Stair-step artifacts in three-dimensional helical CT: an experimental study

We describe 3 sibs, their father, and paternal grandfather with amelogenesis imperfecta. In 2 sibs and the father the defect is associated with a neurological syndrome which has a wide range of phenotypic variability. The proposita has ataxia, EEG abnormalities, moderate dementia, and enamel hypoplasia. This case and the affected relatives are discussed in relation to Kohlschütter-T?nz syndrome and neuroectodermal diseases. The syndrome described here, characterized by the association of a genetic enamel defect and neurological impairment, may be of considerable interest in advancing genetic and clinical knowledge on ectodermal tissues and their development.     

Language disorders and learning disabilities in school-refusing adolescents

OBJECTIVE: We undertook this study to test the hypothesis that school-refusing adolescents hospitalized on an inpatient psychiatric unit have more language and learning disabilities than diagnosis-, age-, and sex-matched psychiatric controls. METHOD: The Woodcock-Johnson Tests of Achievement-Revised (WJTA-R), the WISC-R, the Adolescent Language Screening Test, the Clinical Evaluation of Language Fundamentals-Revised, and the Test of Language Competence (TLC) were given to a group of well-characterized, primarily depressed school refusers and matched psychiatric controls. RESULTS: We found that school-refusing adolescents had significantly lower WISC-R verbal intelligence scores, lower Math and Written Language subscale scores on the WJTA-R, and lower scores on the TLC than nonrefusers. School refusers were found to have a significantly higher incidence of both language impairments and learning disabilities than controls. CONCLUSIONS: We infer that academic and communicative frustration and the adolescent's resulting inability to meet the academic and social demands in the school environment may play a role in the etiology of school refusal.     

Chloroplast and nuclear gene sequences indicate late Pennsylvanian time for the last common ancestor of extant seed plants

We have estimated the time for the last common ancestor of extant seed plants by using molecular clocks constructed from the sequences of the chloroplastic gene coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) and the nuclear gene coding for the small subunit of rRNA (Rrn18). Phylogenetic analyses of nucleotide sequences indicated that the earliest divergence of extant seed plants is likely represented by a split between conifer-cycad and angiosperm lineages. Relative-rate tests were used to assess homogeneity of substitution rates among lineages, and annual angiosperms were found to evolve at a faster rate than other taxa for rbcL and, thus, these sequences were excluded from construction of molecular clocks. Five distinct molecular clocks were calibrated using substitution rates for the two genes and four divergence times based on fossil and published molecular clock estimates. The five estimated times for the last common ancestor of extant seed plants were in agreement with one another, with an average of 285 million years and a range of 275-290 million years. This implies a substantially more recent ancestor of all extant seed plants than suggested by some theories of plant evolution.     

The misrepresentation of the human pelvis

A representative series of illustrations of the human bony pelvis dating from the sixteenth century to the present is used to demonstrate the persistent misrepresentation in the orientation of the pelvis and in the nomenclature. Early erroneous concepts were probably strongly reinforced by publications of the Belgian anatomist Vesalius in the sixteenth century. In mounting the vertebrae on a vertical iron rod, he erased much of the sacral curvature and, as a consequence, the orientation of the rest of the pelvis was distorted. True versions of the pelvis were executed by Leonardo da Vinci before the time of Vesalius but these drawings were apparently among those that were lost for many years. A relatively small number of similarly accurate depictions of the bony pelvis have appeared down through the centuries and some of these are also included. A persistent error in many anatomical textbooks used today presents a modified inferior view of the pelvis as the "front view" and a nearly accurate front view as a "view from above." No definitive conclusion can be reached concerning the reason(s) for the remarkably long persistence of this error. The figures referenced are presented in the Gallery immediately following this article.     

Molecular cloning and sequence comparison of the S1 glycoprotein of the Gray and JMK strains of avian infectious bronchitis virus

The nucleotide sequences of S1 glycoprotein genes of the Gray and JMK strains of avian infectious bronchitis virus (IBV) were determined and compared with published sequences for IBV. The IBV Gray and JMK strains had 99% nucleotide sequence similarity. The overall nucleotide sequence similarity of the Gray and JMK strains compared with other IBV strains was between 82.0% and 87.4%. The similarity of the predicted amino acid sequence for the S1 glycoproteins of the Gray and JMK strains was 98.8%. Six of the 10 differences in the amino acid sequence were found between residues 99 and 127, suggesting a possible role for that region in the tissue trophisms of the viruses. The S1 glycoprotein of the Gray and JMK strains had 79.5%-84.6% amino acid similarity with the published sequence of other IBV strains. Serine instead of phenylalanine was observed in the protease cleavage site between the S1 and S2 glycoprotein subunits for the Gray and JMK strains, which was similar to the published sequence for the Ark99 and SE17 strains. The significance of that amino acid change is not known. Based on the nucleotide sequence of the Gray and JMK strains, the BsmAI restriction enzyme was selected by computer analysis and was used in restriction fragment length polymorphism analysis to differentiate the two strains.     

Interactions Between Tumor Biology and Targeted Nanoplatforms for Imaging Applications

Although considerable efforts have been conducted to diagnose, improve, and treat cancer in the past few decades, existing therapeutic options are insufficient, as mortality and morbidity rates remain high. Perhaps the best hope for substantial improvement lies in early detection. Recent advances in nanotechnology are expected to increase the current understanding of tumor biology, and will allow nanomaterials to be used for targeting and imaging both in vitro and in vivo experimental models. Owing to their intrinsic physicochemical characteristics, nanostructures (NSs) are valuable tools that have received much attention in nanoimaging. Consequently, rationally designed NSs have been successfully employed in cancer imaging for targeting cancer‐specific or cancer‐associated molecules and pathways. This review categorizes imaging and targeting approaches according to cancer type, and also highlights some new safe approaches involving membrane‐coated nanoparticles, tumor cell‐derived extracellular vesicles, circulating tumor cells, cell‐free DNAs, and cancer stem cells in the hope of developing more precise targeting and multifunctional nanotechnology‐based imaging probes in the future.     

Cycloconverter Control Circuits

Cycloconverter control circuitry is discussed using examples from a practical three-phase to single-phase circulating current free cycloconverter. The voltage biased cosine wave technique is used for phase control. Phase-forward and phase-back limit (PBL) pulses are superimposed on each cosine wave. Spurious gating pulses in the range 180° to 360° are suppressed. A new current zero detector is presented involving continuous monitoring of the voltage across each thyristor. Two types of circulating current elimination logic are used, suitable for 1)resistive and lagging loads, and 2)leading, resistive, and lagging loads. Auxiliary gate pulses are supplied to the incoming converter to prevent large gaps in the load current waveform.     

Ischemic preconditioning and arrhythmogenesis in the rabbit heart: effects on epicardium versus endocardium

The goals of this study were: (1) to determine if preconditioning protects against arrhythmias and contractile dysfunction, and if protection for these two endpoints occurs in parallel; and (2) to investigate the anti-arrhythmic action of preconditioning by examining its effect on electrical activity in epicardium v endocardium. We monitored ECGs, epicardial and endocardial monophasic action potentials (MAP), left-ventricular developed presssure (LVDP) and end-diastolic pressure (EDP) in isolated rabbit hearts. Hearts were subjected to a 30-min test ischemia and 45 min of reperfusion. Preconditioning cycles (PC) consisted of 1-4 ischemic episodes (5 min each separated by 10 min of reperfusion) administered 30 min before the test protocol. The test ischemia caused ventricular fibrillation (VF) in 42% of non-PC hearts. One PC totally suppressed VF (0%). The incidence of VF was 30% in 2 PC, 72% in 3 PC and 47% in 4 PC hearts. A large rise in EDP occurred in non-PC and 1 PC hearts, and this rise was prevented by 2, 3 or 4 PC. None of the protocols improved post-ischemic recovery of LVDP or EDP. The test ischemia generated a large dispersion in MAP duration between epicardium and endocardium (39ms), but this dispersion was markedly reduced after 1 PC (14ms). In conclusion, our results demonstrate that 1 PC completely protects against ischemia-induced VF in rabbit hearts, whereas 2 or more PC are required to prevent the ischemia-induced rise in EDP. Thus, preconditioning against arrhythmias and contractile dysfunction does not occur in parallel. Our data also suggest that 1 PC may exert its anti-arrhythmic effect through reduction of the substrate for reentrant arrhythmias during ischemia (dispersion of repolarization) via effects on MAP changes in endocardium.     

Immunomodulatory and therapeutic properties of alkyl lysophospholipids in mice

This paper describes the immunomodulatory and therapeutic properties of the alkyl lysophospholipids [ALP; 1-O-octadecyl-2-O-rac-glycero-3-phosphocholine (ET-18-OCH₃)]. ALP was able to activate macrophages both in vitro and in vivo as well as to act as an immunoadjuvant for syngeneic tumor vaccines. However, ALP appeared to be transferred, at least in part, to the macrophage membrane, and some of the tumoricidal macrophage-activating properties seem to be associated with the direct cytotoxic effect of membrane-released ALP. ALP also had some therapeutic activity for experimental and spontaneous metastases, requiring administration three but not two times weekly at near-toxic doses; this suggests that at least some of its therapeutic activity is due to direct cytotoxicity.