Knut Liestøl

Changes in physical fitness and changes in mortality

BACKGROUND Point estimates of physical fitness give important information on the risk of death in healthy people, but there is little information available on effects of sequential changes in physical fitness on mortality. We studied this latter aspect in healthy middle-aged men over a total follow-up period of 22 years. METHODS 2014 healthy men aged 40-60 years had a bicycle exercise test and clinical examination, and completed a questionnaire in 1972-75 (survey 1). This was repeated for 1756 (91%) of 1932 men still alive by Dec 31, 1982 (survey 2). The exercise scores were adjusted for age. The change in exercise scores between surveys was divided into quartiles (Q1=least fit, Q4=fittest). An adjusted Coxs proportional hazards model was used to study the association between changes in physical fitness and mortality, with the Q1 men used as controls. FINDINGS By Dec 31, 1994, 238 (17%) of the 1428 men had died, 120 from cardiovascular causes. There were 37 deaths in the Q4 group (19 cardiovascular); their relative risks of death were 0.45 (95% CI 0.29-0.69) for any cause and 0.47 (0.26-0.86) for cardiovascular causes. There was a graded, inverse relation between changes in physical fitness and mortality irrespective of physical fitness status at survey 1. INTERPRETATION Change in physical fitness in healthy middle-aged men is a strong predictor of mortality. Even small improvements in physical fitness are associated with a significantly lowered risk of death. If confirmed, these findings should be used to influence public health policy.

PtdIns(3)P controls cytokinesis through KIF13A-mediated recruitment of FYVE-CENT to the midbody

Several subunits of the class III phosphatidylinositol-3-OH kinase (PI(3)K-III) complex are known as tumour suppressors. Here we uncover a function for this complex and its catalytic product phosphatidylinositol-3-phosphate (PtdIns(3)P) in cytokinesis. We show that PtdIns(3)P localizes to the midbody during cytokinesis and recruits a centrosomal protein, FYVE-CENT (ZFYVE26), and its binding partner TTC19, which in turn interacts with CHMP4B, an endosomal sorting complex required for transport (ESCRT)-III subunit implicated in the abscission step of cytokinesis. Translocation of FYVE-CENT and TTC19 from the centrosome to the midbody requires another FYVE-CENT-interacting protein, the microtubule motor KIF13A. Depletion of the VPS34 or Beclin 1 subunits of PI(3)K-III causes cytokinesis arrest and an increased number of binucleate and multinucleate cells, in a similar manner to the depletion of FYVE-CENT, KIF13A or TTC19. These results provide a mechanism for the translocation and docking of a cytokinesis regulatory machinery at the midbody.

Height, weight and menarcheal age of Oslo schoolchildren during the last 60 years

Every 5th year since 1920 the heights and weights of all Oslo schoolchildren (aged 7 to 18 years) have been measured, and the measurements processed centrally. For ages between 8 and 14 the mean height increased by about 4 cm per decade between 1920 and 1940 for both sexes. A drop of about 1.5 cm occurred during World War II, followed by a rapid catch-up. Since 1950, height has increased only moderately. A weight increase of between 1.5 kg (8 years old) and 3.5 kg (13 years old) per decade before 1940 was followed by a drop during the war equivalent to somewhat less than one decades gain. A rapid catch-up after the war was followed by a slight decrease since 1950, especially for ages above puberty. A stable difference in the social composition of the eastern and western districts of Oslo allowed comparison of the trends for lower and higher social strata. Before the war, children from higher strata were taller than children from lower strata, but this difference has now practically disappeared. Children from the higher strata weighed more until about 1955, but later those from the lower strata weighed markedly more, especially during adolescence. The difference in menarcheal age between social strata was examined in 1928, 1952, 1970 and 1975. The time trend parallels that for weight: menarcheal age was lowest among higher strata until the 1950s, but after that the lower strata experienced the lowest menarcheal age.

CGH-Explorer: a program for analysis of array-CGH data

SUMMARY CGH-Explorer is a program for visualization and statistical analysis of microarray-based comparative genomic hybridization (array-CGH) data. The program has preprocessing facilities, tools for graphical exploration of individual arrays or groups of arrays, and tools for statistical identification of regions of amplification and deletion.

Number and spatial distribution of nuclei in the muscle fibres of normal mice studied in vivo

We present here a new technique with which to visualize nuclei in living muscle fibres in the intact animal, involving injection of labelled DNA into single cells. This approach allowed us to determine the position of all of nuclei within a sarcolemma without labelling satellite cells. In contrast to what has been reported in tissue culture, we found that the nuclei were immobile, even when observed over several days. Nucleic density was uniform along the fibre except for the endplate and some myotendinous junctions, where the density was higher. The perijunctional region had the same number of nuclei as the rest of the fibre. In the extensor digitorum longus (EDL) muscle, the extrajunctional nuclei were elongated and precisely aligned to the long axis of the fibre. In the soleus, the nuclei were rounder and not well aligned. When comparing small and large fibres in the soleus, the number of nuclei varied approximately in proportion to cytoplasmic volume, while in the EDL the number was proportional to surface area. Statistical analysis revealed that the nuclei were not randomly distributed in either the EDL or the soleus. For each fibre, actual distributions were compared with computer simulations in which nuclei were assumed to repel each other, which optimizes the distribution of nuclei with respect to minimizing transport distances. The simulated patterns were regular, with clear row‐like structures when the density of nuclei was low. The non‐random and often row‐like distribution of nuclei observed in muscle fibres may thus reflect regulatory mechanisms whereby nuclei repel each other in order to minimize transport distances.

A phosphatidylinositol 3-kinase class III sub-complex containing VPS15, VPS34, Beclin 1, UVRAG and BIF-1 regulates cytokinesis and degradative endocytic traffic.

The mammalian class III phosphatidylinositol 3-kinase (PI3K-III) complex regulates fundamental cellular functions, including growth factor receptor degradation, cytokinesis and autophagy. Recent studies suggest the existence of distinct PI3K-III sub-complexes that can potentially confer functional specificity. While a substantial body of work has focused on the roles of individual PI3K-III subunits in autophagy, functional studies on their contribution to endocytic receptor downregulation and cytokinesis are limited. We therefore sought to elucidate the specific nature of the PI3K-III complexes involved in these two processes. High-content microscopy-based assays combined with siRNA-mediated depletion of individual subunits indicated that a specific sub-complex containing VPS15, VPS34, Beclin 1, UVRAG and BIF-1 regulates both receptor degradation and cytokinesis, whereas ATG14L, a PI3K-III subunit involved in autophagy, is not required. The unanticipated role of UVRAG and BIF-1 in cytokinesis was supported by a strong localisation of these proteins to the midbody. Importantly, while the tumour suppressive functions of Beclin 1, UVRAG and BIF-1 have previously been ascribed to their roles in autophagy, these results open the possibility that they may also contribute to tumour suppression via downregulation of mitogenic signalling by growth factor receptors or preclusion of aneuploidy by ensuring faithful completion of cell division.

Membrane remodeling by the PX-BAR protein SNX18 promotes autophagosome formation

SNX18 promotes autophagosome formation by remodeling membranes and providing membrane to forming autophagosomes.

Survival meta-analyses for >1800 malignant peripheral nerve sheath tumor patients with and without neurofibromatosis type 1

There are conflicting reports as to whether malignant peripheral nerve sheath tumor (MPNST) patients with neurofibromatosis type 1 (NF1) have worse prognosis than non-NF1 MPNST patients. Large clinical studies to address this problem are lacking due to the rareness of MPNST. We have performed meta-analyses testing the effect of NF1 status on MPNST survival based on publications from the last 50 years, including only nonoverlapping patients reported from each institution. In addition, we analyzed survival characteristics for 179 MPNST patients from 3 European sarcoma centers. The meta-analyses including data from a total of 48 studies and >1800 patients revealed a significantly higher odds ratio for overall survival (OROS) and disease-specific survival (ORDSS) in the non-NF1 group (OROS = 1.75, 95% confidence interval [CI] = 1.28–2.39, and ORDSS = 1.68, 95% CI = 1.18–2.40). However, in studies published in the last decade, survival in the 2 patient groups has been converging, as especially the NF1 group has shown improved prognosis. For our own MPNST patients, NF1 status had no effect on overall or disease-specific survival. The compiled literature from 1963 to the present indicates a significantly worse outcome of MPNST in patients with NF1 syndrome compared with non-NF1 patients. However, survival for the NF1 patients has improved in the last decade, and the survival difference is diminishing. These observations support the hypothesis that MPNSTs arising in NF1 and non-NF1 patients are not different per se. Consequently, we suggest that the choice of treatment for MPNST should be independent of NF1 status.

The Genomic HyperBrowser: inferential genomics at the sequence level

The immense increase in the generation of genomic scale data poses an unmet analytical challenge, due to a lack of established methodology with the required flexibility and power. We propose a first principled approach to statistical analysis of sequence-level genomic information. We provide a growing collection of generic biological investigations that query pairwise relations between tracks, represented as mathematical objects, along the genome. The Genomic HyperBrowser implements the approach and is available at http://hyperbrowser.uio.no.

Copynumber: Efficient algorithms for single- and multi-track copy number segmentation

BackgroundCancer progression is associated with genomic instability and an accumulation of gains and losses of DNA. The growing variety of tools for measuring genomic copy numbers, including various types of array-CGH, SNP arrays and high-throughput sequencing, calls for a coherent framework offering unified and consistent handling of single- and multi-track segmentation problems. In addition, there is a demand for highly computationally efficient segmentation algorithms, due to the emergence of very high density scans of copy number.ResultsA comprehensive Bioconductor package for copy number analysis is presented. The package offers a unified framework for single sample, multi-sample and multi-track segmentation and is based on statistically sound penalized least squares principles. Conditional on the number of breakpoints, the estimates are optimal in the least squares sense. A novel and computationally highly efficient algorithm is proposed that utilizes vector-based operations in R. Three case studies are presented.ConclusionsThe R package copynumber is a software suite for segmentation of single- and multi-track copy number data using algorithms based on coherent least squares principles.