Corneal deepithelialization caused by acute deficiency of isoleucine during treatment of a patient with maple syrup urine disease

Classical Maple Syrup Urine Disease is a serious, autosomal recessive and rare metabolic disorder due to a completely inactive enzyme complex for metabolizing the branched amino acids leucine, valine and isoleucine. If untreated the disease is lethal. Metabolic control achieved by strict dietary treatment results in normal development. In this paper we describe deepithelialization of the cornea together with skin and intestinal symptoms as the result of isolated deficiency of isoleucine during treatment of a critically ill, newborn infant with this unusual disease.

Evaluation of screening procedures for congenital cataracts

AIM

To evaluate the efficacy of two different Swedish screening procedures for early detection of congenital cataracts in comparison with no screening.

METHODS

Children born between January 1992 and December 1998 in Swedish regions with an established eye-screening routine procedure, diagnosed with congenital cataract, and operated on before 1 y of age, were included in a retrospective study. Age at referral and age at time of the operation were compared between regions using different screening procedures: screening in the maternity wards (Region 1), at the well-baby clinics (Region 2) and one region without any screening (Region 3).

RESULTS

Seventy-two children were included in the study. Concerning early diagnosis and surgery, Region 1 differed significantly from Regions 2 and 3, which were more similar and were combined for further analysis. The difference in detected cases was greatest at 21 d of age (55% vs 18%; p < 0.001), but persisted even at 100 d of age (78% vs 64%; p < 0.02). Region 1 screening resulted in more and earlier cases detected than the other two regions (22 vs 15 per 100,000 births). In 72% of all cases, surgery was performed in response to referrals from either the maternity wards (36%), or the well-baby clinics (36%). However, half of the cases from the well-baby clinics were detected too late, i.e. at > 100 d.

CONCLUSION

Eye screening in the maternity ward is preferable to well-baby clinic screening and to no screening at all, since it leads to early detection. Screening should also be performed routinely at well-baby clinics within the period when successful treatment is possible.

Association between visual impairment and functional and morphological cerebral abnormalities in full-term children

PURPOSE

To characterise the nature and degree of ocular disorders and cerebral morphological and functional abnormalities in a population-based group of visually impaired full-term pre-school children.

METHODS

Forty-five children who were born at full-term between 1989 and 1995 in Värmland, Sweden, were reported as being visually impaired. An ophthalmological examination was performed and clinical data regarding mental development and neurological disease were obtained for all children. Cerebral imaging was performed in 35 children.

RESULTS

Twenty-six per cent of the children were found to have ocular disorders only. Forty-two per cent had cerebral morphological abnormalities, verified by cerebral imaging, and 65% had signs of cerebral functional abnormalities. In total, 74% were found to have cerebral morphological and/or cerebral functional abnormalities.

CONCLUSION

The majority of children with visual impairment, including children with ocular disorders, were found to have cerebral morphological and/or cerebral functional abnormalities. We suggest that any child with visual impairment should therefore undergo cerebral imaging and be examined by a paediatrician in order to establish the correct diagnosis.

Visually impaired Swedish children. The 1980 cohort study--aspects on mortality

PURPOSE

Assessment of the burden of mortality in a cohort of visually impaired children in a geographically defined area.

METHODS

A 19-year follow-up of medical records and death certificates.

RESULTS AND CONCLUSIONS

Of the initial 128 patients, born 1962-76, 17 (13%) had died, giving a highly significant increase in mortality compared to the equivalent age-specific Swedish population (p-value <0.000001). All deceased had additional impairments. Respiratory causes of death were found in 12/17 cases. The primary ophthalmological diagnosis was cerebral visual impairment in 8 cases, optic atrophy in 6 cases, one each of congenital cataract, microphthalmus and chorioretinitis. A more pronounced level of visual impairment gave an increased risk of mortality. A significantly higher mortality rate among multiply impaired was seen in the combined group with 'childhood blindness' (visual acuity <0.05) and 'visual impairment, undetermined or unknown' opposed to the group with 'low vision' (visual acuity 0.05-<0.3) (p=0.047).

Visually impaired Swedish children. The 1980 cohort study--a 19-year ophthalmological follow-up

PURPOSE

To assess the ophthalmological outcome in a cohort of visually impaired children in a geographically defined area.

METHODS

A 19-year follow-up of medical records, interview and, if needed, re-examination of the initial 128 patients, born 1962-1976.

RESULTS AND CONCLUSION

Follow-up was possible in 123 patients (96%); 76 (59%) were still visually impaired, 17 (13%) were deceased, while 30 (23%) had acquired a visual function > or = 0.3. The chances of gaining a visual function outside the WHO limits for visual impairment was significantly higher for patients without additional impairments (p=0.0023). The initial ophthalmologic diagnosis remained unchanged in 88%. The diagnoses with improved visual development included albinism and congenital nystagmus, while retinal diseases showed poorer results. An increase in visual function could be seen even in the initially older age-groups, indicating a maturation of visual function beyond what is usually considered the limit of plasticity of the visual system.

Visually impaired Swedish children. Longitudinal comparisons 1980-1999

PURPOSE

To produce the background to a pilot-study of the visual and social outcome of visually impaired children. A study, originally including 219 individuals, done in 1980 in the county of Malmöhus in southern Sweden, was revisited.

METHODS

A revision according to current WHO classification led to a cohort of 128 individuals. This was compared to the corresponding group, comprising 2048 individuals, of the total Swedish registration of visually impaired children of today.

RESULTS AND CONCLUSION

The two groups were mostly similar as regards male/ female distribution, additional impairments, etiological factors and diagnoses. The prevalence of visual impairment due to peri-/neonatal influence had increased (p=0.038; odds ratio (OR): 1.61, 95% confidence interval (CI): 1.04-2.61), while visual impairment due to prenatal infections had decreased (p = 0.0001; OR: 0.26, 95%CI: 0.15-0.49). Regarding diagnoses we saw a significant decrease in chorioretinitis, as well as in microphthalmus and Stargardt's disease, while hypoplasia of the optic nerve increased. In all these, except chorioretinitis, the changes are probably due to altered diagnostic classification.

Visual impairment in Swedish children. III. Diagnoses

PURPOSE

To gain an overview of the spectrum of diagnoses among Swedish visually impaired children.

METHODS

An epidemiological study of all known visually impaired children was made by review of medical records.

RESULTS AND CONCLUSION

In all we found 2373 children, 0-19 years of age, with an age-specific prevalence of 10.9/10,000. The two largest diagnostic groups included neuro-ophthalmological and retinal diseases. The most frequent disorders were cerebral visual impairment, non-hereditary optic atrophy, retinal dystrophy (when regarded as a general entity), congenital hypoplasia of the optic nerve and congenital cataract. Nystagmus secondary to brain disorder, albinism, congenital nystagmus, retinopathy of prematurity and high myopia were also found in a considerable number of patients. The leading diagnoses in children with WHO-defined childhood blindness were non-hereditary optic atrophy, cerebral visual impairment and retinopathy of prematurity. A large proportion of the children, especially in the groups with neuro-ophthalmological disorders and malformations of the posterior segment had additional impairments, emphasizing the importance of a multi-disciplinary approach when assessing multi-handicapped children.

Intrafamilial variation of the phenotype in Bardet-Biedl syndrome

AIMS

To describe the variation of the phenotype within families with several individuals with Bardet-Biedl syndrome.

METHODS

The phenotypes of affected siblings in 11 Scandinavian families with two or more members who had at least three of the features: retinal dystrophy, polydactyly, obesity, hypogenitalism, and mental retardation, were compared [corrected]. Individuals without retinal dystrophy were excluded.

RESULTS

Intrafamilial variation of expressivity of the features obesity, polydactyly, abnormal radiograms of the extremities, hypogenitalism, short stature, paraplegia, and dental abnormalities was found. The retinal dystrophy varied with respect to both the onset of symptoms and the course of the disease. The morphology of the fundus, however, was consistent within the families. The disorder showed statistically significant genetic linkage to the BBS4 locus on chromosome 15 in the affected siblings in two of the families, but the clinical features in these patients did not differ from the other cases of Bardet-Biedl syndrome.

CONCLUSION

Comparison of siblings with the Bardet-Biedl syndrome showed variation of the typical features. In addition, the course of retinal dystrophy varied. No distinctive clinical features were found to separate the BBS4 phenotype from the remaining patients.

Visual impairment in Swedish children. II. Etiological factors

The analysis of etiological factors in a group of visually impaired children is of considerable importance when trying to find guidelines for possible preventive work. In this study we present etiological data on 2373 Swedish children. Data have been obtained by reviewing medical records on all known children with visual impairment throughout the country. In accordance with similar studies from industrialised countries, the group with prenatal etiology was the predominant, comprising 64% of the material. Within this group, half the patients had a disease of genetic origin. A total of 50% of all patients with prenatal etiology had an additional impairment, but in the group with diseases of genetic origin this proportion was smaller, only 40%. On the other hand, many children with additional impairments were found among those with an unspecified prenatal influence. Peri-/neonatal etiologies were found in 20% of the patients. In this group as many as 83% had additional impairments. This was even more pronounced among children delivered at term. The group with infantile/juvenile etiologies was small, 7%, with additional impairments in 66%. In 9% of all patients the etiology was classified as unknown. Among these, 80% had additional impairments. The visual impairment tended to be more pronounced, the later the disease was acquired. A male preponderance was seen in most etiological subgroups and in the material as a whole.

Visual impairment in Swedish children. I. Register and prevalence data

Knowledge of the epidemiology of visual impairment in children forms one of the cornerstones of pediatric ophthalmology. In contrast to e.g. the other Nordic countries, Sweden has had no efficient and continuous registration of visually impaired children. An epidemiological study on this subject has now been done, collecting data on all children and adolescents registered at the Low Vision Clinics throughout Sweden. In this work data on 2373 visually impaired children, 0-19 years of age and living throughout Sweden are presented. Data collected in the study include sex, date of birth, county, ocular diagnosis, systemic diagnosis, classification of visual impairment, aetiology and possible additional impairments. The prevalence of visual impairment as defined by WHO was 10.9/10,000 inhabitants in the current age group. A slight male preponderance was seen compared to the total population 0-19 years. This was not reduced when only non-genetic aetiological factors were taken into consideration. A total of 45% of the children had only a moderate visual impairment (WHO category 1), whereas approximately 25% were found in WHO categories 3,4 and 5, i.e. fulfilled the requirements for blindness. Additional impairments were found in 60% of the children. Mental impairment in combination with motor impairment or mental impairment exclusively were the most common ones seen.

Linkage mapping in 29 Bardet-Biedl syndrome families confirms loci in chromosomal regions 11q13, 15q22.3-q23, and 16q21

Bardet-Biedl syndrome (BBS) is a clinically and genetically heterogeneous autosomal recessive disorder characterized by retinitis pigmentosa, polydactyly, obesity, hypogenitalism, mental retardation, and renal anomalies. To detect linkage to BBS loci, 29 BBS families, of mixed but predominantly European ethnic origin, were typed with 37 microsatellite markers on chromosomes 2, 3, 11, 15, 16, and 17. The results show that an estimated 36-56% of the families are linked to the 11q13 chromosomal site (BBS1) previously described by M. Leppert et al. (1994, Nature Genet. 7, 108-112), with the gene order cen-D11S480-5 cM-BBS1-3 cM-D11S913/D11S987-qter. A further 32-35% of the families are linked to the BBS4 locus, reported by R. Carmi et al. (1995, Hum. Mol. Genet. 4, 9-13) in chromosomal region 15q22.3-q23, with the gene order cen-D15S125-5 cM-BBS4-2 cM-D15S131/D15S204-qter. Three consanguineous BBS families are homozygous for three adjacent chromosome 15 markers, consistent with identity by descent for this region. In one of these families haplotype analysis supports a localization for BBS4 between D15S131 and D15S114, a distance of about 2 cM. Weak evidence of linkage to the 16q21 (BBS2) region reported by A. E. Kwitek-Black et al. (1993, Nature Genet. 5, 392-396) was observed in 24-27% of families with the gene order cen-D16S408-2 cM-BBS2-5 cM-D16S400. A fourth group of families, estimated at 8%, are unlinked to all three of the above loci, showing that at least one other BBS locus remains to be found. No evidence of linkage was found to markers on chromosome 3, corresponding to the BBS3 locus, reported by V. C. Sheffield et al. (1994, Hum. Mol. Genet. 3, 1331-1335), or on chromosome 2 or 17, arguing against the involvement of a BBS locus in a patient with a t(2;17) translocation.

Ocular findings in the Laurence-Moon-Bardet-Biedl syndrome

PURPOSE

To improve the description of the ocular part of the Laurence-Moon-Bardet-Biedl syndrome.

METHODS

We examined 44 Scandinavian individuals who all had retinal dystrophy plus at least 2 more of the traditional cardinal signs of the syndrome: obesity, hypogenitalism, polydactyly and mental retardation.

RESULTS

Full-field electroretinograms were obtained in 36 of the individuals and were abnormal in all. The dark adaptation thresholds were elevated by on average 3.5 log units. Symptoms of night blindness were observed at a mean age of 4 years and visual problems at daytime at 6-7 years. No one exceeding the age of 16 had a best corrected visual acuity of more than 0.1. In the fundus attenuated vessels were noted at all ages while macular pigmentations and a wax-pale optic disc appeared at age 6-7 years. Pigmentary changes in the midperiphery were noted at the earliest at 13 years of age and appeared mainly as bone spicules, however, in a minority of cases the pigmentations were atypical. Ten of the participants had been followed through a period of 9 years. Their visual acuity was reduced by on average 0.3 line (decimals) and the angle of visual fields by approximate 3 degrees (Goldmann standard object V:4e) per year through the adolescence.

CONCLUSION

The ocular disease in Laurence-Mood-Bardet-Biedl syndrome presents early, the prognosis for visual function is poor and the fundus features are atypical and varying.

Full-field electroretinograms in individuals with the Laurence-Mood-Bardet-Biedl syndrome

PURPOSE

To evaluate rod and cone function in individuals with the Laurence-Moon-Bardet-Biedl syndrome.

METHODS

We obtained a full-field electroretinograms in 36 patients. If responses less than 10 microV were recorded with single white flashes a special techniques with narrow band filter and computer averaging was used.

RESULTS

No rod responses to dim blue light could be obtained in any of the patients. Residual cone flicker responses were measurable in 28 of the individuals. Those with amplitudes < 0.05 microV were significantly older than those with amplitudes > 1.00 microV. The ERG pattern was consistent within affected pairs of siblings in 8 families.

CONCLUSION

The retinal dystrophy in Laurence-Moon-Bardet-Biedl syndrome is primarily a rod-cone dystrophy, but even cone flicker amplitudes are severely reduced with further progression with age. There is no intrafamilial variability of the electroretinograms in affected siblings.

Skeletal abnormalities of hands and feet in Laurence-Moon-Bardet-Biedl (LMBB) syndrome: a radiographic study

OBJECTIVE

To identify radiological changes of the hands and feet in a large group of patients with Laurence-Moon-Bardet-Biedl syndrome.

DESIGN

Postero-anterior views of hands and feet were obtained and analysed.

PATIENTS

The material consists of 43 Scandinavian patients with the syndrome (24 males and 19 females; age 3 weeks to 57 years, median 23 years at the time of radiological examination).

RESULTS AND CONCLUSIONS

Polydactyly of the hands and feet is one of the main criteria. This was noted clinically in 33 of 43 patients, but all but 3 had been operated on before this radiological study. Remnants of the extirpated finger or toe noted as exostoses, additional joint surfaces of duplication were found in half the hands and feet, while the remainder showed no radiological changes. Other features found were short, broad bones and flat joint surfaces of the metacarpophalangeal or metatarsophalangeal joints. We also found a high frequency of short or long ulna in relation to the radius and Madelung deformity of the wrist in several patients. Thus, the radiographs showed several non-specific normal variations besides remnants or postoperative changes after polydactyly.

Anomalies in the permanent dentition and other oral findings in 29 individuals with Laurence-Moon-Bardet-Biedl syndrome

This paper reports a clinical and roentgenological examination of the teeth, jaws and saliva of 29 Scandinavian individuals with Laurence-Moon-Bardet-Biedl (LMBB) syndrome, whose cardinal signs are retinal dystrophy, polydactyly, obesity, hypogenitalism and mental retardation. All subjects had at least three of these signs, including retinal dystrophy. Compared with normal subjects, the group had statistically significantly higher frequencies of hypodontia, small teeth and short roots. In addition, the saliva showed a buffering capacity higher than normal. In conclusion, there seem to exist disturbances of both dental and skeletal formation in the LMBB syndrome.

Incidence of registered visual impairment in the Nordic child population

A collaborative, population based, prospective register study on the incidence of visual impairment in children during the year 1993 was carried out in five Nordic countries with a total population of 17 million inhabitants. The child population was 3.8 million individuals aged 0-17 years. The following variables were taken into account: nationality, age, sex, diagnoses, aetiology, degree of visual impairment, and additional impairments. Classification routines from an earlier prevalence study were used. The present study included 304 children corresponding to an incidence of notification of 8/100,000 children, varying from 5.7 to 11.1 in the five countries. Fifty per cent of the visually impaired children were reported before they were 3 years of age. In approximately 45% of the children, visual impairment was due to various brain disorders, with cerebral amblyopia and secondary optic atrophy as the two leading causes. The relative impact of retinopathy of prematurity had decreased from the third most frequent cause (10%) in the prevalence study to seventh place (4%) in the incidence study. Two thirds of the children had additional impairments and these children also suffered from the most severe visual impairments. Among aetiological factors the majority (64%) were prenatal. The overall male:female ratio of 1.4:1 was identical to the sex ratio of the prevalence study.

An extra cysteine in one of the non-calcium-binding epidermal growth factor-like motifs of the FBN1 polypeptide is connected to a novel variant of Marfan syndrome

We present here a family with a clinical phenotype resembling Marfan syndrome (MFS), and displaying joint contracture and episodes of knee joint effusions, but lacking the cardiovascular features of the syndrome. The phenotype of this family represents a unique mixture of connective tissue symptoms, some of which are found in classical MFS and some of which are typical of dominant ectopia lentis. Linkage analyses suggested a linkage (LOD score 2.4; theta = 0) between the phenotype of the family and a polymorphic marker in the vicinity of the fibrillin locus on chromosome 15 (FBN1). Furthermore, a novel transition mutation was identified in the FBN1 gene in all the affected members of the family. In contrast to the majority of fibrillin mutations reported so far, this mutation substitutes a cysteine for arginine, producing an extra cysteine in one of the non-calcium-binding EGF-like motifs of the fibrillin polypeptide, most probably disturbing the formation of one of the three disulfide bridges known to be essential for the normal conformation of this motif.

Full-field electroretinograms during general anesthesia in normal children compared to examination with topical anesthesia

Full-field electroretinograms were obtained from 20 normal children during general anesthesia and compared with electroretinograms obtained with topical anesthesia. Disoprofol and fentanyl induced a reduction in the b-wave amplitudes and an increase in the cone b-wave implicit time, but the changes were small and fall within the range limits seen with topical anesthesia (i.e., average +/- 2 SD).

Electroretinograms in patients with achromatopsia

Eleven patients with X-linked and 9 patients with autosomal recessive achromatopsia were examined with full-field electroretinograms. In the standard full-field ERG's, normal rod responses were obtained, but the amplitude of the cone b-waves was not detectable. With computer averaging and narrow bandpass filtering, residual cone b-wave responses could be detected in 10 of the 20 patients. The residual cone b-wave amplitudes were markedly different in the 3 families with X-linked achromatopsia. In two of them, residual cone b-wave responses were seen in all patients examined. In contrast, such responses were seen only in 2 of 7 patients in the third family. There were also differences in other clinical observations (mainly in the visual acuity and refractive error) and we therefore suggest that there are at least two forms of X-linked achromatopsia. The ratios of the cone response amplitudes to 30 Hz flickering orange and blue-green light suggested that the defect in the X-linked achromatopsia patients was of the protanope type, whereas in the autosomal patients, both the protanope and the deutanope type was seen. In conclusion, measurements of the residual cone b-wave amplitude responses are of diagnostic and may possibly be of prognostic value when examining children and other members of families with achromatopsia.

Modulation of cone horizontal cell activity in the teleost fish retina. III. Effects of prolonged darkness and dopamine on electrical coupling between horizontal cells

The effects of prolonged darkness and dopamine on the coupling between horizontal cells in the isolated, superfused white perch retina were studied. Two assays of coupling were employed; area versus amplitude relationships (area-response curves) and the diffusion of the fluorescent dye Lucifer yellow from intracellularly injected cells to neighboring cells. In prolonged dark-adapted retinas, area-response curves were difficult to determine because of the small light responses; however, light-evoked responses did not increase in size when light spots were larger than 0.8 mm in diameter. Following the presentation of dim background illumination that partially sensitized the retina, responses to light spots of various sizes were enhanced and an area-response curve could be constructed. Subsequent presentation of moderate background illumination that more fully sensitized the retina resulted in reduced responses to small spots (less than 1.6 mm in diameter) and enhanced responses to large spot or full-field stimuli. In retinas exposed to moderate background illumination, Lucifer yellow injected intracellularly into cone horizontal cells diffused into many neighboring horizontal cells. The coupled cells were very similar in morphology, suggesting they were of the same type. In prolonged dark-adapted retinas, on the other hand, the dye was usually restricted to the injected cell and a few adjacent cells. These results indicate that coupling between cone horizontal cells is modulated by prolonged darkness and background illumination. Following dopamine (50 microM) application, in both 6-OHDA-treated and untreated retinas, changes in area-response curves of cone horizontal cells were observed just opposite to those that occurred when prolonged dark-adapted retinas were exposed to background illumination. That is, following 5 min application of dopamine to the retina, responses to small spots (less than 2 mm in diameter) increased in size while responses to larger spots decreased in amplitude compared with control responses. Following 20 min of superfusion with dopamine, the recorded responses were very small, and an accurate area-response curve could not be determined. Following dopamine application to light-sensitized retinas, Lucifer yellow was restricted to the injected cells or to the injected cell and a few neighboring cells. The results suggest that the modulation of coupling between cone horizontal cells by prolonged darkness and background illumination may be mediated by dopamine. Spatial properties of rod horizontal cells were also examined.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of cone horizontal cell activity in the teleost fish retina. I. Effects of prolonged darkness and background illumination on light responsiveness

The effects of prolonged (greater than 2 hr) darkness and background illumination on the light responsiveness of cone horizontal cells were examined in isolated, superfused white perch retinas. In retinas from fish maintained in complete darkness for more than 2 hr, cone horizontal cells had a resting membrane potential of about -18 mV, and they generated only slow, low-amplitude (3-4 mV) responses even when stimulated with bright flashes. Following the presentation of dim background light, the cone horizontal cells slowly hyperpolarized and thereafter remained at a more hyperpolarized level (about -25 mV). Concurrently, their light responses were dramatically enhanced in size, and response amplitudes to bright flashes eventually increased to about 50 mV. This was accompanied by noticeable changes in response waveforms; following light exposure, the responses became faster and showed initial on-transients. The increase in cone horizontal cell responsiveness was graded with intensity of the background light. A similar enhancement in response amplitudes of cone horizontal cells occurred after presenting bright flashes repetitively at intervals of 9 sec. This background sensitization phenomenon was observed in both L- and C-type cone horizontal cells. When light-sensitized isolated retinas were maintained in darkness for long periods (greater than 30 min), the light responsiveness of cone horizontal cells gradually decreased. The changes in membrane potential and response waveform were opposite to those that occurred when prolonged dark-adapted retinas were exposed to background lights; the cells depolarized by 5-7 mV and light-evoked responses became slower. Effects of background illumination on rod-driven horizontal cells were examined as well. Rod horizontal cells were about 2 log units more sensitive to white light than were cone horizontal cells. When recorded in prolonged dark-adapted retinas, rod horizontal cells showed large responses (approximately 50 mV), which could not be further enhanced by background illumination. Cone horizontal cell responsiveness in the carp retina was also depressed by prolonged darkness and increased by illumination in a fashion similar to that observed in the white perch retina. The change in response amplitude was only about 2-fold in carp compared with 5- to 10-fold changes observed in white perch. These results indicate that the light responsiveness of cone horizontal cells in the teleost retina is suppressed in prolonged darkness and that background lights release the cells from suppression.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of cone horizontal cell activity in the teleost fish retina. II. Role of interplexiform cells and dopamine in regulating light responsiveness

Following the destruction of the terminals of the dopaminergic interplexiform cells by intraocular injections of 6-hydroxydopamine (6-OHDA), cone horizontal cells exhibited high light responsiveness in prolonged darkness and their responses to moderate and bright full-field flashes were as large as 60 mV. Furthermore, the light responsiveness of these cells in the 6-OHDA-treated retinas was not enhanced by background illumination. The application of dopamine (50 microM) by superfusion to 6-OHDA-treated retinas resulted in a decrease in light responsiveness and changes in response waveform of the cone horizontal cells. Twenty minutes following dopamine application the responses of the cone horizontal cells closely resembled the response of cells recorded in prolonged dark-adapted retinas. Dopamine caused similar changes in cone horizontal cells recorded in light-exposed retinas, but had no obvious effects on rod horizontal cells. The selective dopamine D1 receptor antagonist, Sch 23390, enhanced cone horizontal cell responsiveness when applied to prolonged dark-adapted retinas, mimicking background illumination. The light responsiveness of cone horizontal cells recorded after application of Sch 23390 was less than that for cells in retinas that had been exposed to background lights, but light responsiveness could not be further enhanced by background illumination. Another dopamine antagonist, (+)-butaclamol, was found to have effects similar to Sch 23390 on cone horizontal cells, but (-)-butaclamol, the inactive enantiomer, did not enhance the light responsiveness of these cells. The results suggest that the dopaminergic interplexiform cells play a crucial role in the regulation of cone horizontal cell responsiveness by prolonged darkness and background illumination. These cells may release dopamine tonically in the dark, which suppresses cone horizontal cell responsiveness. Background illumination may decrease dopamine release and liberate cone horizontal cells from the suppression.

Peptide immunoreactive neurons in the human retina

The distribution of peptide-immunoreactive neurons in the human retina was investigated. Neurons displaying immunoreactivity towards substance P, vasoactive intestinal polypeptide (VIP), somatostatin, neuropeptide Y (NPY) and peptide histidine-isoleucine (PHI) were found in amacrine cells with cell bodies situated in the innermost part of the inner nuclear layer and nerve fibers ramifying in the inner plexiform layer in a manner differing according to the peptide investigated. Two other cell types were found. In the middle of the inner plexiform layer cell bodies showing immunoreactivity towards substance P, VIP and PHI were found. In the ganglion cell layer there were cell bodies showing immunoreactivity towards substance P, somatostatin, VIP and NPY. Substance P immunoreactive, somatostatin and NPY immunoreactive fibers situated at the border between the inner nuclear and outer plexiform layers and traversing the inner nuclear layer were also found.

Neuropeptide Y (NPY) immunoreactive neurons in the retina of different species

Neurons displaying Neuropeptide Y (NPY) immunoreactivity were found among amacrine cells in the retina of baboon, pig, cat, pigeon, chicken, frog, trout, carp and goldfish. The immunoreactive cell bodies were located in the middle and the innermost cell rows of the inner nuclear layer with processes forming one, two or three more or less well-defined sublayers in the inner plexiform layer. The location and the density of the sublayers varied with the species investigated. In the frog retina, bipolar-like cell bodies were found in the middle of the inner nuclear layer as well as sparsely occurring ovoid cell bodies in the ganglion cell layer. Like the amacrine cells, these cells emitted processes ramifying in three sublayers in the inner plexiform layer.

Neurotransmitter release by certain neuropeptides in the chicken retina

The ability of certain neuropeptides (glucagon, somatostatin, leu-enkephalin and neurotensin) to release known neurotransmitters (glycine, GABA, dopamine and 5-hydroxytryptamine) was tested in the chicken retina. Tritiated neurotransmitters were injected intravitreally in chicken eyes. After excision, the retina was stimulated in vitro with the neuropeptide in micromolar concentrations while monitoring the efflux of radioactivity from the retina. A rise of the efflux represents a stimulus dependent release. Neurotensin release [3H] glycine, [3H]dopamine and [3H]5-hydroxytryptamine. Leu-enkephalin released [3H]dopamine and somatostatin released [3H]5-hydroxytryptamine. Glucagon was without effect. [3H]GABA was not released by any of the neuropeptides.

Glucagon and VIP in the retina

Immunoreactive glucagon and immunoreactive vasoactive intestinal polypeptide (VIP) have been demonstrated in neuronal elements in the retina of a number of species by immunohistochemistry. In the present study, the concentrations of glucagon-like and VIP-like material in retinae from different species were determined by radioimmunoassay. The retinal concentration of glucagon-like immunoreactivity was 10-35 pg/mg in goldfish, chicken, pigeon, and frog, whereas retinae from cow, pig, rabbit, and rat contained very little. Retinae from the latter four species were on the other hand rich in VIP-like material whereas retinae from cat, guinea pig, and goldfish contained very little. The glucagon-like immunoreactive material in chicken and frog retina was subjected to gel chromatography and high performance liquid chromatography (HPLC). The results indicate that the extracted protein is of similar molecular size as porcine pancreatic glucagon, distinct from porcine glicentin. VIP immunoreactive material extracted from bovine retina was similar in molecular size as authentic porcine VIP by gel chromatography.

Retinal neuropeptides in the skates, Raja clavata, R. radiata, R. oscellata (Elasmobranchii)

The distribution of immunoreactive neuropeptides was investigated in the retina of three species of skates (Raja clavata, R. radiata, R. oscellata), elasmobranch fish often used in electrophysiological work on the retina. Enkephalins, neuropeptide Y (NPY), substance P and glucagon were found in different types of amacrine cells. All four peptides appeared in cell bodies in the innermost part of the inner nuclear layer. Processes from the cells containing enkephalins were numerous and ramified throughout the inner plexiform layer. Processes from the cells containing glucagon were thick and rare, and were found throughout the inner plexiform layer, at times with a predominance in sublaminae 1 and 4. NPY-immunoreactive fibres appeared mainly in sublamina 1 but also in 2 or 3, and substance-P-immunoreactive fibres in sublaminae 1, 4 and 5. Antisera against somatostatin, VIP or neurotensin did not show any immunoreactivity in the skate retina.

Neuropeptide Y immunoreactive neurons in the guinea-pig uvea and retina

Neuropeptide Y (NPY) is a recently discovered, amidated 36 amino acid residue neuropeptide present in many but not all sympathetic noradrenergic neurons. In the guinea-pig eye, NPY immunoreactive fibers were found to have the same distribution as noradrenergic fibers except that there were fewer at the iris dilator, in the cornea, and in the chamber angle. In the anterior uvea, the NPY immunoreactive fibers disappeared after excision of the homolateral superior cervical sympathetic ganglion, whereas in the choroid, many NPY immunoreactive fibers remained, indicating that they originate elsewhere. NPY immunoreactivity thus is not found in all sympathetic adrenergic neurons nor is it found only in such nerve fibers. In the retina, NPY immunoreactive fibers formed a single layer of processes in sublamina 1 of the inner plexiform layer. NPY immunoreactive cell bodies were found in the innermost cell row of the inner nuclear layer. The immunoreactivity was concentrated to the hillock region of these cells.

Substance P fibres in the anterior segment of the rabbit eye

Some laboratories have obtained diverging results regarding the presence of substance P fibres in the cornea possibly because different antibodies were used. This has been further investigated by comparing results with several antibodies on identically treated sections from the anterior segment of rabbit eyes. In the uvea all antisera gave identical results showing substance P fibres in the iris and ciliary processes. In the cornea, on the other hand, polyclonal rabbit or guinea-pig antibodies gave high background fluorescence and no immunofluorescence fibres were detected. In contrast, the background staining was low with the monoclonal antibody so that substance p immunoreactive fibres could be demonstrated subepithelially, intraepithelially and in the corneal stroma.

Glucagon immunoreactive neurons in the retina of different species

Neurons displaying glucagon immunoreactivity were detected among the amacrine cells in the retina of goldfish, frog and pigeon. Nerve cell bodies were located in the inner nuclear layer with their processes ramifying in 2-3 more or less well-defined sublayers in the inner plexiform layer. The distribution of cell bodies and processes varied with the species. In pigeon retina two separate populations of glucagon immunoreactive neurons were found among the amacrine cells. In frog retina glucagon immunoreactivity was also discerned in cell bodies in the ganglion cell layer. These cell bodies sent processes outwards to the inner plexiform layer. No glucagon immunoreactive neurons were detected in the retina of the rat, rabbit, cat, pig or cow.

Substance P-immunoreactive nerve fibres in the anterior segment of the rabbit eye. Distribution and possible physiological significance

Substance P-immunoreactive nerve terminals were found in several locations in the anterior segment of the rabbit eye. In the iris they occurred in the sphincter muscle and were randomly distributed in the iris stroma with some fibres running close to the dilator muscle. In the ciliary body these immunoreactive elements were few and occurred within bundles of nerve fibres. while in the ciliary processes they were more numerous with a predominantly subepithelial location. Blood vessels in the anterior uvea were often surrounded by substance P-immunoreactive fibres. No substance P-fibres were found in the cornea, while the sclera contained very few such elements. Using conventional in vitro techniques it was found that the sphincter pupillae muscle of the iris responded to electrical stimulation with a contraction that was resistant to cholinergic and adrenergic blockade, but was inhibited by the neuronal blocker tetrodotoxin. This indicates the existence of a non-cholinergic, non-adrenergic neuronal mediator of the contractile response. Exogenously applied substance P produced a long-lasting contraction of the spincter muscle, an observation compatible with the view that substance P is the noncholinergic, non-adrenergic neurotransmitter involved.

Autoradiography of (3H)-5-hydroxytryptamine uptake in the retina of some mammals

The uptake of indoleamines into the retina of rats, rabbits, cows, pigs, baboons. Cynomolgus monkeys, and man was studied by fluorescence microscopy and autoradiography. Indoleamines were either injected intravitreally or the retinas were incubated with them. Fluorescence microscopy failed to show any indoleamine accumulating neurons in all species investigated except rabbit, confirming previous observations. However, autoradiography showed uptake in a distinct class of neurons in cows and pigs. These neurons had their cell bodies among the amacrine cells and most of their processes branched in the middle of the inner plexiform layer. This is in contradistinction to the dopaminergic neurons, which in cows and pigs have all their processes in the outermost sublamina of the inner plexiform layer. The fluorescence microscopy is quite sensitive to small variations in the indoleamine molecule. The discrepancy between the results with fluorescence microscopy and autoradiography therefore suggest that there is an active uptake mechanism for indoleamines in cows and pigs but that the substances are rapidly transformed to compounds not possible to detect in the fluorescence microscope. No specific indoleamine accumulating mechanism was detected in the retina of rats, baboons, cynomolgus monkeys, or man.

Somatostatin and VIP neurons in the retina of different species

Neurons displaying somatostatin or vasoactive intestinal polypeptide (VIP) immunoreactivity were detected among the amacrine cells in the retina of baboon, cynomolgus monkey, squirrel monkey, cow, pig, cat, rabbit, guinea-pig, rat, mouse, frog and goldfish. Generally, immunoreactive cell bodies were located in the inner nuclear layer with processes ramifying in three more or less well-defined sublayers in the inner plexiform layer. The density of the sublayers and their location varied with the peptide and species investigated. In most cases there was a sublayer in the outermost part (Ramon y Cajal's sublamina 1) of the inner plexiform layer and this sublayer was usually the best developed. In some species a few somatostatin fibres were also detected in the outer plexiform layer, suggesting that some interplexiform cells contain somatostatin. In the baboon VIP was found exclusively in interstitial amacrine cells which have their cell bodies and processes entirely within the inner plexiform layer.

VIP (vasoactive intestinal polypeptide)-immunoreactive neurons in the retina of the rat

Immunoreactive vasoactive intestinal polypeptide (VIP) was detected in a population of amacrine cells in the retina of the rat. Processes of these cells reach both the inner and outer half of the inner plexiform layer where they form sublayers. The VIP neurons are different from previously known amacrine cell types.