scholarly journals Gastrulation in the mouse: Growth and regionalization of the epiblast

Development ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 293-303 ◽  
Author(s):  
M. H. L. Snow
Keyword(s):  
Mouse Embryo ◽  
Rapid Growth ◽  
Generation Time ◽  
Primitive Streak ◽  
Small Region ◽  
Cell Generation ◽  
Cell Numbers ◽  
Proliferative Zone ◽  
The Mean

Histological determination of cell numbers in the mouse embryo between 4½ and 7½ days post coitum show that growth during this period, in which gastrulation occurs, is not uniform. Prior to primitive streak formation mean cell generation time is about 9 h. Co-incidental with the appearance of the primitive streak the embryo enters a period of rapid growth, lasting about 24 h, during which the mean cell generation time must be about 5 h in order to account for the increase in cell numbers. A more detailed study, in which variations in mitotic activity in different regions of the embryo have been analysed, has identified a small region, the so-called ‘proliferative zone’, constituting about 10% of the whole epiblast, in which cell generation time may average as little as 2–3 h over a 24 h period. The cell generation time for other epiblast regions is estimated at about 6·5 h. It is calculated that the proliferative zone, in the 24 h period commencing with primitive streak formation, could generate about half the cells in the 7½-day embryo. The topographical consequences of such a rapidly expanding region in the embryo are discussed in the light of other, circumstantial evidence, and it is postulated that the cells generated in the PZ may constitute the ectoderm of later stage embryos.

Memoirs: The Effect of a Temperature Gradient on the Early Development of the Chick

1928 ◽  
Vol s2-72 (287) ◽  
pp. 419-445
Author(s):  
MARIA A. TAZELAAR
Keyword(s):  
Temperature Gradient ◽  
Incubation Temperature ◽  
Primitive Streak ◽  
Blood System ◽  
Area Vasculosa ◽  
Exact Position ◽  
The Mean ◽  
Late Stages ◽  
Lateral Temperature

1. Owing to the difficulty of ascertaining the exact position of the embryo in the egg there was much waste of material. Hens' eggs are not ideal for temperature gradient experiments, for the mean between the temperatures which can be used is below normal incubation temperature. The egg of a cold-blooded animal would be far simpler to deal with. 2. The part most easily affected by a temperature gradient was the area vasculosa and its blood-vessels. This was to be expected, since the size of this extra-embryonic part is not strictly limited; the arrangement of the blood system of the area vasculosa was also modified in some cases. 3. Slight disproportion of parts was effected in some cases. The head was sometimes slightly more developed than the posterior end, and in some cases the posterior limbs were precociously developed. Differences in size between the limb buds on each side also occurred. The ratio of embryo to primitive streak was decreased considerably in the case of two embryos, treated with antagonistic gradients. 4. In some embryos treated with a lateral temperature gradient the somites had become shifted up on the heated side. The greatest effect was obtained in an embryo whose somites of one side alternated with those of the opposite side. It is possible that this condition may be regulated after normal incubation; results, however, were too few for certainty. 5. The numbers used were not sufficient for the conclusive determination of the degree of regulation which experimentally treated embryos underwent. However, all late stages when examined were normal; whether these cases were correctly treated or not it is impossible to say.

An Isotopic Method for Determination of Cell Generation Time

Nature ◽  
1963 ◽  
Vol 198 (4886) ◽  
pp. 1181-1183 ◽  
Author(s):  
YOSH MARUYAMA
Keyword(s):  
Generation Time ◽  
Cell Generation ◽  
Isotopic Method

Gastrulation in the mouse: assessment of cell populations in the epiblast of twl8/tw18 embryos

Development ◽  
1978 ◽  
Vol 47 (1) ◽  
pp. 39-52
Author(s):  
M. H. L. Snow ◽  
D. Bennett
Keyword(s):  
Mitotic Activity ◽  
Primitive Streak ◽  
Small Region ◽  
Cell Number ◽  
Proliferative Zone ◽  
Mitotic Abnormalities ◽  
Number Increase ◽  
High Mitotic Activity ◽  
Very High ◽  
Mitotic Disturbances

Homozygous tW18 embryos die prior to organogenesis. They develop gross abnormalities shortly after primitive streak formation. Anatomically, the lesion appears to be confined to the mesoderm with that tissue showing ultrastructural deficiencies and abnormal migration (Spiegelman & Bennett, 1974), and failing to develop in teratomas produced from mutant embryos (Artzt & Bennett, 1972). Analysis of growth rate by determining cell number increase, and by mapping mitotic activity and planes of cleavage in the epiblast shows that the mutant embryos are small but paradoxically show overall a very high mitotic activity, approximately double that of their normal litter mates. They also show a marked disorientationof the planes of cleavage in most of the epiblast. In pre-primitive streak embryos, before gross abnormality is detectable, two types of embryo can be found. One group constitutes the small embryos which also show the mitotic disturbances characteristic of the later stage mutants. The second group, larger embryos, do not show mitotic abnormalities. The tW18 allele thus seems to act several hours before primitive streak formation. Since there is no difference in the amount of cell death between mutant and normal embryos until 6·75 days p.c. it seems that arrest in division is the cause of the elevated mitotic index in mutants. Significantly a small region of the epiblast in mutant embryos is free of the mitotic abnormalities characteristic of the tissue as a whole. This region is the so-called proliferative zone (Snow, 1977) and the data suggest that it may be from this region that some of the ectoderm of the later embryos is produced.

Detection of Circulating Tissue Factor and Factor VII in a Normal Population

1996 ◽  
Vol 75 (05) ◽  
pp. 772-777 ◽  
Author(s):  
Sybille Albrecht ◽  
Matthias Kotzsch ◽  
Gabriele Siegert ◽  
Thomas Luther ◽  
Heinz Großmann ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Normal Population ◽  
Mean Value ◽  
Factor Vii ◽  
Significant Difference ◽  
Age Dependent ◽  
The Mean ◽  
Highly Correlated ◽  
And Gender

SummaryThe plasma tissue factor (TF) concentration was correlated to factor VII concentration (FVIIag) and factor VII activity (FVIIc) in 498 healthy volunteers ranging in age from 17 to 64 years. Immunoassays using monoclonal antibodies (mAbs) were developed for the determination of TF and FVIIag in plasma. The mAbs and the test systems were characterized. The mean value of the TF concentration was 172 ± 135 pg/ml. TF showed no age- and gender-related differences. For the total population, FVIIc, determined by a clotting test, was 110 ± 15% and the factor VIlag was 0.77 ± 0.19 μg/ml. FVII activity was significantly increased with age, whereas the concentration demonstrated no correlation to age in this population. FVII concentration is highly correlated with the activity as measured by clotting assay using rabbit thromboplastin. The ratio between FVIIc and FVIIag was not age-dependent, but demonstrated a significant difference between men and women. Between TF and FVII we could not detect a correlation.

Determination of Plasminogen in Clots and Thrombi

1966 ◽  
Vol 16 (01/02) ◽  
pp. 038-050 ◽  
Author(s):  
Ulla Hedner ◽  
Inga Marie Nilsson ◽  
B Robertson
Keyword(s):  
Mean Value ◽  
Main Mechanism ◽  
Clot Lysis ◽  
Post Mortem ◽  
Digestion Time ◽  
Normal Volunteers ◽  
Casein Solution ◽  
The Mean

SummaryThe plasminogen content was determined by a casein method in plasma and serum from 20 normal volunteers. The mean plasminogen content was found to be 10.1 ACU (the arbitrary caseinolytic unit defined in such a way that using a 3% casein solution and a digestion time of 20 min. at 37°C, 10 ACU gave an extinction of 0.300). No difference between serum and plasma regarding the plasminogen content was found.Plasminogen was determined in drained and drained plus washed clots prepared from 2 ml plasma. The highest values found in the drained clots were 0.9 ACU/clot and 0.2 ACU/clot in the drained plus washed clots.Plasminogen was also determined in drained and drained plus washed clots prepared from plasma with added purified plasminogen. The plasminogen was recovered in the washing fluid. According to these tests, then, purified added plasminogen is washed out of the clots.The plasminogen content of 20 thrombi obtained post mortem was also determined. The mean value was found to be 0.7 ACU/cm thrombus. Judging from our results, the “intrinsic clot lysis theory” is not the main mechanism of clot dissolution.

SERUM TRIIODOTHYRONINE DETERMINATION BY SATURATION ANALYSIS

1973 ◽  
Vol 72 (4) ◽  
pp. 714-726 ◽  
Author(s):  
A. Burger ◽  
B. Miller ◽  
C. Sakoloff ◽  
M. B. Vallotton
Keyword(s):  
Ionic Strength ◽  
Limit Of Detection ◽  
Improved Method ◽  
Accuracy Of Measurement ◽  
Tracer Amount ◽  
The Mean ◽  
Physiological Values ◽  
Hyperthyroid Patients ◽  
Solvent Blank

ABSTRACT An improved method for the determination of serum triiodothyronine (T3) has been developed. After addition of a tracer amount of the hormone, T3 was extracted from 1 ml serum under conditions of pH and ionic strength which favoured T3 extraction (89%) over thyroxine (T4) extraction (58%). Chromatography of the extracted material on Sephadex LH-20 separated T3 completely from residual T4. The T3 eluate was dried, then re-dissolved in 0.5 ml NaOH 0.04 n. To 0.2 ml duplicate aliquots, a standard amount of TBG was added for the competitive protein analysis. After one hour incubation at 4°C, separation of bound from free T3 was achieved on small Sephadex G-25 columns. Overall recovery was 67 ± 10.8% and correction for the loss was made. The solvent blank was 37 ± 27 (sd) ng/100 ml. Accuracy of measurement of known quantities of T3 added to serum was 98.4%. The coefficient of variation within the assay was 6.2% and between the assays it was 11.4%. The limit of detection (0.1 ng) corresponded to a concentration of 25 ng/100 ml. T4 added to serum did not interfere with T3 determination until high non-physiological values were reached. The mean ± sd serum T3 in 54 euthyroid subjects was 153 ± 58 ng/100 ml and in 24 hyperthyroid patients it was 428 ±186 ng/100 ml; 4 out of the 24 hyperthyroid values were within 2 sd of the mean euthyroid group. All the values found in the euthyroid group were well above the limit of detection of the method.

Determination of the Probability Distribution of the Mean Sound Level

2010 ◽  
Vol 35 (4) ◽  
pp. 543-550 ◽  
Author(s):  
Wojciech Batko ◽  
Bartosz Przysucha
Keyword(s):  
Probability Distribution ◽  
Probability Distribution Function ◽  
Mean Value ◽  
Sound Level ◽  
Function Form ◽  
Noise Levels ◽  
Logarithmic Mean ◽  
The Mean ◽  
Estimation Of Uncertainty

AbstractAssessment of several noise indicators are determined by the logarithmic mean <img src="/fulltext-image.asp?format=htmlnonpaginated&src=P42524002G141TV8_html\05_paper.gif" alt=""/>, from the sum of independent random resultsL1;L2; : : : ;Lnof the sound level, being under testing. The estimation of uncertainty of such averaging requires knowledge of probability distribution of the function form of their calculations. The developed solution, leading to the recurrent determination of the probability distribution function for the estimation of the mean value of noise levels and its variance, is shown in this paper.

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