Biomedical subjects

L Hedin

Publications and source records attributed to L Hedin.

At least 19 recordsLinked to original sources

PubMed2003

Wnt-signalling pathway in ovarian epithelial tumours: increased expression of beta-catenin and GSK3beta.

Beta-catenin is involved in both cell-cell adhesion and in transcriptional regulation by the Wingless/Wnt signalling pathway. Alterations of components of this pathway have been suggested to play a central role in tumorigenesis. The present study investigated, by immunohistochemistry and immunoblotting, the protein expression and localisation of beta-catenin, adenomatous polyposis coli (APC), glycogen synthase kinase 3beta (GSK3beta) and lymphocyte enhancer factor-1 (Lef-1) in normal human ovaries and in epithelial ovarian tumours in vivo and in vitro. Immortalised human ovarian surface epithelium and ovarian cancer cell cells (OVCAR-3) expressed beta-catenin, APC, GSK3beta and Lef-1. Nuclear staining of beta-catenin and Lef-1 were demonstrated only in OVCAR-3 cells. There were significant increases of beta-catenin and GSK3beta, while APC was reduced in ovarian cancer compared to the normal ovary. Beta-catenin and Lef-1 were coimmunoprecipitated in ovarian tumours, but not in the normal ovary. Nuclear localisation of beta-catenin or Lef-1 could not be demonstrated in the normal ovary or in the ovarian tumours. The absence of nuclear localisation of beta-catenin could be due to an increased binding to the cadherin-alpha-catenin cell adhesion complex. In fact, we have earlier reported an increased expression of E-cadherin in ovarian adenocarcinomas. In summary, this study demonstrates an increase in the expression of components of the Wingless/Wnt pathway in malignant ovarian tumours. The increase suggests a role for this signalling pathway in cell transformation and in tumour progression. However, it remains to be demonstrated whether it is an increased participation of beta-catenin in transcriptional regulation, or in the stabilisation of cellular integrity, or both, that is the crucial event in ovarian tumorigenesis.

Adenocarcinoma↗

PubMed2002

Acetazolamide inhibits stimulated feline liver and gallbladder bicarbonate secretion.

Bile acidification is a key factor in preventing calcium carbonate precipitation and gallstone formation. Carbonic anhydrase II (CA II), that is inhibited by acetazolamide, plays a role in regulation of the acid-base balance in many tissues. This study examines the effect of acetazolamide on secretin- and vasoactive intestinal peptide (VIP)-stimulated gallbladder mucosal bicarbonate and acid secretion. Gallbladders in anaesthetized cats were perfused with a bicarbonate buffer bubbled with CO2 in air. In 20 experiments VIP (10 microg kg(-1) h(-1)) and in 10 experiments secretin (4 microg kg(-1) h(-1)) were infused continuously intravenous (i.v.). Hepatic bile and samples from the buffer before and after perfusion of the gallbladder were collected for calculation of ion and fluid transport. During basal conditions a continuous secretion of H+ by the gallbladder mucosa was seen. Intravenous infusion of vasoactive intestinal peptide (VIP) and secretin caused a secretion of bicarbonate from the gallbladder mucosa (P < 0.01). This secretion was reduced by intraluminal (i.l.) acetazolamide (P < 0.01). Bile flow was enhanced by infusion of VIP and secretin (P < 0.01) but this stimulated outflow was not affected by i.v. acetazolamide. The presence of CA II in the gallbladder was demonstrated by immunoblotting. Biliary CA activity has an important function in the regulation of VIP- and secretin-stimulated bicarbonate secretion across the gallbladder mucosa.

Acetazolamide↗

PubMed2001

Acetylation of steroidogenic factor 1 protein regulates its transcriptional activity and recruits the coactivator GCN5.

Steroidogenic factor-1 (SF-1) is an orphan nuclear receptor that plays an essential role in the development of the hypothalamic-pituitary-gonadal axis in both sexes. SF-1 belongs to the hormone nuclear receptor superfamily and possesses an N-terminal DNA binding domain and a C-terminal ligand binding domain. Activation function domain 2 is located C-terminal of the ligand binding domain of SF-1 and is important for the transactivation of target genes. Coactivators with histone acetyltransferase activity such as cAMP response element-binding protein-binding protein and steroid receptor coactivator 1 interact and increase SF-1-mediated transcriptional activity. In this study we demonstrate that SF-1 is acetylated in vivo. Histone acetyltransferase GCN5 acetylates SF-1 in vitro. Moreover, we found that SF-1 recruited a novel coactivator GCN5, which can be a newly identified coactivator for SF-1. Acetylation of SF-1 stimulates its transcriptional activity. Inhibition of deacetylation by trichostatin A, a histone deacetylase inhibitor, increased SF-1-mediated transactivation and stabilized and induced the nuclear export of the SF-1 protein.

Acetylation↗

PubMed2001

Theoretical study of the non-local optical potential in EXAFS spectra.

We study the optical potential effects on the extended x-ray absorption fine structure (EXAFS) and x-ray photoelectron diffraction (XPD) spectra. For the valence electron optical potential we use a local density approximation because the charge density changes fairly slowly, whereas we use a non-local optical potential for the core electron part based on GW-approximation. In the Br K-edge EXAFS spectra the present optical potential gives rise to the phase difference and the amplitude reduction; the agreement with the experimental result is excellent. In the N-1s XPD spectra for N2/Ni(100), the spherical wave effects enhance the effects due to the optical potential.

Journal Article↗

PubMed2001

Theory of spin-polarized optical potential.

We develop an approximation for the non-local spin-polarized optical potential theory for atoms in solids at intermediate and high energy. The present approximation for the optical potential builds on the GW-expression. We separate the RPA polarization propagator into a core electron and a valence electron part, and can then achieve a corresponding separation of the optical potential. For the valence electron optical potential we use a local density approximation because the charge density changes fairly slowly, whereas we use a non-local optical potential for the core electron part. Both of them depend on the spin-polarization. We apply this method to electron-Fe elastic scattering in solid, and discuss the results.

Journal Article↗

PubMed2001

Endothelial nitric oxide synthase protein is reduced in the renal medulla of two-kidney, one-clip hypertensive rats.

OBJECTIVE: We studied endothelial nitric oxide synthase (eNOS) expression in the kidneys of two-kidney, one-clip renal hypertensive rats (2K1C) before and after removal of the clip (unclipping, UC). We hypothesised that the haemodynamic changes induced by 2K1C and UC would change eNOS expression in the two kidneys. METHODS: Six weeks after inducing 2K1C, mean arterial pressure (MAP) was measured in conscious rats and hypertension reversed by UC. Left and right kidney eNOS protein in cortex and outer medulla was semi-quantified using immunoblotting. Groups were; normotensive (n = 10), 2K1C (n = 10), 3 h (n = 10), 48 h (n = 7) and 4 weeks (n = 7) after UC. The effect of 7 days of aldosterone or angiotensin II (Ang II) infusion on medullary eNOS protein was tested as well as the effect of L-NAME (nitric oxide (NO) synthase inhibitor) on medullary blood flow (MBF) in anaesthetized 2K1C. RESULTS: UC reduced MAP from 178 +/- 5 to 134 +/- 3 mmHg after 3 h and normalized MAP at 48 h and 4 weeks. The medulla from 2K1C kidneys contained about 33% less eNOS protein compared with normotensive kidneys (P < 0.05). This difference was still evident at 3 h (P < 0.05), but completely reversed at 48 h and 4 weeks after UC. Similar levels of eNOS expression were seen in the left and right kidney at all time points. Cortical eNOS was increased in kidneys from 2K1C. Neither Ang II nor aldosterone affected eNOS expression in the medulla. MBF was under similar influence of NO in 2K1C compared with normotensive kidneys. CONCLUSIONS: 2K1C is associated with reduced levels of eNOS protein in the renal medulla of both clipped and contralateral kidney. eNOS expression in right and left kidney was not changed despite expected large changes in haemodynamics of the two kidneys. The reduced level of eNOS may be associated with a reduction in MBF and thus be of patho-physiological importance in renovascular hypertension.

Aldosterone↗

PubMed2000

Increased expression of the transcription factors CCAAT-enhancer binding protein-beta (C/EBBeta) and C/EBzeta (CHOP) correlate with invasiveness of human colorectal cancer.

Regulation of cell differentiation is most often impaired in malignant tumors and may represent a key mechanism for the progression of the disease. CCAAT-enhancer binding protein (C/EBP) is a family of transcription factors involved in the regulation of embryonic gut development in rodents, which has also been detected in various malignancies, e.g., liposarcomas and breast and ovarian epithelial tumors. We studied the relationship between C/EBP and tumor histology (Duke's invasive stage and pathological grade) in colorectal cancer. Immunoblotting techniques were used on microdissected fresh frozen tumor specimens, and expression of C/EBPalpha, C/EBPbeta and C/EBPzeta (CHOP) was analyzed in addition to that of the cell-cycle regulator p53 and the proliferation marker PCNA. Expression of C/EBPbeta (LAP isoforms) was markedly increased in all tumors compared with normal colon mucosa. Although the inter-patient variability was large, we found that LIP, the isoform of C/EBPbeta known to inhibit transcription, was expressed at higher levels in Duke's stage B tumors compared with Duke's stage A, whereas Duke's C tumors had the lowest LIP expression. A similar relationship was seen for CHOP. The cell-cycle regulator gene p53 was the only factor that clearly correlated with pathological grade: a decrease in p53 expression was demonstrated. Our data suggest that genetic and cellular events involving C/EBPbeta and CHOP are important for tumor invasion and that these events do not appear to be related to the pathological grade of the tumor.

Aged↗

PubMed2000

Growth hormone induces CCAAT/enhancer binding protein alpha (C/EBPalpha) in cultured rat hepatocytes.

BACKGROUND/AIMS: The transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha) is a transactivator of several genes in the liver, which are regulated by growth hormone. METHODS: Growth hormone (100 ng/ml) was added to primary rat hepatocytes cultured on a laminin-rich matrix. C/EBP mRNA and protein levels were measured by RNase protection assay and Western blotting, respectively. DNA binding activity was measured by electrophoretic mobility shift assay (EMSA). RESULTS: Growth hormone treatment for 6 h to 3 days increased C/EBPalpha mRNA levels. Addition of growth hormone for 24 h and 4 days also enhanced the levels of the 42 and 30 kDa isoforms of immunoreactive C/EBPalpha. EMSA showed that addition of growth hormone for 24 h enhanced the abundance of a protein complex binding to a consensus C/EBP binding DNA oligonucleotide. This protein complex was supershifted by antibodies directed against C/EBPalpha but not against C/EBPbeta. There were no consistent effects on C/EBPbeta mRNA or protein at any timepoint. The growth hormone effect on C/EBPalpha expression was not affected by simultaneous incubation with insulin or glucocorticoids, two hormones that previously have been reported to affect C/EBPs. CONCLUSIONS: Growth hormone enhances the levels of C/EBPalpha mRNA and protein as well as the DNA binding activity of C/EBPalpha in cultured rat hepatocytes.

Animals↗

PubMed2000

E-cadherin-catenin complex in the rat ovary: cell-specific expression during folliculogenesis and luteal formation.

The cadherins and their cytoplasmic counterparts, the catenins, form the adherens junctions, which are of importance for tissue integrity and barrier functions. The development and maturation of the ovarian follicle is characterized by structural changes, which require altered expression or function of the components involved in cell-cell contacts. The present study examined the cell-specific localization and temporal expression of epithelial cadherin (E-cadherin) and alpha- and beta-catenin during follicular development, ovulation and corpus luteum formation in the immature gonadotrophin- and oestrogen-stimulated rat ovary. Immunohistochemistry and immunoblotting demonstrated the expression of E-cadherin in theca and interstitial cells of immature ovaries before and after injection of equine chorionic gonadotrophin (eCG). E-cadherin was not detected in granulosa cells, except in the preantral follicles located to the inner region of the ovary. The content of E-cadherin in theca and interstitial cells decreased after an ovulatory dose of hCG. Granulosa cells of apoptotic follicles did not express E-cadherin. Oestrogen treatment (diethylstilboestrol) of immature rats for up to 3 days did not result in a measurable expression of E-cadherin in granulosa cells. alpha- and beta-catenin were expressed in all ovarian compartments. The concentration of beta-catenin was constant during the follicular phase, whereas the content of alpha-catenin decreased in granulosa cells after treatment with diethylstilboestrol or hCG. The expression of alpha-catenin was also reduced in theca and interstitial cells after hCG. alpha- and beta-catenin were present in most ovarian cells at all stages of folliculogenesis. Therefore, the catenins have the potential to associate with different members of the cadherin family and to participate in the regulation of cytoskeletal structures and intracellular signalling. The restricted expression of E-cadherin in granulosa cells of preantral follicles indicates a role in the recruitment of these follicles to subsequent cycles. The specific decrease of alpha-catenin in granulosa cells and the reduction of both alpha-catenin and E-cadherin in theca cells of ovulatory follicles might reflect some of the molecular changes in cell-cell adhesion associated with ovulation and luteinization.

Animals↗

PubMed1999

The expression of CCAAT/enhancer binding protein (C/EBP) in the human ovary in vivo: specific increase in C/EBPbeta during epithelial tumour progression.

The CCAAT/enhancer binding protein (C/EBP) family of transcription factors is involved in metabolism and differentiation of cells, especially in rodent liver cells and adipocytes. Their roles in vivo and in particular during pathophysiological conditions in humans are largely unknown. We have investigated the presence of C/EBPalpha, -beta, -delta and -zeta in normal ovaries and in epithelial ovarian tumours of different stages. Immunohistochemical experiments demonstrated that C/EBPalpha and C/EBPbeta were preferentially expressed in epithelial/tumour cells irrespective of stage or grade of the tumour. C/EBPbeta was located in the nuclei of the cells, in contrast to C/EBPalpha, which was present only in the cytoplasm of these cells. The nuclear localization of C/EBPbeta indicates an active role of this transcription factor in tumour cells, whereas the cytoplasmic distribution suggests a more passive function of C/EBPalpha. C/EBPdelta and -zeta demonstrated a more diverse distribution with predominant localization to epithelial cells, but stromal distribution was also noted. The intracellular distribution was confined to both the nucleus and the cytoplasm for C/EBPdelta and -zeta. Western blotting demonstrated that C/EBPalpha, -beta, -delta and -zeta were present in a majority of the samples. The amount of C/EBPbeta increased markedly with malignancy, i.e. with degree of dedifferentiation, while the other members of the C/EBP family displayed a more constant expression level. These results demonstrate an association between the expression of members of the C/EBP family and the formation of epithelial ovarian tumours, with C/EBPbeta as a potential marker for these tumours. As C/EBPbeta is known to be expressed during proliferation of cells in vitro, it may participate in the proliferative process of ovarian epithelial tumour cells in vivo and play a central role in tumour progression.

Adenocarcinoma↗

PubMed1999

Isoform-specific regulation of the CCAAT/enhancer-binding protein family of transcription factors by 3',5'-cyclic adenosine monophosphate in Sertoli cells.

The C/EBP (CCAAT/enhancer-binding protein) family of transcription factors is important for differentiation, lipid biosynthesis, and metabolism. Here, we demonstrate for the first time the presence of C/EBP alpha, beta, delta, and zeta messenger RNA (mRNA) and protein in Sertoli cell primary cultures. Treatment with FSH or 8-CPTcAMP strongly induced C/EBP beta mRNA above basal levels with rapid and transient kinetics in Sertoli cell primary cultures as well as in whole testes from hypophysectomized rats. Whereas C/EBP beta mRNA was induced approximately 50-fold, C/EBP delta mRNA was induced 5- to 8-fold by cAMP in Sertoli cells. Messenger RNA for C/EBP beta and delta were induced by inhibition of protein synthesis with cycloheximide and cycloheximide acted synergistically with cAMP. Immunoblots with C/EBP antibodies demonstrated a strong induction of C/EBP beta, delta, and zeta by cAMP. Electrophoretic mobility shift analysis of nuclear proteins from cAMP-treated Sertoli cells using a C/EBP consensus oligonucleotide and antibodies revealed specific binding of C/EBP/DNA complexes, the majority of which were supershifted by C/EBP beta antibody. Transfections of Sertoli cells with a C/EBP reporter construct showed approximately 3-fold induction of reporter gene activity by cAMP. In contrast, the reporter gene vector with a mutated form of the C/EBP binding site, was almost unresponsive to cAMP in transfections of Sertoli cells. Furthermore, C/EBP beta expression increased the activities of two promoters known to be cAMP-responsive in Sertoli cells. Thus, the early induction of C/EBP isoforms by cAMP may play a role in FSH-dependent regulation of late response genes in Sertoli cells.

Animals↗

PubMed1998

The chemotactic cytokine interleukin-8--a cyst fluid marker for malignant epithelial ovarian cancer?

Due to the difficulties in separating malignant and benign ovarian cysts by transvaginal ultrasound and other techniques, there is a need for biochemical markers in serum or cyst fluids. In the present study we have evaluated the levels of the chemokine interleukin-8 (IL-8) in ovarian cysts. IL-8 is known to be expressed in the normal ovary and to influence proliferation and angiogenesis of several nonovarian types of tumors. Cyst fluids from benign (n = 15) and malignant (n = 13) ovarian tumors were analyzed. The levels of IL-8 were found to be significantly (13-fold) higher in cyst fluids from malignant tumors (18.1 +/- 7.5 ng/ml; mean +/- SE) compared to benign cysts (1.3 +/- 0.7 ng/ml). The plasma levels of IL-8 were considerably lower (2.9 and 0.3% of levels in benign and malignant cyst fluids, respectively) than in cyst fluids. No difference in the plasma levels of patients with benign or malignant tumor could be detected. In contrast, the levels of CA 125 were significantly higher in plasma of patients with malignant disease with the inverse relation in cyst fluids. In conclusion, the levels of IL-8 are markedly elevated in cyst fluid from malignant tumors compared to benign. This specific increase indicates a role for this cytokine in ovarian tumor biology.

Biomarkers, Tumor↗

PubMed1998

The selective prostaglandin endoperoxide synthase-2 inhibitor, NS-398, reduces prostaglandin production and ovulation in vivo and in vitro in the rat.

Two isoforms of prostaglandin G/H synthase, PGS-1 and PGS-2, catalyze the formation of prostaglandins (PG). Nonselective PGS inhibitors, e.g., indomethacin, reduce the number of ovulations and PG levels in many animal models. This study evaluated the effects of the selective PGS-2 inhibitor NS-398, compared to indomethacin, on ovulation number and on PG and steroid production both in vivo and in vitro in the rat. NS-398 reduced the synthesis of PGE2 in isolated, LH-stimulated preovulatory follicles incubated in vitro. The inhibition by NS-398 was similar to that of indomethacin. Maximal inhibition was noted from 0.1 microM. Neither progesterone nor cAMP production was affected by NS-398 or indomethacin. The effect of in vivo administration of NS-398 (1, 3, or 10 mg/kg BW, s. c.) to proestrous rats 1 h after the injection of an ovulatory dose of hCG was monitored in follicles extirpated 10 h after hCG. These follicles were incubated in vitro, and NS-398 dose-dependently reduced PGE2 production. The synthesis of cAMP and progesterone was not altered. In separate experiments, the same doses of NS-398 were injected to determine their effect on ovulation in vivo. The number of ovulations was decreased by the highest dose of NS-398. In the in vitro ovarian perfusion model, NS-398 (10 microM) reduced the number of ovulations initiated by LH and isobutylmethylxanthine. Lower doses of NS-398 (0.1 and 1 microM) were less effective. The production of prostanoids (PGE2, PGF2alpha, and 6-keto-PGF1alpha) was reduced in a dose-dependent manner by NS-398. The secretion of steroids was not affected. This study demonstrates that selective inhibition of PGS-2 by NS-398 reduces LH/hCG-stimulated production of prostanoids and the number of ovulations both in vivo and in vitro. These results provide direct evidence to strengthen the role of the inducible, granulosa cell-expressed PGS-2 as one of the key regulators in the ovulatory process and also document that the elevated and perhaps sustained levels of PG are obligatory for ovulation.

1-Methyl-3-isobutylxanthine↗

PubMed1997

The transcription factor C/EBP-beta and its role in ovarian function; evidence for direct involvement in the ovulatory process.

Gonadotropins are responsible for maturation of the ovarian follicle and the oocyte. Ovulation is the ultimate step in this process and involves disintegration of the follicular wall and subsequent release of an oocyte into the oviduct. These events are triggered by a surge of luteinizing hormone (LH). Genes expressed in the ovary, that respond to LH, are likely to be involved in the biochemical pathways that regulate ovulation. The transcription factor C/EBP-beta is induced promptly in the ovary, as a response to an ovulatory dose of gonadotropins. We used an ex vivo perfusion system to demonstrate that a specific reduction in ovarian C/EBP-beta expression inhibits ovulation. In such ovaries the oocytes appeared to be entrapped within the follicle. We have found a correlation between the expression level of the activating isoform of C/EBP-beta and the number of oocytes ovulated in response to gonadotropins. Since a reduction in C/EBP-beta expression does not affect the level of the ovulatory mediator prostaglandin endoperoxide synthase-2 (PGS-2), these findings support the view of C/EBP-beta as an important factor in the ovulatory process and highlight a C/EBP-beta-dependent and PGS-2-independent pathway that takes part in regulation of ovulation.

Animals↗

PubMed1997

E-cadherin expression in human epithelial ovarian cancer and normal ovary.

The ovarian surface epithelium (OSE) is the origin of the majority of human ovarian cancers. These adenocarcinomas are characterized by initial local growth followed by spreading into the peritoneal cavity at later stages of tumor progression. The cell-adhesion molecule E-cadherin (E-cad) plays an important role in maintaining tissue integrity. Disappearance or impaired function of E-cad have often been associated with tumor formation and invasion in vivo and in vitro. The cell-specific expression of E-cad was investigated in normal human ovaries (n = 12), in benign (n = 5) and borderline (n = 4) ovarian epithelial tumors and in adenocarcinomas of different stages and histological grades (n = 18), by immunohistochemistry and immunoblotting. An ovarian cancer cell line (NIH-OVCAR3) was used as a reference. The epithelial origin of the cells was confirmed with cytokeratin (AE1/AE3) staining. In normal ovaries, the expression of E-cad was limited to inclusion cysts or deep clefts lined with OSE, whereas no staining of the OSE could be demonstrated at the surface of the ovary. In contrast, benign and borderline tumors uniformly expressed E-cad. This was observed in malignant tumors of all stages despite their degree of differentiation. E-cad was also present in metastasis from such tumors. The cell-specific expression of E-cad in inclusion cysts of normal ovaries and in epithelial layers of borderline tumors indicates a role for E-cad in the early events of the progression to a malignant phenotype. E-cad was not downregulated in later stages of ovarian cancer progression.

Adenocarcinoma, Mucinous↗

PubMed1997

Prostaglandin synthesis is suppressed by progesterone in rat preovulatory follicles in vitro.

The inducible form of prostaglandin endoperoxide-2 (PGS-2) is transiently induced by activators of the protein kinase A and protein kinase C systems in rat preovulatory (PO) granulosa cells. This induction is suggested to play an important role in the ovulatory process, which shares many of the characteristics of an inflammatory reaction. The purpose of the present study was to explore the role of progesterone (P4) as an "anti-inflammatory" steroid for the regulation of PGS-2 and the synthesis of prostaglandins in the PO follicle. Isolated rat PO follicles were preincubated with different amounts of exogenous P4 before the addition of luteinizing hormone (LH) and 3-isobutyl-1-methylxanthine (IBMX) (LH + 1). Medium levels of prostaglandin E2 (PGE2) were measured by RIA and the protein contents of PGS-1 and PGS-2 were determined by immunoblotting. LH + I. Both the content of PGS-2 and the synthesis of PGE2 were decreased. The content of PGS-1 demonstrated only minor changes in response to P4. These results showed a dual regulation of PGS-2 in the rat PO follicle with both stimulatory and inhibitory pathways. One of the "anti-inflammatory" actions exerted by P4 in the present study was to reduce the expression of PGS-2 and the follicular production of prostaglandins. This action might be of importance for restriction and control of the inflammatory response in the ovulatory process in vivo.

Animals↗

PubMed1997

Changes in expression of CCAAT/enhancer binding protein alpha (C/EBP alpha) and C/EBP beta in rat liver after partial hepatectomy but not after treatment with cyproterone acetate.

BACKGROUND/AIMS: The proliferation rate of adult rat liver is normally very low. It is markedly enhanced during compensatory regeneration, e.g. after partial hepatectomy, or after administration of certain growth promoters, e.g. cyproterone acetate. These two types of liver cell proliferation appear to differ, since the expression of immediate early genes is induced during compensatory regeneration but not after cyproterone acetate treatment. The transcription factor C/EBP alpha, which has been associated with hepatocyte differentiation and growth arrest, is suppressed during compensatory regeneration. In contrast, C/EBP beta, associated with acute phase reaction, is increased during regeneration. We have investigated the effects of the liver growth promoter cyproterone acetate on the hepatic expression of C/EBP alpha and C/EBP beta. METHODS: Adult male rats received either cyproterone acetate treatment or were subjected to partial hepatectomy. Livers were obtained at different time intervals for measurement of C/EBP alpha and C/EBP beta mRNA with solution hybridization/RNAse protection assay, and C/EBP alpha and C/EBP beta content with immunoblotting. RESULTS: The levels of both C/EBP alpha and C/EBP beta mRNA and the corresponding immunoreactivities were unchanged 2-48 h after injection of cyproterone acetate. The levels of C/EBP alpha mRNA and immunoreactivity were significantly suppressed 10-18 h and 18-26 h after partial hepatectomy, respectively. The levels of C/EBP beta mRNA and immunoreactivity were enhanced during compensatory regeneration 2 h after partial hepatectomy. CONCLUSIONS: Liver cell proliferation during regeneration, but not in response to cyproterone acetate treatment, is associated with changes in C/EBP alpha and C/EBP beta expression. This further supports the notion that changes in expression of transcription factors during liver growth in vivo are dependent on the growth inducer.

Animals↗

PubMed1997

The expression of c-myc during follicular growth and luteal formation in the rat ovary in vivo.

The processes of folliculogenesis and formation of corpora lutea involve proliferation and differentiation of the follicular cells. The expression of several oncogenes is associated with the proliferative phase in many cell types. The present study examined the expression and hormonal regulation of the c-myc proto-oncogene during follicular development and the luteal phase of pseudopregnancy. Follicular development was initiated by pregnant mare's serum gonadotropin (PMSG) in immature rats followed two days later by the injection of human chorionic gonadotropin (hCG) to induce ovulation and luteal formation. Ovaries were collected at different time points and the content and distribution of c-myc mRNA/protein were examined. C-myc increased rapidly after the administration of both PMSG and hCG, but the effect of PMSG was less pronounced. The increase after PMSG was transient and localized primarily to the granulosa cells of developing follicles. The ovulatory dose of hCG resulted in a rapid and substantial increase of c-myc mRNA and protein with maximal levels at 1 h and 2-4 respectively. At this stage, the c-myc protein was localized to the follicular cells, the surface epithelium and, to some extent, to the interstitial tissue. There was a subsequent decrease prior to ovulation. The luteal phase was characterized by decreasing levels of c-myc with increasing luteal age. In order to examine the involvement of specific hormones in the regulation of c-myc, hypophysectomized, immature rats were injected sequentially with estradiol (E2) and follicle-stimulating hormone (FSH). Hypophysectomy resulted in a decrease of c-myc compared with intact animals. The administration of E2 resulted in an increase of c-myc mRNA and protein. The subsequent treatment with FSH did not result in a further increase and the levels remained at the same level as with E2 only. However, an ovulatory dose of hCG to E2 and FSH primed animals resulted in an additional increase of c-myc mRNA and protein. The levels after E2 and FSH were considerably lower compared with those of untreated ovaries of intact, immature animals, suggesting the involvement of other endocrine and paracrine factors. The presence of proliferating cell nuclear antigen in cell extracts indicated that the expression of c-myc was associated with phases of increased proliferation of follicular cells after hormonal stimulation. The results demonstrate that c-myc is regulated by hormones (E2, gonadotropins) in the rat ovary during follicular development to the preovulatory stage. The pronounced increase prior to ovulation also suggests a role for c-myc in the regulation of proliferative events involved in luteal formation.

Animals↗