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Biomedical subjects

A D Heyns

Publications and source records attributed to A D Heyns.

67 records · Page 4Linked to original sources
PubMed1979

Thrombotic thrombocytopenic purpura. A case investigated with 111In-oxine-labelled platelets.

A 34-year old woman presented with the clinical and laboratory features of thrombotic thrombocytopenic purpura (TTP). Studies with isologous platelets labelled with 111In-oxine revealed a short half-life of circulating platelets (18,5 hours) and destruction of the transfused platelets in the spleen, liver and bone marrow. There was no scientigraphic evidence of deposition of labelled platelets in the vasculature. The patient was treated with daily fresh frozen plasma transfusions, but no improvement in platelet count or serum urea level was noted. Although there was no clinical evidence of a bleeding tendency at the time, the patient had a fatal cerebrovascular haemorrhage. The findings in this case suggest that an immune type destruction of platelets may occur in TTP.

Adult↗
PubMed1978

[Ferrokinetic studies and the prognosis of aplastic anaemia].

The value of ferrokinetic studies for determining the prognosis of patients with aplastic anaemia was assessed 17 patients. Plasma 59Fe clearance, red cell 59Fe incorporation (at 10 days), sacral and hepatic 59Fe uptake (at 6,0 h, measured by surface counting), and 59Fe bone marrow scanning were compared with peripheral blood pancytopenia and marrow cellularity on aspiration and biopsy. In this limited study no statistically significant correlation could be found between ferrokinetic determinations and other criteria of bone marrow failure, although there was a tendency for plasma 59Fe clearance and sacral 59Fe uptake to show some correlation with marrow cellularity on biopsy and with degrees of reticulocytopenia, thrombocytopenia and neutropenia. Ferrokinetic measurements did not differentiate between patients with favourable and those with poor prognoses.

Adolescent↗
PubMed1978

Uranyl-labelled antibody (ULA) method and its application for Rh antibodies.

The existent labelling materials for studies of antigen--antibody interaction at ultrastructural level, namely ferritin and peroxidase, because of their large molecular size do not fulfill all requirements of excellent markers for electron microscopy (EM). Uranyl acetate has a molecule 354 times smaller than IgG and its uranium atom is electron-dense. These physical characteristics of uranyl acetate make it a labelling material par excellence as described in this article. Quantitative and qualitative studies of Rh antigen-antibody interactions are for the first time presented at the ultrastructural level, and the application of the uranyl-labelled antibody (ULA) method for weak antisera (dilutions 100 to 1000 time higher than the Coombs range of sensitivity) is demonstrated. The ULA method opens a new era for studies of antigens, antibodies and their interactions because it will demonstrate visibly details of the antigen-antibody interaction and is especially suitable for studies of weak antisera.

Antigen-Antibody Reactions↗
PubMed1978

Platelet aggregation in chronic idiopathic thrombocytopenic purpura.

A method for washing platelets by albumin density gradient separation has been modified to prepare platelet rich plasma of thrombocytopenic patients for platelet aggregation studies. The concentration procedure, consisting of centrifuging platelets into a specific gravity gradient between plasma and 40-45% aqueous solution of bovine albumin, does not affect platelet aggregation adversely. Platelet aggregation in eight patients with chronic idiopathic thrombocytopenic purpura was determined by this method. On the basis of the results the patients could clearly be divided into two groups: four patients with normal aggregation and four with a qualitative platelet defect. In contrast to the other patients, the group with an in vitro platelet functional defect all had more prolonged bleeding times and the presence of a serum antiplatelet antibody.

Blood Cell Count↗
PubMed1978

Comparison between the unsaturated plasma folate binder and in vivo labelled plasma folate binder.

Endogenous plasma folate binder denuded of folate by dialysis at pH 3, subsequently bound more methylfolate than folic acid, in contrast with the minor unsaturated plasma binder which bound folic acid in preference to methylfolate. On Sephadex DEAE-A50 chromatography 14C-CH3H4PteGlu bound to acid-denuded endogenous binder, eluted like the endogenous binder-radioactivity, labelled in vivo after oral 14C-CH3H4PteGlu. It is suggested that the endogenous plasma folate binder is not identical with the unsaturated binder.

Blood Proteins↗
PubMed1977

The identification of human T and B lymphocytes by electron microscopy.

Lymphocytes of peripheral blood, bone marrow, spleen, vermiform appendix, tonsil and Mantoux skin reaction were examined by electron microscopy (EM) and classified as T, B and Null cells by E-rosette and immunoglobulin membrane-receptor characteristics. The low pH and ionic strength of the fixative solution for EM, and some other minor procedural modifications, made it possible to distinguish B and T lymphocytes morphologically. T-cells have electron-dense cytoplasm and euchromatin in the nucleus whereas B-cells constantly have electron-lucent cytoplasm and euchromatin in the nucleus. A proportion of lymphocytes were unclassifiable by their ultrastructural features. These unclassifiable cells may be Null cells as determined by the classical techniques. The specificity and simplicity of this EM technique for T and B lymphocytes is especially useful for studies of immunocompetent-cell topography and cell-to-cell interaction in lymphoid organs. It may also be utilized for diagnostic purposes in immunocytic dyscrasias.

B-Lymphocytes↗
PubMed1976

[Pancytopenia and aplastic anemia: a retrospective study].

During January 1971--June 1975 we examined 195 patients with pancytopenia. The cause was bone marrow failure in 67.7% of cases (classic aplastic anaemia in 11.3%) hypersplenism in 7.7%, massive blood transfusions in 1.5%, severe infections in 9.7% (Gram-negative in 3%), and various other conditions in 7.8%. Records were insufficient for diagnosis in 5.6% of cases. Analysis of the 22 patients with aplastic anaemia showed no apparent aetiology in 16 (72.7%), previous phenylbutazone ingestion in 2, and Fanconi-type anaemia in 4 of 7 children. One-year survival was 73.7%, 2-year survival 71.4%, 3-year survival 63.6% and 4-year survival 57.1%. Marrow-investigation of the 21 available samples showed that 6 were acellular, 11 hypocellular and 4 normocellular. All patients received at least temporary therapy with anabolic steroids but its effectivity could not be satisfactorily assessed. Five patients died within 7 months and 5 patients went into remission, needing no further therapy. The initial haematological features of the 5 patients who died were not significantly different from those of the rest of the patients.

Adult↗
PubMedDate not supplied

Kinetics and mobilization from the spleen of indium-111-labeled platelets during platelet apheresis.

The rate and extent of platelet mobilization from the spleen were measured, and their relationship to the removal of platelets from the peripheral blood during discontinuous flow platelet apheresis was determined in four normal volunteers. Autologous platelets were labeled with Indium-111-oxine and in vivo whole body and organ In-111 radioactivity quantitated with a scintillation camera and a computer-assisted imaging system. Dynamic changes in splenic radioactivity were monitored during 12 cycles of platelet apheresis. The number of platelets harvested and changes in whole body and blood In-111 activity were determined during the procedure. The platelet life-span was estimated, and the sites of sequestration of labeled platelets was measured. Platelet apheresis removed a mean of 64 percent of platelets in the circulation; i.e., 48 percent of all platelets in the body. During the procedures, 28.0 +/- 9.4 percent In-111-labeled platelets in the body were removed, splenic radioactivity decreased by 36.5 +/- 13.2 percent, and whole body activity decreased by 34.5 +/- 9.7 percent. In-111 activity in the spleen and whole body decreased in parallel, indicating a dynamic equilibrium between these pools. The life-span of the labeled platelets was 226 +/- 25 hours, similar to that of normal subjects. The major sites of sequestration of senescent platelets were the spleen (37.9 +/- 20%) and liver (30.3 +/- 5.6%); this is similar to that found in normal subjects. We conclude that as platelets are removed from the peripheral blood, the blood pool is rapidly and effectively replenished from the splenic platelet pool. These two pools are in dynamic equilibrium and permit removal of large numbers of platelets without resultant thrombocytopenia. Platelet apheresis does not adversely effect platelet life-span, and the sequestration pattern in the reticuloendothelial system is normal.

Adult↗
PubMedDate not supplied

Aspects of folate metabolism in lactating women studied after ingestion of 14C-methylfolate.

Radioactive methylfolate (14C-5CH3H4PteGlu) (10-14 microgram/kg) was fed to four lactating women presenting with breast abscesses necessitating cessation of lactation. The appearance of radiofolate in milk, plasma and urine over the next 24 hours was investigated. In spite of a minimal postabsorption rise of plasma biofolate, plasma radiofolate (including a dialysis-resistant (bound) fraction) increased steadily to 1.26 to 5.11 microgram/l at 24 hours. Urinary radiofolate excretion was considerable. Total milk biofolate rose significantly by 15 to 28 microgram/l, in contrast with a much smaller radiofolate fraction (1.95-3.88 microgram/l) which at 24 hours was comparable with that of plasma. Milk radiofolate included a dialysis-resistant fraction rising to 0.75 to 1.15 microgram/l at 24 hours. On chromatography (Sephadex-DEAE-A50) plasma, urine and milk showed a nonbound radiofolate peak suggestive of 10-CHO.H4PteGlu. This folate may originate predominantly from the apocrine mammary glands. The in vitro labelled radiofolate milk binder could not be identified chromatographically, but it was shown that the in vitro milk binders of PteGlu and 5CH3H4PteGlu could be separated chromatographically.

Adult↗
PubMedDate not supplied

An evaluation of four methods of 111In planar image quantification.

The accurate quantification of the in vivo distribution of 111In labeled platelets, other cells, and proteins with a scintillation camera is important in clinical and experimental medicine. Planar techniques of image quantification were therefore evaluated with the aim of improving on the accuracy, and simplifying the techniques currently in use. The attenuation of the 172- and 247-keV photons of 111In, singly and in combination, was determined for varying diameter flat sources (3.4 to 16.9 cm). The influence of region of interest (ROI) selection on the shape of the attenuation curves was also determined for five different ROI's. Defining the attenuation curves mathematically generated parameters of fit for three approaches to in vivo quantification, namely: a single exponential geometric mean approach that takes into account source size, depth-dependent, and depth-independent buildup factor approaches to account for the contribution of scatter. The accuracy of these techniques was ascertained and compared to the classical geometric mean method. This was done in a waxen phantom of a human thorax with a hollow liver and spleen. The results indicated that the depth-independent buildup factor is the best method; the error for quantification in the spleen was 0.8% +/- 2.2%. The classical geometric mean approach gave a corresponding error of 43.3% +/- 3.4%. Since the attenuation of the two energies of 111In differ, their ratio changes with depth. This phenomenon was investigated with the goal of determining whether the depth of an object can be estimated from one set of planar images. This was not successful.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMedDate not supplied

Analysis of indium-111 platelet kinetics and imaging in patients with aortic grafts and abdominal aortic aneurysms.

To quantitatively characterize processes of platelet thrombus formation in vivo, the kinetics and incorporation into thrombus of autologous In-111-labeled platelets were compared in six patients with aortic aneurysms and in seven patients with prosthetic aortic grafts. Although platelet survival was comparably shortened in both patient groups (mean, 5.8 days), the maximum radioactivity (percentage of whole body radioactivity) as determined by gamma camera imaging was higher in the aneurysms than in the grafts (3.3% +/- 1.6% vs. 1.6% +/- 1.1%, p = 0.05). Maximum In-111 uptake was also attained more quickly in the aneurysm patients (2.3 +/- 0.8 days vs. 3.5 +/- 1.3 days; p = 0.07). The experimental platelet kinetic and imaging data were subsequently evaluated by compartmental analysis to estimate both normal and disease-related components of platelet destruction. This analysis indicated that deposited platelet radioactivity had a longer residence time on grafts (2.9 +/- 1.7 days vs. 1.4 +/- 0.9 days, p = 0.07) but accumulated at a faster rate in aneurysms (5.0% +/- 3.4% per day vs. 1.4% +/- 0.9% per day, p = 0.02). As determined by imaging, only a proportion of increased platelet destruction was specifically due to the aneurysms (55% +/- 38%) or grafts (17% +/- 11%, p = 0.03). This result indicates additional components of platelet destruction unrelated to graft and aneurysm thrombus formation which, in some graft patients, may reflect a greater severity of vascular disease or other mechanisms causing a preferential shortening of platelet survival. Thus, the analytical approach described may be a useful one for discriminating components of in vivo platelet utilization including platelet removal due to normal hemostatic and senescent mechanisms, localized thrombus formation, and more generalized vascular disease.

Adult↗