Polyphosphate and tyrosine phosphorylation in the N-terminal domain of the human mitochondrial Lon protease disrupts its functions

Phosphorylation plays a crucial role in the regulation of many fundamental cellular processes. Phosphorylation levels are increased in many cancer cells where they may promote changes in mitochondrial homeostasis. Proteomic studies on various types of cancer identified 17 phosphorylation sites within the human ATP-dependent protease Lon, which degrades misfolded, unassembled and oxidatively damaged proteins in mitochondria. Most of these sites were found in Lon's N-terminal (NTD) and ATPase domains, though little is known about the effects on their function. By combining the biochemical and cryo-electron microscopy studies, we show the effect of Tyr186 and Tyr394 phosphorylations in Lon's NTD, which greatly reduce all Lon activities without affecting its ability to bind substrates or perturbing its tertiary structure. A substantial reduction in Lon's activities is also observed in the presence of polyphosphate, whose amount significantly increases in cancer cells. Our study thus provides an insight into the possible fine-tuning of Lon activities in human diseases, which highlights Lon's importance in maintaining proteostasis in mitochondria.

Electron microscopy reveals toroidal shape of master neuronal cell differentiator REST - RE1-silencing transcription factor

The RE1-Silencing Transcription factor (REST) is essential for neuronal differentiation. Here, we report the first 18.5-angstrom electron microscopy structure of human REST. The refined electron map suggests that REST forms a torus that can accommodate DNA double-helix in the central hole. Additionally, we quantitatively described REST binding to the canonical DNA sequence of the neuron-restrictive silencer element. We developed protocols for the expression and purification of full-length REST and the shortened variant REST-N62 produced by alternative splicing. We tested the mutual interaction of full-length REST and the splicing variant REST-N62. Revealed structure-function relationships of master neuronal repressor REST will allow finding new biological ways of prevention and treatment of neurodegenerative disorders and diseases.

Preparation and Cryo-FIB micromachining of Saccharomyces cerevisiae for Cryo-Electron Tomography

Today, cryo-electron tomography (cryo-ET) is the only technique that can provide near-atomic resolution structural data on macromolecular complexes in situ. Owing to the strong interaction of an electron with the matter, high-resolution cryo-ET studies are limited to specimens with a thickness of less than 200 nm, which restricts the applicability of cryo-ET only to the peripheral regions of a cell. A complex workflow that comprises the preparation of thin cellular cross-sections by cryo-focused ion beam micromachining (cryo-FIBM) was introduced during the last decade to enable the acquisition of cryo-ET data from the interior of larger cells. We present a protocol for the preparation of cellular lamellae from a sample vitrified by plunge freezing utilizing Saccharomyces cerevisiae as a prototypical example of a eukaryotic cell with wide utilization in cellular and molecular biology research. We describe protocols for vitrification of S. cerevisiae into isolated patches of a few cells or a continuous monolayer of the cells on a TEM grid and provide a protocol for lamella preparation by cryo-FIB for these two samples.

Antimicrobial activity of aerial parts of Drosera peltata Smith on oral bacteria

The antimicrobial activity of extracts of aerial parts of Drosera peltata Smith against oral bacteria was investigated using agar diffusion and dilution micromethods. The chloroformic extract, active against all the bacteria tested, showed the most significant antimicrobial properties. Plumbagin, isolated from the extract, is the active principle. Results obtained suggest that Drosera peltata extract could be used in the treatment of oral infectious diseases like dental caries and periodontitis.

Antioxidant activities of polyphenolic extracts from flowers, in vitro callus and cell suspension cultures of Crataegus monogyna

Numerous plants synthesize among their secondary metabolites phenolic compounds which possess antioxidant effects. The aim of the present work was to assay the antioxidant activities of phenolics from Crataegus monogyna Jacq. flowers and in vitro tissue culture (calli and cell suspensions) extracts. In the case of tissue culture extracts, the phenolic production is studied at three different stages of one subculture period (initial growth period, increasing and maximal phenolic synthesis phases). Attention was paid to the main categories: flavonoids and proanthocyanidins, and to the principal individual components. Total phenolic amounts decrease in the order: fresh flowers > cell suspension cultures > callus cultures. The antioxidant activities of these different extracts against H2O2 and HOCl, have been determined in vitro. All the extracts are efficient and the scavenging capacity is clearly related to the total phenol content. The scavenging effects of the cell suspension extracts are similar to those of the flowers. Among individual compounds, the flavanol-type derivatives, specially the proanthocyanidin B2, are more efficient. Thus, in vitro plant tissues could be an interesting source of bioactive molecules.

Oxygen species scavenging activity of phenolic extracts from hawthorn fresh plant organs and pharmaceutical preparations

Different extracts of fresh vegetative and reproductive organs from Crataegus monogyna harvested during a whole season and from some pharmaceutical hawthorn preparations exhibit in vitro antioxidant activities using three different models of oxygen reactive species generation (superoxide anion, hydrogen peroxide and hypochlorous acid). All the tested samples show low IC50 values, the most efficient being fresh young leaves, fresh floral buds and pharmaceutical dried flowers. The activities seem to be especially bound to the total phenolic proanthocyanidin and flavonoid contents.

[Camptothecin and derivatives: a new class of antitumor agents]

Camptothecin (CPT), an alkaloid isolated from the stem wood and bark of Camptotheca acuminata native to China, was discovered in the early 60's after a systematic screening of natural products by the National Cancer Institute (NCI). This new anticancer agent displays an unique mechanism of action as it inhibits intranuclear enzyme topoisomerase 1, involved in DNA replication. CPT is poorly water soluble and causes severe and unpredictable toxicities such as haemorrhagic cystitis and diarrhea; for therefore reason, a number of analogues have been synthetized in a attempt to define the features of the molecule that are essential for cytotoxicity and to produce derivatives with increased solubility. Clinical trials of several soluble molecules are in progress in the different countries: irinotecan, topotecan, 9-AC. Encouraging results are observed against solid tumors. Irinotecan was recently commercialized in France. It is a prodrug; the active metabolite SN-38 showed a good activity in metastatic colorectal adenocarcinoma; the limiting toxicities are myelotoxicity and essentially late diarrhea. However, new studies are needed for state precisely the optimal schedule of administration and association with other chemotherapeutic agents.

Activity of anthraquinonic and naphthoquinonic compounds on oral bacteria

The activity of anthraquinonic compounds and naphthoquinones was tested by micromethods against oral bacteria. The more significant results were obtained with naphthoquinones. Plumbagin, juglone and lawsone possess a wide spectrum of activity. The lowest MIC values were observed with plumbagin and the combination of juglone and lawsone results in a synergism against cariogenic bacteria. Among the eight anthraquinonic compounds investigated only rhein showed significant antimicrobial properties. Results obtained could suggest the use of rhein and plumbagin alone or juglone and lawsone combined for treatment of oral infectious diseases.

Antioxidant activities of Crataegus monogyna extracts

Interesting antioxidant activities of extracts from different vegetative and reproductive organs of Crataegus monogyna harvested at different stages of growth have been determined by the malondialdehyde-thiobarbituric acid (MDA) test on hepatic microsomal preparations and compared to the contents in total phenolics, proanthocyanidins, catechins, flavonoids, and phenolic acids. The best correlations were established with total phenols while activities in leaves seem to be influenced by flavonoids and in flowers and fruits by proanthocyanidins and catechins.

Activity of thymol, carvacrol, cinnamaldehyde and eugenol on oral bacteria

The antimicrobial activity of thymol, carvacrol, cinnamaldehyde and eugenol alone or combined was tested by micromethods on eight oral bacteria. The compounds showed an inhibitory activity on seven microorganisms and a synergistic effect was observed with certain combinations. The four compounds can be used alone or combined, as eugenol and thymol, eugenol and carvacrol, thymol and carvacrol, during the treatment of oral infectious diseases.

Are hyperplastic rectosigmoid polyps associated with an increased risk of proximal colonic neoplasms?

Diminutive polyps are frequent findings on screening flexible sigmoidoscopy. To determine the significance of distal diminutive polyps, we conducted a prospective study of 162 asymptomatic, average-risk subjects who were 50 years of age or older. Subjects were divided into four groups: 42 control subjects with no polyps in the rectosigmoid, 66 subjects with at least one diminutive adenoma in the rectosigmoid, 12 subjects with a mixed hyperplastic-adenomatous polyp in the rectosigmoid, and 42 subjects with only hyperplastic polyps in the rectosigmoid. Total colonoscopy was performed on all subjects. The prevalence of proximal adenomas was 42% in the adenoma group, 25% in the mixed group, 14% in the hyperplastic group and 12% in the control group. The prevalence of proximal adenomas was significantly higher (p = 0.006) in the adenoma group as compared with the control and hyperplastic groups. Increasing age was associated with an increased prevalence of proximal adenomas. Nearly two thirds of those over 65 years of age with distal diminutive adenomas had proximal colonic neoplasms. These results indicate that diminutive rectosigmoid adenomas are good markers for proximal neoplasms. Rectosigmoid hyperplastic polyps are not associated with an increased prevalence of proximal neoplasms. Total colonoscopy is not indicated if hyperplastic polyps are the only finding on flexible sigmoidoscopy.

[Antibacterial activity of thymol, carvacrol and cinnamaldehyde alone or in combination]

The antimicrobial activity of thymol, carvacrol and cinnamaldehyde was tested by several methods on bacteria involved in upper respiratory tract infections. Their combinations were investigated too. The broad spectrum of activity and the synergistic effect observed with some combinations (specially thymol and carvacrol) could allowed the use of the three compounds alone or, like thymol an carvacrol, combined during the treatment of respiratory infections.

Procyanidin Production by Fagopyrum esculentum Callus Culture

FAGOPYRUM ESCULENTUM CALLUS cultures grown on B5 medium synthesize procyanidins B2 (0.6-1.8 mg/g dry wt) and B2-3'- O-gallate (3.5-6.0 mg/g dry wt). Sucrose is a better source than other carbohydrates and moderate concentrations (3-4%) stimulate both growth and procyanidin synthesis. While darkness was not a limiting factor, light induced faster growth and increased procyanidin contents. Treatment with gallic acid strongly stimulated the procyanidin B2-3'- O-gallate production, but drastically inhibited growth, leading to a two-step-culture experiment combining convenient growth and increased galloylated dimer synthesis (up to 45 mg/g dry wt).

A seven year survey of antibiotic susceptibility and its relationship with usage

Bacterial susceptibilities to 14 antibiotics of 7385 clinical isolates, belonging to six species of Gram-negative bacilli, were analysed during seven years (1980-86). The recovery of Serratia marcescens, Acinetobacter calcoaceticus and Pseudomonas aeruginosa increased while their sensitivity to antibiotics decreased significantly, especially to aminoglycosides and tetracycline. There were significant correlations between increase in antibiotic use and decrease in susceptibility. There was a striking relationship between third-generation cephalosporin use and increasing number of isolates of the species mentioned above.

[Antibacterial activity of species of the genus Allium]

Garlic, onion and shallot were tested for antimicrobial activity against pathogenic aerobic and anaerobic bacteria. The MIC of aqueous and petroleum ether extracts were determined. Garlic showed the greater activity; the combination garlic-antibiotic is synergistic against Acinetobacter calcoaceticus and leads to indifference against anaerobic bacteria. The active constituent is not probably allicin alone.

Intraocular pressure in uremic patients on chronic hemodialysis

Intraocular pressure (IOP) was measured before and after hemodialysis in 30 uremic patients receiving regular treatment. Osmolality, blood pressure and weight before and after dialysis were also determined. Low IOP of 11.4 +/- 2.7 and 11.5 +/- 3.1 mm Hg was found in the left and right eye, respectively. Following hemodialysis osmolality, blood pressure and body weight decreased significantly but IOP did not rise significantly. This study suggests that there is only a remote possibility for severe IOP increase following hemodialysis in uremic patients on chronic treatment.