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Biomedical subjects

M Ochi

Publications and source records attributed to M Ochi.

At least 163 records · Page 9Linked to original sources
PubMed1995

Long-term enhancement of dopamine release by high frequency tetanic stimulation via a N-methyl-D-aspartate-receptor-mediated pathway in rat striatum.

We studied the effects of high frequency tetanic stimulation of the striatum on the KCl (20 mM)-evoked dopamine release in rat striatal slices. The KCl-evoked dopamine release was potentiated by high frequency tetanic stimulation (10-20 Hz) of the striatum including the corticostriatal fibers, and this potentiation was observed until 3 h after high frequency tetanic stimulation. Potentiation of dopamine release after high frequency tetanic stimulation was induced not only by KCl but also by glutamate in Mg(2+)-free medium, N-methyl-D-aspartate in Mg(2+)-free medium, and by DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid. 2-amino-5-phosphovalerate, 3-[(+/-)-2-carboxypiperazine-4-yl]-propyl-1-phosphonate or dibenzocycloheptaneimine, N-methyl-D-aspartate receptor inhibitors, abolished enhancement by tetanus, whereas, 6,7-dinitroquinoxaline-2,3-dione, an antagonist of DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid ionotropic receptors, or L-2-amino-4-phosphonobutyrate, an antagonist of glutamate metabotropic receptors, showed no effect. Moreover, pretreatment with glutamate or N-methyl-D-aspartate in the absence of Mg2+ also facilitated dopamine release evoked by KCl concentrations. When extracellular Ca2+ was removed from the medium during pretreatment, potentiation by glutamate disappeared. We conclude that activation of N-methyl-D-aspartate receptors on dopaminergic nerve terminals in the striatum produces the long-term changes in efficacy of the response to KCl or glutamatergic agents. That is, plastical phenomena could exist at presynaptic levels between glutamatergic neurons and dopaminergic neurons in striatum.

Animals↗
PubMed1995

Treatment of articular defects with meniscal allografts in a rabbit knee model.

Deep-frozen allogeneic meniscal grafts for the treatment of articular cartilage defects were performed experimentally. Osteochondral defects 3 mm in diameter were created bilaterally on the medial femoral condyles of 50 Japanese white rabbits. A meniscus was then grafted into the defect in the left knee, and the right knee was left untreated. At various periods from 2 to 24 weeks postoperatively, the rabbits were killed and macroscopic and histologic examinations were performed. Two weeks after operation, the grafted meniscus was bonded to the floor of the defect. After 12 weeks, chondrocytes producing matrix granules was shown by electron microscopy. After 24 weeks, a congruous articular surface was formed. With time, cellular elements infiltrated into the graft from the surrounding tissues, and gradually increased in penetration. Weight bearing in the early stage after operation did not degrade the grafted menisci, and no changes were shown in the opposing cartilage of the tibia. Deep-frozen allogeneic menisci may be useful as a biological implant to repair articular cartilage defects in this model.

Animals↗
PubMed1995

Survival and development of reimplanted fetal epiphyses. An experimental study.

An experiment was undertaken to study the survival and development of fetal epiphyses after excision and reimplantation in rats. The proximal part of fibula in the hindlimb was dissected free from surrounding tissues and then reimplanted again. Of 80 fetuses that were operated on, nine that had been operated on survived to birth. Histological examination on the hindlimbs of these rats at four and six weeks after birth showed that the reimplanted segments survived, and the bony nuclei of the epiphyses were present. Radiographically, at 6 weeks old, secondary centres of ossification at proximal ends of the fibulas could be seen in both operated and normal limbs. These results indicate the clinical possibility of correcting congenital musculoskeletal abnormalities in the future by in utero transplantation of epiphyses.

Animals↗
PubMed1995

High intrinsic healing potential of human anterior cruciate ligament. Organ culture experiments.

We studied the intrinsic healing capacity of human semitendinosus tendon specimens, comparing them to human anterior cruciate ligament specimens collected at the time of ligament reconstructions, and using an organ culture model. On the day after cultivation, migration of cells and synthesis of collagen fibers were observed in the ligament group with preserved synovium (PS), the ligament group with resected synovium (RS), and the semitendinosus tendon group (ST). Migrating cells and newly-formed collagen fibers were most prominent in the PS group, followed by the RS, and ST groups. When the area occupied by the migrating cells and newly-formed collagen fibers in the prepared hole was measured, no differences were observed between the groups at week 2. However, differences were noted between the ST and PS or RS groups at weeks 4 and 6. Our findings indicate that the human anterior cruciate ligament possesses a high intrinsic healing capacity. It is also suggested that the synovium plays an important role in enhancing ligament healing capacity.

Adolescent↗
PubMed1995

A case of steroid-induced osteonecrosis of femoral condyle treated surgically.

The clinical course and the established treatment for steroid-induced osteonecrosis of the femoral condyle have not been clarified yet, mainly because of the limited number of reports. Conservative treatment for steroid-induced osteonecrosis of the femoral condyle has been advocated, because the underlying disease tends to be serious and multiple joints are usually involved. Conservative treatment usually is continued until osteonecrosis becomes extensive and osteoarthritis has progressed enough to justify total knee arthroplasty. Reported here is a case of steroid-induced osteonecrosis of the lateral femoral condyle that, according to preliminary results, was treated successfully with a vascularized bone and periosteal graft.

Adolescent↗
PubMed1995

[Stereotactic radiation therapy with linear accelerator: accuracy of alignment and portal film verification].

Stereotactic radiation therapy with a linear accelerator requires precise alignment of therapeutic radiation distribution to the target volume. To verify the accuracy of alignment, differences between the stereotactic coordinates of the center of the therapeutic radiation distribution determined from portal films and those of the target points determined from CT/MRI or CT/angiographic localization were calculated for 58 points. The average values and one standard deviation were--0.02 +/- 0.50mm, 0.37 +/- 0.39mm and 0.01 +/- 0.25mm in the x, y, and z directions, respectively. The average value of the total deviation was 0.73 +/- 0.07mm. Potential sources of misalignment were misaligned laser pointers, wide laser beam width, improperly zeroed target positioner scale, and motion of the patient couch. The accuracy of alignment should be verified prior to irradiation. Portal film verification is indispensable for strereotactic radiation therapy with a linear accelerator.

Cranial Irradiation↗
PubMed1995

[Sequential coronary artery bypass grafting utilizing the internal thoracic and gastroepiploic artery as in situ grafts].

36 consecutive patients (male:female = 33:3, mean age 57.3) underwent sequential coronary artery bypass grafting (CABG) utilizing the left internal thoracic artery (LITA, n = 30), right gastroepiploic artery (RGEA, n = 8) as in situ grafts. Two patients received sequential bypass grafting with both grafts simultaneously. No right internal thoracic arteries were used except for one as a free nonsequential graft. Taking into account the adjunctive venous anastomoses and the arterial nonsequential anastomoses, there were 3.5 anastomoses per patients. Proxymal side-to-side anastomosis of LITAs were all constructed on the diagonal branches except for one on the proxymal Left Anterior Descending Coronary Artery (LAD), whereas that of the RGEAs were on the proxymal Right Coronary Artery (RCA) (2), distal RCA (6) or distal circumflex (1). Distal end-to-side anastomoses of LITAs were all on the LAD, and those of the RGEAs were on the distal RCA (3) or distal circumflex artery (5). Proxymal side-to-side anastomoses were always performed first, allowing us to assess the distal flow through the graft before we anastomose it to the distal branch. We routinely obtain a preoperative angiogram of the arterial grafts, which enable us to fully assess the suitability of the arteries as in situ grafts. There were no perioperative deaths, nor perioperative myocardial infarctions, however, two patients died of extracardiac causes at 42 and 68 days after operation respectively. For the thirty four survivors, followup was complete (4-49 months, average 12.3 months). One still had angina of Canadian Cardiovascular Society Classification (CCSC) class 2, and 33 were free of angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Bilateral carotid artery occlusion causes periventricular leukomalacia in neonatal dogs.

At 14 days of age, seven mongrel puppies were anesthetized and bilateral carotid arteries, not only the common but also the external and internal carotid arteries, were ligated with sutures. Seven sham-operated littermates served as controls. They were sacrificed at 3 months of age, and their brains were examined macro- and microscopically. Neuropathological examination revealed dilated posterior communicating and basilar arteries in bilateral carotid artery occlusion (BCAO) animals. Six out of 7 BCAO brains had uni- or multiloculated cysts in the periventricular white matter which were surrounded by a band of GFAP-positive glial cells. Scattered small areas of gliosis were found in all experimental animals. Four BCAO brains also showed ventricular dilatation. Although the cerebral cortex seemed to be intact, the periventricular white matter and the corpus callosum were reduced in width in experimental animals. Myelination in the white matter was significantly reduced in BCAO animals compared with the controls. This study directly demonstrates that cerebral hypoperfusion alone can produce periventricular leukomalacia in neonatal dogs.

Animals↗
PubMed1994

A facilitatory role of vasopressin in hypoxia/hypoglycemia-induced impairment of dopamine release from rat striatal slices.

The excitatory amino acid, glutamate plays a crucial role in the pathogenesis of brain damage caused by anoxia and/or hypoglycemia. Although vasopressin (VP) also acts as an excitatory transmitter in the CNS, little is known about its effect on hypoxic and/or ischemic brain damage. In this study, we investigated the effect of arginine vasopressin (AVP) on hypoxia/hypoglycemia-induced impairment of dopamine release from striatal slices. Striatal slices were incubated in hypoxia-/hypoglycemia-inducing medium with or without AVP (0.01-1.0 microM) for 20 min. After 1-3 h of washout in normal medium, high K(+)-evoked dopamine release from the slices were examined. Hypoxia/hypoglycemia-induced decrease of striatal dopamine release was reversed by the removal of Ca2+ in the medium, but not by VP1- or VP2-receptor antagonist. In contrast, AVP potentiated the hypoxia/hypoglycemia-induced decrease of dopamine release in the striatum. This AVP-induced deterioration of the striatal response was antagonized by VP2 receptor antagonist, but not by VP1 receptor antagonist. The present results suggest that AVP may play a facilitatory role in hypoxia/hypoglycemia-induced dopamine release deficit mediated through the activation of VP2 receptor.

Animals↗
PubMed1994

Nerve regeneration in predegenerated basal lamina graft: the effect of duration of predegeneration on axonal extension.

We used predegenerated acellular grafts to bridge proximal and distal stumps of transected nerves and studied how the duration of predegeneration might affect axonal regeneration. Predegenerated acellular grafts were prepared by transecting the tibial nerve of donor rats and, after a period of degeneration, freeze-thawing a 40-mm long segment of the distal stump. Five degeneration periods were used: 0 days (for fresh grafts), 3 days, 1 week, 4 weeks, and 8 weeks. Fresh cellular grafts not treated with freeze-thawing were also used for comparison. Each graft was then transplanted to an isogeneic recipient rat, in which it was used to bridge the proximal stump of the transected left tibial nerve and the distal stump of the transected right tibial nerve. Six weeks were allowed for the regeneration of axons in all grafts. The regeneration was then assessed by studying transverse sections of the grafts, to determine the maximum length that the axons had regenerated, and the packing density of axons (percentage of sampled areas occupied by axons). The results show that axons had grown to the maximum length in the 4-week predegenerated grafts, and had the highest packing density in the 1-week predegenerated grafts. Regeneration in the fresh acellular (0-day predegenerated) and 8-week predegenerated grafts, especially the latter, was poor. We examine the results with reference to time-dependent events of Wallerian degeneration and propose that there are beneficial effects of multiple factors on the grafts during the first 4 weeks of predegeneration, causing a slow but significant improvement in their capability to support axonal growth. The subsequent rapid deterioration of such capability may be related to structural changes in the extracellular scaffold.

Animals↗
PubMed1994

Vascular permeability to sodium fluorescein in the rabbit cranial nerve root: possible correlation with normal cranial nerve enhancement on gadolinium-enhanced magnetic resonance imaging.

Vascular permeability in cranial nerve roots was examined after intravenous injection of sodium fluorescein in the adult rabbit. Fluorescence was observed in the distal nerves through the following portions: intracavernous portion of the oculomotor nerve, distal internal auditory canal segment of the facial nerve, and ganglionic portions of the trigeminal, glossopharyngeal and vagus nerves. In the acoustic nerve, the vestibular ganglion showed fluorescence. No fluorescence was observed in the olfactory or optic nerves. During in vivo gadolinium-enhanced magnetic resonance imaging (Gd-MRI) of two separate animals, trigeminal nerve enhancement was observed in the region showing fluorescence. Histologically, intense fluorescence was observed in ganglia and external nerve sheaths of the cranial nerves showing macroscopic fluorescence. A slight fluorescence was also seen in endoneurial connective tissue but not observed within the nerve fibers. The results of this study suggest that the physiological enhancement of human cranial nerves seen on Gd-MRI may correlate with vascular permeability.

Animals↗
PubMed1994

Optimal attachment site for reconstruction of the ulnar collateral ligament. A cadaver study.

To determine the isometric points for ulnar collateral ligament (UCL) reconstruction, we performed a kinematic study of 15 cadaver elbows. The margins of the anterior and posterior oblique ligaments of the UCL were measured. Five humeral and three ulnar attachment sites were also selected and grouped in pairs for measurement. The distances from the proximal center of the trochlea to three ulnar points were recorded. Measurements were obtained for pairs of attachment sites for flexion of 0 degree, 30 degrees, 60 degrees, 90 degrees, and 120 degrees. We found that the anterior margin of the anterior oblique ligament (AOL) tended to lengthen as flexion increased from 0 degree to 60 degrees, and to shorten as flexion exceeded 60 degrees. The posterior margin tended to lengthen with flexion up to 120 degrees. It therefore appears that the AOL consists of functionally different components that remain taut throughout flexion. In all experiments, the location of the humeral attachment site affected the lengths through 120 degrees of flexion. At flexion of 0 degree-120 degrees, isometricity was observed in the approximate center of the trochlea, apparently the optimal attachment site. We conclude that conventional ligament reconstruction methods that locate the attachment site in the AOL origin provide inadequately for the isometricity observed in the natural anatomy.

Adult↗
PubMed1994

The diagnostic value of MRI in traumatic brachial plexus injury.

Findings in 34 patients with traumatic brachial plexus injury documented by surgical exploration and intra-operative somatosensory-evoked potentials were correlated with findings on myelography and magnetic resonance imaging (MRI) to determine whether MRI can identify nerve root avulsion. The coronal and sagittal planes were not able to demonstrate avulsion of the individual nerve roots. The axial and axial oblique planes did provide useful information to determine which nerve root was avulsed in the upper plexus, although it was difficult to clearly delineate the lower cervical rootlets. The accuracy of MRI was 73% for C5 and 64% for C6 and that of myelography 63% for C5 and 64% for C6. Thus, the diagnostic accuracy of MRI for upper nerve roots was slightly superior to myelography. Although its primary diagnostic value is limited to the upper nerve roots whose avulsion is relatively difficult to diagnose by myelography, MRI can provide useful guidance in the waiting period prior to surgical exploration after brachial plexus injury.

Adolescent↗
PubMed1994

Meniscal repair enhanced by an interpositional free synovial autograft: an experimental study in rabbits.

This report describes the methods and effectiveness of interpositional free synovial autografts (IPFSAs) in promoting the healing of lesions in the avascular portion of the knee joint meniscus in rabbits. Thirty-four specimens were divided into two groups: 17 in the study group and 17 in the control group. The medial meniscus of the left knee joint was excised in each rabbit, and an artificial longitudinal tear was created in the avascular zone of the meniscus. In the study group, an IPFSA was sewn into the tear with a single horizontal suture. In the control group, the tear was repaired without synovium in the same manner. The menisci were then implanted into the right knee joint in the respective animals. At intervals the animals were killed, and the menisci were examined grossly and microscopically. Three menisci were eliminated because they had become attached to the synovial wall. In the study group, the lesion completely healed by 4 weeks, except for one. The menisci in the control group never completely healed, particularly at the deeper levels of the lesion. At 8-16 weeks, autolysis of the specimens made microscopic examination difficult and unreliable in both groups. Based on these results, it has been concluded that an IPFSA can promote the healing process in the avascular zone of a torn meniscus in rabbits and that systemic vascularity to the synovium or the meniscus is not essential for healing to occur.

Animals↗
PubMed1994

The diagnostic value and limitation of magnetic resonance imaging on chondral lesions in the knee joint.

Chondral lesions of the knee joint, which have been detected via arthrotomy or arthroscopy, were examined prospectively and retrospectively through a review of previously obtained magnetic resonance images (MRIs). The study group was composed of 34 men and 29 women whose average age was 24.6 years. Of these 63 patients, there were 72 articular cartilage lesions in 65 knees. On retrospective analysis, the sensitivity of MRI, which was defined as a true positive reading for softening, fragmentation, erosion, and/or a full-thickness loss of cartilage, was 14.3%, 57.3%, 75.0%, and 100%, respectively. Although the sensitivity to early changes of chondral lesions was low, indicating the limitation of MRI at the present stage, it has been demonstrated that MRI can delineate intracartilaginous changes associated with softening and thickening of cartilage that cannot be detected even with arthroscopy. Therefore, it may be worthwhile to perform an MRI as well as arthroscopy to clarify the pathogenesis of internal derangement of the knee.

Adult↗
PubMed1994

Clinical evaluation of a new type of centrifugal pump.

The major problems with existing centrifugal pumps are leakage, mechanical trauma, and thrombus formation. In consideration of these problems, a new compact centrifugal pump system was developed. The purpose of this study was to evaluate the new centrifugal pump system clinically. Ten patients underwent open heart surgery with a centrifugal pump or a roller pump. During surgery, hemodynamic and hematological data were obtained. A pulsatile assist device in the pump circuit was used in patients with severe heart disease. There was neither operative death nor hospital mortality, and there was no difference with regard to hemodynamic data between the two groups. The centrifugal pump groups, however, had significantly lower hemolysis, especially during prolonged cardiopulmonary bypass. This centrifugal pump could also create sufficient pulsatile flow with a pulsatile assist device. Postoperative macroscopic and microscopic findings demonstrated the smooth surface of the pump without thrombus formation. This centrifugal pump system might be useful for prolonged cardiopulmonary bypass.

Adolescent↗