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Biomedical subjects

C N Schmidt

Publications and source records attributed to C N Schmidt.

6 recordsLinked to original sources
PubMed1993

Effect of preparation techniques on mixing of additives in intravenous fluids in nonrigid containers.

It has been observed that the procedures of some hospitals do not require any mixing after drugs are added to intravenous bags. Previous studies have shown that mixing often is incomplete in the absence of specific mixing procedures. It has been asserted that mixing is effected by normal handling of bags, and that mixing is sufficient if drug is added to "bottom up" bags, which are then inverted. In this study the extent to which mixing occurred on addition of KCl solution or water to intravenous bags as a function of bag and needle position, additive, speed of addition, and bag handling procedure was determined. Also determined was the extent to which mixing occurred spontaneously. Most important, we determined the effect of incomplete mixing on the concentration of drug actually delivered from the bags. It was concluded that mixing is critically dependent on many factors, and that an effective technique to achieve complete mixing is essential to assure homogenous solutions. The most effective method of mixing solutions in plastic infusion bags is to grasp the bag by its two ends and rapidly invert it twice. This "double inversion" mixing technique, a maneuver requiring only 2 seconds, assures complete mixing of intravenous solutions.

Drug Combinations↗
PubMed1984

Inactive forms of wheat ribulose bisphosphate carboxylase. Conversion from the slowly activating into the rapidly activating form.

Wheat ribulose bisphosphate carboxylase can be converted from the slowly activating into the rapidly activating form by heat or effectors in the absence of CO2 and Mg2+. This conversion process had the same energy of activation of 95.6kJ/mol both in the presence and in the absence of effectors, whereas the free-energy change value ranged from +2.5kJ/mol to -3.4kJ/mol depending on the end product involved. Far-u.v. c.d. spectra measured before and after conversion indicated that ribulose bisphosphate carboxylase is an alpha/beta-class protein and that no significant changes in gross conformation occur. Signals in the near-u.v. region suggested that the main change during conversion is re-orientation of aromatic side chains, probably near the active site; a possible site for effector binding is discussed.

Binding Sites↗
PubMed1982

The reactions between active and inactive forms of wheat ribulosebisphosphate carboxylase and effectors.

The processes of activation and deactivation of ribulose-1,5-bisphosphate carboxylase purified from wheat have been investigated. Two forms of the enzyme are indistinguishable in terms of ribulose-1,5-bisphosphate carboxylation and oxidation but exhibit different rates of activation. One form is slowly activated in saturating CO2 and Mg2+ at moderate temperatures (t0.5 approximately 120 min at 25 degrees C), the other form rapidly activated (t0.5 approximately 8 s). In the presence of the effectors 6-phosphogluconate or NADPH, significantly lower concentrations of the activating co-factors can achieve full activation of both enzyme species. However, with another effector, fructose 1,6-bisphosphate, for the slowly activating species the mode of action is the same as with 6-phosphogluconate or NADPH, whereas the activation of the rapidly activating species is significantly inhibited. The substrate, ribulose 1,5-bisphosphate, also inhibits this rapid activation process. A mechanism is proposed for the reactions involving activation that accounts for the differential rates of activation and the response to effectors.

Carboxy-Lyases↗