NGF及其受体TrkA和p75在发情周期内Wistar大鼠卵巢内的表达

目的 检测NGF及其受体TrkA和p75在发情周期内Wistar大鼠卵巢内的表达.方法 利用免疫组织化学染色技术检测NGF及其受体TrkA和p75在卵巢内的细胞定位及蛋白表达情况;利用原位杂交方法检测在发情周期内大鼠卵巢NGF及其受体TrkA和p75的mRNA表达情况;利用Western blot技术检测发情周期内大鼠卵巢NGF及其受体TrkA和p75的蛋白表达情况.结果 免疫组织化学染色结果显示发情周期内大鼠卵巢内NGF及其受体的表达,在各级卵泡的卵泡细胞、卵母细胞以及黄体内均有不同水平的表达;同时间点的原位杂交检测结果与免疫组织化学染色结果相一致;Western blot检测结果显示整个发情周期内卵巢内的NGF及其受体TrkA和p75的蛋白表达没有明显的波动.结论 NGF及其受体TrkA和p75可促进发情周期内Wistar大鼠卵巢卵泡的卵泡细胞及卵母细胞的发育.     

Physiology of ovarian function

The ovarian function including follicular maturation, ovulation and corpus luteum formation is regulated by a complex control system composed of hypothalamus, pituitary and the ovary itself. These organs communicate via positive and negative feedback loops and can be considered as a functional entity. Special neurons in the hypothalamus produce gonadotropin-releasing hormone (GnRH) being delivered to the anterior pituitary lobe by the pituitary portal vessels. GnRH binds to specific receptors inducing synthesis and release of the gonadotropins FSH and LH into the circulation. After binding to their specific receptors at the ovary FSH and LH induce follicular maturation, ovulation and corpus luteum formation. The ovary responds to gonadotropin stimulation in dual fashion: secretion of sexsteroids and the liberation of a fertilizable oocyte. In addition the ovary is also able to secrete peptide-hormones such as inhibin and activin. Sexsteroids and inhibin modulate the pulsatile secretion of GnRH and gonadotropins. Cooperation of theca- and granulosa cells at the ovarian level and the corpus luteum formation are described and the significance of growth factors and cytocines is emphasized. The effects of estradiol and progesterone are highlighted by the morphological response of the endometrium. The ovary is actively involved in maintaining cyclicity, as reflected by the processes of follicular growth, follicle rupture and formation of the corpus luteum with the dramatic morphological changes involved.     

Is the corpus luteum normal after ovulation induction?

Repeated ultrasound examinations and blood samplings for determination of estradiol (E), progesterone (P), and luteinizing hormone (LH) were carried out in 15 normal and 11 clomiphene citrate (CC)/human menopausal gonadotropin (hMG) stimulated cycles. Human chorionic gonadotropin (hCG) was administered in the stimulated cycles on the day of the expected LH-peak as determined in each woman's normal cycle. Ovulation and normalcy of the luteal phase were confirmed by the hormonal values. Ultrasound examinations showed development of a single follicle in the normal group and development of 4.1 follicles on average, of 15 mm or more in diameter in the stimulated group (total of 45 follicles). Midluteal phase images at the site of the former follicle showed echogenic structures of echo-free structures with scattered echoes in 25 cases in the stimulated group and in 11 cases in the normal group. There was no sign of the former follicle in 1 and 3 cases, respectively, in the two groups. A significantly higher number of "persistent follicles" was seen in the stimulated group: 42% vs. 7%. It is discussed whether a compromised corpus luteum function occurs after stimulation despite a normal luteal phase.     

Ovulation and corpus luteum formation observed by ultrasonography

Ultrasonic observation of the ovary at 8–12 hr intervals reveals typical appearances when ovulation has take place. Shortly after ovulation there is an increase in solid echoes as the cystic follicle decreases in size until a small, less intense echogenic area (“cystic or structural loosening”) stays visible within the ovary. This either stays unchanged during the luteal phase or increases up to a cystic corpus luteum. Premensturally, the ovary regains its more homogenous solid structure. When cystic alteration has taken place, solid echoes invade the cystic corpus luteum which continuously decreases in size once menstruation has started. A cystic structure, similar to a cystic corpus luteum, in the second part of the menstrual cycle possibly signifies luteinisation of the unruptured follicle when no collapse of the follicle is observed before. After multifollicular development, the collapse of the predominant follicle may be difficult to outline when, simultaneous to ovulation, other follicles enlarge as in patients treated with gonadotrophins.     

A novel phenotype related to partial loss of function mutations of the follicle stimulating hormone receptor.

A single natural loss of function mutation of the follicle stimulating hormone receptor (FSHR) has been described to date. Present in the Finnish population it markedly impairs receptor function, blocking follicle development at the primary stage and presenting as primary amenorrhea with atrophic ovaries. When Western European women with this phenotype were examined for FSHR mutations the result was negative, suggesting that other etiologies corresponding to this clinical pattern are markedly more frequent. We now describe a novel phenotype related to mutations provoking a partial loss of function of the FSHR. A woman with secondary amenorrhea had very high plasma gonadotropin concentrations (especially FSH), contrasting with normal sized ovaries and antral follicles up to 5 mm at ultrasonography. Histological and immunohistochemical examination of the ovaries showed normal follicular development up to the small antral stage and a disruption at further stages. The patient was found to carry compound heterozygotic mutations of the FSHR gene: Ile160Thr and Arg573Cys substitutions located, respectively, in the extracellular domain and in the third intracellular loop of the receptor. The mutated receptors, when expressed in COS-7 cells, showed partial functional impairment, consistent with the clinical and histological observations: the first mutation impaired cell surface expression and the second altered signal transduction of the receptor. This observation suggests that a limited FSH effect is sufficient to promote follicular growth up to the small antral stage. Further development necessitates strong FSH stimulation. The contrast between very high FSH levels and normal sized ovaries with antral follicles may thus be characteristic of such patients.     

Overexpression of the epidermal growth factor receptor in human pancreatic cancer is associated with concomitant increases in the levels of epidermal growth factor and transforming growth factor alpha.

The epidermal growth factor (EGF) receptor is activated by both EGF and transforming growth factor-alpha (TGF-alpha). Using immunohistochemical and immunoblotting techniques we now report that the EGF receptor, EGF, and TGF-alpha are found in both pancreatic acini and ducts in the normal human pancreas, and that all three proteins are expressed at higher levels in human pancreatic cancer tissues. Using in situ hybridization techniques, we also report that the mRNA encoding the EGF receptor, EGF, and TGF-alpha colocalize with their respective proteins. Northern blot analysis of total RNA indicates that, by comparison with the normal pancreas, the pancreatic tumors exhibit a 3-, 15-, and 10-fold increase in the mRNA levels encoding the EGF receptor, EGF, and TGF-alpha, respectively. Furthermore, by in situ hybridization, there is a marked increase in these mRNA moieties within the tumor mass. These findings suggest that EGF and TGF-alpha may participate in the regulation of normal pancreatic exocrine function, and that overexpression of the EGF receptor and its two principal ligands may contribute to the pathophysiological processes that occur in human pancreatic cancer.     

Coexpression of platelet-derived growth factor (PDGF) and PDGF-receptor genes by primary human astrocytomas may contribute to their development and maintenance.

The present studies investigated the expression of the two PDGF genes (c-sis/PDGF-2 and PDGF-1) and the PDGF-receptor b gene (PDGF-R) in 34 primary human astrocytomas. Northern blot analysis demonstrated the coexpression of the c-sis/PDGF-2 protooncogene and the PDGF-R gene in all astrocytomas examined. The majority of the tumors also expressed the PDGF-1 gene. There was no correlation between the expression of the two PDGF genes. Nonmalignant human brain tissue expressed the PDGF-R and PDGF-1 genes but not the c-sis/PDGF-2 protooncogene. In situ hybridization of astrocytoma tissue localized the expression of the c-sis and PDGF-R mRNA's in tumor cells. Capillary endothelial cells also expressed c-sis mRNA. In contrast, nonmalignant human brain tissue expressed only PDGF-R mRNA but not c-sis/PDGF-2 mRNA. The coexpression of a potent mitogenic growth factor protooncogene (c-sis) and its receptor gene in astrocytoma tumor cells suggests the presence of an autocrine mechanism that may contribute to the development and maintenance of astrocytomas. The expression of c-sis mRNA in tumor cells but not in nonmalignant brain cells may serve as an additional diagnostic criterion for the detection of astrocytomas in small tissue specimen using in situ hybridization for the detection of c-sis mRNA and/or immunostaining for the recognition of its protein product.     

Osteopontin mRNA is expressed by smooth muscle-derived foam cells in human atherosclerotic lesions of the aorta.

Osteopontin is a phosphorylated, sialic acid-rich, noncollagenous bone matrix protein containing the Arg-Gly-Asp-Ser amino acid sequence responsible for cell adhesion. The protein strongly binds to hydroxyapatite and play an important role in calcification. Expression of osteopontin mRNA was analyzed in human aortic atherosclerotic lesion by Northern blot hybridization, as well as by in situ hybridization. The expression of osteopontin mRNA was detected in 24 out of 25 samples of aorta obtained from 17 autopsy cases, but not in one normal aortic sample. The magnitude of expression was proportional to the stage of atherosclerosis. In situ hybridization revealed that the cells expressing osteopontin mRNA were detected in the wall surrounding atheroma and closely associated with calcification. They were morphologically identified as foam cells and immunohistologically positive with HHF35, appearing to be derived from smooth muscle cells. These findings have suggested that smooth muscle cell-derived foam cells express osteopontin mRNA and play an important role in calcification of the atherosclerotic lesions.     

Cellular localization of AT1 receptor mRNA and protein in normal placenta and its reduced expression in intrauterine growth restriction. Angiotensin II stimulates the release of vasorelaxants.

Angiotensin II (ANG II) is a potent vasoconstrictor and growth promoter. Quantitative receptor autoradiography using the nonselective radioligand [125I]ANG II and subtype-selective competing compounds demonstrated the presence of both ANG II receptor (AT)1 and AT2 receptor recognition sites. In addition, a relatively small population of apparently non-AT1/non-AT2 sites was identified that may represent a novel high affinity ANG II recognition site in human placenta. Using placental membrane preparations, the AT2 receptor antagonist PD123177 failed to compete for [3H]ANG II binding at relevant concentrations, whereas the AT1 receptor antagonist losartan competed in a monophasic manner for all the specific binding, suggesting that the non-AT1/non-AT2 recognition site identified using autoradiography may be a cytosolic binding site. AT1 receptor binding was significantly reduced (P < 0. 02) in intraeuterine growth restriction (IUGR) pregnancies. Western blot analysis confirmed this showing a reduction in AT1 receptor protein. In situ hybridization and immunocytochemistry revealed that AT1 receptor mRNA and protein were localized throughout pregnancy in the cytotrophoblast, syncytiotrophoblast, and extravillous trophoblast, as well as in or around the blood vessels of placental villi. The intensity of the hybridization signal for AT1 receptor mRNA over the syncytium was reduced in IUGR. ANG II evoked a rapid and concentration-dependent release of NO in first trimester cytotrophoblast-like cells that was abolished by the inclusion of the competitive NOS inhibitor NG-monomethyl-L-arginine. Neither losartan nor PD123177 alone significantly inhibited ANG II-evoked NO release, and when cells were stimulated with ANG II in the presence of losartan (10 microM) and PD123177 (10 microM) in combination, NO release was significantly inhibited (P < 0.05). These observations also suggest, for the first time, the existence of a cross-talk between AT1 or AT2 receptors in trophoblast and that the reduction in placental AT1 receptors in IUGR may, in part, account for poor placental function in this disorder.     

Stimulation by thyroid-stimulating hormone and Grave's immunoglobulin G of vascular endothelial growth factor mRNA expression in human thyroid follicles in vitro and flt mRNA expression in the rat thyroid in vivo.

To elucidate the pathogenesis of thyroid gland hypervascularity in patients with Graves' disease, we studied the expression of mRNAs for vascular endothelial growth factor (VEGF) and its receptor, Flt family, using human thyroid follicles in vitro and thiouracil-fed rats in vivo. Human thyroid follicles, cultured in the absence of endothelial cells, secreted de novo-synthesized thyroid hormone in response to thyroid-stimulating hormone (TSH) and Graves' IgG. The thyroid follicles produced VEGF mRNA but not flt-1 mRNA. The expression of VEGF mRNA was enhanced by insulin, tumor-promoting phorbol ester, calcium ionophore, dibutyryl cAMP, TSH, and Graves' IgG. When rats were fed thiouracil for 4 wk, their serum levels of TSH were increased at day 3. VEGF mRNA was also increased on day 3, accompanied by an increase in flt family (flt-1 and KDR/ flk-1) mRNA expression. These in vitro and in vivo findings suggest that VEGF is produced by thyroid follicles in response to stimulators of TSH receptors, via the protein kinase A and C pathways. VEGF, a secretable angiogenesis factor, subsequently stimulates Flt receptors on endothelial cells in a paracrine manner, leading to their proliferation and producing hypervascularity of the thyroid gland, as seen in patients with Graves' disease.     

Sex steroid hormone regulation of follicle-stimulating hormone subunit messenger ribonucleic acid (mRNA) levels in the rat.

Follicle-stimulating hormone (FSH) beta, luteinizing hormone (LH) beta, and alpha subunit messenger RNA (mRNA) levels were examined in rats after castration and sex-steroid replacement. Subunit mRNAs were determined by blot hybridization using rat FSH beta genomic DNA, and alpha and LH beta complementary DNA (cDNA). Rat FSH beta mRNA is 1.7 kilobase in size. After ovariectomy, female FSH beta mRNA levels increased fourfold, whereas those of LH beta and alpha increased twenty- and eightfold, respectively. With estradiol, all subunits returned toward normal levels. Male LH beta and alpha mRNA levels rose eight- and fourfold, respectively, 40 d postcastration, but FSH beta mRNA levels increased minimally. After 7 d of testosterone propionate, LH beta and alpha mRNAs declined to normal levels, whereas FSH beta mRNA increased slightly. We conclude that in female rats FSH beta is negatively regulated by gonadal steroids, but to a lesser extent than LH beta or alpha mRNAs, and there is a differential regulation of FSH beta mRNA levels in males as compared with females at the time points examined.     

Tumor necrosis factor and its receptors in human ovarian cancer. Potential role in disease progression.

The gene for tumor necrosis factor, TNF, was expressed in 45 out of 63 biopsies of human epithelial ovarian cancer. In serous tumors, there was a positive correlation between level of TNF expression and tumor grade. TNF mRNA was found in epithelial tumor cells and infiltrating macrophages, whereas TNF protein localized primarily to a subpopulation of macrophages within and in close proximity to tumor areas. mRNA and protein for the p55 TNF receptor gene localized to the tumor epithelium and tumor, but not to stromal macrophages. The p75 TNF receptor was confined to infiltrating cells. Cells expressing TNF mRNA were also found in ovarian cancer ascites and TNF protein was detected in some ascitic fluids. In 2 out of 12 biopsies of normal ovary, TNF mRNA was detected in a minority of cells in the thecal layer of the corpus luteum. Serum levels of TNF and its soluble receptor did not correlate with extent of TNF expression in matched biopsies. Northern and Southern analysis revealed no gross abnormality of the TNF gene. The coexpression of TNF and its receptor in ovarian cancer biopsies suggests the capacity for autocrine/paracrine action. TNF antagonists may have therapeutic potential in this malignancy.