ABSTRACT
Ustekinumab (USK) was used in the treatment of two pregnant patients with Crohn's disease. It was given in the third trimester and restarted postnatally for both women. One woman remained on USK and in remission throughout pregnancy. The second woman, took a treatment break, flared, and then had remission induced with reintroduction of USK. Both women delivered healthy term infants. The interval from last dose to birth was 11 and 8 weeks respectively. Interestingly, USK levels in cord blood was observed in higher concentrations than in the maternal serum taken in third trimester. While no adverse effect in infants has been observed, clinicians should remain aware of fetal transfer when using USK in pregnancy. An evaluation of risk and benefit may favour continuing USK in pregnancy in patients with refractory disease.
ABSTRACT
Chlorophyll biosynthesis is a process involving approximately 20 different enzymatic steps. Half of these steps are common to the biosynthesis of other tetrapyrroles, such as heme. One of the least understood enzymatic steps is formation of the isocyclic ring, which is a characteristic feature of all (bacterio)chlorophyll molecules. In chloroplasts, formation of the isocyclic ring is an aerobic reaction catalyzed by Mg-protoporphyrin IX monomethyl ester cyclase. An in vitro assay for the aerobic cyclase reaction required membrane-bound and soluble components from the chloroplasts. Extracts from barley (Hordeum vulgare L.) mutants at the Xantha-l and Viridis-k loci showed no cyclase activity. Fractionation of isolated plastids by Percoll gradient centrifugation showed that xantha-l and viridis-k mutants are defective in components associated with chloroplast membranes. The Xantha-l gene, corresponding to Arabidopsis thaliana CHL27, Rubrivivax gelatinosus acsF, Chlamydomonas reinhardtii CRD1, and CTH1 and situated at the short arm of barley chromosome 3 (3H), was cloned, and the mutations in xantha-l(35), xantha-l(81), and xantha-l(82) were characterized. This finding connected biochemical and genetic data because it demonstrated that Xantha-l encodes a membrane-bound cyclase subunit. The evidence suggests that the aerobic cyclase requires at least one soluble and two membrane-bound components.
