Helpers at the nest compensate for reduced maternal investment in egg size in carrion crows.

Life history theory predicts that mothers should trade off current and future reproductive attempts to maximize lifetime fitness. When breeding conditions are favourable, mothers may either increase investment in the eggs to improve the quality of the offspring or save resources for future reproduction as the good raising environment is likely to compensate for a 'bad start'. In cooperatively breeding birds, the presence of helpers improves breeding conditions so that mothers may vary the number, size and quality of the eggs in response to the composition of the group. Here, we show that in cooperatively breeding carrion crows Corvus corone corone, where nonbreeding males are more philopatric and more helpful at the nest than females, breeding females decreased egg size as the number of subordinate males in the group increased. However, despite the smaller investment in egg size, fledglings' weight increased in groups with more male subordinates, improving post-fledging survival and indicating that helpers fully compensated for the initial 'bad start'. These results highlight a 'hidden effect' of helpers that bears profound implications for understanding the ultimate function of helping.

Evolution of tolerance by magpies to brood parasitism by great spotted cuckoos.

Hosts may use two different strategies to ameliorate negative effects of a given parasite burden: resistance or tolerance. Although both resistance and tolerance of parasitism should evolve as a consequence of selection pressures owing to parasitism, the study of evolutionary patterns of tolerance has traditionally been neglected by animal biologists. Here, we explore geographical covariation between tolerance of magpies (Pica pica) and brood parasitism by the great spotted cuckoo (Clamator glandarius) in nine different sympatric populations. We estimated tolerance as the slope of the regression of number of magpie fledglings (i.e. host fitness) on number of cuckoo eggs laid in non-depredated nests (which broadly equals parasite burden). We also estimated prevalence of parasitism and level of host resistance (i.e. rejection rates of mimetic model eggs) in these nine populations. In accordance with the hypothetical role of tolerance in the coevolutionary process between magpies and cuckoos we found geographical variation in tolerance estimates that positively covaried with prevalence of parasitism. Levels of resistance and tolerance were not associated, possibly suggesting the lack of a trade-off between the two kinds of defences against great spotted cuckoo parasitism for magpies. We discuss the results in the framework of a mosaic of coevolutionary interactions along the geographical distribution of magpies and great spotted cuckoos for which we found evidence that tolerance plays a major role.

Characterization of daytime sleepiness and psychomotor performance following H1 receptor antagonists.

BACKGROUND: While first generation H1-receptor antagonists are widely used, there are relatively few data describing their comparative effects on subjective daytime sleepiness and psychomotor performance. OBJECTIVE: To compare the effects of first generation H1 receptor antagonists on subjective daytime sleepiness and psychomotor performance. METHODS: We conducted two single-dose, cross-over studies. In the first, we validated our methodology in 18 healthy subjects by examining the response to diphenhydramine (50 mg), terfenadine (60 mg), and placebo. In the second trial, we evaluated the relative effects following diphenhydramine (50 mg), diphenhydramine (25 mg), chlorpheniramine (4 mg), and placebo. Psychomotor tests included choice reaction time, hand steadiness, and a test that divided attention between tracking and reaction time. Introspective drowsiness was measured using a visual analog scale and the Stanford Sleepiness Scale. Assessments were made prior to dosing and at one, three, and five hours after dosing; a 7-hour post-drug assessment was included in the second trial. RESULTS: In the first trial, 50 mg diphenhydramine produced significant impairment relative to placebo in both subjective and objective assessments (P < .05). Responses following terfenadine did not differ from placebo. In the second study, all three regimens produced subjective and objective soporific effects to a significantly greater degree than placebo. For example, significant introspective sleepiness was noted three hours following all three regimens (P < .05) and slower choice reaction times were noted one and three hours after dosing (P < .05). The general rank order of effects was diphenhydramine (50 mg), followed by diphenhydramine (25 mg), followed by chlorpheniramine (4 mg). Significant differences among the three regimens were, for the most part, confined to greater soporific effects from diphenhydramine relative to chlorpheniramine (P < .05). CONCLUSIONS: Taken together, our observations confirm that subjective and objective measures of sleepiness and psychomotor performance occur following single doses of diphenhydramine and chlorpheniramine, but not terfenadine. Differences in soporific effects do exist among regimens of first-generation compounds.

The effects of phenindamine tartrate on sleepiness and psychomotor performance.

Phenindamine, an H1-receptor antagonist that was developed almost 50 years ago, has been associated with both drowsiness and insomnia. Since its central nervous system profile has not been well characterized, we used a series of psychomotor tests to conduct two studies. In the first, 12 subjects received single oral doses of phenindamine (25 mg), diphenhydramine (50 mg), terfenadine (60 mg), or placebo in a four-way crossover study. Psychomotor tests included choice reaction time (CRT), tracking, and hand steadiness (HS). In the second trial, 15 subjects received single oral doses of phenindamine (25 mg), pseudoephedrine (60 mg), phenindamine and pseudoephedrine, diphenhydramine (50 mg), or placebo in a five-way crossover study. Psychomotor tests included CRT, HS, and a task that divided attention between tracking and reaction time. Introspective drowsiness was measured in both trials with use of a visual analog scale (VAS) and the Stanford Sleepiness Scale (SSS). All assessments were made before and 1, 3, and 5 hours after drug administration. In the first trial, diphenhydramine produced significant impairment relative to placebo (p < 0.05) in CRT, tracking, and HS tasks and higher SSS and VAS scores, with peak effect noted at 3 hours. Phenindamine did not significantly differ from placebo or terfenadine. In the second trial, diphenhydramine produced significant impairment relative to placebo (p < 0.05) in CRT, divided attention, HS, and VAS, and SSS, also peaking at 3 hours. Stanford Sleepiness Scale scores after phenindamine were greater than placebo at 3 hours (p < 0.05) but significantly less than diphenhydramine (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Superficial nasal mucosal blood flow and nasal patency following topical oxymetazoline hydrochloride.

The objective of this study was to evaluate the effect of 60 micrograms oxymetazoline on nasal mucosal blood flow (NMBF) measured by laser Doppler velocimetry. Nasal airflow (measured by anterior rhinomanometry) and subjectively perceived airflow (measured by visual analog scales) were also evaluated. A reduction of NMBF (mL/100 g tissue/min) was observed following local application of 60 micrograms oxymetazoline that was not observed after the vehicle was applied. For example, NMBF at baseline was measured at 78.8 +/- 10.3 mL/100 g tissue/min (mean +/- SEM). During the five minutes following vehicle application, mean values remained at 81.8 +/- 8.8 mL/100 g tissue/min. Five minutes after topical oxymetazoline treatment, NMBF was reduced 49% to 38.3 +/- 10.2 mL/100 g tissue/min. Nasal airflow (mL/sec), which was measured before and after LDV probe placement, was not significantly increased in either the ipsilateral (281.4 +/- 33.1 to 314.3 +/- 31.6) or contralateral nostril (335.7 +/- 26.9 to 262.1 +/- 36.4), probably due to the limited surface application of drug. Subjective assessments of congestion by both the investigator and the subject showed significant improvements in the ipsilateral nostril. We conclude that, under the conditions of our study, localized application of 60 micrograms oxymetazoline significantly reduces superficial nasal blood flow and provides subjectively perceived improvements in nasal stuffiness.

A technique for measuring the perception of added resistive loads during nasal breathing.

The perception of resistive loads added to nasal breathing was assessed in ten healthy adults using established psychophysical methods previously described for oral breathing. Detection threshold, that is, the smallest incremental resistance that the subject could detect 50% of the time, was determined at three different time periods (0, 30, and 60 min) on two separate days to determine the reproducibility of values over time. Nasal airway resistance measurements were made before and after threshold determinations to determine the influence of baseline resistance on the ability to detect added loads as well as to assess any effects of the procedure itself on resting nasal airway resistance. Analyses of the data revealed that subject-to-subject differences were the largest source of variability in threshold values followed by time period-to-time period differences and day-to-day variability. Although it was the smallest variability source, day-to-day variability still was significantly greater than zero. In contrast to previously published reports on resistive load detection during mouth breathing, the degree of baseline resistance did not appear to influence the subject's ability to detect added resistive loads during nasal breathing. These techniques may provide a methodological basis for objectively evaluating the effects of pharmacologic agents on perceived nasal patency.