A comparison of the radiation sensitivities of non-tumorigenic and tumorigenic human hybrid cell lines

The radiation sensitivities of two related non-tumorigenic and two related tumorigenic human hybrid cell lines (HeLa x skin fibroblast) have been studied. The data show that the transformation from the non-tumorigenic to the tumorigenic state, which is accompanied by the loss of skin fibroblast chromosomes 11 and 14, is not associated with any major changes in radiation sensitivity. The data do indicate, however, a trend toward a steeper and longer initial slope to the cell survival curve for the tumorigenic cell lines, along with a subsequent reduced ability to accumulate sublethal radiation injury at low doses. Both nontumorigenic and tumorigenic cell lines have the capability of repairing sublethal injury.

Further studies on the radiation-induced expression of a tumor-specific antigen in human cell hybrids

The neoplastic transformation of human cell hybrids (HeLa x skin fibroblasts) is accompanied by the expression of a cell surface protein for which monoclonal antibodies have been raised. The gamma-radiation-induced neoplastic transformation of these cells has been studied where the expression of this cell surface protein, as detected by immunoperoxidase staining, has been used as an end point. The yield of foci of positively staining cells has been shown to increase with increasing time postirradiation at which the assay is done and decrease with increasing density of viable cells plated postirradiation. The time of plating postirradiation is also an important parameter with transformation frequencies increasing over the first 6 h of postirradiation holding at confluence, followed by a gradual decrease.

Neoplastic transformation of human hybrid cells by gamma radiation: a quantitative assay

Human skin fibroblasts are extremely refractory to neoplastic transformation by ionizing radiation [C. Borek, Nature 283, 776-778 (1980); M. Namba, H. Nishitani, and T. Kimoto, J. Exp. Med. 48, 303-311 (1978)] and are therefore unsuitable for quantitative studies of dose-effect relationships. We show here that a nontumorigenic human hybrid cell line (HeLa X skin fibroblast) can be neoplastically transformed by treatment with gamma radiation. Furthermore, a dose-response relationship has been established. We propose that this human hybrid cell line may be a useful system for mechanistic studies of transformation from the preneoplastic to the neoplastic state by ionizing radiation and other agents.

Repair of potentially lethal radiation damage in confluent and non-confluent cultures of human hybrid cells

The repair of potentially lethal damage (PLDR) in a gamma-irradiated human hybrid cell line (skin fibroblast X HeLa) and its tumourigenic segregant has been studied as a function of cell density at the time of irradiation and during the postirradiation repair period. The data show that PLDR occurs in both non-confluent and confluent cultures of both cell lines. Furthermore, there is evidence that the extent of PLDR is dependent on cell density and that cell-cell contact may be an important factor in this regard.

Radiobiological studies of human hybrid cells (skin fibroblasts X HeLa) and their tumourigenic segregants

Data are presented on the survival characteristics following gamma-irradiation of a human hybrid cell line (skin fibroblasts X HeLa), and its tumourigenic segregant, which indicate that transition from the non-tumourigenic to the tumourigenic state is associated with a decrease in the ability to accumulate and repair sublethal damage. Previous studies have demonstrated that this transition to the tumourigenic state is also associated with loss of specific chromosomes (one copy each of chromosomes 11 and 14). It is suggested that this loss of chromosomes may account for the change in radiosensitivity.

Preliminary studies on a lectin on the surface of adipocytes

A lectin-like component on the surface of porcine adipocytes was identified, chiefly by means of the cell adhesion and hemagglutination assays. This component, named porcine adipocyte lectin (PAL), was isolated with Triton X-100 solubilization followed by affinity chromatography. By SDS-polyacrylamide gel electrophoresis, two hands of PAL stained with Coomassie blue were revealed with the apparent molecular weights of 112,000 and 89,000. Moreover, the glycoprotein nature of PAL, was demonstrated by periodic-Schiff reagent staining. PAL was able to recognize maltose, mannose and mannan and glycoproteins with analogous sugar structure in the presence of Ca. By the finding that adipocytes in suspension could be aggregated by adding PAL, the hypothesis was advanced that PAL may be involved in the recognition and adhesion of adipocytes in vivo.

Effects of positive end expiratory pressure and counterpressurization on circulating prostaglandins in the dog

The effects of the application of positive end expiratory pressure (PEEP) ventilation, with and without body counterpressure (CP), on circulating prostaglandin-like substances (PGL) were studied in chloralose anesthetized dogs. The normal respiratory movements were paralysed with succinylcholine chloride. Arterial levels of PGL were continuously bioassayed using Vane's blood superfusion method. PEEPs of 10 and 20 mm Hg elicited PEEP-related increases in functional residual capacity and circulating PGL levels and decreases in blood pressure, left ventricular dP/dt, and heart rate. The PGL appeared to be PGE or prostacyclin in character. When PEEP and CP were simultaneously applied, the increments or decrements of indices described above were reduced. It is concluded that increases in the levels of circulating PGL are attributable, at least in part, to hyperexpansion of the lungs during PEEP and that some of the cardiovascular deterioration observed during and after PEEP may be the result of the vasodilating and cardiodepressing effects of PGL.

Antagonistic action of alpha- and beta-agonists on the bullfrog atrium

Action of alpha- and beta-agonists on the membrane potential, current and tension components on the bullfrog atrial muscle were studied by means of the single or double sucrose-gap technique. Isoproterenol (10(-9)-10(-5) M) as well as adrenaline (10(-7)-10(-4) M) produced a dose-dependent positive inotropic effect, while methoxamine (10(-8)-10(-4) M) and phenylephrine (10(-8)-10(-3) M) with propranolol (10(-6) M) elicited a negative inotropic effect. The positive inotropic effect was accompanied by slight hyperpolarization and marked increase of over-shoot and plateau level of action potential, and the negative inotropic effect, by opposite changes. Under voltage clamp, isoproterenol and adrenaline produced enhancement of slow inward current (Is), delayed outward current (Ix) and Is-dependent phasic tension, while Is-independent tonic tension was inhibited. Contrarily, methoxamine and phenylephrine depressed these currents and elicited beta-antagonistic inotropic actions, especially when isoproterenol was present. Specific feature of alpha-agonist action in the presence of isoproterenol was an inward shift of the semi-steady I-V relationship. It is thus suggested that, in the bullfrog atrium, alpha-agonists produce a strong beta-receptor blocking action and an inward shift of the background current. A possible relationship between the latter effect and inhibition of the Na-K pump is also suggested.

SV40 T-antigen expression in skin fibroblasts from clinically normal individuals and from ten cases of Fanconi anemia

Previous studies of the expression of SV40 genetic information by skin fibroblasts included limited numbers of cell donors and failed to adequately consider possible effects of age, sex, and ethnic origin on assay results. A population of 76 healthy subjects were selected for study following determination of personal and family disease history and karyological analysis. Skin fibroblasts from these individuals were tested for expression of SV40 T-antigen by indirect immunofluorescent assay. The data were normally distributed and showed no significant differences between the age, sex, or ethnic groups tested. The occurrence of rare karyological anomalies in this control population had no effect on T-antigen expression. Fibroblasts from 10 Fanconi anemia patients demonstrated significantly elevated expression of T antigen compared to the well-defined control population, based on simple statistical criteria. T-antigen expression was elevated in two young patients prior to the onset of anemia and did not appear to correlate with the incidence or severity of other specific symptoms. Thus, elevated T-antigen expression in Fanconi anemia fibroblasts reflects an actual defect at the cellular level, rather than clinical, age, sex or ethnic factors not previously considered.

On the size of the DNA in the mammalian chromosome. Structural subunits

Alkaline degradation of mammalian DNA indicates that the molecule exists in the chromosome as an array of structural subunits. The size of the subunit of single-stranded DNA is circa 5 x 10(8) daltons, and it is of sufficient length to contain a number of synthetic units, replicons. The upper size limit of the multicomponent structure is in excess of 10(10) daltons. Mammalian cells of three different origins have been shown to contain the same basic structural DNA components and these components exist throughout the cell cycle. The nature of the links between the subunits is not known.