M6a acts as a nerve growth factor-gated Ca(2+) channel in neuronal differentiation.

To elucidate the function of M6a, which is a neuron-specific membrane glycoprotein of the brain and possesses putative phosphorylation sites for protein kinase C (PKC), we established rat M6a cDNA expression vector-transfected PC12 cells. These transfectants exhibited high susceptibilities to nerve growth factor (NGF) for neuronal differentiation. Interestingly, we found that Ca(2+) influx in these transfectants was significantly augmented by the treatment of NGF, but not epidermal growth factor (EGF), which stimulates PC12 cell growth. NGF-dependent augmentation of Ca(2+) influx was detected within 3h and severely inhibited by EGTA- and PKC-specific inhibitors. Anti-M6 antibody suppressed both NGF-triggered Ca(2+) influx and neuronal differentiation. These results support the idea that M6a implicates in neuronal differentiation as a novel Ca(2+) channel gated selectively by phosphorylation with PKC in the downstream of NGF signaling pathway.

[Volume measurement of the horizontal extraocular muscles using magnetic resonance imaging].

The volume of the horizontal extraocular muscles of 11 normal adults and three patients with ophthalmoplegia was measured using magnetic resonance imaging (MRI). The MRI examinations were carried out with a Signa Advantage, 1.5 tesla superconductive magnetic system manufactured by General Electric. This method employs the spin echo technique with a 3.0 mm gapless slice, a 350 ms. repetition time, and a 17.0 ms. echo time. The MRI films were projected and magnified on Kent paper using an overhead projector. Then the shapes of the horizontal extraocular muscles were traced. The volume of the muscles was measured as the total weight of Kent papers which were cut out from muscle shapes in all the slices. The average volume of the normal medial and lateral rectus muscles was 690 +/- 87 mm3 and 734 +/- 77 mm3, respectively. Two cases with peripheral nerve palsy showed typical atrophy of the paretic muscles. A case with orbital myositis showed typical hypertrophy of the inflamed muscles. This measurement may prove useful in the analysis and evaluation of extraocular muscles, especially in ophthalmoplegia.

[Eye movement: experimental and clinical study using cine mode MRI].

As a special lecture at the 96th Annual Congress of the Japanese Ophthalmological Society in 1992, we presented experimental and clinical studies on eye movement using magnetic resonance imaging (MRI). MRI is more valuable than X-ray CT in defining external muscle anatomy in the orbit in a variety of pathological changes, and is free from the danger of radiation. Cine mode MRI, which was originally developed to observe cardiovascular function, was utilized experimentally for observation of eye movement. We invented two methods to produce a series of photographs. In the first method, "the moving eye method", the subjects were asked to perform 256 or 512 vertical and horizontal eye movements in synchronization with a sound trigger. In the second, "the fixed eye method", the subjects were asked to gaze at individual points in a 5 to 7 point sequence as indicated by the investigator. In both methods MRI data was generated and the resulting series of photographs were observed in cine mode on a television monitor. Displaying the MRI generated photographs in cine mode enables direct observation of the movement of the eye, optic nerve and extraocular muscles within the orbit. The moving eye method was more accurate in its portrayal of the actual movement of the eye, but the large number of eye movements, at least 256 movements, required about 5 minutes, and caused physical and mental fatigue for the subjects. The fixed eye method did not show actual movement of the eye, but was less fatiguing than the former method, and avoided several of its problems. A large number of ophthalmoplegia cases such as abducens palsy, oculomotor palsy, fracture of the orbital wall, foreign bodies in the orbit, Duane's syndrome, endocrine myopathy, esotropia, exotropia, etc., were examined using the fixed eye method of cine mode MRI. Using this technique, anatomical changes, such as atrophy or hypertrophy and the functional state demonstrated by the contraction and relaxation of the extraocular muscles could be investigated. Transposition of the extraocular muscles, an effective treatment for paralytic squint, was reexamined and a new surgical procedure was developed for abducens palsy. The measurement of the length, thickness and weight of the extraocular muscles from the MRI-generated photographs allowed for more accurate analysis. The three dimensional reconstructive method of MRI is very valuable for diagnosis in the orbit and is expected to contribute to future progress.

Prostaglandins involved in contractions by angiotensin II and bradykinin of isolated dog sphincter pupillae.

1. The dog isolated sphincter pupillae contracted in response to acetylcholine, angiotensin II (AII), bradykinin, prostaglandins F2 alpha, D2, E2 and I2, and thionate thromboxane A2 (sTXA2) in a concentration-dependent manner. 2. AII-induced contractions were suppressed by treatment with saralasin, indomethacin, aspirin and diphloretin phosphate (DPP), a prostaglandin receptor antagonist. Contractions induced by bradykinin were also attenuated by indomethacin, aspirin and DPP. The amount of prostaglandin F2 alpha (PGF2 alpha) in the bathing media was increased approximately 41% following stimulation of the preparations by bradykinin. 3. The potency of contractile responses was in the order of PGF2 alpha greater than PGD2 = sTXA2 greater than PGE2 greater than arachidonic acid greater than PGI2. Contractions induced by PGF2 alpha were not significantly affected by treatment with indomethacin and ONO3708, an antagonist of the vasoconstrictor effect of prostaglandins, but appreciably attenuated by DPP. Arachidonic acid-induced contractions were inhibited by indomethacin. 4. Contractions of dog iris sphincter muscle in response to AII and bradykinin may be mediated via substances synthesized by cyclo-oxygenase from arachidonic acid. The distribution and nature of the prostaglandin receptors appear to differ markedly in iris sphincter and vascular smooth muscles.

Retinal correspondence in typical accommodative esotropia.

Typical (refractive) accommodative esotropia is a form of acquired esotropia caused primarily by hypermetropia; correction of the hypermetropic refractive error with convex lenses generally leads to rehabilitation. A significant number of cases clinically diagnosed as typical accommodative esotropia do not, however, respond satisfactorily to this form of treatment, suggesting the presence of nonrefractive etiological factors. Fifty cases diagnosed by conventional methods as typical accommodative esotropia were examined with the fundus haploscope; abnormal or subnormal retinal correspondence was discovered in nearly 50% of the total. Congenital elements are thought to play a contributory role in these cases.

Anatomical evidence for the overlapped distribution of ipsilaterally and contralaterally projecting ganglion cells to the lateral geniculate nucleus in the cat retina: a morphologic study with fluorescent tracers.

The question of the nasotemporal overlap of ganglion cells in the central retina, which project to the ipsilateral and contralateral lateral geniculate nucleus, was reexamined in the cat by means of a retrograde fluorescent double-labeling technique. The horizontal separation between the ipsilateral and contralateral decussation lines, which corresponded to the width of the median strip of overlap, was approximately 0.2 mm. This is the first direct confirmation of the extent of such overlap in the cat retinal ganglion cells, which had been previously studied by indirect methods.

Complement levels in human tears.

The single radial immunodiffusion technique was modified to determine tear complement component C3 with small sample volume. The C3 levels in the tears from 18 normal subjects and 42 patients with ocular diseases were determined using this method. In the normal subjects, the mean level of tear C3 was 5.12 mg per 100 ml. The physiological level of tear C3 was estimated to be less than 10 mg per 100 ml from the results in normal subjects and patients with noninflammatory ocular diseases. The cases of severe inflammatory diseases such as antiviral keratoconjunctivitis, herpetic keratitis and acute catarrhal conjunctivitis showed a high level of C3 in the tears. The C3 level was relatively low in the cases of mild inflammatory diseases such as allergic conjunctivitis. These results indicated that protein concentration of C3 in the tear was proportional to the severity of inflammation of the anterior ocular segment.