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  • Nuclear reactions  (4,460)
  • Molecular Cell Biology
  • 101
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 14 (1996), S. 97-104 
    ISSN: 0263-6484
    Keywords: Graves' disease ; methimazole ; thyroid hormones ; glucose ; glutamine ; immune function ; lymphocytes ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Several studies have shown that thyroid hormones are able to influence selected immune responses such as cell mediated immunity, differentiation of B lymphocytes and the activity of NK cells. These hormones can also regulate the metabolism of glucose and glutamine in rat macrophages and their effects seem to occur mainly through the Krebs cycle. Alterations in the hexokinase, citrate synthase, glucose-6-phosphate dehydrogenase and glutaminase activities in lymphocytes from patients with Graves' disease, either untreated or on methimazole (MMI) therapy were investigated. Experiments were also done in vitro to determine the activities of these enzymes in normal lymphocytes cultured for 24 h in the presence of MMI, T3 and T4 using concentrations close to the physiological. Changes in the conversion of [U-14C]-glucose and [U-14C]-glutamine to 14CO2 as caused by the addition of MMI, T3 or T4 to the culture medium were also evaluated. The results indicate that high levels of thyroid hormones might stimulate the metabolism of glucose and glutamine for a short period of time but, if the stimulus is maintained, the utilization of glutamine by lymphocytes is then suppressed. Moreover, MMI does affect lymphocyte metabolism but the significance of this finding for its immunosuppressive effect remains to be examined.
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  • 102
    ISSN: 0263-6484
    Keywords: polyenoylphosphatidylcholine ; liver structure, lipids ; pancreatic structure ; pancreatic islets ; β-cells ; ranules ; alloxan ; experimental diabetes ; liver damage ; glucose content ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Polyenoylphosphatidylcholine (PPC: 100 or 300 mg kg-1 b.w., by gastric intubation for 30 days) produced a clearcut protection of the liver of rats treated with alloxan (150 mg kg-1 b.w., i.p.). The liver of rats treated with alloxan was characterized by hydropic dystrophy and lymphocytic infiltrations. Treatment with alloxan increased serum γ-GT and ALAT activities. The liver structure of rats treated with PPC did not differ from the liver of control animals. PPC normalized the biochemical abnormalities caused by the diabetes. The number of pancreatic islets and β/α; cell ratio decreased in the diabetic rats. A number of β-cells in this group did not contain granules. PPC prevented the decrease in the number of islets and the β/α; cell ratio in the pancreas of the diabetic rats. The intensity of staining of β-cell granules in the pancreas of PPC-treated rats had a position intermediate between the control and diabetic groups. Alloxan increased the blood glucose content where treatment with PPC decreased this. The results suggest that PPC acts as a cytoprotector in the liver and pancreas of rats with experimental diabetes induced by alloxan.
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  • 103
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    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 14 (1996), S. 155-155 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 104
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    Cell Biochemistry and Function 14 (1996), S. 156-156 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 105
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    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 14 (1996), S. 291-296 
    ISSN: 0263-6484
    Keywords: fibronectin ; HIV-1 infection ; platelets ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have previously demonstrated that fibronectin (FN) can bind HIV-1 envelope proteins, in particular gp120. The aim of the present study was to determine some biological effects of this phenomenon. Pretreating HIV-1 with human FN increased the infectivity of HIV-1, when a low concentration of the virus was used. In contrast, an RGD-containing pentapeptide (Gly-Arg-Gly-Asp-Ser), which is a fundamental binding site of FN, reduced the infectivity of a suspension of HIV-1 at high concentrations of the virus. It is likely that FN bridges the cell surface and the virions, while the RGD-containing pentapeptide may saturate the HIV-1 binding sites for cell surface receptors. Moreover, gp120 was bound to the FN present on the surface of platelets. The specifity of this binding was confirmed by the inhibition obtained by pretreating platelets with anti-FN antibodies. The consequence of the surface modifications of the platelets could explain the thrombocytopenia that frequently occurs in patients infected with HIV and suggests also the possibility that platelets could be a vehicle for the virus in the circulation.
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  • 106
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    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 14 (1996) 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 107
    ISSN: 0263-6484
    Keywords: proteoglycans ; Pseudoxanthoma elasticum ; fibroblasts ; skin ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Proteoglycans (PGs) were investigated in fibroblast cultures from both apparently normal and involved areas of skin from two patients affected with Pseudoxanthoma elasticum (PXE) and compared to control normal cells. Biochemical analysis showed that cells from the PXE-affected patients produced a PG population with stronger polyanion properties, as well as a markedly increased amount of high hydrodynamic-size PGs. Moreover, PGs from PXE-affected cells showed abnormal hydrophobic interaction properties when examined under associative conditions and included heparan sulphate (HS)-containing populations with anomalous electrophoretic mobility. These phenomena were particularly evident in the case of PGs secreted into the growth medium. In agreement with these findings immunohistochemical study showed alterations affecting decorin and biglycan, as well as a different content and distribution of HS-PGs in PXE-affected cells. The same biochemical and morphological alterations were confirmed for both patients on different cell cultures and were present in cells from both apparently normal and affected skin areas, being more pronounced in the latter. Our results indicate that PXE-affected fibroblasts in culture exhibit an abnormal PG metabolism, which could affect the normal assembly of extracellular matrix.
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  • 108
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    Cell Biochemistry and Function 14 (1996), S. 89-95 
    ISSN: 0263-6484
    Keywords: methylglyoxal ; hydrogen peroxide ; aggregation ; ATP release ; human platelets ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Methylglyoxal generates a slight increase in the basal level of hydrogen peroxide in platelets. The oxidation effect of methylglyoxal significantly potentiated by thrombin, depends on both the ketoaldehyde and the agonist concentrations. A further significant increase in hydrogen peroxide accumulation was obtained in platelets pretreated with the alkylating agent N-ethylmaleimide which depletes GSH and blocks glutathione peroxidase. Resting platelets completely transform the ketoaldehyde into D(-)lactate, whereas stimulated platelets transform about 10-15 per cent of the metabolized methylglyoxal into D(-)lactate. The metabolic modifications generated by methylglyoxal such as the GSH depletion and hydrogen peroxide accumulation induce modifications in platelet function. Methylglyoxal inhibits platelet aggregation induced by several agonists and ATP release induced by thrombin.
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  • 109
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    Cell Biochemistry and Function 14 (1996), S. 155-155 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 110
    ISSN: 0263-6484
    Keywords: glycation ; oxidation ; irradiation ; fluorescence ; albumin ; free radicals ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Oxidation and glycation are non-enzymatic protein modifications involved in the pathogenesis of aging. We evaluated their possible influences in an in vitro system: albumin was oxidized by gamma-irradiation and then exposed to glycation in vitro. Fluorescence modifications were analysed as signals of protein alterations. Both radiolytic oxidation and in vitro glycation provoked a sharp decrease of tryptophan fluorescence (278 nm ex./340 nm em.); their effects tended to be additive, unless a saturation limit was reached. Both individually and in combination, these two non-enzymatic processes induced the appearance of a new fluorescence (335 nm ex./415 nm em.); in this case as well there was an additive effect, with a trend toward saturation. Radiolytic oxidation and in vitro glycation seem to provoke similar damage to the exposed proteins: the observed fluorescence alterations may be due to similar conformational changes, breaks or the development of fluorophores.
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  • 111
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    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 14 (1996), S. 155-155 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 112
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    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 14 (1996), S. 155-155 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 113
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    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 14 (1996), S. 105-110 
    ISSN: 0263-6484
    Keywords: fibronectin ; fibronectin receptor ; neoplastic cells ; HIV-1 infection ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The aim of our study was to evaluate the levels of fibronectin (FN) and its classic receptor (FNR) in various transformed cells lines, especially of leukemic origin, and also the influence of HIV-1 replication on the expression of these proteins (in particular on H9-V cells, chronically infected with HIV-1, and acutely infected MT-4 cells). Monoclonal antibodies were used for indirect immunofluorescence tests; the fluorescein-conjugated recombinant p14, the product of the HIV gene tat, was used as a molecular probe. The results demonstrated a high variability of FN and FNR expression among the various cellular lines studied. Moreover, deficits of such adhesive proteins did not necessarily correlate with a severe reduction of the corresponding receptor. HIV-1 replication in MT-4 and H9-V cells increased the expression of FNR. This seems to correlate with p14-induced phenomena because pretreatment of H9-V cells with recombinant p14 showed an enhancing effect on the expression of this receptor.
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  • 114
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    Cell Biochemistry and Function 14 (1996), S. 222-223 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 115
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    Cell Biochemistry and Function 14 (1996), S. 157-161 
    ISSN: 0263-6484
    Keywords: camphorin ; carcinoma cells ; cinnamomin ; cytotoxicity ; RNA N-glycosidase ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cinnamomin (two-chain) and camphorin (single-chain), two novel ribosome-inactivating proteins (RIPs) purified from the seeds of Cinnamomum camphora, produced inhibitory effects in cultured carcinoma cells. The IC50 of cinnamomin to the human hepatocarcinoma cell-line 7721 and the melanoma cell-line M21 were 18·8 nmol and 11·7 nmol respectively. The IC50 of camphorin to the human hepatocarcinoma cell-line 7721 was 59 nmol, whereas the melanoma cell-line M21 was not susceptible to camphorin. Furthermore, cinnamomin exhibited a remarkable inhibitory effect on the growth of solid melanoma in the skin of the nude mouse. An R-fragment could be isolated from ribosomes of cinnamomin- or camphorin-treated carcinoma cells after incubation with acidic aniline, indicating that the cytotoxicity of these two new RIPs to carcinoma cells might result from modification to the ribosomes.
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  • 116
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    Cell Biochemistry and Function 14 (1996), S. 223-223 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 117
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    Cell Biochemistry and Function 14 (1996), S. 201-208 
    ISSN: 0263-6484
    Keywords: VDAC ; respiration ; mitochondrion ; yeast ; aluminum ; catabolite repression ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mitochondrial respiration in yeast (S. cerevisiae) is regulated by the level of glucose in the medium. Glucose is known to inhibit respiration by repressing key enzymes in the respiratory chain. We present evidence that the early events in this inhibition include the closure of VDAC channels, the primary pathway for metabolite flow across the outer membrane. Aluminum hydroxide is known to inhibit the closure of VDAC. Addition of aluminum acetylacetonate to yeast cells, which should elevate the aluminum hydroxide concentrations in the cytoplasm, caused the inhibition of cell respiration by glucose to be delayed for up to 100 min. No significant effect of aluminum was observed in cells grown on glycerol. Yeast cells lacking the VDAC gene were also unresponsive to the addition of aluminum salt in the presence of glucose. Therefore, the closure of VDAC channels may be an early step in the inhibition of the respiration of yeast by glucose.
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  • 118
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    Cell Biochemistry and Function 14 (1996), S. 49-55 
    ISSN: 0263-6484
    Keywords: redox state ; protein disulfide isomerase ; AP1 ; NF-κB ; electromobility shift assay ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Most transcription factors are multimeric complexes whose subunits depend on strict conformational requirements to form the active unit. Among these requirements is the presence of appropriate sulfhydryl interactions that are critical to transcription factor binding to cognate DNA recognition sites. Our experiments now suggest that modulation of these sulfhydryls may involve the action of thiol-modifying oxido-reductases such as protein disulfide isomerase (PDI). Electrophoretic mobility shift titration experiments incorporating different ratios of GSH:GSSG indicated that changes in GSH and GSSG concentrations corresponding to redox potential differences of as little as ±15 mV enabled or abolished binding of NF-κB and AP1 to their cognate DNA sites. Moreover, this binding range was modulated significantly by the addition of purified protein disulfide isomerase (PDI). Collectively, these results suggest that a reversible oxidation/reduction signalling pathway may exist in the cell whereby localized changes in redox potentials and/or oxido-reductase activity can be functionally relevant in the regulation of critical gene expression events.
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  • 119
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    Cell Biochemistry and Function 14 (1996), S. 139-148 
    ISSN: 0263-6484
    Keywords: frog liver γ-glutamyltranspeptidase ; Rana sylvatica ; freeze tolerance ; thyroid hormone ; thyroid hormone regulation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The freeze tolerant wood frog Rana sylvatica was studied to determine the impact of the freezing and thawing of this frog on the activity of γ-glutamyltranspeptidase in the liver. On exposure to -2·5°C, for 1, 12 and 24 h, frogs were found to be cool, covered with ice crystals and frozen, respectively. Thawing for 24 h at 4°C recovered the frogs completely. A 45 per cent decrease in the liver weight: body weight ratio was notable after 1 h at -2·5°C, suggestive of an early hepatic capacitance response. A glycemic response to freezing was observed: blood glucose levels exhibited a 55 per cent decrease after 1 h at -2·5°C on cooling; a 10·5-fold increase after 12 h at -2·5°C on the initiation of freezing; and a 22-fold increase after 24 h at -2·5°C in the fully frozen state. Blood glucose levels remained elevated four-fold in the thawed state. Plasma insulin levels were increased twofold in the frozen state and 1·8-fold in the thawed state, while plasma ketone levels were increased 1·8-fold in the frozen state and 1·5-fold in the thawed state. Plasma total T3 levels were decreased by 22 per cent in the frozen state and normalized on thawing.In homogenates and plasma membranes isolated from the livers of Rana sylvatica, the activity of γ-glutamyltranspeptidase was found to be elevated at all stages of the freeze-thaw process. After 1, 12 and 24 h at -2·5°C, activities were increased 2·5-, 2·3-, 2·4-fold respectively in the homogenates and 2·5-, 2·2-, 2·4-fold respectively in the plasma membranes. After thawing, activities were still increased 1·9-fold in both homogenates and plasma membranes. In homogenates prepared from the kidneys of Rana sylvatica, the activity of γ-glutamyltranspeptidase was increased 1·4-fold after 1 h at -2·5°C after which it returned to normal. The role of thyroid hormone in producing the increase in γ-glutamyltranspeptidase in the liver of Rana sylvatica in response to freezing is discussed as is the significance of the enzyme increase in terms of hepatic cytoprotection and freeze tolerance.
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  • 120
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    Cell Biochemistry and Function 14 (1996), S. 173-180 
    ISSN: 0263-6484
    Keywords: polyamines ; uptake ; efflux ; placenta ; JAR cells ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Uptake of polyamines has been investigated extensively in many cells, but not in placenta, where the polyamine- polyamine oxidase system is supposed to have an immunoregulatory function in pregnancy. Due to the importance of the transfer in this tissue, we have started this study. JAR human placental choriocarcinoma cells in monolayer at confluency were used as a model for measuring the key enzymes of polyamine synthesis and interconversion, rate of uptake and efflux, and the polyamine content. Polyamines were taken up by JAR cells and released by an independent mechanism. Ornithine decarboxylase and spermidine acetyltransferase activities and the rate of transport in and out of the cell were much higher than in other cells, such as L1210 cells. However the systems used for uptake and release appear in many respects to be similar to those observed in L1210 cells, but different from others. The uptake appears to be regulated by an inhibitory protein. Moreover, protein kinase C appears to be involved in the process. The efflux also is regulated as in L1210 cells, through control of H+ and Ca2+ concentration. In conclusion, this study shows that, in JAR cells, ornithine decarboxylase and spermidine acetyltransferase activities were much higher than in other cells, and so was the rate of transport in and out of the cells. As a result, a much higher polyamine content was observed.
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  • 121
    ISSN: 0263-6484
    Keywords: HB-EGF (heparin-binding epidermal growth factor-like growth) ; hyperosmolarity ; high glucose ; human aortic endothelial cell ; diabetic macroangiopathy ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been shown to be a potent smooth muscle cell (SMC) mitogen and chemoattractant, and might be a candidate factor for the progression of atherosclerosis. We have investigated the effects of high glucose and hyperosmolarity on HB-EGF production in cultured human aortic endothelial cells. Following the culture of the cells for 2 days with high concentrations of glucose or in the hyperosmolar conditions, we measured the content of HB-EGF and the rate of production in the cells using a semi-quantitative immunofluorescent technique and a metabolic radiolabelling method. With high glucose (16.6 mmol) and hyperosmolar conditions (glucose 5.5 mmol + mannitol 11.1 mmol or glucose 5.5 mmol + raffinose 11.1 mmol), the content of HB-EGF was significantly increased and the metabolic rate was also significantly increased (more than a twofold increase, compared to that of 5.5 mmol glucose). In conclusion, conditions of high glucose or hyperosmolarity increase HB-EGF production in human aortic endothelial cells. These results suggest that diabetic macroangiopathy might be attributed at least in part to HB-EGF-related vascular changes which may be induced by glucose.
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  • 122
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    Cell Biochemistry and Function 14 (1996), S. 219-219 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 123
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    Cell Biochemistry and Function 14 (1996), S. 163-171 
    ISSN: 0263-6484
    Keywords: camptothecin resistant topoisomerase ; DNA single- and double-strand breaks ; L5178Y lymphoma sublines ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two L5178Y (LY) murine lymphoma cell sublines, LY-R, resistant, and LY-S, sensitive, to X-irradiation display inverse cross-sensitivity to camptothecin (CPT): LY-R cells were more susceptible to this specific topoisomerase I inhibitor than LY-S cells. After 1 h incubation with CPT, the doses that inhibited growth by 50 per cent (ID50) after 48 h of incubation were 0·54μM for LY-R cells and 1·25 μM for LY-S cells. Initial numbers of DNA-protein crosslinks (DPCs) measured at this level of growth inhibition were two-fold higher in LY-R (5·6 Gray-equivalents) than in LY-S cells (3·1 Gray-equivalents), which corresponds well with the greater in vitro sensitivity of Topo I from LY-R cells to CPT.1,2 Conversely, the initial levels of single-strand DNA breaks (SSBs) and double-strand DNA breaks (DSBs) were lower in LY-R cells (4·2 Gray-equivalent SSBs and 5·8 Gray equivalent DSBs) than in LY-S cells (8·0 Gray-equivalent SSBs and 12·0 Gray-equivalent DSBs). Dissimilarity in the replication-dependent DNA damage observed after 1 h of treatment with CPT was not due to a difference in the rate of DNA synthesis between the two cell lines, but may have arisen from a substantially slower repair of DNA breaks in LY-S cells.3 Release from G2 block by caffeine co-treatment significantly increased cell killing in the LY-S subline, and only slightly inhibited growth of LY-R cells. These results show that after CPT treatment cells arrest in G2, allowing them time to repair the long-lived DSBs. As LY-S cells are slower in repairing the DSBs, they were more susceptible to CPT in the presence of caffeine.
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  • 124
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    Cell Biochemistry and Function 14 (1996), S. 220-220 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 125
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    Cell Biochemistry and Function 14 (1996), S. 220-221 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 126
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    Cell Biochemistry and Function 14 (1996), S. 221-222 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 127
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    Cell Biochemistry and Function 14 (1996), S. 222-222 
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 128
    ISSN: 0263-6484
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 129
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    Springer
    The astronomy and astrophysics review 3 (1991), S. 1-46 
    ISSN: 1432-0754
    Keywords: Nucleosynthesis ; Nuclear reactions ; Stars: abundances ; Interstellar Medium: abundances ; Cosmology ; Galaxies: evolution of
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The basic scheme of nucleosynthesis (building of heavy elements from light ones) has held up very well since it was first proposed more than 30 years ago by E.M. Burbidge, G.R. Burbidge, A.G.W. Cameron, W.A. Fowler, and F. Hoyle. Significant advances in the intervening years include (a) observations of elemental and a few isotopic ratios in many more extrasolar-system sites, including metal-poor dwarf irregular galaxies, where very little has happened, and supernovae and their remnants, where a great deal has happened, (b) recognition of the early universe as good for making all the elements up to helium, (c) resolution of heavy element burning in stars into separate carbon, neon, oxygen, and silicon burning, with fine tuning of the resulting abundances by explosive nucleosynthesis in outgoing supernova shock waves, (d) clarification of the role of Type I supernovae, (e) concordance between elements produced in short-lived and long-lived stars with those that increased quickly and slowly over the history of the galaxy, and (f) calibration of calculations of the evolution and explosion of massive stars against the detailed observations of SN 1987A. The discussion presupposes a reader (a) with some prior knowledge of astronomy at the level of recognizing what is meant by an A star and an AGB star and (b) with at least a mild interest in how we got to where we currently are.
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  • 130
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 161-168 
    ISSN: 0275-3723
    Keywords: phorbol ester prostaglandin F2α ; (Na+ + K+)-ATPase ; cell cycle activation ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The introduction of either PGF2α (10-7 M) or TPA (10-7 M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF2α at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest stimulatory effect, which was similar to that obtained with 10% fetal calf serum. In accord with the idea that modulation of membrane processes such as Na+/K+ pump activity in fibroblasts may reflect important events related to the initiation of DNA synthesis, it was observed that in both 3T3-4 and C3H-1 0T½ cells there were parallel increases in 3H-TdR incorporation and ouabain-sensitive 86Rb+ influxes with 10-7 M TPA, whereas PGF2α stimulated a significant increase in 3H-TdR incorporation in 3T3-4 but not C3H-10T½ cells and only marginal increases in ouabain-sensitive 86Rb+ influx in both. Therefore, although there appears to be a close correlation between Na+/K+ pump activation and subsequent S-phase entry following TPA stimulation, a similar correlation for PGF2α cannot be confirmed.
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  • 131
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 177-191 
    ISSN: 0275-3723
    Keywords: MSA ; somatomedin ; carrier protein ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The rat liver cell line, BRL-3A, is known to produce a family of polypeptides referred to as multiplication-stimulating-activity (MSA). Serum-free conditioned medium from this cell line is a rich source for the purification of these somatomedin-like molecules. Somatomedins in serum, as well as MSA produced by BRL-3A cells in culture, exist primarily as a high molecular weight complex bound to specific carrier proteins. This study describes the purification of the MSA carrier protein (MCP) from conditioned medium using affinity chromatographic procedures. The purified carrier protein is shown to specifically bind labeled MSA and generates a complex with an apparent molecular weight of 60,000-70,000 daltons. Characterization of the carrier protein indicates that it consists of two different noncovalently linked protein chains with apparent molecular weights of 30,000 and 31,500 daltons. The availability of a pure carrier protein should provide a unique opportunity to investigate the functional significance of the carrier protein in the biological activity of the somatomedins.
    Additional Material: 8 Ill.
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  • 132
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 233-242 
    ISSN: 0275-3723
    Keywords: lectins ; slime mold lectins ; vertebrate lectins ; chicken-lactose-lectin-I ; chicken-lactose-lectin-II ; chicken heparin lectin ; Dictyostelium ; secretion ; muscle development ; extracellular materials ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Endogenous lectins in both cellular slime molds and chicken tissues have been localized primarily intracellularly, in contrast with the predominantly extracellular localization of the glycoproteins, glycolipids, and glycosaminoglycans with which they might interact. Here we present evidence that lectins in both of these organisms may be externalized and become associated with the cell surface and/or extracellular materials. In chicken intestine, chicken-lactose-lectin-II is shown to be localized in the secretory granules of the goblet cells, along with mucin, and to be secreted onto the intestinal surface. In embryonic muscle, chicken-lactose-lectin-I is shown to be externalized with differentiation, ultimately becoming localized on the surface of myotubes and in the extracellular spaces. In a cellular slime mold, Dictyostelium purpureum, externalization of lectin is elicited by either polyvalent glycoproteins that bind the small amount of endogenous cell surface lectin, or by slime mold or plant lectins that bind unoccupied complementary cell surface oligosaccharides. These results suggest that externalization of endogenous lectin may be a response to specific external signals. We conclude that lectins are frequently held in intracellular reserves awaiting release for specific external functions.
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  • 133
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 134
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 303-309 
    ISSN: 0275-3723
    Keywords: bleomycin ; DNA repair ; human DNA repair defects ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The ability of human fibroblasts to repair bleomycin-damaged DNA was examined in vivo. Repair of the specific lesions caused by bleomycin (BLM) was investigated in normal cell strains as well as those isolated from patients with apparent DNA repair defects. The diseases ataxia telangiectasia (AT), Bloom syndrome (BS), Cockayne syndrome (CS), Fanconi anemia (FA), and xeroderma pigmentosum (XP) were those selected for study. The method used for studying the repair of DNA after BLM exposure was alkaline sucrose gradient centrifugation. After exposure to BLM, a fall in the molecular weight of DNA was observed, and after drug removal the DNA reformed rapidly to high molecular weight. The fall in molecular weight upon exposure to BLM was observed in all cells examined with the exception of some XP strains. Prelabeled cells from some XP complementation groups were found to have a higher percentage of low molecular weight DNA on alkaline gradients than did normal cells. This prelabeled low molecular weight DNA disappeared upon exposure to BLM.
    Additional Material: 2 Ill.
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  • 135
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 345-358 
    ISSN: 0275-3723
    Keywords: fibronectin ; evolution ; proteolytic fragment ; domain structure ; receptor ; glycoprotein ; cellular adhesion ; adhesion placque ; cell surface protein ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fibronectin is a large, adhesive glycoprotein which is found in a number of locations, most notably on cell surfaces, in extracellular matrixes, and in blood. Fibronectin has been detected in all vertebrates tested and in many invertebrates. Its presence in sponges is significant because this suggests that fibronectin may have appeared very early in evolution, possibly with the most primitive multicellular organisms. Cellular and plasma fibronectins have many striking similarities. However, the locations of the polypcptide chain differences between these two proteins indicate that plasma fibronectin cannot be derived from cellular fibronectin by means of simple post-translational proteolysis. Instead, these different types of fibronectin may be products of different genes or of differentially spliced messenger RNA molecules. Amniotic fluid fibronectin is possibly a third form of the protein. Cellular and plasma fibronectins are composed of at least six protcaseresistant domains which contain specific binding sites for actin, gelatin, heparin, Staphylococcus aureus, transglutarninase, fibrin, DNA, and a cell surface receptor. The relative locations of these domains have been mapped in the primary structure of fibronectin. The cell surface receptor for fibronectin has not been positively identified, but may be a glycoprotein, a glycolipid, or a complex of the two. Although cell-substratum adhesion is mediated by fibronectin, the locations of the areas of closest approach of the cell to the substratum (the adhesion plaques) and fibronectin are not coincident under conditions of active cell growth. Under conditions of cell growth arrest in low scrum concentrations, some fibronectin may become localized at the adhesion plaques. Models describing the domain structure of fibronectin and the molecular organization of the adhesion plaque area are presented.
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  • 136
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 169-176 
    ISSN: 0275-3723
    Keywords: erythropoietin ; macrophages ; silica ; erythrocytic colony-forming units ; polycythemic mouse bioassay ; anti-erythropoietin ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: An erythropoietic stimulating factor (ESF) can be shown to be released from preincubated macrophage-containing cell suspensions from mice by the macrophage-specific, cytotoxic agent, silica. A concentrated silica treated spleen cell supernatant containing ESF is shown to cause a dose dependent increase in 59 Fe incorporation into red blood cells using the in vivo polycythemic mouse bioassay. The ESF from the same supernatant can also be neutralized by anti-erythropoietin. A second concentrated supernatant fractionated using wheat germ lectin-Sepharose 6MB and compared to either unfractionated or fractionated step 111 erythropoietin (Ep), tested in vitro using the erythroid colony-forming technique and 12-day fetal liver as target cells, indicates parallelism of all linear dose-response lines. This, together with the in vivo data, strongly suggests that the ESF released from macrophages treated with silica is, in fact, Ep. Substituting Ca2+ ions for fetal calf serum in the preincubation procedure results in the same activity being released compared to the presence of 1% or 20% fetal calf serum.
    Additional Material: 2 Ill.
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  • 137
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 205-211 
    ISSN: 0275-3723
    Keywords: murine teratocarcinoma ; embryonal carcinoma ; SV40 ; infection ; T antigen ; immunoprecipitation ; replication ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The stem cell of the murine teratocarcinoma is refractory to infection with Simian virus 40 and polyoma. Utilizing various procedures, we attempted to alter this block to infection by modifying the infection procedure. Multiple infections with high-titer SV40 and pretreatment of cells with DEAE-dextran or the carcinogen 4-nitroquinoline l-oxide did not induce embryonal carcinoma cells to produce T- antigen. Co-infection with adenovirus 5, which infects the embryonal carcinoma, and SV40 did not induce the expression of SV40 Tantigen. Therefore, these procedures did not overcome the block to virus infection. The assay for the SV40 T antigen was immunofluorescence; however, the immunoprecipitation technique did not detect T antigen in the infected embryonal carcinoma cells. Finally, the viral DNA present in the embryonal carcinoma was examined for its ability to replicate. These studies showed that viral DNA was not replicating as assayed by the viral DNA's sensitivity to UV irradiation when replicating in the presence of 5-bromodeoxyundine.
    Additional Material: 2 Ill.
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  • 138
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 219-234 
    ISSN: 0275-3723
    Keywords: collagen ; SLS ; phospholipid ; surfactant ; fibrillogenesis ; dipalmitoyl phosphatidyl choline ; electrostatic interactions ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The effect of dipalmitoyl phosphatidyl choline (DPPC), the major phospholipid component of pulmonary surfactant, on the precipitation of collagen in the form of native fibrils and segment-long-spacing (SLS) aggregates was studied in vitro. The effects of DPPC on both phases of collagen fibrillogenesis were analyzed spectrophotometrically, and alterations in the morphology of precipitated fibrils and SLS aggregates were ascertained by transmission electron microscopy (TEM). Low concentrations of DPPC inhibited the growth phase of fibrillogenesis, while higher concentrations were required to inhibit nucleation. Both the meshwork density and mean width of precipitated fibrils were altered by DPPC, as was the size of SLS aggregates. Segment-long-spacing aggregates prepared from pepsin-treated collagen were inhibited to a greater degree than SLS aggregates prepared from untreated collagen, indicating that the pepsin-susceptible residues of the telopeptide extensions of tropocollagen molecules stabilize SLS aggregates against the effects of DPPC. Based on these results and the inhibition of the growth phase at lower concentrations than those which inhibited the nucleation phase of fibrillogenesis, it was concluded that the primary mechanism of DPPC inhibition is electrostatic interference between the positively charged phospholipid molecules and the net positive charge of collagen. It is proposed that pathological conditions involving the pulmonary epithelium may allow interaction between surfactant and collagen, which could further weaken the interstitial connective tissue.
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  • 139
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 315-315 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 140
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 141
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 69-77 
    ISSN: 0275-3723
    Keywords: human breast epithelia ; glycoproteins ; proteinase inhibitors ; organ culture ; α-1-antichymotrypsin ; breast adenocarcinoma ; glandular structure ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The synthesis and release of glycoproteins were studied in organ cultures of human breast surgical specimens and in established breast epithelial cell lines, MCF-7 and MDA-MB-231. Biosynthesis was monitored by the incorporation of 14C-glucosamine. Labeled macromolecules in the culture supernatants were analyzed by biochemical and immunological techniques. One to 8% of the labeled glycoproteins from benign breast and infiltrating ductal carcinoma specimens was precipitated by antibodies produced against human serum 7α-1-antichymotrypsin. Twelve percent of the total glycoproteins from the culture supernatants of the MCF-7 cell line was identified as α-1-antichymo-trypsin. Both the normal serum and the human breast epithelia-derived proteinase inhibitor can be resolved into similar subclasses by two-dimensional gel electrophoresis. MDA-MB-231 and MCF-7 cells which were extensively washed with EDTA, serum-free medium, and phosphate-buffered saline retain this proteinase inhibitor on their cell surfaces. Three to 4% of the total cell-surface iodinated components was immunoprecipitated by these specific antibodies. Since α-1-antichymotrypsin is a potent inhibitor of neutral proteinases such as cathepsin G, the demonstration of its synthesis by benign and malignant breast epithelial cells is of considerable interest. This glycoprotein may represent the epithelia's own protective shield of cell surface components and the cell's attempt to moderate the effects of invading leukocytes. In addition, it may play a regulatory role in the maintenance of three-dimensional glandular structures.
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  • 142
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 99-120 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 7 Ill.
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  • 143
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 153-161 
    ISSN: 0275-3723
    Keywords: difference between cellular and plasma forms ; fibronectin ; monoclonal antibodies ; structure and function ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The reactivity of six monoclonal antibodies with fragments of fibronectin produced with trypsin, chymotrypsin, and Staphylococcus aureus V8 protease is described. All these antibodies reacted with fragments derived from the C-terminal one-third of fibronectin. This region probably contains sites for the binding of fibronectin to cells, and to heparin and may also contain active sites for the reattachment, spreading, and alignment of transformed cells. Analysis of the reactivities of different sets of proteolytic fragments with the antibodies and with other ligands (eg. heparin) allows one to determine overlaps between the fragments and to locate the positions of the different binding sites for antibodies and ligands. One of the antibodies has allowed us to identify a site of structural difference between cellular and plasma fibronectins from hamsters. The site recognized by this antibody is located near to, but not at, the C-terminal end and docs not involve carbohydrate groups. Because of its internal location in fibronectin, this difference suggests that there are probably different genes for cellular and plasma fibronectin. These monoclonal antibodies should be useful for further probing the functions present in the C-terminal regions of fibronectin and for determining their locations.
    Additional Material: 4 Ill.
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  • 144
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 163-181 
    ISSN: 0275-3723
    Keywords: spectrin-actin complex ; membranoskeleton ; immunoelectron microscopy ; membrane remodeling ; endocytosis ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The mature mammalian erythrocyte has a unique membranoskeleton, the spectrin-actin complex, which is responsible for many of the unusual membrane properties of the erythrocyte. Previous studies have shown that in successive stages of differentiation of the erythropoietic series leading to the mature erythrocyte there is a progressive increase in the density of spectrin associated with the membranes of these cells. An important stage of this progression occurs during the enucleation of the late erythroblast to produce the incipient reticulocyte, when all of the spectrin of the former cell is sequestered to the membrane of the reticulocyte. The reticulocyte itself, however, does not exhibit a fully formed membranoskeleton. In particular, the in vitro binding of multivalent ligands to specific membrane receptors on the reticulocyte was shown to cause a clustering of some fractions of these ligand-receptor complexes into special mobile domains on the cell surface. These domains of clustered ligand-receptor complexes became invaginated and endocytosed as small vesicles. By immunoelectron microscopic experiments, these invaginations and endocytosed vesicles were found to be specifically free of spectrin on their cytoplasmic surfaces.These earlier findings then raised the possibility that the maturation of reticulocytes to mature erythrocytes in vivo might involve a progressive loss of reticulocyte membrane free of spectrin, thereby producing a still more concentrated spectrin-actin membranoskeleton in the erythrocyte than in the reticulocyte. This proposal is tested experimentally in this paper. In vivo reticulocytes were observed in ultrathin frozen sections of spleens from rabbits rendered anemic by phenylhydrazine treatment. These sections were indirectly immunolabeled with ferritin-antibody reagents directed to rabbit spectrin. Most reticulocytes in a section had one or more surface invaginations and one or more intra-cellular vesicles that were devoid of spectrin labeling. The erythrocytes in the same sections did not exhibit these features, and their membranes were everywhere uniformly labeled for spectrin. Spectrin-free surface invaginations and intracellular vesicle were also observed with reticulocytes within normal rabbit spleens. Based on these results, a scheme for membrane remodeling during reticulocyte maturation in vivo is proposed.
    Additional Material: 8 Ill.
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  • 145
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 223-230 
    ISSN: 0275-3723
    Keywords: β-galactoside lectin ; galaptin ; erythropoiesis ; murine erythroleukemia cells (MELC) ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Recently, the generic term “galaptins” was proposed for the group of low molecular weight, acidic, β-galactoside-specific protein lectins that have been isolated from a wide variety of animal tissues and are thought to have a role in cell-cell recognition and adhesion. A molecule of this type, called erythroid developmental agglutinin (EDA), has been isolated from rabbit bone marow where it seems to mediate the intererythroblast adhesion seen in erythroblastic islands during erythropoiesis in vivo. Here, we show that after purification, EDA shows 95%-100% Coomassie blue staining as a single component on electrophoresis in native, urea, and SDS polyacrylamide gels and electrofocuses as a single band at pH 5.6. EDA has a subunit molecular weight of 13,000 in SDS gels and, unlike the majority of other galaptins, which arc dimeric, native EDA is monomeric in solution. Another monomeric galaptin, chicken lactose lectin II, has been described recently, and it therefore seems that there may be two classes of galaptin distinguishable by their aggregation state in solution.We have previously reported that EDA agglutinates rabbit erythroblasts in vitro and that this reaction is inhibited by β-galactoside-containing sugars and by anti-EDA Fab fragments suggesting that EDA bridges directly between cell surface glycoproteins. The insensitivity of this reaction to cooling, or to the disruption of cellular metabolism or the cytoskeleton demonstrated here further supports this hypothesis. EDA-mediated erythroblast agglutination was also shown to be independent of divalent cations.Since galaptins are thought to be important in cohesion between normal cells, the possibility that EDA is not active in leukemic erythroid tissue was examined. The murine erythroleukemia cell line (MELC) provided an excellent system for this study since MELC are thought to be derived from an erythroid committed cell transformed at an early stage of development and can be induced by a number of chemical agents to differentiate terminally along the erythroid developmental pathway in culture. EDA of rabbit origin was found to agglutinate mouse erythroblasts in vitro and was used to investigate the response of MELC to EDA. It was found that the transformed cells were not readily agglutinated by EDA but on induction, and the concomitant loss of many of their transformed characteristics, MELC gained aggregation competence for EDA. The possible causes of these differences are discussed.
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  • 146
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 139-153 
    ISSN: 0275-3723
    Keywords: ligatin ; phosphohexose ; acidic hydrolases ; membrane-bound receptor ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Ligatin, a receptor that recognizes phosphorylated sugars, was isolated from plasma membranes of mouse macrophages, rat ileum, and rat brain. Several acidic hydrolases including N-acetyl β-D-glucosaminidase (β-NAG) were solubilized with this receptor. The solubilized β-NAG bound to ligatin in vitro as demonstrated by affinity chromatography using the immobilized receptor. β-N-Acetyl D-glucosaminidase-ligatin complexes were dissociated by low concentrations of mannose 6-phosphate (Man6P) and/or glucose 1-phosphate (Glc 1P). The effectiveness of these two phosphomonosaccharides varied depending on the source of the enzyme: ileal β-NAG-ligatin complexes showed a four-fold preferential dissociation with Man6P; macrophage complexes showed a 160-fold preferential dissociation with Glc 1P. Brain complexes dissociated with nearly equal preference for Man6P and Glc 1P. Heterologous complexes displayed the specificity characteristic of the source of the enzyme regardless of the source of the ligatin. Treatment of the solubilized hydrolases with endoglucosaminidase H released phosphorous-32 label from these enzymes and prevented binding of β-NAG to ligatin. However, treatment of the solubilized hydrolases with alkaline phosphatase reduced the binding of β-NAG to ligatin by no more than 30%. This apparent resistance of β-NAG to dephosphorylation was consistent with the chromatographic behavior on QAE of 3H-labeled acidic oligosaccharides isolated from the solubilized hydrolases. The oligosaccharides that contain phosphorylated hexose were less acidic than phosphomonoesters and were insensitive to alkaline phosphatase until subjected to acid hydrolysis. These results suggested the presence of a phosphodiester on β-NAG analogous to the NAC glucosamine 1 P6 mannose present on β-glucuronidase isolated from mouse lymphoma cells (Tabas I, Kornfeld, S: J Biol Chem 255: 6633, 1980).
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  • 147
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 269-279 
    ISSN: 0275-3723
    Keywords: metabolic activation ; human cells ; polycyclic hydrocarbons ; aromatic amines ; heterocyclic hydrocarbons ; nitrosamines ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Human cells that appear capable of metabolizing various classes of carcinogens have been identified using one of two methods: metabolism of tritiated benzo(a)pyrene to aqueous-acetone soluble forms or inhibition of cellular DNA synthesis. Each of the assay systems was optimized and the results on 15 human epithelial cell lines were compared. One or more cell lines were found to activate each of four classes of carcinogens examined: polycyclic hydrocarbons, aromatic amines, heterocyclic hydrocarbons, and nitrosamines. Cells that appeared capable of metabolizing polycyclic hydrocarbons or aromatic amines by these methods were also found to produce metabolites which were cytotoxic to cocultivated human xeroderma pigmentosum fibroblasts after a 48-hr exposure to the carcinogen.
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  • 148
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 289-301 
    ISSN: 0275-3723
    Keywords: erythrocyte membrane proteins ; Ca2+-loaded erythrocytcs ; transglutaminase ; ionophore A23187 ; γ-glutamyl-∊-lysine cross links ; crossed immunoelectrophoresis ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: An increase in the intracellular concentration of Ca2+ in human erythrocytes results in the formation of γ-glutamyl-∊-lysine cross-linked membrane protein polymers. Following solubilization of the membranes with SDS, these polymers can be isolated on a Lubrol-containing sucrose gradient. Immunoelectrophoresis of the polymeric material with a polyspecific rabbit antibody against human ghosts gave rise to a single, but heterogeneous, precipitate. The polymer was amphiphilic and, on addition to Triton-solubilized erythrocyte membrane proteins, it coprecipitated with spectrin. When the antighost antibody was absorbed with the polymer prior to cross immunoelectrophoresis of normal erythrocyte membrane proteins, the precipitates of glycophorin, acetylcholinesterase, and hemoglobin were normal, whereas the anti-body liters against band 3 protein, spectrin, and ankyrin became reduced. Furthermore, a rabbit antibody raised against the isolated human polymer reacted selectively with the same three membrane proteins. No reactions occurred with lysate proteins.
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  • 149
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 311-336 
    ISSN: 0275-3723
    Keywords: in vitro carcinogenesis ; promoters ; hormones ; retinoids ; radiation protease inhibitors ; human cell transformation ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Mammalian cell cultures offer powerful tools for evaluating qualitatively and quantitatively the oncogenic potential of radiation over a wide range of doses with particular importance at the low dose range that is relevant to human exposure and risk. Our studies have shown that early events in the process of radiation induced transformation in both rodent and human cells requires initial replication for fixation of transformation as a hereditary property of the cells and further clonal expansion for full expression. Early events (fixation) are inhibited by cell-cell contact and high cell density but can be modified at low temperature where repair processes are slowed. Cell-cell contact and communication in tissue organization may be in part responsible for our findings that radiation oncogenesis induced in utero in hamsters is expressed at a lower frequency than that induced in vitro.Quantitative studies carried out on hamster embryo cells indicate that neutrons are more effective in their carcinogenic potential than x-rays but also more toxic, that splitting the dose of x-rays at low doses leads to enhanced transformation, but that at high doses protracted radiation has a sparing effect. At all dose ranges survival was increased by protracting the radiation dose, thus suggesting that different repair processes must be involved for survival and transformation. Similar observations were seen when the protease inhibitor Antipain was found to enhance transformation in rodent and human cells when present at the time of radiation, but was protective when added after radiation. Survival was not modified under any of those conditions, and Antipain did not affect DNA replication and repair. In our qualitative studies, once cells are transformed by radiation, they exhibit a wide range of structural and functional phenotypic changes, some of which are membrane-associated and are expressed within days after induction.Our current studies on nutritional and hormonal influences on radiation transformation indicate the following: Pyrolysate products from broiled protein foods act in synergism with radiation to produce transformation, whereas vitamin A analogs are powerful, preventive agents. Retinoids inhibit both x-ray-induced transformation and its promotion by TPA: these modifications (enhancement by TPA, inhibition by retinoids) are not reflected in sister chromatid exchanges, but are reflected in the level of membrane associated enzymes Na/K ATPase. Whereas retinoids modify late events (expression, promotion), we find that thyroid hormone plays a crucial role in the early phases of radiation and chemically induced transformation. Under hypothyroid conditions no transformation is observed. The addition of triiodothyronine at physiological levels results in a transformation rate that is dose-related.Our recent success in transforming human skin fibroblasts will enable quantitative and qualitative studies of radiation carcinogenesis in a system relevant to man.
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 371-376 
    ISSN: 0275-3723
    Keywords: Chlamydomonas ; flagellar adhesion and deadhesion ; tunicamycin ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The aggregation-dependent loss of flagellar adhesiveness in Chlamydomonas reinhardi has been correlated with changes in flagellar tip morphology during adhesion and deadhesion. As aggregating mt- and impotent (able to adhere, but not fuse) mt+ gametes begin to disaggregate in the presence of the protein synthesis inhibitor cycloheximide, there is a concomitant change in flagellar tip morphology from the activated bulbous form to the nonactivated tapered shape. The requirement of protein-synthetic activity for the maintenance of flagellar adhesiveness during aggregation may be due in part to turnover of proteins involved in formation or stabilization of activated flagellar tips.Incubation of aggregating gametes with tunicamycin indicates that, like protein synthesis inhibitors, this inhibitor of glycosylation also causes adhering gametes to deadhere. The results suggest that protein glycosylation may be essential for maintenance of adhesiveness during aggregation.
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  • 151
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 1-9 
    ISSN: 0275-3723
    Keywords: cell aggregation ; aggregation factor ; sponges ; glycoproteins ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Antibodies were raised against the purified aggregation factor from Geodia cydonium in order to clarify its function during cell aggregation in the homologous and heterologous system. These antibodies inhibited only cell aggregation in the homologous Geodia system and were inactive in the heterologous Tethya lyncurium system. These findings directly indicated that the species-specific reaggregation of sponge cells was initiated by the soluble aggregation factor as already assumed in earlier studies. The amount of neutralizing antibodies was determined by a precipitation reaction with the antigen in capillaries and by microdiffusion. By using the latter technique we got evidence that the Geodia aggregation factor contained a component that was antigenetically related to a galactose-specific lectin present in Geodia cydonium.
    Additional Material: 5 Ill.
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  • 152
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 377-384 
    ISSN: 0275-3723
    Keywords: bone marrow preadipocyte ; bone marrow stroma ; cell lines ; insulin ; insulin-induced marrow stroma ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Adipose cells have been recognized as an integral component of the bone marrow hematopoietic microenvironment in vivo and as an essential cell type required for in vitro maintenance of stem cells. Four stromal cell lines obtained from the adherent cell population of murine bone marrow cultures have been enriched and purified by multiple trypsinizations. We noted that these cell lines exhibited an accumulation of vacuoles of lipid, the extent of which varied be-tween cell lines in response to a change from medium containing 10% fetal calf serum to medium containing 20% horse serum. The lipid was lost when the cell lines were transferred back into the medium supplemented with fetal calf serum. In light of the reported lipogenic and antilipolytic effects of insulin on fibroblasts and adipocytes, we investigated the ability of insulin to induce adipocyte transformation of these bone marrow stromal cell populations. Three cell lines were exposed to bovine insulin at concentrations ranging from 10-9 to 10-6 M. All three cell lines responded to the insulin by accumulating lipid, but the extent of accumulation and the insulin concentration at which maximum lipid content was attained were population specific. One cell line (MC1) responded fully at physiological levels of insulin (10-9 M), whereas the other two showed lipid accumulation only at pharmacological concentrations. The initial growth of MC1 was inhibited in the presence of 10-9 M insulin which is compatible with the observed differentiation to adipocytes. The growth of MC3 was unaltered in the presence of physiological concentrations of insulin, whereas that of MC4 was accelerated. Grafts of organ cultures of the cell lines under the kidney capsule of syngeneic mice developed specific characteristics rep-resentative of the different cell lines. In particular, the majority of the grafts of MC1 consisted primarily of fat cells which were not observed in the grafts of MC3 and MC4. These data strongly suggest that these cell lines comprise cells with different potentialities and that the MC1 line represents a preadipocyte stromal cell of bone marrow.
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  • 153
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 51-60 
    ISSN: 0275-3723
    Keywords: retina ; glycoproteins ; surface label ; cell sorting ; embryonic ; neural cells ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In order to test the hypothesis that the progressive layering and differentiation of cell types during the development of the neural retina are associated with cell surface alterations we have separated distinct cell populations from the 14-day embryonic chick retina. Cells of these populations have been shown to differ in associative behavior and intramembrane particle content. We now report that these cells differ in cell surface glycoproteins. Proteins were labeled with two different extrinsic labels and one metabolic label. We used enzymatic transfer of galactose from UDP-gal to cellular acceptors, and borotritide reduction after galactose oxidation as extrinsic labels. Glucosamine incorporation was used as the metabolic label. In all these cases, we were able to identify bands on electrophoretic gels which were unique to individual populations.
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  • 154
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 27-36 
    ISSN: 0275-3723
    Keywords: Edman degradation ; protein sequencing ; DNA synthesis ; peptide synthesis ; mass spectrometer ; genetic engineering ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A number of cell surface molecules of great theoretical and practical importance simply cannot be obtained in amounts sufficient for molecular analysis using conventional methods and instrumentation. Because of our interest in such studies, we began about eight years ago to explore the possibility of developing new instrumentation for the sequence analysis of very small quantities of polypcptide chains. These efforts have led to the development of two microsequenators which employ one thousandth to one ten-thousandth the material used in the original sequenator described by Per Edman. In addition, in conjunction with the explosion of recombinant DNA techniques, we also have begun to develop instrumentation for the sequence analysis and synthesis of DNA molecules. In this paper we describe briefly several new instruments that have been developed at Caltech. We believe this new instrumentation in conjunction with the recombinant DNA and hybridoma technologies will provide unique opportunities to analyze cell-surface molecules in the years ahead.
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  • 155
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 37-49 
    ISSN: 0275-3723
    Keywords: DNP ; T-independent ; flagellin ; fluoresence photobleaching recovery ; stimulation ; photobleaching ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fluorescence photobleaching recovery techniques have allowed us to measure the lateral mobility of T-independent antigens bound to antigen-specific mouse B cells. The in vitro immunogenicity or tolerogenicity of antigens we have examined, DNP-polymerized flagellin (DNP-POL), and DNP-linear dextran (DNP-DEX), depend upon the antigen dose and epitope density. These factors also determine the mobility of antigen bound to B cell surfaces. For DNP-POL bound to DNP-specific cells, the observed diffusion constants D decrease monotonically with increasing antigen dose and epitope density. Values of D range from 10.4 × 10-11 cm2 sec-1 for DNP0.4-POL at 0.15 μg/ml to 0.8 × 10-11cm2 sec-1for DNP3.5-POL at 30 μg/ml. For receptor-bound DNP-DEX, D depends strongly on antigen epitope density but not observably on antigen concentration. For epitope densities of 1.2 or less, D is close to the value of 21 × 10-11cm2sec-1 observed for single slg receptors. By an epitope density of 4.8, D has fallen to 2.1 × 10-11cm2sec-1. Peak immunogenicities for DNP-POL and DNP-DEX arc observed when antigen- receptor aggregates have mobilities 14-fold and 3-fold lower, respectively, than a single slg molecule.
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  • 156
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 91-98 
    ISSN: 0275-3723
    Keywords: plarelets ; fibronectin ; hemostasis ; cell adhesion ; aggregation ; secretion ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Thrombin stimulation of human platelets causes increased cellular adhesiveness for other platelets (aggregation) and surfaces and increased surface expression of platelet fibronectin antigen. Aggregation occurs concurrently with secretion. In these studies, the threshold thrombin dose for surface expression of fibronectin, as measured by binding of F(ab′)2 antifibronectin, was similar to that for serotonin secretion. Moreover, both processes occurred at similar rates, and inhibition of secretion was associated with inhibition of antifibronectin binding. Thus a hypothesis is proposed in which adhesive proteins within platelet granules become expressed on the platelet surface as a direct consequence of the secretory process. This cluster of adhesive proteins may then contribute to increased cellular adhesiveness.
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  • 157
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 133-146 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 2 Ill.
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  • 158
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 1-13 
    ISSN: 0275-3723
    Keywords: insulin receptors ; photoaffinity labeling ; electrophoresis ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Photoaffinity labeling techniques were used to identify insulin-binding components of the plasma membrane in insulin-responsive, monolayer-cultured hepatoma cells. The activated, photosensitive reagent, an n-hydroxysuccinimide ester of 4-azidobenzoic acid, was coupled with highly purifed insulin, and the hormone derivative was subsequently iodinated, bound to cell surface receptors of intact H4 cells, and photoactivatcd. After dissolution of the cells, labeled proteins were analyzed by SDS/polyacrylamide gel electrophoresis under reducing conditions. The main labeled band exhibited an apparent molecular weight of 130,000. Two minor components of apparent mol wt 95,000 and 40,000 were also identified. Specific labeling of all 3 bands was inhibited by simultaneous incubation of the cells with native insulin, but not by the heterologous hormone, glucagon, prior to photoactivation. Binding of azidobenzoyl-insulin to H4 cells was time-dependent, as was the correlated labeling of receptor components. Band-labeling by the photosensitive insulin derivative was totally light-dependent; spontaneous covalent linking of insulin and receptor was not observed. The labeled receptor-related proteins were not degraded by the cells under our experimental conditions.
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  • 159
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 29-40 
    ISSN: 0275-3723
    Keywords: serum ; neoplastic ; non-neoplastic ; growth ; cell area ; cell spreading ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Both growth factor availability and cell-to-cell contact have been mechanisms used to explain cell growth regulation at high cell density. Recently Folkman and colleagues have shown that changes in cell shape, rather than cell-to-cell contact, can regulate the growth of fibroblasts. However, in those studies the relation between serum and shape regulation of growth was not studied, nor were neoplastic and non-neoplastic cells compared. In this report we have studied these aspects by varying cell spreading and serum concentration independently for 2 non-neoplastic and 3 neoplastic cell lines. Cell spreading (projected cell area) was controlled by decreasing the adhesiveness of tissue culture plastic plates with poly (hydroxyethyl methacrylate) [poly (HEMA)]. Cell growth was measured as the increase in cell number/day. We have found that more spreading increased net growth of both neoplastic and non-neoplastic cells, while less spreading (toward rounded configuration) depressed growth. There were also quantitative differences between neoplastic and non-neoplastic cells. Neoplastic cells continued to grow under conditions of cell rounding, which completely prevented the growth of their non-neoplastic counterparts. Some neoplastic cells also tended to show little or no increase in net cell number for serum concentrations above 10% as cells became more spread; in contrast, all non-neoplastic cells grew more with increasing concentrations of serum as they became well spread. Thus, in normal cells, it appears that the sensitivity of cells to humoral factors is governed by cell spreading. This interaction between serum and cell shape is less prominent in some neoplastic cells.
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  • 160
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 161
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 111-117 
    ISSN: 0275-3723
    Keywords: hatching enzyme ; proteases ; limited proteolysis ; Xenopus ; envelopes ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Hatching in the amphibian Xenopus laevis involves release of an embryo-secreted hatching enzyme, a protease, which weakens the envelope surrounding the embryo. The envelope is not totally solubilized, which infers that only selected envelope components are hydrolyzed by the enzyme. The susceptibility of the glycoprotein components composing the envelope to hydrolysis by the hatching enzyme was investigated. Isolated envelopes in various physical states, ie, particulate and solubilized, were treated with the hatching enzyme, and the resulting envelope hydrolysis products were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The susceptibility of the envelope components to proteolysis was not a function of the state of the envelope. The envelope components most susceptible to proteolysis were the 125K and 11 8K components followed by the 60K and 71 - 77K components. These components are minor constituents of the envelope. The major constituents, 33K and 40K, were relatively resistant to hydrolysis by the hatching enzyme. From these observations, we infer that the envelope components hydrolyzed are components that link or bind together the major structural elements of the envelope, eg, the 33K and 40K components. Selective destruction of the components required for maintaining the structural integrity of the envelope, eg, the “nuts and bolts” of the structure, permits a weakening of the envelope that allows the embryo to hatch without having to destroy totally (hydrolyze) the envelope.
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  • 162
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 153-159 
    ISSN: 0275-3723
    Keywords: bombesin receptors ; guanine nucleotides ; neuropeptide receptors ; vasoactive intestinal polypeptide (VIP) receptors ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The effect of nucleotides on central nervous system neuropeptide receptor binding was investigated. The guanine nucleotides, guanosine-5′-triphosphate and guanylyl-5′-imidodiphosphate, significantly inhibited the binding of radiolabeled vasoactive intestinal polypeptide but not that of [Tyr4]bombesin to rat brain membranes. Vasoactive intestinal polypeptide binding was inhibited by guanine nucleotides in a dose-dependent manner. Using a 20 μM dose, 60% of the specific vasoactive intestinal polypeptide binding was inhibited by guanylyl-5′-imidodiphosphate, which was more potent than guanosine-5′-triphosphate, whereas other nucleotides were not effective. This reduction in binding was a consequence of lower affinity of the receptor for vasoactive intestinal polypeptide, which in turn resulted from an increased rate of dissociation.
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  • 163
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 164
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 193-204 
    ISSN: 0275-3723
    Keywords: neonatal imprinting ; cytochrome P-450 development ; sex-dependent differences ; microsomal drug metabolism ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A new form of cytochrome P-450 was partially purified from hepatic microsomes of neonatally imprinted rats (adult male and adult male castrated at four weeks of age). This new form of cytochrome P-450 appears to have an apparent molecular weight of approximately 50,000 daltons as judged by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It appears that this form of cytochrome P-450 is either absent or present in low concentrations in cytochrome P-450 preparations isolated from neonatally nonimprinted rats (adult female and adult male castrated at birth). Reconstitution of testosterone hydroxylase and benzphetamine N-demethylase activities of this partially purified cytochrome P-450 revealed that the presence of testosterone 16α-hydroxylase activity, an imprintable microsomal enzyme, was in parallel with the imprinting status of the animals; a significantly higher activity was detected in the neonatally imprinted than that of the nonimprinted animals. This was in contrast to the nonimprintable benzphetamine N-demethylase, testosterone 7α-and 6β-hydroxylase activities which exhibited no correlation with the imprinting status of the animals.We have prepared antisera from rabbits using the partially purified cytochrome P-450 preparations from adult male rats as antigens. These antisera inhibited microsomal testosterone 16α- and 7α-hydroxylase activities in a concentration-dependent manner, without impairing 6β-hydroxylase activity. These data suggest that the partially purified cytochrome P-450 from adult male rats consists of both imprintable (16α-) and nonimprintable (7α-) testosterone hydroxylase activities. The antisera formed immunoprecipitant lines in the Ouchterlony double diffusion plates with partially purified cytochrome P-450 from both neonatally imprinted and nonimprinted adult rats. The immunoprecipitant lines, as stained by coomassie blue, suggest the homology of the cytochrome P-450 preparations from neonatally imprinted and nonimprinted rats. Immunoabsorption of the antisera against neonatally nonimprinted, partially purified cytochrome P-450 completely removed the immunoprecipitant lines without appreciably impairing the inhibitory effects of antisera on the microsomal testosterone 16α-and 7α-hydroxylase activities. In contrast, immunoabsorption of the antisera against partially purified cytochrome P-450 from adult male rats (imprinted) abolished completely both the immunoprecipitant lines and the inhibition on microsomal testosterone hydroxylation reaction (16α and 7α). The inhibitory actin of antisera on testosterone hydroxyulation was also abolished upon boiling the antisera at 100°C for 5 minutes.The biochemical and immunochemical data in this study suggest that the neonatally imprintable form or forms of hepatic microsomal cytochrome P-450 accounts for a small fraction of the bulk of total cytochrome P-450. However, the existence of this form of cytochrome P-450 is regulated by gonadal hormones during the neonatal period and accounts for the major imprintable sex difference in drug and steroid metabolism in adulthood.
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  • 165
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 235-251 
    ISSN: 0275-3723
    Keywords: EGF ; coated vesicles ; internalization ; lysosomes ; NH4C1 ; hormone degradation ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Epidermal Growth Factor (EGF), a small polypeptide which acts as a mitogen for many cell types, has previously been shown to bind to a specific plasma membrane receptor on 3T3 cells. If 125I-EGF is bound to 3T3 cells for one hour at 4°C, it remains predominantly associated with the plasma membrane-containing fractions obtained by subjecting cell supernatants to equilibrium sedimentation on sucrose gradients. When binding is followed by a 10-minute incubation at 37°C, over 50% of the 125I-EGF is associated with two internal membrane-containing peaks having higher densities than the plasma membrane. After one hour at 37°C, over 80% of the 125I-EGF is degraded and removed from the cells.The most rapidly labeled internal peak corresponds in density to brain-coated vesicles (CVs). Antiserum prepared against coated vehicles from brain precipitates the 125I-EGF in this peak. In addition, CVs containing 125I-EGF can be co-purified from 3T3 cells exposed to 125I-EGF, using brain as a carrier. Several lines of evidence suggest that the other 125I-EGF-labeled intracellular peak is 125I-EGF in lysosomes.These results provide kinetic and biochemical evidence for a unidirectional pathway for EGF catabolism by 3T3 cells. EGF first binds to the plasma membrane bound receptors, is then moved to the cytoplasm in CVs, and finally appears in lysosomes, where it is degraded and released from the cells. Ten-millimolar NH4Cl blocks lysosomal hydrolysis of EGF almost completely. Subsequently, EGF internalization is inhibited. This finding suggests that the pathway for EGF internalization and degradation is tightly coupled.
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  • 166
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 287-301 
    ISSN: 0275-3723
    Keywords: transforming growth factor ; sarcoma growth factor ; epidermal growth factor ; membrane receptor ; tumor promoter ; retinoid ; growth factors ; transformation ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Transforming growth factors (TGFs) are growth-promoting polypeptides that cause phenotypic transformation and anchorage-independent growth of normal cells. They have been isolated from several human and animal carcinoma and sarcoma cells. One TGF is sarcoma growth factor (SGF) which is released hy murine sarcoma virus-transformed cells. The TGFs interact with epidermal growth factor (EGF) cell membrane receptors. TGFs are not detectable in culture fluids from cells which contain high numbers of free EGF cell membrane receptors. SGF acts as a tumor promoter in cell culture systems and its effect on the transformed phenotype is blocked by retinoids (vitamin A and synthetic analogs). The production of TGFs by transformed cells and the responses of normal cells to the addition of TGFs to the culture medium raise the possibility that cells “autostimulate” their own growth by releasing factors that rebind at the cell surface. The term “autocrine secretion” has been proposed for this type of situation where a cell secretes a hormone-like substance for which it has external cell membrane receptors. The autocrine concept may provide a partial explanation for some aspects of tumor cell progression.
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  • 167
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 335-346 
    ISSN: 0275-3723
    Keywords: cell surface antigen ; cerebellum ; development ; mouse ; indirect immunofluorescence ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A monoclonal antibody designated M2 arose from the fusion of mouse myeloma cells with splenocytes from a rat immunized with particulate fraction from early postnatal mouse cerebellum. Expression of M2 antigen was examined by indirect immunofluorescence on frozen sections of developing and adult mouse cerebellum and on monolayer cultures of early postnatal mouse cerebellar cells. In adult cerebellum, M2 staining outlines the cell bodies of granule and Purkinje cells. A weaker, more diffuse staining is seen in the molecular layer and white matter. In sections of newborn cerebellum, M2 antigen is weakly detectable surrounding cells of the external granular layer and Purkinje cells. The expression of M2 antigen increases during development in both cell types, reaching adult levels by postnatal day 14. At all stages of postnatal cerebellar development, granule cells that have completed migration to the internal granule layer are more heavily stained by M2 antibodies than are those before and in process of migration. In monolayer cultures, M2 antigen is detected on the cell surface Of all GFA protein-positive astrocytes and on more immature oligodendrocytes, that express 04 antigen but not 01 antigen. After 3 days in culture, tetanus toxinpositive neurons begin to express M2 antigen. The same delayed expression of M2 antigen on neurons is observed in cultures derived from mice ranging in age from postnatal day 0 to 10.
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  • 168
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 359-367 
    ISSN: 0275-3723
    Keywords: sulfated glycoconjugates ; endothelial cell ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Endothelial cells derived from human pulmonary arteries incorporate (3H)-glucosamine and 35SO4 into glycosaminoglycans and into the carbohydrate side chains of glycoproteins. These 3H/35S-carbohydrate chains were isolated from cells and culture medium after Pronase digestion. The 3H/35S-glycosaminoglycans were separated from the 3H/35S glycopeptides by chromatography on Sephadex G-50. The distribution of cellular glycosaminoglycans and glycopeptides indicated that 30-60% of the cellular 35S-glycopeptides may be associated with the matrix components that are synthesized by the cell and attached to a plastic substratum. Human pulmonary arterial endothelial cells were grown on collagen or on a matrix derived from vascular smooth muscle cells in order to investigate how smooth muscle cell extracellular matrix components may regulate the synthesis of endothelial cell glycoconjugates. Endothelial cells grown on plastic release various proportions of the glycoconjugates they synthesize into the culture medium. However, these same cells, when grown on substratum composed of extracellular matrix materials, synthesized altered proportions of cell-associated glycosaminoglycans and reduced the levels of total glycosaminoglycans they released into the culture medium. Thus the growth of endothelial cells on a matrix of smooth muscle cell components indicates that the glycosaminoglycan materials released into the culture medium by cells grown on a plastic substratum may not be an accurate reflection of the levels or composition of extracellular matrix materials made by endothelial cells in vivo.
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  • 169
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 170
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 43-52 
    ISSN: 0275-3723
    Keywords: cell recognition ; reversal of cell interaction ; target cell interaction ; cytolytic T lymphocytes ; H-2 recognition ; reversal ; cell adhesion ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A functional assay is described that measures the reversal of specific cytolytic T cell (CTL)-target cell binding. Binding of 51Cr-labeled P815 cells was stable in suspension but could be readily reversed by the addition of unlabeled P815 cells. The reversal of CTL-tumor cell and CTL-spleen cell binding was H-2 specific; only cells of the same H-2 type as the bound target cell could induce reversal. In all cases, tumor cells were substantially more efficient than spleen cells in inducing specific reversal.
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  • 171
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 53-74 
    ISSN: 0275-3723
    Keywords: development ; neurological mouse mutants ; cerebellum ; glial antigens ; monoclonal antibodies ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The distribution of two glial antigens (C1 and M1) has been studied by indi-rect immunofluorescence during postnatal development of the cerebella of normal and neurologically mutant mice (weaver, staggerer, reeler, Purkinje cell degeneration, and wobbler). During the first postnatal week of normal development, C1 antigen is expressed in ependyma, Bergmann glial fibers (BG), and astrocytes of the internal granular layer and white matter. After day 10, C1 antigen is restricted to BG and ependymal cells. During the sec-ond and third week, BG undergo a transient loss of C1 antigen that starts in medioventral areas and spreads in a gradient dorsally and laterally.In reeler, weaver, and staggerer, C1 antigen expression is normal during the first postnatal week, and subsides in BG in a similar spatial gra- dient as described for the normal littermates. However, the loss of C1 anti-gen in BG occurs earlier (first in reeler, then in weaver, and last in staggerer) and is not reversible as it is in normal mice. In Purkinje cell de-generation, C1 antigen expression is diminished in BG after the onset of be-havioral abnormalities. Wobbler is normal with respect to C1 antigen ex-pression at adult ages.M1 antigen is detectable in white matter astrocytes from postnatal day 7 on, and persists in these cells into adulthood. Astrocytes of the internal granular layer and BG express M1 antigen only transiently in normal mice during the second and third weeks. The appearance of M1 antigen in BG occurs in a spatiotemporal gradient, matching the one in which C1 antigen disappears. M1 antigen expression is abnormally maintained in BG of reeler, staggerer, and weaver. In Purkinje cell degeneration, M1 antigen is ex-pressed abnormally at the onset of behavioral abnormalities first in.astro-cytes of the internal granular layer and, with growing age, increasingly also in BG. In wobbler, BG do not express M1 antigen. However, astrocytes of the granular layer are abnormally M1 antigen-positive.
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  • 172
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 173
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 121-131 
    ISSN: 0275-3723
    Keywords: H-2 antigen ; liposomes ; plasma membrane matrix ; cytolytic T lymphocytes ; cell-liposome interaction ; H-2 recognition ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Liposomes containing purified H-2Kk will specifically stimulate generation of a secondary allogeneic cytolytic T lymphocyte response. Effective recognition was found to depend on the structure of the liposomes. Including detergent-insoluble plasma membrane matrix during formation resulted in liposomes having two- to fourfold more activity than those prepared using just lipid and H-2.
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  • 174
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 115-120 
    ISSN: 0275-3723
    Keywords: insulin ; T cell proliferation ; Ia molecules ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The immune responses to several antigens were compared in the I-A mutant mouse strain B6.C-H-2bm12 and the wild-type strain C57BL/6. With a lymph node cell proliferation assay, the response to two of these antigens, beef insulin and (TG)A-L, was demonstrated to be controlled by a gene in the I-Ab region. B6.C-H-2bm12 mice failed to respond to beef insulin, while their responses to (TG)A-L, DNP-OVA and PPD were comparable with those of the wild-type strain C57BL/6. Taken together with previous studies, these data suggest that the product of a single pleiotropic I-A gene, an la molecule, functions as a histocompatibility, la, and MLR antigen, as well as a necessary component for Ir gene function. Furthermore, the data reported here demonstrate that la molecules have multiple functional “Ir determinants,” one of which has been altered in the B6.C-H-2bm12 mutant. The B6.C-H-2bm12 mice, therefore, represent a powerful analytical tool for the understanding of the cellular and molecular basis for Ir gene control of the immune response.
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  • 175
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 155-165 
    ISSN: 0275-3723
    Keywords: polymorphonuclear leukocyte ; rabbit ; tannic acid-glutaraldehyde ; ionophore ; A23187 ; degranulation ; membrane fine structure ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: TAG fixation of normal and Ca2+ ionophore-treated rabbit polymorphonuclear leukocytes (PMN) has revealed membrane components not apparent with conventional glutaraldehyde fixation. These included a 30 Å external electron-dense coating on untreated cells. A somewhat thicker coat (40 Å) was observed in ionophore-treated, nondegranulating PMN. In ionophore-treated, degranulating PMN, a 65 Å cell membrane coat was observed. A similar coat was observed on the inner side of the membrane of some azurophil-type granules, but the electron density and thickness were not so pronounced. Cytoplasmic granules were often closely apposed and often protruded outward at the plasma membrane. Extracellular lamellae, sometimes stacked apposed to the plasma membrane, possibly represent remnants of intense granule extrusion. Sequential degranulation of the respective granules was not apparent.
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  • 176
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 177
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 221-232 
    ISSN: 0275-3723
    Keywords: gap junctions ; protein turnover ; junction synthesis ; junction degradation ; liver ; regenerating liver ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: By the use of a simple, rapid method for the isolation of gap junctions from small amounts of rat liver (2-3 g), we have followed the incorporation of the radiolabeled amino acid precursors 3H-leucine and 35S-methionine into the gap junction protein. In timed studies with 35S-methionine as precursor, the specific activity in the protein is maximal by 4 h after a single injection of 300 μCi/100 g body weight. From the decay in the specific activity with time after a single injection, the gap junction protein has an apparent half-life of about 19 h. Because of problems of reutilization of radiolabeled amino acid with 35S-methionine as precursor, this apparent halflife probably overestimates the true half-life and indicates a surprisingly rapid turnover of the gap junction protein. This short half-life suggests that, in rat liver, the gap junctions may be very responsive to alterations in physiological demands.
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  • 178
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 243-258 
    ISSN: 0275-3723
    Keywords: liposomes ; liposome-protein coupling ; fluorescence ; monoclonal antibody ; cell surface antigens ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have evaluated optimal conditions for coupling monoclonal antibody to small unilamellar lipisomes. Coupling of an IgG2a monoclonal anti-β2-microglobulin antibody, which reacts with human cells, was examined in detail. Liposomes were composed of dipalmitoyl lecithin and cholesterol, and variable quantities of phosphatidylethanolamine substituted with the heterobifunctional cross-linking reagent N-hydroxysuccinimidyl 3-(2-pyridyldithio) propionate (SPDP). They were reacted with antibody derivatized with the same reagent at a 5- to 20-fold molar excess, and activated by mild reduction. This degree of SPDP modification had no effect on the capacity of the antibody to bind to its target antigen. More than 40% of antibody could be reproducibly bound to liposomes, resulting in the coupling of from 1 to 10 antibody molecules per liposome (mean diameter.580 Å). The coupling reaction did not lead to loss of carboxyfluorescein encapsulated within liposomes. At least 80% of liposomes carried nondenatured antibody, as confirmed by precipitation of liposomes and encapsulated carboxyfluorescein by Staphylococcus aureus, strain Cowan I. The liposome-coupled antibody retained its immunological specificity: only cells expressing human β2-microglobulin bound liposomes in vitro, and the binding was inhibited by the free antibody in solution. Results with antibodies of different antigenic specificity confirm that the technique can be generally applied.
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  • 179
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 281-288 
    ISSN: 0275-3723
    Keywords: DNA repair synthesis ; normal human lymphocytes ; nicotinamide ; nicotinamide adenine dinuclcotide (NAD) ; ornithine decarboxylase ; poly(ADP-ribose) ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The effect of nicotinamide on unscheduled DNA synthesis was studied in resting human lymphocytes. In cells treated with UV irradiation or with MNNG, nicotinamide caused a two-fold stimulation of unscheduled DNA synthesis and retarded the rate of NAD+ lowering caused by these treatments. Nicotinamide also reduced the burst of poly(ADP-ribose) synthesis caused by MNNG treat-ment. Thus under conditions that it enhances unscheduled DNA synthesis, nicotinamide causes marked effects on the metabolism of NAD+ and poly(ADP-ribose). The effect of nicotinamide on unscheduled DNA synthesis was shown to be independent of protein or polyamine synthesis.
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  • 180
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    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 337-343 
    ISSN: 0275-3723
    Keywords: neutral filter elution ; human cells ; carcinogenesis ; excision repair ; DNA ; double-strand breaks ; S1 nuclease ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: DNA DSBs are formed in normal human IMR-90 cells during repair incubation after 100 and 300 J·m-2 of UVL. By contrast, no DSBs are formed after UVL in human XPA cells that are unable to excise pyrimidine dimers. The DSBs are not due to immediate cell death since all the cells excluded trypan blue at the time of assay and because XPA cells, which are much more UVL-sensitive than IMR-90, did not form DSBs after UVL. We suggest that these repair-induced DSBs should be potent lesions that might lead to cytotoxicity, chromosome aberrations, deletion mutations, and perhaps cellular transformation, transformation.
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  • 181
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    Keywords: Chemistry ; Molecular Cell Biology
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  • 182
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 11-25 
    ISSN: 0275-3723
    Keywords: sulfhydryl compounds ; Methylthio groups ; macrophages ; serum growth factors ; methylthioadenosine ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Macrophages are shown to replace methylthio disulfides in supporting in vitro proliferation of three cell lines previously characterized as methylthio-dependent. Macrophages have the capacity to generate methylthio groups from methylthioadenosine. It is hypothesized that macrophages stimulate cell proliferation both in normal immune systems and in certain cancers by providing an abundance of methylthio groups. Fetal calf serum is shown to contain methylthio groups. It appears that, in cell cultures containing fetal calf serum, sulfhydryl compounds stimulate cell proliferation by making the methylthio groups in the serum available to the cells.
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  • 183
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 61-67 
    ISSN: 0275-3723
    Keywords: diffusion ; fluorescence photobleaching ; interactions with cytoskeleton ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A theoretical analysis is presented for the interrelated effects of lateral diffusion and a simple form of molecular association (A + B ⇌ C) in biological membranes. Expressions are derived for the characteristic functions measured in fluorescence redistribution after photobleaching experiments, corresponding to both the Fourier transform analysis of concentration in a plane and the normal mode analysis for a spherical surface. The results are related to the reputed binding of integral membrane proteins to submembranous cytoskeletal elements.
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  • 184
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 87-90 
    ISSN: 0275-3723
    Keywords: Xeroderma pigmentosum ; poly(ADP-ribose) ; DNA repair ; UV ; N-methy-n′-nitro-N-notrosoguanidine ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Unscheduled DNA synthesis has been measured in human fibroblasts under conditons of reduced rates of conversion of NAD to poly(ADP-ribose). Cells heterozygous for the xeroderma pigmentosum genotype showed normal rates of UV induced unscheduled DNA synthesis under conditions in which the rate of poly(ADP-ribose) synthesis was one-half the rate of normal cells. The addition of theophylline, a potent inhibitor of poly(ADP-ribose) polymerase, to the culture medium of normal cells blocked over 90% of the conversion of NAD to poly(ADP-ribose) following treatment with UV or N-methyl-N′-nitro-N-nitro-soguanidine but did not affect the rate of unscheduled DNA synthesis.
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  • 185
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 186
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 121-131 
    ISSN: 0275-3723
    Keywords: SV40 ; DNA repair ; SOS functions ; mutagenesis ; carcinogenesis ; recombination ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We describe the use of Simian Virus 40 (SV40) as a molecular probe for studying the cellular functions induced in cultured monkey kidney cells in response to DNA damaging agents. aUltraviolet (UV) irradiation of SV40-infected cells inhibits viral DNA replication. Replication forks are blocked by the first pyrimidine dimer encountered. In some cases, a single-strand break seems to occur at the level of the dimer inhibiting the fork of replication. This break, which can be visualized by electron microscopy studies, might be the first step in an excision repair pathway.bTreatment of monkey kidney cells with acetoxy-acetyl-aminofluorene or UV light before infection with UV-irradiated SV40 induces a mutagenic replication mode, as shown by an increase of the mutation frequency of thermosensitive SV40 mutants.cA possible recombination assay using various SV40 mutants infecting the same cell is proposed and discussed.
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  • 187
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981) 
    ISSN: 0275-3723
    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 188
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 197-211 
    ISSN: 0275-3723
    Keywords: adhesion ; Dictyostelium discoideum ; contact sites A ; development ; immune staining after polyacrylamide gel electrophoresis ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have prepared antisera in rabbits to the “contact sites A” glycoprotein (gp80) purified from Dictyostelium discoideum. IgG isolated from these anti-sera reacts with a number of different proteins in D discoideum lysates, as analyzed by immune precipitation and by antibody staining of gel electropherograms transferred to nitrocellulose. Blocking experiments indicate that this cross-reactivity reflects the presence of common antigeneic determinants on gp80 and other cellular proteins, rather than the presence of extraneous antibodies in the antisera. The spectrum of reactive proteins is different a: different stages of development. In particular, gp80 itself is synthesized only for a restricted period during the cell aggregation phase. The protein persists throughout development and can be detected in spores. Anti-gp80 Fab fragments bind to the surface of developing D discoideum cells and specifically block their developmentally regulated adhesion. After absorption with vegetative cells, the IgG stains only gp80 and (to a lesser extent) one other band in lysates of aggregation-competent cells. The absorbed antibodies also can block adhesion. Several proteins that appear late in development also arc stained by the absorbed IgG.
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  • 189
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 231-244 
    ISSN: 0275-3723
    Keywords: acelylammofluorene ; Z-DNA ; base displacement model ; DNA conformation ; circular dichroism (CD) ; NMR ; nuclease S1 digestion ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Modification of DNA by the carcinogen N-acetoxy-N-2-acetylaminofluorene gives two adducts, a major one at the C-8 position of guanine and a minor one at the N-2 position with differing conformations. Binding at the C-8 position results in a large distortion of the DNA helix referred to as the “base displacement model” with the carcinogen inserted into the DNA helix and the guanosine displaced to the outside. The result is increased susceptibility to nuclease S, digestion due to the presence of large, single-stranded regions in the modified DNA. In contrast, the N-2 adduct results in much less distortion of the helix and is less susceptible to nuclease S1 digestion.A third and predominant adduct is formed in vivo, the deacetylated C-8 guanine adduct. The conformation of this adduct has been investigated using the dimer dApdG as a model for DNA. The attachment of aminofluorene (AF) residues introduced smaller changes in the circular dichroism (CD) spectra of dApdG than binding of acetylaminofluorene (AAF) residues. Similarly, binding of AF residues caused lower upfield shifts for the H-2 and H-8 protons of adenine than the AAF residues. These results suggest that AF residues are less stacked with neighboring bases than AAF and induce less distortion in conformation of the modified regions than AAF.An alternative conformation of AAF-modified deoxyguanosine has been suggested based on studies of poly(dG-dC)·poly(dG-dC). Modification of this copolymer with AAF to an extent of 28% showed a CD spectrum that had the characteristics of the left-handed Z conformation seen in unmodified poly-(dG-dC)·poly(dG-dC) at high ethanol or salt concentrations. Poly(dG)·poly(dC), which docs not undergo the B to Z transition at high ethanol concentrations, did not show this type of conformational change with high AAF modification. Differences in conformation were suggested by single-strand specific nuclease S1 digestion and reactivity with anticytidine antibodies. Highly modified poly(dG-dC)·poly(dG-dC) was almost completely resistant to nuclease S1 hydrolysis, while, modified DNA and poly(dG)·poly(dC) are highly susceptible to digestion. Two possible conformations for deoxyguanosine modified at the C-8 position by AAF are compared depending on whether its position is in alternating purine-pyrimidine sequences or random sequence DNA.
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  • 190
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 275-287 
    ISSN: 0275-3723
    Keywords: spectrin ; erythrocyte ; cytoskeleton ; oligomers ; tetramer ; associations ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Spectrin reversibly self-associates to high molecular weight oligomers through a concentration-driven process characterized by association constants of about 105 mol-1. This association is prominent under physiological conditions of pH, ionic strength, and temperature. It is disrupted by urea, but not Triton X-100. The process of spectrin association appears mathematically to resemble that for tropomyosin, although the mechanism is probably different. Spectrin association is weak compared to other prominent protein-protein associations in the red cell membrane skeleton. The linkage of these weak and strong associations suggests a process whereby the membrane skelton spontaneously assembles. Such affinity-modulated assembly involving weak associations is likely to be the focus of numerous membrane control mechanisms.
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  • 191
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 289-297 
    ISSN: 0275-3723
    Keywords: sickle cell anemia ; endo-β-galactosidase ; cell surface labeling ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Erythrocyte surface glycoproteins from patients with various types of sickle cell anemia have been analyzed and compared with those from normal individuals. By hemagglutination with various anti-carbohydrate antibodies, sickle cells showed profound increase of i antigens and moderate increase of GlcNAcβ1→3Galβ1→3Glc structure, whereas antigenicity toward globosidic structure was unchanged. In parallel to these findings, erythrocytes of sickle cell patients have additional sialylatcd lactosaminoglycan in Band 3. Thus, it can be concluded that erythrocytes of sickle cell patients are characterized by an altered cell surface structure which does not appear to be due to topographical changes of cell surface membrane. It is possible that the anemia or the “stress” hematopoiesis in these patients is responsible for these changes.
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  • 192
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 337-346 
    ISSN: 0275-3723
    Keywords: endocytosis ; GERL ; lectin ; lysosome ; subcellular fractionation ; Wistaria floribunda ; agglutinin ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Subcellular fractionation of Balb/c 3T3 fibroblasts exposed to Wistaria floribunda agglutinin was performed to localize fractions containing internalized lectin. Employing two sequential self-generating silica sol density gradients, the postnuclear supernatant of cell homogenates was resolved into five distinct cellular components. Lysosome enzyme activities were displayed by two populations of vesicles, each separated from plasma membrane, golgi, and mitochondria markers. The more dense of these fractions exhibited morphological and biochemical properties ascribed to secondary lysosomes: The more buoyant population was similar to that reported by Rome et al [11] who noted that it may be a product of vesiculated golgi endoplasmic reticulum lysosome (GERL). Treatment with W floribunda agglutinin of cells, surface radioiodinated demonstrated that plasma membrane proteins were localized within both the buoyant and dense lysosome populations in as little as 10 min after exposure to lectin. Prolonged incubation of the cells with W floribunda agglutinin resulted in maintenance of this distribution. However, when nonradiactive cells were exposed to 125I-labeled W floribunda agglutinin for 10 min, radioactivity was detected only in the buoyant population of lysosomes as well as the plasma membrane/golgi fraction. Treatment of cells with W floribunda agglutinin for 30 min resulted in appearance of lectin associated radioactivity in the dense lysosome fraction in addition to those populations containing radioactivity seen after a 10-min incubation. These data indicate that the endocytosis of W floribunda agglutinin differed substantially from the internalization of a portion of the plasma membrane proteins. Furthermore, we found radioactivity associated with both plasma membrane proteins W floribunda agglutinin in regions of the density gradient fractionation that virtually lacked golgi and lysosome markers. These fractions may have represented populations of nonlysosome vesicles formed during the process of endocytosis.
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  • 193
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981) 
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    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 194
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 377-387 
    ISSN: 0275-3723
    Keywords: down regulation ; pinocytosis ; lysosomotropic drugs ; desensitization ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Epidermal growth factor is internalized into cells and concomitantly induces a massive clearance of up to 90% of its total surface receptors. The hormone-receptor complex is delivered to lysosomes and degraded or inactivated. Lysosomotropic alkylamines block the degradation but not the binding-or internalization of ligand-receptor complexes and thus their presence results in a marked potentiation of intracellular accumulation of epidermal growth factor. We have used these alkylamines as pharmacological tools to trap internalized 125I-labeled epidermal growth factor and now report that the residual population of epidermal growth factor receptors remaining on human fibroblasts after completion of the receptor clearance process is not only accessible for ligand binding but also directs the continued internalization and degradation of this growth factor over prolonged periods of time. We also show that down regulation of epidermal growth factor receptors does not result in desensitization of cells to the mitogenic response.
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  • 195
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 239-318 
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    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 196
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    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 379-448 
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    Keywords: Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 197
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    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 213-218 
    ISSN: 0275-3723
    Keywords: erythrocyte membranes ; electron spin resonance ; LCAT deficiency ; phosphatidylcholine elevation ; cholesterol ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Erythrocytes from patients with familial lecithin:cholesterol acyltransferase (LCAT) deficiency have been shown to exhibit an increase in membrane fluidity which is surprisingly small in view of the extensive alterations both in membrane lipicl composition (namely, an elevation in cholesterol and phosphatidylcholine contents as well as a decrease in phosphatidylethanolamine) and in the functional properties of these cells. In the hope of deriving some information concerning the interrelationship between the structural and functional abnormalities, we have used the spin probe 5-doxyl stearic acid to investigate the temperature-dependent fluidity properties of red cells from two patients with a hereditary hemolytic syndrome (HHS) whose red cells are also characterized by qualitatively similar alterations in phosphatidylcholine and phosphatidylethanolamine but, unlike those in LCAT deficiency, have relatively normal levels of membrane cholesterol. A small increase in membrane fluidity of HHS erythrocytes equivalent to that previously observed in LCAT deficiency was found, indicating that membrane cholesterol level does not exert an important modulatory influence on membrane fluidity in these cells. It is concluded that while the distinct patterns of structural and functional erythrocyte alterations in these two disorders cannot be explained on the basis of differences in bulk membrane fluidity, the marginally increased fluidity may underlie the abnormalities in osmotic fragility and membrane p-nitrophenylphosphatase activity which are shared in common by both types of modified red cells.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 198
    ISSN: 0275-3723
    Keywords: insulin-like growth factor ; somatomedin ; multiplication stimulating activity ; insulin ; receptors: insulin; ; insulin-like growth factor ; fibroblasts ; DNA synthesis ; amino acid transport ; glucose ; leprechaunism ; liver cells ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The properties of multiplication stimulating activity (MSA), an insulin-like growth factor (somatomedin) purified from culture medium conditioned by the BRL 3A rat liver cell line are summarized. The relationship of MSA to somatomedins purified from human and rat plasma are considered. MSA appears to be the predominant somatomedin in fetal rat serum, but a minor component ot adult rat somatomedin. In vitro biological effects of MSA and insulin in adipocytes, fibroblasts and chondrocytes are examined to determine whether they are mediated by insulin receptors or insulin-like growth factor receptors. The possible relationship of a primary defect of insulin receptors observed in fibroblasts from a patient with the rare genetic disorder, leprechaunism, to intrauterine growth retardation is discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 199
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 317-326 
    ISSN: 0275-3723
    Keywords: culture substratum ; influence on morphogenesis ; mouse hepatoma ; phenotypes in vitro ; surface antigens ; modulation by culture substratum; ; tumor malignancy in vivo ; modification by preculture ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have found that a murine hepatoma displays a considerable phenotypic diversification in culture, which depends upon the substratum utilized, and is manifested by the formation of multicellular structures of differing geometry: Monolayer on glass and plastic, thick multilayer pads on Gelfilm, and spheroids on agar and agarose. These multicellular morphological phenotypes were assayed without disruption to ascertain their antigenicity in vitro and their tumorigenicity in vivo and to obtain quantitative information on the effect of the spatial arrangement of the hepatoma cells upon the ability of each multicellular structure to interact, as a whole, with molecules and cells in its surroundings.The antigenicity of the multicellular structures was determined with calibrated probes and a methodology that measures the total antigenicity, as well as antigenicity per unit of surface area. Antigenicity was found to differ in the following decreasing order: Monolayer on plastic 〉 spheroids on agarose 〉 spheroids on agar 〉 multilayer on Gelfilm. At least part of these antigenic variants arise from different degrees of masking of the structures' surface determinants by a trypsin-sensitive material.The multicellular phenotypes also differed in tumorigenicity. When assayed in syngeneic hosts under comparable conditions, agar-grown spheroids produced the fewest tumors, whereas Gelfilm-grown multilayers produced the most.These two independent sets of data show that the various geometries that a tumor tissue is induced to acquire by the culture substratum are accompanied by a distinctive combination of surface and biological properties.
    Additional Material: 4 Ill.
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  • 200
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Supramolecular Structure and Cellular Biochemistry 15 (1981), S. 395-402 
    ISSN: 0275-3723
    Keywords: lectins (vertebrate) ; heparin ; Glycosaminoglycans ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Extracts of young rat lung contain a heparin-inhibitable lectin that closely resembles one recently purified from chicken liver. Both lectins interact with heparin and N-acetyl-D-galactosamine, and were purified by gel filtration on Sepharose CL-2B followed by affinity chromatography on heparin-Sepharose. They both behave as high molecular weight aggregates that can be dissociated into two peptides with apparent molecular weights of 13,000 and 16,000 by gel electrophoresis in SDS. Samples of purified lectin contained up to 20% DNA by weight, and the degree of lectin aggregation and hemagglutination activity was greatly reduced by treatment with micrococcal nuclease without inhibiting heparin-binding activity. Association of lectin with DNA is an artifact of homogenization in high salt, since only 2% of the lectin is found associated with a purified nuclear fraction.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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