Safety Precautions to be Observed with Cooled Premixed Gases

The gas delivered from a cylinder of Entonox (50% nitrous oxide and 50% oxygen) may not contain adequate quantities of oxygen if the cylinder has been cooled and then allowed to warm up in a vertical position.The composition of gas delivered from cylinders cooled to not lower than –40° C. remains unaltered if the cylinders are rewarmed for 24 hours in a horizontal position at a temperature of not less than 5° C.Cylinders of Entonox delivered in cold weather should be stored in a horizontal position at 5° C. or more for at least 24 hours before use.     

The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

Asymptotic forms of tracer clearance curves: theory and applications of improved extrapolations

Tracer clearance curves are conventionally extrapolated beyond times of observation by using monoexponential asymptotic forms. The inadequacy of the resulting predictions, especially as to the mean transit time and quantities derived from it, has been previously demonstrated experimentally. Here improvements in extrapolations and in the resulting predictions are derived theoretically and tested on previously published data, venous as well as externally recorded. First, secure lower bounds on the mean transit times are constructed, and shown to be much higher than conventional outright estimates for venous data (twice as high in some cases). Next, new asymptotic forms of tracer clearance curves from kinetically heterogeneous systems are derived; they are not monoexponential, but they are as robust, contain as few parameters and are as easily connected to data. It is shown theorectically that for real organs these new asymptotic forms should extrapolate and predict better than monoexponentials, and this is demonstrated on previously published venous data from perfused muscle. In particular, the resulting outright predictions of mean transit times are substantially better than the best lower bounds. Furthermore, a correction is derived to the standard estimate of the rate of regional cerebral blood flow. In an application to previously published data recorded externally, that correction reduces the estimated flow rate by 4%.     

Warming and Elevated CO2 Interact to Drive Rapid Shifts in Marine Community Production

Predicting the outcome of future climate change requires an understanding of how alterations in multiple environmental factors manifest in natural communities and affect ecosystem functioning. We conducted an in situ, fully factorial field manipulation of CO₂ and temperature on a rocky shoreline in southeastern Alaska, USA. Warming strongly impacted functioning of tide pool systems within one month, with the rate of net community production (NCP) more than doubling in warmed pools under ambient CO₂ levels relative to initial NCP values. However, in pools with added CO₂, NCP was unaffected by warming. Productivity responses paralleled changes in the carbon-to-nitrogen ratio of a red alga, the most abundant primary producer species in the system, highlighting the direct link between physiology and ecosystem functioning. These observed changes in algal physiology and community productivity in response to our manipulations indicate the potential for natural systems to shift rapidly in response to changing climatic conditions and for multiple environmental factors to act antagonistically.     

Voltage-dependence of contraction in streptozotocin-induced diabetic myocytes

Cardiac contractile dysfunction is frequently reported in human patients and experimental animals with type-1 diabetes mellitus. The aim of this study was to investigate the voltage-dependence of contraction in ventricular myocytes from the streptozotocin (STZ)-induced diabetic rat. STZ-induced diabetes was characterised by hyperglycaemia and hypoinsulinaemia. Other characteristics included reduced body and heart weight and raised blood osmolarity. Isolated ventricular myocytes were patched in whole cell, voltage-clamp mode after correcting for membrane capacitance and series resistance. From a holding membrane potential of –40 mV, test pulses were applied at potentials between –30 and +50 mV in 10 mV increments. L-type Ca²⁺ current (I _Ca,L) density and contraction were measured simultaneously using a video-edge detection system. Membrane capacitance was not significantly altered between control and STZ-induced diabetic myocytes. The I _Ca,L density was significantly (p < 0.05) reduced throughout voltage ranges (–10 mV to +10 mV) in myocytes from STZ-treated rats compared to age-matched controls. Moreover, the amplitude of contraction was significantly reduced (p < 0.05) in myocytes from STZ-treated rats at all test potentials between –20 mV and +30 mV. However, in electrically field-stimulated (1 Hz) myocytes, the amplitude of contraction was not altered by STZ-treatment. It is suggested that in field-stimulated myocytes taken from STZ-induced diabetic hearts, prolonged action potential duration may promote increased Ca²⁺ influx via the sodium-calcium exchanger (NCX), which may compensate for a reduction in Ca²⁺ trigger through L-type-Ca²⁺-channels and lead to normalised contraction. (Mol Cell Biochem 261: 235–243, 2004)