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Life arose on an early Earth which was the product to the conditions present, and processes operating, during formation of the solar system. The formation and early state of the solar system are reviewed in order to better understand the nature of the early Earth, and to constrain the conditions present during the origin and early evolution of life on this planet.
Resource use and phylogeny are often correlated with morphological variation. Moreover, because biological shapes are often complex and evolve depending on several internal constraints, they must be assessed using integrative methods. We analyzed the morphological variation of the turtle skull in the context of an adaptive radiation. Our focus are turtles of the superfamily Testudinoidea, which are remarkably diverse, both in number of species and in ecology. In this study, we depict morphological variation in the turtle skull in three dimensions with respect to diet, phylogeny, and habitat using modern geometric morphometrics. Our study revealed that morphological specialization was related to both diet and habitat. Morphological variation is decomposed in regard of both resource use (habitat and diet) and phylogeny. Feeding mode depending on environment was suggested as a key factor determining morphological evolution and diversification of turtle skulls. Diet (especially durophagy) leads to parallel morphologies in different clades. Phylogeny seemed to constrain only localized features of the skull and remained of minor influence, because overall morphotypes, closely correlated with ecological factors, occurred in both clades. In conclusion, the adaptive radiation of the Testudinoidea is revealed to demonstrate a clear relationship between the skull shape and life style.
The evolutionary history of Spalacidae is reviewed taxonomically, paleontologically and neontologically. We focused selectively on taxonomy, biogeography, paleontology and evolutionary origins, chromosomal evolution, population biology and the species concept in Spalacidae. We concluded that the taxonomy of Spalacidae needs a modern revision based on chromosome and molecular-genetic data, beside that of morphology, physiology and behavior. The subterranean Spalacidae originated probably from a muroid-cricetoid stock in Asia Minor or vicinity, in Upper Oligocene times and adaptively radiated underground in the Balkans, steppic Russia and Middle East, extending into North Africa. The major important evolutionary feature in peripatric or allopatric speciation and adaptive radiation was karyotypic evolution, primarily through Robertsonian changes. More than 30 karyotypes (2n = 38-62; NF = 72-124) earlier represented by 8 classical species, occur primarily allopatrically or parapatrically, with only marginal sympatry, across the Eastern Mediterranean range of the family. Most karyotypes represent biospecies adapted at multiple organizational levels to their different ecologies. A short overview is presented on population biology and life history parameters of the Spalacidae which result in K-selected, "equilibrium species". Speciation in action and adaptive radiation embracing molecular and organismal adptations to the subterranean unique ecotope and to four different climatic regimes, have been multidisciplinarily studied in the Israeli Spalax ehrenbergi superspecies.
We have applied the Pipas-McMahon algorithm based on free energy calculations to the search for a 5S RNA base-pair structure common to all known sequences. We find that a 'Y' shaped model is consistently among the structures having the lowest free energy using 5S RNA sequences from either eukaryotic or prokaryotic sources. Compaison of this 'Y' structure with models which have recently been proposed show these models to be remarkably similar, and the minor differences are explicable based on the technique used to obtain the model. That prokaryotic and eukaryotic 5S RNA can adopt a similar secondary structure is strong support for its resistance to change during evolution.
A series of 55 patients with B-cell chronic lymphocytic leukaemia (CLL) and prolymphocytic leukaemia (PLL) was studied in order to investigate the evolution of prolymphocytoid transformation of CLL. Peripheral blood films were assessed for the percentages of prolymphocytes (%PROL) during a followup period of 2 months to 24 years. The majority of patients with typical CLL (less than or equal to 10% PROL) had minor variations or transient increases in %PROL throughout the course of the disease, but in one third of them a steady rise in the proportion of these cells was documented. Patients presenting with 11-55% PROL, referred to as CLL/PL, exhibited three patterns of evolution: half of them showed stability of the PROL counts, one third had unsustained increases in the %PROL and 18% showed definite progression to a PLL-like blood picture. Patients diagnosed as PLL (greater than 55% PROL) had maintained a high %PROL during the period of observation. Serial marker studies in some CLL and CLL/PL cases showed that the percentage of M-rosettes and the intensity of SmIg remained at the same initial levels in all but two cases. These two cases in the CLL/PL group showed a significant decrease in the percentage of M-rosettes and stronger SmIg staining associated with progressive prolymphocytoid transformation. Patients with CLL and CLL/PL who had a sustained rise in the %PROL responded poorly to treatment compared with those with stable disease.
Genes of the major histocompatibility complex (MHC) play a critical role in immune recognition and are the most genetically diverse loci known. One hypothesis to explain this diversity postulates that pathogens adapt to common MHC haplotypes and thus favour selection of new or rare alleles. To determine whether the pathogenic yeast Cryptococcus neoformans adapts to MHC-dependent immune responses, it was serially passaged in two independent replicate lines of five B10 MHC-congenic strains and Balb/c mice. All passaged lines increased in virulence as measured by reduced host survival. MHC influenced the rate (trajectory) of virulence increase during passages as measured by significant differences in mortality rate (p < 0.001). However, when the post-passage strains were tested, no MHC differences in mortality rate remained and only minor differences in titres were observed. Also contrary to expectations, increased virulence in three lines passaged in B10 mice had a larger effect in Balb/c mice, and the evolution of virulence in lines passaged in alternating hosts was not retarded. To our knowledge, these data represent the first experimental test of MHC-specific adaptation in a non-viral pathogen. The failure to observe MHC effects despite dramatically increased virulence and host-genotype-specific adaptation to non-MHC genes suggests that escape of MHC-dependent immune recognition may be difficult for pathogens with unlimited epitopes or that other virulence factors can swamp MHC effects.
Satellites visible in female but not in male DNA were isolated from the snakes Elaphe radiata (satellite IV, p = 1.708 g x cm-3) and Bungarus fasciatus (BK1 minor, p = 1.709 g x cm-3). The satellites cross hybridize. Hybridization of 3H labelled nick translated BK minor satellite DNA with the total male and female DNA and/or chromosomes in situ of different species of snakes revealed that its sequences are conserved throughout the snake group and are mainly concentrated on the W chromosomes. Snakes lacking sex chromosomes do possess related sequences but there is no sex difference and visible related satellites are absent. The following conclusions have been reached on the basis of these results. 1. The W chromosome associated satellite DNA is related to similar sequences scattered in the genome. 2. The origin and increment in the number of the W satellite DNA sequence on the W chromosome is assoicated with the heterochromatinization of the W. 3. Satellite sequences have become distributed along the length of the W and resulted in morphological differentiation of sex chromosomes. 4. Evolutionary conservation of W satellite DNA strongly suggests that functional constraints may have limited sequence divergence.
We present a case of pleomorphic adenoma of the soft palate parapharyngeal, which is removed using transoral approach with the addition of lateral cervicotomy to control of the great vessels. We remark the unusual location, its large size and we analyse the treatment and evolution.
In addition to the genes for classical H-2 antigens, the H-2 complex of the mouse contains numerous homologous genes belonging to several distinct families. It is not known whether they have any functions. To address this question, I have investigated whether these genes are separately conserved in evolution. Subcloned 5' gene segments, encoding the variable domains, were used as hybridisation probes on genomic DNA blots of various mammals. Only the largest gene family, which includes the classical H-2/HLA genes, is detectable in humans and other mammals. The other gene families, including Qa-2 and T1a, are not conserved even in rodents. Most or all of their coding sequences are therefore redundant.
The sequences of the four larger proteins of rotavirus group C (Cowden strain) are presented and compared with the sequences of the corresponding group A proteins. They exhibit a significant level of homology, allowing gene coding assignment for the group C rotavirus. The coding strategy of the group C virus RNA segment is the same as that for the group A large segments as one long open reading frame is present in each segment. The genome segment 1 encodes the structural protein VP1 which presents the RNA-dependent RNA polymerase consensus motifs. The VP1 protein is the most highly conserved between the rotaviruses of groups A and C. The genome segment 2 encodes the VP2 protein. The deduced protein sequence does not present the putative leucine zippers identified in the group A protein but its amino terminal is hydrophilic and highly charged as previously noted for the group A protein. The genome segment 3 encodes for a protein homologous to the group A outer capsid protein VP4. As observed among the various group A sequences, the amino terminal is the region presenting the fewest similarities. A cleavage region and a putative fusion motif similar to those present in the group A viruses have been identified. For this protein the comparison has been extended to the IDIRV [corrected] VP3 previously sequenced and indicates that groups A and C VP4 proteins are much more related to each other than to the group B equivalent. The genome segment 4 encodes for a protein showing an approximate 40% sequence identity to the minor core protein, VP3, of the group A rotavirus. This remarkable conservation of primary structures argues for severe functional constraint on the evolution of these proteins.
A comprehensive analysis of volatiles in the Chicxulub impact strongly supports the hypothesis that impact-generated sulfate aerosols caused over a decade of global cooling, acid rain, and disruption of ocean circulation, which contributed to the mass extinction at the Cretaceous/Tertiary (K/T) boundary. The crater size, meteoritic content of the K/T boundary clay, and impact models indicate that the Chicxulub crater was formed by a short period comet or an asteroid impact that released 0.7-3.4 x 10(31) ergs of energy. Impact models and experiments combined with estimates of volatiles in the projectile and target rocks predict that over 200 gigatons (Gt) each of SO2 and water vapor, and over 500 Gt of CO2, were globally distributed in the stratosphere by the impact. Additional volatiles may have been produced on a global or regional scale that formed sulfate aerosols rapidly in cooler parts of the vapor plume, causing an early, intense pulse of sulfuric acid rain. Estimates of the conversion rate of stratospheric SO2 and water vapor to sulfate aerosol, based on volcanic production of sulfate aerosols, coupled with calculations of diffusion, coagulation, and sedimentation, demonstrate that the 200 Gt stratospheric SO2 and water vapor reservoir would produce sulfate aerosols for 12 years. These sulfate aerosols caused a second pulse of acid rain that was global. Radiative transfer modeling of the aerosol clouds demonstrates (1) that if the initial rapid pulse of sulfate aerosols was global, photosynthesis may have been shut down for 6 months and (2) that for the second prolonged aerosol cloud, solar transmission dropped 80% by the end of first year and remained 50% below normal for 9 years. As a result, global average surface temperatures probably dropped between 5 degrees and 31 degrees K, suggesting that global near-freezing conditions may have been reached. Impact-generated CO2 caused less than 1 degree K greenhouse warming and therefore was insignificant compare to the sulfate cooling. The magnitude of sulfate cooling depends largely upon the rate of ocean mixing as surface waters cool, sink, and are replaced by upwelling of deep ocean water. This upwelling apparently drastically altered ocean stratification and circulation, which may explain the global collapse of the delta 13C gradient between surface and deep ocean waters at the K/T boundary.
9-Diazofluorene, on treatment with stoichiometric or substoichiometric amounts of quaternary ammonium hydroxide or methoxide or of potassium t-butoxide in solution in aqueous or alcoholic dimethyl sulfoxide or acetonitrile at 30 degrees C, decomposes with evolution of nitrogen to yield fluorenone azine [bis(fluorenylidene)hydrazine] in almost quantitative yield. Studies are reported of the identity of the minor by-products, together with an examination of the kinetics of the reactions and additional spectroscopic experiments. The general rate equation is v = k[FIN2]3/2[Nu-]1/2, where Nu- represents the nucleophile. It is concluded that the oxyanions, most probably after nucleophilic attack on 9-diazofluorene under these basic conditions to generate a new anionic species, are capable of transferring an electron to the diazo-compound. This initiates decomposition of further diazo-molecules in a process of electron-transfer chain catalysis that bears some similarities to, but has also some differences from, that encountered using cathodic initiation. In support of this interpretation it is found that reactions can be accelerated by the introduction of carbon acids (fluorene, 9-phenylfluorene) into the reaction mixtures. The nature of the initiation, propagation and termination steps of the chain mechanism are discussed.
We have cloned and characterized a 9.7-kilobase EcoRI fragment of mouse DNA that contains an alpha-globin gene. The gene is encoded in at least three discontinous segments of DNA interrupted by two small intervening sequences that can be visualized as R-loop structures in the electron miscroscope. The size of the gene and its small intervening sequences fits well with the known size of the alpha-globin mRNA precursor, suggesting that these intervening sequences, like those of beta-globin, are transcribed. Partial sequence analysis indicates that the larger intervening sequence interrupts the alpha-globin gene at a site exactly corresponding to that interrupted by the larger intervening sequences in both the beta-globin major and minor genes. This observation suggests that these sequences were present when the alpha- and beta-globin genes diverged in early vertebrate evolution, more than 500 million years ago. Furthermore, though alpha and betamaj genes are encoded on different chromosomes, when their sequences are compared directly by visualization of heteroduplex structures, only one 150- to 200-base-pair segment of homology is recognized. These homologous sequences are located on the 3'-flanking segments of both genes, about 1.5 kilobases from each.
There is much controversy on the contribution of NADP-dependent glutamate dehydrogenase (NADP-GDH) in NH4+ assimilation in ectomycorrhizal (ECM) fungi and ectomycorrhizas. Experiments reported here provide information on the dispensability of NADP-GDH in various ectomycorrhizal isolates. Glutamate dehydrogenase and glutamine synthetase (GS) enzyme activities were measured on mycelia grown under various nitrogen (N) conditions. The contribution of GDH in ammonium assimilation was further estimated by following 15N incorporation from (15NH4)2SO4 into glutamate, when GS was inhibited by phosphinothricin. Finally, gene amplification on cDNA and genomic DNA was performed using degenerated primers. Two groups of fungi could be distinguished. The GDH+ fungi include Hebeloma cylindrosporum-like fungi, which possess a functional NADP-GDH. The GDH- fungi include Paxillus involutus-like fungi for which the NADP-GDH activity, as well as the GDHA transcripts, were not detected, whatever the growth condition. All the results are consistent with the dispensability of the NADP-GDH function in ECM fungi, suggesting a minor role in ammonium assimilation in ectomycorrhizal fungi. We hypothesize that the lack of a functional NADP-GDH could be an evolutive adaptation in relation to the ecological niche of ECM fungi, rather than a transitional regulation in response to changes in N contents of the extracellular medium.
We evaluated 54 patients with different right heart by-pass by means of contrast echocardiography with rapid venous injection of shaken saline (3 cc, < 20 k; 6cc, > 20 k), in order to detect venous collateral circulation in partial by-pass, pulmonary arteriovenous fistulae in partial and total by-pass, and right-to-left shunt in total by-pass. Forty three patients had partial by-pass: 29 had a bidirectional cavopulmonary anastomosis with additional pulmonary flow (systemic-pulmonary anastomosis and/or restrictive anterograde ventricular flow); 10 had a partial ventricular correction (bidirectional cavopulmonary anastomosis and non restrictive anterograde ventricular flow; two had classical Glenn procedures; two had Kawashima operations (bidirectional cavopulmonary anastomosis and non restrictive anterograde ventricular flow; two had classical Glenn procedures; two had kawashima operations (bidirectional cavopulmonary anastomosis with inferior vena cava interruption), and 11 with total by-pass (10 atriopulmonary anastomosis and 1 with total cavopulmonary anastomosis). The age ranged from 2.5 to 33 years (x = 12.2 years), and the mean postoperative period was 4.3 years. Venous collateral circulation: 32/43 patients (74%) with partial by-pass, specially in those without partial biventricular correction: 29/33 patients (88%) compared to those with partial biventricular correction: 3/10 (30%) p < 0.01. Pulmonary arteriovenous fistulae: 6/43 patients (14%) with partial by-pass; 6/33 (18%) with partial biventricular correction, 0/10 patients with partial biventricular correction, and 0/11 with total by-pass. Right-to-left shunt: 2/11 patients (18%) with total by-pass, all of them with atriopulmonary anastomosis. Contrast echocardiography is an excellent noninvasive method for the initial evaluation of specific dysfunctions of different right heart by-pass. We emphasize the higher frequency of collateral venous circulation in cavopulmonary anastomosis, that would explain the dysfunction with progressive hypoxia in the evolution of these patients. Pulmonary arteriovenous fistulae were detected only in partial by-pass, without partial biventricular correction (p < 0.01). The minor frequency of these fistulae in bidirectional cavopulmonary anastomosis would be due to additional pulmonary flow.
Seventy one patients were treated with mepartricin or placebo in three urological centres for a mean duration of 102 days (extremes: 60 and 142 days). An analysis of the results was carried out for 34 patients in the placebo group and 36 patients in the mepartricin group. The results indicate a significant improvement in both the placebo group and the mepartricin group. The irritative and obstructive symptoms are improved in the active treatment group with a response rate of the order of 70%, compared to approx. 45% in the placebo group. An improvement of the values on the flow meter, though not statistically significant, is observed following treatment with mepartricin, compared to the placebo group. There were no significant differences in the evolution of the prostate gland volume, determined by ultrasound in the placebo group and the active treatment group. Side-effects were minor and only one patient reported epigastric pain.
Salmonellosis are still endemic in Ivory Coast. In 1975 they were responsible for 1,75 p. 100 of the admittances in the pediatric department of Treichville University Hospital. In children, the conventional distinction between major and minor salmonellosis is not always obvious. Interpretation of Widal sero-diagnosis is often difficult and awkward. Chloramphenicol generally leads to satisfactory evolution. Salmonellosis are still a problem for Public Health Service. Immunization, is the only effective prophylaxis, but is not carried out yet in Ivory Coast.
As the HIV/AIDS epidemic neared the end of its first decade in the late 1980s, the US Centers for Disease Control and Prevention (CDC) recognized the disparate impact on racial and ethnic minority communities. In response, a program was initiated to build capacity to prevent the further spread of HIV and other STDs in these communities. Since that time, the program has expanded in scope, intensity of efforts, and funding. Today, the CDC's Capacity Building Assistance (CBA) Initiative serves communities across the nation by building community, organizational, and HIV prevention program/intervention capacity designed to reduce the number of new HIV infections among at-risk populations. This article focuses on the history and evolution of these efforts, lessons learned, and how these were used to develop the current, more responsive system. A conceptual framework is presented that describes the taxonomy of CBA services designed to (1) enhance organizational infrastructure; (2) enhance HIV prevention interventions; (3) strengthen community capacity; and (4) strengthen community planning. It includes language and definitions, approaches and mechanisms for delivering capacity-building services, and a Web-based request-and-referral system that serves as the foundation for tracking, monitoring, and ensuring the delivery of appropriate, efficient, and culturally competent CBA.