Blocking of acidosis-mediated apoptosis by a reduction of lactate dehydrogenase activity through antisense mRNA expression.

Lactic acid produced from the cells is a potential cause of extra- and intracellular acidification. Due to scarce technical tools, lactic acid that leads to acidification could not be reduced and direct evidence of the relationship between metabolic lactate and apoptosis has not yet been elucidated. In this study, we designed a cellular pH regulation system in CHO cells by a reduction of lactate dehydrogenase (LDH) activity through LDH antisense mRNA expression. This inhibited lactate production and, therefore, acidification of the cytosol. Under HCO3(-)-buffered growth conditions, both the parent CHO cells and the engineered CHO cells maintained their extracellular pH and intracellular pH fairly well. However, upon acidification of the cytosol, only the parent CHO cells underwent apoptosis under HCO3(-)-free conditions. In fact, we observed a number of apoptosis-related events only in control cells, including mitochondrial dysfunction, cytochrome c release, and an increase in caspase-3 enzymatic activity.     

Differential Effects of Long-Term Electroconvulsive Shock on Brain Levels of Enkephalin and Humoral-Endorphin

Abstract: Electroconvulsive shock (ECS) administrations repeated for 10 consecutive days cause an elevation in the opioid content of the rat brain. Two different endogenous opioids, enkephalin and humoral-endorphin, undergo independent changes that differ in both their time course and intracerebral localization. These metabolic changes parallel long-term behavioral modifications such as the development and dissipation of tolerance to the analgesic effect of ECS. The activation of two different, independent, endogenous opioid systems by ECS is in agreement with previous behavioral and pharmacological studies.     

PCO(2) threshold for CNS oxygen toxicity in rats in the low range of hyperbaric PO(2).

Central nervous system (CNS) oxygen toxicity, as manifested by the first electrical discharge (FED) in the electroencephalogram, can occur as convulsions and loss of consciousness. CO(2) potentiates this risk by vasodilation and pH reduction. We suggest that CO(2) can produce CNS oxygen toxicity at a PO(2) that does not on its own ultimately cause FED. We searched for the CO(2) threshold that will result in the appearance of FED at a PO(2) between 507 and 253 kPa. Rats were exposed to a PO(2) and an inspired PCO(2) in 1-kPa steps to define the threshold for FED. The results confirmed our assumption that each rat has its own PCO(2) threshold, any PCO(2) above which will cause FED but below which no FED will occur. As PO(2) decreased from 507 to 456, 405, and 355 kPa, the percentage of rats that exhibited FED without the addition of CO(2) (F(0)) dropped from 91 to 62, to 8 and 0%, respectively. The percentage of rats (F) having FED as a function of PCO(2) was sigmoid in shape and displaced toward high PCO(2) with the reduction in PO(2). The following formula is suggested to express risk as a function of PCO(2) and PO(2) [abstract: see text] where P(50) is the PCO(2)for the half response and N is power. A small increase in PCO(2) at a PO(2) that does not cause CNS oxygen toxicity may shift an entire population into the risk zone. Closed-circuit divers who are CO(2)retainers or divers who have elevated inspired CO(2)are at increased risk of CNS oxygen toxicity.     

Is prostaglandin E the neural mediator of the febrile response? The case against a proven obligatory role.

We have reviewed the evidence in favor of a prostaglandin mediator of the thermal responses in fever and found that PGE injected into the hypothalamus does not always cause fever, that cerebrospinal fluid concentrations of PGE are not reliable reflections of hypothalamic events, and that antipyretic drugs may act in ways other than inhibiting PGE synthesis. Fever is not blocked by prostaglandin antagonists, nor by ablation of PGE-sensitive areas of the brain. There is poor correlation between the effects of pyrogens and of PGE on cerebral neurons. There is evidence that at least one prostanoid other than prostaglandin is a mediator of fever, but the prostanoid has not been identified yet. We conclude that PGE may contribute to the neural responses in fever but is not essential.     

A [2Fe-2S] protein from the hyperthermophilic bacterium Aquifex aeolicus.

Overexpression in Escherichia coli of the fdx4 gene from Aquifex aeolicus has allowed isolation and characterization of the first hyperthermophilic [2Fe-2S](Scys)(4) protein, a homodimer of M = 2 x 12.4 kDa with one [2Fe-2S] cluster per subunit. This protein is undamaged by heating to 100 degrees C for at least three hours. The primary structure, in particular the characteristic distribution of the four cysteine ligands of the metal site, and the spectroscopic properties of the A. aeolicus protein relate it to well characterized [2Fe-2S] proteins from Clostridium pasteurianum and Azotobacter vinelandii. These proteins are also homologous to subunits or domains of hydrogenases and NADH-ubiquinone oxidoreductase (Complex I) of respiratory chains. The A. aeolicus [2Fe-2S] protein is thus representative of a presumably novel protein fold involved in a variety of functions in very diverse cellular backgrounds.     

The N terminus of the cardiac L-type Ca(2+) channel alpha(1C) subunit. The initial segment is ubiquitous and crucial for protein kinase C modulation, but is not directly phosphorylated.

The first 46 amino acids (aa) of the N terminus of the rabbit heart (RH) L-type cardiac Ca(2+) channel alpha(1C) subunit are crucial for the stimulating action of protein kinase C (PKC) and also hinder channel gating (Shistik, E., Ivanina, T., Blumenstein, Y., and Dascal, N. (1998) J. Biol. Chem. 273, 17901-17909). The mechanism of PKC action and the location of the PKC target site are not known. Moreover, uncertainties in the genomic sequence of the N-terminal region of alpha(1C) leave open the question of the presence of RH-type N terminus in L-type channels in mammalian tissues. Here, we demonstrate the presence of alpha(1C) protein containing an RH-type initial N-terminal segment in rat heart and brain by using a newly prepared polyclonal antibody. Using deletion mutants of alpha(1C) expressed in Xenopus oocytes, we further narrowed down the part of the N terminus crucial for both inhibitory gating and for PKC effect to the first 20 amino acid residues, and we identify the first 5 aa as an important determinant of PKC action and of N-terminal effect on gating. The absence of serines and threonines in the first 5 aa and the absence of phosphorylation by PKC of a glutathione S-transferase-fusion protein containing the initial segment suggest that the effect of PKC does not arise through a direct phosphorylation of this segment. We propose that PKC acts by attenuating the inhibitory action of the N terminus via phosphorylation of a remote site, in the channel or in an auxiliary protein, that interacts with the initial segment of the N terminus.