bluuebunny/crossref_metadata_2025 huggingface dataset:
The intersegmental anastomoses between spinal nerve roots
Authors: Moriishi Johji , Otani Katsumi , Tanaka Koichi , Inoue Shun‐Ichi
Published: February 2005

Frequency and morphological characteristics of the intersegmental anastomoses between the spinal roots were investigated in 100 adult spinal cords from the cervical to lumbar segments. The frequencies of dorsal root anastomoses were 61, 7, and 22% of the cervical, thoracic, and lumbar cords, respectively. On the other hand, the incidence of anastomosis between the ventral roots was significantly low in both the cervical (10%) and lumbar (5%) cords as compared with that between the dorsal roots in these regions (P < .01). No anastomotic connections were found in the thoracic ventral roots. The anastomoses were classified into four types: types A and B; the borders between the spinal segments were cranially and caudally shifted, respectively; type C, anastomosis attached to the spinal cord at the border between the segments; and type D, anastomosis bridged between the adjacent rootlets and coursing parallel to the cord. The proportions of the four types at each spinal level disclosed that type A was most commonly observed compared with the other three types in the dorsal roots (P < .01). In the lumbar cord, the proportion of type C anastomosis between the dorsal roots increases noticeably toward the sacral level, while a complementary decrease occurred in type A. In the cervical ventral roots, types C and D predominated over the other two types (P < .01). The lumbar ventral roots contained types B and/or C. Type D anastomosis occurred exclusively in the cervical segments.
Morphology of the pterygomandibular raphe in human fetuses and adults
Authors: Shimada Kazuyuki , Gasser Raymond F.
Published: February 2005

The pterygomandibular raphe as described in current anatomy textbooks is not supported by actual observations in cadavers. A study was made on 60 adult Caucasian and Negro cadavers (52 right and 58 left sides, giving a total of 110 sides) providing comparison with an earlier study on Japanese specimens. In addition, 50 fetuses (25 mm crown‐rump length to term) were examined to determine the arrangement of the raphe prenatally. Variations in the morphology of the raphe region were classified into three types: Type A—only the upper portion of the raphe could be identified and had a broad, triangular shape. Type B—the buccinator and superior pharyngeal constrictor muscles were widely separated by a broad, fascial region. Type C—the raphe was absent with complete continuity of the buccinator and superior pharyngeal constrictor muscles. A prominent, narrow, tendinous band with attachments as described in current textbooks was never found in adults. There was a complete absence of the raphe in 36% of the specimens resulting in continuity of the buccinator and superior pharyngeal constrictor muscles (type C). However, the remaining adult specimens (64%) exhibited some form of a broad, fascial region that either completely (type B, 36%) or partially (type A, 28%) separated the two muscles. All of the fetuses exhibited the type B arrangement exclusively, indicating that changes in the shape of the raphe occur postnatally. The frequency of appearance of the raphe types in adults differs significantly according to race.
Patterns of keratin expression in the murine thymus
Authors: Farr Andrew G. , Braddy Steven C.
Published: February 2005

Polyclonal and monoclonal antibodies recognizing different species of keratin molecules were used to characterize the expression of keratins by epithelial cells in the murine thymus. Some of the reagent antibodies used in this study were raised against human keratins and cross‐react with murine keratins. Both cortical and medullary thymic epithelial cells were found to contain keratin with apparent molecular weight of 52 KD, which is considered to be associated with simple or stratified epithelium. In addition, medullary epithelial cells were found to contain other species of keratin molecules, ranging in apparent molecular weight from 40 to 67 KD. This latter population of keratins is thought to be associated with stratified and/or keratinizing epithelia.
Distribution of laminin, collagen type IV, collagen type I, and fibronectin in chicken cardiac jelly/basement membrane
Authors: Little Charles D. , Piquet Dominique M. , Davis Lynn A. , Walters Luanne , Drake Christopher J.
Published: February 2005

Light microscopic immunolabeling studies were designed to identify and locate structural components within the cell‐free extracellular matrix which lies between the embryonic endocardial and myocardial tubes. Affinity‐purified antibodies were used to examine stage 15‐22 embryonic chicken hearts. Specimens were immunolabeled by using three different methodologies: (1) postembedding labeling of 10 μm cryostat sections, (2) preembedding labeling (en bloc) of whole hearts, and (3) postembedding labeling of ethanol/acetic acid‐fixed paraffin sections. Our results establish the spatial distribution of collagen type I and demonstrate for the first time the presence of collagen type IV and laminin in the myocardial‐basement‐membrane/cardiac jelly.
Circadian variation of epidermal growth factor receptor in mouse liver
Authors: Scheving Lawrence A. , Tsai T. H. , Scheving Lawrence E. , Feuers Ritchi E. J. , Feuers Ritchi E. J.
Published: February 2005

The liver undergoes a biochemical and morphological circadian transformation. In this paper, we document circadian variation in the binding parameters of the hepatic epidermal growth factor receptor (EGFR). Liver membranes were prepared from ad libitum fed or fasted male CD2F1 mice killed at different circadian phases at 4 h intervals. Bmax (maximum binding) and Kd (dissociation constant) varied in a rhythmic fashion. The range of change for Bmax along the 24 h time scale was 423%. For Kd, it was 162%. Both peaked late in the dark span, and decreased late in the light span. Fasting and EGF treatment reduced Bmax and the amplitude of circadian variation.
S‐100 protein in white preadipocytes: An lmmunoelectronmicroscopic study
Authors: Cinti Saverio , Cigolini Massimo , Morroni Manrico , Zingaretti M. Cristina
Published: February 2005

Differentiation of adipocytes from their precursor cells (preadipocytes) is an important problem in the study of the pathogenesis of obesity. Unfortunately, among the immature stages of adipocytes, only relatively differentiated forms can be identified by their fine structure; because early preadipocytes cannot be distinguished from fibroblasts solely on the basis of their morphology, it is impossible to assess the size of the preadipocyte population. S‐100 protein has been identified in various mammalian tissues and recently mature adipocytes have been shown to be positive for this protein. Because fibroblasts are negative for S‐100 protein, the present study tested the S‐100 immunoreactivity of preadipocytes by the peroxidase‐antiperoxidase (PAP) preembedding method at the ultrastructural level both in vivo and in culture. Mature adipocytes and early preadipocytes, including fibroblast‐like cells devoid of lipid droplets, were positive both in vivo and in culture. Endothelial cells and pericytes were negative; but flattened, lipid‐free, fibroblast‐like cells surrounding the pericytes were positive. True fibroblasts both in vivo and in culture were negative. Therefore, S‐100 protein can be a useful biochemical marker in distinguishing fibroblasts from early preadipocytes.
Quantitative assessment of the biological effects of follicle regulatory protein on dihydrotestosterone‐maintained spermatogenesis in hypophysectomized rat
Authors: Ahmad Nazir , Toppari Jorma , Dizerega Gere S. , Warren Dwight W.
Published: February 2005

Follicle regulatory protein (FRP) isolated from porcine ovarian follicles influences folliculogenesis through a paracrine mechanism. A similar protein has been found in the testes and seems to have some inhibitory effects on spermatogenesis when administered to intact male experimental animals. On the basis of female and male studies, it has been ascertained that the effects of FRP are at the level of gonads and not the pituitary or the hypothalamus. In the studies with intact males it was not possible to determine the exact site of FRP action on the testes. Dihydrotestosterone (DHT) has been shown to maintain spermatogenesis in hypophysectomized rats. In order to determine if the inhibitory effects of FRP are at steps prior to the formation of DHT, FRP was administered to hypophysectomized rats that were injected with DHT. Groups of adult rats were hypophysectomized and treated daily with FRP, DHT, FRP + DHT, or vehicle alone for 30 days. At necropsy, body, testes, prostate glands, and seminal vesicle weights were recorded. One testis and sexual accessory glands were fixed for histological evaluation. The contralateral testis was decapsulated, six 2 mm segments of seminiferous tubules, representing defined stages of spermatogenesis, were isolated by transillumination‐assisted microdissection, and spermatogenic cells were quantified by DNA flow cytometry. Histologically, the seminiferous tubules of vehicletreated hypophysectomized controls showed advanced regression. Rats treated with FRP alone showed similar degeneration. On the other hand, rats treated with DHT showed maintenance of spermatogenesis comparable to normal controls. The testes of rats treated with FRP + DHT were indistinguishable from those treated with DHT only. Flow cytometric quantification of germinal cells from all groups confirmed the histological findings. In this study FRP did not exert deleterious effects on DHT‐maintained spermatogenesis. This finding suggests that the inhibitory effects of FRP on spermatogenesis in intact animals may not be a direct effect on spermatogenic cells but may impair androgen action or production or DHT formation.
Development and maintenance of a polycystic condition in ovaries autotransplanted under the kidney capsule
Authors: Desjardins Gina C. , Brawer James R.
Published: February 2005

A single injection of estradiol valerate (EV) produces a polycystic ovarian (PCO) condition in the rat. The development of the PCO condition coincides with alterations in the endogenous plasma gonadotropin patterns, suggesting that PCO may be a response to abnormal gonadotropin stimultion. Other factors, however, such as direct autonomic innervation, also contribute significantly to the regulation of the ovary and could be important in generating and/or maintaining PCO. We have, therefore, removed and autotransplanted one ovary in each of eight rats under the capsule of the ipsilateral kidney, thus totally disrupting its innervation. The animals were injected with EV and both ovaries of each animal were examined 8 weeks later. In a second group of animals, we induced the PCO condition, autotransplanted one polycystic ovary in each animal under the kidney capsule, and examined the ovaries 2 weeks later. In both groups the autotransplanted ovaries exhibited the full range of polycystic morphology, as did the intact ovary in each animal. We conclude that since a major perturbation in innervation affects neither the development nor the maintenance of PCO, autonomic innervation does not play a crucial role in this disorder.
Cell polarity changes and migration during early development of the avian peripheral auditory system
Authors: Carney Paul R. , Couve Eduardo
Published: February 2005

The intracellular location of organelles was studied in avian embryos immediately before and during the initial detachment of cells from the dorsoanterolateral wall of the otocyst, using light and electron microscopy. The Golgi apparatus was silver‐impregnated, and its location within the otic epithelium was determined quantitatively. The present study demonstrates that a sub‐population of cells of the dorsoanterolateral otic epithelium changes the intracellular location of its organelles, particularly the Golgi apparatus and the centrosome, from an apical to a basal position. Concomitantly, cells lose specializations characteristically present at apical (tight junctions, microvilli) and basal (basal lamina) surfaces. At basolateral cell surfaces, filopodia form ahead of the Golgi apparatus and centrosome and penetrate the previously continuous underlying basal lamina. Thereafter, cells detach from the otocyst and migrate medially toward the hindbrain. Thus, concomitant with changes in surface polarity, the cells that comprise the dorsoanterolateral wall of the otocyst undergo profound changes in the intracellular location of their organelles, especially the Golgi apparatus and the centrosome, so that by the time cells detach from the otic epithelium a reversal in their “normal” internal polarity has occurred. We suggest that the change in cell polarity may be related to the mechanisms that allow cells to leave the otocyst.
Quantitative study of fungiform papillae and taste buds on the cat's tongue
Authors: Robinson P. P. , Winkles P. A.
Published: February 2005

The number of fungiform papillae has been counted on the tongues of six adult cats and of kittens both at birth and aged 2 and 4 months. Papillae were sampled from different regions of the tongue, and their size and the number of taste buds they contained were determined using histological sections taken parallel to the tongue surface. There were approximately 250 fungiform papillae on the tongues of the adult cats, the papillae were most numerous at the tip of the tongue, and there was no significant difference between the number of papillae on each side. The size of the papillae increased from a mean maximum diameter of 0.28 mm at the tip of the tongue to 0.48 mm at the back; the mean number of taste buds increased correspondingly from 6.9 to 16.6. The kitten tongues had a number and distribution of fungiform papillae similar to that found in the adults. In the neonate, papillae were smaller and contained fewer taste buds; these parameters increased with the corresponding increase in tongue size in the 2‐ and 4‐month‐old kittens.
Cross‐sectional internal diameters of human cervical and femoral blood vessels: Relationship to subject's sex, age, body size
Authors: Mortensen JD , Talbot Steven , Burkart John A.
Published: February 2005

Cross‐sectional internal diameter measurements were made of right and left common carotid and right femoral arteries and right and left internal jugular, superficial femoral, and common femoral veins in 32 normal human subjects utilizing duplex ultrasonography. The relationships of these vessel sizes to the subject's sex, age, height, weight, and body surface area were analyzed statistically; and graphs were constructed, indicating the relationship of blood vessel diameters to the various body size parameters. Findings indicate that (1) for the femoral veins, body surface area had the best correlation with the internal diameter of the vein; (2) for the right internal jugular vein, body weight had the best correlation with the internal diameter of the vein; (3) correlation between vein diameter and body size of the subject is better for the femoral veins than for the internal jugular veins; (4) internal diameter of the femoral and internal jugular veins increases about 20% when they are distended by 15% of positional inclination of the subject's body; (5) neither age nor sex of the subject influences the positional distensibility of the veins examined; (6) the cross‐sectional internal diameter of the femoral and internal jugular veins, as determined by duplex ultrasonography, closely relates to the external diameter of these vessels as measured by direct in vivo application of calipers and to the maximum outside diameter of cannula the vessel will accept.
Embryological development and prevalence of digital flexion creases
Authors: Kimura Sumiko , Schaumann Blanka A. , Plato Chris C. , Kitagawa Tadashi
Published: February 2005

The embryological development and morphology of digital flexion creases were studied in 178 human embryos and fetuses 6‐20 weeks of gestational age. The results suggest the existence of two types of digital flexion creases, that differ from each other in their development. The regular creases, with the exception of the distal crease of the proximal interphalangeal creases, and the oblique and extra creases of the irregular creases, develop concurrently with the appearance of the digital pads by about 11 weeks of gestation. The remaining creases, i.e., the distal crease of the proximal interphalangeal creases and the accessory crease develop later unrelated to the pads but, apparently, secondary to the flexion movements of the hand. Our observations further suggest that, because of their high frequencies, the oblique creases on the ulnar side of digits I and II and on the radial side of digit V and the extra creases on the proximal phalanx of digits I, III, and IV should be considered as “regular” creases.

Previously unreported pads were also found on the middle phalanges at about 11 weeks of gestation. Unlike the single, large pads with high elevation, typically found on the distal phalanges, those on the middle phalanges are multiple, small, and only slightly elevated. This observation provides further support to the concept of the relationship between the fetal digital pads and the development of the epidermal ridge patterns.
SEM and TEM analyses of isolated human retinal microvessel basement membranes in diabetic retinopathy
Authors: Carlson Edward C. , Bjork Nancy J.
Published: February 2005

Human retinas from persons with diabetic retinopathy and agematched controls were rendered acellular by sequential detergent treatment. The resulting network of microvascular extracellular matrix (ECM) materials, including basement membranes (BMs), was compared by TEM and, following cryofracture, by SEM. Our study demonstrates that in diabetics, retinal capillary BM complexes are generally thickened and that their ECM subcomponents, including BM leaflets and BM‐like pericytic matrix (PCM), are differentially altered. Two diabetic microvessel types were identified. In type A vessels, ECM expansion is manifested by loosely arranged combinations of concentric PCM layers and collagen fibrils with thickened subendothelial (EBM) and pericyte (PBM) BM leaflets. Type B vessels show densely compact central PCM masses and poorly recognizable EBMs and PBMs. In both types, Müller cell BMs (MBMs) are relatively unaffected. High‐resolution SEM shows tissue‐specific features in normal EBM and MBM surfaces, but disease‐related topographic changes are not evident. It is possible that the ECM arrangements identified in our study relate to different microvessel domains and that their specific morphological features may play important roles in the pathogenesis of diabetic retinopathy including capillary closure and neovascularization.
Intercellular communication within the rat anterior pituitary Gland. II. castration effects and changes after injection of luteinizing hormone‐releasing hormone (LH‐RH) or testosterone
Authors: Soji Tsuyoshi , Herbert Damon C.
Published: February 2005

This study investigated the relationship between gap junction formation and sex steroids in the male rat anterior pituitary gland. Animals were castrated at 5 days of age and separated into the following three groups: (1) oiltreated controls, (2) those injected with LH‐RH, and (3) those given testosterone. On days 10, 20, 30, and 40, five rats in each group were sacrificed and their hypophyses removed for ultrastructural examination. When compared with age‐matched, intact animals, there was a marked suppression in follicular development and in the number of gap junctions present in the pituitary glands of both the castrated controls as well as the castrates given luteinizing hormone releasing hormone (LH‐RH). In contrast, the morphology of these structures in the animals given testosterone was indistinguishable from that observed in the intact controls. These observations provide more definitive evidence that in the male rat pituitary gland maturation of the structural organization of the follicles, including gap junction formation, requires an intact hypophyseal‐gonadal axis and is highly dependent on the hormone testosterone.
Skeletal structural adaptations to mechanical usage (SATMU): 2. Redefining Wolff's Law: The remodeling problem
Authors: Frost H. M.
Published: February 2005

Basic multicellular unit (BMU)‐based remodeling of lamellar bone causes bone turnover, net gains and losses of bone on some bone surfaces or “envelopes,” and a remodeling space comprising bone temporarily absent due to evolving resorption spaces and incomplete refilling of them by new bone. Those features depend (a) on how many new BMU arise annually, (b) on how much bone each BMU has resorbed and (c) formed upon its completion, and (d) on how long the typical BMU takes to become completed. Because a, b, and c have limiting or maximal values in life that direct and/or indirect effects of mechanical usage of the skeleton can change, the theory presented here derives mechanical usage functions that express what fractions of those maxima a given mechanical usage history allows to happen. The theory predicts some changes in bone formation, resorption, balance, turnover, and remodeling space that depend on how remodeling responds to the vigor of a subject's mechanical usage. The theory can predict specific effects of specific mechanical challenges that experiments can test, and it fits abundant published evidence. As the kernel of a new approach to the problem it awaits critique and refinement by others. It plus the 3‐way rule can redefine Wolff's law conceptually and also in mathematical and quantifiable form.
Cellular regulation of basal and FSH‐stimulated cyclic AMP production in irradiated rat testes
Authors: Kangasniemi Marko , Kaipia Antti , Toppari Jorma , Mali Pekka , Huhtaniemi Ilpo , Parvinen Martti
Published: February 2005

Basal and follicle‐stimulating hormone (FSH)‐stimulated cyclic AMP (cAMP) productions by seminiferous tubular segments from irradiated adult rats were investigated at defined stages of the epithelial cycle when specific spermatogenic cells were low in number.

Seven days post‐irradiation, depletion of spermatogonia did not influence the basal cAMP production, but FSH response increased in stages II‐VIII. Seventeen days post‐irradiation when spermatocytes were low in number, there was a small increase in basal cAMP level in stages VII‐VIII and FSH‐stimulated cAMP production increased in stages VII‐XII and XIII‐I. At 38 days when pachytene spermatocytes and round spermatids (steps 1‐6) were low in number, a decreased basal cAMP production was measured in stages II‐VI and IX‐XII. FSH‐stimulated cAMP output increased in stages VII‐XII but decreased in stages II‐VI. At 52 days when all spermatids were low in number, basal cAMP levels decreased in all stages of the cycle, whereas FSH response was elevated only in stages VII‐XII.

All spermatogenic cell types seem to have an effect on cAMP production by the seminiferous tubule in a stage‐specific fashion. Germ cells appear to regulate Sertoli cell FSH response in a paracrine way, and a part of cAMP may originate from spermatids stimulated by an unknown FSH‐dependent Sertoli cell factor. The FSH‐dependent fuctions may control such phenomena as spermatogonial proliferation, final maturation of spermatids, and onset of meiosis.
Ultrastructure of the pituitary intermediate lobe in aging rats
Authors: Saland L. C. , Samora A. , Desai S.
Published: February 2005

The pituitary intermediate lobe, a source of pro‐opiomelanocortin (POMC) peptides, was examined with light and electron microscopic techniques in Sprague‐Dawley rats aged 5–18 months and Zucker rats aged 18 months. Cysts were common in the intermediate lobe in the Zucker animals, a finding also noted in human pituitary glands by other investigations. The nuclear envelopes were often indented in cells of aging rats, while those of young animals were generally smooth. Lipid droplets and lysosomes, rarely seen in tissue from young animals, were frequently observed in endocrine cells of older rats. Most cells had an abundance of secretory granules, suggestive of enhanced storage of peptides in the cytoplasm. Nerve terminals which were present among endocrine cells contained myelin figures in some of the old rats, and may indicate degenerative changes, while other terminals appeared normal. These morphologic findings suggest that the aging phenomena in intermediate lobe tissue have characteristics in common with nervous tissue, and may also reflect a diminished inhibitory neuroregulation.
Lympho‐epithelial interactions in the turtle Chrysemys scrypta elegans
Authors: Bianchi F. , Giannessi F. , Dolfi A. , Lupetti M.
Published: February 2005

The morphological relationships present in the areas of lymphoid infiltration found in the esophagus in Chrysemys scripta elegans were studied by the use of light and transmission electron microscopy. These infiltrations are wide‐spread and can be observed in the lamina propria and the covering epithelium. Electron microscopy reveals the presence of epithelial cells with differing characteristics at the apex of the lymphoid infiltrations. The introduction of horseradish peroxidase (HRP) into the esophageal lumen revealed that these cells possess a micropinocytotic activity. On the basis of the morphological and experimental results obtained, a hypothesis is advanced of the existence, also in the turtle, of a local system of uptake of extraneous material, which induces local and systemic immunological processes.
Effects of chronic corticostorone treatment on the morphology of rat neuromuscular junctions
Authors: Fahim Mohamed A. , Andonian Marc H.
Published: February 2005

This study examined the effects of chronic corticosterone (CORT) treatment on the morphology of two physiologically different muscles. Nerve terminals from the slow twitch soleus (SOL) and fast twitch extensor digitorum longus (EDL) of Fischer 344 rats were stained using the zinc iodide osmium (ZIO) technique. Nerve terminal area, perimeter, and logitudinal extent legth were measured using computer‐aided morphometry.

Slow and fast muscle fibers from animals which received 5–10 mg CORT per day for 3 months were atrophied compared with controls. Treated animals failed to gain weight during the study, while controls gained 37%. Adrenal weights in treated animals were 30% less than controls, after correction for body weight.

Morphological parameters for SOL nerve terminals were generally larger in the CORT group, while EDL nerve terminals from the CORT group did not differ significantly from controls. Soleus nerve terminal area was 43% greater, perimeter 14% longer, and logitudinal extent length 18% longer than the control nerve terminals. This study demonstrates a greater effect of CORT treatment on slow twitch muscle than has been demonstrated in previous studies. Changes in the nerve terminal morphology of the SOL were also greater than in previous studies and suggest that a functional adaptation or remodelling may occur following CORT treatment to maintain the neuromuscular interface during the enhanced catabolic effects of the steroid.

These steroid‐induced stress changes are similar in some respects to those observed in aging and disuse studies of the vertebrate neuromuscular junction. This suggests that glucocorticoid hormones may play an etiological role in the homeostasis of the neuromuscular junction in response to various stimuli.
Adaptation of cancellous bone to overloading in the adult rat: A single photon absorptiometry and histomorphometry study
Authors: Jee Webster S. S. , Li Xiao Jian
Published: February 2005

Nine‐month‐old female rats were subjected to right hindlimb immobilization or served as controls for 0, 2, 10, 18, and 26 weeks and were double‐labeled with bone markers. The right limb was immobilized against the abdomen and considered unloaded, while the left limb was overloaded during ambulation. Single‐photon absorptiometry was performed on intact femur; static and dynamic histomorphometry were performed on 20 μm thick undecalcified frontal sections of the proximal tibial metaphysis. Changes in the continuously overloaded limb was compared to that in both limbs of age‐matched control animals.

Single‐photon absorptiometry detected increases of bone mineral density of +6%, +6%, and +5% in the proximal and +9%, +7%, and +10% in the distal femoral metaphyses after 10, 18, and 26 weeks of continuous overloading. Morphometrically, significant changes occurred in proximal tibial metaphyses compared to age‐matched controls; trabecular area increased +41% and +45%, trabecular number increased +31% and +32%, and trabecular separation decreased −30% and −31% after 18 and 26 weeks of overloading. A significant increase in mineral apposition rate (+38%) was found only at 26 weeks of overloading. Insignificant decreases in both eroded and labeled bone surfaces occurred at all time periods. The histomorphometric changes indicated that increased cancellous bone mass was caused by an increase in bone formation activity (i.e., increases in mineral apposition and bone formation rates) and a decrease in remodeling space (i.e., decrease in bone eroded surface). These findings indicate that the adult skeleton can quickly adapt to the increased biomechanical needs by increasing its cancellous bone mass with an adequate structural pattern. It further support Frost's postulate that increasing skeletal mechanical usage stimulates bone modeling and depresses bone remodeling to increase and maintain bone mass.
Kinetics of germinal center development in lymph nodes of young and aging immune mice
Authors: Szakal Andras K. , Taylor Janet Kurowski , Smith John P. , Kosco Marie H. , Burton Greg F. , Tew John J.
Published: February 2005

Recent findings imply that germinal center paucity in old mice, at least in part, results from a defect in the mechanisms responsible for the transport of antigens to lymphoid nodules (follicles) and the consequent impairment of the antigen retaining reticulum (ARR) of follicular dendritic cells (FDCs). The present objective was to observe the kinetics of lymph node germinal center development in old mice having antigen transport and ARR deficits. Germinal center development was monitored in popliteal (PLN) and axillary (AXLN) lymph nodes of 6–;8 wk and 23‐mo‐old horseradish peroxidase (HRP) immune C57BL/6 mice. Using the selective binding of germinal center B cells for peanut agglutinin (PNA), germinal centers were identified in serial vibratome sections following histochemical labeling with PNA‐peroxidase conjugates at times 0, 15 min, 1, 3, 5, and 10 days after footpad challenge with 8 μg HRP. To follow the fate of preexisting (environmental antigen‐induced) germinal centers and the development of de novo (HRP‐induced) germinal centers, it was essential to distinguish between these germinal centers. Accordingly, PNA positive germinal centers associated with HRP‐retaining (peroxidase positive) ARR were identified as de novo germinal centers and germinal centers not associated with a peroxidase positive ARR were classified as preexisting germinal centers. Kinetic analysis of PNA positive germinal centers showed the following: (1) Preexisting, environmentally‐induced germinal centers dissociated and disappeared by day 3 as indicated by a decline in their numbers after antigen injection; the process of germinal center dissociation remained unaffected by aging. (2) The latency of de novo germinal center appearance was approximately equal in duration (∼3 days) to the disappearance of preexisting germinal centers. (3) The number and size of de novo HRP‐induced germinal centers increased through the experimental period in young lymph nodes, but in old mice these parameters were depressed, resulting in a significant germinal center deficit. (4) The ratio of HRP‐retaining ARR to de novo induced germinal centers was 1:1 in young and responder old mice. This ratio was not affected by aging. This finding favored the concept that antigen retention in ARR is a requirement of germinal center development. The observations supported our hypothesis that germinal center development, at least in part, depends on a normal antigen transport by showing that in aged mice with defective antigen transport‐related ARR and iccosome deficits there is an impaired development of germinal centers.
Increased density of glutamic acid decarboxylase—containing terminals in the medial preoptic nucleus and the area surrounding the paraventricular hypothalamic nucleus is associated with deoxycorticosterone acetate (DOCA)‐salt hypertension
Authors: Zappia Anthony , Hwang Bang H. , Wu J.‐ Y.
Published: February 2005

γ‐Aminobutyric acid (GABA) is a major inhibitory neurotrans‐mitter and has been shown to exert considerable influence on the neural control of the cardiovascular function. It is not clear, however, which GABAergic systems are involved in salt‐induced hypertension. This study was designed to investigate the GABAergic neurons in specific regions of the brain possibly linked to salt‐induced hypertension. After 4 weeks of deoxycorticosterone acetate (DOCA) and salt treatments, the rats developed cardiac hypertrophy. All of the animals were sacrificed for immunocytochemical localization of GABAergic terminals using specific antibodies to glutamic acid decarboxylase (GAD). GAD‐positive GABAergic terminal densities in discrete regions of the brain were determined by using morphometric quantitation. Results showed that GABAergic terminal densities in the medial preoptic nucleus and the area lateral to the paraventricular hypothalamic nucleus were significantly increased in DOCA‐salt‐treated rats 4 weeks after the experiment as compared with 4 week controls. This study provides new evidence to support further the idea that central GABAergic neurons are closely associated with pathogenesis of salt‐induced hypertension. Different hypertensive mechanisms between salt‐induced hypertension and genetic hypertension are also discussed.
Artificial matrix barriers: A diffusion study utilizing dextrans and microspheres
Authors: Persky Bruce , Hendrix Mary J. C.
Published: February 2005

Eight artificial matrices (AMs) were evaluated for the ability to restrict the passage of diffusion probes. Three AMs were composed exlusively of interstitial type I collagen (Col I) and differed from each other in thickness only. Four AMs consisted of reconstituted basement membrane (RBM) ‐coated polycarbonate filters (containing 10 μm diameter pores) and also only differed in thickness. One AM consisted of an uncoated 10 μm pore polycarbonate filter. The diffusion probes were uncharged fluorescein isothiocyanate‐labeled dextrans, having molecular weights of 17,900, 42,000, 71,200, and 148,900 and negatively charged latex microspheres, having diameters of 0.08, 0.30, and 0.95 μm. Probes were applied to the AMs, incubated for 72 hr at 37°C, and then analyzed spectrophoto‐metrically. Dextran passage was increasingly restricted for Col I matrices as either molecular weight or collagen thickness increased (range 7% to 0.7%). Thin RBM‐coated filters were more permeable to dextrans (range 100% to 30%) than Col I matrices. The diffusion rate of microspheres for Col I matrices (range 3.5% to 0) was similar to both thick and thin RBM‐coated filters (range 4% to 0). The uncoated filter permitted the most diffusion for both dextrans and microspheres (range 100% to 7%). These data demonstrate that the AMs presented in this study will allow direct observation of the degradative and migratory potential of cells in vitro as they interact with various extracellular matrices.
Age‐related immunohistochemical studies of A and D cells in pancreatic islets of C57BL/6J mice
Authors: Slavin Bernard G. , Lerner Steven P.
Published: February 2005

Sections of pancreatic islets from C57BL/6J mice aged 3, 14, and 24 months, consisting of islets derived from the dorsal primordium (DPI) and from the ventral primordium (VPI), were immunostained using the peroxidase‐antiperoxidase (PAP) procedure for localization of glucagon (A cells) and somatostatin (D cells). The density (A or D cell area/islet area) of immunopositive cells were determined using computer‐assisted image analysis. The density of A cells was significantly less in VPI of 14‐ and 24‐month‐old mice compared to 3‐month‐old mice. The density of A cells in 24 month DPI was less than 3 month DPI but no different from 14 month DPI. The mean area (μm2) of A cells (only in DPI) was significantly less at 24 months compared to the 3 and 14 month groups. There were no differences in somatostatin staining when comparing the three age groups, although at all ages the density of D cells was always greater in the DPI. In conclusion, the major difference between the young and older mice was a deficiency of glucagonstained cells in older mice. These results might be important in explaining improved glucose tolerance in aged C57BL/6J mice.
Glycoconjugate unique to migrating primordial germ cells differs with genera
Authors: Fazel A. R. , Schulte B. A. , Spicer S. S.
Published: February 2005

Previous cytochemical studies showing that rat primordial germ cells (PGCs) possess a unique surface glycoconjugate containing terminal α‐Nacetylgalactosamine were extended in this study to determine whether a similar distinctive glycoconjugate coats the surface of PGCs in the mouse. The results showed that mouse PGCs fail to react with peroxidase‐conjugated lectins specific for localizing glycoconjugate with terminal N‐acetylgalactosamine. All available lectin conjugates with affinity for other terminal sugars or internal sugar linkages also failed to stain mouse PGCs except for the conjugates that bind to α‐fucose. One fucose‐specific lectin conjugate stained only PGCs in the early mouse embryo but stained additional sites in more mature embryos and lost reactivity with PGCs after gestational day 14. Another fucose‐specific conjugate stained PGCs until day 15, but with less selectivity, and a third such conjugate bound to several sites, but not to PGCs. The results suggest that the developmental mechanisms mediating cellular interaction, migration, and differentiation may be similar in different genera, but the specific structure of the cell surface glycoconjugate involved in these mechanisms differs.
Cytochemical analysis of the notochord in early rhesus monkey embryos
Authors: Wilson Doris B. , Hendrickx Andrew G.
Published: February 2005

Functional differentiation of the notochord in rhesus monkey embryos at stages 11–12 (25–28 days of gestation) was analyzed by means of ultrastructural cytochemistry. The notochordal cells exhibited well developed Golgi complexes, rough endoplasmic reticulum, mitochondria, and numerous coated vesicles. Large irregular intercellular spaces were common, and some contained fibrils and particulate matter similar to that observed in the perinotochordal space immediately surrounding the notochord. With the glycogen‐specific thiocarbohydrazide‐silver proteinate technique, solitary particles as well as large aggregates of glycogen were present within the notochordal cells. The center of some aggregates was electron lucent and contained collapsed membranous structures. The results indicate that as early as stage 11 the nonhuman primate notochord exhibits ultrastructural features suggestive of secretory activity and cytological complexity.
Formation of ectopic neurepithelium in chick blastoderms: Age‐related capacities for induction and self‐differentiation following transplantation of quail Hensen's nodes
Authors: Dias Mark S. , Schoenwolf Gary C.
Published: February 2005

Hensen's node, regarded as the avian and mammalian homologue of Spemann's neural inducer (i.e., the amphibian dorsal blastoporal lip), has been transplanted in many previous studies to the germinal crescent of avian blastoderms to examine ectopic neural induction. All these studies have suffered from one or more major shortcomings, the most significant of which has been the lack of a reliable cell marker to determine the contributions of graft cells to ectopic embryos. In the absence of such marker, induced (i.e., derived from the host) and self‐differentiated (i.e., derived from the graft) neurepithelium cannot be distinguished from one another with certainty. We have transplanted quail Hensen's nodes to chick host blastoderms and have subsequently used the quail nucleolar heterochromatin marker to identify graft cells unequivocally. We systematically varied both donor and host ages (i.e., stages 3–8 and 3–5, respectively) to examine the effects of age on ectopic neural induction and self‐differentiation. Our results demonstrate that the age of the donor is more critical than that of the host over the stages examined. With advancing donor age, the frequency of host induction decreases, while the frequency of graft self‐differentiation increases. Previous studies not using cell markers have concluded that the craniocaudal level of the induced neuraxis is determined by the age of the donor, that is, young donors induce cranial neuraxial levels, whereas old donors induce caudal levels. By contrast, we found that with grafts from older donors, neurepithelium was more commonly self‐differentiated rather than induced and that progressively more caudal levels of the neuraxis self‐differentiated with advancing donor age. Induction of caudal neuraxial levels never occurred in the absence of induced cranial levels. The frequency of neural induction was inversely correlated with the age of the donor and directly correlated with the quantity of graft endodermal cells contributed to the ectopic embryo, supporting a previous assertion that in avian embryos, the earliest and principal source of neural inducer lies within the endoderm rather than mesoderm. From our results, we propose that the role of neural induction is to produce neurepithelium of unspecified regional character, and that the formation of regional character depends on subsequent morphogenetic events.
Endotoxin‐induced endothelial injury and subendothelial accumulation of fibronectin in rat aorta
Authors: Kang Yuan‐Hsu , Williams Robert
Published: February 2005

Endotoxin (lipopolysaccharide, LPS) induces endothelial injury in arterial vessels. Fibronectin is known to be involved in cell attachment and wound repair. The present study was designed to elucidate the effect of LPS on the production and distribution of fibronectin in relation to injury and repair in rat aortic endothelium. Male Sprague‐Dawley rats were sacrificed for ultrastructural and immunocytochemical evaluations at 1, 3, 6, 24, and 48 hr after a single intravenous injection of 1.5 or 3 mg/kg body weight E. coli LPS. Apparent morphological signs of endothelial injury, including cell detachment, denudation, cell death, and edema were observed 1–48 hr after injection. Parietal thrombosis and leukocyte diapedesis were also observed in the aorta. A profound increase in subendothelial fibronectin was found following LPS treatment. However, no distinct change in intracellular fibronectin was observed in the same endothelium until 24 hr after injection. Using horseradish peroxidase (HRP) and anti‐fibronectin‐HRP antibody as tracers, LPS was also found to increase permeability and extravasation of plasma proteins (fibronectin) of the aortic endothelium. The increase of subendothelial fibronectin possibly resulted from increased influx and sequestration of plasma fibronectin. This increase may provide a firm substratum for reendothelialization after vascular injury.
Ultrastructural analysis of the acrosome reaction in a population of single guinea pig sperm
Authors: Flaherty Sean P. , Olson Gary E.
Published: February 2005

Cauda epididymal guinea pig spermatozoa are arranged in rouleaux, with the sperm heads stacked one on top of the other; the plasma membranes over the apical segment of the acrosomes of adjacent sperm are linked and form non‐fusigenic “junctional” zones. A complex structural and temporal sequence of membrane fusions occurs during the acrosome reaction of guinea pig sperm in rouleaux. In this study, we have devised a procedure for dispersing the rouleaux and isolating a population of single, motile guinea pig sperm, and have investigated the ultrastructural features of the acrosome reaction in single sperm to determine if the pattern of membrane fusions is different from sperm in rouleaux. The rouleaux were dispersed using trypsin, and damaged cells were removed by passing the sperm suspension through a glass bead column; a population of 70–90% motile, acrosome‐intact, single sperm was obtained. Sperm were then induced to undergo lysolecithin‐mediated, “synchronous” acrosome reactions, and processed for transmission electron microscopy. The acrosome reaction involved a complex sequence of membrane fusions between the plasma membrane (PM) and outer acrosomal membrane (OAM). On the convex surface of the apical segment, sheets of hybrid membrane and parallel arrays of hybrid membrane tubules formed; filaments were associated with the luminal surface of the residual OAM in these regions. Hybrid membrane vesicles were produced on the concave surface of the apical segment, but fusion was delayed relative to the convex surface. In the principal segment, branching arrays of hybrid membrane tubules formed and later vesiculated. Hence, in single guinea pig sperm, the sequence of membrane fusions is similar to sperm in rouleaux except that fusion occurs in regions of the apical segment which form the non‐fusigenic PM “junctional” zones in rouleaux. The results suggest that, regardless of whether the acrosome reaction in vivo occurs before or after rouleaux dispersion, it will involve a complex sequence of membrane fusions which is determined by the structural properties of the OAM and PM.
Spermiation and sperm maturation in the marmoset
Authors: Kumar R. Asok , Phillips David M.
Published: February 2005

The scanning and transmission electron microscopes were used to examine the processes of spermiation and sperm maturation in the marmoset. We observe that the heads of late spermatids are embedded in the apical aspect of the large sleeve‐like columnar portion of Sertoli cells. As spermiogenesis progresses, spermatids become associated with numerous small apical Sertoli cell extensions. These finger‐like processes undergo a sequence of changes during spermiation. Spermatozoa from the caput, corpus, and cauda epididymides were examined. In caput epididymis of marmoset, the apical segment of the spermatozoa extends well beyond the rostral edge of the nucleus and folds back on itself. In sagittal sections, the acrosome exhibits a distinct hook shape. In the corpus, the distinctive hookshaped apical segment of the acrosome is observed in some spermatozoa, but the apical extension is significantly smaller or projects out only slightly beyond the nucleus. In cauda epididymis, the extension is absent. A similar acrosomal hook has been reported in the pigtailed monkey, which is an Old World species. We suggest that changes in acrosome structure during sperm maturation may be fairly widespread among primates.