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Biomedical subjects

S Khan

Publications and source records attributed to S Khan.

At least 73 records · Page 4Linked to original sources
PubMed2002

Epidermal growth factor receptor (EGFR) as a prognostic marker: an immunohistochemical study on 315 consecutive breast carcinoma patients.

OBJECTIVE: To assess the independent and interdependent prognostic value of epidermal growth factor receptor (EGFR) in carcinoma of breast in female population. The Type 1 family of growth factor receptors includes epidermal growth factor receptor (EGFR also known as EGFR1). METHODS: The expression of EGFR protein was analysed immunohistochemically on 315 tumour specimens of infiltrating ductal carcinoma of breast. These patients also had axillary lymph nodes sampling. RESULTS: Overexpression and/or amplification of EGFR was observed in 70 (22.00%) tumours. Eleven (16%) were grade I, 43 (61%) grade II and 16 (23%) grade III tumours. Axillary lymph node metastasis had significant correlation with intensified positivity of EGFR (p < 0.05). Significant number of EGFR positive patients developed local recurrence and distant metastases to brain, liver and bone (p < 0.05). EGFR positivity showed significant correlation with the disease free and overall survival (p < 0.05). At a median follow-up of 48 (4 years) months in EGFR positive patients, the overall survival was 3.39 years and disease free survival was 2.86 years. EGFR negative tumour patients showed a better survival. In this group the overall survival was 4.62 years and the disease free survival was 4 years. CONCLUSION: EGFR analysis can be a useful indicator for the selection of patients who are at the high risk, for hormonal therapy decisions and can be useful as a target for new treatment modalities.

Adult↗
PubMed2002

Clinical, pathological and molecular factors predicting axillary node involvement in primary breast cancer in Pakistani women.

BACKGROUND: Axillary lymph node involvement in primary breast cancer is one of its most important prognostic features. Thus any factors that may predict axillary lymph node involvement in this setting could be potentially helpful in treatment planning and other interventions. OBJECTIVE: The objective of this study was to evaluate clinical, pathological and immuno-histochemical markers in univariate and multivariate analysis, which may be helpful predictors of axillary lymph node involvement in breast cancer. METHOD: A retrospective analysis of 555 cases. Of these 58% had axillary nodal positivity and 42% were negative. CONCLUSION: Factors of no significance included patient's age, height, weight, age of first pregnancy, parity, marital status, menopausal status, family history of breast cancer, side of tumor. In univariate analysis the age of menarche, duration of symptoms, tumor size, site in outer quadrant, S phase and skin and nipple involvement all predicted axillary nodal involvement. The length of breast-feeding, increased intraductal component and increased PCNA were inversely proportional to nodal involvement. In multiple regression analysis however only size of the tumor, involvement of the skin and nipple and disease in the outer quadrant of breast were the factors, which assumed significance.

Axilla↗
PubMed2002

Multi-vessel off-pump coronary artery bypass grafting can be taught to trainee surgeons.

BACKGROUND: Although, Off-Pump Coronary Artery Bypass (OPCAB) surgery is being increasingly explored and practised in many cardiac units worldwide, there have been only few reports documenting the training of surgeons in this new technique. The purpose of this study was to address the reproducibility of the OPCAB in a unit where this technique is used extensively. METHODS: Registry data, notes and charts of 64 patients who were operated on by four trainee cardiac surgeons over a period of thirteen months at Harefield Hospital, were reviewed retrospectively. These trainees were part of an accredited training programme for cardiothoracic training and were trained by a single consultant trainer in a cardiac unit after it has had an established recent experience in performing non-selective OPCAB for all coming-in patients. Five (7.8%) patients (with 17 distal anastomoses) consented and underwent early postoperative angiography to check the quality of the grafts and anastomoses. RESULTS: The mean age of the study patients was 65.6 and the mean Parsonnet score was 9.4. There was a mean of 2.9 grafts per patient and circumflex territory anastomoses were performed in 48 (75%) patients. No operation required conversion to Cardiopulmonary Bypass (CPB). Angiography of the five patients revealed satisfactory seventeen (100%) distal anastomoses. CONCLUSION: With appropriate training, it is possible for trainees to learn OPCAB and perform multi-vessel revascularization in relatively high-risk patients with good results.

Adult↗
PubMed2001

Immunoproteasomes largely replace constitutive proteasomes during an antiviral and antibacterial immune response in the liver.

The proteasome is critically involved in the production of MHC class I-restricted T cell epitopes. Proteasome activity and epitope production are altered by IFN-gamma treatment, which leads to a gradual replacement of constitutive proteasomes by immunoproteasomes in vitro. However, a quantitative analysis of changes in the steady state subunit composition of proteasomes during an immune response against viruses or bacteria in vivo has not been reported. Here we show that the infection of mice with lymphocytic choriomeningitis virus or Listeria monocytogenes leads to an almost complete replacement of constitutive proteasomes by immunoproteasomes in the liver within 7 days. Proteasome replacements were markedly reduced in IFN-gamma(-/-) mice, but were only slightly affected in IFN-alphaR(-/-) and perforin(-/-) mice. The proteasome regulator PA28alpha/beta was up-regulated, whereas PA28gamma was reduced in the liver of lymphocytic choriomeningitis virus-infected mice. Proteasome replacements in the liver strongly altered proteasome activity and were unexpected to this extent, since an in vivo half-life of 12 days had been previously assigned to constitutive proteasomes in the liver. Our results suggest that during the peak phase of viral and bacterial elimination the antiviral cytotoxic T lymphocyte response is directed mainly to immunoproteasome-dependent T cell epitopes, which would be a novel parameter for the design of vaccines.

Animals↗
PubMed2001

LC/MS/MS determination of omapatrilat, a sulfhydryl-containing vasopeptidase inhibitor, and its sulfhydryl- and thioether-containing metabolites in human plasma.

Omapatrilat, the most clinically advanced member of a new class of cardiovascular agents, vasopeptidase inhibitors, is under development at Bristol-Myers Squibb Pharmaceutical Research Institute for the treatment of hypertension and heart failure. An electrospray LC/MS/MS method has been developed and validated for the simultaneous determination of omapatrilat and its four metabolites in human plasma. Since omapatrilat and two of the metabolites are sulfhydryl-containing compounds, methyl acrylate was used to stabilize these compounds in human blood and plasma samples. Methyl acrylate reacted instantly with the sulfhydryl group to form a derivative that was stable in blood and plasma. Extraction of the analytes from plasma samples was achieved by semiautomated liquid-liquid extraction, where a robotic liquid handler performed the liquid-transferring steps. The mass spectrometer was operated in the negative ion selected-reaction-monitoring mode. The calibration curve ranges were 0.5-250 ng/mL for omapatrilat and one metabolite and 2.0-250 ng/mL for the other three metabolites.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

Cutting edge: neosynthesis is required for the presentation of a T cell epitope from a long-lived viral protein.

CTLs recognize peptide epitopes which are proteolytically generated by the proteasome and presented on MHC class I molecules. According to the defective ribosomal product (DRiP) hypothesis, epitopes originate from newly synthesized polypeptides which are degraded shortly after their translation. The DRiP hypothesis would explain how epitopes can be generated from long-lived proteins. We examined whether neosynthesis is required for presentation of the immunodominant epitope NP118 of the lymphocytic choriomeningitis virus nucleoprotein, which has a half-life of >3 days. Two days after nucleoprotein biosynthesis was terminated in a tetracycline-regulated transfectant, the presentation of the NP118 epitope ceased. This indicates that NP118 epitopes are generated from newly synthesized nucleoproteins rather than from the long-lived pool of nucleoproteins in the cell. Therefore, the lymphocytic choriomeningitis virus nucleoprotein is the first substrate for which a major prediction of the DRiP hypothesis, namely the requirement for neosynthesis, is shown to hold true.

Animals↗
PubMed2001

Novel mutations of MYO15A associated with profound deafness in consanguineous families and moderately severe hearing loss in a patient with Smith-Magenis syndrome.

Mutations in myosin XVA are responsible for the shaker 2 ( sh2) phenotype in mice and nonsyndromic autosomal recessive profound hearing loss DFNB3 on chromosome 17p11.2. We have ascertained seven families with profound congenital hearing loss from Pakistan and India with evidence of linkage to DFNB3 at 17p11.2. We report three novel homozygous mutations in MYO15A segregating in three of these families. In addition, one hemizygous missense mutation of MYO15A was found in one of eight Smith-Magenis syndrome (del(17)p11.2) patients from North America who had moderately severe sensorineural hearing loss.

Abnormalities, Multiple↗
PubMed2001

Modulation of adipocyte G-protein expression in cancer cachexia by a lipid-mobilizing factor (LMF).

Adipocytes isolated from cachectic mice bearing the MAC 16 tumour showed over a 3-fold increase in lipolytic response to both low concentrations of isoprenaline and a tumour-derived lipid mobilizing factor (LMF). This was reflected by an enhanced stimulation of adenylate cyclase in plasma membrane fractions of adipocytes in the presence of both factors. There was no up-regulation of adenylate cyclase in response to forskolin, suggesting that the effect arose from a change in receptor number or G-protein expression. Immunoblotting of adipocyte membranes from mice bearing the MAC16 tumour showed an increased expression of Galphas up to 10% weight loss and a reciprocal decrease in Galpha. There was also an increased expression of Galphas and a decrease in Galpha in adipose tissue from a patient with cancer-associated weight loss compared with a non-cachectic cancer patient. The changes in G-protein expression were also seen in adipose tissue of normal mice administered pure LMF as well as in 3T3L1 adipocytes in vitro. The changes in G-protein expression induced by LMF were attenuated by the polyunsaturated fatty acid, eicosapentaenoic acid (EPA). This suggests that this tumour-derived lipolytic factor acts to sensitize adipose tissue to lipolytic stimuli, and that this effect is attenuated by EPA, which is known to preserve adipose tissue in cancer cachexia.

Adenylyl Cyclases↗
PubMed2001

Schwannomin isoform-1 interacts with syntenin via PDZ domains.

The neurofibromatosis type 2 gene (NF2) is involved in the pathogenesis of benign tumors of the human nervous system. The NF2 protein, called schwannomin or merlin, is inactivated in virtually all schwannomas and meningiomas. The molecular mechanisms by which schwannomin functions as a tumor suppressor is unknown but believed to involve plasma membrane-cytoskeletal interactions. Two major alternatively spliced isoforms of schwannomin differing in their C termini have been reported. Using the yeast two-hybrid system, we have identified syntenin as a binding partner for schwannomin isoform-1 (sch-1). Syntenin is an adapter protein that couples transmembrane proteoglycans to cytoskeletal components and is involved in intracellular vesicle transport. The C terminus 25 amino acids of sch-1 and the two PDZ domains of syntenin mediate their binding, and mutations introduced within the VAFFEEL region of sch-1 defined a sequence crucial for syntenin recognition. We have showed that the two proteins interacted in vitro and in vivo and localized underneath the plasma membrane. Fibroblast cells expressing heterologous antisense syntenin display alterations in the subcellular distribution of sch-1. Together, these results provide the first functional clue to the existence of schwannomin isoforms and could unravel novel pathways for the transport and subcellular localization of schwannomin in vivo.

3T3 Cells↗
PubMed2001

Mutations of the protocadherin gene PCDH15 cause Usher syndrome type 1F.

Human chromosome 10q21-22 harbors USH1F in a region of conserved synteny to mouse chromosome 10. This region of mouse chromosome 10 contains Pcdh15, encoding a protocadherin gene that is mutated in ames waltzer and causes deafness and vestibular dysfunction. Here we report two mutations of protocadherin 15 (PCDH15) found in two families segregating Usher syndrome type 1F. A Northern blot probed with the PCDH15 cytoplasmic domain showed expression in the retina, consistent with its pathogenetic role in the retinitis pigmentosa associated with USH1F.

Aged↗
PubMed2001

Determinants of chemotactic signal amplification in Escherichia coli.

A well-characterized protein phosphorelay mediates Escherichia coli chemotaxis towards the amino acid attractant aspartate. The protein CheY shuttles between flagellar motors and methyl-accepting chemoreceptor (MCP) complexes containing the linker CheW and the kinase CheA. CheA-CheY phosphotransfer generates phospho-CheY, CheY-P. Aspartate triggers smooth swim responses by inactivation of the CheA bound to the target MCP, Tar; but this mechanism alone cannot explain the observed response sensitivity. Here, we used behavioral analysis of mutants deleted for CheZ, a catalyst of CheY-P dephosphorylation, or the methyltransferase CheR and/or the methylesterase CheB to examine the roles of accelerated CheY-P dephosphorylation and MCP methylation in enhancement of the chemotactic response. The extreme motile bias of the mutants was adjusted towards wild-type values, while preserving much of the aspartate response sensitivity by expressing fragments of the MCP, Tsr, that either activate or inhibit CheA. We then measured responses to small jumps of aspartate, generated by flash photolysis of photo-labile precursors. The stimulus-response relation for Delta cheZ mutants overlapped that for the host strains. Delta cheZ excitation response times increased with stimulus size consistent with formation of an occluded CheA state. Thus, neither CheZ-dependent or independent increases in CheY-P dephosphorylation contribute to the excitation response. In Delta cheB Delta cheR or Delta cheR mutants, the dose for a half-maximal response, [Asp](50), was ca 10 microM; but was elevated to 100 microM in Delta cheB mutants. In addition, the stimulus-response relation for these mutants was linear, consistent with stoichiometric inactivation, in contrast to the non-linear relation for wild-type E. coli. These data suggest that response sensitivity is controlled by differential binding of CheR and/or CheB to distinct MCP signaling conformations.

Bacterial Proteins↗
PubMed2001

Functional IL-2 receptor beta (CD122) and gamma (CD132) chains are expressed by fibroblast-like synoviocytes: activation by IL-2 stimulates monocyte chemoattractant protein-1 production.

The expression of the IL-2R alpha-, beta-, and gamma-chains, CD25, CD122, and CD132, respectively, was investigated on fibroblast-like synoviocytes (FLS) and dermal fibroblasts (DF). Both protein and mRNA for CD122 and CD132 were observed but there was no evidence of CD25 expression. Quantification of the Ag binding sites for CD122 showed that FLS expressed 4 times more receptor molecules than DF. The functional capability of these receptors was confirmed by the production of monocyte chemoattractant protein-1 (MCP-1) in direct response to stimulation by IL-2, which could be inhibited by neutralizing anti-CD122 mAb. Both rheumatoid arthritis (RA) and osteoarthritis (OA) FLS and DF spontaneously produced MCP-1 in culture over a similar range of concentrations. However, RA and OA FLS produced significantly greater levels of MCP-1 following stimulation by IL-2 and IL-1 beta; RA FLS produced significantly more MCP-1 than OA FLS. Addition of exogenous IL-2 caused a slight, but significant, decrease in MCP-1 production by DF. The addition of neutralizing anti-CD122 mAb to FLS cultures partially, but significantly, reduced the IL-2-induced MCP-1 secretion, but did not effect either the spontaneous or IL-1 beta-induced secretion of MCP-1. Increased tyrosine phosphorylation was observed in FLS lysates following 30-min incubation with IL-2. In conclusion, in the inflamed synovium, as activated T cells migrate through the sublining and lining layer, T cell-derived IL-2 may activate FLS to secrete MCP-1, thus recruiting macrophages into the rheumatoid synovium and perpetuating inflammation.

Antibodies, Blocking↗
PubMed2001

Cytochrome P450 2E1 metabolically activates propargyl alcohol: propiolaldehyde-induced hepatocyte cytotoxicity.

Pargyline, an antihypertensive agent and monoamine oxidase inhibitor, induces hepatic GSH depletion and hepatotoxicity in vivo in rats [E.G. De Master, H.W. Sumner, E. Kaplan, F. N. Shirota, H.T. Nagasawa, Toxicol. Appl. Pharmacol. 65 (1982) 390-401]. Propargyl alcohol (2-propyn-1-ol), because of its structural similarity to allyl alcohol, was thought to be activated by alcohol dehydrogenase. However, it is a poor substrate compared to allyl alcohol and it was therefore proposed that propargyl alcohol-induced liver injury involved metabolic activation by catalase/H(2)O(2) [E.G. De Master, T. Dahlseid, B. Redfern, Chem. Res. Toxicol. 7 (1994) 414-419]. In the following we showed that; (1) propargyl alcohol-induced cytotoxicity was markedly enhanced in CYP 2E1-induced hepatocytes and prevented by various CYP 2E1 inhibitors but was only slightly affected when alcohol dehydrogenase was inhibited with methylpyrazole/DMSO or when catalase was inactivated with azide or aminotriazole, (2) hepatocyte GSH depletion preceded cytotoxicity and was inhibited by cytochrome P450 inhibitors but not by catalase/alcohol dehydrogenase inhibitors. GSH conjugate formation during propargyl alcohol metabolism by microsomal mixed function oxidase in the presence of GSH was also prevented by anti-rat CYP 2E1 or CYP 2E1 inhibitors, (3) cytotoxicity was prevented when lipid peroxidation was inhibited with antioxidants, desferoxamine (ferric chelator) or dithiothreitol. Propargyl alcohol-induced cytotoxicity and reactive oxygen species formation were markedly increased in GSH-depleted hepatocytes. All of this evidence suggests that propargyl alcohol-induced cytotoxicity involves metabolic activation by CYP 2E1 to form propiolaldehyde that causes hepatocyte lysis as a result of GSH depletion and lipid peroxidation.

Aldehydes↗
PubMed2001

Interaction of elongation factor 1alpha from Zea mays (ZmEF-1alpha) with F-actin and interplay with the maize actin severing protein, ZmADF3.

EF-1alpha is an abundant eukaryotic protein whose principle function appears to be to bind aminoacyl-tRNA to the ribosome. However, it is also known that EF-1alpha from other sources binds both microtubules and microfilaments. We report the expression of Zea mays EF-1alpha (ZmEF-1alpha) in bacteria and that this protein has similar actin-binding properties as other EF-1alpha members. ZmEF-1alpha bundles actin filaments at low pH (6.5) and inhibits the addition of monomer at both filament ends, possibly as a consequence. ZmEF-1alpha binds actin filaments at all pH values tested (pH 6.0-8.0), indicating that one actin binding site is not pH sensitive. One of the actin-binding sites was determined to reside within domain I (1-223) of ZmEF-1alpha, but this domain did not affect the kinetics of polymerisation. We show that the bundling activity of ZmEF-1alpha is modulated by ZmADF3 a (a Zea mays ADF/cofilin), an actin filament severing protein, in vitro. Bundling of actin filaments caused by ZmEF-1alpha was enhanced in the presence of ZmADF3. The pH-dependent activities of both proteins in vitro suggests that they may work together to respond to temporal and spatial intracellular pH changes to regulate the pattern of the growth of plant cells.

Actin Cytoskeleton↗
PubMed2001

Lysosomal oxidative stress cytotoxicity induced by nitrofurantoin redox cycling in hepatocytes.

1. The enzymes responsible for the reductive activation of NFT are not known. We have now shown that under aerobic conditions, inhibitors of cytochrome P450 or P450 reductase but not DT diaphorase prevented NFT induced cytotoxicity and reactive oxygen species ("ROS") formation. This suggests that NFT was reductively activated by reduced cytochrome P450 and/or P450 reductase. 2. The subcellular organelle oxidative stress effects leading to cytotoxicity are not known. Hepatocyte mitochondrial membrane potential was only slightly decreased by NFT before cytotoxicity ensued. However NFT induced lysosomal damage and hepatocyte protease activation. Endocytosis inhibitors, lysosomotropic agents or lysosomal protease inhibitors also prevented NFT induced cytotoxicity. 3. Lipid peroxidation also preceded cytotoxicity. Furthermore desferoxamine (a ferric chelator), antioxidants or ROS scavengers (catalase, mannitol, TEMPOL or dimethylsulfoxide) prevented NFT cytotoxicity. 4. It is concluded that H2O2 reacts with lysosomal Fe(+2) to form "ROS" which causes lysosomal lipid peroxidation, membrane disruption, protease release and cell death.

Animals↗
PubMed2001

Surgical treatment of hemorrhoids: prospective, randomized trial comparing closed excisional hemorrhoidectomy and the Harmonic Scalpel technique of excisional hemorrhoidectomy.

PURPOSE: The object of this study was to evaluate technique using the ultrasonically activated scalpel as an alternative to closed hemorrhoidectomy in an unbiased evaluation of this new technology. METHODS: Thirty patients with Grade 2 or 3 symptomatic hemorrhoids were prospectively randomized to undergo closed hemorrhoidectomy assisted by electrocautery or hemorrhoidectomy with the ultrasonically activated scalpel, i.e., the Harmonic Scalpel. We evaluated the difference between techniques in operative time, postoperative pain, incontinence, and quality of life (using the Short Form-36 survey), as well as complications. RESULTS: Mean operative time for closed hemorrhoidectomy with electrocautery was 35.7 +/- 3 minutes; for Harmonic Scalpel patients, it was 31.7 +/- 2 minutes (P < 0.37). There was no statistical difference in operative time for two- or three-column hemorrhoidectomy. There was no significant difference in pain measurements reported on Day 1 (5.8 +/- 0.4 for electrocautery and 5.6 +/- 0.6 for Harmonic Scalpel, P < 0.82). On postoperative Day 7, the difference in pain between groups approached significance, with pain reported as 3.7 +/- 0.3 for electrocautery and 5.1 +/- 0.7 for Harmonic Scalpel(R) (P < 0.06). At six weeks, both groups were pain free. There was a significant decrease in pain between postoperative Days 1 and 7 in the electrocautery patients that was not seen in the Harmonic Scalpel patients. Incontinence measured preoperatively, at postoperative Day 7, and at postoperative Week 6 was similar for both groups and reflected occasional incontinence of gas. When the various items of the Short Form-36 survey were compared, there was no significant difference between posttreatment and preoperative values. There was no difference in the number of complications between patient groups. CONCLUSION: Although the Harmonic Scalpel is an effective tool in the treatment of hemorrhoidal disease, we found no specific advantage in postoperative pain, fecal incontinence, operative time, quality of life, or complications compared with traditional closed hemorrhoidectomy.

Adult↗