| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Institute of Endocrinology (T.R., I.S.), and Departments of Neurosurgery (M.H.), Human Genetics (G.B.), and Pathology (D.N.), Chaim Sheba Medical Center, Tel-Hashomer 52621, Israel; and Cedars-Sinai Research Institute (R.Y., S.M.), Los Angeles, California 90048
Address all correspondence and requests for reprints to: Ilan Shimon, M.D., Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer 52621, Israel. E-mail: i_shimon{at}netvision.net.il.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Cell adhesion molecules (CAMs), initially believed to account merely for the mechanical stability of cell-cell interactions, are now known to participate in most fundamental cell activities, including proliferation, differentiation, mitogenesis, and apoptosis (1, 3, 4, 5). The cadherins and the Ig-like molecules are two families of adhesion molecules (6). N-cadherin is a subgroup of the cadherins, referred to as the classical type I cadherin. These transmembrane glycoproteins are located at the plasma membrane of most solid tissues and mediate Ca+2-dependent cell-cell adhesion through homophilic interactions (i.e. similar molecules binding) of their extracellular domains (4, 7, 8). The cytoplasmic domain of classical cadherins is highly conserved and binds several cellular proteins, including the catenins (7). The second adhesion molecule family, the Ig-like CAM superfamily, is characterized by the presence of a motif resembling Ig proteins (8). Neural CAM (N-CAM), a member of this family, is characterized by five extracellular Ig-like and two fibronectin III domains. Unlike the well-established cadherin-catenin interactions, there is no conclusive evidence for N-CAM intracellular domain interactions with cytoplasmic proteins.
Adhesion molecules usually participate in developmental tissue formation, maintenance, and dedifferentiation. Accumulating evidence suggests that pituitary hormone secretion is also regulated by cell-cell contact, mediated by CAMs. N-CAMs are expressed in all fetal and adult rat pituitary cell types (9). N-CAM is detected in most pituitary adenomas, except for prolactinomas, which express low levels of N-CAM (10, 11, 12). In GH4 rat pituitary cells N-CAM induction is associated with extensive cell-cell adhesion and 40-fold prolactin (PRL) elevation (13). In rat somatolactotroph GH3 cells estradiol promotes a nonadherent phenotype accompanied by barely detectable N-cadherin and ß-catenin protein levels (14). In cultured rat anterior pituitaries cell-cell interactions of somatotrophs with lactotrophs result in increased GH responses to epinephrine and dexamethasone (15). Maintaining the three-dimensional pituicyte structure appears essential for GH and PRL induction by IL-11 and ciliary neurotropic factor (16).
GH secretion is regulated by hypothalamic hormones, including GHRH and somatostatin, and by peripheral factors, including ghrelin (17) and IGF-I. In this study, we evaluated the role of N-cadherin and N-CAM adhesion molecules in modulating GH regulation. The results show that both N-cadherin and N-CAM are expressed in fetal and adult pituitary tissues. These CAMs have similar expression patterns in pituitary adenomas, and are expressed in most GH-secreting adenomas, but in only a minority of PRL-secreting tumors. N-cadherin and N-CAM are shown to activate both fetal and adenomatous GH secretion from human pituitary cultures. The results indicate that N-cadherin and N-CAM directly regulate human GH.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Human fetal pituitary tissues of 19–23 wk gestation (males and females) were obtained after therapeutic pregnancy terminations. Studies of human fetal pituitaries followed guidelines of the National Advisory Board on Ethics in Reproduction (18), and written informed consent was obtained from pregnant subjects. Normal adult pituitary tissues were obtained during postmortem examinations. Pituitary adenoma specimens were obtained from transphenoidal surgical resections. Normal (fetal or adult) and adenomatous pituitary tissues were either snap-frozen (for RNA assays), fixed for immunostaining, or placed in culture medium for cell culture studies.
Pituitary RNA extraction
Normal human adult and fetal pituitaries and pituitary adenomas were harvested and kept at –70 C for RNA extraction. After homogenization, total RNA was extracted using guanidium isothiocyanate-phenol-chloroform (TRIzol, Invitrogen, Carlsbad, CA), and aliquots of RNA were electrophoresed through Tris borate EDTA gel to confirm RNA integrity.
RT-PCR
RT, followed by PCR amplification, was performed to detect N-cadherin, N-CAM, and ß-actin mRNA expression in normal and adenomatous pituitary tissues. RNA was treated with deoxyribonuclease before the RT reaction to eliminate contaminating genomic DNA. The reaction was stopped by heating and used in an RT reaction containing 75 mM KCl, 50 mM Tris-HCl (pH 8.3), 3 mM MgCl2, 10 mM dithiothreitol, 1 mM of each deoxy-NTP, 2.5 µM oligo(deoxythymidine)16, and 200 U RT (Superscript II, Invitrogen). RT reactions were incubated at 42 C for 50 min and then at 70 C for 15 min. Samples were also incubated without RT as negative controls. The resulting cDNA and negative controls were used for subsequent PCR amplification of N-cadherin, N-CAM, and ß-actin in reactions containing 50 mM KCl, 20 mM Tris-HCl (pH 8.4), 1.5 mM MgCl2, 200 µM of each deoxy-NTP, 40 pM of each primer, and 5 U Taq DNA polymerase (Invitrogen). After initial denaturation, amplifications were carried out for 35 cycles, with a final 7-min extension step at 72 C. Each cycle consisted of denaturation at 94C for 1 min, annealing for 1 min (at 59, 63, and 60 C for N-cadherin, N-CAM, and ß-actin, respectively), and elongation at 72 C for 1 min and 30 sec. The following primer sets (purchased from Invitrogen) were used: N-cadherin, 5'-CACTGCTCAGGACCCAGAT and 3'-TAAGCCGAGTGATGGTCC (1080–1495 bp); N-CAM, 5'-ATGATGATTCCTCCTCCACC and 3'-TGGACAGGACTATGAATCGG (355–644 bp); and ß-actin, 5'-ATCTGGCACCACACCTTCTACAATGAGCTGCG and 3'-CGTCATACTCCTGCTTGCTGATCCACATCTGC (294–1131 bp). The PCR products thus generated are 415, 291, and 837 bp for N-cadherin, N-CAM, and ß-actin, respectively. The PCR product of N-cadherin was digested by SspI (37-, 105-, and 273-bp restriction products) and N-CAM by BglII (173 and 119 bp; both enzymes from Promega, Madison, WI), and visualized with ethidium bromide after electrophoresis on 2% agarose gel.
Immunofluorescent staining and microscopy
Normal adult and fetal pituitaries and pituitary adenoma tissues were formaldehyde-fixed (4% in PBS), dehydrated, and paraffin-embedded for 5-µm sections. Slides were baked at 60 C for 2 h, dewaxed and rehydrated, microwaved, and stained with the following primary antibodies: mouse anti-N-cadherin (1:100; clone 3B9, Zymed Laboratories, San Francisco, CA), mouse anti N-CAM (1:100; clone 123C3, Santa Cruz Biotechnology, Santa Cruz, CA), rabbit antihuman GH and rabbit antihuman PRL (1:10,000; NIDDK). Rhodamine-labeled goat antimouse (1:500; Molecular Probes, Eugene, OR) and fluorescein-labeled goat antirabbit (1:500; Molecular Probes) secondary antibodies were used. Cells were finally stained with Hoechst 33258 (1:10,000; Molecular Probes) for 5 min. After washing, samples were kept in mowiol and examined with a Nikon TE200 fluorescence microscope (Melville, NY) equipped with a x40 oil immersion objective, appropriate optical filters, and a digital camera.
Human fetal pituitary and pituitary adenoma primary cell cultures
Fetal specimens were harvested from pathological specimens within 0.5–2 h of the termination procedure. Pituitary adenoma specimens were collected during transsphenoidal procedures. Fetal pituitary and tumor specimens were treated similarly and washed in low glucose DMEM supplemented with 0.3% BSA, 2 mM glutamine, and antibiotics, then minced and enzymatically dissociated using 0.35% collagenase and 0.1% hyaluronidase (both from Sigma-Aldrich Corp., St. Louis, MO) for 45–60 min. Cell suspensions were filtered through 80-µm nylon mash (Millipore Corp., Bedford, MA) and resuspended in low glucose DMEM supplemented with 10% fetal bovine serum, 2 mM glutamine, and antibiotics. For primary cultures, approximately 5 x 104 cells were seeded in 48-well tissue culture plates (Costar, Cambridge, MA) in 0.5 ml medium and were incubated for 72–96 h in a humidified atmosphere of 95% air/5% CO2 at 37 C. Coculture preparation is described in detail below. Medium was then changed to serum-free defined (SFD), low glucose DMEM containing 0.2% BSA, 120 nM transferrin, 100 nM hydrocortisone, 0.6 nM T3, 5 U/liter insulin, 3 nM glucagon, 50 nM PTH, 2 mM glutamine, 15 nM epidermal growth factor, and antibiotics. Cells were treated for 6 h with 5 µg/ml N-cadherin-Fc (or as indicated, described below), 5 µg/ml intracellular adhesion molecule-Fc (with separate set of control wells; R&D Systems, Inc., Minneapolis, MN), with GHRH and somatostatin-14 (both 10 nM; from Sigma-Aldrich Corp.), and with 20 µg/ml neutralizing N-cadherin antibody (clone GC4) or IgG1 antibody as a control (both from Sigma-Aldrich Corp.). A single pituitary specimen (either fetal or adenoma) was divided and plated into 60–80 wells depending upon the age and size of the specimen. In each experiment 6–9 wells served as controls (treated with vehicle solution), and groups of 6–9 wells were treated as indicated. Medium was then collected and stored at –20 C for later hormone measurements.
Pituitary and NIH-3T3 cocultures
Parental and CAM-transfected (chick N-cadherin and human muscle glycosylphosphatidylinsitol-linked N-CAM) clones of mouse NIH-3T3 cells, provided by Dr. P. Doherty, King’s College (London, UK) (19, 20), were routinely maintained in high glucose DMEM containing 10% fetal bovine serum and kept in a humidified atmosphere of 5% CO2 at 37 C. Coculture monolayers were established by seeding 3 x 104 parental or CAM-transfected 3T3 cells in 48-well dishes (Costar). Twenty-four hours later, approximately 104 primary fetal or adenomatous human pituitary cells were added to confluent 3T3 monolayers. Cocultures were kept for 24 h in 3 g/liter glucose/DMEM. Medium was then replaced by SFD medium (3 g/liter glucose), and 6–24 h later medium was collected and stored at –20 C for subsequent hormone measurements. For N-cadherin-blocking experiments, cocultures were treated for an additional 6 h with 20 µg/ml N-cadherin antibody (GC4, Sigma-Aldrich Corp.).
Hormone assays
Human GH was measured by RIA (Diagnostic Products, Los Angeles, CA). As absolute hormonal levels differed between fetal and adenoma specimens, all hormonal data were expressed as a percentage of the control.
N-cadherin-Fc chimera production
A chimeric molecule consisting of the Fc region of human IgG (hinge CH2-CH3) and essentially the whole extracellular domain of chicken N-cadherin was constructed using the pIg1 vector (a gift from Dr. P. Doherty, London, UK) (21, 22). After transformation of Escherichia coli MC1061/P3 cells by the plasmid DNA, 293 human embryonic kidney cells were transiently transfected by the plasmid, using calcium phosphate method. The chimeric protein was isolated from the conditioned medium by affinity chromatography using protein A-Sepharose. It was eluted from the column by glycine buffer (pH 2.8) and was immediately neutralized with Tris buffer (pH 9.0). All N-cadherin-Fc-containing fractions were collected, and the protein concentration was determined using a Bradford assay (Bio-Rad Laboratories, Hercules, CA). A sample of each protein-containing fraction eluted was separated by SDS-PAGE (7.5%, wt/vol) and stained with Coomassie Blue (Fig. 1A
) or electroblotted onto a nitrocellulose membrane for Western blotting (Fig. 1B). The Fc chimera was visualized using N-cadherin antibody (1:500; GC4 clone, Sigma-Aldrich Corp.). The purified chimera preparation consists of two major bands of approximately 115 and 130 kDa (Fig. 1A); both bands were immunoreactive with N-cadherin antibody (Fig. 1B).
|
Results were expressed as the mean ± SD. Data were analyzed by one-way ANOVA, followed by Tukey test in all experiments, except Fig. 4B, where t test was used, and Fig. 5A, where results were evaluated by regression analysis. P < 0.05 was considered significant.
|
|
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Total RNA was extracted from normal adult and fetal (21–25 wk gestation) pituitaries and from GH- and PRL-secreting pituitary adenomas. RNA was subjected to RT, followed by PCR amplification for N-cadherin and N-CAM adhesion molecule mRNAs, and ß-actin as an RT-PCR control. PCR results revealed N-cadherin expression in eight of 12 GH-secreting adenomas compared with only one of seven PRL-secreting adenomas (415-bp product; Fig. 2A and Table 1). Normal adult and fetal pituitaries (21, 23, and 25 wk) expressed N-cadherin mRNA. Negative controls (no RT) were consistently free of PCR products (data not shown). As N-cadherin and N-CAM are often coexpressed in other tissues (23, 24, 25, 26), we examined N-CAM mRNA expression in the same specimens and found similar expression patterns for N-cadherin and N-CAM (291-bp PCR product; Fig. 2A). The 415-bp band representing N-cadherin expression was appropriately digested by SspI (Fig. 2B), and the N-CAM PCR product was digested by BglII (Fig. 2B). Table 1, summarizing all pituitary tissues tested, indicates that N-CAM and N-cadherin mRNAs are coexpressed in 58% of GH cell adenomas, and both are undetectable in most PRL cell adenomas. The results of N-cadherin and N-CAM immunostaining of selected GH- and PRL-secreting adenoma specimens confirmed RT-PCR findings (data not shown).
|
|
The effects of N-cadherin homophilic binding on GH secretion from dispersed human pituitary cultures were studied using soluble N-cadherin. Soluble N-cadherin was obtained by transfecting human embryonic kidney 293 cells with a plasmid encoding the extracellular cDNA sequence of N-cadherin fused to the Fc region of human IgG (CH2-CH3 hinge; see Fig. 1
, A and B). GH secretion from human pituitary cultures treated with N-cadherin-Fc for 6 h was enhanced by about 40% (P < 0.05) compared with controls (Fig. 3A). Intracellular CAM-Fc (I-CAM-Fc), an adhesion molecule not expressed in the pituitary, had no effect on GH secretion in these cultures. The effect of GHRH on GH release was higher (
70%; P < 0.0005; Fig. 3A) than that evoked by N-cadherin-Fc. Fetal pituitary cultures were treated with neutralizing N-cadherin antibody, which is known to disrupt and prevent N-cadherin-mediated cell contact while maintaining other adhesion molecules’ contacts intact. GH release was suppressed in cultures treated with a neutralizing antibody by approximately 40% (P < 0.005; Fig. 3B) compared with controls treated with mouse IgG1. The magnitude of GH suppression by anti-N-cadherin is similar to the inhibitory effect of somatostatin-14 (Fig. 3B). The inhibitory effect of N-cadherin-neutralizing antibody was reversed by N-cadherin-Fc (Fig. 3C). Increasing the N-cadherin-Fc concentration restored its stimulatory effect (P < 0.001, vs. control) even in the presence of N-cadherin antibody.
|
Another approach to manipulate CAM-mediated cell-cell contact was culturing human fetal pituitary cells with either parental NIH-3T3 cells or cells stably expressing chicken N-cadherin or human N-CAM. Twenty-four hours after coculture establishment and after 6-h incubation with SFD medium, no differences between cocultures in hormone secretion were observed (Fig. 4A). However, in the subsequent 24 h, GH secretion from fetal pituitary cells cocultured with N-cadherin-3T3 or N-CAM-3T3 cells increased by 45–60% (P < 0.001) compared with secretion from cocultures with parental 3T3 cells (Fig. 4A). The specificity of CAM-dependent GH induction in fetal cocultures was confirmed using anti N-cadherin antibody. GH secretion was modestly inhibited in parental 3T3 cocultures, whereas a marked decrease (40%; P < 0.05) was detected in N-cadherin-expressing 3T3 cocultures (Fig. 4B). GH was not suppressed in N-CAM-expressing cocultures.
N-cadherin homophilic binding modulates GH secretion from human GH-cell adenoma cultures
The observed differences in N-cadherin expression in GH- and PRL-secreting adenomas suggested a role for N-cadherin in GH-secreting adenoma cells. Treatment of GH-secreting adenoma cultures with 1 and 5 µg/ml N-cadherin-Fc for 6 h increased GH secretion up to 75% compared with controls (P < 0.05; Fig. 5A). Interestingly, N-cadherin antibody did not suppress GH secretion from these cultures. Cocultures of 3T3 cells (parental or CAM-transfected) with GH adenoma cells demonstrated elevated GH levels of about 40% (P < 0.05) after 24-h incubation in the presence of cells transfected with N-cadherin or N-CAM compared with parental cells (Fig. 5B).
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Both N-cadherin and N-CAM are abundantly expressed in GH-secreting adenomas in contrast to PRL-secreting adenomas. Unlike N-cadherin, N-CAM expression has been previously studied, and contradictory results have been reported. Several studies showed N-CAM expression in most GH-secreting and nonfunctioning pituitary adenomas, whereas its expression in PRL-secreting adenomas was much reduced (10, 11) or similar (27). These data and the results reported here show that N-cadherin and N-CAM protein and mRNA expression in PRL-secreting adenomas are very low compared with those in GH-secreting adenomas even though ultrasensitive methods could also detect N-CAM in PRL-secreting adenoma cells (27). Normal adult and fetal pituitary express N-cadherin and N-CAM. In rodents, N-CAM is expressed in all cell types in developing and adult pituitaries, with no remarkable differences between cells (9). However, cell type-dependent CAM expression in normal human pituitary has not been reported previously.
Most GH-secreting adenomas expressed N-cadherin and N-CAM, and these adhesion molecules were found to modulate GH secretion. Using two approaches to enhance CAM-mediated cell contact, a soluble N-cadherin-Fc chimeric molecule and pituitary cells cultured with NIH-3T3 cells stably expressing N-cadherin or N-CAM, suggest that homophilic binding of these CAMs induces GH secretion from fetal and adenomatous pituitary cultures. Each of these strategies highlights a different characteristic of cell-cell communication mediated by these adhesion molecules. On the one hand, cocultures simulate extensive cell-cell contact mediated by CAMs. On the other hand, N-cadherin-Fc added to cell medium manifests the ability of CAMs to transmit specific cell signals, similarly to soluble ligands; thus, physical cell-cell contact becomes less apparent. As N-cadherin-Fc stimulates GH secretion similarly to effects obtained in CAM-expressing cocultures, CAMs probably elevate GH secretion through a specific signal transmitted to the somatotroph rather than through nonspecific extensive cell-cell contacts. Furthermore, N-cadherin blocking antibody suppressed fetal GH secretion mainly from N-cadherin-expressing cocultures, indicating the specificity of N-cadherin action on human GH stimulation. It seems that the effect of CAM activation through a soluble molecule is achieved more rapidly than through direct cell-cell contact (6 vs. 24 h), and this time course can be explained by high concentrations of N-cadherin-Fc molecules/pituicyte. Another explanation is that N-cadherin-Fc has access to the entire pituicyte surface, thus activating several endogenous N-cadherin molecules compared with CAM-expressing 3T3 cells. Cocultures, however, probably more closely reflect a physiological state present in the pituitary.
Inhibition of N-cadherin homophilic binding by neutralizing N-cadherin antibody persistently reduced GH secretion from human fetal pituitary cultures, thus emphasizing the role of N-cadherin in regulating GH secretion. Interestingly, GH was not suppressed by this antibody in GH-cell adenoma cultures, indicating that although enhanced cell-cell contact mediated by N-cadherin and N-CAM up-regulates GH secretion in GH-cell adenomas, disruption of that contact does not necessarily lead to reduced GH secretion. This phenomenon may result from constitutive GH gene activation downstream from the N-cadherin disruption effect. It may also be explained by tumor-associated mutations in N-cadherin or other molecules associated with signal transduction pathways, for example, the catenins, which may interfere with the inhibitory actions of the antibody. A recently published work shows abnormal nuclear accumulation of ß-catenin in most pituitary adenomas, associated with mutations in the third exon of ß-catenin and correlated with the Ki-67 proliferation index (28). Thus, mutated ß-catenin may reverse somatotroph susceptibility to disrupted cell contact into a relatively resistant phenotype. However, as the stimulatory pathway is operative in adenoma cultures whereas the inhibitory is not responding, it is possible that GH is partially stimulated by nonspecific factors present in the culture medium.
Several studies have demonstrated a link between pituitary hormone expression and secretion, and CAM expression. 17ß-Estradiol was shown to promote a nonadherent GH3 cell phenotype while elevating PRL expression (14). Antiestrogen treatment reduced PRL and increased N-cadherin and catenin expression together with increased cell-cell adhesion. This was abolished by a blocking N-cadherin antibody (14). In rat 235-1 tumor lactotroph cells, dexamethasone reduces PRL expression while increasing 
- and ß-catenin expression, but has no significant effect on N-cadherin expression (29). These studies suggest, in accordance with our results reporting low CAM expression in PRL-secreting adenomas, that PRL expression is associated with down-regulation of adhesion proteins. These studies also suggest the involvement of nuclear receptors, including those for estrogen and glucocorticoids, in hormone regulation by adhesion molecules. GH regulation by N-CAM was studied in adult N-CAM knockout mice (30). These mice were smaller than wild-type mice, and their pituitary weight was lower, but their pituitary gland contained more somatotrophs (30). This contradictory finding may be explained by a compensatory pituitary response to reduced GH secretion from N-CAM-deleted somatotrophs.
N-CAM expression in the rat pituitary increases during pituitary development and persists until adulthood (9). Cadherin homophilic binding usually leads to increased cadherin expression and cell surface recruitment of cadherin molecules, whereas its disruption causes the opposite effect (31, 32, 33). The results here demonstrate N-CAM and N-cadherin expression in human pituitaries derived from second trimester fetuses. Human pituitary cells are responsive to hypothalamic releasing and inhibitory factors, including somatostatin (34, 35, 36), GHRH (34, 35, 36), and other hypothalamic hormones (34), as early as 10–14 wk gestation, with significant increases in the magnitude of somatotroph responses to somatostatin and GHRH with increasing fetal maturity. Therefore, in the human fetal pituitary, hormonal systems regulating GH are already developed in the first trimester together with other potential mechanisms modulating GH, including growth factors, cytokines, and adhesion molecules (1). Interestingly, in other neuronal model systems N-CAM and N-cadherin activation promote tissue differentiation through glucocorticoid or fibroblast growth factor receptor activation (37, 38, 39, 40), thus emphasizing the possible intimate link among hormones, growth factors, and CAMs in different regulatory functions.
The results shown here support a role for CAM-mediated physical cell-cell contact in pituitary hormone regulation. Therefore, in addition to hypothalamic and peripheral hormones, intrapituitary cytokines, and growth factors (1), the direct interactions between adjacent pituicytes appear to modulate stimulatory and inhibitory tones for GH expression and secretion. This observation may potentially have relevance to clinical situations associated with GH deficiency or GH hypersecretion, and opens new opportunities for the manipulation of GH release. Thus, enhancement of pituitary CAM activity may induce GH secretion in GH-deficient states, whereas interrupting somatotroph-CAM interactions may effectively suppress hormone secretion. Intrapituitary cell-cell contact between pituitary hormone-secreting cells is therefore an added mechanism for regulating hormone secretion.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
Abbreviations: CAM, Cell adhesion molecule; N-CAM, neural CAM; PRL, prolactin; SFD, serum-free defined.
Received January 17, 2003.
Accepted April 24, 2003.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
 |
|
 |
|
  S. R Valdez, A. B Penissi, R. P Deis, and G. A Jahn Hormonal profile and reproductive performance in lactation deficient (OFA hr/hr) and normal (Sprague-Dawley) female rats Reproduction, April 1, 2007; 133(4): 827 - 840. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Gelernter, Y. Yu, R. Weiss, K. Brady, C. Panhuysen, B.-z. Yang, H. R. Kranzler, and L. Farrer Haplotype spanning TTC12 and ANKK1, flanked by the DRD2 and NCAM1 loci, is strongly associated to nicotine dependence in two distinct American populations Hum. Mol. Genet., December 15, 2006; 15(24): 3498 - 3507. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Shintani, M. A. Hollingsworth, M. J. Wheelock, and K. R. Johnson Collagen I Promotes Metastasis in Pancreatic Cancer by Activating c-Jun NH2-Terminal Kinase 1 and Up-regulating N-Cadherin Expression Cancer Res., December 15, 2006; 66(24): 11745 - 11753. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Dudanova, S. Sedej, M. Ahmad, H. Masius, V. Sargsyan, W. Zhang, D. Riedel, F. Angenstein, D. Schild, M. Rupnik, et al. Important Contribution of {alpha}-Neurexins to Ca2+-Triggered Exocytosis of Secretory Granules J. Neurosci., October 11, 2006; 26(41): 10599 - 10613. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Segal-Lieberman, H. Rubinfeld, M. Glick, N. Kronfeld-Schor, and I. Shimon Melanin-concentrating hormone stimulates human growth hormone secretion: a novel effect of MCH on the hypothalamic-pituitary axis Am J Physiol Endocrinol Metab, May 1, 2006; 290(5): E982 - E988. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Bonnefont, A. Lacampagne, A. Sanchez-Hormigo, E. Fino, A. Creff, M.-N. Mathieu, S. Smallwood, D. Carmignac, P. Fontanaud, P. Travo, et al. Revealing the large-scale network organization of growth hormone-secreting cells PNAS, November 15, 2005; 102(46): 16880 - 16885. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
) or monolayers of N-cadherin-expressing 3T3 (
) or N-CAM-3T3 cells (
). Twenty-four hours later medium was replaced by SFD medium, and aliquots were removed at the indicated times (6–24 h) for hormone measurements (A) or were incubated for an additional 6 h with an N-cadherin antibody (GC4; 20 µg/ml) after medium replacement and compared with controls (similar cocultures without blocking antibody (B). Each of the bars represents the mean ± SD GH levels in six to nine wells in one of three independent experiments. *, P < 0.05; **, P < 0.005.
