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At least 19 recordsLinked to original sources
PubMed1992

Purification of platelet-derived endothelial cell growth inhibitor and its characterization as transforming growth factor-beta type 1.

In 1986, Brown and Clemmons (Proc. natl Acad. Sci. USA 83 (1986) 3321) showed that platelets contain a substance, platelet-derived growth inhibitor (PDGI), that inhibits in vitro endothelial cell replication. Although platelets are rich in transforming growth factor beta (TGF-beta), PDGI was considered not to be related to TGF-beta, on the basis of its reported properties (extraction from platelets at neutral pH, binding to heparin-Sepharose). However, we purified PDGI to near homogeneity and showed that on the basis of HPLC retention behavior, in vitro growth inhibitory activities with several cell types, receptor binding, and immunoneutralization of growth inhibitory activity with specific anti-TGF-beta type 1 antibodies, PDGI is most probably identical with TGF-beta type 1.

Animals↗
PubMed1992

Mammary-derived growth inhibitor protein and messenger ribonucleic acid concentrations in different physiological states of the gland.

Expression of mammary-derived growth inhibitor in tissue from lactating and involuting bovine mammary glands was investigated. Seventeen lactating, pregnant (220 to 272 d in gestation) cows were divided in two groups of 8 and 9 cows each. Cows of the first group were slaughtered while in lactation. Cows of the second group (9 involuting cows) were slaughtered at 13 to 52 d following sudden cessation of milking. High concentrations of mammary-derived growth inhibitor (.63% of the total protein) were detected in mammary tissue of lactating cows. Mammary-derived growth inhibitor (less than .10% of the total protein) was dramatically reduced during most of the involution period (13 to 45 d following cessation of milking). Mammary-derived growth inhibitor was again detected (.28% of the total protein) during the last stage of the involution (46 to 53 d after cessation of milking), which coincided with colostrum formation. When steady state concentrations of mammary-derived growth inhibitor mRNA were examined, the results obtained mirrored those obtained at the protein concentration. These data suggest that regulation of mammary-derived growth inhibitor occurs via modulation of the steady state concentration of its mRNA. Furthermore, there is a strong correlation between mammary-derived growth inhibitor expression and lactation in dairy cows.

Animals↗
PubMed1979

Pinitol, a larval growth inhibitor for Heliothis zea in soybeans.

A search for insect growth inhibitors in methanol extracts of soybean leaves resulted in isolation of pinitol. Pinitol caused a 50% reduction in weight gain (ED50) of Heliothis zea larvae at about 0.7% when added to a synthetic diet. Although myo-inositol is a normal component of the insect diet, it also caused growth inhibition at higher concentrations; ED50 4%.

Animals↗
PubMed1975

Growth of calcium oxalate crystals. II. Inhibition by natural urinary crystal growth inhibitors.

A method is described for quantitatively determining the inhibitory activity of pure components, isolates, or mixtures of components (such as urine) on the growth of calcium oxalate crystals. Results with known calcium phosphate crystal growth inhibitors--magnesium, citrate, and pyrophosphate--suggest that these components contribute little to the ability to normal urine to inhibit the growth of calcium oxalate crystals. As yet unidentified urinary components seem to be responsible for most of this activity. The urinary crystal growth inhibitors appear to function by adsorbing on the surface of the growing crystals, thereby preventing the further incorporation of lattice ions. The fit of experimental data to the Langmuir absorption isotherm supports this conclusion.

Calcium↗
PubMed1992

The calcium oxalate crystal growth inhibitor protein produced by mouse kidney cortical cells in culture is osteopontin.

Urine contains proteins that inhibit the growth of calcium oxalate (CaOx) crystals and may prevent the formation of kidney stones. We have identified a potent crystal growth inhibitor in the conditioned media from primary cultures of mouse kidney cortical cells. Conditioned media, incubated with the kidney cells for 6-72 h, was assayed for crystal growth inhibition; inhibitory activity increased 15-fold by 24 h. Inhibitory activity was purified from serum-free media containing proteinase inhibitors using anion-exchange and gel-filtration chromatography. A single band of molecular weight 80,000 daltons was seen after SDS-polyacrylamide gel electrophoresis. The sequence of the N-terminal 21 amino acids of this protein matched that of osteopontin (OP), a phosphoprotein initially isolated from bone matrix. Antisera raised to fusion proteins produced by plasmids containing the N-terminal or C-terminal portions of OP cDNA also cross-reacted with the protein purified from cell culture media on western blots. The effect of the purified protein on the growth of CaOx crystals was measured using a constant composition assay. A 50% inhibition of growth occurred at a protein concentration of 0.85 micrograms/ml, and the dissociation constant of the protein with respect to CaOx crystal was 3.7 x 10(-8) M. The concentration of OP in mouse urine, measured using antibodies raised to the purified protein, was approximately 8 micrograms/ml. We conclude that OP is synthesized by kidney cortical tubule cells and functions as a crystal growth inhibitory protein in urine.

Amino Acid Sequence↗
PubMedDate not supplied

Hormonal induction of functional differentiation and mammary-derived growth inhibitor expression in cultured mouse mammary gland explants.

A method for the cultivation of organ explants from abdominal mammary glands of virgin mice has been established. In a serum-free medium containing aldosterone, prolactin, insulin, and cortisol (APIH medium) mammary gland development was documented by lobuloalveolar morphogenesis. The hormonal requirements for in vitro expression of beta-casein and of the mammary-derived growth inhibitor (MDGI) were tested. To this end, a full length cDNA coding for mouse MDGI was prepared displaying strong homologies to a mouse heart fatty acid binding protein, which is also expressed in the mammary gland. MDGI and beta-casein transcripts were found to be absent in the mammary tissue from primed virgin mice, and were induced upon culture of mammary explants in the APIH medium. An immunohistochemical analysis with specific antibodies against MDGI and casein revealed a different pattern of expression for the two proteins. In the APIH medium, MDGI was expressed mainly in differentiating alveolar cells of the lobuloalveolar structures, whereas beta-casein was present in both ductules and alveoli. The relationship between functional differentiation and MDGI expression was further studied in explants from glands of late-pregnant mice. At this stage of development, MDGI is found both in ducts and in alveoli. If explants were cultured with epidermal growth factor (EGF) and insulin, the lobuloalveolar structure was still present, whereas MDGI disappeared. Reinduction of MDGI expression was achieved by subsequent PIH treatment. Independent on developmental stage, EGF strongly inhibits MDGI mRNA expression. It is concluded that MDGI-expression is associated with functional differentiation in the normal gland.

Aldosterone↗
PubMed1977

Acidic peptide and polyribonucleotide crystal growth inhibitors in human urine.

Urine contains nondialyzable inhibitors of calcium oxalate crystal growth. We have pursued the hypothesis that these inhibitors may, in part, be acidic peptides and polyribonucleotide fragments. Homopolyribonucleotides and RNA inhibit calcium oxalate crystal growth at 5 x 10(-6) M of constituent ribonucleotide, whereas the monomer nucleotides are inactive at 10(-4) M. Poly-L-aspartic or glutamic acid are also inhibitory at 5 X 10(-6) M of amino acid, whereas the monomeric amino acids are inert. Gastric pepsin, a naturally occurring acidic peptide, is inhibitory. Incubation with nonspecific protease reduced the inhibitory effectiveness of normal human urine consistently and significantly, a fact compatible with an important contribution of peptides. A variable additional reduction was produced by subsequent treatment with ribonuclease, suggesting only a small role for polyribonucleotide. Sequential ion exchange and gel filtration chromatography and preparative disc gel electrophoresis yielded inhibitory material enriched with peptides that were strongly acidic and high in proline. Peptides and ribonucleotides seem to contribute to urinary nondialyzable crystal growth inhibitory activity.

Calcium↗
PubMed1978

Crystal growth inhibitors in human urine. Effect on calcium oxalate kinetics.

The nucleation and growth of oxalate trihydrate from supersaturated solutions containing a high molecular weight inhibitor fraction found in urine were sharply reduced to the extend that calcium oxalate dihydrate was formed. The kinetics of the later hydrate were found to be reduced with increasing inhibitor concentration. The effect of the negatively charged urine inhibitor on crystal growth of calcium oxalate was found to correlate with inhibition found in studies involving high molecular weight mucopolysaccharides such as heparin.

Calcium↗
PubMed1992

Interleukin 6: a fibroblast-derived growth inhibitor of human melanoma cells from early but not advanced stages of tumor progression.

Recently we reported that human dermal fibroblasts, or conditioned media obtained from such cells, affect the growth of human melanoma cells as a direct function of tumor progression: melanoma cells obtained from early-stage (metastatically incompetent) primary lesions were growth inhibited, whereas cells obtained from more advanced (metastatically competent) primary lesions, or metastases, were growth stimulated. Ion-exchange and gel-filtration chromatography of fibroblast conditioned medium revealed the inhibitor to be a protein of molecular mass between 20 and 30 kDa and distinct from the stimulator. This is the approximate molecular mass of interleukin 6 (IL-6), a ubiquitous multifunctional cytokine known to affect in particular many kinds of hemopoietic and lymphoid cells. Since this cytokine is known to be made by fibroblasts, we attempted to determine if the human fibroblast-derived growth inhibitor (hFDGI) was identical to IL-6. Neutralizing antibodies specific for IL-6 completely eliminated the inhibitory activity of hFDGI. Moreover, exposure to human recombinant IL-6 was found to inhibit the growth of early-stage melanoma cells obtained from radial growth phase (RGP) or early vertical growth phase (VGP) primary lesions in three of four cases. In contrast, melanoma cells from a number of more advanced VGP primary lesions, or from distant metastases, were completely resistant to this IL-6-mediated growth inhibition. Acquisition of an "IL-6-resistant" phenotype by metastatically competent melanoma cell variants may provide such cells with a proliferative advantage within the dermal mesenchyme (a hallmark of melanoma cells that are malignant), helping them eventually to dominate advanced primary lesions and to establish secondary growths elsewhere.

Chromatography, High Pressure Liquid↗
PubMed1979

Bacterial growth inhibition by amniotic fluid. VIII. Evaluation of a radiometric bioassay for rapid, in vitro demonstration of phosphate-sensitive bacterial growth inhibitor in amniotic fluid.

A radiometric bioassay based on the continuous monitoring of 14CO2 released from labeled glucose in the presence of amniotic fluid or amniotic fluid with added phosphate has been employed to detect the presence of a phosphate-sensitive bacterial inhibitor in amniotic fluid near term. The time required for detection of the inhibitory activity is approximately 12 hours, in contrast to approximately 36 hours required for a previously reported technique. Application of this radiometric bioassay to demonstrate bacterial growth inhibition by amniotic fluid and physicochemical properties of the inhibitory activity yielded results comparable to those obtained with the older method of plate counts of viable bacteria. By the new technique it was possible to demonstrate that the inhibitory activity was phosephate sensitive, heat stable, inactivated by metal chelation, removed by bentonite, and present in a low-molecular-weight fraction of amniotic fluid.

Amniotic Fluid↗
PubMed1992

Identification in human urine of a natural growth inhibitor for cells derived from solid paediatric tumours.

Partially purified urine of healthy human subjects contains several fractions able to inhibit the proliferation of cultured human neuroblastoma cells. One of the most active fractions was further analysed by gas chromatography-mass spectrometry and shown to contain genistein, a substance formed in the human body from precursors obtained by diet. Synthetic genistein was able to inhibit the proliferation of human neuroblastoma cells with a half-maximal effect at 5-10 mumol l-1 concentrations. Genistein displayed similar potencies in inhibiting the proliferation of cells derived from various other solid pediatric tumours. Our results suggest that genistein is a natural antineoplastic agent present in diet and that it could be useful for the therapy of paediatric tumours.

Cell Division↗
PubMed1992

Purification of a mammary-derived growth inhibitor (MDGI) related polypeptide expressed during pregnancy.

The present study was undertaken to screen immunochemically for MDGI-related proteins in the mammary gland. A new form, MDGI 2, not present in lactation could be detected in the bovine gland during pregnancy. It was further distinguished from MDGI by its lower molecular weight, its association with a complex binding to WGA, and by lacking immunoreactivity to an anti-MDGI antibody directed against the C-terminus of MDGI. MDGI 2 was purified by chromatography over DEAE-Sepharose, Bio-Gel P-30 in 1% acetic acid, Sephacryl S-200 in 6 M urea and Mono Q. Final purification included HPLC on TSK G-3000 SW and electroelution from SDS-gels. Cell-free translation of poly (A+)mRNA from glands of pregnant animal yielded one form identical with MDGI. We assume that posttranslational processing of MDGI is involved in its activities.

Animals↗