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Divergent responses of gonadotropin subunit messenger RNAs to continuous versus pulsatile gonadotropin-releasing hormone in vitro 总被引:2,自引:0,他引:2
J Weiss J L Jameson J M Burrin W F Crowley 《Molecular endocrinology (Baltimore, Md.)》1990,4(4):557-564
Episodic GnRH input is necessary for the maintenance of LH and FSH secretion. In the current study we have assessed the requirement of a pulsatile GnRH signal for the regulation of gonadotropin alpha- and beta-subunit gene expression. Using a dispersed rat pituitary perifusion system, GnRH (10 nM) was administered as a continuous infusion vs. hourly pulses. Secretion of free alpha-subunit, LH, and FSH were monitored over 5-min intervals for the entire 12-h treatment period before the responses of alpha, LH beta, and FSH beta mRNAs were assessed. Basal release of all three glycoproteins declined slowly over 6-8 h before reaching a plateau. The cells were responsive to each pulse of GnRH, but continuous GnRH elicited only a brief episode of free alpha-subunit, LH, and FSH release, followed by a return to unstimulated levels. Despite the similar patterns of secretion, differences were observed in the responses of gonadotropin mRNAs to the two modes of GnRH. alpha mRNA increased in response to continuous (1.6-fold) or pulsatile (1.7-fold) GnRH. FSH beta mRNA was suppressed to 48% of the control value after continuous GnRH, but was stimulated over 4-fold by the pulses. LH beta mRNA was unresponsive to either treatment paradigm. We conclude that in vitro 1) alpha mRNA levels are increased in response to GnRH independent of the mode of stimulation; 2) under the conditions studied, LH beta mRNA levels are unresponsive to either mode of GnRH input; and 3) the response of FSH beta mRNA to GnRH is highly dependent on the mode of administration, with levels depressed in response to continuous GnRH, but stimulated by pulsatile GnRH.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献
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A H Barnett A J Spiliopoulos D A Pyke W A Stubbs J Burrin K G Alberti 《BMJ (Clinical research ed.)》1981,282(6277):1656-1658
Forty-eight out of 53 non-insulin-dependent diabetic identical twin pairs were concordant for diabetes. In the five discordant pairs the diabetic twin had only recently been diagnosed. Oral glucose tolerance tests were carried out on the unaffected twins of the five pairs and on matched controls. Fasting concentrations of blood glucose (5.5 +/- 0.6 v 3.7 +/- 0.3 mmol/l; 99.1 +/- 10.8 v 66.6 +/- 5.4 mg/100 ml), haemoglobin A1 (mean 9.1%, range 8.8-9.2% v mean 7.9%, range 7.4-8.4%), lactate, alanine, and glycerol (0.090 +/- 0.017 v 0.045 +/- 0.008 mmol/l); and the lactate: pyruvate ratio were significantly higher in the twins than controls. After glucose challenge blood glucose, lactate, alanine, and glycerol concentrations and lactate: pyruvate ratio were increased in the twins. Insulin response was severely impaired, being almost absent in four of the five twins. The non-diabetic members of the discordant non-insulin-dependent diabetic pairs showed noticeable metabolic abnormalities which would later presumably deteriorate to frank diabetes. These findings, taken with the high concordance rate for non-insulin-dependent diabetic twins, suggest that non-insulin-dependent diabetes is predominantly, possibly entirely, inherited. 相似文献
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