Measurement of respiratory gas exchange during artificial respiration

This paper reports a new system for the continuous measurements of respiratory gas exchange in ventilated subjects. It involves mixing some of the inspired gas with all of the expired gas and withdrawing the mixture at a constant rate through a dry gas meter that measures the flow. The inspired gas and expired gas mixtures are sampled and O2 and CO2 concentrations measured with a paramagnetic gas analyzer and a capnograph, respectively, to an accuracy of 0.01%. Evidence is presented to confirm the necessary stability and sensitivity of these instruments. It is possible to use the system with high inspired O2 concentrations, with ventilators where there is incomplete separation of inspired and expired gas, and in the presence of intermittent mandatory ventilation, positive end-expiratory pressure, and continuous airway pressure. The system was compared with the N2-dilution method and with the collection of expired gas in a Douglas bag in dog experiments and with patients in the intensive therapy unit. Excellent correlation between these methods was found in all circumstances.     

The differential effects of ingested tannic acid on different species of Acridoidea

The growth and development of fifteen species of Acridoidea were studied, with and without the addition of tannic acid in concentrations of up to 20% dry weight. In no case was digestion disturbed, and only at the high levels was there a significant reduction in consumption. Polyphagous species showed no deleterious effects, and in two species tannin was beneficial, while graminivorous acridids showed reduced growth rates and poor survival. The difference lies mainly in the fact that tannic acid penetrates the peritrophic membrane in the graminivorous species, and causes damage to the midgut epithelium with the eventual development of lesions and the occurrence of tannin in the haemocoel.

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Unterschiedliche wirkungen aufgenommener tanninsaeure auf acridoidea-arten

Zusammenfassung Wachstum und Entwicklung von 15 Acridoidea-Arten wurde studiert und zwar mit und ohne Zugabe von Tanninsäure zur Nahrung in Konzentrationen bis zu 20% Trockensubstanz. In keinem Fall wurde die Verdauung beeinträchtigt; nur in den hohen Konzentrationen wurde die Futteraufnahme gesichert vermindert. Polyphage Arten zeigten keine ungünstige Effekte, und bei zwei Arten wirkte Tannin günstig. Dagegen wurde bei grasfressenden Heuschrecken das Wachstum reduziert, und die Überlebensrate war gering. Der Unterschied liegt im wesentlichen darin, dass bei grassfressenden Arten Tanninsäure in die peritrophische Membran eindringt und das Mitteldarmephithel beschädigt, wobei es zu Läsionen kommt und wobei Tannin in die Körperhöhle gelangt.

     

Production and viability of coccoid forms of Campylobacter jejuni

Studies were conducted into the formation and physiological state of coccoid cells of a strain of the human and animal pathogen Campylobacter jejuni. It was found that growth phase and the presence of chloramphenicol did not affect the rate of shape transformation from spiral to coccoid, while nutrient limitation, aeration of the medium and the presence of free-radical scavengers had profound effects. Coccoid cells were found to reduce the tetrazolium salts INT (2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyl tetrazolium chloride) and CTC (5-cyano-2,3-ditolyl tetrazolium chloride) to their respective formazans and this was linked to cellular respiration. However, respiring coccoid cells could not sustain their existence in prolonged adverse conditions, and it was concluded that they represent a degenerative stage rather than a dormant state of the organism.