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At least 397 records · Page 22Linked to original sources
PubMed1997

Hydra regeneration from recombined ectodermal and endodermal tissue. II. Differential stability in the ectodermal and endodermal epithelial organization.

Hydra tissue consists of the ectodermal and the endodermal layers. When the two layers were separated by procaine treatment and then recombined, the ectodermal epithelial cells spread as a single cell layer over the endoderm as in epiboly in vertebrate embryogenesis, and the resultant spherical structure subsequently regenerated into a complete hydra. In this study, light and electron microscopy were used to examine the structural changes which took place in the cells and tissue during this epibolic ectodermal spreading process. Within a few hours after tissue recombination, the endoderm underwent dramatic changes; it lost its epithelial sheet organization, and turned into a mass of irregularly shaped cells without the apical-basal cell polarity initially present. In contrast, the ectoderm maintained its basic epithelial sheet organization as it spread over the endoderm. Later, the endodermal epithelial cells reorganized themselves into a single-layered epithelial sheet underneath the spreading ectodermal layer. The resultant spherical structure consisted of a single layer of ectodermal epithelial cells outside, a single layer of endodermal epithelial cells inside, and an empty cavity in the center as in normal hydra tissue. This structure regenerated into hydra in the following days. These and other observations demonstrate that the two-layered epithelial sheet organization is highly dynamic, and that its stability is maintained by strong interactions between the two layers in normal hydra. It is suggested that this dynamic nature of the hydra tissue, particularly the high plasticity of the endodermal epithelial sheet organization, may be an important element for the high regenerative capacity of this organism.

Animals↗
PubMed1976

[Analysis of breast cell differentiation in tissue culture under the influence of hormones].

Effects of insulin, hydrocortisone and prolactin on cell differentiation were studied in mammary gland tissue culture of pregnant goats. The morphological evidence suggests that the administration of the above hormonal triad during cultivation contributes to the development of "growth zone" around the explantat on the filter and to morphological changes of tissue which become specific of the mammary gland tissue in normally lactating animals. The metabolism of nuclear proteins, DNA synthesis and cell proliferation at the initial stages of epithelium development are demonstrated to be regulated by insulin together with hydrocortisone. The synthesis of milk proteins is influenced by prolactin. The effect of prolactin is realized only in newly-formed postmitotic population of secretory cells.

Animals↗
PubMed2003

Exogenously applied jasmonic acid induces changes in apical meristem morphology of potato stolons.

Hooked apex stolons and initial swelling stolons of potato plants were treated with 3 x 10-8 mol l-1 jasmonic acid (JA) to study the effect of this compound on histology, cell expansion and tissue differentiation. In hooked apex stolons, JA application increased the meristem thickness and reduced the length of the leaf primordia, whereas in initial swelling stolons narrowing of the apical region, absence of leaf primordia and swelling of the subapical meristem were evident. Early vascular tissue differentiation was observed in response to JA treatment, especially of xylem elements from regions proximal to the tunic. Protoxylem elements, such as tracheal elements, were present with thin primary cell walls. The cell area was measured in two zones: zone I, central mother cells situated immediately under the tunic; and zone II, rib meristem cells. JA caused a four- and six-fold increase in cell area in both zones in hooked apex stolons and initial swelling stolons, respectively. Thus, tuber formation is concluded to occur as a consequence of increased cell expansion, a reduction in the length of leaf primordia, enlargement of meristems, and early vascular tissue differentiation.

Cell Differentiation↗
PubMed1998

Identification of a tissue- and differentiation stage-specific enhancer of the VpreB1 gene.

The VpreB and lambda 5 genes encode proteins that associate non-covalently to form the so-called surrogate light (SL) chain. The SL chain complexes with the immunoglobulin heavy chain to form the pre-B cell receptor, which plays a critical role in B cell development. Expression of the murine SL genes is regulated at the level of transcription initiation. Here, we show that a VpreB1 enhancer is located within the 356 bp immediately upstream of the coding sequence. Interestingly, this region exhibits 96% identity to the upstream region of VpreB2. Deletion mapping located the enhancer to between positions -214 and -47 (+1 is the 5'-most transcription initiation site). The enhancer is tissue and differentiation stage specific, and is composed of several DNA elements that are important for its activity. We also show that a transcription factor, early B cell factor, binds to two such elements, and that at least one of these sites is involved in determining enhancer activity.

Animals↗
PubMed1990

Beta spectrin in human skeletal muscle. Tissue-specific differential processing of 3' beta spectrin pre-mRNA generates a beta spectrin isoform with a unique carboxyl terminus.

Spectrin, an important component of the mammalian erythrocyte membrane skeleton, is a heterodimeric protein with alpha and beta subunits of 280 and 246 kDa, respectively. Spectrin-like proteins have also been demonstrated in a wide variety of nonerythroid cells. To examine the hypothesis that nonerythroid beta spectrins may be encoded by the "erythroid" beta spectrin gene, we have isolated cDNA clones from a human fetal skeletal muscle library by hybridization to a previously described red cell beta spectrin cDNA. Detailed comparison of muscle and erythroid beta spectrin cDNAs has revealed sequence identity over the majority of their lengths, confirming that they are the product of the same gene. However, there is a sharp divergence in sequence at their 3' ends. A consequence of this divergence is the replacement of the carboxyl terminus of erythroid beta spectrin with a different, longer carboxyl-terminal domain in skeletal muscle. We hypothesize that tissue-specific differential polyadenylation leads to the selective activation of a donor splice site within the beta spectrin coding sequence, splicing downstream nonerythroid exons into the mature muscle beta spectrin mRNA. We predict that replacement, in nonerythroid cells, of the beta spectrin carboxyl terminus, known to participate in spectrin self-association and phosphorylation, has significant functional consequences. These data may explain previously reported nonerythroid beta spectrin isoforms that resemble red cell beta spectrin by immunochemical analysis.

Amino Acid Sequence↗
PubMed2005

Expression of permeability-glycoprotein (P-gp) and uptake of technetium-99m-hexakis-2-methoxy-isobutyl-isonitrile (99Tcm-MIBI) in malignant tumour of the head and neck.

OBJECTIVES: The purpose of this study is to estimate the role of permeability-glycoprotein (P-gp) in the technetium-99m-hexakis-2-methoxy-isobutyl-isonitrile (99Tc(m)-MIBI) scintigraphy. METHODS: 71 patients with squamous cell carcinoma (39 patients with well differentiated, 19 with moderately differentiated and 13 with poorly differentiated tumour) were examined. Eighteen of these patients underwent 99Tc(m)-MIBI scintigraphy (early and delayed scans). The tumour retention index, obtained from the ratio of the accumulation of the delayed scan to that of the early scan, was divided into three groups. The immunohistochemical evaluation of P-gp expression was performed in all 71 patients. Levels of the P-gp expression were classified into three grades (score 0, 1 and 2). Correlations among the tumour retention index, the P-gp expression and the tumour tissue differentiation were evaluated. RESULTS: 17 of 18 patients showed a decreasing of the tumour retention index ranging from 0.70 to 0.93 (mean+/-SD=0.850+/-0.071). The tumour retention index showed a statistical correlation with the P-gp expression and the tumour tissue differentiation (chi-squared=7.802>7.779, P=0.10 and 16.835>14.860, P=0.005, respectively). Moreover, there was a statistical correlation between the P-gp expression and the tumour tissue differentiation (chi-squared=14.863>14.860, P=0.005). CONCLUSION: There is a possibility that the P-gp expression is high in the high-grade malignant tumours and P-gp causes the decrease of tumour retention index.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Speculations on the roles of RB1 in tissue-specific differentiation, tumor initiation, and tumor progression.

Studies of retinoblastoma clearly identify mutation of the RB1 gene on chromosome 13 as the primary cause of this cancer. However, all retinoblastoma tumors have an abnormal karyotype (1, 2) indicating the presence of additional mutations and suggesting that mutation of both RB1 alleles is insufficient for development of retinoblastoma. In addition, analysis of RB1 expression and of RB1 mutations in different tumors leads to the following dilemma: while the RB1 gene product, p110RB1, is expressed in most dividing cells, germline mutations inactivating the function of p110RB1 predispose primarily to retinoblastoma and to a lesser extent to osteosarcoma, but do not predispose to cancer in general. However, many tumors contain somatic mutations that disrupt RB1 function. Thus, we are faced with the unusual situation in which germline mutations in the RB1 gene predispose to a very limited set of cancers, but somatic mutations in RB1 appear to contribute to malignancy in many tissues. We propose that the role of the RB1 gene is to maintain the cells in a stable, quiescent state required for terminal differentiation and that the effect of RB1 mutations in different tissues depends on the pattern of differentiation in that tissue. In tissues where differentiation follows a linear process from undifferentiated precursors to fully differentiated cells, loss of RB1 function during early stages of differentiation may lead to uncontrolled growth and the development of cancer. On the other hand, in cell renewal systems where cell number is usually maintained by a process of programmed cell death (PCD) or apoptosis, loss of RB1 function may lead to cell death.

Animals↗
PubMed2005

Scintigraphy for interpretation of malignant tumours of the head and neck: comparison of technetium-99m-hexakis-2-methoxyisobutylisonitrile (Tc-MIBI) and thallium-201-chloride (Tl-201).

OBJECTIVES: The purpose of this study was to compare the usefulness of technetium-99m-hexakis-2-methoxyisobutylisonitrile (99Tc(m)-MIBI) and thallium-201-chloride (Tl-201) as scintigraphic agents. METHODS: Dynamic and static scintigraphic imaging with 99Tc(m)-MIBI and Tl-201 were performed on patients with a variety of malignant and benign tumours. Factors of the grade of the static scan, the blood flow index, the early and delayed retention indexes, and the tumour retention index were obtained from the scintigraphy. In addition to these factors, the grade of tissue differentiation and tumour size were evaluated to clarify the difference between 99Tc(m)-MIBI and Tl-201 for the diagnosis of malignant tumours of the head and neck. RESULTS: 99Tc(m)-MIBI accumulation depended upon the blood flow index in the early static scan, but this accumulation did not correlate with tumour size. The accumulation in most subjects decreased in the delayed static scan, and the tumour retention index had a tendency to decrease with the grade of tissue differentiation. Tl-201 accumulation depended upon the blood flow index in the early static scan similar to 99Tc(m)-MIBI, and the accumulation correlated with tumour size, unlike 99Tc(m)-MIBI. The tumour retention index had a tendency to increase with the grade of tissue differentiation. Thus, the tumour retention indexes showed opposite behaviours between 99Tc(m)-MIBI and Tl-201, but they both accurately determined tumour malignancy. CONCLUSIONS: There was no major difference between 99Tc(m)-MIBI and Tl-201scintigraphy with respect to accuracy of diagnosis of malignant tumours of the head and neck. However, 99Tc(m)-MIBI was superior to Tl-201 for small-size tumours and Tl-201 was useful for large-size tumours.

Adenocarcinoma↗
PubMed1986

The molecular through ecological genetics of abnormal abdomen. III. Tissue-specific differential replication of ribosomal genes modulates the abnormal abdomen phenotype in Drosophila mercatorum.

The abnormal abdomen (aa) syndrome in Drosophila mercatorum is controlled by two major X-linked genetic elements. We have previously shown that the major X-linked element of aa is associated with the presence of large inserts in the 28S gene of the ribosomal RNA (rDNA) genes. We show that, in polytene tissue of wild-type D. mercatorum, the uninterrupted rDNA repeats are overreplicated relative to interrupted repeats. Uninterrupted rDNA repeats are also overreplicated in polytene tissue of hybrid larval offspring from wild-type and aa parents. This overreplication of uninterrupted repeats is not observed in diploid tissues of wild-type hybrids (of wild-type and aa parents) and homozygous aa larvae or in polytene tissue of aa larvae. Furthermore, molecular analysis of an aa line that has reverted to the wild type indicates that the reversion phenomenon is associated with the ability to overreplicate uninterrupted rDNA repeats in polytene tissues. The patterns of differential replication of rDNA genes in wild-type hybrids and aa larvae of D. mercatorum offer a possible mechanism for the tissue-specific control of the aa phenotype and suggest that the molecular basis for the second X-linked genetic element of aa is involved in the control of differential replication in polytene tissues.

Abdomen↗
PubMed2002

DNA hypermethylation: when tumour suppressor genes go silent.

The phenotype of the cancerous cell may arise either from genetic alterations that disrupt gene function through sequence modifications (mutations) or epigenetic events that may alter the heritable state of gene expression (i.e. without changing the actual sequence of the genome). Whereas mutations in certain tumour suppressor genes are most often thought of in association with their inactivation during cancer initiation or progression, epigenetic alterations such as DNA methylation appear to be tightly linked to the sequential non-reversible events of normal tissue differentiation and organogenesis. This highlights a link between tissue differentiation and tumourigenesis with respect to the stable nature of certain epigenetic changes. In the case of tumourigenesis, both genetic and epigenetic mechanisms of altered gene expression often go hand in hand; not surprisingly, biallelic inactivation of a given tumour suppressor gene may occur via a combination of mutational and epigenetic events and is entirely consistent with the Knudson two-hit hypothesis of tumourigenesis. This review summarizes recent developments within the field of DNA methylation, highlighting its association with the transcriptional silencing of tumour suppressor genes in a variety of human cancers.

CpG Islands↗
PubMed1989

Stage-dependent expression of the chicken delta-crystallin gene in transgenic fish embryos.

To study the regulation of gene expression of vertebrate crystallin genes, the chicken delta-crystallin gene was introduced into a small freshwater fish, medaka (Oryzias latipes), which lacks this gene, and its expression was examined immunohistologically at several developmental stages before hatching. The gene expression was detected in the central fiber cells of the lens at an early stage, showing a stage-dependent expression. In non-lens tissues, the expression was barely detectable before tissue differentiation. It first became substantial mainly in mesodermal tissues and then later in a greater variety of tissues, including ectodermal and endodermal ones. Thus, the non-lens expression of delta-crystallin was also stage-dependent, with the stage being dependent on the tissue type. These results from lens and non-lens tissues are discussed in relation to tissue differentiation and two categories of delta-crystallin expression.

Animals↗
PubMed2001

Differential expression for tissue-specific isozymes in three species of Hypostomus Lacépède, 1803 (Teleostei: Loricariidae).

The expression patterns of 14 enzymatic systems in skeletal muscle, liver and heart tissues of three species of Hypostomus from the Iguaçu River basin (Brazil) were investigated. Although the patterns were similar for the three species, different tissues showed differential expressions, and the data showed that differential tissue expressions of isoperoxidases may be due to preferential combination or association of polypeptide subunits. The detected patterns for SOD isozymes showed that the quaternary structures of these enzymes were in disagreement with the subunit number reported for the majority of other vertebrate groups. Tissue-specific restriction on heterotetramer formation also were described in LDH and MDHP isozymes. Thus, these tissue-specific gene expression character in the species of Hypostomus have the greatest potential to be recognized and applied in systematic studies among species of Hypostomus.

Journal Article↗
PubMed1993

Erythropoietin triggers a burst of GATA-1 in normal human erythroid cells differentiating in tissue culture.

GATA-1 is a central transcription-activator of erythroid differentiation. In the present work we have studied the kinetics of its expression and activity during development of normal human erythroid progenitors, grown in primary cultures. In response to the addition of erythropoietin (Epo), the cells undergo proliferation and differentiation in a synchronized fashion. This recently developed experimental system allows biochemical dissection of erythroid differentiation in a physiological meaningful environment. No DNA-binding activity of GATA-1 could be detected before the addition of Epo, although a very low level of mRNA was observed. Following Epo addition there was a sharp parallel rise in both mRNA and DNA-binding activity, consistent with positive autoregulation of the GATA-1 gene. After reaching a peak on day 7-9, both mRNA and protein activity decreased. The binding activity of the ubiquitous factor SP1 showed a biphasic pattern; its second peak usually coincided with the GATA-1 peak, suggesting that SP1 also plays a specific role in erythroid maturation. The highest activity of GATA-1 per erythroid cell was found on day 6-8, immediately preceding the major rise in globin gene mRNA and in the number of hemoglobinized cells. The results imply that a high level of GATA-1 activity is necessary for globin gene expression and erythroid maturation, suggesting that a requirement for a threshold concentration of GATA-1 is part of the mechanism that determines the final steps of erythroid maturation.

Adult↗
PubMed1998

Developmentally regulated expression of the novel cancer anti-apoptosis gene survivin in human and mouse differentiation.

Inhibitors of programmed cell death (apoptosis) may regulate tissue differentiation and aberrantly promote cell survival in neoplasia. A novel apoptosis inhibitor of the IAP gene family, designated survivin, was recently found in all of the most common human cancers but not in normal, terminally differentiated adult tissues. The expression of survivin in embryonic and fetal development was investigated. Immunohistochemistry and in situ hybridization studies demonstrated strong expression of survivin in several apoptosis-regulated fetal tissues, including the stem cell layer of stratified epithelia, endocrine pancreas, and thymic medulla, with a pattern that did not overlap with that of another apoptosis inhibitor, bcl-2. A sequence-specific antibody to survivin immunoblotted a single approximately 16.5-kd survivin band in human fetal lung, liver, heart, kidney, and gastrointestinal tract. In mouse embryo, prominent and nearly ubiquitous distribution of survivin was found at embryonic day (E)11.5, whereas at E15 to -21, survivin expression was restricted to the distal bronchiolar epithelium of the lung and neural-crest-derived cells, including dorsal root ganglion neurons, hypophysis, and the choroid plexus. These data suggest that expression of survivin in embryonic and fetal development may contribute to tissue homeostasis and differentiation independently of bcl-2. Aberrations of this developmental pathway may result in prominent re-expression of survivin in neoplasia and abnormally prolonged cell viability.

Animals↗
PubMed2004

G1/S phase cyclin-dependent kinase overexpression perturbs early development and delays tissue-specific differentiation in Xenopus.

Cell division and differentiation are largely incompatible but the molecular links between the two processes are poorly understood. Here, we overexpress G1/S phase cyclins and cyclin-dependent kinases in Xenopus embryos to determine their effect on early development and differentiation. Overexpression of cyclin E prior to the midblastula transition (MBT), with or without cdk2, results in a loss of nuclear DNA and subsequent apoptosis at early gastrula stages. By contrast, overexpressed cyclin A2 protein does not affect early development and, when stabilised by binding to cdk2, persists to tailbud stages. Overexpression of cyclin A2/cdk2 in post-MBT embryos results in increased proliferation specifically in the epidermis with concomitant disruption of skin architecture and delay in differentiation. Moreover, ectopic cyclin A2/cdk2 also inhibits differentiation of primary neurons but does not affect muscle. Thus, overexpression of a single G1/S phase cyclin/cdk pair disrupts the balance between division and differentiation in the early vertebrate embryo in a tissue-specific manner.

Animals↗
PubMed2000

Involvement of BMP-4/msx-1 and FGF pathways in neural induction in the Xenopus embryo.

The msx homeodomain protein is a downstream transcription factor of the bone morphogenetic protein (BMP)-4 signal and a key regulator for neural tissue differentiation. Xmsx-1 antagonizes the dorsal expression of noggin and cerberus, as revealed by in situ hybridization and reverse transcription-polymerase chain reaction assays. In animal cap explants, Xmsx-1 and BMP-4 inhibit the neural tissue differentiation induced by noggin or cerberus. A loss-of-function study using the Xmsx-1/VP-16 fusion construct indicated that neural tissue formation was directly induced by the injection of fusion ribonucleic acid, although the expression of neural cell adhesion molecule (N-CAM) in the cap was less than that in the cap injected with tBR or noggin. In contrast to the single cap assay, unexpectedly, both BMP-4 and Xmsx-1 failed to inhibit neurulation in the ectodermal explants to which the organizer mesoderm was attached. The results of cell-lineage tracing experiments indicated that the neural cells were differentiated from the animal pole tissue where the excess RNA of either BMP-4 or Xmsx-1 was injected, whereas notochord was differentiated from the organizer mesoderm. Neural tissue differentiated from BMP-4-injected ectodermal cells strongly expressed posterior neural markers, such as hoxB9 and krox20, suggesting that the posterior neural cells differentiated regardless of the existence of the BMP signal. The introduction of a dominant-negative form of the fibroblast growth factor (FGF) receptor (XFD) into the ectodermal cells drastically reduced the expression of pan and posterior neural markers (N-CAM and hoxB-9) if co-injected with BMP-4 RNA, although XFD alone at the same dose did not shut down the expression of N-CAM in the combination explants. Therefore, it is proposed that an FGF-related molecule was involved in the direct induction of posterior neural tissue in the inducing signals from the organizer mesoderm in vivo.

Animals↗
PubMed1992

Analysis of gene amplification in archival tissue by differential polymerase chain reaction.

Oncogene amplification is found in many human tumors, and its detection may have important prognostic value. However, analysis of gene amplification may be hampered by inadequate tissue or poor DNA quality. We have previously described a polymerase chain reaction (PCR)-based procedure called differential PCR that can detect variations in gene dosage using miniscule amounts of tumor DNA [Frye, R.A., Benz, C.C. & Liu, E. (1989). Oncogene, 4, 1153-1157]. We now report the optimization of this technique for the analysis of oncogene amplification in paraffin-embedded archival tissues. We find that differential PCR is able to detect amplification of the HER2 (c-erbB-2) and the epidermal growth factor receptor (EGFR) genes and can be used to arrive at a semiquantitative estimate of gene dosage. Furthermore, our approach can determine gene amplification in samples in which the DNA is significantly degraded. Using differential PCR on paraffin-embedded tissues from cases previously investigated by standard DNA extraction and dot-blot procedures, good correlation between the two methods was found. Approaches are described to overcome technical problems posed by factors that affect the differential PCR, including the method of DNA extraction and extreme fragmentation of the DNA (less than 200 base pairs). Furthermore, the resulting analytical algorithm reported herein has proved effective in detecting oncogene amplification in archival breast cancer specimens from standard pathology laboratories. Thus, differential PCR will be particularly helpful in the analysis of tumor specimens that are archived, small in size or rare in occurrence.

Algorithms↗