Mi Casa es Su Casa: how an intracellular symbiont manipulates host biology

Wolbachia pipientis, the most common intracellular infection on the planet, infects 40% of insects as well as nematodes, isopods and arachnids. Wolbachia are obligately intracellular and challenging to study; there are no genetic tools for manipulating Wolbachia nor can they be cultured outside of host cells. Despite these roadblocks, the research community has defined a set of Wolbachia loci involved in host interaction: Wolbachia effectors. Through the use of Drosophila genetics, surrogate systems and biochemistry, the field has begun to define the toolkit Wolbachia use for host manipulation. Below we review recent findings identifying these Wolbachia effectors and point to potential, as yet uncharacterized, links between known phenotypes induced by Wolbachia infection and predicted effectors.     

Alveolar expansion imaged by optical sectioning microscopy.

During lung expansion, the pattern of alveolar perimeter distension is likely to be an important determinant of lung functions as, for example, surfactant secretion. However, the segmental characteristics of alveolar perimeter distension remain unknown. Here, we applied real-time confocal microscopy in the isolated, perfused rat lung to determine the micromechanics of alveolar perimeter distension. To image the alveolar perimeter, we loaded alveolar epithelial cells with a fluorescent dye that we microinjected into the alveolus. Then we viewed single alveoli in a 2-microm-thick optical section at a focal plane 20 mum deep to the pleural surface at baseline. In each alveolus, we identified five to eight segments of the perimeter. For each segment, we determined length (L(seg)) by means of image analysis. At baseline alveolar pressure (P(alv)) of 5 cmH(2)O, L(seg) averaged 46 microm. We hyperinflated the lung to P(alv) of 20 cmH(2)O and identified the same optical section as referenced against morphological landmarks. Hyperinflation increased mean L(seg) by 14%. However, segment distension was heterogeneous, even within the single alveolus. Furthermore, distension was greater in alveolar type 1 than type 2 epithelial cells. These findings indicate that alveoli expand nonuniformly, suggesting that segments that distend the most might be preferred alveolar locations for injury in conditions associated with lung overdistension.     

Traveling waves in the prefrontal cortex during working memory

Neural oscillations are evident across cortex but their spatial structure is not well- explored. Are oscillations stationary or do they form “traveling waves”, i.e., spatially organized patterns whose peaks and troughs move sequentially across cortex? Here, we show that oscillations in the prefrontal cortex (PFC) organized as traveling waves in the theta (4-8Hz), alpha (8-12Hz) and beta (12-30Hz) bands. Some traveling waves were planar but most rotated. The waves were modulated during performance of a working memory task. During baseline conditions, waves flowed bidirectionally along a specific axis of orientation. Waves in different frequency bands could travel in different directions. During task performance, there was an increase in waves in one direction over the other, especially in the beta band.     

Alteration of energy-linked functions in rat hepatic mitochondria following aflatoxin B1 administration

Respiratory activity in hepatic mitochondria have been examined following administration of the carcinogen aflatoxin, (AFB₁) to rats. Measurement in isolated mitochondria of respiration rates in presence of ADP (state 3) and after its depletion (state 4) revealed that these rates were not significantly altered in livers of rats obtained 4–8 hours after single injection of AFB₁ (7 mg/kg of body weight). After 12–24 hours, however, a generalized inhibition in state 3 respiration rate and ADP phosphorylation rate had been evident with several FAD- and NAD-linked oxidizing substrates. But the ADP:0 ratio did not show any alteration. State 4 respiration rates, on the other hand, were increased remarkably (38–94% depending on substrate used), thereby recording in each case a decrease in respiratory control ratio (state 3:state 4 ratio), indicating probable damage to mitochondrial membrane as a result of AFB₁ ingestion. This was also evident from greater basal ATPase and Mg²⁺-ATPase activities and low total ATPase activity. After 48–72 hours of AFB₁ treatment, the respiratory rates as well as the ATPase activities returned to normal levels, suggesting probable recovery of mitochondrial functions from the toxic effects of AFB₁. © 1997 John Wiley & Sons, Inc.     

Benchmarking of a Bayesian single cell RNAseq differential gene expression test for dose–response study designs

The application of single-cell RNA sequencing (scRNAseq) for the evaluation of chemicals, drugs, and food contaminants presents the opportunity to consider cellular heterogeneity in pharmacological and toxicological responses. Current differential gene expression analysis (DGEA) methods focus primarily on two group comparisons, not multi-group dose–response study designs used in safety assessments. To benchmark DGEA methods for dose–response scRNAseq experiments, we proposed a multiplicity corrected Bayesian testing approach and compare it against 8 other methods including two frequentist fit-for-purpose tests using simulated and experimental data. Our Bayesian test method outperformed all other tests for a broad range of accuracy metrics including control of false positive error rates. Most notable, the fit-for-purpose and standard multiple group DGEA methods were superior to the two group scRNAseq methods for dose–response study designs. Collectively, our benchmarking of DGEA methods demonstrates the importance in considering study design when determining the most appropriate test methods.     

High frequency in vitro propagation of Phyllanthus amarus Schum. & Thom. by shoot tip culture

With the aim of micropropagation of Phyllanthus amarus, an important medicinal herb, shoot tips were cultured in Murashige and Skoog's medium supplemented with kinetin/ BAP singly or in combination with IAA. Growth regulators at lower range (0.1-1.0 mg L(-1)) stimulated direct regeneration of shoots. Kinetin was superior to BAP and kinetin-IAA combination was more suitable than kinetin alone. About 15 shoots were yielded per explant after 30 days of culture in the medium containing kinetin and IAA both at 0.1mg L(-1). The cluster of proliferated shoots elongated and rooted simultaneously under the same treatment following another subculture, thus shortening the total time schedule of micropropagation. Shoot tips of regenerated shoots were continuously used to regenerate new shoots with periodic transfer to fresh medium resulting in a steady supply of normal, healthy plants without any deviation in the production rate during a continuous one year culture. Micropropagated plants were successfully established in soil with high survivality (80%).