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PubMed2004

Noninvasive optical imaging in the visual cortex in young infants.

During the developmental stage, the brain undergoes anatomic, functional, and metabolic changes necessary to support the complex adaptive behavior of a mature individual. Estimation of developmental changes occurring in different regions of the brain would provide a means of relating various behavioral phenomena to maturation-specific brain structures, thereby providing useful information on structure-function relationships in both normal and disease states. We used multichannel near-infrared spectroscopy (MNIRS), a new noninvasive imaging technique for revealing the course of neural activity in selected brain regions, to monitor the activities of the visual cortex as mirrored by hemodynamic responses in infants subjected to photostimulation during natural sleep. In the infants, oxyhemoglobin and total hemoglobin decreased and deoxyhemoglobin increased in the visual cortex with photostimulation. This pattern of responses was different from the response pattern in adults reported previously. The different patterns of responses to photostimulation in the visual cortices of infants and adults might reflect developmental and behavioral differences. It may reflect a different functional organization of the visual cortex in infants or ongoing retinal development. Our results demonstrated that regional hemodynamic change could be detected in a small area around the visual cortex. MNIRS offers considerable potential for research and noninvasive clinical applications.

Adult↗
PubMed1995

Germline mutations in the von Hippel-Lindau disease tumor suppressor gene: correlations with phenotype.

von Hippel-Lindau disease (VHL) is an inherited neoplastic disease characterized by a predisposition to develop retinal angiomas, central nervous system hemangioblastomas, renal cell carcinomas, pancreatic cysts, and pheochromocytomas. The VHL gene was recently isolated by positional cloning. The cDNA encodes 852 nucleotides in 3 exons. The VHL gene is unrelated to any known gene families. We identified germline mutations in 85/114 (75%) of VHL families. Clinical heterogeneity is a well-known feature of VHL. VHL families were classified into 2 types based on the presence or absence of pheochromocytoma. The types of mutations responsible for VHL without pheochromocytoma (VHL type 1) differed from those responsible for VHL with pheochromocytoma (VHL type 2). Fifty-six % of the mutations responsible for VHL type 1 were microdeletions/insertions, nonsense mutations, or deletions; 96% of the mutations responsible for VHL type 2 were missense mutations. Specific mutations in codon 238 accounted for 43% of the mutations responsible for VHL type 2. The mutations identified in these families will be useful in presymptomatic diagnosis. The identification of mutations associated with phenotypes contributes to the understanding of fundamental genetic mechanisms of VHL disease.

Adrenal Gland Neoplasms↗
PubMed1994

The Drosophila rolled locus encodes a MAP kinase required in the sevenless signal transduction pathway.

Mitogen-activated protein (MAP) kinases have been proposed to play a critical role in receptor tyrosine kinase (RTK)-mediated signal transduction pathways. Although genetic and biochemical studies of RTK pathways in Caenorhabditis elegans, Drosophila melanogaster and mammals have revealed remarkable similarities, a genetic requirement for MAP kinases in RTK signaling has not been established. During retinal development in Drosophila, the sevenless (Sev) RTK is required for development of the R7 photoreceptor cell. Components of the signal transduction pathway activated by Sev in the R7 precursor include proteins encoded by the gap1, drk, Sos, ras1 and raf loci. In this report we present evidence that a Drosophila MAP kinase, ERK-A, is encoded by the rolled locus and is required downstream of raf in the Sev signal transduction pathway.

Animals↗
PubMed1985

Expression and assembly of the erythroid membrane-skeletal proteins ankyrin (goblin) and spectrin in the morphogenesis of chicken neurons.

The membrane-skeleton of adult chicken neurons in the cerebellum and optic system is composed of polypeptides structurally and functionally related to the erythroid proteins spectrin and ankyrin, respectively. Neuronal spectrin comprises two distinct complexes that share a common alpha subunit (Mr 240,000) but which have structurally distinct polymorphic subunits (beta' beta spectrin; Mr 220/225,000; gamma spectrin, Mr 235,000); the brain-specific form (alpha gamma spectrin or fodrin) and an erythrocyte-specific form (alpha beta' beta spectrin). Two structurally related isoforms of ankyrin have also been identified and are termed alpha (Mr 260,000) and beta (Mr 237,000) ankyrin. Immunofluorescence demonstrates that the variants of spectrin and ankyrin, respectively, have different distributions within neurons. On the one hand, alpha gamma spectrin and beta ankyrin are present throughout the neuron, in the perikaryon, dendrites, and axon, whereas alpha beta' spectrin and alpha ankyrin are localized exclusively in the perikaryon and dendrites where they are actively segregated from alpha gamma spectrin and other components of axonal transport. This asymmetric distribution of spectrin and ankyrin isoforms is established in distinct stages during neuronal morphogenesis. Early in cerebellar and retinal development, alpha gamma spectrin is expressed in mitotic cells. Subsequently beta ankyrin and alpha gamma spectrin are coexpressed in postmitotic cells and gradually accumulate on the plasma membrane in a uniform pattern throughout the neuron during the phase of cell growth. At the onset of synaptogenesis and the cessation of cell growth, their levels of synthesis decline sharply while the assembled proteins remained as stable membrane components. Concomitantly, there is a dramatic induction in the accumulation of alpha ankyrin and alpha beta' spectrin, whose assembly is limited to the plasma membrane of the perikarya and dendrites. These results demonstrate that two successive, developmentally regulated programs of ankyrin and spectrin expression and patterning on the plasma membrane are involved in the assembly of the spectrin-based asymmetry in the neuronal membrane-skeleton, and that their asymmetric distribution is actively maintained throughout the life of the neuron.

Animals↗
PubMed1976

Sporadic bilateral retinoblastoma and 13q- chromosomal deletion.

Unilateral retinoblastoma (Rb) is usually a sporadic occurrence while bilateral (multifocal) cases are often familial. Sporadic bilateral Rb associated with a long-arm deletion of a D-group chromosome has been reported in 8 children. We have studied a 6-year-old female with bilateral sporadic retinoblastoma, treated during infancy by enucleation and radiotherapy. Chromosome banding studies on peripheral lymphocytes revealed an interstitial deletion from the long arm of a chromosome 13: del(13) (q12q14). Three additional patients reported in the literature had interstitial 13q- deletions, involving slightly different though overlapping regions. The only chromosomal region consistently missing in all of these 4 cases appears to be part of the lightly staining band 13q14. We, therefore, propose this site as the precise location of a gene (or genes) involved in retinal development. Our patient lacked features of the classic 13q- or 13-ring syndrome, which involves deletion of a more distal portion of the 13 long arm. When compared to reported patients with Rb and 13q-, it became apparent that there may be a separate recognizable syndrome consisting of moderate growth and developmental delay, characteristic facies and external ears, and bilateral sporadic Rb, which is associated with an interstitial 13q- deletion.

Adult↗
PubMed1995

Conditions for the primary culture of eye imaginal discs from Drosophila melanogaster.

We have established a primary culture system for Drosophila eye imaginal discs. With this system, we were able to obtain neurite outgrowth from intact eye discs, eye disc fragments, and dissociated eye imaginal disc cells. Immunoreactivity to antibody 24B10 indicates that these extending neurites are photoreceptor axons. Three culture media were tested for their ability to support the survival of and neurite extension from eye disc fragments in vitro at 23 degrees C. These, with supplements, were: five parts of Schneider's Drosophila medium with four parts of basal Eagle's medium ("4 + 5"); Leibovitz's L-15 medium (L-15); and Shields and Sang's M3 modified medium (MM3). We obtained the best results with MM3 supplemented with 2% fetal bovine serum (FBS). Eye disc fragments survived in this medium for at least 20 days. Pigmentation in the nonphotoreceptor pigment cells in cultures from the prepupa required the presence of 20-hydroxyecdysone (20-HE) (1 micrograms/ml), whereas neurite outgrowth was seen in the absence of 20-HE. Donor animals had to fall within a range of ages to obtain appropriate eye disc differentiation in vitro. Eye disc from 5-h pupae (P + 5) or older commenced ommachrome synthesis in vitro in a temporal sequence close to that found in vivo, whereas the in vitro synthesis of this pigment was delayed in eye discs from younger flies. Average neurite length was not affected by age among pupae younger than P + 5; but neurite outgrowth from P + 24 was scarce, probably because by this time photoreceptor axons had already grown in vivo and were severed and unable to regenerate in vitro. Eye discs taken from third instar larvae or white prepupae continued their mitotic activity in vitro. Together with the advance of the morphogenetic furrow at the leading edge of retinal development, this observation is consistent with the evidence that pattern formation continues in vitro. Morphogenetic changes were manifested in cultures. Viability tests with calcein AM and ethidium bromide revealed few dead cells in living cultures.

Animals↗
PubMed1997

cDNA cloning and expression analysis of NeuroD mRNA in human retina.

We have shown that bHLH proteins are involved in mammalian retinal development. Here we report the identification and analysis of the expression of a neurogenic differentiation gene, NeuroD, in human retina. In situ hybridization and immunocytochemical analyses of adult retina showed that NeuroD transcripts and NeuroD immunoreactivity are predominantly localized to the outer nuclear layer which contains the photoreceptors. Southern analysis of PCR-amplified cDNA revealed that NeuroD mRNA is also expressed in fetal human retina. Fetal monkey retina was used to analyse the spatial distribution of NeuroD in the developing retina. Both NeuroD transcripts and immunoreactivity are largely detected in the outer neuroblastic layer. Therefore, NeuroD may be involved in the differentiation as well as maintenance of the differentiated properties of photoreceptors.

Adult↗
PubMed2002

The dorsal-ventral axis of the neural retina is divided into multiple domains of restricted gene expression which exhibit features of lineage compartments.

The neural retina is a complex sensory structure designed to receive, integrate, and transmit visual information. An important aspect of retinal development is the establishment of pattern along the dorsal-ventral (D-V) and anterior-posterior (A-P) axes. The recent identification and functional characterization of a dorsal-specific and a ventral-specific transcription factor suggested that the D-V axis is divided into two domains. This study characterizes the expression patterns of these and other D-V markers, and establishes that the retina is subdivided into at least four domains of gene expression along this axis. The composition and spatial relation of these expression domains alters our model of D-V patterning, suggesting more complexity in the way that the retina is patterned than was previously recognized. As domains of gene expression within developing tissues sometimes comprise compartments whose borders are not crossed by clonally related cells, we performed a retroviral lineage study. A strong preference for cells to remain in their original domain of gene expression was observed, suggesting that these borders comprise developmental compartments.

Animals↗
PubMed1993

Differential expression of interphotoreceptor retinoid-binding protein, opsin, cellular retinaldehyde-binding protein, and basic fibroblastic growth factor.

The mRNA for rat interphotoreceptor retinoid-binding protein (IRBP) consists of 5.2 kb and 6.4 kb transcripts which are expressed early during retinal development. Here, we characterized rat IRBP cDNA and genomic clones, determined the mechanism generating the two transcripts and compared their expression to mRNAs for opsin, cellular retinaldehyde-binding protein (CRAlBP) and basic fibroblast growth factor (bFGF). We found that human and rat IRBPs have a high degree of sequence homology (86% amino acid identity over the fourth repeat). RNA-PCR studies and Northern blot analysis, showed that the 6.4 kb mRNA has a longer 3'-untranslated region (UTR) than the 5.2 kb message. Both IRBP transcripts, but not the mRNA for opsin are present in the neonatal and adult pineal. During development, the mRNAs for IRBP and opsin reach one-half of their maximal levels by P5 and P11, respectively. The ratio of the two IRBP mRNAs remains constant throughout life. In contrast, the ratio of the longest to the shortest opsin mRNA decreases between E19 and 1 year of age. Immunohistochemistry demonstrated a marked increase in the amount of IRBP in the interphotoreceptor matrix between P1 and P9 corresponding to the enhanced expression of this mRNA. Up-regulation of opsin mRNA expression during the second postnatal week corresponds to the emergence of the outer segments. The temporal expression of CRAlBP is similar to IRBP while bFGF is not expressed until after photoreceptor differentiation is complete. In summary, two 3'-transcription termination sites explain the difference in IRBP mRNA sizes. The different temporal and tissue specific patterns of IRBP and opsin expression suggest that separate mechanisms control the expression of these two genes. The expression patterns of IRBP and CRAlBP are consistent with the role of vitamin A as a morphogen and bFGF in neuronal maintenance.

Age Factors↗
PubMed1999

Interphotoreceptor retinoid-binding protein (IRBP) is rapidly cleared from the Xenopus interphotoreceptor matrix.

The interphotoreceptor matrix (IPM) is a highly-organized extracellular matrix critical to retinal development and function. Although the concentrations of its components are carefully regulated, little is known about the mechanisms of this regulation. Interphotoreceptor retinoid-binding protein (IRBP) is the most abundant soluble protein component of the IPM. Although its rate of clearance is thought to be an important factor regulating the concentration of IRBP within the IPM, no study has measured the rate of its extracellular turnover. Here we determine the rate of turnover of matrix IRBP in Xenopus. The rate of IRBP turnover was estimated by measuring the loss of radioactivity from protein labeled by a single injection of a radiolabeled protein precursor. To provide an estimate of the rate of IRBP turnover, we have examined the following issues: (1) Quantitative extraction of IRBP from the IPM for biochemical analysis. (2) Routes of delivery of radiolabeled precursor to achieve a pulse label in vivo. (3) Selection of labeled precursor in order to minimize reutilization of radiolabel. Using Western blot analysis, immunoprecipitation and immuno-electron microscopy, we found that IRBP can be quantitatively extracted from the IPM by a simple saline wash. IRBP was radiolabeled by systemic or intravitreal injection of either [35S]methionine or carboxyl-terminal labeled [1-14C]leucine. The specific activity of matrix IRBP was determined by either phosphorimaging or fluorography of Coomassie blue-stained SDS-polyacrylamide gels. Intravitreal injection of tracer was more effective than systemic delivery in achieving a pulse of radiolabel to the retina. This may be due to intravitreal injection allowing the body to act as a 'sink' for radiolabeled amino acid. When radiolabeled precursor was delivered by intravitreal injection, the calculated half-life of matrix IRBP using [35S]methionine was 25. 6+/-0.82 hr; in contrast, it was 10.7+/-2.9 hr using [1-14C]leucine. The faster apparent IRBP turnover using [1-14C]leucine is interpreted in context of the early decarboxylation of leucine during its degradation. Our results demonstrate rapid turnover of IRBP in the Xenopus IPM in vivo and suggest that the IPM is a dynamic structure undergoing continuous renewal.

Animals↗
PubMed1996

Pars plana lensectomy in cases of cataract with juvenile chronic uveitis.

BACKGROUND: Classical cataract extraction in young patients with secondary cataract following juvenile chronic uveitis often is complicated by serious problems such as severe postoperative uveitis, hypotonia oculi and phthisis bulbi. Lensectomy with partial anterior vitrectomy might be a less inflammatory way of handling these cases. METHODS: Over a 15-year period we have treated 10 eyes of 9 young patients (age from 8 to 30 years) with secondary cataract after chronic uveitis by pars plana lensectomy with partial anterior vitrectomy. A classical two-port technique was used with incisions at 4 mm from the limbus. The follow-up period varied from 3 to 12 years with an average of 8 years. There were five patients with chronic iridocyclitis, two with Fuch's heterochromic irridocyclitis, one with sympathetic ophthalmia and one with idiopathic panuveitis. RESULTS: Seven eyes were corrected with contact lenses. During the entire follow-up period six had 20/20 visual acuity and one, 20/40. None of these patients reported tolerance problems with the contact lens. One patient has 20/20 visual acuity with spectacles. One patient who initially had 20/20 visual acuity with a contact lens developed retinal detachment 2 years after surgery, during pregnancy, and now has 20/40 vision after retinal surgery. She prefers not to wear the contact lens any longer because of diplopia. The visual acuity of one patient was no better than hand movement and his aphakia was never corrected. Complications included one vitreous haemorrhage necessitating a second vitrectomy, one retinal detachment during pregnancy and one retinal detachment with proliferative vitreoretinopathy. One patient with sympathetic ophthalmia has 20/20 vision after 9 years' follow-up but still needs systemic steroids and cyclosporine. CONCLUSION: Pars plana lensectomy, with anterior vitrectomy appears to be a relative safe way to treat secondary cataract in patients during the first 30 years of life.

Adolescent↗
PubMed1983

Ontogeny of the photoreceptors in the embryonic retina of the viviparous guppy, Poecilia reticulata P. (Teleostei). An electron-microscopical study.

Ultrastructural analyses of retinal development in the guppy embryo show that at midgestation all types of photoreceptors are differentiated in the fundus, and at birth differentiation extends over the whole retina. Formation of discs of outer segments is more rapid in rods than in cones. Double cones differentiate simultaneously with long single cones and are formed by the adhesion of two primordial inner segments; short single cones develop last. Wherever cones are differentiated, they are arranged in an adult-type square mosaic. The rods in the embryo, as opposed to the adult, are likewise regularly arranged within the mosaic unit. These results are at variance with the generally held opinion that adult teleosts which possess duplex retinae have larvae with pure cone retinae, and that rods, double cones and mosaics appear in late larval life or only at metamorphosis. In the double cones of the guppy embryo subsurface cisternae develop along the adjoining primordial inner segments. Additionally, regularly distributed subsurface cisternae are formed in the regions of intimate contact of long single cones with double cones and rods. We suggest that the early development of rods and double cones, and a square-mosaic with regular distribution of rods and subsurface cisternae, provide the newly born with a fully functional optical apparatus, especially suited to perception of movements. This is necessary for its survival against predatory, especially maternal, attacks.

Animals↗
PubMed1983

Scanning electron microscopic studies of the hyaloid vascular system in newborn mice exposed to O2 and CO2.

It has been suggested that the tunica vasculosa lentis of newborn mice undergoes vasoproliferation after oxygen exposure and might be used as an experimental model for intraocular neovascularization. A scanning electron microscopic technique which provides visualization of the entire hyaloid vascular system was used to study its response in mice exposed to various gas mixtures (70% O2/30% N2, 10% CO2/90% air, 10% CO2/70% O2/20% N2). Marked differences were found between hyaloid regression in gas exposed mice compared to air control mice, but no evidence of neovascularization was found in any group. The data support the possibility that changes in the hyaloid may be the consequence of the hydrostatic coupling which exists between this atrophic, possibly flow-resistant vasculature and the developing retinal vasculature whose blood flow characteristics are significantly altered by exposure to CO2 and O2.

Age Factors↗
PubMed1992

Autopsy findings in two siblings with infantile Refsum disease.

Recognition of adrenal atrophy during a review of autopsy findings in two sisters who died at 8 months and 3 1/2 years prompted estimation of very long chain fatty acids, phytanic acid and pristanic acid on wet liver fixed in formalin for 12 years. These were shown to be markedly increased and defects in multiple peroxisomal functions and decrease in particulate catalase were shown in cultured fibroblasts, confirming an abnormality of peroxisomal biogenesis. The patients had presented with failure to thrive, recurrent diarrhoea and vomiting, poor mental development, retinal pigmentation, blindness and in the older patient deafness, with only mild dysmorphic features. Autopsy in the older patient showed adrenal atrophy, cirrhosis, and foamy histiocytes in multiple organs. The brain showed no demyelination, little cytoarchitectural abnormality, occasional perivascular histiocytes in the grey matter and meninges and prominent Purkinje cells in the molecular layer of the cerebellum. In the younger patient the changes were very subtle in spite of the marked clinical similarity. Despite the young age at death the clinicopathological features are most suggestive of infantile Refsum disease. In many situations anatomical pathology can be very useful in the recognition and study of peroxisomal disorders.

Adrenal Glands↗
PubMed1988

Development of retinofugal neuropil areas in the brain of the alpine newt, Triturus alpestris. II. Topographic organization and formation of projections.

The development of retinal projections and the formation of their retinotopic organization were studied by means of anterograde transport of horseradish peroxidase in the newt, Triturus alpestris. All tracts found in the adult on the contralateral brain side are established during embryonic stages. At this stage a few uncrossed fibers are also detectable. Retinal fibers project first to the contralateral optic tectum. These are followed by contralateral projections to the thalamic recipient areas. Beginning at embryonic stages, the projections from the retinal quadrants into the optic tectum are topographically organized. The other terminal areas innervated by the marginal optic tract (MaOT) show a topographic order from midlarval stages. The terminal areas innervated by the medial optic tract (MeOT) show no clear topographic organization at any stage. The contralateral projection of the MeOT originates from the central area of the retina, whereas the uncrossed projection originates from the temporal peripheral retina. Ipsilateral (uncrossed) retinal projections develop during metamorphic climax. The MeOT is more distinct than the MaOT. The latter shows a clear retinotopic organization. The topography of the ipsilateral MaOT and its corresponding terminal areas are mirror-symmetric to the contralateral tract and terminal areas.

Animals↗
PubMed1994

Muscarinic receptors binding in retinal pigment epithelium during rat development.

[3H]Quinuclidinyl benzylate (3H-QNB) specific binding of the developing rat retinal pigment epithelium (RPE) and neural retina has been examined. The binding of 3H-QNB to RPE was saturable and displaced by the antagonist pirenzepine. Scatchard analysis of 3H-QNB binding showed two high affinity sites to RPE, with KB = 2.6nM and 45 nM. Specific 3H-QNB binding membranes from neural retina exhibited a characteristic developmental profile. RPE showed a high density of 3H-QNB binding sites through all developmental periods studied. The major onset of binding sites is at the time of RPE differentiation. Our data open the possibility of muscarinic receptors being involved in differentiation and/or proliferation of RPE.

Animals↗
PubMed2001

An ocular cat-scratch disease patient positive for cytoplasmic anti-neutrophil cytoplasmic antibody.

BACKGROUND: We report a case of ocular cat-scratch disease with permanent vision reduction in a patient who was cytoplasmic anti-neutrophil cytoplasmic antibody (C-ANCA) positive. METHODS: Case report and review of the literature. RESULTS: While taking steroids and antibiotics, a 52-year-old man with uveitis associated with cat-scratch disease developed retinal vein occlusion and a macular exudate. His final visual acuity was poor because of residual macular degeneration and optic atrophy. Serum C-ANCA increased and decreased in parallel with ocular inflammatory activity. CONCLUSION: C-ANCA is an indicator of vasculitis and may be useful as an indicator of severe cat-scratch disease.

Ampicillin↗
PubMed2001

Tyrosinase gene expression in zebrafish embryos.

The enzyme tyrosinase is required for the conversion of tyrosine into the pigment melanin. Thus, tyrosinase gene expression is a useful marker for studying the differentiation of melanin-expressing cells during embryogenesis. We describe the spatiotemporal pattern of transcription of the tyrosinase gene and the presence of active enzyme in whole embryos of the zebrafish, Danio rerio. At 16.5 h post-fertilisation the tyrosinase gene is transcribed in the dorsal extremity of the developing retinal pigment epithelium, approximately 7 h before visible pigmentation. Shortly thereafter, transcription in neural crest-derived melanocytes is first observed dorsolateral to the mesencephalon and diencephalon and the posterior hindbrain/anterior spinal cord. A wave of gene activation and cell migration is then observed moving towards the posterior of the animal. DOPA staining for tyrosinase activity shows the presence of active enzyme in embryos at least 3 h before visible pigmentation.

Animals↗