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PubMed2006

Surfactant assemblies and their various possible roles for the origin(s) of life.

A large number of surfactants (surface active molecules) are chemically simple compounds that can be obtained by simple chemical reactions, in some cases even under presumably prebiotic conditions. Surfactant assemblies are self-organized polymolecular aggregates of surfactants, in the simplest case micelles, vesicles, hexagonal and cubic phases. It may be that these different types of surfactant assemblies have played various, so-far underestimated important roles in the processes that led to the formation of the first living systems. Although nucleic acids are key players in the formation of cells as we know them today (RNA world hypothesis), it is still unclear how RNA could have been formed under prebiotic conditions. Surfactants with their self-organizing properties may have assisted, controlled and compartimentalized some of the chemical reactions that eventually led to the formation of molecules like RNA. Therefore, surfactants were possibly very important in prebiotic times in the sense that they may have been involved in different physical and chemical processes that finally led to a transformation of non-living matter to the first cellular form(s) of life. This hypothesis is based on four main experimental observations: (i) Surfactant aggregation can lead to cell-like compartimentation (vesicles). (ii) Surfactant assemblies can provide local reaction conditions that are very different from the bulk medium, which may lead to a dramatic change in the rate of chemical reactions and to a change in reaction product distributions. (iii) The surface properties of surfactant assemblies that may be liquid- or solid-like, charged or neutral, and the elasticity and packing density of surfactant assemblies depend on the chemical structure of the surfactants, on the presence of other molecules, and on the overall environmental conditions (e. g. temperature). This wide range of surface characteristics of surfactant assemblies may allow a control of surface-bound chemical reactions not only by the charge or hydrophobicity of the surface but also by its "softness". (iv) Chiral polymolecular assemblies (helices) may form from chiral surfactants. There are many examples that illustrate the different roles and potential roles of surfactant assemblies in different research areas outside of the field of the origin(s) of life, most importantly in investigations of contemporary living systems, in nanotechnology applications, and in the development of drug delivery systems. Concepts and ideas behind many of these applications may have relevance also in connection to the different unsolved problems in understanding the origin(s) of life.

Fatty Acids↗
PubMed1988

Ethical considerations of the new reproductive technologies. By the Ethics Committee (1986-87) of The American Fertility Society in light of Instruction on the Respect for Human Life in its Origin and on the Dignity of Procreation issued by the Congregation for the Doctrine of the Faith.

In September 1986, The American Fertility Society issued a report, Ethical Considerations of the New Reproductive Technologies, setting forth the then-held ethical position of the Society on the various new reproductive technologies. In 1987, the Congregation for the Doctrine of the Faith issued the Instruction on the Respect for Human Life and Its Origin and on the Dignity of Procreation. While both documents state that very similar moral criteria were used to derive ethical positions with respect to various reproductive procedures, the conclusions as to the ethical acceptability of the various procedures differ sharply in the two documents. The question can be raised about the procedure used by the Congregation of the Faith to derive its conclusions from the stated premises. Thus, while stating that "the individual integrally and adequately considered" is to be the basis of the moral judgment, the fact is that most conclusions are based on and referenced to past Catholic statements. While the difference in conclusion from similar premises may be troubling to society, it can be especially paralyzing to four groups: (1) those who face problems that might be solved by one or another of the new reproductive technologies; (2) those who are involved in applying them; (3) those who are responsible for institutional policies where such techniques may be applied; and (4) those who are in a position to influence public policy in a legislative or regulatory way. Because of the conflicting conclusions of the two documents, the present Ethics Committee (1986-87) of The American Fertility Society was convened and considered these guidelines in the light of the Instruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioethics↗
PubMed2003

Does life's rapid appearance imply a Martian origin?

The hypothesis that life's rapid appearance on Earth justifies the belief that life is widespread in the universe has been investigated mathematically by Lineweaver and Davis (Astrobiology 2002;2:293-304). However, a rapid appearance could also be interpreted as evidence for a nonterrestrial origin. I attempt to quantify the relative probabilities for a non-indigenous versus indigenous origin, on the assumption that biogenesis involves one or more highly improbable steps, using a generalization of Carter's well-known observer-selection argument. The analysis is specifically applied to a Martian origin of life, with subsequent transfer to Earth within impact ejecta. My main result is that the relatively greater probability of a Martian origin rises sharply as a function of the number of difficult steps involved in biogenesis. The actual numerical factor depends on what is assumed about conditions on early Mars, but for a wide range of assumptions a Martian origin of life is decisively favored. By contrast, an extrasolar origin seems unlikely using the same analysis. These results complement those of Lineweaver and Davis.

Earth, Planet↗
PubMed2004

Does sarcopenia originate in early life? Findings from the Hertfordshire cohort study.

BACKGROUND: Sarcopenia is defined as the loss of skeletal muscle mass and strength with aging. Recent epidemiological studies have shown that men and women who grew less well in early life have lower muscle strength. Our objective was to investigate the relationship between birth weight, infant growth, and the development of sarcopenia. METHODS: We studied 730 men and 673 women, of known birth weight and weight at 1 year, who were born in Hertfordshire, U.K., between 1931 and 1939. Participants completed a health questionnaire, and we measured their height, weight, and grip strength. Standard deviation scores for birth weight, and for infant growth conditional on birth weight, were analyzed in relation to grip strength before and after adjustment for adult size. RESULTS: Grip strength was most strongly associated with birth weight in men (r = 0.19, p < .001) and women (r = 0.16, p < .001). These relationships remained significant after adjustment for adult height and weight. In contrast, the associations with infant growth were weakened after allowing for adult size. Adjustment for age, current social class, physical activity, smoking, and alcohol did not affect these results. CONCLUSIONS: Birth weight is associated with sarcopenia in men and women, independently of adult height and weight. The influence of infant growth on long-term muscle strength appears to be mediated through adult size. Sarcopenia may have its origins in early life, and identifying influences operating across the whole life course may yield considerable advances in developing effective interventions.

Adult↗
PubMed1999

Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions.

Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids.

Formates↗
PubMed1999

Astrobiology: exploring the origins, evolution, and distribution of life in the Universe.

The search for the origins of life and its presence beyond Earth is strengthened by new technology and by evidence that life tolerates extreme conditions and that planets are widespread. Astrobiologists learn how planets develop and maintain habitable conditions. They combine biological and information sciences to decipher the origins of life. They examine how biota, particularly microorganisms, evolve, at scales from the molecular to the biosphere level, including interactions with long-term planetary changes. Astrobiologists learn how to recognize the morphological, chemical, and spectroscopic signatures of life in order to explore both extraterrestrial samples and electromagnetic spectra reflected from extrasolar planets.

Biological Evolution↗
PubMed1994

Life in a ligand sphere.

The most fundamental divide in biology is that between heterotrophic and autotrophic ways of life. Two of the leading proponents of a heterotrophic origin of life ("hetero-origin") in a prebiotic broth, C. de Duve and S. L. Miller, have criticized my theory of a pyrite-pulled chemo-autotrophic origin of life ("auto-origin") [De Duve, C. & Miller, S. L. (1991) Proc. Natl. Acad. Sci. USA 88, 10014-10017]. This criticism is now answered.

Biological Evolution↗
PubMed2001

People's feelings and ideas about receiving transplants of different origins--questions of life and death, identity, and nature's border.

The aim of this study was to explore the public's feelings and ideas with regard to receiving transplants of different origins. Sixty-nine individuals with varying sociodemographic background, selected from samples who had responded to a questionnaire on receiving and donating organs, were interviewed in-depth. A wide variety of reactions was displayed. The feelings and ideas about receiving organs were summarized in ten categories: 1) the emergency situation; 2) the functioning of the transplant; 3) the influence of transplants on personality, behaviour, and appearance; 4) the influence of transplants on body image; 5) disgust; 6) cannibalism; 7) trespassing nature's border; 8) tradition; 9) ethical considerations; and 10) the debt of gratitude. Most individuals were willing to accept at least one organ. Animal organs were the least preferred. The hierarchy of organ preferences--with organs from a relative at the top and animal organs at the bottom was explained in terms of rational, magical, and analogy thinking. Finally, the consequences for the encounter between health care personnel and transplantation candidates were briefly discussed.

Adult↗
PubMed2003

Hyperthermophily and the origin and earliest evolution of life.

The possibility of a high-temperature origin of life has gained support based on indirect evidence of a hot, early Earth and on the basal position of hyperthermophilic organisms in rRNA-based phylogenies. However, although the availability of more than 80 completely sequenced cellular genomes has led to the identification of hyperthermophilic-specific traits, such as a trend towards smaller genomes, reduced protein-encoding gene sizes, and glutamic-acid-rich simple sequences, none of these characteristics are in themselves an indication of primitiveness. There is no geological evidence for the physical setting in which life arose, but current models suggest that the Earth's surface cooled down rapidly. Moreover, at 100 degrees C the half-lives of several organic compounds, including ribose, nucleobases, and amino acids, which are generally thought to have been essential for the emergence of the first living systems, are too short to allow for their accumulation in the prebiotic environment. Accordingly, if hyperthermophily is not truly primordial, then heat-loving lifestyles may be relics of a secondary adaptation that evolved after the origin of life, and before or soon after separation of the major lineages.

Adaptation, Physiological↗
PubMed2004

Ruptured cerebral aneurysm in the early stage of life--a congenital origin?

We report the case of a large fusiform aneurysm of the anterior cerebral artery in a 3-month-old girl presenting with generalized seizures and complicated by a cardiorespiratory arrest needing resuscitation. The native cerebral CT scan revealed a diffuse subarachnoid hemorrhage (Fischer III grade); CT angiography showed an aneurysm of the distal A1 segment of the anterior cerebral artery (ACA). Successful treatment was achieved through surgical trapping of the aneurysm and sacrifice of the distal A1 segment. A histological study of the aneurysmal wall revealed the absence of elastic fibers in an otherwise fibromuscular media and showed no signs of previous hemorrhage. Intracranial aneurysms of the ACA are very rare in the early stage of life and their pathogenesis is not clear. This case is of interest as the location and shape of the aneurysm, the absence of relevant familial and medical history, and the histopathological findings raise the hypothesis of a congenital origin. It further describes the value of CT angiography for studying aneurysms in the very young.

Aneurysm, Ruptured↗
PubMed2002

How congenital heart disease originates in fetal life.

Knowledge of the early development of the heart has increased rapidly in recent years as microscopic techniques, experimental models using animal, avian and insect species, and various genetic techniques have been brought to bear on the mysteries of human fetal cardiac development. The development of the heart occurs rapidly from embryonic day 18 in humans to the twelfth week of fetal life. The stages include gastrulation and formation of the primitive heart tube with rhythmic contractions appearing at day 21, segmentation of the primitive heart tube, looping, realignment of inflow and outflow segments, septation of the atria, ventricles and outflow segments, formation of atrio-ventricular valves, and development of aortic and pulmonary trunks and aortic arches. The genes and factors currently known to be involved in cardiac development are reviewed, but much is still to be determined as the field is evolving with extraordinary rapidity.

Aorta↗