Modulation of rat pituitary growth hormone by 670 nm light.

In rat pituitary somatotrophs, cytochrome oxidase is co-packaged with growth hormone (GH) in some storage granules. Because this enzyme is thought to be the molecular photoacceptor of red-near infrared light, and because exposure of diverse tissue systems to 670 nm visible light affects their biological responses (e.g., wound healing), we tested the idea that exposure of rat pituitary cells, rat hemi-pituitary glands and rat pituitary homogenates to 670 nm light in vitro might alter GH storage and/or release. In this report we offer evidence to show that light treatment (670 nm, 80s, intensity 50 mW/cm(2), energy density 4 J/cm(2)) up-regulates GH release, in part by breakdown of intracellular, oligomeric GH as determined by gel filtration chromatography.

Environmental Sensitivity of Soybean Cultivar Response to Sclerotinia sclerotiorum.

ABSTRACT The sporadic occurrence of Sclerotinia stem rot in soybeans often is attributed to the sensitivity of Sclerotinia sclerotiorum to environmental factors. Environmental sensitivity in soybean response to the pathogen also could contribute to the unpredictable nature of this disease. We used stability analysis to determine whether soybean cultivar response to S. sclerotiorum was sensitive to light and temperature. Five greenhouse experiments examined the response of seven cultivars to limited-term inoculation with S. sclerotiorum. The cultivars, selected at random from Pennsylvania variety trials, represented maturity groups grown in Pennsylvania and other states sharing that latitude. Photon flux density of photosynthetically active radiation (PAR) and temperature were recorded hourly and varied among experiments. Environmental sensitivity was detected in the response of five cultivars to S. sclerotiorum when individual cultivar disease ratings (assessed 6 days after inoculation) were regressed against the mean disease rating of each experiment. Stability analysis with temperature during the 48-h inoculation period as the environmental index found that all cultivars responded similarly to the number of hours that temperatures were <19 degrees C, 19 to 22 degrees C, or >22 degrees C. In contrast, cultivars separated into PAR-sensitive and PAR-insensitive groups when the environmental index was moles of PAR at a photon flux density >/=475 mumol m(-2) s(-1) during the inoculation period. The photon flux density of PAR on a cloudy day in the field is