Comparative studies on insulin-like growth factor-I at the molecular and endocrine levels:

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" Comparative studies on insulin-like growth factor-I at the molecular and endocrine levels: "
M. C. McGuinness W. L. Bacon

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113248
Doc. No	:	TLpq304441806
Main Entry	:	M. C. McGuinness
	:	W. L. Bacon
Title & Author	:	Comparative studies on insulin-like growth factor-I at the molecular and endocrine levels:\ M. C. McGuinnessW. L. Bacon
College	:	The Ohio State University
Date	:	1998
student score	:	1998
Degree	:	Ph.D.
Page No	:	221
Abstract	:	Insulin-like growth factor I (IGF-I) is an important hormonal regulator of embryonic development and postnatal growth. The IGF-I gene expression is complex, with heterogeneity of mRNA structure arising during transcription and splicing of primary RNA transcripts. The chicken has been reported to have a much simpler IGF-I transcript structure than mammalian species, which would distinguish it as the only non-heterogeneous IGF-I cloned thus far. The purpose of the research was to perform comparative studies in two avian species to determine the mRNA structure and gene expression patterns of IGF-I, and to relate these to plasma hormone concentrations. Molecular protocols using alternate methods for RNA cloning were validated for use in reverse transcription-polymerase chain reaction (RT-PCR) cloning of IGF-I from broiler chickens and Japanese quail. Analysis of the 5 regions of chicken and quail IGF-I transcripts showed the presence of two mutually exclusive, alternate leader exons. Therefore, the complexity of IGF-I transcripts was similar among avian and mammalian species. The cDNA sequences of the turkey and Japanese quail IGF-I mature peptide coding region were at least 98% homologous to that of the chicken, and all three species have identical amino acid sequences for IGF-I. Plasma hormones levels and hepatic gene expression during post-hatch growth through sexual maturity were determined in Japanese quail selected for high or low 4 week body weight (BW). Interestingly, the low BW quail were generally hyperpituitary, with significantly higher (p <.05) plasma levels of growth hormone (GH), prolactin, triiodothyronine (T3) and IGF-I. Hepatic expression of GH receptor and plasma GH levels were inversely related. High plasma GH concentrations down-regulated GH receptor expression in low BW birds, and there was a concomitant decrease in GH receptor binding activity in native liver membranes (p <.05). The IGF-I mRNA levels paralleled the relationship seen for plasma IGF-I concentrations among the selected lines. In conclusion, plasma GH and IGF-I levels and IGF-I gene expression were negatively associated with selection for BW. Restriction fragment length polymorphisms in the IGF-I gene were present among the quail lines, indicating gene polymorphisms or alternate IGF-I alleles associated with selection for low or high body weight.
Subject	:	Anatomy physiology
	:	Animals
	:	Biological sciences
	:	chicken
	:	Japanese quail
	:	turkey