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A Somogyvari-Vigh

Publications and source records attributed to A Somogyvari-Vigh.

12 recordsLinked to original sources
PubMed2001

GH mRNA levels are elevated by forskolin but not GH releasing hormone in GHRH receptor-expressing MtT/S somatotroph cell line.

The MtT/S somatotroph cell line should be a growth hormone-releasing hormone (GHRH)-responsive model system for the study of physiological control of growth hormone (GH) transcription because GH secretion from these cells is stimulated by GHRH. To examine the GH transcriptional activity of these cells, endogenous GH mRNA levels were measured using a ribonuclease protection assay following treatment under a variety of hormonal conditions. While omission of serum led to reduction of GH mRNA to 22% of control levels by 2 days and to 8% by 5 days (P<0.05 for both), GH mRNA levels were maintained at control values in serum-free medium containing 5 nM dexamethasone and 30 pM triiodothyronine (TDM). However, the addition of 10 nM GHRH under any treatment condition did not significantly alter GH mRNA levels. Characterization of the MtT/S cells showed that GHRH-receptor (GHRH-R) mRNA was detectable by reverse transcription-polymerase chain reaction (RT-PCR) amplification. Measurement of extracellular cAMP showed that the MtT/S cells have basal levels of > or =20 nmol/10(6) cells per h in both serum-containing and serum-free media, and that GHRH had no effect on cAMP levels, suggesting constitutive activation. To rule out the possibility of autocrine stimulation by GHRH produced endogenously, GHRH mRNA was not detectable in MtT/S cells using RT-PCR amplification. The stimulatory G-protein alpha subunit, mutations of which are known to activate adenylate cyclase constitutively in acromegaly, was sequenced but found not to differ from normal pituitary in the regions most commonly mutated. Finally, treatment with 10 microM forskolin, to directly activate adenylate cyclase, increased GH mRNA to 140% of controls in TDM, and to 163% in serum-free medium after 2 days, and to 166% in TDM-treated cells and 174% in serum-free culture after 5 days (all P<0.05). Taken together, these data indicate that although MtT/S cells express the GHRH-R, GHRH cannot stimulate adenylate cyclase to increase GH transcription due to constitutive elevation of cAMP levels, by a means that may be similar to that in cases of acromegaly not caused by oncogenic gsp mutations.

Adenylyl Cyclases↗
PubMed2000

Postischemic spontaneous hyperthermia and its effects in middle cerebral artery occlusion in the rat.

This study examined the time course and effects of postischemic spontaneous hyperthermia after transient and permanent focal ischemia. Rats underwent a 90-min, 120-min, or permanent middle cerebral artery occlusion (MCAO). Body temperatures started rising 15-20 min after MCAO and reached 39-40.5 degrees C during the first hour. Sustained hyperthermia was observed during the rest of the first 24 h. In another experiment, rats were subjected to the same interventions, but a normothermic body temperature was maintained. Spontaneous hyperthermia significantly increased the infarct volumes measured 48 h after MCAO in all groups. Reperfusion 2 h after the onset of ischemia was not beneficial in the hyperthermic animals in contrast to the normothermic group. We also examined the effect of spontaneous hyperthermia on the temporal progression of infarcted and penumbral areas 4, 12, or 48 h after MCAO. During spontaneous hyperthermia, penumbral areas became infarcted areas more rapidly, which was most expressed at 4 h. These findings demonstrate that severe spontaneous hyperthermia can occur in rats after MCAO and that it not only increases the infarct volumes in both transient and permanent ischemia, but also accelerates the incorporation of penumbral areas into necrotic areas, which significantly decreases the window of opportunity for therapeutic interventions.

Animals↗
PubMed2000

Neuroprotective effects of PACAP38 in a rat model of transient focal ischemia under various experimental conditions.

In the study reported here, we investigated the neuroprotective effect of PACAP38 in a rat model of middle cerebral artery occlusion (MCAO) under various experimental conditions. Stroke patients often develop mild hyperthermia that increases the infarct size and worsens the outcome. We compared the neuroprotective effect of PACAP38 in normothermic and moderately hyperthermic animals. Brain damage was more extensive in the hyperthermic animals, but PACAP38 significantly reduced the infarct size, measured 48 h after MCAO, in both the normothermic and the moderately hyperthermic animals, by more than 50%. However, a significant neuroprotection with PACAP38 could only be demonstrated when animals with no definite circling behavior and/or convulsions were excluded from the evaluations. In conclusion, moderate hyperthermia did not influence the effect of PACAP38, but animals with questionable brain damage or convulsions must be excluded from the sample in order to demonstrate the neuroprotection with PACAP38.

Animals↗
PubMed2000

Delayed systemic administration of PACAP38 is neuroprotective in transient middle cerebral artery occlusion in the rat.

BACKGROUND AND PURPOSE: Many substances have been shown to reduce brain damage in models of stroke, but mainly when given either before or shortly after the onset of ischemia. Delayed systemic administration of pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to attenuate the neuronal damage in the hippocampus in a model of global ischemia in rats. The present study examined the neuroprotective action of delayed systemic administration of PACAP38 in a model of transient focal ischemia produced by middle cerebral artery occlusion (MCAO) in rats. METHODS: We administered PACAP38 as an intravenous bolus (20 nmol/kg body wt) followed by an intravenous infusion for 48 hours using a micro-osmotic pump at a rate of 160 pmol/microL per hour, beginning 4, 8, or 12 hours after a 2-hour transient MCAO using a filament model. The size of the infarct was determined by examining 2-mm-thick brain sections stained with triphenyltetrazolium chloride, followed by image analysis. Control animals received intravenously 0.1% bovine serum albumin in 0.9% saline as a bolus and infusion at the same time intervals. RESULTS: The administration of PACAP38 beginning 4 hours after MCAO significantly reduced the infarct size by 50.88%. Treatment with PACAP38 starting 8 or 12 hours after the onset of ischemia did not result in a significant reduction of the infarct size, although infarct volumes tended to be smaller than in the control groups. CONCLUSIONS: Systemic administration of PACAP38 should be clinically useful for reducing brain damage resulting from stroke even when administration is delayed for several hours.

Animals↗
PubMed1998

Testis-specific prohormone convertase PC4 processes the precursor of pituitary adenylate cyclase-activating polypeptide (PACAP).

The physiological substrate for proprotein convertase (PC) 4, which is expressed only in the testis, has remained unknown. Pituitary adenylate cyclase activating polypeptide (PACAP), originally isolated from the hypothalamus, exists as two amidated forms with 38 (PACAP38) and 27 (PACAP27) residues. PACAP-like immunoreactivity (PACAP-li) is found not only in the brain, but also in the peripheral tissues, and is especially abundant in the testis. Immunohistochemistry of the rat testis demonstrated strong PACAP-li in spermatids in the cap and acrosome phases. The nearly simultaneous expression of PC4 transcripts and PACAP-li in spermatids during spermatogenesis led to the hypothesis that PACAP precursor is processed by PC4. To investigate this possibility, rat pituitary GH4C1 cells were stably transfected with human PACAP cDNA, and some of these cells were co-transfected with mouse PC4 cDNA. The acid extracts of the cells were fractionated by reversed-phase HPLC. Each fraction was examined for PACAP-li using three antisera which recognize PACAP precursor, PACAP38 and/or PACAP27. Negligible PACAP-li that eluted with synthetic PACAP38 or PACAP27 was detected from cells transfected with PACAP cDNA; however, PC4 co-transfected cells showed marked PACAP-li peaks with the retention times for both PACAP38 and PACAP27. Moreover, Western blot analysis revealed immunostained bands, corresponding to the Mr for PACAP38 and PACAP27, in the PC4 co-transfected cells. Bioactivity, as indicated by stimulation of cAMP production in pituitary cell cultures, was found only in the extracts of PC4 co-transfected cells. These results provide evidence that PACAP precursor in the testis is a substrate for PC4. The processing of PACAP precursor by PC4 at a critical time in spermatogenesis suggests an important regulatory role of PC4 and PACAP in the maturation of germ cells in the testis.

Animals↗
PubMed1997

Localization and gene expression of the receptor for pituitary adenylate cyclase-activating polypeptide in the rat brain.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a recently identified member of the secretin/vasoactive intestinal polypeptide (VIP) family. There are at least two types of receptor for PACAP: type I (PACAPR), which specifically binds PACAP; and type II (VIP/PACAPR), which binds both PACAP and VIP. The localization of PACAPR in the rat brain was determined by in situ hybridization and immunocytochemistry. We raised antisera against a synthetic peptide that corresponds to the carboxy-terminal cytoplasmic domain which is found in all subtypes of PACAPR in order to localize PACAPR-like immunoreactivity (PACAPR-LI) in the rat brain. In general, the distribution of PACAPR-LI correlated well with the distribution of PACAPR transcripts. Particularly strong PACAPR mRNA expression was detected in the olfactory bulb, hippocampus, cerebellum and hypothalamus and moderate labeling was detected in other scattered regions. At the cellular level, PACAPR-LI appeared to be concentrated predominantly in neuronal perikarya and dendrites. At the ultrastructural level, strong immunostaining for the PACAPR was found in plasma membranes, rough endoplasmic reticulum, cytoplasmic matrix, and at synapses. This study provides the basis for a better understanding of the functions of PACAP in the rat brain.

Animals↗
PubMed1994

Developmental changes of pituitary adenylate cyclase activating polypeptide (PACAP) and its receptor in the rat brain.

The developmental changes of PACAP and its receptor in the rat brain were investigated. The levels of PACAP and its receptor in the brain were determined by radioimmunoassay (RIA) and radioreceptor assay, respectively. The [125I]PACAP27 binding to the whole brain membrane preparations from embryonic day (E)18 rats was specific, rapid, and temperature dependent. Scatchard plot analysis revealed only a single class of receptor with Kd for PACAP27 = 1.015 +/- 0.049 nM, Kd for PACAP38 = 0.105 +/- 0.003 nM, and Bmax for both ligands = 8.64 +/- 1.29 pmol/mg protein. The Kd for PACAP38 was significantly lower than that for PACAP27. The binding site for PACAP was detected as early as E14. The Bmax for PACAP gradually increased throughout development to reach a plateau between 1 and 4 months old (MO). The content of PACAP38 in the whole brain was detected by RIA as early as E14. The concentration of PACAP38 in the whole brain, hippocampus, neocortex, and cerebellum gradually increased throughout the pre- and postnatal periods to reach a peak at 1 MO and then tended to decrease between 1 and 4 MO. On the other hand, PACAP38 concentration in the diencephalon rapidly increased between E18 and the birth (P0), and then increased more slowly throughout the postnatal period to reach a peak at 1 MO. In view of a neurotrophic activity of PACAP, these findings may support the notion that PACAP plays a regulatory role in neuronal growth and development.

Animals↗
PubMed1994

Cyclic lactam analogues of ovine pituitary adenylate cyclase activating polypeptide (PACAP): discovery of potent type II receptor antagonists.

Binding of [125I]PACAP-38 to rat liver membranes was investigated. It was rapid at 37 degrees C, reversible, and saturable, and it was time, concentration, and temperature dependent. Scatchard plots showed that [125I]PACAP-38 bound to single noninteracting site(s), and [125I]VIP bound to high- and low-affinity binding site(s). The order of potency of displacing [125I]PACAP-38 from rat liver membranes was: PACAP-38 > PACAP-27 > VIP (IC50 = 5, 180, and 350 nM, respectively). Surprisingly, the order of potency of displacing [125I]VIP was also the same (IC50 = 1, 8, and 52 nM, respectively). The order of potency of stimulating adenylate cyclase to release cyclic AMP was: PACAP-27 > VIP > PACAP-38 (EC50 = 0.06, 1, and 6 nM, respectively). Modification of PACAP-27 or PACAP-38 structures either through deletions, substitutions, or cyclization involving amino acid residues, Asp3, Asp8, Lys15, Lys20, or Lys21 indicated that the N-terminal region of the molecule is important for both binding and transduction. Of the various lactam analogues synthesized, cyclo[Asp3,Lys15]PACAP-38 and cyclo[Asp8,Lys15]PACAP-38 appear to be competitive receptor antagonists of the release of cAMP by PACAP-38. The results presented suggest that liver membranes possess distinct PACAP and VIP receptors, and that the PACAP receptor(s) is probably similar, but not identical, to type I receptor(s) characteristic of the brain.

Animals↗
PubMed1991

Neuropeptide regulation of interleukin-6 production from the pituitary: stimulation by pituitary adenylate cyclase activating polypeptide and calcitonin gene-related peptide.

Interleukin 6 (IL-6) production was shown to be stimulated by vasoactive intestinal peptide via cAMP dependent signal transduction pathway in the pituitary. We were interested in whether other hypothalamic neuropeptides, which activate adenylate cyclase in the pituitary, also stimulate pituitary IL-6 production. Whereas vasoactive intestinal peptide was effective in stimulating pituitary IL-6 production only at concentrations of 10(-6) M or higher, pituitary adenylate cyclase activating polypeptide with 38 residues (PACAP38) and calcitonin gene-related peptide (CGRP) at concentrations from 10(-10) to 10(-9) M significantly stimulated IL-6 production. Similar effective concentrations of each peptide were required for activating adenylate cyclase, as measured by extracellular cAMP accumulation. H89, a specific inhibitor of cAMP dependent protein kinase (protein kinase A), inhibited IL-6 production stimulated by PACAP38, CGRP, and (Bu)2cAMP. However, H89 failed to inhibit the IL-6 production stimulated by lipopolysaccharide, a ligand which enhanced IL-6 production in the absence of cAMP accumulation. Two other peptides which are known to activate pituitary adenylate cyclase, corticotropin-releasing factor and GRF failed to stimulate IL-6 production in pituitary cells. Using discontinuous Percoll gradients to fractionate the pituitary cells, the greatest PACAP38-stimulated IL-6 secretion was observed in the low density fraction 1 (F1). This fraction also contained the highest percentage of folliculo-stellate (FS) cells, one of the nonhormone secreting pituitary cells. However, the largest PACAP38-induced accumulation of cAMP was observed in F4. These results suggest that the production of IL-6 stimulated by PACAP and CGRP is mediated by the adenylate cyclase/protein kinase A signal transduction system. FS cells appear to be the most likely target cell type for PACAP-induced IL-6 production. However, IL-6 producing FS cells may not be an exclusive target for PACAP in the pituitary.

Animals↗
PubMed1985

Radioimmunoassay for 6-D-tryptophan analog of luteinizing hormone-releasing hormone: measurement of serum levels after administration of long-acting microcapsule formulations.

A sensitive and specific radioimmunoassay for [6-D-tryptophan]luteinizing hormone-releasing hormone [( D-Trp6]LH-RH) was developed and used for following the rate of liberation of [D-Trp6]LH-RH from a long-acting delivery system based on a microcapsule formulation. Rabbit antibodies were generated against [D-Trp6]LH-RH conjugated to bovine serum albumin with glutaraldehyde. Crossreactivity with LH-RH was less than 1%; there was no significant crossreactivity with other peptides. The minimal detectable dose of [D-Trp6]LH-RH was 2 pg per tube. Intra- and interassay coefficients of variation were 8% and 10%, respectively. The radioimmunoassay was suitable for direct determination of [D-Trp6]LH-RH in serum, permitting the study of blood levels of the analog after single injections into normal men and after once-a-month administration of microcapsules to rats. In men, 90 min after subcutaneous injection of 250 micrograms of the peptide, serum [D-Trp6]LH-RH rose to 6-12 ng/ml. Luteinizing hormone was increased 90 min and 24 hr after the administration of the analog. Several batches of microcapsules were tested in rats and the rate of release of [D-Trp6]LH-RH was followed. The improved batch of microcapsules of [D-Trp6]LH-RH increased serum concentrations of the analog for 30 days or longer after intramuscular injection. This was accompanied by suppression of testosterone levels for more than 30 days. This radioimmunoassay should be of value for monitoring [D-Trp6]LH-RH during long-term therapy.

Animals↗
PubMed1983

Radioimmunoassay of CRF-like material in rat plasma: validation of the method.

The availability of antibodies against the ovine corticotropin releasing factor (CRF), which cross-react with a CRF-like immunoreactivity (CRF-LI) in the rat, has enabled us to develop a radioimmunoassay (RIA) for rat CRF-LI in plasma and crude hypothalamic extracts. 125I-Tyr CRF 1-41 was used as the tracer, and synthetic ovine CRF as the reference hormone. The precision profile of the assay indicates a high degree of reproducibility except for the lower dose range. The minimum detectable dose was 20 pg/tube. This assay can detect differences in plasma CRF-LI levels after various manipulations that simultaneously alter the ACTH levels in plasma. A wide range of CRF concentrations has been found in plasma of normal rats. Caution should be exercised in the interpretation of the values obtained since an ovine RIA system was used.

Adrenocorticotropic Hormone↗