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Biomedical subjects

R H Wagner

Publications and source records attributed to R H Wagner.

At least 19 recordsLinked to original sources
PubMed1995

Technetium-labelled red blood cell scintigraphy: is it useful in acute lower gastrointestinal bleeding?

Radionuclide scintigraphy is commonly utilized as a screening examination before performing more invasive procedures in the work-up of patients with lower gastrointestinal (GI) bleeding. We reviewed our institutional experience with technetium-labelled red blood cell scintigraphy (TRCS) in detecting and localising acute lower GI bleeding. The study group included 72 patients who had 80 red cells scans over a five year period. Thirty-eight scans were positive (47.5%), and 42 were negative (52.5%). Sites of lower GI bleeding were confirmed by endoscopy, arteriography, surgery and/or pathology in 22 of the 38 positive scans. There were four false-negative scans (9.5%). The overall sensitivity and specificity of TRCS in detecting lower GI bleeding was 84.6% (22/26) and 70.4% (38/54), respectively. The accuracy of localization of bleeding sites in the patients with confirmed positive scans was 72.7% (16/22). Thirty mesenteric arteriograms were performed on patients in this series. Eleven arteriograms were performed after negative TRCS; one was positive. Technetium-labelled red blood cell scintigraphy appears to be a useful screening examination for patients with lower GI bleeding who are hemodynamically stable. This may avoid the potential morbidity of arteriography in patients who are not actively bleeding.

Acute Disease↗
PubMed1995

Neck radionuclide scanning: a pitfall in parathyroid localization.

UNLABELLED: Radionuclide parathyroid scans are widely used to localize abnormal parathyroid glands. They are especially valuable for identifying ectopic glands, including those in the mediastinum. Two patients with hyperparathyroidism who had mediastinal glands that were not identified because only the neck was scanned prompted our review of the technique of parathyroid scanning at hospitals in our region and of the frequency of mediastinal parathyroid glands identified by scanning at our own institution. The nuclear medicine departments at 72 area hospitals were surveyed. Parathyroid scans were performed at 51 of these hospitals but only 13 (25%) routinely scanned the mediastinum and chest. At our institution 480 parathyroid scans were performed during a 9-year period. Twenty-six mediastinal parathyroid glands were identified by routine scanning of both the neck and mediastinum. Most of these glands could be removed through a cervical incision. However, four required formal thoracotomy and two thoracoscopy. CONCLUSIONS: A radionuclide parathyroid scan limited to the neck is an incomplete study. Scans that do not include the thorax will miss mediastinal glands that occurred in 5 per cent of the patients in our series. Despite this, radionuclide parathyroid scanning was limited to the neck in 75 per cent of surveyed hospitals. This practice increases the chance for failed surgical exploration and increases potential patient morbidity.

Adenoma↗
PubMed1994

Ultraviolet sensitivity of three cone types in the aphakic observer determined by chromatic adaptation.

Sensitivities at 5.5 deg off-fovea from the aphakic observer superimposed on orange, purple and blue fields were obtained to estimate short-, middle- and long-wavelength cone spectra respectively. The middle-wavelength mechanism had a visible wavelength maximum resembling a nomogram plus an UV sensitivity fitting a cis-peak. The short (and, to a lesser extent, the long) wavelength cone sensitivities are higher in the UV than expected.

Adaptation, Ocular↗
PubMed1994

Treatment of radiation exposure and contamination.

For treatment of radiation accident victims, procedures for handling trauma patients must be modified to ensure proper care and prevent contamination of hospital facilities and personnel. The radiation accident management plan should be instituted in advance. Exposure and contamination victims are treated differently. Exposed patients have sustained either partial or whole-body exposure but do not carry radioactive material; contaminated patients have also been exposed, but they have radioactive material either externally or internally and thus are continually exposed to radiation until the contaminant is removed. The treatment area and personnel must be protected with use of isolation, clean transfer techniques, and appropriate attire. After clothing has been removed, the patient's medical condition is assessed, stabilized, and treated. Samples from the affected areas, eyes, nose, and mouth are obtained for analysis and planning definitive treatment. For external contamination, the skin is washed with normal saline or mild detergent. Treatment of internal contamination is based on the isotopes involved and may include saturation of the crucial organ, dilution therapy, isotope displacement, or use of chelating agents. After a survey to ensure that no residual contamination remains, the patient is transferred to a care unit. Effects of exposure are seen over periods ranging from days to weeks to years, depending on the total dose received. Knowing the dose allows clinicians to predict what effects may ultimately occur.

Accidents↗
PubMed1993

Abnormal ambulatory left ventricular ejection fraction in heart transplant arteriopathy.

The morbidity and mortality from heart transplantation has been reduced dramatically over the last several years. However, the long-term survival in heart transplant recipients is limited by arteriopathy in the allograft coronary arteries, the pathophysiology of which is poorly understood. The diagnosis of this arteriopathy is at present limited to cardiac catheterization. Noninvasive studies have proven to be of limited benefit in diagnosing this arteriopathy. The authors performed cardiac vest studies in nine heart transplant recipient patients. Six of the vest studies were abnormal; five of the patients had documented transplant coronary artery disease by cardiac catheterization. They found that the sensitivity and negative predictive value of the cardiac vest in identifying arteriopathy in transplant recipients was 100%. The authors propose that cardiac vest could be a sensitive, noninvasive screening test for identifying arteriopathy in heart transplant recipients.

Ambulatory Care↗
PubMed1989

Errors in the determination of left ventricular functional parameters.

Gated blood-pool scans of the left ventricle are routinely employed for determination of the left ventricular ejection fraction. Recently, attempts have been made to evaluate other left ventricular functional parameters. These values include peak emptying rate (PER), time to peak emptying rate (TPER), peak filling rate (PFR), and time to peak filling rate (TPFR). In studying these parameters clinically, we identified many software errors and assumptions that impact on these values. These errors may also affect the determination of left ventricular ejection fraction (EF). We conclude that before any serious investigation of left ventricular functional parameters is undertaken, a detailed evaluation and standardization of the acquisition and edge detection algorithms must be performed.

Diagnostic Errors↗
PubMed1987

Two affinity immunoelectrophoretic methods for studying collagen interaction with von Willebrand factor antigen.

Two new immunoelectrophoretic methods are described for studying the interaction of collagen fibrils with von Willebrand factor antigen (vWF: Ag). In the first, the sample was electrophoresed through a collagen-agarose wedge into an antibody-agarose area, and immunoprecipitin lines was detected by staining. Different immunoprecipitin patterns were obtained with the vWF: Ag of normal plasma, commercial FVIII preparations, and von Willebrand disease (vWD) type IIa plasma as the result of collagen binding of vWF: Ag. In the other method, the sample was electrophoresed into agarose for preliminary separation of forms, followed by migration in the second dimension through a collagen spacer gel into an antibody-agarose area. This method demonstrated preferential binding of high molecular weight forms of vWF: Ag in normal plasma and slight binding of the lower molecular weight forms of antigen found in vWD type IIa plasma. The affinity wedge method is a convenient general method for finding quickly a useful concentration of affinity reagent.

Antigens↗
PubMed1986

A paradoxical effect of antibody concentration on vWF-dependent platelet agglutination distinguishes between botrocetin and ristocetin-induced agglutination.

Several heterologous antisera directed against either human or porcine von Willebrand factor (vWF), inhibited botrocetin-induced vWF-dependent agglutination at high concentrations but were found to enhance this reaction at low concentrations. Purified IgG from these immune sera also potentiated botrocetin-induced agglutination as did its F(ab)'2 fragments. However, monovalent Fab fragments of the purified IgG did not. The requirement for a divalent antigen combining region suggests that one possible mechanism of enhanced agglutination may involve intra or inter-molecular cross-linking of vWF multimers by the antibody. Another possible mechanism could be a conformational change in the vWF molecule induced by antibody binding. Such a conformational change may provide additional active sites on the vWF molecule that, in the presence of botrocetin, lead to enhancement of the agglutination reaction. Antisera to human vWF that showed this paradoxical inhibitory/enhancing effect on botrocetin-induced agglutination also inhibited ristocetin-induced platelet agglutination at high concentrations, but failed to enhance agglutination at any concentration. The different effects of these antisera on botrocetin and ristocetin-induced platelet agglutination suggest that no single mechanism can explain the action of both of these mediators.

Adjuvants, Immunologic↗
PubMed1986

Visualization of von Willebrand factor multimers by immunoenzymatic stain using avidin-biotin peroxidase complex.

A technique for the detection of von Willebrand factor multimers separated by discontinuous SDS agarose electrophoresis has been developed using non-radioactive compounds. The multimeric patterns were visualized by monospecific anti-human vWF:Ag followed by incubation with biotinylated antibody. After addition of avidin-biotin-peroxidase complex, the peroxidase activity was detected by 4-chloro-1-naphthol, giving sharp bands with a clear background. By this method, the differences of vWF:Ag multimers could be easily observed between normal plasma and the plasmas from variant type vWD (IIA, IIB, platelet-type). Large and intermediate multimers were absent in the plasma with vWD type IIA, while only large multimers were absent in the plasma with vWD IIB and platelet-type. The absence of large multimers was also observed in two commercial FVIII preparations having the ratio of vWF/vWF:Ag 0.18 and 0.63. The preparation with the ratio of 0.63 showed the presence of larger intermediate multimers. Electrophoresis in SDS 1.5% agarose gel revealed triplet structure of each small multimer, and a relative increase of the smallest subband was observed in vWD IIA plasma, platelet-type vWD plasma and commercial FVIII preparations. The procedures described are easy and safe to perform and are useful for screening or classifying cases with vWD in general laboratories.

Avidin↗
PubMed1985

Parallel characterization of bovine von Willebrand protein (factor VIII-associated protein) by light scattering and SDS gel electrophoresis.

Highly purified bovine von Willebrand protein (vWP) has been studied with two complementary techniques. Light scattering measurements on different samples give weight average molecular weights in the range from 7 to 13 million, radius of gyration between 75 and 140 nm and diffusion coefficient near 4.15 X 10(-8) cm2/sec. Scans after electrophoresis in sodium dodecyl sulfate on 2% agarose gels, stained with Coomassie blue, allow calculation of a mass distribution over a series of oligomers with relative size in a range from 1 to 20. The ratio of the average mol. wt. from light scattering and the average size for the observed distribution, which is the mol. wt. increment for successive vWP oligomers, has been determined and found to be 1.0 million. This implies that the molecules of vWP are oligomers of subunits themselves consisting of 4 polypeptide chains each of mol. wt. circa 250,000.

Animals↗
PubMed1984

A light-scattering study of bovine factor VIII.

Classical light-scattering measurements made on bovine Factor VIII preparations, which contain a series of multimers ranging from 1 greater than 12 X 10(6) molecular weight, gave a weight average molecular weight of about 8 X 10(6) and a z-average radius of gyration of about 3000 A. Characteristic dimensions for variously shaped models were calculated.

Animals↗
PubMed1984

Platelet-collagen interactions: increase in rate of adhesion of fixed washed platelets by factor VIII-related antigen.

A simple technique using an aggregometer and fixed washed human platelets (FWP) and fibrillar collagen has been used to evaluate the contribution of the two components of the factor VIII (FVIII) complex to platelet-collagen interactions. FWP bound individually to collagen fibrils in suspension, and both the total number of FWP bound and the rate of adhesion increased with increasing collagen concentration. Von Willebrand's disease (vWD) type I or normal plasma immunoadsorbed with anti-factor VIII-related antigen (anti-FVIIIR:Ag) antiserum gave 20% and vWD type IIa gave 50% of the rate of adhesion obtained with normal, hemophilia A, or hemophilia A with inhibitor plasma, but the same percent adhesion was found with all plasmas. The rate of adhesion of both vWD type I and type IIa was corrected by the addition of purified FVIII complex. These results indicated that the FVIIIR:Ag and not the factor VIII coagulant activity (FVIII:C) in normal plasma or purified FVIII complex caused an accelerating effect on the rate at which FWP bound to collagen. Collagen fibrils not only bound FWP, but also adsorbed the FVIII complex with preferential adsorption of the forms of FVIIIR:Ag with the greatest ristocetin cofactor (FVIIIR:RCoF) activity. Saturation of collagen with FWP did not change the adsorption pattern of the FVIII complex. Also anti-FVIIIR:Ag blocked the accelerating effect of the FVIII complex but not the adhesion of FWP. Thus, FWP and FVIIIR:Ag appeared to bind to separate sites on collagen.

Adult↗
PubMed1984

A quantitative method for studying platelet adhesion to collagen.

A simple turbidimetric method is described that permits quantitation of both the number and the rate at which human fixed washed platelets adhere to fibrillar collagen in suspension. Fixed washed platelets were mixed with buffer or test sample in an aggregometer cuvette. Collagen was added, and the change in light transmission was recorded at 37 degrees C. Percent adhesion was obtained from the maximum change in light transmission within 5 minutes, and the adhesion rate was calculated from the initial slope of the adhesion curve. In this system, the percent adhesion was optimal at ionic strengths of 0.1 to 0.15 in a pH range of 7.0 to 8.0. Percent adhesion could be increased either by lowering the platelet number or by increasing the collagen concentration. No adherence of fixed washed platelets to heat-denatured collagen or Cytodex 3 beads was observed. Adhesion rate increased with greater stirring speed, but decreased with increasing concentrations of bovine serum albumin or normal human plasma, but the percent adhesion remained relatively constant. The rate of adhesion in 20% normal human plasma was greater than that in 1% to 4% bovine serum albumin buffer. This suggests that normal plasma contains some factor(s) that can overcome the inhibitory effect of protein on the rate of adhesion of fixed washed platelets to fibrillar collagen.

Blood Platelets↗
PubMed1983

Botrocetin (venom coagglutinin): reaction with a broad spectrum of multimeric forms of factor VIII macromolecular complex.

Botrocetin, originally called venom coagglutinin, is a Bothrops factor that causes aggregation of blood platelets in the presence of the von Willebrand component of the factor VIII macromolecular complex. The complex consists of a series of multimers with a molecular weight of about 1-20 x 10(6). Ristocetin, another agent that causes platelet aggregation dependent on von Willebrand factor, reacts with only the higher molecular weight multimers. We report on the reactivity of botrocetin in relation to the multimeric structure of the factor VIII complex. Several plasmas or plasma fractions with abnormal distribution of the multimeric sizes were examined, including variant von Willebrand disease type IIA with lack of the higher molecular weight forms, commercial antihemophilic factor concentrates with a preponderance of lower molecular weight forms, cryoprecipitate-free plasma containing mainly the smaller multimers, and a chromatographic fraction of plasma containing only the highest molecular weight polymers. Factor VIII-related antigen content was adjusted to 25-100%. All of the preparations lacking the high molecular weight forms caused prompt platelet aggregation with botrocetin, but none of them caused aggregation in the ristocetin test made isochronal with the botrocetin test. The very high molecular weight polymers were equally effective with botrocetin and ristocetin. These findings indicate that the Bothrops factor is reactive with a broad spectrum of high to low molecular weight forms of the factor VIII complex, suggesting that bioassays of von Willebrand factor with botrocetin should correlate better with immunoassays for factor VIII-related antigen and could reflect better the full platelet-aggregating function of the complex than do ristocetin determinations.

Adolescent↗