Dual stop codon suppression in mammalian cells with genomically integrated genetic code expansion machinery

Stop codon suppression using dedicated tRNA/aminoacyl-tRNA synthetase (aaRS) pairs allows for genetically encoded, site-specific incorporation of non-canonical amino acids (ncAAs) as chemical handles for protein labeling and modification. Here, we demonstrate that piggyBac-mediated genomic integration of archaeal pyrrolysine tRNA (tRNAPyl)/pyrrolysyl-tRNA synthetase (PylRS) or bacterial tRNA/aaRS pairs, using a modular plasmid design with multi-copy tRNA arrays, allows for homogeneous and efficient genetically encoded ncAA incorporation in diverse mammalian cell lines. We assess opportunities and limitations of using ncAAs for fluorescent labeling applications in stable cell lines. We explore suppression of ochre and opal stop codons and finally incorporate two distinct ncAAs with mutually orthogonal click chemistries for site-specific, dual-fluorophore labeling of a cell surface receptor on live mammalian cells.

Electrostatic interactions guide substrate recognition of the prokaryotic ubiquitin-like protein ligase PafA

Pupylation, a post-translational modification found in Mycobacterium tuberculosis and other Actinobacteria, involves the covalent attachment of prokaryotic ubiquitin-like protein (Pup) to lysines on target proteins by the ligase PafA (proteasome accessory factor A). Pupylated proteins, like ubiquitinated proteins in eukaryotes, are recruited for proteasomal degradation. Proteomic studies suggest that hundreds of potential pupylation targets are modified by the sole existing ligase PafA. This raises intriguing questions regarding the selectivity of this enzyme towards a diverse range of substrates. Here, we show that the availability of surface lysines alone is not sufficient for interaction between PafA and target proteins. By identifying the interacting residues at the pupylation site, we demonstrate that PafA recognizes authentic substrates via a structural recognition motif centered around exposed lysines. Through a combination of computational analysis, examination of available structures and pupylated proteomes, and biochemical experiments, we elucidate the mechanism by which PafA achieves recognition of a wide array of substrates while retaining selective protein turnover.

In utero meconium aspiration by the baboon fetus

Meconium aspiration syndrome occurs more commonly in infants subjected to fetal distress. The baboon model was utilized to produce in utero aspiration of meconium in the presence of fetal acidosis. Fifteen fetal baboons underwent acute catheterization of the femoral artery and a Swan-Ganz balloon was placed in the maternal aorta. Meconium was added to the amniotic fluid and the balloon was repetitively inflated to produce hypoxemia in 3 fetuses and hypoxemia and acidosis in 4. Two fetuses served as controls and the balloon was not inflated. Acidosis alone was produced in 3 others by maternal cooling. Maternal administration of fentanyl, a narcotic analgesic and respiratory depressant drug, was found to reduce the degree of in utero meconium aspiration in 3 distressed fetuses by inhibiting gasping respirations. It is concluded that fetal respiratory depressants may be useful in this circumstance but only when expert resuscitative capability is present in the delivery room.

In utero distal pulmonary meconium aspiration

We have recently had eight cases of severe meconium aspiration syndrome which occurred despite clearing of the posterior pharynx of meconium after delivery of the head but before delivery of the body. Seven of the eight cases had documented fetal distress before delivery. Two stillborns with meconium aspiration are presented and illustrate that electronic fetal monitoring and aggressive obstetric intervention should be coupled with the suctioning technic to prevent significant mortality and morbidity associated with meconium-stained deliveries.

Response of immature baboon fetal lung to intra-amniotic betamethasone

Intra-amniotic betamethasone (6 mg.) given to six immature fetal baboons, at four and again at three days prior to delivery by cesarean section, between 147 and 158 days' gestation (term = 180 days), significantly increased the amniotic fluid lecithin/sphingomyelin (L/S) ratio. At delivery, treated animal lungs were more mature in that they had a significantly increased deflation stability and significantly decreased minimum surface tension in minced lung when compared to five control animals. Changes in maximum air distensibility lagged behind changes in deflation stability. The major molecular species of pulmonary phosphatidylcholine were analyzed by gas liquid chromatography as the diacylglycerol derivatives. The proportions of 14:0/16:0, 16:0/16:0, and 16:0/18:0, were significantly increased over control proportions while unsaturated species tended to decrease in animals exposed to intra-amniotic betamethasone. The immature fetal baboon pulmonary system responded to intra-amniotic betamethasone with a synchronous increase in the L/S ratio, improved pulmonary stability, and a more mature pulmonary lecithin composition, but did not demonstrate a synchronous increase in tissue distensibility.

Antenatal glucocorticoid therapy for the prevention of respiratory distress syndrome in the premature infant

A double-blind study was designed to investigate the effects of antenatal glucocorticoids on the incidence of respiratory distress syndrome (RDS) in 128 premature human infants. There was a significant reduction (P less than 0.05) in the incidence of RDS in the betamethasone-treated infants to 8.7% compared to an incidence of 22.6% in the saline-treated controls and 25.0% in infants whose mothers received methylprednisolone. The effectiveness of betamethasone in reducing RDS was limited to premature infants delivered to mothers with intact fetal membranes and with an initial L/S ratio less than 2.0. The time between administration of the glucocorticoid and delivery did not significantly affect the incidence of RDS in this study. The failure of methylprednisolone to reduce the development of RDS in premature infants suggests its potential use in maternal therapy during pregnancy with minimal effects on fetal maturation.

Cervical incompetence. A diagnostic and prognostic scoring system

Recognition of the incompetent cervical as a cause of midtrimester abortion and prematurity has led to the development of surgical methods of repair. Diagnosis of the condition has generally relied on clinical findings and historical information from the patient. A scoring system based on clinical and historical criteria is suggested for selection of patients for surgical correction. Thirty-one cases of cervical incompetence tested surgically over the past 10 years are reviewed. Patients who had higher scores had a higher postoperative pregnancy success rate than the patients with lower scores. The scoring of patients preoperatively appears useful for selection of patients as well as prognostically.