The Foraging Ecology of Migratory Shorebirds in Marine Soft-sediment Communities: The Effects of Episodic Predation on Prey Populations

This paper explores the extent to which life histories of infaunalprey have been molded and maintained by predation. It is arguedsuch relationships should be most evident for episodic predation,where the predation is predictable, intense and short-lived.Migratory shorebirds are used herein as model episodic predators.Four stop-over areas in North America, for which experimentaldata exist, are compared. Evidence exists that SemipalmatedSandpipers in the upper Bay of Fundy maintain the observed lifehistory of their major prey, the amphipod Corophium volutator.In southeastern Massachusetts, shorebirds significantly reducethe abundance of their prey but in a frequency-dependent fashion,precluding life history responses of the prey. For Grays Harbor,Washington and Delaware Bay, there is no detectable effect ofshorebird predation on the infauna. In three of the four studies,there is no apparent effect of early shorebird migrants in significantlyincreasing the required stop-over of later migrants by depressionof prey densities. The data support the characterization ofsoft-sediment communities as loosely organized assemblages whosespecific constitution is determined more by ecological combiningability than by specific evolutionary responses to associatedspecies.     

High-performance liquid chromatographic determination of PEG 600 in human urine

Polyethylene glycols (PEGs) are non-ionic, water-soluble synthetic polymers which have been widely used for many applications. Since they are of very low toxicity and are readily excreted in urine, PEGs in the molecular weight range 400–6000 have been used extensively in the study of intestinal physiology in man. A high-performance liquid chromatographic (HPLC) method has been developed for the determination of PEG 600 in human urine, which includes a pre-column derivatisation step. The dibenzoate derivatives of PEG 600 can be quantitatively prepared, and this, coupled with ultraviolet detection at 230 nm, has greatly improved the limit of detection for the determination of PEGs by HPLC. A suitable extraction procedure has also been developed which enabled PEG levels in urine to be monitored with much greater sensitivity than any previously reported method.     

Social Spacing in Small Mammals: Patterns of Individual Variation

The pattern of social spacing in small mammals differs fromthat observed in many other vertebrates. Small mammals frequentlyhave non-exclusive territories and tolerate a large amount ofoverlap with other conspecifics. The determinant factors ofhome range or territory size in small mammals are not knownfor most species. We carried out a study of the determinantfactors of home range size in a model small mammal, the easternchipmunk, Tamias striatus. The population was studied for fiveyears. The effect of experimental perturbations on food supplyand population density offered strong evidence that the meanhome range size in the population was determined by resourceabundance. Changes in population density had little or no measurableeffect. We noted that even when mean home range size decreasedsignificantly in response to an increase in available food,a great deal of variability in individual home range sizes remained.We hypothesized that this pattern of variation among individualswas also resource related; large home ranges would be locatedin areas of low resource density and small home ranges wouldbe located in areas of high resource density. Our data to datedo not offer support for this hypothesis; however our researchhas shown that the data needed to convincingly reject the nullhypothesis are very complex. We discuss the evidence requiredto study patterns of individual variation, and how models ofoptimal territory size may be useful. Research that examinespatterns of individual variation are few in number, yet studiesof individual variation will ultimately provide the best insightson the dynamics of evolutionary ecology.     

Cardiovascular and Other Physiological Correlates of Hibernation in Aquatic and Terrestrial Turtles

Recent research has provided new insight into the physiologyof hibernation in freshwater, marine, and terrestrial turtles.In this paper I review what is known about the mechanisms thatpermit the hearts of these turtles to withstand several monthsof hypoxia or anoxia. I also report new research that indicatesthat a terrestrial turtle, unlike freshwater and marine species,does not experience hypoxia in its winter burrow and thus doesnot rely on glycolysis to supply ATP, at least under moderatewinter conditions.     

Acute effects of thoracic irradiation on lung function and structure in awake sheep

To investigate the acute physiological and structural changes after lung irradiation, the effects of whole-lung irradiation were investigated in fourteen sheep. Ten sheep were prepared with vascular and chronic lung lymph catheters, then a week later were given 1,500 rad whole-lung radiation and monitored for 2 days. Four sheep were given the same dose of radiation and were killed 4 h later for structural studies. Lung lymph flow increased at 3 h after radiation (14.6 +/- 2.1 ml/h) to twice the base-line flow rate (7.5 +/- 1.3), with a high lymph-to-plasma protein concentration. Pulmonary arterial pressure increased twofold from base line (18 +/- 1.6 cmH2O) at 2 h after radiation (33 +/- 3.8). Cardiac output and systemic pressure in the aorta did not change after lung radiation. Arterial O2 tension decreased from 85 +/- 3 to 59 +/- 4 Torr at 1 day after radiation. Lymphocyte counts in both blood and lung lymph decreased to a nadir by 4 h and remained low. Thromboxane B2 concentration in lung lymph increased from base line (0.07 +/- 0.03 ng/ml) to peak at 3 h after radiation (8.2 +/- 3.7 ng/ml). The structural studies showed numerous damaged lymphocytes in the peripheral lung and bronchial associated lymphoid tissue. Quantitative analysis of the number of granulocytes in peripheral lung showed no significant change (base line 6.2 +/- 0.8 granulocytes/100 alveoli, 4 h = 10.3 +/- 2.3). The most striking change involved lung airways. The epithelial lining of the majority of airways from intrapulmonary bronchus to respiratory bronchiolus revealed damage with the appearance of intracellular and intercellular cell fragments and granules. This new large animal model of acute radiation lung injury can be used to monitor physiological, biochemical, and morphological changes after lung radiation. It is relevant to the investigation of diffuse oxidant lung injury as well as to radiobiology per se.     

In-vivo and in-vitro measurements of lead and cadmium

Tibia lead is measured in vivo using X-ray fluorescence. A¹⁰⁹Cd source is used to excite Pb K X-rays, and this signals is normalized to that from Rayleigh scattering to remove geometrical variations. The lower limit of detection is 10 μg/g for a mean absorbed dose, to the exposed section of the leg, of 100 μGy. Tibia lead correlated positively with age in normal volunteers (r=0.615,p=0.004) and with duration of exposure in occupationally exposed subjects (r=0.847,p=0.0001). When the X-ray fluorescence technique was applied to autopsy specimens previously analyzed by atomic absorption spectrometry there was excellent agreement between measurement techniques. Cadmium is measured in vivo by neutron activation analysis. The detection limit in liver is 6.5 μg/g for a local skin dose equivalent of 0.5 mSv and in kidney is 6.4 mg for a dose equivalent of 0.9 mSv to the skin. Detailed analysis of the γ-ray spectrum will produce only slight improvements in detection limit. Uncertainties in organ position during measurement, even after ultrasonic localization, are likely to produce uncertainties of 20–25% in cadmium measurement. Autopsy samples were measured, using a fast neutron activation method, from people previously measured in vivo. The results are broadly consistent, but show differences greater than those accounted for by counting statistics.     

25-Azasteroid inhibition of development and conversion of C28 and C29 phytosterols to cholesterol in Spodoptera litura (F.)

Larvae of Spodoptera litura (F.) grown on an artificial diet completed larval development in 19.2 days and attained a maximum weight of 873.2 mg. When fed dietary concentrations of 50 ppm of 25-azacholesterol or 10 ppm of 25-azacholestane, the larval developmental period increased to 28.4 and 23.4 days, and the larval weights were 447.5 and 542.3 mg, respectively. Both compounds induced distinct melanization effects and caused production of larval-pupal intermediates and severe mortality. Treatments with concentrations of 50 ppm or more of either azasteroid caused a decline in pupal period and earlier eclosion and emergence of abnormal adults. Egg laying and hatchability decreased with increasing concentrations of azasteroids in the larval diets. When 1 ppm or more of 25-azasteroid is added to the artificial diet, the insect larvae contain identifiable amounts of desmosterol, in addition to cholesterol, campesterol, and sitosterol, which are present in Spodoptera grown on artificial diet alone. Desmosterol accumulation in the insect body is due to an inhibition of the Δ²⁴-sterol reductase by 25-azasteroids. An increase in the concentration of these azasteroids in the diet results in an increase in sitosterol concentration and simultaneous reduction in the cholesterol levels due to inhibition of conversion of sitosterol. This inhibition appears to be more pronounced with 25-azacholestane treatment than with 25-azacholesterol.     

THE PSYCHOPHYSICAL RELATIONSHIP BETWEEN COLOR AND SALT CONCENTRATIONS IN CHICKEN FLAVORED BROTHS

Taste panelists evaluated the effect of color on salt perception in chicken flavored samples using magnitude estimation. Samples were colored to simulate commercial chicken broth. Five color intensities were added to 5 NaCl concentrations ranging from 0.34 to 0.66% (w/v). Color had no influence on salt perception. Panelists were able to perceive color differences among samples (P <0.001) and these were correlated with the objective color function cot⁻¹ (a/b) calculated from the L,a,b values obtained from the Gardner XL-23. Overall flavor preference was evaluated by a taste panel using the technique of magnitude estimation. NaCl concentrations ranged from 0.52 to 0.80% (w/v). Overall flavor preference was unaffected by color. A reduction in NaCl concentration from 0.80% (w/v) to 0.52% (a 35% reduction) did not alter flavor preference. A 50 member consumer panel using a paired comparison test found no difference in flavor preference between an uncolored sample containing 0.80% (w/v) NaCl and a colored sample containing 0.72% (w/v) NaCl.