Abnormal processing of the glycoprotein IIb transcript due to a nonsense mutation in exon 17 associated with Glanzmann's thrombasthenia

We analyzed the molecular genetic defect responsible for type I Glanzmann's thrombasthenia in a Japanese patient. In an immunoblot assay using polyclonal anti-GpIIb-IIIa antibodies, some GPIIIa (15% of normal amount) could be detected in the patient's platelets, whereas GPIIb could not (< 2% of normal amount). Nucleotide sequence analysis of platelet GPIIb mRNA-derived polymerase chain reaction (PCR) products revealed that patient's GPIIb cDNA had a 75-bp deletion in the 3' boundary of exon 17 resulting in an in-frame deletion of 25 amino acids. DNA analysis and family study revealed that the patient was a compound heterozygote of two GPIIb gene defects. One allele derived from her father was not expressed in platelets, and the other allele derived from her mother had a 9644C--> T mutation which was located at the position -3 of the splice donor junction of exon 17 and resulted in a termination codon (TGA). Moreover, quantitative analysis demonstrated that the amount of the abnormal GPIIb transcript in the patient's platelets was markedly reduced. Thus, the C --> T mutation resulting in the abnormal splicing of GPIIb transcript and the reduction in its amount is responsible for Glanzmann's thrombasthenia.

Molecular basis of CD36 deficiency. Evidence that a 478C-->T substitution (proline90-->serine) in CD36 cDNA accounts for CD36 deficiency

CD36 deficiency is divided into two subgroups: neither platelets nor monocytes express CD36 (type I deficiency), and monocytes express CD36 in spite of the lack of platelet CD36 (type II deficiency). We have already demonstrated that a 478C-->T substitution (proline90-->serine) in platelet CD36 cDNA predominates in type II deficiency (Kashiwagi, H., S. Honda, Y. Tomiyama, H. Mizutani, H. Take, Y. Honda, S. Kosugi, Y. Kanayama, Y. Kurata, and Y. Matsuzawa. 1993. Thromb. Haemostasis. 69:481-484). In this study, we revealed that monocyte CD36 cDNA from two type II deficient subjects was heterozygous for C478 and T478 form, while platelet CD36 cDNA of these subjects consisted of only T478 form. In a type I deficient subject, both platelet and monocyte CD36 cDNA showed only T478 form. Expression assay using C478 or T478 form of CD36 cDNA transfected cells revealed that there was an 81-kD precursor form of CD36, and that the maturation of the 81-kD precursor form to the 88-kD mature form of CD36 was markedly impaired by the substitution. The mutated precursor form of CD36 was subsequently degraded in the cytoplasm. These results indicate that the 478C-->T substitution directly leads to CD36 deficiency via defects in posttranslational modification, and that this substitution is the major defects underlying CD36 deficiency.

Disposition of DN-2327, a new anxiolytic, in rats, dogs, and monkeys

The disposition of DN-2327 after oral dosing of 14C-labeled DN-2327 ([14C]DN-2327) to rats, dogs and monkeys was studied. DN-2327 was absorbed from the small intestine after oral administration. In the plasma of these animals, a small amount of unchanged compound and M-I were detected, with M-II (a pharmacologically active metabolite) as a major component. The concentration of the unchanged compound in rat plasma attained a peak (Cmax 0.002 microgram/ml), then declined, with a half-life (t1/2) of 3 h. Tmax, Cmax and t1/2 of DN-2327 in dogs and monkeys were 0.6 h, 0.332 microgram/ml and 1.5 h, and 2.3 h, 0.036 microgram/ml and 6.2 h, respectively. About 60, 75 and 48% of the radioactivity dosed was absorbed in rats, dogs and monkeys, respectively, whereas the bioavailability in rats, dogs and monkeys was less than 1, 34 and 10%, respectively, indicating that DN-2327 had been subjected to the first pass effect. In rats given [14C]DN-2327 orally, the radioactivity was distributed widely in various tissues, including the brain. In the brain regions, DN-2327 and M-II were distributed and M-II was major component, indicating that the pharmacological effects of DN-2327 may depend largely on M-II. In these animals, [14C]DN-2327 was excreted in feces via bile mostly as metabolites. During repeated oral administration, DN-2327 and its metabolites did not accumulate in rat tissues, except in the kidney.

Effect of ingestion of 20 pesticides in combination at acceptable daily intake levels on rat liver carcinogenesis

Exposure of agricultural workers and the general population to pesticides is a major concern, and possible summation or synergistic effects deserves particular attention. In this study, however, combined dietary administration of 19 organophosphorus compounds and one organochlorine pesticide, each at acceptable daily intake (ADI) levels, did not enhance rat liver preneoplastic lesion development initiated by diethylnitrosamine. In contrast, a mixture of 100 times ADI significantly increased the number and area of lesions. The results thus provide direct support for the present safety factor approach to the quantitative hazard evaluation of pesticides.

Somatostatin receptor on the afferent nerve terminals in the rat hepatoportal area

To determine whether somatostatin receptor (SSR) actually exists on the nerve terminals in the rat hepatoportal area, the area was immunostained by the labeled streptoavidin-biotin complex method using a monoclonal antibody against rat brain SSR. The SSR staining revealed many fiber arborizations with terminal nodular swellings like the afferent nerve endings in the neural body, which was located beneath the endothelium of the large branches of the intrahepatic portal vein. The results indicate that SSR is expressed on the characteristic structure, adding further evidence for our previous observation which showed the hepatic vagal reception for intraportal somatostatin and the somatostatin-binding neural body as a relevant structure.

Slant-propagation characteristics in tapered optical waveguides: analysis

Although several analysis methods for tapered waveguides have been proposed, they dealt with the problem of a light wave traveling parallel to the tapered direction of the waveguide. Light waves that propagate at a slant in the tapered direction are discussed as mode-coupling problems, including radiation modes that are made discrete by the hypothetical boundary method. We propose a method of determining the three-dimensional wave vectors of the discrete radiation modes in the slant propagation; the slant-propagation characteristics, such as the transmission efficiency of the tapered waveguide, are analyzed.

Cyclic thrombocytopenia associated with IgM anti-GPIIb-IIIa autoantibodies

We studied a female patient with cyclic fluctuation in platelet count following splenectomy for autoimmune thrombocytopenia. The cyclical fluctuation appeared to be in phase with her menstrual cycle and her platelet count was low during menses. Bone marrow examinations performed at the peak as well as the bottom of the platelet count showed normal or increased numbers of megakaryocytes. The patient's platelet count increased rapidly after intravenous gamma-globulin (IVIgG) therapy, suggesting that a failure of platelet production is unlikely to account for the cycle. Platelet-associated IgM (PAIgM) was markedly elevated, whereas PAIgG was normal at any stage of the cycle. MACE assay demonstrated that PAIgM contained IgM anti-glycoprotein (GP) IIb-IIIa autoantibodies. Comparison between MACE assay using untreated and EDTA-treated platelets at 37 degrees C demonstrated that the platelet-associated IgM autoantibodies mainly recognized divalent cation-dependent conformation(s) of GPIIb-IIIa. No antibodies were, however, detected in her serum. The levels of IgM anti-GPIIb-IIIa showed an inverse relationship with the platelet count. In spite of the marked increase in platelet count after IVIgG, however, the levels of IgM anti-GPIIb-IIIa remained elevated. These findings suggest that platelet-associated IgM anti-GPIIb-IIIa autoantibodies are of pathogenic significance in this patient.

Energy restriction prevents and reverses immune thrombocytopenic purpura (ITP) and increases life span of ITP-prone (NZW x BXSB) F1 mice

Male (NZW x BXSB)F1 (W/BF1) mice develop immune thrombocytopenic purpura (ITP), which involves antiplatelet autoantibodies and shortened platelet life span. To determine whether reduction of dietary energy can prevent the development or reverse the progression of ITP, male W/BF1 mice were separated into five experimental groups and either given free access to semipurified diet (designated Group A, n = 50) or consumed 32% less energy from an otherwise comparable diet (Group B6, n = 20), or were initially allowed free access to diet then switched to energy restriction at ages 14, 17 or 22 wk (Groups B14, n = 10; B17, n = 20; B22, n = 20). Thrombocytopenia was prevented by energy restriction in Group B6 mice. Platelet-associated IgG (PAIgG) autoantibody levels and the number of splenic antiplatelet antibody-forming cells were low (P < 0.01) and the survival of injected IgG-coated RBC was extended in energy-restricted Group B6 mice (P < 0.01) compared with mice in Group A. Group A mice became progressively thrombocytopenic, with platelet counts as low as 34 x 10(10)/L. Progression of thrombocytopenia was reversed when energy restriction was initiated in Groups B14, B17 and B22, with platelet counts > or = 88 x 10(10)/L and reduction of PAIgG. Life span was extended among early onset energy-restricted Group B6 and Group B14 mice (P = 0.0001 and P = 0.005) but not among late onset energy-restricted Group B17 and Group B22 mice (P = 0.06 and P = 0.35) compared with Group A mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissimilar frequency of hepatoblastomas and hepatic cystadenomas and adenocarcinomas arising in hepatocellular neoplasms of D2B6F1 mice initiated with N-nitrosodiethylamine and subsequently given Aroclor-1254, dichlorodiphenyltrichloroethane, or phenobarbital

Aroclor-1254 (Ar-1254) and dichlorodiphenyltrichloroethane (DDT) were compared to phenobarbital (PB) for their ability to promote hepatocellular proliferative lesions to hepatocellular adenomas and carcinomas and to hepatoblastomas in D2B6F1 male mice initiated with N-nitrosodiethylamine (NDEA). Hepatocellular neoplasms developed in all mice given NDEA and were more numerous in mice fed promoters. Multiplicities decreased in the order Ar-1254 > PB > DDT, indicating that Ar-1254 was more potent than either PB or DDT at the dosage levels used. PB was the most effective of the 3 agents in stimulating the evolution of hepatocellular neoplasms to hepatoblastoma. The incidence of hepatoblastomas in the NDEA.PB group was 72% but was only 27% in NDEA-initiated, DDT-promoted mice and 33% in low-dose and only 9% in high-dose Ar-1254-promoted mice. In contrast, lesions resembling benign and malignant cholangiocellular neoplasms were frequently found within hepatocellular tumors in Ar-1254-promoted mice but not in mice fed PB or DDT, either alone or after NDEA. Some cystic glandular structures in Ar-1254-promoted mice contained mucous cells, argentaffin cells, and Paneth cells and thus constituted intestinal metaplasia. Hepatoblastoma and intestinal metaplasia/cholangiocellular tumor morphology appear to constitute different patterns of genetic programming induced by certain promoters in expanding clones of initiated hepatocytes, on favorable genetic backgrounds such as that of D2B6F1 male mice.

Thirteen-week oral toxicity study of magnesium chloride in B6C3F1 mice

Magnesium chloride (MgCl2.6H2O) was administered at dietary levels of 0 (control), 0.3, 0.6, 1.25, 2.5 or 5% to groups of 10 male and 10 female B6C3F1 mice for 13 weeks. In both sexes of the 5% treatment group a decrease in body weight was observed. While clinical signs and hematological or blood biochemistry parameters showed no treatment-related effects, histopathologically, vacuolation of kidney tubular cells was apparent in males of the 2.5 and 5% concentration groups. Thus, the study demonstrated that diet containing over 2.5% MgCl2.6H2O exerts toxic effects in B6C3F1 mice. We therefore conclude that a 2.5% level of MgCl2.6H2O in the diet is the minimal toxic dose.

Identification of molecular defects in a subject with type I CD36 deficiency

We performed a molecular analysis of a subject whose platelets and monocytes did not express any cell surface CD36 (designated as a type I CD36 deficiency). Amplification of the 5' half of platelet and monocyte CD36cDNA (corresponding to nucleotide [nt] 191-1009 of the published CD36 cDNA sequence [Oquendo et al, Cell, 58:95, 1989]) showed that two different-sized CD36 cDNAs existed. One cDNA was of predicted normal size, whereas the other was about 150 bp smaller than that predicted for normal CD36 cDNA. Amplification of the 3' region of CD36 cDNA (nt 962-1714) in this subject showed only normal-sized CD36 cDNA. Cloning and nt sequence analysis of the cDNAs showed that the smaller sized CD36 cDNA had 161-bp deletion (from nt 331 to 491), and a dinucleotide deletion starting at nt position 539. The same dinucleotide deletion was also detected in the normal sized CD36 cDNA. Both deletions caused a frameshift leading to the appearance of a translation stop codon. RNA blot analysis and quantitative assay using the reverse transcription-polymerase chain reaction (RT-PCR) showed that the CD36 transcripts in both platelets and monocytes were greatly reduced. Comparison of the determined cDNA sequences with the genomic DNA sequence for the human CD36 gene showed that the dinucleotide deletion was located in exon 5, and that the 161-bp deletion corresponded to a loss of exon 4. PCR-based analysis using genomic DNA showed that this subject was homozygous for the dinucleotide deletion in exon 5. Except for the dinucleotide deletion, we could not find any abnormalities around exon 3, 4, and 5 including the splice junctions. These results suggested that the deletions in CD36 mRNA were likely to be responsible for instability of the transcripts, and the dinucleotide deletion in exon 5 might affect the splicing of exon 4.

Comparative hyaline droplet nephropathy in male F344/NCr rats induced by sodium barbital and diethylacetylurea, a breakdown product of sodium barbital

Hyaline droplet nephropathy in male rats due to alpha 2u-globulin accumulation in proximal tubules is caused by chemicals from several chemical classes. We have previously shown that the well-known sedative/hypnotic barbiturate, sodium barbital, and its breakdown product, diethylacetylurea, are renal toxins and renal tumor promoters. To determine comparative induction of hyaline droplets in renal tubules by sodium barbital and diethylacetylurea, male F344/NCr rats, 6 weeks of age, were given diets containing 0, 170, 341, 500, or 1000 ppm of diethylacetylurea or containing 500, 1000, or 4000 ppm of sodium barbital for periods of 2 or 10 weeks. Rats were terminated at 2 or 10 weeks and the histology of the kidney was evaluated using light microscopy with hematoxylin and eosin staining and staining by the Heidenhain method. Quantitative analysis showed dose responses for the degree of droplet accumulation in the P2 and P3 segments of the proximal tubules. Diethylacetylurea was more potent. Immunohistochemistry and ultrastructural evaluation revealed the nature of the droplets. Western blotting confirmed the presence of alpha 2u-globulin. Renal tubular necrosis, regeneration, and increased levels of cell proliferation using proliferating cell nuclear antigen immunohistochemistry were also found. Female rats similarly exposed to each chemical did not show tubule droplet accumulations nor renal lesions. We confirm for the first time that these two chemicals can be added to the enlarging list of nephrotoxic chemicals inducing alpha 2u-globulin nephropathy and possessing tumor promoting and renal carcinogenic properties.

Calorie restriction prevents the occlusive coronary vascular disease of autoimmune (NZW x BXSB)F1 mice

Male (NZW x BXSB)F1 (W/BF1) mice develop systemic autoimmunity involving autoantibodies, thrombocytopenia, lupus nephritis, and coronary vascular disease (CVD) with myocardial infarction. To determine whether this murine lupus-associated CVD can be prevented by the reduction of dietary calories, male W/BF1 mice were separated into five experimental groups and fed either ad libitum (designated group A, n = 50), fed 32% fewer calories of an otherwise comparable diet (designated group B6, n = 20), or initially fed ad libitum and then switched to reduced calorie intake (RCI) feeding at ages 14, 17, or 22 weeks (designated B14, n = 10; B17, n = 20; or B22, n = 20). Occlusive CVD was prevented by RCI. Life-span was significantly extended among the early onset RCI cohorts, B6 and B14 (P = 0.0001 and P = 0.005), compared to group A mice. Mean anti-cardiolipin autoantibody titers and mean levels of circulating immune complexes were also lowered in RCI mice when all RCI mice were compared to ad libitum fed group A mice. Histological grades of both coronary vascular and glomerular lesions were significantly less than those of group A mice (P < 0.001). Immunoprecipitates indicative of immunoglobulin deposition within coronary or glomerular vascular walls were also substantially less than those of group A mice. These findings indicate a possible causal role for anti-cardiolipin autoantibody in development of autoimmune CVD in W/BF1 mice and suggest that regulating dietary calories can influence the mechanism involved in pathogenesis of autoimmune-associated CVD development.

[Detection of anti-neutrophil antibodies by enzyme linked immunosorbent assay--comparison of results obtained by ELISA with those by leukocyte agglutination test and granulocyte cytotoxicity test]

We examined anti-neutrophil antibodies in 12 patients with various disorders using enzyme-linked immunosorbent assay (ELISA), and the results obtained by ELISA were compared with those obtained by leukocyte agglutination test (LAT) and granulocyte cytotoxicity test (GCT). IgG anti-neutrophil antibody was positive in 7 of 12 patients, and IgM type antibody was positive in 6 patients. There was a significant correlation between IgG and IgM anti-neutrophil antibodies. The results obtained by ELISA were not in accord with those obtained by LAT or GCT. In addition, we examined anti-neutrophil antibodies in serially collected serum samples from two patients with immune neutropenia. The results obtained by ELISA correlated with their neutrophil counts, suggesting that anti-neutrophil antibodies detected by ELISA have pathological relevance.

Demonstration of a marked reduction in the amount of GPIIb in most type II patients with Glanzmann's thrombasthenia

In this study employing a sensitive immunoblot assay, we have characterized GPIIb and GPIIIa in thrombasthenic platelets from seven type II and four type I patients from 10 unrelated families. The amounts of GPIIb and GPIIIa were both markedly reduced in all these patients, and abnormal molecular weight GPIIb or GPIIIa was not detected. In all of four type I patients the amount of GPIIb was much lower than that of GPIIIa. In this study, however, we found that the amount of GPIIb was also lower even in six out of seven type II patients. Immunodepletion of patients' platelets with AP2 (a monoclonal antibody specific for the GPIIb-IIIa complex), AP3 (specific for GPIIIa) or AMF7 (specific for alpha v) further confirmed that GPIIIa existed in excess, and demonstrated that excess GPIIIa were mostly in free form and not associated with GPIIb or alpha v. The reduction of GPIIb may represent an abnormality in GPIIb processing in these type II and type I thrombasthenic platelets. It remains unclear whether these two subgroups represent distinct categories.

Selective effects of alcohols on gamma-aminobutyric acid A receptor subunits expressed in human embryonic kidney cells

Several previous studies implicated alpha 6 and gamma 2L subunits as potential determinants of gamma-aminobutyric acid A (GABAA) receptor channel sensitivity to alcohol modulation. The effects of ethanol and n-octanol were studied on GABA-induced currents in human embryonic kidney cells transfected to express one of three different GABAA receptor channel subunit combinations: alpha 1 beta 2 gamma 2S, alpha 6 beta 2 gamma 2S or alpha 6 beta 2 gamma 2L. No increase in the current amplitude of any subunit combination was observed after the coapplication of GABA and physiological concentrations (10-100 mM) of ethanol. By contrast, the coapplication of GABA and 100 microM octanol increased the current amplitude by 50% to 100% in all three subunit combinations. Octanol produced a shift of the current dose-response curve toward lower concentrations of GABA. Ethanol was effective in increasing the rate of desensitization produced by higher concentrations of GABA in the alpha 6 beta 2 gamma 2S cells but not the alpha 1 beta 2 gamma 2S combination. This ethanol-induced modification of desensitization was not altered by the presence of the protein kinase inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7). These experiments indicate that the presence of alpha 6 or gamma 2L subunits, in itself, does not result in the potentiation of GABA-induced currents by ethanol, as described in some reports. However, the presence of either the alpha 6 or alpha 1 subunit may determine whether the desensitization rate of the GABAA current is affected by the alcohol.

High-titer antinuclear antibodies, anti-SSA/Ro antibodies and anti-nuclear RNP antibodies in patients with idiopathic thrombocytopenic purpura

The clinical significance of high-titer antinuclear antibodies (ANA) and autoantibodies to cellular antigens such as SSA/Ro and nuclear RNP (nRNP) antigens in idiopathic thrombocytopenic purpura (ITP) was examined in a prospective evaluation of 66 adult patients with chronic ITP. ANA were positive in 29 (44%) of 66 patients with chronic ITP. The titers of ANA were high (1:160 or higher) in 14 of 29 ANA-positive patients. Furthermore, 10 of 66 patients had precipitating antibodies to nuclear antigens; seven patients had anti-SSA/Ro antibodies and the other three had anti-nRNP antibodies. None of high-titer ANA- or precipitating antibody-positive patients developed systemic lupus erythematosus (SLE) throughout the follow-up period of 3 years. In addition, we investigated retrospectively precipitating antibodies in stocked sera from 8 patients. These patients had already precipitating antibodies average of 7.7 years before. None of 8 patients developed SLE or Sjogren's syndrome (SS). These data demonstrate that high-titer ANA and antibodies to SSA/Ro or nRNP antigens are often found in patients with ITP, and indicate that the detection of high-titer ANA or the existence of antibodies to SSA/Ro or nRNP antigens by itself is not enough to identify those patients with ITP who are at risk of developing SLE or SS.

Alcohol modulation of cloned GABAA receptor-channel complex expressed in human kidney cell lines

The effects of n-octanol on GABA-induced currents were examined on the alpha 1 beta 2 gamma 2s and alpha 1 beta 2 combinations of GABAA receptor subunits expressed in a human kidney cell line (HEK 293), using the whole-cell variation of the patch clamp technique. The EC50 of the GABA dose-response curve for the alpha 1 beta 2 combination was lower than that for the alpha 1 beta 2 gamma 2s combination. n-Octanol at 100 microM augmented the GABA-induced currents in a dose-dependent manner, decreasing the EC50 of the GABA dose-response curve without affecting the maximal response. The magnitude of n-octanol potentiation was nearly the same in both combinations. In contrast, a benzodiazepine agonist, chlordiazepoxide, augmented the currents of the alpha 1 beta 2 gamma 2s combination only. We conclude that the potentiation of GABAA receptor-mediated currents by a long carbon chain n-alcohol does not require the gamma 2 subunit.

Elevated platelet-associated IgG in SLE patients due to anti-platelet autoantibody: differentiation between autoantibodies and immune complexes by ether elution

The level of platelet-associated IgG (PAIgG) is reported to be elevated in patients with systemic lupus erythematosus (SLE). However, the nature of PAIgG is unclear. We have investigated whether the PAIgG of SLE consists of anti-platelet autoantibodies or immune complexes (IC). The PAIgG values measured by flow cytometry were elevated in 11/25 patients with SLE. 3/6 SLE patients with thrombocytopenia had a high level of PAIgG (the mean fluorescence intensity > 10). We used an ether elution technique to determine whether elevated PAIgG consists of anti-platelet antibodies or IC. Preliminary experiments showed that the eluates prepared from platelets sensitized with anti-HPA-4a antibody reacted with normal platelets, while the eluates prepared from platelets sensitized with heat-aggregated IgG or model IC failed to react with normal platelets. These results indicate that the reactivity of eluates can distinguish between platelet-bound antibody and IC. We applied this technique to analysis of the PAIgG of SLE platelets. The eluates from SLE platelets (the mean fluorescence intensity > 10) reacted with normal platelets, indicating that the PAIgG of SLE platelets has the nature of antiplatelet autoantibodies. Furthermore, we investigated the target antigens which bind PAIgGs of SLE, using the direct immunoprecipitation procedure and modified antigen capture ELISA (MACE). Both methods identified GPIIb/IIIa as the target antigens. We conclude that the ether elution technique can distinguish between anti-platelet antibodies and IC, and that the PAIgGs of SLE with a high PAIgG value and thrombocytopenia have the nature of anti-platelet autoantibodies.

Cell proliferation not associated with carcinogenesis in rodents and humans

Cell proliferation has often been found to be associated with carcinogenesis in rodents and humans at different stages of the multistage carcinogenesis process. The multistage process includes initiation, promotion, and progression phases. At each phase, increasing the normal level of cell turnover of target cells may enhance carcinogenesis. However, we present evidence that normal levels of cell turnover, or increasing the rate of cell turnover at these different stages, do not necessarily lead to enhanced carcinogenesis. In normal tissues, the length of the cell cycle depends on the age of the host and varies from tissue to tissue. Tissues with normal short cell cycles, such as intestine and bone marrow, do not show a high rate of spontaneous tumors in most species. Cells with higher turnover should be more susceptible to carcinogens at the initiation stage of carcinogenesis if cell proliferation per se causes cancer and if these cells or their progeny survive. Cancer in humans is more often associated with specific etiological factors rather than with the natural proliferative rate of specific tissues. For many tissues of humans and rodents, age-related diseases develop in a progressive, irreversible manner. Often, naturally occurring chronic degenerative and inflammatory changes in a tissue (e.g., kidney, liver, heart, reproductive tract) lead to chronic regeneration of the damaged tissue. Yet, cancer is rarely found in these tissues. In rodent carcinogenesis experiments, chronic toxic lesions, accompanied by increases in normal levels of cell turnover, have sometimes been observed in target organs of nongenotoxic carcinogens. More often, however, organ-specific nongenotoxic toxins are not carcinogens. These toxins include compounds toxic for the liver, kidney, and nasal cavity. In 19 inhalation bioassays conducted by the National Toxicology Program, 5/5 nasal carcinogens and 12/14 nasal noncarcinogens caused nasal lesions usually associated with chronic cell proliferation. Although cell proliferation may contribute to multistage carcinogenesis, cell proliferation is not necessarily a tumor promoter or cocarcinogen.

Prevention and induction of occlusive coronary vascular disease in autoimmune (W/B)F1 mice by haploidentical bone marrow transplantation: possible role for anticardiolipin autoantibodies

Male (NZW x BXSB)F1 (W/BF1) mice develop systemic autoimmunity involving autoantibodies, thrombocytopenia, lupus nephritis, and coronary vascular disease with myocardial infarction (CVD). To determine whether this murine lupus-associated CVD could be transferred to otherwise autoimmune-resistant (C57BL/6 x C3H/He)F1 (B6C3F1) mice via W/BF1 T-cell-depleted marrow (TCDM) transplants, or conversely whether the CVD of W/BF1 mice could be prevented by the reciprocal transplant, reciprocal haploidentical transplants of TCDM were performed. CVD developed only in mice with systemic autoimmunity. Mice that developed lupus had glomerulonephritis and thrombocytopenia and also had elevated titres of autoantibodies to double-strand DNA, cardiolipin, and platelets and elevated levels of circulating immune complexes. Of control W/BF1 mice, 80% developed lupus, and of these, 81% developed CVD with a mean grade of 2.5 +/- 0.8. Engraftment of W/BF1 mice with B6C3F1 marrow protected 90% of the recipients from the development of lupus, and none developed CVD. Engraftment of B6C3F1 mice with W/BF1 marrow induced lupus in 60% of the recipients, and of those, 33% developed CVD with a mean grade of 1.3 +/- 0.3. The B6C3F1 recipients of W/BF1 marrow which developed CVD had significantly higher titres of autoantibodies to cardiolipin (aCL; P < .01). These findings show that genetic abnormalities present in the W/BF1 hematopoietic stem cells contribute to autoantibody development, including aCL, and suggest that thrombogenic mechanisms induced by aCL may contribute to the development of CVD in this form of murine lupus erythematosus.

Development and characterization of monoclonal antiplatelet autoantibodies from autoimmune thrombocytopenic purpura-prone (NZW x BXSB)F1 mice

Male (NZW x BXSB)F1 (W/BF1) mice develop systemic autoimmunity involving autoantibodies, progressive thrombocytopenia, lupus nephritis, and degenerative coronary vascular disease with myocardial infarction. Platelet-associated IgG (PAIgG) on the platelet surface mediates platelet destruction by the reticuloendothelial system in the autoimmune thrombocytopenic purpura (ATP) of W/BF1 mice. Because the epitopes targeted in ATP by PAIgG have not been identifiable using serum from thrombocytopenic W/BF1 mice, we developed seven hybridomas secreting antiplatelet monoclonal antibodies (MoAbs) using splenocytes of thrombocytopenic W/BF1 mice. Epitopes recognized by three MoAbs were similar to those recognized by PAIgG, because eluted IgG from platelets of thrombocytopenic W/BF1 mice inhibited platelet binding by MoAbs in competitive micro-enzyme-linked immunosorbent assay. Hybridoma cells or purified Ig from the ascites of two clones (2A12 and 6A6), when injected into nude mice produced acute thrombocytopenia, elevated the levels of PAIgG, purpura, and megakaryocytosis. MoAbs of two clones also reacted with single-stranded DNA or double-stranded DNA, and one of these clones (4-13) bound to cardiolipin (CL) but was nonpathogenic in nude mice, suggesting that anti-CL and antiplatelet autoantibodies can be distinct. On immunoblotting analysis, antiplatelet MoAbs frequently bound a 100-Kd platelet protein. These MoAbs contribute to an understanding of the etiopathogenesis of ATP and the several antigens and autoantibodies involved.

Alterations in populations of GST-p-immunoreactive single hepatocytes and hepatocellular foci after a single injection of N-nitrosodiethylamine with or without phenobarbital promotion in male F344/NCr rats

The fate of placental glutathione S-transferase (GST-P)-immunoreactive hepatocytes, detectable in livers of rats soon after treatment with N-nitrosodiethylamine (DEN), was examined sequentially with or without phenobarbital (PB) promotion. Group 1 male F344/NCr rats were administered a single i.p. injection of 200 mg DEN per kg body weight at 5 weeks of age. Group 2 rats were given 500 ppm PB in the diet two weeks after the DEN treatment. Groups of six rats were sequentially sacrificed 16, 42, 70, 126 and 238 days after DEN injection. In DEN-treated rats, GST-P immunoreactive hepatocytes (single cells and multiple cell foci) were detectable 16 days after DEN, the total numbers decreasing by day 70 and thereafter rising again. In the early stages the proportion of single immunoreactive hepatocytes was prominent, but with time a gradual increase in small GST-P+ hepatocellular foci and larger foci became evident. Feeding of PB to rats for 16-238 days after a single DEN injection resulted in increases of both single cells and foci, especially foci composed of more than three hepatocytes. The growth response was increasingly pronounced with time. Adenomas or carcinomas were only observed at 126 or 238 days. Numbers of GST-P+ foci far exceeded the numbers of foci visible in hematoxylin-eosin (H & E) stained sections, and a few H & E foci were negative for GST-P. Many GST-P+ foci smaller than ten cells were composed of histologically normal hepatocytes. Almost all GST-P+ foci identifiable in H&E stained sections were larger than ten cells, consisted of clear cells (in both groups) or mixed (clear-eosinophilic) cells in PB-exposed rats, and appeared to be evenly distributed throughout the three zones of the liver. These results suggest that the promotive effect of PB is most evident as an increase in larger hepatocyte populations composed of more than three GST-P+ hepatocytes, rather than in increasing the populations of single GST-P immunoreactive cells. PB may cause clonal expansion of these single GST-P reactive hepatocytes. This study provides evidence for the hypothesis that some of the GST-P reactive hepatocytes are initiated cells.

A novel polymorphism in glycoprotein IV (replacement of proline-90 by serine) predominates in subjects with platelet GPIV deficiency

To clarify the molecular basis of the deficiency of glycoprotein IV (GPIV) of the platelet surface, we analyzed GPIV cDNA synthesized from platelet RNA of five unrelated Japanese subjects whose platelets did not express GPIV. We confirmed the presence of normal-sized GPIV mRNA in platelets from subjects with GPIV deficiency. The sequence of platelet GPIV cDNA from GPIV deficient subject showed three differences when compared with the published sequence; 1) a replacement of a 478CCT codon for proline-90 by TCT for serine, 2) a four-base insertion in the 3'-noncoding region, and 3) a substitution of A for 79C in the 5'-noncoding region. The replacement of Pro90 by Ser predominates in subjects with GPIV deficiency; that is, four out of five platelets with GPIV deficiency contained GPIV mRNA encoding GPIVSer-90, while all platelets from 17 GPIV positive subjects had GPIV mRNA encoding GPIVPro-90. The sequence of platelet GPIV cDNA which did not encode GPIVSer-90 from a subject with GPIV deficiency revealed no abnormality in the coding region. The four-base insertion in the 3'-noncoding region and the substitution of A for 79C in the 5'-noncoding region seems to be unrelated to the expression of GPIV. The substitution of Ser for Pro90 might alter the GPIV structure or impair GPIV biosynthesis, resulting in a lack of detectable GPIV. This hypothesis remains to be tested.

Induction of micronucleated erythrocytes by recombinant human erythropoietin

Induction of micronucleated erythrocytes by a recombinant human erythropoietin (rhEPO) was examined using both in vitro and in vivo test systems. A small, significant and dose-related increase in the frequency of micronucleated polychromatic erythrocytes (MNPCE) in bone marrow of mice administered i.p. with 12,500-50,000 IU/kg rhEPO was induced at 48 h sampling time. A clear positive dose--response relationship and significant increase in the frequency of micronucleated reticulocytes (MNRET) in peripheral blood of mice administered i.p. with 400-50,000 IU/kg rhEPO was noted at 48, 72 and 96 h sampling times. Conversely, in bacterial reverse mutation tests, no noticeable increase of auxotrophic revertants was observed in Salmonella typhimurium, TA100, TA98, TA1535, TA1537, or Escherichia coli, WP2 uvrA-, by treatment with 188-6000 IU/plate of rhEPO, with or without S9 mix. Furthermore, rhEPO at 750-6000 IU/ml did not induce chromosomal aberrations in vitro in CHL cells or human peripheral blood lymphocytes in a direct method nor in a metabolic activation method. Moreover, chromosomal aberrations were not detected in bone marrow cells of CD-1 male mice, even at high rhEPO concentrations (100,000 IU/kg) in vivo. Consequently, it was concluded that errors in the process of enucleation or differentiation of the erythrocytes should be equally considered as possible mechanisms for the increased frequencies of MNPCE and MNRET alongside induction of DNA damage or errors in the process of DNA repair.

Comparative studies in induction of micronuclei by three genetically recombinant and urinary human erythropoietins

Comparative studies on the induction of micronucleated erythrocytes by three recombinant human erythropoietins (rhEPOs) such as epoetin alpha, epoetin beta, and SNB-5001, and by urinary human EPO (uhEPO) were carried out in vivo. Small but significant increases in the frequency of micronucleated polychromatic erythrocytes (MNPCEs) in bone marrow of mice following a single intraperitoneal (i.p.) administration of each of the three rhEPOs and uhEPO (25,000 IU/kg) were observed at the 48 h sampling time. Clear, significant increases in the frequency of micronucleated reticulocytes (MNRETs) in the peripheral blood of mice similarly treated with the four hEPOs at 50,000 IU/kg were noted at the 48, 72 and 96 h sampling times. When mice were dosed with 50,000 IU/kg of each of the hEPOs once each day for 6 days and micronucleus preparations were made 24 h after the last administration, micronucleus induction in the bone marrow was not clearly demonstrated. As before, MNRETs in these mice were significantly induced in all cases. Consequently, it was concluded that induction of MNPCEs and MNRETs was a common characteristic of both native and genetically recombinant EPO.

[Anti-platelet antibodies in patients with autoimmune disorders]

The levels of platelet-associated IgG (PAIgG) are reported to be elevated in patients with systemic lupus erythematosus (SLE). However, the nature of PAIgG is unclear. We investigated whether PAIgGs of SLE are anti-platelet autoantibodies or immune complexes (IC). PAIgG levels measured by flow cytometry in patients with SLE (n = 25) were 12.7 +/- 41.0 (expressed by mean channel), slightly high (but not significant) compared with healthy subjects (2.5 +/- 0.7). Three of 6 SLE patients with thrombocytopenia had high level of PAIgG (mean channels > 10). To determine whether elevated PAIgGs are composed of anti-platelet antibody or IC, we applied elution technique. Preliminary experiments showed that the eluate prepared form platelets sensitized with anti-HPA-4a antibody reacted with normal platelets, while the eluates prepared from platelets sensitized both with heat aggregated IgG and with model IC did not react with normal platelets. These results indicated that the reactivity of eluates could discriminate between platelet-bound antibody and IC. We applied this method for the analyses of PAIgG of SLE platelets. The eluates from SLE platelets (mean channels were more than 10) reacted with normal platelets, indicating that PAIgGs of SLE platelets are anti-platelet autoantibody, not IC. Furthermore, we investigated the target antigens which bound PAIgGs of SLE, using the direct immunoprecipitation and modified antigen capture ELISA (MACE). Both methods identified GPIIb/IIIa as target antigens. We concluded that 1) ether elution technique could differentiate between anti-platelet antibody and IC, 2) PAIgGs of SLE had a nature of anti-platelet autoantibody, 3) the target antigens of PAIgG were GPIIb/IIIa.

Genotoxicity of genetic recombinant human erythropoietin in a novel test system

The nude (athymic) mouse was used as a novel test system for the evaluation of genotoxicity of genetic recombinant human erythropoietin (rhEPO). A fibroblast cell line derived from the kidneys of baby hamsters, BHK-21, or a subclone of BHK-21 transfected with an expression vector containing the human EPO gene, named BXE cells, were implanted in nude mice. The concentration of EPO in the plasma of mice bearing BXE increased in relation to the increase in the weight of the tumor formed from growth of BXE cells. Increased values of hematocrit (Ht), ratio of reticulocytes to erythrocytes (RET ratio) and the number of red blood cells in mice bearing BXE indicated that excessive hematopoiesis was occurring in the host. However, the concentrations of EPO in the plasma of the mice bearing BHK-21 did not increase in relation to the cell mass and consequently the Ht values and RET ratios in these mice were not affected. Marked increases in the frequencies of micronucleated polychromatic erythrocytes (MNPCE) and micronucleated RET (MNRET) were noted in the mice bearing BXE, although no chromosomal aberrations were found in the spleen and marrow cells of the same mice. The increased levels of RET, MNRET and MNPCE seemed to result from acceleration of erythroblastic maturation and proliferation by rhEPO. It is, therefore, concluded that errors in the processes of enucleation or differentiation of erythrocytes should be equally considered as possible mechanisms alongside errors in genetic repair processes for the increased frequencies of MNPCE and MNRET.

Presence of the entire coding region of GP IV mRNA in Nak(a)-negative platelets

It has been reported that Nak(a)-negative platelets lack GP IV. To examine the GP IV genetic defects in Nak(a)-negative platelets, we studied four unrelated Nak(a)-negative subjects by amplifying their GP IV cDNA, which were synthesized from platelet mRNA using the reverse transcriptase/polymerase chain reaction (RT/PCR). We detected the entire coding region of GP IV mRNA in the platelets of all four subjects. Restriction enzyme analysis of the amplified GP IV cDNA showed fully predictable cutting sites. These results suggest that no gross deletion or insertion had occurred in the GP IV mRNA of Nak(a)-negative platelets.

Influence of aging on multi-organ carcinogenesis in rats induced by N-methyl-N-nitrosourea

The effects of aging on the multi-organ carcinogenesis induced in rats by N-methyl-N-nitrosourea (MNU), a direct carcinogen which does not need metabolic activation to exert carcinogenicity, were examined in male F344 rats. In the first experiment, rats at 6, 52, and 98 weeks of age were treated with MNU (20 mg/kg body weight, i.p.) twice weekly for 6 weeks and then maintained without any further treatment for 24 weeks in the case of young and middle-aged rats and for 18 weeks in the case of the old rats. In young rats, malignant lymphomas, particularly thymic types, were observed at significantly high incidence. A striking result in the middle-aged rats was the significantly higher incidence of adenocarcinomas in the small intestine than in young or old animals. The induction of proliferative and neoplastic lesions of the large intestine also tended to be increased in middle-aged rats. In addition, epithelial hyperplasia of the tongue, but not the forestomach, occurred at the highest incidence in the middle-aged group. There were no differences in the induction of epithelial lesions in the urinary bladder among the groups. In a second experiment, investigation of DNA synthesis in the tongue, small and large intestines, urinary bladder and lymph nodes did reveal significant increases or tendency for increase in the MNU-treated groups, but without differences with age. In contrast, the thymus of young rats showed significantly increased incorporation of BrdU label after administration of MNU, whereas it was markedly reduced in middle-aged rats. In a third experiment, O6-methyldeoxyguanine (O6-medG) DNA adduct formation was immunohistochemically detected in various organs including the thymus, forestomach, and small intestine without any differences with age. Thus, the results demonstrated that while the target organs of MNU are modified by the age of the animals, levels of DNA synthesis and O6-medG DNA adduct formation in most cases can not explain the observed differences in carcinogenic susceptibility.

Pathology of preneoplastic and neoplastic renal tubular lesions induced in F-344 rats by sodium barbital, a nongenotoxic renal carcinogen and nephrotoxin

Sodium barbital (NaBB), a long-duration sedative/hypnotic barbiturate, is a nongenotoxic nephrotoxin and induces chronic persistent increases in rates of cell proliferation in renal cortical tubules of male F-344/NCr rats. In 5 of our 2-stage carcinogenesis experiments with NaBB at doses of 500, 1,000, or 4,000 ppm for periods of up to 106 wk of age, renal tubular cell tumors were found in incidences of up to 25% in rats receiving only NaBB while fewer than 1% of controls had renal epithelial tumors. We reviewed renal tubular proliferative lesions found in these studies and classified the lesions based on morphology, histogenesis, and immunohistochemical findings. Renal dysplastic tubules (DTs; atypical hyperplasia), putative preneoplastic lesions rarely seen in controls, were found in the renal cortex of more than 50% of the NaBB-exposed rats. DTs were classified into grades 1-3, based on lesion size and growth patterns. All renal adenomas were usually of the basophilic phenotype, and 70% of basophilic adenomas displayed solid patterns, while tumors with papillary, cystic, or tubular patterns were seen less commonly. By serial or step sectioning of the DTs and tumors, evidence was found indicating that the high grades (grade 2 or 3) of DTs, some of which arose in the P1 or P2 segment of the proximal tubules, were sometimes connected to the adenomas. Vimentin expression was demonstrated immunohistochemically in NaBB-induced renal tubular adenomas but not in normal tubules. Tumors were usually not immunoreactive for glutathione S-transferase, placental form, but heterogeneous immunoreactivity was also seen in some tumors. Lysozyme was absent in preneoplastic and neoplastic lesions induced by NaBB, while some intact normal proximal convoluted tubules were immunoreactive. The common tumor phenotype induced by NaBB, the basophilic solid adenoma, was similar to the most common type of spontaneous renal tumor found in untreated aging F-344 rats. NaBB may promote naturally occurring renal preneoplastic or neoplastic tubular lesions of this unique phenotype, but it is also possible that it may induce these lesions de novo.

[A case of dermatomyositis complicated by thrombotic thrombocytopenic purpura (TTP) which responded to combination of gamma globulin and vincristine--clinical analysis on TTP cases in the Japanese literatures]

A rare case of dermatomyositis and thrombotic thrombocytopenic purpura (TTP), which responded dramatically to high-dose gamma globulin and vincristine is presented. A 42-year old man was admitted for evaluation of polymyalgia and skin change of the face and fingers. Findings of muscle biopsy was consistent with the diagnosis of dermatomyositis. During the course of his hospital stay, he had diffuse purpura, hematuria, high fever, and his consciousness became disturbed. The hemoglobin level and the platelet count decreased. Based on microangiopathic hemolytic anemia, thrombocytopenia and neurological abnormality, a clinical diagnosis of TTP was made. Therapy included high-dose gamma globulin, vincristine, corticosteroids and dextran. One week later, his consciousness became clear, hematological findings improved, and prolonged remission has been maintained for more than 19 months at the time of this report. This case suggests that gamma globulin and vincristine are effective in some with TTP cases. Case reports that have appeared in the Japanese literature are summarized and reviewed in terms of treatment.

[Pathogenic relevance of platelet-associated autoantibodies in chronic ITP--studies before and after splenectomy in three patients with chronic ITP by direct immunoprecipitation procedure]

This study was designed to investigate the pathogenic relevance of platelet-associated autoantibodies in chronic ITP, since the titer of platelet-associated autoantibodies does not appear to correlate with the severity of the disease. Employing a direct immunoprecipitation procedure, we examined platelets from three ITP patients with platelet-associated autoantibodies against GPIIb-IIIa and an unidentified 56 kD protein before and after splenectomy. In two patients, platelet-associated autoantibodies disappeared after splenectomy, and these two patients attained complete remission. In one patient, however, the amount of platelet-associated autoantibodies did not decrease after splenectomy. Although this patient's platelet count transiently increased to 500 x 10(3)/microliters after splenectomy, it decreased to 55 x 10(3)/microliters within a short time. These findings suggest that platelet-associated autoantibodies play a key role in platelet destruction in chronic ITP.

Vimentin metaplasia in renal cortical tubules of preneoplastic, neoplastic, aging, and regenerative lesions of rats and humans

Vimentin expression was studied immunohistochemically in renal cortical tubules of untreated male rats of various ages, rats exposed to toxins (barbital sodium, folic acid) and carcinogens (streptozotocin, N-bis(2-hydroxypropyl)nitrosamine, barbital sodium, and in humans of various ages with or without renal epithelial tumors. Fetal, neonatal, and young adult rats did not express vimentin in renal cortical tubules. Regenerative renal tubular lesions from rats with aging nephropathy and from rats with toxic nephropathy both expressed vimentin. Mitogenic lesions induced by folic acid at 24 hours, however, were not immunoreactive for vimentin. Carcinogen-induced preneoplastic renal cortical tubular lesions in rats were most often focally immunoreactive whereas strong vimentin expression was found in almost all induced renal tumors. In kidneys of three children (younger than 2 years of age), vimentin was not found in renal cortical tubular cells except in rare individual cells in one case. Vimentin was abundant in basophilic regenerative tubules in kidneys of aged individuals, however. Most (7/10) human renal carcinomas and latent preneoplastic or neoplastic renal tubular lesions found incidentally at autopsy (2/4) showed vimentin expression. The authors suggest that the switching to vimentin expression in phenotypically normal renal cortical tubular cells in rats and humans, which do not usually express the intermediate filament protein vimentin, should be considered vimentin metaplasia. Vimentin expression is dissociated from increased cell proliferation in hyperplastic and neoplastic lesions, however. Instead the degree of dedifferentiation of the tubule cells and changes in phenotype were associated with vimentin expression.

[Clinical significance of antinuclear antibody in patients with idiopathic thrombocytopenic purpura]

The clinical significance of antinuclear antibodies (ANA) in patients with chronic idiopathic thrombocytopenic purpura (ITP) was evaluated. Serum samples of 55 patients with ITP without clinical features of systemic lupus erythematosus (SLE) were examined. The average follow-up period was 5.5 years. Positive ANA was found in 23 of the 55 patients. Twelve of these 23 showed a high-titer of ANA. There was no difference in platelet counts between ANA positive patients and negative patients, and there was no correlation between platelet counts and antibody titers. Ten of the 23 positive sera had precipitating antibodies to nuclear antigens; 7 SS-A and 3 RNP antibodies. The platelet counts of the 7 cases with anti-SS-A antibody positive were slightly low compared with those of the anti-SS-A antibody negative patients. None of the 10 patients developed SLE during the average follow-up period of 8.1 years. These results suggest that ITP patients who have a high-titer of ANA or antibody against SS-A do not always develop SLE. It was concluded that ANA with a high titer or precipitin to nuclear antigens, particularly SS-A, dose not predict a high risk of developing SLE in the future.

Synergism of environmental carcinogens and promoters on bladder cancer development initiated by N-butyl-N-(4-hydroxybutyl)nitrosamine in F344 rats

Synergistic or additive effects of combined treatments with carcinogens or promoters on N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-initiated rat bladder carcinogenesis were examined. Male F344 rats were given BBN as an initiator followed by low doses of 3 sodium salts (sodium bicarbonate, sodium L-ascorbate and sodium citrate) and/or 3 antioxidants (butylated hydroxyanisole, butylated hydroxytoluene and tertiary butylhydroxyquinone). Combined treatments with 3 sodium salts or 3 antioxidants, and especially all 6 chemicals together promoted bladder carcinogenesis. In addition, these combined treatments were associated with increased DNA synthesis of the bladder epithelium. Combined administration of the carcinogens, o-anisidine, p-cresidine, and 4-chloro-o-phenylenediamine at low doses also enhanced BBN-initiated bladder carcinogenesis. These results indicate that environmental carcinogens or promoters can exert synergistic or additive actions on bladder cancer induction.

Expression of the differentiated phenotype of chondrocyte in adjuvant induced arthritis of rat

Rat cartilage tissue was found to produce two types of proteoglycan monomers distinguished by density gradient centrifugation under dissociative condition and with different molecular size (PG I and PG II) as observed in cultured rabbit costal chondrocyte and human cartilaginous tissues. The incorporation of 35S-sulfate and distribution of the molecular size of proteoglycan (PG) were studied to determine the differentiated phenotypes of chondrocyte in adjuvant induced arthritis of rats. The cartilaginous tissue from the acute inflammatory phase shows a low incorporation of 35S-sulfate into PGs but produce the same hydrodynamic size as that of the control. After that acute phase the incorporation recovered suggesting of a repair phase. But in the chronic phase both the incorporation and the produced hydrodynamic size of PGs were severely alternated. With our method this paper shows the drastic alternation about the cartilaginous properties of rat chondrocytes under these circumstances.

Effects of splenectomy on immune thrombocytopenic purpura in (NZW x BXSB) F1 mice: analyses of platelet kinetics and anti-platelet antibody production

Effects of splenectomy on platelet kinetics and production of anti-platelet antibodies were studied in male (NZW x BXSB) F1 (W/B F1) mice, which are known as the animal model of immune thrombocytopenic purpura (ITP). Studies on organ localization of radiolabeled platelets revealed that splenic uptake significantly increases in W/B F1 mice in comparison with that of normal controls. W/B F1 mice showed a significant increase in platelet counts and, in contrast with sham-operated controls, high levels of platelet counts were maintained up to 6 weeks after splenectomy. Platelet lifespans (PLSs) did not reach normal levels, although prolonged PLSs were observed. In addition, platelet-associated antibody (PAA) values showed a tendency towards transient decrease, but there was no change in platelet-bindable serum antibodies (PBAs). These findings indicate that the suppression of anti-platelet antibody production is essential to the treatment of ITP; splenectomy may not be effective in treating severely affected ITP patients because, although the spleen is one of the major sites of platelet sequestration and antibody production, reticulo-endothelial systems (RESs) (liver, bone marrow, lymphnodes, etc.) other than the spleen are also responsible for the destruction of platelets. We therefore consider the W/B F1 mouse to be a useful model of human ITP, and believe that it provides valuable information for the development of new therapeutic agents in patients with ITP, especially those who do not respond to splenectomy.

The Arg-Gly-Asp (RGD) recognition site of platelet glycoprotein IIb-IIIa on nonactivated platelets is accessible to high-affinity macromolecules

We have characterized a murine IgG monoclonal antibody, OP-G2, specific for platelet glycoprotein (GP) IIb-IIIa (alpha IIb beta 3). OP-G2 Fab fragments inhibit fibrinogen-mediated platelet aggregation and competitively inhibit adenosine diphosphate-induced binding of 125I-fibrinogen to washed platelets. OP-G2 binding to GPIIb-IIIa is specifically inhibited by RGD-containing peptides but not the fibrinogen gamma-chain carboxy-terminal peptide, and OP-G2 Fab fragments, like RGD-containing peptides, alter the conformation of GPIIb-IIIa resulting in the expression of a ligand-induced binding site (LIBS) recognized by PMI-1. OP-G2 fails to bind to the recombinant Cam variant of GPIIb-IIIa (alpha III beta 3Cam) wherein an Asp119 to Tyr119 substitution in GPIIIa abrogates the ability to recognize RGD. These data indicate that OP-G2 recognizes an epitope at or in very close proximity to the RGD recognition site of GPIIb-IIIa and that, in every aspect tested, OP-G2 behaves like a macromolecular RGD ligand. Interestingly, two-color flow cytometry shows that OP-G2 IgG can bind to nonactivated platelets. Quantitative binding assays indicate that nonactivated platelets bind approximately 50,000 125I-OP-G2 molecules/platelet. Furthermore, the affinity of OP-G2 for platelets activated with thrombin is roughly fivefold higher (nonactivated, kd = 24.8 nmol/L; activated, kd = 4.9 nmol/L). These results suggest that the RGD recognition site of GPIIb-IIIa is available to macromolecules that contain RGD even on nonactivated platelets, provided that the affinity of the ligand is adequate.

Effects of aminoglycoside antibiotics on the auditory brainstem response and post rotatory nystagmus in rats

Effects of three aminoglycoside antibiotics, amikacin (AMK), tobramycin (TOB), and gentamicin (GM), on the auditory and vestibular functions were assessed in rats, the most frequently used species in toxicity studies. Chronic electrodes for auditory brainstem response (ABR) recording were implanted on the epidural surface, and those for post rotatory nystagmus (PRN) were implanted at the nictitating membrane and the outer canthus. AMK, TOB, and GM were given intramuscularly twice daily for 3-4 weeks at a daily dose of 350, 150, and 100 mg/kg, respectively. The amplitude of each wave of the ABR was decreased or disappeared in the groups treated with AMK, TOB, and GM. In the PRN, the duration of the nystagmus was decreased in the TOB group and completely lost in the GM group. No abnormality was observed in the PRN in the AMK group. These results were similar to those reported in the ototoxicity studies of these drugs in guinea pigs and indicate that ototoxicity can be evaluated in rats as successfully as in guinea pigs by this procedure.

[Efficacy of leukocyte-depleted platelet concentrates for prevention of HLA-alloimmunization in patients with frequent platelet transfusions: a prospective multi-institutional study using a polyester platelet filter]

A prospective multi-institutional study was conducted to assess the efficacy of leukocyte-depleted platelet concentrates, prepared by a method using a newly developed polyester filter, in the prevention of HLA-alloimmunization in patients with hematological disorders. Patients who were expected frequent platelet transfusions, were assigned into two groups, receiving either standard platelet concentrates (control group) or leukocyte-depleted platelet concentrates prepared through a polyester platelet filter, Sepacell-PL (filtered group). All patients received leukocyte-depleted red cell products. Of III patients enrolled, 72 were evaluable, 23 in the control and 49 in the filtered group. Both groups were comparable according to age, sex ratio, underlying disorders, previous exposure to alloantigens by transfusion and/or pregnancy. There was no statistically significant difference in the number and duration of transfusion in the two groups. There were significant differences in HLA-alloimmunization rate (9 cases out of 23, 39% in the control group versus 4 cases out of 49, 8% in the filtered group; p less than 0.01) and refractoriness to platelet transfusion from random donors (6 cases out of 23, 26% in the control group versus 2 cases out of 49, 4% in the filtered group; p less than 0.05). These results indicated that leukocyte-depleted platelet concentrates prepared through the polyester platelet filter are beneficial to reduce HLA-alloimmunization in patients with frequent platelet transfusions.

Lack of renal tumour-initiating activity of a single dose of potassium bromate, a genotoxic renal carcinogen in male F344/NCr rats

The renal tumour-initiating activity of potassium bromate (KBrO3), a known genotoxic rat renal carcinogen, was investigated in male F344/NCr rats. 6-wk-old rats were given KBrO3 intragastrically as a single dose of 300 mg/kg body weight, which was confirmed by our preliminary toxicity study as a maximum tolerated single dose for this strain of rat. Starting 2 wk after KBrO3 treatment, groups of 39 rats received either a basal diet or a diet containing 4000 ppm barbital sodium (BBNa) as a promoting regimen and were killed at 30, 52, or 104 wk. Control rats received either dietary BBNa (4000 ppm) or the basal diet alone from wk 2 to 52 or 104 wk. Nephropathy was observed in all rats treated with KBrO3 followed by BBNa at 30 wk and in rats receiving BBNa alone, but not in rats exposed to KBrO3 alone. Dysplastic renal tubular cell foci (DTF), putative preneoplastic renal tubular cell lesions were found associated with nephropathy in rats exposed to KBrO3 followed by BBNa from 47 wk. The incidences and multiplicities of DTF and renal tubular cell tumours observed from 31 to 104 wk revealed no initiating effect of KBrO3 treatment. These results indicate that the KBrO3 dose of 300 mg/kg did not initiate renal carcinogenesis.

Mechanisms of corticosteroid action in immune thrombocytopenic purpura (ITP): experimental studies using ITP-prone mice, (NZW x BXSB) F1

To determine the mechanism by which platelet counts increase after corticosteroid therapy for human immune thrombocytopenic purpura (ITP), we studied the platelet kinetics using prednisolone (PDN)-treated ITP-prone mice, (NZW x BXSB) F1 (W/B F1). An increase in platelet counts was observed in W/B F1 mice (n = 10, mean +/- SD, 1,202 +/- 202 x 10(3)/microL) 4 weeks after treatment with PDN (2 mg/kg/d); no increase occurred in nontreated W/B F1 mice (n = 5,651 +/- 126, P less than .005). Prolonged platelet life-spans (PLSs) were observed in treated W/B F1 mice (1.29 +/- 0.40 days), but not in nontreated controls (0.60 +/- 0.24 days, P less than .01). No increase in platelet production (platelet turnover) was found in PDN-treated W/B F1 mice, but significant decreases in platelet-associated antibodies (PAAs) and platelet-bindable serum antibodies (PBAs) were noted. Studies on organ localization of radiolabeled platelets showed that hepatic uptake significantly decreased in the treated W/B F1 mice, but not in nontreated W/B F1 mice. To elucidate the effect of PDN on the reticulo-endothelial phagocytic activity in W/B F1 mice, we studied in vivo clearance of IgG-sensitized, 51Cr-labeled autologous erythrocytes. W/B F1 mice treated with PDN showed a marked impairment of their ability to clear these cells, although PDN had little effect on the number of splenic or hepatic macrophage Fc gamma receptors. These results and our previous findings of splenectomy suggest that PDN improves platelet counts not only by suppressing systemic reticulo-endothelial phagocytic function but also by reducing antibody production.

Dose-dependent renal tubular toxicity of harman and norharman in male F344 rats

The renal toxicity of harman and norharman, administered for 2 or 4 weeks at dietary levels of 1,000, 500, or 0 parts per million (ppm), was investigated in 6-week-old male F344/DuCrj rats. Although rats fed 1,000 ppm harman or norharman, but not the 500 ppm level, demonstrated marked body weight retardation from 1 week to termination, no mortalities occurred. Marked elevation of water consumption was evident in rats given harman or norharman at 1,000 ppm, but not at 500 ppm, together with large increases in urine of low specific gravity. Urinary lysosomal enzymes (N-acetyl-beta-D-glucosaminidase, NAG, and lactate dehydrogenase, LDH) and sugar levels were increased, and the brush border enzymes (gamma-glutamyl transpeptidase, GGT, and alkaline phosphatase, ALP) decreased. Furthermore, serum biochemistry revealed clear elevation of parameters indicating renal toxicity in these rats. Histopathologically, rats fed 1,000 ppm harman or norharman, but not 500 ppm, demonstrated focal toxic renal degenerative/necrotic and regenerative lesions in proximal, distal, and collecting tubules. These changes were associated with a clearly increased labeling index (LI) of the nuclei of renal tubular epithelial cells on immunohistochemical staining for 5-bromo-2'-deoxyuridine (BrdU). Chemical specific crystal formation within tubular lumina was evident in rats fed 1,000 ppm, but not 500 ppm, this being considered the cause of the renal tubular lesions. It was concluded that harman and norharman exert renal toxicity at the dietary level of 1,000 ppm, but not 500 ppm, in male F344 rats.

[Anti-platelet antibody and platelet function]

The effect of anti-platelet antibodies, including murine monoclonal antibodies, autoantibodies and alloantibodies, on platelet function was analyzed. The target antigen of these antiplatelet antibodies, investigated in the present study, was a glycoprotein IIb/IIIa, which is a receptor of fibrinogen and plays an important role in platelet aggregation. Some of these antibodies inhibited agonist-induced platelet aggregation. The target antigen of one murine monoclonal antibodies, designated OP-G2, was a glycoprotein IIb/IIIa and interestingly, this antibody induced platelet aggregation, which required divalent cation and fibrinogen. We compared the epitope of these antibodies by inhibition assay and found the epitope of these antibodies to be very close. The binding of OP-G2 to the platelets required Ca2+. These data suggest that OP-G2 recognizes an epitope at or in very close proximity to the fibrinogen binding site of GPIIb/IIIa, as compared with other antibodies.

Impaired suppressor function of T cells induced by autologous mixed lymphocyte reaction in patients with idiopathic thrombocytopenic purpura

Autologous mixed lymphocyte reaction (AMLR)-induced suppressor function was studied in 12 patients with chronic idiopathic thrombocytopenic purpura (ITP). The function was found to be significantly impaired (20 +/- 55%; p less than 0.005) compared with normal subjects (69 +/- 25%). AMLRs in these patients were significantly decreased (p less than 0.05) compared with normal subjects. There was no significant correlation between AMLR-induced suppressor function and platelet counts. Nine patients were studied for AMLR-induced suppressor function before and after splenectomy. The platelet counts increased significantly as a result of splenectomy, but the AMLR-induced suppressor function showed no significant improvement. The results of this study suggest that suppressor dysfunction in ITP may be an immunologic defect irrespective of disease activity. We consider that this abnormality may reflect in vivo failure of the immunoregulatory (feedback) mechanism in ITP.