Arctic systems in the Quaternary: ecological collision, faunal mosaics and the consequences of a wobbling climate.

Climate oscillations and episodic processes interact with evolution, ecology and biogeography to determine the structure and complex mosaic that is the biosphere. Parasites and parasite-host assemblages are key components in a general explanatory paradigm for global biodiversity. We explore faunal assembly in the context of Quaternary time frames of the past 2.6 million years, a period dominated by episodic shifts in climate. Climate drivers cross a continuum from geological to contemporary timescales and serve to determine the structure and distribution of complex biotas. Cycles within cycles are apparent, with drivers that are layered, multifactorial and complex. These cycles influence the dynamics and duration of shifts in environmental structure on varying temporal and spatial scales. An understanding of the dynamics of high-latitude systems, the history of the Beringian nexus (the intermittent land connection linking Eurasia and North America) and downstream patterns of diversity depend on teasing apart the complexity of biotic assembly and persistence. Although climate oscillations have dominated the Quaternary, contemporary dynamics are driven by tipping points and shifting balances emerging from anthropogenic forces that are disrupting ecological structure. Climate change driven by anthropogenic forcing has supplanted a history of episodic variation and is eliminating ecological barriers and constraints on development and distribution for pathogen transmission. A framework to explore interactions of episodic processes on faunal structure and assembly is the Stockholm Paradigm, which appropriately shifts the focus from cospeciation to complexity and contingency in explanations of diversity.

Roles of cysteine proteinases of trypanosomes and Leishmania in host-parasite interactions.

Trypanosomes and Leishmania contain an abundance of stage-regulated cysteine proteinases encoded by several gene families. Analysis of parasites rendered defective in cysteine proteinase function, either through genetic manipulation or through the use of specific inhibitors, has revealed roles for the enzymes in parasite virulence, in modulation of the host's immune response and in parasite differentiation.

Parasite systematics in the 21st century: opportunities and obstacles.

Taxonomic names and phylogenetic hypotheses are indispensable tools for modern biological research, both basic and applied. Like all disciplines, parasitology suffers from the 'taxonomic impediment' - a global shortage of professional taxonomists and systematists. Only a fraction of the species of parasites on this planet have been identified, and the evolutionary relationships of only a minority of those are understood; thus, information on how to manage parasite biodiversity, including known and potential disease agents, is incomplete. A renewal of systematic parasitology has a key role in redefining the relationship between mankind and the organisms whose biology fascinates us so much.

A mutation-specific PCR system to detect sequence variation in the dihydropteroate synthetase gene of Plasmodium falciparum.

Sulphur-based antimalarial drugs targeted at dihydropteroate synthetase (DHPS) are frequently used in synergistic combination with inhibitors of dihydrofolate reductase (DHFR) to combat chloroquine-resistant malaria. We have previously shown that lines of Plasmodium falciparum resistant to the most commonly used sulpha drug, sulphadoxine, carry point mutations in the DHPS coding region, relative to the sequence of sensitive strains (Brooks et al., Eur. J. Biochem. 224 (1994) 397-405). We have now developed PCR diagnostic assays based on allele-specific amplification that are able to detect such mutations. The four tests described can reliably discriminate all of the mutations observed to alter codons 436, 581 and 613, yielding allele-specific amplification products of different sizes in each case. Moreover, by careful adjustment of primer length and the degree of mismatch to target and non-target alleles, we were able to standardise all four tests to a single set of PCR conditions, allowing all possible mutations to be monitored simultaneously on one thermocycler. These assays should prove invaluable in further assessing the contribution of specific base changes in the DHPS gene of the parasite to the sulphadoxine resistance phenotype and to the clinical failure of the sulphadoxine/pyrimethamine combination Fansidar.

The treatment of patients with infected implantable cardioverter-defibrillator systems.

OBJECTIVE: The purpose of this study was to evaluate the treatment of patients with infected implantable cardioverter-defibrillator systems. METHODS: Retrospective analysis was done of the cases of 21 patients treated for implantable cardioverter-defibrillator infection during an 11-year period. RESULTS: Of 723 cardioverter-defibrillator implantations (550 primary implants, 173 replacements), nine (1.2%) were complicated by early postoperative device-related infections. Late infections developed in two patients 19 and 22 months, respectively, after implantation. Ten other patients were transferred to our institution for treatment of cardioverter-defibrillator infection. The time from implantation to overt infection was 2.2 +/- 1.3 months, excluding the two late infections. The responsible organisms were Staphylococcus aureus (9), Staphylococcus epidermidis (6), Streptococcus hemolyticus (1), gram-negative bacteria (3), Candida albicans (1), and Corynebacterium (1). All patients were treated with intravenous antibiotic drugs. Total system removal was done in 15 patients and partial removal in 2; in 4, the cardioverter-defibrillator system was not explanted. There were no perioperative deaths. A new implantable cardioverter-defibrillator system was reimplanted in 7 patients after 2 to 6 weeks of antibiotic therapy. Ten patients were treated without reimplantation (2 arrhythmia operation, 8 antiarrhythmic drugs). Four patients (3 patients without explantation and 1 with partial system removal) were treated with maintenance long-term antibiotic therapy. During a mean follow-up of 21 +/- 2.8 months, no patient had clinical recurrence of infection. One patient treated with antiarrhythmic drugs without system reimplantation died suddenly. CONCLUSIONS: Infections that involve implantable cardioverter-defibrillator systems can be safely managed by removing the entire system with reimplantation after intravenous antibiotic therapy. In selected patients in whom the risk for system explantation is high and anticipated life expectancy is short, long-term antibiotic therapy to suppress low-virulence infections may represent an acceptable alternative.

The nature of the organism. Life has a life of its own.

The question of closure in biological systems is central to understanding the origins of the biological variation and complexity upon which various forms of selection act. Much of evolutionary theory, especially in the second half of the twentieth century, is concerned with the consequences of environmental selection acting on bio-diversity, but neglects questions of the origin of that diversity. This has permitted us to act as if an explanation of consequences was the ultimate explanation in biology. However, Darwin understood that evolution was both information driven and information constrained. The link between evolutionary constraints and closure can be profitably explored by starting with Darwin's notion of the primary of "the nature of the organism" over "the nature of the conditions" articulated in the sixth edition of Origin of Species. Contemporary ideas of self-organization, emergence, complexity, and inherent (developmental and phylogenetic) constraints can be seen as an elaboration and refinement of Darwin's views if we adopt the following perspective: (1) information is cheap, not costly, to produce, but may have costly consequences; and (2) information is produced by systems that are informationally closed but remain thermodynamically open.

Stable transformation of trypanosomatids through targeted chromosomal integration of the selectable marker gene encoding blasticidin S deaminase.

The susceptibilities of the protozoan parasites Leishmania mexicana and Trypanosoma brucei to the nucleoside antibiotic blasticidin S were assessed. A concentration of 10 microg ml(-1) was sufficient to cause cell death within 72 h of L. mexicana promastigotes and bloodstream forms of T. brucei in vitro. The gene encoding blasticidin S deaminase (BSD) was therefore incorporated into cassettes for targeting to the cysteine proteinase C locus of L. mexicana (CPC::BSD) and the tubulin locus of T. brucei (tub::RAD51-BSR). Following transfection of mutant parasites that contained other well-established selectable marker genes (HYG, NEO, BLE, PAC and SAT), clones resistant to 10 microg ml(-1) blasticidin S were shown by PCR and Southern blotting to have integrated the cassettes by homologous recombination. The results confirm that BSD can be used as a selectable marker gene for targeted chromosomal integration during genetic manipulations of trypanosomatids.

Health status and health care use of Massachusetts women reporting partner abuse.

BACKGROUND: Studies indicate that women abused by their intimate partners are at increased risk for a number of health problems and have increased rates of health care utilization. However, these findings are based mainly on studies using clinic or health plan populations. In this study, we examined the association between intimate partner abuse (IPA) and health concerns and health care utilization in a population-based sample of adult women. METHODS: We analyzed data on 2043 women aged 18 to 59 who participated in the 1998 Massachusetts Behavioral Risk Factor Surveillance System (BRFSS), a population-based health survey that included questions on IPA. IPA was defined as experiencing physical violence by, fear of, or control by an intimate partner. Consequences of IPA and self-rated health status and health care utilization of women experiencing IPA were examined. RESULTS: A total of 6.3% of Massachusetts women aged 18 to 59 reported IPA during the past year. Women experiencing IPA were more likely than other women to report depression, anxiety, sleep problems, suicidal ideation, disabilities, smoking, unwanted pregnancy, HIV testing, and condom use. Women experiencing IPA were less likely to have health insurance, but received routine health care at similar rates as other women. CONCLUSIONS: These results indicate that women in the general population experiencing IPA are at increased risk for several serious emotional and physical health concerns. Most of these women are in routine contact with health care providers. These findings also suggest that the BRFSS may provide a valuable mechanism for tracking state-based IPA prevalence rates over time.

Lower use of dental services among long term cigarette smokers.

STUDY OBJECTIVE: Given the advanced stage of most oral cancer cases at diagnosis, it is hypothesised that a significant proportion of higher risk adults do not visit a dentist annually. The study objectives were to assess whether long term smokers were less likely to visit the dentist. DESIGN: Data from the 1998 Massachusetts Behavioral Risk Factor Surveillance System, a population-based, random digit dial telephone health survey, were used to evaluate whether adults at higher risk of oral cancer attributable to long term cigarette smoking were less likely to go to the dentist, controlling for socioeconomic, demographic, and health related characteristics. PATIENTS: A representative sample of 2119 Massachusetts adults aged 35 and older. MAIN RESULTS: Adults who were long term smokers were less likely than never smokers to have visited the dentist in the previous year (adjusted OR = 0.69, 95% confidence intervals (CI) = 0.48, 0.99). Moreover, adults who were at higher risk from both long term smoking and low fruit and vegetable consumption were even less likely to visit the dentist than adults with neither risk factor (adjusted OR = 0.39, 95% CI = 0.22, 0.68). Among long term smokers, the likelihood of a yearly examination decreased with increasing smoking duration and amount smoked per day. CONCLUSIONS: These findings support the hypothesis that adults at higher risk of oral cancer attributable to long term cigarette smoking are less likely to have routine dental examinations, even controlling for socioeconomic and health related differences.

Support for condom availability and needle exchange programs among Massachusetts adults, 1997.

This study was conducted to determine whether demographic factors, variables related to HIV risk status, or personal attitudes predicted public support for condom availability programs in high schools and needle exchange programs. Data for these analyses were collected from the 1997 Massachusetts Behavioral Risk Factor Surveillance System (BRFSS) among adults aged 18-64. Overall, 79% of Massachusetts adults aged 18-64 supported condom availability programs, and 60% supported needle exchange programs. Younger age was the strongest demographic predictor of support for condom availability, and higher socioeconomic status was the strongest predictor of support for needle exchange programs. Support for both programs was weakly associated with personal HIV risk status but strongly associated with positive attitudes toward teaching about HIV in schools and advising sexually active teens to use condoms. Our data suggest that there is broad-based public support for implementation of condom availability and needle exchange programs as tools for HIV prevention.

The importance of protistan phylogeny for macroevolution.

Explicit estimates of protist phylogeny should play a key role in the development of macroevolutionary theory. Nearly half the evolutionary history of living systems involved only protists, and many trends and traits of macroevolutionary significance originated in protist groups. Special areas of research that can make use of protist phylogenies include: (1) origin of life studies, (2) biotic aspects of the evolution of the environment, (3) developmental biology and evolution, and (4) macroevolutionary trends in the diversification of life.

Phylogenetics and the future of helminth systematics.

Phylogenetic systematics is a relatively new formal technique that increases the precision with which one can make direct estimates of the history of phylogenetic descent. These estimates are made in the form of phylogenetic trees, or cladograms. Cladograms may be converted directly into classifications or they may be used to test various hypotheses about the evolutionary process. More than 20 phylogenetic analyses of helminth groups have been published already, and these have been used to investigate evolutionary questions in developmental biology, biogeography, speciation, coevolution, and evolutionary ecology.

Origins, diversification, and historical structure of the helminth fauna inhabiting neotropical freshwater stingrays (Potamotrygonidae).

Members of the freshwater stingray family Potamotrygonidae occur throughout the major river systems of eastern South America that empty into the Atlantic Ocean. Ichthyologists have tended to assume that the ancestor of the potamotrygonids was an Atlantic marine or euryhaline stingray that dispersed into freshwater, presumably during the last marine ingression 3-5 million years ago. The helminth parasites that inhabit potamotrygonids suggest an alternative perspective on their origin. Phylogenetic and biogeographic analysis of the helminths inhabiting potamotrygonids suggest that the hosts are derived from an ancestral Pacific urolophid stingray that was trapped in freshwater by the uplifting of the Andes beginning perhaps as early as the early Cretaceous period and ending by the mid-Miocene epoch, changing the course of the Amazon River, which previously had flowed into the Pacific Ocean.

The phylogeny of the cercomeria (Platyhelminthes: Rhabdocoela) and general evolutionary principles.

The unified theory of evolution is an expansion of Darwinian theory that asserts that evolution is driven by entropic accumulation of genetic information that is constrained and organized primarily by the genealogical effects of phylogenetic history and developmental integration, and secondarily by ecological effects, or natural selection in its classical mode. Phylogenetic systematic analysis of the 8 major groups of parasitic rhabdocoelous platyhelminths permits empirical macroevolutionary evaluation of these postulates. Of the 131 characters considered, 127 are phylogenetically constrained, and 4 show evidence of 1 case of convergence each. Data from different developmental stages are phylogenetically congruent, despite differences in ecology among those stages. Ecological diversification, indicated by phylogenetic association of definitive hosts and parasites, and by changes in ecological components of life cycle patterns, is more conservative evolutionarily than diversification in developmental patterns, indicated by the appearance of unique larval stages, asexual proliferation of larvae, polyembryony, and heterochronic changes. These observations support the macroevolutionary postulates of the unified theory.

Two tetraphylidean cestodes from the freshwater stingray Potamotrygon magdalenae Dumeril 1852 (Chondrichthyes: Potamotrygonidae) from Colombia.

Two new tetraphyllidean cestodes are described from the freshwater stingray Potamotrygon magdalenae from Colombia. The new genus Potamotrygonocestus is proposed for P. magdalenensis, which differs from Pedibothrium by having a bilobed rather than X-shaped ovary, and simple rather than bifid hooks. It further differs from Pachybothrium hutsoni by having bothridial hooks inserted immediately posterior to an accessory sucker rather than inserted in the middle of a thick muscular pad. Potamotrygonocestus magdalenensis is unique among known tetraphyllideans by possessing vitellaria which are compact, cylindrical bands in the lateral portions of the middle of the proglottid. The second new species, Rhinebothrium moralarai, resembles R. scorzai by having its genital pore and terminal genitalia at the ovarian level, greatly reduced poral ovarian lobes, and by parasitizing a freshwater stingray. It differs from R. scorzai in number of bothridial loculi, testes per proglottid, and proglottids per strobila; by having quadrate rather than canoe-shaped bothridia; and by parasitizing Potamotrygon magdalenae rather than P. hystrix.

Phylogenetic analysis of Alloglossidium Simer, 1929 (Digenea: Plagiorchiiformes: Macroderoididae) with discussion of the origin of truncated life cycle patterns in the genus.

Alloglossidium comprises 9 species of North American plagiorchiiform digeneans using ictalurid catfish, freshwater crustacea, and hirudinid leeches as definitive hosts. Two hypotheses about the evolution of this array of definitive hosts were examined using phylogenetic systematic analysis. Two most parsimonious trees, based on 15 homologous series derived from morphological data, each indicated the 2 species utilizing ictalurid catfish definitive hosts are basal members of the group, whereas the 2 species using freshwater crayfish definitive hosts and the 5 utilizing leech definitive hosts each comprise relatively derived monophyletic sister groups. The results suggest that species using crustaceans as definitive hosts are derived by life cycle truncation, whereas those using leeches as definitive hosts appear to be derived through a switch from crustaceans to leeches.

Rhinebothrium devaneyi n. sp. (Eucestoda: Tetraphyllidea) and Echinocephalus overstreeti Deardorff and Ko, 1983 (Nematoda: Gnathostomatidae) in a thorny back ray, Urogymnus asperrimus, from Enewetak Atoll, with phylogenetic analysis of both species groups.

The new species is a member of an apparently monophyletic group within the genus that includes R. flexile, R. walga, R. himanturi, R. burgeri, R. euzeti, R. hawaiiensis, R. urobatidium, R. paratrygoni, R. ditesticulum, R. tetralobatum, R. margaritense, R. biorchidum, and R. spinicephalum. All of these species have bothridia with medial longitudinal septa, a constriction at mid-bothridium, and, primitively, at least 42 loculi per bothridium and 17-22 testes per proglottid. Of the above, the new species is apparently most closely related to R. burgeri, with which it shares an increased number of testes (30-43) per proglottid, a V-shaped ovary, and a muscular genital pore. The new species is distinct by virtue of possessing 94-152 loculi per bothridium--no other known species has more than 78. This is the second report of Echinocephalus overstreeti from a stingray. It represents a new host, U. asperrimus, and a new location, Enewetak Atoll. Phylogenetic and biogeographic analysis of each species group suggests an ancient Tethys Sea-circum-Pacific origin and evolution. This supports the hypothesis of ancient Pacific origins for potamotrygonid stingrays.

Escherbothrium molinae n. gen. et n. sp. (Eucestoda: Tetraphyllidea: Triloculariidae) in Urotrygon chilensis (Chondrichthyes: Myliobatiformes: Urolophidae) from the Gulf of Nicoya, Costa Rica.

Cestodes collected in spiral valves of the stingray Urotrygon chilensis from the Pacific coast of Costa Rica represent an undescribed species of Tetraphyllidea. By possessing more than 2 loculi as well as an apical sucker on each bothridium, the new species is diagnosably distinct from all other tetraphyllidean genera; therefore, a new genus is proposed for it. The new species also possesses globular structures irregularly arranged on the surface of the bothridia. We found similar structures on the bothridial faces of Trilocularia acanthiaevulgaris, possibly indicating phylogenetic relationships with the new species. This possibility is enhanced by the observation that the bothridia of T. acanthiaevulgaris comprise 2 loculi and an apical sucker, rather than 3 loculi.

Cestode parasites in Potamotrygon motoro (Natterer) (Chondrichthyes: Potamotrygonidae) from southwestern Brazil, including Rhinebothroides mclennanae n. sp. (Tetraphyllidea: Phyllobothriidae), and a revised host-parasite checklist for helminths inhabiting neotropical freshwater stingrays.

Specimens of 5 species of cestodes were collected in 6 specimens of the freshwater stingray species Potamotrygon motoro (Natterer), collected in the vicinity of Corumba, Mato Grosso do Sul, Brazil. Acanthobothrium regoi, Potamotrygonocestus orinocoensis, Rhinebothroides venezuelensis, and Rhinebothrium paratrygoni are reported from P. motoro and from southwestern Brazil for the first time. Rhinebothroides mclennanae n. sp. appears to be the sister species of Rhinebothroides glandularis, the only other member of the genus exhibiting darkly staining glandular cells lying free in the parenchyma surrounding the terminal genitalia. The new species resembles Rhinebothroides glandularis, Rhinebothroides freitasi, and Rhinebothroides scorzai by having poral ovarian arms that extend anteriorly beyond the posterior margin of the cirrus sac, coiled vaginae, and vitelline follicles not interrupted on the poral side in the vicinity of the genital pore. It differs from all 6 previously described members of the genus by possessing an average of 31 testes per proglottid, compared with an average of 45 for R. glandularis, 55 for R. freitasi and R. venezuelensis, 77 for Rhinebothroides circularisi and Rhinebothroides moralarai, and 80 for R. scorzai. An updated phylogenetic tree for Rhinebothroides is presented.

Halipegus eschi n. sp. (Digenea: Hemiuridae) in Rana vaillanti from Guanacaste Province, Costa Rica.

Halipegus eschi n. sp. is described from the esophagus of Rana vaillanti from Guanacaste Province, Costa Rica. The new species differs from other known species of Halipegus on the basis of relative testis size, lateral extent of the uterus, vitelline follicle arrangement, egg size, and polar filament length.