Growth in Axenic Culture of Isolated Shoot Apices of Eichhornia crassipes

Apical meristem culture of Eichhornia crassipes has shown that for successful regeneration, the excised meristem dome must be associated with at least the youngest leaf primordium as part of the explant and a culture medium containing coconut milk (10 %, v/v), IAA (0.1 mg/l) and kinetin (1 mg/l) as growth supplements with 2 % sucrose as carbon source.     

5-aza deoxycytidine-induced inhibition of differentiation of spermatogonia into spermatocytes in the mouse

In order to explore the significance of DNA methylation in proliferation and differentiation of germ cells in testis, 5-aza,2′-deoxycytidine (5-azaCdR), a hypomethylating agent, was administered in vivo to neonatal mice having only spermatogonial (premeiotic) cells. End-labeling of the Mspl, Hpall, and Hhal digested DNA revealed considerable loss of methylation following the treatment. Cellular and histological preparations of the testis showed complete inhibition of differentiation into spermatocytic stage. Analysis of protein synthesis in the treated and control testis by growing the cells in ³⁵S-Methionine medium and resolving the lysate by SDS-PAGE revealed that the programme of expression of at least 5 polypeptides (35.0, 31.5, 27.0, 22.5, and 18.0 KD) was altered as a result of 5-azaCdR incorporation. It appears that DNA methylation plays a critical role in the differentiation of gonia into primary spermatocytes. © 1995 wiley-Liss, Inc.     

Substrate Deformation Predicts Neuronal Growth Cone Advance

Although pulling forces have been observed in axonal growth for several decades, their underlying mechanisms, absolute magnitudes, and exact roles are not well understood. In this study, using two different experimental approaches, we quantified retrograde traction force in Aplysia californica neuronal growth cones as they develop over time in response to a new adhesion substrate. In the first approach, we developed a novel method, to our knowledge, for measuring traction forces using an atomic force microscope (AFM) with a cantilever that was modified with an Aplysia cell adhesion molecule (apCAM)-coated microbead. In the second approach, we used force-calibrated glass microneedles coated with apCAM ligands to guide growth cone advance. The traction force exerted by the growth cone was measured by monitoring the microneedle deflection using an optical microscope. Both approaches showed that Aplysia growth cones can develop traction forces in the 10⁰–10² nN range during adhesion-mediated advance. Moreover, our results suggest that the level of traction force is directly correlated to the stiffness of the microneedle, which is consistent with a reinforcement mechanism previously observed in other cell types. Interestingly, the absolute level of traction force did not correlate with growth cone advance toward the adhesion site, but the amount of microneedle deflection did. In cases of adhesion-mediated growth cone advance, the mean needle deflection was 1.05 ± 0.07 μm. By contrast, the mean deflection was significantly lower (0.48 ± 0.06 μm) when the growth cones did not advance. Our data support a hypothesis that adhesion complexes, which can undergo micron-scale elastic deformation, regulate the coupling between the retrogradely flowing actin cytoskeleton and apCAM substrates, stimulating growth cone advance if sufficiently abundant.     

Slow muscle myoblasts differentiating in vitro synthesize both slow and fast myosin light chains

Whether fast and slow skeletal muscles of the embryo develop from cells of a common origin or from two separate cellular origins is not known. Recent evidence suggests that prior to innervation all muscles of the embryo are of one type, the fast type, i.e., all synthesize fast but not slow myosin light chains. Innervation has been thought to play the central role in the shift of a fast to a slow muscle. Experiments reported here demonstrate that myoblasts from slow muscle regions of the embryo when isolated in tissue culture differentiate into myotubes which synthesize both fast and slow myosin light chains, and that innervation is not required to initiate slow myosin light-chain synthesis.     

Molecular Dynamics Simulations of Ibuprofen Binding to Aβ Peptides

Using replica exchange molecular dynamics simulations and the implicit solvent model we probed binding of ibuprofen to Aβ_10-40 monomers and amyloid fibrils. We found that the concave (CV) fibril edge has significantly higher binding affinity for ibuprofen than the convex edge. Furthermore, binding of ibuprofen to Aβ monomers, as compared to fibrils, results in a smaller free energy gain. The difference in binding free energies is likely to be related to the presence of the groove on the CV fibril edge, in which ibuprofen tends to accumulate. The confinement effect of the groove promotes the formation of large low-energy ibuprofen clusters, which rarely occur on the surface of Aβ monomers. These observations led us to suggest that the ibuprofen binding mechanism for Aβ fibrils is different from that for monomers. In general, ibuprofen shows a preference to bind to those regions of Aβ monomers (amino terminal) and fibrils (the CV edge) that are also the primary aggregation interfaces. Based on our findings and on available experimental data, we propose a rationale for the ibuprofen antiaggregation effect.     

Community-Effectiveness of Temephos for Dengue Vector Control: A Systematic Literature Review

The application of the organophosphate larvicide temephos to water storage containers is one of the most commonly employed dengue vector control methods. This systematic literature review is to the knowledge of the authors the first that aims to assess the community-effectiveness of temephos in controlling both vectors and dengue transmission when delivered either as a single intervention or in combination with other interventions. A comprehensive literature search of 6 databases was performed (PubMed, WHOLIS, GIFT, CDSR, EMBASE, Wiley), grey literature and cross references were also screened for relevant studies. Data were extracted and methodological quality of the studies was assessed independently by two reviewers. 27 studies were included in this systematic review (11 single intervention studies and 16 combined intervention studies). All 11 single intervention studies showed consistently that using temephos led to a reduction in entomological indices. Although 11 of the 16 combined intervention studies showed that temephos application together with other chemical vector control methods also reduced entomological indices, this was either not sustained over time or–as in the five remaining studies—failed to reduce the immature stages. The community-effectiveness of temephos was found to be dependent on factors such as quality of delivery, water turnover rate, type of water, and environmental factors such as organic debris, temperature and exposure to sunlight. Timing of temephos deployment and its need for reapplication, along with behavioural factors such as the reluctance of its application to drinking water, and operational aspects such as cost, supplies, time and labour were further limitations identified in this review. In conclusion, when applied as a single intervention, temephos was found to be effective at suppressing entomological indices, however, the same effect has not been observed when temephos was applied in combination with other interventions. There is no evidence to suggest that temephos use is associated with reductions in dengue transmission.