摘要:

AbstractSkeletal muscle fibers are capable of regeneration following ischemia, traumatic injury, or transplantation. Although the time course of the regenerative process has been studied in detail histologically, little is known about the time of activation of myogenic precursor cells which are primarily responsible for muscle regeneration.This study was designed to determine the initiation peak proliferative activity, and cessation times of muscle precursor replication in small skeletal muscle transplants. Forty‐eight young male BALB/c mice had the extensor digitorum longus muscles of both hind legs autotransplanted to a different site in the same leg. At various time intervals after transplantation (from 24 hours to 14 days), mice were injected once with a small dose of tritiated thymidine in order to label proliferating myogenic precursor cells.The transplants were allowed to regenerate for 14 days, before being removed, processed for autoradiography, and analysed by light microscopy. The presence of labelled myotube nuclei in regenerated transplants showed that myogenic precursors had been replicating at the time of tritiated thymidine injection. Myogenic precursor replication was initated late on the second day (42–48 hours) after transplantation, peaked after 6 days, and was complete within 10 d

ISSN:0003-276X    

DOI:10.1002/ar.1092240102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA characteristic banding pattern can be visualized at the surface of the rat incisor in the maturation zone of amelogenesis by staining with glyoxal bis(2‐hydroxyanil) (GBHA). Other banding patterns can be obtained with certain histological and fluorochrome stains and by radioautography following45Ca injection. In this study, several histochemical reagents known to complex with different states of calcium were used to stain the surface of enamel. Rat incisors were quickly dissected and immediately immersed in solutions containing the following calcium‐binding reagents: arsenazo III, calmagite, murexide, N, N‐naphthaloylhy‐droxylamine, and calcein. Routinely, one contralateral lower incisor from each pair was counterstained with GBHA in order to relate each of the staining patterns to the banded distribution of maturation ameloblasts that is reflected by the characteristic GBHA staining pattern in the enamel. Each of the reagents used in this study demonstrated a staining pattern consisting of a series of broad bands running transversely and obliquely across the enamel. In all cases, the dyes stained predominantly that enamel associated with ruffle‐ended ameloblasts, i.e. enamel left unstained by GBHA. Some of the reagents also stained enamel in the secretion zone. The appearance and distribution of the staining patterns reflect the banded distribution of maturation ameloblasts and appear to be controlled on a time scale related to the rapid modulation of th

ISSN:0003-276X    

DOI:10.1002/ar.1092240103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe apperance and distribution of extracellular matrix (ECM) was documented along the migratory route of chicken primordial germ cells (PGCs). The antimouse embryonal carcinoma cell antibody, EMA‐1, was used to label PGCs (Urven et al.:Development103:299–304, 1988). Antibodies against laminin, fibronectin, chondroitin sulfate proteoglycan and collagen type IV were used to label extracellular matrix components. When the PGCs emerged from the epiblast, all four ECM molecules were restricted principally to the basement membrane of the epiblast. Chondroitin sulfate was also located between hypoblast cells during this period. In late germinal crescent stages, when the PGCs entered the lumina of blood vessels, the same ECM molecules were more widespread in the mesoderm and in extracellular spaces. In addition, laminin and collagen type IV were identified on lateral surfaces of ectodermal cells at this stage. When the germ cells moved through the mesenchyme into the germinal ridge, the ECM molecules were found around mesenchymal cells, and, in the cases of laminin, fibronectin and collagen type IV, in the basement membranes of the germinal ridge epithelia. Because the appearance of these ECM components is temporally and spatially correlated with the movement of PGCs, we suggest that early PGC migration may depend on their timely appeara

ISSN:0003-276X    

DOI:10.1002/ar.1092240104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractLabeling of hepatic glycogen derived from3H‐galactose and3H‐glucose was compared shortly after intravenous injection in control‐fed rats. The rats were allowed to accumulate 5‐8% glycogen prior to receiving label. Fifteen minutes to 2 hours after labeling, liver was excised and processed for routine light (LM) and electron microscopic (EM) radioautography (RAG) or biochemical analysis. After injection of3H‐galactose, LM‐RAGs revealed that the percentage of heavily labeled hepatocytes increased from 37% after 15 minutes to 68% after 1 hour but showed no further increase after 2 hours. α‐Amylase treatment removed most glycogen and incorporated label; thus few silver grains were observed, indicating little incorporation of label except into glycogen. EM‐RAGs demonstrated that most label occurred where glycogen was located. Biochemical analysis showed initially a high blood level of label that rapidly plateaued at a reduced level by 5 minutes. Concomitantly, glycogen labeling determined by liquid scintillation counting reflected the increases observed in the RAGs. After injection of3H‐glucose, LM‐RAGs revealed that only 12% of the hepatocytes were heavily labeled at 1 hour and 20% at 2 hours. In tissue treated with α‐amylase, glycogen was depleted and label was close to background level at each interval observed. EM‐RAGs showed most grains associated with glycogen deposits. Biochemically, blood levels of label persisted at a high level for 30 minutes and tissue levels increased slowly over the 2‐hour period. This study shows that incorporation from3H‐galactose was more rapid than incorporation of3H‐glucose; however, label derived from both carbohydrates appeared to be in

ISSN:0003-276X    

DOI:10.1002/ar.1092240105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractPrevious work has demonstrated that adult newt cardiac myocytes possess a proliferative ability in response to an experimentally induced in jury, in vivo. This study describes an in vitro model in which the proliferative events of the adult cardiac myoctye may be studied. Ventricles were minced and then enzymatically dissociated in a Ca++‐ and MG++‐free salt solution containing 0.5% trypsin and 625 U/ml of CLS II collagenase for 8 to 10 hours at 25°C. Enzyme digests were preplated and then cultured on bovine corneal endothelial‐derived basement membrane “carpets” in either serum‐free or serumsupplemented modified Leibovitz's medium for up to 30 days. Light and transmission electron microscopic characterization demonstrated that a majority of the myocytes underwent an initial period of disorganization characterized by a “rounding up” of the cell and a loss of myofibrillar organization. Once the myocytes had attached to the culture substratum they began to spread out, underwent a reassembly of their contractile elements, resumed spontaneous contractions, and demonstrated ultrastructural evidence of protein synthesis. Mitosis was observed in several myocytes 8 to 15 days following isolation. In 15‐day serum‐supplemented and serum‐free cultures, 6.5% ± 0.9% and 8.1% ± 1.4% of the myocytes were binucleated, respectively. These results demonstrate that adult newt ventricular myocytes can be successfully placed into primary culture and are capable of undergoing mitosis. This work may be considered as a foundation for future investigations which will focus on the mechanisms which control cardi

ISSN:0003-276X    

DOI:10.1002/ar.1092240106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe chicken ultimobranchial glands are richly supplied with nerve fibers originating from both the main trunk of the vagus nerve and its branch‐the recurrent laryngeal nerve. C cells immunoreactive for calcitonin were invariably found in the large nerve bundles distributed throughout the ultimobranchial glands. In addition, these cells were often present within the distal vagal ganglia and the recurrent laryngeal nerves. The frequency of occurrence and the pattern of distribution of the C cells in the distal vagal ganglia and the recurrent laryngeal nerves were determined in chickens of various ages by means of an immunoperoxidase method with anticalcitonin and antineurofilament antisera. The left and right sides of the ultimobranchial region were asymmetrical. The left ultimobranchial gland was in close contact with the vagus nerve trunk, especially with the distal vagal ganglion, but it was separated from the recurrent laryngeal nerve. The right gland contacted the recurrent laryngeal nerves, its medial edge being frequently penetrated by the nerve, but the gland was separated from the distal vagal ganglion. On the left side, C cells were found in 25 out of 39 distal vagal ganglia but they were not distributed in the recurrent laryngeal nerve. On the right side, the cells were present in 28 out of 43 recurrent laryngeal nerves but absent in the distal vagal ganglia. The results indicate that the C cells secreting a hormone calcitonin can enter into nerves, but their occurrence is restricted to the nerves in close proximity to the ultimobranchial glands. Electron microscopic studies revealed that C cells in the nerves received numerous axon clusters enveloped with Schwann cell cytoplasm. Naked axons regarded as axon terminals were found in direct contact with the surface of C cells. They were mainly composed of efferent‐type nerve endings showing the accumulation of numerous small clear vesicles and a few large dense‐cored vesicles. In addition, C cells were partly covered with the long cytoplasmic processes of Schwann cells and were also in contact with the Schwann cell perikarya. The C cells in nerves appear to be controlled by neural stimul

ISSN:0003-276X    

DOI:10.1002/ar.1092240107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractDirect cellular contact between thymocytes and thymus stromal cells within the thymus appears to contribute to the maturation of thymocytes. Thymocyte‐stromal cell complexes, formed in vivo, have been isolated by others and postulated to play a role in T‐cell differentiation. These previous studies have been hampered, however, by a time‐consuming isolation procedure from which only small numbers of these complexes are recovered. We have examined a model to study thymocyte‐stromal cell complexes in vitro in which thymocytes are added to primary cultures of thymus stromal cells. In the present study, we found that thymocytes were histotypically selective in their attachment to thymus stromal cells. We also investigated the kinetics of thymocyte attachment to these thymus stromal cells. Cultures were examined at selected time intervals from 5 min through 3 days of incubation. Thymocyte attachment to stromal cells was a biphasic interaction, with maximum surface attachment at 15 min of cocultivation, followed by migration of thymocytes into the cultures. Morphological studies were confirmed by using3H‐leucine‐labeled thymocytes and liquid scintigraphy. With increased time in culture, thymocytes became amoeboid and migrated between the layers of stromal cells where thymocyte mitotic figures were seen at 4 and 8 hr. In some cases it appeared that stromal cells, which often grew two to three cell layers deep, played an active role in enclosing thymocytes within the cultures. Large numbers of viable thymocytes were observed in the cultures at 24 hr. The number of thymocytes then decreased progressively on days 2 and 3, when relatively few were found within the layers of

ISSN:0003-276X    

DOI:10.1002/ar.1092240108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractFiber type distribution and mean fiber area were determined for seven sites in diaphragm muscles of premature (140 days gestation), full‐term (180 days gestation), and adult baboons. Within a group, data did not differ significantly amongst the seven sites. The diaphragm of premature animals had a large proportion [56(±2)%] of type IIc fibers, smaller proportions of type I, IIo, and IIh fibers [16(±2), 21(±1), and 7(±2)%, respectively], and no type IIg fibers. Full‐term animals had fewer type IIc [2(±1)%] fibers, greater proportions of type I [46(±2)%], IIh [23(±1)%], and IIg [11(±1)%]fibers, and a similar proportion of type IIo fibers [17(±1)%]. Diaphragm from adult baboons had similar proportions of type I, IIo, IIh, IIg, and IIc fibers in females [39(±4), 20(±2), 1(±1), 41(±5), and 1(±1)%]and males [48(±2), 16(±1), 0(±0), 36(±2), and 3(±2)%]. Fiber area for premature [143(±9), 210(±15), 231(±15), and 156(±16) μm2for type I, IIo, IIh, and IIc fibers], newborn [317(±32), 374(±36), 468(±42), 498(±43), and 322(±37) μm2for type I, IIo, IIh, IIg, and IIc fibers], and for type I, IIo, IIg, and IIc fibers from adult female [1,759(±130), 2,365(±284), 5,026(±742), and 1,843(±111) μm2] and adult male [2,513(±221), 3,987(±267), 6,102(±376), and 2,833(±151) μm2] baboons indicated growth which correlated with body weight. Our results also show that metabolic and contractile enzymes develop normally, but growth of respiratory muscle fibers is arreste

ISSN:0003-276X    

DOI:10.1002/ar.1092240109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractControl of dorsoventral patterns in the chick at the prelimb stages resides in the limb mesoderm. Recombination experiments at stage 14, with dorsoventrally reversed ectoderm, result in wings with mesodermal dorsoventral polarity. Similar recombinations at stage 16 show that the ectoderm has acquired dorsoventral information and can impose this polarity on the patterns of mesodermal differentiation in the distal regions of the wing. The dorsoventral information in the ectoderm comes from the mesoderm, which transfers this information to the overlying ectoderm between stages 14 and 16. The initial dorsoventral information in the ectoderm is not stable and can be reprogrammed by stage 14 mesoderm. Subsequently, there is a gradual stabilization of the ectodermal information. At the same time the mesoderm loses its capacity to reprogram dorsoventral information in the ectoderm.

ISSN:0003-276X    

DOI:10.1002/ar.1092240110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractCytoplasmic RNA was demonstrated in neurons of the developing rat brain using acridine orange (AO) as a histochemical marker. Fetuses of 18 days and postnatal rats of 1, 7, 14, and 21 days as well as adults several months old were studied. Neuroblasts of the germinal matrix exhibited minimal or no orange‐red AO‐RNA fluorescence, but immature nerve cells in migration within the cerebral hemispheres of the rat showed a weak but definite orange colour. This finding contrasts with the absence of AO‐RNA fluorescence in migrating human neuroblasts. Neurons of the neocortical plate showed uniformly strong fluorescence. In the hippocampus, the most pronounced increase in AO‐demonstrated RNA was in pyramidal and granule cells during the first postnatal week. The cerebellum showed a paradoxically stronger fluorescence of granule cells in the 18‐day fetus than at birth, and almost no AO‐RNA fluorescence of granule cells at 21 days of age or in adults. Motor neurons showed the strongest fluorescence of all neurons. It is likely that the increase in cytoplasmic RNA in neurons corresponds to the onset of neurotransmitter biosythesis, but transitory fetal neuropeptides may explain stronger fluorescence of some neurons in young individuals. The reliable and simple AO method provides a supplementary means of studying one aspect of neuronal

ISSN:0003-276X    

DOI:10.1002/ar.1092240111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY