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Biomedical subjects

R Pabst

Publications and source records attributed to R Pabst.

At least 145 records · Page 8Linked to original sources
PubMed1994

Lymphoid and non-lymphoid cells in the epithelium and lamina propria of intestinal mucosa of pigs.

The jejunum and ileum of 5 day old and adult normal pigs and of 45 day old germ free pigs were used to study the lymphocyte pools in the epithelium and lamina propria by sequential treatments with EDTA, four hours, and 12 hours of collagenase treatment. In adult animals the incubation of the jejunal wall with EDTA resulted in mean (SD) 26.8 (10.9) x 10(6) intraepithelial lymphocytes per g of tissue. The ileal wall gave lower cell yields. After complete digestion of the lamina propria by collagenase a further yield of 35.2 (10.2) x 10(6)/g lymphocytes was achieved. The separation of the gut wall from 5 day old pigs resulted in a 10-fold lower total lymphocyte yield, and the tissue was totally digested after four hours of collagenase treatment. Many eosinophils and mast cells were found in the suspensions from adult animal tissues after the collagenase treatment; 4.7 x 10(6)/g and 4.8 x 10(6)/g, respectively. The suspensions after 12 hour collagenase incubation contained up to 30% plasma cells. Almost all cells isolated by EDTA incubation were CD8+ T cells. After collagenase incubation CD4+ and CD8+ T lymphocytes were found in all animal groups, and in adult animals up to 20% surface Ig+ cells were harvested. When the incorporation of the thymidine analogue bromodesoxyuridine was used to study the lymphocyte production in vivo 3 to 7% lymphocytes in the epithelium were labelled 24 hours later (lamina propria T lymphocytes about 1%). In this study lymphoid as well as non-lymphoid cells have been analysed in mucosal cell suspensions. The absolute cell yield per gram of mucosal tissue is a basis to estimate the pool sizes of intraepithelial and lamina propria lymphocytes.

Aging↗
PubMed1993

Overseas electives.

Explore the source record for details and available documents.

Clinical Clerkship↗
PubMed1993

IFN-gamma influences the migration of thoracic duct B and T lymphocyte subsets in vivo. Random increase in disappearance from the blood and differential decrease in reappearance in the lymph.

Thoracic duct lymphocytes (TDL) continuously patrol through the body, facilitating immune responses at most sites. IFN-gamma might regulate immune responses by influencing the migration of TDL. Therefore, it was investigated in vivo whether IFN-gamma affects the migration of thoracic duct B, T, CD4+, and CD8+ lymphocytes from blood to lymph. Labeled TDL were injected i.v. into rats continuously receiving IFN-gamma via a central venous catheter. The numbers of B, T, CD4+, and CD8+ lymphocytes were determined in blood and thoracic duct lymph for 120 h. IFN-gamma increased the disappearance of TDL from the blood to a similar extent in all subsets. In contrast, the reappearance of B and T lymphocyte subsets in the lymph was decreased: B lymphocytes were affected significantly more than T lymphocytes, whereas CD4+ and CD8+ lymphocytes were affected to a similar extent. Our study suggests that differential retention within the tissue rather than preferential immigration into the tissue creates a microenvironment with a distinct composition of lymphocyte subsets.

Animals↗
PubMed1993

Gross anatomy: an outdated subject or an essential part of a modern medical curriculum? Results of a questionnaire circulated to final-year medical students.

Final-year undergraduate medical students were given a questionnaire on the gross anatomy curriculum they had experienced in their first year at medical school 5 years earlier. They were asked to evaluate the relevance of the dissection course, lectures and seminars in gross anatomy for clinical courses, clerkships, and everyday practical work on the ward. About two-thirds of the students found the time spent on 10 different regions in anatomy to be adequate, and a considerable number of students would have liked even more details. The vast majority expressed a wish to repeat topographical anatomy during their clinical teaching. Furthermore, approximately 75% of the students showed interest in short, specialized dissection courses during the clinical curriculum. Medical students just before graduation ranked gross anatomy with the dissection course and integrated clinical topics as a keystone for their clinical courses. The results of such surveys should be taken into consideration when discussing modifications to teaching gross anatomy or arguing about a balanced dissection course.

Anatomy↗
PubMed1993

Lymphoid cells in afferent and efferent intestinal lymph: lymphocyte subpopulations and cell migration.

Gut wall emigrating cells have been characterized in the intestinal lymph. The intestinal lymph duct was cannulated in 6-month-old minipigs. Under non-restraining conditions the efferent lymph from the mesenteric lymph nodes was collected in seven normal animals. Lymph coming directly from the gut (afferent lymph) was also collected in 18 pigs after resection of the mesenteric lymph node chains 3 months previously. The intestinal lymph flow was similar in both groups (around 18 ml/h). The lymphoid cell yield was 1.2 +/- 1.0 x 10(6)/h in control animals, while in mesenteric lymph node resected pigs it was around 20 times higher (26.2 +/- 17.6 x 10(6)/h). In the gut-derived lymph 76.5 +/- 8.8% T lymphocytes were observed (CD4+, 48.1 +/- 15.5%; CD8+, 53.6 +/- 12.7%). The percentage of immunoglobulin-positive cells was lower (IgM+, 10.1 +/- 4.5; IgA+, 1.7 +/- 1.1). In 14 mesenteric lymph node resected pigs a mean of 5.6 +/- 3.1 x 10(8) lymphocytes from the gut lymph were labelled in vitro with a fluorescent dye and retransfused. The labelling index of fluorescent cells in the intestinal lymph increased rapidly and remained at a high level until 44 h after cell transfusion. A four-to-ten times lower labelling index was found in the spleen, various lymph nodes and Peyer's patches. Most of the recovered lymphocytes were T cells. This model provides access to the cell pool leaving the gut wall, thus allowing an examination of its role in the gastrointestinal tract and other mucosal-lined organs.

Animals↗
PubMed1992

Random entry of circulating lymphocyte subsets into peripheral lymph nodes and Peyer's patches: no evidence in vivo of a tissue-specific migration of B and T lymphocytes at the level of high endothelial venules.

Lymphocytes continuously migrate through the body and thus immune competent cells are constantly delivered to most tissues. They interact with high endothelial venules (HEV) via specific homing receptors and vascular addressins, and these molecules seem to be the reason for a preferential homing of B lymphocytes into Peyer's patches and of T lymphocytes into peripheral lymph nodes. When lymphocytes derived from lymph node cell suspensions were applied in the in vitro lymphocyte/endothelium binding assay, the well-known preference of mouse lymph node B lymphocytes for Peyer's patch HEV compared to peripheral lymph node HEV was confirmed in the rat (2.8 times). When in the same in vitro assay thoracic duct lymphocytes (TDL) were used this preference was far less obvious (1.4 times). However, by injecting rat TDL intravenously and by tracing them directly in HEV, B, T, CD4+ and CD8+ lymphocytes are seen to enter Peyer's patches and peripheral lymph nodes in vivo without preference. Thus, in contrast to lymphocytes from lymph node cell suspensions, no evidence was found of a tissue-specific migration of thoracic duct B, T, CD4+ and CD8+ lymphocytes at the HEV level. This finding demonstrates the importance of considering both experimental conditions and the cell source used when investigating lymphocyte traffic.

Animals↗
PubMed1992

Distribution of lymphocyte subsets and natural killer cells in the human body.

The frequency and distribution of B and T lymphocyte subsets have been determined in many body tissues and fluids by preparing cell suspensions and tissue sections from lymphoid and nonlymphoid organs. In humans these studies often concentrate on the blood or on one particular cell source for obvious reasons. However, such data can only be interpreted correctly if the whole immune system is taken into consideration [64]. To facilitate this, reports on the frequencies and the absolute numbers of B and T lymphocyte subsets within various human tissues and fluids have been collected from a wide variety of journals and are briefly summarized here. Since the size of lymphoid organs varies with age (e.g. thymus, tonsils), only the data of adult individuals were included, unless otherwise stated. Natural killer (NK) cells are morphologically quite similar to lymphocytes [59], but very different functionally. For example, they are not able to recirculate from the blood via the lymph nodes and the thoracic duct back to the blood as lymphocytes do [19]. Thus, human NK cells have been compared with lymphocytes with respect to number and distribution.

Body Fluids↗
PubMed1992

Low incidence of bronchus-associated lymphoid tissue (BALT) in chronically inflamed human lungs.

The relevance of bronchus-associated lymphoid tissue (BALT) in man is still under discussion. Animal experiments indicate that the development of BALT is dependent on microbial stimulation. Therefore, the incidence of BALT was investigated retrospectively in specimens removed during surgical procedures on patients with chronic pulmonary inflammation. All these patients had severe chronic bronchitis and bronchiectasis, but BALT was found in only 8%. In patients with BALT and a malignant tumor, occlusion of a bronchus with poststenotic pneumonia was always present and BALT was observed exclusively in areas peripheral to the occlusion. In man other compartments of the lung must be responsible for the immune function of BALT found in animals.

Adolescent↗
PubMed1992

Splenic autotransplantation provides protection against fatal sepsis in young but not in old rats.

Splenectomy increases the risk of contracting infections with high mortality. Thus, splenic tissue should be repaired orthotopically whenever possible. If all attempts fail, splenic autotransplantation might be a suitable method for splenic salvage. The protective function of such transplants in adults has been questioned, leading to a decreased frequency of splenic autotransplantations. However, the regeneration of splenic tissue is better in the young organism than in the old, suggesting that the protection provided by regenerated splenic tissue might be more reliable in children than in adults. In addition, children are at a higher risk in the case of overwhelming postsplenectomy sepsis. The protection warranted by regenerated splenic tissue after autotransplantation at different ages was examined using a highly standardized animal model. Sham operation, splenectomy, and splenic autotransplantation were performed on adult, weanling, and newborn rats, and Streptococcus pneumoniae was applied intranasally 9 months after the operation. After pneumococcal challenge about 80% of the splenectomized animals in the different age groups died of infection, whereas only 20% of the sham operated rats died. Regenerated splenic tissue resulting from splenic autotransplantation performed on adult or weanling rats demonstrated no protective function. However, in newborn rats with transplanted splenic tissue, both survival rate and survival time were increased significantly. Determination of lymphocyte subsets in the blood did not allow the protective role of splenic transplants to be predicted. This study indicates that disappointing results of splenic autotransplantation in adult patients should not lead to false pessimism about the role of this operation in children.

Age Factors↗
PubMed1992

Is BALT a major component of the human lung immune system?

Bronchus-associated lymphoid tissue (BALT) has been shown to be an important component in the immune system of the lung of several species, notably the rabbit and the rat. Does BALT fulfil the same function in the human lung? Reinhard Pabst thinks not and proposes an integrated model of the lung immune system, in which BALT plays but a minor role.

Animals↗