Incubation

About: Incubation is a research topic. Over the lifetime, 5748 publications have been published within this topic receiving 126541 citations.

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.

The Effect of Egg Size and Incubation Temperature on Growth in the Turtle, Malaclemys terrapin

Abstract: We conducted an incubation and rearing experiment to test the effects of incubation tem- perature and egg size on hatchling size and growth of the emydid turtle, Malaclemys terrapin. Eggs from four clutches were assigned randomly to two incubation temperatures, 26 C and 32 C. Half of the hatchlings were sacrificed and sexed after five months and the remainder were raised for three years in a common environment. Similar to other studies of emydid turtles, low and high temperature treatments produced exclusively males and females, respectively. Egg size was more variable among the four clutches than within each clutch. Egg mass accounted for 96% and 97% of the variance in hatchling mass for females and males, respectively. Both clutch and incubation temperature influenced post-hatching growth. The clutch effect was due to both differences in egg mass among clutches and the effects of egg size on hatchling size. Egg mass explained 59% of the variation in size among 3 year old females, but did not explain size variation among 3 year old males. Differences in female growth attributable to egg size could result in as much as a three year difference in age at first reproduction based on the growth trajectories of terrapins from a natural population.

Lactate and force production in skeletal muscle

Abstract: Lactic acid accumulation is generally believed to be involved in muscle fatigue. However, one study reported that in rat soleus muscle (in vitro), with force depressed by high external K+ concentrations a subsequent incubation with lactic acid restores force and thereby protects against fatigue. However, incubation with 20 mm lactic acid reduces the pH gradient across the sarcolemma, whereas the gradient is increased during muscle activity. Furthermore, unlike active muscle the Na+–K+ pump is not activated. We therefore hypothesized that lactic acid does not protect against fatigue in active muscle. Three incubation solutions were used: 20 mm Na-lactate (which acidifies internal pH), 12 mm Na-lactate +8 mm lactic acid (which mimics the pH changes during muscle activity), and 20 mm lactic acid (which acidifies external pH more than internal pH). All three solutions improved force in K+-depressed rat soleus muscle. The pH regulation associated with lactate incubation accelerated the Na+–K+ pump. To study whether the protective effect of lactate/lactic acid is a general mechanism, we stimulated muscles to fatigue with and without pre-incubation. None of the incubation solutions improved force development in repetitively stimulated muscle (Na-lactate had a negative effect). It is concluded that although lactate/lactic acid incubation regains force in K+-depressed resting muscle, a similar incubation has no or a negative effect on force development in active muscle. It is suggested that the difference between the two situations is that lactate/lactic acid removes the negative consequences of an unusual large depolarization in the K+-treated passive muscle, whereas the depolarization is less pronounced in active muscle.

Incubation periods of Yellow fever virus.

Abstract: . Yellow fever virus is a global health threat due to its endemicity in parts of Africa and South America where human infections occur in residents and travelers. To understand yellow fever dynamics, it is critical to characterize the incubation periods of the virus in vector mosquitoes and humans. Here, we compare four statistical models of the yellow fever incubation periods fitted with historical data. The extrinsic incubation period in the urban vector Aedes aegypti was best characterized with a temperature-dependent Weibull model with a median of 10 days at 25°C (middle 95% = 2.0–37 days). The intrinsic incubation period, fitted with a log-normal model, had a median of 4.3 days (middle 95% = 2.3–8.6 days). These estimates and their associated statistical models provide a quantitative basis to assist in exposure assessments, model potential outbreaks, and evaluate the effectiveness of public health interventions.