bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of tumor necrosis factor‐α (TNFα)‐cross‐reactive proteins during early chick embryo development
Authors: Wride M. A. , Sanders E. J. 
Published: February 2005

AbstractWe have investigated the expression of tumor necrosis factor‐α (TNFα)‐cross‐reactive proteins during the early development of the chick embryo from day 1 to day 6 (H‐H stages 5–29) using a polyclonal antibody and two monoclonal antibodies to recombinant mouse TNFα. We have confirmed the cross‐reactivity of the antibodies with chicken tissue in Western blotting studies. Proteins of 50 kDa and 70 kDa, showing anti‐TNFα cross‐reactivity, have been identified during early chick development. In addition, both monoclonal antibodies recognize a 120 kDa protein. These molecules probably represent cytosolic or transmembrane TNF‐α‐like proteins, similar to those previously identified on the surface of cytotoxic T‐lymphocytes. We show by ultrastructural cytochemistry that immunoreactivity can be detected at the surfaces of some cells, suggesting that at least some of the antigen is membrane‐associated. The proteins are shown to have a widespread tissue distribution during this period of development. Immunoreactivity is first detected in the gastrulating embryo, in the mesoderm and the endoderm. By day 2, expression is confined to the ectoderm and the endoderm, while at day 3 expression appears in the myotome, the notochord, and in nervous tissue. At day 4 the distribution of reactivity is more extensive and includes the notochord, the sclerotome, and the myotome, while the cranial and spinal nerves also become intensely immunoreactive. Also at this stage, neural tube reactivity becomes localized to the marginal neuroepithelial zone, and the lens fibers become positive. This distribution of staining then persists until 6 days of development. We hypothesize that the expression of TNFα‐cross‐reactive proteins in early development could be indicative of a role for them in programmed cell death (apoptosis) during differentiation of the notochord, the lens, and the nervous system, and in tissue remodeling. © 1993 Wiley‐Liss, Inc.
Retinoic acid receptor isoform β2 is an early marker for alimentary tract and central nervous system positional specification in the chicken
Authors: Smith Susan M. 
Published: February 2005

AbstractIn this study I describe the distribution of one variant of retinoic acid receptor‐β (RAR‐β), the RAR‐β2 isoform, during the stages before organogenesis of the chick embryo. Unlike the situation in older embryos, at these stages its distribution does not differ qualitatively from that of all RAR‐β transcripts. During the presomite headfold stage, RAR‐β2 transcripts are simultaneously upregulated in two different locations. These locations define positional identities within the anlage of the chick alimentary tract and within the central nervous system (CNS). As development proceeds the transcript expression maintains its spatial restriction within those two regions. At presomite stages RAR‐β2 transcripts are enriched within the proamnion, which contains the presumptive foregut and precardiac cells; somewhat later it is present within the foregut endoderm at the site where foregut and the lateral amniocardiac vesicles fuse to form the coelom and cardiac tube. As the foregut continues its caudal extension, RAR‐β2 expression defines an anteroposterior boundary at the level of the pharynx within the alimentary tract. The second expression site of RAR‐β2 mRNA first appears within the posterior neural plate at the level where Hensen's node commences its caudal regression. This boundary lies at the border between the future rhombomeres 5 and 6 within the hindbrain. Expression of RAR‐β2 transcripts is also spatially restricted within some migrating cranial neural crest cells. The expression of RAR‐β2 in cranial neural crest cells is consistent with what is known about the mechanisms by which cranial neural crest cell fate is determined. These data support the hypothesis that retinoids may contribute to positional specification of anteroposterior body axis, and perhaps also to the formation and identity of the developing alimentary tract and heart tube. © 1994 Wiley‐Liss, Inc.
Male‐sterile phenotype of the neurological mouse mutant weaver
Authors: Harrison Susan M. W. , Roffler‐Tarlov Suzanne 
Published: February 2005

AbstractThe autosomal recessive murine mutation weaver (wv) affects postnatal differentiation in at least three neuronal populations in the brain: dopamine‐containing neurons in the midbrain, and granule and Purkinje cells in the cerebellum. Neuronal populations vulnerable to the actions of weaver die in the midst of development. In addition, homozygous weaver males are sterile. We show by a histological analysis of epididymides and testes that the cause of male sterility in weaver is lack of sperm. The epididymides of the adult weaver mice examined were devoid of sperm, and few seminiferous tubules in the adult weaver's testes contained elongated spermatids. Most tubules were marked by moderate to severe degeneration of the seminiferous epithelium. A developmental study showed that the mutant phenotype emerged after the third postnatal week. By postnatal day 28, the development of weaver sperm lagged behind that of the wild‐type and some seminiferous tubules contained degenerating germ cells. By postnatal day 35, terminal differentiation of spermatids appeared to be arrested in many tubules and degeneration of the seminiferous epithelium was widespread. The heterozygotes were unaffected at all ages sampled. We conclude that the normal allele at the weaver locus is necessary for spermiogenesis and the maintenance of spermatogenesis. © 1994 Wiley‐Liss, Inc.
Effect of in ovo retinoic acid exposure on forebrain neural crest: In vitro analysis reveals up‐regulation of N‐CAM and loss of mesenchymal phenotype
Authors: Shankar Kavita R. , Chuong Cheng‐Ming , Jaskoll Tina , Melnick Michael 
Published: February 2005

AbstractIn a prior study of in ovo exogenous retinoic acid (RA) exposure, we observed a prolonged expression of cell surface N‐CAM in cranial neural crest (NC) cells exhibiting migratory failure. In the present studies, we employed an experimental strategy in which embryos were first exposed to exogenous RA in ovo and incubated for 45–60 hr; this was followed by extirpation and in vitro culturing of these same RA‐exposed cranial neural tubes. NC cell outgrowth from the explant was assayed, as was the immunohistochemical localization of HNK‐1 and N‐CAM antigens. In RA‐exposed explants, the size of the NC cell outgrowths were comparable to controls. However, almost all NC cells lost their mesenchymal phenotype and were arranged in an “epithelioid” pattern of tightly packed polygonal cells that expressed N‐CAM at adjacent cell boundaries. By contrast, control NC cells were flattened and multipolar in shape and expressed HNK‐1, rarely co‐expressing N‐CAM. These observations indicate that RA modulates NC cell N‐CAM expression and microanatomical phenotype, a finding consistent with prior in ovo studies of RA‐exposure. Several possible explanations are considered. © 1994 Wiley‐Liss, Inc.
Precardiac mesoderm is specified during gastrulation in quail
Authors: Antin Parker B. , Taylor Richard G. , Yatskievych Tatiana 
Published: February 2005

AbstractThe establishment of precardiac mesoderm and the role of anterolateral endoderm and ectoderm in regulating heart muscle cell development have been studied in quail using explant cultures. Mesoderm from precardiac regions of stage 4+–6 embryos was explanted alone or in combination with adjacent endoderm or ectoderm, cultured for 12 to 72 hr in several types of culture media, and then assayed by morphological and immunocytochemical criteria for the presence of differnetiated cardiac myocytes. Results show that mesoderm from heart forming regions is capable of differentiating into beating cardiac myocytes in a defined medium lacking potential signaling molecules by stage 4+, the earliest time at which we could isolate mesoderm from adjacent cell layers. Although an interaction with anterolateral endoderm from stage 4+onward is therefore not required for the specification of precardiac mesoderm in quail, explants consisting of mesoderm plus endoderm show an enhanced rate of myocyte differentiation and a shortened delay between expression of myosin heavy chain and the onset of beating. Endoderm also plays a central role in early heart morphogenesis since beating heart tubes from only in explants that contain both mesoderm and endoderm. In contrast, ectoderm from stage 4+–5+embryos does not support development of precardiac mesoderm. These results suggeest that early heart muscle cell development involves an initial specification step that occurs prior to or during gastrulation and which leads to the appearance of myocardial precursor cells, and a subsequent differentiation step during which endoderm plays a central role in enhancing the rate of myocyte differentiation and the degree of heart tube morphogenesis. © 1994 Wiley‐Liss, Inc.
Murine PGK‐1 promoter drives widespread but not uniform expression in transgenic mice
Authors: McBurney Michael W. , Staines William A. , Boekelheide Kim , Parry David , Jardine Karen , Pickavance Lucy 
Published: February 2005

AbstractPgk‐1 is an X‐linked gene encoding 3‐phosphoglycerate kinase, an enzyme necessary in every cell for glycolysis. The regulatory sequences of the Pgk‐1 gene were used to drive the E. coli lacZ reporter gene and 2 strains of transgenic animals created with this Pgk‐lacZ transgene carried on autosomes. The levels of expression of Pgk‐1 varied from one adult tissue to another and the transgene was similarly regulated. However, in situ staining of the β‐galactosidase encoded by the transgene indicated extensive cell‐to‐cell variability in its level of expression. A reproducible subset of cells stained darkly for the transgene product. Some of these β‐galactosidase positive cells were rapidly proliferating while others appeared to be metabolically very active, suggesting that the Pgk‐1 promoter is regulated so as to be more active in cells requiring high levels of glycolysis. Although Pgk‐1 is X‐linked and subject to X chromosome inactivation, the transgenes were not inactivated in either female somatic or male germ cells. Thus, the Pgk‐1 promoter drives transgene expression in all tissues but the levels of expression are not uniform in each cell. © 1994 Wiley‐Liss, Inc.
Heart specification in the Mexican axolotl (Ambystoma mexicanum)
Authors: Easton Heather S. , Armstrong John B. , Smith Steven C. 
Published: February 2005

AbstractThe concept of the morphogenetic field has been used extensively in developmental biology. However, little is known about the mechanisms that partition these broad areas of tissue into the smaller areas which actually form the corresponding structures, and the remaining tissue. In the Mexican axolotl, the heart field forms as the anterior lateral plate mesoderm migrates over the underlying pharyngeal endoderm between stages 14 and 28. We have previously shown that both the mid‐ventral and lateral walls of the pharyngeal cavity have considerable inductive capacity at stage 14. If this inductive capability, and the competence of the mesoderm to respond, is retained between stages 14 and 28, a much broader area of mesoderm would be induced than actually participates in heart development. In this paper, we use explant cultures to establish that pharyngeal endoderm retains its inductive activity, and that both pre‐cardiac mesoderm and lateral plate mesoderm caudal to the pharyngeal cavity remain competent to respond to the induction throughout this period. We also map the specified region of the antero‐lateral mesoderm between stages 14 and 28 by placing carefully measured areas of mesoderm in culture without inductive endoderm. We found that the region capable of initiating a spontaneous beat approximately doubles in size during this period. Since the specified region is larger than the actual heart primordium, some mechanism must exist to partition “induced” mesoderm into heart‐forming and non‐heart‐forming areas. One possibility is a reaction‐diffusion mechanism involving local activation of the first mesodermal cells to contact the inductive endoderm, accompanied by production of a diffusible inhibitor that limits the extent of the heart‐forming region. © 1994 Wiley‐Liss, Inc.
Retarded chondrogenesis in transgenic mice with a type II collagen defect results in fracture healing abnormalities
Authors: Hiltunen Ari , Metsäranta Marjo , Virolainen Petri , Aro Hannu T. , Vuorio Eero 
Published: February 2005

AbstractWe have examined the biological and biomechanical consequences of defective type II collagen production for fracture repair employing a genetically engineered mouse line Del1 which was generated by microinjection of a 39‐kb mouse proα1(II) collagen gene construct containing a deletion of exon 7 and intron 7 (Metsäranta et al. [1992] J. Cell Biol. 118:203–212). Standardized tibial fractures were produced in transgenic Del1 mice and their nontransgenic littermates were used as controls. The fracture callus tissues were analyzed at days 7, 9, 14, 28, and 42 using radiography, histomorphometry, biomechanical testing, and Northern analysis of mRNAs for several tissue‐specific matrix components. Deficient production of cartilage in Del1 mice resulted in reduced radiographic callus size, smaller cross‐sectional area, and impaired biomechanical properties when compared with fractures of nontransgenic control mice. The differences were most evident in 14‐day fracture calluses. Consequently mRNAs for cartilage‐specific type IX and X collagens and aggrecan were also reduced in Del1 calluses. Levels of type II collagen mRNAs were unaffected since the mutated transgene produced additional type II collagen mRNA molecules. Further abnormalities in the fracture repair process of Del1 mice were observed in callus remodeling. In the control animals a typical feature of external callus remodeling was reduction of callus size during endochondral ossification between days 14 and 28. Such reduction was not observed in the transgenic mice. Histological examination of fracture calluses suggested also a reduction in trabecular surface area, which was found to be even more pronounced in metaphyseal bone of Del1 mice. Despite these differences the biomechanical properties of the calluses in the two groups became similar by day 28 of fracture healing. The results thus suggest that reduced chondrogenesis due to the presence of mutated transgenes in Del1 mice not only causes a temporary impairment in biomechanical properties of healing fractures but also affects later stages of callus remodeling. © 1994 Wiley‐Liss, Inc.
Time‐lapse total internal reflection fluorescence video of acetylcholine receptor cluster formation on myotubes
Authors: Wang Michelle Dong , Axelrod Daniel 
Published: February 2005

AbstractTo study when and where acetylcholine receptor (AChR) clusters appear on developing rat myotubes in primary culture, we have made time‐lapse movies of total internal reflection fluorescence (TIRF) overlaid with schlieren transmitted light images. The receptors, including the ones newly incorporated into the membrane, were labeled with rhodamine α‐bungarotoxin (R‐BT) continuously present in the medium. Since TIRF illuminates only cell‐substrate contact regions where almost all of the AChR clusters are located, background fluorescence from fluorophores either in the bulk solution or inside the cells can be suppressed. Also, because TIRF minimizes the exposure of the cell interior to light, the healthy survival of the cell culture during imaging procedures is much enhanced relative to standard epi‐ (or trans‐) illumination. During the experiment, cells were kept alive on the microscope stage at 37°C in an atmosphere of 10% CO2· Two digital images were recorded by a CCD camera every 20 min: the schlieren image of the cells and the TIRF image of the clusters. After background subtraction, the cluster image was displayed in pseudocolors, overlaid onto the cell images, and recorded as 3 frames on a videotape. The final movies are thus able to summarize a week‐long experiment in less than a minute. These movies and images show that clusters form often shortly after the myoblast fusion but sometimes much later, and the formation takes place very rapidly (a few hours). The clusters have an average lifetime of around a day, much shorter than the lifetime of a typical myotube. The brightest and largest clusters tend to be the longest‐lived. The cluster formation seems to be associated with the contacts of myotubes at the glass substrate, but not with cell‐cell contacts or myoblast fusion into myotubes. New AChR continuously appear in preexisting clusters: after photobleaching, the fluorescence of some clusters recovers within an hour. © 1994 Wiley‐Liss, Inc.
Enhancement of skeletal muscle regeneration
Authors: Bischoff Richard , Heintz Catherine 
Published: February 2005

AbstractWe have studied the effect of adding extra satellite cells or soluble factors from crushed muscle on regeneration of minced fragments from rat tibialis muscle. The muscle mince was wrapped in an artificial epimysium to prevent adhesions and cell immigration from adjacent muscles. Regeneration was quantitatively assessed by electrophoretic determination of the muscle‐specific form of creatine kinase. Control minces exhibited three periods of change in creatine kinase activity during a 7‐week regeneration period. Activity fell rapidly during the first week, then rose gradually from 1–3 weeks and increased more rapidly from 3–7 weeks. To augment the original complement of myogenic cells, satellite cells were isolated from the contralateral muscle, purified by density gradient centrifugation, and expanded in culture for 3 days before adding to the muscle mince. The added cells resulted in a 3‐fold enhancement of creatine kinase activity throughout the regeneration period. Soluble muscle extract incorporated into a collagen matrix also stimulated regeneration when added to muscle mince. The extract accelerated the rate of creatine kinase increase during the 1–3 week period beyond that observed in the control or cell augmented mince, suggesting that factors in the extract may facilitate revascularization or reinnervation. The specific activity of creatine kinase was increased in regenerates augmented with both cells and extract, indicating that the effects enhance primarily myogenic processes. © 1994 Wiley‐Liss, Inc.
Immunohistochemical studies indicate multiple enteroendocrine cell differentiation pathways in the mouse proximal small intestine
Authors: Aiken Kimberly D. , Kisslinger Jeffrey A. , Roth Kevin A. 
Published: February 2005

AbstractThe enteroendocrine cell system of the mammalian gastrointestinal tract is comprised of at least 16 different subpopulations. Each subpopulation shows a characteristic distribution along both the crypt‐villus and cephalocaudal axes. In both the small intestine and colon of adult mice, multilabel immunohistochemistry has demonstrated that two or more neuroendocrine products can be coexpressed in various combinations in single cells along the crypt‐villus axis, suggesting that enteroendocrine phenotypes may be actively regulated. Using bromodeoxyuridine (BrdU) incorporation and multilabel immunohistochemistry, we have previously demonstrated an enteroendocrine cell differentiation pathway consisting of two subpopulations of cells in the mouse proximal small intestine—one involving the sequential expression of substance P, serotonin, and secretin in cells migrating out of the crypts into the villi, and a second involving the expression of substance P and serotonin in cells which remain in the crypts. In this report, we use double label immunohistochemistry and BrdU incorporation to define the temporal and spatial interrelationships between gastrin, cholecystokinin (CCK), glucagon‐like peptide‐1 (GLP‐1), and gastric inhibitory peptide (GIP) immunoreactive cells in the mouse proximal small intestine. The expression of these products was compared with that of substance P, serotonin, and secretin. Minimal overlap of expression was found in cells immunoreactive for substance P or serotonin with gastrin, CCK, GLP‐1, or GIP; however, secretin was found colocalized in villus‐associated gastrin, CCK, and GLP‐1 containing cells. We demonstrate that, similar to the bidirectionally migrating substance P and serotonin expressing cells, gastrin, CCK, GLP‐1, and secretin are expressed in upwardly migrating cells, and gastrin, CCK, and GLP‐1 are expressed in downwardly migrating cells that fail to express secretin. GIP containing cells only rarely coexpressed any of the products examined, but were found both in the villi and the crypts, suggesting both upwardly and downwardly migrating populations. These findings demonstrate several novel enteroendocrine cell differentiation pathways. In addition, the expression of secretin in the villi, but not in the crypts, by two otherwise distinct differentiation pathways, and the lack of secretin expression by villus‐associated GIP expressing cells, suggests that local factors present in the crypts and/or on the villi are necessary, but not sufficient, for secretin expression. © 1994 Wiley‐Liss, Inc.
Caenorhabditis elegans sqt‐3 mutants have mutations in the col‐1 collagen gene
Authors: van der Keyl Harjeet , Kim Hwaok , Espey Richard , Oke C. Valerie , Edwards M. Kaye 
Published: February 2005

Abstractsqt‐3 mutants of Caenorhabditis elegans form dumpy larvae and adults and display allele‐specific defects in locomotion, fertility, and viability. We have determined that the sqt‐3 locus encodes COL‐1 collagen. We physically mapped the col‐1 gene to a cosmid on chromosome V whose position is consistent with the location of the sqt‐3 gene. We also observed morphological defects in sqt‐3 mutants at stages that correlate with the mRNA expression patterns of col‐1. Sequence analysis of the col‐1 gene in the three temperature‐sensitive mutants revealed that each allele of sqt‐3 has a unique missense mutation causing arginine or glutamic acid to replace glycine in a Gly‐X‐Y triple helical domain. These glycine substitutions may result in longer non‐collagenous domains, which may decrease the thermal stability or impart additional flexibility to mutant trimers. In addition, we describe four corrections to the published sequence of col‐1, including one fifteen nucleotide addition that completes a conserved domain in the amino terminal coding region. © 1994 Wiley‐Liss, Inc.