Morphological Parameters Associated with Ruptured Posterior Communicating Aneurysms

The rupture risk of unruptured intracranial aneurysms is known to be dependent on the size of the aneurysm. However, the association of morphological characteristics with ruptured aneurysms has not been established in a systematic and location specific manner for the most common aneurysm locations. We evaluated posterior communicating artery (PCoA) aneurysms for morphological parameters associated with aneurysm rupture in that location. CT angiograms were evaluated to generate 3-D models of the aneurysms and surrounding vasculature. Univariate and multivariate analyses were performed to evaluate morphological parameters including aneurysm volume, aspect ratio, size ratio, distance to ICA bifurcation, aneurysm angle, vessel angles, flow angles, and vessel-to-vessel angles. From 2005–2012, 148 PCoA aneurysms were treated in a single institution. Preoperative CTAs from 63 patients (40 ruptured, 23 unruptured) were available and analyzed. Multivariate logistic regression revealed that smaller volume (p = 0.011), larger aneurysm neck diameter (0.048), and shorter ICA bifurcation to aneurysm distance (p = 0.005) were the most strongly associated with aneurysm rupture after adjusting for all other clinical and morphological variables. Multivariate subgroup analysis for patients with visualized PCoA demonstrated that larger neck diameter (p = 0.018) and shorter ICA bifurcation to aneurysm distance (p = 0.011) were significantly associated with rupture. Intracerebral hemorrhage was associated with smaller volume, larger maximum height, and smaller aneurysm angle, in addition to lateral projection, male sex, and lack of hypertension. We found that shorter ICA bifurcation to aneurysm distance is significantly associated with PCoA aneurysm rupture. This is a new physically intuitive parameter that can be measured easily and therefore be readily applied in clinical practice to aid in the evaluation of patients with PCoA aneurysms.     

Scale-dependent interactions between intrinsic and extrinsic processes reduce variability in protist populations

Interactions between intrinsic processes and extrinsic fluctuations can positively impact population persistence in ways often not predicted by classic ecological models. These interactions only arise when the intrinsic and extrinsic processes operate on the proper relative scales in time or space. Both metapopulation theory and resonance/attenuation theory suggest that interactions which lower population variability will occur when the intrinsic and extrinsic process occur on similar time scales. I performed an aquatic protist microcosm experiment to investigate how the relative frequencies of extrinsic density perturbations and intrinsic resource pulses impacted population variability. Population variability was lowest in the treatments of intermediate frequency, in which the extrinsic fluctuations and intrinsic processes were on the same time scale. This result is consistent with general theoretical predictions, and empirically documents the importance of considering scale in interactions between intrinsic and extrinsic processes that positively impact population persistence.     

Calcium-Dependent Release of Tyrosine in Brain Elicited by Stimulation of Neuropeptide Receptors

We sought to establish whether the endogenous opiate-receptor agonist Met-enkephalin (m-ENK) selectively modulates the release of endogenous tyrosine (Tyr) from brain slices prepared from the corpus striatum (CS). Amino acids (AAs) released from slices of CS and, for comparison, cerebral cortex (Cx) were measured by HPLC. Incubation of slices with m-ENK (1-10 microM) increased the basal release of Tyr (up to 293% of control) from CS, but not Cx, whereas other nonneurotransmitter AAs, phenylalanine (Phe) and valine (Val), were unchanged. The release of the putative neurotransmitter AAs glutamate (Glu), taurine (Tau), and glycine (Gly) were similarly increased by 50-150% with m-ENK in slices of CS, but not Cx. The enhanced release of AAs by m-ENK was prevented by removal of extracellular Ca2+ or by preincubation with the opiate receptor antagonist naloxone. Neuronal depolarization by potassium (5-55 mM) in the presence of Ca2+ did not affect the release of Tyr, whereas release of neurotransmitter AAs such as gamma-aminobutyric acid (GABA) were markedly increased. The increase in basal Tyr release by m-ENK was not the result of a decreased uptake of Tyr. Relative to slices, the basal release of Tyr, Phe, and Val from a synaptosomal (P2) preparation of CS was small (8-51%) compared to that of GABA, Gly, Glu, and Tau (49-123%). Nonetheless, m-ENK (10 microM) markedly increased the release of Tyr (to 833%), but not Glu, Gly, and Tau from the P2 fraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Structure and expression of the overlapping ND4L and ND5 genes of Neurospora crassa mitochondria

Summary Genes homologous to the mammalian mitochondrial NADH dehydrogenase subunit genes ND4L and ND5 were identified in the mitochondrial genome of the filamentous fungus Neurospora crassa, and the structure and expression of these genes was examined. The ND4L gene (interrupted by one intervening sequence) potentially encodes an 89 residue long hydrophobic protein that shares about 26% homology (or 41% homology if conservative amino acid substitutions are allowed) with the analogous human mitochondrial protein. The ND5 gene (which contains two introns) encodes a 715 residue polypeptide that shares 23% homology with the human analogue; a 300 amino acid long region is highly conserved (50% homology) in the two ND5 proteins. The stop codon of the ND4L gene overlaps the initiation codon of the downstream ND5 gene, and the two genes are contranscribed and probably cotranslated. A presumed mature dicistronic (ND4L plus ND5) RNA was detected. The postulated mRNA (about 3.2 kb) contains 5 and 3 non-coding regions of about 86 and 730 nucleotides, respectively; this species is generated from very large precursor RNAs by a complex processing pathway. The ND4L and ND5 introns are all stable after their excision from the precursor species.Abbreviations bp base pairs - rRNA ribosomal RNA - ND NADH dehydrogenase - URF unidentified reading frame - kDal kilodaltons; a.a., amino acid