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Biomedical subjects

R Pabst

Publications and source records attributed to R Pabst.

At least 217 records · Page 12Linked to original sources
PubMed1986

Evidence of extensive lymphocyte death in sheep Peyer's patches. II. The number and fate of newly-formed lymphocytes that emigrate from Peyer's patches.

The emigration of newly produced lymphocytes from Peyer's patches (PP) of lambs was studied. Mesenteric lymph nodes (MLN) were excised from most animals a few weeks after birth, and then at 8 to 10 wk of age, the dividing cells in 3 to 4 m of the small intestine were labeled in situ with [3H]thymidine. An extracorporeal perfusion system was used to restrict the 15-min period of labeling to the perfused lengths of intestine, which included either the large continuous ileal PP or a number of smaller jejunal PP. One or 3 days later, the number of labeled cells in the perfused tissue and in other lymphoid organs was studied by autoradiography. In the perfused tissues, labeled lymphocytes accounted for 63.7% of ileal PP cells by 1 day and for 86.7% by 3 days compared with only 9.6% of lymphocytes in the perfused MLN. Labeled lymphoid cells in the perfused PP were nearly all in the follicles. Labeled lymphocytes that must have been produced in the segments of ileum or jejunum at the time of the perfusion, subsequently emigrated via the lymphatics, and were identified in the spleen, MLN, other lymph nodes, blood, jejunal PP, and at a lower frequency in the thymus, nonperfused ileal PP, and bone marrow. In lymph nodes, spleen, and nonperfused PP, more than 80% of the immigrant newly formed PP-derived cells were small- and medium-sized lymphocytes, and about 15% were large lymphocytes. The nature of the labeled cells in the lamina propria of the nonperfused small intestine was quite different in that approximately 50% were plasma cells as early as 24 hr after the cells were born in the perfused gut. It is proposed that terminal B cell differentiation was most likely initiated within the PP in response to the entry of antigen. It was estimated that at both 1 and 3 days after perfusion there were about 100 times more labeled cells in the perfused ileal PP than could be accounted for by emigration to other organs. It was concluded that these results provide additional support for the view that PP in lambs produce a tremendous number of lymphocytes, but relatively few leave their site of production; most apparently die in situ.

Animals↗
PubMed1986

Integration of clinical problems in teaching gross anatomy: living anatomy, X-ray anatomy, patient presentations, and films depicting clinical problems.

In addition to lectures and the dissection course, four supplements are described to stimulate first-year medical students to learn gross anatomy. All topics are coordinated with the dissection course. The additional options are living anatomy, X-ray anatomy by a roentgenologist, presentation of patients by clinicians, and films on clinical problems. This integrated curriculum of basic and applied anatomy generates a high level of student interest in gross anatomy.

Anatomy↗
PubMed1986

Comparison of lymphocyte production in lymphoid organs and their compartments using the metaphase-arrest technique.

Lymphocyte proliferation was studied in normal young anesthetized pigs by the metaphase-arrest technique using vincristine (VCR). In each animal biopsies were taken simultaneously from the thymus, mesenteric lymph nodes, spleen, palatine tonsil and Peyer's patches from the ileum and jejunum. After taking the first samples, 0.25 mg VCR/kg body weight was injected i.v. and then four more biopsies were excised for up to 3.5 h after VCR. Imprints of the lymphoid organs were evaluated as an overall index for each organ, and histological sections were used to determine the mitotic index in typical B- and T-lymphocyte areas in these organs. In follicles of mesenteric lymph nodes, tonsils and the two types of Peyer's patches a comparable increase in the mitotic index was found, 3.62% per hour. In the corona the increase was also comparable but much lower, 0.43% per hour and in the interfollicular area similarly 0.38% per hour. In the spleen the mitotic rate was 0.69% for the white pulp and 0.42% per hour for the red pulp. In the thymic cortex the mitotic index increased by 0.49% and in the medulla by a surprisingly high value of 0.32% per hour. The metaphase-arrest technique in larger animals enables a comparison of lymphocyte production among organs and their different compartments, and demonstrates the important contribution of peripheral lymphoid organs to the renewal of the lymphocyte pools.

Animals↗
PubMed1986

[Functional anatomy of the human spleen].

For surgery of the spleen the variability of the splenic artery and the lack of major intrasplenic anastomoses are important. The latter enables segmental resections. Lymphocyte subsets, macrophages and dendritic cells, which are necessary for immune responses of the spleen, show a specific localisation in the splenic compartments. The spleen is the most important organ for lymphocyte recirculation. Intracellular particles and membrane defects of red cells are removed from the erythrocytes as they pass through the pulp cords of the red pulp. A knowledge of the functional anatomy of the spleen helps to interpret the effects of splenectomy and splenic transplantation.

Dendritic Cells↗
PubMed1986

Autotransplantation of splenic tissue.

Autotransplantation of splenic fragments has already been carried out in humans. The optimal size of the particles and amount of tissue required for this procedure has yet to be found. In normal young pigs and miniature piglets, autologous splenic tissue was transplanted into the greater omentum. The regenerated splenic mass, splenic blood flow, and histology were studied six months later. Implanting small splenic particles produced comparable results to implanting thin slices of splenic tissue. The mass of regenerated splenic tissue was only 3.1 g after implanting the whole spleen and 4.5 g after transplanting half of the spleen, which means 5.3% and 7.8% respectively of the weight of control spleens. The blood flow per gram in the regenerated splenic tissue was much lower than in the normal spleen. The blood flow in the whole of the splenic tissue is important for the clearance function of the spleen. Six months after transplanting the whole or half of the spleen, the blood flow to the regenerated splenic tissue was only 1% of that in the control minipigs. When half of the spleen was left in situ, as a model for a partial splenectomy, and the other half transplanted, the regenerated mass was only 3.4% of all splenic tissue and the blood flow 1.5% of the total splenic blood flow. In this model the regenerated splenic mass was independent of the size of the implants and the mass of implanted tissue. The extremely low blood flow indicates an inadequate clearance function and thus the protective function would probably be negligible.

Animals↗
PubMed1986

Autotransplantation of splenic fragments: lymphocyte subsets in blood, lymph nodes and splenic tissue.

Abnormal ratios of T helper-type to T suppressor-type lymphocytes in the blood of patients with replanted autologous splenic tissue led to the present study in rats. Lymphocyte subsets were studied in the blood, mesenteric lymph nodes and spleen after autotransplantation and compared to splenectomized and control rats. In the blood of transplanted rats the percentage of T and T helper-type lymphocytes was lower, in the spleen B lymphocytes higher and T lymphocytes and their subsets lower. Comparable changes were seen in the lymph nodes. The data of the mesenteric lymph nodes in autotransplanted rats did not differ from splenectomized animals. Even after 37 weeks the regenerated splenic tissue only reached 13% of the weight of control rats and the absolute lymphocyte number was only 2.5% of a normal spleen. Splenic autotransplantation results in a small hypocellular mass of splenic tissue with a different composition of lymphocyte subsets and does not correct the obvious effect of splenectomy on lymphocyte subpopulations in lymph nodes.

Animals↗
PubMed1986

Numbers and phenotype of lymphocytes emigrating from sheep bone marrow after in situ labelling with fluorescein isothiocyanate.

In normal young lambs the bone marrow was selectively labelled with fluorescein isothiocyanate by a temporary perfusion of one hind-leg. One day later, the incidence of bone marrow emigrants in different lymph nodes, spleen, Peyer's patches, thymus, non-perfused bone marrow and blood was determined. The emigrants were also phenotyped by the use of monoclonal antibodies and classified into monocytes or lymphocyte subsets. Large numbers of lymphocytes left the bone marrow of the perfused leg during 1 day. Considerable numbers of cells migrated to other bone marrow compartments. Varying numbers of mononuclear emigrants were found in peripheral lymphoid organs, with labelling indices ranging from 1.06% in the blood to 0.004% in the thymus. In the spleen, comparable numbers of B- and T-lymphocyte emigrants from the bone marrow were found, whereas in the blood, lymph nodes and jejunal Peyer's patches many more emigrants were T lymphocytes than B lymphocytes. In the prescapular lymph nodes, for instance, 90.4% of emigrants were T cells but only 9.6% were B cells. Based on the large numbers of lymphocytes emigrating from the bone marrow, their phenotypes and their entry into other bone marrow compartments, it it can be concluded that the bone marrow of young lambs is an integral part of the migratory route of lymphocytes.

Animals↗
PubMed1986

No aggravation of the course of experimental glomerulonephritis in spontaneously hypertensive rats.

Functional and morphologic glomerular alterations induced by antiglomerular basement membrane (anti-GBM) nephritis were investigated in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto controls (WKY) for assessment of the role of systemic hypertension in immunologically mediated renal injury. Over a 6-week period serial measurements of systolic blood pressure (BP), serum creatinine (SCreat), creatinine clearance (CCreat), and urinary albumin excretion (UAlbV) were obtained with inulin clearances (CInulin) at the end of the study. Renal tissue was examined by light microscopy (LM), electron microscopy, immunofluorescence, flash 3H-thymidine autoradiography (AR), and staining for nonspecific esterase (NSE). Immunologic humoral response was evaluated by measurement of rat anti-rabbit IgG antibody production. At all time periods studied, SHR and WKY rats with anti-GBM nephritis demonstrated comparable elevations in SCreat and UAlb V as well as diminution of CCreat and CInulin as compared with non-nephritic control rats of each strain. In nephritic WKY rats mild hypertension developed, whereas in nephritic and control SHR rats marked elevations in BP developed. Morphologic injury as assessed by percent glomerular crescents and hypercellularity on LM, numbers of monocyte macrophages by NSE staining, immunofluorescence for IgG, C3, fibrinogen and Ia positivity, and numbers of glomerular 3H-thymidine-labeled cells by AR was notably comparable in both nephritic strains. Humoral antibody responses were also shown to be similar in all rats studied. These results demonstrate that the 5-week course of experimental anti-GBM nephritis is not exacerbated by systemic hypertension. Glomerular autoregulatory capacity may be important in determining the extent of immune-mediated renal injury.

Albuminuria↗
PubMed1986

[The palatal tonsils as a part of the lymphatic system. Inflow and outflow of newly-formed lymphocytes].

Many lymphocytes continuously migrate from one lymphoid organ to another. The tonsils are also included in the migratory stream of long-lived lymphocytes. We investigated the question whether newly formed lymphocytes, for example, those produced in the spleen or mesenteric lymph nodes, also migrate to the tonsils and to which compartment. The spleen and mesenteric lymph nodes of normal young pigs were selectively labelled with the DNA precursor 3H-thymidine and one day later smears and sections of the tonsils were autoradiographed. About 1% of all spleen-derived young lymphocytes and about 0.5% of all emigrated mesenteric lymph node lymphocytes were found in palatine tonsils. These were almost exclusively small to medium sized lymphocytes. These cells were mainly found in the interfollicular area around high endothelial venules. Surprisingly high numbers were also located in the reticular epithelium of the crypts, in the corona and even in follicles. In a second series of experiment palatine tonsils were selectively labelled by multiple minute injections of 3H-thymidine. The follicles showed a very high labelling index but labelled lymphocytes were also identified in other compartments. One day later tonsil-derived lymphocytes were found in the spleen and lymph nodes. There is thus a continuous exchange of newly formed lymphocytes between the tonsils and other lymphoid organs.

Animals↗
PubMed1985

Enhanced regeneration of transplanted splenic tissue by increased work load to the splenic compartments.

Autologous splenic tissue regenerates after subperitoneal transplantation in laboratory animals and in man. Qualitatively it resembles normal splenic tissue but the quantity usually only attains a small proportion of the normal spleen. In the prevention of overwhelming post-splenectomy sepsis a critical mass and a considerable blood flow to the regenerated spleen seem to be essential. By increasing the work load to splenic transplants in rats, significantly more splenic tissue was regenerated. This was achieved by: stimulating the white pulp by repetitive injections of xenogeneic red cells; stimulating the red pulp by damaging red cells with phenylhydrazine; a combination of 1 and 2; and stimulating the reticuloendothelial system by IP injections of methylcellulose. Stimulating the red pulp and the reticuloendothelial system were more effective than the injection of antigens. As the splenic mass is obviously regulated by the work load, we conclude that this effect should be used to attain the critical splenic mass and to increase the blood flow for effective clearance of bacteria from the blood.

Animals↗
PubMed1985

Surface markers on lymphocytes leaving pig lymph nodes.

Mesenteric lymph nodes of normal young pigs were perfused in vitro at physiological temperature. Cell-free perfusion medium was pumped into the artery for more than 2.5 hr, and lymphocytes were continuously released into the venous effluent. Recirculating lymphocytes emigrate from pig lymph nodes by entering the blood vasculature directly and not via efferent lymphatics. The presence of lymphocytes in paracortical venular walls after 2 hr of perfusion with new medium suggests that these are the sites of emigration. The rate of emigration of lymphocytes from mesenteric lymph nodes was estimated to be 6 X 10(7)/hr. Study of the lymphocyte populations emerging from the perfused lymph nodes showed that B lymphocytes and E-rosette forming T lymphocytes, but almost no Null lymphocytes, are involved. While the proportion of B lymphocytes remained constant during the perfusion period, E-rosette forming lymphocytes increased significantly. Lymphocyte subpopulations differ profoundly in their capacity to migrate through lymph nodes.

Animals↗