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G Sainte-Marie

Publications and source records attributed to G Sainte-Marie.

At least 37 records · Page 2Linked to original sources
PubMed1986

Diffusion of a lymph-carried antigen in the fiber network of the lymph node of the rat.

A lymph-carried antigen is retained preferentially in those areas of the subcapsular sinus of a lymph node overlying the extrafollicular zone of the peripheral cortex. There, it becomes associated with the reticular fibers crossing these particular sinus areas. We wondered whether the antigen thereafter diffuses along the extensions of these fibers which form a peculiar network in the "cortical pathways of migration of circulating lymphocytes" (CPMCL), leading to the different cell populations effecting the immune responses. Fluorescein isothiocyanate (FITC)-conjugated antigens were injected locally into rats sacrificed 0.5-24 h later. The antigens diffused along the fibers of the CPMCL. It is proposed that this diffusion constitutes one mechanism of stimulation of recruited circulating lymphocytes and of orientation of their migration towards the proper effector-cell population.

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PubMed1986

Morphological anomalies in the lymph nodes of 13-month-old thymus-grafted nude mice.

The purpose of the present work was to investigate whether the grafting of a thymus to 7-day-old BALB/cByJ nude mice prevents the occurrence of the nodal anomalies recently observed in non-grafted nude mice. We found that the anomalies were still present, but attenuated, in the grafted mice. Furthermore, we observed differences between anomalies occurring in grafted and in non-grafted nude mice. The differences appear to be interrelated and to result from changes in the pattern of lymphocyte migration in the nodes of grafted nude mice, due to a lesser deficiency of the immune system.

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PubMed1985

The narrowing of high endothelial venules of the rat lymph node.

The lymph node contains blood vessels of a special type, termed "high endothelial venules" (HEVs), which are involved in the process of lymphocyte recirculation. In standard tissue sections, many HEVs exhibit a nearly closed or closed lumen containing small lymphocytes but few, if any, erythrocytes. The question arose as to whether the appearance of HEVs in tissue sections is influenced by the routine method of animal sacrifice and/or of tissue processing. Therefore, the present work investigated the effects on HEVs of sacrificing rats as well as of excising and fixing their nodes with various procedures. It was observed that procedures involving animal bleeding or blood loss from nodes increase the percentage of HEVs exhibiting a nearly closed or closed lumen. The results further revealed that the endothelial thickness and other morphological features of HEVs are modified by this artifactual narrowing of HEVs. The possible significance of the phenomenon is discussed.

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PubMed1985

Distribution pattern of drained antigens and antibodies in the subcapsular sinus of the lymph node of the rat.

A recent study of lymph nodes of the rat showed that they are morphologically and physiologically compartmentalized. A compartment of a node includes a portion of subcapsular sinus into which the lymph, entering via the related afferent lymphatic opening, is filtered. The study also showed that colloidal carbon injected locally in a small dose becomes predominantly associated with the areas of the inner wall of the subcapsular sinus that cover the extra-follicular zone of the peripheral cortex. Little carbon is seen over the folliculo-nodules (follicles with a nodule or germinal center). The question arose as to whether drained natural substances, as antigens and antibodies, follow the same pattern of distribution in the subcapsular sinus as the carbon. Therefore, small doses of fluorescein isothyocyanate (FITC)-conjugated antigens were injected locally into normal rats whose own antibodies in the nodes were stained by immunofluorescence. The pattern of distribution of the antigens in the draining nodes was found to be the same as that of the carbon. Furthermore, the lymph-carried antibodies of the rats were found to follow the same pattern. The morphological basis for such a pattern is explained. The results are further discussed with regard to the probable normal entry route of lymph-carried antigens in the parenchyma of nodes.

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PubMed1985

Evidence for the existence of a subsinus layer of the peripheral cortex in the lymph node of the rat.

The peripheral cortex of a lymph node consists of folliculo-nodules (follicles with a nodule or germinal center) and an extrafollicular zone. In the course of an analysis of the nodes in rats under various experimental or abnormal conditions, our attention became focused on the particularities of a thin layer of peripheral cortex underlying the subcapsular sinus. The present paper reports on observations which led to the identification of the "subsinus layer" of the peripheral cortex. The observations suggest that this layer complements the activity of the inner wall of the subcapsular sinus. The layer probably contributes to the selection of certain elements from the afferent lymph and guides them towards the node area where they can join the cell population involved in the immunological activity in which they are to participate.

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PubMed1985

Lymph nodes of the N:NIH(S)II-nu/nu mouse.

In N:NIH(S)II-nu/nu mice, which express the nu and the Xid genes, T and B lymphocytes are deleted. We studied their lymph nodes in the light of new knowledge of the morphology of the nodes of normal and athymic animals. Histologic preparations of the nodes from various anatomical sites were analyzed in 9-week-old mice. Node sections were also stained for IgM or IgG. The study revealed that, the frameworks of the peripheral cortex, the deep cortex, and the medulla were developed in these nodes, although they were quite devoid of lymphocytes or plasmocytes. However, the outermost (or subsinus) layer of the peripheral cortex of some nodes was populated with lymphocytes. In some cervical nodes, a few follicles, lymphocyte clusters, and a well-developed plasmocyte population were also present. The lymphocytes of the subsinus layer and the clusters were B cells with an increased expression of IgM. The modifications of these nodes are discussed on the basis of recently developed concepts of node functioning.

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PubMed1984

Tridimensional study of the deep cortex of the rat lymph node: VIII. The deep cortex units of the athymic nude rat.

The deep cortex of the lymph node of various species actually consists of hemispherical structures, termed deep cortex "units." Each unit is centered under an opening of an afferent lymphatic and comprises a center and a periphery. In a recent work on the nude mouse, we found that the congenital athymic state inhibits the development of the lymphocyte population in the center of the units as well as in a related area of peripheral cortex, and that it also modifies other nodal components. In the present work, we wanted to compare the effects of the athymic state on the rat nodes. Therefore, nodes from various anatomical locations in 8-week-old nude rats were submitted to a tridimensional analysis. The overall effects of the congenital athymic state were found to be comparable in rats and mice. However, marked differences were noticed in the modifications of the node histology, in both species of nude animals. Their significance is discussed together with new findings.

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PubMed1984

Development of the lymph nodes in the very young, and their evolution in the mature, nude rat.

We recently revised the concepts on the morphology of the lymph nodes of the young adult athymic nude rat. The present work studied the postnatal development of its nodal structures and their evolution with aging. The structural development of the deep cortex "units" was found to progress as usual. However, while the concentration of lymphocytes appeared to develop normally in the periphery of a unit, the center of the unit remained lymphocyte-depleted. Further, the peripheral cortex failed to develop over the middle part of a unit center. With aging, the peripheral cortex over the remainder of a unit center could atrophy and disappear completely. The present findings did not yield information as to whether thymic elements are necessary to trigger the development of a unit, but they revealed that its further development is determined by stimuli. It was concluded that, in the absence of T-cells, stimuli for cellular immune responses provoke the proliferation of the reticular or interdigitating cells of a unit center. On the other hand, an increase of these stimuli was concluded to cause the peripheral cortex to fail to develop over part of a unit center and, later, to atrophy over the remainder of the unit center. The mechanisms of the phenomena are discussed.

Aging↗
PubMed1984

Modifications of the structures of the rat lymph nodes by neonatal thymectomy.

Until recently, the deep cortex of the lymph node was thought to exist as a layer completely underlying the peripheral cortex. It was known, moreover, that through neonatal thymectomy, the lymphocyte population of the deep cortex could be depleted. Through our current research, however, we have demonstrated that the deep cortex actually consists of hemispherical 'units'. Each unit is centered under an opening of an afferent lymphatic and comprises a center and a periphery with different morphological features and functions. In the light of this new knowledge, we felt it appropriate to reexamine the influence of neonatal thymectomy on node histology. Rats were thymectomized 5 h after birth. When they were 8 weeks old, nodes from various anatomical sites were submitted for morphological analysis. The resulting observations were compared to those made with nodes of nude as well as normal rats. It was found that the histological changes induced by neonatal thymectomy were comparable to those resulting from the congenital athymic state, but with marked differences. Differences were also observed in the nodes of thymectomized and semi-thymectomized rats. The discussion deals with these differences and presents new observations.

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PubMed1983

Depopulation of lymphocyte migration sites in the lymph node by irradiation and colloidal carbon.

The purpose of the present investigation was to examine, in the light of recent histological findings, whether irradiation and colloidal carbon can have a lymphocyte depopulating effect on preferentially particular structures of the rat lymph nodes. Normal eight-week-old Sprague-Dawley rats received a 500 R whole body irradiation or a subcutaneous injection of 0.02 ml of India ink. The animals were then sacrificed at various time-intervals. The histological analysis of the irradiated and draining nodes revealed that both treatments almost completely eliminated small lymphocytes from the affected nodal structures, except in the center of the deep cortex units. The affected structures had been predominantly populated by recirculating lymphocytes.Thus, the treatment had a rather preferential depleting effect on a node population of recirculating lymphocytes. This finding provides another possible explanation for the carbon-induced augmentation of a GVH reaction in nodes. This augmentation had previously been attributed to a stimulation by the carbon of host macrophages, which would mediate the proliferation of antigen-reactive donor cells. From our present findings, it appears that carbon, like irradiation, could act by depleting a node of recirculating lymphocytes, thereby weakening its immunological potential against the inoculated lymphocytes.

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PubMed1983

Structural and cell population changes in the lymph nodes of the athymic nude mouse.

A recent tridimensional analysis of the lymph node demonstrated that its deep cortex is composed of grossly hemispherical "units," adjoining a portion of its peripheral cortex. Each deep cortex unit can be distinguished into a center and a periphery. The periphery was concluded to be a site for migration of circulating lymphocytes, the center, a site where T cells would participate in cellular immune responses. The aim of the present work was to determine the influence of the congenital athymic state on the development of the units and of other components in the lymph nodes of the nude mouse. For this, the lymph nodes at various anatomical locations in adult athymic nude mice were analyzed. The present study revealed that the athymic state did not inhibit the development of the units but severely depleted the lymphocyte population of their center only. However, it did inhibit the development of an area of peripheral cortex located over the middle part of a unit. Such an area of peripheral cortex is, thus, concluded to be thymus dependent, as is the center of a deep cortex unit. The athymic state also prevented the development of the cells of the nodules (germinal centers) and of much of the plasmocytes. On the other hand, it yielded to the enlargement of the follicles, the formation of new structures: medullary "lymphocyte clusters" and the transformation of the medullary venules into high endothelial venules. The various modifications of the nodal structures resulting from the congenital athymic state are discussed in relation to some functions of the organ.

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PubMed1982

Tridimensional study of the deep cortex of the rat lymph node. VI. The deep cortex units of the germ-free rat.

The deep cortex of the normal rat lymph node consists of semirounded lymphocytic structures, termed deep cortex "units," each being centered on the opening of an afferent lymphatic. The aim of the present work was to investigate the morphologic features of the units in germ-free animals, in an attempt to evaluate the influence on natural exogenous antigenic stimulation on the development of the units. For this, the lymph nodes from various anatomic locations from 8-week-old Sprague-Dawley germ-free rats were analysed tridimensionally. The observations revealed that, in comparison with the lymph nodes of normal rats, the units of the cervical and mesenteric lymph nodes of the germ-free animals were underdeveloped, while those of the brachial, inguinal, and popliteal lymph nodes were unchanged. Moreover, the germ-free state modified the units of the mesenteric lymph nodes in a manner not encountered in the remaining lymph nodes. Other morphologic features of the peripheral cortex of the lymph nodes of germ-free rats also differed from those of normal ones. The significance of these differences is discussed with respect to immune responses and the process of lymphocyte recirculation. They are of interest because they support previous proposals regarding some aspects of the functioning of the normal lymph node, accounting for the features of the structures and overall architecture of the organ.

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PubMed1982

[Distribution of a diffusible tracer in the subcapsular sinus and the cortex of lymph nodes in the rat].

The observations of a previous work on the architecture of the rat node suggested that the organ is divided into "physiological compartments". Each compartment corresponds to a node portion stimulated by the immunogenic content poured by an opening of an afferent lymphatic or a branch of it. The same study also investigated the lymph flow in the organ sinuses by analysing the distribution, in draining nodes, of a locally injected small dose of China ink. It was found that the ink, pouring into a node from a lymphatic opening, had spread in a restricted portion of its subcapsular sinus corresponding to that of a compartment. The finding thus supported the proposal on the physiological compartmentation of the organ. However, the question arose as to whether such restricted ink distribution in the sinus did not result from the non-diffusible and unphysiological nature of the ink. We, therefore, repeated the latter analysis with a diffusible and physiological tracer: uridine-3H. The similarity of the results of the latter analysis, with those of the preceeding one, indicate that the observations witness the physiological modalities of the pattern of lymph flow in the organ sinuses. It, therefore, confirms that the node is divided into physiological compartments. Additional observations of present work, further demonstrate that small sized lymph substances diffuse from the subcapsular sinus into the cortex. The process is maximal under a lymphatic opening and decreases along the sinus with distance from the opening.

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PubMed1981

Tridimensional study of the deep cortex of the rat lymph node. I: Topography of the deep cortex.

Diagrams of the lymph node currently represent its deep cortex (paracortex) as a layer of rather uniform thickness underlying the whole peripheral cortex. However, this concept has not been supported by actual observations; previous investigators have observed, instead, related structures whose appearance varied greatly from nodule-like to ill-defined components. Clearly, the present knowledge of the histology of the deep cortex is inadequate and confusing. Therefore, we undertook a tridimensional study of the region in different nodes of rats. The present work, bearing on the topography of the region, revealed that the deep cortex of the rat node is formed of one to several basic "units." Each unit is a semi-rounded structure, varying from semispheric to semi-ovoid in shape and contiguous to a portion of peripheral cortex. The work further showed that two to several units can fuse to form a "complex." The data indicated that the number, the size and the shape of the units and/or of the complexes of a node differ to some extent according to its anatomical location. These differences probably reflect corresponding variations in the nature and importance of the antigenic stimulation in the different sites of the organism. Finally, the study demonstrated the necessity of tridimensional examination of a node to obtain adequate information on its overall architecture and, particularly, on its deep cortex topography.

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PubMed1981

Tridimensional study of the deep cortex of the rat lymph node. II: Relation of deep cortex units to afferent lymphatic vessels.

Recently, we reported that the deep cortex of the rat lymph node is formed of semi-rounded structures, the "deep cortex units," contiguous to the peripheral cortex and bulging into the medulla. It was suggested that a unit represents an accumulation of lymphocytes centered on the opening of an afferent lymphatic vessel. To verify the proposal, we carried out a tridimensional analysis of serially sectioned rat nodes, fixed by perfusion and trimmed in such a way as to preserve their lymphatics. The tridimensional analysis revealed that a constant topographical relationship exists between the units and the openings of the afferent lymphatics. The results demonstrated that the topographical organization of the deep cortex of a rat node correlates with the distribution pattern of the opening(s) of its afferent lymphatic(s). The overall observations suggested the following explanation for the shape and topography of the units: factor(s) present in the lymph would spread in a radial manner from the opening(s) of an afferent lymphatic through the underlying cortex. The factor(s) would induce morphological modifications in the stimulated semi-rounded area which, in turn, would provoke a local accumulation of circulating lymphocytes.

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PubMed1981

Tridimensional study of the deep cortex of the rat lymph node. III. Morphology of the deep cortex units.

Recently we reported that the deep cortex of the rat lymph node is made up of semi-rounded "units," some of which are partially fused into "complexes." We further found that each unit is centered on the opening(s) of an afferent lymphatic vessel, the topographical organization of the deep cortex of a node correlating with the distribution pattern of the opening(s) of its afferent lymphatic(s). The present study aims to clarify the morphology of the deep cortex unit, particularly with regard to its reticular framework, its lymphatic sinuses, as well as its network of postcapillary venules. For that purpose, we analyzed rat nodes from various locations by way of tridimensional reconstruction. The observations revealed that each unit is formed of a "center" and a "periphery," distinguishable from one another on the basis of their morphological features. The center is nearly devoid of reticular fibers, whereas the periphery exhibits a dense framework of fibers. Moreover, the periphery is the site of concentration of most postcapillary venules of a unit and contains lymphatic sinuses which, peculiarly, are often loaded with small lymphocytes. While both regions are populated mainly by small lymphocytes, the periphery usually contains a lower concentration of these cells than the center. The overall findings support the view that the center is a site of cellular retention and proliferation, whereas the periphery is a site of rapid lymphocyte migration in and out of the unit.

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PubMed1981

Tridimensional study of the deep cortex of the rat lymph node. IV. Differential labelling of the deep cortex units with 3H-uridine.

Using tridimensional reconstruction, it was recently found that the deep cortex of rat lymph nodes comprises one to several basic "units." Each unit is a semi-rounded structure contiguous to the peripheral cortex and bulging into the medulla of a node. Other investigators reported that transfused lymphocytes, heavily labelled in vitro by 3H-uridine, became concentrated in an ill-defined region of nodes, referred to as the mid and deep cortex. This suggested to us that the in vivo labelling of nodes with 3H-uridine might allow to further characterize the units on a physiological basis. Therefore, rats were injected intravenously with a dose of 1--20 muCi of 3H-uridine/gm body weight and sacrificed 1 hour to 3 days later. The radioautographs of their nodes were exposed up to 535 days. The observations revealed that a large dose of 3H-uridine combined with a long exposure of the radioautographs yielded a differential labelling of the cell population of the units, characterized by a much more intense reaction than that of the surrounding structures. This demonstrated that the physiology of the lymphocyte population of the deep cortex units differs from the morphologically similar lymphocyte population of the extrafollicular zone of the peripheral cortex. The possible reason(s) for the differential labelling of the units is discussed.

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