PHYSIOLOGICAL ONTOGENY : A. CHICKEN EMBRYOS. XIV. THE HYDROGEN ION CONCENTRATION OF THE BLOOD OF CHICKEN EMBRYOS AS A FUNCTION OF TIME.

We have studied by means of glass electrodes the hydrogen ion concentration of the blood of chicken embryos from 8 to 20 days. When plotted as a curve, the average data show that a constant change takes place in the measurement, being acid at the beginning of this period and becoming alkaline toward its end. The acid reaction we think was characteristic not only of the embryos of fowl, but of the fetuses of cats and indeed as Warburg has shown of rapidly growing tissue in general. We have suggested the possibility, though we have no data to substantiate the suggestion, that the hydrogen ion concentration may under conditions like these, seeing that the curve of change resembles that of oxygen consumption, be expressive of changes in the rate of metabolism.     

PHYSIOLOGICAL ONTOGENY : A. CHICKEN EMBRYOS. IX. THE IODINE REACTION FOR THE QUANTITATIVE DETERMINATION OF GLUTATHIONE IN THE TISSUES AS A FUNCTION OF AGE.

The iodine reaction to determine—SH groups in tissues according to the technique of Tunnicliffe showed that the percentage concentration of such compounds in the dried substance of chicken embryos declines with age chiefly during the third quarter of the incubation period.     

PHYSIOLOGICAL ONTOGENY : A. CHICKEN EMBRYOS. XI. THE PH,CHLORIDE, CARBONIC ACID,AND PROTEIN CONCENTRATIONS IN THE TISSUES AS FUNCTIONS OF AGE.

Investigations of the chicken embryo during its incubation period show that: 1. The pH and the chloride concentration of the tissues decrease with age; the fall is most rapid between the 10th and the 13th days of incubation. 2. The concentration of total CO₂ increases with age. This fact is not considered inconsistent with a possible decrease in the concentration of active bicarbonate ions, since the increased CO₂ might well be the result of absorption of calcium carbonate from the shell and its precipitation as bone in the embryo. 3. The concentration of protein increases with age, especially between the 12th and the 16th days of incubation. The fact that the electrolytes change with the greatest rapidity at about 11½ days, the protein at 14 days, and the fat at 16½ days might be taken as a demonstration of the phenomenon of unequal development in the realm of biochemical differentiation and consequently that some notion of order, depending upon molecular reactivity and mobility would describe the process better than any concept of dynamic equilibrium.     

PHYSIOLOGICAL ONTOGENY : A. CHICKEN EMBRYOS. XIII. THE TEMPERATURE CHARACTERISTIC FOR THE CONTRACTION RATE OF THE WHOLE HEART.

The relation of heart rate frequencies to temperature in intact chicken embryos has been studied and the temperature characteristics calculated for each of a number of ages. These have been found to vary from 14,000 or better 12,000 µ for embryos 3 days old, to about 6,000 µ for others of 15 days. There appears to be a systematic change with time. If this inference is correct, important correlation with other properties of the pace-making function in the intact heart should become possible.     

PHYSIOLOGICAL ONTOGENY : A. CHICKEN EMBRYOS. VIII. ACCELERATIONS OF INTEGRATION AND DIFFERENTIATION DURING THE EMBRYONIC PERIOD.

The chief results of the studies here reported have been (1) the correlation between growth as a whole and the differentiation of gross form (primary redistributions or simple evolution), and (2) the correlation between internal integration or concentration and the differentiation of chemical form (secondary redistributions or compound evolution). With the latter are also associated the catabolic rate and the latent period or reaction time after implantation in plasma as demonstrated in tissue culture experiments. Moreover, it has been shown that these two chief developmental processes occur at different rates, and that they undergo their greatest changes in rate at different periods of embryonic life. Corresponding with Robertson''s growth acceleration periods there may be three cycles or rhythms of which the embryonic phase is the first, each composed of a period of growth followed by a period of differentiation. This conception is somewhat analogous to Roux''s notion of dividing the life span into two chief periods (1) embryonic for the growth of organ rudiments and (2) post-embryonic, characterized by functional development. The first period of total growth and form differentiation seems to cover the time when the main, but bare, outline or scaffolding of the organism is laid down. The second period, correlated as it is with catabolism (function), corresponds, not in time but as a phenomenon, with Roux''s period of functional form development.     

PHYSIOLOGICAL ONTOGENY : A. CHICKEN EMBRYOS. X. THE TEMPERATURE CHARACTERISTIC FOR THE CONTRACTION RATE OF ISOLATED FRAGMENTS OF EMBRYONIC HEART MUSCLE.

1. The Arrhenius equation giving the relationship between the velocity of chemical reaction and temperature, was found suitable for the special case of the contraction rate of embryonic heart muscle fragments. 2. There was no constancy in the values of µ for the rate of contraction in culture, nor was the scattering evenly distributed around certain (more than one) points. 3. There seemed to be no correlation between µ and other functions such as the contraction rate, the site from which the piece was removed, the age of the embryo, etc.     

THYROID PROLIFERATIVE POTENTIAL AS A FUNCTION OF AGE

The effect of a goitrogenic stimulus on thyroid weight and thyroid cell ³HTdR labeling of Sprague-Dawley rats varying from 2 to 40 weeks of age was determined. Propylthiouracil ad libitum in drinking water produced a spurt in follicle cell labeling index and thyroid weight evident after 24 hr for all age groups. The increase in labeling index reached a peak at 5–7 days and then decreased to a level a few times greater than that of the normal unstimulated thyroid. The tritiated thymidine labeling index for thyroid follicle cells and the effect of PTU thereon was determined for August male rats of 3 days to 12 weeks of age. In the older rats, the follicle cell labeling index rose to 5–6% after 4–5 days of PTU treatment and then slowly fell to about 1%, For the unstimulated control rat of comparable age, the labeling index was about 0.1%. At all ages the thyroid showed a rapid response to PTU. Examination of the time sequence of mitotic labeling showed that the DNA synthesis period was 7.5 hr for normal 2-week-old rats and for 10–12-week-old rats that had received PTU for 4 days. There was no second wave of labeled mitoses in either group during the 48-hr interval studied. From the curve of thyroid weight vs time on PTU and from the labeled mitoses curve, inferences regarding the minimum fraction of proliferating follicle cells in the stimulated ‘adult’rat thyroid were made.     

ONTOGENY OF CHICKEN HEMOGLOBIN. III. IMMUNOLOGICAL STUDY OF THE HETEROGENEITY OF HEMOGLOBIN IN DEVELOPMENT

By applying the double diffusion technique of Ouchterlony and the immunoelectrophoresis, sequence in the appearance of antigens reactive with antisera against HbCOs from 5-day embryos and adult chickens, and the major component of adult HbCO in the course of chicken development has been studied.
Antigenic components reacting to antiserum against HbCO from 5-day embryos have been detected throughout development. Three globin-like components specific to early embryos are detectable in embryos to 2 days of incubation. Two Hb components are detectable in embryos from 3 to 5 days of incubation; one is apparently specific to embryos, while the other seems to be somewhat different from adult Hb. After 6 days of incubation only one adult Hb component is detectable.
Antigenic components reacting to antiserum against HbCO from adults have also been detectable throughout embryonic life. One globin-like component specific to early embryos can be found in embryos to 2 days of incubation. One or two Hb components which are probably specific to embryos can be detected in embryos from 3 to 5 days of incubation. After 6 days of incubation one adult Hb component is detectable, while one globin-like component specific to adults can be found after 15 days of incubation. Further, the other globin-like component is detectable after 3 days of incubation.
Antigenic components reacting to antiserum against the major component of adult HbCO have been detected throughout development; one which seems to be somewhat different from either adult Hb components can be found in embryos from 2 to 5 days of incubation, while the other which is identical with the major component of adult Hb is detectable after 6 days of incubation.     

ONTOGENY OF CHICKEN HEMOGLOBIN. I. ELECTROPHORETIC STUDY OF THE HETEROGENEITY OF HEMOGLOBIN IN DEVELOPMENT

Separation of different molecular species of hemoglobin from developing chickens by starch gel electrophoresis has revealed the appearance of early embryonic (embryonic), late embryonic (fetal) and adult hemoglobin (Hb) type during development. In 5-day embryos, there are 3 or 4 forms of embryonic Hb type. They begin to decrease in 6-day embryos and cannot be detected in embryos after 10 days of incubation. In 6-day embryos, two forms of adult Hb type appear, and one of them, which is a major form in adults, becomes t o be a major one in 7-day embryos. One or two forms of fetal Hb type first appear in 10-day embryos and are still present in 5-day posthatching chickens.
Ultracentrifugation of carbonmonoxyhemoglobins from embryos at early and at later stages (fetuses), from newly hatched and from adult chickens has shown that they have a single monodisperse peak. Some heterogeneity, however, has been detected after starch gel electrophoresis, probably owing to aggregation or polymerization.
Subunit analysis of embryonic, fetal and adult Hb type by starch gel electrophoresis in formate buffer at pH 1.9 has indicated that embryonic Hb type contains total 5 subunits, C, D, E, F and G; fetal Hb type, total 2, A and H; and adult Hb type, total 3, B, F and H.     

ONTOGENY OF CHICKEN HEMOGLOBIN II. CHROMATOGRAPHIC STUDY OF THE HETEROGENEITY OF HEMOGLOBIN IN DEVELOPMENT

Some properties of the carbonmonoxyhemoglobin (HbCO) from chicken embryos of ages 5, 10 and 15 days of incubation, from 1-day posthatching and from adult chickens have been investigated by chromatography on carboxymethylcellulose (CM-cellulose) column and by starch gel electrophoresis.
Chromatogram of the hemoglobin (Hb) from 5-day chicken embryos has shown that it consists of at least 6 components. Starch gel electrophoresis of each isolated component from the column in phosphate (pH 6.8), in borate (pH 8.6) and in formate buffer (pH 1.9) has shown later that there are 3–4 embryonic type Hb components in 5-day embryos.
Chromatogram of the hemoglobin from adult chickens has shown that it consists of at least 4 components, but the examination of each isolated component from the column by electrophoresis in phosphate (pH 6.8), in borate (pH 8.6) and in formate buffer (pH 1.9) has shown that there are 4–6 adult type Hb components in adults.
In ontogenic process, embryonic Hb type is detectable in embryos up to 15 days of incubation. Fetal Hb type, which is not detectable in adult chickens, can be first found in 10-day embryos.     

TEMPERATURE CHARACTERISTICS FOR THE METABOLISM OF CHLORELLA : II. THE RATE OF RESPIRATION OF CULTURES OF CHLORELLA PYRENOIDOSA AS A FUNCTION OF TIME AND OF TEMPERATURE

The respiration of the green alga Chlorella pyrenoidosa, suspended in Knop''s solution, has been studied in the dark as a function of time and of temperature. The rates of oxygen consumption and of carbon dioxide production (at constant temperature) decline for about 25 hours to a low, constant level. From an analysis of the curves it is suggested that two substances, A and B, are utilized, whose respiratory quotients are 1 and 0.65 respectively. The values of the temperature characteristics were found to be: for oxidation of A, 19,500 (0.6 to 11.5°C.) and 3,500 (11.5 to 28°C.); for oxidation of B, 5,600 (23.4 to 0.6°C.).     

THE SHOOT APICAL ONTOGENY OF THE PICEA ABIES SEEDLING. IV. PROTOXYLEM INITIATION AND AGE OF INTERNODES

In Picea abies seedlings the distance below the base of the shoot apical dome to the first protoxylem (px) to be differentiated in the internodes beneath is a linear function of apical dome basal diameter. By using mathematical relations derived in earlier papers of this series, we computed the morphogenic age in plastochrons and the chronometric age in days of the internode in which px is first differentiated (n_px). As the seedlings age from 30 to 140 days, the distance from the base of the apical dome to px increases from 186 to 295 μm, the n of n_px increases from 16 to 53, but the chronometric age of n_px remains within the range of 10 to 12 days. Protoxylem differentiation in young internodes is, therefore, more closely related to chronometrie age than it is to morphogenic age or to distance from the base of the shoot apical dome.     

乌龟胚胎及仔龟的卵黄代谢

乌龟卵、卵黄、剩余卵黄和仔龟的含水量分别为６８．８７％、６１．４７％、６０．７５％和７６．４３％;干重分别为２．２９１５±０．２１０１ｇ,１．３０７１±０．２９１３ｇ,０．２６８１±０．０２４１ｇ和１．２３０５±０．２９９４ｇ;脂肪含量分别为１８．０３％、３１．７６％、３２．１０％和１９．３０％。卵黄、剩余卵黄和仔龟的热值分别为６．７１ｋｃａｌ／ｇＤＭ,６．７６ｋｃａｌ／ｇＤＭ和４．１０ｋｃａｌ／     

THE PHYSIOLOGICAL ECOLOGY OF REPTILIAN EGGS AND EMBRYOS. AND THE EVOLUTION OF VIVIPARITY WITHIN THE CLASS REPTILIA

1. Eggs of Crocodilia and Chelonia, like those of birds, have a pair of egg membranes separating a thick layer of albumen from the calcareous shell. In contrast, eggs of oviparous Lepidosauria have only a single shell membrane, upon which relatively small amounts of calcium carbonate are deposited; and the volume of albumen in eggs is extraordinarily small at the time of oviposition. 2. With the possible exception of certain geckos and some chelonians, eggs of oviparous reptiles seem always to absorb water from the substrate during the course of normal incubation. In so far as the rate of water absorption exceeds the rate of water loss by transpiration from exposed surfaces, the eggs swell during incubation. The term ‘cleidoic’ cannot be used to describe eggs of this type. 3. Embryos of lizards and snakes influence the water potential of extra-embryonic fluids contained within their eggs, thereby maintaining or increasing the gradient in water potential that drives water absorption. 4. Embryos of Crocodilia and Chelonia obtain a substantial portion of the calcium used in ossification of skeletal elements from the inner surfaces of the eggshell. In contrast, embryonic lizards and snakes draw upon extensive reserves of calcium present in the yolk, and obtain little (if any) calcium from the eggshell. 5. All reptilian embryos seem to produce substantial quantities of urea as a detoxification product of protein catabolism. Contrary to expectation, uricotelism may not be common among reptilian embryos, even in those few instances where development takes place within a hard, calcareous egg. 6. In eggs of Crocodilia and Chelonia, respiratory gases seem to pass by diffusion through pores in the calcareous eggshell and through spaces between the fibres of the pair of egg membranes. No pores have been observed in the shell of lepidosaurian eggs, and so gases presumably diffuse between the fibres of the single (multilayered) shell membrane. 7. Metabolism of reptilian embryos is temperature-dependent, as is true for most ectothermic organisms. For each species, there appears to be a particular temperature at which embryonic development proceeds optimally, and departures from this optimum elicit increases in developmental anomalies and/or embryonic mortality. 8. Viviparity has evolved on numerous occasions among species of the Squamata, but seemingly never among Crocodilia or Chelonia. Since the evolution of viviparity entails a progressive reduction in the eggshell, only those organisms whose embryos do not depend upon the eggshell as a source of calcium may have the evolutionary potential to become viviparous. 9. Evolutionary transitions from oviparity to viviparity could have been driven by selection related to (i) thermal benefits to embryos consequent upon retention of eggs within the body of a parent capable of behavioural thermoregulation; (ii) protection of the eggs from nest predators and/or soil microbes; and (iii) more effective exploitation of a seasonal food resource by early emerging young.