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PubMed2001

Pericentromeric organization at the fusion point of mouse Robertsonian translocation chromosomes.

In mammals, Robertsonian (Rb) translocation (the joining of two telo/acrocentric chromosomes at their centromere to form a metacentric) is the most effective process in chromosomal evolution leading to speciation; its occurrence also affects human health (through the induction of trisomies) and the fertility of farm animals. To understand the mechanism of Rb translocation, we used the house mouse as a model system and studied the organization of pericentromeric satellite DNAs (satDNA) of telocentrics and Rb chromosomes, both minor and major satDNA. The chromosome-orientation fluorescence in situ hybridization (CO-FISH) technique was used to analyze the major satDNA. To detect the very small amount of minor satDNA, a procedure was developed that combines CO-FISH with primed in situ labeling and conventional FISH and is five times more sensitive than the CO-FISH procedure alone. It was found that both the major and the minor satDNA tandem repeats are oriented head-to-tail in telocentric and Rb chromosomes, and their polarity is always the same relative to the centromere. We suggest that all tandemly repetitive satDNAs in a species probably are locked into such a symmetry constraint as a universal consequence of chromosomal evolution. Rb translocation breakpoints were found localized within the minor satDNA of telocentrics, and these sequences contributed symmetrically to the formation of the centromeric region of the Rb chromosomes. These results are important for an understanding of the geometry of Rb translocations and suggest the study of DNA orientation as a new tool for investigating these rearrangements.

Animals↗
PubMed1998

The complete nucleotide sequence of a snake (Dinodon semicarinatus) mitochondrial genome with two identical control regions.

The 17,191-bp mitochondrial DNA (mtDNA) of a Japanese colubrid snake, akamata (Dinodon semicarinatus), was cloned and sequenced. The snake mtDNA has some peculiar features that were found in our previous study using polymerase chain reaction: duplicate control regions that have completely identical sequences over 1 kbp, translocation of tRNALeu(UUR) gene, shortened TpsiC arm for most tRNA genes, and a pseudogene for tRNAPro. Phylogenetic analysis of amino acid sequences of protein genes suggested an unusually high rate of molecular evolution in the snake compared to other vertebrates. Southern hybridization experiments using mtDNAs purified from multiple akamata individuals showed that the duplicate state of the control region is not a transient or unstable feature found in a particular individual, but that it stably occurs in mitochondrial genomes of the species. This may, therefore, be regarded as an unprecedented example of stable functional redundancy in animal mtDNA. However, some of the examined individuals contain a rather scanty proportion of heteroplasmic mtDNAs with an organization of genes distinct from that of the major mtDNA. The gene organization of the minor mtDNA is in agreement with one of models that we present to account for the concerted evolution of duplicate control regions.

Amino Acid Sequence↗
PubMed1999

The Effect of Cholesterol on the Solution Structure of Proteins of Photosystem II. Protein Secondary Structure and Photosynthetic Oxygen Evolution.

Cholesterol induces large perturbations in the physical properties of membranes, especially in the structural organization of the phospholipid bilayers and the aggregation and solubility of proteins at physiological temperatures. This study was designed to examine the interaction of cholesterol with lipid and proteins of chloroplasts photosystem II (PSII) submembrane fractions in air dried film at pH 6-7 with cholesterol concentrations of 0.01 to 20 mM. Fourier transform infrared difference spectroscopy with its self-deconvolution and second derivative methods as well as curve-fitting procedures are used, in order to determine the cholesterol binding mode, the protein conformational changes, and the structural properties of cholesterol-protein complexes. Correlations between the effect of cholesterol on the protein secondary structure and the rate of oxygen evolution in PSII are also established. Spectroscopic evidence showed that at low cholesterol concentration (0.01 and 0.1 mM), minor chol-protein and chol-lipid interactions (through hydrogen bonding) occur with no major perturbations of the protein secondary structure. As cholesterol concentration increases (5 and 10 and 20 mM), major alterations of the protein secondary structure are observed from that of the alpha-helix 47% (uncomplexed protein) to 43-39% (complexes) and the beta-sheet structure 18% (uncomplexed protein) to 22-26% (complexes). Those changes coincide with a partial decrease in the rate of the oxygen evolution (8-33%) is observed in the presence of cholesterol at high concentration. Copyright 1999 Academic Press.

Journal Article↗
PubMed1994

Darwinian evolution patterns in food products and beverages.

Although the development and survival of food products are regulated by mechanisms that bear little resemblance to those operating in the living world, their general evolutionary patterns share certain common features. These include punctuated equilibria, convergent evolution, the coevolution, the equivalence of symbiosis, and, rarely, even parasitism. The evolution of food products, like that of living organisms and other systems, is a nonlinear process. Consequently, its path can be affected not only by major events that drastically alter the environment but also by very minor events that may be unnoticeable at the time of their occurrence.

Animals↗
PubMed2002

Convergent maternal provisioning and life-history evolution in echinoderms.

In marine invertebrates, the frequent evolution of lecithotrophic nonfeeding development from a planktotrophic feeding ancestral developmental mode has involved the repeated, independent acquisition of a large, lipid-rich, usually buoyant egg. To investigate the mechanistic basis of egg-size evolution and the role of maternally provisioned lipids in lecithotrophic development, we identified and quantified the egg lipids in six sea urchin species and five sea star species encompassing four independent evolutionary transformations to lecithotrophy. The small eggs of species with planktotrophic development were dominated by triglycerides with low levels of wax esters, whereas the larger eggs of lecithotrophs contain measurable triglycerides but were dominated by wax ester lipids, a relatively minor egg component of planktotrophs. Comparative analysis by independent contrasts confirmed that after removing the influence of phylogeny, the evolution of a large egg by lecithotrophs was correlated with the conspicuous deposition of wax esters. Increases in wax ester abundance exceeded expectations based solely on changes in egg volume. Wax esters may have roles in providing buoyancy to the egg and for postmetamorphic provisioning. Experimentally reducing the amount of wax esters in blastula stage embryos of the lecithotroph Heliocidaris erythrogramma resulted in a viable but nonbuoyant larvae. During normal development for H. erythrogramma, wax ester biomass remained constant during development to metamorphosis (five days postfertilization), but decreased during juvenile development before complete mouth formation (12 days postfertilization) and was further reduced at 18 days postfertilization. The function of wax esters may be specific to the lecithotrophic developmental mode because there were negligible wax esters present in competent pluteus larvae of Strongylocentrotus drobachiensis, a planktotrophic species. These data suggest that this seminal evolutionary modification, the production of a large egg, has been accomplished in part by the elaboration of a preexisting oogenic component, wax esters. The modification of preexisting oogenic processes may facilitate the observed high frequency of transformations in larval mode in marine invertebrates.

Animals↗
PubMed1986

Somatosensory cortical representation in the Australian ghost bat, Macroderma gigas.

Bats of the two suborders Microchiroptera and Megachiroptera have a modified hand in which the digits of the forelimb are caudally oriented to form the wing. In a previous study of a megachiropteran species, this modification of body plan was found to be reflected in the somatosensory cortical representation such that the orientation of the digit representation was reversed compared with walking mammals. This finding suggests that the precise details of arrangement of topographical maps are functionally significant and do not merely reflect an order imposed by peripheral innervation. Recent evidence for separate origins of Microchiroptera and Megachiroptera raises the question of whether the cortical somatosensory representation in Microchiroptera will also have a reversal of digit orientation compared with walking mammals. We recorded multiunit activity from the somatosensory cortex of a microchiropteran bat, Macroderma gigas. We found two orderly representations of the body surface, SI and SII, in both of which the digit orientation was opposite to the head orientation in accordance with adaptation for flight, and reversed with respect to equivalent maps in other mammals. We also found minor variations in body surface representation compared with Megachiroptera, in line with their proposed independent evolution.

Animals↗
PubMed1998

Conflict among individual mitochondrial proteins in resolving the phylogeny of eutherian orders.

The phylogenetic relationship among primates, ferungulates (artiodactyls + cetaceans + perissodactyls + carnivores), and rodents was examined using proteins encoded by the H strand of mtDNA, with marsupials and monotremes as the outgroup. Trees estimated from individual proteins were compared in detail with the tree estimated from all 12 proteins (either concatenated or summing up log-likelihood scores for each gene). Although the overall evidence strongly suggests ((primates, ferungulates), rodents), the ND1 data clearly support another tree, ((primates, rodents), ferungulates). To clarify whether this contradiction is due to (1) a stochastic (sampling) error; (2) minor model-based errors (e.g., ignoring site rate variability), or (3) convergent and parallel evolution (specifically between either primates and rodents or ferungulates and the outgroup), the ND1 genes from many additional species of primates, rodents, other eutherian orders, and the outgroup (marsupials + monotremes) were sequenced. The phylogenetic analyses were extensive and aimed to eliminate the following artifacts as possible causes of the aberrant result: base composition biases, unequal site substitution rates, or the cumulative effects of both. Neither more sophisticated evolutionary analyses nor the addition of species changed the previous conclusion. That is, the statistical support for grouping rodents and primates to the exclusion of all other taxa fluctuates upward or downward in quite a tight range centered near 95% confidence. These results and a site-by-site examination of the sequences clearly suggest that convergent or parallel evolution has occurred in ND1 between primates and rodents and/or between ferungulates and the outgroup. While the primate/rodent grouping is strange, ND1 also throws some interesting light on the relationships of some eutherian orders, marsupials, and montremes. In these parts of the tree, ND1 shows no apparent tendency for unexplained convergences.

Animals↗
PubMed1986

The group selection of variola minor in the Americas: an anthroponootic analogue for the myxomatosis epizootic in Australia.

It is an axiom of many parasitology texts that host-parasite systems coevolve toward a state approximating commensalism. While this hypothesis has an apriori intuitive appeal there is little empirical evidence to support it. The only documented case of a parasite evolving toward avirulence is the group selection of less virulent strains of the myxoma virus in the Australian rabbit population. It is hypothesized here that group selection also accounted for the appearance of variola minor in the Americas.

Americas↗
PubMed2005

Detection of hepatitis B virus genotypes and mutants: current status.

Characterization results of the hepatitis B virus (HBV) genome before, during and after antiviral treatment have changed in the last year for a number of reasons. First of all, with the introduction of more nucleoside and nucleotide antiviral therapies, it has become clear that variants or mutants do emerge in time. Viral genomic changes in the HBV polymerase gene can result in a direct antiviral effect, but compensatory mutations can also be identified during prolonged treatment periods. Furthermore, there is an increasing number of reports suggesting that HBV genotypes can be related to, for example, disease progression or the effect of antiviral treatment itself (alpha-interferon or lamivudine). Combined with HBV DNA viral load monitoring, an increase in viral load or a limited reduction during treatment is indicative of genomic changes related to resistance. However, these genomic changes can also be present in the absence of an increase in HBV DNA. Methodologies for the detection of these variants, as well as the determination of genotypes, are rather straightforward. Sequence analysis is time-consuming and expensive, but provides the most information, particularly if not all information on mutations related to antiviral resistance is known. However, the sensitivity of direct sequencing for the presence of minor variant populations is poor, and no mixtures of variant populations are, in general, detected. The ability to detect minor populations and, if possible, even quantify them, gives more insightful information on the dynamic evolution of the virus itself. Antiviral treatment can result in the appearance of more than one population of variants, which can be present for a prolonged period of time, and even remain undetected with current technologies. However, screening specifically for these variant populations before starting treatment for so-called untreated patients (who have received no antiviral treatment for, e.g., 6 months) has already shown that the effects of treatment can be biased. Furthermore, the detection of more dynamic viral populations - including both wild-type and resistant variants - during, but also after therapy, does provide helpful information in the analysis of virological data. Technologies enabling the detection and quantification of these variant populations are presented and discussed.

Antiviral Agents↗
PubMed2005

Fluorescence probing investigation of the mechanism of formation of MSU-type mesoporous silica prepared in fluoride medium.

The mechanism of formation of a MSU-type siliceous material from tetraethyl orthosilicate (TEOS) in the presence of the nonionic surfactant tergitol T-15-S-12, sulfuric acid, and sodium fluoride has been investigated using mainly fluorescence probing techniques and, to a lesser extent, dynamic light scattering (DLS) and 29Si NMR spectroscopy. The tergitol micelles present in the systems obtained by progressively generating the reaction mixture giving rise to the mesostructured material by adding to an appropriate tergitol solution sulfuric acid, TEOS, and NaF were characterized by fluorescence probing (micelle aggregation number, micropolarity, and microviscosity) and also by dynamic light scattering (apparent micelle diameter). 29Si NMR experiments were also performed on selected systems after hydrolysis of the TEOS. The fluorescence probing techniques were also used to follow the changes of micelle characteristics with time during the evolution of the full reaction mixture from a limpid solution to a system containing a minor amount of condensed siliceous material. The synthesized solid material was characterized by X-ray diffraction and nitrogen adsorption-desorption analyses. The micelle aggregation number N was found to change only little, and the micropolarity remained constant when going from the tergitol solution to the full reaction mixture. The results of DLS measurements agree with this finding. Besides, while the condensation of silica took place after addition of NaF, the N value increased only very little with time up to the point where a small amount of mesostructured material precipitated out. These results indicate that the interaction between tergitol micelles and the siliceous species formed in the system by the hydrolysis of TEOS and also between micelles and the growing siliceous species must be very weak. As in our previous studies of the mechanism of formation of MCM41-type material from sodium silicate in the presence of cetyltrimethylammonium bromide, it appears that the locus of formation of the mesostructured material is not the micelle surface but the bulk phase. Micelles only act as reservoirs of surfactant providing surfactant monomer that binds to the growing siliceous species.

Journal Article↗
PubMed1999

The high-dose sequential (Milan) chemotherapy/PBSC transplantation regimen for patients with lymphoma is not cardiotoxic.

BACKGROUND: The high-dose sequential (HDS) regimen developed in Milan for high-grade lymphomas is very active, but its toxicities are still partly unknown. We evaluated prospectively by doppler-echocardiography the cardiotoxicity of this treatment. PATIENTS AND METHODS: Over seven weeks, 20 patients received a sequence of cyclophosphamide, methotrexate, etoposide, mitoxantrone and melphalan, each at its maximum tolerable dose, and the latter in conjunction with autologous peripheral stem-cell transplantation. Echocardiography was performed at baseline, before administration of mitoxantrone and 2, 6 and 12 months after transplantation. The following parameters of the left ventricular systolic and diastolic functions were determined: end diastolic (LVD) and end systolic (LVS) dimensions, the ejection fraction (EF), and the Doppler derived diastolic parameters: peak velocity of the early (E) and late (A) transmitral flow, the E:A ratio, deceleration time of the E wave (DT) and isovolumetric relaxation time (IVRT). A group of 20 normal volunteers served as control. RESULTS: At baseline, in comparison to controls, the patients had altered diastolic function (diminished E:A ratio) and, although still within the normal range, a slightly reduced systolic function (EF). During treatment or in the course of follow-up none of the patients showed clinical signs or symptoms of cardiac failure, nor significant changes of systolic or diastolic parameters, apart from a transient increase in the E:A ratio after the first three chemotherapy cycles (from 1.14 to 1.37, P < 0.05). The EF remained constant during, and up to six months after, transplantation, decreasing only slightly after one year (from 62% to 59%, P < 0.05). Using analysis of covariance we showed that the major determinants of baseline cardiac function and of its evolution over time were patient age and gender, with previous treatment with anthracyclines having a minor role. CONCLUSIONS: The HDS chemotherapy regimen produced no significant sign of cardiotoxicity up to one year after transplantation in patients with normal baseline cardiac function and no history of cardiac disease, pretreated with up to 550 mg/m2 of doxorubicin.

Adult↗
PubMed1995

Pancreaticoduodenectomy in childhood for rare pancreatic ductal anomalies--case reports.

In the past 9 years, 3 children suffering rare pancreatic disorders have undergone cephalic pancreaticoduodenectomy (Whipple procedure) required after the failure of initial conservative treatments. Ductal anomalies such as pancreas divisum or predominant Santorini duct can be managed conservatively (especially by papillotomy of the minor papilla), unless the extent of the fibrotic lesions of the pancreas jeopardizes the final evolution of the pancreatic disease. Intrapancreatic gastric duplications remain extremely rare. Even to-day, diagnosis was made only on pathologic specimens after radical surgery. Better knowledge of this rare pathology, with emphasis on its radiological features, may help better assessment. Hemoductal pancreatitis is evocative of the coexistence of gastric duplication and pancreatic aberrant duct. However, when fibrotic and necrotic changes in the duodenopancreatic region are considerable, assessment of this anomaly becomes difficult. Radical though it is, pancreaticoduodenectomy may be necessary to treat cephalic pancreatic lesions in childhood after the failure of reasonable attempts of conservative treatment.

Child, Preschool↗
PubMed2004

Chemistry of rocks and soils in Gusev Crater from the alpha particle x-ray spectrometer.

The alpha particle x-ray spectrometer on the Spirit rover determined major and minor elements of soils and rocks in Gusev crater in order to unravel the crustal evolution of planet Mars. The composition of soils is similar to those at previous landing sites, as a result of global mixing and distribution by dust storms. Rocks (fresh surfaces exposed by the rock abrasion tool) resemble volcanic rocks of primitive basaltic composition with low intrinsic potassium contents. High abundance of bromine (up to 170 parts per million) in rocks may indicate the alteration of surfaces formed during a past period of aqueous activity in Gusev crater.

Alpha Particles↗
PubMed1994

Effects of sieving, storage, and incubation temperature on the phospholipid Fatty Acid profile of a soil microbial community.

Disturbances typically associated with the study of soil microbial communities, i.e., sieving, storage, and subsequent incubation at elevated temperatures, were investigated with phospholipid fatty acid (PLFA) analyses. Treatment effects were quantified by statistical analyses of the mole percentage distribution of the individual fatty acids. Changes in the concentrations of individual fatty acids over a 7-week storage period at 4.5 degrees C were generally not statistically significant. Sieving effects (mesh size, 4 or 2 mm) on CO(2) evolution and the PLFA profile were monitored over 3 weeks; the physical disturbance had only minor effects, although some damage to fungal hyphae by the first sieving (<4 mm) was suggested by a decrease in the signature fatty acid 18:2 omega6c. Temperature effects were investigated by incubating soil for up to 3 weeks at 4.5, 10, or 25 degrees C. Principal component analyses demonstrated a significant shift in the PLFA composition at 25 degrees C over the first 2 weeks, while changes at the other two temperatures were minor. Several of the changes observed at 25 degrees C could be explained with reference to mechanisms of temperature adaptation or as a response to conditions of stress, including a decrease in the degree of unsaturation, an increased production of cyclopropyl fatty acids, and increased ratios of the branched-chain fatty acids iso-15:0 and iso-17:0 over anteiso-15:0 and anteiso-17:0, respectively. A decrease in the total amount of PLFA was also indicated.

Journal Article↗
PubMed2003

Strategies to create and sustain a diverse faculty and student body at the Boston University School of Dental Medicine.

The challenges and opportunities inherent in creating and sustaining a diverse student body and a diverse faculty, staff, and administration are discussed in the context of the experience of the Boston University School of Dental Medicine. The role of the school's evolution as a learning organization is highlighted as an essential contributing factor to success in minority recruitment and retention efforts.

Boston↗
PubMedDate not supplied

[A comparative study of the euthanasia laws of Belgium and the Netherlands].

Recently, laws on euthanasia have been adopted in the Netherlands and Belgium. In both countries the legality of euthanasia is conditioned by adherence to strict conditions and by confirmation after a notification procedure. Although both laws are rather similar, the Belgian law is more fastidious on the requirements of prudent practice. The Belgian law does and the Dutch law does not distinguish between terminal conditions and non-terminal or slowly evolutive chronic conditions. In Belgium, the law only applies to adults, whereas in the Netherlands, minors over 12 years of age may under certain conditions receive euthanasia. However, the Belgian National Medical Disciplinary Board has recently mitigated differences by drafting guidelines which reflect a broad interpretation of the law. A major difference between the two countries is that in the Dutch society the norm setting on euthanasia developed more through jurisprudence and endorsement by the Medical Association than through legislation. We anticipate that the implementation of the new law and the notification procedure may be more difficult in Belgium than in the Netherlands. In order to promote the quality of the euthanasia practice, the euthanasia notification procedure in the Netherlands is followed by systematic feedback to the physicians. The strict anonymity of the Belgian notification procedure will be broken only when the control commission finds some anomaly or deficiency in the declaration. Therefore, unless the Evaluation and Control Commission makes ample use of its prerogative to contact the physician, the Belgian physicians may be less supported by the notification procedure to improve their knowledge and skills in euthanasia.

Belgium↗
PubMed1984

Studies on the mung bean trypsin inhibitor--reduction and reoxidation of the disulfide bonds of the Lys active fragment.

Two peptide chains A1 and A2 of the Lys active fragment, linked via a couple of inter-disulfide bonds, could be separated from each other after reduction with dithiothreitol and gel filtration on Sephadex G-25. Reoxidation of the reduced peptide chain A1 resulted in recovering the inhibitory activity with 25% yield, based on the original activity of the Lys fragment. The A1 active fragment was further purified by affinity chromatography with immobilized trypsin. Sephadex G-25 gel filtration produced two forms of the A1 active fragment, the major fraction being a monomer and the minor one being a dimer with lower activity. The results obtained offered evidence of the evolution of mung bean inhibitor from an ancestral single-headed inhibitor by fused gene duplication with A2 as a connecting peptide. The CD spectra of the Lys fragment and the reoxidized peptide chain A1 were also compared.

Amino Acids↗
PubMed2004

Evolution and migration history of the Chinese population inferred from Chinese Y-chromosome evidence.

Y-chromosomes from 76 Chinese men covering 33 ethnic minorities throughout China as well as the Han majority were collected as genetic material for the study of Chinese nonrecombinant Y-chromosome (NRY) phylogeny. Of the accepted worldwide NRY haplogroups, three (haplogroups D, C, O) were significant in this sample, extending previous assessments of Chinese genetic diversity. Based on geographic, linguistic, and ethnohistorical information, the 33 Chinese ethnic minorities in our survey were divided into the following four subgroups: North, Tibet, West, and South. Inferred from the distribution of the newly found immediate ancestor lineage haplogroup O*, which has M214 but not M175, we argue that the southern origin scenario of this most common Chinese Y haplogroup is not very likely. We tentatively propose a West/North-origin hypothesis, suggesting that haplogroup O originated in West/North China and mainly evolved in China and thence spread further throughout eastern Eurasia. The nested cladistic analysis revealed in detail a multilayered, multidirectional, and continuous history of ethnic admixture that has shaped the contemporary Chinese population. Our results give some new clues to the evolution and migration of the Chinese population and its subsequence moving about in this land, which are in accordance with the historical records.

Biological Evolution↗