Replacement of the invariant tyrosine in the CAGY region of the human chorionic gonadotropin β subunit

The mammalian glycoprotein hormone β subunits contain a highly conserved amino acid sequence, Cys-Ala-Gly-Tyr-Cys (residues 34–38 of human chorionic gonadotropin β), that is denoted as the ‘CAGY region’. Using site-directed mutagenesis we have replaced Tyr-37 in hCGβ, i.e., the invariant Tyr in all known mammalian CG, LH, FSH, and TSH β subunits, with two hydrophobic amino acid residues, Phe and Leu. The resultant mutant forms were characterized for α subunit binding and the resulting heterodimers were analyzed for biological activity using two in vitro assays with transformed murine Leydig cells (MA-10). Chinese hamster ovary cells containing a stably integrated gene for bovine α were transiently transfected with a eukaryotic expression vector containing a Rous sarcoma viral promoter and the wild-type and mutant cDNAs. The hCGβ(Phe-37) mutant bound to α essentially to the same extent as hCGβ wild-type, while the hCGβ(Leu-37) mutant formed somewhat less heterodimer. The heterologous heterodimeric mutant and wild-type gonadotropins were equipotent in a competitive binding assay with [¹²⁵I]hCG. In a steroidogenic assay, the mutant hormones were active, but they appeared slightly less potent than the wild-type form. Thus, this invariant Tyr can be replaced with another aromatic amino acid residue or with a hydrophobic, but not aromatic amino acid residue in hCGβ without any dramatic effect on function. These results indicate that Tyr-37 in hCGβ, while not obligatory, may participate, either directly or indirectly, in subunit assembly and that the hydroxyl group may function in a modulatory role in signaling.     

Is human chorionic gonadotropin directly involved in the regulation of human implantation?

The regulation of human implantation is not fully understood. hCG as one of the earliest embryonal signals may be a major regulator in the parakrine embryo-endometrial communication. The expression of full-length hCG/LH-receptor mRNA could be demonstrated in human endometrium throughout the follicular and secretory phase of the menstrual cycle. In contrast, in early pregnancy decidua only truncated variants could be detected. To investigate direct effects of hCG on the human endometrium, an intrauterine microdialysis device was developed to measure parakrine mediators within the uterine cavity in vivo. Using this system, hCG was applied in the secretory phase and the endometrial response was evaluated. The administration of hCG (500 IU/ml) provoked a significant inhibition of intrauterine IGFBP-1 and M-CSF, while LIF, VEGF and MMP-9 were significantly stimulated. Taken together there appear to be multiple direct effects of hCG on the endometrium that precede the classical endocrine role of the hormone.     

Time course of the serum gonadotropin surge, inhibins, and anti-Müllerian hormone in normal newborn males during the first month of life

CONTEXT: Newborns with ambiguous genitalia or males with nonpalpable gonads usually require an early assessment of the presence and functional state of testicular tissue. OBJECTIVE: Our objective was to characterize the precise ontogeny of the serum patterns of gonadotropins, testosterone, anti-Müllerian hormone (AMH), and inhibins in normal newborn boys. DESIGN: We conducted a cross-sectional and longitudinal study. SUBJECTS: Serum samples were obtained in 57 boys and 13 girls on d 2 of life. A second sample was obtained on d 7, 10, 15, 20, and 30 (boys) and on d 30 (girls). MAIN OUTCOME MEASURES: Serum levels of gonadotropins, testosterone, AMH, and inhibins were measured. RESULTS: In males, LH and FSH were undetectable or very low on d 2. By d 7, LH increased to 3.94 +/- 3.19 IU/liter (mean +/- sd) and FSH to 2.04 +/- 1.67 IU/liter. LH/FSH ratios were 0.40 +/- 0.11 (d 2) and 2.02 +/- 0.20 (d 30). AMH rose from 371 +/- 168 pmol/liter (d 2) to 699 +/- 245 pmol/liter (d 30), and inhibin B rose from 214 +/- 86 ng/liter (d 2) to 361 +/- 93 ng/liter (d 30). The inhibin alpha-subunit precursor (pro-alphaC) remained stable during the first month of life. Testosterone levels were 66 +/- 42 ng/dl (d 2), 82 +/- 24 ng/dl (d 20), and 210 +/- 130 ng/dl (d 30). A sexual dimorphism was observed in AMH and inhibin B (lower in girls on d 2 and 30), in LH/FSH ratio (lower in girls on d 30) and in testosterone (lower in girls on d 30). CONCLUSIONS: Sertoli cell markers AMH and inhibin B are the earliest useful markers indicating the existence of normal testicular tissue.     

Is gonadotrope expression of the gonadotropin releasing hormone receptor gene mediated by autocrine/paracrine stimulation of an activin response element?

Expression of the FSHbeta subunit and GnRH receptor (GnRHR) genes in gonadotropes is stimulated by activin. We sought to identify the cis-acting element(s) in the murine GnRHR gene promoter which confer activin responsiveness. We established that 600 bp of 5'flanking sequence from the murine GnRHR gene were sufficient to confer activin responsiveness in the gonadotrope-derived alphaT3-1 cell line. Since alphaT3-1 cells, like gonadotropes, secrete activin, we examined the ability of follistatin, an activin binding protein, to block the activin response. Increasing concentrations of follistatin from 0 to 100 ng/ml resulted in a dose dependent decrease in activity of the -600 promoter. Contained within this region are three elements important for expression in alphaT3-1 cells: a Steroidogenic Factor-1 binding site (SF-1), an Activator Protein-1(AP-1) element, and an element termed the GnRH receptor activating sequence or GRAS. A block mutation of GRAS inhibited the ability of the promoter to respond to follistatin. A more refined analysis using a series of two-bp mutations which scan GRAS and flanking sequence revealed exact convergence of GRAS with activin/follistatin responsiveness. Finally, a construct consisting of 3 copies of GRAS placed upstream of a heterologous minimal promoter (3xGRAS-PRL-LUC) was responsive to both activin stimulation and follistatin inhibition in alphaT3-1 cells. Thus, autocrine/paracrine stimulation of gonadotropes by activin illustrates a unique mechanism for cell-specific gene expression.     

The role of human chorionic gonadotropin β subunit elevation in small-cell lung cancer patients

Human chorionic gonadotropin (HCG)-like immunoreactivity has been found in many nontrophoblastic tumours, but the biological behaviour of HCG-producing cells has not been clarified yet. The aim of the study was to estimate the frequency of serum HCG subunit (sßHCG) elevation in patients with small-cell lung cancer (SCLC) and to assess its possible prognostic role in this type of tumour. An attempt was also made to reclassify the histology in selected cases to see whether the elevated (sßHCG) level is connected with any special subtype of small-cell lung cancer. A total of 156 SCLC patients entered the study: 93 men, 63 women, median age 58 years. sßHCG activity was measured by immunoenzyme assay (Abbott EIA ßHCG 15–15) before treatment. sßHCG elevation (above 5 mIU/ml) was found in 21 of 156 patients (14%). Response to treatment after chemotherapy (complete and partial response) was obtained in only 48% of those patients in whom elevated sßHCG was found, in comparison to the 73% response rate observed in the remaining patients. Only 5% of patients with elevated sßHCG survived 2 years, in comparison to 21% surviving for 2 years among the remaining patients. The prognostic significance of elevated sßHCG and extent of disease were independent of each other (Cox's proportional-hazard model). Thus sßHCG elevation in SCLC seems to be a marker of more resistant tumours and of poor prognosis. We have not found any connection between the subtype of small-cell lung cancer and elevated sßHCG. Elevated sßHCG was found in 2 out of 11 patients with oat-cell carcinoma, in 3 out of 10 patients with an intermediate cell type and in 5 out of 13 patients with small-cell lung cancer in which the assessment of the subtype was not possible.Abbreviations HCG human chorionic gonadotropin - SCLC small-cell lung cancer     

When does the good of the group override the advantage of the individual?

In a system of N populations of n reproductive individuals apiece, in which each population has constant variance v² and lasts L generations, group selection on a quantitative character has a reasonable chance of overriding selection within populations if (and only if) the populations never exchange migrants, each population is founded by colonists from a single parent population, and the number of populations exceeds the effective number of reproductive individuals per population. If each population derives from a single parent population, then the exchange of a single successful migrant per population per L generations can triple the strength of group selection required to overcome a given selection within populations. If populations exchange no migrants, then the derivation of one in every N populations from two equally represented parents (while the others all derive from a single parent) doubles the strength of group selection required to prevail. Group selection is accordingly likely to be effective only in certain categories of parasites.     

Stochastic simulations of the exponential-beta function as an assessment of the validity of the choice of the Wagner-Nelson method for the analysis of ¹³C-octanoic acid breath tests

A compartmental model that generates the exponential-beta function μkβ(1 - e(-kt))(β - 1)?e(-kt) in order to run stochastic simulations has been constructed. The mathematical considerations that lead to the development of the model and the comparison of its performance with real data sets obtained from the studies of gastric emptying in healthy volunteers using 13C-octanoic acid breath tests are demonstrated. Stochastic simulations have been used to introduce randomness. These confirmed the choice of an exponential-beta function to model the physiological system, as agreement was obtained between experimental and theoretical data. The comparisons were made by visual inspection only, as the intention was to demonstrate that the stochastic exponential-β model would generate the full range of observed curve shapes.     

Anterior fissure of the right liver — the third door of the liver

Background/Purpose

Although the anterior segment of the liver has been divided into segments 8 and 5, we have, during surgical or interventional procedures, occasionally encountered patients in whom the right anterior portal vein does not bifurcate into the superior and inferior branches. Thus, the in vivo anatomy of the right liver was reevaluated to clarify the segmental anatomy.

Methods

We evaluated the hepatic venous and portal ramification patterns, using three-dimensional images reconstructed from computed tomography. In addition, liver volumetry was performed.

Results

All branches arising from the anterior trunk were divided into two groups: the right ventral portal branches (RVP) and the right dorsal portal branches (RDP), and the anterior fissure vein crossed between the RVP and RDP. The ventral and dorsal regions of the anterior segment were approximately equal from a volumetric point of view.

Conclusions

The anterior segment seems to be divided into the ventral and dorsal segments by the anterior fissure, and we propose a reclassification of the right liver that divides the right liver into three segments. Dissection of the parenchyma along the anterior fissure makes the third door of the liver open, resulting in the exposing of all Glissonian pedicles of the right liver. The introduction of our segmental anatomy and surgical procedure will allow more systematic and limited liver resections.