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At least 1,333 records · Page 74Linked to original sources
PubMed1986

Stability of rubella virus after long-term persistence in human cell line.

Primary infection of HEp-2 cells with rubella virus resulted in non-cytophatic long-term persistent infection. During four years of persistence the virus was produced in sufficient quantities (up to 6 logs PFU/ml) and did not differ from the parental variant in its pathogenicity for BHK-21 or RK-13 cells, or hemagglutinating activity, but formed smaller plaques. Persistent virus preserved the original antigenicity as judged from reciprocal hemagglutination-inhibition or plaque reduction-neutralization tests with polyclonal antisera. Both original and persistent rubella viruses were thermoresistant (T 56 degrees C) and slightly temperature-sensitive. Clonal analysis revealed presence of ts-mutants among both original and persistent virus clones with different degrees of plating efficiency at 40 degrees/34 degrees C. RNA fingerprinting showed only minor changes in persistent rubella virus.

Antigens, Viral↗
PubMed1987

Selection and adaptation for rapid growth in culture of cells from delayed sarcomas in nude mice.

More than 1000 cells of a spontaneously transformed line of BALB/3T3 cells are required to initiate tumors in half the nude mice inoculated s.c., although the cells clone with an efficiency approaching 100% in culture. The cells of two tumors with prolonged latent periods, initiated by 2 X 10(4) and 5 X 10(3) cells, were chosen for detailed clonal analysis in culture. The cells from the tumors grew very poorly in culture in the first passages, but with increasing speed and efficiency in later passages. Cells derived directly from the two tumors cloned in agar with an efficiency of 0.01 and 0.002%. The growth rates on plastic of the rare successful clones derived from agar were generally low but extremely varied. Some clones lost the capacity for multiplication in a few passages, while others persisted but fluctuated unpredictably in growth rate in the early passages. The graded increase in growth rate of the uncloned tumor cell populations was probably the result of selection of the more rapidly growing clones. One of the slower-growing clones was subcloned. About half of the subclones grew at a slower rate than the parental clone. These, however, increased progressively in growth rate over six successive weekly passages, suggesting the occurrence of a gradual physiological adaptation. We conclude that selection of fast-growing clones contributes a major part of the gradually improving growth of tumor cell populations in culture, but that a physiological adaptation extending over many cell generations makes a significant contribution. The mechanism in either case is unknown, and indeed there may not be a unique mechanism in the scientifically rigorous sense.

Animals↗
PubMed1974

[Interaction of the homoeotic mutations aristapedia and polycomb during ontogenesis of Drosophila melanogaster].

The manifestation of 5 alleles of aristapedia and 2 alleles of Polycomb was studied in initial stocks and in flies of Pc ssa/+ssa genotype. Mutual enhancement of homoeotic effects of ssa and Pc genes was observed. Differences in intergenic interaction were aristapedia, rather than Polycomb specific. Possible role of homoeotic mutations as mutations of regulatory genes and the bearing of the data on their interaction on the results of clonal analysis of homoeosis are discussed.

Alleles↗
PubMed1979

Regeneration and compartments in Drosophila.

A clonal analysis was performed in order to study the process of regeneration in wounded wing discs of Drosophila. Regeneration was induced either by cutting the disc in situ, or by shifting gynandromorphic larvae whose male tissue was hemizygous for a temperature-sensitive cell lethal to the restrictive temperature. Fast growing M+ clones, labelled with y and/or mwh, were produced by X-irradiation of the following genotypes: y; scJ4(y+)M(3)i55/mwh jv M+ (series I), and l(1)ts 504 sn3 l(1)ts 5697/ In(1)wvC; M(3)i55/mwh M+ (series II). The clones were induced either before or after the experimental lesion. Clones initiated one day prior to the lesion were able to cross compartment boundaries whereas clones initiated one day after the lesion did not do so. It is concluded that cells involved in the process of regeneration lose their compartmental commitment, but that later on the growing population of cells again becomes subdivided into the same compartments.

Animals↗
PubMed1979

The time of action of three mutations affecting Drosophila eye morphogenesis.

Histology and clonal analysis are used to look at the time of action of the mutant Drosophila genes eyeless, eyeless dominant and sine oculis. The findings suggest that eyeless dominant has its effect during the first two larval instars, whilst eyeless and sine oculis act during the third larval instar.

Animals↗
PubMed1980

Experimentally segregated attenuated tick-borne encephalitis virus: altered behaviour after prolonged storage at subzero temperatures.

In an attenuated variant of tick-borne encephalitis virus, western subtype (TBEV) with an ic+ sc s t e us character and lost virulence for monkeys, a distinct inhomogeneity together with a decrease in titre was observed after 8.7--9.6 years of storage at 4 and -14 (+/- 2) degrees C, with several interruptions due to failures in refrigeration systems. Proved by clonal analysis, the inhomogeneity concerned plaque polymorphism, increased thermo-resistance and degree of virulence for mice and monkeys. Marker studies of materials stored for up to 14.5 years yielded comparable findings. The possibility of the presence in the virus stocks in addition to a prevailing attenuated component also of minor component(s) having the advantage for survival under storage conditions, is discussed taking into account the intrinsic mutational capacity of the virus and known differences in resistance to environmental stresses between attenuated and virulent TBEV variants.

Animals↗
PubMed1984

In vitro stimulation of IgE production at a single precursor level by human alloreactive T helper clones.

Human alloreactive proliferating T cell clones were isolated by a combination of allogeneic stimulation and interleukin 2-dependent growth. When cultured with B cells and macrophages bearing the appropriate alloantigens, the helper clones induced the production of high levels of IgE, while in the absence of the appropriate stimulation B cells produced undetectable IgE levels. Allogeneic peripheral blood T cells did not provide any help, but rather suppressed the IgE production induced by the alloreactive clones. The development of culture conditions where the help provided by specific T cell clones is non-limiting and suppressor-cytotoxic T cells are absent allowed the set up of limiting dilution experiments to determine the frequency of the B cells activated to high rate IgE production. One in 2,200-6,000 B cells in the peripheral blood of normal donors was activated to produce measurable amounts of IgE. This experimental system will allow the clonal analysis of the IgE antibody repertoire, in different physiological and pathological conditions.

B-Lymphocytes↗
PubMed1984

[Independence from the substrate of multiplication in nonclonal and clonal tumor cell populations].

Experiments were made with sarcoma PS-103 cells cultured in vitro. The sarcoma was induced by implantation of a plastic plate into CBA mice. Clonal analysis of the cell culture demonstrated that 1) all 3 clones isolated from substrate (SB) grew in 1.2% methyl cellulose (MC) at the same efficiency as parental cells; 2) all 5 clones isolated from MC formed in a semi-solid medium 10-100-fold more colonies than PS-103. During the subcloning of one of PS-103 clones in solid substrate and in MC, it turned out that the majority of MC and SB subclones had the plating efficiency in MC similar to that in PS-103. Apparently, the PS-103 population contains clones with different degrees of anchorage independence.

Animals↗
PubMed1983

Genetic and developmental characteristics of the homeotic mutation bx1 of Drosophila.

The mutations at the bithorax locus produce a transformation of anterior haltere into anterior wing. The bx1 allele presents unusual features when compared with other bx alleles. The phenotype of bx1 homozygotes is temperature sensitive but only with regard to the distal and not to the proximal transformation, thus suggesting two different components in the bithorax transformation. The phenotype of bx1 homozygotes is stronger than that of bx1 over the deletion of the gene, suggesting a trans interaction of the bx1 chromosomes which results in mutual partial inactivation. We show by temperature shift and clonal analysis experiments that the decision on whether to differentiate haltere or wing structures is taken at the end of the proliferation period of the mutant disc.

Alleles↗
PubMed1983

Ultrastructure of cell death in gamma- or X-irradiated imaginal wing discs of Drosophila.

When Drosophila larvae were irradiated with 1300-1500 R of gamma rays both apoptotic and necrotic cell death were observed in imaginal wing discs. The ultrastructure of cell death by apoptosis was characterized by fragmentation of dead cells into highly condensed, membrane-bound particles. The ultrastructure of cell death by necrosis was characterized by cell lysis and organelle degeneration. Marked contrast was also seen in the distribution of the two types of cell death: apoptosis was universal in irradiated discs and affected widely distributed single cells, or small groups of cells, whereas necrosis formed lesions by afflicting large numbers of contiguous cells. It was noted that even where there were large lesions in the epithelial cell layer, which is the primary component of imaginal discs, the basement membrane associated with this epithelium always remained intact. Lesions could be identified in freshly extirpated discs by staining with trypan blue and were found in 50-70% of irradiated discs (depending on the larval age at the time of irradiation). Lesions were seen in all regions of the wing disc and varied greatly in size. In spite of extensive necrotic cell death wing discs developed into normal adult wings. Regenerative growth in this case would appear to require significant reorganization of cells. Implications of this for the appropriate interpretation of clonal analysis are discussed.

Animals↗
PubMed1983

Studies on differentiation of human mammary epithelial cells in culture: distinctive specificities of conditioned media.

Epithelium cultured from human milk contains cells of two types distinguishable by morphology and keratin pattern. First, the "open" type comprises cells which are isolated from one another, and which do not form typical epithelial sheets. Second, the "joined" type grow as tightly adjoining cell sheets. Clonal analysis shows that open cells, besides reproducing the same phenotype, can give rise to mixed colonies containing joined cells, thus indicating a pathway of in vitro differentiation. When conditioned medium was used to enhance colony growth it was found that human embryo lung fibroblasts release an activity which specifically enhances the open type of mammary epithelial cell. On the contrary the Nil 8 hamster fibroblast line and certain other cells release activities which primarily affect the joined cell type. This suggests that there are naturally occurring factors with specificities for distinct stages in mammary epithelial cell differentiation.

Animals↗
PubMed1983

A new muscle phenotype is expressed by subcultured quail myoblasts isolated from future fast and slow muscles.

Differentiation of quail myoblasts, isolated from thigh pectoralis and anterior latissimus dorsi muscle, was analyzed in primary cultures and in cultures obtained following repeated subculturing. Our study shows that quail myoblasts can survive many generations without losing their ability to form myotubes. However, during these subcultures the cells progressively express a new phenotype. This phenotype is characterized by a mixture of myosin light chains such that LC1F, LC2F, and LC2S are present in roughly equimolar amounts, each accounting for 25 to 30% of the total light chain synthesis while LC1S accounts for the remaining 10 to 15%, and by a mixture of fast and slow alpha tropomyosin in which alpha S accounts for 10 to 15% of the alpha subunits synthesis. Clonal analysis indicates that all cells in the population express this phenotype which is also characteristic of subcultures obtained from both future fast and slow muscles. Relationships between this phenotype and muscle development are discussed.

Animals↗
PubMed1983

Use of repetitive DNA sequences to distinguish Mus musculus and Mus caroli cells by in situ hybridization.

Mammalian chimaeras have proved useful for investigating early steps in embryonic development. However, a complete clonal analysis of cell lineages has been limited by the lack of a marker which is ubiquitous and can distinguish parental cell types in situ. We have developed a cell marker system which fulfils these criteria. Chimaeric mice were successfully produced from two mouse species which possess sufficient genetic differences to allow unequivocal identification of parental cell types. DNA-DNA in situ hybridization with cloned, species-specific sequences was performed to distinguish the parental cell types. We have identified a cloned, Mus musculus satellite DNA sequence which shows hybridization differences between Mus musculus and Mus caroli DNA. This clone was used a a probe in in situ hybridizations to bone marrow chromosomes from Mus musculus, Mus caroli, and an interspecific F1 hybrid. The clone could qualitatively distinguish Mus musculus from Mus caroli chromosomes after in situ hybridization, even when they were derived from the same F1 hybrid cell. Quantitation of this hybridization to interphase nuclei from bone marrow spreads indicates that the probe can successfully distinguish Mus musculus from Mus caroli cells and can determine the percentage contribution of Mus musculus in mixtures of bone marrow cells of these species and in chimaeric bone marrow cell preparations.

Animals↗
PubMed1982

The production of committed hemopoietic colony-forming cells from multipotential precursor cells in vitro.

Murine fetal liver cells have been fractionated by fluorescence-activated cell sorting into two fractions termed. For convenience, the pre-CFC and CFC (colony-forming cell) fractions, which differ in their relative binding of the lectin, pokeweed mitogen. The CFC fraction contained a high frequency of CFC (26%) and in liquid cultures stimulated with colony-stimulating factors generated large numbers of differentiated progeny. Consequently, residual CFC could not be detected in such cultures after day 4. In contrast, the pre-CFC fraction contained relatively few CFC (1%) but contained the majority of CFU-S and was able to generate large numbers of new CFC after 5-7 days in liquid culture. This production of CFC from precursor cells was absolutely dependent on factors present in pokeweed-mitogen-stimulated spleen cell conditioned medium (PWM-SCM) or postendotoxin serum (ES) but was not stimulated by known granulocyte or macrophage colony-stimulating factors. CFC production occurred from multipotential precursor cells and all types of CFC were detected (excluding lymphocytes). Clonal analysis of pre-CFC showed that most of the generated CFC arose from relatively few multipotential precursors some of which could generate up to 500 CFC. The data suggested a differentiation sequence of the multipotential precursor cells in which differentiation potentials are successively restricted in the order macrophage, eosinophil, granulocyte-macrophage leads to granulocyte, megakaryocyte, erythroid. The frequency of CFC-generating cells in the pre-CFC fraction was significantly less (ten-fold) than that of CFU-S, suggesting that pre-CFC may be a more ancestral subset of CFU-S. The cell fractions and assay systems described should be of use in defining and purifying factors regulating early phases of hemopoietic differentiation and in defining the differentiation steps involved in the restriction of potentialities of multipotential cells.

Animals↗
PubMed1980

Hemin does not cause commitment of murine erythroleukemia (MEL) cells to terminal differentiation.

The effect of hemin on the differentiation program of murine erythroleukemia (MEL) cells has been investigated. While hemin treatment does induce increased levels of globin mRNA and hemoglobin, it fails to lead to other biochemical changes associated with MEL cell differentiation induced by DMSO and thioguanine. These include increased levels of the nuclear protein IP25 and of the enzyme cytidine deaminase. Clonal analysis of hemin-treated cells revealed that unlike other inducers, hemin does not cause a reprogramming of MEL cells to a specific limitation of proliferative capacity. These observations suggest that hemin differs from DMSO and thioguanine in that it exerts specific effects on globin expression in MEL cells without triggering commitment to the terminal differentiation program.

Animals↗
PubMed1982

Development of long-term cell lines and lymphoid clones reactive against murine and human tumors: a new approach to the adoptive immunotherapy of cancer.

We have investigated the use of T-cell growth factor (TCGF) to isolate and grow, in long-term culture, lymphoid cells with immunologic reactivity directed against syngeneic murine and autologous human tumors. Splenocytes from mice immune to a methylcholanthrene-induced sarcoma were expanded in TCGF, both before and after in vitro mixed lymphocyte-tumor cultures, and expressed high levels of cytotoxicity for fresh syngeneic solid tumor cells. Cloned lines have been isolated with a high level of specific lysis for the immunizing tumor. Similar studies of cytotoxic reactivity to a syngeneic FBL-3 lymphoma have given rise to long-term cytotoxic cell lines growing in TCGF capable of curing mice with disseminated lymphoma in adoptive transfer studies. Exposure to TCGF, of human peripheral lymphoid cells from cancer-bearing patients, results in the development of cytotoxicity to autologous fresh tumor. We have used clonal analysis by limiting dilution techniques to isolate individual cloned cells with this autologous antitumor reactivity. Infusion to autologous cytotoxic cells expanded 10,000-fold in TCGF and labeled with 111In into three cancer patients resulted in cell localization initially to the lung and subsequently to the liver and spleen. The application of these techniques for the cloning and expansion of antitumor T-lymphoid cells in TCGF has offered a new approach to adoptive immunotherapy.

Animals↗
PubMedDate not supplied

[Strain properties of the Aina/1448 serotype of the tick-borne encephalitis virus].

Four strains of tick-borne encephalitis (TBE) virus isolated in the Irkutsk region were shown by the agar gel diffusion and precipitation test with adsorbed sera to comprise a single antigenic group differing from members of the eastern and western TBE virus serotypes (Sophyin and 256 strains). The group includes the strains isolated during 20 years (1960 - 1980) from patients with chronic TBE form (Aina/1448 and 763 strains), from the brain of root vole (Microtus oeconomus Pall) (strain 147), and from Ix. persulcatus ticks (Irkutsk-6 strain). The clonal analysis showed the Aina/1448 strain population to be antigenically homogeneous.

Animals↗
PubMed1980

Formation of bone and cartilage by marrow stromal cells in diffusion chambers in vivo.

When freshly isolated rabbit marrow cells were cultured either in vitro or in diffusion chambers in vivo, the hemopoietic cells disappeared and there was a proliferation of the stromal cell population. The colonies formed in vitro were mainly fibroblastic, and this cell type predominated in confluent cultures. Staining for alkaline phosphatase activity and for the Von Kossa reaction was negative in in vitro cultures. However, marrow cell suspensions or fibroblasts harvested from in vitro culture of marrow cells, gave rise to a mixture of bone, cartilage and fibrous tissue in diffusion chambers implanted into the peritoneal cavity. In contrast, only a soft fibrous tissue developed from spleen fibroblasts in diffusion chambers. Differentiation of osteogenic tissue within diffusion chambers fell into two categories: (1) Formation of bone in a fibrous layer surrounding cartilage; (2) intramembranous bone formed directly within fibrous tissue unassociated with cartilage. In both cases alkaline phosphatase activity appeared before the onset of mineralization, and decreased as the first signs of mineral became apparent. The present results suggest that postnatal marrow contains osteogenic precursors with the potential to differentiate via either of the two major paths followed during skeletal development in the embryo. Clonal analysis of the marrow stromal cell population will be required to clarify whether osteo-, chondro-, and fibrogenic cells are the products of one stromal cell line modulated by the microenvironment, or whether there are distinct cell lines for each type.

Alkaline Phosphatase↗