Biomedical subjects

C M Wathes

Publications and source records attributed to C M Wathes.

At least 37 records · Page 2Linked to original sources

PubMed1992

A comparison of plasma vasopressin and oxytocin concentrations during the oestrous cycle of the ewe.

Blood samples were collected twice daily (09.30 and 17.00 h) via indwelling jugular-vein cannulae from five ewes throughout an entire oestrous cycle. Additional frequent samples were taken at 30-min intervals for 8 h on each of days 3 (early luteal phase), 9 (midluteal phase), 12 (late luteal phase) and 0 (day of oestrus). Plasma concentrations of arginine vasopressin and oxytocin were measured in all samples by radioimmunoassay and progesterone was measured in the twice-daily samples only. Both oxytocin and progesterone showed the expected pattern of plasma concentrations, increasing during the early luteal phase, reaching a plateau and declining either preceding (oxytocin) or at (progesterone) luteolysis. Vasopressin concentrations showed a significant dependence on the day of cycle (P less than 0.05, analysis of variance) with concentrations lowest at oestrus and minor peaks on days 4 and 8-9. There was no correlation between the concentrations of vasopressin and progesterone. Vasopressin values were significantly higher in the morning than in the afternoon samples (1.3 cf. 0.9 pmol/l; P less than 0.001). Analysis of the frequent samples showed a significant (P less than 0.001) dependence on the time of day for vasopressin but not oxytocin. Values were high throughout the morning, declined to a trough at 15.00 h and rose again by 17.00 h. We conclude that there is a minor variation in the vasopressin concentration during the oestrous cycle, which is not related to the circulating progesterone concentration but could be regulated by oestradiol. We also provide evidence for a diurnal rhythm in the release of vasopressin into the plasma in the ewe.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

The ability of airborne Klebsiella pneumoniae to colonize mouse lungs.

A strain of Klebsiella pneumoniae was aerosolized and its survival in air at different relative humidities was studied. Survival was dependent upon relative humidity and aerosols were most stable during storage at a relative humidity of 60%. Mice were exposed to aerosols of K. pneumoniae produced at this humidity and lung samples taken at timed intervals after exposure. Fifteen strains of K. pneumoniae were tested for their ability to colonize mice, but only five were detectable in mouse lungs 7 days after exposure. Three of these strains persisted without an increase in bacterial numbers, regardless of the initial inoculum used. Two strains of K. pneumoniae, designated strains 15 and 16, persisted in a similar manner when used at a low dose; however, when the dose received per lung was increased there was a rapid multiplication of bacteria in the lungs.

Aerosols↗

PubMed1991

Transmission of salmonellae among calves penned individually.

An analysis of the spatial and temporal patterns of excretion of salmonellae by calves penned individually showed that non-contagious routes were more important than contagious routes in disease spread. The avoidance of aerosol production, and the effective cleaning and disinfection of utensils between feeds and of buildings between batches, are likely to be more important than pen design in the control and prevention of calf salmonellosis.

Aerosols↗

PubMed1991

Physical protection against airborne pathogens and pollutants by a novel animal isolator in a level 3 containment laboratory.

A containment laboratory unit for research with aerosols of group 2 pathogenic microorganisms is described. The design criteria are based on current UK guidelines, which imply containment at group 3 level during aerosol production, storage, exposure of animals and sampling. Within the aerosol laboratory, primary containment is provided by a Henderson apparatus operating at a negative pressure to the external environment. Flexible film isolators under negative pressure are used for all hazardous microbiological work, e.g. tissue homogenization, and for housing infected laboratory rodents. A novel feature of the animal isolator is the separate ventilation of each cage, which minimizes the risk of cross-infection by aerosol transmission and ensures a similar environment within each cage. The results of an intentional release of a cloud of non-pathogenic microorganisms are presented to show the effectiveness of the containment barriers. Recommendations are given for the safe operation of a containment unit based upon practical experience.

Aerosols↗

PubMed1991

Air hygiene in a pullet house: effects of air filtration on aerial pollutants measured in vivo and in vitro.

1. The natural history of air hygiene in a pullet house was assessed at three-weekly intervals using a combination of in vitro and in vivo assays. The performance of an internal air filter was also examined as an experimental technique for providing clean air. 2. Overall, air hygiene was poor by comparison with occupational standards for human health. The mass concentrations of respirable and inspirable dust were 1.4 and 11.3 mg/m3 compared to human exposure limits of 5 and 10 mg/m3 respectively. The concentration of ammonia was typically about 20 ppm. 3. The majority (greater than 99%) of airborne particles were non-viable. Commensal bacteria from the skin were the most numerous airborne bacteria. Scopulariopsis and Aspergillus spp. were the most prevalent fungi recovered from the air and bird's lungs respectively. The concentrations of airborne and lung fungi were positively correlated with ammonia concentrations. 4. The differences between in vivo and in vitro assays of airborne microorganisms suggest that an aerosol sampler should be devised which better mimics the physical and biochemical environment of the respiratory tract.

Air Microbiology↗

PubMed1991

Thermal preferences of chicks brooded at different air temperatures.

1. The thermal preferences of small flocks of 400 chicks brooded under radiant heaters were determined at air temperatures of 21, 24 and 27 degrees C from observations of behavioural thermoregulation. 2. At 1 d of age the upper limits of the preferred black bulb temperature increased with air temperature. Preferences for radiant temperature declined with air temperature. 3. Compensation for cold air temperature was imperfect because the chicks avoided zones of high radiant flux. The maximum tolerable radiant temperature was approximately 50 degrees C. 4. Radiant heaters are preferable to convectors in poultry husbandry because the inherent lack of spatial homogeneity in thermal environments ensures that chicks can satisfy their individual thermal preferences.

Analysis of Variance↗

PubMed1991

Serum antibody responses in mice to intermittent inhalation of ovalbumin dust.

Serum antibody production and induction of antibody tolerance were monitored in mice following intermittent inhalation of ovalbumin dust (mass concentration = 4.2 mg m-3; diameter of 80% of particles less than 2.6 microns). Repeated inhalation of microgram quantities of dust stimulated serum antibody production and development of tolerance. The sequence of these responses is analogous to that following oral presentation of antigen, but is produced by a much lower dose when antigen is presented via the respiratory tract.

Administration, Intranasal↗

PubMed1991

Influence of oxytocin infusion during oestrus and the early luteal phase on progesterone secretion and the establishment of pregnancy in ewes.

In Experiment 1, an osmotic minipump containing oxytocin was implanted s.c. in ewes for 12 days beginning on Day 10 of the oestrous cycle, producing approximately 100 pg oxytocin/ml in the plasma. Two days after the start of infusion, all ewes were injected with 100 micrograms cloprostenol and placed with a fertile ram. At slaughter 22 days later, 9 (75%) of the 12 control (saline-infused) ewes were pregnant compared with 1 (11%) of the 9 ewes infused with oxytocin. In the control group, midcycle plasma concentrations of oxytocin were significantly higher in nonpregnant than in pregnant ewes. In Experiment 2, an infertile ram was used throughout to avoid any possible effects of pregnancy and oxytocin infusions were given at different stages of the oestrous cycle. Otherwise the protocol was similar to that in Exp. 1. Oxytocin infusion during luteolysis and the early follicular phase had no effect on the subsequent progesterone secretion pattern, but infusions beginning the day before cloprostenol-induced luteolysis and lasting for 7 or 12 days and infusions beginning on the day of oestrus for 4 days all delayed the subsequent rise in plasma progesterone by approximately 3-4 days. In these animals, the cycle tended to be longer. It was concluded that an appropriate oxytocin secretion pattern may be necessary for the establishment of pregnancy in ewes and that a high circulating oxytocin concentration during the early luteal phase delays the development of the young corpus luteum.

Animals↗

PubMed1990

The airborne survival of Pasteurella haemolytica and its deposition in and clearance from the mouse lung.

Pasteurella haemolytica A1 was aerosolised by a Collison nebuliser in a Henderson apparatus and its survival in air was measured. The organism was fragile in aerosol and survived best at high humidity and warm temperature. Mice were exposed to the aerosol and clearance from the lung measured. Deposition in the mouse lung showed a good linear correlation with bacterial concentration in the spray suspension fluid. Clearance from the lung was rapid over 24 h although some bacteria could be detected 2 and 4 days after exposure. Mice which received a second exposure 2 weeks later exhibited accelerated clearance from the lung whereby no bacteria could be detected after 12 h. This was associated with serum IgG antibody production, and local and splenic lymphocyte responses to bacterial antigen in vitro.

Aerosols↗

PubMed1989

The effect of titanium dioxide inhalation on the pulmonary clearance of Pasteurella haemolytica in the mouse.

Four inhalation exposure chambers were designed and built in which up to 80 mice per chamber could be accommodated. Exposure for several weeks to an inert inorganic particulate aerosol of titanium dioxide at a respirable aerosol concentration of 20 mg m-3 impaired the clearance of Pasteurella haemolytica in proportion to the duration of exposure. Other groups exposed to a lower respirable concentration of 2 mg m-3 exhibited similar clearance rates relative to mice maintained in clean air. A recovery experiment showed that inhalation of TiO2 at 20 mg m-3 for 10 days impaired bacterial clearance at least 10 days after cessation of exposure to TiO2.

Administration, Inhalation↗

PubMed1989

Pulmonary clearance of Pasteurella haemolytica and immune responses in mice following exposure to titanium dioxide.

The effects of dust inhalation on immune responses in mice to aerosolized Pasteurella haemolytica were investigated. Animals exposed to titanium dioxide dust (TiO2) at a respirable aerosol concentration of approximately 20 mg m-3 for 20 hr per day, before or after aerosol vaccination, had impaired pulmonary bacterial clearance relative to animals kept in clean air. Additionally, lymphocytes from the local (mediastinal) lymph nodes had depressed responses to bacterial antigen in vitro in mice exposed to dust immediately after vaccination. However, there were no differences in the splenic lymphocyte responses between groups, while serum antibody responses were low and variable. A second experiment showed that aerosol vaccinated and nonvaccinated animals, which were exposed to a respirable aerosol concentration of TiO2 at 20 mg m-3 immediately after inoculation with a bacterial aerosol, had impaired clearance compared to their respective controls maintained in clean air.

Aerosols↗

PubMed1989

Air hygiene in a broiler house: comparison of deep litter with raised netting floors.

1. Deep litter and raised netting flooring systems in broiler houses were compared for their effects on air quality and bird health during an 8-week growing period. 2. Weekly measurements were taken of respirable dust, numbers of airborne microorganisms and concentrations of gaseous pollutants. Airborne fungi and bacteria were identified to species. 3. At the end of the experimental period, randomly sampled bird lungs were examined for the presence of viable microorganisms and for pathological changes. Bird health and performance were monitored throughout the 8 weeks. 4. Respirable dust concentrations and numbers of airborne microorganisms were significantly higher in the litter rooms. The type of floor had no effect on concentrations of gaseous ammonia. 5. Floor type had no significant effect on bird mortality but birds on litter had a slightly better gain:food ratio. However, birds on litter were observed to have a higher incidence of lung damage and more of the birds on litter had viable microorganisms present in the lungs at necropsy.

Air Microbiology↗

PubMed1989

Air hygiene in a pullet house: spatial homogeneity of aerial pollutants.

1. The spatial distribution of aerial pollutants was measured in a large deep-litter pullet house, initially holding 10,000 birds, at 12 sites within the birds' breathing zone: on 6 occasions when the birds were between 8 and 27 d of age and on two occasions when the birds were 29 and 34 d of age and the flock size was halved. 2. The distribution of most pollutants appeared uniform, implying that all sites could be considered representative of the overall concentration of pollutant. 3. The concentration of ammonia differed between sites, probably because of local variations in the rate of release from the litter. The number concentration of non-respirable particles (greater than 5 microns in diameter) became heterogeneous when the flock size was halved. 4. The operation of two punka fans had no effect on the spatial distribution of aerial pollutants, but increased the maximum air speed from 0.08 to 0.16 m/s. 5. Recommendations are given for the minimum number of sampling sites necessary for a predetermined level of statistical accuracy. Eight sites at least are recommended for most aerial pollutants, though more are needed for the concentration of gaseous ammonia.

Air Pollutants↗

PubMed1989

Relationship between pre-partum relaxin concentrations and farrowing intervals in the pig.

Gilts were treated on Day 112 of gestation with saline or a prostaglandin (PG) F-2 alpha analogue. In control gilts there was a rise in the relaxin concentration from 48 h before the onset of delivery, peaking between 12 and 28 h pre partum followed by a steep fall. The relaxin concentrations at each 1-h time interval were analysed in relation to the farrowing interval for each gilt using correlation analysis. There was a significant (at least P less than 0.05) positive correlation between the relaxin concentration and the farrowing interval at every time period from 14 to 2 h before delivery. In contrast there was little relationship between concentrations of progesterone, oestrone and oestradiol-17 beta and farrowing intervals. The gilts treated with PGF-2 alpha analogues had steroid profiles indistinguishable from those in controls but differing relaxin secretion patterns. Relaxin concentrations peaked at 1-2 h after PGF-2 alpha injection and this was followed by a second smaller increase closer to the time of delivery in 7 out of 12 gilts. The 'two-peak' gilts had significantly higher relaxin concentrations at farrowing and took significantly longer to farrow than did the 'one-peak' gilts (P less than 0.005). These results suggest that high relaxin concentrations during the last 14 h before the onset of parturition are associated with increased farrowing times, but are not associated with any increase in neonatal mortality.

Animals↗

PubMed1988

Aerosol infection of calves and mice with Salmonella typhimurium.

The likelihood of airborne spread and infection by Salmonella typhimurium was studied in calves and mice. S typhimurium survived in air sufficiently long to present a significant hazard of airborne spread. In a dry climate (32 per cent relative humidity) its predicted viability five minutes after aerosolization was 4 per cent relative to its initial value. This increased to 24.8 per cent in a humid atmosphere (72 per cent relative humidity). Inhalation of S typhimurium by mice caused disease and death at times dependent upon the dose. Even the lowest dose of about 150 colony forming units (cfu) produced disease. Inoculation of approximately 10(4) to 10(6) cfu S typhimurium by either 'mouth and nose only' or 'whole body' aerosol exposure caused infection in calves. The consequences for the control of salmonellosis in intensive calf husbandry are discussed in the light of this demonstration that airborne transmission can be a primary mode of infection of S typhimurium.

Aerosols↗

PubMed1987

Air hygiene in stables. 1: Effects of stable design, ventilation and management on the concentration of respirable dust.

The concentration of fungal spores, the main constituents of respirable dust in stables, is determined by rates of release from fodder and bedding and rate of clearance, principally by ventilation. This paper outlines the principles that govern the application of natural ventilation to the control of air hygiene in barns and individual boxes for horses. When release rates are low, ventilation rates over four air changes per hour are satisfactory. Ventilation was satisfactory in individual boxes but usually unsatisfactory in barns and specific recommendations are made for improvement. Preliminary observations in stables with clean, well-managed bedding revealed only small differences between straw, wood shavings and paper. In these circumstances hay tended to be the major source of respirable spores.

Air Microbiology↗

PubMed1987

Survey of the designs of racehorse stables in the south west of England.

The design of 96 racehorse stables in the south west of England were surveyed. The 'typical' racehorse is kept in a loose box, bedded on straw and remains indoors while the stable is cleaned. It is given a floor area of 12 m2 and shares its airspace of 39 m3 with seven other horses. Overall, the predicted minimum rate of air change by natural convection in calm winds is 6.6 air changes/h but this is reduced to 2.2 if the top door of the stable is closed. On balance, racehorse stables in use today are based on designs which are worse overall than the best available in the 19th century.

Air Movements↗

PubMed1987

Transmission of Pasteurella multocida in rabbits.

Contact and airborne transmission of P. multocida in rabbits was evaluated in an artificially controlled environment. Transmission by contact occurred more readily from rabbits with acute infections than from rabbits with chronic infections. However, airborne transmission to rabbits in adjacent cages did not occur.

Air Microbiology↗