Phenotypic variation in food utilization in an outbreak insect herbivore

The effects of nutrition may have subtantial impact on insect evolution by shaping different components of phenotypes. The key to undestanding this evolutionary process is to know how nutritional condition affects additive and nonadditive components of the phenotype. However, this is poorly understood in outbreaking insects. We investigated the additive and nonadditive variation present in food utilization traits in spruce budworm individuals subjected to chronic nutritional stress. A total of 160 full‐sib families of spruce budworm (Choristoneura fumiferana Clem.) were raised under laboratory conditions, feeding on 2 diets (high and low energy) during 3 generations. Variables tested were pupal mass, consumption rate (RCR), growth rate (RGR), approximate digestibility (AD), the efficiency of conversion of digested food (ECD) and the efficiency of conversion of ingested food (ECI). Our results show that all traits tested presented a high percentage of nonadditive effects that modulate phenotype expression. We found a significant impact of family × diet interaction on pupal mass, RGR and ECD. Furthermore, these traits exhibited the greatest heritability. There was no evidence of presence of maternal effects. The results revealed that food utilization traits may evolve through epigenetics effects, such as phenotypic plasticity. This information can be used by modellers to improve forecast of spruce budworm population dynamics.     

Adult neural stem cells bridge their niche

Major developments in the neural stem cell (NSC) field in recent years provide new insights into the nature of the NSC niche. In this perspective, we integrate recent anatomical data on the organization of the two main neurogenic niches in the adult brain, the ventricular-subventricular zone (V-SVZ) and the subgranular zone (SGZ), with signaling pathways that control the behavior of NSCs. NSCs in the adult brain stretch into physiologically distinct compartments of their niche. We propose how adult NSCs' morphology may allow these cells to integrate multiple signaling pathways arising from unique locations of their niche.     

Characterization of oxylipins and dioxygenase genes in the asexual fungus Aspergillus niger

Background  

Aspergillus niger is an ascomycetous fungus that is known to reproduce through asexual spores, only. Interestingly, recent genome analysis of A. niger has revealed the presence of a full complement of functional genes related to sexual reproduction [1]. An example of such genes are the dioxygenase genes which in Aspergillus nidulans, have been shown to be connected to oxylipin production and regulation of both sexual and asexual sporulation [2–4]. Nevertheless, the presence of sex related genes alone does not confirm sexual sporulation in A. niger.     

Assessment of intraluminal impedance for the detection of pharyngeal bolus flow during swallowing in healthy adults

Intraluminal impedance, a nonradiological method for assessing bolus flow within the gut, may be suitable for investigating pharyngeal disorders. This study evaluated an impedance technique for the detection of pharyngeal bolus flow during swallowing. Patterns of pharyngoesophageal pressure and impedance were simultaneously recorded with videofluoroscopy in 10 healthy volunteers during swallowing of liquid, semisolid, and solid boluses. The timing of bolus head and tail passage recorded by fluoroscopy was correlated with the timing of impedance drop and recovery at each recording site. Bolus swallowing produced a drop in impedance from baseline followed by a recovery to at least 50% of baseline. The timing of the pharyngeal and esophageal impedance drop correlated with the timing of the arrival of the bolus head. In the pharynx, the timing of impedance recovery was delayed relative to the timing of clearance of the bolus tail. In contrast, in the upper esophageal sphincter (UES) and proximal esophagus, the timing of impedance recovery correlated well with the timing of clearance of the bolus tail. Impedance-based estimates of pharyngoesophageal bolus clearance time correlated with true pharyngoesophageal bolus clearance time. Patterns of intraluminal impedance recorded in the pharynx during bolus swallowing are therefore more complex than those in the esophagus. During swallowing, mucosal contact between the tongue base and posterior pharyngeal wall prolongs the duration of pharyngeal impedance drop, leading to overestimation of bolus tail timing. Therefore, we conclude that intraluminal impedance measurement does not accurately reflect the bolus transit in the pharynx but does accurately reflect bolus transit across the UES and below.     

Chemical modification ofSemele solida arginase by diethyl pyrocarbonate: Evidence for a critical histidine residue

Arginase from the gills of the bivalveSemele solida was inactivated by diethyl pyrocarbonate (DEPC) in a pseudo-first-order reaction with a bimolecular rate constant of 160 M⁻¹ min⁻¹. The reaction order with respect to DEPC concentration was 1, the inactivation followed a titration curve for a residue with a pK_a of 6.4 at 25°C and the enzymatic activity was restored by hydroxylamine. It is concluded that inactivation results from the modification of a single histidine residue. Borate, a noncompetitive inhibitor with respect to arginine, protected the enzyme from inactivation by DEPC.     

Zinc supplementation decreases hepatic copper accumulation in LEC rat

The effect of dietary zinc (Zn) supplementation on copper (Cu)-induced liver damage was investigated in Long-Evans Cinnamon rats (LEC), a model for Wilson's disease (WD). Four-week-old LEC (N=64) and control Long-Evans (LE) (N=32) female rats were divided into two groups; one group was fed with a Zn-supplemented diet (group I) and the other was given a normal rodent diet (group II). LEC rats were killed at 6, 8, 10, 12, 18, and 20 wk of age; the LE control rats were killed at 6, 12, 18, and 20 wk of age. Cu concentration in the liver was reduced in LEC rats fed the Zn-supplemented diet compared with LEC rats on the normal diet between 6 and 18 wk of age. Metallothionein (MT) concentration in the livers of LEC rats in group I increased between 12 and 20 wk of age, whereas hepatic MT concentration in LEC rats from group II decreased after 12 wk. Hepatocyte apoptosis, as determined by TUNEL, was reduced in Zn-supplemented LEC rats at all ages. Cholangiocellular carcinoma was observed only in LEC rats in group II at wk 20. These results suggest that Zn supplementation can reduce hepatic Cu concentration and delay the onset of clinical and pathological changes of Cu toxicity in LEC rats. Although the actual mechanism of protection is unknown, it could be explained by sequestration of dietary Cu by intestinal MT, induced by high dietary Zn content.     

Chronic morphine treatment and withdrawal increase extracellular levels of norepinephrine in the rat bed nucleus of the stria terminalis

Extracellular levels of norepinephrine (NE) and glutamate (Glu) in the ventral bed nucleus of the stria terminalis (vBNST) of saline- and chronic morphine-treated rats, with or without withdrawal, were studied by means of the in vivo microdialysis technique in anesthetized rats. In addition, the tissue concentration of NE was studied at different rostrocaudal levels of the vBNST. Chronic morphine treatment significantly increased extracellular levels of NE, but not Glu, in vBNST. At 48 h after naloxone-induced morphine withdrawal there was a further significant increase in the extracellular levels of NE, but not Glu, in vBNST. The presence of UK 14304, an alpha(2)-adrenergic agonist, induced a significant decrease in NE extracellular levels in all experimental groups. In contrast, UK 14304 induced a significant decrease in Glu extracellular levels only in saline-treated rats. The results also show that the vBNST presents a rostrocaudal gradient of NE and contains 9.4% of total brain NE. The increase in NE extracellular levels in vBNST induced by chronic morphine treatment and the further increase in NE levels 48 h after naloxone-induced morphine withdrawal suggest that NE in vBNST may be involved in the pharmacological effects of chronic morphine and withdrawal.