bluuebunny/crossref_metadata_2025 huggingface dataset:
An analysis of Tomes' granular layer
Authors: Ten Cate A. R.
Published: February 2005

Seventy‐five‐ to one‐hundred‐micron slices of undemineralized human teeth were examined by transmitted light, incident light and polarized light microscopy, to determine the nature of Tomes' granular layer in root dentine. Transmitted light examination showed that the granules occupied differing levels within the section. Incident light microscopy showed that the granules were true spaces and polarized light microscopy showed that fibre orientation was not the cause of the granular layer. When thin sections (1 μ‐0.75μ) of a tooth slice containing Tomes' granular layer were examined by light and electron microscopy no evidence of any spaces were found in the region where they had been demonstrated in the thick 75‐100 μ section. Looping of the terminal portions of the dentinal tubules was found. A model system has been used to show that sectioning of this loop region could produce a space visible in thick sections and corresponding to a granule of Tomes' layer. It is suggested that this looping of dentinal tubules in root dentine, and not in the dentine beneath enamel, is the result of different rates of dentine deposition in these two areas.
Prolonged survival of fragments of liver transplanted to an ectopic site in the mouse
Authors: Seller Mary J.
Published: February 2005

Fragments of liver were successfully transplanted to an ectopic site in the kidney cortex of the mouse. Survival was followed for varying periods of time. In some cases both syngeneic grafts and allogeneic grafts placed in mice previously made immunologically tolerant to the genotype of the donor were still alive one year later. However, extensive amounts of liver tissue would not survive, at the best, strips of about 30 cells thick grew, and various measures tried to promote an increase in this amount were not successful.
The specialized lingual papillae of Tachyglossus aculeatus I. Gross and light microscopic features
Authors: Doran G. A. , Baggett H.
Published: February 2005

The tongue of the echidna, Tachyglossus aculeatus is divided structurally and functionally into two distinct parts; a free rostral portion covered by stratified squamous epithelium bearing filiform papillae and a fixed caudal portion formed by a trapezoidal pad which bears highly specialized keratinized spines. These spines are similar in their morphology to the horny teeth of the living cyclostome Myxine and the hard keratin of rat filiform papillae.

The gross and light microscopic structure of the lingual spines is described and their use as a masticatory organ (by occlusion with a similar set of spines on the palate) is discussed in relation to the animal's diet and method of feeding.
Tissue interactions between epithelium and mesenchyme of urogenital and integumental origin
Authors: Cunha Gerald R.
Published: February 2005

Trypsin‐separated epithelia and mesenchyme were prepared from the following urogenital and integumental tissues of embryonic mice: seminal vesicle, urogenital sinus, preputial gland, and back, snout, and plantar surface foot plate skin. These components were rejoined in control (homotypic) and experimental (heterotypic) recombinants and were subsequently grown for one to three weeks as intraocular grafts to adult male hosts. Grafts of intact rudiments provided additional control data.

In heterotypic recombinants composed of urogenital epithelia (urogenital sinus or seminal vesicle) and integumental mesenchyme (back, snout, or plantar), the epithelium responded as if androgens were absent, i.e., urogenital sinus epithelium formed a keratinized structure, while seminal vesicle epithelium developed into a small tubule of columnar epithelium. On the other hand, plastic integumental epithelia (snout or plantar) was transformed by urogenital mesenchyme of the urogenital sinus or seminal vesicle into a glandular epithelium characteristic of the mesenchymal source. Similarly, the normally glandular preputial gland epithelium could be induced to form keratinized, hair‐bearing skin by back and snout skin dermis, and although preputial gland mesenchyme did not manifest inductive properties when associated with integumental mesenchyme, it was able to participate in typical skin differentiation.

These data demonstrate (1) the importance of the mesenchyme in mediating epithelial response to androgens, (2) the stability of urogenital epithelia, (3) the plasticity of integumental epithelia, and (4) the inductive properties of urogenital and integumental mesenchyme.
On the presence of mononuclear leucocytes in dorsal root ganglia following transection of the sciatic nerve
Authors: Smith Marshall L. , Adrian Erle K.
Published: February 2005

To label circulating blood mononuclear cells, adult male mice were given multiple injections of tritiated thymidine on the day prior to transection of the right sciatic nerve. These animals and uninjured controls that received a similar sequence of tritiated thymidine injections were sacrificed at intervals up to 64 days following the injury. In the dorsal root ganglia associated with the injured sciatic nerves there were more satellite cells per neuron at all time intervals after the first day than were in the ganglia from the uninjured nerves. The percentage of satellite cells that were labeled was also higher in the ganglia from the injured nerves at all times after injury except the first day. Because no tritiated thymidine should have been available at the time of injury or afterward to label cells proliferating in response to the injury, most of the labeled cells in these ganglia must have been cells labeled before the injury or must be derived from such cells through division. The only large population of labeled cells available to the ganglion was that of the labeled blood mononuclear leucocytes, and the increase in number of labeled cells in the injured ganglia is attributed to infiltration of these cells.
Light and electron microscopic studies on the gastrointestinal tract of the suckling echidna (Tachyglossus aculeatus)
Authors: Krause William J.
Published: February 2005

The stomach of the suckling echidna is lined by a tall columnar epithelium that is bounded basally by a delicate basement membrane. Adjacent cells are held in close apposition by tight junctions near the apex and by extensive implications of the remaining lateral surfaces. The basal cell surface is smooth and without apparent specialization. The lining epithelium is characterized by an abundance of mitochondria and a relative paucity of other organelles. Scattered argentaffin cells extend between the bases of the gastric lining cells and rest upon the luminal side of the basement membrane.

Absorptive cells lining the small intestine of the suckling echidna exhibit in‐vaginations of the apical plasma membrane which branch and anastomose, forming a dense network of tubules in the apical cytoplasm. Adjacent to this network is a series of small vacuoles of varying diameters which come into direct relation with a single, large, supranuclear vacuole. The vacuolar system contains both a fine granular substance and clusters of a flocculent amorphous material thought to be of a proteinaceous nature. The surrounding cytoplasm contains numerous profiles of smooth endoplasmic reticulum, several Golgi systems, and a relative abundance of mitochondria. Clusters of homogeneous droplets are found in the cytoplasm and in the intercellular space.
The nuclear envelope in guinea pig spermiogenesis
Authors: Gordon Mildred
Published: February 2005

In early stages of flagellar development the nuclear envelope on either side of the implantation fossa develops numerous pores. With condensation of the nucleus the envelope becomes excessive and these annulated portions of the envelope are reflected off the surface of the nucleus into the cytoplasm of the neck. The evaginated nuclear membranes enclose a residual mass of nucleoplasm which remains after the rest of the nucleus has polymerized, indicating either a storage of previously synthesized substances or a reserve of metabolically active nucleoplasm which may serve for the continued development of flagellar structures. A portion of the evaginated envelope is differentiated from the rest in lacking annuli and having a consistent 150 Å–200ÅA cisternal space. This unannulated section differentiates in association with the adjunct of the proximal centriole and eventually surrounds the terminal end of the adjunct.
Glycogen in the liver during starvation: A histochemical and biochemical investigation
Authors: Otter W. Den , De Minjer A.
Published: February 2005

During a carbohydrate‐rich diet the liver contains a large amount of evenly distributed glycogen. During a fat‐rich diet glycogen is located mainly in zone 1 of the liver acinus. These results suggest that different acinar enzyme patterns can be induced by different diets. The acinar glycogen patterns remain unchanged during prolonged starvation.

The curve of glycogen percentage vs. starvation time has the same general shape as the curve representing the changes in resistance during the general‐adaptation‐syndrome.
Variation in the silver staining of the Golgi complex along the epithelium of the intestinal villi in the adult rat
Authors: Josephson R. L. , Altmann G. G.
Published: February 2005

A light microscopic study was carried out on the Golgi complex of the absorptive epithelial cells of the small intestine of adult male rats. Silver impregnation methods (Da Fano's, Aoyama's, and Elftman's) were used. Deposits of silver in the Golgi complex were heaviest in the lower half of the villi. Thereafter, a progressive diminution in the reaction occurred. In the uppermost quarter of the villus no reaction was visible. Villi of the duodenum, midgut, and terminal ileum all exhibited this phenomenon regardless of variations in fixation method, concentration and pH of the silver solutions, exposure time to the silver solutions, and various dietary regimens (high fat, no fat, and starvation). The change observed in the silver reaction of the Golgi complex probably reflects a structural or functional change of this organelle as the absorptive epithelial cells migrate along the villi toward the extrusion zones.
The morphology of enamel rods in thin sections
Authors: Quigley Mervyn B.
Published: February 2005

Various methods of ENcalcification, processing and staining have been investigated to study thin sections of human enamel. EDTA‐Na2 in a phosphate buffer was found to be the ENcalcifier of choice, and a stain utilizing SnF2 and H2S solutions was found to stain the sections a rich dark brown. The sections produced showed a keyhole outline of enamel rods in cross section with no eviENnce of interrod material.
Daily variation in 5‐hydroxytryptamine in rat spleen and the effect of stimuli on the rhythm
Authors: Scheving Lawrence E. , Dunn Jon C. , Pauly John E. , Harrison William H.
Published: February 2005

Fluorometric measurements were made of 5‐hydroxytryptamine levels in spleens obtained from separate subgroups of adult male rats killed at two‐hourly intervals over four separate 24‐hour time spans. For three weeks prior to obtaining tissue, all rats were standardized carefully and were subjected to 12 hours of light (0600–1800) followed by 12 hours of darkness. Analyses showed in each study very significant fluctuation over the 24‐hour time scale; the range of change over this period was as great as 131%. The phasing of the rhythms, in spite of the rigid environmental synchronization, was not similar in any of the four studies. Possible explanations for this unexpected desynchronization are discussed. Spleen weights also fluctuated with a significant 24‐hour circadian frequency.

In addition, the rhythm characterizing this amine was described in female rats as well as the effect of different stimuli on the same rhythm. These stimuli were ether, immobilization and a ‘novelty’ situation; and all three significantly increased the levels of 5‐HT in spleen when the overall 24‐hour mean values of each experimental group were compared with controls. However, in all cases there were discrete time points when significant differences in 5‐HT levels could not be obtained with any of the stimuli. This study demonstrates that the effect of the stimuli used depends on the phase of the rat's circadian system during which it was applied. The necessity of considering the natural rhythmic fluctuation in any investigation evaluating this biogenic amine in spleen is demonstrated.
A reexamination of motility patterns of rat epididymal spermatozoa
Authors: Fray C. S. , Hoffer A. P. , Fawcett D. W.
Published: February 2005

The swimming motion of rat epididymal spermatozoa was reexamined using high speed cinematography. Sperm were filmed at 100 frames per second and viewed at a reduced speed for detailed study. The flagella of spermatozoa from the caput epididymidis exhibit a rigid curved middle piece proximal to the cytoplasmic droplet and a flexible portion distal to the droplet. Bending waves begin at the caudal end of the immobile middle piece and propagate distally. The large majority of sperm from this region of the epididymis swim in a circular fashion, clockwise or counterclockwise, depending on the orientation of the curved midpiece. A few spermatozoa, however, manage to achieve a form of forward progression by alternation of the direction of curvature of their inflexible anterior segment. Spermatozoa from the cauda epididymidis swim progressively forward and rotate frequently about their axis of progression. Propagated waves of bending arise in the neck region and involve the midpiece as well as the more distal segments of the tail. The changing pattern of motility of sperm as they mature in the epididymis is consistent with the hypothesis, suggested by others, that the components of motility may develop independently and sequentially and further suggests that the site of initiation of bending waves is not limited to the centriole.
Penetration of ruthenium red into peripheral nerve fibers
Authors: Singer Marcus , Krishnan N. , Fyae Derek A.
Published: February 2005

Living peripheral nerves immersed in ruthenium red‐Ringer solution in vivo or in vitro and subsequently fixed for electron microscopy reveal dye in the axon and myelin‐Schwann sheath. There is rapid penetration into the agranular reticulum of the axon first at the node of Ranvier and later in the internodal region. Dye is also sequestered in the Schwann cell body, Schmidt‐Lanterman cleft and adaxonal and paranodal Schwann cytoplasm. Moreover, dye is deposited in the major electron dense line of the myelin wrapping.
Cell division in normal and neoplastic mammary gland tissue in the rat
Authors: Grahame R. E. , Bertalanffy F. D.
Published: February 2005

Mitotic rates of epithelial cells in Sprague‐Dawley rat mammary glands were investigated in the virgin rat, and during pregnancy, lactation and involution. In addition, rates of cell division were determined in mammary gland neoplasms induced by dimethylbenz(a)anthracene (DMBA). The mammary gland epithelium of the virgin rat exhibited a slight but continuous mitotic activity through all phases of the estrous cycle, indicating a low rate of cell renewal. During pregnancy the rate increased markedly, attaining a peak on the twelfth day. The rates of mitosis declined during lactation and involution. The majority of DMBA induced mammary gland neoplasms exhibited mitotic rates lower than the normal mammary gland during pregnancy.
Fertilization of guinea pig eggs in vitro
Authors: Yanagimachi R.
Published: February 2005

Guinea pig eggs can be fertilized in vitro in a chemically defined medium originally developed by Biggers, Whitten and Whittingham for the cultivation of fertilized mouse eggs. When unfertilized eggs were inseminated in this medium (abbr. BWW) with fresh epididymal spermatozoa, sperm penetration occurred not earlier than two hours after insemination. Quick and efficient sperm penetration occurred when the eggs were inseminated with spermatozoa pre‐incubated in BWW for 11‐18 hours. Spermatozoa started to pass through the zona pellucida as early as 10‐15 minutes following insemination and all the eggs were penetrated by spermatozoa within one hour. The time needed for functional capacitation of guinea pig spermatozoa is estimated to be no less than two hours under the experimental conditions used, the optimal time possibly being 8‐12 hours or even longer. The possibility of in vitro sperm capacitation and fertilization of eggs in media much simpler than BWW (e.g., Earle's solution with or without albumin) is suggested.
The organization of dense projections in synapses of the brain of a marsupial, Setonix brachyurus
Authors: Jones D. G. , Brearley R. F. , Doran G. A.
Published: February 2005

Synaptic junctions from the lateral geniculate nucleus of the quokka brain have been examined by electron microscopy after glutaraldehyde fixation and PTA staining. Junctions can be divided into two groups: discontinuous‐continuous and continuous‐continuous, depending on the continuity or lack of it of the presynaptic membrane. The postsynaptic membrane always has a continuous appearance.

The dense projections have the following characteristics: 1. an irregular outline due to the presence of spikes; 2. in some cases, an external electron‐opaque “skin” and an internal, relatively electron‐translucent core; 3. adjacent projections may have one or more stands of the presynaptic network between them and extending to the internal coat of the presynaptic membrane; 4. the gap between the bases of dense projections varies from 5 to 69 nm, with a mean value of 23 nm. Seventy‐six percent of these measurements fall within the range 5‐25 nm, while many of the larger gaps separating dense projections are subdivided into smaller components by the presence of one or more strands of the presynap‐tic network.

Features 2 and 3 have not been previously described in exactly the form seen here. It is not known whether they are confined to marsupial synapses or whether they highlight important general features of synaptic organization.
Electron microscopic studies on von Korff fibers in the human developing tooth
Authors: Whittaker D. K. , Adams D.
Published: February 2005

Deciduous tooth germs were removed from the anterior region of human fetuses between 13‐16 weeks of age and fixed in glutaraldehyde. Some were post fixed in osmium tetroxide whilst others were block stained with silver nitrate and prepared for electron microscopy. Thick Araldite embedded sections were cut at 1 μm and stained in various ways for examination by light microscopy. Thin sections of bulk silver stained material were examined with the electron microscope before and after staining with heavy metals.

Fibers lying between the developing odontoblasts were demonstrable under the light microscope and their appearance was consistent with the classical description of von Korff fibers. With the electron microscope bundles of collagen fibers up to 1 μm in diameter were present between newly differentiated odontoblasts. Heavy metal staining of sections from bulk silver impregnated material revealed that silver deposition was associated mainly with collagen fibrils. It is concluded that in the crown of human developing teeth, bundles of collagen fibrils are present between the newly differentiated odontoblasts and that these bundles represent those usually described as von Korff fibers.

Similar results were found using material from developing molar teeth of mice.
Effect of testosterone, dexamethasone and hypophysectomy on membranous whorls in the adrenal gland of the Mongolian gerbil
Authors: Nickerson Peter A.
Published: February 2005

The effect of stress‐induced release of ACTH or suppression of ACTH release on concentric whorls of rough endoplasmic reticulum has been studied in the adrenal gland of the Mongolian gerbil. The border zone between the zona fasciculata and reticularis appears to be a zone of transition, and stress may transform these cells into typical zona fasciculata cells. Absence (hypophysectomy) or reduction (testosterone, dexamethasone) of ACTH however causes neither atrophy nor hypertrophy of whorls. The stress of saline injections for five days caused disappearance of whorls and a rise in blood cortisol to 1.5 times that in controls. Whorls were replaced by a focal accumulation of smooth endoplasmic reticulum. Testosterone or dexamethasone as well as transaural hypophysectomy prevented the disappearance of whorls in spite of the stress of injection. Testosterone caused a 50% reduction in blood cortisol levels whereas both dexamethasone and hypophysectomy reduced blood cortisol to 25% of that in controls.
Structural changes in the proximal tubule of kidneys from hypophysectomized rats
Authors: Evan Andrew P. , Simone P. George , Solomon Sidney , Loker Edward F.
Published: February 2005

The present study was undertaken to determine what structural changes hypophysectomy would cause in the rat kidney. Proximal convoluted tubule cells from hypophysectomized rats were smaller and their length was decreased when compared to kidneys from control animals of approximately the same weight as the hypophysectomized animals. Electron microscopic observation of the kidneys from the hypophysectomized rats revealed that the cells of the proximal convoluted tubules had (1) an increase in size and number of dense bodies (type II cytosome); (2) a decrease in smooth endoplasmic reticulum (SER); (3) a decrease in basilar infoldings; (4) an increase in the frequency of mitochondria cristae aligned in their longitudinal axis and (5) a change in the character of the profiles of smooth endoplasmic reticulum (SER) related to microbodies (type I cytosome) from a vesicular to tubular arrangement. The changes noted in the cells of the proximal convoluted tubules of hypophysectomized rats were similar to previously described changes observed in tubular atrophy.
Twenty‐four‐hour rhythmicity in carbonic anhydrase activities of choroid plexuses and pineal gland
Authors: Quay W. B.
Published: February 2005

Carbonic anhydrase (CA, carbonate hydro‐lyase, EC 4.2.1.1) activity of choroid plexuses (ventricles I + II and IV) and pineal glands of adult male rats was determined by microtitration. Autopsies at precise times in relation to a daily photoperiod 14 hours long allowed in replicate series evaluation of 24‐hour rhythmicity. A slightly lower choroid CA activity during the light phase was variable and marginal in significance. A highly significant and reproducible daily fall in pineal CA activity near the onset of light was paralleled by, and probably originated from, a fall in pineal content of erythrocytes. Low pineal CA activity is consistent with its endocrine nature. Its morning changes in hemodynamics are likely to be due to local changes in content and release of norepinephrine and other vasoactive agents.
The nuclear envelope: Its breakdown and fate in mammalian oogonia and oocytes
Authors: Szollosi Daniel , Calarco Patricia G. , Donahue Roger P.
Published: February 2005

The dissolution of the nuclear envelope (NE) has been studied ultrastructurally in mouse oocytes maturing in vitro. NE breakdown begins with the undulation of the nuclear envelope followed by the disappearance of nuclear pores. Subsequently, extensive NE convolutions, possibly caused by impinging microtubules, result in the apposition of adjacent NE segments, the appearance of breaks and the formation of NE doublets. Doublets may also be formed by the apposition of intranuclear cisternae to the inner leaflet of the NE. Nuclear envelope breakdown in mouse oocytes takes approximately three and one‐half hours in vitro.

The fate of the resulting nuclear envelope fragments has been followed in both mouse oocytes and human oogonia. In the mouse, NE doublets separate into individual cisternae, indistinguishable from endoplasmic reticulum, by the time of the first meiotic metaphase. A different fate for NE doublets is suggested in human oogonia which retain NE doublets throughout the division cycle. The nuclear envelope of the daughter cells reforms, at least in part, from NE doublets by separation of the apposed cisternae into single units and the re‐establishment of chromosomal contact. Thus, at least some of the NE appears to be conserved in actively dividing human oogonia.
A morphological and histochemical evaluation of sexual dimorphism in androgen‐insensitive pseudohermaphroditic mice
Authors: Andrews Edwin J. , Bullock Leslie P.
Published: February 2005

Examination of the morphology in the submandibular salivary gland, adrenal gland and renal cortex of androgen‐insensitive, tfm/ Y mutant mice has revealed predominantly female characteristics. A sexual dimorphism in alkaline‐phosphatase (AP) activity was seen in the submandibular salivary gland of this strain of mice; the AP activity in the mutants was similar to females. There was no dimorphism in renal AP activity.
Correlation of vascularity with mineralization in human fetal teeth
Authors: Tobin Charles E.
Published: February 2005

The qualitative relationship of dental vascularity to mineralization of dentin and enamel was studied in 50 normal human fetuses 11.5 to 18 weeks of age, obtained unembalmed within 12‐24 hours after abortion. A 50‐50 suspension of India ink and 10% neutral formalin was injected manually into the umbilical vein (intact fetuses) or internal carotid arteries (autopsied fetuses), using sufficient pressure on the syringe to fill but not rupture nor overdistend the blood vessels. After immersion of the injected fetuses in 10% neutral formalin for three to five days, the maxillae and mandibles were removed and stained with alizarin red S for identification of calcium salts. Under magnification the dental sacs were exposed, removed intact and opened to observe: (1) the dental papilla, (2) its size and vascularity, and (3) the extent of mineralization of the crowns and cusps. Macroscopic preparations and microscopic sections were made of selected tissues from these specimens. The degree of mineralization appeared to be correlated more closely with the vascularity of the dental papilla than with the total size of the dental sacs, or that of the cusps or crowns. Blood vessels were present at the peripheral edge of both the developing enamel and dentin but no blood vessels were found to traverse the stellate reticulum nor were any blood cells found within it normally; whereas if abnormal pressure had been applied to the fetus or if the specimens were undergoing maceration, blood cells were observed within the stellate reticulum.
The annulate lamellae of chick embryo liver cells in organ culture
Authors: Benzo Camillo A.
Published: February 2005

Cytoplasmic annulate lamellae are described as occurring in the cells of chick embryo liver during raft‐type organ culture on Eagle's minimum essential medium. These transitory structures, prominent in the cells of early (5‐day) embryonic liver during culture, were closely associated with the outer nuclear membrane and mitochondria, and were frequently continuous with portions of the rough endoplasmic reticulum. In contrast, annulate lamellae were not found in any cell examined during organ culture of older (11‐day) embryonic liver. These observations, together with correlative enzymatic studies, are discussed with regard to the possible role of annulate lamellae in the differentiation of the liver cell, in the light of current hypotheses on the origin and function of these widely‐occurring organelles.
Further evidence for the vitality of chondrocytes in the mandibular condyle as revealed by 35S‐sulfate autoradiography
Authors: Silbermann Michael , Frommer Jack
Published: February 2005

Histochemical and autoradiographic studies using 35S‐sulfate indicate that the majority of the cartilage cells in the developing mandibular condyle of the young mouse are active, vital cells. Concomitant with the increase of hypoxic conditions within the deeper layers of the cartilage, an increase in sulfated glycosaminoglucuronoglycans synthesis takes place. Hypertrophic chon‐drocytes in the premineralized and mineralized zones reveal marked 35S‐sulfate uptake in comparison with the less differentiated cells in the chondroblastic and perichondrial zones. These observations of radiosulfate activity support the concept that calcification processes in the condylar cartilage are not necessarily accompanied by degeneration and death of the hypertrophic chondrocytes. The radiosulfate activity of the surviving chondrocytes in the vicinity of the ossification front indicates possible modulation into osteoprogenitor cells.
Studies on the peripheral blood cell parameters and morphology of the red paradise fish, Macropodus opercularis. Effect of food deprivation on erythropoiesis
Authors: Weinberg Sheila R. , Siegel Charles D. , Gordon Albert S.
Published: February 2005

A description is presented of the peripheral blood cell values and blood cell morphology of both the normal and the starved red paradise fish. An inhibitory influence of food deprivation upon erythropoiesis was demonstrated in this fish by the significant decrease in red blood cell and hematocrit values. A comparative study showed that the size and numbers of erythrocytes present in teleost blood reflect its habitat, activity, and degree of evolution.
Uptake of adenovirus by intestinal absorptive cells of the suckling rat. I. The Neonatal Ileum
Authors: Worthington Bonnie B. , Graney D. O.
Published: February 2005

Light and electron microscopic analysis of adenovirus‐infused ileal loops disclosed virus particles within the tubulo‐vacuolar apparatus of absorptive cells. Tissue observed from five‐minute loops contained virus particles largely within apical tubules and vesicular profiles. Similar particles were observed within cisternae and supranuclear vacuoles as well as within apical tubules in tissue samples from 10‐ and 15‐minute loops. Loops maintained for 30 minutes demonstrated virions predominantly in the supranuclear vacuole of each absorptive cell. In no instance was a virion seen free within the cytoplasm or nucleus and none was apparent elsewhere in the mucosa. It appears that absorptive cells of the ileum are capable of sequestering exogenous virions and conveying them to established lysosomal bodies in the supranuclear cytoplasm. Here they may be either stored or degraded, thus impeding their progress to other intra‐ or extracellular locations. The possible significance of these findings is discussed in detail, and it is proposed that sequestration of ingested virions by the tubulo‐vacuolar apparatus of the ileal absorptive cell may serve some protective function in the developing neonate. It is suggested that direct infusion of “purified” virus into intestinal loop preparations is an efficient means of observing virus‐intestinal cell interactions in the living animal. This experimental model might prove effective in future studies of viral infection in the intestine, particularly if it is combined with both serological and morphological methods.
Uptake of adenovirus by intestinal absorptive cells of the suckling rat. II. The neonatal jejunum
Authors: Worthington Bonnie B. , Graney D. O.
Published: February 2005

Histological and ultrastructural observations of adenovirus‐infused jejunal loops revealed virus particles in small apical tubules and in underlying vacuoles and lysosome‐like bodies. Tissue selected from loops maintained for five and ten minutes disclosed virions largely within the intestinal lumen and in sparse tubular profiles beneath the microvilli. Jejunal preparations of longer duration disclosed increasing numbers of virus particles in small and large lysosome‐like bodies above the nucleus. In no instance were virions apparent free within the cytoplasm or nucleus and none was observed elsewhere in the mucosa. It is concluded, therefore, that the jejunal absorptive cell behaves like its ileal counterpart in absorbing and sequestering adenovirus particles in intracytoplasmic lysosomal organelles. It is further proposed that this behavior might serve a protective role during the vulnerable period of immunologic immaturity in the neonatal mammal.
Explants of rat adrenal medulla. A light and electron microscopic study
Authors: Piezzi Roman S. , Cavicchia Juan C.
Published: February 2005

Unilateral explants of rat adrenal medulla grown in the anterior chamber of the eye were studied with light and electron microscopy. The surviving chromaffin cells are in proximity to the abundant vessels at 21 days after explantation. However, the typical arrangement of anastomosed cellular cords, such as can be always seen in the normal medulla, is replaced here by clusters, cords and irregular groups of cells. Two types of chroma & cells can be described. The predominant cells are polygonal or elongated in shape and have polymorphous and elongated norepinephrine‐positive granules. The other type, less numerous, has a pale cytoplasm with round chromafh cells. This type is norepinephrine negative. Several cytological characteristics of some of the chromaffin cells are also described. These morphological observations are in agreement with the biochemical findings previously published and confirm that a signscant decrease of epinephrine cells occurs in the explant.
A comparative ultrastructural analysis of the third cerebral ventricle of the North American mink (Mustela vison)
Authors: Scott David E. , Kozlowski Gerald P. , Dudley Gerda Krobisch
Published: February 2005

The third ventricular walls and floor of male and female mink (Mustela vison) were analyzed with comparative light microscopy, transmission and scanning electron microscopy. Distinct regional fine structural variations were noted in the appearance of the dorsal, middle third and lower portions of the ventricular wall and floor. These variations were characterized by an abrupt decrease in the density of ciliated ependymal surfaces in the middle one‐third of the ventricular wall. The ventral walls and floor of the lateral and infundibular recesses displayed smoother contours with numerous bleb‐like protrusions and blunt villiform processes. Occasionally multipolar neuron‐like cells were observed to lie upon the floor of the infundibular recess. Speculation is raised relative to the differing functional capacities of these various ventricular areas.
Differentiation of human limb buds in vitro
Authors: Yasuda Yoshiko
Published: February 2005

Seventy‐five human embryos, at stages ranging from XII to XVIII of Streeter's horizon, four to six weeks postconceptional age, were obtained from healthy women by curettage. Limbs were cultured in nutrient agar medium for four to 18 days. Excepting a few cases which resulted in total necrosis, differentiation of mesenchyme into cartilage or bone primordia and other supporting tissues took place similarly to in vivo, though it occurred more slowly compared to in vivo. Such developmental retardation was milder in the lower limbs than in the upper limbs. In horizons XIV through XVIII, the limbs cultured for longer period than four days showed developmental dissociation of mesenchymal tissues, i.e., the maturation of cartilage advanced more than did the development of other tissues of the limb. The time lapse between the curettage and the culture ranged from 1.5 hours to seven days, but this had no close relationship with the occurrence of degenerative changes. Comparing the data obtained here with the corresponding results of a similar study in mice, it was concluded that the differentiation of the human limb occurs far slower than the mouse limb and shows some different patterns. These results suggest that it is possible to study in vitro comparison of effects of some teratogens on human and mouse limbs.
Penetration of the testicular‐tubular barrier by horseradish peroxidase induced by adjuvant
Authors: Willson John T. , Jones Norbert A. , Katsh Seymour , Smith Stuart W.
Published: February 2005

Adjuvant‐induced penetration of horseradish peroxidase (HRP) into seminiferous epithelium was studied as a model of adjuvant‐induced entry of other proteins, e.g., immunoglobulins. HRP intravenously injected 20 minutes prior to sacrifice (by peraortic perfusion with Karnovsky's fixative) into male guinea pigs that had received Freund's complete adjuvant (FCA) + saline or FCA + testicular homogenate (TH) intradermally seven days previously, entered the peritubular spaces of a moderate number of seminiferous tubules. In those tubules HRP became uniformly distributed in the cytoplasmic matrices (but very rarely in membrane‐bound vesicles) of some of the Sertoli cells and presumptive type B spermatogonia. By contrast, HRP injected into normal animals, into animals that had received FCA + saline or FCA + TH 3 or 14 days previously or into animals that had received Freund's incomplete adjuvant + saline 3, 7, or 14 days previously gained entry into only occasional peritubular spaces but was never found in any cells of the seminiferous epithelium.

These findings are discussed in conjunction with previous findings on immune aspermatogenesis. Hypotheses concerning the intratesticular mechanisms of production of both active and passive immune aspermatogenesis as activated by FCA and the mechanisms whereby FCA may enable or potentiate production of immune globulins are proposed and discussed.
Changes in the protein content of blastocysts from normal and delayed implanting mice
Authors: Weitlauf Harry M.
Published: February 2005

Total protein content of preimplantation mouse embryos was measured at 06.00 and 16.00 hours on day 5 of pregnancy (day 1, the day of vaginal plug formation). During this ten hour period, just prior to implantation, the amount of protein increased from 23 to 35 ng per blastocyst; a net increase of 52%. In contrast, protein content was unchanged in delayed implanting embryos recovered from ovariectomized animals during a comparable period on days 5 or 10 (day 5, 24 ng at 06.00 hours and 24 ng at 16.00 hours; day 10, 29 ng at 06.00 hours and 30 ng at 16.00 hours).

These results demonstrate that the different uptake and incorporation of amino acids between normal and delayed implanting embryos (Weitlauf and Greenwald, '65, '68; Weitlauf, '73) reflect a difference in the actual net synthesis of protein by the two types of blastocysts.
Regional variations in endoplasmic reticulum in the vas deferens of normal and vasectomized rats
Authors: Flickinger Charles J.
Published: February 2005

The fine structure of the epithelium of different parts of the rat vas deferens was studied in normal rats and at intervals of up to nine months after vasectomy. The cytology of the columnar epithelial cells showed regional variations particularly in the type and extent of endoplasmic reticulum. Cells of the proximal part of the vas deferens were characterized by basal and perinuclear granular endoplasmic reticulum, a large Golgi apparatus, and numerous apical microvilli, vesicles, and vacuoles. In contrast, the columnar cells of the distal portion of the vas deferens contained large amounts of smooth endoplasmic reticulum, much of which assumed the form of large whorls of smooth membranes. In the distal segment the number of microvilli, vesicles, and vacuoles was less but mitochondria were more numerous than in the proximal part. Cells in the middle portion of the vas deferens showed some features of both proximal and distal parts. These structural characteristics, along with previous experiments, suggest that in the proximal portion of the vas deferens absorption of material from the lumen is an important function, while the cells of the distal part may synthesize steroids. Thus, these regional differences in ultrastructure probably reflect regional differences in function along the length of the vas deferens. After vasectomy the regional specializations were retained and did not appear to be altered. The possibility that this structural and functional sequence is significant for normal fertility and its relation to attempts to reconnect the vas deferens after vasectomy are considered.
Early steps in estradiol‐induced vaginal cornification in spayed mice: Kinetic study with 3H‐thymidine
Authors: Galand P. , Vandenhende J.
Published: February 2005

The formation of a third, intermediate, layer of cells in the mouse vaginal epithelium 12 hours after estradiol administration was investigated. Making 3H‐thymidine continuously available during the first 12 hours following estradiol administration to spayed mice and killing the treated animals after this period, revealed the intermediate layer of cells as constituted essentially of unlabeled cells. To the contrary, when animals were treated with estradiol 48 or 60 hours following pulse‐labeling with 3H‐thymidine, and killed 12 hours after hormone injection, autoradiography showed that labeled cells (which were in some part of G1 at the time estradiol was given) become a part of the intermediate cell layer. Grain count distribution in this material confirmed that they do so without undergoing further division. These results support our assumption that the formation of an intermediate layer of cells in the vaginal epithelium of spayed mice within the 12 first hours of estradiol action does not require division of basal cells under the presence of estrogen.
The substructure of crystalloids in secretory granules of dog pancreatic islet B cells
Authors: Machino Mitsuo
Published: February 2005

The B cells of dog pancreatic islets were studied by electron microscopy. The crystalloid core of secretory granules in B cells is unique. The crystallization of the secretory granule core appears to be accomplished in the Golgi apparatus. The square or hexagonal network with a periodicity of 30–60 Å that is produced suggests that the unit cell is either hexagonal or rhombohedral. The electron opaque dots which constitute the periodic densities may represent the insulin molecule itself in a crystalloid array.
The effect of isoproterenol on the postnatal differentiation and growth of the rat submandibular gland
Authors: Srinivasan R. , Chang W. W. L. , Van Der Noen H. , Barka T.
Published: February 2005

Administration of isoproterenol (IPR), twice daily for five days, to five day old rats resulted in a hypertrophy and hyperplasia of the submandibular gland as indicated by an increase of the total DNA, RNA, and protein contents of the gland. Four different cell types, the acinar cell, the terminal tubule cell, the intercalated duct cell and the striated duct cell were distinguished in 1 μ thick, Epon‐embedded sections and their rates of proliferation were estimated from radioautographs prepared following the incorporation of 3H‐thymidine. IPR treatment increased both the frequency and the absolute number of the acinar cells as compared to those of control animals. Concomitant with this there was a decrease in the number of terminal tubule cells from 50% in the control to about 15% in the IPR‐treated rat submandibular gland. These findings indicate that IPR accelerated the postnatal differentiation and proliferation of acinar cells. Eleven days after withdrawal of the drug the gland showed chemical and morphological evidence of regression of the IPR‐induced hypertrophy and hyperplasia and the numbers of acinar cells and terminal tubule cells in the glands of control and IPR‐treated rats were the same. Thus the IPR‐induced advanced differentiation of the gland was not maintained after the cessation of the IPR‐administration.
Effects of cytochalasin B on the ultrastructure of Rana pretiosa tadpole epidermis
Authors: Larsen John H.
Published: February 2005

Immersion of Rana pretiosa tadpole tail integument in 1 μg/ml of cytochalasin B (CCB) for 45 minutes disrupted various cell structures of the two‐squamous cell‐layered epidermis including macromolecular components within microvilli and subjacent to the apical plasmalemma, the unit membrane which bounds mucinogenic vesicles and various other supranuclear structures. Surface cells exhibited the greatest degree of organelle disorganization when pieces of excised tail fin (“discs”) were treated with the antibiotic. This may indicate a differential response to the drug by various regions of the cytoplasm or that the concentration of CCB and/or exposure period was only adequate to penetrate the most superficial layers of this epithelium. The effect(s) of the penetrate the most superficial layers of this epithelium. The effect(s) of the antibiotic on filaments and filament related kinetic processes is discussed and the possibility of dissimilarities in CCB‐sensitivity between immature and differentiated plasmalemma and among unit membrane of various organelles is considered.
Phagocytosis of supernumerary spermatozoa by two‐cell mouse embryos
Authors: Thompson Robert S. , Zamboni Luciano
Published: February 2005

Phagocytosis of supernumerary spermatozoa contained within the perivitelline space was observed in 7 of 28 two‐cell mouse embryos cultured for 45 hours post‐insemination (approximately 20–24 hours after cleavage). The spermatozoa were incarcerated as a result of elevations of the blastomere cytoplasm which gradually surrounded the sperm, overlapped and fused, thus forming a typical phagocytic vacuole. Phagocytosis was not observed in two‐cell embryos cultured for less than 20–24 hours after cleavage; this indicates that the blastomeres of two‐cell mouse embryos in vitro require approximately 24 hours to develop one of the characteristics of somatic cells, i.e., the ability to recognize and phagocytize foreign material.
Maturation of nonmyelinated fiber bundles in a strain of dwarf (Snell's) Mice
Authors: Reier P. J. , Froelich J. S. , Sawchak J. A. , Hughes A. F. W.
Published: February 2005

Postnatal maturation of nonmyelinated fiber bundles (Schwann bundles) was studied in the sciatic nerves of Snell's dwarf mice. The homozygous recessive of this strain has been previously shown to be characterized by multiple pituitary hormone deficiencies and secondary hypothyroidism.

In the normal littermates a reduction occurred between 10 and 14 days in the number of fibers per fascicle, or subdivision, of each Schwann bundle, and by 26 days nearly all of the axons were separately embedded in cytoplasmic furrows of their associated Schwann cells. Only a few large fascicles were seen in normal sciatic nerve specimens at 26 and 50–53 days. In contrast, fiber bundle fascicles in the mutant nerves were still represented, even at 50–53 days, by numerous tightly‐packed axons, as seen in the immature nerves at 10–12 days post‐partum.

On the basis of the dwarf's physiological background, these results suggest an involvement of the endocrine system during later stages of peripheral nerve maturation. The possible mechanisms affected by postnatal endocrine deficiency and thereby leading to delayed segregation of nonmyelinated fibers within Schwann bundles are discussed.
The effect of cyclophosphamide on the morphogenesis of the cerebellum in chick embryos
Authors: Singh Shamer , Sanyal A. K. , Kar A. K.
Published: February 2005

The morphogenesis of cerebellum has been studied in 6–19 day old chick embryos after a single injection of 0.05 mg of cyclophosphamide into the yolk sacs on the fifth day of incubation. Besides degeneration of Purkinje cells, rate of development was markedly retarded as evidenced by late appearance of the fissures and folia of the cerebellum. Purkinje cells remained disorganised up to 18 days of incubation, though in controls they were arranged in a single line by the fifteenth day. The thickness of the external granular layer increased and persisted for a longer period in the treated embryos. The cytoarchitecture returned to normal on nineteenth day of incubation, but the size of the cerebellum was significantly smaller than that of controls (P < 0.001). Such transient disorganisation of the morphogenetic events in the neural tube may lead to inadequate and defective induction of surrounding mesenchyme, thereby resulting in defective skull formation through which the brain can herniate, i.e., exencephaly as reported in our earlier studies after cyclophosphamide administration in chicks (Singh et al., '71; Singh and Gupta, '72) and rats (Singh et al., '72).