bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for a structural relationship between sarcoplasmic reticulum and Z lines in dog papillary muscle
Authors: Edge Maxine B. , Walker Sheppard M.
Published: February 2005

Electron micrographs of dog papillary muscle fibers show the sarco‐plasmic reticulum (SR) as an extensive three‐dimensional network of diverging and converging tubules that is continuous throughout each sarcomere and in successive sarcomeres. The network surrounds each myofibril and is continuous across the fiber. Tubules of the SR network are oriented transversely and longitudinally. Interconnections of transversely and longitudinally oriented SR tubules form circular pathways in the network. A structural relationship appears to exist between the Z line and longitudinally and transversely oriented tubules of the SR network at their points of apposition with the Z line. A rather constant space approximately 100 Å wide is seen between SR tubules apposed at the Z line in cross‐sections and in favorable longitudinal sections of fibrils. This space is traversed by electron‐opaque strands which appear to be connections between SR tubules and the Z line. Other lines of evidence support the view that Z lines and SR tubules are connected. One of these is the change of position of Z line SR tubules in relation to the change of position of Z lines in adjacent fibrils. Another line of evidence is the continuity of SR apposed at the Z line and SR connected to the sarcolemma.
Ultrastructure of cortical synapses after failure of presynaptic activity in ischemia,
Authors: Williams Vick , Grossman Robert G.
Published: February 2005

The fine structure of cerebral cortical synapses was investigated during failure of synaptic transmission produced by ischemia. Presynaptic and postsynaptic potentials evoked in the anterior sigmoid gyrus of the cat by stimulation of the nucleus ventralis lateralis and the DC potential between cortical layer IV and the white matter were recorded with micropipettes during cerebral ischemia produced by arterial hemorrhage in paralyzed, artificially ventilated animals. After failure of the spontaneous electrocorticogram and postsynaptic responses, the presynaptic volley failed with development of depolarization of intracortical fiber terminals and loss of axon terminal excitability. The gyrus was then biopsied and fixed in collidine‐buffered OsO4. An altered pattern of distribution of synaptic vesicles was observed after presynaptic afferent fiber terminal activity was abolished by 3.5 to 4.0 minutes of cerebral ischemia. Clumping of vesicles in a region away from the cynaptic cleft was seen in about 10% of synaptic endings, and there was more than a two‐fold increase in the number of presynaptic profiles devoid of vesicles in ischemic cortex.
The fate of fragments of liver implanted in ectopic sites
Authors: Tavassoli Mehdi , Crosby William H.
Published: February 2005

Implanted fragments of liver in ectopic sites do not survive. The failure of survival is associated with lack of vascularization. This results in necrosis of coagulative type which later is replaced by connective tissue. An invasion of polymorphonuclear leukocytes can enhance the rate of this process. Regenerative stimuli such as partial hepatectomy do not change this sequence of events. The lack of vascularization of implants may be due to failure of eliciting an invasive vascular phenomenon which is seen in the implanted fragments of those tissues that survive in ectopic sites.
Effect of fibrillar structure of pericanalicular and intercanalicular bone on X‐ray absorption
Authors: Vose George P. , Baylink David J.
Published: February 2005

The apparent hypermineralization which is often seen adjacent to canaliculi (∼ 2000 Å) and dentinal tubules in microradiographs may be the result of a reversal in orientation of microcanaliculi (∼ 500 Å) and adjacent mineralized fibrils at these sites. Microcanaliculi and adjacent mineralized fibrils, as seen by electron microscopic surface replication, extended at right angles from canaliculi for a distance of about 1–2 μ. In contrast, beyond this zone microcanaliculi were also observed but were oriented at right angles to the microcanalculi that were closer to the canaliculi. Although the significance of the difference in orientation of microcanaliculi in pericanalicular as compared with intercanalicular regions is not known, we demonstrated that when a porous material is x‐rayed parallel to and then at right angles to the longitudinal axis of the porous phase an apparent difference in density is observed. These findings suggest that the apparent hypermineralization of bone adjacent to canaliculi described in former investigations utilizing microradiography may be the result of a difference in orientation of microcanaliculi and adjacent mineralized fibrils rather than a true variation in mineral density.
Ultrastructural changes in articular chondrocytes of mice fed a lard‐enriched diet
Authors: Silberberg Ruth , Aufdermaur Max , Hasler Mary
Published: February 2005

Weanling male mice of strain C57B1. were fed a lard‐enriched diet for periods of 1, 4, 7, 10, 14, or 28 days. Beginning during the second week of consumption of this ration, articular chondrocytes of the femoral heads were increased in number and size and showed ultrastructural changes. The latter manifested themselves in nuclear enlargement, intensification of organellar development and in acceleration of regression. There was no evidence of abnormal deposition of lipid material within the chondrocytes beyond that due to organellar disintegration. It was concluded that the early effects of a lard‐enriched diet on articular cartilage consist of an overall stimulation of cell function followed by premature exhaustion. The primary site of action of the dietary fat remains unknown.
In vitro differentiation of tooth rudiments of embryonic mice. II. Growth of isolated thirds of embryonic mouse incisors
Authors: Koch William E. , Koch Barbara A. , Ledbury Priscilla A.
Published: February 2005

The mandibular incisor of the 16 day embryonic mouse was divided into three visibly equal thirds; each third was explanted in vitro to test its capabilities for independent development. Ameloblasts and odontoblasts, present in the distal third at the time of isolation, fail to continue their differentiation. This third flattens, and the tissues become disorganized. Grouping several distal thirds in a single culture did not promote tissue differentiation. The embryonic proximal third remains cohesive The tissues differentiate; both ameloblasts and odontoblasts deposit extracellular matrix. Approximately half of the cultures of the intermediate third show differentiated odontoblasts and extracellular matrix after 11 culture days. Measurements of the volume changes of ameloblasts, odontoblasts, and general mesenchyme were taken over the first six culture days for each third of the rudiment. The volume changes recorded, and the counts of mitotic figures reflect the developmental behavior of each fraction of the rudiment.
Special structural features of the rat portal vein
Authors: Ts'ao Chung‐Hsin , Glagov Seymour , Kelsey Billy F.
Published: February 2005

Unlike other rat veins of comparable diameter, the smooth muscle cells of the extrahepatic segment of the portal vein are arranged in two distinct mutually perpendicular layers. The relatively narrow inner layer is nearly circumferential and devoid of vasa vasorum; the cells resemble those seen in other veins. In the longitudinal outer layer, vasa are abundant and the cells contain unusual numbers of mitochondria and abundant pinocytotic vesicles, indicating relatively increased metabolic activity. Between the layers, the connective tissue contains nerve fibers, suggesting coordinated reflex activity.
Hypothalamic‐hypophysial adrenal and thyroid systems: Observations in fetal rats subjected to hypothalamic destruction, brain compression and hypervitaminosis A
Authors: Fujita Tsuneo , Eguchi Yasunobu , Morikawa Yoshio , Hashimoto Yoshiyuki
Published: February 2005

Regulation by fetal hypothalamus of adrenocorticotrophic and thyrotrophic function of the fetal anterior hypophysis in the rat was studied by: (1) destruction of the fetal hypothalamic area with an electrocoagulator, (2) compression of the fetal brain by injected paraffin into the fetal skull and (3) induction of fetal exencephaly by hypervitaminosis A in the mother.

The body weight of fetuses in which the hypothalamus was damaged was significantly less than that of littermate controls. Volume of the anterior hypophysis was small in fetuses injected with paraffin. The anterior hypophyses were present in all exencephalies, and showed abnormal forms but no reduction in volume. The adrenals were very small in all fetuses in which the hypothalamus was damaged, accompanied by conspicuous shrinkage of cortical cells, while the thyroids were not changed in volume. The height of the follicular cells decreased slightly.

The observations suggest that in the late period of fetal life in rats, the hypophysial‐adrenal system is regulated largely by the hypothalamus, but that the hypophysial‐thyroid system is not fully under the control of the hypothalamus.
Intercellular bridges between germ cells in the developing ovary of the tadpole, Rana pipiens
Authors: Ruby John R. , Dyer Robert F. , Skalko Richard G. , Volpe E. Peter
Published: February 2005

Ovaries obtained from the tadpole, Rana pipiens, and examined with the electron microscope revealed that many of the developing germ cells were joined together by intercellular bridges. All connections exhibited electron‐dense material on the inner surface of the plasma membrane, thus demonstrating the same basic structure as intercellular bridges described in other species. However, the presence of a sleeve‐like subsurface cistern beneath the dense border in the tadpole produces a morphologically more complex connection. A variety of cytoplasmic organelles, including mitochondria and elements of the endoplasmic reticulum, were seen within the confines of these bridges. Possible functions of intercellular bridges are discussed and it is suggested that certain developing germ cells function as nurse cells like those described in some invertebrates.
The reproductive organs of the male spotted skunk (Spilogale putorius)
Authors: Mead Rodney A.
Published: February 2005

A relatively well developed prostrate is the only accessory sex gland present in the spotted skunk (Spilogale putorius). The distal end of the vas deferens is quite glandular, but there is no distinct ampullary swelling. The gross morphology of this species is compared with that of several other members of the family Mustelidae.
The carotid body of the weddell seal (Leptonychotes weddelli)
Authors: Morita Ernesto , Chiocchio Sara R. , Tramezzani Juan H.
Published: February 2005

Light and electron microscopy of the carotid body of the Weddell seal shows two types of cells, the main and the sustentacular cells.

The main cells contain dense osmiophilic granules in variable amount. Their cytoplasma shows either a high or a low electron density. On this basis light and dark main cells were distinguished.

The differences in cytoplasm electron density and the great variability in the number of granules were interpreted as expressions of different stages in a process of secretory nature.

A very rich innervation with outstanding nerve endings was observed in the carotid body of the Weddell seal. This picture is similar to that observed in stimulated carotid bodies. The carotid body of the Weddell seal a marine mammal that stays underwater for a long stretch of time, may be considered as subjected to frequent stimulations.
Brunner's glands of the echidna
Authors: Krause William J.
Published: February 2005

Brunner's glands of the echidna form a thick, interwoven collar confined to the submucosa of the most distal portion of the stomach. The glandular mass ends immediately proximal to the pyloroduodenal junction and empties onto a surface lined by stratified squamous epithelium. Histochemical studies indicate that the secretion elaborated by the glands is an acid mucopolysaccharide.

Secretory tubules in the glands consist of large, pyramidal‐shaped cells resting on a delicate basal lamina. They contain large, pale or granular secretory droplets which are membrane bounded and are found in close association with extensive Golgi complexes and also at the apex of the cells. Secretary granules, occasionally fused into irregularly‐shaped complexes in the apical region, appear to rupture the cell membrane and discharge their contents into the adjacent lumen. Small, dense granules are also present but less abundant. The granular endoplasmic reticulum is confined mainly to the perinuclear region and comprises dilated cisternae containing amorphous material. Several small vesicles apparently formed from smooth membrane areas of the ergastoplasm are seen adjacent to the Golgi networks.

The epithelium lining the duct is devoid of large secretory granules and contains relatively few organelles.
Shapes and sizes of synaptic vesicles in the cerebellum of the Syrian hamster‐cortex and deep nuclei
Authors: Duncan Donald , Morales Ricardo , Benignus V. A.
Published: February 2005

Material was obtained from eight adult apparently healthy Syrian hamsters perfused with 3.2% glutaraldehyde in phosphate buffer. Cortex and deep nuclei were prepared for electron microscopy by osmication and Epon embedding. Measurement of size and shape of vesicles was from printx × 50,000. Vesicle profiles whose least diameter was 75% or more of the maximum diameter were classified as round (spherical). If the greatest dimension was more than twice the least, the vesicle was termed flattened, all others oval. So defined, the synaptic sacs in the deep nuclei, large sacs of the granular layer and small sacs of the molecular layer contained more round vesicles than oval and flat combined and differences between these three locations were slight. In large sacs of the molecular layer, oval and flattened vesicles slightly outnumbered round ones. Average sizes were deep nuclei 468 Å, large sacs of granular layer 494 Å, small sacs of molecular layer 452 Å and large sacs of molecular layer 414 Å. Statistical analysis indicated that the mean size of vesicles was significantly different when each of the four locations was compared with the others. These differences are too small to be apparent by inspection. Since the vesicles in the deep nuclei are intermediate in size between those in mossy terminals and the axospinous ones of the molecular layer it was concluded that size and shape of vesicles did not distinguish between excitatory and inhibitory synapses in Syrian hamster cerebellum.
The fine structure of the arteriovenous anastomosis and its nerve supply in the human nasal respiratory mucosa
Authors: Cauna Nikolajs
Published: February 2005

The fine structure of the arteriovenous anastomosis was investigated in the normal human nasal mucosa. The tissues were fixed in 2% osmic acid solution, embedded in Epon and stained with uranyl acetate and lead citrate solutions.

It was found that the endothelial basement membrane of the arterial segment of the anastomosis was discontinuous. The anastomosing artery possessed subendothelial cushions of longitudinal smooth musculature which expanded into a thick uniform layer before the artery joined the vein. The fine morphology of these muscle cells did not show epitheloid modification. An elastic membrane of a peculiar structure separated the subendothelial musculature from that of the tunica media. The membrane was continuous with the internal elastic membrane of the proximal artery and with the adventitial elastic mesh of the vein. The anastomosis was supplied by a non‐myelinated periarterial nerve plexus which contained cholinergic and adrenergic axons characterized by agranular and fine granular vesicles respectively. The wall of the vein was devoid of musculature and nerves. It mainly consisted of elastic meshes interspersed with bundles of collagen fibers and occasional fibrocytes.

It was suggested that the musculature of the tunica media of the artery was controlled by the cholinergic and adrenergic nerves of the autonomic system, and by the sensory nerves in the form of axons reflexes. The subendothelial musculature was controlled by agents carried in blood and was not influenced by the adventitial nerves.
An electron microscopic study of mesenchyme during development of interdigital spaces in man
Authors: Kelley Robert O.
Published: February 2005

Cell movements and degenerations occur normally during embryogenesis and have received particular attention during development of limbs in the chick. The present investigation suggests that similar phenomena occur during formation of interdigital spaces in man. Upper limb buds were dissected from a human embryo (CR 15.5 mm, age estimated at 6 weeks postfertilization), fixed in phosphate buffered glutaraldehyde, and prepared for electron microscopy. Mesenchymal cells in developing interdigital zones appeared to be undergoing either mitosis or necrosis. Macrophagy of necrotic mesenchymal cells, which begins distad in the appendage bud, contributes to the final formation of an interdigital space.
Pineral structure and composition in the orangutan (Pongo pygmaeus)
Authors: Quay W. B.
Published: February 2005

Microscopic structure and histochemistry were studied in the pineal organ of a male orangutan (34 kg body weight, 7 years radiological age). Although small in size (1.7 mm long by 1.1 mm wide dorsoventrally) the pineal of this species appears active and has a number of distinctive characteristics: broad exposure on the third ventricle at the pineal recess; permeation by recesses and channels from the dorsal sac; extensive penetration by loops of myelinated fibers from the habenular and posterior commissures; lack of intrapineal nerve cell bodies; presence of different parenchymal cell types having granular and vacuolated cytoplasm; and a densely cellular stroma containing melanin.
Extracellular specializations associated with hemidesmosomes in the fetal rat urogenital sinus
Authors: Flickinger Charles J.
Published: February 2005

Specializations of extracellular structures opposite hemidesmosomes at the basal surface of epithelial cells of the fetal rat urogenital sinus are described. A moderately dense band or lamella ∼ 100 Å wide forms a cap about 50 Å from the plasma membrane. The normally electron‐lucent inner zone between the plasma membrane and the basal lamina is increased in density and may be traversed by filaments or strands of material extending from the cell surface. The basal lamina is thickened and its density is increased locally opposite hemidesmosomes. The possible role of these specializations in adhesion between epithelial cells and the underlying extra‐cellular structures is considered.
Aortic arches in the chick embryo: Origin of the cells as determined by radioautographic mapping
Authors: Rosenquist Glenn C.
Published: February 2005

The origin of the cells which form the aortic arches in the chick embryo was determined by tracing the movements of tritiated thymidine‐labeled grafts excised from medium streak (MS) to head process (HP) stage embryos and transplanted to the epiblast, streak and endoderm‐mesoderm layers of similarly staged recipient embryos.

Between the MS and HP stages, the preaortic arch cells migrate in epiblast to the primitive streak, invaginate, and move anteriorly and laterally from the streak into mesoderm; at the HP stage they are lateral to the cells which will form the anterior parts of the dorsal aortae, and medial to the heart‐forming regions. The most anterior prearch cells form the first arch and the more posterior cells form the more posterior arches. The prearch cells are closely associated during migration with the endoderm cells which will form the adjacent branchial arches and clefts.

Cells which will form the posterior end of the aorta are still in the epiblast layer at the late medium streak (LMS) stage, but have moved to the primitive streak at the HP stage; they migrate from the streak into mesoderm posterior and medial to the mesoderm destined for the heart and aortic arches.
Histochemistry of the aldosterone‐stimulated urinary bladder of the toad, Bufo marinus
Authors: Symonds Daniel A. , Lentz Thomas L.
Published: February 2005

Histochemical changes were observed in the epithelium of the toad urinary bladder following in vitro and in vivo stimulation by aldosterone to determine the cell types affected by this hormone. A marked pyrinophilia was observed in comparison to control tissue affecting all cell types, as well as slight increases in cytoplasmic PAS staining within the granular cells, under both sets of conditions. An increased number of mitochondria was demonstrated with the PTAH stain within the granular cells under in vivo conditions but not in vitro. Under in vivo conditions, marked increases in the enzymes of the oxidative pathway (DPND, TPND, SDH, and cytochrome oxidase) were observed in granular cells. Enzymes of the oxidative pathway were unchanged under in vitro conditions was more intensely localized to the cell membrane and cytoplasm of all cells. Granular cells from in vitro studied tissue were slightly more reactive for G6PD and 6PGD than control tissue; granular cells were even more heavily reactive for these enzymes under in vivo conditions. Thus, under prolonged aldosterone stimulation, the granular cell approached the histochemical profile of the mitochondria‐rich cell. The hormone may therefore act upon the granular cell, which comprises the largest number of cells within the epithelium, as well as the mitochondria‐rich cell.
Intracellular distribution of mucosubstances in the major sublingual gland of the rat
Authors: Enomoto Shoji , Scott Bronnetta L.
Published: February 2005

The intracellular distribution of mucosubstances in the acinar cells of the rat sublingual gland has been studied at the electron microscopic level by means of two histochemical techniques: PA‐silver methenamine for the detection of vicinal glycols and colloidal thorium for the detection of polyanions. By both methods the secretory granules in the mucous acinar cells were selectively stained. The reaction products were visualized as dense closely packed precipitates covering the entire matrix of the individual mucous granules. Similar reaction products were also often observed within the Golgi apparatus of the mucous cells. In striking contrast, the secretory granules and Golgi apparatus of the demilunar cells exhibited no demonstrable selective staining by either method. It is concluded that the secretory granules of the mucous acinar cells are largely composed of mucosubstances containing vicinal glycols and polyanions and that the secretory granules in demilunar cells contain no demonstrable content of such mucosubstances.
Direct contribution of the cytotrophoblast to the syncytiotrophoblast in the diffuse labyrinthine endotheliochorial placenta of the bat
Authors: Stephens R. J. , Cabral L.
Published: February 2005

In the molossid bat, Tadarida brasiliensis cynocephala, there is a prominent diffuse endotheliodichorial placenta over the parietal area of the uterus prior to mid‐gestation. During the neural groove stage the syncytium rapidly increases in quantity, and cells from the cytotrophoblast have been observed being contributed to the syncytium. The transitional cells become swollen and the plasma membranes between the syncytium and the transitional cell fuse, become porous, and rupture. The contents of the transitional cell then “flow” into the syncytial area.
The sarcoplasmic reticulum and development of z lines in skeletal muscle fibers of fetal and postnatal rats
Authors: Walker Sheppard M. , Edge Maxine B.
Published: February 2005

In electron microscope examinations of leg muscles from fetal and postnatal rats the development of SR tubules precedes the development of Z lines and the formation of fibrils, thus showing that a function of SR in Z line development is possible. Early stages of fibril formation reveal very small Z lines (0.06 μ thick) which are encircled by SR tubules separated from the Z lines by a space about 100 Å wide, and this space is traversed by electron‐opaque strands which appear to be connections between SR tubules and Z lines. The encircling SR tubules are observed from the beginning to the completion of Z line development. The small Z lines contain dense lines transversely oriented between thin filament tips that resemble transversely oriented dense lines found in fully developed Z lines. It is concluded that Z line enlargement involves growth in circumference of encircling SR tubules as the tubules incorporate additional layers of thin filament tips. It is suggested that the substance represented by electronopaque strands connecting SR tubules and Z lines might provide precursors for the substance represented by transversely oriented dense lines between thin filament tips.
Functional anatomy of the cardiac nerves in the baboon
Authors: Randall Walter C. , Armour J. Andrew , Randall David C. , Smith Orville A.
Published: February 2005

In 17 anesthetized baboons, the autonomic innervation of the heart was carefully exposed and electrically stimulated to determine the course of fibers having direct inotropic and/or chronotropic actions. The superior cervical and nodose ganglia are intimately associated by means of short but large interconnections, and the sympathetic and parasympathetic trunks descend with the carotid artery in a common epineural sheath. The middle cervical ganglion is invariably well defined and completely separated from the vagus trunk in the upper portion of the thoracic cage. Direct nervous connections between the sympathetic and vagal trunks are frequent at all levels within the thorax. Both systems also send small nerves into the phrenic and recurrent laryngeal nerves. Separate inferior cervical and first thoracic ganglia were not found, but rather, a large and well defined stellate ganglion extending across the heads of the first and second ribs. The stellates are connected to the middle cervical ganglia by means of both dorsal and ventral ansae subclavia of varying size. Although fine nerves arising from the upper thoracic trunk were located, they appeared to have no direct inotropic or chronotropic actions. The major sympathetic and parasympathetic nerves converge upon richly interconnected dorsal and ventral cardiopulmonary plexuses and several minor (superior vena cava, left atrial, pulmonary veins) plexuses. Both ipsilateral and contralateral control of cardiac function is possible through these pathways. The baboon cardiac innervation thus appears to resemble that of man in some respects and the dog in others.
An electromyographic study of reciprocal activity of muscles
Authors: Patton N. J. , Mortensen Otto A.
Published: February 2005

An electromyographic study of elbow flexors and extensors was conducted using 20 adult human subjects to determine if cocontraction occurred during voluntary movement. The interplay of proprioceptive reflex influences arising in the primary and secondary endings of the muscle spindle and in the Golgi tendon organ provide the neurophysiological basis for cocontraction. Whether or not cocontraction occurs during a movement is dependent on the degree to which one proprioceptive influence predominates over the others. This in turn appears to be dependent on factors such as those described below.

Incidence and degree of cocontraction was greater during extension than during flexion movements. This may be attributed to the influence of muscle spindle secondary endings.

Cocontraction increased with increasing load. Proprioceptive reflexes arising in tendon organs may be involved in this phenomenon.

No evidence was found to indicate that the incidence of cocontraction increased with increasing precision of movement. In general, cocontraction was less in skilled and strong subjects than in average subjects during all types of movements.

Under the special circumstances of voluntarily attempted cocontraction, evidence of reciprocal inhibition of the antagonist appeared. Proprioceptive reflex activity from tendon organs and from muscle spindle secondary endings are implicated as primarily responsible for this inhibition.
Freeze‐etch observations of rat lung
Authors: Belton John C. , Branton Daniel , Thomas Heriberto V. , Mueller Peter K.
Published: February 2005

The freeze‐etch technique was used to study the fine structure of the terminal respiratory membranes of rat lung. Special emphasis was given to the ultrastructure of the type II alveolar cell and its role in formation of the surface active material. Our morphological evidence supports the theory that membrane‐bound multivesicular bodies in the cytoplasm of type II cells accumulate phospholipid material to form lamellar structures which are extruded onto the alveolar surface as one of the components of the surface active material. Subsequent loss of the lamellar configuration in the surface active layer is discussed. Electron micrographs demonstrate numerous microindentations that extend into the base of alveolar cells and help establish a close relation with the basal lamella.
Inhibition by cycloheximide of ACTH‐induced internal differentiation of mitochondria in cortical cells in tissue cultures of fetal rat adrenals
Authors: Kahri Arvi I.
Published: February 2005

Tissue cultures of fetal rat adrenals were used to study effects of cycloheximide on the ACTH‐induced synthesis of mitochondrial inner membranes in the cortical cells. Cycloheximide alone added to the culture medium in concentrations of 100‐0.25 μg/ml killed the cortical cells during six days of treatment. At the dosage level of 0.15 μg/ml/6 days, it induced a decrease in the size of mitochondria and an increase in the pleomorphism of mitochondria. Cycloheximide at a concentration of 0.015 μg/ml/6 days induced no change in the ultrastructure of cortical cells. When cycloheximide in concentrations of 0.15 μg/ml/6 days was added to the culture medium together with 100 mU/ml/6 days of ACTH, the ACTH‐induced changes of mitochondrial inner membranes (formation of 600 Å vesicles) was completely inhibited. It also suppressed the ACTH‐induced development of smooth surfaced endoplasmic reticulum, hypertrophy of Golgi apparatus, development of microvilli and accumulation of lipids. However, it had no effects on the ACTH‐induced increase in the number of polysomes 01 the increase of heterochromatin in the nucleus. Cycloheximide (0.08 μg/ml/6 days) given together with 100 mU/ml/6 days of ACTH had incomplete inhibitory effects on the ACTH‐induced differentiation of the cortical cells. Cycloheximide (0.015 μg/ml/6 days) given together with ACTH resulted in only slight inhibition of ACTH‐induced ultrastructural differentiation of adrenal cortical cells in vitro.

The present observations suggest that (1) the stimulatory effect of ACTH on mitochondrial protein synthesis is dependent upon nuclear control of protein synthesis; (2) a specific cytoplasmic mitochondrial protein synthesis stimulating factor in the cytoplasm of cortical cells is dependent on ribosomal protein synthesis and is a mediator of ACTH action on the mitochondrion; (3) despite their apparent autonomy, the mitochondria in cortical cells are kept under nuclear control; (4) the only direct locus for the trophic effect of ACTH is in the nucleus.
Postnatal development and properties of ultimobranchial follicles in the rat thyroid
Authors: Wollman Seymour H. , Nève Pierre
Published: February 2005

Mature ultimobranchial follicles in the Fischer rat thyroid are characterized by being lined by two or more layers of cells (U cells) and by having an abundance of desquamated cells in the lumen. Such follicles, of variable size and shape, were found in almost every lobe in rats at least 30 days old. They were usually in the interior of the lobe in contact with perivascular connective tissue. Ultimobranchial follicles with multiple layers of cells were not observed in the two‐day‐old rat indicating that these follicles are an example of postnatal development. The most common precursor in the rat was a follicle, relatively large compared with the usual thyroid follicle, containing some cells or debris. Other precursor structures included narrow tubes, sheets or spheroids of cells characteristically having little cytoplasm. Intermedlate forms between these precursors and mature ultimobranchial follicles were recognized. Cells were desquamated while nucleated, and, later, the nuclei disappeared. Thus, in some follicles non‐nucleated debris accumulated. Many follicles were composed of mixed populations of cells, both typical thyroid epithelium and U cells. The relative abundance of the two cell types varied markedly as did the proportions of colloid and cell debris.
Stimulation of DNA synthesis in mammalian cell cultures by receptor‐destroying enzyme and neuraminidase
Authors: Caso Louis V.
Published: February 2005

Receptor‐destroying enzyme (RDE) and purified neuraminidase (V. cholerae) were added in varying concentrations to cultures of L929 fibro‐blasts, HeLa cells and FL amnion cells. After 96 hours incubation at 36oC, RDE was found to enhance the growth of L929 fibroblasts and FL amnion cells, as measured spectrophotometrically by total DNA synthesis. Neuraminidase was found to stimulate growth in the three cell lines, using the same method of DNA determination. Neuraminidase, moreover, significantly increased the mitotic indices of the three cell lines after 72 hours incubation.
Studies of human adipose tissue in culture I. Incorporation of glucose and release of glycerol
Authors: Smith Ulf
Published: February 2005

Explants of human adipose tissue were incubated in Parker's medium 199 and the rates of glucose incorporation into the lipids and release of glycerol determined. Both of these parameters increased in a linear fashion for about seven to eight days. After this period of time there was a decrease in the metabolic rates of explants with a mean cell size larger than about 90‐95 μm. The incorporation of glucose into the lipids was mainly recovered in the glycerol moiety of the triglycerides. Cellular enlargement was associated with an increase in glucose incorporation as well as glycerol release, i.e., an increased turnover of the glyceride‐glycerol. Addition of insulin increased the incorporation of label into the lipids. The stimulatory effect of a single dose of insulin was pronounced for two days and was only slightly discernible after 14 days. Addition of the enzyme inhibitor iodoacetate at a concentration of 10−4 M reduced the incorporation of glucose to about 5% of the controls. The method of tissue culture used in the present investigation may be a useful tool for metabolic as well as morphologic studies of human adipose tissue in vitro.
Immobilization and cartilage transformation into bone in the embryonic chick
Authors: Haal B. K.
Published: February 2005

The fate of the secondary cartilage present on the membrane bones of the embryonic chick has been studied after immobilization. Immobilization was achieved by the in vivo injection of paralysing drugs (tubocurare or decamethonium), by grafting membrane bones onto the chorioallantoic membrane, or by organ‐culturing membrane bones in vitro. In all three situations the cartilage was transformed into a bone‐like tissue, the matrix losing its acid muco‐polysaccharide, accumulating collagen and undergoing calcification. The chondrocytes shrank in size, came to resemble osteoblasts (osteocytes) and acquired alkaline phosphatase activity.

In normal development this cartilage is not transformed into bone but is partly replaced by bone and partly converted into a fibrocartilage which forms the definitive articular cartilage. Immobilization prevented this normal sequence.

Past studies on the transformation of cartilage to bone are reviewed and are seen to be adaptations of a highly labile tissue to functional demands.
Anatomical observations on the arterial supply to the lumbosacral spinal cord of the cat
Authors: Chambers Gail , Eldred Earl , Eggett Chris
Published: February 2005

The pattern of arterial supply to the cat's lumbosacral spinal cord was examined in a dozen latex‐injected specimens with a view to determining what precautions might be taken in the procedure of rhizotomy to minimize embarrassment of the cord's circulation. The single ventral spinal artery was found to receive on an average 4.1 significant radicular contributions, of which one or two arteries at the fourth or third lumbar levels on the left were invariably of especially large size. Equal numbers, about six to eight, of contributions to the two dorsolateral arterial trunks were present. Anastomotic channels greater than 50 m̈ in diameter were rather poorly developed between dorsolateral and ventral arterial channels, especially across the middorsum. The dorsal radicular artery in 82 of 97 roots examined was seen to pierce the ventral root in order to reach a position along the ventral aspect of the dorsal root. In most cases this penetration occurred central to the ganglion. The bearing of this feature on reported differences in behavioral effects from rhizotomy by intradural section and by ganglionectomy is discussed, as well as other aspects of the effect of rhizotomy on cord criculation.
Identification and enzyme quantitation of the stages of the seminiferous epithelial wave in the rat
Authors: Ant Martti Parvinen , Vanha‐Perttula Tapani
Published: February 2005

Based on differences in light absorption the stages of the rat seminiferous epithelial wave were identified by a transillumination technique. The most marked difference was encountered in the boundary between stages VIII and IX where the mature spermatozoa are released into the tubular lumen. Other characteristic transitions were observed between stages VI and VII as well as stages XII and XIII. All stages could be divided into four major, easily recognizable zones. Within the zones the stages could be identified with an accuracy of ± 1 stage. The characteristic changes take place in the tubular center and are due to the development of the acrosome in the spermatid. The acrosome appears to contain material with a strong light absorption capacity.

Based on these observations a method was developed to isolate identified fragments of the rat seminiferous tubule in native condition. These fragments were used to quantify the activity of three previously described enzymes: specific tubular acid phosphatase III and IV as well as aminopeptidase III.

The tubular acid phosphatase IV showed a high activity in stages corresponding to the final maturation process of the spermatid, whereas acid phosphatase III was evenly active in the different stages. Also aminopeptidase III showed a peak of activity during stages V‐VII coincident with that of acid phosphatase IV, The possible role of these enzymes in the morphological maturation of spermatid and the destruction of the residual body is discussed.
A comparison of a systematic sampling method with complete random sampling for estimating total numbers of nerve fibers
Authors: Tang Douglas B. , Ebbesson Sven O. E.
Published: February 2005

This paper considers the sampling precision of a systematic sampling method for estimating total number of nerve fibers exposed on cross section of a nerve trunk. The mean square error (MSE) associated with systematically selecting every Kth grid square (traversing the section in a serpentine pattern) was determined in each of nine nerve fiber populations and compared to the MSE obtained using a completely random selection of grid squares.

For both sampling methods sampling errors of approximately 10% could be achieved by counting in 10% (K = 10) of the available grid squares. To reduce the MSE to 5% or less necessitated, for both methods, counting approximately 50% (K = 2) of the cross sectional area.

Although the results of this investigation are based on the study of but one class of nerve fiber population (cervical sympathetic nerve trunks), the authors believe that certain of the results will have practical application in similar quantitative studies. More important, it is hoped that this study will motivate further investigations into the precision of sampling methods currently employed (and others which may be proposed) in the quantitative study of the nervous system.
The role of androgens in the epithelio‐mesenchymal interactions involved in prostatic morphogenesis in embryonic mice
Authors: Cunha Gerald R.
Published: February 2005

Standard tissue culture and epithelio‐mesenchymal separation and recombination techniques were applied to the question of sex determination of the male urogenital sinus of embryonic mice. Explants of urogenital sinuses from 12‐ to 17‐day old embryos were cultured in an androgen‐free environment to a gestational age equivalency of 18 to 20 days. The developmental response of these explants led to the following conclusions: (1) Androgens are necessary for initiation of prostatic bud outgrowth; (2) The effect of androgens can be demonstrated at the stage when the fetal testis begins to secrete androgens; and (3) Prior to the appearance of prostatic buds, the urogenital sinus has the capacity to pursue that developmental end‐point independently of further androgen stimulation. In addition, the developmental response of recombinants composed of androgen‐treated and untreated epithelium and mesenchyme from the urogenital sinus has shown that it is the epithelium which is primarily determined by androgens during prostatic morphogenesis.
The ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat epididymis
Authors: Hoffer Anita P. , Hamilton David W. , Fawcett Don W.
Published: February 2005

The ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat caput epididymidis was examined with the electron microscope. Specializations of the principal cells associated with absorption include numerous endocytic invaginations of the cell surface, numerous coated vesicles and multivesicular bodies in the apical cytoplasm. It was demonstrated that particulate tracers are taken into the cells and sequestered in secondary lysosomes and multivesicular bodies. Morphological features consistent with secretory activity are also found in the principal cells and include numerous cisternae of rough endoplasmic reticulum with a flocculent grey content and an extremely well‐developed Golgi apparatus. The speculation that the principal cells are actively secretory despite the absence of secretory granules formed in the Golgi and of a visible mechanism for release of the product at the cell surface is discussed.

The “halo cells” in the epididymal epithelium were also examined and it is shown that many of these cells are not typical migratory lymphocytes. Chief among the differences are their granule‐containing multivesicular bodies and more abundant endoplasmic reticulum. Nonetheless, it is conceivable that the halo cells are lymphocytes and that the conditions they encounter as they leave the circulation and enter the epididymal epithelium may stimulate morphological changes. The possible immunological significance of these observations is discussed.
A study of endocardial endothelium using freeze‐drying and scanning electron microscopy
Authors: Wheeler E. E. , Gavin J. B. , Herdson P. B.
Published: February 2005

The ventricular endocardium of 20 rats and five dogs was examined with a scanning electron microscope after careful washing with phosphate‐buffer, glutaraldehyde fixation and freeze‐drying. Endothelial cells formed a continuous sheet lining the ventricle in both species. Individual cells were identifiable by a central bulge corresponding to the nucleus and were separated by a polyhedral pattern of intercellular lines. The intimal surfaces of these cells were relatively smooth, although sometimes transverse ridges, small pseudopod‐like projections or indentations suggestive of macropinocytosis were present. Endothelial cells were relatively easily lost in preparation and shrinkage artefacts were also observed. These observations are compared with other scanning electron microscopic studies of endothelium and are discussed with particular reference to the effects of preparative procedures.
Intranuclear annulate lamellae in giant cells of the mouse chorioallantoic placenta
Authors: Pope Robert S. , Ollerich Dwayne A.
Published: February 2005

Intranuclear annulate lamellae were initially observed on day 9 of gestation. They increased in frequency until day 12, after which a decline in frequency was noted. Numerous IAL were in close association with nucleoli on days 11 and 12 and numerous large dilatations of the intermembranous space were present. IAL were also associated with cytoplasmic invaginations and inclusions of the nucleus. The frequency of invaginations and inclusions also increased from day 9 to 12 and brought increased amounts of cytoplasm into contact with the nucleus. Continuity of the intermembranous space of the IAL with the perinuclear space and the latter with the cisterns of rough endoplasmic reticulum suggested a possible route for nuclear‐cytoplasmic exchange in either direction.
Tubular myelin assembly in type II alveolar cells: Freeze‐fracture studies
Authors: Smith Una , Smith D. S. , Ryan J. W.
Published: February 2005

We have undertaken a study to coordinate examination of thin sections with that of freeze‐etched material. Results suggest that (1) lamellar bodies have a much more regular structure than hitherto believed. (2) The leaflets of some lamellar bodies reveal a unique substructure of ribs and intramembranous particles displayed in form and spacing (400‐500 Å) like those of tubular myelin as seen in the airspace. (3) As in other membranes of high metabolic activity the fracture face is covered with particles 80‐100 Å in diameter. Our freeze‐etch findings of the previously undetected organization and suborganization of lamellar bodies suggest an entirely new set of morphological criteria for evaluating the maturation of lamellar bodies and their role in the intracellular assembly of the reticular components of the airspace lining.
Axon diameter and myelin thickness—unusual relationships in dorsal root ganglia
Authors: Spencer Peter S. , Raine Cedric S. , WiśNiewski Henryk
Published: February 2005

Peripheral nerve fibers close to the sensory neurons of dorsal root ganglia displayed unusually thin myelin sheaths in relation to their axon diameter. Myelinated internodes along each fiber showed large differences in the numbers of myelin lamellae. These fibers are thought to represent spatial progression in degree of myelination as the axon egresses from the nonmyelinated glomerulus to the position of axonal bifurcation. This region is termed the initial complex of dorsal root ganglion cells. While the usual relationship between axon diameter and myelin sheath thickness is seen in the majority of dorsal root ganglion fibers, the fiber comprising each initial complex shows an atypical relationship in that the myelin sheath is unusually thin. Since the pattern of myelination in this small area is incongruous with previous reports attributing the control of myelin sheath thickness solely to axon diameter, the present findings indicate that other, unknown factors are operative in the control of myelination.