Phenotypic alteration of a human BK (hSlo) channel by hSlobeta subunit coexpression: changes in blocker sensitivity, activation/relaxation and inactivation kinetics, and protein kinase A modulation

A human homolog of the large-conductance calcium-activated potassium (BK) channel beta subunit (hSlobeta) was cloned, and its effects on a human BK channel (hSlo) phenotype are reported. Coexpression of hSlo and hSlobeta, in both oocytes and human embryonic kidney 293 cells, resulted in increased Ca2+ sensitivity, marked slowing of BK channel activation and relaxation, and significant reduction in slow inactivation. In addition, coexpression changed the pharmacology of the BK channel phenotype: hSlo-mediated currents in oocytes were more sensitive to the peptide toxin iberiotoxin than were hSlo + hSlobeta currents, and the potency of blockade by the alkaloid BK blocker tetrandrine was much greater on hSlo + hSlobeta- mediated currents compared with hSlo currents alone. No significant differences in the response to charybdotoxin or the BK channel opener NS1619 were observed. Modulation of BK channel activity by phosphorylation was also affected by the presence of the hSlobeta subunit. Application of cAMP-dependent protein kinase increased P(OPEN) of hSlo channels, but decreased P(OPEN)of most hSlo + hSlobeta channels. Taken together, these altered characteristics may explain some of the wide diversity of BK channel phenotypes observed in native tissues.

Molecular detection of bacterial DNA in venereal-associated arthritis

OBJECTIVE

To evaluate the utility of polymerase chain reaction (PCR) amplification in detecting DNA from venereal-associated microorganisms in the synovial fluid of patients with inflammatory arthritis.

METHODS

Oligonucleotide primers were developed for nested PCR based on Chlamydia, Ureaplasma, and Neisseria DNA sequences. PCR products were detected by gel electrophoresis and dot-blot hybridization. Primers specific for the target bacterial DNA were used to search for bacterial DNA in 61 synovial fluid specimens from patients with inflammatory arthritis, including several clinically associated with venereal infection.

RESULTS

Five of the 61 synovial fluid specimens were positive for Neisseria gonorrhoeae DNA. Four of the 5 patients had clinical diagnoses of gonococcal arthritis; the other patient had an unexplained monarthritis. One specimen from a patient with a clinical diagnosis of gonococcal arthritis was negative for N gonorrhoeae. Three of the 61 specimens were positive for Chlamydia DNA. Two were derived from patients with clinical diagnoses of reactive arthritis or Reiter's syndrome, and 1 was from a patient with unexplained monarthritis. One of the 61 specimens was positive from Ureaplasma DNA; this sample was from a patient with a clinical diagnosis of Reiter's syndrome. In an additional patient with Reiter's syndrome, Ureaplasma DNA was also found in prostate biopsy tissue and a urine sample obtained after prostate massage (synovial fluid not available).

CONCLUSION

These data support the classification of these 3 venereal-associated arthritides as infectious processes, and suggest that PCR for bacterial DNA is a useful method for detecting infectious agents in synovial fluid.

Pbx modulation of Hox homeodomain amino-terminal arms establishes different DNA-binding specificities across the Hox locus

Pbx cofactors are implicated to play important roles in modulating the DNA-binding properties of heterologous homeodomain proteins, including class I Hox proteins. To assess how Pbx proteins influence Hox DNA-binding specificity, we used a binding-site selection approach to determine high-affinity target sites recognized by various Pbx-Hox homeoprotein complexes. Pbx-Hox heterodimers preferred to bind a bipartite sequence 5'-ATGATTNATNN-3' consisting of two adjacent half sites in which the Pbx component of the heterodimer contacted the 5' half (ATGAT) and the Hox component contacted the more variable 3' half (TNATNN). Binding sites matching the consensus were also obtained for Pbx1 complexed with HoxA10, which lacks a hexapeptide but requires a conserved tryptophan-containing motif for cooperativity with Pbx. Interactions with Pbx were found to play an essential role in modulating Hox homeodomain amino-terminal arm contact with DNA in the core of the Hox half site such that heterodimers of different compositions could distinguish single nucleotide alterations in the Hox half site both in vitro and in cellular assays measuring transactivation. When complexed with Pbx, Hox proteins B1 through B9 and A10 showed stepwise differences in their preferences for nucleotides in the Hox half site core (TTAT to TGAT, 5' to 3') that correlated with the locations of their respective genes in the Hox cluster. These observations demonstrate previously undetected DNA-binding specificity for the amino-terminal arm of the Hox homeodomain and suggest that different binding activities of Pbx-Hox complexes are at least part of the position-specific activities of the Hox genes.

Hox homeodomain proteins exhibit selective complex stabilities with Pbx and DNA

Eight of the nine homeobox genes of the Hoxb locus encode proteins which contain a conserved hexapeptide motif upstream from the homeodomain. All eight proteins (Hoxb-1-Hoxb-8) bind to a target oligonucleotide in the presence of Pbx1a under conditions where minimal or no binding is detected for the Hox or Pbx1a proteins alone. The stabilities of the Hox-Pbx1a-DNA complexes vary >100-fold, with the proteins from the middle of the locus (Hoxb-5 and Hoxb-6) forming very stable complexes, while Hoxb-4, Hoxb-7 and Hoxb-8 form complexes of intermediate stability and proteins at the 3'-side of the locus (Hoxb-1-Hoxb-3) form complexes which are very unstable. Although Hox-b proteins containing longer linker sequences between the hexapeptide and homeodomains formed unstable complexes, shortening the linker did not confer complex stability. Homeodomain swapping experiments revealed that this motif does not independently determine complex stability. Naturally occurring variations within the hexapeptides of specific Hox proteins also do not explain complex stability differences. However, two core amino acids (tryptophan and methionine) which are absolutely conserved within the hexapeptide domains appear to be required for complex formation. Removal of N- and C-terminal flanking regions did not influence complex stability and the members of paralog group 4 (Hoxa-4, b-4, c-4 and d-4), which share highly conserved hexapeptides, linkers and homeodomains but different flanking regions, form complexes of similar stability. These data suggest that the structural features of Hox proteins which determine Hox-Pbx1a-DNA complex stability reside within the precise structural relationships between the homeodomain, hexapeptide and linker regions.

The effect of "chi-han (hot nature)" Chinese herbs on the secretion of IL-1 beta and TNF-alpha by mononuclear cells

The effect of "chi-han (hot nature)" Chinese herbs on the secretion of the cytokines IL-1 beta and TNF-alpha was investigated by studying the in vitro effect of the "hot nature" Chinese herbs Radix aconiti, Evodia rutaecarpa, Zingiberis rhizoma, and Cortex cinnamomi. An ethanolic extract of each of these Chinese medicinal herbs was added to human peripheral mononuclear cell culture medium and allowed to react for various specified lengths of time. The culture medium supernatants were collected and tested for their cytokine levels at specified time intervals. We found different reaction patterns of cytokine secretion among these "hot nature" Chinese herbs. Radix aconiti extract showed an augmentative effect on the secretion of cytokines IL-1 beta and TNF-alpha with 20% to 50% concentrations of the pure herbal extract, especially when the reaction time was 18 or 24 hours. Evodia rutaecarpa extract showed a biphasic effect on the secretion of IL-1 beta and TNF-alpha when the reaction time was 18 or 24 hours. The secretion of cytokines was stimulated by low concentrations of the herbal extract, but inhibited by higher concentrations of the extract. Zingiberis rhizoma extract also showed a biphasic effect on the secretion of cytokine IL-1 beta when the reaction time was 18 or 24 hours. As for Cortex cinnamomi extract, no significant augmentative effect on cytokine secretion was found in our study. In consideration of the pyrogenic property of cytokines, it would appear that "hot nature" Chinese herbs can be further divided into different subgroups with minute differences based on their different effects on cytokine secretion.

Molecular basis of spinal muscular atrophy in Chinese

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Use of fluorine-18 fluorodeoxyglucose positron emission tomography in the detection of thymoma: a preliminary report

Thymomas are lacking in malignant cytological features. Their staging is defined by the invasiveness of the tumour. This study aimed to analyse the uptake patterns of fluorine-18 fluorodeoxyglucose (FDG) in thymomas of different stages. FDG positron emission tomography (PET) scan was performed in 12 patients suspected of having thymoma and in nine controls. Qualitative visual interpretation was used to detect the foci with FDG uptake higher than that of normal mediastinum. Tumour/lung ratio (TLR) was calculated from the counts of ROIs over the mass and over comparable normal lung tissue in thymoma patients. Mediastinum/lung ratio (MLR) was calculated from the counts of ROIs over the anterior mediastinum and lung in controls. The PET scan patterns of distribution of foci with FDG uptake and TLRs were correlated with the computed tomography (CT) or magnetic resonance imaging (MRI) findings, and staging of the thymomas. Thymectomy was performed in ten patients and thoracoscopy was done in two patients. The results revealed ten thymomas (two stage I tumours, two stage II, four stage III and two stage IV, according to the Masaoka classification), and two cases of thymic hyperplasia associated with myasthenia gravis. Myasthenia gravis was also noted in four thymoma patients. FDG studies showed (a) diffuse uptake in the widened anterior mediastinum in patients with thymic hyperplasia, (b) confined focal FDG uptake in the non-invasive or less invasive, stage I and II thymomas, and (c) multiple discrete foci of FDG uptake in the mediastinum and thoracic structures in stage III and IV advanced invasive thymomas. The thymomas had the highest TLRs, followed by the TLRs of thymic hyperplasia and the MLRs of control subjects (P <0.005). No significant difference was found between thymomas in different stages or between thymomas with and thymomas without myasthenia gravis. In comparison with CT and/or MRI, FDG-PET detected more lesions in patients with invasive thymomas and downgraded the staging of thymoma in four patients. Our preliminary results suggest that FDG-PET is useful in the assessment of the invasiveness of thymomas, and may have the potential to differentiate thymomas from thymic hyperplasia.

New anastomotic gun for biofragmentable anastomotic ring in low anterior resection

PURPOSE

The biofragmentable anastomotic ring remains difficult to use for low rectal anastomosis. The authors report their experience of clinical application of the biofragmentable ring in low anterior resection with a newly designed instrument.

METHODS

In this series, 31 patients underwent sphincter-preserving low anterior resections for rectal tumors from May 1993 to November 1994. With the assistance of a self-developed anastomotic instrument (biofragmentable anastomotic ring gun), biofragmentable ring anastomoses were performed following low anterior resection.

RESULTS

There was no operative mortality. One patient had clinical evidence of anastomotic leakage. In postoperative follow-up, there was no anastomotic stenosis or incontinence.

CONCLUSION

Therefore, we believe biofragmentable ring rectal anastomosis is a safe and reliable alternative to other anastomotic methods in rectal surgery.

The "Fisherman's Waders" sign in a bone scan of inferior vena cava thrombosis associated with nephrotic syndrome

This paper presents a 61-year-old male patient with nephrotic syndrome, hypercoagulability and IVC thrombosis. Increased soft tissue uptake below the level of the mid chest was seen in his bone scan. The term "Fisherman's Waders" sign is suggested for this finding, whose recognition may permit the identification of inferior vena cava obstruction in bone scans. The existence of a cavo-portal shunt was also confirmed by dynamic scintigraphy.

Rapid diagnosis of beta-thalassaemia by mutagenically separated polymerase chain reaction (MS-PCR) and its application to prenatal diagnosis

We have developed a rapid and simple PCR-based method which is modified from the mutagenically separated polymerase chain reaction (MS-PCR) to detect the molecular defects of beta-thalassaemia. We can use this technique to amplify normal and mutant alleles of the beta-globin gene in the same reaction tube, using different-sized allele-specific primers. This mutagenesis separates the amplification reactions of alleles performed in the same tube. Subsequent gel electrophoresis shows at least one of the two allelic products at the same locus or at least two of the several allelic products at different loci. Therefore, in addition to simple handling, MS-PCR provides a within-assay quality control for the exclusion of false negative results. The five most common mutations of beta-thalassaemia and haemoglobin E which occur in the Taiwanese population were tested, and 14 prenatal samples were checked with accurate results. This method is simple, rapid and accurate, and can be used routinely in prenatal diagnosis. The principle used here can also be applied to other genetic diseases.

Identity of the segment of human complement C8 recognized by complement regulatory protein CD59

CD59 antigen is a membrane glycoprotein that inhibits the activity of the C5b-9 membrane attack complex (MAC), thereby protecting human cells from lysis by human complement. The inhibitory function of CD59 derives from its capacity to interact with both the C8 and C9 components of MAC, preventing assembly of membrane-inserted C9 polymer. MAC-inhibitory activity of CD59 is species-selective and is most effective when both C8 and C9 derive from human or other primate plasma. Rabbit C8 and C9, which can substitute for human C8 and C9 in MAC, mediate virtually unrestricted lysis of human cells expressing CD59. In order to identify the segment of human C8 that is recognized by CD59, recombinant peptides containing human or rabbit C8 sequence were expressed in Escherichia coli and purified. CD59 was found to specifically bind to a peptide corresponding to residues 334-385 of the human C8 alpha-subunit, and to require a disulfide bond between Cys345 and Cys369. No specific binding was observed to the corresponding sequence from rabbit C8 alpha (residues 334-386). To obtain functional evidence that this segment of human C8 alpha is selectively recognized by CD59, recombinant C8 proteins were prepared by co-transfecting COS-7 cells with human/rabbit chimeras of the C8 alpha cDNA, and cDNAs encoding the C8 beta and C8 gamma chains. Hemolytic activity of MAC formed with chimeric C8 was analyzed using target cells reconstituted with CD59. These experiments confirmed that CD59 recognizes a conformationally sensitive epitope that is within a segment of human C8 alpha internal to residues 320-415. Our data also suggest that optimal interaction of CD59 with this segment of human C8 alpha is influenced by N-terminal flanking sequence in C8 alpha and by human C8 beta, but is unaffected by C8 gamma.

The effect of Chinese medicinal herb Zingiberis rhizoma extract on cytokine secretion by human peripheral blood mononuclear cells

The ethanolic extract of the Chinese medicinal herb Zingiberis rhizoma, the rhizome of Zingiber officinale Roscoe (Zingiberaceae), was found to show biphasic effects on secretion of cytokines by human peripheral blood mononuclear cells in vitro. In this study, the augmentative effect of Zingiberis rhizoma extract on cytokine secretion was shown to be time dependent. No significant secretion of cytokine was noted when the reaction time was 1 or 3 h. Secretion of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and granulocyte-macrophage colony-stimulating factor (GM-CSF) by the mononuclear cells was markedly increased in the presence of a low concentration of Zingiberis rhizoma extract, varying from 10-30 mg/ml, when the reaction time was 18 or 24 h. A higher concentration of the herbal extract did not show similar or stronger augmentative effect as did low concentration of the herbal extract.

Rapid detection of hemoglobin variants by mutagenically separated polymerase chain reaction (MS-PCR)

The detection of molecular defects of hemoglobin variants using mutagenically separated polymerase chain reaction (MS-PCR) was applied in this study. Using different lengths of allele-specific mutagenic primers, normal and mutant alleles of hemoglobin genes were amplified in the same reaction tube. Subsequent gel electrophoresis showed at least one of the two allelic products at the same loci or at least two of the several allelic products at different loci. We employed MS-PCR to test the following hemoglobin variants: Hb Constant Spring (Hb CS), Hb E, Hb G-Taichung, Hb J-Meinung, and Hb Kaohsiung. The results were the same as those obtained by amplified created reaction sites (ACRS) or direct sequencing. We conclude that the MS-PCR provides a rapid and simple alternative to other techniques for mutation detection in hemoglobin variants. Moreover, the principle can be extended to other genetic diseases.

Neonatal coxsackievirus B1 infection associated with severe hepatitis: report of three cases

Coxsackievirus B infection may cause fulminant disease in the neonate. In most reports the prominent symptoms have been recognized as myocarditis and meningoencephalitis, and a majority were caused by type B2 to B5. Coxsackie B1 was a rare cause. From December 1993 to April 1994 three newborns were admitted to this Hospital with similar presentations of acute hepatitis and thrombocytopenia. Coxsackie B1 virus was isolated from all at one or two sites including rectal swab, throat swab and urine. One fatal case had had symptoms from birth; the disease progressed rapidly initially with a strikingly high liver enzyme; respiratory failure was noted; acute renal failure then happened later and the baby expired in two weeks. The other two patients survived, though one also had severe fulminant hepatitis. In that case onset of the disease was late at 28 days old. The other's clinical course was mild from the beginning. Myocarditis or central nervous system involvement were apparently not the significant presentations. Because the three babies all came from areas near this city (Chung-Ho and Pan-Chiao), attention should be drawn to the prevalence of coxsackie B1 virus infection in the total community.

Tc-99m phytate bone marrow scintigraphy showing multiple areas of focal hyperactivity in a patient with lung cancer. A case report

Focal hyperactivity indicative of metastases is a rare finding in bone marrow imaging. In a lung cancer patient with multiple bony metastases, the Tc-99m phytate bone marrow imaging revealed multiple focal areas of increased radioactivity corresponding to the bone scan findings. The findings presented are consistent with a previous animal study, which found that phytate distribution was similar to that of diphosphonate in the skeletal system of rats and rabbits. The authors conclude that Tc-99m phytate should not be used as a bone marrow imaging agent. Further studies of Tc-99m phytate bone marrow scintigraphy on human beings are under way.

Effects of inhalation of steroids on lung permeability in patients with asthma

This study evaluated the effect of inhalation of steroids on lung permeability in patients with asthma by measuring the clearance of Tc-99m DTPA aerosol from the alveolar to vascular space. Twenty patients with asthma were studied in the supine position with a gamma camera and the clearance half time (T 1/2) was calculated. The base line lung permeability study was performed before treatment with inhalation of 100 micrograms beclomethasone dipropionate four times daily for 1 week, then the study was repeated. After treatment with inhalation of steroid, there was a change in T 1/2 from 76.4 +/- 37.4 minutes to 86.6 +/- 48.2 minutes (P = 0.08). This preliminary study suggests that lung permeability is not altered by inhaled steroid therapy.

5-Fluoro-2-pyrimidinone, a liver aldehyde oxidase-activated prodrug of 5-fluorouracil

5-Fluorouracil (5-FU) is an effective antitumor agent used in treating various cancers. Because of its metabolism by intestinal and other cells, 5-FU has an inconsistent bioavailability that limits its oral use. 5-Fluoro-2-pyrimidione (5-FP), a 5-FU prodrug, was synthesized and found to be converted to 5-FU by aldehyde oxidase, an enzyme present in high concentrations in the livers of mice and humans but not in the gastrointestinal tract. Using BDF1 mice, the pharmacokinetics of 5-FP were studied and compared with those of 5-FU. The bioavailability of 5-FP given orally was 100% at a dosage of 25 mg/kg and 78% at a dosage of 50 mg/kg. The half-lives of both doses of 5-FP were at least 2-fold longer than the half-lives of the same doses of 5-FU, and the clearance rates of 5-FP were 3-fold slower. 5-FP was converted rapidly to 5-FU, in vivo. The resulting 5-FU was measured at a steady-state level of 40-70 microM in plasma, at a dosage of 25 mg/kg, that was sustained for at least 4 hr. Also, when given orally, 5-FP was shown to have potent activity against Colon 38 tumor cells and P388 leukemia cells in mice. The therapeutic index of 5-FP was similar to that of 5-FU in these mouse tumor models. The potential clinical use of 5-FP as a prodrug of 5-FU should be considered.

Pbx proteins display hexapeptide-dependent cooperative DNA binding with a subset of Hox proteins

The human proto-oncogene PBX1 codes for a homolog of Drosophila extradenticle, a divergent homeo domain protein that modulates the developmental and DNA-binding specificity of select HOM proteins. We demonstrate that wild-type Pbx proteins and chimeric E2a-Pbx1 oncoproteins cooperatively bind a consensus DNA probe with HoxB4, B6, and B7 of the Antennapedia class of Hox/HOM proteins. Specificity of Hox-Pbx interactions was suggested by the inability of Pbx proteins to cooperatively bind the synthetic DNA target with HoxA10 or Drosophila even-skipped. Site-directed mutagenesis showed that the hexapeptide motif (IYPWMK) upstream of the Hox homeo domain was essential for HoxB6 and B7 to cooperatively bind DNA with Pbx proteins. Engraftment of the HoxB7 hexapeptide onto HoxA10 endowed it with robust cooperative properties, demonstrating a functional role for the highly conserved hexapeptide element as one of the molecular determinants delimiting Hox-Pbx cooperativity. The Pbx homeo domain was necessary but not sufficient for cooperativity, which required conserved amino acids carboxy-terminal of the homeo domain. These findings demonstrate that interactions between Hox and Pbx proteins modulate their DNA-binding properties, suggesting that Pbx and Hox proteins act in parallel as heterotypic complexes to regulate expression of specific subordinate genes.

Endocytosis and lysosomal targeting of epidermal growth factor receptors are mediated by distinct sequences independent of the tyrosine kinase domain

Ligand-induced internalization of the epidermal growth factor receptor (EGFR) leads to accelerated receptor degradation. Two models have been proposed to explain this. In the first model, induced internalization expands the intracellular pool of receptors, leading to enhanced lysosomal targeting. The second model proposes that activation of intrinsic receptor kinase activity induces inward vesiculation of endosomes, thus interrupting receptor recycling. To test these models, we created EGFR mutants that lack the conserved tyrosine kinase domain, but retain different parts of the distal carboxyl terminus regulatory region. Mutants lacking all distal regulatory sequences underwent slow internalization (0.02 min-1) and turnover (t1/2 approximately 24 h), similar to unoccupied, holo-EGFR. Mutant receptors that lacked the kinase domain, but retained the entire distal regulatory domain, were constitutively internalized and targeted to lysosomes, even in the absence of EGF. The turnover of these receptors (t1/2 approximately 11 h) was similar to that of occupied, kinase-active holo-EGFR (t1/2 approximately 9.5 h). These results show that receptor tyrosine kinase activity is not required for the targeting of EGFR to lysosomes. Receptor mutants which expressed previously identified endocytic sequences underwent rapid internalization. Unexpectedly, enhanced turnover of EGFR mutants required additional sequences located between residues 945 and 991 in the holo-EGFR. Thus, internalization and lysosomal targeting of EGFR are separate processes mediated by distinct sequences. Our results indicate that induced internalization is necessary, but not sufficient, for enhanced EGFR degradation. Instead, down-regulation requires exposure of previously cryptic internalization and lysosomal targeting sequences. Occupied EGFR thus appear to be handled by the endocytic machinery in the same fashion as other constitutively internalized or lysosomally targeted receptors.

Ras oncogene and p53 gene hotspot mutations in colorectal cancers

Ras oncogene and p53 gene mutations are frequently observed in colorectal cancers. The role of co-operation between these two genes in the tumorigenesis of colorectal cancer was evaluated. Point mutations in K-ras oncogene and hotspot codons of p53 gene of colorectal cancers were evaluated by naturally created or amplified created restriction site method. Nine of 42 cases (21.4%) of colorectal cancer showed K-ras oncogene mutations. Six of 42 cases (14.3%) of colorectal cancer showed p53 gene hotspot point mutations. The low frequency of p53 gene mutation in this series may be due to racial difference or different hotspot codons. When six cases with mutated p53 gene were examined, only one (16.7%) showed concurrent K-ras oncogene codon 12 and p53 gene codon 248 mutations. We concluded that the co-operation between ras oncogene and p53 gene hotspot point mutations in the tumorigenesis of colorectal cancer in Chinese was not common. Other factors such as adenomatous polyposis coli gene mutations, oncogene activation or tumour suppression gene inactivation may be involved.

The effect of Evodia rutaecarpa extract on cytokine secretion by human mononuclear cells in vitro

The effect of Evodia rutaecarpa extract on cytokine secretion by human mononuclear cells in vitro was investigated. Evodia rutaecarpa extract of various concentrations in mononuclear cell culture medium showed biphasic effects on the secretion of interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and granulocyte-macrophage colony stimulating factor (GM-CSF) by the mononuclear cells. Generally speaking, a low to medium level of Evodia rutaecarpa extract, in concentrations ranging from 10% to 30%, showed significant stimulating effects on the secretion of IL-1 beta, IL-6, TNF-alpha and GM-CSF. On the other hand, high level of Evodia rutaecarpa extract, with concentration more than 40%, lost its stimulating effects. Moreover, reaction time affected the stimulating effects of Evodia rutaecarpa extract on cytokine secretion by mononuclear cells. Mononuclear cell culture medium containing Evodia rutaecarpa extract that was allowed to react for 18 or 24 hours showed significantly better stimulating effects than that reacted for 1 or 3 hours.

Detection of T cell receptors in early rheumatoid arthritis synovial tissue

Synovial tissue is rarely available from patients with early synovitis, with the exception of synovial biopsies. However, T cell populations early in the development of synovitis may be enriched in antigen-specific cells and critical to disease pathogenesis. To investigate the T cell repertoire in early synovitis, we utilized a PCR protocol for detection of T cell receptor (TCR) transcripts present in small amounts of synovial tissue. To expand the substrate for PCR, preamplification of cDNA was performed with a 3' constant region primer plus either a mixture of variable region primers or random hexanucleotides. Utilizing this method improved the sensitivity of detection. This technique is applied here to the analysis of TCR transcripts in synovial biopsies from individuals with early rheumatoid arthritis (RA) and non-RA synovitis. TCR alpha-chain transcripts were detectable in 5/5 RA and 4/4 non-RA specimens evaluated, with beta-chain transcripts detected in 4/5 early RA and 4/4 non-RA specimens evaluated. Confirmation of transcripts by sequencing of cloned PCR products verified the specificity of amplification. The most frequently expressed TCR V region families in early RA synovitis were V alpha 11, V alpha 14, V alpha 28, V beta 7, V beta 9 and V beta 17. Several of these V regions have previously been implicated in studies of chronic RA synovitis. J alpha and J beta region usage was similar to that seen in chronic RA, and conserved N region motifs were apparent. We conclude that it is possible to detect TCR transcripts in small synovial biopsies from individuals with early arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Identity of a peptide domain of human C9 that is bound by the cell-surface complement inhibitor, CD59

The CD59 antigen is a plasma membrane glycoprotein that serves as an inhibitor of the C5b-9 complex of complement. This inhibitory activity appears related to the capacity of CD59 to bind with high affinity to sites that are nascently exposed in the alpha-chain subunit of human C8, as well as within the C9b domain (amino acid residues 245-538) of human C9, during assembly of the C5b-9 complex on the target membrane (Ninomiya, H., and Sims, P. J. (1992) J. Biol. Chem. 267, 13675-13680). The CD59 binding site in C9 was first investigated by N-terminal sequencing of CD59-binding peptides generated by limited digest of the isolated C9b domain. These experiments revealed a 17-kDa fragment (starting at C9 residue Thr-320) that retained affinity for CD59, suggesting the possibility for localizing the CD59 binding site by mapping with small C9-derived peptides. Peptides spanning the entire C9b sequence were expressed in Escherichia coli and then probed with CD59. CD59 bound specifically to all peptides starting N-terminal to C9 residue 359 with C termini extending beyond residue 411. Little to no CD59 binding was observed for various C9-derived peptides that started C-terminal to residue 359 or that were truncated N-terminal to residue 411. Affinity-purified antibody against C9 residues 320-411 inhibited CD59 binding to C9 by > 50% and completely inhibited its binding to the isolated C9b domain. Little to no specific binding of CD59 was detected for peptides restricted to the putative hinge domain within C9b (residues 245-271). These results indicate that a CD59 binding site is located between residues 320 and 411 of the C9 polypeptide and suggest that the affinity of this site is principally determined by residues 359-411.