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Biomedical subjects

D A Gabriel

Publications and source records attributed to D A Gabriel.

66 records · Page 4Linked to original sources
PubMed1983

Hereditary dysfibrinogenemia in a patient with thrombotic disease.

A new case of congenital dysfibrinogenemia, in which the patient has severe thrombotic disease, is reported. The abnormal fibrinogen molecules are characterized by normal fibrinopeptide release with thrombin and defective polymerization in the formation of fibrin. Clotting times with ancrod and reptilase are significantly prolonged. All other coagulation tests (except those for fibrinogen function) are normal, and the patient has no other underlying disease. The apparent paradox of defective fibrinogen, which clots abnormally and is yet associated with thrombotic disease, can be explained by further analysis of the patient's fibrinogen. The two important functional properties of this fibrinogen are: (1) it forms fibrin gels that are extremely rigid, and (2) the fibrin is highly resistant to lysis by plasmin. Thus, although the abnormal fibrinogen forms defective clots, the fibrin that is formed cannot be removed by the fibrinolytic system. These results provide a molecular explanation for the thrombotic disease in this patient. This abnormal fibrinogen appears to have unique characteristics and has been designated as fibrinogen Chapel Hill Ill.

Adolescent↗
PubMed1983

The influence of immunoglobulin (IgG) on the assembly of fibrin gels.

The presence of immunoglobulin is shown to alter the network structure of gels formed from purified fibrinogen. Turbidity measurements were used to calculate the effect of increasing concentrations of immunoglobulin on the mass-length ratio of fibrin fibers composing the gels. Normal pooled, human IgG was found to reduce the mass-length ratio of fibrin fibers composing the gel from 7 X 10(12) daltons/cm with no immunoglobulin to 1 X 10(12) in the presence of 40 mg/ml. Monoclonal IgGk was found to be more effective in the reduction of the mass-length ratio than normal IgG. This observation indicates that the immunoglobulin must decrease lateral association of fibrin protofibrils. As the mass-length ratio decreased, the rigidity of the gels increased as the immunoglobulin concentration was elevated (1.2 dynes/cm2 with no immunoglobulin to 2.9 at 15 mg/ml). Since the fibrin fiber diameters were decreased, the number of interfiber crosslinks must have been increased to explain the increase in rigidity. Antifibrinogen, antifibrin intermediate, and antithrombin antibody activity of the immunoglobulins were proved unlikely.

Antibodies, Monoclonal↗
PubMed1982

Tracer diffusion coefficients of oxyhemoglobin A and oxyhemoglobin S in blood cells as determined by pulsed field gradient NMR.

It is demonstrated that tracer diffusion coefficients can be determined for oxyhemoglobin A (HbA-O2) and oxyhemoglobin S (HbS-O2) in intact blood cells by means of pulsed field gradient NMR (PFG-NMR). This is possible because the method discriminates between both rapidly moving water molecules and molecules having small proton transverse relaxation times (T2). The results indicate that only hemoglobin molecules contribute to the echo signals when large field gradients are used. The dependence of the measured diffusion coefficients on osmolarity and pH are attributed to changes in hemoglobin concentration resulting from changes in cell volume.

Anemia, Sickle Cell↗
PubMed1981

The physical characterization of an aggregating IgG heteropolymer containing rheumatoid factor.

An IgG heteropolymer containing rheumatoid factor activity was isolated from the serum of a patient with the polyclonal hyperviscosity syndrome. This aggregating system was characterized using ultracentrifugation, classical light scattering, and rheological methods. The degree of polymerization is shown to be reversible and dependent on both pH and concentration. Light-scattering studies show a minimum stable intermediate consisting of four IgG monomers to exist at pH 7.4. The theoretical intrinsic viscosity and radius of gyration for the feasible configurations of such a tetramer were calculated. These models were compared to the experimental values. A cyclic structure is shown to be most compatible with the experimental data. Immunochemical analysis suggests that each tetramer contains two IgG1 rheumatoid factors binding to determinants on IgG3 Fc regions.

Blood Viscosity↗
PubMed1980

The effect of dextran 70 on the structure of plasma-derived fibrin gels.

Measurements of fiber mass-length ratios and fibrin gel elastic modulus as a function of dextran 70 concentration are reported for fibrin gels derived from human plasma. Dextran 70 at 0.1 mg/ml produces a 50% reduction in the storage modulus of fibrin gels obtained from human plasma diluted 1:10 with saline. Since the fibrin fiber diameter increases as only a weak function of the dextran 70 concentration, the lower elastic modulus most likely results from a reduction in network branch points. Aprotinin is also shown to modulate the dextran effect.

Aprotinin↗
PubMed1979

Physical studies on isolated human prothrombin fragment-2. Comparisons with human prothrombin fragment-1.

Variation of pH strongly affects the fluorescence intensity of human prothrombin fragment-1 in a manner suggesting contributions from a number of protropic equilibria including groups with apparent pKa values near 3.0. These results suggest a structural role for pK1a of gamma-carboxyglutamic acid noieties. Added calcium ions (9 mM calcium chloride) quench the fluorescence titration curve uniformly above pH 4. Below pH 4, however, the titration curve in the presence of calcium ions suggests that calcium-ion-dependent processes leading to fluorescence quenching are pH-dependent. Upon back titration of human fragment-1, from pH 9, hysteresis is observed. Human prothrombin fragment-2 fluorescence titration curves are relatively broad at low pH suggesting the titration of normal carboxyl groups. The titration curves of fragment-2 are not affected by the presence of calcium ions, and hysteresis occurs upon back titration from low pH values. Circular dichroism (CD) Cotton effects appear at 232 nm and 280 nm and a trough appears at 203 nm in the CD spectrum of human prothrombin fragment-2. The Cotton effects in the region from 230 nm to 300 nm are sensitive to pH, ellipticity values at 232 nm increasing from approximately 300 at pH 2.5 to 1300 (degree-cm/decimole) at neutral pH and finally become negative at high pH values. In contrast to fragment-1, at neutral pH the fragment-2 Cotton effect at 232 nm is insensitive to the presence of 8 mM calcium chloride.

Calcium↗
PubMedDate not supplied

Reliability of SEMG spike parameters during concentric contractions.

This study examined the reliability of four surface electromyographic (SEMG) spike parameters during concentric (isotonic) contractions: mean spike amplitude, mean spike frequency, mean spike slope, and the mean number of peaks per spike. Eighteen subjects performed rapid elbow flexion on a horizontal angular displacement device that was used to measure joint torque. The SEMG activity of the biceps brachii was monitored with Beckman Ag/AgCl electrodes. The testing schedule consisted of four hundred trials distributed equally over four sessions. The stability of the means across sessions and the consistency of scores within subjects was determined for the first five (1-5) and last five (96-100) trials of each session to examine the possible influence of a "warm up" effect. All measures exhibited a significant (p < 0.01) increase across test days. However, the intraclass correlation coefficients for the first five (1-5) trials ranged from 0.76 to 0.83, which was quite good. The stability and consistency for most of the criterion measures increased for the last five (96-100) trials of each session. This resulted in a higher range of coefficients from 0.85 to 0.93. Subjects became more homogeneous with respect to the mean number of peaks per spike and the R decreased to 0.65. It was concluded that the four SEMG spike parameters could be reliably measured to assess changes in muscle activity patterns. The adaptations in SEMG spike activity suggest that repetitive dynamic contractions enhanced the ability to recruit more fast-twitch motor units across test days.

Adult↗