Paper - A study of pathological cat embryos (1909)
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A Study of Pathological Cat Embryos
By H. E. Jordan.
From the Anatomical Laboratory of the Vmversiiy of Virginia.
The science of descriptive teratology is founded mainly on facts relating to the embryonic pathology of man. Recently, Denison (1) made a study of ten abnormal pig embryos and reported results in harmony with the conclusions of Mall (2) regarding the origin of merosomatous human monsters. The results of a microscopic study, which I am making of diseased cat embryos, are thus far also strikingly consonant with recent opinion respecting the etiology of human terata.
Schwalbe (3) regards "amniotic constrictions and bands" as among "the most abundant of anomalies of the amnion" and states that ' "abnormalities thus produced are manifold" (p. 192-193). Mall in his article on "The Origin of Human Monsters" says, "No amniotic bands are found in any of the 169 specimens which I have studied." Denison likewise finds no amniotic bands in pig embryos, but the "amnion is often thickened, rough and smaller than normal." Ballantyne (4) in summarizing his chapter on "Amniotic Diseases in Teratogenesis" says that in the case of some of the terata at least, "the amnion would seem to act by pressure, and so delay, or altogether stop the progress of events in ontogenesis."
In one horn of the uterus of a cat I found two embryos measuring 12 mm. and 9 mm., respectively, and in the other horn one embryo measuring 7 mm. The first two embryos with their adnexa appeared normal. The third embryo was enveloped in a closely fitting amnion which was adherent to the uterus over a wide area (Fig. 1). The amnion had formed a band extending across the body between the two limb-buds, and the constriction associated with the band had produced a partial separation of the posterior from the anterior portion of the embryo. Three additional minor constrictions of the amnion produced adhesions with the ectoderm of the head, fore-limb and the body-wall in the region of the heart. The eyes were faintly visible externally. No sign of somites could be recognized. The head appeared considerably swollen. The embryos and a portion of the uterine wall were immediately fixed in Zenker's fluid.
The first striking fact is the great variation in length between embryos from the same uterus and probably of the same age. Professor McClure, who has studied many cat embryos, in his work on the development of the venous system and lymphatics, writes me that from 1 to 1.5 mm. is the greatest diflFerence he has ever noted. He says, moreover, that he has not found many embryos with amniotic bands. In the case under consideration one naturally infers that the amniotic band interfered with the nutrition of the smallest embryo and prevented normal growth. However, the difference of 3 mm. between the larger embryos indicates the influence of a more primary malevolent factor. I undertook a comparative study of the pathological embryo with the amniotic band and the two apparently normal embryos from the same uterus. The sectioned material showed that all three embryos were similarly pathological though in varying degrees, thus indicating a common fundamental inciting cause.
Fig. 1. — Photograph of 7 mm. cat embryo showing the area of fusion between the closely-fitting amnion and the wall of the uterus; also the deep amniotic constriction between the limb-buds. Magnification about 3 diametei-s. (Made by Prof. Theo. Hough.)
Fig. 2. Semidiagrammatic drawing of transverse section through region of fore-brain showing solid cord and brain (the unstippled areas represent an acidophile coagulum) ; also the engorged right anterior cardinal vein (V. A. C).
The above facts combined with others even more obvious, make it improbable that the union between amnion and chorion represents an incomplete original separation. The union is intimate (Fig. 6), but is probably due to secondary fusion following amnionitis. A better understanding of the early development of the cat would aid in distinguishing a primary from an acquired adhesion. The problem is complex, since, in early stages, there is an allantois-amnion, an allantois-chorion, and a yolk-sac placenta. (O. Schultze) (5).
Both amnion and chorion have become much thickened in places, and both may perhaps be best described by the term "fibro-cystic" adopted by Denison for apparently similar changes. Cells with large fragmenting nuclei lie in the cyst-like interstices of the chorionic mesodermal tissue. The cells of the amnion are for the most part smaller, the fibrous tissue is less compact, and the lacunae are wanting. Sections of the uterine wall show that chorionic villi are present and apparently normal in some regions, while in others they are covered with an exfoliating epithelium or are absent. In short there is evidence of necrosis, but no sign of inflammation.
Neither umbilical cord nor vesicle is present. The embryo appears attached directly to the amnion and chorion (Figs. 3 and 4). Extreme strangulation evidently obtained, centering about the point of entrance of the blood supply of the embryo. Since there was no endometritis, the pathological condition may be the result of the "faulty implantation" (Mall) or some other elusive cause producing "disorderly ontogenesis". (Ballantyne.)
Sections of the 7 mm. embryo reveal the following points: The embryo is much deformed in the facial region. A portion of the head has fused with the wall of the thorax thus obliterating the mouth and involving the base of the tongue (Fig. 2). However, the mandible, maxilla and two gill-arches can be distinguished. No distinct epidermal ectoderm can be recognized. The left forelimb has turned upward (dorsal ward, Fig. 3) and rests over a thickened area of the chorion. Caudalward from the fore-limb, the bodywall is much deformed (Fig. 5). In the region where the amniotic band has. not cut through the entire body-wall, the internal organs are much compressed and misshapen (Figs. 4 and 5); they have been invaded by blood cells. Still more posteriorly the remains of chorionic villi, appear with exfoliating epithelium and necrotic areas.
The brain and spinal cord are enlarged and almost solid. Their cavity is filled with a mass of coagulum and round cells, probably derived from the dissociating nervous elements. No wandering blood cells are present. The nerves are merely masses of pale disintegrating fibres, and the ganglia are in process of dissociation.
Fig. 3. — Semidlagrammatic drawing of transverse section through the region of the fore-limbs and heart, showing a necrotic area (N) in the chorion; also the area of fusion between body-wall and amnion (X) and the fusion of heart with body-wall and the amnion with the right forelimb. X 20.
The epithelium of the ear has broken down and the cells are disintegrating. The eye appears as a confused mass of broken elongate cells (the product of the dissociating and disintegrating lens), surrounded by a layer of dissociating retinal cells, and by large pigment granules (the residue of disintegrating choroid cells).
Fig. 4. — Drawing of region 85 sections posterior to the last, showing enlarged area of fusion (X) between amnion and body-wall, and the strangnlated condition of the blood vessels and intestines in the region of the umbiUcus. X 20.
The epithelium of the trachea, oesophagus, stomach, duodenum and mesonephros is also detached from its basement membrane and dissociating. The liver is represented merely by an amorphous mass of round hepatic cells mixed with blood cells (Fig. 4). The pharynx is small ; the infundibulum, thyroid gland and thymus are dissociating.
Fig. 5. — Drawing of section through the mesonephron and the associated posterior cardinal veins (V. P. C), showing also tlie thickened character of the amnion and the malformation due to pressure of the amniotic band. X 20.
The aortic arches are very small and filled with dissociating endothelial cells. The blood vessels and the heart are filled with blood. The right anterior and posterior cardinal veins are much dilated and engorged with blood.. (Fig. 2.) In a few cases the walls of the blood vessels have disappeared and erythroblasts have wandered into the surrounding tissues. Many of these have fragmented nuclei. The heart appears almost normal, though the atria are small and irregular and there are signs of tissue dissociation.
Fio. 6. — Photomicrograph of region of fusion between amnion and chorion. X 300. (Made by Dr. Frank P. Smart.)
In the head region the mesenchymal tissue seem oedematous and the nuclei of the cells are fragmented. In other regions the mesenchyme appears generally in healthy condition. At points of fusion between the embryo and the amnion the mesoderm seems continuous from one to the other. In the region of the heart the body-wall has fused with the amnion over a wide area (Fig. 3), and the heart has fused with the mesenchyme of the body-wall.
Myoblasts are sparsely scattered here and there through the dorsal regions of the body. Precartilage and cartilage everywhere appear normal. The notochord is in process of dissociation.
Sections of the 9 mm. embryo show similar pathological changes, though it is plain that the embryo has attained a slightly later stage of development. There is a smaller area of fusion between amnion and chorion. The umbilical cord is very short and compressed, and the yolk-sac has disappeared. The embryo is misshapen and flattened in the region of the umbilicus. In the oral region and the spinal cord the embryo is more nearly normal. But again the brain is solid, enlarged and filled with round cells; the epidermal ectoderm is lacking; ganglia, nerves, eyes and epithelial linings are dissociating.
The liver is a confused mass of large round cells. The walls of the blood vessels have very generally disappeared and the blood cells have invaded the tissues. The aorta and aortic arches are filled with dissociating and probably proliferating endothelial cells. Myoblasts are more numerous, but never aggregated in myotomes. Mesenchyme and cartilage again appear perfectly normal.
The 12 mm. embryo has attained a considerably later stage of development, but similar diseased conditions prevail in the tissues, apparently with great severity. There is no blood in the heart or vessels. The walls of the vessels have disappeared. The tissues including the brain are invaded with nucleated blood cells. Here also the brain and cord are solid. The area of adhesion of amnion to chorion is very small; but there is undoubted strangulation and consequent interference with nutrition. The face in the region of the mouth is much misshapen. All the tissues except cartilage and mesenchyme have dissociated as in the other embryos. Myoblasts are very numerous and individually they appear in good condition. There are regions where mucoid degeneration has taken place. All the organs belonging to this stage of development are present, but dissociating, the liver, brain and blood vessels being most seriously affected.
The stage of development is inversely proportional to the area of adhesion between amnion and chorion or to the degree of strangulation. Barring the deformity due to the pressure of the amnion and the presence of an amniotic band in the 7 mm. embryo, the degree of abnormality varies slightly but directly as the development, as indicated more especially by the character of the blood vessels. Since the three embryos of the same uterus are similarly diseased and since only one has an amniotic band, the latter can only have been secondary to some underlying more primary cause. This was not endometritis, but some other pathologic agent producing necrotic areas in the placenta, destruction of chorionic villi, fusion of amnion and chorion, strangulation of the cord and interference with nutrition. Another interesting fact is the selective influence of the disease-producing factor on the various tissues. Liver, brain, cord, nerves and blood vessels show progressively less susceptibility to the morbid agent in the order named. Mesenchyme and cartilage seem most resistant. The pathological cat embryos agree among themselves and with certain human and pig embryos in being hydrocephalic and oedematous, with tissue dissociation and local histolysis. The results of this study support the position of Mall respecting human embryos that amniotic bands are secondary factors in the production of merosomatous monsters.
1. H. S. Denison, Anat. Record, Vol. 2, No. 7, 1908.
2. F. P. Maix, Jour. Morph., Vol. 19, No. 1, 1908.
3. E. ScHWALBE, Die Morph ologie der Missbildungen des Menschen und der Thiere, Jena, Pt. 1, 1906.
4. J. W. Ballantyne, Manual of Antenatal Pathology and Hygiene 2 Vols., Edinburgh, 1904.
5. O. ScHULTZE, Grundriss der Entwickelungsgeschichte des Menschen und der Sttugerthiere, 2 Vols., Leipzig, 1896-97.
Cite this page: Hill, M.A. (2020, September 26) Embryology Paper - A study of pathological cat embryos (1909). Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_A_study_of_pathological_cat_embryos_(1909)
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