CHANGES IN PHYSIOLOGICAL TREMOR RESULTING FROM SLEEP DEPRIVATION UNDER CONDITIONS OF INCREASING FATIGUE DURING PROLONGED MILITARY TRAINING

The aim of the study was to define the changes of the characteristics of physiological postural tremor under conditions of increasing fatigue and lack of sleep during prolonged military training (survival). The subjects of the study were 15 students of the Polish Air Force Academy in Dęblin. The average age was 19.9±1.3 years. During the 36-hour-long continuous military training (survival) the subjects were deprived of sleep. Four tremor measurements were carried out for each of the subjects: Day 1 – morning, after rest (measurement 0); Day 2 – morning, after overnight physical exercise (measurement 1); afternoon, after continuous sleep deprivation (measurement 2); Day 3 – morning, after a full night sleep (measurement 3). The accelerometric method using an acceleration measuring kit was applied to analyse tremor. A significant difference between mean values of the index evaluating tremor power in low frequencies L_2-4 in measurement 0 and measurement 3 was observed (p<0.01). No significant differences were found in mean values of index L_10-20. Mean frequencies F_2-4 differed significantly from each other (F_2,42=4.53; p<0.01). Their values were 2.94±0.11, 2.99±0.9, 2.93±0.07 and 2.91±0.07 for successive measurements. A gradual, significant decrease of F_8-14 was observed (F_2,42=5.143; p<0.01). Prolonged sleep deprivation combined with performing tasks demanding constant physical effort causes long-lasting (over 24 hours) changes of the amplitude of low-frequency tremor changes. This phenomenon may significantly influence psychomotor performance, deteriorating the ability to perform tasks requiring movement precision.     

Atomic force microscopy study of DNA flexibility on short length scales: smooth bending versus kinking

The apparently anomalous flexibility of DNA on short length scales has attracted a lot of attention in recent years. We use atomic force microscopy (AFM) in solution to directly study the DNA bending statistics for small lengths down to one helical turn. The accuracy of experimental estimates could be improved due to a large data volume and a refined algorithm for image processing and measuring bend angles. It is found that, at length scales beyond two helical turns (7 nm), DNA is well described by the harmonic worm-like chain (WLC) model with the bending persistence length of 56 nm. Below this threshold, the AFM data are also described by the WLC model assuming that the accuracy of measured bend angles is limited by the physical width of the double helix. We conclude that the double helical DNA behaves as a uniform elastic rod even at very short length scales. Strong bends due to kinks, melting bubbles and other deviations from the WLC model are statistically negligible.     

Application of T-DNA activation tagging to identify glutamate receptor-like genes that enhance drought tolerance in plants

Key message

A high-quality rice activation tagging population has been developed and screened for drought-tolerant lines using various water stress assays. One drought-tolerant line activated two rice glutamate receptor-like genes. Transgenic overexpression of the rice glutamate receptor-like genes conferred drought tolerance to rice and Arabidopsis.

Abstract

Rice (Oryza sativa) is a multi-billion dollar crop grown in more than one hundred countries, as well as a useful functional genetic tool for trait discovery. We have developed a population of more than 200,000 activation-tagged rice lines for use in forward genetic screens to identify genes that improve drought tolerance and other traits that improve yield and agronomic productivity. The population has an expected coverage of more than 90 % of rice genes. About 80 % of the lines have a single T-DNA insertion locus and this molecular feature simplifies gene identification. One of the lines identified in our screens, AH01486, exhibits improved drought tolerance. The AH01486 T-DNA locus is located in a region with two glutamate receptor-like genes. Constitutive overexpression of either glutamate receptor-like gene significantly enhances the drought tolerance of rice and Arabidopsis, thus revealing a novel function of this important gene family in plant biology.     

Quantitative proteomics reveals differentially expressed proteins in murine preneoplastic intestine in a model of intestinal tumorigenesis induced by low dietary folate and MTHFR deficiency

Colorectal cancer risk is increased when dietary folate intake is low, with or without a deficiency in methylenetetrahydrofolate reductase (MTHFR). We have observed that intestinal tumors are induced in mice fed low‐folate diets, and that tumor incidence is increased when these mice also have MTHFR deficiency. This study was undertaken to identify differentially expressed proteins in conditions favoring initial steps of murine carcinogenesis in normal preneoplastic intestine. We compared the proteome of BALB/c normal intestine in Mthfr^+/+ mice fed control diets for 1 year (low susceptibility to tumorigenesis) with the proteome of Mthfr^+/? animals fed low folate diets (higher tumor susceptibility). Our data suggest that the NuRD complex, KRAS‐related proteins, the protein synthetic machinery, and fatty acid‐related metabolic proteins are upregulated in the early stages of tumorigenesis. These proteins may serve as biomarkers or targets for colorectal cancer diagnosis or therapy.     

ARFGAP1 Is Dynamically Associated with Lipid Droplets in Hepatocytes

The ARF GTPase Activating Protein 1 (ARFGAP1) associates mainly with the cytosolic side of Golgi cisternal membranes where it participates in the formation of both COPI and clathrin-coated vesicles. In this study, we show that ARFGAP1 associates transiently with lipid droplets upon addition of oleate in cultured cells. Also, that addition of cyclic AMP shifts ARFGAP1 from lipid droplets to the Golgi apparatus and that overexpression and knockdown of ARFGAP1 affect lipid droplet formation. Examination of human liver tissue reveals that ARFGAP1 is found associated with lipid droplets at steady state in some but not all hepatocytes.     

Cellular events during interfascicular cambium ontogenesis in inflorescence stems of Arabidopsis

Development of cambium and its activity is important for our knowledge of the mechanism of secondary growth. Arabidopsis thaliana emerges as a good model plant for such a kind of study. Thus, this paper reports on cellular events taking place in the interfascicular regions of inflorescence stems of A. thaliana, leading to the development of interfascicular cambium from differentiated interfascicular parenchyma cells (IPC). These events are as follows: appearance of auxin accumulation, PIN1 gene expression, polar PIN1 protein localization in the basal plasma membrane and periclinal divisions. Distribution of auxin was observed to be higher in differentiating into cambium parenchyma cells compared to cells within the pith and cortex. Expression of PIN1 in IPC was always preceded by auxin accumulation. Basal localization of PIN1 was already established in the cells prior to their periclinal division. These cellular events initiated within parenchyma cells adjacent to the vascular bundles and successively extended from that point towards the middle region of the interfascicular area, located between neighboring vascular bundles. The final consequence of which was the closure of the cambial ring within the stem. Changes in the chemical composition of IPC walls were also detected and included changes of pectic epitopes, xyloglucans (XG) and extensins rich in hydroxyproline (HRGPs). In summary, results presented in this paper describe interfascicular cambium ontogenesis in terms of successive cellular events in the interfascicular regions of inflorescence stems of Arabidopsis.     

Membranes in the miotic apparatus of barley cells

Membranes in the mitotic apparatus have been investigated ultrastructually in dividing cells of barley (Hordeum vulgare). After osmium tetroxide- potassium ferricyanide or ferrocyanide postfixation (OsFeCN) of material that had been fixed in glutaraldehyde in the presence of Ca(++), the nuclear envolope (NE)-endoplasmic reticulum (ER) complex is selectively stained, permitting observations on the cellular pattern and structural ramifications of this membrane system that have not been previously recognized. Specifically, it is observed that membrane system that have not been previously recognized. Specifically, it is observed that during mitosis the NE-ER forms a continuous membrane system that ensheathes and isolates the mitotic apparatus (MA). Elements of ER progressively accumulate in the region of the spindle pole, becoming most concentrated by early anaphase. Within the MA itself, there are striking spindle- membrane associations; in particular, tubular elements of predominantly smooth NE-ER invade the spindle interior selectively along kinetochore microtubules. The membrane elements at the pole and surrounding the MA consist of tubular reticulum and fenestrated lamellae. Membranes of the MA thus resemble in considerable detail the tubular network and fenestrated elements of the sarcoplasmic reticulum of muscle. It is suggested that the NE-ER of the dividing barley cell may function in one or both of the following ways: (a) to control the concentration of free Ca(++) in the MA and (b) to serve as an anchor to chromosome motion.     

Biodecolourization of azo and triphenylmethane dyes by <Emphasis Type="Italic">Dichomitus squalens</Emphasis> and <Emphasis Type="Italic">Phlebia</Emphasis> spp

Nine white-rot fungal strains were screened for biodecolourization of brilliant green, cresol red, crystal violet, congo red and orange II. Dichomitus squalens, Phlebia fascicularia and P. floridensis decolourized all of the dyes on solid agar medium and possessed better decolourization ability than Phanerochaete chrysosporium when tested in nitrogen-limited broth medium. Journal of Industrial Microbiology & Biotechnology (2002) 28, 201–203 DOI: 10.1038/sj/jim/7000222 Received 12 July 2001/ Accepted in revised form 22 October 2001