Biomedical subjects

A Saleem

Publications and source records attributed to A Saleem.

At least 37 records · Page 2Linked to original sources

PubMed1999

The incidence, natural history, and outcome of secondary intervention for persistent collateral flow in the excluded abdominal aortic aneurysm.

OBJECTIVE: The goal of abdominal aortic aneurysm (AAA) repair is the prevention of rupture. Exclusion of the infrarenal AAA by means of operation or endovascular graft placement is an alternative therapy to achieve this goal. However, thrombosis of the excluded aneurysm sac does not always occur and further intervention may be needed. This study examines the efficacy of available screening methods to detect the persistence of aneurysm sac flow and the outcome of secondary procedures to treat this problem. METHODS: During the past 14 years, 1218 patients have undergone operative retroperitoneal exclusion of AAA. To date, 48 patients have been found to have persistent flow in the excluded AAA sac with duplex scanning. Twenty-seven patients underwent surgical intervention, and seven of these procedures were performed for rupture. Six patients have undergone treatment with interventional techniques (four successfully). The patients were evaluated for preoperative angiographic, anatomic, and comorbid factors that may have predisposed them to failed exclusion. Also, perioperative morbidity and mortality, estimated blood loss, and survival were assessed in the patients who required surgical treatment. RESULTS: There were no perioperative parameters that correlated with postoperative persistent flow in the excluded AAA sac. The mean time to secondary intervention was 51 months (range, 2 to 113 months). Two patients had false-negative computed tomographic angiogram results, eight patients had false-negative angiogram results, and six patients had duplex scan examinations that had initially negative results that were then positive for flow in sac. Reoperation had a 7.4% mortality rate (two deaths) and a median blood loss of 2600 mL, as compared with 500 mL for primary procedures. CONCLUSION: Secondary operations for patent excluded aortic aneurysm sacs have higher mortality and intraoperative blood loss rates than do primary procedures for AAA repair. The localization of branch leaks with computerized tomographic angiography, angiography, and duplex scanning were imprecise, and better methods are needed to adequately diagnose patent sacs. Expansion of AAA sac may be the only reliable factor.

Adult↗

PubMed1998

High-performance liquid chromatographic quantitation of total and lactone 20(S)camptothecin in patients receiving oral 20(S)camptothecin.

We have developed a sensitive high-performance liquid chromatography (HPLC) assay to quantitate total and lactone forms of 20(S)camptothecin (CPT) in human plasma. Lactone and total CPT were extracted using solid-phase extraction and liquid-liquid extraction, respectively. The extracted lactone samples could be stored without immediate HPLC analysis. The two forms of CPT were quantitated by reversed-phase HPLC with fluorescence detection. The extraction efficiencies were about 100% and 92% for the total and lactone forms, respectively. The lower limit of quantitation was 5.74 nM for the two forms. The method was reproducible with a mean interday and intraday variability of 6% for total CPT and 4% and 6%. respectively, for lactone CPT. The assay could effectively quantitate lactone and total CPT in patients receiving single dose and multiple doses of oral CPT.

Antineoplastic Agents, Phytogenic↗

PubMed1998

Interaction between the N-terminus of human topoisomerase I and SV40 large T antigen.

We have attempted to identify human topoisomerase I-binding proteins in order to gain information regarding the cellular roles of this protein and the cytotoxic mechanisms of the anticancer drug camptothecin, which specifically targets topoisomerase I. In the course of this work we identified an interaction between the N-terminus of human topoisomerase I and the SV40 T antigen that is detectable in vitro using both affinity chromatography and co-immunoprecipitation. Additional results indicate that this interaction does not require intermediary DNA or stoichiometric quantities of other proteins. Furthermore, the interaction is detectable in vivo using a yeast two-hybrid assay. Two binding sites for T antigen are apparent on the topoisomerase I protein: one consisting of amino acids 1-139, the other present in the 383-765 region of the protein. Interestingly, nucleolin, which binds the 166-210 region of topoisomerase I, is able to bind an N-terminal fragment of topoisomerase I concurrently with T antigen. Taken together with our prior identification of nucleolin as a topoisomerase I-binding protein, the current results suggest that helicase-binding is a major role of the N-terminus of human topoisomerase I and that the resultant helicase-topoisomerase complex may function as a eukaryotic gyrase.

Antigens, Polyomavirus Transforming↗

PubMed1997

Mechanisms of resistance in a human cell line exposed to sequential topoisomerase poisoning.

Camptothecins are a new class of anticancer drugs that target DNA topoisomerase I; current efforts are directed toward elucidating optimal combinations of these drugs with other antineoplastic agents. A rationale for the use of sequential therapy involving the combination of camptothecins with topoisomerase II-targeting drugs, such as etoposide, has arisen from observations of increased topoisomerase II protein levels in cell lines resistant to camptothecin. In an effort to understand potential mechanisms of resistance to this strategy, we developed a U-937 cell subline, denoted RERC, that is capable of surviving exposure to sequential topoisomerase poisoning. The RERC cells are 200-fold resistant to camptothecin, 8-fold resistant to etoposide, and 10-fold hypersensitive to cisplatin compared to the parental U-937 cells. Biochemical analyses indicate that the resistant phenotype involves alterations in both topoisomerase I and topoisomerase IIalpha. Topoisomerase I catalytic activity in the resistant cells is similar to that of the parental line but is resistant to camptothecin. Moreover, the resistant cells express a single mRNA species of topoisomerase I that codes for a mutation in codon 533. In addition, topoisomerase IIalpha protein levels are decreased 10-fold in the resistant line, coincident with a two-fold decrease in the expression of topoisomerase IIalpha mRNA. Collectively, these results indicate that resistance to sequential topoisomerase poisoning may involve a reduction in total cellular topoisomerase activity.

Antineoplastic Agents↗

PubMed1997

Hepatic hemangioma: a review.

Hemangioma is a common hepatic lesion. The incidence is reported to be around 2%. The etiology of these lesions is unclear. Hemangioma should be regarded as benign with distinct clinicopathological features. Although most patients are asymptomatic, some may present with abdominal mass, cardiac failure, coagulopathy, or rupture. Hemangioma presents a diagnostic challenge. The surgeon should be aware of this lesion to avoid the pitfalls in differential diagnosis. A misinterpretation of hypervascular metastasis may lead to marked mismanagement. We emphasize the necessity of relatively specific and sensitive investigations in the differential diagnosis of a liver nodule. Surgery alone is usually unnecessary. Therapeutic options include steroids, hepatic artery ligation, therapeutic embolizations, radiation therapy, and chemotherapy. Available data suggest a favorable prognosis.

Hemangioma↗

PubMed1996

Nuclear signaling induced by ionizing radiation involves colocalization of the activated p56/p53lyn tyrosine kinase with p34cdc2.

The Src-like protein-tyrosine kinase p56/p53lyn associates with cell membranes and transduces signals from activated cell surface receptors. In the present work, cell fractionation and confocal microscopy studies demonstrate expression of Lyn in the nucleus. We also demonstrate that exposure of intact cells to ionizing radiation is associated with selective activation of nuclear Lyn. Similar findings have been obtained following irradiation of purified nuclei. Immunoprecipitation studies of nuclear lysates demonstrate radiation-induced binding of Lyn to p34cdc2. Nuclear colocalization of Lyn with Cdc2 has been confirmed by confocal microscopy. Other studies with glutathione S-transferase-Lyn fusion proteins demonstrate that the binding of Lyn to nuclear Cdc2 is associated with inhibition of Cdc2 activity. These findings suggest that the association of activated Lyn with Cdc2 in the nucleus may contribute to regulation of a DNA damage-dependent premitotic checkpoint.

CDC2 Protein Kinase↗

PubMed1995

Ionizing radiation stimulates a Grb2-mediated association of the stress-activated protein kinase with phosphatidylinositol 3-kinase.

The stress-activated protein (SAP) kinases are induced by tumor necrosis factor, oncoproteins, and UV light. The present studies demonstrate that ionizing radiation (IR) activates p54 SAP kinase. IR-induced activation of SAP kinase is associated with binding to the SH2/SH3-containing adaptor protein Grb2. This interaction is mediated by the SH3 domains of Grb2 and the proline-rich sequence PPPKIP in the carboxy-terminal region of SAP kinase. We also demonstrated that SAP kinase and the p85 alpha-subunit of phosphatidylinositol (PI) 3-kinase form a complex in irradiated cells. The results indicate that this complex involves binding of the p85 alpha subunit of PI 3-kinase to the SH2 domain of Grb2. The functional role of linking SAP kinase to PI 3-kinase is further supported by the finding that wortmannin, an inhibitor of PI 3-kinase, stimulates SAP kinase activity. These results suggest that the cellular response to IR may include regulation of SAP kinase by a PI 3-kinase-dependent signaling pathway.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Defective induction of stress-activated protein kinase activity in ataxia-telangiectasia cells exposed to ionizing radiation.

The activity of stress-activated protein (SAP) kinase is stimulated by diverse agents such as tumor necrosis factor, UV light, and protein synthesis inhibitors. The present study demonstrates that ionizing radiation (IR) exposure is also associated with the induction of SAP kinase activity. Cells derived from patients with ataxia-telangiectasia (A-T) are characterized by hypersensitivity to IR. In this study, we demonstrate that IR-induced activation of SAP kinase is defective in A-T cells. In contrast, exposure of A-T cells to UV light or anisomycin results in the induction of SAP kinase activity. These findings indicate that IR-induced signals involved in SAP kinase activation are defective in A-T cells.

Anisomycin↗

PubMed1995

Stimulation of human monocytes with macrophage colony-stimulating factor induces a Grb2-mediated association of the focal adhesion kinase pp125FAK and dynamin.

Macrophage colony-stimulating factor (M-CSF) is required for the growth and differentiation of mononuclear phagocytes. In the present studies using human monocytes, we show that M-CSF induces interaction of the Grb2 adaptor protein with the focal adhesion kinase pp125FAK. The results demonstrate that tyrosine-phosphorylated pp125FAK directly interacts with the SH2 domain of Grb2. The findings indicate that a pYENV site at Tyr-925 in pp125FAK is responsible for this interaction. We also demonstrate that the Grb2-FAK complex associates with the GTPase dynamin. Dynamin interacts with the SH3 domains of Grb2 and exhibits M-CSF-dependent tyrosine phosphorylation in association with pp125FAK. These findings suggest that M-CSF-induced signaling involves independent Grb2-mediated pathways, one leading to Ras activation and another involving pp125FAK and a GTPase implicated in receptor internalization.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Monocyte colony-stimulating factor stimulates binding of phosphatidylinositol 3-kinase to Grb2.Sos complexes in human monocytes.

Monocyte colony-stimulating factor (M-CSF) is required for the proliferation of mononuclear phagocytes. The activated M-CSF receptor associates with phosphatidylinositol 3-kinase (PI 3-kinase). In the present studies, we demonstrate that M-CSF also induces direct interaction of PI 3-kinase (p85 alpha subunit) with the SH2/SH3 adaptor protein Grb2. Tyrosine-phosphorylated PI 3-kinase interacts with the SH2 domain of Grb2. A pYRNE (pY408) site in PI 3-kinase is potentially involved in this interaction. The results also demonstrate that the PI 3-kinase.Grb2 complex associates with the guanine nucleotide exchange protein Sos. Since Sos binds to the SH3 domains of Grb2 and thereby associates with Ras at the cell membrane, formation of the PI 3-kinase.Grb2.Sos complex provides a potential mechanism for growth factor-induced interactions of PI 3-kinase and Ras.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Activation of serine/threonine protein kinases and early growth response 1 gene expression by tumor necrosis factor in human myeloid leukemia cells.

The early growth response 1 (EGR-1) gene is induced by mitogenic and differentiating signals in diverse cell types. The present studies have examined the effects of TNF-alpha on the induction of EGR-1 expression in human myeloid leukemia cells and the potential cytoplasmic signaling cascades that transduce TNF-induced signals to the nucleus. The results demonstrate that treatment of HL-60 cells with TNF is associated with the transient induction of the EGR-1 gene. The results also demonstrate that TNF treatment is associated with activation of the serine/threonine kinase, pp90rsk, which acts upstream to EGR-1 gene induction. Partial purification of pp90rsk by affinity chromatography demonstrated an increase in S6 peptide phosphorylation in response to TNF treatment. Because TNF activates sphingomyelin hydrolysis, we also studied the effects of sphingomyelinase (SMase) on induction of EGR-1 and pp90rsk. The results demonstrate that SMase also activates pp90rsk and induces EGR-1 gene expression. Previous work has demonstrated that mitogen-activated protein (MAP) kinase activates pp90rsk. The present studies further show that treatment with TNF or SMase is associated with induction of both the pp42/44 MAP and the related Jun kinases. Induction of pp42/44 MAP kinase activity is temporally related to activation of pp90rsk and the EGR-1 gene. These findings support the involvement of an MAP kinase/pp90rsk/EGR-1 cascade in the response of myeloid leukemia cells to TNF.

Amino Acid Sequence↗

PubMed1995

Transdermal delivery of physostigmine. A pretreatment against organophosphate poisoning.

Physostigmine absorption through isolated human skin and inhibition of plasma and red blood cell cholinesterases in guinea-pigs have been measured to assess the feasibility of its transdermal delivery as a pretreatment for organophosphate poisoning. Penetration of radiolabelled physostigmine across human epidermis was measured in-vitro using glass diffusion cells and optimization of physostigmine delivery was achieved by changes in vehicle formulation and use of penetration enhancers. Two-component vehicles consisting of propionic acid/isopropyl myristate (50:50) and propionic acid/oleic acid (50:50) produced the highest transdermal delivery of physostigmine. A comparison of formulations containing propionic acid alone with propionic acid plus oleic acid when applied to guinea-pigs, showed that inclusion of oleic acid allowed the amount of physostigmine and the size of the transdermal patch to be substantially reduced, whilst maintaining effective delivery rates. The formulation containing oleic acid was not irritant to guinea-pigs when applied to the skin for 48 h. It is concluded that a mixture of propionic acid and oleic acid containing physostigmine is a good candidate for transdermal delivery of physostigmine as a pretreatment for organophosphate poisoning.

Administration, Cutaneous↗

PubMed1995

Involvement of stress-activated protein kinase in the cellular response to 1-beta-D-arabinofuranosylcytosine and other DNA-damaging agents.

The cellular response to 1-beta-D-arabinofuranosylcytosine (ara-C) includes activation of Jun/AP-1, induction of c-jun transcription, and programmed cell death. The stress-activated protein (SAP) kinases stimulate the transactivation function of c-jun by amino terminal phosphorylation. The present work demonstrates that ara-C activates p54 SAP kinase. The finding that SAP kinase is also activated by alkylating agents (mitomycin C and cisplatinum) and the topoisomerase I inhibitor 9-amino-camptothecin supports DNA damage as an initial signal in this cascade. The results demonstrate that ara-C also induces binding of SAP kinase to the SH2/SH3-containing adapter protein Grb2. SAP kinase binds to the SH3 domains of Grb2, while interaction of the p85 alpha-subunit of phosphatidylinositol 3-kinase complex. The results also demonstrate that ara-C treatment is associated with inhibition of lipid and serine kinase activities of PI 3-kinase. The potential significance of the ara-C-induced interaction between SAP kinase and PI 3-kinase is further supported by the demonstration that Wortmannin, an inhibitor of PI 3-kinase, stimulates SAP kinase activity. The finding that Wortmannin treatment is also associated with internucleosomal DNA fragmentation may support a potential link between PI 3-kinase and regulation of both SAP kinase and programmed cell death.

Adaptor Proteins, Signal Transducing↗

PubMed1994

Activation of the pp90rsk and mitogen-activated serine/threonine protein kinases by ionizing radiation.

The cellular response to ionizing radiation (IR) includes induction of the c-jun and EGR1 early response genes. The present work has examined potential cytoplasmic signaling cascades that transduce IR-induced signals to the nucleus. The results demonstrate activation of the 40S ribosomal protein S6 kinase, pp90rsk, in human U-937 myeloid leukemia cells. Partial purification of pp90rsk by affinity chromatography demonstrated an increase in S6 peptide phosphorylation when comparing irradiated with control cells. IR-induced activation of pp90rsk was further confirmed in immune-complex kinase assays. In contrast to these findings, there was no detectable induction of pp70S6K. Previous work has demonstrated that mitogen-activated protein kinase activates pp90rsk. The present results further show that IR treatment is associated with induction of mitogen-activated protein kinase activity and that this event is temporally related to activation of pp90rsk and early response gene expression. These findings suggest that activation of the mitogen-activated protein kinase/pp90rsk cascade is involved in the response of cells to IR exposure.

Base Sequence↗

PubMed1994

Ionizing radiation induces rapid tyrosine phosphorylation of p34cdc2.

Eukaryotic cells respond to ionizing radiation exposure with cell cycle arrest. However, little is known about the signaling mechanisms responsible for this effect. The present work has asked whether ionizing radiation exposure is associated with changes in phosphorylation of proteins in HL-60 myeloid leukemia cells. The results demonstrate increased tyrosine phosphorylation of a M(r) 34,000 substrate. This effect was detectable at 1 to 10 min after irradiation and was induced by doses of 50 to 500 cGy. Immunoprecipitation studies further suggest that this substrate is the serine/threonine p34cdc2 protein kinase. Since p34cdc2 is required for entry into mitosis, these findings support the posttranslational modification of a cell cycle regulatory protein in the response to ionizing radiation.

CDC2 Protein Kinase↗

PubMed1994

Activation of Raf-1 and mitogen-activated protein kinases during monocytic differentiation of human myeloid leukemia cells.

Treatment of human myeloid leukemia cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C (PKC), is associated with induction of monocytic differentiation. Since PKC can act immediately upstream to the cytoplasmic Raf-1 serine/threonine protein kinase, we studied activation of Raf-1 during induction of the differentiated monocytic phenotype. The results demonstrate that Raf-1 is activated during TPA-induced monocytic differentiation of HL-60 cells. In contrast, there was little effect of TPA on this kinase in an HL-60 variant, designated HL-525, which is resistant to TPA-induced differentiation. Treatment of both HL-60 and HL-525 cells with okadaic acid, an inhibitor of serine/threonine protein phosphatases 1 and 2A, was associated with Raf-1 activation and induction of the monocytic phenotype. Since Raf-1 can activate the mitogen-activated protein (MAP) kinases, we also studied the relationship between MAP kinase activation and monocytic differentiation. Treatment of HL-60, but not HL-525, cells with TPA was associated with increased MAP kinase activity as determined by phosphorylation of myelin basic protein and the c-Jun Y peptide. Okadaic acid-induced differentiation of both HL-60 and HL-525 cells was similarly accompanied by increases in MAP kinase activity. These findings indicated that activation of Raf-1/MAP kinase signaling is associated with induction of a differentiated monocytic phenotype and that okadaic acid bypasses a defect in this cascade in TPA-treated HL-525 cells. While recent studies have shown that HL-525 cells are deficient in PKC beta, the present results demonstrate that PKC beta expression is up-regulated in the HL-525 variant by treatment with retinoic acid. The results also demonstrate that retinoic acid-treated HL-525 cells respond to TPA with activation of Raf-1 and MAP kinase, as well as induction of monocytic differentiation. Taken together, the results indicate that activation of Raf-1/MAP kinase signaling is associated with monocytic differentiation and that stimulation of serine/threonine protein phosphorylation by TPA or okadaic acid is sufficient for reversal of the leukemic HL-60 phenotype.

Amino Acid Sequence↗

PubMed1994

Comparative skin testing with PPD tuberculin, Mycobacterium avium and M. scrofulaceum sensitin in schoolchildren in Saudi Arabia.

SETTING: Jizan region, Saudi Arabia. OBJECTIVE: To test methodology for studies of tuberculin sensitivity and effectiveness of BCG vaccination programme. DESIGN: School children (n = 315) aged 6-12 years simultaneously tested intradermally with PPD tuberculin RT23, 2TU and 0.1 microgram Mycobacterium avium or M. scrofulaceum sensitin. Presence of BCG scar as evidence of previous BCG vaccination. Cervical lymph nodes palpated. RESULTS: BCG coverage was 75%. The prevalences of positive reactions (induration > or = 6 mm) were higher among children with than without scar. Prevalences of positive reactions to PPD and M. scrofulaceum sensitin were higher among girls than boys. In children with scar, the mean size of positive reactions to PPD was larger among girls than boys, and the prevalence of positive reactions was smaller in this group among children with than without palpable cervical lymph nodes. The sizes of reactions both to M. avium and to M. scrofulaceum sensitin were correlated to the size of the tuberculin reactions. Previous admission to hospital was reported less often by children with than without scar. CONCLUSIONS: The technique applied and training of staff was satisfactory. In further studies, however, we will apply three simultaneous tests to each person.

Age Factors↗

PubMed1994

Activation of early growth response 1 gene transcription and pp90rsk during induction of monocytic differentiation.

The present work has studied mechanisms responsible for induction of early growth response 1 (EGR-1) gene expression during monocytic differentiation of U-937 myeloid leukemia cells. Differentiation of U-937 cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of the serine/threonine protein kinase C, was associated with transcriptional activation of EGR-1 promoter-reporter constructs. The EGR-1 promoter contains six CC(A/T)6GG (CArG) motifs. The two 5'-most distal CArG sequences conferred TPA inducibility. In contrast, there was little effect of TPA on EGR-1 transcription in a TPA-resistant U-937 cell variant, designated TUR. Treatment of both U-937 and TUR cells with okadaic acid, an inhibitor of serine/threonine protein phosphatases 1 and 2A, was associated with induction of monocytic differentiation and EGR-1 transcription through the 5'-most CArG element. Since these findings supported the involvement of serine/threonine protein phosphorylation in the regulation of EGR-1 expression, we studied activation of the 40S ribosomal protein S6 serine/threonine kinases, pp70S6K and pp90rsk. Although both kinases participate in regulating cell growth, there was no detectable activation of pp70S6K during TPA- or okadaic acid-induced monocytic differentiation. Moreover, rapamycin, an inhibitor of pp70S6K activation, had no effect on induction of EGR-1 expression. In contrast, analysis of pp90rsk activity by phosphorylation of a peptide derived from S6 protein demonstrated stimulation of this kinase in TPA-treated U-937, and not TUR, cells. Okadaic acid treatment of both cell types was associated with activation of pp90rsk.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Differentiation↗