[Effects of icarrin on secretive function of cultured granulosa and adrenal cortical cells of rats]

Icarrin was added to cultured cells and the hormones in culture fluid were determined after 3 hours of incubation. The results showed that icarrin (30-1000 micrograms/L) could promote the estradiol production of granulosa cells. The most effective concentration was 100 micrograms/L. Icarrin also exerted a stimulatory effect on corticosterone production at the highest dosage (1000 micrograms/L).

The bovine papillomavirus E6 oncoprotein interacts with paxillin and disrupts the actin cytoskeleton

The E6 oncoprotein of bovine papillomavirus type 1 (BPV-1) has been shown to transform cells through a p53-independent pathway, but its transforming mechanism is unknown. Here we demonstrate in vitro and in vivo interactions between BPV-1 E6 and the focal adhesion protein paxillin. The ability of BPV-1 E6 to complex with paxillin correlated with its ability to transform; E6 mutant proteins impaired in their transformation function also were impaired in their abilities to bind paxillin. E6 binding to paxillin also may contribute to the carcinogenic potential of the human papillomavirus (HPV); we were able to show in vitro binding of paxillin to the E6 proteins of the cancer-associated type HPV 16 but not of the nononcogenic types 6 and 11. The association of E6 with paxillin was affected by depolymerization of the actin fiber network, and overexpression of BPV-1 E6 led to disruption of actin fiber formation. Disruption of the actin cytoskeleton is a characteristic of many transformed cells, and, in BPV-1 transformed cells, may be mediated by BPV-1 E6 through its interaction with paxillin.

[Methods for detecting mycobacterium tuberculosis in the air of wards for tuberculosis patients]

OBJECTIVE

To explore useful methods for detecting M. tuberculosis in the air of inpatient's wards of tuberculosis.

METHODS

Thirty samples were collected by using LWC-I air sampler from the air of wards housing sputum positive patients. The samples were washed with 0.85% sodium chloride solution, then centrifuged, and finally detected M. tuberculosis by L-J medium culture, BACTEC method, guinea pig experiment, PCR and Southern blotting.

RESULTS

The positive rates by PCR and Southern blotting were 47% (14/30) and 60% (18/30) respectively. In the experimental group containing 30 guinea pigs, two were positive by culture from the animal tissues (spleens or lungs), and another one was pathologically positive. Ten guinea pigs in control group were negative. Thirty samples were all negative by L-J and BACTEC.

CONCLUSIONS

It is indicated that using air sampling to detect M. tuberculosis in the air is practicable. PCR and Southern blotting are very helpful in detecting M. tuberculosis in the air because they have the advantages of high sensibility and specificity, and they remarkably shorten the time of detection. Animal experiment can provide compensation to PCR and Southern blotting.

Rapid swelling of a CHO-K1 aspartate/glutamate transport mutant in hypo-osmotic medium

Two Chinese hamster ovary cell (CHO-K1) mutants selected for defective glutamate transport via system X-AG are also highly permeable to small neutral molecules. Light microscopy demonstrated that exposure of one of these mutants, Ed-A1, to hypo-osmotic medium led to extremely rapid swelling, presumably due to increased water flux. When placed in 20% saline, Ed-A1 cells swelled to three times their original volume within 15 sec, a sixfold larger increase than parental CHO-K1. In spite of this rapid volume increase, mutant and wild-type cells remained viable for 20 min in dilute saline. A regulatory volume decrease in Ed-A1, and the continual swelling of CHO-K1, resulted in the two cells achieving equal size after 5 min in 20% saline. The time course of these volume changes permitted analysis of large numbers of cells by a hydrodynamic technique, steric field flow fractionation (FFF). Steric FFF demonstrated the expected inhibition of osmotic swelling of human erythrocytes by the mercurial, p-chloromercuribenzenesulfonic acid (PCMBS). However, PCMBS increased the apparent swelling rate of Ed-A1 and CHO-K1, suggesting that an aquaporin-like molecule is not responsible for any significant fraction of the water fluxes into either line. PCMBS also strongly inhibited aspartate transport by system X-AG. By taking advantage of their different swelling rates in hypotonic medium, steric FFF can separate mixtures of CHO-K1 and Ed-A1.

Comparative study of human red blood cell analysis with three different field-flow fractionation systems

An extensive multi-laboratory study was conducted to compare three different field-flow fractionation (FFF) systems for use in the analysis of human erythrocytes. The object of this study was to determine the relationship between the FFF elution properties for each system and the traditional hematological blood cell parameters. One centrifugal system (Utah) and two gravitational systems (Paris and Abbott) were compared. In order to analyze erythrocyte populations with a broad range of hematological indices, blood samples were collected from individuals heterozygous for sickle cell anemia (A/S) and also from normal controls (A/A), and these were analyzed at each site. Identical samples were analyzed by the Abbott and Utah sites. With all three systems, blood samples from each category produced narrow, overlapping distributions of FFF retention ratios, with the Abbott and Utah systems showing slight elevations in the mean retention ratios for the sickle cell samples. Blood cell elution peak characteristics were compared with standard hematological parameters for each of the FFF systems, and negative correlations were consistently found between mean corpuscular volume (MCV) and retention ratios. Positive correlations were found between red cell distribution width (RDW) and retention ratios. Elevated FFF retention ratios were frequently found with blood samples having abnormal hematological profiles. These results demonstrate that the three differently configured systems all produce similar analysis profiles for erythrocytes from the classes studied here. The relationships between FFF parameters and hematological indices were consistent for all systems.

Fixing of volume holograms in ferroelectric K(1-y)Li(y)Ta(1-x)Nb(x)O(3)

We report on the fixing of photorefractive volume holograms in potassium lithium tantalate niobate with ionic gratings and also with ferroelectric domain-reversed gratings. A diffraction efficiency of 55% is obtained with domain reversal in a 2-mm-thick ferroelectric phase K(1-y)Li(y)Ta(1-x)Nb(x)O(3) crystal doped with Co, V, and Ti. We measured the decay rate of the domain gratings and also of the initial electron gratings and ion gratings. The domain grating decay agrees with Vogel-Fulcher fits. The activation energies for ionic and electronic conductivity are 0.76 and 0.12 eV, respectively.

Separation and characterization of red blood cells with different membrane deformability using steric field-flow fractionation

Human red blood cells were treated in different ways to alter their membrane deformability, and the hydrodynamic behavior of these altered cells was studied using the steric field-flow fractionation (FFF) technique. The relationships between cell retention in the FFF channel, flow-rate of the carrier fluid and the applied field strength were studied for normal and glutaraldehyde-fixed human red cells, and separation conditions were optimized. The effect of flow-induced hydrodynamic lift forces on red cell retention in the steric FFF channel was studied, and the results suggest that the membrane deformability of the red cell is an important factor contributing to the lift force, besides other previously described effects due to density and flow velocity. Using steric FFF, a mixture of normal and glutaraldehyde-fixed human red cells was completely separated with a resolution twice that found in published data from gel permeation, another hydrodynamic separation technique. Partial loss of membrane deformability, induced by different degrees of glutaraldehyde-fixation, by diamide, or by a thermal treatment, has also been studied. Steric FFF is thus shown to have potential for rapid separation and differentiation of red cells with different density and membrane deformability, conditions known to be associated with, e.g., cell senescence and certain hematological diseases.

The Epstein-Barr virus nuclear antigen leader protein associates with hsp72/hsc73

Epstein-Barr virus nuclear antigen leader protein (EBNA-LP) is important for primary B-lymphocyte growth transformation. We now demonstrate that the W repeat-encoded domain of EBNA-LP significantly associates with proteins of the heat shock protein 70 family (hsp72/hsc73). hsp72/hsc73 may mediate the previously observed interaction between EBNA-LP and the retinoblastoma protein or p53.

The Epstein-Barr virus nuclear protein 2 acidic domain forms a complex with a novel cellular coactivator that can interact with TFIIE

Epstein-Barr virus nuclear antigen 2 (EBNA 2) activates transcription of specific genes and is essential for B-lymphocyte transformation. EBNA 2 has an acidic activation domain which interacts with general transcription factors TFIIB, TFIIH, and TAF40. We now show that EBNA 2 is specifically bound to a novel nuclear protein, p100, and that p100 can coactivate gene expression mediated by the EBNA 2 acidic domain. The EBNA 2 acidic domain was used to affinity purify p100. cDNA clones encoding the p100 open reading frame were identified on the basis of peptide sequences of the purified protein. Antibody against p100 coimmunoprecipitated p100 and EBNA 2 from Epstein-Barr virus-transformed lymphocyte extracts, indicating that EBNA 2 and p100 are complexed in vivo. p100 overexpression in cells specifically augmented EBNA 2 acidic domain-mediated activation. The coactivating effect is probably mediated by p100 interaction with TFIIE. Bacterially expressed p100 specifically adsorbs TFIIE from nuclear extracts, and in vitro-translated p56 or p34 TFIIE subunit can independently bind to p100. p100 also appears to be essential for normal cell growth, since cell viability was reduced by antisense p100 RNA and restored by sense p100 RNA expression.

Kinetic monitoring of enzymatic reactions in real time by quantitative high-performance liquid chromatography-mass spectrometry

The study of enzyme kinetics under steady-state conditions represents a common and very useful method for investigating the mechanisms of enzymatic reactions. We report the use of mass spectrometry (MS) coupled with HPLC for the kinetic analysis of enzymatic reactions in real time. The hydrolysis of dinucleotides with bovine pancreatic ribonuclease A (RNase A) and the substrate-specific hydrolysis of lactose with beta-galactosidase can be monitored using ion-spray (pneumatically assisted electrospray) mass spectrometry as a sensitive and specific detector for the native substrates. The resulting data can be used to calculate both KM and Vmax for each system. Kinetic parameters obtained for RNase A and beta-galactosidase paralleled those obtained by conventional techniques. These findings suggest the possibility of developing alternative techniques, based on mass spectrometric detection, for performing kinetic analyses of enzymatic processes where no simple spectrophotometric assay is feasible. In addition to enabling the determination of kinetic parameters for authentic substrates, and not chromogenic analogs, such assays would also be useful in situations where very high sensitivity and specificity are desired.

Chiral separation and detection of terbutaline and ephedrine by capillary electrophoresis coupled with ion spray mass spectrometry

The enantiomers of both terbutaline and ephedrine were separated by capillary electrophoresis using electrolyte solutions of heptakis(2,6-di-O-methyl)-beta-cyclodextrin in low pH buffers. The analytes were detected by ion spray mass spectrometry using selected ion monitoring or by selected reaction monitoring in the positive ion mode. Both the free drug enantiomers and the noncovalent enantiomer-cyclodextrin inclusion complexes for terbutaline can be detected simultaneously using this method. The feasibility of using CE/MS for chiral purity determination is demonstrated. In addition, a comparison of UV detection versus mass spectrometry detection for a spiked urine sample is included to demonstrate the selectivity and sensitivity advantages of the mass spectrometer as a CE detector.

Fixing of photorefractive volume holograms in K(1-y)Li(y)Ta(1-x)O(3)

We report the fixing of photorefractive holographic gratings with high efficiency in a sample of K(1-y)Li(y)Ta(1-x)Nb(x)O(3) doped with Cu, V, and Ti. Holograms are thermally fixed through the screening of a photorefractive space-charge f ield by a nonphotoactive species at elevated temperatures. Fixed holograms are revealed by illumination at lower temperatures. Diffraction efficiencies of 25% in a 0.54-cm-thick sample are measured. Holograms undergo thermal decay with a 0.67-eV activation energy.

The 62- and 80-kDa subunits of transcription factor IIH mediate the interaction with Epstein-Barr virus nuclear protein 2

EBNA 2 (Epstein-Barr virus nuclear antigen 2) is an acidic transactivator essential for EBV transformation of B lymphocytes. We show that EBNA 2 directly interacts with general transcription factor IIH. Glutathione S-transferase (GST)-EBNA 2 acidic domain fusion protein depleted transcription factor IIH activity from a TFIIH nuclear fraction. The p89 (ERCC3), p80 (ERCC2), and p62 subunits of TFIIH were among the proteins retained by GST-EBNA 2. Eluates from the GST-EBNA 2 beads reconstituted activity in a TFIIH-dependent in vitro transcription assay. The p62 and p80 subunits of TFIIH independently bound to GST-EBNA 2, whereas the p34 subunit of TFIIH only bound in the presence of p62. A Trp-->Thr mutation in the EBNA 2 acidic domain abolishes EBNA 2 transactivation in vivo and greatly compromised EBNA 2 association with TFIIH activity and with the p62 and p80 subunits, providing a link between EBNA 2 transactivation and these interactions. Antibodies directed against the p62 subunit of TFIIH coimmunoprecipitated EBNA 2 from EBV-transformed B lymphocytes, indicating that EBNA 2 associates with TFIIH in vivo.

Calcium- and protein kinase C-dependent basal tone in the aorta of hypertensive rats

We examined the regulatory influence of nitric oxide on development of calcium- and protein kinase C-dependent basal tone in rings of thoracic aortas from rats with aortic coarctation-induced hypertension and from normotensive controls. Aortic rings from hypertensive rats but not those from normotensive rats, bathed in Krebs' bicarbonate buffer and subjected to 2 g of passive stretch, were relaxed by removal of calcium from the buffer and by the protein kinase C inhibitors staurosporine and calphostin C. Protein kinase C activity was much greater in homogenates of aortae from hypertensive rats than in those from normotensive controls (2124 +/- 785 versus 608 +/- 73 pmol.min-1.mg protein-1, respectively). Relaxant responses to removal of calcium and to staurosporine were greater in aortic rings rubbed to remove the vascular endothelium than in endothelium-intact rings (-1.07 +/- 0.12 versus -0.70 +/- 0.10 g tension/mg tissue, respectively, for calcium removal and -1.10 +/- 0.12 versus -0.65 +/- 0.08 g tension/mg tissue, respectively, for staurosporine). Treatment with an inhibitor of nitric oxide synthesis increased calcium-dependent tone in both intact and endothelium-denuded aortic rings from hypertensive rats. Conversely, the administration of sodium nitroprusside or L-arginine reversed tone in both intact and denuded aortic rings from hypertensive rats, but acetylcholine reversed tone only in intact rings. The relaxant effects of these agents were paralleled by increases in cyclic guanosine monophosphate in aortic tissue. We conclude that aortic rings from rats with aortic coarctation-induced hypertension display calcium-dependent, protein kinase C-mediated tone in the absence of exogenous vasoconstrictors.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium pentobarbital versus alpha-chloralose anesthesia. Experimental production of substantially different slopes in the transmural CP/ATP ratios within the left ventricle of the canine myocardium

BACKGROUND

Transmural analyses of the creatine phosphate (CP)/ATP ratio in various lamina of the canine myocardium have previously revealed significant variations in the CP/ATP ratio, with the subendocardial layer displaying a decreased ratio relative to the subepicardial layer. Without exception, these results were obtained under sodium pentobarbital anesthesia. These findings have been interpreted to imply that the normal endocardium may be operating in the oxygen-limited domain or that there are transmurally varying set points for the regulation of oxidative phosphorylation.

METHODS AND RESULTS

In this work, we examine the effect of the anesthetic regimen on the transmural CP/ATP ratio within the left ventricular wall of the canine myocardium using spatially localized 31P-nuclear magnetic resonance (NMR) and an open-chest model. Two anesthetics were compared, alpha-chloralose and sodium pentobarbital. Under sodium pentobarbital, the CP/ATP ratio ranged from 1.92 +/- 0.06 to 2.51 +/- 0.08 from endocardium to epicardium, resulting in a transmural slope in the CP/ATP ratio of 0.149 +/- 0.047 (n = 22). Under alpha-chloralose, CP/ATP ratios ranged from 2.18 +/- 0.05 to 2.32 +/- 0.06, with a transmural slope of 0.035 +/- 0.018 (n = 38). Thus, the transmural slope in CP/ATP ratio was nearly four times greater with sodium pentobarbital than with alpha-chloralose, and the difference in these slopes was statistically significant (P = .029). No difference was observed in average CP/ATP obtained from the entire wall with either anesthetic.

CONCLUSIONS

These results demonstrate that the transmural trend in CP/ATP ratio previously reported in the myocardium is likely to be a direct reflection of the sodium pentobarbital anesthetic regimen, not truly reflecting the trend in the normal unanesthetized animal. Moreover, since the transmural variation in CP/ATP ratio was greatly reduced with alpha-chloralose, it appears unlikely that the endocardium in the normal unanesthetized heart is operating in the oxygen-limited domain. These results also point to the importance of the anesthetic regimen in biochemical analysis, indicate the necessity of increased caution in directly translating results obtained under anesthesia, and demonstrate the unique power of in vivo NMR to extract such subtle biochemical information.

The Epstein-Barr virus nuclear protein 2 acidic domain can interact with TFIIB, TAF40, and RPA70 but not with TATA-binding protein

The Epstein-Barr virus nuclear antigen 2 (EBNA-2) acidic domain is essential for B-lymphocyte growth transformation and can activate transcription when brought to a promoter by a sequence-specific DNA-binding domain. We now show that the EBNA-2 acidic domain has slightly less activity than the proteotypic acidic transactivator VP16 in depleting nuclear extracts of basal transcription activity. Like VP16, EBNA-2 associates with TFIIB, TAF40, and RPA70. However, EBNA-2 has much less avidity for TATA-binding protein. A Trp-to-Thr mutation within the acidic domain abolishes EBNA-2 transactivating activity and greatly compromises the association with TFIIB, TAF40, and RPA70, establishing a genetic linkage between transactivating activity and these associations.

Epstein-Barr virus nuclear protein 2 transactivation of the latent membrane protein 1 promoter is mediated by J kappa and PU.1

Expression of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) oncogene is regulated by the EBV nuclear protein 2 (EBNA-2) transactivator. EBNA-2 is known to interact with the cellular DNA-binding protein J kappa and is recruited to promoters containing the GTGGGAA J kappa recognition sequence. The minimal EBNA-2-responsive LMP-1 promoter includes one J kappa-binding site, and we now show that mutation of that site, such that J kappa cannot bind, reduces EBNA-2 responsiveness by 60%. To identify other factors which interact with the LMP-1 EBNA-2 response element (E2RE), a -236/-145 minimal E2RE was used as a probe in an electrophoretic mobility shift assay. The previously characterized factors J kappa, PU.1, and AML1 bind to the LMP-1 E2RE, along with six other unidentified factors (LBF2 to LBF7). Binding sites were mapped for each factor. LBF4 is B- and T-cell specific and recognizes the PU.1 GGAA core sequence as shown by methylation interference. LBF4 has a molecular mass of 105 kDa and is probably unrelated to PU.1. LBF2 was found only in epithelial cell lines, whereas LBF3, LBF5, LBF6, and LBF7 were not cell type specific. Mutations of the AML1- or LBF4-binding sites had no effect on EBNA-2 transactivation, whereas mutation of the PU.1-binding site completely eliminated EBNA-2 responses. A gst-EBNA-2 fusion protein specifically depleted PU.1 from nuclear extracts and bound in vitro translated PU.1, providing biochemical evidence for a direct EBNA-2-PU.1 interaction. Thus, EBNA-2 transactivation of the LMP-1 promoter is dependent on interaction with at least two distinct sequence-specific DNA-binding proteins, J kappa and PU.1. LBF3, LBF5, LBF6, or LBF7 may also be involved, since their binding sites also contribute to EBNA-2 responsiveness.

Genetic and biochemical evidence that EBNA 2 interaction with a 63-kDa cellular GTG-binding protein is essential for B lymphocyte growth transformation by EBV

Epstein-Barr virus (EBV) nuclear protein 2 (EBNA 2) is an acidic transcriptional transactivator of virus and cell gene expression and is essential for growth transformation of primary B lymphocytes. EBNA 2 transactivation of response elements (E2REs) can be mediated by interaction with a GTGGGAA-specific DNA-binding factor(s). We now purify the factor by S-Sepharose and EBNA 2 affinity chromatography and identify it as a single 63-kDa protein. The protein is shown to specifically coimmunoprecipitate with EBNA 2 from lymphoblasts transfected with an EBNA 2 FLAG expression vector. Mutation of GTG to TCT in a GTGGGAA motif common to the Cp, LMP2, and LMP1 promoters results in loss of recognition by p63. EBNA 2 amino acids 310-336 are sufficient for p63 binding. The only motif in this 27 amino acid sequence which is common to the EBNA 2 genes of EBV types 1 and 2 is GPPWWPP (I/V) (C/R) DP, which is therefore likely to mediate p63 interaction. Mutation of WW to SS or FF ablates interaction with p63, indicating that both the hydrophobic and aromatic characteristics of WW are essential for its "key" interaction with p63. EBNA 2 with a WW mutated to SS is also unable to marker rescue primary B lymphocyte transforming virus from cells infected with an EBNA 2-deleted virus, while otherwise isogenic wild-type EBNA 2 readily marker rescues transforming virus in parallel experiments. EBNA 2 transactivation through the Cp E2RE is completely abolished by the WW to SS mutation while transactivation of -234 to +40 LMP1 E2RE is only partially affected. These genetic and biochemical experiments support the hypothesis that EBNA 2 WW interaction with a p63 GTGGGAA-binding protein is essential for EBV-mediated cell growth transformation because it specifically associates EBNA 2 with its response elements. This enables the EBNA 2 acidic domain to transcriptionally transactivate specific genes.

The EBNA-2 arginine-glycine domain is critical but not essential for B-lymphocyte growth transformation; the rest of region 3 lacks essential interactive domains

Since deletion of region 3 (amino acids [aa] 333 to 425) of Epstein-Barr virus nuclear protein 2 (EBNA-2) results in EBV recombinants which cannot transform primary B lymphocytes (J. I. Cohen, F. Wang, and E. Kieff, J. Virol. 65:2545-2554, 1991), the role of domains of region 3 was investigated. Deletion of the Arg-Gly repeat domain, R-337GQSRGRGRGRGRGRGKG354, results in EBV recombinants that transform primary B lymphocytes with modestly decreased activity. The transformed cells grow slowly and are difficult to expand. EBNA-2 deleted for the Arg-Gly domain does not associate with the nuclear chromatin fraction. The Arg-Gly repeat has an intrinsic ability to bind to histone H1, to other proteins, including EBNA-1, and to nucleic acids, especially poly(G). Two independent deletions of each part of the rest of region 3 (aa 359 to 383 and 385 to 430) have little effect on transformation, while deletion of the rest of region 3 (aa 361 to 425) as a single segment substantially reduces transformation efficiency. EBNA-2 deleted for all of region 3 can still transactivate the LMP1 promoter in transient expression assays but is less active than EBNA-2 in transactivating the BamHI-C promoter. EBNA-2 deleted for the Arg-Gly domain is better than EBNA-2 at transactivating the LMP1 promoter and is as active as EBNA-2 in transactivating the BamHI-C promoter. These data are most compatible with a model in which the Arg-Gly domain of region 3 is a modulator of EBNA-2 interactions and activities, while the rest of region 3 is important in positioning the region 2 J kappa binding domain relative to the region 4 acidic transactivating domain. Despite the null phenotype of the region 3 deletion, region 3 is unlikely to mediate essential interactions with other proteins.

The Epstein-Barr virus nuclear antigen 2 transactivator is directed to response elements by the J kappa recombination signal binding protein

Epstein-Barr virus nuclear antigen 2 (EBNA-2) plays an essential role in primary B-lymphocyte growth transformation. EBNA-2 is an acidic transcriptional transactivator that is brought to virus and cell EBNA-2 response elements by interaction with a factor that recognizes the double-stranded sequence MNYYGTGGGAA, where M is A or C, N is any nucleotide, and Y is a pyrimidine. A 63-kDa protein that recognizes this DNA sequence has now been purified by S-Sepharose and oligonucleotide affinity chromatography. p63 peptide sequence is identical to the predicted amino acid sequence for the human J kappa immunoglobulin recombination signal binding protein. Purified or recombinant in vitro-translated J kappa binds to the MNYYGTGGGAA EBNA-2 response element sequence and interacts with EBNA-2. Surprisingly, J kappa does not bind to the J kappa 1 heptamer recombination signal sequence (CACTGTG), and its prior identification as a heptamer binding protein was most likely due to the addition of a BamHI restriction site to the native heptamer creating a near EBNA-2 response element consensus (CACTGTGGGAT).

Cells and viruses with mutations affecting viral entry are selected during persistent infections of L cells with mammalian reoviruses

Previous studies demonstrated that both cellular and viral mutants are selected during maintenance of persistent infections established in murine L cells with high-passage stocks of mammalian reoviruses. In particular, when one culture was cured of persistent infection, the resulting cells were found to support the growth of viruses isolated from persistently infected cultures (termed PI viruses here) better than that of wild-type (wt) viruses (R. Ahmed, W. M. Canning, R. S. Kauffman, A. H. Sharpe, J. V. Hallum, and B. N. Fields, Cell 25:325-332, 1981). To address the nature of cellular and viral mutations selected during maintenance of persistent reovirus infections, we established independent, persistently infected cultures with L cells and high-passage stocks of wt reovirus. These cultures served as sources of new PI viruses and cured cells for study. We found that although wt viruses grew poorly in cured cells when infection was initiated with intact virions, they grew well in cured cells when infection was initiated with infectious subvirion particles generated from virions by in vitro treatment with chymotrypsin. This finding indicates that the block to growth of wt viruses in cured cells involves an early step that is unique to infection by virions, such as proteolytic processing in an endocytic compartment. We also found that PI viruses grew better than wt viruses in L cells treated with ammonium chloride, a weak base that inhibits the pH decrease in endosomes and lysosomes. Because ammonium chloride blocks an early step in infection by intact virions, probably the proteolytic processing of viral outer capsid proteins by acid-dependent cellular proteases in late endosomes or lysosomes, this finding indicates that PI viruses differ from wt viruses with respect to viral entry into cells. Therefore, these results indicate that both cells and viruses evolve mutations that affect one or more early steps in the viral growth cycle during maintenance of L-cell cultures persistently infected with reoviruses.

Solid phase purification in automated DNA sequencing

A solid phase purification method has been utilized to investigate the effect of template DNA and other contaminants present in enzymatic DNA sequencing reactions upon data quality in automated DNA sequence analysis. The primer oligonucleotide is prepared with an internal biotin group and one of four fluorescent tags at the 5' terminus. The fluorescently labeled DNA fragments produced in the sequencing reactions are separated from other reaction components, including template DNA, using superparamagnetic streptavidin beads. Template DNA and other reaction components may then be added back to the purified material to assess their effect upon sequence data. It is found that band intensity and base calling accuracy are decreased by the presence of the template DNA and other reaction components.

CP-MAS 13C NMR investigation of phase structure in mixtures of poly(ethyl acrylate) ionomers with sodium palmitate

A solid-state NMR study of mixtures of poly(ethyl acrylate) (PEA) or poly(ethyl acrylate-co-sodium acrylate) (PEA-i) with sodium palmitate (SP) shows that (1) there is a change in the electron density of the carboxylate carbons of SP in the mixtures compared to pure SP; (2) the T1ρH value for SP in the mixtures with PEA or PEA-i is depressed in comparison with pure SP for mixtures containing over 4 mol% SP. This can be interpreted as a result of interfacial magnetization transfer from the protons of PEA or PEA-i to the protons of SP; (3) deuterated SP (D-SP) shows a similar growth in magnetization as a function of contact time when pure or when mixed with PEA. The growth is significantly slower in its mixtures with PEA-i. All these findings can be explained by a PEA-i:SP mixture morphology involving bilayers of carboxylate ions at the interface; the same tendency exists in the PEA:SP mixtures, only in this case the ester groups of PEA are preferentially located at the interface.

Solid-phase method for the purification of DNA sequencing reactions

A solid-phase method for the purification of the single-stranded DNA molecules produced in enzymatic sequencing reactions has been developed. A primer oligonucleotide is synthesized containing a biotin moiety at an internal position. This primer is utilized in enzymatic extension reactions, and the resulting products are bound to streptavidin-coated magnetic beads. Contaminating species such as protein, salts, template DNA, and unincorporated or degraded deoxy and dideoxy nucleotide triphosphates may be removed by washing the beads after immobilizing them in the sample tube with a fixed magnet. The resulting pure single-stranded DNA fragments are removed from the solid support by heating in 10 mM EDTA, 95% formamide, loading dye at 90 degrees C, and may then be directly loaded onto a polyacrylamide gel for sequence analysis. This method was used to investigate the effect of various contaminants upon DNA sequence data.

Characterization of an Epstein-Barr virus receptor on human epithelial cells

Epstein-Barr virus (EBV) adsorption to human B lymphocytes is mediated by the viral envelope glycoprotein, gp350/220, which binds to the cell surface protein, CD21, also known as the CR2 complement receptor. Human epithelial cells also express an EBV receptor. A candidate surface molecule of 195 kD has previously been identified on an epithelial cell line and explanted epithelial tissue by reactivity with the CD21 specific monoclonal antibody (mAb), HB-5a. In experiments to further characterize the epithelial cell EBV receptor, we have found that two human epithelial cell lines, RHEK-1 and HeLa, specifically bind intact EB virions. A 145-kD protein, similar in size to B lymphocyte CD21, was specifically precipitated from surface iodinated RHEK-1 cells using the HB-5a mAb, or using purified soluble gp350/220 coupled to agarose beads. The previously identified 195-kD protein did not bind to gp350/220 or react with two other anti-CD21 mAbs. CD21 homologous RNA, similar in size to the B lymphocyte CD21 mRNA, was detected in both RHEK-1 and HeLa cells. The nucleotide sequence of the epithelial cell cDNA was identical to B lymphocyte CD21. The longest clone differs from previously reported CD21 cDNAs in having additional 5' untranslated sequence. Polymerase chain reaction amplification of RHEK-1- or B lymphoblastoid-derived cDNA verified that most CD21 transcripts are initiated at least 30-50 nucleotides upstream of the previously reported mRNA cap site. These experiments demonstrate that human epithelial cells can express CD21, and that CD21 is likely to mediate EBV adsorption to epithelial cells.