Occurrence of hydroxypyruvate-L-glutamate transaminase in Escherichia coli and its separation from hydroxypyruvate-phosphate-L-glutamate transaminase

Blatt, L. (University of Wisconsin, Madison), F. E. Dorer, and H. J. Sallach. Occurrence of hydroxypyruvate-l-glutamate transaminase in Escherichia coli and its separation from hydroxypyruvate-phosphate-l-glutamate transaminase. J. Bacteriol. 92:668-675. 1966.-The formation of l-serine from hydroxypyruvate by a transamination reaction with l-glutamate has been demonstrated in extracts of Escherichia coli. The level of activity with hydroxypyruvate is approximately one-tenth that observed with hydroxypyruvate-phosphate in cell-free extracts. The transamination of hydroxypyruvate, but not hydroxypyruvate-phosphate, is inhibited by inorganic phosphate. No marked differences in the levels of activity with hydroxypyruvate were observed in extracts from bacteria grown under different conditions. Heat treatment of enzyme preparations at 65 C rapidly destroys the activity with hydroxypyruvate-phosphate, but not that with hydroxypyruvate. Fractionation of extracts with lithium sulfate and alumina Cgamma resulted not only in a 10-fold purification, but also in a complete separation of the two activities, thereby establishing that two different enzymes are involved in the transamination of hydroxypyruvate and hydroxypyruvate-phosphate. Hydroxypyruvate transaminase is present in two mutants that require serine for growth. The inability of hydroxypyruvate to replace the growth requirement for serine, even to a limited extent, was shown to be due to the inability of the bacteria to accumulate this compound actively.     

Non-vertebrate hosts in the analysis of host-pathogen interactions

Mutations in bacterial pathogens have been isolated using many strategies. In contrast, the hosts they attack are significantly less tractable. To overcome this problem, a number of model host systems have been developed for isolation and investigation of mutations that modulate pathogen growth. These novel host models are either unicellular organisms, intact invertebrates or cells derived from invertebrates.     

Characterization and localization of myosin in the brush border of intestinal epithelial cells

The brush border of intestinal epithelial cells consists of a tightly packed array of microvilli, each of which contains a core of actin filaments. It has been postulated that microvillar movements are mediated by myosin interactions in the terminal web with the basal ends of these actin cores (Mooseker, M.S. 1976. J. Cell. Biol. 71:417-433). We report here that two predictions of this model are correct: (a) The brush border contains myosin, and (b) myosin is located in the terminal web. Myosin is isolated in 70 percent purity by solubilization of Triton-treated brush borders in 0.6 M KI, and separation of the components by gel filtration. Most of the remaining contaminants can be removed by precipitation of the myosin at low ionic strength. This yield is approximately 1 mg of myosin/30 mg of solubilized brush border protein. The molecule consists of three subunits with molecular weights of 200,000, 19,000, and 17,000 daltons in a 1:1:1 M ratio. At low ionic strength, the myosin forms small, bipolar filaments with dimensions of 300 X 11nm, that are similar to filaments seen previously in the terminal web of isolated brush borders. Like that of other vertebrate, nonmuscle myosins, the ATPase activity of isolated brush border myosin in 0.6 M KCI is highest with EDTA (1 μmol P(i)/mg-min; 37 degrees C), intermediate with Ca++ (0.4 μmol P(i)/mg-min), and low with Mg++ (0.01 μmol P(i)/mg-min). Actin does not stimulate the Mg-ATPase activity of the isolated enzyme. Antibodies against the rod fragment of human platelet myosin cross-react by immunodiffusion with brush border myosin. Staining of isolated mouse or chicken brush borders with rhodamine-antimyosin demonstrates that myosin is localized exclusively in the terminal web.     

Single visit versus multiple visit root canal

Single visit endodontics offers many advantages over multi visit treatment. Therefore, it is of interest to assess the preference of single visit over multiple visit root canals. We used 86,000 patient records and selected 9017 records matching the inclusion criteria for the analysis using statistical tools (Chi square test at p value <0.05). Data shows that people between 26 to 45 years are often affected with dental caries. Available data is biased towards multi visits rather than single visit regardless number of canals.     

Characterization of Helicobacter pylori factors that control transformation frequency and integration length during inter-strain DNA recombination

Helicobacter pylori is a genetically diverse bacterial species, owing in part to its natural competence for DNA uptake that facilitates recombination between strains. Inter-strain DNA recombination occurs during human infection and the H. pylori genome is in linkage equilibrium worldwide. Despite this high propensity for DNA exchange, little is known about the factors that limit the extent of recombination during natural transformation. Here, we identify restriction-modification (R-M) systems as a barrier to transformation with homeologous DNA and find that R-M systems and several components of the recombination machinery control integration length. Type II R-M systems, the nuclease nucT and resolvase ruvC reduced integration length whereas the helicase recG increased it. In addition, we characterized a new factor that promotes natural transformation in H. pylori, dprB. Although free recombination has been widely observed in H. pylori, our study suggests that this bacterium uses multiple systems to limit inter-strain recombination.     

Influence of glutamate and GABA transport on brain excitatory/inhibitory balance

An optimally functional brain requires both excitatory and inhibitory inputs that are regulated and balanced. A perturbation in the excitatory/inhibitory balance—as is the case in some neurological disorders/diseases (e.g. traumatic brain injury Alzheimer’s disease, stroke, epilepsy and substance abuse) and disorders of development (e.g. schizophrenia, Rhett syndrome and autism spectrum disorder)—leads to dysfunctional signaling, which can result in impaired cognitive and motor function, if not frank neuronal injury. At the cellular level, transmission of glutamate and GABA, the principle excitatory and inhibitory neurotransmitters in the central nervous system control excitatory/inhibitory balance. Herein, we review the synthesis, release, and signaling of GABA and glutamate followed by a focused discussion on the importance of their transport systems to the maintenance of excitatory/inhibitory balance.     

Incidence and Characteristics of Total Stroke in the United States

Background and Purpose  

Stroke, increasingly referred to as a "brain attack", is one of the leading causes of death and the leading cause of adult disability in the United States. It has recently been estimated that there were three quarters of a million strokes in the United States in 1995. The aim of this study was to replicate the 1995 estimate and examine if there was an increase from 1995 to 1996 by using a large administrative claims database representative of all 1996 US inpatient discharges.