Biomedical subjects

C L Teng

Publications and source records attributed to C L Teng.

23 records · Page 2Linked to original sources

PubMed1988

The effect of compactional pressure on urease activity.

Jack bean urease is a proteinaceous enzyme, MW approximately 489 kD, readily soluble in water but losing activity when sheared in solution at stresses as low as 2.5 Pa. There is a need for controlled-release forms of many of the new genetically engineered peptide and polypeptide drugs with high specific activities. The simplest form of controlled release would be a sterile compressed pellet of the active component inserted subdermally. However, "activity" may be lost on compaction. Urease can be regarded as a model protein which may lose activity when sheared during compaction in the dry state. Tablets of urease weighing 100 mg were compressed over a range of pressures from 60 to 1750 MPa. No relative loss of activity would be detected following compaction at pressures up to 474 MPa. Above this limiting pressure there was a 50% loss of relative activity, evidently by a compactional effect on the protein quaternary and tertiary structures. No direct relationship was observed between stress (compactional pressure) and inactivation.

Calibration↗

PubMedDate not supplied

A novel approach to anticoagulation control.

Heparin used in extracorporeal therapy often leads to bleeding complications. Protamine used for heparin reversal can cause adverse hemodynamic responses. To control both types of complications, a cellulosic hollow-fiber filter device containing immobilized protamine (defined as a protamine filter) was developed. In vivo experiments with dogs showed that the filter not only removed more than 80% of the anticoagulant activity of heparin, but also caused no clinically significant hemodynamic response. In addition, the protamine filter also significantly attenuated both the thrombocytopenic and granulocytopenic responses associated with the use of protamine. Moreover, the use of immobilized protamine considerably reduced activation of the blood complement system by free protamine.

Animals↗

PubMedDate not supplied

Rapid and precise whole blood protamine titration.

A rapid and precise whole blood protamine titration method was developed. The method uses azure A dye as the titration indicator and thereby replaces the tedious and time-consuming clotting assay with a facile colorimetric assay. The method provides the same accuracy in estimating the titration end-point, but allows the processing time to be shortened to that required by current clinical methods. The simplicity, flexibility, speed, and accuracy offered by the method, and the ability to use whole blood specimens for the measurements, should allow the method to be used by clinicians in the operating room or during a surgical procedure to estimate the adequate protamine dose required for heparin reversal.

Azure Stains↗

PubMedDate not supplied

A filter device for the prevention of both heparin- and protamine-induced complications associated with extracorporeal therapy.

When extracorporeal blood circulation (ECBC) is used, systemic heparinization is necessary to prevent clotting of the blood in the extracorporeal circuit. However, the high circulating heparin concentration needed often leads to bleeding complications. To avoid these, protamine, a heparin antagonist, is administered at the conclusion of the ECBC procedure to reverse the anticoagulant activity of heparin. Intravenous administration of protamine can cause hypotension and shock. To date, there has been no real alternative to control the bleeding risks associated with systemic use of heparin and the adverse effects resulting from heparin reversal with protamine. A novel approach that might control both the heparin- and the protamine-induced complications is suggested. It consists of placing a blood-compatible filter device containing immobilized protamine (a protamine filter) at the distal end of the ECBC apparatus. The filter removes heparin after heparin serves its anticoagulant purpose in the extracorporeal circuit and before blood is returned to the patient. The filter also allows for an external protamine treatment. Since protamine toxicity results from the direct contact of protamine with cells of the liver, lungs, and other organ tissues, the use of an external protamine treatment would minimize it. Protamine was covalently immobilized onto a cellulosic hollow fiber bundle obtained from a clinically used hemodialyzer. The bundle was accessed to the vascular system of a dog by femoral artery and vein cannulation. In in-vivo experiments the protamine-bound fiber bundle not only removed heparin from the extracorporeal circuit, but also caused no clinically significant hemodynamic change in the animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗

PubMedDate not supplied

A protamine filter for extracorporeal blood heparin removal.

Heparin employed in extracorporeal circuits often leads to hemorrhagic complications. Protamine employed for heparin neutralization can cause adverse hemodynamic responses. To control both types of complications, the authors propose an approach that consists of placing a filter device containing immobilized protamine (defined as a protamine filter) at the termination of the extracorporeal blood circulation (ECBC) procedure. This protamine filter would remove heparin from the extracorporeal circuit before heparin is returned to the patient. Meanwhile, the filter would also permit external protamine treatment. Since protamine toxicity generally results from the interaction of protamine with certain cells present in the liver, lungs, and tissues, the use of external protamine would minimize its potential adverse effects. Protamine was immobilized on a hollow fiber bundle obtained from a conventional hemodialyzer. Preliminary studies show that the protamine bound bundle is capable of neutralizing the anticoagulant activity of heparin both in vitro and in vivo. In addition, the protamine filter has abolished the hypotensive response normally associated with protamine reversal of heparin, as indicated by the insignificant changes in blood pressure, pulse rate, pulmonary artery systolic/diastolic pressures, and cardiac output. Further in vivo studies involving the use of dogs, as well as investigation of the activation of the complement system by the protamine filter, are currently being conducted.

Animals↗