LH3, a "homologue" of the mastadenoviral E1B 55-kDa protein is a structural protein of atadenoviruses

Ovine adenovirus serotype 7 (OAdV), the prototype atadenovirus, has gene homologues for most mastadenovirus structural proteins but lacks proteins V and IX. Instead, OAdV has structural proteins of 32 and 42 kDa although the gene encoding the latter had not previously been identified. The presently reported studies of OAdV virions have now identified a minor structural polypeptide of approximately 40 kDa as the product of the L1 52/55-kDa gene and, more surprisingly, shown that the 42-kDa protein is encoded by LH3. This gene product was previously thought to be a homologue of mastadenovirus E1B 55 kDa, which is a multi-functional, non-structural protein that cooperates with E1A in cell transformation. The lack of transforming activity previously demonstrated for OAdV combined with a structural role for the LH3 product indicates that the protein has a different function in atadenoviruses. We discuss the abundance and likely core location of LH3 in the virion and the possible derivation of the E1B 55-kDa gene from the LH3 gene.     

Insulin resistance causes impaired vasodilation and hypofibrinolysis in young women with polycystic ovary syndrome

INTRODUCTION: Insulin resistance, a novel cardiovascular risk factor, is often associated with increased plasminogen activator inhibitor-1 levels and impaired vasodilation. Insulin infusion in the forearm induces plasminogen activator inhibitor-1 and tissue plasminogen activator expression and endothelium-dependent vasodilation in normal subjects. The present study explores the relationship between insulin-induced vasodilatory and fibrinolytic properties of the endothelium in women with polycystic ovary syndrome, frequently affected by insulin resistance and early atherosclerosis. MATERIALS AND METHODS: Metabolic, hormonal and fibrinolytic parameters were evaluated in 64 patients with polycystic ovary syndrome (19 insulin-resistant and 45 insulin-sensitive) and in 25 controls. In 16 women with polycystic ovary syndrome, 8 insulin-resistant and 8 insulin-sensitive, blood flow, plasminogen activator inhibitor-1 and tissue plasminogen activator expression were evaluated during insulin infusion into the forearm. RESULTS: Elevated basal plasminogen activator inhibitor-1 levels were found in women with polycystic ovary syndrome, correlating directly with insulin levels. Plasminogen activator inhibitor-1 expression increased during insulin infusion in all women with polycystic ovary syndrome, but was delayed and sustained in insulin-resistant patients (p<0.01). Vasodilatory response to insulin was blunted (p<0.01) and tissue plasminogen activator expression abolished in insulin-resistant patients (p<0.01). CONCLUSION: Our study demonstrates that women with polycystic ovary syndrome and insulin resistance show a blunted endothelial-dependent vasodilation. The impaired endothelial release of tissue-plasminogen activator and the sustained plasminogen activator inhibitor-1 release during insulin infusion suggest a hypofibrinolytic state in PCOS patients with insulin resistance. This hemodynamic and fibrinolytic derangement may contribute to the pathogenesis of early atherosclerosis in insulin resistance.     

Aging alters norepinephrine release in the medial preoptic area in response to steroid priming in ovariectomized rats

Changes in luteinizing hormone (LH) secretion that are observed in aging animals have been attributed to a reduction in hypothalamic norepinephrine (NE). The reason for the reduction in NE levels with aging is unclear. We hypothesized that the responsiveness of noradrenergic neurons to ovarian steroids is altered during aging. To test this, regularly cycling female Sprague-Dawley rats (young: 4-5 months old and middle age: 8-11 months old) were implanted with a push-pull cannula in the medial preoptic area (MPA) and ovariectomized bilaterally. On the 8th day after ovariectomy, they were injected with estrogen (30 microg/100 microl corn oil, s.c.) at 1000 h and on the 9th day they were implanted with a jugular catheter. On the 10th day they were injected with progesterone (2 mg/100 microl corn oil, s.c.) at 1000 h and subjected to push-pull perfusion. Perfusate samples from the MPA were collected at the rate of 10 microl/min every 30 min from 1300 to 1800 h and blood samples (0.3 ml) were collected hourly. The perfusate samples were analyzed for NE and dopamine (DA) concentrations using high performance liquid chromatography with electrochemical detection and serum LH levels were determined by RIA. In young animals, NE release (mean+/-S.E., pg/min) was 4.0+/-1.1 pg/min at 1300 h and increased significantly (p<0.05) to 10.4+/-4.3 pg/min at 1500 h and remained elevated until 1600 h and then declined to 6.8+/-2.5 at 1730 h. In contrast, the increase in NE release occurred briefly in middle-aged animals and was delayed by an hour. LH patterns in both age groups followed the pattern in NE release. There was no change in the release of DA in both young and middle-aged animals. It is concluded that the altered responsiveness of noradrenergic neurons to steroid priming in middle-aged rats probably plays a critical role in the alterations seen in LH secretion in older animals.     

Hemodynamic changes induced by urinary human chorionic gonadotropin and recombinant luteinizing hormone used for inducing final follicular maturation and luteinization

OBJECTIVE: To compare the safety of recombinant human luteinizing hormone (LH) with that of urinary hCG in terms of the hemodynamic changes when they are used to induce final follicular maturation in patients undergoing in vitro fertilization (IVF). A secondary end point was efficacy in terms of IVF outcome. DESIGN: Prospective, randomized clinical trial. SETTING: University teaching hospital. PATIENT(S): Thirty IVF patients. INTERVENTION(S): Ovarian stimulation was induced with FSH under pituitary suppression. Patients were randomized to receive either hCG or recombinant human LH as a trigger of oocyte maturation (5,000 IU) and for luteal phase support (5,000 IU, 2,500 IU, and 2,500 IU on the day of follicular aspiration, 2 days later, and 5 days later, respectively). MAIN OUTCOME MEASURE(S): Mean arterial pressure, cardiac output, peripheral vascular resistance, and serum levels of progesterone, plasma concentrations of aldosterone, norepinephrine, and plasma renin activity were measured in all patients on postovulatory day 7 of the spontaneous menstrual cycle preceding IVF (baseline) and 7 days after the hCG/recombinant human LH ovulatory injection during the IVF cycle. RESULT(S): Ovarian response and IVF outcome (pregnancy rate, 60%) were similar in both treatment groups. On the seventh day after hCG/recombinant human LH administration, the peripheral vascular resistance was significantly lower and serum progesterone concentrations significantly higher in the hCG group as compared with the recombinant human LH group. The percentage change from baseline values during IVF cycles in all hemodynamic and neurohormonal variables investigated was higher (albeit not statistically different) in the group treated with hCG vs. the group treated with recombinant human LH. CONCLUSION(S): Recombinant human LH is associated with less intense circulatory changes than hCG when it is given to induce final follicular maturation and luteal phase support in IVF procedures.     

The clinical therapeutic window for luteinizing hormone in controlled ovarian stimulation

Objective: To discuss the clinical therapeutic window for LH during the follicular phase.

Design: Review of selected papers that were retrieved through a Medline search and a review of clinical trials, the results of which are in the process of publication.

Patient(s): Women undergoing infertility treatment.

Intervention(s): Recombinant human LH (r-hLH) was administered SC as a supplement to FSH during controlled ovarian hyperstimulation.

Main Outcome Measure(s): Follicular development, E₂ production, and endometrial thickness.

Result(s): Optimal follicular maturation is the result of both FSH and LH stimulation. In patients with hypogonadotropic hypogonadism, 75 IU of r-hLH and 150 IU of FSH per day resulted in more follicles and provided sufficient E₂ for optimal endometrial proliferation. Additional r-hLH (>250 IU/day), in patients with either hypogonadotropic hypogonadism or polycystic ovary disease, may precipitate a series of deleterious physiological actions leading to atresia of developing follicles. Adding r-hLH to FSH in women treated with GnRH agonist showed no benefits in terms of number of mature oocytes, fertilization, and cleavage. However, those who experience profound pituitary desensitization may benefit from adding LH to the stimulation protocol. No obvious clinical criteria have been established to define this group of patients.

Conclusion(s): A “threshold” and “ceiling” level for LH (therapeutic window) is proposed, below which E₂ production is not adequate and above which LH may be detrimental to follicular development.     

Cloning of cDNAs encoding the three pituitary glycoprotein hormone beta subunit precursor molecules in the Japanese toad,Bufo japonicus

Complementary DNAs encoding precursor molecules of the beta subunits of three pituitary glycoprotein hormones (LH, FSH, and TSH) of the Japanese toad (Bufo japonicus) were isolated and sequenced. Unexpectedly large numbers of single nucleotide substitutions were found in all three beta subunit cDNAs. The eight isolated LH beta precursor cDNA clones were classified into six forms of nucleotide sequence, with four nucleotide substitutions each in the apoprotein coding region and in the 3' untranslated region (UTR). In the deduced amino acid sequence, the LH beta subunit showed two forms with a single amino acid substitution. The seven isolated FSH beta subunit cDNAs were classified into two forms, which differed from each other at 11 positions in the 3' UTR. The six isolated TSH beta subunit clones were classified into four forms with 2 and 5 nucleotide substitutions in the signal peptide and apoprotein coding regions, respectively. However, all the substitutions in the apoprotein coding region were silent. The substitution in the signal peptide coding region could produce three forms of signal peptide. Amino acid sequence comparison revealed that the toad LH beta subunit is more similar to the fish GTH II beta subunit than to mammalian and avian LH beta subunits. We found that the toad LH beta subunit molecule is a partial chimera of LH and FSH; amino acid residues located in 36th to 42nd and 96th to 99th are identical or similar to those of not LH- but FSH-beta subunit in mammalian, whereas it is more similar to LH- than FSH-beta subunit in total. We also found that the toad FSH beta subunit is more similar to the fish GTH II beta subunit than to the fish GTH I beta subunit and that the toad TSH beta subunit is more similar to tetrapod TSH beta subunits than to fish TSH beta subunits.     

Is there a physiological role for gonadotrophin oligosaccharide heterogeneity in humans? III. Luteinizing hormone heterogeneity: a medical physiologist's perspective

Clinical evidence for a physiological impact of luteinizing hormone (LH) isoforms includes their unequal in-vitro bioactivity and altered in-vivo LH kinetics. For example, alkaline LH isospecies emerge in an oestrogen-rich milieu, and show greater bioactivity in vitro along with more rapid metabolic removal in vivo. More acidic LH isotypes are predominant in eugonadal men with end-stage renal failure and in postmenopausal women. The relevance of changes in charge distribution in puberty to sexual maturation is not clear. Molecular LH variants may be associated with decreased testis size and reduced linear growth in boys, menstrual irregularity and/or subfertility in women, and possibly protect against polycystic ovarian syndrome (PCOS). This article summarises the provisional physiological implications of LH isotypes based on current evidence.     

The effect of oestradiol and progesterone on hypoglycaemic stress-induced suppression of pulsatile luteinizing hormone release and on corticotropin-releasing hormone mRNA expression in the rat

Corticotropin-releasing hormone (CRH) is implicated in the suppression of pulsatile luteinizing hormone (LH) secretion by a variety of stressful stimuli; 17beta-oestradiol (E2) has been shown to modulate this inhibitory response. The present study in ovariectomized (OVX) rats was designed to investigate the effect of E2 and progesterone (P4) on hypoglycaemic stress-induced changes in pulsatile LH secretion and on the associated changes in both central and peripheral components of the hypothalamic-pituitary-adrenal axis. E2 enhanced the hypoglycaemic stress-induced suppression of LH pulses; P4 in addition to E2 further potentiated the inhibitory response. The rise in plasma corticosterone following insulin-induced hypoglycaemia (IIH) was highest in the E2 + P4 group. Nevertheless, when such levels were achieved by administration of corticosterone, the occurrence of LH pulses was completely unaffected, irrespective of ovarian steroid milieu. E2 and E2 + P4 up-regulated basal CRH mRNA expression in the paraventricular nucleus (PVN) as measured by in situ hybridization; this signal was also increased in the medial preoptic nucleus (MPN) following E2. IIH resulted in a rise in CRH mRNA in the PVN, but not in the MPN; this rise may reflect a more significant role for the PVN in the present context. Changes in neuropeptide mRNA expression may signal changes in neuronal activity; nevertheless, the profound differences in LH pulse suppression in OVX, E2 and E2 + P4 rats following IIH were not reflected in the concurrent changes in CRH mRNA in the PVN. The results suggest that while corticosterone has no acute effect on LH pulses in the rat, the up-regulation by ovarian steroids of basal CRH mRNA in the PVN and/or MPN may contribute to the central regulation of these pulses in response to stress.