Karyotype of NIH, C57BL/6 and Razi strains of laboratory mice [Mus musculus]

The laboratory mouse is recognized as the pre-eminent model for genetic research. Awareness of chromosomal patterns of experimental animals increases their value for a variety of different fields of study. We aimed to study mitotic chromosome preparations from NIH, C57BL/6 and Razi strains of mice, which are outbred, inbred and partially inbred laboratory mice respectively. Bone marrow cells were prepared from 36 male and female mice, 12 from each strain, and stained by use of Giemsa staining and G-banding methods. Karyotyping of the samples showed that there was no difference in chromosomal numbers among the three mice strains, also the metaphase preparations of their diploid cells contained 40 chromosomes [2n = 40] and all chromosomes were telocentric. However, some differences in band tonality and the size of chromosomes were seen

[Time effect of oocyte collection from oviducton number and quality of oocyte and its effect on in vitro fertilization in rabbit]

Quality and quantity of ovum are major determinants in invitro fertilization. The aim of the present study was to determine effect of the time of oocyte collection and also distance of HCG injection to oviduct flushing on the quantity, quality and fertilizing ability of rabbit oocyte. Accordingly, sixty two adult female rabbit selected and randomly allocated to seven groups. The rabbits were superovulated with PMSG [50 IU/head] followed by HCG [45 IU/head]. Semen specimens were collected from two adult fertile male bucks using artificial vagina. Results showed, superovulation of 62 does yielded 412 oocytes [average 6. 6 oocyte/rabbit] and mean 7.8 +/- 1.7, 5.3 +/- 2.8, 5.2 +/- 2.7, 7.6 +/- 2.8, 4.3 +/- 2, 7.3 +/- 4 and 18.3 +/- 7.7 oocyte / animal for seven groups respectively. So, when flushing done after 23-30 hours of HCG injection and between hours of 19-24 of day, maximum oocyte were collected and in contrast the oocytes were minimum when flushing performed between hours of 9-14 of day at the same period, mean 18. 3 in contrast 4. 3 oocyte/rabbit respectively, this difference was significant [p<0. 01]. In 7 groups value of grade Aoocyte were 12.9, 8.1, 49.3, 26.2, 60.0, 18.2 and 54.8 percent respectively, so the difference of the first, second and sixth groups with the third, fifth and seventh groups and also forth with seventh group were high significant [p<0. 001]. From 223 oocytes were used for 27 times IVF experiments,%31 [n=69] of them were fertilized, so this value for 7 groups were 38. 5, 15. 6, 37. 6, 11. 0, 32. 0, 42. 0 and 100. 0 percent, respectively, and maximum significant difference was between seventh group with second and forth groups [p<0. 001]. Results of this study proposed that the best time for oocyte collection is hours between 19-24 of day, together with 23-30 hours after HCG injection, which produce maximum number, and fertilizable oocyte in Dutch laboratory rabbit

Study of biological characteristics and incidence of spontaneous mammary tumor in razi mice, a worthwhile model for mammarytumor, iranian origin

Razi mouse is originally established from native Iranian mice at Razi institute and is susceptible to spontaneous mammary tumor. In this study, incidence, age and predisposing factors of tumor and some of biological characteristics of this strain were studied. There were significant differences in incidence of mammary tumor in Razi virgin females as compared with normally breeding and hormone treated breeding females in p < 0.05 but was the same with virgin NMRI females foster-nursed on Razi dams. However incidence in virgin Razi females foster-nursed on NMRI dams was very lesser than three mentioned groups. All mammary tumor tissues were histopathologically diagnosed adenocarcinoma. No significant differences were found in the levels of biological factors studied in tumor bearing and nonbearing Razi mice [p < 0.05]. Our results showed that milk factor may play the most important role in compare with genetic background and hormonal stimulation for development of mammary tumor in Razi mouse. Razi strain may represent a unique model to study of mammary tumor etiology and anticancer therapy

Comparative evaluation of pregnancy rates in dutch laboratory rabbit after insemination and natural breeding

Artificial insemination [AI] is a selective method which has been used in commercial rabbitries and for research purposes. The results of pregnancy rates were observed here which were comparable with natural mating. This experiment is conducted to provide the potentials of AI in the breeding center and also to compare this technique with on going natural mating method. One hundred sexually matured Dutch does were randomly divided into two equal groups. Does from experimental group were inseminated with diluted fresh semen and single dose of 0.2 ml of GnRH analog [Receptal] to each/doe was immediately injected intramuscularly. Does of control group were naturally mated with mature Dutch bucks. The environmental conditions were same in the both groups. The results of study showed that the 62% of does in control group had developed pregnancy where as in AI group 60% were pregnant. This result indicates the conception rate is similar in both groups and differences are not statistically significant