Roger E. Bawdon

Transfer of inflammatory cytokines across the placenta.

OBJECTIVE: The purpose of this study was to determine whether the placental transfer of interleukin (IL)-1α, IL-6, and tumor necrosis factor-α (TNF-α) occurs. METHODS: Four normal-term placentas were perfused for maternal–fetal transfer of the cytokines, 2 placentas for fetal–maternal transfer, and 4 additional placentas were used for an endogenous control. The ex vivo isolated cotyledon human placental perfusion model was used. The reference compound antipyrine was used to determine the transport fraction and clearance index of the cytokines. The cytokines were added to either the maternal or fetal circulations, and samples were collected for 1 hour in a constant-flow open circulation. Cytokine levels were compared between the study and control placentas. Concentrations of the cytokines were measured by sandwich enzyme immunoassay. RESULTS: The clearance index for the maternal–fetal transfer of IL-1α and TNF-α was 0.001, suggesting minimal transfer to the fetal circulation. The clearance index for IL-6 was 0.30, indicating transfer to the fetal circulation. When the cytokines were added to the fetal circulation, the clearance index for IL-1α was 0.001, again indicating minimal transfer. The clearance index for TNF-α in the fetal–maternal study was not determined. IL-6 had a clearance index of 0.23, which was similar to that observed with maternal–fetal transfer. IL-6 concentrations in the study placentas were higher than the concentrations found in the controls. CONCLUSION: There appears to be bidirectional transfer of IL-6 in the healthy-term human placental perfusion model. LEVEL OF EVIDENCE: II-2

Nonadherence in Adolescent Oncology Patients: Preliminary Data on Psychological Risk Factors and Relationships to Outcome

Published nonadherence rates in the adolescent oncology population range from 33 to 60% though little is known about the psychological factors that contribute to adherence and the relationship between outcome and nonadherence. Our study was designed to investigate psychological and family factors related to adherence and the relationship between adherence and survival in this population. We evaluated 44 (27 males, 17 females) patients with cancer (13–17 years) who were at least 6-months postdiagnosis. Adherence with trimethoprim/sulfamethoxazole (TMP/SMX) was determined at one point in time, using serum assay. Twelve of the patients (27%) had no detectable TMP/SMX. Patients without detectable drug had higher levels of depression, lower self-esteem, and higher levels of parent–child incongruence. Survival rates, 6 years after the initiation of the study, were lower in the group of participants categorized as nonadherent. These findings, if confirmed, have implications for the management of nonadherence and mood in this population.

Divergent activities of an engineered antibody in murine and human systems have implications for therapeutic antibodies

The MHC class I-related receptor, neonatal Fc receptor (FcRn), plays a central role in regulating the transport and in vivo persistence of immunoglobulin G (IgG). IgG–FcRn interactions can be targeted for engineering to modulate the in vivo longevity and transport of an antibody, and this has implications for the successful application of therapeutic IgGs. Although mice are widely used to preclinically test antibodies, human and mouse FcRn have significant differences in binding specificity. Here we show that an engineered human IgG1 has disparate properties in murine and human systems. The mutant shows improved transport relative to wild-type human IgG1 in assays of human FcRn function but has short in vivo persistence and competitively inhibits FcRn activity in mice. These studies indicate potential limitations of using mice as preclinical models for the analysis of engineered antibodies. Alternative assays are proposed that serve as indicators of the properties of IgGs in humans.

Metabolism of cocaine by human placentas: Implications for fetal exposure

To assess placental metabolism of cocaine, placentas were obtained at the time of delivery and the microsomes were extracted by ultracentrifugation within 2 hours. Placental microsomes were cultured with cocaine at physiologic plasma concentrations similar to those of cocaine users (0.75 micrograms/ml). Two control groups were established. In the first group an anticholinesterase was added to the culture to suppress enzyme activity, and in the second cocaine was cultured alone without placental microsomes to obtain baseline spontaneous conversion of the drug. The results indicate that cocaine is biotransformed by the human placenta, presumably by cholinesterase activity. This suggests that the placenta may provide a moderate degree of protection from cocaine-induced morbidity, such as abruptio placentae and fetal growth retardation, by converting cocaine into less active metabolites. These results also have pharmacogenetic implications because cholinesterase activity varies among individuals. Hence placentas that cannot transform the drug may place the conceptus at greater risk of developmental abnormalities.

Markers of acute and chronic asphyxia in infants with meconium-stained amniotic fluid

OBJECTIVE Cord blood pH, lactate, hypoxanthine, and erythropoietin levels have all been used as markers of either acute or chronic asphyxia. We sought to determine whether these index values were significantly different in infants with or without meconium-stained amniotic fluid. STUDY DESIGN Fifty-six pregnant women in spontaneous labor at term were divided into two groups on the basis of the presence or absence of meconium-stained amniotic fluid. All meconium-stained fluid was centrifuged, and the volume percentage of particulate matter (i.e., meconium) was recorded. Umbilical artery blood and mixed arterial and venous cord blood were obtained at each delivery. Lactate, hypoxanthine, and erythropoietin levels were measured. Statistical analysis included Student t test and rank sum statistics where appropriate. Normal and Spearman correlation coefficients were also used. RESULTS There were no significant differences in mean umbilical artery pH (7.26 +/- 0.06 vs 7.25 +/- 0.10), lactate levels (32.8 +/- 10 mg/dl vs 30.4 +/- 14.2 mg/dl), and hypoxanthine levels (13.4 +/- 6.7 mumol/L vs 14.0 +/- 6.0 mumol/L) in newborns with meconium (n = 28) compared with controls (n = 28). Erythropoietin levels were significantly greater in newborns with meconium (median 39.5 mIU/ml vs 26.8 mIU/ml, p = 0.039). There was no correlation between the amount of particulate matter and any marker of asphyxia. CONCLUSIONS There was no correlation between markers of acute asphyxia (i.e., umbilical artery blood pH, lactate, or hypoxanthine) and meconium. However, erythropoietin levels were significantly elevated in newborns with meconium-stained amniotic fluid. This latter marker may better correlate with chronic asphyxia.

Ampicillin for neonatal group B streptococcal prophylaxis: How rapidly can bactericidal concentrations be achieved?

OBJECTIVE Our purpose was to determine how rapidly bactericidal concentrations of ampicillin against group B streptococci are achieved in amniotic fluid and cord blood after a 2 gm maternal infusion. STUDY DESIGN Ampicillin was administered at varying time intervals between 3 and 67 minutes before elective cesarean delivery in 40 women. Samples of amniotic fluid were obtained by amniocentesis just before the uterine incision was made. Umbilical and maternal blood were obtained at the time of delivery. Ampicillin concentrations were measured by high-pressure liquid chromatography. RESULTS The mean concentrations of ampicillin measured in maternal and umbilical cord sera all exceeded the minimum bactericidal concentrations reported for group B streptococci (0.25 to 2.0 micrograms/ml) and were achieved as soon as 5 minutes after ampicillin infusion. Similarly, bactericidal levels of ampicillin in the amniotic fluid could be detected as early as 5 minutes. However, such concentrations of ampicillin in the amniotic fluid were achieved in only 85% of the pregnancies studied. CONCLUSIONS Bactericidal levels of ampicillin against group B streptococci can usually be achieved rapidly in both fetal blood and amniotic fluid after a standard 2 gm intravenous dose given to the mother for neonatal prophylaxis.

Placental transfer of ritonavir with zidovudine in the ex vivo placental perfusion model

OBJECTIVE The object was to determine the placental transfer of ritonavir alone and in combination with zidovudine. STUDY DESIGN Twelve placental perfusion studies were performed at trough (1-2 microg/mL) and peak (approximately 20 microg/mL) combinations of ritonavir and zidovudine. Accumulation of ritonavir was determined. RESULTS Transfer of ritonavir at trough concentrations was undetectable (<0.025 microg/mL). The clearance index of ritonavir at peak concentration was 0.085 +/- 0.05 and was unaffected by zidovudine. The fetal concentration of ritonavir was 0.0758 +/- 0.22 microg/mL at a maternal concentration of approximately 20 microg/mL and 25.5 +/- 6.9 microg/mL at a concentration of 100 microg/mL. There was no tissue accumulation of ritonavir either alone or with zidovudine. CONCLUSION The clearance index of ritonavir at therapeutic levels was extremely low, with little accumulation in the fetal compartment and no accumulation in placental tissue. Zidovudine does not significantly affect the transfer or accumulation of ritonavir.

Collagen shield delivery of amphotericin B

By using a high-pressure liquid chromatography assay, we investigated the ability of collagen shield therapeutic contact lenses to release amphotericin B and deliver it to the anterior segment of rabbit eyes. In vitro studies showed that presoaked collagen shields released most of the amphotericin B within the first hour of elution. We compared the corneal and aqueous humor amphotericin B levels produced by collagen shields soaked in amphotericin B and frequent-drop therapy at four time points over a six-hour period. The collagen shields soaked in amphotericin B produced corneal levels that were higher than those produced by frequent-drop therapy at one hour, equivalent to drop therapy at two and three hours, and lower than drop therapy at six hours. There were no differences in amphotericin B levels in aqueous humor at any time point between rabbits treated with collagen shield delivery and rabbits treated with frequent-drop delivery. The results of this study suggest that amphotericin B delivery to the cornea by collagen shields is comparable to frequent-drop delivery but has the potential benefit of added convenience and compliance.

The Metabolism and Transplacental Transfer of Oseltamivir in the Ex Vivo Human Model

Oseltamivir phosphate is extensively metabolized in the ex vivo human placenta model, and the transplacental passage of the metabolite oseltamivir carboxylate is incomplete. Objective. To evaluate the metabolism and transplacental transfer of oseltamivir (Tamiflu) in the ex vivo human placental model. Study Design. Perfusion studies were performed in six placentas from term, uncomplicated deliveries. Concentrations of oseltamivir phosphate (OP) that were 5-6 fold, 20–30 fold, and 600–800 fold above the therapeutic peak were tested, as neither OP nor its active metabolite, oseltamivir carboxylate (OC), could be detected at near-therapeutic concentrations. The transplacental transfer and accumulation of OC were assessed using the 14C antipyrine reference method. Results. OP was extensively metabolized to OC. In the 4 placentas with the highest concentration of OP, OC had a mean clearance index of 0.13 ± 0.08, suggesting that transplacental passage occurs at a relatively low rate. Measurable fetal accumulation occurred in the two placentas with the highest initial concentrations. Conclusions. Oseltamivir phosphate was extensively metabolized in the ex vivo model. Transplacental transfer of the metabolite was incomplete and accumulation was minimal.

The ex vivo human placental transfer of the anti-HIV nucleoside inhibitor abacavir and the protease inhibitor amprenavir.

OBJECTIVE: The transfer of abacavir, a new nucleoside inhibitor, and amprenavir, a new protease inhibitor, used for the treatment of human immunodeficiency virus, has been studied in the ex vivo human placental model. METHODS: The ex vivo human placental model used C14 antipyrine to determine the transport fraction and clearance index of these compounds at both the peak and trough serum concentrations. The clearance index accumulation and tissue concentrations were determined for each drug by high pressure liquid chromatography. RESULTS: The clearance index of abacavir was 0.47 +/- 0.19 and 0.50 +/- 0.07 at peak and trough concentrations, respectively. The clearance index of amprenavir was 0.38 +/- 0.09 and 0.14 +/- 0.08 at peak and trough concentrations, respectively. There was no unusual accumulation of either drug in the media or tissue when the perfusion system was closed. CONCLUSION: Abacavir is the first nucleoside compound studied in the perfusion system with a high clearance index. The transfer of the protease inhibitor amprenavir had a clearance index 2.75 times greater than the clearance index of ritonavir at peak concentration determined in a previous study. At trough concentration the clearance index was much less than at the peak concentration. A similar result was found with ritonavir.