Chemotaxis in Borrelia burgdorferi

Borrelia burgdorferi is a motile spirochete which has been identified as the causative microorganism in Lyme disease. The physiological functions which govern the motility of this organism have not been elucidated. In this study, we found that motility of B. burgdorferi required an environment similar to interstitial fluid (e.g., pH 7.6 and 0.15 M NaCl). Several methods were used to detect and measure chemotaxis of B. burgdorferi. A number of chemical compounds and mixtures were surveyed for the ability to induce positive and negative chemotaxis of B. burgdorferi. Rabbit serum was found to be an attractant for B. burgdorferi, while ethanol and butanol were found to be repellents. Unlike some free-living spirochetes (e.g., Spirochaeta aurantia), B. burgdorferi did not exhibit any observable chemotaxis to common sugars or amino acids. A method was developed to produce spirochete cells with a self-entangled end. These cells enabled us to study the rotation of a single flagellar bundle in response to chemoattractants or repellents. The study shows that the frequency and duration for pausing of flagella are important for chemotaxis of B. burgdorferi.

Neutral endopeptidase 24.11 loss in metastatic human prostate cancer contributes to androgen-independent progression

Neutral endopeptidase 24.11 (NEP) is a cell-surface enzyme expressed by prostatic epithelial cells that cleaves and inactivates neuropeptides implicated in the growth of androgen-independent prostate cancer (PC). We report that NEP expression and catalytic activity are lost in vitro in androgen-independent but not androgen-dependent PC cell lines. In vivo, NEP protein expression is commonly decreased in cancer cells of metastatic PC specimens from patients with androgen-independent but not androgen-dependent PC. Overexpression of NEP in androgen-independent PC cells or incubation with recombinant NEP inhibits PC cell growth. Furthermore, in androgen-dependent PC cells, expression of NEP is transcriptionally regulated by androgen and decreases with androgen withdrawal. These data suggest that decreased NEP expression, common in androgen-independent PCs, is facilitated by the elimination of androgens, and that NEP loss plays an important role in the development of androgen-independent PC by allowing PC cells to use mitogenic neuropeptides as an alternate source to androgen in order to stimulate cell proliferation.

A novel human luteinizing hormone receptor gene

A novel human luteinizing hormone receptor (LHR) gene was isolated from a human placental genomic library. This gene (Gene II) differs from that previously isolated from a lymphocyte library (Gene I) by several base changes in the 5' flanking region and the deletion of 6 nucleotides in the coding region (+55 to +60). The sequence of the exon 1 coding region of gene II conforms to the sequence of the human ovarian LHR cDNA. Furthermore, primer extension and reporter gene analyses indicate that both the Gene II promoter and the human ovarian LHR mRNA transcriptional start sites are located within the -176 bp TATA-less 5' flanking domain. Additional upstream transcriptional start sites (> -176 bp) were identified in human testicular mRNA and the human choriocarcinoma JAR cell. Restriction enzyme analysis verifies that both LHR genes are present in the human genome, and gene dosing reveals four copies of the human LHR in contrast to a single copy in the rat genome. Chromosomal mapping localizes all copies of the human LHR to the chromosome 2p16-21 loci. These studies suggest that tissue-specific LHR promoter utilization and LHR gene expression may be correlated with gene diversity.

A DnaK homolog in Myxococcus xanthus is involved in social motility and fruiting body formation

Myxococcus xanthus is a gram-negative soil bacterium which exhibits a complex life cycle and social behavior. In this study, two developmental mutants of M. xanthus were isolated through Tn5 transposon mutagenesis. The mutants were found to be defective in cellular aggregation as well as in sporulation. Further phenotypic characterization indicated that the mutants were defective in social motility but normal in directed cell movements. Both mutations were cloned by a transposon-tagging method. Sequence analysis indicated that both insertions occurred in the same gene, which encodes a homolog of DnaK. Unlike the dnaK genes in other bacteria, this M. xanthus homolog appears not to be regulated by temperature or heat shock and is constitutively expressed during vegetative growth and under starvation. The defects of the mutants indicate that this DnaK homolog is important for the social motility and development of M. xanthus.

Optimization of Long-Term Stability of Magnetic Fluids from Magnetite and Synthetic Polyelectrolytes

Nanometer-sized suspensions of magnetite (Fe3O4) stabilized with polymeric surfactants, principally poly(methacrylic acid) (PMAA), were prepared by precipitation or sonication and studied by a variety of techniques. The long-term stability of the ferrofluids made with PMAA was optimal at pH 7 (close to the measured isoelectric point of the magnetite, 5.9) and improved at all pH values with increasing surfactant concentration. With extended times of sonication the molecular weight and polydispersity of the PMAA decreased, although magnetite in the ferrofluid was not oxidized (X-ray). Particle diameters of 9-38 nm were measured by saturation magnetization, electron microscopy, and dynamic light scattering. Centrifugation at 8,000 rpm removed the magnetite from the suspensions together with roughly one molecule of PMAA for each magnetite particle in the fluid, with the average number increasing with higher concentrations and average molecular weights of the polymer.

Cyclin D2 is an FSH-responsive gene involved in gonadal cell proliferation and oncogenesis

THE D-type cyclins (D1, D2 and D3) are critical governors of the cell-cycle clock apparatus during the G1 phase of the mammalian cell cycle. These three D-type cyclins are expressed in overlapping, apparently redundant fashion in the proliferating tissues. To investigate why mammalian cells need three distinct D-type cyclins, we have generated mice bearing a disrupted cyclin D2 gene by using gene targeting in embryonic stem cells. Cyclin D2-deficient females are sterile owing to the inability of ovarian granulosa cells to proliferate normally in response to follicle-stimulating hormone (FSH), whereas mutant males display hypoplastic testes. In ovarian granulosa cells, cyclin D2 is specifically induced by FSH via a cyclic-AMP-dependent pathway, indicating that expression of the various D-type cyclins is under control of distinct intracellular signalling pathways. The hypoplasia seen in cyclin D2(-/-) ovaries and testes prompted us to examine human cancers deriving from corresponding tissues. We find that some human ovarian and testicular tumours contain high levels of cyclin D2 messenger RNA.

Selective activation of the mitogen-activated protein kinase subgroups c-Jun NH2 terminal kinase and p38 by IL-1 and TNF in human articular chondrocytes

Previous studies suggested that tyrosine kinase activation is an important signal transduction event in the IL-1 response of chondrocytes. The present study identifies the mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase (ERK)-1 and ERK-2 as major tyrosine phosphorylated proteins in IL-1 stimulated chondrocytes. Kinase assays on immunoprecipitates with myelin basic protein as substrate showed that ERK-1 and ERK-2 activation was detectable within 5 min after IL-1 stimulation and decreased to baseline within 60 min. Analysis of other members of the MAP kinase family showed that chondrocytes also express c-Jun NH2 terminal kinase (JNK)-1, JNK-2, and p38 proteins. These kinases were time-dependently activated by IL-1. Among other chondrocyte activators tested, only TNF activated all three of the MAP kinase subgroups. JNK and p38 were not activated by any of the other cytokines and growth factors tested. However, ERK was also activated by PDGF, IGF-1, and IL-6. Phorbol 12-myristate 13-acetate, calcium ionophore, and cAMP analogues only increased ERK activity but had no significant effects on JNK or p38. These results suggest differential activation of MAP kinase subgroups by extracellular stimuli. ERK is activated in response to qualitatively diverse extracellular stimuli and various second messenger agonists. In contrast, JNK and p38 are only activated by IL-1 or TNF, suggesting that these kinases participate in the induction of the catabolic program in cartilage.

The genomic structure of the rat corticotropin releasing factor receptor. A member of the class II G protein-coupled receptors

Isolation and structural characterization of the rat corticotropin releasing factor receptor (CRFR) gene was performed to determine the exon/intron organization of the coding region and the potential for splice variants. The CRFR gene contains 13 exons and 12 introns, and the positions of the exon/intron junctions are similar to those of other Class II G protein-coupled receptor genes including the parathyroid hormone and glucagon receptors. The promoter resides within 593 base pairs of the initiation codon and the major transcriptional start site at nucleotide -238. This domain does not possess a TATA box but contains multiple Sp1 and AP-2 sites upstream and downstream of the major transcriptional start site. Intron junctions were identified in the extracellular, transmembrane (TM), and cytoplasmic (C) domains of the CRFR, giving the potential for differential signal transduction by splice variants. CRFR cDNAs derived from rat Leydig cell mRNA included the pituitary Form A, which spans exons 1-13, and two splice variants with deletion of exon 3 or exons 7, 11, and 12. An evolutionary link between the intronless TM/C module of the glycoprotein hormone receptors and the intron-containing TM/C module of the CRFR is suggested by the common position of the luteinizing hormone receptor Form D alternate acceptor splice site and the CRFR intron 12.

Treatment of a human breast cancer xenograft with an adenovirus vector containing an interferon gene results in rapid regression due to viral oncolysis and gene therapy

Treatment of a human breast cancer cell line (MDA-MB-435) in nude mice with a recombinant adenovirus containing the human interferon (IFN) consensus gene, IFN-con1 (ad5/IFN), resulted in tumor regression in 100% of the animals. Tumor regression occurred when virus was injected either within 24 hr of tumor cell implantation or with established tumors. However, regression of the tumor was also observed in controls in which either the wild-type virus or a recombinant virus containing the luciferase gene was used, although tumor growth was not completely suppressed. Tumor regression was accompanied by a decrease in p53 expression. Two other tumors, the human myelogenous leukemic cell line K562 and the hamster melanoma tumor RPMI 1846, also responded to treatment but only with ad5/IFN. In the case of K562 tumors, there was complete regression of the tumor, and tumors derived from RPMI 1846 showed partial regression. We propose that the complete regression of the breast cancer with the recombinant virus ad5/IFN was the result of two events: viral oncolysis in which tumor cells are being selectively lysed by the replication-competent virus and the enhanced effect of expression of the IFN-con1 gene. K562 and RPMI 1846 tumors regressed only as a result of IFN gene therapy. This was confirmed by in vitro analysis. Our results indicate that a combination of viral oncolysis with a virus of low pathogenicity, itself resistant to the effects of IFN and IFN gene therapy, might be a fruitful approach to the treatment of a variety of different tumors, in particular breast cancers.

Effects of nicotine on the immune response. II. Chronic nicotine treatment induces T cell anergy

Previously, we have shown that both T and B lymphocytes from chronically nicotine-treated (NT) animals exhibit tolerance to activation by Ags (ligation of Ag receptors), as indicated by their decreased ability to mobilize intracellular calcium and, at least in T cells, arrest of cells in the G0/G1 phase of the cell cycle. Herein, we demonstrate that NT T cells significantly lose their ability to up-regulate inositol trisphosphate synthesis in response to TCR ligation or nonspecific activation of G proteins by AIF-4. However, increases in cAMP concentrations of T cells following activation of G protein-sensitive adenylate cyclase by cholera or pertussis toxin were not significantly affected by the nicotine treatment. Interestingly, compared with control T cells, the background levels of inositol trisphosphate were significantly elevated in NT T cells, indicating some degree of activation in these cells. This inference was further supported by observations that naive T cells from NT animals exhibit tyrosine phosphorylation of several substrates, including phospholipase C-gamma1, which were either absent or underphosphorylated in unstimulated control T cells. Moreover, when, after 4-wk nicotine treatment, nicotine pumps were removed and serum cotinine levels fell to background, inhibition of the Ab-forming cells and Ca2+ responses continued for at least 2 more wk. These results suggest that chronic in vivo nicotine exposure leads to T cell anergy and may contribute to nicotine/cigarette smoke-induced immunosuppression.

Effects of nicotine on the immune response. II. Chronic nicotine treatment induces T cell anergy

Previously, we have shown that both T and B lymphocytes from chronically nicotine-treated (NT) animals exhibit tolerance to activation by Ags (ligation of Ag receptors), as indicated by their decreased ability to mobilize intracellular calcium and, at least in T cells, arrest of cells in the G0/G1 phase of the cell cycle. Herein, we demonstrate that NT T cells significantly lose their ability to up-regulate inositol trisphosphate synthesis in response to TCR ligation or nonspecific activation of G proteins by AIF-4. However, increases in cAMP concentrations of T cells following activation of G protein-sensitive adenylate cyclase by cholera or pertussis toxin were not significantly affected by the nicotine treatment. Interestingly, compared with control T cells, the background levels of inositol trisphosphate were significantly elevated in NT T cells, indicating some degree of activation in these cells. This inference was further supported by observations that naive T cells from NT animals exhibit tyrosine phosphorylation of several substrates, including phospholipase C-gamma1, which were either absent or underphosphorylated in unstimulated control T cells. Moreover, when, after 4-wk nicotine treatment, nicotine pumps were removed and serum cotinine levels fell to background, inhibition of the Ab-forming cells and Ca2+ responses continued for at least 2 more wk. These results suggest that chronic in vivo nicotine exposure leads to T cell anergy and may contribute to nicotine/cigarette smoke-induced immunosuppression.

Regulation of cyclin E transcription by E2Fs and retinoblastoma protein

Cyclin E is critical for the advance of cells through the G1 phase of their growth cycle. Transcription of the cyclin E gene is known to be cell cycle-dependent. We have shown previously that mRNA levels of cyclin E are regulated positively by mitogens and negatively by TGF-beta. Much circumstantial evidence implicates both E2F transcription factors and the retinoblastoma protein (pRB) in the control of cyclin E expression. However, the molecular basis of this control has remained unclear. We report here the cloning of the cyclin E promoter and the identification of several putative E2F binding sites within the promoter sequence. We have found that cell cycle regulation of cyclin E transcription is mediated by E2F binding sites present in the promoter. The activity of this promoter can be regulated negatively by pRB. Our results suggest the operation of a positive-feedback loop in late G1 that functions to ensure continued cyclin E expression and pRB inactivation.

Gene therapy with an adeno-associated virus carrying an interferon gene results in tumor growth suppression and regression

Adeno-associated virus (AAV) vectors were constructed containing both a synthetic type I interferon gene, (IFN-con1) and the bacterial neomycin-resistant gene. Recombinant virions were used to infect a number of human tumor cell lines, including 293, Hela, K562, and Eskol (a hairy cell leukemia-like cell), and geneticin-resistant cells were selected. All IFN-con1-transduced cell lines produced low levels of IFN-con1 and grew at the same rate as nontransduced cell lines. Although these cell lines were resistant to IFN in vitro, when injected into nude mice, 293, K562, and Eskol cells failed to form tumors up to 3 months after the initial inoculum, although mice receiving nontransduced cells developed tumors within 7 to 10 days. Transduced Hela cells grew much slower in vivo and formed much smaller tumors than did the parental cells. When equal numbers of transduced and nontransduced cells were injected into nude mice, tumors initially developed slowly and then completely regressed. Treatment of an established Eskol tumor (histologically a malignant immunoblastic lymphoma) with AAV/IFN-con1-transduced 293 cells resulted in tumor regression, whereas treatment of Eskol tumors with IFN-con1 resulted in a small decrease in tumor size. These results indicate that the human IFN-con1 gene in a viral vector can be used successfully in the treatment of tumors both directly and by tumor-targeted gene therapy.

Effects of nicotine on the immune response. I. Chronic exposure to nicotine impairs antigen receptor-mediated signal transduction in lymphocytes

Previous work has demonstrated that chronic exposure of rats to cigarette smoke causes inhibition of the antibody-forming cell (AFC) response and that the particulate phase of cigarette smoke, containing most of the nicotine in cigarette smoke, is essential for immunosuppression. Using intradermally implanted miniosmotic pumps, LEW rats were exposed to nicotine or its principal metabolite, cotinine, at the rate of about 14 micrograms/hr for 3-4 weeks. Serum cotinine levels in nicotine-treated (NT) animals of 219 +/- 40 ng/ml (on Day 10) were comparable to average human smokers. No significant differences between control (CON) and NT animals were observed in the distribution of lymphocyte subsets. However, nicotine, but not cotinine, treatment for 3 to 4 weeks inhibited both the T-dependent and T-independent AFC responses and proliferation to anti-CD3. Con A response was observed in 4-week but not in 3-week NT animals. Cell cycle analysis revealed that upon stimulation with Con A or anti-CD3, in spite of comparable surface expression of IL-2 receptors and class II MHC molecules, significantly fewer NT T cells entered the S and G2/M phases than CON T cells, indicating an arrest in the G0/G1 phase. Furthermore, B and T cells from NT animals were unable to elevate the intracellular calcium levels normally in response to ligation of antigen receptors, although Ca2+ responses of salivary gland cells to acetylcholine were normal. Thus, nicotine may significantly contribute to the immunosuppressive effects of chronic smoking by inducing a state of anergy in lymphocytes and may be related to their impaired response to antigen-induced signaling.

Tumor suppressor activity of the human consensus type I interferon gene

Type I interferons have potent antiproliferative activity both in vitro and in vivo, and their tumor suppressor activity has been suggested. A series of eukaryotic vectors containing a synthetic human consensus type I interferon gene (IFN-con1) under the control of different promoters (cytomegalovirus early promoter, murine metallothionein promoter and the Rous sarcoma virus LTR) were constructed and stably transfected into type I IFN-deficient myelogenous leukemic K562 cells. Constitutive expression of IFNcon1 reverted the malignant phenotype, as indicated by loss of tumorgenicity in nude mice. When stably transformed cells were mixed with parental tumor cells, there was retardation of tumor growth. Constitutive expression of IFNcon1 reverted the malignant phenotype in vitro, as indicated by growth inhibition in culture, and reduction in colony formation on soft agar. Furthermore, IFNcon1 gene expression resulted in elevated erythroid differentiation, growth arrest in S phase and induced apoptosis. Thus the presence of an active IFNcon1 gene overcomes the oncogenic potential of K562 by coordinated modulation of cell proliferation, differentiation and programmed cell death, and it acts as a tumor suppressor in vivo.

Expression of the p16 and p15 cyclin-dependent kinase inhibitors in lymphocyte activation and neuronal differentiation

The cyclin-dependent kinase inhibitors p16INK4/MTS1 and p15INK4B/MTS2 have been mapped to a region in chromosome 9 (921) that is deleted frequently in acute lymphoblastic leukemias and malignant gliomas. To gain insight into the functions of these inhibitors in lymphocytes and neuronal cells, we studied the expression of p15 and p16 during lymphocyte mitogenesis and neuronal differentiation. Expression of p15 was extinguished during lymphocyte activation, concomitant with an increase in retinoblastoma kinase activity. The differentiation of the embryonic teratocarcinoma cell line NT2 into postmitotic neurons (hNT) was associated with enhanced expression of p15 and p16 proteins. These findings suggest that p15 and p16 play a role in maintaining cell quiescence in lymphocytes and neuronal cells, respectively. Deletions of these genes may thus promote unrestrained growth.

The retinal nerve fiber layer defects in patients with anterior ischemic optic neuropathy

PURPOSE

To demonstrate the effects of optic nerve ischemia on retinal nerve fiber layer (RNFL) and the associated visual dysfunction.

METHODS

23 patients (25 eyes) with anterior ischemic optic neuropathy (AION) underwent fundus fluorescein angiography (FFA), and then red-free light pictures were taken via SE-40 exceiter filter. All pictures were printed for RNFL analysis. Humphrey central field analysis was conducted. All data obtained from FFA and visual field defects were analysed statistically.

RESULTS

The RNFL defects and the corresponding visual field defects were presented in 23 of 25 eyes (92%). The optic disc filling defects, RNFL defects and visual field defects were found to be highly correspondent to each other. The RNFL defects were mainly the local losses of RNFL which were correspondent to the ischemic regions.

CONCLUSION

The poor optic disc filling or ischemia can result in the RNFL defects which cause the associated visual dysfunction. Because RNFL defects are irreversible changes, the potential values in predicting the prognosis of visual field defects caused by RNFL damages were suggested.

Regulation of cyclooxygenase-2 expression in normal human articular chondrocytes

This study analyzes cyclooxygenase II (COX-2) gene expression, protein synthesis, and PGE2 release in normal human articular chondrocytes. Stimulation of chondrocytes in primary culture resulted in a dose-dependent induction of COX-2 mRNA in response to IL-1 with an ED50 between 0.1 and 1 ng/ml. COX-2 mRNA was detectable after 2 h, reached high levels at 6 h, and showed a remarkably long duration of expression for at least 72 h. Analysis of other extracellular stimuli showed that COX-2 mRNA was inducible by other cytokines including TNF-alpha, IL-6, and LIF and by bacterial LPS. Dexamethasone completely inhibited IL-1-induced COX-2 mRNA expression. Analysis of signaling pathways showed that PMA and calcium ionophore A23187, but not dibutyryl cAMP, induced COX-2 mRNA. The combination of IL-1 and A23187 resulted in synergistic increases. IL-1 effects were not reduced by the protein kinase C inhibitor staurosporine or by the protein kinase A inhibitor H89 but blocked by the protein tyrosine kinase inhibitor herbimycin A. COX-2 protein was detected at 71 kDa by Western blotting in IL-1-stimulated, and to almost similar levels in A23187-treated, cells. Flow cytometric analysis showed that after IL-1 stimulation 78% of the chondrocytes expressed COX-2 protein. The patterns of COX-2 protein expression and the levels of PGE2 release correlated with the effects of the different stimuli and inhibitors on mRNA expression.

Regulation of cyclooxygenase-2 expression in normal human articular chondrocytes

This study analyzes cyclooxygenase II (COX-2) gene expression, protein synthesis, and PGE2 release in normal human articular chondrocytes. Stimulation of chondrocytes in primary culture resulted in a dose-dependent induction of COX-2 mRNA in response to IL-1 with an ED50 between 0.1 and 1 ng/ml. COX-2 mRNA was detectable after 2 h, reached high levels at 6 h, and showed a remarkably long duration of expression for at least 72 h. Analysis of other extracellular stimuli showed that COX-2 mRNA was inducible by other cytokines including TNF-alpha, IL-6, and LIF and by bacterial LPS. Dexamethasone completely inhibited IL-1-induced COX-2 mRNA expression. Analysis of signaling pathways showed that PMA and calcium ionophore A23187, but not dibutyryl cAMP, induced COX-2 mRNA. The combination of IL-1 and A23187 resulted in synergistic increases. IL-1 effects were not reduced by the protein kinase C inhibitor staurosporine or by the protein kinase A inhibitor H89 but blocked by the protein tyrosine kinase inhibitor herbimycin A. COX-2 protein was detected at 71 kDa by Western blotting in IL-1-stimulated, and to almost similar levels in A23187-treated, cells. Flow cytometric analysis showed that after IL-1 stimulation 78% of the chondrocytes expressed COX-2 protein. The patterns of COX-2 protein expression and the levels of PGE2 release correlated with the effects of the different stimuli and inhibitors on mRNA expression.

Increased intracellular Ca2+ selectively suppresses IL-1-induced NO production by reducing iNOS mRNA stability

This study addresses the role of intracellular calcium (Ca2+) in the expression of iNOS, an IL-1 inducible gene in human articular chondrocytes. The calcium ionophore A23187 and ionomycin did not induce NO release or iNOS expression but inhibited dose dependently IL-1-induced NO release with IC50 of 200 nM and 100 nM, respectively. Increased intracellular Ca2+ induced by thapsigargin or cyclopiazonic acid, inhibitors of the endoplasmic reticulum Ca2+ ATPase, had similar inhibitory effects with IC50 of 1 nM and 3 microM, respectively. LPS and TNF alpha induced NO production were also suppressed by these Ca2+ elevating drugs. Levels of IL-1-induced iNOS protein were reduced by A23187, thapsigargin, and cyclopiazonic acid. These drugs as well as Bay K 8644 and KCl inhibited IL-1-induced iNOS mRNA expression. To analyze the role of Ca2+ in the expression of other IL-1 responsive genes in chondrocytes, these Ca2+ modulating drugs were tested for effects on COXII. In contrast to the inhibitory effects on iNOS mRNA, these drugs induced COXII mRNA expression and in combination with IL-1, enhanced COXII mRNA levels. Ca2+ mediated increases in COXII mRNA expression were associated with an increase in COXII protein. The kinetics of Ca2+ effects on IL-1-induced iNOS mRNA levels suggested a posttranscriptional mechanism. Analysis of iNOS mRNA half life showed that it was 6-7 h in IL-1-stimulated cells and decreased by A23187 to 2-3 h. In conclusion, these results show that Ca2+ inhibits IL-1-induced NO release, iNOS protein, and mRNA expression in human articular chondrocytes by reducing iNOS mRNA stability. Under identical conditions increased Ca2+ enhances IL-1-induced COXII gene and protein expression.

Tyrosine kinases are involved with the expression of inducible nitric oxide synthase in human articular chondrocytes

The present study characterizes mechanisms involved with the induction of nitric oxide (NO) production, nitric oxide synthase (NOS) enzymatic activity and mRNA expression in human articular chondrocytes. Activation of chondrocytes with lipopolysaccharide (LPS) or IL-1 resulted in time- and dose-dependent increases in iNOS mRNA followed by increased NOS enzymatic activity and NO release. The protein tyrosine kinase (PTK) inhibitors herbimycin A or genistein reduced IL-1 or LPS-induced NO release and NOS enzymatic activity. This was associated with inhibition of iNOS mRNA expression as determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. In contrast, inhibitors of protein kinase C (PKC) or protein kinase A (PKA) did not affect these responses. These results were confirmed in experiments with second messenger agonists where neither activation of PKC, nor increases in cyclic adenosine monophosphate (cAMP) or increased intracellular calcium levels were associated with the induction of iNOS mRNA or NO release. These results suggest that PKC, PKA and calcium-dependent signals are not required or sufficient for the stimulation of NO production. However, NO production is dependent on tyrosine kinases due to their role in the expression of iNOS mRNA.

Differentiation-dependent effects of IL-1 and TGF-beta on human articular chondrocyte proliferation are related to inducible nitric oxide synthase expression

This study analyzed the effect of chondrocyte differentiation on iNOS expression and responses to IL-1 and TGF-beta. During subculturing of chondrocytes, the growth-stimulatory effects of TGF-beta decreased, and cells in later passages even were growth inhibited by TGF-beta. IL-1 beta responses showed an inverse pattern. The antiproliferative effects of IL-1 beta decreased, and, after passage 6, IL-1 beta became a growth stimulator for chondrocytes. This change in growth factor response pattern was associated with a decrease in type II collagen expression. To determine whether these changes in the growth regulatory effects of IL-1 beta and TGF-beta were related to nitric oxide (NO), inducible nitric oxide synthase (iNOS) expression and NO release were analyzed. In primary chondrocytes, TGF-beta did not stimulate iNOS mRNA expression or NO release, and, during co-incubation, it did not detectably alter the IL-1 beta effect. Preincubation with TGF-beta resulted in a time-dependent increase in IL-1-induced NO. With increasing passage number, the IL-1 beta effects decreased, and, after passage 6, IL-1 beta no longer detectably stimulated iNOS expression or NO release. However, TGF-beta increased NO production synergistically with IL-1 beta during the same culture period when it lost its growth-stimulatory effects. The antiproliferative effects of TGF-beta in late passage chondrocytes were reversed by the NO synthase inhibitor NG-monomethylarginine. These results suggest a novel pattern of iNOS regulation by IL-1 and TGF-beta and show that the factors that modulate iNOS expression and proliferation are dependent on the differentiation status of the cells.

Differentiation-dependent effects of IL-1 and TGF-beta on human articular chondrocyte proliferation are related to inducible nitric oxide synthase expression

This study analyzed the effect of chondrocyte differentiation on iNOS expression and responses to IL-1 and TGF-beta. During subculturing of chondrocytes, the growth-stimulatory effects of TGF-beta decreased, and cells in later passages even were growth inhibited by TGF-beta. IL-1 beta responses showed an inverse pattern. The antiproliferative effects of IL-1 beta decreased, and, after passage 6, IL-1 beta became a growth stimulator for chondrocytes. This change in growth factor response pattern was associated with a decrease in type II collagen expression. To determine whether these changes in the growth regulatory effects of IL-1 beta and TGF-beta were related to nitric oxide (NO), inducible nitric oxide synthase (iNOS) expression and NO release were analyzed. In primary chondrocytes, TGF-beta did not stimulate iNOS mRNA expression or NO release, and, during co-incubation, it did not detectably alter the IL-1 beta effect. Preincubation with TGF-beta resulted in a time-dependent increase in IL-1-induced NO. With increasing passage number, the IL-1 beta effects decreased, and, after passage 6, IL-1 beta no longer detectably stimulated iNOS expression or NO release. However, TGF-beta increased NO production synergistically with IL-1 beta during the same culture period when it lost its growth-stimulatory effects. The antiproliferative effects of TGF-beta in late passage chondrocytes were reversed by the NO synthase inhibitor NG-monomethylarginine. These results suggest a novel pattern of iNOS regulation by IL-1 and TGF-beta and show that the factors that modulate iNOS expression and proliferation are dependent on the differentiation status of the cells.

Effects of caffeine or EDTA post-treatment on EMS mutagenesis in soybean

Seeds of soybean cultivar LD4 were mutagenically treated with EMS (0.3, 0.5, 0.6, 0.9, 1.5 and 1.8%) for 3 h only or plus caffeine (50 mM) or EDTA (1 mM) post-treatment for 5 h. The experimental results indicated that: (1) of the different concentrations of EMS treatment, the M2 mutation frequency induced with 0.6% EMS was the highest (9.7%). When the EMS concentration was over 0.9%, the mutation frequency decreased rapidly. (2) Of the EMS treatments plus caffeine or EDTA post-treatment, the mutagenic effect of 0.6% EMS was the best for inducing morphological variations. Caffeine post-treatment decreased notably the mutation frequency of EMS treatment; when concentrations of EMS were very high (1.5% and 1.8%), mutation frequencies of EDTA post-treatment were still 5.0% and 4.88%, but no mutants were found in EMS treatment or plus caffeine post-treatment. (3) In the M2 mutation spectrum, 11 kinds of mutant types were observed in EMS treatment or plus caffeine or EDTA post-treatment. Relative frequencies of some mutant types (growth period, plant height, grain size, leaf shape and sterility, etc.) were similar among the three treatments, but EDTA post-treatment could change the relative frequencies of yield characteristics (number of pods and grains, grain weight/plant) induced by EMS treatment only.

[A convenient and accurate computer program for computing the free Ca2+ concentration in experimental solution]

A computer program for computing the free Ca2+ concentration in the experimental solution containing multiple metals and ligands used for the experimentals of myofibrillar AT-Pase or skinned muscle cell is presented. This program is convenient and accurate.