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L J Simar

Publications and source records attributed to L J Simar.

At least 55 records · Page 3Linked to original sources
PubMed1980

Cytochemistry of mouse mast cell reaction to polylysine.

The modifications of mouse mast cells incubated in solutions of polylysine at two different concentrations are studied. At higher dose (0.5 mg/ml), the polycation has evident toxic effects. At lower dose (0.5 micrograms/ml), it induces some modifications of the granule morphology. Cytochemical reactions to demonstrate polyanions, basic proteins and organic bases are used to study the granule content. A polylysine treatment promotes the release of basic groups (vaso-amines) and sulphydryl-containing compounds (basic protein) from the mast cell granules. On the contrary, polyanions remain in the cells and correspond to the granule matrix persisting after amino-liberator treatment.

Amines↗
PubMed1979

[Effect of vinblastine on the blast population of the thymus subcapsular zone in the mouse].

It is well admitted that blast cells of the thymic subcapsular zone play an important role in murine leukemogenesis. Previous ultrastructural investigations have revealed the morphological heterogeneity of this population which is formed by lymphoblasts, X cells and ring shaped nucleolus cells. These aspects could correspond to different positions in the cell cycle of an unique cell type. After administration of vinblastine, a drug blocking mitosis in metaphasis, the percentage of lymphoblasts decreases whereas the percentage of X cells increases. There is no modification of the number of ring-shaped nucleolus cells. This suggests that at least a part of lymphoblasts gives rise to x cells.

Animals↗
PubMed1977

Ultrastructural autoradiographic study of blast cells in the mouse thymus. Interest for radioleukemia research.

Ultrastructural autoradiographic studies of mouse thymic blast cells after H3 Tdr injection show that their fine nuclear structure is related to their position in the cell cycle. The variations in the composition of the subcapsular blast cell population during radiation-induced leukemogenesis indicate kinetic changes in thymic lymphopoiesis, which are probably due to the oncogenic process.

Animals↗
PubMed1976

[Influence of thymectomy on the lymphoid regeneration of hematopoietic bone marrow after sublethal irradiation].

In C57BL mice, bone marrow lymphoid regeneration after a sublethal irradiation is modified by a graft of normal marrow cells. This effect is suppressed in thymectomized mice since a lymphoid peak is observed after a 350 R irradiation; its composition is heterogeneous: small lymphocytes, lymphoblasts and peculier cells named "X cells". The same phenomenon is observed in mice where all the thymocytes and thymus derived and peripheral lymphocytes are destroyed. These results exclude that bone marrow lymphoid regeneration after irradiation is due to a migration of lymphoid cells of thymic origin to the marrow. They could be explained by the effect of a humoral thymic factor on marrow lymphopoiesis.

Animals↗
PubMed1975

Quantitative study of left bundle branch fibrosis in left anterior hemiblock: A stereologic approach.

Serial sectioning of the interventricular septum was carried out in 16 hearts, 8 from elderly subjects with no conduction disturbance and 8 from patients with chronic left anterior hemiblock. The histologic slides were studied stereologically, and the relative density of fibrosis was quantitatively assessed by the point counting technique at various levels of the main subdivisions of the left bundle branch system. Statistical analysis revealed the following: (1) Although some fibrosis was found in the control hearts, the density of fibrosis was consistently and significantly greater throughout the conduction system in patients with left anterior hemiblock. (2) In the group with hemiblock, the relative density of fibrosis tended to increase significantly from the posterior ramification to the midseptal fibers and, finally, to the anterior fascicle. (3) Among the eight patients with hemiblock, fibrosis appeared to be evenly distributed throughout the conduction system in four. It was predominantly located in the anterior and midseptal fibers in one patient and showed an increasing severity from the posterior to the midseptal and anterior fibers in the remaining three patients. From this quantitative study, it is concluded that left anterior hemiblock is a reliable sign of left bundle branch disease but that the underlying lesions are more widely distributed than would be from the expected electrocardiographic terminology since they were found predominantly in the anterior ramifications in only half of the studied cases.

Adult↗
PubMed1975

[Kintetics of lymph node reaction during humoral immunization. Ultrastructural autoradiographic study].

An ultrastructural autoradiographic analysis was done in order to study the kinetics of the lymph node cellular reactions during primary immunization of the mouse with heterologous red blood cells. A single injection of 3H-thymidine is given 24 hours or 48 hours after the antigen administration ; the animals are sacrified 2 to 48 hours later. The localisation of the labelled immunoblasts varies : they are first concentrated in the germinal centers to be dispersed later in the paracortical area and to infiltrate finally the medullar cords, where they change into plasma cells. These results suggest strongly the existence of an immunoblast migration from the cortex to the medulla.

Animals↗
PubMed1975

[Stereologic analysis of differentiation of immunocompetent cells during reactions of humoral type].

Previous investigations have shown that, during a primary reaction against a single injection of heterologous red blood cells in the Mouse, immunoblasts migrate from the lymph node germinal centers to the medullary cords through the paracortical area. In that study, we combined ultrastructural examination with stereological methods in order to analyze the differentiation of the immunocompetent cells during this migration. The data permit one to characterize two important events in this differentiation. Between the 12th and 24th hour after the antigen injection, when the germinal centers are being dispersed, the cytoplasmic volume of the cells increases 2.5 fold. The estimated number of ribosomes per cell increases from 350,000 to 1 X 10(6) and the volumetric and surface densities of endoplasmic reticulum increase by a factor of 10. Four days later, 120 hours after the antigen administration, the immunoblasts, now located in the medullary cords, show a spectacular increase in the volume and surface density of endoplasmic reticulum, and in the surface density of Golgi membranes. This change results in the transformation of immunoblasts into young plasma cells. Between these two developments, there is a three day period during which the immunoblasts undergo little change.

Animals↗
PubMed1975

Cytological and ultrastructural study of the lymphoid-like and X cell populations in mouse bone marrow during the neonatal period.

During the recovery period following a sublethal irradiation, lymphoid-like cells accumulate in the bone marrow of the mouse. Among these cells, a peculiar element called 'X cell' has been previously described. Its morphological aspects are different from the precursors of the various hemopoietic lines. The 'X cell' could be an ancestral element normally repressed in the adult marrow. The aim of the present work is to determine whether this peculiar element can be detected in the bone marrow of young mice during the first month of life. The myelograms showed that on the day of birth, the marrow was almost exclusively composed of erythrocytic cells. During the postnatal period up to day 20, there was a progressive increase of granulocytic cells. The percentage of lymphoid-like cells increased from 5 per cent at birth to 28 per cent on day 20. The absolute number of these elements, calculated from the percentages obtained on the myelograms and from the number of nucleated cells per two femurs, increased from 20,000 at birth to 7,000,000 at day 30. The ultrastructural analysis demonstrated that the lymphoid-like population was composed of small lymphocytes, lymphoblasts and X cells, the proportions of which varied in relation to the age of the animals. X cells and lymphoblasts were found to be especially numerous around the 4th or 5th day, whereas the small lymphocytes were scarce.

Aging↗
PubMed1975

Histological modifications of the lymph nodes in mice bearing syngeneic grafts of tumours induced by methylcholanthrene.

Light and electron microscopical studies demonstrate that regional but also non-regional lymph nodes of C57BL mice grafted by tumours, induced by methylcholanthrene, are able to elicit a complex immunological response of the cellular, as well as of the humoral types. No significant difference was found according to the growth rate and the immunogenicity of the six tumours investigated. The cellular immunization is predominant during the two first weeks. It is mainly characterized by the appearance in the paracortical area of numerous immunoblasts which are in close connexions with'dendritic' macrophages showing multiple long cytoplasmic expansions. During the same period of time, the reticulum cells become hyperplasic in the sinus. From the 15th day to the death of the animals, the cellular immunizaiton progressively regresses while a humoral immunity develops. It shows itself as an hypertrophy of the lymph follicles and an increase in the number of medullary cord plasma cells.

Animals↗