Single-stranded DNA from abutilon mosaic virus is present in the plastids of infected Abutilon sellovianum

The leaf mosaic of Abutilon sellovianum is caused by abutilon mosaic virus (AbMV), a geminivirus that has a circular single-stranded DNA genome. DNA was isolated from intact plastids of AbMV-infected and noninfected plants. Plastids from infected plants were shown to contain the single-stranded AbMV DNA by Southern-blot hybridization experiments that used a probe made from highly purified AbMV DNA. The possibility of adsorption of AbMV virions or viral DNA onto the plastid envelope was ruled out by several in vitro experiments with DNase I and protease. Furthermore, the lamellar system of plastids from AbMV-infected plants was degenerated and substituted by amorphous electron-dense material. The transport of AbMV DNA across the plastid envelope has implications for the development of a chloroplast transformation vector.     

Affinity purification of heparin-dependent antibodies to platelet factor 4 developed in heparin-induced thrombocytopenia: biological characteristics and effects on platelet activation

Antibodies to heparin platelet factor 4 (H-PF4) complexes were purified from the plasma of three patients with heparin-induced thrombocytopenia (HIT) using affinity chromatography. From each plasma, the largest amount of antibodies was eluted with 2 M NaCl at pH 7.5 (peak 1) and the remainder was obtained using 0.1 M glycine/0. 5 M NaCl at pH 2.5 (peak 2). In an enzyme-linked immunosorbent assay (ELISA), we then showed that each patient had developed antibodies to PF4 displaying different characteristics. In patient 1, peak 1 IgG reacted almost exclusively with H-PF4 complexes, whereas peak 2 IgG had similar reactivity with PF4 whether or not heparin was present. Patient 2 expressed a mixture of IgA, IgM and IgG and both fractions bound to PF4 alone or to H-PF4 complexes. Finally, IgG in patient 3 only bound to H-PF4 and was unreactive with PF4 alone. Using [14C]-serotonin release assays, the antibodies developed in the three patients and exhibiting the strongest ability to activate platelets with heparin were those having the highest affinity to H-PF4. These results strongly support the hypothesis that HIT antibodies to PF4 are heterogeneous regarding their affinity and specificity for target antigens and this may greatly influence their ability to activate platelets and their pathogenicity.     

Comparative tissue factor pathway inhibitor release potential of heparins.

Tissue factor pathway inhibitor (TFPI) is released following the administration of unfractionated heparin, low-molecular-weight heparins, defibrotide and PI-88. In this study, the comparative effects of heparin, a low-molecular-weight heparin-gammaparin and a heparin-derived oligosaccharide mixture-subeparin (C3) were studied on functional and immunologic tissue factor pathway inhibitor activity levels in a non-human primate (Macaca mulatta) model. The dose-dependent effect was studied following intravenous and subcutaneous administration. Following the administration of 1 mg/kg of heparin, gammaparin, and C3, the functional levels of TFPI at 5 minutes were 2.40, 2.56, and 1.08 U/mL and the corresponding TFPI immunologic levels were 4.3-, 4.0-, and 2.1-fold, increased, respectively, over the baseline value. From these results, it can be concluded that heparin and gammaparin produced similar levels of TFPI release. Hence, gammaparin and heparin have similar TFPI release potential despite their differences in molecular weight. The influence of molecular weight, charge density, and interactions with heparin cofactor II on TFPI release are also discussed.     

Unfractionated heparin compared with low-molecular-weight heparin as related to heparin-induced thrombocytopenia

PURPOSE OF REVIEW: Heparin-induced thrombocytopenia is a severe side effect of treatment with unfractionated heparin. The relation of low-molecular-weight heparin to heparin-induced thrombocytopenia is less well understood. This review will summarize what is known about the similarities and differences between thrombocytopenia induced by low-molecular-weight heparin and that induced by unfractionated heparin. RECENT FINDINGS: The pathophysiology of unfractionated heparin-induced thrombocytopenia, caused by the development of antibodies to heparin/platelet factor 4 complexes, holds true for low-molecular-weight heparin because the molecules of the latter are of the same saccharidic structure as those of unfractionated heparin. Owing to their smaller size, however, low-molecular-weight heparin does not interact with platelet factor 4 and platelets as efficiently as does unfractionated heparin. This translates to a two- to threefold lower risk of immune sensitization (antibody generation and occurrence of clinical heparin-induced thrombocytopenia). Low-molecular-weight heparin-induced thrombocytopenia antibodies are more often immunoglobulin A and immunoglobulin M, in contrast to the immunoglobulin G antibodies generated with unfractionated heparin-induced thrombocytopenia, which tend to be more often associated with clinical heparin-induced thrombocytopenia. The clinical expression of low-molecular-weight heparin-induced thrombocytopenia is generally similar to that of unfractionated heparin-induced thrombocytopenia but can have a slower onset, more severe thrombocytopenia, and slower platelet count recovery. Given that low-molecular-weight heparin, of itself, is linked with heparin-induced thrombocytopenia pathophysiology and it can interact with most preexisting heparin-induced thrombocytopenia antibodies generated after exposure to unfractionated heparin, treatment of heparin-induced thrombocytopenia patients with low-molecular-weight heparin is contraindicated. SUMMARY: The risk of the development of heparin-induced thrombocytopenia with low-molecular-weight heparin treatment is reduced relative to the frequency of unfractionated heparin-induced thrombocytopenia, but it is not eliminated, and platelet counts should be monitored with treatment.     

Pharmacodynamic considerations in the selection of dosage of tinzaparin for various indications: experimental studies in primates

Like unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs) are polypharmacologic agents that can modulate the hemostatic system at multiple points. Thus, to select an optimal dose of LMWH for a given indication, it is necessary to consider multiple actions of the drug. In this study, nonhuman primates were treated with intravenous or subcutaneous boluses of the LMWH tinzaparin or UFH. Doses were selected on the basis of the expected prophylactic (75 U/kg) and therapeutic (175 U/kg) dosing of tinzaparin. Blood samples were drawn periodically up to 24 hours after administration. Circulating anti-Xa and anti-thrombin (anti-IIa) activities determined using amidolytic assays were used to estimate plasma tinzaparin (heparin) concentrations. In addition, total tissue factor pathway inhibitor (TFPI) levels were measured in these primates. Subcutaneous administration of 75 U/kg tinzaparin resulted in plasma levels of approximately 0.2 to 0.3 U/mL, concentrations sufficient for DVT prophylaxis. Such drug levels were not associated with a significant release of TFPI. Intravenous administration of the same dose resulted in a peak drug level of approximately 1.5 anti-Xa U/mL. The elimination half-life was approximately 1 hour. Thus, intravenously administered tinzaparin may be useful for providing anticoagulation during coronary interventions. Subcutaneous administration of 175 U/kg resulted in tinzaparin levels of approximately 0.7 anti-Xa U/mL and a significant increase in TFPI levels. Interestingly, the increase in TFPI levels occurred over a different time frame than anticoagulant activity. Intravenous administration of 175 U/kg resulted in peak drug concentrations of almost 5 anti-Xa U/mL. The pharmacokinetic behavior of intravenously administered tinzaparin was comparable to that of UFH. The data show that the pharmacokinetic and pharmacodynamic effects measured using different assays widely differ. For a proper pharmacodynamic analysis, multiple assays should be considered, given that both UFH and LMWHs are polycomponent in nature.     

Deficiency of platelet membrane glycoprotein Ia associated with a decreased platelet adhesion to subendothelium: a defect in platelet spreading

A bleeding disorder with absent collagen-induced platelet aggregation and adhesion has been described in a patient whose platelets failed to express surface glycoprotein Ia. We studied the interaction of her platelets with subendothelium in an annular perfusion chamber and the interaction with purified human collagen type III in a rectangular perfusion system under flow conditions. Platelet adherence was almost completely absent both at low and high shear rates. The few platelets which adhered remained in the contact stage without subsequent spreading and aggregate formation. Addition of a monoclonal antibody, which was directed against the von Willebrand moiety of FVIII-VWF, to the blood, completely abolished platelet adherence at high shear rates and had a partial effect at low shear rates. These data indicate that von Willebrand factor plays a role in the initial attachment (contact stage) of platelets to subendothelium. We conclude that the bleeding disorder and excessively prolonged bleeding time in our patient are caused by a new specific defect of the platelet-vessel wall interaction.     

Infectious pathogens and risk of esophageal,gastric and duodenal cancers and ulcers in China: A case-cohort study

Infection by certain pathogens is associated with cancer development. We conducted a case-cohort study of ~2500 incident cases of esophageal, gastric and duodenal cancer, and gastric and duodenal ulcer and a randomly selected subcohort of ~2000 individuals within the China Kadoorie Biobank study of >0.5 million adults. We used a bead-based multiplex serology assay to measure antibodies against 19 pathogens (total 43 antigens) in baseline plasma samples. Associations between pathogens and antigen-specific antibodies with risks of site-specific cancers and ulcers were assessed using Cox regression fitted using the Prentice pseudo-partial likelihood. Seroprevalence varied for different pathogens, from 0.7% for Hepatitis C virus (HCV) to 99.8% for Epstein–Barr virus (EBV) in the subcohort. Compared to participants seronegative for the corresponding pathogen, Helicobacter pylori seropositivity was associated with a higher risk of non-cardia (adjusted hazard ratio [HR] 2.73 [95% CI: 2.09–3.58]) and cardia (1.67 [1.18–2.38]) gastric cancer and duodenal ulcer (2.71 [1.79–4.08]). HCV was associated with a higher risk of duodenal cancer (6.23 [1.52–25.62]) and Hepatitis B virus was associated with higher risk of duodenal ulcer (1.46 [1.04–2.05]). There were some associations of antibodies again some herpesviruses and human papillomaviruses with risks of gastrointestinal cancers and ulcers but these should be interpreted with caution. This first study of multiple pathogens with risk of gastrointestinal cancers and ulcers demonstrated that several pathogens are associated with risks of gastrointestinal cancers and ulcers. This will inform future investigations into the role of infection in the etiology of these diseases.     

Epidemiology of dermatomycoses of humans in central Poland. Part I--Superficial infections caused by yeasts and moulds.

This work presents the epidemiology of dermatomycoses and their etiological agents of people living in the ?ód? region, Central Poland, over the years 1987–1996. The analysis involved subjects referred by physicians to three major mycological laboratories in ?ód? (covering the entire mycological diagnostics of the ?ód? region). The study comprised a total of 25 737 persons aged 1–82. Positive results of mycological examinations were obtained for 14 084 (54.7%) patients. The total number of 14 295 positive mycological results included 6902 (48.3%) isolations of non-dermatophyte fungi. The non-dermatophytes included: Candida-like (69.8%), moulds (26.9%) and lipophilic yeasts (3.3%). The distribution of non-dermatophytes was characterized by dependence on sociodemographic features such as subjects’ age, place of residence, education and occupation. Candida-like fungi are etiological factors of superficial infections of all clinical types whereas moulds were found to cause infections of finger and toe nails and periungual walls.     

Epidemiology of dermatomycoses of humans in Central Poland. Part II--Non-dermatophyte infections of nails and periungual walls.

This study presents the epidemiology of dermatomycoses and their etiological agents of people living in the ?ód? region, Central Poland, over the years 1987–1996. The study comprised a total of 25 737 patients. Positive mycological results were obtained for 14 084 patients (54.7%). The total number of 14 295 of positive mycological results included 6902 (48.3%) isolations of non-dermatophyte fungi. Among these positive results, isolations from subjects with infections of nails and periungual walls amounted to 2034 (29.5%). Candida albicans (59.9%) and Aspergillus sp. (17.3%) were major etiological factors of those infections. The decade in question was marked by a steady growth in incidence of the infections studied, especially over the years 1994–1996.