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Biomedical subjects

F Mohammed

Publications and source records attributed to F Mohammed.

18 recordsLinked to original sources
PubMed2006

Liposarcoma in the nasal cavity of a cow.

Liposarcomas are rare neoplasms in domestic animals, but have been reported to occur in many species. In humans, liposarcoma is one of the most common malignant mesenchymal tumors. Classification of liposarcomas in humans has been well established and categorization by type can be of prognostic value; no such unique classification scheme has been established for liposarcomas in animals. Liposarcoma of the head and neck in humans are uncommon, and are rarely reported in the nasal cavity, sinuses, and nasopharynx. To our knowledge, a liposarcoma has never been reported in the nasal cavity of a domestic animal. In this report we describe a liposarcoma that developed in the nasal cavity of a cow, with local invasion into the oral cavity.

Animals↗
PubMed2005

Crystallization and preliminary X-ray diffraction analysis of calexcitin from Loligo pealei: a neuronal protein implicated in learning and memory.

The neuronal protein calexcitin from the long-finned squid Loligo pealei has been expressed in Escherichia coli and purified to homogeneity. Calexcitin is a 22 kDa calcium-binding protein that becomes up-regulated in invertebrates following Pavlovian conditioning and is likely to be involved in signal transduction events associated with learning and memory. Recombinant squid calexcitin has been crystallized using the hanging-drop vapour-diffusion technique in the orthorhombic space group P2(1)2(1)2(1). The unit-cell parameters of a = 46.6, b = 69.2, c = 134.8 A suggest that the crystals contain two monomers per asymmetric unit and have a solvent content of 49%. This crystal form diffracts X-rays to at least 1.8 A resolution and yields data of high quality using synchrotron radiation.

Calcium↗
PubMed2005

Sex identification of normal persons and sex reverse cases from bloodstains using FISH and PCR.

UNLABELLED: Sex identification of dry blood is of crucial importance in forensic medicine. SUBJECTS AND METHODS: Sixty normal (with matching phenotypic and genotypic sex) persons (36 males and 24 females), and 7 cases of sex reverse, i.e., persons with one genotypic sex and ambiguous or external genitalia of the opposite sex (3 phenotypic females with Swyer syndrome and the 46,XY karyotype, and 4 phenotypic Klinefelter-like males with the 46,XX karyotype) were subjected to sex identification by FISH and PCR using bloodstains. RESULTS: The FISH technique using an X/Y cocktail probe (DXZI & DYZI, Oncor) has identified the sex correctly in 91.69% of interphase nuclei of the 36 males of the study, and in 92.29% of cells of the 24 females and incorrectly identified the 3 phenotypic females with Swyer syndrome as males and the 4 Klinefelter-like males as females. The 60 normal individuals in the study were correctly typed to their phenotypic sex by the 2 PCR methods used, i.e., the single PCR using the amelogenin sequence specific for the X and Y chromosomes and the multiplex PCR using SRY gene (male-specific) and the AR gene (X-specific). Out of the 7 sex reverse cases, one Klinefelter-like male was incorrectly identified by PCR as female due to the absence of amplification of the SRY gene and the amelogenin male-specific 788 bp fragment. CONCLUSION: The present study demonstrates that both FISH and PCR techniques are fast, easy to perform, reliable and efficient for sex identification but PCR is more accurate. It also emphasises that the sex identified is the genotypic sex which does not necessarily correspond to the phenotypic one and if evidences at the scene of crime indicate opposite sex of the accused, persons with sex reverse have to be ruled out using different X- and Y-specific probes and PCR.

Blood Stains↗
PubMed2004

The atomic resolution structure of methanol dehydrogenase from Methylobacterium extorquens.

The crystal structure of methanol dehydrogenase (MDH) from Methylobacterium extorquens has been refined without stereochemical restraints at a resolution of 1.2 A. The high-resolution data have defined the conformation of the tricyclic pyrroloquinoline quinone (PQQ) cofactor ring as entirely planar. The detailed definition of the active-site geometry has shown many features that are similar to the quinohaemo-protein alcohol dehydrogenases from Comamonas testosteroni and Pseudomonas putida, both of which possess MDH-like and cytochrome c-like domains. Conserved features between the two types of PQQ-containing enzyme suggest a common pathway for electron transfer between MDH and its physiological electron acceptor cytochrome cL. A pathway for proton transfer from the active site to the bulk solvent is also suggested.

Alcohol Dehydrogenase↗
PubMed2004

The structure of the C-C bond hydrolase MhpC provides insights into its catalytic mechanism.

2-Hydroxy-6-ketonona-2,4-diene-1,9-dioic acid 5,6-hydrolase (MhpC) is a 62 kDa homodimeric enzyme of the phenylpropionate degradation pathway of Escherichia coli. The 2.1 A resolution X-ray structure of the native enzyme determined from orthorhombic crystals confirms that it is a member of the alpha/beta hydrolase fold family, comprising eight beta-strands interconnected by loops and helices. The 2.8 A resolution structure of the enzyme co-crystallised with the non-hydrolysable substrate analogue 2,6-diketo-nona-1,9-dioic acid (DKNDA) confirms the location of the active site in a buried channel including Ser110, His263 and Asp235, postulated contributors to a serine protease-like catalytic triad in homologous enzymes. It appears that the ligand binds in two separate orientations. In the first, the C6 keto group of the inhibitor forms a hemi-ketal adduct with the Ser110 side-chain, the C9 carboxylate group interacts, via the intermediacy of a water molecule, with Arg188 at one end of the active site, while the C1 carboxylate group of the inhibitor comes close to His114 at the other end. In the second orientation, the C1 carboxylate group binds at the Arg188 end of the active site and the C9 carboxylate group at the His114 end. These arrangements implicated His114 or His263 as plausible contributors to catalysis of the initial enol/keto tautomerisation of the substrate but lack of conservation of His114 amongst related enzymes and mutagenesis results suggest that His263 is the residue involved. Variability in the quality of the electron density for the inhibitor amongst the eight molecules of the crystal asymmetric unit appears to correlate with alternative positions for the side-chain of His114. This might arise from half-site occupation of the dimeric enzyme and reflect the apparent dissociation of approximately 50% of the keto intermediate from the enzyme during the catalytic cycle.

Amino Acid Sequence↗
PubMed2004

Crystallization and preliminary X-ray analysis of the controller protein C.AhdI from Aeromonas hydrophilia.

Single crystals of purified homodimeric controller protein from Aeromonas hydrophilia (C.AhdI) have been grown under several different conditions using vapour diffusion. X-ray diffraction data have been collected using synchrotron radiation from crystals of both the native and a selenomethionine (SeMet) derivative of the protein. The native crystal form belongs to space group P2(1) and data were collected to a resolution of 2.2 A. Two crystal forms of the SeMet protein have been obtained and were found to belong to space groups P1 and P2(1); data have been recorded to 2.0 and 1.7 A resolution, respectively, for the two crystal forms. Three-wavelength MAD data were collected to 1.7 A for the SeMet derivative crystal, which is isomorphous with the native P2(1) crystal.

Aeromonas↗
PubMed2003

A case report of post-traumatic facial reconstruction in the West Indies.

The radial forearm free flap is one of the most commonly used free flaps in reconstructive surgery. It is a recognized option for facial reconstruction internationally, but, to our knowledge, it has not been widely used in the Caribbean. We present a patient who posed a difficult reconstructive problem, for which the radial forearm free flap was the ideal solution, utilizing the flap's features of a long length of pedicle, large area of coverage, minimal tissue bulk, and options for further cosmetic revision.

Adolescent↗
PubMed2003

Latissimus dorsi muscle flap based on arterial branch to serratus anterior as salvage of a failed bipedicled transverse rectus abdominis muscle flap. A case report.

We present a case of a failed bipedicled (unilateral rectus flap with superior epigastric pedicle preserved and inferior epigastric vessels anastomosed to the thoracodorsal trunk as the second pedicle) transverse rectus abdominis muscle flap that had compromised the dominant pedicle of the latissimus dorsi muscle. A salvage procedure was possible using this muscle as a pedicle flap based on the back-flow from the serratus anterior arterial branch with success. The use of the reconstructive ladder is highlighted.

Arteries↗
PubMed2003

Free vascularized fibula graft for a cystic femoral head and neck lesion in the West Indies.

A case is presented of an 18-year-old athlete with fibrous dysplasia of the femoral neck and head. The approach was by joint plastic and orthopaedic teams, which minimized operating time and allowed the option of vascular bone grafting. The lesion was curetted through a greater trochanteric window and the defect reconstructed with a free vascularized fibula graft with excellent result. Weight bearing was achieved in six months and there was minimal donor site morbidity. We believe the free vascularized fibula graft to be a reconstructive option, in difficult orthopaedic problems, facilitated by microsurgery and there is immense benefit of a joint effort between the orthopaedic and plastic surgical teams.

Adolescent↗
PubMed2002

Prediction of the position of the intraparotid portion of the facial nerve on MRI and CT.

Despite developments in imaging technology, visualisation of the intraparotid portion of the facial nerve is not possible. Three separate radiological techniques have been described to predict the position of the facial nerve: Conn's arc; a plane extending posteriorly from the outer surface of the mandibular ramus; and soft-tissue structures, including the posterior belly of the digastric muscle, the retromandibular vein and the lateral border of the masseter muscle. We investigated the reliability of these techniques in predicting the relationship of tumours to the facial nerve. Cross-sectional imaging of the parotid glands was performed prior to the removal of a parotid mass in 26 patients. Twenty patients underwent MRI, and six had CT scans. We removed 14 malignant neoplasms, nine benign lesions and three non-neoplastic lesions. The relationship of the tumour to the facial nerve was assessed radiologically by each of the three techniques, and compared with the findings at surgery. In 18 patients the tumour involved the parotid gland deep to the facial nerve. The above techniques predicted the position of the facial nerve in 69%, 58% and 46% of cases, respectively. When planning parotid surgery, it is important that the surgeon understands the advantages and limitations of the radiological assessment of the position of parotid tumours in relation to the facial nerve.

Adult↗
PubMed2002

Pedicled flaps in reconstructive surgery.

An audit was conducted of pedicled flaps used in reconstructive surgery in Trinidad from 1983 to 2000. This consisted of 65 flaps. There were four cases of partial flap necrosis: three involving tram flaps and the other involving the metacarpal artery flap. There were no cases of total flap loss. Pedicled flap coverage provides immediate closure of potentially difficult wounds. This early cover reduces the risk of infection as a result of increasing the blood supply and providing a physical barrier. This contributes to a shorter hospital stay and earlier rehabilitation. Our present team approach with the inclusion of a reconstructive surgeon now allows for uncompromised débridement in trauma and oncological resection.

Female↗
PubMed2001

Site-directed mutagenesis and X-ray crystallography of the PQQ-containing quinoprotein methanol dehydrogenase and its electron acceptor, cytochrome c(L).

Two proteins specifically involved in methanol oxidation in the methylotrophic bacterium Methylobacterium extorquens have been modified by site-directed mutagenesis. Mutation of the proposed active site base (Asp303) to glutamate in methanol dehydrogenase (MDH) gave an active enzyme (D303E-MDH) with a greatly reduced affinity for substrate and with a lower activation energy. Results of kinetic and deuterium isotope studies showed that the essential mechanism in the mutant protein was unchanged, and that the step requiring activation by ammonia remained rate limiting. No spectrally detectable intermediates could be observed during the reaction. The X-ray structure, determined to 3 A resolution, of D303E-MDH showed that the position and coordination geometry of the Ca2+ ion in the active site was altered; the larger Glu303 side chain was coordinated to the Ca2+ ion and also hydrogen bonded to the O5 atom of pyrroloquinoline quinone (PQQ). The properties and structure of the D303E-MDH are consistent with the previous proposal that the reaction in MDH is initiated by proton abstraction involving Asp303, and that the mechanism involves a direct hydride transfer reaction. Mutation of the two adjacent cysteine residues that make up the novel disulfide ring in the active site of MDH led to an inactive enzyme, confirming the essential role of this remarkable ring structure. Mutations of cytochrome c(L), which is the electron acceptor from MDH was used to identify Met109 as the sixth ligand to the heme.

Alcohol Oxidoreductases↗
PubMed2001

A comparison of 'Early' and 'Late' stage brain activation during brief practice of a simple motor task.

This research study addresses the question: does the neural circuit implementing a motor task undergo change as a function of even limited practice? To detect potential neural changes associated with limited practice we compared brain activation at the early and late stages of motor performance on a simple task over one relatively brief session. Single-finger opposition served as cognitive stimulation during collection of BOLD fMRI signal. We predicted prefrontal cortex activation would be prominent early, with basal ganglia activation becoming prominent during late stage performance. Results revealed that both early and late performance involve areas in the cerebellum, prefrontal, mid-temporal, extrastriate, and parietal cortices, but that the particular regions within these broad areas differed for the two points of performance. The strongest dissociation between early and late performance involved the corpus striatum, thalamus, and cingulate gyrus. The findings suggested the neural circuit implementing this simple task varied over a relatively brief window of practice. Implications for defining the neurocognitive function of the structures involved, particularly the cerebellum, are discussed.

Adult↗
PubMed2001

Extrapelvic endometriosis presenting as unusual swellings of the buttock and thigh.

We present the first case of extrapelvic endometriosis (EPE) presenting as combined swellings of the thigh and buttock in a 28-year-old nulliparous woman. The diagnosis was aided by the history of cyclical symptoms, needle aspirate, ultrasonography and computed tomography scan and was confirmed by histological analysis of the excised specimens. Of note, laparoscopy showed the pelvis to be free of gross disease. Surgical excision combined with hormonal suppression therapy proved adequate treatment in preventing recurrence as well as the complications of wound implantation.

Adult↗
PubMed1983

Comparative study of white cell count and differential leukocyte count in school children at Dead Sea level and at Amman.

White cell and differential counts were studied in school children living at Amman (group A), Dead Sea natives (group B), and residents of the Dead Sea area who originated from different areas (group C). A total of 159 subjects from group A, 146 from group B, and 38 from group C, were studied. Significant leukopenia was observed in group B, as compared with groups A and C (p less than 0.005). This was due to selective neutropenia in group B (p less than 0.005). Careful analysis revealed that this difference was genetic and not environmental. Living at 390 m below sea level does not affect the white cell or the differential count.

Adolescent↗
PubMedDate not supplied

Cytogenetic analysis of Down syndrome in Libya.

The frequency of Down syndrome in Libya was 1 in 516 live births. The mean age of Down mother was 35.62 years. Eighty two percent of the Down mothers were over 30 years of age as compared to 36% of the control Libyan mothers. As there was a greater percentage of late conceptions, the maternal age appears to be influential in the birth of Down syndrome in Libya. Cytogenetically 96% of the cases were that of trisomy 21. There was one case each of mosaic and 21/21 translocation, and four cases of 14/21 translocation as evidenced by Giemsa banding. Twenty two percent of the cases of Down syndrome also had other associated congenital abnormalities. The unique features involved in genetic counselling in this population are discussed. This study reflects the enormous problem of Down syndrome in the Arab world.

Adult↗