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Biomedical subjects

Masahiro Zako

Publications and source records attributed to Masahiro Zako.

At least 19 recordsLinked to original sources
PubMed2006

The lower eyelid retractor consists of definite double layers.

PURPOSE: To examine whether the lower eyelid retractor consists of a single layer or multiple layers. DESIGN: Retrospective clinical case series and dissectional study. PARTICIPANTS: Fifty-one lower eyelid retractors (31 right, 20 left) of 44 patients (ages, 63-95 years) during entropion surgeries and 10 lower eyelids (5 right, 5 left) of 5 Oriental cadavers (73-91 years old at death) were observed macroscopically. Specimens from 20 postmortem lower eyelids of 12 Orientals (11 right, 9 left; 66-96 years old at death) were used for microscopic observations. METHODS: Macroscopically, we bluntly or, in parts, sharply dissected lower eyelid retractors into 2 layers during entropion surgeries. Cadaveric lower eyelids also were used to investigate relationships between the lower eyelid retractor and the Lockwood ligament. Cadaveric lower eyelids with sagittal full-thickness sections of the central part were examined microscopically using Masson trichrome staining. MAIN OUTCOME MEASURES: Anatomical findings in the lower eyelid retractor. RESULTS: Lower eyelid retractors easily were detached into 2 layers. Macroscopically, the anterior layer was defined as a coarse tissue continuing from the Lockwood ligament, which joined with the lower orbital septum, and constituted the lower conjoined fascia. The posterior layer appeared to be a dense fibrous sheet with a lustrous surface. Microscopically, the lower eyelid retractor consisted of a definite double layer. The anterior layer, a coarse fibrous tissue, consisted of the suborbicularis fascial layer, orbital septum, and superficial part of the capsulopalpebral fascia, which continued to the anterior lamellae of the lower eyelids. The posterior layer consisted of dense fibers of the capsulopalpebral fascia with smooth muscle continuing to the tarsus. CONCLUSIONS: The lower eyelid retractor consists of a definite double layer. The posterior dense layer containing smooth muscle is the main tractional component of the lower eyelid retractor.

Aged↗
PubMed2006

Molecular cloning and characterization of chick SPACRCAN.

MY-174, a monoclonal antibody that reacts with specific sialylated O-linked glycoconjugates of chick SPACR (sialoprotein associated with cones and rods), also recognizes another molecule of 300 kDa. Here, we verified that this 300-kDa molecule is chick SPACRCAN (sialoproteoglycan associated with cones and rods), another member of a novel interphotoreceptor matrix molecule family. Screening for chick SPACRCAN was carried out by plaque hybridization using a probe for chick SPACR. Specific polyclonal antibodies raised against chick SPACRCAN were used for the following experiments. To determine whether the 300-kDa molecule detected by MY-174 was identical to 300-kDa chick SPACRCAN, the migrations of these bands were examined after various glycosidase digestions. Furthermore, the expression levels were measured during retinal development and compared with those of chick SPACR. The results demonstrated that the 300-kDa molecule recognized by MY-174 was chick SPACRCAN, and we further identified it as a proteoglycan with chondroitin sulfate chains. SPACRCAN had heavily sialylated N- and O-linked glycoconjugates, and its MY-174 antigenicity was abolished by O-glycanase treatment after neuraminidase treatment, as observed for chick SPACR. During retinal development, the mRNA and core protein expression levels, MY-174 antigenicity, and hyaluronan binding ability of SPACRCAN peaked around embryonic day 17 and then gradually decreased, whereas the corresponding expression levels of SPACR simply increased, but not its hyaluronan binding ability. The MY-174 reactivity of SPACRCAN in the adult retina was decreased compared with that in the newborn retina, whereas that of SPACR was increased. The decreased hyaluronan binding of SPACR was induced by an inhibitory effect of the excess of sialic acids in the adult stage. Thus, with similar core protein structures and specific sialylated glycoconjugates but distinct chondroitin sulfate chains, SPACRCAN and SPACR may have separate roles in the retina due to their differing expression profiles during development.

Amino Acid Sequence↗
PubMed2006

Adult medial orbital wall trapdoor fracture with missing medial rectus muscle.

We report the case of a 28-year-old man presenting with a medial orbital wall trapdoor fracture with a missing medial rectus muscle. We believe this to be the first case report of an adult medial orbital wall trapdoor fracture. Trapdoor fractures most commonly occur in the pediatric population, and those involving the medial orbital wall generally occur in areas with less developed ethmoid air cells. Since the present case followed neither pattern, a different injury mechanism was considered. The ethmoid air cells in this case were well developed, which may have played an important role in the pathogenesis of this adult medial orbital wall trapdoor fracture. Based on our findings, we propose a possible mechanism for a medial orbital wall trapdoor fracture in an adult. The cellular frames enable the medial bone to shift just minimally, regardless of the high orbital pressure during a blow. The excess volume of the orbital content escapes into the cells through narrow cracks; therefore, after a blow, it cannot move back completely into the orbit. Consequently, it pushes the shifted bone towards the orbit, becoming trapped in a manner similar to that of a check-valve mechanism.

Adult↗
PubMed2006

An anomalous muscle linking superior and inferior rectus muscles in the orbit.

Dissections of the bilateral orbits in a 45-year-old female cadaver, who had no ocular movement disorders in her lifetime, revealed anomalous muscles linking the superior and inferior rectus muscles. The muscles, situated between the optic nerve and the lateral rectus muscle, originated from the annulus of Zinn and branched off two heads; one inserted into the medial inferior side of the superior rectus muscle and the other inserted into the central superior side of the inferior rectus muscle. Each insertion was located on a distal site of the myoneural junction of each rectus muscle. Histological investigations showed that the muscles had a striated muscle structure. No definite nerve insertion was observed in the muscles. Although this type of anomalous muscle has been reported in a few Caucasian cases, the present study is the first report in an Asian person. Anomalous orbital structures, which are a rare cause of strabismus, are important in the differential diagnosis of intra-orbital space-occupying lesions, rather than the differential diagnosis of strabismus.

Asian People↗
PubMed2006

Myoneural junctions of extraocular muscles: distances from the orbital rim and widths.

PURPOSE: To examine both the distances from the orbital rim to the myoneural junctions (MNJs) and the widths of the MNJs of all extraocular muscles. METHODS: Six orbits of 3 post-mortem cadavers were used. The cadavers (1 female and 2 males) were all Japanese with an average age of 76.3 years. The MNJs of the extraocular muscles and their motor nerves were exposed, and then the distance from the orbital rim to each MNJ and the width of each MNJ were examined. RESULTS: The distance from the orbital rim to each MNJ in the 6 extraocular muscles ranged from 24.4 to 33.6 mm and the width of each MNJ ranged from 5.0 to 8.5 mm. CONCLUSIONS: It is essential for orbital surgeons to understand both the distance from the orbital rim to MNJs and the widths of MNJs. This information not only aids the understanding of MNJ damage, but also prevents iatrogenic nerve impairment during orbital surgery.

Aged↗
PubMed2006

Lateral canthal support system in Japanese.

The present study aimed to elucidate microscopically the precise structure of the generally termed 'lateral canthal tendon' (LCT). Specimens from 9 post-mortem lower eyelids of 6 Japanese aged from 72 to 91 years old at death were fixed in 10% buffered formalin, and microscopically examined. Specimens were excised as exenterated samples including an area 5 mm wider than the orbital aperture. The removed contents were further incised longitudinally on the central eyelid and also incised parallel to the upper eyelid margin on the site 3 mm from its margin. After the preparation of microscopical examination, sections of all 9 eyelids were stained with Hematoxylin and Eosin. We found that the structure generally termed LCT consisted of two definitive different layers microscopically. The superficial layer was only an orbital septum (septal band). It was mainly constituted of thick fibers between adipose-rich tissues. The deep layer continued from the tarsus and projected posteriorly; which was a ligament (tarsoligamentous band). This tissue was constituted by thin, minute fibers with little adipose tissues. The structure generally termed LCT is not a tendon but a complex constitution of an orbital septum and a ligament; which we named, in a mass, 'lateral canthal bands', cooperatively supporting the lateral canthus.

Aged↗
PubMed2005

Expression profile of heat shock protein 108 during retinal development in the chick.

In the developing chick retina, heat shock protein 108 (HSP108), which exhibits transferrin binding activity, has been demonstrated at the mRNA level, while transferrin shows two expression peaks. Here, we investigated the expression profile of HSP108 in the developing chick retina at the protein level. The localization of HSP108 in embryonic days 15 (E15), E18, and postnatal day 2 (P2) chick retina was examined immunohistochemically using monoclonal antibody 9G10 specific for chick HSP108, while the expression levels of HSP108 in developing chick retina from E12 to P2 and adult were measured by Western blot analysis. HSP108 was expressed in the ganglion cell layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, inner segments of photoreceptors and retinal pigment epithelium. Two peaks of HSP108 expression were found at around E13 and E18, respectively. Since the two HSP108 peaks appeared to be correlated with the transferrin expression peaks during retinal development, HSP108 may be associated with iron metabolism during the development of the retina.

Animals↗
PubMed2005

The lacrimal canaliculus and sac bordered by the Horner's muscle form the functional lacrimal drainage system.

PURPOSE: To clarify the relationship between the orbicularis oculi muscle, lacrimal canaliculus, and lacrimal sac and to propose a new theory of the lacrimal drainage system. DESIGN: Dissection study. PARTICIPANTS: Sixteen Asian cadavers (29 upper eyelids). METHODS: Gross dissections of the orbicularis oculi muscle in the medial canthus of 10 Asian cadavers were performed, and the relationship between the orbicularis oculi muscle, lacrimal canaliculus, and lacrimal sac was examined. The upper eyelids of the remaining 6 cadavers were dissected grossly, and sections of the lacrimal sac, common lacrimal canaliculus, and upper canaliculus were examined microscopically. The relationship between the lacrimal passage and its surrounding tissues also was examined. RESULTS: The lacrimal canaliculus and sac both were divided into 2 distinct compartments in relation to the Horner's muscle. The upper half of the lacrimal sac was related to the Horner's muscle through the posterior branch of the medial canthal tendon and connective tissue, and the lower half was related to the capsulopalpebral fascia and orbital fat. The lateral part of the lacrimal canaliculus was covered with the Horner's muscle. The medial part of the lacrimal canaliculus, namely the common lacrimal canaliculus, was not covered by the Horner's muscle, but was covered by the preseptal and orbital parts of the orbicularis oculi muscle on the anterior surface. CONCLUSIONS: The lacrimal canaliculus and sac were divided into 2 distinct compartments by the Horner's muscle, and it is possible that both contribute to the lacrimal drainage system.

Aged↗
PubMed2005

Expression of a chondroitin sulfate proteoglycan, versican (PG-M), during development of rat cornea.

PURPOSE: To understand the role of chondroitin sulfate proteoglycans during the development of rat cornea, expression of chondroitin sulfate and versican (PG-M) was studied. METHODS: Chondroitin sulfate and keratan sulfate in rat cornea were analyzed by immunohistochemical techniques. Reverse transcription polymerase chain reaction (RT-PCR) for chondroitin sulfate proteoglycans was performed. Versican expression was studied by RT-PCR, immunohistochemical, and dot blot analyses. Expression of hyaluronan was evaluated histochemically using biotinylated hyaluronan binding protein. RESULTS: Chondroitin sulfate was abundant in rat cornea at postnatal day 1 (P1) and became undetectable at P14. RT-PCR analysis showed that versican mRNA was highly expressed at P1 but was little expressed at P42. mRNAs for other chondroitin sulfate proteoglycans including biglycan, aggrecan, and decorin did not change much between P1 and P42. Expression for all versican splicing isoforms (V0-V3) was detectable from P1 through P14 but was undetectable after P21. mRNA for V0, the largest form with many chondroitin sulfate binding sites, decreased markedly in early stages from P1 to P14, whereas mRNA for V3, the shortest form with no chondroitin sulfate binding site, increased. mRNAs for middle-sized forms, V1 and V2, remained little changed during these periods. Immunohistochemical and dot blot analyses showed that versican is highly expressed at early stages of development and little expressed at adulthood. Similarly, hyaluronan, a versican-bound glycosaminoglycan, was highly expressed at early stages and little expressed at adulthood. CONCLUSIONS: Versican and hyaluronan, which can form a large molecular complex, may play an important role in the early phase of corneal development.

Aging↗
PubMed2005

Chemical toxicity of indocyanine green damages retinal pigment epithelium.

PURPOSE: To investigate the chemical toxicity of indocyanine green (ICG). METHODS: Surface active and precipitating effects of ICG were quantitatively analyzed by determining bovine serum albumin dissolved or precipitated in the presence or absence of salt solutions. The effects of precipitation on serum and cytotoxicity were evaluated by measuring the viability of retinal pigment epithelium (RPE) in vitro. RESULTS: ICG functioned as a surfactant without salts, but with nearly physiological concentrations of balanced salts, it functioned as a unique precipitating factor. This rendered the soluble molecules in serum that are indispensable in the culture of RPE cells insoluble during a 12-hour exposure, resulting in poor cell survival in vitro. Cytotoxicity in serum-free medium was also shown during brief exposures. CONCLUSIONS: Commonly used dosages of ICG directly applied into the vitreous cavity, which not only contact the retina but also invade the space between the retina and RPE through a macular hole, may be sufficient to induce retinal disorders after the damaging chemical property of ICG has disturbed the microenvironment.

Acetates↗
PubMed2005

Fibrous connective tissue between Müller's muscle and the palpebral conjunctiva as a reinforcement structure and a natural barrier for the upper eyelid.

This study was performed to illustrate and discuss the significance of fibrous connective tissue between the Müller's muscle and the palpebral conjunctiva. Nine upper eyelids of 6 Oriental cadavers were microscopically examined; ages at death ranged from 72 to 91 years. Tissue of the posterior lamella of the upper eyelid was removed without the orbital septum and orbital fat. Removed eyelids were incised perpendicularly at the center of the eyelid. After pretreatment, sliced sections were stained with Hematoxylin and Eosin and examined microscopically. A thick fibrous connective tissue was found to exist between the Müller's muscle and the palpebral conjunctiva. The connective tissue continued proximally to the intermuscular transverse ligament and was distally attached to the posterior site of the upper aspect of the tarsus. All cases showed infiltration of lymphocytes from the conjunctiva; however, these were completely blocked by the fibrous connective tissue and never reached Müller's muscle. This connective tissue supports eyelid traction and is a natural barrier for the Muller's muscle against conjunctivitis.

Aged↗
PubMed2005

The levator aponeurosis consists of two layers that include smooth muscle.

PURPOSE: To investigate the two-fold structure of the levator aponeurosis, which is partly composed of independent smooth muscles. MATERIALS AND METHODS: Fifteen upper eyelids of 12 Asian postmortems, with age at death ranging from 72 to 91 years, were examined. In 9 eyelids, posterior lamella tissue of the upper eyelid was removed to observe the stratified structures of the levator aponeurosis. Six full-thickness eyelids were used to observe the attachment site or the continuity between the levator aponeurosis and its surrounding tissues. The eyelids were incised perpendicularly in the center of the eyelid; samples were stained with Masson trichrome and antismooth muscle actin antibody and examined microscopically. RESULTS: Masson trichrome staining demonstrated the two-layered nature of the levator aponeurosis. The anterior layer was characterized by thick, robust fibrous tissue, and the posterior by thinner fibrous tissue. Although both layers contained muscle structures, the posterior layer contained more than the anterior. Immunostaining with antismooth muscle actin antibody revealed that the muscle in both layers was smooth muscle. The anterior layer continued to the orbital septum and the submuscular fibroadipose tissue; the posterior layers, located in front of Müller muscle and its tendon, attached to the anterior inferior one-third of the tarsus. Part of the anterior layer went through the orbicularis oculi muscle and attached to the subcuticular tissue. CONCLUSIONS: The levator aponeurosis is stratified, consisting of two layers than contain smooth muscle components in their proximal portions. It pulls mainly the preaponeurotic fat and anterior eyelid lamella. This partially regulates the tension of the eyelid and contributes to the ordered movement of the upper eyelid.

Actins↗
PubMed2005

The levator aponeurosis consists of two layers that include smooth muscle.

PURPOSE: To investigate the two-fold structure of the levator aponeurosis, which is partly composed of independent smooth muscles. MATERIALS AND METHODS: Fifteen upper eyelids of 12 Asian postmortems, with age at death ranging from 72 to 91 years, were examined. In 9 eyelids, posterior lamella tissue of the upper eyelid was removed to observe the stratified structures of the levator aponeurosis. Six full-thickness eyelids were used to observe the attachment site or the continuity between the levator aponeurosis and its surrounding tissues. The eyelids were incised perpendicularly in the center of the eyelid; samples were stained with Masson trichrome and antismooth muscle actin antibody and examined microscopically. RESULTS: Masson trichrome staining demonstrated the two-layered nature of the levator aponeurosis. The anterior layer was characterized by thick, robust fibrous tissue, and the posterior by thinner fibrous tissue. Although both layers contained muscle structures, the posterior layer contained more than the anterior. Immunostaining with antismooth muscle actin antibody revealed that the muscle in both layers was smooth muscle. The anterior layer continued to the orbital septum and the submuscular fibroadipose tissue; the posterior layers, located in front of Müller muscle and its tendon, attached to the anterior inferior one-third of the tarsus. Part of the anterior layer went through the orbicularis oculi muscle and attached to the subcuticular tissue. CONCLUSIONS: The levator aponeurosis is stratified, consisting of two layers than contain smooth muscle components in their proximal portions. It pulls mainly the preaponeurotic fat and anterior eyelid lamella. This partially regulates the tension of the eyelid and contributes to the ordered movement of the upper eyelid.

Actins↗
PubMed2004

Chondroitin sulfate chains on syndecan-1 and syndecan-4 from normal murine mammary gland epithelial cells are structurally and functionally distinct and cooperate with heparan sulfate chains to bind growth factors. A novel function to control binding of midkine, pleiotrophin, and basic fibroblast growth factor.

A comparative analysis was carried out of heparan sulfate (HS) and chondroitin sulfate (CS) chains of the ectodomains of hybrid type transmembrane proteoglycans, syndecan-1 and -4, synthesized simultaneously by normal murine mammary gland epithelial cells. Although the HS chains were structurally indistinguishable, intriguingly the CS chains were structurally and functionally distinct, probably reflecting the differential regulation of sulfotransferases involved in the synthesis of HS and CS. The CS chains of the two syndecans comprised nonsulfated, 4-O-, 6-O-, and 4,6-O-disulfated N-acetylgalactosamine-containing disaccharide units and were significantly different, with a higher degree of sulfation for syndecan-4. Functional analysis using a BIAcore system showed that basic fibroblast growth factor (bFGF) specifically bound only to the HS chains of both syndecans, whereas midkine (MK) and pleiotrophin (PTN) bound not only to the HS but also to the CS chains. Stronger binding of MK and PTN to the CS chains of syndecan-4 than those of syndecan-1 was revealed, supporting the structural and functional differences. Intriguingly, removal of the CS chains decreased the association and dissociation rate constants of MK, PTN, and bFGF for both syndecans, suggesting the simultaneous binding of these growth factors to both types of chains, producing a ternary complex that transfers the growth factors to the corresponding cell surface receptors more efficiently compared with the HS chains alone. The involvement of the core protein was also shown in the binding of MK and PTN to syndecan-1, suggesting the possibility of cooperation with the HS and/or CS chains in the binding of these growth factors and their delivery to the cell surface receptors.

Animals↗