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R Pabst

Publications and source records attributed to R Pabst.

At least 55 records · Page 3Linked to original sources
PubMed2000

[Major differences in procedure in receiving the academic title "ausserplanmaessiger Professor". Criteria and evaluation of research and teaching at German medical schools].

The academic title "Privatdozent", unique to the German speaking countries, is awarded after the "Habilitation", a qualification to teach and perform research on a high level and independent of supervision by a professor. A few years after the "Habilitation", committees of medical faculties decide whether the title "ausserplanmaessiger Professor" can be awarded. This is an academic title independent of a specific university or extramural position. The rules of all German medical faculties were evaluated with regard to when and by what criteria the faculties decide. There were major differences, e. g. the minimum time after the "Habilitation" (4 years n = 9; 5 years n = 14; 6 years n = 7), the numbers and quality of published papers and abstracts, the amount and quality of teaching and the number and qualification of external reviewers. For applications for university positions, but even more for leading positions in hospitals and industry, the title of "apl. Prof." is still of major relevance. Therefore a certain degree of standardization but still leaving space for special criteria in different faculties, is proposed.

Faculty, Medical↗
PubMed2000

Blockade of leucocyte function-associated antigen-1 (LFA-1) decreases lymphocyte trapping in the normal pulmonary vasculature: studies in the isolated buffer-perfused rat lung.

Adhesion molecules regulate the migration of lymphocytes in lymphoid and non-lymphoid organs. In the lung, little is known about lymphocyte sticking and migration through the pulmonary vascular endothelium in physiological or pathological situations. Therefore the isolated buffer-perfused rat lung was used to investigate the mobilization of lymphocytes out of the normal lung into the venous effluent and to the bronchoalveolar space. The lymphocyte subset composition was characterized in the venous effluent, the lung tissue and the bronchoalveolar lavage (BAL) using immunocytology. Lymphocytes continuously left the normal lung at a total of 5.0 +/- 0.7 x 106 cells within the first hour of perfusion. The injection of 200 x 106 lymphocytes via the pulmonary trunk increased the venous release of lymphocytes by 170%. To investigate the effect of LFA-1 and CD44 on the adhesion of lymphocytes to the pulmonary endothelium, lymphocytes preincubated with an anti-LFA-1 MoAb, which blocks the interaction of LFA-1 and intercellular adhesion molecule-1 (ICAM-1), or lymphocytes preincubated with an anti-CD44 MoAb, were injected. The injection of LFA-1-blocked lymphocytes led to an increase by 70% of injected cells recovered in the perfusate within the first hour, whereas anti-CD44 treatment of injected lymphocytes had no effect. The LFA-1-blocked lymphocytes showed higher numbers of T and B cells in the effluent. Thus, the present experiments demonstrate that LFA-1 influences the trapping of lymphocytes in the vasculature of the healthy rat lung.

Animals↗
PubMed2000

Differences in lymphocyte subsets in the wall of high endothelial venules and the lymphatics of human palatine tonsils.

Lymphocyte trafficking plays a critical role in disseminating specifically primed lymphocytes all over the body. Most concepts on the interaction of adhesion molecules on lymphocyte subsets and specialized endothelia such as those in high endothelial venules (HEV) are based on animal experiments as kinetic studies cannot be performed in humans. We therefore characterized lymphocyte subsets in the wall of HEV and in the lumen of lymphatics of 18 human palatine tonsils by immunohistology. All subsets studied were found in the wall of HEV (% of lymphocytes): 32% CD20+, 50% CD3+, 14% CD4+, 32% CD8+ and also 21% CD45RA+ and 39% CD45RO+. In the lymphatics, used to indicate lymphocytes emigrating from the tonsils, a different composition was found; e.g. many more T cells and three times more CD45RA+ than RO+ lymphocytes. Thus, HEV are not a selective entry site nor lymphatics an exit for specific lymphocyte subsets only, at least in these tonsils with chronic stimulation.

Adult↗
PubMed2000

Megakaryocytes and platelets in the spleen of the dromedary camel (Camelus dromedarius).

This study was carried out on spleens of clinically healthy camels (n = 35) of both sexes (0.5-15 years) by routine histology, electron microscopy and immunohistochemistry using 12 anti-bovine platelet antibodies. Megakaryocytes were observed in the red pulp. Their number decreased with age: they were found in the spleens of all camels under 8 years old but only in 57% of camels over 8 years old. Only two antibodies (IVA37 and IVA38) cross-reacted with camel platelets. A large number of platelets were found in the splenic cords and the marginal zone. Ultrastructurally, the platelets were oval in shape surrounded by a plasma membrane, and their cytoplasm was rich in glycogen and contained less dense granules. Microtubules and microfilaments were found at their periphery. Several platelets were observed in the red pulp. There are similarities in some surface antigens of bovine and camel platelets. The presence of megakaryocytes in the camel spleen indicates a thrombopoietic function of the spleen until adulthood but that this decreases with age thereafter.

Aging↗
PubMed2000

The spleen of the one humped camel (Camelus dromedarius) has a unique histological structure.

The histology and structure of 38 spleens of the dromedary (aged 0.5-15 y) were studied in relation to age. The spleen was found to have a thick capsule (292+/-106 mm) divided into an outer layer (113+/-39 mm) composed mainly of connective tissue and an inner layer (180+/-81 mm) consisting mainly of smooth muscle cells. Vascular and avascular trabeculae extend from the capsule, the former containing arteries and nerves but no trabecular veins, the latter being divided structurally into primary and secondary trabeculae. Subcapsular and peritrabecular blood sinuses around primary and vascular trabeculae are unique to the camel spleen. The central artery emerges from the periarterial lymphatic sheath and branches into up to 4 penicilli which extend as sheathed arterioles (42+/-8 microm). These are found near or surrounded by blood sinusoids of the red pulp. A wide marginal zone surrounds the white pulp and contains sheathed arteries but no marginal sinuses. The red pulp is characteristically divided into cords by secondary trabeculae and contains venous sinusoids of different sizes. The camel spleen is of a sinusal type that can store blood. The thick muscular capsule and trabeculae pump the stored blood according to the body's need. Both closed and open circulations are found. The venous return is unique as the blood flow is from the venous sinusoids of the red pulp to the peritrabecular sinuses to the subcapsular sinuses to the splenic vein. No significant structural differences related to age were found.

Aging↗
PubMed2000

[Recruitment of immunocompetent cells in a transplanted lung is not impaired despite incompletel reinnervation].

BACKGROUND: It is not clear whether surgical intervention during lung transplantation which includes cutting vegetative nerves, lymphatic vessels and bronchial arteries, leads to alterations in immune responses. Thus, it was studied in an animal model whether an induced pulmonary immune reaction after syngenic lung transplantation was impaired without the influence of immunosuppression and rejection. The recruitment of leukocytes and the status of reinnervation was examined. METHODS: Syngenic transplantation of the left lung was performed in Lewis rats without rejection and therefore without immunosuppressive therapy. In a subgroup of animals host and donor leukocytes were distinguished. An ovalbumin (OVA)-specific pulmonary immune response was induced four months after transplantation. Bronchoalveolar lavage (BAL) and interstitial leukocytes were examined using flow cytometry and immunocytology, comparing the right lung and the grafted left lung. Immunohistology was performed to detect nerve fibers on cryostat sections. RESULTS: An induced cellular inflammation was observed in the right host lung as well as in the grafted left lung. However, the CD4 T cell numbers in the BAL were increased in the left lung. Single donor-type leukocytes could still be observed four months after transplantation. A partial reinnervation was found. CONCLUSIONS: The recruitment of immune cells into the lung interstitium and bronchoalveolar space of grafted lungs is not impaired. The incomplete reinnervation has no influence on leukocyte recruitment.

Animals↗
PubMed2000

Lymphocytes migrate from the blood into the bronchoalveolar lavage and lung parenchyma in the asthma model of the brown Norway rat.

Lymphocyte migration from the blood into the lung has been suggested as being responsible for the increase of lymphocytes, in particular CD4 T cells, in the bronchoalveolar lavage (BAL) and bronchial mucosa in human asthma, but so far there has been no direct proof. We studied lymphocyte immigration and lymphocyte subpopulations in three lung compartments in ovalbumin (OVA)-sensitized and -challenged brown Norway (BN) rats. Increased numbers of CD4 and interleukin 2 (IL-2) receptor-positive T cells were found in the BAL and lung parenchyma in treated animals, but also increased numbers of CD8 T cells, B cells, and natural killer (NK) cells. For direct proof of lymphocyte migration from the blood into the lung, leukocytes were labeled with a fluorescent dye, 5- (and 6-) carboxyfluorescein-diacetate-succinimidyl-ester (CFSE), and injected intravenously immediately prior to OVA aerosol challenge. One day after challenge the number of CFSE(+), i.e., newly immigrated lymphocytes, was determined by flow cytometry gated on the lymphocyte cluster. A 15 times (1.5 times) higher number of CFSE(+) lymphocytes was found in the BAL (the lung parenchyma) of treated animals in comparison with control rats. In the BAL 51.8% of CFSE(+) cells were CD4-positive (parenchyma 72.7%) and 29.4% IL-2 receptor-positive (parenchyma 34.2%). There was no difference whether the leukocytes for labeling and injection were obtained from untreated or from OVA-sensitized donor animals. Our data show that lymphocyte immigration is at least in part responsible for the increase in lymphocyte numbers in the BAL and lung parenchyma in this animal asthma model.

Animals↗
PubMed2000

The carina as a landmark in central venous catheter placement.

Location of the tip of a central venous catheter (CVC) within the pericardium has been associated with potentially lethal cardiac tamponade. Because the pericardium cannot be seen on chest x-ray (CXR), an alternative radiographic marker is needed for correct placement of CVCs. The anatomy of the region was studied in 34 cadavers. The carina was a mean (SEM) distance of 0.4 (0.1) cm above the pericardial sac as it transverses the superior vena cava (SVC). In no case was the carina located below the pericardial sac. The carina is a reliable, simple anatomical landmark for the correct placement of CVCs. In almost all cases, the carina is radiologically visible even in poor quality, portable CXRs. CVC tips should be located in the SVC above the level of the carina in order to avoid cardiac tamponade.

Aged↗
PubMed2000

Leukocyte mobilization induced by hypervolemia is due to a combined alpha- and beta-adrenoceptor activation.

A phenomenon of leukocytosis induced by hypervolemic stress was discovered. Although a single injection of 350 microl of saline (equivalent to approx. 70 ml in humans, 1 ml/kg of body weight) did not have an effect on the leukocyte counts in long-term intravenously cannulated, freely behaving rats, a single injection of 750 microl of saline (equivalent to approx. 150 ml in humans, 2.1 ml/kg) induced rapid leukocytosis of 160% within 1 minute followed by a gradual increase up to 180% after 1 hour. Measurement of serum norepinephrine concentration revealed a significant increase in rats of the hypervolemic group, compared with those of the low volume group. Pretreatment with either the beta-adrenoceptor antagonist nadolol or the selective alpha2-adrenoceptor antagonist yohimbine prevented both leukocyte peaks in the high volume group, suggesting a combined receptor activation. This critical dependence of leukocyte counts on changes in blood volume should be taken into consideration in experiments with laboratory animals (the quantity of volume applications can falsify results of experiments).

Adrenergic alpha-Antagonists↗
PubMed1999

Lymphocyte migration in the intestinal mucosa: entry, transit and emigration of lymphoid cells and the influence of antigen.

Lymphocyte migration is important to transport immunological information between the different compartments of the intestinal immune system. Large numbers of lymphocytes emigrate from the Peyer's patches and reach the blood circulation after expansion and maturation within the mesenteric lymph nodes. So far the frequency of antigen specific lymphocytes emigrating from the Peyer's patches after oral stimulation is not known. After mesenteric lymph node resection those cells emigrating from the intestinal wall are accessible by calculating the major intestinal lymph duct. The first antigen specific cells draining from the intestines are obviously not lymphocytes but dendritic cells, thus the antigen is rapidly trapped in the parenchyma of the lymph nodes in vivo. When lymphocytes were taken from intestinal lymph, labeled in vitro and retransfused, marked numbers of B-cells were re-detected in intestinal lymph. Later preferentially T-cells recirculated through the gut wall. After immigration into the intestinal lamina propria the lymphocytes may enter the space between epithelial cells, where they are present as intraepithelial lymphocytes. Lymphoid cells in the S-phase of the cell cycle have been detected in all compartments of the intestinal wall. Apoptosis is probably a further important mechanism for the regulation of intestinal immunity in removing cells reacting against harmless dietary antigens to maintain oral tolerance.

Animals↗
PubMed1999

Postnatal development of lymphocyte subsets in different compartments of the small intestine of piglets.

In contrast to rodents, all compartments of the porcine small intestine contain lymphoid cells at birth. During the first few days of life maternal antibodies and leukocytes are taken up by the intestinal epithelium. The number of intraepithelial lymphocytes (IEL) increases by a factor of 12 from Day 1 to Day 60, but in germfree pigs only a minor increase is observed. Immediately after birth, low numbers of T cells are present in the small intestinal lamina propria (LP), and many of these express neither CD4 nor CD8 on their surface. This type of subset composition is still present in germfree pigs at an age of 1.5 months. The appearance of IgA+ and IgM+ lymphocytes in the LP differs. Many more of these B cells are found in the LP of the crypts than of the villi. The development of the discrete jejunal Peyer's patches (PP) differs from that of the continuous PP in the terminal ileum. The lymphocyte subset composition shows the most obvious differences between conventional and germfree piglets and between the jejunal and ileal PP at an age of 1.5 months. Several markers, e.g. for antigen-presenting cells, memory T cells, M cells in the domes of PP, have recently become available for the pig. These should now be applied in experiments on pigs in the early postnatal period to study the mechanisms of the development of tolerance and protective immune reactions.

Animals↗
PubMed1999

B and also T lymphocytes migrate via gut lymph to all lymphoid organs and the gut wall, but only IgA+ cells accumulate in the lamina propria of the intestinal mucosa.

In pigs the lymphocytes emigrating from the intestinal wall were collected by cannulating the lymphatics, labeled in vitro using a fluorescent dye and retransfused. The injection of 6.6+/-4.2 x 10(8) cells resulted in a labeling index between 1.5% in intestinal lymph, 0.2% in the spleen and lymph nodes, approximately 0.1% in the intestinal lamina propria and 0.003% in intraepithelial lymphocytes. About 25 % of the injected cells were present in the blood and 1 % was recovered in the lymph. T cells were found in similar proportions in the injected and the recovered cells in the organs (70-80%). The proportion of IgA+ cells among the immigrated cells in the intestinal lamina propria ranged from 5 to 8%, which in absolute numbers was up to 60% of the injected IgA+ cells. T and IgM+ cells did not show a higher accumulation in any organ. These experiments in conventional, unrestrained animals revealed that (1) T cells immigrate into the intestinal lamina propria, (2) preferential migration of IgA+ cells from gut lymph to the intestinal lamina propria is obvious under in vivo conditions and (3) the immigrated IgA+ cells represent a very small population which is difficult to detect when analyzed in relative numbers.

Animals↗
PubMed1999

Airway exposure to bacterial superantigen (SEB) induces lymphocyte-dependent airway inflammation associated with increased airway responsiveness--a model for non-allergic asthma.

Although immunological consequences of systemic superantigen administration have been extensively studied, the effects of local mucosal exposure to superantigens are not well defined. The purpose of this study was to delineate the type of immune response triggered by superantigen exposure to the airway mucosa in mice. In dose-response experiments we determined a low dose of staphylococcal enterotoxin B (SEB) that triggered an inflammatory response characterized by mucosal and airway recruitment of lymphocytes, eosinophils and neutrophils together with elevated levels of IL-4, but not IFN-gamma, in bronchoalveolar lavage (BAL) fluids. TCR Vbeta analysis revealed that superantigen-responsive and -non-responsive T cells were equally recruited into the airways. SEB markedly enhanced the frequency of TNF-alpha-positive BAL macrophages as well as the amount of TNF-alpha in BAL fluids. These responses were associated with the development of increased airway responsiveness (AR) in SEB-treated mice. This effect occurred in an antibody-independent fashion. Furthermore, this type of response was observed in IgE-high responder BALB/c as well as in IgE-low/intermediate responder C57BL/6 mice. The development of increased AR was CD4+ T cell dependent as shown by transfer experiments into BALB/c nu/nu mice. These results suggest that the local immune response following mucosal superantigen administration triggers a unique inflammatory response in the airways resembling many features of "intrinsic asthma".

Administration, Intranasal↗
PubMed1999

Activated T cells enter rat lymph nodes and Peyer's patches via high endothelial venules: survival by tissue-specific proliferation and preferential exit of CD8+ T cell progeny.

Activated T cells reach the lymph nodes via afferent lymphatics but it is unknown to what extent they also enter them directly via high endothelial venules (HEV). Little is known about the mechanism mediating the proliferation of activated T cells within lymphoid tissues in vivo or the subsequent fate of the progeny. Therefore, we stimulated rat T cells via TCR and CD28 in vitro and after injection identified them in the blood and the HEV of lymphoid organs at several time points. In addition, the proliferation of these cells was studied after entering different lymphoid organs. Our results show that, firstly, activated T cells continuously enter lymph nodes and Peyer's patches directly via HEV. Second, they proliferate within lymphoid organs, the rate significantly depending on the microenvironment. Third, mainly CD8+ progeny are able to leave the tissues and re-enter the blood. Thus, the distribution of activated T cells circulating through the body can be regulated during entry, but also within the tissue by influencing their proliferation and subsequent release.

Animals↗
PubMed1999

M cells at locations outside the gut.

Lymphoid tissue associated with mucosal membranes is found not only along the gastrointestinal tract, but also in the tonsils, the upper and lower airways, and the conjunctiva of the eye. The epithelia overlying this mucosa-associated lymphoid tissue (MALT) contain membranous (M) cells which transport antigenic matter across the mucosal membrane to initiate immune responses. Although the morphology and function of intestinal M cells have been thoroughly studied, relatively little is known about the presence and properties of M cells in MALT outside the gut. The available data on ultrastructure, histochemistry, and antigen sampling function of the epithelia in tonsils, nasal-, larynx-, bronchus-, and conjunctiva-associated lymphoid tissue are reviewed and critically discussed. It is concluded that, in principle, the concepts of mucosal immune protection can be applied to these sites of MALT. However, it is questionable whether a separate cell type similar to intestinal M cells exists and performs antigen sampling in the different MALT epithelia. Further studies combining functional and morphological techniques are essential to understand the initiation of immune reaction at the mucosal membranes.

Animals↗
PubMed1999

Enhanced expression of fas ligand (CD95L) on T cells after segmental allergen provocation in asthma.

BACKGROUND: Little is known about the termination of the T-cell driven inflammation found in patients with allergic asthma. OBJECTIVE: Because signals delivered through Fas/Fas ligand can lead to T-cell apoptosis, we investigated the expression of Fas and Fas ligand on peripheral blood- and bronchoalveolar lavage fluid (BALF)-derived T cells and the percentage of apoptotic BALF cells in asthma. METHODS: Nine atopic subjects with mild asthma and 9 control subjects underwent segmental sham and allergen challenge. Flow cytometry was used to determine the T-cell expression of Fas and Fas ligand, and the terminal dUTP nick end labeled technique was applied to detect apoptotic BALF cells. RESULTS: In asthmatic and control subjects almost all T cells in the BALF expressed Fas antigen without changes after saline or allergen challenge. A small percentage of T cells in BALF expressed the Fas ligand. In asthmatic subjects, but not in control subjects, there was a significant increase in Fas ligand after allergen challenge (CD3: 0.8% +/- 0.6% [baseline] vs 3.2% +/- 1.2% [allergen challenge]; CD4: 1.8% +/- 0.0% vs 4.3% +/- 1.8%; CD8: 2.8% +/- 2.4% vs 9.1% +/- 4.8%) but not after saline challenge, with a significant correlation to the percentage of BALF eosinophils. Apoptotic BALF cells were localized exclusively in macrophages at a very low frequency (0.03% to 0.15%) and without changes after saline or allergen challenge in both groups. CONCLUSION: In asthma there is an upregulation of Fas ligand on T cells in BALF after allergen challenge. Because there is no evidence for increased apoptosis, this phenomenon may reflect antigen-induced T-cell activation rather than apoptosis.

Adult↗