bluuebunny/crossref_metadata_2025 huggingface dataset:
Cooperative model of epithelial shaping and bending during avian neurulation: Autonomous movements of the neural plate, autonomous movements of the epidermis, and interactions in the neural plate/epidermis transition zone
Authors: Moury J. David , Schoenwolf Gary C.
Published: February 2005

Morphogenetic movements during neurulation cause a tissue to change shape within the plane of the epithelium (e.g., conversion of the oval neural plate into the narrow spinal plate and the wide brain plate), cause bending out of the plane of the epithelium (e.g., raise the neural folds and curl the neural plate into a tube), or contribute to both phenomena. In this study, pieces that contain neural plate alone, epidermis alone, or both tissues (with or without underlying tissues) are cut from chick embryos and allowed to develop for up to 24 hr. Examination of histological sections through such isolates allows analysis of the formation of neural folds. When the neural plate/epidermis transition zone is disrupted, neural folds do not form. Conversely, when the transition zone remains intact, neural folds form. Neural folds form even when most of the medial neural plate and lateral epidermis has been removed, leaving only the isolated transition zone. These data indicate that the transition zone is both necessary and sufficient for the formation of neural folds. The transition zone may play a number of roles in epithelial bending including organizing, focussing, and redirecting movements that are autonomous to the neural plate or epidermis. Time‐lapse video recording, and sequential photographs allowed the documentation of such movements. Neural plate isolates exhibit autonomous rostrocaudal lengthening and mediolateral narrowing. Isolated strips of epidermis exhibit autonomous movements which, unlike wound‐healing movements, are unidirectional (mediad), and region‐specific (beginning and reaching their greatest extent in the cranial region). Isolated pieces of neural plate or epidermis remain flat instead of bending, providing further evidence that the transition zone is necessary for the formation of neural folds. © 1995 wiley‐Liss, Inc.
Protein characterization and targeted disruption of Grg, a mouse gene related to the groucho transcript of the Drosophila enhancer of split complex
Authors: Mallo Moisés , Gendron‐Maguire Maureen , Harbison Margaret L. , Gridley Thomas
Published: February 2005

The Grg gene encodes a 197 amino acid protein homologous to the amino‐terminal domain of the product of the groucho gene of the Drosophila Enhancer of split complex. Analysis with a polyclonal antisera specific for the Grg protein revealed that Grg is a 25 kd nuclear protein that can participate in specific protein‐protein interactions. A null mutation of the Grg gene was constructed by gene targeting. Mice homozygous for this mutation completed embryogenesis and were born, but exhibited varying degrees of postnatal growth deficiency. No dosage‐sensitive genetic interaction was detected between the Notch1 and Grg genes in mice heterozygous for a Notch1 mutant allele and homozygous for the Grg null mutation. © 1995 wiley‐Liss, Inc.
Patterns of oriented cell division during the steady‐state morphogenesis of the body column in hydra
Authors: Shimizu Hiroshi , Bode Patricia M. , Bode Hans R.
Published: February 2005

In an adult hydra, the tissue of the body column is in a dynamic state. The epithelial cells of both layers are constantly in the mitotic cycle. As the tissue expands, it is continuously displaced along the body axis in either an apical or basal direction, but not in a circumfer‐ential direction. Using a modified whole mount method we examined the orientation of mitotic spindles to determine what role the direction of cell division plays in axial displacement. Surprisingly, the direction of cell division was found to differ in the two epithelial layers. In the ectoderm it was somewhat biased in an axial direction. In the endoderm it was strongly biased in a circumferential direction. For both layers, the directional biases occurred throughout the length of the body column, with some regional variation in its extent. As buds developed into adults, the bias in each layer increased from an almost random distribution to the distinctly different orientations of the adult. Thus, to maintain the observed axial direction of tissue displacement, rearrangement of the epithelial cells of both layers must occur continuously in the adult as well as in developing animals. How the locomotory and contractile behavior of the muscle processes of the epithelial cells may effect changes in cell shape, and thereby influence the direction of cell division in each layer, is discussed. © 1995 wiley‐Liss, Inc.
Sequence and expression pattern of the Stra7 (Gbx‐2) homeobox‐containing gene induced by retinoic acid in P19 embryonal carcinoma cells
Authors: Bouillet Philippe , Chazaud Claire , Oulad‐Abdelghani Mustapha , Dollé Pascal , Chambon Pierre
Published: February 2005

The cDNA sequence of Stra7, a retinoic acid (RA)‐inducible gene in P19 embryonal carcinoma (EC) cells, was determined. The deduced Stra7 protein contains a homeodomain highly similar to that of the previously described chicken CHox7 gene product, and is highly conserved during evolution, from hemichordates to vertebrates. The mouse Stra7 cDNA corresponds to the full‐length form of the 77 bp homeodomainencoding cDNA fragment which was previously cloned and termed MMoxA or Gbx‐2. Reversetranscriptase‐PCR analysis revealed the presence of Stra7/Gbx‐2 transcripts in the adult brain, spleen, and female genital tract, whereas no expression could be observed in heart, liver, lung, kidney, or testes. In situ hybridization analysis showed a restricted expression pattern of Stra7/Gbx‐2 in the three primitive germ layers during gastrulation. Restricted expression was also detected in the pharyngeal arches. Subsequently, there were specific expression domains in the developing central nervous system, at the midbrain/hindbrain boundary and later in the cerebellum anlage, in certain rhombomeres, in dorsal regions of the spinal cord, and in the developing dorsal thalamus and corpus striatum. © 1995 wiley‐Liss, Inc.
Restricted expression of the ron gene encoding the macrophage stimulating protein receptor during mouse development
Authors: Quantin Béatrice , Schuhbaur Brigitte , Gesnel Marie‐Claude , Dollé Pascal , Breathnach Richard
Published: February 2005

The human ron gene codes for a transmembrane protein tyrosine kinase which is a receptor for the macrophage stimulating protein. The ron receptor, together with the hepatocyte growth factor/scatter factor receptor encoded by the proto‐oncogene met, and the product of the c‐sea proto‐oncogene, make up a family of structurally related receptors. We have cloned murine ron cDNA sequences and used them as probes for in situ hybridization and Northern blot experiments. We show that ron gene expression occurs relatively late in development, and is much more restricted than that of the met gene. ron gene expression is detected in specific areas of the central and the peripheric nervous system, as well as in discrete cells in developing bones, and in the glandular epithelia along the digestive tract. © 1995 wiley‐Liss, Inc.
Expression of the integrin subunit α9 in the murine embryo
Authors: Wang Angela , Patrone Laura , McDonald John A. , Sheppard Dean
Published: February 2005

The α9 integrin subunit is expressed in adult skeletal muscle, visceral smooth muscle, hepatocytes, squamous epithelium, and airway epithelium. The in vivo function of this protein is unknown. Thus far, only a single α9‐containing integrin has been identified (α9β1) and only a single ligand (tenascin) has been found for this integrin. In order to gain insight into the potential function of α9 integrin(s), we examined the spatiotemporal distribution of the α9 subunit and tenascin during murine embryogenesis. In all tissues where α9 was expressed, its appearance was associated with other evidence of cell differentiation. In developing airway, visceral, and vascular smooth muscles, the onset of α9 expression either coincided with or immediately followed the expression of α‐SM actin. Expression of α9 in epithelia was restricted to the choroid plexus and the basal cell layer of squamous epithelia where its appearance coincided with the development of stratification. α9 immunostaining was first detected in developing skeletal musculature when skeletal myotubes formed. Tenascin expression was detected in many, but not all tissues found to express α9. For example, the hair germs of maturing hair follicles exhibited high levels of α9 staining, but no tenascin immunoreactivity was detected either within the hair germ themselves or in the adjacent dermis. In some tissues where tenascin expression colocalized with α9, expression patterns were not synchronous. Although α9 expression was associated with the onset of tissue differentiation, its expression was not limited to terminally differentiated cells. In fact, in the skin, α9 expression appeared restricted to cells known to retain the capacity to proliferate, i.e., basal cells and hair germs. Thus, α9 integrin(s) are not likely to contribute to the early steps in organ formation, but probably play a role in the maturation and/or maintenance of a variety of differentiated tissues. The expression of α9 without its only known ligand, tenascin, suggests the existence of additional ligands. © 1995 wiley‐Liss, Inc.
Changes in the expression of fibroblast growth factor receptors mark distinct stages of chondrogenesis in vitro and during chick limb skeletal patterning
Authors: Szebenyi Györgyi , Savage Mary Pfann , Olwin Bradley B. , Fallon John F.
Published: February 2005

Members of the fibroblast growth factor (FGF) family of growth factors are key regulators of limb skeletal patterning and growth. Abnormal expression of FGFs or mutations in their receptors (fgfrs) result in skeletal disorders. Here we show that changes in the expression of fgfrs are intrinsic properties of differentiating cartilage. In mesenchymal micromass cultures differentiating into cartilage, as in ovo, fgfr 1 mRNA was found predominantly in undifferentiated, proliferating mesenchyme, fgfr 2 in precartilage cell aggregates, and fgfr 3 in differentiating cartilage nodules. Thus, our data suggest that switches in the expression of fgfr 1, 2, and 3 mRNAs are associated with phases of cartilage patterning both in vitro and in ovo, and mark distinct stages in the development of the limb skeleton. © 1995 wiley‐Liss, Inc.
Histochemical characteristics of mucopolysaccharides in salivary and exorbital lacrimal glands
Authors: Spicer S. S. , Duvenci Jale
Published: February 2005

Comparison of results obtained by S35O4= autoradiography with those from histochemical staining methods and evaluation of the effect on the staining resulting from prior sialidase digestion, methylation, methylation and saponification, or sulfation, substantiates the selectivity of some procedures for sialomucin and others for sulfomucin. These two types of mucopolysaccharide may be differentiated by the high iron diamine‐alcian blue or aldehyde fuchsin‐alcian blue sequences or comparison between staining with the alcian blue pH 2.5‐PAS sequence and staining with the alcian blue pH 1.0‐PAS method. These techniques reveal that some rodent or lagomorph salivary glands form sialomucin alone, others apparently only sulfomucin, whereas a number produce both types of acid mucopolysaccharide either in different mucous cells throughout the gland or in the same cell.

Differences in affinity for basic dyes, periodate reactivity, and susceptibility to elimination of basophilia by methylation or enzymatic digestion are evident among both the sulfo‐ and the sialomucins in different glands. After brief saponification the sialomucin in rat sublingual glands becomes sialidase digestible and gains alcohol resistant metachromasia.

Several serous or seromucous glands secrete neutral mucopolysaccharides; others secrete polysaccharides containing sulfate or sialic acid groups whose affinity is masked for some but not for other basic dyes.
Thalidomide injury to an implanted armadillo blastocyst
Authors: Marin‐Padilla Miguel
Published: February 2005

Thalidomide injury to an implanted armadillo blastocyst is presented. This finding confirms the specific damage by thalidomide to the embryoblastic cells. The lack of damage to the trophoblast at this stage permits a normal implantation of the blastocyst in the uterine mucosa.
Unusual duodeno‐pancreatic relationships associated with incomplete rotation of mid‐gut loop
Authors: Wilson Paula M.
Published: February 2005

A 79 year‐old European female cadaver presented the usual features of second stage arrested mid‐gut rotation accompanied by unusual mesenteric attachments and pancreatico‐duodenal relationships.

The mesentery, whose root extended from the lower pole of the right kidney diagonally across the posterior abdominal wall to end just medial to the left sacroiliac joint, enclosed most of the small bowel and the proximal large bowel. The unusually short duodenum began 2.5 cm to the left of the mid‐line and described a 13 cm U loop with an upward concavity in which rested the pancreas; this loop and the related pancreas were enclosed in a persistent, transversely placed mesoduodenum. The common bile duct crossed the anterior surface of the pancreas to open at the greater duodenal papilla 2.5 cm from the pylorus. the main pancreatic duct lay much closer to the anterior than to the posterior aspect of the gland. The lesser duodenal papilla was situated on the posterior wall of the duodenum. The hepatic artery arose in common with the superior mesenteric artery and encircled the pancreas. The pancreatico‐duodenal vessels were predominantly distributed upon the posterior aspect of the pancreas and duodenum.

It appears that in this specimen the anterior and posterior aspects of the duodenum are transposed, the reversal of surfaces also involving the pancreas. Causative factors are discussed with reference to the literature.
A comparative histochemical study of interstitial tissue and follicular atresia in the mammalian ovary
Authors: Guraya Sardul S. , Greenwald Gilbert S.
Published: February 2005

The distribution and origin of interstitial tissue has been studied in various mammalian ovaries with histochemcal techniques for lipids. The interstitial tissue contains sudanophilic droplets of different sizes consisting of phospholipids, triglycerides and cholesterol and its esters; the lipids are comparatively unsaturated.

The granulosa of normal follicles contains heterogeneous lipid bodies of various sizes composed of unsaturated phospholipids. With the start of atresia these lipid bodies also develop neutral fats (triglycerides). Besides the heterogeneous lipid bodies, another type of sudanophilic lipid droplets of atresia, consisting of triglycerides, cholesterol and its ester and little phospholopids, are formed in the granulosa cells. When the number of these lipid droplets is sufficiently increased, the heterogeneous lipid bodies disappear from the atretic follicles. The theca of such atretic follicles hypertrophies and persists to form the interstitial tissue whereas the granulosa cells, along with the lipid droplets, regress and disappear.

In the rat ovary, the interstitial tissue occurs as scattered patches of various sizes that are derived from the theca of atretic preantral and antral follicles. Most of the lipid droplets of the interstitial tissue are mobilized from the preovulatory rat ovary. All of the bat ovary is occupied by interstitial tissue except for the cortex; the tissue is formed in the same way as in the rat. In the cat ovary, the interstitial tissue is sparsely scattered between the follicles and originates from the theca and adjacent stromal cells of normal and atretic follicles. In the dog ovary the interstitial tissue has a similar origin and also arises from invaginations of germinal epithelium. In the opossum ovary the interstitial tissue is present in the form of sparsely scattered patches of cells which arise from the theca of large preantral follicles. A few lipid bodies, consisting of unsaturated phospholipids, appear in the interstitial tissue.
Chorio‐allantoic membrane touch preparations
Authors: Cuadra Manuel
Published: February 2005

A simple method for separating the ectodermal (chorionic) and entodermal (allantoic) layers of the chorio‐allantoic membrane has been devised. It consists of placing, unfolded, a membrane fragment on a rubber balloon filled with water; air is blown briskly upon the membrane by means of a rubber bulb until its shiny surface becomes dull; following this, a glass slide is applied on it, surface to surface, and then it is suddenly taken off, whereby the desired epithelial layer becomes attached to the glass surface. The microscopic observation of the layers thus individualized shows, on frontal view, their histological architecture, and the characteristic structural details of the constituent cells (cytoplasm, nucleus, nucleolus, cytoplasmic inclusions, mitochondria, stages in mitotic cell division, etc.).
The mesonephric duct in female camel fetuses
Authors: Shehata Ramzy
Published: February 2005

The mesonephric duct was studied in female camel fetuses (Gärtner's duct). All fetuses were well developed, aged from two to three months. The female internal genital organs were sectioned at 10 μ and stained with hematoxylin‐eosin or Van Gieson's stain.

In camel fetuses, the duct is usually lined with one layer of cuboidal or columnar epithelium which may be ciliated. Degeneration and cavitation occur in the lower vaginal part, which finally obliterates the previous structure, or changes it to many layers. These two processes occur in succession at different levels of the vaginal portion and are not uniform stages along the whole duct. The appearance of the duct is variable at different levels and at the same level in different ducts. The two ducts may leave the submucosa superiorly and enter the musculature of the vagina at different levels. No glands opening into the mesonephric duct were observed. The upper (mesosalpingeal) part is smaller in caliber than the lower and seems to be immune to the obliteration and cavitation mentioned.
Some electron microscopic observations on the lamina propria of the gut, with comments on the close association of macrophages, plasma cells, and eosinophils
Authors: Deane Helen Wendler
Published: February 2005

An electron microscopic study has been made of the constituents of the lamina propria of the stomach, small intestine and large intestine of the mouse. This layer is highly cellular in the intestines, less so in the stomach. The connective tissue cells are often crowded together without detectable fibers or ground substance between.

Below the basement (boundary) membrane of the epithelium attenuated fibrocytes form an almost continuous layer. The appearance of a fibroblast in mitotic division is described.

In the connective tissue spaces are abundant plasma cells, macrophages, undifferentiated cells and eosinophils. The fine structure of each is described and illustrated.

Particularly evident is the frequency with which plasma cells lie in direct contact with macrophages and with eosinophils. In some instances, vesicles of similar appearance occur in apposed plasma cell and macrophage, suggestive of exchange of material.

These close relations of macrophages, plasma cells, and eosinophils are discussed in terms of the role each plays in the defense of the organism against foreign antigens.
The pharyngeal pouches of the dog
Authors: Hendrickx Andrew G.
Published: February 2005

The four pharyngeal pouches, pharyngeal grooves, and closing membranes of the dog form in an antero‐posterior sequence but the encroachment of head mesoderm which results in obliteration of the closing membranes occurs in a posteroanterior sequence. No pharyngeal clefts are formed. The anlage of the auditory tube arises as a dorso‐lateral extension from the dorsal surface of the first pharyngeal pouch and expands into an elongated tube directed toward the developing ear. The second pharyngeal pouch develops into a distinct tonsillar sinus dorso‐lateral to the base of the tongue. The palatine tonsil extends into the tonsillar sinus, and both become covered by a fold of epithelium. The third pharyngeal pouch extends medially toward the developing thyroid after contacting the cervical sinus. The distal tip of the third pouch differentiates into Complex III which transforms into parathyroid III and thymus III. The distal tip of the fourth pharyngeal pouch, Complex IV, also extends in a medial direction after contacting the cervical sinus. Complex IV transforms into parathyroid IV and the ultimobranchial body.
Procurement and use of turtle embryos for experimental procedures
Authors: Yntema C. L.
Published: February 2005

Procedures for experiments on the embryo of the turtle are described. Methods of obtaining the gravid females, their handling, and preoperative preparation of the egg are described. The actual operation can be carried out much as it is done on the chick embryo. Post‐operative care is described. Survival can be satisfactory. Hazards of the procedure are discussed and means of controlling them indicated. Most of the experiments were done with embryos of the common snapping turtle, Chelydra serpentina. A few experiments were done with embryos of the painted turtle, Chrysemys picta, and of the soft‐shelled turtle, Trionyx spiniferus. The embryos of the painted turtle promise to be well suited to use for experimental studies. The soft‐shelled turtle is not such a promising form.
Effect of size of intracellular ice on consumption of oxygen and nuclear alteration of mouse kidney cells
Authors: Sherman J. K.
Published: February 2005

Large intracellular ice formations are assumed to be more damaging than small ones. Nuclear alteration, such as pycnosis, generally is considered a reflection of reduced vital cellular functions. Evidence is presented which shows, on the basis of rate of oxygen consumption, that survival of kidney cells is greater after the formation of large rather than small intracellular ice artifacts, and that nucelar alteration such as pycnosis does not indicate the degree of damage to a vital function, their respiratory activity. Findings agree with those based upon autotransplantation of skin (Anat. Rec., 144: 171–191, '62). It is suggested that mitochondria are one of the cellular sites of freeze‐thaw injury and that the mechanism of freezing injury may differ in nucleus and ctyoplasm.

Microscopic appearance of ice artifacts formed in cells of mouse kidney slices after slow (1.5° and 3.0°C/min) and rapid (19° and 38°C/sec) freezing to −75° and −196°C was preserved by the author's freeze‐drying method. Control (unfrozen) and frozen‐thawed slices were fixed in Bouin's fluid and processed routinely for study of microstructure. Oxygen consumption of parallel groups of control and frozen‐thawed slices was measured by the conventional Warburg manometric technique. The data revealed that: (1) the size of intracellular ice artifacts was 5 to 17 times larger in slices frozen at slow than at rapid rate; (2) Q02 of cells in slowly frozen tissue slices (average of 21% of control Q02) was significantly greater than rapidly frozen cells (average of 9% of control Q02); (3) Nuclear pycnosis, crenation and vacuolation were more extensive in cells which were frozen slowly.
Focal radiation, a method for inducing structural modifications in the immature rat brain
Authors: Pulliam James A. , Glasser Stanley R.
Published: February 2005

A new and relatively simple technique for conducting developmental neurology experiments is described. This technique consists of subjecting rats less than four days in age to a collimated source of external beta radiation that can be directed to selected parts of the brain. Use of this method yields the following advantages: (1) the size relationships of the parts of the brain can be altered, (2) bilateral asymmetry of the cerebrum, and/or cerebellum can be produced, (3) chronic functional defects which develop as the rat develops can be obtained, (4) the experimenter may selectively destroy any site in the brain provided that it is superficial enough, and (5) foci of epilation appear on the scalp and serve as markers. The limitations of this method are also discussed.
Cell morphology in tissue underlying skin grafts
Authors: Walker Bruce E. , Yates Robert D. , Duncan Donald
Published: February 2005

Host tissue underlying skin homografts and isografts was removed 4 to 8 days after grafting and fixed in osmium tetroxide for electron microscopy. The skin homograft bed was composed of a dense mass of cells, with bundles of collagenous fibers interspersed. Two types of large, elongated cells with elongated nuclei were commonly seen, one characterized by extensive granular endoplasmic reticulum and the other by masses of free ribosomes. The former corresponds to descriptions of fibroblasts and the latter resembles a lymphoid cell but is considerably larger than those seen in peripheral blood. These two cell types contain most of the ribosomes present in the graft bed. Numerous macrophages and neutrophils were present also. The skin isograft bed was similar except that no large elongated cells with masses of free ribosomes were found. The cell types identified with the electron microscope correspond to the cell types proposed earlier on the basis of light microscope radioautography with thymidine‐H3. It is suggested that the elongated, hypertrophied, lymphoid cell, rather than the macrophage, is responsible for homograft rejection.
Actions of betaine, carnitine and choline on the pattern of hepatic liposis in mice fed a high‐fat, low‐protein diet
Authors: Ball Carroll R.
Published: February 2005

Four stocks (C, C‐57 Bl, DBA and Swiss albino) of mice were fed a high‐fat (28%), low‐protein (8%), hypolipotropic diet for 3–480 days. Lipotropic activities of supplements of betaine and carnitine were evaluated. There were no strain‐limited hepatic responses to the diet or to the action of the lipotropes. Without lipotropic supplements, parenchymal liposis (sudanophilia of frozen sections) was progressively incremental in all lobular zones for approximately 90 days. Subsquently, lobular liposis decreased and the remaining fat was concentrated in the middle zone within cords of fat‐laden cells radiating in a stellate pattern. With choline supplemention, liposis was limited to small amounts of fat within cells that composed the stellate pattern. Betaine displayed a level of lipotropic activity approximating one‐half to three‐fourths that of choline. The lipotropic activity of carnitine was marginal and inconsistent. The combination of betaine and carnitine demonstrated some synergistic action. No parenchymal hyperplasia was observed. The intralobular reticulum increased in some livers, primarily around the central and intercalated veins, but no lobular distortion resulted.
Histochemical study of morphogenesis and teratogenesis of the palate in mouse embryos
Authors: Jacobs Richard M.
Published: February 2005

Aggregation of acid mucopolysaccharides in normal palates and cleft palates in mouse embryos was studied by various histochemical methods. An “index of staining intensity” was introduced as a mean numerical value derived from the visual grading of all sections of each litter. Animals were killed at 20 different points of gestation period, from thirteenth to seventeenth day. In this manner a composite staining intensity — time table could be obtained for both experimental groups. The observed data seem to indicate some correlation between the concentration of acid mucopolysaccharides in palatine shelves and the competence of embryonic mechanism of palate closure.
Application of an idealized model to morphometry of the mammalian tracheobronchial tree
Authors: Phalen R. F. , Yeh H. C. , Schum G. M. , Raabe O. G.
Published: February 2005

Quantitative anatomical descriptions (morphometry) of the tracheobronchial airways are of importance in many applications including the preparation of successful mathematical models describing airflow patterns and deposition patterns of airborne particles in the lung. Morphometric data are also useful in studies of comparative anatomy and in describing normal and diseased states of an organ. The collection of such data is aided by the use of idealized models of airway branches of the tracheobronchial airways. Morphometric measurements from the lungs of several mammalian species are presented using a model that consists of three connected tubular segments. The morphometric model uniquely defines an identification number for each branch segment, a branching angle, an airway segment length and diameter, an inclination of a segment to gravity and the degree of alveolarization of each segment. Designed to be compatible with computerized data handling, the model is unambiguous and realistic, but flexible so that anomalous anatomical structures can be classified and noted. Morphometric data describing the variation of structure with depth in the tracheobronchial airways are presented in the form of graphical representations of anatomical measurements on replica casts of the human, dog, rat and hamster airways. These distributions describe the anatomical character of the tracheobronchial airways concisely, quantitatively, and characteristically for each species.
A histological study of the development of the avian middle ear and tympanum
Authors: Jaskoll T. F. , Maderson P. F. A.
Published: February 2005

The development of the middle ear and tympanum of Gallus gallus has been studied in embryos Hamilton‐Hamburger stages 20‐46. Particular attention was paid to the pattern of expansion of the pharyngeal pouch forming the tympanic cavity, and the histogenesis of the tissues of the region of the vestibular window. It is concluded that pouch expansion is brought about by simple epithelial growth into regions devoid of mesenchyme. The mesenchyme does not show significant cell death, but differentiates as connective tissue, macro‐phages, and sinus vascular spaces. The epithelium of the mature cavity is of endo‐dermal origin, and there is no indication of celomic contributions. We provide a detailed morphological analysis of the development of the footplate from cells of both the second visceral arch and the otic capsule. These detailed observations on the patterns of chondrification of columella and capsular tissues permit the presentation of a model for cellular interactions leading to the differentiation of the annular ligament.
The histogenesis of lymph nodes in rat and rabbit
Authors: Eikelenboom P. , Nassy J. J. J. , Post J. , Versteeg J. C. M. B. , Langevoort H. L.
Published: February 2005

The histogenesis of the popliteal lymph node in the rat and the popliteal and inguinal lymph nodes in the rabbit was examined by light microscopy. Special emphasis has been laid on the initial lymphocyte population in the lymph node anlage. In the rat on the seventeenth day of gestation lymphoid cells populate a limited mesenchymal area along the vein wall. The next day the mes‐enchyme shows a bulb‐shaped outgrowth causing an indentation in the wall of a lymph vessel, running parallel to the vein and having a saccular widening at this place. The bulb‐shaped lymphoid outgrowth fills up the widened lymph vessel; the subcapsular sinus originates from the remaining parts of the lymph vessel. At birth the lymph node can be divided into a primitive cortex consisting of an area with evenly scattered lymphocytes among the basic network of reticular cells and a medulla. About three days after birth an ovoid area containing a dense concentration of lymphocytes is observed in the inner cortex. In the next days it expands in both lateral and medullary direction but not into the outer cortex. Primary follicles appear in the outer cortex 18 days after birth.

The development of the inguinal and popliteal lymph nodes in the rabbit shows the same characteristics as the histogenesis of the popliteal lymph node in the rat.

The morphogenesis of the lymph node is summarized in a schematic diagram.
Supraependymal cells in the third ventricle of the neonatal rat
Authors: Walsh Raymond J. , Brawer James R. , Lin Peck Sun
Published: February 2005

Supraependymal cells in the third ventricle of neonatal male and female rats were examined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Supraependymal cells in the third ventrical of adult male rats were also studied with SEM. Many neonate supraependymal cells were round to oval in shape and exhibited varying degrees of surface irregularity. Small finger‐like processes or narrow pseudopodia projected from the cell bodies over the underlying ependymal cells. Some neonatal supraependymal cells exhibited flattened cell bodies with broad pseudopodia and few surface irregularities. TEM revealed a variety of cell profiles. Prominent within the cytoplasm of many supraependymal cells were lysosomes, smooth and coated vesicles suggesting pinocytosis, subplasmalemma vacuoles, and occasional lipid droplets. The morphological characteristics of neonatal supraependymal cells suggested they were mononuclear phagocytes. Adult supraependymal cells exhibited more pleomorphic cell shapes with numerous cell processes, varying widely in size and shape, and often extending over the ventricular surface for considerable distances. These observations, in combination with previous studies by other investigators, suggest that some adult supraependymal cells may also be phagocytic in nature. The differences in morphology between adult and neonatal supraependymal phagocytes may relate to the differing third ventricle environment between adult and neonates and/or differences in the origin of the phagocytes with age.
Mouse uterine glands during the delayed and induced implantation periods
Authors: Given Randall L. , Enders Allen C.
Published: February 2005

Mouse uterine glandular epithelium during the lactationally delayed implantation period and after estradiol induction of implantation was investigated using light and electron microscopy. During the delayed implantation period the lumen of this simple tubular gland is narrowed. The glandular epithelial cells have a well developed Golgi complex lateral to the nucleus, and numerous cisternae of smooth and rough endoplasmic reticula (RER) and many electron lucent apical vesicles of sizes up to 0.2 μm in diameter near the luminal border. The basal region contains lipid droplets and dispersed, irregular cisternae of RER. Twenty‐four hours after the administration of 17β‐estradiol the glandular lumina become dilated but the luminal content does not stain with azure B. Ultrastructurally the glandular cells are not remarkably different from those seen during the delay period. However, by 48 hours after estradiol administration the glandular lumina are not only dilated but filled with material which stains intensely with azure B and is ultrastructurally dense and homogeneous. The apical region of the glandular cells contains granules up to 0.4 μm in diameter composed of electron dense material similar in density to that seen in the glandular lumen. In addition, the Golgi complex has assumed a position apical to the nucleus, and the basal RER has an increased number and more orderly arrangement of cisternae.

The changes seen in the uterine glands after the induction of implantation during the delay period are apparently indicative of increased secretory activity of the glandular epithelia. However, the contribution of the glands to the changes in uterine fluid composition has yet to be established.
Serous cysts of the aging guinea pig ovary. II. Scanning and transmission electron microscopy
Authors: Quattropani Steven L.
Published: February 2005

Ovarian cysts which developed spontaneously from the rete ovarii in the ovaries of guinea pigs have been examined in 1‐ and 2‐year‐old animals by scanning and transmission electron microscopy. Two cell types have been described, a tufted cell with numerous motile cilia and a non‐tufted cell with a solitary cilium. While the non‐tufted cell exhibited numerous smooth coated vesicles in its lateral and basal regions, no signs of secretion to the lumen of the cyst have been seen and occluding junctions have not been observed.
Changes in the satellite cells of growing muscle following denervation
Authors: Schultz Edward
Published: February 2005

Satellite cells exhibit a number of distinct morphological changes after denervation which appear to be a direct response to nerve section or altered functional state of the muscle fibers. These changes appear generally related to increased movement and overall activation of the cells. After longer periods of denervation many satellite cells appear to separate from their fibers and become free cells in the interstitial space. It is proposed that this mechanism provides a cellular source for the small‐diameter, immature fibers dispersed throughout the muscle after two to three weeks. Although neo‐formation of myofibers appears to be a feature of denervated growing muscle, an increase in total fiber population was not observed. It is suggested that in the absence of a viable nerve supply the new fibers degenerate.
The freeze‐fracture study of alveolar type II cells and alveolar content in fetal rabbit lung
Authors: Kikkawa Yutaka , Manabe Toshiaki
Published: February 2005

Freeze‐fracture replication technique was utilized to study the morphology of type II alveolar epithelial cells and alveolar contents in the late gestation of rabbit fetuses. It was shown that the lamellar inclusion bodies of type II cells were enveloped by the usual type of unit membrane with membraneassociated particles of 15 nm diameter. The interior of the inclusion bodies was composed of multiple stacks and/or whorls of membranes which were devoid of membrane‐associated particles. Small vesicles within the inclusion were found more frequently with this technique than in chemically fixed thin‐sectioned preparations.

The intra‐alveolar contents were comprised of two components; spherical bodies, which were identical to the internal contents of the lamellar bodies of type II cells, and tubular elements. These tubules most often appeared rectangular on cross‐fractured faces. Triangular and hexagonal fracture faces were also noted. The tubules were seen to rest on the surfaces of the spherical components. Our observations suggest that the tubular element of the alveolar contents is formed through the interaction between the discharged lamellar body content and the alveolar fluid, and further suggest that at least the major constituent of type II cell lamellar bodies is lipid not bound to protein.

Three new observations were made in this study; the absence of membraneassociated particles on the interior of the lamellae of the inclusions, the crossfractured profiles of tubular elements of the alveolar contents, and the occasional multicompartmental nature of type II cell inclusions.
The structure of the epididymis, efferent ductules and ductus deferens of the guinea pig: A light microscope study
Authors: Hoffer Anita P. , Greenberg Jon
Published: February 2005

In the guinea pig, the narrow part of the epididymis that traverses the upper pole of the testis and passes downward over the entire length of the gonad is composed exclusively of efferent ductules and the initial segment (zone I) of the epididymal duct. At the beginning of zone II, the narrow contour of zone I expands into a large globular region which lies adjacent to the caudal pole of the testis. The globular region of the guinea pig epididymis is commonly referred to as the cauda epididymidis but in the present study, examination with the light microscope reveals that it is composed of five histologically distinct zones (zones III through VII). A detailed histological analysis of the characteristics of the epithelium in the seven zones of the guinea pig epididymis and in the efferent ductules and ductus deferens was undertaken to obtain a better understanding of structure‐function relationships in the epididymis of the guinea pig. It was found that each of the zones could be readily distinguished on the basis of its histological features and primarily on the basis of the appearance of the principal cells.
Rat adrenocortical carcinoma 494: An integrated structural, stereological, and biochemical analysis
Authors: Moore Robert N. , Penney David P. , Averill Kathy A.
Published: February 2005

Snell adrenocortical tumor 494 was implanted into male Sprague‐Dawley rats and recovered 7, 14, 21, 28 or 35 days following initial detection by palpation (7‐10 days following transplantation). Electron microscopic, stereologic and biochemical analyses of the tumor were compared to adrenals of normal animals to serve as a baseline for further studies of the effects of chemotherapeutic agents on tumor cells. Tumor cells possessed oval or elongated mitochondrial profiles with tubular cristae, one or two very large (> 5μ) lipid droplets, abundant ribosomes and coated vesicles, and sparse rough and smooth endoplasmic reticulum. Stereologic evaluation revealed that tumor lipid volume was 41% and mitochondrial volume 29% that of the normal adrenal controls. Tumor nuclei were 2.5 times larger than adrenocortical nuclei while cellular volumes were similar. On a net weight basis, tumor cholesterol was 55%, cholesterol ester 2.2%, and lipid phosphate 25% of respective mean values for normal adrenal glands. The tumor cholesterol: cholesterol ester ratio progressively decreased with time, but remained 18‐fold greater than the normal adrenal. Plasma corticosterone levels in tumor‐bearing rats were elevated 3‐fold by 14 days after initial detection. The adrenals of the tumor‐bearing host exhibited marked involution, the extent of which was directly related to tumor size.
Ultrastructure of the harderian gland in male albino rats
Authors: Brownscheidle Carol M. , Niewenhuis Robert J.
Published: February 2005

Harderian glands of adult male albino rats were examined by light and transmission electron microscopy. The animals were divided into the following experimental groups: (1) castrated only, (2) castrated with testosterone replacement and (3) sham operated controls.

Two types ofsecretory cells, designated as A and B, comprise the glandular epithelium and are distinguished on the basis of morphologic differences in the following cellular components:cytoplasmic secretory vacuoles, mitochondria and smooth endoplasmic reticulum (SER). Cell type A is more numerous and contains larger secretory vacuoles than cell type B which is characterized by the presence of large numbers of mitochondria and packet‐like arrangement of SER profiles. The glandular secretion appears to be elaborated via merocrine mechanisms and consists primarily of lipids and a fibrogranular substance. The latter component may consist of porphyrin compounds.

Nerve endings are found in the connective tissue interstices of the gland. Direct synapses were not observed in association with either gland cells or myoepithelial cells.

Castration did not produce significant alterations in the morphology of the glandular epithelium.

Results of the investigation suggest that the rat Harderian gland may serve as a useful model for the study of cellular mechanisms involved in the production of human porphyrias.
The ultrastructure of the normal human thymus: A study of 36 cases
Authors: Bearman Robert M. , Levine Gerald D. , Bensch Klaus G.
Published: February 2005

Electron microscopy of the normal human thymus demonstrates a supporting framework of epithelial‐reticular cells with long branching cytoplasmic processes joined by desmosomes. In the interstices of the epithelial‐reticular cell processes lie lymphocytes, macrophages, and rare myoid cells. Both small and large lymphocytes are evident. No desmosomes are observed between the lymphocytes and the epithelial‐reticular cells. Macrophages are most numerous in the cortex where they often contain phagocytized nuclear debris. The possible functional significance of the above‐described fine structural features is discussed.
The cingulate bridge between allocortex, isocortex and thalamus
Authors: Powell Ervin W.
Published: February 2005

The Fink‐Heimer silver impregnation and the autoradiographic methods were used to study the fiber projections of the cingulate cortex in the squirrel monkey. It was found that this cortex provides inputs to the striatum, thalamus and several areas of isocortex. Evidence was found for a number of fiber projections (1) Fibers from the anterior limbic area were traced to the central part of the head of the caudate nucleus, putamen, septum, dorsomedial nucleus of the thalamus, anterior hypothalamus and lateral basal nucleus of the amygdala. (2) Projections from the cingulate area were traced to the lateral part of the head of the caudate nucleus, putamen, and to the centromedian, anterior, lateral dorsal, and lateral ventral thalamic nuclei and to medial nuclei of the base of the pons. (3) There were projections from the retrosplenial area of the anterior, lateral dorsal, dorsomedial, and posterior thalamic nuclei and lateral nuclei of the pons. These results indicate that most of the cingulate gyrus is an intermediate structure between the thalamus and overlying cortex. The anterior limbic area forms a bridge between the thalamus and other areas of the cingulate gyrus and the frontal cortex. (4) The retrosplenial area and the posterior part of the cingulate area bridge the adjacent visual sensory association cortex and pelvic areas of the sensory motor cortex, respectively. These areas of the cingulate gyrus project directly to the striatum as well as to the thalamus, structurally providing limbic system input to subcortical motor structures.
Ultrastructure of the corneal nerves after fixation with potassium permanganate
Authors: Tervo Timo , Palkama Arto
Published: February 2005

The innervation of the rat cornea was investigated electron microscopically after KMnO4 fixation. Myelinated nerve fibres were observed only in the limbal margin of the cornea, whereas the axons located in the stroma of the avascular cornea were surrounded by the Schwann cell cytoplasm. Axon profiles with small (300‐500 A) granular vesicles and another type with agranular vesicles were seen among the non‐vesiculated fibres in all parts of the cornea. After superior cervical ganglionectomy it was not possible to find any axons with small granular vesicles. On the other hand, some degenerating axon profiles were observed in the stromal nerve trunks after ganglionectomy. In the epithelium‐naked axons with an occasional mitochondrion and a few agranular vesicles penetrated between the epithelial cells. Moreover, axons filled with several mito‐chondria were rarely observed in the epithelium, but these were difficult to differentiate from the surrounding epithelial cells.

The role of the different nerve types observed in the cornea is discussed. The results suggest that the rat cornea has a dual vegetative innervation.
Fenestrations in endothelium of rat liver sinusoids revisited by freeze‐fracture
Authors: Montesano Roberto , Nicolescu Paul
Published: February 2005

The freeze‐fracture appearance of fenestrations of sinusoidal endothelial cells has been reassessed in perfusion‐fixed rat liver. Fenestrations, limited to the attenuated portions of the endothelial cell cytoplasm are usually round or oval in shape, with diameters ranging from 40‐600 nm. Within a given fenestrated region, they are disposed in clusters forming sieve plates. In addition, the presence of wide, irregularly shaped openings suggest that adjacent fenestrations may coalesce and result in the larger openings. Our data thus confirm the existence of both small and large fenestrae in the endothelial wall, in contradistinction to previous studies showing only regular, medium‐sized (100 nm) openings.