On the concept and elucidation of endogenous retroviruses

Endogenous retrovirus (ERV) genomes integrated into the chromosomal DNA of the host were first detected in chickens and mice as Mendelian determinants of Gag and Env proteins and of the release of infectious virus particles. The presence of ERV was confirmed by DNA hybridization. With complete host genomes available for analysis, we can now see the great extent of viral invasion into the genomes of numerous vertebrate species, including humans. ERVs are found at many loci in host DNA and also in the genomes of large DNA viruses, such as herpesviruses and poxviruses. The evolution of xenotropism and cross-species infection is discussed in the light of the dynamic relationship between exogenous and endogenous retroviruses.     

On the origins of narrative

Stories consist largely of representations of the human social environment. These representations can be used to influence the behavior of others (consider, e.g., rumor, propaganda, public relations, advertising). Storytelling can thus be seen as a transaction in which the benefit to the listener is information about his or her environment, and the benefit to the storyteller is the elicitation of behavior from the listener that serves the former’s interests. However, because no two individuals have exactly the same fitness interests, we would expect different storytellers to have different narrative perspectives and priorities due to differences in sex, age, health, social status, marital status, number of offspring, and so on. Tellingly, the folklore record indicates that different storytellers within the same cultural group tell the same story differently. Furthermore, the historical and ethnographic records provide numerous examples of storytelling deliberately used as a means of political manipulation. This evidence suggests that storyteller bias is rooted in differences in individual fitness interests, and that storytelling may have originated as a means of promoting these interests.     

On the origins of esterases

Comparisons among the primary sequences of five cloned eukaryotic esterases reveal two distinct lineages, neither bearing any significant overall sequence similarity to the functionally related serine protease multigene family. We have not eliminated the possibility that the esterases may have residual conformational similarities to the serine proteases. However, our profile analysis and analyses of the predicted conformations of the esterases reveal little similarity to the serine proteases. Four of the esterase proteins share 27%-53% overall sequence similarity and evidence of a catalytic mechanism involving the same Arg- Asp-Ser or His-Asp-Ser charge relay. We propose that these four esterases, three of them cholinesterases, form part of a multigene family essentially separate from the serine proteases.      

In situ hybridization: general infectivity assay for retroviruses.

We have devised a general infectivity assay for retroviruses. A virus-specific [32P]DNA probe is hybridized in situ to a monolayer culture, and foci of infected cells in the monolayer are detected by exposure of the hybridized culture to X-ray films. The method is quantitative, in that it gives the same titer for Moloney murine leukemia virus as does the standard UV-XC test. The specificity of the assay is indicated by the fact that murine leukemia virus and baboon endogenous virus do not cross hybridize under the conditions used. The assay is completed within 1 to 3 weeks and should be broadly applicable for retroviruses which replicate without altering cellular morphology: its use is demonstrated with mouse mammary tumor virus and the helper virus of the reticuloendotheliosis complex.     

On the origins of nitric oxide

Nitric oxide (NO) is widely recognized for its role as signaling compound. However, the metabolic mechanisms that determine changes in the level of NO in plants are only poorly understood, despite this knowledge being crucial to understanding the signal function of NO. To date, at least seven possible pathways of NO biosynthesis have been described for plants, although the molecular and enzymatic components are resolved for only one of these. Currently, this represents the most significant bottleneck for NO research. In this review, we provide an overview of the multiplicity of NO production and scavenging pathways in plants. Furthermore, we discuss which areas should be focused on in future studies to investigate the origin of fluctuations in the level of NO in plants.     

On the origins of the Mendelian laws

The two laws usually attributed to Mendel were not considered as laws by him. The first law, the law of independent segregation occurs in Mendel's paper as an assumption or hypothesis. Hugo de Vries refers to this as a law discovered by Mendel. This appears to be the first use of an expression equivalent to Mendel's law. In his paper de Vries did not associate the observable characters with structures having a causitive role. That was done by Correns, who transformed the law of segregation of characters into a law of the segregation of anlagen. The second law, the law of independent assortment, is present in embryonic form in Mendel's paper. Here the independent assortment of characters appears as a secondary conclusion to a series of experiments involving several pairs of traits. Mendel repeats the primary conclusion later in the paper but not the secondary one. This leads us to believe that he considered the secondary conclusion as of lesser importance. We note in this context that the 9:3:3:1 ratio commonly associated with the idea of independent assortment, and attributed to Mendel, also does not occur in his paper. A careful reading of the papers of his discoverers shows it was Correns who first drew attention to this ratio. However, he did not formulate the second Mendelian law even though it was clearly implied. Neither was it stated by de Vries. Indeed, the first clear separation of the two laws and the naming of the second law was by T. H. Morgan some 13 years later.     

On the origins of triterpenoid skeletal diversity

The triterpenoids are a large group of natural products derived from C(30) precursors. Nearly 200 different triterpene skeletons are known from natural sources or enzymatic reactions that are structurally consistent with being cyclization products of squalene, oxidosqualene, or bis-oxidosqualene. This review categorizes each of these structures and provides mechanisms for their formation.     

On the origins of New World paleopathology

Many of the lesions found in American Indian bones do not resemble those found in human bones from the Old World, suggesting that the American Indians suffered from a distinct group of illnesses. If Old World pathogens did not follow man to the New World, what were the sources of pre-Columbian Indian diseases? As in the Old World, humans were susceptible to diseases endemic in the local animal populations. Exposure to these diseases varied with culturally conditioned animal contacts. As the New World population increased, the probability for disease increased, to the point where it is likely that even in pre-Columbian times, disease rather than war or climatic changes may have been a major influence in changing settlement patterns. The generalization that the only Old World plants and animals found in the New were those brought by man seems to hold as true for the pre-Columbian disease organisms as it is for larger forms of life.     

On the origins of genetic variants.

Two contrasting mechanisms responsible for the creation of genetic variants are described: one is the manifestation of the limited accuracy of the cellular machinery for DNA replication, the other results from the ability of cells to repair damaged DNA. Replication-dependent variants and those caused by episodical DNA damage enhance the probability that a small fraction of a cell population may survive a sudden (physical or biological) change of environmental conditions. Replication-independent variants arise during persistent but not immediately lethal stress (e.g. starvation) of a non-dividing population. The variants observed under these conditions are of selective advantage because they are able to cope with the particular stress situation. The molecular basis of their creation is a matter of intensive debate.     

The origins of “new assimilation theory”

Boundaries play an important role in Richard Alba’s articulation of new assimilation theory, as is evident in the major works he has produced during the past two decades. This article traces his interest in boundaries to “The Twilight of Ethnicity among Americans of European Ancestry: The Case of Italians”, an article he published in ERS in 1985. It is in this article and a related book published the same year that one can begin to trace the evolution of his thinking on both ethnic boundaries and the cultural content contained within those boundaries.     

On the origins of ultra-fine anaphase bridges

Comment on: Chan KL, Palmai-Pallag T, Ying S, Hickson ID. Replication stress induces sister-chromatid bridging at fragile site loci in mitosis. Nat Cell Biol 2009; 11:753-60.     

On the origins of arrestin and rhodopsin

Background  

G protein coupled receptors (GPCRs) are the most numerous proteins in mammalian genomes, and the most common targets of clinical drugs. However, their evolution remains enigmatic. GPCRs are intimately associated with trimeric G proteins, G protein receptor kinases, and arrestins. We conducted phylogenetic studies to reconstruct the history of arrestins. Those findings, in turn, led us to investigate the origin of the photosensory GPCR rhodopsin.