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J D Rice

Publications and source records attributed to J D Rice.

10 recordsLinked to original sources
PubMed1992

Differential depolymerization mechanisms of pectate lyases secreted by Erwinia chrysanthemi EC16.

The four pectate lyases (EC 4.2.2.2) secreted by Erwinia chrysanthemi EC16 have been individually produced as recombinant enzymes in Escherichia coli. Oligogalacturonates formed from polygalacturonic acid during reactions catalyzed by each enzyme have been determined by high-performance liquid chromatography analysis. PLa catalyzes the formation of a series of oligomers ranging from dimer to dodecamer through a random endolytic depolarization mechanism. PLb and PLc are trimer- and tetramer-generating enzymes with an identical combination of endolytic and exolytic mechanisms. PLe catalyzes a nonrandom endolytic depolymerization with the formation of dimer as the predominant product. The pectate lyases secreted by E. chrysanthemi EC16 represent a battery of enzymes with three distinct approaches to the depolymerization of plant cell walls.

Bacterial Proteins↗
PubMed1982

Photosynthetic response of seagrasses to ultraviolet-a radiation and the influence of visible light intensity.

Inhibition of photosynthesis by ultraviolet-A radiation (UV-A, 315-380 nanometers) was examined in three marine angiosperms: Halophila engelmannii Aschers, Halodule wrightii Aschers, and Syringodium filiforme Kütz. Sensitivity to UV-A and photosensitization to UV-A by photosynthetically active radiation (PAR, 380-700 nanometers) were characterized.Net photosynthesis by Halodule and Syringodium was unaffected by UV-A irradiation in the absence of PAR. Irradiation of Syringodium by a combined beam of UV-A and PAR resulted in photosynthetic inhibition. The depression of net photosynthesis was found to be a function of PAR intensity at a fixed level of UV-A irradiation. Inhibition of photosynthesis in Halodule by the combined beam was minimal and suggests adaptation to environmental irradiation levels.Halophila was the only species examined, subject to photosynthetic inhibition by UV-A in the absence of PAR. Irradiation with PAR intensities characteristic to Halophila in the natural system as the combined beam, appeared to negate the inhibition. Increasing the PAR component of the combined beam above environmental norms resulted in photosynthetic inhibition greater than that observed for UV-A alone.

Journal Article↗
PubMed1981

Inhibition of seagrass photosynthesis by ultraviolet-B radiation.

Effects of ultraviolet-B radiation on the photosynthesis of seagrasses (Halophila engelmanni Aschers, Halodule wrightii Aschers, and Syringodium filiforme Kütz) were examined. The intrinsic tolerance of each seagrass to ultraviolet-B, the presence and effectiveness of photorepair mechanisms to ultraviolet-B-induced photosynthetic inhibition, and the role of epiphytic growth as a shield from ultraviolet-B were investigated.Halodule was found to possess the greatest photosynthetic tolerance for ultraviolet-B. Photosynthesis in Syringodium was slightly more sensitive to ultraviolet-B while Halophila showed relatively little photosynthetic tolerance. Evidence for a photorepair mechanism was found only in Halodule. This mechanism effectively attenuated photosynthetic inhibition induced by ultraviolet-B dose rates and dosages in excess of natural conditions. Syringodium appeared to rely primarily on a thick epidermal cell layer to reduce photosynthetic damage. Halophila seemed to have no morphological or photorepair capabilities to deal with ultraviolet-B. This species appeared to rely on epiphytic and detrital shielding and the shade provided by other seagrasses to reduce ultraviolet-B irradiation to tolerable levels. The presence of epiphytes on leaf surfaces was found to reduce the extent of photosynthetic inhibition from ultraviolet-B exposure in all species.Observations obtained in this study seem to suggest the possibility of anthocyanin and/or other flavonoid synthesis as an adaptation to long term ultraviolet-B irradiation by these species. In addition, Halophila appears to obtain an increased photosynthetic tolerance to ultraviolet-B as an indirect benefit of chloroplast clumping to avoid photo-oxidation by intense levels of photosynthetically active radiation.

Journal Article↗
PubMedDate not supplied

Using laptop computers as a BMET field service tool.

This system has been in operation for approximately two years at the time of this writing, and involves more than a dozen laptop computers. The true test of whether something is successful is the degree of acceptance that is generated by the people who must use it. Approximately two months after beginning this process, our biomedical equipment technicians (BMETs) asked us to expand utilization of this system to a greater segment of our client base because it was so much simpler than our prior paper method. Our ability to track events that occur in the field is much improved with any problems identified in procedures being communicated through the private comments. Not only are the printed PM forms far more legible than the prior hand-entered results, but the concept of test-to-standards now is far more practical because the testing protocols are a keypress away, and the question of whether the technician would take the time to look up in the cumbersome procedure manuals those things that he or she was only slightly unsure of is addressed. Additionally, we have seen more than a 25% reduction in data-handling associated with the processing of the PM inspections in this fashion. Even with the time necessary to create the data disks, upload them, and process them through the filter, we are still saving substantial time over the manual handling of paper.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomedical Engineering↗