the endothelium or after exposure to the EDRF inhibitors. CONCLUSIONS: The results confirm that ACh has a hyperpolarizing action in rabbit small mesenteric resistance arteries that is independent of EDRF inhibitors but blocked by the K+ channel blocker TEA. The ACh relaxation in these resistance arteries thus appears to consist of distinct EDRF-mediated and hyperpolarization-mediated components. Isoflurane, enflurane, and sevoflurane inhibited both components of the ACh-induced relaxation in these small arteries, indicating a more global depression of endothelial function or ACh signaling in endothelial cells, rather than a specific effect on the EDRF pathway. All these anesthetics exerted vasodilating action in the presence of NE, the primary neurotransmitter of the sympathetic nervous system, which plays a major role in maintaining vasomotor tone in vivo. This strongly indicates that the vasodilating action of these anesthetics probably dominates over their inhibitory action on the EDRF pathway and, presumably, contributes to their known hypotensive effects in vivo. Finally, the vasodilating action of these anesthetics is, at least in part, independent from endothelium.

Acetylcholine↗

PubMed1995

Potentiation of endothelium-dependent hyperpolarization to serotonin by dietary intake of NC 020, a defined fish oil, in the porcine coronary artery.

The membrane potential of vascular smooth muscle cells of the porcine coronary artery was measured to examine whether serotonin evokes endothelium-dependent hyperpolarization, and if it does, whether the electrical responses are modulated by the chronic dietary intake of NC 020, a defined fish oil. Serotonin induced transient, concentration-dependent hyperpolarizations of coronary arterial smooth muscle cells. The hyperpolarization was observed in tissues with, but not in those without endothelium. In coronary arteries obtained from pigs fed chronically with NC 020, serotonin induced significantly larger hyperpolarizations than those observed in control arteries. These results suggest that endothelium-dependent hyperpolarization may contribute to the endothelium-dependent relaxation evoked by serotonin and to its potentiation by the dietary intake of fish oil (NC 020).

Animals↗

PubMed1995

Time course of appearance of ofloxacin in human scalp hair after oral administration.

The time course of appearance of antimicrobial ofloxacin (OFLX) in human scalp hair was monitored in three healthy male volunteers after the oral administration of 100 mg OFLX three times daily for 2 consecutive days. Hair samples were collected from each subject by plucking several strands of frontal hair every day from 1 till 16 days after administration. A single hair was dissolved in 1 M NaOH to extract OFLX by chloroform, and the drug was measured by high-performance liquid chromatography and fluorescence detection. OFLX started to appear in the hair 1 to 3 days after administration and reached the maximal level approximately 4 to 9 days, remaining at almost the same level thereafter. This finding suggests the slow transfer of OFLX from hair follicle cells to hair matrix may be due to the slow dissociation of OFLX from bound melanin.

Administration, Oral↗

PubMed1995

Analysis of naturally processed human histocompatibility leukocyte antigen class I-bound peptides from hepatocellular carcinoma tissues in vivo.

Naturally processed self-peptides bound to human histocompatibility leukocyte antigens (HLA) class I molecules of human hepatocellular carcinoma tissues (HLA-A2.1, -B44, -B13) in vivo were isolated for sequence analysis. Acid-eluted peptides were subjected to reversed-phase high-performance liquid chromatographic separation and single-fraction sequencing was performed by Edman degradation. The peptides were found to be octamers or nonamers and they were derived from the processing of intracellular proteins. Three independent sequences were obtained from HLA-A2.1 molecules. One of the peptides showed sequence homology to the hepatitis B virus (HBV) pre-S protein, one to aldehyde dehydrogenase, and the other to no known protein. Two independent sequences were obtained from HLA-B44, B13 molecules: one showed sequence homology to the human c-abl protein, the other showed no homology to any known protein. A synthetic biotinylated peptide based on the HBV pre-S peptide sequence was confirmed to bind to HLA-A2.1 gene-transfected L cells. These data suggested that peptides potentially recognized by cytotoxic T cells can bind to HLA class I molecules on tumor cells in vivo.

Amino Acid Sequence↗

PubMed1995

Pharmacokinetic and pharmacodynamic analysis of a novel leukotriene biosynthesis inhibitor, MK-0591, in healthy volunteers.

1. The pharmacokinetic and pharmacodynamic properties of a novel 2-indolealkanoic acid derivative (MK-0591), a potent inhibitor of leukotriene biosynthesis, were investigated in healthy male Japanese volunteers. Single oral doses of 50, 125, 250 and 500 mg and multiple oral doses of 125 mg twice daily for 9.5 days and 250 mg once daily for 10 days were administered. 2. After the single-dose administration following overnight fasting, Cmax and AUC of MK-0591 in plasma increased in a dose-dependent manner, while elimination half-life remained constant (11.2-13.2 h) irrespective of dose. Food intake decreased Cmax and AUC by 71% and 68%, respectively, at a dose of 250 mg. With respect to multiple-dose administration before meals, there were no significant differences in the pharmacokinetic parameters between the first and last days, indicating a lack of significant accumulation of MK-0591 in plasma. Urinary recovery as the unchanged form was negligible throughout the study. 3. Ionophore-stimulated production of leukotriene B4 (LTB4) in blood ex vivo was inhibited significantly from 1 h until 12 to 48 h after single-dose administration as compared with predose value. In parallel, the urinary excretion of endogenous leukotriene E4 (LTE4) was significantly decreased from 4 to 8 h until 48 to 72 h after drug administration. Reduction of ionophore-stimulated LTB4 biosynthesis and urinary excretion of LTE4 following single administration of MK-0591 was statistically significant as compared with placebo group, and the duration of inhibition of LTB4 biosynthesis was dose-related.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1995

Optimal dosage and differences in therapeutic efficacy of IGIV in Kawasaki disease.

In an initial study, three groups of patients with Kawasaki disease received either aspirin alone or alkylated immunoglobulin G intravenous preparation (IGIV) 200 mg/kg daily x 3 days + aspirin, or 400 mg/kg alkylated IGIV daily x 3 days + aspirin. In a second study, three groups of patients were treated with either 100, 200 or 400 mg/kg of native IGIV in combination with aspirin daily for 5 days. While the regimen of 200 mg/kg native IGIV daily x 5 days was found to be effective, the incidence of coronary artery lesions (CAL) was even less on a regimen of 400 mg/kg daily x 5 days. It is therefore suggested that a better therapeutic effect can be achieved with a 400 mg/kg dose of native IGIV. Based on the results from these two studies, it is assumed that native IGIV is more effective in inhibiting CAL formation and persistence than the chemically modified preparation in which the biological activity of the Fc region in the immunoglobulin G molecule is altered.

Aspirin↗

PubMed1995

Antithrombotic effect of a novel recombinant hirudin analogue, CX-397, in a rat arterial thrombosis model.

1. The antithrombotic effect of a new specific thrombin inhibitor, CX-397, was examined in a photochemically-induced arterial thrombosis model in the rat femoral artery and compared with that of heparin. 2. Pretreatment with CX-397 (10, 20 and 40 micrograms kg-1 min-1, i.v.) from 15 min before the experiment prolonged the time required for thrombotic occlusion of the artery in a dose-dependent manner. The antithrombotic efficacy of CX-397 was associated with modest increases in activated partial thromboplastin time (APTT) and template bleeding time. 3. On the other hand, heparin at a dose of 450 micrograms kg-1 markedly prolonged APTT and the bleeding time, but did not inhibit thrombo-occlusion. 4. CX-397 selectively inhibited platelet aggregation and concurrent secretion of 5-hydroxytryptamine (5-HT) and thromboxane A2 (TXA2) production from platelets in response to thrombin, but not to collagen and ADP, in a dose-dependent manner (5-100 ng ml-1). 5. CX-397 at 10 micrograms kg-1 combined with vapiprost, a TXA2 receptor antagonist, at 0.1 mg kg-1 significantly prevented occlusion, whereas, at these doses, neither drug alone had much effect. 6. These results demonstrate that CX-397 may prove to be more efficient for preventing platelet-rich thrombosis than heparin. Thrombin may play an important role in the rat thrombosis model. 7. The additive antithrombotic effect of the combination of thrombin inhibitor and TXA2 receptor antagonist at low doses suggests that thrombin and TXA2 may work in concert to produce thrombosis.

Animals↗

PubMed1995

Pharmacokinetics and tolerance of DU-6859a, a new fluoroquinolone, after single and multiple oral doses in healthy volunteers.

The pharmacokinetics and tolerance of DU-6859a, 7-[(7S)-7-amino-5-azaspiro[2,4]heptan-5-yl]-8-chloro-6-fluor o-1-[(1R, 2S)-2-fluoro-1-cyclopropyl]-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid sesquihydrate, were investigated in healthy male Japanese volunteers after single (25, 50, 100, and 200 mg) and multiple (100 mg three times a day for 6 days plus once a day on the 7th day and 50 mg every 12 h for 13 doses) oral doses. DU-6859a was well tolerated at all doses, and all 36 subjects completed the study; mild transient soft stool in five volunteers and mild transient diarrhea in one volunteer on the multiple-dose (100 mg three times a day) study were the only side effects reported. No drug crystals were observed in the urine after the single 200-mg dose and the 100-mg three times a day regimen. DU-6859a was rapidly absorbed in the fasted state. The mean maximum concentration in serum (Cmax) ranged from 0.29 to 1.86 micrograms/ml for the 25- to 200-mg dose, and the mean time to reach Cmax ranged from 1.0 to 1.3 h. The terminal half-life ranged from 4.4 to 5.0 h. The area under the curve increased dose dependently. The serum protein binding of the drug was approximately 50%. The apparent volume of distribution clearly exceeded 1 liter/kg, suggesting good tissue penetration. Within 48 h, the cumulative urinary recovery of unchanged drug amounted to 69 to 74% of the dose administered, while fecal excretion up to 48 h after the 200-mg dose accounted for ca. 3% of the dose. Food intake did not affect the rate and extend of absorption of DU-6859a to a clinically significant extent. During multiple oral dosing, the accumulation of the drug in serum was close to the theoretically predicted values, which indicated that there was virtually no drug accumulation.

Administration, Oral↗

PubMed1995

Single- and multiple-dose pharmacokinetics of AM-1155, a new 6-fluoro-8-methoxy quinolone, in humans.

The pharmacokinetics of AM-1155, a new 6-fluoro-8-methoxy quinolone, was examined in healthy male volunteers after the oral administration of a single dose of 100, 200, 400, or 600 mg and multiple doses of 300 mg twice daily for 6.5 days (13 total doses). Throughout the whole study period, AM-1155 was well tolerated in every subject. In the single-dose study, the concentrations in serum reached a peak between 1 and 2 h, and the peak concentrations were 0.873, 1.71, 3.35, and 5.41 micrograms/ml at the doses of 100, 200, 400, and 600 mg, respectively. The elimination half-life was 7 to 8 h, independently of the doses. The unchanged drug was excreted mainly in the urine, with 82 to 88% of the doses appearing for 72 h. The fecal recovery of the unchanged drug amounted to 5.7% for 72 h after a single oral administration of a 400-mg dose. Urinary excretion of metabolites was minimal. The serum protein binding was 20%, independently of the concentrations in serum. The concentrations in saliva were approximately 80% of those in serum. The intake of food had no effect on the pharmacokinetic parameters and urinary excretion of AM-1155 except the slight decrease in area under the concentration-time curve. The concurrent administration of probenecid prolonged the elimination half-life, increased the area under the concentration-time curve, and decreased the apparent total body clearance, renal clearance, urinary recovery of unchanged drug, and the excretion ratio (intrinsic renal clearance of AM-1155/creatinine clearance). This indicated that the tubular secretion contributed to the renal excretion of AM-1155. In the multiple-dose study, the concentrations of AM-1155 in serum and urine reached a steady state within 2 to 3 days. The measured concentrations in serum fitted well the simulation curve, which reflected the persistence of linear pharmacokinetics of AM-1155. In conclusion, AM-1155 is expected to be clinically useful because of its potent antibacterial activity and favorable pharmacokinetics.

Adult↗

PubMed1995

A compilation of partial sequences of randomly selected cDNA clones from the rat incisor.

The formation of tooth organs is regulated by a series of developmental programs. We have initiated a genome project with the ultimate goal of identifying novel genes important for tooth development. As an initial approach, we constructed a unidirectional cDNA library from the non-calcified portion of incisors of 3- to 4-week-old rats, sequenced cDNA clones, and classified their sequences by homology search through the GenBank data base and the PIR protein data base. Here, we report partial DNA sequences obtained by automated DNA sequencing on 400 cDNA clones randomly selected from the library. Of the sequences determined, 51% represented sequences of new genes that were not related to any previously reported gene. Twenty-six percent of the clones strongly matched genes and proteins in the data bases, including amelogenin, alpha 1(I) and alpha 2(I) collagen chains, osteonectin, and decorin. Nine percent of clones revealed partial sequence homology to known genes such as transcription factors and cell surface receptors. A significant number of the previously identified genes were expressed redundantly and were found to encode extracellular matrix proteins. Identification and cataloging of cDNA clones in these tissues are the first step toward identification of markers expressed in a tissue- or stage-specific manner, as well as the genetic linkage study of tooth anomalies. Further characterization of the clones described in this paper should lead to the discovery of novel genes important for tooth development.

Amelogenesis↗

PubMed1995

Defining the major antibody epitopes on the human thyrotropin receptor in immunized mice: evidence for intramolecular epitope spreading.

To evaluate the B cell response to the extracellular domain of the human TSH receptor (hTSHR-ecd), we used recombinant hTSHR-ecd to immunize BALB/c mice (group A) and CBA/J mice (groups B and C). Mice from groups A and B were boosted once, and mice from group C received three antigen boosts. All individual mice developed highly specific hTSHR-ecd antibodies (hTSHR-ecd-Ab), confirmed by Western blot analyses. The B cell epitopes recognized by these murine hTSHR-ecd-Ab were mapped by enzyme-linked immunoassays using 26 synthetic overlapping peptides spanning the entire mature hTSHR-ecd [amino acids (aa) 22-415], i.e. without the signal sequence. Although all BALB/c and CBA/J mice antisera recognized peptide 1 (aa 22-41), the hyperimmunized CBA/J mice (group C) demonstrated recognition of additional peptides (numbers 21-26) clustered toward the carboxyl-terminus of the hTSHR-ecd (aa 322-415). Furthermore, group C serum blocked the binding of [125I]bTSH to native porcine TSHR, whereas sera from groups A and B were inactive. We were also able to map the B cell epitopes of antisera from rabbits immunized repeatedly with hTSHR-ecd and found the same recognition pattern of peptide 1 and additional peptides clustered near the carboxyl-terminus of the hTSHR-ecd (aa 322-341 and 367-415). These rabbit antisera also inhibited the binding of [125I]bTSH to native porcine TSHR. These data provide a comprehensive B cell epitope-mapping study of induced hTSHR-ecd-Ab and demonstrate intramolecular spreading of the epitopes recognized. Although the N-terminal region was highly antigenic, repeated immunization induced hTSHR-ecd-Ab targeted to a region critical for TSH binding.

Animals↗

PubMed1995

Effects of losartan, an angiotensin II antagonist, on the development of cardiac hypertrophy due to volume overload.

To investigate the contribution of a cardiac renin-angiotensin system to cardiac hypertrophy due to volume overload, the effects of losartan, a non-peptide angiotensin (Ang) II type 1 (AT1) receptor antagonist on left ventricular hypertrophy (LVH) was studied. LVH was produced in male Wistar rats by volume overload secondary to aortic insufficiency (AI). Losartan (10 mg/kg/d) was orally administered for 2 weeks after surgery to both AI and sham-operated (control) rats. Two weeks after surgery, aortic pulse pressure and left ventricular (LV) weight were markedly increased in the AI rats as compared with the control group, whereas cardiac angiotensin converting enzyme (ACE) activity remained unchanged. The effects of the chronic administration of losartan an AT1 receptors were verified by the blockade of Ang II pressor response. Losartan treatment produced a significant reduction in LVH in AI rats without affecting the systolic blood pressure. In separate groups of rats, to elucidate the mechanisms of the attenuation of LVH by treatment with losartan, we determined plasma and LV immunoreactive Ang II content and plasma renin activity (PRA). LV Ang II content increased in AI rats, while plasma Ang II content, PRA and II concentration were increased by the treatment. There was a significant positive correlation between LV weight and LV Ang II content. These results suggest that cardiac Ang II, rather than circulating Ang II, plays an important role in the LVH due to volume overload via the AT1 receptor.

Angiotensin II↗

PubMed1995

Inhibitory effect of clopidogrel, vapiprost and argatroban on the middle cerebral artery thrombosis in the rat.

This study investigated the roles of thromboxane A2 (TXA2), ADP and thrombin in middle cerebral artery (MCA) thrombosis in the rat. The rat MCA was occluded by a thrombus induced by the photochemical reaction of rose bengal by green light that causes endothelial damage followed by platelet adhesion, aggregation and formation of a platelet and fibrin-rich thrombus at the site of the photochemical reaction. Vapiprost, a specific TXA2-receptor antagonist; clopidogrel, which has the thienopyridine structure of ticlopidine and is a more potent inhibitor of ADP-induced platelet aggregation than ticlopidine; argatroban, a specific thrombin inhibitor; or heparin was administered intravenously before rose bengal injection. The MCA local blood flow was monitored by a laser Doppler flowmeter. The MCA was occluded by thrombus about 5 min after the initiation of the photochemical reaction. Vapiprost, clopidogrel and argatroban all significantly prolonged the time taken for the thrombotic occlusion of the MCA, but in this respect, heparin was ineffective. Our observations suggest that vapiprost and clopidogrel are useful antithrombotic agents against platelet and fibrin-rich thrombi. The effect of argatroban is attributable to inhibition of thrombin-induced platelet activation and fibrin generation. The thrombosis model described in this study is useful for understanding the mechanism(s) of thrombogenesis in the rat MCA and may be applied to other mammalian species.

Animals↗

PubMed1995

An experimental myocardial infarction model in the rat and its properties.

The photochemical reaction between rose bengal and light (540 nm) produces thrombotic occlusion in rat coronary artery. We have now developed an experimental myocardial infarction (MI) model by photochemically induced thrombosis (PIT) in rats and investigated the mechanisms responsible for the induction of MI. PIT in the coronary artery induced myocardial ischemia, which was determined by tissue oxygen tension (tpO2), and resulted in MI. Pretreatment with a thromboxane (TX) A2-receptor antagonist, vapiprost, prevented a decrease in myocardial tpO2 and markedly reduced the MI area, although vapiprost inhibited collagen-induced platelet aggregation by 30% ex vivo. An ADP-induced platelet aggregation inhibitor, clopidogrel, also reduced the MI area. In contrast to vapiprost, clopidogrel inhibited collagen-induced platelet aggregation by 90% ex vivo. Pretreatment with a 5-HT2-receptor antagonist, ketanserin, which did not inhibit collagen-induced platelet aggregation ex vivo, prevented the decrease in myocardial tpO2 and reduced the MI area. These results suggest that TXA2, 5-HT and ADP play a role in the induction of MI and that platelet aggregation and other factors induce ischemia in this model.

Animals↗

PubMed1995

Effect of argatroban on microthrombi formation and brain damage in the rat middle cerebral artery thrombosis model.

Ischemic cerebral infarcts induce hypercoagulation and microthrombosis in the surrounding region, thus leading to vascular occlusion. We determined whether microthrombi contribute to the spreading of ischemic lesions following thrombotic middle cerebral artery (MCA) occlusion and also determined whether argatroban, a selective thrombin inhibitor, reduces the formation of the microthrombi and the area of the ischemic lesions. The rat left MCA was occluded by a platelet-rich thrombus formed following the photochemical reaction between rose bengal and green light. Microthrombi were histologically identified in the left hemisphere. The extent of ischemic lesions and microthrombi containing fibrin increased in a time-dependent manner after MCA occlusion. Argatroban inhibited the formation of microthrombi up to 3 hr after MCA occlusion; beyond 3 hr, it was ineffective. Argatroban also significantly (P < 0.01) reduced the size of ischemic cerebral lesions at 6 hr after MCA occlusion. It is concluded that the formation of microthrombi contributes to the progression of ischemic lesions in the early stage. It is likely that thrombin generated following thrombotic MCA occlusion contributes to the progression of ischemic lesions by promoting the formation of microthrombi. Argatroban can reduce the formation of microthrombi and ischemic lesions in the early stage.

Animals↗

PubMed1995

Establishment and characterization of a malignant epithelioid hemangioendothelioma from mouse thyroid tumor.

A mouse epithelioid hemangioendothelioma (mEHE) cell line, passagable in vivo without TSH stimulation, was established from a thyroid tumor. Before establishment of the cell line, the primary thyroid tumor which was co-transplanted with a TSH-producing pituitary adenoma showed signs of hyperplasia and then transformed during several in vivo transplantable passages. The cell line which was established from an in vitro culture, was deficient in thyroid-specific differentiation function and had characteristics of endothelial cell origin such as vascular cavity formation and factor VIII expression. The cell growth of mEHE/CH1-5 cell lines was independent of TSH but was inhibited by c-AMP and vitamin D3. c-Myc proto-oncogene expression was also suppressed by vitamin D3 treatment. Both serum depletion and heparin treatment induced morphological changes in mEHE/CH 5 from an epithelial cell-like to an endothelial cell-like shape. Immunohistochemical analysis showed that epithelial membrane antigen expression was decreased and factor VIII expression was increased in relation to the morphological changes. In a further in vivo transplantation experiment, the histology of the mEHE/CH5 cell tumor had an angiosarcoma-like structure. These results indicate that this cell line established from a thyroid tumor possesses both epithelial and endothelial characteristics. The mEHE/CH5 cells might provide a good model for analyzing thyroid tumorigenesis and allow functional characterization of endothelial cells.

Animals↗