Isolation, characterization, and location of a donor-acceptor unit from cross-linked fibrin

The cross-linking systems of bovine and human fibrins were studied by the introduction of a radioactive substitute donor as an inhibitor of fibrin cross-linking, separation of the constituent polypeptide chains after sulfitolysis, and tryptic digestion of the labeled gamma-chains. The information gathered from this approach enabled us to isolate and characterize the complete donor-acceptor unit in tryptic digests of fibrin gamma-gamma cross-linked systems. In both bovine and human fibrin, this kind of cross-linking is accomplished by reciprocal bridging between overlapping carboxy-terminal segments of neighboring gamma-chains. The amino acid sequence of the carboxy-terminal heptadecapeptide of the bovine gamma-chain was determined and an alignment of the corresponding region of the human gamma-chain established.

Identification of the polypeptide chains involved in the cross-linking of fibrin

The stabilization of fibrin clots by activated factor XIII involves two different sets of cross-linked chains. In one case (type I) two gamma-chains are linked to each other, indicating that gamma-chains have both donor (suitable lysyl-) and acceptor (suitable glutaminyl-) functions. A second system (type II) consists of a gamma-chain linked to an alpha-chain. Experiments with a substitute donor (glycine ethylester) indicate that only gamma-chains have enzyme-accessible acceptor sites, suggesting that alpha-chain participation is limited to lysyl side chains. A model molecular arrangement for fibrin has been suggested which accommodates all the data.

A double antibody immunoassay for glucagon

A double antibody adaptation of the glucagon radioimmunoassay is described in detail. Guinea pig antiserum allowing the assay of 2,500 unknowns per milliliter of undiluted serum was induced by biweekly immunization. Glucagon was iodinated with I-125 and purified by elution from a cellulose column, maximal immunoprecipitibility approximating 80 per cent. Standard curves in buffer were sensitive to purified glucagon in amounts of less than 100 μμg.

Rapid degradation of labeled glucagon added to human blood was demonstrated. Trasylol was confirmed as an effective inhibitor of this degradation. Endogenous plasma immunoreactive glucagon (IRG) appeared less labile and may have interfered with the quantitative detection of unlabeled exogenous beef-pork glucagon in plasma recovery studies.

The hypothesis is offered that plasma IRG, herein measured at 400 ± 220 (S.D.) μμg./ml., may be composed of a pancreatic and an extrapancreatic fraction of similar but not identical immunological activity. The cross-reactivity of the two components remains a problem in the interpretation of the glucagon immunoassay as applied to plasma.

Cell model for quantum fluids. III. Compressional waves in liquid hydrogen

The velocity of sound is calculated for each of the isotopic forms of liquid hydrogen using the quantum cell model. The velocity of sound increases as the pressure increases and decreases as the temperature increases. Also the reduced velocity of sound decreases as the value of the quantum parameter, Λ*, increases. In addition, the thermodynamic properties of liquid hydrogen compressed by a shock wave are calculated.

Advanced Chinese NiTi alloy wire and clinical observations

Chinese NiTi wire was studied on the bench with six other nickel-titanium-alloy wires. Bending and torsional tests were conducted and temperatures of phase transformation compared. The Chinese NiTi wire was found to have a low stiffness, high springback and constant bending and torsional moments on unloading, in a very large deformation region. It can produce a gentle, nearly constant force. These factors make it desirable for clinical application. Included in this paper are clinical observations of case selected from over 100 patients in current treatment with Chinese NiTi wires. Chinese NiTi wire reduced the leveling and alignment phase of treatment without discomfort to the patient. Chinese NiTi wire can be used in both children and adults.