The Showa University Journal of Medical Sciences

令和6年度　昭和大学学士会学術奨励賞　受賞論文

35 巻 (2023) 4 号 p. 171-177

Effect of mastication on adult hippocampal neurogenesis in mice

Fumika Miyano, Junichi Watahiki, Junichi Tanaka, Tomoki Nampo, Tomohiro Taguchi, Yuta Ichikawa, Kana Nose, Kenji Mishima, Koutaro Maki

The number of neurons in the brain increases over time, even in adults. This phenomenon, known as “neurogenesis”, is associated with neural stem cells present only in the dentate gyrus of the hippocampus. However, the frequency of neurogenesis is regulated by various factorsand mastication has been suggested as one such factor. In the present study, we examined the effects of varying the input of masticatory stimulation on neural stem cells using feed with different degrees of hardness. Male C57BL/5 mice were used in a comparative study. After weaning at 3weeks old, experimental mice were fed a soft or hard diet for 4 or 11weeks. To study the dynamic behavior of neural stem cells, the expression of two markers （nestin, a neural stem/progenitor cell marker; and doublecortin, a microtubule-associated protein） was quantitatively analyzed via immunostaining, whereas gene expression was analyzed by real-time polymerase chain reaction （RT-PCR）. Immunostaining-based quantification and gene expression analysis by RT-PCR revealed the decreased expression of markers in the hippocampus in the soft diet group compared to that in the hard diet group. Based on these results, the repression of neurogenesis by a soft diet was associated with changes in neural stem cells in the hippocampus and the frequency of neurogenesis.

35 巻 (2023) 2 号 p. 39-45

Secondary bladder cancer after permanent iodine-125 brachytherapy for prostate cancer

Kidai Hirayama, Takashi Fukagai, Masashi Morita, Kazuhiko Oshinomi, Nishimura Kota, Jin Yamatoya, Yoshihiro Nakagami, Kosuke Toyofuku, Akifumi Niiya, Rei Kobayashi, Emi Nishimura, Masako Kato, Madoka Morota, Yoshinori Ito

Bladder cancer has been observed in patients after permanent iodine-125 brachytherapy （hereafter referred to as brachytherapy） for prostate cancer. We investigated secondary bladder cancer after brachytherapy. From January 2005 to March 2021, a total of 1,478 patients underwent brachytherapy for localized prostate cancer at Showa University Hospital and Showa University Koto Toyosu Hospital. A standardized incidence rate was calculated from the incidence of secondary bladder cancer after brachytherapy and compared with the national cancer registry general incidence data. The median follow-up was 4.7 years. Secondary bladder cancer occurred in 15 of 1478 patients （median age: 71 years）. The incidence was 198 cases/100,000 persons/year. The incidence was 2.84 times higher than that of Japan’s national cancer registry. In addition, as a characteristic of secondary bladder cancer, the malignancy tended to be high regardless of the depth of invasion. The relative risk between cases with a secondary bladder cancer period until occurrence of ＞5 years and cases with a secondary bladder cancer period until occurrence of ≤5 years was 1.61 times （95％ CI: 0.57-4.50）, but the difference was not significant. In this study, we found that the incidence of bladder cancer was 2.84 times higher than that of the general population of Japan, suggesting that brachytherapy increases the risk of developing bladder cancer. To our knowledge, this study is the first to compare the incidence of brachytherapy and general bladder cancer in Japan. The results of this study suggest that although brachytherapy is effective for prostate cancer, attention should be paid to the early detection of bladder cancer because of the risk of secondary cancer development.

35 巻 (2023) 2 号 p. 82-91

Characteristics of burst-generating networks released by disinhibition in the spinal cord of neonatal rats

Shu Takahashi, Yoshihiro Mikami, Makito Iizuka, Masahiko Izumizaki

Although （i） spinal cord disinhibition can cause spontaneous burst activities in the phrenic nerve and （ii） this propriospinal network can be harnessed to allow diaphragm function after a spinal cord injury, the characteristics of this network are unclear. To characterize this network, we cut the isolated spinal cord from neonatal rats aged 0-4 days into four blocks consisting of three spinal segments （C3-C5, T6-T8, L2-L4, and L6-S2）, and motor activities were recorded from C4, T7, L3, and S1 ventral roots （VRs）. Under control conditions, few spontaneous activities occurred in all VRs. When 10-µM strychnine （a broad antagonist of glycine and GABAA receptors） was applied, spontaneous burst activities were observed in all VRs, suggesting that a burst-generating network （BGN） exists in each segment. In spinal cord preparations from segments C3 to S2, local application of strychnine to the C3-C5 segments resulted in spontaneous bursts concurrently in not only the C4VR but in all other VRs. In spinal cord preparations, repetitive electrical stimulations to the phrenic afferent evoked burst activities in not only the phrenic nerve but also in other C4 and C5 spinal nerves under strychnine. In the C3-C5 block preparation, phrenic afferent stimulation failed to evoke burst activities in the phrenic motor nerve, whereas C4 spinal afferent stimulation evoked burst activities in not only the C4 and C5 spinal nerves but also in the phrenic motor nerve. Thus, it is difficult to specifically activate the BGN for the phrenic nerve in the neonatal rat spinal cord by local disinhibition of C3-C5 segments or by phrenic afferent stimulation.

35 巻 (2023) 1 号 p. 11-18

Dual Energy CT for determining the severity of acute pancreatitis

Hirotaka Hamada, Tomoki Fujii, Daisuke Kittaka, Yuichi Nakai, Hisaya Sato, Kyoichi Kato

We aimed to quantitatively compare the iodine concentration measured by Dual Energy Computed Tomography （CT） between acute and mild pancreatitis cases and to evaluate the accuracy of the severity assessment of acute pancreatitis using Dual Energy CT. The contrast CT grade based on the guidelines in Japan and definitive diagnoses were evaluated. Iodine concentrations and C-reactive protein （CRP） levels were compared between mild and severe acute pancreatitis. The CECT grading diagnosed five false negative cases out of 41 patients. Only when the CRP reached the highest level, there was a significant difference between severe and mild cases. There were significant differences between the iodine concentration of severe and mild cases. Our results demonstrated measuring iodine concentration using Dual Energy CT is useful for severity assessment of acute pancreatitis.

35 巻 (2023) 2 号 p. 63-72

Application of optical dental impression data for personal identification

Yuriko Usuda, Hikaru Izawa, Yu Kataoka, Shouji Hironaka

The identification of corpses is according to physical characteristics. Among these, teeth are often used for personal identification because they are insusceptible to post-mortempostmortem alterations. Recently, different types of digital data, like optical impressions, have been employed in dentistry. This research identified three indices on the teeth of Standard Triangled Language （STL） data collected using optical impression-taking and evaluated the possibility of personal identification by examining the area of the triangle obtained from three indices. STL data generated from intraoral plaster models （n＝140） were fabricated virtual antemortem （VAM） data. STL data collected directly from the intraoral cavity （n＝24） were employed as virtual post-mortempostmortem （VPM） data. Three indices were identified for each first premolar, second premolar, and first molar. Two techniques were devised to find the three points. The area of the triangle created utilizing the three measurement points were employed to assess the conditions under which each VPM data could be excluded from the VAM data group. Although no significant difference existed between the two techniques, one method was preferred for screening. Optimal conditions for both methods were screening carried out with two teeth, including the second premolar. In both methods, only the individual was screened out of 140 individuals when the second premolar was added in the two-teeth condition. This study demonstrated the possibility of personal identification by assessing the area obtained using three measurement points on teeth as indices, indicating a potential application in forensics in the future.

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