Anisocoria and middle cerebral artery saccular (berry) aneurysm in a rhesus macaque (Macaca mulatta)

A 27-year-old female rhesus macaque (Macaca mulatta) developed anisocoria. The left pupil was dilated and unresponsive to light. The macaque was euthanized because of unrelated reasons and the body was submitted for necropsy. On gross examination, a berry aneurysm of the right middle cerebral artery causing marked compression of the right optic tract was found. Arteriosclerotic changes were observed microscopically in the right middle cerebral and in the internal carotid arteries. The left iris was markedly degenerated, with atrophy of the constrictor muscle. Compression of the right optic tract may cause homonimus hemianopsia. A dilated and unresponsive left pupil indicated a lesion in the ipsilateral parasympathetic efferent pathway. In the absence of appreciable lesions of the left oculomotor nerve, the most likely cause of mydriasis was the iridic lesion. Intracranial aneurysms are common in humans (2 to 5%), but not in other species. Only about 10% of unruptured aneurysms are associated with neurologic deficits related to mechanical compression, such as visual deficits or anisocoria. Meticulous investigation of the ocular vascular and neural pathways led us to conclude that the anisocoria was unrelated to the aneurysm. To our knowledge, this report represents the first documented case of a naturally occurring intracranial aneurysm in nonhuman primates.     

Dissecting the involvement of LC3B and GATE-16 in p62 recruitment into autophagosomes

Autophagy is a major intracellular trafficking pathway that delivers proteins and organelles from the cytoplasm into lysosomes for consequential degradation and recycling. Mammalian Atg8s are key autophagic factors that undergo a unique ubiquitin-like conjugation to the lipid phase of the autophagosomal membrane. In addition to their activity in autophagosome formation, several Atg8s directly bind p62/SQSTM1. Here we show that LC3 and GATE-16 differ in their mode of p62 binding. While the soluble form of both LC3 and GATE-16 bind p62, only the lipidated form of LC3 is directly involved in p62 recruitment into autophagosomes. Moreover, by utilizing chimeras of LC3 and GATE-16 where their N-terminus was swapped, we determined the regions responsible for this differential binding. Accordingly, we found that the chimera of GATE-16 containing the LC3 N-terminal region acts similarly to wild-type LC3 in recruiting p62 into autophagosomes. We therefore propose that LC3 is responsible for the final stages of p62 incorporation into autophagosomes, a process selectively mediated by its N-terminus.     

Small‐scale spatial variability in the distribution of ectomycorrhizal fungi affects plant performance and fungal diversity

The effects of spatial heterogeneity in negative biological interactions on individual performance and species diversity have been studied extensively. However, little is known about the respective effects involving positive biological interactions, including the symbiosis between plants and ectomycorrhizal (EM) fungi. Using a greenhouse bioassay, we explored how spatial heterogeneity of natural soil inoculum influences the performance of pine seedlings and composition of their root‐associated EM fungi. When the inoculum was homogenously distributed, a single EM fungal taxon dominated the roots of most pine seedlings, reducing the diversity of EM fungi at the treatment level, while substantially improving pine seedling performance. In contrast, clumped inoculum allowed the proliferation of several different EM fungi, increasing the overall EM fungal diversity. The most dominant EM fungal taxon detected in the homogeneous treatment was also a highly beneficial mutualist, implying that the trade‐off between competitive ability and mutualistic capacity does not always exist.     

LC3 and GATE-16 N termini mediate membrane fusion processes required for autophagosome biogenesis

Autophagy is a unique membrane trafficking pathway describing the formation and targeting of double membrane autophagosomes to the vacuole/lysosome. The biogenesis of autophagosomes and their delivery to the vacuole/lysosome depend on multiple membrane fusion events. Using a cell-free system, we have investigated the ability of LC3 and GATE-16, two mammalian Atg8 orthologs, to mediate membrane fusion. We found that both proteins promote tethering and membrane fusion, mediated by the proteins' N-terminal α helices. We further show that short, 10 amino acid long synthetic peptides derived from the N terminus of LC3 or GATE-16 are sufficient to promote membrane fusion. Our data indicate that the fusion activity of LC3 is mediated by positively charged amino acids, whereas the activity of GATE-16 is mediated by hydrophobic interactions. Finally, we demonstrate that LC3 and GATE-16 N termini in general and specific residues needed for the fusion activity are essential for the proteins role in autophagosome biogenesis.     

The A locus that controls anthocyanin accumulation in pepper encodes a MYB transcription factor homologous to Anthocyanin2 of Petunia

Pepper plants containing the dominant A gene accumulate anthocyanin pigments in the foliage, flower and immature fruit. We previously mapped A to pepper chromosome 10 in the F₂ progeny of a cross between 5226 (purple-fruited) and PI 159234 (green-fruited) to a region that corresponds, in tomato, to the location of Petunia anthocyanin 2 (An2), a regulator of anthocyanin biosynthesis. This suggested that A encodes a homologue of Petunia An2. Using the sequences of An2 and a corresponding tomato expressed sequence tag, we isolated a pepper cDNA orthologous to An2 that cosegregated with A. We subsequently determined the expression of A by Northern analysis, using RNA extracted from fruits, flowers and leaves of 5226 and PI 159234. In 5226, expression was detected in all stages of fruit development and in both flower and leaf. In contrast, A was not expressed in the sampled tissues in PI 159234. Genomic sequence comparison of A between green- and purple-fruited genotypes revealed no differences in the coding region, indicating that the lack of expression of A in the green genotypes can be attributed to variation in the promoter region. By analyzing the expression of the structural genes in the anthocyanin biosynthetic pathway in 5226 and PI 159234, it was determined that, similar to Petunia, the early genes in the pathway are regulated independently of A, while expression of the late genes is A-dependent.Communicated by R. Hagemann     

Nitric oxide-endothelin-1 interactions after acute ductal constriction in fetal lambs

Acute partial compression of the fetal ductus arteriosus (DA) results in an initial increase in pulmonary blood flow (PBF) that is followed by acute vasoconstriction. The objective of the present study was to determine the role of nitric oxide (NO)-endothelin-1 (ET-1) interactions in the acute changes in pulmonary vascular tone after in utero partial constriction of the DA. Twelve late-gestation fetal lambs (132-140 days) were instrumented to measure vascular pressures and left PBF. After a 24-h recovery period, acute constriction of the DA was performed by partially inflating a vascular occluder, and the hemodynamic variables were observed for 4 h. In control lambs (n = 7), acute ductal constriction initially increased PBF by 627% (P < 0.05). However, this was followed by active vasoconstriction, such that PBF was restored to preconstriction values by 4 h. This was associated with a 43% decrease in total NO synthase (NOS) activity (P < 0.05) and a 106% increase in plasma ET-1 levels (P < 0.05). Western blot analysis demonstrated no changes in lung tissue endothelial NOS, preproET-1, endothelin-converting enzyme-1, or ET(B) receptor protein levels. The infusion of PD-156707 (an ET(A) receptor antagonist, n = 5) completely blocked the vasoconstriction and preserved NOS activity. These data suggest that the fetal pulmonary vasoconstriction after acute constriction of the DA is mediated by NO-ET-1 interactions. These include an increase in ET(A) receptor-mediated vasoconstriction and an ET(A) receptor-mediated decrease in NOS activity. The mechanisms of these NO-ET-1 interactions, and their role in mediating acute changes in PBF, warrant further studies.