Cloning and Sequence Analysis on cDNA of Growth Hormone Releasing Hormone Receptor Gene from Wuzhishan Miniature Pig

[Objective] cDNA of growth hormone releasing hormone （GHRH） receptor gene from Wuzhishan miniature pig was cloned and its sequence was also analyzed. [Method] Using genomic DNA extracted from porcine ear tissues of Wuzhishan miniature pig as the template, three pairs of primers were designed by the reported cDNA sequence of porcine GHRH, and cDNA was also amplified by RT-PCR. After being recovered and purified, PCR products were ligated to pMD18-T and then transformed into Escherichia coli DH5a. The transformation products were analyzed by PCR and double enzyme digestion to screen positive clones, and the positive clones were sequenced after identification in LB liquid medium. [ Result] cDNA of Wuzhishan miniature pig GHRH receptor gene was obtained successfully, and its length was 1 577 bp coding 423 amino acids. BLAST analysis showed that there were only 23 nuoleotides in difference between this fragment and pomine GHRH receptor gene, and its homology was 98%. However, both GHRH receptor genes were constituted by 423 amino acids with the sequence homology of 96%. [ Conclusion] This study provides theoretical basis for further studies on the dwarf mechanism of Wuzhishan miniature pig.

TPA Enhances Growth Horm one (GH) Secretion Effect ofGH-Releasing Horm one (GHRH) by Hum an gsp-PositivePi-tuitary Som atotrophinom as

In recent years, one of the most exciting advances in the researches of pituitary adenomas is the discovery that 30 %-40 % of human pituitary somatotrophinomas carry somatic mutations of the gene for the α subunit of the stimulatory GTP binding protein, G s (G sα). These mutations, termed gsp oncogenes, may play an important role in the tumorigenesis of pituitary adenomas. Of 10 somatotrophinomas examined, 3 (30 %) were proved to be gsp positive, as determined by sequence analysis of DNA generated by the polymerase chain reaction (PCR). GHRH exerted a significant stimulatory effect on GH secretion in 2 of 3 gsp positive and 4 of 7 gsp negative tumors. Moreover, phorbol ester, 1, 2 tetradecanoylphorbol 13 acetate (TPA), enhanced stimulation of lated the GH secretion effect exerted by GHRH in gsp positive somatotrophinomas, whereas this effect was not observed in gsp negative tumors. This result suggests that the protein kinase C signal system as well as adenylyl cyclase cAMP protein kinase A intracellular signal transduction system plays a pivotal role in GH secretory control of GHRH, which may work together via a cross talk mechanism.

The Role of Protein Kinase C and Its Effect on GHRH in the Regulation of Hormone Secretion by Somatotrophinomas

Summary: Phorbol ester-induced release of growth hormone (GH) and prolactin (PRL) from hu- man somatotrophic tumors was examined in vitro. 12-O-tetradecanoyl-phorbol-13-acetate (TPA) strongly stimulated GH and PRL secretion and showed an additive effect on GH secretion if used in combination with GH releasing hormone (GHRH). In contrast, staurosporine exerted a variable inhibitory effect on GH release. There was no correlation between such effects and gsp mutations. The findings suggested that TPA doesn't act directly through cAMP signal transduction system.

Targeted therapy in advanced metastatic colorectal cancer: Current concepts and perspectives

The introduction of new cytotoxic substances as well as agents that target vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) signaling has improved clinical outcome of patients with metastatic colorectal cancer (mCRC). In this review we summarize the most relevant clinical data on VEGF and EGFR targeting regimens in mCRC. The effects of available treatment strategies for mCRC are often temporary, with resistance and disease progression developing in most patients. Thus, new treatment strategies are urgently needed. Some GI peptides including gastrin and gastrin releasing peptide, certain growth factors such as insulin-like growth factor-I and II and neuropeptides such as growth hormone releasing hormone (GHRH) are implicated in the growth of CRC. Experimental investigations in CRC with antagonistic analogs of bombesin/gastrin-releasing peptide, GHRH, and with cytotoxic peptides that can be targeted to peptide receptors on tumors, are summarized in the second part of the review.

THE ROLE OF CALCIUM ION IN THE PATHOGENESIS OF HUMAN PITUITARY GH－SECRETING ADENOMAS

To study the role of Ca2+ in the pathogenesis of pituitary growth hormone secreting adenomas, the function of Ca2+ in 23 cases of human Prturtary GH-secreting adenoma was investigated in monolayer cell culture. It was found that Ca2+ channel blockers nicardipin and nifedipin inhibrted basal and growth hormone releasing hormone (GRH)stimulated GH secretion in 87. 5 % and 100. 0 % of the GH adenomas . respectively, demonstrating that in most human pituitary GH adenomas, the basal and GRH regulated GH secretion is Ca2+ dependent. The GRH and sometostatin (SRIF) agonist octreotide regulated the processes of GH secretion via Ca2+ had defects in different steps including receptor ,postreceptor Ca2+ channel and Ca2+GH secreting coupling in 6 (66. 6%) and 5 (55. 5 % ) cases of 9 GH adenomas respectively. Among them,the defects in GRH receptor and SRIF regulated Ca2+ channel are the main causes of the dysfunction of GH adenomas. These defects may be related to GH hypersecretion in GH adenomas. Our data provides advance evidences for intrinsic defects of GH adenomas.