Sister chromatid differential staining pattern in prematurely condensed chromosomes

Summary Application of sister chromatid differential (SCD) procedure on G₁, S and G₂ prematurely condensed chromosomes (PCC) of cells in the second and third cycle of DNA replication in medium containing BrdU reveals differential staining patterns characteristic of their respective stages in the cell cycle. These findings also suggest a structural similarity between PCC and metaphase chromosomes.Supported in part by grants from the National Foundation-March of Dimes (grant No. 1-327) and from the National Cancer Institute (grant No. CA-16480).     

Binding of aflatoxins B1 and G1 to human serum proteins

Zusammenfassung In vitro Experimente mit¹⁴C-markiertem, gereinigtem Aflatoxin zur Untersuchung der Bindung von Aflatoxin B₁ und G₁ an verschiedene Serumproteine ergaben, dass Aflatoxin B₁ hauptsächlich mit-Globulin, G₁ dagegen vorwiegend mit Albumin bindet.

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This work was supported by part by a grant from the China Medical Board of New York, Inc., and was performed during one of us (S.S.L.) received a class C. research award from the National Science Council, Republic of China.     

Resolution of small G1 and G2 populations of L1210 leukemia by flow microfluorometric analysis aided by velocity sedimentation

L1210 leukemic cells grown in vitro were subjected to kinetic analysis using a flow microfluorometer. A single broad peak was found for the DNA content distribution if unfractionated cells were used; prior fractionation using lg velocity sedimentation allowed the separation of small peaks with smaller (G1) and larger (G2) DNA contents from the dominant S phase peak with intermediate DNA content.     

Arrest of somatic cells at G2 by Sevin (pesticide)

Summary The treatment of onion root meristems with the pesticide Sevin [carbaryl (1-naphthyl n-methyl carbamate)] induces an accumulation of interphase nuclei with a larger diameter, and a subsequent decrease in the index of smaller nuclei. It is concluded that Sevin depresses mitosis by arresting cells at G₂ without affecting DNA synthesis.The authors are grateful to Prof. K. S. Bilgrami, Head of the Postgraduate Department of Botany, Bhagalpur University, for providing facilities and to Prof. B.N. Mookerjee for his valued suggestions.     

Cation inhibition of DNA synthesis in mammary epithelial cells in vitro

Zusammenfassung Lithium- und Ammoniumionen verhindern den Anfang der DNA-Synthese im Milchdrüsenepithel in vitro. Die Replikation von DNA, nach dem Anfang derS-Periode, wird jedoch nicht verhindert. Diese spezifische Verhinderung der Dauer derG ₁-Periode durch die ionale Umgebung zeigt, dass Mechanismen, die für die Regulierung der Zellproduktion wichtig sind, während derG ₁-Periode intervenieren.

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This work was supported in part by grant No. CA 10268 from the U.S. Public Health Service.     

Induction of vanadium accumulation and nuclear sequestration causing cell suicide in human Chang liver cells

Very little is known about the modulation of vanadium accumulation in cells, although this ultratrace element has long been seen as an essential nutrient in lower life forms, but not necessarily in humans where factors modulating cellular uptake of vanadium seem unclear. Using nuclear microscopy, which is capable of the direct evaluation of free and bound (total) elemental concentrations of single cells we show here that an NH₄Cl acidification prepulse causes distinctive accumulation of vanadium (free and bound) in human Chang liver cells, concentrating particularly in the nucleus. Vanadium loaded with acidification but leaked away with realkalinization, suggests proton-dependent loading. Vanadyl(4), the oxidative state of intracellular vanadium ions, is known to be a potent source of hydroxyl free radicals (OH^.). The high oxidative state of nuclei after induction of vanadyl(4) loading was shown by the redox indicator methylene blue, suggesting direct oxidative damage to nuclear DNA. Flow cytometric evaluation of cell cycle phase-specific DNA composition showed degradation of both 2N and 4N DNA phases in G₁, S and G₂/M cell cycle profiles to a solitary 1N DNA peak, in a dose-dependent manner, effective from micromolar vanadyl(4) levels. This trend was reproduced with microccocal nuclease digestion in a time response, supporting the notion of DNA fragmentation effects. Several other approaches confirmed fragmentation occurring in virtually all cells after 4 mM V(4) loading. Ultrastructural profiles showed various stages of autophagic autodigestion and well defined plasma membrane outlines, consistent with programmed cell death but not with necrotic cell death. Direct intranuclear oxidative damage seemed associated with the induction of mass suicide in these human Chang liver cells following vanadium loading and nuclear sequestration.     

The influence of partial synchronization of cell growth on the inhibition of L1210 cell viability by mouse thymus DNA

Résumé Nous avons trouvé que le cycle de la vie de la cellule L1210 règle les effets inhibitoires du DNA du thymus de la souris sur la viabilité cellulaire. Les cellules obtenues à la phase G₂ des cultures partiellement synchronisées étaient inhibitées presque 2 fois plus que les cellules obtenues des cultures asynchroniques. Le DNA n'avait guère d'effet toxique sur les cellules obtenues aux phases S et M. Les fluctuations dans la viabilité cellulaire n'étaient pas causées par des changements proportionnels dans l'absorption du DNA.

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This work was supported in part by grant No. GW-733 of the NSF and by grant No. CA-08763 of the USPHS.     

Activation of ataxia telangiectasia muted under experimental models and human Parkinson’s disease

In the present study we demonstrated that neurotoxin MPP⁺-induced DNA damage is followed by ataxia telangiectasia muted (ATM) activation either in cerebellar granule cells (CGC) or in B65 cell line. In CGC, the selective ATM inhibitor KU-55933 showed neuroprotective effects against MPP⁺-induced neuronal cell loss and apoptosis, lending support to the key role of ATM in experimental models of Parkinson’s disease. Likewise, we showed that knockdown of ATM levels in neuroblastoma B65 cells using an ATM-specific siRNA attenuates the phosphorylation of retinoblastoma protein without affecting other cell-cycle proteins involved in the G₀/G₁ cell-cycle phase. Moreover, we demonstrated DNA damage, in human brain samples of PD patients. These findings support a model in which MPP⁺ leads to ATM activation with a subsequent DNA damage response and activation of pRb. Therefore, this study demonstrates a new link between DNA damage by MPP⁺ and cell-cycle re-entry through retinoblastoma protein phosphorylation.     

Paradoxical effect of 1-β-D-arabinofuranosyl cytosine triphosphate on bleomycin-induced unscheduled DNA synthesis in permeable sarcoma cells

Summary 1--D-Arabinofuranosyl cytosine-5-triphosphate (araCTP), an inhibitor of DNA synthesis, paradoxically enhanced unscheduled DNA synthesis (USD) induced by bleomycin in permeable mouse sarcoma cells. A greater enhancing effect of araCTP on bleomycin-induced USD was observed with lower concentrations of dCTP in the assay mixture. USD measured without bleomycin in nuclei isolated from mouse sarcoma cells was not enhanced, but inhibited by araCTP.Acknowledgments. The authors wish to thank Nippon Kayaku Co. (Tokyo, Japan) for providing copper-free bleomycin A₂. This research was supported in part by a grant from the Japan Ministry of Education, Science and Culture.     

Hypophysial hormones and a G1 block in the lens epithelium of the adult frog (Rana pipiens)

Summary Mechanical injury initself may be responsible for the transition of lens epithelial cells from the G₀ to the G₁ compartment of the cell cycle. This traverse which does not depend on DNA-dependent hypophysial hormones may be in part reversible.     

Appearance of growth-inhibiting activity (G1 chalone) during ontogenetic development of rat and chick epidermis in vivo and in vitro

Summary A comparative study was carried out between the stage of embryonic development of epidermis and its content of growth-inhibitory activity (G₁ chalone). Injections of aqueous extracts from keratinized fetal rat or chick embryo epidermis led to a depression of DNA-synthesis in adult mouse epidermis, whereas extracts from undifferentiated epidermis did not contain such an activity.This investigation was supported by the Deutsche Forschungsgemeinschaft.     

Production and characterization of antibody against aflatoxin M1

Summary Antibody against aflatoxin M₁ was obtained after immunization of rabbits with bovine serum albumin-afla M₁ oxime conjugate. The antibody has greatest binding efficiency for afla M₁, and was less efficient for afla B₁. Cross-reaction of antibody with aflatoxin Q₁, aflatoxicol, and aflatoxin B_2a was weak. Aflatoxin B₂, G₁, and G₂ and afla B₁-guanine adduct showed almost no cross-reaction with the antibody. The sensitivity of the binding assay for aflatoxin M₁ detection is in the range of 1–10 ng per assay. Detailed methods for the preparation of the conjugate, production of immune serum, and methods for antibody determination are described.Supported by the College of Agricultural and Life Sciences, North Central Regional project NC-129, the University of Wisconsin-Madison, and by Public Health Service research grant number CA 15064 from the National Cancer Institute, NIH.The authors wish to thank Dr R.C. Garner for providing aflatoxin-B-guanine adduct, and Dr Dennis H. Hseih for providing aflatoxicol and aflatoxin Q₁.     

Der Mitosezyklus im diploiden und triploiden Wurzelmeristem vonScilla sibirica

Summary In meristematic root tip cells ofScilla sibirica (2n=12 and 3n=18) the following results were obtained with the aid of autoradiography: 1. The average duration of the mitotic cycle (2n=12) is 69.5 h. The G₁-phase lasts 36.5 h, the DNA synthetic phase 17.5 h, the G₂-phase 8 h and mitosis 7.5 h. 2. There are no marked differences in the lengths of the cell cycles nor in the duration of the various phases between diploid and triploid plants.     

Differential sensitivity to ethidium bromide of replicative DNA synthesis and bleomycin-induced unscheduled DNA synthesis in permeable mouse sarcoma cells1

Summary Replicative DNA synthesis in permeable mouse sarcoma cells was more sensitive to ethidium bromide (EtBr) than bleomycin-induced unscheduled DNA synthesis (UDS). A similar difference in sensitivity to EtBr was observed between DNA polymerases and . The difference in sensitivity to EtBr of replicative DNA synthesis and UDS in the present system seems to reflect mainly the sensitivity difference between DNA polymerases and .Acknowledgments. The authors wish to thank Nippon Kayaku Co. (Tokyo, Japan) for providing copper-free bleomycin A₂. This research was supported in part by a grant from the Japan Ministry of Education, Science and Culture.     

Effect of diphosphonates on ATP and Pi content,Pi uptake and energy charge of cultured calvaria cells

Summary In previous studies we have shown that glycolysis is strongly inhibited in cultured calvaria cells treated with ethane-1-hydroxy-1, 1-diphosphonate (EHDP) or dichloromethanediphosphonate (Cl₂MDP). This study shows that the energy charge of the adenylate pool, and the ATP and Pi content, were not changed by treatment with diphosphonates except for a slight decrease of ATP and Pi at 0.25 mM Cl₂ MDP. The uptake of Pi was diminished by 50% and 20% in cells treated for 6 days with Cl₂MDP or EHDP, respectively, but not when diphosphonates were present only during the uptake studies.Acknowledgments. We thank Miss B. Wyss for her skilled technical assistance. This work has been supported by the Swiss National Science Foundation (grant Nos 3.725.76 and 3.824.79), by the Procter & Gamble Company, USA, and by the Ausbildungs- und Förderungsfonds der Arbeitsgemeinschaft für Osteosynthese (AO), Chur, Switzerland.     

Importance of G2 for the cytokinesis of plant cells: Specific blocking by deoxyguanosine

Summary The modalities of the deoxyguanosine blocking effect on meristematic root cells of Allium sativum L. reveals that, during G₂ phase, fundamental processes leading to cytokinesis take place.     

Increased incidence of lymphomas in survivors of the host-versus-graft syndrome

Summary When (SB)F₁ spleen cells were injected into perinatal parental B strain mice a lethal runting syndrome was induced. The survivors showed a significantly increased incidence of lymphomas in old age. the tumors occurred much later and less frequently than in the reverse reaction, B(SB)F₁ GVHD.Supported by U.S.P.H.S. grant No. 15,500.     

Enzymatic synthesis of trisialoganglioside by particulate fractions of rat liver

Summary Rat liver contains a particulate (membrane-bound) glycosyl transferase, concentrated in Golgi apparatus fractions, which catalyzes the synthesis of a trisialoganglioside from the ganglioside precursor disialohematoside (G_D3). Sialic acid was not incorporated into exogenous G_D1a from CMP-N-acetylneuraminic acid suggesting that G_D1a is an endproduct of the monosialoganglioside pathway. Thus, the disialoganglioside pathway may be a primary source of trisialoganglioside and higher ganglioside homologs in adult rat liver.     

Prostaglandin E1 induced salivary secretion

Summary PGE₁ but not PGF₂ at 500–1000 g/kg induced a slow and sparse flow from the parotid and no flow at all from submaxillary glands. Composition of PGE₁-induced parotid saliva was quite different from that evoked by any autonomic agonists. The present study suggests that PGE₁ might act directly on parotid acinar cells.Acknowledgment. This work was supported by NIDR grant DE05633. The authors wish to thank Ms Sonya Wynn for her technical assistance.     

Synthesis of sulfated glycosaminoglycans by the three cell types of the rabbit cornea in culture

Summary Rabbit corneal cells were cultivated for 21 days and then exposed to Na₂ ³⁵SO₄, a precursor of sulfated glycosaminoglycans (GAG). All 3 cell types of the cornea, the fibroblasts, the epithelial as well as the endothelial cells, synthesize GAG. The fractionation-patterns of the epithelial and endothelial GAG are almost identical and differ clearly from the one of fibrolastic GAG.Supported by SNSF, grant No. 3.534.71.