Antiviral activity of magnesium and magnesium/poly r(A-U) combinations against two RNA viruses

Magnesium (Mg2+) potentiated the anti-vesicular stomatitis virus (VSV) activity of poly r(A-U) or poly r(G-C) and the anti-HIV-1 activity of poly r(A-U). Mg2+ did not affect the anti-VSV activity of poly (rI).poly (rC), poly (dA-dT).poly (dA-dT) or poly (dG-dC).poly (dG-dC). Modulation of one or more nuclear (nucleolar) processes of the host cell may be responsible for the synergistic antiviral activity.

Boranophosphate nucleic acids--a versatile DNA backbone

Important chemical and biochemical properties of boranophosphate DNA and RNA oligonucleotides are reviewed. Stereoregular boranophosphate oligomers can be synthesized enzymatically and form stable duplexes with DNA. Fully boronated, non-stereoregular oligothymidylates, synthesized chemically, form hybrids with poly(A) that have lower melting points than oligothymidylate:poly(A), yet they nevertheless can support the RNase H mediated cleavage of RNA.

Enrichment of a precore-minus mutant of duck hepatitis B virus in experimental mixed infections

A precore-deficient mutant of duck hepatitis B virus (DHBV) produced by site-directed mutagenesis was tested for its ability to compete with wild-type virus in a mixed infection of 3-day-old ducklings. The mutation was shown to produce a cis-acting defect, resulting in a replication rate that was about one-half that of wild-type virus. Accordingly, wild-type virus was rapidly selected during the spread of infection. During the chronic phase of the infection, however, two selection patterns were seen. In 4 of 10 ducks, the wild-type virus slowly replaced the precore mutant. In another four ducks, the precore mutant virus slowly replaced the wild-type virus. In the remaining two ducklings, ratios of wild-type and precore mutant virus fluctuated, with wild-type virus slowly predominating. The replacement of wild-type virus was not due to the emergence of a rapidly replicating variant of the precore mutant, since genomes cloned from the infected ducks retained their original replication defect. Replacement of wild-type virus, however, correlated with elevated anti-core antibody titers, which continued to increase with time. The selection of a precore-negative strain of DHBV may be analogous to the selection for precore mutants of HBV during chronic hepatitis in humans.

Acute liver injury following infection with a cytopathic strain of duck hepatitis B virus

A variant avian hepadnavirus that has been shown to destroy hepatocytes in vitro was found to be cytopathic in vivo. A single amino acid change of glycine to glutamic acid at position 133 (G133E) in the preS protein of duck hepatitis B virus (DHBV) caused an increase in the intranuclear pool of viral covalently closed circular DNA (cccDNA), resulting in a transient elevation of viral replication and eventual hepatocyte destruction. In vivo viral infection with the G133E virus was compared with infection with wild-type virus over a 72-day period. Birds were inoculated with virus at day 2 post-hatch to ensure a high percentage of infected hepatocytes and potential persistence of virus. Birds infected with the G133E virus had increased periportal cellular proliferation and numerous lysed apoptotic hepatocytes following 100% infection of hepatocytes. The liver damage within G133E virus-infected birds subsided over time, resulting in mild chronic hepatitis that was similar to that observed within wild-type virus-infected birds. The subsidence of liver damage in G133E virus-infected birds coincided with a reduction of viral cccDNA to wild-type virus levels in the liver. Our study indicates that maintenance of wild-type levels of viral cccDNA promotes persistence of virus infection by establishing a noncytopathic infection.

Competition in vivo between a cytopathic variant and a wild-type duck hepatitis B virus

Several examples of human hepatitis B virus strains with enhanced replication in vitro have been described. To understand whether this characteristic could be a cause of liver disease, we have studied a variant of the closely related duck hepatitis B virus (DHBV) that had enhanced levels of cccDNA accumulation, previously shown to be cytopathic in vitro, as a model for the pathogenesis of analogous viruses in humans. In vivo liver damage caused by this variant (G133E) occurred only during the first 2 weeks p.i., after which time cccDNA levels and liver histology returned to near normal despite continued virus replication. To determine whether recovery was due to the emergence of noncytopathic revertant, we tested whether wild-type virus would have a selective advantage in competition with the cytopathic mutant in a fully infected liver. In a mixed infection of ducklings with G133E and a small amount of wild-type virus, the wild-type virus was detected as the predominant genotype after recovery of normal liver histology. Two candidate revertant viral genomes were cloned directly from the serum virus of G133E-infected birds after recovery and tested for (i) control of cccDNA levels in primary hepatocyte cultures and (ii) their ability to compete with wild-type virus in a mixed infection. At least one noncytopathic revertant was identified by these two criteria. The results support the conclusion that the recovery from liver damage in G133E-infected ducklings was due to the emergence of spontaneous noncytopathic revertants rather than to host suppression of virus cytotoxicity. The results indicate that acute liver injury may result from infection with a cytopathic hepadnavirus but that such viruses may be rapidly replaced by noncytopathic variants during persistent infection.

Infection of ducklings with virus particles containing linear double-stranded duck hepatitis B virus DNA: illegitimate replication and reversion

Double-stranded linear DNA is synthesized as a minor viral DNA species by all hepadnaviruses. In a previous study (W. Yang and J. Summers, J. Virol. 69:4029-4036, 1995) we showed that virus particles containing linear DNA of the duck hepatitis B virus (DHBV) could initiate an infection of primary duck hepatocytes. In cells infected by linear DNA containing viruses the transcriptional template, covalently closed circular DNA, was formed by circularization of linear DNA by nonhomologous recombination between the two ends. This process was shown to result in viral DNA replication through multiple generations of linear DNA intermediates, a process we called illegitimate replication. In this study we showed that viruses containing linear DHBV DNA produced by engineered insertions in the r sequence, which encodes the 5' end of the pregenome, could infect hepatocytes in vivo, and these hepatocytes proceeded to carry out illegitimate replication. Nonhomologous recombination quickly produced revertants and partial revertants in which all or part of the insertion was deleted. One such partial revertant that replicated primarily through circular DNA intermediates, but which synthesized elevated levels of linear DNA, could be sustained for several days as the predominant genotype in vivo, but this mutant was eventually displaced by variants showing full reversion to legitimate replication and that synthesized normal low levels of linear DNA. Full revertants did not necessarily contain the wild-type r sequence. The results suggest that the linear DNA produced during DHBV infection initiates cycles of illegitimate replication by generating mutants with altered r sequences. Some r sequence mutants carry out a mixture of legitimate and illegitimate replication that can contribute to elevated production of linear DNA in individual cells.

Abnormalities in the stride length-cadence relation in parkinsonian gait

The purpose of this investigation was to clarify abnormalities in the stride length-cadence relation in gait hypokinesia in Parkinson's disease (PD). A second aim was to investigate the effect of levodopa medication on the foot-step pattern. In the first experiment, 20 subjects with idiopathic PD and 20 age-, sex-, and height-matched controls performed a series of 10 m walking trials at cadence rates ranging from 40 steps/min to 180 steps/min. Cadence rates were set by an electronic metronome, and gait patterns were measured by using a footswitch stride-analyzer system. By instructing subjects to concentrate on walking in time to the metronome beat, the baseline stride length could be monitored for a range of velocities with the compensatory effects of cadence removed. Linear-regression analysis revealed that the mean slope for the regression of stride length against cadence was not different from normal in PD, although there was a statistically significant difference in mean intercept between the PD group (0.25) and the control group (0.59); [t (19) = -4.76; p = 0.0001]. The second experiment evaluated the effects of levodopa on stride-length regulation in 10 subjects with idiopathic PD on average 45 min before and after the first morning dose was administered. There was a statistically significant increase in stride length for all cadence rates from premedication to postmedication phases and the maximal stride length was achieved at higher cadence rates after medication. The slope of the regression of stride length against cadence did not alter according to medication status, although the mean intercept was significantly lower before levodopa (-0.06) compared with after levodopa (0.27); [t (9) = -3.83; p = 0.004]. These results suggest that defective scaling of stride length underlies gait disturbance in PD.

Perception-action relationships in strategic-type settings: covert and overt processes

In this paper, we present a new approach to studying the perception-action linkage in sport. The approach and the sport-specific paradigms associated with it are aimed at exploring the 'covert' processes underlying decision-making and decision alterations before and during the course of action execution. The approach introduced here is based on Coles' (1989) work applying the chronometric approach in various paradigms using warning and imperative stimuli (i.e. valid and invalid cueing). Coles also demonstrated the efficacy of the 'lateralized readiness potential' as a measure which reflects the correct and incorrect activation of motor responses (i.e. the covert processes underlying error elicitation). The chronometric approach, which takes into account the warning and imperative stimuli as well as action initiation, execution and alteration, is recommended for the study of expertise behaviour in sport. It is predicted that lateralized readiness potential patterns will differ between experts and novice performers. Several hypotheses are derived, and paradigms suggested, to explore the 'covert processes' underlying expertise in the motor domain.

College women's perceptions regarding resistance to sexual assault

College women's perceptions about resistance to sexual assault were examined. Twenty-one percent of the 334 women surveyed stated that they had been sexually assaulted. The vast majority of participants had changed their lifestyles to prevent a sexual assault. Less than 1 woman in 5 of those surveyed had taken a self-defense class. Participants believed that resisting sexual assault by a stranger with a weapon was more likely than resisting an unarmed attacker to increase their chances of being physically harmed, raped, or murdered. Twenty-two percent of the participants said they were "very likely" to resist sexual assault by a stranger with a weapon; 52% would resist a stranger without a weapon. The findings indicate the need for an increase in the number of women taking self-defense classes and a revision in women's perceptions about resisting sexual assault.

A novel transcriptional element in circular DNA monomers of the duck hepatitis B virus

We report the presence of two elements, pet and net, that are required for proper transcription of the duck hepatitis B virus (DHBV). These regions were previously identified by using plasmid clones of the virus in transient expression assays (M. Huang and J. Summers, J. Virol. 68:1564-1572, 1994). In this study, we further analyzed these regions by using in vitro-synthesized circular DHBV DNA monomers to mimic the authentic transcriptional template. We observed that pet was required for pregenome transcription from circular viral monomers, and in the absence of pet-dependent transcription, expression of the viral envelope genes was increased. We found that deletion of net in circularized DNA monomers led to the production of abnormally long transcripts due to a failure to form 3' ends during transcription. In addition, we report the presence of a net-like region in the mammalian hepadnavirus woodchuck hepatitis virus. These results are consistent with a model that net is a region involved in transcription termination and that in DHBV, pet is required for transcription complexes to read through this region during the first pass through net.

Increasing return rates to a mail survey among health educators

This study indicated a combination of methods increased the return rate (80%) in a national survey of health educators (n = 546). Also, use of a $1.00 bill incentive was not significantly more effective than no incentive, and the rate of double responses in this anonymous mail survey was very low (1%).

Indices of renal tubular function in perinatal asphyxia

AIMS

To determine and compare two urinary indices of renal tubular function, N-acetyl-glucosaminidase (NAG) and beta 2-microglobulin (beta 2 M), in healthy term neonates and babies with perinatal asphyxia.

METHODS

In a prospective case-control study using asphyxiated (n = 35) and normal control (n = 55) infants, urinary NAG and beta 2 M were assayed at 24-48 hours of life, 4-6 days, and 4-6 weeks.

RESULTS

NAG and beta 2 M were significantly increased at 24-48 hours and 4-6 days in the asphyxiated infants compared with the controls. Increased NAG values reflect the degree of perinatal asphyxia more than do beta 2 M. Gentamicin also increased NAG excretion, but to a lesser extent than did perinatal asphyxia.

CONCLUSIONS

NAG (+/- beta 2 M) may be a useful marker of perinatal asphyxia. Urinary NAG concentrations correlate with the severity of perinatal asphyxia.

Major differences between WHV and HBV in the regulation of transcription

Studies were carried out to further characterize enhancer and promoter elements on the woodchuck hepatitis virus (WHV) genome. We were able to confirm the existence of WHV promoters analogous to the major promoters of the related human hepatitis B virus (HBV) and of an enhancer analogous to the recently described WHV E2 element (Ueda, K., Wei, Y., and Ganem, D., Virology 217, 413, 1996). However, we were unable to identity an enhancer analogous to the E1 element of (HBV), despite the fact that these two viruses share a high degree of sequence homology and genetic organization. Some factor binding sites in the E1 region appeared to be conserved between the two viruses and may be required for the activity of the overlapping X gene promoter of WHV. Others did not appear to be essential for WHV X gene promoter activity, and their functional activity, if any, was not revealed. Our failure to detect a functional enhancer element in the region of WHV homologous to the HBV E1 enhancer may indicate that (i) fundamental differences exist in transcriptional regulation of the small circular genomes of WHV and HBV; (ii) WHV contains an E1 element which is functional in the context of the intact viral genome, but which is unable to function in the context of the various expression constructs used in our experiments; or (iii) correct regulation of WHV transcription via an E1 element is dependent upon transcription factors which are not expressed in the liver-specific cell lines used in our experiments.

Covalently closed circular viral DNA formed from two types of linear DNA in woodchuck hepatitis virus-infected liver

We found that livers from woodchucks chronically infected with woodchuck hepatitis virus (WHV) contained covalently closed circular DNA (cccDNA) molecules with deletions and insertions indicative of their formation from linear viral DNA by nonhomologous recombination, as we previously described for the duck hepatitis B virus (W. Yang and J. Summers, J. Virol. 69:4029-4036, 1995). However, evidence for two different types of linear precursors was obtained by analysis of the recombination joints in WHV cccDNA. Type 1 linear precursors possessed the structural properties that correspond to those of in situ-primed linear DNA molecules, which constitute between 7 and 20% of all viral DNA replicative intermediates synthesized in the liver. Type 2 linear precursors are hypothetical species of linear DNAs with a terminal duplication of the cohesive-end region, between DR1 and DR2. This type of linear DNA has not been previously described and was not detected among the DNA species present in nucleocapsids. A fraction of cccDNAs formed from both type 1 and type 2 linear DNAs are predicted to be functional for further DNA synthesis, and some evidence for the formation of two or more generations of cccDNA from linear DNA was observed.

Duration illusions in a train of visual stimuli

The first stimulus in a sequential train of identical flashes of light appears to last longer than those in the middle of the train. Four flashes (each 600 or 667 ms) were presented and the first was shortened until it appeared to have the same duration as that of the next. The duration of the first stimulus was found to be overestimated by about 50%. The illusion was unaffected by stimulus contrast, size, or interflash interval (between 100 and 600 ms). For some subjects, the last stimulus in the train also appeared to be about 50% longer than the penultimate flash. The results are discussed in terms of theories of how attention, arousal, and stimulus processing can affect duration perception. The mechanisms activated are peculiar to the visual system, since no similar illusion of duration was consistently experienced with a train of auditory tones.

Illegitimate replication of linear hepadnavirus DNA through nonhomologous recombination

Linear hepadnavirus DNA in primary hepatocyte cultures efficiently participates in intra- and intermolecular nonhomologous recombination at its ends. The products of this recombination are (i) monomeric covalently closed circular DNAs (cccDNAs) with deletions and insertions around the site of joining and (ii) oligomeric forms in which monomers are joined near the ends in random orientation. A fraction of monomeric cccDNAs can serve as intermediates in further DNA replication through at least five generations of nonhomologous recombination in a process we call illegitimate replication. We suggest that the monomeric and oligomeric linear DNAs produced by illegitimate replication may be precursors of the integrated and other high-molecular-weight hepadnaviral DNA forms seen in chronic infection.

Pseudomonas aeruginosa wound infection associated with a nursing home's whirlpool bath

Whirlpool baths are fitted with hydrojet circulation and/or air induction bubble systems. Water in a whirlpool bath, unlike a spa pool, is not filtered or chemically treated but the bath is drained and cleaned between each bather. This is, we believe, the first report of Pseudomonas aeruginosa wound infection associated with the use of a whirlpool bath in a nursing home. Microbiologically confirmed infections with P. aeruginosa of identical antibiotic sensitivity patterns arose in one week in wounds of four of 24 residents who used a whirlpool bath from which P. aeruginosa was also isolated. P. aeruginosa was not isolated from the wounds of a further seven residents who did not use the whirlpool bath. The incident control team advised that use of the whirlpool bath should be restricted to continent residents with intact skin, and that the bath should be cleaned with a degreasing agent and disinfected with hypochlorite between use by individual residents. The hazard of infection posed by whirlpool baths, particularly in nursing homes, needs to be assessed. National guidance for their cleaning, maintenance, and disinfection is required.

Psychiatric morbidity associated with acquired immune deficiency syndrome-related grief resolution

This study examined acquired immune deficiency syndrome (AIDS)-related grief resolution and psychiatric morbidity in 286 human immunodeficiency virus (HIV)-positive and HIV-negative gay men examined between 1989 and 1993 in San Diego, CA. Psychiatric morbidity, mood ratings, and bereavement assessments were obtained using the Structured Clinical Interview for DSM-III-R, Hamilton Rating Scales for Depression and Anxiety, and Texas Revised Inventory of Grief. Sixty percent of the men (N = 171) reported a loss within the previous 12 months. Eighteen percent of the bereaved met criteria for unresolved grief. No differences were evident in lifetime psychiatric disorders, yet men with unresolved grief demonstrated an elevated prevalence of current major depression and panic disorder when compared with resolved grievers. Clinician sensitivity to the grief process and its relationship to psychiatric complications is an important component of comprehensive psychiatric and medical care of men at high risk for HIV during this era of AIDS.

High school students' perceptions of nonconsensual sexual activity

A total of 588 secondary students completed a 25-item survey on perceptions regarding nonconsensual sexual activity. Subjects included an equal percentage of males and females and were predominantely White (61%), freshmen (67%), and of lower academic achievement (< 3.0 GPA = 57%). Females, African Americans, and those with low academic achievement were more likely to perceive that all or most of their same sex peers were having sex. African American students and those with low academic achievement were significantly more likely than White students and students with high academic achievement (> 3.0 GPA) to perceive that all or most of their close friends were having sex. Females were more knowledgeable of nonconsensual sexual activity than were males. Significant differences existed on attitudes and behavioral intentions by gender, race, academic achievement, and perceived sexual activity of close friends.

Construction of avian hepadnavirus variants with enhanced replication and cytopathicity in primary hepatocytes

Hepadnaviruses cause persistent noncytopathic infections of hepatocytes in humans and other animals. Virus replication depends on the pool of viral covalently closed circular DNA (cccDNA) molecules, which serve as transcriptional templates in the nuclei of infected cells. The size of this pool of cccDNA molecules is regulated by the ability of the large envelope protein of the virus to direct newly synthesized viral DNAs into a pathway for viral secretion and thereby inhibit their utilization for viral cccDNA synthesis. In this study, we showed that single amino acid changes in the large envelope protein could cause profound changes in cccDNA levels in transfected permissive cells or in infected cultured hepatocytes. While defects in cccDNA regulation were accompanied by a decrease of enveloped virus production in transfected cells, primary hepatocytes infected by such mutant viruses transiently produced wild-type or higher levels of enveloped virus. Moreover, high levels of cccDNA were always associated with cytopathic effects in the infected hepatocytes. The results demonstrate that the large envelope protein promotes persistent noncytopathic infection of hepatocytes by acting as an overall repressor of virus replication.

Analysis of the binding of a host cell surface glycoprotein to the preS protein of duck hepatitis B virus

We have previously identified a 180-kDa host cell glycoprotein (gp180) that specifically binds the surface envelope of duck hepatitis B virus (DHBV) and whose binding is inhibited by neutralizing antiviral monoclonal antibodies. Here we map the viral determinants required for gp180 binding to a 66-amino acid region within the preS domain of the envelope coding region. This region includes both major neutralizing preS epitopes previously defined by monoclonal antibodies. Examination of a series of linker-substitution mutations throughout preS indicates that all mutations that block gp180 binding ablate virus infectivity. Interestingly, two mutations that do not prevent binding can also impair infectivity.

Multiple functions of capsid protein phosphorylation in duck hepatitis B virus replication

We have investigated the role of phosphorylation of the capsid protein of the avian hepadnavirus duck hepatitis B virus in viral replication. We found previously that three serines and one threonine in the C-terminal 24 amino acids of the capsid protein serve as phosphorylation sites and that the pattern of phosphorylation at these sites in intracellular viral capsids is complex. In this study, we present evidence that the phosphorylation state of three of these residues affects distinct steps in viral replication. By substituting these residues with alanine in order to mimic serine, or with aspartic acid in order to mimic phosphoserine, and assaying the effects of these substitutions on various steps in virus replication, we were able to make the following inferences. (i) The presence of phosphoserines at residues 245 and 259 stimulates DNA synthesis within viral nucleocapsids. (ii) The absence of phosphoserine at residue 257 and at residues 257 and 259 stimulates covalently closed circular DNA synthesis and virus production, respectively. (iii) The presence of phosphoserine at position 259 is required for initiation of infection. The results implied that both phosphorylated and nonphosphorylated capsid proteins were necessary for a nucleocapsid particle to carry out all its functions in virus replication, explaining why differential phosphorylation of the capsid protein occurs in hepadnaviruses. Whether these differentially phosphorylated proteins coexist on the same nucleocapsid, or whether the nucleocapsid acquires sequential functions through selective phosphorylation and dephosphorylation, is discussed.

Coordinate regulation of replication and virus assembly by the large envelope protein of an avian hepadnavirus

We have used linker scanning and site-directed mutagenesis in an attempt to distinguish among the known functions of the duck hepatitis B virus large envelope protein, p36. We found that linker-encoded amino acid substitutions in at least one region of the pre-S envelope protein p36 produced defects in both the production of enveloped virus and the regulation of covalently closed circular DNA (cccDNA) synthesis. Most linker substitutions, typically in the 5' two-thirds of the pre-S region of the p36 gene did not affect either cccDNA regulation or enveloped virus production but did destroy the infection competence of the enveloped particles produced. Single amino acid substitutions of residues 128 and 131 demonstrated a similar correlation between defects in the ability of p36 to support enveloped virus production and to control cccDNA levels. We concluded from these studies that virus production and cccDNA regulation probably require a common activity of p36.

Ethical issues in healthcare reform: the experts and the public compared

Those of us in the healthcare industry have done a good job in demonstrating the value of our services in relationship to other activities government might undertake. We have done less well in recognizing the demands of individuals to make decisions about their own lives and the healthcare benefits they want. We continue to believe we know best, even to the point that we distrust the public to make appropriate decisions on their own behalf. A major part of freedom is the opportunity to learn from mistakes. When professionals restrict our freedom to choose, we all lose important rights. As the various bills make their way through Congress, we should look beyond our healthcare blinders and see that the public will reject industry-driven plans with almost the same level of suspicion given to the government and business.

Phosphorylation of the duck hepatitis B virus capsid protein associated with conformational changes in the C terminus

The capsid protein of duck hepatitis B virus (DHBV) is phosphorylated at multiple sites during viral infection. A cluster of sites is located near the C terminus of the 262-amino-acid protein. We have used site-directed mutagenesis to show that three serines and one threonine serve as phosphate acceptor amino acids in the C terminus. An additional six potential phosphate acceptor sites in this region were apparently not utilized. Each serine or threonine that served as a phosphate acceptor was adjacent to a downstream proline, while all six serines that were not acceptors for phosphate residues lacked adjacent downstream prolines. Mutation of the downstream proline to glycine at each site had the same effect as mutating the serine itself, suggesting an SP or TP motif as an essential feature for capsid protein phosphorylation. Phosphorylation at these four sites resulted in complex shifts in electrophoretic mobility in sodium dodecyl sulfate gels of the capsid protein or of a C-terminal peptide containing the phosphorylated sites, suggesting that specific conformations of the C terminus are associated with different combinations of phosphorylated serines. We speculate that distinct functions of the C terminus may be associated with different phosphorylated domains on the intact capsid.

Two regions of an avian hepadnavirus RNA pregenome are required in cis for encapsidation

We have constructed a series of deletion mutants spanning the genome of duck hepatitis B virus in order to determine which regions of the viral genome are required in cis for packaging of the pregenome into capsid particles. Deletion of sequences within either of two nonadjacent regions prevented replication of the mutant viral genomes expressed in a permissive avian hepatoma cell line in the presence of functionally active viral core and P proteins. Extraction of RNA from cells transfected with these replication-defective mutants showed that the mutants retained the capacity to be transcribed into a pregenomic-size viral RNA, but that these RNA species were not packaged into viral capsids. The two regions defined by these deletions are located 36 to 126 (region I) and 1046 to 1214 (region II) nucleotides downstream of the 5' end of the pregenome and contain sequences which are required in cis for encapsidation of the duck hepatitis B virus pregenome.

pet, a small sequence distal to the pregenome cap site, is required for expression of the duck hepatitis B virus pregenome

We have found that transcription of the pregenome of an avian hepadnavirus, duck hepatitis B virus (DHBV), is dependent on the presence of a small element in the 5' transcribed region of the pregenome-encoding sequence. This element, which we have named pet (positive effector of transcription), exerts its effect in cis in a position and orientation-dependent manner, suggesting that it may function as part of the nascent pregenome transcript. The requirement for pet depends on the presence in the transcription unit of a region of the DHBV genome located upstream of the envelope promoters, which specifically suppresses transcription of templates lacking pet. In the presence of this region, deletion of pet activates transcription from downstream promoters, suggesting that pregenome transcription complexes fail to reach the downstream promoters. In vitro transcription experiments support the model that pet is required for transcription elongation on the DHBV template. We speculate that pet is required to suppress transcription termination during the first passage of pregenome transcription complexes through a viral termination region on the circular viral DNA.

Ethical issues in intelligence gathering

Unless healthcare reform changes circumstances dramatically, you will feel some pressure to know and report the activities of your competitors. This is especially true for materiel managers because of the sheer number of contacts they have.

Role stress among physician executives

On the one hand, physician executives are clinicians who place value on professional autonomy. As clinicians, the best interests of the patient drive their decision making and their value system. On the other hand, as managers, physician executives serve as agents of an organization. Because of the differences in the two cultures, some physicians have called the physician executive position a "no man's land" To address these issues and answer the questions that surround them, the authors developed a survey that was mailed to a random sample of the membership of the American College of Physician Executives. Parts of the survey served in other studies of role conflict and role ambiguity. Parts of the survey are new, developed specifically to analyze the physician executive role. The findings are reported in this article.

Audit reduces the reluctance to use single fractions for painful bone metastases

We have conducted three audits of the number of fractions used within our department to treat symptomatic bone metastases. The initial audit identified 133 patients treated for bone metastases in a 3-month period using 538 fractions (mean number of fraction = 4.1, range 1-14). These figures were presented at our audit meeting along with a literature review which provided no evidence of any advantage of multiple fractions over single fractions. Departmental guidelines recommending the use of single fractions were established. A subsequent audit identified 149 patients treated with 520 fractions (mean number of fractions = 3.5, range 1-11). A third audit identified 148 patients treated with 335 fractions (mean number of fractions = 2.3, range 1-10). Audit has resulted in a reduction in the number of fractions used to treat bone metastases in our department. The major effect was seen after the second audit.

Replication of DHBV genomes with mutations at the sites of initiation of minus- and plus-strand DNA synthesis

We have examined the consequences on duck hepatitis B virus DNA synthesis of deleting the 5' and 3' copies of the 12 base sequence, DR1, from the viral pregenome. With the wild-type virus, reverse transcription initiates at nt 2537 within the 3' copy of DR1. When this sequence was deleted, initiation of reverse transcription was found at two other sites located closer to the 3' end of the pregenome (nt 2576 and nt 2644). The 3-base motif UUA was the only sequence common to these sites as well as the wild-type initiation site in DR1. Deletion of the 5' copy of DR1 did not alter minus strand synthesis, but led to aberrant priming of plus strand synthesis to generate predominantly linear rather than relaxed circular, double-stranded viral DNA, in agreement with the recent report by Loeb et al. (EMBO J. 10, 3533-3540, 1991). A mutant lacking only the 3' copy of DR1 rapidly converted to wild type in transfected cells. This apparently occurred as a consequence of conversion of newly synthesized relaxed circular to covalently closed circular (CCC) DNA, which might then serve as a template for the synthesis of wild-type viral RNAs. A mutant lacking only the 5' copy of DR1 did not exhibit this behavior. These results support the conclusion that amplified CCC DNA serves as transcriptional template.

Infection initiated by the RNA pregenome of a DNA virus

We describe experiments demonstrating that after transfection into permissive cells, the RNA pregenome of an avian hepadnavirus, the duck hepatitis B virus, is infectious. Using a Sindbis virus expression vector, we showed that cytoplasmic synthesis of the pregenome resulted in hepadnaviral DNA synthesis. Moreover, complete infectious virus was produced from cells transfected with hepadnaviral pregenomic RNA. We conclude that the pregenome of hepadnaviruses can express all the proteins required for DNA synthesis as well as serve as a template for reverse transcription and that DNA resulting from pregenome expression can be utilized to establish a productive infection in pregenome-transfected cells.

A domain of the hepadnavirus capsid protein is specifically required for DNA maturation and virus assembly

Mutations introduced into the capsid gene of duck hepatitis B virus (DHBV) were tested for their effects on viral DNA synthesis and assembly of enveloped viruses. Four classes of mutant phenotypes were observed among a series of deletions of covering the 3' end of the capsid open reading frame. Class I mutant capsids were able to support normal single-stranded and relaxed circular viral DNA synthesis; class II mutant capsids supported normal single-stranded DNA synthesis but not relaxed circular DNA synthesis; class III mutant capsids resembled class II capsids, but viral DNA synthesis was inhibited 5- to 10-fold; and class IV capsids were severely restricted in their ability to support viral DNA synthesis. Class I capsids were assembled into enveloped virions, but class II, III, and IV capsids were not. Viral DNA synthesized inside class II capsids was normal with respect to minus-strand DNA initiation, plus-strand DNA initiation, and circularization of the DNA, but plus strands failed to be elongated to mature 3-kb DNA. The results suggest that a function of the capsid protein specifically required for viral DNA maturation is also required for assembly of nucleocapsids into envelopes. Thus, class II mutants appear to be defective in the appearance of the "packaging signal" for virus assembly (J. Summers and W. Mason, Cell 29:403-415, 1982).

Asset disposal: follow company policies or follow the law?

Several ethical issues can arise in disposing of assets. The proper management of these issues involves awareness of the applicable laws and development of policies and enforcement that respect those laws. Several examples of appropriate policy, following classical management principles, served to document the points under discussion.