Ultrastructural changes and immunocytochemical localization of microtubule-associated protein 1 in guinea pig optic nerves after acute increase in intraocular pressure.
OBJECTIVE
To investigate ultrastructural changes and localization of microtubule-associated protein 1 (MAP 1) in optic nerves of guinea pigs in conditions of acute increase in intraocular pressure (IOP).


METHODS
Intraocular pressure was increased acutely in 40 guinea pig eyes, and 40 eyes were examined in 20 normal control animals. Analytic methods included quick-freezing and deep-etching (QF-DE) and conventional fixation. Microtubule-associated protein 1 immunocytochemistry was performed.


RESULTS
In conventional ultrathin sections, an alteration of the axoplasmic ultrastructure was seen only at the level of the lamina cribrosa sclerae. The number of microtubules was significantly decreased in the axoplasm that exhibited accumulations of membranous organelles. Cross-bridged filaments on microtubules were significantly reduced in number when determined by the QF-DE method. The immunostaining of tubulin or MAP 1 was less positive than in other samples with normal IOP, revealed by light microscopic immunocytochemistry. Immunoelectron microscopy demonstrated that MAP 1 was significantly decreased in the axoplasm that showed accumulations of membranous organelles.


CONCLUSIONS
The acute alteration of axoplasmic ultrastructures in some parts of the optic nerves at the level of the lamina cribrosa involves a decrease in the amount of MAP 1 and a decrease in the number of axonal cross-bridges on microtubules in a condition of acutely increased IOP, which could be related to microtubule instability and abnormal organelle transport in the axoplasm.
Ou
B
B
Department of Ophthalmology, Yamanashi Medical University, Tamaho, Japan.
Ohno
S
S
Tsukahara
S
S
D000208:Acute Disease; D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D019084:Fluorescent Antibody Technique, Indirect; D005613:Freeze Etching; D006168:Guinea Pigs; D007429:Intraocular Pressure; D016253:Microscopy, Immunoelectron; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009798:Ocular Hypertension / Q000150:complications*; D009900:Optic Nerve / Q000378:metabolism* / Q000648:ultrastructure*; D009901:Optic Nerve Diseases / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D016707:Tissue Fixation
D008869:Microtubule-Associated Proteins