In vitro culture of testicular germ cells: Regulatory factors and limitations

Spermatogenesis is regulated mainly by endocrine factors and also by testicular paracrine/autocrine growth factors. These factors are produced by Sertoli cells, germ cells, peritubular cells and interstitial cells, mainly Leydig cells and macrophages. The interactions and the ratio between Sertoli and germ cells in the seminiferous tubules ensure successful spermatogenesis. In order to culture spermatogonial stem cells (SSCs) in vitro, researchers tried to overcome some of the obstacles—such as the low number of stem cells in the testis, absence of specific markers to identify SSCs—in addition to difficulties in keeping the SSCs alive in culture. Recently, some growth factors important for the proliferation and differentiation of SSCs were identified, such as glial cell line derived neurotrophic factor (GDNF), stem cell factor (SCF) and leukemia inhibitory factor (LIF); also, markers for SSCs at different stages were reported. Therefore, some groups succeeded in culturing SSCs (under limitations), or more differentiated cells and even were able to produce in vitro germ cells from embryonic stem cells.

Thus, success in culturing SSCs is dependent on understanding the molecular mechanisms behind self-renewal and differentiation. Culture of SSCs should be a good tool for discovering new therapeutic avenue for some infertile men or for patients undergoing chemotherapy/radiotherapy (pre-puberty or post-puberty).     

Peptide growth factors and preimplantation development

This paper examines some of the problems and questions thatmust be considered in relation to research on the role of growthfactors in preimplantation embryos. It reviews and summarizesthe large body of work on gene expression of growth factor receptorsand ligands in preimplantation embryos and in oviduct and uterinetissue. It also reviews the literature on the effects of geneknockout in preimplantation embryos and concludes with a reviewof work on the effects of growth factors on cultured embryos.     

The phakomatoses as paracrine growth disorders (paracrinopathies)

A microcomputer database management system retrieved all 170 probands with phakomatoses evaluated through the genetic clinics at the University of South Florida between January 2, 1982 and December 31, 1987. Neurofibromatosis (NF) was the diagnosis of 118 of them; 42 had other phakomatoses and 10 had transitional phenotypes difficult to classify. The analysis of the hamartomas of all probands indicated disorganized differentiation and overgrowth of cell species characteristic for the involved tissue and location. Abundance of extracellular fibrillary components was also evident in most hamartomas. Adequate blood supply was a conditio sine qua non. This was seen in monogenic, sporadic, transitional and combined phakomatoses alike and implied a common pathogenesis. The paracrine growth factors and their regulation emerged as the most plausible common denominator for the pathogenesis. A unitary pathogenetic hypothesis is proposed that the phakomatoses represent paracrine growth regulation disorders (paracrinopathies). Conditions such as fibromatoses, lipomatoses, lipodystrophies, hemihyper/hypotrophies, including Russell-Silver and Beckwith-Wiedemann syndromes may be proven to be paracrinopathies as well.     

人胚中肾发育和生长因子及其受体的表达

目的:观察第3~8周人胚中肾的发育和生长因子及其受体的表达。方法:第3~8周人胚,H-E和免疫组织化学染色,光镜观察。结果:人胚中肾于第3周末出现,并从头尾方向同时进行生长和退化过程。中肾于第8周退化。发育第5周中肾的肾小管和肾小球细胞强表达碱性成纤维细胞生长因子(bFGF)和转化生长因子β1(TGF-β1)及其受体。中肾内有核血细胞于第4周出现,第7周数量达到高峰。表皮生长因子、胰岛素样生长因子I、bFGF和TGF-β1及其受体在发育第5~8周中肾的有核血细胞表达。结论:人胚中肾的发育主要在第3~7周。第6~7周人胚中肾内的有核血细胞数量达高峰。人胚中肾内的有核血细胞、肾小管内皮细胞、肾小囊和肾小球细胞表达多种生长因子。     

Relationship between human oocyte maturity, fertilization and follicular fluid growth factors

Follicular fluid concentrations of growth hormone (GH), insulin-likegrowth factor-I (IGF-I), epidermal growth factor (EGF) and oestradiolwere related to diversities in oocyte maturation and fertilizationamong oocytes obtained for invitro fertilization (IVF). Follicularfluid GH, IGF-I and oestradiol concentrations were significantlycorrelated with increasing follicular size. Follicles with immatureoocytes had concentrations of oestradiol that were significantlylower when compared to follicles with intermediate and matureoocytes. Follicular fluid EGF concentration was similar forall oocyte maturational stages. In follicular fluids with matureoocytes we found IGF-I and GH concentrations were significantlyhigher compared to those of follicular fluid with atretic oocytes.Follicular fluids with Immature and intermediate oocytes hadsimilar concentrations of GH and IGF-I to follicular fluid containingmature oocytes and higher concentrations than follicular fluidwith atretic oocytes. No statistically significant differencewas found between fertilized and unfertilized oocytes. We concludethat maturation of oocytes Is associated with higher concentrationsof GH, IGF-I and oestradiol, but follicular fluid IGF-I andGH concentrations cannot serve as a predictor for IVF.     

Sex hormones and cardiovascular risk.

Inspection of the age-incidence curve of ischaemic heart disease in both sexes shows an increase in slope for women around the menopause, approaching that of men at older ages. Although the increase is likely to be related to the menopause, epidemiological evidence is not defined. Likewise, there is some suggestion that reproductive factors may be related to the subsequent risk of cardiovascular diseases, since a few studies found an elevated risk in women with an earlier first birth. In terms of prevention and public health considerations, treatments via exogenous hormones are, however, much more important. A systematic overview of the available epidemiological evidence indicates that oestrogen replacement treatment is protective against ischaemic heart disease. The overall relative risks based on 18 studies and greater than 3300 cases was 0.81, with a narrow 95% confidence interval (0.76-0.85), thus suggesting a protective effect of 15-25%. This protection has a plausible biological interpretation in terms of increased high density lipoprotein (HDL) levels. The serum lipoprotein pattern can be unfavourably influenced by progestin supplementation. With reference to oral contraceptives, the relative risk for cardiovascular mortality was increased about twofold in current users. There appears now to be convincing evidence that the elevated risk is restricted to current users.(ABSTRACT TRUNCATED AT 250 WORDS)     

Insulin-like growth factors and their binding proteins in human follicular fluid.

Increasing evidence suggests that insulin-like growth factors I and II (IGF-I, IGF-II) have a regulatory role in animal granulosa cells. This study was undertaken to investigate the presence of IGF-I and IGF-II, as well as that of their binding proteins (BP), IGFBP-1 and IGFBP-3 in human serum and follicular fluid (FF). Preovulatory FF was obtained from 51 patients undergoing in-vitro fertilization. The IGFBP-1 level was found to be significantly higher (P less than 0.01) in FF than in serum, whereas IGF-I and IGFBP-3 values remained markedly lower (P less than 0.01) in FF. Serum IGF-II levels were slightly but not significantly elevated compared to values obtained in the FF of patients. A positive correlation (P less than 0.001) between individual serum and FF levels was observed only for IGF-I. When a group of poor responders was compared to patients with normal stimulation characteristics, no significant difference was found in either IGF or IGFBP levels in the FF. It is concluded that IGFBP-1 is produced locally, whereas the serum may possibly be the major source of IGF-I. No clear conclusions can be drawn regarding the source of FF IGF-II and IGFBP-3. Neither the absolute level nor the relationship of IGFs to their transport proteins could explain the poor response to ovarian stimulation.     

Identification of the major fibroblast growth factors released spontaneously in inflammatory arthritis as platelet derived growth factor and tumour necrosis factor-alpha.

Rheumatoid arthritis is characterized by chronic inflammation and proliferation of a number of important elements within the joint including the synovial fibroblasts. Elevated levels of a number of cytokines such as Il-1, IL-2, IL-6, interferon-gamma (IFN-gamma), transforming growth factor-beta and tumour necrosis factor-alpha (TNF-alpha) have been detected in the synovial fluid of patients with rheumatoid arthritis and other inflammatory arthritides. It seems likely that local release of such mediators may be responsible for the proliferation and overgrowth of connective tissue elements in these disorders. In order to ascertain whether there was evidence to suggest local production or release of fibroblast growth factors in the joint in inflammatory arthritis, and to determine their identity, cells were obtained from the synovial fluid of 15 patients with chronic inflammatory arthritides. All subjects' synovial fluid cells spontaneously released growth factor activity for fibroblasts. This was present in large amounts, being detectable in culture supernatants diluted to a titre of at least 1/625. By a series of depletion experiments using solid-phase bound antibodies to cytokines, it was possible to demonstrate that this activity was due to TNF-alpha and platelet-derived growth factor (PDGF). Thus, this study showed for the first time that functionally active PDGF was released from synovial fluid cells. Both PDGF and TNF-alpha appeared to contribute in approximately equal amounts to this fibroblast growth factor activity, and were synergistic in effect. Thus this study provides evidence for the local production and release of these two cytokines and suggests that together they are the dominant factors in fibroblast proliferation within the synovial cavity.     

造血生长因子的临床应用

造血生长因子(Hemtopoietic Growth Factors, HGF)是细胞因子中的一大类，可以在体内、外刺激造血干/祖细胞增殖、分化、成熟和释放。随着生物医学工程的急速发展和制药工艺的进步，目前研制出多种造血生长因子供临床使用或试用。其中，促红细胞生成素(EPO)、粒细胞集落刺激因子(G-CSF)、粒-巨噬细胞集落刺激因子(GM-CSF)、白细胞介素3(IL-3)、白细胞介素11(IL-11)和促血小板生成素(TPO)已有较多的临床经验，本文分别对这些HGF的应用作一简介。1 促红细胞生成素(EPO)EPO是分子量为18kDa的蛋白，充分糖基化后，分子量在34—39k…     

Optimizing the effectiveness of hematopoietic growth factors

Hematopoiesis is regulated in a very precise fashion by a balance between both positive and negative growth factor signals in the hematopoietic microenvironment. Many of these growth factor signals have been identified and are available as recombinant proteins. At the present time, the approved uses for hematopoietic growth factors involve their use to facilitate blood cell production in situations of hematopoietic suppression or in cases where endogenous growth factor production is inappropriately low. Recent studies with the hematopoietic growth factors are looking at innovative strategies for their use and new clinical situations in which to evaluate their effectiveness. This review looks at some of these new uses for hematopoietic growth factors.     

Mast cells as sources of cytokines,chemokines, and growth factors

Mast cells are hematopoietic cells that reside in virtually all vascularized tissues and that represent potential sources of a wide variety of biologically active secreted products, including diverse cytokines and growth factors. There is strong evidence for important non-redundant roles of mast cells in many types of innate or adaptive immune responses, including making important contributions to immediate and chronic IgE-associated allergic disorders and enhancing host resistance to certain venoms and parasites. However, mast cells have been proposed to influence many other biological processes, including responses to bacteria and virus, angiogenesis, wound healing, fibrosis, autoimmune and metabolic disorders, and cancer. The potential functions of mast cells in many of these settings is thought to reflect their ability to secrete, upon appropriate activation by a range of immune or non-immune stimuli, a broad spectrum of cytokines (including many chemokines) and growth factors, with potential autocrine, paracrine, local, and systemic effects. In this review, we summarize the evidence indicating which cytokines and growth factors can be produced by various populations of rodent and human mast cells in response to particular immune or non-immune stimuli, and comment on the proven or potential roles of such mast cell products in health and disease.     

Expression of growth factors,growth inhibiting factors,and their receptors in invasive breast cancer. I: An inventory in search of autocrine and paracrine loops

The aim of the present study was to investigate which growth factors, receptors, and growth inhibiting factors are expressed in invasive breast cancer. Five (angiogenic) growth factors and their receptors: platelet-derived growth factor A chain (PDGF-AA) and PDGF receptor alpha (PDGFαR), PDGF-BB and PDGF beta receptor, transforming growth factor alpha (TGFα) and its receptor epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGF) and its receptors vascular endothelial growth factor receptor I (Flt-1) and vascular endothelial growth factor receptor II (Flk-1/KDR); two growth inhibiting factors: transforming growth factor beta-1 (TGFβ1) and TGFβ2) and their receptor couple transforming growth factor beta receptor I (TGFβR-I) and TGFβR-II; and basic fibroblast growth factor (bFGF) were stained by standard immunohistochemistry on frozen sections in 45 cases of invasive carcinoma of the breast. Staining was scored as negative or positive in tumour epithelium, stroma, and blood vessels. TGFβ1 and TGFβ2 were expressed in the tumour cells in 67 per cent and 76 per cent of cases, respectively, whereas PDGFβR and TGFβR-II were expressed in 0 per cent and 2 per cent, respectively. The other factors showed variable expression in tumour cells. All factors were expressed in the stroma in most cases, except Flt-1, Flk-1/KDR, TGFβ2, and TGFβR-II, which showed variable expression, and EGFR, which showed no expression. The endothelium was in most cases positive for bFGF, PDGF-AA, PDGF-BB, VEGF, PDGFαR, PDGFβR, and TGFβ1 but TGFβ2 was negative in most cases and TGFα, EGFR, Flt-1, Flk-1/KDR, TGFβR-I, and TGFβR-II were variably expressed. The most interesting possible auto/paracrine loops, as demonstrated on serial sections and by fluorescence double staining, were the TGFα/EGFR, TGFβs/TGFβR, VEGF/Flt-1, and the VEGF/Flk-1 combinations. In conclusion, growth factors, growth inhibiting factors, and their receptors are frequently expressed in invasive breast cancer. Indications for some possible auto-and paracrine loops have been found, which should encourage further study on the role of these factors in breast cancer proliferation and angiogenesis. © 1998 John Wiley & Sons, Ltd.     

Predicted secondary structure and hydrophobic cores of T-cell (TCGF or IL-2) and platelet-derived growth factors as well as of transforming protein p28sis of simian sarcoma virus are similar to those of interferons

Estimation of a content of secondary structures from amino acid composition of IL-2 (TCGF), PDGF and transforming protein p28sis of simian sarcoma virus by means of the previously suggested nomograms (V.P. Zav'yalov and A.I. Denesyuk (1982) Immunol. Lett. 4, 7-14) allowed us to conclude that a dominant secondary structure of these proteins should be alpha-helix. Its content in PDGF and p28sis was estimated to be approximately equal to 50%, and that in IL-2 to be 50-65%. The content of beta-pleated structure in PDGF and p28sis does not exceed 10%, and that in IL-2 is found to be 20-30%. In all the proteins investigated five alpha-helical segments can be distinguished, of which one of the surfaces contains clusters of bulky hydrophobic side chains. As the number of alpha-helical segments satisfying the principles of packing into a hydrophobic core as well as the overall length of a polypeptide chain of IL-2 and PDGF coincided with those for IFNs, it was decided to arrange alpha-helices of these proteins into a globular structure by analogy with IFNs (V.P. Zav'yalov and A.I. Denesyuk (1984) Doklady Akad Nauk S.S.S.R. 275, 242-246). In consequence, identical side chains of amino acid residues were found at 9 out of 29 positions in hydrophobic cores of IFN-beta and IL-2, p28sis (PDGF), respectively. Thus the homology of hydrophobic cores of the proteins compared is greater than 30%. Probability of chance coincidences of amino acid residues in the hydrophobic cores of p28sis (PDGF) and IFN-beta is found to be 0.03, and that deduced from comparison of IL-2 and IFN-beta is 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)     

神经营养因子和生长因子在神经干细胞中的研究进展

神经营养因子(neurotrophic factors,NF)包括神经生长因子(nerve growth factor,NGF)、脑源性神经营养因子(brain-derived neural neurotrophic factor,BDNF)等.生长因子(growth factors,GF)家族成员有酸性成纤维细胞生长因子(acidic fibroblast growth factor,aFGF)、碱性成纤维细胞生长因子(basic fibroblast growth factor,bFGF)、血管内皮生长因子(vascular endothelial growth factor, VEGF)等,两大家族均对神经系统的发育以及维持神经干细胞(neural stem cells,NSCs)的存活、促进其增殖、分化并诱导其定向迁移等众多方面发挥着重要作用.本文简要概括介绍NF中的重要成员之一脑源性神经营养因子,GF家族中的重要成员VEGF和bFGF对NSCs的影响.     

The epidermal growth factor receptor in human pancreatic cancer.

The epidermal growth factor receptor (EGFR) and its ligands are thought to be important in the control of proliferation of many epithelial systems, including the exocrine pancreas. Abnormalities in expression of two of the known ligands of the EGFR, transforming growth factor alpha and epidermal growth factor, occur frequently in ductal adenocarcinoma of the human pancreas. We have examined an archival series of cases of pancreatic pathology for expression of the EGFR using the anti-EGFR antiserum 12E and found that there is almost ubiquitous overexpression of EGFR in pancreatic cancer and in chronic pancreatitis. Southern blot analysis showed no evidence of amplification or rearrangement of the EGFR gene. We conclude that an autocrine loop involving the EGFR system may be involved in the genesis of both neoplasia and reactive hyperplasia of pancreatic ductal epithelium.     

Properties of cryptic epitopes and their corresponding antibodies as indicated by the study of human and ovine growth hormones

Antibodies (Ab) directed to hidden antigenic determinants (cryptotopes) are undesirable because they are not neutralizing. Additionally, we have previously demonstrated a close association between the extent of Ab to cryptic determinants and the expression of autoantibodies (autoAb) under some experimental conditions. Thus, the first objective of this work was to establish the physicochemical characteristics of Ab to cryptotopes and the second one was to examine the structural features of cryptic epitopes themselves. Using human and ovine growth hormones (hGH and oGH) as antigenic models and competition ELISA under different conditions of temperature, pH or ionic strength, we did not find any difference between the binding properties of anti-cryptic epitope antibodies (Ab) and anti-native epitope Ab. Then, using synthetic peptides and tryptic digests and direct and competition ELISAs we studied the structures of cryptic hGH and oGH epitopes. Isolated peptides either in solution or adsorbed on microplates failed to react. Partially digested hGH was recognized only when insolubilized on microplates, and anti-oGH Ab only reacted with a large fragment of the hormone either in solution or insolubilized. These results indicate that, at least in the case of hGH and oGH, cryptic epitopes are not simple linear sequences, as commonly referred without any evidence, but new exposed conformational structures different from those found in the native antigen.     

Resolving causes of developmental continuity or “tracking.” I. Longitudinal twin studies during growth

Models of developmental continuity and change in quantitative phenotypes may be tested using longitudinal data from twins. We illustrate a procedure for establishing the power and required sample sizes for detecting developmental transmission against an alternative common-factor hypothesis. We explore the general effects of different heritabilities, different fidelities of environmental and genetic developmental transmission, and varying numbers of occasions of measurement. In addition, a constraint of wide application is postulated for the action of the environment; either environmental effects are transmitted (learned) and occasion specific or they exert a constant influence which is not transmitted (learned). While the situations we examine are necessarily restricted here, our explorations of power show that, providing that we measure on at least four occasions, it is easy to detect developmental transmission with workable sample sizes.This work was supported in part by Grants AG04954, MH40828, GM30250, AA06781, and HL31010 from the National Institutes of Health.