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Biomedical subjects

F Fiedler

Publications and source records attributed to F Fiedler.

At least 19 recordsLinked to original sources
PubMed1992

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.

Amidohydrolases↗
PubMed1992

Kinetics of bond cleavages at kallidin release by tissue kallikrein: cleavage of two peptide bonds in a single enzyme-substrate complex?

The kinetics of the release of kallidin, L- and KL-chains from bovine L-kininogen by porcine tissue kallikrein were followed and individual kinetic constants for cleavage of the Met-360 and the Arg-370 bond determined. The results suggest that both these bonds in L-kininogen r are hydrolyzed "simultaneously" without appearance of a free singly-nicked intermediate. Kallidin release in the human analogous system is also compatible with such a mechanism.

Animals↗
PubMed1992

Contribution of tumor necrosis factor to host defense against staphylococci in a guinea pig model of foreign body infections.

The contribution of the cytokine tumor necrosis factor (cachectin; TNF) to host defenses against staphylococcal foreign body infections was studied in vivo. In tissue cages subcutaneously implanted into guinea pigs, progressive infection was initiated by a very low inoculum (100 cfu) of Staphylococcus aureus with a success rate of 100%, as is frequently encountered in related clinical situations. Locally injected autologous bacterial components derived from the cell wall of S. aureus, in particular peptidoglycan, were very active in raising TNF levels in tissue cage fluid and in preventing the development of infection by the 100% infective dose of the test strain. Furthermore, injection of murine recombinant TNF into tissue cages could substitute for the bacterial components in preventing experimental infection by S. aureus. The protective effect of TNF-eliciting bacterial components could be neutralized by anti-TNF antibodies. A local increase in TNF levels might improve host defenses against staphylococcal foreign body infections.

Animals↗
PubMed1991

Metabolic and hormonal studies of type 1 (insulin-dependent) diabetic patients after successful pancreas and kidney transplantation.

Long-term normalization of glucose metabolism is necessary to prevent or ameliorate diabetic complications. Although pancreatic grafting is able to restore normal blood glucose and glycated haemoglobin, the degree of normalization of the deranged diabetic metabolism after pancreas transplantation is still questionable. Consequently glucose, insulin, C-peptide, glucagon, and pancreatic polypeptide responses to oral glucose and i.v. arginine were measured in 36 Type 1 (insulin-dependent) diabetic recipients of pancreas and kidney allografts and compared to ten healthy control subjects. Despite normal HbA1 (7.2 +/- 0.2%; normal less than 8%) glucose disposal was normal only in 44% and impaired in 56% of the graft recipients. Normalization of glucose tolerance was achieved at the expense of hyperinsulinaemia in 52% of the subjects. C-peptide and glucagon were normal, while pancreatic polypeptide was significantly higher in the graft recipients. Intravenous glucose tolerance (n = 21) was normal in 67% and borderline in 23%. Biphasic insulin release was seen in patients with normal glucose tolerance. Glucose tolerance did not deteriorate up to 7 years post-transplant. In addition, stress hormone release (cortisol, growth hormone, prolactin, glucagon, catecholamines) to insulin-induced hypoglycaemia was examined in 20 graft recipients and compared to eight healthy subjects. Reduced blood glucose decline indicates insulin resistance, but glucose recovery was normal, despite markedly reduced catecholamine and glucagon release. These data demonstrate the effectiveness of pancreatic grafting in normalizing glucose metabolism, although hyperinsulinaemia and deranged counterregulatory hormone response are observed frequently.

Adult↗
PubMed1991

Urodilatin, a kidney-derived natriuretic factor, is excreted with a circadian rhythm and is stimulated by saline infusion in man.

Urodilatin is a recently described, presumably kidney-derived member of the atrial natriuretic peptide family. The first data on a physiological role for urodilatin in the regulation of sodium homeostasis in humans is presented in this work. Urinary urodilatin excretion during a 9-day study in healthy volunteers paralleled the circadian rhythm in urinary sodium excretion. Furthermore, urodilatin and sodium excretion were slightly increased during the first 3 h after an acute isotonic saline infusion and about three-fold elevated during 14 h postinfusion; both parameters remained closely correlated up to 28 h postinfusion. These data suggest that urodilatin is involved in the circadian regulation of sodium excretion and is a physiological regulator of long-term sodium excretion after an acute saline infusion.

Adult↗
PubMed1991

[Peripheral oxygen saturation during dental surgery with and without premedication].

83 adults undergoing dental surgical procedures in local anesthesia were monitored continuously with a pulse oximeter for hypoxemia. 30 patients received as premedication either a combination of a neuroleptic drug and an opiate or a benzodiazepine. There was a drop in the oxygen saturation in 80% of the patients with premedication but only in 66% of the patients without. There were statistical highly significant more periods of hypoxemia in patients with premedication compared to the others. (1548 periods versus 659 periods p less than 0.001). The kind of premedication/sedation does not influence the number of hypoxic episodes. We conclude that especially patients with premedication should only be treated by surgeons with sufficient clinical experience in coping with emergency situations.

Anesthesia, Dental↗
PubMed1990

Occurrence and structure of lipoteichoic acids in the genus Staphylococcus.

Lipoteichoic acids were isolated from eleven species of the genus Staphylococcus using phenol-water partition and hydrophobic chromatography on octyl-Sepharose CL-4B. The lipoteichoic acids purified could be visualized by SDS-PAGE. They were shown to be composed of a hydrophilic poly(glycerophosphate) chain covalently linked to gentiobiosyldiacylglycerol, the common lipid anchor of these molecules. Glycerophosphate units of the hydrophilic chain were found to be partly substituted with ester-linked D-alanine, except in the case of S. cohnii. The lipoteichoic acids isolated from S. cohnii, S. hominis, S. saprophyticus and S. simulans contain alpha(1-2)-linked N-acetylglucosamine as an additional substituent of the poly(glycerophosphate) backbone.

Chromatography, Gas↗
PubMed1990

Evidence that urodilatin, rather than ANP, regulates renal sodium excretion.

Urodilatin, a closely related member of the atrial peptide family, was discovered recently in human urine. Urodilatin (ANP 95-126) is believed to be produced within the kidney and is natriuretic; evidence indicates that most of the ANP-like immunoreactivity in the kidney elutes with urodilatin rather than with ANP. Moreover, urodilatin is little affected by renal enzymes that inactivate atriopeptin. To determine the relative importance of urodilatin versus ANP in the regulation of renal sodium excretion, we studied intact and cardiac-denervated conscious dogs under three experimental conditions: (1) spontaneous sodium excretion, (2) intravenous infusion of saline, and (3) left atrial distension. Urodilatin was measured in urine with a newly developed radioimmunoassay that selectively measures urodilatin without any cross-reactivity with alpha-human atrial natriuretic peptide (alpha-hANP); alpha-hANP was measured in plasma by radio-immunoassay because it is rapidly inactivated in the kidney by enzymatic activity. In each group of experiments, sodium excretion correlated better with urodilatin than it did with circulating alpha-hANP. The correlation coefficient (r value) between urodilatin excretion and renal sodium excretion exceeded 0.8 in 13 of 18 experiments and was below 0.6 in only 2 experiments. On the other hand, the correlation between circulating atriopeptin and sodium excretion exceeded 0.8 in only 3 of 18 experiments and was below 0.6 in 10 experiments. A negative correlation between plasma atriopeptin and renal sodium excretion was observed during left atrial distension in the cardiac-denervated dogs. These results and other considerations suggest that urodilatin, rather than atriopeptin, is the member of the ANP family that is primarily involved in the regulation of renal sodium excretion.

Animals↗
PubMed1990

Effect of intraduodenal bile and Na- taurodeoxycholate on exocrine pancreatic secretion and on plasma levels of secretin, pancreatic polypeptide, and gastrin in man.

The effect of intraduodenally administered cattle bile (CB) and Na-taurodeoxycholate (TDC) on basal pancreatic secretion and plasma levels of secretin, pancreatic polypeptide (PP), and gastrin were investigated on two separate days in 10 fasting volunteers. Doses of 2-6 g CB and 200-600 mg TDC were given intraduodenally at 65-min intervals. Volume, bicarbonate, lipase, trypsin, amylase, and bilirubin were measured in 10-min fractions of duodenal juice, and GI peptides determined by radioimmunoassay. CB and TDC enhanced significantly and dose-dependently volume, bicarbonate and enzyme secretion, and plasma secretin and PP levels. In contrast, plasma gastrin showed only a marginal increase. We conclude that the hydrokinetic effect of intraduodenal CB and TDC is at least partially mediated by secretin. Gastrin could be ruled out as a mediator of the ecbolic effect, whereas other GI peptides, primarily CCK, and/or neural mechanisms must be considered possible mediators. Both pathways may also play a role in the PP release observed.

Adult↗
PubMed1988

Biochemistry of the cell surface of Listeria strains: a locating general view.

The cell surfaces of Listeria strains are composed of various compounds. These include peptidoglycan, teichoic acids and lipoteichoic acids. The structural features of these polymers are described and a macromolecular model of the organization of the cell wall of a Listeria cell is given. The occurrence of further components at the cell surface and biological aspects are briefly discussed.

Bacterial Outer Membrane Proteins↗
PubMed1987

Effects of secondary interactions on the kinetics of peptide and peptide ester hydrolysis by tissue kallikrein and trypsin.

Kinetic constants for the hydrolysis by porcine tissue beta-kallikrein B and by bovine trypsin of a number of peptides related to the sequence of kininogen (also one containing a P2 glycine residue instead of phenylalanine) and of a series of corresponding arginyl peptide esters with various apolar P2 residues have been determined under strictly comparative conditions. kcat and kcat/Km values for the hydrolysis of the Arg-Ser bonds of the peptides by trypsin are conspicuously high. kcat for the best of the peptide substrates, Ac-Phe-Arg-Ser-Val-NH2, even reaches kcat for the corresponding methyl ester, indicating rate-limiting deacylation also in the hydrolysis of a peptide bond by this enzyme. kcat/Km for the hydrolysis of the peptide esters with different nonpolar L-amino acids in P2 is remarkably constant (range 1.7), as it is for the pair of the above pentapeptides with P2 glycine or phenylalanine. kcat for the ester substrates varies fivefold, however, being greatest for the P2 glycine compounds. Obviously, an increased potential of a P2 residue for interactions with the enzyme lowers the rate of deacylation. In contrast to results obtained with chymotrypsin and pancreatic elastase, trypsin is well able to tolerate a P3 proline residue. In the hydrolysis of peptide esters, tissue kallikrein is definitely superior to trypsin. Conversely, peptide bonds are hydrolyzed less efficiently by tissue kallikrein and the acylation reaction is rate-limiting. The influence of the length of peptide substrates is similar in both enzymes and indicates an extension of the substrate recognition site from subsite S3 to at least S'3 of tissue kallikrein and the importance of a hydrogen bond between the P3 carbonyl group and Gly-216 of the enzymes. Tissue kallikrein also tolerates a P3 proline residue well. In sharp contrast to the behaviour of trypsin is the very strong influence of the P2 residue in tissue-kallikrein-catalyzed reactions. kcat/Km varies 75-fold in the series of the dipeptide esters with nonpolar L-amino acid residues in P2, a P2 glycine residue furnishing the worst and phenylalanine the best substrate, whereas this exchange in the pentapeptides changes kcat/Km as much as 730-fold. This behaviour, together with the high value of kcat/Km for Ac-Phe-Arg-OMe of 3.75 X 10(7) M-1 s-1, suggests rate-limiting binding (k1) in the hydrolysis of the best ester substrates.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗
PubMed1987

Na-taurodeoxycholate acts as a specific intestinal stimulus of exocrine pancreatic secretion in man.

The effect of intraduodenally administered cattle bile, Na-taurodeoxycholate, and Na-taurocholate on secretin-stimulated exocrine pancreatic secretion was investigated on 40 fasting young healthy volunteers. Intraduodenal bile stimulated significantly and dose-dependently hydrokinetic and ecbolic pancreatic secretion. Only bile, but not secretin intravenously, both applied in a dosage equivalent with respect to their hydrokinetic action, caused a significant increase of enzyme output and enzyme concentration as well. Intraduodenal Na-taurodeoxycholate enhanced also dose-dependently secretin-stimulated volume, bicarbonate, and enzyme secretion. The effect was related to the load, not to the concentration of this bile salt. On the other side, Na-taurocholate had only a weak and not dose-dependent hydrokinetic and no ecbolic effect. It is concluded that not bile salts in general, but only certain of them--like Na-taurodeoxycholate--are the effective constituents of bile, acting as specific intraduodenal stimulants of hydrokinetic and ecbolic pancreatic secretion.

Adult↗
PubMed1986

Individual reaction steps in the release of kallidin from kininogen by tissue kallikrein.

At low pH values (around 6), porcine pancreatic beta-kallikrein B attacks at first the C-terminal ARg bond of the kinin moiety in bovine HMW kininogen. Arg-cleaved kininogen accumulates as an intermediate in the solution. Kallidin is released by cleavage of the aminoterminal Met-Lys bond in a second step. At pH values between 7.6 and 9, however, Arg-cleaved kininogen does not occur as a free intermediate. The participation as a (free, not only enzyme-bound) intermediate of Arg-cleaved kininogen in a short-lived especially reactive conformation or of Met-cleaved kininogen is also unlikely. Probably, both the Met and the Arg bonds are hydrolyzed in one enzyme-substrate complex which does not dissociate between these two events. Kinetic constants for the release of kallidin from native single-chain HMW kininogen and from Arg-cleaved kininogen (even if this Arg residue is removed) remarkably have the same values. Evidently, the rate of the reaction is determined by steps leading to the hydrolysis of the Met bond. As the state of the C-terminal Arg residue has no influence, the efficient cleavage of the Met bond by tissue kallikrein is probably not due to some strain in the kininogen molecule in the region of this bond. As modification of Arg residues of kininogen prevents cleavage also of the Met bond, some Arg residue(s) appear(s) to play a crucial role in this process. kcat/Km (1.4 x 10(6) M-1 sex-1 at pH 9, 25 degrees C) is very high for a proteolytic reaction, mainly because of the low value of Km (0.6 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The tissue kallikrein-kinin system in human seminal plasma--biochemical and functional aspects.

At least three species of tissue kallikrein-like antigens are present in human seminal plasma which differ in their molecular masses and enzymatic activities. At least one of these species is a genuine tissue kallikrein as judged by the criteria of molecular mass, immunoreactivity, inhibition by aprotinin and non-inhibition by soybean trypsin inhibitor, and the ability to release kallidin from kininogen. The prostatic gland was identified as the origin of the seminal fluid tissue kallikrein first by indirect studies and then by demonstrating the presence of immunoreactive tissue kallikrein both in prostatic tissue and secretion.

Humans↗
PubMed1986

Biochemical and immunochemical properties of the cell surface of Renibacterium salmoninarum.

The biochemical composition of the cell envelope of Renibacterium salmoninarum was investigated in a total of 13 strains isolated from different salmonid fish species at various geographical locations of the United States, Canada, and Europe. A marked similarity with the type strain R. salmoninarum ATCC 33209 was found both in the peptidoglycan and the cell wall polysaccharide. The primary structure of the peptidoglycan was found to be consistent with lysine in the third position of the peptide subunit, a glycyl-alanine interpeptide bridge between lysine and D-alanine of adjacent peptide subunits, and a D-alanine amide substituent at the alpha-carboxyl group of D-glutamic acid in position 2 of the peptide subunit. The cell wall polysaccharide contained galactose as the major sugar component which was accompanied by rhamnose, N-acetylglucosamine, and N-acetylfucosamine. The polysaccharide amounted to more than 60% of the dry weight of the cell walls. It was found to be covalently linked to the peptidoglycan and was released by hot formamide treatment. On gel filtration chromatography the extracted polysaccharide behaved like a homogeneous polymeric compound. The purified cell wall polysaccharide showed antigenic activity with antiserum obtained by immunization of rabbits with heat-inactivated trypsinized cells of R. salmoninarum. Immunoblotting experiments with nontrypsinized cell walls and antisera raised against R. salmoninarum cells revealed that antigenic proteins were attached to the cell walls.

Amino Acids↗
PubMed1985

Characteristics of the binding of aminoglycoside antibiotics to teichoic acids. A potential model system for interaction of aminoglycosides with polyanions.

The binding of the aminoglycoside antibiotic dihydrostreptomycin to defined cell-wall teichoic acids and to lipoteichoic acid isolated from various gram-positive eubacteria was followed by equilibrium dialysis. Dihydrostreptomycin was used at a wide range of concentration under different conditions of ionic strength, concentration of teichoic acid, presence of cationic molecules like Mg2+, spermidine, other aminoglycoside antibiotics (gentamicin, neomycin, paromomycin). Interaction of dihydrostreptomycin with teichoic acid was found to be a cooperative binding process. The binding characteristics seem to be dependent on structural features of teichoic acid and are influenced by cationic molecules. Mg2+, spermidine and other aminoglycosides antibiotics inhibit the binding of dihydrostreptomycin to teichoic acid competitively. The binding of aminoglycosides to teichoic acids is considered as a model system for the interaction of aminoglycoside antibiotics with cellular polyanions. Conclusions of physiological significance are drawn.

Aminoglycosides↗