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Biomedical subjects

C J Nicol

Publications and source records attributed to C J Nicol.

At least 37 records · Page 2Linked to original sources
PubMed1998

Prevention of crib-biting: a review.

Crib-biting is a common oral stereotype. Because of perceived deleterious effects on the health and appearance of subjects the prevention of crib-biting is regularly attempted. The resourcefulness of horses in satisfying their motivation to perform this behaviour often frustrates owners' efforts at prevention. This paper reviews the efficacy and observable consequences of attempting to prevent crib-biting by a variety of methods. These include attempts to prevent the grasping of objects, to interfere with air-engulfing and to introduce punishment for grasping and neck-flexion. Other approaches include the use of surgery, acupuncture, pharmaceuticals, operant feeding and environmental enrichment. A remedy that is effective for every crib-biter remains elusive. We conclude that, rather than concentrating on remedial prevention, further research should be directed at establishing why horses crib-bite and how the emergence of crib-biting can be avoided.

Animals↗
PubMed1997

Oxidative damage in chemical teratogenesis.

The teratogenicity of many xenobiotics is thought to depend at least in part upon their bioactivation by embryonic cytochromes P450, prostaglandin H synthase (PHS) and lipoxygenases (LPOs) to electrophilic and/or free radical reactive intermediates that covalently bind to or oxidize cellular macromolecules such as DNA, protein and lipid, resulting in in utero death or teratogenesis. Using as models the tobacco carcinogens benzo[a]pyrene (B[a]P) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the anticonvulsant drug phenytoin, structurally related anticonvulsants (e.g. mephenytoin, nirvanol, trimethadione, dimethadione) and the sedative drug thalidomide, we have examined the potential teratologic relevance of free radical-initiated, reactive oxygen species (ROS)-mediated oxidative molecular target damage, genotoxicity (micronucleus formation) and DNA repair in mouse and rabbit models in vivo and in embryo culture, and in vitro using purified enzymes or cultured rat skin fibroblasts. These teratogens were bioactivated by PHS and LPOs to free radical reactive intermediary metabolites, characterized by electron spin resonance spectrometry, that initiated ROS formation, including hydroxyl radicals, which were characterized by salicylate hydroxylation. ROS-initiated oxidation of DNA (8-hydroxy-2'-deoxyguanosine formation), protein (carbonyl formation), glutathione (GSH) and lipid (peroxidation), and embryotoxicity were shown for phenytoin, its major hydroxylated metabolite 5-(p-hydroxyphenyl)-5-phenylhydantoin [HPPH], thalidomide, B[a]P and NNK in vivo and/or in embryo culture, the latter indicating a teratologically critical role for embryonic, as distinct from maternal, processes. DNA oxidation and teratogenicity of phenytoin and thalidomide were reduced by PHS inhibitors. Oxidative macromolecular lesions and teratogenicity also were reduced by the free radical trapping agent phenylbutylnitrone (PBN), and the antioxidants caffeic acid and vitamin E. In embryo culture, addition of superoxide dismutase (SOD) to the medium enhanced embryonic SOD activity, and SOD or catalase blocked the oxidative lesions and embryotoxicity initiated by phenytoin and B[a]P, suggesting a major contribution of ROS, as distinct from covalent binding, to the teratologic mechanism. In in vivo studies, other antioxidative enzymes like GSH peroxidase, GSH reductase and glucose-6-phosphate dehydrogenase (G6PD) were similarly protective. Even untreated G6PD-deficient mice had enhanced embryopathies, indicating a teratological role for endogenous oxidative stress. In cultured fibroblasts, B[a]P, NNK, phenytoin and HPPH initiated DNA oxidation and micronucleus formation, which were inhibited by SOD. Oxidation of DNA may be particularly critical, since transgenic mice with +/- or -/- deficiencies in the p53 tumor suppressor gene, which facilitates DNA repair, are more susceptible to phenytoin and B[a]P teratogenicity. Even p53-deficient mice treated only with normal saline showed enhanced embryopathies, suggesting the teratological importance of endogenous oxidative stress, as observed with G6PD deficiency. These results suggest that oxidative macromolecular damage may play a role in the teratologic mechanism of xenobiotics that are bioactivated to a reactive intermediate, as well in the mechanism of embryopathies occurring in the absence of xenobiotic exposure.

Abnormalities, Drug-Induced↗
PubMed1996

Space and density effects on group size preferences in laying hens.

1. T-maze preference tests were used to study group size and space preferences in laying hens kept on deep litter. The first experiment revealed a non-significant tendency to prefer a larger group (120 hens) in a large space (9 m2) over a smaller group (5 hens) in a small space (1 m3), but when the space was constant and large, a strong preference for the smaller group in a large space emerged. 2. In experiment 2, 5 different group size/space options were tested using a T-maze and test hens were non-randomly selected, choosing more aggressive "peckers' and more subordinate "receivers'. Chi-squared tests showed preferences for (1) a larger group (70 over 4 or 0 hens), (2) a larger space (9 m2 over 1 m2) and (3) 4 hens rather than an empty space. Although both peckers and receivers preferred the same size companion hen groups, receivers were more consistent in their choice than peckers. 3. The results have important implications for hens in all group size and suggest that while smaller group sizes may be important, they need to be combined with sufficient space. Furthermore, the "ideal group size' may differ depending on the individual hen's dominance status.

Analysis of Variance↗
PubMed1995

Effects of the sucking louse (Linognathus vituli) on the grooming behaviour of housed calves.

The behaviour of cattle with and without louse infestation was studied for eight weeks. Thirty-two crossbred calves were housed in groups of four at 20 weeks old. Sixteen of the calves were artificially infested with the long-nosed cattle louse Linognathus vituli and 16 were left uninfested as controls. In infested animals the number of lice on the shoulders averaged 2.3 per 10 cm length of parted hair. The recorded frequency of irritation, manifested by rubbing and self-licking, was significantly greater in the louse-infested calves than in the uninfested controls. The infested calves spent 28 s/h rubbing and 95 s/h self-licking, compared with 8 s and 62 s/h spent by the uninfested controls. The infested calves also spent more than twice as long scratching as the controls. There were no significant effects of the infestation on social grooming.

Animals↗
PubMed1995

The prevalence of abnormal behaviours in dressage, eventing and endurance horses in relation to stabling.

The behaviour of horses competing in different disciplines was studied and the relationship between the time they spent out of the stable and the prevalence of abnormal behaviour was examined. The owners of dressage, eventing and endurance horses were sent a questionnaire and a total of 1101 responses were received, giving data on 1750 horses. The behaviours studied were wood-chewing, weaving, crib-biting/wind-sucking and box-walking. The reported percentage prevalences of abnormal behaviour for the dressage, eventing and endurance horses were 32.5, 30.8 and 19.5, respectively. The relationship between the time spent in the stable and the prevalence of abnormal behaviour was examined by chi 2 tests which showed that there were significant linear trends for the eventing group (P < 0.001) and the dressage group (P < 0.05). It is concluded that the time a horse spends out of the stable is related to the discipline for which it is being trained and in dressage and eventing horses the time spent in a stable is correlated with an increased risk of abnormal behaviour.

Animal Husbandry↗
PubMed1995

A teratologic suppressor role for p53 in benzo[a]pyrene-treated transgenic p53-deficient mice.

DNA damage may mediate birth defects caused by many drugs and environmental chemicals, therefore p53, a tumour suppressor gene that facilitates DNA repair, may be critically embryoprotective. We have studied the effects of the environmental teratogen, benzo[a]pyrene, on pregnant heterozygous p53-deficient mice. Such mice exhibited between 2- to 4-fold higher embryotoxicity and teratogenicity than normal p53-controls. Fetal resorptions reflecting in utero death were genotyped using the polymerase chain reaction and found to be increased 2.6-fold and 3.6-fold respectively with heterozygous and homozygous p53-deficient embryos. These results provide the first direct evidence that p53 may be an important teratological suppressor gene which protects the embryo from DNA-damaging chemicals and developmental oxidative stress.

Abnormalities, Drug-Induced↗
PubMed1995

Management factors associated with stereotypic and redirected behaviour in the thoroughbred horse.

A greater knowledge of the effect of management factors is required to investigate the ontogeny of abnormal behaviour in the stabled horse. A postal survey of racehorse (flat) trainers yielded information about 22 yard and management factors. The relationship of the factors to the prevalence of abnormal behaviour was analysed by logistic regression. Management factors related to the time spent in the stable showed the strongest associations with stereotypic behaviour. The risk of horses performing abnormal behaviour increased: 1) as the amount of forage fell below 6.8 kg/day, 2) when bedding types other than straw were used, 3) when the total number of horses on the yard was fewer than 75, 4) in association with box designs that minimised contact between neighbouring horses, 5) when hay, rather than other types of forage, was used.

Animal Husbandry↗
PubMed1995

Radiographic and endoscopic study of horses performing an oral based stereotypy.

There is confusion in the veterinary literature concerning the definition of oral based stereotypies in the horse. This study reports the use of fluoroscopy and endoscopy during cribbiting/wind-sucking in afflicted horses. This permitted observations of movements of the pharyngeal and oesophageal tissues and of the air column within during the stereotypic behaviour. The findings reported show that the sequence of events during crib-biting/wind-sucking is not related to deglutition and that air is not swallowed to the stomach. Transient dilation of the upper oesophagus was recorded and the characteristic noise of wind-sucking coincided with the in-rush of air through the cricopharynx. The oesophageal distension was relieved when the air returned to the pharynx although small quantities passed caudally. It is proposed that the role of contraction of the strap muscles of the neck is to create a pressure gradient in the soft tissues surrounding the oesophagus which provokes movement of air from the pharynx into the oesophagus. The findings suggest that the definitions currently used in the sale of horses are in need of revision.

Animals↗
PubMed1991

Aversiveness of motion and noise to broiler chickens.

1. The aversiveness of motion and noise to broiler chickens was examined using a passive avoidance technique. Birds were initially trained to peck a key a fixed number of times to obtain food. After training, food could still be obtained by key pecking, but feeding was immediately followed by 1 min exposure to noise or motion. Birds could delay or avoid exposure by delaying or avoiding key pecking, hence foregoing food. Reduced pecking rate was therefore taken as a measure of aversion. 2. In experiment 1, simultaneous motion and noise, but not noise alone, resulted in a significant decrease in pecking rate in comparison with baseline rates obtained after training. 3. In experiment 2 there was no significant difference in the pecking rates of 4 groups of broilers during training. However, after exposure to 1 of 4 types of motion, strongly significant differences in pecking rates were found between the groups. The mean latency to peak 3 times was significantly greater for birds exposed to gentle vibration, with a single jolt after 55 s, than for birds exposed to simple harmonic motion in either the horizontal or vertical plane. Birds exposed to circular motion in the horizontal plane had a significantly greater mean pecking latency than birds exposed to simple harmonic motion in the vertical plane. 4. Baseline latencies to keypeck in experiments 1 and 2 were longer than expected. In experiment 3 a direct comparison of baseline pecking was made between broilers and laying hens. The hens had significantly shorter pecking latencies.

Animals↗
PubMed1990

Tonic immobility in spent hens after catching and transport.

Tonic immobility tests were used to obtain information about the levels of fear in end-of-lay hens after they had been transported to four commercial processing plants. They stayed in a condition of tonic immobility longer than hens which had only been caught and removed from cages. There was no evidence that they became habituated to transport during journeys of up to five hours, but there were significant differences between the levels of fear expressed by birds transported by the different processors.

Animal Husbandry↗
PubMed1987

Effect of cage height and area on the behaviour of hens housed in battery cages.

Medium hybrid hens were housed as pairs and observed at three cage heights: 30.0, 42.5 and 55.0 cm, and at three area allowances per bird: 570, 807 and 1045 cm2. With increased height, head stretching, head scratching and body shaking were performed at a higher rate and feeding and cage pecking at a lower rate. There was also an increase in the time spent sitting. With increased area, head scratching, body shaking and feather raising were performed at a higher rate and cage pecking at a lower rate. It is concluded that spatial restriction may increase the cost of performing certain 'comfort' activities, resulting in the reductions in performance rate observed in the above experiments. Welfare implications are briefly discussed and considered to depend on the motivational state of the birds.

Animal Welfare↗
PubMed1984

Capillarization, mitochondrial densities, oxygen diffusion distances and innervation of red and white muscle of the lizard Dipsosaurus dorsalis.

The white and red regions of the iliofibularis muscle of the lizard Dipsosaurus dorsalis were analyzed using histologic and morphometric analysis. These regions are composed of fast glycolytic (FG) and both fast oxidative, glycolytic (FOG) and tonic fibers, respectively. Endplate morphology and number of endplates per fiber were estimated from fibers from both areas. Capillary volume densities of the red and white regions were quantified from transverse sections. Mitochondrial volume of fibers from the red and white regions were estimated from electron micrographs. All fibers from the white region of the iliofibularis possessed a single, well defined endplate, as did most red region fibers. The remaining red fibers (28 +/- 5%) possessed an average of 14.7 +/- 3 endplates each, distributed along the entire length of the fiber at intervals of approximately 1124 micron. Red fibers possessed twice the mitochondrial volume of white fibers (7.6 +/- 0.4%, red; 3.8 +/- 0.3%, white). Mitochondria were distributed uniformly through the fibers from both regions. Capillary anisotropy was low (gamma = 1.018) in both regions. Capillary densities of the red region (629 +/- 35 mm-2) were much greater than those of the corresponding white region (73 +/- 8 mm-2). The data indicate that capillary densities, mitochondrial volumes and theoretical diffusion distances correlate well with the oxidative capacity of lizard muscle fibers. Tonic fibers of this species appear oxidative and therefore metabolically capable of functioning during locomotion. The similar mitochondrial volumes and capillary densities of reptilian and mammalian muscles suggest that the greater oxidative capacity of mammalian muscle is due in part to possession of more oxidatively active mitochondria rather than to possession of more mitochondria per se.

Animals↗
PubMed1984

Cyclic nucleotide changes and contractility in the rat anococcygeus muscle.

The rat anococcygeus muscle can be activated by three different agonists, NA, ACh and KCl, each of these displaying a different degree of pharmacomechanical coupling. Investigation of cyclic nucleotide changes in the muscles when activated showed that changes in cAMP/cGMP ratio parallel changes in contractility. However, the cyclic nucleotide changes seem incidental to the process of contraction, rather than causally related to it.

Acetylcholine↗
PubMed1982

Contractile properties and fibre composition of rat skeletal muscle: effect of mild hyperthyroidism.

The effect of a chronic mild elevation of plasma triiodothyronine levels upon the contractile properties and fibre distribution of skeletal muscle was studied. The isometric twitch characteristics and passive tension-length relationship were studied in the soleus and extensor digitorum longus muscles of anaesthetized rats injected for increasing periods with triiodothyronine. This treatment results in a progressive speeding in the rates of isometric contraction and relaxation of the soleus and in a concomitant decrease in the elasticity of the muscle. There was also a conversion of slow to fast fibre types in the soleus, demonstrated histochemically. It is concluded, in view of differences in the magnitudes and time courses of the various changes, that triiodothyronine increases the rates of contraction and relaxation of existing slow fibres and contraction in the soleus muscle as a whole before any change occurs which is attributable to slow-fast fibre interconversion. The possible mechanisms of the early thyroid hormone effects on muscle are discussed.

Animals↗
PubMed1981

Effect of hyperthyroidism on the contractile and histochemical properties of fast and slow twitch skeletal muscle in the rat.

Male Wistar rats were made hyperthyroid by intraperitoneal injections on alternate days for 1-6 weeks, of 200 micrograms/kg triiodothyronine (T3). The effects of this treatment on the contractile properties of the soleus, a slow twitch and the extensor digitorum longus (EDL), a fast twitch skeletal muscle, were studied in vivo in the anaesthetized animal. Post mortem, serial frozen sections of both muscles were stained histochemically for myosin ATPase, succinic dehydrogenase and phosphorylase. Muscle fibres were classified as either slow twitch (SO), fast twitch oxidative glycolytic (FOG) or fast twitch glycolytic (FG). Elevation of plasma T3 levels is associated with progressive alterations in the muscle fibre populations of both muscles. In the soleus there is conversion of SO to FOG fibres while in the EDL the main effect is FG to FOG conversion. There are also marked changes, mainly confined to the soleus muscle, in contractile properties; progressive increases in isometric twitch and tetanic tension and in the rates of contraction and relaxation during both twitch and tetanus. The effect of T3 on slow muscle contractility may be related to its effect on muscle phenotype. However, changes in the former precede detectable fibre population changes. T3 may influence properties such as the CA2+ binding activity of sarcoplasmic reticulum of existing slow twitch fibres before the later changes associated with the interconversion of fibre types occur.

Adenosine Triphosphatases↗
PubMed1978

Accumulation of amines by rabbit erythrocytes in vitro.

1. Accumulation of noradrenaline (NA), 5-hydroxytryptamine (5HT) and tyramine by rabbit erythrocytes was measured at 37 degrees C in vitro. 2. Of the amines used only NA was broken down during incubation. This was a result of intracellular catechol-O-methyl transferase activity. 3. NA and 5HT entered the red cells by similar processes which were temperature-sensitive (cooling to 0 degrees C inhibited accumulation) and had saturation kinetics. The entry of NA was partially stereospecific; the (-)-isomer accumulated twice as fast as did (+)-NA. 5HT and NA competed for entry. Tyramine entry was unaffected by cooling, was not saturable and did not affect the entry of either NA or 5HT. NA and 5HT entered the erythrocytes at rates which were proportional to their lipid solubilities. 4. Metabolic inhibitors had no effect on amine transport. Inhibitors of amine transport in other tissues produced only small non-specific reductions of NA accumulation in the red cells. 5. Amine accumulation was a symmetrical process (no amine was retained by the red cells if the concentration gradient was reversed). It is concluded that NA and 5HT enter the cells by facilitated diffusion. The entry of NA and 5HT displayed countertransport, an additional feature of facilitated diffusion. 6. The relationship between the physical properties of the amines and the routes by which they entered the erythrocytes is discussed.

Animals↗