Assessment of myelin thickness and axon circularity in a dorsal root of the mouse.

Previous studies of peripheral nerves and ventral roots have shown that myelin thickness increases non-linearly with axon size and that axon circularity may be dependent on axon size (e.g. Arbuthnott et al. 1980; Biscoe et al. 1982; Ceballos et al. 1999). In this study, we present preliminary data relating myelin thickness and axon circularity to axon size for the central end of a dorsal root in a mouse cervical segment. A CD1 strain mouse was anaesthetized with sodium pentobarbitone (50 mg.kg-1 I.P.) and fixed by transcardial perfusion with a Karnovsky fixative. The left C5 dorsal root ganglion, along with the corresponding dorsal and ventral roots, was removed and placed in fresh fixative overnight at 4°C. The tissue was post-fixed with OsO4 prior to embedding in Araldite. Semithin serial sections (0.5 μm) were cut using an ultramicrotome and stained with 1% toluidine blue in 1% borax. A composite photomicrograph of the central end of the C5 dorsal root was constructed with a resolution of 10 pixels/μm and a magnification of x1000. Areas and perimeters of nerve fibres (axon plus myelin) and of their axons alone were determined using the freeware program Reconstruct (Boston University, Boston, MA, USA; see Fiala, 2005). Fibres were excluded from the analysis if they displayed internal folds, Schwann cell nuclei, Schmidt-Lantermann incisures or paranodal characteristics. From the area measures, axon (DA) and fibre (DF) diameters were computed for the equivalent circles. Myelin thickness was calculated as (DF - DA)/2. An index of circularity (IC) of the axon was computed by dividing the observed axonal area by the area of a circle with the same perimeter. Observations on 590 fibres, revealed that for DA≤6μm, myelin thickness increased linearly with a slope of 0.15. For DA>6μm, myelin thickness remained approximately constant (regression slope of -0.03), with a mean value of 1.17μm. Thus, myelin thickness initially increases with axon size prior to reaching a plateau. This conclusion is consistent with data from myelinated axons in peripheral nerves in the mouse (Ceballos et al. 1999). The IC has been reported to depend on axon size (Biscoe et al. 1982; Ceballos et al. 1999) but the results are conflicting. Biscoe et al. (1982) report higher values for smaller axons, whilst Ceballos et al. (1999) reported the converse. Our data for IC showed no clear tendency to vary with axon size, with an overall mean value of 0.78. Possible explanations for the differences between these sets of data might be that: (i) the observations of Biscoe et al. (1982) were based on lumbar ventral roots which would also include an autonomic component; (ii) our criteria for exclusion of axon profiles appear to be more stringent than those of Ceballos et al. (1999)

Leiomiossarcoma pulmonar e renal em cão: relato de caso Pulmonary and renal leiomyosarcoma in dog: a case report

Este relato descreve um caso de leiomiossarcoma pulmonar e renal em cão da raça Husky Siberiano, macho, de nove anos de idade e com histórico de emagrecimento progressivo há mais de três meses. Ao exame clínico, o animal apresentava palidez discreta das mucosas e dor intensa à palpação abdominal, além de aumento de volume acentuado dos rins. No hemograma, foi evidenciada anemia discreta e na urinálise foram observados isostenúria e grumos de células do epitélio renal. Os níveis plasmáticos de uréia e creatinina estavam dentro dos limites considerados normais. O animal foi sacrificado após a confirmação de neoplasia renal bilateral por laparotomia exploratória. À necropsia, os rins apresentavam vários nódulos de 0,5 a 4cm de diâmetro, esbranquiçados e firmes. Na região do hilo e no lobo apical esquerdo dos pulmões havia aumento de volume, com 11 × 7cm de extensão, de superfície irregular e bem vascularizada, esbranquiçada e com áreas de consistência ora firmes, ora friáveis. No lobo apical direito também havia um nódulo com 1cm de diâmetro, firme e esbranquiçado. Secções histológicas dos pulmões e dos rins foram coradas pela hematoxilina-eosina, Masson e Van Gieson. Foi detectada positividade, pela imuno-histoquímica, para a vimentina e actina alfa de músculo liso. Não houve imunomarcação para citoqueratinas 1, 5, 10, 14, 8 e 7, proteína S100 e para CD68. Com base nos achados anatomopatológicos e imuno-histoquímicos foi firmado o diagnóstico de leiomiossarcoma pulmonar e renal, sem, no entanto, definir o sítio primário da neoplasia.<br>This report describes a case of pulmonary and renal leiomyosarcoma in a nine-year-old Siberian Husky male dog with a history of progressive weight loss. Clinically, the animal had mildly pale mucosae and severe abdominal pain. Kidneys enlargement also was observed. On hemogram, a mild anemia was observed. On urinalysis, isosthenuria and renal epithelial cells were detected. Urea nitrogen and creatinine levels were normal. Bilateral renal neoplasia was diagnosed by laparotomy and the animal was submitted to euthanasia. On necropsy, many whitish firm nodules ranging from 0.5 to 4cm in diameter were found in the kidneys. The region of the hilum and the left apical lobe of the lungs had a mass with 11× 7cm in area which was well vascularized and had an irregular whitish surface with either firm or friable areas. There was also a whitish firm nodule with 1cm in diameter in the right apical lobe. Histological sections were stained by hematoxilin-eosin, Masson and van Gieson. Positivity for the vimentin and smooth muscle actin were detected by immunohistochemistry. Cytokeratin 1, 5, 10, 14, 8 and 7, protein S100 and CD68 markers showed negative reactions. The anatomopathological and immunohistochemistry features allowed the diagnosis of pulmonary and renal leiomyosarcoma. However, it was not possible to determine the primary site of the neoplasia