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Background The compound 6:2 chlorinated polyfluorinated ether sulfonic acids (6:2 Cl-PFESA) has been demonstrated abilities of strong bioaccumulation and placental barrier penetration, and it can also cross the blood-brain barrier. However, the mechanism of its neurodevelopmental toxicity in offspring induced by early-life exposure is still unknown. Objective To explore effects of 6:2 Cl-PFESA on the growth and the α-amino-3-hydroxy-5-methylisoxazole-4-propionic (AMPA) receptor gene expression in the hippocampus of offspring mice by establishing a 6:2 Cl-PFESA exposure animal model. Methods Thirty Kunming pregnant mice were randomly divided into five groups: control group, and 2, 10, 50, and 250 μg·L−1 6:2 Cl-PFESA exposure groups. The treatment groups were exposed to designed doses of 6:2 Cl-PFESA through drinking water from the first day of gestation until the end of lactation. The pups were weaned on postnatal day (PND) 21, and continued to be exposed to 6:2 Cl-PFESA through drinking water. Birth weight and body length of the offspring were recorded. Offspring mice were anesthetized and sacrificed respectively on PND7, PND21, and PND35, then their hippocampus was peeled from harvested brain tissue. The ultrastructure of hippocampus was observed via transmission electron microscopy; and the expression of AMPA receptors GluR1, GluR2, and GluR3 in the hippocampus was evaluated by real-time reverse transcription polymerase chain reaction. The learning and memory ability of the PND35 mice was measured by Morris water maze test before they were sacrificed. Results The birth weights and the lengths of the pups in the 10, 50, and 250 μg·L−1 6:2 Cl-PFESA exposure groups were (2.23±0.36), (1.92±0.20), (1.88±0.31) g, and (33.73±0.98), (32.91±1.30), (32.52±2.07) mm, respectively, which were lower than those in the control group, (2.78±0.35) g and (36.46±2.34) mm (P<0.05), respectively. The results of Morris water maze showed that the escape latencies in the orientation navigation experiment on the 4th day in the 250 μg·L−1 6:2 Cl-PFESA exposure group and on the 5th day in the 10, 50, and 250 μg·L−1 6:2 Cl-PFESA exposure groups were longer than those in the control group (P<0.05). In the space exploration experiment, the times of crossing platform in the 50 and 250 μg·L−1 6:2 Cl-PFESA exposure groups were decreased when compared with the control group (P<0.05), and the time of staying in the target quadrant of the 250 μg·L−1 6:2 Cl-PFESA exposure groups were also decreased (P<0.05). Via transmission electron microscopy, compared with the control group, the postsynaptic density was decreased and the synaptic cleft width was widened on PND35 in the 250 μg·L−1 6:2 Cl-PFESA exposure group. The mRNA expression levels of GluR1, GluR2, and GluR3 in the hippocampus of pups exposed to 250 μg·L−1 6:2 Cl-PFESA during different developmental stages were significantly lower than those in the control group (P<0.05). Except for the 2 μg·L−1 6:2 Cl-PFESA exposure group on PND7, the 6:2 Cl-PFESA exposure inhibited the mRNA expression levels of GluR1, GluR2, and GluR3 in the hippocampus of pups at different developmental stages (P<0.05). Among them, the 6:2 Cl-PFESA exposure during early development resulted in the highest decrease in the expression levels of GluR1 and GluR2 mRNA in the hippocampus of pups on PND7; GluR3 mRNA expression level in the hippocampus of the exposed pups on PND21 showed the maximum inhibitory effect; the expression levels of GluR1, GluR2, and GluR3 mRNA all showed the least decrease in the hippocampus of the exposure groups on PND35. Conclusion Early-life exposure to 6:2 Cl-PFESA may affect the growth and development of offspring mice, alter the hippocampal synaptic structure, and influence the learning and memory abilities, which may be related to their inhibitory effects on the expression levels of AMPA receptor subunits GluR1, GluR2, and GluR3 genes in the hippocampus of offspring mice at various developmental stages.
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Objective@#To investigation the situation of cold chain on vaccine in parts of Zhejiang Province and to provide recommendations for the management.@*Methods@#From October to December, 2016, we each selected an immunization clinic in Cangnan County of Wenzhou, Yongkang City of Jinhua, Jianggan District of Hangzhou. Temperature recorder and vaccine viral monitor (VVM) labels were used to monitor the cold chain during all the storage and transportation process. In Jianggan District, we use optical density sensor to detected 20 VVM labels every time when the vaccine was stock in and out.@*Results@#In total, 54 958 records were collected by temperature recording devices in all the three immunization clinic. 275 records exceeded the temperature limit required for store and transportation, of which 270 (98.2%) were above 8 ℃ and 5 (1.9%) were under 2 ℃. Excessive temperature exposure mainly occurred during the transportation (38.2%, n=105), followed by storage process in CDCs at different levels (26.2%, n=72), stock in and out (20.7%, n=50) and storage in the refrigerators in immunization clinics (14.9%, n=41). The average optical density difference between VVM labels and the reference circular decreased from 0.404 to 0.344 when the vaccines were delivered from the Zhejiang provincial CDC to immunization clinics. The color of VVMs did not significantly changed before use.@*Conclusions@#The potential risk of vaccine cold chain in the monitoring sites is over-temperature. The weak links of cold chain management include the transportation, storage process, and stock in and out.