Relative Performance of Non-Local Cultivars and Local, Wild Populations of Switchgrass (Panicum virgatum) in Competition Experiments.

The possibility of increased invasiveness in cultivated varieties of native perennial species is a question of interest in biofuel risk assessment. Competitive success is a key factor in the fitness and invasive potential of perennial plants, and thus the large-scale release of high-yielding biomass cultivars warrants empirical comparisons with local conspecifics in the presence of competitors. We evaluated the performance of non-local cultivars and local wild biotypes of the tallgrass species Panicum virgatum L. (switchgrass) in competition experiments during two growing seasons in Ohio and Iowa. At each location, we measured growth and reproductive traits (plant height, tiller number, flowering time, aboveground biomass, and seed production) of four non-locally sourced cultivars and two locally collected wild biotypes. Plants were grown in common garden experiments under three types of competition, referred to as none, moderate (with Schizachyrium scoparium), and high (with Bromus inermis). In both states, the two "lowland" cultivars grew taller, flowered later, and produced between 2x and 7.5x more biomass and between 3x and 34x more seeds per plant than local wild biotypes, while the other two cultivars were comparable to wild biotypes in these traits. Competition did not affect relative differences among biotypes, with the exception of shoot number, which was more similar among biotypes under high competition. Insights into functional differences between cultivars and wild biotypes are crucial for developing biomass crops while mitigating the potential for invasiveness. Here, two of the four cultivars generally performed better than wild biotypes, indicating that these biotypes may pose more of a risk in terms of their ability to establish vigorous feral populations in new regions outside of their area of origin. Our results support an ongoing assessment of switchgrass cultivars developed for large-scale planting for biofuels.

Economic benefits of hepatitis B vaccination at sexually transmitted disease clinics in the U.S.

OBJECTIVE: This study assessed the long-term economic implications of a national program to vaccinate all adults treated at sexually transmitted disease (STD) clinics in a single year. METHODS: A model was developed to track the long-term disease outcomes and costs among a hypothetical cohort of 2 million STD clinic clients accessing services in one year, using data from published sources and demonstration projects at STD clinics in San Diego (California), Illinois, and Denver (Colorado). The model estimated net economic benefits of a routine hepatitis B vaccination policy at STD clinics nationwide compared with no vaccination. RESULTS: Without a vaccination program, an estimated 237,021 new hepatitis B virus (HBV) infections would occur over the lifetimes of the 2 million STD clinic clients seen in a single year. HBV-related medical costs and productivity losses would be $1.6 billion. In a national program for routine vaccination at STD clinics, 1.3 million adults would be expected to receive at least one vaccine dose, and an estimated 45% of the new HBV infections expected without vaccination would be prevented. The vaccination program would cost $138 million, HBV infections occurring despite the program would cost $878 million, and clients' time and travel would cost $45 million. The net economic benefit (savings) of routine vaccination would be $526 million. If the indirect costs of lost productivity due to HBV infection are not considered, routine vaccination would have a net cost of $28 million. CONCLUSIONS: Estimates from this model suggest a national program for routine hepatitis B vaccination of adults at STD clinics would be a cost saving to society.

On the time course of surgically induced compensatory muscle hypertrophication of the rat plantaris muscle.

1. The time course of the hypertrophy and hyperplasia of the rat plantaris muscle was determined from measurements of total muscle mass and cross-section analysis of fixed muscle. 2. Muscle enlargement was induced by the surgical removal of the plantaris synergist muscles, the gastrocnemius and the soleus. 3. From the date of surgery through the third post-operative week, muscle enlargement is due to fiber hypertrophication (approximately 100% increase in diameter). After post-operative week three, muscle enlargement is due to a combination of hyperplasia and hypertrophy. At week four the cross-sectional areas return to control values. 4. The neuromuscular junction area was determined by measuring Karnovsky stained post-synaptic membrane. Only a modest 10-30% increase was noted at weeks 2 and 3 with a return to control levels at week 4. The differences were not statistically different.