Atomistic Brownian dynamics simulation of peptide phosphorylation

We report the implementation of an all-atom Brownian dynamics simulation model of peptides using the constraint algorithm LINCS. The algorithm has been added as a part of UHBD. It uses adaptive time steps to achieve a balance between computational speed and stability. The algorithm was applied to study the effect of phosphorylation on the conformational preference of the peptide Gly-Ser-Ser-Ser. We find that the middle serine residue experiences considerable conformational change from the C(7eq) to the alpha(R) structure upon phosphorylation. NMR (3)J coupling constants were also computed from the Brownian trajectories using the Karplus equation. The calculated (3)J results agree reasonably well with experimental data for phosphorylated peptide but less so for doubly charged phosphorylated one.

Prebiotic chemistry in clouds

In the traditional concept for the origin of life as proposed by Oparin and Haldane in the 1920s, prebiotic reactants became slowly concentrated in the primordial oceans and life evolved slowly from a series of highly protracted chemical reactions during the first billion years of Earth's history. However, chemical evolution may not have occurred continuously because planetesimals and asteroids impacted the Earth many times during the first billion years, may have sterilized the Earth, and required the process to start over. A rapid process of chemical evolution may have been required in order that life appeared at or before 3.5 billion years ago. Thus, a setting favoring rapid chemical evolution may be required. A chemical evolution hypothesis set forth by Woese in 1979 accomplished prebiotic reactions rapidly in droplets in giant atmospheric reflux columns. However, in 1985 Scherer raised a number of objections to Woese's hypothesis and concluded that it was not valid. We propose a mechanism for prebiotic chemistry in clouds that satisfies Scherer's concerns regarding the Woese hypothesis and includes advantageous droplet chemistry. Prebiotic reactants were supplied to the atmosphere by comets, meteorites, and interplanetary dust or synthesized in the atmosphere from simple compounds using energy sources such as ultraviolet light, corona discharge, or lightning. These prebiotic monomers would have first encountered moisture in cloud drops and precipitation. We propose that rapid prebiotic chemical evolution was facilitated on the primordial Earth by cycles of condensation and evaporation of cloud drops containing clay condensation nuclei and nonvolatile monomers. For example, amino acids supplied by , or synthesized during entry of, meteorites, comets, and interplanetary dust would have been scavenged by cloud drops containing clay condensation nuclei. Polymerization would have occurred within cloud systems during cycles of condensation, freezing, melting, and evaporation of cloud drops. We suggest that polymerization reactions occurred in the atmosphere as in the Woese hypothesis, but life originated in the ocean as in the Oparin-Haldane hypothesis. The rapidity with which chemical evolution could have occurred within clouds accommodates the time constraints suggested by recent astrophysical theories.

Transcriptional hyperactivity of human progesterone receptors is coupled to their ligand-dependent down-regulation by mitogen-activated protein kinase-dependent phosphorylation of serine 294

Breast cancers often exhibit elevated expression of tyrosine kinase growth factor receptors; these pathways influence breast cancer cell growth in part by targeting steroid hormone receptors, including progesterone receptors (PR). To mimic activation of molecules downstream of growth factor-initiated signaling pathways, we overexpressed mitogen-activated protein kinase (MAPK; also known as extracellular signal-regulated kinase) kinase kinase 1 (MEKK1) in T47D human breast cancer cells expressing the B isoform of PR. MEKK1 is a strong activator of p42 and p44 MAPKs. MEKK1 expression increased progestin-mediated transcription 8- to 10-fold above normal PR-driven transcription levels. This was dependent on the presence of a progesterone response element and functional PR. PR protein levels were unchanged by MEKK1 alone but were extensively down-regulated by MEKK1 plus the progestin R5020. MEKK1 expression resulted in phosphorylation of PR on Ser294, a MAPK consensus site known to mediate ligand-dependent PR degradation. MEK inhibitors blocked phosphorylation of Ser294 and attenuated PR transcriptional hyperactivity in response to MEKK1 plus R5020; stabilization of PR by inhibition of the 26S proteasome produced similar results. T47D cells stably expressing mutant S294A PR, in which serine 294 is replaced by alanine, fail to undergo ligand-dependent down-regulation and are resistant to MEKK1-plus-R5020-induced transcriptional synergy but respond to progestins alone. Similarly, c-myc protein levels are synergistically increased by epidermal growth factor and R5020 in cells expressing wild-type PR, but not S294A PR. Thus, highly stable mutant PR are functional in response to progestins but are incapable of cross talk with MAPK-driven pathways. These studies demonstrate a paradoxical coupling between steroid receptor down-regulation and transcriptional hyperactivity. They also suggest a link between phosphorylation of PR by MAPKs in response to peptide growth factor signaling and steroid hormone control of breast cancer cell growth.

A novel method for the preparation of amino-substituted hypocrellin B

A series of amino-substituted hypocrellins derived from hypocrellin B (HB) were synthesized by a novel mild method, in which the peri-hydroxylated perylenequinone structure of hypocrellin was preserved by the reaction of HB with an amine. The red absorption of the resulting products was significantly enhanced relative to the parent hypocrellins, which will significantly improve its photodynamic therapy effectiveness.

EPR investigation of the free radicals generated during the photosensitization of TiO2 colloid by hypocrellin B

The cation radical of dye produced from the interfacial electron transfer from a surface chelated dye to the conduction band of the colloidal TiO2 was studied by laser flash photolysis and electron paramagnetic resonance (EPR) techniques. The study employed hypocrellin B (HB), a natural photodynamic pigment with strong absorption over the visible light region, as a sensitizer and titanium dioxide as a colloid semiconductor. HB formed a chelate with this colloid semiconductor and exhibited a red-shifted and strongly enhanced absorption in the visible spectrum. Laser photolysis indicated that the electron excitation in the visible absorption band of the chelate resulted in extremely rapid and efficient electron injection from the excited triplet state of the dye into the conduction band of the semiconductor. A transient absorption of cation radical of HB at 570 nm was observed. The appearance of cation radical of HB was characterized by EPR spectrometry: the photoinduced EPR signal was not quenched by oxygen and its intensity decreased in the presence of NaI, a typical hole scavenger. The generation of conduction band electrons in HB-sensitized TiO2 system was also verified by the spin elimination of a stable cyclic nitroxide, 2,2, 6,6-tetramethylpiperidine-1-oxyl (TEMPO), and by the reduction of methyl viologen (MV2+) to its radical MV+.

Photobleaching of hypocrellin B and its butylamino-substituted derivative in solutions

The photobleaching of hypocrellin B (HB) and its derivative butylamino-substituted hypocrellin B (BAHB), both of which are potent sensitizers for photodynamic therapy (PDT), were investigated by studies of absorption spectra and quenching experiments and by the determination of photoproducts. Control experiments indicated that the sensitizer, oxygen and light were essential for the photobleaching of HB and BAHB, which suggested that it was a photodynamic process, e.g. the photobleaching processes of both HB and BAHB were mainly self-sensitized photooxidations. The illumination of HB with visible light in oxygenated nonpolar solvents generated singlet oxygen efficiently [phi(1O2) = 0.76] which in turn attacked the sensitizer HB with the subsequent formation of an endoperoxide product. The endoperoxide of HB is unstable at room temperature and undergoes loss of singlet oxygen with regeneration of the parent HB. The singlet oxygen released from the endoperoxide of HB was detected with chemical trapping experiments. The quenching experiments indicated that in increasingly polar solvents the superoxide anion mechanism (type I) as well as the singlet oxygen mechanism (type II) contributed to the photobleaching of HB. The introduction of the electron-donating butylamino group not only enhanced the yield of the superoxide anion generation but also altered the position of attack in the BAHB molecule by the activated oxygen species. No endoperoxide product was observed, and no singlet oxygen released from the photobleaching process of BAHB was detected. The photobleaching process of BAHB was more complex. Both the singlet oxygen and superoxide anion mechanism played important roles in the photobleaching of BAHB in all organic solvent used here, even in aerobic nonpolar solvents such as CHCl3.

Analysis of a 10-ns molecular dynamics simulation of mouse acetylcholinesterase

A 10-ns molecular dynamics simulation of mouse acetylcholinesterase was analyzed, with special attention paid to the fluctuation in the width of the gorge and opening events of the back door. The trajectory was first verified to ensure its stability. We defined the gorge proper radius as the measure for the extent of gorge opening. We developed an expression of an inter-atom distance representative of the gorge proper radius in terms of projections on the principal components. This revealed the fact that collective motions of many scales contribute to the opening behavior of the gorge. Covariance and correlation results identified the motions of the protein backbone as the gorge opens. In the back-door region, side-chain dihedral angles that define the opening were identified.

Spectroscopic studies and photodynamic actions of hypocrellin B in liposomes

Hypocrellin B (HB), a lipid-soluble natural pigment of perylenequinone derivative, is considered as potential photosensitizer for photodynamic therapy. Liposomes loaded with HB can constitute a simple model system, appropriate for better understanding the photodynamic action of HB in vivo. The steady-state absorption and emission spectra, quantum yield and lifetime of fluorescence of HB incorporated into egg L-a-phosphatidyl-choline (EPC) liposome were examined. The photochemical properties (Type I and/or Type II) of HB have also been studied in aqueous dispersions of small unilamellar liposomes of EPC using electron paramagnetic resonance and spectrophotometric methods, respectively. The quantum yield of 1O2 generated by HB is ca 0.76 in chloroform solution and it did not change upon the incorporation of HB into liposomes of EPC. The superoxide anion radical was generated by the electron transfer from the anion radical of HB (HB.-) to oxygen. The disproportionation of O2.- can generate H2O2 and ultimately the highly reactive .OH via the Fenton reaction. It could be that the disproportionation proceeded too fast, so we could not detect O2.- directly in aqueous dispersions of liposome EPC. Moreover, the self-sensitized photooxygenation of HB embedded in liposomes was studied, and almost fully (87%) inhibiting this reaction of HB by p-benzoquinone (as the quencher of O2.-) in aqueous dispersion of liposome EPC indicated that the radical mechanism (Type I) might be mainly involved in this oxygenation. All these findings suggested that the photodynamic action of HB proceeded via both Type-I and -II mechanisms, but Type-I mechanism might play a more important role in the aqueous dispersion.

Spectroscopic studies and photodynamic actions of hypocrellin B in liposomes

Hypocrellin B (HB), a lipid-soluble natural pigment of perylenequinone derivative, is considered as potential photosensitizer for photodynamic therapy. Liposomes loaded with HB can constitute a simple model system, appropriate for better understanding the photodynamic action of HB in vivo. The steady-state absorption and emission spectra, quantum yield and lifetime of fluorescence of HB incorporated into egg L-a-phosphatidyl-choline (EPC) liposome were examined. The photochemical properties (Type I and/or Type II) of HB have also been studied in aqueous dispersions of small unilamellar liposomes of EPC using electron paramagnetic resonance and spectrophotometric methods, respectively. The quantum yield of 1O2 generated by HB is ca 0.76 in chloroform solution and it did not change upon the incorporation of HB into liposomes of EPC. The superoxide anion radical was generated by the electron transfer from the anion radical of HB (HB.-) to oxygen. The disproportionation of O2.- can generate H2O2 and ultimately the highly reactive .OH via the Fenton reaction. It could be that the disproportionation proceeded too fast, so we could not detect O2.- directly in aqueous dispersions of liposome EPC. Moreover, the self-sensitized photooxygenation of HB embedded in liposomes was studied, and almost fully (87%) inhibiting this reaction of HB by p-benzoquinone (as the quencher of O2.-) in aqueous dispersion of liposome EPC indicated that the radical mechanism (Type I) might be mainly involved in this oxygenation. All these findings suggested that the photodynamic action of HB proceeded via both Type-I and -II mechanisms, but Type-I mechanism might play a more important role in the aqueous dispersion.

Determination of the dominant language hemisphere by functional MRI in patients with temporal lobe epilepsy

OBJECTIVE

To determine the dominant language hemisphere in patients with intractable temporal lobe epilepsy before surgical treatment by using functional MRI (fMRI).

METHODS

Twelve patients underwent fMRI. Among them, 4 patients also underwent the Wada test. Anterior temporal lobectomy was performed on patients with epileptic focus on the non-dominant hemisphere, and selective amygdalo-hippocampectomy on patients with epileptic focus on the dominant hemisphere.

RESULTS

Ten patients had left dominance, and 2 right dominance. The fMRI results were concordant with Wada test results in the 4 patients who accepted the Wada test. Seven patients underwent anterior temporal lobectomy, and 5 underwent selective amygdalo-hippocampectomy. There was no post-operative dysphasia.

CONCLUSION

fMRI is an alternative method of noninvasive functional mapping for language dominance in patients with temporal lobe epilepsy.

[Expression of adhesion molecules on CD34(+) hematopoietic precursor cells from normal human bone marrow, cord blood and mobilized blood]

OBJECTIVE

To investigate the expression of adhesion molecules on CD(34)(+) hematopoietic precursor cells from normal human bone marrow, cord blood and mobilized peripheral blood, and the mechanism of peripheral blood precursor cells mobilization.

METHODS

CD(34)(+) hematopoietic cells were separated from bone marrow, cord blood and mobilized peripheral blood by CD(34) MultiSort Kit immunomagnetic bead system. The purity was examined by FACSort. The CD(34)(+) cells and post-short-term cultured CD(34)(+) cells were labeled in an indirect immuno-fluorescence procedure with adhesion molecules CD(11a), CD(18), CD(44), CD(49d), CD(54), CD(58) and CD(62L) monoclonal antibodies and assayed by FACSort.

RESULTS

The expression of CD(11a), CD(18), CD(49d), CD(54), CD(58) and CD(62L) of mobilized peripheral blood CD(34)(+) cells was lower than that of bone marrow ones, especially for CD(49d) and CD(62L). Similar to mobilized peripheral blood CD(34)(+) cells, cord blood CD(34)(+) cells also showed a lower expression of CD(11a), CD(18), CD(44), CD(49d), CD(62L) than that of bone marrow ones, especially for CD(62L), but expression of CD(54) was higher than that of bone marrow and mobilized peripheral blood CD(34)(+) cells.

CONCLUSION

The expressions of cell adhesion molecules on CD(34)(+) cells in normal bone marrow, cord blood and mobilized peripheral blood were quite different, the mechanism of peripheral blood precursors mobilization might be related to downregulation of cell adhesion molecule expression.

The GLFG regions of Nup116p and Nup100p serve as binding sites for both Kap95p and Mex67p at the nuclear pore complex

Our previous studies have focused on a family of Saccharomyces cerevisiae nuclear pore complex (NPC) proteins that contain domains composed of repetitive tetrapeptide glycine-leucine-phenylalanine-glycine (GLFG) motifs. We have previously shown that the GLFG regions of Nup116p and Nup100p directly bind the karyopherin transport factor Kap95p during nuclear protein import. In this report, we have further investigated potential roles for the GLFG region in mRNA export. The subcellular localizations of green fluorescent protein (GFP)-tagged mRNA transport factors were individually examined in yeast cells overexpressing the Nup116-GLFG region. The essential mRNA export factors Mex67-GFP, Mtr2-GFP, and Dbp5-GFP accumulated in the nucleus. In contrast, the localizations of Gle1-GFP and Gle2-GFP remained predominantly associated with the NPC, as in wild type cells. The localization of Kap95p was also not perturbed with GLFG overexpression. Coimmunoprecipitation experiments from yeast cell lysates resulted in the isolation of a Mex67p-Nup116p complex. Soluble binding assays with bacterially expressed recombinant proteins confirmed a direct interaction between Mex67p and the Nup116-GLFG or Nup100-GLFG regions. Mtr2p was not required for in vitro binding of Mex67p to the GLFG region. To map the Nup116-GLFG subregion(s) required for Kap95p and/or Mex67p association, yeast two-hybrid analysis was used. Of the 33 Nup116-GLFG repeats that compose the domain, a central subregion of nine GLFG repeats was sufficient for binding either Kap95p or Mex67p. Interestingly, the first 12 repeats from the full-length region only had a positive interaction with Mex67p, whereas the last 12 were only positive with Kap95p. Thus, the GLFG domain may have the capacity to bind both karyopherins and an mRNA export factor simultaneously. Taken together, our in vivo and in vitro results define an essential role for a direct Mex67p-GLFG interaction during mRNA export.

Association between angiotensin-converting enzyme gene and late onset Alzheimer's disease in Han chinese

There is now overwhelming evidence that the varepsilon4 allele of apolipoprotein (APOE) gene is a major risk factor for late-onset Alzheimer's disease (AD). However, the APOE locus only accounts for a proportion of the overall genetic risk for AD. The angiotensin-converting enzyme (ACE) is widely expressed in the brain and may have a role in AD. Recently an insertion/deletion (I/D) DNA polymorphism at the intron 16 of ACE gene has been found associated with late-onset AD, but the results are not consistent. We have examined ACE gene in a cohort of Han Chinese AD cases and controls. We have found the ACE-I allele was enriched in our cases compared to controls (odds ratio (OR)=2.09, P=0.0043). The phenomenon was restricted to cases presenting with AD after the age of 70 years (P<0.0005), and was independent of APOE genotype. We conclude that ACE genotype is a risk factor for late onset AD.

[Determination of vanillymandelic acid in urine by high performance liquid chromatography]

OBJECTIVE

To develop a high performance liquid chromatography(HPLC) for determining vanillylmandelic acid(VMA) in urine.

METHODS

The analytical column was packed with Nova-Pak C18. Flow rate was 0.9 ml.min-1. The mobile phase was 40 mmol.L-1 NaH2PO4 buffer. The VMA of 30 healthy people in 24 hour urine were tested by the internal standard method and with electrochemical detector.

RESULT

The linear range was from 5 mumol.L-1 to 200 mumol.L-1. The mean analytical recovery rate was 99.1%. The mean within-day coefficient of variation(CV) was 5.8%, and the mean day-to-day CV was 7.7%. The detection limit was 0.28 mumol.L-1. The VMA of 24 hour urine was 18.13 +/- 6.17 mumol in healthy people.

CONCLUSIONS

The method is suitable for routine determination of VMA in urine.

Measurements of Rn-222, Rn-220 and their decay products in the environmental air of the high background radiation areas in Yangjiang, China

For the renewal of dose estimation from internal irradiation in the high background radiation areas (HBRA) of Yangjiang, the measurements of radon, thoron and their decay products in the environmental air were conducted, including: (1) integrating measurements of Rn-222 and Rn-220 concentrations; (2) eqilibrium factor F for Rn-222 and alpha-potential energy value of Rn-220; (3) external gamma radiation in places where radon measurements were undertaken; (4) cumulative exposure to indoor radon for each family in a case-control study on lung cancer. The Rn-Tn cup monitor method was used for the integrating measurement of Rn-222 and Rn-220 concentration. An alpha track detector was used for the integration measurement of Rn-222 concentration in the case-control study on lung cancer. The results of measurements show that although the investigated areas are located between the Equator and the Tropic of Cancer, and that people live in well-ventilated dwellings, the concentrations of radon, especially of Rn-220 are significantly higher in the indoor air of HBRA than those in the control area. The value of equilibrium factors for Rn-222, the alpha potential energy of decay products from Rn-222 and Rn-220 are determined.

New long-wavelength perylenequinones: synthesis and phototoxicity of hypocrellin B derivatives

Five new derivatives of hypocrellin B were obtained from the reactions of hypocrellin B with ammonia and ethanolamine. Their photophysical and photochemical properties were investigated. The phototoxicity of one compound on AH cells irradiated with red light (lambda = 600-700 nm) was also studied. Their significantly enhanced red absorptivities at wavelengths longer than 600 nm and singlet oxygen-generating function qualify them as promising photodynamic therapy agents.

Induction of IkappaBalpha mRNA expression in the brain by glucocorticoids: a negative feedback mechanism for immune-to-brain signaling

Peripheral injection of bacterial endotoxin lipopolysaccharide (LPS) induces brain mRNA expression of the proinflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha and the cytokine-responsive immediate-early gene IkappaBalpha. Peripheral LPS also increases levels of plasma glucocorticoids. Whether the induction of IkappaBalpha mRNA in the brain after peripheral LPS injection is caused by the feedback action of glucocorticoids has not been determined. In this study, we examined the mRNA expression of IkappaBalpha and IL-1beta in the rat brain by in situ hybridization histochemistry. Injection of the glucocorticoid agonist dexamethasone induced IkappaBalpha mRNA expression in the brain in a pattern identical to that of LPS injection. LPS but not dexamethasone also induced IL-1beta mRNA expression. Pretreatment with dexamethasone 30 min before LPS injection enhanced the expression of IkappaBalpha mRNA in the brain in a dose-dependent manner. Immobilization of rats for 2 hr (which raises glucocorticoid levels) also induced IkappaBalpha mRNA expression without inducing the expression of IL-1beta. Brain IkappaBalpha expression induced by peripheral LPS injection was attenuated by pretreatment of rats with the glucocorticoid antagonist RU-486. Finally, increased expression of IL-1beta mRNA in the brain was observed at 4 hr after peripheral LPS injection in adrenalectomized rats compared with sham-operated rats. These results reveal that in the brain glucocorticoids selectively induce IkappaBalpha mRNA expression, which serves as a negative feedback mechanism for peripheral LPS-induced synthesis of proinflammatory cytokines. Such an inhibitory control mechanism may be important for preventing prolonged expression of proinflammatory cytokines in the brain after peripheral immune challenge.

Photodynamic action of amino substituted hypocrellins: EPR studies on the photogenerations of active oxygen and free radical species

A novel method has been employed to prepare 2-butylamino-2-demethoxy hypocrellin A (BADMHA) and 2-butylamino-2-demethoxy hypocrellin B (BADMHB). Both compounds exhibit stronger absorption at the phototherapeutic window (600-900 nm). The spin trapping and spin counteraction studies have shown that they are both efficient generators of the active oxygen (1O2, O2*-) in the aerobic condition. Under the anaerobic condition they generate non-oxygen free radical (semiquinone radical anion), and the active oxygen mechanism of photosensitization can be converted into non-oxygen free radical mechanism with the depletion of oxygen. The quantum yields of 1O2 generation of BADMHA and BADMHB are 0.46 and 0.44, respectively. Both are lower than those of their parent compounds HA and HB. But the productions of superoxide anion are enhanced significantly compared with HA and HB, indicating they are both favorable Type I phototherapeutic agents.

New potential photodynamic therapeutic anti-cancer agents: synthesis and characterization of demethoxy amino-substituted hypocrellins

A novel method was used to obtain demethoxy amino-substituted hypocrellin derivatives. The reaction condition was mild and amino substitution occurred at position 2 or 11 of hypocrellins with high yield. The photophysical and photochemical properties of the amino-substituted hypocrellins derivatives were investigated, and their significantly enhanced red absorptivities and strong active oxygen-generating functions qualified them as promising photodynamic therapeutic anti-cancer agents.

Two new acyclic diterpene-gamma-lactones from Salix matsudan

Two new phytane-type diterpene-gamma-lactones named hanliuine I (1) and hanliuine II (2), were isolated from leaves of Salix matsudana (chinese name "hanliu", Berberidaceae). Their structures were deduced from 1D and 2D NMR techniques.

Different Interactions between Isomeric Tetrakis-(N-Hexadecylpyridiniumyl) Porphyrins and CdS Nanoparticles

Using porphyrin amphiphiles TC(16)PyP(2), TC(16)PyP(3), and TC(16)PyP(4) as photosensitizers, the interaction between amphiphilic porphyrins and colloidal CdS nanoparticles was studied by observing their absorption spectra, fluorescence spectra, and fluorescence lifetimes. The experimental results reveal that upon addition of CdS nanoparticles to a TC(16)PyP(3) or TC(16)PyP(4) solution, TC(16)PyP(3) or TC(16)PyP(4) is adsorbed onto the surface of the colloidal nanoparticles due to electrostatic action. The absorption spectra display the characteristic absorption of metalloporphyrin. Moreover, this adsorption also leads to red-shifted fluorescence spectra and the quenching of fluorescence emission. These changes are related to the formation of complexes. Nearly 90% of the fluorescence emission of 5x10(-6) mol/L TC(16)PyP(4) can be quenched with 6.8x10(-4) mol/L CdS colloid nanoparticles. Only 60% of the fluorescence emission of 5x10(-6) mol/L TC(16)PyP(3) can be quenched with 6.8x10(-4) mol/L CdS nanoparticles. The fluorescence quenching is attributable mainly to static quenching. According to the fluorescence quenching curves, the apparent association constants of TC(16)PyP(4) and TC(16)PyP(3) with colloidal CdS nanoparticles are 1.42x10(3) (mol/L)(-1) and 6.76x10(2) (mol/L)(-1), respectively. However, TC(16)PyP(2) does not adsorb onto the surface of colloid nanoparticles due to its larger steric hindrance; its absorption and fluorescence spectra are unchanged. Copyright 2000 Academic Press.

Electrostatic steering of substrate to acetylcholinesterase: analysis of field fluctuations

Based on previous molecular dynamics simulation results for acetylcholinesterase dimer, we calculate and analyse the electrostatic field fluctuations around the enzyme. The results show that dynamic features of the electrostatic field favor attraction of the positively-charged substrate. An Internet link to an animation of the results is also provided.

Phosphorylation of human progesterone receptors at serine-294 by mitogen-activated protein kinase signals their degradation by the 26S proteasome

Ligand-dependent down-regulation that leads to rapid and extensive loss of protein is characteristic of several nuclear steroid receptors, including human progesterone receptors (PRs). In breast cancer cells, >95% of PRs are degraded 6 h after the start of progestin treatment. The mechanism for down-regulation is unknown. We examined the role of PR phosphorylation by mitogen-activated protein kinases (MAPKs) in this process. Lactacystin and calpain inhibitor I, specific inhibitors of the 26S proteasome, blocked progestin-induced down-regulation, and ubiquitinated conjugates of PR accumulated in cells. Ligand-dependent PR degradation was also blocked by specific inhibition of p42 and p44 MAPKs. To define the targets of phosphorylation by this kinase, two serine/proline MAPK consensus sites on PR were mutated. We demonstrate that mutation of PR serine-294 to alanine (S294A) specifically and completely prevents ligand-dependent receptor down-regulation. We also find that rapid, ligand-independent degradation of immature PR intermediates occurs by a proteasome-mediated pathway. These results demonstrate that PR destruction, by either of two alternate routes, is mediated by the 26S proteasome. Specifically, down-regulation of mature PRs occurs by a mechanism in which ligand binding activates PR phosphorylation by MAPKs at a unique serine residue, which then targets the receptors for degradation.

Expression of GPC3, an X-linked recessive overgrowth gene, is silenced in malignant mesothelioma

Gene expression changes in rat asbestos-induced malignant mesothelioma (MM) cells were investigated by differential mRNA display. A mRNA transcript identified by this approach was abundant in normal rat mesothelial cells but not expressed in rat MM cell lines. Northern blot analysis confirmed that this transcript is uniformly silenced in rat MM cell lines and primary tumors. Nucleotide sequence analysis revealed that this transcript is encoded by the rat glypican 3 gene (GPC3), whose human homolog is mutated in the Simpson-Golabi-Behmel overgrowth syndrome. Allelic loss at the GPC3 locus was infrequent (6.9%) in MM cell lines, and no mutations were found. GPC3 transcript levels were markedly decreased in 16 of 18 primary tumors and 17 of 22 human MM cell lines. Most of the cell lines were shown to have aberrant methylation of the GPC3 promoter region. In two of four human MM cell lines tested, GPC3 expression was restored after 2-deoxy 5-azacytidine (DAC)-mediated demethylation of its promoter region. Ectopic expression of GPC3 inhibited in vitro colony formation of human MM cells. Collectively, these data suggest that down-regulation of GPC3 is a common occurrence in MM and that GPC3, an X-linked recessive overgrowth gene, may encode a negative regulator of mesothelial cell growth.

Bone marrow cell trafficking following intravenous administration

To address trafficking of transplanted marrow cells immediately after intravenous infusion, we examined the early fate of infused non-adherent, low-density donor bone marrow cells in a syngeneic mouse model. The presence of infused donor cells, marked with indium-111 oxine (111In), with the fluorescent dye PKH26, or by a detectable transgene marker, was evaluated at 3-48 h in a variety of tissues, including peripheral blood. All three cell-marking methods indicated a rapid (< 4 h) influx of cells into the bone marrow, liver, spleen, muscle and other tissues. Moreover, these tissues remained positive for the 48 h observation period. Interestingly, analysis of PKH26-positive cells in non-myeloablated animals demonstrated that approximately 17% of infused donor marrow cells localized to the marrow space within 15 h, whereas a smaller proportion of donor cells (approximately 1-2%) localized to the marrow in recipients preconditioned by irradiation. In an effort to enrich for cells that specifically home to the bone marrow, PKH26-labelled donor marrow cells were recovered from the first host and infused into a secondary recipient. Although this was a phenotypically undefined population of cells, no increase was observed in the relative fraction of PKH26-labelled cells returning or 'homing' to the marrow of the second recipient. Taken together, these data suggest both that marrow engraftment may be mediated by non-specific 'seeding' rather than a specific homing signal, and that efficient targeting of transplanted cells to the marrow is a complex multifaceted process.

Tentative association of the serotonin transporter with schizophrenia and unipolar depression but not with bipolar disorder in Han Chinese

The serotonin transporter gene (SERT) plays an important role in the serotonin uptake into neurons. Recently, several polymorphisms including a variable-number-tandem-repeat (VNTR) in the second intron and an insertion/deletion polymorphism (5-HTT linked polymorphic region, 5-HTTLPR) were identified and reported to be associated with a variety of mental illnesses, including major depression, bipolar disorder, anxiety-related traits, and autism. In our study, we performed an association study between the SERT VNTR polymorphism and schizophrenia (n = 260), bipolar disorder (n = 137), and unipolar depression (n = 33) in the Han Chinese. A large group of ethnically matched control individuals (n = 362) were also genotyped. Allele 12 of the VNTR polymorphism was associated with schizophrenia (P = 0.007) and unipolar depression (P = 0.011). Bipolar disorder was not associated with the VNTR (P = 0.93). Thus, we conclude that the SERT VNTR polymorphism may be a risk factor for both schizophrenia and unipolar depression, but not for bipolar disorder, in the Han Chinese.

Three-dimensional electron beam CT angiography in the diagnosis of intracranial aneurysms

OBJECTIVE

To assess the accuracy of three-dimensional electron beam CT angiography (3D-EBCTA) in the detection of intracranial aneurysms.

METHODS

31 patients with suspected cerebral aneurysms (including 3 post-operative patients) were examined by 3D-EBCTA. Those receiving angiography or surgery acted as controls. Maximum intensity projection (MIP) and shaded surface display (SSD) reconstruction ways were selected.

RESULTS

24 aneurysms were found in 23 patients. Of the 31 patients, false positive was noted in 1 patient, and false negative in 2 on 3D-EBCTA. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 92.0%, 88.9%, 91.2%, 95.8% and 80.0% respectively.

CONCLUSION

3D-EBCTA is an noninvasive, rapid, valuable method in diagnosis and screening of patients with suspected aneurysms. The reconstruction modes such as MIP and SSD should be used together to optimise the visualization.

Classification and digital subtraction angiography evaluation of carotid cavernous fistulas

OBJECTIVE

To investigate the role of digital subtraction angiography (DSA) in evaluation of carotid cavernous fistulas, and to initiate a new classification for carotid cavernous fistula.

METHODS

Cerebral angiography and selective external and internal carotid angiography were carried out in 56 patients who were classified into 5 types according to their hemodynamic features.

RESULTS

The types were A (38 patients), B (4), C (10), D (2), and E (2). One of the 38 direct fistulas was located at C1 of the cavernous segment. Fistulas at C2 were observed in 10 patients, at C3 in 4, at C4 in 10 and at C5 in 5. The anterior communicating arteries were patent and well compensated in 33 of the 56 patients. The posterior communicating arteries were patent and well compensated in 39 patients. Both communicating arteries were well compensated in 31 patients. Fifty of the 56 patients were drained by ophthalmic veins, 47 by inferior petrous sinuses, 18 by cortical veins, and 8 to the posterior fossa region.

CONCLUSIONS

Digital subtraction angiography was helpful in localization of the rents in carotid cavernous fistulas, in evaluation of function of Willis circles and provided valuable information for treatment of carotid cavernous fistulas. Carotid cavernous fistulas were divided into 5 categories: type A, B, C, D and E, among which type E was not previously described elsewhere.

Multidrug resistance-associated protein (MRP) mediated transport of daunomycin and leukotriene C4 (LTC4) in isolated plasma membrane vesicles

Studies have been carried out to examine in vitro drug transport in plasma membrane vesicles isolated from HL60/ADR cells that overexpress MRP. The results demonstrate that glutathione (GSH) enhances transport of daunomycin. A greater increase in transport activity occurs when the reaction is carried out in the presence of both GSH and sodium chloride. Sodium chloride alone has no effect on daunomycin transport. It has also been observed that GSH in the presence of sodium chloride induces a major increase in the transport level of LTC4. Thus far, no metal ion other than sodium chloride has been found to be active in the drug transport system. Kinetic analysis reveals that GSH in the presence of sodium chloride greatly reduces Km and increases Vmax, for daunomycin. Additional studies show that ATPase activity in isolated plasma membrane from HL60/ADR cells is greatly enhanced in the presence of both GSH and sodium chloride. These results suggest the possibility that GSH and sodium chloride stimulate MRP-mediated transport as a result of increased ATPase activity.

Comparative study of photophysical properties of isomeric tetrapyridyl- and tetra-(N-hexadecylpyridiniumyl) porphyrins

Photophysical properties (absorption spectra, fluorescence spectra, lifetimes and quantum yields) were studied for the three isomers of tetrapyridylporphyrins (TPyPs) in CHCl3 and tetra-(N-hexadecylpyridiniumyl) porphyrins (TC16PyPs) in CHCl3, CH3OH and Triton X-100 micelle solution. While the ground-state and excited-state properties are very similar for the three isomers of neutral TPyP, significant differences exist among the isomers of amphiphilic TC16PyP. Amphiphilic porphyrins bearing hydrophilic pyridinium and hydrophobic long-chain alkyl groups are characterized by reduced fluorescence quantum yields, biexponential fluorescence decay, and appreciable aggregation in nonpolar solvents. The observed biexponential fluorescence decay of amphiphilic porphyrins can be interpreted in terms of mixing of the S1 and a close-lying CT state in which an electron is transferred from the porphyrin core to the electron-deficient pyridinium group.

Protein sequencing by matrix-assisted laser desorption ionization-postsource decay-mass spectrometry analysis of the N-Tris(2,4,6-trimethoxyphenyl)phosphine-acetylated tryptic digests

We have recently reported a simple procedure by which low picomole quantities of peptides can be modified to the corresponding N-Tris(2, 4,6-trimethoxyphenyl)phosphonium-acetyl (TMPP-Ac) derivatives (Z. H Huang, J. Wu, D. A. Gage, and J. T. Watson, Anal. Chem. 69, 137-144, 1997). This modification significantly facilitates sequence interpretation by providing exclusively N-terminal product ions (mainly a-type ions) in the fast-atom bombardment-MS/MS and matrix-assisted laser desorption ionization-postsource decay(MALDI-PSD)-MS spectra. The TMPP-Ac derivatization approach has been extended now for the direct derivatization of tryptic digests originating from 1-5 microg of proteins with molecular weights from 10-120 kDa. Our new procedure involves tryptic digestion in aqueous solution buffered to pH 8-8.2 with phosphate or Tris-HCl, followed by reaction with TMPP-acetic acid N-hydroxysuccinimide ester (TMPP-AcOSu bromide, 2-4 nmol reagent/microg protein, rt, 20 min) to provide N-terminally derivatized products, while the epsilon-NH2 groups in lysine remain unchanged. The resultant derivatized peptide mixture or its partially separated HPLC fractions are subsequently analyzed by MALDI-PSD-MS using 0.5- to 1-pmol aliquots, giving rise to product ion spectra that are easily interpretable. As there is no need for material transfer and change of buffer media, the tandem enzymatic-chemical reaction/MS analysis process is usually carried out with very high throughput (digestion, 1 h; reaction, 1/3 h; HPLC, 1 h; MALDI-PSD, 3-4 fragments/h). This procedure will be of potential use for obtaining sequence information directly from mixtures or as an adjunct of peptide mass mapping to provide protein identification with high confidence.

Detection of loss of heterozygosity on chromosome 9q22.3 in microdissected sporadic basal cell carcinoma

Identification of loss of heterozygosity (LOH) at specific genetic loci in cancer cells suggests the presence of a tumor suppressor gene within the deleted region. A basal cell carcinoma (BCC) susceptibility gene, human homolog of drosophila patched (PTC), has been recently cloned and localized on chromosome 9q22.3. Mutation and deletion of this region has been reported in BCCs using frozen tumor tissue. The objective of this study was to test whether LOH of human PTC on chromosome 9q22 could be detected in archival sporadic BCCs. We studied 20 randomly selected sporadic BCCs by microdissection and polymerase chain reaction using paraffin-embedded, formalin-fixed material on glass slides. In all cases, analysis was performed with the polymorphic markers D9S53, D9S15, D9S287, and D9S303. The LOH frequencies were 30%, 42%, 56%, and 75% with D9S15, D9S287, D9S53, and D9S303, respectively. LOH at 9q22 was identified in 12 of 20 cases (60%) with at least one marker. Seven cases showed LOH with two markers, two cases with three markers, and one case showed LOH with all four markers. The results indicate that BCC LOH can be frequently identified in paraffin-embedded BCC after routine processing.

[The study on the structure of 5,10,15,20-tetra-(4-hexadecylpyridiniumyl)porphyrin LB films]

The film-forming properties of 5,10,15,20-tetra-(4-hexadecylpyridiniumyl)porphyrin bromide (TC16PyP) on the air/water interface were studied. LB films of the amphiphilic porphyrin were prepared on the glass, quartz and SnO2 OTE substrates. The morphology and structure of TC16PyP LB films were characterized by scanning tunnelling microscope, UV-Vis absorption spectra, fluorescence spectra and low-angle X-ray diffraction. The experimental results indicated that the amphiphilic porphyrin TC16PyP has good film-forming properties on the air/water interface, its LB films are stable, in TC16PyP monolayer or LB films the long alkyl chains are not straight and the porphyrin macroring is lying nearly parallel to the substrate surface.

[Association of VNTR region of the human serotonin transporter gene with bipolar disorder among the Han Chinese]

OBJECTIVE

The serotonin transporter gene (SERT) plays an important role in the serotonin uptake into neurons. This paper reports a population and association study among the Han Chinese.

METHODS

DNA were extracted from peripheral blood samples of 50 patients with bipolar disorder (DSM-IIIR), 170 unrelated healthy Han Chinese individuals and 10 healthy trios for polymerase chain reaction. The VNTR locus was amplified and PCR products were separated on the 2% agrose gel.

RESULTS

All the three alleles(9,10 and 12 copies of repeat unit) reported in other studies were observed in this study with frequency 0.0029, 0.0676 and 0.9294, respectively. Four genotypes distributed in Caucasian: 12/12, 12/10, 12/9 and 10/10 were also found in the Han Chinese population. A significant difference in the allele frequency between the Han Chinese and Caucasian populations was found(P 0.000000001). No disequilibrium was observed after checking the Hardy-Weinberg equilibrium (P=0. 9995). The hereditary stability of this locus in accordance with the rules of Mendelian inheritance was demonstrated in the analysis of ten trios. In addition, a significant increase of frequency of the allele 10 in female patients with bipolar disorder was found (P=0. 043).

CONCLUSION

The data of association study might indicate a different mechanism of aetiology of bipolar disorder in male and female.

Convergence of progesterone and epidermal growth factor signaling in breast cancer. Potentiation of mitogen-activated protein kinase pathways

During late stages of breast cancer progression, tumors frequently acquire steroid hormone resistance with concurrent amplification of growth factor receptors; this alteration predicts a poor prognosis. We show here that following treatment with the progestin, R5020, breast cancer cells undergo a "biochemical shift" in the regulation of epidermal growth factor (EGF)-stimulated signaling pathways: R5020 potentiates the effects of EGF by up-regulating EGFR, c-ErbB2 and c-ErbB3 receptors, and by enhancing EGF-stimulated tyrosine phosphorylation of signaling molecules known to associate with activated type I receptors. Independently of EGF, R5020 increases Stat5 protein levels, association of Stat5 with phosphotyrosine-containing proteins, and tyrosine phosphorylation of JAK2 and Shc. Furthermore, progestins "prime" breast cancer cells for growth signals by potentiating EGF-stimulated p42/p44 mitogen-activated protein kinase (MAPK), p38 MAP kinase, and JNK activities. Although the levels of cyclin D1, cyclin E, and p21(WAF1), are up-regulated by R5020 alone, they are synergistically up-regulated by EGF in the presence of R5020. Up-regulation of cell cycle proteins by EGF is blocked by inhibition of p42/p44 MAPK only in the presence of R5020, supporting a shift in the regulation of these cell cycle mediators from MAPK-independent to MAPK-dependent pathways. In summary, progesterone selectively increases the sensitivity of key kinase cascades to growth factors, thereby priming cells for stimulation by latent growth signals. These data support a model in which breast cancer cell growth switches from steroid hormone to growth factor dependence.

[Effects of Chinese herbs xianzhen tablet on the deformability of erythrocyte in non-insulin-dependent diabetes mellitus patients with deficiency of both qi and yin and deficiency of kidney with blood stasis]

OBJECTIVE

To explore the effects of Xianzhen Tablet (XZT) on the hemorheology of type 2 diabetes (NIDDM) on the basis of previous studies in XZT, that have indicated its ability to deplete fasting blood glucose, to reduce the injury of free radical to the body, to improve the Na(+)-K(+)-ATPase in the erythrocyte membrane of NIDDM.

METHODS

Erythrocyte deformability and aggregation were studied with Ektacytometer in a total of 60 type 2 diabetes who were randomly divided into two groups. One was ZXT treated group, another was placebo group.

RESULTS

(1) The erythrocyte deformability of type 2 diabetes was lower than that in normal subjects (P < 0.001), but the erythrocyte aggregation increased abnormally than that of health people (P < 0.001). The correlation test indicated there were negative correlation with plasma fibronogen and positive correlation with blood cholesterol (P < 0.05). (2) The erythrocyte deformability in the ZXT treated group with 30 patients improved after 8 weeks treatment (P < 0.01), with the decreased fasting blood glucose and plasma fibrinogen (P < 0.05). Compared with placebo group, there was significant statistical difference (P < 0.01).

CONCLUSIONS

XZT could improve the erythrocyte deformability in the type 2 diabetes.

Expression of adenylyl cyclase mRNAs in the denervated and in the developing mouse skeletal muscle

Changes in the activity and in the expression of adenylyl cyclase (AC) were examined in mouse skeletal muscle after denervation and during development. Four isoforms of AC (AC2, AC6, AC7, and AC9) were detected by Northern blot analysis in gastrocnemius muscle, AC9 being the most abundant. After denervation, the levels of AC2 and AC9 mRNA decreased, whereas those of AC6 and AC7 increased. AC activity in response to several neurotransmitters was increased after denervation. During development, AC activity was high in fetus and neonate and declined in the adult; the sensitivity of AC activity to various neurotransmitters was the highest on the third postnatal day. The levels of AC6 and AC7 mRNAs were high on the third postnatal day and then decreased in adult, paralleling the decline in AC activity. All the characteristics of AC expression and activity in fetus and neonate resembled those observed in denervated adult muscle. These results indicate that changes in AC activity and AC mRNAs play an important role in the various physiopathological states of skeletal muscle, especially during muscle atrophy.

Toward a broader definition of heat-related death: comparison of mortality estimates from medical examiners' classification with those from total death differentials during the July 1995 heat wave in Chicago, Illinois

The classification of heat-related deaths solely according to body temperatures underestimates the magnitude of heat-related mortality during heat waves. Broader classifications are often used, but their utility in defining the mortality and identifying at-risk populations has not been evaluated. Using death data from the July 1995 heat wave in Chicago, the authors compared heat-related mortality rates based on the classification of heat-related deaths by the Cook County Medical Examiner's Office (CCMEO), with excess mortality rates based on total mortality differentials during and before the heat wave. In July 1995, the overall mortality in Chicago was 19 deaths per 100,000 population for heat-related mortality and 24 to 26 deaths per 100,000 population for excess mortality. Across Chicago community areas, the two mortality rates were closely related (r = 0.73-0.79; p < .01), but heat-related mortality rates were lower than excess mortality rates in community areas where excess mortality rates were higher (slope < 1; p < .01), a finding indicating an underestimation of heat-related deaths in such areas. The underestimation could not be explained by uncertainties in estimating excess mortality rates or by differences in socioeconomic and demographic characteristics among communities. These results support using the broader CCMEO classification of heat-related deaths as a relative indicator to target communities for prevention and relief efforts, but not as an adequate measure of actual heat-related mortality in a high-risk neighborhood.

Stability of the vasopressin V2 receptor-adenylyl cyclase system in rat kidney

In the Brattleboro rat with diabetes insipidus vasopressin V2 receptor mRNA and the mRNA of various adenylyl cyclase (AC) isoforms are moderately reduced compared with those of normal rats. In the present study renal vasopressin V2 receptor mRNA was modestly higher (by 34%), as was expression of AC 5, 6 and 9 mRNAs (up to 22% greater), in BDI rats treated with the vasopressin V2 receptor agonist desamino-[Arg8] vasopressin than in untreated controls. AC 4 mRNA was decreased by 17% following desamino-[Arg8s] vasopressin treatment. While the stimulatory Gsalpha mRNA was little affected by the desamino-[Arg8] vasopressin treatment, two of the inhibitory G proteins were raised (Galphai-2 by 54% and Galphai-3 by 57%). Treatment of Sprague-Dawley rats with a specific vasopressin V2 receptor antagonist (SR 121463A) was not associated with any marked changes in mRNA expression. These results indicate that the vasopressin V2 receptor adenylyl cyclase system mediating the antidiuretic response to vasopressin is relatively stable. The Gi proteins may be involved in the stabilizing mechanism.

Spectral Characteristics and Photosensitization Effect on TiO2 of Fluorescein in AOT Reversed Micelles

The microenvironment in reverse micelles composed of water, aerosol OT (AOT, sodium bis(2-ethylhexyl)sulfosuccinate), and isooctane has an important effect on the spectral properties of fluorescein (FL). The absorption peaks of FL red-shifted by about 10 nm from the corresponding positions in aqueous solution. Moreover, the absorption extinction coefficient of FL in reversed micelles increased with the water content, omega. The fluorescence of FL was more effectively quenched in AOT reversed micelles than in aqueous solution. In addition, aggregation occurred for FL in reversed micelles, which hindered the photo-induced electron transfer from the excited singlet of FL to the conduction band of TiO2. Copyright 1998 Academic Press. Copyright 1998Academic Press

[Cloning and expression of the E. coli serine hydroxymethyltransferase gene (glyA)]

The E. coli K12 glyA gene(13 kb), encoding serine hydroxymethyltransferase (SHMT), has been cloned in the plasmid vector pBR329 using insertion inactivation and complementation test. Subcloning of segments of the original insert (13 kb) into plasmids pBR322, pBR329 and pSMY901 established that a 2.6 kb PstI-EcoR fragment carries the glyA gene. The 12 strains of transforments containing recombined plasmid. were obtained. SHMT and glyA gene product level in strains carrying glyA plasmids were different. No SHMT activity was observed in host strains. The glyA gene products for JM109(pSM13), K12(pSM13), K12(pSM14) and K12(pSM15) account for 15.7%, 15.4%, 11.8%, and 9.48% of the total dissoluble cell protein, respectively.

Localization and differential expression of adenylyl cyclase messenger ribonucleic acids in rat adrenal gland determined by in situ hybridization

The expression of adenylyl cyclases (ACs) in the adult rat adrenal gland was examined. In situ hybridization revealed specific patterns of AC messenger RNA (mRNA) distribution. AC1 was limited exclusively to the adrenal medulla. AC5 and AC6 were mainly expressed in the adrenal medulla, with a weak expression in the zona glomerulosa. AC9 was found in all the three regions of the adrenal cortex but not in the adrenal medulla. All these ACs were detected on postnatal day 1 (PN1), and their pattern of expression was unchanged on PN7, PN21, and PN90 (adult). We analyzed the response of these ACs to various physiological conditions known to affect the synthesis of aldosterone and corticosterone in the adrenal cortex. Our study demonstrates a specific increase of AC6 but not AC5 mRNA in the zona glomerulosa of rats given a low sodium diet. AC9 mRNA was increased in all the three cortical zones of rats treated with ACTH. We suggest that AC6 and AC9 play important roles in different pathways associated with the regulation of aldosterone and corticosteroid production.

Changes in the expression of adenylyl cyclases in the rat uterus during the course of pregnancy

The changes in the expression of the various adenylyl cyclases (ACs) in the rat uterus during the course of pregnancy and after delivery were examined by Northern blot analysis and AC assay. Northern blot analysis revealed that five isoforms of ACs (AC2, AC4, AC6, AC7, and AC9) were expressed in the rat uterus, AC6 being the most abundant. The level of expression of these ACs increased 1.7- to 3.4-fold during the course of pregnancy and diminished near term and after delivery. The highest level of expression in each type of AC was consistently seen on Day 17 of pregnancy, and the relative increase of expression, as compared to that in nonpregnant rats, was as follows: AC2 > AC4 > AC7 > AC9 > AC6. In agreement with these findings, both basal and forskolin-stimulated AC activities exhibited a 2- to 3-fold increase during the course of pregnancy, followed by a decrease near term. Our data indicate that post-receptor events, namely marked changes in the level of AC mRNA (and presumably proteins) occur during pregnancy and after delivery and that they contribute to the essential role of cAMP in maintaining uterus quiescence.

Reconstitution of bile acid transport in a heterologous cell by cotransfection of transporters for bile acid uptake and efflux

The rat liver canalicular bile acid transporter/ecto-ATPase/cell CAM 105 (CBATP) is a 110-kDa transmembrane phosphoglycoprotein that is thought to have bile acid efflux, ecto-ATPase, and cell adhesion properties. Its extracellular amino-terminal domain is highly homologous to carcinoembryonic antigen (CEA), a glycophosphatidyl inositol-anchored membrane protein with cell adhesion properties and a marker for adenocarcinoma. In the current study, we examined the possibility of more clearly defining the role of CBATP in bile acid efflux by cotransfecting a heterologous cell, the COS cell, with cDNAs for a bile acid importer, the ileal bile acid transporter (IBAT), as well as for CBATP. The results show that when IBAT mediates uptake of [3H]taurocholate to a level 20-fold higher than that achieved previously by nonspecific pinocytosis, CBATP mediates time-, temperature- and concentration-dependent efflux. Efflux of [3H]taurocholate mediated by CBATP in the cotransfected COS cells is saturable and has curvilinear kinetic characteristics (Vmax = 400 pmol/mg protein/min, Km = 70 microM). It is inhibited by 4,4'-diisothiocyanostilbene-2,2-disulfonic acid and dependent on ATP but not dependent on membrane potential. Although CEA could not mediate bile acid efflux in COS cells cotransfected with IBAT and CEA, efflux of [3H]taurocholate was detected in COS cells cotransfected with IBAT and a chimeric molecule having the carboxyl-terminal tail and membrane spanning domain of CBATP and the amino-terminal extracellular tail of CEA. Taken together, these data provide further evidence that CBATP confers bile acid efflux properties on heterologous cells and that its cytoplasmic tail and membrane spanning segment are integral to this property. The data also establish a model system for more clearly defining the molecular determinants of bile acid transport mediated by this molecule.

The Surface Chemistry of Hybrid Nanometer-Sized Particles

Nanometer sized Au/TiO2 particles were synthesized by irradiation of a HAuCl4 solution containing colloidal TiO2 with light of wavelength (lambda) >330 nm. The absorption maximum attributed to the surface plasmon band of gold was observed at 530 nm, a red shift of about 10 nm from the position in aqueous solution. The particle size of Au/TiO2 determined by TEM was about 25 nm. The Au clusters are situated on the surface of TiO2 in terms of microcrystallite, which was confirmed by HRTEM, EDS, and XRD. A negative shift of binding energy in the Au 4f7/2 for gold cluster on the surface of TiO2 was found, and the electronic interaction between the metal and the support was discussed.

Expression of adenylyl cyclase mRNAs in the adult, in developing, and in the Brattleboro rat kidney

The activity and expression of adenylyl cyclases (AC) were examined in the adult rat renal cortex and medulla. Northern blot analysis and in situ hybridization demonstrated that AC-6 was the predominant isoform in the adult rat kidney, whereas AC-4, -5, and -9 had a lower expression. AC-4 expression was higher in the cortex, and AC-5 and AC-6 were higher in the medulla. AC-9 expression was at the same level in both regions. AC activity was high in the fetus and declined in the adult. At all stages, AC activity was sensitive to parathyroid hormone, whereas no stimulation by vasopressin and isoproterenol was found in the fetus and the neonate. AC-5 and AC-6 mRNAs increased at day 1 and then markedly decreased, paralleling the decline in AC activity. The mRNA of AC-4 did not change and that of AC-9 increased markedly until adult. In the homozygous Brattleboro rat kidney, the expression of all these isoforms was decreased.