Showing papers on "Incubation published in 2000"

Evolution of passerine incubation behavior: influence of food, temperature, and nest predation.

Abstract: Incubation behavior is one component of reproductive effort and thus influences the evolution of life-history strategies. We examined the relative importance of body mass, frequency of mate feeding, food, nest predation, and ambient temperature to explain interspecific variation in incubation behavior (nest attentiveness, on- and off-bout durations, and nest trips per hour) using comparative analyses for North American passerines in which only females incubate. Body mass and frequency of mate feeding explained little variation in incubation behavior. We were also unable to detect any influence of food; diet and foraging strategy explained little interspecific variation in incubation behavior. However, the typical temperature encountered during reproduction explained significant variation in incubation behavior: Species breeding in colder environments take shorter bouts off the nest, which prevents eggs from cooling to temperatures below the physiological zero temperature. These species must compe...

Effects of ambient temperature on avian incubation behavior

Abstract: Ambient temperature is commonly thought to influence avian incubation behavior. However, results of empirical studies examining correlations between ambient temperature and bout duration are equivocal. We propose that these equivocal results can be partly explained by developing a conceptual understanding of how we should expect temperature to influence incubation. We demonstrate why linear correlation analyses across a wide range of temperatures can be inappropriate based on development of an incubation model for small birds that incorporates how ambient temperature influences both embryonic development and adult metabolism. We found support for predictions of the model using incubation data from orange-crowned warblers (Vermivora celata) in Arizona. Both off- and on-bout duration were positively correlated with ambient temperature between 9 and 26C, but unrelated to ambient temperature 9 and 26–40C. Bout durations declined as ambient temperature approached or exceeded 40C. Incubating orange-crowned warblers appeared to avoid bouts off the nest 7 min and bouts on the nest 20 min. Time of day, duration of the previous bout, and variation among nests all explained variation in both onand off-bout duration. Although we found support for the general shape of the incubation model, temperature still explained only a small portion of the overall variation in on- and off-bout duration. Results of previous studies were generally consistent with the model for off-bout duration; most studies in colder environments reported positive correlations with temperature, and the one negative correlation reported was from a hot environment. However, the relationships between on-bout duration and temperature reported in previous studies were less consistent with our model and our data. Although some discrepancies could be explained by considering our model, some studies reported negative correlations in cold environments. The effect of ambient temperature on duration of on-bouts probably differs among species based on the amount of fat reserves females typically carry during incubation and the extent of male incubation feeding. Additional studies of the effects of temperature on avian incubation will help improve the general model and ultimately aid our understanding of energetic and ecological constraints on avian incubation. Key words: ambient temperature, foraging, incubation behavior, incubation model, incubation rhythm, nest attentiveness, on-bout duration, off-bout duration. [Behav Ecol 11:178–188 (2000)]

Incubation period and sources of exposure for cutaneous Mycobacterium marinum infection: case report and review of the literature.

Abstract: The diagnosis of cutaneous Mycobacterium marinum infection is often delayed for months after presentation, perhaps because important clinical clues in the patient's history are frequently overlooked. Knowledge of the incubation period allows the clinician to target questions about the patient's history. Prompted by a case with a prolonged incubation period, we sought to determine more precisely the incubation period of M. marinum infection. The MEDLINE database for the period 1966-1996 was searched for information regarding incubation period and type of exposure preceding M. marinum infection. Ninety-nine articles were identified, describing 652 cases. Forty cases had known incubation periods (median, 21 days; range, 5-270 days). Thirty-five percent of cases had an incubation period > or =30 days. Of 193 infections with known exposures, 49% were aquarium-related, 27.4% were related to fish or shellfish injuries, and 8.8% were related to injuries associated with saltwater or brackish water. Because the incubation period for cutaneous M. marinum infection can be prolonged, patients with atypical cutaneous infections should be questioned about high-risk exposures that may have occurred up to 9 months before the onset of symptoms.

Influence of incubation temperature on morphology, locomotor performance, and early growth of hatchling wall lizards (Podarcis muralis)

Abstract: Eggs of wall lizards (Podarcis muralis) were incubated at three temperatures ap- proaching the upper limit of viability for embryonic development in this species (26, 29, and 32°C) to assess the influence of temperature on various aspects of hatchling phenotype likely affecting fitness. The thermal environment affected size and several morphometric characteristics of hatchling lizards. Hatchlings from eggs incubated at 32°C were smaller (snout-vent length, SVL) than those from 26 and 29°C and had smaller mass residuals (from the regression on SVL) as well as shorter tail, head, and femur relative to SVL. Variation in the level of fluctuating asymmetry in meristic and morphometric traits associated with incubation temperatures was quite high but not clearly consistent with the prediction that environmental stress associated with the highest incubation temperatures might produce the highest level of asymmetry. When tested for locomotor capacity in trials developed at body temperatures of 32 and 35°C, hatchlings from the 32°C incubation treatment exhibited the worst performance in any aspect considered (burst speed, maximal length, and number of stops in the complete run). Repeated measures ANCOVAs (with initial egg mass as covariate) of snout-vent length and mass of lizards at days 0 and 20 revealed significant effects of incubation temperature only for mass, being again the hatchlings from eggs incubated at 32°C those exhibiting the smallest final size. All together, our results evidenced a pervasive effect of thermal regime during incubation (and hence of nest site selection) on hatchling phenotypes. How- ever, incubation temperature does not affect hatchling phenotypes in a continuous way; for most of the analysed traits a critical threshold seems to exist between 29 and 32°C, so that hatch- lings incubated at 32°C exhibited major detrimental effects. J. Exp. Zool. 286:422-433, 2000. © 2000 Wiley-Liss, Inc.

Effect of incubation temperature on morphology, growth, and survival of juvenile sceloporus undulatus

Abstract: Incubation temperature affects a wide range of phenotypic traits of hatchling rep- tiles. The main objective of this research was to determine if such phenotypic traits persist long enough in the field to have an effect on fitness. Eggs of Sceloporus undulatus lizards were incubated at six temperature regimes, five constant and one fluctuating, with means ranging from 23-33 C. Hatchlings were measured and their subsequent morphology, growth, and survival were monitored for 7-9 months, one to two months before individuals reached adult size. Phenotypic traits of lizards that hatched at the field site were used for comparative purposes. Morphological traits persisted for 7-9 mo. In contrast, growth rates did not differ among incubation temperature treatments after individuals were released in the field. Overall, 29 (27%) of 107 individuals that were released survived to the spring following hatching, and individuals from eggs incubated at the lowest tem- perature had higher survival than individuals from all other groups. The phenotypes of lizards incubated at intermediate temperatures tended to be most similar to those of field hatched lizards. We rejected two predictions about phenotypic responses to incubation temperature. The first pre- diction was that extreme incubation temperatures would be associated with the most deviant phe- notypes. Observed phenotypic responses to temperature were either linear or, only one extreme temperature produced a deviant phenotype. The second prediction was that hatchlings incubated at warm temperatures and that hatched early in the season would have higher survival in general and higher overwinter survival in particular than hatchlings incubated at cool temperatures and that hatched later in the season. The reverse was true; observed survival was greatest for hatchlings from the coolest incubation treatment that hatched last.

Variation of microcystin content of Microcystis aeruginosa relative to medium N:P ratio and growth stage

Abstract: Changes in the microcystin content of Microcystis aeruginosa UTEX 2388 were investigated at several N:P ratios of the medium and various growth stages. Under the P-fixed condition, the microcystin content of the cells changed with different medium N:P ratios, with the highest at 2748 microg g-1 at a N:P ratio of 16 after incubation for 7 d. The microcystin content of M. aeruginosa exhibited a high correlation with the total N content regardless of an N-fixed or P-fixed culture. When the N:P ratio of the medium was fixed to 16 : 1, the microcystin content of M. aeruginosa at various growth stages was highest at 2191 microg g-1 after an incubation of 4 d and the chlorophyll-a content showed a similar tendency. There was a highly significant relationship between the microcystin content of M. aeruginosa and the chlorophyll-a concentration in the culture during the incubation. Accordingly, the microcystin content of M. aeruginosa during incubation can be easily estimated and monitored by measuring the in vivo fluorescence changes in the culture.

Influence of cadmium on the metabolic quotient, L-:D-glutamic acid respiration ratio and enzyme activity:microbial biomass ratio under laboratory conditions.

Abstract: This study was carried out to investigate the effect of very high cadmium concentrations (50 and 500 μg Cd g–1 soil) on some biochemical and microbiological measurements under laboratory conditions involving daily soil samplings. The data for both DTPA- and water-soluble Cd showed two distinctive patterns during soil incubation; from 0 to 4 days, values were about 50–500 and 1–100 μg g–1 dry weight soil, whereas they decreased markedly after 7 days. Both daily respiration and the ATP content but not the microbial biomass C determined by the fumigation–extraction method were lowered by high DTPA- and water-soluble Cd concentrations. Dehydrogenase and phosphatase activities as well as both enzyme activity : microbial biomass ratios were decreased by the high DTPA- and water-soluble Cd concentrations. In the first 2 days of incubation, the metabolic quotient (qCO2) was also decreased by the highest values of available Cd. The early (after 6 h) mineralization of l- but not d-glutamic acid to CO2 was inhibited during the 0–4 day incubation period by the highest Cd concentration. Possibly the l-enantiomer was used by a larger fraction of soil microorganisms than the d-enantiomer or, if they were used by the same fraction of soil microorganisms, the d-enantiomer was mineralized at a lower rate. The l- : d-glutamic acid respiration ratio was decreased by the high available Cd content because under polluted conditions soil microorganisms probably discriminated less between the two stereoisomers of glutamic acid.

Plant Species and Plant Incubation Conditions Influence Variability in Epiphytic Bacterial Population Size.

Abstract: The influences of plant species and plant incubation conditions on the variability in bacterial population sizes among leaves were investigated in field and growth chamber studies Pseudomonas syringae strains TLP2 and Cit7 were inoculated onto plants and population sizes were measured at intervals after inoculation Total bacterial population sizes were also assessed in field studies Levels of leaf-to-leaf variability in both P syringae population size and bacterial community size differed significantly among plant species For all plant species, variability among leaves in population sizes of inoculated bacteria was consistently greater than the leaf-to-leaf variability in numbers of total bacteria Considering levels of variability in population size immediately prior to and following incubation under either wet or dry physical conditions, leaf-to-leaf variability in the population sizes of inoculated P syringae strains increased significantly following incubation under dry, but not under wet, conditions Measurements of leaf-to-leaf variability immediately prior to and following incubation were positively correlated regardless of whether the incubation was under wet or dry conditions, though the correlation was greater following dry incubation These data provide insight into the biological and physical factors that may be important in generating variability in bacterial population sizes among leaves, and they have important implications for the design of appropriate strategies for sampling leaf surface microbial populations

Evolutionary routes to joint-female nesting in birds

Abstract: Cooperative breeding systems in birds vary widely in terms of group composition and degree of reproductive skew among male and female group members. A new classification scheme based on different combinations of male and female skew is proposed. A review of cooperative species reveals a fundamental dichotomy between low-skew joint-female species on the one hand, and joint-male and high-skew helper species on the other. All cooperative joint-female systems are characterized by male-biased incubation, whereas either gender (but usually females) may perform the majority of incubation in non–joint-female systems. Male incubation is thus a necessary, but not a sufficient, precursor for the evolution of communal laying. Other characteristics of joint-female systems, such as mating system, group composition, and nestling developmental mode, differ greatly. Three evolutionary scenarios for the evolution of male incubation and joint laying are outlined: (1) large body size relative to egg size, which enables the successful incubation of more eggs than a single female can lay (e.g., ratites and magpie goose); (2) energetically costly egg laying, incubation, and nestling care, coupled with adaptations permitting incubation of very large clutches (e.g., anis); and (3) cooperative polyandry in lineages with male-biased incubation (e.g., woodpeckers and gallinules). All three scenarios presume that an incubating male resource increases the selective pressure on females to lay joint clutches. Available evidence for the origin and maintenance of the critical precursors, constraints, and adaptations are summarized and shown to be absent in non–joint-laying species. These factors and conditions affect the critical parameters of the skew models in ways that are predicted to result in low reproductive skew.

Chemical and biological processes leading to the neutralisation of acidity in soil incubated with litter materials

Abstract: Plant materials containing high amounts of ash alkalinity can be utilized to increase the pH of acid soils but the chemical and biological processes involved in the release of this alkalinity are not fully understood. In this laboratory study fresh leaf litter from two tree species (Melia azedarach, Castanea sativa) and sugarcane (Saccharum oAcinarum) trash containing ash alkalinities of 288, 141 and 33 mmolc kg ˇ1 respectively, were mixed at three diAerent rates (4, 16, 32 mg g ˇ1 ) with acidic topsoil from a Ultic Palexeralf and incubated at 90% WHC and at 258C for 20 d while monitoring CO2-evolution. Treatment eAects were assessed by measuring changes in pH, acid buAering curves and exchangeable cations before and after incubation. Furthermore, soluble organic compounds, mineral N-forms were determined in soil extracts. Immediately after mixing, up to 50% of the added alkalinity was available for acid neutralisation. After incubation, acid neutralisation capacity at pH 4 (ANCpH4) and the pH of the soils with the two higher amendment rates had increased in all treatments. The changes were most pronounced in the Melia amended soils, followed by Castanea and sugarcane and reflected the added amounts of ash alkalinity. In all treatments, soil respiration increased with amendment rate and was closely related to a decline in soluble organic carbon during incubation. Together with the shift from stronger to weaker acidity observed after incubation, this is evidence for the microbial decarboxylation of soluble organic anions. 7 2000 Elsevier Science Ltd. All rights reserved.

Sex differentiation and mRNA expression of P450c17, P450arom and AMH in gonads of the chicken.

Abstract: The present study was conducted to reveal effects of in ovo injection of nonsteroidal aromatase inhibitor (Fadrozole) or estradiol at day 3 of incubation on mRNA levels of P45017ahydroxylase (P450c17), P450 aromatase (P450arom) and anti- Mullerian hormone (AMH) in the chicken gonads. The mRNA levels in the gonads at days 4-8 of incubation were assessed by in situ hybridization analysis using digoxigenin labeling method. The in situ hybridization data were analyzed by relative expression of specific hybridizable signals of each mRNA corrected by the non-specific background by employing an image ana- lyzer. P450c17 mRNA expression increased rapidly at day 6 of incubation in the male but decreased thereaf- ter. In contrast to the transient expression in the male, the expression was gradually increased in the female. P450arom mRNA was not expressed in the male but was detectable in the female as early as day 6 and increased subsequently with days of incubation. AMH mRNA was expressed as early as day 5 of incubation followed by a sharp increase on day 6, which was maintained in the male thereafter. In contrast, the female showed very little expression. The injection of Fadrozole caused no effect on P450c17 mRNA expres- sion, while it suppressed P450arom mRNA expression but increased AMH mRNA expression in the female. In contrast, the injection of estradiol induced P450arom mRNA expression significantly but suppressed AMH mRNA expression in the male. These results indicate that expression of P450arom and AMH is sexually dimorphic and is reciprocally regulated during early ontogenic life in chicken gonads. Mol. Reprod. Dev. 55:20-30, 2000. r 2000 Wiley-Liss, Inc.

Estrogen effects on Candida albicans: a potential virulence-regulating mechanism.

Abstract: Three Candida albicans strains were tested in the presence of 17-beta-estradiol (10-6 M and 10-9 M) for increased growth and for enhanced survival during incubation at nonpermissive temperatures. All 3 test organisms showed increased growth in the presence of estradiol compared with estrogen-free controls. Likewise, all 3 strains, when treated with estradiol, survived incubation at 48 degrees C better than did controls. Cytoplasmic extracts were probed with an anti-hsp90 antibody, and results suggested that intracellular hsp90 was up-regulated in the presence of 10-9 M 17-beta-estradiol. The results were confirmed by reverse-transcriptase polymerase chain reaction with primers specific for C. albicans hsp90. A kinetic study revealed that peak hsp90 expression occurred within 2 h of exposure to 17-beta-estradiol. In addition, estrogen increased the amount of cdr1 (Candida multidrug resistance) mRNA compared with cells not treated with estrogen. Coumarin and phenol also up-regulated hsp90 and cdr1 mRNAs, indicating that the estrogen-sensing and -response systems in C. albicans may lack specificity.

Scrapie infections initiated at varying doses: an analysis of 117 titration experiments

Abstract: An analysis of 117 titration experiments in the murine scrapie model is presented. The experiments encompass 30 years' work and a wide range of experimental conditions. To check that the experimental designs were reasonably consistent over time, comparisons were made of size, duration, source of inoculum, etc., in each experiment. These comparisons revealed no systematic trends that would render invalid comparisons across experiments. For 114 of the experiments it was possible to calculate the dose at which half of the challenged animals were infected (the ID50). These 114 experiments were then combined on the basis of relative dose (i.e. tenfold dilution relative to the ID50). This created a data set in which over 4000 animals were challenged with doses of scrapie ranging from four orders of magnitude below to five orders of magnitude above the ID50. Analysis of this data reveals that mean incubation periods rise linearly with logarithmic decreases in dose. A one unit increase in relative dose (i.e. a tenfold increase in actual dose) will, on average, decrease the incubation period by 25 days. At ID50 the average incubation period in this data set is 300 days. Within a single dose, in a single experimental model, incubation periods have a distribution close to normal. Variability in incubation period also rises linearly as dose decreases. There is no age or sex effect upon the probability of infection, but female mice have incubation periods that are, on average, nine days shorter than their male counterparts and young mice have incubation periods that are longer by seven days. Although many of these patterns are apparent in the results of single titration curves, they can be more rigorously investigated by considering the outcome for thousands of mice.

In vitro viability, mitogenicity and clonogenic capacity of periodontal ligament cells after storage in four media at room temperature

Abstract: The choice of storage medium for preserving traumatically avulsed teeth is important for the success of future replantation. The objective of this study was to compare the effectiveness of four recommended storage media (Hank's balanced salt solution [HBSS], culture medium, alpha minimal essential medium [alpha-MEM], and ViaSpan) to preserve cultured periodontal ligament fibroblasts (PDLF) at room temperature (22 degrees C). PDLF were obtained from explants of extracted healthy human teeth. Plates with confluent PDLF were soaked in the various media for 2, 8 and 24 h at room temperature. A control group was incubated with culture medium at 37 degrees C. After incubation, viability of the cells was determined by trypan blue exclusion test. Viable cells were then analyzed for mitogenic (with thymidine) and clonogenic capacity (by culturing one cell/well). Viability of PDLF stored up to 24 h was comparable in all tested media, and the differences were limited to 1%-3%. PDLF stored for up to 24 h in various media had statistically comparable mitogenicity to the control group. After 8 h of storage, the differences were limited to 2%-9%, except for the alpha-MEM group which had 23%-29% lower mitogenic capacity compared to the control group. Increasing the storage time up to 24 h further decreased the mitogenicity of the cells by 22%-47%. The highest mitogenicity after 24 h of storage was found in PDLF stored in culture medium or HBSS, and the lowest in alpha-MEM. PDLF stored for 2-8 h in various media had a comparable clonogenic capacity to the control group. However, after 24 h, the cells' clonogenic ability dropped by 14%-66%. A similar trend of reduction was noted in the mitogenic and clonogenic capacity, although it was statistically significant only in the clonogenic capacity. Culture medium and ViaSpan, followed by HBSS, were the most effective in preserving the clonogenic capacity of PDLF after 24 h of storage. The lowest clonogenic capacity after 24 h of storage was in the alpha-MEM group (66%, P < 0.0025). In conclusion, culture medium, followed by HBSS and ViaSpan, was the most effective media for preserving the viability, mitogenicity and clonogenic capacity of PDLF stored for up to 24 h at room temperature. The lowest functional abilities were found in PDLF stored in alpha-MEM.

The use of incubation behavior to adjust avian reproductive costs after egg laying

Abstract: Reproduction in birds requires the input of time and energy during discrete breeding phases leading to investment trade-offs between laying date, clutch size, body mass, and incubation constancy. We investigated costs during incubation by experimentally enlarging 25 clutches of white-tailed ptarmigan Lagopus leucurus. The experiment was conducted in 2 years, one with harsh weather that forced a natural delay in reproduction. When forced to delay egg-laying, females began incubation with poorer body condition and foraged more during incubation. Rates of mass loss during incubation were not affected by clutch enlargement, and did not differ between harsh and benign years; however, females that were heavier at the start of incubation lost more mass than lighter females. Clutch-enlarged females had reduced nest attendance compared to control birds in both years and incubation periods increased by up to 2 days relative to controls. In the harsh year, there was a trend for clutch-enlarged females to have lower nest success, but there was no effect on overwinter survival. Different behavioral responses by females in the 2 years showed that incubation costs may depend on other factors such as female quality, food supply, or weather conditions. Incubation is a dynamic period during which birds may adjust energy balances by varying body condition and food intake.

Patterns of nest attendance in female wood ducks

Abstract: We examined sources of variation in incubation patterns among female Wood Ducks (Aix sponsa), and investigated the effect of female nest attentiveness on incubation period. Data were collected from 44 females (n = 911 days) using temperature data loggers to monitor nest attendance throughout incubation. Mean (± SE) incubation constancy was 86.9 ± 0.6% and incubation period averaged 30.9 ± 0.2 days. Females took an average of two bimodally-distributed recesses per day. Duration of recesses averaged 98.6 ± 3.4 min, but were shorter in the morning than in mid-day or late afternoon. Body mass of incubating females declined 0.68 ± 0.2 g day−1, but there was no relationship between constancy and early incubation body mass or weight change of females. Incubation constancy was not correlated with length of the incubation period. For most females, incubation constancy and recess frequency did not change as incubation progressed. The fact that incubating females only lost an average of 3% of body mass, and...

Lipid Hydroperoxide Determination in Dark Chicken Meat through a Ferrous Oxidation−Xylenol Orange Method

Abstract: A ferrous oxidation-xylenol orange (FOX) method was adapted to measure lipid hydroperoxides (LHP) in raw and cooked dark chicken meat. Its applicability was evaluated using samples with different alpha-tocopherol contents or unsaturation degrees (both modulated by dietary supplementation). The FOX assay can work as an induced method because there is some oxidation of the sample extract during the incubation of the reaction. Consequently, it allows assessment of sample susceptibility to oxidation (response after some hours of incubation) and comparison of samples that are highly oxidized or readily susceptible to oxidation through their absorbance after 30 min of incubation. It is highly specific for LHP and showed a linear relationship between volume of meat extract and absorbance. However, the most suitable volume of extract and incubation time must be studied for each kind of sample. The use of butylated hydroxytoluene during this incubation is strongly discouraged because it attenuated the reaction by radical stabilization, thus diminishing Fe(III) formation and leading to a lower response.

17β-Estradiol modulates endothelin-1 expression and release in human endothelial cells

Abstract: Objective: In this study the role of 17β-estradiol (E2) in the regulation of endothelin-1 (ET-1) mRNA expression and secretion was investigated in cultured human umbilical vein endothelial cells (HUVECs). Methods: Endothelial cells were either deprived of or treated with 17β-estradiol (10−9, 10−7 M) for 48 h. After the incubation, the effect of E2 on ET-1 gene expression was evaluated by Northern blot analysis. ET-1 release into the media was measured by radioimmunoassay after 6 h of incubation under basal conditions and upon stimulation with thrombin (4 U/ml). In addition, the cyclic guanosine 5′-monophosphate (cGMP) content of cells was assayed by immunoassay. In order to exclude the role of nitric oxide (NO) in E2-induced effects on endothelin-1 gene expression and secretion, nitric oxide synthase (NOS) inhibitor, N -nitro l-arginine methyl ester (1 mM) (l-NAME) was added to the media of some cultures. Results: Incubation of HUVECs with 10−9 and 10−7 M E2 for 48 h resulted in a 30 and 47% inhibition of ET-1 mRNA expression, respectively. Incubation with E2 also decreased the basal and thrombin-stimulated ET-1 release while increasing the cGMP content of cells significantly. NOS inhibitor l-NAME increased the release of ET-1 from E2-incubated cells but did not alter the ET-1 release from hormone-deprived cells. However, ET-1 secretion of E2-treated cells were significantly less than the deprived ones. Northern blot analyses also demonstrated that inhibition of NOS only partly attenuated the effect of E2 on ET-1 gene expression. In the presence of l-NAME, treatment with 10−7 M E2 caused a 12% decrease in ET-1 gene expression. Conclusion: The results demonstrate that E2 may play both direct and indirect role in regulation of ET-1 gene expression and production in human endothelial cells. E2-induced increase in NO but decrease in ET-1 production may partly explain the mechanism of the protective effects of the hormone on the cardiovascular system.

Effect of short periods of high incubation temperature on hatchability and incidence of embryo pathology of turkey eggs.

Abstract: 1. Turkey eggs were incubated at 38.0 degrees and 38.5 degrees C at different stages of embryo development and for periods of 3 to 25 d. Results were compared with control eggs incubated at 37.5 degrees C. The age of mortality, the incidence of malpositions and the incidence of morphological abnormalities were recorded from all unhatched eggs. 2. Eggs incubated at 38.5 degrees C for 5 or more days hatched significantly less well than eggs incubated at 37.5 degrees C. Eggs incubated at 38.5 degrees C for 3 d hatched worse than controls but not significantly so. Eggs incubated between 0 and 25 d and 7 and 12 d but not between 0 and 6, 13 and 18 and 19 and 25 d, at 38.0 degrees C had significantly lower hatchabilities than eggs incubated at 37.5 degrees C. 3. Lowest hatchabilities were obtained when the eggs were incubated at high temperatures between 7 to 12 d and 6 to 10 d, indicating that embryos at this stage of development are more likely to succumb to high temperature than at other ages. 4. Increases in embryo mortality due to overheating were seen in weeks 3 and 4 of incubation and at the pipping stage. This was observed even when the period of overheating occurred in weeks 1 and 2 of incubation. 5. Embryos malpositioned with their head in the small end of the egg were seen at a higher incidence when overheating in the 2nd or 3rd quarter of the incubation period.

Developmental changes in plasma catecholamine concentrations during normoxia and acute hypoxia in the chick embryo.

Abstract: 1In the mammalian fetus, the cardiovascular responses to acute hypoxaemia include a redistribution of the cardiac output away from the periphery towards the adrenal, myocardial and cerebral circulations. A component of the peripheral vasoconstriction is mediated by increased release of catecholamines into the fetal circulation during acute hypoxaemia. Previously, we have shown that the chick embryo also shows an increase in peripheral vascular resistance during acute hypoxaemia and that this response becomes progressively larger towards the end of the incubation period. However, the ontogeny of the catecholaminergic response to acute hypoxaemia has not been investigated in this species. 2Fertilised chicken eggs were studied on days 10, 13, 16 and 19 of incubation (hatching is at 21 days). At each stage of incubation, blood samples were obtained from the chorioallantoic artery of the chick embryos during normoxia and after 5 min of hypoxaemia for measurement of plasma concentrations of adrenaline and noradrenaline by HPLC. 3Basal plasma adrenaline and noradrenaline concentrations by the end of the incubation period were much higher in the chick embryo than values reported for mammalian fetuses during late gestation. During normoxia, basal plasma noradrenaline concentration remained unchanged during development but plasma adrenaline concentration showed a developmental increase from < 25.1 pmol l−1 at day 10 to 3 nmol l−1 at day 19 of incubation. Acute hypoxaemia caused an increase in plasma noradrenaline and adrenaline from day 13 and day 16 of incubation, respectively. In addition, the increase in plasma adrenaline and noradrenaline and in the ratio of plasma adrenaline to noradrenaline during acute hypoxaemia became progressively larger by the end of the incubation period. 4These data show an ontogenic increase in basal plasma catecholamines and in the catecholaminergic response to acute hypoxaemia in the chick embryo during the last third of the incubation period.

A seminal vesicle autoantigen of mouse is able to suppress sperm capacitation-related events stimulated by serum albumin.

Abstract: We studied the effect of a mouse seminal vesicle autoantigen (SVA) on BSA-stimulated functions of mouse sperm. Uncapacitated, capacitated, and acrosome-reacted stages of sperm were morphologically scored, and the cellular zinc content was examined cytologically in a modified Tyrode solution at 37 degrees C for 80 min. More than 85% of control cells remained uncapacitated. Addition of 0.3% SVA to the cell incubation did not affect the cell status. Approximately 65% of cells were capacitated in the incubation medium containing 0.3% BSA. Only 30% of the cells became capacitated after incubation with 0.3% BSA and 0.3% SVA together. The decapacitation effect by 0.3% SVA could be subdued by more than 3% BSA in the cell incubation. Whereas BSA did, SVA did not cause removal of Zn(2+) from sperm, but SVA could suppress the BSA effect. The tyrosine phosphorylated proteins in sperm were detected after incubation in a modified HEPES medium containing 0.3% BSA and/or 0.3% SVA at 37 degrees C for 90 min. Whereas BSA enhanced greatly, SVA did not cause phosphorylation of proteins in the range of M:(r) 40 000-120 000. The BSA-stimulated protein tyrosine phosphorylation could be suppressed by SVA in the cell incubation.

Costs of incubation and immunocompetence in the collared flycatcher.

Abstract: This paper investigates the costs of incubation in terms of reduced reproductive success and investigates whether incubation competes with immune function for resources. I performed a clutch size manipulation experiment in which two eggs were either removed from or added to the nests of collared flycatchers, Ficedula albicollis, for 1 week during incubation and subsequently returned to their original nests before hatching. To induce immune response, the females were challenged with sheep red blood cells. While the duration of incubation, hatching success and fledgling number did not differ between experimental groups, fledgling condition was significantly lower in broods that had been enlarged during incubation. Neither the females' condition nor their ability to respond to a novel antigen differed between treatments. The relationship between antibody production and female condition was significantly positive, but only among females incubating reduced clutches. I conclude that the costs of incubation in the collared flycatcher are not negligible and are manifested only at the chick-rearing phase.