A comparative study of peroxisomal structures in Hansenula polymorpha pex mutants

In a recent study, we performed a systematic genome analysis for the conservation of genes involved in peroxisome biogenesis (PEX genes) in various fungi. We have now performed a systematic study of the morphology of peroxisome remnants (‘ghosts’) in Hansenula polymorpha pex mutants (pex1–pex20) and the level of peroxins and matrix proteins in these strains. To this end, all available H. polymorpha pex strains were grown under identical cultivation conditions in glucose-limited chemostat cultures and analyzed in detail. The H. polymorpha pex mutants could be categorized into four distinct groups, namely pex mutants containing: (1) virtually normal peroxisomal structures (pex7, pex17, pex20); (2) small peroxisomal membrane structures with a distinct lumen (pex2, pex4, pex5, pex10, pex12, pex14); (3) multilayered membrane structures lacking apparent matrix protein content (pex1, pex6, pex8, pex13); and (4) no peroxisomal structures (pex3, pex19).

The Effects of Avatar Personalization and Human -Virtual Agent Interactions on Self -Esteem

Extant literature has suggested that VR may be a potential avenue to enhance self-esteem. However, the understanding toward the underlying technological mechanisms and their corresponding effects on the self are still not comprehensive. To address this research gap, the current study designed a series of social interactions in VR where participants (N = 171) embodied either a personalized or non-personalized avatar and had either positive or negative interactions with a virtual agent. Findings showed that participants who embodied a personalized avatar experienced a positive change in self-esteem from pre- to post-simulation, regardless of the virtual agent interaction quality.</p

A Peroxisomal Lon Protease and Peroxisome Degradation by Autophagy Play Key Roles in Vitality of Hansenula polymorpha Cells

In eukaryote cells various mechanisms exist that are responsible for the removal of non-functional proteins. Here we show that in the yeast Hansenula polymorpha (H. polymorpha) a peroxisomal Lon protease, Pln, plays a role in degradation of unfolded and non-assembled peroxisomal matrix proteins. In addition, we demonstrate that whole peroxisomes are constitutively degraded by autophagy during normal vegetative growth of WT cells. Deletion of both H. polymorpha PLN and ATG1, required for autophagy, resulted in a significant increase in peroxisome numbers, paralleled by a decrease in cell viability relative to WT cells. Also, in these cells and in cells of PLN and ATG1 single deletion strains, the intracellular levels of reactive oxygen species had increased relative to WT controls. The enhanced generation of reactive oxygen species may be related to an uneven distribution of peroxisomal catalase activities in the mutant cells, as demonstrated by cytochemistry. We speculate that in the absence of HpPln or autophagy unfolded and non-assembled peroxisomal matrix proteins accumulate, which can form aggregates and lead to an imbalance in hydrogen peroxide production and degradation in some of the organelles.

Partial generalization in pigeons trained to discriminate morphine from saline: Applications of receptor theory

In pigeons trained to discriminate 5.6 mg/kg of morphine from saline, cyclazocine, l-N-allyl-normetazocine (l-NANM, l-SKF10,047), and ketamine, but not U50,488, produced partial generalization, i.e., a maximum level of drug-appropriate responding between the levels produced by saline and by the training drug. The generalization gradient of cyclazocine and of l-NANM, but not that of ketamine, was less steep than the gradient of morphine. Cyclazocine and l-NANM, but not U50,488 and ketamine, antagonized partially the discriminative stimulus (DS) effects of morphine. Naltrexone antagonized the DS effects of morphine, cyclazocine, and l-NANM, but not ketamine. Increasing the training dose of morphine shifted the morphine gradient to the right, increased the antagonist effects of cyclazocine and of l-NANM, and decreased their agonist effects, but did not alter the effects of ketamine. Decreasing the training dose of morphine shifted the morphine gradient to the left and increased the agonist effects of cyclazocine, but did not alter the effects of l-NANM and ketamine. The full generalization produced by cyclazocine when the training dose of morphine was lowered could be blocked completely by naltrexone and l-NANM, but not by ketamine. These results suggest that cyclazocine and l-NANM, but not ketamine, produced partial generalization because of their low efficacy at the receptor that underlies the DS effects of morphine. However, the results obtained with ketamine suggest that partial generalization may also be produced through other mechanisms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50214/1/430160211_ftp.pd

Gravitational lensing, memory and the Penrose limit

In this paper, we discuss the gravitational field of ultrarelativistic extended spinning objects. For this purpose, we use a solution of the linearized gravitational equations obtained in the frame where such an object is translationally at rest, and boost this solution close to the speed of light. In order to obtain a regular limiting metric for non-spinning matter, it is sufficient to keep the energy of the boosted body fixed. This process is known as the Penrose limit. We demonstrate that in the presence of rotation, an additional rescaling is required for the angular momentum density components in the directions orthogonal to the boost. As a result of the Lorentz contraction, the thickness of the body in the direction of the boost shrinks. The body takes the form of a pancake, and its gravitational field is localized in the null plane. We discuss light and particle scattering in this gravitational field, and calculate the scattering parameters associated with the gravitational memory effect. We also show that by taking the inverse of the Penrose transform, one can use the obtained scattering map to study the gravitational lensing effect in the rest frame of a massive spinning object.Comment: 14 pages, 5 figures. 2 new references are adde