Prevalence, epidemiology and geographical distribution of Sporothrix schenckii infections in Gauteng, South Africa

Forces exerted on the right and left lingual and buccal flanges of Kennedy Type I mandibular dentures were studied using an 8 channel recording technique, during resting, swallowing, talking, reading and simulated mastication. The effects of adaptation, head position and incremental thickening of the flanges were determined. Highest forces were recorded when swallowing, with smaller differences between the other activities. Lingual forces were higher than buccal, and posterior forces higher than anterior ones. There was a highly significant relationship between increases in flange thickness of 2 and 3mm and increases in peak forces. Evidence for adaptation and effects related to head position was weaker.     

Molecular evolution of olfactomedin

Olfactomedin is a secreted polymeric glycoprotein of unknown function, originally discovered at the mucociliary surface of the amphibian olfactory neuroepithelium and subsequently found throughout the mammalian brain. As a first step toward elucidating the function of olfactomedin, its phylogenetic history was examined to identify conserved structural motifs. Such conserved motifs may have functional significance and provide targets for future mutagenesis studies aimed at establishing the function of this protein. Previous studies revealed 33% amino acid sequence identity between rat and frog olfactomedins in their carboxyl terminal segments. Further analysis, however, reveals more extensive homologies throughout the molecule. Despite significant sequence divergence, cysteines essential for homopolymer formation such as the CXC motif near the amino terminus are conserved, as is the characteristic glycosylation pattern, suggesting that these posttranslational modifications are essential for function. Furthermore, evolutionary analysis of a region of 53 amino acids of fish, frog, rat, mouse, and human olfactomedins indicates that an ancestral olfactomedin gene arose before the evolution of terrestrial vertebrates and evolved independently in teleost, amphibian, and mammalian lineages. Indeed, a distant olfactomedin homolog was identified in Caenorhabditis elegans. Although the amino acid sequence of this invertebrate protein is longer and highly divergent compared with its vertebrate homologs, the protein from C. elegans shows remarkable similarities in terms of conserved motifs and posttranslational modification sites. Six universally conserved motifs were identified, and five of these are clustered in the carboxyl terminal half of the protein. Sequence comparisons indicate that evolution of the N-terminal half of the molecule involved extensive insertions and deletions; the C-terminal segment evolved mostly through point mutations, at least during vertebrate evolution. The widespread occurrence of olfactomedin among vertebrates and invertebrates underscores the notion that this protein has a function of universal importance. Furthermore, extensive modification of its N-terminal half and the acquisition of a C-terminal SDEL endoplasmic-reticulum-targeting sequence may have enabled olfactomedin to adopt new functions in the mammalian central nervous system.     

Evolutionary dynamics of genetic variation in Epstein-Barr virus isolates of diverse geographical origins: evidence for immune pressure-independent genetic drift

The question whether immune pressure exerted by cytotoxic T lymphocytes (CTLs) can influence the long-term evolution of genetically stable viruses such as Epstein-Barr virus (EBV) has generated considerable scientific interest, primarily due to its important implications for the overall biology of the virus. While arguing for a role of CTLs in the evolution of viruses, it is important to differentiate between genetic variation in virus and immune recognition of these variant virus by CTLs. To assess the role of genetic selection in the long-term evolution of EBV, we have analyzed a large panel of type 1 EBV isolates from African, Southeast Asian, Papua-New Guinean (PNG), and Australian Caucasian individuals. Seven different regions of the EBV genome, which include nine CTL epitopes restricted through a range of HLA class I alleles, were sequenced and compared. Although numerous nucleotide changes were identified within these isolates, comparison of synonymous and nonsynonymous substitutions in the CTL epitope indicated that the genetic variation was generated mostly independently of immune selection pressure. Surprisingly, an inverse correlation between genetic variation within certain CTL epitopes and the frequency distribution of HLA alleles that present the CTL epitopes was seen, suggesting that the evolutionary pressures on the CTL epitopes of the virus may be toward their conservation rather than their inactivation. Furthermore, molecular evolutionary genetic analysis of nucleotide sequences revealed that viral isolates from PNG are evolving as a lineage distinct from isolates from African, Southeast Asian, and Australian Caucasian individuals.     

Molecular evolution of retinal and nonretinal opsins

Vision and the circadian rhythms of various biological functions are triggered by phototransduction. The retinal and nonretinal (pineal gland-specific) opsins are traced back to a single common ancestor. Evolutionary analyses of these opsins identify amino acid changes that are potentially important in the regulation of wavelength absorption of photosensitive molecules-visual pigments. Such theoretical predictions can now be tested experimentally using site-directed mutagenesis; expressing the mutagenized opsins in tissue culture cells, reconstituting with 11-cis retinal, and measuring the absorption spectra of the regenerated visual pigments.     

Molecular packing in virus crystals: geometry, chemistry, and biology

Recombinant human erythropoietin (EPO) and fluorescein isothiocyanate-labelled dextran (FITC-dextran) loaded biodegradable microspheres were prepared from poly(lactide-co-glycolide) (PLG) by a modified spray-drying technique. This microencapsulation method was compared with the water-in-oil-in-water (w/o/w) double-emulsion method. As expected, microsphere morphology, particle size and particle size distribution strongly depended on the production process. The spray-drying method was found to have a number of advantages compared to the w/o/w double-emulsion technique. The content of residual dichloromethane (DCM) in the final product was significantly lower in case of the microspheres prepared by spray-drying. Concerning EPO loaded microspheres, spray-drying yielded higher encapsulation efficiencies. Although the microspheres obtained by spray-drying are subjected to intensive mechanical and thermal stress during the preparation, the amount of aggregates of EPO in PLG microspheres were not increased compared to the w/o/w technique. Depending on the manufacturing method, addition of cyclic DL-lactide dimers (referred to as monomers in the following) affected the in vitro release profiles of EPO and FITC-dextran from PLG microspheres. Using differential scanning calorimetry it was shown that these low molecular weight substances only seem to be present inside the microspheres produced by spray-drying. DL-Lactide significantly reduced the initial burst release of both EPO and FITC-dextran. While the following release period of EPO was not affected by the DL-lactide content, a more linear FITC-dextran release pattern could be achieved. It can be concluded that the spray-drying technique provides a number of advantages compared to the w/o/w method. The modulation of protein release using low molecular weight additives is of particular interest for parenteral depot systems.     

Molecular biology and evolution of resistance of toxicants

To the prevailing biochemical/physiological classification of mechanisms of organismal resistance to toxicants, an additional molecular dimension is proposed. Predictions are developed regarding the relative prevalence of different classes of mutations and are found to compare favorably with reports from the literature. In particular, point mutations in target loci were the dominant form of resistance for both lab and field selection. Amplifications of target loci were less common than structural mutations, and more common for lab-selected than for field-selected strains. Amplification was the most common mechanism of up-regulation of metabolizing enzymes. In comparison, only one mutation involving cis-regulation and several involving trans-acting regulation were found. Mutations involving gene disruption and down-regulation were uncommon, but were found in appropriate cases, i.e., when toxicants stimulated rather than inhibited target function and when metabolizing enzymes converted toxicants into more toxic metabolites. Additional phenomena of likely but uncertain importance are genetic "succession," recombinational limitation, and negative cross-resistance. More work on these phenomena and on quantification of fitness costs of resistance is recommended.     

Cooperative breeding and monogamy in prairie voles: influence of the sire and geographical variation

Mammalian monogamy is characterized by pair bonding and a relative absence of sexual dimorphism in body size. Alloparental behaviour is a characteristic of mammalian cooperative breeding systems. Studies of prairie voles, Microtus ochrogaster, from stock captured in a resource-abundant habitat in Illinois have supported the assumption that this species is a monogamous, cooperative breeder, while other studies of prairie voles from a more arid habitat in Kansas have called this assumption into question. We hypothesized that reported differences between these populations represented true intraspecific variation. Patterns of sexual dimorphism in body size, partner preferences and parental contact behaviour were compared in prairie voles from stocks originating in Illinois or Kansas. Both Illinois and Kansas voles showed a strong preference for a familiar partner, which is suggestive of monogamy. Sexual dimorphism in body size was observed in Kansas, but not Illinois voles. Illinois voles displayed significantly higher levels of parental contact behaviour than did voles from Kansas. When animals from Illinois and Kansas were crossed, the expression of parental contact behaviour of the 'hybrid' offspring followed the pattern seen in the population of origin of the sire. Removal of the sire prior to the birth of the litter increased alloparenting in Kansas voles, but removal of the sire was associated with lower levels of alloparenting in Illinois voles. Thus, some traits associated with the social system may show intraspecific variation and can be influenced by the presence or absence of the sire during rearing. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Molecular evolution of RNA in vitro

Experimental studies of RNA evolution in vitro are reviewed in the context of Eigen's 1971 theory and its subsequent extensions. Current research activity and future prospects for using automated molecular biology techniques for in vitro evolution experiments are surveyed.     

德兴铜矿变配电网络地理信息系统设计与实践

介绍了矿山变配电地理信息系统的设计与实施。     

Analysis of the geographical distribution of anesthesia manpower in the United States

The 1970 geographical distributions of total anesthesia manpower, anesthesiologists, and nurse anesthetists by state were analyzed by multiple regression to account for their unevenness. Independent variables included factors relating to prior professional contact in the state, professional satisfaction, practice income, demand for services, and environment. The distribution of training programs accounted for 41 per cent of the variance in the distribution of total manpower, but 55 per cent was explained by the number of operations, location of nurse anesthesia schools, and proportion of total state employment in service occupations (a proxy for the availability of consumer services). Location of training programs and the absence of the other type of personnel were good predictors for the manpower subgroups. The distribution of nurse anesthesia schools, anesthesiologists, number of surgical operations, and the relative value schedule conversion factor together accounted for 60 per cent of the variance in the nurses' distribution. The location of residency programs (or positions) was a better predictor for the anesthesiologists' location than medical schools or factors characterizing the demand for services. The distribution of nurse anesthetists, hospital cost per day (considered a proxy for a satisfying professional life and for regionalization of services), and residency programs explained 81 per cent of the variance in the anesthesiologists' distribution. Although the regression predicts that increasing the number of residency programs in an underserved state should be associated with an increase the number of anesthesiologists, such a policy may be infeasible dur to pending federal health manpower legislation unless matched by decreasing a greater number of programs in relatively oversupplied states.     

Molecular evolution of the photolyase-blue-light photoreceptor family

The photolyase-blue-light photoreceptor family is composed of cyclobutane pyrimidine dimer (CPD) photolyases, (6-4) photolyases, and blue-light photoreceptors. CPD photolyase and (6-4) photolyase are involved in photoreactivation for CPD and (6-4) photoproducts, respectively. CPD photolyase is classified into two subclasses, class I and II, based on amino acid sequence similarity. Blue-light photoreceptors are essential light detectors for the early development of plants. The amino acid sequence of the receptor is similar to those of the photolyases, although the receptor does not show the activity of photoreactivation. To investigate the functional divergence of the family, the amino acid sequences of the proteins were aligned. The alignment suggested that the recognition mechanisms of the cofactors and the substrate of class I CPD photolyases (class I photolyases) are different from those of class II CPD photolyases (class II photolyases). We reconstructed the phylogenetic trees based on the alignment by the NJ method and the ML method. The phylogenetic analysis suggested that the ancestral gene of the family had encoded CPD photolyase and that the gene duplication of the ancestral proteins had occurred at least eight times before the divergence between eubacteria and eukaryotes.     

Intestinal parasites in swine in the Nordic countries: prevalence and geographical distribution

In Denmark (DK), Finland (FIN), Iceland (I), Norway (N), and Sweden (S), 516 swine herds were randomly selected in 1986-1988. Individual faecal analyses (mean: 27.9 per herd) from eight age categories of swine showed that Ascaris suum, Oesophagostomum spp., Isospora suis, and Eimeria spp. were common, while Trichuris suis and Strongyloides ransomi-like eggs occurred sporadically. Large fatteners and gilts were most frequently infected with A. suum with maximum prevalences of 25-35% in DK, N and S, 13% in I and 5% in FIN. With the exception of the remarkably low A. suum prevalence rates in FIN, no clear national differences were observed. Oesophagostomum spp. were most prevalent in adult pigs in the southern regions (21-43% in DK and southern S), less common in the northern regions (4-17% adult pigs infected), and not recorded in I. I. suis was common in piglets in DK, I, and S (20-32%), while < 1% and 5% were infected in N and FIN, respectively. Eimeria spp. had the highest prevalences in adult pigs (max. 9%) without clear geographical differences. I. suis and Eimeria spp. were recorded for the first time in I, and I. suis for the first time in N.     

Aminoglycoside volume of distribution and illness severity in critically ill septic patients

The volume of distribution of amikacin and the APACHE II score were determined in 42 critically ill patients being treated for a gram-negative infection. The mean volume of distribution (Vdt) was 0.41 +/- 0.12 l/kg with a wide range (normal of 0.25 l/kg). There was a good relationship between the Vdt and illness severity as measured by the APACHE II score (r = 0.70; P < 0.001). Critically ill patients should receive larger loading doses of aminoglycosides in order to achieve therapeutic blood levels. The aminoglycoside Vdt may be useful in determining the degree of capillary leak and tissue oedema that accompanies sepsis.     

Molecular phylogenetics and the evolution of antarctic notothenioid fishes

The monophyly of the antarctic fish suborder Notothenioidei and the monophyly of its earliest family the Bovichtidae have been investigated with 12S and 16S mitochondrial DNA sequences. New data from Cottoperca, Pseudaphritis, Harpagifer and several outgroups, in addition to available sequences, show that the bovichtids are paraphyletic. Pseudaphritis is the sister group of all the non-bovichtid notothenioids. The same results are found from two independent genetic markers, the nuclear 28S rDNA and the 12S and 16S mitochondrial rDNA. This reliably refutes a previous hypothesis that placed Pseudaphritis as the sister group of all the remaining notothenioids (including Cottoperca and Bovichtus). Bootstrap analyses show that the Notothenioidei are monophyletic (although members of the suborder Trachinoidei have not been surveyed). Subsequent data from hemoglobin composition confirm the present relationships. After discussions between members of the European Science Foundation (ESF) network during its last two meetings, we point out here some fundamental aspects of comparative biology to improve understanding between the physiologist community and phylogeneticists. The most important points are differences in how the concept of homology is used and differences in the consideration of adaptation. When adaptation is evoked or questioned, endless speculations and untestable scenarios are often developed. We strongly advocate the use of phylogenetic trees for testing hypotheses of adaptation (through multiple character mapping). Such a "research program" in comparative biology has the power to improve knowledge because it can potentially lead to new experiments for testing adaptive hypotheses.     

Molecular phylogeography and the evolution and conservation of Amazonian mammals

The phylogeographic structure of 15 genera of Amazonian marsupials and rodents is summarized based on comparative sequence of the mitochondrial cytochrome b gene. The data are limited in geographical coverage, with samples widely scattered throughout Amazonia from the base of the Andes in Peru to the Guianan coast and eastern Brazil. We use this approach to define species boundaries, based minimally on the principle of reciprocal monophyly, in conjunction with morphological or other genetic discontinuities. The taxa so defined are older than previously appreciated, with many lineages dating from 1 to more than 3 Myr, and thus apparently predating the early Pleistocene. We relate patterns of concordant geographical shifts with underlying tectonic history and to current positions of major rivers. Finally, we provide comments on the utility of these data and patterns to conservation, articulating a need to incorporate phylogeographic information as part of the rationale in establishing conservation priorities at the organismal and geographical area levels.