Pharmacology of apolipoprotein A-I.

The role of HDL and its main protein component the apolipoprotein A-I as being antiatherogenic is well established. Experimental data give support for the involvement of at least three different types of mechanism: (1) the reverse cholesterol transport, (2) anti-inflammatory mechanisms and (3) antithrombotic mechanisms. Depending upon the stage and type of atherosclerosis, different mechanisms may be more or less important. Knowledge of pharmacology of apolipoprotein A-I has strongly increased during past years and clinical studies have started with infusions of apolipoprotein A-I phospholipid complexes.

Inhibition of antigen-induced acute bronchoconstriction, airway hyperresponsiveness, and mast cell degranulation by a nonanticoagulant heparin: comparison with a low molecular weight heparin.

Inhaled heparin prevents antigen-induced bronchoconstriction and inhibits anti-IgE-mediated mast-cell degranulation. We hypothesized that the antiallergic action of heparin may be dependent on molecular weight and related to its nonanticoagulant properties. Therefore, in the present investigation we studied the effects of a nonanticoagulant fraction of heparin (LA-heparin) on antigen-induced bronchoconstriction, airway hyperresponsiveness (AHR), and mast-cell degranulation, and compared its antiallergic activity with that of a low molecular weight heparin (LMW-heparin, fragmin). Specific lung resistance (SRL) was measured in 15 sheep before, immediately after, and serially for as long as 2 h after airway challenge with Ascaris suum antigen, without and after pretreatment with inhaled fractionated heparins at doses of 2.5 and 5 mg/kg. Airway responsiveness was estimated before, and 2 h after antigen as the cumulative provocating dose (PD400) of carbachol in breath units, which increased SRL by 400% (one breath unit was defined as one breath of 1% carbachol solution). LA-heparin caused a dose-dependent inhibition of antigen-induced bronchoconstriction, and a 5-mg/kg nebulized dose caused a 67% inhibition of allergic bronchoconstriction, whereas a 2.5-mg/kg dose was ineffective (20% inhibition). Inhaled fragmin was more potent than LA-heparin, as shown by 84% (2.5 mg/kg) and 82% (5 mg/kg) inhibition of allergic bronchoconstriction. Fragmin (5 mg/kg) also attenuated the postantigen AHR, whereas LA-heparin was ineffective. In vitro, preincubation with both LA-heparin and fragmin inhibited the anti-IgE-induced degranulation of rat peritoneal mast-cells in a dose-dependent fashion. LA-heparin was fourfold more potent than fragmin, with IC50 of 80 and 320 microg/ml, respectively. These data suggest that: (1) fractionated heparins attenuate antigen-induced acute bronchoconstriction, (2) nonanticoagulant fractions mediate the antiallergic activity of inhaled heparin, and (3) antiallergic activity of nonanticoagulant heparin and LMW-heparin may be related to prevention of mast-cell degranulation.

Oxyphil cell adenoma (oncocytoma) of the lacrimal sac. Review of the literature.

A case of oncocytoma of the lacrimal sac is presented. An 84-year-old woman with a mass in the lacrimal sac area and epiphora was operated with excision. Histological and electron microscopic examination revealed it to be an oncocytic adenoma. Oncocytic tumours of the lacrimal sac are very rare and to our knowledge this is the 14th case to be reported. Oncocytomas are composed of polyhedric cells with abundant oxyphil cytoplasm which is granular and contains large numbers of abnormal mitochondria. Non-neoplastic oncocytes may arise from the secretory epithelium of the sac in various chronic inflammatory states. They may also occur at an old age, as a result of the normal aging process.

Colorectal cancer surveillance in patients with ulcerative colitis.

In a prospective study carried out between 1977 and 1991, 131 patients with ulcerative colitis from an area of 65,000 inhabitants were followed by clinical visits and regular colonoscopy with biopsy. At the end of the study 58 patients had had total colitis for more than 10 years, 38 had left the programme (16 after radical operations, nine because of death--one from colitis, one from carcinoma--and 13 for other reasons) and 632 colonoscopies had been performed. Colorectal carcinoma was diagnosed in four patients, of whom two were included in the programme with a diagnosis of cancer. Dysplasia was diagnosed in 24 patients, other than those with malignancy; in four this was of high grade. Carcinoma and dysplasia occurred mainly in the left colon and in patients with total colitis. The surveillance programme was resource consuming and the cost-benefit must be questioned.

Variables influencing the clot lysis assay of streptokinase.

Clot lysis induced by streptokinase has been studied and the influences of pH and the concentrations of plasminogen, fibrinogen and buffer composition investigated. Variations in the concentrations of plasminogen strongly effect the SK apparent activity, maxima being obtained at different plasminogen concentrations linearly dependent on the concentration of fibrinogen. Buffer composition and pH also effect the apparent activity and the maxima obtained are dependent on the fibrinogen concentration. Analytical conditions are discussed and suitable sample and reagent volumes, as well as concentrations of the reactants and buffer environment, are suggested.

Lipolytic effects of heparin and low molecular weight heparin and their importance in hemodialysis.

The incidence and the degree of uremic hypertriglyceridemia in a hemodialysis population are exacerbated by the use of UF heparin as anticoagulant therapy. This hypertriglyceridemia is associated with an increase in the levels of triglyceride-rich remnant particles that are thought to be particularly atherogenic. Since arteriosclerosis and its related diseases are the major causes of morbidity and mortality in this dialysis population, the LMW heparins with their reduced stimulation of plasma lipolytic activity may provide a clinically superior alternative to UF heparin for anticoagulation therapy in long-term hemodialysis. One may also speculate that it may be more advantageous to use LMW heparin for all long-term treatments with heparin.

Factor VIII procoagulant protein interacts with phospholipid vesicles via its 80 kDa light chain.

In a previous report, we detailed fractionation of polyclonal human anti-Factor VIII:C into a component directed exclusively against the phospholipid-binding site on Factor VIII (PL-site antibody) and another directed at other sites (non-PL-site antibody). The location on the F.VIII molecule of its PL-binding site has now been studied by two different methods using this fractionated 125I-labelled anti-F.VIII:C Fab'. The first method was modified from that of Weinstein et al. (Proc Natl Acad Sci USA 1981; 78: 5137-41), involving electrophoresis of F.VIII peptide-125I-Fab' A/F.VIII immunocomplexes in SDS-polyacrylamide gels. PL-site antibody reacted with F.VIII peptides of apparent Mr approximately 80 kDa and sometimes 160 kDa in plasma and concentrate, but not with larger peptides. Non-PL-site antibody, however, reacted with a range of peptides of apparent Mr 90 kDa to 280 kDa. In addition, when purified F.VIII containing heavy and light chains (HC + LC), and isolated LC peptides were analysed, PL-site antibody bound to LC peptides whereas non-PL-site antibody did not. The second method used the antibody pools in immunoradiometric assays (IRMA's) of purified F.VIII peptides. Both labels measured similar amounts of F.VIII:Ag in a sample of purified F.VIII containing both HC and LC; on assaying an HC preparation, however, PL-site label measured only 2% of F.VIII:Ag found by non-PL-site label, indicating that PL-binding sites are absent in HC preparations. These results indicate that F.VIII binds to PL via its 80 kDa light chain.

Properties and catabolism of heat treated antithrombin III concentrate.

Heat treatment is employed to diminish the transmission of hepatitis when blood products are administered. It is possible that such a procedure could reduce the biological activity of the proteins and induce changes in structure and aggregation state. We have therefore made in vitro and pharmacokinetic studies of heat treated antithrombin III (AT III) concentrate using both radiolabelled and non-labelled preparations. The purification, heat treatment and the radiolabelling procedures did not induce any changes in the AT III molecules with exception of a decrease in heparin affinity in about 10% of the molecules. The in vivo studies using 125I AT III showed that the fractional catabolic rate was increased and the half-life was shortened by about 20-25% compared to our previous studies on non-heat treated AT III concentrate. Our present findings indicating a mean half-life of 3.0 days are quite comparable to studies by others on non-heat treated AT III, however.

Localization of a factor VIII binding domain on a 34 kilodalton fragment of the N-terminal portion of von Willebrand factor.

Factor VIII (F.VIII) was tested for its ability to bind in solid phase system to von Willebrand Factor (vWF) or fragments obtained with Staphylococcus aureus V-8 protease, ie, SpIII (N-terminal), SpI (central), and SpII (C-terminal). Bound F.VIII was estimated in situ by clotting and chromogenic assays. F.VIII bound in a dose-dependent manner to immobilized vWF and SpIII but not to SpII or SpI. Binding was inhibited by 0.25 mol/L CaCl2 as well as by an excess of vWF or SpIII. Accordingly, immobilized F.VIII specifically bound 125I-vWF and SpIII but not SpII or SpI. Twelve monoclonal antibodies (MoAbs) directed towards SpIII, specifically blocking binding of F.VIII to vWF or SpIII, were used for the mapping of plasmic or tryptic fragments of vWF or SpIII. We thus established that a F.VIII binding domain of vWF is located on a 34 kilodalton (kd) fragment of the N-terminal portion of vWF, between residues 1 and 910, and that it is distinct from the GPIb and collagen binding domains.

Autoregulation of capillary pressure and filtration in cat skeletal muscle in states of normal and reduced vascular tone.

The controversial hypothesis that capillary pressure (Pc) is autoregulated in response to arterial pressure (PA) alterations was tested in sympathectomized cat skeletal muscle by studying the relation between Pc and PA under conditions of well preserved vascular tone and reactivity, during papaverine-induced maximal vasodilatation (passive vascular bed), and during impaired vascular reactivity caused by preparatory surgery, or by low dose isoproterenol administration. The latter states resembled such under which Pc autoregulation unintentionally seems to have been studied previously. Capillary pressure was assessed with the Pcvenule method for continuous direct pressure recordings from capillaries/postcapillary venules (Mellander et al. 1987) and simultaneously derived from observed net transvascular fluid flux divided by CFC. Resistances in the whole vascular bed and in its pre- and postcapillary segments (Ra and Rv) were determined from recordings of blood flow, PA, Pc, and PV. During preserved vascular reactivity, Pc was found to be virtually constant, that is, almost perfectly autoregulated, over the PA range from 50 to 180 mmHg, whereas in the passive vascular bed there was a direct linear relation between Pc and PA (y = 0.137x + 11.69; r = 0.97). The delta Pc/delta PA ratio was about 1/70 in the normal reactive, and 1/7 in the passive, vascular bed, implying an increase in Pc by 1 mmHg for every 70 mmHg and every 7 mmHg increase in PA, respectively. Capillary pressure autoregulation was explained by precise adjustments of Ra/Rv in relation to PA elicited by myogenic and metabolic regulatory mechanisms. This protective reaction against plasma loss during increased PA was abolished during maximal vasodilation, and was much impaired by surgical trauma, partly via a beta-adrenergic inhibitory effect, and by isoproterenol, in turn causing gross transcapillary fluid fluxes. The latter findings might explain failing Pc autoregulation in some previous studies undertaken under seemingly similar conditions.

Isolation and characterization of human factor VIII: molecular forms in commercial factor VIII concentrate, cryoprecipitate, and plasma.

Human factor VIII has been isolated from a high purity factor VIII concentrate by immunoaffinity chromatography and HPLC on Mono Q gel. Two fractions of factor VIII were obtained with a specific activity of approximately equal to 7000 units/mg. The major fraction contained eight peptide chains of 200, 180, 160, 150, 135, 130, 115, and 105 kDa plus one doublet chain of 80 kDa. The minor fraction contained one peptide chain of 90 kDa plus the chain of 80 kDa. Both fractions were activated by thrombin to the same extent. Amino-terminal amino acid sequence analysis was performed on the 180-kDa, 130-kDa, and 90-kDa chains and showed an identical amino-terminal sequence in these chains. Each chain from 200 kDa to 90 kDa was linked to one 80-kDa chain by a metal-ion bridge(s). Studies on factor VIII in plasma and cryoprecipitate, prepared and gel filtered in the presence of protease inhibitors, showed that one 200-kDa plus one 80-kDa chain were the only or dominating chains in the materials and may represent native factor VIII. The results indicated that all chains from 180 kDa to 90 kDa are fragments of the 200-kDa chain. All of these more or less fragmented chains form active factor VIII complexes with the 80-kDa chain.

Studies on the influence of reactants and buffer environment on clot lysis induced by human plasminogen activators.

Clot lysis induced by tissue plasminogen activator and urokinase has been studied and the influences of pH, ionic environment and reactant concentrations have been determined. Both pH and ionic strength strongly affect the rate of clot lysis and distinctly different dependency profiles are obtained for tissue plasminogen activator and urokinase. Variations in concentration of plasminogen also profoundly affect the rate of clot lysis, maxima being obtained at different plasminogen concentrations depending on the concentration of fibrinogen. For urokinase, these maxima occurred at about a tenfold higher concentration of plasminogen than for the tissue plasminogen activator. The lysis times are directly dependent on the concentration of fibrinogen. Variation in thrombin concentration did not significantly affect the lysis times. Suitable conditions for the assays of tissue plasminogen activator and urokinase are suggested.

Decrease in survival time in beta 2-adrenoceptor blocked cats exposed to bleeding.

Our previous investigations have indicated that beta 2-adrenergic regulatory mechanisms contribute to important compensatory hemodynamic adjustments in hemorrhage. In the present study an attempt was made to examine, by comparative observations after standardized fatal hemorrhage on cats with intact and 'selectively' blocked beta 2-adrenoceptors (ICI 118,551), whether such compensatory effects are crucial for survival. On the average, the survival time after bleeding was 686 min in cats with intact and 427 min in cats with blocked beta 2-adrenoceptors (p less than 0.05), the difference thus approaching 4.5 h. It is suggested that the reduced survival time after beta 2-blockade, at least partly, can be ascribed to interference with the circulatory beta 2-adrenergic control in hemorrhage aimed at improving tissue perfusion.

Elimination of intravenously administered radiolabelled antithrombin III and heparin in humans.

Antithrombin III was purified from normal plasma by DEAE-Sephadex chromatography and heparin affinity chromatography; the protein was subsequently radiolabelled with 125I. 125I-antithrombin III alone and 125I-antithrombin III in the presence of high affinity 35S-heparin fractions were injected into normal humans. 125I-radiolabel and protein bound 35S-radioactivity were followed separately. In semilogarithmic plots 125I-antithrombin III disappeared according to a double exponential curve with a half-life in the second phase of 56.8 hr in the absence of heparin and of 33.7 hr in the presence of heparin. Protein bound 35S-radioactivity disappeared much faster than the 125I-radiolabel. These data support the concept that heparin disappears as free heparin from the equilibrium heparin - antithrombin III in equilibrium heparin + antithrombin III. Immuno-reactive antithrombin III decreased from 100% to 85-90% immediately after injection of 125I-antithrombin III in the presence of heparin and returned to normal values within 30 min. This suggests that antithrombin III is transiently sequestered, possibly in trimolecular complexes consisting of antithrombin III, heparin and either lipases or other vascular bound proteins.

Elimination of high affinity heparin fractions and their anticoagulant and lipase activity.

High and low affinity heparin (HA and LA heparin) were prepared from commercial heparin by affinity chromatography to insolubilized antithrombin III. HA heparin was radiolabeled with 35S and subdivided by gel chromatography into high molecular weight (HMW, average 17,000-26,000 daltons), intermediate molecular weight (MMW, average 12,000-13,000 daltons), low molecular weight (LMW, average 5,000-7,000 daltons), and very low molecular weight (VLMW, average 4,600 daltons) fractions. The kinetics of lipolytic and anticoagulant activity and protein-bound radioactivity were studied after intravenous injection of these fractions. LA heparin failed to induce anticoagulant activity but released the hepatic triglyceride lipase (H-TGL) and lipoprotein lipase (LPL) activities normally. VLMW and LMW heparin failed to release both lipolytic enzymes and did not induce anticoagulant activity measurable by the activated partial thromboplastin time (APTT). A powerful anticoagulant effect was found in the anti-Xa assay, which disappeared according to a continuously concave curve in semilogarithmic plots, with elimination rates similar to those of the protein-bound radiolabel. The other heparin preparations induced all activities measured. Heparin anticoagulant activity estimated by the two assays disappeared following a convex curve, preceded by a rapid initial elimination phase in semilogarithmic plots. The disappearance rates of plasma protein-bound heparin radioactivity and heparin anticoagulant activity estimated by factor Xa inactivation were similar. Peak values of the two lipolytic activities were attained rapidly. H- TGL activity, as well as LPL activity, disappeared following convex curves in semilogarithmic plots, with elimination rates similar to those of plasma protein-bound heparin radioactivity. On the basis of these kinetics, we suggest that, after intravenous administration of heparin, the two lipolytic enzymes present in plasma are complexed with heparin, analogous to the heparin-antithrombin III complex. Finally, the kinetic data indicate that elimination of these activities is determined by the heparin part of the complexes, probably by removal of free heparin.

Binding of native and thrombin activated factor VIII to platelets.

The interaction of human Factor VIII with platelets has been studied using discontinuous albumin gradient centrifugation. When purified Factor VIII complex was mixed with released platelets about 10% of the recovered Factor VIII activity became associated with the platelets. In the corresponding experiment with thrombin-activated Factor VIII about half of the Factor VIII activity was bound to the platelets. This binding was reversible; dilution of the platelet suspension containing bound Factor VIII resulted in dissociation of part of the Factor VIII activity. With non-released platelets very little binding of Factor VIII activity occurred. A mechanism for the in vivo formation of the Factor X activator complex is suggested.

Effect of phospholipid on factor VIII coagulant activity and coagulant antigen.

Incubation of purified factor VIII/von Willebrand factor complex or plasma with certain phospholipid preparation induced a two to threefold increase in apparent factor VIII activity, while a slight decrease of factor VIII coagulant antigen was observed. Between six or eightfold activity increases occurred when 10-3 units/ml of thrombin was present during the incubation. When the phospholipid was added first and the thrombin added 30 minutes later a twofold increase in apparent factor VIII activity occurred during the first part and this activity was then increased threefold further after the addition of thrombin. In separate experiments using gel filtration on Sepharose 2B, association of factor VIII activity to phospholipid vesicles could be demonstrated. This phospholipid bound factor VIII could be activated by thrombin. The relationship between these observations and the formation of factor X activating complex is discussed.

Mechanisms of anticoagulant effects of some sulphated polysaccharides.

The anticoagulant activity of a partially reduced sulphated alginic acid, a partially reduced aminated and sulphated alginic acid and sulphated guaran have been studied. The anticoagulant activities in the APTT assay were 28, 39 and 70 IU/mg respectively. None showed any activity in anti-factor Xa assay. Studies on binding to Antithrombin III - Sepharose showed that sulphated guaran and a fraction of the aminated and sulphated alginic acid was bound, whereas no binding occurred with sulphated alginic acid. The inhibition of thrombin activity by these polysaccharides was studied in purified systems with or without added Antithrombin III, using both fibrinogen clotting and chromogenic peptide substrate assays. The two alginic acid preparations showed Antithrombin III-dependent inhibition of thrombin, whereas the sulphated guaran inhibits both by Antithrombin III-dependent and independent mechanisms.

Isolation and characterization of lipid-protein particles containing platelet factor 3 released from human platelets.

Lipid-protein particles with platelet factor 3 measured by the Stypven clotting-time test [Hardisty & Hutton (1966) Br. J. Haematol. 12, 764-776] have been isolated from platelet-release supernatant. Starting material was washed platelets, which were released by treatment with collagen. Purification of the particles from other components in the release material was accomplished by gel filtration on Sepharose CL-4B followed by affinity chromatography on poly-L-lysine-Sepharose CL-4B gel. Chemical characterization showed that the particles were composed of 40% protein, 42% phospholipids, 13% cholesterol and 5% triacylglycerols. The phospholipid composition was 38% phosphatidylcholine, 25% phosphatidylethanolamine, 9% phosphatidylserine, 2% phosphatidic acid and 26% sphingomyelin. No carbohydrate was detected. Electron-microscopic studies revealed the presence of membranous particles with diameters between 70 and 170 nm.