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PubMed2003

Arbuscular mycorrhizae of the palm Astrocaryum mexicanum in disturbed and undisturbed stands of a Mexican tropical forest.

Tropical forests are dynamic systems with extensive natural disturbance, gaps in the canopy being one of the most important types. Tree and branch fall are often the principal cause of natural disturbance. This research was done on adult individuals of a very abundant palm ( Astrocaryum mexicanum Liebm, Arecaceae), which is found in the understorey of the forest at Los Tuxtlas, Mexico. Percentages of colonization by arbuscular mycorrhizae were determined for individuals selected randomly from plots located both in gaps and under closed canopy. The highest percentages of total colonization, as well as those of hyphae and vesicles, were recorded for gaps. In forest with closed canopy, arbuscules had the highest percentages of colonization; on these sites the palm has been observed to grow less. The higher production of arbuscules may favour nutrient capture in this microenvironment, which is characterized by strong competition.

Arecaceae↗

PubMed2004

Forest gap dynamics and the Ising model.

The vegetation height in forest ecosystems is spatially heterogeneous. Canopy gaps (sites with low vegetation) are formed by treefalls, and they recover to canopy sites (with high vegetation) either by growth of small trees or by branch extension of surrounding trees. The dynamics of canopy gaps have been studied using a spatial Markov chain with nearest neighbor interaction. (1) If the canopy recovery rate is constant and if the gap formation rate for a site increases exponentially with the number of neighboring gap sites, the equilibrium distribution is the same as the one generated by the Ising model in statistical mechanics. Here, we extend the equivalence to the situation in which both the gap formation and canopy recovery depend on the neighborhood, as shown in recent forest data. (2) We develop a statistical test of whether a given spatial pattern is a random sample from the Ising model. The test is based on the conditional probability of configurations on a partial lattice. We apply the method to vegetation height data from the Ogawa forest reserve, Japan, measured on a 5x5 m grid in 1976, 1981, 1986, and 1991. The spatial pattern of the original forest data deviates significantly from the Ising model. We examine whether a larger sampling distance or the removal of the effects of the topography can reduce this deviation.

Ecosystem↗

PubMed1997

The safety and efficacy of amocarzine in African onchocerciasis and the influence of ivermectin on the clinical and parasitological response to treatment.

The hundred men from a forest area of Ghana, without vector control or ivermectin distribution, were randomized to receive a single dose of ivermectin (150 micrograms/kg body weight) on day 1 followed by amocarzine (3 mg/kg twice daily after meals) on days 8, 9 and 10 (34 patients), the ivermectin alone (33 patients) or the amocarzine alone (33 patients). Detailed clinical and laboratory examinations were made before, during and after drug administration. On day 120, all palpable nodules were excised, fixed, sectioned, stained and examined by two blinded observers and the results compared with those for nodules from untreated controls. Mazzotti-type reactions, such as itching, rash, peripheral sensory phenomena and swellings, were more severe or frequent with amocarzine than ivermectin. Pretreatment with ivermectin markedly suppressed these reactions to amocarzine but did not affect other manifestations such as dizziness and gaze-evoked nystagmus. Ocular effects were minor in all groups. Ivermectin produced minor macrofilaricidal effects on the adult male worms, marked degeneration of intra-uterine embryos, and potent microfilaricidal effects and suppressed skin microfilariae. Amocarzine did not affect the male worms or the intra-uterine embryos, was a less potent microfilaricide and did not suppress skin microfilariae. The efficacy of ivermectin plus amocarzine was similar to that of ivermectin alone. The present results do not support the findings from the Americas and show that amocarzine has no role in the treatment of onchocerciasis in Africa.

Adolescent↗

PubMed2006

Patterns in soil fertility and root herbivory interact to influence fine-root dynamics.

Fine-scale soil nutrient enrichment typically stimulates root growth, but it may also increase root herbivory, resulting in trade-offs for plant species and potentially influencing carbon cycling patterns. We used root ingrowth cores to investigate the effects of microsite fertility and root herbivory on root biomass in an aggrading upland forest in the coastal plain of South Carolina, USA. Treatments were randomly assigned to cores from a factorial combination of fertilizer and insecticide. Soil, soil fauna, and roots were removed from the cores at the end of the experiment (8-9 mo), and roots were separated at harvest into three diameter classes. Each diameter class responded differently to fertilizer and insecticide treatments. The finest roots (< 1.0 mm diameter), which comprised well over half of all root biomass, were the only ones to respond significantly to both treatments, increasing when fertilizer and when insecticide were added (each P < 0.0001), with maximum biomass found where the treatments were combined (interaction term significant, P < 0.001). These results suggest that root-feeding insects have a strong influence on root standing crop with stronger herbivore impacts on finer roots and within more fertile microsites. Thus, increased vulnerability to root herbivory is a potentially significant cost of root foraging in nutrient-rich patches.

Animals↗

PubMedDate not supplied

Protostelids from tropical forests, woodlands and deserts in Australia.

Most of what is known about the distribution of protostelids is limited to results from surveys carried out in North and Central America. To increase our knowledge about protostelid diversity and distribution we surveyed protostelids from 12 study sites in northern Queensland and the Northern Territory of Australia during May-Jun 2003. Aerial litter and ground litter samples were randomly collected along a 200 m transect at each site. Study sites ranged from tropical forests to deserts. We recovered 10 species and two apparently undescribed species from samples of aerial (dead but still attached plant parts) and ground litter. Samples from a woodland site characterized by intermediate moisture conditions had the greatest species richness, followed by samples from dry woodland, tropical forest and desert sites. When species richness for a particular microhabitat was considered, samples of aerial litter yielded more species than samples of ground litter. Percentages of samples colonized with protostelids were similar for the aerial and ground litter microhabitats within a given habitat type except for dry woodlands, in which aerial litter samples were characterized by higher numbers of species than ground litter samples. Two species (Protostelium mycophaga and Soliformovum irregularis) that in temperate North America are associated with aerial litter microhabitats also were recovered from aerial litter in dry habitats in Australia. Schizoplasmodiopsis pseudoendospora, a North American temperate ground litter species, was equally abundant in aerial litter and ground litter in Australia. This study is the first of its kind for protostelid ecology in Australia and the most extensive study of protostelids in the southern hemisphere. These data complement ongoing research on protostelid distribution from around the world.

Australia↗

PubMed2003

Genetic diversity of the tropical tree Terminalia amazonia (Combretaceae) in naturally fragmented populations.

The effect of long-term fragmentation on the genetic diversity of populations of the neotropical tree species, Terminalia amazonia, was studied using random amplified polymorphic DNA (RAPD) analysis. Leaf material from 104 trees was collected from three naturally fragmented gallery forest patches and three plots in nearby continuous forest in the Mountain Pine Ridge, Belize. In total, 30 RAPD bands generated by five decamer primers were used to compare the genetic diversity of the six populations in the two groups. Genetic variation within the populations (H0), as estimated by the Shannon diversity index, ranged from 0.32 to 0.38, with an overall diversity of 0.38 (Hspecies). Analysis of molecular variation revealed that most (94.4%, P<0.001) of the variation was attributable to differences among individuals within populations. Population differentiation was significantly (P=0.038) lower among the fragmented populations than among continuous forest populations. On average, the fragmented populations also had slightly, but statistically significant (P=0.046) lower levels of genetic diversity. However, one gallery forest site had a higher level of genetic diversity than two of the continuous forest sites. We suggest that the long-term effect of fragmentation on the genetic diversity of tropical trees will depend upon the amount of local forest cover in proximity to the fragmented populations.

DNA, Plant↗

PubMed2003

Arbuscular mycorrhizal fungi associated with Araucaria angustifolia (Bert.) O. Ktze.

Specimens of Araucaria angustifolia from a native forest reserve and a reforested area in the State Park of Campos do Jordão were studied to determine the number and diversity of spore populations of arbuscular mycorrhizal fungi (AMF) and root colonization. Six randomly chosen plots (planted with 8- to 12-year-old plants) were delimited, four in the native forest and two in the reforested area. Rhizosphere and root samples were collected during two periods of the year corresponding to the rainy and dry seasons. A greenhouse experiment was set up for multiplication of field propagules (from the native forest and reforested area) for two consecutive generations. Araucaria leaves from the experimental plots were collected during the first sampling for nutrient analysis. Twenty-four AMF taxa were found and percent AM colonization was determined in all plots. Not all AMF species observed in the field were re-isolated through the recovery pot cultures, even after a second cultivation cycle. The foliar nutrient analysis showed higher nutrient levels in plants from the native forest than the reforested area. Generally, spore richness and diversity were highest during the warmer and more humid period and in the native forest plants.

Brazil↗

PubMed2005

Responses of floodplain forest species to spatially condensed gradients: a test of the flood-shade tolerance tradeoff hypothesis.

Previous work in southeastern US floodplains led to the hypothesis that a tradeoff between flood and shade tolerance underlies species-specific responses to flooding and light, which drive forest regeneration. In systems where community turnover can occur with small-scale environmental changes, testing this hypothesis requires recognizing that turnover of species along the two gradients can be large relative to the spatial distances involved. We test the tradeoff hypothesis in an old-growth bottomland hardwood forest by (1) comparing shade and moisture profiles of woody juveniles versus random points and (2) using individual-based sampling of woody juveniles to model probability of occurrence in response to distance-to-water table and canopy openness gradients. We found that juveniles of all species combined occupied a similar range of distance-to-water table compared to measurements taken at random points, but average canopy openness above seedlings was significantly higher than at random points. On average, shade-tolerant species, with the exception of Acer rubrum, were found in shaded areas that were also drier, whereas less shade-tolerant taxa, plus A. rubrum, were found in wetter, more open areas, suggesting a tradeoff between flood and shade tolerance. Predictive models of species occurrence, which incorporate the availability of canopy and microtopographic conditions, indicated that three taxa (Fraxinus pennsylvanica, Quercus spp., and Ulmus americana) had patterns consistent with a flood-shade tolerance tradeoff. In contrast, Asimina triloba, Celtis laevigata, and Liquidambar styraciflua had positive responses when the joint stresses of flooding and shade were diminished. A. rubrum appeared to be the most tolerant to both stresses. Our work not only lends support to the flood-shade tradeoff hypothesis but also indicates that a more general model is needed that includes a "flood-shade release" component. We also suggest that responses to small-scale gradients should not be overlooked, particularly in systems where the gradients are ecologically steep.

Disasters↗

PubMed1985

Introgression between two cutthroat trout subspecies with substantial karyotypic, nuclear and mitochondrial genomic divergence.

The authors used allozymes encoded by nuclear genes and restriction enzyme analysis of mitochondrial DNA (mtDNA) to study secondary contact between westslope (Salmo clarki lewisi) and Yellowstone cutthroat trout (Salmo clarki bouvieri) in Forest Lake, Montana. Eleven diagnostic allozyme loci identified this as a random-mating hybrid swarm. No parental, first-generation hybrid or backcross genotypes were detected in the sample (N = 33), and genotype distributions at all the variable loci conform to binomial expectations. There is little linkage disequilibrium between the diagnostic loci, indicating that the nuclear genomes of the two subspecies are largely randomly associated. The allozymes and mtDNA give identical estimates of the proportional genetic contribution of each subspecies. Thus, males and females from both subspecies have contributed equally to this hybrid swarm. Although these subspecies have accumulated substantial genetic divergence between their nuclear (Nei's D = 0.34) and mitochondrial (2% sequence divergence) genomes, this has not resulted in a genetic barrier to exchange between them.

Alleles↗

PubMed2026

Targeted Next-Generation Sequencing for Improved Clinical Outcomes in People Living With Rare Diseases in Global South: Protocol for a Systematic Review and Meta-Synthesis.

BACKGROUND: Rare diseases affect many individuals and pose major challenges in diagnosis and treatment, especially in Global South countries where health care resources are limited. Targeted next-generation sequencing (NGS) has significantly advanced diagnostic accuracy and clinical care for rare diseases globally; however, its implementation and impact within the Global South context remain insufficiently studied. OBJECTIVE: This study aims to evaluate the use, clinical benefits, challenges, and implementation outcomes of targeted NGS for diagnosing and managing rare diseases in Global South populations. Specifically, it seeks to quantify the diagnostic yield of NGS, examine its influence on subsequent clinical decision-making, and identify principal barriers to, and facilitators of, the implementation of targeted NGS approaches in these contexts. METHODS: This protocol follows the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We will systematically search PubMed, Scopus, and Web of Science for studies published between 2005 and 2025 that report on the use of targeted NGS in Global South population with rare diseases. Two reviewers will independently perform study selection, data extraction, quality assessment, and evaluation of risk of bias by using QUADAS-2 for diagnostic accuracy studies and the risk of bias assessment tool for nonrandomized studies. Meta-analyses will be conducted to estimate pooled outcomes for diagnostic yield, with heterogeneity assessed using random effects models. Heterogeneity will be further examined through visual inspection of forest plots and by evaluating the chi-square test and I² statistic. RESULTS: The protocol has been registered with PROSPERO (CRD420251078455). Database search or screening, data extraction, and data synthesis are planned to commence in June 2026 and conclude by September 2026. Study findings will synthesize the diagnostic yield, clinical impact, and contextual determinants influencing the implementation of targeted NGS in Global South health care settings. CONCLUSIONS: This review will provide evidence on the application, advantages, limitations, and clinical outcomes of targeted NGS for individuals affected by rare diseases in countries of the Global South. The finding will identify priorities for capacity strengthening, policy development, and future genomic research. TRIAL REGISTRATION: PROSPERO CRD420251078455; https://www.crd.york.ac.uk/PROSPERO/view/CRD420251078455. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/85150.

Rare Diseases↗

PubMed1985

Rickettsia-like organisms in ticks and antibodies to spotted fever-group rickettsiae in mammals from northern Mississippi.

Studies were conducted from April through August during 1974 and 1975 on 30 randomly selected trapping sites in Wall Doxey State Park, Holly Springs National Forest, and 1.6 km south of the park in Marshall County, Mississippi to provide information on the occurrence of ticks involved in the maintenance and transmission of spotted fever-group rickettsiae in nature. Of 365 animals (14 species) collected, 186 (51%) were parasitized by 4,169 ticks. Species of ticks collected included: Dermacentor variabilis; Amblyomma americanum; Rhipicephalus sanguineus; Haemaphysalis leporispalustris; and Ixodes texanus. Of 2,105 ticks examined, 116 (5.5%) were positive for rickettsia-like organisms.

Agglutination Tests↗

PubMed1999

Annual and seasonal variation of tick-borne encephalitis virus (TBEV) prevalence in ticks in selected hot spot areas in Germany using a nRT-PCR: results from 1997 and 1998.

The prevalence of tick-borne encephalitis virus (TBEV) in Ixodes ricinus tick populations in endemic areas of Germany with the highest TBE risk is unknown. Annual and seasonal differences in TBEV prevalence have also not been studied. Against this background, in May 1997 we started a systematic virus surveillance programme in ticks collected in locations known to have a high incidence of autochthonous TBE cases. These were 5 locations in Baden-Württemberg (Black Forest) and 8 locations in Bavaria (surrounding Passau). Field-collected ticks were randomly assigned to pools of 10 adults or 20 nymphs, respectively. The tick pools were tested for the presence of TBEV-RNA using a newly developed, sensitive nested reverse transcriptase polymerase chain reaction assay (nRT-PCR). The primer pairs were selected from the 5'-terminal noncoding region, a highly conserved part of the virus. The specificity was tested by computer homology searches of sequences, as well as by sequencing of the first and the second amplificates, by Southern blot hybridisation with a DIG-labelled oligonucleotide probe, and by restriction enzyme analysis. The method has proved to be very sensitive, with a detection limit of 20 fg of TBEV RNA per PCR run, or a single positive tick. Based on biostatistical considerations a sample size of at least 1000 ticks per estimation point was chosen. The estimated TBEV prevalence and confidence intervals (CI) were calculated from the nRT-PCR results of pooled samples (10 adults or 20 nymphs) using appropriate formulae for pooled testing. In order to identify the estimated TBEV prevalence as well as to assess the influence of annual and seasonal factors on TBEV prevalence, ticks were sampled twice a year (May and September) in 1997 and 1998 at exactly identical sites. These sites were selected because they were known to have had the highest incidence of autochthonous TBE cases during the previous 10 years. On sampling days, relevant local meteorological data were also noted. In total, 8500 I. ricinus ticks were investigated in this study, 4270 (3540 nymphs, 730 adults) from the Black Forest habitats, and 4230 (3680 nymphs, 550 adults) from the Bavarian locations. In the foci near Freiburg (Black Forest), the estimated virus prevalence was relatively high in the whole tick population, during 1997 with only slight seasonal differences [3.4% (confidence interval, CI, 2.3-4.8%) in May and 2.9% (CI 1.7-4.5%) in September]. In contrast, in 1998, in the same foci the estimated TBEV prevalence was considerably lower [1.1% (CI 0.5-2.0%) in May and 0.6% (CI 0.2-1.4%) in September]. Thus, while the seasonal differences again remained low, the annual variation was marked. In the Bavarian foci in 1997, the estimated virus prevalence of the whole tick population studied was lower than in the Black Forest foci and the seasonal fluctuations were low: in May 1997 0.9% (CI 0.4-1.8%) of the ticks were positive, in September 1.1% (CI 0.5-1.9%). In 1998, in May 2.0% (CI 1.1-3.3%) of the ticks were positive, and in September 1.1% (CI 0.5-2.1%). For the whole study period, every 50th to 100th I. ricinus nymph or adult in the Passau region was calculated to give a positive signal in the nRT-PCR. The TBEV prevalence data indicate that residents and visitors of areas in Germany known for high endemic activity take a significant risk of contracting TBEV infection, if bitten by ticks. In addition, the data suggest that annual fluctuations may exist in the whole tick population studied. Seasonal fluctuations of the virus prevalence in ticks were small.

Adult↗

PubMed2005

Memantine for dementia.

BACKGROUND: Memantine, a low affinity antagonist to glutamate NMDA receptors, may prevent excitatory neurotoxicity in dementia. OBJECTIVES: To determine efficacy and safety of memantine for people with Alzheimer's disease (AD), vascular (VD) and mixed dementia. SEARCH STRATEGY: The Specialized Register of the Cochrane Dementia and Cognitive Improvement Group was searched on 28 October 2004. This register contains references from all major healthcare databases and many ongoing trial databases and is updated regularly. In addition the search engines Copernic and Google were used to identify unpublished trials through inspection of the websites of licensing bodies like the FDA , EMEA an Nice and of companies' websites (Lundbeck, Merz, Forest, Suntori etc). SELECTION CRITERIA: Double-blind, parallel group, placebo-controlled, randomized trials of memantine in people with dementia. DATA COLLECTION AND ANALYSIS: Data were pooled where possible. Intention-to-treat (ITT) and observed case (OC) analyses are reported. MAIN RESULTS: 1. Moderate to severe AD. A major study (MD-01) is unpublished. Published data from two six month studies show a small beneficial effect of memantine at six months on cognition (4.12 SIB points, 95% Confidence Interval (CI) 2.14 to 5.74, P < 0.00001), activities of daily living (1.70 ADCS-ADLsev19 points, 95% CI 0.63 to 2.76, p = 0.002) and behaviour (3.64 NPI points, 95% CI 1.38 to 5.90, p = 0.002), supported by clinical impression of change (0.27 CIBIC+ points, 95% CI 0.10 to 0.43, p = 0.002). The unpublished study would need to have found a detrimental effect of memantine to overturn the statistical significance of the benefits apparent in the two published studies. 2. Mild to moderate AD. In a single six month trial, memantine had a beneficial effect on ITT analysis of cognition, (1.9 ADAS-Cog points, 95% CI 0.35 to 3.43, p = 0.02) and behaviour (3.50 NPI points 95% CI 0.15 to 6.85, p = 0.04) supported by clinical global impression of change (0.30 CIBIC+ points, 95% CI 0.09 to 0.51, p = 0.005), but no effect on activities of daily living or OC analysis of cognition. The statistical significance of these benefits could be overturned by data from two unpublished studies which are known to show no significant effect. 3. Mild to moderate vascular dementia. In two six month studies, memantine improved cognition (1.85 ADAS-Cog points, 95% CI 0.88 to 2.83, p = 0.0002), and behaviour (Weighted Mean Difference (WMD) 0.84 95% CI 0.06 to 0.91, p = 0.03) but this was not supported by clinical global measures.4. Patients taking memantine were less likely to develop agitation (Odds Ratio (OR): 0.65, 95% CI 0.48 to 0.89, p = 0.007). The effect on agitation which is already present is unknown.5. Memantine is well tolerated. AUTHORS' CONCLUSIONS: Published data suggest a small beneficial effect of memantine at six months in moderate to severe AD. The beneficial effect on cognition in patients with mild to moderate vascular dementia was not clinically discernible at six months. Whether memantine has any effect in mild to moderate AD is unknown.

Activities of Daily Living↗

PubMed2004

Natural occurrence of moulds and aflatoxin B1 in melon seeds from markets in Nigeria.

Shelled melon seeds (Colocynthis citrullus L.) were purchased from markets in randomly selected villages and towns in three states in each of the rain forest (Ogun, Oyo and Osun) and Northern guinea savanna (Kaduna, Niger and Bauchi) zones of Nigeria. The seed samples were analysed for incidence of visibly diseased seeds, moisture content, moulds and aflatoxin B1 contamination. The incidence of diseased seeds ranged from 6.4% to 50.4% in the forest, and 4.3% to 34.3% in the savanna, and the moisture content was 5.6% to 12.6% and 4.5% to 10.3%, respectively. Mould evaluation revealed that Aspergillus was the most frequent genus, followed by Penicillium, Botryodiplodia, Cladosporium and Rhizopus in decreasing sequential order. Aspergillus flavus had the highest individual count in melon seed from both zones. Aflatoxin B1 was detected at levels above 5 microg/kg in 32.2% of samples, while only 3.5% of the samples contained the toxin above the 20 microg/kg Nigerian tolerance level in food. The percentage of samples contaminated with aflatoxin B1 was statistically comparable for the pooled data of villages and towns. The median level of aflatoxin B1 was less than 5 microg/kg in the seed samples, while the mean aflatoxin B1 levels was 14.1 microg/kg in the forest and 13.0 microg/kg in the savanna samples.

Aflatoxin B1↗

PubMed2004

Effect of dietary phosphorus concentration on estrous behavior of lactating dairy cows.

The objective of this study was to determine the effect of dietary phosphorus (P) concentrations of 0.38 (adequate) or 0.48% (excess) of the total mixed ration (TMR) (dry matter basis) on estrous behavior of lactating cows as measured by a radiotelemetric system (HeatWatch; De Forest, WI, USA). At calving, 42 Holstein cows (n=21 per treatment) were randomly assigned to one of two dietary P treatments. Cows were milked twice daily and milk weights were recorded. Cows were housed in a free-stall barn and were fitted with a radiotelemetric transmitter 40 days postpartum to record estrous mounting activity. The total number of estruses recorded for the 42 cows were 72 (37 and 35 for cows in the adequate and excess P groups, respectively). The mean duration of estrous cycles was 22 +/- 0.6 days and 21 +/- 0.4 days for cows fed the adequate and excess P diets, respectively (P=0.14). The mean duration of estrus was 8.9 +/- 1.1 h and 8.6 +/- 1.2 h (P=0.86), the average number of mounts during estrus was 7.0 +/- 1.2 and 8.2 +/- 1.7 (P=0.57), and the total mounting time was 27.1 +/- 4.3 s and 30.8 +/- 6.5 s (P=0.64) for cows fed the adequate and excess P diets, respectively. Phosphorus treatment had no significant effect on intensity or duration of estrus.

Animal Nutritional Physiological Phenomena↗

PubMed1994

Genetic variation estimated in three Shorea species by the RAPD analysis.

Three species of Shorea (S. leprosula, S. acuminata and S. cursitii) were collected from a natural forest reserve of Malaysia and analyzed for genetic variation using the technique of random amplification of polymorphic DNA (RAPD) by the polymerase chain reaction (PCR). The average number of nucleotide substitutions was estimated. The nucleotide diversities within species were very similar and larger than those found in Drosophila melanogaster. The nucleotide divergences between these species are about 1.5 times the nucleotide diversities within the species, indicating that these species diverged from a common ancestor relatively recently.

Base Sequence↗

PubMed1999

The impact of predation on burrow use by arctic ground squirrels in the boreal forest.

In sedentary animals, the choice of a suitable home site is critical to survival and reproductive fitness. However, habitat suitability may vary with predation risk. We compared habitat use of Arctic ground squirrels (Spermophilus parryii plesius) living in the boreal forest under conditions of fluctuating predation pressure. In our study area, predators show ten-year cycles in numbers that track that of their primary prey, the snowshoe hare (Lepus americanus). In 1993, we compared burrows that continued to be occupied following the period of intense predation during the hare decline of 1990-1992 with those that became vacant, and with random locations. We contrasted these sites to those in a predator exclosure where predation pressure was minimized. Burrows on control sites were located on sloped sites with high visibility. Burrows that remained occupied during the period of intense predation were more likely to be in open areas with fewer fallen trees than burrows that became vacant. We used discriminant functions derived from the control sites and found that 89% of the burrows on the predator exclosure were classified as being similar to the random locations on control sites. We conclude that the distribution of Arctic ground squirrels in the boreal forest is a direct function of predator presence.

Animals↗

PubMed2006

Diagnostic accuracy of human papillomavirus testing in primary cervical screening: a systematic review and meta-analysis of non-randomized studies.

OBJECTIVE: This is a meta-analysis of studies comparing HPV testing to cytology with regard to their accuracy in the detection of underlying high grade cervical intraepithelial neoplasia in primary cervical cancer screening. METHODS: A systematic review was conducted following the Cochrane Collaboration Guidelines. A systematic search was performed in 8 electronic databases. Strict selection criteria were applied in terms of types of participants, types of interventions and methods to limit verification bias. Where possible we calculated the sensitivity, specificity, positive and negative predictive value of cytology and the HPV test, as well as sensitivity and specificity ratios for the detection of CIN2 or worse. Random effect models were used for pooling accuracy parameters. The results were displayed using forest plots. RESULTS: We identified 25 studies fulfilling the inclusion criteria. The pooled sensitivity of HC2, PCR, cytology (ASCUS or worse) and cytology (LSIL or worse) was 90%, 80.9%, 72.7% and 61.6%, respectively, and the pooled specificity was 86.5%, 94.7%, 91.9% and 96.0%, respectively. The ratio of the sensitivity of HC2 to cytology (ASCUS) was 1.25 (95% CI=1.20-1.29), and the corresponding specificity ratio was 0.97 (95% CI=0.96-0.98). The ratio of the sensitivity of combination of HC2 and cytology (ASCUS) to HC2 alone was 1.05 (95% CI=1.04-1.06) and the ratio of the specificity 0.95 (95% CI=0.94-0.96). For women over 30 years, the sensitivity of HC2 was 94.8% and the specificity 86.0%. CONCLUSIONS: Compared to cytology, the HC2 and PCR are substantially more sensitive for prevalent CIN2 or worse but significantly less specific. The combination of HC2 and cytology has the highest sensitivity and lowest specificity. However, reduction of the incidence of or mortality from invasive cervical cancer among HPV screened subjects compared to cytologically screened subjects has not yet been demonstrated.

Female↗