Search PubMed⌕ Search

Biomedical subjects

R L Lundblad

Publications and source records attributed to R L Lundblad.

At least 19 recordsLinked to original sources
PubMed1992

Affinity chromatography of platelets on immobilized thrombin: retention of catalytic activity by platelet-bound thrombin.

Radioactivity from I125-labeled human platelets was measured to estimate the extent of binding of platelet surface proteins to immobilized thrombin. 1-3% of the radioactivity was bound with 10-20% of this amount apparently irreversibly bound to the thrombin matrix. Site-specific chemical modification of thrombin with pyridoxal-5'-phosphate, N-bromosuccinimide or tetranitromethane resulted in a variable reduction of the amount of radiolabel bound. When thrombin modified with H-D-PheProArg-chloromethyl ketone (PPACK) was coupled to the matrix, there was no difference in the binding of platelet membrane proteins when compared to a control thrombin preparation while thrombin modified with tosyl-Lys-chloromethyl ketone (TLCK) coupled to the matrix did not bind radiolabel any more effectively than albumin which served as the control. However, when thrombin was modified with PPACK after coupling to the agarose matrix, ability to bind radiolabel was lost. Thrombin bound to platelets remained catalytically active when assayed with a peptide nitroanilide substrate. These results suggest tight binding between thrombin and platelets that is not only not dependent on active site integrity but leaves the bound thrombin catalytically competent.

Amino Acid Chloromethyl Ketones↗
PubMed1992

Molecular diversity of tissue kallikrein in human saliva.

The present study was conducted to explore the extent of heterogeneity of tissue kallikrein in saliva using immunological analysis and to demonstrate that such heterogeneity resulted from secretory phenomena and not degradation secondary to secretion. Human mixed saliva was collected by paraffin-stimulation and centrifuged at 10,000 rpm for 10 minutes. Special collectors were used to obtain parotid and submandibular/sublingual saliva using citric acid stimulation. Western blot analysis of human mixed saliva demonstrated major immunoreactive species with molecular masses of < 20 KD, 45 KD, 60 KD, 90 KD and > 200 KD. The polyclonal antibody used for these blotting studies was monofunctional with respect to reaction with purified salivary tissue kallikrein. Only the < 29 KD and 45 KD species were active using an enzyme overlay technique. While a similar distribution of molecular weight material was observed in both parotid and submandibular saliva, the amount of immunoreactive material was markedly less in parotid secretion. In addition, the < 20 KD material was essentially absent in parotid saliva. Treatment of the saliva with thermolysin eliminated the immunoreactive band at 60 KD while treatment with various glycosidases also eliminated some heterogeneity. These results demonstrate considerable variation in tissue kallikrein expression in salivary gland secretions.

Amino Acid Sequence↗
PubMed1992

The influence of age, sex and race on salivary kallikrein levels in human mixed saliva.

Variation in the level of salivary kallikrein in human saliva has been reported as a function of systemic conditions such as reduced salt intake and during the menstrual cycle. Higher levels of salivary kallikrein have been observed in subjects with tumors distant from the oral cavity when compared to control subjects. These studies have not evaluated factors, such as age, which might influence the concentration of glandular kallikrein in saliva. The purpose of the present study was to determine the variation of salivary kallikrein concentration as a function of age. Differences attributable to sex or race were also evaluated. Mixed saliva was collected from 114 subjects, ages 5-91, by paraffin stimulation. Samples were centrifuged and stored at -20 degrees C for subsequent analysis. Glandular kallikrein activity was assayed using D-ValylLeucylArginine-p-nitroanilide as the substrate. In a linear regression model which included sex, race, and age, levels only the factor of age had a significant effect on kallikrein levels. The p-value for the reduced model including only the factor of age was 0.0406 and the R-square was 0.038. Further analysis revealed that females did exhibit significantly higher kallikrein in individuals 40 years or older and that the effect of age appeared to be limited to females. It is concluded that both gender and age must be considered when evaluating salivary kallikrein changes in relationship to systemic disease.

Adolescent↗
PubMed1991

Linkage between blood coagulation and inflammation: stimulation of neutrophil tissue kallikrein by thrombin.

There has been major interest in the potential interaction between blood coagulation and inflammation. Most of the effort has focused on cellular interactions involving platelets and polymorphonuclear leukocytes (PMNS). The recent discovery of tissue kallikrein(TK) activity in PMNs prompted the study of the possible role of thrombin(IIa) in this process. Human PMNs were isolated by density gradient centrifugation. Human IIa was compared with fMLP with respect to chemotaxis and enzyme release. Results from the challenges by IIa and fMLP were compared to a NaCl control using Student's paired t-test. IIa was a potent chemotactic agent for PMNs (p less than or equal to 0.0121) and stimulated the release of TK (p less than or equal to 0.0001) as determined by hydrolysis of S-2266. FMLP significantly stimulated PMN chemotaxis (p less than or equal to 0.0028) but had no effect on TK release. Release of TK was confirmed by Western Blot analysis and 35S-methionine incorporation into a 35 KD protein after IIa challenge. These results demonstrate that IIa is chemotactic for PMNs and can cause release of tissue kallikrein demonstrating a direct role for blood coagulation in the regulation of the inflammatory response.

Blood Coagulation↗
PubMed1991

Differentiation of myeloperoxidase and glandular peroxidase in biological fluids: application to human saliva.

A modification of the assay system for peroxidase activity in human mixed saliva using 2,2'-azinobis-(-ethylbenzthiazoline-6-sulphonic acid) (ABTS) as the substrate is reported. The modifications permit differentiation between glandular peroxidase (SPX) and myeloperoxidase (MPX) activity. In addition, factors endogenous to saliva such as thiocyanate did not adversely affect the modified assay system. The basic peroxidase assay utilized 1.0 mM ABTS and 0.1 mM H2O2 in 0.1 M sodium acetate, pH 4.7. The addition of 100 mM NaCl to the assay inhibited 90% of the activity of purified MPX but only 40% of the SPX activity in parotid saliva presumed to be free of MPX. Addition of Cl- to the assay had varied effects on the mixed saliva SPX activity (44-68% inhibition), suggesting that MPX is present in varying amounts in mixed saliva. Assay of mixed saliva from patients with different states of periodontal health indicated that the amount of Cl- inhibition is dependent on amount of inflammation and thus amount of MPX present. The results suggest that the modified assay yields a reliable estimate of relative SPX activity in mixed saliva.

Benzothiazoles↗
PubMed1979

The covalent differences between bovine alpha- and beta-thrombin. A structural explanation for the changes in catalytic activity.

The partial covalent structure of bovine beta-thrombin has been determined by the use of automated Edman degradation and carboxypeptidase digestion of the component polypeptide chains separated by gel filtration following either reduction and carboxymethylation or performic acid oxidation. beta-Thrombin has been found to contain three peptide chains derived by proteolysis of the parent alpha-thrombin molecule. The A chain of alpha-thrombin has been cleaved at two points yielding a peptide (A1 chain) which contains 17 amino acids, beginning with threonine 14 and ending with lysine 30. The B chain of alpha-thrombin has been cleaved at two positions to yield a B1 chain which begins with the NH2-terminal isoleucine and terminates with lysine 65 and a B2 chain which begins with lysine 74 and continues through COOH-terminal serine 259. The A1 chain and B2 chain are linked by a disulfide bridge. Although there is no evidence for a covalent bond between the B1 chain and the B2-A1 chains, the B1 chain is tightly bound to the remainder of the molecule, for separation is achieved only under denaturing conditions.

Amino Acid Sequence↗
PubMed1979

Correlation of in vivo and in vitro inhibition of thrombin by plasma inhibitors.

Rabbit antithrombin III and thrombin were purified to homogeneity to determine the in vivo relationship of these proteins in an autologous system. These proteins, radiolabeled with Na[125I], were injected into rabbits to determine the circulatory half-life. The mean half-life values were 125I-antithrombin III, 54.75 +/- 3.10 hr; 125I-thrombin, 7.25 +/- 1.49 hr; 125I-thrombin-antithrombin III, 7.25 +/- 1.09 hr; 125I[thrombin-antithrombin III], 11.13 +/- 0.88 hr; and Tos-Lys-CH2Cl-125I-thrombin, 27.75 +/- 3.18 hr. All the mean half-life values were statistically different from that of thrombin alone except for the two forms of thrombin-antithrombin III complex. Following injection of the radiolabeled proteins, plasma samples were obtained and gel-filtered to analyze the molecular weight distribution of the radiolabel. An identical elution position on gel filtration of 125I-antithrombin III with native antithrombin III was observed. The 125I-thrombin distributed into two peaks of radioactivity, with a molecular weight of 100,000 (79%) and a molecular weight greater than 200,000 (21%). The 100,000 dalton peak is consistent with a thrombin--antithrombin III complex, and the greater than 200,000 dalton peak is consistent with a thrombin-alpha 2-macroglobulin complex as confirmed by in vitro immunochemical studies. Thrombin inactivated with Tos-Lys-CH2Cl also showed two peaks of radioactivity on gel filtration, one peak which was excluded from the column and the other peak with an elution volume that was consistent with the position of native thrombin.

Antithrombin III↗
PubMed1978

On the preparation of bovine alpha-thrombin.

An improved method for the preparation of bovine alpha-thrombin is described. The procedure involves that activation of partially purified prothrombin with tissue thromboplastin followed by chromatography on Sulfopropyl-Sephadex C-50. The purified enzyme is homogeneous on polyacrylamide discontinuous gel electrophoresis and has a specific activity toward fibrinogen of 2.200-2,700 N.I.H. U/mg. Its stability on storage in liquid media is dependent on both ionic strength and temperature. Increasing ionic strength and decreasing temperature result in optimal stability. The denaturation of alpha-thrombin by guanidine hydrochloride was found to be a partially reversible process with the renatured species possessing properties similar to "aged" thrombin. In addition, the catalytic properties of alpha-thrombin covalently attached to agarose gel beads were also examined. The activity of the immobilized enzyme toward fibrinogen was affected to a much greater extent than was the hydrolysis of low molecular weight, synthetic substrates.

Animals↗
PubMed1978

Thrombin binding to thrombasthenic platelets.

Platelets from two patients with Glanzmann's thrombasthenia showed decreased iodination of surface glycoproteins GPIIb and GPIII. Despite these changes, the binding of [125I] alpha-thrombin to the thrombasthenic platelets was normal. Binding was linear up to a thrombin concentration of 0.1 to 0.2 U/ml, at which point a change in the slope of the binding curve was observed. At lower concentrations of thrombin, 1,000 to 2,000 molecules of thrombin were bound per platelet, with an apparent Kdiss of 0.1 to 0.3 U/ml. With high concentrations of thrombin, thrombasthenic platelets bound 30,000 to 65,000 molecules of thrombin per platelet at saturation, with an apparent Kdiss of 5 to 10 U/ml. The release of [14C]serotonin by thrombasthenic platelets as a function of thrombin concentration was also similar to release by normal platelets. These studies indicate that the receptor(s) for thrombin on the plasma membrane of platelets from patients with Glanzmann's disease are intact and that membrane glycoproteins GPIIb and GPIII play little or no role in either the initial binding of thrombin to platelets or the transmission of this surface stimulus to release-inducing mechanisms.

Adult↗
PubMed1977

Structure-function relationships in the interaction of alpha-thrombin with blood platelets.

Highly purified alpha-thrombin has been chemically modified in an attempt to determine which features of the molecule are important for normal platelet-thrombin interactions. Modifying agents included diisopropylphosphorofluoridate and 1-chloro-3-tosylamido-7-amino-L-2-heptanone, which modify serine and histidine, respectively, at the catalytic site, as well as N-bromosuccinimide and 2-hydroxy-5-nitrobenzyl bromide, which modify a single tryptophan at or near the fibrinogen-binding site. Active site-directed modification did not appreciably affect the binding characteristics, but prevented platelet activation. In contrast, modification of tryptophan at the macromolecular substrate-binding site resulted in the loss of high affinity binding of thrombin to platelets, while low affinity binding was apparently unaffected. This modification altered but did not abolish the ability of thrombin to effect platelet aggregation and release of [14C]serotonin. These results suggest that residues at the catalytic site are not involved in binding and that the macromolecular substrate-binding site of alpha-thrombin participates in high affinity binding to platelets. These data are also consistent with the existence of at least two types of binding sites for thrombin on the platelet surface as well as more than one platelet-binding region on the thrombin molecule.

2-Hydroxy-5-nitrobenzyl Bromide↗
PubMed1977

The modification of tryptophan in bovine thrombin.

2-Hydroxy-5-nitrobenzyl bromide, at a 100-fold molar excess, was observed to react withthrombin at pH 4.0 to give a modified enzyme which possessed 20% of the fibrinogen clotting activity and 80% of the esterase activity compared to a control preparation. Spectrophotometric analysis of the modified protein indicated that this effect on catalytic activity was associated with the incorporation of 1 mol of reagent per mol of thrombin. Amino acid analysis showed no loss of amino acids other than tryptophan. The reaction of N-bromosuccinimide with thrombin at 2-fold molar excess resulted in the modification of one tryptophan per mol of enzyme with the loss of 80% of the fibrinogen clotting activity with, as above, a considerably smaller loss of esterase activity. Oxidation of thrombin with N-bromosuccinimide decreased the extent of subsequent tryptophan modification with 2-hydroxy-5-nitrobenzyl bromide. Thrombin modified with 2-hydroxy-5-nitrobenzyl bromide showed a 3-4 fold increase in Km and a decrease in V for the ester substrate. The reaction of thrombin with 2-acetoxy-5-nitrobenzyl bromide, a substrate analogue, also resulted in the inactivation of the enzyme. The data are interpreted to show the presence of a tryptophan residue at or near the enzyme's substrate binding site.

2-Hydroxy-5-nitrobenzyl Bromide↗