Measuring oxygen consumption with an all-electronic multi-range digital respirometer
Oxygen consumption of animals is often measured for studies in physiological ecology. Usually a closed respiration chamber containing a carbon-dioxide-absorbing substance is used. Oxygen consumed by the animal is either compensated by reduction of the vessel volume (Kratochvil 1976) or replaced by electrolysis (Heusner etal. 1965; Rufeger 1968, 1980). Manometers of various kinds are always employed for pressure transmission. All chambers are kept at constant temperature by a thermostatically controlled water bath. The advantage of an electrolytic respirometer is that the quantity of oxygen generated is linearly dependent only on current and independent of air pressure and temperature. The breathing air composition before, during, and after measurement is constant. After equilibration such a system allows direct oxygen consumption measurements at various environmental temperatures without making corrections. In the apparatus described here power supply, time pulse generator, constant current generator, and the processor which controls the operation and calculates the results are joined in a common box. In front of it the counter displays and the switch board with optical and acoustic signals are arranged. A newly designed manometer with adjustable sensitivity and an infra-red sensor drives a digital position discriminator. This amplification of the manometer reading permits a very simple zero adjustment. All the usual types of gas chamber may be used, for instance equipment consisting only of an electrolytic cell, respiration chamber, and compensating chamber (Heusner et al. 1965), as well as extensive additional fittings, with pump-driven air circulation and separate carbon dioxide and humidity absorption vessels (Moyat 1957; Rufeger 1968, 1980). Contact manometers constructed earlier may be connected on a separate input.
Application de la coulometrie a la mesure de la consommation d’oxygene
SommaireL’appareil décrit permet d’enregistrer pendant de longues durées (jusqu’à deux semaines) de très faibles consommations d’oxygène (50 μl h−1 à 10.000 μl h−1). On remplace quantitativement le volume d’oxygène consommé par de l’oxygène produit par électrolyse.Le volume d’oxygène consommé est détecté à l’aide d’un manomètre et mesuré indirectement par la coulométrie. L’enregistrement se ramène soit au comptage de volumes-unités d’oxygène consommés pendant un temps donné, soit à l’enregistrement à intervalles réguliers du volume d’oxygène consommé. La description de l’appareil est précédée d’une étude théorieque de la détection et de la mesure d’un petit volume d’oxygène. L’appareil est susceptible d’être utilisé pour enregistrer la consommation d’oxygène de petits organismes très variés, aussi bien animaux que végétaux.AbstractThe apparatus described allows the recording over long periods (up to two weeks) of very small oxygen consumption rates (50 μl h−1 to 10,000 μl h−1). The quantity of oxygen consumed is balanced by fresh oxygen produced electrolytically.The volume of oxygen consumed is detected by a monometer and is measured, indirectly, by coulometry. The record may display either the total oxygen consumed in a given time, or the rate of consumption at regular intervals.The description of the apparatus is preceded by a theoretical treatment of the problem of detection and measurement of small volumes of oxygen.The equipment may be used to recored the oxygen consumption of a wide variety of small organisms, both animal and vegetable.ZusammenfassungDer hier beschriebene Apparat ermöglicht es den Sauerstoffverbrauch (50 μl h−1 bis 10.000 μl h−1) längere Zeit (zwei Wochen) automatisch genau zu registrieren.Der verbrauchte Sauerstoff wird quantitativ duch elektrolytischen Sauerstoff ersetzt. Diese Vorgang wird durch einen präzisen Manometer gesteuert. Das Registrieren wird entweder durch einen Zähler oder durch den beschriebenen Schreiber bewerkstelligt. Die dem Geräte zu Grunde liegenden Prinzipen und die Fehlerquellen werden eingehend behandelt.Mit dem Apparat wurde der Sauerstoffverbrauch von sehr verschiedenen Tieren registriert (Fische, Insekten, Wasserschildkröten und Hühnerembryo)РезюмеОписываемый аппарат позволяет регистровать чреавычайно малые поглощения кислорода (от 50 микролитров в час до 10.000 микролитров в час) в течении продолжительных периодов времени (до 2−x недель). Поглощенный кислород количественно возмещается свежим кислородом, получаемым эликтролитическим способом.Объем поглощенного кислорода определяется манометром и косвенно измеряется амперметром. Запись может показывать либо общее количество кислорода, поглощенного за определенное время, сибо степеня поглощения в течении определенных промежутков времени.Описанию аппарата предшествует теоритическое изучение проблемы выявления и измерения малых количеств кислорода.Аппарат может быть исполязован для определения поглощения кислорода самыми разнообрзными мельчайшими организмами, как животного, так и растительного мира.
X-rays and photocarcinogenesis in hairless mice
It is well known that excessive X-ray radiation can cause non-melanoma skin cancers. With the increased incidence of sun-related skin cancer there is a need to investigate the combination of sunlight and X-rays. Immunocompetent C3.Cg/TifBomTac mice (n = 298) were divided into 12 groups. Mice were irradiated with 12, 29 or 50 kV X-rays. The mice received a total dose of 45 Gy. They were irradiated with 3 SED simulated solar radiation (SSR) either before or after irradiation with X-rays. The groups irradiated with X-rays alone, 0, 3, 9 and 10 mice (0, 12, 29 and 50 kV, respectively) developed squamous cell carcinoma. In the groups irradiated with SSR after X-rays the development of tumours was significantly faster in the 50 kV group than in the corresponding control group (175 vs. 194 days, p < 0.001). In the groups irradiated with SSR prior to the X-ray radiation the development of tumours was significantly faster in the 29 and the 50 kV groups than in the corresponding control group (175 vs. 202 days, p < 0.001 and 158 vs. 202 days, p < 0.001, respectively). In conclusion, X-ray radiation alone is a weak carcinogen in hairless mice. There is an added carcinogenic effect if X-ray radiation is given on prior sun-exposed skin or if the skin is sun-exposed after X-rays. We still believe that X-ray radiation is a safe and effective therapy for various dermatological diseases but caution should be observed if a patient has severely sun-damaged skin or has a high-risk sun behaviour.