In vitro fertilization of rabbit ova in tubal fluid

The aversive effects of 90 per cent argon in air, 30 per cent carbon dioxide in air or 90 per cent carbon dioxide in air were investigated in slaughter weight pigs. Aversion was assessed from their reluctance to enter the three gaseous atmospheres to obtain a reward (apples). The pigs did not show any aversion to the inhalation of 90 per cent argon in air. The majority of the pigs did not show aversion to the presence of 30 per cent carbon dioxide in air. By contrast, the inhalation of 90 per cent carbon dioxide was aversive to the majority of the pigs. Fasting them for up to 24h prior to testing did not overcome the pigs ‘ reluctance to enter an atmosphere containing 90 per cent carbon dioxide.

The severity of respiratory distress occurring prior to loss of posture during exposure to: 20, 30, 40, 50, 60, 70, 80 or 90 per cent carbon dioxide in air; 2 or 5 per cent residual oxygen in argon; 30 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen; or 40 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen, was subjectively determined in pigs from their behaviour. The results indicated that exposure to 2 per cent oxygen in argon (anoxia) induced minimal respiratory distress, 30 per cent carbon dioxide in argon with 2 per cent residual oxygen induced a moderate distress and exposure to all the concentrations of carbon dioxide in air induced severe respiratory distress in the pigs. From the animal welfare point of view, using 2 per cent oxygen in argon (anoxia) appears to be the optimum choice for gas stunning pigs. Secondly, a mixture of 30 per cent carbon dioxide in argon with 2 per cent residual oxygen is preferred to 90 per cent carbon dioxide in air.

The reactions of turkeys to the presence of either 90 per cent argon in air (anoxia), 72 per cent carbon dioxide in air or a mixture of 30 per cent carbon dioxide and 60 per cent argon in air with 3 per cent residual oxygen were tested. The majority of the turkeys did not avoid a feeding chamber containing either argon or the mixture of carbon dioxide and argon, but 50 per cent of the turkeys avoided a feeding chamber containing 72 per cent carbon dioxide in air. It is concluded that from the point of view of welfare, either 90 per cent argon in air or a mixture of 30 per cent carbon dioxide and 60 per cent argon in air, would be preferable to a high concentration of carbon dioxide for stunning/killing turkeys.

SINCE blood has a pH of about 7.4, media used for organ and tissue culture are usually adjusted to this hydrogen ion concentration. However, when the chemically defined medium BGJb1 was first formulated, sodium bicarbonate was added in excess (3.5 g/l.), with the result that the medium had a pH of 7.68 when equilibrated with 5 per cent carbon dioxide in air. Mouse fallopian tubes continued to function2 and embryonic long bones developed1 under these alkaline conditions. Paff3 studied the effect of hydrogen ion concentration on embryonic chick femora cultivated on plasma clots in the presence of both air and 5 per cent carbon dioxide in air. The pH of the media under these conditions was 7.8–8.0 and 7.0–7.3 respectively. After cultivation for 14 days, the femora grown at the lower pH contained more bone and had a higher calcium content. However, the conditions required for mineralization may be quite different from those needed for cell division and cellular hypertrophy in the cartilaginous rudiment. We have, therefore, investigated the influence of hydrogen ion concentration on the growth of cartilaginous tibiotarsi of the embryonic chick. This was done by varying the bicarbonate concentration of the medium while maintaining a constant atmosphere of 5 per cent carbon dioxide in air.

The times to the loss of somatosensory evoked potentials (SEPs) and the onset of suppressed and isoelectric electroencephalogram (EEG) were investigated in turkeys as they were stunned with gas mixtures consisting of one of three mixtures: (A) 30 per cent carbon dioxide and 60 per cent argon in air (2 per cent residual oxygen and 8 per cent residual nitrogen); (B) 90 per cent argon in air (2 per cent residual oxygen and 8 per cent residual nitrogen); (C) 65 per cent carbon dioxide in air (7 per cent residual oxygen and 28 per cent residual nitrogen). The time to the loss of SEPs, EEG suppression and the onset of an isoelectric EEG, respectively, were 22, 16 and 35 seconds in mixture A, 44, 41 and 101 seconds in mixture B, and 15, 15 and 67 seconds in mixture C. Stunning turkeys with mixture A or B would be suitable under commercial conditions. Mixture C, containing 65 per cent carbon dioxide in air, is considered on humanitarian grounds to be unacceptable for stunning turkeys owing to the pungency of the carbon dioxide at this concentration.

Pigs were exposed individually to either 90 per cent argon in air (anoxia), a mixture of 30 per cent carbon dioxide and 60 per cent argon in air (hypercapnic anoxia)...

The efficacy for the euthanasia of day-old chicks of mixtures of carbon dioxide and air, or carbon dioxide and argon containing 1, 2 or 5 per cent residual oxygen, or argon containing 1 or 2 per cent residual oxygen was tested in three experiments. The time to the onset of unconsciousness of individual chicks, determined from the time to loss of posture, was similar during their exposure to 2 per cent oxygen in argon, 20, 30 or 40 per cent carbon dioxide in argon with 2 per cent residual oxygen, or 90 per cent carbon dioxide in air. The exposure of chicks in batches of 20 to a mixture of 20, 30 or 40 per cent carbon dioxide in argon resulted in the death of all the chicks within two minutes. However, a residual oxygen level of 5 per cent in these mixtures resulted in the survival of some chicks for longer than two minutes. With argon alone the level of residual oxygen was critical; less than 2 per cent was essential to achieve 100 per cent mortality within three minutes, and a rise from 2 to about 3 per cent resulted in up to 20 per cent of the chicks surviving for seven minutes.

The effect of breathing 2.5 to 10 per cent carbon dioxide in air on specific airway conductance was determined by plethysmography in 9 normal subjects and in 8 subjects with mild asthma. In 9 normal subjects, during breathing of 5, 7.5, and 10 per cent carbon dioxide, mean (± SE) values of specific airway conductance decreased by 15.8 ± 6.1, 24.4 ± 6.0, and 28.4 ± 7.9 per cent with increases in end-tidal carbon dioxide tension of 5.0 ± 1.6, 12.3 ± 2.3, and 20.2 ± 2.5 mm Hg, respectively. These changes were not significantly affected by prior administration of atropine or propranolol except that atropine prevented the decrease in specific airway conductance during 5 per cent carbon dioxide breathing. Isocapnic hyperventilation decreased specific airway conductance (15 ± 6 per cent) but to a lesser extent than during similar increases in ventilation due to breathing of 10 per cent carbon dioxide. In contrast, in 8 subjects with asthma, specific airway conductance did not change during carbon dioxide breathi...

Extracellular glycollate is liberated by Chlorella pyrenoidosa during growth in medium bubbled with air or 3 per cent carbon dioxide in air. With air the rate of release of glycollate per cell decreases, with 3 per cent carbon dioxide it increases, with increase in cell number. Glycollate is released during short-term experiments when C. pyrenoidosa, grown under low light and high carbon dioxide, is transferred suddenly to high light and low carbon dioxide. No other combina tion of these factors produces a comparable release of glycollate. The quantity of glycollate released in short-term experiments increases exponentially with the relative growth-rate of the culture from which the cells are derived. A crucial condition for maximum glycollate release is that growth of the culture prior to the experiment should not be limited by carbon-dioxide concentration. The effect of pH is related to its effect on growth-rate; i.e. C. pyrenoidosa has a lower relative growth-rate at pH 8 3 and produces correspondingly less glycollate than faster growing cultures at pH 6-4. During short-term experiments under high light and low carbon dioxide the rate of glycollate release drops after 50-100 minutes suggesting exhaustion of the glycollate precursor.

A Study of Gastric Secretions in Chronic Obstructive Pulmonary Emphysema

Spontaneous electroencephalograms (EEG) and somatosensory evoked potentials (SEPS) were recorded in turkeys while they were kept in an atmosphere of either 49 or 86 per cent carbon dioxide in air. The time to the loss of SEPS was not related to the concentration of carbon dioxide, but the time to the onset of an isoelectric EEG was shorter at the higher concentration of carbon dioxide. In comparison with other gas stunning methods it was considered that stunning with these high concentrations of carbon dioxide would not have any welfare advantages over stunning in argon with 2 per cent residual oxygen or in a mixture of 30 per cent carbon dioxide and 60 per cent argon in air.

Autoagglutination and the specificity of the indirect fluorescent antibody test applied to the identification of Taylorella equigenitalis

The effects of inhaling 5 per cent carbon dioxide in air on the pulmonary arterial blood pressure and flow were studied in 5 subjects with normal pulmonary circulations and in 10 patients with chronic pulmonary emphysema. In the 5 control subjects, with an average increase in arterial P CO CO2 of 6 mm. Hg (37 to 43) and a 3-fold increase in minute ventilation, both pulmonary arterial blood pressure and flow remained unchanged. In the 10 patients with chronic pulmonary emphysema with a similar increase in arterial P CO CO2 (45 to 52) and a 2-fold increase in minute ventilation, there was a 14 per cent increase in cardiac output and a rise in pulmonary arterial mean pressure of 4 mm. Hg. In these patients an increment in pulmonary arterial pressure was invariably associated with an appreciable increment in blood flow. The present study affords no support for the view that the breathing of air enriched with carbon dioxide elicits pulmonary vasoconstriction in either normal subjects or in patients with chronic pulmonary disease.

Shelled green peas (ripening seeds of Pisum sativum var. Onward) were kept in the dark for 2 or 3 days in an atmosphere, either of air or 10 per cent carbon dioxide in air, containing 14C02. Samples were removed at intervals, the acids of the T.C.A.C. extracted, estimated, and their content of 14C measured. Incorporation of 14C was mainly into the carboxyl carbon atoms of the acids which, with the exception of citrate, rose in specific activity rapidly for the first 4-6 h and then levelled off and rose slowly for the rest of the experiment. The final values attained, again with the exception of C-6 of citrate, were much below that of the tissue carbon dioxide. The cause of this failure to equilibrate with tissue carbon dioxide is discussed. Two main carboxylation reactions are proposed, one from pyruvate (or other three carbon acid) to malate and the other from a-oxoglutarate to oxalsuccinate and so to C-6 of citrate. The value of the velocity constant of the first of these reactions was shown to be markedly decreased by increase in tissue carbon dioxide while that for the second carboxylation was unaffected. 14C moved into soluble amino-acids rapidly at first and then more slowly; protein received 14C at a high rate throughout the experiments mainly by isotopic exchange reactions. Calculations were made of the rate of movement of carbon in the T.C.A.C. which would have been required to give the observed changes in specific activity of the metabolites but no scheme tested fitted all the results satisfactorily.

The emergence of tissue engineering has led to the development of three‐dimensional cellular scaffolds that reconstruct the tissue structure. Research into the use of biodegradable materials in scaffolds has grown; the aim is that when tissue growth is complete, the scaffold degrades completely. This research aims to design novel scaffolds and investigates biodegradable polylactide (PLA) yarns; in particular, poly(l‐lactide) (PLLA) yarns extruded in‐house. To study degradation and determine the effect on the biodegradable yarns/textiles, they were immersed in phosphate buffer solution (PBS, pH=7.4) for various durations at 37°C. Mechanical properties were evaluated on tensile testing rigs and they were observed, before and after the immersion period. Cells were then cultured (37°C, 5 per cent carbon dioxide in air) on the textiles for 1 week. As expected, after immersion, the yarns exhibit a decrease in elongation and tenacity. Initial results indicate that the yarn properties influence cell attachment and spreading.