基于超声内镜的智能胰腺癌变检测网络

为对超声内镜检测返回的胰腺图像实现智能癌变诊断,将经典分类识别网络AlexNet和SE注意力机制进行结合,提出的SE-AlexNet网络可以准确检出癌变图像,判别正常图像所属胰腺部位。为验证该算法的可靠性与优胜性,在自制数据集下的一系列比较实验,包括基础网络AlexNet与其他经典分类网络的模型比较实验,以及在不同位置插入不同注意机制改进得到的各种模型的比较实验。结果表明：SE-AlexNet模型总体精确率和召回率可达99.56%和98.69%,对于癌变图像,检测精确率和召回率为100%,能够为现实超声内镜胰腺癌检查实现有效的辅助诊断。     

Role of glutamic acid decarboxylase in the pathogenesis of type 1 diabetes

Glutamic acid decarboxylase (GAD) is considered to be one of the strongest candidate autoantigens involved in triggering β-cell-specific autoimmunity. The majority of recent onset type 1 diabetes patients and prediabetic subjects have anti-GAD antibodies in their sera, as do nonobese diabetic (NOD) mice, one of the best animal models for human type 1 diabetes. Immunization of young NOD mice with GAD results in the prevention or delay of the disease as a result of tolerizing autoreactive T cells. Autoimmune diabetes can also be prevented by the suppression of GAD expression in antisense GAD trans genic mice backcrossed with NOD mice for seven generations. These results support the hypothesis that GAD plays an important role in the development of T-cell-mediated autoimmune diabetes. However, there is some controversy regarding the role of GAD in the pathogenesis of diabetes. Whether GAD truly plays a key role in the initiation of this disease remains to be determined. The examination of the development of insulitis and diabetes in β-cell-specific GAD knockout NOD mice will answer this remaining question. Received 12 April 2002; received after revision 24 May 2002; accepted 27 May 2002 RID="*" ID="*"Corresponding author.     

胰酶水解干酪素的动力学行为

研究了胰酶水解干酪素制备蛋白胨过程中胰酶在不同温度下的失活行为,以及底物浓度对反应速率和平衡的影响,ｐＨ对反应浓度和平衡的影响。胰酶在４０℃下４ｈ基本不丧失水解大分子的活力;在５０℃,ｍｉｎ、５５℃,１００ｍｉｎ、６０℃,９０ｍｉｎ完全丧失对大分子的水解活性。胰酶短时间在高温下丧失的活性,当其返回到４０℃时可部分恢复。底物和产物对反应有抑制作用。底物初始浓度高,最终平衡转化率低。当ｐＨ８时的反应速     

Development and hormonal control of thioredoxin and the thioredoxin-reductase system in the rat liver during the perinatal period

Summary The development and hormonal regulation of thioredoxin and of the thioredoxin-reductase system were investigated during the perinatal period in rat liver. An immunological procedure was developed in order to quantify thioredoxin in fetal and neonatal hepatocytes. Both immunoreactive thioredoxin and thioredoxin-reductase activity appeared on day 16.5 of pregnancy. The level of immunoreactive thioredoxin increased during the late fetal period, and its level was the same 24 h after birth. Moreover, its development was not subjected to hormonal regulation by corticosteroids and glucagon. In contrast, thioredoxin-reductase activity increased 3 times during the late fetal period and presented a marked increase 24 h after birth. In the absence of glucocorticoids there was no increase in the level of thioredoxin reductase, while administration of hydrocortisone acetate and glucagon to fetuses prematurely evoked its activity. This study suggests that if thioredoxin acts physiologically, this activity is related to the state of reduction of the molecule rather than to the total concentration in the liver.     

Bombesin promotes pancreatic growth in suckling rats

Summary The pancreatic growth promoting effect of long term administration of bombesin was investigated in suckling rats. The authors showed that bombesin given in 10 g/kg b.wt doses s.c. every 8 h for 10 days from the day of parturition stimulated pancreatic growth: it increased pancreatic weight, protein and DNA content, trypsin and amylase activity and trypsin/DNA ratio. Conclusion: Bombesin is an effective stimulator of pancreatic growth in suckling rats.     

Ontogenic development of peptide hormones in the mammalian fetal pancreas

Summary The ontogeny of insulin, glucagon, PP and somatostatin in the mammalian fetal pancreas has been examined in recent years largely by immunocytochemistry and in some instances by radioimmunoassay. Complete ontogenic data are available only for the rat, human pig and sheep. Figure 3 compares the time of appearance of the endocrine cell-types within the fetal pancreas when the periods of gestation of the four species are converted to a uniform scale. The striking ontogenic difference in the rat probably reflects the immaturity of the rodent fetus at birth compared with the human, pig and sheep. In the fetal pancreas, differences in cell number of glucagon and PP cells in the dorsal and ventral lobes become apparent from an early gestational period. Factors responsible for the functional and structural maturation of the fetal pancreatic endocrine cells and the processes involved in pancreatic organogenesis are poorly understood. Studies in these areas would have clinical implications since it may be possible in the future to employ agents for selective replication of fetal -cells for transplantation in patients with Type I diabetes, bearing in mind that such cells must have the capacity to respond to normal stimuli and repressors when transplanted. The presence of the other islet cell-types may be obligatory for these appropriate responses. This would require a more complete knowledge of those factors which produce the normal selectivity of the four hormonal cell-types.     

Glucagon and pancreatic polypeptide immunoreactivities co-exist in a population of rat islet cells

Summary In mammalian pancreas, glucagon and pancreatic polypeptide have been shown to be present in distinct cell types. The present communication reports that, in rat pancreas, in addition to glucagon and pancreatic polypeptide cell populations, there is a small population of cells which contain both glucagon and pancreatic polypeptide immunoreactivities.     

水飞蓟宾通过上调P15~(INK4B)和P21~(WAF1/CIP1)活化JNK诱导人胰腺癌细胞G1期阻滞及细胞凋亡

目的:探讨水飞蓟宾对胰腺癌As PC-1细胞的增殖抑制作用及其作用机制.方法:MTT法和克隆形成抑制实验观察水飞蓟宾对人胰腺癌As PC-1细胞的增殖抑制作用,碘化丙锭(PI)单染色检测细胞周期改变,Annexin V-FITC/PI双染流式细胞术检测细胞凋亡水平,Western blotting检测细胞周期及细胞凋亡相关蛋白的表达.结果:不同浓度的水飞蓟宾对胰腺癌As PC-1细胞的生长均有抑制作用,且呈剂量-效应和时间-效应关系(P0.05),水飞蓟宾作用于As PC-1细胞48、72 h的IC50浓度分别为224.20、87.25μmol/L;克隆形成抑制实验显示,随着水飞蓟宾浓度增加,As PC-1细胞克隆形成逐渐减少.细胞周期检测结果显示,随着水飞蓟宾浓度的增加,胰腺癌As PC-1细胞出现明显G1期阻滞;水飞蓟宾处理组细胞的周期蛋白Cyclin D1、Cyclin E2、Cyclin A、Cyclin B1表达下降,细胞周期蛋白激酶CDK4、CDK6表达不变,细胞周期素依赖性蛋白激酶抑制蛋白P15INK4B、P21WAF1/CIP1表达升高,与流式检测的结果相一致.不同浓度水飞蓟宾作用48 h后,出现明显的凋亡细胞群;同时发现Caspase-9、Caspase-3活化降解,Caspase3下游效应蛋白PARP出现切割条带.JNK蛋白表达增加并磷酸化活化,Bcl-2蛋白家族中抗凋亡蛋白Bcl-2、Bcl-x L、Mcl-1表达明显降低,促凋亡蛋白Bax表达基本不变,BH3-only蛋白Bclxs、Bid、Bim表达增加.结论:水飞蓟宾明显抑制胰腺癌细胞增殖,通过诱导P15INK4B、P21WAF1/CIP1表达阻滞细胞周期在G1期,并通过诱导JNK活化激活线粒体细胞凋亡途径,进而诱导胰腺癌As PC-1细胞凋亡.     

自由和固定化猪胰脂肪酶在有机相中催化丁酸甲酯和四氢糠醇的酯交换反应

本文用自由和聚苯乙烯载体固定化猪胰脂肪酶在有机相中催化丁酸甲醋和四氢糠醇的酯交换反应．研究了不同有机溶剂、底物浓度、含水量、加酶量、温度及振荡速度等对反应的影响，对比了酶固定化前后的催化性能．结果表明，用疏水性交联聚苯乙烯载体固定化猪胰脂肪酸能减少扩散限制，固定化酶在有机相中催化活性比自由酶高约２５％．     

Ca2+ signals induced from calcium stores in pancreatic islet β cells

In single rat pancreatic β cells, using fura-2 microfluorometry to measure [Ca²⁺]i response upon different stimuli, the ways of calcium regulation have been studied. When the extracellular calcium concentration was 2.5 mmol/L, either 60 mmol/L KCl, 20 mmol/L D-glucose or 0.1 mmol/L tolbutamide induced increase in [Ca²⁺]i. Such increase in [Ca²⁺]i was absent when the same stimuli were applied under zero extracellular calcium. These results indicate that the increase of [Ca²⁺]i is induced by the activation of voltage-dependent calcium channels in β cells. The manifold forms of [Ca²⁺]i change induced by glucose imply that the effects of glucose are complex. 5 mmol/L caffeine or 5 mmol/L MCh increase the [Ca²⁺]i, which is independent of the external calcium, suggesting that [Ca²⁺]i can be regulated by Ca²⁺ release from not only the IP₃-sensitive but also the ryanodine sensitive calcium stores in β cells. The latency of Ca responses for IP₃ pathway (5 s) is faster than that for ryanodine pathway (30 s). It is concluded that there are multiple calcium stores in rat pancreatic β cells.