Control of human luteal steroidogenesis: role of growth hormone-releasing hormone, vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide

OBJECTIVE

To examine the possible effect of growth hormone-releasing hormone (GHRH), vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide on basal and hCG-stimulated P production by human luteal cells.

DESIGN

Cultures of human luteal cells from the early and midluteal phase.

SETTING

All corpora lutea were obtained from the Obstetrics and Gynecology Department of the Università Cattolica, a public care center.

PATIENT(S)

Ten nonpregnant women between 35 and 47 years of age underwent surgery for various nonendocrine disorders, such as leiomyomatosis.

INTERVENTION(S)

Corpora lutea were obtained at the time of hysterectomy.

MAIN OUTCOME MEASURE(S)

Luteal cells were incubated with GHRH, vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide with or without hCG at different concentrations.

RESULT(S)

Pituitary adenylate cyclase-activating peptide stimulated P production in a dose- and time-dependent manner, whereas GHRH and vasoactive intestinal peptide did not affect luteal steroidogenesis. None of the three peptides were found to synergize with hCG.

CONCLUSION(S)

Pituitary adenylate cyclase-activating peptide can influence human luteal steroidogenesis.

Influence of chronic naltrexone treatment on growth hormone secretion in normal subjects

OBJECTIVE

To verify if a chronic opioid blockade could affect the GH/IGF-I axis.

DESIGN

We have investigated the effects of naltrexone (NTX) treatment on GH response to GHRH in normal women.

METHODS

GHRH test (50 micrograms i.v.) performed in seven normal female volunteers (age 25-38 years, with a body mass index ranging from 19.8 to 23.1 kg/m2) before and after 4-weeks NTX treatment (50 mg p.o. daily).

RESULTS

Basal GH, IGF-I, insulin-like growth factor binding protein-3 (IGFBP-3) plasma levels and the IGF-I/IGFBP-3 molar ratio remained unaffected by NTX. NTX significantly reduced the GH peak values (15.52 +/- 3.59 vs 4.78 +/- 0.49 micrograms/l; P < 0.01), and GH area under curve (918.93 +/- 253.96 vs 401.09 +/- 79.63 micrograms/l; P < 0.01).

CONCLUSIONS

This finding suggests that the long-term opioid receptor blockade has an inhibitory role on GHRH-induced GH secretion. A central influence on neurotransmitter control of GH might be hypothesised. The inhibition of stimulated GH release, without interference with the basal level, could indicate an enhanced somatostatin secretion and/or activity. Opioids could be involved only in the regulation of GH dynamics and not in basal secretion. Nevertheless, a direct involvement of opioids at the pituitary level, which could be modified by NTX, cannot be excluded.

Opposite influence of the metabotropic glutamate receptor subtypes mGlu3 and -5 on astrocyte proliferation in culture

In non-synchronized, subconfluent secondary cultures of rat cortical astrocytes, the selective group-I metabotropic glutamate (mGlu) receptor agonist 3,5-dihydroxyphenylglycine (DHPG) increased [methyl-3H]-thymidine incorporation. This effect was mediated by the activation of the mGlu5 receptor, which was shown to be present by either RT-PCR or Western blot analysis. The mixed mGlu receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine reduced the increase in both intracellular Ca2+ and [methyl-3H]-thymidine incorporation produced by DHPG. In contrast, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV), a potent and selective agonist of group-II mGlu receptors, reduced [methyl-3H]-thymidine incorporation in non-synchronized astrocyte cultures. The antiproliferative effect of DCG-IV was prevented by the selective group-II mGlu receptor antagonist (2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG-IV). The opposite effect of DHPG and DCG-IV on astrocyte proliferation was confirmed in cultures deprived of serum for 48 hours and then stimulated to proliferate with either epidermal growth factor (EGF) or the metabolically stable ATP analogue adenosine 5'-(beta,gamma-imido)-triphosphate (AMP-PNP). We conclude that activation of mGlu5 receptors enhances proliferation in cultured astrocytes, whereas activation of a receptor with pharmacological characteristics similar to those of mGlu2/3 receptors reduces proliferation.

A neural-specific hypomethylated domain in the 5' flanking region of the glial fibrillary acidic protein gene

In the present study we examined the methylation status of the glial fibrillary acidic protein (GFAP) gene promoter, analyzing various CG sites in both the human and rat gene in GFAP-expressing and nonexpressing tissues. Moreover, we studied the methylation of specific CG sites in different rat brain areas during postnatal development, in cell cultures highly enriched in specific neural- or non-neural-cell types (fibroblasts), and in human gliomas. The obtained results do not support a simple correlation between demethylation and expression of the GFAP gene but help to identify a cluster of CG sites in the 5'flanking region (from -1176 to -1471 in the rat) that are hypomethylated in neural cell types and localized in a region highly conserved between rat, mouse and human GFAP promoters. Neural-specific hypomethylation of this conserved zone can be observed also in the human GFAP gene both in normal brain tissue and neoplastic glial cells. A higher demethylation of the -1176 site at early stage of postnatal life was observed in specific rat brain areas, such as hippocampus and cerebellum. The most dramatic differences were observed in the cerebellum where a peak of demethylation of the -1176 site was detected at 15 days of postnatal life, followed by an intense remethylation of this site. Results of experiments in the CG4 glial progenitor cell line showed that demethylation of the -1176 site is already established before transcriptional activation of the GFAP gene. Moreover, results of experiments in primary cell cultures show that in neuronal cell types, such as cerebellar granule cells and embryonic cerebral hemisphere neurons, the level of demethylation of the -1176 site is comparable to that observed in cultured astrocytes. In contrast a high level of methylation can be observed in cultured non-neural cell types (fibroblasts). Such neural-specific hypomethylation could be established in a very early stage in the progression along the neural cell lineage and could play a role in maintaining a local open chromatin conformation which is then necessary to allow the interaction with specific regulatory factors present in astroglial cells.

Complete genome sequence of Methanobacterium thermoautotrophicum deltaH: functional analysis and comparative genomics

The complete 1,751,377-bp sequence of the genome of the thermophilic archaeon Methanobacterium thermoautotrophicum deltaH has been determined by a whole-genome shotgun sequencing approach. A total of 1,855 open reading frames (ORFs) have been identified that appear to encode polypeptides, 844 (46%) of which have been assigned putative functions based on their similarities to database sequences with assigned functions. A total of 514 (28%) of the ORF-encoded polypeptides are related to sequences with unknown functions, and 496 (27%) have little or no homology to sequences in public databases. Comparisons with Eucarya-, Bacteria-, and Archaea-specific databases reveal that 1,013 of the putative gene products (54%) are most similar to polypeptide sequences described previously for other organisms in the domain Archaea. Comparisons with the Methanococcus jannaschii genome data underline the extensive divergence that has occurred between these two methanogens; only 352 (19%) of M. thermoautotrophicum ORFs encode sequences that are >50% identical to M. jannaschii polypeptides, and there is little conservation in the relative locations of orthologous genes. When the M. thermoautotrophicum ORFs are compared to sequences from only the eucaryal and bacterial domains, 786 (42%) are more similar to bacterial sequences and 241 (13%) are more similar to eucaryal sequences. The bacterial domain-like gene products include the majority of those predicted to be involved in cofactor and small molecule biosyntheses, intermediary metabolism, transport, nitrogen fixation, regulatory functions, and interactions with the environment. Most proteins predicted to be involved in DNA metabolism, transcription, and translation are more similar to eucaryal sequences. Gene structure and organization have features that are typical of the Bacteria, including genes that encode polypeptides closely related to eucaryal proteins. There are 24 polypeptides that could form two-component sensor kinase-response regulator systems and homologs of the bacterial Hsp70-response proteins DnaK and DnaJ, which are notably absent in M. jannaschii. DNA replication initiation and chromosome packaging in M. thermoautotrophicum are predicted to have eucaryal features, based on the presence of two Cdc6 homologs and three histones; however, the presence of an ftsZ gene indicates a bacterial type of cell division initiation. The DNA polymerases include an X-family repair type and an unusual archaeal B type formed by two separate polypeptides. The DNA-dependent RNA polymerase (RNAP) subunits A', A", B', B" and H are encoded in a typical archaeal RNAP operon, although a second A' subunit-encoding gene is present at a remote location. There are two rRNA operons, and 39 tRNA genes are dispersed around the genome, although most of these occur in clusters. Three of the tRNA genes have introns, including the tRNAPro (GGG) gene, which contains a second intron at an unprecedented location. There is no selenocysteinyl-tRNA gene nor evidence for classically organized IS elements, prophages, or plasmids. The genome contains one intein and two extended repeats (3.6 and 8.6 kb) that are members of a family with 18 representatives in the M. jannaschii genome.

Effect of pituitary adenylate cyclase-activating peptide on meiotic maturation in follicle-enclosed, cumulus-enclosed, and denuded rat oocytes

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a novel bioactive peptide isolated from ovine hypothalamus. Recently, its presence and action have been demonstrated also in peripheral tissues such as testis and ovary. On the basis of sequence similarity, PACAP is included in the vasoactive intestinal peptide (VIP)/glucagon/secretin/growth hormone-releasing factor (GRF) family of neuropeptides. Because both VIP and GRF stimulate oocyte maturation in the rat ovary, we wanted to evaluate whether PACAP also could influence this process. Granulosa cells and follicle-enclosed, cumulus-enclosed, and denuded oocytes were obtained from immature eCG-treated rats. The addition of PACAP-38 significantly accelerated meiotic maturation in follicle- and cumulus-enclosed oocytes from treated rats and in follicle enclosed-oocytes from immature untreated rats, while VIP was effective only on follicle-enclosed oocytes. Interestingly, when used on denuded oocytes, PACAP was able to directly affect the meiotic process. In fact, the neuropeptide delayed oocyte maturation by maintaining elevated levels of intracellular cAMP. Our results clearly demonstrate an involvement of PACAP in oocyte meiotic maturation. Furthermore, for the first time, a direct effect of a peptide on the oocytes has been shown. Moreover, the differences in the action of PACAP and VIP on granulosa cells and oocytes suggest the presence of PACAP type I receptors on both cell types. Our results, along with the data demonstrating the presence of the peptide in the ovary, strongly suggest a potential relevance of PACAP in ovarian physiology.

Metabotropic glutamate receptor expression in cultured rat astrocytes and human gliomas

In order to confirm the existence of metabotropic glutamate receptors in astroglial cultures and to provide information on different receptor subtypes, the expression of different mGluRs was analysed in cultures highly enriched in rat astroglial cells. mRNA levels for mGluR1, 2, 3, 4, 7 were undetectable by Northern blot analysis in primary type-1 astroglial cultures derived from total cerebral hemispheres, cerebral cortex and striatum. Interestingly, these cultures expressed a low, but detectable, level of mGluR5 mRNA. The more sensitive technique Reverse Transcription-Polymerase Chain Reaction (RT-PCR) confirmed the presence of mGluR5 transcript in cultured astrocytes and, in addition, revealed the presence of mGluR3 mRNA. The lack of expression of mGluR5 in CG-4 cells, a rat cell line able to differentiate in type-2 astrocytes or oligodendrocytes depending on the culture conditions, suggested that the presence of mGluR5 was not a general feature of cells of glial origin. Moreover, all the examined mGluR transcript were undetectable by RT-PCR in CG4 cells. In order to confirm the possible expression of mGluR5 in cell of glial origin we examined the mRNA levels for this receptor in tissue samples from human gliomas obtained after surgical resection of the tumors: only 1 sample (grade II astrocytoma), out of 8 examined, showed the presence of mGluR5 mRNA. In conclusion our data show that the only cloned metabotropic receptor linked to phosphoinositide hydrolysis, whose expression is detectable in cultured type-1 astrocytes, in mGluR5. It remains to be established if the low level of expression of mGluR3 could be responsible for the group II metabotropic glutamate receptor activity previously observed in cultured astroglial cells.

Further evidence of increased aromatase activity in granulosa luteal cells from polycystic ovary

This study evaluated the effect of atamestane (a competitive inhibitor of P-450 aromatase) on granulosa luteal cells from polycystic and normal ovaries. Treatment with atamestane (10 micromol/l) determined a strong inhibition of basal aromatase activity in both types of cells; however, its effect was markedly more pronounced in granulosa cells from normal ovary than in granulosa cells from polycystic ovaries (PCO; P < 0.01). Concomitant treatment with insulin (25 microg/ml) and increasing doses of atamestane (0.01-10 micromol/l) caused a dose-dependent inhibition of insulin-stimulated aromatase activity, but again with marked differences between the two types of cells. In granulosa cells from PCO, the minimal effective dose of atamestane was 1 micromol/l and it had an EC50 of 2.23 +/- 0.4 micromol/l and a maximal inhibitory effect of 75%; in granulosa cells from normal ovary, the minimal effective dose of atamestane was 0.01 micromol/l, the EC50 was 0.4 +/- 0.07 micromol/l, and the maximal inhibitory effect was 94%. Significant differences were observed between the different cells at all the studied dose points. Reversibility studies showed that resumption of aromatase activity in granulosa cells from PCO is basally greater and more inducible with insulin treatment. This study provides further evidence of an increased in-vitro function of the aromatase complex in granulosa cells from PCO, that could be induced by an altered cellular autoregulation.

Heterogeneity in beta cell activity, hepatic insulin clearance and peripheral insulin sensitivity in women with polycystic ovary syndrome

The aim of this study was to evaluate the impact of reduced peripheral insulin sensitivity, beta cell hypersecretion and reduced hepatic insulin clearance in the hyper-insulinaemia of lean and obese PCOS patients. A total of 35 women with polycystic ovary syndrome (PCOS) and 10 lean normo-ovulatory controls underwent an oral glucose tolerance test and an euglycaemic-hyper-insulinaemic clamp study. PCOS patients were classified into four groups according to their BMI and insulin secretion (normo-lean; normo-obese; hyper-lean; hyper-obese), and results were compared between groups and with the controls. All the PCOS groups showed significantly higher insulin secretion than controls; there were no differences in insulin response to glucose load between lean and obese normo- and hyper-insulinaemic patients. Secretion of c-peptide was greater in PCOS groups than controls. All the hyper-insulinaemic PCOS patients had lower values of hepatic insulin clearance, independent of BMI, when compared either with controls (P < 0.001) or with PCOS normo-insulinaemic women (P < 0.01). Normo- and hyper-insulinaemic obese patients had similar total body glucose utilization (M value), which was lower than in lean PCOS subjects and controls. Our results suggest that evaluation of insulin resistance alone does not fully characterize the PCOS population; differences in liver metabolism of insulin are present in obese insulin resistant subjects and in lean patients with normal insulin sensitivity when divided into normo- and hyper-insulinaemic subgroups. Insulin resistance and hyper-insulinaemia may represent two distinct features of the insulin disorder in PCOS: the former appear to reflect the presence of obesity, while the latter may be a primary feature of PCOS.

Heparin and low-dose aspirin restore placental human chorionic gonadotrophin secretion abolished by antiphospholipid antibody-containing sera

This study was conducted to determine whether drugs used for conventional treatments of pregnant women with antiphosholipid syndrome might be able to restore the gonadotrophin-releasing hormone (GnRH)-induced secretion of placental human chorionic gonadotrophin (HCG) in vitro. We tested this hypothesis using a modified enzyme-linked immunosorbent assay (ELISA) and an in-vitro placental culture system. Pharmacological dose of low molecular weight heparin (20 IU/ml) significantly (P < 0.02) reduced the antiphospholipid antibody (aPL) binding in the ELISA and was able to restore GnRH-induced HCG secretion (P < 0.05) in presence of aPL-containing sera. Low-dose aspirin (0.03 M) did not modify aPL binding in the ELISA, but partially restored HCG secretion (P < 0.05). These observations may help to explain the role of these treatments in antiphospholipid syndrome.

Effect of amylin in various experimental models of gastric ulcer

Subcutaneous administration of amylin (20-40 micrograms/kg) prevented, in a dose-dependent manner, reserpine- and serotonin-induced gastric damage, but the anti-ulcer effect was not present when lesions were induced by pylorus ligation. The protective effect of amylin was inhibited by pretreatment with capsicin as well as CGRP-(8-37), a calcitonin gene-related peptide (CGRP) and amylin receptor antagonist, and was significantly reduced by domperidone, a dopamine D2 receptor antagonist, or neostigmine, an inhibitor of acetylcholinesterase. Our data suggest that the gastroprotective activity of amylin in some experimental models of gastric ulcers involves capsaicin-sensitive fibers and CGRP receptors. Moreover, the peptide interferes, at least in part, with the dopaminergic and parasympathetic systems.

The hypothalamic-pituitary-luteal axis in women: effects of long-term orally active opioid antagonist (naltrexone) administration

Aim of our study is to assess the effect of a long-term oral opiate antagonist treatment during the luteal phase on the hypothalamic-pituitary-ovarian axis. Fourteen normovulatory women participated to the study. Immediately after the ovulation, the patients were randomly divided in two groups: in the first one women received naltrexone 50 mg/die orally (Antaxone Zambon Italy) from day 1 of the luteal phase for 7 days. In the second patients were treated with placebo for the same period and served as control group. On day 7, patients were hospitalized for a pulse pattern study followed by a GnRH test. LH, FSH, Estradiol, Progesterone were assayed. The naltrexone administration strongly increased the number as well as the amplitude of the gonadotropin pulses. The circulating P levels were also significantly higher in treated patients. The GnRH injection significantly increases the gonadotropin secretion in all patients. The stimulated LH and FSH secretion was significantly greater in treated patients when compared to controls. Such discharge of LH determined a significant increase of progesterone production in controls, but failed to stimulate the corpus luteum in treated patients. In conclusion the present paper strengthen an important role of the opioidergic system in the regulation of GnRH pulsatility in luteal phase. Moreover, our findings confirms the sensibility of the corpus luteum to LH and the possibility to stimulate the P secretion during the luteal phase.

Fatty acid dietary intake and the risk of ischaemic stroke: a multicentre case-control study. UFA Study Group

A low dietary intake of unsaturated fatty acids has been found in male patients with stroke as compared with controls in Italy, and a high consumption of meat has been associated with an increased risk of stroke in Australia. We present a case-control study, comparing the unsaturated and saturated fatty acids content of red cell membranes (which reflects the dietary intake of saturated and unsaturated fats) in 89 patients with ischaemic stroke and 89 controls matched for age and sex. In univariate analysis, besides hypertension, atrial fibrillation, ischaemic changes in ECG and hypercholesterolaemia, stroke patients showed a lower level of oleic acid (P = 0.000), but a higher level of eicosatrienoic acid (P = 0.009). Conditional logistic regression (dependent variable; being a case) showed that the best model included atrial fibrillation, hypertension, oleic acid and eicosatrienoic acids. These results confirm a possible protective role of unsaturated fatty acids against vascular diseases; however, we did not find any difference in the content of omega3 acids, which have been considered in the past to protect against coronary heart disease. We conclude that the preceding diet of patients with ischaemic stroke may be poor in unsaturated fatty acids (namely, oleic acid), and this defect is independent of other vascular risk factors. Only further studies will show whether changes in diet and/or supplement of unsaturated fatty acids might reduce the incidence of ischaemic stroke.

Impact of long-term naltrexone treatment on growth hormone and insulin secretion in hyperandrogenic and normal obese patients

The growth hormone (GH) response to stimulation tests is impaired in obesity. Moreover, obese patients exhibit a "paradoxical" increase of GH to GH-releasing hormone (GHRH) stimulation after food ingestion; this paradoxical response is reversed by naloxone infusion. On the other hand, beta-endorphin seems to exert profound effects on insulin release. Recent studies also demonstrated an impairment of GH response to several stimuli in polycystic ovary syndrome (PCOS), a condition associated with obesity, hyperinsulinism, and insulin resistance. Chronic inhibition of opioid tone by the opioid antagonist naltrexone (NTX) is able to reduce the insulin response to an oral glucose tolerance test (OGTT) in hyperinsulinemic PCOS patients. Since insulin and GH may reciprocally influence their secretion and the opioid system may have a role in the pathogenesis of hyperinsulinemia and reduced GH secretion, we have explored the involvement of these neuroendocrine mechanisms in essential obesity and in obesity associated with hyperandrogenism by a long-term treatment with an opiate antagonist. We tested seven obese patients affected by PCOS, seven matched women with essential obesity (EO), and five non-obese control subjects. All patients, in the follicular phase, underwent an OGTT (75 g) and basal hormone assay. Two days later, patients were subjected to a GHRH test. The patients then had 4 weeks of treatment with NTX 50 mg/d. Following continuation of the treatment, OGTT and GHRH tests were repeated. Insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) plasma concentrations were also determined in the basal condition before and after NTX treatment. NTX treatment reduced fasting insulin levels in patients with EO (P < .05) and restored a normal GH response to GHRH without affecting IGF-1 and IGFBP-3 levels. In PCOS subjects, NTX reduced the insulin response to a glucose load and failed to modify the blunted GH response to GHRH. Our data suggest a significant difference in opioid system function in PCOS and EO subjects, indicating a particular form of obesity in PCOS. The opiate antagonist treatment in EO may act through the reduction of negative insulin feedback on GH secretion. In PCOS patients, the failure to improve GH secretion in obese hyperandrogenized patients may be related to a high opioidergic tone or to the inhibitory predominance of other neurotransmitters.

The use of prostaglandin E2 for cervical ripening in patients requiring induction of labour

A total of 290 women who required induction of labour for medical or obstetric reasons were given single or multiple doses of prostaglandin E2 gel (0.5 mg) to induce cervical ripening. Onset of labour occurred in 185 (63.8%) of the women treated with the gel, without any further treatment. The overall Caesarean section rate was 27.2% (79/290) and was significantly higher among those with an initially low Bishop score than in those with a higher initial score (34.7% versus 22.1%; P = 0.025). Prostaglandin E2 gel appears to be of considerable clinical benefit, especially where no other options are available except Caesarean section or a very long, difficult labour that may result in significant fetal distress.

T cells from individuals in advanced stages of HIV-1 infection do not proliferate but express activation antigens in response to HIV-1-specific antigens

Like T cells from healthy subjects, those of HIV-1-infected patients are capable of expressing activation antigens on their surface after antigenic or mitogenic stimulation, but their proliferative activity is strongly reduced or even absent, especially in patients with advanced stages of the disease. The characteristic of expressing activation antigens in response to different stimuli in the absence of cell proliferation is shared by CD4+ and CD8+ T-cell subsets from HIV-1-infected patients. The number of T cells capable of expressing CD25 and CD71 in response to HIV-1-related antigens but not of proliferating increased significantly with the progression of the disease, but the number of T cells capable of expressing the two activation antigens in response to the classic tetanus toxoid recall antigen decreased. The higher numbers of T cells capable of responding to HIV-1-related antigens in conjunction with a reduction in the number of T cells responding to recall antigens may explain the occurrence of different infections, including opportunistic microorganisms, during the more advanced stages of HIV-1 infection. Because the increase in the number of HIV-1 antigen-responding T cells (defined by CD25 and CD71 activation antigen expression) is a characteristic of symptomatic HIV-1-infected patients, expression (by flow cytometry) of these activation antigens on T cells in response to HIV-1 antigens could be used as a new marker of disease progression.

Ciliary neurotrophic factor activates JAK/Stat signal transduction cascade and induces transcriptional expression of glial fibrillary acidic protein in glial cells

In recent reports, ciliary neurotrophic factor (CNTF) has been implicated as an injury factor involved in regulating astrogliosis in the CNS. In this study, we used a rat oligodendroglial progenitor cell line that is highly responsive to CNTF to examine CNTF-induced alterations that may play a role in activation of the glial fibrillary acidic protein (GFAP) gene. We determined that CNTF induces the transient translocation of Stat1 alpha/p91 to the nucleus. This nuclear translocation was followed by GFAP promoter activation and an up-regulation of GFAP mRNA and protein. Level of CNTF-alpha receptor mRNA, however, were unaffected by addition of the ligand. Transfection studies using an upstream 5'-flanking, 1.9-kb rat GFAP promoter linked to a luciferase reporter gene revealed CNTF-induced transcriptional activation within 1 h of ligand exposure. Moreover, serial-deleted constructs identified a distal (-1,857 to -1,546 bp) and a proximal (-384 to -106 bp) region as being important for CNTF-induced GFAP promoter activation. These two regions showed a strong degree of overlap for CNTF- and serum-induced activation of the GFAP gene. Analysis of the two regions revealed several cis-elements that are thought to be involved in GFAP regulation and/or the regulation of other genes by members of the interleukin-6 family of cytokines. Moreover, we are the first to report the presence of several putative CNTF-responsive elements within our identified distal and proximal regions in the GFAP gene promoter.

The neuroprotective activity of group-II metabotropic glutamate receptors requires new protein synthesis and involves a glial-neuronal signaling

The group-II metabotropic glutamate (mGlu) receptor agonists (2S,1'R, 2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV), S-4-carboxy-3-hydroxyphenylglycine (4C3HPG), and (2S,1'S, 2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I) protected mouse cortical neurons grown in mixed cultures against excitotoxic degeneration induced by a 10 min pulse with NMDA. Protection was observed not only when agonists were added in combination with NMDA but also when they were transiently applied to cultures 6-20 hr before the NMDA pulse. In both cases, neuroprotection was reduced by the group-II mGlu receptor antagonist (2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG-IV), as well as by the protein synthesis inhibitor cycloheximide (CHX). Both neurons and astrocytes in mixed cultures were immunostained with an antibody that recognized mGlu2 and mGlu3 receptors in recombinant cells. To determine whether astrocytes played any role in the neuroprotection mediated by group-II mGlu receptors, we exposed pure cultures of cortical astrocytes to DCG-IV, 4C3HPG, or L-CCG-I for 10 min. The astrocyte medium collected 2-20 hr after the exposure to any of these drugs was highly neuroprotective when transferred to mixed cultures treated with NMDA. This protective activity was reduced when CHX was applied to astrocyte cultures immediately after the transient exposure to group-II mGlu receptor agonists. We conclude that neuroprotection mediated by group-II mGlu receptors in cultured cortical cells requires new protein synthesis and involves an interaction between neurons and astrocytes.

Thrombolysis for prosthetic valve thrombosis: indications and results

BACKGROUND AND AIMS OF THE STUDY

Prosthetic valve obstruction is caused by thrombi or fibrous tissue overgrowth, or both; thrombolysis avoids reoperation-related risks, but is effective only on clots. Hence, the study aims were to: (i) further assess our indication criteria for thrombolysis in prosthetic valve thrombosis; and (ii) evaluate treatment and follow up in a large patient population.

METHODS

Between January 1991 and January 1994, 20 cases of prosthetic thrombosis were treated with thrombolysis using recombinant tissue type plasminogen activator (rt-PA). Indication criteria for thrombolysis were: (i) recent onset of symptoms; (ii) transesophageal echocardiographic (TEE) evidence of clots on the valve or cardiac chambers; and (iii) a partially preserved disc excursion. All patients were fitted with mechanical valves (four caged balls, 10 tilting discs, six bileaflets), with 17 valves located in the mitral and three in the aortic position. Symptoms of obstruction comprised cardiac failure in 11 cases and/or embolism in 10.

RESULTS

After rt-PA infusion, normal prosthetic function was restored in all patients, though one underwent successful reoperation five days later. During infusion, five patients had a transient ischemic attack and one a minor transient peripheral embolism. Recurrence of thrombosis occurred in three patients during follow up; subsequent thrombolysis was successful in two, without complication.

CONCLUSIONS

As treatment proved satisfactory, the reliability of our indicational criteria was confirmed. Only transient complications arose during treatment with recurrent thrombosis most common in those patients who had more thrombogenic valve prostheses.

The impact of insulin secretion on the ovarian response to exogenous gonadotropins in polycystic ovary syndrome

The aim of the study was to evaluate the influence of insulin level on the ovarian response to FSH when inducing ovulation in patients affected by polycystic ovarian syndrome (PCOS). To evaluate the presence of hyperinsulinemia, 34 patients affected by PCOS were studied by an oral glucose tolerance test, then patients were stimulated for 52 cycles using FSH to induce ovulation. The ovarian response to therapy was evaluated by ultrasounds and as estradiol (E2) and androstenedione (A) plasma level determinations. On the basis of the insulinemic response to the glucose challenge, 20 patients were considered to be hyperinsulinemic and 14 normoinsulinemic. The hormonal features of each group were similar. The ovulation rate was similar in hyperinsulinemic and normoinsulinemic subjects, whereas the incidence of ovarian hyperstimulation was significantly higher in the hyperinsulinemic group. The increase in ovarian dimensions observed in hyperinsulinemic subjects after gonadotropin stimulation was more marked than that observed in normoinsulinemic ones. This was caused by the development of a larger number of immature follicles. E2 levels gradually increased after gonadotropin stimulation in both groups of subjects; however, higher levels were observed in hyperinsulinemic patients. During stimulation, the higher E2/A ratio suggests the presence of a greater aromatization activity in hyper-insulinemic patients. In conclusion, the present study suggests that, in PCOS, the insulinemic pattern may influence the ovarian response to gonadotropin administration; thus, hyperinsulinemic subjects may be at greater risk of ovarian hyperstimulation syndrome than normoinsulinemic subjects.

Natural antibodies to IL-2

Natural antibodies to human interleukin-2 are present in sera of patients infected with human immunodeficiency virus and also, at a lower titre, in sera of healthy individuals. These antibodies could be purified by affinity-chromatography. Purified human anti-hIL-2 antibodies can interfere with lymphocyte proliferation both in the lymphokine activated killer cell assay and in the mixed lymphocyte culture. The neutralizing activity observed in vitro suggests that these antibodies play a role in the elaborate cytokine network by which the immune system regulates its response.

Flow cytometric analysis of activation markers on stimulated T cells and their correlation with cell proliferation

The expression of activation antigens, namely CD25, CD69, CD71, and HLA-DR on T cells from 15 healthy individuals stimulated with different mitogens and specific antigens was evaluated by immunofluorescence assay and flow cytometric analysis and compared with cell proliferation as a function of [3H]thymidine incorporation. CD69 was the earliest expressed antigen on stimulated cells, while HLA-DR was the latest. Regardless of the stimulus used, lymphocytes expressing CD25 and CD71 were always more numerous than cells expressing CD69 and HLA-DR. Variations in the proportion of CD4+ and CD8+ T cells expressing each activation marker were observed with different antigenic stimuli. The expression of each activation marker showed overall agreement with the [3H]thymidine incorporation assay in discriminating between positive and negative immune response. However, no correlation was observed between the percentage of CD25-, CD69-, CD71-, and HLA-DR-positive T cells and the amount of [3H]thymidine incorporation. Moreover, low doses of mitogens and antigens as well as short time of stimulation were sufficient to induce T cells to express activation antigens but not to proliferate. Our data show that results obtained by flow cytometry and [3H]thymidine incorporation may differ qualitatively, at least under certain conditions; this suggests that the 2 assays are complementary, and when combined, may gives a clearer understanding of events leading to efficient cell-mediated immune response.

Natural antibodies to interferon-gamma

Natural antibodies to interferon (IFN)-gamma were detected in the serum of virus-infected patients and also, at a low titre, in the serum of healthy subjects. The increased titre of antibodies to IFN-gamma in the sera of virus-infected patients, and its decrease with clinical resolution, indicate that these antibodies are related to viral infection and probably reflect IFN-gamma production as a result of antigenic stimulation in vivo. Natural antibodies to IFN-gamma were affinity purified and studied for their capability to interfere in vitro with the multiple activities of the lymphokine. Data obtained show that these human anti-IFN-gamma antibodies have no inhibitory effect on the antiviral and antiproliferative activity of IFN-gamma and do not interfere with the binding of the lymphokine to its specific cell receptor. Instead, they can inhibit the expression of HLA-DR antigens induced by IFN-gamma on U937 cells and interfere, in mixed lymphocyte culture, with the proliferation of lymphocytes and the generation of cytotoxic lymphocytes. Experiments in animal models suggest that natural antibodies to IFN-gamma may have a role in the immunoregulatory process limiting the intensity and/or duration of immune response. As they can interfere only with the immunomodulating activities of IFN-gamma, these antibodies might open up new therapeutic approaches to diseases with evidence of activated cell-mediated immunity.