Logistic advantages of four-section helical CT in the abdomen and pelvis

Background: Multisection helical computed tomography (CT) has the potential for providing data sets with better section profiles, more anatomic coverage, and shorter breath-holding periods. Our purpose was to quantitate these advantages in a clinical setting when imaging the abdomen and pelvis. Methods: CT parameters including collimation, timing, z-axis coverage, and milliamperes were gathered retrospectively for the image set of both single-section (GE CT/i with 0.8-s rotation) and four-section (GE QX/i Lightspeed with 0.8-s rotation) helical CT scanners. Data were recorded for the abdomen and pelvis CT (n= 30 each), dual-phase liver CT including the pelvis (n= 15 each), and dual-phase pancreas CT (n= 15 each). Results: The abdominal and pelvic CT averaged 128.4 ± 5.4 s for single-section scanners (70-s delay, two breath-holds of 21.1 and 17.7 s with a 19.5-s interscan delay) and 92.2 ± 2.2 s for the four-section scanner (70-s delay and a 22.2-s breath-hold; p < 0.0001). For the dual liver and pelvis CT, single-section scanners averaged 119.9 ± 7.5 s (30-s delay, 15.8-s arterial phase, 20.0-s interscan delay, 21.2-s venous phase, 19.5-s interscan delay, and 14.2 s for the remaining abdomen and pelvis), whereas the four-section scanner averaged 86.8 ± 2.5 s (30-s delay, 6.7-s arterial phase, 27.9-s interscan delay, and 21.8-s venous phase including the pelvis; p < 0.0001). For the dual pancreas CT, single-section scanners averaged 86.7 ± 2.5 s (20-s delay, 28.3-s arterial phase, 17.8-s interscan delay, 21.7-s venous phase), whereas the four-section scanner averaged 78.0 ± 2.9 s (20-s delay, 9.7-s arterial phase, 30.7-s interscan delay, 13.0-s venous phase; p < 0.0001). Conclusion: CT scanners having four-section technology can reduce overall data acquisition times by 10–30% and total milliamperes by 50–60% depending on the protocol with thinner slice profiles. RID=" ID=" <E5>Correspondence to:</E5> R. C. Nelson Received: 8 December 1999/Revision accepted: 22 March 2000     

Coexisting pathologies in the brain: influence of vascular disease and Parkinson’s disease on Alzheimer’s pathology in the hippocampus

The finding of more than one coexisting brain pathology in dementia sufferers is not unusual. However, it is unclear how these different diseases may interact or influence the evolution of one another. In this study we analyse the hippocampal expression patterns of hyperphosphorylated tau, paired helical filament (PHF)-related protein, β-amyloid and synaptophysin in a group of Alzheimer’s disease (AD) sufferers with and without additional pathology. Compared to cases with only AD-type pathology we found that the presence of additional vascular disease augmented the accumulation of hyperphosphorylated tau in the CA1 region of the hippocampus without affecting PHF formation in cases with mild AD changes and reduced the extent of PHF formation in the CA2/3 and CA4 regions of the hippocampus in cases with severe AD pathology. We also found that synaptophysin immunoreactivity in the CA4 and dentate gyrus in pure AD was inversely related to the extent of amyloid accumulation but not to neurofibrillary pathology in the same regions. These relationships were lost when additional pathology was present. Memory scores obtained during life correlated closely with hyperphosphorylated tau and PHF-related protein expression in CA1 in pure AD but not in AD with additional pathology. Total amyloid and synaptophysin expression in the hippocampus did not correlate with memory scores in any patient group. Our findings suggest that the interactions of two pathologies in the hippocampus are complex and may differ depending on the stage reached in the evolution of a progressive disease such as AD. Received: 26 July 1999 / Revised, accepted: 12 October 1999     

Modeling of a periodic instability in paired helical filaments reveals an axial repeat

Ultrastructural studies of paired helical filaments (PHF) have been facilitated by the ability to isolate enriched fractions of detergent-insoluble forms of PHF. These fractions are composed of a relatively homogeneous population of short (usually < 400 nm) highly fragmented PHF. A small proportion of isolated PHF have highly stereotyped angled profiles that represent deformations due to structural instability. These distorted PHF can be characterized quantitatively using a simple numerical procedure that reveals that the axial instabilities occur with predictable regularity over the length of the PHF. Using a structural model of PHF, it is shown that the periodicity of the axial instability can be correlated to an axially repeated subunit of uniform size. The upper limit for the axial extent of the repeated segment was calculated to be 80 nm, similar to the size of a single one-half twist in the PHF ribbon. It is proposed that this segment may represent one type of particle in the hierarchy of structural subunits in the PHF ribbon, or an oligomeric intermediate species in PHF assembly. Received: 16 June 1999 / Revised, accepted: 7 September 1999     

Extending the concept of template-assembled synthetic proteins

Abstract: The creation of native-like macromolecules in copying nature’s way represents a fascinating challenge in protein chemistry today. In the absence of a detailed knowledge of the complex folding pathway the ultimate goal in protein de novo design, the construction of artificial proteins with predetermined three-dimensional structure and tailor-made functions based on a defined, generally valid set of rules, appears to be still out of reach. With progress in synthesis strategies and biostructural characterization methods, topological templates have become a versatile tool for inducing and stabilizing secondary and tertiary structures, such as protein loops, β-turns, α-helices, β-sheets and a variety of folding motifs. In this article, we extend the concept of template-assembled synthetic proteins for the construction of protein-like topologies with multiply bridged, oligocyclic chain architectures termed locked-in tertiary folds that exhibit unique physicochemical and folding properties because of the highly confined conformational space. Furthermore, we show that some fundamental questions in protein assembly can be approached applying the template concept. Using covalent template trapping of self-associated peptide assemblies in aqueous solution the structural and physical forces guiding protein folding, supramolecular assembly and molecular recognition processes can be studied on a molecular level.     

CT仿真内窥镜在鼻科的临床应用

探讨ＣＴ新技术仿真内窥镜在鼻科的临床应用价值。方法：对１５例鼻部疾病患者行螺旋ＣＴ扫描后经软件处理进行仿真内窥镜成像,并与鼻内窥镜所见对照研究。结果：ＣＴ仿具内 显示鼻内正常解剖结构,鼻部病变的位置,范围与鼻内窥镜所见类似,并可进行鼻内窥镜无法到达的腔道,如鼻窦内,狭窄的鼻道内以及病变梗阻的远端。结论ＣＴ仿真内窥镜是对鼻部二维ＣＴ、多平面成像的补充,具有一定的应用潜力,值得临床进一步推广应用。     

Influence of the hydrophilic face on the folding ability and stability of α‐helix bundles: relevance to the peptide catalytic activity

Although not the sole feature responsible, the packing of amino acid side chains in the interior of proteins is known to contribute to protein conformational specificity. While a number of amphipathic peptide sequences with optimized hydrophobic domains has been designed to fold into a desired aggregation state, the contribution of the amino acids located on the hydrophilic side of such peptides to the final packing has not been investigated thoroughly. A set of self‐aggregating 18‐mer peptides designed previously to adopt a high level of α‐helical conformation in benign buffer is used here to evaluate the effect of the nature of the amino acids located on the hydrophilic face on the packing of a four α‐helical bundle. These peptides differ from one another by only one to four amino acid mutations on the hydrophilic face of the helix and share the same hydrophobic core. The secondary and tertiary structures in the presence or absence of denaturants were determined by circular dichroism in the far‐ and near‐UV regions, fluorescence and nuclear magnetic resonance spectroscopy. Significant differences in folding ability, as well as chemical and thermal stabilities, were found between the peptides studied. In particular, surface salt bridges may form which would increase both the stability and extent of the tertiary structure of the peptides. The structural behavior of the peptides may be related to their ability to catalyze the decarboxylation of oxaloacetate, with peptides that have a well‐defined tertiary structure acting as true catalysts.     

Animal models to investigate drug effects on coronary physiology

Coronary blood flow is regulated by local intrinsic mechanisms according to the oxygen need of the myocardium, but the coronary circulation is also modulated by nervous, humoral, and extravascular influences. Therefore, any method used to study drug effects on the coronary circulation must take into account not only the direct effects of the drug but also any secondary drug effects that might indirectly influence the coronary vasculature. The simplest methods involve the use of isolated vessels. With these methods, the environment of the vessel can be precisely controlled, although usually only vessels larger than true resistance vessels can be studied. Isolated heart models have also been successfully employed, and in these models, effects of the drug on the myocardium must be considered. More complex models include in vivo anesthetized animal techniques with intracoronary drug administratiorl. With these models, drug effects on the coronary circulation as well as on other cardiac variables can be examined. The use of conscious, instrumented animals perhaps provides the most physiologic preparation and is very useful, particularly if intracoronary administration of drugs is employed.     

多层螺旋CT血管成像在椎基底动脉供血不足病因诊断中的应用

目的探讨多层螺旋CT血管成像(MSCTA)在诊断椎-基底动脉供血不足中的临床价值。方法对临床确诊VBI患者32例,进行颅脑CTA、颈部血管彩超、经颅多普勒超声(TCD)检查。结果VBI患者TCD检查阳性率为68.8%,颈部血管彩超阳性率为56.3%,颅脑CTA阳性率为90.6%。结论在VBI诊断方面,CTA检查较颈部血管彩超、TCD检查有明显的优势,提示CTA可以作为诊断VBI的首选方法之一,值得临床推广。     

Ferritin is a component of the neuritic (senile) plaque in Alzheimer dementia

Summary A strong immunoreactivity for ferritin was observed in the neuritic (senile) plaques in Alzheimer's disease hippocampus. The ferritin accumulation was almost exclusively associated with the microglia, which appeared to have proliferated greatly. These cells were also positive for HLA-DR, a putative marker for reactive microglia. In contrast, in the diffuse plaques, which were without neuritic pathology, the ferritin-stained microglia appeared to be normal. Microglia were seen frequently in contact with neurons undergoing neurofibrillary changes but only the tangles in the extracellular space were ferritin positive. No ferritin was detected, by Western blots, in paired helical filaments isolated from Alzheimer's disease brain, suggesting that ferritin was most likely weakly associated with and was not a constituent of these fibrils. No correlation between increased ferritin/microglia activity and blood-brain barrier leakage was detected. Ferritin, an iron-storage protein, might have a role in the formation of amyloid through the action of free radicals generated during the release of iron from the ferritin molecule. Alternatively, the ferritin/microglia system might be secondarily involved in the removal and processing of the amyloid.Supported in part by the New York State Office of Mental Retardation and Developmental Disabilities and National Institutes of Health grants NS18105, AG05892 and AG04220. H. L. was funded by a grant from the Ministry for Science and Research, Austria, J. G. J. and J. F. were funded by the Council for Tobacco Research. Parts of this paper have been reported at the 9th International Conference on Proteins of Iron Transport and Storage, Brisbane, Australia, June 1989 and at the 2nd International Conference on Aluminium and Health, Orlando, Fla, USA, December 1989