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Biomedical subjects

F S Peng

Publications and source records attributed to F S Peng.

At least 19 recordsLinked to original sources
PubMed1997

Ectasias of the subcapsular sinus in lymph nodes of athymic and euthymic rats: a relation to immunodeficiency.

This paper describes a morphologically unusual feature occurring in lymph nodes of some aged euthymic animals but mostly athymic animals. It initially consists of small alveole-like excrescences of the cortical wall of the subcapsular sinus. With dilatation, an excrescence becomes an ectasia which expands into the cortex. Observations suggest that ectasias enlarge under the influence of an increased pressure of the afferent lymph of a node. Such condition conceivably results from a greater lymph formation due to inflammation of the drained tissue site, combined with an impairment to the flow of lymph from the subcapsular sinus into medullary sinuses. A probable relation of ectasia formation to immunodeficiency is discussed. This formation results in the atrophy of the affected lymphoid cell populations of a node which likely contributes to aggravate the deficiency of the immune system.

Aging↗
PubMed1996

High endothelial venules of the rat lymph node. A review and a question: is their activity antigen specific?

BACKGROUND: The high endothelial venules (HEVs) of the lymph nodes are sites for transvascular lymphocyte traffic. Due mostly to the wide scale of variations manifested by the HEVs and to frequently restricted conditions of observation, reports often differed on their morphological or functional features, which has led to opposing views on aspects of the functioning of HEVs. METHODS: In the present review, we analyze previous reports and attempt to derive comprehensive proposals to reconcile variations in actual observations under diverse conditions. RESULTS: This analysis shows that the features typical of the HEV endothelial cells (HEV cells) are stimulated to emerge by antigens and the proper lymphocytes and mediators. The stimulation would implicate drained lymphocytes migrating in the perivascular channel, immediately cuffing an HEV's endothelium. A marked pleomorphism of HEV cells betrays the fact that they undergo individual stimulation and a somewhat heterogeneous activity. Other facts indicate that the subendothelial spaces of HEV cells are sites of interactions between drained lymphocytes, HEV cells, and recruited blood lymphocytes. Facts also reveal time- and site-related variations in the intensity of recruitment of blood lymphocytes by HEV cells and topographically related variations in the nature of the recruited cells. CONCLUSIONS: Analysis of some other observations, often ignored, lead to the conclusion that recruitment of lymphocytes by HEV cells for the sake of participating in local specific immune activities is antigen specific, despite the implication of homing receptors of lymphocytes.

Animals↗
PubMed1995

Association of neutrophils with high endothelial venules in the neonatal rat lymph nodes: a probable relation to immunoincompetence.

The endothelium of the high endothelial venules (HEVs) of lymph nodes is normally considered to inhibit an association with neutrophils. The present paper shows that for a few weeks after birth, however, neutrophils are commonly associated with the walls of HEVs, the extent depending on the site of the lymph node. Overall, neutrophils increase in numbers in rat nodes from birth until about day 11, and vanish progressively thereafter. Moreover, neutrophils are more abundant in the nodes of standard neonates than in the nodes of pathogen-free neonates raised in an aseptic milieu. It is concluded that the postnatal recruitment of neutrophils by nodal HEVs relates to the then prevailing state of immaturity of the immune system. An explanation is proposed as to why neonatal HEVs of nodes recruit neutrophils and not only lymphocytes, as is the case later in ontogeny.

Analysis of Variance↗
PubMed1995

A study on binding of suspended nodal lymphocytes to high endothelial venules in sections of frozen rat lymph nodes.

Live lymphocytes were previously shown to bind selectively to endothelial cells (HEV cells) of the high endothelial venules (HEVs) in sections of frozen lymph nodes. This study examines aspects of the assay that have so far not been considered or which have been incompletely addressed. It was found that bound lymphocytes form a cytoplasmic veil, and that about half of them form small groups in which they are linked together by cytoplasmic bridges. It was also found that at least 83% of the lymphocytes bind to HEV walls, but very unevenly, and that 5% also bind to medullary venules. In addition, 31% of the lymphocytes were estimated to bind to the abluminal face of HEV cells and probably to tissue lymphocytes present in subendothelial spaces or in perivascular channels (spaces). This would reflect cell interactions occurring, in vivo, between HEV cells and/or subendothelial lymphocytes. It is suggested that antigen specificity of lymphocyte retention by HEV cells accounts for the uneven binding to HEVs.

Animals↗
PubMed1991

Dilatation of high endothelial venules in compartments of rat lymph nodes with abundant cortical mast cells.

Previous work has shown that the method of killing animals and of fixation of lymph nodes determines the appearance of high endothelial venules. Routine procedures produce a narrowing of the high endothelial venules whilst in situ fixation of lymph nodes results in their dilatation. More recently, routine procedures have demonstrated that lymph nodes from athymic and some euthymic ageing rats have occasional compartments in which the high endothelial venules are dilated in association with an increased population of cortical mast cells. These observations suggest that mast cell products may influence the physiological state of the high endothelial venules and affect the recruitment of blood lymphocytes.

Animals↗
PubMed1990

Atrophy of compartments of rat lymph nodes related to an entry of lethally altered lymphocytes.

This paper reports the occurrence of an accumulation of lethally altered lymphocytes in the subcapsular sinus of a compartment or compartments of some lymph nodes, an unusual feature best developed in nodes of the mesenteric site in aging athymic animals. Many of these cells are rod-like. In other compartments, similar lymphocytes occurred at various depths in the nodal parenchyma. This was accompanied by the disappearance of a compartment's populations of normal lymphoid cells. The observations reveal that lymphocytes, altered in a tissue, may reach the subcapsular sinus of the draining node compartment and migrate into its parenchyma which then undergoes atrophy. The likely involvement of mast cells is discussed.

Aging↗
PubMed1990

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.

Age Factors↗
PubMed1990

Retention of lymphocytes in the subcapsular sinus of lymph nodes: a physiological event?

This study examined the lymphocyte content of the subcapsular sinus of lymph nodes of diverse anatomical sites, from euthymic and athymic animals of various ages. One unusual feature which prevailed in young euthymic animals consisted of the accumulation of lymphocytes on the outer wall of the subcapsular sinus, following differential patterns with respect to diverse domains or areas of the subcapsular sinus of a node compartment. It is concluded that such an accumulation is due to the retention of lymphocytes on the sinus outer wall. Whether the retention reflects a step in unspecific defence mechanisms, in an immunological reaction pathway, or a transient state of the misfunctioning of lymph-carried cells, is considered. Some findings favor the latter possibility. In this case, retention would be due to a mild form of lymphocyte alteration caused by the emergence of an abnormal milieu in a drained tissue, and conceivably involving mast cell products. Whatever the case, the retention on the outer wall of the subcapsular sinus, instead of on its inner wall, would prevent any hindering of the usual activity of the latter wall.

Animals↗
PubMed1990

Atrophy of lymph node compartments lacking lymph-carried lymphocytes in athymic rats.

This paper reports on a form of atrophy of lymph node compartments occurring in mesenteric nodes of athymic nude rats whose perinodal tissue had become unusually rich in mast cells and fibrotic. The subcapsular sinus of an affected compartment was depleted of lymphocytes, while the medullary sinuses were loaded with macrophages. A progressive expansion of medullary sinuses into the medullary cords, the extrafollicular zone, the deep cortex unit and, finally, the folliculo-nodules of the compartment was accompanied by a gradual atrophy of the usual lymphoid cell populations of these nodal components. The occurrence of such a mode of atrophy of a compartment, associated with a lack of lymphocytes in the afferent lymph, agrees with our previous proposal that lymphocytes of the afferent lymph provide the stimuli for the development and maintenance of the structures of the node. The involvement of mast cells and fibrosis in the emergence of the present form of nodal atrophy, which further weakens the immune system of an immunodeficient animal, is considered.

Animals↗
PubMed1990

Formation of morphologically unusual features, associated with immunodeficiencies, in lymph nodes of gnotobiotic rats exposed to a conventional milieu.

Athymic animals are characterized by unusual features in lymph nodes, which are indicative of immunodeficiencies. These features include hypertrophy of follicles, atrophy of the peripheral cortex above the center of deep cortex units, and the formation of lymphocyte clusters at the periphery of these units as well as of compartment replicas in the capsules. Such features were recently observed in some nodes of a minority of aged euthymic animals and we concluded that they probably also reflected immunodeficiencies, since immunodeficiencies may emerge in aging euthymic animals. In an attempt to validate this conclusion, we exposed one-year-old gnotobiotic animals to a conventional milieu, thereby presumably rendering these euthymic animals somewhat immunodeficient, and checked their nodes for unusual features. Nodal unusual features, similar to those encountered in nodes of athymic and of some aged euthymic animals, arose rapidly and the ex-gnotobiotic animals either manifested signs of infections or died. These findings support our previous conclusion that the arising of such features reflects a progressive emergence of a certain state of immunodeficiency with aging.

Aging↗
PubMed1987

The formation of "compartment replicas" in the lymph nodes of athymic animals.

This communication describes a new anomaly that can affect the capsule of lymph nodes of athymic animals. Lymphocytes infiltrate a segment of the capsule above the variably atrophied peripheral cortex overlying the center of the deep-cortex unit of a node compartment. Lymphocytes thereafter form a capsular mass. The developing mass of lymphocytes is invaded by outgrowths of the node's subcapsular sinus while it fuses with the parenchyma of the related node compartment. Eventually, this new nodal element acquires structures resembling those of nodes and becomes a more or less exact replica of the original node compartment. Replicas stem from node compartments that are overchallenged by uncontrolled antigens. Aspects of the formation of replicas are explained by recent findings on events occurring in nodes of athymic animals and on the pattern of antigen distribution in the subcapsular sinus of a node. It is concluded that the formation of a compartment replica constitutes a mechanism allowing the organism to compensate somewhat for the partial atrophy or deficiency of a node compartment.

Aging↗
PubMed1987

Morphological anomalies associated with immunodeficiencies in the lymph nodes of aging mice.

Immunodeficiencies can emerge in aging normal animals. We wondered whether the morphological taking place in nodes of normal but aging animals comprise anomalies associated with immunodeficiencies. We analyzed the nodes of various anatomical sites in 20 normal mice, aged 12 or 24 months. The same morphological anomalies described recently in nodes of young athymic animals and reflecting immunodeficiencies were found to develop in present mice, though varying in extent with age, individuals, anatomical site of a node, and compartments of a given node. Some anomalies reflect deficiencies of cellular immune responses; others reflect deficiencies of humoral immune responses. Practicality restricts the variety of antigens which can be tested to recognize the possible emergence of immunodeficiencies in an aging animal. A morphological analysis of its nodes can thus indicate if immunodeficiencies occur with respect to a fraction of the challenging antigens.

Aging↗
PubMed1986

The stroma of the thymus of the rat: morphology and antigen diffusion, a reconsideration.

This work reconsiders aspects of the morphology of the capsule, of the blood vasculature, of the distribution of reticular fibers, and of the diffusion of intramediastinally injected antigens in the stroma of the thymus of the rat. This was done by an analysis of standard sections of normal thymuses, of sections of thymuses perfused with colloidal carbon, of silver-impregnated sections, and of sections of thymuses of rats injected intramediastinally with a fluorescent antigen or intravenously with Trypan blue, and by electron microscopy of the thymic capsule. The capsule consisted of two layers: an outer layer covering the entire periphery of a thymic lobe, and an inner layer which outlined the entire convoluted peripheral cortex of a lobe. Cortical vessels entered the capsule and septa in which they formed a capillary network. These capsular capillaries were fenestrated and leukocytes were often present near them. Adipocytes were also seen near these vessels in some areas of the capsule, and often at the bases of septa and trabeculae. Furthermore, much of the medulla had a dense network of coarse reticular fibers, whereas the remainder of the medulla and the cortex contained a loose network of fine fibers stretching out from the capsule, septa, and trabeculae. Intramediastinally injected fluorescent antigens were observed to spread in the capsule and septa and to diffuse in the fiber networks stretched across the cortex and the medulla. Fluorescence also highlighted cortical reticular cells but not the thymocytes. Intravenously injected Trypan blue stained the capsule, the septa, the cortical reticular cells, and the autofluorescent cells outlining the corticomedullary junction of each lobule. The unusual penetration of capillaries from the thymic parenchyma into the thymic capsule suggested that the capsular capillaries participate in peculiar thymic events, such as the recruitment of blood stem-cells. It is concluded that small amounts of blood antigens normally exude from capsular capillaries and diffuse into the fibers extending from the capsule across the cortex. The phenomenon would be increased under conditions causing thymic involution. An explanation is proposed to account for the development of involution which involves the exudation of antigens from the capsular capillaries. A comparable mechanism could also account for the development of a particular experimental immune tolerance.

Animals↗
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.

Animals↗
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.

Animals↗
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.

Animals↗
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.

Animals↗