bluuebunny/crossref_metadata_2025 huggingface dataset:
Linkage of manchette microtubules to the nuclear envelope and observations of the role of the manchette in nuclear shaping during spermiogenesis in rodents
Authors: Russell Lonnie D. , Russell Jill A. , MacGregor Grant R. , Meistrich Marvin L.
Published: February 2005

Structural features of the mouse and rat manchette and the role of the manchette in shaping the spermatid nucleus were investigated. Rod‐like elements about 10 nm in diameter and 40–70 nm in length were seen linking the innermost microtubules of the manchette and the outer leaflet of the nuclear envelope in step 8 through step 11 rat and mouse spermatids that either had been routinely fixed for electron microscopy or had been isolated and detergent extracted. Rod‐like linkers were also seen joining the nuclear ring to the plasma membrane and nuclear envelope. These linkers may ensure that under normal conditions the manchette remains in a defined position relative to these membranous components. A variety of compounds (taxol, cytoxan, and 5‐fluorouracil) were found to perturb the manchette and to affect nuclear shaping. In addition, sys and azh mutant mice were used to determine the consequences of defective manchette formation. These genetic conditions and chemical treatments either produced manchettes that were not in their normal position (azh, sys, and taxol) and/or caused the manchette to appear abnormal (azh, sys, cytoxan, 5‐fluorouracil, and taxol), and all resulted in a deformation of the step 9–11 spermatid nucleus. In all instances where the manchette was present, either in normal or ectopic locations, the sectioned nuclear envelope was parallel to the long axis of the microtubules of the manchette. In general, areas of the nuclear envelope where the manchette was not present, or where it was expected to be present but was not, were rounded (normal animals, sys, cytoxan). In addition, there are indications using certain compounds (cytoxan and 5‐fluorouracil) as well as in the azh and sys mouse that the manchette may exert pressure to deform the nucleus. It is suggested that the rod‐like linkages of the manchette ensure that the nuclear envelope remains at a constant distance from the manchette microtubules and that this is a major factor acting to impart nuclear shape changes on a region of the head caudal to the acrosome during the early elongation phase of spermiogenesis. The manchette microtubules, which are also known to be linked together, may act as a scaffold to deform this part of the nucleus from its spherical shape, perhaps in concert with forces initiated by other structural elements. Evidence from sys animals indicates that structural elements, such as the acrosomal complex over the anterior head (acrosome‐actin‐nuclear envelope), may affect nuclear shaping over the acrosome‐covered portion of the spermatid head. It is suggested that chromatin condensation primarily reinforces the shape changes already brought about by the manchette and other structural elements acting on the nucleus. After chromatin condensation, spermatid nuclear shape changes are minor.
Short‐term Morphological response of the rat testis to administration of five chemotherapeutic agents
Authors: Russell Lonnie D. , Russell Jill A.
Published: February 2005

As cancer survival rates improve, there is increasing concern about the adverse effects of chemotherapeutic agents on male fertility. Five chemotherapeutic agents (amethop‐terin, AP or methotrexate; doxorubicin, DX; cytoxan or cyclophosphamide, CP; cisplatinum, CDDP; and 5‐fluorouracil, 5‐FU) which belong to three different categories of chemotherapeutic agents (antimetabolite, antibiotic, alkylating agent, alkylating agent, antimetabolite, respectively) were given systemically to adult rats to determine the short‐term morphological patterns of response in the testis, and the testes were examined by light microscopy. Morphological patterns of response were found to be highly characteristic for each agent, and some shared morphological responses were evident. All except one chemotherapeutic agent (5‐FU) caused spermatogonial damage. Among the defects seen were probable degenerating meiotic spermatocytes (CDDP), presence of micronuclei (DX), “arrested” spermatid development (5‐FU), and abnormally shaped step 15 spermatids (5‐FU). Damage that could be due to the effect of an agent on the Sertoli cell was failure of sperm release (5‐FU, CDDP, DX, and AP), increase in the Sertoli cell lipid (5‐FU), and malorientation of step 8 spermatids (5‐FU, DX). The varied patterns of damage observed are a possible explanation of why the reproductive recovery potential in cancer patients undergoing chemotherapy is variable and drug‐specific.
Testis structure in the sys (symplastic spermatids) mouse
Authors: Russell Lonnie D. , Hikim Amiya P. Sinha , Overbeek Paul A. , MacGregor Grant R.
Published: February 2005

Testes of mice with the recessive insertional mutation termed symplastic spermatids (sys) were assessed for structural and developmental abnormalities. Homozygous (sys/sys) males are infertile due to an abnormality in spermatogenesis leading to azoospermia. The major interruption to spermatogenesis occurs when the intercellular bridges that connect round spermatids open prematurely resulting in the formation of symplasts. Symplasts contain as many as 285 nuclei. Development of spermatids within symplasts is arrested just before, or just after, elongation of the spermatid nuclei begins. Symplasts degenerate and appear to be phagocytized by Sertoli cells and by intratubular macrophages. In addition, degeneration of young round spermatids and also spermatocytes occasionally is observed. Spermatocyte degeneration is substantial in some tubules and leaves them depleted of cells other than basal compartment cells. Sertoli cell abnormalities are prominent and include intracellular vacuolation, absence of apical processes surrounding round spermatids, degeneration, and occasional sloughing. Although reduplication and infolding of the basal lamina is also seen, this does not appear as a common phenomenon. The sys phenotype is first manifest in animals between 19 days and 22 days of age. Considerable variability is seen in testis histology of prepubertal animals; some display degenerating pachytene spermatocytes and virtually no Sertoli cell vacuoles, while others display vacuoles without apparent elevated numbers of degenerating spermatocytes. Although this study has not revealed the primary cell type(s) affected by the insertional inactivation event, it is possible that the abnormalities in the Sertoli cells are responsible for germ cell degeneration as it is generally recognized that deficits in the Sertoli cell can result in major germ cell abnormalities but not vice versa.
Reinitiation of spermatogenesis by exogenous gonadotropins in a seasonal breeder, the woodchuck (Marmota monax), during gonadal inactivity
Authors: Hikim Amiya P. Sinha , Hikim Indrani Sinha , Amador Armando G. , Bartke Andrzej , Woolf Alan , Russell Lonnie D.
Published: February 2005

The present study was undertaken (1) to document structural and functional changes in the testes of seasonally breeding woodchuck during active and inactive states of spermatogenesis and (2) to evaluate the ability of exogenous gonadotropins to reinitiate spermatogenesis outside the breeding season. During seasonal gonadal inactivity, there were significant (P < 0.05) reductions in volumes of several testicular features (testis, seminiferous tubules, tubular lumen, interstitial tissue, individual Leydig cells, Leydig cell nuclei, and Leydig cell cytoplasm) as compared with gonadally active animals. The diameter of the seminiferous tubules was decreased by 26%, and Leydig cell numbers also declined in the regressed testes. These changes were accompanied by a decline in testosterone (T) levels in both plasma and testis, and reduction in epithelial height of accessory reproductive organs. A hormonal regimen was developed that would reinitiate spermatogenesis in captive, sexually quiescent woodchucks. A combination of PMSG and hCG markedly stimulated testicular growth and function and restored spermatogenesis qualitatively. Quantitatively normal spermatogenesis was restored in 2 of 6 treated males. Morphometric analyses revealed substantial increases in seminiferous tubular diameter and in the volume of seminiferous tubules, tubular lumen, total Levdig cells, and individual Leydig cells in the hormone‐treated animals. These increased values corresponded to 99, 75, 68, 51, and 200%, respectively, of the values measured in naturally active woodchucks. Leydig cell numbers, however, remained unchanged and approximated only 31% of the number found in naturally active testes. Hormonal stimulation also resulted in a significant rise in serum T as well as in the total content of testicular T, and a marked increase in epithelial height in various accessory reproductive glands. The most effective hormonal protocol for stimulating spermatogenesis was treatment with 12.5 IU of PMSG twice a week for 4 weeks followed by 12.5 IU of PMSG + 25 IU of hCG twice a week for 4 weeks.
The role of hematogenous and intrinsic precursor cells in lymphocyte production in murine bone marrow and thymus
Authors: Mejino Jose L. V. , Lee Minako , Hamilton Brian L. , Rosse Cornelius
Published: February 2005

It is well recognized that the bone marrow contains cells that can repopulate a depleted thymus as well as cells that can be induced to express phenotypic markers characteristic of T cells. It is not known, however, to what extent thymocytopoiesis in the normal thymus relies on immigrant, bone marrow‐derived cells, nor whether some T cell precursors have entered the bone marrow from the circulation. We used the parabiotic system to test whether thymocytopoiesis relies on progenitors intrinsic to the thymus or on cells that enter the organ from the circulation. In the same system, we have also investigated whether Thy‐1− bone marrow lymphocytes that respond to phytohemagglutinin (PHA) by proliferation and Thy‐1 expression are produced by my‐elogenous or hematogenous progenitors.

Syngeneic CBA/HT6 and CBA/CaJ mice were joined in parabiotic union at 4–6 weeks of age. Cross circulation between the two partners was verified by the equilibration of Evans' blue dye injected into one partner and by the equilibration of PHA‐responsive T cells in the spleen of the parabionts. Chromosome spreads were prepared from the PHA‐stimulated T cell‐depleted bone marrow and from spontaneously proliferating thymocytes as well as from thymocytes stimulated by PHA or Concanavalin A (Con A). The exchange of spleen colony‐forming units (CFU‐S) in the femoral marrow was assessed by karyotyping individual spleen colonies.

Regardless of the length of parabiotic union, ranging from 4 to 20 weeks, Thy‐1−, PHA‐responsive bone marrow lymphocytes remained predominantly of the host type with only 3% being derived from the opposite partner. The same held true for CFU‐S in the femur; only around 5% of this cell population were of the nonhost type. Thus, although some Thy‐1−, PHA‐responsive lymphocytes in the bone marrow may be derived from hematogenous stem cells, the majority of them are generated by precursors resident in the bone marrow.

Likewise, regardless of the length of parabiotic union, at least 95% of spontaneously proliferating cells in the thymus of each partner possessed the karyotype of the host, and this held true also for PHA‐ or Con A‐stimulated thymocytes, indicating that the small population of spontaneously proliferating immigrant cells cannot account for the production of the large number of postmitotic (mitogen‐responsive) thymocytes.

Our findings, therefore, demonstrate a high degree of self‐maintenance for Thy‐1−, PHA‐reponsive lymphocytes in the bone marrow and also for intrathymic T cell precursors. In the unperturbed, postnatal thymus, thymoctye production does not rely on cell input from the circulation; the vast majority of thymoctyes are generated by an intrathymic precursor pool that is independent of immigrant myelogenous T cell precursors.
Congenitally osteosclerotic (os/os) rabbits are not cured by bone marrow transplantation from normal littermates
Authors: Popoff Steven N. , Marks Sandy C.
Published: February 2005

The osteopetrotic (os) rabbit is a lethal mutation of autosomal recessive inheritance characterized by hypocalcemia, hypophosphatemia, fibrosis of marrow spaces, and ultrastructural abnormalities in both osteoclasts and osteoblasts. Procedures involving the transplantation of cells from normal hemopoietic tissues, which are sources of osteoclast precursors, are known to cure osteopetrosis in several mutations including some children. We tested the ability of transplanted bone marrow and/or spleen from normal littermates to reverse the skeletal sclerosis in os rabbits. Treatment of 15 neonatal mutants consisted of immunosuppression by whole‐body irradiation followed by transplantation of normal bone marrow and/or spleen cell suspensions. This treatment failed to prolong life span or to cure osteopetrosis judged radiographically and histologically for up to 3 weeks posttreatment, the longest time of survival. These data indicate that transplantation of stem cells from multiple hemopoietic tissues, procedures known to cure osteopetrosis in other mutations, is not effective in the os rabbit. These results support the hypothesis that the skeletal microenvironment is not capable of supporting the development and function of normal osteoclasts in this mutation.
Structure‐Function relationships during preovulatory development of porcine follicles following equine chorionic gonadotropin stimulation
Authors: King G. J. , Chapeau C. , Ackerley C. A.
Published: February 2005

Porcine follicular maturation begins by recruitment from a continually proliferating pool of small antral follicles; those receiving the appropriate stimulus differentiate rapidly through a series of structural and functional changes. Such ovarian activity can be induced in prepubertal gilts with a single injection of equine chorionic gonadotropin (eCG). Average follicular diameter in eCG treated females increased from approximately 2 mm before stimulation to 3.5 mm by 24 hr after injection, with subsequent growth to ovulatory size (8 or 9 mm) by 96 hr. Both theca and granulosa layers increased in thickness and complexity, and a prominent capillary bed evolved immediately outside the basement membrane separating the two layers. Cytoplasmic organelles associated with increased metabolic activity and steroidogenesis proliferated within the first 24 hr. Progressive changes included increasing amounts of lipid and rough and smooth endoplasmic reticulum, with the latter occurring in vesicular or lamellar forms and as lipid‐associated whorls. Bizarre mitochondrial forms also appeared, often associated with lipids.

The amount and proportion of rough and smooth endoplasmic reticulum shifted dramatically as follicles matured. By 24 hr, rough endoplasmic reticulum in thecal cells increased from 4.2 to 7% of cell volume, while the amount in granulosa cells increased from less than 3.5% to more than 10%; the quantity remained relatively constant in the theca but declined to prestimulation values in the granulosa layer. Rough endoplasmic reticulum predominated over smooth in the first 24 hr following stimulation but the proportions were then reversed, so that more than 10% of both layers was composed of smooth endoplasmic reticulum by the time ovulation was imminent.

Some follicles had or were in the process of ovulating by 96 hr. Their walls were collapsed into prominent folds with the two cell types beginning to mix. Slight undulations and some regions of discontinuity were observed in basement membranes of large unovulated follicles at this time. In specimens collected at 96 hr poststimulation and processed for retention of lipid, lipid‐like material was noticeable in the extracellular matrix surrounding cells that contained organelle configurations suggestive of steroidogenesis.
The vasculature of the rat penis: A scanning electron microscopic and histologic study
Authors: Fernandez Erika , Dail William G. , Walton Guy , Martinez Girard
Published: February 2005

As a basis for understanding the mechanism of erection in an animal model frequently used in research in reproductive biology, the angioarchitecture of the penis of the rat has been described using scanning electron microscopy. Study of the penile vasculature of the rat indicates that the corpora cavernosa penis and the corpus spongiosum are independent erectile tissues, each with its own arterial and venous vessels. The large vascular spaces and abundant smooth muscle of the penile crura are compatible with its role in regulating blood flow to more distal penile tissues. Helicine arteries of the crura, but not the parent deep penile artery or arteries elsewhere, have muscular cushions in their walls. The venous drainage of the penile crura is via subtunical veins which are thought to be compressed during erection to elevate pressure within the penis. Large, paired cavernous veins drain the shaft of the penis. A unique method for inhibiting blood flow from the penis is indicated by the division of the cavernous veins into smaller channels prior to joining the subtunical venous plexus. Erectile tissue in the bifid origins of the corpus spongiosum has abundant cavernous muscle, while in the remainder of the corpus spongiosum little smooth muscle lines the cavernous spaces. The cavernous spaces on either side of the urethra coalesce to form vessels, each of which communicates with cavernous spaces in the glans. In addition, a bypass of the glans is effected by communication of these vessels directly with the deep dorsal vein. The apparent absence of muscular pads in vessels of the spongiosum, the relative paucity of cavernous smooth muscle, and the ample venous drainage provided by the deep dorsal vein may account for the lack of a venous occlusive mechanism similar to that of the corpora cavernosa penis.
Geographic distribution of xanthine oxidase, free radical scavengers, creatine kinase, and lactate dehydrogenase enzyme systems in rat heart and skeletal muscle
Authors: Apple Fred S. , Hyde John E. , Ingersoll‐Stroubos Ann Marie , Theologides Athanasios
Published: February 2005

The geographic distribution of the following enzyme systems is described in the rat heart (left and right ventricles) and in different skeletal muscles (soleus, plantaris, and red and white gastrocnemius): xanthine oxidase and dehydrogenase, creatine kinase isoenzymes, lactate dehydrogenase isoenzymes, and the free radical scavenger enzymes superoxide dismutase, glutathione reductase, and glutathione peroxidase. No substantial difference in enzyme activities was observed between the left and right ventricles. Skeletal muscles showed a clear distinction between enzyme activities depending on their composition of oxidative fibers and glycolytic fibers.
Chorioallantoic placenta formation in the rat: II. Angiogenesis and maternal blood circulation in the mesometrial region of the implantation chamber prior to placenta formation
Authors: Welsh Alerick O. , Enders Allen C.
Published: February 2005

Rat gestation sites were examined on days 7 through 9 of pregnancy by light microscopy and transmission and scanning electron microscopy to determine the extent of vascular modifications in the vicinity of the mesometrial part of the implantation chamber (mesometrial chamber). At a later time, the mesometrial chamber is, in conjunction with the uterine lumen, the site of chorioallntoic placenta formation. On day 7, in the vicinity of the mesometrial chamber, vessels derived from a subepithelial capillary plexus and venules draining the plexus were dilating. By early day 8, this network of thin‐walled dilated vessels (sinusoids) was further enlarged and consisted primarily of hypertrophied endothelial cells with indistinct basal laminas. Sinusoids were frequently close to the mesometrial chamber's luminal surface which was devoid of epithelial cells but was lined by decidual cell processes and extracellular matrix. By late day 8, cytoplasmic projections of endothelial cells extended between healthy‐appearing decidual cells and out onto the mesometrial chamber's luminal surface, and endothelial cells were sometimes found on the luminal surface indicating that endothelial cells were migrating. The presence of maternal blood cells in the mesometrial chamber lumen suggested that there was continuity between the chamber and blood‐vessel lumens. On day 9, the mesometrial chamber was completely lined with hypertrophied endothelial cells, and sinusoid lumens were clearly continuous with the lumen of the mesometrial chamber. Mesometrial sinusoids and possibly the mesometrial chamber lumen were continuous with vessels in the vicinity of the uterine lumen that were fed by mesometrial arterial vessels. Clearing of the mesometrial chamber lumen during perfusion fixation via the maternal vasculature indicated the patency of this luminal space and its confluence with mesometrial arterial vessels and sinusoids. The conceptus occupied an an‐timesometrial position in the implantation chamber on days 7 through 9, and it was not in direct contact with uterine tissues in the vicinity of the mesometrial chamber. These observations suggest that angiogenesis, not trophoblast invasion or decidual cell death, plays a major role in the opening of maternal vessels into the mesometrial chamber lumen before the formation of the chorioallantoic placenta.
Trophoblast‐Uterine interactions during equine chorionic girdle cell maturation, migration, and transformation
Authors: Enders Allen C. , Liu I. K. M.
Published: February 2005

The structure of the equine chorionic girdle between days 28 and 42 of gestation was examined. Of particular interest were differentiation of trophoblastic cells within the girdle, adhesion between girdle and endometrium, invasion and displacement of the uterine epithelium, and the nature of the endometrium when girdle cells migrate into it to form endometrial cup cells. The chorionic girdle, identified initially as a band of tall columnar cells, becomes a stratified columnar epithelium indented by clefts and pits. Adhesion to and penetration through the endometrial luminal epithelium are rapid and occur initially in very limited areas. Stromal invasion occurs as strands of contiguous trophoblast cells invade through the basal lamina. Only girdle cells that are adjacent to the basal lamina or have entered the endometrial stroma undergo hypertrophy and differentiate into cup cells. At the initiation of trophoblastic invasion, the luminal epithelium contains numerous, large, intra‐epithelial, granular lymphocytes; small lymphocytes then accumulate in the stroma, but by day 42 lymphocytes are largely confined to the periphery of the cup. Although adhesion of trophoblast to the endometrial surface is initiated by small groups of girdle cells on restricted areas of the endometrial folds, the area is then increased by new areas of adhesion and by expansion of the initial invasion. Areas of girdle cells that do not attach undergo necrosis, as do superficial portions of areas of invasion. Consequently the girdle cells that form cups may be a minority of the original population. It is suggested that the differentiation of girdle cells is closely programmed and that cells that do not reach the stroma become necrotic at the same time that endometrial cup cells are differentiating.
Growth of mouse ectoplacental cone cells in subcutaneous tissues. Development of placental‐like cells
Authors: Bevilacqua Estela Maris A. F. , Faria Miriam R. , Abrahamsohn Paulo A.
Published: February 2005

Ectoplacental cones of mouse embryos collected on day 8 of pregnancy were grafted into the dorsal subcutaneous tissue of host mice. The grafts were collected between days 3 and 8 after transfer and processed for light and electron microscope morphological analysis as well as for cytochemistry of nonspecific alkaline phosphatase. Fragments of normal mouse placentas collected between days 12 and 18 of pregnancy were processed similarly. About 37% of the grafts were nonhemorrhagic nodules formed by different kinds of trophoblastic cells. These cells had many morphological and cytochemical features of cells present in normal mouse placentas. Nonphagocytic giant cells, glycogen cells, as well as cells with a well‐developed granular endoplasmic reticulum were similar to cells found in the placenta and were always present in the grafts. Cells showing features intermediate between the above‐mentioned cells and those whose cytoplasm was poor in organelles also were found in the grafts. The latter resembled cells of layer 1 of the labyrinth of the placenta. These results suggest that trophoblastic cells of the ectoplacental cones had differentiated into placental cells following their transfer to the subcutaneous tissue.
Hyaluronic acid influences the migration of myoblasts within the avian embryonic wing bud
Authors: Krenn Veit , Brand‐Saberi Beate , Wachtler Franz
Published: February 2005

Myoblasts migrate in a proximodistal direction within the avian embryonic wing bud during normal limb development. Since the presence and distribution of hyaluronic acid within the wing bud coincide with the time and with the direction of the migration of myoblasts, we microinjected hyaluronic acid into chicken wing buds that had received grafts containing quail myoblasts. It was found that injected hyaluronic acid has a strong positive effect on the migration of myoblasts: it causes a migration of myoblasts in donor‐host combinations in which this is normally not the case, and it can cause migration in a proximal direction, a phenomenon not observed during normal development. From this it may be concluded that hyaluronic acid can influence myoblast migration in vivo. A similar effect could be observed after the microinjection of dextran sulfate, a synthetic compound having similar physicochemical properties. Hyaluronic acid, therefore, may play an important role in the control of the migration of myogenic cells in vivo by its physicochemical properties.
Growth and development of the human infant breast
Authors: Anbazhagan R. , Bartek J. , Monaghan P. , Gusterson B. A.
Published: February 2005

Seventy‐two samples of infant breasts, aged from newborn to 2 years, were collected at necropsy. Whole‐mount preparations and histological sections were made. A system of classification was devised to study the extent of the structural development of the ductal system (morphological types I, II, and III) and the functional differentiation of the lining epithelium (functional stages I to V). There was no correlation between the age of the infant and the type of development of the ductal system. In contrast, the epithelial differentiation followed a chronological pattern, starting with secretory changes and apparently going through a period characterized by apocrine metaplasia before post‐secretory involution. These epithelial changes were not associated with the morphological type of the ductal system. There were no distinguishing features between the breasts from the two sexes.

Immunoperoxidase staining for actin and kappa‐casein was carried out to study the myoepithelial cells and secretory cells, respectively. Myoepithelial cells were present at all stages and prominent staining for casein was observed up to 2 months of age. Embryonic‐type adipose tissue was seen in 7 cases, in one of which it was associated closely with the developing ductal system. Extramedullary hematopoiesis was observed in the periductal connective tissue until 4 months of age.

This paper describes the most extensive anatomical and histological study of the human infant breast to date and lays the foundation for a detailed study of the epithelial and stromal changes that take place during human breast development.
Numbers of myosatellite cells in white axial muscle of growing fish: Cyprinus carpio L. (teleostei)
Authors: Koumans J. T. M. , Akster H. A. , Booms G. H. R. , Lemmens C. J. J. , Osse J. W. M.
Published: February 2005

By means of transmission electron microscopy (TEM), the percentage of myosatellite cells was shown to decrease from about 6% in carp of 5 cm standard length (SL) to less than 1% in carp larger than 18 cm SL. The ratio between muscle nuclei and non muscle nuclei remained constant. These TEM data, combined with data on the amount of DNA per gram of muscle tissue and per nucleus, were used to calculate the numbers of myosatellite cells per gram of tissue (TEM‐DNA method). Total numbers of myosatellite cells could be calculated from the TEM‐DNA data and the calculated amounts of muscle tissue per fish. After a slight initial increase, the total number of myosatellite cells in the white axial muscle of a carp appears to be rather constant during the growth phase of the fish. But the myosatellite cells become more and more diluted over an increasing number of myonuclei with age. In addition, the reliability of two new light microscopic methods for the determination of numbers of myosatellite cells was examined. The percentages of myosatellite cells were determined by counting the numbers of total nuclei and of heterochromatic nuclei situated inside the muscle fibers' basal laminae which were stained using an antibody against laminin. These percentages were not significantly different from those determined with TEM. The yield of myosatellite cells per gram of muscle tissue, isolated with a previously developed dissociation method, showed a direct relation to the number of myosatellite cells calculated to be present in the tissue (TEM‐DNA method), but at a 1% level. Both methods are alternative ways to determine numbers of myosatellite cells when it is impossible or difficult to use TEM (e.g., large sample sizes, combination with immunohistochemical methods).
Myofiber orientation in the weanling mouse heart
Authors: McLean Miriam , Prothero John
Published: February 2005

This study provides a quantitative description at the cellular level of myofiber orientation throughout the ventricles of the mouse heart. We employed computer‐based methods of three‐dimensional reconstruction from 3 μm plastic‐embedded serial sections. Registration marks were introduced by drilling minute holes into each plastic block. Subfields of selected sections were photographed at 20 x magnification, using a computer‐controlled microscope. The 35‐mm film frames were projected onto a digitizer tablet and the epi‐ and endocardial boundaries were digitized manually. The “heads” and “tails” of linear segments of a representative myofiber sample present in each projected image were digitized in point mode. The many x‐, y‐, z‐coordinate tables generated by digitization were reassembled automatically, giving a numerical description of the myofiber pattern. This pattern was studied interactively on a high‐performance graphics workstation. We find that the heart wall is, to a first approximation, a “sandwich,” in which the myofibers in the middle layer run mainly circumferentially, whereas those in the inner and outer layers run parallel or oblique to the apical‐basal axis, a variant of the classical model of the myofiber pattern. We observed a “sleeve” in the interventricular septum, formed by longitudinal and oblique myofibers, a feature which apparently has not been described previously. Myofibers not running parallel to the transverse or longitudinal planes were not resolved in this study. We conclude that three‐dimensional reconstruction of the cardiac myofiber pattern at the light‐microscopic level, while laborious, is technically feasible and scientifically worthwhile.
The role of growth factors in the embryogenesis and differentiation of the eye
Authors: Tripathi Brenda J. , Tripathi Ramesh C. , Livingston Amit M. , Borisuth NavaneetS. C.
Published: February 2005

The vertebrate eye is composed of a variety of tissues that, embryonically, have their derivation from surface ectoderm, neural ectoderm, neural crest, and mesodermal mesenchyme. During development, these different types of cells are subjected to complex processes of induction and suppressive interactions that bring about their final differentiation and arrangement in the fully formed eye. With the changing concept of ocular development, we present a new perspective on the control of morphogenesis at the cellular and molecular levels by growth factors that include fibroblast growth factors, epidermal growth factor, nerve growth factor, plateletderived growth factor, transforming growth factors, mesodermal growth factors, transferrin, tumor necrosis factor, neuronotrophic factors, angiogenic factors, and antiangiogenic factors. Growth factors, especially transforming growth factor‐β, have a crucial role in directing the migration and developmental patterns of the cranial neural‐crest cells that contribute extensively to the structures of the eye. Some growth factors also exert an effect on the developing ocular tissues by influencing the synthesis and degradation of the extracellular matrix. The mRNAs for the growth factors that are involved in the earliest aspects of the growth and differentiation of the fertilized egg are supplied from maternal sources until embryonic tissues are able to synthesize them. Subsequently, the developing eye tissues are exposed to both endogenous and exogenous growth factors that are derived from nonocular tissues as well as from embryonic fluids and the systemic circulation. The early interaction between the surface head ectoderm and the underlying chordamesoderm confers a lens‐forming bias on the ectoderm; later, the optic vesicle elicits the final phase of determination and enhances differentiation by the lens. After the blood–ocular barrier is established, the internal milieu of the eye is controlled by the interactions among the intraocular tissues; only those growth factors that selectively cross the barrier or that are synthesized by the ocular tissues can influence further development and differentiation of the cells. An understanding of the tissue interactions that are regulated by growth factors could clarify the precise mechanism of normal and abnormal ocular development.
Monkey photoreceptor calycal processes and interphotoreceptor matrix as observed by scanning electron microscopy
Authors: Rana M. W. , Taraszka S. R.
Published: February 2005

Photoreceptors and the interphotoreceptor matrix of monkey retina were observed by scanning electron microscopy. Cone photoreceptors are easily distinguished from rod photoreceptors by their wide conical inner segments. The calycal processes of 50 rods and 50 cones were counted and measured. The calycal processes of cones were distinct, short, and uniform in diameter (0.1 μm). They were arranged equidistantly and, in most cases, were not continuous with longitudinal inner segment ridges, as previously suggested. In contrast to cones, rod calycal processes were fewer in number, were about one‐fourth the number of the cones, were of variable length (0.7 μm to 3.0 μm), and tapered to a fine point at their distal ends. The interphotoreceptor matrix appeared spongelike, made up of anastomosing plates and strands filling the interphotoreceptor space. Other than an increased amount of matrix around cones, no structural difference between rod‐ and cone‐associated interphotoreceptor matrix was observed.
Human spinal arachnoid septa, trabeculae, and “rogue strands”
Authors: Parkinson Dwight
Published: February 2005

This study was undertaken because of confusion arising from a diversity of names, descriptions, and drawings of the human spinal subarachnoid septa and trabeculae in the standard texts and dictionaries. Sixty‐two complete human cords were examined under the dissecting scope. The finely “woven” adult arachnoid membrane was two‐layered, and there were essentially no connecting septa or trabeculae between the cord and the arachnoid membrane anteriorly. Posteriorly, in the upper cervical region there is a scanty series of connecting fibers and fenestrated sheets 1 or 2 mm on either side of the midline; these become progressively more extensive in the lower cervical region, remain extensive to the lumbar enlargement, beyond which they progressively dwindle to end abruptly at the filum terminale origin. Throughout the cauda equina, strands are haphazardly arranged connecting the roots and supporting blood vessels. These occasionally become tangentially adherent to the arachnoid membrane. Throughout the length there are many unexplained, redundant, nonbranching, beaded, thicker “rogue strands”. All of the above are of a different character from the right‐angle fiber arrangement of the denticulate ligament, the two leaves of which are often separated to form segmental longitudinal tunnels. The nerve rootlets (fila radicularia) for each dermatome are joined by strands and webs to each other. There was no evidence of change in number or type of connection with age.
S‐Antigen and glial fibrillary acidic protein immunoreactivity in the in situ pineal gland of hamster and gerbil and in pineal grafts: Developmental expression of pinealocyte and glial markers
Authors: Li Kang , Welsh Marcia G.
Published: February 2005

Postnatal development of S‐Ag and GFAP immunoreactivity in the in situ pineal glands of golden hamsters and gerbils was examined using the avidin‐biotin‐peroxidase immunohistochemical technique. S‐Ag was present in the gerbil pineal gland on the first postnatal day (P1), whereas it did not appear in the hamster pineal until P6. GFAP‐immunoreactive astrocytes were first observed in the hamster pineal gland on P7 and in the gerbil pineal gland on P10. The number of S‐Ag‐immunoreactive pinealocytes and GFAP‐immunoreactive astrocytes in the pineal glands of hamsters and gerbils increased with increasing age from P7 to 3 weeks. By 4 weeks, strong S‐Ag and GFAP immunoreactivity was observed in both hamster and gerbil pineal glands. GFAP‐immunoreactive stellate astrocytes were distributed evenly throughout the gerbil superficial pineal gland, but they were more often located in the peripheral region of the hamster superficial pineal. For the pineal grafts, pineal glands from neonatal (3–5 day old) hamsters were transplanted into the third cerebral ventricle (infundibular recess or posterior third ventricle) or beneath the renal capsule of adult male hamsters. S‐Ag immunoreactivity appeared in the pineal grafts within 1 week following transplantation. By 4 weeks the pineal grafts showed strong S‐Ag immunoreactivity which was maintained until at least 12 weeks after transplantation. The time course of glial cell maturation in the cerebroventricular pineal grafts is generally parallel to the hamster pineal gland in situ before 4 weeks. By 12 weeks, however, more astrocytes differentiated and developed GFAP‐immunoreactivity in the pineal grafts than in the in situ pineals. These studies have described the postnatal development of S‐Ag and GFAP immunoreactivity in in situ pineal glands and in neonatal pineal grafts.
Reorganization of the ependyma during axolotl spinal cord regeneration: Changes in intermediate filament and fibronectin expression
Authors: O'Hara Christina M. , Egar Margaret W. , Chernoff Ellen A. G.
Published: February 2005

Changes in intermediate filament content and extracellular matrix material showed that the injury response of ependymal cells in lesioned axolotl spinal cord involves an epithelial‐to‐mesenchymal transformation, and that fibrous astrocytes are excluded from the remodeling lesion site. Antibody localization was used to visualize cytokeratin‐, vimentin‐, and glial fibrillary acidic protein‐ (GFAP‐) containing intermediate filaments, as well as the adhesive glyco‐protein fibronectin. In normal axolotl spinal cord cytokeratins were found near the apical surface of the ependymal cells. Transmission electron microscopic examination suggested that these cytokeratins were in tonofilaments. Cytokeratin expression was lost and vimentin production was initiated in ependymal cells 2–3 weeks following spinal cord injury. There was a period of approximately 1–2 weeks when cytokeratins and vimentin were co‐expressed in vivo. This co‐expression was maintained in vitro by culture on a fibronectin‐coated substratum. As the central canal reformed, vimentin expression was lost. Ependymal cells lacked GFAP intermediate filaments, but GFAP was present in fibrous astrocytes of the neuropil and white matter. Following injury, GFAP localization showed that fibrous astrocytes disappeared from the remodeling lesion site and reappeared only after the ependymal epithelium reformed and newly myelinated axons were found. Fibronectin expression closely followed the expression of vimentin during mesenchymal ependymal cell outgrowth. These results suggest that the ependymal cell outgrowth requires changes in cell shape followed by changes in production of extracellular matrix.
Onset of expression and regional deposition of alpha‐smooth and sarcomeric actin during avian heart development
Authors: Sugi Yukiko , Lough John
Published: February 2005

The sequential appearance of mRNAs for smooth, cardiac, and skeletal alpha‐actin has been described during development of the chicken heart (Ruzicka, D.L., and R.J. Schwartz 1988 J. Cell Biol., 107:2575–2586). To assess whether this reflects the deposition of corresponding isoproteins, we have immunocytochemically localized smooth and sarcomeric (cardiac and skeletal) alpha‐actin in Hamburger‐Hamilton (H‐H) stage 7–18 embryos using monoclonal antibodies. Within the developing embryo at stage 9‐, smooth muscle alpha‐actin was exclusively detected in the developing heart, upon fusion of the endocardial tubes; sarcomeric alpha‐actin was observed later (stage 9). By the onset of contraction at stage 10 +, intense immunostaining of both smooth and sarcomeric isoproteins was observed in the ventricle; at this time smooth muscle alpha‐actin was also detected in splanchnic mesoderm of the pre‐vitelline area, in a cellular layer adjacent to the only embryonic cells that exhibited factor VIII (von Willebrand factor) antigens. Double immunostaining of the myocardium at stage 11, at which time striations were first detected, revealed the co‐existence of smooth and sarcomeric actin in developing sarcomeres. Intense expression of sarcomeric actin continued in the heart after stage 11, whereas smooth muscle alpha‐actin was down‐regulated in the ventricle and became regionalized to the inflow and outflow tracts. As expected, smooth muscle alpha‐actin was detected around intra‐ and extra‐embryonic vascular structures at later developmental stages, while sarcomeric actin was observed in somites.
Changes in cellular dynamics during the development of the ciliary epithelium
Authors: Reichman Eric F. , Beebe David C.
Published: February 2005

Eye growth and the formation of the ciliary folds during development depend on the maintenance of normal intraocular pressure. In this study we measured labeling index, packing density, height, and volume of the prospective ciliary epithelial cells during the early development of the eye in chicken embryos. Changes in these values were related to the formation of the ciliary folds and to experimental alterations of intraocular pressure. These variables changed independently in the outer, pigmented layer and the inner, non‐pigmented epithelial layer of the ciliary epithelium. The labeling index in the pigmented epithelium declined steadily throughout development. Decreases in cell density and increases in cell height resulted in a four‐fold increase in calculated average cell volume in the pigmented epithelium during Hamburger‐Hamilton stages 29 and 30, the day before the formation of the ciliary folds. In the non‐pigmented epithelium, the labeling index increased abruptly at stage 31, the stage at which ciliary folds begin to form. At the same time there was a three‐fold increase in average cell volume. When intraocular pressure was reduced by intubating the eye, the formation of ciliary folds was prevented. Intubation also blocked the increase in labeling index and blunted the increase in cell volume that normally occur in the non‐pigmented epithelium at the time of fold formation. In the pigmented epithelium, intubation caused a sustained, three‐ to six‐fold increase in cell volume, but had no effect on labeling index. Based on these data, we suggest that increases in cell number and volume just before and during the formation of ciliary folds contribute to the formation of the ciliary folds.
Effects of heat shock on the pattern of fibronectin and laminin during somitogenesis in Xenopus laevis
Authors: Danker K. , Hacke H. , Wedlich D.
Published: February 2005

Heat shock causes partial disruption of the segmentation pattern during somitogenesis in Xenopus as well as in other vertebrates. However, Xenopus undergoes a different type of somite formation than that of most vertebrates: Somites are formed by rotation of cell blocks out of the paraxial mesoderm. We attempted to determine whether or not the segmentation disorder following heat shock is caused by an altered pattern of fibronectin and/or laminin, that could then effect the rotation of cell blocks. Therefore, we carried out heat shock experiments and analyzed the distribution of both ECM proteins in correlation to the position of somitic cells.

Our results reveal that heat shock causes an incorrect deposition of fibronectin as well as laminin during somite formation. This leads to an intermingling of cells from different segments and to an anchorage of cells at the lateral matrix. Immunoblots show that the defects in the pattern of these ECM proteins do not correlate with a decrease of both proteins. However, immunohistological staining patterns demonstrate that oversized blocks of 20‐cell width, instead of the normal ones of about 9‐cell width, are separated out of the paraxial mesoderm following heat shock treatment. This indicates that the altered pattern of fibronectin and laminin might be a secondary effect caused by incorrect segregation and detachment of cell blocks during somitogenesis. Since anchorage of somitic cells is mostly affected by the altered distribution of fibronectin and laminin, it is more likely that both ECM proteins function in anchorage of migrating presomitic cells and in maintaining of segment borders rather than in stimulating cell rotation movements.
The role of hyaluronan‐binding protein in assembly of pericellular matrices
Authors: Yu Qin , Banerjee Shib D. , Toole Bryan P.
Published: February 2005

Hyaluronan‐dependent pericellular matrices or “coats” are expressed by a variety of cell types in culture and modulation of their expression may be important in regulation of cell interactions in vivo during development. Monoclonal antibody IVd4, which recognizes hyaluronan‐binding protein with the properties of a hyaluronan receptor, was shown to block formation of these coats by a variety of cells. Using rat fibro‐sarcoma cells, it was found that the antibody not only blocked initial formation of the coats but also caused their loss when added subsequent to formation. The loss of preformed coats in the presence of antibody occurred at 4° and 37°, implying that the function of hyaluronan‐binding protein in coat formation is not in mediating metabolic processes. The antibody also had no significant effect on hyaluronan production by the fibrosarcoma cells. In addition, hyaluronan hexasaccharide, a competitive inhibitor of the interaction between polymeric hyaluronan and its cell surface receptor, was found to inhibit coat formation. Thus it is concluded that a hyaluronan‐binding protein with the properties of a hyaluronan receptor is required for pericellular matrix formation.