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Biomedical subjects

G Keller

Publications and source records attributed to G Keller.

At least 19 recordsLinked to original sources
PubMed1992

Factor-dependent erythroid cell lines derived from mice transplanted with hematopoietic cells expressing the v-src oncogene.

Transplantation of spleen cells from primary reconstituted mice expressing the v-src oncogene to secondary and tertiary irradiated recipients resulted in the emergence of erythroid precursors with a transformed phenotype. When cultured in methyl cellulose, these precursors generated colonies of undifferentiated cells that could be expanded into continuously growing factor-dependent cell lines in liquid culture. All lines tested had a similar phenotype and expressed the v-src oncogene. In addition they responded to factors that regulate normal erythroid development, namely erythropoietin (Epo), interleukin-3 (IL-3), and mast cell growth factor (MGF), the ligand to the c-kit encoded receptor. When cells from one of the lines were maintained in the absence of factor, a "factor independent" subpopulation emerged that appeared to grow in an autocrine fashion. Conditioned medium from these cells stimulated their own growth as well as the growth of broad spectrum of normal precursors. Studies with neutralizing antibodies indicated that the predominant colony-stimulating factor produced by these cells is IL-3.

Animals↗
PubMed1992

Experimental changes in mineral content of juvenile mouse femora.

Juvenile laboratory mice were exposed to hypergravity (8 g), burrowing exercise, swimming to exhaustion, an anabolic steroid, and swimming and an anabolic steroid for 30 days to determine the variability of skeletal mineralization during growth. Changes in mineralization were correlated with changes in bending strength. Experimental mouse femora were loaded to failure in a cantilever beam configuration to determine bending strength, and ashed to determine total mineral content. Between experimental groups, mineral content ranged from 66.0 to 71.2% with the greatest change from the control being a 4.7% decrease in mineralization in the male swimming exercise group (P less than 0.001). Within two age-matched experiments, the first showed that the group with the greatest decrease in mineralization also had the greatest reduction in bending strength (P less than 0.001). The second age-matched experiment showed that the group with the greatest reduction in mineralization had bending strength greatly reduced (P less than 0.001). However, in this experiment, the weakest femora were in the anabolic steroid group that did not have the mineral content reduced. We conclude that (1) mineralization of juvenile mouse femora is extremely variable given varied conditions of exercise or loading; (2) mineralization of normal bone is decreased more often and to a greater extent than increased from normal exercise controls; (3) the decrease in mineralization seen here can decrease bending strength; and (4) the decrease in mineralization seen was not caused by a decrease in a mechanical loading but was probably due to a corticosterone-mediated psychological stress response.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Hematopoietic stem cells.

Recent studies indicate that hematopoietic stem cells that provide long-term reconstitution can be separated from more mature hematopoietic cells that provide radioprotection and short-term repopulation. With these findings it is now possible to design assays that will specifically measure long-term repopulating stem cells, as well as to develop culture systems that can be used to analyze the effects of known and putative novel cytokines on their growth and differentiation.

Animals↗
PubMed1992

Influence of metabolic inhibitors on the degradation of tight junctions in HT29 cells.

The human colon adenocarcinoma cell line HT 29 grows in culture without tight junctions (TJ). Tight junction strands of the fascia occludens type can be induced by treatment with proteases and are subsequently degraded during a period of about 3 h. Experiments using a variety of metabolic inhibitors such as 2-deoxyglucose, 2,4-dinitrophenol, and CCCP show that the degradation of TJ is retarded under conditions of ATP depletion. Thus it appears that the removal of TJ from the cell surface is an energy-dependent process. Moreover, DNP can specifically inhibit the degradation of TJ even in the absence of ATP depletion. The possible involvement of a proton gradient in the mechanism of TJ degradation is discussed.

2,4-Dinitrophenol↗
PubMed1992

Rescue of erythroid development in gene targeted GATA-1- mouse embryonic stem cells.

Development of definitive (fetal liver-derived) red cells is blocked by a targeted mutation in the gene encoding the transcription factor GATA-1. We used in vitro differentiation of GATA-1- mouse embryonic stem (ES) cells to reveal a requirement for GATA-1 during primitive (yolk sac-derived) erythropoiesis and to establish a rescue assay. We show that the block to development includes primitive, as well as definitive, erythroid cells and is complete at the level of globin RNA expression; that the introduction of a normal GATA-1 gene restores developmental potential both in vivo and in vitro; and that efficient rescue is dependent on a putative autoregulatory GATA-motif in the distal promoter. Use of in vitro differentiated ES cells bridges a gap between conventional approaches to gene function in cell lines and analysis of loss of function mutations in the whole animal.

Animals↗
PubMed1991

Fractionation of mouse bone marrow by adherence separates primitive hematopoietic stem cells from in vitro colony-forming cells and spleen colony-forming cells.

Fractionation of mouse bone marrow by adherence to tissue culture plastic was used to characterize the adhesive properties of hematopoietic stem (HS) cells capable of long-term reconstitution. The adherent fraction that represents approximately 13% of the total marrow population was virtually devoid of in vitro colony-forming cells and spleen colony-forming cells but did contain approximately 30% of the total HS cells recovered from the procedure. These cells could be detected by both the competitive repopulation assay and by repopulation of W/Wv recipients. In approximately 60% of the recipients from the competitive repopulation experiments, the contribution of the adherent marrow cells was relatively low early (8 to 10 weeks) after transplantation. With time, however, the hematopoietic contribution from these cells increased, reaching a stable level 20 to 30 weeks posttransplantation. In the remaining recipients (40%), the contribution from adherent cells was already significant within 8 to 10 weeks of transplantation and did not change dramatically throughout the course of the experiment. Adherent bone marrow containing significant numbers of HS cells was unable to protect mice from radiation death, indicating that these early cells in the absence of later-stage progenitors are unable to provide this function.

Alleles↗
PubMed1991

Multiple hematopoietic lineages develop from embryonic stem (ES) cells in culture.

When embryonic stem cells are cultured directly in semisolid media (methyl cellulose), they proliferate and differentiate to generate colonies known as embryoid bodies (EBs). These EBs consist of differentiated cells from a number of lineages including those of the hematopoietic system. Following 10 days of culture in the presence of 10% fetal calf serum, more than 40% of all EBs from three different ES cell lines, CCEG2, D3 and SQ1.2S8 contained visible erythropoietic cells (i.e. red with hemoglobin). Beta H1 (z globin) mRNA is detectable in EBs within 5 days of differentiation, whilst beta(maj)-globin RNA appears by day 6. In the presence of erythropoietin (Epo), the frequency of EBs with erythropoietic activity increases to greater than 60%; Epo also prolongs this erythropoietic activity. Interleukin-3 (IL-3) does not significantly increase the frequency of EBs that contain erythroid cells, but increases slightly the number of erythropoietic cells associated with them. In the presence of IL-3, in addition to cells of the erythroid lineage, macrophages, mast cells and in some instances neutrophils are found within differentiating EBs. The development of macrophages is significantly enhanced by the addition of IL-3 alone or in combination with IL-1 and M-CSF or GM-CSF. When well-differentiated EBs are allowed to attach onto tissue-culture plates and grown in the presence of IL-3, a long-term output of cells from the mast cell lineage is observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Initial experience with placental protein 4 (PP-4) as tumor marker in cervical and endometrial cancer.

PP-4, a recently characterized glycoprotein from human placenta was studied using a specific double-antibody radioimmunoassay in sera of 130 volunteers, 74 cervical cancer patients and 43 endometrial cancer patients. Elevated levels (greater than 3 micrograms/l) were found in 35 (47.3%) cervical cancer patients and in 18 (41.9%) endometrial cancer patients. Degree of elevation were not correlated with clinical stage, histology, and histological degree of differentiation. 36 patients with cervical cancer and 20 patients with endometrial cancer were monitored on two to seven occasions during four to 50 weeks. Rising, remaining unchanged of falling levels of PP-4 correlated with progression, stabilization or regression of disease 55.5% in patients with cervical and 65.0% in patients with endometrial cancer. During and some months after external telecobalt irradiation therapy wide range of PP-4 levels were observed in some patients. The study suggest that PP-4 can be regarded as a tumor associated protein which most likely can serve as tumor marker in cervical and endometrial cancer.

Annexin A5↗
PubMed1990

Cell-type control of membrane biogenesis induced by HMG-CoA reductase.

Quantitative increases in HMG-CoA reductase, the rate-limiting enzyme in sterol biosynthesis, induce membrane biogenesis in both yeast and mammalian cells. The subcellular organization of the resulting membrane differs in the two cell types: mammalian cells generate crystalloid endoplasmic reticulum whereas yeast cells assemble karmellae. We examined the consequences of heterologous expression of HMG-CoA reductase to distinguish features of this response that were cell-type specific from those that were isozyme-specific. This analysis demonstrated that membrane proliferation was induced in both mammalian and yeast cells by HMG-CoA reductase from either organism. However, the morphology of the induced membranes was determined by the cell type rather than the particular isozyme. Thus, both yeast and mammalian HMG-CoA reductase contained functional signals for membrane proliferation that were operational in either cell type, but the qualitative response to those signals was cell-type specific.

Animals↗
PubMed1979

Oxygen consumption during maintenance hemodialysis.

The influence of hemodialysis on oxygen consumption was studied in 15 patients on maintenance dialysis. Red cell 2,3-DPG, P50, an inverse measure of oxygen affinity of hemoglobin, arterial and central venous blood gases and cardiac index were measured. 2,3-DPG remained unchanged, whereas in vivo P50 fell significantly during dialysis due to a rise of pH (Bohr effect). Arterial PO2 was lower after than before dialysis, but arterial and central venous oxygen saturations did not change significantly. Cardiac index increased from 3.66 to 4.0k liter/min/m2. Oxygen consumption rose from 120.5 to 131.7 ml/min/m2 (p less than 0.05), the rise being accounted for by an increase in cardiac index and by a slight post-dialysis hemoconcentration. However, even correcting for these parameters did not reveal a decrease in oxygen consumption. It is concluded that, contrary to previous assumptions, the hemodialysis-induced rise in pH with its consequent increase of oxygen hemoglobin affinity did not impair oxygen delivery in this group of patients on maintenance dialysis.

Adult↗
PubMed1978

[A study of the retinal pigmentary epithelium in vitro (author's transl)].

The different phases of phagocytosis by retinal pigment epithelium in vitro were studied by scanning (SEM) and transmission electron microscopy (TEM). Organotypical and histiotypical cells were stimulated by polystyrene microspheres in the presence of inhibitors of microfilament contraction (cytochalasine B) and cellular translocation (colchicine). The possible function of microfilaments and microtubules during the phagocytosis is briefly discussed.

Animals↗
PubMed1977

Effects of colchicine on phagosome-lysosome interaction in retinal pigment epithelium. II. In vitro observations on histio-organotypical retinal pigment epithelial cells of the pig (a preliminary report).

Phagocytic activity of histiotypical and organotypical retinal pigment epithelial cells was studied by SEM and EM. After a latent period polystyrene microspheres of different diameter were captured by newly formed microvilli. No mechanism of discrimination according to the size of microspheres was observed. After engulfment, microvilli of histiotypical cells decreased in length and finally disappeared. Lysosomes increased in number when compared to unstimulated cells and fused with many latex-containing phagosomes. Colchicine, when added at 5 X 10(-5) M to the medium, inhibits phagosome-lysome interaction, thus confirming in vivo observations.

Animals↗