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Biomedical subjects

M Claeys

Publications and source records attributed to M Claeys.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1994

Postoperative pain treatment after cholecystectomy with epidural sufentanil at lumbar or thoracic level.

The difference in analgesic activity following lumbar (group I) or thoracic (group II) epidural administration of 50 micrograms sufentanil was studied after cholecystectomy. Fifteen patients in each group were evaluated for pain relief using a linear analog scale (LAS), heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peak expiratory flow (PEF), forced vital capacity (FVC), forced expiratory volume (FEV1) and arterial CO2 tension (PaCO2). In five additional patients in each group 75 micrograms sufentanil was injected for determination of serum levels. Pain scores were lower than three in both groups after 10 min, while mean pain scores remained below one from 20 min until 2 h following injection in both groups. Satisfactory pain relief lasted for 4 h. RR was significantly decreased from two until 360 min. in the lumbar group and from five until 120 min in the thoracic group. PaCO2 was raised in both groups only during the first hour. PEF and FVC were significantly improved compared to control 1, 2 and 4 h following injection. Serum sufentanil levels reached a maximum of 0.299 +/- 0.052 ng.ml-1 in the lumbar group and 0.377 +/- 0.076 ng.ml-1 in the thoracic group after 5 min. There were no significant differences between the two groups in the variables studied.

Aged↗
PubMed1994

Orbital myositis secondary to systemic lupus erythematosus.

A 41-year-old woman presented to our department with a 2-year history of unilateral painful swelling of the right eye. Clinical and laboratory evaluation ruled out endocrine, infectious and neoplastic disorders, and suggested the diagnosis of systemic lupus erythematosus. Echographic examination of the orbit and CT-scan revealed enlargement of the lateral and inferior rectus muscles at the right side, and enlarged medical rectus muscle at the left side. Despite the involvement of the extraocular muscles the patient did not have any ocular motility defects nor diplopia. The condition responded rapidly to systemic corticosteroids associated with immunosuppressive agents.

Acute Disease↗
PubMed1994

Acute retinal necrosis: a result of immune dysfunction? Report of a case with subacute evolution and relapses in a patient with impaired cellular immunity.

We report an atypical case of acute retinal necrosis (ARN) with a subacute course and relapses lasting for more than 4 years in an apparently immunocompetent 71-year-old female who had been followed for 4.5 years for recurrent retinochoroidal lesions with transient exudative retinal detachments and areas of consecutive chorioretinal atrophy. The diagnosis of varicella-zoster virus (VZV)-induced ARN was finally made on the basis of anterior granulomatous uveitis, typical retinal necrosis and the detection of anti-VZV antibodies in the aqueous humor. A widespread lumbar zoster dermatitis, cutaneous anergy and depressed in vitro lymphocyte activation indicated depressed cellular immunity. Absolute and relative numbers of B lymphocytes were increased. It is suspected that depressed cellular immunity and maintained B cell function might possibly be at the origin of ARN. The protracted course of ARN in this patient also suggests that the dysregulation of the immune system has probably existed for a long time.

Aged↗
PubMed1993

Posttranslational processing of proenkephalins and chromogranins/secretogranins.

Posttranslational processing of peptide-precursors is nowadays believed to play an important role in the functioning of neurons and endocrine cells. Both proenkephalins and chromogranins/secretogranins are considered as precursor molecules in these tissues, resulting in posttranslationally formed degradation products with potential biological activities. Among the proteins and peptides of neuronal and endocrine secretory granules, the enkephalins and enkephalin-containing peptides have been most extensively studied. The characterization of the post-translationally formed degradation products of the proenkephalins have enabled the understanding of their processing pathway. Chromogranins/secretogranins represent a group of acidic glycoproteins, contained within hormone storage granules. The biochemistry, biogenesis and molecular properties of these proteins have already been studied for 25 years. The chromogranins/secretogranins have a widespread distribution throughout the neuroendocrine system, the adrenal medullary chromaffin granules being the major source of these storage components. Recent data provide evidence for a precursor role for all members of the chromogranins/secretogranins family although also several other functions have been proposed. In this review, some of the methods applied to study proteolytic processing are described. In addition, the posttranslational processing of chromogranins/secretogranins and proenkephalins, especially the biochemical aspects, will be discussed and compared. Recent exciting developments on the generation and identification of potential physiologically active fragments will be covered.

Amino Acid Sequence↗
PubMed1993

Isolation of a dihydrobenzofuran lignan from South American dragon's blood (Croton spp.) as an inhibitor of cell proliferation.

Dragon's blood is a red viscous latex extracted from the cortex of various Croton spp. (Euphorbiaceae), most commonly Croton lechleri, Croton draconoides (or Croton palanostigma), and Croton erythrochilus. It is used in South American popular medicine for several purposes, including wound healing. Bioassay-guided fractionation of dragon's blood, using an in vitro test system for the stimulation of human umbilical vein endothelial cells, has resulted in the isolation of a dihydrobenzofuran lignan, 3',4-O-dimethylcedrusin or 4-O-methyldihydrodehydrodiconiferyl alcohol [2-(3',4'-dimethoxyphenyl)-3-hydroxymethyl-2,3-dihydro-7-methoxybenzo furan-5- propan-1-ol] [1] as the biologically active principle. A related compound, 4-O-methylcedrusin [2-(3',4'-dimethoxyphenyl)-3-hydroxymethyl-2,3-dihydro-7-hydroxybenzo furan-5- propan-1-ol] [2], and the alkaloid taspine [3], also isolated from dragon's blood, were not active in the same assay. A cell proliferation assay, measuring the incorporation of tritiated thymidine in endothelial cells, showed that compound 1 did not stimulate cell proliferation, but rather inhibited thymidine incorporation, while protecting cells against degradation in a starvation medium.

Alkaloids↗
PubMed1992

Antimicrobial peptides from Amaranthus caudatus seeds with sequence homology to the cysteine/glycine-rich domain of chitin-binding proteins.

Two antimicrobial peptides (Ac-AMP1 and Ac-AMP2) were isolated from seeds of amaranth (Amaranthus caudatus), and their physicochemical and biological properties were characterized. On the basis of fast atom bombardment mass spectroscopy, Ac-AMP1 and Ac-AMP2 have monoisotopic molecular masses of 3025 and 3181, respectively. Both proteins have pI values above 10. The amino acid sequence of Ac-AMP1 (29 residues) is identical to that of Ac-AMP2 (30 residues), except that the latter has 1 additional residue at the carboxyl terminus. The sequences are highly homologous to the cysteine/glycine-rich domain occurring in many chitin-binding proteins. Both Ac-AMP1 and Ac-AMP2 bind to chitin in a reversible way. Ac-AMP1 and Ac-AMP2 inhibit the growth of different plant pathogenic fungi at much lower doses than other known antifungal chitin-binding proteins. In addition, they show some activity on Gram-positive bacteria. The antimicrobial effect of Ac-AMP1 and Ac-AMP2 is strongly antagonized by cations.

Amino Acid Sequence↗
PubMed1992

Mass spectrometric characterization of bovine chromaffin granule peptides related to chromogranin B.

Peptides were extracted from the lysate of isolated bovine chromaffin granules. Following reversed-phase HPLC purification, the fractions were analyzed by FAB/MS. The presence of methionine-enkephalin and leucine-enkephalin was indicated by their chromatographic retention time and by the m/z value of their protonated molecules. As to five new peptides related to chromogranin B, prominent protonated molecules were observed at m/z 1746, 1446, 1333, 977 and 901. Trypsinolysis resulted in a common loss of a component with mass 545, pointing to a structural relationship and a common precursor molecule. The peptide showing a (M+H)+ ion at m/z 1746 could be identified as a novel, recently reported, neuropeptide derived from chromogranin B, whereas the other peptides with (M+H)+ ions at m/z 1446, 1333, 977 and 901 could be characterized as smaller fragments of this peptide. Peptidase-guided sequence analysis and MS/MS analysis provided sequence information.

Amino Acid Sequence↗
PubMed1992

External vibration interference of activity based rate responsive pacemakers.

The change of the pacing rate in response to external vibration interference was assessed in four rate responsive pacemakers with a piezoelectric crystal (Medtronic Activitrax 8403, Siemens Sensolog 3, Biotronik Ergos 01, and Medtronic Legend 8417) and one with an accelerometer (CPI Excel VR 1119). They were tested in the laboratory. External vibration was simulated in vitro by exposing the different pacemakers to a controlled sinusoidal vibration force generated by a Millar pressure vibration amplifier type MGM-30 (Millar Instruments, Inc., Houston, TX, USA). All pacemakers were programmed at standard settings. Two types of vibration forces were applied: (1) one with varying amplitude but with constant vibration frequency; and (2) one with varying frequency but with constant vibration amplitude. In this manner curves of pacing rate versus vibration forces versus vibration frequency were obtained. High vibration forces and low vibration frequencies were associated with the highest pacing rate response. In this experimental setting, the pacemaker based on the accelerometer principle apparently was the least sensitive to high frequency vibrations, which are known to be related to environmental interference. It also seemed more appropriately responsive in the lower frequency range, which is more appropriate for the detection of true physiological activity.

Acceleration↗
PubMed1991

[Anaphylaxis induced by exertion].

A 44-year-old man with a two-year history of episodes of exercise-related urticaria and facial angioedema was admitted to our department because of vascular collapse during an athletic activity. The diagnosis of exercise-induced anaphylaxis was established after excluding other causes of shock. This clinical syndrome was described recently; it consists of urticaria, local angioedema and/or cardiorespiratory failure following exercise. Factors possibly associated with or predisposing to attacks include personal and family histories of atopy, food ingestion and weather conditions. Not every effort evokes these reactions, indicating the presence of other, still unknown variables and therefore complicating the diagnosis because provocation tests often have false-negative results. With reference to this case, the clinical syndrome, its pathophysiology and its treatment are discussed.

Adult↗
PubMed1991

Comparison of the isolation of adducts of 2'-deoxycytidine and 2'-deoxyguanosine with phenylglycidyl ether by high-performance liquid chromatography on a reversed-phase column and a polystyrene-divinylbenzene column.

2'-Deoxycitidine (dCyd) and 2'-deoxyguanosine (dGuo) were subjected to reaction with phenylglycidyl ether (PGE) in methanol in order to study the formation of the corresponding 2'-deoxynucleoside adducts. Separation methods were developed on analytical and semi-preparative scales using high-performance liquid chromatography with photodiode-array detection on a reversed-phase column and on a polystyrene-divinylbenzene column. The use of the latter column was prompted by decomposition of the preparatively isolated dGuo-PGE adducts on the reversed-phase column. The use of a polystyrene-divinylbenzene column solved this problem and also revealed the presence of one more peak in both the dCyd- and dGuo-PGE reaction mixtures. The adducts of dCyd and dGuo were isolated on preparative reversed-phase and polystyrene-divinylbenzene columns and characterized by UV, fast atom bombardment mass and 360 MHz 1H NMR spectrometry. The adducts of dCyd were the diastereomers of N-3-(2-hydroxy-3-phenoxypropyl)-2'-deoxycytidine and N4-(2-hydroxy-3-phenoxypropyl)-2'-deoxycytidine whereas those of dGuo were the two diastereomers of N-7-(2-hydroxy-3-phenoxypropyl)-2'-deoxyguanosine and a third peak which appeared to be mainly N2-(2-hydroxy-3-phenoxypropyl)-2'-deoxyguanosine.

Chromatography, High Pressure Liquid↗
PubMed1991

Mass spectral characterization of C-glycosidic flavonoids isolated from a medicinal plant (Passiflora incarnata).

The four major C-glycosidic flavonoids isolated from Passiflora incarnata were identified as schaftoside, isoschaftoside, isovetexin-2''-O-glucopyranoside and isoorientin-2''-O-glucopyranoside on the basis of mass spectral and 13C NMR data. The daughter ion spectra of [M + H]+ ions of schaftoside and isoschaftoside showed differences for the [M + H - 104]+ ions, which could be rationalized by hydrogen bonding effects. In the negative-ion mode, pronounced differences were found for the [M - H - 90]- and [M - H - 120]- ions, formed by prevalent fragmentation in the C-6-linked sugar moiety. With respect to isovitexin-2''-O-beta-glucopyranoside and isoorientin-2''-O-beta-glucopyranoside, the daughter ion spectra of both the [M + H]+ and [M - H]- ions provided evidence for a 1----2 linkage in the diglucosidic moiety. Support for C-6 glucosylation was obtained by recording the daughter ion spectra of [M - H - 162]- ions, which were in good agreement with that obtained for [M - H]- ions of isovitexin.

Chromatography, High Pressure Liquid↗