Abnormality of the N-terminal portion of von Willebrand factor in type IIA and IIC von Willebrand disease

We have established a new analytical method which allows the characterization of von Willebrand factor (vWF) degradation fragments in minute amounts (10 microliters) of plasma, without the need for immunopurification of vWF. Plasma vWF was hydrolysed by S aureus V-8 protease (V-8 protease) and the cleaved fragments separated by SDS-agarose gel electrophoresis followed by staining with 125I-labeled polyclonal or monoclonal antibodies against vWF and autoradiography. Quantification of the amount of each product was estimated by counting the incorporated radioactivity following excision. V-8 protease limitedly hydrolysed vWF in normal as well as type I von Willebrand disease (vWD) plasma and produced two distinct fragments with identical electrophoretic and antigenic characteristics to those produced from purified vWF, i.e. a C-terminal SpII and a series of N-terminal SpIII fragments (SpIIIa, b and c). The method was applied to further characterize the molecular abnormalities of vWF in eighteen patients with type II vWD. In seven individuals with type IIA and five patients with type IIC, SpIII appeared significantly modified as compared to normal. In type IIA, there was a marked decrease or absence of SpIIIa and an increase of SpIIIb and c. In type IIC, SpIIIb was lacking. In three patients with type IIB and in three patients with type IID, there was no significant modification of SpIII. In all cases, SpII was apparently not modified. In conclusion, the molecular abnormality of vWF in type IIA and IIC vWD appears to reside in SpIII, the N-terminal portion of the vWF-subunit (residues 1 to 1,365).     

Comparison of tryptic fragments of von Willebrand factor involved in binding to thrombin-activated platelets with fragments involved in ristocetin-induced binding and binding to collagen

Previously we have studied the binding domains on von Willebrand factor (vWF) involved in ristocetin-induced binding to platelets (ristocetin binding domain, RBD) and in the binding of vWF to collagen (collagen binding domain, CBD) using tryptic fragments of 125I-labelled vWF (21, 23). We have also reported on the RBD, CBD and the domain on vWF involved in the binding to thrombin activated platelets (thrombin binding domain, TBD) using vWF-fragments prepared by digestion with staphylococcal protease V8 (25). In the present study, we have digested 125I-vWF with TPCK-trypsin and we have performed at various times of digestion immuno-precipitation with Mab 9, the antibody inhibiting binding of vWF to thrombin activated platelets. The data were compared with the immunoprecipitation patterns simultaneously obtained with CLB-RAg 35 which inhibits binding of vWF in the presence of ristocetin and with CLB-RAg 201, which inhibits binding of vWF to collagen. At 90 min, Mab 9 and CLB-RAg 201 precipitated similar high molecular weight bands, whereas CLB-RAg 35 precipitated bands at 180 and 120 kDa. After 24 h, Mab 9 precipitated bands at 200, 155, 116 and 85 kDa; CLB-RAg 201 precipitated a band at 48 kDa and CLB-RAg 35 a band at 116 kDa. Two-dimensional electrophoresis demonstrated that the high molecular weight bands, precipitated by Mab 9 and CLB-RAg 201 at 90 min, were identical. The 116 kDa fragment recognized by CLB-RAg 35 had a different subunit composition than the 116 kDa fragment precipitated by Mab 9.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growing Ignorance of COVID-19 Preventive Measures in Ethiopia: Experts' Perspective on the Need of Effective Health Communication Strategies

Despite the recent surge of COVID-19 infections in Ethiopia, we are observing a profound ignorance of preventive measures by the general public and leaders at different levels. This is presenting considerable challenges in the effort to contain and control the pandemic. We believe that the current health communication approach implemented by the health authorities and media outlets need to be redesigned to bring a sustainable COVID-19 preventive behavior. The purpose of this perspective paper, therefore, is to stimulate discussions on effective health communication strategy to help the public persistently practice COVID-19 preventive measures over the long term. We undertook a series of discussions amongst the authors in order to synthesize individual viewpoints into ‘experts'' perspective’ driven by our daily observations and our expertise in the health service research. In light of this, we suggested that an effective health communication strategy need to address context specific situations to avoid temptation to ignore the ramifications of this very serious pandemic. This strategy includes trying to make sense of daily reported COVID-19 cases, being highly selective regarding sources of information, and being sensitive and responsive to religious and cultural factors. The media, health professionals, and leaders need to teach us how to live with the pandemic informed by robust scientific sources.     

Levels and Trophic Transfer of Selected Pesticides in the Lake Ziway Ecosystem

The levels of 30 selected pesticides and trophic biomagnification of DDT were investigated in biota samples of the Lake Ziway in the Rift valley region, Ethiopia. Carbon source and trophic position were calculated by using ¹³C and ¹⁵N stable isotopes, individually, and trophic magnification factors (TMFs) were inferred. Only DDT and its metabolites were quantified in all samples analyzed. The most prominent metabolite was p,p?-DDE with mean concentration ranging from the 0.82–33.69 ng g^?1 lipid weight. Moreover, the ratio of DDT/DDD?+?DDE in all the biota samples was less than 1 signifying historical DDT application. Regression of log [ΣDDT] vs TL (trophic level) among all biota species showed a significant correlation, indicating that DDTs are biomagnifying along with the food web of Lake Ziway with an estimated TMF of 2.75. The concentrations of DDTs and other organochlorine pesticides found in biota from Lake Ziway were, in general, lower than studies found in previous studies carried out in the same lake.

     

Musculoskeletal problems and associated risk factors among health science students in Ethiopia: a cross-sectional study

Journal of Public Health - Musculoskeletal disorders (MSDs) are the most common cause of severe long-term pain and physical disability. High prevalence of musculoskeletal pain among medical and...     

The Differential Effects of an Opt-Out HIV Testing Policy for Pregnant Women in Ethiopia When Accounting for Stigma: Secondary Analysis of DHS Data

Individual factors associated with HIV testing have been studied across multiple populations; however, testing is not just an individual-level phenomenon. This secondary analysis of 2005 and 2011 Ethiopia Demographic and Health Survey data was conducted to determine the extent to which the 2007 institution of an opt-out policy of HIV testing during antenatal care increased testing among women, and whether effects differed by women’s stigmatizing beliefs about HIV. A logit model with interaction between pre-/post-policy year and policy exposure (birth in the past year) was used to estimate the increased probability of past-year testing, which may be attributable to the policy. Results suggested the policy contributed to a nine-point increase in the probability of testing (95% CI 0.06–0.13, p?<?0.0001). A three-way interaction was used to compare the effects of exposure to the policy among women holding higher and lower HIV stigmatizing beliefs. The increase in the probability of past-year testing was 16 percentage points greater among women with lower stigmatizing beliefs (95% CI 0.06–0.27, p?=?0.002). Women with higher stigmatizing beliefs were less likely to report attending antenatal care (ANC), testing at their last ANC visit, or being offered a test at their last ANC visit. We encourage researchers and practitioners to explore interventions that operate at multiple levels of socio-ecological spheres of influence, addressing both stigma and structural barriers to testing, in order to achieve the greatest results in preventing HIV.     

The arginine-552-cysteine (R1315C) mutation within the A1 loop of von Willebrand factor induces an abnormal folding with a loss of function resulting in type 2A-like phenotype of von Willebrand disease: study of 10 patients and mutated recombinant von Willebrand factor

The study identified 10 patients from 6 families with prolonged bleeding time, decreased von Willebrand factor (vWF) ristocetin cofactor activity (RCoF) to vWF:Ag (antigen) ratio, and reduced ristocetin-induced platelet agglutination as well as ristocetin- or botrocetin-induced binding of plasma vWF to platelet glycoprotein Ib (GpIb). In addition, all patients showed a decrease of intermediate-molecular-weight (intermediate-MW) and high-molecular-weight (HMW) multimers of vWF. In the heterozygous state, a cysteine-to-threonine (C --> T) transversion was detected at nucleotide 4193 of the VWF gene of all patients and lead to the arginine (R)522C substitution in the A1 loop of vWF mature subunit (R1315C in the preprovWF). By in vitro mutagenesis of full-length complementary DNA (cDNA) of vWF and transient expression in COS-7 cells, the mutated C552 recombinant vWF (C552rvWF) was found to exhibit decreased expression, abnormal folding, and lack of intermediate-MW and HMW multimers. In addition, direct binding of botrocetin to C552rvWF, as well as ristocetin- and botrocetin-induced binding of C552rvWF to GpIb, was markedly decreased. Although being localized in an area of the A1 loop of vWF where most of the type 2B mutations that induce a gain-of-function have been identified, the R552C mutation induces a 2A-like phenotype with a decrease of intermediate-MW and HMW multimers as well as a loss-of-function of vWF in the presence of either ristocetin or botrocetin. (Blood. 2001;97:952-959)     

Discrepancy between IIA phenotype and IIB genotype in a patient with a variant of von Willebrand disease

Type IIA and IIB von Willebrand disease (vWD) result from qualitative abnormalities of von Willebrand factor (vWF) characterized by an absence in plasma of high molecular weight vWF multimers and an abnormal reactivity of vWF towards platelet glycoprotein (GP) Ib, which is decreased in type IIA and increased in type IIB. In this report, we describe the case of a patient having a IIA vWD phenotype associated with an intermittent thrombocytopenia atypical in this subtype but observed in type IIB vWD. The patient plasma vWF showed an absence of high molecular weight and intermediate multimers and had a decreased binding capacity to GPIb. The affinity of botrocetin was normal for plasma vWF from the propositus. Analysis of the propositus vWF gene showed the presence of a substitution Val 551 to Phe of the mature vWF subunit. This mutation is localized within a 509-695 disulphide loop of the vWF that plays an important role in the binding to GPIb and is where most of the molecular defects described so far were associated with type-IIB vWD. We have reproduced the Val 551 Phe substitution onto the vWF cDNA, expressed it in COS-7 cells, and performed structural and functional analysis of the mutant recombinant protein (rvWFPhe 551). The rvWFPhe 551 had a normal multimeric structure and showed the capacity to spontaneously interact with GPIb. Botrocetin had a decreased affinity for rvWFPhe 551. In conclusion, the Val 551 Phe mutation modifies the affinity of vWF for platelet GPIb, as does a type IIB mutation, and may be responsible for the thrombocytopenia of the patient and the clearance of the high molecular weight and intermediate- sized multimers of vWF from the plasma. The study of the rvWFPhe 551 has confirmed the discrepancy between the IIA phenotype and the IIB genotype of the patient.