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PubMed2002

Mitochondrial genome diversity of Native Americans supports a single early entry of founder populations into America.

There is general agreement that the Native American founder populations migrated from Asia into America through Beringia sometime during the Pleistocene, but the hypotheses concerning the ages and the number of these migrations and the size of the ancestral populations are surrounded by controversy. DNA sequence variations of several regions of the genome of Native Americans, especially in the mitochondrial DNA (mtDNA) control region, have been studied as a tool to help answer these questions. However, the small number of nucleotides studied and the nonclocklike rate of mtDNA control-region evolution impose several limitations to these results. Here we provide the sequence analysis of a continuous region of 8.8 kb of the mtDNA outside the D-loop for 40 individuals, 30 of whom are Native Americans whose mtDNA belongs to the four founder haplogroups. Haplogroups A, B, and C form monophyletic clades, but the five haplogroup D sequences have unstable positions and usually do not group together. The high degree of similarity in the nucleotide diversity and time of differentiation (i.e., approximately 21,000 years before present) of these four haplogroups support a common origin for these sequences and suggest that the populations who harbor them may also have a common history. Additional evidence supports the idea that this age of differentiation coincides with the process of colonization of the New World and supports the hypothesis of a single and early entry of the ancestral Asian population into the Americas.

Base Sequence↗
PubMed1996

Population dynamics of flaviviruses revealed by molecular phylogenies.

The phylogeny of 123 complete envelope gene sequences was reconstructed in order to understand the evolution of tick- and mosquito-borne flaviviruses. An analysis of phylogenetic tree structure reveals a continual and asymmetric branching process in the tick-borne flaviviruses, compared with an explosive radiation in the last 200 years in viruses transmitted by mosquitoes. The distinction between these two viral groups probably reflects differences in modes of dispersal, propagation, and changes in the size of host populations. The most serious implication of this work is that growing human populations are being exposed to an expanding range of increasingly diverse viral strains.

Animals↗
PubMed1975

Mitosis and early meiosis in Tetrahymena pyriformis and the evolution of mitosis in the phylum Ciliophora.

The micronuclear mitotic spindle of Tetrahymena pyriformis contains several distinctive elements. The 150 or so continuous microtubules (MTs) form a peripheral sheath just inside the inner nuclear membrane while the kinetochore bundles traverse the center of the nucleoplasm. A new set of microtubules, the separation spindle, appears during the 10-fold nuclear elongation which occurs during the late anaphase. Both the separation spindle and peripheral sheath MTs are present in the macronucleus during macronuclear division but there are no definite kinetochore MTs. In the cresent stage of meiotic prophase both peripheral sheath and kinetochore MTs are present in the micronucleus. By using our own, and other workers', data in conjunction with the phylogenetic scheme for the ciliates which has been designed by Corliss (1974, 1975), we have attempted to trace out the evolutionary history of the various elements of the ciliate mitotic spindle. For example, the micronuclear separation spindle can be followed, from its point of origin within the primitive gymnostomes, throughout the phylum. The separation spindle of the macronucleus, by contrast, is lost at the level of the heterotrichs. Similarly, the anaphase breakdown and reconstitution of the nuclear envelope, which occurs in the primitive Loxodes magnus, can be followed up some phyletic branches, such as the heterotrichs, but in the suctorians and some other groups this feature seems to have been lost. Tracing the evolution of the ciliate mitotic spindle is made very difficult both by the incompleteness of the data and by what appear to be a number of cases of secondary reduction and parallel evolution. In general, however, the evolution of mitosis correlates well with the phylogeny of the ciliates constructed by Corliss and we consider this an independent substantiation of the general correctness of his phylogeny.

Biological Evolution↗
PubMed1998

The evolution of veterinary surgical oncology.

Tremendous change and progress have occurred in the field of oncology over the last several decades. Progression in diagnostic techniques, patient support, adjuvant therapies and surgeon training has allowed the field of surgical oncology to make continued improvements in the human cancer field. Although a relatively young field, veterinary surgical oncology has followed in the progressive footsteps of our human counterparts. This article describes the evolution of this rapidly expanding field of veterinary medicine.

Animals↗
PubMed1984

Ethanol from Whey: Continuous Fermentation with a Catabolite Repression-Resistant Saccharomyces cerevisiae Mutant.

An alternative method for the conversion of cheese whey lactose into ethanol has been demonstrated. With the help of continuous-culture technology, a catabolite repression-resistant mutant of Saccharomyces cerevisiae completely fermented equimolar mixtures of glucose and galactose into ethanol. The first step in this process was a computer-controlled fed-batch operation based on the carbon dioxide evolution rate of the culture. In the absence of inhibitory ethanol concentrations, this step allowed us to obtain high biomass concentrations before continuous fermentation. The continuous anaerobic process successfully incorporated a cell-recycle system to optimize the fermentor productivity. Under conditions permitting a low residual sugar concentration (</=1%), maximum productivity (13.6 g liter h) was gained from 15% substrate in the continuous feed at a dilution rate of 0.2 h. Complete fermentation of highly concentrated feed solutions (20%) was also demonstrated, but only with greatly diminished fermentor productivity (5.5 g liter h).

Journal Article↗
PubMed1993

Evaluation of ifenprodil efficacy on exercise-induced tissue ischemia in stage II arteriopathy by measurement of transcutaneous oxygen tension during a standard treadmill test: double-blind study of injectable ifenprodil versus placebo.

Measurement of transcutaneous oxygen tension (TcPO2) is a noninvasive and easily reproducible method for objectifying and quantifying exercise ischemia in patients with stage II occlusive arterial disease. This technique is also used at rest to evaluate the therapeutic effect of vasoactive treatments. To objectively assess the effectiveness of a vasoactive treatment on the conditions of tissue perfusion, a randomized double-blind study of ifenprodil tartrate versus placebo was performed in 20 patients, whose TcPO2 was continuously measured while they walked on a treadmill. Patients treated with ifenprodil improved significantly as compared with the placebo group, for both the half-hypoxia area, representing the overall evolution of the tissue ischemia (+34.9% and -16.0%, respectively, p = 0.01), and the half-hypoxia recovery time, estimating the postexercise recovery time (+30.2% and -3.6%, respectively, p < 0.05). This study confirms that the continuous measurement of TcPO2 during the recovery phase after exercise represents an objective method for the evaluation and follow-up of patients with stage II intermittent claudication. The results enabled the objective assessment of ifenprodil efficacy on the evolution of tissue hypoxia.

Blood Gas Monitoring, Transcutaneous↗
PubMed1992

Evolution of the capsid protein genes of foot-and-mouth disease virus: antigenic variation without accumulation of amino acid substitutions over six decades.

The genetic diversification of foot-and-mouth disease virus (FMDV) of serotype C over a 6-decade period was studied by comparing nucleotide sequences of the capsid protein-coding regions of viruses isolated in Europe, South America, and The Philippines. Phylogenetic trees were derived for VP1 and P1 (VP1, VP2, VP3, and VP4) RNAs by using the least-squares method. Confidence intervals of the derived phylogeny (significance levels of nodes and standard deviations of branch lengths) were placed by application of the bootstrap resampling method. These procedures defined six highly significant major evolutionary lineages and a complex network of sublines for the isolates from South America. In contrast, European isolates are considerably more homogeneous, probably because of the vaccine origin of several of them. The phylogenetic analysis suggests that FMDV CGC Ger/26 (one of the earliest FMDV isolates available) belonged to an evolutionary line which is now apparently extinct. Attempts to date the origin (ancestor) of the FMDVs analyzed met with considerable uncertainty, mainly owing to the stasis noted in European viruses. Remarkably, the evolution of the capsid genes of FMDV was essentially associated with linear accumulation of silent mutations but continuous accumulation of amino acid substitutions was not observed. Thus, the antigenic variation attained by FMDV type C over 6 decades was due to fluctuations among limited combinations of amino acid residues without net accumulation of amino acid replacements over time.

Amino Acid Sequence↗
PubMed1999

Tile automation: a model for an architecture of a living system.

To understand an architecture of a living system, "Tile Automaton" is introduced as an abstract model of chemical reaction of molecules scattered over a space. The model consists of tiles of various shapes that stand for molecules. The chemical reaction, induced by the collisions of tiles, is represented by the change of the tile shapes. The rules for reaction are deterministic, and the evolution of the system strongly depends on mutual spatial relationship among tiles. The evolution often leads to self-organization of a "factory," a set of tiles that produces tiles continuously and keeps its structure. Several interesting phenomena, such as a deformation or a division of a factory, are also observed. It is proposed that the formation of the factory is due to the interference between different aspects of tiles - the shape and the motion. The concept of "entanglement" is introduced as a mechanism of living systems.

Biochemical Phenomena↗
PubMed2005

The evolution of thoracic anesthesia.

The specialty of thoracic surgery has evolved along with the modem practice of anesthesia. This close relationship began in the 1930s and continues today. Thoracic surgery has grown from a field limited almost exclusively to simple chest wall procedures to the present situation in which complex procedures, such as lung volume reduction or lung transplantation, now can be performed on the most severely compromised patient. The great advances in thoracic surgery have followed discoveries and technical innovations in many medical fields. One of the most important reasons for the rapid escalation in the number and complexity of thoracic surgical procedures now being performed has been the evolution of anesthesia for thoracic surgery. There has been so much progress in this area that numerous books and journals are devoted entirely to this subject. The author has been privileged to work with several surgeons who specialized in noncardiac thoracic surgery. As a colleague of 25 years, the noted pulmonary surgeon James B.D. Mark wrote, "Any operation is a team effort... (but) nowhere is this team effort more important than in thoracic surgery, where near-choreography of moves by all participants is essential. Exchange of information, status and plans are mandatory". This team approach between the thoracic surgeon and the anesthesiologist reflects the history of the two specialties. With new advances in technology, such as continuous blood gas monitoring and the pharmacologic management of pulmonary circulation to maximize oxygenation during one-lung ventilation, in the future even more complex procedures may be able to be performed safely on even higher risk patients.

Anesthesia↗
PubMed2001

[Genetics and the origin of human races].

In the last decades, the concept of human races was considered scientifically unfounded as it was not confirmed by genetic evidence. None of the racial classifications, which strongly differ in the number of races and their composition, reflects actual genetic similarity and genealogy of human populations inferred from variability of classical markers and DNA regions. Moreover, intercontinental ("interracial") variability was shown to be far lower than that within populations: the former constitutes 7 to 10% and the latter, about 85% of the total genetic variation. It is believed that the low level of differentiation of regional population groups contradicts their race status and suggests a recent origin of humans from one ancestral population. The results of studies of various genetic systems are in agreement with last conclusion rejecting the hypothesis of regional continuity. According to this hypothesis, the populations of continents regarded as large races have developed during long evolution from local types of archaic humans, in particular, Neanderthals. Phenotypic similarity of different, sometimes unrelated, populations united into one "race" is explained by strong selection since race-diagnostic traits characterize body surface and thus are directly subjected to the influence of environmental (primarily climatic) factors. It has been recently established that variability of the most important of these traits, body and hair pigmentation, is largely controlled by one locus (MC1R), which accounts for its high evolutionary lability. Other traits used for race identification are also likely to be labile and controlled by major genes. However, the fact that the currently existing race classifications are groundless does not mean that such classifications are impossible in principle. Commonly used argumentation (races do not exist because populations are not genetically separated) does not hold water. A polytypic species is characterized by genetic continuity of allopatric populations rather than the presence of narrow genetic boundaries between them. Borderlines between races are usually conventional and arbitrary. As to intergroup variation in humans, it is indeed low but comparable with that in some other species. There are no obstacles to the development of genetic systematics of human races.

Biological Evolution↗
PubMedDate not supplied

Hormones in mammalian evolution.

Animals that produced increased levels of prolactin and dehydroepiandrosterone (DHEA) survived the period of mass extinctions at the end of the Cretaceous period. DHEA increases thermogenesis and supported existence through the extended episode of cold and dark. Further increases in DHEA and prolactin produced continual physiological and anatomical changes which eventually produced all of the characteristics of mammals.

Animals↗
PubMed1987

Optimised analysis of tamoxifen and its main metabolites in the plasma and cytosol of mammary tumours.

Recent biochemical and pharmacological findings concerning tamoxifen (TMX) have proven that both the unchanged drug and the main metabolites, N-desmethyltamoxifen (NDT) and 4-hydroxytamoxifen (4OHT) are biologically active. An HPLC method based on on-line post-column UV irradiation with fluorescence detection is described. Optimized conditions allowed complete and rapid separation of TMX 4OHT, NDT and two other recently reported metabolites, Y and Z. This method was applied to plasma and cytosol drug and metabolite analyses. In plasma, from the moment of initial drug administration until the steady state (after 1 month or more of continuous oral TMX treatment), the values of NDT to TMX ratios were completely reversed: 22 to 215 in mean %, P less than 0.01. The presence of metabolites Y and Z is significant. 4OHT, hardly detectable at the first dose, was measured at the steady state with high interpatient variability. It is hypothesized that metabolite evolution with time may be due to auto-induction of drug metabolism. In cytosols, which were all obtained during continuous TMX treatment, the ratios between TMX and metabolites were comparable to those observed in plasma, but with greater interpatient variability. Metabolite Y was not detectable in cytosols. This variability was not linked to the levels of cytosolic oestradiol receptors before initiation of treatment.

Breast Neoplasms↗