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Biomedical subjects

D B Stephens

Publications and source records attributed to D B Stephens.

At least 19 recordsLinked to original sources
PubMed1994

Polyclonal antibodies and catalysis.

Some recent results involving catalytic polyclonal antibodies are described. Polyclonal antibodies isolated directly from serum contain the complete distribution of different IgG antibodies elicited via immunization, so catalytic results obtained with polyclonal antibodies can be used to characterize the overall catalytic activity produced in an animal in response to a given hapten. This new window on catalytic antibodies should be especially useful for identifying general trends relating hapten structure to antibody catalytic activity, for monitoring the maturation of catalytic activity during immunization, and for studying the variability of catalytic activity elicited in different animals immunized with the same hapten. Furthermore, studying the catalytic activity of polyclonal antibodies in serum may aid in the development of novel immunization-based therapies.

Animals↗
PubMed1993

Catalytic polyclonal antibodies.

The production and characterization of rabbit polyclonal antibodies that catalyze the hydrolysis of trityl protecting groups is described. The catalytic activity increased throughout the immunization regimen, exhibiting a later and steeper rise than the simple hapten-specific antibody titer. The catalytic polyclonal antibodies displayed saturation behavior, consistent with classic Michaelis-Menton kinetics. An apparent catalytic rate enhancement (kcat/kuncat) of 125 and a Km of 31 microM were measured for the polyclonal sample. Inhibition studies indicated that 12% of the antibodies either binds the hapten or is a catalyst. Analyzing polyclonal antibodies for catalytic activity is proposed as a substantially faster, more cost effective and more general way to screen new hapten designs for their relative abilities to produce antibodies with catalytic activity.

Animals↗
PubMed1988

A review of experimental approaches to the analysis of emotional behaviour and their relation to stress in farm animals.

The aims of the present paper are firstly to review the methods and techniques that have been developed to analyse and quantify the variables that can produce psychological distress; and, using an integrated approach, with examples where possible, to consider the significance of the information available relating to the keeping of domestic animals under present husbandry conditions. Secondly, suggestions for future research relevant to evaluating and improving farm animal welfare are discussed.

Animal Husbandry↗
PubMed1987

Variations in the monoamine oxidase-inhibitory activity ("tribulin?") in pig's urine.

Sandler and his colleagues (see Sandler, 1982) have demonstrated the presence of an endogenous inhibitor of the enzyme monoamine oxidase (MAO) and of benzodiazepine receptor binding in the urine and blood plasma of man and rat. The concentrations of this material increased under stress conditions and it has been named "tribulin". In the present experiments MAO-inhibitory activity was found in extracts of urine and plasma samples of domestic pigs. Evidence was obtained that the inhibitory activity was higher when pigs experienced slight discomfort. Thus it appears that pigs produce a substance similar to tribulin. It may become possible to use such MAO-inhibitory activity as an indicator in the assessment of interaction with the environment in pig husbandry.

Animals↗
PubMed1986

Monoamines in tubero-hypophyseal structures of farm animals.

Dopamine (DA) and 5-hydroxytryptamine (5-HT) were measured in several regions of the pituitary gland of Jersey steers, Soay ewes and two breeds of pigs. The glands were collected from animals which had not been stressed and the amine concentrations were comparable to those found previously in the pituitary glands of laboratory animals. Metabolites of both amines were present in the infundibulum, the pituitary stalk, the combined neural and intermediate lobe and the anterior lobe of all glands analysed indicating that the amines are being utilized in these structures under "near physiological" conditions.

Animals↗
PubMed1986

Observations on the effects of vibration and noise on plasma ACTH and zinc levels, pregnancy and respiration rate in the guineapig.

The responses of female guineapigs to vibration and noise were examined with the use of an apparatus designed to simulate transport. Peak levels of plasma ACTH and zinc concentrations were attained after 4 min of exposure to vibration and 80-90 dB of noise. The respiration rate, normally around 90/min, was increased to 103/min when the animals were moved (while still in their cages) to the experimental area; it rose to 129/min when the apparatus was switched on to expose the animals to vibration and noise. Those left adjacent to the apparatus and exposed to noise alone elevated their respiration rates to 115/min. Respiration rates returned to normal within 2.5 h. There was no apparent effect on the maintenance of pregnancy, gestation length, litter size or post-partum growth of the young born to guineapigs exposed to this vibration and noise for a period of 1 h at mid-term.

Adrenocorticotropic Hormone↗
PubMed1986

The influence of transportation on the induction of estrus in gilts of different ages.

Six series of experiments, involving 72 gilts in groups of 4 were carried out to investigate the effects of transportation, vibration and noise, and proximity of sexually mature adult breeding stock on attainment of first estrus in gilts of different ages. The animals grew normally during the periods of observation. Gilts aged 120 days (n = 12) at the start of the observations did not display estrus in response to exposure to vibration and noise or a 2 hr road journey. Similarly aged groups housed near adult breeding stock, but not exposed to vibration and noise, displayed estrus during the first 30 days of observation. All gilts aged 140 days (n = 12) displayed estrus within 5 days of being housed adjacent to adult breeding stock. Others, not housed near adult stock, but exposed to vibration and noise, or a road journey, did not consistently display estrus. When the observations were repeated on gilts aged 160 days (n = 12), the observations were similar. It was concluded that proximity of adult breeding stock and not transportation per se was the critical factor in inducing estrus behavior in normally growing gilts.

Animals↗
PubMed1985

Influence of intraduodenal glucose on meal size and its modification by 2-deoxy-D-glucose or vagotomy in hungry pigs.

Young growing pigs which had been trained to press a panel in order to obtain small deliveries of food and adapted to eating all their food in one meal per day were surgically fitted with an exteriorized cannula connected to the duodenum. An infusion of 250 ml 15% (w/v) glucose solution 10 min before the meal did not influence meal size, whereas a similar infusion shortly after beginning a meal significantly reduced meal size. When the membrane transport and metabolism of glucose was reduced by infusing the antimetabolite, 2-deoxy-D-glucose, before the glucose infusion, the suppression of appetite was attenuated. Intrathoracic truncal vagotomy abolished the effects of intraduodenal glucose. The possibility that a receptor sensitive to transport and metabolism of glucose exists in the duodenum is discussed.

Animals↗
PubMed1985

An analysis of some behavioural effects of the vibration and noise components of transport in pigs.

The reactions of pigs to the vibration and noise components of transport were examined with the use of an apparatus which simulated these factors. The pigs were trained to switch off the apparatus by pressing a switch panel with their snouts. It was found that vibration was aversive but that noise was not. The pigs switched off the apparatus more frequently when the vibration was fast and when they had been fed a large meal before the test. Although the sedative tranquillizing drug azaperone decreased the number of times the apparatus was switched off, the effect appeared to be non-specific because azaperone also reduced the number of responses that pigs would make in order to receive food.

Animals↗
PubMed1985

Effects of water availability on plasma protein and sodium concentration, haematocrit and plasma osmolality in the pig.

Eighteen young growing pigs of the Large White breed were housed in individual pens or metabolism stands and habituated to drinking their water from a bowl. Those housed in the metabolism stands were surgically fitted with a catheter placed in he jugular vein to allow collection of blood samples. The voluntary intake of water after periods of progressively increasing water deprivation was measured. The measurements were made by allowing the pigs to drink to satiety after either a 2, 4, 8, 12 or 18 h period of water deprivation. Voluntary water intake was a function of the duration of water withdrawal and the rate of intake increased with progressive deprivation. Changes in plasma concentration of sodium and protein, haematocrit and osmolality could be detected after 12 and 18 h of dehydration. The progressive changes in plasma sodium concentration ([Na+]), osmolality, protein concentration and haematocrit during adaptation to dehydration when water was withheld for 72 h were examined in six pigs. Using a technique of continuous blood sampling, the rapid changes in the same blood parameters during rehydration, when water was made freely available at the end of the 72 h period, were also monitored. The [Na+] and osmolality dropped precipitously following the onset of drinking. From the 15 min stage to the 4 h stage with water available ad libitum, the values of both parameters remained below their control levels. However, the plasma protein concentration and the haematocrit values remained significantly above their pre-dehydration control levels up to the 4 h stage, even with water freely available, thus showing that drinking stopped even though the extracellular fluid phase remained dehydrated. Only with food available did the blood measures return to normal. It is concluded that the cellular fluid phase forms an integral part of the mechanisms involved in the termination of drinking in the pig.

Animals↗
PubMed1984

The influence of transportation, proximity of adults and other stimuli on the age of onset of first puberty in the gilt.

Four series of experiments involving 44 animals were carried out to investigate the influence of transportation, proximity of sexually mature adults and other stimuli on the onset of puberty in the gilt. Transportation per se, either real or simulated, did not induce early puberty in the gilt. In contrast, the most effective stimulus was provided by accommodating the gilts in pens adjacent to mature breeding stock. Gilts housed in a sow yard exhibited oestrus when aged between 153 and 184 days, i.e. 4-6 weeks after the beginning of the experiment. This compares with 189 to 227 days, i.e. 9-12 weeks after the start of the experiment for those gilts not housed adjacent to adult stock.

Animal Husbandry↗
PubMed1983

An investigation into some cerebral mechanisms involved in schedule-induced drinking in the pig.

When pigs were fed small amounts at regular short intervals (5-10 min), drinking followed each ingestion. This resulted in a greatly increased total water intake (schedule-induced polydipsia: s.i.p.). Injection of angiotensin II into the lateral cerebral ventricle of water-replete pigs on normal feeding also produced a significant increase in water intake. Prior administration of the angiotensin II antagonist, saralasin, attenuated the dipsogenic effect of angiotensin II, but did not modify s.i.p. The tranquilizing drug, azaperone, had no effect on normal water intake and did not modify the response to angiotensin II. However, azaperone reduced the water intake of animals on scheduled feeding. From this, it was concluded that the increased drinking due to scheduled feeding did not involve the renin-angiotensin system but it is tentatively suggested that it may involve central dopaminergic neuronal systems.

Angiotensin II↗
PubMed1983

Effects of vibration, noise and restraint on heart rate, blood pressure and renal blood flow in the pig.

Pigs and other farm animals are usually transported at least once during their lives; for example, all meat animals are finally taken to the abattoir for slaughter. The vibration, noise and handling associated with such transportation is usually novel to the animals, and therefore constitutes a potential 'stressor'. Such adverse stimuli may trigger physiological and psychological changes which rapidly produce profound changes in blood flow to peripheral organs, particularly the kidney, whose blood vessels are richly supplied with sympathetic nerve fibres. In the present study, ultrasonic techniques have been used with chronically implanted flow sensors for measuring heart rate (HR) and changes in renal blood flow (RBF) in conscious, freestanding and unanaesthetized pigs to monitor their cardiovascular responses to vibration, noise and various handling procedures. In addition, arterial blood pressure (BP) was measured via a catheter placed in the carotid artery. To ensure that vibration and noise could be accurately reproduced, a transport simulator (TS) was constructed in the laboratory. A small decrease of approximately 5% was observed in RBF during the first few minutes of exposure to vibration and noise, but this returned to the control levels monitored in undisturbed animals within a few minutes. Thereafter, RBF became significantly elevated for the remaining period of exposure to vibration and noise. In contrast, HR remained significantly increased throughout. BP was not significantly changed as a result of the experimental manipulation. Restraint and handling of the animals appeared to cause maximal disturbance. HR and BP were more than doubled compared with the resting value, but there was a concomitant marked decrease in RBF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗