Search PubMed⌕ Search

Biomedical subjects

J L Samuel

Publications and source records attributed to J L Samuel.

At least 55 records · Page 3Linked to original sources
PubMed1996

Expression of fibronectin ED-A+ and ED-B+ isoforms by human and experimental colorectal cancer. Contribution of cancer cells and tumor-associated myofibroblasts.

Alternative splicing of primary fibronectin (FN) mRNA results in the synthesis of different isoforms. ED-A+ and ED-B+ FN isoforms are absent from plasma FN and are representative of cellular FN. Their expression was studied in human and rat normal colon, in human colorectal carcinomas, and in transplanted tumors derived from a chemically-induced rat colon cancer. In normal colon, only the ED-A+ FN isoform was expressed as a thin deposit between crypt colonocytes and pericryptal myofibroblasts. Conversely, heavy ED-A+ FN deposits and lighter ED-B+ FN expression were found in the stroma of colorectal tumors in association with myofibroblasts surrounding tumor glands. Some colonic cancer cells also contained intracellular FN isoform granules and expressed FN mRNA. Tumor-associated myofibroblasts and some cancer cell lines were able to synthesize and deposit extracellular ED-A+ and ED-B+ FN in vitro. FN isoform deposition by tumor-associated myofibroblasts was not modulated by colon cancer cell-conditioned medium, but was strongly enhanced when myofibroblasts were cultured on colon cancer cell extracellular matrix or on laminin. These results show that the ED-A+ and ED-B+ FN isoforms were overexpressed in colorectal cancer. Cancer cells can deposit these FN isoforms directly and also stimulate their deposition by tumor-associated myofibroblasts.

Actins↗
PubMed1995

Accumulation of fetal fibronectin mRNAs after balloon denudation of rabbit arteries.

BACKGROUND: Fibronectin (FN), a component of the extracellular matrix, influences cellular migration and differentiation. It is a prominent component of the extracellular matrix of normal arteries and is thought to play an important role in the pathogenesis of restenosis after angioplasty. FN exists in multiple forms that arise from a single RNA transcript that can be alternatively spliced. EIIIA- and EIIIB-containing FN mRNAs predominate in the embryo, whereas in the adult, most of the normal tissue FN lacks these domains. Since few data were available concerning pattern of expression of the different alternatively spliced forms of FN mRNA in arteries after endoluminal injury, we analyzed the expression of EIIIA and EIIIB FN isoforms at different times after experimental angioplasty. METHODS AND RESULTS: The spatial and temporal alterations in FN expression were studied in an in vivo model of endothelial denudation in the rabbit aorta and iliac artery by a combination of immunochemistry and in situ hybridization methods. Alternatively spliced forms of FN EIIIA and EIIIB were detected in the media and the adventitia of both types of vessels 24 to 48 hours after injury. Two weeks after injury, EIIIA and EIIIB mRNAs were found to accumulate within the luminal layers of the neointima. The cellular form of FN protein was not found until 2 weeks after the injury and accumulated in the inner part of the neointima. CONCLUSIONS: These data demonstrate that FN upregulation is an early and long-lasting process after arterial injury. These results suggest that the induction of the embryonic FN isoforms may be involved in the restenotic process that follows balloon denudation of arteries.

Animals↗
PubMed1995

Fibronectin isoforms are differentially expressed in normal and adenomatous human anterior pituitaries.

The expression of fibronectin (FN) isoforms containing the extradomains A and B (ED-A+ and ED-B+ FNs) as well as a differentially O-glycosylated oncofetal form of the protein (onf-FN) was investigated in 6 normal human anterior pituitaries and 25 human pituitary adenomas. In normal tissue, immunohistochemical experiments showed the presence of FN molecules lacking the extradomains A and B (ED-A- and ED-B- FNs) without onf-FN immunoreactivity. These proteins were localized in the connective tissue compartment and especially in the vessel walls. Analysis of FN mRNA demonstrated an in situ synthesis of ED-A- and ED-B- FNs in the normal anterior pituitary. By contrast, in the adenomas, immunoreactivity for ED-A+ FN was observed in all cases. ED-B+ and onf-FN immunoreactivities were observed in 14 and 8 adenomas, respectively, regardless of the type, grade or invasiveness of the adenomas. ED-A+ FN mRNA was expressed in all adenomas studied, and ED-B+ FN mRNA was present in ED-B+ immunoreactive cases only. In pituitary adenomas, these 3 forms of FN were specifically associated with the endothelium and vascular smooth-muscle cells. Our results demonstrate that the processes of remodelling of the connective tissue compartment that occur in adenoma angiogenesis are associated with pre- and post-translational alterations of FN synthesis leading to the expression of ED-A+, ED-B+ and oncofetal FNs.

Adenoma↗
PubMed1995

Fibronectin expression during physiological and pathological cardiac growth.

Fibronectin (FN) is a dimeric glycoprotein found in the extracellular matrix of most tissues that serves as a bridge between cells and the interstitial collagen meshwork and influences diverse processes including cell growth, adhesion, migration, and wound repair. Multiple FN forms arise by the alternative splicing of a primary transcript originating from a single gene. The spatial and temporal alterations in FN expression in the myocardium has been studied in models of cardiac growth in vivo such as fetal development, and hypertrophy secondary to pressure overload. This review focuses on the differential expression of FN isoforms that are observed in different models of cardiac growth. Using a combination of qualitative and quantitative analyses it is shown that in the rat myocardium: (1) the FN phenotype is developmentally regulated, (2) the re-expression of the fetal FN isoforms is observed in different models of cardiac hypertrophy secondary to a sudden or progressive hypertension and (3) the changes in cardiac FN expression affect mostly the coronary artery smooth muscle cells.

Alternative Splicing↗
PubMed1995

Differential expression of alpha- and beta-enolase genes during rat heart development and hypertrophy.

We have analyzed the transition between isoforms of the glycolytic enzyme enolase (2-phospho-D-glycerate hydrolyase; EC 4.2.1.11) in rat heart during normal and pathological growth. A striking fall in embryonic alpha-enolase gene expression occurs during cardiac development, mostly controlled at pretranslational steps. In fetal and neonatal hearts, muscle-specific beta-enolase gene expression is a minor contributor to total enolase. Control mechanisms of beta-enolase gene expression must include posttranscriptional steps. Aortic stenosis induces a rapid and drastic decrease in beta-enolase transcript level in cardiomyocytes, followed by the fall in beta-subunit level. In contrast, alpha-enolase transcript level is not significantly altered, although the corresponding subunit level increases in nonmuscle cells. We conclude that, like fetal heart, hypertrophic heart is characterized by a high ratio of alpha- to beta-enolase subunit concentrations. This study indicates that the decrease in beta-enolase gene expression may be linked to beneficial energetic changes in contractile properties occurring during cardiac hypertrophy.

Aging↗
PubMed1995

Differential effects of pressure and flow on DNA and protein synthesis and on fibronectin expression by arteries in a novel organ culture system.

Structural adaptation of the blood vessel wall occurs in response to mechanical factors related to blood pressure and flow. To elucidate the relative roles of pressure, flow, and medium composition, we have developed a novel organ culture system in which rabbit thoracic aorta, held at in vivo length, can be perfused and pressurized at independently varied flow and pressure for several days. Histology and histomorphometry, as well as scanning electron microscopy, revealed a well-preserved wall structure. In arteries perfused and pressurized at 80 mm Hg, endothelial injury led to a 2-fold increase in [3H]thymidine incorporation in the media, which peaked at 3 to 5 days and returned to baseline level at 6 to 8 days. In intact endothelialized vessels cultured for 3 days under no-flow conditions, pressure per se had no effect on DNA synthesis. In contrast, in the presence of serum, total protein synthesis, as assessed by [35S]methionine incorporation into the media, was enhanced 6-fold at 150 mm Hg compared with vessels pressurized at 0 or 80 mm Hg. In intact vessels perfused at a constant flow of 40 mL/min for 3 days, DNA synthesis was unchanged regardless of the pressure level when vessels were cultured in the presence of serum but increased 8-fold at both 80 and 150 mm Hg in the absence of serum. Unlike DNA synthesis, total protein synthesis was enhanced 12-fold by flow regardless of the presence or absence of serum. Expression of fibronectin was markedly enhanced at high transmural pressure, and serum potentiated its expression in the arterial wall. This novel organ culture system of perfused and pressurized vessels allowed identification of differential effects of pressure, flow, and serum on DNA and total protein synthesis, including cellular fibronectin expression.

Animals↗
PubMed1995

Fibronectin expression in the cardiovascular system.

Fibronectin (FN) is a dimeric glycoprotein found in the extracellular matrix (ECM) of most tissues and serves as a bridge between cells and the interstitial collagen meshwork. It also influences diverse processes including cell growth, adhesion, migration, and wound repair. Multiple FN forms arise by the alternative splicing of a primary transcript originating from a single gene. The spatial and temporal alterations in FN expression in the cardiovascular system have been studied in vitro in cell culture and in vivo during fetal development, hypertrophy, infarction, arterial injury and aging. This review describes characteristics of FN expression in cardiovascular system: 1. the FN phenotype is regulated during development. A high FN mRNA level is related to an early cardiac organogenesis and a progressive decrease that begins at the fetal stage and continues through senescence. During cardiac ontogeny, there is a linear correlation between total FN mRNA accumulation and the relative amounts of FN-EIIIA and EIIIB RNA. This correlation is absent during cardiac growth in the adult. 2. A differential reexpression of the FN isoforms is observed in both myocardium and aorta in different models of hypertension or infarction but with different threshold and time course. Changes in total FN mRNA levels in hypertensive models vary depending on the authors. Nevertheless the differences in the expression of the fetal forms of FN mRNA observed among the various models of hypertension-induced hypertrophy indicate that the process of FN pre-mRNA splicing in the adult myocardium is specifically regulated and depends on the pathological situations and the type of cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

In situ mRNA distribution of sarco(endo)plasmic reticulum Ca(2+)-ATPase isoforms during ontogeny in the rat.

The Sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) plays a crucial role in maintaining the Ca2+ homeostasis, which itself, controls various essential cellular function. The existence of several SERCA isoforms, encoded by three different genes and produced by alternative splicing of pre-mRNA transcripts, has been established by cDNA cloning. However, the temporo-spatial evolution of their expression during ontogeny was unknown. We have used in situ hybridization to determine the cellular distribution of three of these mRNA isoforms, SERCA 2a, SERCA 2b and SERCA 3 during rat ontogeny and focused our study on the cardiovascular system. We demonstrate that early in embryogenesis, SERCA 3 mRNA is highly expressed in the heart tube and is also present in the yolk sac. In 14-16 days embryos, SERCA 3 mRNA has disappeared from the heart but is expressed in the aorta and in discrete foci of the liver. Later on, its expression in the cardiovascular system is restricted to the arterial endothelium. SERCA 2a mRNA is coexpressed with SERCA 3 mRNA in the heart tube and remains expressed in the cardiomyocytes throughout life. It is transiently expressed in skeletal muscle at the onset of differentiation. In early foetal life, SERCA 2b is expressed in the mesenteric area and thereafter in all cell types at various levels. Our data indicate that (i) expression of SERCA 2b is neither tissue-specific nor developmentally regulated (ii) expression of SERCA 2a and SERCA 3 isoforms is regulated in a cell specific manner during development and suggest that the SERCA 3 gene plays a role in controlling the function of endothelial cells during vasculogenesis.

Aging↗
PubMed1994

Expression of fibronectin during rat fetal and postnatal development: an in situ hybridisation and immunohistochemical study.

OBJECTIVE: Fibronectin is a protein of the extracellular matrix with numerous binding sites to the other elements of the matrix and to the cells. The aim of this study was to determine the relative importance of fibronectin isoform expression (FN-EIIIA, FN-EIIIB) during fetal and postnatal development of the rat heart. METHODS: In situ hybridisation and immunolabelling approaches were used to describe the cellular synthesis of fibronectin and its distribution throughout the rat heart from 11 d postconception until adulthood. The distribution of fibronectin was compared to that of laminin and of alpha type III procollagen. RESULTS: The accumulation and pattern of distribution of the major fibronectin mRNA isoforms were identical, that is, there was a progressive decrease in their accumulation as a function of time after 11 d postconception, resulting in a complete absence in the adult. The distribution of fibronectin and procollagen type III mRNAs were, however, quite distinct. At the protein level the time course of synthesis and secretion of the locally synthesised fibronectin (c-FN) did not follow fibronectin mRNA expression, the accumulation of the protein being rather poor, except just before birth, where it was found mainly in the coronary vessels. CONCLUSIONS: During the development of the fetal rat heart fibronectin gene transcription is active and progressively decreases with age, whereas the translation of the mRNAs into their corresponding proteins is always relatively poor. If fibronectin is involved in fetal and postnatal morphogenesis of the rat myocardium, it is the plasma form (p-FN) that is most probably involved in the process of growth and differentiation of the rat heart.

Animals↗
PubMed1994

[Effects of angiotensin II and pressure on cellular fibronectin in the vascular wall in organotypic culture].

Fibronectin is a dimeric glycoprotein found in the extracellular matrix of most tissues, which can influence processes, including cell growth, adhesion and migration. Fibronectin synthesis has been shown to be overexpressed in hypertension. However, the respective effects of humoral factors, including angiotensin II, versus mechanical factors in vascular remodeling have not yet been clarified. To study fibronectin de novo synthesis in the arterial wall, we have developed a new model for organ culture of rabbit thoracic aorta. Arteries held at their in vivo length were incubated and perfused (40 ml/min) in DME medium containing antibiotics, supplemented with 20% fetal calf serum or with 5% bovine serum albumin. In a series of experiments, angiotensin II (10(-6) M) and indomethacin (10(-5) M) were added to culture media. Vessels were pressurized at 0, 80 or 150 mmHg, and kept for 3 days in incubator at 37 degrees C under 5% CO2. De novo synthesis of fibronectin was detected by immunofluorescence using anti-cellular fibronectin antibodies (1/200). In the absence of angiotensin II and serum, fibronectin was expressed in the sub-endothelium at 80 mmHg, and in the inner media at 150 mmHg. In the presence of serum, fibronectin expression was increased by the high pressure. When angiotensin II was added, a gradient of fibronectin became apparent in the inner media at 80 mmHg with a marked expression at the luminal side. Angiotensin II markedly enhanced fibronectin expression at 150 mmHg, the protein being detected in almost the whole media. Our results indicate that both angiotensin II and transmural pressure can induce fibronectin expression in the arterial wall, and both act synergically.

Angiotensin II↗
PubMed1994

Differential splicing of fibronectin pre-messenger ribonucleic acid during cardiac ontogeny and development of hypertrophy in the rat.

BACKGROUND: Fibronectin, an extracellular matrix protein, exists as multiple isoforms expressed in a time- and cell-dependent manner. Since the developmental pattern of fibronectin expression has not been determined in the heart, the first issue of this study was to investigate the expression of total fibronectin mRNA as well as its isoforms during cardiac ontogeny. In adults, pressure overload induces a shift towards the fetal form of proteins expressed by either muscle or nonmuscle cardiac cells. Fetal forms of fibronectin mRNA being found in smooth and nonmuscle cardiac cells soon after imposition of pressure overload, the pattern of fibronectin expression during the development of pathological growth was analyzed to determine whether the two conditions of cardiac growth resulted in an identical pattern of fibronectin expression. EXPERIMENTAL DESIGN: Total RNA were isolated from rat heart (a) during in utero and postnatal life and (b) at varying periods of time after imposition of a pressure overload induced by coarctation of the thoracic aorta in 25-day-old rats. Fibronectin-EIIIA+ or -EIIIB+ and total fibronectin mRNAs were quantitated by reverse transcription-polymerase chain reactions and dot-blot analysis, respectively. RESULTS: Fibronectin mRNA, abundant in the 14-day-old fetal heart, rapidly decreased during cardiac physiologic growth (> 5-fold); no changes in the fibronectin mRNA level was observed during the development of pressure-induced cardiac hypertrophy. The percentages of fibronectin transcripts containing EIIIA or EIIIB exons, very high in the early fetal heart (> 45%), harmoniously decreased during cardiac maturation (< 12%). Aortic coarctation resulted in an early, transient (12 to 48 hours) and preferential expression of fibronectin-EIIIA+ mRNA (approximately 40%). CONCLUSIONS: In rat heart, neither physiologic nor pressure-induced growth requires increased amounts of fibronectin mRNA but the growth conditions specifically modulated the fibronectin pre-mRNA splicing.

Animals↗
PubMed1993

The sarco(endo)plasmic reticulum Ca(2+)-ATPase mRNA isoform, SERCA 3, is expressed in endothelial and epithelial cells in various organs.

The sarco(endo)plasmic reticulum Ca(2+)-ATPase mRNA isoform, SERCA 3, was previously shown to be expressed in a great variety of muscle and non-muscle tissues [(1989) J. Biol. Chem. 264, 18568] but its cellular localization within these organs was unknown. We have used in situ hybridization and RNase protection techniques to demonstrate that SERCA 3 mRNA is expressed in specific cell types, namely the endothelial and epithelial cells.

Animals↗
PubMed1993

Contractile protein gene expression in serum-free cultured adult rat cardiac myocytes.

The effects of two adhesion substrates (serum and laminin) and time in culture on the expression of genes encoding myosin heavy chain (MHC) isoforms and alpha-skeletal actin were analysed in myocytes isolated from adult rat heart and maintained in serum-free culture. Relative messenger ribonucleic acid (mRNA) abundances were quantitated by dot-blot analysis. Gene expression was not influenced by the substrate used. Time in culture induced a decrease in total mRNA abundance and an up-regulation of beta-MHC and alpha-skeletal actin genes. It is proposed that atrophy of adult myocytes is associated with a pattern of gene expression similar to the fetal program.

Actins↗
PubMed1993

Oral vaccination of chickens with the V4 strain of Newcastle disease virus. Cooked and raw white rice as a vehicle.

Uncooked white rice and cooked white rice were tested as vehicles for the V4 strain of oral Newcastle disease vaccine. The results of feeding experiments were evaluated by the measurement of haemagglutination inhibition antibodies against Newcastle disease virus. Little of the virus applied to uncooked white rice could be recovered, even immediately after mixing, whereas when the virus was applied to cooked white rice most of it could be recovered. In 4 separate experiments, chickens failed to respond serologically to vaccine supplied on uncooked white rice. In all of 4 experiments with cooked white rice, there were serological responses in vaccinated chickens, from 45% to 100% of the chickens developing titres sufficiently high to indicate protection against challenge with virulent virus. Development of haemagglutination inhibition antibodies in some control chickens indicated the ability of the vaccine virus for lateral spread or persistence in the environment.

Administration, Oral↗
PubMed1993

Diuretic effects on cardiac hypertrophy in the stroke prone spontaneously hypertensive rat.

OBJECTIVE: The aim was to compare the effects of two diuretics, indapamide and hydrochlorothiazide, on cardiac hypertrophy in stroke prone spontaneously hypertensive rats (SHR-SP). METHODS: Six week old SHR-SP, on a 1% sodium chloride water intake, were treated with oral indapamide (3 mg.kg-1 x d-1) or hydrochlorothiazide (20 mg.kg-1 x d-1) over a 44 d period. The hypertrophic process was evaluated by classical indices and by the morphological analysis of myocyte cross sectional area, coronary artery thickness, and immunohistochemical analysis of interstitial fibrosis. RESULTS: In the untreated SHR-SP on 1% sodium chloride, all animals developed severe hypertension and cardiac hypertrophy when compared to normotensive salt loaded WKY by 13 weeks of age. In salt loaded SHR-SP treated with indapamide or hydrochlorothiazide, systolic blood pressure was moderately decreased by the end of the treatment when compared with untreated SHR-SP, at 259(7) and 245(7) mm Hg respectively, v 300(11) mm Hg, p < or = 0.05. Myocyte enlargement appears to be the main feature involved in the development of cardiac hypertrophy in the SHR-SP. By the end of treatment both indapamide and hydrochlorothiazide prevented the development of cardiac hypertrophy evaluated by heart weight to body weight ratio [4.69(0.07) and 4.61(0.08) respectively, v 5.39(0.13), p < or = 0.001] and myocyte hypertrophy (-33% and -21% of the SHR-SP values, p < or = 0.001). Myocardial interstitial fibrosis and perivascular fibrosis were practically absent in the two treated groups. CONCLUSIONS: Our results allow the characterisation of SHR-SP cardiac hypertrophy and indicate that the two types of chronic diuretic treatment prevent SHR-SP cardiac hypertrophy with a drug specific efficiency.

Animals↗