Effect of different penicillin derivatives on complement components in human serum

The effect of different penicillin derivatives on the human complement system has been studied in vitro. Four penicillins tested (benzylpenicillin, oxacillin, methicillin, azlocillin) were found to inactivate total hemolytic complement dose dependently. This effect is caused by direct inactivation of C2, C5 and one or more of the components C6-9 as well as by activation of the alternative pathway. At relatively high concentrations, penicillins induce a conformational change in C3 and C4, leading to the C3b-like or C4b-like forms of these molecules, respectively. Prominent effects on the complement system occur at penicillin concentrations exceeding those achieved in plasma under regular therapeutic use. However, a synergism of penicillins with drugs acting similarly on the complement system, such as iodinated radiographic contrast media, may be expected.

Natural antibodies against a polysaccharide (Bo) from sugar cane mediate its complement-activating effect

The interaction of a complement activating glucan from sugar cane (Bo) with immunoglobulins was studied. Bo precipitates a small fraction of IgG from human serum. In combination with this fraction, it activates complement by the classical pathway, not in its absence. Bo is adsorbed to and can be eluted from Sepharose containing covalently coupled IgG; it is not bound when the IgG-Sepharose is lacking the Bo-reactive IgG fraction. Bo-IgG complexes activate and fix C1. The binding of C1 to aggregated IgG is not inhibited by Bo. This is in contrast to the strong inhibition of C1 fixation by the Fc-binding protein A. It is concluded that normal human serum contains natural antibodies against Bo which form complement-activating immune complexes with Bo by binding it to their F(ab) region. The antibodies do not cross-react with dextran, a glucan from barley, nor with surface constituents of E. coli.

Effect of radiographic contrast media on complement components C3 and C4: generation of C3b-like C3 and C4b-like C4

Various water soluble iodinated radiographic contrast media (RCM) have been studied for their effect on complement components C3 and C4, purified and in serum. Hepatotropic RCM, and at higher concentration also some nephrotropic RCM, were found to exert a direct effect on purified C3 and C4. RCM treated human C3 and C4 are characterized by (a) loss of haemolytic function, (b) retention of activity in the formation of fluid phase C3 convertases and (c) an antigenic relationship to activated C3 and C4 (C3b and C4b, respectively). This direct alteration of C3 and C4 can probably also occur in serum since loss of haemolytic function is observed at similar RCM concentrations after incubation of serum and of purified components. It is concluded that RCM treated C3 and C4 represent altered forms of these components that resemble C4b and C3b in activity and conformation (C3b-like C3 and C4b-like C4). The alteration is probably caused by binding of RCM, exerting a mild denaturing effect. C3b-like C3 is a potential activator of the alternative pathway, and both C3b-like C3 and C4b-like C4 are known to be cleaved by serum inactivators. A possible pathological significance of the generation of C3b-like C3, C4b-like C4 and their split products remains to be evaluated.

Activation of the classical complement pathway by a polysaccharide from sugar cane

The effects of an immunostimulating polysaccharide, Bo, from sugar cane, on the complement system have been investigated. Bo, a glucan of about 10,000 mol wt, was found to activate complement in whole human and guinea pig serum in vitro by the classical pathway. Complement consumption was also demonstrated in guinea pigs upon intravenous injection. Specifically, C1 is activated, and C4 and C2, as well as C3, are consumed. The activation is prevented when Ca++ ions are chelated by ethyleneglycoltetraacetic acid, and when C1q is lacking. Hence, it does not rest on direct activation of C1s. Supplementation of C1q-deficient human serum with purified C1q restores the ability to be activated by Bo. The alternative pathway of complement is little if at all affected by the polysaccharide. The activation of C1 seems to be mediated by immune complex formation between Bo and naturally occurring immunoglobulins. Complement in sera from two severely hypogammaglobulinemic patients was not activated by Bo, but was made reactive by addition of purified human immunoglobulin G.

Chain structure of cobra venom factor from Naja naja and Naja haje venom

The chain structure of cobra venom factor, whether isolated from Naja naja venom (CVFn) or from Naja Haje (CVFh) is similar. Both homologous proteins are composed of three disulphide-linked chains (A, B, and C) with apparent molecular weights of 72,000, 54,000, and 27,000-35,000 for CVFn and 68,000, 51,000 and 30,000-32,000 CVFh. That all three polypeptides are integral parts of CVF was demonstrated by investigation of the chain pattern after partial reduction. Reduction with 1-2 mM dithiothreitol under non-denaturing conditions yielded free B-chain, together with an intermediate product composed of disulphide-linked A- and C-chains. The C-chain was heterogenous when investigated by electrophoresis in polyacrylamide slab gels in the presence of SDS. Similarly, isoelectric focusing of CVFn and CVFh showed a multiplicity of bands in the pH range 5.2-6.4. Limited tryptic digestion resulted primarily in the fragmentation of the B-chain. CVFh is much more sensitive to tryptic attack than CVFn. In all our preparations of CVFh a partial, trypsin-like fragmentation of the B-chain was detectable to various extents.

Role of histamine in the spasmogenic effect of the complement peptides C3a and C5a-desArg (classical anaphylatoxin)

The role of endogenous histamine in the spasmogenic effect of the complement-derived peptides C3a and C5a-desArg (isolated from yeast-activated hog serum) was studied in strips of terminal guinea-pig ileum. The effect of C3a is apparently histamine-independent; it neither induces histamine release from the test organ nor is its spasmogenic action inhibited by the H1-antihistaminics pheniramine and triprolidine, used in concentrations effective against histamine. However, endogenous histamine may be involved in the spasmogenic effect of C5a-desArg; when applied repeatedly C5a-desArg induces histamine release during its first and second application. Furthermore, both H1-antihistaminics inhibited C5a-desArg-induced contractions considerably, though less efficiently than those of added histamine.

Factors in cobra venoms affecting the complement system

Three constituents of cobra venoms are known to interact with complement: the "cobra venom factor" (CVF), a high-molecular-weight factor (H-CoF), and the "cobra inhibitor" (CI). CVF and CI act by forming complexes with certain complement components. In doing so, CVF replaces an endogenous component, C3b, and hence activates the alternative pathway and leads to C3 (and C5) consumption. In contrast, CI competes with essential complex formations of endogenous components and thus inhibits various reactions. Both, CVF and CI, are useful tools to study the biochemistry of complement and its pathophysiological involvements. The effect of H-CoF on complement has not yet been studied in detail.

Analysis of free stool porphyrins by high-performance liquid chromatography

The determination of stool porphyrins is necessary for the diagnosis of some porphyrias in clinical laboratories. Quantitative methods for the analysis of faeces for porphyrins are unpleasant and difficult to perform. An extraction and ion-pair reversed-phase high-performance liquid chromatographic procedure is described for the separation and determination of individual free stool porphyrins. The within-assay coefficients of variation range from 2 to 6%. A linear response curve is observed between 38 and 380 nmol/g for coproporphyrin I in dry stool The method can be applied to the routine analysis of free stool porphyrins in the clinical laboratory.

[Determination of triiodothyronine in serum with a heterologous enzyme immunoassay: results of a group survey]

This paper summarises the results of the evaluation of a heterologous enzyme immunoassay in antibody coated tubes for the determination of triiodothyronine (T3) by a group of 11 laboratories. The assay procedure is analogous to an established heterologous thyroxine enzyme immunoassay. The evaluation demonstrated that 1. the specificity of the assay and its analytical range between 0.46 and 9.2 nmol/l meet diagnostic requirements, 2. the intra- and interassay precision was in accordance with that commonly found in radio immunoassays, 3. the recovery of added T3 was between 90 and 103%, 4. the results agreed well with those of self-established radio immunoassays and were comparable with commercial RIA kits, 5. there was no interference by hyperbilirubinaemia or by high concentrations of bile acids, but interference can occur in very haemolytic and lipaemic samples. The great advantage of T3 enzyme immunoassays lies in the absence of restrictions and any authorization needed for working with radioactive substances.

Cluster-oriented discriminant analysis; taxonomic classification of the thyroid function

A computer assisted procedure for the diagnosis of thyroid diseases, based on seven clinical chemical parameters, is proposed. The population studied consisted of 592 consecutive outpatients with a tentative diagnosis of thyroid disease. Thyroxine, triiodothyronine, T3 uptake test, TSH before and after TRH application, its difference and thyroxine binding globulin have been determined. The patients were clinically examined and in each case a Tc-scintigram was obtained. As a first step, 20 biochemical patterns were defined by cluster analysis (pattern cognition). T check how good in grouping process was, linear discriminant analysis was applied after which the reclassification rates were very satisfactory. The clusters found corresponded well to the pathophysiological situations with some exceptions. As a second step, patients were assigned to these patterns by use of the derived discriminant functions (pattern recognition). The proposed method seems to have some advantages over other diagnostic models published hitherto.

Treatment of human complement components C4 and C3 with amines or chaotropic ions. Evidence of a functional and structural change that provides uncleaved C4 and C3 with properties of their soluble activated froms, C4b and C3b

Treatment of human components C4 and C3 with amines like hydrazine, ammonium hydroxide, and neutral ammonium salts or with chaotropic salts like KSCN and NaBr leads to complete loss of haemolytic activity. The pretreated components are, however, still active in formation of soluble C3 convertases. This activity pattern is reminiscent of the activities of C4 and C3 that have been activated by cleavage in the fluid phase. Indeed, the antigenic properties of pretreated C4 and C3 are similar to soluble C4b and C3b. The polypeptide chain structure of pretreated C4 and C3, is, however, identical to that of the untreated components when investigated by SDS gel electrophoresis. Pretreatment even reduces greatly the susceptibility of C4 to cleavage by C1s and of C3 to cleavage by classical and alternative pathway C3 convertases. Pretreated components have lost the ability to combine with EAC1 and EAC142, respectively; this fact explains their failure to exhibit haemolytic activity. In serum, pretreated C4 and C3 are cleaved in a manner similar to C4b and C3b. Amines and chaotropic ions cause the same functional and structural alterations, which are best explained by assumption of a conformational change. A similar transformation can also occur in C4 and C3 during preparation or storage.

Evaluation of a new valproic acid enzyme immunoassay and comparison with a capillary gas-chromatographic method

A new homogeneous immunoassay (EMIT) for valproic acid was evaluated. Besides testing the manual version of this enzyme immunoassay, we also developed two mechanized procedures for centrifugal analyzers (the CentrifiChem and the COBAS system), which take less time and are more precise than the manual method. Within-assay precision (CV) was 4.5% with the manual technique and 2% with the analyzers. Between-assay precision (CV) ranged from 4 to 13% for all three techniques. Accuracy of th manual method was checked by dilution and analytical recovery experiments. Our comparison of the EMIT results with those obtained by a comparison method (capillary gas chromatography) showed no significant difference. No interference from hemolysis, hyperbilirubinemia, or aliphatic amino acids was observed. At high concentrations of bile acids and with lipemic sera the analytical recovery rates decreased slightly, to 87% and 92%, respectively.

Evaluation of a new valproic acid enzyme immunoassay and comparison with a capillary gas-chromatographic method

A new homogeneous immunoassay (EMIT) for valproic acid was evaluated. Besides testing the manual version of this enzyme immunoassay, we also developed two mechanized procedures for centrifugal analyzers (the CentrifiChem and the COBAS system), which take less time and are more precise than the manual method. Within-assay precision (CV) was 4.5% with the manual technique and 2% with the analyzers. Between-assay precision (CV) ranged from 4 to 13% for all three techniques. Accuracy of th manual method was checked by dilution and analytical recovery experiments. Our comparison of the EMIT results with those obtained by a comparison method (capillary gas chromatography) showed no significant difference. No interference from hemolysis, hyperbilirubinemia, or aliphatic amino acids was observed. At high concentrations of bile acids and with lipemic sera the analytical recovery rates decreased slightly, to 87% and 92%, respectively.

Comparison of Naja n. naja and Naja h. haje cobra-venom factors: correlation between binding affinity for the fifth component of complement and mediation of its cleavage

Two cobra-venom factors, one from Naja n. naja (CVFn), the other from Naja h. haje venom (CVFh), have been purified and compared, functionally and structurally. Both factors interacted with human factors B and DS to form a potent C3 convertase, CVFBb. However, while the convertase formed with CVFn did also efficiently cleave C5, CVFhBb had very little C5-cleaving potency only, in particular when human C5 was used as substrate. Studies with agarose-linked CVF preparations indicated that CVFh has only low binding affinity for C5gp and C5hu whereas CVFn binds to both C5 species with much higher affinity. Since C5-binding (to CVF or to C3b) is a prerequisite for its cleavage by C3/C5 convertases, the difference in binding potency explains the different C5-cleaving activity of the two CVF preparations. When a ligand for C5, surface-fixed C3b, is present, CVFhBb is also capable of cleaving C5. The difference in activities of CVFn and CVFh is reflected in their different potency to interfere with immune haemolysis and in causing indirect lysis by their complexes with activated factor B. By gel chromatography of the CVF preparations in C5-containing medium, a stoichiometric complex CVFn-C5 (1 + 1) could be demonstrated. An analogous complex of C5 was neither found with CVFh, nor with C3hu or soluble C3bhu. Structural differences between CVFn and CVFh were revealed by immunodiffusion analysis and by polyacrylamide-gel electrophoresis in presence of SDS. The data available so far provide, however, no clear information about the structure of the C5 binding site.

Diagnosis of porphyrias by ion-pair high-performance liquid chromatography

Ion-pair reversed-phase high-performance liquid chromatography together with fluorescence detection is useful in the analysis of urinary porphyrin carboxylic acids. The sensitive and quantitative detection facilitates the clinical diagnosis of porphyrias. The method described permits the detection of porphyrins down to 0.1 ng directly from urine without laborious sample pre-treatment. A linear response curve was obtained from 0.2 up to 200 ng for coproporphyrin I. The within-assay correlation coefficients ranged from 2.5 to 10.1%. Recovery experiments gave an accuracy of 89-109%. The rapidity and simplicity of the method allows its application to the routine analysis of urinary porphyrins in the clinical laboratory.

Highly sensitive method for the quantitation of homovanillic acid in cerebrospinal fluid

Homovanillic acid in minute samples (50-100 microliters) of cerebrospinal fluid can be quantitated as its O-dimethylthiophosphinate methyl ester. The derivative is determined after glass capillary gas chromatography (GC) with high sensitivity by using a phosphorus-specific thermionic detector or by mass fragmentography, combined with a large sample volume split-splitless injector. The dimethylthiophosphinic esters show excellent stability against moisture and air. The precision of the overall procedure is 5.4% (GC) and 3.8% (GC-mass spectrometry). The method shows good linearity (r = 0.9999) over three orders of magnitude, from 500 pg to 500 ng. The lowest detectable concentration of homovanillic acid is 2-5 ng/ml. Concentrations of homovanillic acid determined in cerebrospinal fluid were 9.9-63.1 ng/ml (n = 10, mean = 30.9 ng/ml).

Is the determination of serum digoxin concentration useful for the diagnosis of digitalis toxicity?

In a prospective symptom-oriented study, patients with (n = 81) or without (n = 206) digoxin toxicity were not discernible on their serum digoxin concentration (SDC) because of a large overlap between toxic and non-toxic groups. There was, however, a significant difference between the mean values of the groups (p < 0,01). Serum creatinine, the presence or absence of ischemic heart disease, and/or chronic pulmonary heart disease were significantly different (both p < 0,025) between toxic and non-toxic groups. It is concluded that a decision on digitalis toxicity should be made by a synopsis of the influencing factors in the individual case. Dosage, serum creatinine and cardiac status seem to be the most important factors to be taken into account. Lack of agreement between SDC and digoxin effects could be demonstrated in differences in "T 1/2" between SDC and the normalisation of prolonged PQ-time after digoxin withdrawal. The inability of the SDC to describe all alterations important for digitalis effects and side effects seems to be that it does neither mirror the glycoside concentration at the receptor site, nor the changes of receptor affinity, nor the changes of (Na+ + K+)-ATPase activity.

Aggregation of leukocytes induced by the complement-derived peptides C3a and C5a and by three synthetic formyl-methionyl peptides

The highly purified hog complement peptides C3a and C5a and three formylmethionyl peptides induced dose-dependent aggregation of human leukocytes. For the effect Ca2+ and Mg2+ ions were required; in their absence the peptides induced specific desensitization. Human serum albumin (1 and 2%) reduced aggregation, whereas equivalent or even higher concentrations of plasma or serum were not inhibitory. SH reagents, protease inhibitors (N-tosyl-L-lysyl-chloromethyl ketone, N-tosyl-L-phenylalanyl-chloromethyl ketone), and colchicine also inhibited aggregation, whereas cytochalasin B greatly enhanced it. Dose-response studies under comparable conditions showed that aggregation is induced in similar dose ranges as chemotaxis. This suggests that complement-derived peptides generated in vivo may contribute to leukocyte accumulation in two ways, first by causing adherence of leukocytes to endothelium (equivalent to aggregation) and then by promoting migration to the inflammatory site.

Purification and partial amino acid sequence of classical anaphylatoxin from pig serum: identification with Des-Arg-C5a

Complement was activated in hog serum and the biologically active peptide(s) derived from the fifth component of complement were purified. Treatment of the serum with yeast, without any precautions to inhibit serum arginine carboxypeptidase, allowed the recovery of only one active fraction, the classical anaphylatoxin; it was identified as des-Arg-C5a. When hog serum was activated with yeast in the presence of 1M epsilon-aminohexanoic acid (inhibitor of arginine carboxypeptidase), two active C5-derived fractions were obtained, C5a and des-Arg-C5a. A partial amino acid sequence of the classical anaphylatoxin (19 N-terminal and 12 C-terminal amino acids) has been elaborated. With one exception it is identical with hog C5a as far as that structure is known (12 N-, 3 C-terminal amino acids). The only difference is the C-terminal region: arginine, present in C5a, is absent from des-Arg-C5a which ends with ... Asn-Ile-Gln-Leu-Gly-OH. The finding that des-Arg-C5a, virtually free of any significant contamination with C5a, has considerable spasmogenic activity demonstrates that it is the classical anaphylatoxin, and that for spasmogenic activity arginine as the C-terminal amino acid is not absolutely essential.

Biological activities of C5a and C5adesArg from hog serum

The complement-derived peptides C5a and C5adesArg (highly purified from yeast-activated hog serum) were both active in the following biological assays: in aggregation of human leukocytes (potency ratio for C5a:C5adesArg 3:1), in aggregation of guinea pig platelets (10:1), in chemotaxis of peritoneal rabbit leukocytes (10:1), and in contraction of isolated guinea pig ileum (1.4:1). The fact that C5adesArg preparations have 30 and 40% of the activity of C5a in leukocyte aggregation and smooth muscle contraction but only 10% of C5a chemotactic activity, clearly indicates that aggregation and spasmogenic activity are inherent properties of C5adesArg. Evidence that C5adesArg owns all activities studied is further given by the following findings: chromatographic separation of mixtures of C5a and C5adesArg results in the appearance of two peaks of spasmogenic activity; treatment of C5adesArg with carbopeptidase B does neither lead to release of detectable arginine nor abrogate any of the biological effects; treatment of C5a with carboxypeptidase B reduces the activities quantitatively to those of C5adesArg, and liberates the theoretically expected amount of arginine.

Activation of human lymphocyte subpopulations by protein A from Staphylococcus aureus bacteria

Cowan I strain Staphylococcus aureus bacteria were found to be mitogenic for human peripheral and cord blood lymphocytes. Experiments with lymphocyte supopulations otained by nylon wool filtration and/or E-rosette separation revealed that T-lymphocytes are the main target cells, whereas isolated B cells did not respond significantly. Further experiments suggested that B cells could be activated in the presence of mitomycin-treated T cells. Null cell-enriched lymphocyte suspensions could be stimulated by Con A but not by the bacteria or by PHA.

[Determination of thyroxine in serum by a heterogeneous enzyme immunoassay: results of a joint trial]

This paper describes the evaluation of a heterologous enzyme immunoassay for the determination of total thyroxine in serum by a group of seven clinical chemical laboratories. The test follows the principles of the enzyme linked immunosorbent assay (ELISA) and uses peroxidase as a marker. The evaluation of analytical reliability yielded the following results within the analytical range from 39 unto 322 nmol/l: 1. Within-batch precision ranged from 3.1 unto 10.4% (coefficient of variation) with single analyses. 2. Between-batch precision ranged from 3.7 unto 20.4% with single analyses. 3. Between-laboratories precision ranged from 5.4 unto 6.8%. 4. Pure thyroxine, added to serum or thyroxine-free serum, gave recoveries between 93 and 120%. 5. Analysis of control sera gave results essentially comparable to the assigned values based upon radioimmunoassays. 6. Analysis of 288 clinical sera gave slightly higher results by the enzyme immunoassay than by the analogous radioimmunoassay from the same manufacturer. 7. Comparison with other methods of analysis (radioimmunoassays, competitive protein ligand assays, hormonal iodine assay) yielded partly comparable, partly higher results. 8. Comparison with the homogenous enzyme immunoassay (EMIT) led to comparable results. 9. Interference due to hyperlipemia or hemolysis was not observed. 10. There might be an interference in hyperbilirubinaemic sera, due to an as yet unknown factor. With respect to practicability the ELISA-test compares favourably with the analogous solid phase radioimmunoassay. The main differences are the absence of radioactive material and a longer shelf-live of reagents. Following the manual procedure the time taken to perform the enzyme immunoassay is slightly longer than for the analogous radioimmunoassay.

Incompatibility between complement components C3 and C5 of guinea-pig and man, an indication of their interaction in C5 activation by classical and alternative C5 convertases

The use of heterologous combinations of guinea-pig and human complement components for titration of C5 with convertases of the alternative and classical pathway has been investigated. In addition to the known unfavourable combination of C2hu with C4gp partial incompatibilities were detected between heterologous C3 and C5 as well as between CZhu and C5gp. The incompatibility between heterologous C3 and C5 is of special interest since it indicates an interaction of these two non-enzymic components. Concomitant binding studies have demonstrated that a reduced efficiency of C5 convertases correlates with decreased binding affinity of surface-fixed C3b for C5 when heterologous components are offered. Hence, the present studies give further evidence that surface-bound C3b has the function of a co-factor which binds C5; this interaction is required for C5 activation via the classical as well as the alternative pathway, i.e. by the C3/C5 convertases C42 and C3bB.

Interference of propamidine with binding of the fifth component of complement to surface-fixed C3b, and with C5 activation

The effects of propamidine and their dose dependency, on utilization of the third and fifth complement components in immune haemolysis have been compared. While C3 utilization is not disturbed that of C5 is markedly inhibited by propamidine in concentrations as low as 0.5 mM. Both, binding of C5 to surface-fixed C3b and cleavage of C5 by convertases C42 and C3bBb, are also inhibited in the presence of propamidine. Since neither C3 cleavage by these enzymes nor even C5 cleavage by the cobra venom factor-supported convertase CFVBb is significantly reduced a general convertase-inhibiting effect of propamidine is ruled out. Rather the effect on utilization of C5 is the result of interference with binding of C5 is the result of interference with binding of C5 to C3b and hence impairment of its accessibility to the convertases. These findings thus further support the role of surface fixed C3b in C5 activation proposed earlier.

Multiple effects of a diamidine (propamidine) on complement activation

Propamidine, one of the diamidines used against infections with babesiae has inhibitory and enhancing effects on complement activation as assessed by immune haemolysis of sensitized sheep red cells. Utilization of C1 is powerfully, that of C3 weakly improved by propamidine while activation and/or fixation of C4, C5 and to a lesser degree of C8 and C9 are inhibited. At low concentrations of propamidine (less than 2 mM) the enhancing effects, at higher concentrations the inhibitory effects predominate. Inhibition is produced, in some cases certainly, in others likely, by interference of propamidine with binding properties of complement components. None of the complement enzymes, C1s, C42 or C3bBb was inhibited in its hydrolytic activity. The possible significance of propamidine actions is discussed.

Chemotactic effects of the complement-derived peptides C3a, C3ai and C5a (classical anaphylatoxin) on rabbit and guinea-pig polymorphonuclear leukocytes

The complement-derived peptides C3a, C3ai and C5a (= classical anaphylatoxin) were purified from hog serum and examined for chemotactic activity on rabbit and guinea-pig polymorphonuclear leukocytes (PMN) with the Boyden chamber technique (with filters of 3,0 micrometer pore size). When media containing albumin or serum were used all peptides induced chemotaxis of both cell species. Only C3a showed a pronounced species dependence in that it was much more active on rabbit than on guinea-pig PMN. No gross differences were found between the influence of 0.5% BSA and 10% heated (56 degree, 30 min) homologous serum added to the medium. In the absence of protein chemotaxis did not occur.

Quantitation of adrenaline and noradrenaline from human plasma by combined gas chromatography--high-resolution mass fragmentography

A gas chromatographic--high-resolution mass fragmentographic method for the simultaneous determination of adrenaline and noradrenaline from human plasma is presented. The catecholamines are separted by adsorption on alumina and converted by a selective, two-step procedure to the corresponding N-trifluoroacetyl-N-trimethylsilyl derivatives. The benzylic fragment C16H31O3Si3 (m/e 355.1568) of these derivatives is detected at a mass spectrometric resolving power of 5000. This high resolution detection was necessary to differentiate this fragment from others with the same nominal mass of 355 originating from the biological matrix and/or the bleeding from column and septum.

Performance of various mathematical methods for computer-aided processing of radioimmunoassay results

Interpolation and regression methods are available for computer aided determination of radioimmunological end results. We compared the performance of 6 algorithms (weighted and unweighted linear logit log regression; quadratic logit log regression, smoothing spline interpolation with a large and small smoothing factor, respectively, and polygonal interpolation and the manual curve fitting on the basis of three radioimmunoassays with different reference curve characteristics (digoxin, estriol, human chorionic somatomammotrophin (HCS)). Great store was set by the accuracy of the approximation at the intermediate points on the curve, i.e. those points that lie midway between two standard concentrations. These concentrations were obtained by weighing and inserted as unknown samples. In the case of digoxin and estriol the polygonal interpolation provided the best results, while the weighted logit log regression proved superior in the case of HCS.

Hydrolytic Activation of the Fifth Component of Complement (C5) by C3 Convertases Depends on its Binding to Surface-fixed C3b; Specific Interference with Binding, by Properdin, Factor B, or Propamidine, Leads to Inhibition of C5 Cleavage and Utilization

The C3 convertases of the classical and alternative pathways, and C3bBb (P) are capable of cleaving C5 only in the presence of C3b fixed to a solid surface (S-C3b) immediately subsequent to its release at that surface (e.g., on red cells, agarose, zymosan). The fact that fluid-phase and to a lesser degree soluble , attack C5 in the presence of S-C3b in EDTA medium, indicates that S-C3b interacts with and modulates the substrate, C5, rather than the convertase. In fact, reversible binding occurs between S-C3b and C5. Soluble C3b shows no indication of C5 binding, and does not support C5 cleavage by or C3b Bb. Cobra venom factor (CVF) which supports a B-dependent C5-cleaving enzyme, CVFBb, combines with C5 even in solution. While CVFBb cleaves C5 efficiently only when substrate (C5) and enzyme (Bb fragment) are bound to the same CVF molecule (free CVF added to a mixture of CVFBb and C5 is inhibitory), S-C3b has to be free of other ligands in order to function as a C5-binding site.

Absence of non-DFP-Inhibitable Activities of Factor D̄

Factor D is an active serine esterase capable of specifically cleaving factor B in the presence of C3b and thereby generating the active C3- and C5-convertase C3bBb. In the absence of C3b when nephritic factor (NF) or activated properdin (P̄) is available, D̄ appears to have a different function. Native C3, B, and NF or P̄ form a complex which, dependent on traces of D̄ has C3 cleaving, C3b generating activity. B seems to remain in this complex in its uncleaved form [Schreiber et al., J. Exp. Med. 142, 760 (1975)]. This suggested to us that D̄ might have other than hydrolytic activities, the more so as we found it difficult to completely block its functional activity in the generation of B-dependent enzymes by the esterase inhibitor, DFP.

Mass spectrometry of dimethylthiophosphinates of aromatic hydroxy compounds

The mass spectra of 20 differently substituted dimethylthiophosphinic esters of aromatic hydroxy compounds are presented. Fragmentation routes were investigated using high resolution mass measurements, decoupled metastable determinations and deuterium labelling. All compounds exhibited abundant molecular ions and typical phosphorus-containing ions. Characteristic elimination processes strongly dependent upon the respective type of substitution were observed. Due to their high stability, their great ease of formation and their good gas chromatographic properties these new types of derivatives are of special interest for establishing gas chromatography mass spectrometry profiles of acidic catecholamine metabolites.

A new function of the activated third component of complement: binding to C5, an essential step for C5 activation

Incubation of factor B, factor [unk]D, (properdin) and C3b—or of C1[unk]s, C4b and C2—with C3 and/or C5 in a fluid system leads to the generation of C3 cleaving activity while C5 remains unaffected. C5 can be cleaved—activated—when in addition to the enzyme-generating components of either pathway C3b is present which has been fixed to a solid surface immediately after its release from C3 by a surface-fixed enzyme. This has been demonstrated with three C3b-carrying solids: agarose to which C3b was fixed after cleavage of C3 by agarose-coupled trypsin (Ag-C3b), zymosan incubated with human serum (Z-C3b) and sheep red cells in the state EAC43. C3b fixed to these surfaces after release in the fluid phase by soluble enzymes does in general not support C5 cleavage. C3b species active in C5 cleaving processes differ from those inactive by having a newly discovered property: active C3b is capable of reversibly binding C5. Fluid C3 convertase C3b[unk]B cleaves C5 in the presence of surface-fixed active C3b also under conditions under which it cannot interact with the latter. This indicates that two C3b molecules having different functions are involved in this system, one which is incorporated in the enzyme complex and another which binds and thereby prepares C5 for cleavage. The binding requires a special configuration of C3b which is preserved only by fixation immediately after its generation from C3. Efficient binding is possible only when C3b is free of other ligands such as factor B or properdin; these components interfere with binding and cleavage of C5 when having access to active C3b. C5 cleavage by the convertase of the classical complement pathway, C42, appears to proceed by the same mechanism, i.e. free C42 per se attacks C5 when this is bound to active C3b. It is concluded from the results that C5-cleaving complement enzymes do not differ in composition from C3 convertases. The active C3b which is essential for C5 cleavage, and existent only on surfaces, serves to modulate the substrate configuration to make it accessible to the enzyme.

Indomethacin treatment of acute experimental pancreatitis in the rat

Indomethacin given orally or intramuscularly before or shortly after induction of acute sodium-taurocholate or olive-oil-induced pancreatitis in rats reduced the lethality. Neither the enzyme content of serum, ascites, and pancreatic tissue nor the damage to the organ itself were changed under the influence of indomethacin. Thus a modification of systemic effects of acute pancreatitis may be responsible for the beneficial effect of indomethacin.

[Cardiac effects of antikaliuretic diuretics-clinical and biochemical investigation (author's transl)]

Recently direct myocardial effects of antikaliuretic diuretics with respect to contractility parameters and prevention of digitalis-induced arrhythmias were published. In order to test the value of these reports we measured the effect of potassium-canrenoate and triamterene on cardiac output and on digitalis-induced arrhythmias in patients during diagnostic and the therapeutic flow directed right heart catheterization (Swan-Ganz) in our intensive care unit. In addition the influence of these drugs on (Na+ + K+)-ATPase and on (3H)g-strophanthin binding to human cardiac cell membranes was investigated to gain information on the mechanism of their action. Triamterene (100-200 mg p.o.) was without any effect on cardiac output, the same was found true for potassium-canrenoate given in a single dose (200-1000 mg intravenously). However, when applied in two doses (200 mg i.v. and 60 min later 400 mg i.v.), potassium-canrenoate increased cardiac output by 11 percent (p less than 0.05). Only in 2 out of 14 patients potassium-canrenoate (200-400 mg i.v.) suppressed digitalis-induced ventricular ectopic beats. Canrenone, the active metabolite of potassium-canrenoate displaces [(3H)]g-strophanthin from its binding sites in human cardiac cell membranes and inhibits (Na+ + K+)-ATPase activity. These in vitro effects were measured at the same concentrations as found in vivo after "therapeutical" doses. The effects of triamterene in this respect were found only in extremely high concentrations. Our results imply that canrenone has cardiac glycoside-like effects in human cardiac cell membranes.