Murine cytomegalovirus containing a mutation at open reading frame M37 is severely attenuated in growth and virulence in vivo

A pool of murine cytomegalovirus (MCMV) mutants was generated by using a Tn3-based transposon mutagenesis procedure. One of the mutants, RvM37, which contained the transposon sequence at open reading frame M37, was characterized both in tissue culture and in immunocompetent BALB/c and immunodeficient SCID mice. Our results provide the first direct evidence to suggest that M37 is not essential for viral replication in vitro in NIH 3T3 cells. Compared to the wild-type strain and a rescued virus that restored the M37 region, the viral mutant was severely attenuated in growth in both BALB/c and SCID mice after intraperitoneal infection. Specifically, titers of the Smith strain and rescued virus in the salivary glands, lungs, spleens, livers, and kidneys of the SCID mice at 21 days postinfection were about 5 x 10(5), 2 x 10(5), 5 x 10(4), 5 x 10(3), and 1 x 10(4) PFU/ml of organ homogenate, respectively; in contrast, titers of RvM37 in these organs were less than 10(2) PFU/ml of organ homogenate. Moreover, the virulence of the mutant virus appeared to be significantly attenuated because none of the SCID mice infected with RvM37 had died by 120 days postinfection, while all animals infected with the wild-type and rescued viruses had died by 26 days postinfection. Our results suggest that M37 probably encodes a virulence factor and is required for MCMV virulence in SCID mice and for optimal viral growth in vivo.

Tyrosine phosphorylation of cortactin is required for H2O2-mediated injury of human endothelial cells

Injury of endothelial cells induced by reactive oxygen species plays an important role in the development of early stages of vascular diseases such as hypertension and atherosclerosis. Exposure of human umbilical vein endothelial cells to hydrogen peroxide (H(2)O(2)), a common form of reaction oxygen species, triggers a series of intracellular events, including actin cytoskeletal reorganization, cytoplasm shrinkage, membrane blebbing and protein-tyrosine phosphorylation. The effect of H(2)O(2) on endothelial cells is dramatically enhanced when a survival pathway involving extracellular signal-regulated kinase is blocked by PD098059. In contrast, the injury of endothelial cells mediated by H(2)O(2) is inhibited by PP2, a selective specific inhibitor for protein-tyrosine kinase Src. Cortactin, a filamentous actin (F-actin)-associated protein, becomes phosphorylated at tyrosine residues upon stimulation by H(2)O(2) in a manner dependent on the activity of Src. The level of tyrosine phosphorylation of cortactin is correlated with the formation of membrane blebs. Overexpression of wild-type cortactin tagged with green fluorescent protein in endothelial cells via a retroviral vector substantiates the H(2)O(2)-induced morphological changes, whereas overexpression of a green fluorescent protein-cortactin mutant deficient in tyrosine phosphorylation renders endothelial cells resistant to H(2)O(2). The functional role of cortactin in H(2)O(2)-mediated shape changes was also evaluated in NIH 3T3 cells. Stable 3T3 transfectants expressing wild-type cortactin in the presence of either H(2)O(2)/PD098059 or H(2)O(2) alone at 200 microm exhibited a dramatic shape change characterized by rounding up or aggregation. However, the similar changes were not detected with cells overexpressing a cortactin mutant deficient in tyrosine phosphorylation. These data demonstrate an important role of the Src/cortactin-dependent actin reorganization in the injury of endothelial cells mediated by reactive oxygen species.

Isolation of three distinct CycD3 genes expressed during fruit development in tomato

Tomato (Lycopersicon esculentum Mill.) is an important fruit crop world-wide and a model for studying fruit development. As determined using flow cytometry, fruit growth was characterized by high cell division activity in tomato during the first week after anthesis and followed by endoreduplications (DNA replication without cell divisions). D-type cyclins are considered to be important parts of the signal transduction for stimulation of DNA replication and cell division. To study the function of D cyclins in fruit development, full-length cDNA clones for three D cyclin genes were isolated from young tomato fruit. They were classified as D3 cyclins by sequence similarities and a phylogenetic analysis and named as LeCycD3;1, LeCycD3;2 and LeCycD3;3. The deduced amino acid sequences for LeCycD3;1-3 contained a retinoblastoma-binding motif and a PEST-destruction motif. Pollination and fertilization were followed by a high increase in the transcript levels of LeCycD3;1-3 in young fruit. Using in situ hybridization, high expression of LeCycD3;3 was detected in the vascular tissue of young fruit suggesting a role in vascular development. The D3 cyclins are probably involved in transducing the signals leading to fruit growth by cell divisions. Distinct differences were detected in their temporal and spatial expression patterns suggesting that they play different roles in fruit development as well as in the development of other plant organs.

Cell volume-dependent phosphorylation of proteins of the cortical cytoskeleton and cell-cell contact sites. The role of Fyn and FER kinases

Cell volume affects diverse functions including cytoskeletal organization, but the underlying signaling pathways remained undefined. We have shown previously that shrinkage induces Fyn-dependent tyrosine phosphorylation of the cortical actin-binding protein, cortactin. Because FER kinase was implicated in the direct phosphorylation of cortactin, we investigated the osmotic responsiveness of FER and its relationship to Fyn and cortactin. Shrinkage increased FER activity and tyrosine phosphorylation. These effects were abolished by the Src family inhibitor PP2 and strongly mitigated in Fyn-deficient but not in Src-deficient cells. FER overexpression caused cortactin phosphorylation that was further enhanced by hypertonicity. Exchange of tyrosine residues 421, 466, and 482 for phenylalanine prevented cortactin phosphorylation by hypertonicity and strongly decreased it upon FER overexpression, suggesting that FER targets primarily the same osmo-sensitive tyrosines. Because constituents of the cell-cell contacts are substrates of Fyn and FER, we investigated the effect of shrinkage on the adherens junctions. Hypertonicity provoked Fyn-dependent tyrosine phosphorylation in beta-catenin, alpha-catenin, and p120(Cas) and caused the dissociation of beta-catenin from the contacts. This process was delayed in Fyn-deficient or PP2-treated cells. Thus, FER is a volume-sensitive kinase downstream from Fyn, and the Fyn/FER pathway may contribute to the cell size-dependent reorganization of the cytoskeleton and the cell-cell contacts.

In vitro and in vivo characterization of a murine cytomegalovirus with a transposon insertional mutation at open reading frame M43

We have recently generated a pool of murine cytomegalovirus (MCMV) mutants by using a Tn3-based transposon mutagenesis approach. In this study, one of the MCMV mutants, RvM43, which contained the transposon inserted in open reading frame M43, was characterized. Our results provide the first direct evidence to suggest that M43 is not essential for viral replication in vitro in NIH 3T3 cells. Moreover, RvM43 exhibited a titer similar to that of the wild-type virus in the lungs, livers, spleens, and kidneys of both BALB/c and SCID mice and was as virulent as the wild-type virus in killing SCID mice that had been intraperitoneally infected with the viruses. In contrast, titers of the mutant virus in the salivary glands of the infected animals at 21 days postinfection were significantly (100 to 1,000-fold) lower than those of the wild-type virus and a rescued virus that restored the M43 region and its expression. Thus, M43 appears to be not essential for viral growth in vivo in the lungs, livers, spleens, and kidneys of infected animals and is also dispensable for virulence in killing SCID mice. Moreover, our results suggest that M43 is an MCMV determinant for growth in the salivary glands. Studies of viral genes required for replication in the salivary glands are important in understanding the mechanism of viral tropism for the salivary glands and shedding in saliva, which is believed to be one of the major routes of CMV transmission among healthy human populations.

Propofol stimulates ciliary motility via the nitric oxide-cyclic GMP pathway in cultured rat tracheal epithelial cells

BACKGROUND

Airway ciliary motility is impaired by inhaled anesthetics. Recent reports show that nitric oxide (NO) induces upregulation in ciliary beat frequency (CBF), and others report that propofol, an intravenous anesthetic, stimulates NO release; this raises the possibility that propofol increases CBF by stimulating the NO-cyclic guanosine monophosphate (cGMP) signal pathway. In this study, the authors investigated the effects of propofol on CBF and its relation with the NO-cGMP pathway using the pharmacologic blockers NG-monomethyl-l-arginine (l-NMMA), an NO synthase inhibitor; 1H-[1,2,4]oxidazole[4,3-a]quinoxalin-1-one (ODQ), a soluble guanylyl cyclase inhibitor; and KT5823, a cGMP-dependent protein kinase inhibitor, in cultured rat tracheal epithelial cells.

METHODS

Rat tracheal tissues were explanted and cultured for 3-5 days. Images of ciliated cells were videotaped using a phase-contrast microscope. Baseline CBF and CBF 25 min after exposure to propofol or blocker were measured using video analysis.

RESULTS

Vehicle (0.1% dimethyl sulfoxide; n = 11) increased CBF by 0.2 +/- 1.7% (mean +/- SD) from baseline. Propofol stimulated CBF significantly (P < 0.01) and dose dependently (1 microM, 2.0 +/- 1. 9%, n = 6; 10 microM, 8.2 +/- 6.7%, n = 9; 100 microM, 14.0 +/- 4.7%, n = 10). Intralipid (0.05%), the clinical vehicle of propofol, did not affect CBF (-0.2 +/- 2.2%; n = 5). The enhancement of CBF with use of 100 microm propofol was abolished (P < 0.01) by coadministration of 10 mmicroM l-NMMA (2.4 +/- 3.6%; n = 5), 100 microM ODQ (-0.3 +/- 2.2%; n = 6) or 30 microM KT5823 (-0.1 +/- 4. 1%; n = 8). l-NMMA, ODQ, or KT5823 alone did not change CBF.

CONCLUSIONS

These results show that propofol stimulates CBF viathe NO-cGMP pathway in rat tracheal epithelial cells, suggesting a possible advantage of propofol in decreasing respiratory risk.

Regulation of ciliary beat frequency by the nitric oxide-cyclic guanosine monophosphate signaling pathway in rat airway epithelial cells

Nitric oxide (NO) upregulates ciliary beat frequency (CBF). The present study evaluates mechanisms of the NO-cyclic guanosine monophosphate (cGMP) pathway regulation of CBF. Rat tracheal explants were loaded with 4,5-diaminofluorescein diacetate for the demonstration of NO production by ciliated epithelial cells after L-arginine (L-Arg) stimulation. CBF was measured using phase contrast microscopy and videotape analysis. The roles of NO, soluble guanylate cyclase (sGC), cGMP-dependent protein kinase (PK) G, and phosphodiesterase (PDE) V in regulation of CBF were evaluated. NO synthase (NOS) was activated with L-Arg or inhibited with N(G)-monomethyl-L-Arg. sGC was stimulated with NO donors 1-hydroxy-2-oxo-3- (N-ethyl-2-aminoethyl)-3-ethyl-1-triazene and S-nitroso-L-glutathione or mimicked by 8-bromo-guanosine 3', 5'-cyclic monophosphate (8-Br-cGMP) and inhibited with 1H-[1,2, 4]oxadiazole[4,3-a]quinoxalin-1-one. The effects of the PKG inhibition with KT5823 and PDE V inhibition with Zaprinast were also examined. The studies demonstrate that ciliated epithelial cells produce NO, which is correlated with CBF stimulation. L-Arg dose- and time-dependently increases CBF, and NO donors, 8-Br-cGMP, and Zaprinast also enhance CBF. Inhibitors of NOS, sGC, and PKG can block the stimulant effect of L-Arg on CBF. Thus, NO is a regulator of CBF acting via sGC and PKG. The NO-cGMP signaling pathway regulates CBF in an autocrine manner in cultured rat ciliated airway epithelium.

Construction and characterization of murine cytomegaloviruses that contain transposon insertions at open reading frames m09 and M83

A transposon derived from Escherichia coli Tn3 was introduced into the genome of murine cytomegalovirus (MCMV) to generate a pool of viral mutants, including two recombinant viruses that contained the transposon sequence within open reading frames m09 and M83. Our studies provide the first direct evidence to suggest that m09 is not essential for viral replication in mouse NIH 3T3 cells. Studies in cultured cells and in both BALB/c-Byj and CB17 severe combined immunodeficient (SCID) mice indicated that the transposon insertion is stable during viral propagation both in vitro and in vivo. Moreover, the virus that contained the insertion mutation in m09 exhibited a titer similar to that of the wild-type virus in the salivary glands, lungs, livers, spleens, and kidneys of both the BALB/c and SCID mice and was as virulent as the wild-type virus in killing the SCID mice when these animals were intraperitoneally infected with these viruses. These results suggest that m09 is dispensable for viral growth in these organs and that the presence of the transposon sequence in the viral genome does not significantly affect viral replication in vivo. In contrast, the virus that contained the insertion mutation in M83 exhibited a titer of at least 60-fold lower than that of the wild-type virus in the organs of the SCID mice and was attenuated in killing the SCID mice. These results demonstrate the utility of using the Tn3-based system as a mutagenesis approach for studying the function of MCMV genes in both immunocompetent and immunodeficient animals.

Cross-talk filtering in four dye fluorescence-based DNA sequencing

We have addressed two important issues of nonlinear cross-talk and baseline adjustment in DNA data processing. An important aspect in the processing of the four-dye fluorescence-based data is the cross-talk filtering. Typically, a matrix M, which is a function of the fluorophores and the fluorescence detection system, is used in the multicomponent analysis. In this deconvolution process the matrix is applied directly to the raw signal, on a linear cross-talk assumption. This necessitates the signal to be aligned to the baseline before the filter is applied. The various techniques used for aligning the raw data have the negative effect of adding distortion to the signal. An algorithm for cross-talk removal is presented in this paper. The algorithm uses the intensity difference of the signal rather than the actual value itself, thus making the cross-talk removal possible before the base line adjustment. In addition, a supplementary filtering step is proposed in order to account for the nonlinear nature of the cross-talk. This second step is based on a matrix T that accounts for the correlation of each of the signals with the other three. The overall result is a more precise presentation of the DNA data and less information loss through filtering.

[Discussions on some problems related to fluid inclusion analysis by SXRF]

X-ray fluorescence experiments were carried out at Beijing Synchrotron Radiation Facilities (BSRF) using synchrotron radiation as excitation source. The samples were made by mixing national reference standard GBW07106 and certain amount of reagent NaCl and KCl, and pressed into pellets. The purpose of the experiment is to verify the detection ability of the XRF setup at BSRF for elements in geological samples, especially for light elements. The beam size was 20 x 20 microns2, and the current in the storage ring was about 40 mA. The gap between the sample and the Si(Li) detector was 2 cm. With measuring time of 200 sec., The relative and absolute detection limits for 10 elements have been calculated. The sampling depth and sampling weight, which are critical in individual fluid inclusion analysis, have also been estimated. Some problems concerning the individual fluid inclusion analysis by SXRF, such as inclusion depth determination, effect of the inclusion depth on XRF intensity etc., are discussed based on the experiment results.

[Inhibition of lung cancer cell line growth in vitro by telomerase anti-sense oligonucleotides.]

BACKGROUND

To research the inhibition of lung cancer cell line by telomerase anti-sense DNA , and explore the possibility of its clinical application.

METHODS

A phosphorothioate oligonucleotide (PS-ODN) with sequence identical to the repeat sequence of the mammaliam telomere [5'- d(TTAGGG)-3'] and a control scrambled sequence 5'- d(TGTGAG)-3' were incubated with a lung cancer cell line 801-D , and the effects of PS-ODN on cell line growth , colony-forming and growth shape were detected.

RESULTS

Telomerase anti-sense DNA inhibited telomerase activation cell line 801-D growth and colony-forming. The activity of the 6-mer telomere mimic demonstrated a dose dependency. No activity was observed with the scrambled controls.

CONCLUSIONS

These results demonstrated the inhibitive effects of a short hexameric oligonucleotide telomere mimic on lung cancer cell line growth in vitro and the potential utility of telomerase anti-sense DNA as cancer cell inhibitors.

[Effect of chrysotile on nitric oxide production and anti-oxidasic activity in rabbit alveolar macrophages]

This study aimed to explore the role of nitric oxide (NO) and nitric oxide synthase (NOS) in chrysotile asbestos-caused diseases. The production of NO2-/NO3- (the final product of NO) and the alterations of NOS, SOD and GSH-Px activity were investigated when rabbit alveolar macrophages (AM) were stimulated by UICC chrysotile. The results revealed that with the dosage elevation of UICC chrysotile, the rabbit alveolar macrophages showed: (1) increased mortality, decreased survival activity; (2) increased product of NO2-/NO3-, decreased SOD and GSH-Px activity; (3) increased NOS activity in the lower dosage groups, but decreased NOS activity in the higher dosage groups. There was significantly negative correlation between NO release and SOD (or GSH-Px) activity (r1 = -0.7125, P < 0.05; r2 = -0.8496, P < 0.05 respectively). Moreover, the significantly positive correlation between NO release and NOS activity was found in the lower dosage groups, but significantly negative correlation in the higher dosage groups. These findings suggest that chrysotile could induce the alveolar macrophages to increase NO release and to decrease SOD and GSH-Px activity, which may play a role in the process of asbestos-caused diseases.

Mutagenesis of murine cytomegalovirus using a Tn3-based transposon

A transposon derived from Escherichia coli Tn3 was introduced into the genome of murine cytomegalovirus (MCMV) to generate a pool of viral mutants. We analyzed three of the constructed recombinant viruses that contained the transposon within the M25, M27, and m155 open reading frames. Our studies provide the first direct evidence to suggest that M25 and M27 are not essential for viral replication in mouse NIH 3T3 cells. Studies in cultured cells and Balb/c mice indicated that the transposon insertion is stable during viral propagation both in vitro and in vivo. Moreover the virus that contained the insertion mutation in M25 exhibited a titer similar to that of the wild-type virus in the salivary glands, lungs, livers, spleens, and kidneys of the Balb/c mice that were intraperitoneally infected with these viruses. These results suggest that M25 is dispensable for viral growth in these organs and the presence of the transposon sequence in the viral genome does not significantly affect viral replication in vivo. The Tn3-based system can be used as a mutagenesis approach for studying the function of MCMV genes in both tissue culture and in animals.

Src is required for cell migration and shape changes induced by fibroblast growth factor 1

Fibroblast growth factor 1 (FGF-1) is a potent chemotactic factor and induces tyrosine phosphorylation of a cortical actin-associated protein (cortactin). The tyrosine phosphorylation of cortactin induced by FGF-1 requires the tyrosine residues 421, 482 and 466, which are targeted by the protein tyrosine kinase Src in vitro. Furthermore, FGF-1 is unable to induce tyrosine phosphorylation of cortactin within the cells derived from Src knockout mice (Src-/-), indicating that Src is required for the tyrosine phosphorylation of cortactin induced by FGF-1. Although Src-/- cells are able to undergo rapid proliferation, they are impaired to respond to FGF-1 for the shape change and cell migration. Morphological analysis further reveals that FGF-1 fails to induce the formation of polarized lamellipodia and the translocation of cortactin into the leading edge of Src-/- cells. Consistent with the mitogenic response to FGF-1, the lack of Src does not affect the tyrosine phosphorylation of Snt (or Frs2), a FGF-1 early signaling protein that links to Ras. Therefore, our data support the notion that Src and cortactin participate in a FGF signal pathway for cell migration and shape change rather than mitogenesis.

Facilitating the formation of disulfide bonds in the Escherichia coli periplasm via coexpression of yeast protein disulfide isomerase

Sacchromyces cerevisiae protein disulfide isomerase (yPDI) was expressed in the E. coli periplasm by using plasmids encoding the OmpA-yPDI-(His)(6) fusion gene under the control of the araBAD, trc, or T7 promoter. The expression levels of yeast PDI under these promoters were compared. Our results showed that yeast PDI expressed into the periplasm could catalyze the formation of disulfide bonds in alkaline phosphatase, restoring the phoA(+) phenotype in dsbA(-) mutants. The yeast PDI was purified from the Escherichia coli periplasm and shown to exhibit catalytic properties comparable to those of the rat enzyme with reduced RNase as substrate. In vivo, coexpression of the yeast PDI increased the yield of bovine pancreatic trypsin inhibitor (BPTI) in E. coli by 2-fold, similar to the effect seen previously with the coexpression of the rat enzyme. However yeast PDI was more effective than rat PDI in facilitating the expression of active tissue plasminogen activator (tPA). These results point to differences in the substrate specificity of various PDI enzymes, at least in the context of the E. coli periplasm.

Immunohistochemical evidence for the NO cGMP signaling pathway in respiratory ciliated epithelia of rat

Airway epithelia play a crucial role in protecting the lung from the external environment. Ciliated airway epithelial cells contribute to mucociliary transport systems via ciliary beating and electrolyte transport mechanisms to defend against respiratory tract infection. Both of these activities are regulated by nitric oxide (NO)-dependent mechanisms. To better understand the role of the NO-cGMP signal transduction cascade in these responses, we investigated the localization of endothelial nitric oxide synthase (eNOS), soluble guanylyl cyclase (sGC), cGMP-dependent protein kinase (PKG) I-alpha, and PKG I-beta in the tracheas and lungs of normal rats by immunohistochemistry. Mouse anti-eNOS, rabbit anti-sGC, PKG I-alpha, and PKG I-beta antibodies were used. Strong immunostaining for eNOS was detected in ciliated tracheal, bronchial, and bronchiolar epithelia, in Clara cells, and in Type II alveolar cells. The pattern of sGC and PKG I-beta immunostaining showed striking parallels with that of eNOS staining. No staining was detectable in ciliated epithelium with the anti-PKG I-alpha antibody. Taken together, these observations suggest that PKG I-beta might transduce NO-sGC signaling into biological responses in ciliated respiratory epithelia.(J Histochem Cytochem 47:1369-1374, 1999)

[Preliminary observation of immunotherapy on asthmatic guinea pig]

OBJECTIVE

To observe the effect of the anti-IL-5 monoclonal antibody(McAb) on eosinophils of the guinea pigs with asthma.

METHOD

Sensitized guinea pigs by OVA were divided into two groups randomly, which were treated with the McAb and normal saline (NS), respectively. Difference of peripheral blood eosinophil count (PBEC) among basal pre-treatment and post-treatment, and the difference of bronchoalveolar lavage fluid eosinophil count (BALFEC) between two groups above were compared.

RESULT

The PBEC after treatment with the McAb [(1.63 +/- 0.26) x 10(9)/L] was lower than that before treatment [(1.76 +/- 0.27) x 10(9)/L] (P < 0.05) and the BALFEC of treatment group with the McAb was lower than that with NS [(0.41 +/- 0.06) x 10(9)/L vs. (0.46 +/- 0.07) x 10(9)/L] (P < 0.05).

CONCLUSION

The anti-IL-5 McAb has the ability to reduce the PBEC and the BALFEC.

The role of tyrosine phosphorylation of cortactin in the locomotion of endothelial cells

Cortactin, a filamentous actin cross-linking protein and a substrate of Src protein tyrosine kinase, is phosphorylated at tyrosine residues upon stimulation by extracellular signals. We have previously demonstrated that the filamentous actin cross-linking activity of cortactin is attenuated by Src (Huang, C., Ni, Y., Gao, Y., Haudenschild, C. C., and Zhan, X. (1997) J. Biol. Chem. 272, 13911-13915). In vitro, tyrosine phosphorylation of cortactin occurs specifically within the region between the proline-rich sequence and the Src homology 3 domain. Among the nine tyrosine residues in this region, mutations at Tyr421, Tyr466, and Tyr482 significantly reduced Src-meditated tyrosine phosphorylation both in vitro and in vivo. Ectopic expression of wild-type cortactin in ECV304, a spontaneously transformed human umbilical endothelial cell line, resulted in an enhanced cell migration. In contrast, overexpression of a cortactin mutant deficient in tyrosine phosphorylation impaired the migration of endothelial cells. These findings reveal an intracellular signaling mechanism whereby the motility of endothelial cells is regulated by a Src-mediated tyrosine phosphorylation of cortactin.

Effect of iodinated contrast media on neutrophil adhesion to cultured endothelial cells

PURPOSE

To investigate the influence of contrast media (CM) on endothelial cells (ECs) with respect to cytotoxicity and to neutrophil adhesion.

MATERIALS AND METHODS

Human umbilical vein ECs were incubated with chromium-51-labeled human neutrophils in the presence of CM (diatrizoate, ioxaglate, iopamidol, and iodixanol) in three concentrations: 2, 20, and 50 mg I/mL. CM was compared with glucose solutions prepared from plain, buffered glucose solutions, iso-osmolar to the corresponding CM solution. Neutrophil adhesion to the EC monolayer, EC morphology, and cytotoxicity were evaluated.

RESULTS

The effect of CM on neutrophil adhesion was dependent on dose, with increased adhesion at low CM concentrations (2 and 20 mg I/mL) and decreased adhesion at high CM concentration (50 mg I/mL). The response was observed only if ECs and neutrophils were exposed to CM simultaneously in a shared environment. Glucose solutions with the same osmolarity did not show similar effect. Both diatrizoate and ioxaglate had a greater cytotoxic effect on ECs and neutrophils than did iodixanol and iopamidol.

CONCLUSION

The altered neutrophil adhesion to ECs may be due to CM-induced cytotoxicity or CM-induced EC activation because the glucose solutions did not cause a similar change at equal osmolality. The lack of cell death, combined with altered neutrophil adhesion implies modulation of cell adhesion molecules by CM. The results could be pertinent to the pathogenesis of peripheral vascular lesions and the endothelial response in immunosuppressed or septic patients receiving CM during imaging studies.

[Effects of extraneous wild type p53 on malignant growth of human lung cancer cell line.]

BACKGROUND

To study the effects of extraneous wild type p53 on malignant phenotype of human lung cancer cell line (801-D) with mutant type p53 gene.

METHODS

The human lung cancer line (801-D) with mutant type p53 was selected and characterized with PCR-SSCP and DNA sequence analysis. Recombinant plasmid PZiPp53 was constructed , which expressed wild type p53. A transfected cell line , 801-D-p53 was obtained after transfering the plasmid into 801-D cell line by gene gun mediated and selected by G418. The wild type p53 and the alteration of malignant phenotype were detected in the transfected cell line by PCR method and cell line culture and heteroplastic transplant study.

RESULTS

The extraneous wild type p53 gene was detected in 801-D-p53 cell line cultured in vitro one year after transfection. The growth of the transfected cell line was inhibited comparing the parent cell line. The colony formation inhibition rate of the cell line was 96% and the tumorigenicity in nude mice was suppressed. The tumor growth significantly slow and the average volume of the transplant tumor was 1/28 of that of the parent cell line.

CONCLUSIONS

Extraneous wild type p53 gene may stably exist in the human lung cancer cell line with mutant type p53 after wild type p53 transfection and suppress the malignant phenotype of the transfected cell line. These results indicate that the recombinant plasmid expressing wild type p53 may be useful for gene therapy of human lung cancer.

Role of phosphatidylinositol 4,5-bisphosphate in Ras/Rac-induced disruption of the cortactin-actomyosin II complex and malignant transformation

Oncogenic Ras mutants such as v-Ha-Ras cause a rapid rearrangement of actin cytoskeleton during malignant transformation of fibroblasts or epithelial cells. Both PI-3 kinase and Rac are required for Ras-induced malignant transformation and membrane ruffling. However, the signal transduction pathway(s) downstream of Rac that leads to membrane ruffling and other cytoskeletal change(s) as well as the exact biochemical nature of the cytoskeletal change remain unknown. Cortactin/EMS1 is the first identified molecule that is dissociated in a Rac-phosphatidylinositol 4,5-biphosphate (PIP2)-dependent manner from the actin-myosin II complex during Ras-induced malignant transformation; either the PIP2 binder HS1 or the Rac blocker SCH51344 restores the ability of EMS1 to bind the complex and suppresses the oncogenicity of Ras. Furthermore, while PIP2 inhibits the actin-EMS1 interaction, HS1 reverses the PIP2 effect. Thus, we propose that PIP2, an end-product of the oncogenic Ras/PI-3 kinase/Rac pathway, serves as a second messenger in the Ras/Rac-induced disruption of the actin cytoskeleton and discuss the anticancer drug potential of PIP2-binding molecules.

[Clinical significance of cytokine and eosinophil cationic protein concentrations in sputum of asthmatic patients]

OBJECTIVE

To examine whether levels of inflammatory cytokines and eosinophil cationic protein (ECP) in the sputum reflect the severity of bronchial asthma.

METHOD

We collected sputum expectorated spontaneously from 15 asthmatics with acute attacks of moderate to severe degree (MS group) and 10 subjects with acute attacks of mild asthma (M group). The interleukin (IL)-5(35 ng/L) tumor necrosis factor (TNF)-alpha(M 149 +/- 59 ng/L, MS 267 +/- 147 ng/L), soluble IL-2 receptor (sIL-2R) (M 348 +/- 107 kU/L, MS 488 +/- 127 kU/L) levels in the sputum were measured with enzyme-linked immunosorbent assay, and sputum ECP (M 127 +/- 95 micrograms/L, MS 278 +/- 150 micrograms/L) concentration were measured by Immuno-CAP System.

RESULT

Sputum IL-5, TNF-alpha, sIL-2R, ECP concentrations in moderate to severe patients were significantly higher than in mild subjects.

CONCLUSION

These findings suggest that inflammatory cytokines and mediator levels are detectable in the sputum from asthmatics and they might participate in the exacerbation of asthma.

Determination of rate order for degradation of drugs with nonisothermal stability experiment

The inability of ordinary nonisothermal experiments to determine the rate order (n) of drug degradation is discussed on the basis of a theoretical study of simulated nonisothermal data. In ordinary nonisothermal experiments, using either r or sigma(C[experiment] C[compute])2 as the measure of goodness of fit, the rate order cannot be assessed because the same set of c-t data can be well fitted by different combinations of estimates for n and the activation energy (E). Hence, a new nonisothermal heating-and-cooling model is introduced as a revision, in which sigma(C[experiment] C[compute])2 changes significantly with various kinetic models. Therefore, all the kinetic parameters, including the rate order, can be obtained in one nonisothermal stability experiment. Furthermore, the ability to determine rate order is significantly affected by the extent of drug degradation and experimental error, though not by sampling frequency or temperature change. To demonstrate the applicability of the heating-and-cooling model, the stability and rate order of degradation of vitamin C tablets was studied by this method.

[The relationship between pulmonary function and work ability of aging workers]

To explore the relationship between pulmonary function and work ability, a field study was conducted in 285 aging workers (aged 40 to 60) of different occupations in Chengdu area. The pulmonary function indices included FVC, FEV1, FEV1%, MMEF, and the pulmonary function index (PFI) which was the sum of the rating values from the first three indices. The work ability index (WAI) was also measured. Between work types, the indices, including FVC and FEV1%, showed significant difference (P < 0.05); FVC also showed significant difference between male and female workers (P < 0.05). There was a significant relationship between PFI (including FEV1% and MMEF) and WAI (P < 0.05), but the relationship between FVC (or FEV1) and WAI was not statistically significant (P > 0.05). Moreover, the agreement percentage between the classifications of PFI and WAI was 43.8%; the disagreement percentage was 4.56%. The results suggest that FEV1% and MMEF may be beneficial to the objective evaluation of the work ability of aging workers.

The isolated RNase H domain of murine leukemia virus reverse transcriptase. Retention of activity with concomitant loss of specificity

Retroviral RNases H are similar in sequence and structure to Escherichia coli RNase HI and yet have differences in substrate specificities, metal ion requirements, and specific activities. Separation of reverse transcriptase (RT) into polymerase and RNase H domains yields an active RNase H from murine leukemia virus (MuLV) but an inactive human immunodeficiency virus (HIV) RNase H. The "handle region" present in E. coli RNase HI but absent in HIV RNase H contributes to the binding to its substrate and when inserted into HIV RNase H results in an active enzyme retaining some degree of specificity. Here, we show MuLV protein containing the C-terminal 175 amino acids with its own handle region or that of E. coli RNase HI has the same specific activity as the RNase H of RT, retains a preference for Mn2+ as the cation required for activity, and has association rate (KA) 10% that of E. coli RNase HI. However, with model substrates, specificities for removal of the tRNAPro primer and polypurine tract stability are lost, indicating specificity of RNase H of MuLV requires the remainder of the RT. Differences in KA, while significant, appear insufficient to account for the differences in specific activities of the bacterial and viral RNases H.

Proteolysis of platelet cortactin by calpain

Cortactin, a substrate of pp60(c-)src and a potent filamentous actin binding and cross-linking protein, is abundant in circulating platelets. After stimulation of platelet aggregation with collagen, cortactin undergoes a dramatic increase in tyrosine phosphorylation followed by a rapid degradation. The cleavage of platelet cortactin was detected in lysates prepared using either Triton-containing buffer or SDS-sample buffer. However, the degradation of cortactin was not observed in platelets derived from a Glanzmann's patient, who lacked functional integrin alphaIIbbeta3 (GPIIb-IIIa). In addition, the proteolysis of cortactin was abolished by treating platelets before but not after collagen stimulation with EGTA or calpeptin. Furthermore, recombinant cortactin was digested by mu-calpain in vitro in a dose-dependent manner, indicating that cortactin is a substrate for calpain. We also observed that the calpain-mediated digestion in vitro is dependent on the presence of a sequence containing a proline-rich region and multiple tyrosine residues that are phosphorylated by pp60(c-)src. Tyrosine phosphorylation by pp60(c-)src up-regulates the activity of calpain toward cortactin. Our data suggest that the calpain-mediated proteolysis of tyrosine-phosphorylated cortactin may provide a mechanism to remodel irreversibly the cytoskeleton in response to platelet agonists.

The protein cofactor allows the sequence of an RNase P ribozyme to diversify by maintaining the catalytically active structure of the enzyme

To study the effect proteins have on the catalysis and evolution of RNA enzymes, we simulated evolution of RNase P catalytic M1 RNA in vitro, in the presence and absence of its C5 protein cofactor. In the presence of C5, functional M1 sequence variants (not catalytically active in the absence of C5) were selected in addition to those identical to M1. C5 maintains the catalytically active structure of the variants and allows for an enhanced spectrum of M1 molecules to function in the context of a ribonucleoprotein (RNP) complex. The generation of an RNP enzyme, requiring both RNA and protein components, from a catalytically active RNA molecule has implications for how modern RNP complexes evolved from ancestral RNAs.

Exponential heating in drug stability experiment and statistical evaluation of nonisothermal and isothermal prediction

A new nonisothermal heating model (exponential heating model) for drug stability experiments, based on a theoretical study of simulated nonisothermal data, is presented. In the model, the heating rate dT/dt is increased by 2-4 times at every increase of 10 degrees C in temperature: dT/dt = a(T-T0)/10.(dT/dt)0 where a is the times by which the heating rate is increased at every increase of 10 degrees C. A computation method with optimization and Simpson integration for the experiment was also introduced. The estimates for the shelf-life and activation energy obtained by the exponential and other nonisothermal heating models were statistically evaluated and were compared with those obtained by the isothermal method under various conditions. The results indicated that under the same experimental conditions, the estimates obtained by the exponential heating model were significantly more accurate and precise than those obtained by the linear, reciprocal, and logarithmic heating models. The accuracy and precision of the estimates were independent of the shelf-life of drugs and experimental period. The estimates obtained by the isothermal method were somewhat more accurate and precise than those obtained by the exponential heating model. However, the experimental period needed by the isothermal method was about five times longer than that needed by the exponential heating model. The results also showed that in each of the heating models, the estimates are more accurate and precise by increasing the extent of drug degradation, changing temperature range or sampling frequency, or by having the mean temperature closer to room temperature. To demonstrate its applicability, the exponential heating model was used to study the stability of vitamin C tablets and predict their shelf-life.

Down-regulation of the filamentous actin cross-linking activity of cortactin by Src-mediated tyrosine phosphorylation

Cortactin, a prominent substrate for pp60(c-src), is a filamentous actin (F-actin) binding protein. We show here that cortactin can promote sedimentation of F-actin at centrifugation forces under which F-actin is otherwise not able to be precipitated. Electron microscopic analysis after negative staining further revealed that actin filaments in the presence of cortactin are cross-linked into bundles of various degrees of thickness. Hence, cortactin is also an F-actin cross-linking protein. We also demonstrate that the optimal F-actin cross-linking activity of cortactin requires a physiological pH in a range of 7.3-7.5. Furthermore, pp60(c-src) phosphorylates cortactin in vitro, resulting in a dramatic reduction of its F-actin cross-linking activity in a manner depending on levels of tyrosine phosphorylation. In addition, pp60(c-src) moderately inhibits the F-actin binding activity of cortactin. This study presents the first evidence that pp60(c-src) can directly regulate the activity of its substrate toward the cytoskeleton and implies a role of cortactin as an F-actin modulator in tyrosine kinase-regulated cytoskeleton reorganization.

Upregulation of cortactin expression during the maturation of megakaryocytes

Cortactin is a potent filamentous actin-binding protein acting as a prominent substrate of Src tyrosine kinases. We have evaluated cortactin expression in a series of murine tissues and shown an abundant expression of cortactin in megakaryocytes and platelets. Cortactin, but not its related protein HS1, is upregulated during the phorbol 12-myristate 13-acetate (PMA)-mediated maturation of a human megakaryoblastic cell line CMK. Although the expression of Src-related kinases is also upregulated more rapidly than cortactin in PMA-treated CMK cells, tyrosine phosphorylation of cortactin appears to be only transiently elevated 4 days after PMA stimulation. In addition, cortactin expression is induced by thrombopoietin and interleukin-3 in megakaryocytes derived from murine bone marrow cells. Thus, cortactin represents a megakaryocyte-specific gene in bone marrow and the interaction of Src kinases with cortactin may be involved in the maturation of megakaryocytes.

Molecular modeling and deletion mutagenesis implicate the nuclear translocation sequence in structural integrity of fibroblast growth factor-1

The sequence NYKKPKL in the NH2 terminus of fibroblast growth factor (FGF)-1 has been proposed to affect the long term activities of FGF-1 through its function as a nuclear translocation signal or its role in stabilization of the structure required to sustain binding and activation of the transmembrane receptor kinase. A dynamic molecular model of FGF-1 docked into a duplex of the FGF receptor ectodomain and a hexadecameric heparin chain suggests that the NYKKPKL sequence does not directly interact with heparin or the receptor, but rather the lysine-leucine residues within the sequence indirectly stabilize a major receptor-binding domain. Concurrent with a marked increase in dependence on exogenous heparin for optimal activity, sequential deletion of residues in the NYKKPKL sequence in FGF-1 resulted in a progressive loss of thermal stability, resistance to protease, mitogenic activity, and affinity for the transmembrane receptor. The largest change resulted from deletion of the entire sequence through the lysine-leucine residues. In the presence of sufficiently high concentrations of heparin, the deletion mutants exhibited mitogenic activity equal to wild-type FGF-1. The results confirm that a primary role of the NYKKPKL sequence domain is to maintain the structural integrity of FGF-1 required for optimal binding to and activation of the heparan sulfate-transmembrane receptor complex.

Pharmacokinetic, angiographic, and histologic comparison of catheter-directed chemoembolization versus systemic chemotherapy in a canine model

Chemotherapy with selective intraarterial embolization may promote sustained contact of the drug with the tumor and thus could be more effective in the treatment. In this phenomenon, pharmacokinetics of a drug such as mitomycin C (MMC) play a significant role in guiding the therapy. Therefore, we have compared the pharmacokinetics of MMC and assessed angiographic, morphologic, and histologic changes in the kidney following intravenous MMC versus renal artery infusion with and without embolization with embolic agents, Rhizoma Bletillae (RB) and Gelfoam (GF). Dogs randomly divided into four groups underwent selective infusion protocols. Blood samples from renal and common iliac veins were analyzed for MMC levels. Angiography and pathology were performed at 4 days. Intravenous MMC (IV-MMC) caused significantly lower renal vein MMC levels than intraarterial MMC (IA-MMC) and GF + MMC. RB + MMC produced the lowest MMC levels in both veins (p < 0.05). Common iliac MMC levels were not significantly different after IV-MMC, IA-MMC, or GF + MMC. Angiographic and histologic studies showed extensive bleeding, necrosis, and vasculitis with thrombosis of the target kidneys after RB + MMC, GF + MMC, or IA-MMC, but not IV-MMC. Selective Rhizoma Bletillae chemoembolization can decrease systemic levels of MMC. Gelfoam does not provide sustained local release of MMC or decrease systemic levels of MMC compared with intravenous infusion. Selective renal MMC infusion without an effective embolic agent does not reduce systemic levels compared with intravenous delivery.

The expression and characterization of human recombinant proinsulin-like growth factor II and a mutant that is defective in the O-glycosylation of its E domain

In humans, newly synthesized proinsulin-like growth factor II (pro-IGF-II), i.e. IGF-II with an E domain extension of 89 amino acids, is 0-glycosylated on Thr75. As an approach to define the role that glycosylation of the E domain serves in the processing, secretion, and biological activities of IGF-II and to identify the sites of endoproteolytic processing, we constructed a mutant that encodes carbohydrate-free prepro-IGF-II. The mutant and wild-type prepro-IGF-II were expressed in NIH-3T3 cells, and the protein products were analyzed by SDS-PAGE followed by immunoblots with antipeptide antibodies to human and homologous rat E domain sequences. Transfectants that express glycosylated pro-IGF-II, i.e. xz97 and G11 cells, have intracellular forms of the growth factor with apparent Mr (appMr) of 21, 23, and 27K. NIH-3T3 xz95 cells, i.e. transfected with DNA that is missing the 0-glycosylation sequence, could also synthesize pro-IGF-II with an appMr of 21K. However, they did not accumulate the 23K and 27K forms of presumably glycosylated growth factor. None of the transfected NIH 3T3 cells processed much pro-IGF-II intracellularly, as the appMr 21K, 23K, and 27K forms had terminal E domain amino acid sequences that were recognized by antibodies to the homologous rat peptide sequence Met117 to Gln156. Subsequent to their secretion, the IGF-II in xz97 and G11 cells accumulated in the conditioned medium mostly as two partially processed species with appMr, of 17K and 14K, respectively. The IGF-II that accumulated in the conditioned medium of the xz95 cells had an appMr of 11K. As evidenced by a decrease in mass after treatment with neuraminidase and 0-glycosidase, the 17-kDa form of pro-IGF-II secreted by the NIH-3T3 xz97 cells was 0-glycosylated, whereas that secreted by the xz95 cells was oligosaccharide free. All of the pro-IGF-II forms have E domain amino acid sequences that reacted with antipeptide Ab to the Asp69 to Lys88 sequence. However, appMr 17K IGF-II, but not 14K IGF-II, also contained a larger E domain that was recognized by Ab to the sequence Phe89 to Arg101. The final step in the processing of 11- to 17-kDa IGF-II at Arg68 and the generation of mature IGF-II did not occur in the NIH-3T3 transfectants and is similar to what has been observed in human embryonic cells and mesenchymal tumors. The failure to remove the glycosylated E domain peptide from appMr, 14K and 17K IGF-II did not affect their binding to IGF-II/cation-independent mannose-6 phosphate receptors or presumably to IGF-I receptors, because in in vitro mitogenic assays they were equipotent with mature IGF-II. Unglycosylated pro-IGF-II from the NIH-3T3 xz95 cells also bound to these receptors. However, it was about 10 times more potent than IGF-II in stimulating thymidine incorporation into NIH-3T3 i24 IGF-IR cells, possibly because of the absence of negatively charged sialic acid and/or steric occlusion.

[A 5-year before-and-after comparison of lung function in asbestos workers]

A 5-year before-and-after comparison of lung function was carried out in 119 male asbestos workers. Of them 50 were healthy workers (0), 25 were patients with suspectable asbestosis (0+), 36 with Stage I asbestosis (Ias) and 8 with Stage II asbestosis (II as). The findings measured for before and after 5 years revealed that FVC, FEV and DLco declined in the four groups over the whole period of observation. The decrease in FVC and DLco was most marked and the differences were statistically significant (P < 0.05). Comparison among four groups showed that all indices of lung function in Group II as reduced significantly after 5 years (P < 0.01), indicating a rapid decrease of lung function in Group II as. It is suggested that FVC and DLco are the most sensitive indices in detecting very early abnormalities of lung function in asbestos workers.

[Concentrations and size distributions of aerosols in middle summer of Chengdu]

Statistical concentrations and size distributions of aerosols in middle summer of Chengdu city were measured by using optical scattering method. The influence of climate and its daily change affects on the concentration and distribution were analysed. The results showed: many of the distributions agreed with the Junge distribution; the peak concentration appeared near the noon; the relative humidity had strong influence on concentration; the clean-up effect of rain fall was evident. The measured results are useful for evaluating the environmental sanitation of the city.

Kinetic study on the photostability of solid vesnarinone and the equivalent relationship between daylight and lamplight

The photostability of solid vesnarinone on exposure to daylight and lamplight was studied. The equivalent influences of light from different sources on the photostability of solid vesnarinone were observed. Results show that the relationship between the surface reflectance of solid vesnarinone and the cumulative illuminance of light from different sources can be accurately expressed by a curve fit, R = A + B(Et) + C/(Et + D); the daylight can be replaced by lamplight in photostability studies.

Mutagenesis of the BC1 and BV1 genes of African cassava mosaic virus identifies conserved amino acids that are essential for spread

The products of three open reading frames encoded by the bipartite geminiviruses have been implicated in viral spread: AC2, BV1 and BC1. Alignment of the DNA B encoded gene products, BV1 and BC1, from African cassava mosaic virus (ACMV) with six other bipartite geminiviruses showed several highly conserved regions. Specific amino acids were selected for mutagenic studies to ascertain the tolerance of the virus to change and to identify the regions within these two proteins required for normal functioning. Various mutant DNA B constructs, and a wild-type construct, were inoculated onto three host plant species with an equivalent DNA A construct. Three of the mutant constructs were infectious on Nicotiana benthamiana and N. clevelandii, but only two induced ACMV disease symptoms on N. tabacum cv. Samsun. Sequencing of the viral DNA extracted from the sap of systemically infected plants confirmed the maintenance of introduced base changes. The amino acid at position 95 on the BV1 gene product was identified as non-essential for normal functioning of the protein. The alteration of the amino acid at position 145 in BC1 demonstrated the ability of the virus to tolerate a conservative change. The lack of tolerance to other changes in amino acids has given an indication of the importance of maintaining protein structure for these proteins to function normally.

Intact and functional fibroblast growth factor (FGF) receptor-1 trafficks near the nucleus in response to FGF-1

Exogenous fibroblast growth factor-1 (FGF-1) associates with the nucleus in a receptor-dependent manner during the entire G1 period of the BALB/c 3T3 cell cycle (Zhan, X., Hu, X., Friesel, R., and Maciag, T. (1993) J. Biol. Chem. 268, 9611-9620). To further study the role of the FGF receptor (FGFR) during this translocation, the intracellular fate of FGFR-1 protein and enzymatic activity was examined. Immunoprecipitation using multiple FGFR-1 antibodies followed by an in vitro tyrosine kinase activity assay enabled us to identify FGFR-1 as a 130-kDa phosphotyrosine-containing protein associated with the nuclear fraction of NIH 3T3 cells exposed to FGF-1. While FGFR-1 tyrosine kinase activity could be detected as a nuclear-associated protein after a 2-h exposure of the NIH 3T3 cells to FGF-1, this activity appeared to be maximal in the nuclear fraction between 4 and 12 h after FGF-1 treatment. In addition, analysis by confocal immunofluorescence microscopy of quiescent and FGF-1-stimulated NIH 3T3 cells reveal a prominent perinuclear FGFR-1 staining pattern in the cells exposed to FGF-1 but not in the quiescent population. We also observed FGFR-1 associated with the nuclear fraction in FGFR-1-transfected L6 rat myoblasts, which are known to be refractive to exogenous FGF-1 and express relatively low levels of endogenous FGFR-1. In addition, these cells also exhibited the presence of a 145-kDa phosphoprotein in the nuclear fraction that was recognized by FGFR-1 antibodies. These results suggest that the FGFR-1 may be translocated near the nucleus upon interaction with its ligand during the entire G1 period of the NIH 3T3 cell cycle as a structurally intact and functional tyrosine kinase that may be accessible to perinuclear polypeptides as a regulatory enzyme.

Cigarette smoking increases monocyte adherence to cultured endothelial cell monolayer

Leukocyte adherence to endothelium represents one of the early responses to injury. Although the underlying mechanisms of atherosclerosis and intimal hyperplasia remain unclear, monocytes/macrophages are associated with this phenomenon. Since cigarette smoking has been identified as a major risk factor for cardiovascular disease, we examined the effects of chronic cigarette smoking on human leukocyte adherence (monocytes, lymphocytes, and neutrophils) to cultured human umbilical vein endothelial cells (HUVEC's) in vitro. Among the cells, the basal adherence of monocytes only was significantly elevated in the smoking group (p < 0.05) compared to the non-smokers. Furthermore, the increase is related to increasing pack per day consumption (p < 0.01). These novel data suggest an alteration of the circulating monocytes by cigarette smoking, resulting in increased adherence to endothelial cells.

Association of fibroblast growth factor receptor-1 with c-Src correlates with association between c-Src and cortactin

The initiation of maximal DNA synthesis by fibroblast growth factor (FGF)-1 requires the presence of the growth factor during the entire G0 to G1 transition period of the cell cycle (Zhan, X., Hu, X., Friesel, R., and Maciag, T. (1993) J. Biol. Chem. 268, 9611-9620). During this time, the phosphorylation of several novel proteins on tyrosine residues occurs, and one of these phosphotyrosyl-containing proteins has been characterized as the murine homolog of the chicken cortactin gene (Zhan, X., Hu, X., Hampton, B., Burgess, W.H., Friesel, R., and Maciag, T. (1993) J. Biol. Chem. 268, 24427-24431), a putative substrate for v-Src. We have examined the possibility that FGF-1 employs c-Src or Src-like kinases as signaling intermediates during the mid and late G1 phase of the NIH 3T3 cell cycle using immunoprecipitation and immunoblot analysis. We have demonstrated that c-Src can associate with cortactin in a FGF-1-dependent manner. We have also demonstrated that a monoclonal antibody prepared against FGF receptor (R)-1 is able to co-precipitate Src-related proteins in lysates from FGF-1-treated NIH 3T3 cells. Furthermore, a kinase-active form of FGFR-1 expressed in a bacterial system was also able to associate with Src kinases in a manner dependent on the phosphorylation status of the FGFR-1 protein. Lastly, the Src homology (SH)-2 domain of v-Src was able to recognize a recombinant form of FGFR-1. Because (i) the association between FGFR-1 and Src-like kinases exhibits kinetics similar to those observed between the Src kinases and cortactin and (ii) the Src-SH2 domain is likely to be involved in the association with FGFR-1, we propose that the association of c-Src with activated FGF receptors may be responsible for the tyrosine phosphorylation of cortactin during the mid to late G1 phase of the cell cycle.

Mutagenesis of the nuclear localization sequence in EGF-1 alters protein stability but not mitogenic activity

Fibroblast growth factor (FGF)-1 is able to translocate to the nucleus as an exogenous protein and a deletion of the nuclear localization sequence near the NH2-terminus of FGF-1 (FGF-1(28-154)) yields a recombinant polypeptide with impaired mitogenic activity. To study the significance within this region (NYKKPK), five FGF-1 point mutations were constructed and their recombinant protein forms analyzed. Interestingly, none of the mutant protein products showed a significant reduction in mitogenic activity when compared to wild-type protein. Because these data suggested possible structural instability within the FGF-1(28-154) deletion mutant, protein structure was examined by fluorescence spectroscopy. Indeed, the FGF-1 point mutations which had similar mitogenic activity to wild-type FGF-1 displayed similar thermal fluorescence spectroscopy patterns as wild-type protein, but FGF-1(28-154) exhibited altered fluorometric profiles. However, the mitogenic activity and structural stability of FGF-1(28-154) was dependent upon the method used to purify the recombinant, whereas purification methods did not effect FGF-1(21-154) mitogenic activity. These studies suggest that the reduced mitogenic activity observed in preparations of the FGF-1(28-154) deletion mutant may be the result of structural instability and fluorescence spectroscopy cannot be used to predict FGF-1 stability.

Catalytically distinct conformations of the ribonuclease H of HIV-1 reverse transcriptase by substrate cleavage patterns and inhibition by azidothymidylate and N-ethylmaleimide

The RNase H activity of recombinant HIV-1 reverse transcriptase (RT) has been characterized with respect to inhibition by azidothymidylate (AZTMP) and N-ethylmaleimide (NEM) and to cleavage patterns using either poly(rA)/poly(dT) or poly(rG)/poly(dC) as model substrate and either Mg2+ or Mn2+ as divalent cation activator. The inhibitory potency of AZTMP and other nucleotide analogues was found to be dependent on both the composition of the substrate and the divalent cation. The enzyme was significantly more sensitive to AZTMP inhibition with poly(rG)/poly(dC) than with poly(rA)/poly(dT) as substrate and in Mn2+ than in Mg2+ with either substrate. Kinetic studies indicated that AZTMP is a competitive inhibitor with respect to the substrate in Mn2+ whereas it behaves as an uncompetitive inhibitor in Mg2+. These results suggest that the enzyme may exist in two distinct forms depending on whether Mg2+ or Mn2+ is the divalent cation activator. Consistent with this suggestion is the alteration in the mode of cleavage of the substrate upon substitution of Mg2+ with Mn2+. In Mg2+, hydrolysis of poly(rA)/poly(dT) appears to be solely endonucleolytic, whereas in Mn2+, hydrolysis is both endonucleolytic and exonucleolytic. With poly(rG)/poly(dC) as substrate, hydrolysis is both endonucleolytic and exonucleolytic in either Mg2+ or Mn2+. There is a positive correlation between sensitivity to AZTMP and production of mononucleotides, suggesting that the exonuclease activity of RNase H is preferentially inhibited by AZTMP. The sensitivity of RNase H to inhibition by N-ethylmaleimide was also found to be markedly influenced by the substrate composition and the divalent cation activator, being most sensitive under conditions in which endonucleolytic activity predominates.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiorespiratory responses elicited by right atrial injections of iodinated contrast media. Comparative evaluation of four agents

RATIONALE AND OBJECTIVES

The purpose of this study is three-fold: 1) to quantify the cardiorespiratory responses to rapid right atrial injections of meglumine/sodium diatrizoate, ioxaglate, iotrolan, and iopamidol; 2) to compare the effects of each contrast medium to that of its corresponding vehicle and saline; and 3) to evaluate the role of the vagus nerve in the cardiorespiratory responses.

METHODS

Seventeen anesthetized dogs, breathing spontaneously, were used. Injections of 2.0 mL/kg were given into the right atrium in 2 seconds. Each contrast medium, along with its vehicle and saline, was tested on 4 dogs (5 dogs for diatrizoate). Blood pressure, air flow, tidal volume, upper airway pressure, esophageal pressure, mean arterial pressure and heart rate, breathing frequency, dynamic lung compliance, upper airway resistance, and total lung resistance were recorded or calculated.

RESULTS

Diatrizoate and its vehicle caused a significant increase in blood pressure, tidal volume, esophageal pressure, and a decrease in mean arterial pressure with an increase in heart rate. These responses were not mediated by vagal afferents. Ioxaglate and iotrolan, but not their vehicles, increased breathing frequency; this response was abolished by vagal block. Ioxaglate decreased mean arterial pressure and increased heart rate; the decrease in mean arterial pressure was still present during vagal block. Iopamidol and its vehicle did not alter respiratory parameters. Iopamidol, but not its vehicle, caused only a minimal and transient increase in mean arterial pressure before and during vagal block. None of the contrast media changed upper airway resistance, total lung resistance, and dynamic lung compliance.

CONCLUSION

Both diatrizoate and its vehicle elicited the largest changes in respiratory and cardiovascular functions, not mediated by vagal afferents and caused by osmolality of the solution. Ioxaglate, iotrolan, and iopamidol induced smaller cardiorespiratory changes, mediated by vagal afferents. Their respective vehicles did not cause any effects, which suggests that the chemical structure plays a role. Nonionic contrast media elicited only minor and transient cardiorespiratory alterations.