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S Oya

Publications and source records attributed to S Oya.

At least 37 records · Page 2Linked to original sources
PubMed1999

Characterization of [(123)I]IDAM as a novel single-photon emission tomography tracer for serotonin transporters.

Development of selective serotonin transporter (SERT) tracers for single-photon emission tomography (SPET) is important for studying the underlying pharmacology and interaction of specific serotonin reuptake site inhibitors, commonly used antidepressants, at the SERT sites in the human brain. In search of a new tracer for imaging SERT, IDAM (5-iodo-2-[[2-2-[(dimethylamino)methyl]phenyl]thio]benzyl alcohol) was developed. In vitro characterization of IDAM was carried out with binding studies in cell lines and rat tissue homogenates. In vivo binding of [(125)I]IDAM was evaluated in rats by comparing the uptakes in different brain regions through tissue dissections and ex vivo autoradiography. In vitro binding study showed that IDAM displayed an excellent affinity to SERT sites (K(i)=0.097 nM, using membrane preparations of LLC-PK(1) cells expressing the specific transporter) and showed more than 1000-fold of selectivity for SERT over norepinehrine and dopamine (expressed in the same LLC-PK(1) cells). Scatchard analysis of [(125)I]IDAM binding to frontal cortical membrane homogenates prepared from control or p-chloroamphetamine (PCA)-treated rats was evaluated. As expected, the control membranes showed a K(d) value of 0.25 nM+/-0.05 nM and a B(max) value of 272+/-30 fmol/ mg protein, while the PCA-lesioned membranes displayed a similar K(d), but with a reduced B(max) (20+/-7 fmol/ mg protein). Biodistribution of [(125)I]IDAM (partition coefficient =473; 1-octanol/buffer) in the rat brain showed a high initial uptake (2.44%dose at 2 min after i.v. injection) with the specific binding peaked at 60 min postinjection (hypothalamus-cerebellum/cerebellum =1.75). Ex vivo autoradiographs of rat brain sections (60 min after i.v. injection of [(125)I]IDAM) showed intense labeling in several regions (olfactory tubercle, lateral septal nucleus, hypothalamic and thalamic nuclei, globus pallidus, central gray, superior colliculus, substantia nigra, interpeduncular nucleus, dorsal and median raphes and locus coeruleus), which parallel known SERT density. This novel tracer has excellent characteristics for in vivo SPET imaging of SERT in the brain.

Animals↗
PubMed1999

Single-photon emission tomography imaging of serotonin transporters in the non-human primate brain with the selective radioligand [(123)I]IDAM.

A new radioligand, 5-iodo-2-[[2-2-[(dimethylamino)methyl]phenyl]thio]benzyl alcohol ([(123)I]IDAM), has been developed for selective single-photon emission tomography (SPET) imaging of SERT. In vitro binding studies suggest a high selectivity of IDAM for SERT (K(i)=0.097 nM), with considerably lower affinities for norepinephrine and dopamine transporters (NET K(i)= 234 nM and DAT K(i)>10 microM, respectively). In this study the biodistribution of SERT in the baboon brain was investigated in vivo using [(123)I]IDAM and SPET imaging. Dynamic sequences of SPET scans were performed on three female baboons (Papio anubis) after injection of 555 MBq of [(123)I]IDAM. Displacing doses (1 mg/kg) of the selective SERT ligand (+)McN5652 were administered 90-120 min after injection of [(123)I]IDAM. Similar studies were performed using a NET inhibitor, nisoxetine, and a DAT blocker, methylphenidate. After 60-120 min, the regional distribution of tracer within the brain reflected the characteristic distribution of SERT, with the highest uptake in the midbrain area (hypothalamus, raphe nucleus, substantia nigra), and the lowest uptake in the cerebellum (an area presumed free of SERT). Peak specific binding in the midbrain occurred at 120 min, with a ratio to the cerebellum of 1.80+/-0.13. At 30 min, 85% of the radioactivity in the blood was metabolite. Following injection of a competing SERT ligand, (+)McN5652, the tracer exhibited rapid washout from areas with high concentrations of SERT (dissociation rate constant in the midbrain, averaged over three baboons, k(off)=0. 025+/-0.002 min(-1)), while the cerebellar activity distribution was undisturbed (washout rate 0.0059+/- 0.0003 min(-1)). Calculation of tracer washout rate pixel-by-pixel enabled the generation of parametric images of the dissociation rate constant. Similar studies using nisoxetine and methylphenidate had no effect on the distribution of [(123)I]IDAM in the brain. These results suggest that [(123)I]IDAM is suitable for selective SPET imaging of SERT in the primate brain, with high contrast, favorable kinetics, and negligible binding to either NET or DAT.

Animals↗
PubMed1999

Single-photon emission tomography imaging of serotonin transporters in the nonhuman primate brain with [(123)I]ODAM.

We have described previously a selective serotonin transporter (SERT) radioligand, [(123)I]IDAM. We now report a similarly potent, but more stable IDAM derivative, 5-iodo-2-[2-[(dimethylamino)methyl]phenoxy]benzyl alcohol ([(123)I]ODAM). The imaging characteristics of this radioligand were studied and compared against [(123)I]IDAM. Dynamic sequences of single-photon emission tomography (SPET) scans were obtained on three female baboons after injection of 375 MBq of [(123)I]ODAM. Displacing doses (1 mg/kg) of the selective SERT ligand (+)McN5652 were administered 120 min after injection of [(123)I]ODAM. Total integrated brain uptake of [(123)I]ODAM was about 30% higher than [(123)I]IDAM. After 60-120 min, the regional distribution of tracer within the brain reflected the characteristic distribution of SERT. Peak specific binding in the midbrain occurred 120 min after injection, with an equilibrium midbrain to cerebellar ratio of 1. 50+/-0.08, which was slightly lower than the value for [(123)I]IDAM (1.80+/- 0.13). Both the binding kinetics and the metabolism of [(123)I]ODAM were slower than those of [(123)I]IDAM. Following injection of a competing SERT ligand, (+)McN5652, the tracer exhibited washout from areas with high concentrations of SERT, with a dissociation kinetic rate constant k(off)=0.0085+/-0.0028 min(-1) in the midbrain. Similar studies using nisoxetine and methylphenidate showed no displacement, consistent with its low binding affinity to norepinephrine and dopamine transporters, respectively. These results suggest that [(123)I]ODAM is suitable for selective SPET imaging of SERT in the primate brain, with higher uptake and slower kinetics and metabolism than [(123)I]IDAM, but also a slightly lower selectivity for SERT.

Animals↗
PubMed1999

Vascular permeability factor expression in cerebellar hemangioblastomas: correlation with tumor-associated cysts.

The presence of vascular endothelial growth/permeability factor (VEG/PF) has been studied in histological specimens from a series of 16 cerebellar hemangioblastomas. In this series, the tumors were classified as presenting a macroscopic solid pattern (4 cases), a mainly solid pattern with macroscopic cysts (4 cases) or a mainly cystic pattern (8 cases). Solid tumors showed a low degree (75% of cases) or moderate degree (25% of cases) of VEG/PF positivity. The mainly solid tumors containing macroscopic cysts showed a moderate degree (50% of cases) or high degree (50% of cases) of VEG/PF positivity. Nevertheless, mainly cystic hemangioblastomas showed a high degree (87.5% of cases) or moderate degree (12.5% of cases) of VEG/PF positivity. These findings suggest that the predominance of a cystic or solid macroscopic appearance of cerebellar hemangioblastomas may be influenced by the degree of VEG/PF expression within the tumor tissue.

Cerebellar Neoplasms↗
PubMed1998

Expression of vascular endothelial growth factor in cerebellar hemangioblastomas does not correlate with tumor angiogenesis.

The relation between angiogenesis and tissue expression of vascular endothelial growth factor (VEGF) was studied in a series of 14 capillary cerebellar hemangioblastomas. In the present series, the number of intratumoral microvessels, identified by the endothelial marker CD34, does not correlate with the degree of VEGF expression. This finding suggests that endothelial growth factors other than VEGF may regulate tumor angiogenesis in these neoplasms.

Antigens, CD34↗
PubMed1998

Immune-cell system provides the development of extraneural tumors in the ethyl-nitrosourea model of neurocarcinogenesis.

Immunological suppression of the immune-cell system by means of cyclosporin-A was performed at a stage corresponding to microtumor development in the ethyl-nitrosourea (ENU) model of neurocarcinogenesis. The results that we have obtained suggest that this immunological manipulation is related to the appearance of extraneural undifferentiated tumors, suggesting that the immune-cell system is effective in immunocompetent rodents for providing extraneural ENU carcinogenesis.

Animals↗
PubMed1998

Small and neutral Tc(v)O BAT, bisaminoethanethiol (N2S2) complexes for developing new brain imaging agents.

Bisaminoethanethiol (BAT) ligands with various gem-dimethyl and amide groups were prepared, and the corresponding neutral Tc-99m complexes were prepared and evaluated for their relative stabilities by ligand-exchange reactions. It was demonstrated that technetium complexes containing gem-dimethyl substituents have higher lipophilicities, whereas those with an amide group possess greater stability, which enhances ligand-exchange reaction. The most interesting observation was that the brain uptake in rats is not determined only by lipophilicity. Apparently, Tc-99m complexes with an amide functional group display lower brain uptakes in rats compared to those without an amide group. The brain uptake was strongly influenced by substituents on the BAT ligand. These factors are critically important and should be taken into consideration when designing Tc-99m-labeled agents for CNS receptor imaging.

Animals↗
PubMed1996

Gangliosides modulate the growth rate and cell phenotype of a murine primitive neuro-ectodermal tumour.

Intratumoural administration of gangliosides (GSD) into a murine primitive neuro-ectodermal tumour, growing in the epicranial subcutaneous tissue of syngenic rats, results in a decrease in the tumour growth rate and causes a more differentiated phenotype of tumour cell, with immunohistochemical expression of neuronal markers. These findings suggest that the potential usefulness of intralesional administration of GSD for the control of tumours of primitive neuro-epithelial character could be considered.

Animals↗
PubMed1996

Novel TcVO(III) N2S2 complexes: interconversion by redox reaction.

To improve the versatility of ligands suitable for complexing a TcVO center core, a new bisaminoethanethiol (BAT) ligand, 7, was synthesized. A neutral and stable complex, [99mTc]7 (reduced), was initially formed. The reduced form of the Tc-99m complex can be converted to the oxidized form, and vice versa. Both Tc-99m complexes showed moderate uptakes in rat brain (0.17% and 0.1% dose/organ at 30 min for the reduced and oxidized forms, respectively). It may be possible to use the same reaction schemes to prepare various derivatives for further studies of these neutral and stable Tc-99m complexes.

Aniline Compounds↗
PubMed1996

Pituitary apoplexy after subtotal thyroidectomy in an acromegalic patient with a large goiter.

A case of pituitary apoplexy occurring after subtotal thyroidectomy in an acromegalic woman with a large adenomatous goiter is described. The patient had severe apnea because the large goiter was causing airway compression. Prior to the planned hypophysectomy, a subtotal thyroidectomy was performed to relieve tracheal stenosis. Shortly after the operation, the patient developed a headache that lasted for several days. The serum levels of growth hormone and somatomedin-C spontaneously normalized seventeen days after this episode and have remained normal for two years. Pituitary apoplexy was thought to have caused the observed results without deterioration of the pituitary function.

Acromegaly↗
PubMed1995

Growth-inhibiting effect of intratumoral recombinant human tumor necrosis factor on an experimental model of primitive neuroectodermal tumor.

The effect of intratumoral administration of recombinant human tumor necrosis factor on an experimental model of primitive neuroectodermal neoplasia was studied. A clear inhibition of tumor growth was achieved by immunotherapy that consisted in intralesion injections of 100 micrograms of tumor necrosis factor daily, the first three days of each week, for a period of four weeks. At this time, tumor size was 2.21 +/- 0.66 cm2 (mean +/- standard deviation) in the treated group, versus 7.62 +/- 0.43 cm2 in the control group. These data support previous studies on the influence of tumor necrosis factor on the development of ethyl-nitrosourea-induced tumors, and suggest the potential usefulness of this cytokine in human primitive neuroectodermal neoplasms.

Animals↗
PubMed1995

New bisaminoethanethiol (BAT) ligands which form two interconvertible Tc-99m complexes.

Most commonly used radiopharmaceuticals in diagnostic nuclear medicine are labeled with Tc-99m. This is due to its superior physical characteristics (T1/2 = 6 h and gamma energy 140 KeV) and convenient availability from the 99Mo/99mTc generator. In an attempt to fine tune the properties of Tc-99m complexes, the synthesis and radiolabeling of two novel N2S2 ligands, N,-2-mercaptobenzyl-N'-(1-oxo-2-mercapto-2-methyl)propyl ethylene-diamine, 8, and N,-2-methylthiobenzyl-N'-(1-oxo-2-mercapto-2-methyl)propyl ethylenediamine, 11, with an ionizable SH or unionizable SMe group, respectively, for the formation of complexes with TcvO center cores, have been examined. Both ligands initially formed one apparently stable, lipophilic and neutral complex (HPLC, Rt = 7 min, reverse-phase column, acetonitrile: buffer, pH 7.0; 55/45; V/V; partition coefficient between 1-octanol and buffer of 410 and 335, respectively) with [99mTc]pertechnetate in the presence of stannous chloride. After treatment with a reducing agent, NaCNBH3, the initial [99mTc]8 and 11 complexes were reduced; the reduced complexes were less lipophilic (shorter retention time, Rt = 5 min, on the same reversed phase HPLC). However, only the oxidized form showed sufficient stability. The reduced forms of both [99mTc]8 and 11 were readily and completely converted back to the oxidized forms by a stream of air. Biodistribution studies in rats demonstrated that the [99mTc]8 (oxidized form) penetrated the blood-brain barrier (0.67% dose/organ at 2 min postinjection), but washed out from the brain quickly (0.29% dose/organ at 30 min postinjection).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[In vitro antimicrobial activity of a new quinolone, levofloxacin, against atypical mycobacteria].

We measured th in vitro antimicrobial activity of a new quinolone, levofloxacin (LVFX) against seven clinically isolated species of atypical mycobacteria, including 30 strains of M. avium complex. 8 of M. fortuitum, 4 of M. scrofulaceum, 2 of M. kansasii, 2 of M. gordonae, and 1 of M. chelonae (subsp chelonae). LVFX showed a potent antimicrobial activity against M. kansasii, M. gordonae and M. chelonae (subsp chelonae). In addition, it was suggested that LVFX may be effective for the treatment of infections caused by M. avium complex, since satisfactory antimicrobial activity was displayed against some strains of M. avium complex. Considering the fact that LVFX shows good concentration levers in sputum, this drug could be used in the chemotherapy against the infection with M. avium complex.

Anti-Infective Agents↗
PubMed1994

Influence of the postnatal administration of tumor necrosis factor plus interferon-alpha 2b on the development of ethyl-nitrosourea-induced brain tumors in rats.

Using the experimental model of brain tumors induced by ethyl-nitrosourea (ENU), interferon-alpha 2b and human recombinant tumor necrosis factor-alpha (TNF) have been administered to Wistar rats between 100 and 130 days of life (one injection each week, by intraperitoneal route, of 100 micrograms of TNF and 10(4) IU of interferon-alpha 2b, in a total volume of 1 ml per injection). The results obtained suggest, that at this time, this association achieves a reduction in the number of so-called 'malignant schwannomas', but it does not influence the time of appearance nor the number of so-called 'malignant schwannomas', but it does not influence the time of appearance nor the number of so-called 'oligodendroglioma-like tumors'. On the basis of previous observations about cytokine modulation of these ENU-induced neoplasms, a different course of time for obtaining a postnatal biomodulation of both type of tumors is suggested.

Aging↗
PubMed1994

Gangliosides modulate the development of ethyl-nitrosourea induced brain tumors in rats.

The possible effect of gangliosides as biological modifiers of the ethyl-nitrosourea (ENU) model of neurocarcinogenesis in rats is studied. Wistar rats that were exposed to ENU during fetal life, were treated with gangliosides at a postnatal age corresponding to a stage of pretumor or microtumor development. The results obtained suggest that postnatal administration of gangliosides can influence the development of ENU-induced brain tumors, delaying the appearance of symptomatic neoplasms and improving survival with respect to controls. This finding suggests the potential usefulness of gangliosides in the control of neuroectodermal tumors.

Animals↗
PubMed1994

Experimental induction of primitive neuro-ectodermal tumours in rats: a re-appraisement of the ENU-model of neurocarcinogenesis.

A series of 122 experimental brain tumours, induced in the Wistar rat by means of prenatal exposition to ethyl-nitrosourea, were studied with histological, immunohistochemical and ultrastructural techniques. Although with conventional histological techniques, most of the induced tumours showed morphological features suggesting their classification as malignant schwannomas or oligodendroglioma-like neoplasms, their study by means of immunohistochemistry and electron microscopy suggested that they are, in fact, primitive neuroectodermal tumours, with a tendency toward neuronal differentiation. This finding obliges us to re-appraise the ethyl-nitrosourea model of neurocarcinogenesis and to consider its possible usefulness for the experimental study of therapeutic approaches with potential applications in human neuro-ectodermal neoplasms.

Animals↗
PubMed1993

Effect of fibrin glue on postlaminectomy scar formation.

An experimental study in rats has been carried out with the aim of studying the scar formation over the spinal dura in the presence of fibrin glue. Although the main action of fibrin glue is the enhancement of wound healing by increasing the fibrous tissue, our present data suggest that this re-absorbable biomaterial diminishes the epidural scar formation, at least the first two weeks after laminectomy. This finding leads us to consider the use of fibrin glue over spinal duramater when it is likely that reoperation may become necessary in a short period of time after a laminectomy.

Animals↗