The Experimental Study Of The Mechanism And Morphological Observation Of The Neural Tube Defects Caused By Passive Smoking

Objectives: On the basis of established animal model of the neural tube defects caused by passive smoking, the histological alterations during generation of malformed embryos were observed by light and electron microscopy, and temporospatial changes in surface carbohydrates of the embryonic neural epithelium and its basement membrane, notochord and the mesenchyme around the neural tube were explored. And the possible mechanisms of teratogenesis caused by passive smoking were investigated.Methods: The pregnant golden hamsters were randomly divided into two groups. In the selfmade chamber for passive smoking, the animals of the treated group were exposed to smoke from embryonic day 4 to 7. At twelve o'clock and eighteen o'clock of embryonic day 8, eight o'clock of embryonic day 9 and eight o'clock of embryonic day 10 respectively, the pregnant golden hamsters of both treated group and control group were sacrificed by perfusion fixation, the uteri were removed and processed by following proceduces: The scanning electron microscope and the stereomicroscope were used to observe the effects of passive smoking on the development of golden hamsters' neural tube. Routine preparation of transmission eletron microscopy (TEM) sample, some embryos were sliced into Zum-sections with a ultramicrotome, the pyknotic cells and mitotic figures were selected by the observation of toluidine blue stained semithin sections. The other embryos were sliced into ultraslices, stained with both uranyl acetate and lead citrate, to observe the effects of passive smoking on the ultrastructure of neural epithelia with TEM. For immunohistochemistry and affinitive cytochemistry, the whole pregnant uteri were routinely embedded with paraffin, sectioned transversely in series, to display fibronectin and with concannavalin ensifomis agglutinin (ConA) and ulex europeaus agglutinin (UEA) which these lectins were used as moleculeprobes to explore the qualify, distribution and quantify of the related surface carbohydrates of the embryonic neural epithelium and its basement membrane, notochord and the mesenchyme around the neural tube.Results: 1 Ultrastructral observation shows: In embryoes of every passive passive smoking group neuroepithelial cells arranged irregularly. The intercellular spaces became wide. The apical portion of many neuroepithelial cells bulged out into the lumen and many microvilli were shorted and swollen. A lot of vacuolation appeared in the cytoplasm. The cristae of mitochondria reduced even disappeared, and some mitochondria became elongate. Irregular nuclear, split nucleolus, increased heterochromatin and karyopycnosis/karyorrhexis were observed easily. Perinuclear cisternae partially swollen a'nd embraced tangible material. Some death cell's decomposed a lot of apoptotic bodies. Most of the apoptotic bodies were found within the cytoplasm of otherwise healthy-looking or healthy cells. 2 By counting pyknotic cells and mitotic figures, we found that the number of pyknotic cells within the neuroepithelial of every passive smoking group increased more than 1 times compared with the corresponding control group (P< 0.01), besides that the cell damages, we also found that of mitotic figures were higher than each group of corresponding control (P< 0.01). 3 The embryos of passive smoking group demonstrated the obvious fetal growth retardation. The embryos of exposure to cigarette smoke were smaller than corresponding each control group. At embryonic day 10, unfusional anterior and posterior neuropores still could be found in part of the treated embryos. 4 The results of immunohisochemistry and affinitive cytochemistry staining: The results showed that the staining intensity for fibronectin in each treated group was significantly less than those in the controls (P<0.01), and for ConA and UEA in each treated group was significantly higher than those in the controls (P<0.01).Conclusions: (1) Tobacco smoking might induce excess degeneration, death, and cells loss in the neural tube and mesenchyme, thereby resulting in failure...