Tritrophic interactions in the context of climate change: a model of grasses, cereal Aphids and their parasitoids

Biologists have been challenged to envisage the likely consequences of increases in atmospheric carbon dioxide concentrations, and the suite of accompanying environmental changes (e.g. rising temperature, changing rainfall patterns, etc.) on our biotic systems. Research to date on plant responses has been extensive, but work on herbivore responses has been less complete, and work on higher trophic levels nearly nonexistent. One group of herbivores that has been reasonably well studied is aphids, and at least for this group, researchers have even begun to investigate responses at higher trophic levels, to include parasitoids. In this paper, we develop a mechanistic mathematical model of the general interaction between grasses, cereal aphids and their parasitoids. We used this model to investigate the interacting effects of rising CO₂ and temperature. The model suggests that, while parasitoids do have an impact on the aphid colony population dynamics, they do not fundamentally alter the aphid response to climate change. The model predicts that for both aphids and their parasitoids, the population responses to combined effects of elevated CO₂ and temperature will be more similar to current ambient conditions than we might expect from the individual effects of CO₂ or temperature increases. This interaction has important consequences for the interpretation of results from experiments that study only the effect of rising CO₂.     

Simple inexpensive laboratory equipment for cultivation of plants under various CO2 concentrations

A simple equipment was developed to cultivate young cereal plants under enhanced CO₂ concentration. Cultivation system permits growing of about 40 barley seedlings for about 2 to 3 weeks. The system consists of two identical growth chambers (volume about 30 dm³), gas conditioning circuit and measuring circuit with an infra-red CO₂ analyser. Capabilities of the whole equipment were tested by growing barley plants under 330 and 1000 cm³ (CO₂)m⁻³ and in combination with high or low nitrate level.     

Antibody production and growth of mouse hybridoma cells in Nutridoma media supplements

Traditionally, cell culturists have relied upon the addition of serum to culture medium for the growth and maintenance of cell lines. However, many aspects of the use of serum in tissue culture are problematic. Cell culture supplements that circumvent the need for serum are readily available and provide a consistent protein composition. This defined environment allows the antibody to be more easily purified from culture supernatants. Nutridoma media supplements were formulated to support the growth of lymphoblastoid cells in a defined culture environment. In this study, Nutridoma media supplements were tested in parallel with serum-containing cultures to determine if Nutridoma supplemented medium is effective in supporting hybridoma cell growth and antibody production in three hybridoma cell lines. Data, based on cell growth and antibody production, show the importance of basal media selection when serum is replaced with Nutridoma media supplements. SDS-PAGE results show that cell supernatants from Nutridoma supplemented cultures contain very few contaminating proteins.     

Field endoscopy for identifying gender, reproductive stage and gonadal anomalies in free-ranging sturgeon (Scaphirhynchus) from the lower Mississippi River

Thirty-six sturgeon ( Scaphirhynchus spp.) were captured from the lower Mississippi River using baited trot-lines, anesthetized using tricaine methanesulfonate, and subjected to endoscopic evaluation of their coelom (coelioscopy) on the river bank. Using a 2.7 mm rod-lens telescope and gravity–fed sterile saline infusion, gender and reproductive stage were determined in the field, and later re-evaluted and confirmed by histology of endoscopic biopsies in the laboratory. Gender and reproductive stage were determined endoscopically in all fish without complication, and proved to correlate 100% with biopsy histology. Modern rod-lens telescopes and sterile saline insufflation can be used under field conditions, provide superior visualization of sturgeon gonads, and offer a high degree of accuracy even with inactive gonads. Rigid endoscopy is recommended as a minimally-invasive means of assessing the reproductive organs of sturgeon and other fish.     

Effects of epidermal growth factor on collagen expression by rat kidney mesangial cells in culture.

Increased collagen production by mesangial cells plays a key role in the development and progression of glomerular sclerosis. These changes reflect in part the impact of growth factors on mesangial cells. Since mesangial cells possess receptors for epidermal growth factor (EGF) and since previous studies have documented that EGF affects collagen synthesis in other cell types, we have examined the effects of EGF on collagen biosynthesis by rat kidney mesangial (RKM) cells in culture. Exposure for 24 h to EGF did not substantially affect the growth rate of RKM cells. While the types of collagen produced by RKM cells (types I, III, IV and V) were unaltered by exposure to EGF, total collagen production was reduced ( approximately 50%). This decrease in collagen expression was not uniform for each collagen type. Type I collagen production was inhibited by approximately 50%, both type III and type IV expression were each reduced by approximately 30%, but type V collagen production was suppressed by only approximately 15%. The reduction in type I collagen synthesis was accounted for mainly by a decrease in type I homotrimer production. Since type I molecules represent approximately 95% of the total collagen produced, the decrease in overall collagen expression reflects a specific suppression by EGF on type I homotrimer production in mesangial cells. As EGF exposure resulted in a decrease in collagen production, these results suggest that the increases in synthesis and deposition of collagen observed in several glomerular diseases likely do not reflect the short-term effects of EGF on mesangial cells. Rather, these findings suggest the possibility that EGF or EGF-like growth factors may ameliorate the effects of other soluble factors that cause enhanced matrix production and deposition in renal diseases.