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Biomedical subjects

Z Ahmed

Publications and source records attributed to Z Ahmed.

At least 37 records · Page 2Linked to original sources
PubMed2001

Functional effects of APS and SH2-B on insulin receptor signalling.

APS [for 'adapter protein with a pleckstrin homology (PH) and Src homology 2 (SH2) domain'] belongs to a family of adapter proteins involved in signalling by the receptors for insulin, insulin-like growth factor 1, platelet-derived growth factor and nerve growth factor. Other members include alternatively spliced SH2-B isoforms (SH2Balpha, SH2-Bbeta and SH2-Bgamma) and Lnk. These have a C-terminal SH2 domain, a central PH domain and an N-terminal proline-rich region. SH2Balpha, APS and Lnk have a conserved C-terminal tyrosine phosphorylation site, whereas the alternatively spliced SH2-Bbeta and SH2-Bgamma have distinct C-termini. There is considerable sequence similarity between APS, SH2-B and Lnk, particularly in the SH2 domain. Both APS and SH2-Balpha interact with the insulin-receptor activation loop phosphorylation sites and undergo insulin-stimulated tyrosine phosphorylation, although the phosphorylation of SH2-B is considerably weaker. APS couples c-Cbl to the insulin receptor, resulting in ubiquitination of the insulin receptor. We established cell lines [Chinese hamster ovary (CHO). T-APS and CHO. T-SH2-B cells] overexpressing APS and SH2-Balpha to study their roles in insulin receptor signalling. Either adapter protein enhances insulin receptor and ERK (extracellular-signal-regulated kinase) phosphorylation. In CHO. T-APS cells, Akt phosphorylation is observed earlier than in CHO.T-SH2-B cells. Both enhance insulin-stimulated Akt activation but APS seems to cause greater activation. Thus APS and SH2-B have similar effects on insulin receptor signalling, although the effects of SH2-B are independent of its phosphorylation.

Animals↗
PubMed2001

Are antipsychotic drugs the right treatment for challenging behaviour in learning disability?: The place of a randomised trial.

People with learning disability sometimes display challenging behaviour. This can be managed by use of antipsychotic medication or behavioural therapy or both. There is no solid evidence, however, that these therapies are safe and effective. A randomised controlled trial of antipsychotic medication has been proposed to deliver such evidence. However, this presents difficult issues in the ethics of research with learning disabled people. In particular, is a trial the most efficient and fairest way to evaluate practice in this area? This paper reviews the clinical situation, gives the rationale for the trial, and analyses the ethical arguments for and against such a trial.

Antipsychotic Agents↗
PubMed2001

Treatment of bipolar affective disorder in clinical practice.

A case note survey of 100 outpatients with a clinical diagnosis of bipolar affective disorder in a UK inner city teaching hospital revealed monotherapy with a mood stabilizer in only 23% of patients, mostly lithium (15%). Overall, 51% of patients were prescribed lithium, 19% carbamazepine and 5% valproate with only 8% receiving a combination of two mood stabilizers. Treatment appeared to be inadequate in 13/51 of patients on lithium, 9/19 of those on carbamazepine and 1/5 of those on valproate. Antipsychotics were used as monotherapy in 20% of patients and combined with a mood stabilizer in 43% of patients. Only 6% of patients were on atypical antipsychotics. These findings suggest that the treatment for many patients does not match recommendations. Clearer evidence on the place of combination mood stabilizers and adjunctive antipsychotics, particularly atypicals is needed in the treatment of bipolar affective disorder.

Adolescent↗
PubMed2001

Histological pattern of central nervous system neoplasms.

OBJECTIVE: To see in a large series of patients the histological pattern of CNS neoplasms and to provide a comprehensive data about the frequency of CNS neoplasms in Pakistani patients and to give a clearer idea about their prevalence. METHOD: Retrospective study of all consecutive cases of CNS neoplasms diagnosed at The Aga Khan University Hospital (AKUH) between 1st January, 1994 and 31st December, 1999. SETTING: The section of Histopathology, AKUH, Karachi. OBSERVATION: Our series included a large number of cases i.e., 1110. There are very few local studies on CNS tumours and none so large. Our data was correlated with published Western and Pakistani data. Glial tumours were the commonest primary CNS neoplasms followed by meningiomas. Among glial tumours, astrocytomas comprised the largest group and the majority were high grade (III and IV) astrocytomas. Percentages of anaplastic oligodendrogliomas and ependymomas were also significant. Male to female ratio was 1.6:1. However, meningiomas were more common in females. Almost half of the CNS tumours in patients 15 years or younger were in the posterior cranial fossa. Metastatic tumours were much lower as compared to the West. CONCLUSION: Except for the high percentages of anaplastic oligodendrogliomas and ependymomas and the low percentage of metastatic tumours, most of our findings roughly correspond with the published data.

Adolescent↗
PubMed2000

Abciximab treatment in vitro after aspirin treatment in vivo has additive effects on platelet aggregation, ATP release, and P-selectin expression.

To prevent arterial thrombosis, abciximab is administered together with aspirin. However, whether or not there are benefits to combine abciximab with aspirin is not yet well defined. Healthy volunteers were studied for the effect of aspirin + abciximab using sodium arachidonate and adenosine diphosphate (ADP) alone or in combination to induce platelet activation/aggregation. Abciximab produced complete inhibition of platelet aggregation induced with ADP but only 40% inhibition of aggregation induced by 0.75-mmol/l sodium arachidonate. Abciximab added in vitro to platelet-rich plasma (PRP) from platelets from aspirin-treated donors produced an almost complete inhibition of platelet aggregation. Aspirin, and abciximab alone, did not inhibit adenosine triphosphate (ATP) release as thoroughly as aspirin + abciximab did. Abciximab (3-5 microg/ml) produced inhibition of P-selectin expression induced with 5 (from 46.2 +/- 6.0% to 27.4 +/- 7.0%, P=0.002) and 20-micromol/l ADP (from 53.1 +/- 8.1% to 35.1 +/- 11.0%, P=0.019), but no effect was observed when 0.75-mmol/l sodium arachidonate was used (P=0.721). Aspirin diminished P-selectin expression in sodium arachidonate-stimulated platelets (from 77.7 +/- 11.8% to 40.2 +/- 3.6%, P<0.0001) in non-aspirinated and platelets from aspirin-treated donors, respectively. Abciximab (3, 4, and 5 microg/ml) added to platelets from aspirin-treated donors decreased P-selectin expression in platelets stimulated with sodium arachidonate from 40.2 +/- 8.6% to 25.6 +/- 11.5% (P=0.027), to 20.5 +/- 3.5% (P<0.0001), and to 22.5 +/- 1.8% (P<0.0001). We concluded that the antiplatelet effect of abciximab is greatly increased by aspirin.

Abciximab↗
PubMed2000

Usher syndrome 1D and nonsyndromic autosomal recessive deafness DFNB12 are caused by allelic mutations of the novel cadherin-like gene CDH23.

Genes causing nonsyndromic autosomal recessive deafness (DFNB12) and deafness associated with retinitis pigmentosa and vestibular dysfunction (USH1D) were previously mapped to overlapping regions of chromosome 10q21-q22. Seven highly consanguineous families segregating nonsyndromic autosomal recessive deafness were analyzed to refine the DFNB12 locus. In a single family, a critical region was defined between D10S1694 and D10S1737, approximately 0.55 cM apart. Eighteen candidate genes in the region were sequenced. Mutations in a novel cadherin-like gene, CDH23, were found both in families with DFNB12 and in families with USH1D. Six missense mutations were found in five families with DFNB12, and two nonsense and two frameshift mutations were found in four families with USH1D. A northern blot analysis of CDH23 showed a 9.5-kb transcript expressed primarily in the retina. CDH23 is also expressed in the cochlea, as is demonstrated by polymerase chain reaction amplification from cochlear cDNA.

Alleles↗
PubMed2000

A solid-state NMR study of the phospholamban transmembrane domain: local structure and interactions with Ca(2+)-ATPase.

The structure and dynamics of a double (13)C-labelled 24-residue synthetic peptide ([(13)C(2)]CAPLB(29-52)), corresponding to the membrane-spanning sequence of phospholamban (PLB), were examined using (13)C cross-polarisation magic-angle spinning (CP-MAS) NMR spectroscopy. CP-MAS spectra of [(13)C(2)]CAPLB(29-52) reconstituted into unsaturated lipid membranes indicated that the peptide was mobile at temperatures down to -50 degrees C. The NMR spectra showed that peptide motion became constrained in the presence of the SERCA1 isoform of Ca(2+)-ATPase, and chemical cross-linking experiments indicated that [(13)C(2)]CAPLB(29-52) and Ca(2+)-ATPase came into close contact with one another. These results together suggested that the peptide and the 110-kDa calcium pump were interacting in the membrane. Rotational resonance CP-MAS (13)C-(13)C distance measurements on [(13)C(2)]CAPLB(29-52) reconstituted into lipid bilayers confirmed that the sequence spanning Phe-32 and Ala-36 was alpha-helical, and that this structure was not disrupted by interaction with Ca(2+)-ATPase. These results support the finding that the transmembrane domain of PLB is partially responsible for regulation of Ca(2+) transport through interactions with cardiac muscle Ca(2+)-ATPase in the lipid bilayer, and also demonstrate the feasibility of performing structural measurements on PLB peptides when bound to their physiological target.

Amino Acid Sequence↗
PubMed2000

The APS adapter protein couples the insulin receptor to the phosphorylation of c-Cbl and facilitates ligand-stimulated ubiquitination of the insulin receptor.

The APS adapter protein is rapidly tyrosine-phosphorylated following insulin stimulation. In insulin-stimulated 3T3-L1 adipocytes, APS co-precipitated with phosphorylated c-Cbl. In CHO.T-APS cells overexpressing the insulin receptor and APS, APS co-precipitated with c-Cbl but not in CHO.T cells which do not express APS. APS-mediated recruitment of c-Cbl to the insulin receptor led to rapid ubiquitination of the insulin receptor beta-subunit in CHO. T-APS but not in parental CHO.T cells. These results suggest that the function of APS is to facilitate coupling of the insulin receptor to c-Cbl in order to catalyse the ubiquitination of the receptor and initiation of internalisation or degradation.

Animals↗
PubMed2000

Low concentrations of fibrinogen increase cell migration speed on fibronectin/fibrinogen composite cables.

Optimal cell migration rate in a given direction (velocity) is a function of speed and directional persistence. Migration speed has been reported to be a function of adhesion strength such that optimal cell migration occurs where the cell is able to form enough stable attachments for good traction while allowing attachments at the trailing end to be broken during locomotion. This is particularly important in peripheral nerve regeneration where rapid Schwann cell recruitment across the injury site will lead to better functional recovery and reduced end organ atrophy. The aim here was to investigate the effects of changing adhesion properties of Fn materials by adding fibrinogen in order to design an optimal material for repair processes. Cell migration on Fn/Fg-cables increased with increasing content of %Fg to a peak cell migration velocity (Schwann cells) of 49 microm/h, at 50% Fg. Further increases in Fg content hindered cell migration. Vinculin-rich attachment plaques were reduced in a dose-dependent manner as the content of %Fg was increased whilst cells at the optimum Fg proportion for cell migration were moderately well spread. These results support the idea that optimum cell migration rates occur at intermediate attachment conditions, in this case at 50% Fg. These results show that incorporation of Fg into Fn-based materials will enhance the speed of Schwann cell migration and this would be likely to improve peripheral nerve regeneration. Indeed, directionally aligned Fn-based materials can now be engineered to give optimal cell velocity during repair cell recruitment in a range of tissue repair or tissue engineering applications.

Animals↗
PubMed2000

REDOR NMR on a hydrophobic peptide in oriented membranes.

A method is presented for the calculation of REDOR dephasing for specifically labeled membrane-spanning peptides in uniformly aligned lipid bilayers under magic angle oriented sample spinning (MAOSS) conditions. Numerical simulations are performed for dephasing of (13)C signal by (15)N when the labels are placed in an alpha-helical peptide at the carbonyl of residue (i) and amide nitrogen of residue (i + 2) to show the dependency of REDOR echo intensity on the peptide tilt angle relative to the membrane normal. The approach was applied to the labeled transmembrane domain of phospholamban ([(15)N-Leu(37), (13)C-Leu(39)]PLBTM) incorporated into dimyristoylphosphatidylcholine bilayers. The dephasing observed for a random membrane dispersion showed that the peptide was alpha-helical in the region including the two labels, and dephasing in oriented membranes showed that the peptide helix was tilted by 25 degrees +/- 7 degrees relative to the bilayer normal. These results agree with those obtained by other spectroscopic methods.

Calcium-Binding Proteins↗
PubMed2000

Social deprivation and prevalence of epilepsy and associated health usage.

OBJECTIVES: To examine the relation between social deprivation and the prevalence of epilepsy and associated morbidity using hospital activity data as a proxy. METHODS: The study was conducted in the health district of South Glamorgan, United Kingdom (population 434 000). Routinely available hospital data (inpatient and outpatient), an epilepsy clinic database, and mortality data underwent a process of record linkage to identify records relating to the same patient and to identify patients with epilepsy. Each patient was allocated a Townsend index deprivation score on the basis of their ward of residence. Age standardised correlations were calculated between deprivation score and prevalence of epilepsy, inpatient admissions, and outpatient appointments. Standardised mortality ratios (SMR) were also calculated. All analyses were performed on two cohorts: (1) all patients with epilepsy and (2) those patients with epilepsy without any underlying psychiatric illness or learning disability. RESULTS: The prevalence of epilepsy ranged between 2.0 and 13.4 per 1000 with a median of 6.7. There were positive correlations between social deprivation and prevalence in both populations: (1) r=0.75 (p<0.001) and (2) r=0.70 (p<0.001). After standardising for underlying prevalence there were also correlations for mean inpatient admissions: (1) r=0.62 (p<0.001), (2) r=0.59, (p<0.001) and for outpatient appointments: (1) r=0.53, (p=0.001) and (2) r=0. 51 (p=0.001). The SMR for those deprived was (1) 1.66 (95% confidence interval (95% CI) 1.27-2.05) and (2) 1.80 (95% CI 0.71-1. 67). For the population as a whole (with and without epilepsy) the SMR was 1.25 (95% CI 1.27-2.32). CONCLUSION: This study shows a strong correlation between the prevalence of epilepsy and social deprivation and weaker correlations between social deprivation and mean hospital activity.

Adolescent↗
PubMed2000

Health care provision for people with a learning disability. Record-linkage study of epidemiology and factors contributing to hospital care uptake.

BACKGROUND: We know little about how people with a learning disability access secondary health care. AIMS: To describe the epidemiology of learning disability, the influence of deprivation on prevalence and the pattern of secondary care uptake, including the effect of institutionalisation. METHOD: A record-linkage study of secondary care contacts of 434,000 people between 1991 and 1997. A population with learning disability was identified; their secondary care contact was calculated and compared with the general population's. RESULTS: The distribution of people with a learning disability (n = 1595) correlated significantly with deprivation. The presence of a learning disability hospital significantly affected care uptake. Place of residence also affected acute admission to the learning disability hospital. Former institution residents generated 212 admissions per 1000 patients; community patients generated 18 per 1000. The admission rate with any psychiatric diagnosis to any setting was 26.3 per 1000 people with a learning disability; 16.5% of such patients had a dual diagnosis. CONCLUSIONS: Health provision for people with a learning disability is affected by institutional provision.

Adolescent↗
PubMed2000

Reducing antipsychotic medication in people with a learning disability.

BACKGROUND: The use of antipsychotic drugs in people with learning disabilities is currently receiving intensified scrutiny and attempts are being made to reduce it. AIMS: A randomised controlled trial was designed to investigate factors influencing antipsychotic drug reduction among people with learning disabilities prescribed such medication for behavioural problems. METHOD: Thirty-six participants randomly allocated to the experimental group underwent four, monthly 25% drug reduction stages. There were no planned drug changes for the control group (n = 20). RESULTS: Twelve participants (33%) completed full withdrawal; a further seven (19%) achieved and maintained at least a 50% reduction. Drug reduction was associated with increased dyskinesia and higher activity engagement but not increased maladaptive behaviour. Some setting characteristics were associated with drug reinstatement. CONCLUSIONS: A substantial proportion of people with learning disability prescribed antipsychotic medications for behavioural purposes rather than for treating psychotic illness can have their drugs reduced or withdrawn.

Adult↗