Showing papers on "Incubation published in 1991"

Incubation and the persistence of fixation in problem solving.

Abstract: Extra work on unsolved problems may lead to more improvement if the new work is delayed rather than undertaken immediately after initial solution attempts. Such a result constitutes incubation in problem solving. "Unconscious work" on a problem, commonly assumed to be responsible for incubation effects, may not be necessary to observe the phenomenon. We hypothesize that fixation, a block to successful problem solving, may develop during initial solution attempts and persist, interfering with immediate extra work more than with delayed extra work. Five experiments are reported in which fixation was induced to prevent optimal performance on the initial test of Remote Associates Test (RAT) problems (e.g., Mednick, 1962). After the fixation manipulation in three of the experiments, the effects of incubation intervals were examined by retesting the fixated problems. Both fixation (poorer initial problem-solving performance) and incubation (more improvement after a delayed retest than an immediate retest) were found in all the experiments which tested for the effects. In Experiments 1, 2, and 3, misleading distractors were presented alongside the RAT problems during the initial test of the problems to cause fixation. In Experiment 4, a block of paired associates--pairing the RAT words with the misleading distractors prior to problem solving--successfully induced fixation, indicating that the distractors affected memory retrieval. In Experiment 5, a trial-by-trial technique allowed fixation and incubation to be induced and tested separately for each item. All of our findings of incubation effects appear to have depended upon the initial induction of fixation. Although the experiments may not be representative of all naturally occurring cases of incubation, they provide a methodology for the study of fixation and incubation effects in problem solving in the laboratory.

Nitric Oxide: A Regulatory Mediator of Mast Cell Reactivity

Abstract: Rat serosal mast cells were tested for their ability to generate a nitric oxide (NO)-like factor by two bioassay systems: inhibition of platelet aggregation and stimulation of mast cell guanylate cyclase. The relationship between histamine release and NO-like activity from these cells was also investigated. Incubation with human washed platelets of rat serosal mast cells treated with indomethacin resulted in an inhibition of thrombin-induced platelet aggregation proportional to the number of cells.

Intracranial prolactin perfusion induces incubation behavior in turkey hens.

Abstract: Intracranial perfusion of ovine prolactin (oPrl) via osmotic pump in laying turkey hens caused a sudden onset in incubation behavior, defined as an increase in nest visits. The hens also displayed a gradual decrease in egg laying during the time they were receiving oPrl, another indicator of the onset of incubation. Circulating immunoreactive turkey Prl levels fell during the perfusion period, even though the hens were displaying persistent nesting activity and reduced egg laying. No effects on serum LH were noted. Perfusion of oPrl during the first 14 days of photostimulation delayed the onset of egg laying by several days. No effects on serum Prl or serum LH were noted. It is suggested that incubation behavior is facilitated by central levels of Prl.

Effects of incubation temperature on behavior of hatchling pine snakes: implications for reptilian distribution

Abstract: Incubation temperatures in vertebrates affect incubation periods, and in some reptiles incubation temperature determines sex ratios and some limited behavior. Here I present evidence that incubation temperature in pine snakes (Pituophis melanoleucus) affects not only incubation periods and posthatching behavior in the laboratory, but also the behavior of hatchlings required for successful emergence and survival. These behavioral differences have evolutionary implications for selection of hatchlings from particular temperature nests. With increasing temperature, incubation periods decreased in the laboratory. In addition, incubation temperature affected hatching and emergence times as well as movement speed and foraging ability. Hatchlings from medium temperature conditions emerged from nests in the field in less time than hatchlings incubated at high or low temperatures, and hatchlings from low temperatures moved slower and were less able to capture and eat mice in the laboratory than hatchlings incubated at medium or high temperatures. Taken together, these laboratory and field experiments suggest that hatchlings from low temperature nests, compared to those from higher temperature nests, would be less able to emerge, find food, and locate hibernation sites prior to the onset of cold temperatures in the New Jersey Pine Barrens. These results suggest that incubation temperature affects a whole range of behavior and that distributional ranges of reptiles and other poikilotherms could be affected by summer temperatures (via incubation period and subsequent behavior) as well as ambient winter temperatures.

Aerobic biodegradation potential of subsurface microorganisms from a jet fuel-contaminated aquifer.

Abstract: In 1975, a leak of 83,000 gallons (314,189 liters) of jet fuel (JP-4) contaminated a shallow water-table aquifer near North Charleston, S.C. Laboratory experiments were conducted with contaminated sediments to assess the aerobic biodegradation potential of the in situ microbial community. Sediments were incubated with 14C-labeled organic compounds, and the evolution of 14CO2 was measured over time. Gas chromatographic analyses were used to monitor CO2 production and O2 consumption under aerobic conditions. Results indicated that the microbes from contaminated sediments remained active despite the potentially toxic effects of JP-4. 14CO2 was measured from [14C]glucose respiration in unamended and nitrate-amended samples after 1 day of incubation. Total [14C]glucose metabolism was greater in 1 mM nitrate-amended than in unamended samples because of increased cellular incorporation of 14C label. [14C]benzene and [14C]toluene were not significantly respired after 3 months of incubation. With the addition of 1 mM NO3, CO2 production measured by gas chromatographic analysis increased linearly during 2 months of incubation at a rate of 0.099 mumol g-1 (dry weight) day-1 while oxygen concentration decreased at a rate of 0.124 mumol g-1 (dry weight) day-1. With no added nitrate, CO2 production was not different from that in metabolically inhibited control vials. From the examination of selected components of JP-4, the n-alkane hexane appeared to be degraded as opposed to the branched alkanes of similar molecular weight. The results suggest that the in situ microbial community is active despite the JP-4 jet fuel contamination and that biodegradation may be compound specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Zebra Finch Incubation: Brood patch, Egg Temperature and Thermal Properties of the Nest

Abstract: Incubation was investigated in a wild population of Zebra Finches Taenropygia gurtata in northern Victoria and comparisons made with wild-caught birds. A data logger recorded temperature readings from thermocouples inside eggs, nests, nesting bushes and exposed positions adjacent to nesting bushes. Both sexes incubate but only the female has a brood patch; this forms at the start of incubation and regresses soon after eggs hatch. Females incubated at night and both sexes shared incubation during the day. There were no consistent differences in the temperature of developing eggs heated by the two sexes nor did the sexes differ in their ability to rewarm cold eggs; fluctuations in incubation temperature also did not differ consistently between the sexes. Incubation began the day the fourth egg was laid for clutches ≥ 5 or the day the last egg was laid for smaller clutches. Hatching was more synchronous in the wild than in captivity. The ability of the nest to maintain a temperature differential was limited: air temperatures in the roof of the nesting chamber of enclosed roosting and breeding nests followed ambient temperatures closely when conditions were mild but the nest provided an insulating effect that ameliorated low temperatures.

Actively Synthesizing β-Cells Secrete Preferentially after Glucose Stimulation

Abstract: To establish whether the heterogeneous secretion of glucose-stimulated β-cells correlates with a different biosynthetic activity, we have studied the secretion and biosynthesis of the very same β-cells by combining a hemolytic plaque assay with autoradiography. After a 10-min incubation in 2.8 mm glucose, 52 ± 2% of dispersed rat β-cells incorporated [3H] leucine into newly synthesized proteins, as revealed by autoradiographic labeling. When the incubation was performed in 16.7 mm glucose, larger (P < 0.02) proportions (92 ± 4%) of plaqueforming, i.e. insulin-secreting, and nonplaque-forming β-cells (74 ± 4%) were autoradiographically labeled. Labeled and unlabeled β-cells were stimulated to secrete insulin during a 30- min incubation in 16.7 mm glucose, as revealed by the larger (P < 0.001) formation of hemolytic plaques. Under these conditions, autoradiographically labeled β-cells were recruited preferentially (P < 0.01) and secreted more (P < 0.04) than unlabeled β-cells. Analogous observations were ma...

Mineralization of Nitrogen and Carbon in Soils Amended with Composted Manure

Abstract: A study was conducted under laboratory conditions to determine the quantity of N mineralized from four composted manures incorporated into 2.7 kg of St-Jude sand or Tilly silty loam at rates of 0.05%, 0.10% and 0.20% of total N. With one exception (a hog slurry-sawdust based compost), net cumulative mineralization of N (Nm) during successive incubation periods increased with incubation time and with the rate of addition. After four months of incubation, Nm values varied from 0 to 14% of total added N. A significant third order interaction on Nm values was obtained with compost type, application rate and soil type. Net immobilization of N was apparent at all incorporation rates of hog slurry compost in the two soils. To evaluate C mineralization, composts were applied at the highest N rate and CO2 production measured periodically. One to 8.2% of total added C from manure composts was mineralized after 28 days of incubation. For each compost type, C mineralization was higher with the sandy than wit...

Comparison of direct vs fumigation incubation microbial biomass estimates from ectomycorrhizal mat and non-mat soils

Abstract: Direct estimates of microbial biomass were compared to chloroform fumigation incubation estimates of microbial biomass using samples collected from mesic forest stands. Paired soil samples were collected from ectomycorrhizal mats, which contain visible amounts of fungal material, and from non-mat areas immediately adjacent to the mats but which contain no visible fungal material. As much as 30–50% of the dry wt of soil collected from ectomycorrhizal mats can be comprised of strictly fungal biomass. Direct estimates of microbial biomass from both mat and non-mat soils were 10–300 times higher than biomass estimates obtained using the fumigation incubation method. Fumigation incubation estimates of microbial biomass showed little seasonal variation, while direct estimates revealed that microbial biomass peaked during both the spring and fall when rainfall and temperatures were optimal and were lowest during the dry summer. We compared our values to ones reported for shortgrass prairies and in Jenkinson's original fumigation incubation paper. Fumigation incubation estimates indicated that microbial biomass carbon was the same in both prairie and forest soils, about 0.5 mg C g −1 soil. Direct estimates showed that microbial biomass was actually greater, by factors of 10–300, in these forest soils. Some forest soils, for which fumigation incubation indicated very low microbial biomass, contained visible amounts of fungal hyphae. Our conclusion is that fumigation incubation does not necessarily measure microbial biomass, and that the error can be extremely high when soils contain high quantities of fungal biomass.

Repeated glucose stimulation reveals distinct and lasting secretion patterns of individual rat pancreatic B cells.

Abstract: To determine whether pancreatic B cells show a constant secretion pattern during repeated stimulations, we have used a sequential hemolytic plaque assay to monitor their individual insulin release during several successive 30-min incubations in the presence of 16.7 mM glucose. We have found that the total B cell secretion did not vary significantly in these successive glucose stimulations and that, under these conditions, the majority of B cells that were stimulated to release insulin during the first incubation also secreted during the second, third, and, when this was tested, during the fourth incubation. Similarly, most of the B cells that did not release detectable amounts of insulin during the first incubation did not secrete also during the two (or three) subsequent secretion tests. Together, the two groups of B cells that showed a constant secretory pattern, represented approximately 75% of the entire B cell population. The remaining 25% of B cells shifted from a secreting to a non-secreting state, or vice versa, from one incubation to another. These observations were made under three different time frames in which we tested single B cells as well as B cell clusters at rather different intervals. These findings support the existence of distinct B cell subpopulations differing lastingly in their ability to secrete insulin in response to glucose.

Incubated reminiscence effects.

Abstract: Reminiscence, the recall of material that was not successfully recalled on a previous attempt, was examined in three experiments as a function of the intertest (incubation) interval. Incubation intervals inserted between successive recall tests resulted in increased reminiscence, but the effect was seen primarily in the first retested minute. Neither the duration of the initial test (1–4 mm), nor the incubation activity (maze problems vs. rest) affected this incubated reminiscence effect. The results support models in which recall tests cause output interference, but incubation intervals reduce it.

Incubation time for the cultivation of Renibacterium salmoninarum from Atlantic salmon, Salmo salar L., broodfish

Abstract: . Cultivation plates for the primary isolation of Renibacterium salmoninarum were incubated for 12 or more weeks over 3.5 years. The incubation time for sample of two groups of Atlantic salmon, Salmo solar L., broodfish on a selective agar medium is reported. Samples turned positive over a long time-span. but the longest incubation time recorded for growth of the bacterium was 19 week. In one group, 79% of all positive samples form fish with macroscopic signs of bacterial kidney disease were positive after 6 weeks of incubation and the highest incidence of positive samples occured during the sixth week. From covertly infected fish within the same group.42% of sample were positive after 6 weeks of incubation, and the highest incidence of positive sample occured during the sixth and the ninth weeks of incubation. The growth pattern of the bacterium at primary isolation was characterized by a prolonged lag phase followed by a relatively growth in one week from microscopic to macroscopic size of the colonies.

An assessment of the contribution of net mineralization to N cycling in grass swards using a field incubation method

Abstract: Measurements of net mineralization using a field incubation method were made over a full growing season (180 d). Soil cores, taken from cut swards which for many years had been previously grazed by cattle, were placed in jars in the field for successive incubation periods of 14 d. Acetylene was added to the incubation jars to inhibit nitrification in the soil cores and thereby prevent losses of N through denitrification. Net mineralization over 180 d amounted to 415, 321 and 310 kg N ha−1 under grass/clover, unfertilized grass and grass receiving 420 kg N ha−1 y−1, respectively. At the start of the growing season, an index of potentially mineralizable N in the soil was estimated by a chemical extraction method, but this index was <50% of the estimates obtained by field incubation. The amount of N in herbage harvested regularly from the swards also under-estimated the supply of N from the soil, with apparent recoveries of 53, 82 and 74% and total yields of N of 240, 263 and 538 (kg N ha−1) from grass/clover, unfertilized grass and fertilized grass, respectively. Mineralization rates varied significantly with seasonal soil temperature fluctuations, but the incubation method was apparently less sensitive in relation to changes in soil water content. Rates of N-turnover (as % of total soil N) were highest under grass/clover (9%), but similar under fertilized and unfertilized grass swards (approximately 5%).

The Significance of Body Mass to Female Dabbling Ducks during Late Incubation

Abstract: Allocation of nutrients to eggs and to costs of incubation in waterfowl may be constrained by the need to maintain nutrient reserves to complete incubation. This hypothesis predicts that body mass of successfully nesting females is greater than that of unsuccessful females. This prediction was tested by comparing the body masses of successful and unsuccessful female dabbling ducks captured late in incubation. Successful Mallards (Anas platyrhynchos) and Northern Shovelers (A. clypeata) were significantly heavier than unsuccessful females, and this process constituted evidence of directional selection. Body masses of successful and unsuccessful Blue-winged Teal (A. discors) did not differ. We calculated residual (observed-predicted) body masses using published regression equations relating mass and stage of incubation in independent samples of shovelers and teal to test whether successful females in our study were relatively heavy. Residual body mass estimates of successful shovelers were significantly greater than those of unsuccessful ones; in teal, no relationship was found. Nutrient reserves may influence successful incubation in some prairie-nesting ducks and the relationship may be stronger in larger species that are most capable of storing nutrients.

Variation in the characteristics of 10 mouse-passaged scrapie lines derived from five scrapie-positive sheep.

Abstract: Ten mouse-passaged scrapie lines were initiated from five sheep with clinical scrapie. Of the lines, five were initiated and passaged exclusively in mice with the s7s7 genotype and the remaining five lines were initiated in mice with the p7p7 genotype, with two of these lines subsequently being passaged exclusively in p7p7 mice and two being passaged mainly in p7p7 mice. Lines were passaged three or four times and two parameters were compared: incubation period and the induction of a weight increase during the preclinical period. Considerable variation in the incubation periods was found between the different passage lines at similar passage levels, with a range in s7s7 mice of 113 days to greater than 450 days and a range in p7p7 mice of 219 days to greater than 500 days. All of the lines passaged exclusively in s7s7 mice had shorter incubation periods in this mouse genotype than in p7p7 mice, whereas of the five lines initiated in p7p7 mice, two had shorter incubation periods in p7p7 mouse strains. C57BL mice were used as the indicator strain and most of the lines caused an increase in weight during the preclinical phase of disease compared to control mice injected with normal brain homogenates. For both parameters, incubation period and preclinical weight increase, differences were seen in lines that had identical passage histories, suggesting that an informational molecule separate from host genomic material must specify scrapie strain differences.

Relationships among fresh mass, incubation time, and water loss in Japanese Quail eggs

Abstract: Egg size is commonly assumed to increase the fitness value of hatchlings, and yet, most intraspecific variation in egg size appears to be highly heritable. Because traits strongly associated with fitness are expected to have low heritabilities, these two observations are not mutually compatable unless other factors act to offset the fitness value of large eggs. In this paper, we assess the influence of intraspecific egg-size variation on incubation periods and rates of egg water loss among Japanese Quail (Coturnix japonica) eggs. In contrast to interspecific studies of these relationships, we observed very low correlations between the logarithms of fresh egg mass and incubation time (r2 = 0.016, P = 0.01, n = 378) and between fresh egg mass and daily water loss (r2 = 0.028, P = 0.03, n = 163). Analysis of fresh eggs and newly hatched chicks confirmed that heavier eggs lost proportionately less water during incubation. These observations suggest that statistical relationships derived from interspecific comparisons of egg size and egg physiology are not generally applicable to studies of intraspecific egg-size variation.

Activation of osmolyte efflux from cultured renal papillary epithelial cells.

Abstract: The rabbit renal papillary epithelial cell line PAP-HT25 accumulates sorbitol and other organic osmolytes when cultured in hypertonic media. When returned to isotonic media, PAP-HT25 cells swell because of water influx and then shrink to their normal volume because of rapid osmolyte and water efflux (volume regulatory decrease, VRD). Sorbitol efflux from PAP-HT25 cells during VRD was reduced to 18% of control by incubation of the cells with 100 μm eicosatetraynoic acid (ETYA), indicating that an enzyme that metabolizes arachidonic acid (AA) is a key component of the efflux process. Sorbitol efflux was unaffected by incubation with cyclooxygenase and lipoxygenase inhibitors but was reduced to 9% by incubation with 100 μm ketoconazole and to 37% by incubation with 100 μm SKF-525A, indicating that the cytochrome P-450 limb of the AA cascade is involved in the efflux process. The efflux of other organic osmolytes betaine and myoinositol, but not glycerolphosphorylcholine, was also inhibited by incubation with ETYA and ketoconazole.

Is the incubation period of AIDS lengthening

Abstract: Data from a cohort study of 1,637 homosexual men in Los Angeles are used to estimate the distribution of times from HIV infection to AIDS, and to detect any changes in the distribution. We find weak, but not statistically significant, evidence that the incubation period is lengthening. When the incubation period distribution is assumed not to have changed, we estimate that the proportion developing AIDS within 6 years of HIV infection is 27%, with a 95% confidence interval of (23%, 31%). However, if we assume that the incubation period distribution began to change in July 1987, then we estimate that for individuals infected in the first half of 1979, 28% develop AIDS within 6 years, and for those infected in the first half of 1983, 25% develop AIDS in 6 years. Four different hypotheses are suggested for a lengthening of the incubation period; these are a treatment hypothesis, a cofactor hypothesis, a better health care hypothesis, and a changing virus and disease hypothesis. The statistical method used is semiparametric modeling of the joint distribution of the date of infection and the incubation period for the participants in the study. These methods, although computationally intensive, are an attractive way of analyzing data from a prevalent cohort because only minimal parametric assumptions are made.

Glucose regulation of guinea-pig sperm motility.

Abstract: Washed guinea-pig spermatozoa from the vas deferens re-acquired progressive motility within 1-2 min of incubation in minimal culture medium containing pyruvate and lactate. When glucose was added, either at the beginning or after 15 min of incubation, the cells showed stimulated motility (increased straight-line velocity, linearity and beat-cross frequency, P less than 0.01). Re-acquisition of progressive motility was preceded by a significant (P less than 0.005) transient increase in sperm concentration of cyclic adenosine 5'-phosphate (cAMP) with or without glucose in the medium. Papaverine caused another large significant (P less than 0.001) increase in cAMP concentration; and 5.56mM glucose with papaverine caused a further stimulation in cAMP beyond that with papaverine alone (P less than 0.005). Although 0.05 or 5.56mM glucose plus alpha-chlorohydrin stimulated sperm motility, they did not further stimulate the increase in cAMP after 30 s of incubation. Thus, there was no apparent correlation between the glucose-stimulating effect on sperm motility and the enhancement of cAMP at 30 s. However, there was a close correlation between glucose-stimulated motility and enhancement of ATP (P less than 0.05) by glucose even under incubation conditions in which glucose caused the Crabtree effect (decrease in respiration rate).

Enhancement of acrosome reaction and subzonal insemination of a single spermatozoon in mouse eggs.

Abstract: The acrosome reaction in mouse spermatozoa was induced by various means. These were 1) varying incubation time in T6 medium, 2) incubation in T6 medium with added A23187, 3) incubation in T6 medium with added dbcGMP and imidazole, 4) exposure to an electric field, and 5) a combination of incubation in a medium with dbcGMP and imidazole and electroporation. The mean percentages of acrosome-free spermatozoa obtained by these various methods and assessed on the basis of both Bryan's stain and immunolocalization by FITC-labeled monoclonal antibodies increased by steps from 36% to 67%, 73%, 86%, and 92%. Individual spermatozoa from the various treatments were afterwards microinjected under the zona pellucida of a mouse oocyte. The fertilization rate for eggs microinjected with a spermatozoon treated with A23187, dbcGMP, and imidazole, by electroporation and by a combination of the last two methods also increased by steps from 17% to 34%, 36%, and 70%, respectively. Ninety-five percent of the fertilized oocytes reached the early blastocyst stage, thirty-eight percent of these blastocysts implanted in pseudopregnant mice, and twenty-eight percent developed to term. These results indicated the varying degrees of success of different ways of inducing acrosomal loss in spermatozoa and their subsequent success rates in fertilization and further in vitro and in vivo development.

Effects of dietary exposure to methyl parathion on egg laying and incubation in mallards

Abstract: An outdoor pen study was conducted with mallards (Anas platyrhynchos) to evaluate the effects of an 8-d dietary exposure to methyl parathion (400 ppm) on egg laying and incubation when treatment was initiated at different times in the nesting cycle. Treatment groups were defined as egg laying (chemical initiated after fourth egg laid in nest), early incubation (initiated after day 4 of incubation), late incubation (initiated after day 16 of incubation) and control (no chemical). Forty-eight pairs (12/group) were allowed to nest and hatch broods. In the egg laying group, daily egg production was reduced significantly during the treatment period compared to controls, but 4 of 10 hens resumed production post-treatment. One of ten control hens abandoned its nest, whereas 17 of 23 hens in the early and late incubation groups either died or exhibited changes in incubation behavior, with 7 hens abandoning their nests and 6 displaying reduced nest attentiveness for one or more days during treatment. Reproductive parameters were not significantly different between treatment groups, but the number of hatchlings per nest was 61, 43 and 58% of controls for the egg laying, early incubation and late incubation groups, respectively. This study showed that nesting success may be impacted by short dietary exposures to methyl parathion, particularly during early incubation.