bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scanning electron microscopic study of chylomicrons incubated with lipoprotein lipase
Authors: Blanchette‐Mackie E. Joan , Scow Robert O. 
Published: February 2005

AbstractThe effects of lipolysis on the structure of chylomicrons were studied with the scanning electron microscope using rat chylomicrons incubated with purified bovine milk lipoprotein lipase for 20 minutes at pH 8.1. Since the amount of albumin added to the medium was limited, some of the free fatty acids and partial glycerides formed by lipolysis accumulated in the chylomicrons. Lipolyzed chylomicrons fixed with OsO4 at pH 7.4 appeared in scanning electron micrographs as spheres with multiply indented irregular surfaces, while those fixed at pH 5.5, as well as control chylomicrons fixed at both pHs, appeared as spheres with smooth surfaces. Sections of OsO4‐fixed specimens, viewed with the transmission electron microscope, showed that the core of lipolyzed chylomicrons fixed at pH 7.4 contained numerous circular electron‐lucent areas at the periphery, thus accounting for the indented surfaces observed above, while the core surfaces of the other specimens were circular and smooth. These findings confirm an earlier report that aqueous spaces form in chylomicrons during lipolysis when albumin in the medium is limited, and that the aqueous spaces disappear when specimens are prepared at pH 5.5 for microscopy. Thin sections of specimens that had been prepared for scanning electron microscopy showed that the gold‐palladium coating was deposited directly on the indented surface of the lipid core of lipolyzed chylomicrons fixed at pH 7.4. It is concluded that vacuum dehydration during specimen preparation ruptures the outer wall of the aqueous spaces in lipolyzed chylomicrons and thereby exposes the interior of the spaces to gold‐palladium coating and viewing with the scanning electron microscope.
A freeze‐fracture study of sarcoplasmic reticulum from fast and slow muscle of the mouse
Authors: Beringer Theodore 
Published: February 2005

AbstractSarcoplasmic reticulum (SR) of fast extensor digitorum longus (EDL) and slow soleus (SOL) muscles of the mouse was examined by freeze‐fracture techniques. A distinctive feature of sarcoplasmic reticulum from the EDL is the presence of hillocks on the A‐face within the terminal cisterns. These hillocks are usually arranged in a single row which is deployed parallel to the long axis of the adjacent T‐tubule. Center‐to‐center spacing of hillocks within a row is about 70–75 nm. Hillocks are also found scattered within the collar region. The EDL of ten week mice was characterized by sheet‐like terminal and intermediate cisterns, the latter being replaced in 37 week animals by thin tubular longitudinal elements of the SR which contain no hillocks or dimples.Hillocks occur only occasionally in SR from 10 or 20 week SOL muscle. In such cases the hillocks occur singly rather than in rows as in the terminal cisterns of EDL. The predominant form of SR in the SOL contains no hillocks.Total particles in the A‐face of EDL‐SR (2996 particles/μ2; S.D. = ± 287) slightly exceeded that of SOL‐SR (2558 particles/μ2; S.D. = ± 274 8 nm). Packing density of 8 nm particles was slightly higher for EDL (750/μ2) vs. SOL (700/μ2). The possible significance of these features of SR in fast and slow muscle is discussed.
Catecholamine‐containing nerve terminals in piloarrector muscles of stump‐tailed macaques (Macaca arctoides) and the effects of local injection of 6‐, and 5‐hydroxydopamine
Authors: Uno Hideo , Montagna William 
Published: February 2005

AbstractThe fluorescence histochemical method of Falck‐Hillarp ('62) demonstrates dense plexuses of catecholamine‐containing nerves in the piloarrector muscles of adult stump‐tailed macaques. When these muscle fibers are viewed under the electron microscope, most of the axon terminal profiles between them contain numerous dense‐cored vesicles (adrenergic); the rest of the terminals contain mainly agranular vesicles (cholinergic). Intradermal injections of 6‐hydroxydopamine (6‐OHDA, 1 and 5 mg) or 5‐hydroxydopamine (5‐OHDA, 10 mg) into the scalp caused the fluorescence from the nerve fibers in the muscles to completely disappear. The 6‐OHDA injections induced severe degenerative changes in the adrenergic terminals whereas the 5‐OHDA injections caused only the granules in the vesicles to increase in numbers. Thus, the piloarrector muscles of these macaques are innervated with both adrenergic and cholinergic terminals, but the former are more numerous than the latter.
The origin, migration and morphology of the primordial germ cells in the chick embryo
Authors: Fujimoto Toyoaki , Ukeshima Atsumi , Kiyofuji Ranko 
Published: February 2005

AbstractChick primordial germ cells (PGCs) which separated from the “germinal crescent” entoderm in the period from stages 4 to 8 circulated mostly through the developing blood vessels from stage 10 onward and finally migrated into the gonad. The PGCs making their appearance up to this stage were generally spherical in profile, about 14 μm in diameter. Some of the PGCs, in contrast, did not enter the blood vessels but remained in the tissue (mesenchyme) of the embryo proper (tissue PGCs) and possessed pseudopodial processes, suggesting their migration by means of amoeboid movements. The circulating PGCs emerged from blood vessels in the vicinity of developing gonads by three days (gonadal PGCs). The principal mechanism responsible for the subsequent migration of gonadal PGCs is assumed to be amoeboid movements as in the case of tissue PGCs. Notable amounts of PAS‐positive glycogen were demonstrated in the cytoplasm of PGCs in all stages observed. They also contained yolk and lipids intracytoplasmically, the former dissipating in relatively early stages of development. Electron microscopic observation revealed the electron‐opaque, “fragmented nucleolus” in the large nucleus (8 μm in diameter), which represented another prominent feature of chick PGCs. PGCs contained a well developed Golgi complex and endoplasmic reticulum.
Transplantation of the fetal rat pancreas: Quantitative morphological analysis of islet tissue growth
Authors: Hegre Orion D. , Leonard Robert J. , Rusin James D. , Lazarow Arnold 
Published: February 2005

AbstractWhen pancreases from fetal rats were transplanted beneath the kidney capsule of isologous normal adult recipients, continued growth and differentiation of the endocrine portion of the pancreas occurred. While limited amounts of acinar tissue were identifiable in the early transplant period (7 days), such cells were absent in long term transplants (14 and 21 days). In contrast, while few definitive islet beta cells were present at the time of transplantation, following 21 days at the kidney site large circumscribed islets comprised of heavily granulated beta cells in association with duct epithelial cells predominated. Mitotic figures were seen in both these cell populations. Total islet mass had increased over 20‐fold during the transplantation period. Similar results were observed if fetal pancreases were grown in organ culture for ten days prior to transplantation. Continued islet and duct cell growth, as evidenced by mitotic figures and an increase in absolute islet cell mass was obtained in such cultured explants when transplanted to either isogenic or allogenic recipients.These observations support the hypothesis that fetal pancreas may be the best source of donor material for transplantation to diabetic recipients, in part, due to the continued growth and differentiation of the islet tissue during the transplantation period.
The number of satellite cells in normal human muscle
Authors: Schmalbruch H. , Hellhammer U. 
Published: February 2005

AbstractThe satellite cell population in skeletal muscles of ten normal subjects aged 7 to 73 years was quantitated by electron microscopy. In all 1,414 nuclei were assessed. Satellite cell nuclei comprised 4% (standard deviation 2%) of all nuclei within the fibre basal lamina. The lowest incidence (0.6%) was found in a 73‐year‐old man. The study confirms, that satellite cells are regularly present in human skeletal muscle.
Scanning electron microscopy of cell surfaces following removal of extracellular material
Authors: Evan Andrew P. , Dail William G. , Dammrose Douglas , Palmer Charles 
Published: February 2005

AbstractThe application of scanning electron microscopy to the study of cell surfaces is limited in intact tissues, because extracellular material may often obscure the details of nonluminal surfaces. To remove connective tissue elements we have treated human skin and both kidney, and an autonomic ganglion of the rat with hydrochloric acid and collagenase. Regional variations in the basal surface of the nephron are noted following removal of the basement membrane. The basilar interdigitations of the cells of the proximal tubule appeared as parallel ridges encircling the tubule. Ridges on the parietal epithelium of Bowman's capsule were randomly arranged and alternated with smooth surfaces. The dermal surface of the human epidermis has an alveolar or honeycomb appearance due to the elevation of the epidermal ridges and numerous pits for the dermal pegs. At higher magnifications the basal surface of cells of the stratum germinativum possessed numerous and irregular projections. Neurons with their processes are evident in the autonomic ganglion. The soma of the neurons are enclosed by flattened satellite cells. Irregular spaces between opposed satellite cells are interpreted as regions for the passage of processes related to the ganglion cells. Nodes of Ranvier were clearly seen along nerve fibers. Some pitting of the nerve fibers was also noted. The HCl‐collagenase method has the advantage of the removal of collagen and basement membrane while preserving the structural integrity of the cell surface.
A quantitative histotopologic analysis of the variation in lobulo‐alveolar mitotic activity in the Lewis/Mai rat mammary gland during the estrous cycle
Authors: Purnell Dallas M. , Kopen Pamela 
Published: February 2005

AbstractQuantitative microscopic techniques were employed to determine relative mitotic activity of lobulo‐alveolar tissue in thick sections obtained from the inguinal mammary glands of colchicine‐treated post‐pubertal Lewis/Mai rats sacrificed at different phases of the estrous cycle. It was found that the magnitude of lobulo‐alveolar cell mitotic activity and the proportion of the lobulo‐alveolar tissue with mitotic activity undergo significant fluctuations during the estrous cycle. The frequency distribution of mitotic activity in lobulo‐alveolar tissue was different and heterogenous at each phase of the estrous cycle. The frequency distribution of nuclei in lobulo‐alveolar tissue during the estrous cycle showed only minor variations and could not explain the variation in mitotic activity. Similarly, no morphological differences were observed in the mammary gland which could account for the variation observed in mitotic activity.It was concluded that the variation in mitotic activity of lobulo‐alveolar tissue is probably related to alterations in the generation time of lobulo‐alveolar cells imposed by cyclical variation in ovarian hormones during the estrous cycle.
Holocrine cell Lysis in the rat preputial sebaceous gland. Evidence of autophagocytosis during cell involution
Authors: Mesquita‐Guimarãtes José , Coimbra Antonio 
Published: February 2005

AbstractThe fine morphological and cytochemical (acid phosphatase) changes occurring during holocrine cell lysis in the sebaceous preputial gland of the adult rat were investigated. When cells reach full differentiation cisternae of the widespread rough endoplasmic reticulum show invaginations of the wall. Cytoplasmi areas comprising such altered cisternae, normal RER and some mitochondria, are later sequestered into autophagic vacuoles, either surrounded by a single membrane (type I‐bodies), or by a thick wall formed by concentric membranes (type II‐bodies). Other vacuoles with similarly stratified wall and containing debris and acid phosphatase appear in cells at the next stage of involution. These autophagic vacuoles (type III‐bodies) are probably derived from type II‐bodies, and become gradually transformed into residual bodies rich in myelin figures, while the cell membrane and the nuclear envelope rupture. These findings show that prior to cell disintegration most of the cell cytoplasm, with the exception of the lipid and proteinaceous secretion granules and some mitochondria, is focally degraded within autophagic bodies.
Analysis of cell populations of normal and injured mouse lens epithelium. II. Contribution of local and migrating cells to wound healing
Authors: Rafferty Nancy S. 
Published: February 2005

AbstractThe contribution of progenitor cells in the normal peripheral region of mouse lens epithelium to healing of a centrally located wound was studied using an autoradiographic technique designed to follow migrating 3H‐thymidine labeled cells. It was found that few progenitor cells labeled before or at the time of injury migrate toward the wound and hence contribute little to the repair of the wound. Moreover, the central injury did not delay or reverse the normal migration of the labeled peripheral cells in the opposite direction into the bow. It is concluded from this and other studies that a central injury to the mouse lens is healed mainly by numerous local cells which are stimulated for the most part to traverse one replicative cycle of normal duration, and that the injury does not affect formation of new lens fibers. These findings are thought to be related to the observed low incidence of traumatic cataract in the mouse.
Ultrastructural arrangement and distribution of smooth muscle and striated muscle fibers in the cremaster of the guinea‐pig
Authors: Ninomiya Jesus G. , Merchant Horacio , Alonso‐Deflorida Francisco 
Published: February 2005

AbstractBesides the well‐known striated muscle fibers, the cremaster muscle of the guinea‐pig contains smooth muscle fibers, which appear either as isolated elements or as networks. These smooth muscle fibers are embedded within a matrix of the compact fibrous coat of collagenous connective tissue which covers the vaginal surface of the striated muscle layer. Presumably the smooth muscle fibers maintain the initial, fast contraction produced by the striated muscle fibers, thus attaining an economical, tonic elevation of the testicle.
Logarithmic growth of the hominoid mandible
Authors: Hildyard L. T. , Moore W. J. , Corbett M. Elisabeth 
Published: February 2005

AbstractThe growth of the basal unit of the mandible was studied by plotting the position, relative to the median plane, of the oval, mandibular and mental foramina in immature and adult skulls of Man, chimpanzee and gorilla. In Man, the basal unit was found to grow out along a constant logarithmic spiral. In the apes, the basal unit grew along a progressively unfolding logarithmic spiral, the amount of unfolding being greater in the gorilla than in the chimpanzee. It is argued that the mode of growth seen in the apes evolved, as these forms became more prognathous, because it requires less compensatory rotation of the mandible, while the mode seen in Man is probably closer to that which occurred in the common ancestral form.
Urogenital anomalies in fetal rats produced by the anticancer agent 4(5)‐(3,3‐dimethyl‐1‐triazeno) imidazole‐4‐carboxamide
Authors: Chaube Shakuntala , Swinyard Chester A. 
Published: February 2005

AbstractPregnant Wistar rats injected intraperitoneally on gestational day 12 with single doses (100–1,000 mg/kg) or 600 mg/kg of 4(5)–(3,3‐dimethyl‐1‐triazeno)imidazole‐4‐carboxamide (DIC) were autopsied on day 21 (100–1,000 mg/kg) or at 24‐hour intervals on days 13–20 (600 mg/kg). Controls received CMC on the same schedule. All fetuses were weighed and examined for urogenital system (UGS) malformations. Those given 600 mg/kg were also studied histologically.DIC produced significant growth retardation at all doses on day 21 (18–72%). UGS malformations occurred in 27–67% of the fetuses at 200–400 mg/kg and in 100% of those given 600 mg/kg or more of DIC. Abnormalities included renal growth inhibition, fusion, ectopia, and ureteropelvic dilatation. At 600 mg/kg renal and body weights were reduced 40 and 55%, respectively. Ureteropelvic dilatation was common, and cortical glomeruli, nephric collecting tubules, and papillae were retarded in development. The juxtamedullary glomeruli were well developed. Proximal nephric tubular mitotic activity was 85% greater than in control animals (day 17).On the basis of pertinent morphological and physiological data, it is postulated that the dilated upper urinary tracts represent functional hydronephrosis incident to severe renal retardation and its resultant compensatory response.
DNA synthesis in the oocyte of the mature mouse: A radioautographic study
Authors: Hoage Terrell R. , Cameron Ivan L. 
Published: February 2005

AbstractMice were injected three times over an 8‐hour period with a total of 48 m̈ci 3H‐T/gm of body weight and were sacrificed 1, 3, 5, 9 and 17 days afterwards. Radioautographs of the ovaries showed significantly higher grain counts in oocytes of follicles that are in the antrum formation stage. The radioautographic visualization of DNase digestible 3H‐thymidine incorporation into the juxtanucleolar region in oocytes of mature mice occurs in association with oocyte growth in follicles that are in the antrum formation stage.The scheduled disappearance of this juxtanucleolar oocyte DNA and its label during later oocyte growth suggests a degradation or dispersion of this labeled DNA prior to ovulation.
An electron microscopic study of the spleen of the rat in an acute myelogenous leukemia
Authors: Chen Li‐Tsun , Handler Evelyn E. 
Published: February 2005

AbstractThe spleens of rats were studied by light and electron microscopy during the course of an acute myelogenous leukemia, with special reference to infiltration of leukemic myeloblasts in the spleens and to the correlation of leukemic cell infiltration with splenic hematopoiesis and splenomegaly. Leukemic myelo‐blasts infiltrated the cordal space of the red pulp. Many of them appeared in groups. Even in spleens which were heavily infiltrated, leukemic myeloblasts did not penetrate the white pulp. Massive infiltration and proliferation of the leukemic myeloblasts in the red pulp resulted in splenomegaly. The spleen increased its he‐matopoietic activity, while the medullary hematopoiesis diminished due to the invasion of leukemic myeloblasts in the bone marrow. Compensatory splenic hemato‐poiesis occurred in most of the leukemic spleens, but diminished in spleens which were very heavily infiltrated with leukemic myeloblasts. Thus, the degree of splenomegaly and splenic hematopoiesis did not necessarily correspond to the percentage of leukemic myeloblasts in the bone marrow, but rather related to the number of leukemic myeloblasts present in the spleen. A possible role for the splenic sinus walls in promoting compensatory hematopoiesis in the spleen is discussed. A consistent association of type “C” virus particles with leukemic myeloblasts was observed.
Intracellular collagen in the nonpregnant and IUD‐containing rat uterus
Authors: Dyer Robert F. , Peppler Richard D. 
Published: February 2005

AbstractAn experiment designed to study the effects of the copper IUD on the virgin rat uterus has revealed the presence of intracellular collagen fibrils in control uteri and in uteri that have contained a copper IUD for three months. The cells containing the collagen are found in the stroma in close proximity to the uterine epithelium. The collagen is found within membrane‐bound cytoplasmic vacuoles that vary in morphology. In some cases the fibrils are tightly packed and linear, with no other material evident in the vacuole. In other examples, the fibrils are randomly arranged and the vacuoles contain a punctate material which is characteristic of phagolysosomes. Finally, cytoplasmic vacuoles are seen which contain ill‐defined debris and poorly‐visualized structures that exhibit a periodicity, suggesting a terminal phase of fibril breakdown. All animals were sacrificed in metestrus, and the results indicate that intracellular collagen is present in the nulliparous rat uterus at this stage of the cycle. In addition, this phenomenon does not appear to be influenced by the presence of a copper IUD over a period of three months.
Myelinated granule cell bodies in the cerebellum of the monkey (Saimiri sciureus)
Authors: Cooper Margaret H. , Beal John A. 
Published: February 2005

AbstractElectronmicrographs of both the vermis and hemisphere of the cerebellum of the squirrel monkey (Saimiri sciureus) show numerous granule cell bodies partially or completely surrounded by myelin. The myelin is of the compact type and consists of 1 to 13 lamellae. In several cases of partially ensheathed cells the myelin is clearly derived from extensions of myelin sheaths that surround small caliber axons. Either all or only the outer lamellae surrounding the axon contribute to the extensions. In the first instance the myelin buckles at its mesaxon pole and the resulting doubled flap extends for a variable distance along the cell surface.
Stimulation of cell division in ectopic kidney grafts following unilateral removal of the lung
Authors: Simnett John , Walton John , Oates Christine 
Published: February 2005

AbstractSmall fragments of kidney tissue were grafted into the right lung (Xenopus laevis) and the left lung was subsequently removed. This stimulated compensatory hyperplasia (increased mitotic rate) in alveolar tissue of the right lung and in the kidney graft. This suggests that the stimulus to compensatory hyperplasia is location‐specific rather than tissue‐ or organ‐specific. After implantation into the lung the kidney grafts are revascularized by the surrounding pulmonary supply. Damage or functional impairment of an organ usually produces a localized increase in the rate of blood flow and we therefore propose that this may lead to an increased rate of cell division in one of two ways: by permitting an increased functional capacity in the tissue concerned, or by causing a more rapid local clearance of mitotic control factors.
Enamel rod formation in the monkey observed by scanning electron microscopy
Authors: Skobe Ziedonis 
Published: February 2005

AbstractScanning electron microscopy of permanent tooth buds of the monkey confirmed that mineralizing interrod enamel surrounds Tomes' processes on three sides, forming pits that restrict enamel rod formation. The forming face of the enamel rod, which is the floor of the pit, angled toward the tooth surface at the apical edge of the pit, the side nearest the cervical region of the tooth. Consequently, the apical edge of each pit was the only site where both rod and interrod enamel were formed at the nascent tooth surface.The ameloblasts had two secretory surfaces. One was the microvillous surface of the short Tomes' process abutting the forming face of the enamel rod. The other surface, closer to the ameloblast, was between Tomes' processes, abutting the crests of interrod enamel which formed the pits. At each site forming enamel crystallites had specific orientations.Due to the angle of the forming face of the rod and the short Tomes' process, crystallites with both rod and interrod orientation form at the same time and the same plane within the apical (cervical) margin of each rod. It is hypothesized that indistinct boundaries between rod and interrod enamel at the apical margin of each rod are due to both secretory surfaces of ameloblasts secreting at the same time and at the same site.