Oral behaviour following forebrain ablations in Gallus Domesticus

The oral behaviour of adult Brown Leghorn hens was recorded in response to oral stimulation with water, 2 M sodium chloride, 2 M acetic acid and 0.1 M quinine hydrochloride before and after surgical ablation of either the anterior telencephalon or the entire telencephalon and/or the diencephalon. It was found that beak wiping behaviour could be abolished by the removal of the anterior telencephalon. Head shaking behaviour was abolished only by the complete removal of the forebrain (telencephalon and diencephalon) whereas beak and tongue movements persisted after forebrain removal. Although these three behaviour patterns occur together in response to the stimulus, they appear to be controlled in different areas of the brain. The results are discussed in relation to the current work on the control of oral behaviour in mammals.     

A Ca2+-insensitive form of fura-2 associated with polymorphonuclear leukocytes. Assessment and accurate Ca2+ measurement

The new, fluorescent Ca2+ indicator, fura-2, promises to expand our understanding of the role of subcellular changes in Ca2+ underlying cell function. During an investigation of the role of Ca2+ in the polarization response of human polymorphonuclear leukocytes to formyl-methionyl-leucyl-phenylalanine, we found that fura-2 trapped by cells incubated with the acetoxy-methyl ester of fura-2, F2-AM, yielded measurements of Ca2+ that were depressed at rest and during the response to formyl-methionyl-leucyl-phenylalanine. Fura-2, trapped by the cells, exhibited a spectrum in the presence of saturating Ca2+ that differed from that of fura-2 free acid. We have shown that the cellular fluorescence can be spectrally decomposed into two components: one with Ca2+ sensitivity identical to fully deesterified fura-2, and another which is Ca2+-insensitive. The Ca2+-insensitive component appears to be more fluorescent than F2-AM as well as spectrally different from F2-AM. The insensitive form probably results from incomplete deesterification of F2-AM by the cells. In order to accurately measure Ca2+ in polymorphonuclear leukocytes, it is imperative to check for the presence of Ca2+-insensitive fluorescence. The contribution of Ca2+-insensitive fura-2 fluorescence can be assessed routinely from spectral data obtained by calibration of intracellular fura-2 with known [Ca2+] using ionomycin. The end-of-experiment calibration step not only ensures accurate [Ca2+] measurements in polymorphonuclear leukocytes and in other cell types that display Ca2+-insensitive, contaminating fluorescence but also yields the spectral characteristics of the insensitive species.     

Chemiluminescence associated with phagocytosis of foreign particles in rabbit alveolar macrophages

Rabbit alveolar macrophages exhibit a chemiluminescent response which is associated with phagocytosis of zymosan and polystyrene-butadiene particles. The chemiluminescence reaches a peak in 15 to 25 minutes and then gradually diminishes over the next 1 to 3 hours. During the time of maximal light emission there appears to be no actual uptake of particles, but the response is dependent upon the particle concentration. The metabolic inhibitor, DNP (2,4-dinitrophenol), causes a rapid inhibition of the chemiluminescent response. The addition of ATP to the medium prior to exposure of the cells to particles causes the chemiluminescent response to be greatly diminished, i.e., 0.3mM ATP virtually abolishes the response. These experiments suggest that some metabolic response of the cell to phagocytosis is responsible for the chemiluminescence.     

Protists have divergent effects on bacterial diversity along a productivity gradient

Productivity and predation are thought to be crucial drivers of bacterial diversity. We tested how the productivity–diversity of a natural bacterial community is modified by the presence of protist predators with different feeding preferences. In the absence of predators, there was a unimodal relationship between bacterial diversity and productivity. We found that three protist species (Bodo, Spumella and Cyclidium) had widely divergent effects on bacterial diversity across the productivity gradient. Bodo and Cyclidium had little effect on the shape of the productivity–diversity gradient, while Spumella flattened the relationship. We explain these results in terms of the feeding preferences of these predators.     

Daphniopsis australis nov.sp. (Crustacea: Cladocera), a further daphniid in Australian salt lakes

Daphniopsis australis, a new species of cladoceran in Australian salt lakes, is described, and some brief comments on its distribution are given.     

The influence of straining maneuvers on the pressor response during isometric exercise

Experiments were performed to determine to what extent increments in esophageal and abdominal pressure would have on arterial blood pressure during fatiguing isometric exercise. Arterial blood pressure was measured during handgrip and leg isometric exercise performed with both a free and occluded circulation to active muscles. Handgrip contractions were exerted at 33 and 70% MVC (maximum voluntary contraction) by 4 volunteers in a sitting position and calf muscle contractions at 50 and 70% MVC with the subjects in a kneeling position. Esophageal pressure measured at the peak of inspirations did not change during either handgrip or leg contractions but peak expiratory pressures increased progressively during both handgrip and leg contractions as fatigue occurred. These increments were independent of the tensions of the isometric contractions exerted. Intra-abdominal pressures measured at the peak of either inspiration or expiration did not change during inspiration with handgrip contractions but increased during expiration. During leg exercise, intraabdominal pressures increased during both inspiration and expiration, reaching peak levels at fatigue. The arterial blood pressure also reached peak levels at fatigue, independent of circulatory occlusion and tension exerted, averaging 18.5-20 kPa (140-150 mm Hg) for both handgrip and leg contractions. While blood pressure returned to resting levels following exercise with a free circulation, it declined by only 2.7-3.8 kPa after leg and handgrip exercise, respectively, during circulatory occlusion. These results indicate that straining maneuvers contribute 3.5 to 7.8 kPa to the change in blood pressure depending on body position.