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INTRODUÇÃO: O tratamento cirúrgico das estenoses uretrais com enxertos limita-se ao emprego de materiais orgânicos, mais freqüentemente autoenxertos. O sucesso no uso de biomateriais sintéticos em diferentes áreas da medicina motivou a pesquisa desses materiais na reconstrução uretral. A informação de que o uso de prótese mamária de silicone recoberta com espuma de poliuretano revelou menor retração cicatricial que as próteses convencionais e o fato desses polímeros já serem empregados como elastômero na confecção de cateteres urinários, levou à escolha deste material para estudo. MÉTODOS: Foi realizada a ressecção de segmento dorsal da uretra anterior de 20 coelhos machos NZW. O defeito uretral foi tratado com o implante no leito uretral dorsal de uma placa não tubularizada de silicone, revestida externamente com espuma de poliuretano (Si-Pu). Como controle foi confeccionado o grupo Sham (GS) com 12 animais. Este grupo foi submetido à uretrotomia dorsal longitudinal e uretrorrafia, sem qualquer tipo de implante. As análises foram feitas com 2, 4, 8 e 24 semanas após a cirurgia. Analisaram-se alterações da circunferência da uretra e complicações cirúrgicas. Fez-se estudo histológico com coloração de Tricrômico de Mason, Hematoxilina-eosina e Picrosírirus red. Foram avaliadas: intensidade e características da resposta inflamatória, espessura da parede da uretra (edema) e concentração do colágeno na submucosa da uretra. Foi realizada análise microbiológica e pesquisa de incrustação do implante por termogravimetria. Os achados foram comparados com os dados de três coelhos que não sofreram qualquer intervenção. RESULTADOS: Não foram encontradas fístulas, estenoses, obstrução, calcificação, retração cicatricial ou deiscências. Ocorreu expulsão do implante em 1/5 dos animais após 4 semanas, em 2/5 com 8 semanas e em 3/5 com 24 semanas. Não houve redução da circunferência da uretra na comparação entre os grupos Experimental (GE) e GS, exceto para o intervalo de 8 semanas. Ocorreu infecção do sítio cirúrgico em 11 de 12 animais do GS e em 13 de 20 animais do GE. As bactéria mais comumente encontradas foram Staphylococcus DNAse negativa (9/32) e Escherichia coli (5/32). A presença de infecção por Enterobacter cloacae foi acompanhada de menor ganho de peso pelos animais (P=0,02), fato não observado na infecção com outras bactérias. A circunferência uretral foi maior (P=0,006) na vigência de infecção por Staphylococcus do que nas amostras estéreis. A histologia do GE mostrou processo inflamatório severo e substituição das fibras musculares da lâmina própria por colágeno com regressão do edema e das células inflamatórias, tardiamente. No GS ocorreu deposição tardia de colágeno e inflamação leve, porém constante. Houve re-epitelização da uretra nos dois grupos. A concentração de colágeno na área manipulada foi maior apenas na comparação entre os GE e GS com 24 semanas (P<0,001). O edema da parede uretral foi maior no GE que no GS nos intervalos de 2 semanas e de 4 semanas com P<0,001, e após 8 semanas com P<0,05. Após 24 semanas não se verificou diferença entre as espessuras da submucosa. Na análise descritiva da termogravimetria observou-se incrustação de material orgânico no implante, que não se mostrou significante estatisticamente na análise quantitativa de perda de massa. A incrustação de material inorgânico ao implante foi desprezível. CONCLUSÕES: O uso do Si-Pu leva à formação de cápsula colágena que permite a re-epitelização da uretra sem ocasionar retração local, funcionando como um biomolde, porém a expulsão do implante limita seu uso / BACKGROUND: Actually, the treatment of urethral stenosis employs biological grafts, usually autologous grafts. The success with synthetic biomaterials in others medical specialtys motivated the search of these materials in urethral reconstruction. The knowledge about the silicone mamarian prosthesis covered with polyurethane foam reduces capsular contracture in breast implants and because these polymers are already used in the urinary tract like catheters make the choice for these materials. METHODS: The resection of dorsal segment of anterior urethra of 20 male rabbits NZW was carried through. The urethral defect was treated with the on lay dorsal graft in urethra, compound a silicone not tabularized, coated with polyurethane foam in one face (Si-Pu). The control group (sham) was confectioned with 12 animals was submitted to longitudinal dorsal uretrotomy and suture, without any type of implantation (SG). The analyses intervals were 2, 4, 8 and 24 weeks after surgery. The circumference of urethra and surgical complications had been analyzed. Material for histological evaluation was stained with Massons thrichrome, hematoxylin and eosin and Picrosirius red. Intensity and characteristics of the inflammatory response, thickness of the urethra (oedema) and concentration of the collagen in the submucosa had been evaluated. Still, was performed microbiological analysis and research of implants incrustation with thermogravimetry. The findings had been compared with the data of three rabbits that had not suffered any intervention. RESULTS: The morfological analysis not founded fistula, obstruction, stenosis, cicatricial retraction, calcification and dehiscence. The graft was extruded after 4 weeks in 1/5 of the animals, in 2/5 after 8 weeks and after 24 weeks, 3/5 of the animals had failure of union with the surrounding tissue. Except for the interval of 8 weeks, It did not have urethral circumference reduction in the comparison between groups, Experimental (EG) and SG. Infection of the surgical place occurred in 11 of 12 animals of the GS and in 13 of 20 animals of EG. Staphylococcus DNAse-negative and Escherichia coli were the most frequent bacterium founded, and occurred in 9/32 and 5/32, respectively. The infection with Enterobacter cloacae was associated to lesser weight gain for the animals (P=0,02), fact not observed in infection with other bacteria. The Staphylococcus infection was associated to larger urethral circumference (P=0,006), when compared to sterile samples. The EG histological analysis showed early severe inflammatory process and substitution of smooth muscle fibers for collagen and regression of edema and inflammatory cells decrease laterly. Occurred delayed deposition of collagen and slight inflammation in the SG, however this process was constant. Was observed urothelial reepithelialization in both groups. The collagen concentration in urethral wall at surgical site was larger in EG with 24 weeks when compared to SG at same time (P< 0.001). There was significantly less urethral wall oedema in SG at 2 weeks, at 4 weeks (P< 0.001) and after 8 weeks (P< 0,05) than EG at the same time. After 24 weeks no difference was verified in submucosa thickness between the groups. The descriptive thermogravimetric analysis showed graft incrustation with organic material, however without statistic significance in quantitative analysis of mass loss. The inorganic graft incrustation was negligible. CONCLUSIONS: The use of Si-Pu implants in urethra originated a fibrous collagen capsule that allows reepitelialization without local contracture, like a biological skeleton. Nevertheless, grafts extrusion limits their clinical employment

O tratamento das lesões ósseas cavitárias com autoenxerto ainda é considerado o padrão-ouro. Seu uso, entretanto, é limitado, devido principalmente à baixa disponibilidade e à morbidade do sítio doador. Os enxertos ósseos sintéticos são estudados com o objetivo de superar as limitações decorrentes da retirada de autoenxerto ou da disponibilidade de bancos de tecidos. O vidro bioativo é um material sintético osteoindutor, osteocondutor e antibacteriano, à base de sílica e cria um arcabouço para o crescimento ósseo. Objetivo: comparar o vidro bioativo com o autoenxerto, com relação às características histomorfométricas. Métodos: foi realizado um estudo experimental prospectivo caso-controle em animais, para comparar o vidro bioativo com o autoenxerto com relação às características histomorfométricas. Oito coelhos foram submetidos a uma cirurgia em que um defeito cavitário foi criado em ambos os fêmures proximais; de um lado, o defeito ósseo criado foi preenchido com os grânulos de vidro bioativo; do outro, o defeito ósseo foi preenchido com o autoenxerto retirado do lado contralateral. Os lados foram randomizados. Catorze dias após a cirurgia os animais foram sacrificados. Resultados: a análise histológica revelou que a neoformação óssea entre os dois grupos foi equivalente, e que a contagem de osteoblastos foi superior nos fêmures tratados com vidro bioativo. A contagem de osteócitos, por outro lado, foi menor. A semelhança na intensidade de neoformação óssea coincide com o encontrado na literatura. As diferenças de contagem celular são concordantes com o mecanismo de ação do vidro bioativo: aumento do turnover ósseo, estímulo dos osteoblastos e retardo na sua diferenciação para osteócitos. Conclusão: o vidro bioativo promove neoformação óssea semelhante ao autoenxerto neste modelo animal de defeito ósseo cavitário. Nível de evidência III, estudo caso-controle / Autograft is still considered the gold standard in the treatment of cavitary bone lesions. The low availability and donor site morbidity, however, limits its use. Synthetic bone grafts have been studied in order to overcome the limitations of autograft or allograft. Bioactive glass is an osteoinductive, osteoconductive and antibacterial silica-based synthetic material. It promotes the creation of a scaffold for bone growth. Objectives: to compare bioactive glass and autograft regarding their histomorphometric characteristics. Methods: the author conducted a prospective case-control experimental study on animals, to compare the histomorphometric characteristics of bioactive glass versus autograft. Eight rabbits underwent surgery in which a cavitary defect was created in both proximal femurs. On one side, the bone defect was filled with bioactive glass granules and on the other, the defect was filled with autograft grafted from the contralateral side. The sides were randomized. Fourteen days after surgery, the animals were euthanized. Results: histologic analysis revealed that bone neoformation was equivalent among the two groups and the osteoblasts cell-count was higher in the femurs treated with bioactive glass. The osteocytes cell-count, however, was lower. The similarity in bone formation between both groups was also found in the literature. The differences in cell-count of osteocytes and osteoblasts are in accordance with the mechanism of action of the bioactive glass: increase in bone turnover, stimulation of osteoblasts and inhibition of their differentiation into osteocytes. Conclusion: bioactive glass is similar to autograft regarding bone neoformation, in this animal model of cavitary bone defects. Level of evidence III, case-control study

Aspects of the ecology of B. monticularis were studied with a view to the species' conservation. This investigation indicates that the present distribution is half that of the past distribution and that only one third of the original habitat remains uncultivated. It is estimated that this area could, theoretically, support 1435 rabbits. The shrubs, Pteronia erythrocaetha and Kochia pubescens constitute the bulk of the species' diet; grasses are included in the diet whenever rainfall gives rise to new growth. Spatial use, social structure and activity pattern conform to the general leporid pattern of polygamy, solitary living and nocturnality. The breeding season extends from August to May and litters of one, possibly two, altricial young are produced after a gestation of 35-36 days. / Dissertation (MSc)--University of Pretoria, 1989. / gm2013 / Zoology and Entomology / Unrestricted

In 220 rabbits (65 mature and 155 immature) the effects of dislocation, persistant dislocation and reduction at varying intervals (immediately, 12, 24 and 48 hours after dislocation) of the left hip were studied by microangiographic, histological and radiographic examination. Dislocation of the left hip was induced manually under anaesthesia by a doraally applied force with the hip held adducted and internally rotated. Reduction was effected by ventral traction with the hip in the same position. The right hip was untouched and used as a control in all cases. In 135 animals, a tracer dye was infused into the abdominal aorta proximal to its bifurcation under standard conditions of temperature and pressure. This infusion was done at 10 minutes, and at 1, 3, 5, and 7 days after dislocation or reduction. The femoral heads were then processed and studied under stereomicroscopy. Histological and radiographic studies were made in the remaining 85 animals at intervals between 3 and 10 weeks after dislocation or reduction. In immature animals, severe dye perfusion defecit was observed in all cases within 10 minutes of dislocation. This was maximal in the antero-medial half of the femoral head. The defecit was increased at 24 hours and persisted until 5 days after dislocation. At the seventh day recovery had commenced. A profound perfusion defecit was also noted within 10 minutes of immediate reduction, however, recovery was observed at 24 hours and was almost complete at 5 - 7 days. The rate of recovery in those animals in which the dislocation was reduced at 12, 24 and 48 hours did not differ from that observed in unreduced animals. In adult animals, significant circulatory disturbance was infrequently observed after dislocation and persistant dislocation. Consequently, the beneficial effects of reduction, if any, were obscured. The epiphyseo-metaphyseal vascular anastomoses across the epiphyseo scar were filled with dye in all mature rabbits and seemed to act as a route of blood supply and drainage in adult animals.. Extensive histological avascular necrosis of the femoral head was observed in the majority of animals, but was significantly more common in immature rabbits. Less extensive and less common avascular necrosis was observed in immature animals after immediate reduction. However, reduction delayed to 12 hours or later was not associated with a lower incidence of bone death. Abnormal radiological findings were common and varied. Specific alteration in density and outline of the femoral head was however infrequently observed, but corelated well with the histological findings. Decreased biodensity was associated with inbalanced bone resorption and hyperaemia, and increased radiodensity with bone death and new bone apposition. It is concluded that traumatic dislocation causes embarassment and sequential changes in the circulation within the femoral head in rabbits. The perfusion defecit is more severe in immature animals as the intra-osseous epiphyseo-metaphyseal vessels minimize this circulatory disturbance in adult animals. Early reduction enhances early and complete recovery of blood supply in immature animals. Varying degrees of avascular necrosis of the femoral head occur in both adult and immature animals with and without reduction, but is more common and extensive in immature animals. Abnormal radiological features within the femoral head are infrequently observed up to ten weeks after dislocation but correlate well with the histological findings when present. / Surgery, Department of / Medicine, Faculty of / Graduate

Vasopressin, a hormone released from the neurohypophysis, contributes to the regulation of body fluid balance through its known actions on the kidney and the vasculature. Release of vasopressin is influenced by plasma osmolality and by afferent activity from sensory receptors in the high and low pressure vascular systems. Previous studies have not defined the relative importance of the carotid sinus baroreceptors, aortic baroreceptors and atrial receptors in the control of the plasma concentration of vasopressin in the rabbit. Experiments were carried out in anaesthetized rabbits to define the quantitative relationship between stimulation of the carotid sinus baroreceptors and the plasma concentration of vasopressin. This relationship was examined in the presence and absence of afferent input from the aortic and atrial receptors. Changes in blood volume were induced to produce a change in the stimulus to the aortic baroreceptors and atrial receptors at high or low, constant carotid sinus pressure. Section, of the aortic depressor nerves and the vagus nerves allowed examination of the individual contributions of atrial receptors or aortic baroreceptors on the plasma concentration of vasopressin. It was also possible to examine the interaction between the carotid sinus baroreceptors and the aortic and atrial receptors. The results showed that plasma concentration of vasopressin was reduced by minimal stimulation of carotid sinus baroreceptors and that maximal inhibition of the release of vasopressin was achieved with a relatively low total arterial baroreceptor input. No influence of carotid sinus baroreceptors on vasopressin release was seen in the presence of intact aortic baroreceptors demonstrating the important interaction between the effects of stimulation of these two sets of receptors. It was not possible to demonstrate, in the rabbits used in this study, a significant contribution of atrial receptors to the control of vasopressin release either in response to changes in carotid sinus pressure or in response to changes in blood volume. To minimize the inhibitory effect of arterial baroreceptors on the release of vasopressin the aortic depressor nerves were cut and carotid sinus pressure was set at a low level. It was still not possible to demonstrate an effect of a reduction in blood volume on vasopressin release, confirming the absence of a contribution from atrial receptors in the anaesthetized rabbit. There appears to be considerable variation between species in the contribution of the different receptor groups to the release of vasopressin. The results suggest that in the normal rabbit there is likely to be significant tonic inhibition of the release of vasopressin by stimuli arising from arterial baroreceptors. The absence of a demonstrable influence of atrial receptors in these rabbits is consistent with findings in primates but differs from those in dogs. It is unlikely that changes in plasma vasopressin concentration induced by small changes in blood volume contribute to the control of arterial pressure through direct effects on vascular resistance and capacitance. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

Vasodilator and vasodepressor properties of angiotensins have been reported, and mediation by prostaglandins or nitric oxide has been proposed. Other studies indicate that angiotensin AT2 receptors might mediate a depressor action, and the present study was designed to delineate and explore this possibility in a conscious rabbit model. Large intravenous boluses of angiotensin III (15 nmol/kg) produced a predictable pressor peak (82±4 mm Hg) followed by a depressor phase (20±3 mm Hg), whereas equipressor doses of angiotensin II were less effective at producing depressor responses. Angiotensin-(1-7) did not exert a depressor action, and the reduced potency of angiotensin IV (relative to angiotensin III) was similar for both the pressor and depressor phases (≈100-fold). It is clear that specific angiotensin IV or angiotensin-(1-7) receptors do not mediate depressor effects in this model. The AT1 antagonist losartan (1 mg/kg) blocked both the pressor and depressor components of the angiotensin III response, whereas the AT2 antagonist PD 123319 (35 mg/kg) had no effect on either element of the response. The data obtained with the angiotensin receptor subtype-selective compounds, losartan and PD 123319, suggest that the depressor action is an AT1-mediated effect and give no indication that AT2 receptors could be involved. Paradoxically, the greater potency of angiotensin III as a vasodepressor belies the conclusion that the response is AT1-mediated, because AT1 receptors have a greater affinity for angiotensin II versus angiotensin III.