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Biomedical subjects

J Ahmed

Publications and source records attributed to J Ahmed.

At least 19 recordsLinked to original sources
PubMed2006

Amodiaquine and artemether-lumefantrine select distinct alleles of the Plasmodium falciparum mdr1 gene in Tanzanian children treated for uncomplicated malaria.

The artemisinin-based combination therapies artemether-lumefantrine (AL) and amodiaquine (AQ) plus artesunate have been adopted for treatment of Plasmodium falciparum malaria in many African countries. Molecular markers of parasite resistance suitable for surveillance have not been established for any of the component drugs in either of these combinations. We assessed P. falciparum mdr1 (Pfmdr1) alleles present in 300 Tanzanian children presenting with uncomplicated falciparum malaria, who were enrolled in a clinical trial of antimalarial therapy. Pfmdr1 genotype analysis was also performed with isolates from 182 children who failed AQ monotherapy and 54 children who failed AL treatment. Pfmdr1 alleles 86Y, 184Y, and 1246Y were more common among treatment failures in the AQ group than among pretreatment infections. The converse was found in the AL-treated group. Children presenting with the 86Y/184Y/1246Y Pfmdr1 haplotype and treated with AQ were significantly more likely to retain this haplotype if they were parasite positive during posttreatment follow-up than were children treated with AL (odds ratio, 33.25; 95% confidence interval, 4.17 to 1441; P, <0.001). We conclude that AL and AQ exert opposite within-host selective effects on the Pfmdr1 gene of P. falciparum.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2006

Outcome of imported liver allografts and impact on patient access to liver transplantation.

Liver allografts declined by local transplant centers are then offered regionally or nationally as imported grafts. Most of these grafts are declined because of poor donor quality. We retrospectively reviewed the medical records of patients who underwent liver transplantation between January 2004 and December 2005. There were 102 liver transplants in 98 recipients. They were divided into two groups: imported graft recipients (n = 37) and locally procured grafts recipients (n = 61). Eighty-six percent (32 of 37) of imported grafts were obtained from extended criteria donors defined as subjects treated with high doses of ionotropes with elevated liver enzymes, donor age over 70 years, macrosteatosis above 25%, positive hepatitis C or hepatitis B core antibody serology, systemic disease, history of cancer, hypernatremia, or with infection. The remaining grafts were declined due to unavailability of suitable recipients or social history. Recipient age and etiology of liver disease were similar for both groups. The mean MELD score was 22.1 +/- .9 among the imported graft recipients and 26.1 +/- 1 for the locally procured graft recipients (P < .01). There was no difference in blood loss or postoperative complications. Postoperative mean peak total bilirubin was similar in both groups. However, imported graft recipients had significantly higher mean peak AST (2436 +/- 282 vs 1380 +/- 165 U/L, P < .001) and ALT (1098 +/- 114 vs 803 +/- 87 U/L, P < .05). Primary graft nonfunction as well as 30 day and 1-year patient and graft survivals were similar for both groups. In conclusion, imported grafts can be transplanted in selected patients with outcomes comparable to locally procured grafts.

Hepatitis C↗
PubMed2006

A bifid intra-tympanic facial nerve in association with a normal stapes.

A rare facial nerve anomaly was incidentally discovered whilst performing a tympanoplasty and ossicular reconstruction on a patient with an acquired unilateral conductive hearing loss. The nerve was seen to bifurcate and straddle a normal stapes superstructure as it ran posteriorly through the middle ear, a unique and as yet unreported combination. This case highlights the importance of vigilance regarding facial nerve anatomical variations encountered during middle-ear surgery thus avoiding inadvertent damage. The purported embryological mechanism responsible for such anomalies of the intra-tympanic facial nerve is discussed.

Facial Nerve↗
PubMed2006

An anatomical comparison of Blair and facelift incisions for parotid surgery.

BACKGROUND: The rhytidectomy approach for parotidectomy allows the incision to be hidden, and post-operative scarring minimised. Furthermore, separate elevation of the Superficial Musculo-Aponeurotic System (SMAS) reduces the incidence of Frey's syndrome, and provides vascularized soft tissue for contour reconstruction. The technique has gained popularity particularly with plastic surgeons, but concerns persist that with this approach, particularly with lesions located anteriorly, access to the gland may be inadequate, and facial nerve identification may be compromised. MATERIALS AND METHODS: We undertook an anatomical study to quantitatively compare the surgical access achieved using the facelift approach with the conventional Blair incision, by comparing the distances between the parotid edge and the retracted flaps. RESULTS: Despite reduced tissue elasticity due to formaldehyde fixation, it proved possible to demonstrate all regions of the parotid gland to the operating surgeon with either approach. There were no significant differences in the distance between the parotid edge and the retracted skin flaps (P > 0.1; paired t-test). CONCLUSIONS: The facelift approach provides at least equal access to all regions of the parotid gland when compared to a Blair's incision. It is a superior approach aesthetically and its more widespread use in parotid surgery is advocated.

Adenoma, Pleomorphic↗
PubMed2006

A technique for tracking intravascular fluorescent microspheres for the determination of arteriolar blood flow in rats.

Fluorescent microspheres have been used in multiple particle tracking studies. Our laboratory is working towards the use of fluorescent microsphere particle tracking in the study of the retinal circulation. The first stage of this project was to develop a technique for measurement and analysis of the particle tracking data. We intravenously injected 2.0 microm diameter, polystyrene microspheres, labeled with fluorescent dye, in anesthetized rats. Using a microscope with a fluorescence attachment, we viewed the fluorescent particles flowing through the surface vessels of the intestine. Data was recorded then analyzed frame by frame. The path of each microsphere was plotted on a transparency sheet and measured. Using a magnification ratio, the velocity and blood flow rate were calculated for 235 particles in five different blood vessels. We found this technique to be an effective method for studying blood flow in an arteriole. The results were comparable to other blood flow studies and showed characteristic trends of typical laminar blood flow.

Animals↗
PubMed2005

Airway obstruction: a rare complication of thrombolytic therapy.

Bleeding into head and neck structures as a complication of thrombolysis is extremely rare but potentially lethal. It is usually associated with local trauma. We describe a case of a 67-year-old woman who developed spontaneous, massive pan aerodigestive tract haemorrhage precipitating airway obstruction following administration of streptokinase for myocardial infarction; a previously unreported complication. This case highlights the importance of being vigilant of airway symptoms following such treatment, prompting early involvement of anaesthetic and otolaryngology personnel.

Aged↗
PubMed2005

Selective protein adsorption on micro-textured P-type and N-type silicon wafers.

There has recently been a great deal of effort put towards the development of bioMEMS-based electrochemical biosensors for use in implantable devices. Currently, the primary issue limiting the lifespan of implantable sensors is protein and cell adhesion (biofouling) to the sensor surface, which impedes the sensor's access to analyte. To better understand this problem, it would be useful to have an understanding of how silicon-based microdevices interact with proteins in a physiological environment. To help answer this question, we investigated the interactions of proteins with microtextured silicon wafers. Bulk micromachining techniques were used to create micro-textures that varied between 5 and 80 microns in size nd spacing. We used n-type and p-type silicon wafers with a <100> crystal orientation. Shapes such as rectangles, circles, and triangles were fabricated that were recessed into the silicon substrate. The features were estimated to be between 3 and 8 microns in depth. After the features were created, the wafers were coated with a layer of silicon dioxide. Once fabrication was complete, the wafers were incubated in vitro ith fluorescently tagged Albumin (500 microg/ml in Phosphate-Buffered Saline, PBS) for 5 minutes. The wafers were then rinsed with PBS solution and viewed using an epifluorescence microscope. Albumin adsorbed selectively onto the micropatterned wafers. Depending on the type of wafer we found that albumin adsorbed selectively onto either the bulk surface, the sidewalls, or the bottom of the etched feature.

Adsorption↗
PubMed2004

Design and testing of a fluorescence glucose sensor which incorporates a bioinductive material.

One main hurdle in the development of implantable biosensors is that their lifetime is limited by scar tissue formation around the implant. One way to ameliorate this issue would be to use a bioinductive coating to allow normal tissue ingrowth around the sensor. Here, we report design, development and in vitro testing of a prototype fluorescence-based glucose sensor that incorporates a bioinductive material at its tip. Glucose is sensed via a fluorescence-based assay system (Amplex reagent) which is confined to a small chamber separated from the bulk glucose solution by a semipermeable membrane. Excitation is provided by a 530 nm laser, while the emitted light is detected by a photomultiplier tube. In vitro testing of this prototype was done in the presence and absence of a bioinductive material covering the membrane at the sensor/solution interface. In response to a step change in glucose concentration, the output of the sensor increased linearly over time due to accumulation of fluorescent marker molecules as glucose diffused into the recording chamber. The slope of this response increased linearly with increasing glucose concentration, with a sensitivity if 2.1 x 10(-4) V/min per ml glucose/dl solution. The presence of the bioinductive layer did not alter the function of the sensor at the lowest glucose concentrations tested, although responses to higher concentrations saturated, presumably because of depletion of the Amplex reagent within the chamber. In summary, we report that the use of a bioinductive material in an implantable biosensor does not appreciably alter sensor function.

Biosensing Techniques↗
PubMed2003

Delayed presentation of paediatric penile constrictive band injury.

We report the case of a child with delayed presentation of partial amputation of the penis with complete transaction of the urethra following a self-inflicted constrictive band injury. Single-stage reconstruction of the urethra and corporae achieved a satisfactory immediate outcome.

Child↗
PubMed2003

Characterization of immunoglobulin E responses in Balb/c mice against the major allergens of timothy grass (Phleum pratense) pollen.

BACKGROUND: Grass pollen, such as that from timothy grass (Phleum pratense), represents a major cause of type I allergy. OBJECTIVE: To characterize the IgE immune response and to identify the major allergens eliciting an IgE response in a mouse model using pollen extract of P. pratense for sensitization, in order to assess analogies to human hyperreactivity and to gain information on the allergenic potential as determined by the IgE-reactivity kinetics of defined allergens. METHODS: Balb/c mice were sensitized with pollen extract or with purified natural allergens. Serum IgE levels, the induction of specific IgE antibodies and immediate hypersensitivity were monitored by ELISA, Western blot and a skin test, respectively. RESULTS: The sensitized mice mounted a strong IgE response and showed IgE-reactivity first against Phl p 5a and 5b, then Phl p 4 and 13 and lastly against Phl p 6. No IgE response was mounted against Phl p 1. However, all purified fractions examined (Phl p 5a, 5b, 6 and 1) induced specific IgE and showed similar kinetics of IgE induction as pollen extract (first Phl p 5a and 5b, then Phl p 6). Skin test experiments demonstrated positive reactivity only in sensitized mice. CONCLUSION: The IgE reactivity induced by the major allergens in Balb/c mice was very similar to that found in allergic patients, with the exception of Phl p 1. The kinetics of the specific IgE response was comparable using either pollen extract or the purified major allergens, indicating that the intrinsic properties of the allergens are of importance rather than their proportionate amounts in pollen extract. This model should prove to be suitable for investigations regarding the mechanisms of induction and manifestation of timothy grass pollen allergy and for the evaluation of therapeutic strategies.

Allergens↗
PubMed2003

Effect of high-hydrostatic pressure and temperature on rheological characteristics of glycomacropeptide.

The influences of high pressure and temperature on the rheological characteristics of glycomacropeptide (GMP) were studied using a controlled rate rheometer. GMP dispersions at a concentration of 12.5% (w/w) were subjected to high pressure from 100 to 400 MPa for 30 min and temperature from 20 to 80 degrees C for 15 min followed by rheological measurements at a shear rate ranged between 0 and 200 s-1. Shear stress-shear rate data of both pressure and heat induced GMP samples fitted Herschel-Bulkley model well with yield stress. It exhibited shear-thinning behavior with flow behavior index ranged between 0.882 and 0.996. Consistency coefficient and apparent viscosity increased with pressure up to 300 MPa while those parameters decreased at 400 MPa. The rheology of GMP was influenced by temperature. The consistency coefficient and apparent viscosity at 100 s-1 obeyed the Arrhenius relationship with activation energies ranged between 8.17 to 12.38 kJ/mol. Lower activation energy signified lesser molecular aggregation or unfolding of protein molecules during thermal treatment of GMP.

Animals↗
PubMed2003

Do weak adapting backgrounds uncover multiple components in the electroretinogram of the horseshoe crab?

The lateral eye of the horseshoe crab, Limulus polyphemus, has been used as a model system for over a century to study visual and circadian processes. One advantage of this system is the relative simplicity of the retina. The input pathway of the retina consists of photoreceptor cells that are electrically coupled to the dendrite of a second-order cell, which sends action potentials to the brain. Electroretinograms (ERGs) recorded from the lateral eye show a biphasic shape, with a leading negative wave and a later positive peak. The purpose of these experiments was to determine whether adapting backgrounds could be used to uncover multiple adaptation mechanisms within the ERG. To test this idea, ERGs were elicited using variable intensity flashes presented under dark-adapted conditions, as well as in the presence of weak adapting backgrounds. Flashes and backgrounds were generated using green LEDs (lambda max = 525 nm) under software control. ERGs were recorded using a corneal wick electrode placed on the lateral eye of the horseshoe crab. Preliminary results suggest that ERGs recorded in the presence of adapting backgrounds are linearly scaled versions of dark-adapted FRGs. This suggests that there is a single adaptation stage in the Limulus retina. This is in contrast with analogous results from mammals, including mouse, cat and monkey, which show multiple stages of adaptation within their more complex retinas.

Adaptation, Ocular↗
PubMed2003

Antioxidant vitamins improves hemoglobin level in children with group a beta hemolytic streptococcal infection.

A study was done on school children infected with group A beta hemolytic streptococci to examine whether antioxidant vitamins play a role in improving the hemoglobin level. A total of 606 primary school children aged 5 to 15 years were randomly divided into two intervention groups. Group 1 (n=299) was treated with pehnoxymethyl penicillin V and group 2 (n=307) was treated with phenoxymethyl penicillin V plus antioxidant vitamins for eight weeks. From each group two blood samples were drawn in acute and convalescent (after eight weeks) states. Before treatment, mean hemoglobin values were 11.0 and 10.8 mg/dL in groups 1 and 2 respectively. After treatment hemoglobin values were 10.5 and 11.6 mg/dL respectively. Values were significantly decreased in group 1 (P=0.0001), whereas increased in group 2 (P=0.001). Adjustment for age and sex by ANCOVA confirmed the difference in hemoglobin levels between group (LS means-0.5 vs 0.8 in groups 1 and 2 respectively (P=0.0001). Hemoglobin level increases after antioxidant vitamin supplementation in children suffering from group A beta hemolytic streptococcal infection.

Adolescent↗
PubMed2003

Identification of serogroups of beta hemolytic streptococci in children with tonsillo-pharyngitis.

Rheumatic fever and post streptococcal glomerulonephritis are common sequelae of beta hemolytic streptococci among Bangladeshi children. The occurrence of these serious complications of beta hemolytic streptococcal throat infections are related to the epidemiology of group A beta hemolytic streptococci. Little is known about the epidemiology of beta hemolytic streptococci in Bangladesh. We have studied 6890 school boys and girls of Narayangonj to find out the prevalence of beta hemolytic streptococcal infections of throat. From them we selected 2175 children, who were suffering from tonsillo-pharyngitis. This cross sectional study was conducted during March-December 1999. All statistical analysis was done by using statistical package SPSS windows version 8. The mean (SD) age of the children was 11.1 (3.3) years. Four hundred and twenty eight isolates of beta hemolytic streptococci were recovered from tonsillo-pharyngeal swab cultures obtained from 428 children. Among the isolated beta hemolytic streptococci, 92 (21.5%) belonged to group A, 5 (1.2%) to group B, 14 (3.3%) to group C and 317 (74.0%) to group G. These findings demonstrated the predominance of group G followed by A infection among school children. Therefore special attention should be paid not only to group A but also to group G. Further studies to determine prevalence of M serotypes are necessary.

Adolescent↗
PubMed2002

Streptococcal antibodies among rural school children in Bangladesh.

The upper limit of normal values of group A streptococcal antibodies should be known for a population concerned because it is influenced by many local conditions. As yet the reference value of the these antibodies has not been determined by using a quantitative method among Bangladeshi children. We determined the reference value of anti-streptolysin O and anti-deoxyribonuclease B among 361 apparently healthy rural Bangladeshi primary school children (aged 5 to 14 years, mean 9.2 years). Anti-streptolysin O was measured by an auto-analyzer and antideoxyribonuclease B was measured by microtitre method. The geometric mean titres for the entire group was 241 IU/ml and 222 IU/ml for anti-streptolysin O and anti-deoxyribonuclease B respectively. The upper limit of normal values (80th percentile) was 390 and 340 for anti-streptolysin O and anti-deoxyribonuclease B, respectively. These limits should be of value to physicians, epidemiologists and clinical laboratory personnel as well.

Adolescent↗
PubMed2001

Measurement of blood flow through the retinal circulation of the cat during normoxia and hypoxemia using fluorescent microspheres.

The most successful method for measuring absolute blood flow rate through the retinal circulation has been the use of radioactive microspheres. The purpose of this study was to develop a microsphere method that did not have the drawbacks associated with radioactivity and to use this method to make measurements of retinal blood flow in the cat. Blood flow measurements were made by injecting 15-microm-diameter polystyrene microspheres into the left ventricle of anesthetized, artificially ventilated cats. These microspheres were labeled with one of three fluorescent dyes. Retinal blood flow measurements were made by determining the number of spheres that were embedded in the retina and comparing them to the number found in a reference sample. Spheres in the retina were counted by making retinal whole mounts and taking retinal images with a CCD camera mounted on an epifluorescence microscope equipped with filter sets appropriate for imaging the dyes used to label the spheres. Blood flow measurements made under normal conditions showed a mean retinal blood flow of 19.8 +/- 12.4 ml/min 100 g tissue (mean +/- SD; n = 15 cats). Since the retinal circulation perfuses only the inner half of the retina, the effective flow rate in that region is about twice this value. RBF increased during hypoxemia (P(a)O2 < 42 mm Hg) to 336% of the normoxic value on average. Analysis of sphere deposition patterns showed that the central retina had a higher blood flow than the peripheral retina, although this difference was significant only during hypoxemia. We conclude that even with a relatively small number of spheres deposited in the retina, the technique can reveal important properties of the retinal circulation.

Animals↗