Universal learning network and its application to chaos control

Universal Learning Networks (ULNs) are proposed and their application to chaos control is discussed. ULNs provide a generalized framework to model and control complex systems. They consist of a number of inter-connected nodes where the nodes may have any continuously differentiable nonlinear functions in them and each pair of nodes can be connected by multiple branches with arbitrary time delays. Therefore, physical systems, which can be described by differential or difference equations and also their controllers, can be modeled in a unified way, and so ULNs may form a super set of neural networks and fuzzy neural networks. In order to optimize the ULNs, a generalized learning algorithm is derived, in which both the first order derivatives (gradients) and the higher order derivatives are incorporated. The derivatives are calculated by using forward or backward propagation schemes. These algorithms for calculating the derivatives are extended versions of Back Propagation Through Time (BPTT) and Real Time Recurrent Learning (RTRL) of Williams in the sense that generalized node functions, generalized network connections with multi-branch of arbitrary time delays, generalized criterion functions and higher order derivatives can be deal with. As an application of ULNs, a chaos control method using maximum Lyapunov exponent of ULNs is proposed. Maximum Lyapunov exponent of ULNs can be formulated by using higher order derivatives of ULNs, and the parameters of ULNs can be adjusted so that the maximum Lyapunov exponent approaches the target value. From the simulation results, it has been shown that a fully connected ULN with three nodes is able to display chaotic behaviors.

[Peripartum cardiomyopathy]

Heart failure in the last month of pregnancy or with in 5 months after delivery has long been recognized as peripartum cardiomyopathy. Additional criteria include the absence of other identifiable causes of heart failure and the absence of other prior heart disease. Estimate of the incidence vary from 1 in 1300 to 4000 pregnancies. The mortality rates of this disorder in the acute phases and subacute phases range from 25 to 50 percent the prognosis is especially poor in patients with cardiomegaly persisting > 6 months and in patients with low left ventricular ejection fraction.

Role of the vasopressin V(1) receptor in regulating the epithelial functions of the guinea pig distal colon

Vasopressin has a wide spectrum of biological action. In this study, the role of vasopressin in regulating electrolyte transport in the colon was elucidated by measuring the short-circuit current (I(sc)) as well as the Na(+), K(+), and Cl(-) flux in a chamber-mounted mucosal sheet. The cytosolic Ca(2+) concentration ([Ca(2+)](i)) was also measured in fura 2-loaded cells by fluorescence imaging. Serosal vasopressin decreased I(sc) at 10(-9) M and increased I(sc) at 10(-7)-10(-6) M. The decrease in I(sc) was accompanied by two effects: one was a decrease in the amiloride-sensitive Na(+) absorption, whereas the other was an increase in the bumetanide-sensitive K(+) secretion. The increase in I(sc) was accompanied by an increase in the Cl(-) secretion that can be inhibited by serosal bumetanide or mucosal diphenylamine-2-carboxylate. Vasopressin caused an increase in [Ca(2+)](i) in crypt cells. These responses of I(sc) and the [Ca(2+)](i) increase in crypt cells were all more potently inhibited by the vasopressin V(1) receptor antagonist than by the V(2) receptor antagonist. These results suggest that vasopressin inhibits electrogenic Na(+) absorption and stimulates electrogenic K(+) and Cl(-) secretion. In all of these responses, the V(1) receptor is involved, and the [Ca(2+)](i) increase may play an important role.

Prevention of encephalomyocarditis virus-induced diabetes in mice by inhibition of the tyrosine kinase signalling pathway and subsequent suppression of nitric oxide production in macrophages

Macrophages comprise the major population of cells infiltrating pancreatic islets during the early stages of infection in DBA/2 mice by the D variant of encephalomyocarditis virus (EMC-D virus). Inactivation of macrophages prior to viral infection almost completely prevents EMC-D virus-induced diabetes. This investigation was initiated to determine whether a tyrosine kinase signalling pathway might be involved in the activation of macrophages by EMC-D virus infection and whether tyrosine kinase inhibitors might, therefore, abrogate EMC-D virus-induced diabetes in vivo. When isolated macrophages were infected with EMC-D virus, inducible nitric oxide synthase mRNA was expressed and nitric oxide was subsequently produced. Treatment of macrophages with the tyrosine kinase inhibitor tyrphostin AG126, but not tyrphostin AG556, prior to EMC-D virus infection blocked the production of nitric oxide. The infection of macrophages with EMC-D virus also resulted in the activation of the mitogen-activated protein kinases (MAPKs) p42(MAPK/ERK2)/p44(MAPK/ERK1), p38(MAPK), and p46/p54(JNK). In accord with the greater potency of AG126 than of AG556 in blocking EMC-D virus-mediated macrophage activation, the incidence of diabetes in EMC-D virus-infected mice treated with AG126 (25%) was much lower than that in AG556-treated (75%) or vehicle-treated (88%) control mice. We conclude that EMC-D virus-induced activation of macrophages resulting in macrophage-mediated beta-cell destruction can be prevented by the inhibition of a tyrosine kinase signalling pathway involved in macrophage activation.

Control of autoimmune diabetes in NOD mice by GAD expression or suppression in beta cells

Glutamic acid decarboxylase (GAD) is a pancreatic beta cell autoantigen in humans and nonobese diabetic (NOD) mice. beta Cell-specific suppression of GAD expression in two lines of antisense GAD transgenic NOD mice prevented autoimmune diabetes, whereas persistent GAD expression in the beta cells in the other four lines of antisense GAD transgenic NOD mice resulted in diabetes, similar to that seen in transgene-negative NOD mice. Complete suppression of beta cell GAD expression blocked the generation of diabetogenic T cells and protected islet grafts from autoimmune injury. Thus, beta cell-specific GAD expression is required for the development of autoimmune diabetes in NOD mice, and modulation of GAD might, therefore, have therapeutic value in type 1 diabetes.

Megalencephaly, hydrocephalus and cortical dysplasia in severe dwarfism mimicking leprechaunism

This report concerns an autopsy case of megalencephaly exhibiting a unique combination of physical and brain malformations. A 4-year-old boy had a peculiar face, a severe reduction of subcutaneous adipose tissue, severe growth failure and frequent hypoglycemic episodes. These clinical features were compatible with leprechaunism; however, the absence of hyperinsulinemia and insulin resistance prevented the diagnosis of leprechaunism. The autopsy disclosed complex cardiac and brain malformations. Although hydrocephalus coexisted, the brain weight after complete removal of the cerebrospinal fluid was 2260 g, which was greater than the average brain weight of normal Japanese children of the same age. The neuronal density in the cerebral cortex was decreased, while the surface area of the cerebral cortex and white matter were greater than those in an age-matched control. There was cortical dysplasia in the frontal and parietal lobes. Endocrine tests and immunohistochemical analysis of the brain did not demonstrate any abnormalities in the hypothalamus-pituitary system. Megalencephaly can be associated with dwarfism, and this case is important for consideration of the interrelationship between neuronal proliferation and physical growth.

A molecular cytogenetic analysis of 7q31 in prostate cancer

Gains of chromosome 7 and alterations of the 7q-arm have been frequently observed in multiple cancers using various cytogenetic and molecular genetic techniques. Using PCR analysis of microsatellite markers, we have previously reported that allelic imbalance of 7q31 is common in prostate cancer and is associated with higher tumor grade and advanced pathological stage. In an effort to better understand the chromosome 7 alterations in prostate cancer, we undertook a molecular cytogenetic study of 25 prostate specimens using fluorescence in situ hybridization (FISH) with DNA probes for the chromosome 7 centromere and for 5 loci mapped to 7q31 (D7S523, D7S486, D7S522, D7S480, and D7S490) and 1 locus at 7q11.23 (ELN). Six tumors had no apparent anomaly for any chromosome 7 probe. Nine tumors showed apparent simple gain of a whole chromosome 7, whereas one tumor had apparent simple loss of a whole chromosome 7. Four tumors had gain of the chromosome 7 centromere and additional overrepresentation of the 7q-arm. One tumor had overrepresentation of 7q31 without any apparent anomaly of the chromosome 7 centromere, and one tumor had apparent loss of the chromosome 7 centromere with no apparent anomaly of the 7q-arm. Three tumors had gain of the chromosome 7 centromere and loss of the 7q31 region. Gain of 7q31 was strongly correlated with tumor Gleason score. Multiplex PCR studies of these specimens supported these FISH observations. Mutation screening and DNA sequencing of the MET gene, which is mapped to 7q31, revealed only the presence of simple sequence polymorphisms but no apparent acquired disease-associated mutations. FISH analysis of metaphases from an aphidicolin-induced, chromosome 7 only, somatic cell hybrid demonstrated that the DNA probe for D7S522 spans the common fragile site FRA7G at 7q31. Our data indicate that the 7q-arm, particularly the 7q31 region, is genetically unstable in prostate cancer, and some of the gene dosage differences observed may be due to fragility at FRA7G.

Bedside wellness--development of a virtual forest rehabilitation system

The present study aims at the development of a new concept system that will contribute toward improving the quality of life for bedridden patients and the elderly. The results of a basic study showed the possibility of a virtual reality system reducing stress and pain, provided VR sickness does not occur. A Bedside Wellness System which lets a person experience a virtual forest walk and provides a facility of rehabilitation was proposed based on the basic study and developed. An experiment to assess the developed system using healthy subjects was executed. The data suggested the positive effects of the system; however, some points to be improved were also extracted. After a few improvements, the system will be available for clinical use.

Apoptosis of murine hepatocytes induced by high doses of galactosamine

Apoptosis induced by high doses of Galactosamine (GalN) was investigated in mice hepatocytes in vivo. In mice intraperitoneally (i.p.) treated with GalN 3 g/kg, the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells were first observed at 6 hr postadministration (PA). Both acidophilic bodies in hematoxylin and eosin (HE)-stained sections and TUNEL-positive cells were markedly found at 24 hr PA. At 48 hr PA, cellular degeneration and necrosis of hepatocytes were prominently observed, and TUNEL-positive cells were scarcely found. In the mice ip treated with GalN 1.5 g/kg, the lesion was milder than that in those treated with GalN 3 g/kg. Acidophilic bodies and TUNEL-positive cells were scarcely found at 24 hr PA, whereas they were markedly seen at 48 hr PA. In addition, a ladder-like DNA fragmentation pattern by agarose gel electrophoresis was observed most remarkably at 24 hr PA with GalN 3 g/kg and at 48 hr PA with GalN 1.5 g/kg, and less distinctly at 48 hr PA with GalN 3 g/kg. On the other hand, sGOT and sGPT activities increased prominently at 48 hr PA with GalN 3 g/kg. These results suggest that the cell death induced by high dose of GalN may be caused by apoptosis, and subsequently by necrosis in vivo.

Equine inhibin/activin beta A-subunit mRNA is expressed in the endometrial gland, but not in the trophoblast, during pregnancy

The expression of both inhibin alpha- and inhibin/activin beta A-subunit mRNA was examined in equine uteroplacental tissues collected during pregnancy (days 90 to 300). Northern blot analysis revealed that 5 transcripts (7.0, 4.1, 3.4, 2.6, 1.5 kb) of beta A-subunit were present, and the most abundantly expressed transcript was the 1.5 kb one. Relatively high levels of the 1.5 kb transcript were seen in the second trimester of pregnancy compared to what was found in the third trimester. To identify the tissue localization of beta A-subunit mRNA, in situ hybridization was performed, and the positive signal was observed exclusively in the endometrial glands, but not in the fetal placental tissue (trophoblast) at days 150, 210, and 300 of pregnancy. On the other hand, inhibin alpha-subunit transcript could not be detected at any stage of pregnancy examined either by Northern blot analysis or in situ hybridization. Although the factor(s) regulating the gene expression of beta A-subunit in this equine tissue is currently unknown, these results suggest that activin, but not inhibin, is predominantly produced in the endometrial glands of the pregnant mare, and thus produced activin may play a paracrine or endocrine role during pregnancy in this species.

Galactosamine-induced apoptosis in the primary mouse hepatocyte cultures

Galactosamine (GalN)-induced apoptosis was investigated in cultured hepatocytes from mice. The percentage of fragmented DNA measured by the ELISA method increased in a concentration-dependent manner from the very early stage, i.e. 0.5 hrs, after GalN-exposure. In addition, a ladder-like fragmentation pattern by agarose gel electrophoresis appeared first at 3 hr-exposure to 20 mM GalN, at 6 hr-exposure to 10 mM GalN and at 12 hr-exposure to 5 mM GalN, respectively. On the other hand, cytotoxicity indicated by leakage of lactate dehydrogenase from cultured hepatocytes to culture medium was first detected at 24 hrs after GalN-treatment. Morphologically, formation of blebs and apoptotic bodies was observed from 12 hr-exposure to 20 mM GalN and from 24 hr-exposure to 10 mM GalN, respectively. Thus GalN could induce apoptosis in primary hepatocyte cultures from mice.

Role of macrophages and macrophage-derived cytokines in the pathogenesis of Kilham rat virus-induced autoimmune diabetes in diabetes-resistant BioBreeding rats

The diabetes-resistant BioBreeding (DR-BB) rat, derived from diabetes-prone forebears, does not normally develop spontaneous insulitis or diabetes, but when infected with Kilham rat virus (KRV) this animal develops autoimmune diabetes similar to the diabetes-prone BioBreeding (DP-BB) rat. In this study, we attempted to determine whether macrophages and macrophage-derived cytokines play a role in the development of KRV-induced diabetes in DR-BB rats. Seventy-eight percent of DR-BB rats treated with KRV and poly(I:C) develop diabetes, whereas depletion of macrophages with liposome-encapsulated dichloromethylene diphosphonate (lip-Cl2MDP) in KRV and poly(I:C)-treated DR-BB rats results in the near-complete prevention of insulitis and diabetes. Measurement of the macrophage-derived cytokines IL-12, TNF-alpha, and IL-1beta revealed a selective increase of their expression, after KRV infection, in the splenic lymphocytes and the pancreatic islets. Measurement of CD4+ T cell-derived cytokines revealed that IL-2 and IFN-gamma cytokine gene expression closely correlates with an elevation of IL-12, but IL-4 and IL-10 do not change. Depletion of macrophages before the isolation of splenic lymphocytes from DR-BB rats treated with KRV and poly(I:C) resulted in the loss of ability to transfer diabetes to young DP-BB rats. On the basis of these observations, we conclude that macrophages and macrophage-derived cytokines play a critical role in the cascade of events leading to the destruction of pancreatic beta cells, culminating in the development of insulin-dependent diabetes mellitus.

Expression and cellular localization of inhibin alpha-subunit mRNA in equine fetal gonads

The expression of inhibin alpha-subunit mRNA in equine fetal gonads during pregnancy (Days 90 to 300) was examined by means of Northern blot analysis. In all samples examined, a single species of transcript was detected at the size of 1.5 kb. A digoxigenin-labeled antisense cRNA probe specific to equine inhibin alpha-subunit was synthesized and in situ hybridization analysis to locate the inhibin alpha-subunit mRNA positive cells was performed using frozen tissue sections of equine fetal ovary (day 150 of pregnancy) and equine fetal testis (day 180 of pregnancy). In the fetal ovary, positive cells were seen throughout the interstitial area but did not show any particular localization. In the fetal testis, on the other hand, the antisense cRNA hybridized almost exclusively to the interstitial cells surrounding developing seminiferous cords and Sertoli cells within the cords. Positive signals were also detected in a limited number of the interstitial cells located away from the cords. These results suggest that in equine fetal gonads, inhibin and/or inhibin alpha-subunit related molecules such as the monomeric form are produced and these molecules may have a paracrine/autocrine role within the gonads.

Role of macrophages and macrophage-derived cytokines in the pathogenesis of Kilham rat virus-induced autoimmune diabetes in diabetes-resistant BioBreeding rats

The diabetes-resistant BioBreeding (DR-BB) rat, derived from diabetes-prone forebears, does not normally develop spontaneous insulitis or diabetes, but when infected with Kilham rat virus (KRV) this animal develops autoimmune diabetes similar to the diabetes-prone BioBreeding (DP-BB) rat. In this study, we attempted to determine whether macrophages and macrophage-derived cytokines play a role in the development of KRV-induced diabetes in DR-BB rats. Seventy-eight percent of DR-BB rats treated with KRV and poly(I:C) develop diabetes, whereas depletion of macrophages with liposome-encapsulated dichloromethylene diphosphonate (lip-Cl2MDP) in KRV and poly(I:C)-treated DR-BB rats results in the near-complete prevention of insulitis and diabetes. Measurement of the macrophage-derived cytokines IL-12, TNF-alpha, and IL-1beta revealed a selective increase of their expression, after KRV infection, in the splenic lymphocytes and the pancreatic islets. Measurement of CD4+ T cell-derived cytokines revealed that IL-2 and IFN-gamma cytokine gene expression closely correlates with an elevation of IL-12, but IL-4 and IL-10 do not change. Depletion of macrophages before the isolation of splenic lymphocytes from DR-BB rats treated with KRV and poly(I:C) resulted in the loss of ability to transfer diabetes to young DP-BB rats. On the basis of these observations, we conclude that macrophages and macrophage-derived cytokines play a critical role in the cascade of events leading to the destruction of pancreatic beta cells, culminating in the development of insulin-dependent diabetes mellitus.

Possible role of macrophage-derived soluble mediators in the pathogenesis of encephalomyocarditis virus-induced diabetes in mice

Pancreatic islets from DBA/2 mice infected with the D variant of encephalomyocarditis (EMC-D) virus revealed lymphocytic infiltration with moderate to severe destruction of pancreatic beta cells. Our previous studies showed that the major population of infiltrating cells at the early stages of infection is macrophages. The inactivation of macrophages prior to viral infection resulted in the prevention of diabetes, whereas activation of macrophages prior to viral infection resulted in the enhancement of beta-cell destruction. This investigation was initiated to determine whether macrophage-produced soluble mediators play a role in the destruction of pancreatic beta cells in mice infected with a low dose of EMC-D virus. When we examined the expression of the soluble mediators interleukin-1 beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS) in the pancreatic islets, we found that these mediators were clearly expressed at an early stage of insulitis and that this expression was evident until the development of diabetes. We confirmed the expression of these mediators by in situ hybridization with digoxigenin-labelled RNA probes or immunohistochemistry in the pancreatic islets. Mice treated with antibody against IL-1beta or TNF-alpha or with the iNOS inhibitor aminoguanidine exhibited a significant decrease in the incidence of diabetes. Mice treated with a combination of anti-IL-1beta antibody, anti-TNF-alpha antibody, and aminoguanidine exhibited a greater decrease in the incidence of disease than did mice treated with one of the antibodies or aminoguanidine. On the basis of these observations, we conclude that macrophage-produced soluble mediators play an important role in the destruction of pancreatic beta cells, resulting in the development of diabetes in mice infected with a low dose of EMC-D virus.

Detection of viral RNA by electron microscopic in situ hybridization (ISH-EM) in the germinal epithelium of mice infected with encephalomyocarditis (EMC) virus

Electron microscopic in situ hybridization (ISH-EM) was first applied to the detection of viral RNA in the germinal epithelium of mice inoculated i.p. with 10(5) plaque-forming units/mouse of the D variant of encephalomyocarditis virus (EMC-D). Signals of viral RNA were first detected in a small number of Sertoli cells showing mild degeneration at 2 days post inoculation, and 2 days later, they were also detected in germinal cells and spermatogonia when Sertoli cells showed prominent degeneration. The results clearly demonstrated that the first site of viral attack in the germinal epithelium was Sertoli cell in the case of EMC-D-induced mouse orchitis.

Variation in serum creatine phosphokinase activity as indicated in two-phase EMC-D virus-induced myocarditis

In this study, myocardial damage in the D-variant of encephalomyocarditis (EMC-D) virus-induced myocarditis has been investigated consecutively by measuring serum creatine phosphokinase (CPK) activity. CPK activity in 8 week-old male BALB/cAJcl mice inoculated with EMC-D virus increased to a peak at 4 or 5 days postinoculation (DPI) and then gradually decreased. The CPK activity rose again after 7 DPI until it reached a second peak. In view of the kinetics of CPK activity, two-phase (early and late phase) myocardial damage in EMC virus infection were considered. In the late phase, an increase in cellular infiltration in the myocardium and a decrease in viral titer in the heart were observed. It was therefore suspected that the increase in CPK in the late phase may be caused by cellular infiltration, but not by viral replication. In our results, we suggested that a serial measurement of serum CPK activity might be a useful method for throwing more light on the myocardial damage caused by the autoimmune response. We also used a pathological (TUNEL) method to detect apoptotic cells and some apoptotic myocytes in the myocardium in late phase EMC virus-induced myocarditis.

Molecular cloning and characterization of a new member of the rat placental prolactin (PRL) family, PRL-like protein D (PLP-D)

The rat placental PRL family consists of molecules structurally similar to PRL and GH, and to date, seven members have been identified. During investigation of pregnancy stage-specific placental factors by the differential display method, we obtained a complementary DNA (cDNA) fragment (199 bp) encoding a peptide homologous to PRL-like protein (PLP)-C. By using the 3' and 5' rapid amplification of cDNA ends method, a full-length cDNA was cloned and tentatively named PLP-D. The cDNA encoded a mature protein of 240 amino acids, including a 29-amino acid signal sequence. PLP-D contains one putative N-glycosylation site and six cysteine residues that are highly conserved in the placental PRL family. Sequence comparison between PLP-D and other members of the placental PRL family showed that PLP-D is highly homologous to PLP-C (80%) and decidual PRL-related protein (73%). Northern blot analysis revealed that PLP-D messenger RNA (mRNA) first appeared at day 14 of pregnancy, and that its expression increased until term. In situ hybridization analysis indicated that PLP-D mRNA was specifically expressed in spongiotrophoblast cells and trophoblast giant cells of the placental junctional zone. Differentiated Rcho-1 cells also expressed PLP-D mRNA, whereas undifferentiated Rcho-1 cells did not.

[Primary right atrial hemangiosarcoma manifesting as cardiac tamponade: a case report with transesophageal echocardiography]

A 39-year-old woman presented with a right atrial hemangiosarcoma manifesting as cardiac tamponade with complaints of chest discomfort and dyspnea. Transthoracic echocardiography revealed remarkable pericardial effusion and a right atrial mass. Transesophageal echocardiography disclosed the tumor extending into the right atrial cavity. Surgery found the tumor was poorly demarcated, immobile and adhered to the adjacent right atrial wall and septum. The echocardiographic findings correlated well with the surgical and autopsy findings.

Depletion of Mac1-positive macrophages protects DBA/2 mice from encephalomyocarditis virus-induced myocarditis and diabetes

DBA/2 mice treated with anti-Mac1 monoclonal antibody (MAb) failed to develop encephalomyocarditis virus (EMCV)-induced diabetes and myocarditis. Virus concentrations and the number of viral RNA-positive cells in the pancreas and heart were significantly reduced in mice treated with anti-Mac1 MAb. Mac1-positive macrophages seem to be involved in EMCV-induced disease and to affect the replication of EMCV in target organs.

Relation between distribution of viral RNA and development of histopathological changes in encephalomyocarditis virus-induced orchitis in mice

The relation between the distribution of viral RNA and the development of histopathological changes was investigated in the early stage of encephalomyocarditis (EMC) virus-induced orchitis in mice. Signals of viral RNA were first detected by in situ hybridization in a few Sertoli cells in almost intact germinal epithelia at 2 days post-inoculation (d.p.i.). The number of Sertoli cells bearing signals of viral RNA increased at 3 d.p.i. when mild degenerative changes were exceptionally found in germinal epithelia. Signals of viral RNA came to be detected not only in Sertoli cells but also in a small number of germinal cells and spermatogonia at 4 d.p.i. when mild to moderate degenerative changes developed in germinal epithelia, resulting in desquamation of degenerated cells. At the same time, virus-like particles were observed by electron-microscopy in the degenerated and desquamated germinal cells. At and after 5 d.p.i., luminal obstruction with cellular debris and inflammatory cells was generally found. These results suggest that EMC virus carried to seminiferous tubules via the blood first attacks Sertoli cells and then damages germinal cells and spermatogonia.

Involvement of macrophages in the development of encephalomyocarditis (EMC) virus-induced diabetes in mice

The role of macrophages in the development of diabetes following infection with encephalomyocarditis (EMC) virus was examined in 3 strains of mice (DBA/2 and BALB/c: susceptible, C57BL/6: resistant). After infection with 100 plaque forming units (PFU)/head of EMC-D (highly diabetogenic variant), the incidence of diabetes at 3 days post infection (DPI) (DBA/2: 7/8, BALB/c: 3/8, C57BL/6: 0/8) was well correlated with the severity of macrophage infiltration with beta cell damage in the pancreatic islets (DBA/2: sever, BALB/c: moderate, C57BL/6: slight). Silica-pretreatment depleted macrophage infiltration in the pancreatic islets and decreased the incidence of diabetes at 7 DPI from 100% to 40% in DBA/2 and from 80% to 0% in BALB/c mice, respectively. These results suggest that macrophages play a critical role in the process of pancreatic beta cell damage in EMC virus infection in mice.