[A study on heart weight and electrocardiogram of germfree, ex-germfree and conventional ICR mice (author's transl)]

The heart weight of germfree mice has been reported to be lighter than that of conventional mice. The difference in heart function between these mice, however, has not been well investigated. In the present study, we recorded ECGs of germfree, ex-germfree and conventional mice anesthetized with pentobarbitone sodium and weighed the hearts of these animals. On ECGs, there was no significant difference between germfree and conventional mice except QT and PP intervals, which were shorter in male germfree mice than those in male conventional mice. It was found that the heart weight of germfree mice was significantly lighter than that of conventional mice in both sexes. It was concluded that although the heart weight between germfree and conventional mice was different, the heart function evaluated using the ECG was not.

[Use of CO2 euthanasia cabinet for experimental animals (author's transl)]

The process of CO2 euthanasia on mouse, rat, guinea pig and rabbit was observed using a CO2 euthanasia cabinet. The cabinet was filled with CO2 gas and the caged animal was placed into the cabinet. These animals quietly collapsed and their respiratory movement ceased within 25--225 seconds. A-V block was the first arrhythmia recognized on ECG in all cases. The arrhythmia recorded on ECG included complete A-V block, A-V dissociation, ventricular escape rhythm, atrial fibrillation, ventricular flutter and ventricular fibrillation. It could be concluded that euthanasia was satisfactorily performed on these species by means of the CO2 euthanasia cabinet.

[Mechanical properties of microfilled composite resins (author's transl)]

The various mechanical properties of seven microfilled composite resins were evaluated, comparing with two conventional composite resins. The following results were obtained. 1) Though microfilled composite resins were more excellent than conventional ones on surface roughness after polishing or brushing, but they were inferior to conventional ones on the resistance to brushing abrasion. 2) Tensile, compressive and bending strength were dependent on inorganic filler content and properties of matrix resin. Particularly, their mechanical properties in the wet condition were strongly influenced by whether matrix resin was hydrophilic or hydrophobic. Compared with conventional composite resins, microfilled ones contained 30 to 40 wt% of filler had lower values of tensile and bending strength, and near values of compressive strength. While, microfilled ones contained 50 to 60 wt% of filler had higher values of compressive strength, and near values of tensile and bending strength, compared to conventional ones. 3) Modulus of elasticity and hardness were mainly dependent on inorganic filler content. Moduli of elasticity of microfilled composite resins were about 25 to 33% of them of conventional ones, and hardnesses of microfilled ones were approximately 50% of them of conventional ones except some materials. Hardnesses of microfilled composite resins with 50 to 60 wt% of filler were similar to them of conventional ones.

Bacterial flora of ex-germfree mice after oral inoculation of feces from various species of conventional animals

Emulsions of fresh feces from a conventional mouse, rabbit, dog or cynomolgus monkey were administered orally to germfree and conventional ICR mice. Various fecal floras bearing a striking resemblance in pattern to those in the inoculant became established in the inoculated ex-germfree mice. Reinoculation of these ex-germfree mice with fecal emulsions from a conventional mouse made 21 days after the original inoculation (conventionalization) led to alteration of their floras to the indigenous pattern of conventional mice. The administration of feces from the conventional animals of different species did not appreciably modify the fecal flora of conventional mice. The results indicate that intestinal flora of animals is determined in the first stage by that of the contaminants, but this would be altered later under the predominant influence of the various host factors.

Cyclic changes in cervical mucus and LH levels in the bonnet macaque (Macaca radiata)

Vaginal cytology, cervical mucus, and serum LH were studied in adult female bonnet macaques (Macaca radiata). Ovulation was observed by laparoscopy. The cytology of vaginal smears and ferning pattern of cervical mucus were not well demarcated. Water content of cervical mucus increased gradually before ovulation and decreased soon after ovulation. The disc gel electro-Serum LH phoresis of cervical mucus revealed four bands. A single mid-cycle peak in concentration was detected in most cases. Basal LH concentration of approximately 500 ng/ml and LH surge of 2,000-2,500 ng/ml were observed between days 14 and 16.