The complete nucleotide sequence and multipartite organization of the tobacco mitochondrial genome: comparative analysis of mitochondrial genomes in higher plants

Tobacco is a valuable model system for investigating the origin of mitochondrial DNA (mtDNA) in amphidiploid plants and studying the genetic interaction between mitochondria and chloroplasts in the various functions of the plant cell. As a first step, we have determined the complete mtDNA sequence of Nicotiana tabacum. The mtDNA of N. tabacum can be assumed to be a master circle (MC) of 430,597 bp. Sequence comparison of a large number of clones revealed that there are four classes of boundaries derived from homologous recombination, which leads to a multipartite organization with two MCs and six subgenomic circles. The mtDNA of N. tabacum contains 36 protein-coding genes, three ribosomal RNA genes and 21 tRNA genes. Among the first class, we identified the genes rps1 and psirps14, which had previously been thought to be absent in tobacco mtDNA on the basis of Southern analysis. Tobacco mtDNA was compared with those of Arabidopsis thaliana, Beta vulgaris, Oryza sativa and Brassica napus. Since repeated sequences show no homology to each other among the five angiosperms, it can be supposed that these were independently acquired by each species during the evolution of angiosperms. The gene order and the sequences of intergenic spacers in mtDNA also differ widely among the five angiosperms, indicating multiple reorganizations of genome structure during the evolution of higher plants. Among the conserved genes, the same potential conserved nonanucleotide-motif-type promoter could only be postulated for rrn18-rrn5 in four of the dicotyledonous plants, suggesting that a coding sequence does not necessarily move with the promoter upon reorganization of the mitochondrial genome.

Randomized phase III study of bevacizumab plus FOLFIRI and bevacizumab plus mFOLFOX6 as first-line treatment for patients with metastatic colorectal cancer (WJOG4407G)

BACKGROUND

FOLFIRI and FOLFOX have shown equivalent efficacy for metastatic colorectal cancer (mCRC), but their comparative effectiveness is unknown when combined with bevacizumab.

PATIENTS AND METHODS

WJOG4407G was a randomized, open-label, phase III trial conducted in Japan. Patients with previously untreated mCRC were randomized 1:1 to receive either FOLFIRI plus bevacizumab (FOLFIRI + Bev) or mFOLFOX6 plus bevacizumab (mFOLFOX6 + Bev), stratified by institution, adjuvant chemotherapy, and liver-limited disease. The primary end point was non-inferiority of FOLFIRI + Bev to mFOLFOX6 + Bev in progression-free survival (PFS), with an expected hazard ratio (HR) of 0.9 and non-inferiority margin of 1.25 (power 0.85, one-sided α-error 0.025). The secondary end points were response rate (RR), overall survival (OS), safety, and quality of life (QoL) during 18 months. This trial is registered to the University Hospital Medical Information Network, number UMIN000001396.

RESULTS

Among 402 patients enrolled from September 2008 to January 2012, 395 patients were eligible for efficacy analysis. The median PFS for FOLFIRI + Bev (n = 197) and mFOLFOX6 + Bev (n = 198) were 12.1 and 10.7 months, respectively [HR, 0.905; 95% confidence interval (CI) 0.723-1.133; P = 0.003 for non-inferiority]. The median OS for FOLFIRI + Bev and mFOLFOX6 + Bev were 31.4 and 30.1 months, respectively (HR, 0.990; 95% CI 0.785-1.249). The best overall RRs were 64% for FOLFIRI + Bev and 62% for mFOLFOX6 + Bev. The common grade 3 or higher adverse events were leukopenia (11% in FOLFIRI + Bev/5% in mFOLFOX6 + Bev), neutropenia (46%/35%), diarrhea (9%/5%), febrile neutropenia (5%/2%), peripheral neuropathy (0%/22%), and venous thromboembolism (6%/2%). The QoL assessed by FACT-C (TOI-PFC) and FACT/GOG-Ntx was favorable for FOLFIRI + Bev during 18 months.

CONCLUSION

FOLFIRI plus bevacizumab was non-inferior for PFS, compared with mFOLFOX6 plus bevacizumab, as the first-line systemic treatment for mCRC.

CLINICAL TRIALS NUMBER

UMIN000001396.

Enhanced expression of endothelial oxidized low-density lipoprotein receptor (LOX-1) in hypertensive rats

Oxidized low-density lipoprotein (Ox-LDL) has been implicated in the attenuated endothelium-dependent vasodilatation in atherosclerotic arteries and, possibly, in hypertension. The aim of the present study was to investigate gene expression of recently-identified endothelial Ox-LDL receptor (LOX-1) in hypertensive state. SHR-SP, WKY, Dahl salt-sensitive (DS) and salt-resistant rats (DR) were fed salt-loaded or control diet. RNA was extracted from the aorta and vein. LOX-1 expression was examined by Northern blotting. LOX-1 mRNA was low in the aorta and vein of WKY, whereas it was markedly upregulated in those of SHR-SP. LOX-1 expression was low in the aorta of DR on both diets and of DS on a control diet, whereas it was elevated in that of salt-loaded DS. These results indicated that LOX-1 expression in the aorta and vein was upregulated in hypertensive rats, which may be involved in the impaired endothelium-dependent vasodilation in these rats.

Diabetes enhances lectin-like oxidized LDL receptor-1 (LOX-1) expression in the vascular endothelium: possible role of LOX-1 ligand and AGE

Diabetes mellitus accelerating atherosclerosis was associated with the enhanced glycoxidative modification of lipoproteins. LOX-1, the endothelial oxidized LDL receptor might be involved in the pathogenesis of diabetic atherosclerosis. In this study, we examined the vascular expression of LOX-1 in streptozotocin-induced diabetic rats. We found that LOX-1 was significantly increased in diabetic rat aorta compared with nondiabetic control. Immunohistochemistry revealed that the most distinctive staining of LOX-1 was in the endothelial cells, especially in the bifurcations of artery branches from aorta. In cultured aortic endothelial cells, diabetic rat serum and advanced glycation endproducts-BSA induced LOX-1 expression, while control rat serum along with high glucose did not. Applying a competitive inhibition assay, we found that LOX-1 ligand activity was accumulated in the diabetic rat serum, mainly in VLDL/LDL fractions. In addition, VLDL/LDL prominently increased LOX-1 among all the lipoprotein fractions of diabetic rat serum. In conclusion, diabetes markedly upregulated LOX-1 expression in the aortic endothelial cells. The enhanced glycoxidative modification of lipoproteins may contribute to the underlying mechanisms.

Redox-sensitive regulation of lox-1 gene expression in vascular endothelium

Oxidative stress has been implicated in atherosclerosis and its underlying conditions. LOX-1 is a novel endothelial receptor for oxidized low-density lipoprotein which might mediate endothelial dysfunction and subsequent atherogenesis. In the present study, we examined LOX-1 gene regulation by oxidative stress. First, superoxide anions generated by hypoxanthine and xanthine oxidase as well as hydrogen peroxide increased LOX-1 mRNA expression in cultured aortic endothelial cells. Homocysteine, an atherogenic substance believed to exert its effects through oxidative stress, enhanced endothelial LOX-1 gene expression, which was suppressed by N-acetylcysteine. Second, rats receiving angiotensin II for 10 days manifested hypertension and LOX-1 upregulation in aortic endothelium via AT1 receptor. Tempo, a superoxide dismutase mimetic, alleviated LOX-1 augmentation induced by angiotensin II. These results indicated redox-sensitive upregulation of LOX-1 mRNA in both in vitro and in vivo systems, suggesting its potential role in atherosclerosis.

Genomic organization and regulation of expression of the lectin-like oxidized low-density lipoprotein receptor (LOX-1) gene

Lectin-like oxidized low-density lipoprotein receptor (LOX-1) is a recently identified receptor for oxidized low-density lipoprotein, one of the major atherogenic substances. Although LOX-1 was reported to be expressed abundantly in endothelial cells, including atheromatous lesions, the regulation of LOX-1 gene has not yet been clarified. In the present study, we isolated the rat LOX-1 gene and investigated the regulation of gene expression. The rat LOX-1 gene was encoded by a single copy gene spanning over 19 kilobases and consisted of eight exons. Exon boundaries correlated well with the functional domain boundaries of the receptor protein. The promoter region contained putative TATA and CAAT boxes and multiple cis-elements such as NF-kappaB, AP-1 and AP-2 sites, and a shear stress response element. Northern blot analysis revealed that LOX-1 gene expression was up-regulated 9-fold by shear stress, 21-fold by lipopolysaccharide, and 4-fold by tumor necrosis factor-alpha, in cultured vascular endothelial cells. LOX-1 was also expressed in macrophages but not in vascular smooth muscle cells. These data provide important information for elucidating the molecular mechanisms of LOX-1 gene regulation and suggest a role for LOX-1 in the pathophysiology of atherosclerotic cardiovascular disease.

Impact of dialysis therapy on insulin resistance in end-stage renal disease: comparison of haemodialysis and continuous ambulatory peritoneal dialysis

BACKGROUND

Insulin resistance contributes to the pathogenesis of atherosclerotic cardiovascular disease and, thus, has an important impact on the mortality of uraemic patients. Haemodialysis (HD) is known to improve insulin resistance observed in uraemia. However, it is not known whether continuous ambulatory peritoneal dialysis (CAPD) alleviates insulin resistance in adult uraemic patients. The objective of this study was to compare the effect of two different dialysis modalities, HD and CAPD, on insulin resistance in adult uraemic patients and to identify the possible predictive factors for changes in insulin resistance.

METHODS

Insulin resistance was examined in 19 non-diabetic patients with end-stage renal disease (ESRD) before and after dialysis therapy (HD, n=10; CAPD, n=9), as well as in 10 healthy controls using the hyperinsulinaemic euglycaemic glucose clamp technique. The glucose disposal rate (GDR mg/kg/min) was used as an index of insulin sensitivity during the clamp technique. We also determined which of various biochemical parameters might be associated with change in insulin resistance by carrying out multiple logistic regression analysis.

RESULTS

GDR was significantly lower (6.44+/-1.76) in ESRD subjects than in normal subjects (9.90+/-2.01). HD and CAPD therapies significantly normalized GDR from 6.53+/-1.84 to 9.74+/-2.88 and from 6.35+/-1.65 to 8.18+/-1.76 respectively. Multiple logistic regression analysis showed that changes in BUN, haematocrit and plasma bicarbonate were significant predictive factors for the change in insulin resistance.

CONCLUSION

CAPD therapy, in spite of its possible adverse effects in patients with atherosclerotic disease, has been shown to improve insulin resistance in adult uraemic patients, similarly to HD therapy.

Differential effects of different forms of hydroxyapatite and hydroxyapatite/tricalcium phosphate particulates on human monocyte/macrophages in vitro

A possible complication associated with the use of hydroxyapatite (HA) or HA/tricalcium phosphate (HA/TCP) coating on the surfaces of prosthetic devices used for dental and orthopedic implants is their potential to fragment and thus exist as wear debris. In contrast to the so-called osteoconductive properties of HA or HA/TCP coatings, in particulate form these materials may lead to an adverse pattern of cellular and tissue responses at the bone-implant interface. We have established an in vitro cell culture system to characterize the biologic and biochemical effects of various particulate materials. The present study demonstrates that the HA/TCP particles derived from different sintering temperatures exhibit differential effects on cultured human monocyte/macrophages (M/M). The HA/TCP particles dried at 110 degrees C were the most biologically active, stimulating significant release of interleukin 1 beta (IL-1 beta), IL-6, tumor necrosis factor alpha, and prostaglandin E2 (PGE2), products implicated as important mediators of inflammation in diverse pathologic conditions. Other particles, sintered at either 900 or 1200 degrees C, did not stimulate production of cytokines or PGE2. HA/TCP particles from plasma-spray coatings also failed to release proinflammatory products. These results suggest that the biochemical and crystalline structural properties of particles markedly affects their capacity to modulate M/M function. This in vitro culture system should be useful in characterizing the specific physical and chemical properties of HA or HA/TCP particulates that are responsible for stimulating proinflammatory cell responses.

Increased levels of transforming growth factor-beta in HIV-associated nephropathy

BACKGROUND

Human immunodeficiency virus-associated nephropathy (HIVAN) is a renal disease of unknown pathogenesis. Recent evidence suggests that the fibrogenic cytokine transforming growth factor-beta (TGF-beta) might be involved. We hypothesized that overproduction of TGF-beta in the kidney might be involved in the pathogenesis of HIVAN.

METHODS

The mRNA and protein expression of TGF-beta isoforms, TGF-beta 1, TGF-beta 2, and TGF beta 3, deposition of matrix proteins induced by TGF-beta, and levels of HIV Tat protein were studied in HIVAN. Controls included normal and diseased kidneys from HIV-positive and -negative patients. The ability of Tat to induce production of TGF-beta and matrix proteins was also studied in human mesangial cells.

RESULTS

Normal kidneys, thin basement membrane nephropathy, and minimal change disease were negative for the three TGF-beta isoforms and Tat. In HIVAN, levels of TGF-beta isoforms and Tat were significantly increased, along with the expression of TGF-beta mRNA and deposition of matrix proteins stimulated by TGF-beta. Increased levels of TGF-beta isoforms, but not Tat, were also found in other glomerular diseases characterized by matrix accumulation. HIV infection, in the absence of HIVAN, was not associated with an increase in TGF-beta or Tat expression. Tat stimulated the expression and production of TGF-beta 1 and matrix proteins by human mesangial cells.

CONCLUSIONS

Our findings suggest that overproduction of TGF-beta is involved in the pathogenesis of HIVAN.

Involvement of ovarian innervation in steroid secretion

The effects of electrical stimulation of the brain on the ovarian venous plasma concentrations of estradiol (E2) and progesterone (P) were investigated in female rats hypophysectomized and adrenalectomized at 1000 h on the day of proestrus. Stimulation was applied during the proestrous critical period under pentobarbital anesthesia, and contralateral ovarian venous blood was collected from 105-120 min after the stimulation E2 and P concentrations, estimated by RIA, were significantly increased by stimulation of the medial basal prechiasmatic area (PVA), ventromedial hypothalamus, and areas in the mesencephalon and decreased by stimulation of the dorsal hippocampus, lateral amygdala, and mesencephalic areas. Ovarian blood flow was not affected by these stimulations. Ovarian nervotomy in the proestrous rats abolished E2 secretion induced by PVA stimulation. In intact proestrous rats, electrochemical stimulation of the PVA but not the preoptic suprachiasmatic area increased E2 and P concentrations, although stimulation of both areas commonly potentiated gonadotropin secretion. Present findings suggest that the efferent neural system from the brain to the ovaries is supplementary to the brain-pituitary-ovarian hormonal mechanisms in the regulation of ovarian steroid secretion, and the system may be required for the adjustment of ovarian responsiveness and sensitivity to gonadotropins. In addition, evidence for neural feedback on basal FSH secretion in the ovarian-denervated proestrous rats is presented in this study.

T-2 toxin induces thymic apoptosis in vivo in mice

A single intraperitoneal injection of T-2 toxin (0.35, 1.75, or 3.5 mg/kg body wt) induced time- and dose-dependent thymic atrophy in young female BALB/c mice. T-2 toxin (1.75 mg/kg) induced maximal atrophy by day 3 with complete recovery by day 7. Flow cytometric analysis showed that the CD4(+)CD8(+) double positive thymocyte population decreased markedly. Histopathological examination of the thymus indicated that the pattern of cell death in the thymocytes had a characteristic apoptotic morphology with cell shrinkage and nuclear condensation. The in vivo effects of T-2 toxin included the induction of DNA fragmentation of approximately 200 base pairs in ladder form and cell death in thymocytes. Furthermore, flow cytometric analysis of PI-stained thymocytes from animals dosed with T-2 toxin revealed the formation of apoptotic cells. Of nine kinds of trichothecene mycotoxins tested, T-2 toxin appeared to be the most potent agent to induce apoptosis in the thymus. We sought insight into the mechanism of T-2 toxin-induced apoptosis in vivo. Administration of the protein synthesis inhibitor, CHX (15 mg/kg ip), 5 min after T-2 toxin (1.75 mg/kg ip) inhibited the induction of apoptosis in thymocytes, suggesting that the de novo protein synthesis was necessary. By using adrenalectomized mice and anti-TNF-alpha antibody-injected mice, it was shown that neither endogenous glucocorticoid nor TNF-alpha appeared to be involved in the apoptotic process. Taken together, these findings suggest that T-2 toxin-induced thymic atrophy is associated with cell death through a mechanism of apoptosis.

Pharmacokinetics of meropenem in patients with various degrees of renal function, including patients with end-stage renal disease

The pharmacokinetics of meropenem were studied after intravenous infusion in 13 patients grouped according to the impairment of their renal function. Creatinine clearance (CLCR) was greater than 50, 50 to 30, and less than 30 ml/min in groups I, II, and III, respectively. Two other groups, groups IV and V, each comprising four patients with end-stage renal disease (CLCR, < 5 ml/min), were also studied, the former on days off of hemodialysis and the latter on days of hemodialysis. The elimination half-lives of meropenem were 1.54 +/- 0.70 h in group I patients, 3.36 +/- 1.02 h in group II patients, and 5.00 +/- 1.05 h in group III patients. Cumulative urinary excretion accounted for 48.5% of the dose in group I patients and decreased progressively with a decline in renal function. Hemodialysis shortened the elimination half-life of meropenem from 7.0 h to 2.9 h. H-4295, the main metabolite of meropenem, had a peak level in plasma of 0.5 to 1.0 h in patients with renal failure. The level of H-4295 decreased with hemodialysis. The dosing interval of meropenem should be prolonged in a regular proportion to the decline in CLCR (12 h in group II patients and 24 h in group III patients). In patients receiving hemodialysis, dosing after each hemodialysis session is recommended.

Visceral mast cell tumors in dogs: 10 cases (1982-1997)

OBJECTIVE

To characterize the clinical features of visceral mast cell tumors (MCT) without associated cutaneous involvement in dogs.

DESIGN

Retrospective study.

ANIMALS

10 dogs with histologically confirmed MCT without associated cutaneous lesions.

PROCEDURE

Information on signalment, clinical signs, laboratory examinations, and time from first admission to death was obtained from the medical record of each dog.

RESULTS

Purebred male dogs of miniature breeds appeared to have a higher prevalence of visceral MCT. Clinical signs included anorexia, lethargy, vomiting, and diarrhea. Anemia (n = 7), hypoproteinemia (5), and mastocythemia (5) were detected. Treatments, including glucocorticoids, were not successful. Primary sites of tumors were the gastrointestinal tract (n = 6) and the spleen or liver (1); the primary site was not confirmed in the remaining 3 dogs. In 7 dogs, tumors were categorized as grade II or III, on the basis of histologic findings. The prognoses were poor, and all dogs died within 2 months after first admission.

CONCLUSIONS AND CLINICAL RELEVANCE

Visceral MCT is uncommon in dogs, and the prognosis is extremely poor. Biological behavior and drug susceptibility of visceral MCT may be different from cutaneous MCT. The lack of specific clinical signs may result in delay of a definitive diagnosis. The rapid progression of clinical signs and difficulty in diagnosis contributes to a short survival time.

Apoptosis induction by T-2 toxin: activation of caspase-9, caspase-3, and DFF-40/CAD through cytosolic release of cytochrome c in HL-60 cells

The molecules participating in apoptosis induced by T-2 toxin in human leukemia HL-60 cells were investigated. The rank order of the potency of trichothecene mycotoxins to induce internucleosomal DNA fragmentation was found to be T-2, satratoxin G, roridin A >> diacetoxyscirpenol > baccharin B-5 >> nivalenol, deoxynivalenol, 3-acetyldeoxynivalenol, fusarenon-X, baccharin B-4=vehicle control. Western blot analysis of caspase-3 in T-2-treated cells clearly indicated the appearance of its catalytically active fragment of 17-kDa. Increased caspase-3 activity was also detected by using a fluorogenic substrate, DEVD-AMC. Next, cells exposed to T-2 led to cleavage of PARP from its native 116-kDa form to the 85-kDa product. Moreover, DFF-45/ICAD were cleaved to give a 12.5-kDa fragment via T-2 treatment. T-2 caused the release of cytochrome c from mitochondria into the cytosol. Increased enzymic activity of caspase-9 on LEHD-AMC was shown. These data indicate that T-2-induced apoptosis involves activation of caspase-3 and DFF-40/CAD through cytosolic accumulation of cytochrome c along with caspase-9 activation.

Tissue distribution and localization of natriuretic peptide receptor subtypes in stroke-prone spontaneously hypertensive rats

OBJECTIVE

To investigate tissue distribution and localization of the natriuretic peptide receptor (NPR) subtypes' messenger RNA (mRNA) and to compare their expression between stroke-prone spontaneously hypertensive rats (SHR-SP) and Wistar-Kyoto (WKY) rats.

METHODS

Total RNA was extracted from organs of SHR-SP and WKY rats aged 13 weeks. The mRNA level was examined by RNase protection assay. The localization of the transcripts was determined by in-situ hybridization.

RESULTS

In SHR-SP aged 13 weeks, NPR-A was expressed most abundantly in the adrenal gland, lung and aorta, in that order. NPR-B was expressed highly in the uterus and ovary, and also in the lung, adrenal, and brain. NPR-C was expressed predominantly in the atrium and mesentery, less so in the lung, vein, and kidney. In the adrenal gland, NPR-A was expressed mainly in zona glomerulosa cells. In the atrium, NPR-C was expressed throughout the wall. In the mesentery, NPR-C mRNA was detected mainly in adipocytes. In the kidney, NPR-C was found predominantly in podocytes. Whereas the levels of expression of NPR subtypes in most tissues examined did not differ between SHR-SP and WKY rats, the NPR-C mRNA level was significantly greater in the kidneys of SHR-SP than it was in those of WKY rats.

CONCLUSIONS

These results indicated that each NPR subtype had a distinct tissue distribution pattern and that the expression of NPR-C in the kidneys of SHR-SP was greater than that in the kidneys of WKY rats.

Contrast enhancement patterns of hepatic tumours during the vascular phase using coded harmonic imaging and Levovist to differentiate hepatocellular carcinoma from other focal lesions

The purpose of the study was to assess contrast enhancement patterns of hepatic tumours during the vascular phase using contrast-enhanced ultrasound and Levovist to differentiate hepatocellular carcinoma from other hepatic tumours. 89 hepatic tumours in 82 consecutive patients were evaluated using coded harmonic ultrasound imaging. The procedure used a phase inversion harmonic technique and coded technology. We observed images for 2 min from the beginning of the administration as the vascular phase using continuous transmission and intermittent transmissions of 1 s or 2 s. The contrast agent Levovist was administered intravenously as a bolus infusion of 2.5 g. Tumour vessels with flow spreading into the tumour and/or homogeneously stained hyperechoic images were observed in 34 of the 41 hepatocellular carcinomas (sensitivity, 82.9%; specificity, 93.8%). Peripheral enhancements were characteristic of intrahepatic cholangiocarcinoma and metastatic hepatic tumours (sensitivity, 60.0% and 83.3%; specificity, 65.5% and 76.4%, respectively). Pooling at the periphery or throughout the tumour was apparent only in haemangioma (sensitivity, 76.5%; specificity, 100%). A tortuous feeding artery and spoke-like vascularization were evident only in the two focal nodular hyperplasias. Contrast-enhanced ultrasound using coded harmonic ultrasound imaging and Levovist provided detailed information about tumour vascularity and contrast enhancement patterns in hepatic tumours.

Expression of types I, II, and III TGF-beta receptors in human glomerulonephritis

Protein and mRNA expression of transforming growth factor-beta (TGF-beta) receptor type I (TbetaRI), type II (TbetaRII), and type III (TbetaRIII) were studied in serial sections of kidney samples obtained from patients with glomerulonephritis. In minimal change disease, weak expression of TbetaRI and TbetaRII was observed mainly in glomerular endothelial cells, peritubular capillaries, and interstitial arteriolar endothelial cells, whereas TbetaRIII expression was found mainly in the interstitium. Expression of all three TGF-beta receptors (TbetaR) was increased remarkably in glomerular and Bowman's capsular cells comprising the tuft adhesions to Bowman's capsules in glomerulonephritis with increased matrix accumulation, including IgA nephropathy, lupus nephritis, focal and segmental glomerulosclerosis, myeloperoxidase-antineutrophil cytoplasmic antibody-associated crescentic glomerulonephritis, and membranoproliferative glomerulonephritis. Increased expression of the three TbetaR was also seen in glomerular epithelial cells in the vicinity of glomerulosclerotic lesions, in crescent cells, and in some tubules and infiltrative mononuclear cells found in the periglomerular and tubulointerstitial lesions with increased matrix deposition. In contrast, no remarkable TbetaRII expression was noted in mesangial proliferative lesions in IgA nephropathy, lupus nephritis, and membranoproliferative glomerulonephritis. These data suggest that distinctive modulation of TbetaR expression may be involved in the development of adhesive, sclerotic, and proliferative renal lesions in human glomerulonephritis.

Toxicity of silica-containing calcium phosphate glasses demonstrated in mice

Suspensions of calcium phosphate glass containing various concentrations of silica (glass composition (moles): 100 Ca(PO3)2 to x SiO2,x = 0, 5, 10, 15 or 40) dispersed in normal saline were injected intraperitoneally into C57BL/6 mice to determine the mortality within 30 days. The mortality was 0/10, 3/10, 9/10, 10/10 and 10/10 at x = 0, 5, 10, 15 and 40 mol of silica, respectively. By means of inductively coupled plasma analysis, the amount of dissolved silica (Si4+) in water at 37 degrees C from the calcium phosphate glass depended on the amount of silica in the glasses. The mortality of mice was directly proportional to the silica content of the glass injected intraperitoneally. These results clearly show that the dissolved silica (Si4+) from the glass, monomeric or low molecular silicic anion, is highly toxic. The SiO2 component in biomaterials has toxic potential when dissolved in the body.

Unique repetitive sequence and unexpected regulation of expression of rat endothelial receptor for oxidized low-density lipoprotein (LOX-1)

We report the identification of a unique repetitive sequence in the rat endothelial receptor for oxidized low-density lipoprotein (LOX-1) and unexpected blood-pressure-associated regulation of its expression, a new link between lipid metabolism and blood-pressure control. A rat aorta cDNA library was constructed and screened with a probe synthesized by degenerate PCR. Rat LOX-1 cDNA encoded a protein of 364 amino acids that showed approximately 60% similarity to its bovine and human counterparts. The protein consisted of intracellular N-terminal, transmembrane and extracellular lectin-like domains. Rat LOX-1 was unique in having three repeats of a 46-amino-acid motif between the transmembrane and lectin-like regions. Two isoforms of mRNA were found to be generated by alternative use of two polyadenylation signals in a tissue-specific manner. The 3'-untranslated region contained multiple A+U-rich elements for rapid degradation of mRNA. Northern-blot analysis revealed that LOX-1 mRNA was expressed predominantly in the lung. Quite unexpectedly, the expression was dramatically up-regulated in the aorta in hypertensive SHR-SP/Izm rats compared with very low levels in control WKY/Izm rats, suggesting a potential role for LOX-1 in the pathogenesis of hypertension as well as atherosclerosis.

Present features of gallstones in Japan. A collective review of 2,144 cases

A collective review of 2,144 patients operated on for cholelithiasis during the last twenty-two months has shown that younger Japanese adults have predominantly cholesterol stones in their gallbladders and that elderly persons still frequently have bilirubin stones not only in their gallbladders but also in their common bile ducts. Recent westernization of dietary habits in Japan is considered to be the most probable factor causing the increased incidence of cholesterol stones. The decreased incidence of bilirubin stones is considered to be caused by the decreased incidence of biliary infection and increased intake of proteins in food.

Structure-function relationship of T-2 toxin and its metabolites in inducing thymic apoptosis in vivo in mice

Recently we found that a single administration of T-2 toxin (T-2), a trichothecene mycotoxin, into mice induced DNA fragmentation, a biochemical hallmark of apoptosis, in the thymus. In this study, we investigated the effective chemical structure(s) of T-2-derived metabolites capable of inducing thymic apoptosis in vivo in mice. Metabolic conversion of T-2 to 3'-hydroxy-T-2 toxin (3'-OH-T-2) did not diminish the apoptosis-inducing activity, since essentially the same level of fragmented DNA was detected in the thymus taken from mice injected with either T-2 or 3'-OH-T-2. In contrast, hydrolysis of T-2 and 3'-OH-T-2 at the carbon-4 (C-4) position to HT-2 toxin (HT-2) and 3'-hydroxy-HT-2 toxin (3'-OH-HT-2), respectively, greatly decreased the level of DNA fragmentation. Similarly, hydrolysis of T-2 at the carbon-8 (C-8) position to neosolaniol strongly diminished its ability to induce DNA fragmentation. T-2 tetraol, having no ester groups, was unable to induce apoptosis. Based on the data presented in this study, we concluded that both the acetyl group at the C-4 position and the isovaleryl or 3'-hydroxyisovaleryl group at the C-8 position of the T-2 molecule are important for inducing cell death through apoptosis in the thymus.

Intra-GBM site of the functional filtration barrier for endogenous proteins in rats

The passage of various endogenous proteins [such as albumin, transferrin, immunoglobulin G (IgG), and immunoglobulin M (IgM)] across GBM was studied in vivo in normal Munich-Wistar rats. Glomeruli were fixed by three different methods: in situ drip-fixation, perfusion- and immersion-fixation; then they were processed for immunogold electron microscopy. The most reproducible results were obtained with in situ drip-fixation. Albumin, transferrin and IgG penetrated into GBM, but IgM did not. Morphometry revealed that density of albumin increased towards the inner 1/5 to 1/3 of GBM (junction of lamina rara interna and lamina densa) and decreased towards the subepithelial region of GBM, whereas density of IgG and transferrin was the highest at the subendothelial site and declined towards the subepithelial side of GBM. These findings suggest that central and/or outer zone of GBM constitute the main filtration barrier for albumin, and that subendothelial zone may contribute also to the charge-selective barrier. It is also suggested that the subendothelial zone acts more effectively as a filtration barrier for IgG and transferrin than for albumin. In the outer zone of GBM, which roughly corresponds to lamina rara externa visualized by conventional electron microscopy, the relative density of IgG and transferrin was higher than that of albumin. Since the pI of albumin was lower than that of IgG and transferrin, this finding suggests that subepithelial zone of GBM also acts as a charge-selective barrier. In conclusion, the main GBM filtration barrier for albumin might be the central and outer zones of GBM, and that for transferrin and IgG might be the entire width of GBM.(ABSTRACT TRUNCATED AT 250 WORDS)

IgG-mediated histamine release from canine mastocytoma-derived cells

BACKGROUND

Recent data suggest that normal tissue mast cells can express functional receptors for IgG under certain conditions. However, little is known about IgG receptor expression and functional consequences in mast cell neoplasms.

METHODS

In this study, neoplastic mast cells were obtained from a dog with cutaneous mastocytoma (CM-MC) and from a dog with visceral mastocytoma (VI-MC). Both cell populations were characterized morphologically and functionally.

RESULTS

Most cells proliferated constantly in suspension without particular supplements. Doubling times of CM-MC and VI-MC were 52.2 and 27.5 h, respectively. Both cell types were sensitive to formalin fixation, did not contain heparin and were tryptase and chymase positive. Electron microscopy showed fine granules with electron-dense content in both cell populations. The total histamine content of CM-MC and VI-MC was 0.25 and 0.10 pg/cell, respectively. Calcium ionophore A23187 and substance P induced dose-dependent histamine release, whereas compound 48/80 had no effect. Most significantly, both cell types, when sensitized with monomeric dog IgG, released histamine upon stimulation by anti-dog IgG.

CONCLUSIONS

Dog mastocytoma-derived cells may be useful to study the regulation of neoplastic mast cell growth and differentiation, as well as IgG receptor-mediated activation in neoplastic mast cells. Further research is required to clarify the pathophysiological significance of constitutive expression of IgG receptors in neoplastic (canine) mast cells.