Detection of Staphylococcal Enterotoxin A,B, and C in Milk By an Elisa Procedure

Enterotoxigenic reference strains of Staphylococcus aureus were cultivated in sterile whole and skim milk for 18 h at 37°G. Staphylococcal enterotoxin A, B, and C were detected directly in the milk by an enzyme linked immunosorbent assay (ELISA), sensitive down to 1 ng/ml. Enterotoxins in the range of 1 ng–20 µg/ml milk were detected without any concentration or extraction. Skim and whole milk were almost identical as medium for enterotoxin production.     

Pathogenicity for Chickens of a Paramyxovirus Type 1, Isolated from Racing Pigeons in Sweden

Strains of paramyxovirus type 1 (PMV-1) have been isolated from diseased racing pigeons in Sweden. One of these isolates was selected for studies of the pathogenicity and contagiousness in chickens. The same isolate was previously found to have a high intravenous pathogenicity index (IVPI) in 6 weeks old chickens. In three experiments it was found that the PMV-1 isolate was very pathogenic for 1 week old chickens but not pathogenic for 120 day old pullets inoculated intranasally and ocularly. Symptoms in the young chickens were similar to those seen in the neurotropic form of Newcastle disease. The mortality was high and the incubation period 5–11 days. The disease easily spread to young chickens kept in contact with diseased birds. The microscopic examination revealed an interstitial nonpurulent pneumonia and a nonpurulent encephalitis in the young chickens. In the pullets the only finding was a mild encephalitis. PMV-1 was recovered from all young chickens but not from the pullets. Both the chickens and the inoculated pullets developed antibodies to PMV-1.     

Unusual peaks of oxygen consumption under special alimentary conditions

Oxygen consumption (VO2), carbon dioxide production (VCO2), the resulting respiratory quotient (RQ), and motor activity were recorded simultaneously by an on-line computer every ten seconds during 16-20 hours in two decerebrate male rats. Being aphagic and adipsic the rats were fed twice daily by gastric intubation with a mixture of powdered milk plus sugar or plus sunflower oil (approx. 300 KJ daily) in 10-20 ml tap water. In all seven tests performed on these rats the recordings presented very steep reductions of RQ due every time to steep increases in VO2 without increases in VCO2. Mean number of VO2 peaks in all experiments was 12.4 +/- 1.8 (SE) with mean duration of 21.3 +/- 2.8 min. Two normal male rats were fed the same diet and on the same schedule: they presented similar VO2 peaks in 8 out of 12 experiments. Mean number was 8.7 +/- 1.0 with mean duration of 13.6 +/- 2.2 min. The VO2 peak periods never occurred in rats fed ad libitum. In the two normal rats oil ingestion produced more effect than sugar. It is suggested that the phenomenon could be due to a metabolic imbalance possibly of hepatic origin, more evident in decerebrate rats. VO2 peaks could be produced by enhanced ketogenesis, gluconeogenesis and/or extra-mitochondrial (peroxisomal, microsomal) oxidation.     

Stereological and biochemical analysis of prolactin and growth hormone secreting rat pituitary cells in culture

Summary The secretion of prolactin is increased by treatment of prolactin producing rat pituitary cells with the hypothalamic tripeptide thyroliberin. To investigate the underlying mechanisms we used three closely related rat pituitary tumor cell strains (GH₁2C₁, GH₃ and GH₄C₁), which synthesize and spontaneously secrete prolactin and/or growth hormone. Growth hormone and prolactin released into the culture medium over a period of 24 h were measured by radioimmunoassay. Initial rates of synthesis were measured by immunoprecipitation of intracellular growth hormone and prolactin after incubation of cell cultures with ³H-leucine. The observed increase in prolactin synthesis and release was correlated with morphological effects of thyroliberin treatment. The volume density of Golgi complexes and the volume and surface densities of rough endoplasmic reticulum were compared in untreated cells and thyroliberin treated cells. As normal distribution could not be assumed, the non-parametric rank test of Wilcoxon was used whereby the densities calculated for each cell section were ranked. Alle three morphological parameters increased after thyroliberin treatment in cells secreting prolactin only (GH₄C₁), implying that the increase of prolactin secretion, at lest in part, is due to increased prolactin synthesis.     

Paradoxical effects of maternal stress on fetal steroids and postnatal reproductive traits in female mice from different intrauterine positions

We examined effects of maternal stress on prenatal serum concentrations of testosterone and estradiol and on postnatal reproductive traits in female mice from different intrauterine positions. On Day 18 of fetal life, control females positioned in utero between two male fetuses (2M females) had higher concentrations of testosterone and lower concentrations of estradiol in serum than control female fetuses located between two females (0M females). Control females positioned between a male and a female fetus (1M females) had intermediate levels of both hormones. Prior intrauterine position in control females accounted for differences in genital morphology (length of the anogenital separation) at birth and length of estrous cycles during adulthood. Maternal stress eliminated these postnatal differences due to prior intrauterine position: all 0M, 1M, and 2M female offspring of stressed mothers exhibited postnatal traits that were indistinguishable from those of control 2M females. Maternal stress resulted in an increase of over 1 ng/ml in serum testosterone in all female fetuses; the magnitude of the increase was similar for 0M, 1M, and 2M females. There was no effect of maternal stress on serum concentrations of estradiol in 0M and 2M female fetuses. Maternal stress resulted in a dramatic change in the postnatal traits of 0M females, whereas 2M females showed no change. Since the effect of maternal stress on sex steroids was similar among fetuses from different intrauterine positions but postnatal response to maternal stress varied by intrauterine position, other components of the endocrine system may mediate effects of maternal stress on these postnatal characteristics.     

Shapes and functions of species–area curves (II): a review of new models and parameterizations

This paper has extended and updated my earlier list and analysis of candidate models used in theoretical modelling and empirical examination of species–area relationships (SARs). I have also reviewed trivariate models that can be applied to include a second independent variable (in addition to area) and discussed extensively the justifications for fitting curves to SARs and the choice of model. There is also a summary of the characteristics of several new candidate models, especially extended power models, logarithmic models and parameterizations of the negative-exponential family and the logistic family. I have, moreover, examined the characteristics and shapes of trivariate linear, logarithmic and power models, including combination variables and interaction terms. The choice of models according to best fit may conflict with problems of non-normality or heteroscedasticity. The need to compare parameter estimates between data sets should also affect model choice. With few data points and large scatter, models with few parameters are often preferable. With narrow-scale windows, even inflexible models such as the power model and the logarithmic model may produce good fits, whereas with wider-scale windows where inflexible models do not fit well, more flexible models such as the second persistence (P2) model and the cumulative Weibull distribution may be preferable. When extrapolations and expected shapes are important, one should consider models with expected shapes, e.g. the power model for sample area curves and the P2 model for isolate curves. The choice of trivariate models poses special challenges, which one can more effectively evaluate by inspecting graphical plots.     

Investigating alginate production and carbon utilization in Pseudomonas fluorescens SBW25 using mass spectrometry-based metabolic profiling

Metabolic profiling of Pseudomonas fluorescens SBW25 and various mutants derived thereof was performed to explore how the bacterium adapt to changes in carbon source and upon induction of alginate synthesis. The experiments were performed at steady-state conditions in nitrogen-limited chemostats using either fructose or glycerol as carbon source. Carbon source consumption was up-regulated in the alginate producing mutant with inactivated anti-sigma factor MucA. The mucA- mutants (also non-alginate producing mucA- control strains) had a higher dry weight yield on carbon source implying a change in carbon and energy metabolism due to the inactivation of the anti-sigma factor MucA. Both LC–MS/MS and GC–MS methods were used for quantitative metabolic profiling, and major reorganization of primary metabolite pools in both an alginate producing and a carbon source dependent manner was observed. Generally, larger changes were observed among the phosphorylated glycolytic metabolites, the pentose phosphate pathway metabolites and the nucleotide pool than among amino acids and citric acid cycle compounds. The most significant observation at the metabolite level was the significantly reduced energy charge of the mucA- mutants (both alginate producing and non-producing control strains) compared to the wild type strain. This reduction was caused more by a strong increase in the AMP pool than changes in the ATP and ADP pools. The alginate-producing mucA- mutant had a slightly increased GTP pool, while the GDP and GMP pools were strongly increased compared to non-producing mucA- strains and to the wild type. Thus, whilst changes in the adenosine phosphate nucleotide pool are attributed to the mucA inactivation, adjustments in the guanosine phosphate nucleotide pool are consequences of the GTP-dependent alginate production induced by the mucA inactivation. This metabolic profiling study provides new insight into carbon and energy metabolism of the alginate producer P. fluorescens.     

Methicillin-Resistant Staphylococcus aureus (MRSA) Is Increasing in Norway: A Time Series Analysis of Reported MRSA and Methicillin-Sensitive S. aureus Cases, 1997–2010

Background

Accurate estimates of the incidence and prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections are needed to inform public health policies. In Norway, where both MRSA infection and carriage are notifiable conditions, the reported incidence of MRSA is slowly increasing. However, the proportion of MRSA in relation to all S. aureus isolates is unknown, making it difficult to determine if the rising incidence is real or an artifact of an increasing number of tests performed.

Aim

To characterize recent trends in MRSA infections and obtain a more complete understanding of the MRSA level in Norway.

Methods

All reported cases of MRSA and methicillin-sensitive S. aureus (MSSA) from Oslo County (1997–2010) and Health Region East (2008–2008), representing approximately 11% and 36% of the Norwegian population, respectively, were analyzed using a stochastic time series analysis to characterize trends.

Results

In Oslo County, the proportion of methicillin-resistant cases increased from 0.73% to 3.78% during the study period and was well modeled by an exponential growth with a doubling constant of 5.7 years (95% CI 4.5–7.4 years). In Health Region East, the proportion of MRSA cases increased from 0.4% to 2.1% from 2002 to 2008, with a best-fitting linear increase of 0.26% (95% CI 0.21–0.30%) per year. In both cases, the choice of a linear or exponential model for the time trend produced only marginally different model fits. We found no significant changes due to revised national MRSA guidelines published in June 2009. Significant variations in the increasing time trend were observed in the five hospitals within the region. The yearly reported incidence of MSSA was relatively stable in both study areas although we found seasonal patterns with peaks in August.

Conclusion

The level of MRSA is increasing in Norway, and the proportion of methicillin resistance in all S. aureus isolates are higher than the reported proportion of MRSA in invasive infections.