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T Bartfai

Publications and source records attributed to T Bartfai.

At least 163 records · Page 9Linked to original sources
PubMed1991

Protective immunogenicity of synthetic peptides selected from the amino acid sequence of Bordetella pertussis toxin subunit S1.

Five synthetic peptides identified as antigenic sites on the S1 subunit of pertussis toxin (PT) were coupled to the diphtheria toxin cross-reactive mutant protein CRM 197 or BSA. All peptide conjugates were immunogenic in animals. Two peptide-CRM-conjugates, corresponding to amino acids 1-17 and 169-186, induced especially high antibody titers against native PT in mice (Balb/c, C57/Black and outbred NMRI) as measured by ELISA. Upon in vivo PT challenge (0.5 microgram toxin) of the NMRI mice both the CRM and BSA conjugates of these two peptides fully protected the mice from PT induced leucocytosis. Some of the protected mice receiving peptide 1-17 conjugate had very low antibody titers against PT but high titers against the peptide as measured by ELISA, showing that PT-ELISA does not always reflect in vivo protection. A booster response against PT was noted upon challenge with PT in mice receiving peptide 1-17 or peptide 169-186 conjugate. Antibodies against peptide 170-186 could not be evaluated by ELISA since conjugates of this peptide (like PT itself) bind to immunoglobulins. They may also caused clustering of CHO cells. Rabbit antiserum to the peptide 1-17-CRM conjugate was highly efficient in inhibiting the ADP-ribosylating activity of PT with bovine transducin as substrate whereas the rabbit antiserum raised against the peptide 169-186-CRM conjugate neutralized the clustering effect of PT on CHO cells. Thus there is no concise correlation between the in vivo protection against PT challenge and the in vitro methods used for measuring antibody levels against PT (neutralization of the enzyme activity, the CHO cell clustering activity and titers in PT-ELISA). The CRM-conjugates of these two peptides constitute the first synthetic pertussis vaccine candidate with the ability to provide a chemically well defined, safe and efficient pertussis vaccine.

Amino Acid Sequence↗
PubMed1990

The N-terminal 1-16, but not C-terminal 17-29, galanin fragment affects the flexor reflex in rats.

The biological activity of two galanin (GAL) fragments, GAL-(1-16) and GAL-(17-29), was tested in vivo by using a spinal nociceptive flexor reflex model in the rat. Intrathecal (i.t.) GAL-(1-16) had a similar biphasic effect on the flexor reflex, with facilitation at lower doses and facilitation followed by depression at higher doses, as the full length peptide GAL-(1-29). GAL-(1-16) also effectively depressed the facilitation of the flexor reflex caused by i.t. substance P (SP) or C-fiber conditioning stimulation (CS) and potentiated the depressive effect of i.t. morphine on the reflex, both actions that have been reported earlier with GAL-(1-29). In contrast, i.t. GAL-(17-29), even at high doses, did not induce changes in the amplitude of the flexor reflex, nor did it interact with the effects of i.t. SP, morphine or C-fiber CS. It is concluded that the N-terminal portion of GAL-(1-29) is critical for the biological activity of the intact peptide in the dorsal horn of the rat spinal cord. The similarity between the effects of GAL-(1-16) and GAL-(1-29) indicates that they probably act on the same GAL receptor.

Animals↗
PubMed1990

Substance P and neurokinin A, two coexisting tachykinins stimulating the release of [3H]5-HT from rat cerebral cortical slices.

Substance P (SP) and neurokinin A (NKA), two coexisting neuropeptides of the tachykinin family, stimulated the basal (5 mM K+) and evoked (40 mM K+) release of [3H]5-HT (5-hydroxytryptamine) from tissue slices of the rat cerebral cortex. Spantide ([DArg1,-DTrp7,9,Leu11]SP; 10(-5) M) inhibited the effects of SP but potentiated the effects of NKA. The effects of SP and NKA appear to be exerted at distinct receptors but involve a common post-receptor mechanism as no full additivity of the SP- and NKA-mediated stimulation of [3H]5-HT could be observed. The effects of the 3 tachykinins, SP, NKA and NKB, are compared with respect to stimulation of the release of [3H]5-HT.

Animals↗
PubMed1990

Protective immunogenicity of two synthetic peptides selected from the amino acid sequence of Bordetella pertussis toxin subunit S1.

Two peptides, corresponding to amino acids 1-17 and 169-186 of the amino acid sequence of pertussis toxin (PT) subunit S1, were synthesized and coupled to the diphtheria toxin cross-reactive mutant protein CRM 197 and evaluated for immunogenicity and protective capacity against PT challenge in vivo. The peptide-CRM conjugates induced high antibody titers against native toxin in mice (BALB/c, C57/Black, and outbred NMRI) as measured by ELISA. Upon PT challenge (0.5 microgram of toxin) of the NMRI mice, the CRM conjugates of peptides 1-17 and 169-186 fully protected the mice from PT-induced leukocytosis. Immunization with the corresponding bovine serum albumin conjugates of these two peptides also fully protected mice. Rabbit antiserum to the peptide 1-17-CRM conjugate was highly efficient in inhibiting the ADP-ribosylating activity of PT but did not neutralize the clustering effect of PT on Chinese hamster ovary cells. In contrast, the rabbit antiserum raised against the peptide 169-186-CRM conjugate neutralized the clustering effect of PT on Chinese hamster ovary cells but did not inhibit the enzymatic activity of PT. Peptide 169-186-CRM conjugates mimic the immunoglobulin binding properties of PT and also cause clustering of Chinese hamster ovary cells. The CRM conjugates of these two peptides constitute a synthetic pertussis vaccine candidate with the ability to provide a chemically well-defined, safe, and efficient pertussis vaccine.

Amino Acid Sequence↗
PubMed1990

Atropine treatment induced cholinergic supersensitivity at receptor and second messenger levels in the rat salivary gland.

Physiological, biochemical and morphological correlates of chronic treatment of rats with the classical muscarinic antagonist atropine for 14 days (20 mg kg-1 day-1 s.c.) were studied in submandibular salivary glands. The amount of saliva collected from submandibular glands following a single injection of isoproterenol (30 mg kg-1 i.p.) was significantly larger and had higher protein concentration in rats treated with atropine than in saline-treated animals. In the glands of atropine-treated rats a conspicuous increase in the amount of rough endoplasmic reticulum (RER) along with a decrease in the mucous volume was observed in the acinus when examined by light microscopy. Several biochemical changes were observed in an enriched plasma membrane fraction from the submandibular gland of the atropine-treated rats: (1) an increase in the number of muscarinic antagonist binding sites (31 + 3.4%), (2) a decrease in the specific activity of basal adenylate cyclase, (3) a significantly lower Vmax of the adenylate cyclase in the presence of GTP (10 microM) and varying concentrations of Mg2+ (0-22.5 mM) with no apparent change in affinity of the enzyme for Mg2+ but (4) higher magnitude of stimulation in the presence of GTP (100 microM), vasoactive intestinal polypeptide (5 microM), isoproterenol (100 microM), NaF (10 microM) and forskolin (10 microM). There was however no change in the density of beta-adrenergic receptors upon atropine treatment. In tissue slices from the submandibular glands of atropine-treated rats we found lower basal cAMP levels (decrease 29 +/- 6.9%) and no significant change in the phosphatidylinositol breakdown stimulated by carbachol (10(-6) to 10(-4) M). It appears that chronic blockade of an inhibitory muscarinic input to the adenylate cyclase system is compensated by lowered adenylate cyclase activity. Phosphoinositide metabolism is not subject to the same adaptation, suggesting that cAMP may be the pivotal second messenger in the supersensitive salivary response.

Adenylyl Cyclases↗
PubMed1990

Muscarinic antagonist binding to intact rat thymocytes.

The presence and properties of muscarinic receptors on intact rat thymocytes have been studied by the use of the muscarinic antagonists [3H]-3-quinuclidinyl benzilate (3H-QNB), [3H]-4-N-methylpiperidinyl benzilate ([3H]-NMBP) and [3H]-N-methylscopolamine (3H-NMS). The course of binding of 3H-QNB reveals a maximum at 5 min, and shows a subsequent decrease of bound radioactivity, suggesting internalization of the receptor 3H-3-QNB complex. This phenomenon has also been studied by the use of another muscarinic antagonist, 3H-NMPB, which has a faster on and off rate than 3H-QNB, and which may be rapidly displaced by an excess of unlabeled muscarinic antagonist, atropine. Bound 3H-NMPB is highly susceptible to atropine displacement only within the first two minutes of incubation with thymocytes at 37 degrees C. The kinetics of binding of the less lipophilic muscarinic antagonist 3H-NMS to thymocytes, show no maximum as a function of incubation time and 3H-NMS is susceptible to displacement by atropine up to 30 min incubation time with the thymocytes. These data suggest that binding of lipophilic benzilate type antagonists (3H-QNB and 3H-NMPB) may be followed by internalization and/or isomerization of the receptor-benzilate antagnist complex while the 3H-NMS-receptor complex is not subject to these processes.

Animals↗
PubMed1990

Activity of centrally administered galanin fragments on stimulation of feeding behavior and on galanin receptor binding in the rat hypothalamus.

Synthetic fragments of galanin 1-29 were administered intraventricularly or into the paraventricular nucleus of the hypothalamus for analysis of the critical amino acid sequence necessary to stimulate feeding behavior in rats. Galanin 1-29 and galanin fragment 1-16 significantly increased feeding at doses of 6 nmol microinjected into the lateral ventricles and 1 nmol microinjected into the hypothalamus. There was no significant effect of D-TRP2 galanin 1-16 microinjected into the hypothalamus, and no significant effect of galanin fragments 1-9, 10-20, 12-29, 17-29, or 21-29 microinjected intraventricularly, on food consumption. Synthetic fragments of galanin 1-29 were assayed for displacement of 125I-galanin 1-29 binding to rat hypothalamic membranes. The efficacies of the galanin fragments in the feeding paradigm were consistent with the relative affinities of these fragments for the hypothalamic galanin receptor in equilibrium binding experiments. The first 16 N-terminal amino acids appear to contain galanin agonist activity on increasing food consumption and to bind to the galanin receptor in the rat hypothalamus.

Animals↗
PubMed1989

Galanin receptor and its ligands in the rat hippocampus.

Receptors for the 29-amino-acid peptide, galanin, in membranes from the rat ventral hippocampus were examined using chloramine-T-iodinated porcine galanin as ligand. The equilibrium binding of 125I-galanin showed the presence of a high-affinity binding site (Kd = 1.91 +/- 0.40 nM). The concentration of the high-affinity-binding sites was 107 +/- 15 fmol/mg membrane protein. The on rate constant was estimated to be 2.6 +/- 0.1 M-1 min-1 at 37 degrees C. The affinity of rat galanin (differing in three amino acid residues from the porcine protein) was equal to that of porcine galanin. The 125I--galanin-binding site is a trypsin-sensitive membrane protein, which is heat-denaturated at 60 degrees C within 5 min. The effect of GTP and its analogs and of pertussis-toxin-catalyzed ADP-ribosylation on the binding of 125I-galanin suggest that the galanin receptor is coupled to an inhibitory G protein (Gi protein). 127I-galanin was shown to be a ligand with affinity equal to that of galanin in displacing 125I-galanin. The 125I-galanin-binding site in the ventral hippocampus recognizes as a ligand the tryptic fragments 1-20 and 21-29 of rat galanin and the synthetic fragments 12-29, 18-29 and 21-29 of porcine galanin. None of these afforded full inhibition of the binding of fragment 1-29 of 125I-galanin at a concentration of 1 microM.

Animals↗
PubMed1989

Interleukin-1 in adrenal chromaffin cells.

Interleukin-1, first identified as a macrophage factor of importance in infections and inflammation, is a protein with properties of an endogenous pyrogene and lymphocyte activating factor. Occurrence of interleukin-1-like immunoreactivity was demonstrated in the noradrenergic chromaffin cells of the rat and mouse adrenal gland by means of two antisera raised against synthetic peptides corresponding to the amino acid sequences 169-194 and 201-215 of the murine interleukin-1 precursor protein. These antisera also inhibited stimulation of interleukin-2 receptor expression by purified human interleukin-1. Reserpine, which is known to deplete catecholamines, also caused release of the interleukin-1-like immunoreactive material. The interleukin-1 content of the rat adrenal medulla was estimated by radioimmunoassay, and if released the adrenal interleukin-1 pool may result in plasma interleukin-1 levels of about 10(-12). The interleukin-1-immunoreactive material obtained from the rat adrenal gland was characterized as a trypsin-sensitive protein with a molecular weight in the range of 13,000-19,000. This protein fraction stimulated interleukin-2 receptor expression on human T-cells as earlier shown for interleukin-1.

Adrenal Medulla↗
PubMed1989

N-terminal galanin-(1-16) fragment is an agonist at the hippocampal galanin receptor.

The galanin N-terminal fragment [galanin-(1-16)] has been prepared by solid-phase synthesis and by enzymic cleavage of galanin by endoproteinase Asp-N. This peptide fragment displaced 125I-labeled galanin in receptor autoradiography experiments on rat forebrain and spinal cord and in equilibrium binding experiments from high-affinity binding sites in the ventral hippocampus with an IC50 of approximately 3 nM. In tissue slices of the same brain area, galanin-(1-16), similarly to galanin, inhibited the muscarinic agonist-stimulated breakdown of inositol phospholipids. Upon intracerebroventricular administration, galanin-(1-16) (10 micrograms/15 microliters) also inhibited the scopolamine (0.3 mg/kg, s.c.)-evoked release of acetylcholine, as studied in vivo by microdialysis. Substitution of [L-Trp2] for [D-Trp2] resulted in a 500-fold loss in affinity as compared with galanin-(1-16). It is concluded that, in the ventral hippocampus, the N-terminal galanin fragment [galanin-(1-16)] is recognized by the galanin receptors controlling acetylcholine release and muscarinic agonist-stimulated inositol phospholipid breakdown as a high-affinity agonist and that amino acid residue [Trp2] plays an important role in the receptor-ligand interactions.

Animals↗
PubMed1989

Differential release of coexisting neurotransmitters: frequency dependence of the efflux of substance P, thyrotropin releasing hormone and [3H]serotonin from tissue slices of rat ventral spinal cord.

In few systems has the release of coexisting classical and peptide neurotransmitters been studied. Here the release of substance P-like immunoreactivity (SP-LI), thyrotropin releasing hormone-like immunoreactivity (TRH-LI) and [3H]serotonin ([3H]5-HT) from tissue slices of rat ventral spinal cord was investigated in a superfusion system. The slices were stimulated electrically with field stimulation (900 pulses, 2 ms duration, 36 V) at frequencies between 0.25 Hz and 40 Hz. The evoked fractional release of SP-LI increased significantly from 0.46 to 1.24% of the total tissue store when the frequency of stimulation was changed from 3 to 10 Hz, while the evoked fractional release of TRH-LI increased significantly from 0.28 to 0.71% of the total tissue store with increasing frequency of stimulation between 0.5 and 3 Hz. The evoked fractional release of [3H]5-HT did not show any significant change when the frequency of stimulation was changed in the frequency range of 0.25-40 Hz but remained between 5.6 and 7.2% of the total tissue store. It appears that at frequencies lower than 0.5-1 Hz these 5-HT/SP/TRH neurons may function predominantly as serotonergic neurons. At 3 Hz stimulation with 900 pulses the extracellular Ca2+ concentration required for half-maximal release of [3H]5-HT was 1.2 mmol l-1, while for half-maximal release of SP-LI significantly higher concentrations of Ca2+ (4.2 mmol l-1) would be required.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Synthesis, cloning and expression in Escherichia coli of artificial genes coding for biologically active elongated precursors of the vasoactive intestinal polypeptide.

Synthetic genes coding for elongated precursors of the vasoactive intestinal polypeptide (VIP) were synthesized and cloned in a highly efficient Escherichia coli expression vector. The synthetic genes code for VIP with its methionine (at position 17) replaced by leucine and elongated at the C-terminus by Gly (vasoactive intestinal polypeptide-Gly, i.e. VIPa) or by Gly-Lys-Arg (vasoactive intestinal polypeptide-Gly-Lys-Arg, i.e. VIPb). The synthetic genes fused to the N-terminal part of the E. coli beta-galactosidase gene were expressed to yield high amounts of fusion proteins reaching upon induction at least 60% of the total cellular protein. The fusion proteins of 314 and 316 amino acids carrying in their C-terminal portion either the 29 or 31 amino acids long VIP precursor polypeptide were shown to be immunoreactive with VIP antisera and were further purified and cleaved by CNBr. The resulting purified peptide precursors (VIPa and VIPb) were recognized by VIP receptors in rat liver plasma membranes and by antibodies to porcine VIP in a radioimmunoassay. Both precursors activated adenylate cyclase in rat liver membranes and stimulated pancreatic secretion in the cat. The affinity and potency of the cloned precursors is close to that of VIP purified from porcine intestine, suggesting that the elongated VIP precursors may act even without being converted into the C-terminal amide form of the peptide. The elongated VIP precursors expressed in E. coli may provide a cheap, large-scale source of experimental material for studies on VIP actions.

Amino Acid Sequence↗
PubMed1988

Long-term atropine treatment lowers the efficacy of carbachol to stimulate phosphatidylinositol breakdown in the cerebral cortex and hippocampus of rats.

The effect of long-term treatment with atropine, a muscarinic antagonist, known to cause up-regulation of receptor numbers, was examined on the muscarinic-receptor-mediated stimulation of phosphoinositide breakdown in the rat cerebral cortex and hippocampus. Although the numbers of both M1 muscarinic receptors, as measured by [3H]pirenzepine binding, and M1 and M2 receptors increased in both brain regions, the maximal breakdown of myo-[3H]inositol-labelled phosphoinositides was unaltered in the presence of carbachol at a saturating concentration (10(-2) M). In fact the efficacy of carbachol was decreased in slices from atropine-treated cerebral cortex [EC50 (concentration producing half-maximal effect) = 93 microM] as compared with the saline-treated control (EC50 = 23 microM)(P less than 0.005). Similarly the EC50 value (23 microM) in hippocampal slices from saline-treated rats increased in atropine-treated rats to 126 microM (P less than 0.005). This lowered efficacy of muscarinic stimulation could not be explained in terms of residual atropine in the tissue from treated rats. The noradrenaline- or serotonin (5-hydroxytryptamine)-stimulated breakdown or the K+ potentiation of the muscarinic-receptor-stimulated breakdown of [3H]phosphoinositides was not affected by the atropine treatment. Chromatography of the released [3H]inositol phosphates shows that atropine treatment did not cause any qualitative change in the pattern of [3H]inositol phosphates released by carbachol stimulation.

Animals↗