Traveling behavior of a termite in tunnels with different curvatures and base surface roughness

This study focused on understanding the termite traveling behavior. Artificial tunnels with different curvatures and base surface roughness were constructed. Each tunnel was 50 mm in length, with widths of W (W = 2, 3, or 4 mm). The distance between the two ends of the tunnel was D (D = 20, 30, 40, or 50 mm). A higher value of D means a lower curvature. The roughness, R (R = 60, 120, 240 and ∞), was generated by uniformly sanding the substrate with a sanding machine. A higher R value means a finer base surface. The symbol ∞ represents a smooth surface. Time (τ) taken by a termite to pass through the tunnel was measured. τ was longer in tunnels with a smooth surface compared with the tunnels with a rough surface. When W = 2, there was no effect of the roughness on speed. This is because the narrow tunnel width diluted the effects of the smoothness of the surface. When W = 3, τ was statistically shorter for R = 240, than for R = 60 and 120. This suggests that an appropriate surface roughness could positively contribute to the traveling speed.     

GATC motifs may alter the conformation of DNA depending on sequence context and N6-adenine methylation status: possible implications for DNA-protein recognition

As part of our analysis of the role of a uniquely clustered set of dam methylation sites (the motif GATC) within the origin of DNA replication in Escherichia coli, we have studied the effect of GATCs in various methylation states on the intrinsic curvature of DNA. We have designed a set of DNA linkers and used commercially available linkers containing GATC motifs. The linkers were ligated and the electrophoretic mobility of the resulting multimers in different states of methylation was tested relative to reference fragments. We report that properly phased GATCs in certain sequence environments modulate DNA curvature and that these effects may be enhanced by N⁶-adenine methylation of the GATCs. These structural alterations may in turn affect DNA-protein interactions, especially those involving proteins that rely on both primary sequence and structure for recognition. We present an example, where introduction of a GATC within an integration host factor (IHF) binding site, which does not alter the consensus sequence, reduces the binding affinity of the protein for the modified site. Received: 16 December 1997 / Accepted: 24 February 1998     

Motor unit activation patterns during concentric wrist flexion in humans with different muscle fibre composition

Muscle activity was recorded from the flexor carpi radialis muscle during static and dynamic-concentric wrist flexion in six subjects, who had exhibited large differences in histochemically identified muscle fibre composition. Motor unit recruitment patterns were identified by sampling 310 motor units and counting firing rates in pulses per second (pps). During concentric wrist flexion at 30% of maximal exercise intensity the mean firing rate was 27 (SD 13) pps. This was around twice the value of 12 (SD 5) pps recorded during sustained static contraction at 30% of maximal voluntary contraction, despite a larger absolute force level during the static contraction. A similar pattern of higher firing rates during dynamic exercise was seen when concentric wrist flexion at 60% of maximal exercise intensity [30 (SD 14) pps] was compared with sustained static contraction at 60% of maximal voluntary contraction [19 (SD 8) pps]. The increase in dynamic exercise intensity was accomplished by recruitment of additional motor units rather than by increasing the firing rate as during static contractions. No difference in mean firing rates was found among subjects with different muscle fibre composition, who had previously exhibited marked differences in metabolic response during corresponding dynamic contractions. It was concluded that during submaximal dynamic contractions motor unit firing rate cannot be deduced from observations during static contractions and that muscle fibre composition may play a minor role. Accepted: 5 May 1998     

The Effects of Boric Acid and Gibberellic Acid on the Growth of Fiber of Phragmites cormmuhis Trin

Water-cultured young plants of Phragmites communis Trin. were used in this experiment. They were treated with boric acid and gibberellic acid, separately or in combination, by method of foliage spraying. The results are summarized as follows: 1. In comparation with the controls, the length of the fibre cells was remarkably increased following the treatment with boric acid at concentrations ranging from 1 to 200 μmol/l. The optimum concentration of boric acid was found to be 100 μmol/l. Gibberellic acid alone at the concentration of 50 μmol/l also enhanced the length of the fibre cells. However, the best result was obtained in the group treated with a combination of boric acid and gibmberellic acid at a ratio of 200:50 μmol/l. A maximum increasement of fibre length and a greater ratio of length to width were observed in this experimental group. 2. Microscopic study indicates that the increase in both the number of the fibre cells and ,the thickness of the fibre layer are apparent in histological preparation. 3. In addition, The authors have also found that the incorporation of H3-glucose into the fibre cell wall was greatly enhanced by such combination treatment. 4. In conclusion, it has been demonstrated clearly that the boric acid and the gibberellic acid, when used in combination, produces an augmentative effect on both the growth and the development of the fibre cells of Phragmites communis Trin.     

Application of iterative robust model‐based optimal experimental design for the calibration of biocatalytic models

The aim of model calibration is to estimate unique parameter values from available experimental data, here applied to a biocatalytic process. The traditional approach of first gathering data followed by performing a model calibration is inefficient, since the information gathered during experimentation is not actively used to optimize the experimental design. By applying an iterative robust model‐based optimal experimental design, the limited amount of data collected is used to design additional informative experiments. The algorithm is used here to calibrate the initial reaction rate of an ω‐transaminase catalyzed reaction in a more accurate way. The parameter confidence region estimated from the Fisher Information Matrix is compared with the likelihood confidence region, which is not only more accurate but also a computationally more expensive method. As a result, an important deviation between both approaches is found, confirming that linearization methods should be applied with care for nonlinear models. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1278–1293, 2017     

The lysophospholipid acyltransferase antagonist CI-976 inhibits a late step in COPII vesicle budding

The mechanism of coat protein (COP)II vesicle fission from the endoplasmic reticulum (ER) remains unclear. Lysophospholipid acyltransferases (LPATs) catalyze the conversion of various lysophospholipids to phospholipids, a process that can promote spontaneous changes in membrane curvature. Here, we show that 2,2-methyl- N -(2,4,6,-trimethoxyphenyl)dodecanamide (CI-976), a potent LPAT inhibitor, reversibly inhibited export from the ER in vivo and the formation of COPII vesicles in vitro . Moreover, CI-976 caused the rapid and reversible accumulation of cargo at ER exit sites (ERESs) containing the COPII coat components Sec23/24 and Sec13/31 and a marked enhancement of Sar1p-mediated tubule formation from ERESs, suggesting that CI-976 inhibits the fission of assembled COPII budding elements. These results identify a small molecule inhibitor of a very late step in COPII vesicle formation, consistent with fission inhibition, and demonstrate that this step is likely facilitated by an ER-associated LPAT.     

Effect of dietary fibre type on physical activity and behaviour in kennelled dogs

Dog diets may differ in their effectiveness of maintaining satiety after a meal. Consequently, sensations of hunger, feeding motivation, physical activity, and sensitivity to environmental stressors may be increased. Dietary fibre may be effective in prolonging postprandial satiety depending on type and inclusion level. This study evaluated the effect of fibre fermentability on behaviour in dogs. Sixteen healthy adult dogs were housed individually and fed a low-fermentable fibre (LFF) diet containing 8.5% cellulose or a high-fermentable fibre (HFF) diet containing 8.5% sugar beet pulp and 2% inulin. Dogs were fed two equal portions at 8:30 and 18:30 according to energy requirements. Behaviour of dogs in their home-cage was recorded and analyzed by instantaneous scan sampling (2 × 24 h with 15 min intervals) and focal sampling continuous recordings (10 min per animal per hour, from 9:00 until 18:00). Dogs were subjected to a behaviour test composed of the subtests open-field, sudden-silence, novel-object, and acoustic-startle. The behavioural responses of each dog were recorded. Scores for the scan and focal samples were expressed per clock hour and DIET × TIME effects were tested statistically using Residual Maximum Likelihood (REML). Data from the tests were examined using principal component analysis resulting in the compilation of two components. Data were tested statistically for DIET and DIET × SUBTEST effects using REML. Variables specific for the open-field and novel-object test were analyzed using analysis of variance. For the scans, a significant DIET × TIME effect was found for resting. At night and in the morning, HFF dogs rested more compared to LFF dogs, but they rested less between 14:00 and 17:00. For the continuous recordings, the main findings were a tendency for DIET × TIME effect for time spent resting with a pattern consistent with that for the scans. The interaction was significant for inactive-alert (lie with head up or sitting) with HFF-fed dogs having lower values around 10:00–11:00 and higher values hereafter. Finally, time spent tail wagging was significantly higher for LFF-fed dogs just before the evening meal that may indicate higher level of arousal. For the behaviour tests, no significant DIET or DIET × SUBTEST effects were detected. It is concluded that compared to the LFF diet, the HFF diet increased inactivity in kennelled beagle dogs likely through the prolongation of postprandial satiety. This effect did not change the reaction to stressful events in kennelled laboratory dogs. Enhanced susceptibility to environmental stressors at times of hunger in sensitive companion dogs may occur but requires further study.     

Effects of source of fibre on the development and pH of the gastrointestinal tract of broilers

The effects of different sources of dietary fibre on gastrointestinal tract (GIT) development and digesta pH were studied in 25-day-old broilers. There were four diets: a control diet low in fibre content (37.3 g neutral detergent fibre and 16.0 g acid detergent fibre/kg) and three additional diets in which 30 g/kg of cellulose (CEL), sugar beet pulp (SBP) or oat hulls (OH) were included at the expenses of sepiolite (a complex magnesium silicate clay). The relative weight (RW, %BW) of the GIT was greater with the SBP – than with the CEL – and the control diets. Also, gizzard RW was higher with the diet containing OH than with the diet containing CEL or the control diets, with the SBP diet being intermediate (P≤0.001). Fibre inclusion modified the pH of the GIT (P≤0.05) but the effects depended on the type of fibre. Crop pH was higher and proventriculus pH lower with SBP than with the other diets. However, gizzard pH was reduced with SBP and OH but not with CEL (P≤0.05). The pH of the digesta of the duodenum was similar for all diets but that of the jejunum, Meckel's diverticulum and ileum increased with SBP and decreased with CEL inclusion (P≤0.05). We concluded that dietary fibre affects the development and pH value of the different segments of GIT and that the effects differ according to the physico-chemical characteristics of the source of fibre used.     

Modeling protein-mediated morphology in biomembranes

The equilibrium theory for lipid membranes is used to describe the structure of nuclear pores and the membrane shapes accompanying endocytosis. The commonly used variant of the theory contains a fixed parameter called the spontaneous curvature which accounts for asymmetry in the bending response of the membrane. This is replaced here by a variable distribution of spontaneous curvature representing the influence of attached proteins. The required adjustments to the standard theory are described and the resulting model is applied to the study of membrane morphology at the cites of protein-assisted nuclear pore formation and endocytosis.     

Lipid cosorting mediated by shiga toxin induced tubulation

To maintain cell membrane homeostasis, lipids must be dynamically redistributed during the formation of transport intermediates, but the mechanisms driving lipid sorting are not yet fully understood. Lowering sphingolipid concentration can reduce the bending energy of a membrane, and this effect could account for sphingolipid depletion along the retrograde pathway. However, sphingolipids and cholesterol are enriched along the anterograde pathway, implying that other lipid sorting mechanisms, such as protein-mediated sorting, can dominate. To characterize the influence of protein binding on the lipid composition of highly curved membranes, we studied the interactions of the B-subunit of Shiga toxin (STxB) with giant unilamellar vesicles containing its glycosphingolipid receptor [globotriaosylceramide (Gb3)]. STxB binding induced the formation of tubular membrane invaginations, and fluorescence microscopy images of these highly curved membranes were consistent with co-enrichment of Gb3 and sphingolipids. In agreement with theory, sorting was stronger for membrane compositions close to demixing. These results strongly support the hypothesis that proteins can indirectly mediate the sorting of lipids into highly curved transport intermediates via interactions between lipids and the membrane receptor of the protein.