Micromanipulation of amyloplasts with optical tweezers in Arabidopsis stems

Intracellular sedimentation of highly dense, starch-filled amyloplasts toward the gravity vector is likely a key initial step for gravity sensing in plants. However, recent live-cell imaging technology revealed that most amyloplasts continuously exhibit dynamic, saltatory movements in the endodermal cells of Arabidopsis stems. These complicated movements led to questions about what type of amyloplast movement triggers gravity sensing. Here we show that a confocal microscope equipped with optical tweezers can be a powerful tool to trap and manipulate amyloplasts noninvasively, while simultaneously observing cellular responses such as vacuolar dynamics in living cells. A near-infrared (λ=1064 nm) laser that was focused into the endodermal cells at 1 mW of laser power attracted and captured amyloplasts at the laser focus. The optical force exerted on the amyloplasts was theoretically estimated to be up to 1 pN. Interestingly, endosomes and trans-Golgi network were trapped at 30 mW but not at 1 mW, which is probably due to lower refractive indices of these organelles than that of the amyloplasts. Because amyloplasts are in close proximity to vacuolar membranes in endodermal cells, their physical interaction could be visualized in real time. The vacuolar membranes drastically stretched and deformed in response to the manipulated movements of amyloplasts by optical tweezers. Our new method provides deep insights into the biophysical properties of plant organelles in vivo and opens a new avenue for studying gravity-sensing mechanisms in plants.     

Activator of G Protein Signaling 8 (AGS8) Is Required for Hypoxia-induced Apoptosis of Cardiomyocytes: ROLE OF G�¦� AND CONNEXIN 43 (CX43)*

Ischemic injury of the heart is associated with activation of multiple signal transduction systems including the heterotrimeric G-protein system. Here, we report a role of the ischemia-inducible regulator of Gβγ subunit, AGS8, in survival of cardiomyocytes under hypoxia. Cultured rat neonatal cardiomyocytes (NCM) were exposed to hypoxia or hypoxia/reoxygenation following transfection of AGS8siRNA or pcDNA::AGS8. Hypoxia-induced apoptosis of NCM was completely blocked by AGS8siRNA, whereas overexpression of AGS8 increased apoptosis. AGS8 formed complexes with G-proteins and channel protein connexin 43 (CX43), which regulates the permeability of small molecules under hypoxic stress. AGS8 initiated CX43 phosphorylation in a Gβγ-dependent manner by providing a scaffold composed of Gβγ and CX43. AGS8siRNA blocked internalization of CX43 following exposure of NCM to repetitive hypoxia; however it did not influence epidermal growth factor-mediated internalization of CX43. The decreased dye flux through CX43 that occurred with hypoxic stress was also prevented by AGS8siRNA. Interestingly, the Gβγ inhibitor Gallein mimicked the effect of AGS8 knockdown on both the CX43 internalization and the changes in cell permeability elicited by hypoxic stress. These data indicate that AGS8 is required for hypoxia-induced apoptosis of NCM, and that AGS8-Gβγ signal input increased the sensitivity of cells to hypoxic stress by influencing CX43 regulation and associated cell permeability. Under hypoxic stress, this unrecognized response program plays a critical role in the fate of NCM.     

Two guaiane-type sesquiterpene lactones and their related sesquiterpene lactones from Porella japonica

Two new guaiane-type sesquiterpene dilactones, porelladiolide and 3α,4α-epoxyporelladiolide and a new germacranolide, 3β-hydroxycostunolide, together with the previously known germacranolides, guaianolides, pinguisane-type sesquiterpenes, and a sacculatane-type diterpene dialdehyde have been isolated from the liverwort, Porella japonica and their structures have been established by the spectral evidence and some chemical transformations. Porelladiolide, 3α,4α-epoxyporelladiolide and the sesquiterpene with α-methylene γ-lactone group showed inhibitory activity toward the germination and growth of roots of rice in the husk.     

Antiepileptic and neuroprotective effects of human umbilical cord blood mononuclear cells in a pilocarpine-induced epilepsy model

Status epilepticus (SE) is a condition of persistent seizure that leads to brain damage and, frequently, to the establishment of chronic epilepsy. Cord blood is an important source of adult stem cells for the treatment of neurological disorders. The present study aimed to evaluate the effects of human umbilical cord blood mononuclear cells (HUCBC) transplanted into rats after induction of SE by the administration of lithium and pilocarpine chloride. Transplantation of HUCBC into epileptic rats protected against neuronal loss in the hippocampal subfields CA1, CA3 and in the hilus of the dentate gyrus, up to 300 days after SE induction. Moreover, transplanted rats had reduced frequency and duration of spontaneous recurrent seizures (SRS) 15, 120 and 300 days after the SE. Our study shows that HUCBC provide prominent antiepileptic and neuroprotective effects in the experimental model of epilepsy and reinforces that early interventions can protect the brain against the establishment of epilepsy.     

Synthesis of purine bases having a di(hydroxymethyl)cyclopentenyl group by means of high-pressure reaction and their anti-HIV activity.

The 1'- and 5'-hydroxymethyl derivatives of carbovir and related purine derivatives were synthesized from 5-hydroxymethylcyclopentadiene. The anti-HIV activity evaluation of these compounds has revealed that 9-(c-4,t-5-dihydroxymethylcyclopent-2-en-r-1-yl)-9H-adenine is a prospective chemotherapeutic agent against AIDS.