Fast implementation of the single scatter simulation algorithm and its use in iterative image reconstruction of PET data

In positron emission tomography (PET), scatter correction is usually performed prior to image reconstruction using a more or less exact model of the scatter processes. These models require estimates of the true activity and object density distributions of the imaged object. The problem is that these estimates are computed from measured data and, therefore, already contain scattered events. The purpose of this work was to overcome this problem by incorporating scatter characteristics directly into the process of iterative image reconstruction. This could be achieved by an optimized implementation of the single scatter simulation (SSS) algorithm, which results in a significant speed-up of the scatter estimation procedure. The scatter simulation was then included in the forward projection step of maximum likelihood image reconstruction. The results demonstrate that this approach leads to a more exact estimation of the scatter component which cannot be obtained by a simple sequential data processing strategy.     

4E-binding protein phosphorylation and eukaryotic initiation factor-4E release are required for airway smooth muscle hypertrophy

The molecular mechanisms of airway smooth muscle hypertrophy, a feature of severe asthma, are poorly understood. We previously established a conditionally immortalized human bronchial smooth muscle cell line with a temperature-sensitive SV40 large T antigen. Temperature shift and loss of large T cause G1-phase cell cycle arrest that is accompanied by increased airway smooth muscle cell size. In the present study, we hypothesized that phosphorylation of eukaryotic initiation factor-4E (eIF4E)-binding protein (4E-BP), which subsequently releases eIF4E and initiates cap-dependent mRNA translation, was required for airway smooth muscle hypertrophy. Treatment of cells with chemical inhibitors of PI 3-kinase and mammalian target of rapamycin blocked protein synthesis and cell growth while decreasing the phosphorylation of 4E-BP and increasing the binding of 4E-BP to eIF4E, consistent with the notion that 4E-BP1 phosphorylation and eIF4E function are required for hypertrophy. To test this directly, we infected cells with a retrovirus encoding a phosphorylation site mutant of 4E-BP1 (AA-4E-BP-1) that dominantly inhibits eIF4E. Upon temperature shift, cells infected with AA-4E-BP-1, but not empty vector, failed to undergo hypertrophic growth. We conclude that phosphorylation of 4E-BP, eIF4E release, and cap-dependent protein synthesis are required for hypertrophy of human airway smooth muscle cells.     

Metastatic potential of human CX-1 colon adenocarcinoma cells is dependent on the expression of sialosyl Le a antigen

Several lines of evidence indicate that sialosyl Le a , tumor-associated carbohydrate antigen present on human colon carcinoma cells, is involved in formation of metastases. To study the role of this carbohydrate structure in development of metastases, we have used the clone of human colon carcinoma CX-1 cells transfected with antisense expression vector containing fragment of cDNA for a1,3/4-fucosyltransferase (FT III), which is involved in synthesis of sialosyl Le a tetrasaccharide. It has been reported previously that, in contrast to the parental cells, the antisense-transfected CX-1.1AS5 cells do not express sialosyl Le a and do not adhere to E-selectin-expressing CHO cells. In the present work we have studied the formation of liver metastases by CX-1.1AS5 cells after their orthotopic or intrasplenic implantation into athymic nu/nu mice. After orthotopic implantation of sialosyl Le a -negative colon carcinoma CX-1.1AS5 cells, the number of mice with liver metas-tases was markedly lower (21% of mice) in comparison with their number after implantation of the parental CX-1.1 cells (86% of mice). However, no differences in ability to form colonies in liver were observed between parental CX-1.1 cells and antisense-transfected CX-1.1AS5 cells after intrasplenic inoculation. The liver metastases were formed in 89% and 84% of mice, respectively. Our data support the thesis on the importance of sialosyl Le a antigen expression in the development of liver metastases by colon cancer cells, and indicate the role of transplantation route and primary tumor localization in formation of metastases.© Kluwer Academic Publishers 1998     

Effects of stimulant medications on the EEG of children with Attention-Deficit/Hyperactivity Disorder Predominantly Inattentive type.

Stimulant medications are the most commonly-used treatments for Attention-Deficit/Hyperactivity Disorder (ADHD) in North America and Australia, although it is still not entirely known how these medications work. This study investigated the effects of stimulant medications on the EEG of children with the Inattentive type of ADHD. An initial EEG was recorded during an eyes-closed resting condition and Fourier transformed to provide absolute and relative power estimates for the delta, theta, alpha and beta bands. Theta/alpha and theta/beta ratios were also calculated. Subjects were placed on a 6-month trial of a stimulant and a second EEG was recorded at the end of the trial. Subjects were included in this study only if they showed a good clinical response during the trial. The unmedicated ADHD group had significantly greater absolute and relative theta, less relative alpha, and higher theta/alpha and theta/beta ratios than the control group. The stimulant medications resulted in a normalisation of the EEG, with changes in the theta, alpha and beta bands being most evident. These results suggest that stimulants act to increase cortical arousal in children with ADHD, normalising their EEG.     

Coamplification of simple repetitive DNA fingerprint fragments and the EGFR gene in human gliomas.

DNA fingerprints were generated by the oligonucleotide probe (GTG)5 from surgically removed tissue and/or primary cell culture of 36 intracranial tumors (31 gliomas, 1 medulloblastoma, 4 metastatic carcinomas) and compared with the constitutional banding pattern obtained from the peripheral blood leukocytes of each patient. A multitude of somatic changes was detected and found to reflect the chromosome alterations identified by parallel karyotype analysis. Gain and/or loss of bands or significant band intensity shifts could be demonstrated in the fingerprints of more than 80% of the tumors investigated. This included a highly amplified fingerprint fragment in five independent gliomas (four of them had double minutes, dmin) which appeared not individual- but tumor-specific (2.4 kilobases, kb, after HaeIII digestion). Rehybridization with the oligonucleotide probes (GT)8 and (GATA)4, respectively, revealed additional amplified fingerprint fragments in the tumor DNA of these patients. While a (ca/gt)n fragment (2.6 kb. HaeIII) was also found to be amplified in all five cases, one band detected with (GATA)4 (1.4 kb, HaeIII) represented a unique feature for one of these tumors only. Amplification of the epidermal growth factor receptor (EGFR) gene via Southern blot hybridization was revealed only in those tumors showing the amplified DNA fingerprint fragments as well. Thus in many gliomas the amplification unit harbors two simple repetitive DNA fingerprint loci, (cac/gtg)n and (ca/gt)n, in addition to the EGFR gene.     

TGFbeta1 enhances formation of cellular Abeta/apoE deposits in vascular myocytes

Brain injury increases the risk of Alzheimer's disease (AD) through unknown mechanisms. We studied deposition of amyloid-beta protein (Abeta) in cells exposed to transforming growth factor beta1 (TGFbeta1), a cytokine that regulates cell metabolism during brain injury, and apolipoproteinE (apoE), the major lipid transporter in the brain. The studies were conducted by using brain vascular smooth muscle cells that are engaged in beta-amyloidosis in vivo and produce Abeta in cell culture. We found that cell treatment with TGFbeta1 together with apoE4 strongly increased the amount of cellular Abeta. The intracellular Abeta co-localized with apoE but not with TGFbeta, similarly as in vascular beta-amyloid. Some cellular Abeta/apoE deposits increased in size and persisted in culture even after the TGFbeta1 and apoE4 were removed. The appearance of cellular deposits of Abeta was associated with increased production of the amyloid-beta precursor protein and cellular retention of its mature form. The results suggest that the concomitant presence of apoE and TGFbeta1 can trigger vascular beta-amyloidosis by inducing intracellular formation of stable Abeta/apoE deposits.     

Consensus statement on the bio-safety of urinary-derived gonadotrophins with respect to Creutzfeldt-Jakob disease

Human transmissible spongiform encephalopathies (TSE) encompass a group of rare neurodegenerative diseases. In April 2004, a group of international experts and regulators met in Buenos Aires, Argentina, to review the safety and to reach consensus on the use of urinary-derived gonadotrophins with respect to TSE. Iatrogenic transmission of Creutzfeldt-Jakob Disease (CJD) from pituitary-derived gonadotrophins has been reported, no infectivity in urine has been demonstrated, and no definite cases of transmission via urine have been reported. It is currently not possible to monitor donor urine or finished product for the presence of prions. Therefore the assessment of risk has to be based on the likelihood of infection in urine, the source of the urine, and the capacity of the manufacturing process to remove any adventitious infection. Urine for the production of medicinal products should be obtained from sources that minimize the possible presence of materials derived from subjects suffering from human TSE. As no strong evidence for TSE infectivity in urine exists, it can be concluded that the risk of disease-generating prions and TSE infectivity being present in donor urine is low. Current evidence indicates that, with respect to the risk of TSE infection, urinary-derived gonadotrophins appear to be safe.     

Glucose Ingestion Attenuates Interleukin-6 Release from Contracting Skeletal Muscle in Humans

To examine whether glucose ingestion during exercise affects the release of interleukin-6 (IL-6) from the contracting limb, seven men performed 120 min of semi-recumbent cycling on two occasions while ingesting either 250 ml of a 6.4 % carbohydrate (GLU trial) or sweet placebo (CON trial) beverage at the onset of, and at 15 min intervals throughout, exercise. Muscle biopsies obtained before and immediately after exercise were analysed for glycogen and IL-6 mRNA expression. Blood samples were simultaneously obtained from a brachial artery and a femoral vein prior to and during exercise and leg blood flow was measured by thermodilution in the femoral vein. Net leg IL-6 release, and net leg glucose and free fatty acid (FFA) uptake, were calculated from these measurements. The arterial IL-6 concentration was lower (   P < 0.05  ) after 120 min of exercise in GLU, but neither intramuscular glycogen nor IL-6 mRNA were different when comparing GLU with CON. However, net leg IL-6 release was attenuated (   P < 0.05  ) in GLU compared with CON. This corresponded with an enhanced (   P < 0.05  ) glucose uptake and a reduced (   P < 0.05  ) FFA uptake in GLU. These results demonstrate that glucose ingestion during exercise attenuates leg IL-6 release but does not decrease intramuscular expression of IL-6 mRNA.     

Differentiation of Cucumber mosaic virus isolates by hybridization to oligonucleotides in a microarray format

A system for microarrays was developed to detect and differentiate Cucumber mosaic virus (CMV) serogroups and subgroups. The coat protein genes of 14 different isolates were amplified using cy3-labelled generic but species-specific primers. These amplicons were hybridized against a set of five different serotype and subgroup specific 24-mer oligonucleotides bound to an aldehyde-coated glass slide via an aminolinker. The results of the hybridization revealed that the method allowed a clear differentiation of the 14 different CMV isolates into the serogroupes 1 and 2, and in addition was able to assign 9 out of 10 different serogroup 1 isolates correctly into subgroups 1a and 1b. This differentiation was not possible by RFLP analysis with the restriction enzyme MspI. The use of amplicons larger than 700 base pairs and their successful differentiation by hybridization to specific oligonucleotides opens avenues to highly parallel, yet sensitive assays for plant viruses.