Evidence of participation of McrB(S) in McrBC restriction in Escherichia coli K-12

The McrBC restriction system has the ability to restrict DNA containing 5-hydroxymethylcytosine, N4-methylcytosine, and 5-methylcytosine at specific sequences. The mcrB gene produces two gene products. The complete mcrB open reading frame produces a 51-kDa protein (McrB(L)) and a 33-kDa protein (McrB(S)). The smaller McrB polypeptide is produced from an in-frame, internal translational start site in the mcrB gene. The McrB(S) sequence is identical to that of McrB(L) except that it lacks 161 amino acids present at the N-terminal end of the latter protein. It has been suggested that McrB(L) is the DNA binding restriction subunit. The function of McrB(S) is unknown, although there has been speculation that it plays some role in the modulation of McrBC restriction. Studies of the function of McrB(S) have been challenging since it is produced in frame with McrB(L). In this study, we tested the effects of underproduction (via antisense RNA) and overproduction (via gene dosage) of mcrBC gene products on restriction levels of the mcrBC+ strain JM107. Among the parameters monitored was the induction of SOS responses, which indicate of DNA damage. Evidence from this study suggests that McrB(S) is necessary for stabilization of the McrBC restriction complex in vivo.     

Chimeric analysis of fibroblast growth factor receptor-1 (Fgfr1) function: a role for FGFR1 in morphogenetic movement through the primitive streak

Fibroblast growth factor (FGF) signaling has been implicated in the patterning of mesoderm and neural lineages during early vertebrate development. In the mouse, FGF receptor-1 (FGFR1) is expressed in an appropriate spatial and temporal manner to be orchestrating these functions. Mouse embryos homozygous for a mutated Fgfr1 allele (fgfr1(delta tmk)) die early in development, show abnormal growth and aberrant mesodermal patterning. We have performed a chimeric analysis to further study FGFR1 function in the morphogenesis and patterning of the mesodermal germ layer at gastrulation. At E9.5, fgfr1(delta tmk)/fgfr1(delta tmk) cells showed a marked deficiency in their ability to contribute to the extra-embryonic, cephalic, heart, axial and paraxial mesoderm, and to the endoderm of chimeric embryos. Analysis at earlier stages of development revealed that fgfr1(delta tmk)/fgfr1(delta tmk) cells accumulated within the primitive streak of chimeric embryos, and consequently failed to populate the anterior mesoderm and endodermal lineages at their inception. We suggest that the primary defect associated with the fgfr1(delta tmk) mutation is a deficiency in the ability of epiblast cells to traverse the primitive streak. fgfr1(delta tmk)/fgfr1(delta tmk) cells that accumulated within the primitive streak of chimeric embryos tended to form secondary neural tubes. These secondary neural tubes were entirely fgfr1(delta tmk)/fgfr1(delta tmk) cell derived. The adoption of ectopic neural fate suggests that normal morphogenetic movement through the streak is essential not only for proper mesodermal patterning but also for correct determination of mesodermal/neurectodermal cell fates.     

Arterial anatomy of the oral cavity: an analysis of vascular territories

Knowledge of the specific cutaneous or surface regions supplied by constant named arterial sources has allowed for increasing clinical application of flap transfers of tissue. Despite the routine use of intraoral flaps for reconstruction of congenital or acquired defects of the oral cavity and pharynx, no previous investigation has centered on understanding the surface or mucosal arterial territories of the oral cavity. In a cadaver study, six mucosal territories of the intraoral cavity were defined using selective ink and lead oxide injections through named arteries. The anatomical boundaries of these territories are predictable and constant in location for different cadavers. The six contiguous territories are based on the buccal, labial, inferior alveolar, ascending palatine, ascending pharyngeal, and lingual arteries. This study supports the safe vascular basis of existing clinical procedures of the intraoral cavity and may have implications for the design of new intraoral reconstructive procedures.     

Reproducibility of color Doppler flow quantification of aortic regurgitation

The preferred method for quantification of aortic regurgitation severity with color Doppler echocardiography is the assessment of the ratio of jet diameter to left ventricular outflow tract diameter and jet area to left ventricular outflow tract area. However, the reproducibility of these measurements is not known and may limit its clinical application. This study was performed to identify sources of variability and reproducibility of the echocardiographic data. We examined 62 color Doppler echocardiographic examinations of patients showing isolated aortic regurgitation after human tissue valve implantation. The mean differences with standard deviations between paired measurements were calculated. The interobserver, intraobserver, and interframe variability showed a close agreement for the jet diameter and left ventricular outflow tract diameter measurements. The agreement for jet area and left ventricular outflow tract area measurements showed a small bias, but a large variance. The reproducibility of jet-left ventricular outflow tract diameter is better than the jet-left ventricular outflow tract area measurement and is more accurate to assess the severity of aortic regurgitation from color Doppler images.     

Status epilepticus in children and adults

Status epilepticus (SE) in children and adults is one of the most common neurology problems confronting the intensivist. Recognition of SE is usually straightforward, but may be complicated by the effects of other diseases or therapies. Emergent treatment is necessary to prevent further brain damage. This article reviews protocols for standard treatments of SE patients and includes recommendations for the management of refractory SE.