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Biomedical subjects

S G Lyon

Publications and source records attributed to S G Lyon.

7 recordsLinked to original sources
PubMed1992

Contrast material iodides: potential effects on radioactive iodine thyroid uptake.

The levels of contaminant, free inorganic iodide and iodine were determined in several commonly used ionic and nonionic intravenous contrast media to gain a better understanding of the roles of these compounds in radioactive iodine uptake inhibition. The method, which involved a reduction-oxidation reaction using sodium nitrite, yielded accurate and precise data for the iothalomate based ionic contrast media as well as the nonionic contrast media. There was no free iodine in any of the contrast media tested. There was considerable variation in free iodide levels, ranging from 1.38 microgram/ml to 20.84 microgram/ml among the different contrast media, although significant differences between the ionic and nonionic media were not found. These levels of contaminant iodide are thought to play a role in the short-term inhibition of radioactive iodine uptake.

Contrast Media↗
PubMed1991

Alpha-2-macroglobulin-kallikrein complex: a temperature-sensitive mediator in contact-system-induced inflammation with a potential role in late and delayed hypersensitivity responses.

Maximal complexing of alpha 2-macroglobulin (alpha 2M) and kallikrein (KK) occurs at a temperature of 22-24 rather than at 37 degrees C. The protease expressivity of the complex is also maximal at 22-24 degrees C. alpha 2M-KK complex, sustained permeability changes in guinea pig skin. These findings suggest that the complex, rather than free KK, could play a role in the kinin release reported in some late-phase reactions, some instances of delayed-type hypersensitivity and some cold-induced reactions.

Animals↗
PubMed1979

Complement and contrast material reactors.

Patients showing systemic reactions to intravascular contrast media and patients receiving contrast media without reaction have significantly different mean values (p is less than 0.05) for functionally determined serum C1-esterase inhibitor (C1 INH) and total hemolytic complement (CH50). The lower concentration of these components in reactors appears in baseline serum samples (as well as after injection), and suggests that many anaphylactoid reactions to contrast media are conditioned by earlier complement consumption, and result directly from contrast-induced activation of complement, and other activation system components in the presence of inhibitor depression.

Complement C1 Inactivator Proteins↗
PubMed1979

Complement and coagulation: causative considerations in contrast catastrophies.

Earlier studies suggest that adverse reactions to injected radiographic contrast media are idiosyncratic. In an attempt to gain a better understanding of pathophysiologic events underlying these reactions, rabbit models injected with lethal dose ranges of a cholangiographic contrast material were studied. These animals showed activation of both the complement and coagulation systems. Externally applied heat potentiated complement consumption and increased mortality. Depleting complement components C3-C9 by cobra venom factor did not prevent activation of coagulation or diminish mortality. However, depleting fibrinogen diminished complement activation and markedly diminished mortality. Heparin, administered at several hourly intervals after contrast challenge, also diminished mortality. These studies suggest that the adverse effects of contrast media in this model system are mediated chiefly by the coagulation system, and that complement, if it participates deleteriously, must involve components up to, but not including, C3. A logical role for the inhibitor of C1 esterase in adverse contrast reactions is considered.

Ancrod↗
PubMedDate not supplied

Effect of endotoxemia on contrast media reactions.

Since complement activation is sharply temperature-dependent, we have examined the effects of fever produced by a very small dose of endotoxin on contrast media lethality in rabbits. After the injection of 8.2 ml/kg of 52% methylglucamine iodipamide, a group of rabbits exhibiting an average temperature elevation of 1.5 degrees C had a 100% mortality rate. This was contrasted to a 30% mortality in control rabbits receiving contrast alone, and no mortality in rabbits receiving endotoxin alone. The rabbits with fever and increased mortality exhibited increased activation of serum complement. From this preliminary data it appears that caution should be observed in performing a contrast examination in a patient with endotoxemia and/or a fever.

Animals↗