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Journal of Bacteriology May 1970A determination of the relative affinity of vancomycin and ristocetin for isolated cell walls and for a peptidoglycan precursor was made. These antibiotics had...
A determination of the relative affinity of vancomycin and ristocetin for isolated cell walls and for a peptidoglycan precursor was made. These antibiotics had previously been shown to adsorb to cell walls and to complex with peptides containing a d-alanyl-d-alanine C-terminus. By using (14)C-uridine diphosphate (UDP)-N-acetylmuramyl pentapeptide, it was shown that the complex which is formed between this peptidoglycan precursor and either vancomycin or ristocetin does not preclude adsorption of the antibiotics to cell walls of Micrococcus lysodeikticus. Complex formation between ristocetin and UDP-N-acetylmuramyl pentapeptide was assured by differential absorption spectra. However, when the complex was mixed with cell walls, the antibiotic was sedimented with the walls, and the radioactivity remained in the supernatant solution. This indication that ristocetin and vancomycin have a greater affinity for walls than for UDP-N-acetylmuramyl pentapeptide and that the complex per se does not bind to cell walls suggests that adsorption of these antibiotics to cell walls is probably responsible for the inhibition of peptidoglycan synthesis. This proposal is strengthened by the observation that complexed antibiotic is no less inhibitory for growth of Bacillus subtilis than free vancomycin or ristocetin.
Topics: Adsorption; Bacillus subtilis; Bacterial Proteins; Carbon Isotopes; Cell Wall; Chromatography, Paper; Depression, Chemical; Micrococcus; Peptides; Ristocetin; Spectrophotometry; Staphylococcus; Ultraviolet Rays; Vancomycin
PubMed: 4986761
DOI: 10.1128/jb.102.2.476-482.1970 -
Blood Oct 1987Progress has occurred in the past several years in the understanding of the structure and function of von Willebrand factor (vWF). This multimeric glycoprotein exhibits... (Review)
Review
Progress has occurred in the past several years in the understanding of the structure and function of von Willebrand factor (vWF). This multimeric glycoprotein exhibits a dual role, that of mediating platelet adhesion and aggregation onto thrombogenic surfaces, and that of functioning as carrier in plasma for the factor VIII procoagulant protein. New insights into the nature of the several functional domains of vWF have led to the identification of the regions of the molecule that interact with factor VIII, heparin, the glycoprotein lb of platelets, and collagen. Alterations of vWF are the cause of von Willebrand disease (vWD), a congenital bleeding disorder. In the majority of patients, the plasma levels of vWF are decreased, but there is no demonstrable structural or functional alteration of the protein. In other patients, however, the structure of vWF is abnormal. This review summarizes the current knowledge on vWF and vWD.
Topics: Chemical Phenomena; Chemistry; Humans; Platelet Aggregation; Ristocetin; von Willebrand Diseases; von Willebrand Factor
PubMed: 3307951
DOI: No ID Found -
Pharmaceuticals (Basel, Switzerland) Oct 2021The protracted global COVID-19 pandemic urges the development of new drugs against the causative agent SARS-CoV-2. The clinically used glycopeptide antibiotic,...
The protracted global COVID-19 pandemic urges the development of new drugs against the causative agent SARS-CoV-2. The clinically used glycopeptide antibiotic, teicoplanin, emerged as a potential antiviral, and its efficacy was improved with lipophilic modifications. This prompted us to prepare new lipophilic apocarotenoid conjugates of teicoplanin, its pseudoaglycone and the related ristocetin aglycone. Their antiviral effect was tested against SARS-CoV-2 in Vero E6 cells, using a cell viability assay and quantitative PCR of the viral RNA, confirming their micromolar inhibitory activity against viral replication. Interestingly, two of the parent apocarotenoids, bixin and β-apo-8'carotenoic acid, exerted remarkable anti-SARS-CoV-2 activity. Mechanistic studies involved cathepsin L and B, as well as the main protease 3CLPro, and the results were rationalized by computational studies. Glycopeptide conjugates show dual inhibitory action, while apocarotenoids have mostly cathepsin B and L affinity. Since teicoplanin is a marketed antibiotic and the natural bixin is an approved, cheap and widely used red colorant food additive, these readily available compounds and their conjugates as potential antivirals are worthy of further exploration.
PubMed: 34832893
DOI: 10.3390/ph14111111 -
American Journal of Hematology Apr 2003Acquired von Willebrand's disease or syndrome (AVWS) is a rare bleeding disorder distinguished from congenital von Willebrand's disease by age at presentation and... (Review)
Review
Acquired von Willebrand's disease or syndrome (AVWS) is a rare bleeding disorder distinguished from congenital von Willebrand's disease by age at presentation and absence of personal and family history of bleeding disorders. We report on 22 patients with AVWS seen over 25 years. Mean age at diagnosis was 61.3 years (range 38-86 years); most patients had a spontaneous or a post-operative hemorrhage at presentation. Gastrointestinal bleeding and epistaxis were the most common spontaneous symptoms. Bleeding time was prolonged in most patients, associated with marked reductions in plasma von Willebrand factor antigen and ristocetin cofactor activity. Plasma VWF multimer distribution was normal (type 1 pattern) in 5 patients, indeterminate (no multimers detectable) in 6 patients (type 3 pattern), and abnormal (decreased higher-molecular-weight multimers, type 2 pattern) in 11 patients. None of 17 patients tested had an inhibitor of ristocetin cofactor activity. An underlying malignant or benign hematologic disease was found in 18 patients, and 1 patient had Crohn's disease. Desmopressin was effective in only half the patients so treated, but all patients responded to treatment with VWF-containing concentrates. Resolution of AVWS occurred with therapy of lymphoma (1 patient) and chronic lymphocytic leukemia (1 patient). Sixteen patients were alive at last follow-up; no deaths were related to bleeding. AVWS may be more prevalent than has been appreciated; we estimate up to 0.04%. Awareness of the existence of AVWS is essential for diagnosis and appropriate management. Therapy of associated diseases may improve the bleeding disorder.
Topics: Adult; Aged; Aged, 80 and over; Antibodies, Monoclonal; Antibody Specificity; Autoantibodies; Autoimmune Diseases; Bleeding Time; Crohn Disease; Deamino Arginine Vasopressin; Female; Hematologic Diseases; Hematologic Neoplasms; Humans; Male; Middle Aged; Minnesota; Paraproteins; Postoperative Hemorrhage; Retrospective Studies; von Willebrand Diseases; von Willebrand Factor
PubMed: 12666134
DOI: 10.1002/ajh.10298 -
Blood Jul 2010
PubMed: 20634385
DOI: 10.1182/blood-2010-04-276394 -
The Journal of Clinical Investigation May 1978Ristocetin will induce the agglutination of platelets in the presence of von Willebrand factor. In previous studies, an electrostatic mechanism was proposed for this...
Ristocetin will induce the agglutination of platelets in the presence of von Willebrand factor. In previous studies, an electrostatic mechanism was proposed for this phenomenon wherein first the platelet's surface charge is reduced by the binding of ristocetin and then the von Willebrand factor acts as a bridge between platelets. To test this hypothesis, the effects of ristocetin and von Willebrand factor, singly and together, on the electrophoretic mobility of normal, trypsinized, and Bernard-Soulier platelets was measured. Ristocetin alone, at concentrations of 0.5 mg/ml or more, produced a statistically significant reduction in the electrophoretic mobility of fresh or fixed platelets. Control experiments showed that the reduction was not due to changes in the ionic milieu of the solution. Therefore, the decrease in platelet mobility is evidence for binding of ristocetin to the platelet surface. Bernard-Soulier and trypsinized platelets also had reductions in mobility with ristocetin, suggesting that ristocetin binds to the platelet at sites other than the binding site for von Willebrand factor. The presence of plasma from a patient with von Willebrand's disease did not alter the reduction in mobility of normal platelets by ristocetin. However, the reduction was markedly enhanced in the presence of normal plasma. This enhancement did not occur with Bernard-Soulier platelets and was inhibited by anti-Factor VIII/von Willebrand factor antiserum or trypsinization of the platelets. Thus, the enhanced reduction appears to be associated with the binding of von Willebrand factor to the platelet surface. These studies indicate that platelets undergo two changes with ristocetin and von Willebrand factor, both of which facilitate agglutination: reduction in net surface charge and binding of von Willebrand factor, a large molecule which can serve as a bridge between platelets. In parallel studies, bovine von Willebrand factor, without ristocetin, agglutinated and reduced the electrophoretic mobility of normal but not Bernard-Soulier or trypsinized platelets; this indicates a similar mechanism of agglutination.
Topics: Antibodies; Binding Sites; Blood Coagulation Factors; Blood Platelets; Electrophoresis; Humans; Movement; Purpura, Thrombocytopenic; Ristocetin; Syndrome; von Willebrand Factor
PubMed: 307006
DOI: 10.1172/JCI109032 -
International Journal of Laboratory... May 2015Von Willebrand disease (VWD) is considered the most common inherited bleeding disorder and may also be the most difficult to diagnose. Clinical symptoms of VWD include... (Review)
Review
Von Willebrand disease (VWD) is considered the most common inherited bleeding disorder and may also be the most difficult to diagnose. Clinical symptoms of VWD include predominantly mild mucosal bleeding; surgical bleeding may occur with specific challenges and joint bleeding can occur in the most severe forms. A family history either of diagnosed VWD or of bleeding symptoms is typically present. Laboratory diagnosis requires a series of assays of von Willebrand factor (VWF) quantity and function, and factor VIII activity, with no single straightforward diagnostic test available to either confirm or exclude the diagnosis. Newer assays of VWF function are becoming more available and useful in determining the laboratory diagnosis of VWD.
Topics: Clinical Laboratory Techniques; Factor VIII; Humans; Reproducibility of Results; Ristocetin; Sensitivity and Specificity; von Willebrand Diseases; von Willebrand Factor
PubMed: 25976955
DOI: 10.1111/ijlh.12345 -
Blood Aug 2009Recent multicenter studies have clarified the molecular basis underlying the different von Willebrand disease (VWD) types, all of which are caused by the deficiency... (Review)
Review
Recent multicenter studies have clarified the molecular basis underlying the different von Willebrand disease (VWD) types, all of which are caused by the deficiency and/or abnormality of von Willebrand factor (VWF). These studies have suggested a unifying pathophysiologic concept. The diagnosis of VWD, remains difficult because its clinical and laboratory phenotype is very heterogeneous and may overlap with normal subjects. Stringent criteria are therefore required for a clinically useful diagnosis. In this paper, we delineate a practical approach to the diagnosis and treatment of VWD. Our approach is based on the critical importance of a standardized bleeding history that has been condensed into a final bleeding score and a few widely available laboratory tests, such as VWF ristocetin cofactor activity, VWF antigen and factor VIII. This approach would help identify those subjects who will probably benefit from a diagnosis of VWD. The next step involves performing a trial infusion with desmopressin in all patients who fail to exhibit an enhanced responsiveness to ristocetin. On the basis of these results and through a series of illustrative examples, the clinician will be able to select the best approach for the optimal management of VWD, according to the patient's characteristics and clinical circumstances.
Topics: Adolescent; Adult; Deamino Arginine Vasopressin; Female; Hemorrhage; Hemostatics; Humans; Male; Middle Aged; Multicenter Studies as Topic; Ristocetin; von Willebrand Diseases; von Willebrand Factor
PubMed: 19474451
DOI: 10.1182/blood-2009-01-153296 -
Blood Oct 1986The contribution of von Willebrand factor (vWF)-platelet binding to platelet-collagen interaction was examined in vitro. The binding of vWF to platelets was mediated and...
The contribution of von Willebrand factor (vWF)-platelet binding to platelet-collagen interaction was examined in vitro. The binding of vWF to platelets was mediated and regulated by ristocetin. Subthreshold concentrations of ristocetin (less than or equal to 1 mg/mL), insufficient to cause ristocetin-induced platelet aggregation (RIPA), were added to platelet-rich plasma (PRP) prior to the addition of collagen. The collagen-induced platelet aggregation (CIPA) was modified by ristocetin and the degree of alteration was dependent on the ristocetin concentration. Response as a function of ristocetin concentration was designated the Collagen-Platelet Aggregation Response (CoI-PAR). In normal PRP the CoI-PAR was a progressive inhibition followed by decreasing inhibition and then an enhanced response. The enhanced response occurred over a narrow range of ristocetin concentrations (0.8 to 1.0 mg/mL). In the absence of vWF (severe von Willebrand's disease, Type I, vWF less than 1%) the CoI-PAR was a progressive, eventually complete inhibition with no enhanced response (with ristocetin concentrations up to 3.0 mg/mL). With addition of vWF to this PRP an enhanced response was observed at a ristocetin concentration inversely proportional to the vWF level. PRP from a patient with severe Hemophilia A showed a response within the normal range. Subthreshold ristocetin did not cause plasma protein precipitation or platelet release of 3H-serotonin, nor induce micro platelet aggregate formation. Digestion of platelet membrane glycoproteins (GP(s] with chymotrypsin demonstrated that upon removal of GPI, RIPA was absent, CIPA retained and the CoI-PAR was progressive inhibition, with no enhancement. With removal of GPs I, II, and III, RIPA, CIPA, and the CoI-PAR were absent. A dose-response 125I-vWF-platelet binding occurred with increasing ristocetin concentrations which was unchanged by the addition of collagen. These results demonstrated that ristocetin-platelet association inhibited CIPA, and vWF-platelet binding enhanced platelet-collagen adhesion and platelet aggregation. The in vitro-enhanced CIPA represents a vWF-dependent aggregation of sufficient magnitude to overcome the inhibitory effect of ristocetin. These studies demonstrate an influential interaction of ristocetin, vWF, and collagen with the platelet membrane and imply an important hemostatic contribution of vWF-platelet binding in platelet-collagen interaction.
Topics: Blood Platelets; Chymotrypsin; Collagen; Dose-Response Relationship, Drug; Heparin; Humans; Platelet Aggregation; Platelet Membrane Glycoproteins; Protein Binding; Ristocetin; Serotonin; von Willebrand Factor
PubMed: 3489493
DOI: No ID Found -
Clinical and Applied... Feb 2009The aim of this study was to assess the plasma levels of von Willebrand factor antigen and ristocetin cofactor activity, which are well-known markers of endothelial...
The aim of this study was to assess the plasma levels of von Willebrand factor antigen and ristocetin cofactor activity, which are well-known markers of endothelial function, in atrial fibrillation (AF) with or without mitral stenosis (MS). Forty-two patients (16 patients with MS and AF [MS(+)AF(+)], 13 patients with nonvalvular AF [MS(-)AF(+)], and 13 patients with MS and sinus rhythm [MS(+)AF(-)]) were included. Von Willebrand factor antigen levels and ristocetin cofactor activities in all participants were assessed. Overall, von Willebrand factor antigen levels and ristocetin cofactor activities in the AF(+) patients were higher than in the AF(-) patients (P = .003 and P = .002, respectively). Von Willebrand factor antigen levels and ristocetin cofactor activities in the 3 groups were found to be different (P = .012 and P = .01, respectively). Von Willebrand factor antigen levels were similar between the MS(+)AF(+) and MS(-)AF(+) groups and were higher than that of the MS(+)AF(-) group. Ristocetin cofactor activity in the MS(-)AF(+) group was significantly higher than in the other 2 groups. The ristocetin cofactor activity and von Willebrand factor antigen levels were significantly higher in diabetic or hypertensive patients than in nondiabetic or normotensive patients. According to the results of this study, circulating von Willebrand factor antigen levels and plasma ristocetin cofactor activities are affected by the presence of AF, MS, and associated comorbidities including type 2 diabetes mellitus and systemic hypertension. Further studies are needed to assess the role of von Willebrand factor antigen and ristocetin cofactor activity in predicting vascular thrombotic events in AF, MS, systemic hypertension, and diabetes mellitus.
Topics: Adult; Aged; Aged, 80 and over; Atrial Fibrillation; Comorbidity; Diabetic Angiopathies; Endothelium; Female; Humans; Hypertension; Male; Middle Aged; Mitral Valve Stenosis; Ristocetin; von Willebrand Factor
PubMed: 18160605
DOI: 10.1177/1076029607305115