bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence of a role for cell death in the disappearance of the embryonic human tail
Authors: Fallon John F. , Simandl B. Kay 
Published: February 2005

AbstractThe development and disappearance of the human tail between stages 14 and 22 were studied using scanning and transmission electron microscopy, supravital staining and light microscopy. The tail is a prominent feature of the human embryo during stage 14 and is composed of paired somites, mesenchyme and extensions of the neural tube, notochord and gut. The tail grows with the embryo through early stage 17 when it extends more than a millimeter from the trunk. Overgrowth by the trunk at the base of the tail may account for the loss of part of its length during late stage 17 and stage 18. However, during stage 17 cells begin to die in all structures throughout the tail. Cell death continues in the succeeding stages reaching massive numbers by stages 18 and 19, and the tail becomes less and less prominent with developmental time. Most of the dead cells are phagocytosed. The debris‐laden macrophages appear to migrate from the tail to the body. By late stage 21 or early stage 22 there is no free tail. We conclude that cell death has a major role in the destruction of tail structures and the concurrent loss of the human tail.
Myocardial morphology in spontaneously hypertensive and aortic‐constricted rats
Authors: Lund Donald D. , Tomanek Robert J. 
Published: February 2005

AbstractThe cellular and subcellular adaptations in the myocardium of spontaneously hypertensive rats (SHR) were compared with those in Kyoto‐Wistar normotensive rats with cardiac hypertrophy induced by constriction of the abdominal aorta (ACR). Hypertensive blood pressure levels were attained at eight weeks of age in SHR and coincided with the surgically‐induced pressure‐overload in ACR at this age. Specimens from the subepicardial and subendocardial regions of the myocardium from glutaraldehyde‐perfused‐fixed hearts of 16‐week‐old animals were compared.Spontaneous hypertension and aortic constriction are associated with significant and comparable increases in heart rate, blood pressure, heart weight, and left ventricular muscle fiber diameter. While the cardiomegaly in both models was accompanied by a decrease in capillary density, the decrement was greater in the aortic‐constricted rats. Stereological analysis of cardiocytes revealed an increase in myofibril/cell‐volume, and a decrease in mitochondria/myofibril‐volume ratios in both models of cardiomegaly. In addition, double intercalated discs and subsarcolemmal foci containing abundant sarcoplasm with numerous small mitochondria, free filaments and Golgi complexes were commonly observed in both experimental groups. Cell diameter increased by a larger increment in the subendocardium than in the subepicardium, but capillary density was similar in these two regions. While aortic constriction was associated with dilatation of T‐tubules and the non‐specialized junctions of the intercalated disc, the myocardial ultrastructure of SHR was characterized by a greater number of lipid droplets and an increased folding of the intercalated discs comprising the subendocardial region.These findings suggest that data based on surgically‐induced pressure‐overload should be extrapolated cautiously to cardiomegaly associated with spontaneous hypertension. The differences between the adaptations in the two models may be due to either (1) the rate at which hypertrophy occurs or (2) some other, possibly genetic, factors unique to SHR.
Localization of human pancreatic polypeptide in an argyrophilic fourth cell type in islets of the rat pancreas
Authors: Schweisthal Michael R. , Schweisthal Janet V. , Frost Cecil C. 
Published: February 2005

AbstractAn argyrophilic fourth cell type in the rat pancreatic islet can be differentiated from other silver‐staining cells by using a modification of the Grimelius aqueous silver nitrate technique. Restaining of the tissues using fluorescent techniques with anti‐HPP (Human Pancreatic Polypeptide) serum results in bright fluorescence in the fourth cell type.
Developmental change in a basicranial line and its relationship to the upper respiratory system in living primates
Authors: Laitman Jeffrey T. , Heimbuch Raymond C. , Crelin Edmund S. 
Published: February 2005

AbstractThis study investigated the relationship between alterations in a basicranial line and changes in the upper respiratory system of selected non‐human primates and of man. This was done through multivariate analysis of craniometric measurements which describe midline exocranial flexion, and compares the analytical results with previous postmortem findings on upper respiratory structure and function.Craniometric analysis has shown that the skulls of the non‐human primate species studied and those of newborn human infants are relatively non‐flexed exocranially between the posterior border of the hard palate and foramen magnum. This finding corresponds to the relatively high position of their upper respiratory structures. In this group the tongue lies entirely within the oral cavity, and the epiglottis is found intranarial.After approximately the second year, humans exhibit marked exocranial flexion between the hard palate and foramen magnum. These basicranial changes coincide with concomitant changes occurring in the positional relationships of the upper respiratory system. After the second year the tongue and larynx have descended considerably into the neck, greatly altering their functional relationships.There thus appears to be a relationship between the exocranial orientation of the basicranium and the positioning of upper respiratory structures. There also appears to be a direct structural, and possible functional, relationship between (1) the position of the larynx, (2) the orientation of the pharyngeal constrictor muscles, and (3) the orientation of the basiocciput.
Neonatal muscle growth: A quantitative study
Authors: Ontell Marcia , Dunn Robert F. 
Published: February 2005

AbstractVarious growth parameters of the rat extensor digitorum longus muscle were studied during the first week of neonatal growth, including changes in weight, length, girth and fiber number. These quantitative studies were supplemented by ultrastructural analysis of fiber diameter and morphology in an attempt to determine the source of “new” muscle fibers in the neonate. In the 2‐day‐old extensor digitorum longus many of the myofibers were enclosed with other filamented cells (a satellite myofiber and/or myotube) in a common basement membrane, forming a cluster. Clusters accounted for 40% of the total independent filamented cells and clusters in 2‐day‐old muscles, for 2% in the 5‐day‐old, and for less than 1% in the 8‐day‐old. The decrease in the percentage of clusters occurred concomitantly with an increase in the number of independent filamented cells. In the 2‐day‐old there were 2,932 ± 130 independent cells and clusters; this number increased by 90% in the 8‐day‐old muscle. Mean diameters of filamented cells (whether found independently or as part of a cluster) increased from 6.5 μm to 7.4 μm and to 9.5 μm on days 2, 5, and 8 respectively. Increased filamented cell diameter between days 2 and 5 was a result of growth of the smallest filamented cells into the medium‐size compartment. Between the fifth and eighth day postpartum, the increase was due to the growth of both small and medium‐size filamented cells. The largest fibers did not increase in diameter during the first week of postnatal development, maximal fiber diameter in the 2‐day‐old being 15.9 μm and in the 8‐day‐old, 16.1 μm. At two‐days the area through the widest girth of the muscle occupied by filamented cells was 35% of the total cross‐sectional area of the extensor digitorum longus. At eight days muscle fibers occupied 59% of the cross‐sectional area. To accommodate the myofibers the muscle belly increased its girth, and there was a decrease in the percentage of the area occupied by interstitial tissue, nerves, and blood vessels.
Histochemical dichotomy of extrafusal and intrafusal fibers in an avian slow muscle
Authors: Ovalle W. K. 
Published: February 2005

AbstractThe avian anterior latissimus dorsi (ALD) is unique amongst vertebrates since it has been considered to be a true slow (or tonic) skeletal muscle. While the structure and function of the extrafusal fibers in the ALD have been intensively investigated, the intrafusal fibers of its muscle spindles and their relationship to the surrounding extrafusal fibers in this muscle have been virtually neglected. Serial frozen sections of this muscle from normal adult domestic chickens were tested for two separate enzymes: myosin ATPase after preincubations at differing pH (Brooke and Kaiser, '69) and NADH‐tetrazolium reductase, a mitochondrial‐bound oxidative enzyme. Both enzyme reactions were able to detect two distinct categories of extrafusal fibers in this muscle, as well as two classes of intrafusal fibers in its muscle spindles.Neither of the extrafusal fiber‐types reacted like typical fast (or twitch) fibers for myosin ATPase; they did not show a characteristic reversal in their relative staining patterns throughout the alkaline (pH 9.4) to acid (pH 4.6 and 4.3) preincubation range. The majority of fibers (type 1) were significantly larger in their cross‐sectional size, consistently stained lightly for ATPase, and showed high NADH‐TR activity. They represented about 84% of the total fiber population (n = 3540 ± 75). The other set of extrafusal fibers (type 2) constituted the remaining 16% of the total fiber population. They were smaller in diameter, exhibited high myosin ATPase activity, and reacted less intensely for the oxidative enzyme.The histochemical characteristics of the two kinds of intrafusal fibers were profoundly different from those observed in the extrafusal fibers. Their crosssectional fiber diameters were not significantly different from each other, and they exhibited a reversal in their staining reactions for myosin ATPase following acid preincubation for this enzyme.The results of this study concur with recently published reports of extrafusal fiber heterogeneity in the slow ALD muscle of the chicken. In addition, this work clearly demonstrates a histochemical dichotomy amongst the intrafusal fibers of muscle spindles in this muscle.
Spermatogonial intercellular bridges in whole‐mounted seminiferous tubules from normal and irradiated rodent testes
Authors: Huckins C. 
Published: February 2005

AbstractWhole‐mounted seminiferous tubules from normal and irradiated rodent testes were examined by light microscopy. These studies reveal the presence of intercellular bridges in all classes of spermatogonia except for the single As stem cells. It was demonstrated that As stem cells divide to produce new As spermatogonia or paired daughter cells that are united by a cytoplasmic bridge. Evidence was given that all subsequent progeny of these paired A's up to and including the production of type B spermatogonia remain linked by cytoplasmic bridges in increasingly larger and more complex syncytial networks.It is proposed that the intercellular bridges mediate both differentiation and degeneration of spermatogonia. The maintenance of synchronous development within cohorts of spermatogonia is attributed to the bridges. Moreover, the fact that spermatogonia in both normal and irradiated testes degenerate in clusters is determined by the presence of intercellular bridges. Lastly, the integrity of the bridges appears essential for normal germ cell development.
Localization of vitamin A‐storing cells in the mouse adrenal gland: An electron microscopic autoradiographic study
Authors: Hirosawa Kazushige , Yamada Eichi 
Published: February 2005

AbstractRadioactive vitamin A acetate was stored in specific cells in the mouse adrenal gland. Radioactivity was detected in lipid droplets of fibroblast‐like cells, whose distribution was from the capsule to the medulla. Their population was highest in the cortex. The morphology of these labeled cells was similar to that of vitamin A‐storing cells in other organs of mouse (Yamada and Hirosawa, 1976).Though functions of these cells are obscure, the fact that they are found in organs where metabolic activity of vitamin A is high suggests that they bear some role in the metabolism and storage of the vitamin.
Scanning electron microscopy of the kidney glomerular epithelium after treatment with polycations in situ and in vitro
Authors: Andrews Peter M. 
Published: February 2005

AbstractChanges in fine structure of glomerular epithelial cells (podocytes) were examined after treatment in situ and in vitro with polycations (i.e., protamine sulfate and poly‐l‐lysine). Scanning and transmission electron microscopic observations indicate that polycation‐induced alterations of the glomerular epithelium are similar in many respects to those resulting from puromycin aminonucleoside nephrosis. These alterations include the formation of junctional complexes between adjacent podocyte processes, flattening and retraction of podocyte processes, extensive folding of the slit diaphragms, formation of interpedicular microbridges, and development of irregular knobby surface‐microprojections. Prolonged treatment in vitro with high concentrations of polycations results in nearly complete loss of podocyte processes and the transformation of these once elaborate cells into simple polyhedral cells. The foregoing observations support the view that pedicel loss in puromycin aminonucleoside nephrosis may be due to a reduction in the glomerular epithelial polyanionic sialic acid surface coat.
Cerebral localization of insulin by immunofluorescence
Authors: Pansky Ben , Hatfield James S. 
Published: February 2005

AbstractAn immunohistochemical procedure was used to detect cells which appear to bind insulin in the mouse brain. Strong fluorescence was observed in the cell bodies and processes of tanycytes lining the third ventricle and in the choroid plexi. These findings suggest that insulin enters the central nervous system, and indicate a route for its possible transport. This adds credence to earlier observations that the hypothalamic ependymal cells and processes form a highly organized and functional system, with different cells selectively absorbing (or sensing) particular substances from the systemic and ventricular circulations and transporting them (or information about them) to specific neuron receptors in the hypothalamus.
Somatostatin‐containing neurons in the rat brain: Widespread distribution revealed by immunocytochemistry after pretreatment with pronase
Authors: Finley James C. W. , Grossman Gail H. , Dimeo Pia , Petrusz Peter 
Published: February 2005

AbstractImmunocytochemical staining after controlled proteolytic treatment of the sections with pronase revealed widespread distribution of neuronal cell bodies with somatostatin‐ like immunoreactivity (SLI) in the rat forebrain. SLI‐positive neurons were found in regions of the neocortex, the pyriform cortex, the cingulate cortex, the striatum, the olfactory tract and tubercle, the nucleus accumbens, the septum, and the hypothalamus. These results are consistent with previous radioimmunoassay findings and suggest the presence of large somatostatin‐like (possibly precursor) molecules in the neurons stained for SLI after pronase treatment.
Hypertrophy of astroglial processes in the dentate gyrus of the senescent rat
Authors: Geinisman Yuri , Bondareff William , Dodge John T. 
Published: February 2005

AbstractQuantitative electron microscopic analysis of the supragranular zone of the dentate gyrus molecular layer has shown that the number and volume fraction of profiles of astroglial processes are significantly increased in senescent rats relative to young adults. These ultrastructural modifications, which are not associated with significant age‐related changes in the number of astrocytes or in the width of the molecular layer, may result from a formation of new astroglial processes and/or elongation of existing ones. In either case, the increase in the number and volume fraction of astroglial process profiles is an indicator of age‐related astroglial hypertrophy. Hypertrophy of astroglial processes, which seems to develop with advanced age as a response to partial deafferentation of neurons, may compensate for a decrease in the dendritic volume fraction, thereby preventing changes in the dimensions of the dentate gyrus molecular layer in senescence.
Quantitative morphology and environmental responses of the pineal gland in the collared lemming (Dicrostonyx groenlandicus)
Authors: Quay W. B. 
Published: February 2005

AbstractCollared lemmings from Churchill, Manitoba, and their descendants were studied in captivity to define neuroendocrine and related histophysiological characteristics and responses, particularly in relation to photic and temperature conditions. Relatively great pineal size (0.1755 ± 0.0167 mm3, or 3.08 ± 0.30 = pineal volume in mm3 × 103/body weight in gm; N = 16) shown in this arctic rodent is consistent with the suggestion that pineal size and significance may tend to be greater in more northern (higher latitude) species. Total number of nucleated cells per pineal averaged 137,000 ± 10,500. Pinealocytes (105,000 ± 8,700/pineal) and other cell types were present in relative numbers typical of mammalian pineal glands, and were not numerically correlated with age, sex, or location or circumstances of birth and early postnatal life. Chronic exposure to warmer (21–27°C) in comparison with colder (−9 to −6°C) environments, whatever the illumination, led to greater pinealocyte activity, as shown especially by nucleolar diameter, throughout most of the nine regions of the organ analyzed cytologically (all regions combined: P < 0.001). Increased pinealocyte activity in chronic darkness was suggested by similar evidence (P < 0.01), but in comparison with the thermal effects, was less marked and more variable in different regions of the organ. These and other findings of this study indicate that the Dicrostonyx pinea organ is morphologically unique, relatively large in size, and cytologically responsive to environmental conditions.
Morphological development of the epithelium of the embryonic chick intestine in culture: Influence of thyroxine and hydrocortisone
Authors: Black Betty L. 
Published: February 2005

AbstractA culture system with defined medium has been utilized to elucidate the role of thyroxine (T4) and hydrocortisone (HC) in growth and differentiation of the epithelium of embryonic chick duodenum during the third week of development. Duodenal explants maintained a basically normal morphology for 48 to 72 hours, but during subsequent culture, muscle and mesenchyme deteriorated, previllous ridges shrank, the epithelial surface became pitted, and the tissue lost weight. These degenerative processes were retarded by addition of HC to the culture medium.Previllous ridges of cultured duodenum failed to develop into true villi and ridge growth was subnormal. Epithelial mitotic counts were increased by T4 or HC, as compared to cultured control tissue, but dropped below values in vivo, by 72 hours in culture.Epithelial differentiation proceeded more rapidly in duodenum cultured without hormones than in vivo. Increase in cell height, flattening of the epithelial surface, attainment of uniform staining of the brush border with periodic acidSchiff, increase in microvillar density, and formation of a terminal web were accelerated by 24 to 48 hours in culture. In the presence of T4, cell height and microvillar growth were stimulated further, reaching the state found at 19 to 21 days in vivo.
Regression of the larval opisthonephros during metamorphosis of the sea lamprey, Petromyzon marinus L.
Authors: Ooi E. C. , Youson J. H. 
Published: February 2005

AbstractThe opisthonephric kidney of larval anadromous sea lamprey, Petromyzon marinus L., undergoes a programmed regression during metamorphosis. Degeneration is initiated in the anterior end of each kidney and progresses posteriorly until the kidneys are reduced to short, pigmented strands by the end of metamorphosis.The first sign of degeneration in both the epithelium of the renal corpuscles and the tubules is a folding of the basal lamina. Autolysis then occurs throughout the entire epithelium of the nephron with the gradual accumulation of larger and greater numbers of acid phosphatase‐containing autophagic vacuoles, cytosomes, and myelin figures. Cytoplasmic debris and electron‐dense material accumulates in the tubular lumina and in the urinary space. Although no definitive evidence is provided for the method of removal of the tubular epithelium, macrophages play a large part in the phagocytosis of the components of the renal corpuscle. Mesangial cells appear to engulf debris from the capillaries while a second type of macrophage is involved in the destruction of podocytes and parietal epithelial cells. The method of programmed degeneration of the renal corpuscle closely resembles descriptions of the mammalian renal corpuscle in diseased conditions. The sole surviving element of the degeneration of the entire nephron epithelium is a pleated basal lamina.The regressing larval opisthonephros has potential as an alternative system for studying a normal developmental pattern such as tissue regression.
The development of the atrioventricular node and bundle in the ferret heart
Authors: Marino Thomas A. , Truex Raymond C. , Marino Deborah R. 
Published: February 2005

AbstractThe development of the atrioventricular (AV) node and bundle in the ferret heart was examined at the light microscopic level. The AV node develops from two primordia which were first observed in the posterior wall of the common atrium during the stage when the single heart tube convolutes. During septation of the heart, the AV nodal primordia eventually fuse and come to lie at the base of the interatrial septum. The right AV nodal primordium is located below the attachment of the right venous valve to the interatrial septum. The left AV nodal primordium maintains a position anterior to the prospective ostium of the coronary sinus. At 16 days of gestation, large pale cells were seen in the dorsal AV canal. By 21 days of gestation these AV canal cells have been replaced by AV bundle cells. At this time the bundle is continuous with both nodal primordia. At birth the AV bundle is continuous mainly with the component of the AV node that is derived from the right AV node primordium. The anulus fibrosus begins to undergo the greatest developmental change after the AV node and bundle attain their final position in the AV junction. However, the anulus does not completely separate the atria from the ventricles during the later stages of development nor at birth, so that accessory AV pathways are present in the newborn ferret heart. Both the AV node and the AV bundle also demonstrated continuity with the myocardial cells of the interventricular septum in the neonatal heart. During development there was no evidence that rings of specialized tissues at the junctions of the cardiac chambers give rise to any component of the cardiac conduction system.
Influence of iron upon the development of tetracycline‐treated mouse tooth germs in vitro
Authors: Kerley Michael A. , Kollar Edward J. 
Published: February 2005

AbstractThe inhibitory action of tetracycline on the development of embryonic mouse incisors cultured in vitro was examined. Explants exposed to tetracycline were severely inhibited in development. In contrast, tooth germs cultured in the presence of both tetracycline and iron escaped inhibition and attained a stage of development which compared favorably with the controls.