bluuebunny/crossref_metadata_2025 huggingface dataset:
Histology and ultrastructure of the pig parotid gland
Authors: Boshell Jerry L. , Wilborn Walter H.
Published: February 2005

Parotid glands of adult pigs were studied by light and electron microscopy. The parenchyma consists of acini, intercalated ducts, striated ducts, and excretory ducts.

Acini had little affinity for periodic acid‐Schiff and were alcian blue‐negative at pH 2.6 or 0.5. These results indicate a paucity of neutral mucins and an absence of sialo‐ and sulfomucins. Histologically, acinar cells had vacuoles which corresponded ultrastructurally to large electron‐lucent secretory granules. The latter contained electron‐dense bodies and lipid droplets. Acinar cells differed histochemically and ultrastructurally from typical serous cells and were classified as special serous.

Intercalated duct cells near acini contained electron‐dense secretory granules and numerous microfilaments. Cells in distal segments lacked secretory granules.

Striated ducts were lined by two types of columnar epithelial cells, light cells and dark cells. Light cells were characterized by numerous infoldings of the basal plasma membrane, mitochondria between the infoldings, and electron‐lucent vesicles in the apical cytoplasm. The mitochondria contained tubular cristae. Dark cells were characterized by an abundance of microfilaments and numerous infranuclear processes which extended to the basement membrane.

Excretory ducts, in addition to light and dark cells, also contained basal cells and goblet cells. Mitochondria in the light cells had flattened rather than tubular cristae.

The pig parotid is a unique salivary gland and the most atypical mammalian parotid gland studied thus far. Mitochondria with tubular cristae and vacuolated special serous cells with lipid in the secretory granules are hallmarks of the pig parotid.
Development of type I cells of the rabbit subclavian glomera (aortic bodies): A light, fluorescence and electron microscopic study
Authors: Hansen John T.
Published: February 2005

The embryogenesis of the subclavian glomera (aortic bodies) is controversial. Past investigators have attributed the development of the Type I cells to mesodermal and/or neural elements. Based on the results of the present light microscopic, fluorescence histochemical and electron microscopic study of rabbit aortic bodies from 16 days of gestation (term: 31 days) to four days postpartum, it appears that the Type I glomus cells are derived from cells of neural crest origin. The subclavian glomus anlage is associated with cells of vagal origin throughout its development. Evidence of Type I cell development from pre‐existing mesodermal condensations is not observed. Type I cells exhibit formaldehyde‐induced‐fluorescence by the twentieth day of gestation. Dense‐cored cytoplasmic vesicles are apparent by the sixteenth day of gestation. The number of cytoplasmic vesicles increases steadily, but the greatest increase of vesicles is observed between the twenty‐eighth day of gestation and birth. Primitive Type I glomus cells exhibit abundant polysomes and rough endoplasmic reticulum indicative of synthetic activity. Nerve terminals are apparent adjacent to Type I cells by the twentieth day of gestation, but synaptogenesis does not occur until sometime between the twenty‐fourth and twentyeighth days of gestation. Abundant vascularity, characteristic of chemosensory glomera, is not achieved until the twenty‐eighth day of gestation.
Epidermal migration during the healing of suction blisters in rat skin: A scanning and transmission electron microscopic study
Authors: Pang Stephen C. , Daniels William H. , Buck Robert C.
Published: February 2005

Fluid‐filled blisters, created on the skin of the inner surface of the pinna of heparinized rats by the application of suction, showed an intact basal lamina through which protruded hairs and remnants of hair follicles. The origin of epithelial cells and their spreading over the basal lamina were studied at intervals over 36 hours using scanning and transmission electron microscopy. The majority of epidermal cells arose from the outer root sheath of hair follicles and began to spread radially before 12 hours. By 36 hours the cells were confluent over most of the blister base. Inflammatory cells were few in number and rested mainly on the bare basal lamina rather than on the resurfacing cells. Some elongated epidermal cells showing tapering foot processes appeared to be migrating in from the epidermis at the edge of the blisters. The cells spreading from hair follicles were flat and polygonal. On these sheets of cells a few small folds and many filopodia were present at intercellular junctions and at the free margin of the leading cells. Large numbers of short microvilli covered the surface of some of the epidermal cells, especially at 24 and 36 hours; other epidermal cells were relatively smooth.
Development of the dorsal cochlear nucleus of the cat: An electron microscopic study
Authors: Kane Eileen S. , Habib Christine P.
Published: February 2005

This developmental study of the dorsal cochlear nucleus (DCN) was based upon electron microscopic and Golgi preparations from many postnatal kittens (newborn‐4 months) and adult cats. Seven developmental stages were defined according to time of first alterations in size of layers, size, shape and packing of fusiform neurons; cytology of cytoplasmic organelles; cytology of fusiform cell layer (FCL) neuropil; and time when each of eight types of synaptic endings (defined in adults) appeared. During stage 1 (newborn‐2.5 days), fusiform and small cells were tightly packed. Fusiform cells, covered with multiform projections, were filled with large Golgi complexes and Nissl bodies. Free ribosomes were packed within invaginations of the nuclear envelope. The FCL expanded during stage 2 (3–6 days), both by growth of fusiform cells and by elaboration of FCL neuropil. Type 1 and type 5 endings appeared. During stage 3 (7–14 days), adult synaptic types 2, 2a, 3 and 4, plus a newly defined type 3a ending were found. Somatic projections decreased in number and length. This decrease continued into stage 4 (15–25 days), when synaptic type 1a appeared. Fusiform cells were separated by further growth of FCL neuropil during stage 5 (26–44 days). Adult synaptic type 5a was first noted during stage 6 (45–95 days), when glomeruli and synaptic nests were also identified. In the final stage 7 (120 days and older), glomeruli and nests matured, while maximally sized fusiform cells had smooth somatic membranes and nuclear envelopes. All adult synaptic types were mature after 120 postnatal days. This long interval for staged DCN development facilitates correlated developmental, electrophysiological studies. The latter might clarify functions of known inputs to DCN by matching maturation times of those inputs with appearance of specific physiological properties.
Postnatal development of the canine kidney: Quantitative and qualitative morphology
Authors: Eisenbrandt David L. , Phemister Robert D.
Published: February 2005

The normal postnatal development of the canine kidney was investigated utilizing qualitative and quantitative histologic methods. Kidneys were examined at 2, 4, 8, 14, 22, 70, and 200 days of age. A subcapsular nephrogenic zone was present in the kidneys until approximately eight days of age. This zone contained tissues which interacted to produce new nephrons and interstitial tissues. Several developmental stages of forming nephrons were identified in this zone. Beneath the nephrogenic zone, renal corpuscles of increasing maturity were located at successively deeper cortical levels. The total number of nephrons was estimated to be 445,000 per kidney. This number did not vary significantly during growth. The corpuscular volume per nephron increased 249% from 14 to 200 days of age. During the same period there was a 303% increase in the tubular volume per nephron. Although the developing kidney differed anatomically from the adult kidney, the individual nephrons maintained volumetric corpuscular‐tubular balance during growth.
Cytochemical localization of cations in the testis of the syrian hamster, utilizing potassium‐pyroantimonate
Authors: Gravis Curtis J.
Published: February 2005

Pyroantimonate has long been used as a cytochemical technique for the localization of cations. Although the technique was originally alleged to be specific for Na+, other cations, including Mg++, Ba++, Ca++, Zn++ and polycationic amines, form pyroantimonate precipitates. In seminiferous tubules treated with antimonate‐osmium fixation, the nuclei of the Sertoli cells and germ cells contained precipitates. In regions of condensed chromatin the precipitates were dense while, in dispersed chromatin, precipitates were sparse or absent. It is postulated that the dense precipitates observed in the condensed chromatin may represent an accumulation of calcium that may facilitate chromatin condensation. The Sertoli cell nucleolar apparatus contained light precipitates in the pars amorpha, moderate precipitates in the nucleolonema, and heavy precipitates in the perinucleolar heterochromatin bodies. The nuclei of the maturation‐phase spermatids lacked any precipitates. The perinuclear ring of the acrosome‐phase spermatids contained pyroantimonate deposits. In the maturation‐phase spermatids, staining occurred in the postacrosomal dense lamina, in the subacrosomal space between the perforatorium and the inner acrosomal membrane, and in the central mass of the residual bodies. Since the postacrosomal dense lamina is the portion of the spermatozoon that initially fuses with the ovum, it is postulated that its cationic properties in some way facilitate this fusion.
Cobalt iontophoresis of sensory nerves in the rat lung
Authors: El‐Bermani Al‐Walid I. , Chang Tien‐Lan
Published: February 2005

By iontophoretically introducing, first, cobalt and, subsequently, sulfide ions into the vagus nerve, it is possible to trace sensory nerves to their endings in the rat lung. Nerve fibers and terminals are found predominantly in the adventitia of the airways and blood vessels. Some nerves are found in the submucosa of the bronchi and bronchioles. Some are found in the cardiac muscle on the periphery of pulmonary veins, and a few nerves are seen to end among smooth muscles of the blood vessels and the airways. At least three types of nerve endings can be identified at the light microscopic level: (1) free nerve endings; (2) brush‐like endings; (3) knob‐like terminals.
A comparative radioautographic study of chondrocytic proliferation in nasal septal cartilage of the 5‐day‐old rat, rabbit, guinea pig and beagle
Authors: Searls James C.
Published: February 2005

Growth sites within the cartilaginous nasal septa of four different species of animals (5‐day‐old rats, rabbits, guinea pigs and beagles) were identified by monitoring cellular proliferation radioautographically. A statistical analysis (MANOVA) was employed. It showed that, of the six combinations compared (rat‐beagle, rat‐guinea pig, rat‐rabbit, beagle‐guinea pig, beagle‐rabbit, and guinea pig‐rabbit), in only one (beagle‐guinea pig) was there any similarity in growth pattern. The other five combinations all were significantly different. Since no particular areas emerged, with any consistency, as common growth sites within any of the four kinds of septa, it was concluded that the nasal septum might well play a passive role in midfacial growth, rather than an active role as previously thought.
Ultrastructural study of granules in the corpora lutea of several mammalian species
Authors: Gemmell R. , Stacy B. D.
Published: February 2005

The ultrastructure of the corpora lutea of the goat, cow, rabbit, pig and guinea pig have been examined at a stage when progesterone was being secreted by the luteal cells. Densely staining granules, 0.2 μm in diameter, are present within the luteal cells of all the species examined. Granules were detected in the extra‐cellular spaces of the corpora lutea of the goat, cow and pig, but not of the rabbit or guinea pig. The luteal cells of the various species have the same basic structure but differ in the amounts of lipid and forms of smooth endoplasmic reticulum present.

A common mechanism of hormone secretion, in granule form, is postulated for all luteal cells.
Formation and fate of ethionine‐induced cytoplasmic crystalloids in rat parotid acinar cells
Authors: Oliver Constance , Auth Regina E. , Hand Arthur R.
Published: February 2005

The formation and fate of cytoplasmic crystalloids in rat parotid acinar cells were investigated during ethionine intoxication and recovery. By day 3 of ethionine treatment, acinar cells had numerous autophagic vacuoles containing recognizable secretory granules and fragments of rough endoplasmic reticulum. By day 5, immature crystalloids were present in many of the autophagic vacuoles, and as the crystalloids matured, a 7‐nm periodicity became apparent. Crystalloids were never observed in the Golgi saccules or in any other organelle associated with secretory granule formation. When ethionine treatment was stopped, the acinar cells rapidly returned to their normal morphology. The majority of the crystalloids and autophagic vacuoles were lost from the cells during the first two to three days of recovery. At this time annulate lamellae were present intracellularly, and macrophages, many contaning crystalloids, were associated with the basal surface of the acinar cells. These results indicate that the cytoplasmic crystalloids are formed in autophagic vacuoles, and do not represent an abnormal secretory product. Additionally, during recovery crystalloids may be removed from the acinar cells by interaction with macrophages. The sequence of autophagic vacuole formation, development of crystalloids, macrophage infiltration and phagocytosis of acinar cell debris appears to be a non‐specific response of the rat parotid gland to cellular injury occurring in a variety of experimental and pathological conditions.
The association of amorphous mineral deposits with the plasma membrane of pre‐ and young odontoblasts and their relationship to the origin of dentinal matrix vesicles in rat incisor teeth
Authors: Almuddaris M. F. , Dougherty W. J.
Published: February 2005

Young and preodontoblasts and matrix vesicles which occur in the presecretory region of incisor teeth of growing rats were examined in stained and unstained ultrathin sections in order to characterize sites involved in the initial mineralization of dentin. Common to pre‐ and young odontoblasts in the presecretory region were hemispherical membrane‐associated amorphous densities, measuring 5‐35 nm in diameter after fixation in glutaraldehyde‐osmium tetroxide or glutaraldehyde only. Amorphous densities were associated also with the limiting membranes of some vesicles in the extracellular matrix. Other vesicles in the extracellular matrix contained needle‐like crystalline deposits typical of dentinal matrix vesicles. Fully differentiated odontoblasts in more incisal regions of the tooth lacked plasma membrane‐associated amorphous densities. Neither amorphous nor crystalline densities were associated with any other cellular or subcellular structures in cells of the presecretory region. Flotation of ultrathin sections on solutions of EDTA or EGTA removed the amorphous densities from the plasma membranes, suggesting that the amorphous densities are calcium‐containing mineral deposits.

Amorphous deposits were associated with the membrane of vesicular structures protruding from the surfaces of pre‐ and young odontoblasts, suggesting that vesicles found in the extracellular matrix arise by budding from the plasma membranes of pre‐ and young odontoblasts. The occurrence of amorphous mineral deposits in association with the limiting membrane of some vesicles in the extracellular matrix, and the occurrence of needle‐like mineral crystals within other matrix vesicles, suggest that an amorphous‐to‐crystalline phase transformation of mineral takes place within the matrix vesicle. The results of this study suggest that calcium‐binding sites associated with plasma membranes of pre‐ and young odontoblasts act as nucleating centers for primary mineral deposition in tooth dentin.
Peritoneal cells in mice: Quantitative and qualitative cell morphology
Authors: Abe Kazuhiro , Honma Sato , Ito Takashi
Published: February 2005

Peritoneal free cells from 86 adult mice of both sexes were studied quantitatively and qualitatively.

Peritoneal free cells were examined by use of a Coulter counter and channelyzer. The size‐distribution curves of peritoneal free cells thus obtained show three peaks, which were almost constant in position in all the cases examined. Thus, peritoneal free cells can be classified into three major populations according to cell size. The total cell numbers of the three populations, composed of small, medium‐sized and large cells are, on the average, 1.60 × 106, 2.47 × 106 and 2.90 × 106 in males and 2.05 × 106, 5.57 × 106 and 3.86 × 106 in females at 65 days of age. The number of medium‐sized cells is significantly greater in females than in males.

Morphologically, three types of peritoneal cells, which constitute the three populations, can be distinguished cytologically and cytochemically, when examined by light microscopy and scanning and transmission electron microscopy. These type I, II, and III cells correspond closely to the three components in the size distribution curves in cell size.

Type I cells are small lymphocytes. Type II cells are medium‐sized, round mononuclear cells which are distinguishable from lymphocytes by their ultrastructural characteristics, and they constitute a major population which can be separated from the other two populations. Type III cells are macrophages. In the peripheral cytoplasm, they have a labyrinth of tubules which open on the cell surface.
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Effects of colchicine on the morphology and prolactin secretion of rat anterior pituitary cells in monolayer culture
Authors: Antakly Tony , Pelletier Georges , Zeytinoglu Fusun , Labrie Fernand
Published: February 2005

The effects of incubation of rat anterior pituitary cells in monolayer culture with 10−6 M colchicine have been investigated during timeintervals extending from 1 to 96 hours. Prolactin release, as measured by radioimmunoassay, was rapidly inhibited by colchicine, this inhibition being accompanied by increased cellular prolactin content for up to 24 hours of treatment and followed by decreased values of cellular prolactin concentration at later time‐intervals. Immunocytochemical localization showed an increased positive reaction for prolactin up to 24 hours after colchicine treatment, whereas transmission electron microscopy demonstrated, in parallel, an increased number of intracellular prolactin secretory granules during the same interval. Longer periods of treatment (24–96 hours) resulted in the appearance of more lysosomes, autophagic vacuoles and microfilaments in the cells, whereas the number of Golgi elements was decreased. Following four hours of colchicine treatment and at later stages, microtubules could no longer be observed in the sections. Scanning electron microscopic data showed that colchicine treatment induced dramatic changes in the cell surface morphology: at short time intervals (4 and 8 hours), the number of microvilli decreased and the cell surface became folded, whereas, later, “bleb”‐like protrusions of variable dimensions partially covered the cell surface and seemed to be released from it. These data show a good correlation between secretory activity of prolactin‐producing cells and morphological changes induced by colchicine treatment.
Intracellular dynamics in pituitary mammotropes throughout the rat estrous cycle. I. Morphometric methodology and hormonal correlations with cellular and nuclear volumes
Authors: Poole Max C. , Mahesh Virendra B. , Costoff Allen
Published: February 2005

Serum prolactin (PRL) levels display regular patterns throughout the 4‐day rat estrous cycle. A morphometric analysis of mammotropes (PRL‐secreting cells) in the anterior pituitary was performed in an effort to quantify some of the ultrastructural events occurring prior to and during the secretion of PRL throughout the estrous cycle. In this study, a systematic sampling protocol applicable to the rat adenohypophysis was developed, which took into account the lack of synchrony in estrous cycles among the animals, the heterogeneity of the gland, and the number of cells required to yield a representative sample. These techniques were used to determine the cell, nuclear, nucleolar, and cytosol volumes, which were correlated with the changing levels of serum estradiol and PRL and pituitary PRL.

Estradiol concentrations rose during late diestrus‐1 and continued rising in a pulsatile manner, reaching maximal levels during proestrus. The elevations of estrogen were accompanied by increases in nucleolar and nuclear volumes. However, at early estrus and on the afternoon of diestrus‐2, times at which it has been reported that progesterone levels are elevated, there was a dampening effect and these volumes declined. During early diestrus‐2, when estradiol levels began to rise, there were increases in nucleolar, nuclear, cellular and cytosol volumes, as well as increases in pituitary PRL; but at late diestrus‐2 there was a marked increase in nuclear and nucleolar volumes which was not accompanied by increases in cellular and cytosol volumes. During proestrus, two peaks of serum PRL were found, at 6 pm and 12 m, which were concomitant with increased nucleolar, nuclear and cellular volumes. The 6‐pm proestrous peak of PRL was preceded by elevated pituitary PRL; however, the 12‐m proestrous peak occurred when the pituitary PRL was minimal, even though nuclear and cellular volumes were elevated. This suggests that the 6‐pm release of PRL was derived from previously synthesized and stored hormone, while the 12‐m peak was the result of the immediate release of PRL, with little storage.
Ultrastructure of secondary neurulation in the chick embryo
Authors: Schoenwolf Gary C. , Delongo Judi
Published: February 2005

Formation of the future lumbosacral level of the spinal cord was studied in two‐day‐old chick embryos by light and electron (transmission and scanning) microscopy. A neurulation overlap zone occupied this level. The dorsal portion of the neural tube formed by bending of the neural plate and approximation and fusion of neural folds (i.e., by primary neurulation), and the ventral part formed during secondary neurulation by cavitation of an initially solid, compact mass of cells, the medullary cord, derived from the tail bud. Secondary neurulation involved four morphogenetic processes: (1) segregation of the cells of the prospective medullary cord from cells of adjacent regions, (2) formation of a precisely delimited medullary cord, (3) cavitation of the central portion of this cord, and (4) coalescence of all lumina into a single, central cavity. Cell segregation was associated with the formation of a layer of primarily extracellular materials between adjacent organ rudiments. The source and composition of these materials are unknown. Formation of the medullary cord entailed considerable elongation of the peripheral cells of this developing structure and the fabrication of small intercellular junctions, first at the basal (outer) ends of the elongating peripheral cells, and then at their apical (inner) ends. These events resulted in the formation of an outer pseudostratified layer of radially arranged, columnar cells, having characteristics similar to those of the neural plate, and an inner cluster of irregularly shaped and arranged cells. Cavitation always occurred first at the junction between these two cellular populations. The central cells of the medullary cord also eventually elongated, like the peripheral cells, and may have been intercalated into the lateral walls of the developing neural tube as lumina coalesced.
The differential distribution of synaptic terminal on marginal and central cells in the cat medial superior olivary nucleus
Authors: Schwartz Ilsa R.
Published: February 2005

Electron microscopic analysis of the perikaryal surfaces of central and marginal cells in the cat medial superior olivary nucleus has revealed three differences in their relationships with synaptic terminals. Marginal cells have a smaller percentage of their surface covered by synaptic terminals; synaptic endings on marginal cells tend to be smaller in size; and a higher proportion of synaptic terminals on marginal cells contain small vesicles. These differences suggest that central and marginal cells differ in the information which they receive, as well as in the cells to which they pass their information.
Innervation of rabbit fetal lungs
Authors: Hung Kuen‐Shan
Published: February 2005

Nerve fibers, autonomic ganglia, and neuroepithelial bodies of the lungs of rabbit fetuses, 17 to 31 days gestational age, were studied with neurohistological techniques including silver impregnation, acetylcholinesterase histochemistry, and glyoxylic‐1acid‐induced histofluorescence for monoamines.

The silver impregnation method showed that nerve fibers and ganglia accompanied the bronchi and large pulmonary blood vessels to enter the developing lungs by the 17th day of gestation. Cholinergic and adrenergic nerves began to appear in the walls of the bronchi on the 21st day. The developing pulmonary arteries had accompanying adrenergic nerves on the 25th day. Acetylcholinesterase‐positive parasympathetic ganglia were seen on the 27th day. Silver‐impregnated nerve fibers in the developing alveolar walls and pleura were found on the 25th day.

Neuroepithelial bodies and specialized single cells which were argyrophilic, acetylcholinesterase‐positive, and fluorescent could be demonstrated in 19–21‐day‐old and older fetuses; and some of these structures were innervated by sensory and autonomic motor fibers. These observations indicated that nervous tissue and neuroepithelial bodies appeared in the lungs during the glandular stage of the lung development and that differentiation of adrenergic and cholinergic nerves began in the late glandular stage.
Precocious development of granular convoluted tubules in the mouse submandibular gland induced by thyroxine or by thyroxine and testosterone
Authors: Gresik E. W. , Barka T.
Published: February 2005

The effects of the administration of thyroxine (T4) and/or testosterone (TP) on the early postnatal differentiation of granular convoluted tubule (GCT) cells of the submandibular glands were studied in Swiss‐Webster mice. From birth, mice were injected daily with T4 up to the time of killing at 15 or 20 days of age. In addition, groups of mice were given one injection of TP eight days before killing. Control animals received vehicles (saline and/or sesame oil). Sections of the glands were stained with toluidine blue, or immunocytochemically by the unlabelled antibody enzyme method, for the localization of protease A, epidermal growth factor, or renin. Supernatants of the gland were analyzed for protease activity (pH 8.5, substrate: tosyl‐glyclyl‐L‐prolyl‐L‐arginine nitroanilide acetate), or by radioimmunoassay for EGF content. At 15 days of age no GCT cells were present in the glands of control or TP‐treated mice. In T4‐injected mice many small GCT cells occurred, while larger and more numerous GCT cells were seen in the glands of mice that received both hormones. TP alone had no effect on levels of EGF or protease activity. In T4‐treated mice, protease levels increased 10‐fold and EGF content rose 28‐fold. TP administration to T4‐treated mice caused a further threefold, increase in both protease activity and EGF content. At 20 days of age the glands of control mice had a few small GCT cells, and both protease activity and EGF content were substantially increased. TP treatment was again without effect. However, daily injections of T4 caused both protease activity and EGF levels to increase 20‐ and 11‐fold, respectively. Just as in 15‐day‐old mice, TP administration to T4‐primed mice resulted in further increases in the two polypeptides. Immunocytochemical staining for protease A and EGF confirmed the chemical data. Renin was detectable immunocytochemically at both ages in the glands of mice that had received T4, but it was seen in the glands of mice that had received TP alone only at 20 days of age. It is concluded that T4 caused a precocious induction of GCT cells and their specific products. Although TP alone had no effect on their early differentiation, it acted synergistically with T4 in inducing GCT cells. There were no obvious sex differences in any of these features in control or treated animals.
The median eminence in normal, ovariectomized, and ovariectomized‐estradiol‐treated hamsters: An ultrastructural study
Authors: Merchant Randall E. , Dollar James R.
Published: February 2005

In an effort to define more clearly the effect various plasma concentrations of estrogen have on the morphology and function of tanycytes, the present investigation examined the median eminence (ME) of normally cycling, ovariectomized, and ovariectomized‐estradiol‐treated hamsters. In normally‐cycling animals, when endogenous estrogen was at its highest level (day 4 or proestrus), numerous microappendages arose from the luminal surfaces of tanycytes located in the ventrolateral region of the ME. Large blebs (1.0–5.0‐μm diameter), miniblebs (1.0‐μm diameter), and microvilli dominated the surfaces of these cells. Large blebs appeared to have been formed by the coalescence of several miniblebs and were composed of cytoplasmic ground substance devoid of organelles. The peduncular shape of many of these blebs suggested their involvement in an apocrinelike secretion by the tanycyte. When endogenous estrogen levels were low (day 1 of the estrous cycle), the tanycytes of normally cycling hamsters possessed slightly fewer microappendages. Following ovariectomy, large blebs were nearly absent from the luminal surfaces of tanycytes, and the number of miniblebs and microvilli were also greatly reduced. Subcutaneous injections of 17‐beta estradiol benzoate restored the large blebs to the tanycyte surface. The number and variety of tanycytic microappendages in these animals resembled those in normally cycling hamsters on day 4 of the estrous cycle. The present study demonstrates that tanycytes of the hamster ME are sensitive to estrogen and vary in their morphology in relation to the animal's reproductive status. These changes in tanycyte morphology can be correlated directly to functions of absorption (microvilli) and secretion (blebs). The sensitivity of tanycytes to estrogen suggests that these cells may also play a role in the hypophyseal‐ovarian feedback mechanism.
Structural characteristics of the corpus luteum during implantation in the rhesus monkey (Macaca mulatta)
Authors: Booher Carolynn , Enders Allen C. , Hendrickx Andrew G. , Hess David L.
Published: February 2005

Corpora lutea were obtained from ten pregnant rhesus monkeys during implantation, and the ultrastructure of granulosa and theca lutein cells was characterized. Specimens were individually staged with regard to the extent of implantation and the relationship to the rise in circulating progesterone and estrogen which is characteristic of early pregnancy. Structural changes characteristic of granulosa lutein cells occurring during implantation included: change in form of endoplasmic reticulum from predominantly agranular tubules to predominantly granular cisternae; reduction in size and number of lipid droplets; increase in area occupied by the Golgi and increase in length of the cisternae of the Golgi complex; development of numerous microvillus‐lined intracellular spaces; increase in numbers of membrane‐bound dense bodies including peroxi‐somelike bodies, multivesicular bodies within lobopodia, and other lysosomelike bodies; and alterations of mitochondrial cristae. These changes were suggestive of the production of a secretory protein, rapid utilization of existing steroid precursor reserves for the production of progesterone, and a reduction in capability for steroid precursor accumulation and processing by granulosa lutein cells. Structural changes characteristic of theca lutein cells occurring during implantation included an increase in size and number of lipid droplets, an increase in agranular endoplasmic reticulum, and an increase in area occupied by the Golgi complex. These changes were suggestive of an increased capability for steroid precursor accumulation and processing, perhaps for estrogen production, by the theca lutein cells.
The stem‐cell zone of the small intestinal epithelium. II. Evidence from paneth cells in the newborn mouse
Authors: Bjerknes Matthew , Cheng Hazel
Published: February 2005

The restriction of Paneth cell formation to the top of the Paneth cell distribution in the adult was suggested to be due either to the existence of a stem‐cell zone or to the influence of a Paneth cell population‐density gradient (Bjerkness and Cheng, 1981). To distinguish between the two possible mechanisms, the development of the Paneth cell distribution in neonatal mice (0–10 days old) was studied. If restricted formation were due to the presence of a population‐density gradient of Paneth cells, then in neonatal animals, in the absence of a Paneth cell population‐density gradient, Paneth cell formation would occur throughout the crypt base. If, on the other hand, restricted formation were due to the presence of a stem‐cell zone, and if this mechanism were operative in the newborn, Paneth cell formation in the newborn would be restricted to the region above the stem‐cell zone. The position of each Paneth cell within the crypt, and the size of its largest granule, were recorded. On day 0, Paneth cells were present, but crypts were poorly developed and positional assignment was not possible. On day 1, immature crypts developed. All Paneth cells found in immature crypts on day 1 were at the crypt‐surface junction (approximately position 5). On day 2, most Paneth cells were at the crypt‐surface junction. Thereafter, Paneth cells began to appear at lower positions. On day 3, there were 15 times more Paneth cells in position 5 than in position 1. On day 4, there were still three times more Paneth cells in position 5 than in position 1. With age, the proportion of Paneth cells in position 1 increased while that in position 5 decreased. On day 10 there were more Paneth cells in position 1 than in 5. At all time intervals, granules of Paneth cells in position 1 were significantly larger than those in position 5, indicating that Paneth cells in position 1 were older than those in position 5. It was concluded that in the neonate, before the establishement of a Paneth cell population‐density gradient, Paneth cell formation was restricted to positions 5 and above. This supports the existence of a stem‐cell zone, not a Paneth cell population‐density gradient, as the underlying mechanism of restricted Paneth cell formation in the adult.
A fine‐structural survey of the pulpal innervation in the rat mandibular incisor
Authors: Bishop M. A.
Published: February 2005

The innervation of the rat incisor pulp has been studied using transmission electron microscopy and light microscopy. Transverse sections of mandibular incisor pulp (380–460 gm rats) from numerous positions in the long axis of the tooth were examined systematically in the electron microscope. Quantitative data on total axon populations were obtained. The nerve fibers were found to pass through the lingual half of the pulp from the apical end to within 2 mm of the incisal tip. Although the nerve fibers were seen to lie amongst the connective tissue cells between the blood vessels, the electron microscopic observations showed that the blood vessels are not innervated. Throughout their pulpal course the nerve fibers showed no trace of perineurial investment. Virtually all the axons were unmyelinated. Total numbers of axons were small (233–328) and peak diameters of 0.3–0.4 μm confirmed the observed immature appearance of the nerve supply. Obvious nerve endings were seldom observed and the axons showed no structural association with odontoblasts. The evidence indicates that, although most axons terminate near the incisal end of the tooth, no specific structure is supplied. The qualitative features of the axons do not suggest autonomic function; however, they are consistent with a sensory role.
Epidermal growth factor in the submandibular glands of inbred mice
Authors: Tom‐Moy May , Barka Tibor
Published: February 2005

Epidermal growth factor (EGF), an androgen‐dependent polypeptide, occurs in high concentration in male mouse submandibular gland. Glands of adult male and female mice of six inbred strains (129/J, C57BL/6J, C58/J, SWR/J, RF/J, A/J) were assayed for EGF by radioimmunoassay. In all strains, the glands of males contained 30 to 500‐fold more EGF than those of females. Furthermore, significant differences in EGF content were found among the various strains in both sexes; the highest amount of EGF was present in RF/J and the lowest in C57BL/6J, with a ratio of three in the males and four in the females of the two strains, respectively.

Factors that effect EGF levels were analyzed further, using these two strains. EGF was measurable in the glands of mice of both strains at 21 days of age and increased rapidly thereafter, up to 14 weeks of age. Throughout postnatal development, the level of EGF was greater in the glands of RF/J mice than in those of the C57BL/6J animals. Thirty days after castration, the EGF levels were reduced by about 98% in both strains, but the strain difference was not abolished. Testosterone implants (1 mg in Silastic tube) in castrated mice induced EGF levels six‐ to ten‐fold compared to castrates. Even in induced animals, which had similar plasma testosterone levels, as measured by radioimmunoassays, the difference in EGF levels between the two strains was manifest. Such a difference, however, was not seen after the daily administration of 5‐alpha‐dihydrotestosterone for 3–14 days. Immunocytochemical staining for EGF also indicated a higher concentration of the polypeptide in the glands of RF/J mice than in those of C57BL/6J animals, and confirmed the exclusive localization of EGF in the cells of the granular convoluted tubules (GCT). According to our morphometric analysis, in the glands of male RF/J mice the GCT compartment occupied a greater portion (8% greater, P<0.001) of the gland volume than in C57BL/6J mice. The difference in the relative GCT volumes in the glands of female mice of the two strains was, however, statistically not significant. There was no direct correlation between the amount of EGF and the relative volume of the GCTs in the two strains. The evidence obtained implies that strain differences in submandibular‐gland EGF levels are determined genetically.
Effects of Ca+2 and Mg+2 deprivation on cell shape in cultured ovarian granulosa cells
Authors: Batten Bruce E. , Anderson Everett
Published: February 2005

After 3 days in culture, rat ovarian granulosa cells assume a flattened epitheloid organization. Ca+2 and Mg+2 deprivation results in cellular rounding which is reversible and was monitored by phase‐contrast time‐lapse cinematography. Concomitant with the shape change is a dispersion of the structural proteins actin and α‐actinin. The arrays of large actin‐containing bundles (stress fibers) are converted to a diffuse network as observed by electron microscopy. Alpha‐actinin, which was observed by immunocytochemistry to be in a periodic array along the actin bundles, is disrupted also and redistributed in the periphery of the cell upon rounding. Measurements made of the culture medium during the rounding process indicate that there is a loss of Ca+2 and Mg+2 from the cell interior. These data led us to speculate that Ca+2 and/or Mg+2 are necessary in order to maintain the integrity of stress fibers and/or restrict the movement of α‐actinin anchoring sites within the membrane.
Vascular pathways in nonsinusal red pulp—an electron microscope study of the cat spleen
Authors: Blue Julia , Weiss Leon
Published: February 2005

The red pulp of the cat spleen, including terminal segments of arterial capillaries, pulp venules, and the reticular meshwork, was studied by transmission electron microscopy. Splenic congestion and contraction were produced by barbiturate anesthetic and norepinephrine.

Terminal segments of arterial capillaries were ampullary and flared. Blood escaped into surrounding pulp spaces through interendothelial gaps. Pulp venules originated as open‐ended vessels in the reticular meshwork near trabeculae and drained into trabecular veins. Venule walls were thin and composed of squamous endothelial cells, a continuous basement membrane, and reticular cells. Venules in congested spleens had many mural apertures, but venules in contracted spleens had few. The interstices of the reticular meshwork in congested spleens contained large amounts of blood, which often was concentrated, many macrophages, lymphocytes, and plasma cells. Fewer blood cells and scant plasma were present in contracted spleens.

The vascular arrangements are anatomically open. Blood takes pathways through the reticular meshwork from arterial terminations to pulp venules. Some pathways through the reticular meshwork probably function as closed vascular channels conveying rapidly flowing blood. Other pathways are functionally open and probably contain slowly moving blood that constitutes a reservoir of red cells.

Macrophages formed associations with mature red cells and with reticulocytes. Mature red cells were attached to macrophages in a manner indicating erythrophagocytosis. Reticulocyte attachment had a different appearance and likely resulted in reticulocyte sequestration. Platelets bore pseudopodia which would impede their passage through irregular and cell‐filled pulp spaces. The change in platelet shape probably is responsible for the formation of the splenic pool of platelets.
Species variation in the structure and function of the marginal zone—an electron microscope study of cat spleen
Authors: Blue Julia , Weiss Leon
Published: February 2005

The marginal zone in the cat spleen consisted of a characteristic mixture of lymphocytes and other blood cells located mainly between the several layers of circumferential reticulum around white pulp. A region of fine‐meshed reticulum between white pulp and red pulp, as present in some species, was absent from the cat spleen. Arterial capillaries to the marginal zone were few. Some were continuations of white pulp capillaries, whereas others were red pulp capillaries that likely were continuations of axial capillaries of periarterial macrophage sheaths (PAMS) (ellipsoids). Blood cells deposited in the marginal zone could reach red pulp by passing through the numerous openings in each layer of circumferential reticulum. Lymphocytes appeared to migrate across the marginal zone both toward and away from white pulp. Macrophages lying on the circumferential reticulum of the marginal zone phagocytized cells but did not ingest Thorotrast, although it coated their surfaces. Because of the scarcity of arterial endings and the lack of a macrophage‐charged reticular meshwork, the marginal zone in cat spleen is not a major site of blood clearance and phagocytosis. These functions are better served in PAMS and red pulp.
The effect of insulin‐glucose on microappendages of the plasmalemma in the early chick embryo
Authors: Highison Gregory J. , Low Frank N.
Published: February 2005

Chick embryos incubated for 18–24 hours (stages 4–6) were immersed for 3–5 minutes in Hanks' Balanced Salt Solution containing either insulin (10−9 M) or D‐glucose (10−1 M) or a mixture of both. The ventral and dorsal surfaces of the entoderm and the ventral aspect of the mesoblast were examined in a scanning electron microscope. D‐glucose alone or insulin alone produced negligible change. When combined these ingredients generated highly pleomorphic microappendages of the plasmalemma. The ventral surface of the entoderm was characterized by a larger number of microvilli, both long and short. Concentrations of microvilli and blebs appeared in recesses at cell margins. Some of these represented mesoblastic protrusions through intercellular apertures in the entoderm. The dorsal entrodermal surface developed stellate clusters of microvilli and blebs. The ventral aspect of the mesoblast became the most pleomorphic area of all. It possessed a variety of microappendages including large populations of microvilli and blebs that resembled the protrusions observed from the subblastodermic cavity. There were also stellate clusters similar to those on the dorsal entodermal surface. The same mesoblastic area in controls was virtually free of microappendages. The mesoblastic protrusions, occuring as they do prior to an established circulation, are interpreted as a “feeding” phenomenon.
Differentiation of the blastocyst of the rhesus monkey
Authors: Enders Allen C. , Schlafke Sandra
Published: February 2005

A method of flushing the oviduct and/or uterus of rhesus monkeys was used to obtain a number of preimplantation stages, of which four cleavage stages and seven blastocysts that were judged to be normal were studied cytologically using transmission electron microscopy. In addition to the usual changes in mitochondria and endoplasmic reticulum that accompany differentiation of the blastomeres, the blastocysts with zonae showed sequestration of areas of cytoplasm. The first indications of junctional complexes were short stretches of parallel membrane with a slightly increased density found in the morula stage. Blastocysts developed typical apical junctional complexes, but in addition showed extensive gap junctions linking trophoblast and inner cell mass, and epiblast and differentiating endoderm. Endodermal differentiation occurred at about the same time that a basal lamina was found under mural trophoblast and epiblast (but not polar trophoblast or endoderm). Enlarged torn zonae were found in association with one blastocyst and unaccompanied by blastocysts, including a case in which the animal subsequently proved to be pregnant. This observation suggests that hatching is a normal feature of zonal escape in this species. The trophoblast of blastocysts without zonae had well‐formed apical absorptive areas and, in some instances, long irregular microvilli in the area near the inner cell mass. Cell debris, vacuoles containing debris and isolated cells, although variable, were common features of the preimplantation stage in the rhesus monkey.
Freeze‐fracture studies on the thin limbs of Henle's loop in Psammomys obesus
Authors: Kriz Wilhelm , Schiller August , Taugner Roland
Published: February 2005

The thin limbs of short and long loops of Henle of the desert rodent Psammomys obesus were studied by freeze‐fracture techniques. Intercellular junctions and internal membrane characteristics of thin‐limb epithelia are of interest with regard to the high urine‐concentrating capacity of this animal.

The epithelium of the descending thin limbs of short loops is remarkably undifferentiated and equipped with multistrand tight junctions. In the descending thin limb of long loops, two segments are to be distinguished. The upper parts are characterized by an extensive cellular interdigitation and single‐strand tight junctions. Thus, the paracellular pathways are prominent from two aspects: the junctional belt is elongated by interdigitation, and its apico‐basal depth is shallow. The transition from the upper to the lower part appears to be abrupt, as indicated by the change in intramembrane particle density. The lower parts are characterized by a noninterdigitating epithelium with junctions consisting of few, but always more than two, strands. In addition, this thin‐limb segment is characterized by regularly distributed infoldings of the basal cell membrane. The ascending thin limbs are established by an interdigitating epithelium, with junctions generally consisting of one strand. Once again, the elongated junctional belt is shallow.

This study presents further evidence that remarkable species differences occur among thin‐limb epithelia, especially concerning the descending thin limbs of long loops. Those differences may well explain discrepant functional findings concerning the transport properties of this segment in various species.