RESUMO
Following kidney donation, short-term quality of life outcomes compare favorably to US normative data but long-term effects on mood are not known. In the Renal and Lung Living Donors Evaluation Study (RELIVE), records from donations performed 1963-2005 were reviewed for depression and antidepressant use predonation. Postdonation, in a cross-sectional cohort design 2010-2012, donors completed the Patient Health Questionnaire (PHQ-9) depression screening instrument, the Life Orientation Test-Revised, 36-Item Short Form Health Survey and donation experience questions. Of 6909 eligible donors, 3470 were contacted and 2455 participated (71%). The percent with depressive symptoms (8%; PHQ-9>10) was similar to National Health and Nutrition Examination Survey participants (7%, p=0.30). Predonation psychiatric disorders were more common in unrelated than related donors (p=0.05). Postdonation predictors of depressive symptoms included nonwhite race OR=2.00, p=0.020), younger age at donation (OR=1.33 per 10 years, p=0.002), longer recovery time from donation (OR=1.74, p=0.0009), greater financial burden (OR=1.32, p=0.013) and feeling morally obligated to donate (OR=1.23, p=0.003). While cross-sectional prevalence of depression is comparable to population normative data, some factors identifiable around time of donation, including longer recovery, financial stressors, younger age and moral obligation to donate may identify donors more likely to develop future depression, providing an opportunity for intervention.
Assuntos
Emoções , Transplante de Rim , Doadores Vivos/psicologia , Adulto , Estudos de Coortes , Depressão/psicologia , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
The Renal and Lung Living Donors Evaluation Study assesses outcomes of live lung (lobectomy) donors. This is a retrospective cohort study at University of Southern California (USC) and Washington University (WASHU) Medical Centers (19932006), using medical records to assess morbidity and national databases to ascertain postdonation survival and lung transplantation. Serious complications were defined as those that required significant treatment, were potentially life-threatening or led to prolonged hospitalization. The 369 live lung donors (287 USC, 82 WASHU) were predominantly white, non-Hispanic and male; 72% had a biological relationship to the recipient, and 30% were recipient parents. Serious complications occurred in 18% of donors; 2.2% underwent reoperation and 6.5% had an early rehospitalization. The two centers had significantly different incidences of serious complications (p < 0.001). No deaths occurred and no donors underwent lung transplantation during 4000+ person-years of follow-up (death: minimum 4, maximum 17 years; transplant: minimum 5, maximum 19). Live lung donation remains a potential option for recipients when using deceased donor lungs lacks feasibility. However, the use of two live donors for each recipient and the risk of morbidity associated with live lung donation do not justify this approach when deceased lung donors remain available. Center effects and long-term live donor outcomes require further evaluation.
Assuntos
Doadores Vivos/estatística & dados numéricos , Pneumopatias/mortalidade , Pneumopatias/cirurgia , Transplante de Pulmão , Adolescente , Adulto , Estudos de Coortes , Bases de Dados Factuais , Feminino , Humanos , Tempo de Internação , Pulmão/cirurgia , Masculino , Pessoa de Meia-Idade , Controle de Qualidade , Projetos de Pesquisa , Estudos Retrospectivos , Resultado do Tratamento , Adulto JovemRESUMO
Live donation benefits recipients, but the long-term consequences for donors remain uncertain. Renal and Lung Living Donors Evaluation Study surveyed kidney donors (N = 2455; 61% women; mean age 58, aged 24-94; mean time from donation 17 years, range 5-48 years) using the Short Form-36 Health Survey (SF-36). The 95% confidence intervals for White and African-American donors included or exceeded SF-36 norms. Over 80% of donors reported average or above average health for their age and sex (p < 0.0001). Donors' age-sex adjusted physical component summary (PCS) scores declined by half a point each decade after donation (p = 0.0027); there was no decline in mental component summary (MCS) scores. White donors' PCS scores were three points higher (p = 0.0004) than non-Whites'; this difference remained constant over time. Nine percent of donors had impaired health (PCS or MCS score >1 SD below norm). Obesity, history of psychiatric difficulties and non-White race were risk factors for impaired physical health; history of psychiatric difficulties was a risk factor for impaired mental health. Education, older donation age and a first-degree relation to the recipient were protective factors. One percent reported that donation affected their health very negatively. Enhanced predonation evaluation and counseling may be warranted, along with ongoing monitoring for overweight donors.
Assuntos
Transplante de Rim , Doadores Vivos/psicologia , Complicações Pós-Operatórias , Qualidade de Vida , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos Transversais , Feminino , Humanos , Masculino , Prontuários Médicos , Pessoa de Meia-Idade , Nefrectomia , Obesidade , Grupos Raciais , Fatores de Risco , Fatores de Tempo , Adulto JovemRESUMO
While cautious criteria for selection of living kidney donors are credited for favorable outcomes, recent practice changes may include acceptance of less than ideal donors. To characterize trends in donor acceptance, the Renal and Lung Living Donors Evaluation (RELIVE) Study evaluated 8,951 kidney donors who donated between 1963 and 2007 at three major U.S. transplant centers. Over the study interval, there was an increase in the percentage of donors >40 years old from 38% to 51%; donors >60 years varied between 1% and 4%. The proportion of donors with obesity increased from 8% to 26% and with glucose intolerance from 9% to 25%. The percentage of hypertensive donors was consistent (5-8%). Accepted donors ≥60 years old were more likely to have obesity, glucose intolerance, and/or hypertension compared to younger donors (p<0.0001). Our results demonstrate important trends in acceptance of older and more obese donors. The fraction of older donors accepted with glucose intolerance or hypertension remains small and for the majority includes mild elevations in glucose or blood pressure that were previously classified as within normal limits.
Assuntos
Pressão Sanguínea , Transplante de Rim/métodos , Doadores Vivos/estatística & dados numéricos , Insuficiência Renal/terapia , Adulto , Idoso , Feminino , Intolerância à Glucose/complicações , Intolerância à Glucose/fisiopatologia , Humanos , Hipertensão/complicações , Hipertensão/fisiopatologia , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Obesidade/complicações , Obesidade/fisiopatologia , Sistema de Registros , Resultado do TratamentoRESUMO
Increasing donor yield, or the number of organs transplanted per donor, has been a focus of the transplant community in recent years. However, an exclusive focus on observed yield, unadjusted for the donor characteristics, ignores important differences between donors and donor case mixes in donation service areas (DSAs). We analyzed deceased donor registry data from the Organ Procurement and Transplantation Network/Scientific Registry of Transplant Recipients from January 2006 to December 2009 (N = 32 116 donors). Overall yields and kidney yields were modeled using ordinal logistic regression, and logistic regression was used to model heart, lung, pancreas and liver yields. Donor characteristics, including demographics, historical information and positive serology were related to overall and organ-specific yield. This study shows the potential value of the yield models as evaluation metrics and as tools that can inform DSA-wide practices in donor management and can improve organ utilization.
Assuntos
Modelos Teóricos , Doadores de Tecidos , Feminino , Humanos , MasculinoRESUMO
Despite the Organ Donation Breakthrough Collaborative's work to engage the transplant community and the suggested positive impact from these efforts, availability of transplanted organs over the past 5 years has declined. Living kidney, liver and lung donations declined from 2004 to 2008. Living liver donors in 2008 dropped to less than 50% of the peak (524) in 2001. There were more living donors that were older and who were unrelated to the recipient. Percentages of living donors from racial minorities remained unchanged over the past 5 years, but percentages of Hispanic/Latino and Asian donors increased, and African American donors decreased. The OPTN/UNOS Living Donor Transplant Committee restructured to enfranchise organ donors and recipients, and to seek their perspectives on living donor transplantation. In 2008, for the first time in OPTN history, deceased donor organs decreased compared to the prior year. Except for lung donors, deceased organ donation fell from 2007 to 2008. Donation after cardiac death (DCD) has accounted for a nearly 10-fold increase in kidney donors from 1999 to 2008. Use of livers from DCD donors declined in 2008 to 2005 levels. Understanding health risks associated with the transplantation of organs from 'high-risk' donors has received increased scrutiny.
Assuntos
Doadores de Tecidos/provisão & distribuição , Doadores de Tecidos/estatística & dados numéricos , Obtenção de Tecidos e Órgãos/estatística & dados numéricos , Obtenção de Tecidos e Órgãos/tendências , Negro ou Afro-Americano/estatística & dados numéricos , Hispânico ou Latino/estatística & dados numéricos , Humanos , Rim , Fígado , Doadores Vivos/estatística & dados numéricos , Pulmão , Grupos Minoritários/estatística & dados numéricos , Grupos Raciais , Estados Unidos/epidemiologiaRESUMO
Alterations in the expression of gap junction proteins have previously been observed in several diseases affecting the central nervous system; however, the status of connexin 43 (Cx43) has not yet been reported in spinal cord remyelination. We studied Cx43 expression in demyelination and remyelination by using a chronic guinea pig model of experimental allergic encephalomyelitis (EAE). Hartley guinea pigs were immunized with homogenized whole CNS and complete Freund's adjuvant. Animals became chronically ill by day 40 postimmunization, and animals with paralysis were entered into the study. Animals were treated on days 40-60 postimmunization with either saline or drugs that promote remyelination: an adenosine amine congener (100 mug/kg), an anti-alpha4-integrin blocker (CT301; ELN 69299; 30 mg/kg), or a combination of both drugs. Remyelination was induced in all drug-treated groups. Cx43 expression was virtually absent in demyelinated lesions of saline-treated controls compared with healthy tissue and normal appearing white matter (P < 0.001), whereas Cx43 was considerably increased (300-500%) in remyelinating lesions of all treatment groups (P < 0.001), most notably in CT301-treated animals. These changes in Cx43 expression indicate that Cx43 may beimportant for recovery from neuroinflammation.
Assuntos
Conexina 43/metabolismo , Conexinas/metabolismo , Encefalomielite Autoimune Experimental/metabolismo , Regeneração Nervosa/fisiologia , Recuperação de Função Fisiológica/fisiologia , Medula Espinal/metabolismo , Adenosina/análogos & derivados , Adenosina/farmacologia , Animais , Anticorpos/farmacologia , Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/fisiopatologia , Feminino , Cobaias , Integrina alfa4/efeitos dos fármacos , Integrina alfa4/imunologia , Bainha de Mielina/efeitos dos fármacos , Bainha de Mielina/imunologia , Bainha de Mielina/patologia , Regeneração Nervosa/efeitos dos fármacos , Recuperação de Função Fisiológica/efeitos dos fármacos , Medula Espinal/patologia , Medula Espinal/fisiopatologia , Regulação para Cima/fisiologiaRESUMO
PURPOSE: To determine the efficacy of a small molecule inhibitor of alpha4 integrin (CT301) at reversing the clinical, pathological and MR-detectable deficits associated with the acute phase of experimental allergic encephalomyelitis (EAE). MATERIALS AND METHODS: EAE was induced in 36 female Hartley guinea pigs, and the treatment period was from day 11 to day 17 post-immunization. Animals received either saline (n = 12), anti-alpha4 integrin antibody (AN100226m; n = 12) or CT301 (n = 12). T2-weighted fast spin echo and T1-weighted pre- and post-contrast scans were performed at the beginning (day 11) and end (day 18) of the treatment period, and scored for cerebral inflammation and gadolinium enhancement. T1-weighted images were further analyzed to quantify this enhancement as a measure of blood-brain barrier integrity. Dissected CNS was evaluated for inflammation and demyelination. RESULTS: CT301 successfully reversed two clinical indicators of disease over the course of the treatment period. These animals showed decreased T2-weighted abnormalities, as well as a reduction in gadolinium leakage on T1-weighted images. Meningeal and perivascular inflammation was decreased by anti-alpha4 integrin treatments. CONCLUSION: CT301 effectively reverses the clinical, pathological and MR-detectable deficits of acute EAE, and may therefore be a promising therapeutic agent in multiple sclerosis (MS).
Assuntos
Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/patologia , Integrina alfa4/metabolismo , Doença Aguda , Animais , Anticorpos/farmacologia , Edema Encefálico/tratamento farmacológico , Edema Encefálico/patologia , Sistema Nervoso Central/patologia , Meios de Contraste , Encefalomielite Autoimune Experimental/imunologia , Feminino , Gadolínio DTPA , Cobaias , Integrina alfa4/imunologia , Imageamento por Ressonância Magnética/métodos , Índice de Gravidade de DoençaRESUMO
Inhibition of alpha(4)beta(1) integrin blocks immune cell influx into the CNS providing benefit to patients with multiple sclerosis and in animal model systems. We have used this mechanism to examine whether the presence of inflammatory cells suppresses spontaneous myelin repair in experimental autoimmune encephalomyelitis. We observed (1) 87% of plaques showed remyelination after 40 days of treatment; (2) myelin repair occurred in half of the total lesion area; (3) half of the animals regained motor function. There was no significant repair or gain of motor function in vehicle-treated animals. Therefore, prolonged inhibition of CNS inflammation, in the absence of targeted myelin repair, facilitates mechanisms of spontaneous remyelination.
Assuntos
Encefalomielite Autoimune Experimental/fisiopatologia , Integrina alfa4/fisiologia , Bainha de Mielina/metabolismo , Regeneração Nervosa/fisiologia , Recuperação de Função Fisiológica , Animais , Anti-Inflamatórios/sangue , Anti-Inflamatórios/uso terapêutico , Doença Crônica , Modelos Animais de Doenças , Encefalomielite Autoimune Experimental/sangue , Encefalomielite Autoimune Experimental/tratamento farmacológico , Feminino , Cobaias , Imuno-Histoquímica/métodos , Atividade Motora/efeitos dos fármacos , Regeneração Nervosa/efeitos dos fármacos , Medula Espinal/efeitos dos fármacos , Medula Espinal/patologia , Medula Espinal/fisiopatologia , Linfócitos T/efeitos dos fármacos , Fatores de TempoRESUMO
CNS leukocytic invasion in experimental allergic encephalomyelitis (EAE) depends on alpha4beta1 integrin/vascular cell adhesion molecule-1 (VCAM-1) interactions. A small molecule inhibitor of alpha4beta1 integrin (CT301) was administered to guinea pigs in the chronic phase (>d40) of EAE for 10, 20, 30 or 40 days. CT301 elicited a rapid, significant improvement in the clinical and pathological scores that was maintained throughout the treatment period. A progressive loss of cells in the spinal cord of treated animals confirmed the resolution of inflammation associated with clinical recovery. Therefore, prolonged inhibition of alpha4beta1 integrin caused a sustained reversal of disease pathology in chronic EAE and may be similarly useful in MS.
Assuntos
Encefalomielite Autoimune Experimental/tratamento farmacológico , Integrina alfa4 , Animais , Doença Crônica , Citocinas/biossíntese , Citocinas/genética , Encefalomielite Autoimune Experimental/diagnóstico , Encefalomielite Autoimune Experimental/patologia , Feminino , Citometria de Fluxo , Cobaias , Cinética , Reação em Cadeia da Polimerase , RNA Mensageiro/biossíntese , Medula Espinal/patologiaRESUMO
The semaphorins constitute a large gene family of transmembrane and secreted molecules, many of which are expressed in the nervous system. Genetic studies in Drosophila have revealed a role for semaphorins in axon guidance and synapse formation, and several in vitro studies in mice have demonstrated a dramatic chemorepellent effect of semaphorin III (Sema III) on the axons of several populations of neurons. To investigate the function of Sema III during in vivo axon guidance in the mammalian CNS, we studied the development of axonal projections in mutant mice lacking Sema III. Projections were studied for which either the in vitro evidence suggests a role for Sema III in axon guidance (e.g., cerebellar mossy fibers, thalamocortical axons, or cranial motor neurons) or the in vivo expression suggests a role for Sema III in axon guidance (e.g., cerebellar Purkinje cells, neocortex). We find that many major axonal projections, including climbing fiber, mossy fiber, thalamocortical, and basal forebrain projections and cranial nerves, develop normally in the absence of Sema III. Despite its in vitro function and in vivo expression, it appears as if Sema III is not absolutely required for the formation of many major CNS tracts. Such data are consistent with recent models suggesting that axon guidance is controlled by a balance of forces resulting from multiple guidance cues. Our data lead us to suggest that if Sema III functions in part to guide the formation of major axonal projections, then it does so in combination with both other semaphorins and other families of guidance molecules.
Assuntos
Axônios/fisiologia , Encéfalo/crescimento & desenvolvimento , Glicoproteínas/deficiência , Fatores de Crescimento Neural/deficiência , Animais , Biomarcadores , Encéfalo/anatomia & histologia , Encéfalo/embriologia , Calbindinas , Peptídeo Relacionado com Gene de Calcitonina/análise , Córtex Cerebral/química , Córtex Cerebral/citologia , Glicoproteínas/fisiologia , Hibridização In Situ , Mesencéfalo/química , Mesencéfalo/citologia , Camundongos , Camundongos Knockout , Morfogênese , Neurônios Motores/química , Neurônios Motores/citologia , Fibras Nervosas/fisiologia , Fatores de Crescimento Neural/fisiologia , Células de Purkinje/química , Células de Purkinje/citologia , Células Piramidais/química , Células Piramidais/citologia , RNA Mensageiro/análise , Rombencéfalo/química , Rombencéfalo/citologia , Proteína G de Ligação ao Cálcio S100/análise , Semaforina-3A , Tálamo/química , Tálamo/citologiaRESUMO
A variety of factors, from cell adhesion to changes in intracellular calcium, are thought to influence neuronal migration. Here we examine the possibility that calcium influx mediated via NMDA receptors regulates migration of neocortical neurons. We have examined the cytoarchitecture of the cortex in transgenic mice lacking functional NMDA receptors. Using cell birthdating techniques we found that cells in the developing neocortex of NMDAR-1 mutant mice have a distribution indistinguishable from that in animals with functional NMDA receptors, implying normal rates and routes of migration. These observations contrast with previous in vitro pharmacological studies of cerebellar granule cell migration, in which a role for NMDA receptors has been demonstrated. Thus, either different mechanisms are responsible for controlling neuronal migration in neocortex versus cerebellum or, more likely, neocortical neurons in NMDAR-1 mutant mice have acquired compensatory mechanisms for cell migration.
Assuntos
Movimento Celular/fisiologia , Neocórtex/fisiologia , Neurônios/fisiologia , Receptores de N-Metil-D-Aspartato/deficiência , Receptores de N-Metil-D-Aspartato/fisiologia , Animais , Cálcio/metabolismo , Cálcio/fisiologia , Movimento Celular/genética , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Neocórtex/citologia , Neocórtex/crescimento & desenvolvimento , Receptores de N-Metil-D-Aspartato/genéticaRESUMO
Distinct classes of primary sensory neurons in dorsal root ganglia subserve different sensory modalities, terminate in different dorsoventral locations in the spinal cord, and display different neurotrophin response profiles. Large diameter muscle afferents that terminate in the ventral spinal cord are NT-3 responsive, whereas small diameter afferents subserving pain and temperature are NGF responsive and terminate in the dorsal spinal cord. Previous in vitro studies showed that the developing ventral spinal cord secretes a diffusible factor that inhibits the growth of sensory axons. Here we show that this factor repels NGF-responsive axons but has little effect on NT-3-responsive axons. We also provide evidence implicating semaphorin III/collapsin, a diffusible guidance molecule expressed by ventral spinal cord cells, in mediating this effect. These results suggest that semaphorin III functions to pattern sensory projections by selectively repelling axons that normally terminate dorsally.
Assuntos
Axônios/fisiologia , Gânglios Espinais/embriologia , Glicoproteínas/farmacologia , Neurônios Aferentes/fisiologia , Medula Espinal/embriologia , Animais , Axônios/efeitos dos fármacos , Sequência de Bases , Diferenciação Celular , Linhagem Celular , Gânglios Espinais/ultraestrutura , Expressão Gênica , Glicoproteínas/química , Glicoproteínas/genética , Humanos , Hibridização In Situ , Camundongos , Dados de Sequência Molecular , Fatores de Crescimento Neural/farmacologia , Neurônios Aferentes/ultraestrutura , Neurotrofina 3 , RNA Mensageiro/metabolismo , Ratos , Semaforina-3A , Homologia de Sequência , Medula Espinal/ultraestruturaRESUMO
Horizontal cells are among the first to mature in the neonatal mammalian retina and they are the first to establish the position of the outer synaptic layer which is subsequently formed by invading terminals of both rod and cone photoreceptors. During the period of cone synaptogenesis, horizontal cells transiently express the full complement of GABAergic properties (uptake, release, synthesis and storage of GABA); later during development of rod terminals, these properties are down-regulated. Given the reports of GABA's role in other developing neuronal systems (for review: 10), we have examined the effect that GABA, produced from horizontal cells, might have on photoreceptor maturation in rabbit retina. Results from our previous studies show that lesioning the horizontal cell with kainic acid in vivo leads to a displacement of cone photoreceptor cells and a disappearance of their synaptic terminals, while rod cells maintain their normal position and produce an overabundance of terminals. Similar effects are seen with the GABA-A receptor antagonists, picrotoxin and bicuculline. New evidence from 3H-thymidine studies suggests that the effects of kainic acid are specific and that cell division, migration and differentiation in other cell types do not appear to be affected. This body of work is summarized and possible mechanisms of action are suggested which could account for the apparent ability of GABA to help maintain the normal position of cone cell bodies and regulate cone synaptogenesis.
Assuntos
Retina/crescimento & desenvolvimento , Ácido gama-Aminobutírico/fisiologia , Animais , Animais Recém-Nascidos , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , DNA/biossíntese , Ácido Caínico/farmacologia , Células Fotorreceptoras/citologia , Células Fotorreceptoras/efeitos dos fármacos , Células Fotorreceptoras/crescimento & desenvolvimento , Coelhos , Retina/efeitos dos fármacos , Sinapses/fisiologia , Ácido gama-Aminobutírico/farmacologiaRESUMO
We have previously demonstrated that the neonatal rabbit retina contains a larger complement of cells that accumulate [3H]-GABA than does the adult. In order for these neurons to be classified as GABAergic, they must also contain endogenous GABA. We now report that these same neonatal cell populations are also immunoreactive to GABA antisera. In frozen sections from rabbit retina, treated with GABA antisera, immunoreactive processes in both synaptic layers were observed at postnatal day 1. The appearance of immunofluorescent fibers precedes that of photoreceptor and bipolar cell terminals in the outer plexiform layer and is diminished by postnatal day 5. Also noted, was a 50% decrease in the density of GABA-immunoreactive cell bodies in the inner nuclear and ganglion cell layers, accompanied by an increase in cell volume and a shift toward a more spherical cell shape of the remaining cells. At postnatal day 1 and 3, we also observed immunoreactive cells having the characteristic morphology of interplexiform cells. This cell type sends branches to both the outer and inner plexiform layers, thus a morphological basis for communication between the two developing plexiform layers is present as early as postnatal day 1. Thus, retinas from neonatal rabbits have a larger complement of cells that stain for endogenous GABA than does the adult. These results coupled with our previous studies suggest that GABAergic properties are expressed by a larger number of cell types in the neonate than in the adult and are consistent with the general hypothesis that GABA functions as a trophic agent during development.
Assuntos
Retina/metabolismo , Ácido gama-Aminobutírico/metabolismo , Animais , Imunofluorescência , Neurônios/metabolismo , Coelhos , Retina/citologia , Retina/crescimento & desenvolvimento , Células Ganglionares da Retina/metabolismoRESUMO
We have investigated two characteristics of the glutamate system in the developing rabbit retina. 1) Glutamate immunoreactivity was observed at birth within developing processes of four cell types; two of which, photoreceptors and ganglion cells, are known to be glutamatergic in the adult. Two other cell types, type A horizontal cells and amacrine cells, are immunoreactive to both glutamate and GABA at birth, suggesting that endogenous pools of glutamate in GABAergic neurons serve as precursor for GABA synthesis. Thus it appears that endogenous glutamate pools are present within neurons prior to synaptogenesis as part of the early expression of either the glutamate or GABA transmitter phenotype. 2) Analysis of 3H-glutamate metabolism during retinal development showed that rapid conversion of glutamate to glutamine does not occur until the second postnatal week, coincident with the expression of Muller (glial) cell activity. In the absence of glial metabolism in the neonate, extracellular concentrations of glutamate remain relatively high and are likely to have major effects on neuronal maturation.
Assuntos
Glutamatos/metabolismo , Retina/crescimento & desenvolvimento , Envelhecimento/metabolismo , Animais , Animais Recém-Nascidos , Ácido Glutâmico , Imuno-Histoquímica , Células Fotorreceptoras/metabolismo , Coelhos , Retina/citologia , Retina/metabolismo , Células Ganglionares da Retina/metabolismo , Ácido gama-Aminobutírico/metabolismoRESUMO
The first synaptic relay in the primary visual pathway occurs between terminals of photoreceptors and second-order neurons within the outer plexiform layer of the retina. During development, one of these types of second-order neurons, the type A horizontal cell, differentiates and assumes mature characteristics several days before any other cells ramifying in that synaptic layer. In neonates, horizontal cells appear to be GABAergic during the first 5 days of postnatal life and in addition they also are responsive to kainic acid. We have previously suggested that they may play a pioneering role in the postnatal development of the outer plexiform layer, perhaps providing structural guidance or trophic substances such as GABA, for synaptic development. To test this hypothesis, we first demonstrated that a single intraocular injection of kainic acid within 24 hr of birth results in a permanent and selective loss of type A horizontal cells in the outer retina. Retinas from animals maintained for 5 days postinjection were harvested for analysis of postnatal development of the outer plexiform layer in the absence of horizontal cells. One of the major findings was that kainic acid treatment caused a reversal of the normal complement of photoreceptor cell types, resulting in an abnormally high rod/cone ratio. The distribution of cell processes within the outer plexiform layer was also altered and normal synaptic connections were not made. In spite of these changes in the constituents of the outer plexiform layer, the normal position of the synaptic layer was not affected by the loss of horizontal cells. These results rule out the possibility that horizontal cells provide a structural barrier which is an absolute requirement for establishing the location of the outer plexiform layer. Rather, these cells may be more involved in cell differentiation and synaptogenesis.