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Biomedical subjects

J M Wills

Publications and source records attributed to J M Wills.

15 recordsLinked to original sources
PubMed1994

Blood-brain barrier permeability in rats is altered by exposure to magnetic fields associated with magnetic resonance imaging at 1.5 T.

We have previously reported that exposure of rats to low-field (0.15 T) magnetic resonance imaging (MRI) increases blood-brain barrier (BBB) permeability. However, a number of investigators have failed to observe this effect when high-field MRI (1.5 T or higher) is used. Therefore, we investigated whether or not we would observe changes using our technique at these higher fields. Adult male Sprague-Dawley rats were anaesthetised and then exposed to a 22.5 min imaging or sham procedure. Immediately following exposure, rats were injected with 1 MBq of 153Gd-DTPA intracardially and then immediately re-exposed for an additional 22.5 min. The rats were killed 1h following the second MRI exposure, at which time the brain was resected and 3 ml of venous blood collected. The ratio of radioactivity per gram of brain to radioactivity per milliliter of blood, known as the brain-blood partition coefficient, was determined and used as a measure of BBB permeability. Groups of animals had different exposures. Group 1 (n = 9) was exposed to a clinically relevant MRI procedure. Group 2 (n = 20) was exposed to the same procedure except the rf specific absorption rate (SAR) was reduced to 25% and the animals were positioned 15 cm from imager centre to increase the time-varying magnetic field from 0.4 to 2.8 T/s. For the sham exposures (n = 21), the animals were placed in the imager with the static field ramped down to zero and exposed to a sound recording simulating a MRI examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

A study of obese cats on a calorie-controlled weight reduction programme.

Twenty-two domestic cats were fed a commercial low calorie diet for the management of obesity for up to 18 weeks and showed an average weight loss of 13.5 per cent of their body-weight. There was no indication that a steady weight loss over the study period had any adverse effect on the hepatic function or general health of the cats. There was an increase in the cats' total serum cholesterol concentration in association with the loss of weight.

Animals↗
PubMed1994

Changes in plasma lipoprotein during the oestrous cycle of the bitch.

Five bitches were kept under controlled conditions of diet and exercise for up to four months. They were monitored at regular time intervals for fasting plasma concentrations of cholesterol, triacylglycerols and apolipoproteins AI and B. Lipoprotein cholesterol and triacylglycerol concentrations were also determined in the fasting plasma. Vaginal cytology and plasma progesterone were monitored at weekly intervals to determine the oestrous state of the bitches. Lipoprotein and apolipoprotein concentrations remained steady during anoestrus but large increases and wide fluctuations were shown in the concentrations of both cholesterol and triacylglycerols during metoestrus. Metabolic studies involving the measurement of lipids in canine blood must take into account the stage of oestrus of any bitches involved.

Animal Feed↗
PubMed1994

Clinical studies in the management of obesity in dogs and cats.

Obesity in companion animals is a common clinical condition, and represents an important challenge to the veterinarian. This paper reports a study in which controlled calorie reduction was used to achieve weight loss in a group of dogs. The food allowance for the study provided approximately 209 kJ metabolisable energy (ME)/kg (target weight)0.75/day, with target weight 15% less than the dog's starting weight. The rate of weight loss achieved averaged approximately 1% per week over a 12 week period. Data reviewed from a second study in cats suggested that an energy intake of approximately 121 kJ ME/kg target weight/day, again with the target 15% less than the current weight, was an appropriate level for obtaining gradual weight loss in this species. These findings are discussed in relation to an alternative method of weight reduction, starvation. The potential value of exercise as an adjunct to controlled calorie reduction for achieving weight loss in companion animals is also considered.

Animal Feed↗
PubMed1993

Plasma lipoprotein lipids in five different breeds of dogs.

Plasma and lipoprotein cholesterol and triglycerides, and apolipoproteins AI and B, were determined in five common breeds of pet dogs, labrador, beagle, West Highland terrier, cairn terrier and dachshund, kept under carefully controlled conditions approximating as closely as possible to normal domestic living. Although the total levels of both cholesterol and triglycerides in plasma did not vary significantly between the breeds, there were significant interbreed differences in the lipoprotein fractions. Thus high density lipoproteins (HDL) which are the major carriers of cholesterol in all dogs, was higher in the smallest breed, the cairn, than in the largest, the labrador. In contrast, the low density lipoprotein (LDL) was lowest in the cairn and highest in the labrador. Variation in HDL cholesterol levels arose from both subfractions, HDL2 and HDL3. Thus metabolic studies involving canine lipids should include measurement of lipoprotein lipids and take account of interbreed variation.

Animals↗
PubMed1992

Chlamydia psittaci infection in horses: results of a prevalence survey and experimental challenge.

Nasal and conjunctival swabs were obtained from 300 horses and Chlamydia psittaci was isolated from 15 of them (5 per cent). Eleven nasal swabs and six conjunctival swabs were positive on culture, but there was no association between the isolation of the organism and the presence of clinical ocular or respiratory disease. Six ponies were challenged with an equine isolate of C psittaci into the eye, nasal cavity or bronchial tree. The organism could be isolated from nasal and conjunctival swabs taken from the ponies for up to 17 days after challenge, but there was no clinical evidence of disease.

Animals↗
PubMed1990

Characterisation of Chlamydia psittaci isolated from a horse.

This paper describes the isolation and characterisation of a strain of Chlamydia psittaci obtained from a nasal swab taken from a horse with serous nasal discharge. Initial isolation was achieved in cycloheximide-treated McCoy cell monolayers. Chlamydial inclusions stained by immunofluorescence either with a rabbit antiserum raised against C. psittaci or with a monoclonal antibody directed against the genus-specific lipopolysaccharide antigen were single and compact. They did not stain with iodine or with a monoclonal antibody reactive against Chlamydia trachomatis. The agent was re-isolated in the yolk sacs of embryonated hens eggs and designated N16. Identification of the agent was confirmed by electron microscopy. Unique plasmid DNA was prepared from a purified suspension of chlamydial elementary bodies (EBs), and analysed by electrophoresis through 1.0% agarose gels stained by ethidium bromide. This strain of C. psittaci grew relatively slowly in cycloheximide-treated McCoy cells, and the yield of elementary bodies during the course of one growth cycle was relatively low.

Animals↗
PubMed1987

Prevalence of chlamydia, toxoplasma, toxocara and ringworm in farm cats in south-west England.

The prevalence of infection with Chlamydia psittaci, Toxoplasma gondii, Toxocara cati and Microsporum canis was examined in 51 cats on 22 sheep farms in the Bristol area. Serum antibody to C psittaci and T gondii was present in 45 per cent and 47 per cent of cats, respectively. At the time of sampling C psittaci was isolated from 6 per cent of the cats, T cati was identified in 63 per cent of faecal samples but neither T gondii nor M canis was isolated. When examined according to the farm of origin, 22.7 per cent of farms had cat populations with no evidence of infection with C psittaci or T gondii. Of the remainder, 45.5 per cent supported cat populations with evidence of both infections and 31.8 per cent had evidence of T gondii infection alone. None of the farms had cat populations with evidence of C psittaci infection alone. Two of the cats infected with C psittaci were excreting viable organisms in the faeces. The possible significance of this to the epidemiology of ovine enzootic abortion is discussed.

Animals↗
PubMed1987

Effect of vaccination on feline Chlamydia psittaci infection.

Experimental ocular infection of specific-pathogen-free cats with the feline pneumonitis strain of Chlamydia psittaci produced an acute, severe conjunctivitis characterized by blepharospasm, conjunctival hyperemia, chemosis, and ocular discharge. Organisms were recovered from the conjunctiva for several weeks, and persistent genital and gastrointestinal infection also resulted from the ocular infection in some cats. Subcutaneous vaccination with live feline pneumonitis C. psittaci 4 weeks before ocular challenge significantly reduced the severity of the conjunctivitis. However, there was no effect on shedding of organisms from the eye or on the transmission of infection to the gastrointestinal and genital tracts. It is suggested that the acute stage of this ocular disease is caused largely by release of pathogenic antigen(s) from chlamydia-infected conjunctival cells, rather than by a direct cytopathic effect of chlamydial replication. Thus, vaccination with whole live organisms reduced the acute disease in experimentally infected cats but did not prevent shedding of the organism. The implications of these findings are discussed.

Animals↗
PubMed1986

Evaluation of a monoclonal antibody based ELISA for detection of feline Chlamydia psittaci.

A commercially available ELISA designed for the detection of C trachomatis in human urogenital specimens was compared with cell culture for the detection of Chlamydia psittaci in cat conjunctival swabs and in twofold dilutions of a cell culture pool of a feline strain of C psittaci. Cell culture was more sensitive than the ELISA test for detection of C psittaci.

Animals↗
PubMed1985

Isolation of felid herpesvirus I from the trigeminal ganglia of latently infected cats.

Felid herpesvirus I (FHV I) is a respiratory pathogen of cats. Recovered animals remain latently infected but episodes of virus shedding may occur, particularly after stress. Previous attempts to identify the site(s) of latency of FHV I using co-culture, explant or tissue homogenization methods have been unsuccessful. Using a tissue fragment culture technique, however, FHV I was isolated from the trigeminal ganglia of three of 17 cats latently infected with field virus. No virus was found in four cats previously infected with a cold-adapted vaccine strain of FHV I, or in four cats given vaccine strain and field virus. The three trigeminal ganglion isolates had similar plaque size and morphology to the vaccine strain, the plaques being significantly smaller (P less than 0.001) than those of the field viruses.

Animals↗