A historical review of the problem of mitogenetic radiation

Summary The miracle of caryokinesis was the starting point that stimulated Alexander G. Gurwitsch to carry out his famous mitogenetic experiments in 1923. The results obtained confirmed his hypothesis of a weak radiation from cells, which is able to trigger the growth of other cells. Extensive experimental work within the first two decades after this discovery indicated that the problem of mitogenetic radiations is generally related to the biological significance of UV-radiation. Both energetic and informational aspects have to be considered, namely radiation effective in activating molecules, and that involved in arranging them into larger units.The molecular organization of biological structures is evidently governed by nonequilibrium conditions needing the uptake or emission of radiation. These concepts of A. G. Gurwitsch can be linked with modern approaches based on hypotheses of coherence in biology, synergetics and dissipative structures. However, the question of causal interrelationships between this part of non-equilibrium radiation and biological matter on different levels of evolution has to be solved now.     

Regulation of the cell cycle following DNA damage in normal and Ataxia telangiectasia cells

A proportion of the population is exposed to acute doses of ionizing radiation through medical treatment or occupational accidents, with little knowledge of the immedate effects. At the cellular level, ionizing radiation leads to the activation of a genetic program which enables the cell to increase its chances of survival and to minimize detrimental manifestations of radiation damage. Cytotoxic stress due to ionizing radiation causes genetic instability, alterations in the cell cycle, apoptosis, or necrosis. Alterations in the G1, S and G2 phases of the cell cycle coincide with improved survival and genome stability. The main cellular factors which are activated by DNA damage and interfere with the cell cycle controls are: p53, delaying the transition through the G1-S boundary; p21^WAF1/CIPI, preventing the entrance into S-phase; proliferating cell nuclear antigen (PCNA) and replication protein A (RPA), blocking DNA replication; and the p53 variant protein p53as together with the retinoblastoma protein (Rb), with less defined functions during the G2 phase of the cell cycle. By comparing a variety of radioresistant cell lines derived from radiosensitive ataxia talangiectasia cells with the parental cells, some essential mechanisms that allow cells to gain radioresistance have been identified. The results so far emphasise the importance of an adequate delay in the transition from G2 to M and the inhibition of DNA replication in the regulation of the cell cycle after exposure to ionizing radiation.     

Biochemical aspects of radiation biology

In order to analyze the mechanisms of biological radiation effects, the events after radiation energy absorption in irradiated organisms have to be studied by physico-chemical and biochemical methods. The radiation effects in vitro on biomolecules, especially DNA, are described, as well as their alterations in irradiated cells. Whereas in vitro, in aqueous solution, predominantly OH radicals are effective and lead to damage in single moieties of the DNA, in vivo the direct absorption of radiation energy leads to 'locally multiply-damaged sites', which produce DNA double-strand breaks and locally denatured regions. DNA damage will be repaired in irradiated cells. Error free repair leads to the original nucleotide sequence in the genome by excision or by recombination. "Error prone repair"(mutagenic repair), leads to mutation. However, the biochemistry of these processes, regulated by a number of genes, is poorly understood. In addition, more complex reactions, such as gene amplification and transposition of mobile gene elements, are responsible for mutation or malignant transformation.     

Experimental design and reporting standards for metabolomics studies of mammalian cell lines

Metabolomics is an analytical technique that investigates the small biochemical molecules present within a biological sample isolated from a plant, animal, or cultured cells. It can be an extremely powerful tool in elucidating the specific metabolic changes within a biological system in response to an environmental challenge such as disease, infection, drugs, or toxins. A historically difficult step in the metabolomics pipeline is in data interpretation to a meaningful biological context, for such high-variability biological samples and in untargeted metabolomics studies that are hypothesis-generating by design. One way to achieve stronger biological context of metabolomic data is via the use of cultured cell models, particularly for mammalian biological systems. The benefits of in vitro metabolomics include a much greater control of external variables and no ethical concerns. The current concerns are with inconsistencies in experimental procedures and level of reporting standards between different studies. This review discusses some of these discrepancies between recent studies, such as metabolite extraction and data normalisation. The aim of this review is to highlight the importance of a standardised experimental approach to any cultured cell metabolomics study and suggests an example procedure fully inclusive of information that should be disclosed in regard to the cell type/s used and their culture conditions. Metabolomics of cultured cells has the potential to uncover previously unknown information about cell biology, functions and response mechanisms, and so the accurate biological interpretation of the data produced and its ability to be compared to other studies should be considered vitally important.     

Bombesin,calcitonin and leu-enkephalin immunoreactivity in endocrine cells of human lung

Summary By immunohistochemistry, bombesin, calcitonin and leu-enkephalin was localized in endocrine cells of human lungs from various age groups. It is suggested that at least 3 different peptide containing endocrine cells may be present in human lung.Acknowledgments. The authors thank Dr Camille Vaillant, University of Liverpool, for advice with immunohistochemical methods and Dr G. Dockray for his generous gift of bombesin antiserum. This work has been supported by Medical Research Council of Canada (MA-7054) and Ontario Thoracic Society.     

Becquerel and the choice of uranium compounds

Conclusion The common assumption that Becquerel had no special reason to study uranium compounds in his search for substances emitting penetrating radiation cannot explain (a) Becquerel's own accounts, which refer to his choice as due to the peculiar harmonic series of bands; (b) Becquerel's systematic test of all uranium compounds (and metallic uranium), in contrast to his neglect of other substances; and (c) Becquerel's belief in invisible phosphorescence as an explanation of the radiation emitted by uranium compounds, even after his discovery that non-luminescent and metallic uranium also emit penetrating radiation.By comparing Becquerel's older studies of uranium to his radioactivity research, this paper has presented a reconstruction that can explain all of these points above. According to the historical evidence presented here, it is likely that Becquerel concentrated his attention on uranium and its compounds because the mechanical theory of luminescence opened up the possibility that, precisely in the case of uranium and its compounds, a violation of Stokes's law could occur, and penetrating short-wavelength radiation could be emitted through a special type of phosphorescence.     

Unscheduled CDK1 activity in G1 phase of the cell cycle triggers apoptosis in X-irradiated lymphocytic leukemia cells

Cyclin-dependent kinase 1 (CDK1) is a major component of the cell cycle progression engine. Recently, several investigations provided evidence demonstrating that unscheduled CDK1 activation may also be involved in apoptosis in cancerous cells. In this article, we demonstrate that X-ray irradiation induced G1 arrest in MOLT-4 lymphocytic leukemia cells, the arrest being accompanied by reduction in the activity of CDK2, but increased CDK1 activity and cell apoptosis in the G1 phase. Interestingly, this increase in CDK1 and apoptosis by ionizing radiation was prevented by pretreatment with the CDK1 inhibitor, roscovitine, suggesting that CDK1 kinase activity is required for radiation-induced apoptotic cell death in this model system. Furthermore, cyclin B1 and CDK1 were detected co-localizing and associating in G1 phase MOLT-4 cells, with the cellular lysates from these cells revealing a genotoxic stress-induced increase in CDK1 phosphorylation (Thr-161) and dephosphorylation (Tyr-15), as analyzed by postsorting immunoprecipitation and immunoblotting. Finally, X-irradiation was found to increase Bcl-2 phosphorylation in G1 phase cells. Taken together, these novel findings suggest that CDK1 is activated by unscheduled accumulation of cyclin B1 in G1 phase cells exposed to X-ray, and that CDK1 activation, at the wrong time and in the wrong phase, may directly or indirectly trigger a Bcl-2-dependent signaling pathway leading to apoptotic cell death in MOLT-4 cells. Received 30 March 2006; received after revision 23 June 2006; accepted 24 August 2006 J. Wu and Y. Feng contributed equally to this work.     

Thomas Clifford Allbutt and Comparative Pathology

This paper reconceptualizes Thomas Clifford Allbutt's contributions to the making of scientific medicine in late nineteenth-century England. Existing literature on Allbutt usually describes his achievements, such as his design of the pocket thermometer and his advocacy of the use of the ophthalmoscope in general medicine, as independent events; and his work on the development of comparative pathology is largely overlooked. In this paper I focus on this latter aspect. I examine Allbutt's books and addresses and claim that Allbutt argued for the centrality of comparative pathology in the advancement of medical knowledge. He held that diseases should be studied as biological phenomena and that medicine should be made a biological science. He also argued that comparative pathology should be based upon the idea of evolution, and its study should embrace other nineteenth-century sciences including neurology, embryology and bacteriology. Allbutt's writings reveal that his endorsement of comparative pathology (1880s to 1920s), his promotion of the use of the ophthalmoscope and the thermometer in clinical medicine (early 1870s), and his support of the hospital unit system (1910s to 1920s) were part of a single programme. All were grounded in his scientific vision of medicine which emphasized a research culture, a stringent nosological attitude and an integration of laboratory sciences and clinical medicine.     

Temperature dependence of the deformability of Carp (Cyprinus carpio) red blood cells

Summary Measurements were made of the deformability of the red cells of carp at different temperatures and compared with previous results obtained with another teleost fish (yellowtail) and human red cells. Changes with temperature are similar to those obtained with yellowtail, but interpretation of differences in terms of mean corpuscular volume alone are insufficient to account for the variations, which seem to be mainly due to differences in cellular deformability of the cells themselves.Acknowledgment. We wish to thank Karlheinz Götz for his excellent technical assistance. Reprint requests should be addressed to G.M.H.     

21世纪初辐射防护的几个基本问题

辐射防护已有近百年的历史。20世纪下半叶随着核能和核技术应用的发展，辐射防护得到了较大的发展。但仍然有许多基本问题有待进一步研究。作为辐射防护基础的线性无阈理论受到挑战。从辐射防护观点出发，基于当前的科学水平，应该认为选择线性无阈模式是合理的。但从科学上说辐射剂量效应模式尚有待进一步研究。辐射环境影响是辐射防护面临的一个新问题。其生物学终点、参考生物和剂量评价模式等都有待深入研究。利益相关者的参与是解决放射性废物管理和核安全困境的重要途径，其参与方式和时机等值得进一步研究。     

Inhibition of tryptophan uptake in Aspergillus fumigatus by tryptamine

Summary The tryptophan uptake was inhibited considerably in tryptamine grown cells. This inhibition was due to feed-back inhibition and not to repression.The authors are greatful to Prof. V. V. Modi for his interest in this work. The award of research fellowship by M. S. University of Baroda to A. R. G. is greatfully acknowledged.     

Radiation physics

A review is presented of the recent literature in the areas of physics which deal with radiation effects on man and animals. Some consideration is given to natural and artificial radiation sources such as cosmic rays, radon and high energy accelerators. The interaction of radiation with matter is treated if it is related to an energy deposition pattern relevant to biological effects. Dosimetry is also treated, with special emphasis on papers dealing with spatial dose distribution on a microscopic level, and radiobiological models relating the energy deposition pattern to biological effects are cited. New techniques in the medical application of radiation in diagnostics and therapy are briefly mentioned.     

Radiation physics

Summary A review is presented of the recent literature in the areas of physics which deal with radiation effects on man and animals. Some consideration is given to natural and artificial radiation sources such as cosmic rays, radon and high energy accelerators. The interaction of radiation with matter is treated if it is related to an energy deposition pattern relevant to biological effects. Dosimetry is also treated, with special emphasis on papers dealing with spatial dose distribution on a microscopic level, and radiobiological models relating the energy deposition pattern to biological effects are cited. New techniques in the medical application of radiation in diagnostics and therapy are briefly mentioned.     

Release of pre-absorbed cadmium from cultured cells by the addition of copper ion

Summary The biological interaction between cadmium and copper has been studied. Cadmium uptake of KB cells was specifically inhibited by the addition of copper ions to the culture medium. Cadmium which had already been taken up by the cells was released following the addition of copper ions.The authors are grateful to Dr. M. Ishizawa for his helpful discussion.     

3H-Thymidine incorporation (DNA synthesis) and radiotoxicity in the ovary of the Japanese quail before and during follicle formation

Summary No evidence was found for ribosomal DNA amplification in the oocytes of the Japanese quail, before or during folliculogenesis. DNA synthesis in the somatic cells, involved in follicle formation, starts at the medullar side of the basement membrane. The localized sterilization of the quail ovary after administration of³H-thymidine (³H-TdR) seems to be due to radiation-induced lesions in the follicle forming somatic cells, rather than to direct radiation damage of the oocyte.The author is very grateful to Prof. Dr L. Vakaet, R.U.C.A.—Antwerpen, for his valuable suggestions and to Mrs D. De Wolf-Van Rompaey for her excellent technical assistance.     

Resting potential of excitable neuroblastoma cells in weak magnetic fields

The mechanism by which static and low-frequency magnetic fields are transduced into biological signals responsible for reported effects on brain electrical activity is not yet ascertained. To test the hypothesis that fields can cause a subthreshold change in the resting membrane potential of excitable cells, we measured changes in transmembrane current under voltage clamp produced in SH-SY5Y neuroblastoma cells, using the patch-clamp method in the whole-cell configuration. In separate experiments, cells were exposed to static fields of 1, 5, and 75 G, to time-varying fields of 1 and 5 G, and to combined static and time-varying fields tuned for resonance of Na+, K+, Ca2+, or H+. To increase sensitivity, measurements were made on cells connected by gap junctions. For each cell, the effect of the field was evaluated on the basis of 100 trials consisting of a 5-s exposure immediately followed by a 5-s control period. In each experiment, the field had no discernible effect on the transmembrane current in the vicinity of zero current (- 50 mV voltage clamp). The sensitivity of the measuring system was such that we would have detected a current corresponding to a change in membrane potential as small as 38 microV. Consequently, if sensitivity of mammalian cells to magnetic fields is mediated by subthreshold changes in membrane potential, as in sensory transduction of sound, light, and other stimuli, then the ion channels responsible for the putative changes are probably present only in specialized sensory neurons or neuroepithelial cells. A change in transmembrane potential in response to magnetic fields is not a general property of excitable cells in culture.     

A micro-electrode amplifier with an infinite resistance current source for intracellular measurements of membrane potential and resistance changes under current clamp

Summary A microelectrode amplifier for intracellular electrophysiological research is described. It is equipped with an electronic infinite resistance constant current source for the injection of current into biological cells. With this amplifier the potential changes, the resistance changes and the dependence on extrinsic current of single cells can be measured independently and simultaneously.Acknowledgments. I am grateful to Dr D.G. Stavenga who inspired me to start the design. I thank P. Cuperus for stimulating discussions and A.J.Th. Liebrand for the construction of the amplifier. This work was supported financially by the Netherlands Organisation for the Advancement of Pure Research (Z.W.O.).     

Biochemical aspects of radiation biology

Summary In order to analyze the mechanisms of biological radiation effects, the events after radiation energy absorption in irradiated organisms have to be studied by physico-chemical and biochemical methods. The radiation effects in vitro on biomolecules, especially DNA, are described, as well as their alterations in irradiated cells. Whereas in vitro, in aqueous solution, predominantly OH radicals are effective and lead to damage in single moieties of the DNA, in vivo the direct absorption of radiation energy leads to locally multiply-damaged sites, which produce DNA double-strand breaks and locally denatured regions. DNA damage will be repaired in irradiated cells. Error free repair leads to the original nucleotide sequence in the genome by excision or by recombination. Error prone repair (mutagenic repair), leads to mutation. However, the biochemistry of these processes, regulated by a number of genes, is poorly understood. In addition, more complex reactions, such as gene amplification and transposition of mobile gene elements, are responsible for mutation or malignant transformation.     

Radioimmunoassay of an invertebrate peptide hormone — the crustacean neurosecretory hyperglycemic hormone

Summary Antibodies against hyperglycemic hormone (CHH) ofCarcinus were raised in rabbits by injection of extract from sinus glands which contain high concentrations of CHH. The antiserum neutralizes the biological activity of CHH and binds¹²⁵J-CHH. A RIA for CHH was established and was used to measure the hormone content of sinus glands.Dedicated to Prof. M. Gersch, Jena, on the occasion of his 70th birthday.This study was supported by the Deutsche Forschungsgemeinschaft (Ke 206/2).We thank S. Grabig. E. schmid and B. Reichwein for expert technical assistance, and Dr D. Breitig and G. Kegel for critical discussions.     

AID and Apobec3G haphazard deamination and mutational diversity

Activation-induced deoxycytidine deaminase (AID) and Apobec 3G (Apo3G) cause mutational diversity by initiating mutations on regions of single-stranded (ss) DNA. Expressed in B cells, AID deaminates C → U in actively transcribed immunoglobulin (Ig) variable and switch regions to initiate the somatic hypermutation (SHM) and class switch recombination (CSR) that are essential for antibody diversity. Apo3G expressed in T cells catalyzes C deaminations on reverse transcribed cDNA causing HIV-1 retroviral inactivation. When operating properly, AID- and Apo3G-initiated mutations boost human fitness. Yet, both enzymes are potentially powerful somatic cell “mutators”. Loss of regulated expression and proper genome targeting can cause human cancer. Here, we review well-established biological roles of AID and Apo3G. We provide a synopsis of AID partnering proteins during SHM and CSR, and describe how an Apo2 crystal structure provides “surrogate” insight for AID and Apo3G biochemical behavior. However, large gaps remain in our understanding of how dC deaminases search ssDNA to identify trinucleotide motifs to deaminate. We discuss two recent methods to analyze ssDNA scanning and deamination. Apo3G scanning and deamination is visualized in real-time using single-molecule FRET, and AID deamination efficiencies are determined with a random walk analysis. AID and Apo3G encounter many candidate deamination sites while scanning ssDNA. Generating mutational diversity is a principal aim of AID and an important ancillary property of Apo3G. Success seems likely to involve hit and miss deamination motif targeting, biased strongly toward miss.