Showing papers by "Heidelberg University published in 1982"

Beyond the random-phase approximation: A new approximation scheme for the polarization propagator

Abstract: Within the framework of the many-body Green's-function method we present a new approach to the polarization propagator for finite Fermi systems. This approach makes explicit use of the diagrammatic perturbation expansion for the polarization propagator, and reformulates the exact summation in terms of a simple algebraic scheme, referred to as the algebraic diagrammatic construction (ADC). The ADC defines in a natural way a set of approximation schemes ($n$th-order ADC schemes) which represent infinite partial summations exact up to $n$th order of perturbation theory. In contrast to the random-phase-approximation (RPA)-like schemes, the corresponding mathematical procedures are essentially Hermitian eigenvalue problems in limited configuration spaces of unperturbed excited configurations. Explicit equations for the first- and second-order ADC schemes are derived. These schemes are thoroughly discussed and compared with the Tamm-Dancoff approximation and RPA schemes.

Injection of subunits of cyclic AMP-dependent protein kinase into cardiac myocytes modulates Ca2+ current.

Abstract: β-Adrenergic stimulation of the heart is thought to increase cardiac muscle contractility by activation of cyclic AMP-dependent protein kinase and concomitant increase in the phosphorylation of certain proteins (for refs see refs 1–6). Electrophysiological studies have shown that the stimulation of cardiac β-adrenoreceptors7, the external application of cyclic AMP or its analogues to Purkinje fibres8, or the injection of cyclic AMP into single myocytes9 can increase the slow inward current (Isi) during the plateau phase of the action potential (AP). In heart muscle this current is mainly carried by Ca2+ (refs 10, 11) and it has been suggested that cyclic AMP-dependent phosphorylation of some component of the calcium channel increases the amount of Ca2+ which enters the cell during depolarization10. We have investigated this hypothesis by examining the electrical responses of isolated guinea pig ventricular myocytes to pressure injections of subunits of the cyclic AMP-dependent protein kinase. We report here that injection of the catalytic subunit (C) resulted in a lengthening of the action potential duration (APD) and an increase in the height of the plateau as well as the amplitude of Isi. By contrast, the injection of regulatory subunit (R) shortened the APD of fast and slow response APs, an effect which was reversed by adrenaline.

Rabl's Model of the Interphase Chromosome Arrangement Tested in Chinese Hamster Cells by Premature Chromosome Condensation and Laser-UV-Microbeam Experiments

Abstract: In 1885 Carl Rabl published his theory on the internal structure of the interphase nucleus We have tested two predictions of this theory in fibroblasts grown in vitro from a female Chinese hamster, namely (1) the Rabl-orientation of interphase chromosomes and (2) the stability of the chromosome arrangement established in telophase throughout the subsequent interphase Tests were carried out by premature chromosome condensation (PCC) and laser-UV-microirradiation of the interphase nucleus Rabl-orientation of chromosomes was observed in G1 PCCs and G2 PCCs The cell nucleus was microirradiated in G1 at one or two sites and pulse-labelled with 3H-thymidine for 2h Cells were processed for autoradiography either immediately thereafter or after an additional growth period of 10 to 60h Autoradiographs show unscheduled DNA synthesis (UDS) in the microirradiated nuclear part(s) The distribution of labelled chromatin was evaluated in autoradiographs from 1035 cells after microirradiation of a single nuclear site and from 253 cells after microirradiation of two sites After 30 to 60h postincubation the labelled regions still appeared coherent although the average size of the labelled nuclear area fr increased from 142% (0h) to 265% (60h) The relative distance dr, ie the distance between two microirradiated sites divided by the diameter of the whole nucleus, showed a slight decrease with increasing incubation time Nine metaphase figures were evaluated for UDS-label after microirradiation of the nuclear edge in G1 An average of 43 chromosomes per cell were labelled Several chromosomes showed joint labelling of both distal chromosome arms including the telomeres, while the centromeric region was free from label This label pattern is interpreted as the result of a V-shaped orientation of these particular chromosomes in the interphase nucleus with their telomeric regions close to each other at the nuclear edge Our data support the tested predictions of the Rabl-model Small time-dependent changes of the nuclear space occupied by single chromosomes and of their relative positions in the interphase nucleus seem possible, while the territorial organization of interphase chromosomes and their arrangement in general is maintained during interphase The present limitations of the methods used for this study are discussed

Factors controlling stable isotope composition of European precipitation

Abstract: The seasonal and spatial variations of stable isotope ratios in present day European precipitation are simulated with a simple multibox model of the mean west-east horizontal transport of the atmospheric water vapour across the European continent. Isotope fractionation during the formation of precipitation leads to an increasing depletion of heavy isotopes in the residual air moisture as it moves towards the centre of the continent. This isotopic depletion is partly compensated, particularly in summer, by evapotranspiration, which is assumed to transfer soil water into the atmosphere without isotope fractionation. The model estimates are based on horizontal water vapour flux data, varying seasonally between 88 and 130 kg m -1 s -1 for the Atlantic coast region, and on the monthly precipitation, evapotranspiration and surface air temperature data available for various locations in Europe. Both continental and seasonal temperature effects observed in the stable isotope composition of European precipitation are fairly well reproduced by the model. The calculations show that the isotopic composition of local precipitation is primarily controlled by regional scale processes, i.e. by the water vapour transport patterns into the continent, and by the average precipitation-evapotranspiration history of the air masses precipitating at a given place. Local parameters such as the surface and/or cloud base temperature or the amount of precipitation modify the isotope ratios only slightly. Implications of the model predictions for the interpretation of stable isotope ratios in earlier periods as they are preserved in ice cores and in groundwater are also discussed. DOI: 10.1111/j.2153-3490.1982.tb01801.x

Glutathione reductase from human erythrocytes. The sequences of the NADPH domain and of the interface domain.

Abstract: 1. Sequence analysis of the NADPH domain (residues 158--293) and of the interface domain (365--478) was based on 12 CNBr fragments, which were isolated using ion-exchange chromatography and paper methods. Fragments with more than 15 residues were digested further with trypsin and chymotrypsin. The isolated peptides were sequenced by automated solid-phase Edman degradation. All sequenced peptides were ordered and overlapped by computerized comparisons with a complete sequence guessed from the electron density map of the protein. In the case of short CNBr fragments, this alignment was confirmed by the sequence analysis of protein fragments resulting from incomplete CNBr cleavage. 2. In the NADPH domain, residue 197, which is involved in an induced-fit mechanism, was identified as a tyrosine. The structure of the NADPH domain is probably homologous with the NAD domain of lipoamide dehydrogenase and with the FAD domain of several proteins, but not with NADPH domains of known chain-fold in other proteins. 3. The paper completes the sequence analysis of glutathione reductase so that the enzyme is now known in atomic detail. The numbering scheme of the chemically determined sequence will be used henceforth in crystallographic studies also. As inferred from the sequence data each of the two identical chains contains 478 amino acid residues, the composition being Cys10, Asp21, Asn17, Thr31, Ser31, Glu29, Gln11, Pro24, Gly43, Ala42, Val44, Met15, Ile29, Leu34, Tyr13, Phe14, Lys34, His16. Arg17, and Trp3. From these data an Mr of 2 x 51 600 was calculated for the FAD-free apoenzyme and an Mr of 2 x 42 400 for the holoenzyme.

Imidazole-buffered osmium tetroxide: an excellent stain for visualization of lipids in transmission electron microscopy

Abstract: The usefulness of imidazole-buffered osmium tetroxide as a stain for lipids in transmission electron microscopy has been investigated. Rat liver and other tissues were fixed by perfusion with glutaraldehyde and post-fixed with osmium-imidazole and the appearance of lipid droplets was compared with that after post-fixation in unbuffered aqueous osmium tetroxide or an osmium solution buffered otherwise. Prominent electron-opaque staining of lipid droplets and of lipoprotein particles was noted after post-fixation with 2% osmium-imidazole, pH 7.5, for 30 min. The lipid droplets appeared well circumscribed with no evidence of diffusion. In contrast, the intensity of staining was much less and there was some diffusion around lipid droplets in material post-fixed in aqueous or cacodylate-buffered osmium tetroxide. Spot tests on filter paper revealed that unsaturated fatty acids, especially linolenic and linoleic acids reacted more intensely with osmium-imidazole than with aqueous osmium tetroxide. These findings demonstrate that osmium-imidazole provides an excellent stain for lipids in transmission electron microscopy and that most probably it stains lipids with unsaturated fatty acids.

Cytogerontology since 1881: A reappraisal of August Weismann and a review of modern progress

Abstract: Cytogerontology, the science of cellular ageing, originated in 1881 with the prediction by August Weismann that the somatic cells of higher animals have limited division potential. Weismann's prediction was derived by considering the role of natural selection in regulating the duration of an organism's life. For various reasons, Weismann's ideas on ageing fell into neglect following his death in 1914, and cytogerontology has only reappeared as a major research area following the demonstration by Hayflick and Moorhead in the early 1960s that diploid human fibroblasts are restricted to a finite number of divisions in vitro. In this review we give a detailed account of Weismann's theory, and we reveal that his ideas were both more extensive in their scope and more pertinent to current research than is generally recognised. We also appraise the progress which has been made over the past hundred years in investigating the causes of ageing, with particular emphasis being given to (i) the evolution of ageing, and (ii) ageing at the cellular level. We critically assess the current state of knowledge in these areas and recommend a series of points as primary targets for future research.

Stochastic stability in some chaotic dynamical systems

Abstract: For a certain class of piecewise monotonic transformations it is shown using a spectral decomposition of the Perron-Frobenius-operator ofT that invariant measures depend continuously on 3 types of perturbations: 1) deterministic perturbations, 2) stochastic perturbations, 3) randomly occuring deterministic perturbations. The topology on the space of perturbed transformations is derived from a metric on the space of Perron-Frobenius-operators.

Cloned HBV DNA causes hepatitis in chimpanzees.

Abstract: Most of our knowledge of the structure and function of the hepatitis B virus (HBV) genome comes from the analysis of the viral DNA sequences cloned in bacteria1–3. Because the physical state of cloned HBV DNA differs from HBV DNA encapsidated in the virion—for example, it lacks the nick-gap structure4, and a covalently linked protein5—the question arises as to whether it can initiate HBV replication in vitro6 or in vivo. We describe here the development of typical acute viral hepatitis, and the detection of HBV-specific DNA sequences in the serum and liver, in a chimpanzee inoculated with cloned HBV DNA. This demonstrates that neither the virion proteins nor the nick-gap structure of the virion DNA are needed for the initiation of replication of HBV in vivo.

Role of Peroxidase in Lignification of Tobacco Cells: II. Regulation by Phenolic Compounds

Abstract: Coniferyl alcohol is the primary substrate for peroxidase-mediated lignification, a process which depends on the generation of H 2 O 2 by NADH oxidation. We measured the concentrations of various phenols (synthetic and natural) at which maximal enhancement of NADH oxidation occurs. Coniferyl alcohol was found to stimulate NADH oxidation at a much lower concentration (0.01 mm) than other natural or synthetic phenols (1-100 mm). In addition, coniferyl alcohol prevented the conversion of active peroxidase into the inactive intermediate compound III—which is usually formed in the presence of NADH—at equally low concentrations. This conversion was found to be a prerequisite for stimulation of NADH-oxidation, but it was not necessarily connected to stimulation. The oxidation of NADH and coniferyl alcohol (or guaiacol) can occur simultaneously, but there is a strong competitive interaction between these two substrates. At pH 5, the presence of NADH at concentrations 30 to 60 times lower than the phenols completely prevents their oxidation. The results are discussed in relation to the role of cell wall peroxidases in conversion of coniferyl alcohol to lignin and in formation of H 2 O 2 .

Experimental-study of opposite-sign dimuons produced in neutrino and antineutrino interactions

Abstract: A large sample of opposite-sign dimuons, produced by the interaction of neutrinos and antineutrinos in iron, is analysed. The data agree very well with the hypothesis that the extra muon is the product of charm decay. They yield information on the strength and space-time structure of the charmproducing weak current. The strange-sea structure functionxs(x) is determined. The difference between neutrino and antineutrino dimuon production is analysed to provide a value of the Kobayashi-Maskawa weak mixing angleθ2.

Analysis of chromosome positions in the interphase nucleus of Chinese hamster cells by laser-UV-microirradiation experiments.

Abstract: Unsynchronized cells of an essentially diploid strain of female Chinese hamster cells derived from lung tissue (CHL) were laser-UV-microirradiated (λ=257 nm) in the nucleus either at its central part or at its periphery. After 7–9 h postincubation with 0.5 mM caffeine, chromosome preparations were made in situ. Twenty-one and 29 metaphase spreads, respectively, with partial chromosome shattering (PCS) obtained after micro-irradiation at these two nuclear sites, were Q-banded and analyzed in detail. A positive correlation was observed between the frequency of damage of chromosomes and both their DNA content and length at metaphase. No significant difference was observed between the frequencies of damage obtained for individual chromosomes at either site of microirradiation. The frequency of joint damage of homologous chromosomes was low as compared to nonhomologous ones. Considerable variation was noted in different cells in the combinations of jointly shattered chromosomes. Evidence which justifies an interpretation of these data in terms of an interphase arrangement of chromosome territories is discussed. Our data strongly argue against somatic pairing as a regular event, and suggest a considerable variability of chromosome positions in different nuclei. However, present data do not exclude the possibility of certain non-random chromosomal arrangements in CHL-nuclei. The interphase chromosome distribution revealed by these experiments is compared with centromere-centromere, centromere-center and angle analyses of metaphase spreads and the relationship between interphase and metaphase arrangements of chromosomes is discussed.

Cell type specificity of a neural cell surface antigen recognized by the monoclonal antibody A2B5

Abstract: The monoclonal antibody A2B5 reacts with the surface membrane of most neurons in monolayer cultures of cerebellum, retina, spinal cord, and dorsal root ganglion of embryonic and early postnatal C57Bl/6 J mice maintained in vitro for culture periods of 2 to 10 days. A small percentage of astroglial cells also expresses A2B5 antigen in murine, chicken and rabbit cerebellum, in chicken retina, and in murine spinal cord and dorsal root ganglion. Less mature astroglial cells are strained for A2B5 antigen to a greater extent than the more mature astrocytes. Astrocytes from rat cerebellum and mouse retina were not found to express A2B5 antigen under the present culture conditons. Some of the less mature oligodendrocytes recognized by 04 antibodies express A2B5 antigen, while the more mature 01 antigen- and galactocerebroside-positive oligodendrocytes were not found to be A2B5 antigen-positive. Fibroblasts or fibroblast-like cells do not express detectable levels of A2B5 antigen. After fixation of the cells with paraformaldehyde and ethanol, all cell types present in culture are labeled by the A2B5 antibody intracellularly.

The nephronophthisis complex. A clinicopathologic study in children.

Abstract: The clinical and morphological findings are described in 27 children with nephronophthisis. Seventeen children were considered as sporadic cases. In 10 familial cases the presumed mode of inheritance was autosomal recessive. The clinical picture was rather uniform: polyuria-polydipsia, hyposthenuria, anemia, growth retardation, and azotemia with progressive renal failure. Six patients presented with tapeto-retinal degeneration. In a further seven children other ocular changes were detected. Two female siblings showed additional non-renal manifestations: mental retardation, pulmonary emphysema, skeletal anomalies, and congenital hepatic fibrosis.

The short- and long-term effects of bezafibrate in the rat.

Abstract: Bezafibrate is a potent hypolipidemic agent, which causes marked proliferation of peroxisomes in rat liver. At the same dosage, bezafibrate is more effective in male than in female rats. This is probably related to divergent pharmacokinetics, which cause differences in drug level in serum and liver. The volume density of peroxisomes and several of their enzymes such as carnitine acetyl transferase and acyl-COA oxidase increase in a dose-related fashion. The hypolipidemic effect of bezafibrate, however, does not correlate with the used dosage. This implies that peroxisomal proliferation may play only a minor role in the hypolipidemic action of bezafibrate. In animals treated for 26 months with 300, 750, or 1500 ppm bezafibrate, the relative liver weight and serum triglycerides did not differ significantly from controls. Peroxisomal proliferation varied in different cells, being most prominent in single hepatocytes. The liver catalase activity was significantly reduced, but carnitine acetyl transferase was increased. Abnormal peroxisomes and mitochondria with longitudinal cristae were quite frequent. In one focus, catalase activity was severely diminished ahd peroxisomes were markedly reduced. The incidence of liver tumors was the same (1-3%) in treated animals as in controls.

Distal tubular segments of the rabbit kidney after adaptation to altered Na- and K-intake. I. Structural changes.

Abstract: Na-K-ATPase activity was measured in the convoluted part of the distal tubule (DCT), the connecting tubule (CNT) and the cortical collecting duct (CCD). The segments were microdissected from freeze-dried kidney tissue of rabbits adapted to various salt diets and exposed to large differences in endogenous and exogeneous mineralocorticoids.

Higher Precision Measurement of the hfs Interval of Muonium and of the Muon Magnetic Moment

Abstract: New higher precision measurements of the hyperfine Zeeman transitions in the ground state of muonium have been performed with use of the high-stopping-density surface ${\ensuremath{\mu}}^{+}$ beam at the Clinton P. Anderson Meson Physics Facility. The results are $\ensuremath{\Delta}\ensuremath{ u}=4463\ensuremath{-}302.88(16)$ kHz (0.036 ppm) and $\frac{{\ensuremath{\mu}}_{\ensuremath{\mu}}}{{\ensuremath{\mu}}_{p}}=3.1833461(11)$ (0.36 ppm). The current theoretical value of $\ensuremath{\Delta}\ensuremath{ u}$ agrees well with experiment within the 0.77-ppm error of $\ensuremath{\Delta}{\ensuremath{ u}}_{\mathrm{theor}}$, which is due principally to inaccuracy in evaluation of the nonrecoil radiative correction term. The most precise current value of $\frac{{m}_{\ensuremath{\mu}}}{{m}_{e}}$ is obtained from our value of $\frac{{\ensuremath{\mu}}_{\ensuremath{\mu}}}{{\ensuremath{\mu}}_{p}}$.

Classical Spin-Glass Model

Abstract: A simple model of a classical spin-glass with weakly correlated disorder is presented. It includes both randomness and frustration, and is exactly soluble, but its solution can be obtained without replicas. Among the several phases of the model a mixed phase is found where spin-glass and ferromagnetism coexist. In addition the characteristic S shape of the spin-glass magnetization is reproduced.

Definition and Classification of the Histamine-Release Response to Drugs in Anaesthesia and Surgery: Studies in the Conscious Human Subject* **

Abstract: In 2 clinical studies in 40 conscious human volunteers and 164 orthopedic patients histamine-release responses were diagnosed, defined and classified. Polygeline (Haemaccel) in its now outdated formulation [40] was chosen as a clinical histamine releaser. The main interest was not concentrated on the extreme, the “classical” anaphylactic response, but on theaverage histamine-release response found in clinical experiments with so many drugs in the last 10 years. In human volunteers 600 ng/kg histamine was i. v. injected. Indicants for a systemic anaphylactoid reaction with the highest incidence ratio were tachycardia, plasma histamine levels >1 ng/ml, “metallic taste”, flush, congestion of head, “wet eyes” and tears, hypertension and headache. Following polygeline none of these subjects developed a life-threatening reaction, but 12 showed a systemic response, 11 a cutaneous reaction and 17 were non-responders. Indicants for a systemic anaphylactoid reaction with the highest incidence ratio were plasma histamine levels >1 ng/ml, tachycardia, wheals, sensation of heat, narrowness of throat, hypertension, headache and wet eyes or tears. In a prolective, cohort study in the orthopedic patients 3 subjects with life-threatening reactions, 27 with systemic response, 96 with cutaneous reaction and 38 non-responders were included. Indicants with the highest incidence ratio were tachycardia, plasma histamine levels >1 ng/ml, erythema and wheals, cough, flush, stuffy nose and facial oedema. With this trial the indicants for diagnosing a systemic histamine release response in volunteers were validated in patients to a large extent. Thus the average histamine-release response was defined by clinical signs such as tachycardia and mild hypertension, scattered hives such as spots of erythema and wheals, respiratory symptoms in the laryngeal and nasal region, such as cough, narrowness in the throat, stuffy nose and sneezingand by pathological plasma histamine levels (>1 ng/ml). In addition histamine-release responses were differentiated as cutaneous responses, systemic responses and life-threatening responses by clinical and operational criteria and by plasma histamine levels. Using clinical trials and medical decision making procedures the incidence of systemic histamine-release responses in patients higher by two orders of magnitude than in other studies reported hitherto.

Role of Peroxidase in Lignification of Tobacco Cells : I. Oxidation of Nicotinamide Adenine Dinucleotide and Formation of Hydrogen Peroxide by Cell Wall Peroxidases

Abstract: The two peroxidase isoenzyme groups (GI and GIII) localized in the cell walls of tobacco (Nicotiana tabacum L.) tissues were compared with respect to their capacity for NADH-dependent H2O2 formation. Peroxidases of the GIII group are slightly more active than those of the GI group when both are assayed under optimal conditions. This difference is probably not of major regulatory importance. NADH-dependent formation of H2O2 required the presence of Mn2+ and a phenol as cofactors. The addition of H2O2 to the reaction mixture accelerated subsequent NADH-dependent H2O2 formation. In the presence of both cofactors or Mn2+ alone, catalase oxidized NADH. However, if the cofactors were absent or if only dichlorophenol was present, catalase inhibited NADH oxidation. No H2O2 accumulation occurred in the presence of catalase. Superoxide dismutase inhibited NADH oxidation quite significantly indicating the involvement of the superoxide radical in the peroxidase reaction. These results are interpreted to mean that the reactions whereby tobacco cell wall peroxidases catalyze NADH-dependent H2O2 formation are similar to those proposed for horseradish peroxidase (Halliwell 1978 Planta 140: 81-88).

Cell type-specific surface antigens in the mammalian nervous system.

Abstract: Interest in the molecular composition of cell surfaces in the nervous system has emerged from several disciplines in neurobiology. Two lines of investigation in particular have turned to the delineation of the differentiative program of neural cell surfaces: the search for cell surface components involved in cell recognition and interaction during development, and the search for cell surface markers that are unique for a particular cell type and a particular developmental stage. The investigation of cell type-specific markers has been stimulated by the need to understand a cell’s specialized task in performing its particular functional assignments. The advantage in deciphering unique molecular designs on the cell surface rather than intracellular ones lies in the possibility that such constellations may not only be involved in cell recognition, but may also serve as a means for the isolation of homogeneous populations of cell types in viable form. The availability of selected populations of all neural cell classes (encompassing not only the major classes of neurons, astrocytes, and oligodendrocytes, but also developmentally distinct subsets of these) is the basis of much research in cellular and molecular neuro biology. The present review will focus on some major aspects of cell typespecific cell surface markers and will summarize our knowledge of immunologically identified markers in the mammalian nervous system, without allusion to function and with a special emphasis on the mouse cerebellum, which has been the center of interest in the author‘s laboratory. Antibodies have played a crucial role in the characterization of cell type-specific markers. The immunological approach has proven to be an extremely versatile one and its possibilities can be summarized as follows. (1) Antibodies can be used to probe for the function of the antigen by blocking or modifying its task. When directed against different antigenic sites on the molecule, antibodies can serve to locate the structural sites involved in function. (2) When complex mixtures of antigens are used for immunization, new, and sometimes minor, cell surface constituents can be discovered and analyzed with the resultant antibodies. (3) When coupled to visual tags (fluorescein, rhodamine, ferritin, peroxidase, gold, and others), these antibodies can be used to define the cellular and subcellular distribution of the corresponding antigens in cell culture and in histological sections. (4) Antibodies can serve as reagents for the analysis of the molecular nature of the corresponding antigens characterized initially by purely immunological methods. ( 5 ) Cell type-specific antibodies can be used to isolate the antigen-positive and -negative cell types from their mixtures, provided that cells can be obtained as single cell suspensions. Isolation can be achieved by fluorescence-activated cell sorting, which allows cell separation not only within a broad range of fluorescence intensities of cells labeled with fluorochrome-coupled antibody, but also according to cell size and other parameters, such as membrane viscosity (Melamed et al., 1979). The more sophisticated the cell sorter’s sensory and motor machineries, the more parameters can serve for cell isolation in a single sorting process. An alternative, less elegant, but sometimes more rapid method for immunoselection makes use of antibody-coupled solid state carriers, such as Sepharose and polyacrylamide beads and microor macrospheres with magnetic cores (Kronick et al., 1978; Meier et al., 1982). Yet another means of im-

Phenotypic and Genotypic Characteristics of a Cell Line From a Squamous Cell Carcinoma of Human Skin

Abstract: A human cell line (SCL-1) from a poorly differentiating cutaneous squamous cell carcinoma (SCC) ws studied through 20 passages during 2 years. Cells maintained their original morphology with low degree of keratinization, as indicated by light and electron microscopy. The keratin peptide pattern resembled the type in SCC tumors, and the corresponding filaments were detected by immunofluorescence at all passage levels. Cells did not grow in soft agar but formed tumor-like nodules in an "organotypic" culture assay (on lifted collagen gels) and grew invasively after transplantation to immunosuppressed inbred C3H mice. After injection into BALB/c nu/nu mice, tumors of SCC morphology were formed. The hypodiploid tumor stem-line was maintained for about 10 passages, when a shift to hyperploidy started, as determined by chromosome and DNA flow microfluorometric analyses. Two stable marker chromosomes (in 100 and 70% of the metaphases, respectively), involving chromosomes 7 and 9, strongly indicated a monoclonal origin of this cell line.