RESUMO
BACKGROUND: Sorafenib (Sor) is acknowledged as a standard therapy for advanced hepatocellular carcinoma (HCC). This trial was conducted to evaluate the effect of addition of hepatic arterial infusion chemotherapy with cisplatin (SorCDDP) to Sor for the treatment of advanced HCC. PATIENTS AND METHODS: We conducted a multicenter open-labeled randomized phase II trial in chemo-naïve patients with advanced HCC with Child-Pugh scores of 5-7. Eligible patients were randomly assigned 2:1 to receive SorCDDP (sorafenib: 400 mg bid; cisplatin: 65 mg/m2, day 1, every 4-6 weeks) or Sor (400 mg bid). The primary end point was overall survival. RESULTS: A total of 108 patients were randomized (Sor, n = 42; SorCDDP, n = 66). The median survival in the Sor and SorCDDP arms were 8.7 and 10.6 months, respectively [stratified hazard ratio (95% confidence interval), 0.60 (0.38-0.96), P = 0.031]. The median time to progression and the response rate were, respectively, 2.8 months and 7.3% in the Sor arm and 3.1 months and 21.7% in the SorCDDP arm. The adverse events were more frequent in the SorCDDP arm than in the Sor arm, but well-tolerated. CONCLUSION: SorCDDP yielded favorable overall survival when compared with Sor in patients with advanced HCC. CLINICAL TRIAL REGISTRATION: UMIN-CTR (http://www.umin.ac.jp/ctr/index-j.htm), identification number: UMIN000005703.
Assuntos
Carcinoma Hepatocelular/tratamento farmacológico , Cisplatino/administração & dosagem , Neoplasias Hepáticas/tratamento farmacológico , Niacinamida/análogos & derivados , Compostos de Fenilureia/administração & dosagem , Adulto , Idoso , Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Carcinoma Hepatocelular/patologia , Intervalo Livre de Doença , Feminino , Humanos , Estimativa de Kaplan-Meier , Neoplasias Hepáticas/patologia , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Niacinamida/administração & dosagem , Sorafenibe , Resultado do TratamentoRESUMO
In order to create Fe2O3 and Fe2O3·H2O nanoparticles, various polymers were used as dispersing agents, and the resulting effects on the dispersibility and nanoparticulation of the iron oxides were evaluated. It was revealed that not only the solution viscosity but also the molecular length of the polymers and the surface tension of the particles affected the dispersibility of Fe2O3 and Fe2O3·H2O particles. Using the dispersing agents 7.5% hydroxypropylcellulose-SSL, 6.0% Pharmacoat 603, 5.0% and 6.5% Pharmacoat 904 and 7.0% Metolose SM-4, Fe2O3 nanoparticles were successfully fabricated by wet milling using Ultra Apex Mill. Fe2O3·H2O nanoparticles could also be produced using 5.0% hydroxypropylcellulose-SSL and 4.0 and 7.0% Pharmacoat 904. The index for dispersibility developed in this study appears to be an effective indicator of success in fabricating nanoparticles of iron oxides by wet milling using Ultra Apex Mill.
RESUMO
BACKGROUND AND OBJECTIVE: The gram-negative anaerobe Porphyromonas gingivalis has been implicated as an important pathogen in the development of adult periodontitis, and its colonization of subgingival sites is critical in the pathogenic process. We previously identified a 35 kDa surface protein (hemin binding protein 35; HBP35) from P. gingivalis that exhibited coaggregation activity, while additional analysis suggested that this protein possessed an ability to bind heme molecules. For development of passive immunotherapy for periodontal diseases, human-type monoclonal antibodies have been prepared using HBP35 as an antigen in TransChromo mice. In the present study, we focused on a single antibody, TCmAb-h13, which is known to inhibit heme binding to recombinant HBP35. The aim of our investigation was to clarify the redox-related function of HBP35 and consider the benefits of human-type monoclonal antibodies. MATERIAL AND METHODS: To examine the antigen recognition capability of TCmAbs with immunoblotting and Biacore techniques, we used the native form as well as several Cys-to-Ser variants of recombinant HBP35. RESULTS: We found that the redox state of recombinant HBP35 was dependent on two Cys residues, (48) C and (51) C, in the thioredoxin active center (WCGxCx). Furthermore, TCmAb-h13 recognized the reduced forms of recombinant HBP35, indicating its inhibitory effect on P. gingivalis growth. CONCLUSION: Hemin binding protein 35 appears to be an important molecule involved in recognition of the redox state of environmental conditions. In addition, TCmAb-h13 had an inhibitory effect on heme binding to recombinant HBP35, thereby interfering with P. gingivalis growth.
Assuntos
Anticorpos Monoclonais Humanizados/imunologia , Proteínas de Bactérias/imunologia , Proteínas de Transporte/imunologia , Hemeproteínas/imunologia , Imunização Passiva/métodos , Porphyromonas gingivalis/crescimento & desenvolvimento , Substituição de Aminoácidos , Animais , Anticorpos Monoclonais Humanizados/química , Proteínas de Transporte/química , Cisteína , Proteínas Ligantes de Grupo Heme , Hemeproteínas/química , Hemina/metabolismo , Humanos , Camundongos , Camundongos Transgênicos , Porphyromonas gingivalis/química , Porphyromonas gingivalis/imunologia , Ligação Proteica/imunologia , Estrutura Terciária de Proteína , Serina , Tiorredoxinas/química , Fatores de Virulência/imunologiaRESUMO
Ovarian stromal hyperthecosis is characterized by diffuse distribution of luteinized stromal cells accompanied by varying degrees of stromal hyperplasia. We report a case of ovarian stromal hyperthecosis with particular regard to magnetic resonance (MR)-pathologic correlation. At initial MR imaging, the central areas of the bilateral ovarian masses showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images, while the peripheries of the bilateral masses showed isointensity to myometrium on T1-weighted images and heterogeneous signal intensities on T2-weighted images. At 15 days after the initial MR imaging examination, a second MR imaging demonstrated shrinkage of the bilateral ovarian masses. Change in the peripheries to predominantly isointensity to myometrium on the T2-weighted images was also observed. The patient underwent bilateral oophorectomy. Microscopic examination revealed scattered nests of lutein cells on a background of densely proliferated ovarian stroma with minimal collagen production in both ovaries. Edema was occasionally seen in the outer portion but was marked in the central zone of the ovaries, particularly on the left. The final pathologic diagnosis was stromal hyperthecosis. With regard to MR-pathologic correlation, the MR findings in the peripheries of the bilateral masses (isointensity relative to myometrium on both T1- and T2-weighted imaging) showed the characteristics of stromal hyperthecosis.
Assuntos
Imageamento por Ressonância Magnética/métodos , Ovário/patologia , Células Estromais/patologia , Meios de Contraste , Feminino , Humanos , Hiperplasia/patologia , Pessoa de Meia-Idade , Ovariectomia , Ovário/cirurgiaRESUMO
BACKGROUND: Host genetic factors may play a key role in determining the long-term outcome of the Helicobacter pylori infection. Toll like receptor 4(TLR4) and CD14-mediated recognition of lipo-polysaccharide (LPS) is required for efficient recognition of Gram-negative bacterial infections. AIMS: We investigated the effects of common polymorphisms of TLR4 Asp299Gly, Thr399Ile and CD14 promoter -C159T on the risk of gastric cancer including its subtypes and clinicopathologic features. We also investigated the effects of these polymorphisms on histologic degree of H. pylori induced gastritis. SUBJECTS: The study was performed in 149 gastric cancer (GC) cases [mean age 64.0 +/- 12.4, M:F = 109:40] and 94 patients without evidence of GC (mean age 64.1 +/- 12.3, M:F = 65:25, Peptic ulcer diseases = 43.6%, gastritis = 56.4%) as the control group. METHODS: TLR4 Asp299Gly, Thr399Ile and CD14 promoter -C159T were determined by PCR-RFLP in all the patients. Gastritis scores of non-cancerous gastric mucosa were assessed according to the updated Sydney system in H. pylori-positive subjects (n = 174). RESULTS: The frequencies of CD14-260 TT and T carrier were significantly lower in patents with intestinal type gastric cancer than in controls (OR = 0.31;95% CI = 0.12-0.78, OR = 0.38; 95% CI = 0.18-0.81, respectively) Compared with patients older than 61 years, the atrophy score in antrum was significantly lower in TT and CT patients. TLR4 Asp299Gly, Thr399Ile were not detected in all the patients. CONCLUSION: Our data suggest that CD14 promoter-159TT and T carrier were associated with lower risk of developing gastric mucosal atrophy in H. pylori infected patients more than 61 years of age, and these genotypes may reduce the risk of intestinal type gastric cancer and TLR4 Asp299Gly, Thr399Ile are very rare in the Japanese population.
Assuntos
Receptores de Lipopolissacarídeos/genética , Polimorfismo Genético , Neoplasias Gástricas/genética , Receptor 4 Toll-Like/genética , Adulto , Idoso , Feminino , Gastrite/etiologia , Gastrite/genética , Genótipo , Infecções por Helicobacter/complicações , Helicobacter pylori , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Risco , Neoplasias Gástricas/etiologiaRESUMO
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers apoptosis in tumor cells without toxicity to normal cells, but some recombinant versions of TRAIL caused hepatocyte death. We generated fully human monoclonal antibodies (mAbs) that bind specifically to TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2), which mediate apoptosis signal when they ligate with TRAIL, to investigate the contribution of each receptor to induce tumor cell apoptosis and hepatocyte toxicity. All of mAbs to TRAIL-R1 and TRAIL-R2 induced cell death in several cancer cell lines susceptible to TRAIL but not in human umbilical vein endothelial cells in vitro. Both anti-TRAIL-R1 mAbs and anti-TRAIL-R2mAbs also caused cell death in hepatocytes. However, a subset of mAbs to TRAIL-R2, which was characterized by the TRAIL blocking activity, did not show strong hepatocyte toxicity. These results indicate that human normal hepatocytes are susceptible to both TRAIL-R1- and TRAIL-R2-mediated apoptosis signal. Cell Death and Differentiation (2004) 11, 203-207. doi:10.1038/sj.cdd.4401331 Published online 24 October 2003
Assuntos
Apoptose , Hepatócitos/citologia , Hepatócitos/metabolismo , Receptores do Fator de Necrose Tumoral/metabolismo , Transdução de Sinais , Animais , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/toxicidade , Caspases/metabolismo , Linhagem Celular Tumoral , Citometria de Fluxo , Humanos , Camundongos , Camundongos Transgênicos , Receptores do Ligante Indutor de Apoptose Relacionado a TNF , Receptores do Fator de Necrose Tumoral/antagonistas & inibidores , Receptores do Fator de Necrose Tumoral/imunologiaRESUMO
Although various cytokines, growth factors, and chemokines are known to regulate hematopoiesis, expansion of hematopoietic stem cells (HSCs) in vitro with the use of such agents has proved problematic. Stromal cells are major components of the microenvironment that surrounds hematopoietic cells and are thought to play an important role in hematopoiesis in vivo. Co-culture of HSCs with stromal cells promotes hematopoiesis and self-renewal of HSCs. Definitive hematopoietic cells first appear during mammalian embryonic development in the aorta-gonad-mesonephros (AGM) region, and it is therefore thought that the microenvironment of this region plays an important role in HSC ontogeny. We have adopted two approaches to studying the contribution of the AGM microenvironment to hematopoiesis. In the first approach, we have developed an in vitro culture system for mouse AGM explants. Hematopoiesis is enhanced in such cultures by the presence of the combination of stem cell factor (SCF), basic fibroblast growth factor, leukemia inhibitory factor, and oncostatin M (SFLO culture). However, transplantation assays revealed that HSCs capable of long-term reconstitution of the hematopoietic compartment of irradiated mice (LTR-HSCs) do not expand in AGM-SFLO cultures; rather, these cultures appear to provide a favorable microenvironment for hematogenic angioblasts that are precursors of both endothelial and hematopoietic cells. In our second approach, we have established various stromal cell lines from the mouse AGM region. The AGM-S3 cell line supports human and mouse primitive hematopoietic cells as well as mouse LTR-HSCs. Maintenance of LTR-HSCs is mediated by a mechanism other than SCF signaling through its receptor (c-Kit). These two in vitro approaches should prove useful for further elucidation of the mechanisms that underlie hematopoiesis and HSC self-renewal.
Assuntos
Aorta/embriologia , Técnicas de Cocultura/métodos , Gônadas/embriologia , Hematopoese/fisiologia , Interleucina-6 , Mesonefro/crescimento & desenvolvimento , Células Estromais/fisiologia , Animais , Comunicação Celular , Linhagem Celular , Células Cultivadas , Ensaio de Unidades Formadoras de Colônias , Fator 2 de Crescimento de Fibroblastos/farmacologia , Sobrevivência de Enxerto , Inibidores do Crescimento/farmacologia , Hematopoese/efeitos dos fármacos , Transplante de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/efeitos dos fármacos , Humanos , Fator Inibidor de Leucemia , Linfócitos/citologia , Linfocinas/farmacologia , Camundongos , Células Mieloides/citologia , Oncostatina M , Técnicas de Cultura de Órgãos , Peptídeos/farmacologia , Quimera por Radiação , Fator de Células-Tronco/farmacologiaAssuntos
Trombocitemia Essencial/sangue , Trombopoetina/sangue , Criança , Feminino , Humanos , Contagem de PlaquetasRESUMO
Complementary DNAs encoding a previously unidentified mouse Notch ligand and its human ortholog were isolated. The new Notch ligand contains a signal sequence, a DSL domain, eight epidermal growth factor-like repeats, a transmembrane domain, and an intracellular region, all of which are characteristics of members of the Delta protein family. The new protein was therefore designated Delta-4. Several previously unidentified sequences in both the extracellular and intracellular regions were shown to be conserved among vertebrate Delta proteins. The tissue distribution of Delta-4 mRNA resembles that previously described for Notch-4 (Int-3) transcripts. However, in situ hybridization with mouse lung revealed that Delta-4 mRNA is abundant in squamous alveolar cells that neighbor endothelial cells; Notch-4 expression is largely restricted to the latter cell type. Soluble forms of the extracellular portion of Delta-4 inhibit the apparent proliferation of human aortic endothelial cells, but not human pulmonary arterial endothelial cells.
Assuntos
Proteínas Sanguíneas/genética , Substâncias de Crescimento/genética , Peptídeos e Proteínas de Sinalização Intercelular , Proteínas Proto-Oncogênicas/química , Receptores de Superfície Celular , Proteínas Adaptadoras de Transdução de Sinal , Sequência de Aminoácidos , Animais , Proteínas Sanguíneas/química , Proteínas Sanguíneas/classificação , Proteínas Sanguíneas/farmacologia , Proteínas de Ligação ao Cálcio , Divisão Celular/efeitos dos fármacos , Clonagem Molecular , DNA Complementar/análise , Endotélio/citologia , Endotélio/efeitos dos fármacos , Endotélio Vascular/citologia , Endotélio Vascular/efeitos dos fármacos , Substâncias de Crescimento/química , Substâncias de Crescimento/classificação , Substâncias de Crescimento/farmacologia , Humanos , Hibridização In Situ , Camundongos , Dados de Sequência Molecular , Filogenia , Receptor Notch4 , Receptores Notch , Análise de Sequência de Proteína , Homologia de Sequência de Aminoácidos , SolubilidadeRESUMO
Thrombopoietin (TPO) is a cytokine that primarily stimulates megakaryocytopoiesis and thrombopoiesis. TPO has a unique C-terminal tail peptide of about 160 amino acids that consists mostly of hydrophilic residues and contains six N-linked sugar chains. In order to investigate the biological function of the C-terminal domain, two series of mutations were performed. One is systematic truncation from the C terminus. Another is elimination of N-glycosylation sites in the C-terminal domain by Asn to Gln mutations. After the mutant proteins were expressed by mammalian cells, it was found that the elimination of the N-linked sugar sites did not affect the biological activity, whereas truncation of the C-terminal domain resulted in elevation of in vitro activity up to 4-fold. The C-terminal peptide itself was found to inhibit the in vitro activity. Moreover, both the C-terminal truncation and the elimination of the N-glycosylation sites decreased the secretion level progressively down to (1)/(10) that of wild type, and the amount of the mutant left in the cell increased. The N-glycosylation in the C-terminal region was found to be important for secretion of TPO. Among six N-glycosylation sites in the C-terminal region, two locations, Asn-213 and Asn-234, were found to be critical for secretion, and two other locations, Asn-319 and Asn-327, did not affect the secretion.
Assuntos
Trombopoetina/fisiologia , Animais , Asparagina/química , Asparagina/genética , Western Blotting , Células COS , Ensaio de Imunoadsorção Enzimática , Glutamina/química , Glutamina/genética , Glicosilação , Humanos , Mutagênese Sítio-Dirigida , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Relação Estrutura-Atividade , Trombopoetina/química , Trombopoetina/genéticaRESUMO
A 48-year-old man with a history of hypertension and diabetes mellitus was hospitalized with sudden onset of severe chest pain. He was in cardiogenic shock with a systolic pressure of 60 mm Hg. His electrocardiogram (ECG) showed ST-segment elevation in the precordial leads suggestive of acute anteroseptal myocardial infarction. The ST-segment returned to baseline after the systolic blood pressure rose to 100 mm Hg with the administration of sympathomimetic agents. Aortography and transesophageal echocardiography demonstrated type A aortic dissection and aortic regurgitation. Aortography and short-axis transesophageal echocardiography showed during diastole almost complete collapse of the true lumen of the ascending aorta caused by the intimal flap. The patient underwent surgical repair of the aortic dissection and implantation of Palmaz stents in the carotid arteries. Decreased blood pressure and the presence of aortic regurgitation accelerated the collapse of the true lumen during diastole in the ascending aorta, resulting in functional obstruction of the left main coronary artery, which may have been related to ST-segment changes in this case.
Assuntos
Dissecção Aórtica/etiologia , Dissecção Aórtica/fisiopatologia , Doença das Coronárias/complicações , Doença das Coronárias/fisiopatologia , Eletrocardiografia , Dissecção Aórtica/cirurgia , Insuficiência da Valva Aórtica/etiologia , Insuficiência da Valva Aórtica/fisiopatologia , Pressão Sanguínea , Doença das Coronárias/cirurgia , Humanos , Masculino , Pessoa de Meia-Idade , Isquemia Miocárdica/etiologia , Isquemia Miocárdica/fisiopatologia , StentsRESUMO
Serum thrombopoietin (TPO) levels in 50 essential thrombocythemia (ET) patients were measured using a highly sensitive sandwich ELISA. In nine cases, TPO levels were measured at two points with different platelet counts. ET patients showed significantly higher serum TPO levels (n = 59, 2.70 +/- 2.74 fmol/mL, P < 0.0001) than those of normal individuals (n = 29, 0.83 +/- 0.36 fmol/mL). Twenty-three previously untreated ET patients also showed significantly higher serum TPO levels (1.33 +/- 0.75 fmol/mL, P = 0.0066) than normal individuals. Extremely high serum TPO levels (5.46 +/- 3.68 fmol/mL) were observed in ET patients with normal platelet counts. Furthermore, a strong inverse correlation was found between serum TPO levels and platelet counts in ET patients (R = -0.729, P < 0. 0001). This inverse correlation also held for each of nine cases with two-point TPO measurements. In the clinical course of ET, megakaryocyte mass may parallel the platelet mass before and after chemotherapy. Although it is unknown whether overproduction of TPO exists or not in ET, total platelet and megakaryocyte mass, i.e., the total number of c-Mpl, may play a role to regulate serum TPO levels.
Assuntos
Contagem de Plaquetas , Trombocitemia Essencial/sangue , Trombopoetina/sangue , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Radiation therapy is a powerful method for the control of cancer. The utilization of abdominal or pelvic radiation has been extended, and the incidence of radiation enteritis appears to be increasing. The majority of the induced lesions is in the distal ileum, sigmoid colon, or rectum. Reported here is an unusual case of radiation enteritis which caused a severe sequelae of stricture in the transverse colon as a long-term effect of therapeutic irradiation for uterine cancer, and required a surgical resection.
Assuntos
Colite Ulcerativa/etiologia , Complicações Pós-Operatórias/etiologia , Lesões por Radiação/etiologia , Radioterapia Adjuvante/efeitos adversos , Radioterapia de Alta Energia/efeitos adversos , Neoplasias do Colo do Útero/radioterapia , Dor Abdominal/etiologia , Anastomose Cirúrgica , Anti-Inflamatórios não Esteroides/uso terapêutico , Colite Ulcerativa/tratamento farmacológico , Colite Ulcerativa/cirurgia , Terapia Combinada , Constrição Patológica/tratamento farmacológico , Constrição Patológica/etiologia , Constrição Patológica/cirurgia , Feminino , Febre/etiologia , Hemorragia Gastrointestinal/etiologia , Humanos , Histerectomia , Melena/etiologia , Pessoa de Meia-Idade , Ovariectomia , Lesões por Radiação/tratamento farmacológico , Lesões por Radiação/cirurgia , Pneumonite por Radiação/etiologia , Sulfassalazina/uso terapêutico , Neoplasias do Colo do Útero/cirurgiaRESUMO
A rare case of an aneurysmal bone cyst (ABC) involving the right coronoid process of the mandible in a 12-year-old girl is presented. The characteristic features with fluid-fluid levels within the lesion observed on Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) was helpful in the preoperative diagnosis.
Assuntos
Cistos Ósseos Aneurismáticos/diagnóstico por imagem , Doenças Mandibulares/diagnóstico por imagem , Cistos Ósseos Aneurismáticos/patologia , Criança , Feminino , Humanos , Imageamento por Ressonância Magnética , Doenças Mandibulares/patologia , Tomografia Computadorizada por Raios XRESUMO
Three patients with liver cirrhosis (LC) and a bleeding tendency due to marked thrombocytopenia of less than 20 x 10(9)/l were admitted to our hospital for further examination. Bone marrow examination revealed megakaryocytic hypoplasia in all three patients. All patients exhibited amegakaryocytic thrombocytopenic purpura, myelodysplastic syndrome, or bone marrow hypoplasia. 111In-labeled platelet kinetic studies revealed decreased platelet production in all patients. Although serum thrombopoietin (sTPO) levels are usually within the normal level in patients with LC, the sTPO levels of our patients were about 10 times higher than the levels of normal subjects (1.22 +/- 0.37 fmol/ml): 13.34, 16.79, and 10.46 fmol/ml, respectively. These sTPO data supported our findings of decreased megakaryopoiesis. Our findings suggest that examination of sTPO levels is useful in determining the etiology of marked thrombocytopenia in LC patients.
Assuntos
Cirrose Hepática/complicações , Trombocitopenia/etiologia , Trombopoetina/sangue , Plaquetas/fisiologia , Medula Óssea/patologia , Feminino , Humanos , Hiperplasia , Cirrose Hepática/fisiopatologia , Masculino , Megacariócitos , Pessoa de Meia-IdadeRESUMO
Thrombopoietin (TPO) isolated from thrombocytopenic plasma of various animal species has previously been shown to comprise only truncated forms of the molecule, presumably generated by proteolysis. Native TPO has now been partially purified from normal human plasma by immunoaffinity chromatography and was confirmed to be biologically active. Gel filtration in the presence of SDS revealed that TPO eluted in two peaks: a major peak corresponding to the elution position of fully glycosylated recombinant human TPO (rhTPO) consisting of 332 amino acid residues, and a minor peak corresponding to a smaller molecular size. Immunoblot analysis also revealed that most plasma-derived TPO migrated at the same position as fully glycosylated rhTPO, corresponding to a molecular size of approximately 80 to 100 kDa. Furthermore, the size distribution of circulating TPO in patients with various haematologic disorders did not differ markedly from that of plasma-derived TPO from healthy individuals. These results indicate that the truncation of circulating TPO is not related to disease pathophysiology, and that the predominant form of TPO in blood is a biologically active approximately 80- to 100-kDa species. The size distribution of TPO extracted from normal platelets was similar to that of TPO in plasma; the proportion of truncated TPO was decreased by prior incubation of platelets with hirudin. indicating that the endogenous truncated TPO, at least in platelet extract, was generated by thrombin-mediated cleavage.