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Biomedical subjects

A S Hussein

Publications and source records attributed to A S Hussein.

At least 19 recordsLinked to original sources
PubMed2003

Regular radon activity concentration and effective dose measurements inside the great pyramid with passive nuclear track detectors.

Radon activity concentrations and equilibrium factors inside the great pyramid of "Cheops" were measured with passive nuclear track detectors. The variation of these concentrations in location was investigated. Seasonal variation of radon activity concentrations with winter maximum and summer minimum were observed inside the pyramid. The 1-y average radon activity concentration ranged from a minimum of 20 to a maximum of 170 Bq m(-3). Results show that the yearly average equilibrium factor between radon and its progeny was assessed as 0.16 and 0.36 inside the pyramid and near entrance, respectively. Moreover, the estimated annual effective dose was 0.05 mSv to tour guides and varied from 0.19 to 0.36 mSv for the pyramid guards; for visitors the average effective dose was 0.15 microSv per visit. These are lower than the 3-10 mSv y(-1) dose limit recommend by ICRP 65.

Administration, Inhalation↗
PubMed2001

Expression level of heterologous proteins in Pichia pastoris is influenced by flask design.

The yeast Pichia pastoris is a convenient production system that enables expression of heterologous proteins in high amounts. As a fermentation method, shaking flasks are very popular because of their simplicity of handling and their low cost. We compared the expression level of the enzyme acetylcholinesterase in a transformed strain of P. pastoris grown in different flasks, presenting various designs but all with the same volume. A several-thousand-fold difference appeared in the expression levels; and the results could not be explained by differences between the flasks in the oxygenation of the medium. The data show that flask design is an important factor to consider for optimising fermentation processes.

Acetylcholinesterase↗
PubMed2001

A study of radon and thoron release from Egyptian building materials using polymeric nuclear track detectors.

The free exhalation rates of both thoron and radon, the specific activities of 224Ra, and 226Ra, and the physical properties, such as the emanation coefficients and radon effective diffusion coefficient of several building material samples were determined using LR-115 and CR-39 polymeric nuclear track detectors. The free areal exhalation rate was measured by the sealed cup-technique, whereas the radium content was obtained by the alpha-autoradiographic method. The calibration coefficient for thoron measurements in air using cylindrical cup equipped with LR-115 detector was estimated. Moreover, the calibration coefficients for measurements of the specific activities of 224Ra and 226Ra were also evaluated. New method was developed for evaluating the emanation coefficient as well as the diffusion coefficient of radon isotopes in the studied materials.

Air Pollutants, Radioactive↗
PubMed2001

Radon activity concentrations and effective doses in ancient Egyptian tombs of the Valley of the Kings.

Radon concentrations and equilibrium factors were measured in three pharaonic tombs during the year 1998. The tombs, which are open to the public are located in a limestone wadi on the West Bank of the River Nile at Luxor, 650 km south of Cairo. The radon activity concentration and equilibrium factor were measured monthly by two-integral nuclear track detectors (bare and diffusion detectors). Seasonal variation of radon concentrations, with summer maximum and winter minimum were observed in all tombs investigated. The yearly mean radon activity concentrations insidc the tombs ranged from 540 to 3115 Bq m(-3). The mean equilibrium factor over a year was found to be 0.25 and 0.32 inside and at the entrance, respectively. Estimated annual effective doses to tour guides ranged from 0.33 to 1.90 mSv, visitors receive doses from 0.65 to 3.80 microSv per visit. The effective dose to tomb workers did not exceed the 20 mSv yr(-1) limit.

Air Pollutants, Radioactive↗
PubMed2001

Acetylcholinesterase assay for rapid expression screening in liquid and solid media.

The synaptic enzyme acetylcholinesterase (AChE), which is the target of many insecticides and potential warfare agents, is implied in Alzheimer's disease and is a good potential candidate to be used in biosensors. This promotes a strong demand for production of recombinant AChE to be used in various studies. A promising expression system is the yeast Pichia pastoris, but the expression efficiency needs to be improved. Optimization studies require a rapid and efficient screening test to detect positive yeast colonies after transformation. Using indoxylacetate as a substrate, we designed a chromogenic test that is not interfered with by the culture media background color and, thus, is suitable for microplate screening. Moreover, it was possible to adapt the test for direct on-plate detection of AChE-expressing colonies.

Acetylcholinesterase↗
PubMed2000

Nippostrongylus brasiliensis: infection induces upregulation of acetylcholinesterase activity on rat intestinal epithelial cells.

Expression of cholines terases and muscarinic acetylcholine receptors in the jejunal mucosa has been investigated during infection of rats with the nematode parasite Nippostrongylus brasiliensis. Selective expression of m3 receptors was observed on epithelial cells from uninfected rats and animals 7 days postinfection, and saturation binding with [(3)H]quinuclidinyl benzilate indicated that receptor expression on cell membranes was unaltered by infection. Butyrylcholinesterase was highly expressed in mucosal epithelia, but acetylcholinesterase was present at low levels in uninfected animals. In contrast, discrete foci of intense acetylcholinesterase activity were observed on the basement membrane of intestinal epithelial cells in animals infected with N. brasiliensis. This was demonstrated to be due to upregulation of expression of endogenous enzyme, which peaked at Day 10 postinfection and subsequently declined to preinfection levels. It is suggested that this occurs in response to hyper-activation of the enteric nervous system as a result of infection, and may benefit the host by limiting excessive fluid secretion due to cholinergic stimulation.

Acetylcholinesterase↗
PubMed2000

Determinants of substrate specificity of a second non-neuronal secreted acetylcholinesterase from the parasitic nematode Nippostrongylus brasiliensis.

We recently reported on a non-neuronal secreted acetylcholinesterase (AChE B) from the nematode parasite Nippostrongylus brasiliensis. Here we describe the primary structure and enzymatic properties of a second secreted variant, termed AChE C after the designation of native AChE isoforms from this parasite. As for the former enzyme, AChE C is truncated at the carboxyl terminus in comparison with the Torpedo AChE, and three of the 14 aromatic residues that line the active site gorge are substituted by nonaromatic residues, corresponding to Tyr70 (Ser), Trp279 (Asn) and Phe288 (Met). A recombinant form of AChE C was highly expressed by Pichia pastoris. The enzyme was monomeric and hydrophilic, and displayed a marked preference for acetylthiocholine as substrate. A double mutation (W302F/W345F, corresponding to positions 290 and 331 in Torpedo) rendered the enzyme 10-fold less sensitive to excess substrate inhibition and two times less susceptible to the bis quaternary inhibitor BW284C51, but did not radically affect substrate specificity or sensitivity to the 'peripheral site' inhibitor propidium iodide. In contrast, a triple mutant (M300G/W302F/W345F) efficiently hydrolysed propionylthiocholine and butyrylthiocholine in addition to acetylthiocholine, while remaining insensitive to the butyrylcholinesterase-specific inhibitor iso-OMPA and displaying a similar profile of excess substrate inhibition as the double mutant. These data highlight a conserved pattern of active site architecture for nematode secreted AChEs characterized to date, and provide an explanation for the substrate specificity that might otherwise appear inconsistent with the primary structure in comparison to other invertebrate AChEs.

Acetylcholinesterase↗
PubMed2000

Acute bacterial meningitis in adults. A 12-year review.

One hundred three episodes of acute bacterial meningitis in adults hospitalized in Edmonton's 2 largest hospitals from 1985 to 1996 were reviewed. Cases complicating neurosurgery were excluded. Most cases were community-acquired (87%). Twenty-three cases remained culture-negative, and there was no statistical relation between culture negativity and antibiotic pretreatment. Streptococcus pneumoniae was the predominant pathogen (52.5%), but Listeria monocytogenes was the second most common isolate, accounting for 12.5% of culture-positive cases. Compared to non-listerial meningitis, those with listeriosis were more likely to have negative cerebrospinal fluid (CSF) Gram stains (p = 0.07), CSF leukocyte counts < 1,000 cells/mm3 (p < 0.003), and normal CSF glucose (p = 0.006). Bacterial antigen detection was found to be of low sensitivity: 33% in all patients, but only 9% in cases with negative CSF Gram stains. The overall mortality was 18%, with 15 deaths directly attributable to acute meningitis; the case-fatality rates for S. pneumoniae and L. monocytogenes were 24% and 40%, respectively. Mortality was significantly higher among those with seizures (34% versus 7%, respectively; p < 0.001; OR = 17.6). Despite the urgency of acute bacterial meningitis, there were considerable delays in the institution of empiric antibiotics; mortality rates were slightly higher in those who experienced such a delay (16% versus 7% respectively; p = 0.18).

Acute Disease↗
PubMed2000

The application of databases and PCR in the cloning of glycosidase genes from the protozoan Tritrichomonas foetus.

Conserved sequence amplification (CSA) has been used to obtain sequence data for two glycosidase genes from the primitive eukaryote Tritrichomonas foetus. Few genes have been cloned from this organism, and there is little information concerning protein sequence. CSA is reliant on the use of database searches to identify short sequences of 3-9 amino acids conserved within a protein across a wide range of species. PCR primers are then constructed based on this sequence data and the DNA is amplified and sequenced. In the case of the beta-galactosidase gene, N-terminal amino acid sequence data were used to construct a primer that replaced the upstream primer to ensure the amplified product was related to beta-D-galactosidase. CSA was also applied to the gene encoding the enzyme beta-N-acetyl-D-glucosaminidase from T. foetus, but in this case a segment of DNA was amplified, which, if correct, should contain a third conserved motif. The products of the CSA were sequenced, and the data obtained were compared to data in the SwissProt database. The results obtained suggest that this approach is useful for the cloning of genes to obtain novel sequence data from organisms where little genetic information is available.

Acetylglucosaminidase↗
PubMed1999

Cloning, expression, and properties of a nonneuronal secreted acetylcholinesterase from the parasitic nematode Nippostrongylus brasiliensis.

We have isolated a full-length cDNA encoding an acetylcholinesterase secreted by the nematode parasite Nippostrongylus brasiliensis. The predicted protein is truncated in comparison with acetylcholinesterases from other organisms such that the carboxyl terminus aligns closely to the end of the catalytic domain of the vertebrate enzymes. The residues in the catalytic triad are conserved, as are the six cysteines which form the three intramolecular disulfide bonds. Three of the fourteen aromatic residues which line the active site gorge in the Torpedo enzyme are substituted by nonaromatic residues, corresponding to Tyr-70 (Thr), Trp-279 (Asn), and Phe-288 (Met). High level expression was obtained via secretion from Pichia pastoris. The purified enzyme behaved as a monomeric hydrophilic species. Although of invertebrate origin and possessing the above substitutions in the active site gorge residues, the enzyme efficiently hydrolyzed acetylthiocholine and showed minimal activity against butyrylthiocholine. It displayed excess substrate inhibition with acetylthiocholine at concentrations over 2. 5 mM and was highly sensitive to both active site and "peripheral" site inhibitors. Northern blot analysis indicated a progressive increase in mRNA for AChE B in parasites isolated from 6 days postinfection.

Acetylcholinesterase↗
PubMed1999

Nippostrongylus brasiliensis: characterisation of a somatic amphiphilic acetylcholinesterase with properties distinct from the secreted enzymes.

We have previously determined that Nippostrongylus brasiliensis secretes three monomeric nonamphiphilic (G1na) variants of acetylcholinesterase (AChE) with broadly similar properties. In this study we have examined AChE expression in somatic extracts of N. brasiliensis and report the identification of an additional enzyme which is not secreted. The enzyme was resolved by sucrose density gradient centrifugation with a sedimentation coefficient of 10.2 S which was shifted to 9.4 S in the presence of Triton X-100, identifying the enzyme as a tetrameric amphiphilic (G4a) form. The amphiphilic properties of this enzyme were confirmed by charge-shift electrophoresis, in which migration was accelerated by interaction with sodium deoxycholate. The enzyme showed low activity with butyrylthiocholine, and a Michaelis constant of 91 +/- 13 microM for acetylthiocholine was determined. It was highly sensitive to the AChE-specific inhibitor bis (4-allyldimethylammoniumphenyl)pentan-3-one dibromide, with an IC50 of 6.5 +/- 0.4 microM, but was also inhibited by the butyrylcholinesterase-specific inhibitor tetramonoisopropylpyrophosphortetramide, albeit with a higher IC50 of 46.5 +/- 6.1 microM. This enzyme can therefore be distinguished from the secreted AChEs by its amphiphilic properties, sedimentation in sucrose gradients, and sensitivity to cholinesterase inhibitors.

Acetylcholine↗
PubMed1998

Persistent müllerian duct syndrome.

We report an 18-month old male presenting with a right-sided inguinal hernia and undescended testes. At herniotomy, a uterus and two fallopian tubes were found in the pelvic peritoneum adjacent to the two gonads which received their blood supply partly along the müllerian duct remnants. The gonads were testes by histological examination. Bilateral orchiopexy was performed without removal of the müllerian structures for fear of jeopardizing the testicular blood supply. The diagnosis of persistent müllerian duct syndrome was confirmed postoperatively by genetic and hormonal investigations.

Anti-Mullerian Hormone↗
PubMed1997

Purification and properties of monomeric (G1) forms of acetylcholinesterase secreted by Nippostrongylus brasiliensis.

Acetylcholinesterase (AChE) activity secreted by Nippostrongylus brasiliensis was resolved by sucrose density centrifugation and gel permeation chromatography in single peaks estimated at 4.3 S and 60-85 kDa, respectively. Sedimentation was unaffected by the inclusion of detergent. AChE was purified by affinity chromatography on 9-[Nbeta-(epsilon-aminocaproyl)-beta-aminopropylamino]-acridinium bromide hydrobromide-coupled sepharose 4B. Three forms of the enzyme (A, B and C) were distinguished by non-denaturating polyacrylamide gel electrophoresis, and displayed apparent masses of 74, 69 and 71 kDa respectively when resolved by SDS-PAGE. All three isoforms showed a preference for acetylthiocholine (ASCh) as substrate. They were highly sensitive to inhibition by the AChE-specific inhibitor bis(4-allyldimethylammoniumphenyl)pentan-3-one dibromide, with inhibitor concentration reducing initial activity by 50% (IC50) between 0.1 and 0.8 microM, but activity was unaffected by tetramonoisopropylpyrophosphortetramide (iso-OMPA) at concentrations up to 10 mM. We conclude that the secreted enzymes are authentic AChEs of hydrophilic monomeric (G1) form and broadly similar properties, but which can be distinguished by molecular mass, inhibitor sensitivities and the degree of excess substrate inhibition.

Acetylcholinesterase↗
PubMed1996

Inhibition of glutathione synthesis of Ascaris suum by buthionine sulfoximine.

We investigated the effect of DL-buthionine-S,R-sulfoximine (BSO), a selective glutathione (GSH)-depleting agent, on the GSH synthesis of Ascaris suum. The GSH concentrations of the reproductive and muscle tissues of A. suum were determined to be 8.5 +/- 0.3 and 14.3 +/- 1.3 (n = 3) nmol/mg protein, respectively. After treatment of the parasites with 10 microM BSO for 24 h, the GSH content of the reproductive tissue of A. suum was totally depleted as compared with that of untreated controls. However, the GSH levels of the muscle tissue were reduced to only 50% after treatment of the worms for 24 h with 10 microM BSO. Exogenous GSH had no significant effect on the GSH level of the parasites when the worms were incubated for 4 h in RPMI 1640 medium supplemented with 1 mM GSH. In the presence of exogenous GSH, BSO was less effective in depleting the GSH levels of the parasites, which may indicate that the parasites can replenish their GSH levels. GSH depletion, which has been discussed as being therapeutically effective when normal and tumor cells or parasites have markedly different requirements for GSH, may have applications in the development of drugs against nematode infections.

Animals↗
PubMed1996

Purification and characterization of gamma-glutamyl transpeptidase from Ascaris suum.

gamma-Glutamyl transpeptidase, which is of central importance in the degradation of glutathione, was purified from Ascaris suum to apparent homogeneity. The enzyme was found to be a predominantly membrane-bound protein and was solubilized by Triton X-100. The purified enzyme, which exhibits a specific activity of 1009 U (mg protein)-1, showed a molecular mass of 70 kDa and was found to be composed of two non-identical subunits of molecular mass 43 and 30 kDa. Concerning the kinetic properties of the enzyme, the data presented in this study showed that various amino acids and dipeptides with L-configuration served as acceptors for the gamma-glutamyl moieties of the enzyme reaction products and showed Km-values in the mM range. The apparent Km-value for the gamma-glutamyl donor L-glutamyl-gamma-7-amido-4-methylcoumarin of the enzyme was found to be 0.03 mM. L- and D-serine in combination with borate ions were competitive inhibitors of the enzyme activity with Ki-values of 0.30 and 0.61 mM, respectively. Acivicin was an irreversible inhibitor of the enzyme with a Ki-value of 0.42 mM and with a pseudo-first-order kinetics (kinact) of 0.18 min-1. In vitro treatment of the adult A. suum with acivicin resulted in a dose-dependent inhibition of the enzyme activity and an increase of the glutathione levels. These findings indicate the physiological role of the gamma-glutamyl transpeptidase of this parasitic nematode in the catabolism of glutathione.

Amino Acids↗
PubMed1996

Effect of dietary protein and energy levels on pullet development.

The effects of protein and energy levels in rearing diets and protein levels in layer diets on pullet development and subsequent layer performance were studied using 576 Single Comb White Leghorn pullets of a commercial strain. Twelve groups of 16 1-d-old chicks were assigned to each of three dietary treatments. All chicks were fed a 19% CP starter diet during Week 1. Respective protein levels in diets fed during Weeks 2 through 6, 7 through 14, and 15 through 18 were 13.5, 15.8, and 18.9% for the increasing protein treatment; 15.8, 15.8, and 15.8% for the constant protein treatment; and 18.9, 15.8, and 13.5% for the decreasing protein treatment. During Weeks 15 through 18, half of the groups in each protein treatment were assigned to a high (3.09 Mcal AMEn/kg) or a low (2.78 Mcal AMEn/kg) energy diet. After 18 wk, half of the pullets within each rearing treatment were fed a layer diet containing 16% CP and 0.34% methionine, whereas the other half were fed a layer diet with 19% CP and 0.40% methionine. Increasing the level of protein fed during Weeks 2 through 6 significantly (P < 0.05) increased body weight and feed intake up to 14 wk of age. High dietary energy increased weight gain and decreased feed intake during Weeks 15 through 18. Mortality and days to 50% egg production, as well as egg production, feed intake, feed conversion, and egg weight during the first 16 wk following photostimulation were not affected by rearing dietary treatments. Egg weight, but not other production parameters, was significantly increased by raising CP in the layer diet from 16 to 19%.

Animals↗
PubMed1995

Purification and characterization of gamma-glutamylcysteine synthetase from Ascaris suum.

We have purified and characterized the Ascaris suum gamma-glutamylcysteine synthetase, the rate-limiting step in the glutathione biosynthesis. The purified enzyme exhibited a specific activity of 18 U (mg protein)-1. Estimation of the molecular mass of the native enzyme by FPLC on Superdex S-200 revealed the presence of two enzyme activity peaks corresponding to molecular masses of 100 and 70 kDa. The higher-molecular-mass component could be dissociated by repeated gel filtration into the 70-kDa protein which is the enzymatically active subunit. The apparent Km values of the A. suum enzyme for L-aminobutyrate, L-cysteine and L-glutamate were 0.31, 0.41 and 0.94 mM, respectively. D,L-Buthionine-S,R-sulfoximine and cystamine showed time-dependent irreversible inhibitory effects on the A. suum enzyme activity with Ki values of 0.05 and 1.11 microM, respectively. The Ki values for the corresponding enzyme from rat kidney with D,L-buthionine-S,R-sulfoximine and cystamine were 7.19 and 22.2 microM, respectively. The time of half-inactivation of the enzyme at infinite concentration of D,L-buthionine-S,R-sulfoximine, tau 50, was determined to be 3.1 and 1.34 min, for the parasite and mammalian enzymes respectively. For cystamine, a tau 50 value of 3.32 min for the A. suum gamma-glutamylcysteine synthetase was determined, while a value of 2 min in case of rat kidney enzyme was found. The A. suum enzyme activity was competitively inhibited by glutathione with a Ki value of 0.11 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗