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Purpose This anatomic, radiographic study investigated locational differences in the C2 pedicle and isthmus [pediculoisthmic component (PIC)] and characterized its narrowest section for clinical application in posterior C2 screw fixation. Methods Structures surrounding the transverse foramina of 30 dry C2s and 10 C3s were compared morphologically. Spinal CT scans of 32 Chinese adults were subjected to volume rendering and multiplanar reconstruction to identify the narrowest C2 PIC, and correlative parameters were measured and analyzed. Results Inferior C2 and C3 structures were morphologically similar. In superior view, the C2 superior facets lay on the transverse foramen and the upper portion between superior and inferior facets was flat (average mediolateral angle, 11.1°± 2.4°). In inferior view, the posteroinferomedial portion of the C2 transverse foramen displayed a partially tubular structure (average mediolateral angle of projection, 42.6°± 4.9°). Average height and width were 11.6 and 6.9 mm. The inner medullary cavity was elliptical and the middle site of endosteal diameter was 3.3 ± 1.9 mm.Medial internal cortical bone was significantly thicker than lateral bone (P \ 0.01). Conclusions The PIC is located between superior and inferior C2 facets. The superior flat area is the isthmus and the inferomedial area connecting the inferior facet and vertebral body is the pedicle. The pedicle is partially tubular and projects posteromedially to the transverse foramen. The narrowest PIC section is the narrowest point of the C2 pedicle. Considering its thin lateral cortical bone, medial and superior pedicle screw placement and preoperative CT reconstruction are recommended.

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The nucleus of the solitary tract (nucleus tractus solitarii; NTS) is a primary center for both visceral afferents and somatic afferents. Previous experiments have demonstrated that the NTS is closely connected to the stomach and acupoints in the Yangming Stomach Meridian of Foot (ST Meridian). In this study, extracellular recording and immunochemistry methods were used to analyze the discharge of neurons and c-Fos protein expression in the NTS following acupuncture at different acupoints and a nonacupoint. A total of 104 discharging neurons were detected in the NTS of 52 rats, of which 86 provided complete data. After acupuncture at Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint, the neuron response rate in the NTS was 65.12%, 51.16%, 46.51%, 34.88% and 31.40% respectively. For neuron response rate, there was a significant difference among Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint (p < 0.01 or p < 0.05). In the other 48 rats, the number of c-Fos immunoreactive neurons in the NTS by electroacupuncture (EA) at Sibai (ST 2) group was significantly higher than that EA at other acupoints and the nonacupoint (p < 0.05 or p < 0.01). EA at both Zusanli (ST 36) and Neiting (ST 44) increased c-Fos immunoreactive neurons significantly over EA at Quanliao (SI 18) and the nonacupoint (p < 0.05 or p < 0.01), while there was no difference between EA at Quanliao (SI 18) and the nonacupoint group (p > 0.05). The experiments demonstrated that the afferent convergence in NTS are different by body surface points stimulus, which suggests that the NTS might be a primary center in the central nervous system receiving acupoints stimulus from the ST Meridian.

Up to now, accurate determination of the growth age and hiatuses of the Co-rich crust is still a difficult work, which constrains the researches on the genesis, growth process, controlling factors, regional tectonics, paleo-oceanographic background, etc. of the Co-rich crust. This paper describes our work in determining the initial growth age of the Co-rich crust to be of the late Cretaceous Campanian Stage (about 75-80 Ma), by selecting the Co-rich crust with clear multi-layer structures in a central Pacific seamount for layer-by-layer sample analysis and using a number of chronological methods, such as Co flux dating, dating by correlation with 187 Os/ 188 Os evolution curves of seawater, and stratigraphic division by calcareous nannofossils. We have also discovered growth hiatuses with different time intervals in the early Paleocene, middle Eocene, late Eocene and early-middle Miocene, respectively. These results have provided an important age background for further researches on the Co-rich crust growth process and the paleo-oceanographic environment evolution thereby revealed in the said region.central Pacific, Co-rich crust, Os isotope dating, growth hiatus