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).

Influence of laser irradiation on endogenous hyaluronan in rabbit iris and aqueous humor.

PURPOSE: To monitor changes of endogenous hyaluronan in the iris tissue and aqueous humor after an isolated trauma to the iris by argon laser irradiation of the anterior surface of the iris. METHODS: Iris and aqueous hyaluronan concentrations in rabbit were measured with a radiometric assay at different time points after laser irradiation. RESULTS: Total hyaluronan content in iris tissue increased 3-fold to a peak concentration of 71-72 microg/g at 1 and 2 days after laser treatment. Aqueous hyaluronan increased to a maximum of about 1.6 microg/ml at 2 h and 12 h after laser irradiation of the iris. CONCLUSIONS: The iris tissue responds with increased hyluronan synthesis to an isolated iris argon laser irradiation and it seems to be the most important source of aqueous hyaluronan.

Cone photoreceptors in laminated retinal transplants.

PURPOSE: To investigate the contents of green- and blue-sensitive cone photoreceptors in laminated rabbit retinal transplants. METHODS: Eleven rabbits each received a sheet of embryonic neuroretina into the subretinal space in one eye. Vitrectomy was used in the procedure and properly polarized flat transplants were placed on the host pigment epithelium. After 17-309 days the transplants were examined immunohistochemically with specific antibodies against COS-1 (green-sensitive cones) and OS-2 (blue-sensitive cones). RESULTS: All grafts displayed normal lamination with well developed photoreceptor outer segments apposed to the host retinal pigment epithelium. Occasionally, rosettes were found at the transplant edges. Both COS-1 positive and OS-2 positive cones were detected. In the laminated part of the grafts, COS-1 positive cones were more numerous than OS-2 positive ones. In the rosetted parts of the transplants the relationship between the cones was reversed. CONCLUSION: Full-thickness embryonic rabbit retinal transplants develop into laminated retinas with well-developed photoreceptor outer segment. Both green- and blue-sensitive cone photoreceptors are present and the ratio between the two cone types is the same as in the normal adult rabbit retina.

Immunohistochemical studies of cone photoreceptors and cells of the inner retina in feline rod-cone degeneration.

Previous studies using electroretinography and immunohistochemistry have shown normal cone function and structure in early stages of hereditary rod-cone degeneration of Abyssinian cats. To further investigate the cone photoreceptors and the inner retina of dystrophic cats, antibodies against green- and blue-sensitive cones and specific cell types of inner retina were used in seven cats with the recessively inherited rod-cone degeneration, and three normal European short-haired cats. There was a reduction in number of both types of cones early in the disease. Changes at early stages of disease also occurred among horizontal cells in which there was an extension and a thickening of their lateral processes. The regular configuration of bipolar cells was changed in the more advanced stages of disease and their apical dendrites were lost. Abnormalities were not observed in the amacrine cells and in the ganglion cell layer in any of the present cases. This study shows that the cone system is morphologically abnormal in young cats at an earlier stage of disease than previously shown. The present findings also support the assumption that the inner retina is largely preserved throughout the disease process.

Decreased reuptake of serotonin in human platelets after surgery.

We have documented earlier a decrease in platelet serotonin and a concurrent increase in plasma serotonin, 5-hydroxytryptamin (5-HT) after various forms of stress, suggesting a disturbed platelet 5-HT reuptake mechanism following stress. In order to further elucidate these findings, we have studied platelet 5-HT reuptake kinetics (Vmax and Km) in nine patients before and 4 days after major, uncomplicated abdominal surgery. We found a significant decrease in the maximal 5-HT reuptake velocity (Vmax) after surgery and changes in Km, verifying alterations in the affinity of the platelet 5-HT transport system. The present results thus confirm the hypothesis that 5-HT reuptake kinetics are altered following adrenergic hyperactivity. A decrease in platelet 5-HT reuptake may bear implications for our understanding of poststress adaptive changes in the cardiovascular system as well as in the central nervous system (CNS) serotonergic neurones following stressful stimulation.

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.

Synthesis of hyaluronan by normal and wounded rabbit iris.

BACKGROUND: Endogenous hyaluronan has been found in different tissues in the normal and traumatized eye. However, the main source, the biological aspects and the full potential role of hyloronan are still unclear. METHODS: Hyaluronan production was studied both in organ culture and in vivo, using a double-label protocol with [35S]sulfate and [3H]glucosamine. RESULTS: [3H]glucosamine and [35S]sulfate were incorporated into hyaluronan and sulfated glycosaminoglycans in normal and in traumatized iris tissue in organ culture and in vivo. There was low relative hyaluronan synthesis in vivo, only 2% of total incorporated [3H]glucosamine in normal irides. Increased relative incorporation of [3H]glucosamine into hyaluronan was seen after operative trauma to iris tissue both in vivo and in vitro. CONCLUSION: Our findings demonstrate synthesis of hyaluronan by normal and traumatized iris. The iris seems to be the most important source of aqueous hyaluronan.

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.

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.

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.

Development of glutamate receptor subunit 2 immunoreactivity in postnatal rat retina.

Previous studies have shown that the expression of glutamate receptor subunits is developmentally regulated and have been implicated in processes of cell differentiation during postnatal life. The tissue localization and developmental pattern of the glutamate receptor 2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA) receptor were investigated by means of immunohistochemistry and immunoblotting. Labeling of amacrine and ganglion cells and the inner plexiform layer appeared early during development, while glutamate receptor 2 subunit expression in the outer plexiform layer started after the first postnatal week. The distribution of labeling within the inner plexiform layer changed from nonorganized to laminated appearance prior to eye-opening. There was an increasing number of positive amacrine and ganglion cell somata during the first 2 weeks, but their number decreased considerably as the retina matured and were seen at least up to 35 days of postnatal development. Little labeling was found in the ganglion cell layer and in the inner plexiform layer of late postnatal and adult retina. Labeling in the outer plexiform layer and of bipolar cell somata appeared to increase in the developing retina. Glur2 labeling of these cells and the outer plexiform layer became discernible during the second postnatal week, and this labeling was present in the adult as well. Immunoblotting showed that GluR2 protein levels were similar at postnatal days 7 and 10, but slightly decreased between the second and fourth postnatal weeks. Our data imply that the immunological expression of glutamate receptor 2 subunit in the inner plexiform layer decreases as a function of age, and is correlated with developmental event(s) in the postnatal retina.

Expression of GABA transporter subtypes (GAT1, GAT3) in the adult rabbit retina.

PURPOSE: GABA transporters (GATs) are of importance for GABA signal systems. They have previously not been examined in rabbit retina, nor has their correlation with neurotransmitter GABA and GABA receptors been examined in the retina of any species. METHODS: The distribution of GATs, GABA and GABA receptors was examined with immunohistochemical methods. RESULTS: Both GAT1 and GAT3 immunoreactivities were found in the inner plexiform layer and in amacrine cells. GAT3 was also present in Müller cells. GAT1 appeared in amacrine cells that also had a high GABA concentration, but not in cells with moderate to low GABA concentration. GAT1 was also present in amacrine cells that did not show GABA immunoreactivity, possibly indicating a postsynaptic GABA uptake system. CONCLUSION: GAT3 is probably involved in both neuronal and glial GABA uptake whereas GAT1 is involved in predominantly neuronal uptake, and possibly also into non-GABA-ergic amacrine cells. Further, there may be at least two populations of GABA containing neurons.

Expression of GABA transporter subtypes (GAT1, GAT3) in the developing rabbit retina.

PURPOSE: Little is known about the expression of GABA transporters (GATs) in the developing retina. We have therefore examined the expression of GABA transporters (GAT1 and GAT3) in the developing rabbit retina. METHODS: The distribution of GATs was examined with immunohistochemical methods. RESULTS: GAT3 immunoreactivity appeared at PN0, whereas GAT1 immunoreactivity appeared first at PN3, both in the inner plexiform layer. From PN5 and onwards, both GAT1 and GAT3 immunoreactivity gradually appeared in numerous amacrine cell somas. At PN10, the immunostaining patterns and the distribution of both GAT1 and GAT3 were similar to that found in the adult rabbit retina. Full staining intensity was reached at PN20. CONCLUSION: GABA neurotransmission starts to develop already the first one to three days after birth, reaches the mature neuron pattern at about PN9 to PN10 but is not fully developed until about PN20. Neither GAT1 nor GAT3 appears to be involved in trophic actions by GABA in the prenatal retina.

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.

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 markers in full-thickness embryonic rabbit retinal transplants.

PURPOSE: To examine immunohistochemical markers in straight, well-laminated retinal transplants with special attention paid to the interphotoreceptor matrix, the Müller cells and the ganglion cells as these three retinal components have been abnormal in transplants produced by previous methods. METHODS: Nine rabbits underwent subretinal transplantation of a complete full-thickness embryonic neuroretina. After 31 or 49 days, the transplants were stained for light microscopy and processed for immunohistochemistry. RESULTS: Six of 9 eyes contained transplants with straight, well-laminated regions with all light-microscopic characteristics of a normal retina. In the outer segment region, the expression of peanut agglutinin showed segmental labeling of cone domains in the interphotoreceptor matrix, and interphotoreceptor retinoid binding protein immunoreactivity was found. Glial fibrillary acidic protein and vimentin immunoreactivity revealed normal Müller cell morphology. In 3 transplants the AB5-antibody-labeled ganglion cells in the ganglion cell layer and all transplants contained nerve fibers in the nerve fiber layer labeled by an antibody against neurofilament of 160 kD. The latter also labeled fibers connecting the transplant with the host. CONCLUSIONS: Full-thickness embryonic retinal transplants develop the normal retinal appearance and display several of the retinal components necessary for normal function which are not found in transplants produced by previous methods.

The expression of GABA(A) receptors during the development of the rabbit retina.

PURPOSE: Gamma-amino butyric acid (GABA) is a major inhibitory neurotransmitter in the retina, possibly participating in its normal development. The distribution of gamma-aminobutyric acid receptors was therefore examined in mature and developing rabbit retina by GABA(A) receptor alpha1 and beta2/3 subunit immunocytochemistry. RESULTS: Beta2/3 subunits appeared already at the E25 stage (25 days after gestation) although only weakly and irregularly. Alpha1 subunit immunoreactivity was first observed at birth. On the fifth postnatal day, immunostaining was clearly seen in the inner plexiform layer, and weaker, in the outer plexiform layer. There were at this stage no well-delineated sublayers in either the inner or the outer plexiform layer, but three clearly defined sublayers appeared in the inner plexiform layer at PN10. Amacrine cell bodies now also appeared, labelling for both the GABA(A) receptor alpha1 and the beta2/3 chains. A punctuate labelling appeared in the outer plexiform layer. From the 20th postnatal day, the immunoreactivity was similar to that seen in adult rabbits. CONCLUSIONS: Like in the adult, the alpha1 and beta2/3 subunits of the GABA(A) receptor thus colocalize predominantly in certain amacrine cells and in processes of the inner plexiform layer during the development of the retina. The GABA(A) receptors appear later than GABA during the development of the rabbit retina, and functioning GABA neurotransmitter circuits appear to be assembled primarily after the 3rd to 5th postnatal day. Our results support the hypothesis that GABA may have other functions than mediating classic synaptic neurotransmission before the formation of receptors containing the alpha1 and beta2/3 subunits. Like in the brain, the alpha subunits may have more selective functions during the development than the beta subunits.

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.