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PubMed2004

Perspective: is human cultural evolution Darwinian? Evidence reviewed from the perspective of the Origin of Species.

The claim that human culture evolves through the differential adoption of cultural variants, in a manner analogous to the evolution of biological species, has been greeted with much resistance and confusion. Here we demonstrate that as compelling a case can now be made that cultural evolution has key Darwinian properties, as Darwin himself presented for biological evolution in The Origin of Species. Culture is shown to exhibit variation, competition, inheritance, and the accumulation of successive cultural modifications over time. Adaptation, convergence, and the loss or change of function can also be identified in culture. Just as Darwin knew nothing of genes or particulate inheritance, a case for Darwinian cultural evolution can be made irrespective of whether unitary cultural replicators exist or whether cultural transmission mechanisms are well understood.

Adaptation, Biological↗
PubMed1991

Chance as an explanatory factor in evolutionary biology.

Darwinian evolutionary biology has often been criticized for appealing to the notion of 'chance' in its explanations. According to some critics, such appeals exhibit the explanatory poverty of evolutionary theory. In response, defenders of Darwinism sometimes downplay the importance of 'chance' in evolution. I believe that both of these approaches are mistaken. The main thesis of this paper is that the term 'chance' encompasses a number of distinct concepts, and that at least some of these concepts serve essential explanatory functions in evolutionary biology. This claim is defended by way of an historical survey of the major concepts of 'chance' in the history of evolutionary biology, especially the concepts used by Jean Baptiste Lamarck, Charles Darwin, and Sewall Wright. An examination of their biologies shows how the concepts of 'chance' used cohere with their major scientific objectives and methods. These concepts survive and continue to function as important explanatory factors in contemporary evolutionary biology. Examples of such usage are given, and the explanatory status of 'chance' assessed.

Adaptation, Biological↗
PubMed1976

Measles virus: study of induced transfer of biological properties. II. Fluorescence studies on rescue of neurotropic strain in cell culture.

HeLa cells are non-permissive for the neurotropic suckling mouse strain of measles virus (MMV), but are permissive for cell-adapted Edmonston strain of measles virus (EDm). Fluorescence and electron microscopy demonstrated no membrane fluorescence and no membrane associated viral components, as well as characteristic lack of nuclear antigen after MMV infection of HeLa cells. This appearance differs markedly from the membrane, cytoplasmic and nuclear fluorescence after Edm infection of HeLa cells. Fluorescence microscopy demonstrates fusion of the two dissimilar syncytia after mixed infection. This suggests Edm envelopment of MMV nucleocapsids may be the means of MMV rescue in this system.

Adaptation, Biological↗
PubMed1998

A bottom up approach towards the acquisition and expression of sequential representations applied to a behaving real-world device: Distributed Adaptive Control III.

Biological systems display a high degree of flexibility in problem solving. In this paper a model is presented, Distributed Adaptive Control III (DACIII), which is aimed at understanding these forms of behavior. DACIII is part of a larger modeling series directed at understanding how biological systems acquire, retain, and express knowledge of the world. This modeling series has its roots, on one hand, in the methodological consideration that brain and behavior need to be modeled from a multi-level perspective. On the other, the importance of the acquisition of representations of events in the world, as opposed to an a priori specification, is emphasized. DACIII is presented against the background of the paradigms of classical and operant conditioning. On the basis of an analysis of these experimental approaches towards the study of animal behavior a theoretical framework is defined aimed at identifying the minimal requirements of a control structure which could display these behaviors. The proposed model is evaluated in different configurations using both simulated and real robots. It is demonstrated that DACIII is able to fully bootstrap itself from a mode of control which solely relies on proximal sensors and predefined reflexes, to a level of control which is dominated by acquired representations of events transduced by distal sensors. This transition is reflected in the performance of the behaving device, from strongly variable trajectories to highly structured behavioral sequences. The results are compared with alternative models of classical and operant conditioning and models which attempt to capture the properties of its underlying neural substrate.

Journal Article↗
PubMed1977

Cold adapted variants of influenza A. II. Comparison of the genetic and biological properties of ts mutants and recombinants of the cold adapted A/AA/6/60 strain.

The genetic and biological properties of 13 recombinant influenza A clones derived at 25 degrees C from the A/AA/6/60-cold variant (by crosses with 4 different wild type strains) were compared with a set of 5-FU induced ts-mutants. The 5-FU mutants had previously been placed into 7 complementation-recombination groups; the A/AA/6/60-cold parent (PI-7) and the 12 cold recombinant clones which were ts were shown to share a lesion with only one of these groups. The parental strain and 5 recombinant clones were evaluated for replication in the lungs and nasal turbinates of hamsters. Each virus appeared to be attenuated; genetic stability correlated with the level of viral replication in the hamster lung, i.e., viruses which grew best showed a tendency to revert to the ts+ phenotype. Characterization of the ts+ revertants for the presence of the cold adaptation property revealed that these viruses exhibited a spectrum of cold adaptation properties. Two viruses, PI-7 (the parental cold variant) and the CR6 recombinant (A/Queensland/6/72) did not revert in either the lungs or nasal turbinates of hamsters.

Animals↗
PubMed2002

Radiation adaptive response of glial cells.

There are various types of radiation in space including high energy particles. It is, therefore, becoming to be important to study the low dose and low dose-rate effects in space radiation biology. Radiation adaptive response (RAR) for cell growth and its mechanism were examined using cultured glial cells. The cells from hippocampus of Wistar rats were irradiated with a low dose (0.1 Gy) of X-rays and 3 h after with a high dose (2 Gy). Decrease in the rate of cell growth with 2 Gy was suppressed by the 0.1 Gy preirradiation, when cells were counted 2 days after irradiation. The inhibitors of protein kinase C (PKC) and DNA-dependent protein kinase (DNAPK) or phosphatidylinositol 3-kinase (PI3K) suppressed RAR. The treatment with the activators of PKC instead of 0.1 Gy-preirradiation also caused adaptive response to 2 Gy-irradiation. Moreover, glial cells cultured from severe combined immunodeficiency (scid) mice, which have lost DNAPK activity, and AT-2KY cells, fibroblasts of an ataxia-telangiectasia (AT) patient, showed no RAR. These results indicated that PKC, ATtM, DNAPK and/or PI3K were involved in RAR for growth of cultured glial cells. Proteomics [correction of preteomics] analysis of these cells exposed to low dose irradiation in now underway.

Aging↗
PubMed2005

A statistical approach for array CGH data analysis.

BACKGROUND: Microarray-CGH experiments are used to detect and map chromosomal imbalances, by hybridizing targets of genomic DNA from a test and a reference sample to sequences immobilized on a slide. These probes are genomic DNA sequences (BACs) that are mapped on the genome. The signal has a spatial coherence that can be handled by specific statistical tools. Segmentation methods seem to be a natural framework for this purpose. A CGH profile can be viewed as a succession of segments that represent homogeneous regions in the genome whose BACs share the same relative copy number on average. We model a CGH profile by a random Gaussian process whose distribution parameters are affected by abrupt changes at unknown coordinates. Two major problems arise: to determine which parameters are affected by the abrupt changes (the mean and the variance, or the mean only), and the selection of the number of segments in the profile. RESULTS: We demonstrate that existing methods for estimating the number of segments are not well adapted in the case of array CGH data, and we propose an adaptive criterion that detects previously mapped chromosomal aberrations. The performances of this method are discussed based on simulations and publicly available data sets. Then we discuss the choice of modeling for array CGH data and show that the model with a homogeneous variance is adapted to this context. CONCLUSIONS: Array CGH data analysis is an emerging field that needs appropriate statistical tools. Process segmentation and model selection provide a theoretical framework that allows precise biological interpretations. Adaptive methods for model selection give promising results concerning the estimation of the number of altered regions on the genome.

Algorithms↗
PubMed2005

The problematic in-vitro embryo in the age of epigenetics.

During use of many assisted reproductive technologies, the embryo spends time in vitro. The immediate and long-term epigenetic impacts of this exposure to an in-vitro environment are discussed in the context of the health of the offspring. Three exemplary types of possible epigenetic impact are discussed: embryonic cell numbers, mitochondria, and genomic imprints. There is evidence that all of these can be affected in the short term and that these short-term impacts can have heritable consequences across developmental cell generations into maturity. There is also evidence of association between the observed impact and pathology, but as yet no unequivocal evidence of causality for humans and mice. The problematic in-vitro embryo is considered paradigmatic for a central question facing biology: how does the environment interact epigenetically with the genome to produce variable phenotypic outcomes?

Adaptation, Biological↗
PubMed2006

Whipsaw cancer treatments: the role of hormesis in endocrine and immune therapies.

In this report, we propose a philosophy of treatment that few physicians may be bold enough to actually embrace, but which we believe may eventually find a place in the oncologist's armamentarium. The proposal is based on two assumptions: (1) that many hormones and other biologicals have reverse effects in biologic systems depending on their dosage or concentration, a phenomenon called hormesis; and (2) that most malignant tumors have a large but slow-moving capacity to adapt to adverse conditions, probably by the selection of cellular variants. We suggest that the phenomenon of hormesis might be used to keep a tumor under hormonal and/or immunologic environments that are inimical to its growth and well-being.

Adaptation, Biological↗
PubMed1997

[Role of intraspecific phenotypic diversity in the ecology of escherichia coli and staphylococcus aureus].

Investigating a complex of biological characteristics, including the inactivating ability of some antiinfectious resistance agents (lysozyme, complement, immunoglobulins, the bactericide component of interferon) in 229 and 257 E. coli and S. aureus strains, respectively, isolated from various sources has revealed the phenotypical polymorphism in the populations of these microorganisms, whose degree and specific features may be characterized by the indices of biological diversity and by the spectra of dominant biological profiles. Interpopulational variability in the bacteria was found to be determined by the specific features of their colonized ecotopes and to reflect the level of their adaptation to their inhabitance. There is a view of the organizational structure of the bacterial species as a whole complex of discrete populations of microorganisms, which include representatives of phenotypically different clone lines that occupy the optimum and some marginal econiches whose relation is supported by migration processes.

Adaptation, Biological↗
PubMed1985

Thermodynamics and the conceptual structure of evolutionary theory.

Thermodynamics and evolutionary theory have spent most of their shared history in adversarial relationship to one another. The point of this paper is to consider some qualitative ways in which thermodynamics can enrich both the theory and epistemology of evolution. The "autonomy of biology" posture in evolutionary theory hangs on the supposed uniqueness of why-questions in biology. With this posture, and with the general obstruction of constructive dialogue between evolution and the physical sciences it fosters, come the perennial accusations that Darwinism deals in adaptational teleology but not mechanisms. Thermodynamics provides for a two-tiered hierarchy of causation in nature in which the why-question is rendered not only legitimate materialistically, but essential to understanding the evolutionary process in its totality--from the emergence of life to the branching of lineages in speciation.

Adaptation, Biological↗
PubMedDate not supplied

[Space biology in the 3d decade].

The paper reviews the major results of experiments on microorganisms, plants and animals flown onboard space vehicles during the past two decades. To explain the experimental findings, it is hypothesized that living beings develop an indirect adaptation to gravity effects which has a bearing only on the phylogenetic process.

Adaptation, Biological↗
PubMed2005

Mongoose rabies in southern Africa: a re-evaluation based on molecular epidemiology.

Relative to the developed world, rabies has been poorly studied in the vast African continent. The southern African countries of Zimbabwe and South Africa, however, are known to sustain a great diversity of lyssaviruses, with large biological variations amongst genotype 1 (rabies viruses) at present more apparent here than elsewhere on the continent. One recognized biotype of rabies virus in the subcontinent appears to be specifically adapted to a variety of mongooses, belonging to the Viverrinae subfamily (family Herpestidae) and are commonly referred to as viverrid viruses, although the term mongoose rabies would be more correct, considering the taxonomic status of the host species involved. It was our objective to study the genetic relationships of 77 rabies virus isolates of this mongoose biotype, isolated in South Africa and Zimbabwe, towards elucidation of the molecular epidemiology of this interesting group of African viruses. In our study of a 592 nucleotide sequence encompassing the cytoplasmic domain of the glycoprotein and the G-L intergenic region of the viral genomes, we provide the first comprehensive data on the molecular epidemiology of these viruses and indicate a history of extended evolutionary adaptation in this geographical domain. The molecular epidemiological observations reported here are highly unlikely to be limited to the small geographical areas of South Africa and Zimbabwe and illustrate the need for lyssavirus surveillance in the rest of sub-Saharan Africa and throughout the entire continent.

Adaptation, Biological↗
PubMed1997

The neurobiology of stress: understanding regulation of affect during female biological transitions.

This article provides an overview of the neurobiology of stress and how dysfunction of the stress system may be related to psychological or behavioral processes that emerge during biological transitions across the life span of a female individual. These transitions involve distinct hormonal changes that may or may not be accompanied by external physical changes and concomitant psychosocial adaptations. The biological transition include the intrauterine and neonatal periods; puberty, including both adrenarche and gonadarche; pregnancy and the postpartum period; and the perimenopausal and menopausal periods. We propose that biological transitions are times of increased psychological and physical vulnerability for some individuals, and this vulnerability may be related to concurrent changes in the reactivity of the stress system. Models for examining hormone-behavior relations during biological transitions are discussed along with specific research and clinical examples of disorders of the stress system temporally associated with female biological transitions.

Adolescent↗
PubMedDate not supplied

Disinfection using ultraviolet radiation as an antimicrobial agent: a review and synthesis of mechanisms and concerns.

Control of microbes in sensitive health care settings cannot be maintained without effective disinfection methods. Recently, increasing microbial resistance to common chemical agents, including antibiotics, has required the implementation of new approaches to disinfection where such sanitary practices are critical. Pharmaceutical manufacturers and many interrelated industries also have a need for effective disinfection and sanitation strategies. As a result, standard practices that direct and maintain effective microbial controls are established. These practices exploit a thorough understanding of biological processes and manipulate them to preserve the quality and safety of a valuable product. Most biological processes are delicately balanced with their surroundings, or environment. When changes are made to the environment during disinfection, damaged microbes may respond by repairing the immediate damage or by adapting their biological processes through developing a resistance. Unless sound disinfection procedures are consistently applied, new strains of environmental microbes that can utilize multiple resistance markers may be artificially selected. Examples of related drug resistance are currently being studied and managed in many large hospitals, but non-chemical methods are also subject to similar concerns. Here, we review the use of ultraviolet-based disinfection practices, the biological basis for them, and some potential desensitization issues that may develop. Finally, we suggest some approaches to study and practically address these effects.

Anti-Bacterial Agents↗