bluuebunny/crossref_metadata_2025 huggingface dataset:
Autoradiographic investigation of calvarial growth in the rat
Authors: De Angelis Vincent
Published: February 2005

Results of autoradiographic investigations utilizing tritiated proline reveal an intricate mechanism of rat calvarial growth and reshaping from age two days through 75 days. Generalized intramembranous bone growth dominates the growth process from two through eight days; however, this simple bony enlargement is terminated early. At eight days a differential apposition‐resorption process begins dorsally in the calvarium and progresses rostrally within a ten day period. This process includes differential apposition on the ectocranial and endocranial periosteal surfaces accompanied by a differential apposition‐resorption pattern on the endosteal surfaces. The wave‐like process begins in the occipital bone and progresses ventrally to the frontal bone resulting in a flattening of the bony components. At 35 days bone accretion is again generalized on most calvarial surfacse. However, at 40 days another change in the growth process evolves on the occipital and frontal bones. These bones are now seemingly displaced in a superior direction as bone apposition continues on their superior surfaces, namely, the ectocranial periosteal and endocranial endosteal surfaces and resorption progresses on the two inferior surfaces. The magnitude and duration of the process described in this paper is sufficient to account for calvarial flattening in the absence of bony spatial reorientation due to bending at sutures. The findings described here when compared to proposed in vitro studies can help put the importance of the so‐called “functional matrix” related to bone growth into its proper perspective.
Cell division in injured spinal cord
Authors: Adrian Erle K.
Published: February 2005

Thymidine‐H3 radioautography was used to study the proliferative response to penetrating wounds of the mouse spinal cord. In one group of animals mononuclear leukocytes which infiltrate nervous tissue wounds were labeled by injecting thymidine‐H3 prior to injury. In two other experimental groups the cells which synthesized DNA in the nervous tissue following the injury were labeled by giving either a single injection of isotope shortly before sacrifice or by giving four injections during the 24 hours prior to sacrifice. The animals were sacrificed over a five day period following spinal cord injury. Although the labeled nuclei in all three groups were similar in appearance, their distribution about the lesion was very different. The labeled blood cells were greatly concentrated at the wound, while the cells that responded to injury by DNA synthesis were much more evenly spread throughout the tissue. When these distributions were converted to straight lines and compared statistically, there was a very low probability that the group of cells labeled before injury and the two groups labeled after injury were samples from the same population. Although mononuclear leukocytes do proliferate in and around nervous tissue wounds, other cells originally present in the nervous tissue wounds, other cells originally present in the nervous tissue must also proliferate.
Ultrastructure of granulated arteriolar cells (juxtaglomerular cells) in kidney of a fresh and a salt water teleost
Authors: Bulger Ruth Ellen , Trump Benjamin F.
Published: February 2005

Granulated juxtaglomerular cells have been identified in the media of afferent arterioles in the fresh water goldfish and in a marine English sole. Electron microscopy demonstrated the following five types of granules in the modified smooth muscle cells: (1) Small homogeneous granules near the Golgi apparatus; (2) larger homogeneous granules throughout the cytoplasm; (3) granules containing a bundle of hexagonally packed tubules; (4) autophagic vacuoles; and (5) granules containing membranous and granular debris. The granulated juxtaglomerular cells are morphologically similar to mammalian granulated cells and therefore may be the site of renin secretion. They exist with no relation to a distal tubule and hence appear to occupy an interesting position in the evolution of the juxtaglomerular apparatus.
Neurocytogenesis. I. Neurofibrils, neurofilaments, and the terminal mitotic cycle
Authors: Sechrist John W.
Published: February 2005

Initial cytodifferentiation of neuroblasts in the retina of chick embryos was investigated by means of silver impregnation, H3‐thymidine autoradiography, and electron microscopy. Utilization of various combined procedures with the same initial fixative demonstrated that the results of neurofibrillar staining are complementary, not contradictory, to information obtained from both autoradiography and electron microscopy.

The question of a homogeneous versus a non‐homogeneous cell population within the neural epithelium was clarified by the closely related appearance of neurofibrils to the terminal mitotic cycle of some presumptive neuroblasts. Neurofibrils were observed in certain apolar pre‐division cells as well as in pairs of transitional apolar and bipolar daughter cells which apparently do not remain in the neural epithelium. At the ultrastructural level, aggregates of 60 Å neurofilaments were observed in configurations that corresponded to neurofibrillar networks. As the bipolar neuroblast moves into the ganglion cell layer, it would appear that much of the neurofibrillar substance is transported within the elongating peripheral process which becomes the optic nerve fiber. Further investigation of the relationship of neurofilaments to neurotubules in the neuroblast undergoing cytodifferentiation is now in progress.
Ultrastructural studies on fetal and early postnatal mouse ovaries. I. Histogenesis and organogenesis
Authors: Odor D. Louise , Blandau Richard J.
Published: February 2005

Ovaries of fetal mice obtained during the twelfth to eighteenth day of gestation and from the first to third postnatal day have been studied by electron microscopy. The interrelationships of follicle cells to oögonia and to connective tissue cells have received special attention. On day 12, when the female gonad can first be distinguished, relatively few large oögonia are visible. These are loosely aggregated and are accompanied by only a few follicle cells.

On days 13 and 14 loose groups of oögonia become better demonstrated, and now are always surrounded peripherally by follicle cells. Beginning on day 14 very thin cytoplasmic processes of the follicle cells are interposed between adjacent oögonia. Subsequently, by following this process the follicle cells are drawn into the groups of oögonia or oöcytes. Increasing numbers of connective tissue cells and capillaries are growing into the cortex from the medulla and hilar regions. By day 18 and postnatal day 1 this ingrowth has separated the groups of oöcytes and follicle cells further. By postnatal days 2 and 3 most oöcytes have become enclosed by a follicular epithelium of either flattened, cuboidal or columnar cells. Many stages of zona pellucida formation can be recognized. It is postulated that the manner of fetal and early postnatal differentiation of the ovary explains a number of follicular configurations which deviate from the normal. At no time have cords of cells been observed to originate from germinal epithelium. By contrast the underlying tunica albuginea is derived by ingrowth of cells from the medulla.
Origin and renewal of goblet cells in the epithelium of the mouse small intestine
Authors: Merzel J. , Leblond C. P.
Published: February 2005

The epithelium of duodenum, jejunum and ileum was investigated in adult female mice given an injection of3 H‐thymidine and sacrificed at times varying from one hour to 14 days later. The tissues were fixed by perfusion with paraformaldehyde and embedded in Epon. One micron thick sections were cut singly or serially, radioautographed and stained with iron hematoxylin and safranin O. In addition, reconstruction of a crypt was made from serial sections of jejunum.

The reconstruction of a crypt shows the well known columnar, goblet, Paneth, and argentaffin cells. There are also little known cell types referred to as oligomucous and granulo‐mucous and pale cells with or without mucus. Of these cells, the only numerous ones are the oligomucous cells, which are located in the lower half of the crypts and contain a few or even only one mucous globule. In the electron microscope, they display long cisterns of rough endoplasmic reticulum parallel to the lateral cell membrane and similar to those observed in goblet cells.

In radioautographs of the crypts neither goblet cells, nor Paneth cells, nor argentaffin cells show mitosis or label one hour after3 H‐thymidine injection. Granulo‐mucous and pale cells are only rarely labeled. In contrast, columnar and oligomucous cells frequently take up label and undergo mitosis. By 12 hours after injection labeled goblet cells have appeared. Since at that time 3 H‐thymidine has left the circulation, the label must have been acquired by transformation of labeled columnar or oligomucous cells. Furthermore, since transitional forms between oligomucous and goblet cells are common, it is concluded that oligomucous cells are those which directly transform into goblet cells.

Eventually, like columnar cells, labeled goblet cells migrate to the villus epithelium, climb to the villus tip and fall into the lumen.

Although oligomucous cells fit the requirements for goblet cell precursors, not enough of them are labeled to account for the rate of renewal of goblet cells. It is therefore speculated that some undifferentiated columnar cells at the base of the crypts participate in the production of oligomucous cells, which in turn yield goblet cells.
Radioautographic studies of glycogen synthesis in the striated muscle of rat tongue
Authors: Coimbra Antonio
Published: February 2005

Glycogen synthesis was studied in rat tongue striated muscle after administration of 3H‐glucose using light and electron microscope radioautography. Neither fasting nor addition of unlabeled glucose were needed to produce incorporation of 3H‐glucose into glycogen, the only radioactive substance found in the tissue. Intense radioautographic reactions indicating glycogen synthesis were already seen 20 minutes after injection and were preferentially located over glycogen accumulations in the intermyofibrillar spaces. A striking variation of silver grain density from fiber to fiber, was a somewhat unexpected finding in a muscle consisting of fibers of uniform metabolic type. Decrease in grain counts at the 90‐minute interval suggested a rapid turnover of muscle glycogen. In agreement with this, there were no morphological signs of glycogen accumulation on glucose administration. PA‐Schiff staining, as well as the number of glycogen granules in electron micrographs, did not increase, nor did granule diameters change significantly during the experiment. Electron microscope radioautographs showed all silver grains to be located over or very near glycogen granules and sarcoplasmic spaces. While all newly‐formed glycogen seemed associated with preexisting granules, there was no evidence for the participation of the sarcoplasmic reticulum in glycogen synthesis.
Origin and early migration of primordial germ cells in the chick embryo: A study of the stages definitive primitive streak through eight somites
Authors: Clawson Robert C. , Domm L. V.
Published: February 2005

The germinal crescent in the chick embryo is characterized by small, PAS‐positive, nonglycogen granules from 1.5 to 5 μ in diameter. The primordial germ cells (PGCs) were found to originate in and separate from the germinal crescent endoderm through stage 7 (2 somites). Shortly after separation most of the granules in the PGCs lost their organization and the PAS‐positive material was distributed irregularly throughout the cytoplasm. A few of these granules remained within the cells indefinitely. Glycogen of an agranular nature which had shifted to one pole of the cell was observed at stage four. Granular glycogen which was distributed throughout the cytoplasm was not observed prior to stage 7 or 8.

Cell counts on individual embryos showed noticeable variations as to the number of germ cells between embryos of the same stage. For example, in stage 4 embryos the minimum number of cells counted, including attached and free, was 78 and the maimum 169, while in stage 9 the minimum was 83 and the maximum 469 cells. After separation the germ cells were observed almost anywhere between the ectoderm and the endoderm although the majority remained in the area where they originated.
The dermal chromatophores of Anolis carolinensis (reptilia, lguanidae)
Authors: Alexander Nancy J. , Fahrenbach Wolf H.
Published: February 2005

Skin of the back, belly, dewlap and parietal eye were studied as illustrations of the principal variations of chromatophore arrangement and color range present in Anolis carolinensis. The fine structure of the chromatophores, disposed in sharply stratified layers, was investigated. The most superficial chromatophore layer consists of xanthophores, which impart a greenish‐yellow color to the skin. These cells are filled with two types of membrane‐bounded inclusions containing pteridines and carotenoids, respectively. Basal to the xanthophores is a 2–4 cell‐deep layer of iridophores. These cells are filled with undulating layers of birefringent rodlets, presumably guanine, arranged parallel to the skin surface. The most basal chromatophores are large melanophores, positioned above a thick collagenous basement lamella. Migration of melanin granules into the dendritic processes, which terminate at the dermoepidermal junction, cause the lizard to change from green to brown. The back skin, which ranges in color from bright green to brown, contains the full complement of dermal chromatophores. The xanthophore region is much reduced in the cream‐colored belly. The dewlap, which is bright red when extended, bears a thick layer of iridophores through which are scattered melanophores, and erythrophores containing red pigment. The dermis over the parietal eye contains only xanthophores and a basement lamella.
Innervation of the abdominopelvic ureter in the cat
Authors: Elbadawi Ahmad , Schenk Eric A.
Published: February 2005

The distribution of cholinergic and adrenergic nerves in the cat ureter was studied by specific histochemical techniques for acetylcholinesterase and norepinephrine. The innervation of the ureter is characterized by (1) a generalized dual cholinergic and adrenergic nerve supply, (2) the presence of muscular innervation, (3) a continuity of terminal muscular and vascular nerves, (4) a widespread distribution of ganglion cells except in the pelviureteric area and (5) regional variations in the density of both cholinergic and adrenergic elements.

On the basis of these findings, it is suggested that in the cat ureter peristalsis has a myogenic origin in the proximal end of the ureter, but its distalward propagation along the abdominal and pelvic segments is controlled by a dual sympathetic and parasympathetic influence which is mediated in part through a system of intrinsic ureteric ganglion cells.
The fine structure of the human corpus luteum of early pregnancy and during the progestational phase of the menstrual cycle
Authors: Crisp Thomas M. , Dessouky Dessouky A. , Denys Francis R.
Published: February 2005

The fine structure of granulosa lutein cells and theca lutein cells of human corpora lutea of early pregnancy and during the progestational phase of the menstrual cycle (i.e., 1 day, 7 days and 9 days after estimated ovulation) is described. Granulosa lutein cells of early pregnancy are distinguished from theca lutein cells in having: (1) a more homogeneous, electron‐lucent nuclear matrix, (2) enlarged pleomorphic mitochondria with irregularly‐shaped, osmiophilic inclusions, (3) numerous isolated regions of the Golgi complex, (4) abundant whorls of granular and agranular endoplasmic reticulum, (5) a folded‐membrane complex, (6) numerous bundles of 50 Å filaments and (7) patches of elongated microvilli bordering intercellular and intracellular canaliculi.

Furthermore, granulosa lutein cells of early pregnancy are distinguished from granulosa lutein cells of corpora taken during the progestational stage of the menstrual cycle by the greater abundance of granular and agranular endoplasmic reticulum, the presence of concentric membranous whorls and large spherical mitochondria, increases in membrane‐bound granules and a more extensive development of intracellular canaliculi. These differences are related to the high titers of serum gonadotrophin (s) during early gestation.

The morphology of human corpora lutea is compared with steroidogenic tissues of other species and is correlated with the capacity of human corpora lutea to synthesize estrogens in addition to progestogens. Based upon morphological evidence, it is suggested that in addition to elaborating steriod hormones, corpora lutea may also secrete a proteinaceous product, perhaps relaxin.

This work was presented as a demonstration to the eighty‐second annual session of the American Association of Anatomists in April, 1969. An abstract has been published (Anat. Rec., 163: 336, '69).
Origin and distribution of portal blood in the cat and the rabbit
Authors: Heath Trevor , House Brian
Published: February 2005

The portal vein in the rabbit is formed by union of the gastrosplenic vein, which extends caudally and to the right, and the relatively larger and cranially directed mesenteric vein, formed from cranial and caudal mesenteric and caudal pancreaticoduodenal tributaries. The gastroduodenal vein, which receives blood from the distal pylorus, greater omentum, pancreas and duodenum, joins the rabbit portal vein opposite the branch to the caudate lobe. In the cat, the portal vein is formed by the junction of the gastrosplenic, which is directed transversely or cranially, and the mesenteric, and receives two main tributaries: the gastroduodenal, which is the main vein from the stomach, and the cranial pancreaticoduodenal.

When 131I‐rose bengal was injected into the spleen of conscious standing cats and entered the portal vein in the gastrosplenic, it was distributed preferentially to the right branch and the left lateral ramus of the left branch. In the rabbit, there was no evidence for preferential distribution of splenic blood, but blood from the cranial mesenteric vein was distributed preferentially to the right and caudate branches and that from the caudal mesenteric to the caudate. This distribution was affected by the entry of blood in the gastrosplenic vein. Although statistically significant differences did occur in the intrahepatic distribution of blood derived from the portal tributaries, the absolute differences were small.
Morphology and histochemistry of the soleus muscle from normal and exercised rats
Authors: Edgerton V. Reggie
Published: February 2005

Sixty white rats were divided into three groups which consisted of (1) rats individually housed in cages having dimensions of 24 × 18 × 18 cm, (2) rats housed in similar cages and forced to swim for 30 minutes a day with a weight equal to 3% of body weight, and (3) rats housed in individual cages equipped with a revolving drum permitting each rat to exercise at will. The third group was also forced to swim for two 30‐minute periods each day with a weight equal to 4% of body weight attached to the tip of the tail. The experimental treatments lasted for a period of 52 days. The rats were exercised six days per week. The day after the final treatment, the left soleus, plantaris and gastrocnemius muscles were removed, frozen, and serial sections treated with a variety of histochemical and histological procedures.

Necrotic, angular and split fibers were observed in the soleus muscle but not the gastrocnemius and plantaris of sedentary, moderately exercised and heavily exercised rats. These features were characteristic of the seemingly normal soleus of sedentary and chronically exercised rats and were not manifestations of any apparent myopathy. No difference was found in the number of fibers that were longitudinally split. However, the number of fibers (“subfibers”) resulting from split fibers was greater in the moderately exercised than in the sedentary rats, but greatest in the heavily exercised group.
Selective inhibition by chloramphenicol of ACTH‐induced reorganization of inner mitochondrial membranes in fetal adrenal cortical cells in tissue cultures
Authors: Kahri Arvi I.
Published: February 2005

Tissue cultures of fetal rat adrenals were used to study effects of chloramphenicol on the ACTH‐induced synthesis of mitochondrial inner membranes in the cortical cells. Chloramphenicol alone added to the culture medium in concentrations of 0.003, 0.03, 0.3, and 0.6 μ mole/ml/6 days induced no changes in the ultrastructure of cortical cells. Chloramphenicol in concentrations of 0.3 and 0.6 μ mole/ml/6 days given together with 100 mu/ml/6 days of ACTH inhibited completely the ACTH induced changes of mitochondrial inner membranes (formation of 600 Å vesicles). Chloramphenicol in concentrations of 0.003 μ mole/ml/6 days caused no inhibition of the ACTH effects. In concentration of 0.03 μ mole/ml/6 days chloramphenicol resulted in incomplete inhibition of ACTH‐induced formation of mitochondrial vesicular cristae. None of these doses of chloramphenicol affected other ACTH‐induced changes in the fine structure of the cells such as increase of smooth surfaced endoplasmic reticulum, hypertrophy of Golgi apparatus, and development of microvillous processes of plasma membranes. Chloramphenicol also caused no inhibition of the ACTH‐induced accumulation of lipid in the cytoplasm. In cultivated cortical cells of Charles River strain albino rats small groups of annulated lamellae are commonly observed.

The present observations suggest that: (1) the development of mitochondrial inner membranes is dependent, at least in part, on mitochondrial protein synthesis; (2) ACTH stimulation of mitochondrial protein synthesis in cortical cells is independent of ACTH‐induced stimulation of nuclear‐DNA‐dependent protein synthesis; (3) doses of chloramphenicol which inhibit specialization of mitochondrial inner membranes of fetal adrenal cortical cells are comparable to those which inhibit protein synthesis in bacteria.
Cytological studies on normal and surviving mast cells in vitro
Authors: Padawer Jacques
Published: February 2005

Cytological features of rat peritoneal fluid mast cells are studied to advantage with differential interference contrast optics (Nomarski System). These cells are particularly sensitive to handling; they rapidly undergo a variety of cytological changes which, in the literature, repeatedly have been interpreted as reflecting physiological activity related to mast cell secretory function. These interpretations are hereby questioned and, alternately, it is suggested that the changes are agonal ones and that an absorptive function must at least be considered.

Some cytological features not detectable with conventional optics are described. The special optics were combined with time‐lapse cinematography and dynamic records were obtained. These support the concept, advanced elsewhere, that sets of mast cell granules are confined within a common membranous sac and that each such set may behave as an independent physiological unit.
The development of the retina of the albino rat
Authors: Braekevelt Charlie R. , Hollenberg Martin J.
Published: February 2005

Morphogenesis of the retina of the Sprague‐Dawley albino rat was studied by light microscopy from day 11 of gestation until 225 days after birth. A quantitative analysis during development of retinal volume, thickness of the entire neural retina and thickness of each of the retinal layers, both posteriorly and peripherally, was made. The results indicate that initially a single neuroblastic layer forms and continually thickens by mitosis at its outer border. The retinal layers then form in sequence, moving from the inner retinal border outward and always beginning posteriorly and then spreading peripherally. The transient layer of Chievitz does not appear. All adult layers are present by eight days after birth and each layer thins after reaching its maximal thickness. Total thickness of the retina excluding pigmented epithelium, is greatest on postnatal day 5, but retinal volume only reaches a peak on postnatal days 7 to 12. The nerve fiber, inner plexiform, outer plexiform and bacillary layers all continue to increase in thickness after the ganglion cell and inner and outer nuclear layers reach their maximal width and are beginning to become thinner.
The fine structure of the guinea pig visceral yolk sac placenta
Authors: King Barry F. , Enders Allen C.
Published: February 2005

The structure of the guinea pig visceral yolk sac from 26 days of gestation to term was studied by transmission and scanning electron microscopy. Particular emphasis was placed on the columnar endoderm cells of the villous portion of the yolk sac. The apical cytoplasm of the endoderm cells contained numerous membrane invaginations, endocytic vesicles, dense tubules and large vacuoles which appeared to form an interrelated absorptive system. The saccular invaginations of the apical cell membrane were specialized by the development of both an amorphous extracellular coat and an internal coat. Both the endocytic vesicles and dense tubules were thought to be derived from the saccular invaginations following detachment of the latter from the cell surface — the endocytic vesicles forming by fusion of saccules creating progressively larger structures, and the dense apical tubules forming by a process involving fluid loss from the saccules. Large vacuoles were present deeper in the apical cytoplasm; these probably were formed by fusion of smaller vesicles. The supranuclear cytoplasm contained numerous dense droplets and a Golgi zone. The possible relationships of the droplets to the vacuoles was discussed.
Granulated vesicles in sympathetic nerve endings in the pineal gland: Observations on the effects of pharmacologic agents by electron microscopy
Authors: Duffy Philip E. , Markesbery William R.
Published: February 2005

The effects of pharmacologic agents upon granulated vesicles in the sympathetic nerve endings of the pineal gland were studied electron microscopically. The most common granulated vesicle measures 400 Å and has an eccentric granule (Type IA); a few vesicles are as large as 1000 Å (Type IB). The vesicles also contain fine grains which may be the subunits of which the granules are composed. Reserpine causes many vesicles to become elliptical, raising the possibility of an effect upon the vesicle membrane. Depletion of granules by reserpine is confirmed and fine grains are also depleted. p‐Chlorphenylalanine, which reduces serotonin concentration, causes a reduction in number of granules but leaves fine grains. p‐Chlorphenylalanine followed by pargyline, induces a reduction in number of granules but a considerable number are present suggesting persistence or re‐accumulation of norepinephrine or other catecholamines. Oxypertine and desmethylimipramine (DMI) deplete granulated vesicles but fine grains remain. Another kind of granulated vesicle has a different ultrastructure than the Type IA and IB and measures 1000 Å (Type II). This kind of granulated vesicle is not depleted by reserpine, p‐chlorphenylalanine, oxypertine or desmethylimipramine suggesting that it contains neither catecholamines nor serotonin.
Efferent projections of the ventral anterior nucleus of the thalamus in the monkey
Authors: Carmel Peter W.
Published: February 2005

Efferent projections of the ventral anterior (VA) thalamic nucleus were investigated in 20 monkeys. In half of these animals degeneration was traced following stereotaxic lesions in the magnocellular (VAmc) or parvocellular (VApc) portions of the nucleus. Chronic cell changes in the VA nucleus were studied following various cortical ablations in the remaining animals.

Stereotaxic lesions in the VA nucleus produced extensive subcortical degeneration (Nauta or Marchi stains). Within the VA nucleus was a dense pattern of degenerated fibers, largely oriented in the sagittal plane. Fibers from the VAmc nucleus projected laterally into the VApc nucleus. Numerous caudally directed fibers arose in the VA nucleus and projected intrathalamically to the rostral intralaminar and parafascicular nuclei. Fibers also entered portions of the centromedian and dorsomedial nuclei. Rostrally directed fibers from the VA nucleus entered the anterior limb of the internal capsule and were distributed widely to the frontal lobe cortex. Rostral projections from the medial VA (VAmc) nucleus were, in part, localized to a portion of the orbitofrontal cortex.

Degeneration was absent or sparse in other ventral tier thalamic nuclei, and no degeneration was seen in the striatum, pallidum or insular cortex.

Restricted cortical lesions in area 4, area 6, orbital cortex, medial frontal cortex, or insular cortex produced no cellular alteration in the VA nucleus. Large lesions involving several frontal cortical areas resulted in cellular changes, which were not as severe as in the adjacent ventrolateral nuclei; after extensive ablations approximately half of the VA cells remained normal.

The VA nucleus appears to be an important link in the thalamic nonspecific system. Efferent projections reach both the nonspecific thalamic nuclei and widespread areas of frontal cortex.
Ultrastructural studies of cleavage stage t12/t12 mouse embryos
Authors: Hillman Nina , Hillman Ralph , Wileman Geraldine
Published: February 2005

A statistical study of embryos obtained from both spontaneously ovulated and superovulated +/t12 females, mated inter se, shows that the range of the lethal phenocritical period of the t12 allele in a homozygous condition is from the 8–12 cell stage to the early blastocyst stage. The majority of t12 homozygotes are developmentally arrested as late morula and the nuclei of these embryos contain lipid droplets and fibrillo‐granular bodies. These same inclusions are found in other t12 embryos which are developmentally arrested either earlier or later than the late morula stage and distinguish 30–40% of the embryos (presumably t12 homozygotes) from their litter‐mates at the 2‐ and 4‐cell stages. Ultrastructural‐cytochemical studies of the fibrillo‐granular bodies show that the fibrillar areas are sensitive to pepsin and the granules to ribonuclease and are thus structurally and chemically similar to definitive nucleoli. Binucleate cells are also present in a high frequency of t12 homozygous embryos. This condition is considered an additional phenotypic expression of the genotype.

Prior to developmental arrest, the nuclear and cytoplasmic organelles of t12 embryos do not differ from those of similarly staged litter‐mates or control +/+ embryos. Homozygous mutant embryos examined shortly following developmental arrest contain cells ranging from structurally normal to degenerative. Asynchronous cell death is common to all t12 homozygous embryos. A chronological description of degenerative cellular changes is presented.
The fine structure of the stannius body of the guppy and its response to deionized water
Authors: Tomasulo Joseph A. , Belt W. Duane , Hayes E. Russell
Published: February 2005

The Stannius corpuscle of the guppy, Lebistes reticulatus, was studied with light and electron microscopy. The relation of the cells to the rich vascular supply is described. The fine structure of the parenchymal cells is consistent with protein synthesis. When animals were subjected to an environment depleted in mineral content, the cells of the Stannius corpuscle showed striking alterations: a prominent swelling of the cisternae of the endoplasmic reticulum and perinuclear cisternae, a reduction in the electron‐opaque material within the Golgi saccules, the appearance of intramitochondrial granules, and vacuolization of the secretory granules. The role of the Stannius body in osmoregulation is discussed.
Innervation of the avian tonus latissimus dorsi anterior muscle
Authors: Hikida Robert S. , Bock Walter J.
Published: February 2005

The motor and cutaneous nerves associated with the pigeon's anterior latissimus dorsi tonus muscle are described. The motor nerve is traced from its origin within the brachialis longus superior nerve of the brachial plexus to within the epimysium of the muscle by means of serial cross sections. The nerve fibers differ in mean diameter at various sites along the nerve. They originate as small fibers within the plexus, become larger as they emerge and then gradually decrease in diameter as they approach the muscle. The number of nerve fibers remains relatively constant until the nerve divides into more than two branches, at which time the number increases.

The cutaneous nerve passing through the anterior latissimus dorsi is described and is assumed not to play any role in the innervation, either sensory or motor, of the fibers in this muscle.
The fine structure of perinotochordal microfibrils in control and enzyme‐treated chick embryos
Authors: Frederickson Richard G. , Low Frank N.
Published: February 2005

Microfibrils in the notochordal sheath of chick embryos of two to four days incubation age were analyzed electron microscopically. Collagenase, trypsin, hyaluronidase and alpha amylase were administered to both “living” and “fixed” embryos. Living embryos were either explanted on an agar‐albumen growth medium or were allowed to survive within the shell during experimental procedures. Fixed embryos were immersed in Karnovsky's aldehyde fixative prior to enzyme digestion. Both living and fixed specimens yielded similar results.

Control embryos possessed microfibrils of ca. 200 Å, ca. 100 Å and less than 100 Å in diameter in the notochordal sheath. The smaller fibrils (100 Å and less) were present in all regions of the sheath, but were especially concentrated near the notochordal boundary (basement) membrane. The larger fibrils (200 Å) were farther removed from the notochord. Flaky amorphous material was attached to all fibrils and was abundant especially in the inner region of the sheath.

Collagenase produced elimination of the 200 Å microfibrils, but the smaller ones remained intact. Trypsin caused digestion of all fibrils. Hyaluronidase digested fibrils chiefly 100 Å and less in diameter. Alpha amylase was similar to hyaluronidase in digesting the small fibrils. This study supports the hypothesis that microfibrils are primarily mucopolysaccharide‐protein precursors of larger collagen‐rich fibrils.
Morphologic evidence that the renal calyx and pelvis control ureteric activity in the rabbit
Authors: Gosling J. A. , Dixon J. S.
Published: February 2005

The structure of the renal calyx, pelvis and upper ureter has been investigated in the adult rabbit. The methods employed for light microscopy were designed to demonstrate smooth muscle, cholinesterase and catecholamine‐containing nerves, elastic and collagenous fibers, and glycogen. Selected areas of the upper urinary tract were also examined using the electron microscope. The wall of the calyx and pelvis includes two layers of muscle cells the inner one of which appears to be continuous with the muscle coat of the ureter. The external layer extends across the renal pelvis from the calyx and ends abruptly in the pelvi‐ureteric region. In some regions cells from this layer run towards and intermingle with the muscle of the inner layer. The muscle cells forming the outer layer are associated with many adrenergic nerves which run in the connective tissue separating individual muscle cells. Numerous elastic fibrils are closely related to these cells which usually contain glycogen. In contrast, the muscle cells forming the inner layer of the pelvis and those of the upper ureter have a relatively poor innervation, are closely packed together without intervening connective tissue, and are usually devoid of glycogen. These observations provide structural evidence in support of the concept that specific regions of the renal calyx and pelvis influence and possbily control the activity of the ureter.
The fine structure of fungiform papillae and epithelium of the tongue of a South American toad, Calyptocephalella gayi
Authors: Stensaas L. J.
Published: February 2005

The epithelium covering the surface of the tongue of the South American toad Calyptocephalella gayi has been analyzed using large electron microscope photo‐montages and has been compared with that covering the tongue of the frog, Rana pipiens. In both species four kinds of epithelia are similarly distributed over the surface, and relatively minor differences in the cytoplasm and intercellular relations have been identified. Stratified ciliated epithelium covers the ventral, nonpapillary surface. A simple columnar epithelium of mucous cells covers most of the irregular dorsal surface. A poorly stratified nonkeratinizing epithelium covers the apex of filiform papillae while stratified, columnar epithelium forms the thick epithelial disc of fungiform papillae. Emphasis is given to fungiform papillae as the basis for functional studies since they are the only structures receiving large numbers of nerve fibers. Sensory terminals do not appear to be acted on directly by chemicals since they are located near the base of the epithelium and since tight junctions unite cells at the outer surface. However, axons selectively contact the base of certain elongate cells which extend to the surface and are presumed to be receptor cells. It seems probable that recent intracellular potential changes, recorded from the toad tongue in response to chemical stimulation, originate from mucous cells. It is suggested that these potentials could affect the receptor cells if low resistance pathways are provided by tight junctions.
Interrelationships between cornification and cell migration of fetal rat epidermis in vitro
Authors: Schwartz J. , Stern I. B.
Published: February 2005

Samples of dorsal skin were obtained from 18‐, 19‐ and 20‐day rat fetuses. Comparative developmental studies were carried out from a portion of the samples, while the remaining samples were cultured for four days in a medium containing tritiated thymidine and studied autoradiographically.

At 18 days the epidermis contained a periderm, a stratum intermedium and a stratum basale. By 19 days the strata granulosum and spinosum had developed. At 20 days, a stratum corneum was present. Cultured samples of 18‐day fetal rat skin resembled those that developed in utero with respect to time, whereas, the samples of 19‐ and 20‐day fetal rat skin developed a more extensive stratum corneum, fewer keratohyalin granules, and a more condensed stratum Malpighii.

Autoradiographic studies were made to determine the time taken for cells to migrate from the stratum basale to the outermost layer of the stratum granulosum (transit time). A similar “transit time” was noted for the three fetal ages studied. The rates of cell migration varied. The results of this study suggest that the extent of cornification impedes cell migration by providing a physical resistance or barrier against the outward forces presumably exerted by the division of basal cells.
The ultrastructure of lymphatic valves in rabbits and mice
Authors: Takada Mitsuya
Published: February 2005

The ultrastructure of lymphatic valves was studied in rabbits and mice. The lymphatic valves usually consist of two cusps but three or four are sometimes present. The cusps are covered by endothelium. Along the free edge of the cusps are endothelial cells which can differentiate morphologically from other endothelial cells. They are named “tip‐cells”; they have pseudopod‐like projections and abundant cytoplasmic filaments 60–90 Å in diameter. Vesicles occur in endothelial cells of both lymphatic vessels and their valves; they are on the luminal or connective tissue side and are never provided with a diaphragm like that frequently observed in blood vessels. Joining endothelial cells are zonulae occludentes but desmosomes are not observed. No open intercellular junctions are encountered along the valvular endothelium. A basement membrane (basal lamina) is more frequently observed in valves than in walls of lymphatic vessels. Connective tissue in the cusps consists of collagenous fibrils, fine filaments and fibroblasts.
Slow muscle fibers in the tensor tympani muscle of the guinea pig
Authors: Seiden David
Published: February 2005

The tensor tympani muscle of the adult guinea pig was studied by light and electron microscopy. Extrafusal muscle fibers with centrally located nuclei were found. On the basis of morphological criteria, they were considered to be slow muscle fibers and others, with typical peripheral nuclei, twitch muscle fibers.
Atrioventricular node and purkinje fibers of the guinea pig heart
Authors: Kim Sangsin , Baba Nobuhisa
Published: February 2005

The ultrastructure of the atrioventricular node and Purkinje fibers of the guinea pig heart was studied. The atrioventricular node consists of slender, irregularly shaped muscle cells which are arranged in a complex network with frequent interdigitation. Nodal cells contact with each other by means of many desmosomes (maculae adherentes) and rare intercalated discs that contain short nexal regions (gap junctions). The Purkinje fibers are much larger and show less cellular interdigitation than the fibers of the atrioventricular node. Desmosomes are infrequent but there are many intercalated discs with rather a long nexus between the Purkinje fibers. The T‐system is not present in the atrioventricular node or in the Purkinje fibers. The most pronounced morphological differences between the atrioventricular node and Purkinje fibers are the size of the cells and the mode of intercellular connection, which may be related to different conduction velocities in these two regions.
Microscopy of the neonatal line in developing human enamel
Authors: Weber Dennis F. , Eisenmann Dale R.
Published: February 2005

The neonatal line in developing human primary teeth was examined by means of phase contrast microscopy, microradiography and transmission electron microscopy. When thin sections were observed by light microscopy, the lateral dimensions of the line were not as extensive as had been previously reported. The line had a “staircase” configuration and appeared to be identical to published light micrographs of the stria of Retzius. On radiograms, the lateral extent of the hypomineralization was also decreased. The ultrastructural basis for the neonatal line appeared to be a localized change in configuration of enamel prisms along with a possible reduction in crystal concentration. The possibility that some rods actually end at the line could not be excluded, however.
A fine structural study of divalent cation‐mediated epithelial union with connective tissue in human oral mucosa
Authors: Scaletta Lawrence J. , MacCallum Donald K.
Published: February 2005

Following incubation in an isotonic saline solution containing 20 mM EDTA, human oral mucosa may be separated into its epithelial and connective tissue components. Ultrastructural study of the separated tissues reveals that the plane of separation is through the lamina lucida. Hemidesmosomal structure is altered by the separation process: the peripheral density is absent but a fine, generally filamentous material remains associated with the outer membrane leaflet of the hemidesmosome. Desmosome structure is not altered. An intact lamina densa remains attached to the connective tissue fragment. Oral mucosa incubated in EDTA‐saline containing calcium, or its return to a divalent cation‐supplemented medium after treatment with EDTA, prevents separation. By maintaining the structural integrity of the hemidesmosome, divalent cations appear to play a principal role in uniting oral mucosal epithelium to the lamina propria.
Cellular modification of interrenal tissue induced by corticoid therapy and stress in three avian species
Authors: Bhattacharyya Tapan K. , Ghosh Asok
Published: February 2005

Corticotropic regulation of the interrenal tissue was explored in three avian species (quail, parakeet and myna) by application of dexamethasone therapy and stress. In response to corticoid administration, atrophy of all cortical layers from periphery to center was pronounced and no regional differences could be detected by histology and histometric analysis. Following exposure to acute formalin stress at the termination of chronic corticoid therapy, the interrenal tissue regularly responded by hypertrophy in all three types of birds. The absence of zonation in experimental atrophy in these species merits consideration in view of the zonal response observed in other avian species. The prompt response of the atrophic interrenal gland to stress indicates that the hypothalamo‐hypophyseal regulation of the interrenal gland is qualitatively different from mammals.
A comparison of freeze‐substitution with other methods for preservation of the pulmonary alveolar lining layer
Authors: Kuhn Charles
Published: February 2005

Rapid freezing of expanded lungs and freeze‐substitution in acetone containing OsO4 partially preserved the pulmonary alveolar lining layer for electron microscopy. The lining layer consisted of granular or flocculent material with a surface film at its interface with the air. It filled the spaces between protruding capillaries and other depressions in the alveolar wall. It is unlikely that this lining material is an artifact resulting from transfer of fluid during freezing because similar results were obtained after fixation by vascular perfusion and by immersion of the intact, air‐filled lung in aqueous fixatives containing glutaraldehyde.
Presence of connections between follicles in juvenile mouse ovaries
Authors: Merchant Horacio , Zamboni Luciano
Published: February 2005

Ovaries of 1 to 12 day‐old mice contain multilaminar follicles connected by tubular formations of granulosal cells. Conjoined follicles appear to be at synchronized stages of maturation. It is probable that the development of these interfollicular connections, which form during fetal stages of ovarian morphogenesis, is related to the presence of intercellular bridges between primordial germ cells.
The pituitary gland of the musk shrew, Suncus murinus L. (insectivora), with special reference to the cytology of the adenohypophysis
Authors: Naik D. R. , Dominic C. J.
Published: February 2005

The pituitary gland of the musk shrew, Suncus murinus L. was studied with special reference to the cytology of the adenohypophysis. In addition to the agranular cells (chromophobes), seven morphologically and tinctorially distinct chromophilic cell types (four mucoid and three acidophilic) were observed in the pars anterior. These cells have been tentatively named as types one to seven. On the basis of their morphology, topography and staining reactions, cells of types one to six were compared, respectively, with the TSH, FSH, ICSH (LH), LTH (prolactin), STH and ACTH cells of other mammals. The identity of type 7 cells could not be determined. Although mucoid cells (types 1, 2) are more concentrated in the rostroventral region of the pars anterior, a definite “zona tuberalis” seems to be lacking.

Since the musk shrew is not a seasonal breeder, the gonadotropic cells (types 2, 3) of the adenohypophysis do not seem to fluctuate in structure during the different times of the year. However, conspicuous hypertrophy, hyperplasia and intense secretory activity of type 4 cells during pregnancy and lactation reinforces the postulation that these cells are lactotropic in function.

Follicular cysts and colloid in the residual cleft were observed in a few instances. Their possible origin and significance are discussed.
Truncus arteriosus malformation in a human embryo
Authors: Maron Barry J. , Hutchins Grover M.
Published: February 2005

Malformation of the heart and great vessels in a human embryo of 23‐mm crown‐rump length (Horizon XXII) is described on the basis of reconstruction of serial sections. A type I truncus arteriosus malformation with right aortic arch and absent ductus arteriosus was present. The left ventricle was anterior and lateral to the right. It is postulated that the malposition of the ventricles produced an abnormal relationship of the outflow blood streams which led to the truncus arteriosus malformation.