An anti-insulin serum, but not a glucagon antagonist, alters glycemia in fed chickens.

Attempts at altering plasma glucose and, as a consequence, food intake were performed in fed broiler chickens by single i.v. injection of des-His1(Glu9) glucagon amide (a glucagon antagonist) or a non-stimulating anti-insulin serum. Plasma glucose level was not altered by des-His1(Glu9) glucagon amide but was rapidly and largely increased (for at least 2 h) by the injection of the insulin-immune serum. Hour and cumulative food intake were unaltered up to 10 h post injection. These results strongly suggest that in fed chickens, plasma glucose is mainly, if not exclusively, controlled by plasma insulin, and that the transient and heavy hyperglycemia evoked by inhibiting insulin action does not alter food intake.     

LEAF CAVITY SIZE DIFFERENTIATION AND WATER RELATIONS IN CAREX ELEOCHARIS

Carex eleocharis leaves contain large intercellular cavities that traverse the length of the leaf above rows of stomata and are roughly constant in size throughout a leaf. Semithin sections (1–2 μm) demonstrate that the substomatal chambers are directly continuous with the intercellular cavities. Leaves of plants inhabiting moist swale regions of the shortgrass steppe, in northeastern Colorado, were found to have larger cavities as compared to leaves of plants inhabiting dry hilltops. Plants collected from a common hilltop site were grown in a controlled environment chamber, and, by manipulating the watering schedule, we obtained water potentials similar to those in the field. Leaves of “well-watered” plants were found to have larger intercellular cavities as compared to “water-stressed” plants. Leaf mesophyll cell sizes did not differ significantly between “well-watered” and “water-stressed” plants, suggesting that cavity size differences are not the result of developmental differences. Leaf cavities were shown to contain gases and to occur along the leaf length above rows of stomata. Additionally, the cavities in unstressed plants were continuous with substomal chambers. It is proposed that the reduction of cavity size is a mechanism to reduce water loss from the leaves during periods of plant water stress.