bluuebunny/crossref_metadata_2025 huggingface dataset:
Multivesicular bodies and related structures of the syncytiotrophoblast of human term placenta
Authors: Martin B. J. , Spicer S. S.
Published: February 2005

Multivesicular bodies and related structures of the syncytiotrophoblast of human term placenta have been studied ultrastructurally and cytochemically. Circular profiles of vesicles termed pre–multivesicular bodies (pre‐mvb's) were observed often near Golgi complexes. Multivesicular bodies (mvb's) with electron lucent matrices (L‐mvb's), mvb's with electron dense matrices (D‐mvb's), and dense bodies were also prevalent organelles of the syncytium. These organelles all exhibited dialyzed iron reactivity and staining characteristics suggesting that the organelles were related. Material within Golgi saccules, Golgi vesicles, vesicles of pre‐mvb's, and vesicles of mvb's were all reactive with osmium zinc iodide (PZI). This OZI reactivity further indicated a relationship between the organelles. The matrix of the mvb's exhibited variable reactivity for acid phosphatase (AcPase) but such activity was not encountered in Golgi elements of syncytiotrophoblast. It is suggested that the mvb's of human term placental syncytium are likely formed by aggregation of vesicles of Golgi origin into pre‐mvb's, that the pre‐mvb's are then capable of transforming into L‐mvb's, D‐mvb's, and finally into dense (residual) bodies. It is also suggested that mvb's may function in the selective hydrolysis and transport of endocytosed proteins, including globulins. Additional bodies with intense acid phosphatase activity were designated elongate bodies. Other Distinctive organelles designated dense cored spheroids were occasionally observed in the syncytioplasm.
The fine structure of pacemaker cells in the pig renal calices
Authors: Dixon J. S. , Gosling J. A.
Published: February 2005

Using the electron microscope, two types of smooth muscle cell have been recognized in the upper urinary tract of the pig. One type is confined solely to the renal attachment of each minor calix and possesses a number of atypical features. These cells are not grouped into bundles but form a loose meshwork. They frequently branch, are comparatively long with very irregular profiles, and are separated by relatively large amounts of connective tissue although maculae adhaerentes are occasionally observed between neighbouring cells. Dense micronbrils occur in the vicinity of the cells which are surrounded by a partial basal lamina. Groups of axons are seen in the region, many of which contain small dense‐cored vesicles. Within the atypical cells, filaments are loosely packed and accumulations of micropinocytotic vesicles are not observed. These features contrast markedly with those of typical muscle cells in other regions of the upper urinary tract where they form tightly packed bundles unrelated to axon profiles. The typical smooth muscle cells are larger and more regular in outline, are surrounded by a complete basal lamina, possess tightly packed filaments, and contain numerous micropinocytotic vesicles and glycogen particles.

Similar modified muscle cells occur in the unicaliceal systems of other species where they are also confined to the proximal end of the urinary tract. It is suggested that the atypical cells are specially adapted to function as spontaneously active “pacemakers” initiating ureteric peristalsis.
The ultrastructural pathology of the rat epididymis after administration of α‐chlorhydrin (U‐5897). I. Effects of a single high dose
Authors: Hoffer Anita P. , Hamilton David W. , Fawcett Don W.
Published: February 2005

The ultrastructural pathology of the initial segment of the rat caput epididymidis was examined after oral administration of a single high dose of the antifertility compound α‐chlorhydrin (U‐5897) at time intervals ranging from two hours to nine days after treatment. At doses in excess of 30 mg/kg this compound produces a lesion specifically localized in the initial segment of the epididymis characterized by sloughing of the epithelium, which leads to obstruction of the lumen of the epididymal duct, spermatocoel and sperm granuloma formation and an ultimate occlusive fibrosis. In rats fed 140 mg/kg of U‐5897 the first effects can be seen as early as two hours after treatment. Within 48 hours after treatment, the lumen of the greater part of the initial segment is filled with degenerating cells and debris which block further passage of sperm along the duct. The present study provides insight into the nature of the early events in the evolution of this epididymal lesion. Possible mechanisms of action of α‐chlorhydrin are discussed.
Changes in distribution of lipid, glucose‐6‐phosphate dehydrogenase and malate enzyme within the liver lobule of the rat during adaptive hyperlipogenesis
Authors: Severson Arlen R. , Hubbard Dorothy D. , Gibson David M.
Published: February 2005

Feeding rats a high‐sucrose, fat‐free diet after two days of starvation resulted in an initial accumulation of hepatic lipid and an increased activity of those enzymes which catalyze and support the formation of fatty acids from acetyl precursors. Rats starved for 48 hours were refed a high‐carbohydrate, fat‐free diet for 1, 2, 3, 5, 7 and 14 days. Frozen sections of liver were stained with Oil Red O for lipids. In adjacent sections glucose‐6‐phosphate dehydrogenase (GDH)and malate enzyme (ME) were localized and the relative enzyme activity evaluated. Enlargement and yellowing of the liver were noted after two to three days feeding of the fat‐free diet, but subsequently the liver appeared normal. Oil Red O staining demonstrated a progressive accumulation of lipid from the periportal to the centrilobular area during the first three days of refeeding. After the seventh day on the fat‐free diet, however, the lipid accumulation was less and the distribution appeared similar to that of animals maintained on a balanced diet. A marked increase in both GDH and ME activity was noted throughout the liver lobule after two days on the fat‐free diet. Enzyme activity remained high throughout the lobule during the balance of the experimental period, with maximum activity in the centrilobular area.
An autoradiographic study of the utilization of tritiated uridine by osteoblasts of young mice,
Authors: Singh I. J. , Tonna E. A.
Published: February 2005

The uptake and turnover of 3H‐uridine by periosteal and endosteal osteoblasts were assessed autoradiographically. Five‐week old mice were injected with 5 m̈CI of 3H‐uridine (Sp. Act. 21 Ci/mM) per gram of body weight and killed at intervals varying from 15 minutes to one month post‐injection. Femora were processed histologically and autoradiographs were prepared from 5 m̈m decalcified sections exposed for 36 days. Autoradiographic grains were counted over the nucleus and the cytoplasm of 600 periosteal and 600 endosteal osteoblasts per time period. 3H‐Uridine was initially rapidly incorporated into the nucleus attaining peak activity one hour after injection. Incorporation of label into cytoplasmic RNA was maximum at one to two days. At one month grain counts were at minimum values. The loss was more gradual from the nucleus than from the cytoplasm. At earlier time periods the nucleus showed a higher label than the cytoplasm. At 8 to 16 hours the label was evenly distributed and at later time periods the cytoplasm exhibited a higher grain count. Dia‐physeal periosteal osteoblasts and metaphyseal endosteal osteoblasts differed in both the quantity of label and the rate of utilization. Endosteal cells exhibited almost twice the activity. RNA biosynthesis appears to be significantly higher in endosteal cells than periosteal cells thus reflecting differences in protein synthesis by these two cell compartments.
Ultrastructure of the fetal rat adrenal gland at full‐term and during prolonged gestation
Authors: Thliveris James A. , Connell Reid S.
Published: February 2005

The ultrastructure of the fetal rat adrenal gland is described at full‐term (day 22) and during artificially prolonged gestation (days 23, 24, 25). The latter was achieved by daily subcutaneous injections of seven mg progesterone to gravid females from the twentieth through the twenty‐fourth day. Cortical and medullary cells contained well developed organelles at all stages. Nonetheless, zonation of the gland was not yet distinct. Whereas the zona glomerulosa and zona fasciculata were fairly well delineated, the zona reticularis and medulla were as yet poorly defined. The latter regions were intermingled, and thus collectively referred to as the “zona reticulo‐medullaris.”

During prolonged gestation (days 24 and 25 only), many cells of the zona fasciculata and zona reticulo‐medullaris contained dilated smooth endoplasmic reticulum and numerous enlarged mitochondria. Enlarged mitochondria were observed also in medullary cells concurrent with a paucity of catecholamine storage granules. Moreover, meconium staining, which is indicative of fetal stress, was also observed on days 24 and 25. The ultrastructural changes observed were interpreted to be an expression of response by the fetal adrenal gland to fetal stress produced by as yet undetermined factors arising during prolonged gestation.
Fine structure and progesterone concentration in the corpus luteum of the african elephant
Authors: Ogle Thomas F. , Braach Harold H. , Buss Irven O.
Published: February 2005

Corpora lutea from one recently post‐partum and six pregnant African elephants (Loxodonta africana) were fixed for electron microscopy. Progesterone concentration was determined for five of these corpora lutea utilizing the competitive protein binding technique.

Lutein cell size and progesterone concentration increased from one and two months of pregnancy to a maximum at three months (P < 0.01). After eight months of pregnancy, lutein cell size decreased to two‐month values and luteal progesterone was similar to the one‐month level. Lutein progesterone was very low in a recently post‐partum animal and lutein cell size was minimum. Maximum lutein progesterone was 4.1 ng/mg, much lower than that reported for other mammals.

Lutein cell fine structure exhibited characteristics typical of lutein cells from other species but with some variation. Unusual features include peripheral distribution of organelles, large stores of lipid and lipofuscin throughout pregnancy, and mitochondria sparsely populated with lamellar cristae. The data indicate that the corpus luteum of the African elephant has significant but limited steroidogenic capabilities.
Relationship of extracellular matrix vesicles to calcification in normal and healing rachitic epiphyseal cartilage
Authors: Simon David R. , Berman Irwin , Howell David S.
Published: February 2005

Nucleation sites for mineralization in rat distal femoral epiphyseal cartilage were studied with the electron microscope. Normal, low‐phosphate, vitamin D deficient rachitic, and healing rachitic rats were used.

The earliest ultrastructural evidence of mineralization in normal animals was the appearance of crystallites inside extracellular matrix vesicles, located in the longitudinal septa of the maturing cell zone in the epiphyseal apparatus. The crystallites were absent throughout the entire hypertrophic cell zone of the rachitic specimens.

The first evidence of mineralization in rachitic animals treated with both phosphate and vitamin D was the presence of crystallites in the extracellular matrix vesicles. These were located in the longitudinal septa of the lower hypertrophic cell zone, near the capillary tufts of the primary spongiosa. Crystallites were first detected by 12 hours after treatment; by 24 to 48 hours, the number of matrix vesicles containing crystallites increased substantially.

Treatment of rachitic animals with phosphate alone effected the same results as phosphate and vitamin D combined. Rachitic animals receiving vitamin D alone did not form mineral in the time periods studied.

The results of this investigation support the view that the deposition of mineral in mammalian cartilage requires nucleation sites in the extracellular matrix. The findings also are consistent with the hypothesis that membrane‐bounded, extracellular matrix vesicles contain the initiating system for calcification of the rat epiphyseal apparatus.
Transmission electron microscopy of critical point dried tissue after observation in the scanning electron microscope
Authors: Meller Samuel M. , Coppe Michael R. , Ito Susumu , Waterman Robert E.
Published: February 2005

Embryonic and adult rodent tissues were fixed and prepared for scanning electron microscopy by dehydration in ethanol followed by critical point drying with liquid carbon dioxide or Freon 13 (E. I. du Pont de Nemours, Inc.). After coating the dried specimens with evaporated metal, the tissues were studied by scanning microscopy. The same tissues were subsequently embedded in Epon‐Araldite, thin sectioned and examined by transmission electron microscopy. The cytological details in these specimens were comparable to tissues embedded directly, without drying or metal‐coating. With this technique it is possible to identify with greater certainty the structures responsible for surface contours revealed by the scanning electron microscope.
Inhibition of ACTH‐induced differentiation of cortical cells and their mitochondria by corticosterone in tissue culture of fetal rat adrenals
Authors: Kahri Arvi I.
Published: February 2005

Tissue cultures of fetal rat adrenals were used to study the effects of corticosterone on the ACTH‐induced ultrastructural differentiation of cortical cells and their mitochondria. Corticosterone in dosages of 0.2, 2.0, 5.0, 10, and 20 μg/ml (corresponding to concentrations of 6 × 10−7, 6 × 10−6, 1.5 × 10−5, 3 × 10−5, and 6 × 10−5 molar) was added alone or together with 100 mU/ml of ACTH to the culture medium, daily from the sixteenth day of cultivation up to and including the twenty‐first day. Corticosterone alone induced no ultrastructural changes in cortical cells. Corticosterone in concentrations of 6 × 10−7 to 3 × 10−5 M given with ACTH induced hypertrophy of Golgi apparatus. Corticosterone in concentrations of 6 × 10−5 M inhibited the ACTH‐induced differentiation of cortical cells. However, the nuclear chromatin increased and Golgi apparatus was strikingly hypertrophied. Mitochondria often aggregated adjacent to the nuclear envelope but their ultrastructure remained undifferentiated with tubular or tubulovesicular cristae. Ribosomes appeared as single particles. A marked increase of smooth surfaced endoplasmic reticulum was noted also in cortical cells treated with 6 × 10−5 M of corticosterone.

The present observations suggest that corticosterone acts as an intracellular inhibitor in cortical cells. It appears to inhibit cytoplasmic protein synthesis at the ribosomal level and prevents synthesis of cytoplasmic mitochondrial protein synthesis stimulating factor and the latter, in turn, inhibits the activation of mitochondrial protein synthesis. A new model is presented to explain the regulation of growth and secretion in the adrenal cortex.
Resorption of calcified cartilage as seen in Meckel's cartilage of rats
Authors: Savostin‐Asling Irene , Asling C. Willet
Published: February 2005

In rats, a portion of Meckel's cartilage — that lying within the mandible but proximal to the rostral convergence of the bars — gives rise to no definitive structures. It offers especially favorable opportunity to study cartilage resorption. By the eighteenth fetal day it is established as a hyaline cartilage bar, and a thin perichondral bone shell starts to form on its lateral aspect, completing encirclement in the next two days. On day 19 cartilage within this bone shows chondrocyte hypertrophy, lacunar enlargement, and matrix calcification. Osteoclasts open a fenestra laterally in the bone and commence removal of calcified cartilage matrix. The erosion front expands rapidly, moving medially (preceded by cartilage hypertrophy and calcification) and extending proximally and distally along the segment. Chondroclasts (multinucleated cells identical with osteoclasts) dominate the erosion front. Capillaries and various mononucleated cells follow. Bone formation is much delayed except in the most rostral extremity, so that, contrary to the situation in endochondral osteogenesis, one is examining calcified cartilage resorption in uncomplicated form. This resorption, including the perichondral bone shell, is virtually complete by day 21, and intramembranous bony reorganization of the site is in progress at birth.

Several features of chondroclasts, including some in dispute or not easily seen in vivo, are well displayed. These include ameboid form with pseudopodial extensions (sometimes filamentous), and fusion of some released chondrocytes with entering chondroclasts. Osteo/chondroclasts are often found in contact with perichondral bone at one extremity and calcified cartilage elsewhere on the same cell. There is evidence that matrix calcification is prerequisite to the chondroclastic activity.
An acardiac human fetus
Authors: Yoshihara H. , Maisel H.
Published: February 2005

A case of an acardiac human fetus is reported. The unique feature found in this specimen was the remarkably advanced development of the fetus as a whole, but especially of its head and brain.
Interaction of the sarcoplasmic reticulum with Z‐lines during myogenesis in amphibian skeletal muscle
Authors: Warren Robert H.
Published: February 2005

Electron microscopic examination of developing myofibrils in regenerating skeletal muscle of Rana pipiens tadpole tails reveals that sarcoplasmic reticulum (SR) is in regular and close association with Z‐lines of young sarcomeres before transverse tubules have formed alongside the myofibrils. SR is also associated with M‐lines of young sarcomeres but on a less regular basis than with Z‐lines. Counts of the number of contact sites of SR with Z‐lines, M‐lines and combined A‐ and I‐bands of longitudinally sectioned sarcomeres of young myofibrils confirms the visual impression that the SR associates with a relatively much greater frequency with Z‐lines and M‐lines than with other regions of the sarcomere. This suggests the formation of a specific bond between SR and Z‐ and M‐lines.

Serial transverse sections of developing myofibrils were examined in order to determine whether Z‐lines displayed SR association at all stages in their formation. Of fifty discrete Z‐lines that were examined, only four smaller Z‐lines appeared to lack SR association. An examination of a comparable number of more diffuse Z‐bodies representing an earlier stage of Z‐line formation suggests that no more than one‐half of these Z‐bodies were accompanied by SR. These observations support the conclusion that SR does not initiate formation of Z‐line precursor elements, but rather associates with Z‐lines as they condense from more diffuse Z‐bodies.
Demonstration of bile canaliculi by an immunofluorescent staining technique
Authors: Armstrong Ernest M. , Macsween Roderick N. M.
Published: February 2005

Using an indirect immunofluorescent technique sera from a group of patients suffering from a variety of liver diseases have been shown to contain an antibody which will specifically stain the bile canaliculi of a wide variety of mammals, birds and amphibia. It is suggested that this method is an effective alternative to the methods presently available for demonstration of bile canaliculi.
Effect of posterior pituitary powder on the mitotic activity of the zona glomerulosa of the adrenal glands in intact and hypophysectomized rats: A preliminary observation
Authors: Isler H.
Published: February 2005

Injections of posterior pituitary powder induced a significant stimulation of mitotic activity in the zona glomerulosa of intact and hypophysectomized rats. Hypophysectomy depressed this activity. The effect of the powder may be due to the presence of vasopressin.
Autoradiographic distribution of collagen loss in skin grafts
Authors: Zika Jocelyn M. , Rudolph Ross , Klein Leroy
Published: February 2005

The spatial distribution of collagen loss in syngeneic grafts of skin was studied autoradiographically. Grafts of radioactive skin from rats that were chronically injected with 14C‐ or 3H‐proline were placed onto unlabeled inbred rats. These radioactive skin grafts were removed at 0, 2, 4, 8 and 20 weeks after grafting, and observed both for distribution of isotope, as determined by autoradiography, and histological changes. Since 91% of the total radioactivity in the skin resided in collagen, the autoradiographs were specific for collagen.

Thick full‐thickness and split‐thickness grafts showed a zonal loss of radioactivity, with isotope being lost most rapidly in the subepidermal region. Collagen newly formed in this area resembled scar collagen.

Thin full‐thickness grafts did not show a zonal reduction of isotope, but instead lost radioactivity in a diffuse manner. The newly synthesized collagen bundles of the thin full‐thickness grafts were similar in thickness to the collagen bundles of control skin, but did not form the lattice network seen in the controls.

Autoradiographic losses and histological changes are related to the biochemical quantification of collagen turnover, to scar formation, and to the cellular control of collagen mass in skin grafts.
The origin of equine endometrial cups. III. Light and electron microscopic study of fully developed equine endometrial cups
Authors: Hamilton D. W. , Allen W. R. , Moor R. M.
Published: February 2005

Equine endometrial cups are localized endometrial outgrowths which develop in mares during early pregnancy and secrete pregnant mares serum gonadotrophin (PMSG).

The principal cell‐type found in endometrial cups is large, regular and epithelioid in appearance. These cup cells have one or two large euchromatic nuclei with dense, characteristic nucleoli. Their cytoplasm is filled with irregular profiles of endoplasmic reticulum containing pale flocculent material. Lipid droplets and a few mitochondria are also present. Golgi material is not prominent and the absence of membrane‐bound secretory granules suggest that the Golgi apparatus does not package a secretory product. The plasmalemma is mostly smooth in outline but is modified in some places to form short microvilli or complex intercrescent folds.
Morphogenesis of the ovarian interstitial tissue in the neonatal mouse
Authors: Quattropani Steven L.
Published: February 2005

The development of the mouse ovarian interstitial tissue was examined by light and electron microscopy at postnatal days 9, 10, 11, 12, and 18. Prior to day 12 the ovarian stroma is composed of fibroblast‐like cells. These cells contain rough endoplasmic reticulum, elongate mitochondria with lamellar cristae, and lipid bodies which appear uniformly electron opaque. On postnatal day 12 islands of lipid containing cells are seen deep in the interfollicular stroma. These cells referred to as interstitial cells have rounded mitochondria with tubular cristae, smooth endoplasmic reticulum, lipid bodies with extracted centers, well‐developed Golgi complexes, and solitary cilia lacking the central tubular elements. By postnatal day 18 similar cells are seen in the thecal regions of normal appearing follicles. Also seen in the theca are cells whose cytoplasm contains characteristics of both fibroblasts and interstitial cell.

It is proposed that the interstitial cells develop from the fibroblast‐like stromal cells, that this development proceeds in a wave from deep in the interfollicular tissue toward the follicle, and that the interstitial cells are the source of ovarian steroid production during this period of development.
Pineal influence on the Harderian glands of female golden hamsters
Authors: Clabough Jeanne W. , Norvell John E.
Published: February 2005

The effects of blinding on cellular structure and porphyrin pigment content were studied in Harderian glands of pinealectomized and non‐pinealectomized adult female golden hamsters. Uterine weights were used as a criterion for pineal activity. Five weeks post‐operatively, no significant changes were observed in the Harderian glands or in the uterine weights of animals in either group. Eleven weeks post‐operatively, the blinded hamsters with intact pineal glands had significantly lowered uterine weights and Harderian glands that exhibited diminished amounts of porphyrin pigments and cellular characteristics of the male hamster. Harderian glands and reproductive organs from the 11‐week blinded‐pinealectomized hamsters did not differ from those of untreated controls.
Quantitative aspects of follicular development in the untreated and PMS‐treated cyclic hamster
Authors: Greenwald Gilbert S.
Published: February 2005

Hamsters injected at 0900 on day 1 of the cycle (metestrus) with either 0, 5 or 15 IU pregnant mare's serum (PMS) were killed at 1500 of days 1 to 4 of the cycle and the ovaries prepared for light microscopy and for a quantitative evaluation of follicular development. In the untreated cyclic hamster, the maximal number of preantral follicles with eight or more layers of granulosa cells occurred between the afternoon of day 4 (proestrus) and day 1, coinciding with the highest blood levels of FSH and LH. It is concluded that the elevated preovulatory levels of gonadotropins not only induce the ovulation of the mature antral follicles but at the same time recruit the next set of follicles for development during the new cycle.

By the afternoon of day 1, treatment with either 5 or 15 IU PMS recruited more follicles into large preantral and incipient antral stages than in the untreated hamsters. However, by day 2 the pattern of follicular distribution was similar between the 5 IU PMS and untreated group whereas considerably more antral follicles had differentiated in the animals given 15 IU PMS. The ability of 15 IU PMS to elicit superovulation therefore depends on the levels being initially high enough to mature more follicles at critical stages of their development; the prolonged biological half life of PMS then sustains these follicles throughout the cycle.
Cytochemical evidence for cation fluxes in parotid acinar cells following stimulation by isoproterenol
Authors: Simson J. A. V. , Spicer S. S.
Published: February 2005

The use of potassium pyroantimonate‐osmium tetroxide as a combined fixative and cation‐capture agent has permitted the observation of finestructural changes in cation distribution in rat parotid acinar cells following administration of isoproterenol (IPR). During the secretory phase of the response, there is a diminution of antimonate‐precipitable cation in the cytoplasm combined with an increase along the plasma membrane and on secretory channels. At four hours after IPR, cytoplasmic precipitates return but deposits disappear along the membrane. Membrane deposits return slowly at later times after the stimulus. Decreased antimonate‐precipitable cation was observed in nuclear heterochromatin between 4 and 20 hours after IPR. This may be related to the induction of cell replication by the drug. During the DNA synthetic phase of the response to IPR, an unusual patchy osmiophobia was observed in nuclei. Mitotic chromosomes contained heavy antimonate deposits. Some of the early changes in cation distribution observed after isoproterenol administration mimicked changes seen in damaged cells.
Ultrastructural changes in vaginal epithelium of mice neonatally treated with estrogen and prolactin
Authors: Mori Takao , Nagahama Yoshitaka , Bern Howard A. , Young Patricia Nelson
Published: February 2005

The vaginal epithelium of the normal estrous mouse shows narrow intercellular spaces, many cytoplasmic fibrils and a continuous basal lamina. At 100 days of age, the vaginal epithelium of mice which had received 5 or 20 μg estradiol‐17β, 20 μg ovine prolactin, or 5 μg estradiol‐17β + 20 μg prolactin within the first few days of postnatal life, shows wider intercellular spaces in the middle epithelial layers than occur in normal estrous mice. In addition, the mice receiving 20 μg estradiol‐17β show prominent intercellular spaces in the basal cell layer and interruptions in the basal lamina, which permit penetration of cytoplasmic processes into the subjacent connective tissue. The relevance of these findings to vaginal carcinogenesis is considered.
The development of the ovary from birth to maturity in the bank vole (Clethrionomys glareolus) and the vole (Microtus agrestis)
Authors: Peters Hannah , Clarke J. R.
Published: February 2005

The postnatal development of the ovary in the bank vole and vole was investigated in order to determine whether the earlier onset of puberty in the vole coincides with a difference in the speed of gonadal development during the immature period in the two species.

The ovarian development differed in three respects: in the vole 4–10% of the germ cells are still oogonia when the animal is born, while in the bank vole oocytogenesis is completed during the embryonic period. Follicles develop earlier and more rapidly in the vole than in the bank vole. The early appearance of fluid accumulation in the follicles and the formation of “fluid sacs” in the vole ovary is characteristic.
Ultrastructural changes of rat blastocysts induced by estrogen during delayed implantation
Authors: Wu Jung‐Tsung , Meyer Roland K.
Published: February 2005

Ultrastructural changes of rat blastocysts during delayed implantation were studied 16, 20, 24 or 30 hours after estrogen was given to induce implantation.

In the inner cell mass the presence of long cytoplasmic processes penetrating deeply into the neighboring inner cell mass cells is seen at 16 hours. Most cells also show an increased number of ribosomes, polyribosomes and granular endoplasmic reticulum.

The trophoblast is featured by the formation of large amounts of glycogen and many inclusion bodies. Glycogen granules appear first in some abembryonic trophoblast cells at 16 hours, and spread to the embryonic pole at 24 hours. New inclusion bodies appear sequentially: multivesicular bodies at 20 hours, multigranular bodies at 24 hours and lamellar bodies at 30 hours. The functions of these inclusion bodies remain to be studied.
Electron microscopic observations on advanced stages of spontaneous polyspermy in rabbit zygotes
Authors: Gulyas Bela J.
Published: February 2005

The fine structural appearance of eight spontaneously polyspermic rabbit zygotes was studied. The zygotes were considered polyspermic only after they met all criteria that excluded other possibilities of the trinucleate state. The presence of accessory male pronuclei, with varying degrees of disintegration of their chromatin in zygotes of similar age, suggests that refertilization can occur during an interval of several hours after penetration of the primary sperm. All of the polyspermic zygotes contained cortical granules intermittently beneath the vitelline (plasma) membrane. One zygote possessed cortical granule‐like structures with ill‐defined or no limiting membrane. Formation of enveloping membranes around the incorporated accessory sperm head was precocious since it occurred prior to disintegration of the chromatin. Advanced stages of accessory pronuclei morphologically resembled the primary pronuclei in the same zygote. In seven out of eight zygotes the accessory male pronucleus was separated from the apposing male and female pronuclei. It was concluded that although the fully expanded accessory male pronucleus is similar to the pronuclei of monospermic fertilization, the temporal events of nuclear envelope formation were disturbed.
Proprioceptive innervation in the masticatory muscle of Temminck's mole, Mogera wogura (Temminck, 1842)
Authors: Kubota Kinziro , Masegi Toshiaki , Osanai Kentaro
Published: February 2005

This investigation was designed to obtain more anatomical information about the neuromuscular mechanism of the jaw movement by a comparative study of the insectivores. The muscle spindle distribution in the masticatory muscles of Temminck's mole showed a strong similarity to that of the Japanese shrew‐mole. Muscle spindles counted were 174 in number in a restricted area of the jaw‐closing muscles, 92 in the horizontal and 39 in the vertical portion of the temporalis muscle, 18 in the medial pterygoid muscle and 25 in the profound portion of the masseter muscle. The lateral pterygoid muscle, and the jaw‐openers, contained no spindles.
Effect of continuous darkness on diurnal rhythm in glycogen content in pineal cells of the mouse: A semiquantitative histochemical study
Authors: Kachi Takashi , Matsushima Shoji , Ito Takashi
Published: February 2005

The effect of continuous darkness on diurnal variation of glycogen content in pineal cells of adult mice was investigated by means of a semiquantitative histochemical method. In dark‐maintained mice, a diurnal rhythm in pineal glycogen content persisted for the first 7 days of darkness. After 14 days or longer of continuous darkness, however, a clear relationship between the glycogen content and time of day became less apparent. Reversed conditions of environmental lighting caused a complete reversal of the glycogen rhythm in the pineal as early as the fifth day. When mice that had been kept in reversed conditions of lighting for 7 days were exposed to continuous darkness, the reversed glycogen rhythm also persisted in darkness of 7 and 14 days, but it was abolished by darkness of 28 days. The nuclear density of pineal cells was significantly lower at 9 am than at 9 pm in controls. In dark‐maintained mice, however, no significant diurnal variation in pineal cell size was generally evident except 2 and 3 days after the initiation of darkness.
Isolation of viable human muscle spindles for electron microscopic and physiologic study
Authors: Kennedy William R. , Poppele Richard E. , Staley Nancy A.
Published: February 2005

Human muscle spindles are isolated from muscle biopsies of Extensor Indicis. A spindle rich portion of muscle is removed, placed into a modified Kreb's solution and microdissected for spindles. Intramuscular nerves and blood vessels provide helpful locating guides. Spindles can be dissected free of extrafusal muscle with an adequate length of nerve for in vitro recording. Another portion of muscle is stretched and placed into a 5% glutaraldehyde fixative in 0.1 M cacodylate buffer. Spindles are dissected free, postfixed, dehydrated, stained, and then studied with the light microscope while in liquid Epon. The equatorial regions are identified, then removed and embedded for examination using the electron microscope. This is the first successful total isolation of viable human spindles. The combined procedures allow correlation of recordings from the primary sensory endings with the fine structure of spindles from normal persons and from patients with neuromuscular disorders.
Light and electron microscopy of the human fetal thymus
Authors: Haar Jack L.
Published: February 2005

The human fetal thymus was studied at stages from 9 to 20 weeks of gestation. At 9 weeks of gestation the human fetal thymus contained lymphoid cells and was vascular although it was not yet lobulated nor did it have a cortex and medulla. By 12 weeks the thymus was lobulated and at 14 weeks a cortex and medulla could be distinguished, although the medulla was often more densely cellular than the cortex. By 18 weeks there were many lobules and a mature looking cortex and medulla. Large lymphocytes at all stages of thymus development studied were irregular in shape and often had blunt pseudopodia‐like cytoplasmic extensions, or more slender cytoplasmic extensions. They also often possessed numerous elongated mitochondria, a large Golgi complex and strongly basophilic cytoplasm. Large lymphocytes were not attached to the epithelial cells by desmosomes although some of the cytoplasmic extensions from them were in association with extensions from epithelial cells. Primitive medium‐sized lymphocytes at all stages studied were round in shape and had fewer mitochondria than the large lymphocytes. Epithelial cells were much less basophilic than the lymphoid cells and usually contained aggregates of glycogen. Occasional macrophages were observed within the developing thymus after 12 weeks of gestation and one granulocyte was observed within the thymus at 9 weeks while numerous granulocytes were seen within an interlobular septa at 14 weeks of gestation. Vessels were present within the thymus at all stages studied and at 9 weeks some had a boundary between the blood and thymus which consisted of only a thin endothelial cell and its basal lamina rather than the usual boundary of an endothelial cell and its basal lamina plus an epithelial cell and its basal lamina.
Ultrastructure of terminal pulpal blood vessels in mouse molars
Authors: Corpron Richard E. , Avery James K. , Lee Soo D.
Published: February 2005

The purpose of this investigation was to study the fine structure of pulpal capillaries located in the odontoblastic layer and immediate subjacent zone. The observations were from first molars of white mice sacrificed at five day intervals from 25–90 days. Both capillaries and small vessels with an incomplete smooth muscular coating appeared in the zone subjacent to the odontoblastic layer from 25–60 days. At the same time, capillaries which exhibited intracellular fenestrations in the endothelial wall were located within the odontoblastic layer.

From 50–90 days, the capillaries among odontoblasts, especially at the pulpal horns, appeared close to the predentinal surface, and an isolated capillary appeared to extend into predentin and run parallel to the outer surface of the odontoblastic layer for a short distance. At these ages, the capillaries subjacent to the odontoblastic layer also exhibited fenestrations along the thin endothelial walls similar to those observed at earlier ages in capillaries among odontoblasts.
Lighting regimen dominates interacting meal schedules and synchronizes mitotic rhythm in mouse corneal epithelium
Authors: Scheving L. E. , Pauly J. E. , Burns E. R. , Halberg F. , Tsai S. , Betterton H. O.
Published: February 2005

Three groups of mice were standardized to a light‐dark cycle with light from 0600 to 1800. One group was fed ad lib; but the other two had access to food for only four hours a day, one during the first part of the light phase and the other beginning at its middle. Two other groups were subjected to a reversed light‐dark cycle (light from 1800 to 0600); one of these had access to food for four hours during the first part of the dark phase and the other for four hours beginning at its middle. All the mice previously had been adjusted gradually over a three‐week period to these feeding schedules, and then they were maintained on the precise routine described for an additional two weeks. After standardization was completed, subgroups of mice were killed at three‐hour intervals over a single 24‐hour period. Corneas were removed and prepared, and the mitotic index in the epithelium was evaluated.

In all five groups a high‐amplitude circadian rhythm was found for the mitotic index, but in all cases this rhythm remained synchronized to the light‐dark cycle; only small changes in the phasing of the rhythm resulted from the restricted feeding. These results are contrary to what has been found for a number of other rhythmic variables which do synchronize to such feeding schedules.

The findings dispel the misconception that all body functions react in the same fashion to different synchronizors and emphasize that one must not generalize about the effects of feeding or lighting.
Comparative analysis of surface charges on luminal epithelial membranes of urinary bladders from toad, frog, turtle, and tortoise
Authors: Danon David , Ekblad E. B. Margareta , Strum Judy M.
Published: February 2005

Cationized ferritin was used to analyze the surface charges on the luminal epithelial cell membranes of urinary bladders from toad (Bufo marinus), bullfrog (Rana catesbiana), turtle (Pseudemys scripta and Clemmys caspica), and tortoise (Geochelone carbonaria and Testudo graeca). The labeling, done at a physiological pH on fixed or unfixed bladders, revealed differences in the distribution and density of negative charges along the luminal membrane surfaces. The epithelial surface of toad bladder did not label with cationized ferritin. Frog bladder labeled lightly and the labeling pattern varied between cell types. The epithelial membrane surfaces of reptile bladders were heavily labeled, in contrast to amphibian bladders. Luminal surfaces from fresh water turtles were not as heavily labeled as those from land tortoises. The degree of labeling varied from cell type to cell type in all reptile bladders except Pseudemys scripta. An analysis of the degree and pattern of labeling by cationized ferritin in bladders of all species studied might reflect a difference in the nature of the glycocalyx of a particular membrane, the presence or absence of negative surface charges or their availability (i.e., interference by mucus), and/or the nature of the chemical groups comprising the surface structure of the membrane.
Some ultrastructural and cytochemical features of fiber populations in the soleus muscle
Authors: Gauthier Geraldine F.
Published: February 2005

The soleus muscle is widely used in biochemical and physiological investigations as an example of a slow‐twitch red muscle, and it has been assumed, for the most part, that it consists of a homogeneous population of either red or intermediate fibers. In the present study, the cytological composition of this muscle was examined in four commonly studied species, namely the rat, guinea pig, rabbit and cat. Using the form and distribution of mitochondria as the principal criteria for identification, two distinct types of muscle fibers can be recognized in the soleus of the guinea pig and rabbit as well as the rat. The soleus muscle is therefore not homogeneous in either species. Preliminary observations suggest that the soleus of the cat is likewise not homogeneous. In addition, although the fibers resemble red and intermediate fibers in other skeletal muscles, the resemblance is only superficial. In the two fiber types of the rat and guinea pig soleus, the Z line is characteristically wide, and therefore, based on this criterion, the fibers are not equivalent to either the red or intermediate fibers of other muscles.
The organization of the seminiferous epithelium in the mouse testis following ligation of the efferent ductules. A light microscopic study
Authors: Ross Michael H.
Published: February 2005

Seminiferous tubules from mouse testes were studied with the light microscope after the efferent ductules had been ligated for 48 hours. As a consequence of ligation, the tubules became markedly distended by the fluid which they accumulated; the epithelium was reduced in height, and exhibited a significantly less complex stratification than in the normal. Longitudinal sections of the distended tubules, particularly those in the early stages of the seminiferous cycle, revealed pillar‐like epithelial profiles arranged in a repetitive series. Each “pillar” consisted of Sertoli cell cytoplasm along with two generations of spermatids, the older generation embedded within the Sertoli cell, and the younger generation aligned, one cell above the other, along its sides. Oblique or grazing sections through tubules exhibiting the same stages of spermiogenesis revealed band‐like epithelial profiles arranged in parallel array. The two types of epithelial configurations are interpreted as representing a series of circumferentially oriented ridges within the tubule. It is postulated that each spermatid generation within a ridge constitutes a single clone, and that it is the cytoplasmic bridges joining the spermatids, in combination with their attachment to the Sertoli cells, which provide the organization, delineation, and structural stability of the ridges.
Perinatal changes in size of pancreatic acini in the rat with special reference to effects of fetal decapitation and fetal or neonatal oral administration of water or milk
Authors: Morikawa Yoshio , Arishima Kazuyoshi , Eguchi Yasunobu , Hashimoto Yoshiyuki
Published: February 2005

Normally, the size of pancreatic acini is remarkably decreased after birth in the rat.

Administration of water or milk on day 21 of gestation resulted in decreased acinar size a day later in intact fetuses and in fetuses decapitated immediately after administration of water or milk. The same treatments of premature newborn rats obtained by Caesarean section on day 22 of gestation induced similar effects a day later On the other hand, in starved Caesarean newborn rats, there were no histologic changes in acini. In spontaneous newborn rats which were allowed to suckle maternal milk and then starved for one day, there was an increase in acinar size as compared with that of 2‐day‐old normal rats.

These results suggest that the fetal pancreatic acini at least near term (on day 21 of gestation) can respond to some signals conveyed from digestive tracts which have responded to exogenous stimuli, that the brain during fetal days does not play any role in digestive tract‐pancreatic acini interrelations in secretion of zymogen granules and that the neonatal decrease in acinar size is caused by the intake of maternal milk.
Lipid droplet accumulation in cardiac muscle cells of the bat: Potential auto‐toxicity of the cardiac sympathetic innervation
Authors: Nunez Eladio A. , Hagopian Martin , Gershon Michael D.
Published: February 2005

The previously described ability of reserpine and parachlorophenylalanine to induce the accumulation of lipid droplets in ventricular cardiac muscle cells of the bat was investigated. Lipid droplet accumulation was assessed qualitatively by light microscopy and quantitatively by morphometric analysis of electron micrographs. An hypothesis that the action of the drugs was an indirect one, mediated by the cardiac adrenergic innervation, was framed and tested. Lipid droplet accumulation occurred during a time of intense sympathetic activity, that of arousal from hibernation. The ability of the two drugs to produce the effect was antagonized by prior sympathectomy with 6–dopamine. The effect was mimicked by administration of exogenous norepinephrine together with inhibitors of its catabolic enzymes, monoamine oxidase and catechol‐omethyl transferase. These observations are all consistent with the initial hypothesis and raise the possibility that endogenous norepinephrine in the cardiac sympathetic innervation might be, at least potentially, auto‐toxic.
Structural modifications of lutein cell gap junctions during pregnancy in the rat and the mouse
Authors: Albertini David F. , Anderson Everett
Published: February 2005

By use of lanthanum tracer and freeze‐fracture procedures it was found that granulosa‐lutein cells of the pregnant mouse and rat ovaries are connected by gap junctions and septate‐like zones of contact. Lutein cell gap junctions enlarge and become partially internalized by the end of the first week of gestation. Expansion of the gap junction domain appears to be due initially to intercalation of particles along borders of small gap junctions devoid of smaller non‐junctional particles. The number of gap junction lined processes appearing at the cell border increases concomitantly with hypertrophy of the lutein cell during the second week of pregnancy. Strands of particulate or grooved membrane emanate from the margin of larger gap junctions undergoing interiorization. Most large gap junctions are intimately associated with elements of the smooth endoplasmic reticulum. Spherical gap junctional profiles assume a deeper location in the lutein cell and may form concentric arrays by term while true surface gap junctions appear to fragment in the post‐partum corpus luteum. The modifications observed are interpreted with respect to biogenesis of the gap junction and the hormonal control of lutein cell function.