bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and size of the teeth of Macaca mulatta
Authors: Trotter Mildred , Hixon Barbara B. , MacDonald Barbara J.
Published: February 2005

A cross‐sectional sample of 151 skulls from Macaca mulatta of known age and similar rearing in U.S. Primate Centers was analyzed to determine age‐related “norms” of stages of development and size of teeth.

The stages of development from the follicle of a deciduous incisor in the fetus to completion of the root with apex closed of the permanent third molar were related to age. The age range observed for eruption of each tooth was noted and related to its stage of development. The crown of each erupted tooth was found to be completely developed, but growth of its root continued for a longer, indeterminate period. When a deciduous tooth was exfoliated, the crown of the permanent successor was found to be completed and root growth had begun.

Measurements of both mesiodistal and faciolingual diameters and of crown length of the teeth in situ and of total length and root length on roentgenograms were examined for sexual dimorphism. The faciolingual diameter of the deciduous mandibular second incisor and of both second molars showed the greatest sexual dimorphism among both diameters of all deciduous teeth.

The mesiodistal and faciolingual diameters of the mandibular premolars were found to be the best dimensions in discriminant functions for identifying sex in the absence of permanent canines.
The effects of induced lathyrism on Sr85 uptake in rats during late prenatal development
Authors: Goren A. D. , Singh I. J. , Pentel L.
Published: February 2005

During the last one‐third of their gestational period, lathyritic rats incorporate significantly lower amounts of Sr85 as revealed by whole body counting techniques. This difference was maximum at term. The study provides evidence for a lathyritic disturbance in the initial phases of mineralization of hard tissue matrices.
A radioautographic study of chondrocytic proliferation in nasal septal cartilage of the newborn rat
Authors: Searles James C.
Published: February 2005

Growth sites within the newborn cartilaginous nasal septum have been identified by monitoring chondrocytic proliferation radioautographically. Tritiated thymidine was the labeling agent used. The results were tabulated and charted graphically; they showed the overall septum to be relatively active mitotically, yielding an average of 3.54 labeled cells per microscopic field counted. However, certain areas showed greater activity than others, namely the anterior tip (4.51 labeled cells/field), the midportion (3.98 labeled cells/field) and the posterior section of the presphenoidal tail (4.24 labeled cells/field).
A light microscopic study of the saccule and lagena in certain catfishes
Authors: Jenkins David B.
Published: February 2005

The sacculi and lagenae from representatives of five species of catfishes were studied by light microscopy to provide an account of the anatomy of those structures and to determine whether phylogenetic changes can be detected in the inferior division of the membranous labyrinth among closely related ostariophysian fishes. The lagena showed little change among the forms used, while the saccule exhibited marked interspecies modifications. Anatomical variation was evident in the shape of the saccule, positioning of the interconnecting transverse canal, presence or absence of a release membrane, and, more notably, the position of the saccular macula and the shape and fluting pattern of the sagitta. Only minor variations were evident in the saccule and sagitta between the “primitive” conditions displayed in the siluroid form and those in the two bagroid representatives; in the latter forms, however, some positional modification of the posterior part of the macula from the “primitive” arrangement was present. In the bagroid representatives, the general morphology appeared to be stabilized early in the radiation, and individual changes suggest two lines of development within the group. The most significant modifications were evident in the loricaroid group where progression from the early representative to the more advanced form showed major changes in the inferior division of the labyrinth including loss of the anterior part of the saccule and sagitta, modification of the remaining part of the sagitta, and repositioning of the saccular macula. The pattern changes in the saccule generally agreed with the phylogenetic sequence proposed by Chardon (′68) for catfishes.
Ultrastructure of thyroid follicular cells following hypophysial portal vascular infusion of thyrotropin‐releasing hormone
Authors: Yee John A. , Wilbur Donald L.
Published: February 2005

Ultrastructural changes in thyroid follicular cell morphology were studied following the infusion of thyrotropin‐releasing hormone (TRH) for 1 min into a hypophysial stalk portal vessel of adult male rats. At 1, 5, 15 and 30 min following infusion, thyroid glands were removed and prepared for electron microscopic examination. Thyroid follicular cells in unoperated, sham‐operated non‐infused, and saline‐infused control rats were cuboidal, generally lacked intracellular colloid droplets and contained variable numbers of electron‐dense lysosome‐like bodies distributed throughout the cytoplasm. In experimental animals, marked intracellular colloid droplet accumulation was observed 5 min after TRH infusion and remained a constant finding throughout the time‐periods studied. Numerous lysosome‐like dense bodies accumulated in the apical cytoplasm of thyroid follicular cells at 30 min. Fusion of colloid droplets and lysosome‐like bodies had apparently occurred by 30 min. At this time the colloid droplets were smaller, more electron‐dense and were often located more basally within the follicular cell cytoplasm. This study suggests that the morphological response of thyroid follicular cells to hypophysial portal vascular infusion of TRH occurs rapidly and mimics, both temporally and morphologically, the response observed following systemic administration of exogenous TSH.
Morphological changes in isolated lymphocytes during preparation for SEM: Freeze drying versus critical‐point drying
Authors: Billings‐Gagliardi Susan , Pockwinse Shirwin M. , Schneider Gary B.
Published: February 2005

A quantitative comparison of isolated lymphocytes prepared for SEM by the critical‐point drying (CPD) and freeze drying (FD) methods revealed that the mean cellular diameter dropped from 7.9 μm after fixation to a final diameter of 6.9 μm after FD, and to 5.7 μm after CPD. In addition to their larger sizes, FD lymphocytes were immediately distinguishable by their more complex surfaces, featuring wider microvilli which often emanated from ridges on the cell surface and branched extensively near their bases. The mean width of microvilli was 0.22 μm after FD and 0.12 μm after CPD. The number of microvilli per cell was essentially the same by the two methods. In view of these findings, a critical comparison of the CPD and FD methods using the particular cells or tissue to be investigated is an essential prelude to a rigorous SEM study.
Phagocytosis of photoreceptor outer segments during retinal development in utero
Authors: Spira Arthur W. , Huang Peter T.
Published: February 2005

The retinal pigmented epithelium of the fetal guinea pig was examined for evidence of phagocytosis and degradation of outer segments. Beginning at the early stages of outer segment formation and continuing through the remaining fetal period, pigment epithelial cells contained large and small phagosomes with multi‐lamellated internal structure. Thus, mammalian retinal photoreceptor cells which normally develop and mature in utero in the absence of light undergo a process of phagocytosis of outer segment fragments comparable to that found in species whose retinae mature postnatally outside of the uterus.
Specific subclones derived from a multipotential clone of rat anterior pituitary cells
Authors: Shiino Masataka , Ishikawa Hiroshi , Rennels Edward G.
Published: February 2005

Several functional subclones of rat anterior pituitary cells were established from our 2A8 clone which apparently contains a heterogeneous population of committed and uncommitted cells. On the basis of the hormones secreted into the culture media, as measured by radioimmunoassay, these subclones were divided into four categories, i.e., subclones which secrete (1) ACTH only, (2) prolactin only, (3) prolactin and GH or (4) ACTH, prolactin and GH. None of the subclones produced detectable amounts of thyrotrophic or gonadotrophic hormones. Subclones which secrete a single hormone have shown no change in the type of hormone produced, indicating that these subclones were each derived from a committed cell.

The cells of all subclones exhibit a normal diploid karyotype and show good growth characteristics. The cells of the different subclones can be classified by phase contrast microscopy into four categories. However, no clear‐cut ultrastructural features have been observed which can be correlated with the different categories of subclones. On the basis of the results a hypothesis is proposed relative to the functional cytodifferentiation of anterior pituitary cells.
Occurrence of catecholamine‐containing specific granules in the venous endothelia of carp
Authors: Iijima Tadahiko , Wasano Takeo
Published: February 2005

The formaldehyde‐induced fluorescence technique and the argentaffin reaction with ultra‐thin sections were applied to the vessels of carp to demonstrate the presence of a catecholamine. After formaldehyde gas treatment for 30 minutes at 50°C, the venous endothelia emitted a greenish‐yellow fluorescence suggesting the presence of a primary catecholamine. In the endothelial cells of veins, the specific granules, consisting predominantly of spherical granules with a diameter of about 0.3 μm, showed heavily to moderately positive argentaffin reaction. Granules also occurred in the endothelial cells of arteries. However, these granules stained weakly or not at all with ammoniacal silver solution. It is concluded that the specific endothelial granules in veins of carp contain a primary catecholamine.
The atrioventricular node and bundle in the ferret heart: A light and quantitative electron microscopic study
Authors: Marino Thomas A.
Published: February 2005

The cells of the atrioventricular (AV) junction in the ferret heart were examined using light microscopy, a wax‐model reconstruction and quantitative electron microscopy to determine their organization and characteristics. A series of subdivisions of the specialized tissues of the AV junction was apparent at both the light and electron microscopic levels. A transitional zone was observed interposed between the atrial muscle cells and the AV node. The AV node consisted of a coronary sinus portion, a superficial portion and a deep portion. The AV bundle had a segment above the anulus fibrosus, a segment which penetrated the right fibrous trigone, a non‐branching segment below the anulus fibrosus and a branched segment. At the ultrastructural level the AV junctional conduction tissues had fewer irregularly oriented myofibrils than did working atrial myocardial cells. T‐tubules, present in atrial muscle cells, were not observed in the modified muscle cells of the AV node and bundle. Conventional intercalated discs also were not observed between the cells of the AV node or the AV bundle.

Atrial myocardial cells had the highest percentage of the plasma membrane occupied by desmosomes, fasciae adherentes and gap junctions. The AV bundle cells had the highest percentage of appositional surface membrane and a relatively large fraction of plasma membrane occupied by gap junctions. Cells of the superficial portion of the AV node had the smallest percentage of the plasma membrane composed of gap junctions, desmosomes or fasciae adherentes, as well as the smallest fraction of the cell membrane apposed to adjacent cells. The stereological data indicate that the most useful distinguishing characteristic between atrial muscle cells and conduction cells was that a smaller percentage of the conduction cell sarcoplasm was occupied by mitochondria and myofibrils. The most useful characteristics that could be used to differentiate between the regions of the AV junctional conduction tissues were the amounts and types of surface membrane specializations in the respective cell types.
Three‐dimensional architecture of the Golgi apparatus in Sertoli cells of the rat
Authors: Rambourg A. , Clermont Y. , Hermo L.
Published: February 2005

Glutaraldehyde‐fixed testes were stained “en bloc” with the Ur‐Pb‐Cu technique of Thiéry and Rambourg ('76) or post‐fixed and stained with the osmium tetroxide‐potassium ferrocyanide method of Karnovsky ('71). Thin or thick (up to 3 μm) sections were examined with the Philips (301 or 400) EM or the high voltage EM. Stereopairs were prepared with photographs of tilted specimens (± 7°).

At low magnification, in thick sections (0.5–3 μm) stained with Ur‐Pb‐Cu, the whole Golgi apparatus formed a single network of interconnected wavy ribbon or platelike structures extending from the juxtanuclear region toward the apex of the cell. At higher magnifications, with the two staining techniques, this Golgi network showed two distinct types of regions: the “saccular region” corresponding to the conventional stack of saccules and the “intersaccular connecting region” made up of anastomotic tubules which bridge adjacent stacks. In the saccular regions, there was, on the cis‐face of the stack, a tight polygonal meshwork of anastomotic tubules (osmiophilic element). Underlying it there were three to seven closely apposed saccules perforated with pores of various diameters, and finally, on the trans‐face, a network of tubules was usually connected to the last saccule of the stack, which seemed to peel off from the pile,

The intersaccular connecting regions showed proximal and distal zones with regard to the associated stacks. The proximal zone was made up of superimposed and parallel polygonal networks of membranous tubules which were continuous with corresponding saccules of the stack. In the distal zone they interdigitated, intertwined, anastomosed and bridged adjacent saccular regions; others turned at right angles and established connections with tubular extensions arising at various levels of the same stack. While cisternae of endoplasmic reticulum were contiguous with tubules or saccules located on the transface of the Golgi apparatus, a close association between the ER cisternae and the cis‐face of the stacks was not usually observed.
A morphometric study quantifying the mucus content of proliferating colonic epithelial cells
Authors: Porcella Russell A. , Swartzendruber Donald C. , Godbold James H.
Published: February 2005

We report a quantification of the maximum mucus accumulation in proliferating rat colonic epithelial cells. The proliferative potential was determined by radioautographic study of one‐hour pulse exposures to tritiated thymidine, mucous content was determined by Periodic‐acid Schiff (PAS) staining. We examined 55 labeled mucous cells in 0.5‐ to 1‐μm serial sections. The maximum thecal and nuclear profiles of these cells were photographed and their surface areas were determined utilizing a coordinate sensor. The data were expressed as a theca‐to‐nucleus (T/N) ratio. The maximum (T/N) ratio for a labeled mucous cell was 3.0. We performed a similar analysis on 22 unlabeled mucous cells from upper crypt regions and surface epithelium to derive the range of (T/N) ratios for terminally differentiated mature mucous cells. The range of (T/N) ratios from these cells was from 4.8 to 16.4. Our study shows that proliferative potential of mucous cells is determined by the interrelationship between mucus accumulation and nuclear size.
Fiber types in red and white segments of rat sternomastoid muscle
Authors: Dulhunty Angela F. , Dlutowski Monica
Published: February 2005

The contractile, histochemical and morphological properties of fibers from red and white rat sternomastoid segments have been studied. Previous mechanical experiments suggested that both segments were fast‐twitch and the present experiments were done to confirm this observation and to determine other essential characteristics of the fibers.

The ATP'ase and succinic dehydrogenase (SDH) activities of fibers were determined using standard histochemical techniques. Seventy‐six percent of fibers in the red segment had the high ATP'ase and high succinic dehydrogenase activity typical of fast‐twitch‐red fibers. Other fibers in the red segment were typically fast‐twitch‐white (13%) or slow‐twitch‐red (11%). The average cross‐sectional area of red fibers was 2,104 m̈m2. Fibers in the white segment were mostly (84%) fast‐twitch‐white with intermediate ATP'ase activity and low to intermediate SDH activity. The remaining fibers in the white segment were histochemically typical of fast‐twitch‐red fibers. The average cross‐sectional area of white fibers was 5,109 m̈m2. Morphologically, red fibers had three times as many mitochondria as white fibers and a Z‐line thickness 38% greater than that of white fibers.

Although fibers from the red segment were histochemically and morphologically different from fibers in the white segment, the isometric tension characteristics, i.e., contraction time, post‐tetanic potentiation and fatigueability, were very similar and were typical of fast‐twitch‐fatigueable preparations. Thus, histochemical and morphological characteristics of fibers in the sternomastoid muscle are not indicative of the mechanical properties of the fibers.
Morphogenesis of the truncus arteriosus of the chick embryo heart: Tissue reorganization during septation
Authors: Thompson Robert P. , Fitzharris Timothy P.
Published: February 2005

Septation of the truncus arteriosus of the normal chick embryo heart was surveyed systematically with the light microscope. Tissue from replicate samples at successive periods of development was sectioned within an arbitrary coordinate system based on positional reference points along the external surface of the heart. Correlation of several aspects of tissue morphology within this spatial and temporal reference‐frame yielded a new description of tissue associations and kinetics during septation.

A stable complex of tissue structures appeared in the downstream, distal truncus at Stage 25 and persisted throughout the septation process. This complex consisted of (1) the cephalic margin of the myocardial sheath, and (2) the adjacent bifurcation of the vascular lumen, linked together by (3) the newly condensed Y‐shaped strap of cells forming the aorticopulmonary septum. The apparent motion of this septation‐complex toward the ventricle(s), the appearance within the thoracic cavity of the adjacent segments of the aortic arches, and measures of tissue length and width suggested that septation was accompanied, and perhaps initiated, by increased tension along the truncus.

The truncal ridges remained upstream from the complex, with mesenchymal condensations beneath the endocardium differentiating into the definitive semilunar valves. Downstream from the bifurcation, mesenchyme in the aortic arch region condensed around the separate lumens to form the smooth muscular tunica media of the great arteries. The epicardium developed in a caudocephalic direction along the heart tube. Vagal innervation approached the heart cephalocaudally. Capillaries formed along the dividing truncus in both directions. Autoradiography following 3H‐thymidine labelling demonstrated reduced DNA synthetic activity in the cephalic margin of the myocardium and aorticopulmonary septum, compared with the associated loose mesenchyme.
Morphogenetic reaggregation and luteinization of mouse preantral follicle cells
Authors: Nicosia Santo V. , Tojo Ryutaro
Published: February 2005

Small (60‐90 μm) and large (100‐130 μm) preantral follicles were isolated from adult mouse ovaries by a collagenase‐dissection technique. These follicles were composed of resting oocytes surrounded either by granulosa cells, only, or by granulosa and undifferentiated theca cells. Further enzymatic dissociation of primary follicles yielded monodisperse cells characterized by abundant rough endoplasmic reticulum, microfilament‐rich pseudopodia and only scant lipid droplets. These cells reaggregated, when explanted in stationary culture, forming epithelial cords and structures macroscopically reminiscent of native ovarian follicles. Anticipated association of follicular cells in epithelial‐like monolayers was rare (≤ 10% of all cultured cells). Formation and growth of both follicle‐like (FLS) and cord‐like (CLS) structures occurred within 24 hours of culture, continued for 14 days, and was inhibited by cytochalasin B, but not by neuraminidase. FLS and CLS, as well as cell monolayers, underwent luteinization, as indicated by the presence in the culture medium of radioimmunoassayable progesterone and by frequent cytological features suggestive of active steroidogenesis. The present report indicates that (a) specific cell affinities exist among immature follicular cells which may play a role in folliculogenesis; and (b) follicular cells are endowed, from their early developmental stages with intrinsic steroidogenic capabilities which become pheno‐typically expressed after escape from the intraovarian environment.
Differentiation of myoepithelial cells in the developing rat sublingual gland
Authors: Redman Robert S. , Ball William D.
Published: February 2005

Sublingual glands of rats were prepared for light and electron microscopy and for the histochemical demonstration of myofibrils and alkaline phosphatase (AkPase) activity. Through 17 days in utero, the epithelial cells of the glandular rudiment are relatively undifferentiated. At 18 days, the inner cells of the terminal buds begin to assemble around a lumen and accumulate secretory granules, while the outer cells flatten and form long processes. At 19 days, many of the outer cells have dilated cisternae of rough endoplasmic reticulum engorged with finely granular material. At 20 days, some of the outer cells have thin bands of microfilaments in their processes, suggesting that they are differentiating into myoepithelial cells (MEC). Though the secretory cells are almost mature at birth, only a few of the MEC have myofibrils detected with an actomyosin reaction, and AkPase activity is very weak. Progressive increases in AkPase activity and in myofibril size and number continue until the acini and intercalated ducts are fully invested with mature MEC at about 14 days after birth. Thus, the MEC and secretory cells begin to differentiate at the same time, but the MEC subsequently differentiate asynchronously with the secretory cells and with each other. Although the sublingual MEC are only partly differentiated in the newborn rat, their overall development occurs somewhat more rapidly than in the adjacent submandibular gland.
Fetal and neonatal rat pancreas in organ culture: Age‐related effects of corticosterone on the development of the islet cells
Authors: McEvoy Robert C.
Published: February 2005

Fetal (18 days postcoitum) and neonatal (3‐day) pancreatic explants were grown in organ culture with or without supplementation with corticosterone (0.1 μg/ml). After 0, 4, and 8 days of culture, the specific hormone‐positive, islet cell volumes were determined by the use of immunocytochemical and morphometric methods. The insulin, glucagon, and somatostatin contents of the explants were estimated by radioimmunoassays. In the fetal explants, all of the islet cell populations increased in volume and the content of each of the hormones increased over an 8‐day period of culture. Supplementation with corticosterone resulted in a restriction of the increases of the alpha and delta cell volumes and in the somatostatin content of the explants. In the neonatal explants, the volumes of the alpha and delta cells and the glucagon and somatostatin contents decreased over a 4‐day culture period. The presence of corticosterone in the culture medium preserved these cells and their hormone content. Co‐culture of 18‐day fetal and 3‐day neonatal pancreata in control medium for 8 days resulted in a significant decrease in the content of all three of the islet hormones in the fetal explants. These results suggest that a substance harmful to the islet cells is released from the degenerating acinar cells. Thus, the effects of the steroid on the islets may be mediated through its effects on the acinar tissue.
The stem‐cell zone of the small intestinal epithelium. III. Evidence from columnar, enteroendocrine, and mucous cells in the adult mouse
Authors: Bjerknes Matthew , Cheng Hazel
Published: February 2005

In the first two articles of this series we demonstrated restriction of Paneth cell formation to positions 5 and above. Restriction was independent of the Paneth cell population‐density gradient in the crypt base. We concluded that our results were consistent with the presence in the adult of a stem‐cell zone in positions 1–4 in which stem cells received no inducement to differentiate. To further test the stem‐cell zone hypothesis we determined the site of stem‐cell differentiation along mucous, enteroendocrine, and columnar cell lines using radioautography with 3H‐thymidine, as a label.

One hour after injection of 3H‐thymidine, labeled mucous cells were not observed below position 5. Only later did they appear in lower positions and not until 4 days after injection were they observed in position 1. Labeled enteroendocrine cells first appeared above, and then were seen in the top of, and finally in the middle and bottom of the Paneth cell distribution. Thirty hours after injection there were two populations of labeled columnar cells in the crypt base, a heavily labeled population and a lightly labeled one. At this time interval the heavily labeled columnar cells were only observed in position 5 and above, but they appeared in position 1–4 by 66 hours after injection. The above evidence led us to conclude that all differentiated offspring of the common epithelial stem cell originate in positions 5 and above. Most columnar, mucous, and enteroendocrine cells originating in positions 5 and above migrate upward. However, some of these cells migrate down. All differentiated cells found in positions 1–4 migrated down from their origin in position 5 or above. We also found that only stem cells proliferate in positions 1–4. We concluded that in the adult, there is a stem‐cell zone in positions 1–4 where stem cells are not induced to differentiate and persist as stem cells throughout life.
Structural response of adult rat sertoli cells to peritubular fibroblasts in vitro
Authors: Cameron Don F. , Markwald R. R.
Published: February 2005

Sertoli cells were harvested from sexually mature rats and maintained in vitro for up to ten days (Sertoli cell‐enriched cultures) or co‐cultured with rat peritubular fibroblasts. Cultures were examined by differential light microscopy and by scanning or transmission electron microscopy.

The presence of peritubular fibroblasts in co‐culture greatly enhanced plating efficiency and viability of adult Sertoli cells. Sertoli cell aggregates preferentially adhered to peritubular cells, and by ten days had flattened and spread across these cells. Sertoli cells retained their characteristic ultrastructural features. Early in co‐culture a collagen‐like extracellular material was seen bridging Sertoli and peritubular cells, and its appearance was coincident with the presence of swollen rough endoplasmic reticulum in peritubular cells. Interperitubular cell spaces became engorged with a fibrillar material morphologically similar to the basal lamina of the seminiferous tubule wall. In the absence of peritubular cells, in culture medium “conditioned” by prior incubation with peritubular cells but not containing them, or when cultured with other fibroblastic cells, plating efficiency was low; Sertoli cells never flattened and cell ultrastructure progressively degenerated. The results indicate that peritubular cells support adult Sertoh cells in culture, possibly via extracellular material derived from peritubular cells, and suggest that Sertoli cells have an inductive effect on peritubular cell secretory activity.
Unusual cytoplasmic bodies in chromaffin cells of the adrenal medulla of the viscacha (Lagostomus maximus maximus)
Authors: Piezzi Ramon S. , Lucero Roberto O. , Guzman Jorge A.
Published: February 2005

Complex structures can be seen associated with large areas of endoplasmic reticulum of the chromaffin cells in the viscacha adrenal medulla. These structures are cylindrical in shape and are formed by chains of globular subunits. A central lumen is observed within which there are bodies resembling chromaffin granules. Parallel cisternae of the endoplasmic reticulum are arranged surrounding these bodies. The functional significance of these structures is unknown.
Tenotomy of the avian anterior latissimus dorsi muscle. II. Can regeneration from the stump occur in the pigeon?
Authors: Hikida Robert S.
Published: February 2005

Because the chick's anterior latissimus dorsi muscle (ALD) regenerates a fast‐twitch muscular connection after tenotomy, the pigeon's ALD was tenotomized, either at the origin or through the muscle 0.5 cm from the origin, to determine whether this muscle behaves similarly to the chick muscle. These procedures were compared in pigeons operated upon at 7 weeks, versus 5 to 9 months of age. The pigeon's ALD did not regenerate a new connection, and other differences were observed between the pigeon and chick ALD. The pigeon ALD has only a single slow muscle‐fiber type, has fewer fast fibers, and transforms to a fast‐twitch muscle more readily than the chick ALD after tenotomy. The transformation of muscle fiber types occurred more readily in the older pigeons than those tenotomized at 7 weeks of age. Tenotomy induced morphological alterations of the muscle fiber structure in all of the pigeons, which is in contrast to the absence of changes in the tenotomized chick ALD. Therefore the pigeon and chick ALD respond completely differently to tenotomy.
Topochemical aspects of nucleic‐acid and protein metabolism within the neuron‐neuroglia unit of the hypothalamic supraoptic nucleus
Authors: Pevzner Leonid
Published: February 2005

The RNA and both the total and basic protein content of individual cells were determined by cytospectrophotometry in neurons and perineuronal oligodendroglia of the hypothalamic supraoptic nucleus in rats subjected to various stresses, as well as in ground squirrels during natural hibernation. Barbiturate narcosis and deep cooling, which induced a decrease in body temperature in rats and hibernation in squirrels, caused a marked decrease of all macromolecular constituents in neurons. A similar decrease was found in the perineuronal oligodendroglia in rats, but an increase was observed in ground squirrels. After cessation of cooling, while the body temperature of the animals returned to normal, the neurons, but not the oligodendroglia, of rats showed a significant accumulation of RNA, while RNA accumulated in both neurons and perineuronal oligodendroglia in ground squirrels.

Milder cooling of rats, which did not lower their body temperature, induced reciprocal changes in basic‐protein content in neuronal and glial cell nuclei, with the accumulation of protein occurring initially in neurons, and subsequently in glia. When cold adaptation was accomplished, the basic protein content of neurons and glial cells returned to the control level.

Four days after adrenalectomy in rats, the RNA content decreased in oligodendroglia but not in neurons of the supraoptic nucleus. This effect was completely abolished by daily injections of cortisol in the adrenalectomized animals.

The data obtained indicate the existence of differences in metabolic responses to stress between neurons and glial cells of the supraoptic nucleus of the hypothalamus.
Kidney of a juvenile okapi, Okapia johnstoni
Authors: Maluf N. S. R.
Published: February 2005

The kidney of the okapi is of the medullary crest type and is divided transversely into six lobes by encroachments of cortex into medulla. These lobes are demarcated externally by furrows. The collecting ducts open at the apex of the truncated medullary crest. The pelvic part of the kidney, or pars pelvina renis, is the entire inner medulla and is the only part exposed to the pelvic urine. The pelvis has 10 interlobar vascular eminences and extends peripherally along‐side the interlobar vessels as 10 fornices. The vascular eminences are buttressed by 12 free‐edged semilunar eminences, which form pouches across 12 intervascular eminences. At each pole a vascular eminence supplies blood vessels to a dorsal and a ventral intervascular eminence.

The extrahilar portion of the renal vein consists mainly of a thick coat of longitudinal muscle. In the renal sinus this heavy muscular coat is absent. The tributaries of this vein open via conspicuous nonmuscular valves.

The cortex is about 85% of the renal mass and has about 2.89 × 106 glomeruli, which form 4.85% of the cortical mass. The filtering surface of a glomerulus is 0.088 mm2, making the total filtering surface of one kidney 0.219 m2. The number of glomeruli per kidney falls into the line which relates number of glomeruli to adult body weight from mouse to elephant and is expressed by log N = 0.59 log W + 3.2 or by N = 1.585W0.59 where N is number of glomeruli in one kidney and W the adult body weight.
Identification of prolactin and growth hormone cells in the pars distalis of the California leaf‐nosed bat, Macrotus californicus
Authors: Richardson Bruce A.
Published: February 2005

Prolactin (PRL) and growth hormone (GH) cells were immunostained in the anterior pituitary lobe of the California leaf‐nosed bat with antisera against rat PRL and GH by the unlabeled immunoperoxidase technique. The PRL antiserum reacts with a cell that is carmoisinophilic and pleomorphic and occurs in small groups within the ventro‐, dorsocentral, and posteriolateral regions of the pars distalis. The cells that stain with the anti‐GH serum are orangeophilic, smaller than the PRL cells, and randomly scattered throughout the pars distalis, singly or in palisades near capillaries. Morphometric analysis of the immunoreactive PRL and GH cells revealed an inverse relationship between these two cell types.
Dedifferentiation of iris epithelium during lens regeneration in newt larvae
Authors: Reyer Randall W.
Published: February 2005

Early stages in lens regeneration from the pigmented epithelium of the dorsal iris were studied in larval Notophthaimus viridescens by means of transmission electron microscopy. Normal iris epithelium is composed of two layers of low cuboidal cells, packed with melanosomes and surrounded by a basal lamina. Scattered desmosomes attach adjacent cells. Following lens removal, the intercellular spaces enlarge and the epithelial cells increase in size. Some irregular microvilli from these cells extend into the intercellular spaces. Macrophages invade the iris epithelium and phagocytize melanosomes discharged from the pigmented cells. These invading macrophages have numerous microprojections and are often separated from the surface by a very thin layer of iris epithelial cell cytoplasm. In the iris cells, nucleoli become more prominent and granular, polyribosomes increase greatly in number, melanosomes gradually disappear, mitochondria become more numerous, and mitotic activity is greatly augmented. Fine cell processes of adjacent cells interdigitate near the external surface, where numerous micropinocytotic vesicles can be seen. Over the external surface, the basal lamina may be disrupted or duplicated in places where pseudopodia project from iris cells or a macrophage has entered an intercellular space. It is lacking on the lumenal surface. Sloughed membranes are often found in these intercellular spaces.
Degeneration of mouse digital corpuscles
Authors: Idé Chizuka
Published: February 2005

The sequential changes of the morphology and the histochemically demonstrated, nonspecific cholinesterase (ChE) activity of the denervated digital corpuscle (Meissner corpuscle) of the mouse were observed by light and electron microscopy for 6 months after transection of the sciatic nerve. A fragment of the sciatic nerve, approximately 1 cm long, was removed from the distal stump to prevent reinnervation. Within one day following nerve division, the axon terminals began to manifest degenerative changes; the axoplasm became electronopaque and some mitochondria became disorganized. The lamellar cell processes (lamellae) also exhibited atrophic changes; they became thinner and more electron opaque. The lamellar cell body became smaller due to a decreased amount of cytoplasm and contained few organelles except for some free ribosomes. These changes advanced with time. Around 4–6 months after denervation, the corpuscle was small, consisting of a few thin, shrunken, atrophic lamellar cells. The ChE activity persisted and could be demonstrated in the interlamellar spaces, but its intensity decreased with time so that the corpuscle was hardly identifiable by light microscope histochemistry around 4–6 months after denervation. During this time, the precipitates of the reaction product were scattered as small particles throughout the interlamellar spaces. The enzyme activity in the cisternae of the rough endoplasmic reticulum and the nuclear envelope of the lamellar cell body was no longer demonstrable 5 days or less after denervation. These findings indicate that the lamellar cell is dependent on the axon terminal to maintain its normal morphology and the function of ChE synthesis.
Response of tanycytes to aging in the median eminence of the rat
Authors: Brawer James R. , Walsh Raymond J.
Published: February 2005

Age‐related changes in tanycytes of the median eminence were observed at both the light and electron microscopic level in male and female rats at ages 4 weeks to 14 months. The most obvious changes involved a marked progressive increase in number and size of droplets identified histochemically as neutral lipid and the development of complex degenerate bodies in the perivascular contact zone. These degenerate bodies consisted of large multiple complexes of myelin figures containing intercalated channels and pools of electron‐dense material. They often occurred interspersed among large lipid droplets. The degenerate bodies (myelin figure complexes) and associated lipid droplets occupied much of the contact zone in the older animals. Evidence of axonal degeneration and tanycytic phagocytosis of deteriorating neural elements was also present. These age‐related changes occurred independent of sex and were not affected by gonadectomy. This tanycyte response to aging in the median eminence is very similar to the response of neurohypophysial pituicytes to axonal degeneration, suggesting a phagocytic glial role for tanycytes.
Reproductive tract abnormalities in rats treated neonatally with DES
Authors: Ennis Bruce W. , Davies Jack
Published: February 2005

Neonatal female Sprague‐Dawley rats were given daily injections of 3 μg diethylstilbestro (DES) for 5 days beginning within 24 hours of birth. Some of these rats were ovariectomized between the 15th and 18th postnatal days, and on the 60th postnatal day were given daily injections of 3 μg estradiol for 1, 3, or 5 weeks. Intact rats were sacrificed at 60, 95, or 130 days. The morphology of the upper vagina, cervix, and lower uterus was examined by light and scanning electron microscopy. Two abnormalities resulting from neonatal DES exposure were found. The first was squamous metaplasia observed in the uteri of rats given DES and later exposed to exogenous or endogenous estrogen. Metaplasia was seen in both the luminal and glandular epithelium. The longer the rats were exposed to exogenous or endogenous estrogen, the more extensive was the metaplasia. The second was a gross morphologic abnormality seen in all rats given DES regardless of any later treatment. That part of the cervix that protrudes into the cranial limit of the vagina was absent and, thus, a vaginal fornix was nonexistent.

Previous investigations have emphasized abnormalities of the lower reproductive tract. The present study indicates that the upper reproductive tract also must be considered in investigations of the effects of hormones administered to neonates.
Arteries and veins of the normal dog lung: Qualitative and quantitative structural differences
Authors: Michel René P.
Published: February 2005

As a necessary preliminary step to the study of pulmonary hypertension and edema, the structure of the pulmonary vasculature of seven normal dogs was examined in detail to distinguish arteries and veins. For light microscopy and morphometry, the left lung was injected from the arterial and venous sides with pigmented gelatin masses of different colors. The right lung was fixed for electron microscopy. The percentage of medial muscle thickness of arteries was greater (P < 0.05) than that of veins, for vessels over 200 μm diameter. Smooth muscle cells extended more peripherally into arteries (including in vessels less than 50 μm) than into veins. The larger arteries were elastic or transitional in type, whereas larger veins were muscular. The arteries branched with the airways. Fifty percent of arteries under 50 μm and more than 50% of veins under 200 μm were surrounded by alveoli. Muscular arteries had a thick media between distinct internal and external elastic laminae, whereas veins had no internal lamina but had a thin media separated from a thick adventitia by an external elastic lamina. By electron microscopy, the muscular arteries had tightly packed smooth muscle cells with few myoendothelial junctions; the venous smooth muscle cells were arranged loosely, and more numerous myoendothelial junctions were seen. No definite differences were noted between nonmuscular arteries and veins. The functional implications of these morphological findings (differential reactions to pharmacological agents, distensibility of pulmonary arteries and veins, and responses of small vessels to alveolar pressure) are discussed.
Phasic secretion by follicular cells of the bat adenohypophysis during the prearousal period of their annual life cycle
Authors: Nunez Eladio A. , Gershon Michael D.
Published: February 2005

The fine structure of the follicular (nongranulated) cells of the adenohypophysis of the bat was examined at different periods of the annual life cycle. Follicular cells were found in all regions of the pars distalis of both active and hibernating bats. Throughout the active phase of the life cycle and during most of the hibernating period, the structure of follicular cells is unchanged. Toward the end of hibernation, however, striking ultrastructural changes occur. The most obvious of these alterations is the appearance in follicles of dense rodshaped bodies within the follicular luminal space. Just prior to arousal, the rodlike bodies become much wider and appear more as paracrystalline aggregates of dense material. Images indicate that the dense rod‐shaped bodies are packaged in vesicles in the cytoplasm of the follicular cells. The fusion of the membrane of filled vesicles with the plasma membrane of the follicular cell results in the release of their dense rod‐shaped bodies into the follicular lumen by exocytosis. These cyclic ultrastructural changes indicate that follicular cells have a phasic secretory activity.
Neuronal changes induced by neonatal hypothroidism: An ultrastructural study
Authors: David S. , Nathaniel E. J. H.
Published: February 2005

The postnatal development of the neurons of the cuneate nucleus was examined ultrastructurally in euthyroid and hypothyroid rats from birth to the sixth postnatal week. In the euthyroid animals, the neurons at birth displayed mild nuclear invaginations and a scanty cytoplasm with few organelles. By 2 weeks, there was a considerable increase in Nissl bodies. At 3 weeks, the neurons contained short lamellar arrays of endoplasmic reticulum. Between 3 and 6 weeks there was a reduction in the Nissl substance. In the hypothyroid animals, although the sequence of maturational changes generally resembled that of the controls, a number of differences were noted. The neurons at 1 week displayed dilations of perinuclear space, rough endoplasmic reticulum, Golgi complexes, and mitochondria. At 4 weeks both perikaryon and myelinated axons contained glycogen. Several neurons with cytoplasmic inclusions considered to be nonfunctional RNA were seen. The 6‐week hypothyroid neuron exhibited large, clear, cytoplasmic vacuoles associated with a drastic reduction in cytoplasmic organelles. Presynaptic terminals showed a 50% reduction in mitochondrial numbers associated with the presence of glycogen granules. Three changes observed in neurites in all the age groups included: (1) large accumulation of glycogen in presynaptic terminals; (2) clear vacuoles; and (3) the presence of numerous lamellar bodies within reactive axons. Aberrant myelination, such as a single myelin sheath enclosing multiple processes, and instances of collapsed and redundant myelin were encountered.
Ultrastructure of cultured atrial cardiac muscle cells from adult rats
Authors: Moses R. L. , Claycomb William C.
Published: February 2005

Atrial cardiac muscle cells enzymatically isolated from adult rats were maintained in culture for 0–17 days and examined by transmission electron microscopy (TEM). Cells were stained with conventional TEM stains as well as with osmium ferrocyanide and tannic acid. Our results show that cultured adult atrial cells are capable of in vitro ultrastructural reorganization and possess differentiated ultrastructural characteristics including specific atrial granules, sarcomerically arranged myofilaments, appropriately organized sarcoplasmic reticulum (both junctional and nonjunctional), and intercalated disc components. In addition, the cultured atrial cells also posses rare, but ultrastructurally typical, elements of the transverse tubular system. These can be identified on the basis of size, location, association with internal junctional sarcoplasmic reticulum, and accumulation of extracellular tracer. Atrial muscle cells are capable of reestablishing a myotypic ultrastructure, although they have a considerably less complex and organized in vitro ultrastructure than similarly cultured adult ventricular myocytes. This lessened in vitro ultrastructural specialization is in accord with the in vivo comparative ultrastructure of atrial vs. ventricular myocytes.
Microdissection by ultrasonication: Porosity of the intestinal epithelial basal lamina
Authors: McClugage Samuel G. , Low Frank N.
Published: February 2005

The porosity of the epithelial basal lamina of normal rat intestine was studied by SEM. Epithelial removal was accomplished by prolonged fixation of tissue samples in OsO4 or immersion in aqueous H3BO3, followed by dehydration in acetone and microdissection by ultrasonic vibration. The underlying basal lamina of intestinal epithelium reveals numerous pores of variable size. These pores are more numerous in small than in large intestine and penetrate the entire thickness of the basal lamina. Within the basal lamina overlying lymph nodules, they are numerically increased. Their occurrence is evident in fixed and unfixed, sonicated and unsonicated tissue samples. Microprojections of epithelial cytoplasm are often observed within these pores. The results of this study suggest that migrating cells or epithelial‐cell processes induce pore formation in epithelial basal laminae and that these pores may be eventually repaired.