Search

Exposure of adult male CD-1 mice to restraint stress for 60 min increased their hindpaw-licking latency in a hot-plate test (50 degrees C); this analgesia was significantly reduced after exposure to a stable magnetic field (MF) (30-40 G) under white light. In contrast, MF exposure under either red light or total darkness did not alter stress-induced analgesia. Results suggest that in rodents perception of magnetism might involve a light-dependent mechanism as recently found for migratory birds and amphibians.

Only a few studies have attempted to assess in laboratory rodents the maternal toxicity and behavioral changes in offspring caused by prenatal exposure to ozone (O3). In particular, no data are available concerning the behavioral development of mouse offspring after maternal exposure, despite the fact that increasing use is made of this species in behavioral teratology studies for reasons both of economy and in order to increase the effectiveness of subsequent higher-tier studies (e.g., of treatment-genotype interactions). In the present work, female CD-1 mice were exposed during pregnancy (Days 7-17) to different O3 concentrations (0, 0.4, 0.8, or 1.2 ppm); to avoid confounding by postnatal maternal effects, all litters were assigned shortly after birth to foster dams neither treated nor handled during pregnancy. The dams' food and water intake and body weight gain were depressed in a concentration-dependent fashion. Tolerance to these effects developed during continuing exposure; such tolerance was faster in the case of food than water intake. Several measures of reproductive performance, such as proportion of pregnancies carried to term, litter size, sex ratio, frequency of stillbirth, and neonatal mortality, failed to show differences between control and O3 animals. Postnatal body weight gain was slightly but significantly depressed in the 1.2 ppm offspring. Otherwise, the somatic development of O3 pups was indistinguishable from that of controls, save for a delay in eye opening; this effect, however, failed to show a significant concentration dependence. Negative results were obtained in a wide range of assessments concerning (i) the development of various reflexes and responses ("Fox battery") from birth to Day 18; (ii) ultrasonic emissions on Postnatal Days 3, 7, and 11; and (iii) activity, habituation, response to an unfamiliar object, and hyperactivity produced by a monoaminergic stimulant (d-amphetamine) at 60-61 days. The present data differ from those of a previous study on rats raised by their biological mothers after gestational exposure to O3 (1 and 1.5 ppm), which showed a substantial impairment in somatic and neurobehavioral development (R. Kavlock, E. Meyer, and C. T. Grabowski, 1980, Toxicol. Lett. 5, 3-9). This difference, be it due to species factors, to postnatal maternal effects, or to the time of occurrence of maximal O3 effects (e.g., on food and water intake) after the onset of exposure and before adaptation or tolerance, may provide significant cues for the understanding of O3 effects in pregnant and developing organisms.

This study was aimed at investigating the behavioral effects of ozone (O3) exposure in CD-1 mice. Pairs of same-sex adult male and female mice were continuously exposed for 13 days to either 0, 0.4, 0.8, or 1.2 ppm O3. The exposure apparatus consisted of a system for O3 production and delivery into four stainless-steel chambers, each equipped to contain up to 24 home cages, with continuous monitoring and recording of concentrations. Acute behavioral changes were assessed during the first hour of O3 exposure without removing animals from the chambers. The onset of exposure produced remarkable behavioral disturbances consisting of a sharp increase of several responses (rearing, sniffing, grooming, feeding, and social interactions) paralleled by a reduction of bar-holding. These changes were rapidly reversed within 1 hour, suggesting that they constituted a response to strong novel stimulation followed by habituation. Subsequently, brief sessions of videorecording of the animals' activities in freshly cleaned cages (identical to the home cages) were performed outside the chambers after 3, 7, and 10 days of exposure. These tests showed a significant concentration-dependent increase of grooming and rearing and a decrease of crossing and wall climbing. Both food and water intake showed a nonmonotonic trend over time consisting of a concentration-dependent depression (for about 3 and 7 days, respectively) followed by recovery; body weight followed a similar trend. The detailed study of various components of the animal's behavioral repertoire, showing concentration-dependent and time-dependent changes in different directions, appears to be a sensitive tool in the analysis of pollutants' effects.

A high interspecific karyotype variability has been evidenced in birds especially in Falconiformes and Strigiformes. Avian cytogenetic analysis, conventionally used for this study, presents several difficulties. We used flow cytometric analysis in order to obtain further information on the DNA patterns of different species of birds belonging to the above-mentioned orders. Our study was performed on blood samples while chicken erythrocytes and human lymphocytes, with known cytometric DNA content, were used as reference cells. The blood samples of the birds under study were stained, simultaneously to the reference cell, with a lysis-staining buffer containing propidium iodide. The nuclear DNA content of the bird samples was calculated as DNA index in relation to reference cells, and was expressed as nuclear DNA mass in picograms (pg) with respect to the standard value of 7.0 pg per human lymphocyte nucleus. The results obtained showed an interspecific variability of DNA content and evidenced the usefulness of FCM analysis as a rapid and easy tool for studying the DNA pattern of different species of birds. Moreover, our results have confirmed and extended the possibility of sex identification in species of birds characterized by sexual monomorphism by evaluating the small DNA content difference which exists between males and females.

Microalbuminuria (urinary albumin excretion between 20 and 200 micrograms/min) and endothelial dysfunction coexist in patients with essential hypertension. To evaluate whether the two phenomena are related and the determinants of that association, we recruited 10 untreated males with essential hypertension and microalbuminuria without diabetes to be compared with an equal number of matched patients with essential hypertension excreting albumin in normal amounts and 10 normal controls. The status of endothelial function was inferred from circulating von Willebrand Factor antigen (vWF), a glycoprotein secreted in greater amounts when the vascular endothelium is damaged. vWF concentrations were higher in hypertensive patients with microalbuminuria than in hypertensive patients without and controls. Individual vWF and urine albumin-excretion values were correlated (r = 0.55, p < 0.002). Blood pressure correlated with both urinary albumin excretion and vWF. Left ventricular mass index and minimal forearm vascular resistances were comparable in patients with hypertension and higher than in controls; total and low-density lipoprotein cholesterol, triglycerides, lipoprotein-a, Factor VII, and plasminogen activator inhibitor-1 did not differ. Fibrinogen was higher and creatinine clearance lower in microalbuminurics. Albuminuria in essential hypertension may reflect systemic dysfunction of the vascular endothelium, a structure intimately involved in permeability, haemostasis, fibrinolysis, and blood pressure control. This abnormality may have important physiopathological implications and expose these patients to increased cardiovascular risk.

Conditioned place preference (CPP) with both visual and tactile cues, hyperactivity, and stereotypies produced by d-amphetamine (1-10 mg/kg ip, single dose) were studied in CD-1 mice at 2, 3, and 4 weeks from birth. CPP was shown from the youngest age onward in female mice and from 3 weeks in male mice. Hyperactivity was much more pronounced in postweanlings (3 and 4 weeks) than in preweanlings. Stereotypies (at 3.3 and 10 mg/kg) occurred from the youngest age and tended to peak at 3 weeks. Stereotypies may indicate a sickness experience or "poor welfare" (G.J. Mason, 1991; A. Wall, R.E. Hinson, E. Schmidt, C. Johnston, & A. Streather, 1990) due to an aversive component of amphetamine's action. Therefore, the delayed development of fully fledged amphetamine CPP, relative to cocaine CPP (G. Laviola, G. Dell'Omo, E. Alleva, & G. Bignami, 1992), may be due to an age-dependent diminution of the positive hedonic value of the former drug by negative effects that are minimal or absent in the case of the latter drug.

It is known that predator cues (both mammalian odor or avian vocalization) elicit marked analgesia in rodents. The present experiment used olfactory cues produced by an opportunistic rodent predator snake species (100 cc of sawdust scented by Elaphe quatuorlineata). Upon exposure to snake odor (for 30 s, 20 min, or 40 min), adult mice of both the CD-1 and DBA2 strains were assessed for tail-flick or hot-plate analgesia at different times after exposure (from 0 to 40 or 45 min, respectively). In both strains, snake odor exposure induced significant alteration in the frequencies of sniffing, self-grooming, and digging, while it inhibited habituation of locomotor activity in DBA/2 mice. No analgesia emerged with both tests as a consequence of exposure to snake odor. Results suggest that although endogenous analgesia has been demonstrated by other authors to be elicited in response to cues emanating from common and widely distributed mouse predators (such as carnivores or owls), predators such as reptiles, which under natural conditions exert a limited predatory pressure on the house mouse gene pool, may only induce fear-associated behavioral responses but cannot provide ethologically relevant stimuli triggering mouse analgesia.

Prenatally administered oxazepam (OX) impairs adult radial maze performance in mice, possibly by permanent hippocampal changes. CDI mice were tested in swimming navigation, a sensitive indicator for hippocampal damage. Ten males and ten females were exposed to OX on fetal days 12-16 by maternal administration PO of 30 mg/kg/day and fostered at birth to untreated dams, while control mice received vehicle solution. All mice were tested at 8-9 weeks for ability to find a submerged platform in a fixed location (acquisition: 18 trials, 6 trials per day) and for capacity to re-orient towards a new platform position (reversal: 12 trials, 6 trials per day). OX mice showed a slight but significant impairment of swimming navigation during the initial part of training, as indicated by longer swimming paths during the fourth and fifth trial (day 1), an impairment due both to delayed habituation to the novel stressfull condition and acquisition of platform climbing but unrelated to navigational abilities. No treatment-dependent differences were observed in the reversal phase. During reversal, both OX and control females spent significantly more time in swimming across the location of the old platform. Unrelated to navigational performance, females showed a slightly but significantly higher swimming speed than males. Due to the absence of any navigational impairment, data suggest that prenatal exposure to oxazepam exerts long-term influence on adult learning capacities primarily through interaction with brain systems located outside the hippocampus.

Conditioned place preference (CPP) procedures using jointly visual and tactile cues (white compartment with a wide-mesh metal floor versus black compartment with a narrow-mesh floor) were employed to assess the ontogenetic pattern of cocaine reinforcing properties in outbred CD1 mice. A classical 11-day-long schedule, in which the drug experience occurred in the initially less-preferred compartment ("biased" procedure, Spyraki 1988), served to study cocaine (0, 1, 5, or 25 mg/kg IP repeated four times at 48 h intervals) during the early postweaning stage (21-32 days). The result was a fully-fledged CPP at all cocaine doses. A subsequent experiment used a shortened (4-day) "unbiased" CPP schedule (animals assigned at random to drug experience in one or the other compartment); this enabled an assessment of the ontogenetic pattern of the drug action (single treatment, same dose range) in pups of both sexes at three different developmental ages (14-17, 21-24, or 28-31 days). At the 25 mg/kg dose, CPP developed in animals of all ages, while the 5 mg/kg dose was effective only in 21-24 day pups and the 1 mg/kg dose was ineffective. No significant sex differences were found, but the use of the unbiased procedure enabled a demonstration of an interaction between treatment, age, and type of CS. At the preweaning stage, CPP was due mainly to an increased preference for the black/narrow-mesh compartment, while at the early postweaning stage it consisted mainly of an increased preference for the white/wide-mesh compartment; at the late postweaning stage the cue and the treatment factor did not interact.(ABSTRACT TRUNCATED AT 250 WORDS)