Cholinomimetic teratogens. VI. The interaction of cholinomimetic teratogens with the antimalarial drugs chloroquine and chlorguanide

Pre-travel vaccination and medical prophylaxis in the pregnant traveler

BACKGROUND

Practitioners are often fearful of giving vaccinations and prophylactic medications to pregnant travelers. And yet pregnancy is often a time of heightened danger from travel-related infections and illnesses.

METHOD

Literature search and communication with researchers.

RESULTS

With a few exceptions, there is little systematic research regarding the use of prophylactic medications and vaccines during pregnancy. Case reports and small studies do, however, indicate an increased risk in pregnancy from many of the preventable illnesses, and there is some data to support the use of preventive measures.

CONCLUSIONS

The authors present some non-medical interventions that may be used to limit exposure to a number of disease processes. They then review the available information regarding the safety and efficacy of routine and travel-related vaccines as well as prophylactic medications for malaria, diarrhea, motion sickness and altitude sickness. When there are no obstetrical or medical contraindications, travel-related illness can usually be safely prevented during pregnancy in much the same ways as in the non-pregnant state.

Chloroquine accumulation and alterations of proteolysis and pinocytosis in the rat conceptus in vitro

The teratogenicity of chloroquine (CQ) has been hypothesized to result from its effects on lysosomal function, specifically the ability of the visceral yolk sac (VYS) to capture and degrade external macromolecules. Using the rat whole embryo culture system, we evaluated the ability of CQ to accumulate in conceptual tissues and its effects on aspects of VYS function known to be important in the uptake and processing of nutrients. When CQ was added directly to the culture medium, it was found to accumulate rapidly in conceptual tissues, particularly the VYS. Tissue concentrations of CQ in the embryo proper reached approximately 10-fold those in the medium, whereas concentrations in the VYS exceeded by 100-fold the medium concentration within a 4-hr exposure on gestational day (GD) 10. Embryotoxic concentrations of CQ (10-30 microM) enhanced the activity of lysosomal cysteine proteinases measured in vitro under optimum pH conditions in both embryonic and VYS homogenates after a 26-hr treatment from GD 10-11. A different pattern of response in enzyme activity was observed between embryos and VYSs that could be attributed to the preferential accumulation of CQ in the VYS. Nonembryotoxic concentrations of CQ (1-7.5 microM) induced a concentration-dependent increase in VYS enzyme activity that peaked in conceptuses exposed to 20 microM CQ (an intermediate embryotoxic concentration). The enhanced cysteine proteinase activity was time dependent and appeared to increase gradually in conceptuses exposed to 10-20 microM CQ during the 26-hr culture period. This was in contrast to the rapid accumulation of CQ in conceptual tissues seen on gestational day 10. Protein content in the VYS was increased significantly after a 9-hr exposure of whole conceptuses to CQ (20 microM), indicating an inhibition of VYS proteolytic activity in situ. After 24 hr of exposure to 20 microM CQ, VYS protein content was not significantly different from control, but embryonic protein was reduced significantly by 20%. These observations are consistent with a model of reversible inhibition of VYS proteolysis by CQ followed by a compensatory increase in lysosomal proteinase activity. VYS fluid-phase pinocytosis was also assessed after CQ exposure and found to be inhibited only in the highest CQ concentration tested (30 microM). Lower concentrations of CQ that were still embryotoxic (10-20 microM) did not affect VYS fluid-phase pinocytosis, suggesting that inhibition of this activity is not primarily responsible for CQ embryotoxicity.

Chloroquine embryotoxicity in the postimplantation rat conceptus in vitro

The embryotoxicity of the antimalarial drug chloroquine (CQ) was evaluated in vitro using the rat whole embryo culture system. CQ was found to be embryotoxic and dysmorphogenic when added directly to the culture media containing gestational day (GD) 10 rat conceptuses. Twenty-six-hr exposure to CQ elicited dose-related decreases in embryonic crown-rump length, protein and DNA contents and increases in the incidence of morphologically abnormal embryos. At 30 microM CQ, embryonic protein content was decreased to 67% and DNA content to 58% of control while the incidence of morphological abnormalities rose to 100%. Abnormal axial rotation, micro-ophthalmia, and selective cephalic hypoplasia were the most common developmental abnormalities observed. Visceral yolk sac (VYS) vasculature and blood pigmentation were also decreased in a dose-dependent manner, as was VYS DNA content (80% of control at 30 microM). VYS protein content, however, showed an alternate pattern of response, decreasing to 87% of control at 10 microM CQ but increasing to 125% of control at 30 microM. Histologic evaluation revealed that the cytoplasm of the VYS endoderm epithelium was distended due to vacuolization produced by CQ exposure. In the embryo proper, CQ inhibited cranial neural tube development and altered the morphology of cranial neural crest cells. These observations document the in vitro embryotoxicity of CQ and suggest altered VYS histiotrophic nutrition as well as direct embryonic effects as possible mechanisms of CQ embryotoxicity.