Precision measurement of the neutral pion lifetime.

The explicit breaking of the axial symmetry by quantum fluctuations gives rise to the so-called axial anomaly. This phenomenon is solely responsible for the decay of the neutral pion π0 into two photons (γγ), leading to its unusually short lifetime. We precisely measured the decay width Γ of the [Formula: see text] process. The differential cross sections for π0 photoproduction at forward angles were measured on two targets, carbon-12 and silicon-28, yielding [Formula: see text], where stat. denotes the statistical uncertainty and syst. the systematic uncertainty. We combined the results of this and an earlier experiment to generate a weighted average of [Formula: see text] Our final result has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in quantum chromodynamics.

Cellular transformation by human papillomavirus DNA in vitro.

Molecularly cloned DNA's of human papillomaviruses HPV-5 and HPV-l induced morphological transformation of mouse C127 cells in culture. Single-cell clones of cells transformed by papillomavirus contained multiple persistent episomal copies of the transfected DNA species and were analyzed for growth characteristics indicating malignant potential.

Immunological responses in human papillomavirus 16 E6/E7-transgenic mice to E7 protein correlate with the presence of skin disease.

The human papillomavirus (HPV) oncogenes, E6 and E7, are believed to contribute to the development of cervical cancers in women infected with certain HPV genotypes, most notably HPV-16 and HPV-18. Given their expression in tumor tissue, E6 and E7 have been implicated as potential tumor-specific antigens. We have examined an HPV-16 E6- and E7-transgenic mouse lineage for immune responses to these viral oncoproteins. Mice in this lineage express the HPV-16 E6 and E7 genes in their skin and eyes, and on aging, these mice frequently develop squamous cell carcinomas and lenticular tumors. Young transgenic mice, which had measurable E7 protein in the eye but not in the skin, were immunologically naive to E7 protein. They mounted an immune response to E7 on immunization comparable to that of nontransgenic controls, suggesting a lack of immune tolerance to this protein. Older line 19 mice, which are susceptible to skin disease associated with transcription of the E6 and E7 open reading frames, had measurable E7 protein in their skin. These older transgenic mice spontaneously developed antibody responses to endogenous E7 protein, particularly in association with skin disease. Also detected in older mice were delayed-type hypersensitivity responses to E7. These finding parallel the humoral immune response to E7 protein in patients with HPV-associated cervical cancer and suggest that line 19 mice may provide a model for studying the immunobiology of HPV-associated cancers.

The human papillomavirus E7 protein as a transforming and transactivating factor.

The HPV proteins encoded by the early viral genes, including E6 and E7, are thought to subvert the normal regulatory pathways of infected cells to accommodate viral replication. Mechanistically some of this is accomplished by protein-protein interactions between viral proteins and a number of key cellular regulatory proteins that include tumor suppressor gene products. By undermining cellular regulatory pathways the HPV oncogenes cause hyperproliferation and the perturbation of normal cellular differentiation pathways. Although expression of the high-risk HPV-encoded E6 and E7 oncoproteins may be important prerequisites for cellular transformation, it is very likely that additional cellular changes are necessary for carcinogenic progression. The elucidation of the role of the early HPV genes in the initiation and/or maintenance of carcinogenic progression will continue to be a fascinating area of investigation and may reveal new opportunities for antiviral therapy and antitumor intervention.

Searching for antiviral drugs for human papillomaviruses.

The human papillomaviruses (HPVs) are ubiquitous human pathogens that cause a wide variety of benign and pre-malignant epithelial tumours. Of the almost 100 different types of HPV that have been characterized to date, approximately two dozen specifically infect genital and oral mucosa. Mucosal HPVs are most frequently sexually transmitted and, with an incidence roughly twice that of herpes simplex virus infection, are considered one of the most common sexually transmitted diseases throughout the world. A subset of genital HPVs, termed 'high-risk' HPVs, is highly associated with the development of genital cancers including cervical carcinoma. The absence of a simple monolayer cell culture system for analysis and propagation of the virus has substantially retarded progress in the development of diagnostic and therapeutic strategies for HPV infection. In spite of these difficulties, great progress has been made in the elucidation of the molecular controls of virus gene expression, replication and pathogenesis. With this knowledge and some important new tools, there is great potential for the development of improved diagnostic and prognostic tests, prophylactic and therapeutic vaccines, and traditional antiviral medicines.

Transmission of human genital papillomavirus disease: comparison of data from adults and children.

A substantial body of evidence has demonstrated that the primary means of transmission of genital warts in sexually active adults is through sexual contact. However, the epidemiology and social significance of anal-genital warts in prepubertal children is controversial. Debate continues regarding the frequency with which these lesions have resulted from sexual abuse or transmission by other means. An accurate understanding of the dominant means of transmission of anal-genital warts in children is of particular importance because that understanding influences the extent to which child protective services may become involved following a diagnosis. This paper reviews the evolution of the data on the means of transmission of human papilloma virus disease of the genital tract of adults and compares those data with the information available concerning the transmission of anal-genital human papillomavirus-related disease in children. Methods for the diagnosis of child sexual abuse that have developed in the past decade form one of the bases for the evaluation of studies of the transmission of anal-genital human papillomavirus-related diseases to children.

Recent advances in diagnosis and therapy of human papillomaviruses.

Infection with human papillomavirus is extremely common throughout the world. Almost 50% of sexually active young women are infected with human papillomavirus and although most infections are transient, a subset has the potential to progress to invasive cancer. During the last 20 years, our understanding of the human papillomavirus life cycle and the role of human papillomavirus in human cancer has dramatically increased. Recent technological advances in human papillomavirus detection have provided the means to detect the presence of human papillomavirus with great sensitivity. In the context of patient care, there is still substantial debate regarding the optimal diagnostic and prognostic use of information derived from hybrid capture or polymerase chain reaction-based detection. The inventory of available treatment options is growing somewhat slowly. The most promising advances are being made in the clinical evaluation of candidates for prophylactic vaccination. This review is focused on the current status and future directions of prevention, diagnosis and therapy.

Therapeutic evaluation of compounds in the SCID-RA papillomavirus model.

A previous study by Kreider (Kreider et al., 1979) indicated that rabbit skin, which had been transplanted to immunodeficient nude mice, could be successfully infected with cottontail rabbit papillomavirus (CRPV). We have extended this observation in developing a rodent model for evaluation of compounds for activity against the papillomaviruses. In this model (called the SCID-Ra model), rabbit ear skin is transplanted to the dorsum of SCID mice and allowed to heal for 3 weeks. Infection with CRPV by scarification leads to the growth of warty lesions within 2 3 weeks in >95% of the animals. Topical and/or systemic therapy can be initiated at various times post infection (PI). Weekly lesion scores are recorded and compounds are evaluated for their ability to suppress wart growth when compared to untreated control mice. Ribavirin, which has had a suppressive effect both in the clinic for the treatment of respiratory papillomatosis and on the growth of warts in the rabbit back model, was evaluated and showed significant anti-proliferative activity with oral dosing. Both antiviral and antiproliferative compounds including podophyllin and 5-fluorouracil, which have been used clinically for the treatment of human papillomavirus (HPV) infections, were evaluated in this model. The anti-mitotic compound, Navelbine (vinorelbine tartrate), which is used for the treatment of non-small cell lung carcinoma was evaluated in this system and showed significant inhibition of wart growth with somewhat less topical cytotoxicity when compared to podophyllotoxin.

Molecular targets for human papillomaviruses: prospects for antiviral therapy.

A substantial medical need exists for the development of antiviral medicines for the treatment of diseases associated with infection by human papillomaviruses (HPVs). HPVs are associated with various benign and malignant lesions including benign genital condyloma, common skin warts, laryngeal papillomas and anogenital cancer. Since treatment options are limited and typically not very satisfactory, the development of safe and effective antiviral drugs for HPV could have substantial clinical impact. In the last few years, exciting advances have been made in our understanding of papillomavirus replication and the effects that the virus has on growth of the host cell. Although still somewhat rudimentary, techniques have been developed for limited virion production in vitro offering the promise of more rapid advances in the dissection and understanding of the virus life cycle. Of the 8-10 HPV gene products that are made during infection, only one encodes enzymatic activities, the E1 helicase. Successful antiviral therapies have traditionally targeted viral enzymes such as polymerases, kinases and proteases. In contrast, macromolecular interactions which mediate the functions of E6, E7 and E2 are thought to be more difficult targets for small molecule therapy.

Effect of supplemental iron on finishing swine performance, carcass characteristics, and pork quality during retail display.

Crossbred pigs (n = 185) were used to test the effects of dietary Fe supplementation on performance and carcass characteristics of growing-finishing swine. Pigs were blocked by BW, allotted to pens (5 to 6 pigs/pen), and pens (5 pens/block) were allotted randomly to either negative control (NC) corn-soybean meal grower and finisher diets devoid of Fe in the mineral premix, positive control (PC) corn-soybean meal grower and finisher diets with Fe included in the mineral premix, or the PC diets supplemented with 50, 100, or 150 ppm Fe from Availa-Fe (an Fe-AA complex). When the lightest block averaged 118.2 kg, the pigs were slaughtered, and bone-in pork loins were collected during fabrication for pork quality data. During the grower-I phase, there was a tendency for supplemental Fe to reduce ADG linearly (P = 0.10), whereas in the grower-II phase, supplemental Fe tended to increase ADG linearly (P = 0.10). Even though pigs fed NC had greater G:F during the finisher-I phase (P < 0.05) and across the entire trial (P = 0.07), live performance did not (P > or = 0.13) differ among dietary treatments. There were linear increases in 10th-rib fat depth (P = 0.08) and calculated fat-free lean yield (P = 0.06); otherwise, dietary Fe did not (P > 0.19) affect pork carcass muscling or fatness. Moreover, LM concentrations of total, heme, and nonheme Fe were similar (P > 0.23) among treatments. A randomly selected subset of loins from each treatment was further fabricated into 2.5-cm-thick LM chops, placed on styrofoam trays, overwrapped with polyvinyl chloride film, and placed in coffin-chest display cases (2.6 degrees C) under continuous fluorescent lighting (1,600 lx) for 7 d. During display, chops from NC-fed pigs and pigs fed the diets supplemented with 100 ppm Fe tended to have a more vivid (higher chroma value; P = 0.07), redder (higher a* value; P = 0.09) color than LM chops of pigs fed 50 ppm of supplemental Fe. Moreover, greater (P < 0.01) redness:yellowness ratios in chops from pigs supplemented with 100 ppm Fe indicated a more red color than chops from PC-fed pigs or pigs fed diets supplemented with 50 ppm Fe. In conclusion, however, increasing dietary Fe had no appreciable effects on performance, carcass, or LM characteristics, suggesting that current dietary Fe recommendations are sufficient for optimal growth performance, pork carcass composition, and pork quality.

Transcriptional trans-activation by the human papillomavirus type 16 E2 gene product.

We identified a conditional transcriptional enhancer in the long control region (LCR) of human papillomavirus type 16 (HPV-16). This conditional enhancer requires activation in trans by a product of the viral early-region open reading frames (ORFs). Primer extension analysis of chloramphenicol acetyltransferase RNA isolated from transiently transfected CV-1 cells demonstrated that trans-activation of the HPV-16 LCR enhancer operated at the transcriptional level. Mutational analysis of the early ORFs demonstrated that the conditional enhancer of the LCR was trans-activated by the product of the E2 ORF. The E2 gene product of bovine papillomavirus type 1, which can trans-activate the conditional enhancer in the bovine papillomavirus type 1 LCR, was also capable of trans-activating the E2-responsive enhancer of HPV-16. The activity of the HPV-16 LCR enhancer was also assayed in two human cervical carcinoma cell lines, HeLa and SiHa, which harbor transcriptionally active, integrated HPV-18 and HPV-16 DNA sequences, respectively. No endogenous E2 or E2-like activity was detected in either cell line.

Antiviral therapy for human papillomaviruses: rational and prospects.

OBJECTIVE: To review the basic virology of human papillomavirus (HPV) and the natural history of HPV infection and to discuss current and potential therapies. DATA SOURCES: The MEDLINE database (1966 to 1994) was searched to identify English-language articles and abstracts on HPV biology and antiviral chemotherapy. STUDY SELECTION: Peer-reviewed basic science and clinical research studies on the molecular, cellular, and human biology of HPV infection. DATA EXTRACTION: Summaries of data from research studies on the biology of papillomavirus infection and information from review articles on the basic and applied pharmacology of antiviral agents. DATA SYNTHESIS: Papillomavirus infections are very common. Human papillomavirus infections may be asymptomatic or may be manifested in various benign or malignant lesions, most notably anogenital condyloma and anogenital carcinoma. Currently, therapeutic options for HPV infection are limited, expensive, and often ineffective. By understanding the basic virology and natural history of HPV infection, potential sites for pharmacologic intervention can be identified. Although currently available antiviral compounds are inactive against HPV, they serve as models for the rational design of HPV antiviral drugs. CONCLUSIONS: Although HPV infection causes substantial morbidity and expense, uniformly effective therapy for HPV infection is not currently available. Several processes in the HPV infection cycle are appropriate targets for the development of antiviral agents. The development of compounds active against HPV could prevent the benign and malignant diseases associated with HPV infection.

A fluorescence anisotropy study of DNA binding by HPV-11 E2C protein: a hierarchy of E2-binding sites.

Association of the human papillomavirus (HPV) E2 protein with its palindromic DNA-binding site is a necessary step for transcriptional trans-activation. To study the interaction between DNA and E2, the carboxyl-terminal domain of HPV-11 E2 protein (E2C) was expressed in Escherichia coli and purified to homogeneity. The binding affinity of the recombinant E2C protein for a single palindromic DNA recognition site was determined using a 5'-fluorescein-labeled 24 base pair oligonucleotide. Competitive titrations between the fluorescein-labeled oligonucleotide and an unlabeled oligonucleotide of identical sequence yielded a native affinity of 4.5 x 10(-9)M. Sequences from the seven E2-binding sites within the HPV-11 genome were titrated to establish a hierarchy of binding site affinities. All high-affinity E2-binding sites are located within or near the HPV-11 LCR. E2-binding sites distant from the LCR appear to have low affinity for E2. When the location and affinity of each E2-binding site are plotted in relation to a transcription map of HPV-11, it is apparent that the major RNA transcripts produced reflect the high-affinity E2-binding sites within the HPV LCR. To assess the E2C-binding contribution of specific base pairs within the oligonucleotide palindrome, additional double-stranded oligonucleotides were prepared in which the central nonpalindromic sequences were varied. While simple strand transposition of the A4.T4 center had a minimal effect upon the E2C-oligonucleotide binding affinity, replacement with TATA.ATAT or CGCG.GCGC centers substantially decreased the affinity of E2C for its binding site. Alteration of the canonical portions of the E2-binding palindrome reduced the DNA-protein binding affinity dramatically.

Analysis of the thymidine kinase genes from acyclovir-resistant mutants of varicella-zoster virus isolated from patients with AIDS.

Patients with AIDS often experience recurrent infections with varicella-zoster virus (VZV) requiring repeated or prolonged treatment with acyclovir (ACV), which may lead to the development of ACV resistance. The ACV resistance of isolates recovered from such patients is associated with diminished VZV thymidine kinase (TK) function. We determined the nucleotide sequences of the TK genes of 12 ACV-resistant VZV strains purified from nine patients with AIDS. Five VZV strains contained nucleotide deletions in their TK genes, introducing a premature termination codon which is expected to result in the production of a truncated protein. No detectable full-length TK protein could be immunoprecipitated from extracts of cells infected with these virus strains. These TK-deficient strains were cross resistant to the TK-dependent antiviral agents ACV, 9-(4-hydroxy-3-hydroxymethylbutyl-yl)guanine (penciclovir), and 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl) uracil (BVaraU). The remaining seven strains each contained a nucleotide change that resulted in an amino acid substitution in the TK protein. These substitutions occurred throughout the TK protein, namely, in the ATP-binding site, the nucleoside-binding site, between the two binding sites, and at the carboxy terminus of the protein. We determined the effects of these mutations on the stability of TK protein expression in virus-infected cells and on the sensitivity of mutants to the TK-dependent antiviral agents ACV, BVaraU, and penciclovir.