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Biomedical subjects

C M Hawkey

Publications and source records attributed to C M Hawkey.

At least 37 records · Page 2Linked to original sources
PubMed1985

Retinoid toxicity.

The long-term effects of N-ethylretinamide (NER) on the haematology of the rat, and the dose-related effects of retinoids on lymphoid organs of the mouse and rat were investigated. Retinoid-induced long-bone changes were used to develop a method for quantifying skeletal effects. This technique was used to investigate the activity of five retinamides in inducing long-bone changes in the rat. The ability of non-steroidal anti-inflammatory compounds (NSAICs) to prevent retinoid-induced skeletal effects was examined, and preliminary investigations made into the mechanisms of retinoid-induced long-bone remodelling. NER-fed rats had reduced red blood cell counts and fibrinogen values. Retinoids caused dose-related proliferation of the spleen and lymph nodes in the mouse and to a lesser extent in the rat. They induced dose-related reductions in femoral diaphysis and medullary cavity diameters in both rats and mice. Aspirin prevented NER-induced changes of rat long bones, but subsequent studies indicated this effect may be closely dependent on the dose level of both the retinoid and NSAIC administered. Retinoids induce rapid long-bone remodelling in the rat which tends to revert on feeding a control diet, but remodelling processes are different in the young growing rat and the mature animal.

Animals↗
PubMed1985

Normal haematological values of axis deer (Axis axis), Père David's deer (Elaphurus davidianus) and barasingha (Cervus duvauceli).

Full blood counts and fibrinogen estimations were carried out on a number of clinically normal adult axis deer (Axis axis), Père David's deer (Elaphus davidianus) and barasingha (Cervus duvauceli). Apart from the finding of higher total red cell counts and a lower mean red cell volume in axis deer than in Père David's deer and barasingha, there was little interspecies variation. Some individual Père David's deer showed eosinophilia, thought to be associated with subclinical intestinal nematode infestation. The findings should provide a useful reference base for monitoring health in these species.

Animals↗
PubMed1985

Analysis of hematologic findings in healthy and sick adult chimpanzees (Pan troglodytes).

In order to assess the validity of interspecies extrapolation of hematological information, reference values obtained on 63 captive adult chimpanzees were compared with normal values for man. The discriminative power of both chimpanzee and human reference values was tested by the ability of each to identify abnormalities in the blood in 15 sick chimpanzees. The results indicated that human criteria could be applied to most chimpanzee red cell values but species differences were found in erythrocyte sedimentation rates and neutrophil counts.

Animals↗
PubMed1984

Principal components analysis of haematological data from F344 rats with bladder cancer fed N-(ethyl)-all-trans-retinamide.

Several multivariate statistical methods are available which can alleviate the problems of analysing the large volumes of data generated from toxicological experiments. One such technique, principal components analysis, provides a method for exploring the relationships between a number of variables (such as blood parameters) and for eliminating redundant data if strong correlations exist between the characters. It also provides a method for clustering individuals, which may reveal similarities between animals in a treatment group or highlight individual 'outliers'. The application of principal components analysis to a set of haematological data from a trial evaluating the efficacy of a synthetic retinoid against carcinogen-induced bladder cancer in the rat has clearly shown, in two bivariate plots, that while some animals in the carcinogen-treated groups were normal, others were anaemic and that animals fed the synthetic retinoid and killed at 1 year had a microcytic anaemia. A full exploration of the data using conventional univariate statistical analysis would have involved at least 28 graphic representations of the data, as well as the interpretation of more than 130 means and SDs. Principal components analysis provides a valuable additional tool for the statistical analysis and exploration of toxicological data, but it must be used in conjunction with univariate or other multivariate methods if hypothesis testing is required. The use of multivariate techniques in toxicology may best be assessed by their practical application to toxicological data, and this paper presents such an evaluation with the aim of encouraging further exploration of the usefulness of principal components analysis. The raw data on which most analyses have been carried out are given.

Analysis of Variance↗
PubMed1984

Haematological values in mouflon (Ovis musimon): influence of age, sex, season and vitamin E status.

Full blood counts, fibrinogen estimations and red cell osmotic fragility tests were carried out on a number of clinically normal captive mouflon (Ovis musimon) from various locations. Age related differences in red and white cell counts and sex related differences in red cell counts were demonstrated. There was also evidence for seasonal changes in red cell values in adult females. During this study, some mouflon were found to be deficient in vitamin E and were transferred to a vitamin E supplemented diet. Comparison of findings on vitamin E deficient and supplemented animals revealed no significant haematological differences.

Age Factors↗
PubMed1983

Effect of triac and beta-adrenergic blocking agents on the myocardium of developing rats.

Triiodothyroacetic acid, triac, when given to rats during pregnancy, causes hypertrophy and intracellular disarray in the hearts of their offspring and concurrent treatment with dl propranolol can prevent the latter abnormality. Further experiments have been carried out to test the effect of dl oxprenolol and d propranolol on triac-induced myofibrillar disarray. Administration of dl oxprenolol at the same time as triac prevented disarray but a higher dose than that of dl propranolol was required to produce this effect. Disarray was also prevented by d propranolol. Selective consideration of the membrane stabilising, beta blocking and agonist activities of dl oxprenolol and d and dl propranolol leads to the conclusion that although direct or indirect beta stimulation by triac may play a small part in its disruptive effect on the developing myocardium, its main deleterious action can be blocked by membrane stabilisation.

Animals↗
PubMed1983

Age related haematological changes in captive Barbary sheep (Ammotragus lervia).

Full blood counts were carried out on a number of clinically normal newborn, juvenile and adult Barbary sheep. Significant age related differences in the number and size of the red cells and in the absolute and relative numbers of neutrophils and lymphocytes were found. Fibrinogen levels and platelet counts were lowest in newborn animals. These differences could complicate the interpretation of haematological findings on sick Barbary sheep if not taken into account.

Age Factors↗
PubMed1983

Normal and clinical haematology in the yak (Bos grunniens).

Haematological examinations have been carried out on 21 clinically normal male and female adult yaks (Bos grunniens). Animals sedated with xylazine had significantly lower red cell counts, haemoglobin levels and packed cell volumes, fewer lymphocytes and higher monocyte counts than those bled while manually restrained. There were few significant sex differences. Several animals had eosinophilia associated with asymptomatic intestinal nematode infection. Haematological reference values were calculated for clinically normal, xylazine sedated and manually restrained yaks. These were used to identify haematological changes in 10 animals with various abnormal clinical signs. It was concluded that blood counts can provide valuable diagnostic information in this species.

Animals↗
PubMed1982

Haematological findings in healthy and sick African grey parrots (Psittacus erithacus).

Full blood counts and fibrinogen estimations were carried out on 11 clinically normal, adult African grey parrots. Reference values derived from these tests were used to identify abnormalities in the blood counts of 11 sick parrots thought to be suffering from bacterial infections. All sick birds showed higher than normal heterophil counts, paralleled in some cases by lymphocytosis, monocytosis, thrombocytosis and increased fibrinogen levels. Anaemia was present in two birds and several others showed minor red cell abnormalities. The findings indicate that clinical haematology can make a useful contribution to the differential diagnosis of infection in African grey parrots. The findings also suggest that the development of anaemia can be a significant complicating factor in infectious conditions in these birds.

Animals↗
PubMed1982

Haematological findings in red-necked wallabies (Protemnodon rufogrisea) with necrobacillosis.

Results of blood counts on 17 red-necked wallabies (Protemnodon rufogrisea) with confirmed necrobacillosis have been compared with those of 36 clinically normal animals. The most common abnormality in infected animals was a raised fibrinogen level, found in all of the cases tested. Neutrophilia occurred in 10 individuals and neutrophil morphology was abnormal in 15. Some infected animals showed monocytosis, raised erythrocyte sedimentation rates, high platelet counts and changes in their red cells. The findings provide useful information about the response of the blood to severe bacterial infections in red-necked wallabies and demonstrate the potential diagnostic use of clinical haematology in this species.

Animals↗
PubMed1981

Production of cardiac muscle abnormalities in offspring of rats receiving triiodothyroacetic acid (triac) and the effect of beta adrenergic blockade.

As a part of a continuing study on the effects of thyroid hormones on heart muscle, triiodothyroacetic acid (triac), either alone or concurrently with propranolol, has been administered to rats during pregnancy. Control groups received either buffer or propranolol. Offspring, which were given no further treatment, were killed at intervals after birth and their hearts examined histologically, histochemically, and electron microscopically. At 2, 6, and 14 days, offspring of triac-treated rats showed cardiac hypertrophy and, at ultrastructural level, marked disarray of the myofibrils was present. By 28 days, arrangement of the myofibrils had become regular but hypertrophy persisted and was still found in rats examined at 56 days of age, after which time the myocardium was normal. Offspring of rats which had received propranolol at the same time as triac showed a similar pattern of hypertrophy but myofibrillar disarray was not found. Propranolol alone produced no abnormalities. These findings provide further evidence that thyroid hormone analogues can adversely affect heart muscle. When considered in conjunction with previous experiments which showed that thyroxine or triac cause severe hypertrophy but not disarray when given directly to growing rats, they suggest that thyroid hormones can produce a spectrum of abnormalities, thought to depend on the stage of myocardial development at which the stimulus is administered. In the present experiment, the triac-induced myofibrillar disarray but not the hypertrophy was prevented by propranolol, indicating that beta-adrenergic blockade or some other action of propranolol protects the developing myofibrils. Possible mechanisms for the adverse effects of thyroid hormones and the protective action of propranolol are discussed.

Animals↗
PubMed1980

[Protective effect of alpha-linolenic acid in encephalomalacia in chickens].

Encephalomacia is a vitamin E deficiency syndrome which affects the cerebellum of young chicks. The lesion includes degenerative alterations of cellular and fibrillar elements, apparently as the result of the ischaemia caused by thrombotic events in the microvascular system. A supply of linoleic acid, as fatty acid methyl esters prepared from safflower oil (Carthamus tinctorius), caused a high incidence of encephalomalacia. On the other hand, linseed oil esters, rich in alpha-linolenic acid, did not induce any symptoms and protected the chicks to a large extend against the development of signs produced by linoleic acid. Fatty acid esters of cod liver oil, rich in long-chain derivatives of alpha-linolenic acid, exerted a relatively weak protective effect. The analytical results show that a supply of alpha-linolenic acid led to an accumulation of eicosapentaenoic acid, 20:5 omega 3, and a reduced concentration of arachidonic acid in the phospholipds of liver and plasma. The results suggest that, under the conditions leading to encephalomalacia, the prostacyclin-thromboxane balance is shifted in direction of an excessive production of TXA2, causing thrombus formation in the capillaries of the cerebellum, alpha-linolenic acid, by modifying the PUFA profile, exerts a multiple action the main result of which appears to be an antithrombotic effect at the level of the microvascular system of the cerebellum.

Animals↗
PubMed1978

The influence of anaesthetics on the haematology of the patas monkey, Erythrocebus patas.

The effects of phencyclidine, ketamine and an alphaxalone-alphadolone mixture on the haematology of the patas monkeys have been compared. In animals sedated with phencyclidine or ketamine the only significant difference detected was in the mean cell volume. Statistically significant differences in white-cell count and blood coagulation and fibrinolytic activity were found in monkeys which had received alphaxalone-alphadolone. It is suggested that ketamine is a suitable alternative to phencyclidine for haematological studies in these monkeys.

Alfaxalone Alfadolone Mixture↗
PubMed1977

A comparative study of haemoglobins from the Artiodactyla by isoelectric focusing.

1. Isoelectric focusing on 7% acrylamide gels in 2% ampholyte of pH range 6-8 was used to fractionate the haemoglobins of 81 animals, representing 30 species from 4 families of the Order Artiodactyla. 2. Isoelectric points of the major haemoglobins were determined and the relative distribution of minor haemoglobins compared. 3. Marked haemoglobin heterogeneity was observed, with polymorphic and multiple haemoglobins. No one haemoglobin was common to all species.

Animals↗