Production and characterization of monoclonal antibodies to N7-phenylguanine

N7-Phenylguanine, a base adduct possibly formed after arylation of DNA by benzene oxide, the first reaction metabolite during benzene metabolism, was synthesized in our laboratory and used as reference for the production and characterization of monoclonal antibodies. 2-Hydroxymethyl-7-phenylhypoxanthine, a molecule structurally similar to N7-phenylguanine, was coupled by a linker molecule to different carrier proteins. The resulting conjugate was used to immunize BALB/c mice, the spleen cells of which were fused with mouse P3X63-Ag8.653 myeloma cells to obtain monoclonal antibodies. Several hybridoma lines were cultivated in defined media and characterized as to sensitivity and specificity by an enzyme-linked immunosorbent assay (ELISA). Competitive ELISA demonstrated that all antibodies showed a very high affinity for N7-phenylguanine but had a lower affinity towards various other samples including N7-chlorophenylguanines and C8-, N2-and O6-phenylguanine. As little as about 20 pg N7-phenylguanine could be detected with one of the most sensitive antibodies, CE6/G11, with a colorimetric end point while the detection limit could be lowered to about 10 pg N7-phenylguanine when a fluorescent end point was used. The detection limit of other methods used to determine N7-phenylguanine so far is 10 ng for gas-chromatography/mass-spectrometry and 1 ng for high-pressure liquid chromatography. Thus the use of specific monoclonal antibodies seems to be the most sensitive method for the detection of N7-phenylguanine.

Usefulness of metoprolol for unexplained syncope and positive response to tilt testing in young persons

The efficacy of intravenous metoprolol in preventing symptoms during a repeat tilt test was compared with the outcome of chronic oral treatment in 21 patients (14 female, 7 male), age 8 to 20 years (mean 13 +/- 3) with unexplained syncope (> or = 1 episode) and a positive response to tilt testing. A positive response was defined as the development of either syncope or presyncope. During the initial tilt test, a positive response occurred during baseline (14 patients) or isoproterenol (0.03 to 0.1 microgram/kg/min) infusion (7 patients) with a cardioinhibitory (1 patient), vasodepressor (5 patients) or mixed (15 patients) pattern. Metoprolol (0.1 to 0.2 mg/kg) was administered intravenously. During the repeat tilt test, response was negative in 18 patients, including 11 of 14 patients with a positive response in the baseline and 7 of 7 patients with a positive response during isoproterenol infusion. Metoprolol (0.8 to 2.8 mg/kg/day) was administered orally to 15 patients for an average of 10 months. Symptoms were absent (7 patients) or improved (2 patients); metoprolol was discontinued because of adverse effects (3 patients) or recurrence of symptoms (3 patients). In 7 of 12 patients with a negative response and 2 of 3 patients with a positive response after intravenous metoprolol, oral administration of metoprolol prevented or improved symptoms without adverse effects. Many young patients (60%) with recurrent syncope obtained symptomatic improvement from chronic oral metoprolol treatment without adverse effects; repeat tilt testing after intravenous metoprolol did not appear to offer any additional information than would have been obtained from a trial of chronic oral treatment.

Synthetic immunogens. The effect of the conformational space on biological and immunological responses to dimeric hormone constructs

Chimeras of the double chain bis-cystinyl hinge fragment 225-232/225'-232' of the human IgG1 and of peptides related to human little-gastrin were synthesized, whereby the fully bioactive gastrin sequences 2-17 and 5-17 were amide-bond-linked N- and N- or C-terminally, respectively, to the hinge peptide. All the dimeric constructs proved to be efficient immunogens; however, both the configuration of the constructs and the length of the haptenic gastrin molecule were found to drastically affect the specificity of the antibody response and, thus, the type of dominant immune epitope expressed. The different degree of accessibility of the gastrin chains in the dimers is similarly reflected by their binding affinities to gastrin receptors and their bioactivities in vivo. Molecular dynamics simulations of the chimeric compounds clearly revealed that the conformational space of the gastrin peptide chains 2-17 and 5-17 is strongly restricted upon linkage to the hinge peptide. Only in the gastrin-(2-17) construct does sufficient free conformational space seem to be retained, at least for one of the two gastrin chains, in order to allow folding into the bioactive structure. This also agrees with the observation that the dimeric gastrin-(2-17) behaves like a gastrin monomer in terms of receptor binding affinity and biopotency in vivo; but it could additionally explain why an antibody response of gastrin receptor-like specificity could only be induced with this construct. The experimental data may therefore suggest a high degree of parallelism between the mechanism of recognition of the gastrin peptides in the dimeric constructs as hormonal ligands by the gastrin receptors and as haptens by the immune competent cells.

Beta VI turns in peptides and proteins: a model peptide mimicry

To investigate the role of proline in defining beta turn conformations within cyclic hexa- and pentapeptides we synthesized and determined the conformations of a series of L- and D-proline-containing peptides by means of 2D NMR spectroscopy and restrained molecular dynamics simulations. Due to cis/trans isomerism the L-proline peptides adopt at least two different conformations that are analyzed and compared to the structures of the corresponding D-proline peptides. The cis conformations of the compounds cyclo(-Pro-Ala-Ala-Pro-Ala-Ala), cyclo(-Arg-Gly-Asp-Phe-Pro-Gly-), cyclo(-Arg-Gly-Asp-Phe-Pro-Ala-), cyclo (-Pro-Ala-Ala-Ala-Ala-), and cyclo(-Pro-Ala-Pro-Ala-Ala-) form uncommon beta VI turns that mimic the turn geometries found in crystallographically refined protein structures at such a detailed level that even preferred side chain orientations are reproduced. The ratios of the cis/trans isomers are analyzed in terms of the steric demand of the proline-following residue. The conformational details derived from this study illustrate the importance of the examination of small model compounds derived from protein loop regions, especially if bioactive recognition sequences, such as RGD (Arg-Gly-Asp), are incorporated.

[Test battery for objective assessment and differential diagnosis in the early stage of suspected development of presenile dementia of the Alzheimer type]

The clinical diagnosis of organic brain syndromes (especially of primary degenerative dementia) in their early stages is uncertain or only tentative. We used a set of relatively simple tests to support the hypothesis that the disturbance of several operational brain functions precedes memory decline in primary degenerative dementia. Twenty-one patients with early stage, presenile onset of DAT, 14 patients with cardiovascular disease (CVD) and a questionable dementia, an age-matched control group (EC, n = 15), and a younger control group (YC, n = 16) were examined in the following tests: labyrinth learning test, tactile and visual pattern recognition, different reaction time tasks, eye-tracking, finger-tapping, alpha-EEG-blockade, photic driving, flicker fusion frequency, and interaction tasks. The test demonstrated that the patients performed more slowly for all tasks than did control subjects. The CVD patients performed better than the DAT group, but they were also significantly worse in the tests compared with healthy elder subjects. This test battery was found purposeful for early diagnosis of both primary degenerative and other forms of dementia, and may also be helpful to exclude other forms of organic brain syndromes.

Studies on guanine adducts excreted in rat urine after benzene exposure

Investigations with [14C]benzene indicate the formation of base adducts in vivo. Experiments to separate adducts from urine of [14C]benzene-exposed rats suggest the excretion of eight labeled compounds different from benzene metabolites. In order to obtain information about their structure we synthesized N7-, O6-, C8- and N2-phenylguanine. With regard to their chromatographic properties we compared these phenylguanines with products obtained by alkylation of guanine by metabolites of unlabeled and 14C-labeled benzene in vivo with HPLC with UV detection and liquid scintillation counting. Furthermore GC/MS and ELISA techniques were used to detect N7-phenylguanine. Phenylguanines could not be identified in collected DNA fractions. The labeled compounds detected in urine of [14C]benzene-exposed rats also showed deviations from the HPLC elution patterns of our reference substances. Even N7-phenylguanine, formerly suspected to be a urinary metabolite of benzene in the rat, could not be detected with these refined HPLC methods. With GC/MS a compound was found in trace amounts in concentrated rat urine samples, which had a similar fragmentation pattern to N7-phenylguanine. These data could not be confirmed by a sensitive immunological assay (ELISA). No N7-phenylguanine was detected in purified rat urine samples. The results suggest the excretion of a hydroxylated phenylguanine which may be formed in liver or bone marrow DNA by highly reactive hydroxylated intermediates. The OH group might be lost because of the high temperatures during GC/MS measurements. A hydroxy group at the phenyl-ring of N7-phenylguanine will cause other elution properties in HPLC compared to N7-phenylguanine.

Noninducible Tet repressor mutations map from the operator binding motif to the C terminus

We have developed a new genetic selection system for Tet repressor mutations with a noninducible phenotype for tetracycline (TetRs). Extensive chemical mutagenesis of tetR yielded 93 single-site Tet repressor mutations. They map from residue 23 preceding the alpha-helix-turn-alpha-helix operator binding motif to residue 196 close to the C terminus of the repressor. Thirty-three of the mutations are clustered between residues 95 and 117, and another 27 are clustered between residues 131 to 158. Several of the mutants were characterized quantitatively in vivo for induction by tetracycline and anhydrotetracycline. While all of these are severely reduced in tetracycline-mediated induction, only some of them are affected for anhydrotetracycline-mediated induction.

A yeast gene (BLH1) encodes a polypeptide with high homology to vertebrate bleomycin hydrolase, a family member of thiol proteinases

We have purified bleomycin hydrolase from yeast (molecular mass 55,000 Da). Using protein sequence-derived degenerate oligonucleotide primers and amplification by polymerase chain reaction, the yeast gene BLH1 was isolated and characterized. The deduced amino acid sequence (483 amino acids) exhibits surprisingly high homology to vertebrate bleomycin hydrolase (43% identical residues and 22% conserved exchanges). It contains three blocks of sequences found conserved in other members of the thiol proteinase family and thought to be associated with the catalytic centre. BLH1 is non-essential under all growth conditions tested. However, in the presence of 3.5 mg bleomycin/ml medium wild-type cells have a slight growth advantage compared to blh1 mutant cells.

The sulphonylurea drug, glimepiride, stimulates release of glycosylphosphatidylinositol-anchored plasma-membrane proteins from 3T3 adipocytes

Sulphonylurea drugs stimulate glucose transport and metabolism in muscle and fat cells in vitro. The molecular basis for the insulin-mimetic extrapancreatic effects of these oral antidiabetic therapeutic agents is unknown at present. Here we demonstrate that incubation of 3T3 adipocytes with the novel sulphonylurea, glimepiride, causes a time- and concentration-dependent release of the glycosylphosphatidylinositol (GPI)-anchored ecto-proteins, 5'-nucleotidase, lipoprotein lipase and a 62 kDa cyclic AMP (cAMP)-binding protein from the plasma membrane into the culture medium. The change in the localization is accompanied by conversion of the membrane-anchored amphiphilic proteins into their soluble hydrophilic versions, as judged by pulse-chase experiments and Triton X-114 partitioning, and by appearance of anti-cross-reacting determinant (CRD) immunoreactivity of the released proteins as shown by Western blotting. Metabolic labelling of cells with myo-[14C]inositol demonstrates that inositol is retained in the major portion of released lipoprotein lipase and cAMP-binding ectoprotein. The identification of inositol phosphate after deamination of these proteins with nitrous acid suggests cleavage of their GPI membrane anchor by a GPI-specific phospholipase C. However, after longer incubation with glimepiride the amount of soluble versions of the GPI-proteins lacking inositol and anti-CRD immunoreactivity increases, which may be caused by additional drug-stimulated hydrolytic events within their GPI structure or C-termini. Since insulin also stimulates membrane release of these GPI-modified proteins, and in combination with glimepiride in a synergistic manner, sulphonylurea drugs may exert their peripheral actions in adipose tissue by using (part of) the insulin postreceptor signalling cascade at the step of activation of a GPI-specific phospholipase C.

The cAMP-binding ectoprotein from Saccharomyces cerevisiae is membrane-anchored by glycosyl-phosphatidylinositol

Saccharomyces cerevisiae contains an amphiphilic cAMP-binding glycoprotein at the outer face of the plasma membrane (M(r) = 54,000). It is converted to a hydrophilic form by treatment with glycosyl-phosphatidylinositol-specific phospholipases C and D (GPI-PLC/D), suggesting membrane anchorage by a covalently bound glycolipid. Determination of the constituents of the purified anchor by gas-liquid chromatography and amino acid analysis reveals the presence of glycerol, myo-inositol, glucosamine, galactose, mannose, ethanolamine, and asparagine (as the carboxyl-terminal amino acid of the Pronase-digested protein to which the anchor is attached). Complementary results are obtained by metabolic labeling, indicating that fatty acids and phosphorus are additional anchor constituents. The phosphorus is resistant to alkaline phosphatase, whereas approximately half is lost from the protein after treatment with GPI-PLD or nitrous acid, and all is removed by aqueous HF indicating the presence of two phosphodiester bonds. Inhibition of N-glycosylation by tunicamycin or removal of protein-bound glycan chains by N-glycanase or Pronase does not abolish radiolabeling of the anchor structure by any of the above compounds. Analysis of the products obtained after sequential enzymic and chemical degradation of the anchor agrees with the arrangement of constituents in GPIs from higher eucaryotes. Evidence for anchorage of the yeast cAMP-binding protein by a GPI anchor is strengthened additionally by the reactivity of the GPI-PLC-cleaved anchor with antibodies directed against the cross-reacting determinant of trypanosomal variant surface glycoproteins.

Conformation/activity studies of rationally designed potent anti-adhesive RGD peptides

The Arg-Gly-Asp (RGD) sequence is a universal cell-recognition site of various extracellular proteins that interact with integrin cell-surface receptors. In order to design low-molecular-mass RGD protein antagonists, the determination of the biologically active conformation is a prerequisite. We present a method that yields detailed insight into the steric factors which govern the binding of the ligands to their receptors by systematically scanning the conformational space accessible for the tripeptide sequence RGD. The investigation is based on the conformationally controlled design of homodetic cyclic oligopeptides and their structural determination, coupled with biological assays. For this purpose, a whole set of cyclic pentapeptides and hexapeptides has been synthesized and their three-dimensional structures in solution analyzed by modern two-dimensional NMR techniques in combination with restrained and free molecular dynamics simulations. Their biological activity was compared with that of linear GRGDS in inhibition assays of tumor cell adhesion to laminin P1 and vitronectin substrates. An up to 100-fold, and in part selective, increase in activity was observed for two cyclic pentapeptides. Most other peptides showed a decreased activity which, however, was useful to correlate activity with rather small variations in conformation. Detailed comparative studies of the systematically designed conformations and the corresponding anti-adhesive activities offer an access to lead structures for a rational indirect drug design of peptide and peptidomimetic pharmaceuticals with strong interfering activity for integrin-mediated cell-cell and cell-matrix interactions.

Pituitary factors in blood plasma are necessary for smooth muscle cell proliferation in response to injury in vivo

Intimal thickening in response to vascular injury is inhibited in animals previously subjected to hypophysectomy. We have investigated the nature and cell kinetics of this effect in a balloon catheter model of injury to the rat carotid artery. The ability of injury to stimulate [3H]thymidine labeling 48 hours after injury was almost completely eliminated in hypophysectomized (hypox) compared with control animals (0.1% versus 32.1%). Total DNA content of the developing neointima 14 days after injury was only 30% of the values found in ballooned carotid arteries of normal rats. If hypox rats were treated with recombinant human growth hormone, the proliferative response was not restored. There are two possible general explanations for the reduction of proliferative response in hypox animals: 1) that smooth muscle cells in the hypox animals have lost the ability to respond to the stimulus of injury or 2) that the ability of the smooth muscle cells to respond has not been reduced by prior hypophysectomy, but that the response itself requires the presence of pituitary-dependent factors. Transplantation experiments were performed in vivo to distinguish between these possibilities. Carotid arteries in inbred Lewis rats were excised 1 hour after balloon injury to give platelets the opportunity to adhere. These vessels were then transplanted from hypox into control animals and vice versa. At 48 hours, proliferation of smooth muscle cells in "control-to-hypox" transplants was 0.3% compared with 14.3% in "control-to-control" transplants, whereas vessels from hypox rats increased their indices to 4.8% if transplanted into control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

[Laser in surgery of vascular anastomoses]

The disadvantages of present-day microvascular suturing techniques include suture-induced foreign-body granulomas, stenoses and aneurysms. In comparison, argon laser-assisted anastomoses show a more favorable histomorphology and a low rate of stenoses and aneurysms. Laser-assisted anastomoses pass through the same familiar healing phases seen in common wound-healing.

Functional roles of amino acid residues involved in forming the alpha-helix-turn-alpha-helix operator DNA binding motif of Tet repressor from Tn10

The Tn10 derived Tet repressor contains an amino acid segment with high homology to the alpha-helix-turn-alpha-helix motif (HTH) of other DNA binding proteins. The five most conserved amino acids in HTH are probably involved in structural formation of the motif. Their functional role was probed by saturation mutagenesis yielding 95 single amino acid replacement mutants of Tet repressor. Their binding efficiencies to tet operator were quantitatively determined in vivo. All functional mutants contain amino acid substitutions consistent with their proposed role in a HTH. In particular, only the two smallest amino acids (serine, glycine) can substitute a conserved alanine in the proposed first alpha-helix without loss of activity. The last position of the first alpha-helix, the second position in the turn, and the fourth position in the second alpha-helix require mostly hydrophobic residues. The proposed C-terminus of the first alpha-helix is supported by a more active asparagine compared to glutamine replacement mutant of the wt leucine residue. The turn is located close to the protein surface as indicated by functional lysine and arginine replacements for valine. A glycine residue at the first position in the turn can be replaced by any amino acid yielding mutants with at least residual tet operator affinity. A structural model of the HTH of Tet repressor is presented.

[Diagnostic potential of biochemical and cytological parameters in bronchoalveolar lavage fluid in healthy calves and calves with pneumonia]

Bronchoalveolar lavage fluid (LF) was obtained from cranial as well as from caudal regions of the bovine lung in healthy and pneumonic calves. LF was investigated biochemically, cytologically, and bacteriologically. In healthy lungs free of pneumonic lesions, no differences due to the different parts of the lung were established. An increase in both protein content and number of cells and a marked influx of neutrophils were found to be the most important alterations caused by pneumonic lesions. The diagnostic potential of lactate dehydrogenase, alkaline phosphatase and the size of alveolar macrophages in LF was validated.

[Malondialdehyde concentration in blood plasma of patients with liver diseases]

Malondialdehyde (MDA) level was determined spectrophotometrically with thiobarbituric acid method on 50 healthy persons and 160 patients with alcoholic and nonalcoholic liver diseases. Alcoholics without liver damage show normal plasma MDA values. Alcoholic fatty liver, alcoholic hepatitis and alcoholic liver cirrhosis cause an increase of MDA values. The highest concentrations of MDA were found on patients with acute virus hepatitis. Also noninfectional hepatitis and nonalcoholic liver cirrhosis showed an elevated MDA-Level. Liver damage and lipid peroxidation are considered as closely connected processes.

Impaired tactile pattern recognition in the early stage of primary degenerative dementia compared with normal aging

Tactile pattern recognition of ten different patterns which were engraved upon 4 x 4 cm plastic plaquettes with one hand and thereafter drawing with the other or the same hand was tested in 21 patients with a mild stage primary degenerative presenile onset dementia of Alzheimer type (DAT) and in 14 patients with a questionable dementia on the background of a chronic cardiovascular disease (CVD) in comparison to 15 healthy subjects of the same age (51 years old, elder controls, (EC)) and 16 younger subjects (22 years old, younger controls, (YC)). Patients made about four times more errors than the EC group. Duration from the begin of touching to the end of drawing was significantly longer in patients than in controls. In a second task the subjects had to recognize four subsequent patterns, then to perform a standard multiplication task and afterwards to draw all four patterns in their correct sequence. Patients made about ten times more errors in pattern recognition and series reproduction than age-matched controls.