Arylsulphatase activity associated with phenanthrene induced digestive cell deletion in the marine mussel Mytilus edulis

Summary The acid hydrolase arylsulphatase has been localized at the ultrastructural level in digestive cells of the marine musselMytilus edulis for control and phenanthrene-treated (200µg/l) animals. In untreated mussels the activity was generally restricted to the lysosomal—vacuolar system and the Golgi apparatus. It was associated with all types of vesicle, although not all individual vesicles were reactive. In heterolysosomes which were filled with precipitate the reaction product was most densely associated with the limiting membranes. Lipid inclusions commonly occurred in the digestive cells; these sometimes showed limited reaction for enzyme activity. The striking difference between normal and phenanthrene-treated samples was the presence in all treated animals of reaction product in the inter-cellular spaces and varying degrees of cytoplasmic activity in a number of digestive cells. This is interpreted as a sign of impending cell deletion. Sections for morphological examination showed evidence of increased digestive cell deletion in phenanthrene-treated mussels. The process results in release of membrane-bound bodies into the tubule lumen.     

Variability in host plant resistance of Sorghum to Striga Hermonthica infestation in West Africa

Fourteen elite sorghum lines were evaluated for their resistance to Striga hermonthica at three locations in Nigeria and Mali. Results showed that many of the lines especially MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64 (Keninkédié) and the check SRN 39 remained resistant to Striga in all locations with low emerged Striga counts, while SAMSORG 14 had the highest Striga infestation in all locations. Considerable variation in reaction to Striga infestation was observed on Séguètana, 97-SB-F5DT-63 (Wasa), 97-SB-F5DT-65, CMDT 38, CMDT 39 and CMDT 45 which were susceptible to Striga at Samaru, Nigeria but were resistant to Striga at both locations in Mali. Based on low Striga resistance and high grain yield, lines MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64, 97-SB-F5DT-65, CMDT 39 and SAMSORT 14 have been nominated for wider evaluation across more West African countries.     

Smoking,restaurants and bars: the Toronto experience

Rural physicians and other professionals attending a recent conference in St. John''s reached consensus on a number of issues surrounding the role of nurse practitioners. The issue is important for rural doctors, since some people think NPs can help solve the physician shortage in rural areas.     

Two common nonsynonymous paraoxonase 1 (<Emphasis Type="Italic">PON1</Emphasis>) gene polymorphisms and brain astrocytoma and meningioma

Background  

Human serum paraoxonase 1 (PON1) plays a major role in the metabolism of several organophosphorus compounds. The enzyme is encoded by the polymorphic gene PON1, located on chromosome 7q21.3. Aiming to identify genetic variations related to the risk of developing brain tumors, we investigated the putative association between common nonsynonymous PON1 polymorphisms and the risk of developing astrocytoma and meningioma.     

Long-term effects of graduated compression stockings on cardiorespiratory performance

The use of graduated compression stockings (GCS) in sport has been increasing in the last years due to their potential positive effects for athletes. However, there is little evidence to support whether these types of garments actually improve cardiorespiratory performance. The aim of this study was to examine the cardiorespiratory responses of GCS during running after three weeks of regular use. Twenty recreational runners performed three tests on different days: test 1) – a 5-min maximal effort run in order to determine the participants’ maximal aerobic speed; and tests 2) and 3) – a fatigue running test of 30 minutes at 80% of their maximal aerobic speed with either GCS or PLACEBO stockings at random. Cardiorespiratory parameters (minute ventilation, heart rate, relative oxygen consumption, relative carbon dioxide production, ventilatory equivalents for oxygen and carbon dioxide, and oxygen pulse) were measured. Before each test in the laboratory, the participants trained with the randomly assigned stockings (GCS or PLACEBO) for three weeks. No significant differences between GCS and PLACEBO were found in any of the cardiorespiratory parameters. In conclusion, the present study provides evidence that running with GCS for three weeks does not influence cardiorespiratory parameters in recreational runners.     

An internal model architecture for novelty detection: implications for cerebellar and collicular roles in sensory processing

The cerebellum is thought to implement internal models for sensory prediction, but details of the underlying circuitry are currently obscure. We therefore investigated a specific example of internal-model based sensory prediction, namely detection of whisker contacts during whisking. Inputs from the vibrissae in rats can be affected by signals generated by whisker movement, a phenomenon also observable in whisking robots. Robot novelty-detection can be improved by adaptive noise-cancellation, in which an adaptive filter learns a forward model of the whisker plant that allows the sensory effects of whisking to be predicted and thus subtracted from the noisy sensory input. However, the forward model only uses information from an efference copy of the whisking commands. Here we show that the addition of sensory information from the whiskers allows the adaptive filter to learn a more complex internal model that performs more robustly than the forward model, particularly when the whisking-induced interference has a periodic structure. We then propose a neural equivalent of the circuitry required for adaptive novelty-detection in the robot, in which the role of the adaptive filter is carried out by the cerebellum, with the comparison of its output (an estimate of the self-induced interference) and the original vibrissal signal occurring in the superior colliculus, a structure noted for its central role in novelty detection. This proposal makes a specific prediction concerning the whisker-related functions of a region in cerebellar cortical zone A(2) that in rats receives climbing fibre input from the superior colliculus (via the inferior olive). This region has not been observed in non-whisking animals such as cats and primates, and its functional role in vibrissal processing has hitherto remained mysterious. Further investigation of this system may throw light on how cerebellar-based internal models could be used in broader sensory, motor and cognitive contexts.     

Spatial-temporal modelling of bacterial colony growth on solid media

The enormous diversity among bacterial colonies of different species, and among colonies of the same species under different environmental conditions, has long interested microbiologists. Yet it is only comparatively recently that quantitative, rather than merely conceptual, models have been developed to explain the dynamics of bacterial colony formation and growth. Understanding the fundamental processes that drive these dynamics is still at a rudimentary level, though a number of advances have been made. This review traces the history of bacterial colony growth modelling, from the pioneering work of Pirt in the late 1960s, through experimental investigations by Wimpenny and his colleagues in the 1970s, and further models extending from that work to understand complex bacterial colony formations. It concludes with recent results which find that both diameter and height of the colony follow simple power-law behaviour over the entire active growth period (from a few hours to several days old), and that the results of Pirt, Wimpenny and their contemporaries can be re-interpreted.