Spores of microorganisms

Calcium-dipicolinate (Ca-DPA)-rich and Ca-DPA-deficientBacillus cereus spores were incubated in a synthetic medium with germination stimulants and in bactopeptone medium with a fairly high calcium ion concentration. In the complex medium the germination of Ca-DPA-rich spores was completely blocked at a concentration of 0.5m CaCl₂, whereas the complete blockage of germination in the synthetic medium required higher concentrations (0.6–0.8m) of calcium chloride. Ca-DPA-deficient spores germinated more slowly and less completely in the synthetic medium than in the bactopeptone medium. The germination of these spores took place, however, even at higher calcium ion concentrations (0.6–0.8m). On the contrary, lower calcium chloride concentrations (0.1–0.4m) accelerated the germination of these spores in the synthetic medium and the final percentage of phase-dark and stainable spores was higher. “H-forms” of the Ca-DPA-rich and Ca-DPA-deficient spores prepared by acid titration germinated in both media. The germination of the latter spores being slower and proceeding less completely. “H-forms” germinated completely or partially in media with a high concentration of calcium chloride. The percentage of germinated spores, however, was strongly influenced by the concentration of this cation, especially the “H-forms” of Ca-DPA-deficient spores. Moreover, the germination of Ca-DPA-deficient spores in this medium was affected by the length of previous storage and, in the case of “H-forms” by the pH at which they were titrated. It was assumed that the increased permeability of calcium into the calciumundersaturated spore periphery in Ca-DPA-deficient and in “H-forms” of spores of both types co-determines (in the presence of germinants) the germinability of bacterial spores.     

The Morphostatic Limit for a Model of Skeletal Pattern Formation in the Vertebrate Limb

A recently proposed mathematical model of a “core” set of cellular and molecular interactions present in the developing vertebrate limb was shown to exhibit pattern-forming instabilities and limb skeleton-like patterns under certain restrictive conditions, suggesting that it may authentically represent the underlying embryonic process (Hentschel et al., Proc. R. Soc. B 271, 1713–1722, 2004). The model, an eight-equation system of partial differential equations, incorporates the behavior of mesenchymal cells as “reactors,” both participating in the generation of morphogen patterns and changing their state and position in response to them. The full system, which has smooth solutions that exist globally in time, is nonetheless highly complex and difficult to handle analytically or numerically. According to a recent classification of developmental mechanisms (Salazar-Ciudad et al., Development 130, 2027–2037, 2003), the limb model of Hentschel et al. is “morphodynamic,” since differentiation of new cell types occurs simultaneously with cell rearrangement. This contrasts with “morphostatic” mechanisms, in which cell identity becomes established independently of cell rearrangement. Under the hypothesis that development of some vertebrate limbs employs the core mechanism in a morphostatic fashion, we derive in an analytically rigorous fashion a pair of equations representing the spatiotemporal evolution of the morphogen fields under the assumption that cell differentiation relaxes faster than the evolution of the overall cell density (i.e., the morphostatic limit of the full system). This simple reaction–diffusion system is unique in having been derived analytically from a substantially more complex system involving multiple morphogens, extracellular matrix deposition, haptotaxis, and cell translocation. We identify regions in the parameter space of the reduced system where Turing-type pattern formation is possible, which we refer to as its “Turing space.” Obtained values of the parameters are used in numerical simulations of the reduced system, using a new Galerkin finite element method, in tissue domains with nonstandard geometry. The reduced system exhibits patterns of spots and stripes like those seen in developing limbs, indicating its potential utility in hybrid continuum-discrete stochastic modeling of limb development. Lastly, we discuss the possible role in limb evolution of selection for increasingly morphostatic developmental mechanisms.     

Terahertz vibrational properties of water nanoclusters relevant to biology

Water nanoclusters are shown from first-principles calculations to possess unique terahertz-frequency vibrational modes in the 1–6 THz range, corresponding to O–O–O “bending,” “squashing,” and “twisting” “surface” distortions of the clusters. The cluster molecular-orbital LUMOs are huge Rydberg-like “S,” “P,” “D,” and “F” orbitals that accept an extra electron via optical excitation, ionization, or electron donation from interacting biomolecules. Dynamic Jahn–Teller coupling of these “hydrated-electron” orbitals to the THz vibrations promotes such water clusters as vibronically active “structured water” essential to biomolecular function such as protein folding. In biological microtubules, confined water-cluster THz vibrations may induce their “quantum coherence” communicated by Jahn–Teller phonons via coupling of the THz electromagnetic field to the water clusters’ large electric dipole moments.     

From view cells and place cells to cognitive map learning: processing stages of the hippocampal system

 The goal of this paper is to propose a model of the hippocampal system that reconciles the presence of neurons that look like “place cells” with the implication of the hippocampus (Hs) in other cognitive tasks (e.g., complex conditioning acquisition and memory tasks). In the proposed model, “place cells” or “view cells” are learned in the perirhinal and entorhinal cortex. The role of the Hs is not fundamentally dedicated to navigation or map building, the Hs is used to learn, store, and predict transitions between multimodal states. This transition prediction mechanism could be important for novelty detection but, above all, it is crucial to merge planning and sensory–motor functions in a single and coherent system. A neural architecture embedding this model has been successfully tested on an autonomous robot, during navigation and planning in an open environment. Received: 28 June 1999 / Accepted in revised form: 26 April 2001     

Question 7: Biosynthesis of Phosphatidic Acid in Liposome Compartments – Toward the Self-Reproduction of Minimal Cells

Self-reproduction is one of main properties that define living cells. In order to explore the self-reproduction process for the study of early cells, and to develop a research line somehow connected to the origin of life, we have built up a constructive ‘synthetic cells (minimal cells)’ approach. The minimal cells approach consists in the investigation of the minimal number of elements to accomplish simple cell-like processes – like self-reproduction. Such approach belongs to the field of synthetic biology. The minimal cells are reconstructed from a totally reconstituted cell-free protein synthesis system (PURESYSTEM) and liposome compartments as containers. Based on this approach, we synthesized two membrane proteins (enzymes), GPAT and LPAAT, which are involved in the phosphatidic acid biosynthesis in bacteria. Both membrane proteins were successfully synthesized by PURESYSTEM encapsulated inside POPC liposomes. Additionally, the enzymatic activity of GPAT was restored by mixing the expressed enzyme with lipid and by forming liposomes in situ. Through these experimental evidences, here we present a possible model to achieve self-reproduction in minimal cells. Our results would contribute to the idea that early cells could have been built by an extremely small number of genes. Presented at the International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006.     

Regulation of the formation of proteinases inBacillus megaterium

The exocellular proteinases of asporogenic and sporogenicBacillus megaterium KM (megaterioproteinase A and S) were found to be active enzymes of the monomer type. The electrophoretic mobility of megaterioproteinase A is higher than that of S on acrylamide gel. After mixing, the enzymes could be separated again. The molecular weight of megaterioproteinase A was found to be 20,000–23,500, that of megaterioproteinase S 16,500–20,000 daltons, according to the “molecular sieving” method. The electrophoretic mobility of both proteinases was determined at different pH and the graphically calculated isoelectric point (pI) was found to be 7.3–7.4. The pK values of the ES complex estimated by plotting the logarithm of the maximum velocity of the enzymic reaction against pH were 6.0–6.1 and 7.8–8.0 for both megaterioproteinases. The activation energy was 13,500–13,600 for both enzymes. It is concluded that the above two enzymes resemble each other in enzymic properties but differ in electrophoretic mobility and probably also in molecular weight.     

Effects of N-uronoyl derivatives of neurotransmitter amino acids on rats under conditions of behavioral tests

Under conditions of a few behavioral tests on rats, we examined the psychotropic activity of novel N-uronoyl derivatives of amino acids: (i) N-(1,2:3,4-di-O-isopropylidene-α-D-galactopyranuronoyl-β-alanine (DAGU-Ala), (ii) DAGU-glycyl-D,L-glutamic acid (DAGU-Gly-Glu), and (iii) DAGU-glycyl-glycine (DAGU-Gly-Gly) injected i.p. in a 50 mg/kg dose. In an open-field test, DAGU-Gly-Glu and DAGU-GLy-Gly showed antistress properties (they decreased the intensity of locomotion, decreased the number of defecation acts, and intensified the research activity), while DAGU-Ala possessed a psychostimulating effect (intensification of locomotor and research activity and an increase in the number of defecations). In the “black-and-white chamber” test, only DAGU-Gly-Gly exerted an anxiolytic effect; it somewhat increased the frequency and duration of emergings of animals from the dark section and duration of visits to the illuminated section of the chamber. DAGU-GLy-Glu manifested antidepressant properties; it increased the time of active swimming of the animal in the Porsolt test and decreased the duration of passive “hanging” of rats in the “suspension by the tail” test. Neirofiziologiya/Neurophysiology, Vol. 39, No. 1, pp. 52–61, January–February, 2007.     

Spectroscopic and metal-binding properties of DF3: an artificial protein able to accommodate different metal ions

The design, synthesis, and metal-binding properties of DF3, a new de novo designed di-iron protein model are described (“DF” represents due ferri, Italian for “two iron,” “di-iron”). DF3 is the latest member of the DF family of synthetic proteins. They consist of helix–loop–helix hairpins, designed to dimerize and form an antiparallel four-helix bundle that encompasses a metal-binding site similar to those of non-heme carboxylate-bridged di-iron proteins. Unlike previous DF proteins, DF3 is highly soluble in water (up to 3 mM) and forms stable complexes with several metal ions (Zn, Co, and Mn), with the desired secondary structure and the expected stoichiometry of two ions per protein. UV–vis studies of Co(II) and Fe(III) complexes confirm a metal-binding environment similar to previous di-Co(II)- and di-Fe(III)-DF proteins, including the presence of a μ-oxo-di-Fe(III) unit. Interestingly, UV–vis, EPR, and resonance Raman studies suggest the interaction of a tyrosine adjacent to the di-Fe(III) center. The design of DF3 was aimed at increasing the accessibility of small molecules to the active site of the four-helix bundle. Indeed, binding of azide to the di-Fe(III) site demonstrates a more accessible metal site compared with previous DFs. In fact, fitting of the binding curve to the Hill equation allows us to quantify a 150% accessibility enhancement, with respect to DF2. All these results represent a significant step towards the development of a functional synthetic DF metalloprotein.     

Physiology and tactic response of the phototrophic consortium “Chlorochromatium aggregatum”

The phototrophic consortium “Chlorochromatium aggregatum” was enriched from sediment samples of a eutrophic freshwater lake and was maintained at high numbers in anoxic sulfide-reduced medium. Growth of intact consortia was observed only in the light and in the presence of 2-oxoglutarate as an organic carbon source. Consortia of “C. aggregatum” reached maximum growth rates at light intensities ≥ 5 μmol quanta m^–2 s^–1. Of ten compounds tested, sulfide, thiosulfate, 2-oxoglutarate, and citrate served as a chemoattractant for “C. aggregatum”. When incubated in the presence of sulfide and in the light, epibionts reduced the fluorochrome 5-cyano-2,3-di-4-tolyl-tetrazolium chloride (CTC). Reduction of CTC was not observed in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) or in the dark, indicating that sulfide serves as an electron donor for the phototrophic epibiont. Motile consortia accumulated scotophobically in microcuvettes at a wavelength of 740 nm. Since this wavelength corresponds to the position of the absorption maximum of bacteriochlorophylls c or d, the photosynthetic pigments are most likely the photoreceptors of the scotophobic response. It is concluded that, within the consortia, a rapid interspecies signal transfer occurs between the nonmotile, green-colored epibiont and the motile, colorless central bacterium. Received: 27 May 1997 / Accepted: 5 September 1997     

Inventory, differentiation, and proportional diversity: a consistent terminology for quantifying species diversity

Almost half a century after Whittaker (Ecol Monogr 30:279–338, 1960) proposed his influential diversity concept, it is time for a critical reappraisal. Although the terms alpha, beta and gamma diversity introduced by Whittaker have become general textbook knowledge, the concept suffers from several drawbacks. First, alpha and gamma diversity share the same characteristics and are differentiated only by the scale at which they are applied. However, as scale is relative––depending on the organism(s) or ecosystems investigated––this is not a meaningful ecological criterion. Alpha and gamma diversity can instead be grouped together under the term “inventory diversity.” Out of the three levels proposed by Whittaker, beta diversity is the one which receives the most contradictory comments regarding its usefulness (“key concept” vs. “abstruse concept”). Obviously beta diversity means different things to different people. Apart from the large variety of methods used to investigate it, the main reason for this may be different underlying data characteristics. A literature review reveals that the multitude of measures used to assess beta diversity can be sorted into two conceptually different groups. The first group directly takes species distinction into account and compares the similarity of sites (similarity indices, slope of the distance decay relationship, length of the ordination axis, and sum of squares of a species matrix). The second group relates species richness (or other summary diversity measures) of two (or more) different scales to each other (additive and multiplicative partitioning). Due to that important distinction, we suggest that beta diversity should be split into two levels, “differentiation diversity” (first group) and “proportional diversity” (second group). Thus, we propose to use the terms “inventory diversity” for within-sample diversity, “differentiation diversity” for compositional similarity between samples, and “proportional diversity” for the comparison of inventory diversity across spatial and temporal scales. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Interactions among biological systems: An analysis of asymptotic stability

An analysis of the interactions among asymptotically stable dynamical systems is formulated by making use of the dynamical system theory. Some results coming from previous mathematical analyses have been slightly modified to take into account some typical biological constraints as the boundedness properties of the solutions. In particular it has been shown that when the “coupling” among the subsystems is “loose” enough (in a sense that has to be made mathematically precise) the asymptotic behaviour of a complex system is the same of that of its individual components. The mathematical theory has been used to analyze two systems of biological significance: the coupling among chemical reactions and the stability properties of a 4-dimensional system describing the kinetics of a chemical transmitter.     

Myosin II activity is required for functional leading-edge cells and closure of epidermal sheets in fish skin ex vivo

Re-epithelialization in skin wound healing is a process in which epidermal sheets grow and close the wound. Although the actin–myosin system is thought to have a pivotal role in re-epithelialization, its role is not clear. In fish skin, re-epithelialization occurs around 500 μm/h and is 50 times faster than in mammalian skin. We had previously reported that leading-edge cells of the epidermal outgrowth have both polarized large lamellipodia and “purse string”-like actin filament cables in the scale-skin culture system of medaka fish, Oryzias latipes (Cell Tissue Res, 2007). The actin purse-string (APS) is a supracellular contractile machinery in which adherens junctions (AJs) link intracellular myosin II-including actin cables between neighboring cells. In this study, we developed a modified “face-to-face” scale-skin culture system as an ex vivo model to study epidermal wound healing, and examined the role of the actin–myosin system in the rapid re-epithelialization using a myosin II ATPase inhibitor, blebbistatin. A low level of blebbistatin suppressed the formation of APS and induced the dissociation of keratocytes from the leading edge without attenuating the growth of the epidermal sheet or the migration rate of solitary keratocytes. AJs in the superficial layer showed no obvious changes elicited by blebbistatin. However, two epidermal sheets without APSs did not make a closure with each other, which was confirmed by inhibiting the connecting AJs between the superficial layers. These results suggest that myosin II activity is required for functional leading-edge cells and for epidermal closure.     

Muscles within muscles: the neuromotor control of intra-muscular segments

The aim of this investigation was to anatomically identify, and then determine the function of, individual segments within the human deltoid muscle. The anatomical structure of the deltoid was determined through dissection and/or observation of the shoulder girdles of 11 male cadavers (aged 65–84 years). These results indicate that the deltoid consists of seven anatomical segments (D1–D7) based upon the distinctive arrangement of each segment's origin and insertion. Radiographic analysis of a cadaveric shoulder joint suggested that only the postero-medial segment D7 has a line of action directed below the shoulder joint's axis of rotation. The functional role of each individual segment was then determined utilising an electromyographic (EMG) technique. Seven miniature (1 mm active plate; 7 mm interelectrode distance) bipolar surface electrodes were positioned over the proximal portion of each segment's muscle belly in 18 male and female subjects (18–30 years). EMG waveforms were then recorded during the production of rapid isometric shoulder abduction and adduction force impulses with the shoulder joint in 40 degrees of abduction in the plane of the scapula. Each subject randomly performed 15 abduction and 15 adduction isometric force impulses following a short familiarisation period. All subjects received visual feed back on the duration and amplitude of each isometric force impulse produced via a visual force-time display which compared subject performance to a criterion force-time curve. Movement time was 400 ms (time-to-peak isometric force) at an intensity level of 50% maximal voluntary contraction. Temporal and intensity analyses of the EMG waveforms, as well as temporal analysis of the isometric force impulses, revealed the neuromotor control strategies utilised by the CNS to control the activity of each muscle segment. The results showed that segmental neuromotor control strategies differ across the breadth of the muscle and that individual segments of the deltoid can be identified as having either “prime mover”, “synergist”, “stabiliser” or “antagonist” functions; functional classifications normally associated with whole muscle function. Therefore, it was concluded that the CNS can “fine tune” the activity of at least six discrete segments within the human deltoid muscle to efficiently meet the demands of the imposed motor task. Accepted: 15 December 1997     

A contribution to the mathematical biology of automobile driving: II. Passing as a case of psychophysical discrimination

The decision to pass or not to pass in view of an oncoming car is considered as a case of comparative judgment in which it is to be decided whether the time it will take to pass safely is greater or less than the time it will take to collide with the oncoming car. H. D. Landahl's well-known theory of psychophysical discrimination is used, and it is assumed that the “distracting stimuli” considered previously (Rashevsky, 1959,Bull. Math. Biophysics,21, 375–85) tend to increase the standard deviation of Landahl's fluctuation function. Effects of the “distracting stimuli” on the threshold of the neuroelements in Landahl's circuit are also considered. On this basis an expression is derived which gives the probability of a collision accident in passing as a function of the “distracting stimuli.”     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Brazil

Until 2000, efforts into organising tissue banks in Brazil had not progressed far beyond small “in house” tissue storage repositories, usually annexed to Orthopaedic Surgery Services. Despite the professional entrepreneurship of those working as part time tissue bankers in such operations, best practices in tissue banking were not always followed due to the lack of regulatory standards, specialised training, adequate facilities and dedicated personnel. The Skin Bank of the Plastic Surgery Department of the Hospital das Clinicas of Sao Paulo, the single skin bank in Brazil, was not an exception. Since 1956, restricted and unpredictable amounts of skin allografts were stored under refrigeration for short periods under very limited quality controls. As in most “tissue banks” at that time in Brazil, medical and nursing staff worked on a volunteer and informal basis undergoing no specific training. IAEA supported the implementation of the tissue banking program in Brazil through the regional project RLA/7/009 “Quality system for the production of irradiated sterilised grafts” (1998–2000) and through two interregional projects INT/6/049 “Interregional Centre of Excellence in Tissue Banking”, during the period 2002–2004 and INT/6/052 “Improving the Quality of Production and Uses of Radiation Sterilised Tissue Grafts”, during the period 2002–2004. In 2001–2002, the first two years of operation of the HC-Tissue Bank, 53 skin transplants were carried out instead of the previous 4–5 a year. During this period, 75 individuals donated skin tissue, generating approximately 90,000 cm² of skin graft. The IAEA program were of great benefit to Brazilian tissue banking which has evolved from scattered make shift small operations to a well-established, high quality tissue banking scenario.     

Physics,biology and sociology: II. Suggestion for a synthesis

In continuation of previous studies (Bull. Math. Biophysics,28, 283–308; 655–661, 1966;29, 139–152, 1967) it is shown that the difference between the “metric” aspects of physics and the “relational” aspects of biological and social sciences disappear by accepting the broader definition of “relation”, such as that given in mathematics and logic. A conceptual superstructure then becomes possible from which all three branches of knowledge may be derived, though none of them can be derived from the others.     

Mutant Bacteriophages,Frank Macfarlane Burnet,and the Changing Nature of “Genespeak” in the 1930s

In 1936, Frank Macfarlane Burnet published a paper entitled “Induced lysogenicity and the mutation of bacteriophage within lysogenic bacteria,” in which he demonstrated that the introduction of a specific bacteriophage into a bacterial strain consistently and repeatedly imparted a specific property – namely the resistance to a different phage – to the bacterial strain that was originally susceptible to lysis by that second phage. Burnet’s explanation for this change was that the first phage was causing a mutation in the bacterium which rendered it and its successive generations of offspring resistant to lysogenicity. At the time, this idea was a novel one that needed compelling evidence to be accepted. While it is difficult for us today to conceive of mutations and genes outside the context of DNA as the physico-chemical basis of genes, in the mid 1930s, when this paper was published, DNA’s role as the carrier of hereditary information had not yet been discovered and genes and mutations were yet to acquire physical and chemical forms. Also, during that time genes were considered to exist only in organisms capable of sexual modes of replication and the status of bacteria and viruses as organisms capable of containing genes and manifesting mutations was still in question. Burnet’s paper counts among those pieces of work that helped dispel the notion that genes, inheritance and mutations were tied to an organism’s sexual status. In this paper, I analyze the implications of Burnet’s paper for the understanding of various concepts – such as “mutation,” and “gene,” – at the time it was published, and how those understandings shaped the development of the meanings of these terms and our modern conceptions thereof.     

Mechanical characteristics of synthetic polyelectrolyte gel as a physical model of the cytoskeleton

A physical model of the cytoskeleton based on synthetic polyelectrolyte hydrogel of polymethacrylic acid has been proposed. From the physicochemical point of view, the structures of polyelectrolyte gel and the cytoskeleton show a high degree of similarity. It has been shown that polyelectrolyte gel can shorten and produce mechanical stress in response to changes in the composition of the surrounding solution. The mechanical properties of the model gel have been evaluated: Young modulus (2–6 kPa), stress relaxation time (0.1–1 s), and apparent viscosity (0.3–3 kPa s). The viscoelastic properties of the gel depend on the degree of its swelling. It has been demonstrated that the mechanical properties of gels of polymethacrylic acid are close to those of biological objects.     

The visual ecology of Puerto Rican anoline lizards: habitat light and spectral sensitivity

The visual ecology of six closely related species of Puerto Rican anoline lizards was investigated and they were found to occupy four distinct habitat types in terms of light conditions: “full shade”, “partial shade”, “no shade”, and “forest canopy.”The habitats differed substantially in total radiance and irradiance as well as in the shape of the irradiance spectrum. The shape of the radiance spectrum was similar in all of the habitats. We used electroretinogram (ERG) flicker photometry to measure spectral sensitivity and found the curves for all six species to be similar. The spectral sensitivity peaked in the range 550–560 nm, which matched the peak in spectral radiance for all of the habitats. The shape of the spectral-sensitivity curve was similar to those of a number of other terrestrial vertebrates. We suggest that the convergence of the shape of the photopic ERG-determined spectral-sensitivity curve in many terrestrial vertebrates may, in part, be due to the fact that the background radiance of many terrestrial habitats is dominated by the reflectance spectrum of green vegetation which peaks at 550 nm. Accepted: 14 May 1997     

Hematopoietic cell renewal systems: mechanisms of coping and failing after chronic exposure to ionizing radiation

On the occasion of the first international workshop on systems radiation biology we review the role of cell renewal systems in maintaining the integrity of the mammalian organism after irradiation. First, 11 radiation emergencies characterized by chronic or protracted exposure of the human beings to ionizing irradiation were “revisited”. The data provide evidence to suggest that at a daily exposure of about 10–100 mSv, humans are capable of coping with the excess cell loss for weeks or even many months without hematopoietic organ failure. Below 10 mSv/day, the organisms show some cellular or subcellular indicators of response. At dose rates above 100 mSv/day, a progressive shortening of the life span of the irradiated organism is observed. To elucidate the mechanisms relevant to tolerance or failure, the Megakaryocyte–thrombocyte cell renewal system was investigated. A biomathematical model of this system was developed to simulate the development of thrombocyte concentration as a function of time after onset of chronic radiation exposure. The hematological data were taken from experimental chronic irradiation studies with dogs at the Argonne National Laboratory, USA. The results of thrombocyte response patterns are compatible with the notion of an “excess cell loss” (compared to the steady-state) in all proliferative cell compartments, including the stem cell pool. The “excess cell loss” is a function of the daily irradiation dose rate. Once the stem cell pool is approaching an exhaustion level, a “turbulence region” is reached. Then it takes a very little additional stress for the system to fail. We conclude that in mammalian radiation biology (including radiation medicine), it is important to understand the physiology and pathophysiology of cell renewal systems in order to allow predicting the development of radiation induced lesions.