Role of mitochondrial and sarcolemmal K(ATP) channels in ischemic preconditioning of the canine heart

We tested whether mitochondrial or sarcolemmal ATP-sensitive K(+) (K(ATP)) channels play a key role in ischemic preconditioning (IP) in canine hearts. In open-chest beagle dogs, the left anterior descending artery was occluded four times for 5 min each with 5-min intervals of reperfusion (IP), occluded for 90 min, and reperfused for 6 h. IP as well as cromakalim and nicorandil (nonspecific K(ATP) channel openers) markedly limited infarct size (6.3 +/- 1.2, 8.9 +/- 1.9, and 7.2 +/- 1.6%, respectively) compared with the control group (40.9 +/- 4.1%). A selective mitochondrial K(ATP) channel blocker, 5-hydroxydecanoate, partially blunted the limitation of infarct size in the animals subjected to IP and those treated with cromakalim and nicorandil (21.6 +/- 3.8, 25.1 +/- 4.6, and 19.8 +/- 5.2%, respectively). A nonspecific K(ATP) channel blocker, glibenclamide, completely abolished the effect of IP (38.5 +/- 6.2%). Intracoronary or intravenous administration of a mitochondria-selective K(ATP) channel opener, diazoxide, at >100 micromol/l could only partially decrease infarct size (19.5 +/- 4.3 and 20.1 +/- 4.4%, respectively). In conclusion, mitochondrial and sarcolemmal K(ATP) channels independently play an important role in the limitation of infarct size by IP in the canine heart.     

Activity and properties of fumarate reductase in ruminal bacteria

Fumarate-reducing bacteria were sought from the main ruminal bacteria. Fibrobacter succinogenes, Selenomonas ruminantium subsp. ruminantium, Selenomonas ruminantium subsp. lactilytica, and Veillonella parvula reduced fumarate by using H(2) as an electron donor. Ruminococcus albus, Prevotella ruminicola, and Anaerovibrio lipolytica consumed fumarate, although they did not oxidize H(2). Of these bacteria, V. parvula, two strains of Selenomonas, and F. succinogenes had a high capacity to reduce fumarate. In all the fumarate-reducing bacteria examined, fumarate reductase existed in the membrane fraction. Based on the activity per cell mass and the affinity of fumarate reductase to fumarate, these bacteria were divided into two groups, which corresponded to the capacity to use H(2): A group of bacteria with higher activity and affinity were able to use H(2) as an electron donor for fumarate reduction. The bacteria in this group should gain an advantage over the bacteria in another group in fumarate reduction in the rumen. Cellulose digestion by R. albus was improved by fumarate reduction by S. lactilytica as a result of an increased growth of R. albus, which may have been caused by the fact that S. lactilytica immediately consumed H(2) produced by R. albus. Thus fumarate reduction may play an important role in keeping a low partial pressure of H(2) in the rumen.     

Protective Effect of Oren-gedoku-to Against Induction of Neuronal Death by Transient Cerebral Ischemia in the C57BL/6 Mouse

We examined the neuroprotective effects of oren-gedoku-to (TJ15), a herbal medicine, after transient forebrain ischemia. Transient forebrain ischemia was induced by occlusion of both common carotid arteries for 15 min in C57BL/6 mice treated with TJ15. In the control ischemic group without TJ15 treatment, histologic examination of brain tissue collected seven days after reperfusion showed death of pyramidal cells in CA2-3 area of the hippocampus, unilaterally or bilaterally. In mice treated with oral TJ15 (845 mg/kg/day) for five weeks, the frequency of ischemic neuronal death was significantly lower. Immunohistochemistry for Cu/Zn-superoxide dismutase (Cu/Zn-SOD) showed strongly reactive astrocytes in the hippocampus of ischemic mice treated with TJ15. Damage to nerve cells by free radicals plays an important role in the induction of neuronal death by ischemia-reperfusion injury. Our results suggest that TJ15 protects against ischemic neuronal death by increasing the expression of Cu/Zn-SOD and suggest that oren-gedoku-to reduces the exposure of hippocampal neurons to oxidative stress.     

Antitumor activity of paclitaxel and epirubicin in human breast carcinoma, R-27

The antitumor effect of paclitaxel, epirubicin, and both in combination was tested using R-27, an estrogen receptor-positive human breast carcinoma. In anin vivo study using nude mice both drugs showed an additive effect, whereas they showed a supraadditive pattern inin vitro MTT assay. The combination of paclitaxel and epirubicin may enhance the antitumor effect on breast carcinoma.     

Functional and Physical Interaction between Rad24 and Rfc5 in the Yeast Checkpoint Pathways

The RFC5 gene encodes a small subunit of replication factor C (RFC) complex in Saccharomyces cerevisiae and has been shown to be required for the checkpoints which respond to replication block and DNA damage. Here we describe the isolation of RAD24, known to play a role in the DNA damage checkpoint, as a dosage-dependent suppressor of rfc5-1. RAD24 overexpression suppresses the sensitivity of rfc5-1 cells to DNA-damaging agents and the defect in DNA damage-induced Rad53 phosphorylation. Rad24, like Rfc5, is required for the regulation of Rad53 phosphorylation in response to DNA damage. The Rad24 protein, which is structurally related to the RFC subunits, interacts physically with RFC subunits Rfc2 and Rfc5 and cosediments with Rfc5. Although the rad24Δ mutation alone does not cause a defect in the replication block checkpoint, it does enhance the defect in rfc5-1 mutants. Furthermore, overexpression of RAD24 suppresses the rfc5-1 defect in the replication block checkpoint. Taken together, our results demonstrate a physical and functional interaction between Rad24 and Rfc5 in the checkpoint pathways.     

Ni–Fe–La(Sr)Fe(Mn)O3 as a New Active Cermet Cathode for Intermediate‐Temperature CO2 Electrolysis Using a LaGaO3‐Based Electrolyte

Various additives to Ni–Fe systems are studied as cermet cathodes for CO₂ electrolysis (973–1173 K) using a La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ (LSGM) electrolyte, which is one of the most promising oxide‐ion conductors for intermediate‐temperature solid‐oxide electrolysis cells in terms of ionic‐transport number and conductivity. It is found that Ni–Fe–La_0.6Sr_0.4Fe_0.8Mn_0.2O₃ (Ni–Fe–LSFM) exhibits a remarkable performance with a current density of 2.32 A cm^?2 at 1.6 V and 1073 K. The cathodic overpotential is significantly decreased by mixing the LSFM powder with Ni–Fe, which is related to the increase in the number of reaction sites for CO₂ reduction. For Ni–Fe–LSFM, much smaller particles (<200 nm) are sustained under CO₂ electrolysis conditions at high temperatures than for Ni–Fe. X‐ray diffraction analysis suggests that the main phases of Ni–Fe–LSFM are Ni and LaFeO₃; thus, the oxide phase of LaFeO₃ is also maintained during CO₂ electrolysis. Analysis of the gaseous products indicates that only CO is formed, and the rate of CO formation agrees well with that of a four‐electron reduction process, suggesting that the reduction of CO₂ to CO proceeds selectively. It is also confirmed that almost no coke is deposited on the Ni–Fe–LSFM cathode after CO₂ electrolysis.     

Delta1 family members are involved in filopodial actin formation and neuronal cell migration independent of Notch signaling

Delta family proteins are transmembrane molecules that bind Notch receptors and activate downstream signaling events in neighboring cells. In addition to serving as Notch ligands, Notch-independent roles for Delta have been suggested but are not fully understood. Here, we demonstrate a previously unrecognized role for Delta in filopodial actin formation. Delta1 and Delta4, but not Delta3, exhibit filopodial protrusive activity, and this activity is independent of Notch signaling. The filopodial activity of Delta1 does not depend on the PDZ-binding domain at the C-terminus; however, the intracellular membrane-proximal region that is anchored to the plasma membrane plays an important role in filopodial activity. We further identified a Notch-independent role of DeltaD in neuronal cell migration in zebrafish. These findings suggest a possible functional link between Notch-independent filopodial activity of Delta and the control of cell motility.     

Sexual process in eight-spored ascus-forming yeast, Schizosaccharomyces japonicus II. Dependency of the sexual process on the carbon source

The carbon-source dependency of the sexual process in Schizosaccharomycesjaponicus was studied. Schiz. japonicus grew well in vegetativemedia containing glucose, sucrose, fructose or raffinose, anddid poorly in one containing mannose. On the other hand, itssexual process proceeded well in sporulation media containingglucose, sucrose or mannose, and was markedly delayed in thosecontaining fructose or raffinose. Neither vegetative growthnor sexual process occurred when non-fermentable carbon sources,such as glycerol, were used. The amount of glucose in the sporulationmedium sufficient for completion of the sexual process varieddepending on the cell-population density. Glucose was requiredfor both zygote and ascus formation but not for spore liberation.Cells were committed to sporulation shortly after the stageof zygote formation. (Received August 3, 1978; )     

Structural stability of covalently linked GroES heptamer: advantages in the formation of oligomeric structure

In order to understand how inter-subunit association stabilizes oligomeric proteins, a single polypeptide chain variant of heptameric co-chaperonin GroES (tandem GroES) was constructed from Escherichia coli heptameric GroES by linking consecutively the C-terminal of one subunit to the N-terminal of the adjacent subunit with a small linker peptide. The tandem GroES (ESC7) showed properties similar to wild-type GroES in structural aspects and co-chaperonin activity. In unfolding and refolding equilibrium experiments using guanidine hydrochloride (Gdn-HCl) as a denaturant at a low protein concentration (50 microg ml(-1)), ESC7 showed a two-state transition with a greater resistance toward Gdn-HCl denaturation (Cm=1.95 M) compared to wild-type GroES (Cm=1.1 M). ESC7 was found to be about 10 kcal mol(-1) more stable than the wild-type GroES heptamer at 50 microg ml(-1). Kinetic unfolding and refolding experiments of ESC7 revealed that the increased stability was mainly attributed to a slower unfolding rate. Also a transient intermediate was detected in the refolding reaction. Interestingly, at the physiological GroES concentration (>1 mg ml(-1)), the free energy of unfolding for GroES heptamer exceeded that for ESC7. These results showed that at low protein concentrations (<1 mg ml(-1)), the covalent linking of subunits contributes to the stability but also complicates the refolding kinetics. At physiological concentrations of GroES, however, the oligomeric state is energetically preferred and the advantages of covalent linkage are lost. This finding highlights a possible advantage in transitioning from multi-domain proteins to oligomeric proteins with small subunits in order to improve structural and kinetic stabilities.