Description and clinical treatment of an early outbreak of severe acute respiratory syndrome (SARS) in Guangzhou, PR China

Severe acute respiratory syndrome (SARS), now known to be caused by a coronavirus, probably originated in Guangdong province in southern China in late 2002. The first major outbreak occurred in Guangzhou, the capital of Guangdong, between January and March 2003. This study reviews the clinical presentation, laboratory findings and response to four different treatment protocols. Case notes and laboratory findings were analysed and outcome measures were collected prospectively. The SARS outbreak in Guangdong province and the outbreak in Guangzhou associated with hospitals in the city are described, documenting clinical and laboratory features in a cohort of 190 patients randomly allocated to four treatment regimens. Patients were infected by close contact in either family or health-care settings, particularly following procedures likely to generate aerosols of respiratory secretions (e.g. administration of nebulized drugs and bronchoscopy). The earliest symptom was a high fever followed, in most patients, by dyspnoea, cough and myalgia, with 24 % of patients complaining of diarrhoea. The most frequent chest X-ray changes were patchy consolidation with progression to bilateral bronchopneumonia over 5-10 days. Thirty-six cases developed adult respiratory distress syndrome (ARDS), of whom 11 died. There was no response to antibiotics. The best response (no deaths) was seen in the group of 60 patients receiving early high-dose steroids and nasal CPAP (continuous airway positive pressure) ventilation; the other three treatment groups had significant mortality. Cross-infection to medical and nursing staff was completely prevented in one hospital by rigid adherence to barrier precautions during contact with infected patients. The use of rapid case identification and quarantine has controlled the outbreak in Guangzhou, in which more than 350 patients have been infected. Early administration of high-dose steroids and CPAP ventilation appears to offer the best supportive treatment with a reduced mortality compared with other treatment regimens.

Spectroscopic studies of interaction of chlorobenzylidine with DNA

Electronic absorbance and fluorescence titrations are used to probe the interaction of chlorobenzylidine with DNA. The binding of chlorobenzylidine to DNA results in hypochromism, a small shift to a longer wavelength in the absorption spectra, and emission quenching in the fluorescence spectra. These spectral characteristics suggest that chlorobenzylidine binds to DNA by an intercalative mode. This conclusion is reinforced by fluorescence polarization measurements. Scatchard plots constructed from fluorescence titration data give a binding constant of 1.3 x 10(5) M(-1) and a binding site size of 10 base pairs. This indicates that chlorobenzylidine has a high affinity with DNA. The intercalative interaction is exothermic with a Van't Hoff enthalpy of -143 kJ/mol. This result is obtained from the temperature dependence of the binding constant. The interaction of chlorobenzylidine with DNA is affected by the pH value of the solution. The binding constant has its maximum at pH 3.0. Upon binding to DNA, the fluorescence from chlorobenzylidine is quenched efficiently by the DNA bases and the fluorescence intensity tends to be constant at high concentrations of DNA when the binding is saturated. The Stern-Volmer quenching constant obtained from the linear quenching plot is 1.6 x 10(4) M(-1) at 25 degrees C. The measurements of the fluorescence lifetime and the dependence of the quenching constant on the temperature indicate that the fluorescence quenching process is static. The fluorescence lifetime of chlorobenzylidine is 1.9 +/- 0.4 ns.

Cellular immunity and memory to respiratory virus infections

Respiratory virus infections, such as those caused by influenza and parainfluenza viruses, are a major cause of morbidity and mortality worldwide. Current vaccines against these pathogens rely on the induction of humoral immune responses that target viral coat proteins. Although this type of immunity provides solid protection against homologous virus strains, it is ineffective against heterologous virus strains that express serologically distinct coat proteins. In contrast, cellular immune responses can target internal antigens that are shared between heterologous viral strains. This form of immunity, sometimes referred to as heterosubtypic immunity, can mediate a substantial degree of protection. Thus, vaccines that emphasize cellular immune responses would be a valuable complement to available humoral vaccines. However, we only have a rudimentary understanding of which T cell subsets mediate protective immunity, how T cell memory is established and maintained, how that memory is recalled in a secondary infection, and why cellular immunity wanes rapidly with time. Here we review the role of CD4+ and CD8+ T cells in the recall response to influenza and parainfluenza viruses. In particular we focus on the recent observation that substantial numbers of memory T cells are established in the lung tissues and discuss the potential role of these cells in mediating a recall response. A thorough understanding of the cellular immune response to infection in the lungs is essential for future vaccine development.

[Clinical value of the symptom-relieving operation in multimodality therapy of stage IIIB and IV lung cancer]

BACKGROUND

To explore the clinical value of the symptom-relieving operation in multimodality therapy of stage IIIB and IV lung cancer for rising quality of life and prolonging survival time.

METHODS

The pain incidence rate, fraction of Karnofsky and anesthesia, clinical effect of treatment and survival rate of 29 cases were statistically analysed using SPSS software, in multimodality therapy of stage IIIB and IV lung cancer, before and after symptom-relieving operation. The difference between before and after operation was compared with Chi-Square and t test. The survival rate was calculate with Kaplan-Meier method.

RESULTS

The complete remission rate for cases of malignant pleural effusion and pericardial effusion was 100% ( 15/ 15) . The 1-year survival rate was 66. 67%, mean survival time was 13. 81± 1. 61 months, and median survival time was 16. 00 months. The 1-year survival rate of cases with bone metastasis was 20. 0%, mean survival time was 9. 90± 0. 99 months, median survival time was 10. 00 months. After therapy, the pain incidence rate of all patients was decreased from 89. 7% to 34. 5% ( P < 0. 001) ; Karnofsky score was increased from 58. 28 ± 2. 17 to 82. 41± 1. 54( P < 0. 001) ; fraction of anesthesia was decreased from 5. 17± 0. 53 to 1. 45± 0. 38 ( P < 0. 001) .

CONCLUSIONS

The symptom-relieving operation for metastasis lesion can rise the quality of life, prolong survival time, decrease dependence of anesthetic and analgesic drugs in multimodality therapy of stage IIIB and IV lung cancer.

Evaluation of the role of lipoprotein metabolism genes in systemic cationic liposome-mediated gene transfer in vivo

Germ line gene disruption and gene insertion are often used to study the function of selected genes in vivo. We used selected knockout and transgenic mouse models to attempt to identify lipoprotein-related genes and gene products that regulate the process of intravenous cationic liposome-DNA complex (CLDC)-based gene delivery. Several observations suggested that proteins involved in lipoprotein metabolism might be important in influencing the delivery and/or expression of CLDC. First, in vitro transfection of either K562 or CHO cells by CLDCs was enhanced by the presence of a functional low-density lipoprotein receptor (LDLR). Second, pretreatment of mice with 4-aminopyrazolopyrimidine (4APP), an agent that alters lipoprotein profiles in mice, significantly decreased expression of luciferase (luc) after intravenous injection of CLDC-luc complexes in mice. Therefore, we tested mouse model systems either deficient for, or overexpressing, selected genes involved in lipoprotein metabolism, for their potential to regulate intravenous, CLDC-based gene delivery. Although homozygous knockout mutation in the apoE gene caused a significant decrease in gene expression in many tissues of apoE-deficient mice, mice with homozygous deletion of both the apoE and LDLR genes showed wild-type levels of gene transfer efficiency. Thus, a secondary event, produced by homozygous deletion of apoE, but compensated for by the concomitant deletion of LDLR, and/or effects resulting from strain-related, genetic background differences, appeared to play a significant role in mediating intravenous, CLDC-based gene delivery. Secondary alterations resulting from germ line knockouts, as well as epigenetic effects produced by strain differences, may limit the ability to assign specific, gene transfer-related functions to the deleted gene.

Infection with Mycobacterium avium differentially regulates the expression of iron transport protein mRNA in murine peritoneal macrophages

Iron is an important element for the growth of microorganisms as well as in the defense of the host by serving as a catalyst for the generation of free radicals via the Fenton/Haber-Weiss reactions. The iron transporter natural resistance-associated macrophage protein 1 (Nramp1) confers resistance to the growth of a variety of intracellular pathogens including Mycobacterium avium. Recently several other proteins that are involved in iron transport, including the highly homologous iron transporter Nramp2 and the transferrin receptor-associated protein HFE (hereditary hemochromatosis protein), have been described. The relationship of these proteins to host defense and to the growth of intracellular pathogens is not known. Here, we report that infection with M. avium differentially regulates mRNA expression of the proteins associated with iron transport in murine peritoneal macrophages. Both Nramp1 and Nramp2 mRNA levels increase following infection, while the expression of transferrin receptor mRNA decreases. The level of expression of HFE mRNA remains unchanged. The difference in the expression of the mRNA of these proteins following infection or cytokine stimulation suggests that they may play an important role in host defense by maintaining a delicate balance between iron availability for host defense and at the same time limiting iron availability for microbial growth.

Redox-mediated effects of selenium on apoptosis and cell cycle in the LNCaP human prostate cancer cell line

The effects of selenium exposure were studied in LNCaP human prostate cancer cells, and this same cell line adapted to selenium over 6 months to compare acute versus chronic effects of sodium selenite, the latter most closely resembling human clinical trials on the effects of selenium in cancer prevention and therapy. Our results demonstrated that oxidative stress was induced by sodium selenite at high concentrations in both acute and chronic treatments, but outcomes were different. After acute exposure to selenite, cells exhibited mitochondrial injury and cell death, mainly apoptosis. After chronic exposure to selenite, cells showed growth inhibition caused by cell cycle arrest, increased numbers of mitochondria and levels of mitochondrial enzymes, and only minimal induction of apoptosis. Immunoblotting analysis revealed that multiple proteins were up-regulated by chronic exposure to selenite. Among them, only up-regulation of manganese superoxide dismutase and the cyclin-dependent kinase inhibitor p21(Waf1/Cip1), proteins known to be redox sensitive and to have cell cycle regulatory functions, correlated with cell growth inhibition. Our results in selenite-adapted cells suggest that selenium may exert its effects in human prostate cancer cells by altering intracellular redox state, which subsequently results in cell cycle block.

[Comparative analysis on the hearing ability of children in iodine deficiency areas born before and after iodine supplementation]

According to the detection of hearings ability of children in iodine deficiency areas who was born before and after iodine supplement, the effects of iodine supplement on hearing system development was evaluated.

METHOD

Hearing was tested by AS-72 type pure zone diagnostic audiometer(made in Denmark). Hearing of 11-14 years old students were tested before iodine supplement in iodine deficiency areas in 1984, the control was students living in non-iodine deficiency areas. Iodine salt (50 mg/kg) were supplied by the end of 1984, the hearings of children born after one year of iodine supplied were tested in 1999. The result showed that the average hearing threshold of students before iodine supplied in iodine deficiency areas was significance higher than of non-iodine deficiency areas. The hearing of children born after one year of iodine salt supplied in deficient areas had no significant difference from that of normal areas. The development of hearing system might be deteriorated by iodine deficiency during pregnant. It was able to meet the need of iodine that pregnant women ate 1:20 thousands iodine salt.

Antibody-independent antiviral function of memory CD4+ T cells in vivo requires regulatory signals from CD8+ effector T cells

Previous studies have shown that vaccine-primed CD4(+) T cells can mediate accelerated clearance of respiratory virus infection. However, the relative contributions of Ab and CD8(+) T cells, and the mechanism of viral clearance, are poorly understood. Here we show that control of a Sendai virus infection by primed CD4(+) T cells is mediated through the production of IFN-gamma and does not depend on Ab. This effect is critically dependent on CD8(+) cells for the expansion of CD4(+) T cells in the lymph nodes and the recruitment of memory CD4(+) T cells to the lungs. Passive transfer of a CD8(+) T cell supernatant into CD8(+) T cell-depleted, hemagglutinin-neuraminidase (HN)(421-436)-immune muMT mice substantially restored the virus-specific memory CD4(+) response and enhanced viral control in the lung. Together, the data demonstrate for the first time that in vivo primed CD4(+) T cells have the capacity to control a respiratory virus infection in the lung by an Ab-independent mechanism, provided that CD8(+) T cell "help" in the form of soluble factor(s) is available during the virus infection. These studies highlight the importance of synergistic interactions between CD4(+) and CD8(+) T cell subsets in the generation of optimal antiviral immunity.

A novel mechanism to ensure terminal initiation by hepatitis C virus NS5B polymerase

Hepatitis C virus (HCV) nonstructural protein 5B (NS5B) RNA-dependent RNA polymerase (RdRp) has acquired a unique beta-hairpin in the thumb subdomain which protrudes toward the active site. We report here that this beta-hairpin plays an important role in positioning the 3' terminus of the viral RNA genome for correct initiation of replication. The presence of this beta-hairpin interferes with polymerase binding to preannealed double-stranded RNA (dsRNA) molecules and allows only the single-stranded 3' terminus of an RNA template to bind productively to the active site. We propose that this beta-hairpin may serve as a "gate" which prevents the 3' terminus of the template RNA from slipping through the active site and ensures initiation of replication from the terminus of the genome. This hypothesis is supported by the ability of a beta-hairpin deletion mutant that utilizes dsRNA substrates and initiates RNA synthesis internally. The proposed terminal initiation mechanism may represent a novel replication strategy adopted by HCV and related viruses.

Characterization of monoclonal antibodies that specifically recognize the palm subdomain of hepatitis C virus nonstructural protein 5B polymerase

The nonstructural protein 5B (NS5B) of hepatitis C virus (HCV) is an RNA-dependent RNA polymerase (RdRp) which plays an essential role in viral RNA replication. Antibodies that specifically recognize NS5B will have utilities in monitoring NS5B production and subcellular localization, as well as in structure-function studies. In this report, three mouse monoclonal antibodies (mAbs), 16A9C9, 16D9A4 and 20A12C7, against a recombinant NS5B protein (genotype 1a, H-77 strain) were produced. These mAbs specifically recognize HCV NS5B, but not RdRps of polivirus (PV), bovine viral diarrhea virus (BVDV) or GB virus B (GBV-B). The mAbs can readily detect NS5B in cellular lysates of human osteosarcoma Saos2 cells constitutively expressing the nonstructural region of HCV (NS3-NS4A-NS4B-NS5A-NS5B). NS5B proteins of different HCV genotypes/subtypes (1a, 1b, 2a, 2c, 5a) showed varied affinity for these mAbs. Interestingly, the epitopes for the mAbs were mapped to the palm subdomain (amino acid 188-370) of the HCV RdRp as determined by immunoblotting analysis of a panel of HCV/GBV-B chimeric NS5B proteins. The binding site was mapped between amino acid 231 and 267 of NS5B for 16A9C9, and between 282 and 372 for 16D9A4 and 20A12C7. Furthermore, these mAbs showed no inhibitory effect on the NS5B polymerase activity in vitro.

[Study on infection of transfusion transmitted virus in serum, breast milk of pregnant women and umbilical venous blood from their newborns]

OBJECTIVE

To study transfusion transmitted virus (TTV) infection in pregnant women and their newborns, and the route of transmission.

METHODS

Serum, breast milk from 150 pregnant women and umbilical venous blood from their newborns were collected. TTV DNA was amplified by semi-nested-polymerase chain reaction, and the positive products were sequenced directly.

RESULTS

The positive rate of TTV DNA in pregnancy serum was 11.3% (17/150). Among the 17 serum positive cases, TTV DNA was detected in 11 breast milk samples, and none in all the umbilical blood. The homologous of partial nucleotide sequence of TTV DNA between the 3 serum samples and their breast milk were 97.6%-99.2%. Compared the 5 serum positive samples (A1-A5) with N22 segments of Japanese original isolate, the homologous of partial nucleotide and amino acid sequence were 71.5%-92.8%, 71.5%-92.8%, respectively.

CONCLUSION

There exists TTV infection in pregnancy serum and breast milk. Transmission by breast feeding may be one of the main pathway causing TTV infection.

Total synthesis of fostriecin (CI-920)

The first total synthesis of the potent antitumor agent fostriecin (CI-920) is described, confirming the relative and absolute stereochemistry assignments. Fostriecin is a unique phosphate monoester which exhibits weak topoisomerase II inhibition (IC(50) = 40 microM) and more potent and selective protein phosphatase 2A and 4 (PP2A and PP4) inhibition (IC(50) = 40-3 nM and 1.5 nM), resulting in mitotic entry checkpoint inhibition. Phase I clinical trials with fostriecin, which were the first to explore the potential of this novel mechanism of action, were halted even before therapeutic concentrations were reached or dose-limiting toxicity established due to problems of drug stability observed during storage of naturally derived material. The synthesis of fostriecin detailed herein is the first stage of efforts that may serve to address these limitations to the clinical examination of this or related promising new antitumor agents.

[Experimental study of motor nerve innervation of uvala muscle]

OBJECTIVE

To investigate the motor nerve innervation of uvala muscle.

METHODS

Horseridish peroxidase (HRP) retrograde tracing technique was used in conjunction with selective intracranial severing of cranial nerve rootlets in 8 rabbies.

RESULTS

Following HRP injection into uvala muscles, labeled motoneurons were located in the rostral section of nucleus ambiguus. No labeled motoneurons were found in the facial nucleus. Labled motoneurons were ipslaterally abolished after the cranial rootlets of accessory nerve on one side were intracranially severed.

CONCLUSIONS

Uvala muscles are innervated by the motoneurons in the nucleus ambiguus. The axons of those motoneurons come out of the cranium through the cranial rootlet of the accessory nerve, then join the vagus, distributed via the pharyngeal branches of vagus.

[Applied anatomical study of blood supply in human palate]

OBJECTIVE

To investigate the origins and distributions of palatal vasculature and the three dimensional architecture.

METHODS

Materials consisted of 14 normal and 10 cleft palate head-and-neck specimens. After vascular infusion, specimens were seprately analysed by stereomicroscopy, radiography, histological study and scanning electron microscopy.

RESULTS

The greater palatine artery was the main vessel to supply the hard palate and the ascending palatine artery provided the principal supply of soft palate. The branches of greater palatine artery formed abundant anastomoses with the neighbor vessels. The ascending palatine artery divided into two branches in the soft palate. The artery branches in hard palate took on tree-like appearance and were arranged parallel. The capillary network was loosely packed. Whereas, the arteries in soft palate were always found to be crooked. The angles of the branches from the main trunk were changeable. The capillary network was packed densely. The vascular origins and courses of the cleft palate specimens were the same as the normal person, but the distributions and anastomoses were different.

CONCLUSIONS

The blood supplies of hard and soft palate come from different vascular vessels and their vascular architectures have their own character.

The sequence of the human genome

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

Localization of the thioredoxin system in normal rat kidney

Components of the thioredoxin system were localized in normal rat kidney using immunoperoxidase techniques at the light microscopic level and immunogold techniques at the ultrastructural level. Results from both methods were similar. Thioredoxin, thioredoxin reductases, and peroxiredoxins showed cell-type-specific localization, with the same cell types (proximal and distal tubular epithelial, papillary collecting duct, and transitional epithelial cells) previously identified as having high amounts of antioxidant enzyme immunoreactive proteins and oxidative damage products also having high levels of proteins of the thioredoxin system. In addition, peroxiredoxins II and IV were found in high levels in the cytoplasm of red blood cells, identified in kidney blood vessels. While thioredoxin and thioredoxin reductase 1 were found in all subcellular locations in kidney cells, thioredoxin reductase 2 was found predominantly in mitochondria. Thioredoxin reductase 1 was identified in rat plasma, suggesting it is a secreted protein. Peroxiredoxins often had specific subcellular locations, with peroxiredoxins III and V found in mitochondria and peroxiredoxin IV found in lysosomes. Our results emphasize the complex nature of the thioredoxin system, demonstrating unique cell-type and organelle specificity.

Activated antigen-specific CD8+ T cells persist in the lungs following recovery from respiratory virus infections

The poor correlation between cellular immunity to respiratory virus infections and the numbers of memory CD8(+) T cells in the secondary lymphoid organs suggests that there may be additional reservoirs of T cell memory to this class of infection. Here we identify a substantial population of Ag-specific T cells in the lung that persist for several months after recovery from an influenza or Sendai virus infection. These cells are present in high numbers in both the airways and lung parenchyma and can be distinguished from memory cell populations in the spleen and peripheral lymph nodes in terms of the relative frequencies among CD8(+) T cells, activation status, and kinetics of persistence. In addition, these cells are functional in terms of their ability to proliferate, express cytolytic activity, and secrete cytokines, although they do not express constitutive cytolytic activity. Adoptive transfer experiments demonstrated that the long-term establishment of activated T cells in the lung did not require infection in the lung by a pathogen carrying the inducing Ag. The kinetics of persistence of Ag-specific CD8(+) T cells in the lung suggests that they play a key role in protective cellular immunity to respiratory virus infections.

The tethered agonist approach to mapping ion channel proteins--toward a structural model for the agonist binding site of the nicotinic acetylcholine receptor

BACKGROUND

The integral membrane proteins of neurons and other excitable cells are generally resistant to high resolution structural tools. Structure-function studies, especially those enhanced by the nonsense suppression methodology for unnatural amino acid incorporation, constitute one of the most powerful probes of ion channels and related structures. The nonsense suppression methodology can also be used to incorporate functional side chains designed to deliver novel structural probes to membrane proteins. In this vein, we sought to generalize a potentially powerful tool - the tethered agonist approach - for mapping the agonist binding site of ligand-gated ion channels.

RESULTS

Using the in vivo nonsense suppression method for unnatural amino acid incorporation, a series of tethered quaternary ammonium derivatives of tyrosine have been incorporated into the nicotinic acetylcholine receptor. At three sites a constitutively active receptor results, but the pattern of activation as a function of chain length is different. At position alpha149, there is a clear preference for a three-carbon tether, while at position alpha93 tethers of 2-5 carbons are comparably effective. At position gamma55/delta57 all tethers except the shortest one can activate the receptor. Based on these and other data, a model for the receptor binding site can be developed by analogy to the acetylcholine esterase crystal structure.

CONCLUSION

Through the use of nonsense suppression techniques, the tethered agonist approach has been made into a general tool for probing receptor structures. When applied to the nicotinic receptor, the method places new restrictions on developing models for the agonist binding site.

The broad-spectrum antiviral ribonucleoside ribavirin is an RNA virus mutagen

The ribonucleoside analog ribavirin (1-beta-D-ribofuranosyl-1,2, 4-triazole-3-carboxamide) shows antiviral activity against a variety of RNA viruses and is used in combination with interferon-alpha to treat hepatitis C virus infection. Here we show in vitro use of ribavirin triphosphate by a model viral RNA polymerase, poliovirus 3Dpol. Ribavirin incorporation is mutagenic, as it templates incorporation of cytidine and uridine with equal efficiency. Ribavirin reduces infectious poliovirus production to as little as 0. 00001% in cell culture. The antiviral activity of ribavirin correlates directly with its mutagenic activity. These data indicate that ribavirin forces the virus into 'error catastrophe'. Thus, mutagenic ribonucleosides may represent an important class of anti-RNA virus agents.

Leukoplakia and angiopoiesis resistance of Herba Erigerontis

OBJECTIVE

To evaluate the effects of Herba Erigerontis on angiopoiesis and carcinogenesis; to seek an effective drug for prevention of leukoplakia progression to carcinoma and to stop the mechanism of angiopoiesis.

METHODS

Carcinomatous conversions of golden hamster cheek pouches induced by Salley way and inhibited by Herba Erigerontis. Ink perfusion, analysis of images, resin cast form of micro-vessel, a-SMA detection and histopathological examination were applied to observe their changing patterns.

RESULTS

The rate of leukoplakia conversion to tumor of the Herba Erigerontis group was half that of model group. The proportion of normal cells was approximately 4 times greater than that of model. The a-SMA levels of the Herba Erigerontis treated group was higher than that of model (P < 0.001). There was no significant difference between angeion vessel area and density (P > 0.05) in these 2 groups, which were elevated compared to the control. Nevertheless, the resin casts of the microvasculature in the Herba Erigerontis group showed that its configuration and spatial arrangement was similar to the control group.

CONCLUSIONS

Herba Erigerontis has the function of inhibiting leukoplakia progression to tumor. This may be due to its ability to upregulate the expression of a-SMA. It has no obvious effect on angio-hyperplasia and expansion in the course of leukoplakia progression to tumor. However, it may preserve the angio-configuration and spatial arrangement and keep intact the angeion vessel wall. Its mechanism of promoting blood circulation may be through removing blood stasis and benign angiopoiesis so as to resist carcinogenesis.

Template nucleotide moieties required for de novo initiation of RNA synthesis by a recombinant viral RNA-dependent RNA polymerase

The recombinant RNA-dependent RNA polymerase of the bovine viral diarrhea virus specifically requires a cytidylate at the 3' end for the de novo initiation of RNA synthesis (C. C. Kao, A. M. Del Vecchio, and W. Zhong, Virology 253:1-7, 1999). Using RNAs containing nucleotide analogs, we found that the N3 and C4-amino group at the initiation cytidine were required for RNA synthesis. However, the ribose C2'-hydroxyl of the initiating cytidylate can accept several modifications and retain the ability to direct synthesis. The only unacceptable modification is a protonated C2'-amino group. Quite strikingly, the recognition of the functional groups for the initiation cytidylate and other template nucleotides are different. For example, a C5-methyl group in cytidine can direct RNA synthesis at all template positions except at the initiation cytidylate and C2'-amino modifications are tolerated better after the +11 position. When a 4-thiouracil (4sU) base analog that allows only imperfect base pairing with the nascent RNA is placed at different positions in the template, the efficiency of synthesis is correlated with the calculated stability of the template-nascent RNA duplex adjacent to the position of the 4sU. These results define the requirements for the specific interactions required for the initiation of RNA synthesis and will be compared to the mechanisms of initiation by other RNA-dependent and DNA-dependent RNA polymerases.

Prevalence and genetic diversity of human caliciviruses (HuCVs) in Mexican children

Human caliciviruses (HuCVs) contain two genera: "Norwalk-like viruses" (NLVs) and "Sapporo-like viruses" (SLVs). The importance of the two genera as a cause of acute gastroenteritis of infants and children remains unknown. Beginning in 1989, a birth cohort of children in Mexico was enrolled and monitored for acute gastroenteritis. A subset of 115 diarrhea stool specimens from 76 children and 66 non-diarrhea stool specimens from 64 children was examined for HuCVs by RT-PCR by using a primer pair (p289/290) that detects both NLVs and SLVs. Twenty-two (19%) of the 115 diarrhea stool specimens and 5 (7%) of 66 non-diarrhea stool specimens produced RT-PCR products of expected size (319 bp for NLVs and 331 bp for SLVs). Twenty of the twenty-seven strains were cloned and sequenced. Pairwise sequence analysis showed that 9 (60%) and 6 (40%) of the 15 strains from the diarrhea stools were NLVs and SLVs, respectively. The same proportions of NLVs (60%) and SLVs (40%) were observed in the non-diarrhea stools. Strains in the NLV genus could be further divided into four clusters: Lordsdale, MxV, and HV and one potentially new cluster. Strains in the SLV genus could be divided into three clusters: Sapporo/82, Lon/92, and a potentially new cluster. Strains from the Lordsdale cluster were the most common among these children. The findings of both genera and multiple clusters of HuCVs co-circulating and the identification of new strains of HuCVs in the population justify the need for future studies of HuCVs in infants and children.

Template/primer requirements and single nucleotide incorporation by hepatitis C virus nonstructural protein 5B polymerase

Nonstructural protein 5B (NS5B) of hepatitis C virus (HCV) possesses an RNA-dependent RNA polymerase activity responsible for viral genome RNA replication. Despite several reports on the characterization of this essential viral enzyme, little is known about the reaction pathway of NS5B-catalyzed nucleotide incorporation due to the lack of a kinetic system offering efficient assembly of a catalytically competent polymerase/template/primer/nucleotide quaternary complex. In this report, specific template/primer requirements for efficient RNA synthesis by HCV NS5B were investigated. For intramolecular copy-back RNA synthesis, NS5B utilizes templates with an unstable stem-loop at the 3' terminus which exists as a single-stranded molecule in solution. A template with a stable tetraloop at the 3' terminus failed to support RNA synthesis by HCV NS5B. Based on these observations, a number of single-stranded RNA templates were synthesized and tested along with short RNA primers ranging from two to five nucleotides. It was found that HCV NS5B utilized di- or trinucleotides efficiently to initiate RNA replication. Furthermore, the polymerase, template, and primer assembled initiation-competent complexes at the 3' terminus of the template RNA where the template and primer base paired within the active site cavity of the polymerase. The minimum length of the template is five nucleotides, consistent with a structural model of the NS5B/RNA complex in which a pentanucleotide single-stranded RNA template occupies a groove located along the fingers subdomain of the polymerase. This observation suggests that the initial docking of RNA on NS5B polymerase requires a single-stranded RNA molecule. A unique beta-hairpin loop in the thumb subdomain may play an important role in properly positioning the single-stranded template for initiation of RNA synthesis. Identification of the template/primer requirements will facilitate the mechanistic characterization of HCV NS5B and its inhibitors.

[Clinical study on treatment of 40 cases of malignant brain tumor by elemene emulsion injection]

OBJECTIVE

To investigate the effect of elemene emulsion injection (EEI) in treating malignant brain tumor.

METHODS

By conducting a retrospective study of 40 patients with brain tumor, 29 of malignant glioma and 11 metastatic tumor, who were treated with EEI from January 1994 to May 1998. EEI 0.4-1.2 g/d was given to each patient by intravenous dripping or/and intravenous infusion by pumps, and directly injected into carotid artery or infused through a carotid artery catheter with pumps. The total dosage of 6-12 g was given in 2-6 therapeutic courses with an interval of 1-1.5 months between courses. The effectiveness of treatment was accessed according to the changes of tumor size, Karnofsky Performance Status (KPS) and survival time of patients. The control group consisted of 29 cases of malignant brain tumor (22 of primary and 7 of metastatic) was treated with chemotherapy 2-3 therapeutic courses with an interval of 1-1.5 months between them.

RESULTS

(1) In the EEI treated group the mean tumor size was changed from 6.70 cm3 (before treatment) to 2.67 cm3 (after treatment), t = 3.02, P < 0.01, it was reduced by 61%; (2) In the EEI treated group 4 cases was CR, 26 PR, the total effective rate being 75.0% (95% credibility interval +/- 13.4%), while in the control group, 2 of CR, 10 PR, and the total effective rate 41.4% (95% credibility interval +/- 17.9%), the difference between the two groups was significant, chi 2 = 3.867, P < 0.05; (3) KPS decreased in the EEI group from 94.7 scores (before treatment) to 88.2 scores (after treatment), the decrement was 6.5 scores (t = 3.5313, P < 0.01); (4) The survival time in the EEI treated group was 25.4 months, and that in the control group was 17.4 months (t = 3.74, P < 0.01).

CONCLUSION

Elemene has significant effect on treatment of malignant brain tumor. It could prolong the high quality survival time of patients and is worthy of further investigation.

RNA-dependent RNA polymerase activity encoded by GB virus-B non-structural protein 5B

Phylogenetic analysis and polyprotein organization comparison have shown that GB virus-B (GBV-B) is closely related to hepatitis C virus (HCV). In this study, the coding region for GBV-B non-structural protein 5B (NS5B) was isolated by reverse transcription-polymerase chain reaction (RT-PCR) from pooled serum of GBV-B-infected tamarins. Expression of soluble GBV-B NS5B protein in Escherichia coli was achieved by removal of a 19-amino acid hydrophobic domain at the C-terminus of the protein. The truncated GBV-B NS5B (NS5BDeltaCT19) was purified to homogeneity and shown to possess an RNA-dependent RNA polymerase (RdRp) activity in both gel-based and scintillation proximity assays. NS5BDeltaCT19 required the divalent cation Mn2+ for enzymatic activity, at an optimal concentration of 15 mM. Interestingly, Mg2+, at concentrations up to 20 mM, did not support the GBV-B NS5B activity. This differs from HCV NS5B where both Mn2+ and Mg2+ can support RdRp activity. Zn2+ was found to inhibit the activity of GBV-B NS5B, with a 50% inhibitory concentration (IC50) of 5-10 microM. Higher concentrations of monovalent salts (NaCl or KCl > 100 mM) and glycerol (> 3%) were also inhibitory. NS5BDeltaCT19 was able to bind to RNA homopolymers, but utilized most efficiently poly(C), the one with the lowest binding affinity for RNA synthesis. Mutational analysis of GBV-B NS5B demonstrated the importance of several conserved sequence motifs for enzymatic activity. Based on sequence homology ( approximately 37% identity and 52% similarity) between GBV-B and HCV NS5B proteins, the active GBV-B RdRp provides a good surrogate assay system for HCV polymerase studies.

Antioxidant enzyme expression and reactive oxygen species damage in prostatic intraepithelial neoplasia and cancer

BACKGROUND

Oxidative stress results in damage to cellular structures and has been linked to many diseases, including cancer. The authors sought to determine whether the expression of three major antioxidant enzymes, copper-zinc superoxide dismutase (SOD1), manganese superoxide dismutase (SOD2), and catalase, was altered in human prostate carcinoma and its likely precursor, high grade prostatic intraepithelial neoplasia (PIN). The level of reactive oxygen species damage was evaluated by measuring the expression of the DNA adduct 8-hydroxydeoxyguanosine.

METHODS

The authors evaluated the tissue expression of the antioxidant enzymes in prostate carcinoma by immunohistochemistry, immunogold electron microscopy, and enzymatic assay. The polymerase chain reaction was used to amplify and screen tissue specimens for the genes of SOD1, SOD2, and extracellular SOD (SOD3). Matched paraffin embedded tissue sections were evaluated by RNA in situ hybridization for expression of SOD1 and immunohistochemically for the DNA adduct 8-hydroxydeoxyguanosine.

RESULTS

All prostatic tissues, including cancer, displayed immunoreactivity for the three antioxidant enzymes in epithelial cells, with no staining of the stroma, inflammatory cells, or endothelial cells. The number of immunoreactive cells was greater in benign epithelium than in PIN and cancer for each enzyme. The mean percentage and intensity of immunoreactive cells was greatest for SOD2, intermediate for SOD1, and lower for catalase. Staining in cancer was heterogeneous. Immunogold ultrasound studies revealed strong mitochondrial labeling for SOD2, which was greater in benign epithelium than in cancer; SOD1 labeling was invariably weaker, with nuclear labeling in benign epithelium and cytoplasmic labeling in cancer cells. There was no difference in enzyme activity for the three antioxidant enzymes between benign epithelium and cancer. No mutations were found in the 5 exons of SOD1, 5 exons of SOD2, and 3 exons of SOD3, except for 3 of 20 cases with polymorphisms for exon 3 of SOD1. Intense nuclear immunoreactivity for 8-hydroxydeoxyguanosine was present in fewer than 3% of epithelial cells, with no apparent differences among benign epithelium, PIN, and cancer.

CONCLUSIONS

SOD1, SOD2, and catalase had lower expression in PIN and prostate carcinoma than in benign epithelium. The number of immunoreactive cells in PIN was similar to cancer, indicating that these are closely related. Enzyme activities were variable, with no difference between benign epithelial cells and cancer, although this lack of change in enzyme activity could have been due to the presence of contaminating benign cells within the cancer specimens. The results of reactive oxygen species damage were found only in the epithelium and not in the stroma. Expression of the DNA adduct 8-hydroxydeoxyguanosine was present in fewer than 3% of cells, with no apparent differences among benign epithelium, PIN, and cancer. These findings suggest that oxidative stress is an early event in carcinogenesis.

Localization of antioxidant enzymes and oxidative damage products in normal and malignant prostate epithelium

BACKGROUND

The risk for prostate cancer seems to be reduced by certain antioxidant compounds (vitamins E and A, and selenium).

METHODS

Antioxidant enzymes and oxidative damage products were localized in normal prostatic epithelium and malignant glands in primary and metastatic prostatic adenocarcinomas, using well-characterized antibodies and immunoperoxidase techniques.

RESULTS

Antioxidant enzymes and four markers of oxidative damage were compared in basal and secretory cells of normal prostatic epithelium and prostate adenocarcinoma cells, and each cell type had unique patterns of enzymes and oxidative damage products. One marker of oxidative damage, a fluorophore derived from 4-hydroxy-2-nonenal-lysine adduction, was found in secretory cells of normal but not malignant epithelium, demonstrating a different oxidative metabolism in normal vs. malignant prostate epithelium. Metastatic lesions from primary prostate cancer had higher levels of manganese superoxide dismutase and nuclear oxidative damage products than did primary tumors.

CONCLUSIONS

Antioxidant enzymes and oxidative damage products are modulated in metastatic compared to primary prostate cancer.

Generation and characterization of a hepatitis C virus NS3 protease-dependent bovine viral diarrhea virus

Unique to pestiviruses, the N-terminal protein encoded by the bovine viral diarrhea virus (BVDV) genome is a cysteine protease (Npro) responsible for a self-cleavage that releases the N terminus of the core protein (C). This unique protease is dispensable for viral replication, and its coding region can be replaced by a ubiquitin gene directly fused in frame to the core. To develop an antiviral assay that allows the assessment of anti-hepatitis C virus (HCV) NS3 protease inhibitors, a chimeric BVDV in which the coding region of Npro was replaced by that of an NS4A cofactor-tethered HCV NS3 protease domain was generated. This cofactor-tethered HCV protease domain was linked in frame to the core protein of BVDV through an HCV NS5A-NS5B junction site and mimicked the proteolytic function of Npro in the release of BVDV core for capsid assembly. A similar chimeric construct was built with an inactive HCV NS3 protease to serve as a control. Genomic RNA transcripts derived from both chimeric clones, P(H/B) (wild-type HCV NS3 protease) and P(H/B(S139A)) (mutant HCV NS3 protease) were then transfected into bovine cells (MDBK). Only the RNA transcripts from the P(H/B) clone yielded viable viruses, whereas the mutant clone, P(H/B(S139A)), failed to produce any signs of infection, suggesting that the unprocessed fusion protein rendered the BVDV core protein defective in capsid assembly. Like the wild-type BVDV (NADL), the chimeric virus was cytopathic and formed plaques on the cell monolayer. Sequence and biochemical analyses confirmed the identity of the chimeric virus and further revealed variant viruses due to growth adaptation. Growth analysis revealed comparable replication kinetics between the wild-type and the chimeric BVDVs. Finally, to assess the genetic stability of the chimeric virus, an Npro-null BVDV (BVDV-Npro in which the entire Npro coding region was deleted) was produced. Although cytopathic, BVDV-Npro was highly defective in viral replication and growth, a finding consistent with the observed stability of the chimeric virus after serial passages.

Mouse numb is an essential gene involved in cortical neurogenesis

During neurogenesis of the mammalian neocortex, neural progenitor cells divide to generate daughter cells that either become neurons or remain as progenitor cells. The mouse numb (m-numb) gene encodes a membrane-associated protein that is asymmetrically localized to the apical cell membrane of dividing cortical progenitor cells and may be segregated to only the apical daughter cell that has been suggested to remain as a progenitor cell. To examine m-numb function during neural development, we generated a loss-of-function mutant allele of m-numb. Mice homozygous for this mutation exhibit severe defects in cranial neural tube closure and precocious neuron production in the forebrain and die around embryonic day 11.5 (E11. 5). These findings suggest that m-numb is an essential gene that plays a role in promoting progenitor cell fate during cortical neurogenesis.

Virus-specific cofactor requirement and chimeric hepatitis C virus/GB virus B nonstructural protein 3

GB virus B (GBV-B) is closely related to hepatitis C virus (HCV) and causes acute hepatitis in tamarins (Saguinus species), making it an attractive surrogate virus for in vivo testing of anti-HCV inhibitors in a small monkey model. It has been reported that the nonstructural protein 3 (NS3) serine protease of GBV-B shares similar substrate specificity with its counterpart in HCV. Authentic proteolytic processing of the HCV polyprotein junctions (NS4A/4B, NS4B/5A, and NS5A/5B) can be accomplished by the GBV-B NS3 protease in an HCV NS4A cofactor-independent fashion. We further characterized the protease activity of a full-length GBV-B NS3 protein and its cofactor requirement using in vitro-translated GBV-B substrates. Cleavages at the NS4A/4B and NS5A/5B junctions were readily detectable only in the presence of a cofactor peptide derived from the central region of GBV-B NS4A. Interestingly, the GBV-B substrates could also be cleaved by the HCV NS3 protease in an HCV NS4A cofactor-dependent manner, supporting the notion that HCV and GBV-B share similar NS3 protease specificity while retaining a virus-specific cofactor requirement. This finding of a strict virus-specific cofactor requirement is consistent with the lack of sequence homology in the NS4A cofactor regions of HCV and GBV-B. The minimum cofactor region that supported GBV-B protease activity was mapped to a central region of GBV-B NS4A (between amino acids Phe22 and Val36) which overlapped with the cofactor region of HCV. Alanine substitution analysis demonstrated that two amino acids, Val27 and Trp31, were essential for the cofactor activity, a finding reminiscent of the two critical residues in the HCV NS4A cofactor, Ile25 and Ile29. A model for the GBV-B NS3 protease domain and NS4A cofactor complex revealed that GBV-B might have developed a similar structural strategy in the activation and regulation of its NS3 protease activity. Finally, a chimeric HCV/GBV-B bifunctional NS3, consisting of an N-terminal HCV protease domain and a C-terminal GBV-B RNA helicase domain, was engineered. Both enzymatic activities were retained by the chimeric protein, which could lead to the development of a chimeric GBV-B virus that depends on HCV protease function.

Regulation of phagocytic leukocyte activities by C-reactive protein

The classic acute phase reactant C-reactive protein (CRP) is classified as an effector of innate host resistance because it activates the classical complement cascade and is opsonic. The latter action occurs via specific CRP receptors (CRP-R) that have recently been identified as both FcgammaRI and FcgammaRII on human phagocytic leukocytes. New findings also suggest an anti-inflammatory role for CRP because it modulates endotoxin shock and inhibits chemotaxis and the respiratory burst of neutrophils. CRP inhibited phorbol myristate acetate-induced superoxide (O2-) production more efficiently than the fMLP-triggered response. An examination of the inhibition of the protein kinase C (PKC)-dependent assembly of the NADPH oxidase complex revealed that both phosphorylation and translocation of PKC-beta2 to the membrane were inhibited by a threshold acute phase dose of approximately 50 microg/mL CRP. Translocation to the membrane and serine-phosphorylation of the major cytosolic p47-phox component of the NADPH oxidase complex was inhibited by CRP. CRP also inhibited membrane localization of activated Rac2, the small G protein regulator of the assembly of the oxidase components in activated neutrophils as well as the cytoskeleton during chemotactic movement. CRP-mediated regulation occurs via the CRP-R because an IgM mouse mAb to the human CRP-R mimicked CRP-induced inhibition of O2- production and chemotaxis. CRP may serve as an antiinflammatory regulator of activities at sites of tissue damage where it selectively accumulates and thus influences neutrophil infiltration and polymorphonuclear neutrophil activities. By contrast, CRP activates cells of the monocyte/macrophage lineage, suggesting differential regulation of these two leukocyte populations at the level of signaling. CRP appears to be a multifunctional protein with the capability of exerting both effector functions for innate host resistance, as well as exerting specific anti-inflammatory effects.

The genome sequence of Drosophila melanogaster

The fly Drosophila melanogaster is one of the most intensively studied organisms in biology and serves as a model system for the investigation of many developmental and cellular processes common to higher eukaryotes, including humans. We have determined the nucleotide sequence of nearly all of the approximately 120-megabase euchromatic portion of the Drosophila genome using a whole-genome shotgun sequencing strategy supported by extensive clone-based sequence and a high-quality bacterial artificial chromosome physical map. Efforts are under way to close the remaining gaps; however, the sequence is of sufficient accuracy and contiguity to be declared substantially complete and to support an initial analysis of genome structure and preliminary gene annotation and interpretation. The genome encodes approximately 13,600 genes, somewhat fewer than the smaller Caenorhabditis elegans genome, but with comparable functional diversity.

CD4+ T cell priming accelerates the clearance of Sendai virus in mice, but has a negative effect on CD8+ T cell memory

Current vaccines designed to promote humoral immunity to respiratory virus infections also induce potent CD4+ T cell memory. However, little is known about the impact of primed CD4+ T cells on the immune response to heterologous viruses that are serologically distinct, but that share CD4+ T cell epitopes. In addition, the protective capacity of primed CD4+ T cells has not been fully evaluated. In the present study, we addressed these two issues using a murine Sendai virus model. Mice were primed with an HN421-436 peptide that represents the dominant CD4+ T cell epitope on the hemagglutinin-neuraminidase (HN) of Sendai virus. This vaccination strategy induced strong CD4+ T cell memory to the peptide, but did not induce Abs specific for the Sendai virus virion. Subsequent Sendai virus infection of primed mice resulted in 1) a substantially accelerated virus-specific CD4+ T cell response in the pneumonic lung; 2) enhanced primary antiviral Ab-forming cell response in the mediastinal lymph nodes; and 3) accelerated viral clearance. Interestingly, the virus-specific CD8+ T cell response in the lung and the development of long-term memory CD8+ T cells in the spleen were significantly reduced. Taken together, our data demonstrate that primed CD4+ T cells, in the absence of pre-existing Ab, can have a significant effect on the subsequent immune responses to a respiratory virus infection.

Inhibition of inositol phosphorylceramide synthase by aureobasidin A in Candida and Aspergillus species

Inositol phosphorylceramide (IPC) synthase is an enzyme common to fungi and plants that catalyzes the transfer of phosphoinositol from phosphatidylinositol to ceramide to form IPC. The reaction is a key step in fungal sphingolipid biosynthesis and the target of the antibiotics galbonolide A, aureobasidin A, and khafrefungin. As a first step toward understanding the antifungal spectrum of IPC synthase inhibitors, we examined the sensitivity of IPC synthase to aureobasidin A in membrane preparations of Candida species (Candida albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei) and Aspergillus species (Aspergillus fumigatus, A. flavus, A. niger, and A. terreus). As expected, preparations from the five Candida species, all exquisitely susceptible to aureobasidin A (MICs, <2 microgram/ml), had IPC synthase activity (specific activity, 50 to 400 pmol/min/mg of protein) sensitive to aureobasidin A (50% inhibitory concentrations [IC(50)s], 2 to 4 ng/ml). Surprisingly, preparations from the four Aspergillus species, including A. fumigatus and A. flavus, which are intrinsically resistant to aureobasidin A (MICs, >50 microgram/ml), had IPC synthase activity (specific activity, 1 to 3 pmol/min/mg of protein) also sensitive to aureobasidin A (IC(50)s, 3 to 5 ng/ml). The mammalian multidrug resistance modulators verapamil, chlorpromazine, and trifluoperazine lowered the MIC of aureobasidin A for A. fumigatus from >50 microgram/ml to 2 to 3 microgram/ml, suggesting that the resistance of this major fungal pathogen is the result of increased efflux.

[Experimental study on the influence of Gynostemma pentaphyllam Mak upon point mutation of Ha-ras oncogene in blocking leukoplakia from canceration]

OBJECTIVE

To study the influence of Gynostemma pentaphyllam Mak (GP) upon point mutation of Ha-ras oncogene the molecular mechanism of GP in blocking canceration, and the relationship between Ha-ras oncogene and canceration of leukoplakia.

METHODS

DMBA induced carcinogeneses of the buccal pouch mucosa of the hamsters were divided into leukoplakia model group(LKG) and GP treated group(GPG). Point mutation (codon 61) of Ha-ras oncogene was detected by PCR-SSCP in both groups.

RESULTS

The mutation incidence of LKG was 22.96%, while the mean incidence of GPG was 7.59% (The incidences of C20-OH group, glucoside group and aglucon group were 5.32%, 6.25% and 11.00% respectively). When treated with DMBA for 4 to 8 weeks, the mutation incidence of LKG ranged from 11.10% to 40.00%, while GPG ranged from 0 to 10.70%.

CONCLUSIONS

GP has outstanding cancer blocking effect chiefly affected by free C20-OH. Mutation of Ha-ras oncogene plays an important role in leukoplakia canceration.

De novo initiation of RNA synthesis by hepatitis C virus nonstructural protein 5B polymerase

RNA-dependent RNA polymerase (RdRp) encoded by positive-strand RNA viruses is critical to the replication of viral RNA genome. Like other positive-strand RNA viruses, replication of hepatitis C virus (HCV) RNA is mediated through a negative-strand intermediate, which is generated through copying the positive-strand genomic RNA. Although it has been demonstrated that HCV NS5B alone can direct RNA replication through a copy-back primer at the 3' end, de novo initiation of RNA synthesis is likely to be the mode of RNA replication in infected cells. In this study, we demonstrate that a recombinant HCV NS5B protein has the ability to initiate de novo RNA synthesis in vitro. The NS5B used HCV 3' X-tail RNA (98 nucleotides) as the template to synthesize an RNA product of monomer size, which can be labeled by ¿gamma-(32)Pnucleoside triphosphate. The de novo initiation activity was further confirmed by using small synthetic RNAs ending with dideoxynucleotides at the 3' termini. In addition, HCV NS5B preferred GTP as the initiation nucleotide. The optimal conditions for the de novo initiation activity have been determined. Identification and characterization of the de novo priming or initiation activity by HCV NS5B provides an opportunity to screen for inhibitors that specifically target the initiation step.

Computerized analysis of mammographic parenchymal patterns for breast cancer risk assessment: feature selection

Our purpose in this study was to identify computer-extracted, mammographic parenchymal patterns that are associated with breast cancer risk. We extracted 14 features from the central breast region on digitized mammograms to characterize the mammographic parenchymal patterns of women at different risk levels. Two different approaches were employed to relate these mammographic features to breast cancer risk. In one approach, the features were used to distinguish mammographic patterns seen in low-risk women from those who inherited a mutated form of the BRCA1/BRCA2 gene, which confers a very high risk of developing breast cancer. In another approach, the features were related to risk as determined from existing clinical models (Gail and Claus models), which use well-known epidemiological factors such as a woman's age, her family history of breast cancer, reproductive history, etc. Stepwise linear discriminant analysis was employed to identify features that were useful in differentiating between "low-risk" women and BRCA1/BRCA2-mutation carriers. Stepwise linear regression analysis was employed to identify useful features in predicting the risk, as estimated from the Gail and Claus models. Similar computer-extracted mammographic features were identified in the two approaches. Results show that women at high risk tend to have dense breasts and their mammographic patterns tend to be coarse and low in contrast.

Inhibition of yeast inositol phosphorylceramide synthase by aureobasidin A measured by a fluorometric assay

Inositol phosphorylceramide synthase (IPC synthase) is an essential and unique enzyme in fungal sphingolipid biosynthesis and is the target of the cyclic nonadepsipeptide antibiotic aureobasidin A. As a first step towards understanding the mechanism of aureobasidin A inhibition, we developed a fluorometric HPLC assay for IPC synthase using the Saccharomyces cerevisiae enzyme and the fluorescent substrate analog 6-[N-(7-nitro-2,1, 3-benzoxadiazol-4-yl)amino]-hexanoyl ceramide (C(6)-NBD-cer). The kinetic parameters for C(6)-NBD-cer were comparable to those for the synthetic substrate N-acetylsphinganine used previously. Aureobasidin A acted as a tight-binding, non-competitive inhibitor with respect to C(6)-NBD-cer and had a K(i) of 0.55 nM.

CUL-2 is required for the G1-to-S-phase transition and mitotic chromosome condensation in Caenorhabditis elegans

The human cullin protein CUL-2 functions in a ubiquitin-ligase complex with the von Hippel-Lindau (VHL) tumour suppressor protein. Here we show that, in Caenorhabditis elegans, cul-2 is expressed in proliferating cells and is required at two distinct points in the cell cycle, the G1-to-S-phase transition and mitosis. cul-2 mutant germ cells undergo a G1-phase arrest that correlates with accumulation of CKI-1, a member of the CIP/KIP family of cyclin-dependent-kinase inhibitors. In cul-2 mutant embryos, mitotic chromosomes are unable to condense, leading to unequal DNA segregation, chromosome bridging and the formation of multiple nuclei.

Loss of pathogenic potential after cloning of the low-passage Borrelia burgdorferi ZS7 tick isolate: a cautionary note

To study clonal polymorphism of Borrelia hurgdorferi antigens in the course of an experimental infection sequence, the low-passage tick isolate ZS7 was cloned by two rounds of agar subsurface plating. The resulting clones showed a variable pathogenic potential after experimental infection of C.B-17. scid mice. The test clone 4.2.II, selected for virulence by two passages in immunodeficient scid mice, failed to establish a successful infection in immunocompetent AKR/N mice, indicating the loss of pathogenicity traits required for evasion of the specific immune response. Cloning of natural or clinical B. burgdorferi isolates is a prerequisite for analyzing genetic and antigenic variation of the pathogen. However, the inevitable propagation in artificial media during cloning may lead to a loss of pathogenic features rendering the subsequent experimental infection of animals impossible. A combined procedure of in vitro cloning and in vivo selection also does not solve the dilemma because B. burgdorferi variants arise by recombinatorial processes in the pathogen's dynamic genome during the course of infection. Consequently, the resulting bacterial isolates from infected animal tissues represent again non-clonal, heterogeneous B. burgdorferi populations. In principle, cloning of a B. burgdorferi population is the appropriate method to analyze the polymorphism of individual molecules during infection. As a caveat, however, one has to envisage that during propagation of individual clones in vitro and in vivo independent genetic variations

Lyme disease: pathogenesis and vaccine development

Research of recent years on Lyme disease has greatly increased our understanding on antigenic structures and genotypic variability of the aetiological agent, Borrelia (B.) burgdorferi sensu lato, as well as on mechanisms underlying host-parasite interactions and induction/mode of action of protective immune responses. A vaccine formula on the basis of the outer surface lipoprotein A (OspA), previously developed in our laboratory, has successfully been tested in a clinical trial involving nearly 10,000 subjects in the USA. The OspA vaccine is unique in that it protects the mammalian host from infection by eliminating spirochaetes from the vector, but does not cure an established disease. This is because spirochaetes express OspA exclusively in the tick, but not when transmitted into the vertebrate host. For Europe, a more complex vaccine formula is required in order to achieve full protection. This is due to the higher degree of heterogeneity of OspA molecules among isolates of B. burgdorferi in Europe and the inability of the monovalent vaccine to convey complete cross-protection.

Expression of superoxide dismutases, catalase, and glutathione peroxidase in glioma cells

Four primary antioxidant enzymes were measured in both human and rat glioma cells. Both manganese-containing superoxide dismutase (MnSOD) and copper-zinc-containing superoxide dismutase (CuZnSOD) activities varied greatly among the different glioma cell lines. MnSOD was generally higher in human glioma cells than in rat glioma cells and relatively higher than in other tumor types. High levels of MnSOD in human glioma cells were due to the high levels of expression of MnSOD mRNA and protein. Heterogeneous expression of MnSOD was present in individual glioma cell lines and may be due to subpopulations or cells at different differentiation stages. Less difference in CuZnSOD, catalase, or glutathione peroxide was found between human and rat glioma cells. The human glioma cell lines showed large differences in sensitivity to the glutathione modulating drugs 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU) and buthionine sulfoximine (BSO). A good correlation was found between sensitivity to BCNU and the activities of catalase in these cell lines. Only one cell line was sensitive to BSO and this line had low CuZnSOD activity.

DLX-1, DLX-2, and DLX-5 expression define distinct stages of basal forebrain differentiation

The homeobox genes in the Dlx family are required for differentiation of basal forebrain neurons and craniofacial morphogenesis. Herein, we studied the expression of Dlx-1, Dlx-2, and Dlx-5 RNA and protein in the mouse forebrain from embryonic day 10.5 (E10.5) to E12.5. We provide evidence that Dlx-2 is expressed before Dlx-1, which is expressed before Dlx-5. We also demonstrate that these genes are expressed in the same cells, which may explain why single mutants of the Dlx genes have mild phenotypes. The DLX proteins are localized primarily to the nucleus, although DLX-5 also can be found in the cytoplasm. During development, the fraction of Dlx-positive cells increases in the ventricular zone. Analysis of the distribution of DLX-1 and DLX-2 in M-phase cells suggests that these proteins are distributed symmetrically to daughter cells during mitosis. We propose that DLX-negative cells in the ventricular zone are specified progressively to become DLX-2-expressing cells during neurogenesis; as these cells differentiate, they go on to express DLX-1, DLX-5, and DLX-6. This process appears to be largely the same in all regions of the forebrain that express the Dlx genes. In the basal telencephalon, these DLX-positive cells differentiate into projection neurons of the striatum and pallidum as well as interneurons, some of which migrate to the cerebral cortex and the olfactory bulb.

Computerized analysis of lesions in US images of the breast

RATIONALE AND OBJECTIVES

Breast sonography is not routinely used to distinguish benign from malignant solid masses because of considerable overlap in their sonographic appearances. The purpose of this study was to investigate the computerized analyses of breast lesions in ultrasonographic (US) images in order to ultimately aid in the task of discriminating between malignant and benign lesions.

MATERIALS AND METHODS

Features related to lesion margin, shape, homogeneity (texture), and posterior acoustic attenuation pattern in US images of the breast were extracted and calculated. The study database contained 184 digitized US images from 58 patients with 78 lesions. Benign lesions were confirmed at biopsy or cyst aspiration or with image interpretation alone; malignant lesions were confirmed at biopsy. Performance of the various individual features and output from linear discriminant analysis in distinguishing benign from malignant lesions was studied by using receiver operating characteristic (ROC) analysis.

RESULTS

At ROC analysis, the feature characterizing the margin yielded Az values (area under the ROC curve) of 0.85 and 0.75 in distinguishing between benign and malignant lesions for the entire database and for an "equivocal" database, respectively. The equivocal database contained lesions that had been proved to be benign or malignant at cyst aspiration or biopsy. Linear discriminant analysis round-robin runs yielded Az values of 0.94 and 0.87 in distinguishing benign from malignant lesions for the entire database and for the equivocal database, respectively.

CONCLUSION

Computerized analysis of US images has the potential to increase the specificity of breast sonography.

Nucleoside triphosphatase and RNA helicase activities associated with GB virus B nonstructural protein 3

GB virus B (GBV-B) is a positive-stranded RNA virus that belongs to the Flaviviridae family. This virus is closely related to hepatitis C virus (HCV) and causes acute hepatitis in tamarins (Saguinus species). Nonstructural protein 3 (NS3) of GBV-B contains sequence motifs predictive of three enzymatic activities: serine protease, nucleoside triphosphatase (NTPase), and RNA helicase. The N-terminal serine protease has been characterized and shown to share similar substrate specificity with the HCV NS3 protease. In this report, a full-length GBV-B NS3 protein was expressed in Escherichia coli and purified to homogeneity. This recombinant protein was shown to possess polynucleotide-stimulated NTPase and double-stranded RNA (dsRNA) unwinding activities. Both activities were abolished by a single amino acid substitution, from the Lys (K) residue in the conserved walker motif A (or Ia) "AXXXXGK(210)S" to an Ala (A), confirming that they are intrinsic to GBV-B NS3. Kinetic parameters (K(m) and k(cat)) for hydrolysis of various NTPs or dNTPs were obtained. The dsRNA unwinding activity depends on the presence of divalent metal ions and ATP and requires an RNA duplex substrate with 3' unpaired regions (RNAs with 5' unpaired regions only or with blunt ends are not suitable substrates for this enzyme). This indicates that GBV-B NS3 RNA helicase unwinds dsRNA in the 3' to 5' direction. Direct interaction of the GBV-B NS3 protein with a single-stranded RNA was established using a gel-based RNA bandshift assay. Finally, a homology model of GBV-B NS3 RNA helicase domain based on the 3-dimensional structure of the HCV NS3 helicase that shows a great similarity in overall structure and surface charge distribution between the two proteins was proposed.

A complex translational program generates multiple novel proteins from the latently expressed kaposin (K12) locus of Kaposi's sarcoma-associated herpesvirus

The most abundantly expressed latent transcripts encoded by the Kaposi's sarcoma (KS)-associated herpesvirus derive from the genomic region surrounding open reading frame (ORF) K12 (kaposin A). Here we show that these transcripts, initially described as limited to ORF K12 itself, more frequently encompass upstream sequences spanning two sets of 23-nucleotide GC-rich direct repeats (DRs) (DR1 and DR2). Although the DRs lack AUG codons and were previously presumed to be noncoding, a monoclonal antibody raised to infected cells detected multiple polypeptides encoded by this region. These proteins are expressed during latency and upon induction of lytic viral replication in both primary effusion lymphoma (PEL) cell lines and KS tumors. Biochemical and genetic analyses reveal that these proteins are derived from variant translational initiation at CUG codons. The predominant translation product in the PEL cell line BCBL-1 derives from the 5'-most CUG codon in the transcript, resulting in a protein (termed kaposin B) which is encoded largely by the repeats themselves and which does not include K12 sequences. Other non-AUG codons in alternate reading frames are also used at lower efficiency, including one that initiates translation of a DR-K12 fusion protein (kaposin C) that is predicted to sort to a different subcellular locale than kaposin B. Thus, the products of the K12 region, which is the most abundantly transcribed region in latency, are surprisingly complex and may encompass multiple biological functions.

[Transmission electron microscopic observations on dentin structures stained with silver]

The purpose of this study was to investigate the ultrastructure of silver deposit regions on human dentin. Three kinds of silver stained specimens were used in this study, the decalcified celloidin section stained with silver, the frozen section of decalcified tooth stained with silver, and the decalcified section of undecalcified tooth treated by the silver iontophorese method. After light microscopic observation of the specimens, these were embedded again in epoxy resin and ultra thin sections were made. Then these ultra thin sections were observed under transmission electron microscope, and the results were as follows: 1. By observing the decalcified celloidin section stained with silver, a deposition of silver particles was found on the surface and inside of the hypocalcified collagen fibrils. 2. By observing the section of decalcified tooth stained with silver, a deposition of silver particles was found on the hypercalcified collagen fibrils. According to the findings, it was concluded that the interglobular net and the dark-line of mineralized striation in dentin are hypercalcified regions. 3. By using the silver iontophorese method, large silver particles were found deposited among the hypocalcified collagen fibrils. 4. It was confirmed that the degree of mineralization of collagen fibrils in hard tissue can be estimated indirectly observing the morphological change of collagen fibrils in a decalcified section.

Autoimmune disease induced by dendritic cell immunization against leukemia

Induction of an optimal immune response will likely be a prerequisite for successful immunotherapy of human leukemias and other malignancies. Dendritic cells are highly effective at inducing an immune response to antigens to which the host is unresponsive, while transgenic expression of the costimulator molecule CD40 ligand (gp39/CD154) and the T cell growth factor interleukin 2 (IL2) are also able to augment immune responsiveness. We therefore investigated whether a combination of these two distinctive approaches to immunostimulation could safely increase the anti-tumor immune response compared to each stimulus alone. We injected BALB/CBYJ mice with syngeneic dendritic cells (DC) exposed to A20 lymphoblastic leukemia cell-derived peptides and proteins which had been acid-eluted from the cell surface. In additional mice, the pulsed DC were mixed with genetically modified syngeneic fibroblasts that were expressing CD40 ligand or secreting interleukin 2 (IL2). Three days after their third, weekly, vaccination, they were challenged with parental A20 cells. Tumor growth was suppressed by responses to pulsed DC alone (P < 0.02). This suppression was further enhanced when pulsed DC were coinjected with fibroblasts expressing CD40 ligand and IL2 (P < 0.0005 compared to DC alone) even though CD40 ligand and IL2-expressing fibroblasts alone offered no significant protection in this model. Mice receiving the full complement of immunostimulants either failed to develop visible tumors or developed small tumors which quickly necrosed and regressed, allowing the mice to become long term tumor-free survivors. Antibody mediated depletion of either CD4+ or CD8+ T-cell subset significantly reduced the level of protection afforded by the vaccination. However, it became evident that this intensive stimulation of the immune system lead not only to tumor eradication but also to destruction of cells bearing normal self antigens. Hence, 60 days after challenge with A20 cells all mice in the DC/IL2/CD40 ligand group developed a severe, systemic autoimmune disorder that resembled graft versus host disease and manifest itself by significant peripheral blood cytotoxicity against autologous fibroblasts, blood dyscrasias, gross hepatosplenomegaly, cachexia and fur loss. This phenomenon depended on CD8+ cytotoxic T lymphocytes. Our results therefore suggest that the most effective strategies of immunotherapy against leukemia may also exceed the threshold of anergic cells, leading to a loss of self tolerance to normal self-antigens and the induction of an CD8+ anti-self effector response.

Resolution of experimental and tick-borne Borrelia burgdorferi infection in mice by passive, but not active immunization using recombinant OspC

Vaccination with outer surface protein A (OspA) of Borrelia burgdorferi prevents subsequent infection and disease in both laboratory animals and humans with high efficacy. OspA-based immunity, however, does not affect established infection due to the loss of OspA expression in the vertebrate host. We show here that repeated passive transfer of mouse and/or rabbit immune sera to recombinant GST-OspC fusion protein resulted in a dose-dependent resolution (1) of fully established arthritis and carditis as well as infection in needle-challenged C.B-17 SCID and (2) of infection in both experimentally and tick-infected BALB/c mice. Unexpectedly, active immunization of disease-susceptible AKR/N mice with GST-OspC only led to prevention but not resolution of disease and infection, in spite of high serum titers of OspC-specific Ab and the expression of ospC in tissue-derived spirochetes. The data suggest that the efficacy of OspC antibody-mediated immunity depends on the immunological history of the recipient and/or environment-dependent regulation of OspC surface expression by spirochetes in vivo. The results encourage further attempts to develop therapeutic vaccination protocols against Lyme disease.