Comparison of the oestrogenic effects of infant milk formulae, oestradiol and the phytoestrogen coumestrol delivered continuously in the drinking water to ovariectomised mice.

The potential oestrogenic effects of infant milk formulae, coumestrol and oestradiol delivered in the drinking water were investigated in ovariectomised mice. None of the infant formulae tested (three soya, two cow's milk) produced any uterotrophic or mitotic responses in the reproductive tract, although the soya milks displayed weak oestrogenic activity in vitro. Studies of the interactions between coumestrol and oestradiol were undertaken to investigate claims that phytoestrogens may act as oestrogen antagonists. The responses to coumestrol (100 g/ml drinking water) and 17-oestradiol (100 ng/ml) given separately were similar. Combined administration begun simultaneously produced only additive effects on uterine weight and cell proliferation in the vagina and uterus. While pretreatment with coumestrol for 24 h reduced the mitotic response of the uterus 48 h after placement of an oestradiol implant, the uterine weight increase was unaffected and the apparent reduction in mitoses reflected the natural fluctuations in the underlying cycle of cell proliferation. These studies indicate that coumestrol acts as a typical oestrogen and shows only additive effects with oestradiol. The results also indicate that infant soya milk formulae do not constitute a large enough source of oestrogenic compounds to invoke oestrogenic effects in the reproductive tract of mature mice.

Dental and life science students: a comparison of approaches to study and course perceptions.

Approaches to study and course perceptions were investigated and compared in both junior and senior students on a vocational course (dentistry) and on a non-vocational course (life sciences) using standard questionnaires. Junior dental students reported significantly greater tendencies towards both Deep and Surface Approaches than junior life science students. They also had significantly higher scores for Achieving Approach, but in senior students this trend was reversed. Final year dental students experienced greater workloads and less freedom in learning than life science students and they also reported less organized study methods. These course perceptions demonstrate similar trends to those reported by Ramsden (1991). The implications for the courses concerned and for curriculum development are considered.

Behaviour of rats in their home cages: daytime variations and effects of routine husbandry procedures analysed by time sampling techniques.

The behaviour of laboratory rats in their home cages was observed on both the mornings and the afternoons of days when cages were cleaned and compared to days when cages were not cleaned. Two different time sampling methods, 'instantaneous sampling' and 'one/zero sampling', were used and compared. In general the rats were more active in the mornings than in the afternoons. Activity, particularly locomotion and that associated with manipulation of the bedding was increased during both the mornings and the afternoons of cleaning days. Defaecation also increased on cleaning days whereas sitting decreased. The cleaning regime appeared to have a greater effect on behaviour than did time of day and the effect of cleaning lasted for several hours after the procedure had been completed. The implications for experimental design are discussed.

Home bedding modifies ultrasonic vocalization of infant bank voles.

Bank vole,Clethrionomys glareolus, pups, similar to many other infant rodents, emit ultrasonic vocalizations when they are removed from the nest and cooled. Infants exposed to bedding from their home cage produced fewer and shorter calls than infants tested without bedding. Sound frequencies were significantly higher in infants exposed to home bedding than in other experimental groups. These results provide evidence that infant bank voles are able to identify the presence of home bedding, probably on the basis of odor. This appears to be the first report of shifts in frequency of pup ultrasonic calls in response to olfactory cues.

Sound levels in rooms housing laboratory animals: an uncontrolled daily variable.

High sound levels are known to have adverse effects on the behaviour and physiology of laboratory animals, yet their acoustic environment is rarely monitored. In particular, high-frequency sounds that are above the limit of human hearing, but are well within the limits of many laboratory species (i.e., ultrasounds), are usually ignored. In this study, the acoustic environment of laboratory animals was investigated in a variety of different animal facilities. Sound pressure levels (dB SPL) were monitored for periods up to 24 h over two frequency ranges: a relatively low range (0.01-12.5 kHz), and a high range (12.5-70 kHz). While background sound levels in undisturbed situations were generally low (i.e., below 50 dB SPL), marked increases in sound levels often occurred during the working day, producing characteristic daily variations in the sound profile. Peak SPLs commonly reached values of 80-95 dB in the low-frequency range and 50-75 dB in the higher range. In most cases, sound levels were low over weekends. The results suggested that human activities were a very important source of sound in most animal facilities. In a few situations (e.g., rabbits, marmosets, dogs), the animals themselves provided a significant contribution to the acoustic environment. It is clear that the acoustic environment of laboratory animals is a daily variable that is usually uncontrolled and that may have important implications for behavioural and physiological experiments and for animal welfare.

The effect of 22 kHz calls and artificial 38 kHz signals on activity in rats.

Ultrasonic calls at 22 kHz are emitted by adult rats Rattus norvegicus when submissive, after and sometimes before copulation and in aversive situations, but the function of these calls, if any, is not known. This study examined the effect of 22 kHz calls on the behaviour of individuals. Rats were exposed singly for 5 min to a tape-recorded test signal; 22 kHz calls or artificial 38 kHz signals or tape noise. All rats were exposed to tape noise before and after the test signal. Both of the ultrasonic signals, and particularly the 22 kHz calls, decreased locomotor activity in rats during replay and for 5 min afterwards. Rats sniffed the loudspeaker less during the replay of 22 kHz calls than during the other test signals. These results complement others showing that constant frequency ultrasound from visual display units and oscilloscopes also depresses activity. In natural aggressive situations 22 kHz calls could allow a subordinate to escape and prevent the dominant wasting time in pursuit. In the laboratory exposure of rats to natural or artificial ultrasound could affect ongoing or subsequent behaviour and so be a confounding experimental variable.

The emission and elicitation of mouse ultrasonic vocalizations: the effects of age, sex and gonadal status.

Subject' mice of varying gonadal status (castrate males; intact or neonatally gonadectomized females and males) were paired for 3-min with intact 'stimulus' females and ultrasonic vocalizations were monitored. Vocalization patterns from home cages differed from the test pairings. The results suggested that the age, experience and gonadal status of the subject influenced the vocalizations from the pair. As the source of ultrasonic calls from these vocally intact pairs could not be individually identified, the 'subjects' were paired with a range of ultrasonically silent (inferior laryngeal nerve-transected) stimulus animals. Vocalizations were detected from all combinations of animals. Gonadally intact females were most effective in eliciting ultrasonic vocalizations from the subjects and gonadally intact males were least effective. The responses of castrate males were lower than from intact males. Anesthetized adults of either sex elicited only poor vocalization responses from other adults. Ultrasonic calls have often previously been studied using vocally intact 'subject' and 'stimulus' animals: the present results confirm the difficulty of establishing who is who in such situations.

Environmental ultrasound in laboratories and animal houses: a possible cause for concern in the welfare and use of laboratory animals.

Many laboratory animals are known to be sensitive to sounds (ultrasounds) beyond the nominal upper limit (20 kHz) of the human hearing range. Sources of sound in laboratories and animal houses were examined to determine the extent of ambient ultrasound. Of 39 sources monitored, 24 were found to emit ultrasonic sounds. Many of these (e.g. cage washers and hoses) also produced sound in the audible range. Running taps, squeaky chairs and rotating glass stoppers created particularly high sound pressure levels and contained frequencies to over 100 kHz. The oscilloscopes and visual display units investigated provided particular cause for concern as they emitted sounds that were entirely ultrasonic and therefore were apparently silent. Ambient ultrasound therefore appears to be common in laboratories and animal houses. It is suggested that its effect on laboratory animals should be investigated and guidelines on acceptable levels be formulated.

Long-term monitoring of mouse ultrasonic vocalizations.

The temporal pattern of ultrasonic vocalizations by mice in an undisturbed 'home' environment can now be assessed using a system based on amplitude discrimination. Within a chosen frequency band, vocalizations of sufficient intensity are detected by an amplitude discriminator. The output from a pulse generator is sent to a microcomputer which records the time of the incoming event. The system has been validated for monitoring ultrasonic vocalizations in the mouse.

Ultrasonic vocalization in rat pups: effects of early postnatal exposure to haloperidol.

The effects of prolonged postnatal administration of haloperidol (H) on ultrasonic vocalization elicited by the removal of rat pups from their nest were investigated. The results show that the number of ultrasonic calls was significantly reduced by H exposure from the 8th until the 14th day after birth. Conversely, this neuroleptic significantly increased the duration of ultrasound from the 4th up to the 16th day of age. Moreover, changes in the frequency of calls were produced by early postnatal treatment with H. These alterations could be due to an impaired functional maturation of the dopaminergic system produced by neonatal exposure to H. Furthermore, the present data suggest that ultrasonic vocalization may be considered as an early sensitive indicator of subtle changes elicited by the postnatal treatment with a dopamine receptor blocking agent at dose levels below those associated with overt signs of neurotoxicity.

Comparative studies of the ultrasonic calls of infant murid rodents.

The ultrasonic calls of 10 species of murid rodents including 3 strains of house mice are described and the significance of interspecific similarities and differences is discussed. The calls of newborn murid rodents may be characterized by their gradual onset and cessation, their comparative lack of amplitude and frequency modulation, and, often, by the presence of only 1 frequency component. These common acoustic characteristics may be important in eliciting and/or maintaining various aspects of maternal behavior, both in and out of the nest.