Mutation and Mutagenesis of thiol peroxidase of Escherichia coli and a new type of thiol peroxidase family

A novel thioredoxin-linked thiol peroxidase (Px) from Escherichia coli has been reported previously (M. K. Cha, H. K. Kim, and I. H. Kim, J. Biol. Chem. 270:28635-28641, 1995). In an attempt to perform physiological and biochemical characterizations of the thiol Px, a thiol Px null (tpx) mutant and a functional-residue mutant of thiol Px were produced. The tpx mutant was viable in aerobic culture but grew more slowly than the wild-type cells. The difference in growth rate became more pronounced when oxidative-stress-inducing reagents, such as peroxides and paraquat, were added to the cultures. The viability of the individual tpx mutant under oxidative stress was much lower than that of wild-type cells. tpx mutants growing aerobically respond to paraquat with a sixfold greater induction of Mn-superoxide dismutase than that of the wild-type cells. The deduced amino acid sequence of the thiol Px was found to be from 42 to 72% identical to the sequences of proteins from Haemophilus influenzae (ToxR regulon), Vibrio cholerae (ToxR regulon), and three kinds of streptococci (coaggregation-mediating adhesins), suggesting that they all belong to a new thiol Px family. Alignment of the amino acid sequences of the thiol Px family members showed that one cysteine, which corresponds to Cys-94 in E. coli thiol Px, is perfectly conserved. The substitution of serine for this cysteine residue resulted in complete loss of Px activity. These results suggest that the members of the thiol Px family, including E. coli thiol Px, have a functional cysteine residue and function in vivo as peroxidases.     

The hypolipidemic effects of 1-acetyl-4-phenyl-1,2,4-triazolidine-3,5-dione in rodents

1-Acetyl-4-phenyl-1,2,4-triazolidine,5-dione (APTD), a potent hypolipidemic agent, lowered both serum cholesterol and triglyceride levels in normo- and hyperlipidemic rats at 10 or 20 mg/kg/day. The agent effectively lowered VLDL-cholesterol (VLDL-C) and LDL-C content and raised HDL-C content in normal and hyperlipidemic rats treated from 4 to 8 weeks. Similar effects on the incorporation of cholesterol into the lipoprotein fractions were observed after drug treatment. Tissue lipids, e.g. cholesterol, were lowered, whereas fecal cholesterol levels were increased. APTD's primary targets were acyl CoA cholesterol acyl transferase (ACAT) for cholesterol ester synthesis and sn-glycerol-3-phosphate acyl transferase (GPAT) and phosphatidylate phosphohydrolase (PPH) for triglyceride synthesis.     

Late reopening of fibrosed capsular bags to reposition decentered intraocular lenses

The infrequent postoperative complication of intraocular lens decentration in the presence of an intact fibrosed capsule has traditionally been treated with lens explantation and exchange for a sulcus-fixated lens. Many of these patients can be managed by reopening the fibrosed capsular bag and repositioning the lens within the bag. These cases can be performed quickly using topical anesthesia regardless of the time since the primary cataract procedure.     

Spontaneous intracranial hemorrhage of structural origin during the first year of life

Symptomatic intracranial hemorrhage (ICH) in term infants is not common, but when it occurs it is usually secondary to trauma, coagulation disorders and/or hypoxia. The possibility of a structural cause for an infantile ICH is unfortunately not seriously considered until very late. In this paper we report the cases of five full-term infants, each of whom developed ICH secondary to a structural lesion during the 1st year of life. Three presented during the newborn period. A congenital saccular aneurysm of the middle cerebral artery in an 8-month old male infant; a posterior fossa arteriovenous malformation in a 2-week old female neonate; a deep parietal cavernous angioma in a 6.5-month-old male infant; a temporoparietal low-grade astrocytoma in a 12-day old male neonate and a temporoparietal desmoplastic ganglioglioma in a 9-day-old male neonate were the structural lesions that were causative for hemorrhage. In all cases but one, the diagnosis was reached by computerized tomography and/or magnetic resonance imaging. All infants underwent surgery for the removal of the hematoma and of the lesion causative for the bleed. All are alive at 19, 3, 11.5, 10, and 5 years, respectively. We discuss the diagnosis of ICH with special emphasis on contemporary imaging modalities and stress the benefits of aggressive and timely surgical treatment. We then consider a concise analysis of the world literature on the occurrence of structural causes of ICH during infancy.     

Escherichia coli transcytosis in a Caco-2 cell model: implications in neonatal necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a serious gastrointestinal disorder of preterm infants. Other than an association with prematurity and gastrointestinal feeding, no single factor or mechanism has been consistently linked to this disease. We have previously demonstrated that Escherichia coli isolates obtained from the stool of infants with NEC caused NEC-like injury in a weanling rabbit ileal loop model; this injury, in turn, could be blocked by coinfection with selected Gram(+) bacteria (Enterococcus faecium) isolated from asymptomatic controls. Using Caco-2 cells in a trans-well system, we now demonstrate that the same E. coli isolates can cross epithelial cell monolayers in the absence of ultrastructural change or damage. These results with E. coli contrast with those seen with Salmonella typhimurium, which passed through the monolayer at a higher rate and were associated with striking ultrastructural damage. Transcytosis of E. coli was reduced 3-5-fold in the presence of E. faecium previously shown to block NEC-like injury in the loop model. There was a mild increase in the rate of E. coli transcytosis when studies were conducted with younger, undifferentiated cells; these immature cells had no brush border, had decreased production of brush border-specific enzymes, but retained well defined tight junctions, as demonstrated by transepithelial electrical resistance and electron microscopy. A further reduction/ complete blockage of E. coli transcytosis was observed when E. faecium was used as the coinfectant in studies with these undifferentiated cells. We hypothesize that the ability of E. coli to cross epithelial cell layer is a critical initial step in the cascade of events which lead ultimately to NEC; blockage or reduction in E. coli transcytosis in the presence of certain Gram(+) organisms may play a significant role in prevention of NEC.