Search PubMed⌕ Search

Biomedical subjects

G M Breinin

Publications and source records attributed to G M Breinin.

At least 19 recordsLinked to original sources
PubMed1994

Aberrant innervational pattern in Duane's syndrome type II without globe retraction.

Using extraocular muscle electromyography we studied a patient with an adduction defect and face turn. The patient was found to have an anomalous firing pattern in the medial and lateral rectus muscles consistent with Duane's syndrome type II but globe retraction was absent. On the basis of this finding we concluded that mechanical factors appear to play a significant role in the globe retraction seen in Duane's syndrome.

Adolescent↗
PubMed1990

Diltiazem reduces the contractility of extraocular muscles in vitro and in vivo.

Diltiazem, a Ca-channel blocker that is used clinically for the treatment of hypertension and cardiac arrhythmias, reduces the contractility of extraocular muscles. Exposure of rabbit extraocular muscle to diltiazem in vitro reduces the sustained tension that is generated by the tonic, multiply innervated fibers, and decreases the baseline, or resting, tension of the muscle. When diltiazem is injected into a selected extraocular muscle in the rabbit in vivo, it causes a temporary weakening of the muscle, which is indicated by a deviation of eye position. These in vivo effects are of short duration, are easily reproducible, and vary with dosage. The results of this study raise the possibility that diltiazem may be used as an alternative to the surgical treatment of strabismus and other oculomotor dysfunctions including blepharospasm.

Adenosine Triphosphatases↗
PubMed1985

Cadmium reduces extraocular muscle contractility in vitro and in vivo.

Cadmium, a blocker of calcium channels in various excitable cells, reduces the contractility of extraocular muscles. When applied to rat extraocular muscles in vitro, it reduces the sustained or tonic tension generated by the tonic multiply innervated fibers of the global layer of the muscles. When injected in vivo into rabbit extraocular muscles, it produces a temporary paralysis of the muscles and a deviation of the eye position. These effects are presumed to involve a blockade of the calcium channels of the muscle fibers and of the neuromuscular junctions. It is proposed that, on the basis of these effects, a non-surgical treatment of strabismus could be developed.

Animals↗
PubMed1984

Intermitochondrial junctions in the extraocular muscle of the rat.

Intermitochondrial junctions with a spacing of 17-21 nm were observed in the superior rectus muscle of a rat. Periodic rounded densities are aligned midway between the apposed outer mitochondrial membranes at some of these junctions. Such densities have a diameter of about 8-10 nm and a center-to-center spacing of about 26-30 nm. These junctions occur in cases where one mitochondrial profile is enclosed within another or where two profiles are interlocked so that their combined overall form has a smoothly contoured profile. Intermitochondrial junctions seem not to have been previously described in muscle, but have been reported in other kinds of tissues. In agreement with those previous reports, the presently observed intermitochondrial junctions usually involve mitochondria that display atypical features indicative of tissue abnormality or stress. Such junctions were never observed in normal extraocular muscle.

Animals↗
PubMed1984

Distribution of mitochondrial and lipidic alterations in abnormal extraocular muscle of rat.

An abnormal superior rectus muscle of rat displayed marked differences in the respective distributions of mitochondrial alterations and excessive lipid accumulations, both of which are thought to be indicators of faulty oxidative metabolism. The mitochondrial alterations were widespread, extending over 46% of muscle length. In contrast, the excess lipids extended over but 11% of the muscle length and were virtually confined to the end-plate region. The end plates themselves were essentially normal. These data raise the possibility that the end-plate region may exhibit a locally greater deficit of oxidative metabolism, due to a possibly higher metabolic requirement needed to support the localized end-plate potential activity.

Animals↗
PubMed1984

Latter reorganization of membrane-glycogen complexes in rabbit extraocular muscle.

Characteristic modes of secondary reorganization were observed in membrane-glycogen complexes of rabbit extraocular muscle. These included (a) an irregular widening or narrowing of the intracisternal space, (b) a loss of the typical intracisternal flocculent densities, and (c) the acquisition of intercisternal flocculent densities. In irregularly widened cisternae, the membranes tended to remain closely adjacent to the intervening glycogen layer, thereby forming triads composed of a glycogen layer enclosed within the apposing membranes of adjacent cisternae. In the absence of glycogen particles from contiguous portions of several lamellae, the membranes became compacted to form myeloidlike figures. Degenerating complexes sometimes displayed distention of intercisternal spaces and layers of atypically small particles. The above modifications of membrane-glycogen complexes would be compatible with the notion that these structures are involved in the process of glycogen metabolism, as opposed to the previously suggested notion that these structures are transient vehicles for the accumulation of glycogen masses.

Animals↗
PubMed1983

Membrane-glycogen complexes in rabbit extraocular muscle.

Analysis of 432 electron micrographs of membrane-glycogen complexes revealed that: (1) Golgi apparatus is closely associated with 4.2% of the complexes, such associations occurring irrespective of the degree of glycogen loading in the complex. (2) Apparent ribosomes are seen in association with about 30% of the complexes, either attached to membranes or enclosed between cisternae. (3) In longitudinal sections of the muscle fibers, complexes may form columns which extend for as much as 40 microns along the fiber. (4) Various cytoplasmic organelles may become enclosed within a complex. (5) Some cisternae of a complex may assume the form of randomly oriented tubules, in contrast to the typical systematic array of flattened cisternae. (6) Some cisternae of a complex may become distended in a wide and uneven manner, in contrast to the typical narrow and even distension.

Animals↗
PubMed1982

Cytoplasmic inclusions in rabbit extraocular muscle.

Cytoplasmic inclusion bodies, similar to those previously described in abnormal and normal human extraocular muscle, were observed in the orbital surface layer of the superior rectus muscle in rabbit. These inclusion bodies are composed of a flocculent material of low density studded with granular foci of increased density. In sequential samples of serially reconstructed muscle fibers visualized by electron microscopy, cytoplasmic inclusion bodies were seen in 4.5% of 1187 samples through multiply innervated fibers that vary systematically in diameter along their length; inclusion bodies were also seen in 0.8% of 354 samples through multiple innervated fibers of constant diameter. Cytoplasmic inclusion bodies were not seen in 1838 samples through singly innervated fibers. These data suggest that such inclusion bodies may occur preferentially in multiply innervated fibers. The present findings are not compatible with previous suggestions that such cytoplasmic inclusion bodies may be indicative of a pathologic or aging process. These findings are consistent with previous suggestions that such inclusion bodies are to be considered as normal structures in extraocular muscle.

Animals↗
PubMed1981

Congenital adduction palsy and synergistic divergence.

Electromyography of the medial and lateral recti muscles in the right eye of a 7-year-old boy with congenital variable exotropia demonstrated cocontraction. This explained the observed simultaneous abduction on attempted levoversion. Abduction of the right eye increased intraocular pressure to 25 mm Hg from 15 mm Hg. This synergistic divergence should be considered a variant of Duane's syndrome, and, like Duane's syndrome, may occur as the result of anomalies of the peripheral oculomotor nerves or of central synaptic alterations, or of a combined central and peripheral mechanism.

Adolescent↗
PubMed1981

Pilocytic astrocytoma of the optic nerve with hemorrhage and extreme cystic degeneration.

Juvenile pilocytic astrocytoma of the optic nerve (glioma of childhood) usually grows slowly. Rapidly evolving proptosis is rare and reflects the accumulation of mucinous or hemorrhagic material within the tumor. Rapid proptosis is more common in those patients beyond the first two decades of life who have long-standing tumors. We studied a 26-year-old woman with rapid proptosis caused by a large blood-filled cyst in a pilocytic astrocytoma of the optic nerve. The cyst was surgically removed along with the intraorbital portion of the optic nerve.

Adult↗
PubMed1980

Variation of mitochondrial volume fraction along multiply innervated fibers in rabbit extraocular muscle.

Mitochondrial volume fraction was compared among three regions along the length of six multiply innervated fibers (MIFs) in the orbital surface layer of rabbit superior rectus. These MIFs are of about 5 micrometer diameter toward the middle of their length, and of about 15 micrometer diameter toward their proximal and distal ends. The region of highest volume fraction (26%) was located toward the proximal end of their segment of minimal diameter, in apparent association with endplate-like nerve junctions. The region of lowest volume fraction (8%) was located at their distal segment of maximal diameter. The region toward the distal end of their segment of minimal diameter displayed an intermediate volume fraction (15%). These mitochondrial volume fractions were further analyzed in terms of the relative contributions of the I-band, the A-band, and the subsarcolemmal mitochondrial clusters. Comparable changes in mitochondrial content occur in both the I-band and A-band; in the fibers' distal segment of maximal diameter, however, the mitochondrial volume fraction in the A-band (5%) is lower than in the I-band (11%). These modifications of mitochondrial content along the fibers' length occur irrespective of the contributions of the subsarcolemmal mitochondrial clusters.

Animals↗
PubMed1980

The distribution of membrane-glycogen complexes in the orbital surface layer of rabbit superior rectus.

The distribution of membrane--glycogen complexes along the length of individual muscle fibers was compared among three fiber populations in the orbital surface layer of rabbit superior rectus. These three populations were (a) 61 singly innervated fibers (SIFs), (b) 10 multiply innervated fibers of relatively constant 10 micrometer diameter (10 micrometer MIFs), and (c) 22 multiply innervated fibers which are of about 5 micrometer diameter toward the middle of their length and of about 15 micrometer diameter toward their proximal and distal segments (5--15 micrometer MIFs). The orbital surface layer was sampled by electron microscopy at 68 sequential locations. Membrane--glycogen complexes were not seen in any of the 1738 samples of the SIFs. In the MIFs, such complexes were observed in 14% of the 1541 samples. However, both the 10 micrometer MIFs and 5--15 micrometer MIFs displayed a preferential concentration of membrane--glycogen complexes toward their distal fiber portions, and such complexes were seen in about 50% of the MIF samples near the beginning of the muscle's distal third. In the distal portion of 5--15 micrometer MIFs, there was a direct relationship between their increasing fiber diameter and their increasing frequency of occurrence of membrane--glycogen complexes.

Animals↗
PubMed1977

Oculocutaneous albinism associated with Apert's syndrome.

Five of nine patients with Apert's syndrome (acrocephalosyndactyly) showed an associated hypopigmentation of hair, skin, and eyes. The hair color of these five patients ranged from light brown to blond, the skin was pale, and the irides hazel or blue. Iris transillumination and hypopigmentation of the fundus were present and associated with absent or diffuse foveal reflexes. Unlike most forms of classic oculocutaneous albinism, however, there was good visual acuity and no pendular nystagmus. The evidence indicated that the lack of pigmentation associated with the characteristic skeletal anomalies of Apert's syndrome resulted from a disturbance of independent, genetically related, processes occurring at a common point in gestation.

Acrocephalosyndactylia↗
PubMed1977

Structural alterations of extraocular muscle associated with Apert's syndrome.

An inferior oblique muscle from a patient with Apert's syndrome was examined by light and electron microscopy. Alterations in the muscle fibres, the myoneural junctions, and intramuscular nerves were observed. These data are not compatible with the widespread notion that motility disturbances in this syndrome are solely due to mechanical limitations.

Acrocephalosyndactylia↗
PubMed1977

Double-membrane arrays in type II fibers of mouse extraocular muscle.

Double-membrane arrays were observed in singly innervated type II fibers of the global region of mouse superior rectus. These arrays were selectively confined to the endplate region of such cells. Close associations and continuities between the cisternae of the arrays with those of the intermyofibrillar sarcoplasmic reticulum suggest derivation of the former from the latter. These proliferations of the cellular smooth membranes might be related to the specialized functional requirements of the innervation site.

Animals↗