Assessment by flow cytometry of peripheral blood leukocyte enzymatic activities in HIV patients

Leukocyte enzymatic activities are important in non-specific protection against bacterial infections, but traditional methods for the detection of intracellular enzymatic activities rely on cumbersome and complex assays. The development of specific substrates, which become fluorescent upon degradation of the biomolecule after its passive entry into intact cells, permits a simplified evaluation of leukocyte enzymatic activities. We have used this method to assess intracellular elastase, collagenase and cathepsin D activities of peripheral blood leukocytes using flow cytometry in a series of HIV patients and healthy controls. Monocytes displayed the highest enzymatic activities for the three proteases tested. In HIV-infected patients, the collagenase and cathepsin D activities of monocytes were significantly lower, whereas the elastase and cathepsin D activities of polymorphonuclear cells were elevated. Slightly higher elastase activity was detected in the lymphocytes of patients. This study demonstrates the feasibility of this new method for the study of intracytoplasmic enzymatic activities. Significant variations were observed in the peripheral blood of HIV-infected patients and different patterns were especially evident in monocytes and polymorphonuclear cells.

The major CD9 and CD81 molecular partner. Identification and characterization of the complexes

By associating with specific partner molecules and with each other, the tetraspanins are thought to assemble multimolecular complexes that may be especially relevant with respect to metastasis. We have previously identified a 135-kDa molecule (CD9P-1) as a major molecular partner of CD9 in cancer cell lines. This molecule was identified, after immunoaffinity purification and mass spectrometry analysis, as the protein encoded by the KIAA1436 gene and the human ortholog of a rat protein known as FPRP. Cross-linking experiments detected a complex of the size of CD9 plus CD9P-1, showing that these glycoproteins directly associate with each other, probably in the absence of any other molecule. The use of chimeric CD9/CD82 molecules revealed the role of the second half of CD9, comprising the large extracellular loop and the fourth transmembrane domain. CD9P-1 was also shown to form separate complexes with CD81 and with an unidentified 175-kDa molecule. It also associated with other tetraspanins under conditions maintaining tetraspanin/tetraspanin interactions. The identification of a protein strongly linked to the tetraspanin web and the production of a specific monoclonal antibody will help to further characterize the role of this "web" under physiological and pathological conditions.

Increases of IgA milk concentrations correlate with IgA2 increment

IgA, IgA1, and IgA2 concentrations were determined in 81 defatted human milk samples: colostrum (days 1-5, n = 42), transitional milk (days 6-14, n = 18) and mature milk (days 15-75, n = 21) by immunonephelometry. Correlations were found between total IgA levels and the concentrations of both IgA subclasses (P < 0.0001). The levels of the three molecules decreased over lactation with significant differences (P < 0.05) between colostrum and transitional milk levels and between colostrum and mature milk. Colostral IgA1 and IgA2 mean concentrations dropped respectively from 10.89 +/- 2.12 g/L, and 15.41 +/- 2.10 g/L to 1.83 +/- 0.73 g/L and 3.40 +/- 1.25 g/L in transitional milk reaching finally to 0.36 +/- 0.07 g/L and 0.27 +/- 0.06 g/L in mature milk. IgA2 concentrations were higher than those of IgA1 when the total IgA level was high. The IgA2 levels in colostrum could be an adaptation resistance of IgA to potentially harmful pathogens able to secrete IgA proteases and also a way to regulate colonization of the microflora in the newborn.

[Skin tests in the study of drug eruptions with suspected immuno-allergic mechanism]

Skin testing (patch tests, prick test and intradermal tests) with the suspected compound has been reported to be helpful in determining the cause of cutaneous adverse drug reactions (ADRs), but the value and specificity of these tests need to be determined. In a previously published study involving 72 patients, we observed positive results in 72% of the cases, in 43%, 24% and 67% in patch, prick and intradermal skin tests, respectively. The results of skin tests varied with the clinical type of cutaneous ADR, as a significantly higher number of positive patch tests was observed in maculopapular rashes (59%) than in urticarial reactions (13%) or in eythrodermic ADR (80%). The results of patch tests varied with the drug tested as frequent positive results were obtained with amoxicillin, pristinamycin, carbamazepine, pseudoephedrine, heparinoids... This study and the analysis of the literature support the value of careful sequential drug skin testing in establishing the cause of cutaneous ADR. Guidelines are proposed for performing these tests, and these include the use of appropriate negative control patients to avoid false-positive results, the determination of the relevance of positive patch tests, a contact sensitization to drug being able to elicite a positive result on patch tests with a preserved oral tolerance to the same drug. These tests have to be performed with a strict medical survey as they can induce a relapse of the cutaneous ADR.

Natural inhibitors of toxic phospholipases A(2)

Endogenous proteins isolated from the serum of snakes have been found to be natural inhibitors displaying anti-hemorrhagic, anti-neurotoxic or anti-myotoxic activity. Some of these proteins inhibit phospholipase A(2) (PLA(2)) activity. We review in brief here the properties, structure and classification of these PLA(2) inhibitors (PLIs), focusing in particular on the mechanism of neutralization of the toxic PLA(2)s by anti-neurotoxic PLIs. We also discuss: 1) the protection provided by these molecules against endogenous snake venom PLA(2)s; 2) their specificity for neurotoxic snake venom PLA(2)s (beta-neurotoxins) and non-toxic mammalian secreted sPLA(2)s; and 3) the domains of the inhibitor and PLA(2) potentially involved in the binding of these two molecules. Purified and characterized natural inhibitors of PLA(2)s may be used to develop more effective therapeutic strategies for dealing with snake envenomation. Moreover, the structural and, in some cases, functional similarity of natural inhibitors to various mammalian proteins suggests that these mammalian proteins may themselves behave as PLA(2) inhibitors. Thus, these proteins may have important physiological functions in regulating the activities of neurotoxic PLA(2) and non-toxic sPLA(2).

Basic residues of human group IIA phospholipase A2 are important for binding to factor Xa and prothrombinase inhibition comparison with other mammalian secreted phospholipases A2

Human secreted group IIA phospholipase A2 (hGIIA) was reported to inhibit prothrombinase activity because of binding to factor Xa. This study further shows that hGIIA and its catalytically inactive H48Q mutant prolong the lag time of thrombin generation in human platelet-rich plasma with similar efficiency, indicating that hGIIA exerts an anticoagulant effect independently of phospholipid hydrolysis under ex vivo conditions. Charge reversal of basic residues on the interfacial binding surface (IBS) of hGIIA leads to decreased ability to inhibit prothrombinase activity, which correlates with a reduced affinity for factor Xa, as determined by surface plasmon resonance. Mutation of other surface-exposed basic residues, hydrophobic residues on the IBS, and His48, does not affect the ability of hGIIA to inhibit prothrombinase activity and bind to factor Xa. Other basic, but not neutral or acidic, mammalian secreted phospholipases A2 (sPLA2s) exert a phospholipid-independent inhibitory effect on prothrombinase activity, suggesting that these basic sPLA2s also bind to factor Xa. In conclusion, this study demonstrates that the anticoagulant effect of hGIIA is independent of phospholipid hydrolysis and is based on its interaction with factor Xa, leading to prothrombinase inhibition, even under ex vivo conditions. This study also shows that such an interaction involves basic residues located on the IBS of hGIIA, and suggests that other basic mammalian sPLA2s may also inhibit blood coagulation by a similar mechanism to that described for hGIIA.

Interaction of the neurotoxic and nontoxic secretory phospholipases A2 with the crotoxin inhibitor from Crotalus serum

Crotalus durissus terrificus snakes possess a protein in their blood, named crotoxin inhibitor from Crotalus serum (CICS), which protects them against crotoxin, the main toxin of their venom. CICS neutralizes the lethal potency of crotoxin and inhibits its phospholipase A2 (PLA2) activity. The aim of the present study is to investigate the specificity of CICS towards snake venom neurotoxic PLA2s (beta-neurotoxins) and nontoxic mammalian PLA2s. This investigation shows that CICS does not affect the enzymatic activity of pancreatic and nonpancreatic PLA2s, bee venom PLA2 and Elapidae beta-neurotoxins but strongly inhibits the PLA2 activity of Viperidae beta-neurotoxins. Surface plasmon resonance and PAGE studies further demonstrated that CICS makes complexes with monomeric and multimeric Viperidae beta-neurotoxins but does not interact with nontoxic PLA2s. In the case of dimeric beta-neurotoxins from Viperidae venoms (crotoxin, Mojave toxin and CbICbII), which are made by the noncovalent association of a PLA2 with a nonenzymatic subunit, CICS does not react with the noncatalytic subunit, instead it binds tightly to the PLA2 subunit and induces the dissociation of the heterocomplex. In vitro assays performed with Torpedo synaptosomes showed a protective action of CICS against Viperidae beta-neurotoxins but not against other PLA2 neurotoxins, on primary and evoked liberation of acetylcholine. In conclusion, CICS is a specific PLA2 inhibitor of the beta-neurotoxins from the Viperidae family.

Discriminative immunophenotype of bronchoalveolar lavage CD4 lymphocytes in sarcoidosis

The diagnosis of pulmonary sarcoidosis relies in part on the observation of alveolar CD4+ lymphocytosis. However, this criterion is not fully discriminative because this anomaly is also found in other types of lung diseases. Among other possible distinctive criteria, we investigated the expression of lymphocyte-addressing molecules, which could differ according to the pathophysiology of lung diseases. We investigated CD103 (alpha(E)beta7 integrin, CD103-beta7), reported to be both expressed on intra-epithelial lymphocytes in mucosal areas, including bronchi, and possibly involved in the recruitment of alveolar lymphocytes. The expression of CD103 was examined on bronchoalveolar lavage lymphocytes from 93 consecutive patients, including 34 patients with CD4+ lymphocytosis. For all patients, the expression of CD19, CD3, CD4, CD8, CD57, LFA1, DR, and CD103 was assessed by flow cytometry. Sarcoidosis seemed remarkably characterized by the lack of CD103 expression on the predominant CD4+ subset. Statistically significant differences were found between patients with sarcoidosis, with other types of CD4+ lymphocytosis, and with other lung disorders in the CD103+ cell levels and in the CD103/CD4 ratio. Combined use of the CD4/CD8 ratio (> 2.5) and the CD103/CD4 ratio (< 0.31) to assess bronchoalveolar lavage lymphocytes is a promising new tool for the diagnosis of sarcoidosis.

[Activated protein C resistance and cardiolipin antibodies in leg ulcers]

BACKGROUND

We conducted a prospective study to determine the prevalence of activated protein C resistance and anticardiolipin antibodies in leg ulcers, whatever venous, arterial or arteriovenous.

PATIENTS AND METHODS

One hundred fifteen patients hospitalized for leg ulcers, without antiphospholipid syndrome were included. The vascular abnormalities were studied by clinical examination, Doppler, duplex Doppler and, when required, arteriography. Activated protein C resistance was isolated by a "classic" test (normalized APTT ratio in PCa presence or absence) and by a "second generation test" (by preliminary dilution with deficient factor V plasma). All patients with abnormal results on the second test were screened for the factor V Leiden (by PCR amplication with use of restriction enzymes). Anticardiolipin antibodies were investigated with an ELISA method with Harris standards as reference, in which the positive threshold was established at 20 units.

RESULTS

Among these 115 patients, 50 venous (43.5 p. 100), 23 arterial (20 p. 100), 42 arteriovenous (36.5 p. 100) leg ulcers were identified. Activated protein C resistance was isolated in 12 cases (10.4 p. 100) (heterozygous carriers): 7 venous ulcers, 3 arteriovenous, 2 arterial. Anticardiolipin antibodies were measured at significant level in 49 cases (42.6 p. 100): 21 venous ulcers, 18 arteriovenous, 10 arterial.

DISCUSSION

In this study, there was no statistical difference between the activated protein C resistance prevalence in leg ulcers when compared with Lorraine population (p=0.27). Factor V Leiden or anticardiolipin antibodies abnormalities were isolated in 56 cases (48.7 p. 100) without statistical difference between the 3 types of ulcers. Finally, the pathophysiology of venous, arterial and arteriovenous leg ulcers remains complex, suggesting several coagulation perturbations.

[Polyclonal T lymphocyte proliferation in drug lymphocyte activation test]

BACKGROUND

We examined the clonality of the specific T cell reaction activated with specific drug antigens in patients with a positive lymphocyte activation test.

PATIENTS AND METHODS

Ten patients were investigated. Their clinical features suggested drug allergy. Six weeks after a skin reaction, skin tests and lymphocyte activation tests were run. For each lymphocyte activation test, we explored the clonality of the T cell proliferation by examining the VJ rearrangement of the TCR gamma locus using polymerase chain reaction and denaturing gradient gel electrophoresis.

RESULTS

All samples gave positive lymphocyte activation tests proving in vitro polyclonal T cell proliferation in reaction to a drug. There was no difference in clonality between the pilot lymphocyte activation test and the lymphocyte activation test after stimulation with phytohemagglutinin or with the drug antigen.

DISCUSSION

Our findings show that in vitro T cell proliferation induced by a specific drug antigen as disclosed by the lymphocyte activation test is a polyclonal or oligoclonal cell proliferation. This lack of production of a preferential T clone in a T cell-mediated immune drug reaction implies that many T lymphocytes can recognize the antigen and be stimulated by the same drug.

A baboon syndrome induced by intravenous human immunoglobulins: report of a case and immunological analysis

Following the second series of intravenous human immunoglobulins (IVIg; 0.4 g/kg) prescribed to treat a sensorimotor polyneuritis, a 28-year-old woman developed pompholyx that recurred after each of the following monthly treatments with IVIg. During the administration of the 10th series, the patient developed a typical baboon syndrome. Immunohistochemical studies of a skin biopsy revealed an unexpected epidermal expression of P-selectin, usually expressed by endothelial cells. Patch, prick and intradermal tests performed with IVIg on the back, arms and buttocks gave negative results on immediate and delayed readings. IVIg were re-administered, with the informed consent of the patient, and induced a generalized maculopapular rash. This is the first reported case of baboon syndrome induced by IVIg. Although extensive skin testing was performed, all test sites remained negative. We wonder whether IVIg could reproduce immunological mechanisms involved in the 3 types of systemic contact dermatitis (pompholyx, baboon syndrome and maculopapular rash), including the epidermal expression of P-selectin.

Changes in the kappa-casein and beta-casein concentrations in human milk during lactation

A microparticle-enhanced nephelometric immunoassay was developed for kappa-casein quantification in human milk. Together with a previously reported beta-casein comparable immunoassay, it was applied to 862 samples milk, collected from 82 mothers, to investigate the changes in casein concentrations in human milk during the first twelve weeks of lactation. kappa-casein immunoassay is sensitive (detection limit in the reaction mixture, 0.02 mg/L) and can be performed in diluted milk, excluding any interference or sample pretreatment. It allowed the quantitation of kappa-casein over a large range of concentrations (0.14-4.56 g/L) with accuracy and precision (coefficients of variation from 3 to 10%). beta- and kappa-casein concentrations and percentages among milk total proteins increase between colostrum (2.6 g/L, 14.3% and 1.2 g/L, 6. 5%, respectively) and transitional milk (4.4 g/L, 33.2% and 1.3 g/L, 9.5%), decrease at different rates from the third to the eighth week, then remain stable at least up to the end of the third month of lactation (2.7 g/L, 25.3% and 0.9 g/L, 8.5%). The beta-casein/kappa-casein ratio is higher in colostrum (0.61) than in transitional and mature milk (0.30) and could be related to a better digestibility of colostrum casein micelles by the neonate during the first days of life.

C3/C4 concentration ratio reverses between colostrum and mature milk in human lactation

The levels of complement fractions C3 and C4 were assayed in human milk in a classic nephelometric assay adapted to this secretion. Concentrations of these molecules were measured in 667 milk samples obtained sequentially from 76 volunteer lactating mothers during the first 12 weeks of lactation. Immunonephelometry was performed using skimmed milk samples diluted 10 times and yielded reproducible (coefficients of variation in within- and between-run precision lower than 9% for C3 and than 14% for C4) and accurate (linear recovery in dilution-overloading assay) data. High concentrations (mean +/- SE) were found for C3 (199.32+/-16.35 mg/L) and C4 (113.42+/-11.16 mg/L) in colostrum samples (n = 159; days 1-5). A significant (P<0.001) and rapid decrease was observed in transitional milk samples (n = 198; days 6-14), containing 57.71+/-5.18 and 72.39+/-4.98 mg/L of C3 and C4, respectively. Stable lower levels were noted in mature milk samples (n = 310; days 15-84) at 30.36+/-1.57 mg/L for C3 (P<0.001) and 53.38+/-3.61 mg/L for C4 (P<0.05). The decrease rate was different for C3 and C4, yielding a reversal of the C3/C4 ratio between colostrum and more mature milk.

Immunological and nutritional composition of human milk in relation to prematurity and mother's parity during the first 2 weeks of lactation

BACKGROUND

To investigate the effect of prematurity and parity on the dynamics of the major immunologic and nutritional proteins of human milk over the first 2 weeks of lactation.

METHODS

Microparticle-enhanced nephelometric immunoassays were developed for the quantification of alpha-lactalbumin, beta-casein, serum albumin, lactoferrin, and lysozyme in human milk. These components, immunoglobulin A, and total proteins were assayed in 368 individual samples collected from 74 mothers.

RESULTS

The dynamics of the major immunologic and nutritional proteins in early lactation presented similar patterns in preterm and term human milks. In comparison with term milk, preterm milk was globally characterized by higher concentrations of immune proteins and lower concentrations of nutritive proteins. These differences were increased by the degree of prematurity, which, however, influenced the absolute and relative protein concentrations differently, depending on the stage of lactation. The protein composition of term milk was similar, whatever the mother's parity. Conversely, the influence of prematurity on the levels of milk proteins during the first days of lactation was even greater in primiparous mothers.

CONCLUSIONS

This precise description of the composition of preterm and term milk, regarding the main nutritional and immunologic proteins, confirms the influence of both prematurity and parity on milk components and demonstrates the combined effect of these two conditions.

Microparticle-enhanced nephelometric immunoassay of lactoferrin in human milk

A microparticle-enhanced nephelometric immunoassay was developed for lactoferrin quantitation in human milk. It is based on the nephelometric measurement of the light scattered during the competitive immuno-agglutination of a microparticle-lactoferrin conjugate with an antilactoferrin antiserum. This immunoassay is sensitive (detection limit in reaction mixture, 0.2 mg/L) and can be performed in diluted milk (1/3,000 in reaction mixture), excluding any interference or sample pretreatment. It allowed the quantification of lactoferrin on a large range of concentrations (0.675-21.6 g/L) with accuracy (linear recovery in dilution-overloading assay) and precision (within- and between-run coefficients of variation from 3% to 6%). Changes in the lactoferrin concentration of human milk during lactation were determined in 190 samples. The concentration and ratio of lactoferrin vs. total protein were found to be significantly higher in colostrum (5.9 g/l, 29%) than in transitional milk (2.9 g/L, 22%) or mature milk (2.5 g/L, 24%).

Generation of lyso-phospholipids from surfactant in acute lung injury is mediated by type-II phospholipase A2 and inhibited by a direct surfactant protein A-phospholipase A2 protein interaction

Lyso-phospholipids exert a major injurious effect on lung cell membranes during Acute Respiratory Distress Syndrome (ARDS), but the mechanisms leading to their in vivo generation are still unknown. Intratracheal administration of LPS to guinea pigs induced the secretion of type II secretory phospholipase A2 (sPLA2-II) accompanied by a marked increase in fatty acid and lyso-phosphatidylcholine (lyso-PC) levels in the bronchoalveolar lavage fluid (BALF). Administration of LY311727, a specific sPLA2-II inhibitor, reduced by 60% the mass of free fatty acid and lyso-PC content in BALF. Gas chromatography/mass spectrometry analysis revealed that palmitic acid and palmitoyl-2-lyso-PC were the predominant lipid derivatives released in BALF. A similar pattern was observed after the intratracheal administration of recombinant guinea pig (r-GP) sPLA2-II and was accompanied by a 50-60% loss of surfactant phospholipid content, suggesting that surfactant is a major lung target of sPLA2-II. In confirmation, r-GP sPLA2-II was able to hydrolyze surfactant phospholipids in vitro. This hydrolysis was inhibited by surfactant protein A (SP-A) through a direct and selective protein-protein interaction between SP-A and sPLA2-II. Hence, our study reports an in vivo direct causal relationship between sPLA2-II and early surfactant degradation and a new process of regulation for sPLA2-II activity. Anti-sPLA2-II strategy may represent a novel therapeutic approach in lung injury, such as ARDS.

Inhibition of prothrombinase by human secretory phospholipase A2 involves binding to factor Xa

Human group II secretory phospholipase A2 (hsPLA2) exhibits significant anticoagulant activity that does not require its enzymatic activity. We examined which coagulation factor was targeted by hsPLA2 and analyzed which region of the protein may be involved in this inhibition. Prothrombin time coagulation assays indicated that hsPLA2 did not inhibit activated factor V (FVa) activity, whereas activated factor X (FXa) one-stage coagulation assays suggested that FXa was inhibited. The inhibitory effect of hsPLA2 on prothrombinase activity of FXa, FV, phospholipids, and Ca2+ complex was markedly enhanced upon preincubation of hsPLA2 with FXa but not with FV. Prothrombinase activity was also strongly inhibited by hsPLA2 in the absence of PL. High concentrations of FVa in the prothrombinase generation assay reversed the inhibitory effect of hsPLA2. By using isothermal titration calorimetry, we demonstrated that hsPLA2 binds to FXa in solution with a 1:1 stoichiometry and a Kd of 230 nM. By using surface plasmon resonance we determined the rate constants, kon and koff, of the FXa/hsPLA2 interaction and analyzed the Ca2+ effect on these constants. When preincubated with FXa, synthetic peptides comprising residues 51-74 and 51-62 of hsPLA2 inhibited prothrombinase assays, providing evidence that this part of the molecule, which shares similarities with a region of FVa that binds to FXa, is likely involved in the anticoagulant interaction of hsPLA2 with FXa. In conclusion, we propose that residues 51-62 of hsPLA2 bind to FXa at a FVa-binding site and that hsPLA2 decreases the prothrombinase generation by preventing FXa.FVa complex formation.

Microparticle-enhanced nephelometric immunoassay of lysozyme in milk and other human body fluids

Quantitation of lysozyme in human milk was performed by a microparticle-enhanced nephelometric immunoassay based on the measurement of the light scattered during the competitive immunoagglutination of a microparticle-lysozyme conjugate with an anti-lysozyme antiserum. This immunoassay has a detection limit of 8 microg/L of reaction mixture and can be performed using diluted milk (1:6000, in reaction mixture), excluding sample pretreatment. Human milk lysozyme can be quantified over the concentration range 0.09-1.50 g/L, with within- and between-run coefficients of variation <5%. Changes in the lysozyme concentration of human milk during lactation were determined in 636 samples. Lysozyme concentrations (mean +/- SE) decreased from colostrum (0.36 +/- 0.02 g/L) to transitional milk (0.30 +/- 0.01 g/L) and mature milk during days 15-42 (0.30 +/- 0.01 g/L), then increased in the mature milk during days 43-56 (0.35 +/- 0.01 g/L) and especially during days 57-84 (0.83 +/- 0.05 g/L). The proportion of lysozyme contributing to total protein was found to rise during lactation and was as follows: colostrum (1.7%), transitional milk (2.3%), and mature milk from days 15-28 (2.7%), days 29-42 (3.1%), days 43-56 (3.8%), and days 57-84 (7.3%). The assay developed for milk was also suitable for the determination of lysozyme in other human body fluids.

Microparticle-enhanced nephelometric immunoassay of lysozyme in milk and other human body fluids

Quantitation of lysozyme in human milk was performed by a microparticle-enhanced nephelometric immunoassay based on the measurement of the light scattered during the competitive immunoagglutination of a microparticle–lysozyme conjugate with an anti-lysozyme antiserum. This immunoassay has a detection limit of 8 μg/L of reaction mixture and can be performed using diluted milk (1:6000, in reaction mixture), excluding sample pretreatment. Human milk lysozyme can be quantified over the concentration range 0.09–1.50 g/L, with within- and between-run coefficients of variation &lt;5%. Changes in the lysozyme concentration of human milk during lactation were determined in 636 samples. Lysozyme concentrations (mean ± SE) decreased from colostrum (0.36 ± 0.02 g/L) to transitional milk (0.30 ± 0.01 g/L) and mature milk during days 15–42 (0.30 ± 0.01 g/L), then increased in the mature milk during days 43–56 (0.35 ± 0.01 g/L) and especially during days 57–84 (0.83 ± 0.05 g/L). The proportion of lysozyme contributing to total protein was found to rise during lactation and was as follows: colostrum (1.7%), transitional milk (2.3%), and mature milk from days 15–28 (2.7%), days 29–42 (3.1%), days 43–56 (3.8%), and days 57–84 (7.3%). The assay developed for milk was also suitable for the determination of lysozyme in other human body fluids.

Purification of a 5-HT uptake inhibitor from the venom of Cerastes vipera

A protein that inhibits the re-uptake of 5-hydroxytryptamine into rat brain synaptosomes was isolated from the venom of the Sahara sand viper (Cerastes vipera) by gel filtration and reverse phase chromatography. It has a molecular weight of 13,739 Da and an IC50 of about 50 nM for blocking uptake of 3H-5-HT into rat brain synaptosomes. It also augmented the responses to 5-HT in a smooth muscle preparation. It has phospholipase A2 activity, but it has no lytic activity as measured by its inability to release lactate dehydrogenase from rat brain synaptosomes. Determination of the N-terminal sequence revealed a similarity with a phospholipase A2 previously isolated from Cerastes cerastes venom.

Apolipoprotein E, transthyretin and actin in the CSF of Alzheimer's patients: relation with the senile plaques and cytoskeleton biochemistry

We measured the levels of two beta-amyloid (Abeta)-sequestering proteins, apolipoprotein (Apo) E and transthyretin (TTR), in ventricular human cerebrospinal fluid (CSF) of Alzheimer's disease (AD) patients and controls in relation to brain histological findings. We also studied actin levels in CSF as a marker of the biochemical role of these two proteins in the cytoskeleton. We show that TTR levels in CSF were significantly decreased in AD patients compared to controls and negatively correlated with the senile plaque (SP) abundance. Moreover, actin levels were positively linked to TTR levels and increased in CSF samples of patients homozygous for the ApoE epsilon4-allele. We propose that TTR and ApoE4 may have competition in the aggregation of Abeta and its deposition in the SP of AD brain. The relationships between ApoE, TTR and actin could suggest a metabolic implication of ApoE genetics and TTR levels in cytoskeletal biochemistry which may be relevant to the pathogenesis of AD.

Ammodytin L, an inactive phospholipase A2 homologue with myotoxicity in mice, binds to the presynaptic acceptor of the beta-neurotoxic ammodytoxin C in Torpedo: an indication for a phospholipase A2 activity-independent mechanism of action of beta-neurotoxins in fish?

A Ser48 phospholipase A2-homologue, ammodytin L, which is myotoxic in mammals and devoid of any phospholipase A2 activity, completely inhibits the specific binding of the neurotoxic phospholipase A2, ammodytoxin C, to fish presynaptic membranes from Torpedo marmorata electric organ. In cross-linking experiments, 125I-ammodytin L labels the same membrane proteins as 125I-ammodytoxin C (70, 38.5-57.4 and 19.7 kDa). The formation of these adducts is completely prevented by the presence of ammodytoxin C but not of a non-toxic phospholipase A2, ammodytin I2. A chimeric phospholipase A2, constructed by associating the N-terminal half of ammodytoxin to the C-terminal half of ammodytin L, possesses a low, but significant phospholipase A2 activity, however it is not toxic to mice, probably due to abolition of the specific neuronal acceptor binding in mammals. Nevertheless, the chimeric phospholipase A2 is able to interact with the ammodytoxin acceptor in Torpedo marmorata electric organ. The existence of neuronal acceptors for ammodytin L and for the chimeric phospholipase A2 suggests that they may act as neurotoxins in fish. As ammodytin L does not possess any enzymatic activity it, therefore, appears to be an excellent tool to investigate the mechanism of action of beta-neurotoxins independently of their phospholipase A2 activity.