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Biomedical subjects

R Holland

Publications and source records attributed to R Holland.

At least 271 records · Page 15Linked to original sources
PubMed1975

Nitrogen analyzer adaptation for use in the presence of halogenated anesthetics.

Interposition of activated carbon between a nitrogen analyzer needle valve and gas mixtures containing halothane, methoxyflurane, enflurane, or isoflurane eliminated the interfering effects of these agents, but added sampling delays. Placement of a carbon-filled Swinney adaptor in the sampling line between the needle valve and analyzer also eliminated the interference. Linearity of response (range 0 to 80 per cent N2) and sampling delay (40 msec) were unchanged. The 90 per cent fall time (step change 80 to 0 per cent N2) increased from 35 to 100 msec. This adaptation allows rapid analysis of nitrogen concentrations during general anesthesia.

Anesthesia, General↗
PubMed1975

Regulation of the L-lactase dehydrogenase from Lactobacillus casei by fructose-1,6-diphosphate and metal ions.

The lactate dehydrogenase of Lactobacillus casei, like that of streptococci, requires fructose-1,6-diphosphate (FDP) for activity. The L. casei enzyme has a much more acidic pH optimum (pH 5.5) than the streptococcal lactate dehydrogenases. This is apparently due to a marked decrease in the affinity of the enzyme for the activator with increasing pH above 5.5; the concentration of FDP required for half-maximal velocity increase nearly 1,000-fold from 0.002 mM at pH 5.5 to 1.65 mM at 6.6. Manganous ions increase the pH range of activity particularly on the alkaline side of the optimum by increasing the affinity for FDP. This pH dependent metal ion activation is not specific for Mn2+. Other divalent metals, Co2+, Cu2+, Cd2+, Ni2+, Fe2+, Fe2+, and Zn2+ but not Mg2+, will effectively substitute for Mn2+, but the pH dependence of the activation differs with the metal ion used. The enzyme is inhibited by a number of commonly used buffering ions, particularly phosphate, citrate, and tris (hydroxymethyl) aminomethane-maleate buffers, even at low buffer concentrations (0.02 M). These buffers inhibit by affecting the binding of FDP.

Acetates↗