Biomedical subjects

A Majima

Publications and source records attributed to A Majima.

At least 19 recordsLinked to original sources

PubMed1996

Histology of fetal eyes with oculocutaneous albinism.

The diagnosis of tyrosinase-negative oculocutaneous albinism (OCA) was made in a 19-week-old fetus by skin biopsy. Because the parents had an 11-year-old son with tyrosinase-negative OCA, they requested that the fetus be aborted at the 20th week of gestation. A histological analysis of the eyes was performed. Throughout the retina, the ganglion cell layer was separated from the inner neuroblastic layer by the inner plexiform layer. However, the number of ganglion cells was decreased and the nerve fiber layer was immature. Bipolar and horizontal cells had begun to segregate into the inner nuclear layer. Rods and cones were identifiable in the posterior, but not peripheral, retina. Cones were more numerous in the center of the retina, and no rod-free area was identifiable. In addition, the ciliary body (epithelial folds, blood vessels in the mesodermal connective tissue core, and ciliary muscle) was less developed than in a normal fetus. Melanosomes in the retinal pigment epithelium only contained filaments without melanization and were therefore classified as stage I or II melanosomes. However, the ciliary epithelium also contained some stage III melanosomes with melanin adherent to the filaments.

Abortion, Therapeutic↗

PubMed1996

[Histochemical studies on two cases of Peters' anomaly].

We examined glycosaminoglycan molecular species in the corneal stroma and the sclera histochemically in two cases of Peters' anomaly. Paraffin-embedded sections were stained with either hematoxylin-eosin or sensitized high iron diamine combined with enzyme digestion and then examined with a light microscope. In the center of the cornea, the histological specimens revealed defects of the corneal endothelium and Descemet's membrane, together with a local defect of the corneal stroma. Disorganized lens materials were detected in the corneal stroma. In the peripheral cornea, the undifferentiated iris adhered to the corneal posterior surface. Based upon the findings mentioned above, these two cases were diagnosed as having Peters' anomaly caused by faulty separation of the lens vesicle. The sclera showed normal structures in the specimen stained with hematoxylin-eosin. In both cases, the corneal stroma involved nearly equal amounts of chondroitin sulfate A/C and B. The sclera, on the other hand, contained a large amount of chondroitin sulfate A/C and a relatively small amount of chondroitin sulfate B. Keratan sulfate was never detected in either the cornea or the sclera. Thus, disorders of glycosaminoglycan molecular species were detected in the sclera as well as in the corneal stroma.

Corneal Opacity↗

PubMed1995

Histological and histochemical studies of the normal and faulty closure of the embryonic fissure in the eye of ICR mouse.

Histological and histochemical studies were carried out in Jcl:ICR mice to determine the changes in microscopic structures and glycosaminoglycan molecular species in the tissues involved in normal or faulty closure of the embryonic fissure. The purpose of this study was to elucidate the mechanism underlying the faulty closure of the embryonic fissure and to identify the key substances involved in normal and faulty closure. To obtain mice with an appropriate faulty closure of the embryonic fissure, ochratoxin A was employed as a teratogenic agent. Serial sections from tissues undergoing normal and faulty closure of the embryonic fissure were cut at a right angle to the fissure. As the staining procedures, a hematoxylin-eosin procedure and a sensitized high iron diamine method were used. A chemical modification (nitrous acid treatment) or an enzyme digestion procedure (chondroitinase ABC digestion procedure) was employed in combination with the sensitized high iron diamine method to identify the glycosaminoglycan molecular species in the tissues. The results obtained in the present study have substantiated the histophysiological importance of glycosaminoglycan molecular species during the course of histogenesis in the normal and the faulty closure of the embryonic fissure of developing murine eyes.

Animals↗

PubMed1995

Effects of local hypothermia on uveal blood flow and postoperative inflammation in vitrectomy.

Effects of local hypothermia on uveal blood flow and postoperative inflammation were evaluated in experimental vitrectomy in albino rabbits. Solutions used for intraocular perfusion were maintained at 9 degrees C, 22 degrees C or 37 degrees C. Following closed vitrectomy, the vitreous cavity was irrigated for 60 minutes. Temperatures at various sites and uveal blood flow were measured before and during the procedure. Aqueous protein concentrations were checked on postoperative days 1, 7 and 14. There was a larger decrease in temperature at the retina than at the choroid or the ciliary body. Blood flow at the ciliary body was reduced to 76.0% and that at the choroid to 77.0% of the preoperative level after 60 minutes of irrigation at 9 degrees C. The decrease was 91.0% and 88.3%, respectively, after 60 minutes of irrigation at 22 degrees C. Aqueous protein concentrations in the 9 degrees C and 22 degrees C groups were significantly lower than those in the 37 degrees C group on the first postoperative day in the eyes irrigated for 60 minutes. In the eyes irrigated for 30 minutes, however, no significant differences were seen. Local hypothermia during prolonged vitrectomy seems to decrease inflammation in the early postoperative stage.

Animals↗

PubMed1994

[Microphthalmos and its pathogenic classification].

Congenital microphthalmos is a common malformation encountered clinically. Microphthalmos in adults is here defined as eyes whose axial length is below 20.4 mm in males and 20.1 mm in females; in under 14-year-old children, it is eyes at least 3 square root of 2/3 below the mean for age-similar controls. Experimental animals with hereditary microphthalmos have been widely investigated, and many environmental factors given to pregnant animals frequently induce microphthalmos. In both clinical and experimental microphthalmos, there are conspicuous variations in size, and various kinds of ocular and systemic complications. Recently, fetal alcohol syndrome produced by alcohol intake during pregnancy has been reported. In this syndrome, microphthalmos is one of the important symptoms. Experimentally, microphthalmos also developed at a high incidence among mouse fetuses whose mothers were given ethanol during pregnancy. The present investigator established a preliminary etiological classification of microphthalmos in 1984. In this paper summing up newly obtained results, the relationship to neural crest cells and histochemical changes of glycosaminoglycan molecular species, the author presents a final pathogenic classification of microphthalmos, which consists of developmental disturbance of the optic vesicle, malformation of the optic cup, mesenchymal dysgenesis of the anterior ocular segment, maldevelopment of the lens, maldevelopment of the vitreous, faulty closure of the embryonic fissure and developmental disturbance of the wall of eyeball.

Adolescent↗

PubMed1994

[Hypothermic effects on uveal blood flow and postoperative inflammation in vitrectomy].

Hypothermic effects on uveal blood flow and postoperative inflammation were evaluated in experimental vitrectomy on albino rabbits. Solutions used for intraocular perfusion were maintained at 9 degrees C and 22 degrees C. Following the vitrectomy, the rabbits' intraocular spaces were irrigated for 60 minutes. The temperature at various sites and the uveal blood flow were measured before and during the procedure. Aqueous protein concentrations were checked on postoperative days 1, 7, and 14. Another solution maintained at 37 degrees C was used as a control. There was a larger decrease in temperature at the retina than there was at the choroid and the ciliary body. Blood flow at the ciliary body decreased to 76.0% and 77.0% at the choroid after 60 minutes of irrigation at 9 degrees C. The decrease at 22 degrees C were 91.0% and 88.3%, respectively. Aqueous protein concentrations at both 9 degrees C and 22 degrees C were significantly lower than at 37 degrees C on the first postoperative day in the eyes irrigated for 60 minutes. In the eyes irrigated for 30 minutes, however, no significant differences were seen. Hypothermia during a prolonged vitrectomy operation seems to decrease inflammation in early postoperative stages.

Animals↗

PubMed1994

[Multicenter prospective study of retinopathy of prematurity--II. Optimum timing of the first examination].

We reviewed the records of 360 cases of retinopathy of prematurity (ROP) in 12 institutions in Japan, and investigated the optimum timing of the first examination. On the basis of the onset of ROP and the timing of the first treatment, the first ophthalmological examination should be performed 3 weeks after birth or 29 weeks of postconceptional age at the latest. Regarding the visibility of the fundus, there was little hazy media after 29 weeks of postconceptional age. Under the basic policy that the severe progressive "plus" disease should be properly treated, we concluded that the first ophthalmological examination should be performed 3 weeks after birth at the latest. When the gestational age at birth is less than 26 weeks, funduscopy at the post conceptional age of 29 weeks is advisable.

Humans↗

PubMed1994

[Multicenter prospective study of retinopathy of prematurity--III. Timing of the coagulation therapy and the course of retinopathy of prematurity after coagulation].

We reviewed the records of 360 cases of retinopathy of prematurity (ROP) in 12 institutions in Japan, and investigated the timing of the coagulation therapy and the course of ROP after coagulation. The first coagulation therapy was performed at 9.6 weeks after birth and 35.9 weeks of postconceptional age on the average. The severity index in individual infants also showed that the disease became worse during the period from 32 to 36 weeks of postconceptional age. However, the fundus was clearly visible and there was no primary hazy media during this period. On the basis of the results of the timing of the first treatment, the visibility of the fundus, and the severity index in individual infants, we concluded that an ophthalmological examination with special care should be performed during the period from 32 to 36 weeks of postconceptional age.

Humans↗

PubMed1994

[Multicenter prospective study of retinopathy of prematurity--IV. Comparison with the data from University of Miami].

We investigated the records of 360 cases of retinopathy of prematurity (ROP) in 12 institutions in Japan (we treated the severe progressive "plus" disease by coagulation therapy), and compared them with data from University of Miami (Ophthalmology 94: 620-629, 1987), as representative of the natural course of ROP without coagulation therapy in those days. The timing of the first examination and the first positive diagnosis were later at University of Miami than in Japan. The time of maximal severity of the disease and occurrence of regression were also later the University of Miami than in Japan. In Japan, the first examination was performed at 29 weeks of postconceptional age or at 3 weeks after birth. At the University of Miami, the first examination was performed at 32 weeks of postconceptional age. If the severe progressive "plus" disease is to be properly treated by photo-coagulation or cryotherapy, it is essential to commence fundus examination earlier.

Florida↗

PubMed1993

[Experimental study on local cooling of the eyeball in ocular surgery (4). The local cooling effect on uveal blood circulation, intraocular pressure, and intravitreous pressure].

The effects of local cooling on the uveal blood circulation, intraocular pressure, and intravitreous pressure were evaluated. Saline solutions maintained at 10 degrees C and 35 degrees C were dripped on the rabbit ocular surface. After 5-minute dripping of 10 degrees C saline solution, the temperature decreased by 10.6 degrees C at the ciliary body, 7.7 degrees C at the choroid and 2.9 degrees C at the central region of the vitreous. Hydrogen clearance with electrolytically generated hydrogen gas was employed to measure the tissue blood flow, which fell to 82.9% of normo-thermal value at the ciliary body and 86.3% at the choroid. The intravitreous pressure dropped by 2.8 mmHg. After 30-minute dripping of 10 degrees C saline solution, the intraocular pressure dropped by 3.0 mmHg. We consider that the reduction of intraocular and intravitreous pressure during local cooling of the ocular surface is related to decrease in the uveal blood flow.

Animals↗

PubMed1989

[Studies on the mechanism of closure of the embryonic fissure (II). A morphological study of a transmission electron microscope].

The object of this study was to elucidate the mechanism of closure of the embryonic fissure with a transmission electron microscope in mouse embryos. Every specimen was cut at right angle to the embryonic fissure. Desmosome-like junctions and gap junctions were found between the cells of the inner wall and those of the outer wall of the optic cup. The lip facing the embryonic fissure of the optic cup was covered with the basal lamina. In the section immediately before closure, the cells composing the lip were flattened and had processes on their margins. In addition, collagen fibrils appeared in some portions on the basal lamina. The more posterior section of the same specimen showed immature cell junctions and fusing parts between the cells of both sides. It was deduced that the cells which composed the lip produced the collagen fibrils on the basal lamina when both lips drew closer together. After the adhesion of both basal laminae, immature cell junctions appeared transiently between the cells on either side. The fusion of these cells resulted from disappearance of the cell junctions.

Animals↗

PubMed1989

[The local cooling effect of anterior chamber irrigation on the blood-aqueous barrier].

Local cooling effect on the breakdown of the blood-aqueous barrier (BAB) following anterior chamber irrigation, including additional direct irritation of the iris, was evaluated fluorophotometrically. The rabbit anterior chamber was irrigated with simulated aqueous humor (S-MA 2) the temperature of which was maintained at 35 degrees C or 10 degrees C. The fluorophotometry was performed before and 4, 24, 48 hours and 7 days after irrigation for 30 or 60 minutes. The temperature changes in the anterior chamber, retrolental vitreous body and posterior retina were also measured with a thermocouple during irrigation at 10 degrees C. The temperature of the anterior chamber and the retrolental vitreous fell to 15.0 degrees C and 28.2 degrees C, respectively, within 30 minutes after starting irrigation, whereas the temperature drop in the posterior retina was only 2.0 degrees C after 60 min. At 4 hours after 60-minute irrigation, the breakdown of the BAB was greater than following 30-minute irrigation. There was no significant difference in the BAB breakdown between eyes irrigated at 10 degrees C and 35 degrees C.

Animals↗

PubMed1988