Antibody-enhanced binding of dengue-2 virus to human platelets

The mechanisms underlying severe thrombocytopenia in dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) are not completely understood. We present here the first evidence that dengue type 2 virus binds to human platelets only in the presence of virus-specific antibody, supporting a role for immune-mediated clearance of platelets in the pathogenesis of thrombocytopenia in DHF/DSS. Antibody-enhanced binding of virus of platelets was also demonstrated with a panel of eight murine monoclonal antibodies specific for the dengue E protein. The degree of binding was dependent on the antibody used but not on the antibody IgG subclass, indicating that factors other than the platelet Fc receptor are involved in binding of virus-antibody complexes to the platelet surface. Confirmation that antibody-dependent virus binding to platelets is not primarily mediated by the platelet Fc receptor was obtained by demonstrating good binding even when platelets were pretreated with the Fc gamma RII-specific antibody IV.3.

Isolation of a gene encoding a human reduced folate carrier (RFC1) and analysis of its expression in transport-deficient, methotrexate-resistant human breast cancer cells

Our laboratory has previously reported the isolation of a murine cDNA which restores reduced folate carrier (RFC) activity and methotrexate (MTX) sensitivity to a MTX-resistant, transport-deficient human breast cancer cell line (MTXR ZR-75-1) (K. H. Dixon et al., J. Biol. Chem., 269: 17-20, 1994). Using this murine cDNA as a probe, we have isolated two homologous overlapping partial cDNAs from a human testis cDNA library. In addition, using human cDNA as a probe, we have isolated a 20-kb human genomic fragment which contains RFC coding regions. Analysis of the nucleotide sequence of these clones revealed that the human RFC gene, RFC1, is approximately 65% homologous to the murine and hamster genes. Using a human genomic P1 plasmid clone containing RFC1, we mapped the location of RFC1 by fluorescence in situ hybridization to the end of the long arm of chromosome 21 (21q22.2-q22.3). Fluorescence in situ hybridization analysis also showed that two copies of RFC1 were present in MTXR ZR-75-1 cells, and showed no evidence of rearrangement of this gene. Northern blot analysis of MTXR ZR-75-1 cells demonstrated a marked decrease in the level of the 3-kb RFC1 transcript relative to the parental cell line, and Western blot analysis using a polyclonal antibody raised against a peptide generated from the RFC1 sequence showed decreased expression of an approximately M(r) 56,000 protein in MTXR ZR-75-1 cells. Finally, MTXR ZR-75-1 cells transfected with an RFC1 gene showed increased MTX uptake, which was more sensitive to competition by folinic acid than by folic acid. Therefore, decreased RFC1 expression appears to be the molecular mechanism of decreased MTX uptake in this MTX-resistant cell line.

Surgical treatment of hallux valgus by reconstruction of metatarsal arch and modified McBride operation (40 cases report)

72 feet with hallux valgus among 40 patients treated by reconstruction of metatarsal arch and modified McBride operation are reported in this paper. After an average of 4.5 years of postoperative follow-up, the results showed an overall 9 degrees and 3 degrees correction of the hallux abductus angle and the intermetatarsal angle, respectively. 95% of the cases of bunions disappeared, 66% calli under the heads of the first and second metatarsal disappeared, and 91% patients were satisfied with the changes of their feet appearance.

[A preliminary study on the mechanism of against human tongue cancer cell line]

Inverted phase contrast microscope and transmission electron microscope examination reveals that, tumor-draining lymphnode lymphocytes (DNL) conjugated with tumor cells very tightly at 12 hours co-culture. The DNL cell nucleus was seen positioned away from the target cells, whereas the cell mitochondria granules were oriented toward the point of contact with the target cells. The injured target cell had a highly condensed cytoplasm and chromatin and formation of cytoplasmic blebs, which were consistent with an apoptotic cell death rather than with a lytic or necrotic cell death. The mechanism was exocytosis of granules containing a pore-forming protein. Holes formed in the target cell's membrane may allow a lethal substance to enter and to induce its death via an apoptotic mechanism.

Utilization of multiple polyadenylation signals in the human RHOA protooncogene

Little is known regarding the regulation of expression of the RHOA protooncogene, a member of the family of genes encoding Ras-related GTP-binding proteins. We have previously reported that the 3' untranslated region (UTR) of RHOA was contained within a genomic sequence which flanked the 5' end of the human glutathione peroxidase 1-encoding gene [J.A. Moscow et al., J. Biol. Chem. 267 (1992) 5949-5958]. Our previous studies revealed the presence of multiple (1.8 and 1.5 kb) RHOA mRNA species in breast cancer cell lines and of three putative polyadenylation signals in the RHOA 3' UTR. In this report, we have isolated several RHOA cDNAs from a multidrug-resistant MCF-7 human breast cancer cell line. Sequence analyses of these RHOA cDNA clones indicate that multiple polyadenylation signals are used to terminate RHOA transcripts. RNase-protection analysis demonstrated that all three polyadenylation signals are utilized in breast cancer cell lines and RNA stability studies demonstrated that RHOA RNA species with different 3' ends have equivalent stability. Since little is known about the RNA expression of RHOA in human tumors, and since both activated and non-activated RHOA genes possess transformation potential, we analyzed RHOA mRNA in lung and colon tumors by Northern blot and RNase-protection analyses. In all eight lung tumors examined, RHOA RNA levels were decreased relative to the level in normal surrounding tissue, whereas RHOA expression was decreased in only two of six colon tumors. We also found that lovastatin-induced cell cycle arrest resulted in increased RHOA RNA expression in breast cancer cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of selenium and DTPA on cadmium excretion in rats]

Fifty-six male wistar rats were selected to study the effects of selenium and DTPA on cadmium excretion. Cadmium levels in urine, feces and tissues of the rats were determined with graphite stove method, and their kidneys were examined pathohistologically. Results showed selenium had stronger effects on cadmium excretion via feces in rats than DTPA did, and combination of both of them showed synergistic effects on it. Also, selenium could accelerate the recovery from kidney injury caused by cadmium, and combination of both of them showed synergism on it.

Spectrum of Ig classes, specificities, and titers of serum antiglycoproteins in chronic idiopathic thrombocytopenic purpura

The characteristic decreased recovery and survival of transfused platelets in nonalloimmunized patients with idiopathic thrombocytopenic purpura (ITP) suggest that plasma antiplatelet autoantibodies (autoAbs) are present in almost all cases. Studies emphasizing reactions of IgG autoAbs with platelet glycoprotein (GP) IIb/IIIa indicate that less than 50% of ITP patients have detectable serum Abs, and that many of these Abs may not be pathogenic because they are directed against epitopes in the cytoplasmic domain of GPIIIa (Fujisawa et al, Blood 77:2207, 1991 and 79:1441, 1992). We evaluated the contribution of Ig classes other than IgG to the overall incidence of serum Abs in 47 patients with chronic ITP and the frequency of reactions with GPs IIb/IIIa, Ib/IX, IV, and Ia/IIa. Abs were further characterized by their reactions with cytosolic or exosolic GP epitopes and their titers and apparent affinities. Using immunobead techniques we found (1) anti-GPs in 85% of sera; (2) IgA and IgG Abs each in 68%, together in 51%; (3) IgM agglutinins in 15%, always with another Ab class; (4) GP Ib/IX, IIb/IIIa, IV, and Ia/IIa targets in 83%, 81%, 38%, and 28% of cases, respectively; (5) 93% of positive sera reactive with more than one GP; but GP IV or Ia/IIa never the sole target; (6) Abs against cytosolic epitopes on one or more of GPs IIIa, Ib alpha, and IIb beta in 66% of sera, always accompanied by Abs against exosolic epitopes of the same or a different GP; (7) autoAbs against cytosolic GP epitopes in 38% of 16 patients recovered from posttransfusion purpura and drug purpura; and (8) evidence that serum ITP Abs, often high-titered, saturate platelets less than alloAbs against the same GPs. Whereas Abs against external GP epitopes are a distinctive marker for ITP in 80% of patients, Abs against internal GP epitopes are likely a secondary phenomenon of platelet destruction and not pathogenic. Anti-GPs against exosolic epitopes were also found in eluates of patient's platelets, suggesting that they have pathogenic significance.

Examination of human tumors for rhoA mutations

rhoA encodes a ras-related GTP-binding protein that is thought to play a role in cytoskeletal organization. Recent evidence has suggested both that rhoA could act either as a dominant oncogene, since transfection of both normal and activated rho genes confer a transformed phenotype on fibroblast cells in culture, or as a recessive tumor suppressor gene, by virtue, in part, of its chromosomal location at 3p21, a site deleted in many human malignancies. In either case, a role for rhoA in the oncogenesis of human tumors would be supported by the finding of rhoA mutations in tumors. We therefore examined human tumors and cell lines for mutations in the protein coding regions of rhoA by RNAase protection analysis. We first examined the expression of rhoA in renal cell carcinoma cell lines in which 3p21 was heterozygously deleted or retained. We found no evidence for rhoA mutations in these specimens. We also examined RNA from lung, breast, colon or ovarian tumors and also found no evidence of activating rhoA mutations. Furthermore, there was no relation between the level of rhoA mRNA expression and the presence or absence of 3p21 deletions in the renal cell carcinoma specimens. Thus, although rhoA has transforming potential in vitro, there is no evidence that it is activated by mutation in human malignancies, or that it could act as a tumor suppressor gene in tumors in which 3p21 is deleted.

HLA-DQA and DQB alleles contribute to susceptibility to insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is strongly associated with the presence of arginine in position 52 of the DQ alpha chain and absence of aspartic acid in position 57 of the DQ beta chain in Caucasians. With the aim of confirming this association in Chinese, extensive oligonucleotide dot blot hybridization of PCR-amplified DQA1 and DQB1 genes was studied using samples from 48 IDDM patients and 46 healthy nondiabetic control subjects. Three major findings emerged from our analysis. 1) DQ alpha 52-Arg and DQ beta 57-non-Asp are strongly associated with IDDM susceptibility as compared with controls (P < 0.001 and 0.005, respectively). 2) DQ beta 57-non-Asp homozygous (NA/NA) is associated with increased susceptibility to IDDM (22.9% vs 2.2% in controls, P < 0.01). DQ beta 57-Asp homozygous (A/A) is associated with protection against IDDM (14.6% vs 47.8% in controls, P < 0.01). 3) In this study, about 14.6% of IDDM patients were homozygous for DQ beta 57-Asp, compared with 0% of American patients. Only 22.9% were homozygous for DQ beta 57-Asp, compared with 96% of American diabetic subjects in a previous study. Thus it is unlikely that the DQ beta 57 amino acid has a major effect on IDDM susceptibility in Chinese.

Fluorescence of peptide N-terminal 2-oxoacyl and quinoxaline derivatives

A peptide reacts with glyoxalic acid resulting in transamination of the N-terminal residue to form a 2-oxoacyl group. This further reacts with o-phenylenediamine, leading to a quinoxaline derivative of the original N-terminal amino acid, which is cleavable in mild acid [Dixon & Fields (1972) Methods Enzymol. 25, 409-419]. The 2-oxoacyl peptides are weakly fluorescent with emission maxima around 410 nm and excitation maxima at about 320 nm, depending on the nature and length of the peptide. Formation of the quinoxaline derivative results in a marked increase of fluorescence, with emission maximum of 363 nm when excited at 303 nm. The fluorescence properties of these derivatives change with the nature and length of the peptides and are affected by the presence of organic solvents, NaCl and denaturants. It is suggested that such fluorescent derivatives could be used as probes for the study of the conformation of the N-terminal region of peptides and proteins.

Structure and function of the 5'-flanking sequence of the human cytosolic selenium-dependent glutathione peroxidase gene (hgpx1)

Human selenium-dependent glutathione peroxidase (hGPx1) (EC 1.11.1.9) is thought to be involved in many critical cellular functions as a result of its role in glutathione-mediated reduction of toxic peroxides, and it is implicated as a mechanism of resistance against oxygen free radicals. Previous studies have demonstrated that the gene encoding hGPx1 (hgpx1) is more highly expressed in multidrug-resistant AdrR MCF-7 human breast cancer cells than in the parental WT MCF-7 cell line. In order to further study the transcriptional regulation of hgpx1, we have cloned the genomic hgpx1 gene and determined its nucleotide sequence. The 2550-base pair (bp) 5'-flanking sequence of hgpx1 contained the terminal 511 bp of the 3' end of a previously reported rhoH12 cDNA (Yeramian, P., Chardin, P., Madaule, P., and Tavitian, A. (1987) Nucleic Acids Res. 15, 1989), a ras-related oncogene. Further downstream from rhoH12, but before the start of transcription of hgpx1, RNase protection analysis revealed a transcribed sequence of at least 270 bp which we have called mid. RNA transcripts homologous to both rhoH12 (1.8 and 1.5 kilobase pairs (kb)) and mid (1.8 kb) are also more highly expressed in AdrR MCF-7 cells than in WT MCF-7 cells. We screened an AdrR MCF-7 cDNA library with the mid sequence and isolated a partial cDNA clone which contains both mid and rhoH12 sequences and is colinear with the genomic sequence which extends from 10 bp 3' to the rhoH12 stop codon to 810 bp 5' to the start of transcription of hgpx1. The start of transcription of hgpx1 in AdrR MCF-7 cells was determined by primer extension analysis. The promoter and 2 kb of the 5'-flanking sequence of hgpx1 was fused to the bacterial chloramphenicol acetyltransferase gene (hGPx1-CAT1). Analysis of deletion constructs of hGPx1-CAT1 revealed three possible cis-acting regulatory regions. The transcriptional regulation of hgpx1 was examined using the hGPx1-CAT hybrid genes and nuclear run-on studies. We found no evidence that increased mRNA transcript formation could account for different levels of hgpx1 RNA either in different breast cancer cell lines or in response to selenium.

High-level expression of staphylococcal nuclease R gene in Escherichia coli

Staphylococcal nuclease R, an analogue of nuclease A, was overproduced under the transcriptional control of the bacteriophage lambda PRPL promoters regulated by temperature sensitive repressors. The expression level reached 200-300 mg l-1 and showed little host dependence in different strains. The investigations of the recombinant nuclease R have revealed that the amino terminal formyl methionine residue of the nuclease is precisely processed, the protein consists of 155 amino acid residues. The experiment shows that the pBV221-DH5 alpha is a quite suitable vector-host system for high-level expression and precise processing of heterologous genes in Escherichia coli. The comparative studies between the codons used in the staphylococcal nuclease R gene and the optimal codon usage in E. coli indicate that high level expression of heterologous genes in E. coli may not always require a high degree of codon usage bias.

[Precancerous and cancerous lesions and their gamma-glutamyl transpeptidase expression in 3-methylcholanthrene-induced lung carcinogenesis in rats]

Lung precancerous and cancerous lesions were induced in Wistar rats by one intrabronchial injection of 3-methylcholanthrene (3-MC). The incidences of atypical hyperplasia of bronchiolar epithelium, adenoid hyperplasia or adenomas, and squamous cell carcinoma were 88.2% (15/17), 70.6% (12/17) and 17.7% (3/17) respectively by the 30th day after 3-MC treatment, and 83.3% (15/18), 23.5% (4/17) and 38.9% (7/18) by the 60th day. Positive expression of gamma-glutamyltranspeptidase (GGT) was identified histochemically in all of the above precancerous lesions and carcinomas. GGT might be used as a marker of precancerous and cancerous lesions of the lung.

[Inhibitory effect of micronutrients and BHA on lung cancer induced in rats]

The combined effect of Vit. A and E, selenium, cysteine and BHA on 3MC-induced lung cancer in Wistar rats was investigated. The supplementation of these compounds at their safe doses reduced the incidence of lung cancer from 47.2% to 31.6% (P less than 0.05). The total superoxide dismutase (SOD) and Mn-SOD activities in the lung cancer tissue were much lower than those in the normal tissue (P less than 0.001). It is possible that in the early stage of carcinogenesis, this change occurs only in the limited focus and does not affect the enzyme level as a whole, so SOD assay of peripheral blood can not reflect the carcinogenesis status in the lung.

New wrinkles on polynucleotide duplexes

Most fibrous polynucleotides of general sequence exhibit secondary structures that are described adequately by regular helices with a repeated motif of only one nucleotide. Such helices exploit the fact that A:T, T:A, G:C, and C:G pairs are essentially isomorphous and have dyadically-related glycosylic bonds. Polynucleotides with regularly repeated base-sequences sometimes assume secondary structures with larger repeated motifs which reflect these base-sequences. The dinucleotide units of the Z-like forms of poly d(As4T):poly d(As4T), poly d(AC):poly d(GT) and poly d(GC):poly d(GC) are dramatic instances of this phenomenon. The wrinkled B and D forms of poly d(GC):poly d(GC) and poly d(AT):poly d(AT) are just as significant but more subtle examples. It is possible also to trap more exotic secondary structures in which the molecular asymmetric unit is even larger. There is, for example, a tetragonal form of poly d(AT):poly d(AT) which has unit cell dimensions a = b = 1.71nm, c = 7.40nm, gamma = 90 degrees. The c dimension corresponds to the pitch of a molecular helix which accommodates 24 successive nucleotide pairs arranged as a 4(3) helix of hexanucleotide duplexes. The great variety of nucleotide conformations which occur in these large asymmetric units has prompted us to describe them as pleiomeric, a term used in botany to describe whorls having more than the usual number of structures. Pleiomeric DNAs need not contain nucleotide conformations that are very different from one another. On the other hand, DNAs carrying nucleotides of very different conformation must be pleiomeric. This is because 4 nucleotides of different conformation are needed to join patches of secondary structure which are as different as A or B or Z. Differences in nucleotide structures may occur also between chains rather than within chains. In poly d(A):poly d(T), the purine nucleotides all contain C3'-endo furanose rings and the pyrimidine nucleotides C2'-endo rings. Analogous heteronomous structures may exist in DNA-RNA hybrids although these duplexes are also found to have symmetrical A-type conformations.