Altered cytokine export and apoptosis in mice deficient in interleukin-1 beta converting enzyme

The interleukin-1 beta (IL-1 beta) converting enzyme (ICE) processes the inactive IL-1 beta precursor to the proinflammatory cytokine. Adherent monocytes from mice harboring a disrupted ICE gene (ICE-/-) did not export IL-1 beta or interleukin-1 alpha (IL-1 alpha) after stimulation with lipopolysaccharide. Export of tumor necrosis factor-alpha and interleukin-6 (IL-6) from these cells was also diminished. Thymocytes from ICE-/- mice were sensitive to apoptosis induced by dexamethasone or ionizing radiation, but were resistant to apoptosis induced by Fas antibody. Despite this defect in apoptosis, ICE-/- mice proceed normally through development.

Activation of interferon-gamma inducing factor mediated by interleukin-1beta converting enzyme

The interleukin-1beta (IL-1beta) converting enzyme (ICE) processes the inactive IL-1beta precursor to the proinflammatory cytokine. ICE was also shown to cleave the precursor of interferon-gamma inducing factor (IGIF) at the authentic processing site with high efficiency, thereby activating IGIF and facilitating its export. Lipopolysaccharide-activated ICE-deficient (ICE-/-) Kupffer cells synthesized the IGIF precursor but failed to process it into the active form. Interferon-gamma and IGIF were diminished in the sera of ICE-/- mice exposed to Propionibacterium acnes and lipopolysaccharide. The lack of multiple proinflammatory cytokines in ICE-/- mice may account for their protection from septic shock.

The nuclear hormone receptor coactivator SRC-1 is a specific target of p300

p300 and its family member, CREB-binding protein (CBP), function as key transcriptional coactivators by virtue of their interaction with the activated forms of certain transcription factors. In a search for additional cellular targets of p300/CBP, a protein-protein cloning strategy, surprisingly identified SRC-1, a coactivator involved in nuclear hormone receptor transcriptional activity, as a p300/CBP interactive protein. p300 and SRC-1 interact, specifically, in vitro and they also form complexes in vivo. Moreover, we show that SRC-1 encodes a new member of the basic helix-loop-helix-PAS domain family and that it physically interacts with the retinoic acid receptor in response to hormone binding. Together, these results implicate p300 as a component of the retinoic acid signaling pathway, operating, in part, through specific interaction with a nuclear hormone receptor coactivator, SRC-1.

iNOS and nitrotyrosine expression after spinal cord injury

Secondary tissue damage after spinal cord injury (SCI) may be due to inflammatory mediators. After SCI, the nuclear factor-kappaB (NF-kappaB) transcription factor can activate many pro-inflammatory genes, one of which is inducible nitric oxide synthase (iNOS). iNOS catalyzes the synthesis of nitric oxide (NO), a key inflammatory mediator, which in turn reacts with superoxide to generate peroxynitrite. Peroxynitrite is a strong oxidant that can damage cellular enzymes, membranes, and subcellular organelles through the nitration of tyrosine residues on proteins. The presence of nitrotyrosine (NT) is an indirect chemical indicator of toxic NO and peroxynitrite-induced cellular damage. Using a New York University (NYU) impactor to induce SCI in adult rats, we examined the temporal and cellular expression of iNOS and NT. We observed a progressive increase in iNOS expression in the injured cord starting at day 1 with maximal expression occurring at day 7, as determined by Western blot analysis. iNOS expression corresponded temporally to an increase in iNOS enzyme activity after SCI. In parallel with the progressive increase in iNOS activity, NT expression also increased with time after SCI. The iNOS and NT immunoreactivity was localized in neurons, astrocytes, endothelial cells and ependymal cells at the epicenter and adjacent to the region of spinal cord impact and injury. Results from the present study suggest that increased iNOS and peroxynitrite anion, as reflected by the progressive accumulation of NT in the injured impacted spinal cord, may contribute to the secondary injury process after SCI.

Scanning microwave-induced thermoacoustic tomography: signal, resolution, and contrast

Scanning thermoacoustic tomography was explored in the microwave region of the electromagnetic spectrum. Short microwave pulses were used to induce acoustic waves by thermoelastic expansion in biological tissues. Cross sections of tissue samples were imaged by a linear scan of the samples while a focused ultrasonic transducer detected the time-resolved thermoacoustic signals. Based on the microwave-absorption properties of normal and cancerous breast tissues, the piezoelectric signals in response to the thermoacoustic contrast were investigated over a wide range of electromagnetic frequencies and depths of tumor locations. The axial resolution is related to the temporal profile of the microwave pulses and to the impulse response of the ultrasonic transducer. The lateral resolution is related to the numerical aperture of the ultrasonic transducer as well as to the frequency spectra of the piezoelectric signals in the time window corresponding to the axial resolution. Gain compensation, counteracting the microwave attenuation, was applied to enhance the image contrast.

Scanning thermoacoustic tomography in biological tissue

Microwave-induced thermoacoustic tomography was explored to image biological tissue. Short microwave pulses irradiated tissue to generate acoustic waves by thermoelastic expansion. The microwave-induced thermoacoustic waves were detected with a focused ultrasonic transducer. Each time-domain signal from the ultrasonic transducer represented a one-dimensional image along the acoustic axis of the ultrasonic transducer similar to an ultrasonic A-scan. Scanning the system perpendicularly to the acoustic axis of the ultrasonic transducer would generate multi-dimensional images. Two-dimensional tomographic images of biological tissue were obtained with 3-GHz microwaves. The axial and lateral resolutions were characterized. The time-domain piezo-electric signal from the ultrasonic transducer in response to the thermoacoustic signal was simulated theoretically, and the theoretical result agreed with the experimental result very well.

Amyloid beta peptide-induced cerebral endothelial cell death involves mitochondrial dysfunction and caspase activation

Amyloid beta peptide (A beta), a 39 to 43 amino acid fragment of the beta-amyloid precursor protein (betaAPP), forms insoluble fibrillar accumulation in neurofibrillary tangles and vascular plaques. A beta has been implicated in neuronal and vascular degeneration in brain regions susceptible to plaque formation because of its cytotoxic effect on neurons and endothelial cells (ECs). The authors used a murine cerebral endothelial cell (CEC) line and primary cultures of bovine CECs to explore the cytotoxic mechanism of A beta. A beta 1-40 and A beta 25-35 peptides caused cell death in a dose-dependent and time-dependent manner. Exposure to either A beta 25-35 or A beta 1-40 at 10 micromol/L for 48 hours caused at least 40% cell death. Cerebral endothelial cell death was characterized by nuclear condensation, mitochondrial dysfunction, and nuclear and mitochondrial DNA damage. A beta 25-35 activated both caspase-8 and caspase-3 in murine CECs. zVAD-fmk, a broad-spectrum caspase inhibitor, prevented A beta 25-35-induced increase in caspase-3 activity and CEC death. N-acetyl-cysteine, an antioxidant, also prevented A beta-induced cell death. Together, these findings indicate that A beta-mediated CEC death is an apoptotic process that is characterized by increased oxidative stress, caspase activation, mitochondrial dysfunction, and nuclear and mitochondrial DNA damage.

The T-cell receptor regulates Akt (protein kinase B) via a pathway involving Rac1 and phosphatidylinositide 3-kinase

The serine/threonine kinase Akt (also known as protein kinase B) (Akt/PKB) is activated upon T-cell antigen receptor (TCR) engagement or upon expression of an active form of phosphatidylinositide (PI) 3-kinase in T lymphocytes. Here we report that the small GTPase Rac1 is implicated in this pathway, connecting the receptor with the lipid kinase. We show that in Jurkat cells, activated forms of Rac1 or Cdc42, but not Rho, stimulate an increase in Akt/PKB activity. TCR-induced Akt/PKB activation is inhibited either by PI 3-kinase inhibitors (LY294002 and wortmannin) or by overexpression of a dominant negative mutant of Rac1 but not Cdc42. Accordingly, triggering of the TCR rapidly stimulates a transient increase in GTP-Rac content in these cells. Similar to TCR stimulation, L61Rac-induced Akt/PKB kinase activity is also LY294002 and wortmannin sensitive. However, induction of Akt/PKB activity by constitutive active PI 3-kinase is unaffected when dominant negative Rac1 is coexpressed, placing Rac1 upstream of PI 3-kinase in the signaling pathway. When analyzing the signaling hierarchy in the pathway leading to cytoskeleton rearrangements, we found that Rac1 acts downstream of PI 3-kinase, a finding that is in accordance with numerous studies in fibroblasts. Our results reveal a previously unrecognized role of the GTPase Rac1, acting upstream of PI 3-kinase in linking the TCR to Akt/PKB. This is the first report of a membrane receptor employing Rac1 as a downstream transducer for Akt/PKB activation.

A guanine nucleotide exchange factor-independent function of Vav1 in transcriptional activation

T cell antigen receptor (TCR) stimulation induces the tyrosine phosphorylation of several intracellular proteins including the protooncogene Vav1. Vav1 expression is necessary for normal T cell development and activation. We previously showed that overexpression of Vav1 in Jurkat T cells potentiates the activity of the transcription factor nuclear factor of activated T cells (NF-AT). The mechanism by which Vav1 participates in TCR signaling events is not clear. Vav1 contains a guanine nucleotide exchange factor (GEF) domain that has specificity for Rac and other Rho GTPases that have been recently implicated in T cell activation events. Significantly, in vitro tyrosine phosphoryation of Vav1 by Lck activates its exchange activity. This Lck-mediated phosphorylation of Vav1 has been reported to depend upon Tyr-174 in Vav1, a site implicated in Vav1 function by other studies as well. In this report, we demonstrated that Tyr-174 is not required for the TCR-induced phosphorylation of Vav1 in vivo. Moreover, mutation of Tyr-174 augmented the ability of Vav1 to up-regulate NF-AT activation as well as the Vav1 GEF function leading to Rac activation. However, we also showed that the GEF activity of Vav1 was neither sufficient nor necessary for potentiation of NF-AT, and thereby we identify a GEF-independent role of Vav1 in potentiating NF-AT-driven transcription. Oncogenic Vav1 in which the amino-terminal 67 amino acids were deleted had elevated GEF activity but did not potentiate NF-AT when overexpressed in Jurkat cells. We also showed that a GEF mutant form of Vav1 that had impaired GEF function could still potentiate NF-AT. These studies reveal a previously unrecognized negative regulatory function of Tyr-174 in Vav1 and suggest that domains other than the Vav1 GEF domain contribute to TCR signals leading to NF-AT activation.

A protective role for nitric oxide in the oxidative modification of low density lipoproteins by mouse macrophages

Low density lipoproteins (LDL) oxidatively modified by macrophages have been shown to be atherogenic in ex vivo studies. We studied the potential role of nitric oxide (NO), a free radical produced by macrophages, in LDL modification. Human LDL (1 mg/ml) were incubated with mouse peritoneal macrophages in Ham's F-10 medium. The cells were then stimulated by interferon-gamma and tumor necrosis factor-alpha to increase their production of NO from 1.3 to 12.2 microM in 24 h, as measured by nitrite. Lipid peroxidation of LDL, as measured by thiobarbituric acid-reactive materials (TBARS), was reduced in stimulated cells in a time-dependent manner. At 24 h, the decrease was about 27%. In the presence of an NO synthase inhibitor (NG-aminophomoarginine), the generation of NO was diminished and the protection against LDL lipid peroxidation was reversed. The extent of LDL protein modification was also assessed by examining its electrophoretic mobility. It was found that macrophage NO reduced the change in LDL electromobility. These data indicate that the production of NO may inhibit the oxidative modification of LDL with cytokine-stimulated macrophages. We suggest that NO plays a protective role in limiting macrophage-induced LDL modification.

Inhibition by probucol of interleukin 1 secretion and its implication in atherosclerosis

Intravenous injection of 1.5 mg of acetylated low-density lipoprotein (LDL) or 100 micrograms of lipopolysaccharide (LPS) to zymosan-primed mice induced a decrease in serum zinc levels measured 6 hours after injection, suggesting the release of interleukin 1 (IL-1). Oral administration of probucol, 100 mg/kg once daily for 14 days, inhibited the LPS-induced fall in serum zinc levels, suggesting inhibition of IL-1 release. Direct evidence for inhibition of IL-1 release by probucol was obtained with an ex vivo system in which, compared with controls, peritoneal macrophages from probucol-treated mice (100 mg/kg orally X 3, or 0.25% in the diet for 3 weeks) secreted 80 to 90% less IL-1 upon LPS stimulation, measured by the C3H/HeJ thymocyte proliferation assay. Inhibition of IL-1 secretion by probucol may contribute to the therapeutic effect of probucol in atherosclerosis since as little as 1 unit of recombinant IL-1 beta was found to induce proliferation of aortic smooth muscle cells. With regard to the endogenous stimulus for IL-1 secretion, oxidized LDL is a putative candidate because it is capable of stimulating peritoneal macrophages to secrete IL-1. Because oxidized LDL is involved in the transformation of macrophages to foam cells, our data on IL-1 induction by oxidized LDL and the mitogenic effect of IL-1 on aortic smooth muscle cells suggest that activated macrophages play an important role in atherogenesis.

Interleukin-1 beta converting enzyme inhibition blocks progression of type II collagen-induced arthritis in mice

To IL-1 beta is a principal mediator in the pathogenesis of inflammatory disease. The IL-1 beta-converting enzyme (ICE), a novel cysteine protease, is required for processing of the 31 kDa IL-1 beta precursor to generate the 17 kDa proinflammatory mature form. We investigated the effect of two irreversible peptidyl ICE inhibitors, VE-13,045 and VE-16,084, on IL-1 production in vitro and in vivo in acute and chronic inflammatory disease models. In vitro, VE-13,045 and VE-16084 inhibited IL-1 beta secretion by LPS-stimulated human adherent mononuclear cells (IC50's of 0.4 microM and 2.0 microM, respectively) and murine splenic monocytes (IC50's of 10 microM and 1.3 microM, respectively). Both VE-13,045 and VE-16,084 also inhibited LPS stimulated IL-1 alpha secretion, although with reduced potency. In vivo, a single intraperitoneal dose of VE-13,045 (50 mg/kg) administered to mice 60 to 75 minutes after a 40 mg/kg LPS challenge significantly reduced IL-1 beta serum levels by 50 to 70%. In the DBA/1J mouse model of Type II collagen-induced arthritis, prophylactic treatment with VE-13,045 (50 and 100 mg/kg/day) significantly delayed the onset of inflammation, with a 60% overall reduction in disease severity. VE-13,045 was more effective than either indomethacin (2 mg/kg/day) or methyl prednisolone (10 mg/kg/day). VE-13,045 was also effective in reducing inflammation and progression of arthritis when administered to mice with established disease. Histological analysis of wrist joints showed a reduction in synovial membrane damage, inflammatory cell infiltration and fibrosis, and cartilage erosion in VE-13,045-treated animals. This is the first demonstration of efficacy for an ICE inhibitor in a chronic disease model and suggests that ICE is an important target for design of anti-inflammatory or disease modifying drugs.

ICE/Caspase-1 inhibitors as novel anti-inflammatory drugs

In recent years, several strategies that selectively inhibit pro-inflammatory cytokines, have yielded effective protein-based therapies for inflammatory disorders, validating the therapeutic hypothesis that intervention in cytokine signalling can provide clinical benefit. However, these protein-based products must be administered by injection, a constraint associated with inconvenience, adverse effects and expense for patients, caregivers and insurers. Besides interfering with the effects of cytokines such as TNF-alpha or IL-1beta that have already been produced, inhibition of pro-inflammatory cytokine production or signalling with low-molecular weight orally-active drugs would combine the convenience of conventional pharmaceuticals with the focused efficacy of the protein therapies. Reducing IL-1beta and IL-18 production by inhibition of IL-1beta converting enzyme (ICE, caspase-1) is one promising strategy because of the key roles of these cytokines in many inflammatory diseases. Pralnacasan, the first orally available, potent and selective ICE inhibitor to enter clinical trials, is currently under investigation in rheumatoid arthritis.

Severity and mortality of experimental pancreatitis are dependent on interleukin-1 converting enzyme (ICE)

Interleukin-1 beta (IL-1 beta) is produced in large amounts during acute pancreatitis and is believed to play a role in disease progression. Because secretion of IL-1 beta is dependent on intracellular processing of pro-IL-1 beta by IL-1 converting enzyme (ICE), we aimed to determine the efficacy of a novel ICE inactivator (VE-13045) in inhibiting secretion of active IL-1 beta in vivo and if the loss of ICE activity would affect the severity and mortality of experimental pancreatitis. Severe hemorrhagic pancreatitis was induced in adult rats by infusion of bile acid into the pancreatic duct. Animals were randomized to receive VE-13045 or vehicle before induction of pancreatitis. To confirm our findings and to ensure that the results were not model dependent, a second series of experiments was conducted using mice possessing a homozygous knockout of the ICE gene in which lethal pancreatitis was induced by feeding a choline-deficient, ethionine-supplemented diet. The severity of pancreatitis was assessed for both experiments by standard surrogate markers, blind histologic grading, and serum IL-1 beta and tumor necrosis factor-alpha (TNF-alpha) levels. Pancreatic IL-1 beta mRNA induction was assessed by differential RT-PCR. Acute pancreatitis was associated with a 120-fold increase in IL-1 beta mRNA, which was not affected by ICE inhibition or gene deletion. Cytokine processing and secretion were affected, as evidenced by decreased serum levels of IL-1 beta and TNF-alpha (p < 0.001) in all animals with an inactive ICE enzyme. This lack of cytokine production increased survival from 32% to 78% following bile salt pancreatitis (p < 0.01) and from 24% to 80% following diet-induced pancreatitis (p < 0.005). Both ICE-defective groups demonstrated decreased pancreatic necrosis, edema, inflammation, wet weight (all p < 0.05), and amylase and lipase (p < 0.01). In vivo blockade or genetic deletion of ICE inhibits pancreatitis-induced secretion of proinflammatory cytokines without altering IL-1 mRNA production and is associated with decreased pancreatitis severity and dramatic survival benefits.

Ex vivo lipopolysaccharide-induced interleukin-1 secretion from murine peritoneal macrophages inhibited by probucol, a hypocholesterolemic agent with antioxidant properties

Probucol, 4,4'-(isopropylidenedithio)bis(2,6-di-tert-butyl-phenol), has been shown to inhibit atherogenesis in genetically hypercholesterolemic (Watanabe) rabbits. Since atherosclerotic lesions contain macrophages capable of screting interleukin 1 (IL 1) and other cytokines that could contribute to the pathogenesis of the disease, we have investigated whether probucol affects IL 1 secretion. Resident peritoneal macrophages from mice dosed with probucol secreted 40-80% less IL 1 than macrophages from control animals when stimulated in vitro with lipopolysaccharide (LPS). The inhibitory effect of probucol was observed when IL 1 was assayed by the standard bioassay, the thymocyte proliferation assay, or a competitive IL 1 receptor binding assay. Probucol treatment had no effect on LPS-induced membrane IL 1 expression; secretion of tumor necrosis factor (TNF); Con A-induced splenic interleukin 2 (IL 2) and interleukin 3 (IL 3) release; and prostaglandin- or zymosan-induced secretion of prostacyclin, leukotriene C4, acid phosphatase, or superoxide anion. In contrast to the effect of oral administration, direct addition of probucol to macrophage cultures did not inhibit IL 1 release. Probucol administration did, however, inhibit the fall in serum zinc level induced by intravenous injection of LPS in zymosan-primed mice but had no effect on the LPS-induced increase in serum triglyceride levels, which indirectly confirms that probucol administration inhibits IL 1 but not TNF secretion. Paw granuloma induced in mice by heat-killed mycobacteria was inhibited by oral administration of probucol, an effect that may be attributable to inhibition of IL 1 secretion. Probucol neither reduced zymosan-induced liver granulomata in mice nor inhibited adjuvant-induced arthritis in rats. We suggest that inhibition of IL 1 secretion from macrophages by probucol contributes to its therapeutic effects in atherosclerosis and may also result in beneficial activity in some chronic inflammatory diseases.

RelB modulation of IkappaBalpha stability as a mechanism of transcription suppression of interleukin-1alpha (IL-1alpha), IL-1beta, and tumor necrosis factor alpha in fibroblasts

Members of the NF-kappaB/RelB family of transcription factors play important roles in the regulation of inflammatory and immune responses. RelB, a member of this family, has been characterized as a transcription activator and is involved in the constitutive NF-kappaB activity in lymphoid tissues. However, in a previous study we observed an overexpression of chemokines in RelB-deficient fibroblasts. Here we show that RelB is an important transcription suppressor in fibroblasts which limits the expression of proinflammatory mediators and may exert its function by modulating the stability of IkappaBalpha protein. Fibroblasts from relb(-/-) mice overexpress interleukin-1alpha (IL-1alpha), IL-1beta, and tumor necrosis factor alpha in response to lipopolysaccharide (LPS) stimulation. These cells have an augmented and prolonged LPS-inducible IKK activity and an accelerated degradation which results in a diminished level of IkappaBalpha protein, despite an upregulated IkappaBalpha mRNA expression. Consequently, NF-kappaB activity was augmented and postinduction repression of NF-kappaB activity was impaired in these cells. The increased kappaB-binding activity and cytokine overexpression was suppressed by introducing RelB cDNA or a dominant negative IkappaBalpha into relb(-/-) fibroblasts. Our findings suggest a novel transcription suppression function of RelB in fibroblasts.

Prevention of experimental autoimmune arthritis with a peptide fragment of type II collagen

Collagen arthritis is induced in inbred rats with the injection of native type II collagen. The pathogenesis of this experimental autoimmune disease is T cell dependent. This study demonstrates that collagen-specific T cells, derived from pathogenic and nonpathogenic rat T cell lines, both recognize the same peptide epitope. The epitope, consisting of amino acids 58-73 of cyanogen bromide fragment 11 of type II collagen, was as effective as whole collagen in stimulating a panel of collagen-specific rat/mouse T cell hybridomas. This peptide may, therefore, constitute a dominant epitope for CD4+ rat T cells in their response to type II collagen. Administration of the peptide to either neonatal or adult rats prevented the subsequent induction of experimental arthritis with whole collagen, demonstrating that the in vivo response to this dominant epitope is, therefore, relevant in the pathogenesis of arthritis. Despite its ability to prevent collagen-induced arthritis, administration of this peptide in incomplete Freund's adjuvant intradermally did not induce disease.

iNOS expression inhibits hypoxia-inducible factor-1 activity

Hypoxia-inducible factor-1 (HIF-1) activates genes important in vascular function such as vascular endothelial growth factor (VEGF), erythropoietin (EPO), and inducible nitric oxide synthase (iNOS). iNOS catalyzes the synthesis of nitric oxide (NO), a free radical gas that mediates a number of cellular processes, including regulation of gene expression, vasodilatation, and neurotransmission. Here we demonstrate that iNOS expression inhibits HIF-1 activity under hypoxia in C6 glioma cells transfected with an iNOS gene and a VEGF promoter-driven luciferase gene. HIF-1 induction of VEGF-luciferase activity in C6 cell is also inhibited by sodium nitroprusside (SNP). Furthermore, pretreatment of C6 cells with N-acetyl-l-cysteine (NAC), an antioxidant, nullified the inhibitory effect of iNOS on HIF-1 binding. These results demonstrate that NO generated by iNOS expression inhibits HIF-1 activity in hypoxic C6 cells and suggest a negative feedback loop in the HIF-1 --> iNOS cascade.

Microwave-induced thermoacoustic tomography using multi-sector scanning

A study of microwave-induced thermoacoustic tomography of inhomogeneous tissues using multi-sector scanning is presented. A short-pulsed microwave beam is used to irradiate the tissue samples. The microwave absorption excites time-resolved acoustic waves by thermoelastic expansion. The amplitudes of the acoustic waves are strongly related to locally absorbed microwave-energy density. The acoustic waves may propagate in all spatial directions. A focused ultrasonic transducer is employed to acquire temporal acoustic signals from multiple directions. Each detected signal is converted into a one-dimensional (1D) image along the acoustic axis of the transducer. The cross-sectional images of the tissue samples are calculated by combining all of the 1D images acquired in the same planes.

The pathology of mesangial IgA nephritis with clinical correlation

Of 710 patients in whom renal biopsies with immunofluorescence, light and electron microscopic and clinical data were available, 239 had idiopathic mesangial IgA nephritis. In these 239 cases IgA was found alone in 45.7%, accompanied by IgG in 50.1%, IgM in 21.4%, C3 in 82.4% and fibrin in 37.2%. Serum immunoglobulin levels including IgA were not significantly raised and complement C3 activation was via the alternative pathway. There was a wide range of glomerular lesions with minor change, minor change with focal and segmental lesions including sclerosis and mesangial cell hypercellularity, diffuse mesangial cell proliferation and, infrequently, diffuse sclerosing glomerulonephritis. The glomerular leions were related to the stage, duration and severity of the disease. There was also a wide variability of clinical presentations, with asymptomatic and symptomatic microscopic haematuria-proteinuria, macroscopic haematuria, recurrent proteinuria, nephrotic syndrome, acute nephritis, hypertension, and uncommonly as acute renal failure and potassium losing nephritis. No aetiological agent was found, and both the streptococcus and HBsAg could not be identified. The disease(s) was the commonest type of primary glomerulonephritis (33.7%) in Singapore, another geographic area in addition to Japan and France, where this lesion has an apparent high incidence.

Microwave-induced thermoacoustic tomography: reconstruction by synthetic aperture

We have applied the synthetic-aperture method to linear-scanning microwave-induced thermoacoustic tomography in biological tissues. A nonfocused ultrasonic transducer was used to receive thermoacoustic signals, to which the delay-and-sum algorithm was applied for image reconstruction. We greatly improved the lateral resolution of images and acquired a clear view of the circular boundaries of buried cylindrical objects, which could not be obtained in conventional linear-scanning microwave-induced thermoacoustic tomography based on focused transducers. Two microwave sources, which had frequencies of 9 and 3 GHz, respectively, were used in the experiments for comparison. The 3 GHz system had a much larger imaging depth but a lower signal-noise ratio than the 9 GHz system in near-surface imaging.

Astrocytes and central nervous system endothelial cells do not express B7-1 (CD80) or B7-2 (CD86) immunoreactivity during experimental autoimmune encephalomyelitis

The identity of cell types within the central nervous system (CNS) capable of activating T lymphocytes is a fundamental issue in the understanding of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). To become fully activated, a T cell must recognize its antigen and receive co-stimulation, the latter being optimally delivered via B7-1 and/or B7-2 molecules expressed by the antigen presenting cell (APC). There are conflicting reports regarding whether astrocytes or CNS endothelial cells (EC) can act as fully competent APCs. The present studies were performed to determine whether astrocytes or CNS EC express B7-1 or B7-2 immunoreactivity during EAE. No expression of B7-1 or B7-2 by either astrocytes or EC was detected during acute, remitting, relapsing or chronic EAE, whether EAE was induced by active immunization or cell transfer using five different myelin antigens. These results suggest that neither astrocytes nor CNS EC can deliver co-stimulatory signals via B7 molecules in the setting of murine EAE, rendering them incapable of acting as fully competent APCs.