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Biomedical subjects

D L Stone

Publications and source records attributed to D L Stone.

At least 55 records · Page 3Linked to original sources
PubMed1990

Red cell antibody identification by solid phase red cell adherence utilizing dried RBC monolayers.

Recent technological advances in the immobilization and drying of red cell monolayers for use in solid phase red cell adherence (SPRCA) assays have resulted in the development of reagent red cells for antibody screening and identification that are stable at mom temperature. Panels consisting of twelve different RBC samples dried onto individual microplate wells were evaluated with 176 samples whose antibody specificities had previously been determined by conventional hemagglutination techniques. Identification tests performed with dried SPRCA panels proved to be more sensitive and less time consuming than hemagglutination tests. The red cell antigens of dried membranes were shown to be stable and reactive following storage for 120 days at mom temperature.

Journal Article↗
PubMed1987

Radionuclide assessment of diastolic function in aortic regurgitation: a critical study of its measurement.

Systolic and diastolic ventricular function was assessed in patients with aortic regurgitation as the peak ejection and filling rates. The measured rate of change of volume was related to the ejection fraction when expressed in end diastolic volumes per second (EDV.s-1) but not when expressed as stroke volumes per second (STV.s-1) suggesting that an apparent variation in left ventricular volume change when expressed as EDV.s-1 may occur as a result of an increase in end diastolic volume rather than any absolute alteration in filling rate. There was a significantly greater increase in peak filling than peak ejection rate with increasing heart rate in patients with aortic regurgitation, and this relation was exaggerated compared with that in controls. No definite difference in these indices of left ventricular function was found in patients with aortic regurgitation of severity varying from mild to severe. Isolated measurements of left ventricular filling rate may not accurately reflect left ventricular compliance since other factors, particularly heart rate, must be considered.

Adult↗
PubMed1987

Radionuclide evaluation of aortic regurgitation: assessment of ventricular function by Fourier phase analysis.

Forty patients with chronic isolated aortic regurgitation were studied by phase analysis of equilibrium radionuclide ventriculography to see whether this technique could detect changes in left ventricular (LV) function before the onset of symptoms. This technique was compared to the radionuclide ejection fraction and echocardiography. The severity of LV volume overload was assessed using the radionuclide regurgitant index. Patients with clinically severe aortic regurgitation had severe volume overload (high regurgitation index), increased echocardiographic left ventricular dimensions and significantly increased phase spread (loss of synchrony of wall motion) compared to mild and moderate groups. All but one had well maintained global left ventricular function assessed by the ejection fraction. All seven patients with definite symptoms had a marked increase in phase spread and severe volume overload.

Adult↗
PubMed1987

Human amnion as a model for IgG transport.

The ability of fresh human amnion to bind and internalize horseradish peroxidase-labeled IgG (IgG-HRP) was examined in an in vitro Ussing chamber system. The amnion demonstrated unique cell membrane receptors for the Fc portion of IgG molecules (Fc gamma R). The Fc gamma R exhibit exquisite specificity and affinity for IgG monomers as demonstrated by staining with labeled IgG. Labeled IgA, IgM, F(ab')2 fragments of IgG, aggregated IgG, and antigen-antibody complexes all failed to bind to the amnionic epithelial cells. Binding was only minimally affected by changes in ionic strength or pH when viewed at the light microscopic level. The Fc gamma R are located on both the apical and basal cell membranes. The binding of IgG-HRP to the amnion cell membrane was detectable within 1 min, and internalization of the ligand occurred within 5 min. No binding of IgG-HRP was observed following treatment of the membrane with 0.25% trypsin for 30 min at room temperature. Incubation of the amnion at 4 degrees C or in the presence of colchicine or cytochalasin D prevented internalization of the IgG-HRP. These experiments demonstrate Fc gamma R on human amnionic epithelial cells that both bind and internalize IgG, thus allowing the amnion to be used as a model system for studying IgG transport.

Amnion↗
PubMed1987

Molecular cloning and sequencing of a rat preprogastrin complementary deoxyribonucleic acid.

Gastrin biosynthesis involves a complex series of posttranslational modifications; their elucidation requires a knowledge of the structure of the gastrin precursor. The complete structure of rat preprogastrin was deduced from the nucleotide sequence of a full length cDNA clone isolated from a rat antral cDNA library. Northern blot hybridization analysis of rat antral RNA together with human antral RNA, reveals a single mRNA species of approximately 670 bases. Comparison of this sequence with those of porcine and human gastrin reveals extensive (73%) homology in the gastrin coding region as well as short regions of conserved nucleotides in the noncoding regions. The rat sequence encodes a preprogastrin of 104 amino acids which consists of a signal peptide, a 37 amino acid prosegment; and the gastrin 34 sequence, followed by a glycine (the amide donor), and flanked by pairs of arginine residues. Cleavage at an internal pair of lysine residues yields gastrin 17. Unlike the human and porcine sequences, rat preprogastrin contains a 9 amino acid carboxy-terminal extension peptide (-Ser-Ala-Glu-Glu-Glu-Asp-Gln-Tyr-Asn) which is homologous to the midportion of gastrin 17 including the site of tyrosine sulfation.

Amino Acid Sequence↗
PubMed1986

A comparison of radionuclide methods of evaluating aortic regurgitation with observations on the effect of exercise and symptoms.

The severity of aortic regurgitation, as assessed by the radionuclide regurgitant index and Fourier amplitude ratio, was compared in 29 patients. Both methods were highly reproducible and agreed in patients with mild-to-moderate regurgitation. The regurgitant index fell with exercise. This change showed a linear relationship with heart rate, allowing the regurgitant index to be corrected for heart rate. There was general agreement between the radionuclide method and echocardiography, but the regurgitant index was unable to select patients with symptoms. The regurgitant index provides an overall guide to the severity of aortic regurgitation, but may be unreliable in the presence of deteriorating ventricular function.

Aortic Valve Insufficiency↗
PubMed1985

Improved selection of patients for aneurysmectomy by combined phase and amplitude analysis of gated cardiac scintigraphy.

Twelve patients undergoing left ventricular aneurysmectomy were studied by combined phase and amplitude analysis of gated blood pool scintigraphy before and after operation, to establish whether the presence of paradoxical systolic movement, as defined by this method, influenced the result of surgical treatment. There was a significant increase in the ejection fraction after operation in those patients with paradoxical systolic movement and no improvement in those with akinesis. The extent of the increase in ejection fraction was related to the size of paradoxical segment resected. It is argued that this improvement in left ventricular function reflects a reduction in the left ventricular and diastolic volume and improved efficiency of ejection of the stroke volume, resulting from resection of the scar. Combined phase and amplitude analysis may help in selecting patients most likely to benefit from aneurysmectomy.

Adult↗
PubMed1985

Quantification of intracardiac shunts by gold-195m, a new radionuclide with a short half life.

Gold-195m, a radionuclide with a short half life (30.5 s) was used to quantify left to right intracardiac shunts. The results of this method were compared with those obtained with technetium-99m, a method that was validated against oximetry. In five patients the pulmonary to systemic flow ratio (greater than 3:1) obtained by both radionuclides indicated that the level of shunting was too high to be measured accurately. In one patient fragmentation of the bolus meant that no satisfactory gamma fit could be obtained. In the remaining 16 patients there was no significant difference between two successive 195mAu studies. The agreement between 99mTc results and 195mAu results was excellent. Oxygen administration, straight leg raising exercise, and the use of oblique projections did not affect the values of the pulmonary to systemic flow ratio. The technique of quantification of intracardiac shunts by 195mAu gives reproducible and accurate results and the low radiation dose means that it is suitable for use in children with suspected left to right shunts.

Adolescent↗
PubMed1984

Arrhythmias after coronary bypass surgery.

Ninety patients undergoing coronary bypass surgery were studied prospectively by bedside and subsequent ambulatory electrocardiographic monitoring to investigate the incidence, possible causes, and prevention of atrial fibrillation. Patients with good left ventricular function were divided randomly into a control group or groups treated with digoxin or propranolol. In the control group the incidence of atrial fibrillation was 27% and of significant ventricular extrasystoles 3%. Propranolol reduced the incidence of atrial fibrillation (14.8%), whereas digoxin had no effect and increased the incidence of ventricular extrasystoles. Age, sex, severity of symptoms, cardiomegaly, heart failure, previous myocardial infarction, and number of grafts did not affect the result. The operative myocardial ischaemic time was related to the occurrence of atrial fibrillation. There was also a significant relation between atrial fibrillation and bundle branch block. Atrial fibrillation is common after coronary artery grafting; it may be due to diffuse myocardial ischaemia or hypothermic injury. The incidence may be reduced by beta blockade.

Adult↗
PubMed1984

Computed tomography in patients with hypertrophic cardiomyopathy.

Computed tomography was undertaken in nine patients (age range 33-69 (mean 48.7) years) with hypertrophic cardiomyopathy. The ventricular septum was demonstrated in each patient and shown to be thickened (mean 25 mm at maximum width). The results agreed with those obtained by echocardiography, except in two patients in whom computed tomography showed preferential thickening of the mid-portion of the ventricular septum. The ventricular free wall was not clearly seen. Computed tomography may prove a valuable technique in the assessment of patients with hypertrophic cardiomyopathy.

Adult↗
PubMed1983

A 195Hgm-195Aum generator for use in first-pass nuclear angiocardiography.

The development of a mercury-195m/gold-195m radionuclide generator system is described, together with the results of preliminary experiments in animals and in man. The daughter radionuclide has a half-life of 30.5 s with a principal gamma emission at 262 keV, ideal for use with the multicrystal camera but suitable also in conjunction with the Anger design. The half-life of the parent radionuclide is 40 h. The eluant in current use is 2.5 mM sodium cyanide, the column being stored under 2% sodium nitrate solution when not in use to prevent radiation damage. Generators capable of delivering 550 MBq of 195Aum in a 0.4 ml bolus have been used for first-pass nuclear angiocardiography, the half-life being long enough to permit administration via peripheral intravenous injection. The radiation dose associated with this radionuclide is much lower than that from conventional 99Tcm-labelled radiopharmaceuticals, permitting multiple sequential studies, even on children.

Animals↗