bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of the embryonic chick otic placode. I. Light microscopic analysis
Authors: Meier Stephen 
Published: February 2005

AbstractAt the 7–8 somite stage of embryonic chick development (29‐31 hours of incubation), a slightly elliptical island of thickened ectoderm appears laterally on either side of the most distal constricture of the rhombencephalon at the level of the anterior intestinal portal. The appearance and extent of this auditory placode is precisely correlated with the subjacent accumulation of neural crest cells. By 33 hours of incubation, there is a distinct depression in the developing otic placode, and by 40 to 45 hours, the placode is visibly invaginated, forming an epithelial vesicle or otocyst. Carefully staged embryos were serially sectioned, and the area underlying the developing otic placode was traced with a planimeter. It was found that placode size (area 60,000 μm2) is nearly unchanged from 30 to 42 hours of development. During this time interval, the placode cells first become columnar, show nuclear orientation, and then pseudostratify. The increase in placode cell number during this time interval is not likely to be the result of localized, accelerated cell division: the population doubling time of placode cells is eight and one‐half hours and the mitotic index of 2.5% is similar to that of cells in an equivalent area of adjacent, non‐placode forming head ectoderm. A model of otic placode formation is proposed which suggests that by 30 hours of development, a discrete population of placode forming cells is segregated from head ectoderm. Subsequent epithelial pseudostratification results from accumulation of this dividing population within the limits of the placode.
Maturation of the glomerular visceral epithelium and capillary endothelium in the puppy kidney
Authors: Hay Don A. , Evan Andrew P. 
Published: February 2005

AbstractThe present study describes the development and maturation of the glomerular visceral epithelium and capillary endothelium in an attempt to clarify kidney function in the neonate. The puppy kidney undergoes nephrogenesis for at least two weeks after birth, and thus possesses nephrons of different ages and levels of maturation. Since nephron development varies considerably from inner to outer cortex, renal corpuscles were examined within three arbitrary zones (outer, middle and inner cortex). The visceral epithelium of the smallest glomeruli, i.e., those of the outer cortex, is composed of cuboidal cells which are densely clustered and rests directly upon the limited number of small capillaries. More deeply within the outer cortex, broad, flat epithelial processes extend around the capillary, but lack any visible pedicels. Mid cortical glomerular capillaries undergo an increase in diameter and length, and at the same time the podocytes flatten and separate from one another. Pedicels begin to appear in this zone as thickened, disorganized processes. Juxtamedullary glomeruli are the largest, due primarily to their extensive capillary branching (looping). Podocytes are nearly adult‐like in appearance, with many long primary processes and pedicels.The endothelial morphology of glomerular capillaries varies from one loop to another, as well as within a single loop. The immature endothelium of outer glomeruli is initially characterized by extensive expanses lacking pores, multiple cellular layers and small, scattered pinholes. Greater capillary maturity is apparent in the mid cortex, due to an increase in pore number and diameter as well as greater attenuation of endothelial cells. However, evidence of remodeling and a lack of pores still exists in some capillaries. The glomerular capillaries of the inner cortex appear the most mature, but possess regions that are still immature when compared to the adult.
The occurrence of uterine stromal and intraepithelial monocytes and heterophils during normal late pregnancy in the rat
Authors: Padykula Helen A. , Tansey Terese R. 
Published: February 2005

AbstractThe steady decline in plasma progesterone level that occurs during the last week of pregnancy in the normal rat (Wiest, '70) provides good opportunity to study the effect of withdrawal of progesterone on uterine differentiation. Evidence is presented that tissue monocytes, heterophils, and eosinophils are regular components of the normal late gestational uterus and that their number increases as term approaches. Uterine monocytes and heterophils are located in the endometrial and myometrial stroma as well as within the basal intercellular compartment of the luminal epithelium. Stromal monocytes are distributed throughout the attenuated endometrium of late gestation, but are more common immediately beneath the luminal epithelium. In the myometrium, monocytes and heterophils occur, often as perivascular clusters, in the connective tissue septum that separates the two layers of smooth muscle. Eosinophils are present especially in the deep endometrial and myometrial stroma, and increase in number as plasma estrogen rises immediately before parturition. A small population of lymphocytes is regularly present.An important feature of the prepartum uterine stroma is the sparseness of macrophages. Near term, however, the beginnings of monocytic‐macrophagic transformation are noticeable as the cell surface becomes more irregular and organelles associated with endocytic activity arise. The prepartum monocytes are positioned in the same histological sites that during the postpartum period of regression will be occupied by macrophages (Padykula and Campbell, '76). Since it is generally accepted that monocytes are precursors of macrophages, this spatial correlation raises the possibility that cellular preparations for regression commence before birth. The possible significance of prepartum monocytic infiltration is discussed in relation to the effect of changing plasma and uterine concentrations of progesterone on uterine collagenase activity. The steady increase in uterine tissue leucocytes which occurs concomitantly with decreasing uterine binding capacity for progesterone supports the hypothesis by Siiteri et al. ('77) that progesterone in high local concentrations has an antiinflammatory effect.
Scanning electron microscopy of developing photoreceptors in the chick retina
Authors: Olson Mark D. 
Published: February 2005

AbstractPhotoreceptor morphogenesis in the sensory retina of chicks of 2 to 20 days incubation age was studied by scanning electron microscopy (SEM) and correlative transmission electron microscopy (TEM). At 9.5 days spherical inner segments extend into the subretinal space (optic ventricle). They are randomly arranged with chiefly smooth surfaces and contain centrioles, polyribo‐somes and microtubules. Microvilli project primarily from Muller cells. By the twelfth day immature ellipsoid and myoid regions have formed. Microvilli are abundant on the lateral surfaces of inner segments and extend over the entire spherical surface by the fifteenth day. Occasional cilia with surrounding depressions at their bases were also observed. Inner segments are more symmetrically arranged due to close proximity of photoreceptor cells. Inner segments elongate during the sixteenth day; many display a transitional ovoid form. Microvilli become less numerous but some persist as calycal processes. By the eighteenth day, conical shaped outer segments appear. Thereafter, all photoreceptor cells are comparable to those in the mature retina. Abundant microvilli on the external surface of the sensory retina suggest a supportive role in supplying adequate nutrition to the sensory retina during morphogenesis. The establishment and continual development of the ellipsoid and myoid appearto be primarily responsible for the elongation of photoreceptor cells.
Morphometry of tubular bodies in endothelial cells in normal, stable isolated perfused, and edematous dog lungs
Authors: Berendsen Peter B. , Defouw David O. 
Published: February 2005

AbstractThe volume densities and dimensions of tubular bodies (Weibel‐Palade bodies) in dog pulmonary capillary endothelial cells were examined by means of stratified random sampling and electron microscopic morphometry. The mean volume density of tubular bodies in normal (control) lungs was 0.43 ± 0.29%. The mean volume densities of tubular bodies in stable, isolated lungs perfused for 1/2 hour, 1 hour, and 2 hours and in lungs made edematous by increasing hydrostatic pressure or by decreasing oncotic pressure did not vary significantly from that of normal lungs. The mean thickness of the endothelium measured at the middle of the tubular bodies of normal dog lungs was nearly twice the mean thickness of the overall capillary endothelial cell sample. The mean endothelial thickness across tubular bodies from stable and from edematous isolated perfused lungs did not differ significantly from that of the control group. The mean width of tubular bodies from normal dog lungs was 0.25 ± 0.06 μm and the mean length was 0.81 ± 0.61 μm. The mean widths and lengths of tubular bodies from stable and from edematous isolated perfused dog lung endothelial cells did not differ statistically from those of normal dog lungs. Thirty percent of the tubular bodies in the sample were found to be adjacent to a mitochondrion in the same plane of section. Tubular bodies contained both tightly packed and loosely grouped tubules. It is concluded that the tubular bodies in canine pulmonary endothelial cells remain stable during the perfusion of isolated lungs and in oncotic and hydrostatic edema of isolated perfused lungs.
Secretory mechanisms of human ceruminous glands: A transmission and scanning electron microscopic study
Authors: Testa‐Riva Francesca , Puxeddu Paolo 
Published: February 2005

AbstractTwo secretory mechanisms (eccrine and apocrine) were observed by transmission and scanning electron microscopy in the same secretory cells of the human ceruminous glands.The eccrine secretion occurs as a typical exocytosis by fusion of the limiting membrane of the secretory granule with the apical plasmalemma. The apocrine secretion is more complex and takes place by sequential steps: bulging of the cellular apex into the lumen, constriction of the projection, and detachment of it from the cell. This mechanism generally causes the removal of the entire projection all at once by decapitation at its base; some variations of this process have been found, however, and are described in the present work.A double membrane, apparently separating the apical protrusion from the rest of the cell, is noticeable in our photographs. Nevertheless, even if this membrane is very similar to a demarcation layer, we consider it as an intercellular double membrane separating two obliquely sectioned cells.
A histochemical analysis of polyanionic compounds found in the extracellular matrix encountered by migrating cephalic neural crest cells
Authors: Bolender David L. , Seliger William G. , Markwald Roger R. 
Published: February 2005

AbstractNeural crest cells destined to form craniofacial primordia initially are “seeded” into and subsequently migrate through the extracellular matrix (ECM) of a cell free space (CFS) between the surface ectoderm and the underlying mesoderm. Utilizing histochemical procedures for polyanionic compounds, we have demonstrated that both sulfated and nonsulfated glycosaminoglycans (GAG) are present in the CFS of the cephalic region of the chick embryo and that their distribution and structural organization vary with the passage of neural crest or mesodermally derived (MD) mesenchymal cells through it. In stages 7 and 8 embryos a predominance of fine filamentous strands composed primarily of nonsulfated, carboxyl‐rich GAG is seen spanning intercellular spaces between adjacent tissues and MD mesenchymal cells. In older embryos (stages 9 and 10) much of the filamentous material is replaced by coarse fibrillar strands or amorphous material which coats the surfaces of MD mesenchymal and neural crest cells as they invade the CFS. Using enzymatic digestions (Streptomyces and testicular hyaluronidase) and the critical electrolyte concentration procedure, data suggest that the fine filamentous matrix onto which the neural crest cells migrate consists mainly of hyaluronate with lesser amounts of chondroitin and some sulfated GAG present. The coarse fibrillar matrix that appears after passage of either neural crest or MD mesenchymal cells through the original CFS contains strongly sulfated polyanionic material, predominantly chondroitin sulfates A, C. Since GAG is located ubiquitously within the ECM of embryos at various stages, the role of GAG, if any, in the transfer of developmental information may be of a general nature (ie, stimulus of motility) rather than of specific morphogenetic cues (for specific differentiation into craniofacial primordia).
An electromyographic study of the human lateral pterygoid muscles
Authors: Lehr Robert P. , Ownes Stephen E. 
Published: February 2005

AbstractAn electromyographic investigation of the lateral pterygoid muscles was undertaken to determine their activity relative to isolated and functional movements of the mandible. Data was obtained from 14 subjects. Intramuscular fine‐wire electrodes were used bilaterally in the lateral and medial pterygoid muscles. Surface electrodes were placed bilaterally on the skin over the temporalis and masseter muscles.Our data strongly suggest that separate roles for the superior and inferior heads of the lateral ptyergoid cannot be supported electromyographically. In addition, the lateral pterygoid is active in protrusive movements, including an incisor clench, and not active in retrusion or a molar clench. Both lateral pterygoid muscles initiate depression of the mandible and the contralateral muscle initiates a lateral transversion. The ipsilateral activity present is not sufficient to be an active stabilizer of the temporomandibular joint. In the chewing cycle, the lateral pterygoids are bilaterally active, both in alternation with and overlapping the elevating musculature. The sequence of the lateral pterygoid activity in the chewing cycle is led by the ipsilateral lateral pterygoid muscle.
Rat ovarian mast cells: Distribution and cyclic changes
Authors: Jones Richard E. , Duvall David , Guillette Louis J. 
Published: February 2005

AbstractNumerous tissue mast cells are present in the ovarian medulla and hilus and in the oviduct of rats. In the medulla, most of these mast cells are in the connective tissue of the stroma near blood and lymphatic vessels. During proestrus, many of the medullary mast cells totally degranulate and thus are not visible histochemically; they then regranulate during estrus. In contrast, the number of stainable mast cells in the ovarian hilus and oviduct does not change during the estrous cycle. Histofluorometric methods demonstrate that mast cells in the ovarian medulla and hilus, as well as the oviduct, contain histamine. In addition, the lining of small blood vessles in the ovarian medulla contains histamine. Thus, mast cell and blood vessel histamine secretion may play a role in ovarian function.
Adaptation of the masseter and temporalis muscles following alteration in length, with or without surgical detachment
Authors: Maxwell Leo C. , Carlson David S. , McNamara James A. , Faulkner John A. 
Published: February 2005

AbstractHistochemical properties, muscle fiber cross‐sectional area, muscle fiber length, and the oxidative capacity of masticatory muscles of female rhesus monkeys were assessed following alteration in functional length by an intraoral appliance or by detachment of the muscle. Experimental groups received the appliance only (A); the appliance and subsequent detachment of the masseter (AD); the appliance and detached masseter, but with surgical reattachment of the masseter to the pterygomasseteric sling (ADR); no appliance, but detachment and reattachment of masseter (DR); or an appliance which was removed after 24 weeks to study posttreatment responses (PT). Animals were sacrificed and the muscles were studied at intervals from 4 to 48 weeks after initiation of the experimental period. The results of these studies led to the following conclusions: (1) Stretching the masseter and temporalis muscles within physiological limits did not significantly alter the proportion of fiber types, although oxidative capacity of the fibers was reduced. (2) Fibers with “intermediate” myofibrillar AT‐Pase activity were no more prevalent in experimental than control muscles. (3) The cross‐sectional area of Type I fibers of masseter muscles decreased following some experimental procedures, indicating that recruitment of these fibers is the most sensitive to altered jaw function. (4) Minimal alteration of muscle capillarity was induced by any of the experimental procedures. (5) The lengths of masseter muscle fibers in Group PT and of temporalis muscle fibers in groups AD and ADR were greater than in control animals.
Three dimensional arrangement of mitochondria and endoplasmic reticulum in the heart muscle fiber of the rat
Authors: Segretain D. , Rambourg A. , Clermont Y. 
Published: February 2005

AbstractThe three‐dimensional arrangement of mitochondria and endoplasmic reticulum was studied in thick sections of the heart left ventricle fixed in glutaraldehyde and impregnated with the Ur‐Pb‐Cu technique and in thin sections of glutaraldehyde‐fixed tissue post‐fixed in potassium ferrocyanide‐reduced osmium. Squarish flattened mitochondria, approximately the size of a sarcomere, were arranged in longitudinal columns in the clefts between the myofibrils. At the periphery of the fiber, the endoplasmic reticulum took the appearance of a subsarcolemmal network of plate‐like and tubular cisternae running parallel to the cell surface. Between the myofibrils, the ER network formed longitudinally oriented repetitive units whose structure varied according to their position in relation to the A‐ or I‐ bands of the myofibrils. In front of the A‐band, the endoplasmic reticulum appeared as a single layered network of anastomotic tubules compressed between the adjacent myofibrils. In front of the I‐band, it formed a multilayered network the three‐dimensional arrangement of which was dependent upon the presence or absence of the T‐tubule. In the absence of the T‐tubule, the ER cisternae were loosely anastomosed and occasionally displayed bulbous terminal swellings. In the presence of T‐tubules, tubular ER cisternae were seen running parallel on both sides of the T‐tubules and were continuous with sheetlike cisternae sandwiched between the distended T‐tubule and adjacent extremities of longitudinally arranged mitochondria. These tubular or flattened cisternae were connected to each other by numerous bridging cisternae around the T‐tubules.
Tridimensional study of the deep cortex of the rat lymph node. V: Postnatal development of the deep cortex units
Authors: Bélisle C. , Sainte‐Marie G. 
Published: February 2005

AbstractABSTRACT Recently, the deep cortex of the adult rat lymph node was shown to be made up of semirounded lymphocytic “units.” Each unit is contiguous to the peripheral cortex, bulges into the medulla, and is centered on the opening(s) of an afferent lymphatic vessel of a node. Furthermore, each unit comprises a “center” and a “periphery,” bearing distinct morphological features. The present study investigated the postnatal development of the units in rats of various ages. One minute after birth, no lymphocytic structures were detected in the nodes. One day after birth, tiny rounded lymphocytic areas were detected in the developing cortex. These areas were topographically related to the openings of afferent lymphatic vessels. One week after birth, small semirounded lymphocytic areas with some morphological features of the adult deep cortex units were observed. Two weeks after birth, typical units were present in the nodes. The observations indicated that the rounded lymphocytic areas observed in nodes of rats aged 1 week or less were actually developing deep cortex units. The overall findings further provided information on the morphological processes involved during the postnatal development of the deep cortex units. Key words: lymph node, deep cortex, development of deep cortex, rat.
Olfactory receptor cell staining using horseradish peroxidase
Authors: Kauer John S. 
Published: February 2005

AbstractIontophoretic injection of horseradish peroxidase into severed olfactory nerve fascicles has been used to stain salamander olfactory receptor cell somata, their associated nerves, and their axonal terminations in the glomerular layer of the olfactory bulb. This technique gives homogeneous, Golgi‐like staining of individually identifiable receptor cells and has permitted preliminary mapping of the topographical relationship between the loci of receptors in the olfactory mucosa and sites of their termination in the glomerular layer in the olfactory bulb.
Ultrastructural analyses of control and enzyme‐treated isolated renal basement membranes
Authors: Carlson Edward C. , Meezan Elias , Brendel Klaus , Kenney M. Cristina 
Published: February 2005

AbstractGlomeruli and tubules were isolated from rabbit kidney cortex by mild homogenization and sieving. Mixtures of these renal components were treated with detergents to prepare pellets of morphologically intact and easily distinguishable tubular (TBM) and glomerular basement membranes (GBM). These BMs were prepared for electron microscopy after: (1) no treatment; (2) treatment with buffer alone; or (3) treatment with enzyme (pronase, trypsin, pepsin, collagenase or testicular hyaluronidase). Mixtures of TBMs and GBMs were treated in the same incubation medium to keep constant the enzyme concentration, temperature, pH, and duration of the treatment. Untreated TBMs showed collapsed, highly folded sheets of electron‐dense material. In contrast, control GBMs were thinner and strikingly resistant to changes in in vivo histoarchitecture. In all enzymatic treatments except hyaluronidase, TBM was more susceptible to digestion than GBM. In general, the effect of pepsin was greater than trypsin, which was greater than pronase. Collagenase also solubilized TBM but was only slightly effective in attacking GBM. Hyaluronidase‐treated BMs were indistinguishable from controls. TBMs and GBMs were both affected least by the enzyme on their epithelial surfaces, which generally remained crisp and sharply demarcated. In contrast, fibrillar materials and BM fragments were released from connective tissue surfaces of TBMs and endothelial‐mesangial surfaces of GBMs. Data in the present study indicate that various BMs are morphologically heterogeneous and that a “non‐unitary” concept of BM is most appropriate. Moreover, the BM “sidedness” demonstrated following enzymatic digestions strongly suggests that macromolecular complexes within laminae densae may be arranged such a manner that opposing surfaces of the same BM are compositionally disparate.