Boundary of pRNA functional domains and minimum pRNA sequence requirement for specific connector binding and DNA packaging of phage phi29

Bacteriophage phi29 utilizes a viral-encoded 120-base RNA (pRNA) to accomplish dsDNA packaging into a preformed procapsid. Six pRNAs bind to the procapsid and work sequentially. The pRNA contains two functional domains, one for binding to the DNA translocating connector, and the other for interacting with another component of the DNA packaging machinery during DNA translocation. By UV crosslinking, the pRNA was found to bind to the connector specifically and not to the capsid or scaffolding proteins. When purified connectors were incubated with pRNA, rosette-like connector oligomers were observed. These oligomers were found to contain pRNA. A series of deletion mutants of the pRNA were constructed and their ability to perform various tasks involved in phi29 assembly were assayed. The minimum sizes of the pRNA needed for the following activities have been determined: (1) specific binding to procapsid or to connectors; (2) connector or procapsid binding with full efficiency compared with wild-type pRNA; and (3) genomic DNA packaging. In summary, bases 37-91 (55 nt) comprised the minimum sequence required for specific connector binding, although with lower efficiency; bases 6-113 (105 nt with the additional deletion of two nonessential bases, C109 and A106) comprised the minimum sequence required for full connector binding activity; and bases 1-117 comprised the minimum sequence needed for full DNA packaging activity. These data indicate clearly that the helical region composed of bases 1-6 and 113-117 plays a crucial role in DNA translocation, but is dispensable for connector binding. A model for the role of the pRNA in DNA packaging was also presented.

[Inhibition of hydrogen peroxide production on chondrocytes induced by fulvic acid by ginger volatile oil]

In order to investigate the effect of ginger on Kashin-Beck disease (KBD), the ginger volatile oil was taken as a scavenger and proved effective in inhibiting the production of hydrogen peroxide in chondrocytes induced by fulvic acid from KBD area.

Sequential action of six virus-encoded DNA-packaging RNAs during phage phi29 genomic DNA translocation

A 120-base pRNA encoded by bacteriophage b29 has a novel and essential role in genomic DNA packaging. Six DNA-packaging RNAs (pRNAs) were bound to the sixfold symmetrical portal vertex of procapsids during the DNA translocation process and left the procapsid after the DNA-packaging reaction was completed, suggesting that the pRNA participated in the translocation of genomic DNA into procapsids. To further investigate the mechanism of DNA packaging, it is crucial to determine whether these six pRNA molecules work as an integrated entity or each pRNA acts as a functional individual. If pRNAs work individually, then do they work in sequence with communication or in random order without interaction? Results from compensation and complementation analysis did not support the integrated model. Computation of the probability of combination between wild-type and mutant pRNAs and experimental data of competitive inhibition excluded the random model while favoring the proposal that the six pRNAs functioned sequentially. Sequential action of the pRNA also explains why the pRNA is so sensitive to mutation, since the effect of a pRNA mutation will be amplified by 6 orders of magnitude after six consecutive steps, resulting in the observed complete loss of DNA-packaging activity caused by small alterations. When any one of the six pRNAs was replaced with an inactive one, complete blockage of DNA packaging resulted, strongly supporting the speculation that individual pRNAs, presumably together with other components such as the packaging ATPase gp16, take turns mediating successive steps of packaging. Although the data provided here could not exclude the integrated model completely, there is no evidence so far to argue against the model of sequential action.

Use of circular permutation to assess six bulges and four loops of DNA-packaging pRNA of bacteriophage phi29

A 120-base phage phi29 encoded RNA (pRNA) has a novel role in DNA packaging. This pRNA possesses five single-base bulges, one three-base bulge, one bifurcation bulge, one bulge loop, and two stem loops. Circularly permuted pRNAs (cpRNA) were constructed to examine the function of these bulges and loops as well as their adjacent sequences. Each of the five single-base bulges was nonessential. The bifurcation bulge could be deleted and replaced with a new opening to provide flexibility for maintaining an overall correct folding in three-way junction. All of these nonessential bulges or their adjacent bases could be used as new termini for cpRNAs. The three-base (C18C19A20) bulge was dispensable for procapsid binding, but was indispensable for DNA packaging. The secondary structure around this CCA bulge and the phylogenetically conserved bases within or around it were investigated. Bases A14C15U16 were confirmed, by compensatory modification, to pair with U103G102A101. A99 was needed only to allow the proper folding of CCA bulge in the appropriate sequence order and distance constraints. Beyond these, the seemingly phylogenetic conservation of other bases has little role in pRNA activity. Each of the three stem loops was essential for procapsid binding, DNA packaging, and phage assembly. Disruption of the middle of any one of the loops resulted in dramatic reductions in procapsid binding, subsequent DNA packaging, and phage assembly activities. However, disruption of the loops at sequences that were close to double-stranded regions of the RNA did not interfere with pRNA activity significantly. Our results suggest that double-stranded helical regions near these loops were most likely not involved in interactions with components of the DNA-packaging machinery. Instead, these regions appear to be merely present to serve as a scaffolding to display the single-stranded loops that are important for pRNA tertiary structure or for interaction with the procapsid or other packaging components.

Approaches to determine stoichiometry of viral assembly components

Due to the rapidity of biological reactions, it is difficult to isolate intermediates or to determine the stoichiometry of participants in intermediate reactions. Instead of determining the absolute amount of each component, this study involved the use of relative parameters, such as dilution factors, percentages probabilities, and slopes of titration curves, that can be more accurately quantified to determine the stoichiometry of components involved in bacteriophage phi29 assembly. This work takes advantage of the sensitive in vitro phage phi29 assembly system, in which 10(8) infectious virions per ml without background can be assembled from eight purified components. It provides a convenient assay for quantification of the stoichiometry of packaging components, including the viral procapsid, genomic DNA, DNA-packaging pRNA, and other structural proteins and enzymes. The presence of a procapsid binding domain and another essential functional domain within the pRNA makes it an ideal component for constructing lethal mutants for competitive procapsid binding. Two methods were used for stoichiometry determination. Method 1 was to determine the combination probability of mutant and wild-type pRNAs bound to procapsids. The probability of procapsids that possess a certain amount of mutant and a certain amount of wild-type pRNA, both with an equal binding affinity, was predicted with the binomial equation [EQUATION IN TEXT] where Z is the total number of pRNAs per procapsid, M is the number of mutant pRNAs bound to one procapsid, and (ZM) is equal to [FORMULA IN TEXT]. With various ratios of mutant to wild-type pRNA in in vitro viral assembly, the percent mutant pRNA versus the yield of virions was plotted and compared to a series of predicted curves to find a best fit. It was determined that five or six copies of pRNA were required for one DNA-packaging event, while only one mutant pRNA per procapsid was sufficient to block packaging. Method 2 involved the comparison of slopes of curves of dilution factors versus the yield of virions. Components with known stoichiometries served as standard controls. The larger the stoichiometry of the component, the more dramatic the influence of the dilution factor on the reaction. A slope of 1 indicates that one copy of the component is involved in the assembly of one virion. A slope larger than 1 would indicate multiple-copy involvement. By this method, the stoichiometry of gp11 in phi29 particles was determined to be approximately 12. These approaches are useful for the determination of the stoichiometry of functional units involved in viral assembly, be they single molecules or oligomers. However, these approaches are not suitable for the determination of exact copy numbers of individual molecules involved if the functional unit is composed of multiple subunits prior to assembly.

Magnesium-induced conformational change of packaging RNA for procapsid recognition and binding during phage phi29 DNA encapsidation

Bacteriophage phi29 is typical of double-stranded DNA viruses in that its genome is packaged into a preformed procapsid during maturation. An intriguing feature of phi29 assembly is that a virus-encoded RNA (pRNA) is required for the packaging of its genomic DNA. Psoralen cross-linking, primer extension, and T1 RNase partial digestion revealed that pRNA had at least two conformations; one was able to bind procapsids, and the other was not. In the presence of Mg2+, one stretch of pRNA, consisting of bases 31 to 35, was confirmed to be proximal to base 69, as revealed by its efficient cross-linking by psoralen. Two cross-linking sites in the helical region were identified. Mg2+ induced a conformational change of pRNA that exposes the portal protein binding site by promoting the refolding of two strands of the procapsid binding region, resulting in the formation of pRNA-procapsid complexes. The procapsid binding region in this binding-competent conformation could not be cross-linked with psoralen. When the two strands of the procapsid binding region were fastened by cross-linking, pRNA could neither bind procapsids nor package phi29 DNA. A pRNA conformational change was also discernible by comparison of migration rates in native EDTA and Mg2+ polyacrylamide gel electrophoresis and was revealed by T1 RNase probing. The Mg2+ concentration required for the detection of a change in pRNA cross-linking patterns was 1 mM, which was the same as that required for pRNA-procapsid complex formation and DNA packaging and was also close to that in normal host cells.

Reduction in infarct size by ischemic preconditioning persists in a chronic rat model of myocardial ischemia-reperfusion injury

Ischemic preconditioning (PC) has been consistently observed to reduce infarct size in models of regional myocardial ischemia. However, it is also known to render the heart resistant to injury for only a finite period of time (< 2 h). Myocardial adenosine is widely believed to be one of the mediators of PC and may produce myoprotection in part through an anti-neutrophil effect during the early reperfusion period. When infarct size is assessed following a relatively short period of reperfusion (< 3 h) PC hearts may appear protected although reperfusion injury in the myocardium may be ongoing. Thus, infarct expansion may occur as the effects of PC fade. To substantiate that PC produces a sustained reduction in myocardial necrosis, 27 male Sprague-Dawley rats were anesthetized with pentobarbital and instrumented for regional coronary occlusion (30 min) and reperfusion (7 days). Animals were randomized to a control group (n = 16) or PC (n = 11), which consisted of 2 cycles of 5 min of ischemia and 5 min of reperfusion immediately prior to coronary occlusion. Successful reperfusion was confirmed visually and the occluding suture was left in the chest during recovery. Seven days later, staining for risk area was made by the injection of Evans blue dye while the occluder was in place and necrosis was detected with triphenyltetrazolium chloride staining. Planimetry was performed by a blinded investigator who found the risk area to be 27.2 +/- 1.6 and 33.6 +/- 1.7% of the left ventricle (p = NS) in PC and controls, respectively. All hemodynamic measurements were comparable between groups at all times during ischemia and reperfusion. PC reduced infarct size from 43.3 +/- 2.0% of area at risk to 20.6 +/- -2.1%, a 48% reduction (p < 0.01), and eliminated transmural necrosis which was common in the control group. From these studies we conclude that ischemic PC results in a permanent reduction in infarct size rather than a transient reduction in infarct size in the context of a gradually evolving infarction due to reperfusion injury.

Dietary soybean protein prevents bone loss in an ovariectomized rat model of osteoporosis

The purpose of this study was to examine whether soybean protein isolate prevents bone loss induced by ovarian hormone deficiency. Thirty-two 95-d-old Sprague-Dawley rats were randomly assigned to four treatment groups [sham-operated (sham); ovariectomized (ovx); ovx+soybean; ovx + 17 beta-estradiol (E2)] and killed after 30 d. Rats in the sham, ovx and ovx + 17 beta-estradiol groups were fed a casein-based diet, and the soybean group was fed soybean protein isolate instead of casein; the diets were otherwise comparable. Rats in the ovx group had significantly lower densities of the right femur (P < 0.001) and the fourth lumbar vertebra (P < 0.05) than rats in the sham group. These lower bone densities were not observed in animals receiving 17 beta-estradiol or fed soybean. The ovx group also had significantly (P < 0.01) greater serum concentrations of 1,25-dihydroxycholecalciferol than the other three groups. Our findings suggest that dietary soybean protein is effective in preventing bone loss due to ovarian hormone deficiency. Because serum activities of both alkaline phosphatase and tartrate-resistant acid phosphatase were significantly greater in the ovx group and in the ovx + soybean group but not in the group receiving 17 beta-estradiol, compared with sham animals, this confirms that ovariectomy enhances and 17 beta-estradiol suppresses the rate of bone turnover. Despite the higher rate of bone turnover in the soybean-fed animals, the vertebral and femoral bone densities of these rats were significantly greater than those of rats in the ovx group, suggesting that formation exceeded resorption. Further studies are needed to clarify whether this protective effect on bone is due to the protein itself or to the presence of isoflavones in soybean protein.

Complete inhibition of virion assembly in vivo with mutant procapsid RNA essential for phage phi 29 DNA packaging

A highly efficient method for the inhibition of bacteriophage phi 29 assembly was developed with the use of mutant forms of the viral procapsid (or packaging) RNA (pRNA) indispensable for phi 29 DNA packaging. Phage phi 29 assembly was severely reduced in vitro in the presence of mutant pRNA and completely blocked in vivo when the host cell expressed mutant pRNA. Addition of 45% mutant pRNA resulted in a reduction of infectious virion production by 4 orders of magnitude, indicating that factors involved in viral assembly can be targets for efficient and specific antiviral treatment. The mechanism leading to the high efficiency of inhibition was attributed to two pivotal features. First, the pRNA contains two separate, essential functional domains, one for procapsid binding and the other for a DNA-packaging role other than procapsid binding. Mutation of the DNA-packaging domain resulted in a pRNA with no DNA-packaging activity but intact procapsid binding competence. Second, multiple copies of the pRNA were involved in the packaging of one genome. This higher-order dependence of pRNA in viral replication concomitantly resulted in its higher-order inhibitory effect. This finding suggested that the collective DNA-packaging activity of multiple copies of pRNA could be disrupted by the incorporation of perhaps an individual mutant pRNA into the group. Although this mutant pRNA could not be used for the inhibition of the replication of other viruses directly, the principle of using molecules with two functional domains and multiple-copy involvement as targets for antiviral agents could be applied to certain viral structural proteins, enzymes, and other factors or RNAs involved in the viral life cycle. This principle also implies a strategy for gene therapy, intracellular immunization, or construction of transgenic plants resistant to viral infection.

Confirmation of the helical structure of the 5'/3' termini of the essential DNA packaging pRNA of phage phi 29

Bacteriophage phi 29 is typical of double-stranded DNA viruses in that its genome is packaged into a preformed procapsid during viral assembly. An intriguing feature of phi 29 is the presence of a 120-base virus-encoded RNA (pRNA) that is indispensable for DNA packaging. Phylogenetic comparison of similar RNAs in numerous phages has revealed that the secondary structure of the pRNA is well conserved. Computer analysis predicts the presence of an extensive segment of helix with three single-base bulges generated by the pairing of the 5' and 3' ends. The desire to understand the role played by the pRNA in DNA packaging has led to a mutational analysis of the 5'-/3'-terminal region, which is believed to be important in DNA translocation. Deletion of 3 bases from the 3' end of the RNA, shortening the pRNA from 120 to 117 bases, was tolerated without loss of activity, but additional deletion of the base 117 resulted in 100-fold less activity, and a 115-base pRNA was virtually nonfunctional. Additionally, the three unpaired one-base bulges within the helical stretches of the paired proximate ends were nonessential for pRNA activity, as demonstrated by deletion of the bulge individually. An extensive series of helix disruptions by single- and multiple-base substitution almost invariably led to the loss of DNA packaging activity. Additional mutations that restored predicted base pairings rescued pRNA activity. This second site suppression confirmed that the 5'- and 3'-end region was paired and was indeed a helical stretch. The secondary structure was of greater importance than the primary sequence, with the exception of the requirement of an adenine at either the third or fourth position. The specific requirement of an adenine in phi 29 pRNA at this position, as well as conservation of this position in other phage pRNAs, implicates that this base may play a special role in either the DNA-packaging reaction or the maintenance of the pRNA tertiary structure.

Inhibition of phage phi 29 assembly by antisense oligonucleotides targeting viral pRNA essential for DNA packaging

A sensitive and efficient system for the functional assay of antisense oligonucleotides (oligos) was developed based on an in vitro viral assembly system. A 120-base RNA (pRNA), which indispensably participates in bacteriophage phi 29 DNA packaging, was the target for antisense action. Antisense oligos bound to pRNA, as revealed by a slower electrophoretic mobility of pRNA/oligo complexes in comparison with native pRNA. Infectious viruses were assembled in vitro with synthetic pRNA and DNA, as well as with viral proteins produced from cloned genes. Up to 10(7) plaque-forming units per milliliter were obtained in the absence of antisense oligos, while as few as zero plaques were detected in the presence of certain antisense oligos. A 1-base mismatch greatly influenced the inhibitory effect of the antisense oligos, but this 1-based mismatch was not important when the mismatch was placed at the end of the oligo. Five oligos did not bind pRNA or inhibit the assembly of the virion, suggesting that the RNA sequences complementary to these oligos are nonessential or buried internally in the RNA. Viral assembly was strongly inhibited by antisense oligos P15 and P10, targeting either the 5'- or the 3'-end of the pRNA, respectively. Viral assembly was also strongly inhibited by oligo P6, targeting an internal region, residues 75-91, of pRNA. Oligo P6 inhibited DNA packaging activity by blocking the binding of pRNA to the procapsid, while P10 and P15 inhibited DNA packaging activity but did not block the binding of pRNA to the procapsid, suggesting that in addition to the reported internal domain for procapsid binding, pRNA contains another domain at the paired 5'/3'-ends with a yet to be defined role in DNA translocation.

In vitro assembly of infectious virions of double-stranded DNA phage phi 29 from cloned gene products and synthetic nucleic acids

Up to 6 x 10(7) PFU of infectious virions of the double-stranded DNA bacteriophage phi 29 per ml were assembled in vitro, with 11 proteins derived from cloned genes and nucleic acids synthesized separately. The genomic DNA-gp3 protein conjugate was efficiently packaged into a purified recombinant procapsid with the aid of a small viral RNA (pRNA) transcript, a DNA-packaging ATPase (gp16), and ATP. The DNA-filled capsids were subsequently converted into infectious virions after the addition of four more recombinant proteins for neck and tail assembly. Electron microscopy and genome restriction mapping confirmed the identity of the infectious phi 29 virions synthesized in this system. A nonstructural protein, gp13, was indispensable for the assembly of infectious virions. The overproduced tail protein gp9 was present in solution in mostly dimeric form and was purified to homogeneity. The purified gp9 was biologically active for in vitro phi 29 assembly. Higher-order concentration dependence of in vitro phi 29 assembly on gp9 suggests that a complete tail did not form before attaching to the DNA-filled capsid, a result contrary to earlier findings for phages T4 and lambda. The work described here constitutes an extremely sensitive assay system for the analysis of components in phi 29 assembly and dissection of functional domains of structural components, enzymes, and pRNA (C.-S. Lee and P. Guo, Virology 202:1039-1042, 1995). Efficient packaging of foreign DNA in vitro and synthesis of viral particles from recombinant proteins facilitate the development of phi 29 as an in vivo gene delivery system. The finding that purified tail protein was able to incorporate into infectious virions might allow the construction of chimeric phi 29 carrying a tail fused to ligands for specific receptor of human cells.

Sequential interactions of structural proteins in phage phi 29 procapsid assembly

The mechanism of viral capsid assembly is an intriguing problem because of its fundamental importance to research on synthetic viral particle vaccines, gene delivery systems, antiviral drugs, chimeric viruses displaying antigens or ligands, and the study of macromolecular interactions. The genes coding for the scaffolding (gp7), capsid (gp8), and portal vertex (gp10) proteins of the procapsid of bacteriophage phi 29 of Bacillus subtilis were expressed in Escherichia coli individually or in combination to study the mechanism of phi 29 procapsid assembly. When expressed alone, gp7 existed as a soluble monomer, gp8 aggregated into inclusion bodies, and gp10 formed the portal vertex. Circular dichroisin spectrum analysis indicated that gp7 is mainly composed of alpha helices. When two of the proteins were coexpressed, gp7 and gp8 assembled into procapsid-like particles with variable sizes and shapes, gp7 and gp10 formed unstable complexes, and gp8 and gp10 did not interact. These results suggested that gp7 served as a bridge for gp8 and gp10. When gp7, gp8, and gp10 were coexpressed, active procapsids were produced. Complementation of extracts containing one or two structural components could not produce active procapsids, indicating that no stable intermediates were formed. A dimeric gp7 concatemer promoted the solubility of gp8 but was inactive in the assembly of procapsid or procapsid-like particles. Mutation at the C terminus of gp7 prevented it from interacting with gp8, indicating that this part of gp7 may be important for interaction with gp8. Coexpression of the portal protein (gp20) of phage T4 with phi 29 gp7 and gp8 revealed the lack of interaction between T4 gp20 and phi 29 gp7 and/or gp8. Perturbing the ratio of the three structural proteins by duplicating one or another gene did not reduce the yield of potentially infectious particles. Changing of the order of gene arrangement in plasmids did not affect the formation of active procapsids significantly. These results indicate that phi 29 procapsid assembly deviated from the single-assembly pathway and that coexistence of all three components with a threshold concentration was required for procapsid assembly. The trimolecular interaction was so rapid that no true intermediates could be isolated. This finding is in accord with the result of capsid assembly obtained by the equilibrium model proposed by A. Zlotnick (J. Mol. Biol. 241:59-67, 1994).

Circularly permuted viral pRNA active and specific in the packaging of bacteriophage phi 29 DNA

A viral-encoded 120-base pRNA has been shown to have an essential role in the packaging of bacteriophage phi 29 DNA. The finding that both the 5'- and 3'-termini of the pRNA are proximate and crucial for biological function (C. Zhang, C. Lee, and P. Guo, 1994, Virology, 201, 77-85) prompted investigation of the activity of circularly permuted pRNAs (cpRNA) and of the expandability and essentiality of bases extending from the termini. A 117-base pRNA with a deletion of three bases downstream of the proximal terminus was active in DNA packaging. Concatemeric DNAs containing two tandem pRNA genes separated by a short or a long loop sequence were constructed. The cpRNAs from these DNA templates were transcribed in vitro and shown to be active in phi 29 DNA packaging, with activity comparable to the parental (noncircularly permuted) pRNA, indicating that neither of the loops tested affected the activity and folding of the cpRNA. As few as four bases were sufficient to serve as a loop for the terminal 180 degree turn, and a loop as long as 27 bases did not affect the cpRNA structure and function. Eight cpRNAs were constructed to assess the effect of openings within the wild-type pRNA structure. Opening of the bulge at residue 38 did not affect cpRNA activity, but opening the bulge at residue 55 greatly reduced it. Although the sequence of the 5',3'-terminal loop was not important for the folding and activity of the cpRNA, the activities of cpRNAs with openings at individual bulges or hairpins were different, indicating that each region plays a different role in pRNA folding and function. Our results indicate that it is possible to generate active circularly permuted pRNA by assigning internal sites of the pRNA as new 3'- and 5'-termini. The creation of new variable ends makes the labeling of internal bases of the pRNA molecule possible and will facilitate the analysis of pRNA secondary and tertiary structure.

Differential diagnosis of infectious laryngotracheitis from other avian respiratory diseases by a simplified PCR procedure

A simple polymerase chain reaction (PCR)-based procedure was developed for the detection of avian infectious laryngotracheitis virus (ILTV) in chicken trachea, chorio-allantoic membrane (CAM), infected hepatoma cells and infectious cell culture supernatant. Samples were prepared by dilution in distilled water. After boiling and low speed centrifugation, samples were used for PCR analysis with two primers without special labeling. The PCR analysis for ILT virus could be completed in less than 8 h. Standard agarose gel electrophoretic analysis of the PCR products revealed a prominent band of 300 base-pairs in samples from ILTV-infected specimens, but not from specimens containing Newcastle disease virus, infectious bronchitis virus, avian adenovirus, fowlpox virus, Pachecoz or Marek's disease virus. One single ILTV infected cell or 10 plaque forming units of ILTV could be detected with this procedure. The procedure can be used for the identification of ILTV and the differentiation of ILTV from other avian respiratory tract infectants.

Serum hyaluronate in the assessment of liver endothelial cell function after orthotopic liver transplantation in the rat

This study was designed to evaluate the use of serum hyaluronate as a marker of liver endothelial cell function after liver transplantation. We performed orthotopic liver transplantation in both isogeneic and allogeneic rejector models. After transplantation, hepatocyte function was assessed on the basis of serum ALT and total bilirubin levels, and liver endothelial cell function was judged on the basis of serum hyaluronate levels. Significant increase of hyaluronate in the rejector model, compared with the isogeneic model, was seen before any significant results could be obtained from conventional liver function tests. The impaired metabolism of hyaluronate in the rejector model was observed after intravenous injection of trace amounts of radioactive material. Serial studies demonstrate that the endothelial cell is a more susceptible target for the immune response than the hepatocyte. Serum hyaluronate concentration may be a better indicator in the early assessment of graft function. We also examined serum hyaluronate levels to evaluate cold ischemia-reperfusion injury to the liver endothelial cells in the isogeneic model. At 2 hr after reperfusion, hyaluronate levels in the 6-hr cold ischemia (nonviable allograft) group were significantly higher than in the 1-hr and 3-hr cold ischemia (viable allograft) groups. However, there was little difference between the viable allograft groups. After an intravenous injection of 1 mg/kg hyaluronate, the hyaluronate elimination rate in the 3-hr group was distinctly slower than that in the 1-hr group. These data indicate that the hyaluronate elimination rate may be a more sensitive marker of liver endothelial cell function in viable liver after a short period of ischemia.

Construction of recombinant avian infectious laryngotracheitis virus expressing the beta-galactosidase gene and DNA sequencing of the insertion region

Avian infectious laryngotracheitis virus (ILTV), a herpesvirus, is a highly contagious pathogen that causes an upper respiratory tract infection in chickens. It is one of the major problems in the poultry industry worldwide. Current vaccines are not satisfactory due to the induction of latent infection. Here we describe a system for the construction of recombinant ILTV. A 4-kbp ILTV EcoRI DNA fragment was cloned into plasmid pUC13 and sequenced. Computer prediction revealed two potential open reading frames with 216 and 259 amino acid residues, respectively. The 259-residue polypeptide was serine-rich. The beta-galactosidase (beta-gal) gene of E. coli was cloned into the XhoI/Bg/II site of this DNA fragment, integrated into the ILTV genome via homologous recombination, expressed under the control of the immediate-early cytomegalovirus promoter, and caused the formation of blue plaques in the presence of X-gal. The insertion of a foreign gene into the ILTV genome and the successful expression of the incorporated gene demonstrated the potential for the construction of attenuated recombinant ILTV vaccines and the development of ILTV as vectors for polyvalent vaccines against avian upper respiratory tract infections.

A highly sensitive system for the in vitro assembly of bacteriophage phi 29 of Bacillus subtilis

A sensitive system for the assay of bacteriophage phi 29 assembly in vitro was developed using 12 recombinant proteins and synthetic pRNA. This system detected in vitro assembled infectious phages up to 10(7) plaque forming units (PFU) per milliliter without any background. phi 29 DNA-gp3 concentration dependence in phage assembly was found to be first order, while the DNA-packaging protein gp16 dependence was higher order. The requirement for specific phi 29 pRNA for phi 29 DNA packaging was confirmed by the finding that no plaques were formed when only Escherichia coli RNAs were present. The activity of a mutant pRNA, with 10(5)-fold reduction in DNA packaging efficiency, was also demonstrated. Additionally, the tail proteins were found to have dual roles, one acting as phage tails and the other stabilizing the DNA-gp3 filled capsids.

The proximate 5' and 3' ends of the 120-base viral RNA (pRNA) are crucial for the packaging of bacteriophage phi 29 DNA

In vitro mutagenesis was performed to identify the DNA packaging domain of the 120-base pRNA essential and specific for DNA encapsidation by bacteriophage phi 29 of Bacillus subtilis. All deletions and mutations targeted the 5' and 3' ends of the pRNA. DNA templates of a control or mutant pRNAs used for in vitro transcription with T7 RNA polymerase were generated by PCR. Fourteen mutant pRNA molecules were synthesized from DNA templates either directly after PCR or after cloning the PCR fragments into the pCR II vector. Ten of the mutant pRNA species were inactive in packaging of the phi 29 genome. Mutation of base one at the 5' end did not affect the pRNA packaging activity. Mutation of the first two bases at the 5' end of the pRNA to noncomplementary bases in the predicted RNA secondary structure (U1 C2/A117G116 to G1 G2/A117G116) resulted in a pRNA with no detectable DNA-gp3 packaging activity assayed by either sucrose gradient sedimentation or agarose gel electrophoresis, and 10(5)-fold reduction in activity was found when measured by plaque-forming units with a new highly sensitive assay system. Changing bases 116 and 117 so that they were complementary to the mutated bases, 1 and 2, from the previous mutant (G1 G2/A117G116 to G1 G2/C117C116) generated an RNA molecule with restored DNA packaging ability. Our results show that, although not essential for procapsid binding, both the 5' and 3' ends of the pRNA were proximate and crucial for phi 29 DNA packaging.

Transactivation of the early SV40 promoter by avian infectious laryngotracheitis virus in avian hepatoma cells

An avian hepatoma cell line has been reported to be suitable for the cultivation of avian laryngotracheitis virus (ILTV) (Scholz et al. (1993) J. Virol. Methods, 273-286; Guo et al. (1993) Am. J. Vet. Res., in press). To provide information for the establishment of avian expression systems and for the construction of avian recombinant viruses, five expression plasmids were constructed to test two avian viral and two mammalian viral promotors for their suitability and strength for gene expression in this cell line. Chicken hepatoma cells were transfected with plasmids carrying the bacterial beta-galactosidase (beta-gal) gene as a reporter gene. The beta-gal gene of three plasmid constructs expressed in both E. coli and avian hepatoma cells, while the beta-gal gene of two other constructs expressed only in avian hepatoma cells. The beta-gal gene expressed independently of any viral infection when under the control of the early Rous sarcoma virus (RSV) promoter or the immediate-early cytomegalovirus (CMV) promoter. However, expression of beta-gal gene under the control of the SV40 early promoter/enhancer and the ILTV TK promoter was greatly potentiated when the transfected cells were co-infected with ILTV. This finding provides a system for the enhancement of gene expression in avian cells, especially when ILTV is used as vector.

Assembly pathway of avian infectious laryngotracheitis virus

Infectious laryngotracheitis virus (ILTV) is the causative agent of a highly contagious upper respiratory tract infection in chickens. At present, ILTV vaccines are not satisfactory because of development of a latent carrier status in vaccinated birds. Development of recombinant virus vaccines has been hampered by the limited information available on the molecular level and organization of this virus. We isolated 3 assembly intermediates, designated A, B, and C from ILTV-infected cells. Analysis of [3H]thymidine-and [35S]methionine-labeled particles, and electron microscopic studies indicated that particle A was the empty capsid, particle B was the procapsid containing scaffolding protein, and particle C was the DNA-filled capsid. The ILTV procapsids could only be found in the nucleus, which indicated that procapsids could not translocate through the nuclear membrane until they packaged the DNA. The DNA-filled capsids migrated through the nuclear membrane and obtained an envelope from the inner membrane of the nucleus. The enveloped particles then migrated through the lumen of the endoplasmic reticulum into vacuoles in the cytoplasm. Infective virions were isolated from within the infected cells, indicating that budding through the cytoplasmic membrane is not a necessary step in ILTV maturation. Abundant arrays composed of tubules about 45 to 50 nm wide were found in the cytoplasm of chicken embryonic liver cells about 30 to 38 hours after infection. Comparison of the assembly intermediates and the DNA packaging pathway of ILTV with that of bacteriophage pi 29 indicates that similarity exists.(ABSTRACT TRUNCATED AT 250 WORDS)

[Scavenging effects of ginger on superoxide anion and hydroxyl radical]

Ginger can significantly scavenge O2-. in hypoxanthinexanthine oxidase system and .OH in ultraviolet exposure of H2O2 system. The scavenging effects of ginger on O2-. and .OH may contribute to explaining some of the pharmacological mechanisms of this drug.

[Studies on the chemical components of essential oil from the aerial parts of Ligusticum chuanxiong Hort]

Qualitative and quantitative analyses of the essential oil steamdistilled from the aerial parts of Ligusticum chuanxiong were made by means of GC-MS and GC. Forty-six components which make up 85.82% of the total oil were identified.

An avian hepatoma cell line for the cultivation of infectious laryngotracheitis virus and for the expression of foreign genes with a mammalian promoter

Infectious laryngotracheitis virus (ILTV) is the causative agent of a highly infectious upper respiratory tract disease in chickens. Vaccine development and basic studies on ILTV have been hampered by the lack of a cell line for the cultivation of this herpesvirus which was identified in 1930. Four different avian cell lines were tested for their suitability to propagate ILTV. Here we report the successful growth of ILTV with a chemically-induced avian hepatoma cell line, while retrovirus transformed cell lines derived from permissive primary cells, were found to be non-permissive for ILTV. After multiple passaging of ILTV in the hepatoma cells, the virus could be grown up to a titre of 1 x 10(7) EID50 per ml with a replication cycle comparable to that in primary hepatocytes. Methods of plaque assay, DNA-transfection, and expression of a reporter gene were established. The gene coding for the bacterial beta-galactosidase gene under the control of the cytomegalovirus (CMV) immediate-early promotor was transiently expressed, indicating that a mammalian herpesvirus promotor was recognized by this avian cell line. Infectious ILTV virions were produced after transfecting this cell-line with purified ILTV DNA. The results indicated that the cell line is suitable for the construction of recombinant ILTV and for the molecular biological study of this important avian pathogen.

The effect of reconstruction after subtotal gastrectomy on release of vasoactive intestinal peptide

To avoid dumping after Billroth gastrectomy, we designed pylorus and antroseromuscular-flap preserving subtotal gastrectomy (PAFPG). The mean maximal plasma level of VIP (vasoactive intestinal peptide) in PAFPG after oral hypertonic glucose was close to that in the control. Compared with PAFPG group, the plasma VIP concentrations after hypertonic glucose ingestion in BI and BII group were significantly higher, and the concentration of plasma VIP in dumpers was significantly higher than that in non-dumpers after BI or BII gastrectomy. The results suggest that the amount of VIP release is related to the type of reconstruction after gastrectomy.

Tracking and elimination of an interfering polypeptide coexpressed with the vaccinia virus mRNA capping enzyme overproduced in Escherichia coli

Vaccinia virus (vv) mRNA capping enzyme is composed of a large and a small subunit encoded by genes D1 and D12, respectively. A 38-kDa interfering polypeptide is copurified with the vaccinia virus capping enzyme overproduced in Escherichia coli, but the origin of this polypeptide is unknown (P. Guo and B. Moss, 1990, Proc. Natl. Acad. Sci. USA 87, 4023-4027). This polypeptide competes with the large subunit in binding to the small subunit during the assembly of the heterodimeric enzyme in the cell, resulting in a reduced yield of the active enzyme. Results from the studies of ribosome-binding site replacement, frame shifting, DNA deletion, and in vitro mutagenesis showed that the interfering polypeptide originated from a new translation initiation site within the D1 gene. Transfection of a plasmid containing an internal eukaryotic ribosome binding site into monkey kidney cells infected with vv producing T7 RNA polymerase resulted in the expression of the large subunit up to 30% of total cellular radiolabeled protein; however, the 38-kDa polypeptide was not detected. This finding suggests that the initiation site was recognized only by E. coli, not by eukaryotic cells. The Shine-Dalgarno sequence is not found in the corresponding region preceding the putative start codon, indicating that an unusual mechanism for ribosome binding exists. Mutagenesis of the putative initiation codon of the interfering polypeptide from ATG (Met), coding for residue 498 of the large subunit, to ATA (Ile) eliminated the expression of the interfering polypeptide. A stable and active mutant enzyme was expressed in E. coli HMS174(DE3) cell without the presence of the interfering polypeptide.

[Pharmacognostical studies on two species of Chinese drug caowu produced in Sichuan]

This paper deals with 2 species of medicinal roots of Aconitum legendrei and A. geniculatum which are used in Sichuan as Caowu. The morphological and histological characteristics of these two roots are described.

[The contents of gamma-aminobutyric acid and glutamic acid in brain affected by coriaria lactone]

Capillary chromatography was applied to studying the contents of gamma-aminobutyric acid (GABA) and glutamic acid (Glu) in brain affected by coriaria lactone. The results showed that there was a significant increase in the content of Glu whereas no significant change in the content of GABA was noted. The precisions for GABA and Glu were 3.3% and 4.98% and the recoveries of them were 80.5% and 85.2%, respectively. Capillary chromatography is a good method for determining the contents of GABA and Glu in brain, which has the characteristics of rapid and high sensitivity.

[Determination of berberine hydrochloride in traditional Chinese medicines containing Coptis chinensis Franch by reversed phase high performance liquid chromatography]

This paper reports a reversed phase high performance liquid chromatography method to determine berberine hydrochloride in Coptis chinensis Franch and in the traditional Chinese medicine containing Coptis chinensis Franch. The result shows that the mobile phase of 0.4mol/L ammonium nitratemethanol (52:48) can give a satisfactory separation. The extraction of sample with 1% H2SO4 solution using the ultrasonic vibration method is simple and easy to operate.

[Botanical origins of Chinese drug caowu produced in Sichuan]

We have made an investigation on the botanical origins of 6 species and 2 varieties of the traditional Chinese drug Caowu produced in Sichuan, and found out that the main species available on the market are Aconitum hemsleyanum and A. hemsleyanum var. leucanthum, while A. legendrei comes second. A key for their identification is presented in this paper.

[Ion-paired high performance liquid chromatographic determination of mitoxantrone hydrochloride injection]

Mitoxantrone (DHAQ) is a new anti-cancer agent. The ion-pair HPLC method to determine mitoxantrone hydrochloride injection was proposed. Mitoxantrone can be separated on Zorbax-ODS column with methanol-water-formic acid (450:50:1.5) containing 3.605g SDS as mobile phase. The pH of mobile phase was adjusted to 2.7. The flow rate was 1.0 ml/min and detection was at wavelength of 254 nm, providing a detection limit of 1ng (r/n, 3:1) of DHAQ. DHAQ was determined by peak area measurement with ametantrone as internal standard. The rectilinear calibration graph in the range of 1-10 micrograms of DHAQ was obtained (r = 0.999 2). The average recovery was 99.62 +/- 2.36% (n = 10), and the results were not interfered by the other ingredients in the injection.

Reflectance diagram-aided technique for optical coating design and monitoring

An amplitude reflectance diagram is a useful tool for visualizing the relationships between the performance of an optical coating and the optical parameters. This paper gives a brief description of the construction and characterization of the reflectance diagrams for different indices. Then, applications of reflectance diagramaided techniques to the design of both phase dispersion-induced narrow reflection and transmission filters, as well as to the optical monitoring of the symmetric multilayers of types (A2BA) and (AB2CBA), are illustrated. Some experimental results of phase dispersion-induced narrowband filters are reported.

Diagnostic value of plasma PABA level in pancreatic diseases

NBT-PABA test was performed in 72 subjects with simultaneous determination of the plasma PABA time-concentration curve. The curve in 25 controls after oral administration of N-benzoyl-L-tyrosyl-P-aminobenzoic acid (NBT-PABA) peaked (3.88 +/- 0.78 micrograms/ml, M +/- SD) at the third hour. In patients with chronic pancreatitis (24) and pancreatic carcinoma (6), the curves were flattened, and peaked at the fifth hour (2.7 +/- 1.4 micrograms/ml, M +/- SD), and fourth hour (3.14 +/- 2.26 micrograms/ml, M +/- SD), respectively. The discrimination between the controls and patients with chronic pancreatitis was most significant in the third-hour plasma PABA concentration (P less than 0.0001). This study shows that determination of the third-hour plasma PABA concentration is better in sensitivity and specificity than the 6-hour urinary excretion of PABA, suggesting that the third-hour plasma PABA concentration after oral administration of NBT-PABA might be a sensitive index of exocrine pancreatic function test.

Initiation events in in-vitro packaging of bacteriophage phi 29 DNA-gp3

Initiation events in the packaging of bacteriophage phi 29 DNA-gp3 (DNA-gene product 3 complex) were studied in a completely defined in-vitro system that included purified proheads, DNA-gp3 and the DNA packaging protein gp16. In the sequential interactions, gp16 first bound to, and was modified by, the prohead. The prohead-gp16 complex then bound to DNA-gp3, resulting in a second modification of gp16 that permitted binding of ATP. DNA-gp3 aggregates were produced, and the hydrolysis of ATP accompanied DNA-gp3 packaging. Binding and hydrolysis of ATP by gp16 was both prohead- and DNA-gp3-dependent. Interruption of packaging by DNase I addition revealed filled heads but few particles containing partial lengths of DNA, suggesting that following a rate-limiting initiation, the translocation of DNA-gp3 into the prohead was much faster in the defined in-vitro system than in extracts.

Prohead and DNA-gp3-dependent ATPase activity of the DNA packaging protein gp16 of bacteriophage phi 29

The ATPase activity of the DNA packaging protein gp16 (gene product 16) of bacteriophage phi 29 was studied in the completely defined in-vitro assembly system. ATP was hydrolyzed to ADP and Pi in the packaging reaction that included purified proheads, DNA-gp3 and gp16. Approximately one molecule of ATP was used in the packaging of 2 base-pairs of phi 29 DNA, or 9 X 10(3) ATP molecules per virion. The hydrolysis of ATP by gp16 was both prohead and DNA-gp3 dependent. gp16 contained both the "A-type" and the "B-type" ATP-binding consensus sequences (Walker et al., 1982) and the predicted secondary structure for ATP binding. The A-type sequence of gp16 was "basic-hydrophobic region-G-X2-G-X-G-K-S-X7-hydrophobic", and similar sequences were found in the phage DNA packaging proteins gpA of lambda, gp19 of T7 and gp17 of T4. Having both the ATP-binding and potential magnesium-binding domains, all of these proteins probably function as ATPases and may have common prohead-binding capabilities. The phi 29 protein gp3, covalently bound to the DNA, may be analogous in function to proteins gpNul of lambda and gpl of phi 21 that bind the DNA.

A defined system for in vitro packaging of DNA-gp3 of the Bacillus subtilis bacteriophage phi 29

The bacteriophage phi 29 DNA-gene product 3 complex (DNA-gp3) has been efficiently packaged into proheads in a completely defined in vitro system. The phi 29 DNA packaging protein gp16, the product of gene 16, was overproduced in Escherichia coli and purified to near homogeneity. The purified gp16 packaged 23% of the DNA-gp3 added to purified proheads in the defined mixture, while gp16 in an extract of phage-infected cells packaged 26% of the DNA-gp3. No host proteins were required in the defined system. ATP-dependent packaging of DNA-gp3 in the defined system was optimal with approximately equal to 100 copies of gp16 per DNA-gp3, an amount similar to the production of gp16 per DNA-gp3 in phi 29-infected cells.