Precocious puberty and Leydig cell hyperplasia in male mice with a gain of function mutation in the LH receptor gene

The LH receptor (LHR) is critical for steroidogenesis and gametogenesis. Its essential role is underscored by the developmental and reproductive abnormalities that occur due to genetic mutations identified in the human LHR. In males, activating mutations are associated with precocious puberty and Leydig cell hyperplasia. To generate a mouse model for the human disease, we have introduced an aspartic acid to glycine mutation in amino acid residue 582 (D582G) of the mouse LHR gene corresponding to the most common D578G mutation found in boys with familial male-limited precocious puberty (FMPP). In transfected cells, mouse D582G mLHR exhibited constitutive activity with a 23-fold increase in basal cAMP levels compared with the wild-type receptor. A temporal study of male mice from 7 days to 24 weeks indicated that the knock-in mice with the mutated receptor (KiLHR(D582G)) exhibited precocious puberty with elevated testosterone levels as early as 7 days of age and through adulthood. Leydig cell-specific genes encoding LHR and several steroidogenic enzymes were up-regulated in KiLHR(D582G) testis. Leydig cell hyperplasia was detected at all ages, whereas Sertoli and germ cell development appeared normal. A novel finding from our studies, not previously reported in the FMPP cases, is that extensive hyperplasia is commonly found around the periphery of the testis. We further demonstrate that the hyperplasia is due to premature proliferation and precocious differentiation of adult Leydig cells in the KiLHR(D582G) testis. The KiLHR(D582G) mice provide a mouse model for FMPP, and we suggest that it is a useful model for studying pathologies associated with altered LHR signaling.

Screening for resistance to Aspergillus flavus and aflatoxin production in groundnut

All the varieties, advanced breeding lines, germplasm lines, and wild species used in the experiments differed significantly for their ability to allow invasion and aflatoxin production by an aflatoxigenicAspergillus flavus strain. Infection and colonisation were strongly correlated (r = 0.82), while there was no relation between infection and aflatoxin content or colonisation and aflatoxin content (r = 0.15). The varieties ICGS11 and S 206 supported less infection and colonisation (range 35 to 40%). Lowest aflatoxin content was recorded in Chitra (3,200 ppb), while it was highest in Kaushal (38,250 ppb). A cross derivative of GAUG1 × NC Ac 17133 R F showed lowest infection and colonisation (86,3 and 25,28%, respectively), and also supported moderate aflatoxin production (4,000 ppb). Among germplasm lines spancross supported lowest aflatoxin production (2,026 ppb) while both the wild species vz. ICG 8127 and ICG 8128 were highly susceptible to infection, colonisation, and aflatoxin production.

Does androgen signaling cause thymic involution? (111.34)

The thymus is the main source of naïve T cell output. As the body ages, the thymus undergoes involution, causing a drop in naïve T cell availability in the peripheral T cell pool. The molecular mechanisms underpinning thymic involution are not well characterized. However, androgen signaling has been associated with involution based on increases in thymus size and thymocyte number in both sex steroid ablated (SSA) mice and those lacking functional androgen receptor (Ar). However, to date there is no clear cellular target or mechanism by which androgen signaling affects involution. The available data consistently point to a thymic stromal target as the major site of androgen action in the thymus. Among these stromal cell types, thymic epithelial cells (TECs) express Ar and have been shown to increase proliferation and production of specific effectors such as CCL25 in response to castration. We have used a Cre-LoxP strategy to selectively delete Ar in TECs. Evaluations of these mice present compelling evidence that TECs are directly involved in androgen signaling within the thymus. While TEC-selective Ar deletion does cause increased thymus size and thymocyte numbers, these mice differ in several ways from previous reports on global Ar deletion or SSA, leading to the possibility that current models of the role of androgens in postnatal thymus may need to be re-evaluated.

Impact of a constitutively active luteinizing hormone receptor on testicular gene expression and postnatal Leydig cell development

The actions of luteinizing hormone (LH) mediated through its receptor (LHR) are critical for testicular steroidogenesis and Leydig cell differentiation. We have previously characterized transgenic mice expressing a genetically engineered, constitutively active yoked hormone-receptor complex (YHR), in which a fusion protein of human chorionic gonadotropin (hCG) was covalently linked to LHR. Elevated testosterone levels were detected in male mice expressing YHR (YHR(+)) at 3 and 5 weeks of age, accompanied by decreases in testicular weight and serum levels of LH and follicle stimulating hormone (FSH). Here we report a temporal study to identify testicular genes whose expression is altered in YHR(+) mice during postnatal development. The mRNA expression levels for the steroidogenic enzymes, P450 17alpha-hydroxylase, 17beta-hydroxysteroid dehydrogenase3 and 5alpha-reductase1 were down-regulated in 3- and 5-week-old YHR(+) testis. This result coupled with an immunohistochemical analysis of Leydig cell specific proteins and quantification of Leydig cell numbers identified a decrease in adult Leydig cells in YHR(+) mice. Surprisingly, no change was detected for cytochrome P450 side-chain cleavage or steroidogenic acute regulatory protein RNA levels between WT and YHR(+) mice. In contrast, mRNA levels for insulin-like growth factor binding protein 3 were up-regulated in 3- and 5-week-old YHR(+) mice. The mRNA levels for several germ cell-specific proteins were up-regulated at 5 weeks of age in both WT and YHR(+) mice. We conclude that premature high levels of testosterone alter the expression of a select number of testicular genes and impair the differentiation of adult Leydig cells in mice.

Incidence, types and clinical implications of a non-metrical variant--mylohyoid bridging in human mandibles

Mylohyoid bridging (MB) is a non-metrical variant of the human mandible. The incidence and types of MB were investigated in 264 mandibles (edentulous 116, semi-dentulous 90 and dentulous 58). No mandible showed a complete type of MB, although 19 (7.2%) mandibles had a partial type. These were classified into two subtypes: distal partial (DP; Type I) and proximal partial (PP; Type II), depending on their location over the mylohyoid groove. The MB was present unilaterally in 7.76% of edentulous mandibles: right side 5.17% (3.45% PP type and 1.72% DP type) and left side 2.59% (1.72% PP type and 0.86% DP type). Of the semi-dentulous mandibles 3.33% had DP type of MB, 1.11% on the right side and 2.22% on the left side, and of the dentulous mandibles 1.72% had DP type of MB on the right side. A total of 13 mandibles out of 264 (4.92%) had unilateral MB. No dentulous mandible had bilateral MB, but 3.45% of edentulous and 2.22% of semi-dentulous mandibles did have. In total, 6 mandibles out of 264 bones (2.27%) had bilateral MB. Of the bilateral incidences 1.72% of edentulous mandibles had a DP-DP combination and the remaining 1.72% had a PP-DP combination. However, both instances of bilateral MB in semi-dentulous mandibles were of PP-DP combination. The incidence or types of MB showed no statistically significant differences between the groups or sides (p > 0.5; chi(2) test). In conclusion, the complete type of MB is a rare occurrence. The incidence increases with age, as edentulous mandibles had a higher incidence of MB than the other two groups. Clinically, MB may compress the mylohyoid neurovascular bundle, leading to neurological or vascular disorders.

Constitutively active luteinizing hormone receptors: consequences of in vivo expression

Activating mutations in the luteinizing hormone receptor (LHR) gene are one of the most common mutations found in the gonadotropin receptor genes. Human males with these mutations exhibit precocious puberty while females do not have an obvious phenotype. To better understand the pathophysiology of premature LHR activation, transgenic mice have been generated with an activating mutation in LHR and a genetically engineered ligand-activated LHR. This review will summarize the major findings obtained with these two genetically modified mouse models and briefly discuss the similarities and differences between them and with the human phenotype.

Influence of concomitant coronary artery bypass graft on outcome of surgery of the ascending aorta/arch

BACKGROUND

Surgery of the ascending aorta with or without arch is being performed in an increasingly elderly population with risks of coexisting coronary artery disease.

AIM

To define specific groups requiring coronary artery bypass graft (CABG) and to analyse the influence of concomitant CABG on outcome.

DESIGN

Over a 10-year period in a single institution, 296 consecutive procedures on the ascending aorta with or without arch were carried out in 291 patients. CABG was required in 42 (14.2%) procedures. In 24 (57%) patients, CABG was planned preoperatively and in 18 (43%) patients, on a salvage basis.

RESULTS

In-hospital mortality for patients undergoing concomitant CABG was higher (21.4% v 11%, p<0.06). Adjusting for baseline and operative characteristics, this was attributable to operative priority, and was not a consequence of concomitant CABG (adjusted OR 0.30, 95% CI 1.1 to 8.31; p = 0.48). However, in-hospital mortality was significantly higher when CABG was performed as salvage rather than as a planned procedure (38.9% v 8.9%, p = 0.025), and this difference remained after adjusting for confounding variables (adjusted OR 16.2, 95% CI 1.03 to >200; p = 0.047). The 3-year survival was significantly lower with concomitant CABG (59% v 81.9%, p<0.001).

CONCLUSIONS

In association with surgery of the ascending aorta with or without arch planned concomitant CABG did not entail any added operative risk. However, salvage CABG, which occurred almost exclusively in association with emergency cases, was associated with a higher early mortality. Patients needing concomitant CABG had worse survival at 3 years compared with those requiring isolated surgery of the ascending aorta with or without arch.

Structure-function relationships of the luteinizing hormone receptor

Of the 800-900 genes in the human genome that appear to encode G-protein-coupled receptors (GPCRs), two are known to encode receptors that bind the three heterodimeric human gonadotropins, luteinizing hormone (LH), chorionic gonadotropin (CG), and follicle-stimulating hormone (FSH). LH and CG bind to a common receptor, LHR, and FSH binds to a paralogous receptor. These GPCRs contain a relatively large ectodomain (ECD), responsible for high-affinity ligand binding, and a transmembrane portion, as in the other GPCRs. The ECD contains nine leucine-rich repeats capped by N-terminal and C-terminal cysteine-rich regions. The overall goal of this research is to elucidate the molecular mechanisms by which CG and LH bind to and activate LHR and the latter, in turn, activates Gs alpha. A combination of molecular modeling and site-directed mutagenesis, coupled with binding and signaling studies in transiently transfected HEK 293 cells expressing wild-type and mutant forms of LHR, has been used to develop and test models for the LHR ECD, the CG-LHR ECD complex, and the structural changes in the transmembrane helices and intracellular loops, particularly loop 2, that accompany receptor activation. In addition, a single-chain CG-LHR complex was designed in which a fusion protein of the two subunits of human CG was linked to full-length LHR. This ligand-receptor complex was shown to be constitutively active in cellular models and in transgenic mice, the latter of which exhibit precocious puberty. From a combination of molecular modeling, site-directed mutagenesis, genetic/protein engineering, and receptor characterization in cellular and animal models, considerable insight is being developed on the mechanisms of normal and aberrant activation of LHR.

Postoperative chest radiographic changes after on- and off-pump coronary surgery

AIM

A variety of chest radiograph abnormalities are recognized after coronary artery bypass grafting (CABG). This study analyzes the appearance of preoperative and postoperative chest radiographs in two groups of patients undergoing myocardial revascularization with or without the use of cardiopulmonary bypass (CPB).

METHODS

Chest radiographs (preoperative and at 1 day, 6 days and 6 to 8 weeks post operatively) were analyzed according to a detailed protocol in cases of conventional CABG on CPB (n=60) or off-pump coronary artery bypass (OPCAB) (n=60) surgery. On each film 17 different major potential postoperative abnormalities were analyzed.

RESULTS

Clinical findings were similar in the two groups. Patients undergoing OPCAB surgery had decreased blood loss, decreased red cell and platelet transfusion, significantly lower intubation time and required less postoperative inotropic support compared with patients undergoing CPB. The CPB group had a significantly higher incidence of left band atelectasis than the OPCAB group (37.6% vs 17.5%, p=0.01) at 6 days postoperatively. There was no other statistically significant difference in any of the 16 remaining major chest radiograph findings between the two groups.

CONCLUSION

Although OPCAB surgery is associated with improved clinical outcome compared with conventional CABG surgery, the analysis of postoperative chest radiographs demonstrated only a minor benefit as shown by a reduced degree of left band atelectasis in the OPCAB group.

Gonadal defects and hormonal alterations in transgenic mice expressing a single chain human chorionic gonadotropin-lutropin receptor complex

To study the effects of premature and chronic ligand-mediated luteinizing hormone receptor (LHR) activation on reproductive development, we have generated transgenic mice expressing a genetically engineered, constitutively active yoked hormone-receptor complex (YHR), in which a fusion protein of human chorionic gonadotropin (hCG) is covalently linked to the N-terminus of rat LHR. YHR-expressing mice (YHR(+)) were analyzed at pre- and post-pubertal ages. Relative to wild type (WT) controls, male mice exhibited prepubertal increases in testosterone levels and seminal vesicle weights, and decreases in serum FSH, serum LH, testes weight, and the size of the seminiferous tubules. In adult male YHR(+) mice, testosterone and LH levels are not significantly different from WT controls. However, FSH levels and testes weights remain decreased. Female YHR(+) mice undergo precocious puberty with early vaginal opening, accelerated uterine development, enhanced follicular development, including the presence of corpora lutea, and an increase in serum progesterone. At 12 weeks of age, the ovary exhibits a relative increase in the amount of interstitial tissue, comprised of cells that are hypertrophic and luteinized, as well as follicles that are degenerating. Additionally, hemorrhagic cysts develop in approximately 25% of the transgenic mice. These degenerative changes are consistent with an aging ovary suggesting that CG-induced LHR activation in female mice leads to precocious sexual development and ovarian lesions. Taken together, these data indicate that the single chain YHR is functional in vivo and demonstrate that YHR(+) mice provide a novel system to further understand the reproductive consequences of aberrant LHR activation.