Bioelectronic detector with monoamine oxidase for halitosis monitoring.

Methyl mercaptan (MM) is known as one of the major chemicals of halitosis (bad breath). In this study, a bioelectronic gas sensor (bio-detector) for gaseous MM was developed and was applied to measure halitosis in breath. The bio-detector consisted of a Clark-type dissolved oxygen electrode, a monoamine oxidase type-A (MAO-A) immobilized membrane and a reaction unit that had liquid and gaseous compartments separated by a hydrophobic porous polytetrafluoroethylene (PTFE) diaphragm membrane. The tip of the electrode covered with MAO-A membrane was placed into the liquid compartment as touching to the PTFE diaphragm membrane. In order to amplify the bio-detector output, a substrate regeneration cycle caused by coupling the monooxygenase with l-ascorbic acid as reducing reaction with reagent system, was applied. The results of MM vapor measurements showed the calibration range of the bio-detector for MM vapor was from 0.087 to 11.5 ppm (correlation coefficient: 0.993) and included the human sense of smell level 5 (0.2 ppm). The bio-detector had good selectivity being attributed to enzyme specificity was obtained for several substances (trimethyl amine, ammonia, dimethyl sulfide, etc.). The bio-detector was applied for halitosis measurement. Expired gases in five subjects were sampled every hour and the concentrations of MM in the expired gases were monitored. The output of bio-detector showed behaviour of halitosis level changes in a day such as increasing with passage of time and decreasing after eating.

Evaluation of protein binding effect on local disposition of oxacillin in rat liver by a two-compartment dispersion model.

The effect of protein binding upon the hepatic uptake of oxacillin was evaluated in the rat isolated perfused liver, based on the two-compartment dispersion model by means of the fast inverse Laplace transform (FILT). The perfusion experiment was carried out using the perfusates without and with bovine serum albumin (BSA, 40 g L-1). Oxacillin was injected as a pulse through the portal vein, and the outflow concentration-time course of oxacillin was fitted to the dispersion model using the non-linear least squares program MULTI(FILT). The partition ratio (k'), which is the measure of the extent of the reversible distribution into the hepatic tissue, was 0.163 +/- 0.041 (s.d.) in the presence of BSA, and 0.095 +/- 0.018 in the absence of BSA, which suggests interaction of the albumin-bound drug with the hepatic tissue. The elimination rate constant (ke) from the perfusate in the absence of BSA was 8.0 +/- 0.55 min-1 and that in the presence of BSA was 3.3 +/- 1.4 min-1 while the unbound fraction of the drug in the presence of 40 g L-1 BSA was 0.282. The hepatic elimination rate of oxacillin was not proportional to the unbound concentration of drug suggesting hepatic uptake of the bound fraction.

Studies of nitrogen balance in male highlanders in Papua New Guinea.

Nitrogen metabolism in Papua New Guinea highlanders was studied by examining their nitrogen balance when they ate their usual diet (experiment 1) or an experimental diet (experiment 2). Studies were made on 39 male highlanders between October and December in 1980 and 1982. In experiment 1, the average protein and energy intakes (mean +/- SD) for three consecutive days of usual diets were 116.2 +/- 31.2 mg N/kg body weight and 46.9 +/- 8.9 kcal/kg body weight in 1980 and 143.5 +/- 54.8 mg N/kg body weight and 47.3 +/- 10.5 kcal/kg body weight in 1982, and thus the nitrogen balances were 27.7 +/- 28.3 and 18.4 +/- 24.2 mg N/kg body weight, respectively. Most dietary protein and energy was derived from sweet potatoes and other vegetable foods, but between 1980 and 1982 the diet changed slightly with increased consumption of imported foods such as rice and canned fish. In the second experiment, when 10 highlanders were given adequate protein diet (about 200 mg N/kg body weight and about 44 kcal total energy/kg body weight for 13 d, much of the dietary nitrogen was retained in their bodies (45.1 +/- 19.3 mg N/kg body weight). When another group of men were fed a sweet-potato diet (81.1 mg N/kg body weight for 8 d followed by a low protein sweet-potato diet containing only 42 mg N/kg body weight with 50 kcal/kg body weight for 14 d, nitrogen true digestibility and net protein utilization increased and their nitrogen balance showed no significant change (-11.0 +/- 5.6 mg N/kg body weight).(ABSTRACT TRUNCATED AT 250 WORDS)