Comparing Charge Transport in Oligonucleotides: RNA:DNA Hybrids and DNA Duplexes.

Understanding the electronic properties of oligonucleotide systems is important for applications in nanotechnology, biology, and sensing systems. Here the charge-transport properties of guanine-rich RNA:DNA hybrids are compared to double-stranded DNA (dsDNA) duplexes with identical sequences. The conductance of the RNA:DNA hybrids is ∼10 times higher than the equivalent dsDNA, and conformational differences are determined to be the primary reason for this difference.

The Type II Secreted Lipase/Esterase LesA is a Key Virulence Factor Required for Xylella fastidiosa Pathogenesis in Grapevines.

Pierce's disease (PD) of grapevines is caused by Xylella fastidiosa (Xf), a xylem-limited gamma-proteobacterium that is responsible for several economically important crop diseases. The occlusion of xylem elements and interference with water transport by Xf and its associated biofilm have been posited as the main cause of PD symptom development; however, Xf virulence mechanisms have not been described. Analysis of the Xf secretome revealed a putative lipase/esterase (LesA) that was abundantly secreted in bacterial culture supernatant and was characterized as a protein ortholog of the cell wall-degrading enzyme LipA of Xanthomonas strains.

An engineered innate immune defense protects grapevines from Pierce disease.

We postulated that a synergistic combination of two innate immune functions, pathogen surface recognition and lysis, in a protein chimera would lead to a robust class of engineered antimicrobial therapeutics for protection against pathogens. In support of our hypothesis, we have engineered such a chimera to protect against the gram-negative Xylella fastidiosa (Xf), which causes diseases in multiple plants of economic importance. Here we report the design and delivery of this chimera to target the Xf subspecies fastidiosa (Xff), which causes Pierce disease in grapevines and poses a great threat to the wine-growing regions of California.

Participation of the Cowpea mosaic virus protease in eliciting extreme resistance.

Extreme resistance of Arlington line cowpea (Vigna unguiculata) to Cowpea mosaic virus (CPMV) is under control of a dominant locus designated Cpa. We transiently expressed, using Tomato bushy stunt virus (TBSV) vectors and Agrobacterium tumefaciens, in nearly isogenic Cpa/Cpa and cpa/cpa cowpea lines, sequences from RNA1, the larger of two CPMV genomic RNAs. Activation of a Cpa-specific response mapped to the CPMV 24K protease (24KPro).

Identification of a novel structural interaction in Columnea latent viroid.

Pairwise sequence comparisons suggest that Columnea latent viroid (CLVd) may have originated from a recombination event involving Potato spindle tuber viroid (PSTVd) and Hop stunt viroid (HSVd). To examine the role of specific structural features in determining the host range of CLVd, we constructed a series of interspecific chimeras by replacing increasing portions of its terminal left and pathogenicity domains with the corresponding portions of PSTVd. Exchanges involving the left side of the pathogenicity domain led to lower rates of progeny accumulation in tomato, but one of the resulting chimeras was still able to replicate in cucumber.

Health care factors related to stage at diagnosis and survival among Medicare patients with colorectal cancer.

Background: With the growth in enrollment of Medicare patients in HMOs the effectiveness of care received by Medicare/HMO patients continues to be of concern. By considering the relationship of insurance to stage at diagnosis, this study inquires whether HMOs emphasize early diagnosis of colorectal cancer to a greater extent than FFS plans, if particular HMO types (group/nongroup models) are more successful in doing so, and how this pertains to survival.

Methods: Data for 1329 Medicare patients with colorectal cancer, diagnosed 1987 to 1993, and residing in northern California, were acquired from a population-based cancer registry.

Switching costs, price sensitivity and health plan choice.

We investigate the extent to which sensitivity to health plan premiums differs across individuals according to characteristics related to the cost of switching plans. Our results indicate substantial variation in price sensitivity related to expected health care costs: younger, healthier employees are between two and four times more sensitive to price than employees who are older and who have been recently hospitalized or diagnosed with cancer. We also find evidence of status quo bias: estimated premium elasticities are significantly higher for new hires than for incumbent employees.

Breast cancer outcomes among older women: HMO, fee-for-service, and delivery system comparisons.

Objective: To analyze the relationship of health insurance status and delivery systems to breast cancer outcomes--stage at diagnosis, treatment selected, survival--focusing on comparisons among women aged 65 or more having Medicare alone, Medicare/Medicaid, or Medicare with group model HMO, non-group model HMO, or private fee-for-service (FFS) supplement.

Design: Retrospectively defined cohort from Sacramento, Calif, regional cancer registry.

Setting: Thirteen-county region in northern California with mature managed care market.

The relationship of HMOs, health insurance, and delivery systems to breast cancer outcomes.

Background: The current climate of anger and frustration with managed care has heightened interest in the quality of health care provided by managed-care plans, particularly health maintenance organizations (HMOs). This breast cancer outcomes study, investigating relationships of health insurance and delivery systems to stage at diagnosis, treatment selected, and survival, is based in a heavily penetrated, highly competitive HMO market.

Methods: Data for 1,788 residents of northern California younger than 65 years of age at diagnosis (1987-1993) were provided by a population-based cancer registry.

Specific inhibition of macrophage TNF-alpha expression by in vivo ribozyme treatment.

The overproduction of the cytokine TNF-alpha is associated with inflammatory and autoimmune diseases. We have developed a means to block TNF-alpha production with ribozymes directed against TNF-alpha mRNA to selectively inhibit its production in vitro and in vivo. Following cationic lipid-mediated delivery to peritoneal murine macrophages in culture, anti-TNF-alpha ribozymes were more effective inhibitors of TNF-alpha secretion than catalytically inactive ribozyme controls.

Broad-spectrum protection against tombusviruses elicited by defective interfering RNAs in transgenic plants.

We have designed a DNA cassette to transcribe defective interfering (DI) RNAs of tomato bushy stunt virus (TBSV) and have investigated their potential to protect transgenic Nicotiana benthamiana plants from tombusvirus infections. To produce RNAs with authentic 5' and 3' termini identical to those of the native B10 DI RNA, the DI RNA sequences were flanked by ribozymes (RzDI). When RzDI RNAs transcribed in vitro were mixed with parental TBSV transcripts and inoculated into protoplasts or plants, they became amplified, reduced the accumulation of the parental RNA, and mediated attenuation of the lethal syndrome characteristic of TBSV infections.

Precisely full length, circularizable, complementary RNA: an infectious form of potato spindle tuber viroid.

The replication of many viral and subviral pathogens as well as the amplification of certain cellular genes proceeds via a rolling circle mechanism. For potato spindle tuber (PSTVd) and related viroids, the possible role of a circular (-)strand RNA as a template for synthesis of (+)strand progeny is unclear. Infected plants appear to contain only multimeric linear (-)strand RNAs, and attempts to initiate infection with multimeric (-)PSTVd RNAs generally have failed.

Does competition by health maintenance organizations affect the adoption of cost-containment measures by fee-for-service plans?

How groups insured by fee-for-service health plans react to increased competition from health maintenance organizations (HMOs) is an unresolved question. We investigated whether groups insured by indemnity plans respond to HMO market competition by changing selected health insurance features, such as deductible amounts, stop loss levels, and coinsurance rates, or by adopting utilization management or preferred provider organization (PPO) benefit options. We collected benefit design data for the years 1985 through 1992 from 95 insured groups in 62 US metropolitan statistical areas.

Changes in benefit payments and health insurance premiums among firms switching health insurance carriers.

Employer-purchased group health insurance is a major source of funding in the US healthcare system, accounting for approximately one third of each healthcare dollar spent. Surprisingly, little is known about employers' behavior in purchasing health insurance or the circumstances leading employers to switch health insurance carriers. We descriptively analyzed data for a cohort of 95 insured groups between 1985 and 1991 to determine the frequency with which employers switch health insurance carriers and the growth pattern in premiums and benefit payments before the switch was made.

Synthesis and two-dimensional electrophoretic analysis of mixed populations of circular and linear RNAs.

Spontaneous cleavage of the less abundant form of tobacco ringspot virus satellite RNA is readily reversible. Capitalizing on earlier observations by Feldstein and Bruening that small 'mini-monomer' RNAs derived from this molecule and containing little more than covalently attached ribozyme and substrate cleavage products are able to efficiently circularize, we have constructed a series of self-circularizing RNAs of precisely known size. Mixtures of linear and circular RNAs synthesized in vitro and containing 225-1132 nt could be completely resolved using a novel two-dimensional denaturing polyacrylamide gel electrophoresis system.

Destabilization of potato spindle tuber viroid by mutations in the left terminal loop.

Infectivity studies with highly infectious RNA inocula generated by ribozyme cleavage were used to compare the biological properties of three apparently nonviable mutants of potato spindle tuber viroid (PSTVd). One of these mutants (PSTVd-P) contains three nucleotide substitutions in the left terminal loop, and mechanical inoculation of tomato seedlings with RNA transcripts at levels equivalent to 10(3)-10(5) times the ID50 for PSTVd-Intermediate failed to result in systemic infection. Viable progeny containing a spontaneous C-->G change at position 4 could, however, be recovered from transgenic Nicotiana benthamiana plants that constitutively expressed PSTVd-P RNA.

The effect of price on switching among health plans.

A recent policy change by the University of California (UC) provides a unique natural experiment for investigating the sensitivity of consumers to health plan premiums. When the UC moved to a policy of limiting its contribution to the cost of the least expensive plan, out-of-pocket premiums increased for roughly one-third of UC employees. We examine the extent to which UC employees switched plans in response to this change in premiums.

Role of the variable domain in modulating potato spindle tuber viroid replication.

Potato spindle tuber viroid (PSTVd) is believed to undergo a series of specific structural transitions during replication. The variable domain of PSTVd is known to contain sequences that are important for replication/accumulation as well as one of three "premelting regions" which control breakdown of the native structure in vitro. We have examined the structural and biological effects of five single and two double nucleotide substitutions within premelting region 3 in an effort to isolate temperature-sensitive mutations affecting PSTVd replication or pathogenesis.

Hospital community benefits other than charity care: implications for tax exemption and public policy.

Recent policy initiatives attempt to link the tax treatment of nonprofit hospitals more closely with the provision of social benefits. A key issue in defining these benefits is the treatment of "community benefit" programs and services. While their costs are often unreimbursed, these programs differ from traditional charity care in terms of the populations whom they benefit and the motivation for their provision.

Consumers' sensitivity to health plan premiums: evidence from a natural experiment in California.

A recent policy change by the University of California (UC) provides a unique natural experiment for investigating how consumers respond to financial incentives when choosing health plans. In 1994 UC went from a premium contribution policy that subsidized more costly plans to a policy of contributing a constant dollar amount. As a result, employee premium contributions increased for roughly one-third of university employees.

Analysis of private health insurance premium growth rates: 1985-1992.

The rate of increase in health care expenditures has been a central policy concern for well over a decade, yet little empirical research has been conducted to examine expenditure growth rates. This study analyzed health insurance premium growth rates for a selected sample of 95 insured groups over the period 1985 to 1992. During this time, premiums increased by approximately 150% in nominal terms and by 45% in real terms.

The impact of HMO competition on private health insurance premiums, 1985-1992.

A critical unresolved health policy question is whether competition stimulated by managed care organizations can slow the rate of growth in health care expenditures. We analyzed the competitive effects of health maintenance organizations (HMOs) on the growth in fee-for-service indemnity insurance premiums over the period 1985-1992 using premium data on 95 groups that had policies with a single, large, private insurance carrier. We used multiple regressions to estimate the effect of HMO market penetration on insurance premium growth rates.

Treatment differences and other prognostic factors related to breast cancer survival. Delivery systems and medical outcomes.

Objective: To determine differences in and relative importance of treatment modalities by hospital type and their effect on survival of breast cancer patients.

Design: Cohort of population-based cancer registry breast cancer patients diagnosed from 1984 through 1990. The analysis was done within this cohort, stratified by hospital type and treatment modality.