Efficient strategy for the occasionally proportional feedback method in controlling chaos

In this work, the generic mechanism of the occasionally proportional feedback (OPF) technique in controlling chaos has been explored extensively. Except for stabilizing the unstable states that are embedded in the chaotic attractors, the OPF method is also found to generate a great number of new states during the control processes. The forms and characteristics of these new states have been addressed. Moreover, we clarify the roles of the parameters in the OPF method and this clarification leads to a practical and systematic approach in adjusting the parameters for control. To demonstrate the validity, an analogous electronic circuit of the resistively shunted Josephson junction oscillator is employed in addition to a numerical illustration of the logistic mapping.

Cold injury in mice: a model to study mechanisms of brain edema and neuronal apoptosis

Small rodents, mice in particular, have been widely used for genetic manipulation because of the extensive knowledge in development, embryology and other molecular aspects of this species. However, the use of mice for neurobiology research in the area of brain edema and neuronal injury has not been common. Here we summarize the studies of cold injury-induced brain edema and neuronal apoptosis using mice. Blood-brain barrier (BBB) permeability, demonstrated by extravasation of a serum albumin tracer, Evans Blue, was increased immediately after the injury and returned to the control level by 24 hr. Water content was maximized at 24 hr, whereas a secondary lesion gradually progressed up to 72 hr after cold injury. The mechanism of the development of the cold injury-induced edema and the secondary lesion, involving of oxygen radicals in particular, was determined using superoxide dismutase (SOD)-1 transgenic (Tg) mice with overexpressed copper, zinc-SOD. All of the parameters, BBB permeability, water content and secondary lesion, were attenuated in the Tg mice as compared to littermate non-Tg mice. This clearly demonstrates that oxygen radicals, superoxide anion in particular, mediate cold injury. We also studied whether apoptosis contributes to brain injury following cold injury. Staining with terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling showed the apoptotic cells widespread throughout the entire lesion while still remaining in the margin. DNA laddering was exhibited by gel electrophoresis. These studies indicate that oxidative mediates the development of cold injury-induced edema and the secondary injury, and induces apoptotic cell death. We believe that cold injury in mice provides a simple animal model to study the pathogenesis of brain edema and apoptosis in genetically altered animals.

Involvement of catecholamines in recall of the conditioned NK cell response

The primary goal of the study was to identify the types of catecholamines and the associated receptors which might be involved in the recall of the conditioned NK cell response. Specific catecholamine receptor antagonists were selected to block the conditioned NK cell response at the recall step. The regional contents of dopamine (DA), norepinephrine (NE), and epinephrine were determined in the brain of the conditioned animals by using the high performance liquid chromatography with electrochemical detection (HPLC/ED). Results showed that pre-disruption of the central alpha1-, alpha2-, beta1-, beta2-, D1-, or D2-receptors at the conditioned recall stage, interrupted the conditioned enhancement in NK cell activity. The NE contents at the cerebellum, and DA contents at the striatum and hippocampus, were significantly higher in the brain of the conditioned animals when compared to that of the control animals. These information indicated the possible roles of the central noradrenergic and dopaminergic systems in regulating the recall of the conditioned NK cell response.

Reduced mitochondrial manganese-superoxide dismutase activity exacerbates glutamate toxicity in cultured mouse cortical neurons

Studies of neuronal injury and death after cerebral ischemia and various neurodegenerative diseases have increasingly focused on the interactions between mitochondrial function, reactive oxygen species (ROS) production and glutamate neurotoxicity. Recent findings suggest that increased mitochondrial ROS production precedes neuronal death after glutamate treatment. It is hypothesized that under pathological conditions when mitochondrial function is compromised, extracellular glutamate may exacerbate neuronal injury. In the present study, we focus on the relationship between mitochondrial superoxide production and glutamate neurotoxicity in cultured cortical neurons with normal or reduced levels of manganese-superoxide dismutase (MnSOD) activity. Our results demonstrate that neurons with reduced MnSOD activity are significantly more sensitive to transient exposure to extracellular glutamate. The increased sensitivity of cultured cortical neurons with reduced MnSOD activity is characteristically subject only to treatment by glutamate but not to other glutamate receptor agonists, such as N-methyl-d-aspartate, kainate and quisqualate. We suggest that the reduced MnSOD activity in neurons may exacerbate glutamate neurotoxicity via a mechanism independent of receptor activation.

Overexpression of SOD1 in transgenic rats protects vulnerable neurons against ischemic damage after global cerebral ischemia and reperfusion

Transient global cerebral ischemia resulting from cardiac arrest is known to cause selective death in vulnerable neurons, including hippocampal CA1 pyramidal neurons. It is postulated that oxygen radicals, superoxide in particular, are involved in cell death processes. To test this hypothesis, we first used in situ imaging of superoxide radical distribution by hydroethidine oxidation in vulnerable neurons. We then generated SOD1 transgenic (Tg) rats with a five-fold increase in copper zinc superoxide dismutase activity. The Tg rats and their non-Tg wild-type littermates were subjected to 10 min of global ischemia followed by 1 and 3 d of reperfusion. Neuronal damage, as assessed by cresyl violet staining and DNA fragmentation analysis, was significantly reduced in the hippocampal CA1 region, cortex, striatum, and thalamus in SOD1 Tg rats at 3 d, as compared with the non-Tg littermates. There were no changes in the hippocampal CA3 subregion and dentate gyrus, resistant areas in both SOD1 Tg and non-Tg rats. Quantitative analysis of the damaged CA1 subregion showed marked neuroprotection against transient global cerebral ischemia in SOD1 Tg rats. These results suggest that superoxide radicals play a role in the delayed ischemic death of hippocampal CA1 neurons. Our data also indicate that SOD1 Tg rats are useful tools for studying the role of oxygen radicals in the pathogenesis of neuronal death after transient global cerebral ischemia.

Copper/zinc superoxide dismutase transgenic brain accumulates hydrogen peroxide after perinatal hypoxia ischemia

Unlike the mature animal, immature mice transgenic for copper/zinc superoxide dismutase (SOD1) have greater brain injury after hypoxia-ischemia than their wild-type nontransgenic littermates. To assess the role of oxidative stress in the pathogenesis of this injury, we measured histopathological damage, lipid peroxidation products, enzymatic activities of catalase and glutathione peroxidase, and hydrogen peroxide (H2O2) concentration in these animals before and after hypoxic-ischemic injury. Lipid peroxidation products were significantly increased 2 hours after the insult in both transgenic and nontransgenic brains in hippocampus, the most damaged brain region. Catalase activity did not increase in response to SOD1 overexpression or injury in either group. However, glutathione peroxidase activity, unchanged in response to overexpression, decreased significantly 24 hours after injury in both groups. At 24 hours after injury, greater H2O2 accumulation was observed in transgenic brains. Because SOD1 dismutates superoxide to H2O2, overexpression of SOD1 in the presence of developmentally low activities of the catalytic enzymes glutathione peroxidase and catalase leads to an increased production of H2O2, and may explain the increased brain injury observed after hypoxia-ischemia in neonatal SOD1 mice.

The role of endothelin-1 in the aorta of post-infarct left ventricular dysfunction rats treated with captopril

OBJECTIVES

There is little information available regarding local vasomotor regulating processes in chronic heart failure. In this study, we tested the hypothesis that chronic heart failure impaired the endothelial function, and long term captopril treatment might reverse endothelial activity through tissue endothelin (ET) pathway.

METHODS

Forty Sprague-Dawley rats were divided into 4 groups including 15 rats in each of the sham-operated with or without captopril-treated groups and 5 rats in each of large infarcted with or without captopril-treated groups.

RESULTS

Concentration-response curves obtained in aortic rings without endothelium revealed no difference in nitroprusside-induced relaxation. With endothelium, rightward shifting was noted only in the untreated large infarct group during acetylcholine-induced relaxation. As compared to the non-treated group, plasma ET-1 concentrations were lower in the captopril-treated with or without large infarct groups. However, endothelin-like immunoreactivity in endothelial cells and cytoplasma of smooth muscle cells of the media of the aorta were lower only in the non-treated large infarct group.

CONCLUSIONS

Endothelial function was impaired in the chronic heart failure model. Coverting enzyme inhibitor might improve endothelial function through the Local endothelin pathway.

Mitochondrial susceptibility to oxidative stress exacerbates cerebral infarction that follows permanent focal cerebral ischemia in mutant mice with manganese superoxide dismutase deficiency

Mitochondrial injury has been implicated in ischemic neuronal injury. Mitochondria, producing adenosine triphosphate by virtue of electron flow, have been shown to be both the sites of superoxide anion (O2-) production and the target of free radical attacks. We evaluated these mechanisms in an in vivo cerebral ischemia model, using mutant mice with a heterozygous knock-out gene (Sod2 -/+) encoding mitochondrial manganese superoxide dismutase (Mn-SOD). Sod2 -/+ mice demonstrated a prominent increase in O2- production under normal physiological conditions and in ischemia, as evidenced by specific oxidation of a fluorescent probe, hydroethidine, reflecting decreased activity of Mn-SOD. A mitochondrial viability assay that used rhodamine 123, which is accumulated by transmembrane potential of viable mitochondria, demonstrated accelerated development of mitochondrial injury. This rapid progress of ischemic injury resulted in exacerbation of infarct size and hemisphere enlargement, causing advanced neurological deficits but without altering DNA fragmentation induction. The present study suggests that O2- overproduced in a mitochondrial compartment, when uncoupled from antioxidant defenses, induces impairment of mitochondrial function and causes exacerbation of cerebral infarction after ischemia.

[Analysis of divergent angle and length of CEJ to furcation entrance in extracted molars]

The purposes of this study were to investigate the furcation entrance angle (FEA) and the distance between cemento-enamel junction (CEJ) and furcation entrance (FE) of the extracted maxillary and mandibular molars. Assay teeth comprised 89 maxillary molars and 93 mandibular molars. All the FEAs and CEJ-FEs of the molars were measured by a stereomicroscope at 2.5 x equipped with a Bioscan OPTIMAS Image Analyzer (BOIA). The results were summarized as follows: (1) The mean FEAs in the buccal, mesial and distal furcations were 96.3 +/- 10.0, 103.8 +/- 9.7, and 107.2 +/- 12.2 degrees in the maxillary molars, and 91.6 +/- 11.7, 101.7 +/- 11.5, and 97.1 +/- 10.7 degrees in the maxillary second molars, respectively. At the buccal and lingual furcations of mandibular first and second molars, they measured 100.5 +/- 9.7/102.7 +/- 8.5, and 93.3 +/- 11.5/91.7 +/- 10.8 degrees, respectively. (2) The mean distance of CEJ-FEs at the buccal, mesial and distal furcations of maxillary molars were 3.42 +/- 1.5mm, 3.55 +/- 0.97 mm, and 3.69 +/- 0.98mm for the first molars, and 3.01 +/- 1.04mm, 4.04 +/- 1.58mm and 3.00 +/- 1.14mm for the second molars. At the buccal and lingual furcations of the mandibular first and second molars, they were recorded as 1.90 +/- 0.08mm and 2.90 +/- 0.07mm, and 2.82 +/- 1.34mm and 3.46 +/- 1.03mm, respectively. It was concluded that buccal FEA of maxillary 2nd molar was the smallest (91.56 +/- 9.68 degrees) as compared to the mesial and distal FEAs; whereas the mean distance of CEJ-FEs at the buccal surface was the smallest (1.90mm +/- 0.08mm) when compared to the others.

Effects on DNA integrity and apoptosis induction by a novel antitumor sesquiterpene drug, 6-hydroxymethylacylfulvene (HMAF, MGI 114)

6-Hydroxymethylacylfulvene (HMAF, MGI 114) is a new alkylating antitumor sesquiterpenoid with promising and often curative antitumor activity in vivo. This study examined the ability of the drug to damage cellular DNA, induce apoptosis, and affect the cell cycle of CEM human leukemia cells. No bifunctional lesions, interstrand DNA cross-links or DNA-protein cross-links were seen (by alkaline sedimentation and K+/SDS precipitation, respectively) when using up to 50 microM HMAF. The drug possibly formed some monoadducts, as DNA from drug-treated cells impeded primer extension by Taq polymerase, although only partial inhibition was seen even at 200 microM HMAF. HMAF also induced secondary lesions in cellular DNA, single-strand breaks that were detectable (by nucleoid sedimentation and alkaline sucrose gradient analysis) after a 4-hr treatment at HMAF levels as low as 2 microM, comparable to the growth inhibition IC50 value (1.7 microM). A post-treatment incubation of cells in drug-free medium generated substantial amounts of DNA double-stranded fragments of several kbp, suggesting apoptotic fragmentation (>30% of total DNA following treatment with 20 microM HMAF and a 17-hr post-treatment incubation). Chromatin condensation (by ultrastructural analysis) and induction of sub-G1 particles and apoptotic strand breakage (by multiparametric flow cytometry) confirmed induction of apoptosis by HMAF. HMAF preferentially inhibited DNA synthesis (IC50 approximately 2 microM), which is consistent with an S phase block, observed by cell cycle analysis. The pattern of apoptotic DNA fragmentation, inhibition of DNA synthesis, and blockage in the S phase suggests that these events play a role in the antiproliferative activity of HMAF.

[The structure correction of villosolside]

The crystal structure of villosolside was determined by X-ray diffraction, which led to some stereochemical amendment of the structure proposed in the article by Xu CJ et al. in Acta Pharm Sin 1985, 20:652.

Reduction of CuZn-superoxide dismutase activity exacerbates neuronal cell injury and edema formation after transient focal cerebral ischemia

Apoptotic neuronal cell death has recently been associated with the development of infarction after cerebral ischemia. In a variety of studies, CuZn-superoxide dismutase (CuZn-SOD) has been shown to protect the brain from ischemic injury. A possible role for CuZn-SOD-related modulation of neuronal viability is suggested by the finding that CuZn-SOD inhibits apoptotic neuronal cell death in response to some forms of cellular damage. We evaluated this possibility in the model of transient focal cerebral ischemia in mice bearing a disruption of the CuZn-SOD gene (Sod1). Homozygous mutant (Sod1 -/-) mice had no detectable CuZn-SOD activity, and heterozygous mutants (Sod1 +/-) showed a 50% decrease compared with wild-type mice. Sod1 -/- mice showed a high level of blood-brain barrier disruption soon after 1 hr of middle cerebral artery occlusion and 100% mortality at 24 hr after ischemia. Sod1 +/- mice showed 30% mortality at 24 hr after ischemia, and neurological deficits were exacerbated compared with wild-type controls. The Sod1 +/- animals also had increased infarct volume and brain swelling, accompanied by increased apoptotic neuronal cell death as indicated by the in situ nick-end labeling technique to detect DNA fragmentation and morphological criteria. These results suggest that oxygen-free radicals, especially superoxide anions, are an important factor for the development of infarction by brain edema formation and apoptotic neuronal cell death after focal cerebral ischemia and reperfusion.

Preclinical antitumor activity of 6-hydroxymethylacylfulvene, a semisynthetic derivative of the mushroom toxin illudin S

6-Hydroxymethylacylfulvene (HMAF; MGI 114) is a novel semisynthetic antitumor agent derived from the sesquiterpene mushroom toxin illudin S. In vitro cytotoxicity determinations produced IC50 concentrations (concentrations required for 50% inhibition of growth) ranging from 160 nM in sensitive MCF-7 human mammary carcinoma cells to 17 microM in relatively insensitive murine B16 melanoma cells. In vivo antitumor activity was consistent with in vitro sensitivity. HMAF was very effective in human tumor xenograft models, including MX-1 breast carcinoma, MV522 lung adenocarcinoma, and HT-29 colon carcinoma, but not murine B16 melanoma or P388 leukemia. Excellent responses were observed in animals bearing MX-1 tumors administered i.v. or i.p. doses of 3-7.5 mg/kg daily for 5 days, with complete regression recorded in 29 of 30 animals administered i.v. HMAF. Extensive tumor shrinkage was also observed with MV522, and significant tumor growth inhibition was obtained with HT-29 when animals received 5 daily i.p. doses ranging from 3.75 to 7.5 mg/kg. Complete regressions were also observed in individual animals with MV522 and HT-29. The excellent activity of HMAF in several human solid tumor xenografts, including the more refractory MV522 and HT-29 models, warrants the further investigation of this novel agent in clinical trials.

The role of 20-hydroxyecdysone in stimulating DNA synthesis in corpora allata of the silkworm, Bombyx mori

Temporal changes in DNA synthesis were examined in the corpora allata of the silkworm Bombyx mori during the penultimate larval stadium. 5'-Bromo-2'-deoxyuridine (BrdU) labeling revealed that allatal DNA synthesis rose early in the stadium, peaking at about 2% of corpus allatum (CA) cells 24 hr after ecdysis. This corresponded to a rising phase of the ecdysteroid titer reported previously. DNA synthesis declined to a nearly undetectable level 1 day later. In larvae fed on leaves coated with 20-hydroxyecdysone (20E), the number of BrdU-labeled cells increased continuously after the normal peak and reached about 8% of CA cells at the end of the stadium. However, total count of CA cells from whole-mount monolayers and colchicine treatment indicated that, regardless of DNA content, CA cells did not divide. To determine if the rise in 20E was responsible for the onset of allatal DNA synthesis, we have established an organ culture system to support de novo DNA synthesis in vitro. The number of BrdU-labeled cells increased with increasing 20E concentration between 0.1 and 0.5 microg ml-1 in the medium, corresponding well to the rising 20E titer in the hemolymph. The level of DNA synthesis in culture was further elevated when 20% hemolymph was added together with 20E, suggesting that other direct stimulatory factors for allatal DNA synthesis may also exist in the hemolymph.

Human telomerase inhibition by 7-deaza-2'-deoxypurine nucleoside triphosphates

Telomeres play an important role in chromosome organization and stability. Human telomerase is a terminal transferase that adds TTAGGG units onto the telomere end. In general, telomerase activity is not detected in normal somatic cells but is present in immortalized cells. Consequently, telomerase might be a selective target for cancer chemotherapy. Using cell-free biochemical telomerase assay, we have found that 7-deaza-2'-deoxyguanosine-5'-triphosphate (7-deaza-dGTP) and 7-deaza-2'-deoxyadenosine-5'-triphosphate (7-deaza-dATP) were potent telomerase inhibitors. The concentrations of inhibitors in which 50% of the telomerase activity was inhibited (IC50 values) were 11 and 8 microM for 7-deaza-dGTP and 7-deaza-dATP, respectively. Additional studies show that both 7-deaza-dGTP and 7-deaza-dATP were also incorporated into telomeric DNA by telomerase. However, incorporation of 7-deaza-dATP or 7-deaza-dGTP results in a telomeric ladder that is prematurely shortened. No difference in the number or position of pause sites were observed when 7-deaza-dATP was compared to dATP as substrates. On the other hand, both a shift and an increase in pause sites was observed when dGTP was replaced by 7-deaza-dGTP. Incorporation of 7-deaza nucleotides by telomerase may be used as a tool for the study of telomerase mechanism and function. In addition, this may be a novel approach in the design of new telomerase inhibitors.

[Furcation entrance dimension, divergent angle and length of CEJ to furcation entrance relate to periodontal therapy]

In previous studies we have investigated the furcation entrance dimension (FED), furcation entrance angle (FEA) and the distance between cementoenamel junction and furcation entrance (CEJ-FE) of the first and second molars and compared the Chinese with the Caucasians. The aim of the present study was to relate the FED, FEA, and distance of CEJ-FE to the clinical significance of periodontal therapy of molar furcations. All the FEDs, FEAs, and distance of CEJ-FEs of the molars were measured by a stereomicroscope equipped with a Bioscan OPTIMAS Image Analyzer and statistically analyzed by Student's paired t-test, multiple regression of ANOVA and correlation analysis. The results are summarized below. (1) There is a significant relationship between FEA and location of buccal, mesial, and distal furcations of maxillary first and second molars (16& 26, p < 0.001; 17&27, p < 0.01). (2) There exists a significant relationship between FEA and FED in the mandibular first and second molars. (3) There exists a significant relationship between FED and FEA in the mandibular second molar (r = 0.370, p < 0.05). (4) The prevalence of mean FED and FEA (type D, FED < or = 0.75 mm and FEA < or = 90 degree) of the maxillary first molar (45%) is twice as high as the maxillary first molar (24%). (5) The prevalence of type D of the buccal (32%) and lingual (37%) furcations on the mandibular second molar is markedly higher than the first molar (buccal = 12%; lingual = 4%, respectively). These results reveal that those topographics of the FED, FEA, and distance of CEJ-FE in second molars have poor prognosis in periodontal therapy when compared with first molars.

Agents that target telomerase and telomeres

Telomeres are guanine-rich regions that are located at the ends of chromosomes and are essential for preventing aberrant recombination and protecting against exonucleolytic DNA degradation. Telomeres are maintained by telomerase, an RNA-dependent DNA polymerase. Because telomerase is known to be expressed in tumor cells, which concurrently have short telomeres, and not in most somatic cells, which usually have long telomeres, telomerase and telomere structures have been recently proposed as attractive targets for the discovery of new anticancer agents. The most exciting current strategies are aimed at specifically designing new drugs that target telomerase or telomeres and new models have been formulated to study the biological effects of inhibitors of telomerase and telomeres both in vitro and in vivo.

Involvement of cytokine gene expression in the age-dependent decline of NK cell response

The molecular mechanism responsible for the age-dependent decline of natural killer (NK) cell response was examined. The responses of NK cells to poly(I:C), Con A, and LPS were compared between the young and the aged animals. We observed that both basal and induced NK cell activity declined with age. To further determine the basis for this change, an effort was made to identify the cytokine genes that might be involved. In addition, the capacity of acetyl-L-carnitine (ALC) to restore NK cell activity was evaluated. In this study, 51Cr release assay and reverse transcriptase-polymerase chain reaction assay were used to measure the NK cell activity and the changes in cytokine gene expression, respectively. Our results show that the decline in NK cell response to poly(I:C) and LPS in aged animals was correlated with decreased expression of the IFN-gamma gene. The decline in the NK cell response to Con A in aged animals was, however, independent of the expression of IL-2 or IFN-gamma genes. Although ALC was reported to restore functions of T cells and macrophages in aged animals, we found that long-term treatment (4 months) with ALC had no effect on either the basal or the induced age-dependent loss of NK cell activity. Our observations suggest that cytokine gene therapy could be a potential approach to improving or even preventing the decline of certain immune functions in the elderly.

Attenuation of acute and chronic damage following traumatic brain injury in copper, zinc-superoxide dismutase transgenic mice

To elucidate the role of oxygen-derived free radicals and superoxide dismutase in traumatic brain injury (TBI), blood-brain barrier (BBB) permeability, brain edema, behavioral function, and necrotic cavity volume (CV) were evaluated after TBI using nontransgenic (nTg) mice and heterozygous and homozygous transgenic (Tg) mice with a 1.5- (Tg 1.5x), 3.1-(Tg3.1x) and five- (Tg5x) fold increase in human copper, zinc-superoxide dismutase (CuZn-SOD) activity. Traumatic brain injury was produced by the weight-drop method. Evans blue dye leakage 4 hours after injury was attenuated in a CuZn-SOD dose-dependent manner with decreases of 18.6%, 40.9%, and 48.8%, in the Tg1.5x, Tg3.1x, and Tg5x groups, respectively. The water content 6 hours after injury in the Tg3.1x (79.64%) and Tg5x (79.45%) groups was significantly lower than in nTg mice (81.37%). There was an initial decrease in body weight and in motor performance, as measured by beam walk and beam balance tasks undertaken 1 day after TBI. However, the average reduction in beam balance and beam walk performance deficits and changes in body weight postinjury were significantly ameliorated in Tg mice. The CV was significantly smaller in Tg mice than in nTg mice (p < 0.01). These results indicate that superoxide radicals play a deleterious role following TBI. Furthermore, Tg mice provide a useful model for demonstrating the beneficial role of an antioxidant enzyme in TBI without the confounding effect of pharmacokinetics, toxicity, and BBB permeability associated with exogenous agents.

Activation of mu-opioid receptors are required for the conditioned enhancement of NK cell activity

The type of opioid receptors involved in the conditioned enhancement of natural killer (NK) cell activity is identified in the present study. In our previous observations, we have demonstrated that the conditioned enhancement of NK cell activity was dependent on beta-endorphin and methionine-enkephalin, but not dynorphin. Based on the interaction of opioids with their homologous receptors, we concluded that mu- and delta-opioid receptors might be involved. To further classify the type(s) of opioid receptors involved in eliciting the conditioned NK cell activity, three opioid receptor antagonists, cyprodime hydrobromide, ICI-174864, and nor-binaltorphimine dihydrochloride, were used to block the conditioned NK cell activity in BALB/c mice. Blocking was conducted by intracisternal injection of the drugs. The results showed that the activation of mu-opioid receptors was required in the conditioned enhancement of NK cell activity, but not the delta- or kappa-type of receptors.

Mechanism of extracellular ATP-induced proliferation of vascular smooth muscle cells

The mitogenic effect of extracellular ATP was examined in cultured rat aortic smooth muscle cells (VSMCs). ATP, 2-methylthio-ATP, and ADP stimulated [3H]thymidine and [3H]leucine incorporation and cell growth. AMP, adenosine, UTP, and P2x agonists showed little of these effects. Reactive blue 2, a P2Y purinoceptor antagonist, was effective in suppressing the mitogenic effect of ATP and 2-methylthio-ATP, indicating that extracellular ATP-induced VSMC proliferation is mediated by P2Y purinoceptors. The P2Y purinoceptor activation was coupled to a pertussis toxin (PTX)-insensitive G protein (Gq) and triggered phosphoinositide hydrolysis with subsequent activation of protein kinase C (PKC), Raf-1, and mitogen-activated protein kinase (MAPK) in VSMCs. In response to ATP, both 42-and 44-kDa MAPKs were activated, and tyrosine was phosphorylated. Western blot analysis using PKC isozyme-specific antibodies indicated that VSMCs express PKC-alpha, PKC-delta, and PKC-zeta. A complete down-regulation of PKC-alpha and PKC-delta was seen after 24-hr treatment with 12-O-tetradecanoylphorbol-13-acetate. When cells were pretreated with 12-O-tetradecanoyl-phorbol-13-acetate for 24 hr and subsequently challenged with ATP, Raf-1 activation and 42-kDa as well as 44-kDa MAPK tyrosine phosphorylation failed to be induced. These results demonstrate that ATP-induced Raf-1 and MAPK activations involve the activation of PKC-alpha and PKC-delta. P2Y purinoceptor stimulation with ATP also caused accumulation of c-fos and c-myc mRNAs. Both Reactive blue 2 and staurosporine significantly blocked this increase by ATP. In conclusion, the mitogenic effect of ATP seemed to be triggered by activation of the Gq protein-coupled P2Y purinoceptor that led to the formation of inositol trisphosphate and activation of PKC. PKC and, in turn, Raf-1 and MAPK were then activated, leading eventually to DNA synthesis and cell proliferation.

Effects of dextran sulphate sodium on intestinal epithelial cells and intestinal lymphocytes

BACKGROUND AND AIMS

The effects of dextran sulphate sodium (DSS) on mouse intestinal epithelial cells and intraepithelial lymphocytes were analysed to investigate the mechanism by which DSS induces colitis and tumours in mice. Cytotoxicity of DSS towards intestinal epithelial cells and intestinal intraepithelial lymphocyte hybridomas or fresh intestinal intraepithelial lymphocytes seems to have concentration, time, and cell type dependency with increasing concentrations and time causing increased cytotoxicity.

RESULTS

Integrin alpha 4 expression was marginally down regulated by 0.5% of DSS, while alpha M290 expression was up regulated. DSS inhibits the binding of 9.1 gamma delta cells to both extracellular matrix (ECM) and epithelial cells. Conversely at high concentrations it increases binding to all ECM except poly-L-lysine. Various cytokines including TGF beta, interleukin 2, and tumour necrosis factor alpha as well as prostaglandin alter the expression of the integrin alpha 4 and M290 subunits at the cell surface, and also alter the adhesion of 9.1 gamma delta cells to epithelial monolayers. The expression of a large number of cell adhesion molecules expressed on intraepithelial lymphocytes is affected by a combination of the abundant gut cytokine TGF beta and DSS, suggesting that DSS induced colitis may ultimately arise from a combination of gut cytokine and DSS. DSS also triggers intraepithelial lymphocyte aggregation on all ECM coated plate tested.

CONCLUSIONS

These data suggest that the potential roles of DSS induced colitis may be: (a) direct cytotoxicity; (b) interference with the normal interaction between intestinal lymphocytes, epithelial cells, and ECMs; (c) aberrant modulation of the expression of the integrin beta 7 receptors, other cell receptors, and their functions.