Biomedical subjects

S Singha

Publications and source records attributed to S Singha.

3 recordsLinked to original sources

PubMed2002

In vitro expansion of cord blood does not prevent engraftment of severe combined immunodeficient repopulating cells.

This study aimed to assess the potential of human cord blood (CB) cells to engraft in the xenogenic non-obese diabetic/severe combined immunodeficient (NOD/SCID) mouse model after in vitro expansion culture. We also studied the quality of human haemopoiesis arising from the transplantation of fresh or expanded cells in this model. Cord blood CD34(+) cells were cultured for 3, 7 or 10 d with stem cell factor, Flt3, thrombopoietin, interleukin 3 (IL-3), IL-6 and granulocyte colony-stimulating factor, all at 10 ng/ml in serum-replete conditions. Transplantation of mice with fresh CB containing 3 x 10(4) CD34(+) cells and 1-2 SCID repopulating cells (SRC) resulted in a median of 7.4% (0.4%-76.8%) human engraftment. When mice received the expanded product of 1-2 SRC, the ability to repopulate NOD/SCID mice was maintained even after 10 d of in vitro culture. Serial dilution of the expanded cells suggested that in vitro expansion had increased SRC numbers two- to fourfold. Expanded SRC produced long-term culture-initiating cells, clonogenic cells and CD34(+) cells in the same proportions as fresh cells after successful engraftment. Therefore, expanded SRC were able to differentiate in the same way as fresh SRC. There was a trend towards lower levels of engraftment when d 7 cultured cells were transplanted (median engraftment 0.8%, range 0.0-24.0%) compared with 1-2 fresh SRC. Our data suggest that this is owing to reduced proliferation of cultured cells in vivo. By utilizing limiting numbers of CB SRC, we confirmed that the engraftment potential of SRC in the NOD/SCID model was preserved after in vitro expansion. Furthermore, dilution experiments strongly suggest two- to fourfold expansion of SRC in vitro. These studies are relevant for developing clinical stem cell expansion strategies.

Animals↗

PubMed2000

Professional and non-professional antigen-presenting cells in the porcine small intestine.

We have previously presented evidence of a highly organized and compartmentalized structure of the small intestinal lamina propria of the pig. In this work, we have identified at least two major populations of cells in this site expressing high levels of major histocompatibility complex (MHC) class II antigens. One is CD45 positive and is a potent initiator of a primary immune response, this is a function usually associated with dendritic cells. These cells have characteristic dendritic morphology, but show evidence of phagocytosis as well as other phenotypic markers of immature dendritic cells. Some cells show evidence of ongoing immune maturation. We have also isolated CD45 negative endothelial cells bearing significant amounts of MHC class II, which do not trigger a mixed lymphocyte reaction. These findings have implications for the functional role of healthy gut lamina propria and clearly implicate this site as capable of differential antigen presentation by a heterogeneous population of antigen-presenting cells.

Animals↗

PubMed1996

Mediastinal tracheostomy.

BACKGROUND: Advanced carcinoma of the lower neck with direct extension to the superior mediastinum is a major therapeutic challenge. Complete removal of the tumors requires a radical operation in order to remove the larynx, portions of trachea and esophagus, and to construct a tracheostomy stoma with intrathoracic trachea. METHODS: We present our experience and technique for removal of difficult tumors in this region and construction of mediastinal tracheostomy. A technique for reconstruction of a very short segment of distal trachea is also proposed. Twelve mediastinal tracheostomies were performed; all except 3 patients underwent total laryngopharyngectomy and resection of tumor with gastric pullup. RESULTS: There were 2 operative deaths, 1 from tracheoinnominate artery fistula and the other from cerebral infarction. Complications included pharyngeal fistula (2 patients), respiratory failure (1), and osteomyelitis of sternum (1). Postoperative survival was disease-dependent. All patients who survived the operation achieved good airway patency and relief of dysphagia. CONCLUSIONS: The method of airway reconstruction by mediastinal tracheostomy is an advance in surgical treatment of malignancies in the cervicothoracic region. By careful selection of patients, successful operation resulted in good palliation and sometimes cure with acceptable quality of life.

Adult↗