Twenty-two stages of the prenatal development of the domestic cat are described for intraspecies comparison in embryological studies. These are assigned to the 15 embryonal periods based on the Nomina Embryologica Veterinaria to make the interspecies comparison possible.

/pdf/periods-and-stages-of-the-prenatal-development-of-the-34g0z9t0or.pdf

Periods and stages of the prenatal development of the domestic cat.

1. A systematic analysis of the relation between 2 parameters of developmental stage — clinically assessed embryonic age and growth — was made for 90 human embryos at Carnegie stages 7–13 from healthy pregnancies. 2. The data showed remarkable individual variation in the relation between age and developmental stage of embryos at stages 11–13. It appears that the mean age for these stages in our specimens was a few days greater than the corresponding age in the currently cited standards, although a definite conclusion must await further studies. 3. The relation between body length and developmental stages in our embryos was not different from the corresponding standards presented by previous investigators. The relation of the number of somites to developmental stage and greatest length in 13 embryos at stages 9–11 was approximately in accord with that reported for several corresponding embryos by other investigators. 4. The oldest age for embryos at each stage in our data may have practical use in denying a causal relation between the exposure of pregnant women to an exogenous agent at such a stage and the subsequent appearance of specific malformations in their progeny.

Normal development of early human embryos: Observation of 90 specimens at Carnegie stages 7 to 13†

Data are presented on the normal intra- and inter-litter variability of the embryonic stages in the common marmoset (Callithrix jacchus) on day 56 of pregnancy. The embryology of the marmoset is described with respect to the susceptible period for the teratogenic action of thalidomide.

Embryotoxic effects of thalidomide derivatives in the non-human primate Callithrix jacchus. II. Elucidation of the susceptible period and of the variability of embryonic stages.

The estimated age of staged human embryos and early fetuses

\n Important data relative to organogenesis and teratogenesis can be learned from the study of early embryos derived from induced abortions, which are legal in Japan. Nearly 1/3 of the conceptuses from the unrecognized period of pregnancy (less than 35 days) possess abnormalities, most of which would normally cause them to be aborted. The commonest findings were degeneration and necrosis and neural tube defects. The timetables for normal organogenesis were included in the \"Atlas of Prenatal Histology,\" published in 1983. The relationship between normal organogenesis (or teratogenesis) and gestational age exhibits a certain amount of variability; also it is not usually possible to determine the exact ovulation age of the embryo. The occurrence of abnormalities in the early intrauterine embryo is far more common than the number of such abnormalities seen in newborns, again indicating that most abnormal embryos are aborted. Early intrauterine embryos also showed a high correspondence of internal to external abnormalities, especially in the case of midline defects, indicating that the embryonic midline acts as a developmental unit. Embryonic tissues from human embryos grafted subcutaneously or intratesticularly into athymic mice were accepted and grew and differentiated to a considerable extent, showing that such tissues could be effectively used experimentally.\n

Study of human post-implantation conceptuses, normal and abnormal.

Wegen der „teratogenetischen Determinationsperioden“ ist es beim Verordnen von Arzneimitteln an Schwangere von groser praktischer Bedeutung zu wissen, in welcher Entwicklungsphase sich der Embryo befindet. Der Arbeit liegen die Ergebnisse bei 555 legalen Unterbrechungen der Fruhschwangerschaft durch schonende Curettage zugrunde. Es wurden die in einer Allgemeinpraxis zu erhebenden Befunde (Schwangerschaftsdauer, Lebensalter, Korpergewicht, Anzahl der vorausgegangenen Geburten und Fehlgeburten) mit dem Entwicklungszustand des Embryo (morphologische Entwicklung, Frischgewicht, Scheitel-Steis-Lange) korreliert und statistisch ausgewertet. Dabei ergibt sich, das der embryonale Entwicklungszustand im einzelnen nicht genau vorhergesagt werden kann. Daraus folgt fur die Praxis, das die „sensible Phase“ nicht zuverlassig zu bestimmen ist und exogene Einflusse auch nach dem Abschlus des 3. Schwangerschaftsmonats noch einen schadigenden Einflus auf die Embryonalentwicklung nehmen konnen.

Zur Vorhersage des embryonalen Entwicklungszustandes beim Menschen

Es wird uber den Gesamtwassergehalt (Frischgewicht minus Trockengewicht) von Decidua, Placenta und embryonalem Gewebe bei 96 Fallen in der Fruhschwangerschaft berichtet. Bei gleichmasiger Verteilung eines Arzneimittels im Gesamtwasser ware demnach in Placenta und embryonalem Gewebe ein um durchschnittlich 5% hoherer Arzneimittelgehalt zu erwarten als in der Decidua (bezogen auf das Frischgewicht der Gewebe).

[Total water content in decidua, placenta and embryonic tissue during early human pregnancy, as a basis for drug-distribution].

Wenn man davon ausgeht, das fur die Wirkung von Arzneimitteln auf die menschliche Frucht dosisabhangige Beziehungen bestehen, ergibt sich die grundsatzliche Frage, wieviel von dem Arzneimittel, welches einer Schwangeren verabfolgt wird, die Frucht erreicht. Anhand von insgesamt 505 legalen Schwangerschaftsunterbrechungen werden die Verteilung von 7 Sulfonamiden (Sulfacarbamid, Sulfisomidin, Sulfafurazol, Sulfadimidin, Sulfamethoxydiazin, Sulfamethoxypyridazin und Sulfadimethoxin) und die ihr zugrunde liegenden Gesetzmasigkeiten untersucht. Dabei zeigt sich, das damit zu rechnen ist, das samtliche Arzneimittel, welche sich im Blut der Schwangeren befinden, auch die menschliche Frucht in der Fruhschwangerschaft erreichen. Das Ausmas des Ubertrittes hangt dabei wesentlich von den physikalisch-chemischen und biologischen Eigenschaften der verabfolgten Substanzen ab. Da es moglich ist, die Arzneimittelverteilung in der Fruhschwangerschaft beim Menschen zu ermitteln, wird vorgeschlagen, bei teratologischen Tierexperimenten auch die Konzentration in Placenta und embryonalem Gewebe zu berucksichtigen. Es ist zu erwarten, das dann die Resultate von Tierexperimenten mehr mit den Beobachtungen beim Menschen ubereinstimmen, als dies jetzt der Fall ist.

Untersuchungen zur Pharmakokinetik von 7 Sulfonamiden in der Frühschwangerschaft beim Menschen

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Zur Vorhersage des embryonalen Entwicklungszustandes beim Menschen

[Total water content in decidua, placenta and embryonic tissue during early human pregnancy, as a basis for drug-distribution].

Untersuchungen zur Pharmakokinetik von 7 Sulfonamiden in der Frühschwangerschaft beim Menschen