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Biomedical subjects

T D Allen

Publications and source records attributed to T D Allen.

At least 145 records · Page 8Linked to original sources
PubMed1981

Friend disease in vitro.

In long-term marrow cultures, hemopoiesis can be maintained for several months, although erythropoiesis is normally suppressed at the most primitive level of development (the erythroid colony-forming cells). Infection of these cultures with a viral complex combining helper-independent murine leukemia virus (F-MuLV) and a spleen focus-forming virus (SFFVp) results in a productive infection of both the replication defective SFFVp and the F-MuLV. After infection, the cultures show a dramatic elevation in the numbers of late erythroid progenitor cells (CFU-E), many of which will grow in the absence of added erythropoietin, and a transient erythropoietin, independent erythropoiesis, including the production of mature, enucleated erythrocytes. Hemopoiesis eventually declines, with no evidence for the generation of Friend tumor cells. When erythropoiesis is induced in the long-term cultures by addition of anemic mouse serum before infection by polycythemia-inducing Friend virus, the generation of erythropoietin-independent CFU-E and erythrocyte formation is followed by the sustained production (greater than 40 wk) of primitive erythroid cells with low spontaneous levels (less than 5%) of hemoglobinization. Although these cells will produce spleen colonies in irradiated mice and can be cloned in soft-gel media, they do not produce autonomous, permanently growing cell lines in vitro, i.e., they retain a dependency upon the marrow-adherent layer for their continued growth. However, following a further passage on a "virgin" marrow environment, permanent cell lines can be established that are able to grow independently of environmental influences. Thus, this system is the first description of a complete in vitro system for the reproducible production and isolation of Friend virus-induced erythroid cell lines.

Anemia↗
PubMed1981

Urinary undiversion in patients with myelodysplasia and neurogenic bladder dysfunction. Report of a workshop.

This workshop was conducted in an attempt to analyze critically the role of reconstruction of the myelodysplastic patient who had undergone urinary diversion and to develop guidelines for selecting those patients in whom urinary undiversion might be undertaken safely. The collective experience initially seems to be acceptable; however, the authors emphasize the gravity of the decision and the complexity of the evaluation which must be undertaken prior to embarking on such reconstructive surgery. Contrary to some reports, we believe that the defunctionalized bladder frequently can be evaluated. Further, many of the contraindications to urinary undiversion have been identified and several of the hazards involved therein can be avoided. We believe that the neurogenic bladder is no longer an absolute contraindication to undiversion. Our experience suggests that undiversion is a reasonable surgical treatment in select patient with neurogenic bladder dysfunction. But, the decision to remove a satisfactorily functioning conduit must not be undertaken lightly. Patients should be selected only after a thorough, detailed, and properly conducted evaluation. A protocol has been developed which will hopefully assist in this evaluation. Perhaps additional shared experience will further refine and delineate the circumstances appropriate for reconstruction of these patients.

Adolescent↗
PubMed1981

Conversion of blebs to microvilli: cell surface reorganisation after trypsin.

The blebbed surface morphology produced by trypsinisation of Chinese hamster ovary cells is subsequently reorganized to a microvillous topography, even in the continued presence of trypsin. Scanning and transmission electron microscope (SEM and TEM) observations of this transition showed the initial formation of a "crown' of densely clustered microvilli at one pole of the cell. At the periphery of this region the blebs coalesced to form ridges which subsequently extended over the entire cell surface. Long, and occasionally branched microvilli were generated from the ridges. Large numbers of membrane associated vesicles were also characteristic of these areas of surface reorganisation.

Animals↗
PubMed1981

Histochemical and ultrastructural characteristics of a cell line from human bone-marrow stroma.

Morphological, enzymic and antigenic data are presented regarding a human bone-marrow stromal cell line maintained for 10 months and subcultured weekly. The main characteristics are a fibroblastoid morphology, diffuse growth in collagen gels, no colony formation in soft gel media, contact inhibition of growth and conversion to adipocytes when treated with hydrocortisone. The cells are non-phagocytic and membrane Fc receptors (i.e. aggregated human immunoglobulin G receptors) are absent, but they show diffuse cytoplasmic non-specific esterase activity, a strong acid phosphatase reaction, and a negative immunofluorescence (direct and indirect) against factor VIII antigen. Other cell lines also have been isolated and maintained in culture and present similar characteristics. These cell lines are thought to be derived from the acid-phosphatase-positive marrow stroma directly associated with bone trabecular matrix and probably represent a component of the haemopoietic inductive microenvironment. As such, they may provide a useful tool for studies in vitro of cell interactions and regulatory processes in the control of human bone-marrow haemopoiesis.

Adipose Tissue↗
PubMed1981

Ultrastructural aspects of colchicine ultrasensitivity in CLL lymphocytes.

Circulating lymphocytes from patients with chronic lymphatic leukaemia show extreme sensitivity to colchicine, with 80%-90% cell death after exposure to 10(-7) M colchicine for 20 h in vitro. This is 100,000-times greater than the dose required (10(-2) M) for a similarly toxic effect on normal lymphocytes. A time course series of fixations during the 20-h exposure of chronic lymphoid leukaemia (CLL) lymphocytes to 10(-7) colchicine revealed an entire spectrum of ultrastructural alterations well in advance of any sign of cell death, previously only ascertained by nuclear pycnosis in the light microscope. The changes included the appearance of large numbers of intermediate filaments, loss of surface microvilli, mitochondrial alterations and the formation of annulate lamellae. Mitochondrial changes included disruption of the cristae, swelling and tight clumping of the entire mitochondrial population into a single region of the cytoplasm.

Adolescent↗
PubMed1981

Haemopoietic microenvironments in vitro: ultrastructural aspects.

Haemopoietically active long-term bone marrow cultures from several species have been investigated ultrastructurally. Human, tree shrew and mouse cultures generally support granulopoiesis, although recently it has been possible to convert a granulopoietic mouse culture to extensive erythropoiesis. The haemopoietic products of the cultures include granulocytes (neutrophil and basophil), mast cells, monocytes, megakaryocytes and all stages of the erythrocytic series. Plasmacytes and occasional lymphocytes have been observed in small numbers in human cultures (possible indicating retention rather than formation). The stromal elements of the adherent layer of these cultures include endothelial cells, reticulum cells, fat cells and fibroblasts. The adherent layers are responsible for the inductive microenvironment within the cultures, and show features specific for the line of differentiation. In the granulocytic cultures there is close association between developing fat cells (reticulum cells) and granulocyte precursors. Endothelial cell monolayers cover large regions of these cultures, and the areas beneath this monolayer are rich in early granulocytes. Mature granulocytes and monocytes migrate through the endothelial layer, demonstrating in vitro "transmural passage". Cultures stimulated for erythropoiesis show a considerable reduction in fat cells, in endothelial cell cover and in the numbers of classical monocytes. Erythropoiesis appears to be promoted by a close association of the entire erythrocytic series with monocytic cells, forming "erythroblastic islets" in vitro. A possible pathway of intracellular communication between differentiating haemopoietic cells and the stromal cells in their microenvironment is suggested.

Adipose Tissue↗
PubMed1981

Molecular and cell biologic aspects of erythropoiesis in long-term bone marrow cultures.

In long-term marrow cultures, proliferation and differentiation of hemopoietic stem cells occurs for several months. Normally, only the most primitive erythroid progenitor cells are produced (the BFU-E). Following treatment with anemic mouse serum (AMS) or normal mouse serum plus erythropoietin, the BFU-E mature into CFU-E, which then go to produce mature nonnucleated red cells. This development is associated with the production of adult type hemoglobin. Furthermore, erythropoiesis and granulopoiesis occur in association with discrete cellular elements of the adherent cell layer in the long-term culture. Following treatment with AMS, erythropoiesis is enhanced while granulopoiesis is depressed, with no apparent competition at the stem cell or progenitor cell level.

Adipose Tissue↗
PubMed1981

The production of putative osteoclasts in tissue culture - ultrastructure, formation and behavior.

A system for culture of cat bone marrow produces multinucleate cells (50-100 nuclei) of large proportions (300 micrometer diameter). Scanning and transmission electron microscopy indicates that these cells (not virally induced syncytia) are true osteoclasts, which exhibit ultrastructural aspects of bone resorption (ruffled border and clear zones in TEM section, active spatulate cytoplasmic extensions in the SEM) even after 6 weeks culture on a plastic substratum. Observations have also been made regarding the formation of the multinucleate cells from apparently specific mononuclear precursors, and the behaviour of these cells on various substrata is also reported.

Animals↗
PubMed1980

Undiverting the ileal conduit.

The experience described herein reinforces the belief that it is worthwhile to consider undiversion of the urinary tract in any patient in whom the indication for diversion initially was, upon re-examination, questionable. In children the optimum time for this appears to as the candidate approaches adolescence, since by then he has outgrown most of the incoordination of childhood and is likely to be highly motivated toward the idea of being freed from the external appliance. Evaluation of such patients requires consideration of many factors but the best guide to bladder potential is probably provided by the placement of a suprapubic catheter followed by bladder filling and voiding exercises. Finally, a careful analysis of the anatomy of the urinary tract is essential if the operation is to be undertaken safely and effectively. None of these steps is easy but the potential rewards are so great as to make them well worth the effort expended.

Adolescent↗