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At least 487 records · Page 27Linked to original sources
PubMed2005

On the nature of the species problem and the four meanings of 'species'.

Present-day thought on the notion of species is troubled by a mistaken understanding of the nature of the issue: while the species problem is commonly understood as concerning the epistemology and ontology of one single scientific concept, I argue that in fact there are multiple distinct concepts at stake. An approach to the species problem is presented that interprets the term 'species' as the placeholder for four distinct scientific concepts, each having its own role in biological theory, and an explanation is given of the concepts involved. To illustrate how these concepts are commonly conflated, two widely accepted ideas on species are criticized: species individualism and species pluralism. I argue that by failing to distinguish between the four concepts and their particular roles in contemporary biological theory, these ideas stand in the way of a final resolution of the species problem.

Biological Evolution↗
PubMed2004

Evolutionary, historical and political economic perspectives on health and disease.

The origin and rise of social inequalities that are a feature of the post-Neolithic society play a major role in the pattern of disease in prehistoric and contemporary populations. We use the concept of epidemiological transition to understand changing ecological relationships between humans, pathogens and other disease insults. With the Paleolithic period as a baseline, we begin with ecological and social relationships that minimized the impact of infectious disease. Paleolithic populations would have retained many of the pathogens that they shared with their primate ancestors and would have been exposed to zoonoses that they picked up as they adapted to a foraging existence. The sparse mobile populations would have precluded the existence of endemic infectious disease. About 10,000 years ago, the shift to an agricultural subsistence economy created the first epidemiological transition, marked by the emergence of infections, a pattern that has continued to the present. Beginning about a century ago, some populations have undergone a second epidemiological transition in which public health measures, improved nutrition and medicine resulted in declines in infectious disease and a rise in non-infectious, chronic and degenerative diseases. Human populations are entering the third epidemiological transition in which there is a reemergence of infectious diseases previously thought to be under control, and the emergence of novel diseases. Many of the emerging and reemerging pathogens are antibiotic resistant and some are multi-antibiotic resistant. Inequality continues to widen within and between societies, accelerating the spread of emerging and reemerging diseases.

Chronic Disease↗
PubMed2005

Cultural transmission of fitness: genes take the fast lane.

Classical population genetics describes how the fate of an allele is driven by four forces: mutation, migration, selection and drift. However, these are sometimes insufficient to explain how the observed allele frequency changes and, therefore, another factor must be invoked: cultural transmission of fitness (CTF). CTF is the non-genetic transmission of any kind of behaviour that affects reproductive success. There are several clearly documented examples of CTF, and theoretical studies have shown that it affects effective population size, linkage disequilibrium and coalescent times. It is therefore a factor that must be taken into account to explain the structure of genetic diversity. In this article, we will present documented cases of how CTF affects the genetic diversity of populations and yields dramatic changes in allele frequencies.

Alleles↗
PubMed1999

Thermochemical studies of the toxic actions of heavy metal ions on Rhizopus nigricans.

By using a LKB2277 BioActivity Monitor (heat conduction microcalorimeter), stopped-flow method, the thermogenetic curves of Rhizopus nigricans growth at 25 degrees C inhibited by four kinds of heavy metal ions are determined, parameters such as growth rate constants k, inhibitory ratio I, half inhibitory concentration IC50 et al. are obtained. The experimental results show that heavy metal ions can inhibit Rhizopus nigricans growth obviously, low concentration of Cu2+ has promoting action. The inhibitory sequence is Cd2+ > Hg2+ > Pb2+ > Cu2+, half inhibitory concentration of them are Cd+ 0.8 micro g x ml(-1), Hg2+ 1.7 micro g x ml(-1), Pb2+ 48.0 micro g x ml(-1), Cu2+ 110 micro g x ml(-1). This microclorimetric bioassay for acute cellular toxicity is based on metabolic heat evolution from cultured cells. The assay is quantitative, inexpensive, and versatile; moreover, toxicological information can be obtained with cell from other species of interest.

Calorimetry↗
PubMed1999

The role of cultural and social factors in the cause of addictive disorders.

For many centuries, generations of young people were protected from the early onset of addictive disorders. Although addiction to drugs and alcohol had been well known for centuries, widespread addiction has occurred only in recent centuries. Because the human gene pool or human biochemistry did not likely change suddenly to produce this result, social and cultural factors likely have produced widespread addiction. From another perspective, the sociocultural factors that once protected our societies against widespread addiction may have become weakened or inoperative. Our social institutions--our families, schools, religions, neighborhoods, and governments--no longer protect us and our young from addiction as they once did. The failure of traditional social institutions to protect us from addiction does not mean that we must seek drug panaceas only in nonsocietal venues, such as medications and psychotherapies. Rather, we should look to those elements of our institutions that have failed us and seek to bolster them. A gradually evolving body of literature on this topic demonstrates that institutional changes can serve to reduce widespread addiction among us. Moreover, these changes can be implemented at many levels: within our families, schools, friendship groups, workplaces, churches, neighborhoods, and legislatures.

Adolescent↗
PubMed2000

Sociocultural conceptions of the borderline personality.

Although sympathetic to most analytic conceptions of the origins of borderline personality disorder, an addendum reflecting the recent and divisive impact of rapid social and cultural changes is proposed. Specifically noted are social customs that exacerbate rather than remediate early errant parent-child relationships and the diminished power of once reparative institutions that no longer compensate for these ubiquitous early problems.

Adult↗
PubMed2002

Mind from genes and neurons: a neurobiological model of Freudian psychology.

A hypothetical neurobiological model of Freud's architecture of the mind is presented in an attempt to unify concepts and data derived from molecular biology (e.g., genomic imprinting), systems neuroscience (e.g., neuroanatomochemical circuitries), evolutionary psychology (e.g., human mating strategies), and Freudian psychology. The model posits that events related to genomic imprinting can be regulated in a tissue-specific manner over the course of neural development such that imprinting along the matriline would favor the development of corticostriatal structures whereas imprinting along the patriline would favor the development of limbic-subcortical structures. A neuropsychological analysis of the brain requirements for successful mating presumably would put an evolutionary premium on the corticostriatal system (matrilineal) in men and limbic-subcortical systems (patrilineal) in women. Additionally, the model emphasizes that the ego and the super-ego of Freudian psychology are dependent on corticostriatal mechanisms (matriline-related), while the id is dependent on brainstem processes (patriline-related). It is hoped that the model herein presented has heuristic value for a rapprochement of psychoanalysis and neurobiology.

Behavior↗
PubMed2003

Genomic structure and promoter analysis of PKC-delta.

Protein kinase C-delta (PKC-delta) is a ubiquitously expressed kinase involved in a variety of cellular signaling pathways including cell growth, differentiation, apoptosis, tumor promotion, and carcinogenesis. While signaling pathways downstream of PKC-delta are well studied, the regulation of the gene has not been extensively analyzed. A mouse genomic DNA fragment containing the PKC-delta gene was sequenced by the primer-walking method, and the subsequent DNA sequence data were used as a query to clone Caenorhabditis elegans and human genomic homologs from the publicly available genomic databases. The genomic structures of C. elegans, mouse, rat, and human PKC-delta were analyzed, and the result revealed that PKC-delta genes comprise 12, 18, 19, and 18 exons for C. elegans, mouse, rat, and human, respectively. The translation start methionine resides in the second exon in mouse and human and in the third exon in rat. The first intron between the first exon and the exon with the translation start methionine in mammalian genes represents a very large gap, as long as 17 kb in human, indicating a complexity involved in gene splicing. Overall exon-intron genomic structure is highly conserved among mammals, while significantly diverged in C. elegans. Putative transcription factor binding sites on the 1.7-kb promoter region of the mouse gene suggest that PKC-delta might be involved in spermatogenesis, embryogenesis, development, brain generation, immune response, oxidative environment, and oncogenesis. Studies on the promoter and subsequent biological testing on mouse keratinocytes indicate that tumor necrosis factor (TNF)-alpha increases the expression of PKC-delta, and this correlates with the time of NFkappaB nuclear translocation and activation. This TNF-alpha-mediated upregulation of PKC-delta is repressed in keratinocytes that are preinfected with IkappaB superrepressor adenovirus, suggesting that NFkappaB is involved directly in PKC-delta expression.

Animals↗
PubMed2004

A gating hinge in Na+ channels; a molecular switch for electrical signaling.

Voltage-gated sodium channels are members of a large family with similar pore structures. The mechanism of opening and closing is unknown, but structural studies suggest gating via bending of the inner pore helix at a glycine hinge. Here we provide functional evidence for this gating model for the bacterial sodium channel NaChBac. Mutation of glycine 219 to proline, which would strongly favor bending of the alpha helix, greatly enhances activation by shifting its voltage dependence -51 mV and slowing deactivation by 2000-fold. The mutation also slows voltage-dependent inactivation by 1200-fold. The effects are specific because substitutions of proline at neighboring positions and substitutions of other amino acids at position 219 have much smaller functional effects. Our results fit a model in which concerted bending at glycine 219 in the S6 segments of NaChBac serves as a gating hinge. This gating motion may be conserved in most members of this large ion channel protein family.

Bacillus↗
PubMed2002

The Salmonella enterica subspecies I specific centisome 7 genomic island encodes novel protein families present in bacteria living in close contact with eukaryotic cells.

We have determined the genetic structure of the Salmonella enterica centisome 7 genomic island (SCI) located at the aspV loci in S. enterica subspecies I strains. The 47-kb long genomic island encodes 37 putative proteins, including the previously described saf fimbrial operon and the sinR transcriptional regulator. Other open reading frames (designated sci A to Z) in the island encode putative proteins with homologies to virulence-associated proteins in a number of gram-negative bacteria such as Pseudomonas aeruginosa, Yersinia pestis and enterohemorrhagic Escherichia coli, bacteria that have the ability to interact with and manipulate eukaryotic cells. The Sci proteins have putative cytoplasmic, periplasmic and outer membrane localizations pointing to a role in extracellular processes such as secretion or organelle biosynthesis. The genes encoding Sci-like proteins are clustered in all sequenced bacterial genomes available in the databases and a core set can be defined by the presence of genes encoding proteins with similarity to the SciB, C, G, H, I, O proteins. The SCI genomic island DNA sequences are restricted to Salmonella strains belonging to S. enterica subspecies I and deletion of the entire island affects the ability of the organisms to enter eukaryotic cells.

Animals↗
PubMed1999

The genomics of adaptation in yeast.

A recent study has combined methods of experimental evolution and DNA microarray technology to examine evolved changes in gene expression in yeast, providing intriguing insights into the genetics of adaptation and functional genomics, and pointing to future uses of microarray technology in evolutionary genetics.

Adaptation, Physiological↗
PubMed2003

Testing evolutionary hypotheses about human biological adaptation using cross-cultural comparison.

Physiological data from a range of human populations living in different environments can provide valuable information for testing evolutionary hypotheses about human adaptation. By taking into account the effects of population history, phylogenetic comparative methods can help us determine whether variation results from selection due to particular environmental variables. These selective forces could even be due to cultural traits-which means that gene-culture co-evolution may be occurring. In this paper, we outline two examples of the use of these approaches to test adaptive hypotheses that explain global variation in two physiological traits: the first is lactose digestion capacity in adults, and the second is population sex-ratio at birth. We show that lower than average sex ratio at birth is associated with high fertility, and argue that global variation in sex ratio at birth has evolved as a response to the high physiological costs of producing boys in high fertility populations.

Adaptation, Physiological↗
PubMed2003

Origin of metazoan stem cell system in sponges: first approach to establish the model (Suberites domuncula).

It is established that Porifera (sponges) represent the earliest phylum which branched off from the common ancestor of all multicellular animals, the Urmetazoa. In the present study, the hypothesis is tested if, during this transition, pluripotent stem cells were formed which are provided-similar to the totipotent cells (archaeocytes/germ cells)-with a self-renewal capacity. As a model system, primmorphs from the sponge Suberites domuncula were used. These 3D-cell aggregates were cultivated in medium (RPMI 1640/seawater) either lacking silicate and ferric iron or in medium which was supplemented with these 'morphogenetic' factors. As molecular markers for the potential existence of stem cells in primmorphs, two genes which encode proteins found in stem cells of higher metazoan species, were cloned from S. domuncula. First, the noggin gene, which is present in the Spemann organizer of amphibians and whose translation product acts during the formation of dorsal mesoderm derivatives. The second gene encodes the mesenchymal stem cell-like protein. Both cDNAs were used to study their expression in primmorphs in dependence on the incubation conditions. It was found that noggin expression is strongly upregulated in primmorphs kept in the presence of silicate and ferric iron, while the expression of the mesenchymal stem cell-like protein was downregulated. These data are discussed with respect to the existence of stem cells in sponges.

Amino Acid Sequence↗