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Biomedical subjects

A Raz

Publications and source records attributed to A Raz.

270 records · Page 15Linked to original sources
PubMed1972

Interaction of prostaglandins with blood plasma proteins. Comparative binding of prostaglandins A 2 , F 2 and E 2 to human plasma proteins.

1. The binding of prostaglandin A(2) and prostaglandin F(2alpha) to human plasma proteins was investigated by DEAE-Sephadex chromatography and polyacrylamide-gel electrophoresis. Both prostaglandins, when added to human plasma in vitro, were found to become bound mainly to plasma albumin. 2. The extent of binding of prostaglandins added to human plasma in low to moderate concentrations was found to be approx. 88, 73 and 58% for prostaglandins A(2), E(2) and F(2alpha) respectively. The order of affinities for the binding of the three prostaglandins to albumin appear to be A(2)>E(2)>F(2alpha). 3. The apparent association constants for the binding of these prostaglandins to human serum albumin were estimated to be approx. 4.8x10(4), 2.4x10(4) and 0.9x10(4) litre/mol for prostaglandins A(2), E(2) and F(2alpha) respectively. The results are compared with previously reported association constants for the binding of long-chain fatty acids to both human and bovine albumins.

Blood Proteins↗
PubMed1972

Extraction and recombination studies of the interaction of retinol with human plasma retinol-binding protein.

Methods have been developed for the removal of retinol from human plasma retinol-binding protein (RBP), so as to form the retinol-free apoprotein, and for the recombination of apo-RBP with retinol to again form the holoprotein. Retinol is removed from RBP by gently shaking a solution of RBP with heptane under controlled conditions. During the shaking, retinol is gradually extracted from the RBP and into the heptane phase. The reassociation of apo-RBP with retinol is achieved by exposing a solution of apo-RBP to Celite coated with a thin film of retinol, followed by isolation of the RBP by gel filtration on Sephadex G-100. This procedure results in the recombination of apo-RBP with an amount of retinol almost identical with that previously removed by extraction. The two-phase extraction procedure was used to explore some of the factors which affect the interaction of retinol with RBP. The retinol-RBP complex was most stable in the lower portion of the pH range 5.6 to 10. The rate of removal of retinol from the RBP-prealbumin complex (the form in which RBP normally circulates in plasma) was markedly less than the rate of its removal from RBP alone. The interaction of retinol with RBP appears to be stabilized by the formation of the RBP-prealbumin complex. The recombination procedure was employed to examine the specificity of the binding of retinol to RBP, by determining whether compounds other than all-trans-retinol would effectively bind to apo-RBP. Apo-RBP did not bind cholesterol, but displayed a slight affinity for phytol. The affinity of RBP for beta-carotene was minimal, whereas both retinyl acetate and retinal were bound about one-third as effectively as all-trans-retinol. In contrast, retinoic acid bound to apo-RBP almost as effectively as did retinol. Each of two isomers of retinol, 13-cis and 11,13-di-cis-retinol, bound to apo-RBP to some extent. The 13-cis isomer appeared to bind somewhat less effectively than did the 11,13-di-cis isomer. The binding of retinol to RBP is highly but not absolutely specific.

Acetates↗
PubMed1970

Radioimmunoassay of human plasma retinol-binding protein.

A radioimmunoassay for human plasma retinol-binding protein (RBP) has been developed utilizing a double antibody precipitation technique. RBP was purified 1500- to 2000-fold by procedures described previously. A specific anti-human RBP antiserum was prepared in rabbits by three once-weekly injections of purified RBP emulsified with Freund's adjuvant. RBP was iodinated with (131)I and the RBP-(131)I was purified by gel filtration on Sephadex G-100 after complex formation with human plasma prealbumin. The RBP-(131)I was completely (> 95%) immunoprecipitable in the presence of an excess of specific antiserum, it was not (< 5%) immunoprecipitable in the absence of specific antiserum, and it could be completely displaced from antibody by excess unlabeled RBP. The standard curve obtained in the immunoassay with normal plasma was identical to that with pure RBP. Duplicate samples differed from their mean by 5 +/-5% (+/-SD). There was a quantitative recovery of pure RBP added in varying amounts to normal plasma. The immunoassay accurately measured RBP in amounts of 10-100 ng per assay tube. There was no significant difference in the immunoreactivity of apo-RBP as compared to holo-RBP. The mean plasma values (+/-SEM) for a group of 76 normal subjects were 47.2 +/-1.6 mug/ml for males and 41.6 +/-1.6 mug/ml for females. Plasma RBP levels were markedly depressed (15 +/-2.3 mug/ml) in 14 patients with acute viral hepatitis. There was a highly significant correlation between the plasma levels of RBP and of vitamin A in both normal subjects and patients with hepatitis. In all subjects plasma RBP was generally saturated with retinol. The data suggest that under normal circumstances RBP circulates almost exclusively as the holoprotein.

Animals↗
PubMed1968

Retinol-binding protein: the transport protein for vitamin A in human plasma.

Vitamin A circulates in human plasma as retinol bound to a specific transport protein. This protein differs from the known low and high density plasma lipoproteins and has a hydrated density greater than 1.21. In order to study this protein, volunteers were injected intravenously with retinol-15-(14)C. Plasma was collected 1-3 days later, and the purification of retinol-binding protein (RBP) was monitored by assaying for (14)C and also by following the fluorescence of the protein-bound retinol. Purification of RBP was effected by the sequence: Cohn fractionation, chromatography on columns of Sephadex G-200 and diethylaminoethyl (DEAE)-Sephadex, preparative polyacrylamide gel electrophoresis, and finally chromatography on Sephadex G-100. These procedures resulted in a preparation of RBP which was at least 98% pure and which had been purified more than 1500-fold. Purified RBP has alpha(1) mobility on electrophoresis and has a molecular weight of approximately 21,000-22,000. There appears to be one binding site for retinol per molecule of RBP. Solutions of RBP are fluorescent (characteristic of retinol) and have ultraviolet absorption spectra with peaks at 330 mmu (resulting from the bound retinol) and at 280 mmu. There are no fatty acid or fatty acyl chains present in purified RBP. The usual concentration of RBP in plasma is of the order of 3-4 mg/100 ml. In plasma, RBP apparently circulates as a complex, together with another, larger protein with prealbumin mobility on electrophoresis. The RBP-prealbumin complex remains intact during Cohn fractionation and during chromatography on Sephadex and on DEAE-Sephadex columns. The complex dissociates during gel electrophoresis, permitting the isolation and subsequent purification of each of the components. The complex is again formed by mixing together solutions of the separated RBP and of prealbumin. Retinol transport in plasma thus appears to involve both a lipid-protein (retinol-RBP) interaction and a protein-protein (RBP-prealbumin) interaction.

Adult↗
PubMedDate not supplied

The demonstration of nonlinear development of experimental lung tumor metastases.

The kinetics of tumor colony formation in the lungs of mice following intravenous inoculation of high and low metastatic cell variants was determined. We have utilized two different tumor systems, the B16 melanoma, and UV-2237 fibrosarcoma; in both tumors the highly metastatic cell variants developed lung metastases in a nonlinear fashion following i.v. inoculation. The possibility that highly metastatic cell variants differ from their low metastatic counterparts not only in their lung colonizing potential, but also in their capability to produce satellite colonies, is discussed.

Animals↗
PubMedDate not supplied

Regional emergence of metastatic heterogeneity in a growing tumor.

Clones and subcloned cell lines of the murine B16 melanoma tumor were used to address the question of whether in vivo and in vitro growing tumors exhibit zonal metastatic heterogeneity. Cell clones were recloned in a semi-solid medium or injected subcutaneously into C57BL/6 mice, sublines of the parental colonies were established in culture from defined colonies that grew in suspension in the same agarose plate and from different regions of an in vivo growing tumor. Induction of experimental lung metastases after intravenous inoculation of 5 X 10(4) viable cells from these cell lines revealed that, both in vivo and in vitro zonal growth may induce the emergence of tumor cells exhibiting metastatic heterogeneity. Furthermore, metastatic diversity in the B16 melanoma clones occurred at a higher frequency during in vivo growth as compared to in vitro cultivation. All the cloned cell lines were found to be aneuploid with unstable chromosome number.

Animals↗
PubMedDate not supplied

Participation of p53 cellular tumour antigen in transformation of normal embryonic cells.

The cellular tumour antigen p53 is found at elevated levels in a wide variety of transformed cells (for reviews see refs 1, 2). Very little is yet known about the precise relationship of p53 to malignant transformation. Although the increase in p53 levels could be a secondary by-product of the transformed state, it is equally possible that p53 is actively involved in altering cellular growth properties, especially as it has been implicated in the regulation of normal cell proliferation. We sought to test whether p53 could behave in a manner similar to known genes in a biological test system, and we demonstrate here that p53 can cooperate with the activated Ha-ras oncogene to transform normal embryonic cells. The resultant foci contain cells of a markedly altered morphology which produce high levels of p53. Cell lines established from such foci elicit tumours in syngeneic animals.

Animals↗
PubMedDate not supplied

Indomethacin inhibits the accumulation of tumor cells in mouse lungs and subsequent growth of lung metastases.

BACKGROUND: The interaction of cancer cells with blood cells and cell wall components evokes inflammatory responses and is a critical event in the metastatic process. Indomethacin is a potent inhibitor of the cyclooxygenase (COX) enzymes and has previously been shown to decrease the growth of primary tumors in vivo. Proinflammatory prostaglandins produced by the two COX enzymes may also play a role in the development of metastases. METHODS: To directly address this question, we tested the effect of indomethacin on the accumulation of circulating [(3)H]-uridine-labeled tumor cells in the lungs and on the subsequent development of lung tumors. RESULTS: We found that inhibition of COX activity in the recipient mice prior to the injection of tumor cells decreased the percentage of the cells arrested in the lungs. This effect was highly significant since it subsequently led to substantial attenuation of lung metastasis development. CONCLUSION: These data thus demonstrate the antimetastatic effect of indomethacin through a mechanism which involves a reduction in tumor cell uptake by the lungs.

Animals↗
PubMedDate not supplied

The effects of ionizing irradiation on production of thromboxane and prostacyclin by the isolated perfused rat kidney.

Exposure to whole body radiation is associated with prompt changes in urinary excretion of prostaglandins. We investigated the separate effects of radiation on rat kidney capillary and tubular system prostaglandin synthesis. Animals were irradiated to the left kidney area with a single dose of 15 Gy. One week later the rats were anesthesized, the renal artery, vein and ureter of the left kidney cannulated, and the kidney removed and perfused with Krebs-Henseleit physiological buffer at a rate of 10-12 ml/min. Effluent fluids were collected separately from the renal vein and from the ureter of irradiated and control (operated sham-irradiated animals) and were assayed by radioimmunoassays for thromboxane A2 (TXB2) and prostacyclin (6 keto PGF1 alpha). Histological examination of the irradiated kidneys showed no significant changes, and electron microscopy revealed minimal interstitial edema. In contrast to these minimal changes, TXB2 assays showed a significant increase both in the venous and ureter effluents. Following stimulation with angiotensin II in the perfusate, a further significant increase in TXB2 production was observed both by the capillary and the tubular systems. With 6 Keto PGF1 a slightly different response was seen. The basal production was increased only in the ureter effluent of the irradiated animals, while there were no changes in the release in the venous effluents. In parallel, radiation significantly increased the angiotensin II stimulated production capacity of prostacyclin by the tubular system. The response of the capillary system following irradiation may create imbalance between these two important substances and lead to the radiation effects in the renal tissue.

Animals↗
PubMedDate not supplied

Multiple use of a signal transduction pathway in tumor cell invasion.

Recent reports have indicated that a poorly characterized signaling pathway involving 12-lipoxygenase and PKC is involved in several steps of the metastatic cascade such as tumor cell adhesion to matrix, lysosomal enzyme release and migration. We investigated here the upstream elements of this signalling pathway looking for receptors which it might be coupled to. We described tumor cell alpha IIb beta 3-like integrin and the AMF receptor, gp78, as two transmembrane receptors which utilize the 12-lipoxygenase/PKC signaling. Furthermore, we compared the in vivo expression of the signal components of the "autocrine motility cycle" (gp78, 12-LOX and PKCa-Tímár et al 1993) in human prostate carcinoma cell lines (PC3 and DU145) with different invasive potential. We report here that all three components of this cycle are overexpressed three fold in vivo in the more aggressive tumor, suggesting that this signalling pathway might regulate the invasive phenotype-at least in the studied tumor cells.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗