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Biomedical subjects

P J Butler

Publications and source records attributed to P J Butler.

180 records · Page 10Linked to original sources
PubMed1971

The effect of variations in heart rate and regional distribution of blood flow on the normal pressor response to diving in ducks.

1. During a 2 min period of submersion of normal ducks, sciatic artery blood flow fell to 10 +/- 1.5% control and carotid artery blood flow was reduced to 71 +/- 7% control. Mean arterial blood pressure (M.A.P.), however, was maintained at 83 +/- 3.5% of control. The whole animal showed a constrictor response during submersion, with the sciatic vascular bed showing average constriction. Both resistance to flow and yield pressure increased in the sciatic bed but changed little in the carotid bed. After 1 min submersion P(a,O2) was 52 +/- 1 mm Hg.2. Upon emersion, as soon as ventilation commenced, the whole animal showed a dilator response. The carotid bed exhibited marked vasodilatation whereas the sciatic bed returned to its control level.3. After alpha-receptor blockade, ducks were submerged for 1 min. During this time M.A.P. fell to 64 +/- 5.6% of control and heart rate was reduced to 49 +/- 8.3% of control. Blood flow through the sciatic and carotid arteries also fell to values of 41 +/- 6.9% of control and 91 +/- 13% of control respectively. There was little change in either resistance to flow or yield pressure in the sciatic bed compared to normal ducks, and the carotid bed showed reductions in resistance to flow and yield pressure during submersion. P(a,O2) after 1 min under water was 41 +/- 1.1 mm Hg.4. beta-receptor blockade had no effect on any of the measured variables during submersion. Upon surfacing, however, although the whole animal response was one of dilatation, the carotid bed was less dilated than in normal ducks at this time and the sciatic bed was more constricted.5. Injection of atropine not only abolished the bradycardia during submersion but also caused a rise in M.A.P. and sciatic blood flow during the period under water. After 1 min submersion P(a,O2) was 30 +/- 1.2 mm Hg.6. It is concluded that stimulation of adrenergic alpha-receptors is responsible for the increase in resistance to flow through the sciatic artery and the maintenance of blood pressure during submersion in the normal animals. This selective constrictor activity and the resulting ischaemia is important in the maintenance of P(a,O2) during submersion. Adrenergic beta-receptors (cardiac and/or peripheral) are involved, to a small extent, in the blood pressure and blood flow changes that occur when ventilation commences upon emersion.

Animals↗
PubMed1970

The preparation of alcohol dehydrogenase and glyceraldehyde 3-phosphate dehydrogenase from baker's yeast.

A procedure has been developed for the preparation of alcohol dehydrogenase and glyceraldehyde 3-phosphate dehydrogenase from the same sample of baker's yeast. The two enzymes were obtained in good yield in a pure crystalline form. The method minimizes the work involved in preparing the two enzymes and would be of particular advantage for preparing the enzymes in radioactive form from yeast grown in a radioactive medium.

Alcohol Oxidoreductases↗
PubMed1970

The effect of progressive hypoxia on the respiratory and cardiovascular systems of the pigeon and duck.

1. During the initial stages of progressive hypoxia in ducks and pigeons (P(a, O2) 100 --> 60 mm Hg) there were no significant changes in heart rate, blood pressure or oxygen uptake, but respiratory frequency increased.2. As hypoxia became more profound (P(a, O2) 60 --> 30 mm Hg), there was a significant tachycardia, and blood pressure fell slightly in both animals. Respiratory frequency continued to increase in both species, and ducks were able to maintain their oxygen uptake at control levels at a lower P(a, O2) than pigeons.3. The response to progressive hypoxia of pigeons and ducks was compared with that of the domestic fowl. The former two birds could maintain control of their cardiovascular system at a lower environmental oxygen concentration than the latter. Arterial P(O2) followed a similar course in all three birds in relation to environmental oxygen content. Pigeons and ducks were therefore able to endure a lower arterial P(O2) than chickens.

Animals↗
PubMed1969

The use of maleic anhydride for the reversible blocking of amino groups in polypeptide chains.

1. Maleic anhydride was shown to react rapidly and specifically with amino groups of proteins and peptides. Complete substitution of chymotrypsinogen was achieved under mild conditions and the extent of reaction could be readily determined from the spectrum of the maleyl-protein. 2. Maleyl-proteins are generally soluble and disaggregated at neutral pH. Trypsin splits the blocked proteins only at arginine residues and there is frequently selectivity in this cleavage, e.g. in yeast alcohol dehydrogenase and pig glyceraldehyde 3-phosphate dehydrogenase. 3. The group is removed by intramolecular catalysis at acid pH. The half-time was 11-12hr. at 37 degrees at pH3.5 in in-maleyl-lysine or in maleyl-chymotrypsinogen. 4. The unblocking reaction can be used as the basis for a ;diagonal'-electrophoretic separation of lysine peptides and N-terminal peptides, as shown by studies with beta-melanocyte-stimulating hormone.

Alcohol Oxidoreductases↗
PubMed1968

Onset of and recovery from diving bradycardia in ducks.

1. No evidence was found of a ;postural reflex' in ducks. Neither the position of the head nor the water temperature affected the cardiac response to diving.2. In ducks with access to air through a tracheal cannula, submersion did not invariably cause apnoea until the water level reached the glottis. Heart rate was closely related to respiratory frequency, and bradycardia did not occur during submersion unless there was a reduction in respiratory frequency or a cessation of ventilation altogether.3. When apnoea and bradycardia did occur during submersion, the first inspiration upon surfacing was 2-3 times larger than normal and was accompanied by an instantaneous rise in heart rate.4. Atropinization or cold block of the vagus abolished diving bradycardia. Only one vagal trunk was involved in cardiac chronotropic control at any one time. This vagal trunk also appeared to be more important in control of respiratory frequency.5. beta-adrenergic receptor blockade did not affect either diving bradycardia or post-dive tachycardia.6. The results show that the cardiac chronotropic response both during and after submergence is controlled solely by changes in parasympathetic vagal activity.

Anesthesia, Conduction↗
PubMed1967

Effect of progressive hypoxia on the respiratory & cardiovascular system of chickens.

1. During the initial stages of progressive hypoxia the intact, unanaesthetized chicken shows increases in heart rate and respiratory frequency with no change in arterial blood pressure and oxygen consumption. During the later stages, heart rate, diastolic and mean blood pressure and oxygen consumption fall, while respiratory frequency increases further.2. Following bilateral cervical vagotomy and adrenergic beta-receptor blockage there is no tachycardia, but the late bradycardia and fall in blood pressure do occur during progressive hypoxia. Respiratory frequency remains at a low level after vagotomy.3. It is suggested that the initial tachycardia is dependent on both the sympathetic and parasympathetic nervous systems, and that the former helps maintain arterial pressure during the early stages of hypoxia. Bradycardia and hypotension seem to be due to anoxia itself, and the vagus is essential for the increase in respiratory frequency.

Animals↗
PubMed1965

Some properties of the rhodanese system of Thiobacillus denitrificans.

1. Rhodanese has been extracted from Thiobacillus denitrificans by ultrasonic disintegration of the cells. 2. Studies with Sephadex columns have shown that the enzyme aggregates, forming a tetramer. 3. The molecular weights of the monomer and of an enzymically active sub-unit one-quarter this size have been determined by gel filtration. 4. Higher-molecular-weight forms of rhodanese are broken down by mercaptoethanol to enzymically active fragments of mol.wt. 7000 and 2000 respectively. 5. It is suggested that these fragments are linked in vivo via disulphide bridges to form the monomer, which can then aggregate via further disulphide links. 6. The fragment of mol.wt. 7000 has been obtained in a substantially pure state. 7. Both disulphide and thiol groups are necessary for enzyme activity. 8. Similarities and differences existing between bacterial rhodanese, mammalian rhodanese and beta-mercaptopyruvate sulphurtransferase are discussed.

Chemical Phenomena↗
PubMedDate not supplied

Impact of externally attached loggers on the diving behaviour of the king penguin.

The impact of relatively small externally attached time series recorders on some foraging parameters of seabirds was investigated during the austral summer of 1995 by monitoring the diving behaviour of 10 free-ranging king penguins (Aptenodytes patagonicus) over one foraging trip. Time-depth recorders were implanted in the abdominal cavities of the birds, and half of the animals also had dummy loggers attached on their backs. Although most of the diving behaviour was not significantly affected by the external loggers (P>0.05), the birds with externally attached loggers performed almost twice as many shallow dives, between 0 and 10 m depth, as the birds without external loggers. These shallow dives interrupted more frequently the deep-diving sequences in the case of birds with external loggers (percentage of deep dives followed by deep dives: 46% for birds with implants only vs. 26% for birds with an external attachment). Finally, the distribution pattern of the postdive durations plotted against the hour of the day was more heterogeneous for the birds with an external package. In addition, these penguins had extended surfacing times between two deep dives compared to birds without external attachments (P<0.0001). These results suggest the existence of an extra energy cost induced by externally attached loggers.

Animals↗
PubMedDate not supplied

Energetic costs of surface swimming and diving of birds.

The energetic costs of swimming at the surface (swimming) and swimming underwater (diving) are compared in tufted ducks (Aythya fuligula) and three species of penguins, the gentoo (Pygoscelis papua), the king (Aptenodytes patagonicus), and the emperor (Aythya forsteri). Ducks swim on the surface and use their webbed feet as paddles, whereas penguins tend to swim just below the surface and use their flippers as hydrofoils, the latter being much more efficient. Penguins are more streamlined in shape. Thus, the amount of energy required to transport a given mass of bird a given distance (known as the cost of transport) is some two to three times greater in ducks than in penguins. Ducks are also very buoyant, and overcoming the force of buoyancy accounts for 60% and 85% of the cost of descent and remaining on the bottom, respectively, in these birds. The energy cost of a tufted duck diving to about 1.7 m is similar to that when it is swimming at its maximum sustainable speed at the surface (i.e., approximately 3.5 times the value when resting on water). Nonetheless, because of the relatively short duration of its dives, the tufted duck dives well within its calculated aerobic dive limit (cADL, usable O(2) stores per rate of O(2) usage when underwater). However, these three species of penguins have maximum dive durations ranging from 5 min to almost 16 min and maximum dive depths from 155 to 530 m. When these birds dive, they have to metabolise at no more than when resting in water in order for cADL to encompass the duration of most of their natural dives. In gentoo and king penguins, there is a fall in abdominal temperature during bouts of diving; this may reduce the oxygen requirements in the abdominal region, thus enabling dive duration to be extended further than would otherwise be the case.

Aerobiosis↗
PubMedDate not supplied

Minimal metabolic rate, what it is, its usefulness, and its relationship to the evolution of endothermy: a brief synopsis.

Minimal metabolic rate represents the minimal cost of living and appears to have the same relative composition of adenosine triphosphate processes in all organisms. Minimal metabolic rate is influenced by temperature and defines the standard metabolic rate (SMR) of animals. Animals that achieve SMR only for a given temperature are strictly ectothermic. Endotherms, on the other hand, are characterized by leakier membranes and an associated increase in cellular metabolism for a given temperature. The increase in cellular metabolism is coupled with an increase in heat production (i.e., obligatory thermogenesis) that, together with SMR, defines the basal metabolic rate of an endotherm. Consideration of minimal metabolic rate must take into account ecological and physiological processes, environmental influences, evolutionary arguments, and body size.

Adaptation, Physiological↗
PubMedDate not supplied

Comparative development in captive and migratory populations of the barnacle goose.

The development of the locomotory muscles and associated skeletal structures of goslings and adults from a captive population of barnacle geese (Branta leucopsis) was compared with that from a wild migratory population. There was no significant difference between flight-muscle development of wild and captive goslings up to 7 wk of age, when the birds are first able to fly. In contrast, mass-specific citrate-synthase activity in the semimembranosus leg muscle of the captive goslings was significantly lower than that of wild goslings by 5 wk of age. During the postfledging premigratory period, captive geese showed significantly higher values for both mass and mass-specific citrate-synthase activity of the leg muscles than those of wild birds. Premigratory wild geese had significantly higher citrate-synthase activity in the pectoralis muscles and larger cardiac ventricular mass (by ca. 20%-25%) than both wild postmoulting and captive premigratory adults. Total flight-muscle mass was only slightly reduced (by ca. 10%) in long-term captive adults compared with wild premigratory adults. Most of the differences between these two populations appear primarily to reflect their relative levels of activity and/or differences in their ambient environment, rather than any intrinsic differences in developmental or adult physiology.

Animals↗
PubMedDate not supplied

Body cooling and its energetic implications for feeding and diving of tufted ducks.

Wintering in a temperate climate with low water temperatures is energetically expensive for diving ducks. The energy costs associated with body cooling due to diving and ingesting large amounts of cold food were measured in tufted ducks (Aythya fuligula) feeding on zebra mussels (Dreissena polymorpha), using implanted heart rate and body temperature transmitters. The effects of diving depth and food ingestion were measured in two sets of experiments: we measured body cooling and energy costs of six tufted ducks diving to different depths in a 6-m-deep indoor tank; the costs for food ingestion and crushing mussel shells were assessed under seminatural winter conditions with the same ducks feeding on mussels in a 1.5-m-deep outdoor pond. Body temperature dropped during feeding bouts and increased gradually during intermittent resting periods. The temperature drop increased linearly with dive duration. The rate of body cooling increased with feeding depth, but it was lower again at depths below 4 m. Half of the increment in energy costs of diving can be attributed to thermoregulatory heat production, of which approximately 50% is generated after diving to warm up the body. The excess costs for ducks feeding on large-sized mussels could be entirely explained by the estimated energy cost necessary to compensate the heat loss following food ingestion, suggesting that the heat production from shell crushing substituted for thermoregulation. Recovery from heat loss is probably a major component of the activity budget of wintering diving ducks.

Adaptation, Physiological↗
PubMedDate not supplied

The use of data loggers to determine the energetics and physiology of aquatic birds and mammals.

By deploying a data logger specifically designed for the purpose, it was possible to record heart rate, fH (beats/min), from free-ranging gentoo penguins, Pygoscelis papua, and Antarctic fur seals, Arctocephalus gazella, at the British Antarctic Survey Base at Bird Island. The heart rate data were then converted into oxygen consumption (VO2, mlO2 min-1 kg-1) and/or energy expenditure (W/kg) using equations that had been derived from calibration experiments. In these experiments the relationships between fH and VO2 were determined in animals at rest and while exercising at different levels on a treadmill or in a static water channel (penguins) and in a variable speed flume (California sea lions, Zalophus californianus, as surrogate fur seals) or in a static water channel (fur seals). The validity of using these relationships was tested by recording simultaneously fH, VO2 by direct respirometry and VCO2 by the doubly labelled water (DLW) technique in six penguins and in six California sea lions during 72 h and 24 h, respectively, at various levels of activity. For the penguins, both indirect methods gave mean algebraic errors within 2% of the measured VO2, whereas for the sea lions, the mean algebraic errors were 36.4% for the DLW method and 2.7% for the fH method. The range of errors was greater for the DLW method, in both species. Field data from 15 penguins indicate that the fH method provides data that are comparable to those obtained using the DLW method, but with the added advantage that they can be broken down into the energy costs for specific types of behaviour. The implanted data loggers also recorded the temperature of the abdominal cavity (T(ab)) and it was evident that this routinely decreased by approximately 2 degrees C during diving bouts and by a maximum of almost 5 degrees C. Such temperature decreases, particularly if representative of similar decreases in other tissues, may at least partly explain why the energy costs of travelling to and from the foraging site and of foraging itself are similar to those for penguins resting in water at 5 degrees C. Field data from 15 female fur seals indicate that, when the animals are ashore, there is good agreement between the values for mean energy expenditure obtained by the fH and DLW methods. However, when the animals are at sea, the values obtained by DLW are substantially greater than those obtained by fH. When the at-sea values are corrected for the apparent overestimations referred to above, there is good agreement between the data obtained using the two methods. The data derived from fH indicate that, as with the penguins, the energy expenditures during travelling to and from the foraging site and during foraging are similar to those of fur seals resting in water at 7 degrees C.

Animals↗