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Biomedical subjects

L M Wang

Publications and source records attributed to L M Wang.

At least 91 records · Page 5Linked to original sources
PubMed1995

Signal transduction through the IL-4 and insulin receptor families.

Activation of tyrosine kinase-containing receptors and intracellular tyrosine kinases by ligand stimulation is known to be crucial for mediating initial and subsequent events involved in mitogenic signal transduction. Receptors for insulin and insulin-like growth factor 1 (IGF-1) contain cytoplasmic tyrosine kinase domains that undergo autophosphorylation upon ligand stimulation. Activation of these receptors also leads to pronounced and rapid tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) in cells of connective tissue origin. A related substrate, designated 4PS, is similarly phosphorylated by insulin and IGF-1 stimulation in many hematopoietic cell types. IRS-1 and 4PS possess a number of tyrosine phosphorylation sites that are within motifs that bind specific SH2-containing molecules known to be involved in mitogenic signaling such as PI-3 kinase, SHPTP-2 (Syp) and Grb-2. Thus, they appear to act as docking substrates for a variety of signaling molecules. The majority of hematopoietic cytokines bind to receptors that do not possess intrinsic kinase activity, and these receptors have been collectively termed as members of the hematopoietin receptor superfamily. Despite their lack of tyrosine kinase domains, stimulation of these receptors has been demonstrated to activate intracellular kinases leading to tyrosine phosphorylation of multiple substrates. Recent evidence has demonstrated that activation of different members of the Janus family of tyrosine kinases is involved in mediating tyrosine phosphorylation events by specific cytokines. Stimulation of the interleukin 4 (IL-4) receptor, a member of the hematopoietin receptor superfamily, is thought to result in activation of Jak1, Jak3, and/or Fes tyrosine kinases.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

The clinical experience of acute cyanide poisoning.

The authors reviewed the clinical manifestations, complications, and the prognosis affected by Lilly Cyanide Antidote in 21 victims of acute cyanide poisoning over a 10-year period. The clinical signs and symptoms in cyanide poisoning are variable. Among 21 cases, loss of consciousness (15), metabolic acidosis (14), and cardiopulmonary failure (9) were the three leading manifestations of cyanide intoxication. Anoxic encephalopathy (6) was not uncommon in the severely intoxicated victims. Diabetes insipidus (1) or clinical signs and symptoms mimicking diabetes insipidus (3) may be an ominous sign to encephalopathy victims. The major cause of fatal cyanide poisoning is the intentional ingestion of cyanide compounds as part of a suicide attempt. Decrease of arteriovenous difference of O2 partial pressure may be a clue for the suspicion of cyanide intoxication. Although the authors cannot show a statistically significant difference (P = .47) for the Lilly cyanide antidote kit in terms of improving the survival rate for victims of cyanide poisoning, the antidote kit was always mandatory in our study in the cases of severely intoxicated victims who survived. Early diagnosis, prompt, intensive therapy with antidote, and supportive care are still the golden rules for the treatment of acute cyanide poisoning, whether in the ED or on the scene.

Acute Disease↗
PubMed1995

[Preventive effect of quinacrine on the development of heat injury by stabilizing membrane phospholipids metabolism and beta-adrenoceptor].

Previous studies have demonstrated that the activation of phospholipase A2 (PLA2) during heat stress would caused disorder of membrane phospholipids metabolism, accompanied by a decrease in phosphatidylcholine and phosphatidyl-serine and an increase in arachidonic acid. In heat stressed rats, a down-regulation of beta-adrenergic receptor in lung tissue was observed due to activation of PLA2. In the present work, it was demonstrated that pretreatment of rats with PLA2 inhibitor, quinacrine (20 mg/kg, I.P.), 1 h before heat stress could block these membrane lipid alterations, and the tolerance of rats to heat exposure was enhanced. The effect of quinacrine on the thermotolerance of marching soldiers with 15 kg of load under hot environment was also investigated. The results indicated that in the soldiers taken orally 200 mg quinacrine 1 h before marching, their heart rate, body temperature, accumulation of blood lactic acid and the changes of index of heart function were significantly improved as compared to the control group at the end of 3 h marching. According to these data, it can be concluded that quinacrine is a useful drug to prevent derangement of beta-adrenoceptor and membrane phospholipids metabolism in the development of heat stress. So as to prevent heat injury, and to improve tolerance to heat stress.

Adolescent↗
PubMed1995

GM-CSF and asparaginase potentiate ara-C cytotoxicity in HL-60 cells.

In preparation for a clinical trial using GM-CSF on days 4-10 of sequential high-dose cytarabine (ara-C) and asparaginase (ASNase) on days 1-3 and 8-10, potential interactions between the protein synthesis inhibitor ASNase and GM-CSF were evaluated. Granulocyte-macrophage colony-stimulating factor (GM-CSF) can stimulate acute myeloid leukemia (AML) cells to proliferate in vitro and in vivo. Log phase HL-60 cells were exposed to ara-C (10 microM x 3 h) and/or ASNase (10 U/ml during the last 2 h of ara-C). Ara-C and/or ASNase was removed and cells were incubated with or without GM-CSF (10 ng/ml). After 24, 48 and 72 h of GM-CSF there was no significant difference in the S phase fraction of cells exposed to ASNase prior to GM-CSF. Soft agar cloning efficiency was determined after retreatment with ara-C +/- ASNase 24 h into the GM-CSF incubation. GM-CSF enhanced cytotoxicity for all combinations, although this effect was of borderline significance (P = 0.0621); addition of ASNase to the treatment regimen significantly (P = 0.0229) enhanced cytotoxicity without any evidence of a negative interaction with GM-CSF. In addition, ara-C metabolism was assessed during simultaneous exposure to ara-C (10 microM x 3 h) +/- ASNase (10 U/ml the last 2 h) +/- GM-CSF (10 ng/ml beginning 24 h prior to ara-C). Ara-C incorporated into DNA (P = 0.0302) and ara-CTP formation (P = 0.0084 and P = 0.0003 at 2 and 3 h timepoints, respectively) were both increased significantly by GM-CSF, with modest non-significant increases with ASNase exposures. Neither ASNase nor GM-CSF inhibited the effects of the other in this in vitro model. Therefore, when appropriately scheduled, both GM-CSF and ASNase may potentiate ara-C cytotoxicity.

Arabinofuranosylcytosine Triphosphate↗
PubMed1994

Rhabdomyolysis in diabetic emergencies.

Rhabdomyolysis (RM) is a clinical and laboratory syndrome resulting from leakage of muscle cell contents into plasma. The increased plasma concentration of the substances released such as creatine kinase (CK) permits the clinician to diagnose this syndrome. Non-traumatic RM has occasionally been reported in patients with diabetic decompensation. We encountered about 44 cases of RM in 265 diabetic emergencies (including DKA or hyperosmolar, or both) during the period from 1984-1 to 1990-6, diagnosed based on (1) serum creatine kinase (CK) > 1000 IU/l and (2) the absence of acute myocardial infarction, stroke and end-stage renal disease. On admission, those who presented with RM had significantly higher concentration of blood urine nitrogen (BUN) (83.3 +/- 5.9 vs. 58.8 +/- 2.4 mg/dl, P < 0.05), creatine (4.45 +/- 0.4 vs. 2.97 +/- 0.1 mg/dl, P < 0.05) and serum osmolarity (386.5 +/- 5.2 vs. 351.6 +/- 2.4 mOsm/kg, P < 0.05). The mortality within 1 week of diabetic emergencies (38.5% for DKA, 35.5% for HHNK) was higher in patients with RM than those without RM (9.7% for DKA, 26.7% for HHNK). There was a correlation (r = 0.49, P < 0.05) between the levels of serum creatinine and CK in patients with RM.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Insulin receptor substrate-1 mediates phosphatidylinositol 3'-kinase and p70S6k signaling during insulin, insulin-like growth factor-1, and interleukin-4 stimulation.

Insulin Receptor Substrate-1 (IRS-1) is an endogenous cellular protein that is tyrosine phosphorylated during stimulation of cells with insulin, IGF-1, and interleukin 4 (IL-4). Phosphorylated IRS-1 regulates multiple regulatory pathways by recruiting signaling molecules containing Src homology 2 domains (SH2 proteins). The 32D myeloid progenitor cell line contains few insulin receptors and no detectable IRS-1. Expression of the insulin receptor alone partially mediates insulin-stimulated microtubule-associated protein (MAP) kinase activation, and the addition of IRS-1 enhances this effect (Myers, M. G., Jr., Wang, L.-M., Sun, X. J., Zhang, Y., Yenush, L. P., Schlessinger, J., Pierce, J. H., and White, M. F. (1994) Mol. Cell. Biol. 14, 3577-3587). Alone, insulin receptors mediate phosphatidylinositol (PI) 3'-kinase and p70S6k activation poorly if at all during insulin stimulation. Expression of IRS-1 alone in 32D cells mediates the stimulation of p70S6k by insulin, IGF-1, or IL-4; addition of insulin receptor to these cells increases the sensitivity of the insulin response. In contrast, full insulin stimulation of PI 3'-kinase requires both the insulin receptor and IRS-1, suggesting that a high level of IRS-1 phosphorylation is required for insulin-stimulated PI 3'-kinase activation, whereas a low level of IRS-1 tyrosine phosphorylation transmits an essential signal to p70S6k. Both insulin receptors and IRS-1 are required for mitogenic signaling in 32D cells suggesting that MAP kinase or p70S6k alone are not sufficient, and that both or additional unknown IRS-1-mediated signals are necessary.

Cell Line↗
PubMed1994

Deoxycytidine kinase is phosphorylated in vitro by protein kinase C alpha.

Deoxycytidine (dCyd) kinase was effectively phosphorylated by protein kinase C. The reaction was rapid, occurring at 4 degrees C as well as at 37 degrees C and approximately 0.7 mol of phosphate could be incorporated per mol of deoxycytidine kinase. Phosphoserine was the primary amino acid to be phosphorylated. Phosphorylation of deoxycytidine kinase resulted in a 100% increase in the Vmax using dCyd as a substrate (52.16 +/- 1.3 versus 104.47 +/- 11.4 nmol/min/mg protein), and an increase in the apparent Km (2.0 +/- 0.2 microM versus 6.9 +/- 1.2 microM). The inactive antimetabolite, ara-C, is activated within a cell by deoxycytidine kinase phosphorylation of the prodrug. Recent studies have shown that ara-C activates protein kinase C in vivo [1]. Furthermore, ara-C has been shown to be metabolized to ara-CDP-choline via reversal of the cholinephosphotransferase [2] producing diglyceride, a cellular activator of protein kinase C. Thus, in situ, deoxycytidine kinase may be phosphorylated by protein kinase C with the result that self-potentiation of ara-C toxicity may occur via increased activity of deoxycytidine kinase.

Cytarabine↗
PubMed1994

An IL-4 receptor region containing an insulin receptor motif is important for IL-4-mediated IRS-1 phosphorylation and cell growth.

Interleukin-4 (IL-4) treatment of 32D cells overexpressing insulin receptor substrate 1 (IRS-1) causes prompt tyrosine phosphorylation of IRS-1. Transfection of truncation mutants of the human IL-4 (huIL-4) receptor into 32D-IRS-1 cells demonstrated that the region from amino acid 437-557 is important for IL-4 signaling. This region of the IL-4 receptor (IL-4R) contains the motif 488PL-X4-NPXYXSXSD502 (insulin/IL-4R [I4R]) found in the insulin and insulin-like growth factor 1 receptors. Mutation of Y497 to F yielded receptors that caused little or no IRS-1 phosphorylation in response to huIL-4 when expressed in 32D-IRS-1 cells. Most cell lines expressing Y497F also failed to proliferate in response to huIL-4. Furthermore, a glutathione-S-transferase fusion protein containing the I4R motif-bound IRS-1, tyrosine kinase(s), and other unidentified phosphoproteins with molecular sizes of 140, 80, and 55 kd. Thus, the central tyrosine of the I4R motif has a major role in IL-4-mediated signal transduction in 32D cells.

Amino Acid Sequence↗
PubMed1994

Tyrosine phosphorylation of protein kinase C-delta in response to its activation.

Retroviral vectors containing five different protein kinase C (PKC) isoenzymes (alpha, delta, epsilon, eta, zeta) were expressed in 32D hematopoietic cells and NIH-3T3 fibroblasts. In an effort to investigate signaling events regulated by PKC activation, we analyzed whether tyrosine phosphorylation of cellular proteins would occur after 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment of the various transfectants. While no detectable tyrosine-specific phosphorylation was observed after treatment of the majority of the transfectants, pronounced TPA-dependent tyrosine phosphorylation of an 82-kDa protein was detected in the 32D/PKC-delta and NIH-3T3/PKC-delta lines. Interestingly, the 82-kDa substrate proved to be PKC-delta itself. Tyrosine phosphorylation of purified PKC-delta by src family or receptor tyrosine kinases in vitro enhanced PKC-delta activity, suggesting that tyrosine phosphorylation of PKC-delta may positively affect its function.

3T3 Cells↗
PubMed1994

Interleukin 4 receptor: signaling mechanisms.

Achsah Keegan and colleagues consider the signaling mechanisms utilized by the interleukin 4 (IL-4) receptor and review evidence suggesting that these mechanisms can account for the known responses of hematopoietic and non-hematopoietic cells to IL-4. Most of these data have been obtained from analyses of the ability of IL-4 to regulate the growth of IL-3-dependent myeloid cell lines. These results have implicated a pathway of activation homologous to that utilized by insulin and insulin-like growth factor 1 (IGF-1). However, it is possible that the regulation of growth responses through the IL-4 receptor (and other receptors), and the differentiative events elicited in lymphocytes, may not be mediated by the same post-receptor events.

Amino Acid Sequence↗
PubMed1994

The bovine papillomavirus type 1 E5 transforming protein specifically binds and activates the beta-type receptor for the platelet-derived growth factor but not other related tyrosine kinase-containing receptors to induce cellular transformation.

The 44-amino-acid E5 protein of bovine papillomavirus type 1 is a highly hydrophobic protein which appears to transform cells through the activation of growth factor receptors. To investigate the specificity of E5-growth factor receptor interactions required for mitogenic signaling, we utilized a nontumorigenic, murine myeloid cell line (32D) which is strictly dependent on interleukin-3 (IL-3) for sustained proliferation in culture. This IL-3 dependence can be functionally substituted by the expression of a variety of surrogate growth factor receptors and the addition of the corresponding ligand. Several receptor cDNAs for the alpha- and beta-type platelet-derived growth factor receptors [alpha PDGFR and beta PDGFR], the epidermal growth factor receptor, and the colony-stimulating factor 1 receptor) were transfected into 32D cells constitutively expressing the E5 protein to test for IL-3-independent growth. Only beta PDGFR was capable of abrogating the IL-3 dependence of 32D cells. The proliferative signal induced by the coexpression of beta PDGFR and E5 was accompanied by stable complex formation between these proteins, constitutive tyrosine phosphorylation of the receptor, and tumorigenicity in nude mice. The lack of cooperative interaction between E5 and the epidermal growth factor receptor, the colony-stimulating factor 1 receptor, and the highly related alpha PDGFR was paralleled by the inability of E5 to bind to these receptors and failure to increase receptor tyrosine phosphorylation. Thus, these data indicate that the ability of E5 to induce sustained proliferation and transformation of 32D cells is a direct consequence of specific interaction between the E5 protein and the beta PDGFR signaling complex and the subsequent stimulation of receptor tyrosine phosphorylation.

Animals↗
PubMed1994

Role of IRS-1-GRB-2 complexes in insulin signaling.

GRB-2 is a small SH2- and SH3 domain-containing adapter protein that associates with the mammalian SOS homolog to regulate p21ras during growth factor signaling. During insulin stimulation, GRB-2 binds to the phosphorylated Y895VNI motif of IRS-1. Substitution of Tyr-895 with phenylalanine (IRS-1F-895) prevented the IRS-1-GRB-2 association in vivo and in vitro. The myeloid progenitor cell line, 32-D, is insensitive to insulin because it contains few insulin receptors and no IRS-1. Coexpression of IRS-1 or IRS-1F-895 with the insulin receptor was required for insulin-stimulated mitogenesis in 32-D cells, while expression of the insulin receptor alone was sufficient to mediate insulin-stimulated tyrosine phosphorylation of Shc and activation of p21ras and mitogen-activated protein (MAP) kinase. The Shc-GRB-2 complex formed during insulin stimulation is a possible mediator of p21ras and MAP kinase activation in IRS-1-deficient 32-D cells. Interestingly, IRS-1, but not IRS-1F-895, enhanced the stimulation of MAP kinase by insulin in 32-D cells expressing insulin receptors. Thus, IRS-1 contributes to the stimulation of MAP kinase by insulin, probably through formation of the IRS-1-GRB-2 complex at Tyr-895. Our results suggest that the Shc-GRB-2 complex and the activation of p21ras-dependent signaling pathways, including MAP kinase, are insufficient for insulin-stimulated mitogenesis and that the essential function(s) of IRS-1 in proliferative signaling is largely unrelated to IRS-1-GRB-2 complex formation.

Adaptor Proteins, Signal Transducing↗
PubMed1994

[A bispecific monoclonal antibody with versatile adaptor mediating different cytotoxicities].

Bispecific monoclonal antibody (bsMAb), secreted by hybrid-hybridoma, has an intact 1g molecule construction with dual antigen binding specificities. bsMAb has several advantages over conventional conjugate in tumor targeting therapy: (1) The damage to both antibody and tumoricidal agents due to chemical crosslinking can be avoided. (2) The antigen modulation can be decreased due to monovalence binding of bsMAb with target antigen. (3) The binding affinity between Fc fragment of bsMAb with heterogenous heavy chains and Fc receptor is decreased, so that nonspecific distribution and side effects can be reduced. (4) The bsMAb can pretarget to tumor site, increasing the T/NT ratio and cytotoxicity. In the present study, A bsMAb with versatile adaptor was designed. In this bsMAb, one arm could react with gastric cancer-associated antigen, and the other with a hapten TNP. The bsMAb could mediate different tumoricidal agents crosslinked to TNP. A variant hybridoma 3H11-HAT(s) secreting McAb against gastric cancer was fused with spleen cells of mice immunized with KLH-TNP. After screening and subcloning, 10 hybrid-hybridomas were obtained, which secreted antibodies against both gastric cancer target cells BGC823 and BSA-TNP. By using special bridge method, only hybrid-hybridomas 6A3 (gamma 2b, mu), and 1G7 (gamma 2b, gamma 2b) were confirmed to secrete bsMAb. Further experiments showed that the bsMAb 6A3 and 1G7 could mediate different cytotoxicities, for example, Ricin-TNP, MMC-HSA-TNP and ADM-BSA-TNP. This system is useful for evaluating different tumoricidal agents in bsMAb targeting therapy, and has potential value in clinics.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Functional superficial parotidectomy.

PURPOSE: To clinically test a new type of parotid surgery termed functional superficial parotidectomy (FSP) to preserve the function of the residual gland. PATIENTS AND METHODS: Sixteen human parotid specimens were dissected, and 19 patients underwent FSP. RESULTS: It was shown that 91.4% of the main parotid ducts were found deep to the surface of the facial nerve. Physical examination, sialography, and scintigraphy showed that function of the residual gland was well preserved by FSP. CONCLUSION: A comparison of the main complications between FSP and conservative superficial parotidectomy showed a significant decrease (P < .01) of Frey's syndrome with FSP.

Adenolymphoma↗
PubMed1993

Purification and characterization of deoxycytidine kinase from acute myeloid leukemia cell mitochondria.

Deoxycytidine kinase is a key anabolic enzyme for the activation of ara-C and other antitumor drugs, as well as normal purine and pyrimidine deoxynucleotides. Previously, two forms of the kinase have been identified; deoxycytidine kinase I (70 kDa) and deoxycytidine kinase II (70 kDa). Deoxycytidine kinase I utilized dCyd and ara-C as substrates, while deoxycytidine kinase II used dCyd and dThd as substrates. Deoxycytidine kinase kinase II had very low activity on ara-C as a substrate. We report a procedure for the purification of a novel deoxycytidine kinase (52 kDa) from isolated human peripheral blood leukemia cell mitochondria. This enzyme has activity similar to deoxycytidine kinase II. The enzyme was extracted from the mitochondria with digitonin (1 mg/8 mg protein) and 0.3 M NaCl, and the extract was purified by DEAE-cellulose chromatography and thymidine-Sepharose affinity chromatography. This procedure produced a near homogeneous enzyme preparation with a yield of 70%. The mitochondrial deoxycytidine kinase was localized to the outer mitochondrial membrane. The enzyme phosphorylated dCyd (Km = 17 microM), however, ara-C was not a good substrate for the mitochondrial deoxycytidine kinase. ATP was the best phosphate donor, whereas dCTP and dTTP were potent inhibitors of mitochondrial deoxycytidine kinase. In contrast, phosphorylation of ara-C by deoxycytidine kinase I utilized GTP, dGTP, or ATP as a phosphate donor.

Chromatography, Affinity↗
PubMed1993

IRS-1: essential for insulin- and IL-4-stimulated mitogenesis in hematopoietic cells.

Although several interleukin-3 (IL-3)-dependent cell lines proliferate in response to IL-4 or insulin, the 32D line does not. Insulin and IL-4 sensitivity was restored to 32D cells by expression of IRS-1, the principal substrate of the insulin receptor. Although 32D cells possessed receptors for both factors, they lacked the IRS-1--related protein, 4PS, which becomes phosphorylated by tyrosine in insulin- or IL-4--responsive lines after stimulation. These results indicate that factors that bind unrelated receptors can use similar mitogenic signaling pathways in hematopoietic cells and that 4PS and IRS-1 are functionally similar proteins that are essential for insulin- and IL-4--induced proliferation.

Animals↗
PubMed1993

Common elements in interleukin 4 and insulin signaling pathways in factor-dependent hematopoietic cells.

Interleukin 4 (IL-4), insulin, and insulin-like growth factor I (IGF-I) efficiently induced DNA synthesis in the IL-3-dependent murine myeloid cell lines FDC-P1 and FDC-P2. Although these factors could not individually sustain long-term growth of these lines, a combination of IL-4 with either insulin or IGF-I did support continuous growth. The principal tyrosine-phosphorylated substrate observed in FDC cells stimulated with IL-4, previously designated 4PS, was of the same size (170 kDa) as the major substrate phosphorylated in response to insulin or IGF-I. These substrates had phosphopeptides of the same size when analyzed by digestion with Staphylococcus aureus V8 protease, and each tightly associated with the 85-kDa component of phosphatidylinositol 3-kinase after factor stimulation. IRS-1, the principal substrate phosphorylated in response to insulin or IGF-I stimulation in nonhematopoietic cells, is similar in size to 4PS. However, anti-IRS-1 antibodies failed to efficiently precipitate 4PS, and some phosphopeptides generated by V8 protease digestion of IRS-1 were distinct in size from the phosphopeptides of 4PS. Nevertheless, IL-4, insulin, and IGF-I were capable of stimulating tyrosine phosphorylation of IRS-1 in FDC cells that expressed this substrate as a result of transfection. These findings indicate that (i) IL-4, insulin, and IGF-I use signal transduction pathways in FDC lines that have at least one major feature in common, the rapid tyrosine phosphorylation of 4PS, and (ii) insulin and IGF-I stimulation of hematopoietic cell lines leads to the phosphorylation of a substrate that may be related to but is not identical to IRS-1.

Animals↗