bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fibrous tissue on the tibia plateau of the kangaroo. A theory on the pressure absorption of joint surfaces
Authors: Fuss Franz K. 
Published: February 2005

AbstractThe central part of the articular surface on the tibia plateau of Macropus agilis consists of fibrous cartilage of soft consistency and the fiber arrangement is macroscopically visible. The peripheral portions of the plateau are covered by hyaline cartilage but do not communicate with the hyaline articular surfaces of the femur, as they are covered by the menisci. The fibrous cartilage covering of the tibia plateau is a compliant or readily deformed pad that could serve the function of deforming enough under high joint loads to allow surrounding regions of the articular cartilage to share in carrying those loads, thereby magnifying the articular contact surface and decreasing the magnitude of the peak unit loads in the region of the fibrous tissue pad. This pressure‐absorbing mechanism represents the evolutionary response to the higher articular stress resulting from kangaroo locomotion. © 1994 Wiley‐Liss, Inc.
Temporal changes in sarcomere lesions of rat adductor longus muscles during hindlimb reloading
Authors: Krippendorf Beth B. , Riley Danny A. 
Published: February 2005

AbstractFocal sarcomere disruptions were previously observed in adductor longus muscles of rats flown approximately two weeks aboard the Cosmos 1887 and 2044 biosatellite flights. These lesions, characterized by breakage and loss of myofilaments and Z‐line streaming, resembled damage induced by unaccustomed exercise that includes eccentric contractions in which muscles lengthen as they develop tension. We hypothesized that sarcomere lesions in atrophied muscles of space flown rats were not produced in microgravity by muscle unloading but resulted from muscle reloading upon re‐exposure to terrestrial gravity. To test this hypothesis, we examined temporal changes in sarcomere integrity of adductor longus muscles from rats subjected to 12.5 days of hindlimb suspension unloading and subsequent reloading by return to vivarium cages for 0, 6, 12, or 48 hours of normal weightbearing. Our ultrastructural observations suggested that muscle unloading (0 h reloading) induced myofibril misalignment associated with myofiber atrophy. Muscle reloading for 6 hours induced focal sarcomere lesions in which cross striations were abnormally widened. Such lesions were electron lucent due to extensive myofilament loss. Lesions in reloaded muscles showed rapid restructuring. By 12 hours of reloading, lesions were moderately stained foci and by 48 hours darkly stained foci in which the pattern of cross striations was indistinct at the light and electron microscopic levels. These lesions were spanned by Z‐line‐like electron dense filamentous material. Our findings suggest a new role for Z‐line streaming in lesion restructuring: rather than an antecedent to damage, this type of Z‐line streaming may be indicative of rapid, early sarcomere repair. © 1994 Wiley‐Liss, Inc.
Development of the tendon of todaro during the human embryonic and fetal periods
Authors: Domènech‐Mateu J. M. , Martínez‐Pozo A. , Arnó‐Palau A. 
Published: February 2005

AbstractThis study covers the development of Todaro's tendon during human embryonic and fetal periods. The tendon primordium first appears when human embryos attain a CR length of 22 mm, but it only becomes well‐defined at 24 mm CR length. The tissue that will form the tendon proceeds exclusively from the inferior endocardial cushion. The tendon establishes a close relationship with the base of the septum secundum during its path towards the right venous valve, carrying myocardial tissue out and forming the fasciculus limbicus inferior to muscular tissue. The tendon's relationship with the superior aspect of the atrioventricular node primordium during the first part of its path is of particular interest. The relationship is most intriguing when the node morphology is least defined. This would explain the possible embryogenesis of extra atrioventricular nodes. We also consider Todaro's tendon to be largely responsible for the development of the sinus band which protrudes as a crest inside the right atrium. This band is particularly well‐developed in the fetal heart and provides an explanation for the large sub‐Eustachian sinus cavity. © 1994 Wiley‐Liss, Inc.
Development of cranial flexure and Rathke's pouch in the chick embryo
Authors: Pikalow Amy S. , Flynn Mary E. , Searls Robert L. 
Published: February 2005

AbstractExperiments were done to investigate the cause of the cranial (mesencephalic) flexure of the chick brain during stages 10 to 14. Measurements of the length and thickness of the roof and floor of the mesencephalon gave values similar to the values obtained previously by others. The labeling index was determined in the roof and floor of the prosencephalon, mesencephalon, and rhombencephalon as a preliminary measure of cell division. The labeling index was about the same in all regions, and was high enough to suggest that most of the cells were dividing. The labeling indices did not suggest that differential growth was caused by differential rates of cell division in the roof and floor of the mesencephalon. It was found through time lapse photography that the foregut and heart remained stationary along the rostrocaudal axis, whereas the prosencephalon moved rostrally and the mesencephalon underwent flexure. Measurements suggested that the neural tube cranial to the otic primordium grew in volume exponentially at a rate consistent with the labeling index. The rostral tip of the neural tube was observed to be linked to the rostral tip of the foregut by the ectoderm that formed Rathke's pouch at the neural tube and the pharyngeal membrane (prospective stomodeum) at the foregut. As the neural tube grew in length, the link between the neural tube and the foregut did not. We suggest that because of this link, the growing neural tube had to bend around the foregut, forming the cranial flexure, and the ectoderm folded where it attached to the prosencephalon, forming Rathke's pouch. © 1994 Wiley‐Liss, Inc.
Insertional mutation that causes acrosomal hypo‐development: Its relationship to sperm head shaping
Authors: Russell Lonnie D. , Ying Li , Overbeek Paul A. 
Published: February 2005

AbstractA family of transgenic mice (OVE 219) was generated by microinjection of a tyrosinase minigene (Ty811C). The transgenic mice demonstrate an atypical and variable coat color pattern and the homozygous males show abnormalities of spermatogenesis that are variably expressed from animal to animal. Heterozygous mice proved to have normal spermatogenesis and along with non‐transgenic mice were used as controls to study the abnormalities in spermatogenesis in OVE 219 homozygous males. These abnormalities shed light on the features controlling normal spermatogenesis. In some homozygous males early spermiogenesis was disrupted as the flagellar microtubules became disorganized within the flagellar process. What appeared to be crystalline tubulin was noted within some of the rounded flagellar processes. Sperm with this defect did not develop a flagellum. In other homozygous males defects were apparent by step 6 or 7 of spermiogenesis when the acrosome did not grow and spread over the nucleus as noted in control animals. The modified nuclear envelope underlying the acrosome continued to develop and spread well beyond one margin of the acrosome. Since the modified nuclear envelope grew independently of the acrosome, the acrosome was not the controlling factor in determining the spread of the modified nuclear envelope. Micrographs revealed that Sertoli ectoplasmic specialization failed to form over most regions of the spermatid head lacking a normal acrosome. In homozygous males, the manchette took origin (proximally) in close relation to the modified nuclear envelope and never in relation to the edge of the spreading acrosome, a feature indicating that manchette placement was influenced by the position of the modified nuclear envelope and not the edge of the acrosome. Thus the modification in the nuclear envelope may be the primary event to signal acrosomal spread and manchette development. In spermatids where the manchette developed from an ectopic site, the result was abnormal caudal head shaping. In some spermatids a portion of the manchette was lacking. When this occurred the caudal head was rounded in the region of the missing manchette. In a minority of spermatids there was no evidence for a manchette. The entire caudal head was gently rounded. These data support the growing body of evidence that the caudal sperm head is shaped, in part, by the manchette. The OVE 219 family of mice provides a useful model to understand the processes involved in periods of spermiogenesis that are critical to development of a normally shaped sperm head. © 1994 Wiley‐Liss, Inc.
Quantitative study of the apical nerve fibers of adult and juvenile rat molars
Authors: Naftel John P. , Bernanke Jayne M. , Qian Xiao‐Bing 
Published: February 2005

AbstractThe rat molar has become an important model for studies of interactions between nerves and the pulp‐dentin complex, yet there is only limited quantitative information on the number and size distribution of axons entering the roots of this tooth. This study was undertaken to provide such a detailed characterization of the apical innervation of the rat molar. An additional objective was to compare the apical nerve composition of young, recently erupted rat molars with that of mature teeth in order to determine whether there is ongoing maturation of the innervation after the teeth have attained functional occlusion.A complete census was made of the nerve fibers entering the roots of both mature and recently erupted juvenile mandibular first molars in Sprague‐Dawley rats. Each of the four roots of the first molars was processed for electron microscopy of thin sections near the apex.The majority of intradental nerve fibers entered the molar via the two larger (mesial and distal) roots. Within the apical root pulp, most, but not all, axons occurred within well‐defined fascicles associated with blood vessels. Molars from adult animals (age 4 months) had a mean total of 232 (S.D. = 49, N = 7 teeth) myelinated fibers and 806 (S.D. = 143) unmyelinated axons entering the four roots. Fibers exceeding the Aδ size range (circumference ≥ 19 μm) accounted for only 4% of the myelinated axons at the apex. Molars from juvenile animals (age 4 weeks) had fewer myelinated fibers (mean 176, S.D. 18, N = 8), but more unmyelinated axons (mean 1,174, S.D. 160) than adults. The mean ratio of unmyelinated axons to myelinated axons was 6.6:1 for juveniles compared to 3.5:1 for adults. Juvenile teeth contained no myelinated fibers that exceeded 19 μm in circumference.These results indicate that the innervation of the rat molar resembles that of teeth of non‐rodent mammals in that (1) innervation density is high, (2) there is a high ratio of unmyelinated axons, and (3) most of the myelinated fibers are of thin caliber. Furthermore, it appears that after the molar erupts, maturation of the nerve fiber composition continues with processes that include both a marked decrease in the number of unmyelinated axons and an increase in the number and size heterogeneity of myelinated fibers. © 1994 Wiley‐Liss, Inc.
Myocardial enlargement in defective heart development
Authors: Creazzo Tony L. , Burch Jarrett , Redmond Shannon , Kumiski Donna 
Published: February 2005

AbstractBackground: The cardiac neural crest (neural crest extending from the mid‐otic placode to the caudal region of somite 3) provides ectomesenchymal cells that contribute to aortic arch development and are essential for aortico‐pulmonary septation of the outflow tract. Bilateral ablation of the cardiac neural crest in the chick embryo, prior to migration, leads to aortic arch anomalies and failure of septation of the cardiac outflow tract, which produces a severe defect known as persistent truncus arteriosus (PTA). Altered hemodynamics resulting from abnormal aortic arch artery development and PTA and other unknown factors related to the absence of neural crest, are likely to alter the developmental history of the myocardium.Methods: In this study the wet and dry weights of ventricles and whole embryos, the total number of myocytes per ventricle and the myocyte density (number of myocytes per unit volume of ventricular myocardium) were compared in control (unwindowed eggs), sham‐operated and cardiac neural crest ablated chick embryos at day 11 of incubation.Results: We found that the wet and dry weights of ventricles from hearts with PTA were not different from normal hearts in control and sham‐operated embryos. However, the embryos with PTA weighed less than embryos with normal hearts. Thus, the ventricle to embryo weight ratios were greater in embryos with PTA compared to control and sham‐operated embryos for both wet (14 and 20%, respectively) and dry (30 and 59%) weights. The data further implied that more water was present with respect to body weight in comparison with sham‐operated and control embryos which indicated that the embryos with PTA were edematous. The total number of myocytes and the number of myocytes per unit volume were not different when comparing sham‐operated with PTA. Further, there was no indication that the myocardium from hearts with PTA was abnormal despite the small size and edema of the embryos.Conclusions: It appears that hemodynamic stresses, resulting from the structural defects produced by neural crest ablation, are insufficient to increase heart growth, although cardiac function is depressed as evidenced by edema and failure of the embryo to thrive. © 1994 Wiley‐Liss, Inc.
Light microscopic studies of pedicle and early first antler development in red deer (Cervus elaphus)
Authors: Li Chunyi , Suttie James M. 
Published: February 2005

AbstractBackground: Although it is known that deer antlerogenic potential resides in the periosteum of an antlerogenic region and antler forms through modified endochondral ossification, how a deciduous antler forms histologically through a permanent pedicle from the periosteum has not been reported.Methods: Histogenesis of the pedicle and the early first antler in red deer was systematically examined using light microscopy techniques.Results and Conclusions: At the pre‐pedicle stage, the frontal lateral crest (under 5 mm in height) consisted horizontally of antlerogenic periosteum and underlying cancellous bone. Both the cellular layer (3.74 times, P<0.01) and the fibrous layer of the antlerogenic periosteum were much thicker than those of the margin of the antlerogenic region or the facial periosteum. The crest was formed through intramembranous ossification. When the pedicle began to develop (5–15 mm in height), some discrete clusters of mature chondrocytes appeared in the bony trabeculae, which signified the beginning of the transition of the ossification pattern from the intramem branous to the endochondral. The pedicle consisted of three portions from distal to proximal, periosteum/perichondrium, osseocartilaginous tissue, and osseous tissue. When the pedicle became visible (about 20 mm in height), it consisted of the same three portions as the pedicle initiation stage, but the osseocartilaginous portion was expanded compared to the initiation stage and the cartilaginous proportion increased distally. When the pedicle grew to 25–40 mm in height, continous cartilaginous trabeculae appeared under the apical perichondrium. The pedicle consisted of four portions from distal to proximal: perichondrium, cartilaginous tissue, osseocartilaginous tissue, osseous tissue. It was formed through endochondral ossification. All these ossification pattern changes could not be seen externally as the overlying integument was characterised by typical scalp skin. When the pedicle grew to about 60 mm in height, antler tissue was visually apparent at the apex as the hair type changed from scalp hair to the velvet‐like hair of growing antler. However, this transformation could not be distinguished internally as the inside tissues were all continuous between pedicle and antler. Therefore, the histogenesis of the deer pedicle and the first antler originated from the antlerogenic cells and covered two phases: an internal phase through which pedicle was formed and an external phase which signalled the beginning of antlerogenesis. © 1994 Wiley‐Liss, Inc.
Shoulder region of the rat: Anatomy and fiber composition of some suprascapular nerve branches
Authors: Norlin R. , Hoe‐Hansen C. , Öquist G. , Hildebrand C. 
Published: February 2005

AbstractBackground: The pathophysiology of chronic supraspinatus tendinitis is not fully understood. This may be due to the scarcity of experimental studies on this issue.Methods: In search for a system suitable for experimental analysis, the present study describes the relevant gross anatomy of the rat shoulder region (dissection), and examines the fiber composition of relevant suprascapular nerve branches (electron microscopy, selective denervations).Results: The rat shoulder region is similar to the human shoulder in terms of gross anatomy. The average suprascapular nerve (SSC) is derived mainly from the spinal cord segment C5 and contains 3,435 axons, 74% of which are unmyelinated. The supraspinatus branch (SSP) contains 627 fibers. Of the SSP fibers, 52% are myelinated, including 32% motor and 20% sensory axons. Of the C‐fibers in the SSP 16% are sympathetic efferents and 32% are sensory. Many of the latter disappear after neonatal capsaicin treatment. The SSC emits a subacromial articular branch (ART), with some 260 axons, about 90% of which are unmyelinated. The myelinated ART fibers are sensory, and of the unmyelinated ones about 24% are sympathetic efferents and 66% are afferents. The latter resist neonatal capsaicin treatment.Conclusions: In view of the anatomy of the supraspinatus muscle, of the subacromial space, and of relevant nerves, the rat shoulder should be appropriate for experimental studies on inflammatory conditions in the subacromial space. © 1994 Wiley‐Liss, Inc.
Porphyrin accumulation in the harderian glands of female Syrian hamster results in mitochondrial damage and cell death
Authors: Antolín Isaac , Uría Higinio , Tolivia Delio , Rodríguez‐colunga María J. , Rodríguez Carmen , Kotler MóNica L. , Menéndez‐peláez Armando 
Published: February 2005

AbstractBackground: The Harderian glands of female Syrian hamsters contain very high concentrations of protoporphyrin (in the range of μg per mg of tissue) which accumulate in the tubulo‐alveoli of the gland. We have studied the process of synthesis, accumulation, and secretion of this cyclic compound by the secretory cells of the hamster Harderian glands.Methods: The animals used were female Syrian hamster of 15, 35, 75, 180, and 360 days of age. Items first examined were (1) percentage of the “clear cells,” (2) area occupied by intraluminal porphyrins, and (3) histological characteristics of “clear cells” by light and transmission electron microscopy (TEM). In a second study the total content of porphyrins was determined. Finally, the levels of mRNA for the enzyme aminolevulinate synthase (ALV‐S) were measured.Results: In the glands of female hamsters, both the tissue concentration and the intraluminal area occupied by protoporphyrin correlate with the appearance of a special type of cell (clear cells) which show signs of cell degeneration. In addition, the expression of the gene for ALV‐S, which is the limiting enzyme in porphyrin production, also parallels the relative number of clear cells. Analyzed under TEM, these clear cells display dilated mitochondria and short and swollen endoplasmic reticulum cisternae. In a late phase of necrosis, the nuclear envelope appears disorganized with scarce chromatin. The mitochondria undergo complete destruction, resulting in electron‐dense bacillar formations which progressively coalesce in large and dense areas of protoporphyrin. The cell dies after this accumulation, being secreted by a “cytogen” mechanism.Conclusions: In view of our results, the Harderian gland of female Syrian hamster may provide a useful model for the study of the mechanism by which the anomalous accumulation of protoporphyrin induces cell damage in human protoporphyria. © 1994 Wiley‐Liss, Inc.
Differences in osteonal micromorphology between tensile and compressive cortices of a bending skeletal system: Indications of potential strain‐specific differences in bone microstructure
Authors: Skedros John G. , Mason Mark W. , Bloebaum Roy D. 
Published: February 2005

AbstractBackground: It has been hypothesized that bone has the capacity to accommodate regional differences in tension and compression strain mode and/or magnitude by altering its osteonal microstructure. We examined a simple cantilevered bone to determine whether regional differences in particular strain‐related features are reflected in the microstructural organization of compact bone.Methods&Results: The artiodactyl (e.g., sheep and deer) calcaneus has a predominant loading condition which is typified by prevailing compressive and tensile strains on opposite cortices, and variations in strain magnitudes across each of these cortices. Microscopic examination showed osteon density and cortical porosity differences between tension (caudal) and compression (cranial) cortices, averaging 11.4% more osteons in the compression cortex (P< 0.01) and 80.2% greater porosity in the tension cortex (P< 0.01). There is 43.5% more interstitial bone in the compression cortex (P< 0.01). Osteons in the compression cortex also have smaller areas in contrast to the larger area per osteon in the tension cortex. Although no definite transcortical gradient in osteonal density or cortical porosity is found, fractional area of interstitial bone is largest and osteon population density is lowest in the endocortical regions of both tension and compression cortices. The endocortical regions also have greater porosity than their corresponding middle and pericortical regions (P< 0.01).Conclusions: These osteonal microstructure and cortical porosity differences may be adaptations related to regional differences in strain mode and/or strain magnitude. This may be related to the disparity in mechanical properties of compact bone in tension vs. compression. These differences may reflect a capacity of bone to process local and regional strain‐related information. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public dotmain in the United states of America.