bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological studies on denervated brown adipose tissue
Authors: Slavin Bernard G. , Bernick Sol
Published: February 2005

Intact and denervated brown fat lobes of normal and cold‐exposed mice were studied by light and electron microscopy. Following two weeks of denervation in normal and cold‐exposed mice, denervated brown fat cells were hypertrophied because of lipid accumulation. In normal mice there was a transient increase in glycogen. In cold‐exposed mice, the quantity of glycogen in intact and denervated brown fat was greater than in normal mice. Mitochondria increased in size, and the number of cristae was greater in intact fat of cold‐exposed mice than in denervated brown fat. Carbon perfusion of blood vessels demonstrated a decreased capillary bed in denervated fat. Capillary constriction noted only in denervated brown fat is indicative of reduced blood flow.
Tridimensional reconstruction of the rat thymus
Authors: Sainte‐Marie Guy
Published: February 2005

Some aspects of the basic histological features of the thymus are still not adequately known. The architecture of the heterogeneous organ, like the thymus, can be revealed by a tridimensional reconstruction only. We carried out such reconstruction of the cortex, medulla and network of interlobular septa of the rat thymus. The serial sections of a 10‐week‐old and of a 5‐day‐old thymus were projected on a cardboard of a thickness proportional to the magnification of the projection. The outlines of the three studied components were traced and cut off. The superposition of the similar cut‐offs yielded a model of each of the three thymic components. The models demonstrated that the current description of the organ is not thoroughly realistic. It was found that there exists bridges of cortex crossing the medulla, whereas buds of medulla are present in the area generally occupied by the cortex. The relationship between the medulla and the cortex is more intricate than currently described. The results revealed that the interlobular septa do not form a network of more or less regular walls designed to divide a lobe into comparable lobules. Instead, this network is irregular, being related to the pathway of the main intrathymic blood vessels.
Innervation of feline perineal musculature
Authors: Martin William D. , Fletcher Thomas F. , Bradley William E.
Published: February 2005

Innervation to muscles of the feline perineum was examined by gross dissection of the sacral nerve plexus and quantitation of efferent and afferent myelinated fibers in selected nerves derived from the plexus. In addition, distribution of muscle fiber sizes and muscle spindle content were determined for muscles innervated by the nerves studied.

Efferent myelinated fiber populations were bimodal in nerves innervating muscles with many spindles and unimodal in nerves innervating muscles in which few or no spindles were observed. Coccygeus and levator ani muscles had similar numbers of muscle spindles, but the spindles were different in the two muscles based on afferent innervation. In both coccygeous and external anal sphincter muscles, primary spindle endings must be associated with relatively small afferent nerve fibers. The pelvic urethra received more large myelinated afferent fibers than the penis. The three divisions of the external anal sphincter muscle had three distinct populations of muscle fibers, based on size distribution. The homologous bulbospongiosus and constrictor vulvae muscles had different populations of muscle fibers.
Histochemical enzyme profile of the masseter muscle in different mammalian species
Authors: Schiaffino S.
Published: February 2005

It has long been known that in certain mammalian species the masseter muscle is a fast‐twitch muscle in spite of its red colour. We have investigated the histochemical fiber composition of this muscle in the rabbit and in different species of rodents. In the mouse, rat and guinea pig the masseter is uniformly composed of fibers displaying alkali‐stable and acid‐labile myosin ATPase activity like most fibers in fast‐twitch hindleg muscles and moderate to high succinate dehydrogenase activity. The homogeneity of the histochemical profile with respect to myosin ATPase activity makes this muscle especially suitable for correlated physiological, biochemical and ultrastructural studies. The rabbit masseter has a basically similar though relatively heterogeneous fiber composition with atypical histochemical properties. A sizable population of fibers in this muscle exhibit high levels of both alkali‐stable and acid‐stable myosin ATPase activity. Mitochondrial α‐glycerophosphate dehydrogenase activity, which reflects the glycolytic capacity of skeletal muscle fibers, varies in the masseter of different species in a way which cannot be exactly predicted on the basis of the reactions for myosin ATPase and succinate dehydrogenase.
Early embryology of the fathead minnow Pimephales promelas rafinesque
Authors: Manner Harold W. , Dewese Casimira M.
Published: February 2005

The fathead minnow, Pimephales promelas (Rafinesque), has been laboratory bred and the early embryos staged and described. At 23°C the embryo requires 33 hours to reach the 13‐somite stage. This period of early embryonic development has been divided into 12 stages. The description of each of these stages is accompanied by photographs.
Ultrastructure of mouse egg cylinders developed in vitro
Authors: Solter Davor , Biczysko Wieslawa , Pienkowski Marek , Koprowski Hilary
Published: February 2005

Mouse blastocysts were grown in vitro and the ultrastructure of resulting egg cylinders was compared with the ultrastructure of egg cylinders isolated from uterus. Egg cylinders grown in vitro had two or three germ layers and were attached to the bottom of the dish through the layer of trophoblastic cells. The entoderm was composed of two cell types intermixed haphazardly: (1) One type had numerous microvilli on the free surface and a large number of dense bodies, autophagic vacuoles, big and small vacuoles and myelin figures in the cytoplasm. (2) The other type had rich, rough endoplasmic reticulum with wide cisternae. The cisternae were filled with fine, granular material similar to that found as a thick membrane separating the entodermal layer from the rest of the embryo. The first type of cell was ultrastructurally similar to cells of the visceral entoderm of egg cylinders isolated from uterus and the second type was similar to cells of the parietal entoderm. The thick basement membrane observed in embryos grown in vitro was similar to Reichert's membrane. Parietal entoderm and Reichert's membrane were never found as separate structures in embryos grown in vitro. It is probable that the entodermal cells in blastocysts differentiate in vitro into both parietal and visceral entodermal cells within the same layer. Mesodermal and ectodermal cells of vitral embryos were similar to such cells in the egg cylinders isolated from the uterus. The cytoplasm was filled with free ribosomes in the form of polysomes and also contained a few profiles of endoplasmic reticulum, well developed mitochondria and Golgi apparatus. Intercellular spaces between mesodermal cells were large and the cells were not attached to one another. Ectodermal cells were tightly packed and inter‐connected with numerous desmosomes. The ultrastructure of egg cylinders in vitro and in vivo was similar. Observed differences might be caused by culture conditions and some of them probably represented the changing pattern of differentiation in vitro.
Cytological effects of salt‐stress and localization of transport adenosine triphosphatase in the lateral nasal glands of the desert iguana, Dipsosaurus dorsalis
Authors: Ellis Richard A. , Goertemiller Clarence C.
Published: February 2005

Each of the bilateral nasal glands of Dipsosaurus is surrounded by a thin cartilagenous capsule. A short excretory duct leads to the vestibule of the nasal cavity. This duct connects with the branched principal secretory tubules that end in small terminal segments. Tall columnar cells line the principal secretory tubules, but mucous and tuft cells form the terminal elements. In salt‐stressed animals the spaces between dark and light principal secretory cells are dilated. Potassium‐dependent, ouabain sensitive, adenosine triphosphatase (Ernst, '72a) was localized within the lateral plications of the principal secretory cells and in the apical microvilli of the tuft cells. These observations are consistent with current concepts of ion transport in salt‐secreting epithelia, and they suggest that the tuft cells, not found in avian salt glands, play a role in the unusual physiology (Templeton, '66) of the nasal glands in this reptile.
Structural and functional homologies of the accessory reproductive glands of two species of sciurids, Cynomys ludovicianus and Citellus tridecemlineatus
Authors: Foreman Darhl
Published: February 2005

The microscopic anatomy of the accessory glands of black‐tailed prairie dogs (Cynomys ludovicianus) and thirteen‐lined ground squirrels (Citellus tridecemlineatus) have been studied. In addition, the glands of a 5 cm fetal prairie dog have been described. Adult and fetal prairie dogs and adult ground squirrels have so‐called seminal vesicles folded dorsally over the dorsal prostate with ducts leading directly to the urethra lateral to, but in the region of, the entrance of both the dorsal prostatic ducts and the deferent ducts. Histological studies of the seminal vesicles of both prairie dogs and ground squirrels showed that they were tubuloalveolar glands and were similar in structure to the dorsal prostates of each species. The fructose concentrations of the dorsal prostate and seminal vesicles of out‐of‐season prairie dogs were similar, and both glands accumulated fructose with the onset of the breeding season or with injection of testosterone propionate but the seminal vesicles accumulated more fructose than the prostate. On the basis of histological structure, anatomical relationships, accumulation of fructose and possible function as a coagulating gland it is proposed that the proper name for the so‐called seminal vesicles in these species is craniodorsal prostate.
Fast and simple identification of adipose tissues in situ with dithizon
Authors: Epple August , Marques Maria , Miller S. B.
Published: February 2005

Minute amounts of white or brown adipose tissue can be localized in situ within seconds by covering the organ surfaces with an alkaline solution of dithizon (diphenylthiocarbazone) in alcohol and water. The adipose tissues stain deep green, while the other organs remain unstained, or appear in various shades of pink and red. This technique has been successfully applied to various groups of vertebrates (mammals, birds, reptiles, amphibians and fishes), and it works in fresh, in deep frozen and in formalin‐fixed specimens. It fails after tissue fixation in mercuric chloride‐containing fluids. In vitro studies show that the staining reaction is due to (1) a preferential solubility of small amounts of dithizon in adipose tissue lipids, and (2) the development of a green color, which appears when dithizon dissolves in lipids or organic solvents.
Retino‐tectal course of optic nerves in cyclopic and synophthalmic zebrafish embryos
Authors: Schmatolla Ernest
Published: February 2005

Factors contributing to the retino‐tectal course of the optic nerves in cyclopic and synophthalmic zebrafish embryos were evaluated. The eye abnormalities were produced by immersing blastula stage eggs in 3% ethanol for two hours. Approximately 50% of cyclopic eyes produced one optic nerve that exits from the eye to innervate one optic tectum. The remaining half of the cyclopic embryos formed optic nerves that were unable to exit from the eyes.

In the synophthalmic embryos, two optic nerves were always produced. These nerves either joined within the partially fused retinas, or shortly after exit from the eyes, to form one nerve which entered the brain and innervated only one optic tectum. Crossing over was not seen within the fused eyes or after exit from the eyes.

The resultant single optic nerves in the cyclopic and synophthalmic embryos innervated the side of the brain penetrated by the nerve. They entered in the floor of the forebrain, diencephalon, or midbrain, usually asymmetrically. Axial growth, directional orientation, and contact guidance of matrix configurations appeared an adequate explanation for the establishment of the retino‐tectal pathway.
The ultrastrcture of wallerian degeneration in the severed optic nerve of the newt (Triturus viridescens)
Authors: Turner James E. , Singer Marcus
Published: February 2005

Wallerian degeneration in the severed newt's (Triturus viridescens) optic nerve is complete between the 10–14th post operative day (p.o.d.). Consequently, the newt optic nerve displays one of the most rapid degenerative responses yet reported for the central nervous system of vertebrates. In most cases it also exhibits the speed of degenerative phenomena in the vertebrate peripheral nervous system.

The degeneration of unmyelinated axons is most rapid and is completed by 2–3 p.o.d., compared to myelinated axons, most of which degenerate between 2–10 p.o.d. Myelin ring formation (vesicular transformation) is the principal form of lamellar breakdown and occurs in a highly organized manner which can be clearly staged.

The glial cell response to Wallerian degeneration is two‐fold: cytoplasmic hypertrophy and myelin‐lytic. Glial hypertrophy subsides by the 10–14 p.o.d. with the ingrowth of numerous regenerating nerve fibers. The myelin‐lytic response accounts for most of the myelin destruction. Leukocyte‐like and microglialike cells also participate in myelin breakdown but to a lesser degree.
Structure of rat ultimobranchial bodies after birth
Authors: Calvert R.
Published: February 2005

The evolution of ultimobranchial bodies in Holtzman rats during the first 64 weeks after birth was studied by reconstructing three‐dimensional models from serial sections stained by the periodic acid‐Schiff technique. Radioautography with 125I was made to see if ultimobranchial cells and/or follicular cells lining the lumen of mixed follicles were able to iodinate proteins. The term ultimobranchial body designates herein an embryonic vesicular structure (derived from the third pharyngeal pouch) whose wall is made of a stratified squamous epithelium. During the first week after birth, the vesicular ultimobranchial body elongates rapidly and becomes a canal or a duct. During the second week, cell desquamation brings about local dilatations in the lumen of these ducts; with further enlargement ultimobranchial follicles will appear. In one‐day‐old rats, mixed follicles are present. Only the follicular component of mixed follicles iodinates proteins as is shown by radioautography. The reconstructed models enlarge rapidly up to the 56th day after birth at which time their weight has increased nineteenfold. These same models show that the three morphological components of ultimobranchial parenchyma, namely ducts, follicles and mixed follicles, are in continuity within the thyroid parenchyma. The formation of new thyroid follicles after birth and the possibility that the ultimobranchial parenchyma may function as an endocrine gland of holocrine type are discussed.
16α‐hydroxy‐progesterone as a sex hormone antagonist: Effect on venous diameters in the female mouse
Authors: Forbes Thomas R. , Taku Elaine
Published: February 2005

Pellets of progesterone plus 1 % 16α‐hydroxy‐progesterone (16α‐OH), testosterone plus 1 % 16α‐OH, and estradiol‐17β plus 1 % 16α‐OH were implanted in the right uterine fat mass in ovariectomized (O) and ovariectomized‐hysterectomized (OH) mice. Three weeks later they were killed and the diameters of the ovarian, uterine, and femoral veins and the inferior vena cava were measured and averaged. The averages were compared with averages for O and OH mice bearing pellets of glass and of progesterone, testosterone, and estradiol‐17β without 16α‐OH. It is concluded that in castrate mice the size of ovarian and uterine veins is influenced not by the presence or absence of the uterus but by sex steroids, that progesterone usually causes decreases while testosterone and estradiol‐17β cause increases in vein diameter, and that both the presence of the uterus and the administration of 1 % 16α‐OH are associated with partial inhibition of increases in vein size induced by steroids. Uterine hypertrophy and urinary bladder distention resulting from the administration of testosterone and estradiol‐17β were not prevented by the addition of 1 % 16α‐OH.
Hematopoiesis in the embryonic mouse spleen. II. Alterations after phenylhydrazine administration to the mothers
Authors: Djaldetti M. , Bessler H. , Fishman P.
Published: February 2005

The effect of phenylhydrazine (PHZ) on the hematopoietic events in the embryonic spleeen of C57Bl/6J mice was examined by light and electron microscopy. Following PHZ injections to the mothers, the embryonic spleen revealed a marked increase in erythroid precursors, with a shift to mature cells. This phenomenon was part of a more generalized stimulation of erythropoiesis, expressed by a shift to mature red cell precursors in the embryonic livers and an increase in the percentage of non‐nucleated cells in the embryonic peripheral blood. Concomitantly stimulation of phagocytosis in the spleen of embryos in the early gestational days and increased vascularity were observed, and a later effect of granulocytopoietic stimulation. The effect on erythropoiesis in the embryonic spleen might be a sequence of erythropoietin stimulation, either in the mothers or the fetuses, due to anemia and hypoxia following PHZ injections.
Conal contribution to the electrocardiogram of chick embryo hearts
Authors: Paff George H. , Boucek Robert J.
Published: February 2005

Contraction of the conus arteriosus (conus) is visibly delayed in the tubular heart of the chick embryo, and since the electromechanical coupling interval of isolated conal segment is similar to other areas of the embryonic heart, the delayed contraction of the conus indicated an impedance in the spread of the depolarization wave across the ventriculo‐conal (VC) junction.

A surface electrode placed on the conus of hearts obtained from the 72‐hour chick embryo records a deflection, termed the C wave, appearing between the QRS complex and the T wave. To establish that the C wave arose from below the atrioventricular sulcus, atria were removed from a series of hearts from 96‐hour embryos and the electrogram revealed a C wave without a P wave.

The VC junction responds to digitoxin just as the atrioventricular tissue. Digitoxin prolongs the interval between the QRS and the C wave prior to a complete block in a manner analogous to the PR interval increase prior to the development of the Wenckebach phenomenon or complete atrioventricular block.

As the embryonic heart developed after 96 hours, the C wave was no longer identifiable in the ECG.
The effects of ringer‐locke or blood infusions on the lateral intercellular spaces of the rat proximal tubule
Authors: Bengele Howard H. , Evan Andrew P.
Published: February 2005

Diuresis and natriuresis follow volume expansion by intravenous infusion of either blood or saline. However, the mechanisms underlying the renal responses seem different for the two types of expansion. It has been suggested that the response to saline expansion is due to changes in physical factors with alterations in the morphology of the lateral intercellular space (LIS). The present study examines the width of the LIS of the proximal tubule after a Ringer‐Locke (1%, 2.3%, or 7% body weight) or whole blood (2.3% body weight) infusion and in nonexpanded control. After Ringer‐Locke infusion, a significant widening of the LIS of the proximal tubule is seen at all levels of expansion. There is a linera relationship between the level of the Ringer‐Locke infusion and the degree of expansion of the LIS. In contrast, after blood volume expansion, the width of the LIS is the same as nonexpanded controls. These studies are consistent with the view that the renal response to saline expansion is mediated at least in part by physical factors affecting the proximal tubule.
Prenatal development of the grey lethal mouse. I. Teeth and Jaws
Authors: Hollinshead May B. , Schneider Lawrence C. , Smith Michael E.
Published: February 2005

Osteopetrosis is a disease in which diffuse sclerosis of the entire skeleton results from an imbalance between the processes of bone formation and bone resorption. The grey lethal is the most severely affected of the three mouse mutants which have been described and its osteopetrosis is transmitted as a simple autosomal recessive gene. Affected mice develop a grey coat at 8–10 days of age and die before one month of age.

Recently we (Hollinshead and Schneider, 1973) reported that grey lethal mice could be identified at birth because the apex of their lower incisors lies anterior to the molar region in the mandible. In this study we show that it is possible to identify affected fetuses from day 18 of gestation using the same and other histologic criteria in examining their teeth.
The influence of function on chondrogenesis at the epiphyseal cartilage of a growing long bone
Authors: Meikle Murray C.
Published: February 2005

In order to study the behaviour of epiphyseal cartilage in a nonfunctional environment, the third metacarpal bone was transplanted intracerebrally as an isograft between 7‐day‐old litter‐mate rats. Host animals were killed 1, 2, 3, 4, 5, 6 weeks post‐operatively, and the cellular kinetics evaluated by means of tritiated thymidine autoradiography. The study was also used to compare the effects of function on chondrogenesis at the epiphyseal cartilage with that previously demonstrated for the condylar cartilage of the mandible (Meikle, '73a).

Transplantation resulted in three major changes in the cartilage; there was a decreased rate of proliferative activity in the cell columns; the cartilage failed to maintain a satisfactory increase in transverse diameter; the cells of the perichondrium differentiated into osteoblasts instead of chondroblasts. Autoradiographic and histological findings suggested that the inability of the cartilage to increase in transverse diameter was related to the decreased rate of proliferative activity in the cell columns and not to the cessation of perichondrial chondrogenesis. On the basis of these findings two conclusions can be made.

1. Extrinsic mechanical stresses associated with function appear to be necessary for the normal interstitial growth of epiphyseal cartilage during postnatal development, suggesting that functional activity can influence the rate of cell proliferation.

2. Functional activity provides the stimulus for the differentiation of perichondrial cells into chondroblasts.
Electron microscopic localization of calcium in vascular smooth muscle
Authors: Debbas Gamil , Hoffman Loren , Landon Erwin J. , Hurwitz Leon
Published: February 2005

Potassium pyroantimonate has been employed in this study to localize calcium in the vascular smooth muscle of the thoracic aorta of the rabbit. The pyroantimonate ion precipitates sodium, magnesium and calcium. Incubation of the isolated thoracic aorta in a high potassium bathing medium which does not contain sodium, magnesium or calcium depletes the tissue of sodium. Addition of 10.8 mM CaCl2 to the incubation medium results in welllocalized depositions of reaction product, presumably that of calcium pyroantimonate, in mitochondria, sarcoplasmic reticulum, and at the plasma membrane. Some or all of these organelles may, therefore, play a vital role in the contractionrelaxation cycle of vascular smooth muscle.
The origin and fate of osteoclasts
Authors: Hall Brian K.
Published: February 2005

Despite intensive and ingenious investigation, the origins and ultimate fate of the osteoclast remain shrouded in mystery. This brief review evaluates some of the recent experimental approaches used in the study of the osteoclast, especially whether they form from intra‐ or extra‐skeletal progenitor cells, whether from the same osteoprogenitor cell as the osteoblast, and whether, once formed, they may modulate to osteoblasts.

That osteoprogenitor cells can, and do, become osteoclasts is well founded, as is the conclusion that such progenitor cells originate as blood‐borne, extraskeletal cells. Evidence that sessile, intra‐skeletal, progenitor cells can form osteoclasts is less direct. There is good evidence that osteoclasts both shed and take‐up nuclei, but no direct evidence that nuclear shedding is accompanied by death of the osteoclast, and no direct evidence for the fate of the shed nuclei. Whether the same osteoprogenitor cell can produce either an osteoblast or an osteoclast also remains an open question.
The effects of prostaglandin F2α on the fine structure of the corpus luteum of the hysterectomized guinea pig
Authors: Bagwell J. N. , Davies D. L. , Ruby J. R.
Published: February 2005

Luteal cell fine structure was studied in hysterectomized control and hysterectomized, prostaglandin‐treated (1–5 days) guinea pigs. In hysterectomized control animals, luteal cells were hypertrophied and were characterized by an abundance of agranular endoplasmic reticulum (AER) suggesting steroidogenic activity. With one day of prostaglandin treatment, little change in the cytological appearance had occurred. After two, or three days of treatment, cells showed a decrease in size and an apparent increase in the number of lipid droplets. Following four days of prostaglandin treatment, luteal tissue was characterized by the presence of large amounts of collagen in the intercellular spaces and by the invasion of fibroblasts. Areas of degenerating luteal cells with numerous myelin figures and lipid droplets were observed. After five days of prostaglandin treatment, most of the luteal cells had undergone extensive luteolytic changes. Typically they contained coalescing lipid droplets, myelin figures and crystalloids, and were surrounded by collagen fibers. These observations suggest that prostaglandin F2α does effect structural luteolysis in this species in the absence of uterine tissue.
Dissection casts of the human brain
Authors: Fix James D. , Gosling Craig G. , Burke Thomas F.
Published: February 2005

A simple, inexpensive method of making accurate permanent casts of brain dissections is described. Dissected brain preparations are used to produce silicone rubber molds. Methyl methacrylate is used to make the hard plastic models.
Changes in numbers of acidophilic and basophilic connective tissue granulated cells in the intestine of the rat during the estrous cycle
Authors: Johnson Shirley M. , Nellor John E.
Published: February 2005

Changes in physiological reproductive states of female Long‐Evans hooded rats were directly correlated with changes in the concentration of acidophilic and basophilic connective tissue granulated cells in the lamina propria of the duodenum. Acidophilic granulated cell numbers were significantly higher at estrus and metestrus than at other stages of the estrous cycle or in the immature state. Acidophilic granulated cell numbers during pregnancy were not significantly different from cell numbers quantified during metestrus, diestrus, or proestrus, but were significantly lower than cell numbers during estrus. Late lactation (21‐25 days) was associated with significant decreases in the numbers of acidophilic granulated cells from numbers observed during the estrous cycle and during pregnancy. Basophilic granulated cell numbers did not differ significantly during the estrous cycle, although the highest numbers were observed during proestrus. Basophilic granulated cell numbers were significantly higher during pregnancy than during the estrous cycle. Basophilic granulated cell counts in late lactation were comparable to numbers quantified in estrus, metestrus, and diestrus, but were significantly lower than during proestrus and pregnancy.
Intercellular junctions of rat endocardium
Authors: Anversa Piero , Giacomelli Filiberto , Wiener Joseph
Published: February 2005

The ultrastructure of the intercellular junctions of rat endocardium has been characterized following lanthanum exposure in vitro and uranyl acetate staining en bloc. The interendothelial clefts of the endocardium run either a relatively straight or convoluted course and possess one or two loci where the plasma membranes are in close apposition or form punctate fusions. Elongate restrictions, that exhibit hexagonal arrays of subunits following lanthanum immersion (gap junctions), are also present in the intercellular endocardial clefts. The occurrence of interendothelial clefts of endocardium lacking occlusive foci can account for the permeability properties of ventricular endocardium, where the direction of diffusion of macromolecules has been attributed to pressure gradients between ventricular cavity and myocardium. The relationship of gap junctions to possible electrical phenomena within the endocardium is also discussed.
Cellular mechanisms involved in cyclic stromal renewal of the uterus. II. The albino rat
Authors: Padykula Helen A. , Campbell Ann G.
Published: February 2005

During the first four days postpartum, heterophils (polymorphonuclear leucocytes) and macrophages occur in the intercellular compartment of the luminal epithelium of the uterine endometrium. Cytochemical and ultrastructural evidence indicates that transepithelial emigration of these stromal cells to the uterine cavity is occurring. This event takes place while the luminal epithelium is proliferating in response to the estrogenic stimulus of the postpartum estrus.

Heterophil emigration precedes that of the macrophages and is most conspicuous during days 1 and 2. Although it has been established that collagen fibrils occur in uterine phagocytes (Schwarz and Güldner, 1967) assumed to be macrophages (Parakkal, 1969, 1972), their precise role in collagen degradation remains undefined. It seems likely that the emigrating macrophages, heavily laden with phagolysosomal derivatives and lipid droplets, are hauling the remnants of the intercellular substance out of the endometrium during days 2–4 postpartum. Ultrastructural evidence indicates that the emigrating macrophage punctures the basal lamina and passes through the intercellular compartment of the luminal epithelium by active penetration.

Another mode of macrophagic egress operates in the deep stroma of the endometrium and myometrium where lymphatic drainage occurs. Macrophages accumulate in the perilymphatic stroma as well as within lymphatic vessels.

Thus macrophagic emigration through the luminal epithelium and lymphatic vessels may provide a cellular mechanism for elimination of the intercellular stromal substance in the regressing uterus. Transepithelial emigration is a mechanism which operates also in the marsupial uterus (Padykula and Taylor, 1976), and thus may be a fundamental mechanism among subprimate mammals that fulfills in part the function that menstruation effects in primates.
The nonuniform distribution of acidic components on the human placental syncytial trophoblast surface membrane: A cytochemical and analytical study
Authors: Nelson D. Michael , Smith Carl H. , Enders Allen C. , Donohue Thomas M.
Published: February 2005

The surface coat of syncytial trophoblast from term human placentas was studied using cytochemical methods (colloidal iron, alcian bluelanthanum nitrate, dialyzed iron) in coordination with tissue enzyme digestions (trypsin, neuraminidase) and sialic acid analyses. The presence of at least two highly acidic anionic components that contribute significantly to the surface negativity of trophoblast has been demonstrated. The first of these, sialic acid, was removed with neuraminidase. Tissue digestion with this glycosidase was accompanied by a decrease in trophoblast surface staining with colloidal iron, a decrease in tissue sialic acid, and an increase in the concentration of sialic acid in the incubating medium. Results from methylation experiments were consistent with the presence of sialic acid. The second anionic component(s) was identified by removal with trypsin of a glycocalyx constituent that stained with both colloidal iron and lanthanum. After trypsinization, tissue sialic acid levels were not significantly different from control values, and no detectable sialic acid was present in the incubating medium. The identity of this anionic component has not been established. Both sialic acid and nonsialic acid acidic components are distributed in higher density on membrane of microvilli than on intermicrovillous surface membrane. In addition, the sialic acid moieties appear to be clustered in the glycocalyx.
Contributions to an analysis of the avian vitelline membrane's potential to promote outgrowth of the yolk sac‐serosal membrane
Authors: Haas Hermann J. , Spratt Nelson T.
Published: February 2005

Explanted blastoderms of freshly laid chicken eggs expand their area during the first 44–45 hours of incubation by a factor of at least 11 if they are placed with the epiblast on the inner surface of explanted fresh chick vitelline membrane and provided with chick egg extract. This expansion is due essentially to the spreading of the yolk sac‐serosal membrane. On turkey and duck membrane the expansion factor is about 6 and 3.8 respectively under otherwise identical conditions, but 1.9 only on a semisolid nutrient agar plate. Only the inner surface of the vitelline membrane has this growth‐promoting potential, which markedly and progressively declines during incubation in ovo because of systemic factors rather than because of a direct influence by the outgrowing yolk sac‐serosal membrane. Trypsinization of fresh chick vitelline membrane (1% trypsin 3 hours) reduces the growth‐promoting potential to about 40% of its normal strength. The outgrowth of the extraembryonic tissues on vitelline membrane is better supported in the presence of a species' own egg extract than by extract from another species.
An autoradiographic study of tritiated uridine incorporation into the larval ovary of Xenopus laevis
Authors: Webb Andrew C.
Published: February 2005

The in vitro incorporation of 3H‐5‐uridine into the germinal and somatic cells of the larval ovary of Xenopus laevis has been studied using both light and electron microscope autoradiography. Incubation for only one hour in the presence of precursor revealed that the follicle cells are highly active in rRNA synthesis, whereas substantial oogonial nucleolar labeling was not detected for several hours. Semi‐quantitative analysis of high‐resolution autoradiograms indicated that the density of silver grains associated with “nuage” in oogonia was almost 4‐fold greater than the surrounding cytoplasm. This strongly suggests that a significant amount of RNA is associated with “nuage” at this stage of Xenopus oogenesis, in addition to its well documented protein composition. “Pulse‐chase” experiments further suggest that the nuage‐associated RNA is stable for at least 24 hours. These results are discussed (within the limitations imposed by the methodology) both in relation to other studies on the composition of nuage in a wide variety of germinal cell types and in the light of growing speculation that nuage and germinal granules are synonymous.
Cell differentiation in the terminal tubule of fetal rat submandibular gland in organ culture
Authors: Rufo Myra Bluestein , Barka Tibor
Published: February 2005

Submandibular glands from 17‐day‐old rat fetuses were maintained in organ culture for five days in a medium consisting of Eagle's MEM (87%), horse serum (10%), and chick embryo extract (3%). Each day of the culture period explants were incubated for the demonstration of peroxidase activity and processed for light and electron microscopic observations. In some experiments cultures were exposed to 3H‐thymidine one hour prior to fixation and incubation for the demonstration of peroxidase activity. Labelling index was determined using radioautographs of 1 μ Epon‐embedded sections. At the time of explantation the submandibular gland rudiment consisted of undifferentiated epithelial cells arranged in cords. On day 3 of culture two additional cell types could be distinguished: terminal tubule cells and proacinar cells. The proacinar cells were characterized by peroxidase activity in their granules and cytoplasm. By day 4 acinar cells begin to appear. On the fifth day of culture the four cell types of the terminal tubule were present in the following proportions: undifferentiated cells, 44%; terminal tubule cells, 19%; proacinar cells, 31%; acinar cells, 6%. These results indicate that the cytodifferentiation of the secretory unit of rat submandibular gland in vitro is comparable to the differentiation in vivo.
Scanning electron microscopic study of chylomicrons incubated with lipoprotein lipase
Authors: Blanchette‐Mackie E. Joan , Scow Robert O.
Published: February 2005

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

Sarcoplasmic reticulum (SR) of fast extensor digitorum longus (EDL) and slow soleus (SOL) muscles of the mouse was examined by freeze‐fracture techniques. A distinctive feature of sarcoplasmic reticulum from the EDL is the presence of hillocks on the A‐face within the terminal cisterns. These hillocks are usually arranged in a single row which is deployed parallel to the long axis of the adjacent T‐tubule. Center‐to‐center spacing of hillocks within a row is about 70–75 nm. Hillocks are also found scattered within the collar region. The EDL of ten week mice was characterized by sheet‐like terminal and intermediate cisterns, the latter being replaced in 37 week animals by thin tubular longitudinal elements of the SR which contain no hillocks or dimples.

Hillocks occur only occasionally in SR from 10 or 20 week SOL muscle. In such cases the hillocks occur singly rather than in rows as in the terminal cisterns of EDL. The predominant form of SR in the SOL contains no hillocks.

Total particles in the A‐face of EDL‐SR (2996 particles/μ2; S.D. = ± 287) slightly exceeded that of SOL‐SR (2558 particles/μ2; S.D. = ± 274 8 nm). Packing density of 8 nm particles was slightly higher for EDL (750/μ2) vs. SOL (700/μ2). The possible significance of these features of SR in fast and slow muscle is discussed.
Catecholamine‐containing nerve terminals in piloarrector muscles of stump‐tailed macaques (Macaca arctoides) and the effects of local injection of 6‐, and 5‐hydroxydopamine
Authors: Uno Hideo , Montagna William
Published: February 2005

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

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

When pancreases from fetal rats were transplanted beneath the kidney capsule of isologous normal adult recipients, continued growth and differentiation of the endocrine portion of the pancreas occurred. While limited amounts of acinar tissue were identifiable in the early transplant period (7 days), such cells were absent in long term transplants (14 and 21 days). In contrast, while few definitive islet beta cells were present at the time of transplantation, following 21 days at the kidney site large circumscribed islets comprised of heavily granulated beta cells in association with duct epithelial cells predominated. Mitotic figures were seen in both these cell populations. Total islet mass had increased over 20‐fold during the transplantation period. Similar results were observed if fetal pancreases were grown in organ culture for ten days prior to transplantation. Continued islet and duct cell growth, as evidenced by mitotic figures and an increase in absolute islet cell mass was obtained in such cultured explants when transplanted to either isogenic or allogenic recipients.

These observations support the hypothesis that fetal pancreas may be the best source of donor material for transplantation to diabetic recipients, in part, due to the continued growth and differentiation of the islet tissue during the transplantation period.
The number of satellite cells in normal human muscle
Authors: Schmalbruch H. , Hellhammer U.
Published: February 2005

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

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

Quantitative microscopic techniques were employed to determine relative mitotic activity of lobulo‐alveolar tissue in thick sections obtained from the inguinal mammary glands of colchicine‐treated post‐pubertal Lewis/Mai rats sacrificed at different phases of the estrous cycle. It was found that the magnitude of lobulo‐alveolar cell mitotic activity and the proportion of the lobulo‐alveolar tissue with mitotic activity undergo significant fluctuations during the estrous cycle. The frequency distribution of mitotic activity in lobulo‐alveolar tissue was different and heterogenous at each phase of the estrous cycle. The frequency distribution of nuclei in lobulo‐alveolar tissue during the estrous cycle showed only minor variations and could not explain the variation in mitotic activity. Similarly, no morphological differences were observed in the mammary gland which could account for the variation observed in mitotic activity.

It was concluded that the variation in mitotic activity of lobulo‐alveolar tissue is probably related to alterations in the generation time of lobulo‐alveolar cells imposed by cyclical variation in ovarian hormones during the estrous cycle.