bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of mucocartilage in the larval anadromous sea lamprey, Petromyzon marinus L.
Authors: Wright Glenda M. , Youson John H.
Published: February 2005

The fine structure of mucocartilage, a tissue unique to larval lampreys, was examined in Petromyzon marinus L. This tissue is surrounded by a perichondrium of vascularized, dense connective tissue composed of fibroblasts, collagen fibrils, and elastic‐like microfibrils, but it is avascular itself and consists of elastic‐like microfibrils, ground substance, and a few diffusely scattered fibroblasts. Fibroblasts possess rough endoplasmic reticulum, many free ribosomes, a well‐developed Golgi apparatus, a tubulo‐vesicular network, and a number of secondary lysosomes containing crystalline material. The appearance of the organelles suggests the involvement of the cell in the synthesis and secretion of the ground substance and microfibrils. Tubular microfibrils, 11–13 nm in diameter, comprise the major portion of the matrix, and they are similar to those described in developing mammalian elastic tissue (Ross and Bornstein, 1969). The retention of the microfibrils may represent either a primitive form of elastic fiber in this “primitive” vertebrate or reflect the larval condition of the lampreys under examination. Scattered spherical to polyhedral‐shaped matrix granules and inter‐granular filaments make up the remainder of the matrix. It was concluded that mucocartilage in larval lampreys is not a conventional type of vertebrate connective tissue.
Ultrastructural visualization of complex carbohydrates in eosinophilic leukocytes
Authors: Parmley Richard T. , Takagi Minoru , Spicer Samuel S. , Thrasher Albert , Denys Francis R.
Published: February 2005

Complex carbohydrates in eosinophils from human, rabbit, and rat marrow were identified and localized by cytochemical and radioautographic methods. The high iron diamine‐thiocarbohydrazide‐silver proteinate (HID‐TCH‐SP), low iron diamine (LID)‐TCH‐SP, and periodate (PA)‐TCH‐SP methods were used for the localization of sulfate, sulfate and carboxyl, and vicinal glycol‐containing complex carbohydrates, respectively. Golgi vesicles and small precursor granules (0.2–0.4 μm in diameter) demonstrated strong HID‐TCH‐SP staining and labeled intensely after a 10‐minute pulse with 35 SO42−. Crystalloid‐free or immature specific granules (0.5–0.9 μm in diameter) labeled heavily after a 60‐minute incubation and 60‐minute chase with 35SO42−. Immature granules were graded according to their HID‐TCH‐SP staining: Type 1 granules demonstrated strong rim staining and similar or somewhat less central staining, whereas type 2 granules only demonstrated rim staining, and type 3 granules lacked staining. Fully mature crystalloid‐containing granules lacked staining. LID‐TCH‐SP similarly stained the HID‐positive sulfated material in cytoplasmic granules. PA‐TCH‐SP stained some Golgi vesicles and diffusely stained all precursor granules and type 1 granules. Weaker staining was observed in type 2 granules and staining was very weak or absent in type 3 and crystalloid‐containing granules. In early eosinophils, tubulovesicular structures (TVS) were observed rosetting and contacting precursor and type 1 granules. These TVS contained material with strong PA‐TCH‐SP staining but lacked HID‐TCH‐SP or LID‐TCH‐SP‐reactive acidic glycoconjugates. Flattened Golgi saccules of early eosinophils stained weakly or not at all with the PA‐TCH‐SP method. Small granules and TVS in late (bilobed) eosinophils displayed PA‐TCH‐SP reactivity and lacked HID‐TCH‐SP staining but differed from TVS in early eosinophils in that they were not associated as rosettes with specific granules. These results indicate that sulfated and vicinal glycol‐containing complex carbohydrates are differently distributed in immature specific granules of eosinophils and presumably become masked to staining as the granule matures.
Nuclear size as a cell‐kinetic marker for osteoblast differentiation
Authors: Roberts W. Eugene , Mozsary Peter G. , Klingler Eliane
Published: February 2005

A nuclear morphometic assay for preosteoblasts is introduced as a cell‐kinetic technique, applicable to routine histological preparations of mineralized tissue. Because this method is a morphological marker for osteoblast precursor cell differentiation, it provides a new dimension for determining the mechanism of osteoblast histogenesis. Osteoblast precursors of the periodontal ligament are a mixed population of progenitors, kinetically separable into two distinct groups according to nuclear size. Preosteoblasts, the immediate proliferating precursors of osteoblasts, have large nuclei (>170 μm3) and are derived from relatively undifferentiated fibroblastlike cells, which have smaller nuclei (<80 μm3). Increase in nuclear volume, during G 1 phase of the cell cycle, is apparently a morphological manifestation of change in genomic expression. This key event in preosteoblast differentiation is related to mechanical stress/strain and may be an important rate‐limiting step in osteoblast histogenesis.
Histochemical and biochemical studies of carbonic anhydrase activity in the opercular epithelium of the euryhaline teleost, Fundulus heteroclitus
Authors: Lacy Eric R.
Published: February 2005

Carbonic anhydrase (CAH) activity was biochemically measured and histochemically localized (at both the light and electron microscope levels) in isolated opercular membranes from teleost fish, Fundulus heteroclitus, adapted to freshwater (FW), seawater (SW), and double‐strength seawater (2 × SW). The normal morphology of this membrane showed that its epithelial portion consisted of five cell types: (1) chloride cells, which have been previously implicated as responsible for the active chloride transport across the epithelium; (2) mucous cells; (3) pavement cells, which formed the major portion of the free epithelial surface; (4) supportive cells, which had an abundance of intermediate (10 nm)‐type filaments suggesting a structural role for these cells; and (5) vesicular cells, which were characterized by various types of membrane‐bound vesicles, including lysosomes, and numerous free ribosomes. Vesicular cells may be stem cells and/or endocrine cells. Hansson's histochemical method for CAH revealed cobalt sulfide reaction product confined to the following structures in fish from each environment: (1) chloride cells: throughout the cytoplasm and some nuclear staining; (2) mucous cells: throughout the cytoplasm, some nuclear staining, and some in mucous granules; (3) vesicular cells: confined to lysosomes, some of the vesicles, and nucleoli; (4) a small portion of the intracellular space between adjacent vesicular cells and supportive cells; and (5) supportive cells: in nucleoli and occasionally in larger membrane‐bound lysosomelike structures. Acetazolamide (10−5 M) and potassium cyanate (KCNO) (10−1 M) in Hansson's incubation medium completely inhibited the formation of reaction product. Biochemical determination of CAH activity on vascularly perfused, isolated opercular membranes showed no statistically significant difference in enzyme activity between environmental groups. The following units of activity/mg opercular membrane protein were measured: FW: 0.63 ± 0.02; SW: 0.43 ± 0.08; 2 × SW: 0.64 ± 0.09.
Observations on Graafian follicles and their oocytes during lactation and after the removal of pouch young in the marsupials Isoodon macrourus and Perameles nasuta
Authors: Lyne A. G. , Hollis D. E.
Published: February 2005

Ovaries from 63 bandicoots (Isoodon macrourus and Perameles nasuta) were collected in order to obtain Graafian follicles close to ovulation for light and electron microscopy. During the first 42 days of lactation (lactation c. 60 days), the follicles were less than 1.0 mm in diameter, whereas from 43 to 52 days, some animals had follicles up to 2.0 mm in diameter, or ovulation had occurred and new corpora lutea were present. This ovulation was associated with the lactation estrus that occurred in some animals.

In general, the largest Graafian follicles of the bandicoots were morphologically similar and resembled those of many other mammals. These follicles protruded from the surface of the ovary and revealed a conspicuous theca interna. The granulosa cells exhibited an unusual feature in that they contained masses of glycogen, often associated with lipid droplets and filaments.

The oocytes were similar in size (diameter c. 150 μm) to those of some other marsupials and were surrounded by a zona pellucida and cumulus cells attached to the granulosa layer. The cumulus cells did not form a corona radiata as in eutherian mammals. The oocyte nuclei were somewhat flattened, peripherally located and similar in size (c. 40 × 19 μm) to those in other marsupials. These nuclei, which stained lightly with Azure A and were electron‐lucent and homogeneous, were unusually irregular in contour. The nuclei were unique in that nucleoli were always absent. Small cytoplasmic bodies which may have been extruded nucleoli were found in the oocytes of I. macrourus, but not in P. nasuta.

The cytoplasm in the bandicoot oocytes resembled that of other marsupials and some eutherians in that it was highly vacuolated with most of the organelles concentrated peripherally. Within the central region of the bandicoot oocytes there were crystalloids which were similar to those in oocytes of primordial follicles and in unilaminar blastocysts of I. macrourus.
The contribution of the inferior endocardial cushion of the atrioventricular canal to cardiac septation and to the development of the atrioventricular valves: Study in the chick embryo
Authors: De La Cruz María V. , Giménez‐Ribotta Minerva , Saravalli Oscar , Cayré Raúl
Published: February 2005

The contribution of the inferior endocardial cushion of the atrioventricular canal to cardiac septation and to the development of the atrioventricular valves was studied in the chick embryo by in vivo labelling techniques. The study was performed in White Leghorn chick embryos in which the dorsal cushion was labelled at stage 20‐21 (Hamburger and Hamilton, 1951), when the endocardial cushions were not yet fused. The embryos were sacrificed at stage 35 (mature heart).

These experiments allow us to conclude that the inferior atrioventricular cushion gives origin to: (a) that part of the cardiac septum between the septal insertion of the antero‐septal leaflet of the mitral valve and the fibrous ridge which is the equivalent to the human septal leaflet of the tricuspid valve (atrioventricular septum); (b) the region of the interatrial and the interventricular septa adjacent to the atrioventricular septum; (c) the portion of the antero‐septal leaflet of the mitral valve which inserts into the septum; (d) the fibrous ridge corresponding to the septal leaflet of the tricuspid valve.

Microdissection shows that, when they appear at stage 18, the superior and inferior endocardial cushions of the atrioventricular canal are in continuity, without boundaries, with both the interatrial and interventricular septa. Therefore, each atrioventricular orifice opens into its corresponding ventricle, there being no stage in the development of the chick embryo heart in which the atrioventricular orifices are connected to the left ventricle at the same time.

The development of the atrioventricular canal is similar in the chick and human.
Cytodifferentiation of the nonciliated bronchiolar epithelial (Clara) cell during rabbit lung maturation: An ultrastructural and morphometric study
Authors: Plopper Charles G. , Alley Janice L. , Serabjitsingh Cosette J. , Philpot Richard M.
Published: February 2005

The nonciliated bronchiolar epithelial (Clara) cell of adult lung is commonly defined by two cellular components: abundant agranular endoplasmic reticulum (AER) and electron‐dense ovoid secretory granules. These reflect the Clara cell's proposed functions as the source of bronchiolar surface secretions and the site of xenobiotic metabolism via the cytochrome P‐450 monooxygenase system. Since previous studies have indicated that Clara cells may not attain a fully functional state until some weeks after birth, the present study was undertaken to characterize systematically the differentiation of this cell type during lung maturation. Lungs were fixed by airway infusion with glutaraldehyde/paraformaldehyde (550 mOsm, pH 7.4) from at least three male rabbits at each of the following ages: 24, 27, and 30 days fetal, and 0–1 day, 3–4 days, 1, 2, 3, 4, 5, 8, 12, 15, 17, and 25 weeks postnatal; and pieces were processed for transmission electron microscopy by a selective embedding procedure. Quantitation was performed on electron micrographs (at 15,750 x) of cell profiles, which included the base, apex, and nucleus. Volume fractions of constituents of a minumum of 30 cells per animal (8 weeks and younger) and 10 per animal in older groups, were estimated by point counting with a Weibel 168‐point test grid. Cell and nuclear size were estimated with a computerized digitizer (Zeiss Videoplan). Nonciliated cells of prenatal animals had large amounts of cytoplasmic glycogen (over 60% of the cell cytoplasm), few mitochondria (less than 15%), little granular endoplasmic reticulum (GER) (20%), minimal AER (less than 5%), and no granules. Postnatal animals 2 weeks of age and younger were similar, except for the presence of secretory granules and slightly more abundant AER (5 to 20%). By 4 weeks postnatal age, nonciliated cells resembled that of older animals with abundant apical AER (over 40%), secretory granules, little glycogen (11%), and GER (10%). We concluded that (1) the Clara cell is immature at birth; (2) differentiation occurs primarily during weeks 3 and 4 of postnatal life; (3) vast amounts of cytoplasmic glycogen are characteristic of the undifferentiated cell; and (4) four cellular constituents, AER, glycogen, mitochondria, and GER, undergo significant shifts in abundance during differentiation. These shifts appear to be in the sequence expected of a cell type undergoing the initiation of biosynthesis of secretory products and biogenesis of agranular endoplasmic reticulum.
Estimation of cell numbers and volumes of bronchiolar epithelium during rabbit lung maturation
Authors: Hyde Dallas M. , Plopper Charles G. , Kass Philip H. , Alley Janice L.
Published: February 2005

To estimate the numbers and volumes of bronchiolar epithelial cells during lung maturation, we examined rabbits at three time points, 30 days gestation and 4 and 17 weeks postnatal age. Morphometric measures (mean caliper diameter, surface area, and volume) of nonciliated and ciliated bronchiolar cell nuclei, using computer modeling from serial sections, showed a significant decrease in nuclear size for both cell types and a significant increase in cell volume for the nonciliated bronchiolar cell during lung maturation. A shape coefficient (β) proved to be the most efficient estimator of the number of cells per unit volume when it was used with estimates of the number of nuclei per unit area and the volumetric density of nuclei. Two‐dimensional estimates of bronchiolar epithelial cell abundance (the number of nuclei per unit length or area) significantly underestimated the percentage of nonciliated bronchiolar cells as compared to three‐dimensional estimates for rabbits 17 weeks of age. We have shown an inverse relationship between nonciliated and ciliated bronchiolar cell abundance during lung maturation. Nonciliated cells decreased while ciliated cells increased.

We have confirmed that cytodifferentiation of the nonciliated bronchiolar cell occurs within the first 4 weeks of postnatal development. The volume of the nonciliated bronchiolar cell increased about twofold during development. Because of the concomitant decrease in nuclear volume, the cytoplasm of the cell showed an even greater increase in volume. Within the cytoplasm of the nonciliated bronchiolar cell, glycogen significantly decreased, and agranular endoplasmic reticulum (AER) and mitochondria significantly increased in volume during development. The biosynthesis of AER closely correlated with pharmacological studies of xenobiotic metabolism during rabbit lung maturation.
Immunocytochemical staining of isolated rat sertoli cells for anti‐FSHβ
Authors: Hon Charlene A. , Gardner Paul J. , Leuschen M. Patricia
Published: February 2005

Sertoli cells are a primary target for the action of follicle‐stimulating hormone (FSH) in the testis. The purpose of this investigation was to verify ultrastructurally that FSH binds to receptors on the plasma membrane of isolated rat Sertoli cells.

A reltaively pure aliquot of Sertoli cells was obtained by first dissociating testicular tissue from immature rats with collagenase and then centrifuging the suspension in Percoll density gradients. Pre‐embedding staining with the peroxidase anti‐peroxidase (PAP) complex technique using anti‐FSHβ as the primary antiserum localized endogenous receptor‐bound FSH on the plasma membrane of isolated Sertoli cells. Staining was considered to be specific since membranes of Sertoli cells derived from hypophysectomized rats were not stained when subjected to the same procedure.

Cytoplasmic vesicles in Sertoli cells from experimental, control, and hypophysectomized groups also stained with PAP. Staining of these structures appeared to be specific since it was obliterated by preabsorption of anti‐FSHβ with FSH. Preabsorption with luteinizing hormone (LH) did not affect the staining of cytoplasmic vesicles.

The results of this investigation provide the first evidence for ultrastructural localization of specific binding sites for anti‐FSHβ on the cell membrane of isolated Sertoli cells using an unlabeled antibody technique, and they further support the contention that Sertoli cells are a primary target for the action of FSH.
Diurnal variations in the photoreceptor synaptic terminals of the newt retina
Authors: Ball Alexander K. , Dickson D. Howard
Published: February 2005

Newt photoreceptor synaptic terminals undergo a variety of morphological changes over a 24‐hr (LD 12:12) cycle. During the day, densecored synaptic vesicles were found to increase in number and accumulate near the synaptic lamellae; during the dark phase, the dense‐cored vesicles decreased in number, while large clear vesicles and profiles of smooth endoplasmic reticulum increased in frequency. The most marked change in photoreceptor synaptic terminal morphology occurred after 10 hr of darkness, at 0730 hr. At this time, photoreceptor synaptic terminal cross‐sectional area was found to increase dramatically. Morphometric analysis showed that the number of synaptic vesicles in these terminals remained constant throughout the day, as did the perimeter of photoreceptor terminal profiles. The observed increase in area of synaptic terminals at 0730 hr was found to be due to a decrease in the folding of the terminal plasma membrane. Qualitative observations showed endocytosis to be occurring at a rapid rate at this time as well; and since the number of synaptic vesicles and terminal perimeter did not change, exocytosis of synaptic vesicles was assumed to be occurring at an equally rapid rate. These findings support an extension to the hypothesis of Monaghan and Osborne (1975), suggesting that photoreceptor synaptic vesicles become “supercharged” with transmitter substance in the light.
Effects of progesterone on the oviductal epithelium in estrogen‐primed prepubertal beagles: Light and electron microscopic observations
Authors: Sawyer H. R. , Olson P. N. , Gorell T. A.
Published: February 2005

A total of 45 prepubertal beagles 6 to 8 weeks of age were used to study the cytological changes that accompany regression of the oviductal epithelium. The oviductal epithelium in untreated pups consisted of undifferentiated low cuboidal cells that measured 10.3 ± 2.0 μm in height. In response to estradiol (E2), low cuboidal cells underwent hypertrophy, hyperplasia, and cytodifferentiation and gave rise to columnar ciliated and secretory cells. After 12 days of E2 treatment the epithelium was fully differentiated and measured 29.4 ± 2.6 μm in height with 56% of the cells possessing cilia. When E2 treatment was continued for an additional 12 days, the epithelium was maintained in a differentiated state. However, if E2 treatment was terminated or progesterone (P) given alone or in conjunction with E2, the oviductal epithelium regressed and after 6 days was composed of low cuboidal cells that ranged in height from 9 to 14 μm with approximately 25% of the cells possessing cilia. A variety of cytological changes characterized the process of regression. The most immediate signs that regression was underway were a reduction in the height of the epithelium and the presence of cells with shrunken, pleomorphic nuclei that lacked prominent nucleoli. Degenerative events included: (1) pinching off and shedding of the apical cytoplasm of cells comprising the epithelium, (2) extrusion of whole cells and/or nuclei, and (3) resorption of cilia and basal bodies. During the first 6 days following E2 withdrawal or P treatment, macrophages and cellular debris were frequently present within the lumen of the oviduct. The process of regression did not proceed synchronously throughout the ampulla of the oviduct, nor did all cells appear to degenerate in the same manner. The cytological changes that accompanied oviductal regression following P treatment were identical to those observed following E2 withdrawal. Results from experiments conducted in the present study show that: (1) E2 induces the oviductal epithelium to differentiate and is required to maintain the epithelium in a differentiated state, (2) E2 withdrawal or P treatment causes the oviductal epithelium to regress, (3) at least three distinct degenerative processes are involved in the transition of columnar ciliated and secretory cells into low cuboidal cells, and (4) regression does not occur synchronously throughout the ampulla region of the oviduct.
Organogenesis of the mouse extensor digitorum logus muscle: A quantitative study
Authors: Ontell Marcia , Kozeka Kenneth
Published: February 2005

A quantitative analysis of the pattern of development and growth of the fetal extensor digitorum longus muscle of the 129 ReJ mouse was carried out in spaced, serial ultrathin sections with computer‐assisted morphometry. Muscle from 12‐, 14‐, 16‐, and 18‐day in utero mice and from newborn and 5‐day postnatal mice was analyzed to determine age‐related changes in such factors as the maximal girth and length of the muscle, the number of myotubes, the “cluster” frequency, and the diameters and lengths of the myotubes and muscle units. A distinct temporal pattern of development was established. It was quantitatively determined that a delay ≥ 2 days occurs between the formation of primary myotubes (present at 12 days in utero, and secondary myotubes (present at 16 days in utero)). By 16 days in utero, groups of myotubes, consisting of one primary myotube and a variable number of secondary myotubes, form “clusters” surrounded by a common basal lamina. Morphometric analyses of diameter distributions establish that most, if not all, secondary‐generation myotubes are formed in association with larger, more mature myotubes. Quantitative data support the hypothesis (Ontell and Kozeka, 1984) that cluster formation and cluster dispersion occur simultaneously, beginning sometime between 16 and 18 days in utero. By 18 days in utero, the adult number of myofibers is present in the developing muscle mass. Analyses of lengths and diameters of the same fibers establish that the pattern of growth of the last‐formed myotubes of the developing muscle mass is different from that of myotubes formed earlier in development.
Graded morphogenetic patterns during the development of the extraembryonic blood system and coelom of the chick blastoderm: A scanning electron microscope and light microscope study
Authors: Kessel Joan , Fabian Barry C.
Published: February 2005

This scanning electron‐ and light‐microscopic study traces the morphogenesis of the yolk‐sac vascular system and extraembryonic coelom in the chick blastoderm. The fate of the mesodermal cells in both the area opaca vasculosa (AOV) and the area pellucida (AP) is followed, and the cellular patterning in these two areas is compared. We describe new details of the formation of coelom lining in the AOV, and new observations of the tendency of the intravascular blood island cells of the AOV to become flattened and attenuated. The morphogenesis of the blood system and coelom is analyzed in terms of polarized morphological patterns with coordinates in two modes: proximodistal (from the AP to the AOV) and dorsoventral (from the ectoderm to the endoderm). By highlighting differences in the methods of formation of blood vessels and coleom lining in the AP and AOV, this paper resolves some paradoxes in the literature.
Sulfation and transport of basement membrane proteoglycans, as visualized by 35S‐sulfate radioautography in the endodermal cells of the rat parietal yolk sac
Authors: Fatemi S. H. , Leblond C. P.
Published: February 2005

In the hope of clarifying the biogenesis of basement membrane proteoglycans, an injection of 35S‐sulfate was given to concepti of 12‐day gestant Sherman rats. The parietal wall of the yolk sac (including endodermal cells and the associated basement membrane known as Reichert's membrane) was removed at times varying from 7 min to 24 hr after injection and processed for electron microscopic radioautography. Silver grains were counted over the organelles of endodermal cells as well as over Reichert's membrane.

Between 7 min and 2 hr after 35S‐sulfate injection, radioactivity was observed in the endodermal cells, while from 4 to 24 hr it was mostly present in Reichert's membrane. Detailed distribution of the cellular radioactivity at 7 and 15 min showed about 20% in the rough endoplasmic reticulum (rER), 60% in the Golgi apparatus, and 8% in secretory granules. The radiactivity present in rER and Golgi apparatus decreased to low levels by 2‐‐4 hr after injection. In secretory granules, radioactivity increased to reach a peak at 2 hr and then declined; moreover, only the granules associated with the trans Golgi face were radioactive at early time intervals, while those scattered through the cytoplasm and along the cell surface became radioactive at later times. Between 4 and 24 hr, radioactivity became negligible over all cell organelles, while it was collected in Reichert's membrane.

Biochemical reports indicate that when 35S‐sulfate is added to organ cultures of Reichert's membrane and endodermal cells, about 90% of the incorporated which these proteoglycans acquire sulfate are likely to be those labeled at 7 min after 35S‐sulfate injection, that is, the Golgi apparatus and to a lesser extent the rER, whereas some labeling of the secretory granules located at the trans Golgi face is explained by rapid acquisition of sulfated proteoglycans from the Golgi apparatus. Label later appears in the secretory granules along the cell surface and, eventually, in Reichert's membrane. It is concluded that secretory granules transport newly formed proteoglycans from the Golgi apparatus to the outside for deposition into Reichert's membrane.
Plasma membrane biogenesis in the avian salt gland: A biochemical and quantitative electron microscopic autoradiographic study
Authors: Sarras Michael P. , Rosenzweig Lionel J. , Addis John S. , Hossler Fred E.
Published: February 2005

The avian salt gland provides an ideal system for the study of plasma membrane (PM) biogenesis. Feeding ducklings 1% sodium chloride (salt stress) induces the secretory cells of the gland to synthesize large amounts of PM, which forms an extensive basolateral PM domain after 7–9 days of treatment. In the present study, the initial biosynthetic events following salt stress were investigated. In vivo studies using 3H‐uridine indicated that increased rates of RNA synthesis could be detected by 2 hr after the beginning of salt stress and continued through at least 12 hr. Under in vitro conditions, increased rates of protein and glycoprotein synthesis (as monitored by 3H‐leucine and 3H‐fucose incorporation, respectively) were also detected after 2 hr and continued through 7–9 days. Increased levels of Na, K‐ATPase, a specific secretory cell PM marker, were detected after 8 hr of treatment as monitored by specific activity and 3H‐ouabain binding. Sodium dodecyl sulfate‐polyacryl‐amide slab gel electrophoresis coupled with fluorography indicated that both 3H‐leucine and 3H‐fucose were incorporated into partially purified preparations of Na, K‐ATPase isolated after 12 hr. Light microscopic autoradiographic analysis of pulse‐chase experiments indicated that in secretory cells of 12‐hr salt‐stressed glands, 3H‐leucine‐ and 3H‐fucose‐labelled products reached the cell periphery by 1–2 hr after the initial pulse. The incorporation of both tritiated precursors was predominately associated with the secretory cells. Quantitative electron microscopic autoradiography indicated that 3H‐leucine is initially taken up by elements of the rough endoplasmic reticulum (RER) and cytoplasm (5 min postpulse), subsequently transported to and concentrated within components of the Golgi apparatus (10 min of chase), and ultimately incorporated into all domains of the plasma membrane of secretory cells by 1–2 hr of chase. The data is consistent with a flow of newly synthesized membrane components from RER to Golgi to plasma membrane and is analogous to the pattern previously found for the synthesis and processing of PM proteins in a wide variety of cell types.
Bimodal variations in subcellular structures of rat thyroid follicular cells during 24 hours: Fine structural and morphometric studies
Authors: Murakami Gen , Uchiyama Yasuo
Published: February 2005

To clarify 24‐hr variations in rat thyroid follicular cells under physiological conditions, their subcellular structures were examined at six evenly spaced times during 24 hr by using a morphometric technique. The volume, surface, and numerical densities of subcellular structures varied distinctly over each 24‐hr period, with a bimodal pattern. The cellular and nuclear volumes varied also bimodally over 24 hr. A decrease in the surface density of the apical plasmalemma at 1200 and 0000 hr coincided with an increase in volume density of cytoplasmic granules representing colloid droplets and dense bodies. Most granules (colloid droplets) appearing at these times were reduced in electron density. At other times, especially at 1600 and 0400 hr, morphometric parameters of rough endoplasmic reticulum (rER), Golgi complex, and subapical vesicles were prominently increased, although values for rER did not peak at 1600 hr. At these times, the volume densities of cytoplasmic granules, most of which were heterogeneous and of homogeneous electron density, were decreased. These findings coincided with immediate and subsequent reactions of follicular cells after injection of thyroid‐stimulating hormone (TSH). From the evidence, it seems likely that variations in follicular cells over a 24‐hr period reflect variations in blood TSH concentration. The total membrane areas of membrane components in follicular cells were calculated from the morphometric measurements. These areas fluctuated unimodally during 24 hr over a 65% range. This suggests that the membranes in follicular cells are subjected to cyclic degradation and regeneration during each 24‐hr period.
Changes in colloid droplets and dense bodies in rat thyroid follicular cells during 24 hours: Fine structural and morphometric studies
Authors: Uchiyama Yasuo , Murakami Gen , Igarashi Masaya
Published: February 2005

Two changes in cytoplasmic granules, corresponding to colloid droplets and dense bodies, in rat thyroid follicular cells during 24 hr were analyzed morphometrically in the apical, intermediate, and basal parts of the cells. The volume and surface densities of the cytoplasmic granules and their volumes and surface areas in the apical and intermediate parts varied bimodally over a 24‐hr day, being high at 1200 and 0000 hr and low at other times. In apical and intermediate regions, colloid droplets were predominant at 1200 and 0000 hr, whereas the cytoplasmic granules became heterogeneously or homogeneously electron‐dense at other times. In the basal part, these morphometric parameters were not synchronized with those in the other two regions, showing lower values. The basal cytoplasmic granules were heterogeneously or homogeneously electron‐dense. Small, homogeneously dense granules appeared in both the apical and intermediate parts and in the basal part with a certain time lag. These granules were often in contact with colloid droplets in the lumenal two parts at 1200 and 0000 hr. Their numerical densities were low in the apical part, but high in the intermediate and basal parts. These results suggest that newly formed colloid droplets migrate from the apical through the intermediate to the basal part, changing in appearance as they go. Moreover, it seems likely that small, homogeneously dense granules are a final form of cytoplasmic granule. They may be reused for degradation of colloidal protein.
Mechanisms of splenic control of murine malaria: Reticular cell activation and the development of a blood‐spleen barrier
Authors: Weiss Leon , Geduldig Ulla , Weidanz William
Published: February 2005

By complex stromal responses, the spleen controls the course of nonlethal Plasmodium yoelii murine malaria. The course of disease may be divided into four phases. In the immediate postinfective phase, lasting several days, the filtration beds of the spleen are open. Parasitized and nonparasitized erythrocytes, many plasma cells, lymphocytes, and macrophages are sequestered from the blood; and most or all of the parasitized erythrocytes are phagocytized. In the following precrisis phase, approximately 1 week long, there is increasing parasitemia and anemia. The filtration beds of the spleen support large‐scale erythropoiesis, lymphopoiesis, plasmacytopoiesis, and monocyte‐to‐macrophage differentiation. Reticular cells, the stromal cells which form the splenic filtration beds, become activated, showing signs of intense protein secretion and increased branching and mitosis. The locules of the filtration beds appear sealed off from the blood by branches of activated reticular cells. A blood‐spleen barrier is thereby formed, protecting splenic hematopoiesis from the parasite. Factors are produced, moreover, which damage intraerythrocytic parasites, producing crisis forms. Crisis follows. It may occur over several days, presaged by the appearance of circulating crisis forms. The filtration beds are opened to the blood. Circulating crisis forms are trapped within the locules of the filtration beds and phagocytized while the stores of reticulocytes produced there in the precrisis period are released to the blood. The malaria, as a result, is no longer patent and the anemia is relieved. In the fourth or postcrisis phase, lasting many months, the normal structure of the spleen is approached. We postulate that reticular cells, normal and activated, have the following functions: to fabricate the locules of the filtration beds; to control the migration of free cells through these beds; to trap free cells, including parasitized erythrocytes, by cell‐surface adherence; to open or close the filtration locules, creating a dynamic blood‐spleen barrier; to control the circulation of the spleen—by contraction and alignment in normal spleens and by activation and closing of locules in enlarged spleens; to synthesize collagen III; to synthesize factors which influence marrow release of monocytes; and to secrete antiplasmodial substances.
Changes in mesenchymal cell‐basal lamina relationships preceding palatal shelf reorientation in the mouse
Authors: Brinkley Linda L.
Published: February 2005

Two specific regions of the future nasal and oral epithelial surfaces of the secondary palatal shelves increase in cell density during shelf reorientation. The relationships of mesenchymal cells to the basal lamina underlying these regions were examined and compared to those of cells underlying adjacent regions which did not change in cell density. CD‐1 mouse fetuses were obtained on day 13.5 of gestation. Some palatal shelves were excised immediately and fixed for electron microscopy; other heads were partially dissected and incubated for 4 hr prior to fixation. Although shelf movement is detected only after 6 hr incubation, the shorter time period was selected in order to detect events which precede reorientation. Electron micrographs were taken of the epithelial‐mesenchymal interface of nasal and oral regions known to increase in epithelial cell density (active segments) and of nasal and oral regions which did not increase (inactive segments). Several measurements were made in a 500‐nm‐wide zone delimited on photographic prints. Distinct differences in mesenchymal cell configuration were found between nasal and oral regions. Active and inactive segments of each region also differed. A filamentous layer attached to the undersurface of the lamina densa was observed to vary in thickness and character between regions as well. After 4 hr incubation, differences in mesenchymal cell configuration and ultrastructure of the sublaminar zone were apparent between regions. These results suggest that local epithelial‐mesenchymal interactions, possibly mediated by the extracellular matrix, precede shelf reorientation. Whether these changes in mesenchymal cell configuration actually reflect mesenchymal cell activities that are necessary for shelf reorientation remains to be elucidated.
Pulmonary acinus: Geometry and morphometry of the peripheral airway system in rat and rabbit
Authors: Rodriguez M. , Bur S. , Favre A. , Weibel E. R.
Published: February 2005

The geometry and morphometry of intraacinar airways in rat and rabbit lungs were studied from silicone rubber casts. Acini, defined as the complex of alveolated airways distal to the “terminal” bronchiole, were trimmed off the bronchial tree. In both species, the acinar volume followed a log‐normal distribution over a range in size of one order of magnitude. At an inflation level of 60% total lung capacity, their mean volume was 1.86 mm3 in the rat and 3.46 mm3 in the rabbit. On a representative sample of acini of different volumes, the branching pattern was characterized as irregular dichotomy, and the segment length and inner and outer diameters were measured. The average acinus had a mean of six generations in the rat and seven in the rabbit. Both showed a decrease in segment length and inner diameter with each generation. The mean longitudinal pathway length‐that is, the distance from the initial acinar segment to the terminal sacs‐was found to depend on the cube root of the acinar volume in both species. It was calculated at 1.46 and 1.95 mm for rat and rabbit, respectively.
Schmidt‐Lanterman clefts: A morphometric study in human sural nerve
Authors: Buchthal Fritz , Carlsen Frits , Behse Friedrich
Published: February 2005

In the human sural nerve, large myelinated fibers contained. 35 Schmidt‐Lanterman (SL) clefts per mm, and small myelinated fibers contained only eight SL clefts per mm. The incidence of SL clefts is linearly related to myelin thickness. The SL clefts extended over 13 μm in large and over 9 μm in small fibers, the total extent of the SL region amounting to nearly 50% of internodal length in large and to 6% in small fibers. In the SL region, the fiber diameter was 6% larger than outside this region, and the axon was 17% smaller in large and 28% smaller in small fibers. The paranodal‐nodal region occupied less than 2% of internodal length in large fibers and 6.5% in small fibers; in the nodal region the axon diameter was reduced by 40–50%.
Effects of cytochalasin D on the integrity of the Sertoli cell (blood‐testis) barrier
Authors: Weber James E. , Turner Terry T. , Tung Kenneth S. K. , Russell Lonnie D.
Published: February 2005

Ectoplasmic specializations (ES) containing packed actin microfilaments are associated with the numerous parallel rows of occluding junctions which form the Sertoli cell (blood‐testis) barrier. To determine if ES regulate the structure of the occluding junctions and/or barrier permeability, we experimentally disrupted ES microfilaments in vivo with intratesticularly injected cytochalasin D (CD). Electron microscopic observations of seminiferous tubules from CD‐treated (150–500 μM CD; 0.5–12 hr) animals indicated that ES was absent from regions where the Sertoli cell barrier is located. Seminiferous epithelial sheets from uninjected or vehicle‐injected animals (1 DMSO: 1 saline) stained with NBD‐phallacidin demonstrated the presence of patterned ES actin surrounding the basolateral regions of adjacent Sertoli cells. After exposure to CD, epithelial sheets exhibited increasingly patchy fluorescence indicating progressive F‐actin disruption. Freeze‐fracture replicas of CD‐injected testes revealed numerous focal alterations in the region of occluding junctions which included disorganization of the parallel arrangement of junctional rows, the presence of free‐ending rows, clustering of intramembranous particles (IMPs) between rows, reduction in the number of rows, and loss of IMPs on both the P‐face and E‐face. Tracer experiments, following CD exposure, were conducted to test the integrity of occluding junctions: lanthanum hydroxide, dextrose, or filipin was added, in separate experiments, to the fixative during perfusion‐fixation. In another study, serum containing an antibody against adluminal germ cells was injected intratesticularly, and frozen sections were processed for immunofluorescence study. A final study consisted of simultaneous intratesticular infusions of CD and radiolabelled inulin with subsequent intraluminal and peritubular fluid sampling. In animals which were injected with CD, lanthanum was found to enter the adluminal compartment; fixative made hypertonic by addition of dextrose caused germ cells within the adluminal compartment to shrink and produce exaggerated intercellular spaces; filipin‐cholesterol perturbations were present between some Sertoli cell junctional rows and on spermatid plasma membranes; and IgG was detected within the adluminal compartment of many seminiferous tubules. None of these adluminal manifestations was noted in control animals or those which received vehicle. Quantitatively, in the in vivo micropuncture experiments, significantly more radiolabelled inulin entered the lumen of seminiferous tubules from CD‐treated animals than from those exposed to vehicle. Collectively, the data suggest that CD treatment alters the functional integrity of the Sertoli cell barrier and that this may be the result of disruption of microfilaments associated with the barrier.
Splenic microenvironment of the CBA/N mouse: Immunohistochemical analysis using monoclonal antibodies against lymphocytes and nonlymphoid cells
Authors: Kraal Georg , Hoeben Karin , Janse Marga
Published: February 2005

CBA/N mice carry an X‐linked immune‐deficiency gene, leading to a defect in the ability to form antibodies against T‐independent type 2 antigens. By using immunohistochemistry, the organization of the spleen of the immune‐deficient male (xid) CBA/N F1 and the normal female F1 were compared. Staining with antilymphocyte markers showed that the total number of cells in the various T‐ and B‐cell areas was smaller in the xid mouse, resulting in very small white pulp compartments. Fewer B cells were seen in the marginal zone. When the spleens of the F1 mice were examined for macrophage markers, the rings of marginal‐zone macrophages and the ring of marginal metallophilic macrophages were much thinner in the xid mouse. In particular, the marginal‐zone macrophages are thought to play a role in the response against thymus‐independent type 2 antigens, and their small numbers in the xid mouse are suggestive of a role for the microenvironment in the defects in these mice.
Renal blood vascular system in the elasmobranch, Raja erinacea mitchill, in relation to kidney zones
Authors: Hentschel Hartmut
Published: February 2005

The arrangement and structure of renal blood vessels were studied in a marine skate with injection of silicone rubber and methacrylate resin after intravenous administration of epinephrine and perfusion fixation. The methacrylate casts were investigated with the scanning electron microscope. Histology was performed by light and transmission electron microscopy of serial sections. The course of the blood vessels is described in relation to the renal zones of lateral bundles and mesial tissue. Each nephron performs two loops in the lateral bundles and two ceilings in the mesial tissue before it joins the collecting duct system.

The lateral bundles contain an elaborate countercurrent arrangement of neck segment, proximal tubule segment PIa, early distal tubule segment, and collecting tubule. Within the bundles, the nephron portions are associated with a blind‐ended central vessel, which is connected with the venous sinuses of the mesial tissue. The microcirculatory bed around the bundles is supplied with arterial blood via small bundle arteries that originate from the intrarenal arteries in parallel to the afferent arterioles of the glomeruli. The efferent arterioles of the glomeruli convey their blood to the peritubular sinuses of the mesial tissue, which is largely irrigated with venous blood of the renal portal system.

The mesial tissue, containing the proximal tubule segments PIb and PII, intermediate segment, and late distal tubule segment LDTb7 receives venous blood from the caudal vein and the lateral musculature via afferent renal and intrarenal veins and from the efferent arterioles of the glomeruli and venuks of the microcirculation of the bundles. The sinuses are drained by efferent renal veins via efferent intrarenal veins. By comparing the renal structures of the skate with those of dogfish, a unique type of circulation‐as related to nephron segments, renal zones, and fine structure of the wall of the vessels‐is revealed in marine elasmobranchs of different evolutionary levels.
Postnatal development of the sertoli cell barrier, tubular lumen, and cytoskeleton of sertoli and myoid cells in the rat, and their relationship to tubular fluid secretion and flow
Authors: Russell L. D. , Bartke A. , Goh J. C.
Published: February 2005

The postnatal development of the Sertoli cell barrier, tubular lumen, fluid flow, and cytoskeletal elements in Sertoli and myoid cells was investigated in the Sprague‐Dawley rat. With the aid of hypertonic fixatives, a barrier to the rapid entry of fluid was noted in the majority of tubules on the 15th and 16th postnatal (p.n.) days and was completely formed in all tubules prior to p.n. day 18. The actin forming the ecto‐plasmic specialization (ES), a cytoskeletal complex related to the occluding junctions composing the barrier, began its development during the period of initial barrier formation (16 p.n. day) and progressively attained its adult prominence. The ES developed its characteristic adult pattern and adult fluorescent intensity at about p.n. day 22. Some seminiferous tubules showed very small lu‐mina as early as p.n. day 10. All tubules were not open until p.n. day 30. The size (diameter) of the lumen increased slowly from p.n. day 10 until p.n. day 30 when it started to increase rapidly until about p.n. day 50. Fluid flow in seminiferous tubules was detected as early as p.n. day 20 and increased in amount thereafter. Myoid cell actin filament bundles, running in parallel, were present at p.n. day 10. Actin formed a meshwork pattern characteristic of the adult on, or slightly prior to, p.n. day 22. These data indicate that there is a temporal relationship between the development of the actin cytoskeleton within the Sertoli cell and initial formation of the Sertoli cell barrier. Similarly, there is a temporal relationship between the development of the actin cytoskeleton of myoid cells and tubular fluid flow. The rapid increase in tubular lumen diameter, however, does not correlate with the initial development of Sertoli and myoid cytoskeletal elements.