bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concepts of epithelial‐mesenchymal interactions during development: Tooth and lung organogenesis
Authors: Slavkin Harold C. , Snead Malcolm L. , Zeichner‐David Margarita , Jaskoll Tina F. , Smith Barry T. 
Published: December 2004

AbstractOne of the major problems in developmental biology concerns how differential gene activity is regionally controlled. One approach to this problem is the use of mesenchyme specification of epithelial‐specific gene expression, such as, during tooth morphogenesis or lung morphogenesis. In the example of tooth morphogenesis, dental papilla ectomcsenchyme induces de novo gene expression as assayed by detection of amelogenin transcripts, or immunodetection of amelogenin poly‐peptidcs within ameloblast cells. This process does not require serum supplementation or exogenous factors during epithelial‐mesenchymal interactions in vitro. In contrast, lung morphogenesis requires hormones to mediate mesenchyme‐derived influences upon type II epithelial cell differentiation and the production of pulmonary surfactant (eg, neutral and phospholipids, surfactant proteins). Glucocorticoids are required to stimulate the release of fetal pneumonocyte factor (FPF) from fibroblasts which, in turn, enhance the production of pulmonary surfactant. Thy‐roxin appears to regulate the relative responsiveness of progenitor type II cells to steroid‐stimulated release of FPF. This review will highlight key concepts associated with these developing organ systems and emphasize the problem of regional controls which regulate epithelial cell‐specific gene activity.
Degradation of extracellular matrix by the trophoblastic cells of first‐trimester human placentas
Authors: Fisher Susan J. , Leitch Mark S. , Kantor Marsha S. , Basbaum Carol B. , Kramer Randall H. 
Published: December 2004

AbstractFirst‐trimester human placental villi were cultured on 3H‐leucine‐labeled extracellular matrices isolated from the PF HR9 and PYS‐2 cell lines. Both cell lines produced an extracellular matrix that contained basement membrane‐specific macromolecules, including type IV collagen, laminin and proteoglycan. Both matrices promoted outgrowth of cells from the villi which, according to morphological criteria, were identified as cytotrophoblastic cells. As the cells migrated from the attachment site, they caused a marked focal dissolution of the matrix which was accompanied by a concomitant release of 3H‐labeled material into the media. Approximately half of this material chromatographed near the inclusion volume of Sephadex G‐50, indicating that the labeled matrix components had been degraded. This phenomenon was dependent on the age of the placenta. Second‐trimester placental villi also adhered to the matrix, but no areas of dissolution were formed and no significant amounts of radioactivity were released into the medium. These results suggest that culture of first‐trimester human placental villi on extracellular matrices may be useful for the study of some of the early embryonic events leading to human implantation, during which the trophoblastic cells erode the uterine epithelium.
Matrix‐cytoskeletal interactions in the developing eye
Authors: Hay Elizabeth D. 
Published: December 2004

AbstractThe embryonic avian corneal epithelium in vitro responds to extracellular matrix (ECM) molecules in either soluble or polymerized form by flattening its basal surface, organizing the basal cortical actin cytoskeleton, and stepping up its production of corneal stroma twofold. Embryonic corncal epithelia, like hepatocytes and mammary gland cells, seem to contain heparan sulfate proieoglycan (HSPG) in their plasmalemma, which may interact with actin on the one hand or underlying collagen on the other. Work on the corneal epithelium suggests that, in addition to HSPG, specific glycoprotein receptors for laminin and collagen exist in the basal plasmalemma and play, the critical role in actually organizing the basal epithelial cytoskeleton. As yet. uncharacterized proteins may link such receptors to actin. We suggest that ECM‐dependent organization of the cytoskeleton is responsible for ECM enhancement of corneal epithelial differentiation. Cell shape and exogenous ECM also affect mesenchymal cell differentiation. In the case of the conical fibroblast migrating in collagen gels, an actin cortex present around the elongate cell seems to interact with myosin in the cytosol to bring about pseudopodial extension. Both microtubules and actin microfilaments are involved in fibroblast elongation in collagen gels. It follows from the rules presented in this review that the mesenchymal cell surface is quite different from the epithelial cell surface in its organization. Nevertheless, epithelial cell surface‐ECM interaction can be modified in the embryo at particular times to permit predesignated epithelial‐mesenchymal transformations, as for example at the primitive streak. Though basal surfaces of definitive, nonmalignanl epithelia adhere rather strictly to the rules of epithelium‐ECM interaction and do not invade underlying ECM, the environment can be manipulated in vitro to cause these epithelia to send out pseudopodia and give rise aberrantly to mesenchymal cells in collagen gels. Further study of this phenomenon should cast light on the manner in which epithelial and mesenchymal cells organize receptors for matrix molecules on their cell surfaces and develop appropriate cytoskeletal responses to the extracellular matrix.
Liver tyrosine kinase activation during early stages of chemical hepatocarcinogenesis
Authors: Olson Jack W. 
Published: December 2004

AbstractProtein phosphorylation at tyrosine residues is believed to he involved in several important cellular processes because tyrosine‐specific protein kinase activation is associated with stimulation of cellular proliferation by hormones and growth factors, embryogenesis, and retroviral cell transformation. Because cell proliferation is thought to be an essential component of chemical carcinogenesis. liver tyrosine‐specific protein kinase activity was examined during the early stages of the Solt and Farber chemical hepatocarcinogenesis model. Rats were given diethylnitrosamine in one dose (200 mg/kg, IP) followed by 2 weeks of dietary 0.02% 2‐acctylamino‐fluorene starting at day 14 after diethylnitrosamine, followed by partial hepatectomy on day 21. By day 32 this regimen produces a relatively synchronized population of hyperplastic liver nodules up to 1.5 mm in diameter. Rats were sacrificed on day 32, their livers were perfused with cold normal saline, homogenized, and centrifuged at 1,000g for 10 min. The resulting supernatant was centrifuged at 30,000g for 30 min and the pellet was assayed for tyrosine kinase activity using the synthetic peptide [Val5]angiotensin II as substrate. Rats that received the complete regimen had a 2.6‐fold increase in their liver tyrosine kinase activity as compared to sham controls (2.4 pmoles/min/mg protein vs 6.4 pmoles/min/mg protein, P < .05). In contrast, rats that received a partial regimen (ie, partial hepatectomy, or 2‐acetylaminofluorene + partial hepatectomy, or diethylnitrosamine + 2‐acetylaminofluorene) did not have elevated tyrosine kinase activity nor did they have hyperplastic nodules. These preliminary data suggest that activation of liver tyrosine kinase is associated with the very early stages of chemical hepatocarcinogenesis.
How do the migratory and adhesive properties of the neural crest govern ganglia formation in the avian peripheral nervous system?
Authors: Duband Jean Loup , Tucker Gordon C. , Poole Thomas J. , Vincent Michel , Aoyama Hirohiko , Thiery Jean Paul 
Published: December 2004

AbstractThe peripheral nervous system derives mainly from the neural crest both in the head and trunk. Using markers such as fibronectin (FN), neural cell‐adhesion molecule (NCAM), the nuclcolar marker for quail cells in chimaeric embryos, and NC‐1, a monoclonal antibody specific to crest cells and their neural derivatives, we have attempted to reconstruct the processes that lead to the formation of peripheral ganglia. Our observations allow us to propose a model of the formation of ganglia based on morphogenetic movements and on variations of crest cell adhesiveness. In most cases, crest cells migrate in morphologically defined and transient pathways that lead them to their final site of arrest; these pathways are always associated with FN, which appears necessary for crest cell attachment and movement in vitro. The directionality of crest cell migration is probably dictated by the cells' motile properties and population pressure in restricted areas suitable for cell movement. The disappearance of the pathways and of the substrate necessary for migration while the population is rapidly dividing may be responsible for the aggregation of crest cells in the case of the sensory ganglia. To the contrary, the aggregation of crest cells into autonomic ganglia (sympathetic, enteric, aid ciliary ganglia) does not seem to obey the same rules, no disappearance of the substratum or of the pathways being obvious; rather, their formation seems correlated with the de novo synthesis of adhesive molecules such as NCAM.
Intracellular features of type II procollagen and chondroitin sulfate proteoglycan synthesis in chondrocytes
Authors: Vertel Barbara M. , Barkman Linda L. , Morrell Jeffrey J. 
Published: December 2004

AbstractThe intracellular compartments of chondrocytes involved in the synthesis and processing of type II procollagen and chondroitin sulfate proteoglycan (CSPG) monomer were investigated using simultaneous double immunofluorescence and lectin localization reactions. Type II procollagen was distributed in vesicles throughout the cytoplasm, whereas intracellular precursors of CSPG monomer were accumulated in the perinuclear cytoplasm. In this study, cytoplasmic vesicles that stained intensely with antibodies directed against CSPG monomer but did not react with type II collagen antibodies, also were observed. A monoclonal antibody, 5‐D‐4, that recognizes keratan sulfate determinants was used to identify the Golgi complex (the site of keratan sulfate chain elongation). Staining with 5‐D‐4 was restricted to the perinuclear cytoplasm. The vesicles outside the perinuclear cytoplasm that stained intensely with antibodies to CSPG monomer did not react with 5‐D‐4. Fluorescent lectins were used to characterize further subcellular compartments. Concanavalin A, which reacts with mannose‐rich oligosaccharides, did not stain the perinuclear region, but it did stain vesicles throughout the rest of the cytoplasm. Because mannos oligosaccharides are added cotranslationally, the stained vesicles throughout the cytoplasm presumably correspond to the rough endoplasmic reticulum. Wheat germ agglutinin, which recognizes N‐acetyl‐D‐glucosamine and sialic acid (carbohydrates added in the Golgi), stained exclusively the perinuclear cytoplasm. By several criteria (staining with the monoclonal antibody 5‐D‐4 and with wheat germ agglutinin), the perinuclear cytoplasm seems to correspond to the Golgi complex. The cytoplasmic vesicles that react with anti‐CSPG monomer and not with anti‐type II collagen contain precursors of CSPG monomer not yet modified by Golgi‐mediated oligosaccharide additions (because they are not stained with wheat germ agglutinin or with the anti‐keratan sulfate antibody); these vesicles may have a unique function in the processing of CSPG.
Further biochemical and physicochemical characterization of minor disulfide‐bonded (type IX) collagen, extracted from foetal calf cartilage
Authors: Ricard‐Blum Sylvie , Tiollier Jérôme , Garrone Robert , Herbage Daniel 
Published: December 2004

AbstractMinor disulfide‐bonded collagen (previously termed X1–X7 and now called type IX collagen) was isolated from foetal calf cartilage after pepsin treatment. At least three native fractions, containing, respectively, the X1X2X3, X4, and X5X6X7 chains, were separated; and from further biochemical and physicochemical experiments (differential scanning calorimetry, electrical birefringence, rotary shadowing), we propose a tentative model for their organization within a parent molecule, X1 and X2 are molecules composed of three chains of apparent Mr 62,000 and 50,000 linked by interchain disulfide bonds and containing pepsin‐sensitive regions. The cleavage of at least three of these sites, present within X2, gives rise to the X3 and X5X6X7 fractions composed of molecules 80–100 nm and 40–55 nm in length, respectively. The X5X6X7 fraction is not digested by pepsin at 30°C owing to its high thermal stability (certainly explained by its high hydroxyproline + proline content). This organization is in good accordance with that proposed for chicken cartilage type IX collagen; differences could only exist in the number and (or) the location of the pepsin‐sensitive sites.
Formyl peptide chemotaxis receptors on the rat neutrophil: Experimental evidence for negative cooperativity
Authors: Marasco Wayne A. , Feltner Douglas E. , Ward Peter A. 
Published: December 2004

AbstractTo examine the existence of negative cooperativity among formyl peptide chemotaxis receptors, steady‐state binding of f Met‐Leu‐[3H]Phe to viable rat neutrophils and their purified plasma membranes was measured and the data were subjected to statistical analysis and to computer curve fitting using the NONLIN computer program. Curvilinear, concave upward Scatchard plots were obtained. NONLIN and statistical analyses of the binding data indicated that a two‐saturable‐sites model was preferable to a one‐saturable‐site model and statistically valid by the F‐test (P < 0.1). In addition, Hill coefficients of 0.80 ± 0.02 were obtained. Kinetic dissociation experiments using purified plasma membranes showed evidence of site‐site interactions of the destabilizing type (negative cooperativity). Thus, unlabeled f Met‐Leu‐Phe accelerated the dissociation of f Met‐Leu‐[3H]Phe under conditions where no rebinding of radioligand occurred. The rate of dissociation of f Met‐Leu‐[3H]Phe from the plasma membranes was dependent on the fold excess of unlabeled f Met‐Leu‐Phe used in the dilution medium; at the highest concentration tested (10,000‐fold excess), the dissociation rate was more than double the dissociation rate seen with dilution alone, In addition, occupancy‐dependent affinity was ascertained directly by studying the effect of increasing fractional receptor saturation with labeled ligand on the dissociation rate of the receptor‐bound labeled ligand. These data showed that the f Met‐Leu‐[3H]Phe dissociation rate was dependent on the degree of binding site occupancy over the entire biologically relevant range of formyl peptide concentrations. Furthermore, monitoring of the time course of dissociation of the receptor/f Met‐Leu‐[3H]Phe complex as a function of receptor occupancy revealed that receptor affinity for f Met‐Leu‐Phe remained occupancy‐dependent during the entire time of dissociation examined (up to 10 min). Finally, the average affinity profile of the equilibrium binding data demonstrated a 60% decrease in receptor affinity in changing from the high affinity to the low affinity conformation.
In situ hybridization of putative somatostatin mRNA within hypothalamus of the rat using synthetic oligonucleotide probes
Authors: Arentzen Rene , Baldino Frank , Davis Leonard G. , Higgins Gerald A. , Lin Yuan , Manning Robert W. , Wolfson Betty 
Published: December 2004

AbstractThe distribution of mRNA with high sequence homology to somatostatin mRNA within the periventricular hypothalamus of rat was assessed using in situ hybridization techniques with synthetic oligodeoxyribonucleotide probes, complementary to the 3′ coding region of rat somatostatin mRNA. The probes (22‐ and 24‐mers) were 5′‐end labeled using T4 polynucleotide kinase and γ‐32P‐ATP. They were used either individually or after ligation with T4 DNA ligase to form a 46‐mer. Serial tissue sections ( < 10 μm) were taken from the level of the preoptic/anterior hypothalamus through the paraventricular hypothalamus. In situ hybridizations were conducted at room temperature in hybridization buffer. Neurons immuno‐reactive with antiserum raised against somatostatin were identified in alternate sections using standard immunocytochemical procedures. The anatomical location of the hybridization signal was determined by autoradiography. Our results show that the peri‐ and paraventricular hypothalamus is rich in transcripts putatively coding for somatostatin and that these transcripts are co‐distributed with neurons immunoreactive with antisomatostatin immunoglobulin.
A β‐type transforming growth factor, present in conditioned cell culture medium independent of cell transformation, may derive from serum
Authors: Stromberg Kurt , Twardzik Daniel R. 
Published: December 2004

AbstractAn alpha‐type transforming growth factor (TGFα) is produced at high levels by rat embryo cells transformed by the Snyder‐Theilen strain of feline sarcoma virus (FeSV). Addition of 2 ng mouse epidermal growth factor (mEGF) during purification identified the presence of a second, EGF‐dependent growth factor of the TGF beta type (TGFβ) in this conditioned medium. This factor had an approximate Mr of 12,000 and eluted at 37% acetonitrile during high performance liquid chromatography. This extracellular type of TGFβ activity also was present in conditioned medium of rat cells after infection with a transformation defective strain of Abelson leukemia virus, and hence expression of this growth factor activity was independent of cell transformation. Moreover, the presence of an EGF‐dependent. 12,000 Mr clonogenic activity in extracts of bovine serum alone suggests scrum as an origin for the B‐type transforming growth factor initially observed in conditioned medium of Snyder‐Theilen FeSV transformed cells. This does not, however, preclude the possibility that TGFβ is also secreted by the transformed rat embryo cells themselves.
Stimulation of phospholipase A2 activity by oxygen‐derived free radicals in isolated brain capillaries
Authors: Au A. M. , Chan P. H. , Fishman R. A. 
Published: December 2004

AbstractAn exogenous free radical generating system added to isolated brain capillaries induces degradation of phospholipids. This inductive effect reflects increased phospholipase activities as measured by fatty acid composition of various phospholipid fractions. The correlation of phospholipid degradation with stimulation of phospholipases was further investigated by using cationic amphiphilic agents, which are known to be phospholipase A2 inhibitors. The breakdown of phospholipids was inhibited by the pretreatment of isolated capillaries with these drugs.
Biosynthesis of collagen
Authors: Fessler John H. , Doege Kurt J. , Duncan Keith G. , Fessler Liselotte I. 
Published: December 2004

AbstractDuring the biosynthesis and assembly of collagen structures, disulfide links can serve several functions. During biosynthesis they successively stabilize intra‐peptide folding and associations of three chains into one molecule. Studies on the refolding and reassociation of reduced and denatured carboxyl propeptides of procollagen I showed that successive interactions of folding and assembly are successively weaker. Disulfide bridges were reestablished within correctly refolded carboxyl propeptides. Rearrangements of disulfide bridges may occur during the processing of type V procollagen molecules as these collagens become incorporated into extracellular matrix. The basement membrane procollagen IV molecules become disulfide linked at each end into networks, and there are indications that further rearrangements of disulfide links may allow additional modulation.
Recent advances in research on fibronectin and other cell attachment proteins
Authors: Yamada Kenneth M. , Akiyama Steven K. , Hasegawa Takayuki , Hasegawa Etsuko , Humphries Martin J. , Kennedy Dorothy W. , Nagata Kazuhiro , Urushihara Hideko , Olden Kenneth , Chen Wen‐Tien 
Published: December 2004

AbstractFibronectin and other cell attachment proteins provide molecular models for beginning to unravel the complex interactions of the cell surface with the extracellular matrix. This area has been reviewed in considerable detail previously [1–10]. Our brief review will therefore be selective rather than comprehensive, and it will focus on some recent generalizations about this class of proteins, as well as on recent advances in the molecular analysis of the functions of these proteins and their receptors. we shall also present various popular or provocative hypotheses and speculations about future work in the field.
Phosphorylation of the insulin receptor by casein kinase I
Authors: Tuazon Polygena T. , Pang Dennis T. , Shafer Jules A. , Traugh Jolinda A. 
Published: December 2004

AbstractInsulin receptor was examined as a substrate for the multipotential protein kinasc casein kinase I. Casein kinase I phosphorylated partially purified insulin receptor from human placenta as shown by immunoprecipitation of the complex with antiserum to the insulin receptor. Analysis of the phosphorylated complex by polyacrylamide gel electrophoresis under nonreducing conditions showed a major phosphorylated band at the position of the α2β2 complex. When the phosphorylated receptor was analyzed on polyacrylamide gels under reducing conditions, two phosphorylated bands, Mr 95,000 and Mr 135,000, were observed which corresponded to the α and β subunits. The majority of the phosphate was associated with the β subunit with minor phosphorylation of the α subunit. Phosphoamino acid analysis revealed that casein kinase I phosphorylated only seryl residues. The autophosphorylated α2β2 receptor purified by affinity chromatography on immobilized O‐phosphotyrosyl binding antibody was also a substrate for casein kinase I. Reduction of the phosphorylated α2β2 receptor indicated that casein kinase I incorporated phosphate into seryl residues only in the β subunit.
A pathway of coagulation on endothelial cells
Authors: Nawroth Peter P. , Stern David M. 
Published: December 2004

AbstractAlthough the endothelial cell is considered antithrombogenic, endothelium has recently been shown to participate in procoagulant reactions. Factor IX bound to specific endothelial cell sites can be activated by the intrinsic and extrinsic pathways of coagulation. Perturbation of endothelium results in induction of tissue factor which promotes factor VIIa‐mediated activation of factors IX and X. thus initiating procoagulant events on the endothelial surface. Cell bound factor IXa, in the presence of factor VIII, promotes activation of factor X. The factor Xa formed can interact with endothelial cell factor V/Va, resulting in prothrombin activation. Thrombin then cleaves fibrinogen and a fibrin clot closely associated with the endothelial cell forms. The perturbed endothelial cell thus provides a focus of localized procoagulant events. This model suggests a simple endothelial‐cell‐dependent mechanism for initiation of coagulation at the site of an injured or pathological vessel.
Structure and chromosomal localization of the human lymphotoxin gene
Authors: Nedwin Glenn E. , Jarrett‐Nedwin Julie , Smith Douglas H. , Naylor Susan L. , Sakaguchi Alan Y. , Goeddel David V. , Gray Patrick W. 
Published: December 2004

AbstractWe have isolated, sequenced, and determined the chromosomal localization of the gene encoding human lymphotoxin (LT). The single copy gene was isolated from a human genomic library using a 32P‐labeled 116 bp synthetic DNA fragment whose sequence was based on the NH2‐terminal amino acid sequence of LT. The gene spans 3 kb of DNA and is interrupted by three intervening sequences. The LT gene is located on human chromosome 6, as determined by Southern blot analysis of human‐murine hybrid DNA. Putative transcriptional control regions and areas of homology with the promoters of interferon and other genes are identified.