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Biomedical subjects

J T Pearson

Publications and source records attributed to J T Pearson.

At least 19 recordsLinked to original sources
PubMed2001

Allometric relationships between embryonic heart rate and fresh egg mass in birds.

Previously, we have measured daily changes (developmental patterns) in embryonic heart rate (fh) in altricial and semi-altricial (ASA) birds (range of mean fresh egg mass approximately 1-20 g), semi-precocial seabirds (egg mass approximately 38-288 g) and precocial birds (egg mass approximately 6-1400 g). An allometric relationship between embryonic fh at 80 % of incubation duration (ID) and fresh egg mass (M) has been derived for six species of precocial bird (fh at 80 % ID=429M(-0.118)). In the present study, additional measurements of embryonic fh in three ASA species, the barn owl Tyto alba, the cattle egret Bubulcus ibis and the lanner falcon Falco biarmicus, were made to extend the egg mass range (20-41 g), and the allometric relationships of embryonic fh for these ASA birds and the precocial and semi-precocial (PSP) groups were investigated from published data. The developmental patterns of embryonic fh in three relatively large ASA species did not show a significant increase prior to the pipping period, unlike those in small ASA birds, but tended to be constant, with a subsequent increase during pipping. The allometric relationship derived for ASA birds was fh at 80 % ID=371M(-0.121) (r=-0.846, P<0.001, N=20) and that for PSP birds was fh at 80 % ID=433M(-0.121) (r=-0.963, P<0.001, N=13). The slopes were parallel, but fh of ASA embryos was low compared with that of PSP embryos with the same egg mass. In ASA birds, embyronic fh was maximal during the pipping (perinatal) period, and the maximum fh (fh(max)) was significantly related to fresh egg mass: fh(max)=440M(-0.127) (r=-0.840, P<0.001, N=20). The allometric relationships for fh at 80 % ID in PSP and fh(max) in ASA embryos were statistically identical. Accordingly, embryonic fh at 80 % ID in PSP birds and fh(max) during pipping in ASA birds can be expressed by a single allometric equation: fh=437M(-0.123) (r=-0.948, P<0.001, N=33).

Animals↗
PubMed2000

Development and regulation of heart rate in embryos and hatchlings of gulls (Larus schistisagus and Larus crassirostris) in relation to growth.

We compared the developmental patterns of mean heart rate in Larus crassirostris and L. schistisagus embryos and chicks with other avian species of different hatchling developmental modes. We proposed that, since mean heart rate is inversely related to fresh egg mass in all birds, larger species reached a higher fraction of their hatchling mean heart rate by the end of the early phase of incubation and that heart rate contributions to supplying the increasing metabolic demands during mid and late incubation phases were less important than in smaller avian species. Mean heart rate was essentially independent of age throughout the mid-incubation phase (33% of normalised incubation until pipping), but increased with time during early (L. schistisagus only investigated) and late-incubation phases in both species. The O2 pulse of L. schistisagus embryos and chicks increased linearly with yolk-free body mass (log-log) after the early-phase of incubation until shortly before pipping, but was independent of body mass in the periods before and after. We conclude that a high heart rate in this first period is probably more important for increasing the circulation of nutrients to the embryo at a stage when extra-embryonic circulation to the yolk sac is limited by the size of the growing area vaculosa. Furthermore, large increases in mean heart rate during the late-incubation phase are probably important for increasing the cardiac output to hatching levels with onset of endothermy. However, mean heart rate is stable over the mid-incubation while O2 pulse increases, suggesting that increases in stroke volume and other circulatory adjustments may be entirely responsible for the largest increases in O2 transport during incubation of large avian species.

Animals↗
PubMed2000

Embryonic heart rate measurements during artificial incubation of emu eggs.

1. Daily changes in embryonic heart rate (HR) of emu were determined non-invasively at 36 degrees C by acoustocardiography (ACG) during the last 30% of artificial incubation (predicted incubation time is 50 d). 2. The pattern of daily changes in mean HR of hatched embryos decreased from about 175 bpm to about 140 bpm towards the end of incubation. 3. The mean HR at 80% of incubation (ca. 170 bpm) was close to the value predicted from an allometric equation reported previously for precocial domesticated birds. 4. ACG could measure embryonic HR even during the external pipping period. 5. If the artificial external pipping procedure is timed correctly after internal pipping, it might aid the embryos in hatching. However, further investigation into this aspect is needed.

Animals↗
PubMed2000

Continuous measurements of instantaneous heart rate and its fluctuations before and after hatching in chickens.

There has been considerable interest in heart rate (fh) fluctuations in relation to cardiovascular control systems and foetal conditions during pregnancy in mammals. Prominent fluctuations in fh also occur in avian embryos, which are an important experimental model for studying developmental physiology. The present study determined the instantaneous fh of seven chick embryos continuously from the last stage of prenatal development (day 18), throughout the pipping (perinatal) period (days 19-21) until hatching and, subsequently, of newly hatched chicks (up to day 2). The distinctive patterns of instantaneous fh fluctuations took the form of specific changes within a broad mean fh baseline. Cyclic oscillations (ultradian rhythm) occurred until an early stage of the perinatal period, when the fh baseline started rising. Subsequently, the baseline dropped and respiratory arrhythmia began to appear concomitant with external pipping. During the final stage of external pipping, when the fh baseline rose again prior to hatching, three unique patterns of instantaneous fh fluctuations were evident: relatively long-lasting cyclic small accelerations, irregular intermittent large accelerations and short-term repeated large accelerations. Furthermore, repeated alternate occurrences of the latter two types of acceleration formed an additional oscillating pattern with a period of 10-15 min. During the early period after hatching, when the fh baseline reached its maximum, instantaneous fh changed relatively slowly accompanied by transient rapid decelerations, probably due to augmented vagal tone. Subsequently, the mean fh baseline dropped to its minimum, and a circadian rhythm and three types of previously reported fh fluctuations (types I-III) appeared. Developmental patterns of mean fh and the appearance of distinctive patterns of instantaneous fluctuations in fh and circadian rhythms were not influenced by an ultimate failure of hatching after a normal development. The demonstration of complex, repeatable patterns of fh fluctuation that change during development suggests that the avian embryo model should be useful in studying the phenomenon of fh fluctuation and its underlying causes.

Animals↗
PubMed1999

Cardiac rhythms in developing chicks.

Instantaneous heart rate (IHR) of chicks was determined by electrocardiogram measured non-invasively from the day of hatch to day 6 for continuity of investigation of HR fluctuations from embryos and for ascertainment of HR diurnal rhythms. In Experiment I, IHR was determined for 1-h periods twice a day, in daytime and at night, to investigate development of heart rate fluctuations (variability and irregularities). Chick IHR was substantially more arrhythmic than embryonic HR and spontaneous acceleration dominated HR fluctuations. Chick HR fluctuations were categorized into three types; [1] Type I as a widespread baseline HR (20-50 bpm) due to respiratory arrhythmia, with a mean oscillatory frequency of 0.74 Hz (range 0.4-1.2 Hz); [2] Type II as low frequency oscillations of baseline HR, at a mean of 0.07 Hz (range 0.04-0.10 Hz), and [3] Type III as non-cyclic irregularities, dominated by frequent transient accelerations. In Experiment II, continuous measurements of HR were made under conditions of a natural photoperiod, thermoneutrality and with feed available throughout the first week after hatching and circadian rhythms of HR were ascertained. HR was very variable in the daytime (250-500 bpm), due in part to feeding and activity, and decreased to a diurnal low (200-350 bpm) at night when mean HR was relatively stable. HR fluctuations persisted throughout the diurnal cycle.

Animals↗
PubMed1999

Development of cardiac rhythms in altricial avian embryos.

Mean heart rate (MHR) was determined during incubation and in hatchlings of 14 altricial avian species to investigate (1) if there is a common developmental pattern of heart rate in altricial embryos and (2) if heart rate changes during incubation are correlated with changes in embryonic growth rate. On the basis of normalized incubation MHR increased approximately linearly in 12 of 14 species from as early as 30-40% of incubation to that of pipped embryos. The MHR of hatchlings was equal to or higher than that of pipped embryos in seven species. Passerine embryos and hatchlings maintained higher MHR in comparison to parrots of similar egg mass, which may reflect phylogenetic differences in development. Embryonic MHR increased at a higher rate while embryonic growth rates were highest during the first 40% of incubation in tit, budgerigar and crow embryos than during subsequent development when relative growth rates decreased. MHR became independent of yolk-free wet mass at a smaller fraction of hatchling mass in budgerigar and crow than in the tit, suggesting that MHR is more likely to increase continuously after 40% of incubation in small altricial species than larger species.

Animals↗
PubMed1999

Long-term measurement of heart rate in chicken eggs.

Taking advantage of acoustocardiogram (ACG), we measured the heart rate (HR) of chick embryos continuously from day 12 until hatching and then investigated the development of HR irregularities (HRI), HR variability (HRV), and the existence of a circadian rhythm in mean HR (MHR). HRI comprised transient bradycardia and tachycardia, which first developed on day 14 and 16 in most embryos, respectively. Transient bradycardia increased in frequency and magnitude with embryonic development and occurred over periods of up to 30 min in some embryos. MHR was maximal on around days 14-15 and thereafter decreased to about 250-260 bpm on days 16-18. Baseline HRV, which is an oscillation of the MHR baseline, occurred as HR decreased from days 15-16 and became predominant on days 17-18. The magnitude of the baseline oscillations reached up to 50 bpm in some embryos and the period ranged between about 40-90 min (ultradian rhythm). A circadian rhythm of MHR was not found in late chick embryos. On days 18-19, embryonic activities were augmented and then breathing movements began to occur, disturbing ACG signals and thus making it difficult to measure the HR. Instead, the development of breathing activities was recorded. Breathing frequency was irregular at first and then increased to a maximum of about 1.5 Hz prior to hatching.

Animals↗
PubMed1999

Cardiac rhythms in chick embryos during hatching.

Avian embryos develop within a hard eggshell which permits the measurement of heart rate while maintaining an adequate gas exchange through the chorioallantoic membrane. Heart rate has been determined from cardiogenic signals detected either noninvasively, semi-invasively or invasively with various transducers. Firstly, we reviewed these previously-developed methods and experimental results on heart rate fluctuations in prenatal embryos. Secondly, we presented new findings on the development of heart rate fluctuations during the last stages of incubation, with emphasis on the perinatal period, which remained to be studied. Three patterns of acceleration of the instantaneous heart rate were unique to the external pipping period: irregular intermittent large accelerations, short-term repeated large accelerations and relatively long-lasting cyclic small accelerations. Besides these acceleration patterns, respiratory arrhythmia, which comprimised oscillating patterns with a period of 1-1.5 s, appeared during the external pipping period. Furthermore, additional oscillating patterns with a period of 10-15 min were found in some externally pipped embryos.

Animals↗
PubMed1998

Development of heart rate irregularities in chick embryos.

Heart rate (HR) irregularities in chick embryos were defined as large fluctuations (>10 beats/min) comprising irregular, brief deceleration and/or acceleration of instantaneous HR (IHR). IHR was determined directly from the arterial blood pressure while adequate gas exchange was maintained through an eggshell and chorioallantoic membrane. Five embryos were examined on each day from day 11 to day 19 of incubation. Baseline HR was stable until day 12-13, and on around day 13-14 transient, rapid deceleration of HR (termed V pattern) began to appear, with a subsequent increase in its frequency and magnitude. The acceleration patterns (lambda, avian omega, and periodic patterns) appeared later, and the IHR became increasingly irregular, with additional, spontaneous deceleration and acceleration patterns toward hatching. Additional experiments with intravenous administration of autonomic drugs clearly showed that rapid deceleration of HR was mediated by parasympathetic nervous function but did not always show clear relations of sympathomimetic and sympathetic blocking agents to the acceleration patterns.

Allantois↗
PubMed1998

Development of heart rate in the precocial king quail Coturnix chinensis.

Our aim was to examine changes in heart rate (fh) during the embryonic and posthatching periods of the smallest precocial avian species, Coturnix chinensis. In experiment I, repeated measurements of mean fh were made for individual quail by ballistocardiogram (BCG) during incubation, and by both piezo-electric film and electrocardiogram (ECG) during the posthatching period (resting and thermoneutral conditions). Mean fh of all embryos increased during the second half of incubation and the first week posthatching, but a few embryos experienced a very brief period of decreased fh prior to internal pipping. After the first week, fh of posthatching quail was maintained at high levels (550-650 beats min-1), then decreased with age and increase in body mass. The maximal fh of quail chicks represents a greater posthatching increase in fh than is found in larger precocial chickens, this difference being attributable to the higher demands of thermoregulation at small body masses in the quail. In experiment II, the mean fh of quail embryos (day 2-16) was recorded by ECG, and embryonic stage, yolk-free embryo mass (wet and dry) and water content were measured. Mean fh was linearly related to embryo mass throughout incubation, except on the day prior to internal pipping, when the fh of a few embryos declined below this linear relationship. Measurements of instantaneous fh of late incubation embryos, young and adult quail all showed spontaneous fluctuations in fh. Two main frequency components of fh fluctuations were identified for the first time in an avian species. Low-frequency (mean 0.09 Hz, 12.6 s) and high-frequency (1.4 Hz, 0.9 s) oscillations in both young chicks and adult quail were detected and are considered to reflect baroreflex mediation of fh and respiratory sinus arrhythmia, respectively.

Analysis of Variance↗
PubMed1998

Pharmacologic hemoglobin reversal: the importance of lipid intermediaries and the proposed involvement of the cAMP and phosphatidylinositol second messenger systems.

Humoral and microenvironmental influences have played a major role in recent research into reversing the Hb F to Hb A switch. Early research in this area focused on hormonal influences and showed both thyroid hormone and prolactin could induce small but statistically significant reversals in hemoglobin phenotype. Recent research has focused on the effect of certain lipids in this process. The current study shows a synergy between thyroid hormone and prolactin in inducing a significant switch in adult rat hemoglobin patterns toward the neonatal pattern. Further, it is hypothesized that this synergy is due to the hormones' effect on lipid intermediaries whose effect in turn are proposed to be mediated by the cAMP and phosphatidylinositol second messenger systems.

Animals↗
PubMed1997

Non-invasive determination of instantaneous heart rate in developing avian embryos by means of acoustocardiogram.

Previous noninvasive studies of the mean heart rate of embryonic birds have prompted an investigation into the instantaneous heart rate (IHR), which may be informative in developmental studies of cardiac rhythm. Using the acoustocardiogram (ACG), a noninvasive, long-term measuring system for embryonic IHR is developed, and the IHR in chickens during the last half of embryonic development is determined. The system, which uses a micro-computer, samples the ACG at a frequency of 50 Hz, restores the ACG wave by sinc function and calculates the IHR with an error in accuracy of less than 1 beat min-1. It was found that characteristic, transient bradycardia begins to appear late in the second week of incubation, and, with the additional development of transient tachycardia, the embryonic cardiac rhythm becomes more arrhythmic towards hatching. Simultaneous measurements of IHR with somatic movements showed no relationship between arrhythmia and embryonic activities. This system is useful, providing new evidence on long-term IHR developmental patterns.

Animals↗
PubMed1997

Ballistocardiogram of avian eggs determined by an electromagnetic induction coil.

As an avian embryo grows within an eggshell, the whole egg is moved by embryonic activity and also by the embryonic heartbeat. A technical interest in detecting minute biological movements has prompted the development of techniques and systems to measure the cardiogenic ballistic movement of the egg or ballistocardiogram (BCG). In this context, there is interest in using an electromagnetic induction coil (solenoid) as another simple sensor to measure the BCG and examining its possibility for BCG measurement. A small permanent magnet is attached tightly to the surface of an incubated egg, and then the egg with the magnet is placed in a solenoid. Preliminary model analysis is made to design a setup of the egg, magnet and solenoid coupling system. Then, simultaneous measurement with a laser displacement measuring system, developed previously, is made for chicken eggs, indicating that the solenoid detects the minute cardiogenic ballistic movements and that the BCG determined is a measure of the velocity of egg movements.

Animals↗
PubMed1996

Developmental patterns of O2 consumption, heart rate and O2 pulse in unturned eggs.

The effects of failure to turn eggs on the developmental patterns of oxygen consumption (MO2), heart rate (fH) and O2 pulse during the second half of incubation of individual chicken eggs were examined. The MO2 of unturned eggs increased at a significantly lower rate than the control toward the end of prenatal incubation, and the plateau MO2 between day 17 and 19 was significantly lower than the control. Lack of turning also resulted in significant changes in the developmental patterns of fH and O2 pulse. It is suggested that the effects of lack of egg-turning on the developmental patterns of MO2 may be attributable to lower embryonic growth rate in addition to impairment of gas exchange through the chorioallantoic gas exchanger.

Agriculture↗
PubMed1996

Effects of pre-incubation egg storage on embryonic functions and growth.

The effect of pre-incubation storage on physiological functions of chick embryos during the last half of incubation and the relationship to embryonic growth were studied. In the first experiment, eggs were stored for 20 or 30 days, respectively, and the developmental patterns of oxygen consumption (MO2), heart rate (fH) and O2 pulse of individual embryos were examined. The MO2 of stored eggs increased at significantly lower rate than the control between day 12 and 17 of incubation, and the stored eggs had a significantly lower plateau MO2 between day 17 and 19. The decrease in MO2 of some stored eggs was correlated with late incubation mortality. Pre-incubation storage also resulted in significant changes in the developmental patterns of fH and O2 pulse. In the second experiment, the eggs were stored for 10 and 20 days, respectively, to also examine the effect of short-term storage on the development of MO2 in relation to embryo growth. Pre-incubation storage for 10 days had no significant effect, but 20 days storage shifted developmental patterns of MO2, wet mass, dry mass and embryo water fraction to the right of the control. Furthermore, MO2 was significantly lower than expected on the basis of embryo mass after day 17 of incubation. Prolonged pre-incubation storage caused not only a rightward shift in MO2 pattern due to retarded growth, but also severe depression of MO2 during the last stages of prenatal development.

Agriculture↗
PubMed1994

Oxygen consumption rates of adults and chicks during brooding in king quail (Coturnix chinensis).

Oxygen consumption rates were measured in chicks (0-17 days of age), and in non-brooding and brooding adults. Brooded chicks maintained a constant oxygen consumption rate at a chamber ambient temperature of 10-35 degrees C (0-5 days of age: 2.95 ml O2.g-1.h-1 and 6-17 days of age: 5.80 ml O2.g-1.h-1) while unbrooded chicks increased oxygen consumption rate at ambient temperature below 30 degrees C to double the brooded oxygen consumption rate at 25 and 15 degrees C for chicks < 5 days of age and > 5 days of age, respectively. The mass-specific oxygen consumption rate of breeding male and females (non-brooding) were significantly elevated within the thermoneutral zone thermal neutral zone (28-35 degrees C) in comparison to non-breeding adults. Below the thermal neutral zone, oxygen consumption rate was not significantly different. The elevation in oxygen consumption rate of breeding quail was not correlated with the presence of broodpatches, which developed only in females, but is a seasonal adjustment in metabolism. Male and females that actively brooded one to five chicks had significantly higher oxygen consumption rate than nonbrooding quil at ambient temperature below 30 degrees C. Brooding oxygen consumption rate was constant during day and night, indicating a temporary suppression of the circadian rhythm of metabolism. Brooding oxygen consumption rate increased significantly with brood number, but neither adult body mass nor adult sex were significant factors in the relationship between brooding oxygen consumption rate and ambient temperature. The proportion of daylight hours that chicks were brooded by parents was negatively correlated with ambient temperature. After chicks were 5 days old brooding time was reduced but brooding oxygen consumption rate was unchanged. Heat from the brooding parent appeared to originate mainly from the apteria under the wings and legs rather than the broodpatch. The parental heat contribution to chick temperature regulation below the chicks' thermal neutral zone is achieved by increasing parental thermal conductance by a feedback control similar to that suggested for the control of egg temperature via the broodpatch. It is concluded that the brooding period is an energetic burden to parent quail, and the magnitude of the cost increases directly with brood number and inversely with ambient temperature during this period.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1994

A rodent model for hemoglobin switching utilizing high performance liquid chromatography.

It has long been recognized that a treatment for beta hemoglobin chain anomalies could result if a way to reverse the Hb F to Hb A switch in humans were found. Studies of hemoglobin switching have been hampered by the fact that small animals normally used in the laboratory do not have a true Hb F. However, several small animal models which take advantage of a switch in minor beta chain proportions in certain strains of inbred mice and rats have been proposed and used. The use of these models has suffered from what, until now, could be considered technically demanding, time-consuming methodologies. In this study we report an effective, rapid and technically streamlined model of hemoglobin switching utilizing Fisher 344 rats and high performance liquid chromatography with a weakly cationic column.

Age Factors↗