Biomedical subjects

I Huhtaniemi

Publications and source records attributed to I Huhtaniemi.

At least 55 records · Page 3Linked to original sources

PubMed2000

The Parkes lecture. Mutations of gonadotrophin and gonadotrophin receptor genes: what do they teach us about reproductive physiology?

Although mutations in human gonadotrophin and gonadotrophin receptor genes are rare, they have greatly elucidated the physiology and pathophysiology of gonadotrophin action. These 'nature's transgenics' have been corroborated by mouse transgenic and knock-out models. An inactivating mutation of the human LHbeta chain and knock-out of the mouse common alpha-chain show that pituitary LH is not needed to stimulate fetal testicular steroidogenesis and male sexual differentiation. In mice, early testicular steroidogenesis is apparently gonadotrophin-independent and, in humans, it is regulated by placental hCG. Pituitary LH becomes necessary only after birth. Inactivating LH receptor mutations block prenatal hCG action, thus inhibiting male-type sexual differentiation. In females, this process is autonomous, and LH becomes important only at puberty; inactivation of LH receptor causes anovulatory infertility. Activating LH receptor mutations cause male-limited gonadotrophin-independent precocious puberty in males, but no apparent phenotype in females. Animal models for LH or LH receptor inactivation are not yet available. Inactivating FSH ligand and receptor mutations cause infertility because of a lack of follicular maturation in women. Findings in men are controversial, since FSHbeta inactivation is related to azoospermia, whereas the cognate receptor inactivation only suppresses spermatogenesis without causing absolute infertility. The FSHbeta and FSH receptor knock-out mice display phenocopies of the human FSH receptor mutation. Information about activating FSH receptor mutations is still insufficient. Hence, the above human mutations have brought important new information about the role of gonadotrophins in reproductive functions. The genetically modified animal models provide useful tools to explore the pathogenesis and new treatment modalities of infertility, and to develop new contraceptive strategies.

Animals↗

PubMed2000

Neonatal exposure to estrogen differentially alters estrogen receptor alpha and beta mRNA expression in rat testis during postnatal development.

The biological actions of estrogens on target cells are mediated by two nuclear receptors: the estrogen receptor (ER) alpha and the recently characterized ER beta. In the male rat, the physiological role of estrogens involves multiple actions, from masculinization of brain areas related to reproductive function and sexual behavior to regulation of testicular development and function. Paradoxically, however, administration of high doses of estrogen during the critical period of neonatal differentiation results in an array of defects in the reproductive axis that permanently disrupt male fertility. The focus of this study was to characterize the effects and mechanism(s) of action of neonatal estrogenization on the pattern of testicular ER alpha and beta gene expression during postnatal development. To this end, groups of male rats were treated at day 1 of age with estradiol benzoate (500 microg/rat), and testicular ER alpha and ER beta mRNA levels were assayed by semi-quantitative RT-PCR from the neonatal period until puberty (days 1-45 of age). Furthermore, the expression of androgen receptor (AR) mRNA was evaluated, given the partially overlapping pattern of tissue distribution of ER alpha, ER beta and AR messages in the developing rat testis. In addition, potential mechanisms for neonatal estrogen action were explored. Thus, to discriminate between direct effects and indirect actions through estrogen-induced suppression of serum gonadotropins, the effects of neonatal estrogenization were compared with those induced by blockade of gonadotropin secretion with a potent LHRH antagonist in the neonatal period. Our results indicate that neonatal exposure to estrogen differentially alters testicular expression of alpha and beta ER messages: ER alpha mRNA levels, as well as those of AR, were significantly decreased, whereas relative and total expression levels of ER beta mRNA increased during postnatal/prepubertal development after neonatal estrogen exposure, a phenomenon that was not mimicked by LHRH antagonist treatment. It is concluded that the effect of estrogen on the expression levels of ER alpha and beta mRNAs probably involves a direct action on the developing testis, and cannot be attributed to estrogen-induced suppression of gonadotropin secretion during the neonatal period.

Animals↗

PubMed2000

Long-term testosterone treatment prevents gonadal and adrenal tumorigenesis of mice transgenic for the mouse inhibin-alpha subunit promoter/simian virus 40 T-antigen fusion gene.

We have developed a transgenic (TG) mouse model for tumorigenesis of gonadal somatic cells using a 6 kb fragment of the mouse inhibin-alpha subunit promoter (Inh-alpha) fused with the simian virus 40 T-antigen (Tag) coding sequence. Gonadal tumors, of Leydig or granulosa cell origin, develop in the TG mice with 100% penetrance by the age of 5-8 months. Conspicuously, if the mice are gonadectomized, they develop adrenal tumors. Gonadal and adrenal tumorigenesis in these mice seem to be gonadotropin dependent. On the other hand, testosterone stimulates the proliferation of a cell line (C alpha 1) established from one of the adrenal tumors. The purpose of the present study was therefore to investigate further whether testosterone affects the growth of these gonadal and adrenal tumors in vivo. Two experimental models were used: (1) Tag TG/hypogonadotropic (hpg) double mutant mice and (2) castrated Tag TG mice. Both were treated between 1-2 and 7-8 months of age with Silastic rods (length 2 cm) containing testosterone. None of the control or testosterone-treated Tag/hpg mice developed gonadal or adrenal tumors. The castrated Tag TG mice displayed, upon microscopical examination, early stages of adrenal tumors, whereas those receiving testosterone did not show such changes. Testosterone increased the weights of gonads in the Tag/hpg mice, and those of uteri and seminal vesicles in both groups. In contrast, the adrenal weights were significantly reduced in both groups by testosterone treatment. Gonadal histology of the testosterone-treated mice showed hyperplasia of testicular Leydig cells and ovarian stroma. Spermatogenesis was induced by testosterone in the Tag/hpg mice. Adrenal histology of the testosterone-treated animals demonstrated the disappearance of the X-zone. Serum levels of FSH in testosterone-treated Tag/hpg mice were significantly increased, while those of serum LH were decreased. In conclusion, the present result indicate that the suppression of gonadotropins by testosterone implants in castrated Inh-alpha/Tag TG mice prevents the tumorigenesis of their adrenals. In intact Tag/hpg mice, testosterone implants were not able to induce gonadal or adrenal tumorigenesis. Although testosterone treatment was able to induce interstitial cell hyperplasia in gonads of the Inh-alpha/Tag mice, direct gonadotropin action is responsible for gonadal and adrenal tumorigenesis.

Adrenal Gland Neoplasms↗

PubMed2000

Genetic variant of luteinizing hormone and risk of breast cancer in older women.

A genetic variant of luteinizing hormone (LH) characterized by two point mutations in codons 8 (TGG-->CGG) and 15 (ATC-->ACC) of the LH beta-subunit gene has been described recently. As compared with wild-type LH, the variant LH appears to have higher in vitro bioactivity but a shortened circulatory half-life, and it has been reported to affect circulating levels of sex hormones. Our purpose was to determine whether the variant form of LH is associated with an altered risk of breast cancer. This hypothesis was addressed in a case-control study nested within a prospective cohort that included 270 cases of breast cancer and twice as many matching control subjects. The study was limited to subjects diagnosed at age 50 years or older. The LH status was determined by the combination of two immunofluorometric assays of serum using monoclonal antibodies. Frequency of the variant LH was similar in breast cancer cases and controls (11.5% versus 10.7%). In conditional regression models, the presence of the variant LH was not associated with a considerable increase of breast cancer risk (odds ratio, 1.07; 95% confidence interval, 0.68-1.69). Adjustment for potential confounders did not notably change the risk estimate (odds ratio, 1.11; 95% confidence interval, 0.69-1.78). These observations do not appear to support the hypothesis that this particular variant of LH is associated with altered risk of breast cancer diagnosed at age 50 years and older.

Adult↗

PubMed1999

Hormonal treatment after cytotoxic therapy stimulates recovery of spermatogenesis.

Previous studies have shown that treatment of rats with gonadotropin-releasing hormone (GnRH) analogues or steroids either before exposure to procarbazine or radiation or after irradiation enhances subsequent levels of spermatogenesis. We demonstrate here that giving a GnRH agonist after procarbazine injection also enhances spermatogenesis and fertility. We also demonstrate that GnRH agonist stimulated recovery of spermatogenesis and fertility not only when the hormone was administered immediately after irradiation, but also at 20 weeks after irradiation, after the decline in spermatogenesis had occurred. These results suggest that GnRH agonist treatment given to azoospermic men after cytotoxic therapy for cancer may stimulate the recovery of spermatogenesis and fertility.

Animals↗

PubMed1999

Mutations and polymorphisms in gonadotropin genes.

Mutations in gonadotropin genes are extremely rare. Only one case of inactivating human luteinizing hormone (LH) beta mutation exists in the literature, a male with absence of Leydig cells, lack of spontaneous puberty and infertility. A total of four cases of inactivating mutation of the follicle-stimulating hormone beta (FSHbeta) gene (two female and two male) are known. The phenotype of the women was primary amenorrhea and absence of follicular maturation, the men were azoospermic. In addition, a common genetic variant (v) of LH was recently discovered. It is caused by two point mutations in the LH beta-subunit gene, resulting in amino acid alterations: Trp8 --> Arg and Ile15 --> Thr. In addition, the latter change introduces an extra glycosylation signal for oligosaccharide attachment to Asn13. The v-LHbeta allele has a carrier frequency ranging from 0 to > 50% in various populations. The variant LH molecule has increased intrinsic bioactivity in vitro, but decreased circulatory half-life in vivo, and the v-LHbeta promoter is about 50% more active in cell line transfections than that of wild-type (wt) LH. These differences in LH synthesis and action in individuals homo- or heterozygous for the v-LH allele are reflected by altered disposition to pathologies of pituitary-gonadal function, such as delayed puberty, polycystic ovarian syndrome and infertility.

Female↗

PubMed1999

Hormonal regulation of proliferation of granulosa and Leydig cell lines derived from gonadal tumors of transgenic mice expressing the inhibin-alpha subunit promoter/simian virus 40 T-antigen fusion gene.

We have produced a transgenic (TG) mouse model expressing the Simian Virus 40 T-antigen (Tag) gene, driven by a 6-kb fragment of the mouse inhibin-alpha subunit promoter (inh-alpha). The mice develop gonadal tumors with 100% penetrance by the age of 5-8 months, of granulosa cell origin in the ovary, and of Leydig cell origin in the testis. In the present study, we characterized the hormonal regulation of proliferation of two immortalized cell lines, BLT-1, originating from a Leydig cell tumor, and NT-1, originating from a granulosa cell tumor. [3H]-thymidine incorporation in both types of cells was stimulated by activin (> or = 10-30 microg/l), while inhibin had no effect. Transforming growth factor (TGF)-beta, at > or = 0.01 microg/l, stimulated proliferation of the granulosa tumor cells, but no effect was found on the Leydig tumor cells. Progesterone inhibited the proliferation of both cell lines, although the granulosa tumor cells were clearly less sensitive than the Leydig cells to this effect ( > or = 3 micromol/l vs. > 10 nmol/l, respectively). hCG had no effect on the Leydig tumor cell DNA synthesis whereas at high concentration (100 microg/l) it stimulated that of the granulosa cells. We also investigated in BLT-1 and NT-1 cells whether the proliferative changes were related to concomitant changes in Tag expression. In BLT-1 cells, this was stimulated by activin, progesterone and hCG, even though the latter substance did not affect cell proliferation. In contrast, TGF-beta inhibited Tag expression. In NT-1 cells, the expression of Tag was stimulated by activin, while hCG had no effect. In contrast, it was reduced by progesterone, inhibin and TGF-beta. In conclusion, our results indicate that the granulosa and Leydig tumor cells, despite similar mechanism of immortalization, respond differently to several mitotic stimuli. The responses in the level of Tag expression in these cells did not always correlate with the changes observed in cell proliferation, indicating the independence of these two phenomena.

Activins↗

PubMed1999

Structure and expression of the rat relaxin-like factor (RLF) gene.

The relaxin-like factor (RLF) is a novel member of the insulin-IGF-relaxin family of growth factors and hormones, and its mRNA is expressed very specifically in the Leydig cells of the testis and in the theca and luteal cells of the ovary. Here we report the cloning of the RLF gene and cDNA from the rat. The 0.8kb mRNA is produced from a small gene comprising two exons situated less than 1 kb downstream of the gene for the signalling factor JAK3. Northern hybridization confirms high RLF mRNA expression in the adult rat testis, and low expression in the ovary, but in no other tissues examined. Northern analysis of fetal and neonatal gonadal tissues showed that RLF mRNA is highly upregulated in the testes of day 19 embryos, but not in later neonatal stages, nor in any ovarian tissue from this period. This would indicate that RLF is a marker for the mature fetal as well as the adult-type Leydig cell, but is not expressed in premature, precursor, or dedifferentiated Leydig cells of either cell type. Finally, RNA was analysed from the testes of rats which had been treated with ethylene dimethane sulfonate (EDS), an alkylating agent that specifically destroys rat Leydig cells. RLF mRNA was absent from the acutely treated testes, but became detectable between 15 and 20 days post-treatment, concomitant with the repopulation of the testes by new Leydig cells. Continuous testosterone substitution of EDS-treated rats suppressed the production of gonadotropins, and LH-dependent Leydig cell differentiation, with the result that RLF mRNA remained undetectable throughout the study period. In conclusion, RLF is a very specific marker for the mature Leydig cell phenotype in both the adult-type and fetal Leydig cell populations of the rat testis.

Amino Acid Sequence↗

PubMed1999

A common polymorphic allele of the human luteinizing hormone beta-subunit gene: additional mutations and differential function of the promoter sequence.

A common genetic variant (V) of the human luteinizing hormone (LH) beta-subunit gene was recently discovered. The V-LH molecules have higher bioactivity in vitro, but shorter half-life in circulation, which apparently is related to the alterations of LH function observed in individuals homo- and heterozygous for the V-LHbeta allele. We have now studied whether additional mutations in the V-LHbeta promoter sequence could contribute to the altered physiology of the LH variant molecules. The 661 bp 5'-flanking region of the V-LHbeta gene, retrieved from human genomic DNA by PCR, contained eight single-nucleotide changes, as compared with the wild-type (wt) LHbeta promoter. The finding was consistent in DNA samples of different ethnic groups. Reporter constructs with various lengths of the wt- and V-LH promoter sequences, driving the firefly luciferase reporter gene, were transfected into an immortalized mouse pituitary cell line, LbetaT(2), known to express the endogenous LHbeta gene, and into a non-endocrine human embryonic kidney cell line, HEK 293. Basal expression levels of the V-LHbeta promoter constructs were on average 36% higher in LbetaT(2)cells ( P < 0.001; n = 29), and 40% higher in HEK 293 cells ( P < 0.001; n = 16), as compared with the respective wt sequences. Numerous qualitative and quantitative differences were found between the two cell lines in responses of the two promoter sequences to stimulation with 12- O -tetradecanoylphorbol-13-acetate, forskolin, 8-bromo-cAMP, progesterone and gonado- tropin-releasing hormone. In conclusion, the V-LHbeta promoter has higher basal activity, and differs in response to hormonal stimulation, as compared with the wt-LHbeta promoter. The altered promoter function of the V-LHbeta gene provides evidence for differences in regulation of the wt- and V-LHbeta genes, which may contribute to the differences observed in pituitary-gonadal function between carriers of the two LHbeta alleles. The findings also suggest a novel evolutionary mechanism whereby polymorphic changes resulting in altered bioactivity of a gene product may be compensated for by additional mutations in the cognate promoter sequence, changing transcription of the same gene.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1999

Molecular cloning of the mouse follicle-stimulating hormone receptor complementary deoxyribonucleic acid: functional expression of alternatively spliced variants and receptor inactivation by a C566T transition in exon 7 of the coding sequence.

The gonadotropin receptors, i.e., those of LH and FSH (FSHR), are pivotal elements in the regulation of gonadal function. Recently, extensive efforts have been made to elucidate the structure-function relationship of these receptors as well as the modulatory mechanism(s) of their function. In the present study, we report 1) characterization of the mouse (m) FSHR cDNA coding sequence and 2) the functional consequences of coexpression of several splice variants of the mFSHR. In addition, we evaluate 3) the impact on mFSHR function of a C566T transition in exon 7 of the coding sequence, a substitution analogous to the inactivating mutation in the human FSHR gene responsible for a hereditary form of hypergonadotropic ovarian failure. Molecular cloning of the mFSHR cDNA was carried out by reverse transcription-polymerase chain reaction (RT-PCR) using 129/Sv mouse testicular RNA and primers complementary to the rat or the partially characterized mouse FSHR sequence. Overlapping partial fragments of receptor cDNA were amplified, sequenced, and engineered to produce the entire cDNA coding sequence, subcloned into the pSG5 expression vector. Using a similar approach, 4 different receptor splice variants, selectively lacking exons 2, 2 and 5, 5 and 6, and 2, 5, and 6 of the coding region, were cloned. Finally, PCR-based site-directed mutagenesis was used to generate the C566T mutant of mFSHR. Sequence analysis showed an open reading frame of 2076 base pairs for the mFSHR cDNA, predicting a putative 17-amino acid signal peptide and a 675-amino acid mature receptor protein, and overall sequence homology of 94% with rat, 87% with human, and 85-84% with bovine, and ovine FSHRs. Functional expression in human embryonic kidney (HEK 293) and mouse granulosa (KK-1) cells demonstrated for the cloned receptor high-affinity binding to recombinant human (rh) FSH and ability to elicit cAMP, inositol trisphosphate (IP3), and progesterone responses. In contrast, transient transfection studies showed that despite successful transcription, the exon-lacking FSHR variants were unable to bind rhFSH either in intact or in solubilized HEK 293 cells, or to elicit cAMP or progesterone responses in KK-1 cells. Furthermore, cotransfections of the splice variants in the context of an ovarian cell line stably expressing the full-length mFSHR failed to demonstrate modulatory effects on the holoreceptor function. Finally, transient expression of the C566T mFSHR mutant in HEK 293 cells revealed that, in accordance with observations on human FSHR, this substitution profoundly impaired the ligand binding and cAMP and IP3 responses to rhFSH stimulation. In conclusion, the present data indicate that, despite extensive splicing of the mFSHR message, a potential role of the exon-lacking receptor transcripts in modulating FSH actions is unlikely. In addition, we provide evidence for mFSHR inactivation by a C566T transition in exon 7 of the coding sequence, thus paving the way for further development of animal models of hypergonadotropic ovarian failure.

Alternative Splicing↗

PubMed1999

Age- and sex-specific promoter function of a 2-kilobase 5'-flanking sequence of the murine luteinizing hormone receptor gene in transgenic mice.

A transgenic (TG) mouse model carrying a 2-kb murine LH receptor (LHR) promoter/beta-galactosidase (beta-GAL) fusion gene was created to study the regulatory function of the 5'-flanking region of the murine LHR gene. Of the five TG mouse lines produced, three displayed high beta-GAL expression in the testis, but none showed any expression in the ovary. In addition, all mouse lines of both sexes expressed beta-GAL consistently in the brain, most prominently in hippocampus, hypothalamus, midbrain, and cortex. Weak staining was found in a few pituitary samples. All other tissues examined were negative for transgene expression. In support of sex-specific gonadal expression of the transgene, transient transfection of the LHR/beta-GAL gene construct into immortalized mouse granulosa (KK-1) and Leydig (mLTC-1) tumor cells revealed a more than 5-fold higher expression level in the Leydig cells. Histological examination of the TG testes demonstrated strong beta-GAL expression in Leydig cells, but, unexpectedly, also in elongating spermatids of adult age and in some spermatogonia of the neonatal testis. The functional significance of the latter findings remains open. The transgene was only expressed in adult Leydig cells; no expression was found in the fetal population of these cells. Hence, these findings indicate that the immediate 2-kb fragment of the murine LHR 5'-flanking sequence is transcriptionally active only in adult Leydig cells and certain brain areas, but other promoter sequences are apparently needed for ovarian and fetal testicular expression of the LHR gene.

Aging↗

PubMed1999

The pattern of inhibin/activin alpha- and betaB-subunit messenger ribonucleic acid expression in rat testis after selective Leydig cell destruction by ethylene dimethane sulfonate.

To further investigate the regulatory mechanisms responsible for the control of testicular inhibin/activin subunit gene expression, inhibin-alpha, -betaA, and -betaB messenger RNA (mRNA) levels were assessed after ethylene dimethane sulfonate (EDS)-induced destruction of Leydig cells (LC) in different animal models: the intact rat, the rat treated with high doses of testosterone, and the unilaterally cryptorchid rat. In intact rats, EDS selectively eliminates the mature adult-type LCs, activating the proliferation and differentiation of preexisting LC precursors into a new population of functionally active LCs. In this model, a single dose of EDS (75 mg/kg BW, ip) induced a significant increase in testicular inhibin-alpha and -betaB mRNA levels 5 days after treatment (5.0- and 5.5-fold increases, respectively), whereas inhibin-betaA mRNA remained undetectable upon Northern hybridization in control and EDS-treated testes. Moreover, in situ hybridization analysis demonstrated that the increased expression of inhibin-alpha and -betaB mRNAs observed 5 days after EDS takes place mainly in Sertoli cells. Along with LC repopulation, the expression level of inhibin-alpha and -betaB messages declined, and inhibin-alpha mRNA returned to control values on day 40 after EDS. This treatment, however, failed to alter the pattern of testicular expression of FSH receptor and androgen-binding protein mRNAs, thus suggesting selectivity for the above effects. In EDS-treated rats supplemented with high doses of testosterone, the preexisting mature LCs are destroyed, but, due to elevated testosterone concentrations, disruption of spermatogenesis is attenuated, and the post-EDS rise in serum gonadotropins is blocked; the latter prevents LC regeneration. In this model, a 5.0-fold increase in inhibin-alpha mRNA levels, similar to that found in intact animals, was detected 5 days after EDS administration, but the rise in inhibin-betaB levels was partially delayed. In addition, the blockade of LC repopulation resulted in permanent elevation of inhibin-alpha and -betaB messages throughout the study period. In unilaterally cryptorchid rats, the abdominal testis shows disrupted spermatogenesis and altered paracrine environment that expedites LC repopulation after EDS treatment. In this model, the abdominal testes showed a significant 2.5-fold increase in inhibin-alpha mRNA levels 5 days after EDS, but no effect was found in those of inhibin-betaB. Further, the faster rate of LC repopulation resulted in precocious decline of inhibin-alpha mRNA levels. Finally, the expression of inhibin/activin subunit mRNAs was monitored during postnatal testicular development, specifically at the time of regression of fetal-type LCs and appearance of those of the adult type. High levels of expression of inhibin-alpha and -betaB mRNAs were detected in neonatal and infantile testes. A sharp decline in both messages took place between days 15-20, i.e. at the time when fetal-type Leydig cells are replaced by adult-type cells. From this time point onward, inhibin-alpha and -betaB mRNA levels remained low, ranging between 15-30% of the maximum. In conclusion, our results suggest that the adult-type LCs differentially modulate the expression of inhibin/activin subunit genes and point to a major inhibitory role in this cell type on expression of the inhibin-alpha gene.

Activins↗

PubMed1999

Oestrogen-dependent expression of LH/hCG receptors in pig Fallopian tube and their role in relaxation of the oviduct.

The current studies investigated the concentration and distribution of LH receptors in the oviduct of ovariectomized gilts at various times after administration of oestradiol benzoate (10 micrograms kg-1 body weight) to determine whether LH participates in the regulation of oviductal contractions. Polyclonal antibodies to the LH receptor were used in immunocytochemical and western blot analyses of oviductal tissues. The mechanical activity of the isthmus and ampullar segments of oviduct, collected from 16 cyclic gilts, was recorded for 30 min after LH or hCG treatment. In the oviduct, there was little competition for receptor occupancy between hCG and pig FSH, bovine thyroid-stimulating hormone (TSH), pig growth hormone (GH) and pig prolactin (1.2, 0.1, 0.01 and < 0.001%, respectively) but pig LH could completely inhibit the binding of [125I]hCG. Oestradiol benzoate increased (P < 0.01) the number of LH binding sites in oviduct 24, 48 and 72 h (0.60 +/- 0.08, 1.62 +/- 0.15, 2.48 +/- 0.35 fmol mg-1 protein; n = 4 per treatment, respectively) after injection compared with the control gilts treated with corn oil (0.20 +/- 0.04 fmol mg-1 protein; n = 4). The affinity of oviductal LH/hCG binding sites (Ka) varied from 4.0 to 8.5 x 10(10) l mol-1 and was similar to that of luteal cell binding sites (6.1 x 10(10) l mol-1). Oestradiol benzoate also resulted in more intense LH receptor immunostaining of the tubal mucosal epithelium, smooth muscle cells and blood vessels as compared with controls. Western blotting has revealed that the pig oviduct, similar to the corpus luteum, contains 75, 48 and 45 kDa immunoreactive LH receptor proteins. Treatment with LH in vitro (100 ng ml-1) affected the contractility of oviduct. During the peri-ovulatory stage of the oestrous cycle, the amplitude, frequency and area under curve(s) of the isthmus decreased (P < 0.05), as did the frequency and area under curve (P < 0.05 and P < 0.01, respectively) of the ampulla (n = 4). The frequency and area under curve of the oviductal contractions were also significantly reduced during the early follicular phase of the oestrous cycle (P < 0.05). There was no effect of LH (or hCG) on the frequency and area under curve of the oviductal contractions during luteal stages of the oestrous cycle (n = 8). These data indicate that (1) the pig oviduct possesses immunoreactive and functional LH receptor, (2) oestradiol promotes the synthesis of LH receptor in the epithelium and smooth muscles, and (3) LH causes the relaxation of oviduct, especially during the peri-ovulatory stage of the oestrous cycle. In summary, the results of the present study indicate that LH can control oviductal contractions directly and may be partially responsible for the relaxation of isthmus during fertilization in pigs.

Analysis of Variance↗

PubMed1999

Ontogeny of LH receptor gene expression in the pig reproductive tract.

In view of the recently documented expression of the LH receptor gene in several nongonadal reproductive tissues, the aim of this study was to analyse further the ontogeny of expression of this gene in the pig reproductive tract in fetal and neonatal life. RT-PCR was used to investigate the expression of the extracellular and transmembrane receptor domains, and to identify the time of onset of transcription of the full-length LH receptor mRNA and its shorter splice variants. Expression of the LH receptor gene was first detected around day 30 of fetal life in both ovary and testis, coinciding with morphological differentiation. The pattern of expression of LH receptor splice variants did not change during postnatal gonadal maturation. Expression of the LH receptor gene in the pig non-gonadal reproductive tract started during fetal life and continued during sexual maturation. A novel pig LH receptor spliced variant, lacking exon 10, was detected for the first time. The transmembrane receptor domain was expressed in fetal tissues, but not in neonatal control tissues. On the basis of the transmembrane domain of the LH receptor mRNA, it is concluded that the ovary and extragonadal tissues of the pig reproductive tract, like the pig testis, synthesize functional LH receptors during fetal life. The presence of LH receptor mRNA in extragonadal reproductive tissues indicates that LH is involved in the control and regulation of reproductive tract maturation.

Animals↗

PubMed1999

Experimental cryptorchidism induces a change in the pattern of expression of LH receptor mRNA in rat testis after selective Leydig cell destruction by ethylene dimethane sulfonate.

In the rat, the cytotoxic drug ethylene dimethane sulfonate (EDS) selectively eliminates mature Leydig cells (LCs) from testicular interstitium, activating a complex process of proliferation and differentiation of pre-existing LC precursors. We observed previously that after EDS treatment, the early LC precursors persistently express a truncated 1.8 kb form of LH receptor (LHR) mRNA. This prompted us to study whether experimental cryptorchidism, known to alter the process of LC repopulation, can influence the pattern of testicular LHR mRNA expression after EDS administration. EDS treatment completely eliminated mature LCs both in control and unilaterally cryptorchid (UC) rats. This response was followed by gradual reappearance of newly formed, functionally active LCs, as evidenced by the recovery in testicular LHR content and plasma testosterone levels in both experimental groups. Noteworthy, the rate of LC repopulation was higher in the abdominal testes of UC rats, in keeping with previous findings. Interestingly, the 1.8 kb LHR transcript was persistently expressed in scrotal testes at all time-points, but undetectable upon Northern hybridization in abdominal testes at early stages after EDS administration, when low levels of expression of truncated LHR transcripts could only be detected by semi-quantitative RT-PCR analysis. In addition, the faster LC repopulation in cryptorchid testes was associated with precocious recovery of the complete array of LHR mRNA transcripts, including the 1.8 kb species. These changes appeared acutely and irreversibly, as unilateral positioning of scrotal testes into the abdomen resulted in a rapid loss of expression of the 1.8 kb LHR transcript, whereas scrotal relocation of the UC testes failed to alter the pattern of LHR gene expression. In conclusion, experimental cryptorchidism changes the pattern of LHR mRNA expression in rat testis after selective LC destruction by EDS. This change, i.e. repression of the 1.8 kb LHR transcript after EDS administration, is acute and irreversible, and likely related to the impairment of testicular microenvironment following cryptorchidism. However, even though at low levels, the expression of truncated forms of LHR mRNA appears to be a universal feature of proliferating LC precursors. The UC testis may represent a good model for analysis of the regulatory signals involved in the control of LHR gene expression.

Analysis of Variance↗

PubMed1999

The prevalence of polycystic ovaries in healthy women.

BACKGROUND: To study the prevalence of polycystic ovaries (PCO) in women of reproductive age. METHODS: A total of 189 healthy volunteers aged 20-45 years were examined. The subjects were divided into two groups according to age: < or =35 and > or =36 years. Transvaginal ultrasonography was performed and blood samples were collected on cycle day 1-6. RESULTS: The prevalence of PCO in the entire study population was 14.2% (27/189). In the age group of < or =35 years the prevalence was 21.6% (19/88) and in the age group of > or =36 years 7.8% (8/101). Compared to women with normal ovaries, those with PCO had significantly higher serum testosterone (T) concentrations. Women with PCO tended to have lower serum FSH concentrations and higher LH/FSH ratios than controls. Women with PCO had significantly more irregular cycles (44% vs. 19%, p=0.001) and problems in conceiving (25.9% vs. 9.2%, p=0.01) than women with normal ovaries. CONCLUSIONS: The findings demonstrate that the prevalence of PCO in healthy women varies with age, being more common among women aged < or =35 years than in those aged > or =36 years. Although the hormonal parameters and clinical findings among women with PCO mimicked those of PCOS, it remains unclear if these women will later develop full-blown syndrome.

Adult↗

PubMed1999

Current challenges of andrology.

As President of the International Society of Andrology, it gives me great pleasure to congratulate the Asian Society of Andrology for its initiative in founding the Asian Journal of Andrology. In doing so, I also send my best wishes for the success of this important journal in spreading the knowledge of andrology throughout the most populous continent in the world. This new journal appears at a very timely moment, at the turn of the millennium and at a time when andrology is receiving the recognition amongst medical specialities that it deserves. In conclusion, I would like to call on all Asian andrologists to support their journal and to work to improve the reproductive health of men.

Humans↗

PubMed1999

[Testis].

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Humans↗