Biomedical subjects

W Mannhardt

Publications and source records attributed to W Mannhardt.

22 records · Page 2Linked to original sources

PubMed1984

Macrophage subpopulations regulate intrathymic T-cell development. II: Ia-negative macrophages decrease thymocyte viability and proliferation by formation of thymocyte-macrophage-rosettes.

The influence of H2-Ia-negative macrophages (Ia-M phi) on thymocyte viability and proliferation was investigated. Peritoneal as well as Ia-M phi of thymic origin were used in this study and yielded similar results. Cocultivation of thymocyte with 4.5% Ia- M phi diminished thymocyte viability by about 70% and mitogen-induced proliferation by about 90% in comparison to control cultures without addition of M phi. These suppressive effects were related to rosette formation between thymocytes and Ia- M phi: more than 80% of Ia- M phi formed rosettes with immature thymocytes. Mature thymocytes (i.e. PNA-negative, steroid-resistant cells) rosetted in only 5% and were consequently not affected by M phi-mediated suppression. Since Cytochalasin B, known to inhibit rosette formation, abolished the suppressive effects of M phi, and supernatants of M phi cultures exhibited no inhibition of thymocytes, close cell contact (rosette) is apparently necessary for the inhibitory phenomenon. Suppression, however, seems to depend further on the functional state of the M phi: ingestion of carbon particles significantly diminished the inhibitory effect on thymocytes despite further presence of rosettes. The results suggest that Ia- M phi have a regulatory function within thymus physiology. While Ia+ M phi promote thymocyte proliferation as described elsewhere, the Ia- M phi may control the number and kind of thymocytes released by the thymus gland.

Animals↗

PubMed1982

T-cell independent reconstitution of the immunoglobulin levels in nu/nu mice.

Nude mice (BALB/c, H-2d) were transplanted under the renal capsule either with allogeneic (CBA, H-2k; C57B1/6, H-2b) or human thymus that were long-term precultured or pretreated in vitro with Carrageenan for three days. None of the thymus tissue transplants showed lymphatic repopulation 9 wk after transplantation. Histological investigation of the peripheral lymphatic tissue did not reveal any change in the thymus-dependent area. On the other hand, plasma cells and germinal centers could be found in significantly increased numbers. In addition, a normalization of the serum immunoglobulin concentrations could be found, as no specific antibodies against thymus-dependent antigens were present after immunization and T-cell function did not improve. Similar results were obtained 9 wk after injection of irradiated thymocyte suspensions or of peritoneal macrophages from immunocompetent donors. It is concluded that thymus epithelial cells could act via macrophages on the polyclonal maturation and differentiation of B cells without involvement of T cells. This would be in agreement with the experience in some patients with severe combined immunodeficiency (SCID) in which reconstitution of the immunoglobulin levels is observed after transplantation of cultured thymus tissue before T-cell reconstitution can be demonstrated.

Animals↗

PubMedDate not supplied

[Pre- and postpartum ultrasound examinations for diagnosis of urogenital abnormalities].

BACKGROUND: The aim of the study was to evaluate prenatal and postpartal sonographic investigations to diagnose congenital uropathies. PATIENTS/METHODS: The Mainz birth defect monitoring system, the "Mainzer Model", was launched in 1990. Over a period of five years (1/90 to 1/95) 19,028 newborns underwent postpartal sonographic examination. Anamnestic data including prepartal sonographic examination were collected. According to a defined ultrasound criteria list, ultrasound findings were considered normal in 94.8% of the neonates, 4.4% were defined as requiring a follow-up examination and 0.8% were pathological. In the current study we analyzed patients with pathological findings with their pre- and postpartal sonographic investigations as well as their clinical data (urinary tract infections, operative procedures). RESULTS: In the study group prenatal ultrasonography showed evidence of severe anomalies only in 51 fetuses (32.9%). Surgical correction was required in 39 cases. 20 (51%) have been diagnosed prenatally. 28 patients presented with urinary tract infections. Out of this group only 11 patients have been detected by prenatal ultrasound. CONCLUSION: In conclusion, postnatal ultrasound is more effective to diagnose anomalies of the urinary tract. To prevent complications i.e. urinary tract infections a neonatal screening program would be valuable.

Female↗

PubMedDate not supplied

[Granulocyte function in premature infants before the 34th week of pregnancy and in mature newborn infants].

BACKGROUND: Preterm and term neonates have an increased risk to develop severe bacterial infections. Impairment of neutrophil function may be responsible for this increased risk. Other diseases related to prematurity like retinopathia of prematurity (ROP) or broncho-pulmonary dysplasia (BPD) on the other hand may be due to poorly controlled O2-radical production. PATIENTS AND METHODS: Blood samples of 112 premature (34 weeks of gestation and older) and term neonates were analysed. Blood samples of 23 healthy adults (18 to 50 years old) served as controls. O2-radical production and phagocytosis of neutrophils were determined by flow cytometry, using a commercial test system. RESULTS: Under the experimental conditions applied, the capacity to produce O2-radicals following vigorous stimulation (E. coli) is comparable between neutrophils of preterm/term neonates and healthy adults. However, unstimulated or weakly stimulated (fMLP) neutrophils of preterm and term neonates show a statistically higher O2-radical production as neutrophils of the control group. The production of oxygen radicals increases during the first 10 days of the life. The capability of neutrophils to phagocytose E. coli is significantly lower in newborns (preterm and term) compared to the adult controls. CONCLUSIONS: The values reported here for phagocytosis and O2-radical production utilizing a commercially available test system may serve as "preliminary normal values" for neonates. No differences were found between the groups of neonates with and without infection. Impaired neutrophil-phagocytosis possibly contributes to the increased risk of preterm and term neonates to acquire bacterial infections. The increased spontaneous O2-radical production, on the other hand, may play a role for the development of so called "free radical diseases" such as ROP or BPD. However, our results cannot add further proof to this hypothesis.

Adult↗