Network adaptation improves temporal representation of naturalistic stimuli in drosophila eye: II Mechanisms

Retinal networks must adapt constantly to best present the ever changing visual world to the brain. Here we test the hypothesis that adaptation is a result of different mechanisms at several synaptic connections within the network. In a companion paper (Part I), we showed that adaptation in the photoreceptors (R1-R6) and large monopolar cells (LMC) of the Drosophila eye improves sensitivity to under-represented signals in seconds by enhancing both the amplitude and frequency distribution of LMCs' voltage responses to repeated naturalistic contrast series. In this paper, we show that such adaptation needs both the light-mediated conductance and feedback-mediated synaptic conductance. A faulty feedforward pathway in histamine receptor mutant flies speeds up the LMC output, mimicking extreme light adaptation. A faulty feedback pathway from L2 LMCs to photoreceptors slows down the LMC output, mimicking dark adaptation. These results underline the importance of network adaptation for efficient coding, and as a mechanism for selectively regulating the size and speed of signals in neurons. We suggest that concert action of many different mechanisms and neural connections are responsible for adaptation to visual stimuli. Further, our results demonstrate the need for detailed circuit reconstructions like that of the Drosophila lamina, to understand how networks process information

Comparative review of human and canine osteosarcoma: morphology, epidemiology, prognosis, treatment and genetics

Osteosarcoma (OSA) is a rare cancer in people. However OSA incidence rates in dogs are 27 times higher than in people. Prognosis in both species is poor, with five year osteosarcoma survival rates in people not having improved in decades. For dogs, one year survival rates are only around ~45%. Improved and novel treatment regimens are urgently required to improve survival in both humans and dogs with OSA. Utilising information from genetic studies could assist in this in both species, with the higher incidence rates in dogs contributing to the dog population being a good model of human disease. This review compares the clinical characteristics, gross morphology and histopathology, aetiology, epidemiology, and genetics of canine and human osteosarcoma. Finally, the current position of canine osteosarcoma genetic research is discussed and areas for additional work within the canine population are identified

Utilização de implante ósseo cortical alógeno conservado em glicerina para preservação de membro torácico: estudo experimental em cães A limb sparing surgery with the use of a cortical allograft preserved in glicerin: an experimental study in dogs

A técnica de preservação de membro é uma alternativa à amputação em cães com osteossarcoma do esqueleto apendicular. OBJETIVO: O desenvolvimento da técnica preservadora aos moldes da original descrita por Straw¹. MÉTODOS: O procedimento cirúrgico foi realizado com modificações, substituindo-se o método de conservação dos implantes pela glicerina e o cimento ósseo utilizado no preenchimento do canal medular do implante pela poliuretana de mamona, e para avaliação da incorporação do implante foram feitos exames clínico, radiográfico e histopatológico em diferentes tempos pós-operatórios. RESULTADOS: Observada a boa função do membro no pós-operatório, a formação de calo ósseo e fechamento das linhas de interfaces com remodelação óssea em avaliação radiográfica e ao exame histopatológico foi notada a reabsorção do implante ósseo com sua substituição por tecido conjuntivo fibroso e tecido ósseo compacto, neovascularização e presença de infiltrado inflamatório plasmocitário. CONCLUSÕES: A poliuretana de mamona mostrou-se uma boa substituta ao cimento originalmente utilizado, aumentando a resistência do implante, sem causar reações do tipo corpo estranho e sem sua osteointegração. O implante ósseo conservado em glicerina apresentou ação osteoindutora e osteocondutora, sem sinais de rejeição; desta forma, a glicerina mostrou ser uma meio alternativo viável. Portanto, a técnica de preservação do membro, com suas modificações, caracterizou-se como alternativa à técnica original e à amputação do membro para cães com osteossarcoma de esqueleto apendicular.<br>A limb-sparing surgery can be an alternative treatment to amputation for dogs with appendicular osteosarcoma. PURPOSE: The purpose of this study was the development of this surgical technique, similar to the original, described by Straw¹, with changes in the procedure of the allografts preservation, and in the bone cement chose to be used intramedullary. METHODS: The surgery was performed in six health dogs, with the osteotomy of one-third of the radio and ulna, section of the distal margin in the radio-carpal joint and reconstruction using a cortical allograft preserved in 98% glycerin. The allograft's medullar channel was filled with a polymer extracted from castor oil (Ricinus communis) and a long dynamic compression plate were used to fix this allograft on the radio, carpal joint and 3rd metacarpal bone, with the arthrodesis of the carpal joint. A medio-lateral radiographs was performed immediately posteoperatively and with 7, 15, 30, 45, 60, 90, 120 and 150 days after surgery, to evaluate the allograft incorporation. The histopatological evaluation was done with 90, 120 and 150 days after surgery. RESULTS: Was notice a bone callus formation on the radiogrhphs exams by 60 days after surgery and bone bridges were closing the interfragmentary space, with remodeling by 90 days. We have noticed resorption of the grapht, with formation of a connective tissue and new bone around the polymer on the histophatological evaluation. A neovascularization and inflammatory cells in the connective tissue was noticed with a decreased in the inflammatory process with the time. CONCLUSIONS: The polymer extracted from castor oil showed to be a good substitute for the bone cement originally used in the limb-sparing surgery, increasing the graft resistance with no foreign body reaction or osteointegration. The allograft preserved in glycerin presented onteoinduction and osteocondution actions, with new bone formation, and no signs of rejection, then, the glycerin showed to be a good alternative preservation procedure. Therefore, the modified technique can be considered an alternative to the original limb-sparing surgery and to amputation for dogs with appendicular osteosarcoma, studies still deserve to be done with sick animals