OBJECTIVE To set up normal ranges for indexes in embryo-fetal development toxicity studies in Sprague-Dawley(SD)rats and to establish a background database to provide reference for the embryo-fetal development toxicity evaluation of drugs.METHODS The data on embryonic develop-ment and fetal growth from embryo-fetal development toxicity studies(11 items)conducted by our center between 2013 and 2022 was statistically analyzed,involving 205 pregnant rats and 3037 fetuses in total,with the mean and standard deviation,coefficient of variation and 95%confidence interval calculated.The indexes included body mass,body mass gain and food consumption during pregnancy,pregnancy outcomes(pregnancy rate,average corpora lutea,average Implant sites,average live conceptuses,live conceptuse rate,resorption rate and dead conceptuse rate),fetal growth and development(fetal mass,placental mass and sex ratio),appearance abnormality rate,visceral abnormality rate,and skeletal abnormality rate.RESULTS The mass of pregnant rats trended up during gestation,with significant increases in the late period.Food consumption increased along with gestation.Caesarean section was conducted on gestation day 20,and the pregnancy rate was 93.2%.The average corpora lutea,Implant sites and live conceptuses were 18.0±3.2,15.9±2.8 and 14.8±3.0,respectively.The live conceptuse rate was 93.4%while the total dead embryo rate was 6.6%.The average mass of fetuses and placenta were respectively 3.6±0.3 and(0.6±0.3)g,and the fetal sex ratio(male/female)was 0.94.The incidence of fetal appearance abnormalities was about 0.2%,and that of soft tissue abnormalities was approximately 0.8%.The rate of skeletal abnormalities was about 1.2%,with higher incidence of non-ossification and incomplete ossification mostly identified on sternum and hyoid bone.The numbers of ossifications of metacarpal bones,metatarsal bones and sacrococcygeal vertebrae were 7.0±0.7,8.0±0.1 and 7.4±0.5,respectively.The rate of ossification of sternumⅠtoⅣwas higher,with an average of about 98.6%-99.9%.The ossification rates of sternum Ⅴ and Ⅵ were(68.0±28.4)%and(82.8±23.9)%.CONCLUSION The background database of indexes in the embryo-fetal development toxicity study on SD rats is established for our GLP laboratory,which provides reference for reproductive toxicity studies.

The adenosine 5'-triphosphate (ATP)-binding cassette (ABC) transporter, IrtAB, plays a vital role in the replication and viability of Mycobacterium tuberculosis (Mtb), where its function is to import iron-loaded siderophores. Unusually, it adopts the canonical type IV exporter fold. Herein, we report the structure of unliganded Mtb IrtAB and its structure in complex with ATP, ADP, or ATP analogue (AMP-PNP) at resolutions ranging from 2.8 to 3.5 Å. The structure of IrtAB bound ATP-Mg2+ shows a "head-to-tail" dimer of nucleotide-binding domains (NBDs), a closed amphipathic cavity within the transmembrane domains (TMDs), and a metal ion liganded to three histidine residues of IrtA in the cavity. Cryo-electron microscopy (Cryo-EM) structures and ATP hydrolysis assays show that the NBD of IrtA has a higher affinity for nucleotides and increased ATPase activity compared with IrtB. Moreover, the metal ion located in the TM region of IrtA is critical for the stabilization of the conformation of IrtAB during the transport cycle. This study provides a structural basis to explain the ATP-driven conformational changes that occur in IrtAB.
Siderophores/metabolism* ; Iron/metabolism* ; Mycobacterium tuberculosis/metabolism* ; Cryoelectron Microscopy ; Adenosine Triphosphate/metabolism* ; ATP-Binding Cassette Transporters

Heme/metabolism* ; Cryoelectron Microscopy ; Membrane Transport Proteins ; Escherichia coli Proteins/metabolism*