Arbuscular mycorrhizal fungi can enhance nutrient acquisition by a plant via their extraradical hyphae. This is particularly true for phosphorus, but the case for nitrogen (N) has been less clear. In our growth systems there was a small air-gap between root and hyphal compartments, which eliminated diffusion of nutrients between compartments. Moreover, our methods allowed us to distinguish between nitrate and ammonium. We found that N transfer to Zea maize L. depends on the sources fed to the hyphae of Glomus aggregatum Schenck & Smith. In experiment 1, despite the fact that plant demand for N was already met, plants received 10 times as much 15 N from ammonium than from nitrate. In experiment 2, 74% of shoot-N was derived from the slow-release urea added to the hyphal compartment while only 2.9% was derived from the nitrate-N. Intraradical hyphae isolated from roots contained a considerable amount of 15 N in the cell wall even when 15 N-nitrate was the source. We conclude that the mycorrhizal fungus can rapidly deliver ammonium-N to the plants, and that while the fungus can absorb nitrate, it apparently lacks the capacity to transfer it to the plant.

Basic fibroblast growth factor (bFGF) has been shown to stimulate wound healing. However, consistent delivery of bFGF has been problematic. We studied the stability of bFGF incorporated into a chitosan film as a delivery vehicle for providing sustained release of bFGF. The therapeutic effect of this system on wound healing in genetically diabetic mice was determined as a model for treating clinically impaired wound healing. A chitosan film was prepared by freeze-drying hydroxypropylchitosan (a water-soluble derivative of chitosan) acetate buffer solution. Growth factor was incorporated into films before drying by mixing bFGF solution with the hydroxypropylchitosan solution. bFGF activity remained stable for 21 days at 5 degrees C, and 86.2% of activity remained with storage at 25 degrees C. Full-thickness wounds were created on the backs of diabetic mice, and chitosan film or bFGF-chitosan film was applied to the wound. The wound was smaller in after 5 days in both groups, but the wound was smaller on day 20 only in the bFGF-chitosan group. Proliferation of fibroblasts and an increase in the number of capillaries were observed in both groups, but granulation tissue was more abundant in the bFGF-chitosan group. These results suggest that chitosan itself facilitates wound repair and that bFGF incorporated into chitosan film is a stabile delivery vehicle for accelerating wound healing.

Summary• Stomatal formation is affected by a plant's external environment, with longdistance signaling from mature to young leaves seemingly involved. However, it is still unclear what is responsible for this signal. To address this question, the relationship between carbon isotope discrimination (Δ) and stomatal density was examined in cowpea (Vigna sinensis).• Plants were grown under various environments that combined different amounts of soil phosphorus (P), soil water, and atmospheric CO 2 . At harvest, stomatal density was measured in the youngest fully expanded leaf. The 13 C :12 C ratio was measured in a young leaf to determine the Δ in mature leaves.• Results indicated that stomatal density is affected by P as well as by amounts of water and CO 2 . However, stomatal responses to water and CO 2 were complex because of strong interactions with P. This suggests that the responses are relative, depending on some internal factor being affected by each external variable. Despite such complicated responses, a linear correlation was found between stomatal density and Δ across all environments examined.• It is proposed that the Δ value is a good surrogate for the long-term mean of the intercellular (C i ) to the atmospheric (C a ) CO 2 concentration ratio (C i : C a ) and may be useful in understanding stomatal formation beyond complicated interactions.

The results suggest that the efficiency of root morphological plasticity is largely determined by the size of the P-enriched patch. Furthermore, the results imply a novel aspect of P-uptake physiology that roots in heterogeneous P cannot demonstrate their potential capacity, as would be observed in roots encountering P continuously; this effect is probably mediated by an internal root factor.

Organs-on-chips are microfluidic devices typically fabricated from polydimethylsiloxane (PDMS). Since PDMS has many attractive properties including high optical clarity and compliance, PDMS is very useful for cell culture applications; however, PDMS possesses a significant drawback in that small hydrophobic molecules are strongly absorbed. This drawback hinders widespread use of PDMS-based devices for drug discovery and development. Here, we describe a microfluidic cell culture system made of a tetrafluoroethylene-propylene (FEPM) elastomer. We demonstrated that FEPM does not absorb small hydrophobic compounds including rhodamine B and three types of drugs, nifedipine, coumarin, and Bay K8644, whereas PDMS absorbs them strongly. The device consists of two FEPM layers of microchannels separated by a thin collagen vitrigel membrane. Since FEPM is flexible and biocompatible, this microfluidic device can be used to culture cells while applying mechanical strain. When human umbilical vein endothelial cells (HUVECs) were subjected to cyclic strain (~10%) for 4 h in this device, HUVECs reoriented and aligned perpendicularly in response to the cyclic stretch. Moreover, we demonstrated that this device can be used to replicate the epithelial–endothelial interface as well as to provide physiological mechanical strain and fluid flow. This method offers a robust platform to produce organs-on-chips for drug discovery and development.