IS WALKING COSTLY FOR ANURANS? THE ENERGETIC COST OF WALKING IN THE NORTHERN TOAD BUFO BOREAS HALOPHILUS

Locomotor mode and the maximal capacity for aerobic metabolism are thought to be co-adapted in anuran amphibians. Species that rely heavily on walking often have high capacities for aerobic metabolism relative to species that rely primarily on saltation. We tested the hypothesis of co-adaptation of gait and aerobic metabolism by investigating the locomotor energetics of Bufo boreas halophilus, a toad that walks, but does not hop. Rates of oxygen consumption during locomotion were measured in an enclosed variable-speed treadmill. The steady-state rate of oxygen consumption (V(dot)O2ss) increased linearly within a range of sustainable speeds [V(dot)O2ss (ml O2 g-1 h-1) = 0.93 x speed (km h-1) + 0.28]. The minimum cost of transport, Cmin (the slope of this relationship), varied significantly among individual toads. When expressed in units of oxygen consumed per distance travelled (ml O2 km-1), Cmin scaled isometrically with body mass: Cmin = 0.69mass1.07. Consequently, mass-specific Cmin (ml O2 g-1 km-1) was uncorrelated with body mass. Variation in Cmin was also unrelated to experimental temperature. Mass-specific Cmin estimates were similar to previous allometric predictions for terrestrial animals of similar size, which contrasts with previous findings for another toad species. Maximum rates of oxygen consumption measured in closed, rotating respirometers were significantly higher than the maximum rates achieved on the treadmill, but lower than those measured previously in other Bufo species. Our results indicate that walking is not necessarily a costly gait for toads and that high maximum rates of oxygen consumption are not associated with reliance on walking within the genus Bufo.

Methotrexate in rheumatoid arthritis--a limited sampling strategy for estimation of the area under the plasma concentration versus time curve

A limited sampling strategy for determination of the area under the plasma concentration versus time curve (AUC) of methotrexate (MTX) in patients with rheumatoid arthritis (RA), treated with weekly oral doses, has been validated. Stepwise linear regression analysis was used for optimal inclusion of data points in mathematical models to estimate AUC. A new plot for evaluation of the accuracy and precision of the estimated AUC values was introduced in the present study. By plotting the ratio of determined/estimated AUC values versus estimated AUC values, the influence of number of sampling points on the precision and accuracy of estimated AUC values was easily validated. Our results show that AUC values of MTX in RA patients can be estimated from a single plasma sample at 3 h or preferably, due to increased precision, by additional samplings at 5 and 1 h. A further increase of the number of sampling points increased the precision of the AUC estimates only to a minor extent. The accuracy of the estimated AUC values was independent of the number of sampling points. A limited sampling procedure can now be used for further studies on the relationship between MTX levels and its effects.

Delayed chemotherapy-induced nausea is augmented by high levels of endogenous noradrenaline

The relation between pretreatment night-time urinary catecholamine excretion and chemotherapy-induced nausea and vomiting was studied. The first cohort included 17 women and three men with various cancer forms receiving low or moderately emetogenic chemotherapy. The second cohort included 42 women receiving cisplatinum (50 mg m-2) for ovarian cancer and ondansetron as an antiemetic (8 mg i.v. x 3 at chemotherapy and 8 mg p.o. x 3 for 5 days). Relatively higher noradrenaline, but not adrenaline, excretion was associated with an increased intensity of delayed nausea following treatment. Vomiting was not consistently related to the excretion of either catecholamine. The results indicate that noradrenaline modulates delayed nausea resulting from chemotherapy.

Evaluation of the antipyretic effect of ketorolac, acetaminophen, and placebo in endotoxin-induced fever

The authors studied the antipyretic effect of three intramuscular doses of ketorolac (15, 30, and 60 mg), acetaminophen 650 mg PO, and placebo in healthy male volunteers using an endotoxin-induced fever model. In this double-blind, double-dummy, parallel study, subjects were assigned randomly with equal probability to one of the above treatment groups. Thirty minutes after study medication administration, a 20 unit per kilogram dose of reference standard endotoxin (RSE) was administered intravenously, and temperature was determined every 15 minutes for an 8-hour period. Compared with placebo, all active treatment groups demonstrated a statistically significant reduction in both adjusted area under the temperature-by-time curve (AAUC) and the maximum increase over baseline temperature (dTmax). Furthermore, the 30 mg intramuscular dose of ketorolac demonstrated approximately the same antipyretic activity as the 650 mg oral dose of acetaminophen, and there was a statistically significant dose response across the three ketorolac doses studied (P < .0001). The majority of side effects reported during this study were symptoms associated with fever, including chills, headache, myalgia, and dizziness, all of which are effects of RSE. The frequency of side effects tended to be less in the treatment groups with the greatest antipyretic activity.

Twelve-year follow-up of respondents in a sample survey in Peninsular Malaysia

"This note reports the experience of an attempt to find and re-interview in late 1988 and early 1989, as part of the Second Malaysian Family Life Survey (MFLS-2), the female respondents to the 1976-77 Malaysian Family Life Survey (MFLS-1) and a sample of their adult children aged 18 or older.... We discuss the field methods used to track the panel members and their adult children, report follow-up rates and analyze the selectivity of attrition from the panel, using data from the MFLS-1 on characteristics of both the missing and the re-interviewed respondents and their families. We then discuss the degree to which these results might be generalized to other such attempts at re-contacting survey respondents."

A non-P-glycoprotein-mediated mechanism of vincristine transport which is affected by resistance modifiers and present in chemosensitive cells

The accumulation and cytotoxicity of vincristine (Vcr), etoposide (VP16), and daunorubicin (Dau) and effect of the resistance modifiers (RM) verapamil (Ver; 10 microM) and cyclosporin A (CyA; 3 microM) were studied in isolated rat cardiac myocytes, peripheral lymphocytes from seven patients with chronic lymphocytic leukemia (CLL), in the human leukemic cell line K562 and its two Vcr resistant mdr1 gene expressing sublines, K562/Vcr30, K562/Vcr150. Both RMs increased the accumulation and cytotoxic effect of Vcr and Dau in the resistant sublines. In K562 cells, lymphocytes from patients with CLL and rat cardiac myocytes, which all were mdr1 RNA negative RMs increased the cellular accumulation and potentiated the cytotoxic effect of Vcr but not that of Dau. K562/Vcr30 and K562/Vcr150 were cross resistant to Dau but not to VP16 and RMs had no effect on the cytotoxicity of VP16 in any of cell lines. The results indicate that chemosensitive cells also have a transport mechanism, not mediated by P-glycoprotein, which transports Vcr but not Dau and VP16. This suggests that addition of RMs to Vcr-containing chemotherapy may enhance the antineoplastic effect also by inhibition of non-P-glycoprotein mediated transport mechanisms.

Chloroquine reduces the bioavailability of methotrexate in patients with rheumatoid arthritis. A possible mechanism of reduced hepatotoxicity

OBJECTIVE

To evaluate the effects of a single dose of chloroquine (CQ) on the pharmacokinetics of methotrexate (MTX) in patients with rheumatoid arthritis.

METHODS

Eleven patients (ages 41-75 years) who were taking oral doses of MTX (15 mg/week) were studied after a dose of MTX alone and after a dose of MTX plus CQ (250 mg). Plasma and urine samples were collected for 24 hours after dose intake, and the concentrations of MTX and its major metabolite 7-hydroxymethotrexate were determined by high-performance liquid chromatography.

RESULTS

Administration of CQ together with MTX caused a reduction in the area under the plasma MTX concentration versus time curve (AUC). The median value of individual AUC ratios (MTX/MTX + CQ) was 1.6 (95% confidence interval 1.2-3.6).

CONCLUSION

The most likely mechanism for the interaction is that CQ reduces the bioavailability of MTX. This gives a possible explanation for a suggested reduction in MTX-associated liver toxicity by coadministration of CQ. The significance of the interaction for the therapeutic effect remains to be elucidated.

Day-to-day variability in azathioprine pharmacokinetics in renal transplant recipients

The intraindividual and the interindividual variability in the pharmacokinetics of azathioprine (Aza) and its main metabolite 6-mercaptopurine (6-MP) were investigated in 10 renal transplant patients on 2 consecutive days, after repeated oral doses of Aza. On the 1st study, the dose-adjusted Aza AUC (0-6 h) ranged from 8.4 to 129.1 ngh*ml-1/mg*kg-1, mean 41.4 (+/- 37.6) ngh*ml-1/mg*kg-1. The corresponding values for the dose-adjusted 6-MP AUC (0-6 h) ranged from 37.9 to 172.0 ngh*ml-1/mg*kg-1, mean 91.7 (+/- 50.7) ngh*ml-1/mg*kg-1. The absolute percentage intraindividual difference in Aza AUC (0-6 h) between the two days ranged from 1.2% to 256.6% (mean 64.7%), and for 6-MP AUC (0-6 h) from 5.9% to 98.5% (mean 49.8%). However, no statistically significant difference was found when comparing the pharmacokinetics on the 2 study days. The mean half-life of Aza was 1.7 h and of 6-MP 1.2 h. Impaired renal function did not seem to affect the pharmacokinetics. No correlation was found between the given dose of Aza and AUC (0-6 h) for Aza or 6-MP. A strong correlation was found between the concentrations of Aza and 6-MP obtained at 2 h after the oral dose and the corresponding AUCs (0-6 h) (Aza: r = 0.85, p < 0.001, n = 20; 6-MP: r = 0.9, p < 0.001, n = 20). We conclude that the intraindividual variability in Aza pharmacokinetics is marked, but it is less pronounced than the even larger interpatient variability found in this study and previously described.

Increased intracellular concentrations of doxorubicin in resistant lymphoma cells in vivo by concomitant therapy with verapamil and cyclosporin A

The tumor cell uptake of doxorubicin was studied in vivo in cells from 2 patients with clinically resistant leukemic lymphomas treated with continuous infusions of doxorubicin 9 mg/m2 and vincristine with oral dexamethasone. After 24 hours, intravenous or oral verapamil was added and in one treatment course intravenous cyclosporin A was given. Plasma and intracellular doxorubicin concentrations and plasma concentrations of verapamil and norverapamil were determined with HPLC. In the 1st patient the intracellular uptake rate of doxorubicin was increased from 0.007 to 0.013 nmol/mg protein/h after the start of verapamil infusion. In the first treatment course of patient number 2, the intracellular concentration of doxorubicin was increased by 280% during a 6-h infusion of verapamil. When this patient in the next treatment course was given oral verapamil, no significant effect on doxorubicin uptake was seen. However, when 100 mg of cyclosporin A was added in three intravenous injections at 8-h intervals, the doxorubicin concentration in the tumor cells increased from 0.027 to 0.086 nmol/mg protein. In conclusion, this study shows that the intracellular concentrations of doxorubicin can be increased also in vivo during patient therapy by the addition of verapamil or cyclosporin A.

Factors modifying the risk of acute and conditioned nausea and vomiting in ovarian-cancer patients

We prospectively studied, how certain patient characteristics modify the risk of chemotherapy induced and conditioned nausea and vomiting. Young age and previous history of nausea and vomiting were factors associated with both chemotherapy induced nausea and vomiting as well as conditioned nausea. Conditioned nausea was significantly associated with having received two-day compared to one-day mode of chemotherapy, previous distress during blood samples and odor memory. Tentative associations were also found between a history of flushing and chemotherapy induced nausea and vomiting as well as between autonomic perception, odor associations and conditioned nausea. The investigated variables explained a larger part of the variance in conditioned compared acute nausea and vomiting.

Cloning the Drosophila homolog of the xeroderma pigmentosum complementation group C gene reveals homology between the predicted human and Drosophila polypeptides and that encoded by the yeast RAD4 gene

A human xeroderma pigmentosum group C (XPC) cDNA has been previously isolated by functional complementation (Legerski and Peterson, Nature, 359, 70-73, 1992). Sequence analysis did not reveal protein motifs which might suggest a possible biochemical function for the putative XPC protein. In order to identify functional domains in the translated XPC sequence the homologous gene from Drosophila melanogaster, designated XPCDM, was cloned by DNA hybridization. Sequence analysis of an apparently full-length cDNA revealed an open reading frame which can encode a predicted polypeptide of 1293 amino acids. Significant homology of the C-terminal 346 amino acids with both the human XPC and Saccharomyces cerevisiae Rad4 protein sequences is observed, suggesting that these proteins are functional homologs.

Coping with the late effects: differences between depressed and nondepressed polio survivors

This study examined differences between depressed and nondepressed individuals with a history of paralytic poliomyelitis in terms of demographics, health status and coping strategies. The prevalence of distress and depression in this group of 116 polio survivors was determined. Subjects completed the Brief Symptom Inventory, the Coping with Disability Inventory and a questionnaire concerning their polio histories and self-perceptions of health. Medical assessments were performed by physicians. Only 15.8% of the sample had scores indicating depression and elevated distress. Depressed/distressed polio survivors were more likely to: be living alone, be experiencing further health status deterioration, seek professional help, view their health as poor, report greater pain, be less satisfied with their occupational status and their lives in general and exhibit poorer coping outcome behaviors in relation to their disability. Three factors in coping with the late effects of polio were identified through a factor analysis of the Coping with Disability Inventory: positive self-acceptance, information seeking/sharing about the disability and social activism. Differences between depressed/distressed and other polio survivors were found across these three factors, with depressed/distressed subjects having significantly lower coping scores. These and other results are discussed.

Releasability of human hypereosinophilic eosinophils is related to the density of the cells

The activity of eosinophils and neutrophils with respect to the release of granule proteins was studied in 11 patients with the hypereosinophilic syndrome (HES). Granulocytes or purified eosinophils were stimulated with serumopsonized Sephadex particles (C3b-induced release), and the released amounts of eosinophil cationic protein (ECP), eosinophils protein-X (EPX) and myeloperoxidase (MPO) were measured by means of specific radioimmunoassays (RIA). Eosinophils obtained from patients with HES released significantly more ECP (P < 0.002) and EPX (P < 0.01) after 20 min of incubation than cells from the control group. The cellular content of ECP and EPX in eosinophils obtained from the patients with HES was significantly reduced to 50% and 62%, respectively, of the content of these granule proteins of eosinophils from the control group. In separated eosinophils light-density eosinophils released more of both ECP and EPX than normal density eosinophils. There was no difference in MPO release between the patients and the control group. We conclude that the eosinophils from patients with HES have an increased propensity to release their granule proteins and the releasability seems to be related to the density of the cells.

Reversal of the decline in breastfeeding in Peninsular Malaysia? Ethnic and educational differentials and data quality issues

Data from the First and Second Malaysian Family Life Surveys in 1976 and 1988, respectively, are analyzed to examine long-term trends in breastfeeding in Peninsular Malaysia, educational and ethnic differences therein, and the quality of retrospective data on infant feeding. The steady decrease between the mid-1950's and mid-1970's in breastfeeding was reversed to become a nearly monotonic increase since 1975. Part of the change is attributable to the changing composition of the Malaysian population. Over time, the percentages of births to subgroups with higher rates of breastfeeding--particularly Malays and more highly educated women--have increased. However, there is also evidence of changes in rates of breastfeeding within these subgroups. Many Malaysian infants have a total duration of breastfeeding (including with supplementation) considerably shorter than WHO's recommended four months of exclusive (unsupplemented) breastfeeding. Moreover, nearly all breastfed infants are first given supplementary food or beverage shortly after birth. Breastfeeding promotion efforts in Malaysia need to emphasize the appropriate timing of and types of supplementary feeding.

Plasma and urine levels of methotrexate and 7-hydroxymethotrexate in children with ALL during maintenance therapy with weekly oral methotrexate

A new high-performance liquid chromatographic assay was used to determine methotrexate (MTX) and its main metabolite, 7-hydroxymethotrexate (7-OH-MTX), in the plasma (n = 17) and urine (n = 14) of children (age 3-12 years) on maintenance therapy for acute lymphocytic leukemia (n = 14) or non-Hodgkin's lymphoma (n = 3). Each child received oral doses of weekly MTX (4.0-29 mg/m2) and daily 6-mercaptopurine (40-111 mg/m2). Plasma samples were collected daily from two children during the 1-week dose interval. A limited sampling strategy was designed, whereby 2 days of blood sampling were used in the other 15 patients. Morning urine samples were collected daily for 1 week following MTX intake from 14 of the children. MTX was detectable in all plasma and urine samples for the entire dose interval. The main metabolite, 7-OH-MTX, could be detected in plasma and urine from all patients on the first day after dose intake but only in a few patients during the whole dose interval. Interpatient variability of MTX and 7-OH-MTX levels was high at all points during the week. Significant correlation were found between the urinary MTX levels on days 2 and 7 and plasma MTX levels on day 2 after intake. No significant correlation was found between drug levels in plasma or urine and liver function tests in the children showing signs of mild liver injury. This assay provides a tool for further studies on the role of pharmacokinetics for the clinical effects of weekly oral low-dose MTX given alone or in combination with 6-mercaptopurine.

Molecular cloning, functional expression and localization of an inward rectifier potassium channel in the mouse brain

We have cloned an inward-rectifier potassium channel from a mouse brain cDNA library, studied its distribution in the brain by in situ hybridization and determined the chromosomal localization of the gene. A mouse brain cDNA library was screened using a fragment of the mouse macrophage IRK1 cDNA as a probe. Two duplicate clones of approximately 5.5 kb were obtained. Xenopus ococytes injected with cRNA derived from the clone expressed a potassium channel with inwardly rectifying channel characteristics. The amino acid sequence of the clone was identical to that of IRK1 recently cloned from a mouse macrophage cell line. In situ hybridization study showed the mouse brain IRK1 to be generally distributed throughout the brain, but in particular subsets of neurons at high levels. The gene was placed in the distal region of mouse chromosome 11, which contains several uncloned neurological mutations. These results provide the first demonstration of the cloning and distribution of an inward rectifier potassium channel from the nervous system.

Induction of stathmin mRNA during liver regeneration

Stathmin is a 19 kDa phosphoprotein, and is proposed to play a role in signal transduction in response to various extracellular stimuli that promote cellular growth and/or differentiation. We examined stathmin mRNA expression during development and liver regeneration in mice. Stathmin mRNA expression declined during the post-natal period and was undetected in adult liver. 36 h after partial hepatectomy, stathmin mRNA was rapidly induced and remained at elevated levels for at least 10 days. In situ hybridization experiments confirmed that stathmin mRNA expression occurred in hepatocytes. These results indicate that the stathmin gene expression appears to be repressed during the post-natal liver development, and is de-repressed by liver regeneration, which suggests that stathmin may be a good molecular marker of liver plasticity.

Conditioned nausea after cancer chemotherapy and autonomic nervous system conditionability

There are marked individual differences in conditioned nausea after cancer chemotherapy. To examine if part of this variation is associated with individual differences in autonomic nervous system conditionability, the present study addressed whether patients with conditioned nausea acquired conditioned heart rate and electrodermal responses at a different rate than patients without conditioned nausea. Of 28 relapse-free patients who had completed cisplatinum treatment for testicular cancer between 1981 and 1986, 10 reported persistent conditioned nausea, 8 extinguished conditioned nausea and 10 no conditioned nausea. These three groups were subjected to a differential conditioning paradigm with 8 sec pictorial stimuli (circles and triangles) serving as conditioned stimuli for an unconditioned electric shock while heart rate and electrodermal activity was monitored. There were 4 habituation, 8 acquisition and 8 extinction trials with each of the two cues. Analyses of variance using nausea status as the independent variable and physiological responses as the dependent lended some support to the notion that conditioned heart rate deceleration developed in response to the reinforced compared to the nonreinforced cue during acquisition in the two groups with persistent or extinguished conditioned nausea but not in the group with no conditioned nausea. In addition, patients that displayed good, as compared to poor heart rate conditionability during acquisition, were more likely to have persistent conditioned nausea, whereas those who showed poor heart rate conditioning mostly were those without conditioned nausea. Electrodermal variables revealed no systematic differences between groups. This tentatively supports that individual differences in parasympathetic but not sympathetic nervous system conditionability may be associated with individual differences in conditioned nausea resulting from cancer chemotherapy.

Genes necessary for expression of a virulence determinant and for transmission of Plasmodium falciparum are located on a 0.3-megabase region of chromosome 9

Virulence of the human malaria parasite Plasmodium falciparum is believed to relate to adhesion of parasitized erythrocytes to postcapillary venular endothelium (asexual cytoadherence). Transmission of malaria to the mosquito vector involves a switch from asexual to sexual development (gametocytogenesis). Continuous in vitro culture of P. falciparum frequently results in irreversible loss of asexual cytoadherence and gametocytogenesis. Field isolates and cloned lines differing in expression of these phenotypes were karyotyped by pulse-field gel electrophoresis. This analysis showed that expression of both phenotypes mapped to a 0.3-Mb subtelomeric deletion of chromosome 9. This deletion frequently occurs during adaptation of parasite isolates to in vitro culture. Parasites with this deletion did not express the variant surface agglutination phenotype and the putative asexual cytoadherence ligand designated P. falciparum erythrocyte membrane protein 1, which has recently been shown to undergo antigenic variation. The syntenic relationship between asexual cytoadherence and gametocytogenesis suggests that expression of these phenotypes is genetically linked. One explanation for this linkage is that both developmental pathways share a common cytoadherence mechanism. This proposed biological and genetic linkage between a virulence factor (asexual cytoadherence) and transmissibility (gametocytogenesis) would help explain why a high degree of virulence has evolved and been maintained in falciparum malaria.

The influence of IL-3, IL-5, and GM-CSF on normal human eosinophil and neutrophil C3b-induced degranulation

The priming effect of interleukin-3 (IL-3), interleukin-5 (IL-5), and granulocyte/macrophage-colony stimulating factor (GM-CSF) on eosinophil and neutrophil degranulation was studied. Granulocytes were obtained from normal donors, and degranulation was induced by incubation with serum-opsonized Sephadex particles. The released amounts of eosinophil cationic protein (ECP), eosinophil protein X (EPX), myeloperoxidase (MPO), and lactoferrin (LF) were measured by radioimmunoassay (RIA). The effect of IL-5 was dose- and time-dependent, with a maximal enhancement of ECP and EPX release of 71% (P < 0.03) and 66% (P < 0.03), respectively. Neutrophil degranulation, however, was unaffected. IL-3 was marginally effective, whereas GM-CSF seemed to act as a secretagogue for both eosinophil and neutrophil degranulation. We conclude that IL-5 selectively primes eosinophil degranulation, whereas IL-3 and GM-CSF seem to act as secretagogues for eosinophils and neutrophils. The results indicate that IL-5 may be involved in the priming of eosinophils as observed in patients with asthma and hypereosinophilic syndrome (HES).

Fetal heart circumference as a predictor of menstrual age in fetuses affected by disturbances in growth

OBJECTIVE

The purpose of this study was twofold: (1) to evaluate the relationship between fetal heart circumference and gestational age and (2) to determine the effect, if any, of disturbances in fetal growth on heart circumference.

STUDY DESIGN

Heart circumference was measured in 262 women with normal gestations (control group) and in two study groups consisting of 52 large-for-gestational age 32 small-for-gestational age fetuses. Standardized, gestational age-adjusted values in the two study groups were compared with normative data provided by the control group.

RESULTS

There was a close correlation (R2 = 0.94) between heart circumference and gestational age in normally growing fetuses. Disturbances of fetal growth (i.e., macrosomia and growth retardation) were found to have an inconsistent effect on heart circumference.

CONCLUSION

Heart circumference cannot be used as an independent parameter for gestational age evaluation in fetuses with disturbances of growth.

Monitoring global change: Comparison of forest cover estimates using remote sensing and inventory approaches

Satellite-based remote sensing offers great potential for frequent assessment of forest cover over broad spatial scales, however, calibration and validation using ground-based surveys are needed. In this study, forest cover estimates for the United States from a recently developed land surface cover map generated from satellite remote sensing data were compared to state-level inventory data from the U.S. National Resources Planning Act Timber Database. The land cover map was produced at the U.S. Geological Survey EROS Data Center and is based on imagery from the AVHRR sensor (spatial resolution ∼1.1 km). Vegetation type was classified using the temporal signal in the Normalized Difference Vegetation Index derived from AVHRR data. Comparisons revealed close agreement in the estimate of forest cover for extensively forested states with large polygons of relatively similar vegetation such as Oregon. Larger forest cover differences were observed in other states with some regional patterns in the level of agreement apparent.Comparisons in inventory- and remote sensing-based estimates of current forested area with potential vegetation maps indicated the magnitude of past land use change and the potential for future changes. The remote sensing approach appears to hold promise for conducting surveys of forest cover where inventory data are limited or where rates of vegetation change, due to human or climatic factors, are rapid.

In vivo accumulation of etoposide in peripheral leukemic cells in patients treated for acute myeloblastic leukemia; relation to plasma concentrations and protein binding

Since etoposide interacts with the nuclear enzyme topoisomerase II, the drug concentrations in the malignant cells during chemotherapy may have clinical correlates. Plasma protein binding of etoposide is extensive (94%) and alterations of the non-proteinbound fraction affect pharmacokinetic behavior of the drug. The pharmacokinetics of etoposide was therefore studied in plasma, total and non-proteinbound concentrations, and in leukemic cells isolated from peripheral blood samples from 22 patients after the first dose of the induction treatment for acute myelocytic leukemia. Fourteen patients received 100 mg/m2 and eight patients 200 mg/m2 as a 1 h infusion. The mean area under the concentration versus time curve AUC(0-infinity) in plasma was at the lower dose level 78.4 +/- 29.1 (mean +/- S.D.) micrograms/ml x h and 201.0 +/- 56.5 micrograms/ml x h at the higher dose level. The fraction of non-proteinbound etoposide in plasma was 5.2 +/- 3.4 and 5.4 +/- 2.1% in the two treatment groups. AUC(0-16h) in leukemic cells was 8.4 +/- 8.7 and 22.4 +/- 12.1 micrograms/ml x h at the two dose levels, respectively. The cellular etoposide concentration was 12.1 +/- 7.9 and 14.7 +/- 5.1% of the plasma concentration at the end of the infusion. The interpatient variability in cellular drug levels was considerable and exceeded the variability in plasma concentrations. Cellular accumulation of etoposide could be important for treatment outcome.