Effects of gaseous environment and temperature on the storage behaviour of Listeria monocytogenes on chicken breast meat

Portions of skinless chicken breast meat (pH 5.8) were inoculated with a strain of Listeria monocytogenes and stored at 1, 6 or 15 degrees C in (1) aerobic conditions; (2) 30% CO2 + air; (3) 30% CO2 + N2; and (4) 100% CO2. When samples were held at 1 degree C the organism failed to grow under any of the test conditions, despite marked differences between treatments in spoilage rate and ultimate microflora. At 6 degrees C counts of L. monocytogenes increased ca 10-fold in aerobic conditions before spoilage of the meat, but only when the inoculum culture was incubated at 1 degree C rather than 37 degrees C. In CO2 atmospheres growth of L. monocytogenes was inhibited on meat held at 6 degrees C, especially under 100% CO2. By contrast, storage at 15 degrees C led to spoilage of the meat within 2 d, in all gaseous environments, and listeria levels increased up to 100-fold. Differences in the behaviour of L. monocytogenes on poultry and red meats are discussed.     

Improvement of Disease Prediction and Modeling through the Use of Meteorological Ensembles: Human Plague in Uganda

Climate and weather influence the occurrence, distribution, and incidence of infectious diseases, particularly those caused by vector-borne or zoonotic pathogens. Thus, models based on meteorological data have helped predict when and where human cases are most likely to occur. Such knowledge aids in targeting limited prevention and control resources and may ultimately reduce the burden of diseases. Paradoxically, localities where such models could yield the greatest benefits, such as tropical regions where morbidity and mortality caused by vector-borne diseases is greatest, often lack high-quality in situ local meteorological data. Satellite- and model-based gridded climate datasets can be used to approximate local meteorological conditions in data-sparse regions, however their accuracy varies. Here we investigate how the selection of a particular dataset can influence the outcomes of disease forecasting models. Our model system focuses on plague (Yersinia pestis infection) in the West Nile region of Uganda. The majority of recent human cases have been reported from East Africa and Madagascar, where meteorological observations are sparse and topography yields complex weather patterns. Using an ensemble of meteorological datasets and model-averaging techniques we find that the number of suspected cases in the West Nile region was negatively associated with dry season rainfall (December-February) and positively with rainfall prior to the plague season. We demonstrate that ensembles of available meteorological datasets can be used to quantify climatic uncertainty and minimize its impacts on infectious disease models. These methods are particularly valuable in regions with sparse observational networks and high morbidity and mortality from vector-borne diseases.     

Developmental changes in Hymenolepis citelli and Hymenolepis diminuta during patency

Stem cell frequency, wet weight, proglottid number, and egg production were measured in Hymenolepis citelli at specific intervals between 20 and 120 days postinfection in an effort to correlate changes in stem cell frequency to other developmental parameters. Considerable variability was seen in wet weight and proglottid number, but differences did not seem to reflect any relation between these parameters and stem cell frequency. Significant differences were observed in egg production at specific postinfection periods. These appeared to correspond to changes seen in stem cell frequency during patency. Similar changes in egg production which also correspond to measured changes in stem cell frequency were recorded for Hymenolepis diminuta. Differences were also seen in number of eggs contained within gravid proglottids at various times postinfection for both species.     

Action of the diaphragm on the rib cage inferred from a force-balance analysis

Displacements of the rib cage are determined by the intrinsic passive properties of the rib cage, rib cage musculature, pleural and abdominal pressures, and the diaphragm. The diaphragm's mechanical actions on the rib cage are inferred from a force-balance analysis in which the diaphragm is seen to cause expansion of the rib cage by pulling cephalad at its insertions on the lower ribs (insertional component) and by raising intra-abdominal pressure, which pushes outward on the diaphragm's zone of apposition to the rib cage (appositional component). Goldman and Mead suggested that the diaphragm, acting alone, could drive both the rib cage and abdomen on their passive characteristics. The force-balance analysis shows that the diaphragm's inspiratory action on the rib cage is less than predicted by Goldman and Mead, but that in the special circumstances of their experiment (low lung volumes), the appositional component is large and the rib cage can be driven close to its passive characteristics. The force-balance analysis is consistent with recent observations by other investigations and is incompatible with the model proposed by Macklem and colleagues and with the Goldman-Mead hypothesis. Experiments on three subjects produced data consistent with the force-balance analysis, showing that the inspiratory action of the diaphragm on the rib cage is greatest at low lung volumes.     

Stability of unsaturated methyl esters of fatty acids on surfaces

The stability of unsaturated methyl esters is greater when they are adsorbed on silica gel than when a glass surface is used. Storage of small samples adsorbed on silica gel may be a convenient addition to conventional methods of protecting labile fats against autoxidation.     

The source of progesterone in preimplantation rabbit blastocysts.

In vitro and in vivo synthesis of progesterone, sequestration of progesterone from the surrounding medium, and its subsequent conversion to metabolites was investigated in 146 hr post coitus preimplantation rabbit blastocysts. No significant conversion of 3H-pregnenolone to 3H-progesterone was observed throughout the 8 hr incubation. Progesterone content in blastocysts and culture medium did not change during the course of an 8 hr incubation. This suggests that the failure to detect incorporation of label into progesterone was not due to the presence of a large endogenous pool of pregnenolone. Significant uptake (p less than 0.05) of 3H-progesterone from the incubation medium was observed as was significant conversion of the 3H-progesterone to unidentified metabolites. Therefore it would appear that the preimplantation rabbit blastocyst is not capable of de novo synthesis of progesterone from pregnenolone prior to implantation but sequesters progesterone from the surrounding medium and converts it to progesterone metabolites.