Induction of nitrate transport in maize roots, and kinetics of influx, measured with nitrogen-13

Unlike phosphate or potassium transport, uptake of nitrate by roots is induced, in part, by contact with the substrate ion. Plasmalemma influx of ¹³N-labeled nitrate in maize roots was studied in relation to induction of the uptake system, and the influence of short-term N starvation. Maize (Zea mays) roots not previously exposed to nitrate had a constitutive transport system (state 1), but influx increased 250% during six hours of contact with 100 micromolar nitrate, by which time the transport mechanism appeared to be fully synthesized (state 2). A three-day period of N starvation prior to induction and measurement of nitrate influx resulted in a greater capacity to transport nitrate than in unstarved controls, but this was fully expressed only if roots were kept in contact with nitrate for the six hours needed for full induction (state 2E). A kinetic analysis indicated a 160% increase in maximum influx in N-starved, induced roots with a small decrease in K_m. The inducible component to nitrate influx was induced only by contact with nitrate. Full expression of the nitrate inducible transport system was dependent upon mRNA synthesis. An inhibitor of cytoplasmic protein synthesis (cycloheximide) eliminated the formation of the transport system while inhibition by chloramphenicol of mitochondrial- or plastid-coded protein synthesis had no effect. Poisoning of membrane-bound proteins effectively disabled both the constitutive and induced transport systems.     

Comparison of the Performance of the TPTest,Tubex, Typhidot and Widal Immunodiagnostic Assays and Blood Cultures in Detecting Patients with Typhoid Fever in Bangladesh,Including Using a Bayesian Latent Class Modeling Approach

Background

There is an urgent need for an improved diagnostic assay for typhoid fever. In this current study, we compared the recently developed TPTest (Typhoid and Paratyphoid Test) with the Widal test, blood culture, and two commonly used commercially available kits, Tubex and Typhidot.

Methodology

For analysis, we categorized 92 Bangladeshi patients with suspected enteric fever into four groups: S. Typhi bacteremic patients (n = 28); patients with a fourfold change in Widal test from day 0 to convalescent period (n = 7); patients with Widal titer ≥1:320 (n = 13) at either acute or convalescent stage of disease; and patients suspected with enteric fever, but with a negative blood culture and Widal titer (n = 44). We also tested healthy endemic zone controls (n = 20) and Bangladeshi patients with other febrile illnesses (n = 15). Sample size was based on convenience to facilitate preliminary analysis.

Principle findings

Of 28 S. Typhi bacteremic patients, 28 (100%), 21 (75%) and 18 (64%) patients were positive by TPTest, Tubex and Typhidot, respectively. In healthy endemic zone controls, the TPTest method was negative in all, whereas Tubex and Typhidot were positive in 3 (15%) and 5 (25%), respectively. We then estimated sensitivity and specificity of all diagnostic tests using Bayesian latent class modeling. The sensitivity of TPTest, Tubex and Typhidot were estimated at 96.0% (95% CI: 87.1%-99.8%), 60.2% (95% CI: 49.3%-71.2%), and 59.6% (95% CI: 50.1%-69.3%), respectively. Specificity was estimated at 96.6% (90.7%-99.2%) for TPTest, 89.9% (79.6%-96.8%) for Tubex, and 80.0% (67.7%-89.7%) for Typhidot.

Conclusion

These results suggest that the TPTest is highly sensitive and specific in diagnosing individuals with typhoid fever in a typhoid endemic setting, outperforming currently available and commonly used alternatives.     

Sequential algorithm for life threatening cardiac pathologies detection based on mean signal strength and EMD functions

Background  

Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the most serious cardiac arrhythmias that require quick and accurate detection to save lives. Automated external defibrillators (AEDs) have been developed to recognize these severe cardiac arrhythmias using complex algorithms inside it and determine if an electric shock should in fact be delivered to reset the cardiac rhythm and restore spontaneous circulation. Improving AED safety and efficacy by devising new algorithms which can more accurately distinguish shockable from non-shockable rhythms is a requirement of the present-day because of their uses in public places.     

Pharmacological evidence for the use of Cissus assamica as a medicinal plant in the management of pain and pyrexia

The existing therapeutic agents for the management of pain and pyrexia are not very efficient and accompanied by numerous side effects. Thus, new effective agents are the most needed. The present study investigates bioactivities and phytochemical screening of different parts of Cissus assamica (Vitaceae), a Bangladeshi tribal medicinal plant. Three plant parts stems, leaves and roots were collected, washed, dried, powdered and then prepared for cold extraction. The methanolic stems and leaves extracts were fractioned with four and two solvents respectively. Different plant extracts were then investigated for in vivo antinociceptive activity and only methanolic leaves extract was investigated for in vivo antipyretic activity. In Swiss-albino mice, 200 and 400 mg/kg body weight doses were used for all extracts. In the peripheral antinociceptive activity, the methanolic stem extract and its dichloromethane, chloroform, pet ether fractions and methanolic roots extract at their both doses showed significant antinociceptive responses when compared to standard diclofenac sodium (60.49% inhibition). In the central antinociceptive activity, the response was found significant for methanolic stem and methanolic roots extract in their both doses compared to standard morphine. In antipyretic activity, methanolic leaves extract significantly reduced pyrexia level at 400 and 200 mg/kg body weight doses after two, three and 4 h of administration when compared to standard. So our findings indicate that this plant possesses noteworthy pharmacological activities which may be a basis for further researches to establish a possible mode of action of its different parts.     

Comparison of ring artifact removal methods using flat panel detector based CT images

Background

Ring artifacts are the concentric rings superimposed on the tomographic images often caused by the defective and insufficient calibrated detector elements as well as by the damaged scintillator crystals of the flat panel detector. It may be also generated by objects attenuating X-rays very differently in different projection direction. Ring artifact reduction techniques so far reported in the literature can be broadly classified into two groups. One category of the approaches is based on the sinogram processing also known as the pre-processing techniques and the other category of techniques perform processing on the 2-D reconstructed images, recognized as the post-processing techniques in the literature. The strength and weakness of these categories of approaches are yet to be explored from a common platform.

Method

In this paper, a comparative study of the two categories of ring artifact reduction techniques basically designed for the multi-slice CT instruments is presented from a common platform. For comparison, two representative algorithms from each of the two categories are selected from the published literature. A very recently reported state-of-the-art sinogram domain ring artifact correction method that classifies the ring artifacts according to their strength and then corrects the artifacts using class adaptive correction schemes is also included in this comparative study. The first sinogram domain correction method uses a wavelet based technique to detect the corrupted pixels and then using a simple linear interpolation technique estimates the responses of the bad pixels. The second sinogram based correction method performs all the filtering operations in the transform domain, i.e., in the wavelet and Fourier domain. On the other hand, the two post-processing based correction techniques actually operate on the polar transform domain of the reconstructed CT images. The first method extracts the ring artifact template vector using a homogeneity test and then corrects the CT images by subtracting the artifact template vector from the uncorrected images. The second post-processing based correction technique performs median and mean filtering on the reconstructed images to produce the corrected images.

Results

The performances of the comparing algorithms have been tested by using both quantitative and perceptual measures. For quantitative analysis, two different numerical performance indices are chosen. On the other hand, different types of artifact patterns, e.g., single/band ring, artifacts from defective and mis-calibrated detector elements, rings in highly structural object and also in hard object, rings from different flat-panel detectors are analyzed to perceptually investigate the strength and weakness of the five methods. An investigation has been also carried out to compare the efficacy of these algorithms in correcting the volume images from a cone beam CT with the parameters determined from one particular slice. Finally, the capability of each correction technique in retaining the image information (e.g., small object at the iso-center) accurately in the corrected CT image has been also tested.

Conclusions

The results show that the performances of the algorithms are limited and none is fully suitable for correcting different types of ring artifacts without introducing processing distortion to the image structure. To achieve the diagnostic quality of the corrected slices a combination of the two approaches (sinogram- and post-processing) can be used. Also the comparing methods are not suitable for correcting the volume images from a cone beam flat-panel detector based CT.     

Increased lignan biosynthesis in the suspension cultures of Linum album by fungal extracts

Linum album accumulates anti-tumor podophyllotoxin (PTOX) and its related lignans, which were originally isolated from an endangered species Podophyllum. In the present study, we examined the effects of five fungal extracts on the production of lignans in L. album cell cultures. Fusarium graminearum extract induced the highest increase of PTOX [143 μg g⁻¹ dry weight (DW) of the L. album cell culture], while Rhizopus stolonifer extract enhanced the accumulation of lariciresinol up to 364 μg g⁻¹ DW, instead of PTOX. Typical elicitors, such as chitin, chitosan, or methyl jasmonate (MeJA), were shown to be less effective in lignan production in L. album cell cultures. These results verified the advantages of fungal extracts to increase lignan production in L. album cell culture, and suggested potential on-demand metabolic engineering of lignan biosynthesis using differential fungal extracts.     

Targeted cleavage of RNA molecules by human RNase P using minimized external guide sequences

The endoribonuclease RNase P processes tRNA-like structures that are assembled out of two separate strands. In these bimolecular constructs, one of the strands is cleaved by the enzyme, and the other one is called the external guide sequence (EGS). A number of EGS with different mutations and deletions were tested for the ability to induce cleavage with human RNase P. Different domains of the original tRNAtyr-like structure were deleted or modified. The anticodon stem and loop and the variable loop could be deleted without a detrimental effect on recognition by RNase P. Modifications in the lengths of T stem and aminoacyl acceptor stem led to a decrease in the relative amount of cleavage, whereas modifications of the D stem were more permissible. Single nucleotide deletions in the T loop reduced cleavage to different extents, depending on the position. Values for the Kd of complex formation of bimolecular constructs with annealing arms of varying lengths ranged from 0.2 nM to 28 nM. A cleavage rate of 1 min(-1) was measured for both the bimolecular target-EGS complex and tRNA precursor.