Comparison of neurotransmitter levels, physiological conditions, and emotional behavior between isolation-housed rats with group-housed rats.

Brain monoaminergic neurotransmitters, such as dopamine (DA), serotonin (5-HT), and noradrenaline (NA), play crucial roles in neuronal and physiological functions, including social behaviors. Isolation housing may induce behavioral and neurochemical abnormalities in rats, although its influence on neurotransmitter levels remains obscure. This study investigated the influence of isolation- or group-housing on core body temperature (Tcore ), locomotor activity (ACT), emotional behavior, and neurotransmitter levels in male Wistar rats. Behavioral changes were monitored using the open field test (OFT) and social interaction test (SIT). After 4 weeks, brain tissues were collected to quantify 5-HT, DA, and NA concentrations. Body weight and basal Tcore during both the light and dark phase were higher in isolation-housed than in group-housed rats, although no significant difference was seen in ACT. No significant differences were observed during the OFT. Isolation-housed rats showed increased line crossing and decreased social behavior during the SIT. Isolation-housed rats exhibited decreased levels of 5-HT in the caudate putamen and amygdala, and elevated and decreased NA levels in the paraventricular hypothalamic nucleus and hippocampus, respectively. However, DA levels were unaffected. Thus, housing environments may affect brain areas that regulate various neuronal and physiological functions, such as memory, stress responses, and emotional behavior.

Effect of heat acclimation on anxiety-like behavior of rats in an open field.

To mitigate the impacts of heat exposure, animals can take some actions to maintain their core body temperature, such as heat acclimation; however, the effect of heat acclimation on anxiety-like behavior in an open field is still not understood. The purpose of this study was to examine the anxiety-like behavior of heat acclimated rats in a temperate or heated open field. After being raised in a 23 °C environment for one week, male Wistar rats were exposed to a heated environment (32 °C) for 3 h (3H), 14 days (14D), or 28 days (28D), with free access to food and water, and compared with rats reared in a temperate environment (23 °C; Cont). After heat exposure, behavioral changes were monitored using an open field test (OFT) in a heated (32 °C) or temperate environment (23 °C). Compared with those in the Cont group, the body weights of rats in the 14D and 28D groups were lower. The OFT in the heated environment showed that grooming time was longer in 3H and 14D rats. In the temperate environment, grooming time was longer in all the heated groups. Rats from the 3H and 28D groups spent longer time in the center square when tested in the temperate environment. Rearing activity increased in 28D rats in the temperate environment, while the number of line crossings did not differ significantly between the heated groups and the two open fields. These results suggest that heat acclimation affected not only the physiological index such as core body temperature but also the anxiety-like behavior, mainly in the temperate open field. These changes might be beneficial when rats are faced with an open field.

Three-dimensional microscopic elemental analysis using an automated high-precision serial sectioning system.

The elemental composition and microscopic-level shape of inclusions inside industrial materials are considered important factors in fracture analytical studies. In this work, a three-dimensional (3D) microscopic elemental analysis system based on a serial sectioning technique was developed to observe the internal structure of such materials. This 3D elemental mapping system included an X-ray fluorescence analyzer and a high-precision milling machine. Control signals for the X-ray observation process were automatically sent from a data I/O system synchronized with the precision positioning on the milling machine. Composite specimens were used to confirm the resolution and the accuracy of 3D models generated from this system. Each of the two specimens was composed of three metal wires of 0.5 mm diameter braided into a single twisted wire that was placed inside a metal pipe; the pipe was then filled with either epoxy resin or Sn. The milling machine was used to create a mirror-finish cross-sectional surface on these specimens, and elemental analyses were performed. The twisted wire structure was clearly observed in the resulting 3D models. This system enables automated investigation of the 3D internal structure of materials as well as the identification of their elemental components.

Difference in the brain serotonin and its metabolite level and anxiety-like behavior between forced and voluntary exercise conditions in rats.

Physical exercise is beneficial to both physical and mental health, though it is unclear whether voluntary and forced exercise have the same effects. We investigated the effects of chronic forced and voluntary wheel running on brain levels of serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and anxiety-like behavioral change in rats. Forty-eight rats were randomly assigned to standard cages (sedentary control: SC); voluntary exercise (free running on a wheel, V-EX); voluntary limited exercise (wheel available only 1 h per day, VL-EX); and forced exercise (running on a motorized wheel, F-EX). After 4 weeks, rats either underwent the open field test (OFT) or their 5-HT and 5-HIAA levels were measured in the major serotonergic neural cell bodies and projection areas. 5-HT and 5-HIAA levels in the dorsal and median raphe nuclei were increased in the V-EX, but not in the VL-EX and F-EX groups, compared with the SC group. In the paraventricular hypothalamic nucleus and caudate putamen, only 5-HT levels were increased in the V-EX group. Interestingly, in the amygdala, only 5-HIAA levels were significantly increased in the V-EX group. Conversely, we found that F-EX rats showed no significant 5-HT changes and increased anxiety-like behavior. VL-EX did not have significant beneficial effects on any of the experimental parameters. These data suggest that only unlimited voluntary exercise stimulates the serotonergic system and suppresses anxiety-like behavior.

Detection of the EGFP sequence in breast muscle of 3-year-old chicken after transfection using sonoporation.

In our continuing effort to generate transgenic chickens, sonoporation was chosen to insert an exogenous gene into the chicken genome. An EGFP expression vector (pCAG-EGFPac) and microbubbles were injected into the central disc of stage-X blastoderm or the germinal crescent of stage-4 embryos, followed by ultrasonic vibration. Nineteen chicks out of 108 treated embryos hatched, six females and six males out of these 19 chicks grew to sexual maturity and two females and three males lived for 3 years. Genomic DNA from 17 out of 35 gonads from embryos and chicks that died before sexual maturity was EGFP-positive by PCR. No EGFP sequence was detected in the genomic DNA of 322 embryos from six sexually mature females and the semen from four sexually mature males by PCR. When genomic DNA was obtained from various tissues of five 3-year-old chickens, the EGFP sequence was amplified from the genomic DNA of the breast muscle of a female (No. 85). The above sequence was subjected to DNA sequencing and verified to be the EGFP sequence. These results showed that sonoporation is an effective tool for the transduction of exogenous genes into chicken embryos for the generation of transgenic chickens.