bluuebunny/crossref_metadata_2025 huggingface dataset:
Increase in zymogen granule volume accounts for increase in volume density during prenatal development of pancreas
Authors: Ermak Thomas H. , Rothman S. S.
Published: February 2005

The sudden increase in volume density of zymogen granules in acinar cells of the fetal rat pancreas was examined with particular attention to the respective roles of granule size and number in this event. Volume density increased some twelvefold, from about 3% of cytoplasmic volume at 17 days to about 45% at 20 days, following a sigmoidal pattern in which the greatest rate of increase occurred during day 18. This increase in volume density was primarily the result of an increase in granule volume. Zymogen granule diameter increased from 0.55 μm at 17 days to 1.20 μm at 20 days, an order of magnitude increase in average granule volume. The total number of granules in the tissue increased in proportion to the increase in organ weight (cell number and size), but changes in the number of granules per unit cytoplasmic volume were minor (+ 40%) in comparison to the increase in volume density. The distribution of granule diameter was roughly normal and unimodal at each time interval, and the increase in average diameter over time was marked by an increase in the upper limit of the size distribution and an increased percentage of large granules. The size of condensing vacuoles also increased during this period, and their distributions were roughly coextensive with those seen for zymogen granules at the same time. The potential origins of changes in granule size are discussed, as well as the important effect that size has on the number of granules observed in “two‐dimensional” tissue sections viewed in the electron microscope. If size is not considered in our estimates, then we underestimate the numerical density in cells with small granules compared to those with large granules. The results indicate the central role of granule size, as opposed to number, in determining granule volume density in the embryonic pancreas.
Identification of human second, third, and fourth metatarsal bones
Authors: Batmanabane Mounissamy , Malathi Santhanagopalan
Published: February 2005

The lateral side of the base of the second (SMT), third (TMT), and fourth (FMT) metatarsal bones displays constant and distinct grooves. The groove on SMT starts just above the middle of the lateral surface of the base and runs toward the shaft forming an angle of 85–111o with the base. TMT has a groove starting at about the middle of the lateral surface forming an angle of 57–72o with the base, while the groove on FMT runs upward more acutely, starting from the lower end of the surface, forming an angle of 37–54o with the base. The presence of these grooves and the usefulness of their characteristics in distinguishing between these metatarsals, especially in forensic medicine, is discussed.
A quantitative ultrastructural analysis of satellite cells in denervated fast and slow muscles of the mouse
Authors: Snow Mikel H.
Published: February 2005

Mononucleated cells located between the external lamina and sarcolemma of denervated muscle fibers within the extensor digitorum longus (EDL) and soleus muscles of adult mice were quantified and examined ultrastructurally from 3 to 65 days after ligating and removing a section of the sciatic nerve. During the first 2 weeks postdenervation, mononucleated cells in denervated muscles were morphologically indistinguishable from satellite cells observed in control muscles. With time, however, many of these satellite‐like cells appeared more active as evidenced by a decrease in their nucleocytoplasmic ratio and an increase in their mean percentage of euchromatin material. The number of satellite cells (expressed as a ratio of satellite cell nuclei to satellite cell nuclei plus myonuclei) did not increase significantly until 30 days postdenervation, at which time the mean percentage for the soleus muscle had risen from a control value of 4.1–8.5%, and for the EDL from 1.2–4.1%. Smalldiameter, presumably regenerating, myofibers were occasionally observed but only after 30 days denervation. The ultrastructural evidence plus comparisons of euchromatin distributions between myonuclei and satellite cell nuclei support the concept that an increase in the number of satellite‐like cells during denervation is more likely due to satellite cell proliferation than to the formation of mononucleated fragments utilizing preexisting myonuclei.
Cytochemical study on the distribution of adenylate cyclase in guinea pig testis
Authors: Pascolini Rita , Vagnetti Daniela , Spreca Antonio , Marinelli Marinella , Lorvik Sergio
Published: February 2005

The distribution of adenylate cyclase in testis, by means of a specific substrate adenylyl‐imidodiphosphate (AMP‐PNP), has been determined. Membrane‐associated reaction products, indicative of adenylate cyclase activity, are localized by a complete cytochemical medium (containing 10 mM NaF) at the level of the basal compartment of the seminiferous epithelium, on the basal surface of Sertoli cells, and on adjacent plasma membranes of Sertoli cells and spermatogonial cells. At the level of the adluminal compartment, reaction products were found on adjacent plasma membranes of Sertoli cells and early or elongated spermatids. Adenylate cyclase reaction products are detectable by a basal incubation medium (without 10 mM NaF) only in the adluminal compartment on the spermatid plasma membranes.
Fluorescence microscopic morphometry of functioning blood vessels and adrenergic nerves in myocardium
Authors: Muntz Kathryn H. , Hagler Herbert K. , Boulas H. Jay , Buja L. Maximilian
Published: February 2005

The purpose of this study was to quantify the percent volume of actively functioning blood vessels in five dogs subjected to ligation of the left anterior descending artery and to localize catecholamine‐containing nerve terminals in the same tissue blocks. Radioactive microspheres were injected to determine the extent of flow reduction in the ischemic zone. After 1 or 3 hr of occlusion, thioflavin‐S (0.125 ml/Kg of a 4% solution) was injected intravenously 15 sec prior to removal of the heart. Tissue samples were reacted with paraformaldehyde to visualize catecholamine‐containing nerve terminals prior to embedding in paraffin. The percent volume of blood vessels labeled with thioflavin‐S was quantitated in tissue sections using a point‐counting technique in which a small dot from a video screen was projected through an image‐projecting tube and moved by computer control over the image of the fluorescent tissue. In the nonischemic zone, the mean blood flow determined by the microsphere technique was 1.29 ml/min/g ± 0.48 (SD), and the mean volume percent of thioflavin‐labeled vessels was 12.67 ± 3.30. In the ischemic and border zone areas, there was wide range of flow reduction, and there was a significant correlation between the blood flow measured with microspheres and the percent volume of thioflavin‐labeled blood vessels (R = 0.80, P < 0.001). In the nonischemic zone, both blood vessels and catecholamine‐containing nerve terminals were visible; however, in the ischemic zone, few labeled vessels were seen, although nerve terminals were often present. A method has been presented here in which blood flow can be predicted microscopically in a small sample of tissue using a unique method of point counting of fluorescent tissue sections.
Evidence for the persistence of axons at the apex of the cat's lower canine tooth after section of the inferior alveolar nerve
Authors: Holland G. R. , Robinson P. P.
Published: February 2005

The aim of this investigation was to establish the degree of denervation produced by inferior alveolar nerve section and to provide histological evidence for the presence of pulpal nerve fibres supplying the teeth which do not travel with the inferior alveolar nerve. Four adult cats were used. Each stage of the experiment was carried out under general anesthesia. The left inferior alveolar nerve was exposed and sectioned near the mandibular foramen. After 56 hours and 7 days, respectively, the jaw opening reflex to electrical stimulation of each lower canine was tested. Recordings were made from the left canine during electrical stimulation of the ipsilateral inferior alveolar nerve central and peripheral to the site of section as well as from the ipsilateral and contralateral inferior alveolar nerve during electrical stimulation of the left canine. Recordings were also made from the lingual nerve. After the recordings were completed two animals were perfused 56 hours after inferior alveolar nerve section, two more 7 days after section. Ultrathin sections of the apices of the lower canine teeth were examined in the electron microscope and each nerve fibre photographed. Each axon was examined to determine whether it was degenerating or normal.

A jaw‐opening reflex could not be elicited by stimulation of the left canine either 2 or 7 days after nerve section, whereas a normal response was evoked by stimulation of the right, control canine. At 2 days small responses could be recorded from the left canine teeth during stimulation of the left inferior alveolar nerve peripheral to the point of section. In one 2‐day animal, responses could be recorded in the lingual nerve during stimulation. No pulpal fibres could be recorded in the inferior alveolar nerve central to the point of section nor from the contralateral inferior alveolar nerve. No pulpal fibres supplying the left canine could be recorded in any of the nerves examined at 7 days.

Extensive degeneration was seen histologically even at 2 days. The canine pulp on the operated side contained only 31%, in one animal, and 26% in the other, of the number of axons of normal appearance that were present on the control side. At 7 days the number of remaining normal axons on the operated side were 5% and 13% of the numbers on the control side. All the axons of normal appearance were nonmyelinated.

It is possible that the remaining axons represent fibres carried by the lingual nerve or some other alternative pathway that could not be detected electro‐physiologically. Alternatively they may be a collateral innervation from adjacent tissues.
Immunocytochemical localization of four hormones in the pancreas of the garter snake, Thamnophis sirtalis
Authors: Rhoten William B.
Published: February 2005

Insulin, glucagon, somatostain, and pancreatic polypeptide (PP) were localized in the pancreas of the common garter snake, Thamnophis sirtalis, by light and transmission electeron microscopic (TEM) immunocytochemistry. Colloidal gold‐protein A was used for TEM localization and the peroxidase containing A cells and the insulin‐positive B cells were the most numerous cell types. The somatostatin‐containing D cells made up about 15% of the endocrine cells. PP‐positive F cells were a minor cell type. The only topographic arrangement of the cells within the endocrine‐rich areas that was apparent was the peripheral localization of the D and F cells. Cells of a specific cell type were sometimes grouped together. At the elctron microscopic (EM) level, the gold particles (indicating the pesence of hormone) were localized nearly exclusively over the secretory grnules of the ractive cells. The α‐granules were the largest found and were predominantly electron dense with a moderately electron‐dense periphery. PP‐containing granules were the smallest. The somatostatin‐reactive δ‐granules were round and moderately electron opaque. The β‐granules were heterogeneous in appearance. The morphognomy of the secretory granules of the major endocrine cell types is qualitatively similar to that of mammals. Wheter or not the quantitative and/or associative differences contribute to the marked metabolic differences between reptiles and mammals, remains to be determined.
Meckel's diverticulum. II. A novel lymphoepithelial organ in the chicken
Authors: Oláh I. , Glick B. , Taylor R. L.
Published: February 2005

We have studied the lymphoid development and structure of Meckel's diverticulum (MD). The lymphoid accumulation began about 2 weeks of age. Between 2 and 5 weeks of age the longitudinal folds were filled with lymphoid tissue. The intensive germinal center formation occurred between 5 and 7 weeks of age. Germinal center formation was associated with the presence of secretory cells. The absence of the secretory cells in the germinal centers was followed by germinal center inactivity which was indicated by the lack of lymphoblasts and the high number of tingible body macrophages.

The lymphoid tissue of MD seemed to be fully developed by 10 weeks of age and remained lymphoid at least until 21 months of age. Meckel's diverticulum produced large numbers of plasma cells which were comparable to those of the gland of Harder. We may regard MD as the third pouch of the intestine and suggest that it may be a novel lymphoepithelial organ in the chicken.
A quantitative study of satellite cells in regenerated soleus and extensor digitorum longus muscles
Authors: Schultz Edward
Published: February 2005

Satellite cells quantitated in the rat soleus and extensor digitorum longus (EDL) muscles following a complete regeneration returned to “normal” percentages of myofiber nuclei in both muscles 3 months after injury. Following cross‐transplantation, the percentage of satellite cell nuclei in the EDL regenerated in the soleus bed was indistinguishable from the percentage in the soleus. Likewise, the soleus muscle regenerated in the EDL bed had a satellite cell percentage characteristic of the EDL. These results suggest that (1) the proportion of satellite cells is reestablished in a regenerated muscle and (2) the innervating nerve determines the proportion of satellite cell nuclei in a muscle.
The development of specific antibody‐containing cells in the spleen of rabbits during the secondary immune response against free or liposome‐associated albumin antigen
Authors: van Rooijen N. , van Nieuwmegen R. , Kors N. , Eikelenboom P.
Published: February 2005

In order to study the distribution pattern of specific antibody containing cells in the spleen of rabbits during the secondary immune response, rabbits were given two intravenous injections of either free or liposome associated human serum albumin (HSA) within an interval of 2 months. Demonstration of specific antibody‐containing cells was performed by incubation of sections of spleen with HSA‐horseradish peroxidase (HRP) conjugates, followed by peroxidase cytochemistry.

Specific anti‐HSA antibody‐containing cells were detected already within 2 days after booster and peak numbers were found 4 days after booster. The bulk of these cells localized in the coaxial lymphocyte sheaths surrounding the terminal arterioles in the spleen. Specific antibody‐containing cells produced immunoglobulin G (IgG) antibodies. From the results, it is also concluded that, after a priming injection with liposome‐associated HSA, liposomes do not further enhance the secondary immune response, when they are also used for the booster injection.
Localization of a synthetic progestin in the reproductive organs of the female baboon
Authors: Weaker Frank J. , Sheridan Peter J.
Published: February 2005

The uptake and retention of a radiolabeled synthetic progestin, ORG 2058, was studied in the female reproductive system of the baboon. Four estrogen‐primed baboons were injected intravenously with 2.5 μ/kg body weight of 3H‐ORG 2058. One animal, which served as a control, received an additional injection of 2.5 mg/kg body weight of unlabeled progesterone. One hour after the injections, the animals were killed and the uterus, cervix, oviduct, vagina, and labia were removed and processed for autoradiography. The cells in the germinative layers of the stratified squamous epithelium of the cervix, vagina, and labia demonstrated nuclear localization of the label. The columnar epithelium, both surface and glandular, of the uterus and cervix sequestered the synthetic steroid; however, the nuclei of the epithelium lining the oviduct were unlabeled. The nuclei of the fibroblasts and of the smooth muscle cells were labeled in all the organs studied. These preliminary observations suggest that there is a stage in the reproductive cycle in which progesterone receptors are contained in the stromal cells of the oviduct but are absent in the epithelium.
Vesicle numerical densities and cellular attenuation: Comparisons between endothelium and epithelium of the alveolar septa in normal dog lungs
Authors: DeFouw David O.
Published: February 2005

The alveolar septa are divided into two anatomically distinct portions: The thin sides consist of capillary endothelium, alveolar epithelium, and their closely apposed (often fused) basal laminae; the thick sides are characterized by prominent interstitial spaces, containing fibrils and cells, which separate the respective basal laminae. Vesicle numerical densities are comparable (approximately 400 vesicles/μm3 cytoplasm) in the endothelial and epithelial cells on both sides of the septa. Mean vesicle diameters, however, are substantially less in the epithelial cells on both the thin and thick sides. The extent of both endothelial and epithelial attenuation is significantly greater on the thin sides of the septa. Further, epithelial attenuation is more marked than endothelial attenuation on both sides of the septa. The attenuated cellular portions, possibly because of their extreme thinness, are void of vesicles but provide relatively short diffusion distances (20–30 nm) from vessel or alveolar lumen to the basal lamina. Whether these structural differences between endothelial and epithelial cells contribute to physiologic evidence that describes the endothelium as more permeable than the epithelium remains to be established.
Distribution of glycogen in the floor plate of the chick spinal cord during development
Authors: Uehara Masato , Ueshima Toshihiko
Published: February 2005

The present study was undertaken to characterize the structural changes and the glycogen distribution in the floor plate of the developing chick spinal cord.

The floor plate consisted of ventricular zone by stage 19 (staged according to Hamburger and Hamilton, 1951). The marginal zone of this plate could be distinguished as a narrow border at stage 21. It increased progressively in thickness and was the same thickness as the ventricular zone at stage 26. It increased again in thickness from stage 38 onward.

Glycogen appeared and subsequently disappeared in the floor plate of the chick spinal cord during development. Little, if any, glycogen appeared in the midportion of the floor plate at stage 19. The floor plate was weakly glycogen positive from the cervical through lumbosacral segments at stage 21. In the floor plate of the lumbosacral enlargement the glycogen staining was the highest and was maximal through stages 34–37. The floor plate of the cervical and thoracic segments except for the cervical enlargement continue to have low concentrations of glycogen. The glycogen staining of the floor plate began to decrease from stage 38, and at the same time neuroglial cells began to migrate into the marginal zone of the floor plate, later than in other regions of the cord. The glycogen staining in the floor plate was barely detectable at stage 40.

The accumulation of the glycogen granules in the floor plate was found only in the radial glial cells.
The microscopic structure of fibrous articular surfaces: A review
Authors: Wilson N. H. F. , Gardner D. L.
Published: February 2005

The present knowledge of the microscopic structure of fibrous articulating surface is reviewed. The influence of dissection, postmortem change, fixation, and dehydration on the microscopic appearances of these surfaces is considered. The results of those studies of surface morphology that investigate intact, supported specimens and that are controlled by surveys of fresh, unfixed, or frozen material are advantageous. New information on the effects of alterations in intermaxillary relationship on the morphology of fibrous articulating surfaces is presented. There is need for further work in this field of research.
Locomotion and scanning electron microscopic observations of primordial germ cells from the embryonic chick blood in vitro
Authors: Kuwana Takashi , Fujimoto Toyoaki
Published: February 2005

The locomotion of chick primordial germ cells (PGCs) in vitro was observed using 16‐mm time‐lapse microcinematography and 35‐mm timelapse film. The PGCs isolated from circulating blood of stage 14 to 16 embryos (Hamburger and Hamilton, 1951) were cultured on a substrate of mesenchymal feeder cells obtained from the dorsal mesentery of stage 40 embryos, using modified medium 199 containing 10% fetal calf serum. The PGCs were found to move actively and to show a tendency to move along the longer axis of the underlying cells. The velocity of PGC locomotion averaged 26 μm/hr and reached 58 μm/hr as a maximum.

After observation, the PGCs were processed for scanning electron microscopy. They had a considerable number of microvilli about 0.2 μm in thickness and some cytoplasmic blebs on their surfaces. It was observed that the PGCs in the migrating phase adhered to the substrate with its filopodia only at the leading edge, while a large part of the cell appeared to be apart from the substrate.
Changes in the secretory acinar cells of the rat parotid gland during aging
Authors: Kim Sun‐Kee
Published: February 2005

The secretory acinar cells of parotid glands from rats of varying ages have been examined by electron microscopy to determine what age‐related changes occur in these cells. The most prominent change noted in these cells is the progressive increase in the amount of lipofuscin granules with age. Lipofuscin granules are membrane‐bound structures consisting of lipids, other subcomponents, and a matrix. In addition, these cells contain lipid droplets that are not associated with any other components and tend to accumulate at the base of the cells in older rats. Also, many acinar cells in the glands of old rats contain altered secretory granules which appear to be in the process of degeneration. The accumulation of lipid and degenerating secretory granules appears to be related to the reduced level of cellular secretory activity in the glands of older rats. It is possible that these two types of inclusions contribute to the formation of lipofuscin granules. Lipofuscin and degenerating secretory granules are associated with acid phosphatase, which is demonstrated cytochemically, indicating that these granules are lysosomal structures.
An immunocytochemical study of the pancreatic islet system of the channel catfish
Authors: McNeill Daniel L. , Brinn Jack E. , Fletcher Donald J.
Published: February 2005

The endocrine pancreas of the channel catfish is segregated into a large primary islet and numerous smaller secondary islets. In view of cell distribution differences in mammalian islets of ventral and dorsal primordia, we have determined the percentage volumes of insulin‐, glucagon‐, and somatostatin‐containing cells in primary and secondary catfish islets to ascertain if these islets correlated with those derived from ventral and dorsal primordia in mammals. Islets were immunocytochemically stained using antisera to anglerfish insulin, porcine glucagon, and synthetic somatostatin and volume densities were quantified on light micrographs by point‐counting procedures. In both primary and secondary islets the insulin‐, glucagon‐, and somatostatin‐containing cells comprised approximately 32%, 23%, and 38% of the endocrine cell volumes, respectively. Therefore, the cell populations did not reflect any embryological differences between the two groups of islets. In this study, the volume densities of insulin‐reactive cells in the primary islet were less than previously reported, and the overall insulin staining was about one‐half of that seen in mammals. The volume density of somatostatin‐reactive cells in primary islets was greater than previously reported. Based on these data, primary and secondary islets of the catfish do not appear to have a similar development to the ventral and dorsal islets of the mammalian system.
Effects of genic substitution at the brown locus on the differentiation of epidermal melanocytes in newborn mouse skin
Authors: Hirobe Tomohisa
Published: February 2005

In the dorsal epidermis of both C57BL/10J (black, BB) and C57BR/cdJ (brown, bb) mice, the number of melanocytes positive to the dopa reaction (melanocyte population) increases from birth to day 3 or 4, and then gradually decreases. However, the number of melanoblasts plus melanocytes positive to the combined dopa‐premelanin reaction (melanoblast‐melanocyte population) remains constant until day 3 or 4 and then decreases in the two strains. Despite the similarity of the developmental dynamics in both black and brown mice, there is a significant difference in the number of differentiated melanocytes. Melanocytes are more numerous and more dopa‐reactive in brown mice than in black. The maximal density of the melanoblast‐melanocyte population on day 3 or 4 does not differ in brown and black mice. Moreover, the maximal density of the melanocyte population in brown epidermis does not differ from that of the melanoblast‐melanocyte population of both brown and black. These results indicate that b allele, when homozygous, enhances the differentiation of epidermal melanoblasts by inducing high tyrosinase activity.
Enrichment of lysozyme‐containing cells from the rabbit endocervix by unit gravity sedimentation
Authors: Chilton Beverly S. , Nicosia Santo V. , Sowinski Janice M.
Published: February 2005

Lysozyme is a bacteriolytic enzyme component of the secretory granules of endocervical mucous cells. In order to study the subcellular distribution of this enzyme in specific cell populations, endocervical cells from estrous and 5‐day pseudopregnant rabbits were separated by unit gravity sedimentation. The application of this technique to pronase‐dispersed endocervical cells from estrous rabbits resulted in the isolation and enrichment of two mucous cell types that were distinguished morphologically into type I and type II cell populations. Lysozyme was identified in both cell types, using an unlabeled antibody enzyme method, and the degree of staining paralleled the number of mucous granules. In the absence of estrogen dominance in 5‐day pseudopregnant rabbits, there was a 50% reduction in the number of mucous cells with a concomitant reduction in both the number of secretory granules per cell and the intracellular concentration of lysozyme. In the absence of ovarian steroid hormones, i.e., 15–16 weeks after ovariectomy, endocervical cells were devoid of secretory granules and lysozyme staining was negative. Enriched populations of endocervical cells represent a potential experimental model for studying the hormonal role in the regulation of lysozyme synthesis by specific cell populations.
Effect of dexamethasone on the fetal mouse small intestine in organ culture
Authors: Beaulieu J.‐F. , Calvert R.
Published: February 2005

The formation of intestinal villi (organogenesis phase) may be studied in organ culture with a completely synthetic medium in 15‐day fetal mouse duodenal explants. However, in these explants absorptive cells remained poorly differentiated with all the hormones studied except with epidermal growth factor. In order to elucidate the role of hormones and other factors on the maturation of absorptive cells (maturation phase) in the fetal rodent in organ culture, we have taken the explants after the organogenesis phase. We have studied different culture conditions and have found that 17‐day mouse duodenal explants can be cultured during 48 hours with Leibovitz L‐15 medium in a 95% O2‐5% CO2 atmosphere provided that the explants are relatively large (5 × 2 mm). With this method, dexamethasone (Dx) has been shown to have a direct effect on the maturation of the fetal duodenal mucosa. The addition of Dx (300 ng/ml) to the completely synthetic medium (1) improves the morphology of the explants, (2) induces a significant increase in maltase activity in the tissues, and (3) reduces significiantly the labeling index of the duodenal explants after 48 hours of culture. Direct action of Dx on the duodenal mucosa is shown for the first time in organ culture using a completely synthetic medium. This method will permit us to study the effects of other intrinsic and extrinsic factors on the regulation of enzymatic maturation in fetal small intestine.
The neonatal porcine lung: Ultrastructural morphology and postnatal development of the terminal airways and alveolar region
Authors: Winkler Gian C. , Cheville Norman F.
Published: February 2005

Morphology and postnatal development of the porcine lung are described in animals ranging in age from newborn through 60 days. Standardized fixation was accomplished by intratracheal instillation of glutaraldehyde under constant pressure. Light microscopic, scanning, and transmission electron microscopic investigations revealed that the porcine lung follows the common architecture of mammalian lungs, but has certain peculiarities as well: intravascular macrophages, ultrastructurally similar to Kupffer cells, are attached to endothelial cells in pulmonary capillaries and are involved in erythrophagocytosis during the first postnatal weeks. Type II pneumocytes of newborn pigs exhibit signs of cell activation, mainly complex nuclear bodies in the cell nuclei. At the same time high levels of 17‐hydroxycorticosteroids are observed in the newborn blood plasma. Terminal airways of the porcine lung are nonalveloarized and are, therefore, of purely conductive function.

At birth the porcine lung exhibits a high degree of maturity, and thickwalled primary saccules, as described in newborn rodents, are not seen. Septa appear straight and smooth, owing to rare ramification. Septal buds are discernible, and two capillary networks visible on both sides of septal cross sections are seen. Further subdivision of the airspaces occurs in the first two postnatal weeks. Precociousness and fast postnatal growth of the porcine species are assumed to be the reason of this advanced degree of lung maturity at birth and the following rapid pulmonary development.
The glial cells in the nerve fiber layer of the rat olfactory bulb
Authors: Doucette J. R.
Published: February 2005

In mammals the olfactory receptor neurons are the only ones that are known to undergo continuous cell renewal in the adult animal. This means that the axon of each newly formed neuron must grow into the olfactory bulb to find its appropriate target cell. It is presumed that astrocytes ensheath the olfactory axons as they course through the nerve fiber layer of the bulb even though the cells in question differ ultrastructurally from typical astrocytes. The purpose of the present study was to examine the glial cells in the nerve fiber layer of the rat olfactory bulb in an effort to resolve this apparent discrepancy. Two morphologically distinct types of glial cell were found in the nerve fiber layer. One type, which resembled the typical astrocytes that are present in other areas of the cental nervous system, contained bundles of filaments in an electron‐lucent cytoplasm. These cells also formed endfeet on blood vessels and formed part of the external glial limiting membrane. They did not, however, ensheath the olfactory axons. The cytoplasm of the other type of glial cell was denser than that of typical astrocytes and contained fewer filaments, which were seldom grouped into bundles. These cells also formed part of the glial limiting membrane at the surface of the bulb and were the only ones that ensheathed the olfactory axons. It is concluded that the cell ensheathing the olfactory axons in the nerve fiber layer of the rat olfactory bulb is a morphological variant of the typical astrocyte. One role of the former cell may be to support or encourage the growth of olfactory axons within the central nervous system.
Freeze‐replica study of lipid droplets in the ito cells of rat liver
Authors: Yamamoto Kouta , Ogawa Kazuo
Published: February 2005

The structure of lipid droplets in the Ito cells was studied by the freeze‐replica method in vitamin A‐treated rats. Most lipid droplets were fractured in planes through their lipid contents. Some of them were surrounded by a membrane structure that had intramembranous particles (IMP), which were more numerous on the protoplasmic face than the exoplasmic face. Those with the membrane containing IMP correspond to the membranebounded lipid droplets (lipid droplets surrounded by lysosomes) seen in the electron microscopic observation of conventional thin section preparations. There were no lipid droplets showing concave or convex multilayered structures in the Ito cells from properly fixed livers. Since these multilayered structures were observed only in the materials fixed by immersion with glutaraldehyde or fixed 40 minutes after the death of animals, it is likely that they represent an artifact, showing an autolytic change, caused by poor fixation or postmortem change.
Myometrial ultrastructure and innervation in Motis lucifugus, the little brown bat
Authors: Buchanan G. Dale , Garfield R. E.
Published: February 2005

Uteri from hibernating bats, Myotis lucifugus, collected periodically from Renfrew County, Ontario, were fixed in 2% glutaraldehyde and processed for electron microscopy or incubated in glyoxylic acid to show adrenergic nerves by fluorescence. The bat uterus is structurally typical of mammalian species; although the right uterine horn is permanently enlarged in parous bats due to hypertrophy of both myometrium and endometrium. Nerves were abundant between both longitudinal and circular layers of muscle cells. Unmyelinated, and some myelinated, axons, ranging from few to many, coursed generally parallel to the uterine long axis. Numerous axonal varicosities containing small dense‐cored (adrenergic) vesicles or, less often, small agranular (cholinergic) vesicles, were found forming close nerve‐muscle contacts between myometrial cells and blood vessels. Fluorescent microscopy showed a dense network of adrenergic nerves in parous uteri, but a sparse network in nulliparous uteri. A specific adrenergic nerve marker, 5‐hydroxydopamine, greatly increased the density and in some instances, the size of granular vesicles, while 6‐hydroxydopamine, which depletes adrenergic neutrotransmitter, reduced the number of dense‐cored vesicles. Nulliparous uteri appeared unchanged by six daily injections of 0.1 μg estradiol‐17β; 0.25 mg progesterone, or both; but parous uteri were greatly enlarged by all regimes. Nerve ultrastructure, however, appeared unaffected by steroid treatment; nor, despite the absolute dextral bias in implantation, were left‐right differences observed. Gap junctions were not found between muscle cells in myometria of any bat uteri. Based on this study, we suggest that M. lucifugus may provide a most useful model for examination of neurogenic regulation of the uterus.
PGE2 stimulates both resorption and formation of bone in vitro: Differential responses of the periosteum and the endosteum in fetal rat long bone cultures
Authors: Nefussi Jean‐Raphael , Baron Roland
Published: February 2005

The ability of PGE2 to stimulate bone resorption in vitro and in vivo is well established but the effects of this compound on bone formation are still controversial. Recent clinical reports have suggested that long‐term infusion of PGE in infants with cyanotic heart diseases led to a stimulation of periosteal bone formation and to hyperostosis.

In the present report, we describe the effects of PGE2 (10−5 M) in bone organ cultures on bone resorption, measured by the release of 45Calcium and the number of osteoclasts in sections of cultured bones, and bone volume, by measuring separately medullary and cortical areas. PGE2 induced a marked increase in 45Ca release and in cortical and medullary osteoclast numbers over 4 days in vitro; despite this increase in bone resorption, cortical bone volume remained constant, indicating a parallel increase in bone resorption and formation at this site. Morphological and quantitative data demonstrated a higher extent of osteoblastic surface along the periosteum of PGE2‐treated bones when compared with control cultures. Medullary bone volume, on the other hand, decreased sharply during the culture period, demonstrating a lack of parallel increase in bone formation at this site.

It is concluded that, under these experimental conditions, prostaglandin E2 stimulated both resorption and formation along the periosteum and only bone resorption along the endosteum of the cultured bones. The overall effect of PGE2 on bone as a whole, however, was net bone loss.
The distribution and spatial organization of the extracellular matrix encountered by mesencephalic neural crest cells
Authors: Brauer Philip R. , Bolender David L. , Markwald Roger R.
Published: February 2005

Cephalic neural crest (NC) cells enter a cell‐free space (CFS) that contains an abundant extracellular matrix (ECM). Numerous in vitro investigations have shown that extracellular matrices can influence cellular activities including NC cell migration. However, little is known about the actual ECM composition of the CFS in vivo, how the components are distributed, or the nature of NC cell interactions with the CFS matrix. Using ultrastructural, autoradiographic, and histochemical techniques we analyzed the composition and spatial organization of the ECM found in the CFS and its interaction with mesencephalic NC cells. We have found that a specific distribution of glycoproteins and sulfated polyanions existed within the CFS prior to the translocation of NC cells and that this ECM was modified in areas occupied by NC. The interaction between the ECM components and the NC cells was not the same for all NC cells in the population. Subpopulations of the NC cell sheet became associated with ECM of the ectoderm (basal lamina) while other NC cells became associated with the ECM of the CFS. Trailing NC cells (NC cells that emerge after the initial appearance of NC cells) encountered a modified ECM due to extensive matrix modifications by the passage of the initial NC cell population.
Variation in basement membrane topography in human thick skin
Authors: Kawabe Thomas T. , Maccallum Donald K. , Lillie John H.
Published: February 2005

Samples of human plantar and palmar skin were excised and incubated in 20 mM EDTA after which the epidermis was gently separated from the dermis with the plane of separation occurring in the lamina lucida. Scanning electron microscopic examination of the dermal component revealed the classically described series of regularly spaced grooves and papillae that characterize the epidermal‐dermal junction in thick skin. Primary dermal grooves exhibited evenly spaced tunnels that were originally occupied by sweat gland ducts. The basement membrane (basal lamina) in the primary grooves was relatively smooth but did exhibit a flattened, reticulated pattern at high magnifications. The basement membrane of secondary dermal grooves and papillae was in the form of numerous, elevated microridges off of which septae arose at roughly right angles. The surface appearance of the basement membrane in these areas was that of a honeycomb owing to the numerous compartments and recesses formed by the ridges and septae. Degradation of the basement membrane by trypsin demonstrated that the foundation for the highly folded and compartmentalized basement membrane was composed of dermal collagen fibrils, 60–70 nm in diameter, that were arranged in a series of variably sized, interconnected collagen bundles or walls. Epidermal basal cells extended cytoplasmic (foot) processes into two or more compartments, formed by the ridges and septae, which considerably amplified the basement membrane surface available for epidermal attachment. Scanning electron microscopic studies of the epidermal‐dermal junction confirm the variable surface character of this interface previously reported by others using sectioned material. This regional variation in surface architecture apparently distinguishes between areas in which epidermal basal cells are specialized for attachment (papillae, secondary dermal grooves) and regions occupied by slow cycling epidermal stem cells from which mitotically active keratinocytes arise.
Sex differences in circadian rhythms of several variables in lymphoreticular organs, liver, kidney, and corneal epithelium in adult CD2F1 mice
Authors: Tsai T. H. , Scheving L. E. , Scheving L. A. , Pauly J. E.
Published: February 2005

In this paper data resulting from an investigation into the influence of sex on selected circadian rhythms in lymphoreticular organs, liver, kidney, and corneal epithelium of adult CD2F1 mice are reported. Increased organ weight, total DNA and RNA in the spleen, total DNA and [3H thymidine ([3H]TdR)] incorporation into DNA in the thymus, and [3H]TdR incorporation into DNA in the liver and bone marrow in female mice compared to male littermates is demonstrated. In contrast, kidney weight and [3H]TdR incorporation into DNA as well as the corneal epithelium mitotic index are greater in male mice. Except for the corneal epithelium mitotic index and total splenic RNA and DNA, circadian rhythmicity in the variables studied is validated using the cosinor method of rhythmometric analysis in male but not in female mice. The lack of sinusoidal rhythmicity in female mice is presumed to be due to asynchrony of estrous cycling between mice within this group. Moreover, a differential organ response to exogenous testosterone enthanate is reported. The administration of this hormone suppresses [3H]TdR incorporation into DNA in the thymus and liver but not in the spleen or bone marrow at 18, 42, or 72 hr after injection.
Penetration of the basal lamina of the uterine luminal epithelium during implantation in the rat
Authors: Schlafke S. , Welsh A. O. , Enders A. C.
Published: February 2005

During early stages of implantation in the rat, as in other species that form a hemochorial placenta, there is a progressive increase in intimacy between blastocyst and endometrium. After initial invasion of the uterine luminal epithelium by trophoblast cells and displacement of epithelial cells, the trophoblast comes to lie adjacent to the residual basal lamina of the displaced epithelium but does not penetrate it. After a pause at the basal lamina, this temporary barrier is breached. To study the interrelation of trophoblast, uterine epithelium, and decidual cells with the epithelial basal lamina during the time of penetration of the basal lamina, implantation sites collected on day 7 of pregnancy were oriented so that the implantation chamber could be sectioned either longitudinally or transversely. Neither trophoblast nor uterine epithelial cells have processes that extend through the basal lamina. However, flange‐like processes from the decidual cells penetrate the basal lamina and underlie both trophoblast and, more rarely, epithelium. Smaller folds of the surface of decidual cells partially surround bundles of collagen fibrils oriented parallel to the long axis of the implantation chamber. Initially the area of penetration of basal lamina by decidual cell processes is quite restricted; as implantation proceeds the basal lamina becomes displaced and is sometimes not discernibl, extracellular materials accumulate, and the relationships become more difficult to follow. It is concluded that the initial breaching of the basal lamina is an activity of the decidual cells, and that contact of basal lamina with trophoblast is not necessary to permit this penetration.
A study of the position of the mandibular foramen in the adult human mandible
Authors: Nicholson Michael L.
Published: February 2005

Eighty dry, adult human mandibles of East Indian ethnic origin and bilateral eruption of third molar teeth were examined to measure the location of the mandibular foramen. The position of the foramen was found to be variable. However, the foramen was predominantly located at the anteroposterior midpoint of the ramus halfway between the mandibular notch and the lower surface of the mandible and two thirds of the way down a line joining the coronoid process to the angle of the mandible. In the majority of the mandibles studied the foramen was located below the occlusal surfaces of the molar teeth. It is concluded that the marked variability in the position of the mandibular foramen may be responsible for an occasional failure to block the inferior alveolar nerve.
Cell differentiation in the retina of the mouse
Authors: Young Richard W.
Published: February 2005

Cell differentiation in the retina of the mouse during the postnatal period was studied by autoradiography. Animals were injected with 3H‐thymidine at ages extending from the day of birth through postnatal day 11. Six weeks later the distribution of labeled nuclei in the cells of the mature neural retina was analyzed to determine when these cells completed their final mitosis prior to differentiating. Central and peripheral zones were analyzed separately. Cell division ceases by 5–6 days in the center of the retina and by 11 days in the periphery. Among cells produced postnatally, 73% differentiate as rods, 20% as bipolar cells, 6% as Müller cells, and 1% as amacrine and ganglion cells. At all stages of embryogenesis, the differentiation of at least three and as many as six distinct types of specialized cells is initiated simultaneously within the ventricular cell population.
Variational anatomy of the deep femoral artery
Authors: Siddharth Padmanabhan , Smith Noel L. , Mason Robert A. , Giron Fabio
Published: February 2005

The deep femoral artery is frequently incorporated in vascular reconstructive procedures in the proximal leg. To study the branching variations of this artery, we dissected 100 legs and then classified the anatomical patterns. The deep femoral artery originates a median distance of 4.4 cm from the inguinal ligament.

The origin of the lateral circumflex artery varied greatly. When it branched from the deep femoral, the origin of the lateral circumflex was 1.5 cm (median) from the origin of the deep femoral. The medial circumflex artery originated from the deep femoral in 63% of the specimens. It arose separately from the common femoral and more proximally in 26% of the specimens, branching an average of 2.15 cm (median) above the deep femoral origin. Familiarity with these variations is essential to the vascular surgeon and, therefore, we have included diagrams based on our study as a ready reference.
Long‐term consequences of cis‐platinum‐induced renal injury: A structural and functional study
Authors: Dobyan Dennis C.
Published: February 2005

Previous studies have shown that a single dose of the antitumor drug, cis‐platinum, causes renal cyst formation in rats 1–6 months after drug injection. This observation led to a further evaluation of the long‐term effects of cisplatinum on the kidney of the rat. Fisher 344 rats (N = 13) were given either a single intraperitoneal injection of cis‐platinum (6 mg/kg body weight) or saline (control) and 15 months later renal function and pathology were assessed. The glomerular filtration rate and urinary osmolality in the cis‐platinum‐treated rats at 15 months were significantly reduced compared to controls, 520 ± 59 μl/min/gm kidney weight versus 799 ± 100 (P < .05) and 871 ± 194 mOsm/kg H2O versus 1471 ± 162 (P < .05), respectively. Renal injury was less marked and of a more chronic type than to that originally described 6 months after cis‐platinum. Morphometric evaluation of renal injury revealed cis‐platinum‐treated rats had greater numbers of abnormal proximal tubules (atrophic or hyperplastic) when compared to control rats. Glomerular sclerosis and interstitial fibrosis were also more prevalent in the animals injected with cis‐platinum. In the inner stripe of the outer medulla, numerous markedly dilated tubules filled with hyaline casts and lined by simple squamous cells were present. To assess why cis‐platinum exerts a chronic effect on the kidney, total platinum levels were measured in different regions of the kidney as a function of time after drug injection. Platinum levels were significantly elevated in the cortex, outer and inner stripe regions, and in the inner medulla for as long as 1 month after cis‐platinum treatment. By 2 months, however, the values were no greater than controls. In summary, cis‐platinum exerts a significant long‐term chronic effect on the structure and function of the rat kidney.