The problem of over-medicalisation: How AOD disease models perpetuate inequity for young people with multiple disadvantage.

Young people who experience multiple disadvantage have been identified as some of the most marginalised and under-serviced people in the alcohol and other drug (AOD) system. In this paper, we draw on a range of research evidence to argue that one of the challenges in responding appropriately to the needs of these young people are models of care which seek to ameliorate 'illness' rather than promote wellness. While disease approaches have some important benefits, overly-medicalised AOD treatment responses also have negative impacts. We argue that disease models rest on understandings of substance use as an individual enterprise and thereby pay insufficient attention to the material disadvantage that shape young people's substance use, creating feelings of shame, failure and a reluctance to return to care if they continue to use. Additionally we draw on literature that shows how disease models construe young people's substance use as compulsive, perpetuating deficit views of them as irrational and failing to account for the specific meanings that young people themselves give to their substance use. By focusing on clinical solutions rather than material and relational ones, medicalised treatment responses perpetuate inequity: they benefit young people whose resources and normative values align with the treatments offered by disease models, but are much less helpful to those who are under-resourced,. We suggest that alternative approaches can be found in First Nations models of care and youth programs that attend to social, cultural, and material wellbeing, making living well the focus of treatment rather than illness amelioration.

Retinal function and histopathology in rabbits treated with Topiramate.

PURPOSE: To evaluate retinal function and histopathology in rabbits treated orally with the anti-epileptic drug topiramate. METHODS: Six rabbits were treated with a daily oral dose of topiramate during a period of eight months. Six rabbits receiving water served as controls. Blood samples were analyzed for determination of topiramate serum levels in order to ensure successful drug exposition. Standardized full-field electroretinograms (ERGs) were performed before treatment and then at 2, 3 and 8 months during the treatment period. After terminating treatment the rabbits were sacrificed and the morphology of the sectioned retina was studied. RESULTS: After eight months of treatment the full-field ERG demonstrated normal rod function in treated and control rabbits, but the light adapted 30 Hz flicker b-wave amplitude was significantly reduced in the treated rabbits. This was the case for both the light adapted (Wilcoxon signed ranks test, P = 0.046) and the dark adapted (Wilcoxon signed ranks test, P = 0.028) 30 Hz flicker response from the treated rabbits. Retinal immunohistology revealed a severe accumulation of GABA in amacrine cells and in the inner plexiform layer in 4 of 6 treated rabbits compared to the controls. CONCLUSIONS: Topiramate, orally administrated to rabbits, may cause a significant reduction of the retinal function demonstrated by the reduced b-wave amplitude in the full-field ERG, as well as changes in immunohistology characterized by a severe accumulation of GABA in the inner retina. The retinal dysfunction and the morphological changes indicate that topiramat may damage the retina, similarly to vigabatrin (another anti-epileptic drug).

Gap junction protein connexin43 is heterogeneously expressed among glial cells in the adult rabbit retina.

The immunohistochemical distribution and ultrastructural immunolocalization of connexin43 (Cx43) in the neural retina of the rabbit was investigated. Cx43 immunolabeling appeared in the form of distinct puncta distributed on different kinds of glial cells and exclusively in the myelinated fiber region of the neural retina. Double-label immunohistochemistry showed that the most obvious Cx43 labeling occurred at processes of glial fibrillary acidic protein-positive astrocytes and on vimentin-positive Müller cells. Cx43-immunoreactive puncta were also evident on cell bodies and processes of 2'-3'-cyclic nucleotide phosphodiesterase-labeled oligodendrocytes. As shown by electron microscopy, immunoreactivity to Cx43 was restricted to gap junctions among the macroglial cell population. The homologous interastrocytic and Müller cell-to-Müller cell, as well as the heterologous astrocyte-to-Müller cell and astrocyte/Müller-to-oligodendrocyte gap junctions were symmetrically labeled. Our results indicate a specific expression of Cx43 at gap junctions between macroglial cells located in the myelinated streak. The extensive Cx43 immunolabeling suggests a substantial amount of gap junctional coupling that establishes a macroglial syncytium.

Gamma-aminobutyric acid- and glutamic acid decarboxylase-immunoreactive neurons in the retina of different vertebrates.

The localization of gamma-aminobutyric acid (GABA)- and L-glutamate 1 carboxy-lyase (GAD)-immunoreactive neurons was compared in the skate, frog, pigeon, chicken, rabbit, and man. Horizontal cells show both GABA and GAD immunoreactivity in the skate, frog, and bird. Certain amacrine cells show GABA and GAD immunoreactivity in all species. The distribution of GABA- and GAD-immunoreactive cell bodies and cell processes was very similar, if not identical, in the skate and man. In the other species, cell populations with GAD immunoreactivity also showed GABA immunoreactivity. However, in the bird, frog, and rabbit, the GABA-immunoreactive amacrine cells were at least twice as numerous as the GAD-immunoreactive cells. In birds, the distributions of the GAD and GABA immunoreactivities were different in the sublayers of the inner plexiform layer. The reason for the difference is currently unknown. GABA-immunoreactive bipolar-like cells were seen in the frog.

Graft-host connections in long-term full-thickness embryonic rabbit retinal transplants.

PURPOSE: To establish neuronal connections in the rod and cone pathway between laminated rabbit retinal transplants and the host retina. METHODS: Fourteen adult rabbits received a complete full-thickness embryonic transplant. After survival times of 3 to 10 months, the retinas were studied under light microscope and with immunohistochemistry. Antibodies against protein kinase C (PKC), parvalbumin, and calbindin were used to label rod bipolar cells, AII amacrine cells, and cone bipolar cells, respectively. The AB5 antibody was used to label ganglion cells. RESULTS: The transplants displayed laminated morphology with layers parallel to the host retinal pigment epithelium. In the oldest specimens (10 months after surgery), laminated layers of graft and host approached each other and almost reconstructed the normal retinal appearance. The ganglion and cone bipolar cells of the host survived well, as was seen with AB5 and calbindin double-labeling. Connections between cone bipolar cells in the graft and ganglion cells in the host were not common. PKC-labeled rod bipolar cells and parvalbumin-labeled AII amacrine cells of host and graft showed sprouting activity directed toward an intermediate plexiform layer located between the graft and host. In specimens double-labeled with PKC and parvalbumin, this intermediate plexiform layer was seen to contain numerous PKC- and parvalbumin-labeled processes. Direct connections between rod bipolar and AII amacrine cells in host and graft were seen in the 10-month specimens. CONCLUSIONS: Full-thickness embryonic transplants survive for at least 10 months, and normal laminated morphology develops. Host and graft fuse and together contribute nerve cell processes to an intermediate plexiform layer. Direct graft-host contacts are also present between neuronal types that in the normal retina participate in the rod pathway.

Immunohistochemical analysis of the developing inner plexiform layer in postnatal rat retina.

PURPOSE: To investigate the development from early postnatal life to adulthood of neural cell processes that establish the circuitry of the inner plexiform layer (IPL). Emphasis was focused on the ontogeny of subsets of cGMP- and protein kinase C (PKC)immunoreactive amacrine and bipolar cells. METHODS: Paraformaldehyde-fixed postnatal and adult retinas were used for light microscopic analysis of immunohistochemical labeling of cryo-sections. Synthesis of cGMP in neural structures was achieved by means of an in vitro stimulation with a well-established nitric oxide donor. RESULTS: In vitro stimulation of postnatal and mature retina with the nitric oxide donor results in NO-activated cGMP synthesis in subsets of bipolar and amacrine cells. NO-activated cGMP immunoreactivity is expressed in specific cell populations during the first postnatal week. Other cell subsets, consisting of amacrine cells and rod bipolar cells, express PKC immunoreactivity during postnatal development. An increasing number of rod bipolar cells start to exhibit cGMP labeling after eye opening, and a colocalization with PKC is established in adult retinas. Processes from these cell populations terminate in several sublaminas in the developing IPL, but cGMP- and PKC-labeled terminals appear to be confined to ON-lamina as the retina matures. CONCLUSIONS: The development of cGMP- and PKC-labeled fibers within the IPL appears to be in concert with events of neural differentiation and synaptogenesis. These results suggest that the nitric oxide/cGMP signaling pathway and PKC may participate in activity-dependent processes during development that establish the mature circuitry of synaptic contacts within the IPL. The presence of cGMP in mature rod bipolar cells suggests a role in the signal transduction of rod bipolar cell-AII amacrine cell pathway.

GABA immunoreactivity in the retina.

Presumed GABA neurons were studied in chick, guinea pig, and rabbit retinae with an immunohistochemical procedure aimed at direct demonstration of the endogenous GABA. In all species, a subset of amacrine cells was immunoreactive, as well as numerous fibers in the inner plexiform layer. In the chick, immunoreactivity was also demonstrated in horizontal cells, and single cell processes could be distinguished in both plexiform layers. The study indicates that the endogenous stores of GABA in GABAergic neurons can be visualized with immunohistochemical techniques. This direct approach thus gives additional information and probably is less subject to nonspecific staining than the demonstration of enzymes linked to GABA synthesis and metabolism. It also gives superior resolution in comparison with the autoradiographic techniques currently used for demonstrating GABA neurons. Invest Ophthalmol Vis Sci 27:674-678, 1986.

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.

Growth of postnatal rat retina in vitro. Development of neurotransmitter systems.

In this study, we demonstrate that explanted neonatal rat retina can be maintained in culture for periods up to 3 weeks. The cultured retinas displayed a distinct layering that was almost identical to litter-matched retinas of the same age, but the majority of the ganglion cells did not survive and photoreceptor outer segments did not develop properly. Distinct synaptophysin immunoreactivity was expressed in both the inner and outer plexiform layers of cultured retina and the pattern mimicked that one observed in vivo. After 2-3 weeks in vitro, the inner retina expressed immunoreactivities to various components of the cholinergic and nitrergic transmitter systems, including nitric oxide activated cyclic GMP immunoreactivity. The investigated cell populations displayed similar distribution patterns as in situ, but morphological differences appeared in vitro. Such differences were mainly observed as irregularities in the arborization patterns in the inner part of the inner plexiform layer. We suggest that these discrepancies may arise as a result of reduced ganglion cell survival. Our observations demonstrate that some neurotransmitter systems develop in vitro and their neural circuitry appears similar to the in vivo situation. The presence of synapses, receptor proteins and transmitter substances implies that neural communication can occur in cultured retinas.

Correlations between cholinergic neurons and muscarinic m2 receptors in the rat retina.

Acetylcholine is well established as the neurotransmitter of starburst amacrine cells in the vertebrate retina but their function is poorly understood. We compared the distribution of muscarinic m2 receptors in the rat retina with the localization of the starburst cell processes. mAChR2 immunoreactivity appeared in a central band in the inner plexiform layer, which did not co-localize with the processes of the cholinergic amacrine cells. We found co-labelling of VAChT and ChAT making it highly unlikely that there are undetected cholinergic neurons in rat retina. Most mAChR2 receptors were located far from the cholinergic neurons, suggesting that most of them are unlikely to be associated with conventional cholinergic synapses.

Neurotransmitter localization in the skate retina.

The retina of the skate (Raja clavata, R. radiata and R. oscellata) was studied by autoradiography following intraocular injections or incubations with [3H]GABA, [3H]isoguvacine, [3H]glycine, [3H]dopamine or [3H]5-hydroxytryptamine. Fluorescence immunohistochemistry was also used to demonstrate the endogenous content, accumulation, and retention of 5-hydroxytryptamine. The [3H]GABA was taken up by glia, and [3H]isoguvacine failed to appreciably label any neurons. [3H]Glycine was accumulated by amacrine cells, possibly of two subtypes. The [3H]dopamine was taken up by a few rare cells in the inner nuclear layer, which sent processes into the inner plexiform layer. Both autoradiography and immunohistochemistry showed 5-hydroxytryptamine to be efficiently accumulated by two types of cells in the inner nuclear layer: a bipolar cell type and an amacrine cell type. The morphology of the bipolar cells suggests they are of the ON depolarizing type. Immunohistochemistry also demonstrated the retention of accumulated 5-hydroxytryptamine by these two cell types, and that the bipolar cells contained far less endogenous 5-hydroxytryptamine than the amacrine cells did. The latter cell type can be presumed to use 5-hydroxytryptamine as its neurotransmitter. The results show the distribution of presumed glycinergic, dopaminergic and indoleaminergic neurons. They also show that there are two fundamentally distinct types of indoleamine neurons, a bipolar cell type with a low and an amacrine cell type with a high content of 5-hydroxytryptamine.

Temporal disparity in pineal and retinal ontogeny.

The development of photoreceptors and two putative neurotransmitter systems in the pineal organ and retina was studied during embryogenesis in the three-spined stickleback Gasterosteus aculeatus L. The investigation was performed by aid of immunocytochemistry using well characterized antisera to the retinal proteins alpha-transducin (TD alpha) and S-antigen (SA) (photoreceptor-markers), antisera against L-glutamic acid decarboxylase (GAD), gamma-aminobutyric acid (GABA), choline-O-acetyltransferase (ChAT) and with acetylcholinesterase (AChE) histochemistry (neurotransmitter-markers). It was possible to set up the following developmental time-table concerning the first appearance of positive immuno- and enzyme-reactive cells in the pineal organ and retina: I AChE-activity and TD alpha- and SA-immunoreactive cells in the pineal organ; II GAD- and GABA-immunoreactive cells in the pineal organ and retina; ChAT immunoreactivity and AChE activity in the retina; III hatching; IV SA-immunoreactive cells in the retina. The obtained results provide good evidence that while photoreceptor cells develop much earlier in the pineal organ than in the retina, neurons develop simultaneously in the pineal organ and retina.

Mercury accumulation in the squirrel monkey eye after mercury vapour exposure.

Squirrel monkeys were exposed to mercury vapour at different concentrations and for different numbers of days. The calculated total mercury absorption ranged between 1.4-2.9 mg (range of daily absorption 0.02-0.04 mg). The monkeys were killed at different intervals after the end of exposure (range 1 month - 3 years) and the eyes were enucleated. Eyes from four un-exposed monkeys were used as control material. Mapping of the mercury distribution in the eye revealed that the non-myelin-containing portion of the optic disc was densely loaded with mercury deposits, which are mostly confined to the capillary walls and the glial columns. The white matter of the brain does not accumulate mercury at these exposure levels, which might suggest that the myelinization process inhibits the accumulation of mercury. The pigmented epithelium of the pars plicata of the ciliary body and of the retina contained a considerable amount of mercury. This finding indicates that mercury is trapped within the melanocytes, which keeps potentially dangerous material from reaching the neural retina. In addition, the retinal capillary walls were densely loaded with mercury deposits, even 3 years after exposure. It was also found that the inner layers of the retina accumulated mercury during a 3-year period. It is known that the biological half-time of mercury in the brain may exceed years. This seems also to be the case for the ocular tissue.

Retinal glial cell immunoreactivity and neuronal cell changes in rats with STZ-induced diabetes.

PURPOSE: To study whether diabetes could influence glial cells, retinal neurons, and pigment epithelial cells and if so, to evaluate whether any changes could be influenced by aminoguanidine (AG) or probucol (PB). METHODS: Streptozocin (STZ)-induced diabetic male Wistar rats and age-matched control rats were fed a normal diet, addition of AG in the drinking water (0.5 g/l for diabetic and 1.0 g/l for control rats) or PB in the pellets (1 % w/w) for one or six months. Paraffin embedded retinal sections were incubated in the primary antibodies GFAP, calbindin, RPE65, and Hu, for glial, horizontal, pigment epithelial, and ganglion cells, respectively, and in fluorescent secondary antibodies. RESULTS: One month after STZ injection, GFAP immunoreactivity was sparse, but after six months it was prominent in glial cells in 5/5 diabetic and 1/7 control retinas (p = 0.015). Neither AG, nor PB influenced this immunoreactivity. Numbers of retinal pigment epithelial cells and cells in the ganglion cell layer, were similar at one and six months of diabetes. By time, the number of horizontal cells decreased (p < 0.001) and branching and numbers of their terminals were reduced (p < 0.001). CONCLUSION: Diabetes for six months resulted in increased glial cell immunoreactivity, and by age, horizontal cell numbers and branching of their terminals decreased, morphological patterns that were unaffected by AG or PB. The numbers of retinal pigment epithelial cells and cells in the ganglion cell layer were unaffected both by age and diabetes.

NPY-induced neurotransmitter release from the rabbit and chicken retina.

Neuropeptide Y (NPY) or closely related peptides are present in the retina of certain vertebrates, but their actions are not known. We have therefore studied the NPY-induced release of [3H]-GABA, [3H]-glycine, [3H]-dopamine, [3H]-5-hydroxytryptamine, and [3H]-choline chloride-derived radioactivity in the rabbit and chicken retina. NPY affected the release of [3H]-glycine, [3H]-dopamine, [3H]-5-hydroxytryptamine, and [3H]-choline chloride-derived radioactivity in rabbit retina and of [3H]-GABA, [3H]-5-hydroxytryptamine and [3H]-choline chloride-derived radioactivity in chicken retina in an energy requiring, NA+K(+)-ATPase dependent and calcium dependent manner. Certain related peptides, APP (= avian pancreatic polypeptide), BPP (= bovine pancreatic polypeptide), and PYY (= peptide YY), had variable and less pronounced effects. The results suggest a neurophysiological role in both chicken and rabbit retina for NPY or some related peptide.

Mercury distribution in the squirrel monkey retina after in Utero exposure to mercury vapor.

Pregnant squirrel monkeys were exposed to mercury vapor during approximately 2/3 of a pregnancy, at a concentration of 0.5 or 1 mg Hg/m(3) air for 4 or 7 h a day, 5 days a week. The offspring were sacrificed at different ages (gestational week 16 to 5 years). The eyes were enucleated and horizontal sections of the retina, comprising the optic disc and the fovea, were processed for autometallographic (AMG) silver enhancement. The AMG mercury distribution was mapped using light and epipolarization microscopy. In young offspring (16-week-old fetus to 3 days old), mercury was detected mainly in the optic nerve, retinal pigment epithelium, inner plexiform layer, vessel walls, and ganglion cells. Three and a half months later, the amount of visualized mercury had decreased in all areas except for the retinal pigment epithelium. In adult monkeys that had survived for 2 to 5 years, only a faint AMG staining was seen in the retinal pigment epithelium, the optic nerve, and in some vessel walls. In conclusion, in offspring sacrificed in utero or shortly after birth, the structures accumulating mercury were the same as those which accumulate mercury following direct exposure through the lungs, as reported previously (K. Warfvinge and A. Bruun, 1996, Toxicology 107, 189-200), although the amount of AMG staining was less in transplacental animals. This demonstrates that inorganic mercury penetrates the blood-retina barrier. In monkeys that had survived 3 to 5 years, only tiny amounts of mercury were detected, which is in contrast to findings from direct exposure, in which large amounts were still found 3 years after exposure. This may suggest that the elimination process in the retina is more efficient in young animals, but a possible adverse effect of mercury on retinal development cannot be ruled out.

Characterization of neuropeptide Y-like immunoreactivity in vertebrate retina.

We have determined the endogenous levels of neuropeptide Y-like immunoreactivity (NPY-LI) in retinal extracts from pigs, cats, rabbits, chickens, and frogs by radioimmunoassay (RIA). The NPY-LI levels varied among the species. The highest concentration was found in frog retina, where seasonal variations were seen, 861 +/- 31 pmol g(-1) wet weight in the autumn and 334 +/- 26 pmol g(-1) wet weight in the spring. Lower levels were demonstrated in chicken and pig retina, 4.1 +/- 0.4 and 3.6 +/- 0.3 pmol g(-1) wet weight, respectively. The lowest concentration was demonstrated in rabbit retina, 2.0 +/- 0.3 pmol g(-1) wet weight. (All values are expressed as mean +/- S.E.M.). The NPY-LI in pig, rabbit, chicken and frog retina was characterized by high-performance liquid chromatography (HPLC). The main part of the extracted NPY-LI had an elution volume close to that to the porcine NPY. We have also analysed the evoked release of endogenous NPY from frog retina, induced either with light flashes (3 Hz, 300 lx), or with potassium depolarization of the neurons (40 mM). Light flashes and potassium induced an increased release of NPY-LI of 61 and 77%, respectively. NPY-LI in the efflux had the same HPLC retention time as that extracted directly from the retina.

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.

Colocalization of (3H)-adenosine accumulation and GABA immunoreactivity in the chicken and rabbit retinas.

Using combined autoradiography and immunohistochemistry, we have compared (3H)-adenosine accumulation and GABA immunoreactivity in the chicken and rabbit retinas. Colocalization of the two markers was observed in a subset of amacrine cells and in certain cell bodies in the ganglion cell layer in both species and in a few horizontal cells in the chicken retina. Cells that contained only (3H)-adenosine or GABA were also seen. The degree of colocalization differed greatly between the two species. The results demonstrate a morphological relationship between the adenosine and GABA systems and provides information on the possible anatomical substrates underlying at least some types of functional interactions.