Strain differences in the branching of the sciatic nerve in rats.

The sciatic nerve in the rat is the site most often used for peripheral nerve regeneration studies. The length of sciatic nerve available for research, however, depends on the point at which the sciatic nerve divides into the peroneal and tibial nerves. In the present study, the hind limbs of 150 adult male rats of five different strains (Sprague-Dawley, Fischer 344, Wistar-Han, Lewis and Nude) were analysed with regard to femur length, the point at which the sciatic nerve divides into the tibial and peroneal nerves, and where these are surrounded by the same epineurium, and the point at which they are encased in individual epineurial sheaths. The results indicate that the lengths of sciatic nerve are fairly constant in all strains of rats. In absolute terms, they amount to about one-third of the length of the femur for stretches of undivided sciatic nerve, and up to nearly half of the femur length for stretches where the tibial and peroneal nerves are already present, but are still enclosed by the same epineurium. In 61.7% of the hind limbs examined in Fischer rats, however, no sciatic nerve could be seen as such, but only in the form of its successors surrounded by the separate epineuria. This makes it highly advisable not to use male adult Fischer rats in peripheral nerve regeneration studies with the sciatic nerve as the point of focus.

Morphological aspects of the ovary of athymic nude rats in the proestrus and metestrus phases of the estrous cycle

En el presente trabajo analizamos, a nivel de microscopía de luz, la morfología del ovario de ratas congenitamente atímicas (rnu/rnu) homocigotas para gen nude y la de sus littermates eutímicas (rnu+), heterocigotas para el mismo gen, de la línea Rowett, en las fases de proestro y de metaestro del ciclo estral. Pudimos observar que la morfología del ovario de ratas atímicas, en las dos fases estudiadas, es semejante a la presentada por las eutímicas y compatible con la morfología del ovario de ratas de otras líneas descritas en la literatura

Ultrastructural characteristics of the endometrial stroma of athymic nude rats in the proestrus and metestrus phases of the estrous cycle

En el presente estudio se observa la ultraestructura del estroma endometrial de ratas congenitamente atímicas (rnu/rnu), homozigotas para el gen nude recesivo y de sus camadas eutímicas (+/rnu), heterozigotas para el mismo gen, ambas de la línea Rowet, con el propósito de detectar posibles alteraciones en las ratas rnu/rnu. Estudios morfológicos del aparato reproductor de éstas, usando microscopio de luz, no muestran diferencias de las ratas +/rnu. Estudios ultraestructurales referentes a este asunto no fueron encontrados en la literatura consultada. La ultraestructura del estroma endometrial de rnu/rnu y +/rnu mostraron fibroblastos con una GER más dilatada en el proestro que el metaestro y una menor frecuencia de eosinófilos y macrófagos en las ratas rnu/rnu que en las +/rnu en proestro. La frecuencia de monocitos fue mas alta en el proestro mientras que la de los neutrófilos fue mas baja en el proestro y metaestro, en ambos grupos de ratas. Los resultados ultraestructurales sugieren que la menor frecuencia de eosinófilos y macrófagos encontrados en la ratas rnu/rnu en fase de proestro pueden estar relacionados con atmia congénita y/o alteraciones en los niveles de hormonas esteroidales encontradas en esas ratas

The athymic nude rat. Immunobiological characteristics with special reference to establishment of non-antigen-specific T-cell reactivity and induction of antigen-specific immunity.

The aim of the present review has been to describe some immunobiological characteristics of the athymic nude rat and on the basis of these to describe the possibilities of establishing non-antigen-specific T-cell reactivity and inducing antigen-specific immunity. After a brief introduction, some general characteristics of the autosomal recessive rnu/rnu rat are outlined. This athymic mutant normally has a longer lifespan than athymic nude mice and is easier to breed. Inbred nude rats are now available with several rat strain backgrounds. Since the rnu/rnu rat is athymic, the morphology and function of the thymus are briefly described. The thymus has two main functions: production of T lymphocytes and production of thymic hormones. The intrathymic T-cell ontogeny is described along with the two thymocyte selection mechanisms, positive and negative selection. Different thymic hormones are mentioned and their possible function outlined. However, thymic hormones still do not play an important role in immunotherapy. There are some striking differences in the morphology of lymphatic tissues of athymic and euthymic rats. The thymic area in nude rats consists only of fat and clusters of epithelial cells. Little research has been performed on bone marrow of athymic nude rats but morphologically there seems to be no difference from findings in normal animals. The thymus-dependent areas of peripheral lymphoid organs, i.e. the paracortical area of lymph nodes, the periarteriolar sheet of the splenic white pulp, and the interfollicular areas of Peyer's patches, are severely cell-depleted in the athymic nude rat. The lower lymphocyte content of these organs is not reflected in the lymphocyte counts of peripheral blood, but the lymphocyte counts of thoracic duct lymph are much lower than those found in euthymic animals. Few T-lymphocyte marker-positive cells are found in the athymic nude rat, and in the epithelium of the intestine there are also lymphocytes bearing neither T nor B markers. These cells probably represent the tau delta receptor-bearing cells. Immunologically the athymic nude rat reflects the thymic aplasia. Normal B-lymphocyte function has been found in both in vitro and in vivo tests, whereas the T-cell function is virtually absent both in vitro and in vivo. Non-MHC-restricted cells with killer activity like NK cells are present in the nude rat, and these cells function normally both in vitro and in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Mast cells and fibrosis in compartments of lymph nodes of normal, gnotobiotic, and athymic rats.

Reports vary on the amount and distribution of mast cells in lymph nodes. We analysed the mast-cell population in compartments of nodes of diverse sites, from euthymic and athymic animals of various ages. Nodal mast cells were few in young animals, occurring mostly in medullary sinuses. Aging is often accompanied by a moderate increase of nodal mast cells. In compartments of a few nodes of some aged athymic and euthymic animals, the mast cells were greatly increased in the extrafollicular zone overlying medulla directly. In certain cases, this great increase was accompanied by pronounced mast-cell degranulation and by fibrosis in the mast cell-rich extrafollicular zone. It is suggested that the mast cells of medullary sinuses relate to non-immunological events, while those of the lymphoid parenchyma relate to elements that can induce humoral immune responses or are somehow involved in nodal processes of such responses. It is further suggested that an occasional emergence, with aging, of a deficiency of particular humoral immune responses may induce an excessive increase of cortical mast cells, and that activities of the resulting dense mast-cell population contribute to the onset of fibrosis.

Quantitative studies of lymphoid organs, blood and lymph in inbred athymic and euthymic LEW rats under germfree and specified-pathogen-free conditions.

Four groups of inbred male LEW rats were examined: A, germfree athymic; B, specified pathogen free (SPF) athymic; C, germfree euthymic; D, SPF euthymic. All animals were killed at 18 weeks and compared with respect to body weight, histological appearance and cell density of the lymphoid organs, haematological values and differential counts of bone marrow, peripheral blood and lymph. Athymic rats had a lower body weight, less densely populated lymphoid organs, and fewer lymphocytes in the blood and lymph compared with euthymic animals. No difference was seen between athymic rats under germfree and SPF conditions, and in general the differences between athymic and euthymic animals were less pronounced under germfree conditions.

Possible single dosage effects of the nude gene: suppression of spontaneous development of thymoma and nephropathy in BUF/Mna-rnu/+ rats.

Single dosage effects of the rat nude gene (rnu) on spontaneous development of epithelial thymoma, muscle atrophy and nephrotic syndrome were studied by comparing littermates of rnu /+ and +/+ rats on a high thymoma strain, BUF/Mna, background. Heterozygous rnu/+ rats had a significantly smaller thymus than the +/+ littermates at 6 weeks of age. The incidence of thymoma at 12 months of age was extremely low in the female rnu/+ rats (3%) as compared with that of the +/+ rats (94%). Development of the nephrotic syndrome but not of the muscle atrophy was also suppressed in the heterozygotes. The results suggest that a recessive mutant gene, rnu, in a single dosage, interfered with critical steps of the disease processes of the thymoma and nephrotic syndrome in BUF/Mna-background rats.

Effects of homozygosity of the nude (rnu) gene in an inbred strain of rats: studies of lymphoid and non--lymphoid organs in different age groups of nude rats of LEW background at a stage in the gene transfer.

Several age groups of nude homozygous rnu/rnu and heterozygous rnu/+ rats of the same genetic background at an early stage of back-crossing (LEW/Mol) were compared as to body and organ weights, histological appearance and cell density of lymphoid organs, haematological values and differential counts of bone marrow and peripheral blood. No thymic tissue was found in the nude animals. 7-week-old nudes were smaller than control animals and had relatively larger non-lymphoid organs and cell-depleted peripheral lymphoid organs. Other age groups showed little difference. Peripheral blood of nude rats showed no signs of lymphopaenia in contrast with the findings in nude mice. The number of thoracic duct lymphocytes was, however, significantly smaller in all age groups of the nude rats, and the bone marrow tended to contain fewer lymphocytes.