Upregulation of hepatic LDL receptor-related protein in nephrotic syndrome: response to statin therapy

Nephrotic syndrome (N-S) is associated with elevated plasma concentration and impaired clearance of VLDL, chylomicrons (CM), and their atherogenic remnants. These abnormalities are largely due to lipoprotein lipase, hepatic triglyceride lipase, and VLDL receptor deficiencies and impaired HDL-mediated shuttling of apoE and apoC between the nascent and remnant VLDL and CM. LRP is a multifaceted endocytic receptor that is heavily expressed in the liver. LRP recognizes at least 30 different ligands including VLDL and CM remnants. These observations prompted the present study to discern the effect of N-S on hepatic LRP gene and protein expressions. The study further sought to explore the effect of lipid-lowering therapy on LRP expression in N-S. Sprague-Dawley rats were randomized to the N-S (given ip injections of puromycin aminonucleoside; 130 mg/kg on day 1, 60 mg/kg on day 14) and placebo-injected control groups. On day 14, animals were subdivided into statin-treated (rosuvastatin; 20 mg x kg(-1) x day(-1) mixed with powdered chow) and untreated groups and studied on day 28. The untreated N-S group exhibited severe proteinuria, hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia, and marked elevation of hepatic tissue LRP mRNA and protein abundance. Statin administration for 2 wk resulted in significant improvements of plasma lipid profile, proteinuria, and hypoalbuminemia as well as hepatic LRP mRNA and protein abundance. In contrast, statin administration had no significant effect on either plasma lipids or hepatic LRP levels in the normal control rats. In conclusion, N-S results in marked upregulation of hepatic LRP expression that is partly reversed with statin administration. These findings exclude depressed hepatic LRP expression as the primary cause of elevated plasma lipoprotein remnants in N-S.     

Characterization of intracellular Ca(2+) stores in gallbladder smooth muscle

The existence of functionally distinct intracellular Ca(2+) stores has been proposed in some types of smooth muscle. In this study, we sought to examine Ca(2+) stores in the gallbladder by measuring intracellular Ca(2+) concentration ([Ca(2+)](i)) in fura 2-loaded isolated myocytes, membrane potential in intact smooth muscle, and isometric contractions in whole mount preparations. Exposure of isolated myocytes to 10 nM CCK caused a transient elevation in [Ca(2+)](i) that persisted in Ca(2+)-free medium and was inhibited by 2-aminoethoxydiphenylborane (2-APB). Application of caffeine induced a rapid spike-like elevation in [Ca(2+)](i) that was insensitive to 2-APB but was abolished by pretreatment with 10 muM ryanodine. These data support the idea that both inositol trisphosphate (IP(3)) receptors (IP(3)R) and ryanodine receptors (RyR) are present in this tissue. When caffeine was applied in Ca(2+)-free solution, the [Ca(2+)](i) transients decreased as the interval between Ca(2+) removal and caffeine application was increased, indicating a possible leakage of Ca(2+) in these stores. The refilling of caffeine-sensitive stores involved sarcoendoplasmic reticulum Ca(2+)-ATPase activation, similar to IP(3)-sensitive stores. The moderate Ca(2+) elevation caused by CCK was associated with a gallbladder contraction, but caffeine or ryanodine failed to induce gallbladder contraction. Nevertheless, caffeine caused a concentration-dependent relaxation in gallbladder strips either under resting tone conditions or precontracted with 1 muM CCK. Taken together, these results suggest that, in gallbladder smooth muscle, multiple pharmacologically distinct Ca(2+) pools do not exist, but IP(3)R and RyR must be spatially separated because Ca(2+) release via these pathways leads to opposite responses.     

Taking the best for learning

Examples of how animals learn when multiple, sometimes redundant, cues are present provide further examples not considered by Hutchinson and Gigerenzer that seem to fit the principle of taking the best. "The best" may the most valid cue in the present circumstances; evolution may also produce species-specific biases to use the most functionally relevant cues.     

Folding, stability and polymerization properties of FtsZ chimeras with inserted tubulin loops involved in the interaction with the cytosolic chaperonin CCT and in microtubule formation

To attain its native conformation, the cytoskeletal protein tubulin needs the concourse of several molecular chaperones, among others the cytosolic chaperonin CCT. It has been previously described that denatured tubulin interacts with CCT in a quasi-folded conformation using several loops located throughout its sequence. These loops are also involved in microtubule formation and are absent in its prokaryote homologue FtsZ, which in vitro folds by itself and does not interact with CCT. Several FtsZ/tubulin chimeric proteins were generated by inserting consecutively one, two or three of the CCT-binding domains of tubulin into the corresponding sequence of FtsZ from Methanococccus jannaschii. The insertion of any of the CCT-binding loops generates in the FtsZ/tubulin chimeras the ability to interact with CCT. The accumulation of CCT-binding loops induces in the FtsZ/tubulin chimeras unfolding and refolding properties that are more similar to tubulin than to its prokaryote counterpart. Finally, the insertion of some of these loops generates in the FtsZ/tubulin chimeras more complex polymeric structures than those found for FtsZ. These results reinforce the notion that CCT has coevolved with tubulin to deal with the folding problems encountered by the eukaryotic protein with the appearance of the new sequences involved in microtubule formation.     

Up-regulation of neuropeptide Y levels and modulation of glutamate release through neuropeptide Y receptors in the hippocampus of kainate-induced epileptic rats

Kainate-induced epilepsy has been shown to be associated with increased levels of neuropeptide Y (NPY) in the rat hippocampus. However, there is no information on how increased levels of this peptide might modulate excitation in kainate-induced epilepsy. In this work, we investigated the modulation of glutamate release by NPY receptors in hippocampal synaptosomes isolated from epileptic rats. In the acute phase of epilepsy, a transient decrease in the efficiency of NPY and selective NPY receptor agonists in inhibiting glutamate release was observed. Moreover, in the chronic epileptic hippocampus, a decrease in the efficiency of NPY and the Y(2) receptor agonist, NPY13-36, was also found. Simultaneously, we observed that the epileptic hippocampus expresses higher levels of NPY, which may account for an increased basal inhibition of glutamate release. Consistently, the blockade of Y(2) receptors increased KCl-evoked glutamate release, and there was an increase in Y(2) receptor mRNA levels 30 days after kainic acid injection, suggesting a basal effect of NPY through Y(2) receptors. Taken together, these results indicate that an increased function of the NPY modulatory system in the epileptic hippocampus may contribute to basal inhibition of glutamate release and control hyperexcitability.     

The tomato early fruit specific gene <Emphasis Type="Italic">Lefsm1</Emphasis> defines a novel class of plant-specific SANT/MYB domain proteins

We describe here a novel plant-specific gene, Lefsm1 (fruit SANT/MYB-like 1) harboring a single SANT/MYB domain. The expression of Lefsm1 is specific to the very early stages of tomato (Lycopersicon esculentum) fruit development. Ectopic expression of Lefsm1 results in severe developmental alterations manifested in retarded growth, and reduced apical dominance during tomato and Arabidopsis seedling development. A promoter sequence residing 1.0 kb upstream to the translation initiation codon confers the organ-specific expression of the gene. Lefsm1 belongs to a novel small gene family consisting of five to six members in tomato, Arabidopsis and rice. The SANT/MYB domain of LeFSM1 and its orthologs in Arabidopsis and rice differs from that of all other plant or animal MYB proteins and from the SANT domains found in part of the chromatin remodeling proteins. Together, our results indicate that Lefsm1 is a founding member of a small family of proteins containing a novel MYB/SANT domain which is likely to participate in the regulation of a plant-specific developmental program.     

Animal models for radiation injury, protection and therapy

Current events throughout the world underscore the growing threat of different forms of terrorism, including radiological or nuclear attack. Pharmaceutical products and other approaches are needed to protect the civilian population from radiation and to treat those with radiation-induced injuries. In the event of an attack, radiation exposures will be heterogeneous in terms of both dose and quality, depending on the type of device used and each victim's location relative to the radiation source. Therefore, methods are needed to protect against and treat a wide range of early and slowly developing radiation-induced injuries. Equally important is the development of rapid and accurate biodosimetry methods for estimating radiation doses to individuals and guiding clinical treatment decisions. Acute effects of high-dose radiation include hematopoietic cell loss, immune suppression, mucosal damage (gastrointestinal and oral), and potential injury to other sites such as the lung, kidney and central nervous system (CNS). Long-term effects, as a result of both high- and low-dose radiation, include dysfunction or fibrosis in a wide range of organs and tissues and cancer. The availability of appropriate types of animal models, as well as adequate numbers of animals, is likely to be a major bottleneck in the development of new or improved radioprotectors, mitigators and therapeutic agents to prevent or treat radiation injuries and of biodosimetry methods to measure radiation doses to individuals.     

Development of a recA gene-based identification approach for the entire Burkholderia genus

Burkholderia is an important bacterial genus containing species of ecological, biotechnological, and pathogenic interest. With their taxonomy undergoing constant revision and the phenotypic similarity of several species, correct identification of Burkholderia is difficult. A genetic scheme based on the recA gene has greatly enhanced the identification of Burkholderia cepacia complex species. However, the PCR developed for the latter approach was limited by its specificity for the complex. By alignment of existing and novel Burkholderia recA sequences, we designed new PCR primers and evaluated their specificity by testing a representative panel of Burkholderia strains. PCR followed by restriction fragment length polymorphism analysis of an 869-bp portion of the Burkholderia recA gene was not sufficiently discriminatory. Nucleotide sequencing followed by phylogenetic analysis of this recA fragment differentiated both putative and known Burkholderia species and all members of the B. cepacia complex. In addition, it enabled the design of a Burkholderia genus-specific recA PCR that produced a 385-bp amplicon, the sequence of which was also able to discriminate all species examined. Phylogenetic analysis of 188 novel recA genes enabled clarification of the taxonomic position of several important Burkholderia strains and revealed the presence of four novel B. cepacia complex recA lineages. Although the recA phylogeny could not be used as a means to differentiate B. cepacia complex strains recovered from clinical infection versus the natural environment, it did facilitate the identification of clonal strain types of B. cepacia, B. stabilis, and B. ambifaria capable of residing in both niches.     

Leishmania: role of P glycoprotein in drug resistance and reversion strategies

Protozoan parasites are important causative agents of morbidity and mortality throughout the world--a problem further complicated by the emergence of drug resistance in these parasites. Mechanisms of drug resistance include the following: decreased uptake of the drug into the cell, loss of drug activation, alterations in the drug target, and over-expression of a well-known multiple drug transporter proteins. In this review, two critical components of resistance are stressed: (1) the role of ATP binding cassette proteins, such as P-glycoproteins, in mediating drug resistance in Leishmania and other protozoans, followed by development of cross-resistance to many structurally and functionally unrelated drugs, and (2) some concepts concerning the reversal mechanism of multidrug resistance by drugs and natural products. Several modulators or chemosensitizers alter the capacity of P-glycoproteins to maintain subtoxic intracellular drug concentrations. Calcium channel blockers such as verapamil act in this mode; however, high concentrations are required for an efficient and effective inhibition and, in addition, produce undesirable side effects. The discovery of new, natural product modulators of P-glycoproteins is stressed. This category of modulators offer potentially improved efficacy and lowered toxicity for the mammalian host.