Folic acid fortified milk increases blood folate and lowers homocysteine concentration in women of childbearing age

Daily consumption of 400 microg folic acid prior to conception and during early pregnancy is recommended for the prevention of neural tube defects (NTD). Strategies to increase folic acid consumption include supplements and fortified foods. Milk is consumed by women and can be fortified with folic acid but little is known about the effect of fortified milk on blood folate concentration in women of childbearing age. The objective of this study was to determine whether daily consumption of milk fortified with 375 microg folic acid increases blood folate and lowers homocysteine concentrations in women of childbearing age. Seventy-three non-pregnant women (aged 18-47 y) were randomized to receive either 75 g/d of a fortified or unfortified (control) milk powder for 12 weeks. Women who consumed the folic acid fortified milk had mean (95% CI) red blood cell and plasma folate concentrations that were 539 nmol/L (436, 641) and 35 nmol/L (30, 41) higher, respectively, than in the control group. Women drinking fortified milk had a 14% lower mean plasma homocysteine concentration at week 12 than women consuming the control milk. Daily consumption of fortified milk powder providing 375 microg folic acid increases blood folate and lowers homocysteine concentrations over 12 weeks in women of childbearing age. Daily consumption of fortified milk would be expected to reduce NTD risk.

Serum vitamin B12 concentrations and atrophic gastritis in older New Zealanders

OBJECTIVE

To determine the serum vitamin B(12) status of older New Zealanders and to assess the impact of atrophic gastritis on vitamin B(12) status.

DESIGN

A cross-sectional nationally representative population-based survey.

METHOD

Serum vitamin B(12) concentrations were used to assess vitamin B(12) status. The presence and severity of atrophic gastritis was classified using serum pepsinogen I and II.

SUBJECTS

A total of 466 noninstitutionalized urban and rural dwelling New Zealanders aged 65 y or older who participated in the 1997 National Nutrition Survey.

RESULTS

The prevalence of deficient (<148 pmol/l) and marginal (148-221 pmol/l) serum vitamin B(12) concentrations was 12 and 28%, respectively. The prevalence of atrophic gastritis was 6.7% (severe 3.1%, mild-moderate 3.6%). While atrophic gastritis increased the relative risk (RR, 95% CI) of having a deficient or marginal serum vitamin B(12) concentration by 21-fold (6-67) and five-fold (1-17), respectively, those who had atrophic gastritis made up only 33 and 6% of the participants with deficient or marginal serum vitamin B(12) concentrations. An intake of vitamin B(12) from food that exceeded the recommended dietary allowance (2.4 mug/day) did not protect against deficient (RR 0.5; 95% CI: 0.2, 1.2) or marginal (RR 0.9; 95% CI: 0.5, 1.7) serum vitamin B(12) status. Vitamin B(12) supplement users had a reduced risk of having deficient and marginal vitamin B(12) status (RR 0.3; 95% CI: 0.1, 0.8).

CONCLUSIONS

There is a relatively high prevalence of deficient and marginal serum vitamin B(12) concentrations among older New Zealanders. However, the prevalence of atrophic gastritis was low in the New Zealand elderly compared with other surveys. Although atrophic gastritis was a risk factor for low vitamin B(12) status, it did not fully explain the prevalence of low serum vitamin B(12).

Citrus pectin and oligofructose improve folate status and lower serum total homocysteine in rats

Low folate status leads to increased total homocysteine (tHcy) concentration, and this has been associated with an increased risk of several diseases. Many colonic bacteria are capable of synthesizing folate, and certain dietary fibers may enhance this effect. We assessed the ability of non-fermentable (cellulose) and fermentable (citrus pectin and oligofructose) fibers to improve folate status and lower tHcy in rats. Weanling Sprague-Dawley rats were fed a folate-deficient diet with 5% cellulose for four weeks. Rats were then randomly assigned to one of five folate-adequate (400 micrograms/kg diet) test diets for 24 days. Diets were as follows: Basal; Basal + Sulfa Drug (succinylsulfathiazole); Cellulose; Citrus Pectin; and Oligofructose. High-fiber diets were formulated by diluting the basal diet such that the final diets contained 10% of the added fiber. Twenty-one days later, 3H-p-aminobenzoic acid was injected into the cecum, and rats were terminated three days later. Rats receiving the Citrus Pectin diet had significantly higher plasma (p = 0.011), erythrocyte (p = 0.035), and colonic tissue folate concentrations (p = 0.013) and lower tHcy (p = 0.003) than rats given the Cellulose diet. Rats receiving the Oligofructose had significantly higher plasma folate (p < 0.001) and lower tHcy (p = 0.032) concentrations than rats receiving the Cellulose diet. 3H-folate was detected in the livers of all rats except those receiving Sulfa Drug. Our study indicates that Citrus Pectin and Oligofructose, but not Cellulose, can significantly increase indices of folate status in rats and lower tHcy. It also confirms the ability of the large bowel to absorb folate.

Effects of once-a-week or daily folic acid supplementation on red blood cell folate concentrations in women

OBJECTIVE

Our aim was to determine if a once-a-week folic acid supplement increases women's red blood cell folate to concentrations (>905 nmol/l) that are associated with a low risk of bearing a child with a neural tube defect.

DESIGN

Randomized control trial.

SETTING

General community.

SUBJECTS

In total, 114 nonpregnant women (18-40 y) volunteers, with red blood cell folate concentrations between 295 and 905 nmol/l at screening.

INTERVENTION

Women were randomized to receive a once-a-week 2800 microg folic acid supplement, a daily 400 microg folic acid supplement or a daily placebo for 12 weeks.

RESULTS

The mean (95% CI) red blood cell folate concentrations increased during the 12-week intervention from 608 (553-668) to 900 (828-978) in the weekly folic acid group (P<0.05) and from 615 (560-677) to 1053 (957-1158) nmol/l in the daily group (P<0.05) during the trial. At week 12, 49% of women ingesting the weekly folic acid supplement had red blood cell folate concentrations greater than 905 nmol/l compared to 74% of women ingesting the daily supplement.

CONCLUSION

A once-a-week 2800 microg folic acid supplement can increase women's red blood cell folate to concentrations associated with a reduced risk of bearing a child with a neural tube defect, but is less effective than a 400 microg daily supplement. Use of a weekly folic acid supplement over at least 12 weeks before conception by women of child-bearing age may prevent neural tube defects.

FUNDING

The Otago Medical Research Foundation (Laurenson Award). Healtheries (New Zealand) provided the supplements.

Vitamin B12 and folate status of older New Zealand women

The primary aim of this study was to assess the biochemical vitamin B12 and folate status of a representative group of elderly women (70-80 y) living in Dunedin, New Zealand. A second aim was to determine the prevalence of hyperhomocysteinaemia and to explore the determinants of homocysteine (hcy) concentration in this population. A cross-sectional study was carried out between June and August of 2000. Two hundred and fifty women were randomly selected from the 1998 electoral roll. Fasting blood samples were analysed for folate, vitamin B12, total hcy, creatinine, and haematological parameters. Of the women selected, 87 did not respond, 37 were not traceable, 23 were not eligible or had died, and 103 agreed to participate. The overall response rate was 46%. Based on a cut-off of 150 pmol/L for serum B12, 13% of participants would be classified as having sub-optimal vitamin B12 status. Of the women, 3 and 5%, respectively, had low serum (< 6.6 nmol/L) and erythrocyte folate (< 317 nmol/L) concentrations. No participant had megaloblastic anaemia. The prevalence of hyperhomocysteinaemia (> 15 mumol/L) in this population was 18%. Hyperhomocysteinaemia in this group may be partly explained by renal insufficiency because there was a significant association between serum creatinine and plasma hcy (P < 0.001). Blood folate levels but not serum B12 were significantly inversely associated with hcy. In conclusion, there was a moderately high prevalence of hyperhomocysteinaemia and suboptimal plasma vitamin B12 concentrations but not low blood folate concentrations in this elderly female population.

Weekly high-dose folic Acid supplementation is effective in lowering serum homocysteine concentrations in women

AIMS

To compare the efficacy of a weekly high-dose (2,800 microg) folic acid supplement with a daily (400 microg) folic acid supplement in lowering homocysteine concentrations in healthy women of childbearing age.

METHODS

Free-living healthy women of childbearing age (n = 138) were randomized to receive a weekly (2,800 microg), a daily (400 microg) folic acid supplement, or placebo. Blood samples were collected at baseline and at 12 weeks and analyzed for serum homocysteine and erythrocyte folate.

RESULTS

At 12 weeks the mean (95% CI) serum homocysteine concentrations declined significantly (p < 0.05) in women receiving the daily [week 12 - baseline: -1.4 (-2.0, -0.70) micromol/l] and the weekly supplement [-1.3 (-2.1, -0.5) micromol/l] versus placebo [0.0 (-0.5, 0.5) micromol/l]. There was no significant difference between the two folate-treated groups (p > 0.05). At 12 weeks the mean erythrocyte folate concentration increased significantly in both supplemented groups versus placebo (p < 0.001). The increase in erythrocyte folate was significantly greater (p < 0.001) in the daily group than in the weekly group [451 (380, 521) vs. 288 (240, 335) nmol/l].

CONCLUSION

A weekly high-dose folic acid supplement was as effective as a daily supplement in lowering homocysteine concentrations in healthy women of childbearing age. Further study is needed to determine if weekly folic acid supplementation is effective in lowering homocysteine concentrations in populations with high homocysteine.

Effect of folic acid supplementation on plasma zinc concentrations of young women

OBJECTIVE

Women of reproductive age are advised to consume supplements or fortified foods containing at least 400 microg/d folic acid for the prevention of neural tubes defects. Concerns exist about the adverse effects of folic acid on zinc status.

METHODS

Seventy-eight women (18 to 49 y) were assigned for 12-wk to receive either a placebo or a 400 microg/d folic acid supplement.

RESULTS

At 12-wk mean (95% CI) red cell folate increased by 431 (350-511) nmol/L in the supplemented group relative to placebo (P < 0.001) but there was no change in plasma zinc in either group (P = 0.213).

CONCLUSIONS

Folic acid supplementation does not reduce plasma zinc concentrations in women of childbearing age.

Comparison of the effect of low-dose supplementation with L-5-methyltetrahydrofolate or folic acid on plasma homocysteine: a randomized placebo-controlled study

BACKGROUND

Food fortification with folic acid has been introduced in several countries for the prevention of neural tube defects. Fortification has lowered total homocysteine (tHcy) concentrations in the US population, a consequence that may have health benefits. However, folic acid fortification could mask vitamin B-12 deficiency. Synthetic L-5-methyltetrahydrofolate (L-MTHF) may be more appropriate than folic acid as a fortificant because it is unlikely to mask the hematologic indicators of vitamin B-12 deficiency.

OBJECTIVE

The objective of the study was to compare the effectiveness of 100 micro g folic acid/d with that of equimolar L-MTHF in lowering tHcy in healthy volunteers.

DESIGN

The study was designed as a 24-wk, randomized, placebo-controlled intervention. Free-living healthy volunteers (n = 167) were randomly assigned to receive a daily supplement containing folic acid (100 microg), L-MTHF (113 microg), or placebo. Blood collected at baseline and at 8, 16, and 24 wk was analyzed for tHcy, plasma folate, and red blood cell folate (RCF) concentrations.

RESULTS

At 24 wk, after adjustment for baseline values, mean (95% CI) tHcy was 14.6% (9.3, 19.5%) and 9.3% (3.7, 14.6%) lower, mean plasma folate was 34% (14, 56%) and 52% (30, 78%) higher, and mean RCF was 23% (12, 35%) and 31% (19, 44%) higher in the L-MTHF and folic acid groups, respectively, than in the placebo group. L-MTHF was more effective than was folic acid in lowering tHcy (P < 0.05). At 24 wk, the increases in plasma folate and RCF concentrations did not differ significantly between the 2 supplemented groups.

CONCLUSION

Low-dose L-MTHF is at least as effective as is folic acid in reducing tHcy concentrations in healthy persons.

Airborne measurements of peroxy radicals using the PERCA technique

The Peroxy Radical Chemical Amplifier (PERCA) technique is a proven method for measurement of ambient levels of peroxy radicals at ground level, but there are no published instances of the technique being used on an aerial platform. Here we describe deployment of a PERCA on the former UK Meteorological Office C-130 Hercules research aircraft. The instrument uses the established method of chemical amplification and conversion of peroxy radicals to nitrogen dioxide (NO2) by doping the sample air-flow matrix with CO and NO, subsequently measuring the NO2 yield with an improved 'Luminox' LMA-3 NO2 detector. NO2 from the amplification chemistry is distinguished from other sources of NO2 reaching the detector by periodically injecting CO approximately 1 s downstream of the NO injection point (termination mode). Chain lengths (CL's) for the amplification chemistry were typically approximately 260 (ground level) to approximately 200 (7,000 m). This variation with altitude is less than the variation associated with the 'age' of the PFA inlet material where the amplification chemistry occurs; CL's of approximately 200 with old tubing to approximately 300 with new clean tubing were typical (ground level values). The CL determinations were made in-flight using an onboard calibration unit based on the 254 nm photolysis of 7.5 to 10 parts per billion (by volume, ppbv) of CH3I in air, producing CH3O2 in a quantitative manner. The noise-equivalent detection limit for peroxy radicals (HO2 + RO2) is 2 parts per trillion (by volume, pptv) at 3,650 m when the background ambient ozone levels are stable, based on a 5 min average of five 30 s amplification cycles and five 30 s termination cycles. This detection limit is a function of several factors but is most seriously degraded when there is large variability in the ambient ozone concentration. This paper describes the instrument design, considers its performance and proposes design improvements. It concludes that the performance of an airborne PERCA in the free troposphere can be superior to that of ground-based instruments when similar sampling frequencies are compared.

Selenium supplements do not increase plasma total homocysteine concentrations in men and women

Studies in rats indicate that plasma total homocysteine (tHcy) is decreased in selenium deficiency and increases with selenium supplementation. The aim of this study was to determine the effect of selenium supplements on plasma tHcy concentrations in a population that has suboptimal selenium status. Subjects from Dunedin, New Zealand (n = 189) were randomly assigned to receive a supplement containing 200 micro g selenium or placebo for 20 wk. At baseline, 67% (n = 112) of the participants had plasma selenium concentrations < 1.2 micro mol/L, a concentration believed to be that necessary for full glutathione peroxidase (Gpx) activity. At 20 wk, plasma selenium concentration and Gpx activity increased in the selenium group by 1.2 micro mol/L [95% confidence interval (CI): 1.1, 1.3] and 5.1 nkat/g protein (3.7, 6.5), respectively, changes that were significantly greater than the changes in the placebo group (P < 0.001). At 20 wk, mean changes in plasma tHcy concentrations were 0.1 micro mol/L (95% CI: -0.4, 0.5) and -0.2 micro mol/L (-0.7, 0.3) in the supplemented and placebo groups, respectively, compared to baseline. There was no difference in the mean changes in plasma tHcy between the supplemented and placebo groups (P = 0.54). These results suggest that selenium supplementation does not influence plasma tHcy concentrations in healthy populations in developed countries, whose selenium status is characterized by lower plasma selenium concentrations.

Increases in blood folate indices are similar in women of childbearing age supplemented with [6S]-5-methyltetrahydrofolate and folic acid

The natural diastereoisomer [6S]-5-methyltetrahydrofolate ([6S]-5-MTHF) may be a safer fortificant than folic acid for neural tube defect (NTD) prevention because it is unlikely to mask vitamin B-12 deficiency. An inverse relationship between NTD risk and blood folate concentrations has been reported. In this randomized, placebo-controlled, double-blind trial, we compared the effects of [6S]-5-MTHF and folic acid supplementation for 24 wk on plasma folate and red cell folate (RCF) in women of childbearing age (18-49 y). Women (n = 104) were randomly assigned to receive a supplement containing [6S]-5-MTHF (113 micro g/d), folic acid (100 micro g/d) or placebo. The mean estimated linear increase in plasma folate concentration was 0.3 [95% confidence interval (CI): 0.1, 0.5], and 0.4 (0.2, 0.6) nmol/(L. wk) in the [6S]-5-MTHF and folic acid groups, respectively. The mean estimated linear increase in RCF was 7.4 (95% CI: 4.5, 10.3), and 8.3 (4.4, 12.3) nmol/(L. wk) in the [6S]-5-MTHF and folic acid groups, respectively. There were no differences in the slopes between the [6S]-5-MTHF group and the folic acid group in either plasma folate (P = 0.48) or RCF (P = 0.70). At 24 wk, estimated mean increases in plasma folate concentrations were 6.9 (95% CI: 1.7, 12.2) and 9.2 (3.3, 15.1) nmol/L, and in RCF, 251 (143, 360) and 275 (148, 402) nmol/L, in the [6S]-5-MTHF and folic acid groups, respectively, relative to the placebo group. These data suggest that low dose [6S]-5-MTHF and folic acid supplementation increase blood folate indices to a similar extent. A steady state in the blood indices had not been reached by 24 wk.

Capture of attention in selective frequency listening

Four signal-detection experiments demonstrated robust stimulus-driven, or exogenous, attentional processes in selective frequency listening. Detection of just-above-threshold signal tones was consistently better when the, signal matched the frequency of an uninformative cue tone, even with relatively long cue-signal delays (Experiment 1) or when as few as 1 in 8 signals were at the cued frequency (Experiment 2). Experiments 3 and 4 compared performance with informative and uninformative cues. The involvement of intentional, or endogenous, processes was found to only slightly increase the size of the cuing effect beyond that evident with solely exogenous processes, although the attention band, a measure of how narrowly attention is focused, was found to be wider when cues were informative. The implications for models of auditory attention are discussed.

Pathophysiology of apolipoprotein E deficiency in mice: relevance to apo E-related disorders in humans

Apolipoprotein E (apo E) deficiency (or its abnormalities in humans) is associated with a series of pathological conditions including dyslipidemia, atherosclerosis, Alzheimer's disease, and shorter life span. The purpose of this study was to characterize these conditions in apo E-deficient C57BL/6J mice and relate them to human disorders. Deletion of apo E gene in mice is associated with changes in lipoprotein metabolism [plasma total cholesterol (TC) (>+400%), HDL cholesterol (-80%), HDL/TC, and HDL/LDL ratios (-93% and -96%, respectively), esterification rate in apo B-depleted plasma (+100%), plasma triglyceride (+200%), hepatic HMG-CoA reductase activity (-50%), hepatic cholesterol content (+30%)], decreased plasma homocyst(e)ine and glucose levels, and severe atherosclerosis and cutaneous xanthomatosis. Hepatic and lipoprotein lipase activities, hepatic LDL receptor function, and organ antioxidant capacity remain unchanged. Several histological/immunohistological stainings failed to detect potential markers for neurodegenerative disease in the brain of 37-wk-old male apo E-KO mice. Apo E-KO mice may have normal growth and development, but advanced atherosclerosis and xanthomatosis may indirectly reduce their life span. Apo E plays a crucial role in regulation of lipid metabolism and atherogenesis without affecting lipase activities, endogenous antioxidant capacity, or appearance of neurodegenerative markers in 37-wk-old male mice.

Selenium and zinc status are suboptimal in a sample of older New Zealand women in a community-based study

The importance of selenium and zinc in the immune functioning of the aged is widely recognized. Seniors in New Zealand are at particularly high risk of low selenium status because of the low selenium soil environment. The zinc status of the New Zealand elderly has never been assessed. In this cross-sectional study, the biochemical selenium, zinc and lipid levels, physical functional capacity and dietary intakes of 103 randomly selected free-living New Zealand women (mean age +/- SD, 75 +/- 3 y) were assessed. Among nonusers of selenium supplements (n = 80), 80% [95% confidence interval (CI): 70; 88%] had plasma selenium levels (0.85 +/- 0.23 micromol/L) below 1.00 micromol/L [ approximately 10% below mean plasma selenium necessary for full expression of glutathione peroxidase (GPx) activity in New Zealand subjects]. Plasma selenium was strongly correlated with GPx: r = 0.56; P < 0.0001. For nonusers of zinc supplements (n = 88), serum zinc concentrations were 12.4 +/- 1.4 micromol/L, with 12% (95% CI: 6; 21%) having levels below the cut-off value (10.7 micromol/L). Estimated mean daily selenium and zinc intakes were 34 +/- 10 microg and 8.7 +/- 2.0 mg, respectively. Subjects in the highest tertile of a functional capacity index had higher biochemical zinc and selenium values than those in the lowest tertile (P < 0.05). The correlation between plasma selenium and GPx indicates that selenium intake in these women is still insufficient for full expression of GPx activity. Lower serum zinc levels also appear to be prevalent. Because a suboptimal trace element status may be more common among those with a poor physical functioning, promotion of the consumption of nutrient dense foods or supplements to improve selenium and zinc status of elderly women in New Zealand may be beneficial.

Capture of attention in selective frequency listening

Four signal-detection experiments demonstrated robust stimulus-driven, or exogenous, attentional processes in selective frequency listening. Detection of just-above-threshold signal tones was consistently better when the, signal matched the frequency of an uninformative cue tone, even with relatively long cue-signal delays (Experiment 1) or when as few as 1 in 8 signals were at the cued frequency (Experiment 2). Experiments 3 and 4 compared performance with informative and uninformative cues. The involvement of intentional, or endogenous, processes was found to only slightly increase the size of the cuing effect beyond that evident with solely exogenous processes, although the attention band, a measure of how narrowly attention is focused, was found to be wider when cues were informative. The implications for models of auditory attention are discussed.

Potential for cross-transmission of Dictyocaulus viviparus between cattle and white-tailed deer

Development of an in vitro culture system for infectious Dictyocaulus viviparus larvae made it possible to study the potential cross-transmission of D. viviparus between white-tailed deer (Odocoileus virginianus) and cattle (Bos taurus). Between 26 September 1995-29 February 1996, six parasite-free bull calves were individually inoculated with 15 to 50 infective third stage larvae (L3)/kg of body weight cultured from adult D. viviparus collected from white-tailed deer. Three bull calves were simultaneously inoculated with 45 L3/kg of body weight recovered from cattle either by the Baermann technique or by in vitro culture as above. All three calves inoculated with the homologous cattle strain became patently infected while all six calves inoculated with the heterologous deer strain remained negative for the presence of D. viviparus in the feces and in the lungs upon necropsy.

Study of the assembly of vesicular stomatitis virus N protein: role of the P protein

To derive structural information about the vesicular stomatitis virus (VSV) nucleocapsid (N) protein, the N protein and the VSV phosphoprotein (P protein) were expressed together in Escherichia coli. The N and P proteins formed soluble protein complexes of various molar ratios when coexpressed. The major N/P protein complex was composed of 10 molecules of the N protein, 5 molecules of the P protein, and an RNA. A soluble N protein-RNA oligomer free of the P protein was isolated from the N/P protein-RNA complex using conditions of lowered pH. The molecular weight of the N protein-RNA oligomer, 513,879, as determined by analytical ultracentrifugation, showed that it was composed of 10 molecules of the N protein and an RNA of approximately 90 nucleotides. The N protein-RNA oligomer had the appearance of a disk with outer diameter, inner diameter, and thickness of 148 +/- 10 A, 78 +/- 9 A, and 83 +/- 8 A, respectively, as determined by electron microscopy. RNA in the complexes was protected from RNase digestion and was stable at pH 11. This verified that N/P protein complexes expressed in E. coli were competent for encapsidation. In addition to coexpression with the full-length P protein, the N protein was expressed with the C-terminal 72 amino acids of the P protein. This portion of the P protein was sufficient for binding to the N protein, maintaining it in a soluble state, and for assembly of N protein-RNA oligomers. With the results provided in this report, we propose a model for the assembly of an N/P protein-RNA oligomer.

Low erucic acid canola oil does not induce heart triglyceride accumulation in neonatal pigs fed formula

Canola oil is not approved for use in infant formula largely because of concerns over possible accumulation of triglyceride in heart as a result of the small amounts of erucic acid (22:1n-9) in the oil. Therefore, the concentration and composition of heart triglyceride were determined in piglets fed from birth for 10 (n = 4-6) or 18 (n = 6) d with formula containing about 50% energy fat as 100% canola oil (0.5% 22:1n-9) or 100% soybean oil, or 26% canola oil or soy oil (blend) with palm, high-oleic sunflower and coconut oil, providing amounts of 16:0 and 18:1 closer to milk, or a mix of soy, high-oleic sunflower and flaxseed oils with C16 and C18 fatty acids similar to canola oil but without 22:1. Biochemical analysis found no differences in heart triglyceride concentrations among the groups at 10 or 18 d. Assessment of heart triglycerides using Oil Red O staining in select treatments confirmed no differences between 10-d-old piglets fed formula with 100% canola oil (n = 4), 100% soy oil (n = 4), or the soy oil blend (n = 2). Levels of 22:1n-9 in heart triglyceride and phospholipid, however, were higher (P<0.01) in piglets fed 100% canola oil or the canola oil blend, with higher levels found in triglycerides compared with phospholipids. The modest accumulation of 22:1n-9 associated with feeding canola oil was not associated with biochemical evidence of heart triglyceride accumulation at 10 and 18 d.

Inhibition of B16 melanoma metastasis by overexpression of the cysteine proteinase inhibitor cystatin C

Progression to metastasis has been correlated with increased cysteine proteinase activity for a number of tumour types. One mechanism of cysteine proteinase regulation in normal cells is by natural protease inhibitors, the cystatins. Here we further characterize a transfected cell line showing increased cystatin C transcription driven by cytomegalovirus (CMV) promoter/enhancer sequences. Properties of this cystatin C altered cell line such as growth in vitro, lung colonization after tail vein injection in mice, production of cystatin, and cysteine proteinase inhibitor activities were examined. Although there was no difference between the growth rate of the cystatin transfected cell line and that of the control, there was a substantial difference in metastatic ability. No increase was noted in cystatin C secretion into the media for the cystatin C transfected cell line compared with the control transfected cell line. There was, however, a difference in cysteine protease inhibitor activity in the cell-free extracts. These results show that alteration of cystatin C levels by overexpression in B16 melanoma alters properties associated with metastasis.

Variability in the trans fatty acid content of foods within a food category: implications for estimation of dietary trans fatty acid intakes

OBJECTIVE

Currently, the published information on trans fatty acid composition of foods is incomplete and of questionable accuracy. Detailed fatty acid analysis of over 200 foods was undertaken for the purpose of determining the variability in trans fatty acid content among foods within a product category, and the significance of this variability to the estimation of trans fatty acids intakes from analysis of dietary intake data.

METHODS

The analysis of food fatty acids used gas-liquid chromatography with 100 m capillary columns and standardized methodologies for food sampling, fat extraction, separation and quantification of trans fatty acid isomers. For the purposes of this report, trans refers to all non-naturally occurring isomers including trans, cis-trans, geometric and positional isomers.

RESULTS

The results show that the amount of trans fatty acids varies considerably among foods within a category, reflecting differences in the fats and oils used in the manufacturing or preparation process. For example, the range of trans fatty acids in 17 brands of crackers was 23 to 51% total fatty acids, representing differences of from 1 to 13 g trans fatty acids per 100 g cracker. The large errors that may arise in estimates of the trans fatty acid intake of an individual are illustrated by analyses of the potential trans fatty acid intake in a sample diet, for each food as calculated using the minimum and maximum values for trans fatty acids within a given category. The results of these analyses show estimates of trans fatty acid intake from a low of 1.4 to 25.4 g a day for the same diet.

CONCLUSION

This study shows that the wide variability in trans fatty acid content of different foods may result in large errors in the estimation of trans fatty acid intake of individuals and, potentially, groups.

Patients' diets and preferences in a pediatric population with inflammatory bowel disease

PURPOSE

To determine the dietary practices of the pediatric inflammatory bowel disease population at the Children's Hospital of the Hamilton Health Sciences Corporation and the reported effectiveness of those diets.

PATIENTS AND METHODS

A questionnaire mailed to 153 pediatric patients was returned by 125 patients (76 Crohn's disease [CD] and 49 ulcerative colitis [UC] patients)--an 82% response rate.

RESULTS

The median age of respondents was 13 years, and 62% were male. Ninety per cent and 71% of CD and UC patients, respectively, had changed their diets since diagnosis. Caloric supplements (eg, BOOST [Mead Johnson Nutritionals]), sole source nutrition, low fibre and lactose-free diets were used by more than 15% of CD patients, whereas lactose-free, nonspicy, low acid, additive-free, caloric supplement and low fibre diets were used by more than 15% of UC patients. A diet supplement was more commonly used in CD patients (P < 0.05) and an additive-free diet in UC patients. Corn and corn products, nuts, milk and bran were avoided by more than 20% of CD and UC patients; however, more CD than UC patients avoided corn and corn products. In addition, UC patients (more than 20%) also avoided tomato, other dairy (nonfluid milk-based products and foods containing milk products), chocolate, cheese, wheat, tomato sauces and fruit juice. A benefit was reported for 103 of 141 reported diets, with the most commonly alleviated symptoms being abdominal pain, diarrhea and flatulence.

CONCLUSION

Many children with inflammatory bowel disease have altered their diets to manage their disease and have attributed symptomatic relief to these diets.

A three-day weighed food record and a semiquantitative food-frequency questionnaire are valid measures for assessing the folate and vitamin B-12 intakes of women aged 16 to 19 years

The purpose of this study was to validate a food-frequency questionnaire (FFQ) and a 3-d weighed food record (3d-WFR) by comparing nutrient intakes estimated using these methods with serum folate, RBC folate and serum vitamin B-12 concentrations in 105 females aged 16-19 y. During an early morning clinic visit, subjects completed a self-administered, 116-item FFQ, blood was collected and they were trained to complete a 3d-WFR. Folate intakes as determined by the 3d-WFR (r = 0.65, P < 0.01) exhibited a stronger association with serum folate than did intakes from the FFQ (r = 0.48, P < 0.01) (P = 0.017). The correlations between folate intakes and RBC folate as determined by the FFQ (r = 0.42, P < 0.01) and 3d-WFR (r = 0.50, P < 0.01) methods did not differ. Vitamin B-12 intakes showed only a modest association with serum vitamin B-12 when supplement users were included in the analyses (FFQ, r = 0.25, P < 0.05; 3d-WFR, r = 0.32, P < 0.05). After excluding supplement users from the analyses, the relationship between vitamin B-12 intakes as determined by FFQ and serum vitamin B-12 was no longer significant. Median daily folate intakes (346 vs. 212 microgram) and vitamin B-12 (4.9 vs. 1.9 microgram) estimated from the FFQ were higher than those obtained from the 3d-WFR. In sum, these data suggest that both the FFQ and 3d-WFR are valid measures of assessing the folate intake of young women, and both appear to be useful in determining vitamin B-12 intake when supplemental users are included. The markedly different conclusions about absolute folate and vitamin B-12 intakes obtained using these two dietary methodologies should be taken into consideration when making recommendations about optimal folate intakes in relation to disease prevention.

Oral contraceptives did not affect biochemical folate indexes and homocysteine concentrations in adolescent females

OBJECTIVE

The study was designed to determine the impact of currently available oral contraceptive agents (OCAs), smoking, and alcohol on biochemical indexes of folate and vitamin B-12 in adolescent females.

DESIGN

Subjects completed a 3-day weighed food record along with a detailed lifestyle questionnaire that included questions on OCA, cigarette, and alcohol use. After subjects had fasted overnight, blood samples were collected and analyzed for levels of serum and red blood cell (RBC) folate and serum B-12 and homocysteine.

SUBJECTS/SETTINGS

Two hundred twenty-nine adolescent females (aged 14 to 20 years) were recruited from southern Ontario, Canada, by advertisements in newspapers, high schools, universities, shopping malls, adolescent drop-in centers, and community groups.

STATISTICAL ANALYSES PERFORMED

Multiple regression models were used to determine the effect of lifestyle factors and covariates (e.g., dietary folate intake, supplemental folate intake, and age) on biochemical indexes.

RESULTS

OCA use, alcohol use, and smoking were not significantly associated with lower serum or RBC folate levels, after controlling for folate intake. Serum homocysteine levels were not associated with smoking or OCA use; however, we estimated a 13% higher concentration among alcohol users than nonusers. Smoking and alcohol use were not associated with serum B-12 levels, but OCA use was associated with an estimated 33% lower serum B-12 level than nonuse.

APPLICATIONS

Our findings provide no evidence to suggest that currently available OCAs have a negative impact on the folate status of adolescent females; thus, dietary advice designed to specifically encourage an increase in folate intake among adolescents who use OCAs is not supported. In contrast, serum B-12 levels were lower among OCA users than nonusers, which suggests that an interaction between OCA and some vitamins may persist. The suboptimal biochemical folate indexes of smokers may have more to do with the dietary quality of smokers than previously appreciated. Thus, efforts to improve dietary folate intakes of adolescents who smoke may be an important strategy for improving the folate status of young women.

Role of sialyloligosaccharide binding in Theiler's virus persistence

Theiler's murine encephalomyelitis viruses (TMEVs) belong to the Picornaviridae family and are divided into two groups, typified by strain GDVII virus and members of the TO (Theiler's original) group. The highly virulent GDVII group causes acute encephalitis in mice, while the TO group is less virulent and causes a chronic demyelinating disease which is associated with viral persistence in mice. This persistent central nervous system infection with demyelination resembles multiple sclerosis (MS) in humans and has thus become an important model for studying MS. It has been shown that some of the determinants associated with viral persistence are located on the capsid proteins of the TO group. Structural comparisons of two persistent strains (BeAn and DA) and a highly virulent strain (GDVII) showed that the most significant structural variations between these two groups of viruses are located on the sites that may influence virus binding to cellular receptors. Most animal viruses attach to specific cellular receptors that, in part, determine host range and tissue tropism. In this study, atomic models of TMEV chimeras were built with the known structures of GDVII, BeAn, and DA viruses. Comparisons among the known GDVII, BeAn, and DA structures as well as the predicted models for the TMEV chimeras suggested that a gap on the capsid surface next to the putative receptor binding site, composed of residues from VP1 and VP2, may be important in determining viral persistence by influencing virus attachment to cellular receptors, such as sialyloligosaccharides. Our results showed that sialyllactose, the first three sugar molecules of common oligosaccharides on the surface of mammalian cells, inhibits virus binding to the host cell and infection with the persistent BeAn virus but not the nonpersistent GDVII and chimera 39 viruses.

Association between dietary fiber intake and the folate status of a group of female adolescents

The main objective of this study was to assess the association between dietary fiber intake and the folate status of Canadian female adolescents. We also assessed dietary folate intakes and evaluated the prevalence of biochemical folate deficiency in these subjects. Female adolescents aged 14-19 y (n = 224) were recruited and fasting blood samples were collected. Dietary intakes (3-d food record) were recorded and participants were classified as lactoovovegetarians, semivegetarians, or omnivores on the basis of food-consumption patterns assessed with food-frequency questionnaires. Fourteen percent, 17%, and 26% of lactoovovegetarians, semivegetarians, and omnivores, respectively, had dietary folate intakes below their predicted requirements; 1%, 4%, and 23%, respectively, had serum folate concentrations indicative of deficiency. Despite low dietary folate intakes and serum folate concentrations, few subjects had homocysteine concentrations indicative of deficiency, suggesting that the degree of folate depletion had not yet produced functional consequences. Most important, results suggest that the consumption of nonstarch polysaccharide is significantly associated with serum folate concentrations (P < 0.001). For each 1-g increase in nonstarch polysaccharide intake, a 1.8% increase in serum folate concentration is expected. In summary, we propose that an increase in nonstarch polysaccharide intake may promote the intestinal biosynthesis of folate, providing a complementary strategy to enhance the folate nutriture of humans.

Advanced practice nurses: change agents for clinical practice

The article presents the role of advanced practice nurses as change agents in the clinical setting. Research utilization is needed to shape and form the basis of nursing practice. As change agents, the advanced practice nurses in one institution established a research-based minimal stimulation protocol for the very low-birth weight infant and implemented it using a video presentation. Knowledge of change theory, research utilization, and video production was necessary in making this project a success.

Synthetic-aperture-radar imaging with a solid-state laser

We report the operation of an imaging Nd:YAG microchip-laser synthetic-aperture radar, with which we imaged two-dimensional (2-D) models of military targets. The images obtained showed spatial resolution significantly better than the diffraction limit of the real aperture in the along-track dimension. The signal processing is described, and the measurement sensitivity is both predicted and verified. In addition, 2-D images with high resolution in both dimensions were generated by using an asymmetric aperture to match the along-track synthetic-aperture resolution with the across-track diffraction-limited resolution.

A cytotoxic diacetylene from Dendropanax arboreus

The crude ethanol extract from the leaves of Dendropanax arboreus (Araliaceae) from Monteverde, Costa Rica, exhibits cytotoxic activity against Hep-G2, A-431, H-4IIE, and L-1210 tumor cell lines, but is not toxic against normal hepatocytes. The active component has been isolated by activity-directed separation and identified by 1H- and 13C-NMR spectroscopy as the acetylenic compound cis-1,9,16-heptadecatriene-4,6-diyne-3,8-diol.

An antibacterial vitamin E derivative from Tovomitopsis psychotriifolia

The crude ethanol extract from the leaves of Tovomitopsis psychotriifolia (Clusiaceae) exhibits antibacterial activity against Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa. The biologically active agent in the extract has been isolated by chromatographic techniques and identified by NMR spectroscopy as trans-delta-tocotrienoloic acid.

Antigenic analysis of Dictyocaulus viviparus by use of test-positive bovine sera

An antigen extract of Dictyocaulus viviparus was analyzed by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the antigen-recognition patterns of serum antibody from cattle not infected, cattle infected with D viviparus, and cattle with unknown history of D viviparus were analyzed by the use of ELISA and western blotting techniques. Cross-reactive antibody-recognition patterns were determined by comparing western blots of D viviparus-positive sera with blots of D viviparus-negative sera obtained from cattle singly infected with Bunostomum phlebotomum, Cooperia oncophora, C punctata, Nematodirus helvetianus, Oesophagostomum radiatum, or Ostertagia ostertagi. Five antigen bands unique to D viviparus were identified, and their frequency of appearance in western blots of sera from verified D viviparus-positive and -negative cattle, and sera from cattle exposed to the parasite, but with unknown D viviparus immune status, were determined. Of the 5 antigens unique to D viviparus, 29- and 19-kd bands had the highest frequencies of reaction (45.9 and 59.0%, respectively) with the test sera. These bands had strong reactivity with sera containing antibodies to D viviparus and did not react with the heterologous sera. We conclude that the 29- and 19-kd antigens may be useful for developing an improved serodiagnostic test for D viviparus infections in cattle.

Solid-state laser synthetic aperture radar

Here we report the operation of an optical synthetic aperture radar employing, for the first time to our knowledge, a solid-state laser as the source. The experimental data-acquisition and digital processing techniques are described, by which spatial resolution superior to that limited by diffraction is demonstrated.

Monoclonal IgM rheumatoid factor-like anti-globulins enhance the inhibitory effects of Plasmodium falciparum-specific monoclonal antibodies in vitro

Monoclonal IgM rheumatoid factor-like anti-globulins were produced by in vitro stimulation of naive BALB/c spleen cells with lipopolysaccharide, and by hyperimmunization of mice with merozoites of Plasmodium falciparum, followed by fusion of the spleen cells to mouse myelomas. In vitro, these anti-globulins augmented the inhibitory effects of P. falciparum-specific polyclonal mouse sera and monoclonal IgG1 and IgG2b antibodies by binding to Fc fragments of IgG molecules attached to blood-stage parasites. In some instances, the presence of anti-globulins correlated with an increase in the number of schizonts which failed to disperse merozoites. In other cases, parasitaemia remained low in the absence of the schizont inhibition phenomenon, suggesting that anti-globulins contribute to host cell protection not only by agglutinating merozoites, but also by increasing the density of the antibody coat surrounding the parasites, thus interfering with parasite receptor-erythrocyte ligand interactions. The anti-globulins were not inhibitory when added to parasite cultures containing IgG not specific for P. falciparum. These results may help explain the function of IgM anti-globulins found at elevated serum levels in some patients with malaria or other chronic infectious diseases.

Identification of common surface antigens among Babesia bigemina isolates by using monoclonal antibodies

A group of monoclonal antibodies (MAb) was used to immunochemically characterize Babesia bigemina surface components. Two surface reactive MAb by an IFAT test were subsequently shown to bind to epitopes on the external surface of the parasite plasma membrane as evidenced by immunoelectron microscopy. Parasite components with relative sizes of 68, 62, 60, 58, 56, 54, 51, 49, 48, 47, 43, 36 kDa were identified with the group of MAb in at least 6 geographically different B. bigemina isolates. The antigenic components were demonstrated to be species-specific and apparently predominant. Both polyclonal antibodies (immune bovine serum) and highly diluted MAb specifically reacted with such bands producing a strong signal in Western blots.

Phosphorimeters for analysis of decay profiles and real time monitoring of exponential decay and oxygen concentrations

A phosphorimeter which can be assembled at low cost from mainly commercially available components and which has better time resolution, data acquisition rate, sensitivity, and flexibility than commercially available instruments is described. As a phosphorescence analyzer the instrument can measure phosphorescence lifetimes ranging from approximately 30 microseconds to seconds from samples with variable intensity, excitation, and emission spectra and which may follow complex decay behavior. Configured as a phosphorescence monitor it is designed for fast, repetitive calculation of phosphorescence lifetime, assuming single-exponential decay, and can be used to calculate oxygen concentration in biological samples in real time.

The oxygen dependence of mitochondrial oxidative phosphorylation measured by a new optical method for measuring oxygen concentration

Oxygen-dependent quenching of phosphorescence has been used to measure the dependence of mitochondrial oxidative phosphorylation on oxygen concentration in suspensions of isolated rat liver mitochondria. An instrument has been designed which simultaneously monitors the phosphorescence lifetime of a fluorophor and the reduction of cytochrome c by dual wavelength spectrophotometry. The phosphorescence lifetime method gives very rapid (less than 100 ms) measure of the oxygen concentration (Vanderkooi, J. M., Maniara, G., Green, T. J., and Wilson, D. F. (1987) J. Biol. Chem. 262, 5476-5482) from concentrations characteristic of air-saturated media to as low as 2 x 10(-8) M. The results may be summarized as follows. For well coupled rat liver mitochondria at pH 7.0 and in the presence of ATP, as the oxygen concentration was lowered, increased cytochrome c reduction was observed to begin at oxygen concentrations greater than 20 microM. For mitochondria in the presence of uncoupler, cytochrome c reduction began at oxygen concentrations less than 1.0 microM. The oxygen dependence of reduction of cytochrome c in well coupled mitochondria treated with ATP was strongly dependent on the pH of the suspending medium. Reduction of cytochrome c began at higher oxygen concentrations as the pH was made more alkaline. The oxygen concentration for half-maximal respiratory rates was much larger for well coupled mitochondria treated with ATP (approximately 0.7 microM) than for mitochondria treated with uncoupler (less than 0.1 microM). It is concluded that the oxygen dependence of mitochondrial oxidative phosphorylation is such that mitochondria could function in their proposed role of tissue oxygen sensors for regulation of such diverse functions as local blood flow and electrical activity in the carotid body.

An optical method for measurement of dioxygen concentration based upon quenching of phosphorescence

An optical method for measuring oxygen concentrations in aqueous solutions is described. This method is based upon the oxygen-dependent quenching of phosphorescence. Phosphorescence excitation and emission spectra and lifetimes of some of the probe molecules suitable for measurement of oxygen in aqueous solutions are given. The probes include fluorescein derivatives, 4'5'-diiodofluorescein, eosin Y, 5(and 6)-carboxyeosin, erythrosin, and 5(and 6)-carboxyerythrosin as well as the Zn(II), Y(III), Sn(IV), Lu(III), and Pd(II) derivatives of meso-tetra-(4-sulfonatophenyl)-porphine, meso-tetra-(N-methyl-4-pyridyl)-porphine and coproporphyrin. The phosphorescence lifetimes of the given probes were found to depend upon the oxygen concentration by a simple Stern-Volmer relationship with a quenching constant of approximately 10(9) M-1 S-1. Binding of the molecules to bovine serum albumin decreased the quenching constant for oxygen by approximately an order of magnitude and also inhibited probe self-quenching, indicating that at the protein binding site the probes are somewhat protected from collision with quenchers. The use of this optical method for measuring oxygen is demonstrated for reactions catalyzed by glucose oxidase and by cytochrome c oxidase. It is shown that, using this method oxygen concentrations can be measured from approximately 250 microM (air saturation) down to the nanomolar range.

A sensitive urea-silver stain method for detecting trace quantities of separated proteins in polyacrylamide gels

An ultrasensitive method using a urea-silver staining procedure to detect trace quantities of proteins in polyacrylamide gels (PAGE) is described. This technique is sensitive enough to detect picogram quantities of proteins resolved on sodium dodecyl sulfate-polyacrylamide gels. The major advantages of our method are that it provides a clear background and it is more sensitive than other techniques allowing it to substitute for radioisotopic techniques in some cases.

A versatile and sensitive method for measuring oxygen

Oxygen dependence of the lifetime of the excited triplet state of phosphorescent molecules can be used to measure the oxygen concentration in aqueous media. These measurements are insensitive to much of the optical interference that limits the usefulness of measurements based on the oxygen dependent quenching of luminescence intensity. The measurements also extend to significantly lower oxygen concentrations than are normally attainable using oxygen electrodes. The phosphorescence lifetimes can be accurately measured from a few microseconds to seconds, permitting a wide dynamic range of oxygen concentration measurements. With currently available probes, for example, it is possible to make continuous measurement of oxygen concentrations from 10(-4) M to 10(-8) M in a single experiment.

Specific detection of Plasmodium falciparum malaria by a molecularly cloned DNA probe

A highly repeated DNA sequence from Plasmodium falciparum was cloned and used as a probe in molecular hybridization to detect malaria. Our results indicate that the probe is specific to P. falciparum but not to other species of Plasmodium and is extremely sensitive. As little as a 20 pg parasite DNA, which is equivalent to about 1000 parasites can be detected. The cloned DNA can be used as a diagnostic tool to follow the course of infection of falciparum malaria.

Organization of Plasmodium falciparum genome: 1. Evidence for a highly repeated DNA sequence

Plasmodium falciparum DNA, isolated from the merozoite stage, was cleaved with HindIII and cloned in pBR322 and lambda L47.1 vectors. Plasmid clones containing 13.4, 7.0, 4.3, 4.1 and 1.5 kb inserts were characterized in some detail. The inserts contain several repeating units of smaller size. Nucleic acid hybridization studies showed that the repeat element is present in the Plasmodium DNA at a very high copy number and appears to be distributed widely throughout the genome.

In vitro cultivation of Babesia bigemina

A strain of Babesia bigemina was isolated from an infected calf and propagated in vitro. Culture conditions included washing of infected and normal bovine erythrocytes in a special solution, and the use of a 5% to 10% (v/v) erythrocyte suspension in medium 199 (with 20% to 50% fresh normal bovine serum) at a depth of 4 mm in a 5% CO2, 2% O2, 93% N2 atmosphere. After 36 days in vitro and 9 subcultures, the cultured organism was inoculated into a susceptible calf. This calf developed clinical signs of disease and recovered when treated with 1% trypan blue solution. The strain was also reisolated from the second calf. The original isolate had been maintained in continuous in vitro cultivation for more than 99 days.

Cloning and characterization of Plasmodium falciparum FCR-3/FMG strain

The FCR-3/FMG African strain of Plasmodium falciparum was cloned by the limiting dilution technique in in vitro culture to obtain parasite populations derived from a single cell. The basic in vitro culture technique used was that of Trager and Jensen, performed in microtiter culture plates. The cloning sequence was repeated serially three times, and three parasite clones with a higher than 99% probability of single cell derivation were isolated. Two of these clones were determined by electron microscopic examination to possess the K+ and one the K- trait. The clones were found to be equally sensitive to chloroquine in vitro but varied in their in vivo pathogenicity for Aotus, the K- clone being non-pathogenic.

A role for rheumatoid factor enhancement of Plasmodium falciparum schizont inhibition in vitro

Studies were undertaken to determine whether rheumatoid factor (RF) was present in immune human and Aotus trivirgatus monkey sera which inhibited Plasmodium falciparum schizonts in vitro and to determine whether RF could be responsible for or contribute to merozoite agglutination in the parasite inhibition test. Additional studies were conducted to determine the effect of exogenous RF on schizont inhibition when used alone or in conjunction with immune or normal sera. RF was not detected in any of the 11 immune monkey sera or the 3 immune human sera which were tested. However, when RF was added to immune human or Aotus sera, levels of schizont inhibition increased significantly over levels obtained with immune serum alone. When RF was used alone or in conjunction with normal sera, levels of schizont inhibition were comparable to those obtained with normal serum. Furthermore, adsorption of the RF with immunoglobulin G-coated erythrocytes removed the enhancing activity. The results of this study indicate that RF, which is sometimes produced during acute or chronic malarial infection, may contribute nonspecifically to the enhanced clearance of plasmodia in vivo.

Activated partial thromboplastin time of owl monkey (Aotus trivirgatus) plasma

Owl monkey plasma samples produced short, reproducible activated partial thromboplastin times, similar to those obtained with samples from many other mammalian species. This was an apparent contradiction to an earlier report of long irreproducible activated partial thromboplastin times from owl monkey samples. The discrepant data could not be explained by differences in anticoagulants (citrate or oxalate), assay reagents (partial thromboplastin with either diatomaceous earth or ellagic acid), or activation incubation times (2, 5, or 10 minutes); nor could they be explained by differences in the monkeys' sex, age or previous experimental exposure to Plasmodium falciparum malaria.