共查询到20条相似文献,搜索用时 15 毫秒
1.
Ishiwata I Tokeida Y Iguchi M Ishiwata C Kiguchi K Yasumoto S Sato K Tachibana T Hashimoto H Ishikawa H 《Human cell》2001,14(4):283-291
Eleven early embryonic stem (EES) cell lines were established using a new novel method. Two cell stage embryos from the ddY mouse strain were cultured in alpha-MEM supplemented with 10% fetal calf serum (FCS) and embryotrophic factors (ETFs) and allowed to develop to the trilaminal germ disc embryonic stage. Only small round cells (EES cells) were isolated by the colony isolating technique and subsequently cultured in the same medium containing the ETFs and leukemia inhibitory factors (LIF-10 ng/ml). The newly established embryonic stem (ES) cells isolated from inner cell mass of blastocysts differentiated from two cell stage embryo in culture. The EES and ES cell lines were maintained in an undifferentiated state using Ham's F12 medium supplemented with 10% FCS and 1 ng/ml of LIF. The EES cells maintained their normal genetic and morphological features as well as their potential to differentiate into a broad spectrum of cell types as well as their ability to contribute to all cell lineages in chimeric mice. Moreover, these cell lines changed and differentiated into various kinds of cells by removing LIF and by the addition of ETFs to the vitro culture system. All 11 EES cell lines and 3 ES cell lines formed embryoid bodies; however, cell line EES-4 formed tube-like structures which extended, anastomosed with each other, and finally formed networks when the LIF were absent. Primitive germ organ-like structures composed of 3 germ layers were recognized in the cultures following the administration of ETFs. In conclusion, the new method devised by us is a novel, easy and reliable technique for establishing EES cell lines. 相似文献
2.
Organogenesis of heart-vascular system derived from mouse 2 cell stage embryos and from early embryonic stem cells in vitro 总被引:2,自引:0,他引:2
Regenerative medical treatment with embryonic stem cells (an ES cell) is a goal for organ transplantation. Structures that are tubular in nature (i.e. blood capillaries) were induced from early embryonic stem (EES) cells in vitro using embryotrophic factor (ETFs). In addition, cardiac muscle cells could be identified as well. However, differentiation of EES cells into a complete cardiovascular system was difficult because 3 germ layer primordial organs are directed embryologically in various ways and it is not possible to guide only cardiovascular organs. Thus, we introduced ETFs after the formation of an embryoid body and were successful in cloning cell clusters that beat, thus deriving only cardiovascular organs. The application of this to the treatment of various cardiovascular diseases is promising. 相似文献
3.
M. Van Puymbroeck M. E. M. Kuilman R. F. M. Maas R. F. Witkamp L. Leyssens A. S. J. P. A. M. Van Miert L. Hendriks D. Vanderzande P. Adriaensens M. -P. Jacobs J. Raus 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,728(2):1289
The metabolism of the illegal growth promoter ethylestrenol (EES) was evaluated in bovine liver cells and subcellular fractions of bovine liver preparations. Incubations with bovine microsomal preparations revealed that EES is extensively biotransformed into norethandrolone (NE), another illegal growth promoter. Furthermore, incubations of monolayer cultures of hepatocytes with NE indicated that NE itself is rapidly reduced to 17α-ethyl-5β-estrane-3α,17β-diol (EED). In vivo tests confirmed that, after administration of either EES or NE, EED is excreted as a major metabolite. Therefore, it was concluded that, both in urine and faeces samples, EED can be used as a biological marker for the illegal use of EES and/or NE. Moreover, by monitoring EED in urine or faeces samples, the detection period after NE administration is significantly prolonged. These findings were further confirmed by three cases of norethandrolone abuse in a routine screening program for forbidden growth promoters. 相似文献
4.
An early embryonic stem cell line, EES-6 cells, was established from 2-cell stage embryos of ddY mice. The cells were maintained in an undifferentiated state with D-MEM/F12 medium supplemented with 10% fetal bovine serum (FBS) (GM) and 1 ng of leukemia inhibitory factor (LIF) without any feeder cells. In this study, EES cells were cultured with a medium containing embryotrophic factors (ETFs) which promoted the differentiation of EES cells into white and brown adipocytes-like cells for a period of 5 days. Lipid droplets in brown adipocyte-like cells were stained with Sudan III; however, large lipid-like droplets in white or brown adipocyte-like cells were unstained with either Sudan III or alcian blue. These findings have numerous possibilities for therapeutic use such as regeneration of skin and wound healing. 相似文献
5.
Alejandro Fábregas-Tejeda Francisco Vergara-Silva 《Theorie in den Biowissenschaften》2018,137(2):169-184
The Extended Evolutionary Synthesis (EES) debate is gaining ground in contemporary evolutionary biology. In parallel, a number of philosophical standpoints have emerged in an attempt to clarify what exactly is represented by the EES. For Massimo Pigliucci, we are in the wake of the newest instantiation of a persisting Kuhnian paradigm; in contrast, Telmo Pievani has contended that the transition to an EES could be best represented as a progressive reformation of a prior Lakatosian scientific research program, with the extension of its Neo-Darwinian core and the addition of a brand-new protective belt of assumptions and auxiliary hypotheses. Here, we argue that those philosophical vantage points are not the only ways to interpret what current proposals to ‘extend’ the Modern Synthesis-derived ‘standard evolutionary theory’ (SET) entail in terms of theoretical change in evolutionary biology. We specifically propose the image of the emergent EES as a vast network of models and interweaved representations that, instantiated in diverse practices, are connected and related in multiple ways. Under that assumption, the EES could be articulated around a paraconsistent network of evolutionary theories (including some elements of the SET), as well as models, practices and representation systems of contemporary evolutionary biology, with edges and nodes that change their position and centrality as a consequence of the co-construction and stabilization of facts and historical discussions revolving around the epistemic goals of this area of the life sciences. We then critically examine the purported structure of the EES—published by Laland and collaborators in 2015—in light of our own network-based proposal. Finally, we consider which epistemic units of Evo-Devo are present or still missing from the EES, in preparation for further analyses of the topic of explanatory integration in this conceptual framework. 相似文献
6.
探究国家重点生态功能区生态-经济-社会系统耦合协调的演化特征,对实现可持续发展目标、建设美丽中国有重要意义。运用耦合协调模型、剪刀差方法、耦合度模型以及VAR模型对2007—2019年阿勒泰地区EES系统耦合协调度的动态演化进行分析。结果表明:(1)2007—2019年阿勒泰地区整体耦合协调度呈现不断上升趋势,由2007年的中度失调(0.271)向2019年的轻度失调(0.371)演进,生态系统与经济系统、社会系统的发展水平呈现“X”型变动趋势,经济系统与社会系统持续上升,而生态系统略微下降。(2)经济系统与社会系统、生态系统与社会系统演化速率的剪刀差在2014年以后出现较大幅度的波动,而生态系统与经济系统演化速率的剪刀差趋于稳定态势,生态系统与经济系统、经济系统与社会系统的耦合度呈现出由无序到有序的初始过渡。(3)由脉冲响应函数及方差分解可得,阿勒泰地区EES系统耦合协调水平的提升是三系统共同作用的结果,前期主要由社会系统、经济系统驱动,后期主要依赖生态系统的改善。研究表明:国家重点生态功能区应着重减轻经济系统对社会系统和生态系统的胁迫强度,进而实现三者的协同发展。 相似文献
7.
Electrical and electronic components in the automotive sector: Economic and environmental assessment
Juan C. Alonso Julia Dose Günter Fleischer Kate Geraghty André Greif Julio Rodrigo Wulf-Peter Schmidt 《The International Journal of Life Cycle Assessment》2007,12(5):328-335
Background Aims and Scope Automotive electrical and electronic systems (EES) comprise an area that has grown steadily in importance in the past decade
and will continue to gain relevance in the foreseeable future. For this reason, the SEES project (Sustainable Electrical &
Electronic System for the Automotive Sector) aims to contribute to cost-effective and eco-efficient EES components. Scenarios
for the recovery of automotive EES are defined by taking into consideration the required improvements in EES design and the
development and implementation of new technologies. The research project SEES is funded by the European Commission (Contract
no. TST3-CT-2003-506075) within the Sixth Framework Programme, priority 6.2 (see 〈www.sees-project.net〉 for more information).
This paper presents the findings of an assessment of the environmental and economic improvements for automotive EES from a
system perspective, taking into account all life cycle steps.
Methods Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) case studies have been employed within the SEES project to define
optimum design and end-of-life scenarios. These case studies have been applied to two selected EES components: an engine wire
harness and a smart junction box, both manufactured by LEAR and assembled in an existing Ford car model. The component design
has a significant impact on the product system and its processes, including its use and end-of-life (EOL) phase. For each
of the analysed components, two potential design alternatives have been compared with the original design, based on designers’
recommendations from the status quo scenario results. These include the use of alternative wiring systems with a reduced copper
content (flat flexible cable), lead-free solder alloys and new fixation mechanisms to facilitate disassembly. The overall
EOL scenario determines the technologies of processes that must be modelled within the EOL phase of a product system. The
analysed end-of-life scenarios include: status quo car recycling and two alternatives: 1. disassembly for specific EES component
recycling; 2. advanced post-shredder recycling of shredding residues. The influences of the different design and EOL treatment
scenarios on the LCA and LCC results have been analysed.
Results The most dominant life cycle phases for the LCA results are manufacturing (including raw material extraction and manufacturing
of materials and components) and the use-phase. Similarly, manufacturing was the predominant phase during the LCC study. Disassembly
costs were shown to be significant during the EOL phase. Among the analysed design alternatives, the highest environmental
improvement potential were gained from the use of alternative wiring systems with reduced weight and copper content, but with
slightly increased life cycle costs. Smaller differences of the results were determined for the different end-of-life scenarios.
Discussion The results of the EOL scenario depend on the component in question. The influence of variations in process data, model choices,
e.g. which LCIA model was used for calculating the Human Toxicity Potential (HTP), which inventory data for copper production
was used and other variables have been assessed in the sensitivity analysis. The sensitivity analysis demonstrates a strong
dependency of results for HTP on the selected model. The presented results are based on a public report of the SEES project.
The study has undergone a critical review by an external expert according to ISO 14040, § 7.3.2.
Conclusions The environmental impacts during the life cycle of the analysed products are generally most strongly influenced by material
production and the use phase of the products. In comparison, improvements during the EOL phase have only a very limited potential
to reduce environmental impacts. The studied design changes displayed clear environmental advantages for (lighter) flat, flexible
cables. Whereas, the lead-free solder design alternatives showed a slight increase in some environmental impact categories.
The application of these design changes has been limited in some cases by technical issues.
Recommendations and Perspectives Focussing only on end-of-life improvements cannot be recommended for automotive EES products. A life-cycle perspective should
be utilised for assessing improvements in individual life cycle stages of a product. The presented results will be an input
for Eco-design guidelines for automotive EES, to be developed at a later stage within the SEES project.
ESS-Submission Editor: Dr. Lester Lave (II01@andrew.cmu.edu) 相似文献
8.
J H Rombout C P van der Grinten F M Binkhorst J J Taverne-Thiele H Schooneveld 《Histochemistry》1986,84(4-6):471-483
A large number of antisera mainly raised against mammalian hormones are tested immunocytochemically on the GEP-endocrine system of mouse and fish (Barbus conchonius). The endocrine pancreas of mouse and fish appeared to contain the same four endocrine cell types; insulin-, glucagon-, PP- and somatostatin-immunoreactive cells. In mouse about 13 GEP endocrine cell types are distinguished: 1. insulin-, 2. somatostatin-, 3. glucagon-, 4. PP-, 5. (entero)glucagon-/PP-like, 6. CCK-like, 7. substance P-, 8. neurotensin-, 9. VIP-, 10. gastrin-, 11. secretin-, 12. beta-endorphin-, 13. serotonin-immunoreactive cells. Based on this and a previous study at least 13 GEP endocrine cell types seems to be present in stomachless fish: 1-9 as described for mouse, 10. (entero)glucagon-like, 11. met-enkephalin, 12. VIP-like, 13. unspecific immunoreactive endocrine cells. Coexistence of glucagon and PP-like peptides is found in the gut and pancreas of mice and in the gut of B. conchonius. In mouse pancreas and fish gut, endocrine cells showing only PP- or glucagon-like immunoreactivity are found too. In mouse stomach some endocrine cells showing only PP-immunoreactivity are demonstrated. In the same region coexistence of C-t-gastrin- and FMRF-amide-immunoreactivity is found in endocrine cells. The importance of these phenomena are discussed. Enteric nerves immunoreactive with antisera raised against substance P and GRP are found in mouse, against somatostatin and met-enkephalin in both mouse and fish and against VIP in fish. 相似文献
9.
10.
几种激素在鳜胃肠道内分泌细胞中存在的免疫细胞化学证据 总被引:24,自引:2,他引:22
用链酶亲和素-生物素过氧化物酶(Strept Avidin-Biotin-Complex,SABC)免疫细胞化学方法,使用4种兔抗消化 道激血清对鳜胃肠道中的内分泌细胞进行鉴别和定位。结果在鳜鱼胃的贲门、幽门及肠道中均发现不同程度地存在着生长抑素和五羟色胺免疫活性内分泌细胞。在鳜的贲门上皮和贲门腺之间,幽门上皮和幽门腺之间均分布有生长抑素免疫活性阳性细胞,在贲门腺和幽门腺处的分布较密。这些含五羟色胺的肽能神经元具有典型的APUD(Amine Precursor Uptake and Decarboxylation)细胞特征,提示鱼类的胃肠道同哺乳动物的胃肠道一样富含肽能神经元;为神经-内分泌系统的研究提供有力的形态学依据,另外两种抗血清-高血糖素和胃泌素的免疫细胞化学染色在鳜的胃肠道的各部位均未发现阳性反应。 相似文献
11.
The cerebral nervous and midgut endocrine systems of the larval corn earworm, Helicoverpa zea, were examined using light microscopy and immunocytochemistry for RF-amide family peptides. Immunoreactivity for a mosquito neuropeptide, Aedes Head Peptide-I (Aea-HP-I,pERPhPSLKTRFa), is widely distributed in this lepidopteran. Immunostaining for Aea-HP-I is localized (1a) in perikarya and axons of the brain, the subesophageal ganglion, and the first thoracic ganglion, (b) in peripheral axons innervating muscles of the midgut, and (2) in numerous midgut endocrine cells. Aea-HP-I-associated activity generally occurs as a subset of FMRF-amide (FMRFa; a molluscan cardioactive peptide) immunoreactivity. Cross-reactivity studies indicate that Aea-HP-I and FMRFa immunoreactivities are heterogeneous in the cerebral nervous system and in axons innervating the muscles of the midgut, but may be homogeneous in midgut endocrine cells. Radioimmunoassay for Aea-HP-I reveals immunoreactivity in hemolymph, as well as in extracts of midguts and heads. 相似文献
12.
《Theriogenology》2013,79(9):1887-1900
Throughout the previous century, the production, use and, as a result, presence of chemicals in the environment increased enormously. Consequently, humans and animals are exposed to a wide variety of chemical substances of which some possess the ability to disrupt the endocrine system in the body, thereby denominated as “endocrine disrupting chemicals” (EDCs) or “endocrine disruptors”. Because the reproductive system is a target organ for endocrine disruption, EDCs are postulated as one of the possible causes of human subfertility. Within the reproductive system, the ovarian follicle can be considered as an extremely fragile microenvironment where interactions between the oocyte and its surrounding somatic cells are essential to generate a fully competent oocyte. In this review, we explore how EDCs can interfere with the well-balanced conditions in the ovarian follicle. In addition, we highlight the bovine ovarian follicle as an alternative in vitro model for EDC and broader toxicology research. 相似文献
13.
Kaori Tano Akiko Oyabu Yasura Tashiro Naoki Kamada Naoko Narita Fumio Nasu Masaaki Narita 《Histochemistry and cell biology》2010,134(1):53-57
Manserin is a recently characterized 40-amino acid neuropeptide derived from secretogranin II, a protein belonging to the
chromogranin family. Although the physiological roles of manserin have not been elucidated to date, manserin has been shown
to distribute in not only the brain but also the endocrine system such as the pituitary and adrenal glands, suggesting its
role in the endocrine system. The present study aimed to explore the occurrence and distribution of manserin in the rat pancreas
using an immunohistochemical technique with a polyclonal antibody against rat manserin. Immunoreactivity for manserin was
readily detected in almost whole islets of Langerhans whereas not at all in the exocrine pancreas. Manserin-expressing cells
were not colocalized with the glucagon-secreting cells (α cells), whereas they colocalized with insulin-secreting cells (β
cells) and somatostatin-secreting cells (δ cells), although their intracellular distribution was different. These results
indicate that manserin, occurring in the endocrine pancreas, may have a potential role in the endocrine system. 相似文献
14.
免疫细胞内源性儿茶酚胺的免疫调节作用 总被引:2,自引:0,他引:2
机体内儿茶酚胺(catecholamines,CAs)包括去甲肾上腺素(norepinephrine,NE)、肾上腺素(epinephrine,E)和多巴胺(dopamine,DA)。CAs由神经元和内分泌细胞合成和分泌,其主要功能是调节心血管、呼吸和消化等内脏活动。近三十年来的研究说明,CAs也参与调控机体的免疫功能,但CAs的这种免疫调节作用一般视为神经和内分泌系统调节的介导作用。然而,近年来的研究发现,免疫细胞也能合成CAs,这是对传统观念的一种补充和提高。免疫细胞内存在经典的CAs代谢途径,既有合成CAs的酪氨酸羟化酶(tyrosine hydroxylase,TH)又有降解CAs的单胺氧化酶(monoamine oxidase,MAO)和儿茶酚氧位甲基移位酶(catechol-O-methyl transferase,COMT)。免疫细胞合成的内源性CAs可以调控细胞的增殖、分化、凋亡和细胞因子生成等多种免疫功能。CAs的这些作用可能主要通过自分泌或旁分泌途径作用于免疫细胞上相应受体和细胞内环磷酸腺苷(cyclicAMP,cAMP)实现。细胞内氧化应激机制可能也参与免疫细胞内源性CAs的免疫调节作用。此外,一些自身免疫性疾病如多发性硬化、风湿性关节炎可能也与免疫细胞内CAs的代谢异常有关。上述发现不仅为免疫系统有可能成为除神经和内分泌系统以外的第三个CA能系统提供了证据,而且为免疫系统内源性CAs的功能意义拓展了认识。 相似文献
15.
I. H. W. M. Rombout C. P. M. van der Grinten F. M. Peeze Binkhorst J. J. Taverne-Thiele H. Schooneveld 《Histochemistry and cell biology》1986,84(4-6):471-483
Summary A large number of antisera mainly raised against mammalian hormones are tested immunocytochemically on the GEP-endocrine system of mouse and fish (Barbus conchonius). The endocrine pancreas of mouse and fish appeared to contain the same four endocrine cell types; insulin-, glucagon-, PP- and somatostatin-immunoreactive cells.In mouse about 13 GEP endocrine cell types are distinguished 1. insulin-, 2. somatostatin-, 3. glucagon-, 4. PP-, 5. (entero)glucagon-/PP-like, 6. CCK-like, 7. substance P-, 8. neurotensin-, 9. VIP-, 10. gastrin-, 11. secretin-, 12. -endorphin-, 13. serotonin-immunoreactive cells.Based on this and a previous study at least 13 GEP endocrine cell types seems to be present in stomachless fish: 1–9 as described for mouse, 10. (entero)glucagon-like, 11. met-enkephalin, 12. VIP-like, 13. unspecific immunoreactive endocrine cells.Coexistence of glucagon and PP-like peptides is found in the gut and pancreas of mice and in the gut of B. conchonlus. In mouse pancreas and fish gut, endocrine cells showing only PP-or glucagon-like immunoreactivity are found too. In mouse stomach some endocrine cells, showing only PP-immunoreactivity are demonstrated. In the same region coexistence of C-1-gastrin-and FMRF-amide-immunoreactivity is found in endocrine cells. The importance of these phenomena are discussed.Enteric nerves immunoreactive with antisera raised against substance P and GRP are found in mouse, against somatostatin and met-enkephalin in both mouse and fish and against VIP in fish.In honour of Prof. P. van Duijn 相似文献
16.
Development of a new xenoestrogen screening system using fission yeast Schizosaccharomyces pombe 总被引:4,自引:0,他引:4
Endocrine disrupters refer to environmental or chemical compounds, which interfere with the endocrine system of organisms. In this study, our aim was to develop a screening method to detect xenoestrogen (an endocrine disrupter that is commonly encountered in our daily life) by using fission yeast Schizosaccharomyces pombe. Although the yeast (the simplest eukaryotic cell) has no endocrine system, estrogen receptors that are created to express in the yeast cell can be activated by estrogen in a similar manner to mammalian cells. First, in order to express the human estrogen receptor (hER) in the yeast cell, we constructed a yeast expression vector that contained hER (pREP42MHN-hER). In the yeast cells that are transformed with the pREP42MHN-hER vector, estrogen receptors could recognize xenoestrogen, which allowed the determination of the presence of xenoestrogen in any given sample. Furthermore, we constructed a yeast strain that contained an estrogen responsive element (ERE) that fused with the Escherichia coli LacZ gene (pERE-LacZ) as a reporter for binding of xenoestrogen with the estrogen receptor. Since this vector system allows determination of the presence and level of xenoestrogen with simple procedures, it is expected that they can serve as an efficient assay system to detect xenoestrogen. 相似文献
17.
M Thompson K A Fleming D J Evans R Fundele M A Surani N A Wright 《Development (Cambridge, England)》1990,110(2):477-481
There has been considerable debate about the ontological origin of gut endocrine cells as being either from the neural crest (or primitive epiblast) or from the endodermal stem cell. We have attempted to define the ontological origin of endocrine cells by applying an experimental system that uses a marker to identify one of the two phenotypes present in chimaeric mice as suggested by Ponder et al. (1985). This study involved two separate experiments. The first made use of the unique staining properties of Dolichos biflorus agglutinin (DBA), a lectin that binds to the N-acetyl galactosamine sugar residues present on the surface of C57Bl mouse gut, but absent from RoRIII mouse gut, in C57Bl----RoIII mouse chimaeras at the ultrastructural level. A four-stage procedure for staining at the EM level was developed. Although mature villous endocrine cells stained for DBA, immature endocrine cells did not, either in the positive crypts of chimaeric mouse gut or in gut from C57Bl positive controls. Thus a second marker was chosen. This experiment combined immunocytochemistry (to identify gastric antral gastrin cells chosen as a representative neuroendocrine cell) with in situ DNA hybridization for the mouse male chromosome repeat sequence PY 353 (to identify XY cells) in XX----XY chimaeric mice. This study showed that the sex chromosomal pattern in the gastrin cells parallels that of other cells in the same gastric gland and therefore are clonal with them. This suggests that gut endocrine cells share a common stem cell with other epithelial cell lineages in the antrum and are endodermally derived. 相似文献
18.
Direct evidence for the pancreatic lineage: NGN3+ cells are islet progenitors and are distinct from duct progenitors 总被引:57,自引:0,他引:57
The location and lineage of cells that give rise to endocrine islets during embryogenesis has not been established nor has the origin or identity of adult islet stem cells. We have employed an inducible Cre-ER(TM)-LoxP system to indelibly mark the progeny of cells expressing either Ngn3 or Pdx1 at different stages of development. The results provide direct evidence that NGN3+ cells are islet progenitors during embryogenesis and in adult mice. In addition, we find that cells expressing Pdx1 give rise to all three types of pancreatic tissue: exocrine, endocrine and duct. Furthermore, exocrine and endocrine cells are derived from Pdx1-expressing progenitors throughout embryogenesis. By contrast, the pancreatic duct arises from PDX1+ progenitors that are set aside around embryonic day 10.5 (E9.5-E11.5). These findings suggest that lineages for exocrine, endocrine islet and duct progenitors are committed at mid-gestation. 相似文献
19.
Takashima S Adams KL Ortiz PA Ying CT Moridzadeh R Younossi-Hartenstein A Hartenstein V 《Developmental biology》2011,(2):85-172
In this paper we have investigated the developmental–genetic steps that shape the entero-endocrine system of Drosophila melanogaster from the embryo to the adult. The process starts in the endoderm of the early embryo where precursors of endocrine cells and enterocytes of the larval midgut, as well as progenitors of the adult midgut, are specified by a Notch signaling-dependent mechanism. In a second step that occurs during the late larval period, enterocytes and endocrine cells of a transient pupal midgut are selected from within the clusters of adult midgut progenitors. As in the embryo, activation of the Notch pathway triggers enterocyte differentiation and inhibits cells from further proliferation or choosing the endocrine fate. The third step of entero-endocrine cell development takes place at a mid-pupal stage. Before this time point, the epithelial layer destined to become the adult midgut is devoid of endocrine cells. However, precursors of the intestinal midgut stem cells (pISCs) are already present. After an initial phase of symmetric divisions which causes an increase in their own population size, pISCs start to spin off cells that become postmitotic and express the endocrine fate marker, Prospero. Activation of Notch in pISCs forces these cells into an enterocyte fate. Loss of Notch function causes an increase in the proliferatory activity of pISCs, as well as a higher ratio of Prospero-positive cells. 相似文献
20.
The term neuroendocrine has been used to define cells that secrete their products in a regulated manner, in response to a specific stimulus. The neuroendocrine system includes neurons and endocrine cells sharing a common phenotypic program characterized by the expression of markers such as neuropeptides, chromogranins, neuropeptide processing enzymes SPC2 and SPC3 (subtilase-like pro-protein convertases) or dense core secretory granules. Various theories such as the APUD (amine precursor uptake decarboxylation) concept, the diffuse neuroendocrine system (DNES) or the paraneuron concept have been put forth to classify neuroendocrine cells as a cohesive group. Neuroendocrine characteristics have been used as evidence of a common embryological origin for normal and neoplastic cells. However, it is now recognized that neuroendocrine characteristics can be observed in various cell types, such as immunocytes, that are not of a common embryological origin with either neurons or endocrine cells. We propose to redefine previous "neuroendocrine" concepts to include the notion that activation of specific genetic switches can lead to the expression of a partial or full neuroendocrine phenotype in a variety of cell types, including immune cells. 相似文献