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Biomedical subjects

M Claeys

Publications and source records attributed to M Claeys.

At least 37 records · Page 2Linked to original sources
PubMed1998

Complement-inhibiting cucurbitacin glycosides from Picria fel-terrae.

Four cucurbitacin glycosides were isolated from Picriafel-terrae and identified by MS and NMR spectroscopy as picfeltarraenin IA (1), picfeltarraenin IB (2), picfeltarraenin IV (4), and a new compound picfeltarraenin VI (3) (picfeltarraegenin I 3-O-beta-D-xylopyranoside). All four compounds acted as inhibitors on both the classical and alternative pathways of the complement system, with compound 3 exhibiting the highest inhibitory activity (IC50 29 +/- 2 microM and 21 +/- 1 microM, respectively). Compounds 1-4 showed no antiviral, antibacterial, or antifungal activities. Picfeltarraenin IA and IB were tested in an in vitro human tumor cell line panel, but displayed no cytotoxic activity.

Anti-Infective Agents↗
PubMed1998

Purification of toxic compounds from larvae of the gray fleshfly: the identification of paralysins.

Larval haemolymph of Neobellieria bullata (Insecta, Diptera) is highly toxic to adults of the same species: injection causes instant paralysis to death. Referring to their dramatic effect in adult insects the responsible compounds were designated paralysins. Two paralysins, soluble in organic solvents and heat stable, were chromatographically purified to homogeneity. They were identified by use of mass spectrometry and nuclear magnetic resonance respectively as beta-alanine-tyrosine (beta-Ala-Tyr) and as 3-hydroxy-kynurenine (3-HK). The quantities of beta-Ala-Tyr and 3-HK in the insect appear to increase steadily during larval development, with peak values prior to the pupal stage. These findings may contribute to a better understanding of some aspects of the process of insect metamorphosis. Orienting experiments in mammals suggest that both compounds, when injected intraspinally, are also neurotoxic to rats. In addition, cytotoxicity tests revealed that 3-HK, but not beta-Ala-Tyr is toxic to human neuroblastoma cells, rat primary cortex neurons as well as to rat glial cells.

Animals↗
PubMed1997

Mass spectrometric identification of phosphorylated vasostatin II, a chromogranin A-derived protein fragment (1-113).

Vasostatin II, an N-terminal chromogranin A-derived protein (CGA1-113), was purified from bovine chromaffin granule lysate and characterized by electrospray mass spectrometry (ES/MS) as being partially phosphorylated. The phosphorylation site was determined to be at the Ser81 position by mass spectrometric peptide mapping and tandem mass spectrometric analysis. This phosphorylation site is close to the processing site (...QKK78HSS(p)81...) yielding vasostatin I, an N-terminal CGA-derived peptide comprising residues 1-76, suggesting that phosphorylation at Ser81 is involved in the formation of vasostatin I in chromaffin cells.

Alkaline Phosphatase↗
PubMed1997

Isolation and identification of intact chromogranin A and two N-terminal processing products, vasostatin I and II, from bovine adrenal medulla chromaffin granules by chromatographic and mass spectrometric methods.

Chromogranin A (CGA) is the most abundant protein of the bovine adrenal medulla and plays an important role as precursor protein of several peptides that act as modulators for endocrine cell secretory activity. Furthermore, it is presumed to play a role in the targeting of peptide hormones and neurotransmitters to granules of the regulated pathway. However, its complete primary structure and proteolytic processing have not yet been identified. This study describes a rapid and efficient procedure for the high yield isolation of bovine CGA and its N-terminal processing products, vasostatin I and II. Using the lysate from bovine adrenal medulla chromaffin granules, the soluble proteins were purified by three consecutive HPLC steps, thereby avoiding the use of buffer solutions. The protein fractions were isolated and characterized by SDS-PAGE and Western blot analysis as well as by mass spectrometry. In the latter analysis, the efficiency of matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) was demonstrated, enabling the unequivocal and sensitive characterization of proteins from crude mixtures. Sufficient amounts of pure protein were obtained by the present procedure to form the basis for detailed structural studies by spectroscopic methods and X-ray crystallography.

Amino Acid Sequence↗
PubMed1997

Adenosine-1 active ligands: cirsimarin, a flavone glycoside from Microtea debilis.

Several plants collected through different approaches were screened on distinct receptors using ligand-binding studies as bioassay. Extracts of Microtea debilis showed high activity on adenosine A1 receptors. Bioassay-guided fractionation using ligand-binding studies resulted in the isolation of an adenosine A1 active ligand, cirsimarin (cirsimaritin 4'-O-glucoside). GTP did not influence the radioligand inhibition curve of cirsimarin, indicating that this compound is acting as an antagonist at the adenosine-A1 receptors. The use of this plant against "proteinuria" in traditional medicine in Suriname (South America) may be explained by the adenosine A1 antagonistic action of cirsimarin. A series of flavonoids was tested in the same assay, but they were less active. No structure-activity relationship could be observed.

Animals↗
PubMed1997

Complement-modulating properties of a kaempferol 7-O-rhamnosylsophoroside from the leaves of Morinda morindoides.

A kaempferol 7-O-rhamnosylsophoroside isolated from the leaves of Morinda morindoides showed dose-dependent complement-modulating properties towards both the classical (inhibiting effect) and alternative (activating effect) pathways of the complement system. Its structure was elucidated by chemical and spectroscopic methods as kaempferol 7-O-[alpha-L-rhamnopyranosyl-(1-->6)]-[beta-D-glucopyranosyl-(1-->2)]-be ta-D-glucopyranoside, a new natural product which was named morindaoside.

Carbohydrate Sequence↗
PubMed1996

Characterization of unstable intermediates and oxidized products formed during cyanogen bromide cleavage of peptides and proteins by electrospray mass spectrometry.

Products formed during cyanogen bromide (CNBr) digestion of alpha-endorphin, beta-endorphin, and horse heart myoglobin are examined using reversed-phase high-performance liquid chromatography and electrospray mass spectrometry. It is demonstrated that unstable intermediate reaction products may be formed, as well as oxidized products when the CNBr reaction is performed in 0.1% TFA in water/acetonitrile (6:4 v/v) and that, under other conditions commonly employed for the CNBr cleavage reaction, unstable intermediate products are also generated. The formation of the expected cleavage products is found to be improved by adjusting the hydrolysis conditions. The structure of the intermediate formed from alpha-endorphin is examined using electrospray mass spectrometry in combination with low-energy collision-induced dissociation and tandem mass spectrometry and is shown to have a cyclic hydrated homoserine iminolactone part. The results obtained in this study explain the formation of partially cleaved proteins in the case of Met-Thr-containing sequences, which likely have a cyclic hydrated homoserine iminolactone part instead of the putative homoserine residue.

Amino Acid Sequence↗
PubMed1996

Triterpenoid saponins from Maesa lanceolata.

Six new homologous triterpenoid saponins were isolated from the methanol extract of the leaves of Maesa lanceolata and characterized as 3 beta-O-[alpha-L-rhamnopyranosyl(1 --> 2)-beta-D-galactopyranosyl (1 --> 3)]-[beta-D-galactopyranosyl(1 --> 2)]-beta-D-glucuronopyranosides alpha-diol, 22 alpha-angeloyloxy-16 alpha-butanoyloxy-13 beta,28-oxydoolean-21 beta,28 alpha-diol, 16 alpha,22 alpha-diangeloyloxy-13 beta,28-oxydoolean-21 beta,-28 alpha-diol, 22 alpha-angeloyloxy-13 beta,28-oxydo-16 alpha-(2-methyl-butanoyloxy)-olean-21 beta,28 alpha-diol, 21 beta-acetoxy-22 alpha-angeloyloxy-13 beta,28-oxydo-16 alpha-propanoyloxyolean-28 alpha-ol, 21 beta-acetoxy-22 alpha-angeloyloxy-16 alpha-butanoyloxy-13 beta,28-oxydoolean-28 alpha-01. The structures were established on the basis of chemical and spectral evidence.

Carbohydrate Conformation↗
PubMed1996

Contact urticaria with systemic symptoms caused by bovine collagen in a hair conditioner.

A case of contact urticaria associated with a serous rhinitis, dyspnea, wheezing, and a dry cough appearing after the application of a hair conditioner on the scalp is reported. Prick test results with the conditioner diluted at 1/16 and 1/8 were strongly positive (+3), as well as a prick test (+3) with one component of the conditioner called "hydrolyzed proteins," which contained hydrolyzed bovine collagen and stearyl trimethylammonium chloride.

Adult↗
PubMed1996

In vitro biological activities of alkaloids from Cryptolepis sanguinolenta.

In our biological screening of higher plants, an aqueous and an 80% EtOH extract from the root bark of Cryptolepis sanguinolenta showed potent antibacterial, anticomplementary, and moderate antiviral activities, but no antifungal effect could be detected. Bioassay-guided fractionation of the 80% EtOH extract led to the isolation of three alkaloids: quindoline (1), hydroxycryptolepine (2), cryptolepine.HCl (3), and the corresponding base cryptolepine (4). All compounds strongly inhibited the growth of Gram-positive bacteria (MIC < or = 100 micrograms/ml) and showed a moderate (MIC = 125 or 250 micrograms/ml), a weak (MIC = 500 micrograms/ml), or no activity (MIC > 500 micrograms/ml) against selected Gram-negative bacteria. They also possessed a bactericidal effect depending on the bacterial strain. Compounds 1, 2 and 3 displayed a dose-dependent inhibitory effect on the classical pathway of the complement system while compounds 2 and 3 activated the alternative pathway, except for compound 1. Compound 3 was found to possess an antiherpetic activity. Compounds 1 and 4 showed no antiviral effect, but were quite cytotoxic in the antiviral test system down to a concentration of 1 microgram/ml.

Alkaloids↗
PubMed1996

Acute Luminal Gain after Stenting: Comparison of Gianturco-Roubin and Palmaz-Schatz Stents.

The Gianturco-Roubin stent has an open coil structure with a clamshell configuration and a relatively large distance between its transversely parallel struts. This stent design results in a low metallic surface area but may possibly also lead to more vessel recoil and less acute luminal gain than that obtained with the more rigid Palmaz-Schatz stent. The present study compares the acute angiographic results obtained with both stents. Quantitative coronary arteriography was performed in 77 patients in whom one of the following was successfully implanted: 1) a Palmaz-Schatz stent (n = 27), 2) a normally sized (n = 25) Gianturco-Roubin stent (n = 25), 3) a one-size oversized Gianturco-Roubin stent (n = 30). Diameter stenosis after stenting was greater in the patients with a normally sized Gianturco-Roubin stent (28 +/- 2%) than in those with a Palmaz-Schatz stent (18 +/- 1.2%, p < 0.05). This difference was in part attributed to a more important acute luminal loss due to elastic recoil and plaque protrusion with Gianturco-Roubin stents (25 +/- 2%) compared with Palmaz-Schatz stents (11 +/- 1.5%, p < 0.0001). However, in the patients with an oversized Gianturco-Roubin stent acute gain was similar to that obtained with Palmaz-Schatz stents (50 +/- 3.2% vs. 48 +/- 3%, p=0.68) and residual stenosis (20 +/- 2%) was less than that with a normally sized Gianturco-Roubin stent (p < 0.05). In the patients with an oversized Gianturco-Roubin stent the actual size during deployment (109 +/- 2.9% of the reference diameter) was smaller than the nominal size (122 +/- 1.7%). Thus, one-size oversizing of the Gianturco-Roubin stent corrects for the smaller actual than nominal diameter of this stent. It also compensates for the greater recoil observed with this stent and leads to similar acute diameter gain as that obtained with a Palmaz-Schatz stent without causing an excessive coronary artery stretching.

Journal Article↗
PubMed1996

Clinical outcome of patients with an uncomplicated myocardial infarction: effect of revascularization.

In 80 patients (pts) with an uncomplicated myocardial infarction (MI) the rate of major cardiac events (MACE) including cardiac death, non-fatal myocardial infarction and recurrent ischemia requiring hospitalization was prospectively assessed over a mean follow-up period of 17 +/- 9 months and related to clinical, angiographic and scintigraphic findings, the latter obtained from adenosine Tc-99m sestamibi SPECT imaging. Decision for revascularization was mainly based on angiographic data and was carried out in a total of 50 patients (angioplasty in 34 pts and cardiac surgery in 16 pts). The overall MACE rate was 24% with a mortality and myocardial infarction rate of 4% and 5%, respectively. Early (< 2 months) revascularization seemed to have a beneficial effect on clinical outcome as was suggested by the following findings: 1) Cardiac events (MACE) were not significantly different in patients with versus without revascularization (MACE 24% versus 23%) although the former constituted a subgroup at higher risk for ischemic events because of a more extensive coronary artery disease state. 2) In the subset of patients with at least one significant coronary artery stenosis the clinical outcome was significantly better in those who were revascularized than in those who underwent no revascularization (MACE 24% vs 47%, p < 0.05. Among a variety of factors, including the scintigraphic and angiographic extent of coronary artery disease and post-MI treatment strategy, multivariate analysis selected hypercholesterolemia (> 240 mg%) as the only independent predictor of MACE with a more than fourfold increase in risk for development of MACE. These data suggest that the natural history, especially the rate of recurrent ischemic events, can be favourably changed by an elective and early revascularization, strategically oriented by the results of the angio-graphic study. Furthermore, our data emphasized the deleterious role of hypercholesterolemia on clinical outcome in patients with a recent MI.

Angioplasty, Balloon, Coronary↗
PubMed1995

Approach to the large-scale preparation of highly pure phosphatidylserine from bovine brain.

An approach to the large-scale preparation of highly pure phosphatidylserine from bovine brain is described in this paper. The method is based on (i) the separation of phosphatidylserine from phosphatidylinositol in bovine brain extract by preparative aminopropyl normal-phase high-performance liquid chromatography using methanol-1 M phosphoric acid (90:10, v/v) as mobile phase and (ii) further purification of phosphatidylserine by anion-exchange chromatography. The main advantage of this approach is that polyunsaturated acid-containing molecular species of brain phosphatidylserine are not lost in the preparation procedure.

Animals↗
PubMed1995

Vasostatins, N-terminal products of chromogranin A, are released from the stimulated calf spleen in vitro.

Vasostatins are the N-terminal chromogranin A peptides 7 approximately 22 kDa. They have been shown to be present in several endocrine tissues and exhibit vasoinhibitory activity in vitro. In a first series of experiments, we investigated the presence and subcellular localization of vasostatins in the bovine splenic nerve. Experimental results, obtained using gradient centrifugation, showed that noradrenaline was enriched 25-fold in the large dense core vesicle fraction, compared with the original homogenate. In the latter fraction, the 7 and 18 kDa peptides were observed following immunodetection with antiserum to chromogranin A1-40 and laser densitometric scanning revealed these two fragments as the major N-terminal fragments. Subsequently, we examined the release of the 7 and 18 kDa peptides from perfused calf spleen during veratridine (20 microM) or 1,1-dimethyl-4-phenylpiperazinium iodide (20 microM) stimulation. In the prestimulation samples, we were not able to detect these peptides, however, following stimulation, the 7 and 18 kDa chromogranin A fragments became apparent. The vasostatin-immunoreactivity, in both bovine chromaffin granule lysate and calf spleen perfusate, elutes at the same retention time on reversed-phase high performance liquid chromatography. The present study demonstrated that vasostatins are present in the large dense core vesicles of sympathetic axons and are released from the nerve terminals in response to stimulation. The release of vasostatins from sympathetic nerves in the spleen suggest an in vivo function for N-terminal chromogranin A products of neuronal origin.

Adrenergic Fibers↗
PubMed1994

Characterization and differentiation of diglycosyl flavonoids by positive ion fast atom bombardment and tandem mass spectrometry.

This study shows that fast atom bombardment (FAB) in combination with collisional activation and tandem mass spectrometric techniques is useful for the characterization of, and the differentiation between, O-diglycosyl, O-C-diglycosyl and di-C-glycosyl flavonoids. A quick differentiation between the three types of glycosyl flavonoids is possible by simply examining FAB mass spectra. Low-energy product ion spectra of [M+H]+ ions have been used for determining the carbohydrate sequence in O-diglycosyl flavonoids and characterizing the terminal monosaccharide in O-C-diglycosyl flavonoids. The data obtained for per-O-deuterated precursor ion species of O-diglycosyl flavonoids indicate that O-linked hydrogen atoms are involved in the formation of Yn+ ions. High-energy product ion spectra of [M+H]+ ions enable further characterization and differentiation of isomeric di-6,8-C-glycosides.

Carbohydrate Sequence↗
PubMed1994

Fragmentation characteristics of neuropeptides related to chromogranin B and proenkephalin B using fast atom bombardment and collision-induced dissociation.

This study deals with the mass spectral characterization of selected neuropeptides related to chromogranin B and proenkephalin B precursor proteins using fast atom bombardment (FAB) ionization in combination with low- and high-energy collision-induced dissociation. Fragmentation pathways were investigated using linked scan and tandem mass spectrometric techniques. First-order FAB mass spectra and product ion spectra of [M+H]+ ions are discussed and analysed for structure-specific information. In the high-energy product ion spectra, abundant y and c ions are found to be indicative of the presence of proline and threonine residues, respectively. With regard to side chain specific ions, diagnostic d and w ions are found, which support the presence of leucine, glutamic acid and glutamine at specific positions in the amino acid sequence.

Amino Acid Sequence↗
PubMed1994

Antibacterial and molluscicidal phenolic acids from Spondias mombin.

Spondias mombin L. (Anacardiaceae), used in traditional medicine because of its antimicrobial properties, was found to contain a series of 6-alkenyl-salicylic acids. They were isolated from the ethanolic extract of leaves and stems of Spondias mombin by a combination of chromatographic methods. Their structure was determined by NMR and MS techniques as (17:3), (17:2) and (17:1) pelandjuaic acid [or 6-(8'Z,11'Z,14'Z-heptadecatrienyl)-salicylic acid, 6-(8'Z,11'Z-heptadecadienyl)-salicylic acid, and 6-(10'Z-heptadecenyl)-salicylic acid, respectively], 6-(12'Z-non-adecenyl)-salicylic acid, and 6-(15'Z-heneicosenyl)-salicylic acid, the two last compounds being new ones. These phenolic acids were shown to have a pronounced antibacterial effect against Bacillus cereus, Streptococcus pyogenes, and Mycobacterium fortuitum (minimal bactericidal concentration in a concentration range of 3-25 micrograms/ml), and a molluscicidal effect against the snail Biomphalaria glabrata, an intermediate host in the schistosome life cycle. Because of their high molluscicidal activity (LC90 down to 1-3 ppm), these long-chain salicylic acid derivatives may be important tools in the prevention of schistosomiasis.

Animals↗