bluuebunny/crossref_metadata_2025 huggingface dataset:
The fine structure of the developing pelvic fin dermal skeleton in the trout Salmo gairdneri
Authors: Géraudie Jacqueline , Landis William J.
Published: February 2005

The morphogenetic and ultrastructural features of the dermal skeleton in the pelvic fin bud of a teleost, the rainbow trout Salmo gairdneri, have been examined by light and electron microscopy. The principal structural components observed are lepidotrichia and actinotrichia. Lepidotrichia consist of two parallel and symmetrical bony demirays that form jointed segments within the fin. The demirays calcify in a proximodistal direction within the extracellular collagen network of the basal lamella belonging to the epidermal‐dermal interface of the fin. Needle‐ and plate‐like particles of a solid mineral phase appear to be associated with the collagen fibrils and with a fine, granular, interfibrillar material central to the demirays. Cellular processes and membrane‐bound vesicles are absent from the regions of calcification. During fin growth, the bony, acellular lepidotrichia are separated from the epidermal‐dermal interface by infiltrating mesen‐chymal cells in proximal fin regions; in distal areas, the lepidotrichia remain within the basal lamella. The actinotrichia are extensive unmineralized rods of elastoidin that occupy the distal margin of the fin and precede the differentiation of lepidotrichia. Once the lepidotrichia form, actinotrichia lie preferentially between their demirays. In some instances, structural interactions are suggested between actinotrichia and lepidotrichia. Considerations of embryologic and structural features of fin components fail to support the hypothesis that individual segments of lepidotrichia are modified scales in all fish.
Age‐related changes in pineal “synaptic” ribbon populations in rats exposed to continuous light or darkness
Authors: King Thomas S. , Dougherty William J.
Published: February 2005

“Synaptic” ribbon (SR) populations in the rat pineal gland were analyzed morphometrically at various ages from birth to early adulthood. The rats were born and raised in continuous light or continuous darkness. SR numbers were high irrespective of the presence or absence of light during the early neonatal period. However, SR numbers decreased substantially during the second neonatal week of continuous light, remaining low at subsequent ages, including early adulthood. In contrast, SR numbers apparently remained elevated during continuous darkness at various ages from the early neonatal period to early adulthood. Stimulation of pineal adrenergic receptors with L‐isoproterenol during continuous light resulted in an acute, reversible increase in SR numbers; blockade of these receptors with L‐propranolol during continuous darkness resulted in an acute decrease in SR numbers. These results indicate that light‐mediated changes in SR populations were (1) age related and (2) related to some component of the pineal beta‐adrenergic receptor mechanism. A hypothesis that SR formation may be related to beta‐adrenergic receptor‐associated membrane turnover is presented.
The pelvic epithelium of the rat kidney: A scanning and transmission electron microscopic study
Authors: Verani Regina , Bulger Ruth Ellen
Published: February 2005

The renal pelvis of the rat is characterized by extensions called specialized fornices that penetrate into the outer zone of the outer medulla (a type II as classified by Pfeiffer, 1968, 1970). The renal pelvic epithelium, therefore, covers areas of the kidney from the inner medulla, the inner and outer stripe of the outer medulla, and the cortex.

The renal pelves of seven rats were studied by transmission and scanning electron microscopy. The transitional epithelium on the nonparenchymal surface of the pelvis was three to four cell layers thick (zone 0–1). This epithelium became thinner where it covered the renal cortex (zone 1–2) or the outer medulla. Although the apical cells of the epithelium retained the asymmetric luminal unit‐membrane plaques, the number of cytoplasmic fusiform vesicles decreased as one studied the epithelium progressing over the zones from cortex toward papilla. Scanning electron microscopy demonstrated a small number of surface cells of a different morphology that were characterized by apical microvilli. The number of these microvillous lining cells increased as the epithelium covering the outer (zone 2–3) and inner (zone 3–4) stripe regions of the outer medulla was viewed, until the inner medulla was entirely covered by this cell type. In a reciprocal manner, the cells with the asymmetric apical plaques decreased in numbers and in their morphologic specialization in each successive region. The epithelium surrounding the inner medulla (zone 6–7) was completely devoid of this transitional cell type. Judging from the morphologic characteristics of the epithelia, one could surmise that little exchange of urea, water, and salts would occur with the extrarenal connective tissue or the cortical parenchyma. Recycling of urea might become more important physiologically with the outer stripe parenchyma, and even more so with the increased surfaces of the inner stripe parenchyma that lined the secondary pyramid, as well as with the epithelium lining the inner medulla.
Physical, biologic, and phenotypic properties of natural regulatory cells in murine bone marrow
Authors: Dorshkind Kenneth , Rosse Cornelius
Published: February 2005

A lymphocyte‐enriched fraction of murine bone marrow (BML) contains natural regulatory cells (NRC) that can inhibit, on a dose‐dependent basis, proliferative and cytotoxic responses to alloantigens in a mixed lymphocyte culture. The objective of this study was to investigate the characteristics of the cells responsible for this phenomenon in CBA mice. Maximal suppression was obtained with BML cells themselves rather than cell products. Light‐scatter analysis of NRC on the fluorescence‐activated cell sorter demonstrated them to be larger than small lymphocytes, and their sedimentation in discontinuous Percoll gradients showed the cells to be of heterogeneous density. This heterogeneity is further reflected by the fact that both plastic adherent and nonadherent BML are suppressive. NRC must be viable in order to mediate suppression; they are cortisone‐resistant and are not affected by doses of gamma irradiation up to 1,000 R. NRC are not T or B lymphocytes or Ia‐bearing macrophages. The involvement of mature granulocytes and macrophages in natural suppression is unlikely in that NRC do not bear Fc receptors. Elimination of cells from BML with the natural killer (NK) surface marker Asialo GM1 does not abrogate suppression. NRC are capable of mediating suppression across major and minor histocompatibility complex barriers. While lymphoid cells are prominent in BML, the contamination of this marrow fraction with immature granulocytes and monocytes makes a morphologic identification of NRC difficult. These characteristics are most consistent with NRC begin immature marrow cells of undetermined lineage. The relationship of NRC to naturally occurring marrow suppressor cells described in other systems is not yet clear and awaits experimental clarification.
Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of 3H‐labeled proline and tyrosine
Authors: Josephsen K. , Warshawsky H.
Published: February 2005

After injection of labeled precursors such as 3H‐proline or 3H‐tyrosine into rats, the incisor dentin contains a continuous and stable record of precursor incorporation into labeled proteins. This record was visualized and quantitated with radioautography in order to evaluate the quantitative changes in enamel where newly secreted proteins randomize with older proteins and both are eventually lost. Up to 4 hours after injection, the pulse‐dose was incorporated as a highly labeled band of predentin. The band was entirely within calcified dentin at 2 days and was further removed from new predentin by 4 and 8 days. Dentin which formed proximal to the heavily labeled band contained an amount of radioactivity reflecting the level of labeled precursor available at that time. A standardizing factor for experimental error was obtained by quantitating the reaction in the heavily labeled band, and a post‐pulse incorporation factor was determined from the amount of radioactivity added per day as weakly labeled dentin. The variation within the heavily labeled band was assumed to reflect experimental error. The number of grains in the bands were averaged from 4 hours to 8 days to give the standardizing factor. This was multiplied by the ratio of enamel to dentin counts in the same section to obtain a corrected enamel count. In this way the coefficient of variation was improved from a high of 17.2% in uncorrected enamel counts to 2.4% in corrected counts. The post‐pulse incorporation factor was higher with tyrosine than with proline. With proline it amounted to 5% increase per day from 1 to 4 days and 2.5% per day from 4 to 8 days after injection. In addition, with 3H‐proline the incorporation into predentin increased from 30 minutes to 4 hours. With tyrosine, the counts increased from 30 minutes to 1 hour, but decreased by nearly one third from 1 to 4 hours. This was interpreted as a loss of short‐lived matrix proteins including procollagen peptides produced during conversion from procollagen to tropocollagen in the predentin.
Intercellular junctions in the hematopoietic compartments of embryonic chick bone marrow
Authors: Sorrell J. Michael , Weiss Leon
Published: February 2005

Avian embryonic marrow is segregated into distinct erythropoietic and granulopoietic compartments. Within each compartment presumptive stem cells and immature blood cells establish intimate contact with their respective stromal cell. In this study we have examined one aspect of potential hematopoietic cell‐stromal cell interaction by looking for the presence of inter‐cellular junctions between these two elements. In previous studies, after aldehyde fixation, junctions were not observed, but after perfusion fixation with tannic acid‐glutaraldehyde, pentilaminar junctions became evident. These junctions were most characteristically located in the intravascular erythropoietic compartment, but were also found in the extravascular granulopoietic compartment. Junctions frequently joined presumptive stem cells with sinusoidal endothelial cells as well as joining immature erythroblasts with sinusoidal endothelial cells; and less frequently, junctions connected adjacent erythroid cells. However, reticulocytes and erythrocytes were never seen to have formed junctions with any other type of cell. Similar junctions within the extravascular compartment connected contiguous reticular cells and also, on occasion, reticular cells with sinusoidal endothelial cells. Hematopoietic cell‐reticular cell junctions were restricted to two classes of blood cells—extravascular presumptive stem cells and mast cells. There was no evidence of junctions connecting mature or maturing granuloid cells and any other cell type. The presence of intercellular junctions between immature blood cells and their respective stromal cells suggests that such interactions might play an important role in avian hematopoiesis. However, further work will be needed to determine if these junctions are merely adherence sites or whether they represent sites of intercellular communication. In either event, these junctions appear to reflect a mechanism whereby the marrow stroma could regulate erythroid maturation.
Ultrastructure of terminally differentiated adult rat cardiac muscle cells in culture
Authors: Moses R. L. , Claycomb William C.
Published: February 2005

Ventricular cardiac muscle cells isolated from adult rats were maintained in culture for 28 to 60 days and examined by transmission electron microscopy. In order to elucidate the detailed ultrastructure of the cultured myocytes, several different electron‐dense stains were used. These included tannic acid, osmium ferrocyanide, osmium tetroxide (applied as a primary fixative), and lanthanum chloride, as well as more widely used stains such as osmium tetroxide, uranyl acetate, and lead citrate. Our results show that, compared to cultured neonatal rat myocytes, cultured myocytes derived from adult rats more closely resemble in vivo adult ventricular cells. The cultured adult myocytes contained typically distributed organelles such as nuclei, mitochondria, and elements of the sarcoplasmic reticulum. Myofilaments were well organized, and typical intercalated disks were observed between adjacent cells. Unlike cultured neonatal myocytes, the adult cells contained numerous residual bodies and a relatively well developed transverse tubular system. The transverse tubular system was identified by its continuity with the extracellular space (as indicated by the penetration of electron‐dense extracellular tracers), location at or near the Z line, large lumenal diameter, and frequent participation in couplings with elements of the sarcoplasmic reticulum.
Atrophy of the zona fasciculata in the adrenal cortex of thyroparathyroidectomized rats: A quantitative study
Authors: Conran Richard M. , Nickerson Peter A.
Published: February 2005

Atrophy of the adrenal gland induced by thyroparathyroidectomy (TPX) is attributable primarily to narrowing of the zona fasciculata. But absolute volumes of the adrenal gland and zona fasciculata, not the zona glomerulosa and zona reticularis, were decreased significantly 7 weeks after TPX. Changes consistent with atrophy were also seen in the zona fasciculata by electron miscroscopy. A slight decrease in volume of cytoplasm in cells of the zona fasciculata was evident 2 weeks after TPX as shown by quantitative stereological techniques. Seven weeks after TPX, there was a significant decrease in average cytoplasmic volume as well as mitochondrial volume and surface density of mitochondrial membranes. A decrease in total volume of the zona fasciculata, as well as volume per cell of mitochondria, correlates directly with decreased production of corticosterone in response to stress in TPX rats. Parathyroidectomy (PX) had no effect on the volume of the adrenal gland, on the volume of the individual cortical zones, or on the volume per cell of cytoplasm or mitochondria; these observations indicate that changes in TPX rats are due primarily to ablation of the thyroid gland.
Quantitative morphological analysis of proliferating and nonproliferating subpopulations of IMR‐90 fibroblasts during aging in vitro
Authors: Pool Thomas B. , Heitman Teri O. , Buck Marilyn A.
Published: February 2005

Early‐, mid‐ and late‐passage cultures (population doubling levels 12, 35, and 51, respectively) of IMR‐90 fibroblasts were exposed to 3H‐thy‐midine for 48 h prior to fixation in situ for morphometric analysis in order to determine quantitatively what ultrastructural changes accompany the loss of proliferative capacity during aging in vitro. Analysis of autoradiographs, both at the light and electron microscopic levels, with an image analyzer followed by ANOVA statistical scrutiny demonstrated that a significant increase in relative cell area, an indicator of cell size, was characteristic of cells unable to incorporate 3H‐TdR at both mid‐ and late‐passage, but not at early‐passage levels. Nuclear size also increased significantly with progressive passage level but was not related to proliferative capacity. No significant difference in the area fraction of nucleoli per unit area of nucleus or of mitochondria, Golgi, or lysosomes was seen in either subpopulation at any passage level. Dilated cisternae of rough endoplasmic reticulum in early‐passage cells were seen if cells were harvested with trypsin and fixed either before or after centrifugation, but were not seen in labeled or unlabeled cells from any passage level when cultures were fixed in situ. We conclude that a significant increase in cell size is the only significant morphological change associated with the loss of proliferative capacity of IMR‐90 fibroblasts. Furthermore, our data indicate that there is no accumulation of secondary lysosomes in human diploid fibroblasts during aging in vitro; we therefore cannot support any hypothesis of aging or proliferative decline that is based mechanistically upon this phenomenon.
Effects of indomethacin on preovulatory follicles in immature, superovulated mice
Authors: Downs Stephen M. , Longo Frank J.
Published: February 2005

In order to demonstrate the possible role of prostaglandins in preovulatory follicular development, immature mice superovulated with pregnant mare serum followed 40 hours later by luteinizing hormone (LH) were treated with the prostaglandin‐synthetase inhibitor, indomethacin. Indomethacin (10 mg/kg) injected at varying intervals prior to or following LH inhibited ovulation most effectively when administered within 2 hours of the ovulatory gonadotropin. This inhibition was accompanied by (1) suppression of the morphological changes normally occurring within the follicular wall during preovulatory development and (2) failure of germinal vesicle breakdown (GVBD) in two‐thirds of the follicles examined. When GVBD occurred, indomethacin treatment appeared to delay meiotic maturation. Cumulus tissue was more compact than in control follicles and maintained a close association with the oocyte. These results suggest that alterations in the morphology of the follicle prior to ovulation—specifically, thinning of the apical follicular wall and meiotic maturation—are regulated by prostaglandins.
Variability of ciliary ultrastructure in normal dogs
Authors: Wilsman Norman J. , Farnum Cornelia E. , Reed Debra K.
Published: February 2005

The incidence of abnormal tracheal cilia from each of seven normal healthy dogs was estimated using samples prepared for TEM and SEM from the dorsal, lateral, and ventral aspects of the 3rd, 12th, and 24th tracheal rings. Some samples were demembranated with Triton X‐100 and stained with tannic acid to visualize microtubular protofilaments. From each region of each ring of each dog on which TEM was done, 500 transversely sectioned cilia were observed, 27,000 cilia overall. Abnormal numbers of central microtubules and abnormal numbers of peripheral microtubules occurred in all samples in about 2% of all cilia. Compound cilia were consistently observed in samples from the 3rd ring and were not observed in any samples from the 24th ring. Therefore, before abnormal ciliary ultrastructure may be associated with disease, the rate of occurrence must exceed that in appropriate control individuals. Additionally, compound cilia, which have previously been associated with a variety of diseases, obviously occur in normal individuals; however, their observation may be a function of biopsy site selection.
Interaction of embryonic cell surface and cytoskeleton with extracellular matrix
Authors: Hay Elizabeth D
Published: February 2005

Evidence for cell‐matrix in vitro and in the embryo is briefly reviewed, and more detailed observations are presented on the reactions of corneal epithelium and mesenchyme to extracellular matrix (ECM) The basal surface of embryonic corneal epithelium blebs when the underlying ECM is removed If the epithelium is cultured on top of the lens capsule or collagen gel, the basal surface flattens and the cortical cytoskeleton reorganizes to resemble that present in vivo The basal surface also responds to soluble matrix molecules (types I‐IV collagens, laminin, fibronectin), and the cells step up synthesis of corneal stroma as measured by incorporation of proline into collagen When embryonic corneal fibroblasts are placed on top of hydrated gels they tend to burrow into the gel rather than sitting on top as does epithelium When grown inside collagen gels, these mesenchymal cells elongate and the entire cell surface and cytoskeleton organize in response to matrix Stress fibers and ruffling membranes characterize the cells grown on glass When embryonic lens or corneal epithelia are placed within, instead of on top of, collagen gels, they give rise to mesenchyme‐like cells from their apical surfaces In vivo, these epithelia do not give rise to mesenchyme The rules for epithelial‐mesenchymal transformation in vivo are discussed in relation to these observations on cell‐matrix interaction.
Morphology of the pineal complex of the anadromous sea lamprey, Petromyzon marinus L.
Authors: Cole W. C. , Youson J. H.
Published: February 2005

The pineal complex of the anadromous sea lamprey, Petromyzon marinus L., has been examined by light and electron microscopy. It consists of two subunits: a dorsomedial pineal organ, and a ventral, left‐lateral parapineal organ, with both remaining cytologically unaltered throughout the life cycle. However, during metamorphosis there is an increase in the size and a rostral migration of the parapineal organ and a dorsolateral displacement of the pineal nerve tract.

The pineal organ is composed of an end bulb, an atrium, and a nerve tract. Two varieties of photoreceptors, termed type I and type II cells, as well as supporting and ganglion cells are present. Supporting cells are ubiquitous, but there are regional variations in the distribution and abundance of the other cell types. Type I cells are a well‐differentiated photoreceptor. Conversely, type II cells exhibit a poorly developed photosensory apparatus but possess some features commensurate with an endocrine activity.

The parapineal organ is composed of an end bulb, a ganglion region, and a nerve tract. The end bulb is dominated by type II photoreceptor and supporting cells, whereas type I and ganglion cells are sparse. The parapineal ganglion and nerve tract include neuropil, polymorphic neurons, and ependymal cells.

It is concluded that the pineal organ of P. marinus is a structurally well‐developed photosensory and photoneuroendocrine organ that is probably capable of transducing photic stimuli into nervous and endocrine messages to the brain and other organs. In contrast, the parapineal of this lamprey species is a poorly developed organ of regressed or rudimentary structure.
Cellular dynamics of the hormonal and developmental induction of hepatic alpha 2u globulin as demonstrated by immunocytochemistry and specific mRNA monitoring
Authors: Antakly T. , Lynch K. R. , Nakhasi H. L. , Feigelson P.
Published: February 2005

This immunoperoxidase study identifies the hepatocytes that synthesize alpha 2u globulin during male ontogeny and other endocrine states wherein its synthesis is modulated. To correlate biochemical parameters with the immunocytochemistry, alpha 2u globulin mRNA (alpha 2u mRNA) sequences were evaluated by Northern blot hybridization and Rot analysis to a cloned alpha 2u globulin cDNA probe and the functional level of this mRNA measured by cell‐free translation. Alpha 2u globulin and its mRNA were detectable in the liver only after male rats reached puberty. During its developmental and hormonal induction, marked heterogeneity was observed; centrolobular hepatocytes showed the strongest staining, whereas periportal hepatocytes were devoid of, or weakly stained for, this protein. This difference between centrolobular and periportal hepatocytes was enhanced during development. Mature male rats exhibited the strongest staining reaction and the highest levels of hepatic alpha 2u globulin mRNA. Almost all hepatocytes in the adult male were stained; however, centrolobular ones were remarkably more stained than periportal ones. Female rat liver was devoid of this protein and of its mRNA. Following androgen administration to castrated female rats, or hydrocortisone administration to adrenalectomized male rats, the alpha 2u globulin mRNA level as well as the number and intensity of centrolobular alpha‐2u‐globulin‐staining hepatocytes were increased in parallel. Following hypophysectomy, almost no alpha 2u globulin could be localized; likewise its mRNA was undetectable. However, when hypophysectomized adult male rats were treated with growth hormone, testosterone, thyroid hormone, and hydrocortisone, the hepatic immunocytochemical staining as well as the level of alpha 2u globulin mRNA sequences and of functional alpha 2u globulin mRNA, and the in vivo biosynthetic rate of alpha 2u globulin, became comparable to that of intact mature male rats. These studies indicate functional heterogeneity among hepatocytes which seems to be determined by their anatomical location within the hepatic lobule. Furthermore, hormonal and developmental induction of alpha 2u globulin involves both an increase in the number of hepatocytes committed to its synthesis and an increase in the rate of its synthesis in already committed cells. These events are accompanied by a concurrent increase in the hepatic alpha 2u globulin mRNA level.
Isolated guinea pig adrenocortical cells in vitro: Morphology and steroidogenesis in control and ACTH‐treated cultures
Authors: Black V. H. , Mierlak J. , Katz T. , Miao P. , Huima T. , McNamara N.
Published: February 2005

Isolated guinea pig adrenocortical cells were maintained in longterm culture in order to perform sequential experiments on the same cell populations. The cells produced fluorogenic steroids, shown by thin‐layer chromatography to be at least aldosterone, cortisol, and corticosterone. In addition, they increased production of these steroids when treated with either ACTH or dibutyryl cyclic AMP. Of particular interest was the fact that cultures treated for the initial 24‐hour culture period with ACTH maintained enhanced levels of secretion for several days in absence of hormone and had an enhanced response to ACTH later in the culture period. Such enhancement of secretion was not seen following early treatment with dibutyryl cyclic AMP. The fine structure of the ACTH‐treated cells was consistent with increased steroidogenesis. They possessed more smooth‐surfaced endoplasmic reticulum, larger mitochondrial cristal surfaces, and larger Golgi complexes than the cells in untreated cultures.
Histologic and fine‐structural anatomy of the adrenorenal portal vessels in the dog
Authors: Katholi Richard E. , Imamura Kikuko , James Thomas N.
Published: February 2005

Reflex vasoconstriction that occurs in the kidney of the dog can be the result of activation of catecholamine flow reaching the kidney directly from the adrenal medulla via adrenorenal portal vessels. This study was undertaken to learn more about the histologic and fine‐structural anatomy of these unusual vessels. We found that they are thin‐walled vessels (200–500 μm) which are accompanied by many capillaries. These portal vessels have distinctive valves and have sparse, longitudinally arranged musculature which is denser at the base of the valves. The valves in the portal vessels are arranged to permit flow in the direction from the adrenal gland toward the kidney. Smooth muscle at the base of the valve is in close proximity to non‐myelinated nerve fibers, suggesting that the opening of these valves may in part be neurally mediated. These unique anatomical features distinguish the adrenorenal portal vessels from other blood vessels and likely have functional importance in control of the adrenorenal circulation.
Studies on prolonged spermatozoa survival in chiroptera: A morphological examination of storage and clearance of intrauterine and cauda epididymal spermatozoa in the bats Myotis lucifugus and M. velifer
Authors: Krutzsch Philip H. , Crichton Elizabeth G. , Nagle Ray B.
Published: February 2005

The cauda epididymidis, uterine corpus, and cornua and uterotubal junction of Myotis function to retain and preserve normal spermatozoa throughout hibernation. In none of the sites do spermatozoa show features that might account for their extended viability. Spermatozoa stored in the uterus and epididymis show no special orientation toward the epithelium lining these sites, whereas an intimate relationship is established between some sperm and the epithelial cells of the uterotubal junction which might either account for extended postcoital sperm survival or forecast their removal from further participation. Transmission and scanning electron microscopic observations do not disclose any morphological changes in stored luminal spermatozoa. A low rate of phagocytosis of sperm is evident in the female tract during hibernation. However, spermatozoa are evidently not vulnerable to being removed from the storage sites until spring arousal when ovulation occurs. Both uterotubal epithelial cells and phagocytes appear to be involved in the disposal of spermatozoa in the female, whereas epididymal spermatozoa apparently are primarily voided during urination. A mechanism that delays capacitation must underlie the ability of spermatozoa to survive in the female reproductive tract of the hibernating bat.
Histological changes in the articular eminence and mandibular fossa during growth of the rhesus monkey (Macaca mulatta)
Authors: Hinton Robert J. , Carlson David S.
Published: February 2005

Unlike the mandibular condyle, the temporal component of the temporomandibular joint (TMJ) has been the object of relatively few investigations concerning its growth and remodeling. This report provides qualitative and quantitative documentation of microanatomical changes in the mandibular fossa and articular eminence during growth of the rhesus monkey (Macaca mulatta). The thickness of the fibrous articular tissue and the presence of cartilage cells in its deeper layers were examined histologically in 43 rhesus monkeys at five maturational levels (neonate, infant, juvenile, adolescent, and young adult). Absolute thickness of the articular tissue increased with maturational level in all areas studied, with the increase somewhat more pronounced on the posterior slope and crest of the articular eminence than in the roof of the mandibular fossa. Relative to condylar size, an increase in articularlayer thickness characterized the first three maturational levels, and was followed by a decrease during adolescent and young‐adult stages. Articular tissue in the fossa roof constituted a steadily decreasing fraction of the total articular‐tissue thickness with age, while relative thickness of the tissue on the posterior slope and crest of the eminence increased with age. These results parallel those obtained for the mandibular condyle, and they are best interpreted to indicate that forces delivered to the joint become directed more anteriorly with age. The overall pattern of topographical variation in articular‐tissue thickness and cartilage‐cell distribution suggests that greater loading of the lateral aspect of the TMJ, postulated in the human TMJ by various workers, may not be as pronounced in the monkey.
The development of alveolar septa in fetal sheep lung. An ultrastructural and immunohistochemical study
Authors: Fukuda Yuh , Ferrans Victor J. , Crystal Ronald G.
Published: February 2005

The morphogenesis of pulmonary alveolar septa in the sheep was studied by light microscopy, transmission electron microscopy and light microscopic immunohistochemistry for the detection of elastin. The primordia of alveolar septa developed in the glandular stage in areas subjacent to the epithelium, and formed alveolar septa by protruding into the glandular lumina. In their earliest stage, the primordia consisted of groups of fibroblasts, which were associated with elastic fibers and unit collagen fibrils and were surrounded by epithelial basement membrane and by more immature fibroblasts. The fibroblasts in the primordia subsequently became myofibroblasts or smooth muscle cells. In the alveolar zone of the glands, elastic fibers were exclusively found in the primordia of alveolar septa in early developing lung. In early developing lung, wavy, thickened epithelial basement membranes were found in the regions of the glands, which eventually underwent considerable expansion of their surface areas, especially in the primordia of alveolar septa and the bifurcations in the alveolar zones. Areas of fusion of the basement membranes of capillary endothelial cells and epithelial cells in the alveolar zone were found after the formation of the primordia of alveolar septa was accomplished. These areas of fusion were not found in the primordia themselves, but in regions between the primordia. Epithelial cell flattening and differentiation occurred after the formation of the primordia of alveolar septa, and flattening was first observed in the areas of the primordia and the bifurcations of the alveolar zones.
Ultrastructure of the thick ascending limb of henle in the rat kidney
Authors: Kone Bruce C. , Madsen Kirsten M. , Tisher C. Craig
Published: February 2005

The thick ascending limb of Henle (TAL) in the rat until recently has been considered a morphologically homogeneous structure despite physiologic and biochemical evidence to the contrary. The present study was designed to examine the ultrastructural characteristics of the TAL in the inner cortex and the outer and inner stripes of the outer medulla using qualitative and quantitative transmission electron microscopy. Kidneys of male Sprague‐Dawley rats were preserved by in vivo perfusion with glutaraldehyde for light and electron microscopy. The peritubular diameter and cell height were determined by direct measurements on tubule cross sections. Morphometric analyses were performed on montages of tubule cross sections. The peritubular diameter of the TAl was similar in the three regions under investigation, but the TAL cells were taller in the inner stripe than in the inner cortex and outer stripe. Morphometry revealed significant differences between the three regions with respect to the mean tubular cross‐sectional area (AT), the surface density (SV), and the surface area per mm of tubule (ST) of apical and basolateral plasma membranes, and the volume density (VV) of mitochondria. The major morphologic division appeared to be between the inner stripe segment and the remainder of the TAL. These findings document the presence of significant morphologic heterogeneity of the rat TAL.
Epithelial cell differentiation in organotypic cultures of fetal rat lung
Authors: Simpson L. L. , Tanswell A. K. , Joneja M. G.
Published: February 2005

The purpose of this investigation was to examine the suitability of an organotypic lung‐cell culture model for the study of factors influencing fetal lung‐cell differentiation. It has been reported that the use of carbonstripped (hormone‐depleted) bovine fetal calf serum in monolayer cell cultures of fetal rat lung prevents continued epithelial cell differentiation in vitro. In this study, organotypic cultures of fetal rat lung cells taken at day 20 of gestation (late canalicular stage) were prepared with a carbon‐stripped medium. These organotypic cultures were examined by light, scanning, and transmission electron microscopy for comparison with controls prepared with unstripped bovine fetal calf serum. Highly organized three‐dimensional tubular epithelial structures resembling saccules of immature lung were observed within the gelatin sponge matrix. Morphometric analysis of day 20 carbonstripped samples revealed that 74.6% of the epithelial cells in the tubular structures contained osmiophilic lamellar bodies characteristic of type II pneumonocytes. Control specimens had 71.2% cells with lamellar bodies and did not differ significantly from the experimental group. These data are similar to those obtained with organ cultures of fetal rat lung but are in contrast to findings with monolayer culture systems. The observations of this study suggest that (1) the hormones extracted from bovine fetal calf serum by carbonstripping are not solely responsible for the continued fetal lung cell differentiation observed in vitro, and (2) that spatial relationships between lung cells in vitro may be a significant factor in the control of differentiation.
An attempt to differentiate further between microglia and fluorescent granular perithelial (FGP) cells by their capacity to incorporate exogenous protein
Authors: Mato Masao , Ookawara Shigeo , Mato Takashi K. , Namiki Takuo
Published: February 2005

It seems established that under pathological conditions, microglia and blood monocytes (invading the cerebral parenchyma) behave as histiocytic cells in the central nervous system. However, it has not been clear whether or not phagocytic cells are present in normal cerebral tissue. Recently, we found a new type of cell having an uptake capacity for exogenous substance at the bifurcations of small cerebral vessels except for capillaries. According to Imamoto et al. (1982), ameboid microglia, a kind of precursor of microglia, appear at a perinatal stage and can incorporate exogenous material. In the present paper, the developmental sequences of ameboid microglia and the unique cells laden with fluorescent granules are compared at a light and electron‐microscopic level.

From this study, it is clear that ameboid microglia are already present in the corpus callosum at 5 days after birth and are potent in their uptake capacity for horseradish peroxidase (HRP). However, at 2 weeks, they transform into star cells and the capacity for incorporation diminishes markedly. The finding is also supported by the quantiative analysis of transformation of ameboid microglia. At 3 months, glial cells do not take the administered HRP under the present conditions. On the other hand, fluorescent granular perithelial (FGP) cells arise from a leptomeningeal tissue (pia mater) and become situated in the perivascular spaces. They are not clearly defined at 5 days, and their uptake capacity for HRP has not yet developed. At 2 weeks, the FGP cells take definite forms with several inclusion bodies, and their uptake capacity for HRP attains a certain degree. Often, they are located at bifurcations of small blood vessels. At 3 months, the FGP cells differentiate completely in appearance, and their pinocytotic capacity reaches a high level. Consequently, the FGP cells belong to a different type of cell from that of ameboid microglia in their developmental sequences and assume a principle role of scavenging waste products in normal cerebral tissue.
Interaction of the peritoneal cavity to intraperitoneal stimulation: A peritoneal model system to monitor cellular and extracellular events in the formation of granulation tissue
Authors: Leak Lee V.
Published: February 2005

The intraperitoneal injection of bacterial toxin and complete Freund's adjuvant in mice produced the classical inflammatory response. However, when allowed to continue, this process led to the formation of granulation tissue of the mesothelial surface. The initial lesion of the reaction was characterized by the deposition of a copious amount of fibrin filaments which were involved in the adhesion and aggregation of peritoneal cells into discrete cellular mounds on the peritoneal mesothelial surface. By 1 week postinjection, fibrin was markedly diminished and appeared as electron‐dense precipitates upon which collagen fibrils were deposited. By 2 weeks, the amount of collagen was greatly increased; and the granular components of fibrin were markedly diminished. Coincident with the deposition of collagen fibrils, there was also a neovascularization of the cellular aggregates. This process occurred when the blood and lymphatic vessels within the submesothelial connective tissue branched and invaded the newly aggregated cellular mounds. By 1 month, the cellular aggregates had taken on the appearance of granulation tissue with foci of closely packed macrophages, fibroblasts, and a network of newly formed blood and lymphatic capillaries. This intraperitoneal stimulation provides an in vivo system in which the various cellular and extracellular events of inflammation leading to the formation of granulation tissue can be monitored.
Distribution of taste and general sensory nerve endings in fungiform papillae of the hamster
Authors: Whitehead Mark C. , Beeman Cynthia S. , Kinsella Brenda A.
Published: February 2005

Sensory endings of chorda tympani and lingual (trigeminal) nerve fibers were identified by selective denervation and localized within specific regions of fungiform pipillae in the hamster. The chorda tympani was resected from the middle ear and the peripheral fibers were allowed to degenerate for 1, 3, or 8 days prior to perfusion‐fixation and electron‐microscopic examination of the anterior tongue. Taste buds were virtually devoid of intact nerves by 3 days following chorda tympani denervation. Remnants of the fibers were restricted to taste buds. Lingual fibers, on the other hand, persist in normal numbers after chorda tympani resection and populate perigemmal areas of connective tissue and extragemmal areas located apically in the squamous, nontaste epithelium surrounding the taste bud. This study provides evidence of a segregation of chorda tympani fibers in the taste bud and lingual nerve fibers in the apical fungiform papilla. The lingual nerve‐epithelial arrangement and superficial location, near the least cornified area of the tongue, may be well suited for relatively sensitive somatosensation, possibly mechanoreception. Thus, the apical fungiform papilla appears to be a site where both taste and tactile oral stimuli interact with receptors.
Nature and function of endocytosis in Sertoli cells of the rat
Authors: Morales C. , Clermont Y. , Hermo L.
Published: February 2005

The endocytic activity taking place at the apex of Sertoli cells was analyzed by using various tracers to demonstrate fluid‐phase and adsorptive endocytosis. Native ferritin and protein‐gold complexes, used to demonstrate fluid‐phase endocytosis, were internalized by Sertoli cells at all stages of the cycle of the seminiferous epithelium. At 5 min after injection, the tracers were found in the large spherical or C‐shaped vesicles seen in the apical processes; at 15 and 30 min, the tracers accumulated in light multivesicular bodies, and at 60 min in dense multivesicular bodies and lysosomes. At later time intervals, an increasing number of lysosomes contained the tracers. Following injection of cationic ferritin or concanavalin A‐ferritin, these tracers, used to demonstrate adsorptive endocytosis, were found to be found to the plasma membrane of Sertoli‐cell apical processes but were not collected by the large cytoplasmic apical vesicles, multivesicular bodies, or lysosomes. As an exception, a few special multivesicular bodies seen in the large apical processes which encapsulate the heads of late spermatids at stage VII of the cycle contained these tracers. During stage VIII of the cycle, the residual bodies which detach from the mature spermatids are phagocytosed by Sertoli cells. Such residual bodies do not contain their own hydrolytic lysosomal enzymes. However, it was observed that the lysosomes which form as a result of the fluid‐phase endocytic activity of the Sertoli cells fuse with the phagocytosed residual bodies and by means of their hydrolytic enzymes contribute to the rapid disintegration of these bodies. Thus, during stage VIII of the cycle, the Sertoli cells integrate two distinct processes, i.e., fluid‐phase endocytosis and phagocytosis.
Proliferation and differentiation sequence of osteoblast histogenesis under physiological conditions in rat periodontal ligament
Authors: Roberts W. Eugene , Morey Emily R.
Published: February 2005

To define the mechanism of osteoblast histogenesis, nuclear morphometry was utilized as a marker for precursor cell differentiation. One hour after 3H‐thymidine injection, groups of 7‐week‐old rats were killed at hourly intervals over one complete 24‐hr photoperiod (LD 12:12). S‐phase and mitosis were assessed in autoradiographs of 3‐μm sections of molar periodontal ligament (PDL) adjacent to a physiological bone‐forming surface. Labeled nuclei were divided into four categories according to morphometry of nuclear size: A (40–79 μm3), B (80–119 μm3), C (120–169 μm3), and D (≥ 170 μm3) cells. C and D cells synthesize DNA during the light and divide in the following dark phase; the rhythm for A cells is the opposite. B cells demonstrated no preference and were subsequently determined to be nonosteogenic. Compared to A cells the S‐phase photoperiod of C and D cells (combined) is approximately a one‐to‐one reciprocal relationship, suggesting two proliferating progenitors in series. Based on arrest points in the histogenesis sequence, five compartments are defined: (1) A cells, less differentiated, self‐perpetuating precursors; (2) A′ cells, committed osteoprogenitors; (3) C cells, G1 stage preosteoblasts; (4) D cells, G2 stage preosteoblasts; and (5) Ob cells, morphologically distinct osteoblasts. Minimal elapsed time for the A →A′ → C → D → Ob sequence is about 60 hr (five alternating dark/light cycles). A stress/strain‐mediated increase in nuclear volume (A′ → C) is an important, rate‐limiting step in osteoblast differentiation.
The effects of the organophosphate insecticide malathion on very young chick embryos: Malformations detected by histological examination
Authors: Wyttenbach Charles R. , Thompson Sandra Collins
Published: February 2005

This histological study sought to determine the nature and incidence of developmental abnormalities induced by one of the reportedly least teratogenic of insecticides injected into very young chick embryos. Using techniques to assure rapid contact between injectant and embryo, eggs incubated for 24, 48, or 72 hr were injected with corn oil or 125 μg‐4.0 mg malathion. The embryos were recovered 48 hr later, paraffin‐embedded, serially cross‐sectioned, and examined in detail. Structures affected (and the nature of the defects) were as follows: (1) wing level notochord and spinal cord (folded or undulated); (2) trunk/leg level spinal cord (variously, neural folds unfused, roof infolded, canal partitioned, etc.); (3) eye (lens misshapen or severely thinned, optic cup incompletely invaginated); (4) diencephalon (epiphysis bifurcated or off‐center, supernumerary outgrowths); (5) cardiovascular structures (atrium and major blood vessels enlarged); and (6) tailbud (curled into hindgut: ourentery). Overall incidence was both dose‐ and age‐related, doubling for each doubling of dose and tripling for each 24 hr less age at exposure. For most (not all) individual structures, incidence was greatest when exposed at 24 hr and nil at 72 hr. Severity of effect was not consistently doseor age‐dependent. We conclude that (1) contrary to previous reports, 24‐ to 72‐ hr embryos are highly vulnerable to insecticide exposure, with the youngest the most vulnerable, and (2) many of the defects detected may be attributed to either of two mechanisms: failure in formation of the supportive sheath, or factors that cause epithelial morphogenesis (e.g., microtubules, microfilaments, extracellular material, cell‐to‐cell adhesion mechanisms). Previous observations that 1‐ to 3‐day embryos are relatively unresponsive to insecticides are probably artifactual owing to imprecise techniques.
Quantitative genetic variation in the skeleton of the mouse: II. Description of variation within and between inbred strains
Authors: Lovell D. P. , Johnson F. M. , Willis D. B.
Published: February 2005

Variation in the skeletons of over 400 male and female mice from 12 genotypes was investigated by using multivariate statistical methods. A series of discriminant functions explains the differences in the shape of six bones: mandible, os coxae, femur, tibia‐fibula, scapula, and humerus. The anatomical features of bone shape described by these functions are summarized together with illustrations of the typical shapes of each bone from the 12 genotypes. Variability within genotypes was investigated by using the Mahalanobis D2 distance—a measure of the difference between two points representing multivariate data—from the group mean. A series of variants were detected ranging from grossly abnormal bones to bones showing subtle differences localized to specific regions. Examples of the variants found are illustrated.