Intragenomic variation in ITS2 rDNA in the louse of humans, Pediculus humanus: ITS2 is not a suitable marker for population studies in this species

The two internal transcribed spacers (ITS) of ribosomal DNA are often used as markers of populations of insects. We studied the ITS2 of the head lice and body lice of humans, to determine whether this gene is a suitable marker of populations of these insects. ITS2 sequences were amplified by PCR from lice from four different countries: Australia, China, Japan and the USA. Direct cycle-sequencing of some of these PCR products gave equivocal nucleotide chromatograms. This indicated that some lice had more than one ITS2 sequence, so we cloned PCR products from these lice. Temperature gradient gel electrophoresis (TGGE) revealed that 50 of the 67 clones we screened had different nucleotide sequences. All lice had several ITS2 types, including those with unequivocal chromatograms. A phylogenetic tree of 15 different ITS2 sequences showed that the sequences from individual lice were not monophyletic. We conclude that the ITS2 is not a useful marker of populations for Pediculus humanus.

Finite-difference time-domain-based studies of MRI pulsed field gradient-induced eddy currents inside the human body

In modern magnetic resonance imaging (MRI), patients are exposed to strong, rapidly switching magnetic gradient fields that, in extreme cases, may be able to elicit nerve stimulation. This paper presents theoretical investigations into the spatial distribution of induced current inside human tissues caused by pulsed z-gradient fields. A variety of gradient waveforms have been studied. The simulations are based on a new, high-definition, finite-difference time-domain method and a realistic inhomogeneous 10-mm resolution human body model with appropriate tissue parameters. it was found that the eddy current densities are affected not only by the pulse sequences but by many parameters such as the position of the body inside the gradient set, the local biological material properties and the geometry of the body. The discussion contains a comparison of these results with previous results found in the literature. This study and the new methods presented herein will help to further investigate the biological effects caused by the switched gradient fields in a MRI scan. (C) 2002 Wiley Periodicals, Inc.

A medial to lateral shift in premovement cortical activity in hemi-Parkinson's disease: Studies of event-related potentials and whole-scalp magneto encephalography

Cortical activity associated with voluntary movement is shifted from medial to lateral premotor areas in Parkinson's disease. This occurs bilaterally, even for unilateral movements. We have used both EEG and MEG to further investigate medial and lateral premotor activity in patients with hemi-Parkinson's disease, in whom basal ganglia impairment is most pronounced in one hemisphere. The CNV, recorded from 21 scalp positions in a Go/NoGo task, was maximal over central medial regions in control subjects. For hemi-Parkinson's disease subjects, activity was shifted more frontally, reduced in the midline and lateralised towards the side of greatest basal ganglia impairment. With 143 channel whole-scalp magneto encephalography (MEG) we are further examining asymmetries in supplementary motor/premotor cortical activity prior to self-paced voluntary movement. In preliminary results, one hemi-Parkinson's disease patient with predominantly left-side symptoms showed strong medial activity consistent with a dominant source in the left supplementary motor area (SMA). Three patients showed little medial activity, but early bilateral sources within lateral premotor cortex. Results suggest greater involvement of lateral premotor rather than the SMA prior to movement in Parkinson's disease and provide evidence for asymmetric function of the SMA in hemi- Parkinson's disease, with reduced activity on the side of greatest basal ganglia deficit.

Expression, purification, crystallization, and NMR studies of the helicase interaction domain of Escherichia coli DnaG primase

in Escherichia coli, the DnaG primase is the RNA polymerase that synthesizes RNA primers at replication forks. It is composed of three domains, a small N-terminal zinc-binding domain, a larger central domain responsible for RNA synthesis, and a C-terminal domain comprising residues 434-581 [DnaG(434-581)] that interact with the hexameric DnaB helicase. Presumably because of this interaction, it had not been possible previously to express the C-terminal domain in a stably transformed E coli strain. This problem was overcome by expression of DnaG(434-581) under control of tandem bacteriophage gimel-promoters, and the protein was purified in yields of 4-6 mg/L of culture and studied by NMR. A TOCSY spectrum of a 2 mM solution of the protein at pH 7.0, indicated that its structured core comprises residues 444-579. This was consistent with sequence conservation among most-closely related primases. Linewidths in a NOESY spectrum of a 0.5 mM sample in 10 mM phosphate, pH 6.05, 0.1 M NaCl, recorded at 36 degreesC, indicated the protein to be monomeric. Crystals of selenomethionine-substituted DnaG(434-581) obtained by the hanging-drop vapor-diffusion method were body-centered tetragonal, space group I4(1)22, with unit cell parameters a = b 142.2 Angstrom, c = 192.1 Angstrom, and diffracted beyond 2.7 Angstrom resolution with synchrotron radiation. (C) 2003 Elsevier Inc. All rights reserved.

Innate immune surveillance of spontaneous B cell lymphomas by natural killer cells and gamma delta T cells

Few studies have demonstrated that innate lymphocytes play a major role in preventing spontaneous tumor formation. We evaluated the development of spontaneous tumors in mice lacking beta-2 microglobulin (beta2m; and thus MHC class I, CD1d, and CD16) and/or perform, since these tumor cells would be expected to activate innate effector cells. Approximately half the cohort of perform gene-targeted mice succumbed to spontaneous disseminated B cell lymphomas and in mice that also lacked beta2m, the lymphomas developed earlier (by more than 100 d) and with greater incidence (84%). B cell lymphomas from perforin/beta2m gene-targeted mice effectively primed cell-mediated cytotoxicity and perform, but not IFN-gamma, IL-12, or IL-18, was absolutely essential for tumor rejection. Activated NK1.1(+) and gammadeltaTCR(+) T cells were abundant at the tumor site, and transplanted tumors were strongly rejected by either, or both, of these cell types. Blockade of a number of different known costimulatory pathways failed to prevent tumor rejection. These results reflect a critical role for NK cells and gammadeltaTCP(+) T cells in innate immune surveillance of B cell lymphomas, mediated by as yet undetermined pathway(s) of tumor recognition.

A long-term study in Merino sheep experimentally infected with Mycobacterium avium subsp paratuberculosis: clinical disease, faecal culture and immunological studies

Two longitudinal experiments involving Merino sheep challenged with either bovine or ovine strains of Mycobacterium avium subsp. paratuberculosis (Map) have been conducted over a period of 54 and 35 months, respectively. Blood samples for the interferon-gamma test, the absorbed ELISA and faecal samples for bacteriological culture were taken pre-challenge and monthly post-challenge. Infections were induced with either a bovine or ovine strain of Map in separate experiments with infections being more easily established, in terms of faecal bacterial shedding and clinical disease when the challenge inoculum was prepared from gut mucosal tissue than cultured bacteria. The patterns of response for shedding and clinical disease were similar. Cell-mediated immune responses were proportionally elevated by at least an order of magnitude in all sheep dosed with either a bovine or ovine strain of Map. Conversely, antibody responses were only elevated in a relatively small proportion of infected sheep. Neither of the clinically affected tissue challenged sheep developed an antibody response despite the presence of persistent shedding and the development and decline in cell-mediated immunity. The results indicated that for sheep the interferon-gamma test may be useful for determining if a flock has been exposed to ovine Johne's disease. (C) 2004 Elsevier B.V. All rights reserved.

Trends in five-year survival and risk of recurrent stroke after first-ever stroke in the Perth community stroke study

Background: Few studies provide information on trends in the long-term outcome of stroke. We aimed to determine trends in survival and recurrent stroke, over 5 years after first-ever stroke, for 2 cohorts of patients enrolled in the Perth Community Stroke Study in 1989 90 and 1995-96. Methods: For 12-month periods beginning February 1989 and February 1995, all individuals with an acute stroke who were resident in a geographically-defined and representative region of Perth, Western Australia, were registered and followed-up prospectively 5 years after the index event. Results: The 5-year cumulative risk of death was 59% (95% confidence interval (CI) 53%, 65%) and 58% (95% CI 52%, 65%) for the 1989-90 and 1995-96 cohorts, respectively (p = 0.94). The 5-year cumulative risk of first recurrent stroke was 32% (95% CI 25%, 40%) and 23% (95% CI 16%, 30%) for the 1989-90 and 1995-96 cohorts, respectively (p = 0.07). Conclusions: Although no statistically significant improvement occurred in 5-year survival after first-ever stroke in Perth between 1989-90 and 1995-96, there was a statistically nonsignificant trend towards a smaller cumulative risk of recurrent stroke over 5 years after a first-ever stroke. Serial community-based studies of the incidence and outcome of stroke are an important means of monitoring the translation of proven preventive interventions to improvements in population health. Copyright (C) 2005 S. Karger AG, Basel.

HRT and breast cancer: Impact on population risk and incidence

This study has calculated the potential impact of hormone replacement therapy (HRT) on breast cancer incidence in Australia and has estimated how changes in prescribing HRT to women could affect this risk. The effects of HRT on breast cancer incidence was estimated using the attributable fraction technique with prevalence data derived from the 2001 Australian Health Survey and published rates of breast cancer relative risks from HRT use. In Australia, 12% of adult women were current HRT users and in 2001, 11783 breast cancers were reported. Of these, 1066 (9%) were potentially attributable to HRT. Restricting HRT use to women aged less than 65 years, ceasing HRT prescribing after 10 years or limiting combined oestrogen and progesterone HRT to five years (but otherwise keeping prescription levels to 2001 levels) may reduce the annual breast cancer caseload by 280 (2.4%), 555 (4.7%) or 674 (5.7%), respectively. In conclusion, this study has demonstrated that when HRT prevalence is relatively high, the effect on breast cancer incidence in the population will be significant. A small modification in HRT prescribing practices may impact breast cancer incidence in Australia with associated financial and health care provision implications. (C) 2005 Elsevier Ltd. All rights reserved.

Incidence and distribution of viruses of Taro (Colocasia esculenta) in Pacific Island countries

Four viruses have been reported from taro; Dasheen mosaic virus (DsMV), Taro bacilliform virus (TaBV) and two putative rhabdoviruses, Colocasia bobone disease virus (CBDV) and Taro vein chlorosis virus (TaVCV). A fifth virus, tentatively named Taro reovirus (TaRV), has also been recently identified. The distribution of these viruses throughout the Pacific Islands, and the symptoms associated with their infection, are unknown in many cases due to a lack of sensitive diagnostic tests. We have used recently developed PCR-based diagnostic tests to survey taro growing in 11 Pacific Island countries for the presence of known viruses. DsMV and TaBV were widespread, whereas TaVCV and TaRV were more restricted in their distribution. CBDV was restricted to PNG and Solomon Islands and was always associated with the two most serious viral diseases of taro; alomae disease and bobone disease, but the causal agent of these two diseases remains unclear.

The effects of predator odors in mammalian prey species: A review of field and laboratory studies

wPrey species show specific adaptations that allow recognition, avoidance and defense against predators. For many mammalian species this includes sensitivity towards predator-derived odors. The typical sources of such odors include predator skin and fur, urine, feces and anal gland secretions. Avoidance of predator odors has been observed in many mammalian prey species including rats, mice, voles, deer, rabbits, gophers, hedgehogs, possums and sheep. Field and laboratory studies show that predator odors have distinctive behavioral effects which include (1) inhibition of activity, (2) suppression of non-defensive behaviors such as foraging, feeding and grooming, and (3) shifts to habitats or secure locations where such odors are not present. The repellent effect of predator odors in the field may sometimes be of practical use in the protection of crops and natural resources, although not all attempts at this have been successful. The failure of some studies to obtain repellent effects with predator odors may relate to (1) mismatches between the predator odors and prey species employed, (2) strain and individual differences in sensitivity to predator odors, and (3) the use of predator odors that have low efficacy. In this regard, a small number of recent studies have suggested that skin and fur-derived predator odors may have a more profound lasting effect on prey species than those derived from urine or feces. Predator odors can have powerful effects on the endocrine system including a suppression of testosterone and increased levels of stress hormones such as corticosterone and ACTH. Inhibitory effects of predator odors on reproductive behavior have been demonstrated, and these are particularly prevalent in female rodent species. Pregnant female rodents exposed to predator odors may give birth to smaller litters while exposure to predator odors during early life can hinder normal development. Recent research is starting to uncover the neural circuitry activated by predator odors, leading to hypotheses about how such activation leads to observable effects on reproduction, foraging and feeding. (c) 2005 Elsevier Ltd. All rights reserved.