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Biomedical subjects

J Uriel

Publications and source records attributed to J Uriel.

At least 55 records · Page 3Linked to original sources
PubMed1989

Morphological characterization of the pathway of endocytosis and intracellular processing of transferrin and alpha-fetoprotein in human T lymphocytes stimulated with phytohemagglutinin (PHA).

Covalent conjugates of transferrin (Tf) and alpha-fetoprotein (AFP) with horseradish peroxidase (HRP) have been used to follow, at the ultrastructural level, the uptake and the intracellular pathway of these proteins in peripheral blood human lymphocytes stimulated by phytohemagglutinin (PHA) to blast formation. Both proteins enter specifically the cells via vesicles (60-70 nm in diameter) and endosomes. They are then observed in multivesicular bodies and tubular vesicular elements in the Golgi region. AFP is thus found in the same subcellular compartments as Tf and is probably also recycled, as most of the 125I-labeled protein leaves the cells undegraded. Unstimulated lymphocytes do not internalize significantly AFP-HRP. The uptake of a noncovalent conjugate of AFP-HRP and [3H]-arachidonic acid [3H-(20:4)] is usually poor, at 37 degrees C, in unstimulated lymphocytes as well as, at 4 degrees C, in lymphocytes stimulated for 72 h. Stimulated lymphocytes incubated at 37 degrees C with the radioactive conjugate show a heavy labeling of cell organelles and more particularly of lipid droplets. AFP could regulate the intracellular delivery of fatty acid molecules.

Endocytosis↗
PubMed1989

Etiology of otospongiotic sensorineural losses.

The etiology of otospongiotic-otosclerotic disease is enzymatic; the proteolytic enzymes released by the otospongiotic-otosclerotic foci damage the inner ear and are also the basis of the bony rebuilding of the OW niche leading to stapedial fixation. The trigger may be an autoimmune process due to the reaction of the enchondral otic capsule against the embryonic cartilaginous remnants, genetically determined to be located in the otic capsule and mainly in the fissula antefenestram.

Antibody Formation↗
PubMed1989

Fatty acids bound to vitamin D-binding protein (DBP) from human and bovine sera.

Human and bovine vitamin D-binding protein (DBP) have been isolated from serum by a method that does not involve denaturing steps. This method includes Cibacron Blue-Sepharose chromatography, gel filtration, DEAE-Sephadex chromatography and albumin immunoadsorption. Analysis of fatty acids bound to the isolated human and bovine DBP showed molar ratios of fatty acid to protein of 0.4 and 1.3 respectively meanwhile human and bovine albumin have bound 1.8 and 1.5 moles per mol respectively. Most of fatty acids bound to human and bovine DBP are monounsaturated and saturated, mainly oleic and palmitic acids, which together account for 50% of the total of fatty acids in both species. By contrast, polyunsaturated fatty acids represented a minor component, less than 5%.

Animals↗
PubMed1988

Fatty acids bound to alpha-fetoprotein and albumin during rat development.

The time-course levels and composition of the fatty acids bound to rat alpha-fetoprotein (AFP) and albumin from several sources, were determined throughout development, and related to the intake of lipids from milk and the compositional changes in brain and liver fatty acids. The major fatty acids bound to AFP were acids bound to AFP were polyunsaturated and mainly docosahexaenoic acid (22:6(n-3], either from fetal serum (23.1%) or whole fetuses (21.6%), whereas palmitic (34.1%) and oleic (29.9%) acids were the main acids bound to albumin from the same sources. Amniotic fluid AFP contained less fatty acids (0.8 mol/mol protein) than that of fetal serum (1.4 mol/mol protein), and especially noticeable was a reduced amount of 22:6 (9.6%). Both AFP-concanavalin A microforms showed identical fatty acid composition. Levels of 22:6 bound to AFP decreased quickly after birth until a minimum at 8-10 days, increasing moderately thereafter. This minimum is coincident in time with a maximal accumulation of this fatty acid by brain and a loss of 22:6 by liver. Except for colostrum, levels of 22:6 in milk lipids were low and fairly constant, but always greater than those of its precursor, linolenic acid (18:3 (n-3]. These results support a specialized role of AFP in the plasma transport and tissue delivery of polyunsaturated fatty acids, and mainly docosahexaenoic acid.

Amniotic Fluid↗
PubMed1987

Specific uptake of alpha-fetoprotein by malignant human lymphoid cells.

We have studied the ability of human B- and T-lymphoblastoid cell lines, as well as of peripheral lymphoid cells from leukemia patients, to take up alpha-fetoprotein (AFP) and other serum proteins. Two technical approaches have been employed, both using fluorescent protein derivatives (FITC-proteins): microscopic examination of labelled cells using epifluorescent illumination and quantitation of endocytosed proteins by fluorescence-activated cell sorting (FACS). Compared to human resting T-lymphocytes, all T- and B-cell lines tested exhibited positive staining for fluoresceinated AFP and transferrin (Tf) and a significant increase, up to 100-fold, of the number of AFP and Tf molecules endocytosed per cell. Labelling was prevented or strongly diminished by a 100-fold excess of unlabelled protein. Preliminary results with peripheral lymphoid cells harvested from leukemia patients showed the presence of AFP- and Tf-positive cells in the blood of all patients examined. Intensity of labelling was related to the type of leukemia cells and/or the degree of cell maturation. Most cell lines exhibited positive staining for alpha 2-macroglobulin (alpha 2M) and also, to a lesser extent, for serum Vitamin D3 binding protein (DBP). In contrast, no labelling was observed with FITC-serum albumin (FITC-Alb) or FITC-ovalbumin (FITC-OVA). Comparative uptake of several FITC-proteins by a single cell population revealed significant quantitative and qualitative differences.

Blood Proteins↗
PubMed1987

alpha-Fetoprotein-mediated transfer of arachidonic acid into cultured cloned cells derived from a rat rhabdomyosarcoma.

alpha-Fetoprotein (AFP) is a major constituent of embryonal plasma and a physiological carrier of free fatty acids. The purpose of the present work was to study the mechanism by which fatty acids bound to AFP are transferred to living cells. Radiolabeled rat AFP and arachidonic acid were used to follow up the uptake and metabolism of both the protein and the fatty acid by rhabdomyosarcoma cells isolated from a nickel-induced rat tumor. Time course uptake of AFP and arachidonic acid by these cells exhibited a saturable profile at both 4 and 37 degrees C. A diffusible nonsaturable uptake of arachidonic acid was observed in experiments at both 4 and 37 degrees C with preparations of fixed AFP content and increased molar amounts of arachidonic acid (up to 8-fold molar excess). On the contrary, saturable binding and uptake of fatty acid and protein were evidenced when the molar ratio of arachidonic to AFP was fixed at 0.5, and the concentration of both increased simultaneously. This suggests that, under physiological conditions (low fatty acid to AFP ratio), the uptake of arachidonic acid by the tumor cells is regulated by the protein. Fatty acid distribution in cell lipids after 2 and 24 h of culture at 37 degrees C, in the presence of arachidonic acid bound to AFP, revealed that this fatty acid was mainly incorporated in cell phospholipids. At 4 degrees C, however, the totality of cell-associated arachidonic acid was in the unesterified form. Pulse-chase experiments showed that about 25 and 40% of the AFP initially taken up by cells were released undegraded after 6 and 60 min, respectively. Under the same conditions, nearly all the arachidonic acid remained in the cells. Taken together, these facts suggest a two-receptor model for the physiological uptake of fatty acids. The AFP binds to an AFP receptor and the fatty acid is then removed and transported inside the cell by a specific fatty acid-binding protein.

Animals↗
PubMed1986

Ultrastructural studies of the intracellular translocation of endocytosed alpha-foetoprotein (AFP) by cytochemistry and of the uptake of 3H-arachidonic acid bound to AFP by autoradiography in rat rhabdomyosarcoma cells.

A covalent conjugate of alpha-foetoprotein (AFP) and horseradish peroxidase (HRP) has been used to follow, at the ultrastructural level, the pathway of AFP uptake and translocation in a rat rhabdomyosarcoma cell line. The cells were incubated for several times at 4 degrees C and/or 37 degrees C, and fixed. AFP-HRP was found to enter the cells via coated pits and receptosomes and to move to tubular elements of the trans-reticular portion of the Golgi. Some observations suggest that AFP can be recycled back to the cell surface. On the other hand, the cells were incubated with a noncovalent conjugate of AFP and 3H-arachidonic acid [3H-(20:4)], and the uptake of the fatty acid molecules studied by ultrastructural autoradiography. The cytoplasmic labeling, very low after an incubation in the presence of [3H-(20:4)]-AFP for 2 hours at 4 degrees C, increased rapidly after transfer of the cells for 5 minutes to 37 degrees C. These observations support the hypothesis that AFP plays a role in the intracellular delivery of polyunsaturated fatty acids.

Animals↗
PubMed1986

The wasted mutant mouse. II. Immunological abnormalities in a mouse described as a model of ataxia-telangiectasia.

Ataxia-telangiectasia (AT) is a complex multiparametric disease associating oculocutaneous telangiectasias, cerebellar ataxia, elevated chromosomal aberration frequency and varied degrees of immunodeficiency. Recently a wasted mutant mouse (wst) has been described as an animal model of AT. We have looked in the wasted mutants for the presence of immune and endocrine abnormalities characteristic of AT. In contrast to the T cell immunodeficiency in AT, wasted mutants had a marked hypoplasia of all lymphoid organs, which affected both T and B lymphocyte subsets. The marked thymic atrophy appearing at the final stage of their disease did not modify the endocrine function of the thymic epithelium which produced normal levels of the thymic hormone thymulin. Although in vitro interleukin 2 (IL-2) production by splenic T cells in response to Con A was markedly diminished, these mice presented normal T and B cell proliferative responses to mitogens. Finally, no significant increase in serum alpha-fetoprotein level (a typical marker of AT) was found throughout the course of the disease. Although by many aspects, i.e. neurological disorder, chromosomal aberrations and early death, wasted mice presented similarities with human AT, major discrepancies in the typical features of immune abnormalities were found between the mouse model and the human disease.

Animals↗
PubMed1985

The uptake of alpha-foetoprotein by C-1300 mouse neuroblastoma cells.

Recent immunocytochemical and biochemical studies have shown the intracellular uptake of alpha-foetoprotein (AFP) by most neural crest and neural tube derivatives of developing mammals and birds. The neural crest origin of neuroblastomas has been known for a long time. While many mouse neuroblastoma cell lines can express several neuronal properties, other lines lack specialized neural functions and may re-express embryonal or foetal antigens, suggesting some reversion towards an earlier stage of differentiation. We have therefore tested the C-1300 Jackson mouse neuroblastoma cell line for its ability to incorporate AFP. The results obtained confirm the significant internalization of protein by these cells, both in vitro and in vivo. External photoscans of mice bearing tumours after injection with [131I]-AFP have proven the usefulness of the protein as a radiotracer for neuroblastoma localization.

Animals↗
PubMed1985

Cell-type-specific receptors for alpha-fetoprotein in a mouse T-lymphoma cell line.

Binding and uptake of alpha-fetoprotein (AFP) by mouse T-lymphoma YAC-1 cells exhibited the characteristics of receptor-mediated endocytosis. The binding saturation curve obtained by incubating YAC-1 cells at 4 degrees C with 125I-labeled AFP at different concentrations (50 ng/ml to 2.5 mg/ml) showed three saturation plateaus. AFP binding was inhibited by unlabeled mouse, rat, or bovine AFP and, to a lesser extent, by rat or bovine serum albumin. No significant competition was observed with transferrin, alpha 2-macroglobulin, IgG, or ovalbumin. Scatchard analysis suggested the presence of three types of receptor sites with a Kd of 2.2 X 10(-9) M (approximately equal to 700 sites per cell), 8.6 X 10(-7) M (approximately equal to 210,000 sites per cell), and 5.7 X 10(-6) M (approximately equal to 910,000 sites per cell), respectively. At 37 degrees C, AFP was rapidly internalized and could be localized in the cytoplasm after incubation of cells with fluoresceinated AFP. After a short residence time, AFP was released undegraded from the cells. Normal adult thymocytes and T lymphocytes, which are counterparts of YAC-1 cells, did not show any significant uptake of AFP. On the other hand, a small subpopulation of fetal and newborn thymocytes was labeled by fluoresceinated AFP.

Animals↗
PubMed1984

Alpha-fetoprotein receptors in a human breast cancer cell line.

Evidence is presented for the existence of specific receptors for alpha-fetoprotein on the surface of MCF-7 human breast cancer cells. At 4 degrees C, the binding of alpha-fetoprotein to these cells displayed a biphasic saturation curve. Scatchard analysis revealed the presence of at least two binding sites with dissociation constants of 4.5 X 10(-9) M (2,000 sites/cell) and 1.3 X 10(-8) M (135,000 sites/cell), respectively. Binding was inhibited by 85% in the presence of a 5,000-fold excess of unlabeled alpha-fetoprotein and by 50% with the same excess of serum albumin. Competition by other serum proteins was not significant. At 37 degrees C, alpha-fetoprotein was endocytosed and the uptake curve reached a plateau after 3-4 hours of incubation.

Binding, Competitive↗
PubMed1984

Incorporation of radiolabelled alphafetoprotein in the brain and other tissues of the developing rat.

The time course of uptake and autoradiographic localization of alphafetoprotein (AFP) were studied in the brain and other organs of fetuses, neonates and young rats injected with homologous radiolabelled AFP. Comparative data of radioactivity accumulation in the brain relative to that of several tissues (blood, liver, tongue, small intestine) showed bimodal patterns reflecting two periods of more active incorporation, with a maximum before the 16th day of fetal development. In brain autoradiographs, the strongest labelling was observed in 17-day-old fetuses 24 h after injection into the mother of [125I]AFP. The labelling included all regions of the brain. The results presented here give experimental support to the hypothesis that the presence of AFP in the developing nervous system of mammals and birds is primarily due to protein uptake rather than in situ synthesis.

Age Factors↗
PubMed1984

Inhibitory effect of mouse interferon on the growth of an embryonal carcinoma in mice.

Embryonal carcinoma cells (F9) were resistant to the inhibitory effects of interferon (IFN) on viral multiplication and cell division in vitro. Nevertheless, daily administration of IFN resulted in a marked inhibition of the growth of this carcinoma injected intraperitoneally (ip) and increased mouse survival time. An incidental finding was that daily IFN treatment increased the serum level of alpha-fetoprotein in normal 129 mice.

Animals↗
PubMed1984

Uptake of radiolabeled alpha-fetoprotein by mouse mammary carcinomas and its usefulness in tumor scintigraphy.

The ability to internalize alpha-fetoprotein (AFP) and serum albumin, which is characteristic of embryonic and fetal elements undergoing differentiation, may reappear in some cultured neoplastic cells (i.e., the MCF-7 human breast cancer cell line). The in vivo uptake of AFP by spontaneous carcinomas of the CH3/Bi mouse was investigated. Nineteen mice were given i.v. injections of approximately 10 muCi of mouse 125I-AFP (0.6 to 4 micrograms of AFP according to the specific ratio of the preparation used). Four to 7 days later, the animals were sacrificed. The radioactivity concentration in the tumor was the highest among all solid tissues examined. Tumor:liver radioactivity ratios were clearly positive [3.6 +/- 0.3 (S.E.)] in 27 of 31 specimens studied. Microscopy examination of autoradiograms from various tissue sections confirmed the selective accumulation of radioactive AFP in the tumors. In order to assess the specificity of AFP uptake by mammary tumors, 4 mice were given simultaneous injections of 125I-AFP and 131I-ovalbumin, respectively. Compared to AFP, the retention of ovalbumin was very low in all tissues studied, including the tumor. The possibility of tumor localization of radiolabeled AFP by external photoscanning was also explored. Two mice were given injections of 131I-AFP, one mouse received 131I-serum albumin, and one was given 131I-ovalbumin. Images were obtained 6 days after with a standard gamma-camera linked to a computer with data display. About 50% of the total radioactivity retained was concentrated in the tumor areas of mice given injections of iodinated AFP, while it was only 15% in the mouse that received 131I-serum albumin. No tumor image could be detected in the mouse given ovalbumin. These results show that the ability to internalize AFP, common to many tissues during ontogenesis, may also be shared by neoplastic cells which develop later in life. They also prove the preferential uptake of AFP by the tumors compared to normal tissues and the usefulness of AFP as a radiotracer for mammary carcinomas. The latter represents a novel approach to tumor detection.

Adenocarcinoma↗
PubMed1984

Incorporation of alphafetoprotein by the MCF-7 human breast cancer cell line.

The intracellular uptake of alphafetoprotein (AFP) and its fluorescein conjugates, by cultures of the MCF-7 human breast cancer cell line, has been demonstrated using an indirect immuno-peroxidase technique or by direct visualization under fluorescent lighting. The protein was localized in the cytoplasm. Ultrastructural autoradiographs of MCF-7 cells incubated with human 3H-AFP showed protein accumulation in several cytoplasmic organelles, particularly in lipid droplets. Nuclei were free of AFP. A significant species-specificity of AFP internalization was observed in comparative assays with human, mouse, pig and chicken AFP. The incorporation of the protein was prevented by incubation at 0 degrees C or by previous treatment of the cultures with 10nM sodium azide. Attention is paid to the reappearance in a human breast carcinoma cell line of a property associated during ontogenic development with ectodermal derivatives, including the epidermis.

Albumins↗
PubMed1983

Alphafoetoprotein uptake by cloned cell lines derived from a nickel-induced rat rhabdomyosarcoma.

Rat, mouse, pig and chicken alphafoetoproteins (AFP), rat serum albumin and egg albumin, or their fluoresceinated conjugates were added to cultures of several cloned cell lines isolated from a nickel-induced rat rhabdomyosarcoma. The intracellular uptake of assayed proteins was revealed by the indirect immunoperoxidase technique and/or by direct fluorescence microscopy. All the clones examined bound AFP, and all but one internalized the protein. The protein localized in the membrane and the cytoplasm, as well as along straight processes interconnecting cells. Nuclei were always AFP negative. The protein uptake of fluoresceinated conjugates of AFP and serumalbumin was already visible 15 min after incubation and progressed with time to reach a plateau 4-5 h later. Ultrastructural radioautographs of cells incubated with [3H]-AFP (rat) showed protein accumulation in several organelles and particularly in lipid droplets. Parallel to these observations, the intracellular presence of AFP within myofibrillar structures was demonstrated in tongue sections of rat foetuses and neonates. The results presented here provide experimental evidence of the reappearance in cloned cell lines derived from a primary rhabdomyosarcoma of a property pertaining to foetal striated muscle.

Animals↗