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Biomedical subjects

A Stern

Publications and source records attributed to A Stern.

At least 91 records · Page 5Linked to original sources
PubMed1994

Melittin inhibits epidermal growth factor-induced protein tyrosine phosphorylation: comparison with phorbol myristate acetate and calcium ionophore A23187.

In HER14 cells, epidermal growth factor (EGF) induces tyrosine phosphorylation of several proteins, including its own receptor. The bee venom peptide, melittin, impaired EGF-dependent protein tyrosine phosphorylation in a calcium-dependent manner. The melittin effect was similarly reproduced by calcium ionophore A23187. The effect of melittin and calcium ionophore A23187 on EGF-dependent protein tyrosine phosphorylation was abolished by treatment of cells with the calcium chelator EGTA. Phorbol-myristate acetate (PMA) inhibited EGF-dependent protein tyrosine phosphorylation, and when compared to melittin or calcium ionophore A23187, only PMA potentiated the EGF-induced tyrosine phosphorylation of two proteins immunologically related to mitogen activated protein (MAP) kinases of 40 kDa and 44 kDa molecular mass. Unlike PMA, the effect of melittin and calcium ionophore A23187 on inhibition of EGF-dependent protein tyrosine phosphorylation was lost neither in protein kinase C-depleted cells nor in cells treated with the protein tyrosine phosphatase inhibitors NaF and Na3VO4. Melittin inhibited high affinity binding of EGF to its receptor in intact cells, but this effect was not prevented by EGTA. It is concluded that melittin and calcium ionophore A23187 differ from PMA in their inhibition of EGF-dependent protein tyrosine phosphorylation in vivo, by acting via a Ca(2+)-dependent pathway, that is independent of protein kinase C, protein tyrosine phosphatase activity and high affinity binding of EGF to its receptor.

3T3 Cells↗
PubMed1994

Inhibition of epidermal growth factor-dependent protein tyrosine phosphorylation by phorbol myristate acetate is mediated by protein tyrosine phosphatase activity.

Incubation of HER14 cells with phorbol myristate acetate (PMA) decreases epidermal growth factor (EGF)-dependent protein tyrosine phosphorylation, except for a 40-kDa MAP kinase II-like protein, whose tyrosine phosphorylation is further enhanced. The inhibitory effect of PMA on EGF-dependent protein tyrosine phosphorylation is reversed if cell are pre-incubated with a combination of Na3VO4 and NaF, two known inhibitors of protein tyrosine phosphatase activity. Protein tyrosine phosphatase activity of cell homogenate was measured on immunopurified EGF receptor, and was found to be enhanced in PMA-treated cells. These data suggest that the inhibitory effect of PMA on EGF-dependent protein tyrosine phosphorylation in HER14 cells may be mediated by protein tyrosine phosphatase activity.

3T3 Cells↗
PubMed1994

Naphthoquinone cytotoxicity to bluegill sunfish BF-2 cells.

Bluegill sunfish BF-2 fibroblasts were used to evaluate the in vitro cytotoxicities of 1,4-naphthoquinone (NQ), 5,8-dihydroxy-1,4-NQ, and 2,3-dichloro-1, 4-NQ (dichlone); comparisons were made with previously obtained data on the response of human hepatoma HepG2 cells. For both cell types, the sequence of potency was 5,8-dihydroxy-1,4-NQ > 1,4-NQ > dichlone. Dichlone, and, although to a lesser extent, 1,4-NQ and 5,8-dihydroxy-1-4-NQ, induced endoreduplication in the BF-2 cells; for the HepG2 cells, endoreduplication was induced only with dichlone. Exposures to the three NQs reduced intracellular glutathione levels in both cell types. For the BF-2 and HepG2 cells, pretreatments with buthionine sulfoximine (BSO), a glutathione-depleting agent, potentiated the cytotoxicity of 5,8-hydroxy-1,4-NQ and dichlone; pretreatment with dicoumarol, an inhibitor of DT-diaphorase, had no effect on toxicity of these two NQs. Apparently, for these two quinones the predominant metabolic pathway in both the BF-2 and HepG2 cells involved redox cycling via a one-electron reduction reaction, generating reactive oxygen intermediates that consumed intracellular glutathione. Pretreatment of the BF-2 cells with BSO, but not with dicoumarol, potentiated the toxicity of 1,4-NQ, again indicating that metabolism occurred via one electron reduction. However, for the HepG2 cells, pretreatment with dicoumarol, but not with BSO, potentiated the cytotoxicity of 1,4-NQ. Apparently, in the HepG2, as compared to the BF-2, cells, 1,4-NQ was metabolized by DT-diaphorase in a reaction involving a two electron reduction.

Animals↗
PubMed1994

Potential role of granulocyte-macrophage colony-stimulating factor as vaccine adjuvant.

The uses of GM-CSF as an immunomodulator and vaccine adjuvant are reviewed. GM-CSF has a variety of effects on immune responses: it induces class II major histocompatibility complex antigen expression on the surface of macrophages; it enhances dendritic cell maturation and migration; it results in a localized inflammation at the injection site; and it has marked effects on maturation of haematopoietic progenitor cells in the bone marrow. Animal and human studies suggest that administration of GM-CSF can increase antibody titres to foreign antigens. Monkeys injected with human interleukin (IL)-3 plus GM-CSF, at a different injection site, developed peak antibody titres which were 8- to 30-fold higher than those in monkeys injected with IL-3 alone. In a study of ovarian cancer patients receiving GM-CSF to prevent chemotherapy-induced neutropenia, two patients who had demonstrated a low titre of antithyroid antibodies prior to the study showed an increase in antibody titre and transient thyroiditis after administration of GM-CSF. Recently a GM-CSF/antigen fusion protein has been tested. An antibody corresponding to a specific idiotype expressed on B-cell lymphomas was fused to GM-CSF and injected into mice with B-cell lymphoma xenografts. The mice developed antibodies to the lymphoma and there was a protective effect against disease progression. Preliminary results of clinical trials using GM-CSF in humans suggest that it enhances antibody responses to hepatitis B vaccine. On the basis of these preliminary results, several clinical trials are being planned and it would appear that GM-CSF has potential as a vaccine adjuvant.

Adjuvants, Immunologic↗
PubMed1994

Effects of H2O2 on protein tyrosine phosphatase activity in HER14 cells.

Oxidative stress has been implicated in protein phosphorylation and dephosphorylation in cells. In our current studies, H2O2 was shown to reversibly inhibit protein tyrosine phosphatase (PTPase) activity in HER14 cells. H2O2 (150 mM) resulted in 40% inhibition of PTPase activity by 15 min and recovery from inhibition was nearly complete by 60 min. H2O2-induced inhibition or recovery of PTPase activity was not affected by cycloheximide, a protein synthesis inhibitor. L-Buthionine-[S,R]-sulfoximine (BSO), an inhibitor of glutathione synthesis, had no effect on H2O2-induced inhibition of PTPase activity but retarded the recovery of activity. Epidermal growth factor (EGF) and EGTA, a Ca2+ chelator, did not influence H2O2-induced inhibition or recovery of PTPase activity. These results suggest that at least 40% of fibroblast PTPase activity can be regulated by cellular redox activity.

3T3 Cells↗
PubMed1994

Membrane changes associated with lysis of red blood cells by hypochlorous acid.

This study was carried out to investigate HOCl-induced lysis of human erythrocytes. Using reagent HOCl with isolated red cells, we showed that the rate of lysis was dependent on the dose of HOCl per red cell rather than on the concentration of oxidant. The process was inhibited by scavengers such as methionine and taurine, but only if they were present at the time of addition of HOCl. Lysis was preceded by a decrease in cell density, a change in the deformability of the membrane as evidenced by ektacytometry, and an increase in K(+)-leak. Electron microscopy showed extensive disruption of the membrane. Increasing doses of HOCl caused progressive loss of membrane thiols, but complete thiol oxidation by N-ethylmaleimide did not result in an equivalent rate of lysis. Restoration of oxidised thiols by incubation with glucose did not significantly alter the pattern of lysis. Taken together, these results suggest that thiol oxidation was not responsible for HOCl-mediated lysis. There was evidence of increasing crosslinking of membrane proteins on electrophoresis, only some of which was due to the formation of disulfides. TLC of the membrane lipids indicated that there may be formation of chlorohydrins by reaction of HOCl with the fatty acid double bonds. This reaction results in the formation of a more polar species which, if formed, would be extremely disrupting to the lipid bilayer. The results indicate that HOCl-mediated damage to the membrane proteins or to the lipid bilayer comprises an initial damaging event that sets the cells on a path toward eventual lysis.

Diamide↗
PubMed1994

Stability and change in outcomes for sexually abused children.

OBJECTIVE: To evaluate sexually abused children and their families at intake and 18 months later, in comparison with a control group. METHODS: Eighty-four sexually abused children aged 5 to 15 years were assessed at intake, with 64 being able to be reassessed at 18 months, the assessment using measures of self-esteem relevant to their age; the Children's Depression Inventory, and the Achenbach Child Behavior Checklist. Parents were assessed with the McMaster Family Assessment Device and the General Health Questionnaire. Control children and families were similarly assessed. Additional measures at follow-up were a structured interview with the parents, the Indices of Coping Responses, and the Newcastle Child and Family Life Events Schedule. Therapists were contacted to obtain information on type and duration of therapy. RESULTS: While the control children's self-esteem, depression, and behavior scores showed little change over time, the abused children's scores were more likely to move toward the normal range although 56% remained in the dysfunctional range for self-esteem, 48% for behavior, and 35% for depression. Improvement in child behavior was related to improvement in family function. While there was no direct relationship between child outcome and the relationship of the abuser to the child, family dysfunction, which was related to child outcome, did correlate with the closeness of the abuser to the child. Sixty-five percent of abused children had received therapy for an average of 9 months. No relationship was found between therapy and outcome. CONCLUSIONS: The major variable relating to improvement in sexually abused children appears to be adequacy of family functioning. There is a need for increased emphasis on the evaluation of treatment.

Adaptation, Psychological↗
PubMed1994

High-dose sequential chemoradiotherapy, a widely applicable regimen, confers survival benefit to patients with high-risk multiple myeloma.

PURPOSE: To assess the toxicity, efficacy, and applicability of high-dose therapy with bone marrow and/or peripheral-blood autotransplantation in high-risk, previously untreated patients with multiple myeloma. PATIENTS AND METHODS: Thirteen consecutive patients with high-labeling index (LI) multiple myeloma received a novel high-dose sequential (HDS) regimen consisting in the high-dose administration of cyclophosphamide (7 g/m2) followed by vincristine (1.4 mg/m2) plus methotrexate (8 g/m2 with leucovorin rescue), etoposide (2 g/m2) and, finally, total-body irradiation (TBI; 10 Gy) plus melphalan (120 mg/m2) with autografting of peripheral-blood hematopoietic progenitor cells. Recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF; 5 micrograms/kg/d) was continuously infused after cyclophosphamide and etoposide both to accelerate hematopoietic recovery and to expand/mobilize the hematopoietic progenitor-cell pool. RESULTS: Among 13 patients, 12 completed the program; 10 (or 77%) achieved a complete response and five are alive and disease-free after a median follow-up duration of 36 months (range, 24 to 52). The durations of both freedom from progression (FFP; median, 38 months) and overall survival (OS; median, 41 months) were significantly superior in the 13 HDS-treated patients as compared with 19 well-matched historical controls. CONCLUSION: HDS emerges as a highly effective, well-tolerated, and widely accessible regimen capable of imparting a survival benefit to patients with high-LI multiple myeloma. Larger studies using this or similar programs in standard-risk myeloma are clearly warranted.

Adult↗
PubMed1994

Go wash your hands!

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Emergency Medical Technicians↗
PubMed1993

Comparative cytotoxicities of selected minor dietary non-nutrients with chemopreventive properties.

The comparative acute cytotoxicities were determined for a varied spectrum of minor dietary non-nutrients that have been implicated as chemopreventive agents. Cytotoxicity was determined with the neutral red (NR) assay, using BALB/c mouse 3T3 fibroblasts as the bioindicators. Based on midpoint cytotoxicity (NR50) values, the range of cytotoxicity for the different chemicals varied by 1000 times. The sequence of potency was tannic acid, tamoxifen citrate, quercetin, benzyl and phenethyl isothiocyanate > glycyrrhetinic acid > indole-3-carbinol > caffeic acid > phytic acid > vanillin > ellagic acid > D-saccharic acid 1,4-lactone. Vanillin, at slight to moderately toxic concentrations, was the only test agent that induced multinucleation in the 3T3 fibroblasts.

3T3 Cells↗
PubMed1993

Inhibition of protein tyrosine phosphatase activity in HER14 cells by melittin and Ca2+ ionophore A23187.

We investigated the effect of melittin and Ca2+ ionophore A23187 on protein tyrosine phosphatase activity in HER14 cells (NIH-3T3 cells transfected with human epidermal growth factor 'EGF' receptor). Cell fractions were used to measure protein tyrosine phosphatase activity in vitro using 32P-labeled poly(Glu/Tyr) (4:1) peptide as a substrate. Treatment of HER14 cells with melittin or with A23187, inhibited protein tyrosine phosphatase activity in the cell sonicate and homogenate, as well as in cytosolic and particulate fractions of these cells. The inhibitory effect of both drugs was prevented by preincubating cells with EGTA (ethyleneglycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid). The cyclooxygenase inhibitor indomethacin enhanced the inhibitory effect of A23187, but not that of melittin. Addition of arachidonic acid to the cells partially prevented the inhibition of protein tyrosine phosphatase activity by melittin or A23187. Preexposure of cells to EGF enhanced the inhibitory effect of melittin--but not that of A23187. Addition of CaCl2, or MgCl2 to the cell homogenate inhibited protein tyrosine phosphatase activity. These results show that protein tyrosine phosphatase activity in HER14 cells is inhibited by melittin and Ca2+ ionophore A23187 through a Ca(2+)-dependent mechanism, and is regulated by arachidonic acid metabolism and EGF receptor activation.

3T3 Cells↗