Biomedical subjects

H Tazawa

Publications and source records attributed to H Tazawa.

At least 37 records · Page 2Linked to original sources

PubMed2000

Conversion of human colonic adenoma cells to adenocarcinoma cells through inflammation in nude mice.

The roles of inflammation in the malignant progression of tumors during multistep carcinogenesis have been much discussed but remain to be elucidated. To determine the direct contribution of inflammation to colon carcinogenesis, we established a new model of progression of human colonic adenoma cells using a nude mouse; the progression is accelerated by coimplantation of a plastic plate. The FPCK-1-1 cell line, derived from a colonic polyp in a patient with familial adenomatous polyposis, is nontumorigenic when injected subcutaneously into nude mice in a cell suspension of up to 5 x 106 cells per mouse. However implantation of 1 x 10(5) FPCK-1-1 cells attached to a plastic plate induced first acute and then chronic inflammation, and formed progressively growing tumors that were histologically determined as moderately differentiated adenocarcinoma in 65% of mice. Moreover cell lines established from the growing tumors were found to be tumorigenic when injected into mice even without a plastic plate. The tumor arising from the adenoma cells implanted attached to a plastic plate was surrounded by highly proliferating fibrous stroma. This fibrous tissue was considered essential for malignant progression, rather than for attachment to the plastic plate substrate, because the tumors were formed after injection of FPCK-1-1 cells into the fibrous tissue from which the plastic plate had been removed before the cell injection. The conditioned medium (CM) obtained from the fibroblasts derived from a plastic plate-associated stromal tissue was found to contain factors that stimulated growth of FPCK-1-1 cells, but not of the derivative progressor cell lines. The factor was stable to heating and neuraminidase treatment, but labile to trypsin treatment. The main growth-potentiating activity was contained in the fraction larger than 100 kDa. In contrast, the activity to promote FPCK-1-1 cell growth was not present in the CM of subcutaneous fibroblasts from untreated nude mice or the fibroblast cell lines C3H10T 1/2 and NIH3T3. These results demonstrated that inflammation-associated stroma promoted the conversion of colonic adenoma cells to adenocarcinoma cells.

3T3 Cells↗

PubMed2000

Total spondylectomy for primary tumor of the thoracolumbar spine.

STUDY DESIGN: Six patients with primary malignant tumor of the thoracolumbar spine who underwent total spondylectomy (TS) by en bloc resection were reviewed retrospectively. OBJECTIVES: To report surgical technique and preliminary results of TS and to evaluate its oncological curability. SETTING: Japan. METHODS: Six patients were treated by TS by en bloc resection of the vertebral tumor. TS through a posterior approach was performed in three cases (T1 osteosarcoma, L1 osteosarcoma and L1 chordoma) and in the others through a single stage anterior and posterior combined approach (T6-8 recurrent giant cell tumor. L4 chordoma and L5 giant cell tumor). Surgical margins of the specimens were evaluated histologically. All patients were followed, and their status was evaluated by clinical and imaging studies. RESULTS: There were no complications related to surgery. Programmed sacrifice of nerve roots were performed in three cases for oncologic excision. A wide surgical margin was achieved in one case, a marginal one in four, and an intralesional margin in one. Five patients were alive without evidence of tumor and one was alive with disease at follow-up evaluation after 2.0-4.8 years. Local recurrence was found in one case of T1 osteosarcoma with an intralesional margin. CONCLUSIONS: These preliminary results suggested that TS is an effective procedure in control of local recurrence with acceptable complications.

Adolescent↗

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↗

PubMed2000

A novel Van91 I polymorphism in the 1st intron of the parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor gene and its effect on the urinary cAMP response to PTH.

This study was designed to identify a parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor gene polymorphism in a healthy Japanese population. All known 13 introns of this gene were amplified by PCR, except the 1st intron, which was amplified by the long-PCR method. No restriction fragment length polymorphisms (RFLPs) were detected by BsmI or XbaI in any of these introns. Twenty-one other restriction enzymes (Hind III, Bgl II, Sty I, Pvu II, Eco81 I, Van91 I, BstX I, Sse8387 I, EcoR I, BamH I, Mbo II, Tth111 I, PshA I, Eam1105 I, Not I, Srf I, Bgl I, Fok I, Sfi I, Apa I, Taq I) were tested on the 1st intron. Furthermore, digestion by Van911 (CCANNNNNTGG) identified a single, two-allele polymorphism with a fragment of approximately 3.5 kb (V allele) or a fragment of 3.1 and 0.4 kb (v allele). The frequency of the Van91 I polymorphism in 106 healthy Japanese volunteers was 77.4% for type vv, 19.8% for type Vv and 2.8% for type VV. In addition, the urinary cAMP response to exogenous [1-34]PTH was studied in 17 healthy volunteers and found to be significantly greater in persons with type Vv than type vv (p<0.05). In conclusion, the Van91 I polymorphism of the PTH/PTHrP receptor gene can be used to study the role of polymorphism in various disorders involving PTH or PTHrP.

Adult↗

PubMed2000

Total spondylectomy for solitary spinal metastasis of the thoracolumbar spine: a preliminary report.

Eight cases of solitary spinal metastasis with neurological deficit in thoracolumbar spine in which total en bloc spondylectomy (TS) was performed by bisecting the affected vertebra through both pedicles using fine thread wire saws were reviewed. Patient age ranged from 40 to 78 (mean, 62) years. Primary lesions were in the lung (2), kidney (2), thyroid (3) and prostate (1). TS was performed through a posterior approach in 5 cases (T6-7, T12, L2, L2 and L2-3) and through a one-stage anterior and posterior combined approach in the others (L2, L3 and L4). The spine was reconstructed with a ceramic vertebral prosthesis and a pedicle screw fixation system in 5 cases, and with augmented anterior spinal instruments in 3 cases. There were neither surgical complications nor surgical mortality. All patients became ambulatory and pain-free after surgery. Histologically, a marginal surgical margin was achieved in only one case. The other 7 cases had intralesional margin at the osteotomized pedicles. Four patients died from causes unrelated to local recurrence 4 to 44 (mean, 19) months after surgery. Effectiveness of surgery was maintained until death in all 4 of these patients. Asymptomatic local recurrence occurred in 2 patients with renal cancer at 10 and 33 months after surgery. These preliminary results suggest that TS for solitary spinal metastasis can achieve good control of local recurrence without major complications and is clinically acceptable surgery.

Adult↗

PubMed1999

Role of DNA aneuploidy, overexpression of p53 gene product, and cellular proliferation in the progression of gastric cancer.

DNA aneuploidy, p53 overexpression, and high cell proliferation frequently occur in gastric cancer. However, little is known about the time of their appearance throughout cancer progression. Therefore, the objective of the present study was to determine when such abnormalities occur during gastric cancer progression. We classified the gastric cancers examined into intestinal (n = 65) and diffuse (n = 34) types. DNA ploidy was examined using flow cytometry and expression of MIB-1 and p53 immunoreactivity were studied using the avidin-biotin complex method in three stages of gastric cancer (mucosal, submucosal, deeply invasive cancer, i.e., advanced cancer). The incidence of DNA aneuploidy in intestinal-type mucosal cancers (15/27, 55.6%) was lower than that of submucosal invasive cancers (14/16, 87.5%) or advanced cancers (19/22, 86.4%), while a low incidence of DNA aneuploidy was observed in each diffuse-type cancer group (mucosal, 1/12, 8.3%; submucosal invasive, 3/9, 33.3%; advanced, 8/14, 57.1%). Although overexpression of the p53 gene in intestinal-type cancer was found in early stage, that in diffuse-type cancer was observed in advanced stage. Among the intestinal-type mucosal cancers, the MIB-1 percent positive was higher in aneuploid tumors than diploid ones. DNA aneuploidy and overexpression of the p53 gene may play an important role in the early tumorigenesis of intestinal-type gastric cancer and in the late event of tumorigenesis of diffuse-type gastric cancer.

Aged↗

PubMed1999

Heart rate responses to altered ambient oxygen in early (days 3-9) chick embryos in the intact egg.

Normal heart rate (HR), and the HR responses to hypoxia and hyperoxia during early heart development in chick embyros have not been studied in detail, particularly in undisturbed embryos within the intact egg. HR was measured in day 3-9 chick embryos at 38 degrees C using relatively noninvasive impedance cardiography. Embryos were exposed to air (control) and to hypoxic (10% O2) or hyperoxic (100% O2) gas for a 2-h or 4-h period, during which HR was continually monitored. Control (normoxic) HR increased from about 150 beats per min (bpm) on day 3 to about 240 bpm on days 7-9. HR in very early embryos showed a variety of moderate responses to hypoxia (all survived), but as development progressed beyond day 6, hypoxic exposure induced a profound bradycardia that frequently terminated in death before the end of the measurement period. In contrast to the marked developmental changes in hypoxic sensitivity, HR showed little response to hyperoxia throughout development, suggesting no "hypoxic drive" to HR. We speculate that hypoxia has little effect early in development because of the embryo's small absolute O2 demand, but as the embryo grows, hypoxia represents a progressively more severe perturbation. Although general trends were identified, there was considerable variation in both HR and HR responses to ambient O2 changes between individuals of the same developmental stage.

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

Dynamical systems analysis of arterial blood pressure signals in relation to heart rate fluctuations in chick embryos.

We attempted a new approach based on a modern dynamical system theory to reconstruct the arterial blood pressure signals in relation to heart rate fluctuations of developing chick embryos. The dynamical systems approach in general is to model a phenomenon that is presented by a single time series record and approximate the dynamical property (e.g. heart rate fluctuations) of a system based only on information contained in a single-variable (arterial blood pressure) of the system. The time-series data of the arterial blood pressure was reconstructed in 3-dimensional space to draw characteristic orbits. Since the reconstructed orbits of the blood pressure should retain information contained in the pressure signals, we attempted to derive instantaneous heart rate (IHR) from the reconstructed orbits. The derived IHR presenting HR fluctuations coincided well with the IHR obtained conventionally from the peak-to-peak time intervals of the maximum blood pressure. Movements of the reconstructed orbits of the arterial blood pressure in 3-dimensional space reflected HR fluctuations (i.e. transient decelerations and accelerations).

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

Analysis of heart rate in developing bird embryos: effects of developmental mode and mass.

Bird embryos may be regarded as developing in their thermo-neutral zone, at rest, and stay in the egg for a fixed period of time until hatching. It is therefore interesting to investigate if they follow the same 'rule' set for adult homeotherms, which states that, within a taxonomically or functionally defined category such as mammals or birds, the number of heart beats throughout the life span (sL) is more or less constant. This rule stems from the allometric relationships between heart rate (fH) and body mass (mB) and between sL and mB. As a step towards understanding the general allometric nature of avian embryonic physiology we analyzed the fH values of avian embryos in relation to their incubation span (sI). Data from 30 species were selected from the scientific literature for the analyses. Values obtained from invasive methods which were judged to grossly alter natural incubation conditions, or from undefined or unmatched temperature conditions were not used. These include most values obtained below the first 30% of the incubation. Also, data obtained after internal pipping were discarded since hatching activity influences them. Values for sI and egg mass (mE) as representatives of embryonic mass were also collected. Embryonic fH was normalized to 70.1-80% sI. At 20.1-30% sI it was only 85% of the value at 70.1-80% sI and increased to a plateau at about 50.1-60% sI. It was almost constant among species between 50.1 and 60% sI and pre-internal pipping (PIP) time and thus, the mean fH value between 50.1 and 60% sI and between 90.1 and 100% excluding pipped eggs (fH) was taken as a representative value for each given species. The fH (min-1) and the corresponding sI (days) values for the 30 species, scaled with mE (g) as follows: fH = 371.1.mE-0.112 and: sI = 12.29.mE+0.209. Both powers were significantly different from 0. The product of fH and sI (fH.sI), representing the total number of heartbeats throughout the incubation, scaled with mE for the entire data set as follows: fH.sI = 6.565 x 10(+6).mE+0.096, where the +0.096 power is significantly different from 0. Values for fH.sI from embryos of altricial birds tended to concentrate at the low mE end of the plot while those of the precocial ones tended towards the high end. Separate analyses showed that the mE power for the combined altricial and semi-altricial species (ASA), and the combined precocial and semi precocial species (PSP), of log fH.sI against log mE regressions, were both insignificantly different from 0. Thus, means of fH.sI for ASA and PSP were calculated. The mean ASA value of 7.27 x 10(+6) heartbeats for fH.sI, was significantly different from the mean PSP value of 10.93 x 10(+6). The difference of 3.66 x 10(-6) (33.5%) heartbeats can be attributed to either the more advanced stage of the PSP hatchlings at hatch, to the larger mE values of these hatchlings, to the difference in water fraction of the hatchlings or all. The result of a linear regression of fH.sI against the rate of sI completion (the inverse of incubation span, fI; day-1) was: fH.10(-6) = 0.205 + 3.940.sI-1. Thus, the faster is the average rate of development accomplished per day (shorter incubation) the higher is daily heart rate. Data tended to cluster such that large eggs, mostly of the PSP type with relatively low fH, complete 2-4% of their incubation per day, while small, ASA type eggs with relatively high fH, complete 6-8% of their incubation time per day. We conclude that, at this stage of knowledge, the data is insufficient to resolve whether the different modes of hatch stage alone can explain differences in the total number of heartbeats throughout embryonic life among all bird species, or egg mass and water content differences contribute variability. This should be investigated on a larger sample of species in more depth.

Animals↗

PubMed1999

Development of heart rate rhythmicity in Muscovy duck embryos.

The heart rate (HR) of Muscovy duck embryos (Cairina moschata f. domestica) was continuously recorded from as early as the 21st day of incubation (D21) until hatching (D34/35). The aim of the study was to investigate the influence of phonoperiods consisting of different acoustic stimuli on the course of HR and the development of HR periodicities during this period. Incubation was carried out at a constant temperature and in constant darkness. Until D25 HR was dominated by decelerative fluctuations only, indicating a main input from the parasympathetic system on the heart. Later sympathetic influences increased progressively. HR periodicity was investigated by means of chi 2-periodogram and fast Fourier transformation. Between D26 and D30 statistically significant and stable HR periodicities developed gradually. They had periods in the range from 5 to 38 h. Ultra-, circa- and infradian rhythms (< 20, 24 +/- 4 and > 28 h, respectively) occurred in parallel in some cases in the same embryo. The for the HR course important periods were dissimilar between individual embryos and had different intensities. There was no indication that acoustic stimulation (phonoperiods) had any effect on the development of HR periodicities.

Acoustic Stimulation↗

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↗

PubMed1999

Effects of drilling holes into the air cell of incubated goose eggs on distribution of oxygen partial pressures under the shell.

The purpose of this work was to measure changes in oxygen pressure in the air cell and under the eggshell (P(A)O2) of pre-pipping goose eggs before and after drilling holes into the air cell. Drilling a 0.6 mm (diameter of 0.9 mm) hole into the air cell caused an increase in air cell P(A)O2 of about 10 Torr. The rate of increase attenuated as hole area increased and reached about 21 Torr when the drilled area was 8.5 mm2. The P(A)O2 of intact eggs was not equally distributed under the shell. It was high in the air cell area (108 Torr) and decreased towards the pointed end (86 Torr). The increase in P(A)O2 after drilling a 4.9 mm2 hole was high in the air cell (18 Torr) and decreased with distance, becoming non-significant at the pointed end. The significant increase in P(A)O2 after drilling was limited to a distance of up to 38 mm along the shell from the edge of the air cell. This indicates that lateral diffusion in the shell membranes under the shell is limited. Drilling a hole of 3.5 to 4.9 mm2 was enough to increase air cell P(A)O2 in most of the eggs above the critical value of 100 Torr for hatching success. The increase in P(A)O2 was limited to about half the area of the shell and the average increase in P(A)O2 was 6.3 Torr (equivalent to a 0.9% increase in ambient O2). However, the blood perfusing chorioallantoic areas further away from the air cell edge may not be fully saturated with O2 and may not be sufficient to compensate fully for the low O2 availability caused by low eggshell conductance.

Animals↗

PubMed1999

pI(Cln) and cytosolic F-actin constitute a heteromeric complex with a constant molecular mass in rat skeletal muscles.

To elucidate the function of pI(Cln), its localization in subcellular organellae was investigated. A specific polyclonal anti-pI(Cln) antibody detected the soluble 38-kDa pI(Cln) exclusively in the cytosols of rat heart, lung, liver, spleen, skeletal muscle, testis, and brain, but not rat kidney. pI(Cln)-associated proteins in skeletal muscle were also analyzed. Native-gradient PAGE showed a single 340-kDa protein band reactive to anti-pI(Cln) antibody. This band also stained with anti-actin antibody. Two-dimensional PAGE and immunoprecipitation analysis indicated that all of the pI(Cln) was present in association with actin of a constant length: the molecular ratio of pI(Cln) to actin was roughly 1:7. In addition, all actin in the cytosol fractions was found in association with pI(Cln). These results suggest the possibility that skeletal muscle pI(Cln) controls the length of cytosolic F-actin.

Actins↗

PubMed1999

Developmental patterns of heart rate in altricial avian embryos and hatchlings

The aims of this study were to determine the patterns of development of heart rate (fH) in altricial avian embryos and hatchlings, and then to examine how fH is regulated to meet metabolic requirements in altricial embryos. Embryonic mean heart rate (fH-) in 12 altricial species (Passeriformes and Psittaciformes) increased during pre-pipping incubation in all species except the cockatiel (Nymphicus hollandicus), in which fH- tended to decrease prior to pipping. The rate of increase in fH- tripled during the pipping phase in all species, and fH- was significantly higher during the pipping period and in hatchlings than during pre-pipping development. The O2 pulse (O2 consumed per cardiac beat) of altricial embryos increased in direct proportion to embryo mass (loge/loge base), although fH- was often low prior to pipping, implying that stroke volume increases in the second half of incubation. We conclude that fH contributes more than other factors towards supplying the metabolic demands of the embryo during the middle of incubation and the final pipping phase, but less during the intervening period of late incubation.

Journal Article↗