Establishment and characterization of Rubus tissue culture systems for in vitro bioassays against phytotoxins from Rubus fungal pathogens

The Rubus species R. parviflorus, R. spectabilis and R. strigosus interfere with conifer seedling establishment on forest regeneration sites in Canada and the United States. As a first step towards microbial metabolite-based control, callus and cell suspension cultures of the Rubus species were developed as a bioassay system to detect phytotoxic compounds that may have relevance in a vegetation control context. Rapidly growing friable callus and suspension cultures were obtained from leaf disks of the three weedy Rubus species using similar culture media conditions (modified Murashige and Skoog) but required different plant growth regulators (R. parviflorus, 4.5 M 2,4-D; R. spectabilis, 26.9 M NAA/0.5 M zeatin; and R. strigosus, 12.4 M picloram). Cell growth and health attributes including callus circumference, degree of browning and suspension culture cell viability as measured by the TTC vital stain assay were developed and were rapid and convenient to use. We have established Rubus tissue culture systems that will make it possible for large scale screening of phytotoxic metabolites.     

Low nitric oxide concentrations in exhaled gas and nasal airways of mammals without paranasal sinuses

To investigatewhether relevant levels of nasal nitric oxide (NO) are produced in theabsence of paranasal sinuses, we studied 17 healthy baboons, mammalswithout any paranasal sinuses. The animals were anesthetized withketamine hydrochloride and breathed spontaneously. While the baboonsbreathed through a face mask (mouths closed) connected to a respirator,NO concentrations in exhaled gas were sampled from the expiratory limband analyzed by chemiluminescence. While the animals were breathingambient air, nasal gas was sampled via a thin plastic tube and analyzed for NO concentrations by chemiluminescence. Mean NO concentration inthe exhaled gas was 1.00 ± 0.59 parts/billion, and NO release was4.28 ± 2.72 nl/min. A NO concentration of 4.79 ± 2.08 parts/billion was found in the nasal gas (NO release: 7.18 ± 3.13 nl/min). An age-dependent increase in nasal NO levelswas not observed. Exhaled and nasal NO concentrations in baboons weremarkedly lower than in mammals with paranasal sinuses, suggesting thatparanasal sinuses might be an anatomic requirement for production ofrelevant nasal NO levels.