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PubMed2004

Plasma d-dimer levels correlate with outcomes in patients with community-acquired pneumonia.

STUDY OBJECTIVES: The aim of this study was to investigate the prognostic value of plasma d-dimer levels in patients with community-acquired pneumonia (CAP). DESIGN: Prospective observational study. SETTING: Hospital Lluis Alcanyis of Xativa, Spain. PATIENTS: Consecutive adult patients admitted to the hospital with CAP from January 2000 to October 2002. MEASUREMENTS AND RESULTS: A total of 302 patients were included. Plasma d-dimer was measured using an automated latex assay. The relationships between plasma d-dimer and prognostic variables included in the pneumonia severity index (PSI) were examined using univariate and multivariate linear and logistic regression analyses. d-Dimer levels were negative (ie, < 500 ng/mL) in 16.9% of the patients. In nonsurvivors, the d-dimer plasma level mean value was 3,786 ng/mL, while in survivors it was 1,609 ng/mL (p < 0.0001). A significant relationship was found between the presence of elevated d-dimer levels and the PSI and APACHE (acute physiology and chronic health evaluation) II score. Elevated d-dimer levels were associated with radiologic pneumonia extension. The d-dimer predictive value for mechanical ventilation therapy showed an area under the curve of 0.78 (95% confidence interval, 0.71 to 0.81). CONCLUSIONS: d-Dimer plasma levels could be useful for predicting clinical outcome in patients with CAP.

Aged↗
PubMed1995

Changes in inhibin-A (alpha-beta A dimer) and total alpha inhibin in the peripheral circulation and ovaries of rats after gonadotrophin-induced follicular development and during the normal oestrous cycle.

Recent modifications to a previously reported two-site IRMA have permitted the measurement of serum/plasma concentrations and ovarian contents of inhibin-A (alpha-beta A dimer) in pregnant mare serum gonadotrophin (PMSG)-treated immature female rats and adult rats throughout the 4-day oestrous cycle. For comparison, total alpha inhibin levels were also measured by alpha subunit-directed inhibin RIA and found to be at least tenfold higher (relative to the same 32 kDa bovine inhibin standard used to calibrate both assays). In immature female rats, serum levels of inhibin-A dimer and total alpha inhibin increased within 3 h of PMSG injection and rose in parallel over the next 48 h to values four- to fivefold higher than pretreatment levels. Ovariectomy led to a rapid and parallel fall in both inhibin-A dimer and total alpha inhibin; initial half-lives (+/- 95% confidence intervals) were 22 +/- 4 and 20 +/- 5 min respectively. In adult rats, marked fluctuations in plasma concentrations and ovarian contents of inhibin-A dimer and total alpha inhibin occurred during the 4-day oestrous cycle, most notably between the morning of pro-oestrus and the morning of oestrus. Plasma levels of inhibin-A dimer and total alpha inhibin peaked on the afternoon of pro-oestrus just before the preovulatory gonadotrophin surge. After ovulation, both inhibin-A dimer and total alpha inhibin fell abruptly (two- to threefold by 0200 h on oestrus; P < 0.001), while FSH showed a secondary rise which peaked at 0700 h on oestrus. Although IRMA- and RIA-derived inhibin values generally followed a similar pattern across the 4-day cycle (plasma: r = 0.52, P < 0.001; ovary: r = 0.41, P < 0.001), a transient rise in plasma and ovarian inhibin-A dimer was detected at 0700 h on oestrus (P < 0.01) which was unaccompanied by a rise in total alpha inhibin. This rise in plasma inhibin-A dimer was probably responsible for terminating the post-ovulatory FSH surge since FSH levels declined steadily over the next 15 h. Overall, plasma inhibin-A dimer and FSH concentrations across the whole cycle were negatively correlated (r = -0.22, P < 0.01) whereas no correlation existed between total alpha inhibin and FSH (r = -0.11, P = 0.12).

Animals↗
PubMed2000

D-dimer concentrations in healthy dogs and dogs with disseminated intravascular coagulation.

OBJECTIVE: To determine sensitivity and specificity of assays of D-dimer concentrations in dogs with disseminated intravascular coagulation (DIC) and healthy dogs and to compare these results with those of serum and plasma fibrin-fibrinogen degradation product (FDP) assays. ANIMALS: 20 dogs with DIC and 30 healthy dogs. PROCEDURE: Semi-quantitative and quantitative D-dimer concentrations were determined by use of latex-agglutination and immunoturbidometry, respectively. Fibrin-fibrinogen degradation products were measured by use of latex-agglutination. A reference range for the immunoturbidometric D-dimer concentration assay was established; sensitivity and specificity of the assay were determined at 2 cutoff concentrations (0.30 microg/ml and 0.39 microg/ml). RESULTS: Reference range for the immunoturbidometric D-dimer concentration assay was 0.08 to 0.39 microg/ml; median concentrations were significantly higher in dogs with DIC than in healthy dogs. Latex-agglutination D-dimer and serum and plasma FDP assays had similar sensitivity (85 to 100%) and specificity (90 to 100%); the immunoturbidometric assay had lower specificity (77%) at the 0.30 microg/ml cutoff and lower sensitivity (65%) at the 0.39 microg/ml cutoff. Sensitivity or specificity of the latex-agglutination D-dimer assay was not significantly improved when interpreted in series or parallel with FDP assays. CONCLUSIONS AND CLINICAL RELEVANCE: Measurement of D-dimer concentrations by latex-agglutination appears to be a sensitive and specific ancillary test for DIC in dogs. Specificity of D-dimer concentrations in dogs with systemic disease other than DIC has not been determined, therefore FDP and D-dimer assays should be performed concurrently as supportive tests for the diagnosis of DIC in dogs.

Animals↗
PubMed2004

Relationship between plasma D-dimer levels and clinicopathologic parameters in resectable colorectal cancer patients.

AIM: To assess the clinical significance of the D-dimer levels and the relationship between plasma D-dimer levels and clinicopathologic parameters in operable colorectal cancer patients. METHODS: The plasma levels of D-dimer were measured pre- and postoperatively in 35 patients with colorectal cancer, and 30 healthy subjects served as controls by the method of quantitative enzyme-linked immunosorbent assay (ELISA). RESULTS: The mean preoperative plasma levels of D-dimer in the patients with colorectal cancer (1.06+/-0.24 mg/L) were significantly higher than those of controls (0.33+/-0.12 mg/L,P<0.01). The D-dimer levels were remarkably elevated on the 1st day after operation (1.22+/-0.55 mg/L, P<0.01). On the 3rd day the level of D-dimer began to stepwise descend and on the 14(th) day nearly returned to control level. The preoperative levels of D-dimer were significantly correlated with the lymph node metastasis and Dukes stage but had no association with tumor location and the degree of differentiation. A stepwise increase in the mean D-dimer levels was found with increase of the tumor stage. CONCLUSION: Hypercoagulation and higher fibrinolytic activities occur in patients with colorectal cancer. The operative trauma could enhance the fibrinolysis in the patients with colorectal cancer. The measurement of preoperative D-dimer levels is considered to be useful for predicting lymph node metastasis and stage of colorectal cancer.

Adult↗
PubMed1999

Determinants of plasma fibrin D-dimer sensitivity for acute pulmonary embolism as defined by pulmonary angiography.

BACKGROUND: The reported operating characteristics of the plasma fibrin D-dimer level for the diagnosis of acute pulmonary embolism vary widely. OBJECTIVE: To determine the sensitivity, specificity, predictive value, and clinical utility of the D-dimer for the diagnosis of pulmonary embolism, and to describe the effect of D-dimer assay method (enzyme-linked immunosorbent assay [ELISA], latex agglutination, membrane ELISA) and discriminate level, patient location at onset, comorbid disease, duration and intensity of concurrent heparin administration, and duration of symptoms on these operating characteristics. DESIGN: Prospective laboratory investigation. SETTING: Community and tertiary care teaching hospital. PATIENTS: Consecutive patients with suspected acute pulmonary embolism referred for pulmonary angiography from April 1993 through March 1996. MEASUREMENTS: Baseline characteristics, the duration and intensity of heparin anticoagulation, the time interval between symptom onset and plasma D-dimer testing, pulmonary angiography, and the D-dimer level on the day of pulmonary angiography. RESULTS: Of 105 consenting patients, 33 (31%) had a positive pulmonary angiogram. The D-dimer sensitivity/ negative predictive value for the ELISA, latex agglutination (American Bioproducts Co/Diagnostica Stago and Biopool International), and membrane ELISA were 100%/100%, 94%/94%, 100%/100%, and 97%/96%, respectively, at a discriminate level of 250 microg/L or less. The clinical utility, defined as the prevalence of a negative test, ranged from 17% to 33%. D-dimer sensitivity was unaffected by patient location at onset, comorbid disease, or heparin therapy but was inversely related to the duration of symptoms. CONCLUSIONS: The sensitivity of the plasma fibrin D-dimer for the diagnosis of pulmonary embolism depends on the assay method, the assay-specific discriminate level, and the duration of symptoms. At the appropriate discriminate level, the plasma D-dimer is a sensitive but nonspecific test for the diagnosis of pulmonary embolism.

Aged↗
PubMed1999

The use of a rapid D-dimer blood test in the diagnostic work-up for pulmonary embolism: a management study.

BACKGROUND: D-dimer assays have a potential to rule out pulmonary embolism in case of a normal test result. We studied the clinical utility of incorporating the SimpliRED D-dimer test result and clinical probability in the routine diagnostic work-up of patients with suspected acute pulmonary embolism. METHODS: In a prospective management study 245 consecutive patients, hospitalised as well as outpatients, were included. A SimpliRED D-dimer test and perfusion/(ventilation) scintigraphy were obtained in all patients, whereas clinical probability was determined in the subgroup of patients with a non-diagnostic scan and normal D-dimer result. A diagnostic algorithm determined the necessity for further testing and decisions about treatment. All patients were followed up for 3 months. RESULTS: In 54 patients (22%) with a normal lung scan and 50 patients (21%) with a high probability lung scan, antithrombotic therapy was withheld or started respectively, irrespective of the D-dimer result. A non-diagnostic lung scan was found in 137 (56%) patients, of whom 70 patients had an abnormal D-dimer test, in whom further testing was ordered. Of the remaining 67 patients with a non-diagnostic lung scan and normal D-dimer test 8 patients had a high clinical probability, and the subsequent ultrasonography and pulmonary angiography yielded pulmonary emboli in 1 patient. In the remaining 66 patients, pulmonary embolism was considered to be absent and antithrombotic treatment was stopped/withheld. During follow-up of these patients only one patient experienced a possible venous thromboembolic event (failure rate 1,5%; 95% CI 0-8%). The SimpliRED D-dimer was normal in 6 of 61 patients with proven pulmonary embolism (sensitivity 90%; 95% CI 80-96%). CONCLUSION: Our findings suggest that it is safe to withhold anticoagulant therapy in those patients with a non-diagnostic lung scan, a normal SimpliRED D-dimer test result, and without a high clinical probability. This results in a substantial decreased need for ultrasonography and pulmonary angiography. The SimpliRED should not be used in isolation to exclude pulmonary embolism.

Adult↗
PubMed2003

Potential use of D-dimer measurement in patients treated with oral anticoagulant for a venous thromboembolic episode.

AIM: We compared the level of plasma D-dimer in patients with previous venous thromboembolism (VTE), receiving or not oral anticoagulant treatment (OAT) and investigated its predictive value for the risk of VTE recurrence after OAT withdrawal. METHODS: We have studied 149 patients, 81 receiving oral anticoagulants and 68 after treatment interruption. Patients with known causes of D-dimer increase were excluded. D-dimer measurements were performed by Vidas analyzer (bioMérieux, France). RESULTS: A significantly lower D-dimer plasma level was found in patients under OAT than in untreated patients, 197+/-134 ng/ml versus 399+/-239 ng/ml, respectively (p<0.001). This decrease was similar in the different age populations and whether the patient had thrombophilia (n=84) or not. There was no correlation between INR and D-dimer levels. During a mean follow-up of 30 months, no recurrence occurred in patients under OAT versus 7 untreated patients. Among them, 3 had a D-dimer below 500 ng/ml, and 3 others had a level above 500 ng/ml. The last patient was not tested. CONCLUSION: The physician should be informed of the decrease of D-dimer under OAT, since the usual cut-off of 500 ng/ml used for deep vein thrombosis (DVT) exclusion is probably lower in such treated patients. It has been recently proposed that normal D-dimer level had a high negative predictive value for VTE recurrence when this dosage was performed 3 months after OAT interruption. The small number of recurrences observed in our study with an available result of D-dimer measured more than 3 months after OAT discontinuation does not allow a definite

Administration, Oral↗
PubMed2004

The importance of D-dimer for the diagnosis of venous thromboses in clinical cardiology.

The aim of the study was to analyze the importance of the rapid assay for D-dimer in the diagnosis of venous thromboses (VT). The study accrued 82 patients. There were 57 (70%) men and 25 (30%) women aged 16 to 86 years. Fifty-three patients were suspected of deep venous thrombosis (DVT) and 29 of pulmonary thromboembolism (PTE). In 49 of the 82 patients, the use of USD, isotope phlebography, x-ray and ventilation-perfusion scintigraphy of the lungs made it possible to verify the diagnosis of VT. In one case, it was verified on autopsy. In 33 patients, the suspicions were rejected. The blood assay for D-dimer was performed using the kit Roche/Diagnostika Stago. The method is based on agglutination of latex particles covered by monoclonal antibodies to D-dimer. Among the 49 patients with a verified diagnosis of VT, D-dimer was positive in 44 (89.8%) and negative in 5 (11.4%) patients. In the group of the 33 patients, in whom the diagnosis of VT was rejected, D-dimer was negative in 26 (78.8%) and positive in 7 (21.8%) patients. Thus, the sensitivity of the assay for D-dimer constituted 89.8% and the specificity 78,8%. The high sensitivity of the assay provides an opportunity of using D-dimer measurement as a screening method in patients suspected of VT. Negative D-dimer is helpful in excluding VT. If D-dimer is positive, the diagnosis should be confirmed by other methods.

Adolescent↗
PubMedDate not supplied

Clinical significance of plasma D-dimer levels and serum VEGF levels in patients with hepatocellular carcinoma.

BACKGROUND/AIMS: Angiogenesis and coagulation system activation are associated with tumor growth and metastasis. Vascular endothelial growth factor (VEGF) has been reported to play a major role in tumor angiogenesis. The elevation of plasma D-dimer level indicates the activation of coagulation and fibrinolysis. The purpose of this study was to: (a) evaluate the correlation between serum VEGF and plasma D-dimer level; (b) analyze the clinical features that might affect the VEGF and D-dimer levels in patients with hepatocellular carcinoma. METHODOLOGY: Twenty patients with hepatocellular carcinoma were included prior to treatment. Serum VEGF levels were measured by enzyme-linked immunosorbent assay. Plasma D-dimer levels were measured by quantitative latex microparticle enhanced turbidimetric immunoassay. RESULTS: The presence of a high plasma D-dimer level was found to be correlated with the presence of central necrosis, higher Child's grade, advanced TNM stage, and the presence of portal vein thrombosis when plasma D-dimer levels were compared between different clinicopathologic groups. Tumors larger than 2 cm in diameter had higher median serum VEGF levels than tumors less than 2cm in diameter. No correlation was found between plasma D-dimer level and serum VEGF level in hepatocellular carcinoma patients (r=0.126, p=0.598). CONCLUSIONS: No correlation was found between the plasma D-dimer level and the serum VEGF level in hepatocellular carcinoma patients. The plasma D-dimer level appeared to reflect the tumor stage and vascular invasion of hepatocellular carcinoma. Serum VEGF level in hepatocellular carcinoma patients showed a positive correlation with tumor size.

Adult↗
PubMed2006

Clinical usefulness of D-dimer testing in cancer patients with suspected pulmonary embolism.

Limited data are available about the diagnostic value of D-dimer testing in cancer patients with clinically suspected pulmonary embolism (PE). Therefore, we evaluated i) the safety and clinical usefulness of an ELISA D-dimer test to rule out PE in cancer patients compared with non-cancer patients and ii) whether adopting a higher D-dimer cut-off value might increase the usefulness of D-dimer in cancer patients. We analysed data from two outcome studies which enrolled 1,721 consecutive patients presenting in the emergency department with clinically suspected PE. Presence of an active malignancy was abstracted from the database. All patients underwent a sequential diagnostic work-up including an ELISA D-dimer test and a 3-month followup. Sensitivity and predictive value (NPV) were 100% in both cancer and non-cancer patients. PE was ruled out by a negative D-dimer test in 494/1,554 (32%) patients without cancer, and in 18/164 (11%) patients with a malignancy. At cut-off values varying from 500 to 900 microg/l, the sensitivity was unchanged (100%, 95% CI: 93% to 100%) and the specificity increased from 16% (95% CI: 11% to 24%) to 30% (95% CI: 22% to 39%). The 3-month thromboembolic risk was 0% (95% CI: 0% to 18%) in cancer patients with a negative D-dimer test. ELISA D-dimer appears safe to rule out pulmonary embolism in cancer patients but it is negative in only one of ten patients at the usual cut-off value. Increasing the cut-off value of D-dimer in cancer patients might increase the test's clinical usefulness.

Aged↗
PubMed2006

Prognostic value of D-dimer in patients with pulmonary embolism.

D-dimer levels appear to be associated with the extent of the thromboembolic burden in patients with pulmonary embolism (PE). We therefore hypothesized that D-dimer levels at admission would be associated with prospective risk of mortality in patients with PE. We used data from 366 patients diagnosed with PE at four hospital emergency departments. A highly sensitive D-dimer test was prospectively performed at admission. The outcome was overall mortality within three months. We divided patients into quartiles on the basis of their D-dimer levels and compared mortality rates by quartile. We estimated sensitivity, specificity, and predictive values for mortality in the first and fourth quartile. Overall mortality was 5.2%. Patients who died had higher median D-dimer levels than patients who survived (4578 versus 2946 microg/l; p = 0.005). Mortality increased with increasing D-dimer levels, rising from 1.1% in the first quartile (<1500 microg/l) to 9.1% in the fourth quartile (>5500 microg/l) (P = 0.049). Sensitivity, specificity, and positive and negative predictive values of D-dimer levels <1500 microg/l to predict mortality were 95%, 26%, 7%, and 99%, respectively. Patients with PE who have D-dimer levels below 1500 microg/l have a very low mortality. Further studies must assess whether D-dimer, alone or combined with other prognostic instruments for PE, can be used to identify low-risk patients with PE who are potential candidates for outpatient treatment or an abbreviated hospital stay.

Aged↗
PubMed1991

Inhibitor stabilization of human immunodeficiency virus type-2 proteinase dimer formation.

We report the first direct observation of the subunit self-association behavior of highly purified recombinant human immunodeficiency virus type-2 (HIV-2) proteinase. Multiple samples of enzyme were subjected to sedimentation equilibrium analytical ultracentrifugation sequentially at 8.8 degrees C and two pH values in the presence and absence of a C2 symmetric, peptidomimetic inhibitor. At both pH values the enzyme exhibited sedimentation equilibrium behavior which fit a monomer-dimer-tetramer model. In the absence of inhibitor, the apparent Kd for dimer formation was less than approximately 100 microM and the apparent Kd for the weaker dimer-tetramer association was greater than approximately 100 microM. In the presence of inhibitor, at either pH, dimer formation was more strongly favored as indicated by a approximately 5-14-fold decrease in the apparent Kd for dimer formation and a approximately 1.2-4-fold increase in the apparent Kd for tetramer formation. The enhanced formation of dimer and decrease in higher order self-associated forms in the presence of an inhibitor is consistent with inhibitor stabilization of an active dimer. The inhibitor-induced stabilization of the dimeric species is consistent with a model for substrate-induced formation of active proteinase dimers in virion assembly.

HIV Protease Inhibitors↗
PubMed1991

Reconstitution of C5 convertase of the alternative complement pathway with isolated C3b dimer and factors B and D.

C5 convertase of the alternative complement pathway is a trimolecular complex consisting of two molecules of C3b and one molecule of Bb. We previously proposed a model of the alternative pathway C5 convertase in which the second C3b molecule binds covalently to the first C3b molecule bearing Bb, and the C5 molecule binds to each C3b molecule of the covalently linked C3b dimer, resulting in its appropriate presentation to the catalytic site on Bb. In the present study, we purified the covalently linked C3b dimer and reconstituted the C5 convertase with the C3b dimer and factors B and D to obtain evidence in support of this model. An insoluble glucan, OMZ-176, was incubated with human serum to activate the alternative pathway and to allow formation of the alternative C5 convertase on the surface of the glucan, and the glucan bearing the C5 convertase was then solubilized by incubation with glucosidases. In this way, the covalently linked C3b dimer was obtained in solution without using a detergent. The C3b dimer was then separated from enzymes, C3b monomer, C3b oligomer, and other materials by chromatographies. SDS-PAGE analysis demonstrated that the purified C3b dimer had intact alpha'-chains. Alternative pathway C5 convertase was reconstituted when the isolated C3b dimer was incubated with factors B and D. The presence of P enhanced C5 convertase formation threefold. These results support the notions that the formation of the covalently linked C3b dimer is a general phenomenon associated with activation of the alternative pathway and that the C3b dimer acts as a part of the C5 convertase.

Complement C3-C5 Convertases↗
PubMed1989

Dimeric dermorphin analogues as mu-receptor probes on rat brain membranes. Correlation between central mu-receptor potency and suppression of gastric acid secretion.

The opioid receptor preference for dermorphin and several dimerized structural analogues was investigated using rat brain synaptosomes and correlated with the potencies of intracerebroventricularly administered dimeric dermorphin peptides to inhibit gastric acid secretion. The carboxyl terminus of dermorphin or amino-terminal dermorphin analogues was bridged by dihydrazide or (poly)ethylenediamine structures. Synaptosomal membranes were prepared for radioligand binding assay in the presence of soybean trypsin inhibitor and preincubated to remove endogenously bound opioid peptides before storage at -70 degrees C. Specific radiolabeled agonists used in the radioligand binding assays were [D-Ala2,N-methyl-Phe4,Gly-ol5] [3H] enkephalin for mu-receptors and [D-Ala2,D-Leu5] [3H]enkephalin for delta-receptors. delta-Receptor binding assays were conducted in the presence of 2.6 microM [N-Me-Phe3,D-Pro4]morphiceptin to suppress peptide binding to mu-receptors. [D-Ala2,N-methyl-Phe4,Gly-ol5]enkephalin and dermorphin had affinities of 1.39 and 1.22 nM for mu-receptors and 355.8 and 178.6 nM for delta-receptors, respectively. Affinities of dimeric-dermorphin0 for mu- and delta-receptors, and the mu-selectivity ratio, exceeded values characteristic of dermorphin. The dimerized amino-terminal dermorphin analogues are peptides whose receptor binding differed from the parent molecule; e.g. the affinity of dimeric tetrapeptides toward mu-receptors was reduced but was increased for delta-receptors relative to monomeric dermorphin-(1-4)-amide. Dimeric tetradermorphin linked by a bridge containing 12 methylene units (di-tetra-dermorphin12), exhibited a dramatic loss in the mu-selectivity ratio as a result of diminished mu-affinity. On the other hand, substitution of Gly4 by Sar in di-tetra-dermorphin2 enhanced binding to mu-receptors: substitution of D-Arg2 for D-Ala resulted in an increased binding to mu-receptors while decreasing binding to delta-receptors, yielding a peptide with the highest mu-selectivity ratio. These substitutions of D-Arg2 and Sar4 in dimeric amino-terminal dermorphin pentapeptides enhanced binding to both mu- and delta-receptors relative to dermorphin-(1-5)-amide, but led to a decrease in its mu-selectivity ratio. Several dimeric dermorphin analogues exhibited an enhanced mu-selectivity ratio relative to their monomeric analogues. Dimeric peptides, which had a relatively high affinity for mu-receptors, were effective in the suppression of gastric acid secretion.

Analgesics, Opioid↗
PubMed1981

Structure of acetylcholine receptor dimer determined by neutron scattering and electron microscopy.

Previous work has shown that the predominant native form of the acetylcholine receptor from the electric tissue of Torpedo californica is a dimer of Mr = 500,000, cross-linked by a disulfide bond between the largest (delta) of the five chains (alpha 2 beta gamma delta) that comprise the monomer. Small-angle neutron scattering of purified receptor dimer in Triton X-100 solution containing 18% D2O, in which the Triton X-100 is contrast-matched, yields a radius of gyration of the dimer of 66 A. Based on the assumptions that the dimer is symmetrical and that the radius of gyration of the monomer does not change in forming dimer, this value, together with the radius of gyration of the receptor monomer (46 A), determined previously, allows the calculation of the distance separating the centers of neutron scattering density of monomers in a dimer; the result is 96 A. Electron microscopy of negatively stained dimers permits an independent measurement of the distance between the apparent centers of mass of the monomers; the average is 96 A, in agreement with the result of the neutron scattering analysis. The electron micrographs of dimer also permit the location of the delta chains at the region of contact of the monomers. A model for the receptor dimer consistent with all available structural information is presented.

Acetylcholine↗
PubMed1994

Mutational analysis of the bipartite dimer linkage structure of human immunodeficiency virus type 1 genomic RNA.

The genome of all retroviruses consists in two homologous RNA molecules associated near their 5' end in a region called the dimer linkage structure. Dimerization of genomic RNA is thought to be important for several functions of the retroviral cycle such as encapsidation, reverse transcription, and translation. In human immunodeficiency virus type 1 (HIV-1), a region downstream of the splice donor site was initially postulated to mediate dimerization. However, we recently showed that the dimerization initiation site is located upstream of the splice donor site and suggested that dimerization may initiate through a loop-loop interaction. Here, we show that single base mutations in the palindromic loop of the dimerization initiation site completely abolish dimerization, while introduction of compensatory mutations restores the process. Furthermore, two single nucleotide mutants that are unable to form homodimers efficiently codimerize, while the wild type RNA and the compensatory mutant, which both form homodimers, are unable to codimerize. These results unambiguously prove the interaction between the palindromic loops of each monomer. By contrast, none of the deletions that we introduced downstream of the splice donor site abolishes dimerization. However, deletions of two purine tracts located in the vicinity of the initiation codon of the gag gene significantly decrease the thermal stability of the HIV-1 RNA dimer.

Base Sequence↗
PubMed1994

[Significance of urinary fibrin/fibrinogen degradation product (FDP) D-dimer measured by highly sensitive ELISA method with a new monoclonal antibody (D-D E72) in various renal diseases].

In order to clarify the abnormalities of the coagulation and fibrinolysis system in patients with various renal diseases, we produced a new monoclonal antibody for FDP (fibrin/fibrinogen degradation product) D-dimer (D-D E72). We also established a new highly sensitive method of enzyme-linked immunosorbent assay (ELISA) for urinary FDP D-dimer using this monoclonal antibody. The urine from 110, patients with various renal diseases was investigated for the FDP D-dimer. The results are summarized as follows: 1) Urinary FDP D-dimer in normal subjects was 0.69 +/- 0.60 ng/ml. 2) The level of urinary FDP D-dimer in patients with primary nephrotic syndrome and in patients with chronic renal failure was significantly higher than that of normal subjects, whereas the urinary FDP D-dimer levels in patients with diabetes mellitus were higher than those of normal subjects. 3) In the CGN and NS groups there was a tendency for an increase in the level of urinary FDP D-dimer in more active forms of the disease. 4) A significant correlation between urinary FDP D-dimer and urinary protein in the CGN and NS groups was demonstrated. 5) In all of the renal diseases investigated in this study, the ratio of urinary FDP D-dimer to total FDP was less than 4%.

Adolescent↗
PubMed1994

Formation of mitogenically active PDGF-B dimer does not require interchain disulfide bonds.

Platelet-derived growth factor (PDGF), a major mitogen for mesenchymal cells, is a disulfide-bonded dimer of two subunit polypeptides named A and B. All of the three possible dimeric forms, i.e. AA, BB, and AB, exist in nature. The dimeric structure has been presumed to be necessary for biological activity, since reduction of the dimer results in loss of activity and simultaneous conversion to monomeric form as determined by SDS-gel electrophoresis. However, reduction of the native molecule destroys intrachain, as well as interchain, disulfide bonds, and it is possible that the former rather than the latter are critical for proper conformation of the active protein. We show here that PDGF-B polypeptides in which all 8 cysteines or the 2nd, 4th, 5th, and 8th cysteines have been mutated to serines fail to form covalent dimers and possess dramatically less mitogenic activity than native PDGF-BB. Another mutant, PDGF-B(C2,4S), in which just the 2 cysteines involved in interchain disulfides were converted to serine, ran as a monomer on SDS-polyacrylamide gels as expected. Somewhat unexpectedly, however, the mitogenic activity of the PDGF-B(C2,4S) analog was similar to the activity of wild-type PDGF-BB disulfide-bonded dimer under physiological conditions. The activity of the analog was more sensitive to the effect of low pH than was the activity of wild-type PDGF-BB. Molecular weight analysis utilizing light scattering and sedimentation equilibrium demonstrated that the PDGF-B(C2,4S) analog exists as a noncovalent dimer at pH 4-7 but dissociates to a monomer at pH 2.5. Disulfide analysis of the mutant protein demonstrated that the intrachain disulfide bonds are the same as those formed in wild-type PDGF-BB homodimers. We conclude that proper formation of intrachain disulfide bonds is critical to maintaining the correct conformation of PDGF monomers, but that appropriately folded monomers can associate into active noncovalent dimers in the absence of interchain disulfide bonds. Interchain disulfide bonds thus appear to increase the stability of the PDGF dimer rather than being crucial to its existence.

Amino Acid Sequence↗