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Ji ZS, Lauer SJ, Fazio S, Bensadoun A, Taylor JM, Mahley RW. Enhanced binding and uptake of remnant lipoproteins by hepatic lipase-secreting hepatoma cells in culture. J Biol Chem 1994; 269:13429-36. [PMID: 8175774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Rat hepatoma McA-RH7777 cells transfected with a human hepatic lipase (HL) cDNA synthesized and secreted 50-80 ng of human HL/mg of cell protein at 4 h, approximately 50% of which was bound to cell-surface heparan sulfate proteoglycans (HSPG). The newly synthesized HL possessed enzymatic activity. When rabbit beta-very low density lipoproteins (beta-VLDL) and canine chylomicrons or chylomicron remnants were incubated with HL-secreting cells, remnant binding and uptake were enhanced 3-fold compared with nontransfected cells. Furthermore, fluorescence microscopy showed enhanced uptake of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine-labeled beta-VLDL by the HL-transfected cells. When 125I-beta-VLDL were added to conditioned medium from HL-secreting cells, the HL in the media enhanced the binding and uptake of the remnant lipoproteins by nontransfected cells about 3-fold. Likewise, surface-bound HL (without HL in the medium) also was able to mediate the enhanced binding of the remnants. This HL-enhanced binding was shown to be mediated by an interaction with cell-surface HSPG. Heparinase treatment to remove cell-surface HSPG or chlorate treatment to prevent HSPG sulfation of the HL-secreting cells abolished all the HL-mediated enhanced binding and uptake. Furthermore, heparinase pretreatment of nontransfected cells prevented the enhanced binding and uptake of beta-VLDL incubated with conditioned medium from HL-secreting cells. As binding was not enhanced in the absence of HSPG, an HL-HSPG initial interaction appears essential. Addition of apolipoprotein (apo) E to the beta-VLDL did not facilitate HL-mediated binding and uptake; in fact, beta-VLDL from apoE-null mice demonstrated a similar degree of enhanced binding as did rabbit beta-VLDL with or without added apoE. On the other hand, beta-VLDL from transgenic mice overexpressing binding-defective apoE(Arg142-->Cys) did not display any enhanced binding and uptake by the HL-secreting cells, and it appears that the apoE(Arg142-->Cys) actually inhibited the HL-mediated interaction. This mutant form of apoE is associated with a dominant mode of expression of type III hyperlipoproteinemia in contrast to the more commonly occurring recessive disorder. Impaired HL interaction with the apoE(Arg142-->Cys) beta-VLDL may contribute to remnant lipoprotein accumulation in the plasma of patients with this mutant form of apoE. Thus, HL contributes to the enhanced cell association of specific types of remnant lipoproteins by initiating their binding to cell-surface HSPG.
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Lazinski DW, Taylor JM. Expression of hepatitis delta virus RNA deletions: cis and trans requirements for self-cleavage, ligation, and RNA packaging. J Virol 1994; 68:2879-88. [PMID: 8151758 PMCID: PMC236776 DOI: 10.1128/jvi.68.5.2879-2888.1994] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The hepatitis delta virus (HDV) genome is a circular, single-stranded, rod-shaped, 1.7-kb RNA that replicates via a rolling-circle mechanism. Viral ribozymes function to cleave replication intermediates which are then ligated to generate the circular product. HDV expresses two forms of a single protein, the small and large delta antigens (delta Ag-S and delta Ag-L), which associate with viral RNA in a ribonucleoprotein (RNP) structure. While delta Ag-S is required for RNA replication, delta Ag-L inhibits this process but promotes the assembly of the RNP into mature virions. In this study, we have expressed full-length and deleted HDV RNA inside cells to determine the minimal RNA sequences required for self-cleavage, ligation, RNP packaging, and virion assembly and to assess the role of either delta antigen in each of these processes. We report the following findings. (i) The cleavage and ligation reactions did not require either delta antigen and were not inhibited in their presence. (ii) delta Ag-L, in the absence of delta Ag-S, formed an RNP with HDV RNA which could be assembled into secreted virus-like particles. (iii) Full-length HDV RNAs were stabilized in the presence of either delta antigen and accumulated to much higher levels than in their absence. (iv) As few as 348 nucleotides of HDV RNA were competent for circle formation, RNP assembly, and incorporation into virus-like particles. (v) An HDV RNA incapable of folding into the rod-like structure was not packaged by delta Ag-L.
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Brooks AR, Nagy BP, Taylor S, Simonet WS, Taylor JM, Levy-Wilson B. Sequences containing the second-intron enhancer are essential for transcription of the human apolipoprotein B gene in the livers of transgenic mice. Mol Cell Biol 1994; 14:2243-56. [PMID: 8139530 PMCID: PMC358591 DOI: 10.1128/mcb.14.4.2243-2256.1994] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
To identify DNA sequence elements from the human apolipoprotein B (apoB) gene required for high-level, correct tissue-specific expression in transgenic mice, we made several constructs that included one or more of the key regulatory elements that were previously characterized with cultured liver-derived and intestine-derived cell lines. Our data show that the apoB promoter alone (-898 to +121) is not sufficient to direct transcription in transgenic mice. An enhancer located in the second intron is absolutely required to specify transcription by the homologous apoB promoter in the livers of transgenic mice; this enhancer does not direct transcription in the small intestines. Thus, the elements controlling transcriptional activation of the apoB gene in the liver and the intestine in vivo are distinct and separable. Analysis of the DNase I hypersensitivity of the integrated human transgenes in various lines of expressing and nonexpressing mice suggests that the formation of DH4, a strong hypersensitive site in intron 2, may be a prerequisite for hepatic expression of the apoB gene. Nuclear matrix association regions (MARs) of the apoB gene may play a role in transgene expression. Constructs including MAR sequences displayed higher levels of expression than those lacking them. However, these MARs did not completely insulate the associated transgenes from position effects.
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Fazio S, Horie Y, Simonet WS, Weisgraber KH, Taylor JM, Rall SC. Altered lipoprotein metabolism in transgenic mice expressing low levels of a human receptor-binding-defective apolipoprotein E variant. J Lipid Res 1994; 35:408-16. [PMID: 8014576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Transgenic mouse lines were produced that expressed low levels of a receptor-binding-defective variant of human apolipoprotein (apo) E, apoE(Arg112, Cys142). In transgenic mice, the human apoE was produced only by the kidney, whereas endogenous mouse apoE was produced mainly by the liver. The plasma concentration of the transgenic protein was about half that of endogenous apoE. The expression of transgenic apoE did not affect total plasma cholesterol and triglyceride levels, but the distribution of the human variant differed from that of endogenous apoE in the intermediate size and density range, where the transgenic protein accumulated selectively. Immunoblots of agarose gels of lipoprotein fractions showed that the transgenic protein occurred primarily on large alpha-migrating particles (HDL1). This phenomenon was not observed in transgenic mice expressing normal human apoE-3, which distributed like endogenous apoE, suggesting that the defective apoE variant perturbed HDL1 metabolism. In mice fed a high-fat, high-cholesterol diet, the transgenic apoE associated primarily with the apoB-containing lipoproteins. A significantly higher increase in very low density lipoprotein cholesterol was observed in fat-fed transgenics compared to fat-fed nontransgenic mice, suggesting a metabolic perturbation of apoB-containing lipoproteins. Thus, the receptor-binding-defective variant, apoE(Arg112, Cys142), expressed at low levels by the kidney, alters lipoprotein metabolism in transgenic mice, presumably by interfering with apoE-mediated removal of the lipoproteins from circulation.
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Kharazi AI, James SJ, Taylor JM, Lubinski JM, Nakamura LT, Makinodan T. Combined chronic low dose radiation-caloric restriction: a model for regression of spontaneous mammary tumor. Int J Radiat Oncol Biol Phys 1994; 28:641-7. [PMID: 8113107 DOI: 10.1016/0360-3016(94)90189-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
PURPOSE This study was carried out to determine whether chronic low dose radiation can act alone or in synergy with restricted diet in down-regulating spontaneously occurring mammary tumor in tumor-susceptible female C3H/He mice and whether immune cells are involved. METHODS AND MATERIALS At 7 months of age, one-half of the experimental mice were maintained on an ad lib diet, and the other half was adapted over a period of 1 month to a diet of 70% of the daily amount of food consumed by the ad lib-fed mice. The food of the restricted diet was enriched such that the vitamin and mineral intake was the same for both groups. Half of the mice in each group was then subjected to chronic low dose radiation (0.04 Gy per exposure from a 60Co source, 3 x-per-week for 4 weeks) and the other half was sham irradiated. The 70% calorically restricted diet was maintained throughout the study. RESULTS Chronic low dose radiation alone was ineffective in down-regulating spontaneous mammary tumor, unlike caloric restriction. However, chronic low dose radiation when combined with caloric restriction promoted regression of mammary tumors, which were infiltrated with massive numbers of CD8+ T cells. These phenomena were not seen in mice subjected to caloric restriction alone. CONCLUSION Combined chronic low dose radiation-caloric restriction appears to be a useful model for promoting spontaneous mammary tumor regression.
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de Silva HV, Lauer SJ, Wang J, Simonet WS, Weisgraber KH, Mahley RW, Taylor JM. Overexpression of human apolipoprotein C-III in transgenic mice results in an accumulation of apolipoprotein B48 remnants that is corrected by excess apolipoprotein E. J Biol Chem 1994; 269:2324-35. [PMID: 8294490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Overexpression of human apolipoprotein (apo) C-III in the plasma of transgenic mice results in hypertriglyceridemia, with up to a 20-fold elevation in plasma triglyceride. Nearly all of the triglyceride accumulates in the d < 1.006 g/ml lipoprotein fraction, which consists predominantly of apoB48-containing particles having a low apoE:apoB48 ratio in contrast to normal mice. The transgenic and nontransgenic d < 1.006 g/ml lipoproteins are similar in size, and they are equivalent substrates for lipoprotein lipase in vitro. Total apoB100 levels are similar in transgenic and normal plasma, but apoB48 levels are increased in transgenic mice. The transgenic d < 1.006 g/ml particles are poor competitors for the binding of low density lipoproteins to the low density lipoprotein receptor in vitro, which is corrected by the addition of exogenous apoE. The rate of clearance of labeled chylomicron remnants in apoC-III-transgenic mice was about half that in nontransgenic mice. The lipoprotein alterations are accompanied by up to a 5-fold increase in circulating nonesterified fatty acids, which may be the cause of fatty livers and increased liver triglyceride production also observed in the transgenic mice. These observations indicate that the primary defect leading to hypertriglyceridemia in apoC-III overexpressers is an impaired clearance of apoB48 remnants due to apoE insufficiency. Therefore, transgenic mice that overexpressed human apoE were cross-bred with the apoC-III overexpressers. Transgenic progeny that produced both human apoE and human apoC-III had normal levels of plasma triglyceride and normal amounts of apoB48 remnants. Thus, our studies suggest that a function of apoC-III is to modulate the apoE-mediated clearance of lipoproteins, and that the concentration of apoC-III relative to apoE is a key determinant of triglyceride levels in plasma.
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Taylor JM, Jacob-Mosier GG, Lawton RG, Neubig RR. Coupling an alpha 2-adrenergic receptor peptide to G-protein: a new photolabeling agent. Peptides 1994; 15:829-34. [PMID: 7984502 DOI: 10.1016/0196-9781(94)90038-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A photoreactive derivative of a tetradecapeptide G-protein activator (peptide Q) derived from the alpha 2-adrenergic receptor was designed and used to label purified G-protein (Go/Gi). N-bromoacetyl-N'-(3-diazopyruvoyl)-m-phenylene-diamine (Br-DAP) was conjugated to the C-terminal cysteine of peptide Q. The DAP-modified peptide Q (DAP-Q) specifically incorporated into the a subunit of Go. The incorporation of DAP-Q into alpha o was blocked by unmodified Q peptide (IC50 = 15 +/- 6 microM; n = 4). Photolysis of sixfold higher concentrations of DAP-Q with ovalbumin or bovine albumin failed to produce cross-linked products. Br-DAP should prove useful in detecting mutual contact sites between peptides and their binding proteins.
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Feingold KR, Hardardottir I, Memon R, Krul EJ, Moser AH, Taylor JM, Grunfeld C. Effect of endotoxin on cholesterol biosynthesis and distribution in serum lipoproteins in Syrian hamsters. J Lipid Res 1993; 34:2147-58. [PMID: 8301233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Infection and inflammation increase serum triglyceride and cholesterol levels in rodents and rabbits. Endotoxin (LPS) has been used as a model of infection and its effects on triglyceride metabolism have been previously characterized. In the present study we demonstrate that both low (100 ng/100 g body weight) and high dose (100 micrograms/100 g body weight) LPS increase serum cholesterol levels in hamsters. The increase in serum cholesterol is first observed 16 h after LPS and persists for at least 24 h. This increase is primarily due to an increase in low density lipoprotein (LDL) cholesterol. High density lipoprotein (HDL) cholesterol levels decrease after LPS treatment. Both low and high dose LPS increase hepatic cholesterol synthesis (low dose 85%, high dose 205%) and total HMG-CoA reductase activity (low dose 2.97-fold, high dose 9.96-fold). However, the proportion of HMG-CoA reductase in the active form is reduced by LPS treatment. Additionally, the mass of HMG-CoA reductase protein in the liver, measured by Western blotting, is increased after LPS. Moreover, LPS increases hepatic HMG-CoA reductase mRNA levels (low dose 3.1-fold, high dose 14.2-fold). The increase in hepatic HMG-CoA reductase mRNA levels is first seen 4 h after LPS and persists for at least 24 h. In contrast, LPS had only minimal effects on hepatic LDL receptor protein and mRNA levels. These results suggest that LPS increases serum cholesterol levels by increasing hepatic cholesterol synthesis. LPS administration decreases apoE mRNA levels in the liver while having no effect on apoA-I mRNA levels. These results suggest that HMG-CoA reductase is a member of a group of hepatic proteins that are positively regulated by inflammatory stimuli (acute phase proteins) while apoE can be considered a negative acute phase protein in hamsters. It is possible that increases in hepatic HMG-CoA reductase provide cholesterol that allows for the increased production of lipoproteins and elevations in serum lipid levels that may be beneficial to the body's host defense.
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Taylor JM, Kim DK. Statistical models for analysing time-to-occurrence data in radiobiology and radiation oncology. Int J Radiat Biol 1993; 64:627-40. [PMID: 7902403 DOI: 10.1080/09553009314551851] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Two different methods for analysing late complications data are contrasted and compared. The two methods are the Cox Proportional Hazards model and the Mixture model. The potential limitations of both methods are described together with the circumstances in which one or the other of the methods is preferable. The results from the two methods of analysis will usually be qualitatively similar and frequently quantitatively similar. For estimating the ratio of parameters, such as the alpha/beta ratio if the linear-quadratic model holds, the Cox model is the preferred method. For estimating the proportion with complications by a given follow-up time, the Mixture model is the preferred method. For data, such as from experimental animals, in which there is little censoring during the time period of interest, the Mixture model will usually be the better analysis. In contrast, for data, such as clinical data, in which there is a lot of censoring throughout the time period in which complications occur, the Cox model will usually give a more reliable analysis especially in situations where there are a small number of complications. Both methods are applied to a mouse spinal cord data set and to a clinical head and neck data set. The bias, efficiency, and coverage rate of confidence intervals and robustness of the two methods are compared in a Monte Carlo simulation.
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Lo Y, Taylor JM, McBride WH, Withers HR. The effect of fractionated doses of radiation on mouse spinal cord. Int J Radiat Oncol Biol Phys 1993; 27:309-17. [PMID: 8407405 DOI: 10.1016/0360-3016(93)90242-n] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
PURPOSE To determine: (a) the dose-response relationship and latent time to paralysis following fractionated doses of radiation in mice, (b) the values of parameters for isoeffect curves, and (c) whether these parameters depend on the size of dose per fraction and the severity of injury. METHODS AND MATERIALS The spinal cords (T9-L5) of 608 C3Hf/Sed/Kam mice were irradiated with fractionated doses of x-radiation. Three levels of neurological damage were used to grade the spinal cord response. Animals which did not develop paralysis were observed for at least 18 months after irradiation. The fractionated schedules consisted of either 2, 3, 4, 6, 10, or 20 fractions in addition to single doses. For the fractionated regimes the daily fraction size ranged from 2 Gy to 24 Gy, and for single doses the range was 12 Gy to 52 Gy. Both the latent time to paralysis and the incidence of paralysis were considered as endpoints. For analysis of the sparing associated with fractionation, the dose points were divided into two groups: a "low damage" group consisting of doses of near or less than the ED50 at 450 days and a "high damage" group consisting of doses much larger than the ED50 at 450 days in which there was 100% incidence of paralysis. RESULTS The latent time depended on the radiation dose; for each fixed fraction number the latent period became progressively shorter with higher total doses. Differences in histology in fractionation sensitivity are observed between the two groups. The low damage data in each fractionation treatment are the important data in the analysis of long-term incidence of paralysis. On the other hand, the high damage data were emphasized for the analysis of latency. Three statistical methods (mixture model, Cox model, and Fe-plot) were used to fit the linear-quadratic dose response model and the "Nominal Standard Dose" (NSD) model. The values of the parameters of these two models depended on the effect evaluated; the latent interval from the high damage region being not very fractionation-dependent, whereas, the incidence of paralysis from the low damage fractionation regimens was strongly dependent on dose per fraction. Specifically, the alpha/beta ratios for latency were large (e.g., 17 to 57 Gy) when fractionation schemes in the high damage region were emphasized. If data from the fractionation schemes in the lower damage region with fraction size less than 15 Gy were emphasized, the alpha/beta ratios for incidence of paralysis were 3.3 (1.8, 6.0, 95% C.I.), 4.1 (2.8, 5.5), and 4.4 Gy derived by the mixture, Cox, and Fe-plot models, respectively. These "low damage" alpha/beta ratios were similar for all levels of injury from mild to complete paralysis, and are those which are more relevant to clinical radiotherapy. The coefficients for the "Nominal Standard Dose" formula in the present study were 0.33 +/- 0.01 (s.e.) (by the Strandqvist-type plot), 0.38 (the Cox model), or 0.40 (the mixture model) for level 2 injury at 450 days. CONCLUSION The values of parameters in the isoeffect models were different when the data analyzed were derived from regimens using fractionated low or high damage doses.
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Hughes SM, Taylor JM, Tapscott SJ, Gurley CM, Carter WJ, Peterson CA. Selective accumulation of MyoD and myogenin mRNAs in fast and slow adult skeletal muscle is controlled by innervation and hormones. Development 1993; 118:1137-47. [PMID: 8269844 DOI: 10.1242/dev.118.4.1137] [Citation(s) in RCA: 287] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Each of the myogenic helix-loop-helix transcription factors (MyoD, Myogenin, Myf-5, and MRF4) is capable of activating muscle-specific gene expression, yet distinct functions have not been ascribed to the individual proteins. We report here that MyoD and Myogenin mRNAs selectively accumulate in hindlimb muscles of the adult rat that differ in contractile properties: MyoD is prevalent in fast twitch and Myogenin in slow twitch muscles. The distribution of MyoD and Myogenin transcripts also differ within a single muscle and correlate with the proportions of fast glycolytic and slow oxidative muscle fibres, respectively. Furthermore, the expression of a transgene consisting of a muscle-specific cis-regulatory region from the myoD gene controlling lacZ was primarily associated with the fast glycolytic fibres. Alteration of the fast/slow fibre type distribution by thyroid hormone treatment or by cross-reinnervation resulted in a corresponding alteration in the MyoD/Myogenin mRNA expression pattern. These findings show that the expression of specific myogenic helix-loop-helix regulators is under the control of innervation and humoral factors and may mediate differential control of contractile protein gene expression in adult muscle.
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Withers HR, Mason KA, Taylor JM, Kim DK, Smathers JB. Dose-survival curves, alpha/beta ratios, RBE values, and equal effect per fraction for neutron irradiation of jejunal crypt cells. Radiat Res 1993; 134:295-300. [PMID: 8316621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Jejunal crypt cell survival after regimens of one, two, three and five fractions was used to reconstruct composite single-dose survival curves for neutrons of five different energies. There is no obvious shoulder, but there is a gradual divergence from linearity that is most evident at low levels of cell survival (high doses). The effect of dose fractionation is relatively small, especially at the low doses characteristic of each treatment session in neutron radiotherapy. The alpha/beta values for the linear-quadratic survival curves range from 27 to 40 Gy. The curves for neutrons are different from the curves for gamma rays mainly in their alpha coefficients, as predicted by Kellerer and Rossi's theory of dual radiation action, but both alpha and beta values are higher the lower the mean neutron energy, which is not consistent with the theory. The ratio of alpha coefficients reported here for various neutron beams to those for gamma rays reported elsewhere ranges between 3.2 and 4.6. This range of values represents the maximum limits for RBEn/gamma values (at very low doses), and is sometimes referred to as RBEm. These values increase with decreasing neutron energy. The ratios of beta coefficients for neutron and gamma-ray survival curves were lower than the alpha ratios, ranging between 0.9 and 1.9, although not reliably distinguished from 1.0. Each of a series of equal dose fractions given at 3-h intervals produced a constant (logarithmic) decrease in cell survival as evidenced by the consistency of the estimate of cell survival from a certain single dose fraction, regardless of the level of cell survival (number of dose fractions) from which the estimate was made. Even more significant than the overlap of individual data points is the excellent fit of all the data to survival curves reconstructed on the assumption of an equal effect per fraction. An implication of these results is that, with neutrons, too little unrepaired injury persists at 3 h to influence the response to a subsequent exposure measurably.
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Netter HJ, Kajino K, Taylor JM. Experimental transmission of human hepatitis delta virus to the laboratory mouse. J Virol 1993; 67:3357-62. [PMID: 8497056 PMCID: PMC237679 DOI: 10.1128/jvi.67.6.3357-3362.1993] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Human hepatitis delta virus (HDV), obtained from the serum of an experimentally infected woodchuck, was injected into either the peritoneal cavity or the tail vein of both adult CB17 mice and mice with a severe combined immunodeficiency (CB17-scid mice). Three lines of evidence indicated that the virus was able to reach the liver and infect hepatocytes: (i) the amount of HDV genomic RNA detected in the liver by Northern (RNA) analysis increased during the first 5 to 10 days postinoculation, reaching a peak that was about threefold the amount in the original inoculum; (ii) also detected in the liver was the viral antigenomic RNA, which is complementary to the genomic RNA found in virions, and is diagnostic for virus replication; and (iii) by immunoperoxidase staining of liver sections, the delta antigen was detected in the nuclei of scattered cells identifiable as hepatocytes. In all of the mice, clearance of the infection occurred between 10 and 20 days after inoculation. The half-life for clearance was about 3 days in CB17-scid mice, indicating that clearance of infection did not involve a T- and B-cell-dependent immune response. Cell-to-cell spread of the initial infection was not detected. One possible interpretation of our results is that HDV infection of hepatocytes is directly cytopathic. Also, the results imply that chronic infection of the liver in humans may require continuous spread of virus within the liver. Alternatively, HDV in the absence of helper virus may be unable to cause a chronic infection of hepatocytes in vivo.
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de Silva HV, Lauer SJ, Mahley RW, Weisgraber KH, Taylor JM. Apolipoproteins E and C-III have opposing roles in the clearance of lipoprotein remnants in transgenic mice. Biochem Soc Trans 1993; 21:483-7. [PMID: 8359515 DOI: 10.1042/bst0210483] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Abstract
Hepatitis delta virus expresses two forms of a single protein, the small (delta Ag-S) and large (delta Ag-L) antigens, which are identical except for an additional 19 residues present at the C terminus of delta Ag-L. While delta Ag-S is required to promote genome replication, delta Ag-L potently inhibits this process and also facilitates packaging of the viral genome by envelope proteins of the helper virus (hepatitis B virus). Regions within the antigens responsible for nuclear localization, RNA binding, and dimerization have been identified, yet it is not clear how these particular activities contribute to the ultimate replication and packaging phenotypes. Here we report the following findings. (i) Although the removal of the nuclear localization signal from either antigen resulted in significant cytoplasmic accumulation, both proteins still had access to the nucleus. As a consequence, no functional defect was observed with either mutant. (ii) The RNA-binding domain, although necessary for delta Ag-S function, could be deleted from delta Ag-L without compromising its ability to either inhibit replication or promote packaging. (iii) In contrast, the coiled-coil dimerization domain was required for both the activation of replication by delta Ag-S and the inhibition of replication by delta Ag-L. This region, with an additional 20 amino acids C-terminal to it, was necessary and sufficient to potently inhibit replication by interacting with the small antigen. (iv) The packaging property of delta Ag-L required a C-terminal Pro/Gly-rich region which is hypothesized to interact with the hepatitis B virus envelope proteins during the assembly process.
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Simonet WS, Bucay N, Lauer SJ, Taylor JM. A far-downstream hepatocyte-specific control region directs expression of the linked human apolipoprotein E and C-I genes in transgenic mice. J Biol Chem 1993; 268:8221-9. [PMID: 7681840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The human apolipoprotein (apo) E and apoC-I genes are located 5 kilobases apart in the same transcriptional orientation on chromosome 19, and they are expressed at high levels in the liver with lower levels of expression in selected other tissues. Analysis of a series of overlapping human apoE and apoC-I genomic fragments in transgenic mice revealed that the expression of these transgenes in the liver requires a common cis-acting regulatory domain. This hepatic control region (HCR) was localized to a 764-base pair region that is located about 18 kilobases downstream of the apoE promoter and about 9 kilobases downstream of the apoC-I promoter. All the transgenic animals that had been prepared with a construct that contained this region had relatively high levels of transgene expression in the liver, whereas constructs that lacked this region showed no expression in the liver. In situ hybridization studies showed that the HCR directed apoE and apoC-I transgene expression in hepatocytes. When the HCR from the apoE/C-I gene locus was ligated proximal to a human apoA-IV gene fragment, which is not normally expressed in the liver, the resulting apoA-IV/HCR fusion construct was expressed at high levels in the liver, indicating that the HCR could direct high level liver expression of a heterologous promoter/gene construct. Expression of the apoE transgene in the liver and kidney, and perhaps other tissues, required the presence of a nonspecific proximal enhancer element in the apolipoprotein E gene promoter, located between 161 and 141 bp relative to the transcription initiation site. However, the proximal apoE gene promoter, including this enhancer element, contained no sequences capable of directing hepatocyte expression in the absence of the HCR. Thus, the far-downstream HCR appears to contain all of the sequences necessary for determining high level liver-specific gene expression.
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Ho HN, Hultin LE, Mitsuyasu RT, Matud JL, Hausner MA, Bockstoce D, Chou CC, O'Rourke S, Taylor JM, Giorgi JV. Circulating HIV-specific CD8+ cytotoxic T cells express CD38 and HLA-DR antigens. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1993; 150:3070-9. [PMID: 8454874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
CD38, a molecule with multilineage distribution but unknown function, and the MHC class II molecule HLA-DR (DR) have markedly elevated levels of expression on CD8+ cells of HIV-infected people. This study investigated the expression of CD38 and DR Ag on circulating HIV-specific CD8+ CTL in HIV-seropositive subjects. Purified CD8+ lymphocytes from 22 participants in the University of California at Los Angeles Multicenter AIDS Cohort Study were screened for CTL activity against autologous EBV-immortalized lymphoblast targets infected with vaccinia vectors that carried HIVIIIB gag, pol, and env genes. Sixty-seven percent (14 of 21), 64% (14 of 22), and 9% (2 of 22), respectively, of the subjects had HIV-specific CD8+ CTL activity against gag, pol, and env proteins. CD8+ cells from 11 of the subjects who had high CTL activity were then FACS-separated using three-color immunofluorescence sorting. Circulating DR-CD38- CD8+ cells had little activity. Highly purified DR+CD38+ CD8+ cells had higher HIV-specific CTL activity than other CD8+ cells. DR+CD38- or DR-CD38+ CD8+ cells also mediated significant activity, but only about half as much on a per cell basis as DR+CD38+ CD8+ cells. This is the first report that the CD38 molecule is expressed in vivo on Ag-specific CD8+ CTL, and confirms previous reports that DR is expressed on these cells. Both asymptomatic HIV-seropositive subjects (144 +/- 132/mm3) and AIDS patients (253 +/- 178/mm3) had markedly elevated levels of DR+CD38+ CD8+ cells compared with the levels in HIV-seronegative controls (7 +/- 3/mm3). However, the level of anti-HIV CTL activity was not correlated with the level of DR+CD38+ CD8+ cells, indicating that enumeration of this lymphocyte population by flow cytometry most likely will not be a useful surrogate for measuring functional CTL activity. Low levels of HIV-specific CTL activity, especially against gag, were correlated with lower CD4+ cells numbers, suggesting that the loss of CD8+ T cell cytotoxic activity against HIV that has been reported to occur with advancing HIV disease progression may reflect in part the extent of CD4+ cell immunodeficiency in HIV-infected subjects.
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MESH Headings
- ADP-ribosyl Cyclase
- ADP-ribosyl Cyclase 1
- Antigens, CD
- Antigens, Differentiation/blood
- Antigens, Differentiation/immunology
- Binding Sites, Antibody
- Binding, Competitive/immunology
- CD8 Antigens/blood
- Cytotoxicity, Immunologic
- Gene Products, env/immunology
- Gene Products, gag/immunology
- Gene Products, pol/immunology
- HIV/immunology
- HIV Infections/immunology
- HLA-DR Antigens/blood
- HLA-DR Antigens/immunology
- Humans
- Immunophenotyping
- Male
- Membrane Glycoproteins
- T-Lymphocytes, Cytotoxic/immunology
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Ho HN, Hultin LE, Mitsuyasu RT, Matud JL, Hausner MA, Bockstoce D, Chou CC, O'Rourke S, Taylor JM, Giorgi JV. Circulating HIV-specific CD8+ cytotoxic T cells express CD38 and HLA-DR antigens. THE JOURNAL OF IMMUNOLOGY 1993. [DOI: 10.4049/jimmunol.150.7.3070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
CD38, a molecule with multilineage distribution but unknown function, and the MHC class II molecule HLA-DR (DR) have markedly elevated levels of expression on CD8+ cells of HIV-infected people. This study investigated the expression of CD38 and DR Ag on circulating HIV-specific CD8+ CTL in HIV-seropositive subjects. Purified CD8+ lymphocytes from 22 participants in the University of California at Los Angeles Multicenter AIDS Cohort Study were screened for CTL activity against autologous EBV-immortalized lymphoblast targets infected with vaccinia vectors that carried HIVIIIB gag, pol, and env genes. Sixty-seven percent (14 of 21), 64% (14 of 22), and 9% (2 of 22), respectively, of the subjects had HIV-specific CD8+ CTL activity against gag, pol, and env proteins. CD8+ cells from 11 of the subjects who had high CTL activity were then FACS-separated using three-color immunofluorescence sorting. Circulating DR-CD38- CD8+ cells had little activity. Highly purified DR+CD38+ CD8+ cells had higher HIV-specific CTL activity than other CD8+ cells. DR+CD38- or DR-CD38+ CD8+ cells also mediated significant activity, but only about half as much on a per cell basis as DR+CD38+ CD8+ cells. This is the first report that the CD38 molecule is expressed in vivo on Ag-specific CD8+ CTL, and confirms previous reports that DR is expressed on these cells. Both asymptomatic HIV-seropositive subjects (144 +/- 132/mm3) and AIDS patients (253 +/- 178/mm3) had markedly elevated levels of DR+CD38+ CD8+ cells compared with the levels in HIV-seronegative controls (7 +/- 3/mm3). However, the level of anti-HIV CTL activity was not correlated with the level of DR+CD38+ CD8+ cells, indicating that enumeration of this lymphocyte population by flow cytometry most likely will not be a useful surrogate for measuring functional CTL activity. Low levels of HIV-specific CTL activity, especially against gag, were correlated with lower CD4+ cells numbers, suggesting that the loss of CD8+ T cell cytotoxic activity against HIV that has been reported to occur with advancing HIV disease progression may reflect in part the extent of CD4+ cell immunodeficiency in HIV-infected subjects.
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Abstract
The near linearity of cellular dose-survival curves for neutrons facilities back-extrapolation to their origin at zero dose. This zero dose intercept is the number of clonogenic cells per circumference, from which the average number of clonogenic cells per crypt can be calculated. The average estimate of clonogenic cell number per crypt (k) from back-extrapolation of 11 single dose neutron survival curves to a common intercept was 100. Multifraction experiments provide an even better estimate of k because more complete dose survival curves can be constructed on the assumption of an equal effect per equal dose fraction. The short back-extrapolation of five such curves to a common intercept yields an estimated k value of 123 (108-140, 95% confidence interval) cells per crypt. These k values were higher than those estimated by Hendry's two-dose gamma-ray method.
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Zhou SY, Kingsley LA, Taylor JM, Chmiel JS, He DY, Hoover DR. A method to test for a recent increase in HIV-1 seroconversion incidence: results from the Multicenter AIDS Cohort Study (MACS). Stat Med 1993; 12:153-64. [PMID: 8446810 DOI: 10.1002/sim.4780120207] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We have formulated the problem of determining whether there has been an upturn in HIV-1 seroconversion incidence over the first five years of follow-up in the Multicenter AIDS Cohort Study (MACS) as that of locating the minimum of a quadratic regression or examination of two-knot piecewise spline models. Under a quadratic model, we propose a method to obtain a direct estimate and a bootstrap estimate for the location of the temporal turning point (local minimum) for HIV-1 seroconversion incidence and three methods to estimate confidence intervals for the location of the turning point for HIV seroconversion incidence: (1) Wald confidence interval estimate with or without log transformation assuming the asymptotic normality and applying the Delta method; (2) asymmetric confidence intervals using Fieller's Theorem and its modification; and (3) bootstrapping confidence intervals. Inferences for the temporal turning point based on Wald tests for a single regression term in a non-linear regression model were not reliable compared to inferences based on confidence intervals placed on calendar time. We present results using these different methods applied to the MACS data and we obtain power estimates to illustrate the performances of different methods.
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Abstract
This paper discusses two points regarding the interpretation of dose-time effects on tumor control in head and neck data. It is shown that the sample size in many clinical series will be too small to be able to statistically detect a dose-response relationship. The results from a non-parametric regression technique applied to control rate data from a large number of institutions suggest an influence of both dose and time on the control rate and qualitatively agree with a previous analysis of these data.
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224
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Abstract
Hepatitis delta virus exists in nature as a satellite of hepatitis B virus. This review emphasizes studies during the past few years that have clarified much about this satellite relationship. Many unique and intriguing features have been assigned to delta and its replication. In addition, certain unresolved questions are emphasized, and consideration is even given to the application of delta as a vector.
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225
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Jackson SM, Wood LC, Lauer S, Taylor JM, Cooper AD, Elias PM, Feingold KR. Effect of cutaneous permeability barrier disruption on HMG-CoA reductase, LDL receptor, and apolipoprotein E mRNA levels in the epidermis of hairless mice. J Lipid Res 1992; 33:1307-14. [PMID: 1402399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Disruption of the permeability barrier results in an increase in cholesterol synthesis in the epidermis. Inhibition of cholesterol synthesis impairs the repair and maintenance of barrier function. The increase in epidermal cholesterol synthesis after barrier disruption is due to an increase in the activity of epidermal HMG-CoA (3-hydroxy-3-methylglutaryl CoA) reductase. To determine the mechanism for this increase in enzyme activity, in the present study we have shown by Western blot analysis that there is a 1.5-fold increase in the mass of HMG-CoA reductase after acute disruption of the barrier with acetone. In a chronic model of barrier disruption, essential fatty acid deficiency, there is a 3-fold increase in the mass of HMG-CoA reductase. Northern blot analysis demonstrated that after acute barrier disruption with acetone or tape-stripping, epidermal HMG-CoA reductase mRNA levels are increased. In essential fatty acid deficiency, epidermal HMG-CoA reductase mRNA levels are increased 3-fold. Thus, both acute and chronic barrier disruption result in increases in epidermal HMG-CoA reductase mRNA levels which could account for the increase in HMG-CoA reductase mass and activity. Additionally, both acute and chronic barrier disruption increase the number of low density lipoprotein (LDL) receptors and LDL receptor mRNA levels in the epidermis. Moreover, epidermal apolipoprotein E mRNA levels are increased by both acute and chronic perturbations in the barrier. Increases in these proteins in response to barrier disruption may allow for increased lipid synthesis and transport between cells and facilitate barrier repair.
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