66 research outputs found
Occurrence of leu(+) revertants under starvation cultures in Escherichia coli is growth-dependent
BACKGROUND: Many investigations have reported that advantageous mutations occurred more frequently under selective conditions than those under non-selective conditions. This phenomenon is referred to as adaptive mutation. Their characteristics are that adaptive mutations are directed and growth-independent. The idea of directed adaptive mutation had been objected by some reports, however, the idea of growth-independent adaptive mutation has been held till today. RESULTS: In this paper, we have observed that under leucine starvation conditions, leu(+) revertants accumulated as a function of time; leu(-) to leu(+) reverse mutation rates and frequencies were higher than those under non starvation conditions; and no divided cells could be monitored by the penicillin method. These results were similar to the time-dependent manner of adaptive mutation from previous reports. However, leucine concentration determinate experiments revealed that certain traces of leucine, which leaked from the E. coli cells, was almost always present in the culture. More numbers of leu(+) revertants appeared when the similar cultures were dropped in small areas on the selective plates than when spread on the whole selective plates. These results have shown that mutations under leucine starving conditions are growth-dependent. Fluctuation analysis of leu(+) revertants indicated that leu(-)leu(+) mutation occurred spontaneously and randomly. In addition, the spectra of leuB gene in the revertants proved that mutations under selective conditions were not specific or directed. CONCLUSIONS: The above investigations led to the conclusion (1) that the occurrence of leu(+) mutations under starvation conditions was growth-dependent. The occurence mutations was also similar to that under non-starvation conditions (2). Under starvation conditions the mutation rates were higher, and was not constant during the long process
Global gene expression analysis reveals reduced abundance of putative microRNA targets in human prostate tumours
<p>Abstract</p> <p>Background</p> <p>Recently, microRNAs (miRNAs) have taken centre stage in the field of human molecular oncology. Several studies have shown that miRNA profiling analyses offer new possibilities in cancer classification, diagnosis and prognosis. However, the function of miRNAs that are dysregulated in tumours remains largely a mystery. Global analysis of miRNA-target gene expression has helped illuminate the role of miRNAs in developmental gene expression programs, but such an approach has not been reported in cancer transcriptomics.</p> <p>Results</p> <p>In this study, we globally analysed the expression patterns of miRNA target genes in prostate cancer by using several public microarray datasets. Intriguingly, we found that, in contrast to global mRNA transcript levels, putative miRNA targets showed a reduced abundance in prostate tumours relative to benign prostate tissue. Additionally, the down-regulation of these miRNA targets positively correlated with the number of types of miRNA target-sites in the 3' untranslated regions of these targets. Further investigation revealed that the globally low expression was mainly driven by the targets of 36 specific miRNAs that were reported to be up-regulated in prostate cancer by a miRNA expression profiling study. We also found that the transcript levels of miRNA targets were lower in androgen-independent prostate cancer than in androgen-dependent prostate cancer. Moreover, when the global analysis was extended to four other cancers, significant differences in transcript levels between miRNA targets and total mRNA backgrounds were found.</p> <p>Conclusion</p> <p>Global gene expression analysis, along with further investigation, suggests that miRNA targets have a significantly reduced transcript abundance in prostate cancer, when compared with the combined pool of all mRNAs. The abnormal expression pattern of miRNA targets in human cancer could be a common feature of the human cancer transcriptome. Our study may help to shed new light on the functional roles of miRNAs in cancer transcriptomics.</p
5-Benzyl-2-phenyl-6,8-dihydro-5H-1,2,4-triazolo[3,4-c][1,4]oxazin-2-ium hexafluoridophosphate
The title compound, C18H18N3O+·PF6
−, is a chiral bicyclic 1,2,4-triazolium salt which contains four rings, viz. a triazolium, a morpholine and two phenyl rings. Analysis of bond lengths shows that the N—CH—N group in the triazolium ring conforms to a typical three-center/four-electron bond (also known as the Pimentel–Rundle three-center model). The structure is completed by a disordered PF6
− counter-ion [occupancies of F atoms 0.678 (8):0.322 (8)], which interacts with the main molecule through weak intermolecular P—F⋯π interactions
Sequencing of Culex quinquefasciatus establishes a platform for mosquito comparative genomics
Culex quinquefasciatus (the southern house mosquito) is an important mosquito vector of viruses such as West Nile virus and St. Louis encephalitis virus, as well as of nematodes that cause lymphatic filariasis. C. quinquefasciatus is one species within the Culex pipiens species complex and can be found throughout tropical and temperate climates of the world. The ability of C. quinquefasciatus to take blood meals from birds, livestock, and humans contributes to its ability to vector pathogens between species. Here, we describe the genomic sequence of C. quinquefasciatus: Its repertoire of 18,883 protein-coding genes is 22% larger than that of Aedes aegypti and 52% larger than that of Anopheles gambiae with multiple gene-family expansions, including olfactory and gustatory receptors, salivary gland genes, and genes associated with xenobiotic detoxification
Trajectory Tracking Control for Underactuated USV with Prescribed Performance and Input Quantization
This paper is devoted to the problem of prescribed performance trajectory tracking control for symmetrical underactuated unmanned surface vessels (USVs) in the presence of model uncertainties and input quantization. By combining backstepping filter mechanisms and adaptive algorithms, two robust control architectures are investigated for surge motion and yaw motion. To guarantee the prespecified performance requirements for position tracking control, the constrained error dynamics are transformed to unconstrained ones by virtue of a tangent-type nonlinear mapping function. On the other hand, the inaccurate model can be identified through radial basis neural networks (RBFNNs), where the minimum learning parameter (MLP) algorithm is employed with a low computational complexity. Furthermore, quantization errors can be effectively reduced even when the parameters of the quantizer remain unavailable to designers. Finally, the effectiveness of the proposed controllers is verified via theoretical analyses and numerical simulations
Trajectory Tracking Control for Underactuated USV with Prescribed Performance and Input Quantization
This paper is devoted to the problem of prescribed performance trajectory tracking control for symmetrical underactuated unmanned surface vessels (USVs) in the presence of model uncertainties and input quantization. By combining backstepping filter mechanisms and adaptive algorithms, two robust control architectures are investigated for surge motion and yaw motion. To guarantee the prespecified performance requirements for position tracking control, the constrained error dynamics are transformed to unconstrained ones by virtue of a tangent-type nonlinear mapping function. On the other hand, the inaccurate model can be identified through radial basis neural networks (RBFNNs), where the minimum learning parameter (MLP) algorithm is employed with a low computational complexity. Furthermore, quantization errors can be effectively reduced even when the parameters of the quantizer remain unavailable to designers. Finally, the effectiveness of the proposed controllers is verified via theoretical analyses and numerical simulations
Management of screwdriver-induced penetrating brain injury: a case report
Abstract
Background
Penetrating brain injury (PBI) can be caused by several objects ranging from knives to chopsticks. However, an assault with long and electric screwdriver is a peculiar accident and is relatively rare. Because of its rarity, the treatments of such injury are complex and nonstandardized.
Case presentation
We presented a case of a 54-year-old female who was stabbed with a screwdriver in her head and accompanied by loss of consciousness for 1\ua0h. Computer tomography (CT) demonstrated that the screwdriver passed through the right zygomatic bone to posterior cranial fossa. Early foreign body removal and hematoma evacuation were performed and the patient had a good postoperative recovery.
Conclusions
In this study, we discussed the clinical presentation and successful management of such a unique injury caused by a screwdriver. Our goal is to demonstrate certain general management principles which can improve patient outcomes
Two occurrences of delayed epidural hematoma in different areas following decompressive craniectomy for acute subdural hematoma in a single patient: a case report
Abstract Background Delayed epidural hematoma (DEH) following evacuation of traumatic acute subdural hematoma (ASDH) or acute epidural hematoma (EDH) is a rare but devastating complication, especially when it occurs sequentially in a single patient. Case presentation A 19-year-old man who developed contralateral DEH following craniotomy for evacuation of a traumatic right-side ASDH and then developed a left-side DEH of the posterior cranial fossa after craniotomy for evacuation of the contralateral DEH. He was immediately returned to the operating room for additional surgeries and his neurological outcome was satisfactory. Conclusions Although DEH occurring after evacuation of ASDH or acute EDH is a rare event, timely recognition is critical to prognosis
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