bluuebunny/crossref_metadata_2025 huggingface dataset:
Perturbations in adiponectin, leptin and resistin levels in acromegaly: lack of correlation with insulin resistance
Authors: Silha Josef V. , Krsek Michal , Hana Vaclav , Marek Josef , Jezkova Jana , Weiss Vladimir , Murphy Liam J.
Published: June 2003

background Insulin resistance, impaired glucose tolerance and type 2 diabetes are common in acromegalic subjects. The mechanism underlying this insulin resistance is unclear.

design We investigated the levels of the adipocytokines, resistin, adiponectin and leptin in a group of 18 acromegalic subjects and 18 control subjects matched for age, gender and body mass index.

results Here we demonstrate for the first time significant elevation in adiponectin levels in acromegalic subjects compared to control subjects 12·5 ± 1·2 vs. 8·97 ± 1·1 mg/l, P = 0·029. The resistin levels were similar in acromegalic subjects and controls; 20·65 ± 2·99 vs. 19·03 ± 4·72 µg/l. No evidence of a correlation between adiponectin and insulin resistance as calculated from HOMA‐R was found. No correlation was observed either between adiponectin or resistin levels and GH levels, total IGF‐I or free IGF‐I levels. Leptin levels were significantly reduced in acromegalic subjects, 8·22 ± 2·26 vs. 18·3 ± 4·1 µg/l, P = 0·004. In control subjects, significant correlations between leptin levels and HOMA‐R and between resistin levels and HOMA‐R were observed. These relationships were not apparent in acromegalic subjects.

conclusion From these data we conclude that changes in resistin and adiponectin levels are unlikely to account for the insulin resistance of acromegaly.
Short‐term effects of prednisolone and dexamethasone on circulating concentrations of leptin and sex hormone‐binding globulin in children being treated for acute lymphoblastic leukaemia
Authors: Wallace A. M. , Tucker P. , Williams D. M. , Hughes I. A. , Ahmed S. F.
Published: June 2003

objective Disturbances in body weight regulation are often encountered during glucocorticoid treatment and are associated with increased insulin resistance and truncal fat accumulation. Children were investigated who were receiving glucocorticoid treatment for acute lymphoblastic leukaemia (ALL). They were randomized to receive either prednisolone or dexamethasone as part of induction of remission. This randomization process provided a suitable opportunity to compare the effects of these two administered steroid on surrogate markers of adipocyte activity (leptin) and hyperinsulinaemia/insulin resistance (SHBG).

design and patients Prospective study over 16 weeks of children randomized to receive prednisolone (40 mg/m2) or dexamethasone (6·5 mg/m2) as part of the MRC‐ALL97/99 induction chemotherapy for ALL. Nineteen children (8 male, 11 female) with a median age 5·9 years (range 2·6–13 years) were recruited into the study. Main outcome measures were body mass index (BMI), serum leptin and sex hormone binding globulin (SHBG).

results Glucocorticoid administration for 5 weeks resulted in significant (P < 0·05) increases in BMI, leptin (corrected for BMI) and the leptin : SHBG ratio and lowering of SHBG. Dose for dose, dexamethasone was significantly more potent than prednisolone in altering these parameters.

conclusions Short‐term glucocorticoid treatment has significant effects on BMI, leptin and SHBG. The leptin : SHBG ratio increase indicates that this may be a novel and sensitive biochemical marker of metabolic change. Our results suggest that glucocorticoid treatment regimens should be kept as short as possible to avoid possible detrimental effects associated with increased adiposity and insulin resistance.
Mothers' involvement in caring for their premature infants: an historical overview
Authors: Davis Leigh , Mohay Heather , Edwards Helen
Published: June 2003

Background. Advances in technology have resulted in increasing survival rates even for extremely premature infants. While sophisticated medical management is vital to infant survival, research has found that social factors and care giving processes are important predictors of infants' later outcome. Consequently, evidence is accumulating to demonstrate the fundamental role of mothers and families to the optimal developmental outcome of premature infants.

Aim. The aim of the work reported here was to undertake an historical overview of premature infant care practices to increase neonatal nurse's knowledge of the crucial role of mothers and families in the care of their premature infants. Understanding past practice and current trends can provide neonatal nurses with critical insight which will assist in formulating current and future care.

Method. Research and historical articles focusing on maternal involvement in preterm infant care from the development of the incubator to the present time were examined. A search of the literature between 1960 and 2002 was conducted using the MEDLINE, CINAHL and PSYCLIT databases. The search terms were premature infant, neonatal intensive care, history, and maternal care.

Findings. Three major themes were identified which reflect the development of neonatal care. Firstly, over the last century advances in medical and public health practice saw a decline in mortality rates for mothers and infants. Secondly, the application of this new knowledge resulted in the institutionalization and professionalization of obstetric and neonatal care which, in turn, resulted in the isolation of infants from their mothers. Finally, concurrent advances in infant research emphasized the importance of mother–infant relationships to infants' developmental outcome, resulting in greater flexibility in hospital practices regarding parental contact with their infants.

Conclusion. As biomedical advances in technology continue to help smaller, sicker premature infants to survive, neonatal nurses are strategically placed to promote positive outcomes for infants and their families through the integration of social science and behavioural research into nursing practice.
Identifying cancer nursing research priorities using the Delphi technique
Authors: Mcilfatrick Sonja J. , Keeney Sinaed
Published: June 2003

Background. Nursing research is an integral component of improving the care of people with cancer. However, for research to be successfully integrated and applied to practice, ownership and identification must come from those in practice. The need for local and national strategies for cancer nursing research and the importance of establishing priorities for cancer nursing research have been repeatedly acknowledged.

Study aim. The aim of the study was to facilitate a strategic approach to cancer nursing research by identifying the research priorities of cancer nurses.

Research method. A three‐round Delphi survey was administered to nurses (n = 112) attending a cancer nursing research conference in Northern Ireland. Participants were asked to identify five research questions that they considered a high priority for cancer nursing. A response rate of 54% (60 delegates) was obtained for round one and this generated 117 statements. These statements were content analysed. Two subsequent quantitative rounds followed this.

Results. The top priority areas identified were psychosocial issues, for example communication and information needs; professional issues relating to nurse burnout, stress and nurse‐led care; and context of care issues including continuity of care.

Limitations. A potential limitation of the study is the use of conference delegates. However, it is argued that these are the people we wanted to target as they could be considered as experts who already had an interest and clinical background in both cancer research and practice.

Conclusion. These priorities have helped to provide both direction and focus for the development of a cancer nursing research strategy for Northern Ireland. It is recommended that future research questions should be focused around the highest ranked priorities.
Influence of patch characteristics on browsing of tree seedlings by mammalian herbivores
Authors: Pietrzykowski E. , McArthur C. , Fitzgerald H. , Goodwin A. N.
Published: June 2003

In south‐eastern Australia, browsing of commercial tree seedlings by mammalian herbivores in plantation forestry incurs a large economic cost to the industry, through its effect on tree survival, growth and form. In the absence of lethal methods to control herbivore populations, appropriate manipulation of vegetation through silvicultural management may reduce browsing but it relies on understanding the feeding responses of the herbivores to such changes.

We evaluated the extent to which vegetation patch characteristics affected browsing of pine Pinus radiata seedlings by generalist mammalian herbivores, including red‐bellied pademelons Thylogale billardierii, Bennett's wallaby Macropus rufogriseus rufogriseus and the common brushtail possum Trichosurus vulpecula.

In field trials, browsing of pine seedlings was greatest when they were located in patches of high quality, i.e. palatable short vegetation (grass), intermediate in high‐quality tall vegetation (Lomandra longifolia) and least in low‐quality tall vegetation (bracken and shrub). Patch structure also affected browsing: in low‐quality patches pine seedlings were browsed more in short vegetation patches (12–24 cm shorter than the seedling) than in tall vegetation patches (at least as tall as the seedling). This difference was at least partly because herbivores took, on average, 2 weeks longer to locate seedlings in tall than in short vegetation.

In trials with captive red‐bellied pademelons and brushtail possums, pine seedlings were browsed similarly in small short grass and soil patches. However, when these patches were large and spatially separated, they were browsed more in short grass than soil patches. Selection at the patch or individual plant level therefore depended on spatial scale and proximity of the patches.

Synthesis and applications. The influence of patch characteristics on browsing has the potential to be exploited for the management of browsing damage to commercially important tree seedlings in forestry plantations. Retention of relatively tall vegetation, particularly if it is unpalatable, in areas at risk of heavy browsing, for example by delaying the use of herbicide, may be a useful management strategy for reducing browsing. This needs to be weighed against the potential detrimental competitive effects of neighbouring vegetation on the seedlings.
Application of merged 1‐m and 4‐m resolution satellite data to research and management in tropical forests
Authors: Read Jane M. , Clark David B. , Venticinque Eduardo M. , Moreira Marcelo P.
Published: June 2003

Until very recently there have been no digital data from satellites for studying events that occur at scales of 10–1000 m2 over large areas (100–100 000 ha). Many phenomena of interest to ecologists, such as impacts of selective logging on forest processes, occur over large extents but at local scales. Here we report results from a pilot project to evaluate through visual interpretation the potential of newly available 1‐m panchromatic and 4‐m multi‐spectral data from the IKONOS satellite, for studying forest structure, dynamics and logging impacts in logged and old‐growth tropical moist forest.

The study area, the Mil Madeireira Itacoatiara Ltda site of Precious Woods Amazon, near Itacoatiara, Amazonas, Brazil, is managed using reduced‐impact logging practices to minimize environmental impacts, and thus represents a lower bound for logging impacts in tropical rain forests.

The IKONOS image was georeferenced using uncorrected global positioning system (GPS) locations for 10 control trees whose crowns were clearly visible in the image. The root mean square error (RMSE) of the geometric transformation was 4 m, while the mean crown diameter of 50 randomly chosen trees in old‐growth forest was 9·4 m. The fact that the RMSE was less than half the average crown diameter implies that it will usually be possible to locate from the ground crowns that are distinct on the image, given sufficiently accurate GPS locations.

IKONOS data are well suited for evaluating and monitoring logging impacts. Many impacts of logging were clearly observable in the image, including major and some minor roads, logging patios and larger logging gaps. Smaller extraction roads and logging gaps were not observable.

Many individual trees were distinct on the IKONOS image, indicating that it is now feasible to conduct demographic studies of tropical rain forest canopy trees based on repeated satellite observations. Linking these remotely sensed data to ground data will require improved GPS positions, because it is currently difficult to obtain accurate GPS readings in tropical rain forest understoreys.

Synthesis and applications. IKONOS 1‐m and 4‐m data were found to be useful for identifying individual trees as well as some logging management features in a tropical moist forest in central Amazonia. These data will have many applications for research and management of intervened and old‐growth tropical forests, including planning and assessment of logging activities, as well as monitoring adherence to certification criteria such as those of the Forest Stewardship Council. Rapid development of these applications will come from building on existing data on forest structure and function, and by fostering collaborations between remote sensing scientists, ecologists and natural resource managers.
The relative roles of domestication, rearing environment, prior residence and body size in deciding territorial contests between hatchery and wild juvenile salmon
Authors: Metcalfe Neil B. , Valdimarsson Sveinn K. , Morgan Ian J.
Published: June 2003

Interactions between captive‐reared and wild salmonids are frequent because hatcheries annually rear millions of fish for release in conservation programmes while many thousands of domesticated fish escape from fish farms. However, the outcome of competition between captive‐reared and wild fish is not clear: wild fish may be smaller and less aggressive than hatchery fish, but they have more local experience and a prior residence advantage. Moreover, it is important to know whether any competitive differences are genetic (due to the process of domestication) or due to the rearing environment.

We therefore examined the factors influencing competition for feeding territories in juvenile Atlantic salmon. We studied the effect of domestication by using three independent stocks of both domesticated and wild‐origin fish, all of which were reared in a common hatchery environment. We also used fish from the same wild stocks that had been living in the wild. Territorial contests were staged in stream tank compartments between pairs of fish differing in origin or rearing environment; the relative importance of body size and prior residence was also assessed.

All three stocks of domesticated fish were generally dominant over wild‐origin fish when both had been raised in a common hatchery environment. If the wild‐origin fish were given a 2‐day period of prior residence on the territory this asymmetry in dominance was reversed. However, domesticated fish did not gain any additional advantage from being prior residents. The relative body size of the two contestants had a negligible effect on contest outcomes.

Truly wild fish (i.e. those of wild origin that had also grown up in the wild) were generally dominant over domesticated or wild‐origin fish that had been hatchery‐reared. Differences in body size between contestants had no effect on the outcome.

Synthesis and applications. These results show that, while juvenile farmed Atlantic salmon are inherently more aggressive than wild‐origin fish, the hatchery environment reduces their ability to compete for territories with wild resident fish. Rearing salmon in conventional hatcheries for later release into the wild where natural populations already exist may not be a prudent conservation measure; it is preferable to plant eggs or first‐feeding fry rather than attempt to ‘help’ the fish by rearing them through the early life stages.
Demography and management of the invasive plant species Hypericum perforatum. II. Construction and use of an individual‐based model to predict population dynamics and the effects of management strategies
Authors: Buckley Yvonne M. , Briese David T. , Rees Mark
Published: June 2003

Hypericum perforatum, St John's wort, is an invasive weed of natural and agro‐ecosystems in south‐eastern Australia. In previous work we used a long‐term data set to determine which plant traits and environmental factors influence population growth and persistence in this species. These results were then used to parameterize an individual‐based model of the population dynamics of H. perforatum, and this model was used to make predictions about what control strategies will be most effective for populations in open and shaded sites.

The model was constructed using multi‐level, mixed‐effects statistical models of growth, survival, fecundity and damage, incorporating intrinsic plant variables, environmental variables, herbivory and spatial and temporal stochasticity.

We found that populations in shaded and open sites had different dynamics and responses to control strategies. Shaded populations took longer to reach infestation densities and were less affected by herbivory and reductions in survival than open populations. Open populations increased faster in response to increases in rainfall, but this was not so for shaded populations.

We used sensitivity testing and management simulations to predict that the most successful control strategies will involve a reduction in vegetative size in both open and shaded sites. Reductions in flowering stem size and survival in shaded and open sites, respectively, are predicted to be the next most successful strategies. Dry conditions in the austral autumn/winter adversely affect populations in both open and shaded sites.

Synthesis and applications. These models have enabled us to rank management strategies based on quantitative analysis of their potential effects on population size. This is an important tool not only for ecologists concerned with control of invasive species but for conservation biologists trying to understand the factors limiting a rare or endangered species.
The relative importance of cattle grazing in subtropical grasslands: does it reduce or enhance plant biodiversity?
Authors: Mcintyre S. , Heard K. M. , Martin T. G.
Published: June 2003

Livestock grazing enterprises have potentially threatening effects on the conservation of plants in grassy subtropical eucalypt woodlands. Commercial levels of grazing could cause local extinctions of sensitive native species and/or reductions in abundance and species richness in native pastures.

We studied the nature of grazing impacts on the diversity and composition of herbaceous plants and used a natural experiment to analyse the effects of disturbances (cattle grazing, soil disturbance, water enrichment) and environment (lithology, slope position, presence of trees) on plant community composition in eastern Australia. We sampled pastures and reserves at 191 sites over an area of 3000 ha.

Canonical correspondence analysis (CCA) was used to explore the relative importance of disturbance and environment in accounting for floristic variation and to examine individual species responses. From individual responses, we identified seven response groups relating to grazing. The factors analysed explained small but significant amounts of floristic variation, and there were interactions between soil disturbance, water enrichment and grazing.

We explored the hypothesis that grazing increased species density at small scales but decreased it at landscape scales, due to the elimination of grazing‐sensitive species. Our data did not support the hypothesis, as there were similar numbers of species that increase with grazing (increasers) and species that decline with increasing grazing (decreasers) in the assemblage. However, there were more native decreasers and more exotic increasers in the assemblage.

Synthesis and applications. For land managers to retain plant diversity on grazed landscapes, it would be desirable to provide all levels of grazing pressure across the landscape, including areas protected from livestock grazing. This would apply to all plant communities where both grazing increasers and decreasers are present. Extensive areas supporting grassland with a tall tussock structure that is selectively grazed are most important, as all plant response groups have some representation and ecosystem function is retained under moderate grazing. In terms of regional conservation planning, the protection and enlargement of areas protected from livestock grazing is important in the study area, as these occur on only about 4% of the landscape and are threatened by on‐going disturbances and land‐use intensification.
The impact of stroke practice guidelines on knowledge and practice patterns of acute care health professionals
Authors: Heinemann Allen W. , Roth Elliot J. , Rychlik Karen , Pe Klaren , King Caroline , Clumpner Jennifer
Published: June 2003

Rationale, aims and objectives  The Agency for Healthcare Research and Quality's Post‐Stroke Rehabilitation Guidelines were developed to improve the quality, appropriateness and effectiveness of rehabilitation practices. An important goal of the guidelines process is to disseminate information to practitioners in order to encourage adoption of effective practices. To date, no systematic evaluation of these guidelines has been completed, nor has a programme been designed to evaluate the effectiveness of an educational programme about the guidelines. The objective was to evaluate changes in knowledge and practice following presentation of a lecture‐based, educational programme about post‐stroke rehabilitation guidelines.

Methods  The research design was a single group, pre‐test–post‐test design without a comparison group. A knowledge and referral practices questionnaire was developed specifically for this study.

Results  Lecture attendance was not associated with an increase in knowledge or referrals. However, we found that respondents who made more referrals at follow‐up had a higher knowledge level at pre‐test. Also, those who completed a follow‐up assessment knew more about the guidelines at the initial assessment than did those who did not complete the follow‐up assessment. In addition, doctors knew more about stroke rehabilitation than the non‐doctors, both at the pre‐test and follow‐up.

Discussion and conclusions  Encouraging behaviour change among doctors and allied health professionals in referrals and clinical practice is a complicated process. Providing individual follow‐up and lengthier contacts, assuring that care providers receive high‐quality evidence that guidelines improve care, and consulting with key decision‐makers about guideline implementation might enhance behaviour change.
Generalizability: beyond plausibility and handwaving
Authors: Shahar MD MPH Eyal
Published: June 2003

The question of how we apply knowledge from biomedical science to medical and public health practice has been the subject of heated debates about generalizability and related concepts, such as applicability and inductive inference. In this essay, I interpret the term from the perspective of two causal models: determinism and indeterminism. I suggest that theories of generalizability can be formulated on the basis of both models and take the form of testable but unverifiable hypotheses, an attribute that is common to all scientific theories. Nonetheless, there is one noteworthy difference between the two models: determinism allows one to rationalize a decision to treat a certain kind of patient but only indirectly a decision to treat any particular patient, whereas indeterminism accommodates both types of decisions.
The state of the science and art of practice guidelines development, dissemination and evaluation in Canada
Authors: Graham Ian D. , Beardall Susan , Carter Anne O. , Tetroe Jacqueline , Davies Barbara
Published: June 2003

The Canadian Medical Association (CMA) maintains a database of clinical practice guidelines (CPGs) developed or endorsed by Canadian organizations. The study purpose was to describe how these guidelines were developed, disseminated and evaluated. A survey was mailed to the developer of each CPG registered in the CMA Infobase between June 1996 and December 1999. Data were received for 730 unique guidelines (response rate of 70%) developed by 75 organizations. Of these, 72% were developed by committees that had a formal process for selecting their members. The scientific literature was reviewed for all of the guidelines, a computerized search undertaken for 88% and the search strategy included 34% of CPG documents. An attempt was made to grade the quality of the evidence underpinning 54% of the guidelines. For most guidelines, consensus about values or judgements was reached by expert opinion through open discussion (78% of guidelines). The most common strategies used to disseminate the guidelines were direct mailing of guidelines to members of the developing organization (80% of all guidelines), publishing guidelines in newsletters/journals (76%), direct mailing to others (73%), electronic dissemination (62%), educational or continuing medical education activities (50%), and providing information about guidelines to patients/consumers (47%). Overall, 5% of the guidelines have been evaluated to determine their impact on health outcomes. During the 5‐year study period (1994–99), the more recent guidelines were more likely to use multidisciplinary development panels, report the literature search strategies and grade the quality of the evidence. The CPG development process in Canada is becoming more rigorous and reproducible, but there is still considerable room for improvement. In addition to encouraging Canadian guideline developers to use more rigorous and transparent methods, considerably more attention must be focused on using and identifying effective and cost‐effective strategies to promote and facilitate the uptake of guidelines by practitioners and to evaluate the impact of guidelines on patient outcomes.
The Australian Centre For Evidence‐based Clinical Practice Generic Audit Tool: Auditmaker for health professionals
Authors: Shakib Sepehr , Phillips Paddy A
Published: June 2003

Audit is an important step in the process of health care evaluation and quality improvement. Some of the barriers to audit include the lack of support in initiating an audit, difficulty with data collection and lack of time. Auditmaker is a computer package that guides the clinician through the initial process of designing an audit, choosing factors and outcomes to analyse, then provides customizable data entry forms, and finally simple reports summarizing the data. It has user‐friendly features, such as help buttons, drop‐down lists and built in comorbidities and outcomes of common interest. It provides a generic tool for performing an audit as well as providing an opportunity for different clinicians in different institutions or practice settings to perform similar audits using the same data collection tool, which can provide the basis of benchmarking. Auditmaker is available for downloading from the ACEPCP website: http:www.acebcp.org.au.
Evidence‐based practice in mental health: practical weaknesses meet political strengths
Authors: Tanenbaum Sandra
Published: June 2003

Rationale, aims, and objectives  Evidence‐based medicine (EBM) has given rise to evidence‐based practice (EBP) in the field of mental health. EBP too is predicated on an evidence hierarchy and has the goal of using the “best evidence” (usually randomized controlled trials) to improve practice. EBP is increasingly influential in mental health care in the U.S. Growing numbers of researchers and public officials endorse its claims and pursue its benefits. The rationale for this paper is to examine the potential of EBP for the field of mental health—and public mental health care specifically. Is it likely to contribute to improved lives for mentally ill people? If so, how?

Methods  This qualitative study relies on archival, and to a much lesser extent, informant interview data. Informants were mostly public mental health officials because they are in a position to implement EBP on a large scale and their policies are a matter of public record. Interviews were semi‐structured, held in person and on the telephone, and lasted one to two hours. Archival research included the substantial literature on EBM and EBP plus studies and articles on the practice and policy of U.S. public mental health care.

Results  The results of this study were that there exists an extensive, coherent literature critical of EBM and of EBP specifically. Attempts to implement EBP will falter on epistemological and organizational barriers. Still, as a public idea—that more science will bring about better mental health practice—EBP may well serve political purposes, especially in the U.S. public mental health system, where more overtly ideological policies have been inadequate in the past. EBP, as a public idea, has the advantage of ambiguity, accountability, quantifiability, etc.

Conclusions  This paper concludes that EBP is growing more influential in public mental health care in the U.S. Its practical strengths, i.e., its improvement of mental health practice, may turn out to be less than its strengths as a public idea in the formulation and dissemination of mental health policy.
Prolactin and Oxytocin Interaction in the Paraventricular and Supraoptic Nuclei: Effects on Oxytocin mRNA and Nitric Oxide Synthase
Authors: Popeski N. , Amir S. , Diorio J. , Woodside B.
Published: May 2003

We investigated the contribution of prolactin and oxytocin to the increase in staining for NADPH‐d and oxytocin mRNA in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) observed at the end of pregnancy, or following a steroid‐priming regimen that mimics the hormonal profile of late pregnant females. Ovariectomized rats received chronic implants of silastic capsules containing oestrogen and progesterone followed by progesterone removal. In experiment 1, oxytocin antagonist (OTA) was administered to rats to investigate whether intranuclear oxytocin release was necessary for NADPH‐d staining. In experiments 2a and b, rats received concurrent treatment with bromocryptine (0.5 mg/day) to suppress endogenous prolactin release, and either systemic prolactin (0.5 mg once daily), or prolactin (2 µg/µl), or vehicle infused twice a day into the third ventricle, or chronic oxytocin infusion (24 ng/day) for 3 days following progesterone removal. Brains were then processed for NADPH‐d histochemistry. In experiment 3, the interaction of prolactin and oxytocin on oxytocin mRNA within the SON and PVN was examined. NADPH‐d staining in the SON and PVN was reduced by the highest dose of the OTA, and by bromocryptine treatment. Central prolactin and oxytocin replacement completely restored NADPH‐d staining in bromocryptine‐treated rats. Finally, both bromocryptine and the OTA suppressed oxytocin mRNA expression and prolactin replacement restored expression levels to that of controls. Together, these data suggest that the increased capacity to produce nitric oxide in the SON and PVN during late pregnancy is dependent on prolactin stimulating oxytocin gene mRNA and hence intranuclear oxytocin release.
Intermittent Footshock Facilitates Dendritic Vasopressin Release but Suppresses Vasopressin Synthesis within the Rat Supraoptic Nucleus
Authors: Onaka T. , Serino R. , Ueta Y.
Published: May 2003

Emotional stress inhibits vasopressin release from the pituitary but may facilitate its release from the dendrites in the hypothalamus. We examined effects of intermittently applied footshock upon the amount of vasopressin heteronuclear RNA in the hypothalamus. The footshock decreased plasma vasopressin concentration but increased its extracellular concentration within the supraoptic nucleus. The contents of the vasopressin heteronuclear RNA in the supraoptic nucleus were significantly decreased after the shock. These data suggest that intermittent footshock decreases not only vasopressin release from the axon terminals in the pituitary, but also vasopressin synthesis in the cell bodies in the hypothalamus while the stimulus facilitates vasopressin release from the dendrites in the hypothalamus. The data also suggest differential control of dendritic vasopressin release and synthesis in the hypothalamus.
Ten families of variant genes encoded in subtelomeric regions of multiple chromosomes of Plasmodium chabaudi, a malaria species that undergoes antigenic variation in the laboratory mouse
Authors: Fischer Katja , Chavchich Marina , Huestis Robert , Wilson Danny W. , Kemp David J. , Saul Allan
Published: May 2003

The chromosome ends of human malaria parasites harbour many genes encoding proteins that are exported to the surface of infected red cells, often being involved in host–parasite interactions and immune evasion. Unlike other murine malaria parasites Plasmodium chabaudi undergoes antigenic variation during passage in the laboratory mouse and hence is a model suitable for investigation of switching mechanisms. However, little is known about the subtelomeric regions of P. chabaudi chromosomes and its variable antigens. Here we report 80 kb of sequence from an end of one P. chabaudi chromosome. Hybridization of probes spanning this region to two dimensional pulsed field gels of the genome revealed 10 multicopy gene families located exclusively in subtelomeric regions of multiple P. chabaudi chromosomes, interspersed amongst multicopy intergenic regions. Hence all chromosomes share a common subtelomeric structure, presumably playing a similar role in spatial positioning as the P. falciparum Rep20 sequence. Expression in blood stages, domains characteristic of surface antigens and copy numbers between four and several hundred per genome, indicate a functional role in antigenic variation for some of these families. We identify members of the cir family, as well as novel genes, that although clearly homologous to cir have large low complexity regions in the predicted extracellular domains. Although all families have homologues in other rodent Plasmodium species, four were previously not known to be subtelomeric. Six have homologues in human and simian malarias.
Opposing selective forces for expression of the gonococcal lactoferrin receptor
Authors: Anderson James E. , Hobbs Marcia M. , Biswas Gour D. , Sparling P. Frederick
Published: May 2003

All isolates of Neisseria gonorrhoeae express receptors that bind human transferrin (Tf). Although lactoferrin (Lf) is abundant on mucosa and in purulent exudates, many gonococci do not express an Lf receptor. The naturally occurring Lf receptor deletion mutant FA1090 (LbpB–LbpA–) is infectious, but a Tf receptor mutant of FA1090 is unable to infect male volunteers [Cornelissen, C.N., Kelley, M., Hobbs, M.M., Anderson, J.E., Cannon, J.G., Cohen, M.S., and Sparling, P.F. (1998) Mol Microbiol 27: 611–616]. Here, we report that expression of an Lf receptor in the absence of the Tf receptor was sufficient for infection, and that expression of both Lf and Tf receptors resulted in a competitive advantage over a strain that made only the Tf receptor in mixed infection of male volunteers. We confirmed that nearly 50% of clinical isolates do not make an Lf receptor. Surprisingly, about half of geographically diverse Lf – isolates representing many different auxotypes and porin serovars carried an identical lbpB lbpA deletion. Among Lf+ strains, all produced the integral outer membrane protein LbpA, but 70% did not express the lipoprotein LbpB. Thus, there are apparently selective pressures for expression of the Lf receptor in the male urethra that are balanced by others against expression of the Lf receptor in niches other than the male urethra.
A well‐conserved Plasmodium falciparum var gene shows an unusual stage‐specific transcript pattern
Authors: Kyes Sue A. , Christodoulou Zoe , Raza Ahmed , Horrocks Paul , Pinches Robert , Rowe J. Alexandra , Newbold Chris I.
Published: May 2003

The var multicopy gene family encodes Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variant antigens, which, through their ability to adhere to a variety of host receptors, are thought to be important virulence factors. The predominant expression of a single cytoadherent PfEMP1 type on an infected red blood cell, and the switching between different PfEMP1 types to evade host protective antibody responses, are processes thought to be controlled at the transcriptional level. Contradictory data have been published on the timing of var gene transcription. Reverse transcription‐polymerase chain reaction (RT‐PCR) data suggested that transcription of the predominant var gene occurs in the later (pigmented trophozoite) stages, whereas Northern blot data indicated such transcripts only in early (ring) stages. We investigated this discrepancy by Northern blot, with probes covering a diverse var gene repertoire. We confirm that almost all var transcript types were detected only in ring stages. However, one type, the well‐conserved varCSA transcript, was present constitutively in different laboratory parasites and does not appear to undergo antigenic variation. Although varCSA has been shown to encode a chondroitin sulphate A (CSA)‐binding PfEMP1, we find that the presence of full‐length varCSA transcripts does not correlate with the CSA‐binding phenotype.
Oligomerization and activation of the FliI ATPase central to bacterial flagellum assembly
Authors: Claret Laurent , Calder Susannah R. , Higgins Matthew , Hughes Colin
Published: May 2003

FliI is the peripheral membrane ATPase pivotal to the type III protein export mechanism underlying the assembly of the bacterial flagellum. Gel filtration and multiangle light scattering showed that purified soluble native FliI protein was in a monomeric state but, in the presence of ATP, FliI showed a propensity to oligomerize. Electron microscopy revealed that FliI assembles to a ring structure, the yield of which was increased by the presence of a non‐hydrolysable ATP analogue. Single particle analysis of the resulting electron micrograph images, to which no symmetry was applied, showed that the FliI ring structure has sixfold symmetry and an external diameter of ≈ 10 nm. The oligomeric ring has a central cavity of 2.5–3.0 nm, which is comparable to the known diameter of the flagellar export channel into which export substrates feed. Enzymatic activity of the FliI ATPase showed positive co‐operativity, establishing that oligomerization and enzyme activity are coupled. Escherichia coli phospholipids increased enzyme co‐operativity, and in vitro cross‐linking demonstrated that they promoted FliI multimerization. The data reveal central facets of the structure and action of the flagellar assembly ATPase and, by extension, the homologous ATPases of virulence‐related type III export systems.
The twin‐arginine translocation (Tat) system is essential for Rhizobium–legume symbiosis
Authors: Meloni Stefania , Rey Luis , Sidler Stephan , Imperial Juan , Ruiz‐Argüeso Tomás , Palacios José M.
Published: May 2003

The Tat (twin‐arginine translocation) system mediates export of periplasmic proteins in folded conformation. Proteins transported via Tat contain a characteristic twin‐arginine motif in their signal peptide. Genetic determinants (tatABC genes) of the Tat system from Rhizobium leguminosarum bv. viciae were cloned and characterized, and a tatBC deletion mutant was constructed. The mutant lacked the ability for membrane targeting of hydrogenase, a known Tat substrate, and was impaired in hydrogenase activity. Interestingly, in the absence of a functional Tat system, only small, white nodules unable to fix nitrogen were induced in symbiosis with pea plants. Analysis of nodule structure and location of green fluorescent protein (GFP)‐tagged bacteria within nodules indicated that the symbiotic process was blocked in the tat mutant at a stage previous to bacteria release into cortical cells. The R. leguminosarum Tat‐deficient mutant lacked a functional cytochrome bc1 complex. This was consistent with the fact that R. leguminosarum Rieske protein, a key component of the symbiosis‐essential cytochrome bc1 complex, contained a typical twin‐arginine signal peptide. However, comparative analyses of nodule structure indicated that nodule development in the tat mutant was arrested at an earlier step than in a cytochrome bc1 mutant. These data indicate that the Tat pathway is also critical for proteins relevant to the initial stages of the symbiotic process.
The Escherichia coli amidase AmiC is a periplasmic septal ring component exported via the twin‐arginine transport pathway
Authors: Bernhardt Thomas G. , De Boer Piet A. J.
Published: May 2003

The N‐acetylmuramoyl‐l‐alanine amidases of Escherichia coli (AmiA, B and C) are periplasmic enzymes that remove murein cross‐links by cleaving the peptide moiety from N‐acetylmuramic acid. Ami– cells form chains, indicating that the amidases help to split the septal murein. Interestingly, cells defective in the twin‐arginine protein transport (Tat) pathway show a similar division defect. We find that both AmiA and AmiC are routed to the periplasm via Tat, providing an explanation for the Tat– division phenotype. Taking advantage of the ability of Tat to export prefolded (fluorescent) green fluorescent protein (GFP) to the periplasm, we sublocalized AmiA and AmiC in live cells using functional fusions to GFP. Interestingly, the periplasmic localization of the fusions differed markedly. AmiA–GFP appeared to be dispersed throughout the periplasm in all cells. AmiC–GFP similarly appeared throughout the periplasm in small cells, but was concentrated almost exclusively at the septal ring in constricting cells. Recruitment of AmiC to the ring was mediated by an N‐terminal non‐amidase targeting domain and required the septal ring component FtsN. AmiC therefore replaces FtsN as the latest known recruit to the septal ring and is the first entirely periplasmic component to be localized.
Three‐way interactions among the Sfh, StpA and H‐NS nucleoid‐structuring proteins of Shigella flexneri 2a strain 2457T
Authors: Deighan Padraig , Beloin Christophe , Dorman Charles J.
Published: May 2003

Shigella flexneri 2a strain 2457T has been found to express Sfh, a new member of the H‐NS‐like family of nucleoid‐structuring proteins. With H‐NS and its paralogue, StpA, this brings to three the number of these proteins expressed in this bacterium. This raises the possibility that three‐way interactions may occur in S. flexneri among these proteins and between the proteins and each other's genes. Such three‐way interactions among H‐NS‐like proteins have not been described previously. The expression of the sfh, stpA and hns genes was studied at the transcriptional and post‐transcriptional levels. The Sfh protein displays growth phase‐dependent regulation that distinguishes it from both H‐NS and StpA. Like H‐NS and StpA, Sfh can bind to its own promoter region, it negatively autoregulates transcription of its own gene, and when overexpressed all three proteins cross‐repress transcription of each other's genes. The presence of highly conserved oligomerization domains within these molecules suggested the possibility of protein–protein interactions. Like H‐NS and StpA, the purified Sfh protein forms homodimers in solution. Using the yeast two‐hybrid assay we show that each of the three proteins also forms homodimers in vivo and, additionally, each protein can form heterodimers with either of its homologues. This raises the possibility that Sfh may modulate the activities of H‐NS and StpA, and vice versa.
Study of the Pathological Effect of Escherichia coli Endotoxin in Rams
Authors: Sokkar S. M. , Darwiesh G. , Madbooly A. , Kaaden O.‐R.
Published: May 2003

This experimental study was carried out on nine adult rams. Rams were injected intravenously with Escherichia coli endotoxin serotype 055:B5. The regimen of injections is described fully. Blood and semen samples were collected periodically to evaluate the changes in blood and semen picture. The reproductive as well as the visceral organs were collected and examined macroscopically and microscopically. The results of the study revealed that sperm cell abnormalities and serum testosterone level were increased, and sperm acrosomal abnormalities were significantly increased. The total leucocytic count was significantly decreased. The histopathological examination revealed severe testicular degeneration in addition to various other lesions in the visceral organs. Scanning electron microscope of the sperm cells revealed detached acrosomes, knobbed acrosomes and coiled tails.
Tolerance of barley seed germination to cold‐ and drought‐stress expressed as seed vigour
Authors: Chloupek O. , HrstkovÁ P. , Jurecka D. , Graner A.
Published: June 2003

In barley, high seed vigour is a precondition for rapid and homogenous field emergence and good malting quality. Seed vigour was defined as germination percentage under stress conditions (10°C, drought stress ‐ 2 Bars) in 7‐8 barley varieties grown in 7‐8 locations in the Czech Republic over 7 years. Three of the 7 years were not suitable for high seed quality, probably because of unsuitable weather, as average seed vigour reached only 61, 77 and 86%, respectively. In the remaining 4 years, the average vigour exceeded 94%. The impact of variety on seed vigour was higher in the ‘bad years’ and the impact of location was higher in the other years. Varieties with higher vigour from all locations in the ‘bad years’ were identified. Lower vigour was related to the high occurrence of fungi (indicated by ergosterol assays) and to lower field emergence rates of seed samples. The results support the possibility of selecting for improvement of barley seed vigour, which is related to tolerance to various conditions during emergence and to homogenous malting.
Fusarium head blight‐resistant wheat line ‘Bizel’ does not contain rye chromatin
Authors: Bourdoncle W. , Ohm H. W. , Weber W. E.
Published: June 2003

Fusarium head blight (FHB), primarily caused by Fusarium graminearum in North America can result in significant losses in the yield and quality of wheat (Triticum aestivum L). Resistance sources have been largely limited to Chinese germplasm and, in particular, Sumai 3 or its derivatives. In recent years, resistance has been identified in Europe. Previous studies using the wheat line ‘Bizel’, developed in France, have shown that it has resistance to Fusarium head blight. Pedigree information shows that one of its progenitors is rye. This experiment was conducted to determine if ‘Bizel’ has rye chromatin, with the goal of developing a strategy for mapping FHB resistance genes. Two methods based on repetitive DNA sequences specific to rye were implemented. With both approaches, it was demonstrated that ‘Bizel’ does not contain rye chromatin. Consequently, wheat SSRs can be used to map ‘Bizel’ resistance genes for FHB.
Interspecific hybridization of a multiploid mutant of durum wheat with rye and Triticum monococcum L. results in pentaploid hybrids
Authors: Klindworth D. L. , Williams N. D. , McIntosh R. A.
Published: June 2003

The multiploid mutant of durum wheat is a genotype that produces unreduced gametes. Our objective was to test the recovery of pentaploid hybrids in crosses of the mutant with rye and Triticum monococcum L. Compared with check crosses, the mutant had a two‐third reduction in percent seed set for rye crosses, but had only a slight decrease in crossability with T. monococcum. Pentaploid hybrids were associated with plump seeds of the mutant/rye cross, and with shrivelled seeds of the mutant/T. monococcum cross. We suggest that the endosperm balance number hypothesis explains the association of pentaploid hybrids with endosperm type. This association made for easy recovery of pentaploid hybrids from crosses to both species. Mature, plump seeds from the mutant/rye cross were germinated and pentaploid hybrids were recovered. One pentaploid hybrid was recovered for every 50.5 and 15.1 florets pollinated with rye and T. monococcum, respectively. Unreduced gametes in the multiploid mutant will facilitate interspecific hybridization by reducing the time to produce pentaploid plants.