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Biomedical subjects

S Omar

Publications and source records attributed to S Omar.

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

Comparison of a rapid culture method combining an immunoperoxidase test and a group specific anti-VP1 monoclonal antibody with conventional virus isolation techniques for routine detection of enteroviruses in stools.

In order to shorten the time required for the detection of enteroviruses in stool specimens, an 18-h immunoperoxidase test combining low-speed centrifugation and the use of a group specific anti-VP1 monoclonal antibody (5-D8/1, Dako) was developed. This rapid culture assay (RCA) was compared blindly to a conventional culture assay (CCA) on a panel of 180 children's stool specimens received for routine diagnosis of enterovirus infection. The same cell lines (human embryonic fibroblasts and KB continuous cell line) were used in both tests. Discrepancies in results were analysed by a PCR technique with primers located in a conserved part of the 5' non-coding region of the enterovirus genome. Fourteen specimens were positive and 158 were negative with both tests. Four samples were positive with the RCA yet negative with the CCA and 3 others showed the opposite pattern; an additional sample positive by RCA was uninterpretable by CCA due to bacterial contamination. Subsequent PCR testing of these 8 samples showed no discrepancies; all were positive. Using CCA as the reference, the sensitivity and specificity of RCA were 77.8 and 98% respectively. Kinetic studies using enterovirus isolates demonstrated that RCA was much more sensitive than CCA during the first three days of culture. These results further suggested that RCA sensitivity could be improved by a factor of at least 10 times by prolonging the incubation period by 24 hr. With this change, the RCA assay described below is suggested as a rapid alternative to CCA for the routine diagnosis of enterovirus infection in stool specimens. When an identification at the serotype level is required, samples found positive using RCA could then be subjected to CCA.

Antibodies, Monoclonal↗
PubMed1997

Prediction of folding stability and degradability of the de novo designed protein MB-1 in cow rumen.

The authors have recently reported on the design of a protein (MB-1) enriched in methionine, threonine, lysine, and leucine. The protein is intended to be produced by rumen bacteria, in a way that would provide high producing lactating cows with limiting amino acids. In this report, MB-1 stability in the rumen is assessed, i.e., where the protein might be found after cell lysis or after being secreted by rumen bacteria. Current in vitro methods used to predict proteolytic degradability in the rumen were used for MB-1, as well as other natural proteins for comparison. MB-1 was found to be more susceptible to degradation than cytochrome c and ribonuclease A. Data indicate that MB-1 will be rapidly degraded if exposed to the rumen environment without protection. The contribution of folding stability to proteolytic stability was also examined. Rumen liquor components were selected to formulate a solution compatible with constraints of thermal denaturation studies. Denaturation curves show that the natural proteins were folded at rumen temperature. The MB-1 denaturation curves indicated that MB-1 does not unfold in a cooperative transition when heated from 20 to 70 degrees C. This suggests that MB-1 structure may be progressively modified as temperature increases, and that a continuum of conformations are available to MB-1. At 39 degrees C, a significant (50%) portion of MB-1 molecules had their tertiary structure unfolded, contributing to proteolytic degradability. Despite the unusual constraints used in MB-1 design (i.e., a maximized content in selected essential amino acids), results show that MB-1 has structural properties similar to previously reported de novo designed proteins.

Amino Acids, Essential↗
PubMed1997

Detection of coxsackievirus B3 in intestinal tissue of orally-infected mice by a standardized RT-PCR assay.

BACKGROUND: Previous studies have reported the role of enteroviruses in chronic diseases, using in-house RT-PCR protocols. A well-standardized PCR assay (Amplicor enterovirus, Produits Roche) designed for the diagnosis of enterovirus meningitis in cerebrospinal fluids (CSF) was recently described. OBJECTIVES: To evaluate this commercially-available PCR assay for the detection of enterovirus in intestinal biopsies. STUDY DESIGN: In order to obtain large quantities of infected material, eight mice were inoculated orally with 2 x 10(5) 50% tissue culture infective doses (TCID50) of coxsackievirus B3 (CBV3); two mice were sacrificed every day from day 1 to day 4 post-infection. Stool specimens and small bowel fragments were taken from infected animals and controls. Four protocols of RNA extraction from intestinal tissue were compared. Extracted RNA was then tested by the Amplicor assay and by a seminested in-house PCR. RESULTS: The best results were obtained with a commercial reagent using a combination of guanidium thiocyanate and phenol (TRI Reagent, Sigma). This procedure allowed the detection of enteroviral RNA in intestinal samples of 7/8 and 8/8 infected mice by Amplicor assay and seminested PCR, respectively, whereas only five samples were tested positive by conventional cell culture. When tested on serial dilutions of CBV3 mixed with intestinal tissue, a sensitivity of 0.2 TCID50/mg was achieved with both PCR assays. CONCLUSIONS: The data demonstrate that the Amplicor enterovirus assay, which is designed to avoid false-positive amplifications, can be used, with a slight modification of the RNA extraction step, for the detection of enterovirus in specimens different from CSF such as intestinal tissue.

Animals↗
PubMed1996

Cathepsin-D and TNF-alpha in bladder cancer.

In a study of 34 normal healthy controls, 35 patients with urinary tract bilharziasis and 93 bladder cancer patients (62 of them are operable cases and 31 are non-operable ones), serum tumor necrosis factor alpha (TNF-alpha) and cytosolic Cathepsin-D were estimated. Though both potential markers were elevated in bladder cancer patients, neither Cathepsin-D nor TNF-alpha showed associations of prognostic value since there were no positive correlations with tumor stages, grades or association of tumors with bilharzial ova or lymph node involvement.

Adolescent↗
PubMed1995

Biomechanical and ultrastructural comparison of cryopreservation and a novel cellular extraction of porcine aortic valve leaflets.

Heart valve substitutes of biological origin often fail by degenerative mechanisms. Many authors have hypothesized that mechanical fatigue and structural degradation are instrumental to in vivo failure. Since the properties of the structural matrix at implantation may predetermine failure, we have examined the ultrastructure, fracture, mechanics, and uniaxial high-strain-rate viscoelastic properties of: (1) fresh, (2) cryopreserved, and (3) cellular extracted porcine aortic valve leaflets. The cellular extraction process is being developed in order to reduce immunological attack and calcification. Cryopreservation causes cellular disruption and necrotic changes throughout the tissue, whereas extraction removes all cells and lipid membranes. Both processes leave an intact collagen and elastin structural matrix and preserve the high-strain-rate viscoelastic characteristics of the fresh leaflets. Extraction does cause a 20% reduction in the fracture tension and increases tissue extensibility, with the percent strain at fracture rising to 45.3 +/- 4 (mean +/- SEM) from 31.5 +/- 3 for fresh leaflets. However, extraction does preserve matrix structure and mechanics over the physiological loading range. Glutaraldehyde fixation produces increased extensibility, increased elastic behavior, and, when applied to extracted leaflets, it causes a marked drop in fracture tension, to 50% of that for fresh leaflets. The combination of extraction and fixation may lead to early degenerative failure. The cellular extraction technique alone may be a useful alternative to glutaraldehyde fixation in preparing bioprosthetic heart valves.

Animals↗
PubMed1995

Field evaluation of alphacypermethrin and lambda-cyhalothrin against Aedes aegypti and Aedes albopictus in Malaysia.

Alphacypermethrin (Fendona) and lambda-cyhalothrin (Icon) were evaluated against sentinel bloodfed adults and 4th-instar larvae of Aedes aegypti in a housing estate in Malaysia. The impact of both pyrethroids on field populations of Ae. aegypti and Aedes albopictus were monitored weekly using oviposition trap samples. Both alphacypermethrin and lambda-cyhalothrin showed adulticidal and larvicidal effects.

Aedes↗
PubMed1994

Detection of alpha-urease dissociation by fluorescence emission spectroscopy.

alpha-Urease (E.C. 3.5.1.5) is a hexameric enzyme that can dissociate into two active trimers and further into six monomers (Hirai M., Kawa-Hirai, R., Hirai T., Ueki T. (1993) Eur. J. Biochem. 215, 55-61). We have attempted to detect these dissociation products using fluorescence emission and polarization spectroscopy. Our data suggest that the hexamer, the trimer and denatured monomer have fluorescence emission maximum at 330nm, 332nm, and 346nm, respectively, under our experimental conditions. We have also found that the conformation of urease subunits is only slightly modified upon dissociation to trimer, but drastically changed upon further dissociation leading to monomer.

Fluorescence Polarization↗
PubMed1994

Transferrin receptors in the parkinsonian midbrain.

Several hypotheses have been put forward to explain the pathogenesis of Parkinson's disease (PD) and recently it has been suggested that alterations in iron homeostasis may be implicated. Because of the central role of the transferrin receptor in providing access of iron to cells, we have studied the distribution and density of transferrin receptors using [3H]-transferrin ([3H]-Tf) binding and tritium film autoradiography in the normal and PD midbrain. High levels of [3H]-Tf binding were found in the dorsal raphé, oculomotor nucleus and periaqueductal grey whilst lower levels of [3H]-Tf binding were found in the tegmentum, red nucleus and substantia nigra. Significant reductions in binding were found in the substantia nigra, red nucleus and oculomotor nucleus in PD, the reductions in [3H]-Tf binding being similar to the loss of nigral neurons in PD. The data suggest that the increased iron content of surviving nigral neurons may reflect a compensatory metabolic response rather than abnormal transferrin receptor expression.

Adult↗
PubMed1993

Attenuation of the ischaemia-induced fall of electrical ventricular fibrillation threshold by a calcium antagonist, diltiazem.

Calcium antagonists have been reported to decrease the incidence of sudden death in postinfarction management and vulnerability to fibrillation secondary to experimental coronary occlusion. In order to confirm such beneficial results regarding ischaemic ventricular fibrillation, the threshold intensity for fibrillation electrically induced with impulses of 100 ms and 180 beats.min-1 was measured during the course of ischaemias obtained by total occlusion of the left anterior descending coronary artery near its origin in open-chest pigs. The variations of electrical fibrillation threshold with ischaemia duration (30, 60, 120, 180, 240, 360 s) were compared under control conditions and after i.v. diltiazem (0.50 mg.kg-1 plus 0.02 mg.kg-1.min-1 over 25 min). Electrical fibrillation threshold was not influenced by diltiazem before, but raised during ischaemia, particularly from the 60th s (1.7 to 4.0 mA), with delay in the triggering of fibrillation which occurs when the fibrillation threshold falls down to the pacing threshold (0.2 to 0.3 mA). In 6 pigs out of 8, fibrillation was even avoided in the longest of the ischaemic periods considered (360 s), for fibrillation threshold ceased falling before reaching the critical level. These experimental results obtained with diltiazem are consistent with the clinical effectiveness of calcium antagonists recently observed in the prevention of postinfarction sudden death, provided that myocardial contractility is not too much adversely affected. But, left ventricular dP/dtmax was not reduced by more than 6.8% in the present experiments.

Animals↗
PubMed1993

Enhancement by ischemia of the risk of cardiac disorders, especially fibrillation, in regional anesthesia with bupivacaine.

The impairment of intraventricular conduction by bupivacaine may result in reentrant arrhythmias including ventricular fibrillation. The concentrations responsible for serious accidents are high (5.0 to 8.0 micrograms/ml), but likely to be lowered by myocardial ischemia which gives rise to similar disorders. Therefore we did an electrophysiological study of bupivacaine's effects in an ischemic area of the myocardium. Monophasic action potential (MAP) of the ventricular myocardium was recorded in 30 anesthetized, open-chest pigs. Conduction time and effective refractory period were also measured. Data were obtained during short periods (10-15 s) of pacing at 180 beats/min, but ventricular beats remained governed by the sinus node in the intervals. Ischemia was produced by occluding the left anterior descending coronary artery completely but transiently (up to 8 min), not far from its origin. Comparison was made between the effects of bupivacaine i.v. (n = 10), ischemia (n = 10) and both factors (n = 10). Two min after injection of bupivacaine 2.0 mg/kg (plasma levels 2.0-3.0 micrograms/ml), the duration of MAP was only slightly (7.5-15%) prolonged and its ischemia-induced shortening only slightly attenuated by bupivacaine. At the same time, conduction time was considerably (75-150%) lengthened and its ischemia-induced lengthening enhanced, so that ventricular fibrillation induced by coronary occlusion occurred sooner (about 100 instead of 300 s) in the presence of bupivacaine. Consequently, bupivacaine should be used only with caution in individuals whose myocardium is ischemic or liable to ischemia episodes.

Action Potentials↗
PubMed1992

Postoperative radiotherapy of carcinoma in bilharzial bladder: improved disease free survival through improving local control.

Two hundred thirty-six patients with T3 bladder cancer who survived radical surgery and proved to have P3a, P3b, or P4a tumors were randomized in two phases into three groups: (a) no further treatment (83 patients); (b) postoperative radiotherapy multiple daily fractionation (MDF), using 3 daily fractions of 1.25 Gy each, with 3 hr between fractions, up to a total dose of 37.5 Gy in 12 days (75 patients); and (c) postoperative radiotherapy conventional fractionation (CF), for a total dose of 50 Gy/5 weeks (78 patients). The tolerance of the patients to postoperative radiotherapy was quite acceptable, with equal acute reactions in MDF and CF groups. The 5-year disease-free survival (DFS) rates amounted to 49 and 44% in MDF and CF postoperative radiotherapy groups, respectively, compared to 25% in the cystectomy-alone group. The 5-year local control rates were 87% and 93% for those treated with multiple daily fractionation and conventional fractionation while it was 50% in the surgery-alone group. The therapeutic benefit of postoperative irradiation was consistent for all tumor types, histological grades, and pathological stages for both the disease-free survival and local control. Patients with nodal metastases demonstrated lower recurrence rates in the postoperative radiotherapy groups, but this was not associated with improved disease-free survival. Multivariate analysis using the Cox Model confirmed these results. The independent prognostic factors affecting both disease-free survival and local control were the addition of postoperative radiotherapy, the nodal status, the pathological stage, and the tumor grade. Late complications of radiotherapy in the skin, small intestine, rectum, and the anastomotic site of the urinary division were lower with MDF than with conventional fractionation.

Adult↗
PubMed1992

Role of asynchronous activation of the ventricular fibres by an ectopic pacemaker in the accidents, especially fibrillation, caused by Ic antiarrhythmic drugs.

Class Ic antiarrhythmic drugs, which are known to slow down conduction in the ventricular muscle, are likely to impair synchrony in activity of the ventricular fibres. Asynchronous activation was first investigated between an ischaemic and a normal area by the simultaneous recording in anaesthetized, open-chest pigs of two left ventricular monophasic action potentials (MAPs) under ventricular pacing at a high rate of 180 beats.min-1. Asynchronous activation was then investigated in the intact myocardium according to the distance separating the recording from the pacing electrode. Furthermore, mechanical effects of left ventricular systole were observed by recording dP/dt(max) and mean arterial blood pressure during the pacing periods. Ischaemia was produced by transient complete occlusion of the left anterior descending coronary artery near its origin; as a result, activation time reached 85 ms in the ischaemic area under flecainide administered iv in a 2.5 mg.kg-1 dose instead of approximately 60 ms in the normal area for fibres equi-distant from the pacing electrode. Similar delays in activation were observed in the intact myocardium, depending on whether the explored region was close to or far from the pacing electrode. In the latter case, the difference in activation time may become markedly greater if the distance or the dose of flecainide are increased. This difference, which possibly exceeds one-third of the MAP duration (practically unchanged by flecainide), may account for the occurrence of fibrillation or the sudden loss of systole mechanical efficacy.

Animals↗
PubMed1992

[Acanthamoeba keratitis. Morphologic and isoenzymatic study of a strain isolated from a medically treated case].

We report here the third case of Acanthamoeba keratitis discovered in France in a 30 year-old man wearing soft contact lenses. Amoebas of Acanthamoeba genus could be isolated twice from his corneal ulcer with simple ocular swabs. Owing to medical treatment alone, a successful healing of his eye was obtained. The isolated strain was studied morphologically and biochemically: the cysts observed microscopically after silver stain possessed less than six arms surrounded by a non reticulated ectocyst and belonged to group II defined by Pussard and Pons. But the isoenzymatic study of the ocular strain by isofocusing did not allow us to identify it with any one of the 18 reference strains used, although these represent 14 different described species.

Acanthamoeba↗
PubMed1991

Seasonal population patterns of Spalangia endius Walker (Hymenoptera: Chalcidoidea) at a refuse dumping ground in Malaysia.

A study on population patterns of the parasitoid Spalangia endius Walker at a dumping ground near Kuala Lumpur city showed that the percentage of S. endius adult emergence varied seasonally. During the relatively heavy rainfall months of August and November 1988, and January, March, and April 1989, the population of S. endius adult emergence were low (0-14.2%) compared to the less rainy months of July, September, and December 1988, and May 1989 (29.3-39.6%). This information could be useful in formulating strategies to reduce house fly population at the refuse dumping ground through integrated pest management programs.

Animals↗
PubMed1991

Is sedation without desaturation possible?

The correlation between the depth of sedation and the degree of oxygen desaturation was studied in 52 patients presenting for surgery under regional anaesthesia. After establishing successful regional anaesthesia, patients were sedated with incremental doses of intravenous midazolam. The various levels of sedation were scored from 0 to IV. Continuous pulse oximetry allowed for correlation of sedation and saturation. Each patient's presedation oxygen saturation served as the control value. This was compared with the saturation at sedation levels II, III and IV and was found to be significantly higher (p less than 0.001). There was also a significant drop in saturation as patients progressed from sedation level II to III (p less than 0.02) and from level III to IV (p less than 0.001). The incidence of saturation falling to less than 90% was 4.35%, 14.71% and 40% at sedation scores of II, III and IV respectively.

Adult↗
PubMed1990

Survey of microhymenoptera (Hymenoptera: Chalcidoidea) parasitizing filth flies (Diptera: Muscidae, Calliphoridae) breeding in refuse and poultry farms in peninsular Malaysia.

Nine species of parasitoids were found parasitizing the pupae of filth flies breeding in refuse dumps and poultry farms throughout peninsular Malaysia. Spalangia were most common, consisting of Spalangia endius Walker, S. cameroni Perkins, S. gemina Boucek, S. nigroaenea Curtis, and two undescribed species. Other parasitoids collected were Pachycrepoideus vindemmiae Rondani, Dirhinus himalayanus Westwood, and an unidentified Hymenoptera. The parasitized fly hosts included Musca domestica L., Chrysomya megacephala (F.), Fannia sp., and Ophyra sp. S. endius was the most common parasitoid attacking M. domestica and C. megacephala at refuse dumps and poultry farms D. himalayanus were found to parasitize only M. domestica pupae collected at poultry farms.

Animals↗
PubMed1987

Effect of varying levels of phosphorus and live yeast culture in caged layer diets.

Dietary levels of .31, .36, .41, .46, .51, .56, and .61% total phosphorus (TP) were incorporated into seven corn-soy diets to determine the minimum TP requirement of caged laying hens. Each diet was fed to six lots of 20 hens each for a test period of 308 days. Egg production, feed efficiency, feed consumption, egg weight, and egg breaking strength were the performance criteria. Egg breaking strength was significantly higher while the other performance measures were significantly inferior for hens receiving the .31 TP diet as compared to those hens receiving the other diets. Performance measures of hens receiving diets with TP levels ranging from .41 to .61% were not significantly different. Although hens receiving the .36% TP diet performed significantly better than those receiving diets containing .31% TP, their performance was not satisfactory when compared with performance of hens fed diets containing higher levels of phosphorus. In a second experiment, dietary levels of 0, .25, and .50% live yeast culture (LYC) were fed in combination with TP levels of .40 and .60% to individually caged hens for nine test periods of 28 days each. Each of the test diets was fed to three lots of 12 hens each. Performance criteria in this experiment were the same as those used in the first experiment. Hen responses to the six test diets did not differ significantly for any performance criterion, except for egg breaking strength, which was significantly higher for eggs produced by hens fed diets containing .40% TP level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗