Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “tissue differentiation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed1993

Multiple neural inductions in area opaca by grafts of the Hensen's node do not retard host chick embryo development.

Four hundred and forty four full primitive streak stage chick embryos were cultured in vitro and 261 were transplanted with 1, 3 or 5 Hensen's nodes in the area opaca. Irrespective of the number of grafts, neural induction was observed in 90% cases. The development of control and grafted embryos and the size of blastoderm area were monitored at the time of grafting and after 20 hr. We find that the induced neural tissue and differentiated tissue of graft-origin neither fuse with the host embryonic axis, nor retard its development.

Animals↗
PubMed1998

A stochastic model of brain cell differentiation in tissue culture.

The timing of cell differentiation can be controlled both by cellintrinsic mechanisms and by cell-extrinsic signals. Oligodendrocyte type-2 astrocyte progenitor cells are known to be the precursor cells that give rise to oligodendrocytes. When stimulated to divide by purified cortical astrocytes or by platelet-derived growth factor, these progenitor cells generate oligodendrocytes in vitro with a timing like that observed in vivo. The most widely accepted model of this process assumes a cell-intrinsic biological clock that resides in the progenitor cell. The intrinsic clock model originally proposed in 1986 remains as the dominant theoretical concept for the analysis of timed differentiation in this cell lineage. However, the results of a recent experimental study (Ibarrola et al., Developmental Biology, vol. 180, 1-21, 1996) are most consistent with the hypothesis that the propensity of a clone of dividing O-2A progenitor cells initially to generate at least one oligodendrocyte may be regulated by cell-intrinsic mechanisms, but that environmental signals regulate the extent of further oligodendrocyte generation. We propose a stochastic model of cell differentiation in culture to accommodate the most recent experimental findings. Our model is an age-dependent branching stochastic process with two types of cells. The model makes it possible to derive analytical expressions for the expected number of progenitor cells and of oligodendrocytes as functions of time. The model parameters were estimated by fitting these functions through data on the average (sample mean) number of both types of cells per colony at different time intervals from start of experiment. Using this method we provide a biologically meaningful interpretation of the observed pattern of oligodendrocyte generation in vitro and its modification in the presence of thyroid hormone.

Animals↗
PubMed2006

Thermal stabilization of collagen molecules in bone tissue.

Differential thermal calorimetry (DSC) analysis of partially dehydrated bovine bone, demineralized bone and bovine tendon collagen was performed up to 300 degrees C to determine factors influencing stability of mineralized collagen in bone tissue. Two endothermal regions were recognized. The first, attributed to denaturation of collagen triple helix, was hydration dependent and had a peak at 155-165 degrees C in bone, 118-137 degrees C in tendon and 131-136 degrees C in demineralized bone. The second region extended from 245 to 290 degrees C in bone and from 200 to 280 degrees C in tendon and was connected with melting and decomposition of collagen. Differences in thermodynamic parameters between cortical and trabecular bone tissue were stated. Activation energy of collagen unfolding in native bone tissue increased with dehydration of the bone. From the results of the present study we conclude that dehydrated bone collagen is thermally very stable both in native and in demineralized bone. Presence of mineral additionally stabilizes bone tissue.

Achilles Tendon↗
PubMed2005

Characterisation and expression of the pathway from UDP-glucose to UDP-xylose in differentiating tobacco tissue.

The pathway from UDP-glucose to UDP-xylose has been characterised in differentiating tobacco tissue. A xylogenic suspension cell culture of tobacco has been used as a source for the purification of the enzymes responsible for the oxidation of UDP-glucose to UDP-glucuronic acid and its subsequent decarboxylation to UDP-xylose. Protein purification and transcriptional studies show that two possible candidates can contribute to the first reaction. Most of the enzyme activity in the cultured cells could be accounted for by a protein with an Mr of 43 kDa which had dual specificity for UDP-glucose and ethanol. The cognate cDNA, with similarity to alcohol dehydrogenases (NtADH2) was expressed in E. coli to confirm the dual specificity. A second UDP-glucose dehydrogenase, corresponding to the monospecific form, ubiquitous amongst plants and animals, could not be purified from the tobacco cell cultures. However, two cDNAs were cloned with high similarity to the family of UDP-glucose dehydrogenases. Transcripts of both types of dehydrogenase showed highest expression in tissues undergoing secondary wall synthesis. The UDP-glucuronate decarboxylase was purified as polypeptides of Mr 87 and 40 kDa. Peptide fingerprinting of the latter polypeptide identified it as a form of UDP-glucuronate decarboxylase and functionality was established by expressing the cognate cDNA in E. coli. Expression of 40 kDa polypeptide and its corresponding mRNA was also found to be highest in tissues associated with secondary wall formation.

Amino Acid Sequence↗
PubMed2004

Reprogramming of epigenetic inheritance by somatic cell nuclear transfer.

Somatic cloning by nuclear transfer returns a differentiated cell to a totipotent stage, a process termed nuclear reprogramming. During this de-differentiation process, genes inactivated during tissue differentiation are re-activated in a temporal and spatial special manner. It is believed that tissue differentiation occurs through epigenetic mechanisms, genetic inheritance that does not involve changes in DNA sequences. Developmental abnormalities and a high mortality rate in cloned offspring have frequently been observed and probably result from incomplete nuclear reprogramming. In this review, the reprogramming of two epigenetic mechanisms, imprinting and X chromosome inactivation, as well as recent attempts to modify pre-existing epigenetic marks in donor cells to improve nuclear transfer efficacy, are discussed.

Animals↗
PubMed2002

From stem cells to tissue-specific differentiation.

Stem cells have been isolated from embryonic, foetal and adult sources. Embryonic stem cells, derived from the pre-implantation embryo, can be expanded indefinitely in vitro. When reintroduced into the blastocyst they contribute to all lineages in vivo. In vitro, differentiated derivatives of embryonic stem cells are obtained by manipulating culture conditions. Embryonic germ cells, derived from the primordial germ cells, display the same degree of pluripotential differentiation. Adult stem cells that repopulate the tissue of origin throughout life possess the ability to differentiate into phenotypes not restricted to the tissue and, in some cases, to the germ layer from which they derive. Although the pluripotential differentiation capability of these stem-cell populations is supported by an increasing amount of evidence, a better understanding of the mechanisms that control differentiation is required for their exploitation in the treatment of human diseases.

Journal Article↗
PubMed2002

Mouse folylpoly-gamma-glutamate synthetase isoforms respond differently to feedback inhibition by folylpolyglutamate cofactors.

Folylpoly-gamma-glutamate synthetase (FPGS) is the enzyme responsible for metabolic trapping of reduced folate cofactors in cells for use in nucleotide and amino acid biosynthesis. There are two isoforms of FPGS expressed in mouse tissues, one is expressed in differentiated tissue, principally liver and kidney, and the other in all rapidly proliferating cell types. The present study sought the functional difference that would explain the evolution of two mouse FPGS species. Recombinant cytosolic mouse isozymes were compared with respect to steady state kinetics, chain length of polyglutamate derivatives formed, and end-product inhibition by the major reduced folylpentaglutamate cofactors. Both isoforms were equally effective in catalyzing the addition of a mole of glutamic acid to reduced folate monoglutamate substrates. Each isoform was also capable of forming long chain polyglutamate derivatives of the model folate, 5,10-dideazatetrahydrofolate. In contrast, the FPGS isoform derived from rapidly proliferating tissue was much more sensitive to inhibition by (6R)-5,10-CH(2)-H(4)PteGlu(5) and (6S)-H(4)PteGlu(5) than the isoform expressed in differentiated tissues, as demonstrated by 13- and 6-fold lower inhibition constants (K(i)), respectively. Interestingly, each isozyme was equally sensitive to inhibition by (6R)-10-CHO-H(4)PteGlu(5). We drew the conclusion that the decreased sensitivity of the FPGS expressed in mouse liver and kidney to feedback inhibition by 5,10-CH(2)-H(4)PteGlu(5-6) and H(4)PteGlu(5-6) may have evolved to permit accumulation of a larger folate cofactor pool than that found within rapidly proliferating tissue.

Amino Acid Sequence↗
PubMed1990

Operating illumination to differentiate dental hard tissues.

This in vitro study was designed to evaluate the ability of fluorescent tubes and dental lights to help operators distinguish tissues (fissures), differentiate between tissues (at the dentinoenamel junction or between carious and sound dentin), and distinguish form of a tooth preparation (Class II and Class V cavities). Operators with "normal" color vision ranked the lights in order of preference for each type of specimen. In general, for the fluorescent illuminants, operators preferred lights with high color temperature values and high color rendering index values. A small group of color-blind observers indicated a preference for an illuminant of low color temperature and low color rendering index value. For dental lights, operators preferred a higher color temperature for examining fissures, the dentinoenamel junction, and the cavity preparation. No particular illuminant was preferred for distinguishing between carious and sound dentin. Many observers had difficulty in choosing a preferred dental luminaire.

Color↗
PubMed2004

Adhesion-contractile balance in myocyte differentiation.

Tissue cells generally pull on their matrix attachments and balance a quasi-static contractility against adequate adhesion, but any correlation with and/or influence on phenotype are not yet understood. Here, we begin to demonstrate how differentiation state couples to actomyosin-based contractility through adhesion and substrate compliance. Myotubes are differentiated from myoblasts on collagen-patterned coverslips that allow linear fusion but prevent classic myotube branching. Post-fusion, myotubes adhere to the micro-strips but lock into a stress fiber-rich state and do not differentiate significantly further. In contrast, myotubes grown on top of such cells do progress through differentiation, exhibiting actomyosin striations within one week. A compliant adhesion to these lower cells is suggested to couple to contractility and accommodate the reorganization needed for upper cell striation. Contractility is assessed in these adherent cells by mechanically detaching one end of the myotubes. All myotubes, whether striated or not, shorten with an exponential decay. The cell-on-cell myotubes relax more, which implies a greater contractile stress. The non-muscle myosin II inhibitor blebbistatin inhibits relaxation for either case. Myotubes in culture are thus clearly prestressed by myosin II, and this contractility couples to substrate compliance and ultimately influences actomyosin striation.

Actins↗
PubMed1976

Chemically-defined medium for growth and differentiation of mixed epithelial and connective tissues in organ culture.

The effect on tissue differentiation and growth in vitro of certain of the factors implicated in collagen synthesis (ascorbic acid, alpha-ketoglutarate and oxygen) and the influence of hydrocortisone was studied using organ cultures of fetal mouse mandible as a mixed epithelial and connective tissue system. Using serum-free Waymouth's MB 752/1 chemically-defined medium, addition of high levels of ascorbic acid (300mug per ml), hydrocortisone (1mug per ml) and oxygen (95%) enhanced differentiation in a number of tissues, in particular skin and appendages, tooth germs and bone, while osteoid and dentine production were noticeable promoted. It is suggested that an essential aspect of media design for organ culture involves the incorporaation of collagen-promoting factors to the in vitro enviornment particularly with regard to the controlling role implicated for collagen in a variety of biological processess.

Animals↗
PubMed2001

Mechanobiology of initial pseudarthrosis formation with oblique fractures.

Mechanical stresses play an important role in regulating tissue differentiation in a variety of contexts during skeletal development and regeneration. It has been shown that some intermittent loading at a fracture site can accelerate secondary fracture healing. However, it has not been shown how the stress and strain histories resulting from mechanical loading of a fracture might, in some cases, inhibit normal fracture healing and induce pseudarthrosis formation. In this study, finite element analysis is used to calculate hydrostatic stress and maximum principal tensile strain patterns in regenerating tissue around the site of an oblique fracture. Using a mechanobiologic view on tissue differentiation, we compared calculated stress and strain patterns within the fracture callus to the histomorphology of a typical oblique pseudarthrosis. Tissue differentiation predictions were consistent with the characteristic histomorphology of oblique pseudarthrosis: in the interfragmentary gap. tensile strains led to "cleavage" of the callus; at the ends of both fracture fragments, hydrostatic pressure and tensile strain caused fibrocartilage formation, and, at discrete locations of the periosteum at the oblique fracture ends, mild hydrostatic tension caused bone formation. We also found that discrete regions of high hydrostatic pressure correlated with locations of periosteal bone resorption. When previous findings with distraction osteogenesis are considered with these observations, it appears that low levels of hydrostatic pressure may be conducive to periosteal cartilage formation but high hydrostatic pressure may induce periosteal bone resorption during bone healing. We concluded that tissue differentiation in pseudarthrosis formation is consistent with concepts previously presented for understanding fracture healing, distraction osteogenesis, and joint formation.

Biomechanical Phenomena↗
PubMed2003

RARRES3 expression positively correlated to tumour differentiation in tissues of colorectal adenocarcinoma.

RARRES3 is a retinoid-inducible class II tumour-suppressor gene. This study analysed the expression of RARRES3 protein in normal, adenoma and carcinoma tissues of the colorectum and its correlation with tumour differentiation. The expression of RARRES3 protein in 151 paraffin-embedded colorectal tissues (11 distal normal mucosa, 20 adenoma and 120 colorectal adenocarcinoma) was determined by immunohistochemistry. RARRES3 protein was expressed in all 11 distal normal, 120 adjacent normal and 20 adenoma tissues. In distal normal tissues, RARRES3 protein was expressed at the highest levels in differentiated mucosal epithelial cells. Among 120 carcinoma tissues, RARRES3 protein was detected in 97.6% (40 out of 41), 79.4% (54 out of 68) and 17.3% (three out of 11) of well-, moderately and poorly differentiated tumours, respectively. The expression of RARRES3 protein was positively correlated to tumour differentiation (test for trend, P<0.0001). Also, levels of RARRES3 protein were found to be higher in the normal tissues adjacent to 14.6% (six out of 41), 51.5% (35 out of 68), and 90.1% (10 out of 11) of well-, moderately and poorly differentiated tumours, respectively. The decreases in tumour differentiation and RARRES3 expression were significantly correlated compared to the adjacent normal tissues (test for trend, P<0.0001). The prognostic implication of RARRES3 protein expression was studied in 107 tumour, and no statistical difference in survival was observed. The expression of RARRES3 protein was positively correlated to cellular differentiation of normal and adenocarcinoma tissues of the colorectum, which supports the role of RARRES3 in normal and malignant epithelial differentiation of colorectum. RARRES3 expression was decreased only in carcinoma tissue, which suggests that altered RARRES3 expression occurs late in colorectal carcinogenesis.

Adenocarcinoma↗
PubMed1995

Soft-tissue calcifications: differential diagnosis and therapeutic approaches.

Calcification of soft tissue may be an unspecific local response or present as only a symptom of a complex underlying disease. Patient approach and treatment vary greatly depending on the cause of soft-tissue calcifications. The review of literature reveals multiple causes but also confusing nomenclature for similar clinical entities. Dystrophic and metastatic soft-tissue calcifications are discerned, but there is also contribution of both types of soft-tissue calcification to some syndromes. Six previously unpublished cases of soft-tissue calcification including Thibièrge-Weissenbach syndrome, scleroderma (progressive systemic sclerosis), calcifying cavernous hemangioma (2 patients), and heterotopic calcifications after burn injury (2 patients) are presented to discuss the differential diagnosis. The correct diagnosis is crucial for successful treatment. Resections of the lateral heads of the gastrocnemius muscles in 2 patients resulted in cure of the problem. The patient suffering from Thibièrge-Weissenbach syndrome had no recurrence during a 30-month postoperative follow-up period. Surgical treatment of scleroderma or soft-tissue calcification after burn injury is aimed toward relief of symptoms. A proposal for patient assessment and indications for surgical correction with regard to soft-tissue calcifications is presented and discussed.

Adolescent↗
PubMed1975

Electron microscopic studies on chick limb cartilage differentiated in tissue culture.

The hind limb-bud mesenchyme of chick embryos 4-4 1/2 days old was cultured in Eagle's Minimum Essential Medium supplemented with both horse serum and fresh chick embryo extract. Whereas no differences are seen at the light-microscope level, at the electron-microscope level the chondroblasts differentiated in tissue culture are noticeably different from those differentiated in vivo, particularly in the possession of some cytoplasmic fibrils and vacuoles. It is proposed that the secretion of the extracellular matrix alone is not sufficient to account for the pattern of cellular arrangement in a cartilaginous condensation.

Animals↗
PubMed1998

Glyoxalases activity during Bufo bufo embryo development.

In this work we have investigated the expression of glyoxalase I (GLO I) and glyoxalase II (GLO II) activities during Bufo bufo embryo development and in some tissues of both male and female adult animals, in order to study how they correlate with cell proliferation and differentiation. The results show that both the activities are expressed at significant levels from the earliest developmental stages, reaching the highest values at the end of embryonic development (stage 25). The GLO I/GLO II ratio is very high at the beginning of the development and then gradually decreases as the development goes on. These data emphasize the importance of GLO I activity in the phases in which elevated cell division is taking place. In the differentiated tissues, a peculiar sexual dimorphism in both GLO I and GLO II activities, with higher values in female than in male, was found. GLO I embryonic activity levels are comparable to those found in female differentiated tissues, but significantly higher than those detected in male differentiated tissues. On the contrary, the GLO II activities found in the adult tissues were always higher than those found in embryos. These results further support the idea that high GLO I/GLO II ratios are a characteristic of the proliferative status, which assures a good scavenging action against the potentially cytotoxic and cytostatic effect of methylglyoxal.

Animals↗
PubMed1995

Thyroid hormone and norepinephrine signaling in brown adipose tissue. II: Differential effects of thyroid hormone on beta 3-adrenergic receptors in brown and white adipose tissue.

UNLABELLED: beta 3-adrenergic receptors (AR) are predominantly expressed in brown (BAT) and white adipose tissue (WAT), being more abundant in the former. There is growing interest in these receptors because of their potential to be pharmacologically targeted to control energy expenditure and lipid accretion. We have examined, in BAT and WAT of rats, the effect of thyroid hormone on the expression of beta 3-AR and their contribution to cAMP generation. Receptor density was assessed with the nonselective beta 3-AR ligand [125I]-cyanopindolol ([125I]-CYP) and the highly selective beta 3-AR agonist CL3216,243. beta 3-AR messenger RNA (mRNA) was analyzed by Northern blotting of total BAT and WAT RNA. Generation of cAMP by brown adipocytes in response to norepinephrine (NE) and CL316,243 was measured by RIA. In BAT, beta 3-AR can account for as much as 50% of the maximal cAMP response to NE, whereas in WAT these receptors probably account for all the effect of NE. In hypothyroidism. BAT beta 3-AR number is increased, as are beta 3-AR mRNA (4- to 6-fold) and the relative contribution of these receptors to the maximal cAMP production. In contrast, both beta 3-AR number and mRNA levels are reduced in WAT of hypothyroid rats. The injection of T3 to hypothyroid rats reverts the changes in beta 3-AR within 24 h, and T3 excess causes a greater than 90% reduction in beta 3-AR mRNA in BAT but a 5-fold increase in WAT. In both tissues, hypothyroidism is associated with a marked reduction in the capacity to generate cAMP, but this is not completely restored even after 2 days of a receptor-saturating dose of T3. CONCLUSIONS: 1) thyroid hormone differentially affects the expression of beta 3-AR in BAT and WAT; 2) these effects of T3 are both rapid and marked and seem to take place at a pretranslational level; 3) in both tissues there is a postreceptor defect in the generation of cAMP that is corrected by T3 much later after the changes in beta 3-AR are reversed; and 4) thyroid hormone is among the known factors that most vigorously affect the expression of beta 3-AR.

Adipose Tissue↗
PubMed1980

Calorimetric study of water in muscle tissue.

Differential scanning calorimetry has been used to investigate the state of water in intact single muscle fibers of the giant barnacle, Balanus nubilus. The shapes of the melting curves suggest the presence of three types of water: unfrozen (or bound), free (or bulk) and intermediate water. The amount of unfrozen water per g protein was constant within experimental error. An increase in water content changed almost exclusively the amounts of free water. The amount of intermediate water varies only slightly with the fiber water content.

Animals↗