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Biomedical subjects

J J Greene

Publications and source records attributed to J J Greene.

34 records · Page 2Linked to original sources
PubMed1984

Developmentally regulated expression of the interferon system during Syrian hamster embryogenesis.

Expression of interferon (IFN) during embryogenesis of the Syrian hamster has been characterized with respect to (1) the antiviral activity to IFN; (2) the activity of the IFN-induced enzyme, 2',5'-oligo A synthetase; (3) the subpopulation of IFN producing cells, and (4) the molecular structure of the elaborated IFN. These components of the IFN system were examined in cell cultures derived from embryos excised at 8-13 days of gestation and determined as a function of both in utero gestation and in vitro passaging. The antiviral responsiveness of nine-day gestation cultures (9 dgc) was 1/4-1/6 of that of 13 dgc, but in vitro passaging increased the responsiveness as did in vivo development. IFN enhancement of the synthetase level in 9 dgc was only minimal when compared with that in 13 dgc. However, the 9 dgc contained an unusually high basal level of the enzyme. During in vivo development and in vitro passaging, the basal levels of the enzymes progressively declined while the IFN-induced levels progressively increased. IFN production in embryo cells following induction by Newcastle disease virus differs substantially, depending on the gestational age of the cells. Using an agarose-overlay "zone of protection" assay, 8 dgc were found to contain 10-12 times the number of cells producing zones of protection than 13 dgc. Passaging of 9 dgc cells reduced the number of zones to the level of the 13 dgc, but had no effect on 13 dgc. Chromatographic analysis of IFN produced by 9 dgc and 13 dgc revealed the presence of an additional, unique species of "embryonic" IFN in 9 dgc which was not observed in IFN from 13 dgc. These observations suggest that the expression of various components of the IFN system are under developmental control during embryogenesis.

2',5'-Oligoadenylate Synthetase↗
PubMed1980

Activation of 2',5'-oligo(A) polymerase and protein kinase of interferon-treated HeLa cells by 2'-O-methylated poly (inosinic acid) . poly(cytidylic acid), Correlations with interferon-inducing activity.

An oligonucleotide polymerase and a protein kinase which require double-stranded RNA (dsRNA) for activation are induced in HeLa cells by human fibroblast interferon. The polymerase synthesizes a series of oligonucleotides from ATP, whereas the kinase phosphorylates a polypeptide of Mr = 72,000 and the alpha subunit of initiation factor eIF-2. Partially or fully 2'-O-methylated derivatives of poly(inosinic acid) . poly(cytidylic acid) (rIn . rCn) were used to determine the structural requirements of dsRNA in the activation of these two enzymes. While fully methylated polymers failed to activate either enzyme, partially methylated polymers activated the enzymes in specific manners. The activation of the kinase by the rIn . rCn analogues was affected more severely by the level of methylation than was the activation of the polymerase. Moreover, fully methylated analogues blocked the activation of the kinase by rIn . rCn but not the activation of the polymerase. These observations are consistent with a biphasic model for enzyme activation similar to that proposed for interferon induction, which required the recognition of a relatively small region of rIn . rCn as the last step. Differences in the activation of the polymerase and kinase are explicable on the basis of the polymerase requirement for a smaller recognition region of the rIn . rCn duplex than the kinase. Dependence of polymerase activation on the level of methylation shows striking similarities with the interferon inducing activities of these analogues, suggesting a possible relationship between polymerase activation and interferon induction.

2',5'-Oligoadenylate Synthetase↗
PubMed1980

Species-specific posttranscriptional regulation of interferon synthesis.

Human fibroblast and Syrian hamster embryo cells were induced to synthesize interferon (IF) with rIn . rCn and rIn . rCn + DEAE-dextran, respectively. Following induction, these cells synthesized IF for only a short time before entering into a repressed state and shutting off the synthesis of IF. Homologous and heterologous whole cell translational systems were developed to investigate the molecular basis for the shut-off of IF synthesis. These systems allowedd for the introduction of exogenous hamster and human IF-mRNAs into intact normal and repressed hamster and human cells via an improved CaCl2 precipitation technique. Human IF-mRNA was translated in normal human and hamster cells and in repressed hamster cells but not in repressed human cells. In contrast, the hamster IF-mRNA was translated in normal human, normal hamster, and repressed human cells but not in repressed hamster cells. These results indicate that a species-specific mechanism inhibiting translation of IF-mRNA is directly responsible for the shut-off of IF synthesis in human fibroblasts and Syrian hamster embryo cells.

Animals↗
PubMed1980

Inter- and intra-examiner variability in scoring supragingival plaque: I. The clinical study.

Twenty-four normal healthy patients were scored for plaque by four examiners with different professional backgrounds and different levels of training. Each patient was examined twice by each examiner according to a predetermined random assignment with the assumption of no change in state. All four examiners scored higher on the second examination and there was no apparent consistent relationship between professional background and level of training in the plaque scoring.

Dental Hygienists↗
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

Studies on spin labeled ribonucleic acids encapsulated by viral proteins.

Spin labeled poly rA (sl-poly rA) was encapsulated by the coat proteins of two plant viruses having different morphologies: TMV, a rigid rod and CCMV, an icosahedral sphere. Electron microscopy showed that the resultant particles were morphologically similar to the parent virus from which the coat protein was obtained. Encapsulation produced progressive immobilization of the spin label. The motion of the spin label attached to TMV-sl-poly rA appears anisotropic with a correlation time about the long axis of approximately 5 x 10(-6) sec. Exogenous nuclease had no effect on the epr spectrum of this nucleo-protein complex. The epr spectrum of CCMV-sl-poly rA was isotropic with a correlation time less than 5 x 10(-7). CCMV-sl-poly rA was partially degraded by T2 ribonuclease. Theoretical calculations of correlation times for the motion of the nucleo-protein particles were similar to the experimentally derived values suggesting that the nucleo-protein particles are tightly packed with little potential for internal motion.

Electron Spin Resonance Spectroscopy↗
PubMed1976

Spin labeled nucleic acids.

Homopolyribonucleotides and E. coli DNA wer spin labeled with an iodoacetamide-nitroxide compound. The extent of labeling is highly dependent upon the nature of the base and the secondary structure of the nucleic acid. This spin label-polymer linkage is unstable at high temperatures and in phosphate buffers. In order to determine the effect of changes in the environment of nucleic acids on the esr signals of their attached spin labels, the polynucleotides were subjected to temperature and viscosity perturbations. An increase in temperature (T) affects a linear decrease in the anisotropy factor of the esr signal. The log tau (tau = correlation time) versus (1/T) profile is linear with a positive slope when the spin label is attached to single stranded polynucleotides but exhibits discontinuities at certain critical temperatures when attached to the duplexes poly (As-U) and poly (I-Cs). These critical temperatures are lower than the optical Tm. Logarithmic increase in viscosity was found to produce a linear increase in tau in aqueous sucrose solutions.

Binding Sites↗
PubMedDate not supplied

Clinical studies with mismatched double-stranded RNA.

Mismatched inducer/activator therapy has demonstrated areas of definite clinical promise in its initial human trials. Indeed, the mismatched dsRNA may even prove more efficacious than conventional (exogenous) interferon therapy for several reasons including: (a) First, the potential for generating multiple species of interferons, thereby removing the possible necessity of targeting a specific type (or subtype) of interferon to a particular cell type, (b) Secondly, the known ability of the mismatched inducer to activate the intracellular mediators which are synthesized after cellular exposure to the various types of interferon, (c) Lastly, the recently demonstrated ability of the inducer/activator in combination with interferon to override acquired cellular resistance to interferon alone (13).

Adult↗