Synthesis of oligonucleotides containing the alkali-labile pyrimidopurinone adduct, M(1)G

An improved method for the synthesis of oligodeoxyribonucleotides containing the endogenous adduct, pyrimido[1,2-a]purin-10(3H)-one (M(1)G), is reported. The key features of the methodology include improved synthesis of the deoxynucleoside of M(1)G by transribosylation with deoxycytidine catalyzed by nucleoside 2'-deoxyribosyltransferase and the use of commercially available 4-tert-butylphenoxyacetyl protecting groups for normal nucleotides. Facile deprotection and removal of the M(1)G-containing oligomers from the solid support were achieved by treatment with a solution of potassium carbonate in methanol. NMR studies were performed to determine the stability of the oligonucleotides at different pHs.

HLA-DRB1 gene polymorphism in patients with dilated cardiomyopathy

To probe into the genetic background and immunopathogenesis of dilated cardiomyopathy (DCM), HLA-DRB1 gene polymorphism in 68 patients with DCM and 175 normal control subjects were analyzed by using the polymerase chain reaction/sequence specific primer (PCR/SSP) techniques. It was found that the frequencies of HLA-DRB1* 15 and HLA-DRB1* 03 alleles were significantly lower in DCM patients than those in normal controls (14.71% vs 29.71% and 4.41% vs 15.43%, respectively), the relative risks (RR) in the DCM patients being 0.41 and 0.25, respectively, all P < 0.05. However, the frequencies of HLA-DRB1* 11 and HLA-DRB1* 12 alleles were significantly higher in the DCM patients than in controls (29.4% vs 12.00% and 36.76% vs 12.57%, respectively) with the RR in the DCM patients being 3.06 and 4.04, respectively, all P < 0.01. These findings further demonstrated that immunogenetics might play a predominant pathogenetic role in partial DCM patients.

Effects of chlorophyll availability on phycobilisomes in Synechocystis sp. PCC 6803

Inactivation of the chlL gene in Synechocystis sp. PCC 6803 resulted in negligible chlorophyll content when the mutant was grown in darkness. Upon phycocyanin excitation at 580 nm, the 77K fluorescence spectrum of dark-grown cells showed three peaks at 648 nm, 665 nm, and 685 nm, this last being the largest. This reflects the functional presence of major components of phycobilisomes, including phycocyanin, allophycocyanin, and the terminal emitter, and efficient energy transfer between these components. As expected, no fluorescence emission peaks corresponding to chlorophyll in the photosystems were observed. Intact phycobilisomes could be isolated from the dark-grown chlL-deletion mutant. However, the phycobilisomes had a lower efficiency of energy transfer than did those isolated from the light-grown mutant, probably because of a decreased phycobilisome stability in the absence of chlorophyll. Exposing the dark-grown chlL-deletion mutant to light triggered the biosynthesis of chlorophyll. For the first 6 h in the light, upon phycocyanin excitation at 580 nm, the 77K fluorescence emission spectrum of greening cells was identical to that of dark-grown cells that lacked significant amounts of chlorophyll. With increased chlorophyll synthesis, gradual energy transfer from phycobilisomes to the two photosystems can be demonstrated.

A novel loop-loop recognition motif in the yeast ribosomal protein L30 autoregulatory RNA complex

The yeast Saccharomyces cerevisiae ribosomal protein L30 negatively autoregulates its production by binding to a helix-loop-helix structure formed in its pre-mRNA and its mRNA. A three-dimensional solution structure of the L30 protein in complex with its regulatory RNA has been solved using NMR spectroscopy. In the complex, the helix-loop-helix RNA adopts a sharply bent conformation at the internal loop region. Unusual RNA features include a purine stack, a reverse Hoogsteen base pair (G11anti-G56syn) and highly distorted backbones. The L30 protein is folded in a three-layer alpha/beta/alpha sandwich topology, and three loops at one end of the sandwich make base-specific contacts with the RNA internal loop. The protein-RNA binding interface is divided into two clusters, including hydrophobic and aromatic stacking interactions centering around G56, and base-specific hydrogen-bonding contacts to A57, G58 and G10-U60 wobble base pair. Both the protein and the RNA exhibit a partially induced fit for binding, where loops in the protein and the internal loop in the RNA become more ordered upon complex formation. The specific interactions formed between loops on L30 and the internal loop on the mRNA constitute a novel loop-loop recognition motif where an intimate RNA-protein interface is formed between regions on both molecules that lack regular secondary structure.

Thermal conformational changes of bovine fibrinogen by differential scanning calorimetry and circular dichroism

The thermal denaturation of bovine fibrinogen has been investigated using differential scanning calorimetry (DSC) and circular dichroism (CD) spectroscopy. Differential scanning calorimetry measurements were carried out while changing the scan-rate. The transition at 57 degrees C was found to be irreversible and highly scan-rate dependent, suggesting that the denaturation is, at least in part, under kinetic control. The secondary structural changes at various temperatures were monitored by far-ultraviolet CD spectroscopy. These results show that the DSC transition for the thermal denaturation of bovine fibrinogen can be interpreted in terms of a kinetic process, N --> F, where k is a first-order kinetic constant that changes with temperature according to the Arrhenius equation. An important transition peak was observed at 78.8 degrees C which is attributed to the C-terminal parts of the Aalpha chains of fibrinogen.

Assignment of the L30-mRNA complex using selective isotopic labeling and RNA mutants

The helix-loop-helix structure formed in the pre-mRNA and the mRNA of L30, a ribosomal protein from the yeast Saccharomyces cerevisiae, serves as an auto-regulatory binding site for the protein to suppress the L30 synthesis upon overproduction. Using a 33-nucleotide model RNA, the structures of the L30 binding site RNA in the presence and absence of the protein were investigated using nuclear magnetic resonance (NMR) spectroscopy. Homonuclear and(13)C/(15)N-based resonance assignments and spectral comparisons indicated that the purine-rich internal loop is dynamic in the free RNA but becomes ordered in the presence of L30 protein. Although the resonances in the loop region are sharper and more disperse in the bound RNA, their assignment was extremely challenging, due to spectral complexity and broadened resonances caused by local dynamics. Two strategies, namely selective(13)C/(15)N-labeling and NMR analyses of five complexes with RNA mutants, were used to overcome these difficulties. Only using these approaches could assignment of the internal loop resonances and identification of the unusual NOEs and nucleotide conformations within the internal loop be made. In the case of structural determination of the L30-mRNA complex, it was critical to be able to take advantage of the available biochemical information in order to complete the structure determination.

Solution structure of an oligodeoxynucleotide containing the malondialdehyde deoxyguanosine adduct N2-(3-oxo-1-propenyl)-dG (ring-opened M1G) positioned in a (CpG)3 frameshift hotspot of the Salmonella typhimurium hisD3052 gene

The refined solution structure for the ring-opened N2-(3-oxo-1-propenyl)-dG derivative of the malondialdehyde deoxyguanosine adduct M(1)G [3-(2'-deoxy-beta-D-erythro-pentofuranosyl)pyrimido[1, 2-a]purin-10(3H)-one] in d(ATCGCXCGGCATG) x d(CATGCCGCGCGAT) [X being N(2)-(3-oxo-1-propenyl)-dG], containing the d(CpG)(3) frameshift hotspot of the Salmonella typhimurium hisD3052 gene, is presented. When inserted into this duplex, M(1)G underwent spontaneous ring opening to N2-(3-oxo-1-propenyl)-dG. NMR analysis revealed that N2-(3-oxo-1-propenyl)-dG induced minor structural perturbations in the hisD3052 oligodeoxynucleotide. However, the stability of the duplex DNA was reduced; the N2-(3-oxo-1-propenyl)-dG-modified hisD3052 oligodeoxynucleotide exhibited a 14 degrees C decrease in T(m) relative to that of the native oligodeoxynucleotide. The modified guanine maintained stacking interactions with neighboring bases but was not Watson-Crick hydrogen bonded. A total of 13 NOEs were observed from the 3-oxo-1-propenyl moiety protons of N2-(3-oxo-1-propenyl)-dG to DNA protons. Molecular dynamics calculations, restrained by 602 distance restraints derived from experimental NOE measurements and 23 empirical distance restraints, converged with pairwise rmsd differences of <0.90 A. The sixth-root residual factor with the NMR data was 9.1 x 10(-2). The cytosine complementary to N2-(3-oxo-1-propenyl)-dG was pushed toward the major groove but maintained partial stacking interactions with its neighboring bases. The modified guanine remained in the anti conformation, while the 3-oxo-1-propenyl moiety was positioned in the minor groove of the duplex. Possible correlations between the relatively small structural perturbations induced in this DNA duplex by N2-(3-oxo-1-propenyl)-dG and the mutagenic spectrum of M(1)G are discussed.

A confrontational naming task produces congruent increases and decreases in PET and fMRI

This work uses the well-established (by PET) confrontation naming task to compare PET and fMRI in a cognitive activation experiment. The signal changes from this task are much less than the changes caused by visual or motor activation tasks used in previous comparisons. ANOVA methods adjusted for multiple comparisons were used to determine significant changes in signal between confrontation naming and figure size discrimination tasks. All 17 significantly increased regions (confrontation naming signal greater) seen on one modality were increased on both modalities. Ten of 13 regions that were significantly decreased on one modality were decreased on the other. Three mismatched regions showed a significant decrease on one modality and a nonsignificant increase on the other. This study could not detect a consistent difference in activation site location between PET and fMRI.

Segmented spin-echo pulses to increase fMRI signal: repeated intrinsic diffusional enhancement

Since its inception, functional magnetic resonance imaging (fMRI) has seen rapid progress in the application to neuroscience. Common gradient-recalled acquisition methods are susceptible to static field inhomogeneities, resulting in signal loss at the medial temporal area important for memory function or at the basal ganglia area for motor control. In addition, they are susceptible to the contaminating signals of large vein origin, such as the signals from its surrounding cerebrospinal fluid (CSF) leading to false-positive activation. Spin echoes overcome these drawbacks. However, they are less sensitive to blood oxygenation level dependent (BOLD) susceptibility changes because of their refocusing mechanism. A method is presented here to enhance the spin-echo fMRI signal by recruiting more spins to participate in the dynamic BOLD process. This method divided a conventional T(2) weighting period into several segments separated by blocks of extra free diffusion time. Before the extra diffusion time spins are restored to the longitudinal axis preventing rapid transverse relaxation. This process allows more spin access to the regions that experience the BOLD field gradient. Because of the increased spin population that is modulated by the capillary BOLD field gradient, the functional signal is increased. Spin-echo echo-planar imaging (EPI) with this enhancement may be a useful technique for fMRI studies at inhomogeneous areas such as the air/tissue interface. Magn Reson Med 42:631-635, 1999.

Local folding coupled to RNA binding in the yeast ribosomal protein L30

The ribosomal protein L30 from yeast Saccharomyces cerevisiae auto-regulates its own synthesis by binding to a structural element in both its pre-mRNA and its mRNA. The three-dimensional structures of L30 in the free (f L30) and the pre-mRNA bound (b L30) forms have been solved by nuclear magnetic resonance spectroscopy. Both protein structures contain four alternating alpha-helices and four beta-strands segments and adopt an overall topology that is an alphabetaalpha three-layer sandwich, representing a unique fold. Three loops on one end of the alphabetaalpha sandwich have been mapped as the RNA binding site on the basis of structural comparison, chemical shift perturbation and the inter-molecular nuclear Overhauser effects to the RNA. The structural and dynamic comparison of f L30 and b L30 reveals that local dynamics may play an important role in the RNA binding. The fourth helix in b L30 is longer than in f L30, and is stabilized by RNA binding. The exposed hydrophobic surface that is buried upon RNA binding may provide the energy necessary to drive secondary structure formation, and may account for the increased stability of b L30.

Continuous functional magnetic resonance imaging reveals dynamic nonlinearities of "dose-response" curves for finger opposition

Linear experimental designs have dominated the field of functional neuroimaging, but although successful at mapping regions of relative brain activation, the technique assumes that both cognition and brain activation are linear processes. To test these assumptions, we performed a continuous functional magnetic resonance imaging (MRI) experiment of finger opposition. Subjects performed a visually paced bimanual finger-tapping task. The frequency of finger tapping was continuously varied between 1 and 5 Hz, without any rest blocks. After continuous acquisition of fMRI images, the task-related brain regions were identified with independent components analysis (ICA). When the time courses of the task-related components were plotted against tapping frequency, nonlinear "dose- response" curves were obtained for most subjects. Nonlinearities appeared in both the static and dynamic sense, with hysteresis being prominent in several subjects. The ICA decomposition also demonstrated the spatial dynamics with different components active at different times. These results suggest that the brain response to tapping frequency does not scale linearly, and that it is history-dependent even after accounting for the hemodynamic response function. This implies that finger tapping, as measured with fMRI, is a nonstationary process. When analyzed with a conventional general linear model, a strong correlation to tapping frequency was identified, but the spatiotemporal dynamics were not apparent.

Duplex DNA catalyzes the chemical rearrangement of a malondialdehyde deoxyguanosine adduct

The primary DNA lesion induced by malondialdehyde, a byproduct of lipid peroxidation and prostaglandin synthesis, is 3-(2'-deoxy-beta-D-erythro-pentofuranosyl)-pyrimido[1, 2-a]purin-10(3H)-one (M1G). When placed opposite cytosine (underlined) at neutral pH in either the d(GGTMTCCG).d(CGGACACC) or d(ATCGCMCGGCATG). d(CATGCCGCGCGAT) duplexes, M1G spontaneously and quantitatively converts to the ring-opened derivative N2-(3-oxo-1-propenyl)-dG. Ring-opening is reversible on thermal denaturation. Ring-opening does not occur at neutral pH in single-stranded oligodeoxynucleotides or when T is placed opposite to M1G in a duplex. The presence of a complementary cytosine is not required to stabilize N2-(3-oxo-1-propenyl)-dG in duplex DNA at neutral pH. When N2-(3-oxo-1-propenyl)-dG is placed opposite to thymine in a duplex, it does not revert to M1G. A mechanism for the conversion of M1G to N2-(3-oxo-1-propenyl)-dG is proposed in which the exocyclic amino group of the complementary cytosine attacks the C8 position of the M1G exocyclic ring and facilitates ring opening via formation of a transient Schiff base. Addition of water to the Schiff base regenerates the catalytic cytosine and generates N2-(3-oxo-1-propenyl)-dG. These results document the ability of duplex DNA to catalyze the transformation of one adduct into another, which may have important consequences for mutagenesis and repair.

Intrastrain variants of herpes simplex virus type 1 isolated from a neonate with fatal disseminated infection differ in the ICP34.5 gene, glycoprotein processing, and neuroinvasiveness

Two intrastrain variants of herpes simplex virus type 1 (HSV-1) were isolated from a newborn with fatal disseminated infection. A small-plaque-producing variant (SP7) was the predominant virus (>99%) in the brain, and a large-plaque-producing variant (LP5) was the predominant virus (>99%) in the lung and gastrointestinal tract. EcoRI and BamHI restriction fragment patterns indicated that SP7 and LP5 are related strains. The large-plaque variants produced plaques similar in size to those produced by HSV-1 KOS. Unlike LP5 or KOS, SP7 was highly cell associated and processing of glycoprotein C and glycoprotein D was limited to precursor forms in infected Vero cells. The large-plaque phenotype from KOS could be transferred into SP7 by cotransfection of plasmids containing the EK or JK EcoRI fragment or a 3-kb plasmid with the UL34.5 gene of HSV-1 KOS together with SP7 DNA. PCR analysis using primers from within the ICP34.5 gene indicated differences for SP7, LP5, and KOS. Sequencing data indicated two sets of deletions in the UL34.5 gene that distinguish SP7 from LP5. Both SP7 and LP5 variants were neurovirulent (lethal following intracranial inoculation of young BALB/c mice); however, the LP5 variant was much less able to cause lethal neuroinvasive disease (footpad inoculation) whereas KOS caused no disease. Passage of SP7 selected for viruses (SLP-5 and SLP-10) which were attenuated for lethal neuroinvasive disease, were not cell-associated, and differed in the UL34.5 gene. UL34.5 from SLP-5 or SLP-10 resembled that of KOS. These findings support a role for UL34.5 in promoting virus egress and for neuroinvasive disease.

Intercalation of the (-)-(1R,2S,3R, 4S)-N6-[1-benz[a]anthracenyl]-2'-deoxyadenosyl adduct in an oligodeoxynucleotide containing the human N-ras codon 61 sequence

The solution structure of the (-)-(1R,2S,3R,4S)-N6-[1-(1,2,3, 4-tetrahydroxy-benz[a]anthracenyl)]-2'-deoxyadenosyl adduct at X6 of 5'-d(CGGACXAGAAG)-3'.5'-d(CTTCTTGTCCG)-3', incorporating codons 60, 61(italic), and 62 of the human N-ras protooncogene, was determined. This adduct results from the trans opening of 1S,2R,3R,4S-1, 2-epoxy-1,2,3,4-tetrahydro-benz[a]anthracenyl-3,4-diol by the exocyclic N6 of adenine. Molecular dynamics simulations were restrained by 509 NOEs from 1H NMR. The precision of the refined structures was monitored by pairwise root-mean-square deviations which were <1.2 A; accuracy was measured by complete relaxation matrix calculations, which yielded a sixth root R factor of 9.1 x 10(-)2 at 250 ms. The refined structure was a right-handed duplex, in which the benz[a]anthracene moiety intercalated from the major groove between C5.G18 and R,S,R,SA6.T17. In this orientation, the saturated ring of BA was oriented in the major groove of the duplex, with the aromatic rings inserted into the duplex such that the terminal ring of BA threaded the duplex and faced toward the minor groove direction. The duplex suffered localized distortion at and immediately adjacent to the adduct site, evidenced by the increased rise of 8.8 A as compared to the value of 3.5 A normally observed for B-DNA between base pairs C5.G18 and R,S,R,SA6.T17. These two base pairs also buckled in opposite directions away from the intercalated BA moiety. The refined structure was similar to the (-)-(7S,8R,9S,10R)-N6-[10-(7,8,9, 10)-tetrahydrobenzo[a]pyrenyl)]-2'-deoxyadenosyl adduct of corresponding stereochemistry at X6 of the same oligodeoxynucleotide [Zegar, I. S., Kim, S. J., Johansen, T. N., Horton, P. J., Harris, C. M., Harris, T. M., and Stone, M. P. (1996) Biochemistry 35, 6212-6224]. Both adducts intercalated toward the 5'-direction from the site of adduction. The similarities in solution structures were reflected in similar biological responses, when repair-deficient AB2480 Escherichia coli were transformed with M13mp7L2 DNA site-specifically modified with these two adducts.

Immunization with a LEAPS heteroconjugate containing a CTL epitope and a peptide from beta-2-microglobulin elicits a protective and DTH response to herpes simplex virus type 1

A ligand epitope antigen presentation system (LEAPS) heteroconjugate vaccine containing a CTL epitope (H1) from the HSV-1 immediate early protein ICP27 (322-332) and a peptide sequence (J) from beta-2-microglobulin (35-50) elicited protection from intraperitoneal viral challenge and promoted DTH responses. The H1 peptide and other H1 containing heteroconjugates did not elicit protection or DTH responses. Antibody to the H1 peptide could not be detected by ELISA following vaccination with peptide, heteroconjugate or natural infection. The LEAPS heteroconjugate appears to prime a Thl-like response which is subsequently boosted by infection. These studies show that attachment of the J peptide can make a CTL epitope into a vaccine which is immunogenic and promotes a protective Th1 type of response.

[An experimental study of viscoelastic properties of articular-cartilage of patella]

OBJECTIVE

To study the viscoelastic properties of human articular cartilages of patella in 8 cadavers, which were obtained from patients ranged in age from nineteen to fifty-one years old and died of acute head injury.

METHODS

The creep and stress relaxation of articular cartilage of patella were abserved in the condition of articular cartilage loaded of 500 Pa, just as the physiological load of articular cartilage of patella in keeping human body standing position with the knee joint flexed 30 degrees, during the experiment. The deformation-time curve under certain load, the load-time curve under certain deformity and related data were obtained.

RESULTS

Creep and stress relaxation showed that obvious changes occured in the first 10-15 minutes during the whole process.

CONCLUSIONS

The data and curve will not only be helpful to understand the pathogenesis of chondromalacia, but also propose a feasible method to study it from biomechanical view, meanwhile provide reference data for designing the prosthesis of patella and material choosing.

[Influence of icariin on cell membrane of highly metastatic human lung tumor cell line]

In this study, flow cytometry (FCM) and fluorescent probe technique were used to explore the influence of icariin (ICA) on cell membrane of PG. The data suggested that ICA could inhance membrane fluidity of PG and increase the expression of membrane HLA-ABC antigen. This could be one of the anticancer mechanisms of ICA.

Profile of the ecdysteroid hormone and its receptor in the salivary gland of the adult female tick, Amblyomma hebraeum

We examined the hemolymph ecdysteroid titer (by radioimmunoassay) and profile of the ecdysteroid receptor (EcR/USP; by [3H]ponasterone A binding, gel mobility shift assay, Western blot) in the salivary gland of the ixodid tick, Amblyomma hebraeum Koch (Acari: Ixodidae) throughout the tick feeding period and first 6 days post-engorgement. Throughout the slow phase of feeding, the hemolymph ecdysteroid titer was approximately 18 pg/microliter. The titer peaked at approximately 52 pg/microliter during the rapid phase of feeding, falling back to approximately 22 pg/microliter on the day of engorgement. Ecdysteroid titer rose again to approximately 750 pg/microliter by day 6 post-engorgement. EcR was undetectable by any of the three assays in unfed ticks. Following the onset of feeding, there appeared both specific ponasterone A binding and two major EcR bands detected by Western blot analysis. Both measurements were sustained throughout the feeding period, but declined after detachment when the salivary glands were degenerating. After ticks reached about 100 mg (by which time most females are mated), a discrete DNA-binding band was shown by gel mobility shift assay using Drosophila hsp27 EcRE as a probe. Moreover, the band intensified when hemolymph ecdysteroid titer reached its peak during the rapid phase of feeding; it declined along with decreasing EcR/USP levels, and with specific ligand binding activity following engorgement. This study suggests a role for the small hemolymph ecdysteroid peak during the rapid phase of feeding in initiating salivary gland degeneration.

DNA binding properties of the ecdysteroid receptor in the salivary gland of the female ixodid tick, Amblyomma hebraeum

Salivary gland degeneration in the female tick, Amblyomma hebraeum Koch (Acari: Ixodidae) is controlled by an ecdysteroid hormone. In an earlier study (Mao, H., McBlain, W.A., Kaufman, W.R., 1995. Some properties of the ecdysteroid receptor in the salivary gland of the ixodid tick, Amblyomma hebraeum. Gen. Comp. Endocrinol. 99, 340-348), we demonstrated that a protein component of a salivary gland extract binds to ponasterone A (Pon A) with high affinity (Kd-1 nM), suggesting a tick ecdysteroid receptor (EcR). In this study, the Pon A binding protein bound to calf thymus DNA; this binding could be dissociated by Drosophila hsp27 EcRE. The binding protein shifted the [32P]hsp27 EcRE band on a gel mobility shift assay; formation of the complex with hsp27 EcRE required KCl (optimal concentration was approximately 75 mM). A number of physiologically effective ecdysteroids enhanced the binding with the following order of potency: Pon A > Mur A > Mak A > 20E > ecdysone, whereas vertebrate steroids (estradiol, cholesterol, corticosterone, progesterone, testosterone) had no such effect. Using monoclonal antibodies against Drosophila EcR and USP, we found that AG 10.2 recognized three bands (90.5, 87.3 and 84 kDa for EcR) and AB11 recognized at least two major bands (50.3 and 47.1 kDa for USP) in the salivary gland extract by western blot analysis. In addition, AB11 supershifted the tick EcR-hsp27 EcRE band on a gel mobility shift assay, indicating that the tick EcR heterodimerized with a USP-like protein for DNA binding. Furthermore, selective mutations to the 15-basepair palindrome of hsp27 EcRE at positions-5, + 2, or adding a base to the spacer, resulted in considerably reduced affinity to the tick EcR/USP. We thus propose a sequence similarity of EcREs between A. hebraeum and its insect counterpart.

In situ observations of a high-pressure phase of H2O Ice

A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10 degrees and 50 degreesC. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.

[The expression study of human stem cell factor (hSCF) in E. coli]

OBJECTIVE

To improve the expression level of recombinant human stem cell factor (rhSCF).

METHODS

With PCR techniques and synthesized oligonucleotide as primers, the number of nucleotides between the SD sequence and the starting codon ATG of human stem cell factor cDNA was altered, and the preferable codons of E. coli in the N-terminal amino acid sequence were selected.

RESULTS

SDS-PAGE electrophoresis indicated that the ratio of expressed rhSCF to total E. coli proteins increased from 12% to 40% by thermal inducing. With DNA sequencing, the reading frame of the gene was proved to be correct. The sequence of 17 N-terminal amino acids of purified recombinant hSCF has been proved to be identical to the natural hSCF, except the first amino acid-Met.

CONCLUSIONS

These studies suggest that the 5'-flanking region of hSCF cDNA plays an important role in its gene expression.

Fluorescence and laser photon counting: measurements of epithelial [Ca2+]i or [Na+]i with ciliary beat frequency

We describe a system we developed that enabled simultaneous measurements of either epithelial calcium ion concentration ([Ca2+]i) or sodium ion concentration ([Na+]i) with the ciliary beat frequency (CBF) in native ciliated epithelia using either Fura-2 (AM) or SBFI (AM) ratiometric fluorescence photon counting along with nonstationary laser light scattering. Studies were performed using native epithelial tissues obtained from ovine tracheae. The dynamic range of the laser light-scattering system was determined by a simulated light "beating" experiment. The nonstationary CBF was demonstrated by the time-frequency analysis of the raw photon count sequences of backscattered heterodyne photons from cultured and native epithelia. Calibrations of calcium and sodium ion concentrations were performed using the respective Fura-2 and SBFI impermanent salts as well as in native epithelia. The cumulative responses of 10(-6), 10(-5), and 10(-4) M nifedipine on [Ca2+]i together with the CBF as well as the cumulative responses of 10(-5), 10(-4), and 10(-3) M amiloride on [Na+]i together with the CBF were also determined. Nifedipine decreased [Ca2+]i but had no effect on CBF. Amiloride decreased [Na+]i and CBF. Stimulation of CBF corresponded with either an increase of [Na+]i or an increase of [Ca2+]i. Decreases of [Na+]i or substantial decreases of [Ca2+]i were associated with decreases in the CBF. These data demonstrate the utility of this system for investigating the regulatory mechanisms of intracellular ions dynamics and the CBF in native epithelia.

[Detection of PSA mRNA from the peripheral blood and pelvic lymph nodes in patients with prostatic cancer by means of reverse transcription-polymerase chain reaction (RT-PCR)]

BACKGROUND AND METHODS

To detect prostate cancer cells in the blood circulation and in the lymph nodes by RT-PCR methods, we examined two kinds of prostate specific antigens (PSA) primers and one prostate specific membrane antigen (PSM). PSa primer 1 was established by us, PSA primer 2 by Moreno et al and PSM primer by Israeli et al.

RESULTS

Both PSA primers were specific for expression of PSA mRNA because in 12 kinds of urogenital culture cells only LNCaP cells, which produce PSA, expressed PSA mRNA by RT-PCR, PSA 1 was more sensitive than PSA 2 for detection of PSA mRNA in the circulating cells since PSA mRNA was detected in the blood circulating cells in 5 cases of stage D2 prostate cancer using PSA primer 1 but in only one was using PSA primer 2. PSM mRNA was detected in all 12 types of urogenital cancer cells and in the blood circulating cells not of prostate cancer patients but also of renal, bladder, testicular cancer patients and normal volunteers. PSA 1 was used to detect PSA mRNA from the samples of fine needle aspiration biopsy (FNAB) of pelvic lymph node, and PSA mRNA was positive in 10 FNAB samples including not only all 6 cytologically positive and two cytologically class III cases but also 2 of 8 cytologically negative cases. RT-PCR for FNAB samples of all 15 cases of bladder cancer were negative for the detection of PSA mRNA.

CONCLUSION

Detection of PSA mRNA by RT-PCR in FNAB samples may be useful to diagnose pelvic lymph node metastasis and to furnish additional information for the cytological diagnosis of prostate cancer.

[Development and clinical significance of SEA-1 emergency micro-ventilator]

To improve the work of emergency care and early cardio-pulmonary-brin resuscitation in our county, which is characteristic of abruptness and contingency, a new type of ventilator is highly required. It is hoped that such a ventilafor has a simple safe valve and does not need electric current from the mains. Also, the ventilator should be small in size, light in weight, simple in operation, easy to carry, swift to assembly, and reliable in ventilation. With the principle of pneumatic logic elements and the design of the integration of pneumatic circuits, we have successfully developed the Emergency Micro-ventilator, which accords with the above requirements. It has been confirmed that the ventilator is very effectual and reliable in ventilation support for the patients(n = 55) under general anesthesia without any case of hypoxemia, hypercapnia, hypotension, arrhythmia and so on, and the mechanical performances are stable.

An intercalated and thermally stable FAPY adduct of aflatoxin B1 in a DNA duplex: structural refinement from 1H NMR

The structure of a formamidopyrimidine (FAPY) adduct arising from imidazole ring opening of the initially formed trans-8, 9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B1 adduct under basic conditions and positioned in the 5'-d(CTATFAPYGATTCA)-3'*5'-d(TGAATCATAG)-3' oligodeoxynucleotide was determined. The FAPY adduct may be a major progenitor of aflatoxin B1-induced mutations in DNA. The freshly prepared sample showed biphasic melting, with transitions at 28 and 56 degreesC. NMR initially showed multiple subspectra. Over a period of several days at 4 degreesC, the sample converted to a single species with a Tm of 56 degreesC, 15 degrees C greater than the unmodified duplex. The deoxyribose was in the beta configuration about the anomeric carbon, evidenced by NOEs between FAPYG5 H3', H2', H2", and H1'. FAPY formation resulted in the loss of the guanine H8 proton, and the introduction of the formyl proton, which showed NOEs to FAPYG5 H1' and A6 N6Ha. A total of 31 NOEs from AFB1 to DNA protons were observed, mostly to the 5'-neighboring base, T4 in the modified strand. Sequential NOEs were interrupted between T4 and FAPYG5 in the modified strand, between C16 and A17 in the complementary strand, and between T4 N3H and FAPYG5 N1H. An NOE between FAPYG5 N1H and C16 N4H showed intact hydrogen bonding at FAPYG5*C16. Upfield chemical shifts were observed for T4 H6 and A17 H8. Molecular dynamics calculations converged with pairwise rmsd differences of <0.9 A. The sixth root residual was 8.7 x 10(-2). The AFB1 moiety intercalated from the major groove between FAPYG5 and T4*A17, and stacked with T4 and FAPYG5 and partially stacked with A17. The base step between T4*A17 and FAPYG5*C16 was increased from 3.4 to 7 A. The duplex unwound by about 15 degrees. The FAPY formyl group was positioned to form a hydrogen bond with A6 N6Ha. Strong stacking involving the AFB1 moiety, and this hydrogen bond explains the thermal stabilization of four base pairs by this adduct, and may be a significant factor in its processing.

[Detection of urogenital malignant cells in the peripheral blood by nested RT-PCR using keratin 19 mRNA]

INTRODUCTION AND OBJECTIVES

It is reported that cytokeratin 19 (CK-19) mRNA is not expressed in the peripheral blood cells of the healthy subjects (Am. J. Pathol. 142: 1111. 1993). Detection of DNA fragments of CK-19 in the peripheral blood suggests the existence of epithelial malignant tumor cells. In this study, we detected CK-19 genes in peripheral blood of patients with urogenital malignancy, and thus clarified the possibility of understanding tumor expansion.

METHODS

Mononuclear cells were separated from the peripheral blood of 39 patients with urogenital tumor and 9 controls. Total cellular RNA was extracted according to the method described elsewhere. The CK-19 gene expression was investigated using nested reverse transcription polymerase chain reaction (nested RT-PCR) and confirmed by Southern Blotting. These results were compared to the clinical stages.

RESULTS

CK-19 mRNA was not detected in any of 9 controls. CK-19 mRNA was detected in 3 out of the 10 bladder cancer cases. Two had metastases and 1 had muscle invasion without metastasis. One of 6 urothelial cancer case of the upper urinary tract showed positive amplification, and had liver, bone and lymphnode metastases. After one course of chemotherapy, mRNA became negative. In prostate cancer cases, three among 7 were positive and all 3 cases had distant metastases. In renal, testicular and penile cancer cases, the positive ratio were 3/6, 1/8 and 2/2, respectively. All positive cases of renal and testicular cancer had distant metastases, but one case of penile cancer had no metastasis.

CONCLUSION

The detection of CK-19 mRNA in the circulating blood by nested RT-PCR makes it possible to detect micrometastasis, to evaluate therapeutic effects and to predict the prognosis.

Multivariable dependence of Fe-Mg partitioning in the lower mantle

High-pressure diamond-cell experiments indicate that the iron-magnesium partitioning between (Fe,Mg)SiO3-perovskite and magnesiowustite in Earth's lower mantle depends on the pressure, temperature, bulk iron/magnesium ratio, and ferric iron content. The perovskite stability field expands with increasing pressure and temperature. The ferric iron component preferentially dissolves in perovskite and raises the apparent total iron content but had little effect on the partitioning of the ferrous iron. The ferrous iron depletes in perovskite at the top of the lower mantle and gradually increases at greater depth. These changes in iron-magnesium composition should affect geochemical and geophysical properties of the deep interior.

Internal iliac arterial infusion chemotherapy for rabbit invasive bladder cancer

BACKGROUND

Internal iliac arterial infusion (IA) chemotherapy has been used clinically for locally invasive bladder cancer, but there have been no experimental studies to actually demonstrate whether IA is more effective than intravenous infusion (i.v.) chemotherapy in this setting.

METHODS

We compared the effects of IA and i.v. using a rabbit invasive bladder cancer model. A 0.2 mL suspension containing 2 x 10(6) VX2 cancer cells was inoculated into the posterior submucosa of the bladder. Two weeks later the rabbits were divided into 3 treatment groups of 8 rabbits each: controls, a group treated with IA consisting of 10 mg/kg carboplatin and 1 mg/kg pirarubicin once a week for 3 weeks (days 14, 21, and 28), and the third treated with the same regimen intravenously.

RESULTS

All bladder tumors of the rabbits in the IA group decreased in size, and 3 of the tumors totally disappeared (37.5%). There was also no evidence of lung metastasis. All tumors in the rabbits in the i.v. treatment group increased in size (tumor volume of IA vs. i.v., P = 0.008) and 2 rabbits had lung metastases. All tumors of the control group increased in size and all rabbits had lung metastases. The concentrations of platinum and pirarubicin in the bladder tumors were significantly higher in the IA treatment group than those in the i.v. treatment group at time points from 5 to 10 minutes (P < 0.05) after drug infusion.

CONCLUSION

The antitumor effect of IA may be due to higher drug concentrations in the early stage after drug delivery, and the initial circulation of high concentrations of drugs may be the most important factor in suppressing tumor growth.

[Inhibition of 5 compounds from Bidens bipinnata on leukemia cells in vitro]

In vitro, inhibition of 5 compounds from Bidens bipinnata on two leukemia cells HL-60 and V397 is presented by determination of MTT living cell in this paper. The result show that the compounds have the action of inhibition, IC50 on V937 < or = 60 micrograms/ml.

Improved large scale culture of Methylophilus methylotrophus for 13C/15N labeling and random fractional deuteration of ribonucleotides

Isotopic labeling of RNA with 13C and 15N has become a routine procedure in structural studies by NMR spectroscopy. The methodology in this paper describes the random fractional deuteration of RNA using the obligate methylotropic bacterium, Methylophilus methylotrophus. This bacterium was grown using a non-deuterated carbon source in 52:48 D20/H20 and we have shown that all protons in the ribonucleotides except for the ribose H1 become 52% randomly fractionally deuterated. Improved growth conditions for this organism are also described that yield higher cell densities in liquid culture, which is applicable for all labeling procedures.

Alpha helix-RNA major groove recognition in an HIV-1 rev peptide-RRE RNA complex

The solution structure of a human immunodeficiency virus type-1 (HIV-1) Rev peptide bound to stem-loop IIB of the Rev response element (RRE) RNA was solved by nuclear magnetic resonance spectroscopy. The Rev peptide has an alpha-helical conformation and binds in the major groove of the RNA near a purine-rich internal loop. Several arginine side chains make base-specific contacts, and an asparagine residue contacts a G.A base pair. The phosphate backbone adjacent to a G.G base pair adopts an unusual structure that allows the peptide to access a widened major groove. The structure formed by the two purine-purine base pairs of the RRE creates a distinctive binding pocket that the peptide can use for specific recognition.

Impact on Salivary Gland Degeneration by Putative Ecdysteroid Antagonists and Agonists in the Ixodid Tick Amblyomma hebraeum

Ecdysteroids cause salivary gland degeneration in female ixodid ticks. We tested the effects of the following compounds on salivary gland degeneration in the ixodid tick Amblyomma hebraeum Koch: HHCS (22S,23S-homocastasterone), SSBR (22S,23S-homobrassinolide), STGM (2alpha,3alpha(OH)2-Delta22-stigmasten-6-one), RH 5849, and RH 5992. The first three are brassinosteroids (putative ecdysone antagonists) and the last two are nonsteroidal mimics of ecdysone in a variety of insects. In vitro, HHCS (up to 4 &mu;g/ml, 8.4 &mu;M) did not attenuate degeneration caused by 20-hydroxyecdysone; on the contrary, it enhanced the degree of salivary gland degeneration. SSBR (up to 4.5 &mu;g/ml, 9 &mu;M) likewise did not reduce 20-hydroxyecdysone mediated degeneration. RH 5849 up to 15 &mu;g/ml (51 &mu;M) and RH 5992 up to 10 &mu;g/ml (28 &mu;M) had no ecdysone-mimicking effect. In vivo, both RH compounds had an ecdysone-mimicking effect. RH 5849 (but not RH 5992) at 10 &mu;g/tick increased ovary wet weight slightly. None of the brassinosteroids displaced a significant amount of [3H]ponasterone A (PoA) from the ecdysone receptor at 6 &mu;g/ml (12-14 &mu;M) or below. RH 5849 (14 &mu;g/ml, 47 &mu;M) displaced 8% of (PoA) binding; at 68 &mu;g/ml (230 &mu;M) displacement was 30%. For RH 5992 inhibition of PoA binding was 16, 33, and 43% at 4.5, 16, and 79 &mu;g/ml (13, 45, and 79 &mu;M), respectively. Overall, the brassinosteroids and the RH compounds do not act on the tick salivary gland ecdysteroid system in a way similar to the way they act on some insect systems.

[Determination of urea in milk by enzyme coupled electrode method]

An Enzyme coupled electrode method for the determination of urea content in milk was studied systematically. The linear range of the method, the detection limit, recovery and relative standard deviation are 2.1-2.1 x 10(3) micrograms/ml, 2 micrograms/ml, 95.3%-101.0% and 1.5%-3.9%, respectively. The reliability of the method was confirmed by comparison with colorimetry (0.2 < P < 0.05). Using this method, we determined the content of urea in seven milk samples from Chengdu. The values range from 152.2-288.5 micrograms/ml and agree with those reported by other authors. This method is simple, rapid, accurate and inexpensive.

Depolarization of cell membrane is associated with an increase in ciliary beat frequency (CBF)

We hypothesize that activation of muscarinic cholinergic receptors depolarizes the cell membrane of the mammalian ciliated cells which in turn causes an increase of CBF. To test this hypothesis, a di-8-ANEPPS fluorescence photon counting and nonstationary heterodyne laser light scattering system was developed to measure cell membrane potential (psi) and CBF in cultured ovine tracheal ciliated cells simultaneously. Carbachol dose dependently depolarized the cell membrane with a corresponding stimulation of CBF. The carbachol induced depolarization of cell membrane and increases of CBF were inhibited by prior application of either atropine or verapamil or amiloride. These novel data suggest that depolarization of the cell membrane and the corresponding stimulation of CBF caused by the activation of muscarinic receptors of the mammalian ciliated cells are dependent on the influx of either extracellular Ca2+ or Na+.

Some properties of the ecdysteroid receptor in the salivary gland of the ixodid tick, Amblyomma hebraeum

Salivary gland degeneration in ixodid ticks is triggered by an ecdysteroid hormone. We used [3H]ponasterone A (PoA) as a specific ligand to detect the ecdysteroid receptor in the salivary glands of large, partially fed female ticks (Amblyomma hebraeum Koch; Acari: Ixodidae). Binding of [3H]PoA was thermolabile and sensitive to pronase, but not to DNase or RNase, indicating that the ligand binds to a protein. Scatchard analysis of [3H]PoA binding strongly suggested the presence of an ecdysteroid receptor in cytosolic and nuclear extracts of the tissue. The Kd and Bmax for PoA binding in cytosol were 0.72 +/- 0.09 nM and 175 +/- 12 fmol/mg protein, respectively (n = 8). Corresponding figures for nuclear extract were 1.1 +/- 0.5 nM and 282 +/- 35 fmol/mg protein, respectively (n = 3; P > 0.05 compared to cytosol). The relative ability of unlabeled ecdysteroids to compete for [3H]PoA binding was (in descending order): PoA > muristerone A > makisterone A > 20-hydroxyecdysone > mesylinokosterone > ecdysone. The Kd estimated for 20-hydroxyecdysone (probably the natural hormone) correlates very well with its physiological potency in inducing salivary gland degeneration in vivo and in organ culture. None of the vertebrate steroids tested (estradiol, testosterone, progesterone, and corticosterone) was able to displace PoA binding at a concentration 10(5) times higher than PoA. The cytosolic form of the receptor migrated to the 3.2 S region of a 10-40% sucrose density gradient.

Interaction of HIV Rev peptides with the Rev response element RNA

As a model system for understanding RNA-protein interactions, we are studying the structure of peptides derived from HIV Rev in complex with an RNA derived from the Rev Response Element (RRE) using NMR spectroscopy. Formation of the Rev peptide-RRE complex is accompanied by formation of two purine-purine base pairs in the RRE. These base pairs create an unusual geometry that widens the major groove of the RRE RNA. The Rev peptide is predominantly in an alpha-helical conformation in the complex. The specific recognition of the RRE by Rev involves widening of the major groove to accommodate the Rev alpha-helix.

Transient picosecond response of the photorefractive effect in InP:Fe

The time lag of the crossed-polarized part of the transmitted probe pulse, which is due to photorefractive energy transfer from the pump pulse, is measured with respect to the original transmitted probe pulse. The average photorefractive response time of the crystal is estimated through theoretical analysis.