A method for the enrichment of auxotrophic mutants of Serratia marcescens with the antibiotic azthreonam

A new method for the enrichment of cultures of Serratia marcescens for auxotrophic mutants has been developed. The method is based on the formation of filaments by growing cells in minimal medium M70 containing azthreonam. Auxotrophic mutants unable to grow in M70 do not form filaments. Mutants are collected from the culture by filtration.     

Evolutionary history of the COII/tRNALys intergenic 9 base pair deletion in human mitochondrial DNAs from the Pacific

Length changes in human mitochondrial DNA (mtDNA) are potentially useful markers for inferring the evolutionary history of populations. One such length change is a nine base pair (9-bp) deletion that is located in the intergenic region between the COII gene and the Lysine tRNA gene (COII/tRNALys intergenic region). This deletion has been used as a genetic marker to trace descent from peoples of East Asian origin. A geographic cline of the deletion frequency across modern Pacific Islander populations suggests that the deletion may be useful for tracing prehistoric Polynesian origins and affinities. Mitochondrial DNA sequence variation within two variable segments of the control region (CR) permits a number of inferences regarding the evolutionary history of the 9-bp deletion that cannot be determined from frequency data alone. We obtained CR sequences from 74 mtDNAs with the 9-bp deletion from Indonesia, coastal Papua New Guinea (PNG), and American Samoa. Phylogenetic and pairwise distribution analysis of these CR sequences pooled with previously published CR sequences reveals that the deletion arose independently in Africa and Asia and suggests possible multiple origins of the deletion in Asia. A clinal increase of the frequency of the 9-bp deletion across the three Pacific populations is associated with a decrease in CR sequence diversity, consistent with founder events. Furthermore, analysis of pairwise difference distributions indicates an expansion time of proto-Polynesians that began 5,500 yr ago from Southeast Asia. These results are consistent with the express train model of Polynesian origins.      

Aspergillus terreus and its toxic metabolites as a food contaminant in some Egyptian Bakery products and grains

A. terreus isolates isolated from some bakery products, corn and rice were found to be able to produce territrems. 90% of theA. terreus isolated from bakery products were able to produce territrem A, with a mean of 0.09 ppm, while 80% ofA. terreus isolates produce territrem B with a mean of 0.24 ppm. On the other hand 31.8% of the isolates ofA. terreus from corn were able to produce territrem A with a mean of 0.44 ppm. ConcerningA. terreus isolates from rice, 66.7% were found to produce territrem A, with a mean of 5.28 ppm, and 77.8% of the isolates produced territrem B with a mean of 1.79 ppm.     

A theoretical experimental method to determine the locus of desensitization

Consider a ligand-gated channel with n agonist binding sites which can undergo desensitization. We present a theoretical experimental procedure for pinpointing the principal receptor state from which there is a transition to the desensitized state. The method is based on the observation that the dependence of the slope of the time constant of desensitization vs agonist concentration, at low concentrations, represents the state from which desensitization occurs. In those receptors where desensitization occurs from the open state (or the one immediately preceding it), the method also enables us to determine the number of binding sites.     

A current 10-year retrospective survey of 199 surgically treated orbital floor fractures in a nonurban tertiary care center.

This study characterizes the surgically treated patient population suffering from orbital floor fractures by use of current data from a large series consisting of 199 cases taken from a nonurban setting. Data were gathered through a retrospective chart review of patients surgically treated for orbital floor fractures at the University of Michigan Health System, collected over a 10-year period. Data regarding patient demographics, signs and symptoms of presentation, cause of injury, nature of injury, associated facial fractures, ocular injury, and associated nonfacial skeleton trauma were collected. In total, there were 199 cases of orbital floor fractures among 189 patients. Male patients outnumbered female patients by a 2:1 ratio and were found to engage in a wider range of behaviors that resulted in orbital floor fractures. Motor vehicle accidents were the leading cause of orbital floor fractures, followed by physical assault and sports-related mechanisms. The ratio of impure to pure orbital floor fracture was 3:1. The most common signs and symptoms associated with orbital floor fractures, in descending order, were periorbital ecchymosis, diplopia, subconjunctival hemorrhage, and enophthalmos. Associated facial fractures were found in 77.2 percent of patients, the most prevalent of which was the zygoma-malar fracture. Serious ocular injury occurred in 19.6 percent of patients, with globe rupture being the most prevalent, accounting for 40.5 percent of those injuries. There was a 38.1 percent occurrence of associated nonfacial skeletal trauma; skull fracture and intracranial injury were the most prevalent manifestations. Associated cervical-spine fractures were rare (0.5 percent). Statistical examination, using odds ratios and chi-squared analysis, demonstrated significant associations that have not previously been reported. Impure and pure orbital floor fractures revealed striking differences in several demographic aspects, including mechanism of injury, signs and symptoms of presentation, spectrum of associated trauma, and the severity of concomitant trauma.     

Size, shape and structural versatility of the skull of the subterranean rodent Ctenomys (Rodentia, Caviomorpha): functional and morphological analysis

Morphological analysis of the skull of the subterranean rodent Ctenomys , a highly speciose genus which uses both claws and teeth when digging, shows that for a broad range of species size, scaling was associated with both variation and maintenance of shape. Our results show that the angle of incisor procumbency (AIP), a character largely viewed as an adaptation to digging with teeth, is highly variable. We found a non-significant relationship between AIP and basicranial axis (basioccipital + basisphenoid) length, a measure of overall skull size. Accordingly, both small and large Ctenomys species possess either high or low AIP. A significant relationship between AIP and diastema length, given the rostral allometry seen in Ctenomys , suggests that hypermorphosis to a certain extent influences AIP. However, the roots of the incisor are lateral to those of the cheek teeth and their position may thus shift freely. This observation supports the notion that skull structural design, and to a certain extent rostral allometry, underlies variation in AIP. On the other hand, the positive allometry of incisor width and thickness indicates that, in larger species, proportionately powerful incisors are able to resist greater bending forces. We found that the out-lever arm of the jaw adductor muscles scales with positive allometry against basicranial axis length. However, we found an isometric relationship between in- and out-lever arms. In this case, conservation of skull proportions, regardless of variation in size, is a feature possibly related to the maintenance of an effective tooth digging capability. Functional and ecological data are discussed when assessing the implications of size and shape variation in the skull of Ctenomys .  © 2003 The Linnean Society of London. Biological Journal of the Linnean Society , 2003, 78 , 85−96.     

SIMPROT: Using an empirically determined indel distribution in simulations of protein evolution

Background  

General protein evolution models help determine the baseline expectations for the evolution of sequences, and they have been extensively useful in sequence analysis and for the computer simulation of artificial sequence data sets.     

Early antibiotic administration but not antibody therapy directed against IL-6 improves survival in septic mice predicted to die on basis of high IL-6 levels

Elevated interleukin (IL)-6 levels correlate with increased mortality following sepsis. IL-6 levels >14,000 pg/ml drawn 6 h after cecal ligation and puncture (CLP) are associated with 100% mortality in ND4 mice, even if antibiotic therapy is initiated 12 h after septic insult. Our first aim was to see whether earlier institution of antibiotic therapy could improve overall survival in septic mice and rescue the subset of animals predicted to die on the basis of high IL-6 levels. Mice (n = 184) were subjected to CLP, had IL-6 levels drawn 6 h later, and then were randomized to receive imipenem, a broad spectrum antimicrobial agent, beginning 6 or 12 h postoperatively. Overall 1-wk survival improved from 25.5 to 35.9% with earlier administration of antibiotics (P < 0.05). In mice with IL-6 levels >14,000 pg/ml, 25% survived if imipenem was started at 6 h, whereas none survived if antibiotics were started later (P < 0.05). On the basis of these results, we examined whether targeted antibody therapy could improve survival in mice with elevated IL-6 levels. A different cohort of mice (n = 54) had blood drawn 6 h after CLP, and then they were randomized to receive either monoclonal anti-IL-6 IgG or irrelevant rat IgG. Anti-IL-6 antibody failed to improve either overall survival or outcome in mice with IL-6 levels >14,000 pg/ml. These results demonstrate that earlier systemic therapy can improve outcome in a subset of mice predicted to die in sepsis, but we are unable to demonstrate any benefit in similar animals using targeted therapy directed at IL-6.