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PubMed1981

Characterization of the T lymphocyte colony-forming cells and evidence for the acquisition of T cell markers in the absence of the thymic microenvironment in man.

The nature of the T colony-forming cell (T-CFC) in agar is still controversial. We present evidence that blood mononuclear cells depleted of T cells by E-rosetting or lysis with OKT 3 and complement can give rise to E+ OKT 3+ colonies in the presence of supernatants of PHA-stimulated lymphocytes (P-SUP) containing a cell growth factor. Both OKT 4+ (67%) and OKT 8+ (32%) cells were found in the colonies, and less than 10% of these cells were Ia+. We consider that colonies in agar can arise from the proliferation and maturation of a circulating immature progenitor (T colony-forming cell, or T-CFC) that does not need the thymic environment to acquire the OKT 3, 4, and 8 antigens or E receptor. In contrast, Ia+ OKT 3+ cells that are maintained by P-SUP in long-term liquid culture are reportedly derived from mature T cells, and this proliferation might represent the counterpart of the in vivo response to any mitogenic stimulation of the peripheral compartment of mature T cells.

Antibodies↗
PubMed1981

Growth stimulation of microenvironment-dependent mouse leukemias by tumor-promoting phorbol esters.

The effects of 12-O-tetradecanoylphorbol 13-acetate (TPA) and related tumor-promoting phorbol esters on 23 symbiotic cell lines from AKR thymic leukemias were studied. The phorbol derivatives with in vivo cocarcinogenic activity increased the viable yield of leukemia cells of most symbiotic cell lines in the absence of growth-supporting adherent cells. Particularly, in 10 cell lines remarkable growth stimulation was observed with 1 to 10 ng TPA/ml. The effect of TPA was reversible, since the leukemia cells exposed to TPA for 48 hours failed to grow without TPA or adherent cells. The leukemia cells from a symbiotic cell line could be maintained in TPA-containing medium for as long as 8 weeks without losing dependence. The leukemia cells were refractory to growth stimulation by TPA after they acquired the capability to grow independently. Furthermore, by affecting the leukemia cells, TPA and active tumor promoters inhibited pseudoemperipolesis (i.e., localization of leukemia cells under or between adherent cells), which is the basic cell interaction in symbiotic complexes. These effects of tumor-promoting phorbol esters are discussed with a special reference to the multistage hypothesis of leukemogenesis.

Animals↗
PubMedDate not supplied

[Fatty acid composition of the bilayer phospholipids in the photoreceptor membranes and aminophospholipids from the rhodopsin microenvironment of warm-blooded and cold-blooded vertebrates].

Studies have been made on the distribution of phospholipids between rhodopsin and free lipids of photoreceptor membranes of the outer segments of retinal rods from cattle, frog Rana temporaria and fish Teragra chalcogramma. comparative investigation of fatty acid composition of phospholipids from rhodopsin microboundary and lipid bilayer in photoreceptor membranes was made as well. Amino phospholipids from rhodopsin microboundry were revealed using glutaraldehyde. This reagent by means of its aldehyde groups links phospholipid amino groups with amino groups of proteins of photoreceptor membranes. After this treatment, free phospholipids of lipid bilayer were extracted from photoreceptor membranes by methanol-chloroform mixture. It was demonstrated that fatty acid composition of phospholipids of lipid bilayer differs from that of amino phospholipids from rhodopsin microboundary. In the animals investigated, fatty acids of phospholipids from lipid bilayer were found to be more unsaturated than fatty acids of amino phospholipids from rhodopsin microboundary. This difference was more pronounced in photoreceptor membranes from the frog and fish than from cattle.

Animals↗
PubMed1980

[Transfer of the hematopoietic microenvironment during heterotopic transplantation of a mixture of isolated bone marrow cells].

New heterotopic bone marrow was formed after syngeneic transplantation of bone marrow cell suspension placed on millipore filters and grafted under kidney capsule. Bone marrow cells produced a bone marrow cavity which later became populated by hemopoietic cells. Bone marrow cells responsible for hemopoietic territory formation could be withdrawn from cell suspension after treatment with carbonyl iron powder.

Animals↗
PubMed1982

Tumor-selective modification of cellular microenvironment in vivo: effect of glucose infusion on the pH in normal and malignant rat tissues.

The pH distributions in transplanted neural (TV1A, BT1A) and hepatic (HV1A3) tumors and in brain and kidney of BDIX rats were analyzed as a function of serum glucose concentration (SGC), tumor size, and tissue architecture. Tissue damage during pH measurements in vivo could be minimized by the use of pH microelectrodes with tip diameters of less than or equal to 10 micrometers. In normoglycemic rats, the pH in TV1A tumors was only slightly lower than in brain or kidney. However, at 6 hr after the induction of hyperglycemia by continuous i.v. infusion of glucose, the average pH in TV1A tumors had fallen to 6.7 at an SGC of 27 mM and to 6.1 at an SGC of 50 mM. A similar glucose-mediated pH reduction was observed in BT1A and HV1A3 tumors. No significant increase in tissue acidity occurred in brain and kidney. The pH in tumors had reached its minimum at 2 hr after the onset of high-dose glucose infusion (SGC, 50 mM) and could be maintained at this level in hyperglycemic rats for at least 48 hr. In hyperglycemic hosts, an increased retention of acidic metabolites in the tumor tissue with decreasing vascular density was reflected by a tumor size (age)-dependent pH reduction and a higher degree of intratumoral pH variation. In partially necrotic tumors, pH values as low as 5.2 were recorded. Oral administration of NaHCO3 to tumor-bearing rats had no effect on the average pH in TV1A tumors.

Animals↗
PubMed1982

Dissecting the hematopoietic microenvironment. IV: regeneration of splenic microstructure- prerequisites and chronology of reconstruction.

A chronologic study was made of whole organ necrosis and subsequent regeneration in the pedicle ligated mouse spleen. The whole organ necrosis involved all but a thin layer of cells including and beneath the splenic capsule. Cellular regeneration issued from these surviving cells and was seen to proceed inward along remaining noncellular reticular fiber tracts throughout the spleen, resulting in complete architectural restoration. Destruction of these fibers resulted in failure of orderly reconstruction of splenic substance. A subcapsular vascular space was made prominent by the ligation and appeared to completely circumscribe the internal splenic substance. Regeneration appeared to begin with cells just central to this space. Reconstruction of the ligated spleen was architecturally complete within 40 days.

Aging↗
PubMed1981

Studies of the hemopoietic microenvironments. V. Changes in murine splenic and bone marrow glycosaminoglycans during post irradiation hemopoietic regeneration.

Changes in the amount of sulphated and unsulphated glycosaminoglycans in the spleen and the bone marrow of lethally irradiated mice were followed up to 11 days after irradiation. One day after irradiation, a sharp decrease in the amount of glycosaminoglycans was observed. In the absence of hemopoietic cells, the remaining stromal elements of spleen and bone marrow underwent subsequently marked changes in the amount of the sulphated and unsulphated components of the glycosaminoglycans in both organs. Reconstitution of irradiated mice with bone marrow cells affected the pattern of changes in the amount of glycosaminoglycans. Although no linear correlation could be observed between the amount of glycosaminoglycans and the number of hemopoietic cells present in the hemopoietic organs, these results suggest an interaction between hemopoietic cells and stromal cells in the hemopoietic organs with regard to the glycosaminoglycan metabolism.

Animals↗
PubMed1977

The thymic microenvironment: localization of a biologically active insoluble fraction.

An insoluble component of the thymus, previously shown to be capable of enhancing stem cell immigration into that organ, has been localized by immunofluorescence in perivascular basement membranes of the thymic medulla. It was found to be antigenically distinct from soluble thymic factor and from thymocyte membranes, and is thought to be responsible, in T-cell maturation, for the differentiation step preceding that imparted by thymic hormone.

Animals↗

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