Oxidative and nonoxidative killing of Actinobacillus actinomycetemcomitans by human neutrophils.

Actinobacillus actinomycetemcomitans is a facultative gram-negative microorganism which has been implicated as an etiologic agent in localized juvenile periodontitis and in subacute bacterial endocarditis and abscesses. Although resistant to serum bactericidal action and to oxidant injury mediated by superoxide anion (O2-) and hydrogen peroxide (H2O2), this organism is sensitive to killing by the myeloperoxidase-hydrogen peroxide-chloride system (K.T. Miyasaki, M.E. Wilson, and R.J. Genco, Infect. Immun. 53:161-165, 1986). In this study, we examined the sensitivity of A. actinomycetemcomitans to killing by intact neutrophils under aerobic conditions, under anaerobic conditions, and under aerobic conditions in the presence of the heme-protein inhibitor sodium cyanide. Intact neutrophils killed opsonized A. actinomycetemcomitans under aerobic and anaerobic conditions, and the kinetics of these reactions indicated that both oxidative and nonoxidative mechanisms were operative. Oxidative mechanisms contributed significantly, and most of the killing attributable to oxidative mechanisms was inhibited by sodium cyanide, which suggested that the myeloperoxidase-hydrogen peroxide-chloride system participated in the oxidative process. We conclude that human neutrophils are capable of killing A. actinomycetemcomitans by both oxygen-dependent and oxygen-independent pathways, and that most oxygen-dependent killing requires myeloperoxidase activity.

Fluoride balance studies in healthy men during bed rest with and without a fluoride supplement..

In a program of studies of disuse osteoporosis, fluoride balances were determined in healthy men during ambulation and then during bed rest for 6 to 17 wk. Control subjects ingested basal diets containing 0.4 mg fluoride per day, whereas experimental subjects received 10-mg fluoride supplements in divided doses with meals. Fluoride and calcium were measured in diets, urine, and feces. Serum analyses included calcium and ionic fluoride. Fluoride balances during both phases were uniformly negative in control subjects (mean -0.46 mg/day) but uniformly positive in supplement subjects (mean +2.58 mg/day). Calcium balances were markedly negative during bed rest in both groups. Serum fluoride concentrations increased proportionally to fluoride intake, averaging 0.016 ppm in the controls and 0.045 ppm in the supplement subjects. The supplement of 10 mg fluoride daily did not protect against bed rest-induced calcium loss, or cause any clinical or laboratory abnormality in any subject.

Fluoride balance studies in ambulatory healthy men with and without fluoride supplements.

Fluoride balances were determined in healthy adult males under metabolic ward conditions. This is the first fluoride study to use the diffusion method in exploring the balances of subjects ingesting basal (i.e., everyday) diets with deionized water for cooking and drinking. Certain groups were given daily supplements of 5 or 10 mg. fluoride as sodium fluoride in divided doses with meals. Fluoride was measured in the diets, sodium fluoride tablets, urine, feces, and serum. Approximately 90% of the fluoride excreted was found in the urine and the remainder in the feces in all groups. In the control subjects, fluoride balances were uniformly negative (mean of -0.40 mg/day); in contrast, balances were uniformly positive (mean of +1.38 and +2.88 mg/day, respectively) in subjects receiving 5 or 10 mg F supplements daily. Serum ionic fluoride concentration increased proportionally to fluoride intake and averaged 0.016, 0.029, and 0.040 ppm in the control, 5-mg and 10-mg groups, respectively. These fluoride supplements did not cause any clinical or laboratory abnormality in any subjects.

Fluoride balances in pregnant and nonpregnant women.

In planning health protection for pregnant as well as nonpregnant women exposed to fluorides, information about their fluoride metabolism is essential. The authors determined fluoride balances in small groups of young women maintained on two different low-fluoride diets for one or two 21-day periods in a metabolic unit. One diet contained an average of 0.41 mg F/day, and the other contained an average of 0.27 mg F/day. Excretion of fluoride in pooled three-day collections for each subject was about 80% in the urine and 20% in the feces. Pregnant (last half of term) and nonpregnant women demonstrated small negative fluoride balances; the averages were about -0.32 mg F/day and -0.15 mg F/day, respectively. Similar values have been found for young males in other studies. Pregnancy in these subjects did not markedly alter normal fluoride metabolism.