Embryonic cardiovascular variables during incubation

Smartphone-Based Device for Non-Invasive Heart-Rate Measurement of Chicken Embryos

Heart rate (HR) is an important parameter in the study of the developmental physiology of chicken embryos and a crucial indicator of dead or live embryo grading in artificial incubation processes. A non-invasive HR measurement technique is required for long-term and routine HR assessment with minimal influence on embryo development. Accordingly, in this study, a non-invasive HR measurement technique of chicken embryos using a smartphone is demonstrated. The detection method of the proposed device is based on the photoplethysmography principle in which a smartphone camera is used for video recording, and the chicken embryonic HR is obtained from the recorded video images using a custom Android application. We used a smartphone to measure the embryonic HR of 60 native chicken eggs and found that it can measure the chicken embryonic HR from day 4 to day 20. The proposed smartphone HR device will be beneficial for scientific research and industrial applications. With internet connectivity, users can utilize their smartphone to measure the HR, display, share, and store the results.

Embryonic control of heart rate: examining developmental patterns and temperature and oxygenation influences using embryonic avian models

Long-term measurements (days and weeks) of heart rate (HR) have elucidated infradian rhythms in chicken embryos and circadian rhythms in chicken hatchlings. However, such rhythms are lacking in emu embryos and only rarely observed in emu hatchlings. Parasympathetic control of HR (instantaneous heart rate (IHR) decelerations) occurs at ∼60% of incubation in both precocial and altricial avian embryos, with sympathetic control (IHR accelerations) becoming more prevalent close to hatching. A large increase in avian embryonic HR occurs during hatching (presumably an energetically expensive process, i.e. increased oxygen consumption M(O) ₂), beginning during pipping when a physical barrier to O(2) conductance is removed. Alterations in ambient O(2) have little effect on early embryonic HR, likely due to the low rate of M(O)₂ of early embryos and the fact that adequate O(2) delivery can occur via diffusion. As M(O)₂ increases in advanced embryos and circulatory convection becomes important for O(2) delivery, alterations in ambient O(2) have more profound effects on embryonic HR. Early embryos demonstrate a wide ambient temperature (T(a)) tolerance range compared with older embryos. In response to a rapid decrease in T(a), embryonic HR decreases (stroke volume and blood flow are preserved) in an exponential fashion to a steady state (from which it can potentially recover if re-warmed). A more severe decrease in T(a) results in complete cessation of HR; however, depending on developmental age, embryos are able to survive severe cold exposure and cessation of HR for up to 24h in some instances. The development of endothermy can be tracked by measuring baseline HR during T(a) changes. HR patterns change from thermo-conformity to thermoregulation (reverse to T(a) changes). Further, IHR low frequency oscillations mediated by the autonomic nervous system are augmented at low T(a)s in hatchlings. Transitions of baseline HR during endothermic development are unique to individual avian species (e.g. chickens, ducks and emu), reflecting differences in life history.

Development of hematological respiratory variables in late chicken embryos: the relative importance of incubation time and embryo mass

Oxygen demand increases during embryonic development, requiring an increase in red blood cells (RBCs) containing hemoglobin (Hb) to transport O(2) between the respiratory organ and systemic tissues. A thorough ontogenetic understanding of the onset and maturation of the complex regulatory processes for RBC concentration ([RBC]), Hb concentration ([Hb]), hematocrit (Hct), mean corpuscular indices (mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration ([MCHb])) is currently lacking. We hypothesize that during the last half of incubation when the respiratory organ (the chorioallantoic membrane) envelops most of the egg contents, mean corpuscular indices will stabilize. Accordingly, Hct, [RBC] and [Hb] must also all change proportionally across development. Further, we hypothesize that the hematological respiratory variables develop and mature as a function of incubation duration, independently of embryonic growth. As predicted, a similar increase in Hct (from 18.7±0.6% on day 10 (d10) to 34.1±0.5% on d19 of incubation), [RBC] (1.13±0.03×10(6)/μL to 2.50±0.03×10(6)/μL) and [Hb] (6.1±0.2 g% to 11.2±0.1 g%) occurred during d10-19. Both [RBC] and [Hb] demonstrated high linear correlation with Hct, resulting in constant [MCHb] (~33 g% from d10 to d19). The decrease in MCV (from ~165 μ(3) on d10 to ~140 μ(3) on d13) and MCH (~55 pg to ~45 pg) during d10-13, may be attributed to a changeover from larger primary to smaller secondary and adult-type erythrocytes with MCV and MCH remaining constant (~140 μ(3) and ~45 pg respectively) for the rest of the incubation period (d13-19). Hematological respiratory values on a given incubation day were identical between embryos of different masses using either natural mass variation or experimental growth acceleration, indicating that the hematological variables develop as a function of incubation time, irrespective of embryo growth.