Physics met biology, and the consequence was..

We summarise the contributions to the discussion and the links between them. The complex relationship between the physical and biological sciences demonstrates three "axes of tension": the role of simulation, the interplay between levels of explanation, and the generality of "laws". We identify examples of true synergy between approaches that genuinely explore new research territory, and underscore the contemporary value of the type of discussions contained in this volume.     

Endomitosis: A reappraisal

Summary The concept and role of endomitosis is reevaluated in the light of observations on three organisms. Endomitosis which morphologically agrees with Geitler's (1939) classical definition is compared in tapetal cells of the liliaceous plant Eremurus, in the septal cells of the testicular follicles of the grasshopper Melanoplus, and in human cells from normal and molar trophoblasts and cervical cancer. These observations, together with those of Kidnadze and Istomina (1980), show that functionally at least two fundamentally different types of endomitosis exist, although morphologically the stages resemble each other in the three organisms. In the first type, exemplified by Eremurus, each endomitosis leads to a chromosome constitution which represents one level higher ploidy, a course that has been assumed to be characteristic of endomitosis in general. The second type, observed in its most characteristic form in the grasshopper, seems to be stationary: no DNA synthesis occurs, but an intensive RNA synthesis takes place. Presumably such cells have reached a final state in their development and are specialized in manufacturing one or more gene products. Endomitosis in normal placenta comes near this type, although DNA synthesis takes place in occasional cells. However, similar endomitotic nuclei in the hydatiform moles are in the process of DNA synthesis. When endomitosis is analyzed in different organisms and tissues, the observation that this process is not one entity should be kept in mind.     

Topology and life: In search of general mathematical principles in biology and sociology

Mathematical biology has hitherto emphasized the quantitative, metric aspects of the physical manifestations of life, but has neglected the relational or positional aspects, which are of paramount importance in biology. Although, for example, the processes of locomotion, ingestion, and digestion in a human are much more complex than in a protozoan, the general relations between these processes are the same in all organisms. To a set of very complicated digestive functions of a higher animal there correspond a few simple functions in a protozoan. In other words, the more complicated processes in higher organisms can be mapped on the simpler corresponding processes in the lower ones. If any scientific study of this aspect of biology is to be possible at all, there must exist some regularity in such mappings. We are, therefore, led to the following principle: If the relations between various biological functions of an organism are represented geometrically in an appropriate topological space or by an appropriate topological complex, then the spaces or complexes representing different organisms must be obtainable by a proper transformation from one or very fewprimordial spaces or complexes. The appropriate representation of the relations between the different biological functions of an organism appears to be a one-dimensional complex, or graph, which represents the “organization chart” of the organism. The problem then is to find a proper transformation which derives from this graph the graphs of all possible higher organisms. Both a primordial graph and a transformation are suggested and discussed. Theorems are derived which show that the basic principle of mapping and the transformation have a predictive value and are verifiable experimentally. These considerations are extended to relations within animal and human societies and thus indicate the reason for the similarities between some aspects of societies and organisms. It is finally suggested that the relation between physics and biology may lie on a different plane from the one hitherto considered. While physical phenomena are the manifestations of the metric properties of the four-dimensional universe, biological phenomena may perhaps reflect some local topological properties of that universe.     

Physics and the origins of molecular biology

Bohr, Delbrück and Schrödinger were physicists who had important influences on biology in the second half of the twentieth century. They thought that future studies of the gene might reveal new principles or paradoxes, analogous to the wave/particle paradox of light propagation, or even new physical laws. This stimulated several physicists to enter the field of biology. Delbrück founded the bacteriophage group which provided one of the roots of molecular biology. Another was X-ray crystallography which led to the discovery of DNA structure. The strength and success of molecular biology came from the many interactions between geneticists, physicists, chemists and biochemists. It was also characterized by a powerful combination of theoretical and experimental approaches.     

Creatine transporters: A reappraisal

Creatine (Cr) plays a key role in cellular energy metabolism and is found at high concentrations in metabolically active cells such as skeletal muscle and neurons. These, and a variety of other cells, take up Cr from the extra cellular fluid by a high affinity Na(+)/Cl(-)-dependent creatine transporter (CrT). Mutations in the crt gene, found in several patients, lead to severe retardation of speech and mental development, accompanied by the absence of Cr in the brain. In order to characterize CrT protein(s) on a biochemical level, antibodies were raised against synthetic peptides derived from the N- and C-terminal cDNA sequences of the putative CrT-1 protein. In total homogenates of various tissues, both antibodies, directed against these different epitopes, recognize the same two major polypetides on Western blots with apparent Mr of 70 and 55 kDa. The C-terminal CrT antibody (alpha-CrTCOOH) immunologically reacts with proteins located at the inner membrane of mitochondria as determined by immuno-electron microscopy, as well as by subfractionation of mitochondria. Cr-uptake experiments with isolated mitochondria showed these organelles were able to transport Cr via a sulfhydryl-reagent-sensitive transporter that could be blocked by anti-CrT antibodies when the outer mitochondrial membrane was permeabilized. We concluded that mitochondria are able to specifically take-up Cr from the cytosol, via a low-affinity CrT, and that the above polypeptides would likely represent mitochondrial CrT(s). However, by mass spectrometry techniques, the immunologically reactive proteins, detected by our anti-CrT antibodies, were identified as E2 components of the alpha-keto acid dehydrogenase multi enzyme complexes, namely pyruvate dehydrogenase (PDH), branched chain keto acid dehydrogenase (BC-KADH) and alpha-ketoglutarate dehydrogenase (alpha-KGDH). The E2 components of PDH are membrane associated, whilst it would be expected that a mitochondrial CrT would be a transmembrane protein. Results of phase partitioning by Triton X-114, as well as washing of mitochondrial membranes at basic pH, support that these immunologically cross-reactive proteins are, as expected for E2 components, membrane associated rather than transmembrane. On the other hand, the fact that mitochondrial Cr uptake into intact mitoplast could be blocked by our alpha-CrTCOOH antibodies, indicate that our antisera contain antibodies reactive to proteins involved in mitochondrial transport of Cr. The presence of specific antibodies against CrT is supported by results from plasma membrane vesicles isolated from human and rat skeletal muscle, where both 55 and 70 kDa polypeptides disappeared and a single polypeptide with an apparent electrophoretic mobility of approximately 60 kDa was enriched. This latter is most likely representing the genuine plasma membrane CrT. Due to the fact that all anti-CrT antibodies that were independently prepared by several laboratories seem to cross-react with non-CrT polypeptides, specifically with E2 components of mitochondrial dehydrogenases, further research is required to characterise on a biochemical/biophysical level the CrT polypeptides, e.g. to determine whether the approximately 60 kDa polypeptide is indeed a bona-fide CrT and to identify the mitochondrial transporter that is able to facilitate Cr-uptake into these organelles. Therefore, the anti-CrT antibodies available so far should only be used with these precautions in mind. This holds especially true for quantitation of CrT polypeptides by Western blots, e.g. when trying to answer whether CrT's are up- or down-regulated by certain experimental interventions or under pathological conditions. In conclusion, we still hold to the scheme that besides the high-affinity and high-efficiency plasmalemma CrT there exists an additional low affinity high Km Cr uptake mechanism in mitochondria. However, the exact biochemical nature of this mitochondrial creatine transport, still remains elusive. Finally, similar to the creatine kinase (CK) isoenzymes, which are specifically located at different cellular compartments, also the substrates of CK are compartmentalized in cytosolic and mitochondrial pools. This is in line with 14C-Cr-isotope tracer studies and a number of [31P]-NMR magnetization transfer studies, as well as with recent [1H]-NMR spectroscopy data.     

Anthropology and sociology in China: A review article

Sociology and Socialism in Contemporary China. Wong Siu‐Lun. Routledge & Kegan Paul. London. 1979. xii + 147 pp. £5.75.

The Dilemma of a Chinese Intellectual. Fei Hsiao‐t'ung. James P. McGough. M.E. Sharpe, Inc., White Plains, N.Y. 1979. 159pp.     

Physics and the canalization of morphogenesis: a grand challenge in organismal biology

Morphogenesis takes place against a background of organism-to-organism and environmental variation. Therefore, fundamental questions in the study of morphogenesis include: How are the mechanical processes of tissue movement and deformation affected by that variability, and in turn, how do the mechanic of the system modulate phenotypic variation? We highlight a few key factors, including environmental temperature, embryo size and environmental chemistry that might perturb the mechanics of morphogenesis in natural populations. Then we discuss several ways in which mechanics-including feedback from mechanical cues-might influence intra-specific variation in morphogenesis. To understand morphogenesis it will be necessary to consider whole-organism, environment and evolutionary scales because these larger scales present the challenges that developmental mechanisms have evolved to cope with. Studying the variation organisms express and the variation organisms experience will aid in deciphering the causes of birth defects.     

Compatibility and thigmotropism in the lichen symbiosis: A reappraisal

The development of many complex stratified lichen thalli is made through stages of complex phenotypic interactions between a filamentous fungus (the mycobiont), and a trebouxioid alga (the photobiont). Typically, the second stage of this symbiotic development is marked by the envelopment of the photobiont by the mycobiont through increased lateral hyphal branching and the formation of appressoria. Previously, the mycobiont’s envelopment of photobiont cells was considered thigmotropic (a growth response due to shape) as a mycobiont can envelop algal sized objects in its environment. However, after growing the mycobiontCladonia grayi with various phototrophs and glass beads, we conclude that the mycobiont does not show this characteristic second stage morphological response when grown in non-compatible pairings. Instead,C. grayi displays a distinctive morphological growth response only in compatible symbiotic pairings, such as with its natural photobiontAsterochlor’is sp.     

生物学的新军——合成生物学

合成生物学是一个新兴而极具研究前景的领域．旨在通过将多种天然或人工设计的生物学元件进行合理组合,创造出重构的或非天然的生物系统。综述了合成生物学这一新兴学科的核心理念、研究内容以及与相关学科的联系,详细介绍了J．CraigVenter研究小组所合成的“人造生命”,并展望了合成生物学广阔的发展前景和所面临的问题。     

Subatomic biology: electronic biology, biosemiconductivity]

The author gives a critical and hystorical review of the existing in biology theories which on the molecular and electronic levels explain a number of mechanisms of vital phenomena such as excitation, muscle contraction etc. The author discusses in the hystorical aspect the problem of formation of electronic and biological semi-conductivity (as the author names it) called to explain the vital mechanisms. He shows is which way this theory can explain the process of excitation.