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Biomedical subjects

W A Carter

Publications and source records attributed to W A Carter.

At least 73 records · Page 4Linked to original sources
PubMed1978

Interferon induction and its dependence on the primary and secondary structure of poly(inosinic acid).poly(cytidylic acid).

The synthetic interferon (IF) inducer rIn.rCn was modified by substituting the ribosyl residues with either their corresponding deoxy(dC or dI) or 2'-O-methyl analogues (mC or mI). The polynucleotide duplexes of these analogues are inactive as IF inducers. Circular dichroism (CD) studies revealed that, while the deoxy substitution produces significant changes in the conformation of rIn.rCn, the 2'-O-methyl substitution produces no detectable change. Biological competition experiments indicated that the methylated duplexes mIn.rCn, rIn.mCn, and mIn.mCn all compete with rIn.rCn for IF induction, while the deoxy duplexes dIn.rCn and rIn.dCn do not. These results are consistent with those predicted from the CD data. Copolymer duplexes (mI,rI)n.(mC,rC)n of varying degrees of methylation and residue clustering were also evaluated for IF induction in human fibroblasts. The IF-inducing capabilities of these duplexes correlated highly with the presence of clusters containing six or more consecutive ribosyl residues. These combined observations suggest that interaction of rIn.rCn with the cell in the induction process may occur in a biphasic manner involving first the topological recognition of a large segment of the RNA to allow for proper binding to the putative cellular receptor, followed by recognition of a much smaller region of the RNA corresponding to 6--12 consecutive ribosyl residues (0.5 to 1 helical turn) which is responsible for the triggering of the induction process.

Circular Dichroism↗
PubMed1978

Molecular size heterogeneity of human leukocyte interferon.

Molecular sieving of human leukocyte interferon revealed an apparent molecular weight of 26,000. However, after denaturation by guanidine hydrochloride in the presence of a reducing agent and reactivation by extensive dialysis, a molecular weight of only 21,000 was observed. The reactivated human leukocyte interferon (mol wt 21,000) gave a single peak of activity when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, confirming that a single molecular weight species was generated by the denaturation and reactivation procedure. A partial unfolding of the molecule was evident when the interferon preparation was heated to 50 degrees C in the absence or presence of an unfolding agent and then sieved on Sephadex G-100 Superfine. These results suggest that the interferon molecule undergoes a proteolytic cleavage probably by a protease present in extracellular fluid. Thus, a peptide fragment dissociates from the parent molecule when human leukocyte interferon is denatured in the presence of a reducing agent, resulting in a drop of 5,000 in molecular weight; interestingly, the resultant 21,000 molecular weight form still retains its antiviral activity.

Humans↗
PubMed1978

Stabilization of human fibroblast interferon purified on concanavalin A-agarose.

Human fibroblast interferon, obtained by chromatography on concanavalin A-agarose, was stable for at least a month in 30--50 per cent ethylene glycol at 4 degrees, --20 degrees, and --70 degrees C. The succinct point of the present finding is that human fibroblast interferon may be stabilized by ethylene glycol alone without the addition of bovine serum albumin and 'back-contamination' of the interferon preparation.

Chromatography, Affinity↗
PubMed1978

Antiproliferative activity of highly purified mouse interferon: brief communication.

The antiproliferative effect of mouse L-cell interferon, purified by bovine serum albumin--agarose chromatography (which yields a sp act of 3 X 10(8) international reference U/ml protein), and its two subcomponents, obtained by CH-Sepharose 4B chromatography, has been studied in Balb/3T3 fibroblast cultues. Four to 10 international reference U of interferon/ml resulted in a 50% inhibition of DNA synthesis and cell growth, as determined by the incorporation of [3H]thymidine and cell counts, respectively. Hence the degree of inhibition produced by the purified interferon preparations was comparable to that produced by the original crude interferon (sp act, 1.5 X 10(6) international reference U/mg protein). Our results, obtained with L-cell mouse interferon purified by two novel affinity ligands, provided further evidence linking the antiviral and antiproliferative activities of this molecule.

Animals↗
PubMed1978

Study of ansamycin inhibition of a ribonucleic acid-directed deoxyribonucleic acid polymerase by an immobilized template assay.

A series of structurally related ansamycins have been analyzed, in a new immobilized template assay, to determine the mechanism by which they inhibit a ribonucleic acid-directed deoxyribonucleic acid (DNA) polymerase from Moloney murine leukemia virus. By this assay, we can better correlate specific structures of these drugs with inhibitory mechanisms. Using an immobilized template, we were also able to observe drug effects on the stability of complexes formed between the polymerase, a template (polyadenylic acid-agarose), and a primer, as well as to monitor the synthesis of DNA in the presence of drug. For each drug, we determined the complex (intermediate in DNA synthesis) which was primarily affected and whether the effect was due to a destabilization process. Although the activity and specificity of the unsubstituted ansamycins (streptovaricins and rifamycin SV) were modulated by conformation of the molecule and electron density of the aromatic ring, the principal mode of inhibition is, apparently, drug binding to a polymerase-template complex; the drug binds in a manner which prevents subsequent formation of a polymerase-template-primer complex. However, some derivatives of rifamycin SV, when substituted at carbon-3 with bulky or hydrophobic side chains, displayed markedly different modes of action. For example, demethyl dimethyl rifampin prevented the formation of polymerase-template complexes, whereas rifazacyclo 16 acted by promoting the dissociation of polymerase-template-primer complexes.

Anti-Bacterial Agents↗
PubMed1978

Aging in vitro and large-scale interferon production by 15 new strains of human diploid fibroblasts.

To develop resources for large-scale production of human fibroblast interferon, we isolated, cryopreserved, and characterized 15 new strains of human diploid foreskin fibroblasts. Their life spans in vitro ranged from 52 to 72 population doublings. We based the selection of cell strains for mass interferon production on the number of population doublings during which consistently high yields of interferon were obtained after "superinduction" in roller bottles; our data show that aging in vitro leads to significant decline in amounts of interferon produced. In contrast, susceptibility to interferon remains largely unaffected by in vitro senescence. Karyotypic analysis indicated that the best interferon-producing strain, MLD (over 60,000 reference units/ml), has a translocation between chromosomes 5 and 15.

Cell Line↗
PubMed1978

Reverse transcriptase activity in extracts of human prostatic tissues.

The extracts of human prostatic tissue specimens contain oncornavirus-like reverse transcriptase activity. This activity was isolated by banding the tissue extract in an equilibrium sucrose density gradient followed by phosphocellulose chromatography of the lysate of the material banding at a density of 1.14--1.20 g/cc. It was characterised by its utilisation of poly (Cm) as a template and its inhibition by selective inhibitors of viral reverse transcriptase. Human prostatic tissues of three histo-pathologic types--normal, hyperplastic and adenocarcinoma--were examined. One out of four normal, five out of six hyperplastic, and two out of two adenocarcinoma specimens displayed virus-like reverse transcriptase activity.

Adenocarcinoma↗
PubMed1978

Enhancement of T cell cytotoxic responses by purified human fibroblast interferon.

Purified polyribonucleotide-induced human fibroblast interferon (HFIF) was tested for its effects on proliferative and cytotoxic human T cell responses to alloantigens. The addition of HFIF (100 to 400 IFU/ml) to mixed leukocyte cultures decreased alloantigen-induced lymphocyte proliferative responses as determined by both recovery of responding cells and by 3H-thymidine incorporation into responding cells. However, HFIF, but not the mock interferon preparation, increased the cytotoxic response of T cells to allogeneic cells by 4- to 5-fold when expressed in terms of lytic units. Although fibroblast and leukocyte interferons have different physicochemical and biologic properties, the results reported here are in concert with previous findings concerning the effects of virus-induced leukocyte interferon on human T cell functions.

Cytotoxicity, Immunologic↗
PubMed1978

Human fibroblast interferon in human neoplasia: clinical and laboratory study.

Human fibroblast interferon (HFIF) produced on a large scale from normal diploid cell strains was highly purified and then evaluated as to its safety clinical investigation. The selective antiproliferative activity of HFIF was observed in vitro against certain human malignant cell lines and in vivo against human bladder tumors grown in nude mice. Direct injections of HFIF into metastatic melanoma lesions of two patients resulted in either the disappearance of malignant cells or the significant reduction in tumor volume.

Animals↗
PubMed1977

Pharmacologic effects of polyinosinic-polycytidylic acid in man.

Twenty-four patients with cancer and concomitant infections with either herpes virus hominis or varicella zoster virus were treated with polyinosinic-polycytidylic acid (rIn.rCn) to determine: 1) the reliability of rIn.rCn to induce interferon production, and 2) the toxicity of the drug. Seven additional patients with herpes zoster were observed as controls. Two lots of rIn.rCn were used; Lot 1 was consistently effective in stimulating serum interferon at doses of 9 and 12 mg/kg, whereas Lot 2 was effective at doses of 3-12 mg/kg. There was no correlation between rIn.rCn doses within these ranges and the resultant interferon levels. Generally, peak serum interferon occurred within the first day. Toxicity to rIn.rCn consisted of fever in 21/24 patients, mild elevation of liver enzymes in 8/24 patients, and laboratory abnormalities of coagulation in 9 patients. The coagulation abnormalities appeared linearly related to the dose of rIn.rCn used. All these abnormalities were reversible, and none were considered severe of life-threatening. Since rIn.rCn was effective in stimulating interferon and since toxicity was considered acceptable, a randomized double-blind study was initiated to determine whether rIn.rCn is effective in the treatment of herpes zoster.

Adolescent↗
PubMed1977

Differential susceptibility of spleen focus-forming virus and murine leukemia viruses to ansamycin antibiotics.

The streptovaricin complex (SvCx) and rifamycin SV derivatives display potent antiviral activity against the polycythemic strain of Friend leukemia virus (FV-P), as measured by a reduction in the number of spleen foci produced in mice. Such reductions may be explained by inactivation of functions of (i) the spleen focus-forming virus (SFFV), (ii) its "helper" murine leukemia virus (MuLV), or (iii) both viruses normally present in FV-P. We noted that preincubation of FV-P with fractionation products of SvCx, or derivatives of rifamycin SV, at low concentrations (3 to 5 mug/ml) reduces the number of spleen foci 80 to 97%, whereas titers of MuLV (from the same inoculum) remain unaffected (MuLV titers were measured by XC, S(+)L(-), and "helper activity" assays). Our findings indicate a remarkable biological selectivity of ansamycins, as well as nonansamycin components of SvCx, against the transforming and defective spleen focus-forming virus as compared to MuLV. Thus, the drugs might be useful in distinguishing other types of oncornaviruses.

Animals↗
PubMed1977

A status report: human prostatic carcinoma, with emphasis on potential for viral etiology.

Several parameters of the biology of cancer of the prostate have been reviewed with a continuing assessment of the possible etiologic role of virus. These aspects include epidemiology, clinical studies, morphology, pathology, enzymology, immunology, endocrinology, model animal studies, in vitro systems, and viral investigations. From available literature it is concluded that, to date, the association with several urogenital tissues of herpes-type viruses has been best documented. It is suggested that a fundamental barrier to more sophisticated virologic and biologic studies is the lack of long term cell cultures of normal and pathologic prostate epithelium from males of all ages.

Acid Phosphatase↗
PubMed1976

Hydrophobic interaction of human, mouse, and rabbit interferons with immobilized hydrocarbons.

Interferons of human, mouse, and rabbit origin bind to straight chain hydrocarbons immobilized on agarose. The hydrophobic nature of binding is established by the following observations: (a) a positive correlation between the length of hydrocarbon ligand and the strength of interaction; (b) a stronger interaction with hydrocarbon ligands terminated with apolar rather than polar head groups; (c) a lack of dependence of binding on ionic strength and pH of the solvent; (d) a reversal of binding by ethylene glycol, a hydrophobic solute; (e) an increasing eluting efficacy of tetraalkylammonium ions with the length of their alkyl substituents. The hydrophobic interactions of human interferon underlie the efficiency of two-step chromatographic procedures. For example, human embryo kidney interferon can be purified about 3,600-fold by sequential chromatography on (a) concanavalin A-agarose, (b) octyl-agarose. Another two-step procedure: (a) concanavalin A-agarose, (b) L-tryptophan-agarose, gives about 10,000-fold purification. The overall recovery of interferon in both cases in close to 90%.

Animals↗
PubMed1976

Binding of human interferons to immobolized Cibacron Blue F3GA: The nature of molecular interaction.

Blue Dextran (Cibacron Blue F3GA-dextran) was immobilized on cyanogen bromide activated agarose and used as a ligand for human fibroblast and leukocyte interferons in a solvent of phosphate-buffered (pH 7.4), physiological saline (0.15 M NaCl). Fibroblast interferon binds completely and is not displaced from the column by an increase in ionic strength of the solvent (1.0 M NaCl); it can be, however, recovered with ethylene glycol, indicating the hydrophobic nature of interaction. Leukocyte interferon also binds to Blue Dextran-agarose but it can be recovered simply by an increase in the ionic strength of the solvent, indicating primarily the electrostatic nature of binding. Attempts to displace both interferons selectively with nucleosides and aromatic amino acids were unsuccessful. When Cibacron Blue F3GA is immobilized directly to agarose matrix or via molecular arm, the strength of binding of fibroblast interfern is significantly decreased, although ethylene glycol is still required for its displacement from the column. Leukocyte interferon, by contrast, does not bind at all under the same solvent conditions; it does bind when the pH value of the solvent is in the range 3-5 i.e., below its isoelectric point. Human fibroblast interferon binds completely to: aminobenzene, aminonaphthalene, and aminoanthracene, all immobilized on agarose, and it can be recovered with ethylene glycol. In contrast, human leukocyte interferon does not bind to benzene-agarose; it is retarded on naphthalene-agarose and completely retained on an anthracene-agarose column. All data point to a higher intrinsic hydrophobicity of human fibroblast interferon vis-á-vis human leukocyte interferon. Selective binding of human fibroblast interferon of Cibacron Blue F3GA-agarose results in a significant purification, about 800-fold.

Binding Sites↗