Biomedical subjects

L Szabo

Publications and source records attributed to L Szabo.

At least 37 records · Page 2Linked to original sources

PubMed1990

Characterization and cloning of a bovine insulin-like growth factor-binding protein.

The primary structure of the insulin-like growth factor-binding protein (IGFBP) produced by the bovine kidney cell line, MDBK, has been deduced from the cDNA clone. The MDBK binding protein precursor consists of a hydrophobic pre-peptide of at least 26 amino acids and a mature protein of 284 amino acids. The predicted protein sequence shares extensive sequence similarity with both the rat (82%) and human (89%) IGFBP-2s, so that the MDBK binding protein is clearly the bovine counterpart of IGFBP-2. The protein has limited similarity with classes 1 (31%) and 3 (31%) human IGFBPs, except that all 18 cysteine residues are conserved. Other features deduced from the bovine IGFBP-2 cDNA include: an abundance of leucine in the pre-peptide, an Arg-Gly-Asp sequence, absence of N-linked glycosylation sites, and an imperfect polyadenylation signal as well as an ATTTA motif in the 3' non-coding DNA. Western blotting indicated that this binding protein is widely distributed in bovine fluids as well as in media conditioned by bovine cell lines. Proteins immunologically related to bovine IGFBP-2 were detected not only in sheep, but also in chickens, indicating that this IGFBP is not exclusively mammalian.

Amino Acid Sequence↗

PubMed1989

A key functional role for the insulin-like growth factor 1 N-terminal pentapeptide.

In order to elucidate the role of the N-terminus of insulin-like growth factor 1 (IGF-1) with respect to its biological properties, we chemically synthesized analogues of IGF-1 truncated by one to five amino acid residues from the N-terminus. In a bioassay that measured the stimulation of protein synthesis in rat L6 myoblasts, the concentrations required to produce a half-maximal response were: IGF-1, 13 ng/ml; des-(1)-IGF-1, 10 ng/ml; des-(1-2)-IGF-1, 13 ng/ml; des-(1-3)-IGF-1, 1.5 ng/ml; des-(1-4)-IGF-1, 5.1 ng/ml; des-(1-5)-IGF-1, 1200 ng/ml. When tested for their abilities to compete with 125I-IGF-1 binding to L6 myoblasts at 3 degrees C, the concentrations required for 50% competition were: IGF-1, des-(1)-IGF-1 and des-(1-2)-IGF-1, 20 ng/ml; des-(1-3)-IGF-1, 14 ng/ml; des-(1-4)-IGF-1, 40 ng/ml; des-(1-5)-IGF-1, greater than 1000 ng/ml. Receptor-binding experiments at 25 degrees C, however, gave results suggesting that the myoblasts were secreting a binding protein selective for the three longest peptides. This interpretation was confirmed by binding studies with medium conditioned by the L6 myoblasts as well as binding protein purified from MDBK-cell-conditioned medium. In both cases IGF-1, des-(1)-IGF-1 and des-(1-2)-IGF-1 competed for tracer IGF-1 binding at least 60-fold better than did the three shorter peptides. The results obtained account for the increased potency of des-(1-3)-IGF-1 and des-(1-4)-IGF-1, since their activities are not attenuated by the binding protein, and the relatively lower potency of des-(1-4)-IGF-1 is a consequence of this peptide binding less well to the L6-myoblast receptor.

Animals↗

PubMed1989

Insulin-like growth factor (IGF)-binding proteins inhibit the biological activities of IGF-1 and IGF-2 but not des-(1-3)-IGF-1.

(1) Many cell types secrete insulin-like growth factor (IGF)-binding proteins that can be expected to sequester free IGF and modify the biological activities of the growth factors. (2) A binding protein purified from bovine kidney (MDBK) cells potently inhibited the ability of IGF-2 to stimulate DNA synthesis or protein accumulation as well as to reduce rates of protein breakdown in chick embryo fibroblasts. The binding protein did not influence the biological activities of des-(1-3)-IGF-1, while effects on IGF-1 were intermediate. Since the chick embryo fibroblasts contain only the type 1 IGF receptor, the MDBK-cell binding protein must have reduced the accessibility of IGF-2 and IGF-1 to that receptor. Binding to the type 2 receptor on L6 myoblasts was also inhibited. (3) Inhibiting effects on both protein breakdown responsiveness to IGF and IGF binding to cell receptors were also observed with human amniotic fluid binding protein, although here IGF-1 and IGF-2 were equipotent. These results contrast with stimulatory responses on different IGF-1 actions of the same binding protein reported previously [Elgin, Busby & Clemmons (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 3254-3258]. (4) The biological potencies of IGF-1, IGF-2 and des-(1-3)-IGF-1 correlate inversely with their binding to proteins released into the medium by cells, so that the enhanced potency of des-(1-3)-IGF-1 is a consequence of it not binding to purified binding proteins or those released by cultured cells.

Animals↗

PubMed1989

Alkylating prazosin analogue: irreversible label for alpha 1-adrenoceptors.

A series of prazosin analogues comprised of N-acyl derivatives of N'-(4-amino-6,7-dimethoxyquinazolin-2-yl)piperazine was prepared and the nature of their binding to alpha 1-adrenoceptors was investigated. Derivatives with alpha, beta-unsaturated acyclic acyls had some affinity but no irreversible action at the receptor. Other potent compounds, also without irreversible activity, contained cinnamoyl or (phenylamino)thiocarbonyl residues. High affinity and irreversible binding were obtained with a bicyclo[2.2.2]octa-2,5-dien-2-ylcarbonyl derivative. The conjugated double bond in this compound was in about the same position and distance from the pharmacophore as in some of the above compounds of high affinity but with no irreversible action. Two consecutive recognition steps were thought to be involved in irreversible blockade: reversible binding of the pharmacophore part of the molecule to the binding site of the receptor, followed by reaction of the chemoreactive part with an adjacent nucleophile of the receptor. The present results suggest that for the second step to occur efficiently, some affinity for the receptor must be present even in the chemoreactive part of the molecule; simple spanning of the binding and nucleophile sites of the receptor was insufficient.

Acylation↗

PubMed1989

Effects of insulin-like growth factors on protein metabolism: why are some molecular variants more potent?

The insulin-like growth factors (IGFs) produce a dual anabolic effect on protein metabolism in cultured cells via a stimulus of the synthetic pathway and an inhibition of the degradative pathway. Accordingly, they offer promise as agents that may retard the extensive and life-threatening negative nitrogen balance that accompanies human polytrauma. In this report we describe the discovery of a novel, more potent, form of IGF-1, des-(1-3)-IGF-1, and explain its increased action as resulting from higher concentrations of the free peptide produced because des-(1-3)-IGF-1 binds very poorly to IGF carrier proteins released from most cell types. The truncated growth factor retains a long biological half-life because it is attached to blood IGF-binding proteins. Further understanding of the biological significance of IGF, coupled with synthetic approaches directed at the production of mutant IGF-1 molecules, can be expected to yield significant advances in the treatment of polytrauma.

Animals↗

PubMed1989

(S)-emopamil, a novel calcium and serotonin antagonist for the treatment of cerebrovascular disorders. 2nd communication: brain penetration, cerebral vascular and metabolic effects.

The cerebral availability of the phenylalkylamine calcium antagonist (S)-emopamil ((2S)-2-isopropyl-5-(methylphenethylamino)-2-phenylvaleronitril e hydrochloride), was investigated in the anesthetized rat by computing the quotient of brain activity and integrated plasma activity 75 min after intraperitoneal injection of the 14C-labeled substance. The relative cerebral concentration defined in this way amounted to 2.05 for emopamil, 0.11 for verapamil and 0.03 ml/g for gallopamil, corresponding to a ratio of 70:4:1. The cerebral uptake of the same substances during a single capillary passage following intracarotid injection was determined by using tritiated water as an internal standard. Relative to the water the following brain uptake indices were obtained: (S)-emopamil 110.3, gallopamil 45.3 and verapamil 40.6%. According to these figures, emopamil is clearly superior to verapamil and gallopamil both with regard to cerebral availability and blood-brain barrier permeability. The effect of emopamil enantiomers on local cerebral blood flow was studied autoradiographically in the artificially ventilated rat anesthetized with nitrous oxide. The test substances were infused intravenously over 30 min, the determination of local cerebral blood flow being carried out 10 min after the end of the infusion. The numerical evaluation included 40 brain structures. In the investigated regions the infusion of 3 and 6 mg/kg (S)-emopamil led to an average blood flow increase of 24 and 52%, respectively. In the latter experimental group the values for the 22 cerebral structures showing a statistically significant effect were between 128 and 208% of control. In contrast, the application of 6 mg/kg (R)-emopamil did not lead to a significant change in blood flow in any of the areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

(S)-emopamil, a novel calcium and serotonin antagonist for the treatment of cerebrovascular disorders. 3rd communication: effect on postischemic cerebral blood flow and metabolism, and ischemic neuronal cell death.

The effect of (S)-emopamil ((2S)-2-isopropyl-5-(methylphenethylamino)-2-phenylvaleronitril e hydrochloride) treatment on postischemic cerebral blood flow and metabolism was investigated in nitrous oxide anesthetized, artificially ventilated rats. Forebrain ischemia was induced and maintained for 20 min by lowering arterial blood pressure to approximately 40 mmHg and clamping both carotid arteries. Local cerebral blood flow and glucose utilization were evaluated autoradiographically in 34 cerebral regions. In the cerebral blood flow studies intravenous infusion of 0.1 mg/(kg min) (S)-emopamil was begun 5 min after the end of ischemia. Local cerebral blood flow was determined 60 min later using [14C]iodoantipyrine. When the animals were treated with saline only, postischemic blood flow of 22 affected forebrain areas fell on average to 42 +/- 13% of nonischemic control. Treatment with (S)-emopamil increased perfusion of the same areas in a region-dependent fashion by an average of 54 +/- 19%, resulting in 63 +/- 17% of control values. The rise of blood flow in structures not directly affected by ischemia amounted to 52 +/- 27% (134 +/- 23% of control). In the studies on cerebral metabolism, the experimental animals received a total of 6 mg/kg (S)-emopamil by slow intravenous infusion before and during the ischemic episode. Determination of local cerebral glucose utilization was initiated after 50 min of postischemic recirculation using [14C]deoxyglucose. In the placebo-treated experimental group average glucose utilization of 14 forebrain areas was significantly lower (74 +/- 9% of control) than in the nonischemic control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Classification of the insulin-like growth factor binding proteins into three distinct categories according to their binding specificities.

Competitive binding experiments with insulin-like growth factor (IGF)-1, IGF-2 and des-(1-3)-IGF-1 have confirmed the interpretation based on limited amino-terminal sequence analysis that at least three types of IGF binding protein occur. In addition to the acid stable subunit of the large serum binding protein which exhibits des-(1-3)-IGF-1 binding only slightly less than IGF-1, the small IGF binding proteins can be separated into two classes based on differences in des-(1-3)-IGF-1 and IGF-2 binding potencies.

Animals↗

PubMed1988

The bovine insulin-like growth factor (IGF) binding protein purified from conditioned medium requires the N-terminal tripeptide in IGF-1 for binding.

The insulin-like growth factor binding protein (BP) secreted by bovine kidney (MDBK) cells has been purified by affinity chromatography on a rat IGF-2 Sepharose column. Purified BP migrated as a single band of Mr 40,000 upon SDS polyacrylamide gel electrophoresis. An N-terminal sequence of 53 residues was obtained which was very similar up to residue 21 to the corresponding rat BRL-3A BP sequence. In competitive binding experiments with bovine IGF-1 and IGF-2, and recombinant human IGF-1, BP had a similar affinity for these ligand when IGF-1 tracer was used, but a higher affinity for IGF-2 with IGF-2 as radioligand. The N-terminal destripeptide truncated form of bovine IGF-1, which has enhanced biological activity, was found to have a markedly reduced affinity for BP compared to intact IGF-1. The increased bioactivity of destripeptide IGF-1 can be explained by this reduced affinity for BP.

Animals↗

PubMed1988

A nationwide evaluation of multiple congenital abnormalities in Hungary.

A population-based study of 7,049 index patients with multiple congenital abnormalities (MCA) born in Hungary during 1973-1982 was organized by the Hungarian Center for Congenital Anomaly Control. All clinically recognized syndromes and associations which were submitted (2,049) were accepted without any further follow-up. New or supplementary information was requested in the case of unspecified MCA (320). A copy of detailed necropsy records was requested from pathologists in lethal cases (2,022). Following these steps, apparent but not true instances of MCA were excluded (399), and an attempt was made to assign as many of the remainder as possible in 17 well-delineated MCA entities (900). The living index patients with severe MCA were referred where possible to the regional centers for evaluation (864). One hundred and seventy entities were identified, and seven cases were excluded as not representing MCA. In the so-called 3,393 unidentified cases for which no diagnosis was possible, the component abnormalities were tabulated according to their number. The final count was 6,643 cases with MCA, which is equivalent to a birth prevalence of 4.0 per 1,000 total births, and to 10% of recorded cases with congenital anomalies. As a result of this program the proportion of recognized syndromes and associations among children with MCA increased from 29% to 47%. The accuracy of diagnoses has improved, e.g., the occurrence of unspecified cases decreased from 4.5% to 2%. As a result of this study, the number of chromosomal (1,700), Mendelian (557), and teratogenic (104) syndromes and associations (758) was considerably greater than the initial notifications indicated.

Abnormalities, Drug-Induced↗

PubMed1988

2-Hydroxypropyldigitonin: synthesis and properties of preparations differing in degree of substitution.

Reaction of propylene oxide with digitonin in strong aqueous alkali yielded water soluble, nontoxic solubilizers of drugs and hormones, the molecular composition of which could be fully deduced from plasma desorption mass spectrometry data. Preparations with average degrees of substitution ranging from 0.7 to 4.5 were investigated, and all the distributions of degrees of substitution observed were relatively narrow and symmetrical; thus, the reactivity of primary and secondary hydroxyls of saponin and of its conversion products had to be quite similar. The effects of the average degree of substitution of 2-hydroxypropyldigitonins on the formation of micelles and on the solubilization of four drugs into aqueous solutions were found to be minor. On the other hand, the ability to hemolyze erythrocytes decreased sharply with an increasing average degree of substitution.

Animals↗

PubMed1988

Possible involvement of queuine in oxidative metabolism.

The possibility that the base, queuine, or the queuine family of tRNAs may play a role in oxidative metabolism has been investigated. (i) The enzymatic insertion of queuine into tRNA requires oxygen. This is true for both the mammalian and bacterial enzyme. (ii) (q-) LM cells (murine fibroblast line) grown in culture had 53% less of the manganese-containing superoxide dismutase than (q+) cells. (iii) There was less thiobarbituric-acid-reactive material in queuine-deficient mouse liver and kidney than in (q+) liver and kidney.

Aerobiosis↗

PubMed1987

Reaction of cyclodextrins with propylene oxide or with glycidol: analysis of product distribution.

Reaction of cyclomalto-hexaose, -heptaose, or -octaose with propylene oxide in strong aqueous alkali gave products in which distribution of the degrees of substitution was relatively narrow and nearly symmetrical, and increased with the average degree of substitution. When an equimolar mixture of cyclomalto-hexaose, heptaose, or -octaose was used, the average degrees of substitution of all three carbohydrates were close to each other. These findings indicate that the reactivities of the hydroxyl groups of cyclomalto-hexaose, -heptaose, or -octaose, and of all their (2-hydroxypropyl) ethers formed in the reactions, are quite similar. Reaction of cyclomaltoheptaose with glycidol also yielded a product having a narrow distribution of degree of substitution, but which was slightly skewed towards the higher degrees. Thus, as it proceeds, this etherification leads to products having higher reactivity towards the epoxide.

Cyclodextrins↗

PubMed1987

Induction by lipopolysaccharide of intracellular and extracellular interleukin 1 production: analysis with synthetic models.

An attempt was made to identify the molecular structures that are present in bacterial LPS and induce the production of intracellular and extracellular pools of IL 1 by peritoneal macrophages of the mouse and by human monocytes. Activities of glycolipids and carbohydrates prepared by synthesis, and structurally related to the hydrophobic (Lipid A) and to the polysaccharide (PS) regions of LPS were compared with those induced by Bordetella pertussis endotoxin and by fragments derived therefrom. Both isolated regions of this LPS (PS and Lipid A) were able to induce IL 1 synthesis by monocytes and macrophages. Among the synthetic glycolipids employed, propyl-2-deoxy-2-[(3R)-3-hydroxytetrade-canamido]-4-O-pho sph ono-6-O-tetradecanoyl-beta-D-glucopyranoside (glycolipid M9) induced IL 1 secretion more efficiently than Lipid A and LPS, whereas the amounts of intracellular IL 1 produced upon induction by these three substances were comparable. Macrophages from C3H/HeJ mice were unresponsive to Lipid A and to glycolipid M9, but produced IL 1 when incubated with PS or with a hydrophilic fragment isolated after methanolysis of the endotoxin. However, all synthetic derivatives of 3-deoxy-D-manno-2-octulosonic acid (KDO) used in this study failed to induce IL 1 production by both mouse macrophages and human monocytes. The implications of these findings for a more precise comprehension of the molecular mechanism of LPS-induced activation of macrophages, and the relations between the molecular structures required for the induction of IL 1 production vs cytostatic activity in macrophages, are discussed.

Animals↗

PubMed1987

Berbanes: a new class of selective alpha 2-adrenoceptor antagonists.

The alpha-adrenoceptor blocking properties of some berbanes have been studied and compared with those of idazoxan, yohimbine, phentolamine, and prazosin. Their effects on presynaptic alpha 2-adrenoceptors were studied on chemical neurotransmission of isolated rat vas deferens and longitudinal muscle strip of guinea pig ileum; xylazine or norepinephrine was employed as agonist. The alpha 1-adrenoceptor blocking activities of the berbanes were tested on isolated rat vas deferens and rabbit pulmonary artery by using phenylephrine or norepinephrine as agonist. The antagonistic activity of the berbanes and the reference compounds on alpha 2- and alpha 1-adrenoceptors was characterized by the apparent pA2 values. Of the compounds studied, [8aS*-(8a alpha,12a alpha,13a alpha)]-11 alpha-hydroxy-5,6,8a,9,10,11,12a,13,13,a-decahydro-8H-benzo[g]-1,3 -benzodioxolo[5,6-a]quinoli zine, 6d, proved to be the most selective antagonist at the presynaptic alpha 2-adrenoceptors (alpha 1:alpha 2 ratio = 1659). Since blockade of alpha 2-adrenoceptors located on noradrenergic axon terminals leads to an increase of norepinephrine release, this compound could have potential as an antidepressant agent.

Adrenergic alpha-Antagonists↗

PubMed1986

Regional metabolism of experimental brain tumors.

Experimental brain tumors were produced in rats by stereotactical implantation of various neoplastic cell lines (RG 2, RG1 2.2, G 13/11, F 98, RN 6, B 104, and E 367). Using autoradiographic, bioluminescence, and fluoroscopic methods, the following regional hemodynamic and metabolic parameters were measured on intact brain sections: blood flow, glucose utilization, pH, and the tissue content of ATP, glucose, and lactate. Tumors exhibited a considerable diversity of regional blood flow and metabolic activity which did not correlate with the implanted cell line, location, or growth pattern. In solid regions of tumors the most consistent finding was a higher glucose utilization rate, a higher lactate, and a higher pH than in the surrounding brain tissue. Tumor ATP was slightly higher and glucose slightly lower than in the brain. In large spherical tumors a declining gradient of blood flow, glucose, and ATP from the periphery to the central parts was frequently observed, the decline being more pronounced for glucose than for ATP. In regions with high ATP tissue pH was usually higher than in the brain, but it decreased in areas in which ATP was depleted. The results obtained indicate that tumors are able to control tissue pH despite increased glycolysis and lactate production, as long as the energy state is not impaired. The mechanisms of pH regulation, therefore, have to be considered for establishing therapeutic procedures which intend to lower tumor pH for induction of tissue necrosis.

Adenosine Triphosphate↗

PubMed1986

Analysis of the lipopolysaccharide-induced cytostatic activity of macrophages, by the use of synthetic models.

Informations on the structural features implicated in the macrophage-dependent cytostatic activity of "lipid A" preparations were obtained by the use of 15 synthetic glycolipids. Four structural requirements were identified: the presence of a reducing glucosamine unit; the presence of a free hydroxyl group on amide-linked 3-hydroxytetradecanoic acids, and the absence of free hydroxyl groups at positions 3 and 6 of the glucosamine. The monosaccharide resembling the reducing unit of the "lipid A backbone," which fulfills these criteria, had the highest cytostatic activity, whereas the compound possessing the substitution pattern of the nonreducing moiety was inactive.

Animals↗

PubMed1985

[Chylaskos in lymphangioleiomyomatosis. Peritoneo-venous drainage with Denver shunt].

Chylous ascites, due to a lymphangiomyomatosis and resistant to conservative therapy, occurred in a 30 year-old female. A distinct subjective and clinical improvement could be attained with the aid of a peritoneo-venous anastomosis employing a Denver-Shunt. With the preconditions that the implantation is correct and that it is reliably managed, we regard the Denver-Shunt system as a recommendable approach to the treatment of chylous ascites not controllable by conservative measures.

Adult↗