A rabbit eye model of neural ischaemia is described that uses an increased pressure in the anterior eye chamber to block the capillary supply to the retina. A microdialysis probe placed very close to the retinal surface was used to monitor release of amino acids during ischaemia. A large (two- to threefold) increase in the release of glutamate and O-phosphoserine (twofold), but not of six other amino acids monitored, occurred during initial ischaemia. During reperfusion after release of intraocular pressure, much larger (five- to 10-fold) increases in the release of these amino acids were observed. Parallel ischaemic retinal tissue damage was observed. This damage was prevented by ketamine applied locally via a superfusion needle, suggesting that glutamate released during ischaemia, and particularly during reperfusion, was responsible for cell death.

Resumo: O processo cicatricial compreende uma sequência de eventos moleculares e celulares que interagem para que ocorra a restauração do tecido lesado. Desde o extravasamento de plasma, com a coagulação e agregação plaquetária até a reepitelização e remodelagem do tecido lesado o organismo age tentando restaurar a funcionalidade tecidual. Assim, este trabalho abrange os diversos aspectos celulares envolvidos no processo cicatricial, bem como os principais medicamentos utilizados no tratamento de patologias relacionadas às deficiências na cicatrização. São abordados também, os aspectos econômicos referentes, sobretudo, às feridas crônicas de pés diabéticos. Palavras-chave: Agentes indutores da angiogênese; Cicatrização de feridas; Permeabilidade capilar Abstract: Wound healing is a dynamic interactive process that involves a sequence of molecular and cellular events. Recent advances in cellular and molecular biology have greatly expanded our understanding of the biological process involved in wound repair and tissue regeneration. From plasma extravasation, with coagulation and platelet aggregation, to reepithelialization and remodeling of injured tissue, the organism acts by trying to restore functionality tissue. Thus, the present study encompasses several cellular aspects involved in the wound healing process, as well as the main drugs used in treating the pathology related to wound healing complications. Economic aspects are also addressed, mainly related to chronic wounds of diabetic feet. Keywords: Angiogenesis inducing agents; Capillary permeability; Wound healing REVISÃO INTRODUÇÃOOs custos dos tratamentos de patologias relacionadas à deficiência cicatricial aumentam a importância dos estudos em busca de medicamentos e curativos capazes de interagir com o tecido lesado, tendo por objetivo acelerar o processo. Por exemplo, o retardo de cicatrização, como ocorre no caso de úlceras de pés diabéticos, constitui grave problema mundial, tanto financeiro quanto social. Dados dos Estados Unidos informam que 15,5% da população mundial com idade superior a 30 anos é composta de diabéti-cos, dos quais cerca de 15% desenvolvem úlceras de difícil cicatrização ao longo da vida, principalmente, nos membros inferiores. Assim, 6% das internações hospitalares relacionadas aos diabéticos são consequência dessas úlceras e, em caso de amputação, o tempo médio de internação é de cerca de três semanas. Esses casos geram para os sistemas de saúde custo extra que varia de U$ 8.000 a U$ 12.000/paciente. Dos amputados vão a óbito em cinco anos cerca de 39 a 68%. 1 No Brasil estima-se a existência de dois milhões de casos, entre os aposentados e os que recebem auxílios-doença em função da diabetes. 2 A cicatrização de feridas é processo complexo que envolve a organização de células, sinais químicos e matriz extracelular com o objetivo de reparar o tecido. Por sua vez, o tratamento de feridas busca o fechamento rápido da lesão de forma a se obter cicatriz funcional e esteticamente satisfatória. Para tanto, é indis-

The present study investigated the biocompatibility of a biopolymer based on vegetable latex extracted from the Hevea brasiliensis rubber tree, implanted into the bony alveolar cavity after dental extraction in rats. A granule of latex (area = 0.25 +/- 0.04 mm(2)) was implanted inside the alveolus immediately after extraction of the upper right incisor, and the animals were sacrificed 7, 21 and 42 days after the procedure. The hemi-maxillas were decalcified and processed for embedding in paraffin to obtain semi-serial longitudinal sections 5 mum thick, and then stained with hematoxylin-eosin. The latex granule was observed in the cervical third of the alveolus without any foreign body reaction, or persistence of the initial acute inflammatory reaction. Bone repair in the areas adjacent to the material was quantified, and a decrease was noted in the thickness of the fibrous capsule surrounding the implants from 92.8 +/- 9.3 microm on day 7 to 9.4 +/- 1.8 microm on day 42 (ANOVA, P = 0.01). The quantitative data confirmed acceleration of bone formation (statistically significant at 5%) in parallel with a decrease of connective tissue in the areas around the implants. These results show that the tested material is biologically compatible, and progressively integrated into the alveolar bone, simultaneously accelerating bone formation and playing an important role in the healing process.

1 In this study, we examined the effects of crude venom from the spider Parawixia bistriata on glutamate and GABA uptake into synaptosomes prepared from rat cerebral cortex. Addition of venom to cortical synaptosomes stimulated glutamate uptake and inhibited GABA uptake in a concentration-dependent manner. 2 The venom was fractionated using reverse-phase high-performance liquid chromatography on a preparative column. The fraction that retained glutamate uptake-stimulating activity was further purified on a reverse-phase analytical column followed by ion-exchange chromatography. 3 The active fraction, referred to as PbTx1.2.3, stimulated glutamate uptake in synaptosomes without changing the K M value, and did not affect GABA uptake. Additional experiments showed that the enhancement of glutamate uptake by PbTx1.2.3 occurs when ionotropic glutamate receptors or voltage-gated sodium and calcium channels are completely inhibited or when GABA receptors and potassium channels are activated, indicating that the compound may have a direct action on the transporters. 4 In an experimental model for glaucoma in which rat retinas are subjected to ischemia followed by reperfusion, PbTx1.2.3 protected neurons from excitotoxic death in both outer and inner nuclear layers, and ganglion cell layers. 5 This active spider venom component may serve as a basis for designing therapeutic drugs that increase glutamate clearance and limit neurodegeneration.

No abstract

Previous studies have shown that a compound purified from the spider Parawixia bistriata venom stimulates the activity of glial glutamate transporters and can protect retinal tissue from ischemic damage. To understand the mechanism by which this compound enhances transport, we examined its effects on the functional properties of glutamate transporters after solubilization and reconstitution in liposomes and in transfected COS-7 cells. Here, we demonstrate in both systems that Parawixin1 promotes a direct and selective enhancement of glutamate influx by the EAAT2 transporter subtype through a mechanism that does not alter the apparent affinities for the cosubstrates glutamate or sodium. In liposomes, we observed maximal enhancement by Parawixin1 when extracellular sodium and intracellular potassium concentrations are within physiological ranges. Moreover, the compound does not enhance the reverse transport of glutamate under ionic conditions that favor efflux, when extracellular potassium is elevated and the sodium gradient is reduced, nor does it alter the exchange of glutamate in the absence of internal potassium. These observations suggest that Parawixin1 facilitates the reorientation of the potassiumbound transporter, the rate-limiting step in the transport cycle, a conclusion further supported by experiments showing that Parawixin1 does not stimulate uptake by an EAAT2 transport mutant (E405D) defective in the potassium-dependent reorientation step. Thus, Parawixin1 enhances transport through a novel mechanism targeting a step in the transport cycle distinct from substrate influx or efflux and provides a basis for the design of new drugs that act allosterically on transporters to increase glutamate clearance.

No abstract

Increases in vascular permeability and angiogenesis are crucial events to wound repair, tumoral growth and revascularization of tissues submitted to ischemia. An increased vascular permeability allows a variety of cytokines and growth factors to reach the damaged tissue. Nevertheless, the angiogenesis supply tissues with a wide variety of nutrients and is also important to metabolites clearance. It has been suggested that the natural latex from Hevea brasiliensis showed wound healing properties and angiogenic activity. Thus, the purpose of this work was to characterize its angiogenic activity and its effects on vascular permeability and wound healing. The serum fraction of the latex was separated from the rubber with reduction of the pH. The activity of the dialyzed serum fraction on the vascular permeability injected in subcutaneous tissue was assayed according Mile's method. The angiogenic activity was determined using a chick embryo chorioallantoic membrane assay and its effects on the wound-healing process was determined by the rabbit ear dermal ulcer model. The serum fraction showed evident angiogenic effect and it was effective in enhancing vascular permeability. In dermal ulcers, this material significantly accelerated wound healing. Moreover, the serum fraction boiled and treated with proteases lost these activities. These results are in accordance with the enhancement of wound healing observed in clinical trials carried out with a biomembrane prepared with the same natural latex.