Search PubMed⌕ Search

Biomedical subjects

M Miyajima

Publications and source records attributed to M Miyajima.

At least 37 records · Page 2Linked to original sources
PubMed2000

Transcranial transsphenoidal approach for tuberculum sellae meningiomas.

OBJECTIVE: A series of 21 patients with tuberculum sellae meningioma who received surgical treatment is reported. PATIENTS AND METHODS: All 9 females and 12 males (mean age 49 years) presented visual disturbances of varying degrees in either one or both eyes. Eighteen of the tumours were less than 3 cm in size, and 3 were larger. Tumour resection of uniform surgical technique was performed in all cases. Following a bicoronal scalp incision, bifrontal craniotomy combined with removal of the orbital rim bilaterally was performed. The frontal dura was opened bilaterally, and the most anterior portion of the superior sagittal sinus was transected. Bifrontal retraction and arachnoid dissection along the proximal olfactory tracts brought the tumour into view. Additional dissection of the interhemispheric fissure extended the operative field to the anterior communicating artery. The anterior skull base was drilled out to resect the basal part of the tumour. In all cases, the optic canal and sphenoid sinus, and additionally in some cases the ethmoid sinus were opened. The tumour uniformly extended inferomedially to the optic nerve, and direct visualization of this portion of the tumour was possible with our approach. The opened paranasal sinuses were reconstructed with adipose tissue harvested from the patient's abdomen and the pericranial flap. RESULTS: In all patients, total or almost total resection of the tumour was accomplished. Postoperatively, visual function was improved in 11 patients, was unchanged in 8, and worsened in 2. There were no operative deaths. Cerebrospinal fluid leakage was occurred in two patients but could be conservatively managed. In a mean 3-year follow-up, tumour recurrence was observed in only one patient who presented a malignant histology. CONCLUSIONS: We are confident that our surgical approach has great clinical value in surgical resection of tuberculum sellae meningioma. The good accessibility to a tumour extending inferomedially to the optic nerve should, in particular, be stressed.

Adult↗
PubMed2000

Prevention of cerebral vasospasm by nicardipine prolonged-release implants in dogs.

The purpose of this study was to determine the efficacy of nicardipine prolonged-release implants for preventing vasospasm in a canine SAH model in a dose-escalating placebo-controlled blind fashion. Drug-release kinetics of copoly(lactic/glycolic acid) pellet containing nicardipine were evaluated in vitro. In vivo, 18 dogs were randomly assigned to one of three groups, i.e. placebo, low-dose (0.8 mg), or high-dose (8 mg) nicardipine. Angiography was performed, followed by right craniectomy, the induction of subarachnoid hemorrhage, and the placement of the pellets in the Sylvian fissure. On Day 7 and Day 14, the angiography was repeated. In the first four days, 61.9% of the actual nicardipine loaded was released and within 10 days, 96%. The average percent reductions of vessel diameters in the middle cerebral artery on Day 7 were 43%, 14% and 7% in the placebo, low-dose, and high-dose groups, respectively (p = 0.0319). The mean concentration of nicardipine in the clots on Day 14 was 9.7 x 10(-7) mol-1 l-1 and 5.1 x 10(-6) mol-1 l-1 in the low-dose and high-dose group, respectively. This drug delivery system prevented vasospasm in dogs significantly even at low dose, while maintaining an appropriate concentration of nicardipine in the clot adjacent to the arteries.

Animals↗
PubMed2000

Possible origin of suprasellar arachnoid cysts: neuroimaging and neurosurgical observations in nine cases.

OBJECT: In this study the authors identify and investigate two new classifications of suprasellar arachnoid cysts. METHODS: The authors used computerized tomography cisternography, magnetic resonance (MR) imaging, and neuroendoscopy to investigate nine cases of suprasellar arachnoid cysts. A communicating cyst with early filling and early clearance of a radioopaque tracer was found in seven of nine cases; a communicating cyst with delayed filling and delayed clearance of the tracer was observed in one case; and a noncommunicating cyst was observed in the other. The MR findings indicated a variation in the position of the basilar artery (BA) bifurcation in relation to the ventral surface of the midbrain. A distance existed between the BA bifurcation and the ventral surface of the midbrain in a communicating cyst with early filling, whereas the BA bifurcation was posteriorly displaced in a communicating cyst with delayed filling and also in a noncommunicating cyst, leaving little space between the bifurcation and the ventral surface of the midbrain. Endoscopic observation revealed, in the case of communicating cysts with early filling and early clearance of tracer, that the BA bifurcation is located inside the cyst with no overlying membrane, whereas in a noncommunicating cyst, the BA and its branches can be observed through the transparent membrane of the lesion. CONCLUSIONS: The authors postulate two different types of suprasellar arachnoid cysts: a noncommunicating intraarachnoid cyst of the diencephalic membrane of Liliequist and a communicating cyst that is a cystic dilation of the interpeduncular cistern.

Arachnoid Cysts↗
PubMed1999

Effect of polymer/basic drug interactions on the two-stage diffusion-controlled release from a poly(L-lactic acid) matrix.

We investigated the effect of drug physico-chemical properties on the release of basic drugs from poly(L-lactic acid) (P(L)LA) cylindrical matrices (rods; 10 mmx1 mm diameter). All the rods were revealed to exhibit two-stage diffusion-controlled release profiles resulting from the transformation of P(L)LA from an amorphous to a semicrystalline state in aqueous medium. On the assumption that interactions between polymer carboxyl residues and basic drugs control the drug release rate, we evaluated the strength of these interactions by the drug partition between the polymer and the aqueous medium. In the first release stage, the drugs diffused through the swollen polymer matrix. The polymer-drug interactions shielded the polymer terminal carboxyl residues, thereby resulting in a less hydrated matrix and consequent diminishment of drug diffusion. In the second release stage, the drugs diffused through the water-filled micropores which had developed as a result of polymer crystallization. The stronger polymer-basic drug interactions reduced the drug diffusion rate by decreasing not only the porosity of the matrix, but also the drug partition to the water-filled micropores. It was also found that the fractional drug release rate in the second stage increased with drug content of the rod at the pH where both the polymer carboxyl residues and the drugs were ionized. Since the polymer-drug interactions must be close to saturation with increasing drug content, we believe this result to be due to an increase in the ratio of the drug partition to the water-filled micropores.

Biocompatible Materials↗
PubMed1999

Mechanism of drug release from poly(L-lactic acid) matrix containing acidic or neutral drugs.

The release profiles of acidic and neutral drugs from poly(L-lactic acid) [P(L)LA] matrices were investigated to reveal their release mechanism. Cylindrical matrices (rods; 10 mmx1 mm diameter) were prepared by the heat compression method. The acidic and neutral drugs investigated were dissolved in the P(L)LA rods. It was found that the release profiles consisted of two sequential stages. At the first release stage, P(L)LA remained in an amorphous state and the drugs diffused through the hydrated matrices. At the second release stage, P(L)LA transformed to a semicrystalline state and the drugs diffused through water-filled micropores developed by polymer crystallization. In addition, the drugs were also found to precipitate out as crystals in the rods, resulting in a transformation of the rods into drug-dispersed matrices. On the basis of these findings, we derived a modified diffusion equation for the drug release at the second stage. This equation showed good fits to the release profiles of these drugs. Furthermore, the availability of the derived equation was supported by the acceleration in the fractional drug release rate noted both with decreases in the drug content in the rod and increases in the pH of the medium.

Biodegradation, Environmental↗
PubMed1999

Effects of erythromycin on experimental extrinsic allergic alveolitis.

BACKGROUND: Recent clinical studies have demonstrated the efficacy of erythromycin for treating patients with chronic lower respiratory tract inflammation. Mechanisms related to the anti-inflammatory action are yet to be determined. OBJECTIVES: The therapeutic efficacy of erythromycin in experimental extrinsic allergic alveolitis (EAA) was evaluated. METHODS: A murine model of EAA was developed by intratracheal inoculations with particulate Trichosporon mucoides followed by erythromycin or josamycin treatment. Cell populations, specific antibodies, chemotactic activities, TNF-alpha, IL-1beta, MIP-2 and KC of bronchoalveolar lavage fluid (BALF); histopathology of the lung and footpad reaction; myeloperoxidase of the whole lung; and immunohistochemistry of intercellular adhesion molecule- (ICAM-1), at 6 and 96 h after the challenge, were examined. RESULTS: There was a marked neutrophilic alveolitis and bronchiolitis at 6 h, and lymphocytic alveolitis and perivenule cuffing at 96 h after the challenge. Increase in total inflammatory cells and neutrophils in BALF at 6h was significantly suppressed by pretreatment with 5 mg/kg/day of erythromycin intraperitoneally for 5 days (P<0.01), with no apparent effect on specific antibodies, chemotactic activity or cytokines. Erythromycin also suppressed the Arthus-type reaction in the footpad (P<0.01). Histopathological studies revealed that erythromycin markedly decreased neutrophils in the lung and skin lesions and myeloperoxidase in the lung, simultaneously with inhibiting ICAM-1 expression. The therapy has no remarkable effects on lymphocytes or 96 h response. Josamycin had no effects on the model. CONCLUSIONS: The therapeutic dosage of erythromycin significantly suppressed acute neutrophil influx into the lung, intradermal Arthus reaction and the expression of ICAM-1 in the lesions of experimental EAA. Erythromycin may be effective for treating subjects with acute EAA.

Alveolitis, Extrinsic Allergic↗
PubMed1999

Urease-positive thermophilic strains of Campylobacter isolated from seagulls (Larus spp.).

Three strains of urease-positive thermophilic Campylobacter (UPTC), designated A1, A2 and A3, were identified by biochemical characterization after isolation from faeces of seagulls in Northern Ireland in 1996. The biochemical characteristics of the strains were identical to those of strains described previously. Analysis by pulsed-field gel electrophoresis (PFGE) after separate digestion with ApaI and SmaI demonstrated that the respective PFGE profiles were indistinguishable. The PFGE analysis also suggested that the genomes were approximately 1810 kb in length. This is the first example of the isolation of UPTC from flying homoiothermal animals, i.e. from seagulls (Larus spp.).

Animals↗
PubMed1999

In vivo performance of wax matrix granules prepared by a twin-screw compounding extruder.

The in vivo performance of wax matrix granules (WMGs) prepared by a twin-screw compounding extruder was evaluated in fasted beagle dogs. In vitro dissolution behavior of the model drug, diclofenac sodium (DS), from WMGs was strongly influenced by pH in a dissolution medium due to its solubility (DS is soluble in pH 6.8 and insoluble in pH 1.2 and 4.0) and was independent of paddle rotation rate (50, 100, and 200 rpm) of the dissolution apparatus. Pharmacokinetics parameters such as mean residence time (MRT) showed a sustained action of WMGs in beagle dogs; however, the transit time of WMGs in the small intestine is found to control total drug absorption. Furthermore, the values of the area under the curve (AUC) of the plasma concentration-time curve and the maximum concentration Cmax significantly decreased with decreases in hydroxypropylcellulose (HPC) content in WMGs. Good correlation between one in vitro dissolution parameter (mean dissolution time, MDT) and two in vivo parameters (AUC12 and MRT) suggested that it would be possible to design WMGs with a desired in vivo performance by controlling HPC content.

Animals↗
PubMed1999

Swelling and ketoprofen release characteristics of thermo- and pH-responsive copolymer gels.

Swelling-controlled drug delivery copolymer gels were newly synthesized by introducing thermo- and pH-responsive methacryloyl-glycine (MA-Gly) or pH-responsive methacrylic acid (MA-Ac) for comparison with thermoresponsive acryloyl-L-proline ethyl ester (A-ProOEt). A homopolymer gel of A-ProOEt was kept at degrees of swelling that were less than 0.5 at a pH from 2.5 to 7.5 at 37 degrees C. The thresholds of swelling for copolymer gels consisting of A-ProOEt/MA-Gly and A-ProOEt/MA-Ac with a composition of 40/60 mol% were found to be pH 3.0 and pH 5.5, respectively, in buffer solutions at 37 degrees C. The diffusion characteristics of 2-(3-benzoylphenyl)propionic acid (ketoprofen) from such copolymer gels was evaluated in buffer solutions at pH's more than 5.5, and it was found that A-ProOEt/MA-Gly gel possesses a case II transport mechanism that is completely linear time dependent in both the amount diffused and the penetrating swelling front position. On the other hand, A-ProOEt/MA-Ac gel exhibited a non-Fickian (or anomalous) diffusion behavior under the same conditions.

Diffusion↗
PubMed1998

Factors influencing the diffusion-controlled release of papaverine from poly (L-lactic acid) matrix.

Effects of drug content and medium pH on the release of papaverine (PAP) from biodegradable poly(l-lactic acid) [P(L)LA] matrix were investigated to reveal the predominant factors affecting the two-stage diffusion-controlled release mechanism. A drug-dissolved cylindrical matrix (rod; 10 mmx1 mm diameter) was prepared by heat compression method. In the case of a PAP content below 10%, pH was found to have a strong effect on the release rate, and drug content was found to have no effect on the release profile. The release profile consisted of two sequential diffusion stages due to P(L)LA transformation from amorphous to the semicrystalline state prior to release. In the first release stage PAP diffused through the swollen matrix. The release accelerated with increasing medium pH due to an increase in water content in the acidic P(L)LA rod. In the second release stage PAP diffused through the water-filled micropores developed as a result of the polymer crystallization. On the assumption that the drug partition between the polymer and the medium in the micropores affects the diffusion and the partition is controlled by pH, we derived a modified diffusion kinetic equation. The observation that the release decelerated with increasing medium pH can be explained by the derived equation as resulting from the increase in the drug partition to the polymer. In the case where the rods contained more than 15% of PAP, the drug precipitated out as crystals during release. Accordingly, these rods showed a slower release.

Chemical Phenomena↗
PubMed1998

Clipping of an aneurysm of a fenestrated basilar artery.

We describe the case of a fenestrated basilar artery aneurysm successfully clipped by means of a right presigmoid petrosal approach. Three-dimensional CT angiography enabled the surgeon to plan an approach to an aneurysm in this unique location, and the presigmoid petrosal approach was suitable for clipping of the aneurysm.

Cerebral Angiography↗
PubMed1998

Prophylactic effect of papaverine prolonged-release pellets on cerebral vasospasm in dogs.

OBJECTIVE: A drug delivery system using copoly(lactic/glycolic acid) was developed for the intracranial administration of papaverine. A rod-shaped implant prepared by a heat compression method was tested to determine its efficacy in preventing cerebral vasospasm in dogs. METHODS: Sixteen dogs were randomly assigned to one of two groups, i.e., placebo or papaverine. Control angiography was performed, followed by right craniectomy and the induction of subarachnoid hemorrhage by the placement of a clot in the Sylvian fissure. Two pellets, containing either 25 mg of papaverine or no papaverine, were placed in the cistern. In in vitro studies, 56% of the actual papaverine loading was released in the first 4 days and 78% within 8 days. On Day 7, angiography was repeated and the animals were killed. A similar experiment using low-dose pellets containing 5 mg of papaverine, half of which was released within 7 days, was performed with 16 mongrel dogs. RESULTS: There were significant differences between the papaverine- and placebo-treated groups in the reductions of vessel diameters of the internal carotid, middle cerebral, and anterior cerebral arteries on the clot side. The mean concentration of papaverine in the clot was 4.5 x 10(-4) mol/L. The low-dose pellet failed to prevent cerebral vasospasm, although the mean concentration of papaverine in the clot was 2.3 x 10(-5) mol/L. CONCLUSION: A prolonged-release preparation of papaverine that could be implanted intracranially at the time of surgery prevented vasospasm significantly while maintaining an appropriate concentration of papaverine in the cistern.

Animals↗
PubMed1998

Optimization of the granulation process for designing tablets.

A computer optimization technique based on surface response methodology was applied to optimize the wet granulation process for designing tablets. Physical properties (mean granule size, granule size distribution, compressibility, granule strength) of a model granule formulation containing ethenzamide were accurately described by a second polynomial equation based on two independent variables (amounts of binder and binder solution). This regression equation also gave a good correlation for three physical properties of tablets (distintegration time, compactibility, compression force variance), but the correlation for tablet hardness and weight variation was poor. These results imply that not only the above physical properties of granules but also the rheological behavior and porous structure of granules are closely related to tablet properties. Using an optimization of five tablet properties using the generalized distance function, the predicted values of the physical properties of both granules and tablets agreed well with experimental values. This agreement indicates that the computer optimization technique is useful for optimizing the granulation process for designing tablets.

Computers↗
PubMed1998

In vivo characteristics of injectable poly(DL-lactic acid) microspheres for long-acting drug delivery.

Poly(DL-lactic acid) (PLA) microspheres containing testosterone (T) were prepared by the solvent evaporation process to evaluate their physical properties such as size distribution, shape, drug content, in vivo controlled drug release, pharmacological influences on the prostate gland in castrated rats, and histopathological findings of tissues surrounding the implants. The in vivo release of T from PLA microspheres containing 30 mg of drug obtained with chloroform was continued over a 6-week period. This effect is attributed to high dispersibility of T in the device when obtained with chloroform. Both serum drug levels and prostate gland weight recovery suggested the effects of a long-acting drug delivery system. The histopathological findings showed that the devices used were completely degraded 10 weeks after injection.

Animals↗
PubMed1998

Simultaneous optimization of wet granulation process involving factor of drug content dependency on granule size.

Computer optimization technique was applied to the simultaneous optimization of wet granulation process by a high-speed mixer granulator. Four pharmaceutical properties, including yield, drug content uniformity, geometrical mean diameter of granules, and uniformity of granule size, were selected to evaluate the quality of the granules. In particular, dependence of drug content uniformity on granule size was investigated using two model drugs, ascorbic acid and ethenzamide. An appreciable dependence of ascorbic acid content on granule size was not observed in model formulations. On the other hand, ethenzamide was contained more in small-size granules, and its content was decreased with an increase in amounts of hydroxypropyl cellulose (HPC-L; used as a binder) and binder solution. These observations suggested that drug content uniformity is influenced not only by drug solubility in the binder solution, but also by the use of HPC-L. A simultaneous optimal point incorporating four pharmaceutical properties was obtained using the generalized distance function. The experimental values of the four response variables obtained in newly prepared granules were found to correspond well with the predicted values of both granules containing ascorbic acid and ethenzamide. These results suggested that computer optimization would benefit the wet granulation process even if drug content segregation was involved in the process. Further, data obtained from computer optimization, in particular the contour diagram, will be valuable in the process validation.

Ascorbic Acid↗
PubMed1998

Preparation and characterization of oil-in-water type poly (D,L-lactic acid) microspheres containing testosterone enanthate.

Poly (D,L-lactic acid) (PLA) microspheres containing testosterone enanthate (ET) were prepared by using an oil-in-water (O/W) emulsion technique. The size distribution of the microspheres obtained could be explained by a log-normal distribution, and as a result, it was found that ET fully incorporates into microspheres even when the drug is loaded at up to 50%. On the other hand, the dissolution behavior of ET from microspheres was strongly dependent on particle size, suggesting that dissolution of the drug from microspheres can be easily controlled by controlling the preparative conditions.

Calorimetry, Differential Scanning↗
PubMed1998

[Efficacy of nicardipine prolonged-release pellet on cerebral vasospasm in dogs].

A drug delivery system using copoly (lactic/glycolic acid) was developed for the intrathecal administration of nicardipine. This system was tested to determine its efficacy in preventing cerebral vasospasm in dogs. A rod-shaped implant (1-mm diameter, 10-mm long and which contained approximately 10% of nicardipine) was prepared by a heat compression method. In in vitro studies, 8% of the actual nicardipine loaded was released during day 1, 17% within day 2, 62% within day 4, and 96% within day 10. In in vivo studies, 12 dogs were assigned to two groups: the placebo group and the group treated with nicardipine. Angiography before the experiment was performed followed by right craniectomy and induction of subarachnoid hemorrhage by the placement of a clot in the Sylvian fissure. Eight pellets, either containing 8 mg of nicardipine or without nicardipine were placed in the cistern. On day 7, the angiography was repeated and cerebrospinal fluid was removed from the cisterna magna. The animals were then sacrificed, and the brain and blood clot were taken out. Cerebral vessels were measured three times with a calibrated optical micrometer, and the mean value was obtained. Average reduction of vessel diameters on the clot side in the placebo and nicardipine groups were -37% and -10% on the internal carotid (IC), -48% and -3% on the middle cerebral (MC), and -28% and -1% on the anterior cerebral artery (AC), respectively. There were significant differences in vessel diameters of IC (p < 0.05), MC (p < 0.005), and AC (p < 0.05) between these groups. No vasospasm was found in the left side. The nicardipine concentration in the clot was determined by high performance liquid chromatography. The mean concentration of nicardipine in the clot was 1.5 x 10(-4)M, at which concentration sufficient relaxation is evoked in vitro. The pellets did not last beyond day 7. Regarding the histological findings, there was a marked difference in vessel diameters between the placebo and the nicardipine treated groups. The arteries were surrounded with red blood cells and inflammatory cells. There were no specific changes related to the pellets and no sign of meningoencephalitis. A prolonged-release preparation of nicardipine that can be implanted intracranially at the time of surgery prevented vasospasm significantly in dogs. These results suggest that this new drug delivery system might be put into effect favorably in patients suffering from vasospasm due to subarachnoid hemorrhage.

Animals↗