[Application of automatic slide-dropping instrument in bone marrow chromosomal karyotyping].

OBJECTIVE: To explore the application of an automatic slide-dropping instrument in bone marrow chromosomal karyotyping. METHODS: The effects of manual and automatic dropping methods under different environmental humidity were retrospectively analyzed, and the repeatability of the automatic dropping method was analyzed. RESULTS: No statistical difference was found between the results of automatic and manual dropping methods under the optimum ambient humidity and high humidity (P > 0.05). At low humidity, there was a statistical difference between the two methods (P < 0.05). With regard to the repeatability, the coefficient of variations of the automatic dropping method for the number of split phases, the rate of good dispersion and the rate of overlap were all lower than those of the manual dropping method. A statistical difference was also found in the number of split phases (P < 0.05) but not in the discrete excellent rate and overlapping rate between the two methods (P > 0.05). CONCLUSION: Better effect can be obtained by the automatic dropping instrument. It is suggested to gradually replace manual work with machine.

Amyloid deposition in a mouse model humanized at the transthyretin and retinol-binding protein 4 loci.

Familial amyloidotic polyneuropathy is an autosomal dominant disorder caused by a point mutation in the transthyretin (TTR) gene. The process of TTR amyloidogenesis begins with rate-limiting dissociation of the TTR tetramer. Thus, the TTR stabilizers, such as Tafamidis and Diflunisal, are now in clinical trials. Mouse models will be useful to testing the efficacy of these drugs. Although several mouse models have been generated, they all express mouse Rbp4. Thus, human TTR associates with mouse RBP4, resulting in different kinetic and thermodynamic stability profiles of TTR tetramers. To overcome this problem, we previously produced humanized mouse strains at both the TTR and Rbp4 loci (Ttr hTTRVal30 , Ttr hTTRMet30 , and Rbp4 hRBP4 ). By mating these mice, we produced double-humanized mouse strains, Ttr hTTRVal30/hTTRVal30 :Rbp4 hRBP4/hRBP4 and Ttr hTTRVal30/Met30 :Rbp4 hRBP4/hRBP4 . We used conventional transgenic mouse strains on a wild-type (Ttr +/+ :Tg[6.0hTTRMet30]) or knockout Ttr background (Ttr-/-:Tg[6.0hTTRMet30]) as reference strains. The double-humanized mouse showed 1/25 of serum hTTR and 1/40 of serum hRBP4 levels. However, amyloid deposition was more pronounced in Ttr hTTRVal30/Met30 :Rbp4 hRBP4/hRBP4 than in conventional transgenic mouse strains. In addition, a similar amount of amyloid deposition was also observed in Ttr hTTRVal30/ hTTRVal30 :Rbp4 hRBP4/ hRBP4 mice that carried the wild-type human TTR gene. Furthermore, amyloid deposition was first observed in the sciatic nerve without any additional genetic change. In all strains, anti-TTR antibody-positive deposits were found in earlier age and at higher percentage than amyloid fibril deposition. In double-humanized mice, gel filtration analysis of serum revealed that most hTTR was free of hRBP4, suggesting importance of free TTR for amyloid deposition.