bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on the sequence of blastemal condensations in the limbs of the mouse embryo
Authors: Forsthoefel Paulinus F. 
Published: February 2005

AbstractIn the forelimbs, the sequence of blastemal condensation is: scapula and humerus, ulna, digit IV, digit V, radius, digit III, digit II, digit I. In the hind limb, the sequence is: innominate bone and femur, fibula, digit IV, digit V, tibia, digit III, digit II, digit I. The sequence described may lead to loss of preaxial parts of the limb in cases of severe over‐all reduction of limb bud material due to genetic or teratogenic agents. The main reason why ectrodactyly and polydactyly in the mouse are usually preaxial is the localization for some unknown reason of alterations in growth rate in the preaxial margin of the footplate. However, the fact that blastemal condensations begin postaxially will tend to confine these and similar skeletal anomalies of the limb to the preaxial part.
Differentiation of vaginal epithelium in mice given estrogen and thymidine‐H3
Authors: Husbands Milton E. , Walker Bruce E. 
Published: February 2005

AbstractAdult mice of the A/Jax strain were given injections of thymidine‐H3 at proestrus and injections of estrogen at one day intervals thereafter, up to eight days. Mice were killed at daily intervals and longitudinal sections of vagina were radioautographed. Cells which were immediately above the basal layer at proestrus, and which would have given rise to the mucous, nucleated cell layer, eventually produced an interruption in the otherwise continuous cornification of the surface layers. A similar experiment, begun at late metestrus, produced comparable results, except that the interruption of cornification was more pronounced.Mice which had been ovariectomized two weeks previously were given injections of estradiol and thymidine‐H3. Cells at the surface continued to show a low frequency of mitotic activity and retained their nuclei after estradiol treatment. They were finally sloughed by the squamous transformation of underlying cells. The latter were derived originally from the basal layer under the influence of estradiol, which led to greatly accelerated mitotic activity in that layer. It is concluded that the course of cellular differentiation in these migrating cells is fixed when they are produced by mitosis of basal cells. This differentiation can only be modified, not reversed, by subsequent estradiol treatment even when the cells involved are still capable of undergoing mitosis.
The site of action of trypan blue in cardiac teratogenesis
Authors: Smith W. N. Adams 
Published: February 2005

AbstractPregnant Wistar rats were injected subcutaneously with trypan blue and the heart was studied in 206 embryos removed at daily intervals from ten and one‐half to fourteen and one‐half days of gestation.Cardiac anomalies appeared to be largely due either to malpositioning of the atria consequent upon an abnormal looping of the bulbo‐ventricular loop, or to a decreased formation of cardiac jelly.The hearts of a further 46 embryos at ten and one‐half days were studied histochemically and 40 of these (24 experimental and 16 control) were stained with Best's carmine. Glycogen granules were found in the hearts of experimental embryos but not in the hearts of control embryos.It is suggested that trypan blue may act directly on the cells of the myoepicardium of the developing rat heart, causing a precocious transition to the biochemical characteristics of the adult tissue with a consequent decrease in the amount of cardiac jelly formed. The abnormal looping of the bulbo‐ventricular part of the cardiac tube might also be consequent upon such a biochemical change.
An electron microscopic study of thymic corpuscles in the guinea pig and the mouse
Authors: Kohnen Paul , Weiss Leon 
Published: February 2005

AbstractThymus of guinea pigs and C3H mice was fixed in 1% osmium tetroxide, embedded in Araldite or Maraglas, and studied under the electron microscope.Hassall's corpuscles showing the typical concentric, lamellated pattern are observed. Reticular cells form layers around central elements of variable appearance. One or more reticular cells or cystic structures often constitute the centers of corpuscles. Nuclear degeneration, swollen cytoplasm, and intracellular fibrils are characteristic findings. Desmosomes may be quite numerous and may cover a large portion of a cell's surface. Intracellular fibrils are particularly dense at membranous sites and often are apparently unrelated to desmosomes. Reticular cells at the periphery of thymic corpuscles may be contiguous with cells of the cytoreticulum. Many reticular cells contain organelles generally associated with protein synthesis or active transport.Intercellular and intracellular cysts are regularly seen and are frequently related to thymic corpuscles. Some cysts may be manifestations of cell synthesis and storage.The epithelial nature of thymic corpuscles and cysts is evident. Thymic corpuscles may arise by localized collapse of the cytoreticulum.
A possible mechanism responsible for the melanocyte distribution of the perineal pigment spot of the mouse
Authors: Schultz John H. , Chase Herman B. 
Published: February 2005

AbstractThe perineal pigment spot of the C57 Black mouse was examined macro‐ and microscopically in animals ranging in age from 14 days post‐fertilization to 28 days post‐parturition. Dendritic pigment‐containing cells first become evident in the dermis of the area on the sixteenth day post‐fertilization. Throughout later stages of development, these pigmented cells continue to be restricted to the dermis of this area. Since the dopa treatment reveals the presence of a melanin synthesizing system within these cells, they are true melanocytes which have become restricted to this layer of the integument.Histological examination reveals a population of melanocytes in the epidermis and/or hair follicles also. These are rarely found over the center of the area but are seen in increasing numbers laterally from the ventral midline. In contrast, dermal melanocytes are heavily concentrated near the ventral midline but decrease in numbers laterally. There are, therefore, two opposing but complementary gradients of melanocytes in the integument of the pigment spot. This suggests the possibility that a precocious differentiation of the basement membrane in this area during embryonic development inhibits the passage of melanoblasts into the epidermis thereby causing them to be restricted to the dermis.
The primary ossification of the human ilium
Authors: Laurenson R. D. 
Published: February 2005

AbstractIn seven human fetuses of C.R. lengths ranging from 38 mm to 100 mm primary ossification of the ilium has been described.In the 38 mm fetus the perichondrium at the caudal border of the ilium in the vicinity of the greater sciatic notch is intensely basophilic and contains osteoblasts. In another 38 mm fetus in the same area new bone is present.In the 50 mm fetus bone has spread cephalad over the internal and external surfaces of the ala of the ilium without invading the underlying cartilage.In the 58 mm fetus pores are present in the bone and through them osteoblasts and vascular elements are invading the disintegrated cartilage to form the primary marrow cavity.In the 66 mm fetus the primary marrow cavity has spread into the ala of the ilium.The whole process is similar to that seen in the primary ossification of the shaft of a typical long bone and follows the sequence described by Streeter ('49).
Histochemical distribution of cholinesterases in the testis, epididymis and vas deferens of the rat
Authors: Risley Paul L. , Skrepetos Chris N. 
Published: February 2005

AbstractTestes, epididymides, and vasa deferentia of rats were examined for the distribution of cholinesterases using the Koelle thiocholine method. Activity of these enzymes was studied from birth to maturity. Acetylcholinesterase appeared first in Schwann cells of the nerve plexus of the vas deferens and auda epididymidis at birth. Epithelial cell pseudo‐cholinesterase appears in the vas deferens at four days, and an adult distribution is attained at thirty days. Testis, rete testis, ductuli efferentes, and upper caput epididymidis are mainly negative for cholinesterases. In the remainder of the epididymis, three zones of intense epithelial cell reactivity are preceded by regions of lesser intensity. Smooth muscles of the epididymis are negative, but the vas deferens musculature reacts for pseudo‐cholinesterase. The nerve plexus is positive for both acetyl‐ and pseudo‐cholinesterase, and is confined to the corpus and cauda epididymidis and vas deferens. The increasing density of the enzyme‐positive nerves, and the cholinesterase reaction of the musculature distally suggests a probable inhibitory role in the regulation of smooth muscle function in these regions under normal conditions. The absence of an enzyme‐positive innervation and the presence of an enzyme‐negative musculature of the caput is correlated with an active rhythmic contractility in this region, which gradually disappears distally.
Renewal of intestinal epithelium in the freshwater turtle, Chrysemys picta
Authors: Wurth Sister Mary Alan , Musacchia X. J. 
Published: February 2005

AbstractThe area of new cell formation, the rate of proliferation, and the manner in which cells are lost from the intestinal epithelium in the turtle, Chrysemys picta, were studied using a cell labeling technique with tritiated thymidine and mitotic inhibiting technique with colchicine.In the intestinal epithelium of Chrysemys picta, cellular proliferation was observed to occur in the layer of cells adjacent to the basement membrane. Mitosis occurred throughout the epithelium at a fairly low rate (mitotic index 0.0016). In the upper intestine fewer labeled cells were found in the apical one‐third of a villusfold than in either the mid or basal one‐third. The time required to renew the intestinal epithelium, was estimated to be about eight weeks in winter turtles maintained at 20° to 24°C.Cell loss from the system appeared to be due to a randomly located movement of cells lumenward from the basement membrane.Mitotic activity in cold torpid turtles (11°C ambient temperature) appeared to be completely suppressed as shown by a lack of incorporation of tritiated thymidine and an absence of mitotic figures in the intestinal epithelium.The term villi‐folds was proposed to provide a category for those animals possessing structures having characteristics both of villi and of folds as found in C. picta.
Correlation between morphometric measurements of the aorta and visual scoring of avian atherosclerosis
Authors: Weiss Harold S. , Griminger Paul , Fisher Hans 
Published: February 2005

AbstractAn analysis was made on 140 adult chickens of the relationship between visual estimation of the degree of encroachment of the lumen of the vessel by plaques and such morphometric variables as weight, length, circumference, thickness, density, and combinations thereof of the thoracic and abdominal segments of the aorta. Aortic weight and thickness functions were found to be significantly correlated to scores, accounting in the two highest cases (thickness and weight/area of the abdominal segment, body weight held constant) for 46% (r = 0.68) and 42% (r = 0.65) respectively, of the variability in score. Correlations were considerably lower in the thoracic segment, the highest being r = 0.36 for weight/circumference. The scoring thoracic segment, the highest being r = 0.36 for weight/circumference. The scoring system thus has a basis in measurable physical changes in the wall of the blood vessel, but scoring apparently evaluates considerably more than was measured by the morphometric variables. The morphometric variables would probably serve best as means of comparing different scoring systems and as objective supplements to scoring. The procedure of choice would appear to be weight/area with body weight held constant (i.e. — partial correlation and/or covariance analysis).
Etiology of trypan blue induced antenatal hydrocephalus in the albino rat
Authors: Stempak Jerome G. 
Published: February 2005

AbstractWistar strain albino rats were injected with 1 cm3 of a 1% solution of trypan blue. Three types of dye were used: Matheson, Coleman and Bell, Chroma‐Gesellschaft and a highly purified sample. The dyes were injected on days 6, 7, and 8 of gestation. Fetuses were excised from days 16 through 20, fixed, decalcified where necessary, embedded in paraffin, serially sectioned and stained. Newborn young were treated similarly. Chroma‐Gesellaschaft trypan blue was without reproductive or teratogenic effect at the above doses. Increasing the dose did not increase the teratogenicity but did yield a decrease in litter size. Both Matheson, Coleman and Bell trypan blue and the purified sample were teratogenic. The most frequent neural defect observed was hydrocephalus. Serial sections of the newborn hydrocephalics showed an occluded or extremely tenotic aqueduct of Sylvius in 31 of 33 sectioned animals. The fetuses collected from days 18 through 20 also had occluded or stenotic aqueducts if hydrocephalic. Aqueductal stenosis or occlusion was present in 17‐day‐old fetuses, but hydrocephalic was not conclusively demonstrated at this age. Sixteen‐day‐old fetuses did not have aqueductal occlusion in any of those examined, but stenosis was evident. It is concluded that the defect predisposing to hydrocephalus in the young of trypan blue treated rats of this strain is aqueductal stenosis or occlusion.
An experimental study of cerebral lesions produced by the balloon cannula method of stereoencephalotmy
Authors: Epstein Joseph A. , Epstein Bernard S. , Smulewicz Jacob , Jacobs George 
Published: February 2005

AbstractA method is described for making simple balloon cannulas. These may be inserted into the depths of the brain of the experimental animal and inflated, resulting in the production of a permanent destructive lesion characterized by hemorrhagic necrosis of the parenchyma, elements of the stroma being preserved peripherally. In time, a smooth, well‐defined membrane delineates the oval shaped cavity resulting in a sharply punched‐out lesion. A reversible lesion cannot be produced by this technique. Such lesions may have further clinical or experimental value. The local application of radioactive isotopes to specific areas of the brain under controlled situations permitting withdrawal of solutions may be possible by this method.
Effects of maternal folic acid deficiency on cytologic phenomena in the rat embryo
Authors: Johnson E. Marshall 
Published: February 2005

AbstractA purified diet lacking folic acid and containing 20 mg% of the antimetabolite, 9‐methyl pteroylglutamic (folic) acid was fed to female Long‐Evans rats during days eight and nine of pregnancy. Embryos were removed at autopsy on the tenth day of gestation for study and comparison with embryos from normal control pregnancies.Analysis of mitotic counts revealed that 18.6% of the cells in control embryos were in mitosis in contrast to only 5.7% in PGA‐deficient embryos. A disproportionate reduction in anaphase and telophase stages was observed in conjunction with an increased percentage of cell at metaphase. Concomitantly with these mitotic changes a marked reduction in histochemically demonstrable RNA and in numbers of ribosomes as revealed by electron microscopy was observed.
An experimental and descriptive analysis of the melanocyte population in the venter of the PET mouse
Authors: Rovee David T. , Reams Willie M. 
Published: February 2005

AbstractAlthough melanoctyes appear to be limited to the hair folicles of adult belly skin of the PET mouse, they are found throughout the integument of the newborn. Trauma applied to the ventral belly skin of newborn PET mice results in the maintenance and augmentation of the melanocytes within the skin, even after the formation and growth of hair. The area immediately surrounding the site of trauma shows an increase in the number of melanocytes, apparently due in part to the disruption of the developing follicles and the consequent release of their pigment cells to the skin. UV irradiation also maintains a system of melanocytes within the ventral belly skin of PET mice.The significance of the maintenance and augmentation of melanocytes from the newborn into the adult by surgical trauma or UV radiation is discussed.
Lymphocyte formation in the thymus of the embryonic chick
Authors: Ackerman G. Adolph , Knouff Ralph A. 
Published: February 2005

AbstractEmbryonic thymus provides a distinct advantage over the definitive thymus because the earliest formation of lymphocyte and lymphocytic precursors can be observed in a relatively simple and uncomplicated situation. Special cytological techniques combined with light, phase, and electron microscopy have been performed in this investigation involving over 150 chick embryos between 5 and 18 days of embryonic development.Sequential cytological changes in the development of the thymus into an active lymphocytopoietic organ indicate that lymphoblasts develop by the gradual proliferation and transformation of “undifferentiated” epithelial cells comprising the primordial thymus. Lymphoblastic transformation begins on the seventh day of embryonic development in the chick and is characterized by increased cytoplasmic and nucleolar basophilia and chromatin condensation. “Undifferentiated” epithelial cells undergo two distinct lines of differentiation between the seventh and tenth days: into lymphoblasts and into stellate reticular‐epithelial cells which constitute the organ parenchyma. All stages of lymphocytic maturation may be observed by 10–11 days as the thymus assumes a predominately lymphocytic character. Absence of lymphocytes or lymphocytic precursors in the connective tissue surrounding the embryonic thymus before and during the period of initial lymphoblastic transformation; presence of a continuous basement membrane surrounding the developing thymus; and absence of cells passing through this membrane during this phase of development indicate that the lymphocytic elements appearing in the embryonic thymus parenchyma are of epithelial rather than mesenchymal derivation. Although a contribution of mesenchymal elements to the lymphocytic population via vascular invasion and lobular formation in later stages of thymic development is unlikely, this question cannot be answered at this time. In spite of functional immunological distinctions between the lymphocytes of the chick thymus and bursa of Fabricius, the similarity of origin of the lymphocytic elements of these lympho‐epithelial organs is apparent.
The ultrastructure of megakaryocytes and blood platelets in the rat spleen
Authors: Han Seong S. , Baker Burton L. 
Published: February 2005

AbstractThe cytoplasm of the megakaryocyte in the rat spleen possesses three zones, the perinuclear, intermediate and marginal. The perinuclear zone is characterized by the presence of Golgi apparatus, ribosomes, endoplasmic reticulum, and mitochondria. These organelles are found also in the more voluminous intermediate zone which in addition exhibits platelet granules and an extensive development of vesicles from smooth‐surfaced endoplasmic reticulum to form demarcation membranes by coalescence. The marginal zone is almost devoid of the organelles and inclusions present elsewhere. Shedding of platelets appears to occur by extension of a paired demarcation membrane from the intermediate zone to the cell membrane and subsequent separation of its lamellae so that all of the essential organelles and inclusions of the intermediate zone may be included within the platelet. In addition, platelets contain vesicles which are probably pinocytotic in nature. Platelets are sometimes engulfed by the cytoplasm of phagocytic cells.
A comparison of the metalophilic reticuloendothelial cells to cells containing acid phosphatase and non‐specific esterase in the lymphoid nodules of normal and stimulated rat spleens
Authors: Pettersen James C. 
Published: February 2005

AbstractThis study was undertaken to determine the relationship between Marshall's metalophilic reticular cells and the cells exhibiting non‐specific esterase and acid phosphatase activity in the rat spleen. Untreated and stimulated animals were used. Observations were made chiefly on the marginal metalophils of Snook. These cells showed strong acid phosphatase activity but only slight non‐specific esterase activity in untreated animals. Following stimulation non‐specific esterase activity increased in these cells. Within the nodules metalophilic reticular cells were always more numerous than cells with enzyme activity. Many of these metalophilic cells developed enzyme activity following stimulation. By the use of a restaining technique it was shown that all reticular cells possessing enzyme activity were also metalophilic but that the converse was not true. No mitotic activity was present in these cells.The results suggest that Marshall's metalophils are cells of the reticuloendothelial system in various stages of maturation and that, following stimulation, they may differentiate into mature phagocytic cells.
Studies of muscle fibers of the tensor tympani of the cat
Authors: Erulkar S. D. , Shelanski M. L. , Whitsel B. L. , Ogle P. 
Published: February 2005

AbstractThe tensor tympani muscle of the cat has been studied using histological and electrophysiological techniques. Histological studies revealed the presence of striated and smooth muscle fibers. The striated muscle fibers could be classified structurally as “Fibrillenstruktur” and “Felderstruktur” fibers, suggesting that both “fast” phasic and “slow” tonic fibers were present. Histochemical studies showed that some of the smaller (25–40 μ) Fibrillenstruktur fibers possessed relatively large end‐plate receptor areas which stained heavily for acetylcholinesterase. The membranes and cytoplasm of even smaller diameter fibers (9–25 μ) stained for acetylcholinesterase, similar to its distribution in muscle spindles of other muscles.Intracellular recordings showed that there were two distribution peaks of the resting membrane potentials — one at 40–50 mV, the other at 70–80 mV. When the nerve to the tensor tympani was stimulated by single square wave pulses, small junctional potentials (40 mV) followed by an after‐hyperpolarization, were recorded only from fibers with low resting membrane potentials — presumably slow Felderstruktur fibers. Large (70–90 mV) potentials which showed overshoot of zero potential, and which were preceded by initial long depolrizing potentials, were recorded from fibers with large resting membrane potentials. These fibers, which showed occasional spontaneous activity were presumably smooth muscle fibers. Potentials similar to those recorded from fast muscle fibers in other muscles were also occasionally recorded.It was concluded that the cat tensor tympani possessed slow and fast striated muscle fibers, smooth muscle fibers, and possible some embryonic type muscle fibers.
Visceral heterotaxy with malformed heart. Similar findings in a child and a puppy
Authors: Ferencz Charlotte 
Published: February 2005

AbstractA cyanotic child and a newborn puppy were found to have a complicated cardiac malformation of essentially identical design. There was situs inversus of the cardiac chambers, hypoplasia of the anatomic left heart with transposition of the great vessels, pulmonary atresia, patent ductus arteriosus and drainage of all pulmonary veins into the anatomic right atrium. There was situs inversus totalis with pivotal levocardia in the child and dextrocardia in the puppy.The patient was markedly improved by a systemic‐pulmonary arterial anastomosis indicating the feasibility of palliative surgery in spite of the servere cardiac abnormality.The association of visceral heterotaxy with an identical complicated malformation of the heart in the human and canine species appears to indicate a common developmental deviation and thus is considered to be of teratologic significance.