细胞因子对肝干细胞分化调节的研究进展

细胞因子是调节肝干细胞分化的重要因素之一,它通过一系列信号途径,诱导和调节肝干细胞逐步分化为成熟肝细胞和胆管上皮细胞,并发育成具有功能的肝脏,同时还在成体肝脏的损伤修复中发挥重要作用。此文就细胞因子对肝干细胞的分化和损伤修复过程的调节作用及其机制作一综述。     

肝脏干细胞调控机制的研究进展

肝脏干细胞在正常肝脏中处于静息状态 ,但当肝脏受到严重损伤和或肝细胞的再生能力受到抑制时 ,肝脏干细胞便活化、增殖并分化为成熟肝细胞及胆管细胞以发挥代偿作用。尽管目前对肝脏干细胞的来源及肝组织内的准确定位还不明确 ,但众多研究己证实肝内肯定存在肝脏干细胞 ,其活化后的子代细胞为卵圆细胞 ,卵圆细胞具备多向分化潜能 ,体内外实验证实其可以分化为肝细胞、胆管细胞、胰腺及肠型上皮 ,1999年Ｐｅｔｅｒｓｏｎ研究证实骨髓细胞可以转化为肝细胞 ,其他学者对骨髓干细胞的体内移植及体外培养的研究中也证实了Ｐｅｔｅｒｓｏｎ的观点…     

细胞因子对肝干细胞分化调节的研究进展

细胞因子是调节肝干细胞分化的重要因素之一，它通过一系列信号途径，诱导和调节肝干细胞逐步分化为成熟肝细胞和胆管上皮细胞，并发育成具有功能的肝脏，同时还在成体肝脏的损伤修复中发挥重要作用。此文就细胞因子对肝干细胞的分化和损伤修复过程的调节作用及其机制作一综述。     

人胎肝干细胞的体外培养及诱导分化

为体外分离培养和诱导分化人胎肝干细胞 ,从原代分离培养人胎肝干细胞集落 ,免疫细胞化学鉴定细胞集落分子标志物的表达 ;在体外特定细胞因子作用下诱导干细胞定向分化为成熟肝脏细胞 ,对其生物学特性进行初步鉴定。结果 ,从人胎肝组织中成功分离表达AFP、Albumin、Cytokeratin等标志物的胎肝干细胞集落 ,在体外特定细胞因子作用下肝干细胞可定向分化为成熟肝脏细胞。因此人胎肝中同样存在具有干细胞特性的原始细胞 ,体外可定向分化为成熟肝细胞。人胎肝干细胞的分离培养对于生物型人工肝的制备及其深入研究奠定了良好的基础     

肝干细胞分化机制及其分子免疫学研究

肝干细胞的可塑性及其分化机制的研究在基础和临床应用等方面均有重要意义。一方面，肝干细胞可能参与肝脏损伤的修复与重建，研究肝干细胞的分化机制有助于阐明肝脏的发育机制；另一方面，肝干细胞分化为具有功能的成熟肝细胞，将为肝细胞移植和生物型人工肝提供重要的细胞来源。肝干细胞分化过程和机制较为复杂，肝干细胞分子免疫学的研究将成为肝干细胞研究的一个重要内容，现将其有关近况做一介绍。     

肝干细胞的基础及应用研究

肝脏具有强大的再生能力．很早就有人提出肝千细胞存在的假说。1958年Wilson和Leduc在研究小鼠营养性肝损伤的修复机制中发现，增殖的毛细血管细胞（终末胆管细胞）具有干细胞样特性，可分化为肝细胞及胆管细胞，于是首次提出原始肝细胞的概念。这一研究提示肝内可能存在具有双向或多向分化潜能的肝干细胞或肝祖细胞。从定义上讲，肝干细胞应当具有无限增殖能力及多向分化潜能。体内有多种细胞符合肝千细胞的特征，如肝脏胚胎发育过程中出现的胎肝干细胞及成肝细胞、成年肝内存在的兼件肝干细胞及其子代细胞卵圆细胞、特定情况下的成熟肝细胞和骨髓／造血干细胞等。     

肝脏疾病的细胞治疗

生理状态下肝实质损伤后再生肝细胞有三个来源：成熟肝细胞、肝源性干细胞(如胆管树及管周围细胞)、循环及骨髓源性干细胞。循环及骨髓源性可塑性干细胞可通过转分化(特殊表位，受体配基依赖性)或与肝前体细胞融合的方式使肝细胞的数量增加。一些非生理干细胞如骨髓间充质细胞、胚胎干细胞可能用于先天遗传和后天获得性肝脏疾病。此综述了我们对这些种类细胞的新近理解以及它们在细胞移植、生物人工肝、细胞因子／化学增活素生理修复治疗途径、基因治疗中应用的可能途径。关于干细胞及祖细胞在肝脏再生中的作用曾有争议。肝脏实质细胞不同于胃肠道上皮、表皮及骨髓等细胞具有周期短、持续更新代谢等特点，其再生中没有明显的干细胞参与过程。通过对人类及其他脊椎动物肝细胞有丝分裂的观察证实了这些细胞成分具有再生潜能并具有完成肝脏强大再生的能力。然而仅仅在近些年，基于人类及啮齿类动物肝脏再生的大量研究才使这一观点广为接受。     

肝脏干细胞研究进展

干细胞是不分化而长期生存,具有自我更新能力且保持多种分化潜能的一种细胞群。从功能上定义,肝脏干细胞（hepatic stemcell,HSC）是指在特定的条件下能增殖分化为有功能的肝脏组织的细胞。根据肝脏干细胞的存在位置,分为内源性肝脏干细胞和外源性肝脏干细胞2种。内源性肝脏干细胞存在于肝脏组织本身,是未分化的、多潜能的、具有干细胞以及肝细胞或胆管细胞标记的、非肝实质细胞的上皮细胞前体细胞,目前认为卵圆细胞和小肝细胞属于这一类。外源性肝脏干细胞,本身不存在于肝脏内,包括：骨髓细胞、胰腺细胞、胚胎干细胞、脐带血细胞等,但在特定的微环境中可以分化为肝细胞和（或）胆管上皮细胞。     

肝干细胞

1958年wilson和Leduc在研究小鼠营养性肝损伤的修复机制中发现,增殖的毛细胆管细胞(终末胆管细胞)具有干细胞样特性,可分化为肝细胞及胆管细胞,于是首次提出原始肝脏细胞的概念。这一研究提示肝内可能存在具有双向或多向分化潜能的肝干细胞或肝祖细胞,因此引起人们的极大兴趣。从定义上讲,肝干细胞应具有无限增殖能力及多向分化的潜能。     

肝干细胞的生物学作用

干细胞是具有自我复制能力和多分化功能的一组细胞。近年来 ,除了造血系统、皮肤等再生力强的组织外 ,在神经系统、骨、肝脏等组织也相继发现了干细胞。本文主要对肝干细胞及其生物学作用进行综述。1　肝干细胞肝干细胞首先是由Ｗｉｌｏｓｎ及Ｌｅｄｎｃ在 195 8年提出的。 2 0世纪 80年代中期Ｚａｊｉｃｅｋ提出了“流肝学说” ,并得到认证。该学说认为肝细胞在肝小叶门脉区生成 ,推向中心静脉区域 ,逐渐成熟至凋亡。他们用3Ｈ -胸腺嘧啶标记分裂期细胞 ,被标记的肝细胞从门脉区向中心静脉区域迁移 ,速度 1 4 4μｍ/天 ,历时 2 0 1天。这提…     

The immunoneuroendocrine role of melatonin

Abstract: A tight, physiological link between the pineal gland and the immune system is emerging from a series of experimental studies. This link might reflect the evolutionary connection between self-recognition and reproduction. Pinealectomy or other experimental methods which inhibit melatonin synthesis and secretion induce a state of immunodepression which is counteracted by melatonin. In general, melatonin seems to have an immunoenhancing effect that is particularly apparent in immunodepressive states. The negative effect of acute stress or immunosuppressive pharmacological treatments on various immune parameters are counteracted by melatonin. It seems important to note that one of the main targets of melatonin is the thymus, i.e., the central organ of the immune system. The clinical use of melatonin as an immunotherapeutic agent seems promising in primary and secondary immunodeficiencies as well as in cancer immunotherapy. The immunoenhancing action of melatonin seems to be mediated by T-helper cell-derived opioid peptides as well as by lymphokines and, perhaps, by pituitary hormones. Melatonin-induced-immuno-opioids (MHO) and lymphokines imply the presence of specific binding sites or melatonin receptors on cells of the immune system. On the other hand, lymphokines such as -γ-interferon and interleukin-2 as well as thymic hormones can modulate the synthesis of melatonin in the pineal gland. The pineal gland might thus be viewed as the crux of a sophisticated immunoneuroendocrine network which functions as an unconscious, diffuse sensory organ.     

Response of rat pineal melatonin to calcium, magnesium, and lithium is circadian stage dependent

Abstract: Herein we documented the response of pineal melatonin production to electrolytes known to be effective on pineal function in view of a possible circadian stage dependence. We studied the release of melatonin by perifused rat pineal glands at 2 different circadian stages corresponding to the middle of the light and dark periods, i.e., respectively, 7 and 19 HALO (Hours After Light Onset, L:D = 12:12). The initial efflux rates were, as expected, much higher in the perifusates of glands removed from rats sacrificed during the dark phase than of those removed during the light phase. After 3 hr of perifusion, melatonin release reached similar levels which were found constant up to the 8th hr of perifusion, whatever the circadian stage. Perifusion of the glands with physiological concentrations for the rat of calcium (5.2 mmol/1) and magnesium (1.34 mmol/1) resulted in a stimulatory effect on the pineal glands removed from rats sacrificed in the middle of the dark period (19 HALO), whereas no effects were observed on the pineal glands removed from rats sacrificed during the light (7 HALO). Lithium (0.28 and 0.55 mmol/1) was ineffective on melatonin release in pineal glands removed 7 and 19 HALO. Our results show differences in the initial efflux rates of melatonin and in the response of perifused pineal glands to calcium and magnesium according to the circadian stage.     

Changes in connexin43, the gap junction protein of astrocytes, during development of the rat pineal gland

Abstract: The abundance of gap junctions between rat pineal astrocytes formed by connexin43 (Cx43) was studied during development. Levels and distribution of Cx43 were measured by immunoblotting and indirect immunofluorescence, respectively. The amount of Cx43 in cells located within the gland was low until about the 7th postnatal day and increased to adult values between the 14th and 21st days postpartum. Although astrocytes, recognized by their vimentin immunoreactivity, were scarce before birth, they were abundant by the 7th postnatal day suggesting that the low levels of Cx43 found at this age corresponded to a low expression of this protein. Localization of the immunoreactivity to Cx43 and vimentin showed a close correlation, indicating that mature or immature pineal astrocytes form gap junctions made of Cx43. Since Cx43 levels attained their adult values at about the time the innervation and the functional state of the gland reached maturity (2–3 weeks after birth), it is proposed that astrocyte gap junctions are involved in the function of the adult rat pineal gland.     

Conservative management of perforated duodenal diverticulum： A case report and review of the literature

Duodenal diverticula are a relatively common condition. They are asymptomatic, unless they become complicated, with perforation being the rarest but most severe complication. Surgical treatment is the most frequently performed approach. We report the case of a patient with a perforated duodenal diverticulum, which was diagnosed early and treated conservatively with antibiotics and percutaneous drainage of secondary retroperitoneal abscesses. We suggest this method could be an acceptable option for the management of similar cases, provided that the patient is in good general condition and without septic signs.     

Presence of immunoreactive growth hormone and prolactin in the ovine pineal gland

Abstract: The use of antisera raised against bovine growth hormone (GH) and ovine prolactin (PRL) enabled the detection of related immunoreactive (ir) sequences of proteins in ovine pineal tissue. The isolation of PRL-like ir-material was accomplished using a 0.25 M ammonium sulphate (pH 5.5) extraction followed by ethanol precipitation, whereas the resulting 2.0 M ammonium sulphate (pH 7.0) precipitate contained a GH-like immunoreactivity. Gel chromatography of the GH-like immunoreactivity (Sephadex G-100) indicated the presence of several GH-like fragments ranging in the M_r range of 7,000 to 55,000. Analyses of the PRL-like ir-material found in pineal tissue on HPLC using a TSK 545-DEAE column led to the resolution into a single peak of immunoreactivity. A single peak of activity was also observed following chromatofocusing and hydrophobic interaction chromatography of the ir-peak from the TSK 545-DEAE column. The PRL-like ir-material inhibited the binding of [¹²⁵I]ovine PRL-S14 to anti-ovine PRL antibodies without showing an affinity for binding to anti-rat PRL or anti-bovine GH antibodies. Scatchard analysis of the binding of pineal PRL-like ir-material and pituitary ovine PRL-S14 to liver membranes from day-20 pregnant rats revealed similar affinity constants (K_a of 4.7 ± 0.2 × 10⁹ M^-1). In addition, the replication of Nb 2 Node rat lymphoma cells was stimulated by pineal PRL-like ir-material, an effect known to be specific for lactogenic hormones. The pineal PRL-like immunoreactivity appeared on sodium dodecyl sulfate polyacrylamide gels as a single major band of M_r 24,000. The functional status of PRL-and GH-like ir-material in the ovine pineal remains to be determined, but evidence is presented that the overall protein synthesis rate of the rat pineal responded to circulating concentrations of PRL.     

Microbiology of human immunodeficiency virus anorectal disease

PURPOSE: Individuals who are seropositive for the human immunodeficiency virus are at high risk for opportunistic infection and anorectal disorders. Little prospective information is available regarding anorectal pathogens in these patients. METHODS: One hundred sixty-three HIV-seropositive patients presented to the colorectal clinic between 1989 and 1992. Forty-seven (29 percent) patients were thought to have an infectious process and were prospectively studied using a standardized multiculture protocol. RESULTS: Mean age was 33 (range, 19–59) years. All were male; high-risk behavior accounted for 87 percent of HIV transmissions. Presenting complaints included anorectal pain (79 percent), pus per anum (28 percent), and blood per anum (26 percent). Examination revealed perianal tenderness (60 percent), condyloma (38 percent), perianal ulcers (38 percent), and anal fissures (34 percent). Sixty-six sets of cultures were performed; 28 patients had one set, 15 had two sets, and 4 had three sets. Thirty-two of these 47 patients (68 percent) had positive cultures including herpes (50 percent), cytomegalovirus (25 percent),Neisseria gonorrhoeae (16 percent), chlamydia (16 percent), acidfast bacilli (2 percent), and others (9 percent). Six of 32 patients with positive cultures had more than one organism cultured. Sixteen (50 percent) patients with positive cultures were treated medically, 8 (25 percent) were treated surgically and 8 (25 percent) were treated with both modalities. Sixty-one procedures were performed on 17 patients for condylomata. Eighteen patients had 20 procedures for abscesses, 50 percent of whom had positive cultures for other than common bowel flora; all improved. Fourteen patients underwent 33 procedures for perianal fistulas.Mycobacterium fortuitum was cultured from one patient who required 13 procedures for abscesses and fistulas. Forty-five (96 percent) patients were followed for an average of 12.5 months ±2.9 SEM (range, 1–94 months). Symptoms were improved or resolved in 22 of 32 (69 percent) patients with positive cultures and in 11 of 13 (84 percent) with negative cultures. CONCLUSIONS: Specific pathogens may often be identified in human immunodeficiency virus-seropositive patients with anorectal disorders if aggressively sought. Although patients without specific pathogens identified may be expected to improve with planned empiric treatment, positive identification allows more directed therapy.