A selection method for the synthesis of triploid hybrids by fusion of microspore protoplasts (n) with somatic cell protoplasts (2n)

Microspore protoplasts (n) isolated at the tetrad stage from plants of Nicotiana tabacum Km(+) (2n=4x=48) were fused with somatic cell protoplasts (2n) of WT N. rustica (2n=4x=48) to produce triploid plants. A total of 21.2×10(6) microspore protoplasts were fused with 11.2×10(6) somatic cell protoplasts using the high pH/Ca(+ +) method. Microspore protoplasts did not divide and WT N. rustica protoplasts stopped dividing when the protoplast-derived colonies were transferred to a selection medium containing kanamycin. A total of 104 actively growing green colonies were recovered on the selection medium. Ninety-six of these colonies were tested for their hybrid nature by PAGE of peroxidases and were found to contain bands characteristic of both parents. Hybrid nature of the plants regenerated from some of the selected colonies was confirmed by IEF of leaf esterases, by NPT II activity assay and by hybridizing total DNAs restricted with EcoR I to a cloned 18s rDNA fragment. Root tip squashes of six of the hybrid plants revealed chromosome numbers ranging from 58-72. From chromosomal and biochemical analysis, it can be concluded that the procedure of fusing microspore protoplasts (n) of species A carrying a dominant selection marker with WT somatic cell protoplasts (2n) of species B can be a convenient selection method for the synthesis of triploid plants. The significance of triploids lies in their subsequent use for transferring alien chromosomes and genes of species A to species B.

Proteoglycan-19, laminin and collagen type IV production is correlated with the levels of mRNA in F9 cell aggregates differentiating in the presence or absence of cyclic AMP

F9 embryonal carcinoma cells differentiate to embryoid bodies containing an outer epithelial layer of visceral endoderm cells when cultured as aggregates in medium containing retinoic acid (RA). Another pathway of differentiation to parietal endoderm is followed when dibutyryl cyclic AMP (cAMP) is added to the medium. We have measured the accumulated levels of RNA transcripts from a chondroitin sulfate proteoglycan gene (PG-19), the type IV collagen alpha 1, alpha 2 subunit genes, and laminin B1, B2 subunit genes during these differentiation processes. Laminin B2 gene is uniquely regulated among the extracellular matrix component genes studied. The level of laminin B2 RNA remains almost invariant during RA induction of differentiation but is induced 11-fold by cAMP with RA. In contrast, laminin B1, collagen IV alpha 1, and alpha 2 genes are induced in two stages with six- to sevenfold accumulation of RNA induced by RA and fourfold greater levels by cAMP (19- to 28-fold overall). All of these matrix-encoding genes except proteoglycan are expressed at low levels in unstimulated F9 cells, whereas PG-19 is completely undetectable and is observed only after 2 days of stimulation with RA. Its increased expression with RA and cAMP induction is at least 100-fold during F9 differentiation. Extracellular matrix transcripts are relatively stable and this accounts in part for high accumulated levels during differentiation. We conclude that several kinds of gene regulation occur among the matrix components and other differentiation markers, and this makes the F9 model system useful to study the differential effects of hormone treatments on cellular events leading to differentiation and loss of tumorigenicity.

An adhesion-defective variant of F9 embryonal carcinoma cells fails to differentiate into visceral endoderm

Adhesion-defective EC cells were isolated from a population of mutagenized F9 cells by serial transfer of cells that did not adhere to gelatin-coated dishes. The variant cells grew in suspension as multicellular clusters of loosely aggregated cells. The cells adhered to, but did not flatten on, fibroblast monolayers and extracellular matrix produced by parietal-like endoderm. Two different mutant cell lines exhibited increased sensitivity to the lectin abrin and decreased sensitivity to wheat germ agglutinin, suggesting that changes in cell surface glycosylation are associated with the mutant phenotype. These adhesion-defective mutants were used to study the relationship between cell-cell adhesion and endodermal differentiation. Unlike wild-type cells, when cultured with low concentrations of retinoic acid (RA) in suspension culture, the mutant cells did not form embryoid bodies but remained as loosely adhering strings of cells. Electron microscopic examination revealed that most of the differentiated variant cells resembled parietal endoderm, and this was confirmed by immunofluorescent staining for TROMA-3 marker. The levels of some of the markers that characterize the differentiative pathways were examined by immunoprecipitation and by enzyme-linked immunosorbent assay (ELISA). The variant line produced higher levels of laminin and type IV collagen compared to the wild-type cells. alpha-Fetoprotein (AFP) was produced at a significantly lower level by the variant compared to wild-type F9 cells during the differentiative process. The results show that variant cells differentiated toward parietal endoderm but have a very much restricted ability to differentiate to visceral endoderm. We conclude that aggregation and/or compaction provide some essential signals during the differentiation of F9 cells into epithelial layers of visceral endoderm.

Effect of liposomes on lymphocytes: induction of proliferation of B lymphocytes and potentiation of the cytotoxic response of T lymphocytes to alloantigens

Liposomes of certain lipid composition prepared by the detergent removal method (Brunner, J. et al., Biochim. Biophys. Acta 1976. 455: 322) induced the proliferation of spleen cells from different mouse strains. Spleen cell populations enriched in B lymphocytes and those obtained from nude mice were induced to proliferate, whereas spleen cell fractions enriched in T lymphocytes and thymocytes were not. The mitogenic effect of liposomes resembled that of lipopolysaccharide (LPS) and it depended upon their lipid composition. Liposomes prepared from dimyristoyl lecithin (DML), 2:1 dimyristoyl lecithin:cholesterol (DML:C), 2:1 dioleoyl lecithin: cholesterol (DOL:C), and 2:1 egg yolk lecithin:cholesterol (EYL:C) were mitogenic, whereas liposomes prepared from egg yolk lecithin (EYL) alone were not mitogenic for spleen cells. The mitogenic effects of these liposome preparations were in the decreasing order DML greater than DOL:C greater than or equal to EYL:C greater than DML:C greater than EYL. The results suggest a correlation between the membrane fluidity of liposomes and their mitogenic effect. Although no proliferative response was induced on T lymphocytes, two of these liposomes, DML and EYL:C, had the ability to potentiate the cytotoxic response of T lymphocytes to alloantigens in mixed leukocyte culture. In responder-stimulator combinations which differed for the H-2K, H-2D or the entire H-2 region, these liposomes potentiated the cytotoxic response significantly. The results suggest that liposomes have an ability to modulate T lymphocyte response.

Conditions affecting the differentiation of F9 teratocarcinoma cells: potentiation of response by cyclic AMP

F9 cells maintained in culture were shown to have a reduced ability to differentiate. The cells produced decreased amounts of alphafetoprotein when induced with retinoic acid. We show that consistent responses can be recovered after passage of F9 cells as a tumor. In addition, optimal differentiation of F9 cells to visceral endoderm may be achieved by the addition of very low concentrations of dibutyryl cyclic AMP (dbcAMP) to the medium.

Evidence for the existence of an early common biochemical pathway in the differentiation of F9 cells into visceral or parietal endoderm: modulation by cyclic AMP

The addition of dibutyryl cyclic AMP (dbcAMP) to aggregate cultures of F9 cells in medium containing retinoic acid (RA) directs the pathway of differentiation into parietal endoderm instead of visceral endoderm. We examined the levels of some of the markers that characterize the two pathways and studied the time of commitment of cells to either direction of differentiation by using immunoprecipitation and enzyme-linked immunosorbent assays (ELISA). For either pathway, the levels and patterns of laminin, type IV collagen, and fibronectin are the same on the first day of differentiation, characterized by slightly decreased levels of laminin and type IV collagen synthesis and an increased level of fibronectin synthesis. These levels reverse on the second day of culture when the pathways diverge markedly. The differentiation pathway, however, can be redirected into the alternate one; parietal endoderm cells become committed after 3 days, whereas visceral endoderm cells are able to change into parietal endoderm cells at any time. Thus, alpha-fetoprotein (AFP)-producing F9 embryoid bodies switched to dbcAMP-containing medium lose the capacity to synthesize AFP and start to express genes characteristic of parietal endoderm. Our results indicate that at least some visceral endoderm cells may redifferentiate into parietal endoderm cells. These phenomena thus mimic features of endoderm differentiation in the mouse embryo.

Relative sensitivity of various spectral forms of photosynthetic pigments to leaf senescence in wheat (Triticum aestivum L.)

The change in the characteristics of the absorption spectrum of chloroplasts which were isolated from the mature and senescing primary wheat leaves, was examined at various wavelengths in which the photosynthetic pigments mostly absorb. Chlorophyll (Chl) a was observed to be relatively more sensitive to leaf senescence than Chl b and carotenoids. Furthermore, the various spectral in vivo forms of Chl a, did not degrade to a similar extent; the far red absorbing forms of Chl a including species that absorb maximally at 692 nm (Chl a-692), 700 nm (Chl a-700) and 708 nm (Chl a 708) were found to be extremely sensitive to senescence induced losses. Both attached and detached senscing primary wheat leaves exhibited nearly similar pattern in the loss of photosynthetic pigments which suggests that the loss in long wavelength absorbing forms of Chl a is a selective indicator of leaf senescence.

Roles of extracellular matrix components in differentiating teratocarcinoma cells

F9 embryonal carcinoma cells treated with 5 X 10(-8) M retinoic acid and cultured in suspension for 8 days form aggregates consisting of an outer epithelial layer of alpha-fetoprotein-producing visceral endoderm cells. We have previously shown (Grover, A., Oshima, R. G., and Adamson, E. D. (1983) J. Cell Biol. 96, 1690-1696) that the differentiation of F9 cells to visceral endoderm is accompanied by the activation of several genes, and increased laminin synthesis is one of the earliest events. Here we analyze in detail the syntheses and secretion of fibronectin, type IV collagen, and laminin during the 8-day process. Employing immunoprecipitation and enzyme-linked immunosorbent assay, we show that the levels of all three components change with different patterns. Unstimulated F9 cells synthesize and secrete relatively high levels of fibronectin and low levels of type IV collagen. Fibronectin synthesis and secretion decreases to 10% of its original level whereas type IV collagen synthesis rises approximately 3-fold during the differentiation process. Laminin synthesis also rises at least 2-fold, and the proportions of its subunits change as the syntheses of B1 and A accelerate starting on day 2. However, unlike fibronectin and type IV collagen, laminin is largely accumulated in the aggregates. The data suggest that fibronectin has a role in aggregation whereas laminin is important in the differentiation process.

Morphologic changes in rat urothelial cells during carcinogenesis: II. Image cytometry

Improved early detection of neoplasia by screening of urothelial cells requires an understanding of the features distinguishing normal and neoplastic cell populations. We have begun a program of study based upon a rat model system for the controlled observation of early-stage lesions produced by the carcinogen N-butyl-N-(4-hydroxybutyl)- nitrosamine. Cells dissociated directly from normal and malignant urothelium were characterized by conventional cytopathology techniques and by quantitative microscopy (for nuclear texture and nuclear and cytoplasmic size, shape, and stain content) to derive a comprehensive picture of bladder tumor development. By following the changes that occur in the dissociated urothelial cells we have found that the nuclear area, total nuclear stain, nuclear shape, and the nuclear chromatin change significantly over a 48-wk interval as the lesions progress toward malignancy.

Sorting out in heterotypic cell aggregates is regulated by differences in the cell surface charge

Random aggregates of heterotypic cells derived from two different embryonic tissues sort out into homotypic zones, one enclosing the other. The specification of the enclosed or enclosing position is based on a tissue hierarchy. Cells differ in their net negative charge as indicated by their different isoelectric points (pI). The cells of higher pI enclose the cells of lower pI. Cell pI is lowered by treatment with heparin. Cells with experimentally altered pI also sort out, and their position is specified by the differences in their pI. It is suggested that the cell surface ionogenic groups determine the free surface energy which controls the positioning of cells in a mixed aggregate.

Role of laminin in epithelium formation by F9 aggregates

The formation and maturation of the outer epithelial layer is essential for maximal alphafetoprotein (AFP) production during differentiation of F9 embryoid bodies in the presence of 5 X 10(-8) M retinoic acid (Grover et al., 1983. J. Cell Biol. 96:1690-1696). The critical phase is between the third and the fourth day when the components of the extracellular matrix organize into a basement membrane. The role of some of these components in the process of epithelium formation and maturation is analyzed in this paper. The role of laminin was investigated by testing the effect of exogenous laminin and antilaminin in cultures of differentiating F9 aggregates. Tests included growth rates, morphological changes, AFP production, determination of AFP mRNA levels, and fluorescent staining for basement membrane components and for epithelial markers. At concentrations greater than 5 micrograms/ml, exogenous laminin inhibited the production of AFP and prevented AFP gene transcription. On the basis of immunofluorescence tests, exogenous laminin appeared to act by preventing the accumulation of a basement membrane and by disrupting the organization of the outer layer into an epithelium. No such effects were produced by fibronectin or collagens type I or IV. Aggregates cultured in the presence of antilaminin also failed to organize an epithelium and did not produce AFP, whereas those in normal rabbit serum differentiated normally. Therefore, endogenous laminin plays a key role not only as a basement membrane structural component but also in organizing the epithelial layer of endoderm cells and hence (indirectly) in gene expression.

Epithelial layer formation in differentiating aggregates of F9 embryonal carcinoma cells

F9 embryonal carcinoma (EC) cells, cultured in suspension in medium containing 5 X 10(-8) M retinoic acid, aggregate and differentiate into embryoid bodies with an outer layer of visceral endoderm cells that synthesize and secrete alphafetoprotein (AFP) (Hogan, B. L. M., A. Taylor, and E. Adamson, 1981, Nature (Lond.). 291:235-237). Here we analyze the formation of the outer layer of cells as a model for epithelial differentiation. Three morphological phases are described, but analyses of cell numbers and the synthetic rates of some proteins, as well as the appearance of markers of visceral endoderm and basement membrane, show that the formation of the outer layer occurs as an orderly progression of multiple events. The markers used to follow the ontogeny of epithelial layer formation include SSEA-1, l, and i blood group antigens, laminin, fibronectin, type IV collagen, cytoskeletal intermediate filament proteins (vimentin, Endo A, and B), and AFP. The onset of epithelium formation occurs between the third and fourth day of culture, but its function is maximally expressed only when it is well organized. We found the rate of AFP secretion to be a measure of the proper alignment and maturity of the epithelium which occurs at the seventh or eighth day. This model of epithelium formation may help to explain how similar processes occur during embryogenesis.

Depression of endostreptosin, streptolysin O and streptozyme antibodies in patients with idiopathic nephrosis with and without a nephrotic syndrome

We determined antibody titers to Endostreptosin (ESS), a recently described protein antigen in the cytoplasm and the plasma membrane of Group A streptococci in 286 normals of different age groups and in 34 children and 19 adults who had or had had at one time a nephrotic syndrome due to idiopathic nephrosis. Antistreptolysin O titers were also determined in 33 of the idiopathic nephrotics. Similarly, antibody titers to Streptozyme were determined in 21 patients with idiopathic nephrosis and 61 normals with a similar age distribution. Severe depression of these antibody titers was found in almost all patients with this disease not only during the presence of a nephrotic syndrome but for long periods up to 20 years following an episode of a nephrotic syndrome when the patients were in complete remission. Patients with a nephrotic syndrome due to chronic glomerulonephritis (5), S.L.E. (4), membranous nephropathy (5), diabetes mellitus (1) or amyloidosis (1) did not show abnormally low values for antibodies to Endostreptosin, Streptolysin O or Streptozyme. High-dose steroid medication as such for prolonged periods of time does not depress Endostreptosin or Streptolysin O antibody titers below the expected mean, as demonstrated in 15 patients with S.L.E.

Estrogen action in rooster liver. Modification of a tRNASer-inactivating activity

The hepatic synthesis of the yolk protein, phosvitin, can be induced in rooster by the administration of estrogen and this provides a model for studying the regulatory mechanisms involved. Since phosvitin is unusually rich in serine the effect of estrogen on the metabolism of serine transfer RNA (tRNASer) was examined. Rooster liver contains an activity capable of inactivating rooster liver tRNASer. This activity has specificity in that it inactivates only part of the tRNASer in the unaminoacylated form. Upon estrogen administration this activity is modified with a change in specificity and the modified activity is able to inactivate only a significantly smaller amount of tRNASer than the unmodified activity. This novel mechanism may be involved in the regulation of some species of tRNASer and thus may be part of the translational control involved in estrogen-induced phosvitin synthesis.

Haematologic changes in rabbits during acclimatisation, deacclimatisation, and reinduction to hypoxia

Haematologic changes were studied in 16 albino rabbits during acclimatisation, deacclimatisation, and reinduction to hypobaric hypoxia. Of these, four animals died during reinduction. Haemoglobin, haematocrit, and red blood cell count attained maximum values by the 15th day during acclimatisation and by the 10th day during reinduction. Reticulocyte count reached maximum level by the fifth day, both during acclimatisation and reinduction. All these parameters returned to initial control levels by the 10th day of deacclimatisation. The erythrocytes became macrocytic during acclimatisation and remained so during deacclimatisation and reinduction. Blood volume increased on acclimatisation, returned to control values during deacclimatisation, and remained low at this level on reinduction. Red cell mass increased both during acclimatisation and reinduction and returned to control levels on deacclimatisation. Plasma volume did not change on acclimatisation and deacclimatisation, but was reduced on reinduction. The erythrocyte life span and erythrocyte glutamic oxaloacetic transaminase (EGOT) decreased during acclimatisation and reinduction. There was no change in RBC osmotic fragility, indicating no change in the integrity of the red cell wall. The deaths during reinduction were possibly due to haemoconcentration and increased blood viscosity as a result of reduction in plasma volume. It has been concluded that reinduction to hypoxia after a phase of deacclimatisation imposes a more severe stress than experienced during acclimatisation.

Body fluid compartments in rabbits on exposure to acute hypobaric hypoxia

Body fluid compartments were studied in rabbits divided into three groups--control, exposed to acute hypoxia, and exposed to hypoxia after treatment with 2 mg frusemide intramuscularly. Total body water, extracellular body water, and plasma space were determined using the triple radiotracer technique. Total body water decreased insignificantly with no change in extracellular body space on exposure to hypoxia. Plasma volume and blood volume showed a significant decrease with a significant increase in haematocrit. In rabbits pretreated with frusemide, total body water, extracellular body water, plasma volume, blood volume, and interstitial fluid space decreased significantly on hypoxic exposure. This study suggested hypohydration on acute hypoxic exposure with a loss of intracellular water, while pretreatment with frusemide resulted in further hypohydration with a loss from both intracellular and extracellular compartments. The results have been discussed in relation to suggested use of diuretics on induction to high altitude.