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M A Abdallah

Publications and source records attributed to M A Abdallah.

At least 37 records · Page 2Linked to original sources
PubMed1996

Specific photoaffinity labelling of a ferripyoverdin outer membrane receptor of Pseudomonas aeruginosa.

In order to identify and characterize the receptors involved in pyoverdin-mediated iron transport in Pseudomonas aeruginosa ATCC 15692, a photoactivatable siderophore has been synthesized. In the dark, this probe is stable and is able to promote iron transport at the same rate as the native pyoverdin. Under irradiation at 312 nm, the molecule is photodecomposed and a clear inhibition of the iron transport is observed. With the radioactive form of this photoactivatable probe, we were able to visualize on a SDS-PAGE gel a labelled protein of approximately 90 kDa molecular mass, which is very likely the FpvA receptor or a yet unknown pyoverdin receptor.

Affinity Labels↗
PubMed1995

Circulating immune complexes in various forms of Behçet's disease.

BACKGROUND: The etiology of Behçet's disease (BD) is uncertain but there is strong evidence that the immune system is implicated in its pathogenesis. METHODS: We assessed circulating immune complexes (CIC) in peripheral blood of 34 patients with BD, forming eight clinical groups, using a laser nephelometer to obtain more insight in the pathogenesis of different clinical forms of BD. Twenty healthy controls and eight patients with recurrent oral ulcerations were also included in the study. RESULTS: Levels of CIC were significantly higher in patients (1.83 +/- 0.93 microgram/mL) than in controls (0.84 +/- 0.51 microgram/mL; P < 0.001). High titers were found in the groups of patients with erythema nodosum (3.14 +/- 0.44 microgram/mL), neurologic manifestations (2.9 +/- 0.58 microgram/mL), and ocular manifestations (2.34 +/- 0.93 microgram/mL). Compared to patients with recurrent oral ulcerations (1.91 +/- 0.77 microgram/mL), the mean value of CIC in patients with BD did not differ significantly, but the groups of patients having erythema nodosum, positive pathergy, and neurologic manifestations had significantly higher levels (P < 0.05) and the group of patients at the mild end of the spectrum (group 8) had a significantly lower level (1.09 +/- 0.41 microgram/mL) (P < 0.05). Only the groups having erythema nodosum, positive pathergy, and neurologic manifestations had significantly higher levels of CIC when compared to other groups lacking these clinical features, whereas group 8 had a significantly lower level (P < 0.05) when compared to all other groups. CONCLUSION: Our results show that CIC may be involved in the pathogenesis of BD, especially in those clinical forms of the disease with erythema nodosum, neurologic manifestations, and ocular manifestations. Patients at the mild end of the BD spectrum do not show significant changes in CIC levels compared to healthy control subjects. We can, therefore, suggest that in BD CIC may be implicated more in the pathogenesis of some features than of others.

Adolescent↗
PubMed1994

Nitrogen Assimilation: Optimization of N-Labelled Azoverdin Production by Azomonas macrocytogenes ATCC 12334.

The effects of various nitrogen sources and of the cultivation time on the biosynthesis of N-labelled azoverdin were studied in batch cultures of Azomonas macrocytogenes ATCC 12334. Growth for 48 h in the presence of ammonium sulfate (0.2 g/liter) resulted in 95% labelling of azoverdin with N. A growth-related synthesis of azoverdin, under both nitrogen-fixing and ammonium-assimilating conditions, was observed.

Journal Article↗
PubMed1994

Iron release from transferrin by pyoverdin and elastase from Pseudomonas aeruginosa.

Pseudomonas aeruginosa produces the siderophores pyoverdin and pyochelin as well as receptors for siderophores in response to iron deprivation. Previously, it has been shown in vitro that at neutral pH purified pyoverdin acquires iron from transferrin only in the presence of P. aeruginosa elastase (LasB), which proteolytically degrades transferrin. We constructed a LasB-negative mutant, PAO1E, by insertional mutagenesis to investigate whether this mutant differs in growth from the parental strain PAO1 in an iron-depleted medium supplemented with transferrin or human serum. PAO1 and PAO1E did not differ in growth with 1.25 microM Fe2-transferrin as the only iron source. Urea gel electrophoresis indicated iron release from intact transferrin during the logarithmic growth phase of PAO1 and PAO1E. A total of 333 microM LasB was synthesized from PAO1 after onset of stationary-phase growth. Quantification of pyoverdin by spectroscopy revealed that up to 900 microM pyroverdin was produced during growth of the strains in medium supplemented with Fe2-transferrin or 10% human serum. Incubation of Fe2-transferrin and purified pyoverdin in concentrations similar to those found in the culture supernatant resulted in release iron from transferrin after 10 h at 37 degrees C. However, LasB significantly enhanced the rate constant for iron acquisition of pyoverdin from transferrin. We conclude that P. aeruginosa can use transferrin as an iron source without further need of LasB or pH changes. This is further supported by experiments with P. aeruginosa K437, which has a defective iron uptake system, and its LasB-negative mutant, K437E. Though K437 and K437E did not differ in growth with Fe2-transferrin as the only iron source, their growth was significantly reduced relative to that of PAO1 and PAO1E.

Bacterial Proteins↗
PubMed1992

Antioxidant and free radical scavenging activities of the iron chelators pyoverdin and hydroxypyrid-4-ones in iron-loaded hepatocyte cultures: comparison of their mechanism of protection with that of desferrioxamine.

The protective effect on iron-supplemented hepatocyte cultures of three iron chelators, pyoverdin Pa and hydroxypyrid-4-one derivatives CP20 and CP22, was compared to that of the widely known desferrioxamine B (Desferal:DFO), on the basis of two criteria: (a) their effectiveness in inhibiting free malondialdehyde (MDA) production as an index of iron-induced lipid peroxidation; and (b) their ability to reduce intracellular enzyme leakage. In view of these two markers of iron toxicity, the protective effect of these chelators was classified as follows: DFO > CP20 > or = CP22 > Pa. The mechanism of cellular protection was elucidated by investigating both the iron-chelating activity and the free radical scavenging property of these agents. As concerns the iron chelation, DFO and Pa exerted the same rank order as for cytoprotection (DFO > Pa). The free radical scavenging property toward hydroxyl radical .OH and peroxyl radical ROO. was investigated in a cell-free experimental model. The two siderophores, DFO and Pa, appeared to have a lower antiradical activity toward .OH than hydroxypyrid-4-one CP22. This .OH scavenging activity was classified as follows: CP22 >> Pa > DFO. Moreover, the chelators exhibited for the quenching of ROO. the same order of effectiveness as that observed for cellular protection: DFO > CP20 > or = CP22 > Pa. These data indicate that, in addition to the iron-chelating activity which represents the most important property for determining the protection capacity of these iron chelators, their free radical scavenging ability also must be taken into account. This direct demonstration of a strong association between the free radical scavenging activity and the protective effect of iron chelators further increases the prospects for the development and clinical applications of new oral chelating drugs.

Animals↗
PubMed1991

Pathological and immunopathological changes in albino mice experimentally infected with Hymenolepis nana.

The pathological and immunopathological effects of H. nana on experimentally infected albino mice were studied, sacrificed one, three and five months post egg inoculation. The results showed that most of the mice had diarrhoea, loss of appetite and were inactive. On the other hand, the liver and spleen showed some pathological changes and cysticercoids were seen particularly in the liver. The kidneys showed cloudy swelling (3/90). The brain showed oedema (15/90) and glyosis (15/90). Intestinal atrophy and ulceration were very marked (30/90) with negative reaction to PAS and Alcian blue stain. Cysticercoids were seen in intestinal villi. The immunoglobulins in sections of the S. intestine changed from moderate to negative (IgA) or to mild (IgM) or from mild to marked (IgG). The whole results were discussed.

Animals↗
PubMed1990

Bacterial siderophores: structures of pyoverdins Pt, siderophores of Pseudomonas tolaasii NCPPB 2192, and pyoverdins Pf, siderophores of Pseudomonas fluorescens CCM 2798. Identification of an unusual natural amino acid.

Pyoverdins were isolated and characterized respectively from the cultures of Pseudomonas tolaasii NCPPB 2192 (pyoverdins Pt, Pt A, and Pt B) and Pseudomonas fluorescens CCM 2798 (Pyoverdins Pf/1, Pf/2, Pf, Pf/3/1, and Pf/3/2) each grown in iron-deficient conditions. Their structures were established by using FAB-MS, NMR, and CD techniques. These siderophores are chromopeptides, and all but one (pyoverdin Pf/3/3) possess at the N-terminal end of their peptide chain the same chromophore that has been reported in pyoverdin Pa from Pseudomonas aeruginosa ATCC 15692 [Wendenbaum, S., Demange, P., Dell, A., Meyer, J. M., & Abdallah, M. A. (1983) Tetrahedron Lett. 24, 4877-4880] and pseudobactin B 10 from Pseudomonas B10 [Teintze, M., Hossain, M. B., Barnes, C. L., Leong, J., & Van der Helm, D. (1981) Biochemistry 20, 6446-6457] which is derived from 2,3-diamino-6,7-dihydroxyquinoline. In pyoverdins Pt this chromophore is bound to a linear peptide chain D-Ser-L-Lys-L-Ser-D-Ser-L-Thr-D-Ser-L-OHOrn-L-Thr-D-Ser-D-OHOrn (cyclic) which has its C-terminal end blocked by cyclic D-N delta-hydroxyornithine. In pyoverdins Pf, the peptide chain is also linear, SerCTHPMD-Gly-L-Ser-D-threo-OHAsp-L-Ala-Gly-D-Ala-Gly-L-O HOrn(cyclic), and contains an unusual natural amino acid which is the result of the condensation of 1 mol of serine and 1 mol of 2,4-diaminobutyric acid, forming a cyclic amidine. The pyoverdins Pt differ only in substituent bound to the nitrogen on C-3 of the chromophore, which is succinic acid in pyoverdin Pt A, succinamide in pyoverdin Pt, and alpha-ketoglutaric acid bound to the chromophore by its C-5 carbon atom in pyoverdin Pt B. Similarly, pyoverdin Pf/1, pyoverdin Pf/2, pyoverdin Pf (the major compound), and pyoverdin Pf/3/2 are substituted respectively by L-malic acid, succinic acid, L-malic amide, and succinamide. Pyoverdin Pf/3/3 has the same chromophore as azotobactin, the peptidic siderophore of Azotobacter vinelandii. These pyoverdins are very similar to pseudobactin B 10, the siderophore of Pseudomonas B10: they are linear peptides containing three bidentate groups strongly chelating Fe(III) and blocked at their N-terminal end by the catecholic chromophore and at their C-terminal end by cyclic N delta-hydroxyornithine. They differ therefore from other pyoverdins such as those from P. aeruginosa ATCC 15692 which contain a partly cyclic peptide [Briskot, G., Taraz, K., & Budzikiewicz, H. (1989) Liebigs Ann. Chem., 375-384].

Amino Acid Sequence↗
PubMed1989

Trypanosoma acomys (Wenyon, 1909): reproductive forms and course of parasitemia in the natural host Acomys cahirinus (Desmarest, 1819).

Trypanosoma acomys (Stercoraria, Trypanosomatidae) was studied in the laboratory-bred spiny mouse Acomys cahirinus. Only trypomastigotes were found in peripheral blood, whereas the thymus of experimentally infected A. cahirinus showed amastigote syncytial reproductive forms whose nuclei of nuclei ranged from 2 to 128. These reproductive forms were detected 9-10 days after the i.p. injection of spiny mice with trypanosomes obtained from primary lung cultures. Transitional trypomastigote-like forms were observed in the thymus; no reproductive or diving forms were encountered in any other tissue, including blood. The course of the parasitemia in spiny mice inoculated i.p. with 1.2 x 10(6) parasites from 26- to 32-day-old cultures initiated from infected lungs was studied. A similar, characteristic pattern was observed in both male and female hosts. Four phases were recognized: latent, logarithmic, stationary, and decline. These phases ended on days 2, 14, 98, and 154 postinoculation, respectively. The decline phase was gradual and the parasites could not be detected by day 154 postinoculation. In contrast, inoculation from older cultures (35-50 days old) showed longer latent and logarithmic phases, a shorter stationary phase, and a sharp drop in parasite density during the decline phase; the parasites were not detected in the peripheral blood by 120 days postinoculation.

Animals↗
PubMed1989

Pregnenolone, dehydroepiandrosterone, and their sulfate and fatty acid esters in the rat brain.

The rat brain contains large amounts of pregnenolone (P) and dehydroepiandrosterone (D) arising from local biosynthetic pathways. We have devised a procedure for the measurement of both "neurosteroids" either unconjugated or released from their sulfate (S) or fatty acid (L) esters. The measurements were performed at the acrophase of the circadian variation of neurosteroids, and confirmed the large accumulation of P (25 +/- 8 ng/g, mean +/- SD) and of PS (19 +/- 6 ng/g) and DS (2.1 +/- 0.5 ng/g) in the brain of adult male rats. We found that fatty acid esters constitute the major species of neurosteroids in brain (PL 46 +/- 14, and DL 36 +/- 7 ng/g, in adult males). The levels of P and DS were increased by daily injection of vehicle to intact males, whereas castration, without or with testosterone or estradiol supplementation (2 mg daily for 7 days), did not produce a significant change of neurosteroids concentrations. Measurements of neurosteroids had not been previously reported in cyclic females. The levels of P, PL, and DS were identical in proestrous females and in intact males, whereas PS (26 +/- 6 ng/g) and DL (50 +/- 16 ng/g) were increased in females. Compared to proestrous females, diestrous females had lower levels of PS (19 +/- 6 ng/g), DS (1.7 +/- 0.4 ng/g), and PL (43 +/- 19 ng/g). These differences suggested a modulatory role of ovarian secretions on the metabolism of neurosteroids.

Animals↗
PubMed1988

Assignment of the configurations of the amino acids in peptidic siderophores.

Pyoverdins and azotobactins contain beta-hydroxyaspartic acid, N delta-hydroxyornithine, citrulline and homoserine, in addition to the common protein amino acids. Configuration assignment of all of these was achieved by acid hydrolysis of the peptide, derivatization of the constituent amino acids to the N-pentafluoropropionyl amino acid esters and gas chromatographic separation of the stereoisomers on capillaries coated with Chirasil-Val. This approach is straightforward for the protein amino acids, but the less common amino acids are either partially degraded during acid hydrolysis or their derivatives exhibit unfavourable gas chromatographic properties. By judicious combination of partial and total hydrolysis and dual derivatization, these problems may be overcome.

Amino Acids↗
PubMed1988

Impact of proteases on iron uptake of Pseudomonas aeruginosa pyoverdin from transferrin and lactoferrin.

The Pseudomonas aeruginosa siderophore pyoverdin was unable to acquire iron from human transferrin or lactoferrin at physiological pH. However, in the presence of P. aeruginosa elastase, rapid iron release and pyoverdin iron uptake from transferrin but not from lactoferrin were detected. Neither P. aeruginosa alkaline protease nor elastase from polymorphonuclear leukocytes revealed this effect.

Carrier Proteins↗
PubMed1988

Iron-chelating substances and inflammation.

The effect of Pseudomonas aeruginosa alkaline protease (AP), elastase (Ela), and the elastase from polymorphonuclear leukocytes (PMN Ela) on iron acquisition of pyoverdin from human transferrin and lactoferrin at physiologic pH was investigated. Incubation of iron-loaded transferrin with iron-free pyoverdin for 10 h at 40 degrees C in the presence of Ela yielded pyoverdin-iron(III) complex, in contrast to incubations of transferrin with pyoverdin alone, AP, or PMN Ela. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of the incubations revealed fragmentation of transferrin by Ela in peptides smaller than 14,000 daltons, whereas AP and PMN Ela cleaved transferrin in fragments of 49,000 d and 43,000 d, respectively. Incubations of lactoferrin with the proteases and pyoverdin or pyoverdin alone did not result in iron acquisition by pyoverdin; however, lactoferrin was fragmented by Ela and AP.

Bacterial Proteins↗
PubMed1984

Reaction of the Z isomer of 4-trans-(N,N-dimethylamino)cinnamaldoxime with the liver alcohol dehydrogenase-oxidized nicotinamide adenine dinucleotide complex.

The Z isomer of 4-trans-(N,N-dimethylamino)-cinnamaldoxime, (Z)-DMOX (lambda maxH2O 354 nm), forms a ternary complex with NAD+ and equine liver alcohol dehydrogenase. The 3-acetyl (3-acetyl-PdAD+), 3-thiocarboxamide (3-thio-NAD+), 3-iodo (io3PdAD+) and nicotinamide mononucleotide (NMN+) analogues of NAD+ also form ternary complexes with enzyme and (Z)-DMOX. These complexes are characterized by large red-shifts in the UV-visible spectrum of bound (Z)-DMOX (lambda max 428 nm for the NAD+ complex) and new spectral bands in the 280-340-nm region associated with the pyridine moieties of NAD+ and the NAD+ analogues. The ternary enzyme-NAD+-(Z)-DMOX complex is weakly fluorescent (lambda ex 430 nm; lambda em max 505 nm) and strongly quenches the residual tryptophan fluorescence of the enzyme-NAD+ binary complex. (Z)-DMOX binds with high affinity to the enzyme-NAD+ complex (Kd less than or equal to 4 X 10(-9) M at pH 8.75 and 25 degrees C), and similarly high affinities were found for the 3-acetyl-PdAD+, 3-thio-NAD+, and io3PdAD+ complexes. Binding is much weaker to the enzyme-NMN+ complex. The active site specifically substituted Co(II), Ni(II), Cu(II), and Cd(II) enzyme derivatives and the enzyme species lacking any metal ion at the active site (apoenzyme) also form ternary complexes with (Z)-DMOX in which the DMOX UV-visible spectrum is red-shifted (ranging from 43 to 83.5 nm). The complexes formed with the Zn(II) and Co(II) enzymes are characterized by relatively high affinities for (Z)-DMOX and by spectra that are independent of pH over the range 6-10. The affinity of the apoenzyme-NAD+ complex for (Z)-DMOX is much lower, and the spectrum of the complex is pH dependent with lambda max = 430 nm at pH 7 and lambda max = 397 nm at pH 10. The rate of (Z)-DMOX dissociation from the apoenzyme complex was found to be approximately 10(3)-fold greater than the rates observed for the metal ion substituted enzymes. The 280-340-nm spectral bands appear to result from the dihydropyridine moieties of covalent adducts formed between (Z)-DMOX and NAD+ and the NAD+ analogues. The large red-shifts of the (Z)-DMOX spectrum result from the bonding of the oxime nitrogen to a strong electrophilic center (either the active site zinc ion or the nicotinamide ring of NAD+.)(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohol Dehydrogenase↗
PubMed1980

The peroxidatic reaction catalyed by horse liver alcohol dehydrogenase. 3. Nuclear magnetic resonance spectroscopic study of NADX.

As previously reported [Favilla, R. & Cavatorta, P. (1975) FEBS Lett. 50, 324-329], the enzyme horse liver alcohol dehydrogenase catalyzes a reaction between NAD+ and H2O2. The final isolated product was then called NADX because of its unknown structure. In this paper the results of spectroscopic investigations on this compound are described. They indicate that only the nicotinamide moiety of the original NAD+ molecule was modified by the action of hydrogen peroxide. From the 1H and 13C nuclear magnetic resonance spectra of NADX the following structure was deduced: adenosine(5')diphospho(5)-beta-D-ribose-NH-CH = C(CHO)-CONH2. This structure is consistent with both ultraviolet and reactivity measurements performed on NADX. A tentative mechanism for the whole peroxidatic reaction pathway leading to NADX is finally proposed.

Adenosine Diphosphate Ribose↗