Persistence of DNA adducts, hypermutation and acquisition of cellular resistance to alkylating agents in glioblastoma

Glioblastoma is a lethal form of brain tumour usually treated by surgical resection followed by radiotherapy and an alkylating chemotherapeutic agent. Key to the success of this multimodal approach is maintaining apoptotic sensitivity of tumour cells to the alkylating agent. This initial treatment likely establishes conditions contributing to development of drug resistance as alkylating agents form the O⁶-methylguanine adduct. This activates the mismatch repair (MMR) process inducing apoptosis and mutagenesis. This review describes key juxtaposed drivers in the balance between alkylation induced mutagenesis and apoptosis. Mutations in MMR genes are the probable drivers for alkylation based drug resistance. Critical to this interaction are the dose-response and temporal interactions between adduct formation and MMR mutations. The precision in dose interval, dose-responses and temporal relationships dictate a role for alkylating agents in either promoting experimental tumour formation or inducing tumour cell death with chemotherapy. Importantly, this resultant loss of chemotherapeutic selective pressure provides opportunity to explore novel therapeutics and appropriate combinations to minimise alkylation based drug resistance and tumour relapse.

Genome size diversity in orchids: consequences and evolution

BACKGROUND

The amount of DNA comprising the genome of an organism (its genome size) varies a remarkable 40 000-fold across eukaryotes, yet most groups are characterized by much narrower ranges (e.g. 14-fold in gymnosperms, 3- to 4-fold in mammals). Angiosperms stand out as one of the most variable groups with genome sizes varying nearly 2000-fold. Nevertheless within angiosperms the majority of families are characterized by genomes which are small and vary little. Species with large genomes are mostly restricted to a few monocots families including Orchidaceae.

SCOPE

A survey of the literature revealed that genome size data for Orchidaceae are comparatively rare representing just 327 species. Nevertheless they reveal that Orchidaceae are currently the most variable angiosperm family with genome sizes ranging 168-fold (1C = 0.33-55.4 pg). Analysing the data provided insights into the distribution, evolution and possible consequences to the plant of this genome size diversity.

CONCLUSIONS

Superimposing the data onto the increasingly robust phylogenetic tree of Orchidaceae revealed how different subfamilies were characterized by distinct genome size profiles. Epidendroideae possessed the greatest range of genome sizes, although the majority of species had small genomes. In contrast, the largest genomes were found in subfamilies Cypripedioideae and Vanilloideae. Genome size evolution within this subfamily was analysed as this is the only one with reasonable representation of data. This approach highlighted striking differences in genome size and karyotype evolution between the closely related Cypripedium, Paphiopedilum and Phragmipedium. As to the consequences of genome size diversity, various studies revealed that this has both practical (e.g. application of genetic fingerprinting techniques) and biological consequences (e.g. affecting where and when an orchid may grow) and emphasizes the importance of obtaining further genome size data given the considerable phylogenetic gaps which have been highlighted by the current study.

Molecular systematics of Gagea and Lloydia (Liliaceae; Liliales): implications of analyses of nuclear ribosomal and plastid DNA sequences for infrageneric classification

BACKGROUND AND AIMS

Gagea is a Eurasian genus of petaloid monocots, with a few species in North Africa, comprising between 70 and approximately 275 species depending on the author. Lloydia (thought to be the closest relative of Gagea) consists of 12-20 species that have a mostly eastern Asian distribution. Delimitation of these genera and their subdivisions are unresolved questions in Liliaceae taxonomy. The objective of this study is to evaluate generic and infrageneric circumscription of Gagea and Lloydia using DNA sequence data.

METHODS

A phylogenetic study of Gagea and Lloydia (Liliaceae) was conducted using sequences of nuclear ribosomal internal transcribed spacer (ITS) and plastid (rpl16 intron, trnL intron, trnL-F spacer, matK and the psbA-trnH spacer) DNA regions. This included 149 accessions (seven as outgroups), with multiple accessions of some taxa; 552 sequences were included, of which 393 were generated as part of this research.

KEY RESULTS

A close relationship of Gagea and Lloydia was confirmed in analyses using different datasets, but neither Gagea nor Lloydia forms a monophyletic group as currently circumscribed; however, the ITS and plastid analyses did not produce congruent results for the placement of Lloydia relative to the major groups within Gagea. Gagea accessions formed five moderately to strongly supported clades in all trees, with most Lloydia taxa positioned at the basal nodes; in the strict consensus trees from the combined data a basal polytomy occurs. There is limited congruence between the classical, morphology-derived infrageneric taxonomy in Gagea (including Lloydia) and clades in the present phylogenetic analyses.

CONCLUSIONS

The analyses support monophyly of Gagea/Lloydia collectively, and they clearly comprise a single lineage, as some previous authors have hypothesized. The results provide the basis for a new classification of Gagea that has support from some morphological features. Incongruence between plastid and nuclear ITS results is interpreted as potentially due to ancient hybridization and/or paralogy of ITS rDNA.

Genetic diversity and differentiation processes in the ploidy series of Olea europaea L.: a multiscale approach from subspecies to insular populations

Geographical isolation and polyploidization are central concepts in plant evolution. The hierarchical organization of archipelagos in this study provides a framework for testing the evolutionary consequences for polyploid taxa and populations occurring in isolation. Using amplified fragment length polymorphism and simple sequence repeat markers, we determined the genetic diversity and differentiation patterns at three levels of geographical isolation in Olea europaea: mainland-archipelagos, islands within an archipelago, and populations within an island. At the subspecies scale, the hexaploid ssp. maroccana (southwest Morocco) exhibited higher genetic diversity than the insular counterparts. In contrast, the tetraploid ssp. cerasiformis (Madeira) displayed values similar to those obtained for the diploid ssp. guanchica (Canary Islands). Geographical isolation was associated with a high genetic differentiation at this scale. In the Canarian archipelago, the stepping-stone model of differentiation suggested in a previous study was partially supported. Within the western lineage, an east-to-west differentiation pattern was confirmed. Conversely, the easternmost populations were more related to the mainland ssp. europaea than to the western guanchica lineage. Genetic diversity across the Canarian archipelago was significantly correlated with the date of the last volcanic activity in the area/island where each population occurs. At the island scale, this pattern was not confirmed in older islands (Tenerife and Madeira), where populations were genetically homogeneous. In contrast, founder effects resulted in low genetic diversity and marked genetic differentiation among populations of the youngest island, La Palma.

Within-population spatial genetic structure in four naturally fragmented species of a neotropical inselberg radiation, Alcantarea imperialis, A. geniculata, A. glaziouana and A. regina (Bromeliaceae)

Studies of organisms on 'terrestrial islands' can improve our understanding of two unresolved issues in evolutionary genetics: the likely long-term effects of habitat fragmentation and the genetic underpinnings of continental species radiations in island-like terrestrial habitats. We have addressed both issues for four closely related plant species of the adaptive radiation Bromeliaceae, Alcantarea imperialis, A. geniculata, A. regina and A. glaziouana. All four are adapted to ancient, isolated inselberg rock outcrops in the Brazilian Atlantic rainforest and are thus long-term fragmented by nature. We used eight nuclear microsatellites to study within-population spatial genetic structure (SGS) and historical gene dispersal in nine populations of these species. Within-population SGS reflected known between-species differences in mating systems. The strongest SGS observed in A. glaziouana (Sp=0.947) was stronger than literature estimates available for plants. Analysis of short- and long-distance components of SGS identified biparental inbreeding, selfing and restricted seed dispersal as main determinants of SGS, with restricted pollen dispersal by bats contributing in some localities. The ability of Alcantarea spp. to colonize isolated inselbergs probably stems from their flexible mating systems and an ability to tolerate inbreeding. Short-ranging gene dispersal (average sigma=7-27 m) is consistent with a loss of dispersal power in terrestrial island habitats. Population subdivision associated with sympatric colour morphs in A. imperialis is accompanied by between-morph differences in pollen and seed dispersal. Our results indicate a high potential for divergence with gene flow in inselberg bromeliads and they provide base-line data about the long-term effects of fragmentation in plants.

Population differentiation and species cohesion in two closely related plants adapted to neotropical high-altitude 'inselbergs', Alcantarea imperialis and Alcantarea geniculata (Bromeliaceae)

Isolated granitic rock outcrops or 'inselbergs' may provide a window into the molecular ecology and genetics of continental radiations under simplified conditions, in analogy to the use of oceanic islands in studies of species radiations. Patterns of variability and gene flow in inselberg species have never been thoroughly evaluated in comparison to related taxa with more continuous distribution ranges, or to other species in the same kingdom in general. We use nuclear microsatellites to study population differentiation and gene flow in two diploid, perennial plants adapted to high-altitude neotropical inselbergs, Alcantarea imperialis and Alcantarea geniculata (Bromeliaceae). Population differentiation is pronounced in both taxa, especially in A. imperialis. Gene flow in this species is considerably lower than expected from the literature on plants in general and Bromeliaceae in particular, and too low to prevent differentiation due to drift (N(e)m < 1), unless selection coefficients/effect sizes of favourable alleles are great enough to maintain species cohesion. Low gene flow in A. imperialis indicates that the ability of pollinating bats to promote gene exchange between inselbergs is smaller than previously assumed. Population subdivision in one inselberg population of A. imperialis appears to be associated with the presence of two colour morphs that differ in the coloration of rosettes and bracts. Our results indicate a high potential for inselbergs as venues for studies of the molecular ecology and genetics of continental radiations, such as the one that gave rise to the extraordinary diversity of adaptive strategies and phenotypes seen in Bromeliaceae.

Punctuated genome size evolution in Liliaceae

Most angiosperms possess small genomes (mode 1C = 0.6 pg, median 1C = 2.9 pg). Those with truly enormous genomes (i.e. > or = 35 pg) are phylogenetically restricted to a few families and include Liliaceae - with species possessing some of the largest genomes so far reported for any plant as well as including species with much smaller genomes. To gain insights into when and where genome size expansion took place during the evolution of Liliaceae and the mode and tempo of this change, data for 78 species were superimposed onto a phylogenetic tree and analysed. Results suggest that genome size in Liliaceae followed a punctuated rather than gradual mode of evolution and that most of the diversification evolved recently rather than early in the evolution of the family. We consider that the large genome sizes of Liliaceae may have emerged passively rather than being driven primarily by selection.

A preliminary study of genetic variation in populations of Monstera adansonii var. klotzschiana (Araceae) from North-East Brazil, estimated with AFLP molecular markers

BACKGROUND AND AIMS

This study sought genetic evidence of long-term isolation in populations of Monstera adansonii var. klotzschiana (Araceae), a herbaceous, probably outbreeding, humid forest hemi-epiphyte, in the brejo forests of Ceará (north-east Brazil), and clarification of their relationships with populations in Amazonia and the Atlantic forest of Brazil.

METHODS

Within-population genetic diversity and between-population dissimilarity were estimated using AFLP molecular markers in 75 individuals from eight populations located in Ceará, the Brazilian Atlantic Forest and Amazonia.

KEY RESULTS

The populations showed a clinal pattern of weak genetic differentiation over a large geographical region (F(ST) = 0.1896). A strong correlation between genetic and geographical distance (Mantel test: r = 0.6903, P = 0.002) suggests a historical pattern of isolation by distance. Genetic structure analysis revealed at least two distinct gene pools in the data. The two isolated Ceará populations are significantly different from each other (pairwise Phi(PT) = 0.137, P = 0.003) and as diverse (Nei's gene diversity, average H(e) = 0.1832, 0.1706) as those in the Atlantic and Amazon forest regions. The population in southern Brazil is less diverse (Nei's gene diversity, average H(e) = 0.127) than the rest. The Ceará populations are related to those of the Atlantic forest rather than those from Amazonia (AMOVA, among-groups variation = 11.95 %, P = 0.037).

CONCLUSIONS

The gene pools detected within an overall pattern of clinal variation suggest distinct episodes of gene flow, possibly correlated with past humid forest expansions. The Ceará populations show no evidence of erosion of genetic diversity, although this was expected because of their isolation. Their genetic differentiation and relatively high diversity reinforce the importance of conserving the endangered brejo forests.

Admixture in European Populus hybrid zones makes feasible the mapping of loci that contribute to reproductive isolation and trait differences

The use of admixed human populations to scan the genome for chromosomal segments affecting complex phenotypic traits has proved a powerful analytical tool. However, its potential in other organisms has not yet been evaluated. Here, we use DNA microsatellites to assess the feasibility of this approach in hybrid zones between two members of the 'model tree' genus Populus: Populus alba (white poplar) and Populus tremula (European aspen). We analyzed samples of both species and a Central European hybrid zone (N=544 chromosomes) for a genome-wide set of 19 polymorphic DNA microsatellites. Our results indicate that allele frequency differentials between the two species are substantial (mean delta=0.619+/-0.067). Background linkage disequilibrium (LD) in samples of the parental gene pools is moderate and should respond to sampling schemes that minimize drift and account for rare alleles. LD in hybrids decays with increasing number of backcross generations as expected from theory and approaches background levels of the parental gene pools in advanced generation backcrosses. Introgression from P. tremula into P. alba varies strongly across marker loci. For several markers, alleles from P. tremula are slightly over-represented relative to neutral expectations, whereas a single locus exhibits evidence of selection against P. tremula genotypes. We interpret our results in terms of the potential for admixture mapping in these two ecologically divergent Populus species, and we validate a modified approach of studying genotypic clines in 'mosaic' hybrid zones.

Barrier to gene flow between two ecologically divergent Populus species, P. alba (white poplar) and P. tremula (European aspen): the role of ecology and life history in gene introgression

The renewed interest in the use of hybrid zones for studying speciation calls for the identification and study of hybrid zones across a wide range of organisms, especially in long-lived taxa for which it is often difficult to generate interpopulation variation through controlled crosses. Here, we report on the extent and direction of introgression between two members of the "model tree" genus Populus: Populus alba (white poplar) and Populus tremula (European aspen), across a large zone of sympatry located in the Danube valley. We genotyped 93 hybrid morphotypes and samples from four parental reference populations from within and outside the zone of sympatry for a genome-wide set of 20 nuclear microsatellites and eight plastid DNA restriction site polymorphisms. Our results indicate that introgression occurs preferentially from P. tremula to P. alba via P. tremula pollen. This unidirectional pattern is facilitated by high levels of pollen vs. seed dispersal in P. tremula (pollen/seed flow = 23.9) and by great ecological opportunity in the lowland floodplain forest in proximity to P. alba seed parents, which maintains gene flow in the direction of P. alba despite smaller effective population sizes (N(e)) in this species (P. alba N(e)c. 500-550; P. tremula N(e)c. 550-700). Our results indicate that hybrid zones will be valuable tools for studying the genetic architecture of the barrier to gene flow between these two ecologically divergent Populus species.

Adaptation to environmental stress: a rare or frequent driver of speciation?

Recent results of evolutionary genomics and other research programmes indicate an important role for environment-dependent selection in speciation, but the conceptual frameworks of speciation genetics and environmental stress physiology have not been fully integrated. Only a small number of model systems have been established for cross-disciplinary studies of this type in animals and plants. In these taxa (e.g. Drosophila and Arabidopsis/Arabis), studies of the mechanistic basis of various stress responses are increasingly combined with attempts to understand their evolutionary consequences. Our understanding of the role of environmental stress in speciation would benefit from studies of a larger variety of taxa. We pinpoint areas for future study and predict that in many taxa 'broad' hybrid zones maintained by ecological selection will be valuable venues for addressing the link between environmental stress, adaptation, and speciation.

Patterns of variability and gene flow in Medicago citrina, an endangered endemic of islands in the western Mediterranean, as revealed by amplified fragment length polymorphism (AFLP)

Medicago citrina is an endangered western Mediterranean endemic that grows only on small islets of the Balearic archipelago and off the eastern Spanish coast. Only 10 isolated subpopulations are currently known (four from Ibiza, three from Cabrera, two from Columbretes and one from an offshore islet in northern Alicante province), constituting a severely fragmented genetic system. Data were analysed with the unweighted pair-group method using arithmetic averages (UPGMA) and principle coordinates analysis (PCOA), revealing several distinct groups. Genetic diversity indices indicated that Ibizan subpopulations had the highest genetic variability (Nei's index: 0.1463; Shannon's index: 0.228), whereas the lowest variability was found in Alicante (Nei's index: 0.035; Shannon's index: 0.050) and Cabrera (Nei's index: 0.068; Shannon's index: 0.104). These latter populations show the highest FST values (FST = 0.548) revealing high differentiation between them. Columbretes subpopulations formed a defined single group, although it also included some Ibizan samples. The smallest FST values, obtained between Ibiza and Columbretes (FST = 0.185), are not correlated with geographical proximity, but appear to be related to the geologically recent volcanic origin of the Columbretes islands (300,000 years ago). According to the distribution of the Ibizan samples in the dendrogram and the FST values, the best hypothesis is to regard the Ibizan subpopulations as the centre of genetic diversity of the currently known subpopulations. Our results suggest migratory scenarios from Ibiza to Columbretes based mainly on zoochory probably by seabirds. Finally, recommendations are provided for management strategies to facilitate the conservation of this endangered species.

Genetics of colonization in Hypochaeris tenuifolia (Asteraceae, Lactuceae) on Volcán Lonquimay, Chile

Understanding the genetics of colonizing populations has been, and continues to remain, an important focus in evolutionary biology. Different theoretical models predict varying levels of genetic variation in colonizing populations depending upon strength of founder effect, gene flow and rate of population growth and immigration following colonization. We analyse overall genetic variation using amplified fragment length polymorphism markers in colonizing populations of Hypochaeris tenuifolia (Asteraceae) in the southern Andes. Volcán Lonquimay newly erupted on 25 December 1988, producing a side cone, La Navidad, and sent lava and ash into surrounding areas. Many domesticated animals (estimated at 10 000) and many natural plant populations were destroyed. Into this new open habitat have come immigrant populations of several angiosperm species, most conspicuously H. tenuifolia that forms leaf rosettes with flowering scapes to 15 cm and orange-yellow heads 1-2 cm in diameter. Genetic diversity in five founder populations in the eruption zone is compared with that from five nearby survivor populations, as well as with eight isolated northern and four southern populations from throughout the entire range of the species in Chile. Results from 477 individuals representing 447 different multilocus phenotypes, yielded 170 DNA fragments of which 144 (85%) were polymorphic. Genetic diversity within founder populations is neither lower than in survivor populations nor in isolated populations throughout the range of the species, but it is lower among founder populations than among other populations immediately and distantly outside the zone of disturbance. Closest genetic similarity occurs between founders and nearby survivor populations as well as those in adjacent southern regions.

Molecular systematics of Iridaceae: evidence from four plastid DNA regions

Iridaceae are one of the largest families of Lilianae and probably also among the best studied of monocotyledons. To further evaluate generic, tribal, and subfamilial relationships we have produced four plastid DNA data sets for 57 genera of Iridaceae plus outgroups: rps4, rbcL (both protein-coding genes), the trnL intron, and the trnL-F intergenic spacer. All four matrices produce similar although not identical trees, and we thus analyzed them in a combined analysis, which produced a highly resolved and well-supported topology, in spite of the fact that the partition homogeneity test indicated strong incongruence. In each of the individual trees, some genera or groups of genera are misplaced relative to morphological cladistic studies, but the combined analysis produced a pattern much more similar to these previous ideas of relationships. In the combined tree, all subfamilies were resolved as monophyletic, except Nivenioideae that formed a grade in which Ixioideae were embedded. Achlorophyllous Geosiris (sometimes referred to Geosiridaceae or Burmanniaceae) fell within the nivenioid grade. Most of the tribes were monophyletic, and Isophysis (Tasmanian) was sister to the rest of the family; Diplarrhena (Australian) fell in a well-supported position as sister to Irideae/Sisyrinchieae/Tigridieae/Mariceae (i.e., Iridoideae); Bobartia of Sisyrinchieae is supported as a member of Irideae. The paraphyly of Nivenioideae is suspicious due to extremely high levels of sequence divergence, and when they were constrained to be monophyletic the resulting trees were only slightly less parsimonious (<1.0%). However, this subfamily also lacks clear morphological synapomorphies and is highly heterogeneous, so it is difficult to develop a strong case on nonmolecular grounds for their monophyly.

Amplified fragment length polymorphisms (AFLP) reveal details of polyploid evolution in Dactylorhiza (Orchidaceae)

The utility of the PCR-based AFLP technique (polymerase chain reaction; amplified fragment length polymorphisms) was explored in elucidating details of polyploid evolution in the Eurasian orchid genus Dactylorhiza. We emphasized Swedish taxa but also included some material from the British Isles and elsewhere in Europe. Three different sets of primers, amplifying different subsets of restriction fragments, independently revealed similar patterns for relationships among the Dactylorhiza samples investigated. The AFLP data support the general picture of polyploid evolution in Dactylorhiza, i.e., that allotetraploid derivatives have arisen repeatedly as a result of hybridization beween the two parental groups D. incarnata s.l. (sensu lato; diploid marsh orchids) and the D. maculata group (spotted orchids). Within the incarnata s.l. group, morphologically defined varieties were interdigitated. The D. maculata group consisted of two distinct subgroups, one containing autotetraploid D. maculata subsp. maculata and the other containing diploid D. maculata subsp. fuchsii. Allotetraploids showed a high degree of additivity for the putative parental genomes, and relationships among them were partly correlated to morphologically based entities, but also to geographic distribution. Thus, allotetraploid taxa from the British Isles clustered together, rather than with morphologically similar plants from other areas.

Rapid and recent origin of species richness in the Cape flora of South Africa

The Cape flora of South Africa grows in a continental area with many diverse and endemic species. We need to understand the evolutionary origins and ages of such 'hotspots' to conserve them effectively. In volcanic islands the timing of diversification can be precisely measured with potassium-argon dating. In contrast, the history of these continental species is based upon an incomplete fossil record and relatively imprecise isotopic palaeotemperature signatures. Here we use molecular phylogenetics and precise dating of two island species within the same clade as the continental taxa to show recent speciation in a species-rich genus characteristic of the Cape flora. The results indicate that diversification began approximately 7-8 Myr ago, coincident with extensive aridification caused by changes in ocean currents. The recent origin of endemic species diversity in the Cape flora shows that large continental bursts of speciation can occur rapidly over timescales comparable to those previously associated with oceanic island radiations.

A phylogenetic analysis of Rhamnaceae using rbcL and trnL-F plastid DNA sequences

Previous tribal classifications of Rhamnaceae have been based on fruit characters, resulting in the delimitation of large and otherwise heterogeneous groups. We evaluated the most recent classification with DNA sequences of two regions of the plastid genome, rbcL and trnL-F, from 42 genera of Rhamnaceae and representatives of the related families Elaeagnaceae, Barbeyaceae, Dirachmaceae, Urticaceae, Ulmaceae, Moraceae, and Rosaceae. The trnL-F trees have higher consistency and retention indices than the rbcL trees, and patterns of change in rbcL and trnL-F are compared. The closest relatives of Rhamnaceae are Dirachmaceae and Barbeyaceae, followed by the urticalean families. The plastid trees support the monophyly of the family and provide the basis for a new tribal classification. Three strongly supported clades are identified, but morphological characters could not be found to underpin a formal taxonomic description of these three clades as subfamilies. We therefore only recognize groups that are also defined by morphological characters. The biogeography of Rhamnaceae is discussed with reference to the molecular trees.

Phylogenetics of flowering plants based on combined analysis of plastid atpB and rbcL gene sequences

Following (1) the large-scale molecular phylogeny of seed plants based on plastid rbcL gene sequences (published in 1993 by Chase et al., Ann. Missouri Bot. Gard. 80:528-580) and (2) the 18S nuclear phylogeny of flowering plants (published in 1997 by Soltis et al., Ann. Missouri Bot. Gard. 84:1-49), we present a phylogenetic analysis of flowering plants based on a second plastid gene, atpB, analyzed separately and in combination with rbcL sequences for 357 taxa. Despite some discrepancies, the atpB-based phylogenetic trees were highly congruent with those derived from the analysis of rbcL and 18S rDNA, and the combination of atpB and rbcL DNA sequences (comprising approximately 3000 base pairs) produced increased bootstrap support for many major sets of taxa. The angiosperms are divided into two major groups: noneudicots with inaperturate or uniaperturate pollen (monocots plus Laurales, Magnoliales, Piperales, Ceratophyllales, and Amborellaceae-Nymphaeaceae-Illiciaceae) and the eudicots with triaperturate pollen (particularly asterids and rosids). Based on rbcL alone and atpB/rbcL combined, the noneudicots (excluding Ceratophyllum) are monophyletic, whereas in the atpB trees they form a grade. Ceratophyllum is sister to the rest of angiosperms with rbcL alone and in the combined atpB/rbcL analysis, whereas with atpB alone, Amborellaceae, Nymphaeaceae, and Illiciaceae/Schisandraceae form a grade at the base of the angiosperms. The phylogenetic information at each codon position and the different types of substitutions (observed transitions and transversions in the trees vs. pairwise comparisons) were examined; taking into account their respective consistency and retention indices, we demonstrate that third-codon positions and transitions are the most useful characters in these phylogenetic reconstructions. This study further demonstrates that phylogenetic analysis of large matrices is feasible.

In vitro propagation of Litsea cubeba (Lours.) Pers., a multipurpose tree

 A rapid clonal propagation system has been developed for Litsea cubeba. Following investigation of a range of cytokinins and a variety of explant sources (shoot tip, node, leaf and petiole) it was established that 6-benzyladenine with shoot tip explants gave optimal multiple-shoot induction. In vitro rooting on growth-regulator-free medium was possible and over 100 plantlets were successfully weaned to the glasshouse.

Systematics of Amaryllidaceae based on cladistic analysis of plastid sequence data

Cladistic analyses of plastid DNA sequences rbcL and trnL-F are presented separately and combined for 48 genera of Amaryllidaceae and 29 genera of related asparagalean families. The combined analysis is the most highly resolved of the three and provides good support for the monophyly of Amaryllidaceae and indicates Agapanthaceae as its sister family. Alliaceae are in turn sister to the Amaryllidaceae/Agapanthaceae clade. The origins of the family appear to be western Gondwanaland (Africa), and infrafamilial relationships are resolved along biogeographic lines. Tribe Amaryllideae, primarily South African, is sister to the rest of Amaryllidaceae; this tribe is supported by numerous morphological synapomorphies as well. The remaining two African tribes of the family, Haemantheae and Cyrtantheae, are well supported, but their position relative to the Australasian Calostemmateae and a large clade comprising the Eurasian and American genera, is not yet clear. The Eurasian and American elements of the family are each monophyletic sister clades. Internal resolution of the Eurasian clade only partially supports currently accepted tribal concepts, and few conclusions can be drawn on the relationships of the genera based on these data. A monophyletic Lycorideae (Central and East Asian) is weakly supported. Galanthus and Leucojum (Galantheae pro parte) are supported as sister genera by the bootstrap. The American clade shows a higher degree of internal resolution. Hippeastreae (minus Griffinia and Worsleya) are well supported, and Zephyranthinae are resolved as a distinct subtribe. An Andean clade marked by a chromosome number of 2n = 46 (and derivatives thereof) is resolved with weak support. The plastid DNA phylogenies are discussed in the context of biogeography and character evolution in the family.

Postsurgical intraperitoneal exposure to glove powders modulates inflammatory and immune-related cytokine production

The objective of the present study was to determine whether intraperitoneal exposure to glove powders modulates the inflammatory and immune responses by altering the influx of inflammatory and immune cells and peritoneal fluid cytokines and thus the outcome of surgically induced peritoneal wound healing. Peritoneal wall injuries were made by scraping the tissue until bleeding occurred in 360 mice. One of the following fluids was then introduced into the peritoneal cavity: phosphate-buffered saline solution, phosphate-buffered saline solution containing glove powders (Biosorb and Keoflo, 100 microg/ml), Hydrocote (Hydrogel film, Biogel 100 microg/ml), latex proteins (1 mg/ml), or lipopolysaccharides (12.5 microg/ml). At intervals of 1 to 28 days after injury, 10 mice per treatment per day and 10 uninjured mice were killed, peritoneal fluids were collected to determine the cytokine levels, the rate of fibrous adhesions formed at the site of injuries was graded, and peritoneal walls with attached fibrous adhesions were removed to determine the degree of inflammatory and immune cell infiltration into the wound. The results indicated that, with the exception of interferon-gamma, the peritoneal fluid levels of transforming growth factor-beta1, tumor necrosis factor-alpha, interleukin-1beta, and granulocyte-macrophage-colony stimulating factor in the phosphate-buffered saline solution-treated injured group significantly increased, reaching maximum between days 4 and 7 (p < 0.05) compared with the uninjured group and returned to uninjured values by day 14 after injury. The level of transforming growth factor-beta1 was higher in glove powders and Hydrocote-treated groups than in latex, lipo-saccharides, or phosphate-buffered saline solution-treated groups until day 14 after surgery (p < 0.05). The levels of tumor necrosis factor-alpha and interleukin-1beta increased in all treatment groups during the first week after injury compared with uninjured controls, with the exception of Hydrocote. The number of T helper/inducers (CD4), total leukocytes (CD11a), B lymphocytes (CD45R), granulocytes (Gr-1), and mononuclear phagocytes (Mac-3) in the wound increased during the first week after peritoneal wounding with no significant difference between treated and untreated groups. The rate of adhesion formation was not significantly altered in treated compared with untreated groups. These data suggest that a mechanism which mediates glove powder-induced peritoneal inflammatory and immune reactions in the postsurgical setting involves augmentation of cytokine production without influencing the influx of inflammatory and immune cells or adhesion formation.

Peritoneal healing with adhesion formation: current comment

Intra-abdominal adhesions are fibrotic structures, which lie in the form of a string or attachment between the abdominal organs and connect these together. They are responsible for serious clinical complications that include intestinal obstruction, infertility, and pelvic pain. During the last century, surgeons' comprehensive understanding of the biology of peritoneal healing and wound repair has allowed them to identify a variety of new therapeutic techniques that limit the development of adhesion formation. New drugs, dextran 70 and poloxamer 407, have been developed to prevent adhesion formation. In addition, three new biomaterials (oxidized regenerated cellulose, hyaluronate membrane, and polytetrafluoroethylene) are synthetic barriers being used to prevent adhesions.

Hand protection against viral pathogens

In today's health care setting, being either a hospitalised patient or a health care worker carries some degree of risk. One significant risk is potential exposure to viruses, bacteria and/or antibiotic-resistant organisms which may be transmitted from the hands of workers or by worker contact with infected patients. The risk of transmission by these pathogens is determined by three main factors: The nature and frequency of contact with blood, body fluids or infectious material The inoculum load and risk of transmission after a single exposure to the pathogen The prevalence of infected, susceptible patients or health care workers. During the past few years, occupational health standards and universal infection control guidelines were enacted to minimise these exposure events. In addition to common sense infection control practices, the new regulations require the use of engineering controls and personal protective equipment to alleviate the chance of personal contact with potentially infectious material.

Fits like a glove

Latex gloves remain the gold standard in barrier protection. Glove allergy costs and environmental clean-up run into billions of dollars each year. Managers must consider the cost of using poorly chosen gloves.

Issues of latex safety in dentistry

The prevalence of reported reactions to natural rubber latex products in both the general population and in dental personnel appears to parallel the rise in glove wearing by health professionals. This paper reviews the irritant and allergic reactions which may be associated with latex products, particularly gloves. The aetiology, pathogenesis, diagnosis and management of immediate Type I (IgE mediated) responses to latex are described in some detail. The paper provides the reader with an insight into factors that may lead to latex allergy and outlines measures for handling 'latex sensitised' individuals in the dental surgery.

Surgical glove powders differentially modulate macrophage and lymphocyte-derived cytokines and eicosanoids production in vitro

The objective of the present study was to determine the effect of surgical glove powders Biosorb, Keoflo, and CaCO(3) and Hydrocote (a powder-free film; Biogel) on cytokine and eicosanoid production by lipopolysaccharide/phorbol 12-myristate 13-acetate activated and unactivated HL60, U937, and RPMI 1788 cells, human monocyte/macrophage, and B lymphocyte cell lines. The unactivated cell culture-conditioned media contained a low level of interleukin-1alpha and -1beta, granulocyte macrophage colony stimulating factor, and tumor necrosis factor-alpha, which significantly increased after activation (p < 0.05). Exposure of unactivated cells to glove powders or Hydrocote (100 microg/ml) had little effect. However, these compounds appeared to have multiple inhibitory and stimulatory action on the production of these cytokines and eicosanoids in lipopolysaccharide/phorbol 12-myristate 13-acetate activated cells. For instance, granulocyte macrophage colony stimulating factor production was inhibited only in U937 cells by Keoflo and CaCO(3), whereas, tumor necrosis factor-alpha production was stimulated by Biosorb and Keoflo in HL-60, and CaCO(3) was found to be predominantly inhibitory on tumor necrosis factor-alpha production by these cells (p < 0.05). Total transforming growth factor-beta(1) production was stimulated by Biosorb and Hydrocote in U937 and HL-60 cells, respectively, but inhibited by Keoflo in U937 cells. However, Biosorb and Keoflo inhibited transforming growth factor-beta(1) production in both HL-60 and RPMI 1788 cells, without any effect on active transforming growth factor-beta(1). With regard to eicosanoids, Biosorb and Keoflo stimulated prostaglandin E(2) production by RPMI 1788 cells, whereas it was inhibited by all glove powders in HL-60 cells. Thromboxane B(2) production was stimulated by Keoflo and inhibited by CaCO(3) and Hydrocote in U937 cells. Finally, Leukotriene B(4) synthesis was found to become stimulated by Keoflo, CaCO(3), and Hydrocote in both HL60 and RPMI 1788 cells (p < 0.05). These data indicate that exposure of activated, but not unactivated, macrophages and lymphocyte to surgical glove powders and Hydrocote differentially effects the release of cytokines and eicosanoids by these cells. Considering that cytokines and eicosanoids play an important role in mediating the inflammatory and immune responses of wound healing, complications arising from glove powder exposure in vivo may involve mechanisms which alter the type and level of cytokine and eicosanoid production.

The effect of surgical glove powder on proliferation of human skin fibroblast and monocyte/macrophage

The effect of surgical glove powders (Biosorb, Keoflo, and CaCO3) and Hydrocote (powder-free lubricating agent, Biogel) was examined on human skin fibroblasts and monocyte/macrophage cell lines (U937 and HL-60). Glove powders (0.1-100 micrograms/ml) in the presence of 10% fetal bovine serum (FBS) had no significant effect on the rate of 3H-thymidine uptake and proliferation of these cells after 48 h and 7 days of exposure, respectively. However, they inhibited HL-60 growth after 10 days, and Biosorb and CaCO3 inhibited U937 after 10-21 days of exposure compared with control. In the presence of low serum (0.5%), Biosorb, but not Keoflo, CaCO3, and Hydrocote, inhibited HL-60 cells after the third day of exposure (p < 0.05), whereas they were without any effect on U937 cells. Further incubation resulted in a significant decrease in cell density in all treatments, as well as controls, because of cell death. In the presence of 2% serum, glove powder-treated HL-60 significantly increased in cell numbers during the first 3 days, and the cells became stationary thereafter, whereas Keoflo and CaCO3-stimulated U937 reached a maximal by 9 days of treatment. Coculturing of fibroblasts directly with macrophages (0.4-5 x 10(5) cells per dish) or incubation with macrophage culture-conditioned media (CCM) stimulated quiescent fibroblast growth equal to that induced by 10% and 0.5% serum, respectively (p < 0.05). However, incubation of fibroblasts with glove powder-treated HL-60 CCM (except CaCO3) inhibited (p < 0.05) and CCM from Biosorb-treated U937 stimulated (p < 0.05) fibroblast proliferation. The CCM from glove powder-treated HL-60 and U937 did not have any significant effect on the rate of 3H-thymidine incorporation into fibroblasts compared with controls. The present observations suggest that glove powder action on fibroblast and macrophage growth in vitro depends on both the serum concentration of the culture medium and the length of exposure. The results imply that glove powders may have an adverse effect in vivo by directly influencing the biologic activity of macrophages, as well as other cell types, leading to alterations in the early phases of wound healing.

Scientific assay methods as the basis for glove selection

Allergies to latex proteins and glove chemicals are increasing in the clinical practice setting. Inasmuch as latex is ubiquitous in the health environment, individuals may be exposed to latex antigens by a number of different routes, including compromised skin, mucous membranes of the respiratory and urogenital tracts, and internally during surgery. As demonstrated by numerous research articles, the key factors that appear to play a role in acquired latex hypersensitivity are chemicals used in the manufacture of products; the level of residual latex proteins, and the presence of glove powder, which binds latex protein. Currently, devices and materials containing latex are not labeled, although this may be rectified by the FDA in the near future. Until products are labeled, it is important for physicians to familiarize themselves with the routes of sensitization, variations in assay methods, and the type and amount of allergen in products in order to select the safest product for patient use and personal protection.

Risk analysis as the basis for surgical glove selection

The growing use of outcomes research will have a significant effect on the way surgeons make decisions concerning glove product selection. These effects will be both direct and indirect, as payers begin to use outcome data to develop practice guidelines. to reduce morbidity and mortality rates, and to alleviate long-term cost and consequences of acquired latex allergy or powder-related postoperative complications in patients. This article reviews elements of risk associated with surgical gloves.

Hand dermatitis. The role of gloves

The wide range of problems that occur in association with occupational skin exposure has brought into focus the need to understand the role of allergens in skin disease. Their impact on health, their role in the causation of skin disease, and the measures that can be instituted to regulate, control, and prevent skin problems are receiving increased attention by OR managers because of the associated costs of skin reactions in OR nurses and the inherent dangers associated with latex allergy. Latex gloves have become a standard part of OR attire, and even though they serve as the primary form of hand protection in the OR, gloves also may serve as one of the key causes of contact or allergic dermatitis in OR personnel. The high frequency of latex glove allergy, especially in OR nurses and surgeons, focuses attention on the need to evaluate the type and quality of surgical latex gloves selected for use. When instances of new skin reactions appear in nursing personnel. OR managers should look for recent changes in glove brands, scrub products, or antimicrobial agents as possible trigger allergens. In such circumstances, managers may wish to use hypoallergenic products as a solution. Although hypoallergenic and/or powder-free gloves or scrub products may be more costly on a unit basis, when compared to the time lost from work, physical discomfort of the worker, and the expense of treatment, they are really quite a bargain.