NMR studies of the structure and dynamics of peptide E, an endogenous opioid peptide that binds with high affinity to multiple opioid receptor subtypes

Structural and dynamic properties of opioid peptide E have been examined in an sodium dodecyl sulfate (SDS) micelle. Structural and dynamic studies both indicate that this peptide exhibits greater segmental mobility than typical structured proteins. An nmr structural analysis of adrenal peptide E in SDS micelles indicated the presence of two well-defined beta-turns, one at the N-terminus encompassing residues 3 to 6, and the second in the region between residues 15 and 18. Certain side chain dihedral angles were also remarkably well defined, such as the chi 1 angle of F4, which exhibited a trans configuration. These calculated structures were based on a set of 9.5 restraints per residue. The backbone dynamics of peptide E in SDS micelles were examined through an analysis of 15N-relaxation parameters. An extended model-free analysis was used to interpret the relaxation data. The overall rotational correlation time is 19.7 ns. the average order parameter S2 is 0.66 +/- 0.15. The N-terminal loop region residues including G3 to R6 have an average order parameter of 0.70 +/- 0.23. The average order parameter lies somewhere between that observed for a random coil (e.g., S2 = 0.3) and that of a well-defined tertiary fold (e.g., S2 = 0.86). This suggests that peptide E in SDS micelles adopts a restricted range of conformations rather than a random coil. Based on the helical structure recently obtained for the highly homologous kappa-agonist dynorphin-A(1-17) and the beta-turn in the same region of peptide E, it is reasonable to assume that these two elements of secondary structure reflect different receptor subtype binding geometries. The intermediate order parameters observed for peptide E in an SDS micelle suggest a degree of dynamic mobility that may enable facile interconversion between helical and beta-turn geometries in the N-terminal agonist domain.

Fluid shear stress stimulates big mitogen-activated protein kinase 1 (BMK1) activity in endothelial cells. Dependence on tyrosine kinases and intracellular calcium

Mitogen-activated protein (MAP) kinases including ERK1/2 and JNK play an important role in shear stress-mediated gene expression in endothelial cells (EC). A new MAP kinase termed big MAP kinase 1 (BMK1/ERK5) has been shown to phosphorylate and activate the transcription factor MEF2C, which is highly expressed in EC. To determine the effects of shear stress on BMK1, bovine aortic EC were exposed to steady laminar flow (shear stress = 12 dynes/cm2). Flow activated BMK1 within 10 min with peak activation at 60 min (7.1 +/- 0.6-fold) in a force-dependent manner. Flow was the most powerful activator of BMK1, significantly greater than H2O2 or sorbitol. An important role for non-Src tyrosine kinases in flow-mediated BMK1 activation was demonstrated by inhibition with herbimycin A, but not with the Src inhibitor PP1 or overexpression of kinase-inactive c-Src. BMK1 activation was calcium-dependent as shown by inhibition with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/acetoxymethyl ester or thapsigargin. As shown by specific inhibitors or activators, flow-mediated BMK1 activation was not regulated by the following: intracellular redox state; intracellular NO; protein kinase A, C, or G; calcium/calmodulin-dependent kinase; phosphatidylinositol 3-kinase; or arachidonic acid metabolism. In summary, flow potently stimulates BMK1 in EC by a mechanism dependent on a tyrosine kinase(s) and calcium mobilization, but not on c-Src, redox state, or NO production.

Crm1p mediates regulated nuclear export of a yeast AP-1-like transcription factor

The yeast AP-1-like transcription factor, Yap1p, activates genes required for the response to oxidative stress. Yap1p is normally cytoplasmic and inactive, but will activate by nuclear translocation if cells are placed in an oxidative environment. Here we show that Yap1p is a target of the beta-karyopherin-like nuclear exporter, Crm1p. Yap1p is constitutively nuclear in a crm1 mutant, and Crm1p binds to a nuclear export sequence (NES)-like sequence in Yap1p in the presence of RanGTP. Recognition of Yap1p by Crm1p is inhibited by oxidation, and this inhibition requires at least one of the three cysteine residues flanking the NES. These results suggest that Yap1p localization is largely regulated at the level of nuclear export, and that the oxidation state affects the accessibility of the Yap1p NES to Crm1p directly. We also show that a mutation in RanGAP (rna1-1) is synthetically lethal with crm1 mutants. Yap1p export is inhibited in both rna1-1 and prp20 (RanGNRF) mutant strains, but Yap1p rapidly accumulates at the nuclear periphery after shifting rna1-1, but not other mutant cells to the non-permissive temperature. Thus, disassembly of export complexes in response to RanGTP hydrolysis may be required for release of substrate from a terminal binding site at the nuclear pore complex (NPC).

[Effects of butylphthalide on extracellular 6-keto-PGF1 alpha, TXB2 and 6-keto-PGF1 alpha/TXB2 ratio in cultured rat cortical neurons]

The effects of 3-n-butylphthalide(NBP) on the levels of 6-keto-PGF1 alpha, TXB2 and 6-keto-PGF1 alpha/TXB2 ratio were studied with methods of RIA. d-NBP and l-NBP(0.1-100 mumol.L-1) concentration-dependently increased 6-keto-PGF1 alpha release, decreased TXB2 release from neuronal cells, and significantly enhanced extracellular 6-keto-PGF1 alpha/TXB2 ratio in primary cultured rat cortical neurons exposed to hypoxic-hypoglycemic media for 5 h or hypoxic-hypoglycemic media for 5 h following normal media for 3 h. Aspirin(0.1-100 mumol.L-1) was also shown to inhibit TXB2 release from cortical neurons in a dose-dependent manner. However aspirin only increased 6-keto-PGF1 alpha/TXB2 ratio at low dose because aspirin inhibited both 6-keto-PGF1 alpha and TXB2 release simultaneously at large dose(10-100 mumol.L-1). This suggests that the action of l-NBP, d-NBP and dl-NBP on the increase of 6-keto-PGF1 alpha/TXB2 ratio might be one of the mechanisms in which NBP enhanced focal cerebral blood flow and improved ischemic brain damage.

[Expression of cell adhesion molecule CD44 variant isoform correlated with the clinical behavior of renal cell carcinoma]

OBJECTIVE

To determinate whether the expression of CD44v in renal cell carcinoma (RCC) is associated with tumor malignant behavior.

METHOD

Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect CD44v in 31 human renal cell carcinoma (RCC) in addition to 18 normal renal tissues from patients with non-malignant disease.

RESULT

Eighteen RCCs showed positive expression while none of normal renal tissue expressed CD44v (P < 0.001). CD44v was expressed in metastatic or high pathological stage RCC, but the expression of CD44v was not correlated with cellular differentiation.

CONCLUSION

Our data indicate that a role for CD44v in human RCC progression and metastases, and CD44v may prove to be a marker for high metastasis potential of RCC.

Retinoic acid-receptor activation of SP-B gene transcription in respiratory epithelial cells

Retinoids are known to play important roles in organ development of the lung. Retinoids exert their activity by modulating the expression of numerous genes, generally influencing gene transcription, in target cells. In the present work, the mechanism by which retinoic acid (RA) regulates surfactant protein (SP) B expression was assessed in vitro. RA (9-cis-RA) enhanced SP-B mRNA in pulmonary adenocarcinoma cells (H441 cells) and increased transcriptional activity of the SP-B promoter in both H441 and mouse lung epithelial cells (MLE-15). Cotransfection of H441 cells with retinoid nuclear receptor (RAR)-alpha, -beta, and -gamma and retinoid X receptor (RXR)-gamma further increased the response of the SP-B promoter to RA. Treatment of H441 cells with RA increased immunostaining for the SP-B proprotein and increased the number of cells in which the SP-B proprotein was detected. An RA responsive element mediating RA stimulation of the human SP-B promoter was identified. RAR-alpha and -gamma and RXR-alpha but not RAR-beta or RXR-beta and -gamma were detected by immunohistochemical analysis of H441 cells. RA, by activating RAR activity, stimulated the transcription and synthesis of SP-B in pulmonary adenocarcinoma cells.

Genotoxicity and chronic health effects of automobile exhaust: a study on the traffic policemen in the city of Lanzhou

A study on the health and genotoxic effects of occupational exposure to automobile exhaust was carried out among traffic policemen in Lanzhou (China) in 1996. A total of 78 traffic policemen working in the field was the exposed group, and 57 household register policemen working in the office was the control group. The health effects were evaluated by health questionnaires. Significant differences were observed between the exposed and control groups with respect to the morbidity of rhinitis, pharyngitis, trachoma, syndrome of neurasthenia and joint pain, apart from disorders in the digestive system. The percentage of rhinitis and pharyngitis obtained in the two groups was significantly higher among the smokers than among the nonsmokers. The frequencies of micronuclei (MN) and sister-chromatid exchanges (SCEs) were measured in peripheral blood lymphocytes from the two groups of volunteers. Compared with the control group, statistically significant increases of MN and SCE were found for the exposed group. The increase in the induction of MN and SCE among the traffic policemen and household register policemen is enhanced further by smoking.

Genistein suppresses adhesion-induced protein tyrosine phosphorylation and invasion of B16-BL6 melanoma cells

Protein tyrosine phosphorylation occurs as one of the earlier events in cancer cell-extracellular matrix (ECM) interaction. With immunoblot analysis and immunofluorescence microscopy, genistein was found to suppress the tyrosine phosphorylation of proteins located at the cell periphery, including a 125 kDa protein, when B16-BL6 melanoma cells attached to and interacted with ECM. When accompanied by the suppression of adhesion-induced protein tyrosine phosphorylation, the invasive potential of B16-BL6 cells through reconstituted basement membrane was decreased significantly. However, neither adhesive capability nor cell growth was significantly affected by genistein. Therefore, the interruption of cancer cell-ECM interaction by suppression of protein tyrosine phosphorylation may contribute to invasion prevention of genistein.

[Protective effects of d-, l-, and dl-3-n-butylphthalide on neuronal damage induced by hypoxia/hypoglycemia in cultured rat cortical neurons]

The effects of l-3-n-butylphthalide(l-NBP) and d-3-n-butylphthalide(d-NBP) on hypoxia/hypoglycemia-induced cytotoxicity in primary cultured rat cortical neurons were studied. l-NBP and d-NBP(1-100 mumol.L-1) were shown to inhibit hypoxia/hypoglycemia-induced LDH release, decrease the percent of cell death and improve the damaged cellular morphology at 10 mumol.L-1 concentration. In addition, l-NBP, d-NBP and dl-NBP were also found to significantly reduce the liberation of polyribosomes from the neuronal rough endoplasmic reticulum and disaggregation of polyribosomes induced by hypoxia/hypoglycemia. These data suggest that l-NBP, d-NBP and dl-NBP can remarkably protect cultured neurons against hypoxia/hypoglycemia induced damage.

The origin of differences in the physical properties of the equilibrium forms of cytochrome b5 revealed through high-resolution NMR structures and backbone dynamic analyses

On the basis of a comparison of high-resolution solution structures calculated for both equilibrium forms of rat ferrocytochrome b5, differences in reduction potential and thermodyanmic stability have been characterized in terms of significant structural and dynamic differences between the two forms. The dominant difference between A and B conformations has long been known to be due to a 180 degrees rotation of the heme in the binding pocket about an axis defined by the alpha- and gamma-meso carbons, however, the B form has not been structurally characterized until now. The most significant differences observed between the two forms were the presence of a hydrogen bond between the 7-propionate and the S64 amide in the A form but not the B form and surprisingly a displacement of the heme out of the binding pocket by 0.9 A in the B form relative to the A form. The magnitude of other factors which could contribute to the known difference in reduction potentials in the bovine protein [Walker, F. A., Emrick, D., Rivera, J. E., Hanquet, B. J., and Buttlaire, D. H. (1988) J. Am. Chem. Soc. 110, 6234-6240], such as differences in the orientation of the axial imidazoles and differences in hydrogen bond strength to the imidazoles, have been evaluated. The dominant effector of the reduction potential would appear to be the lack of the hydrogen bond to the S64 amide in the B form which frees up the propionate to charge stabilize the iron in the oxidized state and thus lower the reduction potential of the B form. The structure we report for the A form, based on heteronuclear NMR restraints, involving a total of 1288 restraints strongly resembles both the X-ray crystal structure of the bovine protein and a recently reported structure for the A form of the rat protein based on homonuclear data alone [Banci, L., Bertini, I., Ferroni, F., and Rosato, A. (1997) Eur. J. Biochem. 249, 270-279]. The rmsd for the backbone atoms of the A form is 0.54 A (0.92 A for all non-hydrogens). The rmsd for the backbone of the B form is 0.51 A (0. 90 A for all non-hydrogen atoms). An analysis of backbone dynamics based on a model-free analysis of 15N relaxation data, which incorporated axially symmetric diffusion tensor modeling of the cytochrome, indicates that the protein is more rigid in the reduced state relative to the oxidized state, based on a comparison with order parameters reported for the bovine protein in the oxidized state [Kelly, G. P., Muskett, F. W., and Whitford, D. (1997) Eur. J. Biochem. 245, 349-354].

[Effects of d-3-n-butylphthalide and l-3-n-butylphthalide on extracellular no level and intracellular cGMP level in primary cultured rat cortical neurons]

The effects of l-3-n-butylphthalide(l-NBP) and d-3-n-butylphthalide(d-NBP) on extracellular nitric oxide (NO) levels and intracellular cyclic GMP (cGMP) levels were studied in primary cultured rat cortical neuronal cells. Nitric oxide and cGMP levels were measured by using spectrometry and radioimmunological analysis(RIA), respectively. The results showed that d-NBP (0.1-100 mumol: L-1) markedly increased extracellular NO levels and intracellular cGMP levels in primary cultured neurons that were exposed for 10 h to hypoxic/hypoglycemic, N-methyl-D-aspartate (NMDA), or KCl media. On the contrary, l-NBP(0.1-100 mumol.L-1) significantly decreased extracellular NO levels and intracellular cGMP levels. It is suggested that there is a contrary effect of d-NBP and l-NBP on NO release and cGMP production induced by hypoxia/hypoglycemia, NMDA, or KCl.

[Study on changes of plasma substance P in essential hypertension with left ventricular hypertrophy patients and the effect of promoting blood circulation and eliminating phlegm]

OBJECTIVE

Exploring the relationship between the plasma substance P(SP) and essential hypertension with left ventricular hypertrophy (EH-LVH) and the effect of promoting blood circulation and eliminating phlegm.

METHODS

Before and after treatment, the changes of SP in patients wiith EH-LVH were measured by radioimmunoassay. Meanwhile, the changes of plasma renin activity (PRA), angiotension II (Ang II), left ventricular mass index (LVMI) and mean arterial pressure (MAP) were measured.

RESULTS

The level of plasma SP in patients with EH-LVH was markedly lower than that of patients without EH-NLVH and healthy subjects (P < 0.001); the levels of PRA and Ang II were higher than those in control group (P < 0.01 or < 0.05). After treatment, the level of SP was significantly increased, while LVMI, MAP, PRA and Ang II were significantly decrease (P < 0.01 or < 0.05). The levels between SP and LVMI, MAP, PRA, Ang II were markedly negative correlated (P < 0.01) while levels between LVMI and PRA, Ang II were markedly positive correlated.

CONCLUSIONS

The SP may be involved in the pathogenesis of EH-LVH; the mechanism of promoting blood circulation and eliminating phlegm reversing LVH might be related to its increasing the plasma SP.

Nuclear localization domain of thyroid transcription factor-1 in respiratory epithelial cells

Thyroid transcription factor-1 (TITF-1) is a homeodomain containing transcription factor that binds to and selectively activates the expression of genes in thyroid and pulmonary epithelial cells. TITF-1 plays a critical role in gene expression and in organogenesis of lung and thyroid. In the present work, epitope-tagged TITF-1 proteins were used to identify the regions of the TITF-1 polypeptide that mediate nuclear localization and transcriptional activity in human lung adenocarcinoma cells. A series of TITF-1-flag deletion mutants was generated and transfected into H441 cells to determine amino acid sequences involved in translocation to the nucleus. Transfection of the TITF-1-flag mutants demonstrated that a nuclear localization signal (NLS) sequence, located at the N-terminus of the homeodomain, is critical for nuclear targeting. The NLS was essential but not sufficient for translocation of TITF-1 to the nucleus, since deletion of the homeodomain itself also blocked nuclear translocation in the presence of NLS. Deletion of the N-terminal transactivation domain of TITF-1 completely abolished its transcriptional activation on the human surfactant protein-B promoter, and deletion of the C-terminal domain partially reduced its stimulatory activity. Nuclear translocation of TITF-1 depends on both an NLS and the homeodomain of the polypeptide. Both C- and N-terminal regions of TITF-1 are involved in transactivation of surfactant protein B gene expression in pulmonary cells.

Hepatocyte nuclear factor-3beta limits cellular diversity in the developing respiratory epithelium and alters lung morphogenesis in vivo

Hepatocyte nuclear factor-3beta (HNF-3beta), a nuclear protein of the winged helix family of transcription factors, is known to play a critical role in the formation of the embryonic node, notochord, and foregut endoderm. HNF-3beta influences the expression of a number of target genes in the respiratory epithelium, activating transcription of thyroid transcription factor-1, surfactant protein-B and clara cell secretory protein. In order to discern the role of HNF-3beta in differentiation and gene expression in the lung, HNF-3beta was expressed in developing respiratory epithelial cells of transgenic mice, under the control of the human surfactant protein C gene promoter. Pulmonary abnormalities were observed in the lungs of fetal mice bearing the HNF-3beta transgene. Differentiation of distal respiratory epithelial cells was arrested in the early pseudoglandular stage. Branching morphogenesis and vasculogenesis were markedly disrupted in association with decreased E-cadherin and vascular endothelial growth factor expression. HNF-3beta limits cellular diversity of developing respiratory epithelium and alters lung morphogenesis in vivo, suggesting that precise temporal-spatial regulation of HNF-3beta expression is critical for respiratory epithelial cell differentiation and lung morphogenesis.

Protein kinase A activation of the surfactant protein B gene is mediated by phosphorylation of thyroid transcription factor 1

Thyroid transcription factor 1 (TTF-1) is a homeodomain-containing nuclear transcription factor expressed in epithelial cells of the lung and thyroid. TTF-1 binds to and activates the transcription of genes expressed selectively in the respiratory epithelium including pulmonary surfactant A, B, C and Clara cell secretory protein. Transfection with a plasmid encoding the cyclic AMP-dependent protein kinase (protein kinase A; PKA) catalytic subunit, Cat-beta, stimulated the phosphorylation of a TTF-1-flag fusion protein 6-7-fold in H441 pulmonary adenocarcinoma cells. Recombinant TTF-1 was phosphorylated by purified PKA catalytic subunit in the presence of [gamma-32P]ATP. PKA catalytic subunit family members, Cat-alpha and Cat-beta, markedly enhanced the transcriptional activation of surfactant B gene promoters by TTF-1 in vitro. Peptide mapping was used to identify a PKA phosphorylation site at the NH2 terminus of TTF-1. A 17-amino acid synthetic peptide comprising this site completely inhibited the PKA-dependent phosphorylation of TTF-1 in vitro. A substitution mutation of TTF-1 (Thr9 two head right arrow Ala) abolished phosphorylation by PKA and reduced transactivation of the surfactant B gene promoter. Transfection with a plasmid encoding the cAMP regulatory element binding factor inhibited transcriptional activity of the surfactant protein B gene promoter. Phosphorylation of TTF-1 mediates PKA-dependent activation of surfactant protein B gene transcription.

A role for the divergent actin gene, ACT2, in nuclear pore structure and function

We have identified a temperature-sensitive allele of the yeast divergent actin gene ACT2, act2-1, which displays defects in nuclear pore complex (NPC) structure and nuclear import at the restrictive temperature. Although defective in nuclear import, act2-1 cells still selectively retain reporter proteins in the nucleus, and by indirect immunofluorescence the actin cytoskeleton appears normal. Previous studies in Acanthamoeba and Saccharomyces cerevisiae reported that the cellular location of Act2p partially overlaps that of conventional actin, indicating that it has a cytoskeletal function. In this study, both immunofluorescence localization and cellular fractionation of different epitope-tagged versions of Act2p also reveal an association with the nucleus, suggesting an independent nuclear function for Act2p. Analysis of act2-1 by electron microscopy, 30 min after a shift to the restrictive temperature (37 degrees C), reveals a striking aberration in NPC morphology; NPCs appear as abnormal densities on either side of, rather than spanning, the nuclear envelope. Immunoelectron microscopy confirms that these densities contain XFXFG nucleoporins. act2-1 is synthetically lethal in combination with a deletion in the XFXFG nucleoporin gene, NUP1, or a mutation in the nuclear localization sequence receptor gene, SRP1. Act2p and Srp1p co-immunoprecipitate, suggesting that the proteins exist in a complex. Together our data argue that Act2p plays an important role in NPC structure and function.

Characterization of a site-directed mutant of cytochrome b5 designed to alter axial imidazole ligand plane orientation

Mutants of cytochrome b5 were designed to achieve reorientation of individual axial imidazole ligands. The orientation of the axial ligand planes is thought to modulate the reduction potential of bis(imidazole) axially ligated heme proteins. The A67V mutation achieved this goal through the substitution of a bulkier, hydrophobic ligand for a residue, in the sterically hindered hydrophobic heme binding pocket. Solution structures of mutant and wild-type proteins in the region of the mutation were calculated using restraints obtained from 1H and 15N 2D homonuclear and heteronuclear NMR spectra and 1H-15N 3D heteronuclear NMR spectra. More than 10 restraints per residue were used in the refinement of both structures. Average local rmsd for 20 refined structures was 0.30 A for the wild-type structure and 0.38 A for the A67V mutant. The transfer of amide proton resonance assignments from wild-type to the mutant protein was achieved through overlays of 15N-1H heteronuclear correlation spectra of the reduced proteins. Side chain assignments and sequential assignments were established using conventional assignment strategies. Calculation of the orientation of the components of the anisotropic paramagnetic susceptibility tensor, using methods similar to procedures applied to the wild-type protein, shows that the orientation of the in-plane components are identical in the wild-type and mutant proteins. However, the orientation of the z-component of the susceptibility tensor calculated for the mutant protein differs by 17 degrees for the A-form and by 11 degrees for the B-form from the orientation calculated for the wild-type protein. The rotation of the z-component of the susceptibility tensor (toward the delta meso proton) is in the same direction and is of the same magnitude as the rotation of the H63 imidazole ring induced by mutation.

The culture of chicken embryo fibroblast cells on microcarriers to produce infectious bursal disease virus

The cultures of chicken embryo fibroblast (CEF) cells in flasks, spinner bottles, and bioreactors were studied. The growth and metabolism characteristics of CEF cells and the feasibility of the CEF cell culture in bioreactor were investigated. The plating process of the CEF cells on GT-2 microcarriers in spinner bottles was studied, and a plating kinetic model was presented. The culture of CEF cells in 1.5 L CelliGen bioreactor to produce infectious bursal disease virus (IBDV) had met success. Whereas the additive microcarriers were fed during the culture, the cell density was increased 10 times as against seed cells adhering to microcarriers and the virus titer was as high as 7.5. All the aforementioned experimental results have laid the foundation for high density culture of CEF cells and process scale-up.

Suppression of adhesion-induced protein tyrosine phosphorylation decreases invasive and metastatic potentials of B16-BL6 melanoma cells by protein tyrosine kinase inhibitor genistein

Protein tyrosine kinase (PTK) appears to be involved in the activation of signaling during cell attachment to and spreading on extracellular matrix (ECM) in the metastatic cascade. To verify the assumption that PTK inhibitors might impair ECM signaling and prevent cancer metastasis, the highly metastatic B16-BL6 mouse melanoma cells were exposed to the PTK inhibitor genistein for 3 days. The ability of the cells to invade through reconstituted basement membrane (Matrigel) and to establish experimental pulmonary metastatic foci in C57BL/6 mice decreased after genistein exposure. The genistein-treated cells were also prevented from attaching to Matrigel and spread extremely poorly on the ECM substratum. Immunoblot analysis showed that tyrosine phosphorylation of a 125-kD protein in response to cell spreading on Matrigel was suppressed in the genistein-treated cells. Adhesion-induced protein tyrosine phosphorylation represents the earlier and specific event in the activation of ECM signaling, so this result implied ECM signaling was impaired in the treated cells. With immunofluorescence microscopy, the adhesion-induced tyrosine phosphorylated proteins were located at the pericytoplasms of well-spread cells, but not at the periphery of poorly spread genistein-treated cells. Therefore, this paper suggests that genistein might impair ECM signaling and subsequently prevent cancer cells from spreading well and invading or establishing metastasis through the suppression of adhesion-induced protein tyrosine phosphorylation. PTKs and adhesion-induced protein tyrosine phosphorylation might play a role in the control of invasion and metastasis.

[Lead exposure level in umbilical cord blood and its related factors]

Six hundred and five specimens of umbilical cord blood were collected from Yangpu District, Shanghai, and blood lead levels were determined with graphite stove atom absorption spectrophotometry in 348 of them to study fetal exposure to lead and its related factors in the people of Shanghai. Survey on household social and environmental health status was conducted in families with the babies whose umbilical cord blood lead were above the 70th percentile and below the 30th percentile with a face-to-face questionnaire. Data were analyzed with multiple regression for the factors which affected the lead level in umbilical cord blood significantly. Results showed that blood lead levels in 348 cases were normally distributed, with a range of 0.08 to 0.84 mumol/L, a mean of 0.44 mumol/L and a standard deviation of 0.15 mumol/L. Specimens with cord blood lead level exceeding the safety criteria of 0.48 mumol/L accounted for 40.8 percent of the total. The study also found that passive smoking during pregnancy, exposure to lead in family members, one's living room adjacent to the major traffic roads, pollution by coal-burning smoke in the environment of one's residence, use of coal as domestic fuel, and eating preserved eggs during pregnancy all were risk factors for lead exposure. Multiple logistic regression analysis revealed that contribution of passive smoking to cord blood lead level was still statistically significant after adjusting other confounding factors. It concluded that environmental lead pollution could cause ad-verse effects on fetal development.

The calmodulin-dependent phosphodiesterase gene PDE1C encodes several functionally different splice variants in a tissue-specific manner

We report here the identification of cDNAs for three new mouse PDE1C splice variants and the characterization of their kinetics, regulation by Ca2+, sensitivities to inhibitors, and tissue/cellular expression patterns. Sequence analysis indicated that these three cDNAs (PDE1C1, PDE1C4, and PDE1C5), together with our previously reported PDE1C2 and PDE1C3, are alternative splice products of the PDE1C gene. The results from RNase protection analysis and in situ hybridization indicated that the expression of the different PDE1C splice variants is differentially regulated in a tissue/cell-specific manner. Particularly, high levels of PDE1C mRNAs were found in the olfactory epithelium, testis, and several regions of mouse brain such as cerebellar granule cells. All of these splice variants have similar kinetic properties, showing high affinities and approximately the same relative Vmax values for both cAMP and cGMP. However, they responded to Ca2+ stimulation differently. In addition, they show different sensitivities to the calmodulin-dependent phosphodiesterase inhibitors, KS505a and SCH51866. Substrate competition experiments suggested the presence of only one catalytic site on these PDE1C isozymes for both cAMP and cGMP. In summary, these findings suggest that the PDE1C gene undergoes tissue-specific alternative splicing that generates structurally and functionally diverse gene products.