bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of streptozotocin on the secretory activity of ameloblasts in rat incisor as revealed by radioautography after 3H‐proline administration
Authors: Karim A. C. , Pylypas S. P. 
Published: February 2005

AbstractThe effect of a diabetogenic dose of streptozotocin on the secretory activity of ameloblasts was investigated in the rat incisor by radioautography. One group of male Sprague‐Dawley rats was injected intravenously with streptozotocin in citrate buffer (pH 4.5). One hour later, this group was again injected intravenously with 3H‐proline (2 mCi/kg). A control group of animals was injected with 3H‐proline only. All the animals were sacrificed in groups of three at 5 min, 1 h, 2 h, 4 h and 8 h after 3H‐proline injection by perfusion with 3% phosphate‐buffered formaldehyde followed by an additional perfusion with 2.5% phosphate‐buffered glutaraldehyde. The incisors were extracted with the jaws, demineralized, and prepared for radioautographic observations and analysis. The principal effects of streptozotocin were as follows: There was an inhibition of 3H‐proline incorporation into the secretory ameloblasts at 5 min after injection. This was followed by a larger uptake and a slower passage of the label out of the cells into the enamel matrix than that seen in the control sample. Finally, there was a slower secretion of labeled proteins out of Tomes' processes between 1 and 4 h after injection.Therefore, streptozotocin had a temporary inhibitory effect on the incorporation and secretion of 3H‐proline by the secretory ameloblasts of the rat incisor. This effect was present for about 4 h and was completely reversed 9 h after streptozotocin injection.
The accessory nerve nucleus in the baboon
Authors: Augustine James R. , White James F. 
Published: February 2005

AbstractIn the savanna baboon, Papio cynocephalus, the accessory nerve nucleus was identified by using a mixture of 20% free horseradish peroxidase (HRP) and 2.5% HRP conjugated to wheat germ agglutinin (WGA) in a 5% aqueous detergent solution (Nonidet P‐40). Following surgical exposure of the appropriate nerve branch to the sternocleidomastoid or trapezius muscle, the nerve was transected, placed in an Argyle tubing collar, and bathed in 5–10 μl of the tracer. After a 48‐hour survival time and vascular perfusion‐fixation, 40‐μm sections of the lower medulla oblongata and the cervical spinal cord were treated according to the tetramethyl benzidine (TMB)‐HRP method of Mesulam (J. Histochem. Cytochem. 26:106–117, 1978). The accessory nucleus extends as a distinct column of neurons from lower medullary levels into the rostral part of C5. One to ten labeled cells were present in each section, and all labeled neurons were located on the side of the bathed nerve. The rostral portion of the accessory nucleus occupies a central position, its intermediate portion occupies a lateral position, and its caudal portion occupies a central position within the ventral horn. All labeled neurons were confined to Rexed's lamina IX, ranged from 15 to 75 μm in diameter, and were either distinctly round (oval) or stellate in shape. Neurons within the baboon accessory nucleus supplying the sternocleidomastoid muscle were located from lower medullary to upper C2 spinal cord levels, while those supplying the trapezius muscle extended from C2 to C5.
Morphology of norepinephrine‐induced acute renal failure in the dog
Authors: Bulger Ruth Ellen , Burke Thomas J. , Cronin Robert E. , Schrier Robert W. , Dobyan Dennis C. 
Published: February 2005

AbstractThe 40‐minute infusion of norepinephrine (NE) into the renal artery of dogs produces a reversible ischemic model of acute renal failure. While the physiology of this model has been extensively studied, no complete description of the pathology exists. This study uses light microscopy and transmission electron microscopy to describe and quantitate the structural and ultrastructural changes which occur in the kidneys of dogs 1, 3, and 24 hours after the intrarenal infusion of 0.75 mg/kg/minute of NE. One hour after a 40‐minute NE infusion the majority of convoluted and straight proximal tubules showed apical blebs, loss of brush border, microvillar whorl formation, and mitochondrial condensation and high‐amplitude swelling with flocculent densities. Necrotic cells were occasionally seen at 1 hour. The injury was progressive after 3 hours and by 24 hours animals had either complete or partial patchy necrosis of all regions of the proximal tubule. The percentages of injured and necrotic proximal tubules in outer, mid‐, and inner cortical regions are presented. We conclude that the extent and pattern of injury seen after NE infusion differs significantly from the renal artery clamping model of ischemia.
Denervation‐induced changes in cell proliferation in the rat molar after wounding
Authors: Chiego Daniel J. , Klein Robert M. , Avery James K. , Gruhl Iris M. 
Published: February 2005

AbstractThe dental pulp has the capacity to initiate and maintain repair after trauma. The purpose of the present study was to quantitatively analyze the role of the peripheral nervous system in regulation of pulpal cell proliferation in response to wounding. Six groups often rats were used in these studies. There was one baseline group (wounded, but innervation intact) and five resection groups. The resection groups included rats with unilateral superior cervical ganglionectomy (SCG), unilateral inferior alveolar nerve resection (IAN), unilateral chorda tympani (CT) resection, IAN + SCG, or a complete unilateral nerve resection (IAN + SCG + CT). One millimeter of enamel and dentin was removed from the first mandibular molar on the experimental (resected) side. Therefore, each rat had an experimental and control molar. Rats were killed at various intervals from day 0 to day 15 after wounding and received 0.5 μCi/g b.wt. 3H‐thymidine 1 hour before death. For the baseline (innervation intact) data a peak in 3H‐thymidine incorporation occurred at 5 days after wounding. In the resected groups, there was a general increase in the number of labeled cells at the zero time point, and a suppression of the 5‐day peak with a delay in the proliferative response to wounding. The SCG + IAN‐resected group maintained the lowest number of labeled cells throughout the entire experimental period compared to the experimental baseline data and the two controls. At the initial and termination points the SCG + IAN‐resected groups demonstrated the highest number of labeled cells. The baseline data indicate that the maximal response to wounding occurs at day 5. Denervation results in a delay of the cell proliferative response to wounding with the most dramatic delay occurring in the IAN + SCG‐resection group. The results indicate that the autonomic and sensory components of the peripheral nervous system may interact in regulating the proliferative response of pulpal cells to wounding.
The structure of the atrioventricular conducting system in the avian heart
Authors: Szabóa Erno , Virágh Szabolcs , Challice Cyril E. 
Published: February 2005

AbstractThe atrioventricular conduction system in three avian species has been studied by light and electron microscopy. A morphologically definable atrioventricular node was not found in any of these. The atrioventricular bundle is a well‐defined structure, the proximal portion of which is in direct continuity with the atrioventricular ring, located in the arterial sheet of the muscular valve of the right atrioventricular opening. In the zone of transition between atrioventricular ring and bundle the compactness of the bundle is loosened, but the fibers do not establish continuity with the atrial fibers. The ring consists of Purkinje‐like fibers, 10–15 μm in diameter, and (peripherally) small 3–5‐μm‐diameter junctional fibers which are in continuity with the common atrial fibers. In the muscular atrioventricular valve the fibers of the ring are insulated from the ventricular myocardium by a connective tissue sheet of the annulus fibrosus. It is suggested that in the avian heart the atrioventricular ring may fulfill a role similar to that of the atrioventricular node of mammals.
Orthogonal arrays of particles in the gastric parietal cell of the rat: Differences between superficial and basal cells in the gland and after pentagastrin or metiamide treatment
Authors: Bordi Cesare , Amherdt Mylègne , Perrelet Alain 
Published: February 2005

AbstractThe basolateral plasma membrane of gastric parietal cells is characterized by the presence of orthogonal arrays of particles revealed by the freeze‐fracture technique. These arrays were quantitatively assessed in freeze‐fracture replicas of the gastric mucosa at two different levels of the gastric gland and after pentagastrin and metiamide treatment. The arrays were small and scarce in parietal cells located in the upper part of the gland, while they were markedly more abundant in parietal cells situated at the base of the gland. In both superficial and basal cells, the concentration of the arrays was significantly decreased after pentagastrin or metiamide treatment. This decrease was not due to an increase in the surface area of the basal plasma membrane. These results indicate that the concentration of the orthogonal arrays is a distinctive feature between superficial and basal parietal cells and that the arrays can be modulated by parietal cell function.
Effects of 30% intestinal resection on whole population cell kinetics of mouse intestinal epithelium
Authors: Cheng Hazel , McCulloch Christopher , Bjerknes Matthew 
Published: February 2005

AbstractThe intestine remaining after resection undergoes a well known compensatory response. Crypts and villi grow in size, and the number of proliferating cells in a crypt increases. The crypt labeling index, however, is unchanged, which is thought to suggest that the growth fraction also remains unchanged and hence that the system is enlarged, but otherwise the new steady‐state is similar to that of the controls. It is also generally accepted that no new crypts or villi are added to the adapting bowel. In this study we applied recently developed tools to study the response of the intestinal epithelium as a whole. Thus, the effects of 30% intestinal resection on whole population cell kinetics were determined by using flow cytometry, Coulter particle counting, and simple morphometric techniques.In addition to the classic response, we found an increase in the rate of crypt production, which was due mainly to a shorter crypt replication cycle. Thus, new crypts were produced at a faster rate in the resected animals than in the transected controls. This resulted in an expansion of the crypt cell population in the epithelium folllowing resection. There was a corresponding expansion of the cycling cell population and thus an increase in the growth fraction of the resected epithelium. We conclude that for the crypt population, the classic story is correct with the exception that new crypts are added to the epithelium after resection. However, for the epithelium as a whole, the classic story is misleading as there appears to be an increase in the growth fraction of the epithelium after intestinal resection.
Telencephalic microvessels of premature beagle pups
Authors: Leuschen M. Patricia , Nelson Robert M. 
Published: February 2005

AbstractThe ultrastructural morphologic and morphometric characteristics of the telencephalic microvasculature of both germinal matrix and border‐zone cerebral cortex are analyzed from premature beagle puppies delivered by caesarean section in order to determine whether differences in the matrical vessels could account for their susceptibility to intraventricular hemorrhage. The germinal matrix microvessels are immature, since they contain intraluminal microvilli and junctional complexes (primarily tight junctions) that are not continuous between the lateral endothelial cell walls. The number of junctional complexes per vessel crosssection is less than either cortical vessels from the same premature animals or tissue from either site in full‐term animals. Morphometric data on the cross‐sectional area of vessels from the two sites indicate that the germinal matrix vessels have a significantly larger cross‐sectional area than the cortical vessels. The increase is due almost exclusively to a larger endothelial cell area per cross section. This pattern is an altogether different one from that seen in the term animals. There the germinal matrix vessels exhibit a steadily decreasing luminal area from birth through 72 hr, whereas endothelial cell cross‐sectional area is static. Here the luminal cross‐sectional area is smaller, but both endothelial cell and total vessel cross‐sectional areas are significantly larger. Structural components of the blood‐brain barrier undergo active modifications during the late prenatal period that are distinct from the modifications during the immediate postnatal period.
Remodeling of bone and bones: Effects of altered mechanical stress on the regeneration of transplanted bones
Authors: Storey Elsdon , Feik Sophie A. 
Published: February 2005

AbstractWe divided 116 rats weighing 50 gm into four groups with tails either left in situ or transplanted as follows: (1) straight in situ: untreated controls; (2) bent in situ: five caudal vertebrae (CV) in the loop; (3) straight transplants: three CV skinned and transplanted autologously; and (4) bent transplants: five CV skinned, bent to form a loop, and transplanted autologously. Tails were radiographed weekly up to 6 weeks and at 12 weeks, and microradiographic and histological studies were undertaken on selected specimens. At 12 weeks the bones in the apex of the loop of tails left in situ appeared bent with a straight‐to‐convex shaft on the outer side and a thicker, more concave one on the inner side. In the transplanted bent segments the bone shaft died and initially the reverse occurred: the outer shaft thickened and the inner resorbed completely. A new concave inner diaphysis then formed so that the bones in both instances were essentially similar in final shape. In the bent transplants the surviving osteogenic tissues regenerated and, adapting to the altered forces, formed a new bone shaft. This involved a change in the direction, amount, and nature of endochondral, periosteal, and regenerative growth and subsequent remodeling of bone. The results support previous observations that, within limits, the strain in the osteogenic envelope is an important factor in adaptation of bones to changing stress and that, where the envelope is deficient, the surviving tissues have the capacity to regenerate and repair defects in the bone so that it best resists the changing stresses applied to it.
Three‐dimensional reconstruction of vesicles in endothelium of blood‐brain barrier versus highly permeable microvessels
Authors: Coomber B. L. , Stewart P. A. 
Published: February 2005

AbstractIn this study the three‐dimensional organization of pinocytotic vesicles in mouse endothelia from permeable (choroid plexus, area postrema, and skeletal muscle) and blood‐brain barrier (bbb) (cerebral gray and white matter) microvessels was examined. Reconstructions of 75 segments of endothelial cells from microvessels were done with very thin (<23 nm) serial sections and tracings. A total of 2,013 vesicles from five tissues were reconstructed for this study. Vesicles were classified as to whether they were attached to other vesicles (fused), connected to golgi or endoplasmic peticulum (tubule‐connected), open to vessel lumen or ablumen (surface‐connected) or isolated in the cytoplasm (free).The densities of tubule‐connected vesicles and free vesicles were the same in all four types of vessels. It seems unlikely, therefore, that these vesicles are related to vascular permeability. Vesicular clusters and surface‐connected vesicles were found in much higher densities in area postrema, choroid plexus, and skeletal muscle vessels than in bbb vessels. Single‐vesicle transendothelial channels were found in attenuated endothelia of area postrema and choroid plexus. These results support the hypothesis that endothelial vesicles play a role in vascular permeability, possibility by transient fusion of vesicle clusters to the plasmalemma, to form transendothelial channels.
Abnormalities of smooth muscle, basal laminae, and nerves in the aganglionic segments of the bowel of lethal spotted mutant mice
Authors: Tennyson Virginia M. , Pham Tuan Duc , Rothman Taube P. , Gershon Michael D. 
Published: February 2005

AbstractThe terminal portion of the bowel of the lethal spotted mutant mouse (ls/ls) lacks an enteric nervous system due to the failure of neural crest precursors to colonize this region during embryonic life. As a result, the mouse develops congenital megacolon. We have postulated that the defect occurs because the microenvironment of the aganglionic segment is segmentally abnormal and does not permit the migration and/or survival of the enteric neural or glial precursors in the affected zone. We have examined the terminal segment of adult ls/ls and control mice by light and electron microscopy to determine if the defect is associated with identifiable structural abnormalities that persist to maturity. A striking abnormality is an overgrowth of the muscularis mucosa in the adult ls/ls mouse, particularly in the outer longitudinal layer. Electron microscopy also reveals an extensive thickening of the basal lamina around smooth muscle cells. In addition, nerves that are derived from fibers that are extrinsic to this area are abnormal. Large bundles of nerve fibers, some of which contain myelinated axons, large‐caliber unmyelinated axons, and abundant collagen, are prominent in the intermuscular region of the aganglionic segments and often reach into the submucosa. The supporting cells of the unmyelinated and myelinated nerves in the aganglionic segment have voluminous perineural cytoplasm typical of immature Schwann cells. They also exhibit intermediate filaments in their cytoplasm. Otherwise they have the typical morphology of peripheral Schwann cells, rather than enteric glia, including individual ensheathment of axons and a surrounding basal lamina. We suggest that the extracellular matrix and/or cells of mesenchymal origin of the terminal bowel of the ls/ls mouse may prevent the ingrowth of the normal precursors of the glia as well as neurons of the enteric nervous system, but may permit or even encourage the ingrowth of abnormal numbers of extrinsic axons.
Effect of 16, 16‐dimethyl prostaglandin E2 methyl ester on weanling rat skeleton: Daily and systemic administration
Authors: Furuta Yoshihisa , Jee Webster S. S. 
Published: February 2005

AbstractThe effects of 0, 0.3, 1.0, and 3.0 mg of 16,16‐dimethyl prostaglandin E2 methyl ester (Di‐M‐PGE2) per kilogram per day administered subcutaneously for 21 days to fluorescent‐labeled weanling rats were studied, by single‐photon absorptiometric and static and dynamic histomorphometric techniques, to determine possible alterations in growth and mineralized tissue mass and their mechanisms of response. Specimens of femurs, proximal tibia, and tibial shaft were analyzed. Di‐M‐PGE2 caused a reduction in bone elongation and a dramatic accumulation in metaphyseal trabecular hard tissue mass. At high doses, the growth cartilage exhibited reduced thickness and degenerative cell size and cell production rate. The increased metaphyseal trabecular hard tissue mass was restricted to the secondary spongiosa region and was observed at all dose levels. The metaphysis was further characterized by an increase in bone and calcified cartilage cores, a marked elevation in osteoblast and osteoclast numbers, in osteoblast‐to‐osteoclast ratios, and in ratios of differentiated cells to osteoprogenitor cells. These findings were consistent with the interpretations that Di‐M‐PGE2 (1) depressed bone elongation by delaying the division and maturation of growth plate chondrocytes; (2) stimulated the differentiation of osteoblasts and osteoclasts, thus generating more differentiated bone cells but suppressing their activities; and (3) incresed metaphyseal trabecular hard tissue by creating an imbalance in osteoblasts over osteoclasts and suppressing hard tissue resorption.
Effect of controlled dietary consistency and cage environment on the rat mandibular growth
Authors: McFadden L. R. , McFadden K. D. , Precious D. S. 
Published: February 2005

AbstractForty Fischer strain inbred albino rats, evenly divided by sex, were obtained at 9 days of age. The animals were weaned at 21 days and randomly divided into the four experimental groups. Two variations on dietary consistency, hard and soft diet, as well as two variations on cage environment, normal and no biting surfaces, constituted the experimental groupings. The experimental period consisted of 16 weeks during which the animals were raised under the designated conditions. At the end of the experimental period the animals were killed with carbon dioxide, and the entire mandible, and both femurs, were dissected free. Weight and volumetric analysis were carried out in a standard fashion on the cleaned specimens. Area and linear measurements were performed and analyzed with a specially designed computer program. The results showed that there was sexual dimorphism in the Fischer rat both with respect to body weight and the weight, volume, area, and linear measurements of the mandible. The effects of dietary consistency had a greater influence on mandibular ramus size and form than did those caused by alteration in cage environment. The posterior region of the mandible, in association with the heavy muscles of mastication, was affected more by dietary consistency than was the anterior region. The entire region of the mandibular ramus acted as an area of adaptation and growth. The findings of this study indicate that dietary consistency has a small but significant effect on mandibular size in specific measurements. The cage environment used in this experiment did not limit function to the extent necessary to see measurable changes in mandibular measurements.
Crypt production in normal and diseased human colonic epithelium
Authors: Cheng Hazel , Bjerknes Matthew , Amar Jack , Gardiner Geoffrey 
Published: February 2005

AbstractNew crypts are added continously to the adult mouse intestinal epithelium by a process of crypt replication. Branching crypts found in the epithelium represent a stage in the process of crypt replication. In “normal” human colonic epithelium we found a small but definite percentage of branching crypts, 0.44 ± 0.16, indicating that new crypts are being produced at a low rate in this epithelium. Significantly higher (P < .001) percentages of branching crypts, 30.4 ± 5.75, 15.1 ± 1.08, and 13.2 ± 1.05, were found in diseased colonic epithelium from patients with ulcerative colitis, Crohn's disease, and multiple polyposis, respectively. These results may be interpreted as suggesting that the rate of crypt production in human colonic epithelium is increased in a number of disease states. We concluded that, as in the mouse intestinal epithelium, the rate of the crypt replication process in human colonic epithelium is plastic and may respond to a variety of conditions.