bluuebunny/crossref_metadata_2025 huggingface dataset:
Alterations in the fine structure of the rat epididymis after vasectomy
Authors: Flickinger Charles J.
Published: February 2005

The fine structure of the epldidymal epithelium of the rat was studied at intervals up to nine months after bilateral vasectomy, unilateral vasectomy, or a bilateral sham operation. Membranous material accumulated in the cytoplasm of the ‘light’ cells of the cauda epididymidis in greater amounts after bilateral vasectomy than following a sham operation. The membranes were found in apical vacuoles, in moderately dense membrane‐bounded bodies in the mid‐region of the cells, and, most prominently, in large infranuclear masses. These large infranuclear membranous masses had a polymorphic interior composed of granules and amorphous material as well as membranes, and thus morphologically resembled large lysosomes or residual bodies. In some instances readily dentifiable parts of sperm were found in apical vacuoles of epithelial cells after vasectomy. It is suggested that these changes may reflect the absorption of parts of sperm by the epithelium of the cauda epididymidis after vasectomy. The nature of the ‘light’ cells is discussed, and the results are compared with alterations in other species after vasectomy.
Spermatogenesis in the dog
Authors: Foote R. H. , Swierstra E. E. , Hunt W. L.
Published: February 2005

The cycle of the seminiferous epithelium of the dog was divided into eight stages, using as criteria the shape of the spermatid nucleus, the location of spermatids and spermatozoa in regard to the basement membrane, the presence of meiotic figures and the release of spermatozoa from the lumen of the tubule. Based upon these criteria, a modification of the eight‐stage system of classification of the cycle of the seminiferous epithelium was developed. Cell populations making up each stage are described. The relative frequencies of stages 1 through 8 were 21.9, 12.7, 2.8, 11.5, 8.3, 15.4, 13.3 and 14.0%, respectively. The duration of one cycle of the seminiferous epithelium was 13.6 days (SE ± 0.7), as determined from cells labeled by tritiated thymidine. The absolute durations of stages 1 through 8 were 3.0, 1.7, 0.4, 1.6, 1.1, 2.1, 1.8 and 1.9 days, respectively. The life span of primary spermatocytes was 20.9 days, of secondary spermatocytes 0.5 days, spermatids with round nuclei 10.5 days, spermatids with elongated nuclei up to the time they are released into the lumen, 10.6 days. Counts of the different types of spermatogenic cells in tubular cross sections revealed little or no germ cell degeneration during the two maturation divisions.
Evidence for refractoriness of the pituitary‐gonadal axis to the pineal gland in golden hamsters and its possible implications in annual reproductive rhythms
Authors: Reiter Russel J.
Published: February 2005

The testes of adult hamsters maintained in short daily photo‐periods (light:dark “LD” cycles of 1:23, in hours) undergo regression within ten weeks and spontaneous regeneration within about 30 weeks. Thereafter (at least up to 80 weeks), as long as these animals are kept in short photoperiods the gonads do not experience a second atrophic response. After the 30 week period of dark exposure, if the hamsters are moved into a long photoperiodic environment (LD 14:10) for either one or ten weeks and are then returned to short photoperiods, the gonads do not involute a second time. However, if the duration of exposure to LD 14:10 is increased to 22 weeks, the return to LD 1:23 causes the gonads to degenerate. The regressive responses of the testes never occur in hamsters that have been pinealectomized indicating that the observed changes are mediated by this gland. The inability of darkness and, thus the pineal gland, to induce a second gonadal involution unless the hamsters are maintained in LD cycles of 14:10 for 22 weeks (after a 30 week period of dark exposure) may be explicable in terms of (1), a transient refractoriness of the brain to the pineal antigonadotropic principle or (2), the temporary failure of the pineal to be activated by short daily photoperiods.
Spinal nerve root degeneration in aging laboratory rats: A light microscopic study
Authors: Gilmore Shirley Ann
Published: February 2005

Degeneration of unknown etiology was noted in the spinal nerve roots of aging rats. These animals (Charles River CD® rats) were included in a study of long‐term effects of ionizing radiation. The initial lesion was a de‐myelination of an individual axon or a few, isolated, scattered axons in the ventral roots of rats between 18 and 20 months of age. As the lesion progressed, the dorsal roots showed involvement, and by 24 months the usual finding was marked degeneration in ventral roots with degenerative changes of a lesser degree in the dorsal roots. When degeneration was complete, connective tissue filled the regions normally occupied by neural tissue. The lesion was unrelated to the radiation procedure, occurring with equal frequency in both irradiated and non‐irradiated animals. Furthermore, lesions occurred with equal frequency in both males and females. The one factor to which the lesion appeared to be related was age since it was not observed in animals less than 18 months old but was seen in 66.7% of those between 18 and 20 months and in 96.0% of those older than 20 months. These data indicate that this lesion needs to be considered when using aging laboratory rats.
Vestibular ampullary structures in the pigeon: A scanning electron microscope overview
Authors: Landolt Jack P. , Young Eric R. , Correia Manning J.
Published: February 2005

A scanning electron microscope (SEM) was used to explore the complex surface features of the ampullary structures in the vestibular apparatus of the pigeon. The depth perspective inherent in SEM microscopy enabled: 1. three‐dimensional views of major ampullary structures such as the crista ampullaris, eminentia cruciata, and the planum semilunatum; 2. identification of a tongue‐like structure, the “lingula,” that is part of the eminentia cruciata; 3. the observation that the base of the eminentia is a projection of the crista ampullaris and not a structural partition; and 4. evidence that the lingulae, together with the torus, partition the crista into two separate regions. Additionally, an examination was made of the surface topography of non‐sensory cells in the membranous ampulla.

The morphology of the cells and gross ampullary structures observed with SEM are compared to those obtained using light microscopy and where advantageous, complimentary light photomicrographs are presented.
Transitional cells in the postnatal thyroid gland of the rat
Authors: Calvert R.
Published: February 2005

In two and four‐week old rats three types of follicles were observed: thyroid follicles made of follicular cells and C cells; ultimobranchial follicles (or cysts) and ducts composed of lumen‐bordering cells and subjacent cells; mixed follicles lined by follicular cells on one side and by lumen‐bordering cells on the other. Occasionally C cells were seen in the wall of mixed follicles. On their basal side the lumen‐bordering cells of mixed follicles were in direct contact with the wall of ultimobranchial ducts or cysts. In the wall of these ducts transitional cells were observed. One type had ultrastructural features of subjacent cells (i.e., hemidesmosomes) and of lumen‐bordering cells (i.e., pale cytoplasm and dispersed tonofilaments). Another type of transitional cell had hemidesmosomes and a deeply indented nucleus, like subjacent cells, but had accumulated slightly distended cisternae of rough‐surfaced endoplasmic reticulum and was displaying long slender microvilli, which is typical of follicular cells. A third type of cells were called “young follicular cells.” They contained slightly distended cisternal profiles of rough‐surfaced endoplasmic reticulum collected in one corner of the cells and few apical vesicles. However, their cisternae were less abundant, less distended and had a more restricted distribution than those found in mature follicular cells. Hence the subjacent cells of ultimobran‐chial ducts might possibly give rise to lumen‐bordering cells and to some follicular cells. The latter are associated with the lumen‐bordering cells in the formation of mixed follicles; at the beginning these new follicular cells seem less active than the mature follicular cells. The origin of C cells after birth is discussed.
Trout hepatoma: Fibrosis and lymphocytosis as suppressive mechanisms in the rainbow trout (Salmo gairdneri)
Authors: Wales J. H. , Sinnhuber R. O.
Published: February 2005

Fibrosis and lymphocytosis are common in aflatoxin‐induced hepatoma in rainbow trout. It is suggested that these reactions may control the growth of tumors and in some cases destroy them. Nearly all of the hepatomas we have observed are fibrotic to some extent. The extent of the fibrosis seems to be age dependent and in advanced cases fibrosis appears to have disorganized the tumors to a degree which we believe is suppressive. The lymphocytosis shows a negative correlation with the size and age of the hepatoma, being found almost exclusively in the very “early” (small) hepatomas and preneoplastic nodules. It is suggested that the invasion of the tumors by lymphocytes is a host defense mechanism.
The fine structure of granulosa cell nexuses in rat ovarian follicles
Authors: Merk Frederick B. , Albright John T. , Botticelli Charles R.
Published: February 2005

An intercellular junction known as the nexus has been identified in developing granulosa tissue of rat ovaries. Nexuses are common in Graafian follicles of mature cycling rats and in similar follicles of immature animals stimulated by exogenous gonadotrophins. The angle at which the plane of section intersects a nexus significantly governs its internal appearance. Within obliquely cut nexuses there is often a cross‐striated pattern of uniform lines in specimens prepared by conventional fixation and staining procedures. These lines could be significant because they may represent points of continuity between communicating cells.

Two forms of nexuses are observed. The abutment form is found at cell surfaces, is continuous with plasma membranes, and is frequently associated with cell processes. The other form of nexus is ring‐shaped and appears free within the cytoplasm. These circular profiles probably represent transverse views through nexus‐girdled cell processes as well as nexus‐bound spheres which may have pinched off the processes. Since the profiles from the two sources are ordinarily indistinguishable, both are designated “annular nexuses” even though some may be cell inclusions. Lanthanum tracer can percolate into the central region of abutment nexuses but is absent from the large majority of annular nexuses, suggesting that many of them are isolated from the extracellular space. Reconstruction of serial sections reveals that some annuli are parts of cell inclusions. Sphere formation could be a means of removing nexuses from cell surfaces.
Fine structure of astrocyte mitochondria in the spinal cord of the dog, cat and monkey
Authors: Duncan Donald , Morales Ricardo
Published: February 2005

After perfusion of the animals with buffered aldehyde solutions, spinal cords of normal dogs, cats and monkeys were prepared for electron microscopic examination by standard methods. Observations were limited to the upper cervical levels in all animals, except in two cats where thoracic and lumbar regions also were studied. Large mitochondria, up to 5.0 μ in diameter, are abundant in astrocytes that form a dorsolateral glial septum in dogs and cats. The septum is present but less well developed in monkeys and the accompanying large mitochondria are smaller and less numerous. These mitochondria have a moderately dense matrix and few or no cristae. They are accompanied by more numerous smaller mitochondria with similar matrix and prismatic cristae. The cristae are of constant size and shape in all three species but vary greatly in numbers and arrangement. It is suggested that local mechanical forces may be responsible for the configuration of these morphologically specialized mitochondria.
Fine structure of photoreceptors in the owl monkey
Authors: Murray Raymond G. , Jones Arthur E. , Murray Assia
Published: February 2005

The owl monkey (Aotes trivirgatus) differs from most primates in being nocturnal in habit and having primarily scotopic vision. Photoreceptor cells of the retina of this species were studied with the electron microscope and compared with corresponding cells of other primates. No striking qualitative differences were noted. Most of the receptors are typical rods, but approximately 5% are cones, based on the following features: shorter, tapering outer segments, discs with smooth rather than scalloped margins and with uniformly narrow internal spaces, the membranes of which in some cases are continuous with the plasma membrane; broad inner segments with numerous mitochondria; nuclei that lie immediately against the outer Junctional zone (outer limiting membrane) with relatively thick inner fibers leading to large pedicles in the floor of which are numerous typical “synaptic triads.” One relatively unusual feature of the rods is the prominence of the striated rootlets associated with the basal bodies of the cilium‐like connecting pieces. An apparently intimate relation of the rootlets to investing mitochondria, especially to their tubular internal cristae, is discussed with regard to the possibility of a function for the rootlet other than static anchoring of the cilium.
Lymphoid cells in the turtle bladder
Authors: Lefevre M. E. , Reincke U. , Arbas R. , Gennaro J. F.
Published: February 2005

Lymphoid nodules and diffuse lymphocytic infiltration are common in turtle urinary bladders. Nodules, usually located immediately beneath the epithelial layer, were found in 15 of 29 different hemibladders surveyed. A whole cross‐section of each hemibladder was examined in the survey. The nodules consisted of aggregates of dense lymphocytes without germinal centers. Erosion of the epithelial layer over the nodule was found in approximately one third of the cases. Scattered lymphocytes were abundant within the epithelial layer and were found in smears from the mucosal surface. Pyroninophilic cells resembling plasma cells were found in all regions of the bladder. Electron micrographs showed lymphocytes and plasma cells in the epithelial layer above the basement membrane.
Metabolic activity during the degenerative and early regenerative stages of minced skeletal muscle
Authors: Snow Mikel H.
Published: February 2005

In the rat, autotransplanted minced skeletal muscle undergoes degenerative changes prior to the regeneration of a whole muscle. In this study, both the degenerative and early regenerative processes were examined using histochemical procedures for the localization of glycogen, neutral lipid, phosphorylase, lactate dehydrogenase, cytochrome oxidase, glucose‐6‐phosphate dehydrogenase and non‐specific esterases. Glycogen and phosphorylase activity disappeared in all muscle fibers within 24 hours after mincing. Vascular injections of ink demonstrated that during the second to tenth days after mincing a central ischemic zone of degenerating minced muscle was surrounded by a vascularized zone of regenerating muscle. Lactate dehydrogenase staining persisted during the first week in the degenerating muscle fragments of the central zone. This latter histochemical observation was supported by quantitative evidence which showed that degenerating muscle isolated from the central zone of four day regenerates produced lactic acid in the presence of glucose. Cytochrome oxidase activity decreased rapidly in the degenerating muscle while succinic dehydrogenase persisted somewhat longer. Although non‐specific esterases and glucose‐6‐phosphate dehydrogenase activities were not significant in normal muscle, they were histochemically detectable in degenerating muscle during the first week. The capacity for anaerobic metabolism apparently persists in the degenerating minced muscle for several days; this energy source may be sufficient to maintain the myogenic cells in an environment of degeneration and ischemia until they become reassociated with a vascular supply.
Identification of neonatal grey lethal mice
Authors: Hollinshead M. B. , Schneider L. C.
Published: February 2005

The grey lethal mouse is an osteopetrotic mutant which cannot be identified by its external appearance (grey fur) until eight days of age and dies within one month of birth. Techniques for the identification of neonatal mutants would greatly facilitate study of the pathogenesis of osteopetrosis and its early treatment.

Under hypothermal anesthesia, the left lower limbs of neonatal mice were amputated just above the knee joint. The external appearance of two day old amputated tibiae could be correlated with the external appearance of the mice at eight days of age. The diaphyses of normal tibiae appeared red under the dissecting microscope due to the presence of hemopoietic tissue occupying the central marrow cavity. Grey lethal tibiae appeared opaque because relatively more unresorbed bone occupied the center of the diaphysis.

Histologic examination showed that in normal mice at birth, the mandibular incisor extended posteriorly to the molar region of the jaw, but that in grey lethals dense bone prevented the incisor from growing posteriorly in this fashion.
Electron microscopic and microradiographic investigation of a morphologic basis for the mineralization pattern in rat incisor enamel
Authors: Glick Paul L. , Eisenmann Dale R.
Published: February 2005

Although it has been established that human enamel mineralization follows the incremental pattern of matrix secretion, microradiographic studies of rodent enamel still support a non‐incremental pattern of mineralization. This study examines the mineralization sequence using microradiography, as well as measurement of crystal size and distribution on electron micrographs of the various regions of rat incisor enamel. The microradiographic density pattern was found to correlate with the major regions of structural variation within the enamel. Measurement of crystals revealed a rather uniform positive gradation in their size from the surface to the dentino‐enamel junction, i.e., crystal size was found to be directly related to crystal age. Crystal distribution analysis demonstrated that an inner region of enamel contains a much larger volume of crystal‐free space than other areas. This is the same region which has been described as being out of step with an incremental pattern of mineralization, in that it is less dense than enamel either superficial or deep to it. It is concluded that mineral accretion follows the same incremental pattern in the rat incisor as in humans and that the misleading microradiographic image merely reflects a non‐homogeneous distribution of crystals.
The morphology of tadpole (Rana catesbeiana) liver under varying conditions of organ culture
Authors: Bennett Thomas Peter , Kreigstein Henry
Published: February 2005

Primary explants from Rana catesbeiana tadpole liver have been maintained in organ culture for six days using methods of cultivation which are described in detail. The organization and morphology of the cells in culture have been defined by light and electron microscopy. By adjustment of the experimental conditions of culture, after six days, the cells are morphologically identical to those freshly excised from tadpole liver. Soon after being put into culture, however, the chromatin of the nuclei becomes condensed, and only after about 30 hours in culture do the original euchromatic characteristics of the nucleus reappear. The effects of changes in the culture conditions on these morphological characteristics are presented.

The system that has been developed is discussed with a view toward elucidating the basis of the cytological changes which occur during anuran metamorphosis.
Golgi impregnation study of a new catecholamine‐containing cell type in the toad hypothalamus
Authors: McKenna Olivia C. , Pinner‐Poole Betty , Rosenbluth Jack
Published: February 2005

A population of catecholamine‐containing subependymal cells bordering the preoptic recess of the toad hypothalamus was studied by the rapid Golgi method to determine whether the cells have the characteristic contours of neurons or are instead secretory cells similar to peripheral chromaffin cells as proposed in an earlier study. Golgi impregnations of these cells reveal that they possess long basal processes which extend toward the lateral surface of the brain and which are covered with clusters of short projections and longer single projections. The relatively large caliber and rough surface of these processes distinguish them from axonal processes of neurons. Instead the cells closely resemble the ependymal cells bordering the preoptic recess with respect to the lateral course of the basal processes and with respect to the projections on these processes. The only qualitative difference between the ependymal and subependymal cells seen in Golgi preparations is the presence of apical processes projecting from the subependymal cell bodies through the ependymal layer to border on the ventricle. On the basis of this and the earlier study it is concluded that the subependymal cells do not have the characteristics of neurons but instead constitute a new cell type similar to ependymal cells but specialized for the synthesis, storage and secretion of catecholamines.
Cytokinesis in the rabbit zygote: Fine‐structural study of the contractile ring and the mid‐body
Authors: Gulyas Bela J.
Published: February 2005

The temporal events of cytokinesis were examined with light‐ and electron‐microscopes during first cleavage of the rabbit zygote. When karyokinesis is at the late anaphase‐to‐early‐telophase stage a shallow indentation appears in the vitelline membrane in a plane perpendicular to the spindle. Microvilli are absent in the indentation although present elsewhere. A band of microfilaments is recognizable under the plasma membrane of this region. Sections which pass through the band of microfilaments contain several early mid‐bodies located centrally in the egg. In later stages of furrowing the band of filaments is 0.1 μ wide and is circumferentially arranged. These filaments which underlie the broad leading edge of the furrow are 50–80 Å in diameter and are components of the contractile ring. The furrow cavity is filled with blebs of the plasma membrane. The microvilli of the lateral furrow walls interdigitate and “primitive” intermediate junctions develop between the two blastomeres. During late cleavage the stem‐bodies fuse into a continuous mid‐body which spans two opposite points of the intercellular bridge and fuses with the filaments of the contractile ring.
Casting the lungs in‐situ
Authors: Phalen Robert F. , Yeh Hsu‐Chi , Raabe Otto G. , Velasquez David J.
Published: February 2005

A method for producing flexible silicone rubber casts of the airways of the lungs in‐situ is described. Casts are made to correspond to lung volumes occurring during normal breathing. The lung is prepared for casting by replacing the air within with CO2 followed by filling with degassed physiological saline. The saline dissolves the CO2 gas within the airways allowing for a bubble‐free finished cast. Casting compound is then slowly injected through the trachea. The saline diffuses out of the lung and passes out of the thorax through several small slits in the thoracic wall. After the injection is completed, the cast lung is allowed to cure in‐situ before it is removed and the tissue digested away. Finished casts have an overall shape corresponding closely to the shape of the thorax. Casts produced by this in‐situ method appear to have more realistic geometrical relationships than those produced from excised lungs.
Golgi studies of the nucleus gracilis in the rat
Authors: Gulley Robert L.
Published: February 2005

With the use of Golgi‐Kopsch and rapid Golgi techniques, seven different neuronal types were described in the nucleus gracilis of the rat. In the caudal part of the nucleus the dendrites were grouped in vertical bundles origented parallel to the collaterals of the fibers in the fasciculus gracilis. Some neurons had dendrites associated with several dendritic bundles separated in the horizontal or parasagittal planes. Two types of interneurons were found in the caudal part of the nucleus. The first had its axon confined within a dendritic column formed in part by its own dendritic arborization. The axon of the second interneuron projected to a nearby dendritic column. In the rostral part of the nucleus, the various neuronal types had dendrites oriented either transversely or along the axis of the nucleus. Fibers from the fasciculus gracilis, at rostral levels, bend to course across the nucleus sending collaterals along the parasagittal plane. Thus the dendrites of the neurons in this region were directed perpendicular and/or parallel to the afferent fibers. Afferent axons to the nucleus gracilis from the pyramidal tract and medullary reticular formation were also described.
Ultrastructural localization of alkaline phosphatase activity in the developing thyroid gland of the rat
Authors: Calvert R.
Published: February 2005

The localization of alkaline phosphatase activity during morphogenesis of the thyroid gland was studied at the fine structural level in Holtzman rats from the fifteenth day of foetal life till the first day after birth. The present work deals with the formation of thyroid follicles in the median thyroid primordium only. Since the rat thyroid does not develop synchronously, the three stages described may overlap during a given day of development. In the precolloid stage that extends roughly from the fifteenth to the nineteenth day of development, alkaline phosphatase activity is localized in Golgi saccules and vesicles and also in smooth membrane tubules and vesicles found in the cytoplasm near the lateral plasma membranes. At the end of this stage the lateral plasma membranes become strongly reactive and a cluster of positive vesicles and tubules appears immediately under the junctional zone. The second phase, the early colloid stage (17–19 days), is characterized by the formation of the colloid cavity in center of the disc‐like junctional zone: at this moment the newly formed apical plasma membrane bearing the microvilli shows the reaction product. During the third stage (18 days onwards), which starts with a gradual increase in the diameter of follicular lumina, a drastic fall in alkaline phosphatase activity is observed. In one day old rats, follicular cells are completely negative. These findings are briefly discussed in connection with thyroid cell differentiation.
The integrated roles of longus colli and sternocleidomastoid muscles: An electromyographic study
Authors: Vitti Mathias , Fujiwara Makoto , Basmajian John V. , Iida Masaru
Published: February 2005

Using bipolar fine‐wire electrodes, we examined the right and left longus colli (LC) and sternocleidomastoideus (StM) muscles electromyographically in ten healthy young adults. Action potentials were recorded on FM magnetic tape and each experiment was also videotaped. The head‐neck motions were recorded using a special neck goniometer. The muscles were studied in sitting, supine, prone and lateral positions, both during free movements and against resistance. There was complete inactivity in both muscles in relaxed sitting, normal breathing, deep expiration, and wet and dry swallowing. There was very marked synchronous EMG activity of the LC and StM muscles during resisted forward flexion, marked activity during neck flexion against head weight in the supine position, and during resisted right and left side‐bending. Variable activity was found in both muscles during deep breathing, coughing, forceful blowing, loading on top of the head, resisted backward extension, neck holding against head weight in the prone position and in twisting movements downwards and upwards. During free flexion‐extension movements, LC and StM act synchronously. During free lateral bending they work homolaterally, but during free rotation to the right, the right LC works with the left StM and vice versa.
The origin of equine endometrial cups. II. Invasion of the endometrium by trophoblast
Authors: Allen W. R. , Hamilton D. W. , Moor R. M.
Published: February 2005

Light and electron microscopic examination of tissues fixed in situ by perfusion of the gravid horn of the uteri of mares between 36 and 38 days of gestation revealed that the equine endometrial cups are composed of trophoblast cells which originate from the discrete annulate portion of the foetal membranes known as the chorionic girdle. This structure consists of closely opposed villous projections of elongated trophoblast cells and it becomes firmly attached to the endometrium around the thirty‐sixth day of pregnancy. The specialized girdle cells invade and phagocytose the endometrial epithelium and then migrate through the basal lamina into the endometrial stroma where they develop into endometrial cup cells.
Electron microscopic study of involuting thymus of “lethargic” mutant mice
Authors: Dung H. C.
Published: February 2005

The thymus, which undergoes spontaneous involution three weeks after birth in “lethargic” mutant mice, was studied by electron microscopy. Ultrastructural alterations observed in the involuting thymus of “lethargic” mice resemble those of acute thymic involution induced by the administration of adrenal corticosteroids. The responsive cells in thymic involution of “lethargic” mice were cortical thymocytes, macrophages, and epithelial cells. The first indication of the involution was the appearance of a large number of degenerating thymocytes in the cortex. Pyknotic nuclei of degenerating thymocytes were observed within the macrophages. Macrophages of the involuting thymus were characterized by their content of thymocyte pyknotic nuclei as well as a variety of cytoplasmic inclusions. Cytoplasmic inclusions were also found in the epithelial cells. The inclusions were of two different types: (a) tonofibrils in markedly increased numbers in relation to a non‐involuted thymus, and (b) large vacuoles with dense bodies and/or myelin figures, as found in a normal cell, but several times the number one would expect to find. A large number of lipid‐laden cells were found in the involuted thymus. This type of cell was not seen in the normal thymus. Numerous Hassall's corpuscles were also found in the involuted thymus of “lethargic” mice.
Fine structure of the agranular cytoplasmic tubules in the lamprey chloride cells
Authors: Nakao Taisuke
Published: February 2005

The chloride cells of the lamprey, Lampetra japonica, have been studied by electron microscopy. The most characteristic feature of the chloride cells in lamprey is that the cytoplasm is filled with a large number of mitochondria and numerous agranular cytoplasmic tubules arranged as bundles or as branched reticular networks. These tubules are frequently continuous with the plasma membrane. They are also characterized by a coating on the cisternal surfaces with a dense material which appears ridge‐like at high magnification. These ridges are oriented spirally along the cisternal surface of the tubule. They are regularly spaced at an interval of about 160 Å and have a pitch of about 45°. The functional significance of the cisternal coat is unknown. Sometimes, intracisternal tubules are observed to be contained within the lumina of the agranular cytoplasmic tubules. These intracisternal tubules are considered to be formed by an intracisternal deflection of only one leaflet of the unit membrane of the agranular cytoplasmic tubules. Membrane fusion is observed to occur between closely associated agranular cytoplasmic tubules.
Specialized intercellular junctions in the intercalated disc of the bat heart
Authors: Hagopian Martin , Anversa Piero , Nunez Eladio A.
Published: February 2005

The intercalated discs of the myocardium from the active and hibernating bat hearts were investigated by means of electron microscopy and use of lanthanum and horseradish peroxidase as tracers. The discs are composed of four zones: intermediate junctions, desmosomes, nexuses, and undifferentiated areas. Of particular interest are the two different types of nexuses. Nexus I without lanthanum displays a 150 Å overall width and an apparent 80 Å intercellular space, ranges from 0.5 to 4.0 μ in length, and is seen in the longitudinal segments of the intercalated disc. With application of lanthanum, however, nexus I shows that the tracer has penetrated a 20 Å gap junction and resembles nexus II. Nexus II with and without lanthanum has a 200 Å overall width and a gap junction of about 20 Å, is generally less than 0.3 μ in length, and is found on the transverse or oblique segment of the intercalated disc. Both nexuses I and II seem to block the passage of peroxidase. The plasma membranes of nexus I may have a different molecular organization from those in nexus II as reflected by their contrasting response to fixation and/or staining. Combinations of the various junctions show that the zones of adhesions (intermediate junctions and desmosomes) are adjacent to the regions of possible lowered resistance (nexus I and II). These findings suggest that adhesion sites insure the proper connection and functioning of the nexuses and support the electrical observations that the heart forms a “physiological syncytium”.
The effect of eifferent estrogen‐progesterone ratios on DNA synthesis in the rat uterus
Authors: Krueger Wayne A. , Bo Walter J. , Garrison Benjamin M.
Published: February 2005

The influence of different estrogen‐progesterone ratios on DNA synthesis in the rat uterus was investigated. Ovariectomized rats were injected subcutaneously daily for three days with either oil, 1 μg estradiol‐17β dipropionate or estradiol and 1, 5, 10 or 15 mg progesterone. Tritiated thymidine was administered one hour prior to necropsy. Thymidine indices were determine for both the luminal and glandular uterine epithelia while the total number of labeled nuclei in the stroma was ascertained. In all tissues studied, significantly more nuclei from uteri of rats given only estrogen replicated DNA than from those of the oil‐treated controls. While concurrent treatment with estradiol and 1 or 15 mg progesterone did not statistically alter the extent of thymidine incorporation in the luminal epithelium and stroma from that observed following estrogen alone, 5 or 10 mg progesterone given with estrogen significantly suppressed the labeling activity in the luminal epithelium and stroma from that of the estrogen‐treated rats. However, the thymidine indices of the glandular epithelium from uteri of rats injected with all combinations of both hormones were significantly lower than that from uteri of estrogen‐treated rats. These data indicate that the estrogen–progesterone ratio is important in regulating cell turnover in the luminal epithelium and stroma of the rat uterus but not in glandular epithelium.
Intramural blood supply of porcine heart. A postmortem angiographic study
Authors: Jöunsson Lennart , Johansson Göuran , Lannek Nils , Lindberg Paul
Published: February 2005

The intramural arteries, arterioles and capillaries of the hearts of 23 crossbred pigs, six months old, of Yorkshire and Swedish landrace were presented.

The vascular pattern was basically the same in both the ventricular walls. Large branches of two types emerged from the extramural arteries and traversed the myocardial wall, terminating in the subendocardial zone. The largest vessels supplied the papillary muscles and trabeculae carneae. The terminals of these branches formed the subendocardial anastomotic network. No other anastomoses were observed in the ventricular walls. The capillaries had a course parallel to the muscle fibers and anastomosed freely. Most of the interventricular septum was supplied by branches from both the left and the right descending arteries. Only a minor part of the septum was supplied by the anterior and posterior septal arteries.

The ventricular vascular pattern of the pig was found to be very similar to that of the human heart. It was concluded that the pig, in contrast to the dog, has ideal attributes for comparative cardiovascular research in man.
Ultrastructure of ependymal cells of the shark median eminence
Authors: Saland L. C. , Evan A. P. , Demski L. S.
Published: February 2005

The ultrastructure of ependymal cells of the median eminence in young Pacific blacktip reef sharks is described. Three major cell types have been observed. The first type is an irregularly‐shaped, electron dense cell with many long microvilli and occasional cilia projecting into the ventricle. A second type contains dense cytoplasmic granules in sizes ranging from 1000–2000 Å, and may be morphologically equivalent to “liquor‐contacting neurons” observed in ependymal linings elsewhere. The third type appears very similar to crown cells of saccus vasculosus of this and other species. Cells of the third type possess large, lipid‐like inclusions, bulbous projections originating from basal bodies, and prominent smooth endoplasmic reticulum. The crown‐like cells are compared to cells of saccus vasculosus of young and adult sharks, and their possible significance is discussed.
Medial occipital projections to the nucleus of Darkschewitsch of rhesus monkey
Authors: Wright Sanford , Hilsz Joyce , Locke Simeon
Published: February 2005

Projection from medial occipital cortex (area OB) to the nucleus of Darkschewitsch is demonstrated in six Macaca mulatta hemispheres by the technique of Fink and Heimer. Degeneration was present as well in the lateral pons, nucleus lateralis dorsalis, nucleus lateralis posterior, lateral pulvinar and nucleus parafascicularis. Centrum medianum, dorsal lateral geniculate body and interstitial nucleus of Cajal were spared.
The postnatal growth of the rat lung. I. Morphometry
Authors: Burri Peter H. , Dbaly Jaroslav , Weibel Ewald R.
Published: February 2005

The postnatal growth of the lung was quantitatively investigated in rats aged 1, 4, 7, 10, 13, 21, 44 and 131 days by light and electron microscopic morphometry.

Lung volume (VL) increased first directly with body weight (W). After day 10 VL followed the function W0.70. Based on the quantitative findings the postnatal lung growth could be divided into three phases.

Lung expansion (up to day 4): Lung volume increase resulted almost exclusively from an 87% enlargement of the existing air spaces.

Tissue proliferation (day 4 to 13): All tissue compartments showed a pronounced mass increase, followed by a high gain in capillary volume. Alveolar and capillary surface areas (Sa, Sc) developed rapidly due to subdivision of the primitive air sacs.

Equilibrated growth (third week to adult age): An initial period of redistribution of tissue mass with septal lengthening and further rapid increase in Sa and Sc was followed by proportionate alveolar growth. In the adult further lengthening of the interalveolar septa or continued alveolar formation could not be excluded.

During the period of fundamental internal remodelling of the lung, its function, as determined by the morphometric pulmonary diffusing capacity, was not impaired.
Evidence for a retinohypothalamic pathway in the golden hamster
Authors: Printz Richard H. , Hall James L.
Published: February 2005

Evidence for a direct neural projection from the retina to the hypothalamus in the golden hamster (Mesocricetus auratus) is presented. In 25 blinded animals degeneration was followed in sections prepared according to the Wiitanen ('69) silver impregnation method. Degenerative axons were found in the optic tract, chiasm, and nerve, terminating in the lateral geniculate body and superior colliculus. A large collateral bundle of degenerating axons was observed curving medially and dorsally to enter the hypothalamus at the level of the mamillary body. This bundle turned diffusely rostrally and terminated on neurons in the ventromedial nucleus of the hypothalamus.

It is proposed that two alternate pathways exist for the effect of photoperiodicity on the reproductive cycle in the hamster, one involving the pineal gland directly and the hypothalamus indirectly, and the other a direct retino‐hypothalamic projection.
The effects of diets enriched with corn oil on the ultrastructure of articular chondrocytes
Authors: Silberberg Ruth , Hasler Mary
Published: February 2005

The ultrastructure of articular cartilage of the femoral head was examined in growing male mice of strain C57Bl fed diets containing supplements of 25 or 40% corn oil for periods of 10 days, 2 and 4 weeks and 2 and 3 months. The ration containing 25% corn oil did not produce conspicuous effects. The ration containing 40% corn oil exerted a slight stimulation on the size, the ER, and the mitochondria of the articular chondrocytes. The findings are consistent with the long range effects of oil‐enriched diets on the knee joints of mice and in particular with the failure of such diets to promote the development of osteoarthrosis in mice of strain C57Bl. The results are discussed in relation to earlier observations of the injurious action of diets containing comparable amounts of saturated fat.
Direct contact between a neuron soma and myocardial cells; an electronmicroscopic finding in the sinus venosus of the turtle heart
Authors: Yamauchi Akio , Fujimaki Yoko , Kumagai Kenichi
Published: February 2005

Electron microscopy of the turtle sinus venosus shows an unusual neuron soma which is immediately surrounded by myocardial cells so as to form a somato‐muscular complex. Studies of 36 sections cut through this neuron soma indicate that 27.4% of the somal surface studied is directly covered by cardiac muscle cells without any intervening basal lamina. Similarly, 18.8% of the somal surface studied is in contact with unmyelinated axons which at places make typical axosomatic synapses. A coupling of peripheral cisterns of the sarcoplasmic reticulum and the sarcolemma exists at the somato‐muscular contiguity as well as at the border between cardiac muscle cells. It is suggested that neural influences upon the pacemaking activity of the turtle heart sinus can well be exerted through the somato‐muscular pathway. Additionally, an axon which is presynaptic to the neuron soma has been observed to be simultaneously in a synaptic relation with a cardiac muscle cell; a remarkable deviation from the classical picture of the efferent nervous outflow to the heart.
Investigations on the innervation of the human diaphragm
Authors: Hidayet M. A. , Wahid H. A. , Wilson A. S.
Published: February 2005

In 2 dogs, 5 cats and 30 human cadavers the diaphragmatic innervation has been studied macroscopically and microscopically. General findings of previous authors regarding phrenic and intercostal nerve contributions have been confirmed and subdiaphragmatic connections from the coeliac plexus to the diaphragm have been clearly demonstrated. The presence of this viscerosomatic interconnection in half of the human subjects studied, highlights the possible importance of autonomic control of diaphragmatic musculature. The finding of comparable autonomic connections in dogs raises the possibility of pursuing the question experimentally by carrying out nerve degeneration studies. In addition the matter of surgical incisions in the diaphragm has been reconsidered and the suggested placements have been illustrated.
Alterations in the epithelial surface of human palatal shelves prior to and during fusion: A scanning electron microscopic study
Authors: Waterman Robert Earle , Meller Samuel M.
Published: February 2005

The surface topography of palatal shelves was examined by scanning electron microscopy prior to and during secondary palate formation in 72 therapeutically aborted human embryos and fetuses ranging in age from 37 days to 12 weeks (post‐fertilization). Alterations in epithelial surface appearance were observed in the prospective region of fusion prior to contact between the shelves. First seen as an elliptical area along the anterior portion of the presumptive medial edge, a zone of alteration spread progressively along the anterior four‐fifths of the medial edge prior to shelf contact, and continued along the posterior one‐fifth of the shelf as fusion proceeded. The altered zone eventually extended onto the oral surface in the middle of the shelf but was restricted to a narrow zone along the medial edge posteriorly. Initially characterized by elongation and “intertwining” of superficial cells, alterations later included cell death, desquamation and possible active migration of surface cells. The shelf epithelium subjacent to the zone of alteration exhibited increased irregularity in thickness and numerous “invaginations” into the underlying mesenchyme. These alterations are thought to reflect intrinsic changes within the shelf and may play a role in the fusion process. Evidence for surface remodeling following fusion was also observed.
Loss of mitotic response of the thyroid gland to TSH in hypophysectomized rats and its partial restoration by anterior and posterior pituitary hormones
Authors: Isler H.
Published: February 2005

The follicular cells of thyroid glands of intact rats respond to TSH challenge by an intense mitotic stimulation and a higher functional activity as measured by the epithelium height. In hypophysectomized rats the same intense response was observed when the thyroid was challenged immediately after hypophysectomy. However, one week later the mitotic response was almost completely absent and the functional response much weaker. This indicates that, although TSH is the main regulating factor of the functional activity and cell proliferation of the thyroid follicle, its effect is conditioned by additional factors. These factors may originate both from the anterior and/or posterior pituitary, since a significantly higher response was obtained by injecting anterior or posterior pituitary powder during the interval between hypophysectomy and TSH challenge. Prolactin, vasopressin and oxytocin also boosted the mitotic response to TSH. Posterior pituitary powder alone (without TSH challenge) was not mitogenic for the thyroid gland either in intact or hypophysectomized rats, while it was mitogenic for the adrenal glomerulosa. The low thyroid mitotic responsiveness does not reflect a general unspecific effect on mitoses of all cells, since the esophageal epithelium was not similarly affected by hypophysectomy or by replacement therapy.
Fine structure of the adrenal gland in the duck (Anas platyrhynchos)
Authors: Cronshaw James , Holmes W. N. , Loeb S. L.
Published: February 2005

Adrenal glands of the domestic duck (Anas platyrhynchos) were fixed in formaldehyde‐glutaraldehyde for light and electron microscopical examination. Each gland is encapsulated by a layer of connective tissue and consists of two major secretory cell types, the interrenal cells and the medullary cells. In section, the medullary cells appear as islands of tissue dispersed throughout the gland. The interrenal cells are characterized by numerous lipid droplets and abundant mitochondria having mainly tubular cristae. They have an extensive Golgi apparatus, moderate amounts of smooth endoplasmic reticulum and a lesser amount of rough endoplasmic reticulum. Lipid droplets and mitochondria in interrenal cells were seen frequently in association with the endoplasmic reticulum. Adjacent interrenal cells had numerous regions of pentalaminar fusion and intermediate junctions.

Medullary cells were characterized by a large population of electron opaque neurosecretory granules. These cells contained fewer mitochondria and cisternae of endoplasmic reticulum than the interrenal cells. In many cases the medullary cells and interrenal cells were closely juxtaposed and were separated by a thin band of extracellular matrix.