Showing papers on "Incubation published in 1995"

Nitric oxide dilates tight junctions and depletes ATP in cultured Caco-2BBe intestinal epithelial monolayers

Abstract: We tested the hypothesis that nitric oxide (NO) modulates the permeability of tight junctions in a model intestinal epithelium (Caco-2BBe monolayers). Incubation with sodium nitroprusside (SNP) resulted in time- and concentration-dependent decreases in transepithelial resistance. Permeability to fluorescein sulfonic acid increased during incubation for 24 h in the presence of 1.25 mM SNP, 5 mM S-nitroso-N-acetylpenicillamine (SNAP), or 1% NO gas. SNP-induced hyperpermeability was not due to loss of cell viability, as confirmed by intact ultrastructure, unaltered lactate dehydrogenase release, and ability to recover baseline permeability. Incubation with SNP increased permeability but only minimally increased intracellular levels of guanosine 3',5'-cyclic monophosphate (cGMP). Incubation with Escherichia coli heat-stable enterotoxin greatly increased cGMP levels with only a minimal effect on permeability. Cellular ATP levels decreased after incubation with SNP, SNAP, or gaseous NO. Incubation with SNP led to diminished fluoresceinphalloidin staining of junctional actin (confocal microscopy) and widened tight junctions (electron microscopy). We conclude that NO reduces ATP levels and reversibly increases the permeability of tight junctions in cultured Caco-2BBe cells.

Phenotypic Plasticity for Growth in the Common Snapping Turtle: Effects of Incubation Temperature, Clutch, and Their Interaction

Abstract: Abstrcact.-We examined a critical component of the Charnov-Bull hypothesis of temperaturedependent sex determination (TSD) by determining the reaction norms of hatchling growth to embryonic incubation temperature in the common snapping turtle, Chelydra serpentina. Hormone manipulations of eggs produced females at male temperatures and vice versa, which thereby permitted same-sex comparisons of hatchling growth across a range of incubation temperatures. In this way, the normally confounded effects of incubation temperature and sex were dissociated experimentally. The resultant hatchlings, including controls and experimentals, exhibited normal gonadal structure and sex steroid profiles. The subsequent growth of hatchlings monitored for 6 mo was strongly affected by embryonic incubation temperature but not by sex. As predicted, growth was enhanced at incubation temperatures that produced males. Clutch effects and interaction effects (clutch by incubation temperature) on growth were significant. In addition, there was a positive genetic covariance among incubation temperatures, but incubation temperature effects varied among clutches. The variation in growth plasticity among clutches was consistent with Charnov-Bull predictions. In this TSD species, incubation temperature is likely to have differential fitness effects on the sexes mediated via differences in growth.

Experimental evidence for the evolutionary significance of temperature-dependent sex determination.

Abstract: The evolutionary significance of sex-determining mechanisms, particularly temperature-dependent sex determination (TSD) in reptiles, has remained unresolved despite extensive theoretical work. To investigate the evolutionary significance of this unusual sex-determining mechanism, I incubated eggs of the common snapping turtle (Chelydra serpentina) at a male-producing temperature (26°C), a female-producing temperature (30°C), and an intermediate temperature that produced both sexes about equally (28°C). Laboratory experiments indicated that two performance variables, but no morphological measurements, were significantly influenced by incubation temperature (P ≤ 0.05): hatchlings from cooler incubation treatments swam faster than turtles from warmer incubation treatments, and hatchlings from 28°C exhibited a greater propensity to run than did individuals from 26°C and 30°C. In the field, hatchlings from the all-male and all-female producing temperatures had significantly higher first-year survivorship than did consexuals from the incubation temperature that produced both sexes (G = 6.622, P = 0.03). Significant directional selection was detected on propensity of hatchlings to run (β' = -0.758, P = 0.05): turtles that tended to remain immobile had a higher probability of first-year survivorship than did individuals that moved readily. Thus, the effects of the gender × incubation temperature interaction on survivorship of hatchling turtles observed in the field experiment may have been mediated by temperature-dependent antipredator behavior. These results provide a possible functional explanation for the evolutionary significance of TSD in turtles that is consistent with predictions of theoretical models.

Does the cost of incubation set limits to clutch size in common eiders Somateria mollissima

Abstract: We examined the effect of natural clutch size on the cost of incubation in a population of common eiders Somateria mollissima nesting in Tromso, northern Norway. The body condition of females at day 5 in the incubation period was not related to clutch size (3–6 eggs), but females incubating large clutches lost more mass and had a lower body condition at day 20 in the incubation period than females incubating small clutches. Females incubating large clutches had a slightly shorter incubation period and a lower egg predation rate. The results do not support the hypothesis that the female's ability to produce eggs is the only ultimate control of clutch size in eider. Instead the results suggest that there may be an interaction between the allocation of body reserves to eggs and incubation, and that females producing large clutches allocate more of their body reserves to incubation than females producing small clutches, in order to shorten the incubation period and to minimise the risk of predation on eggs.

Changes in heated and autoclaved forest soils of S.E. Australia. I. Carbon and nitrogen.

Abstract: The effect of heating and autoclaving on extractable nitrogen, N mineralisation and C metabolism was studied by heating five forest soils in the laboratory, simulating the range of effects of heat due to bushfire. Top soil (0–5 cm) was heated to 60 °C, 120 °C and 250 °C for 30 minutes; unheated soil was taken as a control. Samples of the soil heated to 250 °C were also inoculated with fresh soil to accelerate the recovery of the microbial population. Soil autoclaving was carried out as another heat treatment (moist heat). Soils were analysed immediately after heating and 3 times during seven months of incubation to assess immediate and longer-term effects of heating. Extractable N (organic and mineral forms) increased after heating to 120 °C, but decreased with further heating to 250 °C suggesting the volatilisation of N. N associated with microbial biomass diminished with heating and was barely detectable after the 250 °C treatment. Microbial biomass was an important source of soluble N in heated soils, and only partly recovered during subsequent long incubation. The amount of N mineralised during incubation depended on both soil and temperature. Nitrification did not occur when soils were heated to 250 °C (with or without inoculum), or after autoclaving, demonstrating the high sensitivity of nitrifiers to heat. At the beginning of soil incubation, respiration was enhanced in heated soils (250 °C, 250 °C inoculated) and autoclaved soils, but after 30 days of incubation respiration decreased to values either similar to or lower than those in control. This respiration pattern indicated that a fraction of labile C was released by heating, which was quickly mineralised within 30 days of incubation. These results demonstrate some effects of soil heating on C and N dynamics in forest soils.

A study of the role of corticosterone as a mediator in exercise‐induced stimulation of murine macrophage phagocytosis.

Abstract: 1. It is generally accepted that physical activity provokes changes in the immune system. Previous studies have demonstrated that the stress of physical activity (swimming until exhaustion) increases the phagocytic activity of peritoneal macrophages. However, the precise mechanisms remain unknown. 2. Two experiments were performed in the present study. (A) Peritoneal macrophages from control mice were incubated with plasma from three different groups of mice: (1) mice subjected to swimming until exhaustion with no previous training, (2) mice subjected to the same activity but with 1 month of training (30 min day-1), and (3) a control (non-exercised) group. The differences in the resulting phagocytic (attachment and ingestion) capacity were measured. (B) Changes in the concentration of plasma corticosterone after exercise were also measured, and the effect of incubation with the postexercise plasma corticosterone level on the phagocytic activity of peritoneal macrophages was then studied in vitro. 3. The results were: (A) incubation with plasma from both groups of exercised mice (with and without previous training) led to increased levels of phagocytic capacity (number of C. albicans cells ingested per 100 macrophages). (B) Incubation with a corticosterone concentration of 0.72 mumol l-1 (similar to that observed in plasma immediately after exercise) raised the phagocytic capacity (144 +/- 12 after incubation with 0.72 mumol l-1 vs. 93 +/- 19 after incubation with 0.24 mumol l-1). This increase was also significantly greater than that observed with 7.2 mumol l-1 corticosterone. 4. It is concluded that corticosterone may mediate the increased phagocytic function of peritoneal macrophages induced by exercise.

Rates of net nitrogen mineralization in disturbed and undisturbed soils

Abstract: Quantification of net nitrogen mineralization (NNM) in soils is indispensable in order to optimize N fertilization of crops. Two long-term laboratory incubation methods were applied to determine rates of net nitrogen mineralization (rNNM) of soils from two sites of arable land (sandy loam soil, silty loam soil) at four temperature levels (2°C, 8°C, 14°C, 21°C). Since variability within replicates was small, the modified 12-week incubation method of Stanford and Smith (1972) using disturbed soils allowed to establish reliable Arrhenius functions with reasonable expenditure. The fit of the functions derived from the 5-month incubation of 23 undisturbed soil columns (4420 cm3) was worse. This was caused by greater variability and less differentiation between temperature levels. Results of both experiments could be described best by zero-order kinetics. Mean mineralization rates of disturbed samples were approximately twice as high than those of undisturbed samples. The suitability of both methods for the prediction of NNM at site conditions is discussed. Actual respiration (AR) at incubation temperatures and substrate induced respiration (SIR) were measured at the end of the incubation of undisturbed soil columns. The results presented reveal that soil microbial communities develop in a different manner during long-term incubation at different temperatures. This behavior offends the underlying assumption that soil microbes remain in steady-state during incubation and that rising rates are physiological reactions to temperature enhancement. Therefore soil microbial biomass (SMB) dynamics during the experiment has to be accounted for when rates of NNM and Arrhenius functions are established. R Merck Section editor

Maintenance of denitrification potential in pasture soil following anaerobic events

Abstract: Reduction enzymes involved in the denitrification process which are critical for the kinetics of NO3−, NO2−, N2O and N2 are synthesized under anaerobic conditions and repressed by subsequent aerobic conditions. The enzymes are progressively degraded in aerobic soil but are de-repressed by re-introduction of anaerobiosis. Dynamics of these enzymes after different periods of aerobic incubation were investigated for a soil from permanent pasture. Soil anaerobically incubated for 3 days was then aerobically stored at 25°C for 70 days. On days 0, 3, 7, 14, 28, 49 and 70 of storage, soil was amended with a KNO3 solution and combinations of C2H2, glucose and chloramphenicol (to prevent de novo enzyme synthesis). Additionally, on days 28, 49 and 70, soil was first pre-conditioned anaerobically for 3 days at 25°C and then assayed using the same treatments. The production of CO2 and N2O and the concentrations of NO3− and NO2− were then measured at 2, 5, 12, 24, 36 and 48 h in an anaerobic incubation at 25°C. Nitrate reductase concentration appeared to be high relative to the availability of C substrate at the onset of each anaerobic incubation. The reduction of NO3− and the production of N2O increased when glucose was added to the soil although de novo synthesis of the enzyme was inhibited by chloramphenicol. Concentrations of nitrite and nitrous oxide reductase decreased over storage time under aerobic conditions. The proportion of N2 relative to N2O formed decreased from 49% on day 0 to 28% on day 3 but was still 21% of gaseous N losses on day 49. No detectable N2 was formed on day 70. The ratio between the rate of N2O produced and the rate of CO2 produced decreased sharply from 1.01 to 0.78 between day 0 and 3 but only gradually declined thereafter. The anaerobic prior incubation of 3 days decreased the concentrations of NO2− and the N2O-to-N2 ratio, but increased the N2O-to-CO2 ratio as compared to the unconditioned soil. Chloramphenicol not only increased CO2 and N2O production, but also decreased nitrite reductase and nitrous oxide reductase activity. It was concluded that the duration of aerobiosis affected the concentrations of reduction enzymes involved in the denitrification process and thus the N2O-to-N2 ratio when anaerobic conditions were induced. The link between the C mineralization and the reduction of NO3− not only depends on the composition of the C substrate but also on the period of preceding anaerobiosis.

Are large clutches costly to incubate - the case of the Pied Flycatcher

Abstract: The costs of incubation were studied in a population of Pied Flycatchers Ficedula hypoleuca both by gathering non-manipulative data and performing clutch size manipulations in three successive seasons. Enlarging clutch size caused a prolonged incubation and increased hatching failures in every year. The length of incubation did not differ between control and reduced clutches but was extended by 0.8 d in enlarged clutches. The manipulation of clutch size did not affect the weight of incubating females. However, in 1993 the incubation weight of females was negatively correlated with the length of incubation. Adverse spring weather most likely caused the many abnormalities and failures during incubation in 1993. Seven females disappeared and three dead females were found in nest-boxes during the incubation period. Moreover, in six nests one or two eggs were rolled to the rim of the nest cup presumably by the incubating female. All these observations suggest that incubation might be an energetic bottleneck for breeding and thus could be a contributory factor in the determination of clutch size in this species.

Incubation Behavior and Body Mass of Female Greater Snow Geese

Abstract: Nest attentiveness and behavior of incubating female Greater Snow Geese (Anser caerulescens atlanticus) was monitored on Bvlot Island. NWT in 1990-l 99 1. Females incubated about 94% of the time through much bf the incubation period but nest atten- tiveness declined to 9 1% at approximately 6 days before hatch then rose to close to 100% in the last l-4 days. Females took recesses throughout the 24 day incubation period, but frequency increased in the third week of incubation then decreased markedly in the last l- 4 days. During the latter half of the incubation period, individual females took an average of 5-7 recesses/day during which they remained close to the nest, and most devoted more than 90% of the time to feeding vigorously on sprouting graminoids. Mean recess duration was constant at about 15-16 min, except for the last l-4 days when it increased to ~30 min. Females captured during late incubation had relatively high body mass (X = 2,158 g) which represented a loss of only 17% in mass during incubation and showed that body reserves had not been depleted. Retaining some body reserves through to hatch may increase survival of females and may enhance their capability of caring for the young during brood rearing. In comparison with other large geese, Greater Snow Geese showed a low rate of nest attentiveness and took frequent recesses during which they fed intensively; they relied more heavily on food obtained in the breeding area (as opposed to reserves laid down during migration) and lost a smaller proportion of their initial mass during incubation. This strategy appears to be imposed by the lengthy migration to the high Arctic, which reduces the amount of stored reserves available for the demands of nesting.

Detection and quantification of Phytophthora capsici in soil.

Abstract: Several assay methods were compared for their efficacy in the detection and quantification of specific propagule types of Phytophthora capsici in soil. Zoospores, oospores, or sporangia and mycelial fragments were added to microwave-treated soil and nontreated field soil at densities from 1 to 1 x 10 4 propagules per g (ppg) of soil. Assay methods included standard soil dilution plating on selective medium without prior sample incubation, as well as dilution plating of soil, saturation water, or a pepper leaf disk bioassay after sample saturation, drainage, incubation for 5 days, and a 24-h resaturation period. Zoospore inoculum was detected at 10 ppg of soil or higher with standard soil dilution plating and the leaf disk bioassay, compared to >100 ppg of soil with dilution plating of soil or saturation water after sample incubation. Sporangial inoculum was detected at 1 ppg of soil with all assays when soil water matric potential was controlled during sample incubation. Oospores were detected at 1 ppg of soil with soil dilution and leaf disk assays after sample incubation. Maximum recovery rates were 10 and 100% of added zoospore and sporangial inoculum, respectively, with standard soil dilution plating (no incubation), and 30% of oospore inoculum with soil dilution plating after sample incubation. A constant soil water matric potential of -10 J/kg during the sample incubation period improved inoculum recovery with all assays, compared to incubation without controlled soil water matric potential. The sample incubation and saturation periods stimulated oospore germination and allowed detection and recovery of oospores added to soil. For most assay methods, recovery of all propagule types was lower in field soil than in microwave-treated soil ; however, the lower limits of detection were comparable in both soils. Although no single assay method was suitable for the accurate detection and quantification of all propagule types of P. capsici, the leaf disk assay provided the best detection of all propagule types but was not sufficiently quantitative to estimate inoculum densities. Soil dilution plating without prior sample incubation was the best assay for the quantification of zoospores and sporangia, whereas soil dilution plating after sample saturation and incubation provided the best recovery of oospores.

In vitro studies on glycerol transformation by rumen microorganisms

Abstract: Rumen fluid from sheep (non adapted to glycerol) was incubated up to six hours under anaerobic conditions with buffer and mineral solution. Wheat starch was added as substrate in an amount of 1g DM per vessel. Glycerol was additionally admitted to rumen fluid in amounts of 5 to 50% of starch. Carrier-free 14C-glycerol (1.3-labelled) or 15N-labelled NH4Cl were added to different incubation vessels. The disappearance rate of glycerol depended from the amount of added glycerol and incubation time. More than 90% of glycerol disappeared in 2 hours (5% addition), 4 hours (10% addition) and 6 hours (15 to 25% addition) respectively. The sum of volatile fatty acids elevated significant with a higher glycerol addition and 6 hours incubation time. The concentration of propionic acid increased also in dependence of the added glycerol amount and the longer incubation time. The proportion of acetic acid to propionic acid changed from high values (3.5 to 4.0, without glycerol) to the lowest value from 2.5 after 6 hours incubation time and 25% glycerol addition. The most radioactivity of added 14C-glycerol was found in propionic acid and only up to 11% in CO2. 14C-radioactivity was not detected in methane, lactic acid and acetic acid respectively. The 15N-labelling of TCA-precipitable N-fraction was not influenced by glycerol supplementation but the 15N-incorporation in the bacterial nitrogen fraction was lower in the vessels with glycerol.

Effects of Incubation Time and Temperature on In Vitro Selective Delignification of Silver Leaf Oak by Ganoderma colossum.

Abstract: The effects of incubation time and temperature on the ability of isolates of the chlamydosporic and thermophilic fungus Ganoderma colossum (Fr.) C. F. Baker to cause selective delignification of Quercus hypoleucoides A. Camus were evaluated by standard in vitro agar block tests. Chemical and scanning electron microscopy studies of decayed wood were used to determine the extent of selective delignification or simultaneous decay caused by each fungal isolate. At 35 deg C, the percent weight loss increased from 6.1% after 4 weeks to a maximum of 32.5 to 33.0% after 16 and 20 weeks of incubation. The average percent Klason lignin-chlorite holocellulose ratios (PKL/CHC) decreased from 0.35 in the control wood block to 0.22 in wood blocks incubated for 12 weeks; this indicated selective delignification. The average PKL/CHC increased for the 16- and 20-week incubation periods, indicating greater removal of polysaccharides during longer incubation periods. In temperature studies, the percent weight loss after 12 weeks was 26 to 27% between 30 and 40 deg C and less than 16% for the 25 and 45 deg C treatments. The average PKL/CHC ranged from 0.18 to 0.16 between 35 and 40 deg C, whereas they were 0.23 and 0.31 for the 25 and 45 deg C treatments, respectively. Scanning electron microscopy confirmed an optimum temperature range near 35 to 40 deg C and incubation times of 8 to 12 weeks for selective delignification. Under these conditions, ray parenchyma, fiber tracheids, and vessels were devoid of middle lamella; pit regions of cells were visible with significantly enlarged apertures; and individual cells were separated and clearly delimited. Extensive delignification of wood occurred throughout the wood blocks evaluated. Incubation times longer than 12 weeks resulted in greater degradation of wood cell walls and thus in greater removal of the polysaccharide component of the wood. For incubation times of 4 weeks or a temperature of 25 deg C, limited to no degradation of cells was observed. At 45 deg C, walls of fiber tracheids were eroded and ray parenchymal cells were extensively degraded, indicating that simultaneous degradation of cell walls occurred. Thus, the incubation temperature influenced the type of decay by G. colossum observed on oak wood blocks: extensive selective delignification at 35 to 40 deg C after more than 8 weeks of incubation or simultaneous decay at 45 deg C with 14% weight loss after 12 weeks of incubation. Isolates of G. colossum may prove useful in studies on mechanisms of delignification and biotechnological applications (e.g., biopulping) of lignin-degrading fungi.

Suppression of murine lymphocyte proliferation induced by a small RNA purified from the Taenia solium metacestode

Abstract: A substance fromTaenia solium metacestodes that decreases lymphocyte proliferation induced by concanavalin A was isolated. The molecular weight of this substance was estimated to be slightly more than 1,450 Da. Crude metacestode factor was fractionated through a Bio-gel P-6 column. Peak 1 showed suppressive activity. After incubation with RNase the substance lost its activity. Incubation of this material with trypsin or papain increased its suppressive activity. It was stable at boiling temperature for 10 min. The incubation of this substance with murine macrophages had no effect on [3H]-thymidine uptake by cocultured fresh splenic lymphocytes stimulated with concanavalin A. Conversely, cocultures of lymphocytes pretreated with the substance and fresh splenic lymphocytes showed a decreased incorporation of [3H]-thymidine. These results suggest that this substance is a RNA-peptide molecule whose RNA moiety accounts for its suppressive activity. The findings also suggest that in vivo the factor may be a modulator of the immune response.

Effect of different intensities of fluorescent light on the early development of chick embryos in ovo.

Abstract: Artificial conditions of incubation light have been found to have profound effects on hatchability of chicken and turkey eggs. It has been shown that illumination of eggs throughout the incubation period reduces hatching time by approximately 20 h compared with dark incubation. Experiments carried out in the present study using different intensities of fluorescent light for first 40 h of incubation in ovo indicate significant acceleration of morphogenesis in chick embryos as determined by cell population analysis. The maximum acceleration of growth was observed at intensity range of 1500-3000 lux without any adverse effects as compared with dark-incubated controls (p < 0.01).

Mechanisms of short incubation period in brood-parasitic cowbirds

Abstract: Field estimates of incubation periods of brood parasitic cowbirds (Molothrus spp.) indicate that they are unusually short given the sizes of their eggs. As a consequence, cowbirds usually hatch before host young, even though cowbird eggs are frequently larger. Field-estimated incubation periods, however, have an inherent uncertainty because of in- termittent attendance by incubating birds, and the mechanisms for early hatching are un- known. I report incubation periods of Shiny Cowbird (M. bonariensis) eggs under controlled conditions in the laboratory, and test the hypothesis that cowbirds exhibit accelerated rates of embryo development, by exploring two possible mechanisms for shortening the incubation period of cowbird eggs: (1) cowbird eggs may have a low energy content, which results in a short incubation period because yolk reserves are depleted earlier; or (2) cowbird embryos may have elevated growth rates, which would be reflected in their metabolic rates. Energy content of cowbird eggs was 23.8% lower than expected from egg mass. Mean incubation period in the laboratory was 11.7 days, which is 28.8% shorter than expected from egg mass, but close to the expected from energy content. Similarly, yolk-free, dry hatchling mass was lower than expected from egg mass, but not significantly different from the expected from egg energy content. These results support the hypothesis that cowbirds shorten incubation period by reducing the energy content of the egg, although it results in a slightly smaller hatchling. The hypothesis that cowbird embryos have elevated growth rates, in contrast, was not supported because embryos did not have higher metabolic rates than expected from their size. Although the evidence presented here is correlational, there is experimental evidence that reducing yolk reserves may act as a proximate cue for early hatching in other vertebrates. Received 7 June 1993, accepted 13 November 1993.

More Is Not Always Better: Male Incubation in Two Acrocephalus Warblers

Abstract: This study investigates male and female incubation ability in two monogamous Acrocephalus warblers with overlapping, equally sized territories and similar prey abundance. Given the longer breeding time window of the moustached warbler (A. melanopogon) compared with the reed warbler (A. scirpaceus), the trade-off between the need for biparental care and the cost of inefficient incubation is discussed. Hourly protocols and egg temperature measurements were analyzed with regard to four primary questions: male and female incubation ability, the role of environmental parameters, hatching success and the influence of male incubation on female time allocation. In both species, males increase egg temperature per minute at a slower rate than do females. There is no species difference in the percentage of incubation per hour for males (20%) or females (50%). Ambient temperature influences male incubation only in the moustached warbler during the early season (April) when male incubation correlates with hatching success. The male reed warbler shows daily temporal selectivity throughout the breeding season, increased incubation during rainfall, and no correlation with hatching success. In both species, females receive direct benefits of increased foraging time through male incubation. However, only the female reed warbler adjusts her incubation duration to previous male incubation. Thus, female reed warblers maximise the male component and thereby reduce the total incubation phase with high male effort whereas the incubation phase is increased with above average male effort in the moustached warbler.

Common Goldeneye Nest Attendance Patterns

Abstract: Common Goldeneye (Bucephala clangula) nest attendance was recorded on three Minnesota lakes, 1982-1985. Data were from 22 nests monitored 545 days. Hens increased time at nests and frequency of overnight sessions as incubation approached. Incubation recesses were diurnal; most occurred between 9:00 and 19:00 CST. Recesses were fewest and longest in early incubation, but total recess time was greatest in late incubation. Daily incubation constancy was highly variable, ranging from 36.7 to 96.3%. Lake and year effects influenced the number of daily recesses and total daily recess time. Mean recess length did not differ among lakes and years. Three females monitored in both 1984 and 1985 recessed more daily (χ = 55 min) in 1984, and their yearly ranks were the same for all parameters suggesting strong hen effects. Incubation ranged from 28 to 30 days and was correlated (r = 0.72) with mean daily recess time. Nests incubated 29 and 30 days had mean total incubation times that differed by 13 min. While brooding young, incubation-like patterns were maintained but absences were fewer and shorter. Our results differed slightly from those reported for a recent Ontario study, but the differences may be due to analytical approaches

Oxygen as limiting nutrient for growth of Cryptococcus neoformans.

Abstract: In microbroth cultures with RPMI 1640 medium, the growth yield of seven Cryptococcus neoformans isolates was unaffected by augmentation of the normal (0.2%) glucose concentration in the medium to 2%, and the addition of other potential carbon, nitrogen, and vitamin sources to the medium also failed to produce large changes in growth yield. However, macrobroth cultures of C. neoformans in RPMI 1640 that were agitated by rotation in air gave turbidities 6 to 37 times greater than those in identical cultures incubated statically, and similar levels of increase were seen whether the medium contained 0.2 or 2% glucose. Incubation of microplates under an oxygen atmosphere or with agitation by rotation led to an increase of up to twofold in growth turbidity of the yeast. The maximum increase was achieved by incubation with rotation and was dependent on the brand of microplate used. The findings implicate oxygen as a growth-limiting nutrient for C. neoformans. Incubation of microbroth cultures under conditions that enhance oxygen availability for antifungal susceptibility testing purposes may increase the speed of such tests and enhance the determination of MIC endpoints.

Effects of Incubation and pH on Soil Solution and Exchangeable Cation Ratios

Abstract: Bioavailability of nutrients is dependent on their concentration in the soil solution and on exchange equilibria between solution and adsorbed nutrient species. Elucidation of these nutrient supply relationships has been hampered by the fact that soil solution is not only difficult to extract, but its composition may change significantly during storage or incubation of field-moist soil prior to solution extraction. The objectives of this study were to evaluate the effects of liming on the exchange relationships of the major cations (Ca, Mg, K, and Na) and to determine the causes of incubation-induced changes in their solution concentrations. For periods of up to 1 yr, soil solution was extracted from soils treated in the laboratory with CaCO 3 and incubated at approximately field capacity. Solution samples were also obtained from field-limed soils (lime applied 17 yr previously) after 1 and 10 wk of incubation in field-moist condition. The concentrations of cations in solution increased substantially during incubation. These increases were balanced by NO 3 - , indicating that the changes in cation solubility were microbially mediated. In contrast to cation concentrations, cation ratios (i.e., MglCa, Na adsorption ratio, K adsorption ratio) were little affected by incubation. These ratios were directly related to the composition of the exchange phase and were strongly influenced by liming. Protons generated by mineralization of organic N during incubation displaced exchangeable Ca, Mg, K, and Na in ratios that maintained the equilibrium between solution and exchangeable phases. The results suggest that a reasonable approximation of soil solution cation ratios can be obtained from exchangeable cation data.

Patterns of Wood Duck Nest Temperatures during Egg-Laying and Incubation

Abstract: We studied the thermal environment of Wood Duck (Aix sponsa) nests in southeastern British Columbia. Mean daily nest temperatures (T N ) were correlated with maximum daily air temperatures. T N increased as the egg-laying period advanced among both successful and unsuccessful nests, although T N was lower among unsuccessful nests. Hens began spending nights on nests when there were as few as four eggs in clutches. T N and the precision of nest thermoregulation increased among successful nests as the incubation period advanced, although there was a great deal of variation between days and nests. Length of the incubation period was not correlated with clutch size, nor with mean overall nest temperature during incubation, but was correlated with the variance of T N 's during incubation.

Influence of temperature on incubation rates of Coho Salmon (Oncorhynchus kisutch) from ten Washington populations

Abstract: Konecki et al "Influence of temperature on incubation rates of Coho Salmon (Oncorhynchus kisutch) from ten Washington populations." Northwest Science. 1995; 69(2): 126-132

Oxygen Uptake by Komodo Dragon (Varanus komodoensis) Eggs: The Energetics of Prolonged Development in a Reptile

Abstract: Oxygen consumption was measured during incubation in the eggs of the Komodo dragon (Varanus komodoensis), a reptile that exhibits prolonged embryonic development. Oxygen consumption of eggs (mean mass 175 g) showed a sigmoidal pattern over the course of an incubation period, averaging 235.6 d at 29°C. The rate of oxygen consumption during the plateau prior to hatching averaged 151.1 mL/d. The incubation time was 210% greater and the peak oxygen consumption 53.2% less than predicted by existing allometric equations. Analysis of incubation time data indicates that the Komodo dragon is not unique in having prolonged incubation times relative to those of previously studied reptiles that do not undergo diapause. The cost of development in dragons averaged 329.4 kJ (1.88 kJ/g egg mass), which is significantly higher than predicted. These results are consistent with those predicted from models of developmental energetics based on avian species.