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Biomedical subjects

Y Uchino

Publications and source records attributed to Y Uchino.

At least 19 recordsLinked to original sources

Microkeratome assisted deep lamellar keratoprosthesis.

AIMS: To establish a keratoprosthesis (Kpro) surgical technique that maintains an intact superficial corneal layer. METHODS: A manual microkeratome (Moria LSK-1) was used to create a 130 mum flap of approximately 10 mm diameter in the right eye of Japanese white rabbits. The stoma beneath the flap area was dissected before the removal of a 5.0 mm stromal disc. A 5.0 mm collagen I immobilised poly(vinyl alcohol) (COL-PVA) disc was placed on the exposed posterior stroma close to Descemet's membrane. The flap was repositioned and fixed using 10-0 nylon sutures, which were removed 2 days following surgery. The corneas were followed clinically by slit lamp microscopy and photographs. Rabbits were sacrificed after 6 months, and the transplanted corneas were examined histologically by haematoxylin and eosin staining and immunohistochemistry against vimentin and alpha-smooth muscle actin (alpha-SMA). RESULTS: The transplanted COL-PVA discs remained transparent throughout the study, with no complications related to the flap or overlying epithelium. The interface between COL-PVA and Descemet's membrane remained clear without signs of opacification caused by scarring or cellular deposition. Pathology revealed the intact COL-PVA polymer in the posterior stroma, with minimal cellular infiltration along the anterior and posterior interfaces. Immunohistology shows vimentin and alpha-SMA staining at levels comparable to lamellar keratoplasty control. CONCLUSIONS: Microkeratome assisted deep lamellar keratoprosthesis may be a safe technique for the transplantation of artificial hydrogels for therapeutic purposes.

Animals↗

Otolith and canal integration on single vestibular neurons in cats.

In this review, based primarily on work from our laboratory, but related to previous studies, we summarize what is known about the convergence of vestibular afferent inputs onto single vestibular neurons activated by selective stimulation of individual vestibular nerve branches. Horizontal semicircular canal (HC), anterior semicircular canal (AC), posterior semicircular canal (PC), utricular (UT), and saccular (SAC) nerves were selectively stimulated in decerebrate cats. All recorded neurons were classified as either projection neurons, which consisted of vestibulospinal (VS), vestibulo-oculospinal (VOS), vestibulo-ocular (VO) neurons, or non-projection neurons, which we simply term "vestibular'' (V) neurons. The first three types could be successfully activated antidromically from oculomotor/trochlear nuclei and/or spinal cord, and the last type could not be activated antidromically from either site. A total of 1228 neurons were activated by stimulation of various nerve pair combinations. Convergent neurons were located in the caudoventral part of the lateral, the rostral part of the descending, and the medial vestibular nuclei. Otolith-activated vestibular neurons in the superior vestibular nucleus were extremely rare. A high percentage of neurons received excitatory inputs from two nerve pairs, a small percentage received reciprocal convergent inputs and even fewer received inhibitory inputs from both nerves. More than 30% of vestibular neurons received convergent inputs from vertical semicircular canal/otolith nerve pairs. In contrast, only half as many received convergent inputs from HC/otolith-nerve pairs, implying that convergent input from vertical semicircular canal and otolith-nerve pairs may play a more important role than that played by inputs from horizontal semicircular canal and otolith-nerve pairs. Convergent VS neurons projected through the ipsilateral lateral vestibulospinal tract (i-LVST) and the medial vestibulospinal tract (MVST). Almost all the VOS neurons projected through the MVST. Convergent neurons projecting to the oculomotor/trochlear nuclei were much fewer in number than those projecting to the spinal cord. Some of the convergent neurons that receive both canal and otolith input may contribute to the short-latency pathway of the vestibulocollic reflex. The functional significance of these convergences is discussed.

Animals↗

Selenium deficiency: report of a case.

We report an 18-month-old Japanese boy with selenium deficiency. He had dry skin with irregularly shaped, erythematous changes on the cheeks, groin, hip, and extremities, erosions on the external urethral and anal orifices, and sparse, short, thin, light-coloured hair. He had received parenteral nutrition for 5 months because of juvenile polyposis. At presentation, his serum selenium level was less than 2.0 microg/dL (normal range, 10.6-17.4 microg/dL). His skin lesions responded well to supplementary treatment with sodium selenite. His skin symptoms were similar to those attributable to a deficiency of zinc which, like selenium, is an essential trace element. According to the literature, selenium deficiency is responsible for cardiomyopathy, which was diagnosed in our patient. The clinical similarity to zinc deficiency and the literature yielded important clues for a diagnosis of selenium deficiency in this patient.

Diagnosis, Differential↗

Removal of large acoustic neurinomas (vestibular schwannomas) by the retrosigmoid approach with no mortality and minimal morbidity.

OBJECTIVE: To evaluate the safety and efficacy of removing large acoustic neurinomas (> or =3 cm) by the retrosigmoid approach. METHODS: Large acoustic neurinomas (mean (SD), 4.1 (0.6) cm) were removed from 50 consecutive patients by the retrosigmoid suboccipital approach while monitoring the facial nerve using a facial stimulator-monitor. Excision began with the large extrameatal portion of the tumour, followed by removal of the intrameatal tumour, and then removal of the residual tumour in the extrameatal region just outside the porus acusticus. The last pieces of tumour were removed by sharp dissection from the facial nerve bidirectionally, and resected cautiously in a piecemeal fashion. RESULTS: There were no postoperative deaths. The tumour was removed completely in 43 of 50 patients (86%). The facial nerve was anatomically preserved in 92% of the patients and 84% had excellent facial nerve function (House-Brackmann grade 1/2). One patient recovered useful hearing after tumour removal. Cerebrospinal fluid leak occurred in 4%, but there were no cases of meningitis. All but two patients (96%) had a good functional outcome. CONCLUSIONS: The method resulted in a high rate of functional facial nerve preservation, a low incidence of complications, and good functional outcomes, with no mortality and minimal morbidity. Very favourable results can be obtained using the retrosigmoid approach for the removal of large acoustic neurinomas.

Adolescent↗

Morphological and biochemical studies of human beta-mannosidosis: identification of a novel beta-mannosidase gene mutation.

BACKGROUND: There are seven well-known lysosomal storage diseases that produce angiokeratoma corporis diffusum clinically. beta-Mannosidosis (MANB1; OMIM248510), first reported in humans in 1986, is a rare hereditary lysosomal storage disease caused by a deficiency of the enzyme beta-mannosidase. Since then, 13 cases of beta-mannosidase deficiency in ten families have been described. A human beta-mannosidase mutation has been reported only by Alkhayat et al. in 1998. OBJECTIVES: To clarify its pathogenesis we did electron microscopic, biochemical and molecular biological investigations of a Japanese patient with beta-mannosidosis. METHODS: Ultrastructural analyses, enzyme assays, cell culture and mRNA and genomic DNA were sequenced to find mutations in the beta-mannosidase gene. RESULTS: Electron microscopy of skin biopsy specimens from the patient showed cytoplasmic vacuolation of lysosomes in blood and lymph vessels, endothelial cells, fibroblasts, secretory portions of eccrine sweat glands, neural cells and basal keratinocytes in the epidermis. This vacuolation was also observed in cultured keratinocytes and fibroblasts. Assays of seven enzyme activities in plasma and cultured skin fibroblasts showed a marked decrease of beta-mannosidase activity. Sequencing the beta-mannosidase cDNA revealed a four-base (ATAA) insertion between exons 7 and 8, resulting in a frameshift at codon 321 and termination at codon 325. Analysis of the patient's genomic DNA revealed a novel homozygous A(+1)-->G splice site mutation in intron 7. CONCLUSIONS: To our knowledge, this is the first case of beta-mannosidosis reported in Japan and the second report in which a gene mutation is identified. The biological importance of beta-mannose moieties in glycoproteins in basal keratinocytes is suggested.

Cells, Cultured↗

Properties of utricular-activated vestibular neurons that project to the contralateral vestibular nuclei in the cat.

The properties of utricular (UT)-activated vestibular neurons that send axons to the contralateral vestibular nuclei (commissural neurons) were investigated intracellularly or extracellularly in decerebrate cats. A total of 27 vestibular neurons were orthodromically activated by stimulation of UT nerves and antidromically activated by stimulation of the contralateral vestibular nuclei. All neurons tested were classified as vestibulospinal (VS), vestibulooculospinal (VOS), vestibuloocular (VO), and unidentified vestibular neurons (V) after antidromic stimulation of the spinal cord and oculomotor/trochlear nuclei. Most UT-activated commissural neurons (20/27) received monosynaptic inputs. Twelve of 27 commissural neurons were located in the medial vestibular nucleus, 5 were in the lateral vestibular nucleus, 10 were in the descending vestibular nucleus, and no commissural neurons were recorded in the superior vestibular nucleus. Seven of 27 neurons were commissural VS neurons, 9 of 27 were commissural VOS neurons, and 11 of 27 were commissural V neurons. No commissural VO neurons were found. All VOS neurons and 3 VS neurons issued descending axons via the medial vestibulospinal tract. We also studied convergent inputs from the posterior semicircular canal (PC) nerve onto UT-activated commissural neurons. Five of 27 UT-activated commissural neurons received converging inputs from the PC nerves.

Animals↗

Convergence of the anterior semicircular canal and otolith afferents on cat single vestibular neurons.

The convergence between the anterior semicircular canal (AC) and utricular (UT) inputs, as well as the convergence between the AC and saccular (SAC) inputs in single vestibular neurons of decerebrated cats were investigated. Postsynaptic potentials were recorded intracellularly after selective stimulation of each pair of vestibular nerves AC/UT or AC/SAC. Neurons were recorded from the central parts of the vestibular nuclei, where the otolith afferents mainly terminate. Of a total of 105 neurons that were activated after stimulation of the AC and UT nerves, 42 received convergent inputs. Thirty-eight of these neurons received excitatory inputs from both afferents. Convergent neurons were further classified into vestibulospinal (n=28) and vestibulooculospinal (n=6) neurons by antidromic activation from the border between the C1 and C2 spinal cord and the oculomotor or trochlear nucleus. Eight neurons that were not antidromically activated from either site were classified as vestibular neurons. Forty three percent of the convergent vestibulospinal neurons and most of the convergent vestibulooculospinal neurons projected to the spinal cord through the medial vestibulospinal tract. The remaining vestibulospinal and vestibulooculospinal neurons descended through the ipsilateral lateral vestibulospinal tract. Of a total of 118 neurons that were activated after stimulation of the AC and/or SAC nerves, 51 received convergent inputs (27 vestibulospinal, 4 vestibulooculospinal, 5 vestibuloocular and 15 vestibular neurons). Forty-two of the convergent neurons received excitatory inputs from both afferents. Thirty seven percent of the convergent vestibulospinal neurons and all of the convergent vestibulooculospinal neurons projected to the spinal cord through the medial vestibulospinal tract. The remaining vestibulospinal and vestibulooculospinal neurons descended through the ipsilateral lateral vestibulospinal tract.

Afferent Pathways↗

Convergence of ipsilateral semicircular canal inputs onto single vestibular nucleus neurons in cats.

Convergent inputs from the ipsilateral semicircular canal nerves onto single vestibular nucleus neurons were investigated in decerebrate cats using intracellular recording after selective stimulation of each ampullar nerve. One hundred and seventy-four neurons were activated by stimulating the anterior semicircular (AC) and/or posterior semicircular canal (PC) nerves. These neurons were also antidromically stimulated and classified according to the pattern of their collateral projections to the oculomotor complex and the spinal cord. Four types were found: vestibulo-ocular (VO), vestibulospinal (VS), vestibulo-oculospinal (VOS), and vestibular (V) neurons, the latter of which were not activated by stimulation of either the oculomotor complex or the spinal cord. Of 174 AC- and/or PC-activated vestibular nucleus neurons, 32 (18%) received convergent inputs from both nerves. These convergent neurons included 11 VS, 6 VOS, and 15 V neurons. We found no VO neurons with convergent input. The vast majority (82%) of AC/PC-activated VS and VOS convergent neurons received excitatory inputs from both nerves, 12% received reciprocal inputs (i.e., excitatory from one and inhibitory from the other), and the remaining neurons received inhibitory inputs from both nerves. By stimulating the horizontal semicircular (HC) and/or PC nerves, 183 neurons were activated. Of these, 44 (24%) received convergent inputs from both nerves. These convergent neurons included 19 VS, 5 VOS, 2 VO, and 18 V neurons. Approximately one-half (46%) of HC/PC-activated VS and VOS convergent neurons received excitatory inputs from both nerves and 42% received reciprocal inputs, and the remaining neurons received inhibitory inputs from both nerves. In both nerve pairs, the percentage of VS neurons was higher (AC/PC, 34%; HC/PC, 43%) than that of VOS or VO neurons. Approximately half of these convergent neurons were located in the lateral nucleus. These results suggest that, during mixed angular head accelerations, the vestibulocollic reflex may be partly accomplished by VS and VOS convergent neurons.

Afferent Pathways↗

Potential role of the anterior spinal artery in preventing propagation of thrombus in a therapeutically occluded vertebral artery: angiographic studies before and after endovascular treatment.

Therapeutic occlusion of the vertebral artery (VA) is one of the treatments for unclippable aneurysms and other lesions, although controversy still surrounds the appropriate site for occlusion to attain selective thrombosis of the lesion while avoiding ischaemic complications. The lower two-thirds of the lateral medulla are supplied by perforating branches of both the VA and the posterior inferior cerebellar artery (PICA). However, in patients without a PICA or in whom the origin of the PICA is low (at or below the foramen magnum), the VA is usually the only source of perforating vessels. We retrospectively studied the results of VA occlusion on such anatomically high-risk patients, and propose a safer procedure. Five high-risk patients underwent therapeutic occlusion of the VA for dissecting aneurysms or arteriovenous fistula. A lateral medullary syndrome developed due to propagation of thrombus after the procedure in two patients in whom angiography did not demonstrate the anterior spinal artery (ASA) within the stump of the VA. Ischaemic signs did not develop in the other three patients, in whom the ASA was visible, and retrograde flow was observed proximal to the origin of the ASA. This suggests that the ASA may play a role in preventing propagation of thrombus in the VA distal to the site of occlusion and supply blood to its perforating arteries in high-risk patients. Angiographic assessment of the ASA may be useful for predicting the likelihood of the lateral medullary syndrome developing with therapeutic occlusion of the VA in patients without a PICA or with one whose origin is low.

Adult↗

Otolith-activated vestibulothalamic neurons in cats.

The components of the vestibular ascending pathway that transmit otolith information to the thalamus were studied electrophysiologically in anesthetized cats. Thalamic-projecting vestibular neurons (confirmed antidromically) were recorded extracellularly in the various vestibular nuclei. Otolith inputs to these neurons were examined with selective stimulation of the utricular (UT) or the saccular (SAC) nerves. Vestibular nerve branches other than the tested nerve were transected. Of 40 UT-activated vestibulothalamic neurons, 40% (16/40) were activated by UT nerve stimulation with latencies ranging between 0.9-1.4 ms, suggesting they were second-order neurons from the UT nerve. UT-activated vestibulothalamic neurons were recorded in the medial vestibular nucleus (MVN; 24/40), the lateral vestibular nucleus (LVN; 9/40), the descending vestibular nucleus (DVN; 6/40), and the superior vestibular nucleus (SVN; 1/40). Most of the neurons (38/40) were antidromically activated by focal stimulation of the ventral part of the ipsilateral thalamus. Antidromic stimulation of the pontine area revealed that trajectories of the ascending axons (14 of 38 neurons) to the ipsilateral thalamus passed through the pontine reticular formation, ventral to the ascending tract of Deiters (ATD) and the medial longitudinal fasciculus (MLF). Only three SAC-activated vestibulothalamic neurons were encountered in the LVN. All these neurons were second-order neurons from the SAC nerve and were antidromically activated by stimulation of the contralateral thalamus, in marked contrast to the UT-activated vestibulothalamic neurons. Only three UT-activated and two SAC-activated neurons sent descending collaterals to the spinal cord.

Action Potentials↗

Commissural effects in the otolith system.

We examined whether otolith-activated second- and third-order vestibular nucleus neurons received commissural inhibition from the contralateral otolithic macula oriented in the same geometric plane. For this purpose we performed intracellular recording in vestibular nucleus neurons after stimulation of the ipsi- and contralateral utricular and saccular nerves. More than half (41/72) of the utricular-activated second-order vestibular nucleus neurons received commissural inhibition from the contralateral utricular nerve. The remaining neurons (31/72) showed no visible response to contralateral utricular nerve stimulation. About half (17/36) of utricular-activated third-order neurons also received commissural inhibition from the contralateral utricular nerve. Approximately 10% (7/67) of saccular-activated second-order vestibular neurons received polysynaptic commissural inhibition, whereas 16% (11/67) received commissural facilitation. The majority (49/67) of saccular second-order vestibular neurons, and almost all (22/23) third-order neurons, showed no visible response to stimulation of the contralateral saccular nerve. The present findings suggest that many utricular-activated vestibular nucleus neurons receive commissural inhibition, which may provide a mechanism for increasing the sensitivity of vestibular neurons to horizontal linear acceleration and lateral tilt of the head. Commissural inhibition in the saccular system was less prominent than in the utricular system.

Animals↗

Convergence of the horizontal semicircular canal and otolith afferents on cat single vestibular neurons.

We studied the convergence of two afferent pairs of single vestibular neurons by selective stimulation of the horizontal semicircular canal (HC) and saccular (SAC) nerves, and the HC and utricular (UT) nerves in decerebrate cats. All recorded neurons were classified as vestibulospinal (VS), vestibulo-oculospinal (VOS) or vestibulo-ocular (VO), by antidromic stimulation from the oculomotor/trochlear nuclei and the spinal cord: neurons that could not be activated from any test sites were classified as vestibular (V) neurons. Of a total of 125 neurons activated by stimulation of the HC/SAC nerves, 21(17%) received convergent inputs. Twelve of 21 neurons received monosynaptic excitatory inputs from both nerves. About half (9/21, 43%) of the convergent neurons were classified as VS neurons, the majority of which descended through the ipsilateral lateral vestibulospinal tract (i-LVST). The HC/SAC convergent neurons were located in the rostral part of the descending, the medial and the caudal-ventral part of the lateral vestibular nucleus. In 80 neurons studied by stimulation of the HC/UT nerves, both inputs converged in 12 (15%) neurons, more than half of which were VS neurons. Eight of 12 convergent neurons received excitatory inputs followed by inhibition from both the HC and UT nerves. A few convergent neurons (3/12) projected to the oculomotor/trochlear nucleus. Half of the convergent and non-convergent VS neurons descended to the spinal cord through the i-LVST, and the only one VOS convergent neuron via the medial vestibulospinal tract. Most of the convergent neurons were located in the lateral, the rostral part of the descending and medial vestibular nucleus. The percentages of HC/SAC and HC/UT convergence were half those of the posterior semicircular canal (PC), PC/SAC (33%) and PC/UT (33%) convergence, respectively. The convergent neurons receiving the HC and otolith inputs may contribute at least partly to the vestibulocollic reflex.

Afferent Pathways↗

Computed tomography and magnetic resonance imaging of mild head injury--is it appropriate to classify patients with Glasgow Coma Scale score of 13 to 15 as "mild injury"?

OBJECTIVE: The purpose of this study is to examine the relation between Glasgow Coma Scale (GCS) score and findings on computed tomography (CT) and magnetic resonance (MR) imaging of patients with mild head injury presenting GCS scores between 13 and 15. METHODS: Data were collected from all consecutive patients with mild head injury who were referred to our hospital between July 1 and October 31, 1999. All patients were recommended to undergo CT and MR imaging examinations. Patients younger than 14 years of age were excluded. RESULTS: Ninety patients were recruited into this study. CT scans were obtained in 88 patients and MR imaging were obtained in 65 patients. Of these 90 patients, 2 patients scored 13 points, 5 scored 14 points and 83 (92.2%) 15 points. Patients with GCS score of 13 points demonstrated parenchymal lesions on both CT and MR imaging. Those with 14 points revealed absence of parenchymal abnormality on CT, but presence of parenchymal lesions on MR imaging. Patients in advanced age (chi square test, p<0.0001), and those with amnesia (p=0005, not significant), although scoring 15 points, revealed a tendency to abnormal intracranial lesions on CT scans. CONCLUSION: It is doubtful whether patients with GCS score 13 should be included in the mild head injury category, due to obvious brain damage on CT scans. MR imaging should be performed on patients with GCS score 14, since the parenchymal lesions are not clearly demonstrated on CT scans. Even if patients scored GCS 15, patients with amnesia or of advanced age should undergo CT scans at minimum, and MR imaging when available.

Adolescent↗

Distinct functions of the two protein tyrosine phosphatase domains of LAR (leukocyte common antigen-related) on tyrosine dephosphorylation of insulin receptor.

Most receptor-like, transmembrane protein tyrosine phosphatases (PTPases), such as CD45 and the leukocyte common antigen-related (LAR) molecule, have two tandemly repeated PTPase domains in the cytoplasmic segment. The role of each PTPase domain in mediating PTPase activity remains unclear; however, it has been proposed that PTPase activity is associated with only the first of the two domains, PTPase domain 1, and the membrane-distal PTPase domain 2, which has no catalytic activity, would regulate substrate specificity. In this paper, we examine the function of each PTPase domain of LAR in vivo using a potential physiological substrate, namely insulin receptor, and LAR mutant proteins in which the conserved cysteine residue was changed to a serine residue in the active site of either or both PTPase domains. LAR associated with and preferentially dephosphorylated the insulin receptor that was tyrosine phosphorylated by insulin stimulation. Its association was mediated by PTPase domain 2, because the mutation of Cys-1813 to Ser in domain 2 resulted in weakening of the association. The Cys-1522 to Ser mutant protein, which is defective in the LAR PTPase domain 1 catalytic site, was tightly associated with tyrosine-phosphorylated insulin receptor, but failed to dephosphorylate it, indicating that LAR PTPase domain 1 is critical for dephosphorylation of tyrosine-phosphorylated insulin receptor. This hypothesis was further confirmed by using LAR mutants in which either PTPase domain 1 or domain 2 was deleted. Moreover, the association of the extracellular domains of both LAR and insulin receptor was supported by using the LAR mutant protein without the two PTPase domains. LAR was phosphorylated by insulin receptor tyrosine kinase and autodephosphorylated by the catalytic activity of the PTPase domain 1. These results indicate that each domain of LAR plays distinct functional roles through phosphorylation and dephosphorylation in vivo.

Animals↗