bluuebunny/crossref_metadata_2025 huggingface dataset:
The ultrastructure and cytochemistry of the shell membrane‐secreting region of the Japanese quail oviduct
Authors: Hoffer Anita P.
Published: February 2005

The isthmic mucosa or shell membrane‐secreting portion of the Japanese quail oviduct was examined by light and electron microscopy and by cytochemical techniques. Preliminary studies of the shell membrane were also made.

The mucosa of the isthmus is thrown into numerous longitudinal folds which are covered by a simple columnar epithelium consisting of ciliated and mucussecreting cells. Numerous convoluted simple tubular glands lie densely packed beneath the surface epithelium and are connected to it by short ducts. The tubular glands are made up of a single cell type, the principal cell, which contains numerous large secretory granules. Mature granules display an eccentrically placed dense spherical core surrounded by a less dense cortex. The shell membrane is composed of a meshwork of intersecting fibers oriented randomly in the plane of the membrane; each fiber is made up of a medulla and cortex.

Cytochemical methods indicate that the principal cell secretory granules consist of a complex of carbohydrate with protein. The protein is rich in sulfhydryl groups; the polysaccharide moiety is neither sulfated nor rich in carboxyl groups. The mucigen granules are composed of a nonsulfated carbohydrate‐containing substance. The shell membrane has both carbohydrate and protein components. Speculations are presented on the morphological relationships between the various components of the completed shell membrane and their secretory precursors.
The opisthonephric kidney of the sea lamprey of the great lakes, Petromyzon marinus L. V. The archinephric duct
Authors: Youson John H. , McMillan Donald B.
Published: February 2005

The archinephric duct of ammocoetes consists of two morphologically distinct regions. An anterior and posterior region are lined by a columnar epithelium that often possesses wide, lateral intercellular spaces. Some cells in the anterior region are characterized by an electron‐dense apical cell coat and dense apical vesicles, while others resemble cells of the collecting tubule. In the posterior region all cells possess large accumulations of glycogen, mitochondria, and smooth endoplasmic reticulum. There is reason to believe that transport of ions and fluids may occur in the duct and, although some morphological evidence indicates a role in protein absorption, these cells do not appear to be specialized for this function.

The archinephric duct of the adult lamprey is morphologically distinct from that of the ammocoete and appears to be involved in the production of mucus and in the expulsion of urine by contraction of its muscular wall. Its stratified epithelium is divided into basal, intermediate, and superficial cells and intracellular PAS‐positive granules increase progressively in number from the basal to surface cells. The superficial cells can be further divided into four types and a progression of cell types from the base to the surface of the epithelium is suggested. A thick electron‐dense apical cell coat, apical vesicles, and mucous granules probably account for the intense staining of the surface with PAS. These features indicate that a closer structural relationship exists between the lamprey archinephric duct and the excretory ducts of other lower vertebrates than with the ureter of mammals.
A comparison of the morphology of lipid absorption in the jejunum and ileum of the adult rat
Authors: Jersild Ralph A. , Clayton Robert T.
Published: February 2005

Morphological aspects of lipid absorption were compared in the jejunum, mid‐ and terminal ileum. Physiological fatty chyme was injected into ligated segments of each of the intestinal regions in fasting rats. Tissues were removed at intervals from 5 to 30 minutes and prepared for electron microscopy. The results show the morphological pattern of lipid accumulation to be similar in the jejunum and mid‐ileum. Both show evidence for considerable lipid absorption and transport. The terminal ileum, in contrast, displays an altered pattern of lipid distribution. Numerous lipid droplets begin to form at an early time period in the cytoplasmic matrix, as in the upper intestine. These droplets become larger and more numerous as absorption progresses. Lipid droplets in the endoplasmic reticulum and Golgi apparatus, however, are present in considerably reduced size and numbers through the entire absorptive period examined, as compared to the upper intestine. Few droplets are present in the lamina propria. Considerably less transport of absorbed lipid is indicated. This morphological pattern appears to correlate with a reduced synthesis of triglycerides in the terminal ileum. The evidence suggests that triglyceride synthesis and the formation of membrane‐bound droplets are related events as they normally occur in the upper small intestine.
Localization of obturator and pectineal motoneurons in the dog
Authors: Breit James F. , Cardinet George H. , Tunell Gary L. , Fedde Marion R.
Published: February 2005

The motoneuron columns of the obturator and pectineal nerves were localized within the lumbar spinal cords of dogs by observing retrograde chromatolysis following resection of the respective nerves. The obturator column was located in segments L4 through L6 while the pectineal column was located in segments L4 and L5. The dorsal‐to‐ventral and medial‐to‐lateral boundaries were determined for each column and the pectineal column was located within the boundaries determined for the obturator column in segments L4 and L5. Antidromic stimulation of the pectineal nerve localized the origin of motor fibers from lumbar spinal nerves L4 and L5. The results provide an anatomical basis for studies of motoneurons innervating the pectineus muscles of dogs affected with a developmental myopathy of this muscle.
Myoepithelial cells in the exorbital lacrimal and parotid glands of the rat in frozen‐etched replicas
Authors: Leeson Thomas S. , Leeson C. Roland
Published: February 2005

Light and electron microscopy were combined with the technique of freeze‐etch to study myoepithelial cells. Myoepithelial cells of the rat exorbital lacrimal and parotid glands are found in relation both to secretory units and intercalated ducts. They lie within the basal laminae of secretory acini and intercalated ducts and do not protrude from the external surface. The myoepithelial cell consists of a central nucleus and surrounding cytoplasm with several cytoplasmic arms, the arms being less numerous in those cells associated with the ducts. The cytoplasm is filled with fine fibrils in parallel array. The interrelationship between myoepithelial cells and acinar or ductal cells is described with the aid of frozen‐etched replicas and the nature of the membrane surfaces is discussed. It is concluded that myoepithelial cells are contractile; their resemblance to smooth muscle is noted.
The vertebral‐basilar system of dog in relation to man and other mammals
Authors: Anderson Wesley D. , Kubicek William
Published: February 2005

The basilar artery of the dog was studied and its branches traced to their terminations. The nomenclature used is based on the origin, course and termination of the arteries. The basilar artery arose from a spinal arterial circle formed in the vertebral canal at the level of the atlanto‐occipital articulation by union of vertebral arteries and the ventral spinal artery. The arterial supply to the membranous labyrinth arose from the anterior inferior cerebellar artery. After entering the porus acusticus, one or more tiny labyrinthine arteries arose and the parent trunk then looped dorsally out of the meatus to supply the lower portions of the cerebellum. A branch of the basilar artery, unnamed in the dog, was associated closely with the trigeminal nerve; a separate arterial supply to the caudal colliculus arose from the medial branch of the superior cerebellar artery. It was concluded that branches of the basilar artery of the dog and man are similar since, with exception of the middle inferior cerebellar artery, all branches of the basilar artery in man may be found in dog.
The histochemical and microscopical differentiation of the respiratory glands around the maxillary sinus of the rat
Authors: Vidić Branislav , Greditzer Harry G.
Published: February 2005

To investigate the histochemical and microscopical characteristics of the lateral and maxillary glands, as well as their topographical relationship with the maxillary sinus, 25 adult specimens were used. The tissues were fixed in neutral buffered formalin and serial sections were stained with hematoxylin and eosin, trichrome, Sudan black B, ninhydrin‐Schiff, PAS, alcian blue, and mucicarmine. The objectives were to ascertain: (1) the general morphology of the lateral nasal wall and of the maxillary sinus, (2) the topographical relation between the glands and the maxillary sinus, (3) the microscopical and histochemical characteristics of the maxillary gland, and (4) the microscopical and histochemical characteristics of the lateral nasal gland. In all specimens, the sinus was surrounded by glandular tissue. The lateral gland occupied the submucosa anterior and inferior to the sinus, the maxillary gland extended from the anterior to the posterior recess superior to the sinus. The maxillary gland showed the typical morphology characteristic of a serous gland. The gland drained into the sinus by numerous excretory ducts. The epithelium of the proximal ducts was simple columnar and in the distal ducts, pseudostratified columnar ciliated. The latter type of epithelium, without goblet cells, was found in the maxillary sinus. The lateral gland showed a morphology characteristic of mucous glands. Although the gland contained neither free lipids nor proteins, it was PAS‐positive. A high concentration of acid glucoproteins was detected in the lateral gland. The excretory system of this gland was lined throughout by either a simple columnar or a simple cuboidal epithelium. The possible contribution of the glands to the functioning of the upper part of the respiratory system was discussed.
Ultrastructura observations on ovarian perifollicular smooth muscle in the cat, guinea pig, and rabbit
Authors: Burden Hubert W.
Published: February 2005

The theca externa of large vesicular ovarian follicles of cats, rabbits and guinea pigs was studied with the electron microscope. Fibroblasts and smooth muscle were observed in all species. In the guinea pig, a third cell type, with characteristics of both fibroblasts and smooth muscle, was present. Myelinated and unmyelinated nerves were observed in the theca externa of cats and guinea pigs. Unmyelinated nerves often contained vesicles and mitochondria and were separated from cellular elements by a space of about 2000 Å. It is suggested that coordinated muscular contractions in the theca externa offer the most reasonable explanation for the extrusion of the ovum. This muscle is probably, at least partially, under local neural control.
An electron microscopic study of sperm penetration into the rabbit egg after natural mating
Authors: Bedford J. M.
Published: February 2005

The ultrastructure of fertilization has been studied in rabbit eggs recovered 11 to 15 hours after natural mating. Many sperm passing between the granulosa cells had undergone the acrosomal reaction, but this was not invariable, and, occasionally, intact sperm were present close to the zona pellucida. The cells of the corona radiata sometimes develop pseudopodial processes at the abovular surface and can ingest sperm after natural mating. The bulk of the content of the acrosome and the vesiculated elements formed during the acrosomal reaction, are lost before the sperm penetrates the zona pellucida, at which point the naked inner membrane of the acrosome is brought into intimate apposition with the zona. As the sperm cleaves a path through the zona pellucida, the posterior equatorial segment of the acrosome remains intact, and later persists as such in perivitelline sperm and quite possibly after incorporation of the sperm head into the vitellus.

Sperm head entry into the vitellus is a two‐fold process. The fertilizing sperm invariably fuses first with the vitelline membrane over the midposterior region of the head, whereas the rostral or acrosomal portion is drawn into the vitellus while encased by a flattened vesicle; this vesicle is comprised by the persistent inner membrane of the acrosome and externally by vitelline membrane sequestered from the egg surface. Soon after exposure to ooplasm, the sperm nucleus begins to decondense at a variable rate into a web of electron‐dense strands; this process begins in the midposterior region, and then extends rostrally and caudally. At the same time the encasing membranes are reflected away from the anterior region of the nucleus, exposing subacrosomal material to the ooplasm. At this point the perforatorium remains, but this and the associated membranes are presumed to disintegrate eventually within the egg. After decondensation of the nucleus is complete, the faintly staining chromatin becomes enveloped by a series of compressed vesicles which together will form the porous limiting membrane of the male pronucleus.

The last region to be incorporated is the sperm tail, the plasma membrane of which is lost as organelles of the tail pass into the ooplasm. During its incorporation, the midpiece engenders some reaction at the egg surface, and the mainpiece sometimes becomes fused with surface processes before it enters the body of the egg. The midpiece then commonly disintegrates, with dispersion of the mitochondrial sheath, whereas the mainpiece usually remains essentially intact until the time of syngamy or beyond.
Skeletal muscle regeneration in young rats
Authors: Walker Bruce E.
Published: February 2005

The source of myotube nuclei in regeneration of skeletal muscle in young rats was studied by comparing frequencies of labeled nuclei in two experiments. In a single injury experiment, multiple injections of thymidine‐H3 were given during a three day period, skeletal muscle was injured 12 days later and the rats were killed four days after injury. There were almost no labeled myotube nuclei in this experiment. In a double injury experiment, thymidine‐H3 was injected two days after injury, the muscle was reinjured 12 days later, and the rats were killed four days after the second injury. Half of the myotube nuclei were radioactive and most of the centrally placed nuclei in maturing muscle fibers from the initial injury were radioactive. Since nuclei at the periphery of muscle fibers, including satellite cell nuclei, would have been labeled in both experiments, whereas myonuclei were extensively labeled only in the double injury experiment, it was concluded that the myotube nuclei were derived mainly from myonuclei.
Mast cells, compound 48/80, and prolonged hypothermia in the rat
Authors: Rink Richard D.
Published: February 2005

In the nonhibernating animal the stress of prolonged deep hypothermia is associated with the development of circulatory symptoms like those of burn‐shock. Mast cells are sensitive to a variety of stressors, including thermal ones, and commonly react by releasing vasoactive substances that may facilitate vascular changes similar to those of burnshock. The possible role of mast cells in the complications of prolonged hypothermia was the object of this investigation.

Two groups of female albino rats were subjected to 15° C total body hypothermia for 7.5 hr and then rewarmed artificially. Group I had been treated previously with compound 48/80 which depletes the mast cell content of tissues. Group II constituted controls and possessed a normal complement of mast cells.

Progressive hemoconcentration was noted in both groups. However, the hematocrits of the 48/80‐treated animals were significantly lower at selected intervals than those of control animals. In addition, 100% survival of the 48/80‐treated animals was recorded in contrast to a 60% survival rate for controls. Microscopic examination of the mast cells in several tissues of additional controls suggested a loss of granule density during hypothermia and early rewarming. This investigation offers circumstantial evidence that mast cells of the rat facilitate the development of some of the deleterious effects of prolonged hypothermia.
The development of capillaries in the villi of early human placentas
Authors: Dempsey Edward W.
Published: February 2005

Electron microscopic examinations have been made on 32 early human placentas, seven of which ranged from 7 to 11 weeks menstrual age. In avascular villi, well developed basal laminae separate the trophoblast from their connective tissue cores. At such stages, only undifferentiated mesenchymal cells occur in the stroma. Vessels develop by attachment of two or more of the mesenchymal cells to each other by localized desmosomal contacts, thus forming a real or potential capillary lumen between their apposed plasma membranes. Other mesenchymal cells approach these primitive tubes, enclasp them as pericytes, and thrust processes between adjacent endothelial cells at their attachment points. The capillary enlarges, therefore, by incorporation of mesenchymal pericytes between adjacent endothelia. Mitoses occur in the pericytes but not in early endothelial cells. Hofbauer cells differentiate in the stroma concomitantly with the appearance of capillaries.
Early responses of testicular interstitial cells to stimulation by interstitial‐cell‐stimulating hormone
Authors: Aoki Agustin , Massa Eddy M.
Published: February 2005

The fine structure of testicular interstitial cells from mice submitted to different experimental conditions is described. Following treatment with methallibure (I.C.I. 33,828; 1‐α‐methylallylthiocarbamoyl‐2‐methylthiocarbamoylhydrazine), a selective inhibitor of hypophyseal gonadotropic activity, interstitial cells acquire a quiescent appearance characterized by: (1) accentuated segregation of agranular endoplasmic reticulum from other cytoplasmic organelles and inclusions, (2) increased depots of lipid droplets. A single injection of interstitial‐cell‐stimulating hormone (ICSH or LH) induces prominent changes in the ultrastructure and distribution of cell inclusions and organelles that are seemingly related to augmented secretory activity. The cell surface shows a striking development of cytoplasmic processes that interdigitate with similar processes from adjacent cells. Intercellular spaces form a system of interfacial channels providing a direct connection of the interstitial cell surface with blood vessels and the myoid layer of seminiferous tubules. Gonadotropic stimulation causes an increased number of free ribosomes and expansion of the Golgi complex and rough endoplasmic reticulum. There is a marked depletion of lipid droplets and formation of lipofuscin granules.
Ultrastructure of cardiac muscle from dystrophic mice
Authors: Forbes M. S. , Sperelakis N.
Published: February 2005

The ultrastructure of cardiac muscle from dystrophic mice was compared with that of their non‐dystrophic littermates. Among the abnormalities observed in the fine structure of the muscle fibers in the dystrophic animals were increased lipid, swollen mitochondria, swollen tubules of the sarcoplasmic reticulum, supercontracted myofibrils, and partially separated intercalated discs. The ventricular muscle appeared to be the region most often affected; in only one of eleven animals did the atrium show discernible effects of the dystrophy. Although a progression of degenerative events seemed to occur, a time schedule could not be determined because of the large variation among hearts of dystrophic animals. The ultrastructure of the hearts from non‐dystrophic littermates was normal. It appears that the depressed cardiac function caused by the myopathy may play a major role in the early death of the dystrophic mice, as in the case of dystrophic hamsters and men. Most of the ultrastructural abnormalities observed could be accounted for if there were an elevation of intracellular free Ca++ concentration.
Simultaneous demonstration of catecholamines and acetylcholinesterase in peripheral autonomic nerves
Authors: Ellison Jeffrey P. , Olander Kenneth W.
Published: February 2005

Certain primary catecholamines remain well localized during brief fixation with cold, buffered formalin. In the present study, the diffusibility of catecholamines was further explored, using guinea‐pigs and cats pretreated with Nialamide and norepinephrine. Preliminary experiments showed that catecholamines were well localized after perfusion fixation with buffered formalin. Furthermore, catecholamines remained in situ in tissues immersed in cold fixative or phosphate buffer for as long as six hours. It seemed, therefore, that catecholamines might remain localized in fixed tissue, during incubation for acetylcholinesterase. To test this hypothesis, formaldehyde‐fixed, cryostat sections were incubated in a cold thiocholine medium for two to four hours to demonstrate acetylcholinesterase activity. They were then exposed to formaldehyde gas to demonstrate catecholamines. Acetylcholinesterase‐positive and catecholaminecontaining nerve fibers were identified simultaneously in the same section under mixed ultraviolet and red light. When a dark‐field condenser was used, adrenergic nerves appeared green and acetylcholinesterase‐positive nerves red on a black background. We were able to demonstrate adrenergic presynaptic terminals on cholinergic myenteric ganglion cells and acetylcholinesterase‐positive terminals close to cardiac chromaffin cells. We also have observed contiguities between peripheral adrenergic and cholinesterase‐positive nerves.
Intranuclear inclusions in mammotrophs of the female mongolian gerbil
Authors: Nakayama Iwao , Nickerson Peter A.
Published: February 2005

Membranous and vacuolar inclusions have been identified within the nucleus of mammotrophs in the pituitary of female Mongolian gerbils but are absent in adult male and newborn gerbils of both sexes. Membranous inclusions are observed in focal areas of the nucleus and are frequently in proximity to the inner nuclear membrane. Vacuoles are surrounded by a single membrane and the matrix is structureless and either flocculent or clear. An intermediate form of nuclear inclusion is membrane‐bound and contains typical cytoplasmic organelles. It is suggested that degenerative changes in inclusions originating in the cytoplasm may produce large structureless vacuoles. The increased number of inclusions in testosterone‐treated animals may be a response of mammotrophs to alteration in synthesis or release of hormone.
Projections of adrenocortical cells into sinusoidal lumina. Influence of prostaglandin E1
Authors: Penney D. P. , Averill K. , Olson J.
Published: February 2005

Cytoplasmic projections of adrenocortical cells have been observed within sinusoidal lumina of various species. The projections contain organelles and inclusions which are morphologically identical to those in subjacent functional cortical cells, and appear to be capable of hormone biosynthesis. The frequency with which the projections are observed is markedly enhanced by the administration of prostaglandin E1. Continuity has been observed between the projections and the parenchymal cells. Whether or not these morphological entities reflect a mechanism for an enhanced response to corticotropin stimulation remains uncertain. Their association with cellular autolysis or degradation appears doubtful.
Evidence for spontaneous axon degeneration during peripheral nerve maturation
Authors: Reier Paul J. , Hughes Arthur
Published: February 2005

Ultrastructural examination of sciatic nerves from postnatal mice and rats revealed myelinated and nonmyelinated fibers with structural characteristics similar to those seen in Wallerian degeneration. Such fibers are more commonly found between 7 and 14 days and are believed to represent spontaneous axon degenerations during development.
Anatomical nomenclature 1972
Authors: Zwemer Raymund L.
Published: February 2005

Anatomists have led the way for 75 years in developing internationally acceptable terminology for macroscopic structures of the human body. During the past 12 years terms have been gathered for histology and embryology. Nomenclature in all three areas have been adopted for international use by the Fifth to Ninth International Congresses of Anatomists. Cooperation with biomedical and other scientists will promote better communication and understanding now and provide a useful tool for future science information systems. Embryologists, histologists and gross anatomists can be proud of their current accomplishments, but should continue to work diligently to incorporate new terms as they become generally acceptable.
Serum triiodothyronine concentration in the iodine‐deficient rat
Authors: Volpert Eugene M. , Werner Sidney C.
Published: February 2005

A low iodine diet fed to rats resulted in decreased absolute amounts of circulating triiodothyronine and protein‐bound iodine (PBI), but an increase in the triiodothyronine: protein‐bound iodine ratio. Since baseline protein‐bound iodine values were high, it is possible the “normal” diet fed was in fact a high iodine one. In this event, the fall in protein‐bound iodine with the low iodine diet would be greater than that in thyroxine concentration. The relative increase in triiodothyronine compared to PBI concentration with the low iodine diet could result from preforential synthesis and secretion of triiodothyronine by the iodine‐deficient thyroid; or could be due to accelerated removal of thyroxine due to increased peripheral utilization. Either change could keep body metabolism normal or nearly so over an extended period of iodine want.
Inhibitory effect of hysterectomy on compensatory ovulation in the unilaterally ovariectomized rat
Authors: Peppler Richard D.
Published: February 2005

Cyclic rats were hysterectomized and unilaterally ovariectomized during random stages of the cycle or on day 2 (metestrus) and killed in metestrus after one or two complete estrous cycles. Control (intact and unilaterally ovariectomized) rats were also killed at this time.

Counts of tubal ova revealed that intact rats ovulated an average of 4.9 eggs per ovary (N‐5). Following only unilateral ovariectomy, compensatory ovulation (10.1 eggs per ovary) occurred in all rats (N‐6). However, when both hemicastration and hysterectomy were performed, only 6.5 eggs were shed (N‐19). The findings suggest an inhibitory effect of hysterectomy on compensatory ovulation in the unilaterally ovariectomized rat.
Ultrastructure of the human submaxillary gland IV. Serous granules
Authors: Tandler Bernard , Erlandson Robert A.
Published: February 2005

Acinar serous granules in specimens of human submaxillary gland fixed with aldehydes followed by osmium were examined in the electron microscope. Typical mature granules had a tripartite substructure: (1) an eccentrically placed dense spherule; (2) material of intermediate density adherent to the inner aspect of the granule membrane in the form of a crescent; and (3) a less dense, homogeneously fibrillo‐granular matrix. The dense spherules appeared within expanded Golgi saccules; other granule constituents apparently were of secondary acquisition. A few cells contained atypical serous granules in which material of intermediate density was disposed in random loops, whorls, and striae. Such granules usually lacked dense spherules. It is postulated that the two morphologically distinct types of granules represent separate classes of serous secretory products.
Light and electron microscopic observations on the morphogenesis of the chorioallantoic placenta of the golden hamster (Cricetus auratus). Days seven through nine of gestation
Authors: Carpenter Stanley J.
Published: February 2005

In the mature placental labyrinth of common myomorph rodents (rat, mouse and hamster) fetal capillaries are separated from maternal blood spaces by trabeculae composed of three distinct cytoplasmic layers. To resolve the controversy regarding the embryonic origin(s) of these layers a correlated light and electron microscopic study was made of the developing placental tissues of the golden hamster during the eighth and ninth days of gestation, the critical period of labyrinth morphogenesis in this species. It was determined that the syncytial inner layer (layer III) of the trabeculae, the layer bordering the fetal capillaries, is derived from the “true” chorionic ectoderm which fuses with the undersurface of the Träger (ectoplacental cone) early on the eighth day of gestation. Both the syncytial middle layer (layer II) and the cellular outer layer (layerI) of the trabeculae, on the other hand, were found to differentiate from the trophoblastic cells of the Träger. Allantoic mesenchyme, which approximates the fused chorionic‐Träger tissues late on day eight and is the source of the fetal capillaries and mesenchyme of the labyrinth, was noted to exert a critical inductive effect on the morphogenesis of syncytial layers II and III. On the basis of fine structure, the developing labyrinth appears not to be a major site for maternal‐fetal transfer of macromolecules nor to be involved to a significant degree in the production of proteins or steroids for secretion.
Intercellular connective tissue fibrils in the notochordal epithelium of the early chick embryo
Authors: Carlson Edward C.
Published: February 2005

Chick embryos of the White Leghorn strain were incubated from one‐half to four days and sacrificed by immersion in toto. in Karnovsky's fixative. The cervical region of each embryo was excised and prepared for electron microscopy. Intercellular materials, which appear indistinguishable from the early connective tissue components of the embryonic tissue space, appear within dilated interstices of the notochordal epithelium beginning at approximately Hamburger‐Hamilton stage 14. At progressively older stages this intercellular material appears to organize and aggregate to form fibrils. By stage 22 widely expanded intercellular spaces contain boundary (basement) membrane material, amorphous substance and microfibrils of various sizes. Moreover, larger, more mature fibrils that exhibit collagen‐like periodic striations are present. The existence of connective tissue materials in cellular interstices deep within the central portion of the notochord strongly suggests that these substances are derived from notochordal epithelial cells. Furthermore, the similarity of the intercellular connective tissue components to those deposited on the notochordal surface suggests that these latter materials are likewise a secretory product of the notochord. The significance of the perinotochordal connective tissue (notochord sheath) with respect to the recent emphasis on the role of surface‐associated substances to cytodifferentiation is discussed.
Presence of biogenic amines in early rat development
Authors: Burden Hubert W. , Lawrence Irvin E.
Published: February 2005

Rat ova, zygotes, and (2‐ to 4‐cell) embryos were processed for the fluorescence demonstration of catecholamines and serotonin. Specific endogenous fluorescence, characteristic of catecholamines, was observed in all stages studied. The endogenous fluorescence was intensified by incubation in serotonin or norepinephrine. These observations suggest a role for biogenic amines in early mammalian cleavage, similar to that previously reported in invertebrates.
Morphometric and electron microscopic studies of goiter induced by lithium in the rat
Authors: Heltne Carl E. , Ollerich Dwayne A.
Published: February 2005

Fifty‐two male and female albino rats were used. Lithium‐treated rats (30 animals) received twice daily intraperitoneal injections of lithium carbonate (40 mg/kg body weight) for 80 days. Three control groups were used. The first remained uninjected; the second received sodium chloride solution equal in volume and tonicity to the lithium carbonate solution; the third received sodium carbonate solution in which the carbonate ion concentration was equivalent to that in the lithium carbonate solution. Thyroid weights were analyzed as wet and dry weights, and as wet and dry thyroid weights in milligrams per 100 gm body weight. Morphometric or electron microscopic studies were carried out on Epon‐embedded tissue routinely prepared for light or electron microscopy.

Thyroid weights and values were greater in lithium‐treated animals. A sex‐related effect of lithium was indicated. The differences in thyroid weights between lithium‐treated and control male rats were greater than those between female lithium‐treated and control rats. Morphometric analysis revealed an increase in the mean diameter of sections of follicles and relative amounts of colloid, and a decrease in follicular cell heights in lithium‐treated animals. The electron microscope revealed an enlarged Golgi apparatus in many thyroid follicular cells of lithium‐treated rats. The enlargement of the Golgi apparatus was most evident in male lithium‐treated animals. The relationship of these findings to the mechanism of lithium action was briefly discussed.
The development of the primary vascular reticulum in the spleen of human fetuses (38‐ to 57‐mm crown‐rump length)
Authors: Weiss Leon
Published: February 2005

The development of the primary vascular reticulum and of the capsule was studied electron microscopically in spleens from five human fetuses measuring 38, 42, 43, 50 and 57 mm in crown‐rump length (CRL).

The reticulum developed progressively. At 38 mm CRL reticular cells had short broad processes and the interstitium was quite limited. The reticulum continued to open with advancing age until, in the 57‐mm fetus, reticular cells had long slender processes and formed a reticulum with voluminous interstices. Contiguous cells were attached by junctional complexes of the intermediate type (zonula adherens). The salient cytological features of reticular cells were vacuoles, ribosomes, and rough endoplasmic reticulum. An argyrophilic reticulum was present which, unlike the adult extracellular reticulum, was not closely associated with reticular cells and was composed, in certain sites, primarily of collagen.

A rich vasculature of closed thin‐walled loops was present in the 38‐mm fetus. Thereafter, an open vascular pattern, most pronounced in the 50‐ and 57‐mm CRL fetuses, was observed. Blood and macrophages lay in the interstices of the reticular meshwork and active vasculogenesis with marked differentiation into arteries, capillaries, veins, and vascular sinuses occurred. Endothelial cells were joined by junctional complexes of the intermediate type. The vessels lacked basal laminae or basement membranes. No evidence of significant hematopoiesis was observed.

The capsule consisted of a simple layer of irregularly cuboidal cells having microvilli and cilia on the peritoneal surface, desmosomes and intermediate junctions on their lateral surfaces, cytoplasmic vacuoles, glycogen, fat, ribosomes, and rough endoplasmic reticulum, intercellular and infracellular spaces; the capsule rested on a well‐defined basal lamina.

Thus, a primary vascular reticulum developed and comprised the splenic pulp. Though of simple form, it accomplished the fundamental function of the spleen: a filter and modifier of blood.
The fine structure of the pineal gland in the pocket gopher, Geomys bursarius
Authors: Sheridan Michael N. , Reiter Russel J.
Published: February 2005

The morphology of the pineal gland of the pocket gopher, Geomys bursarius, is of special interest because this species is exposed to extremes of environmental lighting in its natural habitat. The pineal gland of the gopher has been studied in specimens collected as they were about to enter their winter dormant period.

The gopher pineal is similar to other mammalian pineal glands in that it possesses light and dark parenchymal cells, glia, and pigment‐containing‐cells. Vascular‐parenchymal relationships are similar to other species.

Vesicles containing electron‐opaque cores are infrequently encountered in the parenchymal cells. Parenchymal cells and pigment cells occasionally abut a lumen, suggesting an acinar arrangement. Large cytoplasmic vacuoles several microns in diameter are present in the parenchymal cells.
Unusual mitochondrial morphology in the rat adrenal cortex following hypophysectomy
Authors: Sharawy M. , Penney D. P.
Published: February 2005

Unusually long and thin mitochondria (3–4 μ in length and 0.2–0.4 μ in width) were observed in zona fasciculata cells in the hypophysectomized rat adrenal cortex. The elongated mitochondria assumed C‐shape configurations and were frequently in juxtaposition to each other and to lipid droplets. These mitochondrial organizations were considered to be unstable, dependent on the presence of trophic hormone and involved in the formation of bizarre membranous bodies. The relationship of these observations to the process of glandular involution is discussed.
The vascular anatomy of the liver of the monitor lizard (genus varanus)
Authors: Yeager Vernon L.
Published: February 2005

The gross and microscopic anatomy of the vasculature of the monitor lizard liver was studied. The portal vein has a peculiar arrangement of smooth muscle. The tunical media of the entering portal vein has bundles of smooth muscle cells separated by large numbers of collagenous fibers. The amount of smooth muscle decreases as the vessel decreases in diameter and soon one finds intermittent broad, thin bands of smooth muscle. As the caliber of the vessels continues to decrease, the smooth muscle bands become narrower and thicker so that they appear as doughnut‐shaped sphincters. The sphincters are usually found at the beginning of each branch of the portal vein as well as along the course of veins between areas of branching. Some sphincters are found in direct contact with the outer capsule of the liver. Sphincters occur in the terminal branches of the portal vein just proximal to the sinusoids.

Small numbers of scattered smooth muscle cells were seen arranged longitudinally, obliquely, or circularly in the smaller hepatic veins. Even the large hepatic veins had only small amounts of smooth muscle. At no place along the course of hepatic veins could smooth muscle sphincters equivalent to those seen around portal veins be found.

The monitor lizard should be an excellent subject for physiological and pharmacological studies of regulation of intrahepatic portal vein blood flow.
Differentiation of alpha cells in the fetal rat pancreas grown in organ culture
Authors: Schweisthal Michael R. , Frost Cecil C.
Published: February 2005

Alpha cells can be demonstrated in embryonic rat pancreas by a modification of the Grimelius silver nitrate technique. At the start of culture at 18 days of gestation, alpha cells are closely associated with exocrine tubules and beta cells. After ten days of culture they are arranged peripherally around a mass of beta cells, in islets that are characteristic of adult rat pancreas.
Effect of fluorodeoxyuridine, colcemid, and bromodeoxyuridine on developing neocortex of the mouse
Authors: Webster William , Shimada Morimi , Langman Jan
Published: February 2005

The purpose of this study was to obtain information about factors controlling the interkinetic movement of neuroepithelial cells and the cortical migration of neuroblasts in the developing mouse neocortex. In the first experiment 15‐day pregnant mice were injected with a single dose of fluorodeoxyuridine, a compound which inhibits the enzyme thymidylate synthetase thus blocking DNA‐replication. The animals were sacrificed at various hours and days following treatment. Two hours after treatment the mitotic index of the neuroepithelial cells was severely reduced and cells with abnormal nuclei appeared in the DNA‐synthesizing zone of the neuroepithelial layer. By five hours more abnormal cells appeared and many showed degenerating nuclei. By 12 hours cells with abnormal nuclei were seen in the outer half of the neuroepithelial layer and some in the migratory zone. Since they were not seen at the lumen, these observations indicate that fluorodeoxyuridine‐affected nuclei do not move to the lumen and do not divide. By 24 hours abnormal nuclei were seen in the migratory zone and cortical plate suggesting cortical migration without preceding cell division. In the second experiment 15‐day pregnant mice were treated with col‐cemid, a compound which arrests dividing cells in metaphase. Two and four hours after injection a large number of neuroepithelial cells in metaphase accumulated at the lumen. By seven and 12 hours the number of arrested metaphases decreased rapidly, but at the same time cells with dense, darkly stained nuclei appeared in the adjacent neuroepithelium. By 24 hours these abnormal nuclei were present in the migratory zone and cortical plate, suggesting that they were migrating towards the surface of the cortex despite the failure to complete mitosis. In the third experiment 15‐day pregnant mice were injected with bromodeoxyuridine, a compound incorporated into DNA and thought to interfere with differentiation. During the first 12 hours after treatment a striking increase in the number of normal mitotic figures was seen at the lumen. By 16 hours, however, abnormal mitotic figures started to appear. Since the generation time of neuroepithelial cells at this stage of development is about 13 hours, the abnormal mitotic figures must represent cells which have gone through two DNA‐synthetic periods since the beginning of the treatment. The abnormal mitotic figures give rise to cells with dense pycnotic nuclei which by 24 hours are found throughout the width of the developing neocortex. Thus in each experiment cells with abnormal, presumably non‐functional, nuclei were produced. Despite the failure to divide or to carry out a normal division, the nuclei migrate from the neuroepithelial layer towards the cortical plate in a fashion similar to that of normal postmitotic neuroblasts.
The ontogeny of cell‐mediated immunity: The response of the mouse to dinitrofluorobenzene (DNFB)
Authors: Schneider Gary B.
Published: February 2005

Cellular immunocompetence begins to develop in mice during the first week after birth, as indicated by skin allografting and graft‐versus‐host reactions, but delayed hypersensitivity has not yet been detected at this early age. The purpose of this study was to investigate the ontogeny of delayed hypersensitivity in suckling mice.

Dinitrofluorobenzene (DNFB) is an antigenic hapten which, when applied to the skin, can elicit both delayed hypersensitivity and a humoral immune response. In adult mice the induction period of delayed hypersensitivity to DNFB is a blastogenic reaction (accumulation of lymphoblasts) in the diffuse, thymusdependent cortex of the lymph node draining the site of application. This blastogenic reaction reaches a peak three days after initial application of antigen and then subsides, to be followed by the development of germinal centers and numberous plasma cells — indicative of a humoral immune response — a week after initial sensitization.

Suckling mice were sensitized by application of DNFB to the ears, and the auricular lymph nodes wer prepared for light and electron microscopy three and eight days after sensitization. The development of delayed hypersensitivity was assayed by applying DNFB to an ear, 5 to 12 days after initial sensitization, and measuring the increase in thickness of the ear 24 hours later.

The results of these studies indicate that by two days of age, mice have the capacity to develop delayed hypersensitivity as shown by both a blastogenic reaction in the draining lymph node and a positive skin test. Mice sensitized at birth or on the next day did not respond in either way. Mice sensitized prior to two weeks of age did not develop the late phase of the response (the formation of germinal centers and plasma cells), which matured in parallel with the normal maturation of the machinery for antibody production during the third postnatal week.

These observations strengthen the conclusion of previous investigations that the blastogenic response in the regional lymph node is the inductive phase of delayed hypersensitivity. Because the late phase of the response does not appear in mice sensitized before two weeks of age, these animals offer an unusual opportunity to study delayed hypersensitivity relatively uncomplicated by humoral antibody production.
Human retinal development: Ultrastructure of the outer retina
Authors: Hollenberg Martin J. , Spira Arthur W.
Published: February 2005

The morphogenesis of the outer human retina from 6.5 to 18 weeks of gestational age (16–156 mm) was studied by light and electron microscopy. During this period the retinal pigment epithelium changes from a pseudostratified columnar epithelium, with mitoses at its inner edge, to a single layer of cuboidal cells. Initially, mature pigment granules, premelanosomes, polysomes, rough endoplasmic reticulum and a Golgi complex occupy the epithelial cytoplasm. Lateral epithelial surfaces show infoldings and neighboring epithelial cells are bound at their inner borders by a junctional complex consisting of a zonula occludens and zonula adherens. Later, pigment epithelial development is marked by an increase in cytoplasmic organelle content and the appearance of slender processes at the inner epithelial border. Initially, the outer neural retina is formed by a uniform population of elongated cells containing oval nuclei with multiple nucleoli and, in the cytoplasm, mitochondria, polysomes and the Golgi complex. Cell division is common in the proliferative layer at the outer edge of the posterior neural retina until 120 mm crown‐rump length, and cell membrane junctions between outer neuroblasts remain intact during mitosis. Cilia project outwards from outer neuroblasts and invaginate the immediately adjacent pigment epithelium. At 120 mm crown‐rump length, differentiating rods, cones and Müller cell processes are distinguishable and developing ribbon synapses and surface contacts are present at the base of the cone prior to outer segment formation.
Autoradiographical and morphological evidence for apocrine secretion of dipalmitoyl lecithin in the terminal bronchiole of mouse lung
Authors: Etherton John E. , M. Conning David , Corrin Bryan
Published: February 2005

The Clara cell of the mouse terminal bronchiole has been examined by high resolution phase contrast and electron microscopy, and the secretory route of surfactant in the mouse lung has been investigated using both light and electron microscopical autoradiography of a surfactant precursor (palmitic acid). Serial sections of terminal bronchioles examined by phase contrast microscopy demonstrated the appearances of apocrine secretion of amorphous droplets by Clara cells. Electron microscopy showed that the non‐decapitating supranclear region of Clara cells contained numerous rounded mitochondria with scanty achrestic cristae, whilst the apical portion was rich in smooth tubular membranes. Autoradiographical labeling of bronchiolar Clara cells exceeded that of all other cell types within three minutes of administration of the radioactive precursor, with location primarily over the endoplasmic reticulum. Subsequently there was heavy labeling of the bronchiolar lining layer. An hour later, silver grains were most numerous over the lamellated bodies of type II cells. It is suggested that palmitic acid is synthesized in the specialized mitochondria of the non‐secretory region of the Clara cell and is incorporated into dipalmitoyl lecithin in the membranous apex. Subsequent secretion, possibly by the apocrine mechanism, provides a surface‐active bronchiolar lining layer.