Initial Stages Of Differentiation Research Articles

Vascular system in the developing wing bud of normal and talpid3 mutant chick embryos

The vascular limb mesoderm probably plays a prominent role in limb pattern formation in both normal and talpid 3 chick embryos. The differential vascularization, or its consequences, is a factor controlling the initial stages of differentiation in the developing bud. The axial artery runs from the subclavian artery to the distal region of the normal limb bud, whereas in the talpid 3 only secondary blood vessels develop. In the talpid 3, the gene permits the chondrogenic regions to grow and at the same time keeps the peripheral regions to a certain size. The mesenchyme tissue lies within the effective range of a metabolic gradient extending from either the ectodermal surface or the peripheral vessels to the limb axis.

Ultrastructural analysis of the in vitro differentiation of female rat preadipocytes.

In an attempt to characterize the preadipocytes of the adipose tissue of female rat, we studied by electron microscopy the differentiation of the cells into mature adipocytes in in vitro cultures. The preadipocytes arose from the stroma-vascular fraction of perirenal and perigenital adipose tissue. Culture of the preadipocytes in an enriched medium consisting of Dulbecco's medium supplemented with 10% fetal calf serum, antibiotics, rat triglycerides (0.5%), insulin (290 nM) and Tween 80 (0.1 mg/ml) induced their adipose conversion. The morphology of preadipocytes changed progressively. They accumulated fat granules, droplets and finally globules, which fused together. The cell organelles featured qualitative and quantitative modifications. The nucleus migrated with most mitochondria and a part of the Golgi system towards the cell periphery; the rough endoplasmic reticulum, dilated at the initial stage of differentiation became less and less conspicuous; the perinuclear Golgi system was dispersed between lipid droplets during fat accumulation; thick bundles of microfilaments, localized beneath the plasma membrane disappeared; large lipid droplets were surrounded by a network of microfilaments; many microvesicles and some "rosettes" typical of mature adipocytes could be observed. Nevertheless, the ultrastructural criteria did not allow to clearly discriminate the undifferentiated cells: early preadipocytes (without lipid droplets), adipoblasts and fibroblasts, all of these being probably present in the culture system.

Analysis of Male Meiosis in Seven Species of Indian Pill-Millipedes (Diplopoda: Myriapoda)

SUMMARYA sequential study of male meiosis of seven species of Indian pill- millipedes (Sphaerotheriida—Diplopoda), namely, Arthrosphaera davisoni, A. lutescetis, A. disticta, A. magna, A. nitida, A. dalyi and Arthrosphaera sp. was carried out using the air drying technique. Meiotic and mitotic tissues were pretreated with colchicine (0.05%), hypotonic Na citrate (0.016 M) and KCl to secure well spread mitotic and meiotic chromosomes, which, otherwise were found to be cytologically difficult to obtain. The sex chromosomes of pill-millipedes still maintain an initial stage of differentiation and the pairing configurations of chromosomes in male meiosis are only explainable by an XX/XY type of chromosomal sex-determination.

Rescue of terminally differentiating teratocarcinoma cells by fusion to undifferentiated parental cells.

A new clonal CBA mouse teratocarcinoma cell line called H6 grows rapidly without calcium in suspension culture. When attached to a gelatin-coated surface in the presence of calcium, differentiation to large flat cells, which secrete plasminogen activator, occurs after exposure to retinoic acid. Differentiation is terminal after about six cell divisions. H6 variants resistant to 6-thioguanine, 5-bromodeoxyuridine, ouabain, chloramphenicol, retinoic acid, or combinations thereof, have been isolated. Cell hybridizations were made between undifferentiated stem cells and the differentiated derivatives of H6. These experiments indicate that the undifferentiated cells can "rescue" cells in the initial stages of differentiation and that the signs of differentiation are soon lost in such hybrids. Hybridization without "rescue" may also occur, as suggested by small abortive colonies of large cells.

Altered pattern of differentiation and proliferation of HL-60 promyelocytic leukemia cells in the presence of leucocyte conditioned medium

We have examined the response of HL-60 cell line to leucocyte conditioned medium (LCM), as a source of colony stimulating activity, in vitro. HL-60 cells exhibited initially increased proliferation, as assessed by tritiated thymidine incorporation and the rate of increase of viable cell counts, in response to added LCM. Cells cultured in the presence of LCM also exhibited partial differentiation with a myelomonocytic morphologic appearance and the acquisition of strong reactivity with alpha napthyl acetate esterase staining. Cells cultured in the presence of both DMSO and LCM underwent initial stages of differentiation more rapidly than with DMSO alone, but the appearance of terminally differentiated myeloid cells was delayed and cells acquired a macrophage-monocytic appearance.

Initial Stages of Differentiation of Thymocytes in the Plasma Membrane

There is some evidence in the plasma membrane after binding of molecules triggering differentiation processes that different membrane areas exist possessing different functions. We have tried to isolate these different membrane areas, using a type of affinity chromatography on Con A-Sepharose. Our results from binding sites, affinity constant and fatty acid composition seem to reinforce the evidence that heterogeneous plasma membrane areas exist having different functions in the proliferation and differentiation process of thymocytes after triggering with Con A.

The heterocysts of blue-green algae. 3. Differentiation and nitrogenase activity.

The course of heterocyst development in Anabacna cylindrica was studied in relation to the ability to fix nitrogen. When non-differentiated filaments, grown in the presence of ammonium-N, were transferred into a medium free from combined nitrogen and incubated under photosynthetic conditions, the cellular C:N ratio increased from 4.5:1 to 8:1 before the percentage heterocyst frequency and nitrogenase activity reached a steady value. The initial stages of differentiation were observed 24 h after transfer into nitrogen-free medium, but nitrogenase activity was only detected when the formation of the first heterocysts was completed. The transformation of a vegetative cell into a heterocyst is characterized by the dissolution of storage granules, the deposition of a multilayered envelope, the breakdown of photosynthetic thylakoids and the formation of new membraneous structures. The latter appear to develop by the coalescence of small newly formed vesicles arising in regions of pre-existing thylakoids. The course of heterocyst development was paralleled by that of nitrogenase activity both under aerobic and anaerobic conditions. Anaerobic incubation enhanced heterocyst production as well as nitrogenase activity. The results suggest that nitrogenase synthesis in Anabaena cylindrica is associated with heterocyst formation and that the primary factor which may regulate both processes is the cellular C:N balance of the alga.

Chemical modification of cell death in the Bar eye of Drosophila.

Cell death during the development of the mutant Bar of Drosophila melanogaster has been further investigated. The temporal and spatial distribution of degenerating cells was determined by light microscopy of serial sections of Bar eye discs. It appears that the presumptive eye cells die during the initial stage of differentiation; i.e., during their organization into groups of cells corresponding to the future ommatidia.

Antigen-sensitive spleen cells and the adjuvant activity of Bordetella pertussis.

In this study we determined at both the cellular and humoral level whether or not the primary immune response of mice can be significantly enhanced by administration of a bacterial adjuvant after the primary immunization with sheep erythrocytes. As compared to the immunization of mice with 8 × 106 sheep erythrocytes alone, the simultaneous injection of 3 × 109Bordetella pertussis cells and 8 × 106 sheep erythrocytes resulted in an accelerated and prolonged multiplication of hemolysin-forming spleen cells. The adjuvant effect was also documented by increased production of serum hemolysins. When the bacterial adjuvant was given 6, 12, or 24 h after the primary antigenic stimulus, however, neither increased plaque counts nor enhanced serum hemolysin titers were detectable. These findings agree with the concept that B. pertussis cells cause multiplication of antigen-sensitive target cells or affect the initial stages of differentiation of these cells.

Variable Adjuvant Activity of Bordetella pertussis with Respect to the Primary and Secondary Immunization of Mice

We carried out a study on the adjuvant effect of Bordetella pertussis vaccine on the primary and secondary immune responses of the mouse to sheep erythrocytes, quantitating antibody-producing spleen cells and serum antibody. The simultaneous injection of sheep erythrocytes and B. pertussis, when compared to immunization with sheep red blood cells alone, resulted in an increased and prolonged multiplication of antibody-forming spleen cells. The adjuvant effect was also documented by increased production of serum hemolysins and agglutinins. Further, B. pertussis enhanced the priming effect of the antigen for the secondary response. However, when the bacterial adjuvant was given together with a second antigenic stimulus 41 days after the primary immunization, the peak values of direct and indirect plaque-forming spleen cells did not differ from the corresponding control animals further inoculated with sheep erythrocytes alone. Nonetheless, the influence of the bacterial adjuvant was still expressed by the delayed decrease of the numbers of plaque-forming spleen cells. On the basis of the X-Y-Z scheme it is suggested that B. pertussis cells as adjuvant enhance the multiplication of antigen-sensitive X cells or affect the initial stages of differentiation of these cells. This effect of the pertussis vaccine can be distinguished from a general proliferative action on other cells.

Developing Chick Embryo Lethal Response to Dose Variation of 2-Ethyl-5-Methylbenzimidazole

DOSE response has been used widely for determining the potencies of both inhibitors and stimulants in microbiology, pharmacology, vitamin assays, etc. It has also been used for explaining and determining the nature of action of many different types of compounds (Ariëns et al., 1955). However, dose response has not been applied to the study of embryonic development. It appeared that a detailed study of the lethal response of the developing chick embryo to dose variations of a metabolic inhibitor would indicate over-all metabolic changes in the embryo as related to the particular inhibition. 2-ethyl-5-methylbenzimidazole (EMB) was chosen for the study since it is highly inhibitory to the chick embryo (Boggs and Shorb, 1956; Billett and Perry, 1957; Blackwood and Shorb, 1958) causing numerous malformations which predominately involve initial stages of differentiation (Blackwood, 1960 a, b).The metabolic processes interrupted by EMB and other benzimidazoles are not fully understood. However, information …

FORM AND CAUSALITY IN NEUROGENESIS

FORM AND CAUSALITY IN NEUROGENESIS

Origin of Bone Marrow Plasma Cell Associated with Allergic and Immune States in the Rabbit.

The observation of a plasmacytosis of the bone marrow of a man with a fatal endocarditis, coupled with Downey's description of a great number of plasma cells in the bone marrow of a rabbit with an incidental, non-specific, subcutaneous abscess suggested an experimental method for increasing the bone marrow plasma cell content. This reaction was also indicated by the bone marrow from rabbits allergic to and immunized against Streptococcus viridans, obtained through the courtesy of Dr. B. J. Clawson of the Department of Pathology, University of Minnesota. In these animals it was noted that the allergic and immune animals showed a more extensive medullary plasmacytosis than those that were immune but not allergic. Through the study of the myeloid tissue during the development of a plasmacytophilia, we felt something of the origin and function of the bone marrow plasma cell might be determined. There are many conflicting theories regarding the origin of the myeloid plasma cell (Downey, Michels, Rohr, Jordan and Morton, and Osgood and Ashworth). The current theories make the lymphocyte, histiocyte, fibroblast, myeloblast, erythroblast, plasmacytic reticulum cell and specific plasmablast the parent of the bone marrow plasma cell. The procedure we employed was as follows: Obtain a control sample of normal marrow; induce an increase in the plasma cells and follow the bone marrow picture by means of successive biopsies while the increment in plasma cells is in progress. In this manner, we were able to identify the progenitor of these cells during their initial stage of differentiation in the bone marrow. We treated a series of 13 rabbits by Clawson's method, i. e., giving a subcutaneous injection of Streptococcus viridans broth agar mixture and thus making the animal allergic to this antigen.