bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron microscopy of the red pulp of the dog spleen including vascular arrangements, periarterial macrophage sheaths (Ellipsoids), and the contractile, innervated reticular meshwork
Authors: Blue Julia , Weiss Leon
Published: February 2005

The vascular and stromal arrangements of the red pulp in congested and contracted dog spleens were studied by transmission electron microscopy. Each dog had been injected intravenously with Thorotrast to label actively endocytizing cells. Only macrophages ingested Thorotrast. The proximal portion of each arterial capillary was surrounded by a “periarterial macrophage sheath” (PAMS), a term we introduce to replace the term “ellipsoid”. PAMS were composed of a fine meshwork of reticular cells and reticular fibers which held tightly‐packed macrophages and interspersed blood cells. These macrophages, as well as those in the reticular meshwork of red pulp, contained Thorotrast, cell debris, and deposits of hemosiderin. The arterial capillary at the center of each PAMS was formed by parallel, rod‐shaped endothelial cells and discontinuous layers of basement membrane and reticular‐cell cytoplasm. PAMS were tapered at their distal ends; the terminal portion of the arterial capillary continued beyond the PAMS to end in the reticular meshwork of red pulp. Endothelial cells in the terminal arterial capillaries were separated by gaps through which blood cells passed into the spaces of the reticular meshwork of red pulp. The reticular meshwork was formed by reticular cells which appeared to be specialized for contraction. These cells were filled with thin filaments and possessed plasmalemmal dense bodies as found in smooth muscle cells. Furthermore, the reticular meshwork was innervated by unmyelinated adrenergic axons which probably were derived from nerves that followed arterioles. Axons were enclosed in surface invaginations of cells which were similar to reticular cells in shape and cytologic detail and which we called “axon‐bearing reticular cells”. Axon‐bearing reticular cells were inserted between the branches of the reticular cells that formed the meshwork. Venous sinuses formed an anastomosing system of vessels draining into pulp veins which then joined trabecular veins. Sinuses were formed by parallel, rodshaped endothelial cells encircled by strands of basement membrane and reticular‐cell branches. Endothelial cells lay closely side by side except where inter‐endothelial slits were opened by blood cells passing into the lumen or by pseudopodia of macrophages which lay outside the sinus. Cell traffic across the sinus wall was greatest in areas where blood cells were mixed with plasma. Congested spleens stored concentrated red cells in both sinuses and the reticular meshwork; contracted spleens were emptied of blood. The reticular meshwork may contract to assist trabecular and capsular smooth muscle in expelling stored red cells and effecting hemoconcentration.
Myelopoiesis in lymph nodes of mice. Enhancement effect by the injection of trypan blue or india ink after birth
Authors: Sesma P. , Vázquez J. J.
Published: February 2005

Myelopoiesis in lymph nodes was studied in newborn mice under normal conditions and after treatment with trypan blue and carbon particles. In the mouse lymph node, myelopoiesis normally takes place between the fourth and twelfth day after birth, then decreases while an intense proliferation of the lymphocytic population simultaneously takes place. Myelopoiesis manifests itself as clusters of cells, mainly of the neutrophilic line, located around post‐capillary venules (PCV's) in the medulla. The injection of trypan blue or carbon particles (India ink) causes an enhancement of myelopoiesis and a delay in the development of the lymphocytic population. Myelopoiesis includes not only granulopoiesis but also the formation of erythroid clusters and occasional megakaryocytes. Three possibilities should be considered to explain the enhancement of myelopoiesis: (1) blockade of the reticuloendothelial system caused by overloading with particulate matter; (2) induction of humoral myelopoiesis‐stimulating factors; and (3) stimulation of pluripotent stem cells through dye injection.
An immunocytochemical and routine electron microscopic study of LH and FSH cells in the human fetal pituitary (1)
Authors: Currie R. William , Faiman Charles , Thliveris James A.
Published: February 2005

Anterior pituitaries from 17 human fetuses, 9.5 to 16.5 weeks in gestational age, were obtained to study the morphological development of gonadotropes as a function of age and sex.

Routine electron microscopy alone was inadequate in determining which granulated cells produced the gonadotropins, owing to the similarities among granulated cells in the youngest fetuses as well as to the continuing differentiation of these cells. Therefore, electron‐microscopic immunocytochemistry was employed for identification of gonadotropes. LHβ and FSHβ antisera were used, and dilution and absorption tests were performed to determine the degree of cross‐reactivity with LHβ, LH, FSHβ, FSH, CGβ, and CGα. Both antisera completely cross‐reacted in parallel fashion with their respective β subunits, as well as with their respective intact hormones. Cross‐reactivity with the other absorbents was minimal, partial or nonexistent. With the LHβ antiserum, LHβ and intact LH appeared to be equipotent in absorption studies; whereas with the FSHβ antiserum, 10 times as much intact FSH was required to effect displacement as with FSHβ. These specificity studies, coupled with the failure of previous investigators (Kaplan et al., 1976a) to find free β subunits in the human fetal pituitary, suggest that staining of the granules was due to the presence of intact LH or FSH.

Cells containing LH and FSH were identified immunocytochemically in the pituitaries of all the fetuses examined. Sex and age differences were qualitatively assessed. The number of cells and granules per cell stained with either LHβ or FSHβ antiserum, as well as the staining intensity with both antisera, increased as a function of fetal age. A sex difference was also evident, in that pituitaries of older females revealed more granules per cell and more cells stained with either LHβ or FSHβ antisera than those of males of comparable ages.

These findings agree with the concept that the human male fetal pituitary produces less gonadotropin prior to mid‐gestation than the female gland, perhaps because of feedback inhibition by testicular testosterone secretion at this time.
Hormonal effects on the contractile apparatus of the myometrium
Authors: Kelly Robert E. , Verhage Harold G.
Published: February 2005

The effect of estradiol‐17β (E2) and progesterone (P) on the structure of myofilaments of the smooth muscle of the myometrium of cats was studied by electron microscopy. Animals which had been ovariectomized for at least four weeks were divided into three treatment groups. Group I received no additional treatment. Group II animals were treated for 14 days with E2, and Group III animals were treated for 14 days with E2 and then with E2 and P. The smooth muscle of the uterus of Group I animals displayed a single array of thin (< 10nm) filaments only. Group II animals displayed in all cases a double array of thick (14–16 nm) filaments, whereas Group III exhibited a single array of thin (6–8 nm) filaments only. These results suggest that E2 induces assembly of thick filaments in ovariectomized cats while P promotes thick filament disassembly. It is suggested that this alteration of the structure of the thick filament may be involved in the mechanism by which these hormones alter the contractile activity of the myometrium during estrus, pregnancy, and at parturition.
Scanning electron microscopy of the normal and denervated limb regenerate in the newt, Notophthalmus, including observations on embryonic amphibian limb‐bud mesenchyme and blastemas of fish‐fin regenerates
Authors: Geraudie Jacqueline , Singer Marcus
Published: February 2005

The present work deals with the morphology of normal and denervated early limb regenerates in the newt and compares them with early limbbud mesenchyme and blastemas of fish‐fin regenerates using the three‐dimensional properties of the SEM. It shows that blastemal cells are polymorphic, in contrast to those of the stump‐cell population, which are fairly homogeneous and from which blastema cells are said to arise by “dedifferentiation.” The appearance of the cells had not changed by two days following denervation even though previous biochemical studies have detected many changes in metabolism. Longterm denervation (7 days) did result in morphological changes. A comparison between well‐known cell type—myoblasts, Schwann cells, osteoblasts observed in vitro, limb‐bud mesenchyme and mesenchymatous fin blastema—was carried out in order to suggest explanations for the blastema‐cell polymorphism.
Cationized ferritin binding to anionic surfaces in normal and aminonucleoside nephrotic kidneys
Authors: Andrews Peter M.
Published: February 2005

The distribution and effects of polycationized ferritin (PCF) bound to anionic sites on living plasmalemmas and basal laminae of normal and puromycin aminonucleoside nephrotic (PAN) kidneys were studied using an in vitro model system. Immersion of normal glomeruli in physiological saline solutions containing low concentrations of PCF (0.01 to 0.1 mg/ml) for 10 seconds results in preferential binding of PCF to microvillous projections on the glomerular epithelium (i.e., podocytes). Exposure to higher concentrations of PCF (1.0 mg/ml) for 10 seconds results in several layers of PCF distributed evenly over the urinary aspect of epithelial podocytes. In these short treatment times, the thin slit diaphragms which span the filtration slits appear to be impermeable to PCF. Within several minutes after PCF treatment, ferritin is found within caveolae on the surface of epithelial podocytes and within numerous pinosomes and larger endocytic vesicles within these cells. Longer treatment with PCF results in the narrowing of filtration slit spaces and the formation of junctions between adjacent podocyte foot processes. Occurring coincident with these structural changes is a gradual accumulation of PCF in regular patches along the lamina rara externa (LRE) of the glomerular basement membrane. Loss of foot processes and accumulation of PCF in the LRE are prevented by treatment with either cytochalasin B (25 μg/ml), D (2 μg/ml) or incubation at low temperatures (0–4°C). When PCF‐coated glomeruli are incubated in PCF‐free media, the ferritin coat is shed from the free surfaces within 1/2 to 1 hour except at the tips and sides of microvillous projections. Pretreatment of normal glomeruli with neuraminidase or protamine sulfate results in a dramatic reduction in the binding of PCF to the glomerular epithelial free surface. Treatment of PAN glomeruli with PCF often results in patchlike distributions of PCF over the glomerular epithelial free surface. High concentrations of PCF (1.0 mg/ml) bind preferentially to microvillous projections on the parietal epithelial luminal surface and in distinct patchlike patterns along the basal laminae of parietal and tubular epithelial cells.
Lymphopoiesis in the chicken pineal gland
Authors: Cogburn L. A. , Glick B.
Published: February 2005

Pineal lymphoid development was studied in two breeds of chickens from hatching until sexual maturity. No lymphocytes were found in the pineal prior to 9 days of age (da). Lymphocytes migrate through the endothelium of venules into the pineal stroma. Lymphoid tissue reached its maximal accumulation in 32‐da pineal glands of both breeds. At this age, the New Hampshire (NH) breed had a larger proportion of lymphoid volume to total pineal volume (32%) than did pineal glands from White Leghorn (WL) chickens (18%). Averaged over the period 23 to 62 da, NH chickens (a heavy breed) had a lymphoid volume (0.753 mm3) that was about three times greater (P < 0.05) than that of the lighter WL breed (0.251 mm3). Lymphocytes are able to enter cerebrospinal fluid from lymphoid accumulations (LA) embedded in the choroid plexus by migrating between choroid ependymal cells. The 122‐da chickens typically lacked lymphoid tissue in the pineal gland with the exception of occasional LA contained in capsular tissue.

Surgical bursectomy, thymectomy, or their combination at hatching followed with whole‐body irradiation (IR) at 24 hours postsurgery inhibited the initial influx of lymphocytes usually seen in 9‐da pineal glands. Also, these treatments prevented formation of germinal centers normally found in the pineal at 3 and 5 weeks and reduced total pineal volume at each age examined. However, pineal lymphoid volume of the surgical‐IR group did not differ from control‐IR chickens at either 3 or 5 weeks. Pineal glands from birds made agammaglobulinemic (bursa‐cell depleted) by cyclophosphamide treatment in ovo were devoid of germinal centers, although thin strands of lymphocytes were usually found along venous sinuses. These dissociation studies suggest that the normal expression of lymphoid tissue in the chicken pineal gland is dependent on the bursa and thymus. Furthermore, these observations indicate that the pineal gland should be considered a functional component of the chicken's lymphomyeloid complex.
Ultrastructure of the pineal gland of the fox
Authors: Karasek Michal , Hansen John T.
Published: February 2005

The ultrastructure of the pineal gland of the fox was examined and compared with that of other mammals. The pineal gland of the fox is composed of two different populations of pinealocytes (I and II). The pinealocytes I were distributed homogeneously throughout the parenchyma, while pinealocytes II were located generally near blood vessels. A Golgi apparatus, granular endo‐plasmic reticulum, mitochondria, lysosomes, centrioles, and cilia were present in both cell populations. A characteristic feature of pinealocytes I was the presence of dense‐core vesicles, presumably of Golgi origin; whereas glycogen deposits and pigment granules were common features of pinealocytes II. In addition to the pinealocytes, the parenchyma contained fibrous astrocytes. The capillaries of the pineal gland of the fox consisted of a nonfenestrated endothelium. Numerous nerve fibers, presumably adrenergic, were observed throughout the parenchyma.
Arterial branching in various parts of the cardiovascular system
Authors: Zamir M. , Brown N.
Published: February 2005

Angiographic pictures of vascular beds in various parts of the cardiovascular system were analyzed to study the geometrical structure of arterial bifurcations. The sites of arterial bifurcations were enlarged individually, and measurements were made of the branching angles and branch diameters at each site. Results from various parts of the cardiovascular system of man, and some from rabbit and pig, were compared with each other. The measurements were also compared with “optimum” values of branching angles and branch diameters which have been predicted by various theoretical studies. In general the measurements were found to give support to the theoretical premise that branching angles and branch diameters in the cardiovascular system are dictated by certain optimality principles which aim to maximize the efficiency of the system in its fluid‐conducting function. In some parts of the system, however, the measured angles and diameters were found to be decidedly lower than those predicted by theory.
Development of intraosseous fibers of the mouse periodontium: A high‐voltage electron microscopic study
Authors: Johnson Roger B. , Low Frank N.
Published: February 2005

Development of intraosseous fibers was studied in mandibles of Swiss white mice, age 17 days to 45 days. Light microscopic (LM) and high‐voltage electron microscopic (HVEM) techniques were used. In LM, Wilder's reticular stain revealed intraosseous fibers throughout the interdental septum by day 17. Fibers were composed of unit collagen fibrils with abundant interfibrillar matrix. As development proceeded, fibers exhibited less interfibrillar matrix. Channels surrounding the intraosseous fibers became evident. Anchoring fibers attached the intraosseous fiber to bone. Fibroblasts appeared to be absent, suggesting that maintenance of the intraosseous fiber might be the function of the osteocyte. The presence of intraosseous fibers suggested a reevaluation of the fibrous attachment of teeth to bone. The concept of intraosseous fibers may simplify concepts of tooth movement and approximal drift.
Sensory components in the terminal innervation of the ovine cardiac conduction system
Authors: Munnell John F.
Published: February 2005

Neuromuscular relationships in the cardiac conduction system of the ovine heart were studied by means of light and electron microscopy. Fluorescence microscopy was used to demonstrate the distribution of adrenergic nerves. Histochemical methods demonstrated sites of acetylcholinesterase and nonspecific cholinesterase activity at both light and electron microscopic levels. Surgical denervation was used in an attempt to support the identification of different types of nerve endings. A dense plexus of nerves strongly positive for acetylcholinesterase was present in all parts of the conduction system. Nonspecific cholinesterase was found to be limited to large nerve bundles which were presumed to be preganglionic. A dense plexus of adrenergic nerve fibers was identified in both the SA and AV nodes, but such fibers were very sparsely distributed along the AV bundle and its branches.

On the basis of morphology as demonstrated by electron microscopy, three types of nerve endings or varicosities associated with the specialized cells of the conduction system were identified. Cholinergic endings, presumably post‐ganglionic parasympathetic, contained many nongranulated synaptic vesicles. Adrenergic or post‐ganglionic sympathetic endings or varicosities contained granulated synaptic vesicles. Axonal enlargements containing numerous mitochondria and varying numbers of pleomorphic dense bodies were identified as sensory endings on the basis of their morphologic similarity to such endings found elsewhere in the animal body. These were found in 22% of the blocks examined by electron microscopy, were present in all parts of the conduction tissue, and were acetylcholinesterase positive. They did not show obvious signs of degeneration following vagotomies or thoracic sympathectomy, suggesting the possibility that they were endings of neurons intrinsic to the heart. No signs of degeneration were noted in the endomysial plexus following vagotomy either proximal or distal to the distal (nodose) ganglion. Degeneration of small fibers of the plexus was noted following thoracic sympathectomy.

This study provides evidence suggesting a significant sensory innervation to the cardiac conduction system, with the cell bodies of the sensory neurons located in or near the heart.
Localization of relaxin in endometrial gland cells of pregnant, lactating, and ovariectomized hormone‐treated guinea pigs
Authors: Pardo R. J. , Larkin L. H.
Published: February 2005

Uteri taken from guinea pigs in different stages of pregnancy and during lactation, as well as animals that had been ovariectomized and treated with hormones, were examined for relaxin with the peroxidase‐antiperoxidase (PAP) technique employing an antiserum produced against porcine relaxin. While relaxin was not detected in uteri of day 15 pregnant animals, small amounts were noted in a few endometrial glands in day 30 pregnant animals. Uteri from day 45, day 60, and late‐pregnant animals exhibited heavy amounts of relaxin; however, endometrial gland cells from lactating animals contained very little or no relaxin. Injections of estrogen and progesterone that brought a relaxation of the pelvic ligaments in ovariectomized guinea pigs also induced an accumulation of relaxin in the endometrial glands. Relaxin was not detected in nonendometrial portions of the uterus, endometrial stromal components, luminal surface epithelium, or uterine cervical glands. Extracts prepared from uteri of day 45, day 60, and late‐pregnant animals showed positive responses for relaxin in the mouse uterus bioassay.
The uterine progestational response in cats: Ultrastructural changes during chronic administration of progesterone to estradiol‐primed and nonprimed animals
Authors: Boomsma Robert A. , Verhagem Harold G.
Published: February 2005

The development of a progestational response in the glandular epithelium of the cat uterus was studied using electron microscopy and special glycogen staining techniques. In ovariectomized and adrenalectomized animals, the epithelial cells were low cuboidal and lacked an active secretory apparatus. Estradiol treatment induced hypertrophy and the formation of secretory cells which contained numerous profiles of RER, an enlarged Golgi apparatus and apical electron‐opaque secretory granules. The chronic administration of progesterone to estradiol‐primed animals resulted in antagonism of estradiol‐induced cytodifferentiation and the development of a progestational response in the glandular epithelium. After 1 day of estradiol plus progesterone treatment fewer secretory granules were observed, the RER was constricted, and the Golgi apparatus appeared less active; after 2 days, very few secretory granules were observed. Coincident with this antiestrogenic action, progesterone induced additional hypertrophy and the differentiation of cytoplasmic organelles associated with glycogen synthesis. Glycogen deposition occurred between days 2 and 4 of estradiol‐plus‐progesterone treatment. Numerous polyribosomes and circular profiles of membrane appeared to be associated with glycogen deposition. These membranes frequently had glycogen around their perimeter, and sometimes they were found embedded in large glycogen deposits. With continued progesterone treatment, glycogen processing occurred. The RER became extremely dilated, and a few halo granules were observed. Both the dilated RER and the halo granules appeared to be surrounding glycogen, and glycogen was frequently found bound by membrane as well as within the electron‐lucent portion of the halo granule. As glycogen processing continued, the glycogen deposits began to disappear, and some cells appeared to die. The remainder differentiated into shorter residual cells which, after 10–14 days, contained numerous halo granules and constricted RER. The chronic administration of progesterone to nonprimed ovariectomized and adrenalectomized animals resulted in a cytodifferentiation sequence similar to that in the estradiol‐primed animals, except that the response was delayed and was not as uniform between cells from the same animal. Thus, within each epithelial cell of the endometrial glands of the cat, the principal responses induced by progesterone in both estradiol‐primed and nonprimed animals were the synthesis, deposition, and eventual disappearance of glycogen.
Plasmalemmal vesicles (caveolae) of fibrous astrocytes of the cat optic nerve
Authors: Massa Paul T.
Published: February 2005

Plasmalemmal vesicles (caveolae) are described in fibrous astrocytes of the cat optic nerve. In thin sections, astrocytic caveolae appear as flask‐shaped invaginations of the plasma membrane with a 60‐nm lumen that communicates with the extracellular space through a 35‐nm stoma. Occasional bilobed caveolae occur. The caveolae extend approximately 85 nm into the astrocytic cytoplasm and are often embedded within a granular or filamentous ectoplasmic substance connected by 4–8‐nm filament bridges to underlying bundles of 10‐nm glial filaments. In freeze‐fracture replicas, the caveolar stomata appear as dimples on the P face and as craters on the E face, often arranged in hexagonal or linear arrays and spaced at a center‐to‐center distance of 110–130 nm. The caveolar membrane is apparently particle‐free. Fibrous astrocytes related to the connective‐tissue septa of the optic nerve show different densities of caveolae on different areas of their plasma membranes. Plasma membranes apposing a basal lamina have few caveolae, whereas membranes not apposed to the basal lamina but to other astrocytic membranes have up to 17 caveolae/μm2. Caveolae also occur on astrocytic plasma membranes apposed to myelin sheaths. Possible functions of the astrocytic caveolae are discussed in the light of plasmalemmal properties of other types of caveolae‐bearing cells.
Fetal and neonatal rat intestinal capillaries: Permeability to carbon, ferritin, hemoglobin, and myoglobin
Authors: Milici Anthony J. , Bankston Patrick W.
Published: February 2005

The function of the mural components involved in vascular exchange (pinocytotic vesicles, fenestrations, intercellular junctions, and the basal lamina) was assessed by intravascular injection of tracers (carbon, carbon plus histamine, ferritin, hemoglobin, and myoglobin) on separate gestational days in fetal and neonatal rat intestinal capillaries. The continuous capillaries present through day 17 of gestation were impermeable, even at junctions, to all the tracers within the maximum circulation time studied (3 minutes). Most of the luminal pinocytotic vesicles were labeled within 3 minutes with myoglobin (3.3‐nm diameter) or hemoglobin (5.5‐nm diameter), while only occasional vesicles contained ferritin (11‐nm diameter) and none contained carbon (25–50nm diameter). Even though luminal pinocytotic vesicles contained the smaller tracers, no vesicular transport and discharge were ever seen. The fenestrated vessels present from day 18 of gestation allowed a rapid extravasation of ferritin and hemoglobin via diaphragmed fenestrations. At no time period did extravasation of carbon take place, nor did the carbon plus histamine solution induce vascular leakage. Once a tracer gained access to the extravascular space, the developing basal lamina did not seem to retard its movement.
Structure, blood supply, and lymphatic vessels of the sheep's visceral pleura
Authors: Albertine Kurt H. , Wiener‐Kronish Jeanine P. , Roos Philip J. , Staub Norman C.
Published: February 2005

We investigated the morphology of the visceral pleura of 36 sheep, using macroscopic, histologic, and ultrastructural approaches to quantify regional pleural thickness, blood supply, and lymphatic drainage, including the pulmonary ligament and hilar lymphatic distributions. Pleural thickness increased caudally and dorsally, such that the costal pleura of the caudal lobes had a mean minimum pleural thickness of 83 μm. The blood supply to the entire visceral pleura came exclusively from the bronchial arteries. Lymph vessels formed an extensive plexus throughout the serous membrane of all lobes. Trunk lymphatics (> 100 μm diameter) had a density of about 2/cm of pleural length on all lobar surfaces except for the cranial and middle lobes, where their density on the costal surfaces was ≤ 1/cm. Pleural trunk lymphatics coursed to the pulmonary ligaments and to the hilum on their way to regional lymph nodes. At the hilum they anastomose with intrapulmonary lymphatic trunks. The principal lymph nodes to receive pulmonary lymph were the caudal mediastinal node and tracheobronchial nodes. The visceral pleura of sheep is thick, showing considerable regional diversity in morphology.
Leydig cell development of pig testis in the early fetal period: An ultrastructural study
Authors: van Vorstenbosch C. J. A. H. V. , Colenbrander B. , Wensing C. J. G.
Published: February 2005

Leydig cell development in the pig testis occurs in three periods (an early fetal, the perinatal period, and the period from puberty onward). The earliest of these periods was investigated ultrastructurally. The early fetal period starts immediately after gonadal differentiation, approximately 27 days postcoitum (p.c.), and finishes at about 60 days postcoitum. Dates of observation were 35, 52, and 62 days p.c. At 42 days p.c. some animals were decapitated.

Leydig cells at 35 days p.c. are characterized by an oval nucleus, vesicular or branched tubular smooth endoplasmic reticulum (SER), and a small quantity of rough endoplasmic reticulum (RER). The RER has two forms: a short and a long profile. The latter is closely coupled with mitochondria. The mitochondria mostly have tubular cristae. From 52 days p.c. onward the degree of coupling lessens, and it vanishes at 62 days p.c. At 52 and 62 days p.c. a very large amount of 10 nm filaments and a slight decrease in SER can be observed. The SER now has a branched tubular form, and the presence of polygonal dense bodies is also characteristic.

Decapitation does not disturb normal development of the Leydig cells in the observation period. No obvious differences from controls can be observed.
Axonal interactions with connective tissue and glial substrata during optic nerve regeneration in Xenopus larvae and adults
Authors: Bohn R. C. , Reier P. J. , Sourbeer E. B.
Published: February 2005

Axonal elongation through connective tissue and glial environments was compared following resection of the optic nerves in Xenopus tadpoles and frogs. During initial stages of fiber outgrowth, axons encountered connective‐tissue matrices of varying degrees of complexity in the ablation gaps. Many of the neuritic sprouts were randomly directed after leaving the retinal stump, and a neuroma‐like swelling ultimately formed at the cut edge. Although a large number of axons managed to traverse the lesion and associate with the cranial stump, many other fibers were less appropriately directed, especially in the frog where a greater infiltration of dense collagen occurred between the separated segments of the optic nerve. Axons often deviated from their cranially oriented pattern of outgrowth after entering the lesion and invaded surrounding extraocular muscles; others advanced along neighboring blood vessels and cranial nerve branches. In more extreme circumstances, fibers were completely misdirected at the cut end of the retinal stump and ultimately extended adjacent to the retinal segment back toward the eye. A more organized pattern of axonal elongation was observed in the presence of the glial substratum of the central stump, and growth cones appeared to associate preferentially with astrocyte endfeet in both tadpoles and frogs. These observations show that axons in the regenerating optic nerve of the amphibian can interact with a variety of cells and tissues and that the general direction of their outgrowth, at least in more peripheral regions of the visual pathway, appears to be dependent upon the orientation and, possibly, molecular properties of the terrain which they contact. In general, the basic environmental factors which either foster or impede axonal elongation in this regenerating system appear analogous to those influencing fiber outgrowth during regeneration in the peripheral nervous system of various species.
Ultrastructural and functional effects of chronic endogenous stimulation of thyroid cells by thyrotropin
Authors: Krupp Patricia P. , Kavolius J. P. , Golstein J. , Nève P.
Published: February 2005

Following total thyroidectomy, a small quantity of thyroid tissue was transplanted to the spleen in order to study thyroid tissue subjected to chronically elevated levels of endogenous thyrotropin (TSH). Plasma thyroxine (T4) and TSH levels were monitored and correlated with ultrastructural studies of the tissue over a 32‐week experimental period. The effects of administration of an iodine‐poor diet, an exogenous acute dose of TSH, and suppression of endogenous TSH through thyroxine administration were studied in order to evaluate the plasticity of the experimental model.

Plasma T4 decreased after the first week and remained at approximately one half of the initial value until 12 weeks. Plasma TSH increased to a high of 6,220 ng/ml after 6 weeks and gradually declined to one half of that value. The transplanted tissue remained functional throughout the experimental period. The number of pseudopods decreased, and irregularly shaped, dense bodies increased from the time of surgery until 12 weeks later. Administration of an acute dose of TSH at this time resulted in obvious mitotic activity and the formation of numerous pseudopods. The tissue also maintained the ability to take up radioactive iodine and to iodinate thyroglobulin. Inhibition of TSH secretion through T4 administration from the time of surgery did not affect viability. Some cellular hypertrophy persisted after 32 weeks although TSH and T4 had returned to normal.

This study has shown that thyroid tissue remains viable, functional, and experimentally alterable throughout an extended period of chronic stimulation by endogenous TSH, and that it has the reserve capacity to secrete normal levels of T4 at the end of this experimental period.
An ultrastructural study of the effect of a diabetogenic dose of alloxan on the secretory ameloblasts of the rat incisor
Authors: Karim Algernon C.
Published: February 2005

The effect of a single diabetogenic dose of alloxan on the ameloblasts of enamel secretion was investigated in rat incisor teeth prior to the onset of diabetes mellitus. This was compared with tissue from animals that were sacrificed at the onset of diabetes, and with tissue from animals that had been diabetic for 1 month. Male Sprague‐Dawley rats were given a single subcutaneous injection of alloxan at a dose of 150 mg/kg body weight; and the animals were sacrificed at 45 minutes, 2 hours, 24 hours, 48 hours and 29 days after injection. At the electron microscope level the following changes were observed. There was an early accumulation of secretion granules in the vicinity of the Golgi apparatus and within the proximal portion of Tomes' process. These accumulations were present at the onset of diabetes, 24 hours later. At 2 hours after injection a space appeared between the plasma membrane around Tomes' process and the interrod material. This space widened with time, and at 24 hours after injection it became continuous with enlarged intercellular spaces between the proximal portions of Tomes' processes. The widening of the intercellular space was restricted to the area above the distal cell web. At the onset of diabetes this compartment of the cells was similar to that of the control samples. Extracellular material which appeared to be the secretory product of the ameloblast was observed at two sites. On one occasion this material was seen in the wide intercellular spaces between the proximal portions of Tomes' processes 24 hours after injection. It was also seen at the onset of diabetes in the intercellular space at the level of the Golgi apparatus. The changes in the animals that had been diabetic for 1 month were a scarcity of secretion granules within Tomes' processes and an abnormal accumulation of secretion granules within the supranuclear and infranuclear compartents.

This study has shown that the toxic effect of alloxan persists up to the time of onset of diabetes mellitus. However, since different morphological changes were observed during diabetes mellitus, it is suggested that the changes caused by diabetes are a separate entity, initially superimposed on and later replacing the acute, toxic effect of the drug.
Circadian variation in the urinary excretion of electrolytes and trace elements in men
Authors: Kanabrocki Eugene L. , Scheving L. E. , Olwin J. H. , Marks G. E. , McCormick J. B. , Halberg F. , Pauly J. E. , Greco J. , De Bartolo M. , Nemchausky B. A. , Kaplan E. , Sothern Robert
Published: February 2005

Three‐hour urine specimens were collected over a period of 27 hours from 11 healthy adult male subjects. Each specimen was analyzed for Na, K, Ca, Mg, and Zn using atomic absorption spectrophotometry. Each sample was also dialyzed, pH 7.35, and subsequently analyzed for Na, K, P, Ca, Mg, Zn, Fe, Pb, Al, Ni, Cu, Mo, Hg, Cr, Cd, and Mn using a multielemental argon‐plasma emission system. The data were evaluated on conventional time plots (chronograms) and as computer‐determined “cosinor” plots. A population circadian rhythm with a statistical significance was detected for total Na, K, Ca, and Mg, and for nondialyzable Na, K, P, Ca, Zn, and Mo. For almost every element studied the increase from lowest to highest 3‐hour group mean along the 24‐hour time scale was more than 100%. The 24‐hour excretion of Na, K, Ca, Mg, and Zn appeared in good agreement with the so‐called “normals.” The nondialyzable levels of Fe, Pb, Al, Ni, Cu, Mo, Hg, Cr, Cd, and Mn were similar to the total urinary excretions reported in the literature.
Morphological changes in the hypothalamic arcuate nucleus and median eminence in the golden hamster during the neonatal period
Authors: Lamperti Albert , Mastovich John
Published: February 2005

The purpose of the present investigation was to study the ultrastructure of the arcuate nucleus (ARC) and median eminence of hamsters on days 1–15 of the neonatal period. From days 1–6, the neurons of the ARC had large nuclei and a small amount of cytoplasm which contained polysomes, mitochondria, RER, lysosomes and Golgi complexes. From days 7–15 there was an increase in the amount of cytoplasm as well as more extensive Golgi complexes and RER. Astrocytes were the predominant glial component in both the ARC and median eminence. Astrocytic processes were in juxtaposition to unmyelinated axons, dendrites, and synapses. Axodendritic and axosomatic synapses containing clear vesicles were observed in the neuropil on day 1. There was an increase in the number of dense‐core vesicles in the axonal endings beginning on day 4.

Concomitantly, there were increasing numbers of clear and dense‐core vesicles (64–70 nm) in terminals of the external layer of the median eminence, whereas larger dense‐core vesicles (105–140 nm) were distinguishable by day 10 immediately dorsal to the external layer. The capillaries of the median eminence were composed of nonfenestrated endothelium from days 1–9. Fenestrae began to appear about day 10. Ependymal cells lining the third ventricle had pinocytotic vesicles, microvilli, and bleb‐like protrusions on their apical surfaces. Ependymal processes were adjacent to nerve processes in the neuropil of the ARC and in the external layer of the median eminence, where they contacted the perivascular space.

Two types of supraependymal cells were seen in animals throughout the neonatal period. One resembled a neuron which sent processes along the ependymal surface and often between cells. The second type was similar to a macrophage. The results of this study demonstrate the maturation of the neural elements in the ARC/median eminence area of the neonatal hamster.
The distribution of actin in cultured ovarian granulosa cells
Authors: Batten Bruce E. , Anderson Everett
Published: February 2005

Ovarian granulosa cells grown on glass coverslips were split by a “sandwich” technique. Using this technique we describe a complex filamentous network in the cytoplasm of cultured granulosa cells that was composed of a branching and anastomosing lattice of filaments 20–40 nm in diameter. Since filament identification impossible on the basis of size, split cells were decorated with S‐1 fragments of rabbit skeletal muscle myosin. It was readily apparent that the major constituent of the filamentous lattice was actin. Actin was organized in large bundles in which individual filaments were longitudinally aligned. Actin was also observed organized in a loose network throughout the remainder of the cytoplasm. Actin appeared to be intimately associated with organelle and plasma membranes. Coated pits were also a site of actin‐filament interaction. Filament polarity was generally away from the membrane with which filaments were associated.
Occlusion and reformation of the rat uterine lumen during pregnancy
Authors: Welsh Alerick O. , Enders Allen C.
Published: February 2005

Implantation sites were obtained from rats at various stages of pregnancy and were studied by light microscopy and scanning electron microscopy. Early in pregnancy the uterine luminal epithelium and the decidual cells in the implantation site formed an implantation chamber containing the conceptus. The epithelial cells lining the chamber and the mouth of the chamber degenerated, and the uterine lumen that was mesometrial to the conceptus was obliterated such that the uterine lumen became discontinuous, and the luminal epithelia of intersite areas were isolated. As the conceptus continued to grow, the decidua‐conceptus unit bulged into the intersite areas and was partially covered by an epithelium that eventually became discontinuous and degenerated. Once this had occurred, the luminal epithelium of the intersite areas reestablished contact antimesometrial to the decidua‐conceptus unit, and the uterine lumen was again continuous. However, the epithelium lining the lumen was not complete in the mesometrial region because of the vascular connections between the uterine stroma and the placenta. Factors influencing the restructuring of the uterine luminal epithelium were discussed.
The embryonic origins of avian cephalic and cervical muscles and associated connective tissues
Authors: Noden Drew M.
Published: February 2005

The objective of these experiments was to determine the embryonic origins of craniotacial and cervical voluntary muscles and associated connective tissues in the chick. To accomplish this, suspected primordia, including somitomeres 3–7. somites 1–7, and cephalic neural crest primordia have been transplanted from quail into chick embryos. Quail cells can be detected by the presence of a species‐specific nuclear marker. The results are summarized as follows:

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These results indicate that muscles associated with branchial arch skeletal structures are derived from paraxial mesoderm, as are all other voluntary muscles in the vertebrate embryo. Thus, theories of vertebrate ontogeny and phylogeny based in part on proposed unique features of branchiomeric muscles must be critically reappraised. In addition, many of these cephalic muscles are composites of two separate primordia: the myogenic stem cells of mesodermal origin and the supporting and connective tissues derived from the neural crest or lateral plate mesoderm. Defining these embryonic origins is a necessary prerequisite to understanding how the mesenchymal primordia of cephalic muscles and connective tissues interact to form patterned, species‐unique musculoskeletal systems.
Abnormal distribution of fiber types in the slow‐twitch soleus muscle of the C57BL/6J DY2J/DY2J dystrophic mouse during postnatal development
Authors: Ovalle W. K. , Bressler B. H. , Jasch L. G. , Slonecker C. E.
Published: February 2005

The postnatal development of extrafusal fibers in the slow‐twitch soleus muscle of genetically dystrophic C57BL/6J dy2J/dy2J mice and their normal age‐matched controls was investigated by histochemical and quantitative methods at selected ages of 4, 8, 12, and 32 weeks. The majority of fibers in the soleus consisted of two kinds, fast‐twitch oxidative‐glycolytic (FOG) and slow‐twitch oxidative (SO), according to reactions for alkaline‐stable and acid‐stable myosin ATPase and the oxidative enzyme, NADH‐tetrazolium reductase. A minor population of fibers, stable for both alkaline‐ and acid‐preincubated ATPase, but variable in staining intensity for NADH‐TR, were designated “atypical” fibers.

With age, the normal soleus exhibited a gradual increase in the number and proportion of SO fibers and a reciprocal, steady decline in the percentage of FOG fibers. Atypical fibers were numerous at 4 weeks, but were substantially diminished at later ages. Since total extrafusal fiber number remained relatively constant between the periods examined, this change in relative proportions reflects an adaptive transformation of fiber types characteristic of normal postnatal growth.

A striking alteration in the number and distribution of fiber types was associated with the dystrophic soleus. At 4 weeks an 18% reduction in total fiber number was already noted. Subsequently, by 32 weeks a further 22% diminution in overall fiber number had occurred. With age, the absolute number and proportion of dystrophic SO fibers were drastically reduced. In contrast, the percentage of dystrophic FOG fibers increased significantly while their absolute numbers between 4 and 32 weeks remained relatively constant. Atypical fibers in the dystrophic solei were found in elevated numbers at all age groups, particularly at 12 weeks. They may, in part, represent attempts at regeneration or an intermediate stage in fiber‐type transformation. Microscopically, both of the major fiber types appeared affected, albeit differently, by the dystrophic process. We suggest that a failure or retardation in the normal postnatal conversion of fiber types within the soleus muscle occurs in this murine model for muscular dystrophy.
Kinematics of cranial vault growth in rabbits
Authors: Alberius P. , Selvik G.
Published: February 2005

To characterize mathematically the spatial rearrangement of cranial vault bones of the rabbit during growth, a longitudinal study was undertaken from age 4–20 weeks. Initially, at least three nonlinear tantalum bone markers were implanted in the parietal, frontal, and the combined nasal bones. Thereafter, the animals were followed regularly with roentgen stereo‐photogrammetrical analysis. The parietal bones were found to rotate laterally upward (3°), while the frontal bones rotated downward (2°) relative to their contralaterals. The frontal bones rotated rostrally upward (12°) and outward (3°) as well as laterally downward (5°) in relation to the parietal bones. Due to the morphology of the rabbit head, the examination positioning used in this study, and the direction of the growth process, growth at the coronal suture correlated fairly well with longitudinal axis translations; but the growth at the frontonasal suture relative to the frontal bones was directed about 45° downward. This points to the importance of the bone‐marker positioning, so that their connecting line is directed along the axis of growth. Also, this approach makes it possible to obtain new information on the development and treatment of craniofacial aberrations.
Tridimensional architecture of the golgi apparatus in the atrial muscle cell of the rat
Authors: Rambourg A. , Segretain D. , Clermont Y.
Published: February 2005

The tridimensional structure of the Golgi apparatus of atrial muscle cells has been studied in thin and thick sections with low‐and high‐voltage electron microscopes. Cardiac tissue was inpregnated with osmium, stained to demonstrate phosphate activity (i.e., nicotinamide adenine dinucleotide phosphatase or NADPase; thiamine pyrophosphatase or TPPase; cytidine monophosphatase or CMPase) or postfixed and stained with potassium ferro‐cyanide‐reduced osmium. At low power, in thick (3–10 μm) sections, the cis‐osmiophilic element and the NADPase‐and the TPPase‐positive saccules each appeared as a continuous irregular ribbon that formed, at the two poles of the nucleus, two conical masses connected to each other by beltlike bands encircling the nucleus. At higher magnifications, the continuous Golgi apparatus showed saccular regions along its length connected by short intersaccular tubular regions. In the saccular regions, the following five superimposed elements formed a stack: (1) the cis‐osmiophilic network of anastomosed tubules; (2) a chromophobic, dilated saccule perforated with numerous pores; (3) a thin NADPase‐positive saccule showing few pores; (4) a thin TPPase‐positive saccule perforated with numerous minute pores; and (5) a CMPase‐positive trans‐element that showed saccular and tubular regions and was often partly separated from the overlying saccule. In the intersaccular tubular regions, membranous tubules connected and bridged saccules of two adjacent saccular regions. Secretory granules usually appeared in this region as dilations of the tubules connected to all elements of the Golgi stack except the cis‐osmiophilic element.