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At least 613 records · Page 34Linked to original sources
PubMed2002

Eye defects in receptor protein-tyrosine phosphatase alpha knock-down zebrafish.

Receptor protein-tyrosine phosphatase alpha (RPTP alpha) is highly expressed in the developing retina of different species, but little is known about its function there. Here, we report that injection of antisense morpholinos in zebrafish embryos reduced RPTP alpha expression to almost nondetectable levels up to 3 days postfertilization (dpf). RPTP alpha was detectable again from 4 dpf onward. RPTP alpha knock-down resulted in smaller eyes. Examination of sections of the retina at different developmental stages demonstrated that already at 28 hours postfertilization (hpf) fewer cells were present in the retina of RPTP alpha-morpholino-injected embryos. At 3 dpf, the layered organization of the retina was absent. In addition, the morphology and labeling with an axon specific antibody, acetylated tubulin, demonstrated that most cells appeared to be undifferentiated. Strikingly, at 5 dpf the lamination of the retina was partially restored, concomitant with re-expression of RPTP alpha protein. Although cells in the retina were now differentiated, the layering of the retina remained disrupted and significant gaps were observed in the amacrine cell layer. Therefore, knock-down of RPTP alpha protein provides evidence that RPTP alpha is essential for normal retinal development.

Animals↗
PubMed1995

pipsqueak encodes a novel nuclear protein required downstream of seven-up for the development of photoreceptors R3 and R4.

Photoreceptor induction in the Drosophila eye is mediated by activation of the Ras signal transduction cascade. Although this process is well understood, little is known about how the diversity of photoreceptor subtypes is generated. The pipsqueak (psq) gene is expressed at high levels in the R3/R4 precursors during eye development and this expression depends on seven-up (svp) gene function. Moreover, strong psq alleles are dominant suppressors of a svp-induced cone cell transformation phenotype. Although the gene was previously identified and described as a member of the maternal posterior group of genes, the strong semilethal alleles isolated here demonstrate a specific requirement for psq function downstream of svp for the development of photoreceptors R3/R4. The gene has three independent 5' ends and codes for several nuclear protein isoforms, some containing the POZ domain which has been implicated in protein-protein interactions. Interestingly, all viable alleles with a maternal posterior group phenotype cluster around one specific 5' exon, while all semilethal alleles have lesions which map to a different alternative 5' exon.

Alleles↗
PubMed2001

Open interconnected model of basal ganglia-thalamocortical circuitry and its relevance to the clinical syndrome of Huntington's disease.

The early stages of Huntington's disease (HD) present with motor, cognitive, and emotional symptoms. Correspondingly, current models implicate dysfunction of the motor, associative, and limbic basal ganglia-thalamocortical circuits. Available data, however, indicate that in the early stages of the disease, striatal damage is mainly restricted to the associative striatum. Based on an open interconnected model of basal ganglia-thalamocortical organization, we provide a detailed account of the mechanisms by which associative striatal pathology may lead to the complex pattern of motor, cognitive, and emotional symptoms of early HD. According to this account, the degeneration of a direct and several indirect pathways arising from the associative striatum leads to impaired functioning of: (1) the motor circuit, resulting in chorea and bradykinesia, (2) the associative circuit, resulting in abnormal eye movements, "frontal-like" cognitive deficits and "cognitive disinhibition," and (3) the limbic circuit, resulting in affective and psychiatric symptoms. When relevant, this analysis is aided by comparing the symptomatology of HD patients to that of patients with mild to moderate Parkinson's disease, since in the latter there is similar dysfunction of direct pathways but opposite dysfunction of indirect pathways. Finally, we suggest a potential novel treatment of HD and provide supportive evidence from a rat model of the disease.

Animals↗
PubMed1999

Dorsal-ventral patterning defects in the eye of BF-1-deficient mice associated with a restricted loss of shh expression.

Brain factor 1 (BF-1) is a winged-helix transcription factor with restricted expression in the anterior optic vesicle and in the telencephalic neuroepithelium of the neural tube. We have previously found that targeted disruption of the BF-1 gene results in hypoplasia of the cerebral hemispheres, which is more severe in structures derived from the ventral telencephalon. Here we show that the loss of BF-1 leads to multiple developmental anomalies of the eyes. The most ventral structure arising from the optic vesicle, the optic stalk, is missing and is replaced by an expanded retina. Ventral closure of the optic cup and choroid fissure does not occur. These dorsal-ventral patterning defects are not limited to the BF-1-expressing (anterior) cells, but also involve the cells of the posterior optic vesicle. Sonic hedgehog (shh) expression within the ventral telencephalic neuroepithelium is specifically lost in the BF-1(-/-) mutant. Taken together, these findings suggest that shh produced at this site plays a role in patterning the developing eye. This localized deficit in shh expression may also contribute to the prominence of the ventral defects in the telencephalon of the BF-1(-/-) mutant.

Animals↗
PubMed2002

The homeobox gene Six3 is a potential regulator of anterior segment formation in the chick eye.

The anterior segment of the vertebrate eye consists of highly organized and specialized ocular tissues critical for normal vision. The periocular mesenchyme, originating from the neural crest, contributes extensively to the anterior segment. During chick eye morphogenesis, the homeobox gene Six3 is expressed in a subset of periocular mesenchymal cells and in differentiating anterior segment tissues. Retrovirus-mediated misexpression of Six3 causes eye anterior segment malformation, including corneal protrusion and opacification, ciliary body and iris hypoplasia, and trabecular meshwork dysgenesis. Histological and molecular marker analyses demonstrate that Six3 misexpression disrupts the integrity of the corneal endothelium and the expression of extracellular matrix components critical for corneal transparency. Six3 misexpression also leads to a reduction of the periocular mesenchymal cell population expressing Lmx1b, Pitx2, and Pax6, transcription factors critical for eye anterior segment morphogenesis. Moreover, elevated levels of Six3 attenuate proliferation of periocular mesenchymal cells in vitro and differentiating anterior segment tissues in vivo. These results suggest that, in addition to its function in eye primordium determination, Six3 plays a role in regulating the development of the vertebrate eye anterior segment.

Animals↗
PubMed1993

Changes in the retinal ganglion cell layer and optic nerve of rats exposed neonatally to cocaine.

The effects of neonatal exposure to cocaine upon the structure of the visual system are poorly understood despite the evidence of eye abnormalities in infants exposed in utero to cocaine. We previously demonstrated alterations in the optic nerve of rats exposed neonatally to cocaine, although no changes were detected in the number of its axons. This study was undertaken to investigate the retinal ganglion cell layer and the size distribution of the optic axons, in an attempt to assess further changes in the visual pathways. Groups of rats (Wistar strain) were given subcutaneous injections of cocaine hydrochloride (15 mg kg-1 body weight day-1) divided into two daily doses, from the day following birth until postnatal day 30 Controls were given subcutaneous saline throughout the same experimental period. Per group, five animals from three different litters were evaluated morphometrically. Following perfusion with aldehydes, samples from the median ventral and dorsal parts of the retina and the optic nerves were processed for electron microscopy. Morphometric techniques at light and electron microscopic levels allowed us to determine the following. (a) In the optic nerve: (1) frequency size-distribution of myelinated nerve fibres; and (2) number of myelin sheaths per fibre. (b) In the retina: (1) thickness of the layers; (2) frequency size-distribution of ganglion layer neurons; (3) mean cell nuclear size; and (4) packing density of ganglion cell layer neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

A second gene for cerulean cataracts maps to the beta crystallin region on chromosome 22.

Congenital cataracts are one of the most common major eye abnormalities and often lead to blindness in infants. At least a third of all cases are familial. Within this group, highly penetrant, autosomal dominant forms of congenital cataracts (ADCC) are most common. ADCC is a genetically heterogeneous group of disorders, in which at least eight different loci have been identified for nine clinically distinct forms. Among these, Armitage et al. (Nature Genet. 9: 37-40, 1995) mapped a gene for cerulean blue cataracts to chromosome 17q24. Bodker et al. (Am. J. Med. Genet. 37: 54-59, 1990) described a large family with cerulean blue cataracts, in which the affected daughter of affected first cousins was presumed to be homozygous for the purported gene. We report linkage in this family to the region on chromosome 22q that includes two beta crystallin genes (CRYBB2, CRYBB3) and one pseudogene (CRYBB2P1). The affected female in question is homozygous at all markers.

Cataract↗
PubMed1991

Border disease of sheep--aspects for diagnostic and epidemiologic consideration.

Border Disease (BD) is a condition of newborn sheep that results from congenital infection by a non-cytopathic pestivirus, occurring during the first half of gestation. The variations in expression of the virus directly relate to the age of the fetus at the time of infection. There are four distinct disease syndromes: (1) early embryonic death, (2) abortion and stillbirth, (3) birth of lambs with malformations, and (4) birth of small, weak lambs, lacking characteristic clinical signs, but bearing features of immunosuppression. In the newborn, the BD virus may be recovered from all tissues and teratogenic lesions are found in the endocrine, nervous, skeletal, integumentary and immune systems. These effects of virus infection are manifest in the clinical signs characteristic of the disease, such as tremors, ataxia, hairy birthcoat, low birth weight, facial bone malformations, short-boxy stature, and eye abnormalities. The consequences of the BD compromised immune system is an increased susceptibility to infection, a failure to produce specific antibody to BD virus, and an inability to clear the virus; features characteristic of the immuno-tolerant state. The lifelong shedding and persistence of virus is of epidemiologic importance. The persistently infected BD ewe remains a source of infection for the flock both through horizontal transmission (virus shedding) and congenital transmission (a persistently infected ewe will always bear a BD lamb). Detection of persistently infected individuals within a flock is difficult: clinical signs abate with time and most frequently no antibody to BD is produced.

Animals↗
PubMed1981

Genetics of microphthalmos.

This is a survey of the genetics of microphthalmos and the heritable syndromes in which microphthalmos occurs. New syndromes are delineated such as the autosomal dominant anophthalmos-microphthalmos-coloboma syndrome, the autosomal dominant microphthalmos, microcephaly, lacunar retinal atrophy syndrome, the autosomal recessive anophthalmos-microphthalmos-coloboma syndrome, the autosomal recessive syndrome with anophthalmos or microphthalmos and genital malformations, and the autosomal recessive syndrome with microphthalmos, microcephaly and retinal falciform folds. Nanophthalmos is described as a poorly defined phenotype and rejected as a genotype. Several other genetic entities with microphthalmos are reviewed and recent descriptions are surveyed.

Adolescent↗
PubMed1977

Duane's uniocular micro-tremor or superior oblique myokymia of Hoyt and Keane.

Two cases of intermittent unilateral motor disturbance of the superior oblique muslce are presented and compared with cases reported previously by Duane, Clark and Hoyt & Keane and briefly mentioned by Duke-Elder in his System of Ophthalmology. The first case is a girl with longstanding history of oscillopsia, vertical and tortional oscillatory diplopia. No abnormal eye movements were observed but objective evidence of the disturbance was obtained in the form of electromyography during which relationship of the superior oblique was established. In contrast, the second case experienced episodes of static vertical and tortional diplopia similar to the case reported to by Clark. Again the relationship in the condition was unilateral involving the superior oblique muscle. There was no corroboratory evidence to support the diagnosis of an intermittent superior oblique tendon sheath syndrome. Hoyt & Keane's theory based on their electromyography findings that the lesion is in the lower motor neuron unit is reported and the significance of the oscillopsia as corroboratory evidence is discussed.

Adult↗
PubMed1982

Vestibulo-ocular reflex and optokinetic nystagmus in adult cats reared in stroboscopic illumination.

Cats reared in stroboscopic illumination (strobe reared cats) have been found to have abnormal eye movements. Visual and vestibular evoked compensatory eye movements were inefficient. Vestibulo-ocular reflex in the dark had a maximum gain of 0.6 (1.0 in normal animals). Optokinetic nystagmus had a mean gain which approached unity only at stimulus velocities around 7 degrees/S (up to 30 degrees/S in normal animals). The asymmetry of the optokinetic nystagmus resulting from monocular stimulation was more pronounced in strobe reared cat than in normal animals. Interaction between vestibulo-ocular reflex and optokinetic nystagmus to give adequate compensatory eye movements was absent in strobe reared cats: visual suppression of vestibulo-ocular reflex was absent when the animal was rotated in an illuminated environment which remained stationary with respect to the head. Optokinetic nystagmus failed to improve the gain of the vestibulo-ocular reflex when the animal was rotated in a normally lit environment. The deprived animals showed no signs of recovery after 5 months exposure to normal lighting.

Animals↗
PubMed1986

A case of progressive familial encephalopathy in infancy with calcification of the basal ganglia and chronic cerebrospinal fluid lymphocytosis.

The authors report the ninth case of progressive familial encephalopathy in infancy, with calcification of the basal ganglia and chronic cerebrospinal fluid (CSF) lymphocytosis, as recently described by Aicardi and Goutieres. The encephalopathy appears during the first year of life with bilateral spasticity, continuing microcephaly, abnormal eye movements, and a rapid course toward a behavioral vegetative state. In every case, there is a mild lymphocytosis in the CSF and brain atrophy with calcification of the lenticular nuclei. No evidence of an infectious disease has been discovered. This syndrome constitutes a distinct type of leukodystrophy, transmitted as an autosomal recessive trait. Our case is a reminder that the presence of CSF lymphocytosis in infants, with encephalopathy and calcification of the lenticular nuclei, may be due to genetic degenerative encephalopathy.

Atrophy↗
PubMed1975

An electro-oculographic study of ocular bobbing and intermittent vertical oscillations occuring in the same patient.

A surviving patient with two rare types of abnormal eye movements, typical ocular bobbing and subsequently developed intermittent vertical oscillations of the eyes, is described, and a follow-up series of electro-oculographic recordings of these eye movements is analyzed. It is suggested that these two types of vertical eye movements might have a common pathophysiological background and the activity of remaining functional oculomotor pathways may play an important role in their occurrence.

Cerebrovascular Disorders↗