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Biomedical subjects

Masahiro Zako

Publications and source records attributed to Masahiro Zako.

36 records · Page 2Linked to original sources
PubMed2004

Causes of undercorrection of medial palpebral fissures in blepharoptosis surgery.

PURPOSE: To ascertain the cause of undercorrection of the medial palpebral fissure in blepharoptosis surgery. METHODS: Twelve upper eyelids of 6 Asian cadavers, 4 male and 2 female (average age at death, 77.5 years), were studied. After exposing the levator muscle by removing bone of the superior orbital rim, the levator muscle and medial and lateral horns of aponeurosis were observed. RESULTS: The levator muscle was located in the anterolateral direction. Bifurcation angles of the medial horn were steeper than those of the lateral horn, but the lateral horn was wider than the medial horn (Student's t test; P < 0.0001). The inferior edge of the superior expansion of the aponeurosis extensively covered the lateral horn but only slightly covered the medial horn. Accordingly, most of the medial horn was constituted by only the thin structure of the middle and inferior expansion of the aponeurosis. CONCLUSIONS: Because the medial horn is structurally weaker and less dynamic than the lateral horn, the lateral side of the aponeurosis is pulled more strongly than the medial, often resulting in medial undercorrection in blepharoptosis surgery. To prevent this, the medial part should be fixed more widely than the lateral.

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PubMed2004

No raphe identified in the orbicularis oculi muscle.

This study was performed to elucidate whether the raphe of the orbicularis oculi muscle (raphe) exists or not. Nine upper eyelids of 6 Oriental cadavers with ages at death ranging from 72 to 91 years were dissected; 6 for gross dissections and 3 for histological slice sections. After removing the lateral half of the eyelid skin, the lateral part of the orbicularis oculi muscle and its subjacent tissue were observed macroscopically. The full layered tissue of the 8 mm lateral part from the orbital rim was incised perpendicularly and sections sliced, which were then observed microscopically after staining with the hematoxylin and eosin. The raphe was not identified macroscopically or microscopically. The lateral part of the orbicularis oculi muscle was continuous without the tendinous intercalation; under it, fibrous connective tissue corresponding to the lateral orbital thickening was observed, and in which the band configuration, microscopically the tendinous structure, was formed. The raphe was not identified. The physiological role of the lateral part of the orbicularis oculi muscle is maintained by a less tight attachment of the lateral orbital thickening, but not by the raphe.

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PubMed2004

Three ligaments reinforce the lower eyelid.

This study was performed to elucidate the ligamentous structures in the lower eyelid other than the Lockwood ligament. Ten lower eyelids (right 5, left 5) of 5 Oriental post-mortems were dissected. The orbital septum was incised along the orbital rim, and then turned over toward the eyelid margin. The orbital fat was exposed and removed as much as possible without injuring the ligamentous structures. The ligamentous structures in the lower eyelid were then investigated macroscopically. There were two other ligaments in the lower eyelid in addition to the Lockwood ligament. All three ligaments originated from the posterior lacrimal crest, but went in different directions. The superior ligament ran on the junction of the orbital septum and the capsulopalpebral fascia, and in the lateral area, it ran on the posterior aspect of the orbital septum and attached to the periosteum of the lateral orbital rim. The inferior ligament went toward the posterior aspect of the inferior oblique muscle after separating from the Lockwood ligament. Ligaments other than the Lockwood ligament were revealed in the lower eyelid. These ligaments are thought to reinforce the fragility of the lower eyelid.

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PubMed2003

Syndecan-1 and -4 synthesized simultaneously by mouse mammary gland epithelial cells bear heparan sulfate chains that are apparently structurally indistinguishable.

Many of the biological functions attributed to cell surface heparan sulfate (HS) proteoglycans, including the Syndecan family, are elicited through the interaction of their HS chains with soluble extracellular molecules. Tightly controlled, cell-specific sulfation and epimerization of HS precursors endows these chains with highly sulfated, iduronate-rich regions, which are major determinants of cytokine and matrix-protein binding and which are interspersed by N-acetylated, poorly sulfated regions. Until this study, there have been no comprehensive structural comparisons made on HS chains decorating simultaneously expressed, but different, syndecan core proteins. In this paper we demonstrate that the HS chains on affinity-purified syndecan-1 and -4 from murine mammary gland cells are essentially identical by a number of parameters. Size determination, disaccharide analyses, enzymatic and chemical scission methods, and affinity co-electrophoresis all failed to reveal any significant differences in fine structure, domain organization, or ligand-binding properties of these HS species. These findings lead us to suggest that the imposition of the fine structure onto HS occurs independently of the core protein to which it is attached and that these core proteins, in addition to the HS chains, may play a pivotal role in the various biological functions ascribed to these macromolecules.

Animals↗
PubMed2002

Molecular cloning and characterization of chick sialoprotein associated with cones and rods, a developmentally regulated glycoprotein of interphotoreceptor matrix.

MY-174 is an IgM class monoclonal antibody originally established against chick PG-M/versican. The antibody specifically stains the photoreceptor layer, where we recently reported an absence of PG-M/versican. In this study, we re-characterized the antibody and identified the molecule that reacts to MY-174 at the photoreceptor layer. Immunohistochemistry localized the antigen to the matrix surrounding photoreceptors. A variety of glycosidase digestions showed that the antigen is the 150-kDa glycoprotein that has sialylated N- and O-linked glycoconjugates having a molecular mass of more than 30-kDa. The peptide sequences obtained from purified MY-174 antigen showed we had sequenced a full-length cDNA with an open reading frame of 2787 base pairs, encoding a polypeptide of 928 amino acids, with 56 and 54% identities to human and mouse sialoprotein associated with cones and rods (SPACRs), respectively, and with the structural features observed in SPACRs. The specific sialylated O-glycoconjugates here are involved in the epitope structure for MY-174. SPACR first appeared by embryonic days 15-16, and expression increased with developmental age, paralleling the adhesion between neural retina and retinal pigment epithelium. Thus, we concluded that the MY-174 antigen at the photoreceptor layer, a developmentally regulated glycoprotein, is identical to chick SPACR and may be involved in a novel system mediating adhesion between neural retina and retinal pigment epithelium.

Amino Acid Sequence↗
PubMedDate not supplied

Magnetic resonance imaging of pre- and postoperative lower eyelid states in involutional entropion.

PURPOSE: To disclose pre- and postoperative lower eyelid gradients in involutional entropion using sagittal magnetic resonance imaging (MRI). METHODS: Three female patients, average age 82 (two right eyes and one left), were operated on for involutional entropion by the Jones procedure. Before and after the surgery, the lower eyelid gradient was evaluated by MRI and photography. RESULTS: Preoperatively, each lower eyelid presented anterior protrusion, and the retractor was apart from the globe. Postoperatively, no anterior protrusion was observed, and the retractor was pulled posteroinferiorly and located parallel to the globe. CONCLUSIONS: The MRI visualization of pre- and postoperative changes of gradient in the lower involutional entropion supports surgical reconstruction.

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PubMedDate not supplied

The medial canthal tendon is composed of anterior and posterior lobes in Japanese eyes and fixes the eyelid complementarily with Horner's muscle.

PURPOSE: To report that the medial canthal tendon (MCT) is not simply the aggregate of the orbicularis oculi muscle (OOM) and its tendon. METHODS: Twenty eyelids of 10 cadavers were used. The cadavers, seven male and three female, were all Japanese, with an average age of death of 76.2 years. The relationship between the MCT and the OOM, and between the tarsus and Horner's muscle were investigated. Histological findings were obtained with hematoxylin and eosin staining. RESULTS: The MCT was structured with an anterior lobe, the tendon from the tarsal area of the OOM, and a posterior lobe, the muscle-tendon transition area in the orbital area of the OOM. The nasal aspect of the tarsus was fixed by Horner's muscle. CONCLUSIONS: The MCT and Horner's muscle are located in an important area of the eyelid; therefore, it is essential to understand their precise anatomy.

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PubMedDate not supplied

Incarceration of the inferior oblique muscle branch of the oculomotor nerve in two cases of orbital floor trapdoor fracture.

BACKGROUND: Incarceration of the inferior oblique muscle (IO) branch of the oculomotor nerve may occur in cases of orbital floor trapdoor fracture. CASES: Two orbital floor trapdoor fracture cases, with lesions located just outside of the inferior rectus muscle but without its incarceration, were examined pre- and postoperatively for visual acuity, intraocular details, the nine diagnostic ocular positions of gaze, binocular single vision field with the Hess chart, and by computed tomography (CT). One case was also examined by magnetic resonance imaging (MRI; T1-weighted images). A forced duction test was conducted intraoperatively. OBSERVATIONS: Each case presented good visual acuity and neither globe showed any injury. Motility disturbance of the IO was shown in each case by binocular single vision field testing and the Hess chart. The possibility of the incarceration of the IO branch of the oculomotor nerve, which runs from the incarcerated lesion to the superior belly of the IO, in an orbital floor trapdoor fracture was shown on CT and MRI. Intraoperative forced duction testing revealed a restriction due to the incarceration of the connective tissue septa. CONCLUSIONS: As inferred from the CT and MRI analyses conducted in this study, IO palsy may be one of the causes of ocular motility disturbance of the IO in an orbital floor trapdoor fracture, in addition to the ocular motility disturbance due to the connective tissue septa.

Adult↗
PubMedDate not supplied

Posterior aspect of the orbital septum is reinforced by ligaments.

PURPOSE: To investigate the ligaments reinforcing the posterior aspect of the orbital septum. METHODS: Sixteen upper eyelids of eight cadavers of Asians were dissected. Ten were subjected to gross dissections to investigate the ligaments attached to the posterior aspect of the orbital septum and to investigate the relationships with the associated ligamentous structures, and six were used for histological sections to elucidate the ligament anchoring sites in the septum. RESULTS: The ligaments were attached to the posterior aspect of the orbital septum in both upper and lower eyelids in all cases. Some septa in the upper eyelids were supported by the lower-positioned transverse ligament in the lateral area. In all cases, part of the Lockwood ligament was attached to the posterior aspect of the orbital septum in the lower eyelids. Histologically, the ligaments were anchored to the posterior aspect of the orbital septum. CONCLUSIONS: The ligaments were attached to the posterior aspect of the orbital septum. These ligaments, in cooperation with the associated ligaments, are thought to complement the fragility of the orbital septum.

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PubMedDate not supplied

Intraoperative quantification using finger force for involutional blepharoptosis without postoperative lagophthalmos.

PURPOSE: To report intraoperative quantification using finger force for involutional blepharoptosis, which helps in the prevention of postoperative lagophthalmos. METHODS: We carried out levator resection on 20 involutional blepharoptic eyelids. Fissure height was examined intraoperatively to evaluate the extent of resection. If a patient presented more than 3 mm of lagophthalmos in voluntary eyelid closure but could fully open the eye, we forcibly closed the eyelid, using a finger, after voluntary eyelid closure. If more than 3 mm of lagophthalmos was still observed after forced eyelid closure, we corrected eyelid tension until lagophthalmos became less than 2 mm. RESULTS: Six of the ten patients (20 eyelids) presented with full eyelid opening but more than 3 mm of lagophthalmos in voluntary eyelid closure. After the upper eyelids were forcibly lowered, all six eyelids showed less than 2 mm of lagophthalmos. There were no cases of lagophthalmos 1 month postoperatively. CONCLUSIONS: Additional finger force makes precise quantification of blepharoptosis surgery possible and prevents postoperative lagophthalmos.

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PubMedDate not supplied

Microscopic anatomy of Asian lower eyelids.

PURPOSE: To elucidate the microscopic anatomy of the Asian lower eyelid. METHODS: Specimens (full-thickness sections of lower eyelids from 19 postmortem lower eyelids) from 11 Asians aged 73 to 96 years at death were fixed in 10% buffered formalin and microscopically examined. After pretreatment, sagittal sliced sections of the central part were stained with Masson trichrome. RESULTS: The distinct junction of the orbital septum to the capsulopalpebral fascia (CPF) was confirmed in 7 eyelids in which orbital septum was clearly stained, with an average distance from the tarsus to the junction of 2.38 mm. The other 12 eyelids did not show a distinct junction, and the orbital septum was poorly defined anteriorly and indistinct posteriorly. There was a distinct layer between the orbicularis oculi muscle and the orbital septum. The inferior and the posterior attachments of the CPF to the tarsus were seen in all eyelids. Seventeen of the 19 eyelids had attachment of the CPF on the anterior aspect of the tarsus, from which an extension of the CPF through the pretarsal orbicularis oculi muscle was observed. All eyelids had anterior extension of the CPF through the preseptal orbicularis oculi muscle, which was overridden on the pretarsal orbicularis oculi muscle. CONCLUSIONS: The microscopic findings of Asian lower eyelids, especially fascial components, were mostly similar to those of non-Asian eyelids, but differences existed in higher or indistinct septum fusion, anterior and superior orbital fat projection, and the overriding of the preseptal orbicularis oculi muscle.

Aged↗
PubMedDate not supplied

The medial horn and capsulopalpebral fascia in the medial canthus are significant antagonists of the orbicularis oculi muscle for lacrimal drainage.

PURPOSE: The anatomical relationship indicates that the medial horn of the levator aponeurosis (MH) and the capsulopalpebral fascia (CPF) are the potential candidates for antagonists of the orbicularis oculi muscle (OOM). This study sought to disclose the relationships among the MH, CPF and OOM, and to discuss their roles in the lacrimal drainage system. METHODS: Twelve medial canthuses of 6 cadavers were studied. After peeling eyelid skin from the OOM, we carefully observed the MH, CPF and OOM in the medial canthus. RESULTS: The MH attached to the superior aspect of the medial canthal tendon. The CPF, which attached to the lower tarsal margin, traveled just under Horner's muscle in the medial canthus and dispersed from a lateral aspect of the lacrimal sac to the posterior lacrimal crest. CONCLUSIONS: As the movement of a muscle can be determined by its origin and insertion, the MH and the CPF are considered to be the antagonists of the OOM, and as such must be taken into consideration for an understanding of the lacrimal drainage system.

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