The impact of ticks on pheasant territoriality

Pheasants are competent reservoir hosts for the Lyme disease spirochaete, Borrelia burgdorferi s.l., and carry large, but highly over-dispersed, infestations of the vector ticks, Ixodes ricinus . The effects of experimental reduction of tick infestation levels on the survival and territorial behaviour of male pheasants were studied. Over three years in two woodlands in southern England, birds were marked individually and half were fitted with a slow-release acaricide, which substantially reduced their tick burdens from March to August. Acaricide treatment affected reproductive success but had no discernible impact on the survival rates of male pheasants. The degree of wattle inflation by males, an indicator of territorial status and a correlate of harem acquisition, was significantly greater among treated males. In each year, a significantly higher proportion of treated (overall 44%) than control (22%) males acquired harems. Males that acquired females ranged over small areas on field edges. By contrast, those with no females ranged more widely in woods and the adjoining fields, increasing their exposure to questing ticks. The relative contribution of such roving males to tick-borne pathogen transmission may thus increase.     

Nearly right or precisely wrong? Natural versus laboratory studies of vector-borne diseases

Recent studies that compare experimental vector-borne disease systems incorporating elements of natural pathogen-vector-host interactions with model systems using unnatural associations have highlighted quantitative, and even qualitative, differences in the results. Here, Sarah Randolph and Pat Nuttall argue that the use of mathematical models to explore epidemiological processes and patterns depends on accurate parameter values obtained from natural systems.     

The populations, characterization and activity of suspended bacteria in the Welsh River Dee

In a 29 month study of bacterial populations at three sites on the Welsh River Dee, the aerobic heterotrophic bacteria increased from an average basal level of about 1.2 times 10⁴ colony-forming units (cfu)/ml near the source of the river, to 2 times 10⁵ cfu/ml in the lower reaches. The ratio, total bacterial cell count: viable count, decreased from 70 in the upland reaches to 10 in the lower parts of the river. There was no apparent seasonal variation in bacterial numbers but on occasions the bacterial populations in both upland and lowland reaches of the river increased simultaneously. Fluctuations in bacterial numbers over a 50-fold range were observed in this study. Bacterial isolates from both upland and lowland sites were predominated by two groupings of bacteria, the Pseudomonas—Agrobacterium—Alcaligenes group and the Flavobacterium—Cytophaga—Flexibacter group. Results suggested that the latter group may have been part of the autochthonous population. Seasonal variation in heterotrophic potential ( V _max) for acetate uptake was shown to occur over a 30-fold range in the lowland reaches of the River Dee. Peaks in activity at the lowland site occurred during the summer months, the range of V _max values for acetate ranged from 0.2 to 30 μg/1/h. Fluctuations in V _max values from the upland site were not seasonal but were instead linked to faecal pollution, V _max values from this site range from 0.04 to 3 μg/1/h.     

Effect of prostaglandin E1 administration on the heart glycogen synthase and phosphorylase systems

The effects of intravenous administration of PGE₁ on the glycogen synthase and phosphorylase system in rat heart were studied.Unlike the consistent effects of PGE₁ on glycogen synthase in liver, the response in heart was variable. A significant decrease in the per cent synthase occurred in fasted intact rats while a significant increase was seen in adrenalectomized hydrocortisone treated fasted rats. No significant effect was seen on the synthase system in either fed intact or fasted adrenalectomized rats.Phosphorylase activity was increased significantly following PGE₁ administration in fed intact rats and slightly increased in adrenalectomized fasted rats. The phosphorylase system was not affected in fasted intact and fasted adrenalectomized rats given glucocorticoid replacement. With our present state of knowledge an adequate explanation for the response of these heart enzymes to PGE₁ under the various conditions of this study does not appear possible.     

Epidemiology of Staphylococcus aureus Bacteraemia at a Tertiary Children’s Hospital in Cape Town,South Africa

Background

Staphylococcus aureus is an important pathogen in paediatric patients with bloodstream infections. The epidemiology of S. aureus bacteraemia, however, has not been well documented in children in South Africa.

Methods

A retrospective study was conducted at a children’s hospital in Cape Town, South Africa, to investigate the epidemiology of S. aureus bacteraemia from 2007-2011. The incidence, clinical presentation, risk factors, management and outcomes of methicillin sensitive S. aureus (MSSA) and methicillin resistant S. aureus (MRSA) bacteraemia were compared.

Results

Over the five year study period, 365 episodes of S. aureus bacteraemia were identified. The annual incidence was 3.28 cases per 1000 hospital admissions. MRSA was responsible for 26% of S. aureus bacteraemia and 72% of nosocomial infections. Only six possible cases of community-acquired MRSA infections were described. MSSA bacteraemia was more likely to present as pulmonary and bone or joint infections, while bacteraemia without a source was the most common presentation with MRSA.  Infants, children with malnutrition, and residents of long-term care facilities were at highest risk for MRSA bacteraemia. The overall case fatality rate for S. aureus bacteraemia was 8.8% over five years, with MRSA being the only significant risk factor for mortality.

Conclusion

The incidence of S. aureus bacteraemia and MRSA bacteraemia in children has remained stable over the past five years. MRSA is a predominantly nosocomial pathogen in children with S. aureus bacteraemia in Cape Town, South Africa.     

FlyGEM, a full transcriptome array platform for the Drosophila community

We have constructed a DNA microarray to monitor expression of predicted genes in Drosophila. By using homotypic hybridizations, we show that the array performs reproducibly, that dye effects are minimal, and that array results agree with systematic northern blotting. The array gene list has been extensively annotated and linked-out to other databases. Incyte and the NIH have made the platform available to the community via academic microarray facilities selected by an NIH committee.     

Integrated effects of multiple modulators on human liver glycogen phosphorylase a

Hepatic glucose production is increased in people with type 2 diabetes. Glucose released from storage in liver glycogen by phosphorylase accounts for approximately 50% of the glucose produced after an overnight fast. Therefore, understanding how glycogenolysis in the liver is regulated is of great importance. Toward this goal, we have determined the kinetic characteristics of recombinant human liver glycogen phosphorylase a (HLGPa) (active form) and compared them with those of the purified rat enzyme (RLGPa). The Michaelis-Menten constant (K(m)) of HLGPa for P(i), 5 mM, was about fivefold greater than the K(m) of RLGPa. Two P(i) (substrate) concentrations were used (1 and 5 mM) to cover the physiological range for P(i). Other effectors were added at estimated intracellular concentrations. When added individually, AMP stimulated, whereas ADP, ATP and glucose inhibited, activity. These results were similar to those of the RLGPa. However, glucose inhibition was about twofold more potent with the human enzyme. UDP-glucose, glucose 6-phosphate, and fructose 1-phosphate were only minor inhibitors of both enzymes. We reported previously that when all known effectors were present in combination at physiological concentrations, the net effect was no change in RLGPa activity. However, the same combination reduced HLGPa activity, and the inhibition was glucose dependent. We conclude that a combination of the known effectors of phosphorylase a activity, when present at estimated intracellular concentrations, is inhibitory. Of these effectors, only glucose changes greatly in vivo. Thus it may be the major regulator of HLGPa activity.     

C-terminal extension of phaseolin with a short methionine-rich sequence can inhibit trimerisation and result in high instability

In an attempt to increase the content in essential amino acids methionine and tryptophan of the trimeric storage protein phaseolin, we fused a Met- and Trp-rich sequence to the C-terminus of a phaseolin variant lacking its vacuolar sorting signal, with the aim to target the protein for secretion and accumulation into the apoplast. The fate of the mutant protein, denominated Y3, was studied in transiently transfected tobacco protoplasts. We report that the presence of the additional sequence causes structural defects which inhibit trimerization and lead to partial aggregation of Y3. The protein interacts with the ER chaperone BiP prior to being degraded very rapidly, in a process that does not require vesicular transport from the ER. The rate of degradation of Y3 is higher than that observed for another assembly defective mutant of phaseolin, 360, which remains monomeric and does not aggregate. This indicates that the plant ER quality control machinery can dispose of defective proteins with different kinetics and perhaps mechanisms, depending on the nature of their defect.     

Vasodilatory activity in horsefly and deerfly salivary glands

Salivary gland extract (SGE) of four horsefly species (Hybomitra bimaculata Macquart, Hybomitra ciureai Séguy, Tabanus bromius L., Tabanus glaucopis Meigen) and one deerfly species (Chrysops relictus Meigen) (Diptera: Tabanidae) were shown to contain vasodilatory activity. Aliquots equivalent to 1, 5 and 10 pairs of salivary glands (SG) relaxed rat femoral artery (with intact endothelium) pre-constricted with phenylephrine. Vasodilatory activity was dose-dependent. SGE of one horsefly species (Haematopota pluvialis L.) did not induce relaxation. The kinetics of vasodilation induced by SGE of four horsefly species differed from the deerfly. These results indicate that tabanid species may produce more than one type of vasodilator to aid blood feeding.