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In the present study, intraperitoneal injection of lipopolysaccharide (10 mg/kg) to anaesthetized rats produced a gradual fall in mean arterial pressure in 6 h. Aortic rings from lipopolysaccharide-treated rats showed a significant reduction in the contractile response to vasoconstrictors. Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine, two nitric oxide synthase (NOS) inhibitors, abolished this vascular hyporeactivity. In ventricular myocytes isolated from lipopolysaccharide-treated rats, both electrically induced Ca(2+) transients and the intracellular Ca(2+) response to beta-adrenergic stimulation were significantly depressed when compared with those recorded from myocytes from sham control rats. L-NAME and aminoguanidine alone had no effects on electrically stimulated Ca(2+) transients in ventricular myocytes either from control or lipopolysaccharide-treated rats. However, these two NOS inhibitors augmented the intracellular Ca(2+) response to beta-adrenergic stimulation in myocytes from lipopolysaccharide-treated rats, but not in control myocytes. In addition, 1H-[1,2,4]oxadiazolo[4, 3-a]quinoxalin-1-one (ODQ), an inhibitor of nitric oxide (NO)-sensitive guanylyl cyclase, also reversed the intracellular Ca(2+) hyporesponsiveness to beta-adrenergic stimulation in myocytes from lipopolysaccharide-treated rats. In cardiac myocytes from lipopolysaccharide-rats pretreated with aminoguanidine, the intracellular Ca(2+) hyporesponsiveness to beta-adrenergic stimulation was abolished. However, there still existed a depressed Ca(2+) response to electrical field stimulation. These data indicate that NO following lipopolysaccharide stimulation contributes to vascular hyporeactivity and the depressed intracellular Ca(2+) response to beta-adrenergic stimulation in lipopolysaccharide-treated rats, but is not responsible for the reduced Ca(2+) response to electrical stimulation in our experimental conditions. more...

Objective: To illustrate the automatic modulation of refractoriness of His-Purkinje system during atrioventricular nodal reentrant tachycardia (AVNRT) and to discuss the possible mechanisms., Methods: Programmed electrical stimulations were performed in high right atrium (HRA) in 8 patients with AVNRT before ablation to induce tachycardia and electrocardiagraphic recordings were done synchronically when AVNRT appeared., Results: All the patients had 2:1 atrioventricular (A-V) conduction when AVNRT began, 2 of whom were blocked below His bundle, 5 above His bundle and 1 unclear. After a duration of 14.03 +/- 10.03 s of 2:1 A-V conduction, 1:1 A-V conduction with bundle banch block appeared, 3 of which were right bundle branch block (RBBB), 3 left bundle branch block (LBBB), and 2 with both. Bundle branch block disappeared after a duration of 6.87 +/- 11.26 s., Conclusion: Effective refractory period (ERP) of His-Purkinje system at the beginning of AVNRT was modulated automatically within less than 30-60 s and thus facilitated nodal-ventricular conduction. The mechanism of this is electrical remodeling. more...

Objective: To obtain the genetic information on Necator americanus and to search for the purpose genes., Methods: mRNA was isolated from the third stage larvae of Necator americanus maintained in hamsters. Double strand cDNA was synthesized and ligated to lambda ZAPII vector to construct the cDNA library. Expressed sequence tages (ESTs) were obtained by single pass sequencing of randomly isolated cDNA clones from the established library., Results: A cDNA library of N. americanus was successfully constructed with high recombinant efficiency. The titer of unamplified library was 1 x 10(7). The insert size was about 750-3,000 bp. Of 11 ESTs obtained from the library, 7 have a significant homology with certain functional genes., Conclusion: A high quality and high representative cDNA library of N. americanus was constructed at the first time and some functional genes were identified from the library by ESTs. more...

Background: The activation of transcription factor nuclear factor-kappa B (NF-kappa B) by extracellular stimuli has been shown to protect cells from apoptotic cell death. Inhibition of NF-kappa B activity should result in increased tumor cell killing in response to apoptotic stimuli. This study evaluated the effect of inhibition of NF-kappa B on a series of sarcoma and normal cell lines., Methods: Human sarcoma cell lines (HT1080, SKLMS-1, and MFH) and normal cell lines (NLF and BSMC) were infected with an adenoviral dominant-negative mutant Ad5I kappa B alpha M in vitro. Control cells were infected with the empty adenoviral vector and mock-infected with media alone. Viable cell counts were determined by microscopic evaluation on days 1 to 6 after infection. Cell proliferation was determined at 48 hours by MTT (1-[4,5-dimethylthiazol-2-yl]-3,5-dephenylformazan) assay., Results: All cell lines showed evidence of successful adenoviral infection as evidenced by the infection of all cell lines with the adenoviral marker gene Ad5 LacZ. All the tumor cells were found to have a significant decrease in cell viability and proliferation after treatment with the Ad5I kappa B alpha M gene compared with both mock-infected cells and cells infected with empty vector (P < .0001). The normal cell lines, although able to be successfully infected, did not show a significant decrease in cell viability or proliferation with adenoviral-mediated I kappa B alpha M infection., Conclusions: Inhibition of NF-kappa B through adenoviral-mediated infection of the dominant-negative inhibitor I kappa B alpha M resulted in a significant decrease in tumor cell viability and proliferation while having no deleterious effect on normal cell lines. The Ad5I kappa B alpha M gene therefore could be potentially used as a clinical treatment for patients with soft-tissue sarcoma. more...

Objective: To investigate the relationship of heart function and lung function in RHD patients., Methods: We compared heart posterior-anterior film, lung function test results, PaO(2) and O(2) Sat of blood gas analysis before and after motion before operation, early postoperation, late postoperation, according to heart function and cardiothoracic ratio in 98 RHD patients., Results: With worsening of heart function and enlargement of cardiothoracic ratio, lung function worsened too. PaO(2) and O(2) Sat did not change apparently. The lung function of early postoperation did not improve significantly. The lung function improved gradually with better heart function and shortening of heart in later postoperation. But small air way obstruction and diffuse function and function residue volume changed slowly., Conclusions: Heart function affects the lung function directly. They were positively correlated. more...

In order to delve into the mechanism governing the treatment of apoplexy by acupuncture at yangming channel points as main points, we observed the changes in the endothelin (ET) level in plasma, TXB2 and 6-Keto-PGF1 alpha levels in urine in convalescent apoplexy patients during acupuncture treatment. The results showed that the ET level in plasma in convalescent apoplexy patients was significantly higher than that in healthy subjects (P < 0.05), and the ET level in plasma in patients was decreased after one course of acupuncture treatment. It was found that before treatment the TXB2 level in urine in apoplexy patients was significantly higher than in healthy subjects, and the 6-Keto-PGF1 alpha level in urine in the patients was significantly lower than that in healthy subjects, with an increased ratio of TXB2 to 6-Keto-PGF1 alpha. After acupuncture treatment, the TXB2 level in urine was lowered with a decrease in the ratio of TXB2 to 6-Keto-PGF1 alpha. All this indicated that one of the mechanisms governing acupuncture treatment of apoplexy acupuncture at yangming channel points as main points was that acupuncture could produce therapeutic effects by adjusting the imbalance of important vaso-active substances, ET, TXA2, and PGI2. more...

Aim: To identify the genetic diversity between Ancylostoma duodenale and Necator americanus., Methods: Mitochondrial cytochrome C oxidase subunit 1 (CO1) gene was amplified from genomic DNA of human hookworms collected from infected patients in Hejiang County, Sichuan Province, and the purified PCR products were directly sequenced by using Licor auto-sequencer., Results: The PCR products were about 700 bp. Alignment of CO1 gene fragment sequences showed 89.7% similarity between Ancylostoma duodenale and Necator americanus, but still certain nucleotide variations (10.3%) existed., Conclusion: CO1 gene sequence can be used as a marker to identify the two species of human hookworms. more...

RecA protein will bind to a gapped duplex DNA molecule and promote a DNA strand exchange with a second homologous linear duplex. A double-strand break in the second duplex is efficiently bypassed in the course of these reactions. We demonstrate that the bypass of double-strand breaks is not explained by a mechanism involving homologous interactions between two duplex DNA molecules, but instead requires the ATP-mediated generation of DNA torsional stress brought about by the action of RecA. The results suggest new pathways for the repair of double-strand breaks and underline the need for new paradigms to explain the alignment of homologous DNAs during genetic recombination. more...

ATP hydrolysis (by RecA protein) fundamentally alters the properties of RecA protein-mediated DNA strand exchange reactions. ATP hydrolysis renders DNA strand exchange unidirectional, greatly increases the lengths of hybrid DNA created, permits the bypass of heterologous DNA insertions in one or both DNA substrates, and is absolutely required for exchange reactions involving four DNA strands. There are at least two viable models to explain how ATP hydrolysis is coupled to DNA strand exchange so as to bring about these effects. The first couples ATP hydrolysis to a redistribution of RecA monomers within a RecA filament. The second couples ATP hydrolysis to a facilitated rotation of the DNA substrates. The RecA monomer redistribution model makes the prediction that heterology bypass should not occur if the single-stranded DNA substrate is linear. The facilitated DNA rotation model predicts that RecA protein should promote the separation of paired DNA strands within a RecA filament if one of them is contiguous with a length of DNA being rotated about the filament exterior. Here, a facile bypass of heterologous insertions with linear DNA substrates is demonstrated, providing evidence against a role for RecA monomer redistribution in heterology bypass. In addition, we demonstrate that following a four-strand DNA exchange reaction, a distal segment of DNA hundreds of base pairs in length can be unwound in a nonreciprocal phase of the reaction, consistent with the direct coupling of an ATP hydrolytic motor to the proposed DNA rotation. more...

The role of ATP hydrolysis in RecA protein-mediated DNA strand exchange reactions remains controversial. Competing models suggest that ATP hydrolysis is coupled either to a simple redistribution of RecA monomers within a filament to repair filament discontinuities, or more directly to rotation of the DNA substrates to drive branch movement unidirectionally. Here, we test key predictions of the RecA redistribution idea. When ATP is hydrolyzed, DNA strand exchange is accompanied by a RecA exchange reaction, between free and bound RecA protomers in the interior of RecA filaments, that meets a central prediction of the model. The RecA protomer exchange is not required for, and does not occur during, the "search for homology" in which the single-stranded DNA within a RecA-ssDNA nucleoprotein filament is homologously aligned with the duplex DNA. Instead, the RecA exchange is triggered by the completion of strand exchange (a strand switch to generate a hybrid DNA product) in any given segment of the filament. In effect, formation of hybrid DNA leads to a change in filament conformation to one with properties approximating those of RecA filaments bound to double-stranded DNA. Addition of the RecA K72R mutant protein to a reaction with the wild type protein leads to the formation of mixed filaments and a poisoning of the DNA strand exchange reaction. Under some conditions, a facile RecA protomer exchange is observed, and significant ATP is hydrolyzed, even though DNA strand exchange is entirely blocked by the mutant protein. A redistribution of RecA protomers coupled to ATP hydrolysis is not sufficient in itself to explain how ATP hydrolysis facilitates DNA strand exchange. A RecA protomer exchange may nevertheless play an important role in the DNA strand exchange process. more...

RecA protein filaments formed on circular (ssDNA) in the presence of ssDNA binding protein (SSB) are generally stable as long as ATP is regenerated. On linear ssDNA, stable RecA filaments are believed to be formed by nucleation at random sites on the DNA followed by filament extension in the 5' to 3' direction. This view must now be enlarged as we demonstrate that RecA filaments formed on linear ssDNA are subject to a previously undetected end-dependent disassembly process. RecA protein slowly dissociates from one filament end and is replaced by SSB. The results are most consistent with disassembly from the filament end nearest the 5' end of the DNA. The bound SSB prevents re-formation of the RecA filaments, rendering the dissociation largely irreversible. The dissociation requires ATP hydrolysis. Disassembly is not observed when the pH is lowered to 6.3 or when dATP replaces ATP. Disassembly is not observed even with ATP when both the RecO and RecR proteins are present in the initial reaction mixture. When the RecO and RecR proteins are added after most of the RecA protein has already dissociated, RecA protein filaments re-form after a short lag. The newly formed filaments contain an amount of RecA protein and exhibit an ATP hydrolysis rate comparable to that observed when the RecO and RecR proteins are included in the initial reaction mixture. The RecO and RecR proteins thereby stabilize RecA filaments even at the 5' ends of ssDNA, a fact which should affect the recombination potential of 5' ends relative to 3' ends. The location and length of RecA filaments involved in recombinational DNA repair is dictated by both the assembly and disassembly processes, as well as by the presence or absence of a variety of other proteins that can modulate either process. more...

A model is presented describing the thermoelastic photoacoustic interaction in a layered medium within a transparent fluid, where a polymer transducer is used for the detection of ultrasonic pulses. By taking the optical absorption coefficient and finite layer thickness into account, the amplitude and shape of photoacoustic transients are calculated for both forward and backward travelling directions. Additionally, photoacoustic transient interaction with the PVDF transducer has been characterised using a discrete-time algorithm for the transducer response. Good agreement with experimental waveforms are demonstrated, so that this may form the basis of system characterisation when miniature laser-ultrasound probes are used in various applications. more...

We characterize aspects of the conformation and dynamic state of RecA filaments when bound to dsDNA that are specifically linked to the presence of the second of the two bound DNA strands. Filaments bound to dsDNA exhibit a facile exchange between free and bound RecA monomers or oligomers in the filament interior that is not seen on ssDNA. The RecA mutant K72R, which binds but does not hydrolyze ATP, forms mixed filaments with wild type RecA protein under some conditions. In the presence of dATP, mixed filaments are formed on dsDNA or ssDNA in which the RecA K72R content approximately reflects the proportion of the K72R mutant in the total RecA protein present when the filament is formed. In the presence of ATP, mixed filaments are formed on dsDNA, but the mutant protein strongly inhibits the binding of wtRecA protein to single-stranded DNA. When RecA K72R is added to pre-formed filaments containing only wild-type RecA protein on single-stranded DNA, little of the mutant protein exchanges into the filament. Exchange occurs readily, however, when the filament is bound to double-stranded DNA. The presence of a second DNA strand in RecA-dsDNA filaments produces as altered and more dynamic filament state relative to filaments formed on single-stranded DNA. The results point to a substantial alteration in filament state when synapsis occurs during RecA protein-mediated DNA strand exchange. more...

Replacement of lysine 72 in RecA protein with arginine produces a mutant protein that binds but does not hydrolyze ATP. The protein nevertheless promotes DNA strand exchange (Rehrauer, W. M., and Kowalczykowski, S. C. (1993) J. Biol. Chem. 268, 1292-1297). With RecA K72R protein, the formation of the hybrid DNA product of strand exchange is greatly affected by the concentration of Mg2+ in ways that reflect the concentration of a Mg.dATP complex. When Mg2+ is present at concentrations just sufficient to form the Mg.dATP complex, substantial generation of completed product hybrid DNAs over 7 kilobase pairs in length is observed (albeit slowly). Higher levels of Mg2+ are required for optimal uptake of substrate duplex DNA into the nucleoprotein filament, indicating that the formation of joint molecules is facilitated by Mg2+ levels that inhibit the subsequent migration of a DNA branch. We also show that the strand exchange reaction promoted by RecA K72R, regardless of the Mg2+ concentration, is bidirectional and incapable of bypassing structural barriers in the DNA or accommodating four DNA strands. The reaction exhibits the same limitations as that promoted by wild type RecA protein in the presence of adenosine 5'-O-(3-thio)triphosphate. The Mg2+ effects, the limitations of RecA-mediated DNA strand exchange in the absence of ATP hydrolysis, and unusual DNA structures observed by electron microscopy in some experiments, are interpreted in the context of a model in which a fast phase of DNA strand exchange produces a discontinuous three-stranded DNA pairing intermediate, followed by a slow phase in which the discontinuities are resolved. The mutant protein also facilitates the autocatalytic cleavage of the LexA repressor, but at a reduced rate. more...

A long life election spin resonance (ESR) signal at g = 2.0006 was observed in the normal lens epithelium and cortical fibers. During ultraviolet (UV) exposure, a new ESR signal at g = 2.0060 was found in the lens epithelium. But this specific signal was not detected in the lens cortical fibers. This suggested that lens epithelial cells were more susceptible to the free radical formation which was induced by UV light. By means of ESR spin probe oximetry, the oxygen uptake of lens epithelial cells was measured. The more the oxygen uptake, the higher the K value was. The K value of the oxygen consumption of epithelial cell linearly correlated with time of consumption (20-60 min) and increased as a function of UV exposure time (1-5 min). The oxygen consumption rate of lens epithelial cell was approximately 1.38 x 10(6) and increased to 7.1 x 10(6) O2 molecules per cell per sec. The oxygen consumption rate increased more than 5 times. These results indicates that UV light can accelerate the respiratory function of lens epithelial cells. The necessity of excess oxygen of lens epithelial cells may play a role in the cataract formation induced by UV light. more...